|Publication number||US2743335 A|
|Publication date||Apr 24, 1956|
|Filing date||Sep 4, 1953|
|Priority date||Sep 4, 1953|
|Publication number||US 2743335 A, US 2743335A, US-A-2743335, US2743335 A, US2743335A|
|Inventors||Moyer David F|
|Original Assignee||Gen Motors Corp|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (7), Referenced by (14), Classifications (7)|
|External Links: USPTO, USPTO Assignment, Espacenet|
April 24, 1956 D. Ff MOYER 2,74
C IRCUIT BREAKER Filed Sept. 4, 1953 2 Sheets-Sheet l m1 'ENTOR. DAV/D FMOYEJQ WFW A ORNEY April 24, 1956 Filed Sept. 4, 1955 CIRCUIT BREAKER 2 Sheets-Sheet 2 6/ U I I 1.2 $2 a 7 20a Md.
53/ I l I my 4 a 47 J JNVENTOR. 52 DA |//.D FMo YER gw wwg I ATTORNEY United States Patent Motors Corporation, Delaware assignor to General Detroit, Mich., a corporation of Application September 4, 1953, Serial No. 378,555 3 Claims. (Cl. 200-138) This invention relates to a thermal control device,
and particularly to a small inexpensive thermostat for making and breaking electric circuit in response to ambient temperature conditions, and a method of assembling and initially adjusting the thermal control device.
The device of this invention particularly concerns thermal control devices of the bimetallic type wherein deflection of a bimetal member directly effects opening and closing of a pair of contacts, and even more specifically wherein a contact member is carried directly by a bimetal arm that deflects relative to a second contact carrying member to open and close the contacts by deflection of the bimetallic arm. In such controlled devices there is a point at which the contacts are about ready to open, this point resulting in substantially no contact pressure between the contacts which results in a high resistance to flow of electric current between the contacts thereby effecting heating of the bimetal member with resultant disturbance in the calibration of the movement of the bimetallic member.
Further, when such a control device closes contacts, the initial closing of the contact carried by the bimetallic arm upon the closing contact is at a time when very light contact pressure exists between the contacts. Here again the light contact pressure results in high contact resistance causing heatingof the bimetal with resultant opening of the contacts. Such opening of the contacts causing cooling of the bimetal and reclosing of the contacts until such time as deflection of the bimetal is sufficiently strong to establish sufficient contact pressure upon closing of the contacts as will reduce the contact resistance sufiiciently as to substantially eliminate the heating of the bimetal. Such operation of the thermal control device results in erratic control operations and a high degree of arcing of the contacts.
It is therefore an object of this invention to provide a simplified structure of a thermal control device incorporating a direct acting contact carrying bimetallic arm which will eliminate the aforementioned difficulties by effecting an increase of contact pressure at the time the contacts are opening or immediately after the initial closing of the contacts until the bimetallic arm has suflicient deflection under ambient temperature conditions to result in either a positive opening or closing of the contacts with resultant elimination of the contact resistance heating and normal deflection of the bimetallic member under response to ambient temperature conditions.
It is still another object of the invention to provide a thermal control device in accordance with the foregoing object wherein the bimetallic arm is provided with a return bend portion that carries a contact member, the return bend portion having less deflection in response to ambient temperature conditions than the main portion of the bimetallic arm to thereby render the bimetallic arm sensitive only to ambient temperature responses but with the return bend portion being directly responsive to contact resistance heating to establish thereby increased con- 2 tact pressure without effecting any substantial change in the responses of the main bimetallic arm to ambient temperature changes.
It is another object of the invention to provide a sim plified structure of a direct acting bimetal thermal control device which is completely sealed and provided with an initial factory setting by deflection of the bimetal member under controlled conditions.
It is another object of the invention to provide a method to establish an initial factory adjustment on a direct acting bimetal thermal control device of the type referred to in the foregoing objects wherein the control device controls its own initial setting.
Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred form of the invention is clearly shown.
In the drawings:
Figure l is a longitudinal cross sectional view of a thermal control device incorporating features of this invention.
Figure 2 is an end view of the device of Figure 1, as viewed from the right hand end thereof.
Figure 3 is a longitudinal cross sectional view similar to Figure 1 but illustrating the device under certain conditions of operation.
Figure 4 is a transverse cross sectional view taken along line 44 of Figure 1.
