CA2282100A1 - Method and apparatus for operating a retractable arm - Google Patents
Method and apparatus for operating a retractable arm Download PDFInfo
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- CA2282100A1 CA2282100A1 CA002282100A CA2282100A CA2282100A1 CA 2282100 A1 CA2282100 A1 CA 2282100A1 CA 002282100 A CA002282100 A CA 002282100A CA 2282100 A CA2282100 A CA 2282100A CA 2282100 A1 CA2282100 A1 CA 2282100A1
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- travel
- limit
- reciprocating member
- motor
- magnetic sensor
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60Q—ARRANGEMENT OF SIGNALLING OR LIGHTING DEVICES, THE MOUNTING OR SUPPORTING THEREOF OR CIRCUITS THEREFOR, FOR VEHICLES IN GENERAL
- B60Q1/00—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor
- B60Q1/26—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor the devices being primarily intended to indicate the vehicle, or parts thereof, or to give signals, to other traffic
- B60Q1/50—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor the devices being primarily intended to indicate the vehicle, or parts thereof, or to give signals, to other traffic for indicating other intentions or conditions, e.g. request for waiting or overtaking
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Power-Operated Mechanisms For Wings (AREA)
Abstract
A method and apparatus for operating a reciprocating or retractable member driven by a motor, such as a school bus safety arm mechanism, includes a magnet mounted in fixed relation to the member and first and second magnetic sensors positioned so that the magnet is in actuating proximity of the first magnetic sensor when the reciprocating member is at its first limit of travel, and in actuating proximity of the second magnetic sensor when the reciprocating member is at its second limit of travel. The magnet thus actuates the sensors to stop the motion of the member at the selected limits of its path of travel.
Description
METHOD AND APPARATUS FOR OPERATING A RETRACTABLE ARM
Field of Invention This invention relates generally to reciprocating or retractable devices.
In particular, this invention relates to a method and apparatus for limiting the motion of a retractable arm or sign such as those commonly used on a school bus.
Background of the Invention School buses and other forms of mass transportation pick up and discharge their passengers at designated points along a route. At these pick-up or drop-off points, the bus or other vehicle is frequently stopped in the road, which is shared by other motorists. It is therefore a concern that the driver, and other motorists on the road, be adverted to the presence of passengers entering or leaving the bus.
This is particularly true in the case of school buses, where the passengers are often young children who are not as cognizant of the rules of the road, or as observant, as their elders. A passenger, especially a young child, may exit the bus and pass immediately in front of the vehicle in order to cross the street. This practice gives rise to a twofold risk: first, that the driver of the bus cannot see the child in front of the vehicle, and second, that a motorist approaching from behind the bus as the child crosses the street will have too little reaction time to avoid a collision.
Safety devices designed to address these concerns are described in the prior art. One such device is a stop sign mounted on the side of a bus, for example as taught in U.S. Patent No. 4,916,372 issued April 10, 1990 to Reavell et al.
One side of the stop sign is fixed to a hinge attached to the mounting device. When not in use, the stop sign is in a retracted position generally parallel to the side of the vehicle.
When extended perpendicularly to the side of the bus, the stop sign is visible to oncoming motorists and motorists approaching the bus from behind on the side on which the sign is mounted.
Another type of safety device, such as is taught in U.S. Patent No.
4,559,518 issued December 17, 1985 to Latta, Jr., is a crossing arm or gate mounted on the front of a bus at approximately bumper height. The arm is hinged on the end closest to the roadside when the bus stops for pick-up or drop-off. When not in use, the arm lies generally parallel to the front of the bus. When deployed, the arm extends at a right angle to the front of the bus, effectively preventing a pedestrian on the side of the road from crossing in front of the bus over the length of the crossing arm.
In such devices the retractable member is hingedly mounted on the vehicle and undergoes an angular displacement by a drive member in communication with a motor, to move the retractable member between retracted and extended positions. It therefore becomes necessary to identify the retracted and extended positions for the purpose of controlling the motor, such that displacement of the unit stops once the unit has reached either terminal position. The solution of visually ascertaining the position of the unit and manually switching off the drive motor is unsatisfactory, and several automatic solutions have been devised that remove this task from the driver's responsibilities, allowing the driver to concentrate on other duties.
These solutions involve the use of a physical limiting device, such as a limit switch, to stop the apparatus once it has reached its fully extended or retracted position. Such physical limiting devices are triggered by lateral or rotational movement in the safety unit. For example, U.S. Patent No. 4,766,413 issued August 23, 1988 to Reavell, teaches a motor connected to a link arm which in turn is connected to the safety arm hinged to the housing mounted on the vehicle. The link arm moves forward and backward with respect to the side of the vehicle. The link arm is provided with an actuator pin which travels between two limit switches which are in a fixed position relative to the side of the vehicle. The limit switches are thus opened or closed as the link arm reaches its extreme positions, which correspond with the retracted and extended positions of the safety arm or stop sign.
Another example of a limiting device is described in U.S. Patent No.
5,357,239 issued October 18, 1994 to Lamparter, in which a peg extends radially outward from the rotating drive member which communicates with the safety unit.
When the drive member rotates past a predetermined point, the peg abuts the housing or other component of the safety apparatus, thus physically preventing the drive member from rotating any further.
Other examples of similar physical extension-limiting devices are taught in U.S. Patent Nos. 2,155,617 to Roan et al. and 4,916,372 to Reavell et al.
Because of their nature such limit switches, which utilize a physical means of limit detection, are subject to fatigue or other mechanical failure, blockage due to accumulation of debris and corrosion due to exposure to the elements.
It would therefore be advantageous to control the safety apparatus using limiting means that does not require physical contact between parts and is thus not vulnerable to environmental conditions.
