US1494650A - Thermally-responsive electric switch - Google Patents

Description

May 20 1924.

J. TWARDOWSKY THERMALLY RESPONSIVE ELECTRIC SWITCH Filed Dec. 27. 1921 2 Sheets-Sheet. l

NIX

Patented May 20: 1924.

UNITED STATES 1,494,650 PATENT OFFICE.

JOHN 'IWARDOWSKY, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO UNIVERSE CORPORATION, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

THEBMALLY-RESPONSIVE ELECTRIC SWITCH.

Application filed December 27, 1921. Serial No. 524,991.

To all whom it may concern:

Be it known that I, JOHN TWARnowsKY, citizen of Russia, residing at Chicago, in the county of Cook and State of Illinois, have invented certain new anduseful Improvements in a Thermally-Responsive Electric Switch; and I do hereby declare the following tobe a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

My invention relates to electric switches and in one of its general objects aims to provide a switch which will automatically be moved to its on and off positions in response to predetermined variations in the pressure of a normally gaseous fluid. In another general aspect, my invention relates to a thermally responsive electric switching appliance in which the changes in temperature vary the extent to which an inclosed fluid is liquefied, so as to produce corresponding and relatively large changes in the pressure of the vaporized fluid portion, and

' in which these pressure changes are then utilized for actuating the switch. Furthermore, my invention aims to provide an electric switching appliance of the above type or types which will be simple and durable in construction, and in which all needed adjustments can be made easily and quickly without taking any portions of the mechanism apart. y

In one of its important commercial applications, the. thermally responsive electric switch of my invention is particularly applicable for use' in controlling the motor which operates the fluid compressor in a mechanical refrigerator of the expansion type. To make such. refrigerators independent of the vigilance of an attendant, it is desirable that the motor which drives the compressor should be started whenever a given temperature is exceeded within the refrigerator, and that the running of the motor should be stopped whenever the refrigerator has been cooledto a certain degree. Various thermostatic arrangements depending on the expansion of metals wlth an increase of temperature have been employed for this purpose for controlling the motor in response to such expansion, but these have been unsatisfactory in practice both owing to the uncertainty of the relays which had to be interposed between the thermostatically governed control circuit and the motor circuit, and also because of the comparatively slight expansion or contraction effected in metals within the temperature range desirable in the refrigerator and of the consequent lack of adequate sensitiveness.

As a substitute for such a thermo-electric arrangement, the appliance of my invention first translates the temperature changes into changes in the pressure of a fluid inclosed in certain passages, part of which passages are subjected to the temperature changes within the refrigerator, which my invention employs the resulting pressure changes for ac.- tuating the switch proper and preferably for directly actuating a switch controlling the motor circuit.

As part of the equipment for such a purpose, I aim to provide a simple and easily installed pressure tube adapted to have its the tu'beand hence producing decided pressure changes Within the tube. Then my invention employs these pressure changes in the fluid for actuating a switch-throwing lever through the medium of an expansible casing which .forms part of the total passages containing the said fluid. My invention also aims to provide a simple mounting for such a pressure-responsive chamber, and desirably aims to provide a simple mountin for the entire appliance so arranged at it easily can be attached to any convenient support and so that the main portions of the same can be rotated to any desired plane without affecting the tightness of any joints or requiring any changes in the electrical connections.

Moreover, my invention aims to[ provide simple and easily manipulated means for adjusting the fluid pressures at which the switch will automatically be operated in one direction or the other, thereby correspondin'gly adjusting the temperature ranges in response to which the switch will operate. It also aims to provide a simple, inexpensive and strong switch construction suitable for this purpose and one in which the contacts will be self-cleaning, and aims to provide simple mountings for the various parts and simple means for making those important adjustments which may be needed for insuring a positive and sensitive action of the throw-over part of the mechanism. Still further and also more detailed objects will appear from the following specification and from the accompanying drawings in which Fig. 1 is an elevation of a refrigerator, with a portion of its front broken away to show the mounting of my appliance within the same.

Fig. 2 is an enlarged side elevation of all except the tubular coil portion of the same appliance, showing the switch in its off position.

Fig. 3 is a similar view showing the switch in its on position.

Fig. 4 is a plan view of the same parts, taken with the switch in its off position.

Fig. 5 is a side elevation of the head of the switch taken from the right hand of either Fig. 2 or Fig. 3.

Fig. 6 is an enlarged vertical section through the portion of the appliance which transmits the pressure changes to the throwover lever, taken along the correspondingly numbered line in Fig. 4.