Figure 5 is a transverse cross sectional view taken along line 5-5 of Figure 1.
Figure 6 is a schematic view of an apparatus providing a method for establishing initial factory adjustment of the thermal control device of this invention.
Referring to Figures 1 to 5, the thermal control device comprises a hollow casing 10 having a substantially rectangular chamber 11 therein. The end 12 of the easing is closed while the end 13 is open. A current conducting arm 14 is placed within the chamber 11 and rests against the side 15 of the rectangular opening in the casing 10.
The current conducting arm 14 has a contact portion 16 on one end thereof. The opposite end of the member 14 has a formed portion 17 that engages the end wall 18 of the casing 10 to control the entry of the arm 14 into the casing 10 and thus the position of the contact member 16 is controlled relative to the end 18 of the casing 10.
A bimetal thermal control arm 20 is placed within the opening 11 of the casing 10. This arm 20 has a formed portion 121 that engages the end wall 18 of the casing 10 to control the entry of the bimetal member 20 into the opening 11, and thus position the contact 21 on the end thereof in cooperating engagement with the contact 16 on the current conducting arm 14. The bimetal member 20 is also a current conducting member.
The bimetal arm 20 has one end thereof provided with a return bend portion forming a leg portion 22 that is substantially shorter than the main bimetal leg portion 23. Since the bimetal member 20 is adapted to move the contact 21 from the contact 16 upon a rise in ambient temperature, the high expansion metal of the bimetal member 20 will be on the side 24 thereof with the low expansion metal being on the side 124. Thus, the return bend leg portion 22 is adapted to deflect downwardly, as viewed in Figure 1, while the leg portion 23 deflects upwardly, in response to a rise in temperature.
However, since the leg portion 22 has a total length that is substantially less than the total length of the leg 23, the degree of deflecting activity of the leg portion 22 in response to ambient temperature conditions will be substantially less than the degree of deflection activity of the leg 23 in response to small rise in temperature such since the bimetal 20 isad'apted inthis invention to carry the normal current; l'oad required of the device without sufficient heating of the bimetal as to affect its response toambientiternperature conditions.
The bimetal member: 211 and the current conducting arm 14, which is a temperature and current insensitive material,:relatiyely speaking, are retained in position in the casing 102 by means of a spacing member 25. The
spacing member 25lfrictionally engages the members 20' and 14 to; hold them in engagement with the sides 15 and 26 respectively of the rectangular opening 11 in the casing 1.0. Also, the spacing member; 25 provides means for establishinguthe initial opening point of the contact 21 from the contact 16 in a manner hereinafter described.
The bimetal-member 20 has an angular portion 30 that is engaged by the spacer member-25101 the purpose of regulating the initialopening pointor the contact 21 from the. contact 16 Assuming the thermal control device to have been assembled and". properly adjusted, in a manner hereinafter described, the bimetal member 20 will therefore open. contact 21 from contact 16 at a predetermined temperature upon a rise in temperature.
Since themovement' of the bimetal 20 is aslow movement, thebreak between: the contact 21 andthe contact 16 is made extremely slow. Thus, a position of the bi-' metalLZllisreachedat which the contact 21 barely touches the:contact 16.with resulting loss of any substantial contact pressure between the contacts.
This. loss: of contact pressure between the contacts 21 and: 16 results. in a high: resistance being established between. the. contacts 21 and: 16 which causes substantial heating. This heating resulting from contact resistance, is transmitted to the end portion 22' of the bimetal 20, and since the degree and rateof heat involved is substantially .above that at which the ambient temperature is. afiecti'ngthe leg portion 23 of the bimetal, the leg portion 22. of the bimetal willdeflect downwardly, as viewed in- Figure. 1, toiincrease the pressure of the contact 21 upon the contact 16 and thereby substantially red'nceathecontact resistance between the contacts. However, since the: leg portion 22 is substantially shorter than the:- leg portion 23, and substantial travel is required for theheat entering: the leg 22 to be transmitted to the leg 23; of thebimetal, and a large dissipating area is provided in the legportion 23, the leg portion 23 0f the bimetal 20 will be substantially insensitiveto the heat eiiectof the leg portion 22 of: the bimetal'20.
Thus, thev resistance heating of the leg portion 22 provides deflection of this leg portion relative to the leg portion 23 to increase the contact resistance without any substantial efi'ect onv the responsiveness of the leg 23 of the bimetal20 to ambient temperatures.