Summary of the Invention The invention provides a method and apparatus for operating a reciprocating or retractable device between a fully retracted position and a fully extended position which addresses the problem of fatigue or mechanical failure in relation to the limiting device utilized to stop the motor once the arm has reaches its fully extended or fully retracted position.
The invention accomplishes this by providing a magnetized element such as a permanent magnet actuating a magnetic sensor positioned to detect when the retractable member has reached a predetermined limit in its path of travel. In a first preferred embodiment the magnet is mounted on a reciprocating drive mechanism transmitting the rotational motion of the motor to the retractable member. The motor and drive member are contained in a housing, with first and second magnetic sensors mounted in fixed positions relative to the housing such that the first magnetic sensor detects the proximity of the magnet at one limit of the reciprocating member's path of travel, for example a fully retracted position, and the second magnetic sensor detects the proximity of the magnet at the other limit of the reciprocating member's path of travel, for example a fully extended position. When the magnet is in proximity to either the first or second magnetic sensor, that magnetic sensor transmits an electrical signal to the control circuitry to connect the drive motor to a power source or disconnect the drive motor therefrom.
Thus, the invention provides a means for detecting the preset limits of motion of a reciprocating member driven by the motor, for example for extending and retracting a retractable arm, without requiring physical contact between components.
The invention may be used advantageously in a vehicle stop arm of the type typically used on school buses, which is mounted on the side of the vehicle. The invention may be used in other types of apparatus controlling the reciprocating movement of a gate, arm, sign or other device for example a parking gate, and is not limited to an apparatus for mounting on vehicles.
The invention thus provides an apparatus for moving a retractable member, comprising: a stationary housing, a drive mechanism comprising a motor affixed to the housing, for selectively driving the retractable member along a path of travel defined between a first limit and a second limit, a magnetized element disposed in fixed relation to a moving component of the drive mechanism, and a circuit for selectively connecting the motor to a power source for alternately activating the motor in a first direction and in a second direction opposite to the first direction, comprising a first magnetic sensor and a second magnetic sensor respectively disposed in fixed relation to the housing such that the magnetized element moves into actuating proximity with the first magnetic sensor when the retractable member reaches the first limit of travel, and the magnetized element moves into actuating proximity with the second magnetic sensor when the retractable member reaches the second limit of travel, whereby actuation of the first magnetic sensor by the magnetized element deactivates the motor rotating in the first direction and actuation of the second magnetic sensor by the magnetized element deactivates the motor rotating in the second direction.
The invention further provides, in an apparatus for operating a reciprocating member between predetermined first and second limits of travel, the reciprocating member being actuated by an arm and moving along a path of travel between the first and second limits of travel, a control device for arresting motion of the reciprocating member at predetermined limits of travel comprising: a magnetized element mounted in fixed relation to the arm; a motor-driven drive unit coupled to the arm; a circuit for selectively connecting the drive unit to a power source, the circuit comprising initial and terminal magnetic sensors disposed in relation to said magnetized element such that the magnetized element is in actuating proximity with the initial magnetic sensor when the reciprocating member is at its first limit of travel and is in actuating proximity with the terminal magnetic sensor when the reciprocating member is at its second limit of travel; whereby when the reciprocating member is at the first limit of travel and the control switch is opened, the reciprocating member moves to the second limit of travel, and when the control switch is closed the reciprocating member moves to the first limit of travel.
The invention further provides a method for controlling a reciprocating member moving toward a limit of travel, the reciprocating member being operatively coupled to a drive mechanism driven by a motor, the drive mechanism being provided with a magnetized element in fixed relation to a moving component of the drive mechanism, comprising the steps of: (a) closing a circuit supplying power to the motor to move the reciprocating member toward the limit of travel; (b) sensing the magnetized element when it reaches the limit of travel using a magnetic sensor; and (c) opening the circuit in response to sensing the magnetized element.
Brief Description of the Drawings In drawings which illustrate by way of example only a preferred embodiment of the invention, Figure 1 is a rear perspective view of a conventional school bus with a retractable stop sign mounted on its side;
Figure 2 is a perspective view of the retractable stop sign in the retracted position;
Field of Invention This invention relates generally to reciprocating or retractable devices.
In particular, this invention relates to a method and apparatus for limiting the motion of a retractable arm or sign such as those commonly used on a school bus.
Background of the Invention School buses and other forms of mass transportation pick up and discharge their passengers at designated points along a route. At these pick-up or drop-off points, the bus or other vehicle is frequently stopped in the road, which is shared by other motorists. It is therefore a concern that the driver, and other motorists on the road, be adverted to the presence of passengers entering or leaving the bus.
This is particularly true in the case of school buses, where the passengers are often young children who are not as cognizant of the rules of the road, or as observant, as their elders. A passenger, especially a young child, may exit the bus and pass immediately in front of the vehicle in order to cross the street. This practice gives rise to a twofold risk: first, that the driver of the bus cannot see the child in front of the vehicle, and second, that a motorist approaching from behind the bus as the child crosses the street will have too little reaction time to avoid a collision.
Safety devices designed to address these concerns are described in the prior art. One such device is a stop sign mounted on the side of a bus, for example as taught in U.S. Patent No. 4,916,372 issued April 10, 1990 to Reavell et al.
One side of the stop sign is fixed to a hinge attached to the mounting device. When not in use, the stop sign is in a retracted position generally parallel to the side of the vehicle.
When extended perpendicularly to the side of the bus, the stop sign is visible to oncoming motorists and motorists approaching the bus from behind on the side on which the sign is mounted.
Another type of safety device, such as is taught in U.S. Patent No.
