US3283097A - Thermo-electric timer - Google Patents

Description

M. R. KOEPPEL ETAL THERMO-ELECTRIG TIMER Nov. 1, 1966 Filed June 6, 1962 FIG. 1

FIG 2 I I l /9 i [B [0 v A w a FIG.

Inventors:

Merle R. Koeppel Ludwig E. Dobrovolny their Ar'rorney United States Patent 3,283,097 THERMO-ELECTRIC TIMER Merle R. Koeppel and Ludwig E. Dobrovolny, Roanoke, Va., assignors to Graham-White Sales Corporation, Salem, Va, a corporation of Virginia Filed June 6, 1962, Ser. No. 200,462 4 Claims. (Q1. 20(l122) This invention relates to electric timers and has for its primary object the provision of a thermo-electric timer for controlling the cyclic operation of an electrical device.

In controlling the cyclic operation of an electrical device, it has heretofore been the practice to employ as the timer for the devices on and off cycles a cam operated by an electric motor. Such timers not only are expensive but are very diflicult to render shock-proof and thus are subject to frequent breakdowns in installations, such as on diesel locomotives, in which they are subjected in service to rather severe shocks. Consequently, in such inst-allations resort has ordinarily been had to something other than an electric timer for controlling the operation of a device required to be cyclically operated. Thus, for lack of an electric timer of ample ruggedness and reasonable cost, automatic drain valves for periodically draining accumulated moisture from a compressed air reservoir in an air line of a diesel locomotive heretofore have been operated pneumatically rather than electrically, using as the control the difierence in the pressure in the unloader line of the air compressor in its pumping and idling cycles.

An object of the present invention is to provide an improved timer for controlling the cyclic operation of an electrical device which is both less expensive and more rugged than timers heretofore employed for the purpose.

Another object of the invention is to provide an improved thermo-electric timer whereby a thermal switch and heater are so arranged and constructed as to enable the on and off cycles of an electrical device to be controlled automatically.

An additional object of the invention is to provide a thermo-electric timer for controlling the cyclic operation of a self-inductive electrical device wherein a thermal timer and heater are so connected to each other and to the device as to eliminate arcing at the switch.

Other objects and advantages will appear herein-after in the detailed description, be particularly pointed out in the appended claims and be illustrated in the accompanying drawings, in which: 7

FIGURE 1 is a front elevational view of a preferred embodiment of the thermo-electric switch of the present invention with the cover plate of its housing removed to more clearly illustrate certain of its detail-s of construction;

FIGURE 2 is a horizontal sectional view taken along lines 2-2 of FIGURE 1; I

FIGURE 3 is a vertical sectional view taken along lines 3-3 of FIGURE 1;

FIGURE 4 is a fragmentary vertical sectional view taken along the lines 44 of FIGUREv 1; and

FIGURE 5 is a wiring diagram of the timer of the preceding figures connected to an electrical load for automatic cyclic operation of the latter.

Referring now in detail to the drawings in which like reference characters designate like parts, the improved thermoelectric timer of the present invention is particularly designed for controlling the cyclic operation of electrical devices which, in service, are required to operate under severe conditions over extended periods of some latitude permissible in the nicety of the control. As typical of such applications, the timer may be used to enable an automatic drain valve, such as disclosed in Frantz application, Serial No. 160,866, filed on December 20, 1961, to be actuated by a solenoid, rather than pneumatically, for automatically draining at intervals the moisture accumulating in a compressed air reservoir in an air line of a diesel locomotive.

As will ordinarily be desirable, the illustrated thermoelectric timer, designated as 1, is provided with a housing or casing 2 having a removable cover plate 3- and adapted for removable attachment to a base 4, which, suitably, may be the housing of a solenoid-actuated valve or other electrical device, the cyclic operation of which the timer is to control. Mounted in the housing 2, conveniently on a mounting plate or board 5 of insulating material screwed or otherwise removably attached to the housing, are the main elements of the timer, a thermal switch 6 and a heater 7. Of these elements, the switch 6 normally is closed and it and the heater 7 are connected in series and so arranged within the housing 2 that the heater when energized directs heat upon a bimetallic or thermally responsive element 8 of the switch and, by flexing tor bending of that element, causes the switch to open and the heater consequently to be deenergized. Conversely, relieved of the heat from the heater, the bimetallic element 8 will cool and ultimately flex or bend back to initial position, causing the switch to close and the cycle to repeat itself. It is this interaction of the switch and heater that, through the cyclic opening and closing of the switch, is employed for controlling the cyclic operation of the solenoid or other electrical device to which the timer is applied.

