US1949689A - Relay system - Google Patents

Description

March 9, 1934. A. H. LAMB 1,949,689

RELAY SYSTEM Filed May 7, 1932 (LA ,go wg Fatentecl Mar. 6, 1934 UNITED STATES PATENT oFFicE RELAY SYSTEM Application May '7, 1932, Serial No. 609,911

9 Claims.

This invention relates to relay systems and particularly to a system adapted to control the closing and opening of an electric circuit in accordance with the intensity of stimuli which are g'subject to minor fluctuations that, if not compensated for, would cause chattering of the closure means for the circuit which is to be controlled.

In the application of relay systems for coniotrolling the closing of electric circuits to service wherein the intensity of the stimulus is subject to minor fluctuations, such as where a relay circuit is employed to energize a light source in accordance with the intensity of illumination at lt' a predetermined point, certain difficulties have been encountered.

An object of the present invention is the provision of a relay system, responsive to a stimulus of predetermined intensity to energize an eleczfltric circuit, which system is effective to energize the circuit only when the intensity of the stimulus obtains a predetermined value for a predetermined period of time. Another object of the invention is the provision of a relay sys- Zii-tem for energizing a source of light, such as that employed for flood lighting, advertising signboards or similar uses, wherein the light source is energized when the intensity of illumination at a predetermined point decreases to a predetermined value and for deenergizing the source when the intensity increases to the same, or another, predetermined value, which system is er"- iective to energize or deenergize the source only when the critical value of illumination is main tained for a predetermined period of time.

Another object of the invention is to provide a simple and reliable relay system of the stated type which is sensitive to relatively slight variations in the actuating stimulus but which operates 49 to close the main circuit only when the intensity or" the stimulus remains below a predetermined value for a predetermined proportion of a predetermined period of time.

These and other objects of the invention will appear from the following description taken with the accompanying drawing, wherein:

Fig. 1 illustrates diagrammatically a relay system embodying the invention, and

Fig. 2 is a fragmentary view showing a modi- 59 fication.

A light-sensitive element 1, such as a photoelectric cell, is disposed at the point at which the illumination or light intensity is to control the operation of the relay system. The cell 1 is connected to the moving coil 2 of a sensitive relay 3 having a contact arm 4 movable between two contacts 5, 6. The contact arm 4 of relay 3 is biased towards the contact 5 and will be held away from that contact only so long as the current from the cell 1 exceeds a predetermined 4 value, and will he moved into engagement with contact 6 only when the current output reaches a somewhat higher and predetermined value. Contacts 5, 6 are connected to the relay terminals 7, 8, respectively, and the contact arm 4 is connected to a terminal 9.

The relay 3 is connected to a thermal interlocking relay 10 which closes and opens a circuit including a pair of conductors ll, 12 to which a load or power relay 13 is connected.

The interlocking relay 10 has a pair of cooperating main contacts 14, 15 constituting a main switch 16, one contact 15 being connected to the power relay conductor 11 and the other contact 14 being carried by and electrically connected to 7 the bimetallic strip 17, that is, in turn, connected to the relay terminal 9.-

The arm 17 also carries an auxiliary contact 18 electrically connected thereto and disposed for engagement with a stationary contact 19 to form an auxiliary switch 20. At normal temperature, the bimetallic strip 1'? is so positioned that both sets of contacts controlled thereby are open, and the contacts i l, 18 are so arranged that the auxiliary switch 26 closes before the main switch 16 when the bimetallic strip 1'7 is deflected by an increase in temperature.

The stationary contact 19 of the auxiliary switch 20 is connected to a second thermally-responsive contact strip 21 that, at normal temperatures, holds its contact 22 in engagement with a cooperating stationary contact 23. These contacts form a second auxiliary or thermally controlled switch 2 or" which the stationary contact 23 is connected to the terminal '7 of relay 3.

A heater coil 25 for bimetallic strip 17 is connected between the terminals 7 and 9 of relay 3 through a source of current, such as a battery 26, and a heater coil 27 for bimetallic strip 21 is similarly connected, through battery 26, between terminals 8 and 9 of relay 3.