4,559,518 issued December 17, 1985 to Latta, Jr., is a crossing arm or gate mounted on the front of a bus at approximately bumper height. The arm is hinged on the end closest to the roadside when the bus stops for pick-up or drop-off. When not in use, the arm lies generally parallel to the front of the bus. When deployed, the arm extends at a right angle to the front of the bus, effectively preventing a pedestrian on the side of the road from crossing in front of the bus over the length of the crossing arm.
In such devices the retractable member is hingedly mounted on the vehicle and undergoes an angular displacement by a drive member in communication with a motor, to move the retractable member between retracted and extended positions. It therefore becomes necessary to identify the retracted and extended positions for the purpose of controlling the motor, such that displacement of the unit stops once the unit has reached either terminal position. The solution of visually ascertaining the position of the unit and manually switching off the drive motor is unsatisfactory, and several automatic solutions have been devised that remove this task from the driver's responsibilities, allowing the driver to concentrate on other duties.
These solutions involve the use of a physical limiting device, such as a limit switch, to stop the apparatus once it has reached its fully extended or retracted position. Such physical limiting devices are triggered by lateral or rotational movement in the safety unit. For example, U.S. Patent No. 4,766,413 issued August 23, 1988 to Reavell, teaches a motor connected to a link arm which in turn is connected to the safety arm hinged to the housing mounted on the vehicle. The link arm moves forward and backward with respect to the side of the vehicle. The link arm is provided with an actuator pin which travels between two limit switches which are in a fixed position relative to the side of the vehicle. The limit switches are thus opened or closed as the link arm reaches its extreme positions, which correspond with the retracted and extended positions of the safety arm or stop sign.
Another example of a limiting device is described in U.S. Patent No.
5,357,239 issued October 18, 1994 to Lamparter, in which a peg extends radially outward from the rotating drive member which communicates with the safety unit.
When the drive member rotates past a predetermined point, the peg abuts the housing or other component of the safety apparatus, thus physically preventing the drive member from rotating any further.
Other examples of similar physical extension-limiting devices are taught in U.S. Patent Nos. 2,155,617 to Roan et al. and 4,916,372 to Reavell et al.
Because of their nature such limit switches, which utilize a physical means of limit detection, are subject to fatigue or other mechanical failure, blockage due to accumulation of debris and corrosion due to exposure to the elements.
It would therefore be advantageous to control the safety apparatus using limiting means that does not require physical contact between parts and is thus not vulnerable to environmental conditions.
Summary of the Invention The invention provides a method and apparatus for operating a reciprocating or retractable device between a fully retracted position and a fully extended position which addresses the problem of fatigue or mechanical failure in relation to the limiting device utilized to stop the motor once the arm has reaches its fully extended or fully retracted position.
The invention accomplishes this by providing a magnetized element such as a permanent magnet actuating a magnetic sensor positioned to detect when the retractable member has reached a predetermined limit in its path of travel. In a first preferred embodiment the magnet is mounted on a reciprocating drive mechanism transmitting the rotational motion of the motor to the retractable member. The motor and drive member are contained in a housing, with first and second magnetic sensors mounted in fixed positions relative to the housing such that the first magnetic sensor detects the proximity of the magnet at one limit of the reciprocating member's path of travel, for example a fully retracted position, and the second magnetic sensor detects the proximity of the magnet at the other limit of the reciprocating member's path of travel, for example a fully extended position. When the magnet is in proximity to either the first or second magnetic sensor, that magnetic sensor transmits an electrical signal to the control circuitry to connect the drive motor to a power source or disconnect the drive motor therefrom.
Thus, the invention provides a means for detecting the preset limits of motion of a reciprocating member driven by the motor, for example for extending and retracting a retractable arm, without requiring physical contact between components.
The invention may be used advantageously in a vehicle stop arm of the type typically used on school buses, which is mounted on the side of the vehicle. The invention may be used in other types of apparatus controlling the reciprocating movement of a gate, arm, sign or other device for example a parking gate, and is not limited to an apparatus for mounting on vehicles.
The invention thus provides an apparatus for moving a retractable member, comprising: a stationary housing, a drive mechanism comprising a motor affixed to the housing, for selectively driving the retractable member along a path of travel defined between a first limit and a second limit, a magnetized element disposed in fixed relation to a moving component of the drive mechanism, and a circuit for selectively connecting the motor to a power source for alternately activating the motor in a first direction and in a second direction opposite to the first direction, comprising a first magnetic sensor and a second magnetic sensor respectively disposed in fixed relation to the housing such that the magnetized element moves into actuating proximity with the first magnetic sensor when the retractable member reaches the first limit of travel, and the magnetized element moves into actuating proximity with the second magnetic sensor when the retractable member reaches the second limit of travel, whereby actuation of the first magnetic sensor by the magnetized element deactivates the motor rotating in the first direction and actuation of the second magnetic sensor by the magnetized element deactivates the motor rotating in the second direction.
The invention further provides, in an apparatus for operating a reciprocating member between predetermined first and second limits of travel, the reciprocating member being actuated by an arm and moving along a path of travel between the first and second limits of travel, a control device for arresting motion of the reciprocating member at predetermined limits of travel comprising: a magnetized element mounted in fixed relation to the arm; a motor-driven drive unit coupled to the arm; a circuit for selectively connecting the drive unit to a power source, the circuit comprising initial and terminal magnetic sensors disposed in relation to said magnetized element such that the magnetized element is in actuating proximity with the initial magnetic sensor when the reciprocating member is at its first limit of travel and is in actuating proximity with the terminal magnetic sensor when the reciprocating member is at its second limit of travel; whereby when the reciprocating member is at the first limit of travel and the control switch is opened, the reciprocating member moves to the second limit of travel, and when the control switch is closed the reciprocating member moves to the first limit of travel.
