US3451029A - Thermostat and tip switch assembly - Google Patents

Description

June 17; 1969 LEvlNN ET AL 3,451,029

IX'HBRMOS'INI AND TIP SWITCH ASSEMBLY Filed 001:. 23, 1967 Sheet 01*2 JNVEN'TORS ROBERT N. LEVINN JOSEPH K. MOYER y MELVIN J. ROSE ATTORNEYS June 17, 1969 R. N. LEVINN ET AL 3,451,029

THERMOSTAT AND TIP SWITCH ASSEMBLY Filed Oct. 25, 1967 Sheet 2 of 2 FIG.4

FIGB

INVENTORS ROBERT N. LEVINN JOSEPH K. MOYER BY MELVIN J. ROSE ATTORNEYS United States Patent US. Cl. 337349 12 Claims ABSTRACT OF THE DISCLOSURE The thermostat and tip switch assembly comprises a bimetallic strip, a contact strip having a contact, and a spring strip with a contact for engaging the first contact. These strips are disposed collaterally, with the ends of the bimetallic strip and the spring strip projecting beyond the end of the contact strip. An insulation push rod is disposed between the projecting ends, so that the bimetallic strip controls the opening or closing of the contacts in response to temperature change. The switch is used in an appliance, typically a space heater, and if the appliance falls over from its normal position, a pendulum swings to a different position, which opens the contacts as a safety feature. In the present improvement the pendulum has a cam which is pivoted at a point approximately in alignment with the push rod, and the latter has a cam follower pin which projects through the bimetallic strip to the cam, so that the pendulum works directly on the same push rod that is operated by the metallic strip, but its operation is independent of the action of the bimetallic strip. This arrangement is compact in structure as well as effective in operation.

Background of the invention It is already known to provide a thermostat having a bimetallic strip, and collateral contact strips with contacts the engagement or disengagement of which is controlled by the bimetallic strip. For this purpose the bimetallic strip moves an insulation member which is operatively connected to one of the contact strips. For safety, when used on an appliance such as a space heater, it is also known to provide a so-called tip switch, operated by a pendulum which on swinging to abnormal position opens the electrical circuit to the heater. It has been suggested to combine the two switches, but the addition of the tip switch to the thermostat has substantially increased the size and complexity of the structure.

Summary of the invention Our improved thermostat and tip switch assembly again uses a bimetallic strip, contact strips, and an insulation member operatively connecting the bimetallic strip to one of the contact strips, but the insulating member'has a cam follower, and the pendulum has a cam for operating the cam follower and thereby moving the insulation memberto open the contacts when the pendulum is displaced from its normal position. In preferred form the ends of the bimetallic strip and one contact strip project beyond the end of the other contact strip, and the insulation member is a push rod disposed between the projecting ends. The pendulum cam is pivoted at a point approximately in alignment with the push rod, and the cam follower is simply a pin projecting from the push rod through the bimetallic strip to the cam for actuation thereby. A base plate may be provided on which the bimetallic strip and contact strips are fixedly secured at one end, and the pendulum is pivotally mounted on the other end of the base plate. The cam follower pin passes ice through the base plate to the cam. In preferred form an additional mounting plate is disposed above the collateral strips, and has an externally threaded mounting bushing fixed thereon. A threaded control shaft passes through the bushing and bears against one of the contact strips. This varies the position of the contact strip in order to provide for adjustment of the temperature at which the thermostat operates the switch contacts. The assembly may be designed for mounting in different positions, as on a horizontal appliance wall, or a vertical appliance wall, with no change in the parts of the assembly other than the pendulum arm.

The foregoing and additional features are described in the following detailed specification, which is accompanied by drawings in which:

FIG. 1 is an end elevation of a thermostat and tip switch assembly embodying features of the invention;

FIG. 2 is a plan view thereof;

FIG. 3 is a side elevation thereof;

FIG. 4 is a side elevation showing a variant form of the assembly;

FIG. 5 is an elevation drawn to enlarged scale showing the insulating push rod;

FIG. 6 is a bottom view thereof; and

FIG. 7 is a plan view of a spring contact strip forming a part of the thermostat.