A separate source of current may be provided for energizing the power relay 13 upon the closing of the main switch 16 but, as illustrated, the battery 26 is employed to actuate the relay 13 by connecting the lead 12 or" the power relay to the lead extending from source 26 to the heater coils.

As shown in the fragmentary view, Fig. 2, which represents an alternative form of that portion of the Fig. 1 circuit which lies to the right of the broken line, the power relay 13 may be omitted when the load, shown as a bank of lights 28, is of such magnitude that it may be operated directly from the current source 26.

The operation of the system is as follows:

It the intensity of the light falling upon the cell 1 is between predetermined critical values, the several switches will assume the positions shown in Fig. 1. When the intensity of illumination decreases below the lower critical value, the current through the circuit which includes the cell 1 and moving coil 2 decreases to such a value that the arm 4 rotates into engagement with the contact 5, thus completing a circuit through the battery 26 and the heating coil 25.

If the intensity of illumination remains below the lower critical value for a predetermined period of time, the arm 17 is heated and deflected by the current flow through coil 25 to bring the contact 18 into engagement with the contact 19. A circuit in parallel with the contacts 4, 5 is thereby completed through battery 26 and heater coil 25 by the arm 17, the auxiliary switch 20, the second arm 21 and second auxiliary switch 24. This circuit serves as a holding circuit for the heater coil 25 for the reason that, even if the illumination increases to a value above the lower critical value and the relay contacts 4 and 5 are opened, the coil 25 will be energized.

As the current flow through the coil 25 continues to heat the arm 17, the latter is still further deflected until the contacts 14 and 15 are brought into engagement to close the main circuit connecting the conductors 11 and 12, thus energizing the load line that is controlled by the power relay 13.

This condition obtains until the illumination at cell 1 increases to such magnitude that the contact arm 4 of the sensitive relay 3 is moved into and held in engagement with contact 6 for such a period that current flow through the heater coil 2'7 deflects the bimetallic strip 21 to open contacts 22, 23 of the auxiliary switch 24 of the holding circuit. This interruption of current flow through coil 25 and the consequent cooling of the bimetallic strip 17, separates the contacts 14 and 15, thus deenergizing the load relay 13 to open the load circuit.

As will be apparent from the foregoing, although the light-sensitive element 1 is so aiiected by shadows and other variations in the illumination falling thereon, as to actuate the relay 3, the interlocking relay 10 is not active to close the main switch 16 until the relay 3 has been closed a surficient proportion of a predetermined period for the heating coil 25 to heat the arm 1'? to effect movement of the contact 18 into engagement with the contact 19. If, after this auxiliary switch 20 is closed, the illumination increases above the critical value, the switch 20 will not be opened since the holding circuit through the second thermal switch 24 does not include the relay 3. Similarly, the power relay 13 will not be opened when the light intensity increases to bring contact arm 4 into momentary engagement with contact 6, but remains closed until current flow through heater coil 27 persists for such time as to open the auxiliary switch 24.

It should be obvious that the relay system herein disclosed is capable of other applications than the one disclosed. The light sensitive element may be replaced by any element which is responsive to a variable stimulus which it is de-- sired to have control the closing and opening of a circuit, such as temperature, humidity 01 other analogous variable stimuli. A sensitive relay and an interlocking delay relay of the described type may therefore be used to prevent chattering in systems in which a load circuit is controlled by other factors which may be subject to short period fluctuations.

I claim:

1. The combination with a load circuit and a relatively sensitive control relay, of relay means for energizing said load circuit only when said control relay is closed for a predetermined period of time, said means comprising a thermally-responsive main switch in said load circuit, actuating means for said switch including said control relay and a heating coil, means independent of said control relay for maintaining the energization of said heating coil, and means including said control relay for rendering inoperative said maintaining means.