The invention further provides a method for controlling a reciprocating member moving toward a limit of travel, the reciprocating member being operatively coupled to a drive mechanism driven by a motor, the drive mechanism being provided with a magnetized element in fixed relation to a moving component of the drive mechanism, comprising the steps of: (a) closing a circuit supplying power to the motor to move the reciprocating member toward the limit of travel; (b) sensing the magnetized element when it reaches the limit of travel using a magnetic sensor; and (c) opening the circuit in response to sensing the magnetized element.
Brief Description of the Drawings In drawings which illustrate by way of example only a preferred embodiment of the invention, Figure 1 is a rear perspective view of a conventional school bus with a retractable stop sign mounted on its side;
Figure 2 is a perspective view of the retractable stop sign in the retracted position;
Figure 3 is a perspective view of the retractable stop sign in the extended position;
Figure 4 is an elevation of the drive unit; and Figure 5 is a schematic diagram of a relay circuit for controlling the motion of the stop sign; and Figure 6 is a schematic elevation of a circuit board showing one preferred positioning of the magnetic sensors.
Detailed Description of the Invention Referring to Figure 1, a conventional school bus safety apparatus comprises a stop sign 2 attached to a housing 3 mounted on the side of a bus 4, facing the passing lane or the centre of a two-way highway. Doors (not shown) for the ingress and egress of passengers are provided on the other side of the bus 4.
Figure 2 shows the stop sign 2 in a retracted position. The stop sign 2 is affixed to a bracket 5 which is pivotally mounted to housing 3 as by hinge pins 5a, 5b. The control circuitry, motor 7, and drive train are concealed within the housing 3.
In the embodiment shown the stop sign 2 is provided with lights 6 which may be operated in conjunction with the deployment of the sign 2 to the extended position shown in Figure 3.
As shown in Figure 4 by way of example, the drive train comprises a link arm 11 coupled at one end to the bracket 5 and coupled at the other end to a pin 10 mounted on orbital drive arm 9. Drive arm 9 is in turn coupled to the shaft of motor 7 via a gear train 8. This design is similar to that shown and described in U.S.
Patent No. 4,816,804 to Reavell. Any other suitable drive unit may be used in the apparatus of the invention.
In the preferred embodiment of the invention a magnetized element such as a permanent magnet 24 is provided in fixed relation to one of the moving parts. Reverse and forward magnetic sensors 68 and 70 are provided in fixed relation to the housing 3, such that when the stop sign 2 is in its retracted position magnet 24 is in proximity to the reverse magnetic sensor 68, and when stop sign 2 is in its fully extended position magnet 24 is in proximity to forward magnetic sensor 70.
Magnetic sensors 68 and 70 act in conjunction with an activating switch 60 (shown in Figure 5) to switch the control circuitry described below and thus selectively supply power to the motor 7. In the preferred embodiment the switch 60 is the same switch that operates the door of the bus, so that when the bus door is opened the motor 7 drives the stop sign 2 to the extended position, and when the bus door is closed the motor 7 drives the stop sign 2 to the retracted position. The positioning of the forward and reverse magnetic sensors 68, 70 operate to deactivate the motor 7 when the apparatus has reached the fully extended or fully retracted position.
The magnet 24 may be mounted on any moving component of the apparatus, with the reverse and forward magnetic sensors 68, 70 mounted in the path of travel of the moving component such that the magnet 24 activates the magnetic sensor 68 or 70 as the stop sign approaches the fully extended or fully retracted position, respectively. In the embodiment shown the magnet 24 is mounted on the link arm 1 l, however the magnet 24 may alternatively be mounted on the bracket 5 or on the stop sign 2, each of which moves along a defined path of travel as the safety apparatus is extended and retracted. In these embodiments the magnetic sensors and 70 remain fixed relation to the housing and are mounted at the appropriate position to function in the manner described above.
One preferred configuration for the control circuitry utilized in the invention is shown in Figure 5. The circuit comprises three dual pole relays, 30, 40, and 50, each respectively comprising a coil 32, 42, and 52 and a wiper 34, 44, and 54, with normally closed contacts 36, 46, and 56 (i.e. closed when the coil 32, 42 or 52 is quiescent) and normally open contacts 38, 48, and 58 (i.e. open when the coil 32, 42 or 52 is quiescent). The circuit also comprises normally closed magnetic sensors 68, 70, which open to break a circuit therethrough in the presence of a magnetic field.
Reverse magnetic sensor 68 is connected to one end of coil 32. The other end of coil 32 and the normally open wiper contact 38 of relay 30 are connected _7_ to a power supply, which in the preferred embodiment is the +12 volt DC power supply used to power all electrical components of the vehicle. Wiper 34 is connected to the normally closed contact 46 of relay 40. One end of coil 42 is grounded, and the other end of coil 42 is connected to the switch 60, in the embodiment shown, the vehicle door switch. Wiper 44 is connected to terminal 64 of motor 7.
One end of coil 52 is connected to the switch 60, and the other end of coil 52 is connected to the forward magnetic sensor 70. Wiper 54 is connected to terminal 66 of motor 7. Normally open contact 58 of relay 50 is connected to the power supply. Normally open contact 48 of relay 40 and normally closed contact of relay 50 are permanently grounded. The switch 60 in the CLOSED position is grounded (or at floating potential), and in the OPEN position passes 12 V to coils 42, 52, as described below.
Also shown is magnetized element 24, which moves with the drive mechanism as the sign 2 is extended and retracted due to its fixed relation to link arm 11, as described above. Motor 7 is coupled to the drive mechanism of the safety unit, such that when motor 7 is engaged in a forward direction, the sign 2 is extended, and when motor 7 is engaged in a reverse direction, the sign 2 is retracted.