Fig. 7 is a perspective View of a fork which forms the base of theswitch. v In applying my invention for thepurpose of controlling the motor which actuates a mechanical refrigerator, I dispose a fluid container within a cooled chamber of the refrigerator and for this purpose desirably employ a tube 1 having its major portion.

coiled into a flat'spiral and disposed within a cooling chamber'of the refrigerator 2, the coiling permitting me to expose a large area of tube surface to the temperature within the said. chamberi This tube 1 is here shown as closed at. the inner end of its said coiled portion and as having its other end threaded into a cup 3 which opens into a diaphragm chamber 4 as shown in Fig. 6. This latter collar 6 on this cup after the manner shown in Fig. 6, it being understood that all joints mentioned by nie may be made fluid-tight by any customary auxiliary means. Thus arranged, the receptacle 4 forms an expansible chamber which will have its ends flexed away from each other by any increase in internal pressure, and I utilize such a flexing for moving a plunger 7 which desirably engages a flat pressure-distributing disk 8 secured to the upper end ofthe re ceptacle 4. The plunger 7 is continuously urged towards the said receptacle by a spiral spring 9 interposed between the lower head of the plunger and a bushing 10 threaded into the upper portion 11 of the supporting member of my appliance. This supporting member desirably includes a'base plate 12 equipped with perforations 13 for receiving.

screws by which the sup orting member may be secured to a side 0 the refrigerator or to some other convenient object, the part 11 being secured to this base plate 13 by screws 14 and the parts 11 and 13 being spaced from each other by sleeves 15 through which the screws 14-extend. These sleeves space the said parts sufliciently to provide ample room for the expansible receptacle 4 and the pressure-distributing disk 8, and the spacing may also be such that the part 11 acts as a stop for limiting the upward movement of the disk 8 by the flexing of the closed port, thereby permitting a convenient assembling of the parts and also facilitating the adjusting of the position of the switch with respect to the plunger 7 and the said throw-over connections.

As a simple and highly effective arrangement for this general purpose, I desirably provide a supporting rod 16 threaded into a portion of the supporting member (and here shown as threaded into the part 11 of the latter and extending parallel to the plungers This rod 16 extends slidably through a bore in a fork 17 which forms the supporting base of my switch and which is clamped to the stem by a screw 18. Fastened to the fork 17 and desirably extending parallel to the stem 16 are a pair of insulating shanks 18 (desirably made of bakelite, redmanol or the like) each of which carries one of the circuit terminals andcontact fingers. For this purpose, I am 19 as respectivelyclamped to the two insulators 18 by. lock nuts 20,.each of these look nuts being threaded on a screw 21 which is threaded into thev adjacent insulator 18 axially of the latter. Each screw 21 also has a thumb-screw 22 threaded upon it, so that the end of one of the wires 23 can be The here showing resilient metal contact fingers I clamped between these thumb-screws and the adjacent lock nut as shown in Fig. 2.

To cooperate with the two resilient fingers 19 which thus provide contact members respectively connected to the two wire terminals of the circuit, I provide a contact bar 2 secured to an insulating block which in turn is fastened to a rocking lever 26. This rocking lever 26 is desirably forked and has each of its arms pivoted to one fork of the base 17 of the switch as shown in Fig. 5. Then -I also provide suitable means for limiting the movement of the rocking lever in both directions and for that purpose desirably provide a stop arm j 27 having a perforation through which the supporting stem 16 extends, this perforation being elongated transversely of that stem (as shown in Fig. 4) so that its end walls are adapted to engage the stem 16 for limiting the movement of the rocking lever in both directions. The stop arm 27 is desirably fastened to the insulator 25 conjointly with an eye 28 which is connected by a tension spring 29 to the free end of the longer arm of a bell-crank lever forming a portion of the throw-over connection between the rocking switch lever and the plunger 7. This rocking lever is pivoted on an axis transverse of the axis of the plunger and parallel to the pivoting axis of the switch lever 26 and has its shorter arm 31 extending over the top of the plunger 17, the free end of this shorter arm being connected by a tension spring 32 with some portion of the supporting member-and desirably with a stiffening web 33 on the part 11. To provide for any adjustments which may be needed, I desirably pivot the bellcrank lever on a support which is movable with respect to both the supporting member of my appliance and the switch proper, and for this purpose preferably employ a bracket 34 slidable 'upon the supporting stem 16 and clamped in any desirable position on the latter by a screw 35. I also dejsirably do not have the shorter arm 31 of fthis lever engage the plunger 17 directly,

but interpose a screw 30 threaded through this arm 31-,and having its tip in engagement with the plunger 17, this screw being latched in any adjusted position by alock nut 37 Furthermore. I space the pivots of the switch lever andof the bell-crank from the supporting rod 16 so that the longer arm 30 of the bell-crank will swing past the plane connecting the axis of the pivots 38 with that of the bell-crank pivot 38 during the swinging of the switching lever from its one extreme position to the other.