2. In a relay system, the combination with a sensitive relay actuated by changes in the magnitude of a variable quantity, and a load circuit to be controlled from said sensitive relay, of an interlocking relay interposed between said sensitive relay and load circuit, said interlocking relay including a main switch for controlling said load circuit, a heat-responsive actuating means for said main switch, a circuit controlled by said sensitive relay and including a coil for heating said actu ating means, means operative upon the flow of current through said coil for a predetermined period to close a holding circuit through said coil independently of said sensitive relay, heat-responsive means for opening said holding circuit, and a second circuit controlled by said sensitive relay and including a coil for actuating said second heat-responsive means.

3. The combination with a load circuit and a relatively sensitive control relay, of relay means for energizing said load circuit only when said control relay is closed for a predetermined period of time, said means comprising a main switch for closing said load circuit, an actuating coil for said main switch, a circuit including said coil and said control relay, a holding circuit for said coil, a holding switch operable to closed position by the actuating coil of said main switch, the contacts of said holding switch being in said holding circuit and adapted to engage prior to the closing of said main switch, an auxiliary switch in said holding circuit, an actuating coil for said auxiliary switch, and a circuit including said second actuating coil and said control relay.

4. In a relay system, the combination with means for alternatively closing one of two circuits, of a relay having two main circuits controlled by said means, each of said circuits including a source of current and the heating coil of a thermally responsive switch actuator, a main switch and an auxiliary switch controlled by the first of said actuators, a second auxiliary switch controlled by said second actuator, and a holding circuit including said auxiliary switches in series for supplying current to the heating coil of said first actuator independently of said circuit closing means.

5. The combination with a relay including a contact arm movable between two contacts, a circuit between the contact arm and each contact,

a source of current and a heating coil in each 1 of said circuits, a heat-responsive strip positioned adjacent each heating coil to receive heat energy from the respective coils, the first of said strips carrying a pair of contacts, a holding circuit for supplying current to the heating coil of said first strip, said holding circuit including a stationary contact cooperating with one of said strip contacts, and switch means controlled by said second strip for opening said holding circuit when current is supplied to said second heating coil for a predetermined period.

6. In a relay system for controlling the energization of an electric circuit, the combination with a load circuit, and a two position relay for alternatively closing one of two circuits, of heating coils and a source of current in each of said circuits, a thermally responsive main switch actuated by one of said coils, and means for closing a holding circuit to supply current to the heating coil of said main switch, said means including auxiliary switches serially connected in said holding circuit and actuated by the respective heating coils, the auxiliary switch actuated by the heating coil of said main switch being open at normal temperatures and the second auxiliary switch being closed at normal temperatures, whereby the energization for a predetermined period of the relay circuit including the heating coil of said main switch efiects the closing of the auxiliary switch associated therewith and thereby completes the holding circuit.

'7. The invention as set forth in claim 6, wherein the contacts of the main switch and the auxiliary switch associated therewith are positioned to effect closure of said main switch subsequent to the closure of its associated auxiliary switch.

8. In a relay system for controlling a load circuit in response to variations in light intensity, a light-sensitive device, a sensitive relay included in circuit with said device and having a contact arm movable into engagement alternatively with one of two contacts when the light intensity reaches predetermined higher and lower values, circuits including a source of current and a heating coil connected between the contact arm and the respective contacts, a heat-responsive strip adjacent the first of said coils and carrying the movable contacts of a main switch and of an' auxiliary switch, a stationary contact cooperating with the movable contact of said auxiliary switch for closing a holding circuit through the said first coil independently of said relay contacts after current flow through the said first coil heats said strip to a predetermined temperature, a heat-responsive strip adjacent the second of said heating coils, and a switch in said holding circuit and controlled by said second heat-responsive strip, said last switch being normally closed and being actuated to open position by the flow of current through said second heating coil.

9. The invention as set forth in claim 8 wherein the stationary contact of said main switch is positioned to be engaged by its movable contact only after the said strip is heated to a higher temperature than that effective to close said holding circuit.

ANTHONY H. LAMB.

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