Referring to Figure 6, in a preferred embodiment magnet 24 is embedded near the end of the link arm 11 which is coupled to pin 10 and orbital drive arm 9. Magnet 24 thus does not provide any physical impediment to the operation of the drive arm 9 or link arm 11. The control circuitry is mounted on a circuit board 28 which is in turn mounted to a wall of the housing 3 in the vicinity of the drive arm 9 (see Figure 4). Circuit board 28 is large enough to both support the required circuit components and to position the forward and reverse magnetic sensors 68, 70 such that the magnet 24 activates the magnetic sensor 68 or 70 as the stop sign approaches the fully extended or fully retracted position, respectively. The orbital path of the magnet 24 during extension and retraction of the stop sign is shown by the arrow in Figure 6.
The preferred embodiment of the control circuitry operates as follows:
_g_ Prior to initial activation of the door switch 60, the vehicle door is closed and the apparatus is in a ready state with the relay coils 32, 42, 52 in a quiescent state and wipers 34, 44, and 54 in their positions respectively against normally closed contacts 36, 46 and 56 (designated NC in Figure 5). The safety unit is at rest and the sign 2 is in the retracted position such that magnet 24 is in actuating proximity with reverse magnetic sensor 68. Thus, reverse magnetic sensor 68 applies ground potential to one end of coil 32. Thus, coil 32 is quiescent and wiper 34 is at floating potential. With door switch 60 is in its CLOSED (grounded) position and forward magnetic sensor 70 closed, both ends of coil 42 and of coil 52 are held at ground.
When door switch 60 is initially thrown to the OPEN position the vehicle door (not shown) starts opening.. Initially, magnet 24 is still in actuating proximity with reverse magnetic sensor 68, breaking the circuit to ground.
Wiper 34 therefore remains in the normally closed position. Door switch 60 applies 12 V
to one end of coils 42 and 52, the other ends of which are grounded so wipers 44 and 54 are switched to the normally open contacts 48 and 58, respectively. The power supply is thus connected via normally open contact 58 (through resistor 62) to terminal 66 of the motor 7, and the other motor terminal 64 is grounded through wiper 44 and normally open contact 48. The motor 7 rotates in the forward direction, driving the sign 2 to the extended position.
As the sign 2 moves to the extended position, the influence of magnet 24 is removed from the reverse magnetic sensor 68, thus grounding one end of coil 32. The other end of coil 32 is biased to 12 V so coil 32 becomes active and wiper 34 is switched to the normally open contact 38, thus connecting normally closed contact 46 through wiper 34 to the 12 volt power supply (at this point wiper 44 is still held against the normally open contact 48).
The motor 7 continues rotating and extending the sign 2 until the sign 2 reaches the fully extended position, at which point magnet 24 moves into actuating proximity with forward magnetic sensor 70, which opens to break the circuit to ground from the end of coil 52. Coil 52 goes quiescent and wiper 54 returns to the normally closed contact 56, thus connecting ground through the wiper 54 to motor terminal 66. Since coil 42 is active and motor terminal 64 is at ground potential through wiper 44, the motor 7 stops rotating and the sign 2 stops in the fully extended position shown in Figure 3.
Once the sign 2 has reached the extended position, as long as door switch 60 remains in the OPEN position the safety apparatus will remain in the extended position with the magnet 24 in proximity to the forward magnetic sensor 70.
When the door switch 60 is switched to the CLOSED position, the vehicle door starts closing and the 12 V supply is removed from coils 42 and 52 so wipers 44 and 54 return to the quiescent state against normally closed contacts 46 and 56, respectively. With wiper 34 still in the open position, the 12 V power source connected to normally open contact 38 is applied to motor terminal 64. Motor terminal 66 is grounded through normally closed contact 56. The motor 7 is thus engaged in a reverse direction and commences retraction of the sign 2. As the magnet 24 moves away from the forward magnetic sensor 70, the magnetic sensor 70 closes and ground is restored to the end of coil 52.
As the apparatus returns to the fully retracted position shown in Figure 2, magnet 24 moves back into proximity with reverse magnetic sensor 68.
Magnetic sensor 68 opens and the ground is removed from the end of coil 32, so coil 32 goes quiescent and switches wiper 34 back to normally closed contact 36. This disconnects the motor 7 from the 12 V power source at contact 38, and the motor 7 stops rotating to return the safety apparatus to the ready state with the control circuitry in its rest condition and all relay coils 32, 42, 52 in a quiescent state.
Although in the above description of the circuitry operation the circuit is controlled by the door switch 60, control over the safety apparatus may use a separate switch. Also, the preferred embodiment utilizes the vehicle 12 VDC
power supply to control the apparatus and associated circuitry, however a separate power supply could equally be used. As noted above, the invention may be used in association with other moving devices with a limited path of travel, such as parking gates and the like.
In another embodiment of the invention (not shown) a pair of magnetized elements 24 can be mounted in fixed relation to the housing 3, and magnetic sensors 68, 70 mounted in fixed relation to a moving part such as the link arm 11. The magnetic sensors 68, 70 would cooperate with control circuitry in the manner discussed above to produce the same result, however the wiring of components may be somewhat more involved because portions of the control circuitry would move with the apparatus in this embodiment.
Preferred embodiments of the invention having been thus described by way of example, modifications and adaptations will be apparent to those skilled in the art. The invention includes all such modifications and adaptations as fall within the scope of the appended claims.
Figure 4 is an elevation of the drive unit; and Figure 5 is a schematic diagram of a relay circuit for controlling the motion of the stop sign; and Figure 6 is a schematic elevation of a circuit board showing one preferred positioning of the magnetic sensors.