With the parts thus'arranged, it will be obvious from Fig. 6 that an upward flexing of the top of: the expansible receptacle 4 by an increase of pressure within the latter elongating the spring 29 and causing the latter to pull the rocking lever 26 from the position of Fig.2 to that of Fig. 3. It therefore moves the contact bar 24 to the position in which it closes the circuit connection between the two contact fingers 19. Likewise, when the pressure within the receptacle 4 falls, the springs 32 and 9 will cooperate in causing the plunger to slide in. a direction away from the switch, and the spring willcause the bell crank lever to follow this movement by swinging in a clockwise direction. As soon as the upper end of the long arm 30 has moved sutficiently, the spring 29 will throw the switching lever back to its off position of Fig. 2, thereby opening the circuit. By turning the bushing 10 in one direction or the other, and by varying the resiliency of the springs 9 and 32, I can readily adjust both the initial pressures and pressure differences at which the above described movements of the switching member will be effected, and by loosening the screws 35 and 40 I can readily make such corresponding adjustments as may be needed in the position of the switch and ofthe pivotal support for the bellcrank lever which forms part of the throwover mechanism.

In practice, I desirably employ sulphur dioxide as the expansible medium within the receptacle 4 and the control tube 1 connected to the latter and I have found it practical to introduce this sulphur dioxide in such a quantity that the pressure within the receptacle and tube will be approximately or pounds per square inch at a surrounding temperature of F. Then I adjust the various parts-of the mechanism so that the switch is in circuit-closing position with such a pressure in the controlling chambers. When the control tube is'coole to a temperature of 40 or less by the resulting action of the refrigerator, a part of the inclosed gaseous sulphur dioxide is liquefied into a mist and the pressure within the control tube and the receptacle drops" accordingly, thereby operating the switch although the pressure within these control chambers may still be. considerably above that of the atmosphere. The circuit is then opened automatically, thus stopping the operation of the refrigerator until the chamber housing the control tube 1 rises sufficiently in temperature to evaporate the previouslyliquefied portion of the gas and restore the initial -pressure, whereupon the corresponding expanding of the receptacle 4 actuates the plunger in the opposite direction and moves the switch back to its circuit-closing position.

With such a charge of sulphur dioxide, I have found that by suitably adjusting the various parts of the mechanism, Ican easily cause the switch to respond to variations of less than 5 F. so as to maintain the temperature within the refrigerator say between 36 and 40 F. .I have also found that the presence of some air mixed with Sulphur dioxide does not materially afiect the operation at such a temperature range, so that it is not necessary to exhaust the air from the receptacle 4 and the control tube 1 before admitting the sulphur dioxide. However, these portions may previously be exhausted if it is desired to employ my in- Vention for response to temperature variations in which the maximum is lower than that above mentioned, and so that I do not wish to be limited in thisrespect. Nor do I wish to be limited to the use of sulphur dioxide, as other gaseous mediums such as ammonia may be employed, provided that the metal parts are constructed of correspondingly suitable materials.

Neither do I wish to be limited to the details of the switching construction, throwover mechanism or other portions of the arrangement above described, although I have found it highly advantageous to employ insulating switching portions afi'ording long leakage surfaces, together with a self-cleaning switching arrangement and a triple adjustment for the connections be-' tween the switch and the expansible casing. Obviously, all of these various features might be varied in many ways without departing fromthe s irit of my invention, so that I do not wish to be limited to the same, nor to the employment of all of the features in connection with each other or for the particular purpose above recited.

Furthermore, the location and position of my appliance may readily be varied, as the same will operate equally well in vertical, horizontal or inclined positions, while the mounting of the cup 3 permitsthe control tube 1 to be swung about the axis of thiscup in any direction.

I claim as my invention 1. A pressure-responsive switch including an expansible fluid container, a slidable stem bearing at one end against and movable by the expansion of the container, a spring associated with the stem for resisting movement thereof in one direction, a throw-over switch including. a bell-crank lever having one arm connected to the switch mechanism, a spring connected to the other arm of the lever, and an adjustable connection between the said other arm and the stem.

2. A pressure-responsive switch including 4 an expansible fluid container, a slidable stem bearing at one end against and movable by the expansion of the container, a spring associated with the stem for resisting movement thereof in one direction, a throw-over switch including a bell-crank lever having one arm connected to the switch mechanism, a spring connected tothe other arm of the lever, and a screw threaded upon the said other arm of the lever and engaging the free end of the stem.

3. A pressure-responsive switch as per claim 1, in which both of the said springs resist a movement of the stem in response to an increase of pressure in the container.

4. A pressure-responsive switch as per JOHN TWARDOWSKY.

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