With the leg. portion 22 deflected downwardly to increase the contactpressure between the contacts 21 and 16, a further rise in ambient temperature is required to move the leg'portion 23 upwardly until such time. as the leg portion 23 physically disconnects the contact 21 from the contact 16. Instantly upon such disconnection heating of the leg portion 22 ceases sothat the leg portion 22 moves upwardly to further increase the gap 16 and the contact 21; This insures positive opening of the contact 21' from the contact 16.
Also, since there" was required an increase rise in ambient temperature suflicient to produce physical breaking of the contact 21. from the contact. 16 above that which would normally be required without any deflection of the leg portion 22, a substantial decrease in ambient temperature is required before the contact 21 again closes on contact 16. This creates the desired temperature differential of operation to. the; thermal control device.
Upon closing of contact 21 upon contact 16, the light contact pressure occurring at the instant of closing again results in high resistance to flow. of current between the contacts and resultant heating of the leg port-ion 22; of the bimetal 20. The quick response of the leg'portioni22 to the heating effect of the contact resistance deflects. the leg portion 22 downwardly to increase the contact pressure and thereby preventreopeningpf the contacts after the initial closing. This insures positive closing of the contacts and elimination of arcing.
In Figure 3 there is illustrated the thermal control device of this invention wherein the bimetal members has the leg portion 23.. thereof and the leg portion 22 deflected in a manner occurring at: the instant of initial contact break between the-contact 21 and the contact 16.
The thermal control device illustrated in Figures 1 to 5 is assembled by first placing the current conducting member 1'4 and thebimetal member 20 within the casing 10 with the formed portions 17 and 121- respectively engaging the. end wall TS-of the casing 10. The spacer-member or plug isthen insertedbetween themembers 14" and 20 to frictionally retain themin the position illustrated in- Figure 1. At this time however the initial calibrated break point between contact 21 and contact 1'6 has not been established.
An apparatus and method to establish the initial break point between the contact 21 and. the contact 16 is illustrated in- Figure 6. This apparatus comprises a transfer belt 40 having a plurality of sleeves 41 secured therein. The sleeves 41 have fiexiblefingers 42 adapted to receive and frictionally engage a thermal control device 50.
The transfer belt 40 passes through a chamber 43 that has the temperature thereof controlled internally at a predetermined value. The transfer belt 40 moves the control device 50 positioned thereon to a work-station position atwhich there is provided a fluid motor 4'4 and afluidlmotor 45' disposed in alignment. The fluid motor' 441 comprises a cylinder 46 having a piston 47' that carries a plunger 43 provided with a cup shaped member 490m the end thereof" that is adapted to engage the bottom end of the control device 50 that is moved into alignment with. the fluidj motor 44. Thecup shaped member 49 has flexible fingers 51 adapted to engage the thermal control device 50;
The fluid motor 44 has a pressure connection 52 for moving the piston 47- upwardly. An internal spring 53 in the motor 44 is provided for retracting thepiston 17 and the plunger 48.
The fluid motor 45 comprises a cylinder having a piston 61 provided with a plunger 62 that projects through a guide sleeve 63 of insulating material andis adapted to engage the spacer or plug 25 of the thermal control device Sil. Electric spring contacts 64 and 65 are provided in the insulating guide sleeve 63 for engagement by the terminal end-s 14a and 20a of the current conducting arm 14 and the bimetal 26 respectively.
The cylinder 68 is supplied with liuid under pressure from any suitable source, such as the pump 70. The cylinder 60 has an outlet 71 controlled by'an electrically operated valve 72, the valve '72 being adapted to open or close the outlet connection 71 of the cylinder 60' with a conduit 73 that returns to a reservoir 74 from which the pump is supplied.
The electrically operated valve 72 has a solenoid actuator 75 that is in series circuit with the spring contact 64 and 65 and is energized when the thermal control device 51) has the terminals thereof engaging the spring contacts.
A spring 76 is provided to return the piston 60 and thus the plunger 62.
When a thermal control device 50 is moved into alignment with the fluid motors 44 and 45, the fluid motor 44 is supplied with fluid under pressure through the conduit 52 to move the piston 47 upwardly and thus move the terminal ends 20a and 14a into engagement with the spring contacts 64 and 65. The upward position of the control device 50 relative to the fluid motor 45 is controlled by a stop 80 that engages the end wall 18 of the casing of the control device.