Detailed Description of the Invention Referring to Figure 1, a conventional school bus safety apparatus comprises a stop sign 2 attached to a housing 3 mounted on the side of a bus 4, facing the passing lane or the centre of a two-way highway. Doors (not shown) for the ingress and egress of passengers are provided on the other side of the bus 4.
Figure 2 shows the stop sign 2 in a retracted position. The stop sign 2 is affixed to a bracket 5 which is pivotally mounted to housing 3 as by hinge pins 5a, 5b. The control circuitry, motor 7, and drive train are concealed within the housing 3.
In the embodiment shown the stop sign 2 is provided with lights 6 which may be operated in conjunction with the deployment of the sign 2 to the extended position shown in Figure 3.
As shown in Figure 4 by way of example, the drive train comprises a link arm 11 coupled at one end to the bracket 5 and coupled at the other end to a pin 10 mounted on orbital drive arm 9. Drive arm 9 is in turn coupled to the shaft of motor 7 via a gear train 8. This design is similar to that shown and described in U.S.
Patent No. 4,816,804 to Reavell. Any other suitable drive unit may be used in the apparatus of the invention.
In the preferred embodiment of the invention a magnetized element such as a permanent magnet 24 is provided in fixed relation to one of the moving parts. Reverse and forward magnetic sensors 68 and 70 are provided in fixed relation to the housing 3, such that when the stop sign 2 is in its retracted position magnet 24 is in proximity to the reverse magnetic sensor 68, and when stop sign 2 is in its fully extended position magnet 24 is in proximity to forward magnetic sensor 70.
Magnetic sensors 68 and 70 act in conjunction with an activating switch 60 (shown in Figure 5) to switch the control circuitry described below and thus selectively supply power to the motor 7. In the preferred embodiment the switch 60 is the same switch that operates the door of the bus, so that when the bus door is opened the motor 7 drives the stop sign 2 to the extended position, and when the bus door is closed the motor 7 drives the stop sign 2 to the retracted position. The positioning of the forward and reverse magnetic sensors 68, 70 operate to deactivate the motor 7 when the apparatus has reached the fully extended or fully retracted position.
The magnet 24 may be mounted on any moving component of the apparatus, with the reverse and forward magnetic sensors 68, 70 mounted in the path of travel of the moving component such that the magnet 24 activates the magnetic sensor 68 or 70 as the stop sign approaches the fully extended or fully retracted position, respectively. In the embodiment shown the magnet 24 is mounted on the link arm 1 l, however the magnet 24 may alternatively be mounted on the bracket 5 or on the stop sign 2, each of which moves along a defined path of travel as the safety apparatus is extended and retracted. In these embodiments the magnetic sensors and 70 remain fixed relation to the housing and are mounted at the appropriate position to function in the manner described above.
One preferred configuration for the control circuitry utilized in the invention is shown in Figure 5. The circuit comprises three dual pole relays, 30, 40, and 50, each respectively comprising a coil 32, 42, and 52 and a wiper 34, 44, and 54, with normally closed contacts 36, 46, and 56 (i.e. closed when the coil 32, 42 or 52 is quiescent) and normally open contacts 38, 48, and 58 (i.e. open when the coil 32, 42 or 52 is quiescent). The circuit also comprises normally closed magnetic sensors 68, 70, which open to break a circuit therethrough in the presence of a magnetic field.
Reverse magnetic sensor 68 is connected to one end of coil 32. The other end of coil 32 and the normally open wiper contact 38 of relay 30 are connected _7_ to a power supply, which in the preferred embodiment is the +12 volt DC power supply used to power all electrical components of the vehicle. Wiper 34 is connected to the normally closed contact 46 of relay 40. One end of coil 42 is grounded, and the other end of coil 42 is connected to the switch 60, in the embodiment shown, the vehicle door switch. Wiper 44 is connected to terminal 64 of motor 7.
One end of coil 52 is connected to the switch 60, and the other end of coil 52 is connected to the forward magnetic sensor 70. Wiper 54 is connected to terminal 66 of motor 7. Normally open contact 58 of relay 50 is connected to the power supply. Normally open contact 48 of relay 40 and normally closed contact of relay 50 are permanently grounded. The switch 60 in the CLOSED position is grounded (or at floating potential), and in the OPEN position passes 12 V to coils 42, 52, as described below.
Also shown is magnetized element 24, which moves with the drive mechanism as the sign 2 is extended and retracted due to its fixed relation to link arm 11, as described above. Motor 7 is coupled to the drive mechanism of the safety unit, such that when motor 7 is engaged in a forward direction, the sign 2 is extended, and when motor 7 is engaged in a reverse direction, the sign 2 is retracted.
Referring to Figure 6, in a preferred embodiment magnet 24 is embedded near the end of the link arm 11 which is coupled to pin 10 and orbital drive arm 9. Magnet 24 thus does not provide any physical impediment to the operation of the drive arm 9 or link arm 11. The control circuitry is mounted on a circuit board 28 which is in turn mounted to a wall of the housing 3 in the vicinity of the drive arm 9 (see Figure 4). Circuit board 28 is large enough to both support the required circuit components and to position the forward and reverse magnetic sensors 68, 70 such that the magnet 24 activates the magnetic sensor 68 or 70 as the stop sign approaches the fully extended or fully retracted position, respectively. The orbital path of the magnet 24 during extension and retraction of the stop sign is shown by the arrow in Figure 6.
The preferred embodiment of the control circuitry operates as follows:
_g_ Prior to initial activation of the door switch 60, the vehicle door is closed and the apparatus is in a ready state with the relay coils 32, 42, 52 in a quiescent state and wipers 34, 44, and 54 in their positions respectively against normally closed contacts 36, 46 and 56 (designated NC in Figure 5). The safety unit is at rest and the sign 2 is in the retracted position such that magnet 24 is in actuating proximity with reverse magnetic sensor 68. Thus, reverse magnetic sensor 68 applies ground potential to one end of coil 32. Thus, coil 32 is quiescent and wiper 34 is at floating potential. With door switch 60 is in its CLOSED (grounded) position and forward magnetic sensor 70 closed, both ends of coil 42 and of coil 52 are held at ground.