Referring to the drawing, and more particularly to FIGS. 1, 2 and 3, the device comprises a bimetallic strip 12, a contact strip 14 having a contact 16, and a spring strip 18 having a second contact 20 for engaging the contact 16 when the switch is closed. The strips 12, 14 and 18 are all disposed collaterally, with the free end parts of the bimetallic strip 12 and the spring strip 18 projecting beyond the end of the contact strip 14.

A push rod 22 made of insulating material is disposed between the said projecting ends so that upward movement of the bimetal 12 moves the spring contact 18 upward and so separates the contacts 16 and 20 to open the circuit being controlled thereby.

The assembly further comprises a pendulum 24 which is pivoted, as by means of an appropriately shouldered rivet 26, at a point which is substantially in alignment with the push rod 22. A weight 28 is fixed on the lower end of the pendulum, and the upper end of the pendulum is shaped as shown at 30 (FIG. 1) to provide a cam which moves with the pendulum. The pusher 22 has a cam follower pin 32 projecting downward through a hole in the bimetal 12 to the cam 30 for actuation thereby. The switch assembly may be used in an appliance such as a space heater, and if the heater is tipped over or falls from its normal position, the pendulum 24 swings to a different position, causing the cam 30 to move the push rod 22, and so to open the contacts 16, 20 for safety. Thus, the same push rod and contacts are moved for either purpose, but the operation of the safety switch is althogether independent of the action of the bimetallic strip 12, and the latter need not move when the pusher is moved by the pendulum.

In the illustrated structure there is a base plate 34, and the collateral strips 12, 14 and 18 are fixedly secured to the base plate with insulating spacers 36, 38 and 40 therebetween. The pendulum 24- is pivotally mounted on a small angle piece or bracket 42 which is fixedly secured to the base plate 34, as by means of spot welding. In such case the cam follower pin 32 of the push rod 22 passes through the base plate 34 and bracket 42, as well as the bimetal 12, in order to reach the cam 30.

The complete structure further includes a mounting plate 44 which is above the collateral strips, and is held in fixed position by the same rivet or eyelet 46 which holds the strips on the base 34. A control shaft 48 passes through the mounting plate 44 and through the spring strip 18, so that its rounded lower end 50 bears against Y the contact strip 14. The part 50* is preferably made of insulating material. The control shaft 48 may receive a control knob, not shown, the knob having a hole to receive shaft 48, and having a recess to receive a spring key 52, which helps hold the knob on the shaft as well as insuring rotation of the shaft with the knob. If desired the upper end of the shaft may be provided with a slot 54 for a screw driver adjustment where that is preferred.

The mounting plate 44 preferably has an externally threaded mounting bushing 56 permanently fixed thereon. This bushing is designed to pass through a hole in the appliance wall and to be secured in position by means of a nut (not shown) received over the bushing. The bushing is internally threaded to mate with an external thread on the control shaft 48. A bit of the latter thread is visible at 58 in FIGS. 1 and 2. It will be understood that rotation of shaft 48 then varies the position of the contact strip 14, thus providing for adjustment of the temperature at which the thermostat contacts are opened or closed.

A part 51 on the bushing may be provided to act as a stop which limits the rotation of the shaft 48 to less than one full rotation. Stop 51 is engaged by the lower end of spring key 52. The threaded bushing 56 may be provided with one or more flats, not shown, to be received in a mating non-circular hole, in order to prevent rotation of the thermostat when mounted.

The stacked assembly of strips shown in FIGS. 1, 2 and 3 also includes terminals 60 and 62, the terminal 60 engaging and forming an extension of the spring strip 18, and the terminal 62 engaging and forming an extension of the contact strip 14. The terminal strips may be angularly related as is best shown in FIG. 2. Appropriate circuit wires may be connected to the terminals, as by soldering, but in the present case the terminals have threaded holes 64 and 66 to receive screws around which the ends of the wires are bent and clamped.

The pusher 22 is preferably made of a heat resistant insulating material such as ceramic. It is shown to greatly enlarged scale in FIGS. and 6, including the cam follower pin 32 which is formed integrally with and projects downwardly from the body 22 of the pusher. At the lower end of body 22 there are diametrical projections 70 which project at each side of the pin 32 and which bear against the bimetallic strip 12. The bimetal 12 may be recessed somewhat, as shown at 72 in FIG. 3, to receive the parts 70 of the pusher.

The upper end of the pusher 22 carries a projection or neck 74 best shown in FIGS. 2, 3 and 5, and also shown in broken lines in FIG. 6. The spring strip 18 has a hole 76 cut therethrough to receive the projection 74. This hole is preferably rectangular rather than square, it being elongated somewhat as shown in FIG. 2 in order to accommodate angularity of the spring strip 18 as it is moved. The spring strip 18 may be channeled transversely at each side of the hole 76, as shown at 78, and the depressions 78 rest on the top of the body 22, that is on the shoulder formed around the neck 74. The neck 74 and the cam follower pin 32 are preferably molded integrally with the body 22.

The configuration of the spring strip 18 is shown in FIG. 7. The hole 80 receives the assembly eyelet (46 in FIGS. 2 and 3). The rectangular hole 76 receives the square projection 74 (FIG. 5) at the upper end of the pusher, and the channels 78 are located at the sides of the hole 76. The movable contact 20 is shown in broken lines, it being beneath the strip. The hole 82 serves for passage of the pin 50 of the control shaft 48- (see FIG. 3) and the hole is preferably elongated somewhat as shown in order to accommodate movement and angularity of the spring strip.

It will be seen that the structural arrangement shown is compact and simple in structure, as well as effective in operation. Another advantage is that the switch assembly may be mounted in different positions with substantially no change in the parts of the assembly other than the pendulum arm 24. In FIGS. 1-3 it is assumed that the switch is to be mounted on a horizontal appliance wall. A modified structure which is designed to be mounted on a vertical appliance wall is shown in FIG. 4. The identity of substantially all of the parts will be evident from inspection of the drawing. Only two changes are needed. One is that the bracket 42 is turned or oriented away from the position shown in FIG. 3 when securing the bracket to the base plate 34. The other change is in the shape of the pendulum arm 84, the cam 86 of which is located at the side instead of at the top of the pendulum arm. Here again the pivot axis 88 is preferably disposed in alignment with the axis of the pusher 22 and its cam follower pin 32. It will be evident that displacement of the pendulum to either side, as suggested by the arrows 90, will cause cam 86 to move the pusher 22 in proper direction to open the contacts 16 and 20 of the switch. Here again the movement is independent of the position of the bimetallic element 12, because the cam follower pin 32 is freely movable through the hole in the element 12.

The assembly may be mounted in a different position on a vertical appliance wall. This has not been illustrated, but with reference to FIG. 4 the threaded bushing 56 may be secured to a vertical appliance wall with the collateral strips 12, 14 and 18 in horizontal rather than vertical position. The same pendulum 84 is employed, but the bracket 42 is secured to the base plate 34 in a position turned 90 from that shown in FIG. 4. The bracket then takes the same position that is shown in FIG. 3, while using a pendulum arm like that shown at 84 in FIG. 4. The pendulum normally hangs downward, and if displaced by falling over of the appliance, the switch contacts are opened.

It is believed that the construction and operation of our improved thermostat and tip switch assembly, as well as the advantages thereof, will be apparent from the foregoing detailed description. It will also be apparent that while we have shown and described the structure in preferred forms, changes may be made without departing from the scope of the invention, as sought to be defined in the following claims.

We claim:

1. A thermostat and tip switch assembly comprising a bimetallic strip, a first contact strip having .a contact, a second contact strip having a contact for engaging the first contact, said strips being generally collateral, an insulating member operatively connecting the bimetallic strip to one of the contact strips for opening or closing the contacts, said insulating member having a cam follower, .and a pendulum having a cam for operating on said cam follower and thereby moving the insulating member to open the contacts when the pendulum is displaced from its normal position.

2. A thermostat and tip switch assembly as defined in claim 1, in which the ends of the bimetallic strip and one contact strip project beyond the end of the other contact strip, and in which the insulating member is a push rod disposed between the said projecting ends, and in which the pendulum cam is pivoted at a point approximately in alignment with the push rod, and in which the cam follower is a pin projecting from the push rod through the bimetallic strip to the cam for actuation thereby.

3. A thermostat and tip switch assembly as defined in claim 2, in which there is a base plate, and in which said collateral strips at one end are fixedly secured with insulating spacers therebetween to one end of the base plate, and in which the pendulum is pivotally mounted on the other end of the base plate, and in which the cam follower pin of the push rod passes through the latter end of the base plate to the cam.

4. A thermostat and tip switch assembly as defined in claim 3, in which there is a mounting plate above the collateral strips, and a control shaft passing through said mounting plate and one contact strip to bear against the other contact strip, said control shaft being threaded and thereby usable to vary the position of the second contact strip in order to adjust the temperature at which the bimetallic strip operates the switch contacts.

5. A thermostat and tip switch assembly as defined in claim 4, in which the mounting plate has an externally threaded mounting bushing fixed thereon, and in which the bushing is internally threaded to mate with the threaded control shaft.

6. A thermostat and tip switch assembly as defined in claim 1, in which the collateral strips are disposed in generally horizontal position, and in which the pendulum normally hangs approximately perpendicularly to the collateral strips and beneath the push rod.

7. A thermostat and tip switch assembly as defined in claim 1, in which the collateral strips are disposed in generally vertical position, and in which the pendulum normally hangs in the same direction as the collateral strips.

8. A thermostat and tip switch assembly as defined in claim 5, in which the collateral strips are disposed in generally horizontal position, and in which the pendulum normally hangs approxiamtely perpendicularly to the collateral strips, and beneath the push rod, and in which the mounting bushing is disposed vertically for mounting the assembly on a horizontal wall.

9. A thermostat and tip switch assembly as defined in claim 5, in which the collateral strips are dispose-d in generally vertical position, and in which the pendulum normally hangs approximately perpendicular to the colstrips, and in which the externally threaded mounting bushing is disposed in horizontal position for mounting the assembly on a vertical wall.

10. A thermostat and tip switch assembly as defined in claim 1, in which there is a base plate, and in which said collateral strips at one end are fixedly secured with insulating spacers therebetween to one end of the base plate, and in which the pendulum is pivotally mounted on the other end of the base plate.

11. A the-remostat and tip switch assembly as defined in claim 1, in which there is a mounting plate above the collateral strips, and a control shaft passing through said mounting plate to bear against one of the contact strips, said control shaft being threaded and thereby usable to vary the position of the said contact strip in order to provide for adjustment of the temperature at which the bimetallic strip operates the switch contacts.

12. A thermostat and tip switch assembly as defined in claim 11, in which the mounting plate has an externally threaded mounting bushing fixed thereon, and in which the bushing is internally threaded to mate with the threaded control shaft.

References Cited UNITED STATES PATENTS 3,175,059 3/1965 Chesnut 200-61.52 3,201,548 8/1965 Mertler 337-355 3,271,546 9/1966 Chesnut 20061.52

BERNARD A. GILHEANY, Primmy Examiner. R. L. COHRS, Assistant Examiner.

US. Cl. X.R.

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