The control device is assembled with the contacts 21 and 16 in closed position. Thus the contacts in the control device 50 close circuit for the valve 72 to provide closing of the valve and thus entrapment of fluid under pressure within the cylinder 60 above the piston 61 to cause the plunger 62 to move downwardly. When the plunger 62 moves downwardly it engages the plug or spacer member 25 to move it longitudinally between the current conducting member 14 and the bimetal member with the forward wall 81 of the plug engaging the angular portion of the bimetal member 20. This forward movement of the plug 25 deflects the bimetal member 20 tending to move the contact 21 away from the contact 16.
Since the operation of moving the plug 25 forwardly into the casing 10 of the control device occurs in a controlled temperature atmosphere at a temperature at which the control switch will normally break contact or circuit through the same, the initial setting of the control device is occasioned under actual operating conditions. Thus the initial break of the contact 21 from the contact 16 will be occasioned under temperature conditions representing actual working conditions with the bimetal 20 free to function under its normal operating conditions heretofore described.
When the plug 25 is moved inward of the casing 10 a suflicient distance to cause the initial break of contact 21 from contact 16, electric circuit will be broken through the electrically controlled valve 72 to immediately stop further advancement of the plunger 62 of the fluid motor 45. The valve 72 at this time opens to release pressure from above the piston 61 to allow the plunger 62 to return under the action of the spring 76 to its normal position.
Thereafter, pressure is released from the fluid motor 44 to allow return of the piston 47 by the spring 53 and withdrawal of the control device 50 from engagement with the spring contact 64 and 65 so that the transfer belt can be moved forwardly to place another control device in the work-station.
While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted as may come within the scope of the claims which follow.
What is claimed is as follows:
1. A thermal control device, comprising, a hollow casing having an open end, a current conducting rigid member in said casing, a current conducting flexible bimetallic arm in said casing spaced from said member having a portion thereof disposed angular relative to said member, and a closure plug closing the said open end of said casing and positioned between said current conducting member and said bimetallic arm to retain the same in spaced relationship and engaging said angular portion to position said bimetallic arm relative to said member.
2. A thermal control device, comprising, a hollow casing having an open end provided with parallel facing walls and side walls connecting the said facing walls, a first current conducting arm in said casing having a contact portion thereon within said casing having an end portion engaging one of said facing walls and including a formed portion engaging one end of said casing to restrict entry of the said arm into said casing, a current conducting bimetallic arm positioned within said casing having a contact member thereon for cooperative engagement with said contact portion, said bimetallic arm having an end portion engaging the other of said facing walls and having a formed portion thereon engaging the said one end of said casing to restrict entry of said bimetallic arm into said casing, said bimetallic arm also having a portion formed angular relative to said first arm, and a closure plug in the said open end of said casing between said first arm and said bimetallic arm to retain said arms in said casing and engaging said connecting walls to close said open end and engaging said angular portion to establish the adjusted break point between said contacts.
3. A thermal control device, comprising, a hollow casing having an open end provided with parallel facing walls and side walls connecting the said facing walls, a first current conducting arm in said casing having a contact portion thereon within said casing and including a formed portion engaging one end of said casing to restrict entry of the said arm into said casing, a current conducting bimetallic arm positioned within said casing and having a return bend portion at one end thereof provided with a contact at the end of the return bend portion for cooperative engagement with said contact portion, said bimetallic arm having an end portion engaging the other of said facing walls and having a formed portion thereon engaging the said one end of said casing to restrict entry of said bimetallic arm into said casing, said bimetallic arm also having a portion formed angular relative to said first arm, and a closure plug in the said open end of said casing between said first arm and said bimetallic arm to retain said arms in said casing and engaging said connecting walls to close said open end and engaging said angular portion to establish the adjusted break point between said contacts.
References Cited in the file of this patent UNITED STATES PATENTS 1,916,671 .Hanser et al. July 4, 1933 2,004,963 Scharf June 18, 1935 2,116,858 Winckler May 10, 1938 2,137,309 Smulski Nov. 22, 1938 2,248,531 Harris July 8, 1941 2,321,338 Ulanet June 8, 1943 2,641,050 Graybill et al. June 9, 1953
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|U.S. Classification||337/372, 337/381, 337/379, D13/160|