When door switch 60 is initially thrown to the OPEN position the vehicle door (not shown) starts opening.. Initially, magnet 24 is still in actuating proximity with reverse magnetic sensor 68, breaking the circuit to ground.
Wiper 34 therefore remains in the normally closed position. Door switch 60 applies 12 V
to one end of coils 42 and 52, the other ends of which are grounded so wipers 44 and 54 are switched to the normally open contacts 48 and 58, respectively. The power supply is thus connected via normally open contact 58 (through resistor 62) to terminal 66 of the motor 7, and the other motor terminal 64 is grounded through wiper 44 and normally open contact 48. The motor 7 rotates in the forward direction, driving the sign 2 to the extended position.
As the sign 2 moves to the extended position, the influence of magnet 24 is removed from the reverse magnetic sensor 68, thus grounding one end of coil 32. The other end of coil 32 is biased to 12 V so coil 32 becomes active and wiper 34 is switched to the normally open contact 38, thus connecting normally closed contact 46 through wiper 34 to the 12 volt power supply (at this point wiper 44 is still held against the normally open contact 48).
The motor 7 continues rotating and extending the sign 2 until the sign 2 reaches the fully extended position, at which point magnet 24 moves into actuating proximity with forward magnetic sensor 70, which opens to break the circuit to ground from the end of coil 52. Coil 52 goes quiescent and wiper 54 returns to the normally closed contact 56, thus connecting ground through the wiper 54 to motor terminal 66. Since coil 42 is active and motor terminal 64 is at ground potential through wiper 44, the motor 7 stops rotating and the sign 2 stops in the fully extended position shown in Figure 3.
Once the sign 2 has reached the extended position, as long as door switch 60 remains in the OPEN position the safety apparatus will remain in the extended position with the magnet 24 in proximity to the forward magnetic sensor 70.
When the door switch 60 is switched to the CLOSED position, the vehicle door starts closing and the 12 V supply is removed from coils 42 and 52 so wipers 44 and 54 return to the quiescent state against normally closed contacts 46 and 56, respectively. With wiper 34 still in the open position, the 12 V power source connected to normally open contact 38 is applied to motor terminal 64. Motor terminal 66 is grounded through normally closed contact 56. The motor 7 is thus engaged in a reverse direction and commences retraction of the sign 2. As the magnet 24 moves away from the forward magnetic sensor 70, the magnetic sensor 70 closes and ground is restored to the end of coil 52.
As the apparatus returns to the fully retracted position shown in Figure 2, magnet 24 moves back into proximity with reverse magnetic sensor 68.
Magnetic sensor 68 opens and the ground is removed from the end of coil 32, so coil 32 goes quiescent and switches wiper 34 back to normally closed contact 36. This disconnects the motor 7 from the 12 V power source at contact 38, and the motor 7 stops rotating to return the safety apparatus to the ready state with the control circuitry in its rest condition and all relay coils 32, 42, 52 in a quiescent state.
Although in the above description of the circuitry operation the circuit is controlled by the door switch 60, control over the safety apparatus may use a separate switch. Also, the preferred embodiment utilizes the vehicle 12 VDC
power supply to control the apparatus and associated circuitry, however a separate power supply could equally be used. As noted above, the invention may be used in association with other moving devices with a limited path of travel, such as parking gates and the like.
In another embodiment of the invention (not shown) a pair of magnetized elements 24 can be mounted in fixed relation to the housing 3, and magnetic sensors 68, 70 mounted in fixed relation to a moving part such as the link arm 11. The magnetic sensors 68, 70 would cooperate with control circuitry in the manner discussed above to produce the same result, however the wiring of components may be somewhat more involved because portions of the control circuitry would move with the apparatus in this embodiment.
Preferred embodiments of the invention having been thus described by way of example, modifications and adaptations will be apparent to those skilled in the art. The invention includes all such modifications and adaptations as fall within the scope of the appended claims.
Claims (22)
- THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
An apparatus for moving a retractable member, comprising:
a stationary housing, a drive mechanism comprising a motor affixed to the housing, for selectively driving the retractable member along a path of travel defined between a first limit and a second limit, a magnetized element disposed in fixed relation to a moving component of the drive mechanism, and a circuit for selectively connecting the motor to a power source for alternately activating the motor in a first direction and in a second direction opposite to the first direction, comprising a first magnetic sensor and a second magnetic sensor respectively disposed in fixed relation to the housing such that the magnetized element moves into actuating proximity with the first magnetic sensor when the retractable member reaches the first limit of travel, and the magnetized element moves into actuating proximity with the second magnetic sensor when the retractable member reaches the second limit of travel, whereby actuation of the first magnetic sensor by the magnetized element deactivates the motor rotating in the first direction and actuation of the second magnetic sensor by the magnetized element deactivates the motor rotating in the second direction. - 2. The apparatus of claim 1 wherein the first limit of travel is an extended state of the retractable member and the second limit of travel is a retracted state of the retractable member.
- 3. The apparatus of claim 2 wherein the retractable member is a safety arm.
- 4. The apparatus of claim 1 wherein the retractable member is mounted on a side surface of a motor vehicle.
- 5. The apparatus of claim 1 wherein the drive mechanism is operatively coupled to the retractable member such that the retractable member is driven in the direction of the second limit of travel by the same motor that drives the retractable member in the direction of the first limit of travel.