Although the bimetallic element 8 might serve as the switch element of the thermal switch 6, this is not true of the switch of the illustrated embodiment. Instead, in the preferred switch, the bimetallic element does not itself form part of the electrical circuit but, rather, actuates a separate switch element 9. The prefenred thermal switch is comprised of a generally cylindrical body or block 10 of molded plastic or other suitable insulating material, to one end of which the bimetallic element 8 in the form of ,a diaphragm is attached by an open-ended sleeve or collar 11 with the axial spacing between the body and the diaphragm such that the latter is free to flex or bend under the influence of the heater 7 without contacting the body or any part fixed thereto other than the sleeve.

As other elements, the switch 6 has a pair of spaced contact-s or contact plates 12 at the same end of the body 10 as and within the bimetallic or thermally responsive diaphragm 8 and a pair of spaced terminal plates 13 at the other end of the body, each contact and one of the terminal plates being both electrically connected to each other and fixed to the body by one of a pair of transversely spaced conductor bars 14 extending axially through the body. Using, as its terminals, screws 15 threaded into the terminal plates 13, the switch 6- has its switch element 9 for electrically connecting the contacts 12 formed of a disc or plate 16 fitting in a socket or pocket 17 in the body 10 and fixed to a rod or pin 18 sliding or recipnoca'ble in an axial bore 19 in the body and projecting or extending through the disc, past the contacts 12, tothe confronting or inner face 29 of the diaphragm -8. With the rod 18 of the switch element 9 concentric and in contact with the diaphragm 8 and the disc 16 normally yieldably held in contact The other of the main components of the timer l, I

the heater 7 may also be mounted on the insulating plate 5 and, as in the illustrated embodiment, may have a U-shaped heating coil 22 extending across the outer face 23 of the diaphragm 8 adjacent thereto and supported in and insulated from a channel-shaped bracket 24 attached, as by bolting, t the mounting plate.

As indicated in FIGURE 5, when the timer 1 is connected to a solenoid or other electrical device or load 25, the thermal switch 6 is connected in series with both the heater 7 and the load. In turn, the load 25 preferably is connected across the terminals 26 of and in parallel with the heater. This preferred arrangement of the load and the heater is of especial importance when the load is self-inductive, since it enables the heater to act as a field discharge resistance for the load on opening of the switch 6 and so prevents arcing between the switch element 9 and the contacts 12.

The particular arrangement of leads by which the timer 1 is electrically connected to the load 25will depend upon the nature of the load and the types of electrical connection employed. If, as in the illustrated embodiment, the connections of the thermal switch 6 to the load 25 and to the power source (not shown) are made by quick connectors each formed of a tab and a spring clip in which the tab is received, a tab 27 connected by a lead 27a to one of the terminals 15 of the thermal switch 6 may be mounted on a second insulator plate or board 29 in the housing 2 of the timer :and itself mounted on the main insulator plate a right angles thereto by a pair of angles 30. A spring clip (not shown) on an end of one of the outside or external leads 31 to the power source may then be connected to the tab 27 for the thermal switch, while the other of the main leads is connected in like fashion to corresponding terminals of the load 25 and the heater 7, the auxiliary lead from this terminal of the heater being indicated at 32 in FIG- URES 1-3. A second auxiliary lead indicated at 33 in FIGURES 1-3 connects to the other terminal of the heater 7 and has a branch 34 connected to the second of the terminals 15 of the thermal switch 6. Both auxiliary leads may pass through the second or secondary mounting plate 29 and the second auxiliary lead 33 is connectable to the second terminal of the load 25 to complete the circuit shown in FIGURE 5.

Since the timer 1 is dependent for its cyclic action upon the alternate heating and cooling of the diaphragm 8 of the thermal switch 6 and the heater is in the electrical circuit, the on and off cycles of the timer will be affected by the operating voltage. The on and oif cycles also will be affected somewhat by variations in the ambient temperature, although the effect will be more on the relative durations of the on and the off cycles than on the full cycle, since the shortening of the on cycle at high ambient temperatures will be attended by an increase in the off cycle during which the diaphargm 8 cools to the point at which it snaps back to normal position. Too, with its cyclic action controlled by the flexing of a single element, the diaphragm 8, in response to changes in the temperature to which it is exposed, the timer is not readily adapted for controlling an electrical device which is required to have prolonged on and off cycles of hours rather than minutes duration. However, the timer 1 is practically shock-proof and, although not capable of matching the fineness of control possible with a finely cut motor-actuated cam in a conventional electric timer, can provide an operating cycle automatic drain valve of the type earlier described and,

despite its single control element, readily is capable withscope of the appended claims.

Having described our invention, we claim: 1. In an electrical circuit connectable to a power source, the combination of a self-inductive electrical device and r a thermo-electric timer for cyclically operating said dethe combination of a self-inductive electrical device and a thermo-electric timer for cyclically operating said device, said timer comprising a heater, a normally closed switch connected in series with said device and heater, said heater being connected in parallel with said device for preventing arcing at said switch on opening thereof, and thermally responsive means exposed to said heater for actuating said switch, said means throughout the connection of said circuit to said power source being responsive to the condition of said heater for causing said switch to open and close after predetermined intervals respectively on energizing and de-energizing of said heater.

3. In an electrical circuit connect-able to a power source,

- the combination of a self-inductive electrical device and that is satisfactory for the operation of a wide variety 2 a thermo-electric timer for cyclically operating said device, said timer comprising a heater, and a normally closed thermal switch including contacts connected in series with. said device and heater, said heater being connected in parallel with said device for preventing arcing at said switch on opening thereof, switch means normally bridging said contacts, and a thermally responsive element exposed to said heater for actuating said switch means, said element throughout the connection of said circuit to said power source being responsive to the condition of said heater for causing said switch means to break and make contact between said contacts after predetermined intervals respectively on energizing and deenergizing of said heater.

4. In an electrical circuit connectable to a power source, the combination of a self-inductive electrical device and a thermoelectric timer for cyclically Operating said device, said timer comprising a housing, a normally closed thermal switch insulatedly mounted in said housing and connected in series with said device, and a heater mounted in said housing adjacent said switch and connected in series with said switch, said heater being connected in parallel with said device for preventing arcing at said switch on opening thereof, said switch including thermally [responsive means exposed to said heater and responsive thereto throughout the connection of said circuit to said power source for causing said switch to open and close after predetermined intervals respectively on energizing and tie-energizing of said heater.

(References on following page) 5 6 References Cited by the Examiner 2,840,666 6/1958 Greenhut 200122 X UNITED STATES PATENTS 3,004,203 10/ 1961 Epstein 318221 8/1937 80mm 200*122 3 6 9/ 9 3 pstem 20%122 1;; 3 g y 3 3 22? 5 BERNARD A. GILHEANY, Primary Examiner.

unn 7 195 Merfler 200 13 JAMES Exammer- 2/1958 Moonhead 200138 L. A. WRIGHT, Assistant Examiner.

Claims (1)

1. IN AN ELECTRICAL CIRCUIT CONNECTABLE TO A POWER SOURCE, THE COMBINATION OF A SELF-INDUCTIVE ELECTRICAL DEVICE AND A THERMO-ELECTRIC TIMER FOR CYCLICALLY OPERATING SAID DEVICE, SAID TIMER COMPRISING A NORMALLY CLOSED THERMAL SWITCH CONNECTED IN SERIES WITH SAID DEVICE, AND A HEATER CONNECTED IN SERIES WITH SAID SWITCH AND IN PARALLEL WITH SAID DEVICE RESPECTIVELY FOR HEATING SAID SWITCH AND PREVENTING ARCING THEREAT ON OPENING THEREOF, SAID SWITCH THROUGHOUT THE CONNECTION OF SAID CIRCUIT TO SAID POWER SOURCE BEING RESPONSIVE TO THE CONDITION OF SAID HEATER AND OPENING AND CLOSING AFTER PREDETERMINED INTERVALS RESPECTIVELY ON ENERGIZING AND DE-ENERGIZING OF SAID HEATER.

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