- 6. The apparatus of claim 5 wherein the motor rotates in one direction when the retractable member is driven in the direction of the second limit of travel and in an opposite direction when the retractable member is driven in the direction of the first limit of travel.
- 7. The apparatus of claim 1 wherein the drive mechanism comprises a reciprocating link arm and the magnetized element is affixed to the link arm.
- 8. The apparatus of claim 1 wherein the first and second magnetic sensors are supported on a circuit board supporting the circuit mounted to the housing.
- 9. In an apparatus for operating a reciprocating member between predetermined first and second limits of travel, the reciprocating member being actuated by an arm and moving along a path of travel between the first and second limits of travel, a control device for arresting motion of the reciprocating member at predetermined limits of travel comprising:
a magnetized element mounted in fixed relation to the arm;
a motor-driven drive unit coupled to the arm;
a circuit for selectively connecting the drive unit to a power source, the circuit comprising initial and terminal magnetic sensors disposed in relation to said magnetized element such that the magnetized element is in actuating proximity with the initial magnetic sensor when the reciprocating member is at its first limit of travel and is in actuating proximity with the terminal magnetic sensor when the reciprocating member is at its second limit of travel;
whereby when the reciprocating member is at the first limit of travel and the control switch is opened, the reciprocating member moves to the second limit of travel, and when the control switch is closed the reciprocating member moves to the first limit of travel. - 10. The apparatus of claim 9 wherein the first limit of travel is an extended state of the reciprocating member and the second limit of travel is a retracted state of the reciprocating member.
- 11. The apparatus of claim 10 wherein the reciprocating member is a safety arm.
- 12. The apparatus of claim 9 wherein the reciprocating member is mounted on a side surface of a motor vehicle.
- 13. The apparatus of claim 9 wherein the drive unit is operatively coupled to the reciprocating member such that the reciprocating member is driven in the direction of the second limit of travel by the same motor that drives the reciprocating member in the direction of the first limit of travel.
- 14. The apparatus of claim 13 wherein the motor rotates in one direction when the reciprocating member is driven in the direction of the second limit of travel and in an opposite direction when the reciprocating member is driven in the direction of the first limit of travel.
- 15. The apparatus of claim 9 wherein the drive mechanism comprises a reciprocating link arm and the magnetized element is affixed to the link arm.
- 16. The apparatus of claim 9 wherein the first and second magnetic sensors are supported on a circuit board supporting the circuit mounted to the housing
- 17. A method for controlling a reciprocating member moving toward a limit of travel, the reciprocating member being operatively coupled to a drive mechanism driven by a motor, the drive mechanism being provided with a magnetized element in fixed relation to a moving component of the drive mechanism, comprising the steps of:
(a) closing a circuit supplying power to the motor to move the reciprocating member toward the limit of travel;
(b) sensing the magnetized element when it reaches the limit of travel using a magnetic sensor; and (c) opening the circuit in response to sensing the magnetized element. - 18. The method of claim 17 in which the reciprocating member moves between a first limit of travel and a second limit of travel.
- 19. The method of claim 18 wherein the reciprocating member is a safety arm.
- 20. The method of claim 17 wherein the reciprocating member is mounted on a side surface of a motor vehicle.
- 21. The method of claim 18 wherein the drive mechanism is operatively coupled to the reciprocating member such that the reciprocating member is driven in the direction of the second limit of travel by the same motor that drives the reciprocating member in the direction of the first limit of travel.
- 22. The apparatus of claim 21 wherein the motor rotates in one direction when the reciprocating member is driven in the direction of the second limit of travel and in an opposite direction when the reciprocating member is driven in the direction of the first limit of travel.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002282100A CA2282100A1 (en) | 1999-09-13 | 1999-09-13 | Method and apparatus for operating a retractable arm |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002282100A CA2282100A1 (en) | 1999-09-13 | 1999-09-13 | Method and apparatus for operating a retractable arm |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2282100A1 true CA2282100A1 (en) | 2001-03-13 |
Family
ID=4164118
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002282100A Abandoned CA2282100A1 (en) | 1999-09-13 | 1999-09-13 | Method and apparatus for operating a retractable arm |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2282100A1 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108583419A (en) * | 2018-01-17 | 2018-09-28 | 江苏高博智融科技有限公司 | Device for reminding opening of automobile door |
| WO2020010470A1 (en) * | 2018-07-13 | 2020-01-16 | Smartrend Supply Ltd. | School bus stop arm and drive unit therefor |
| CN110769950A (en) * | 2017-06-19 | 2020-02-07 | 株式会社牧田 | Fastening tool |
| US11554715B2 (en) | 2018-07-13 | 2023-01-17 | Smartrend Manufacturing Group (Smg), Inc. | School bus stop arm and drive unit therefor |
-
1999
- 1999-09-13 CA CA002282100A patent/CA2282100A1/en not_active Abandoned
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110769950A (en) * | 2017-06-19 | 2020-02-07 | 株式会社牧田 | Fastening tool |
| US11117185B2 (en) | 2017-06-19 | 2021-09-14 | Makita Corporation | Fastening tool |
| CN108583419A (en) * | 2018-01-17 | 2018-09-28 | 江苏高博智融科技有限公司 | Device for reminding opening of automobile door |
| WO2020010470A1 (en) * | 2018-07-13 | 2020-01-16 | Smartrend Supply Ltd. | School bus stop arm and drive unit therefor |
| US11554715B2 (en) | 2018-07-13 | 2023-01-17 | Smartrend Manufacturing Group (Smg), Inc. | School bus stop arm and drive unit therefor |
| US11820283B2 (en) | 2018-07-13 | 2023-11-21 | Smartrend Manufacturing Group (Smg), Inc. | School bus stop arm and drive unit therefor |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |