US3825868A - Thermally responsive switch - Google Patents

Thermally responsive switch Download PDF

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Publication number
US3825868A
US3825868A US00323616A US32361673A US3825868A US 3825868 A US3825868 A US 3825868A US 00323616 A US00323616 A US 00323616A US 32361673 A US32361673 A US 32361673A US 3825868 A US3825868 A US 3825868A
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US
United States
Prior art keywords
contact elements
container
pair
cover member
disposed
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US00323616A
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English (en)
Inventor
T Jess
W Jackson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Robertshaw Controls Co
Original Assignee
Robertshaw Controls Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to AU39040/72A priority Critical patent/AU458613B2/en
Priority to GB725472A priority patent/GB1357044A/en
Priority to FR7205217A priority patent/FR2125521B1/fr
Priority to CA134,866A priority patent/CA956682A/en
Application filed by Robertshaw Controls Co filed Critical Robertshaw Controls Co
Priority to US00323616A priority patent/US3825868A/en
Priority to US00323617A priority patent/US3816910A/en
Application granted granted Critical
Publication of US3825868A publication Critical patent/US3825868A/en
Assigned to BANKERS TRUST COMPANY reassignment BANKERS TRUST COMPANY SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ROBERTSHAW CONTROLS COMPANY A CORP. OF DELAWARE
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H37/00—Thermally-actuated switches
    • H01H37/02—Details
    • H01H37/12—Means for adjustment of "on" or "off" operating temperature

Definitions

  • integral support base molded from a mass of thermosetting material which is cured at the desired operating temperature for the switch.
  • the contact elements I each have a protruding stop and are biased during manufacture such that the stops abut the support base while the contact ends are maintained in a predetermined relationship with each other whereby the switch is calibrated at the same time the thermosetting material is cured.
  • the present invention relates generally to thermally responsive switches and more particularly to an improved thermally responsive switch and method for works to have or break an electrical circuit in response to sensed heat energy. It is often desired to have such control networks operate at a precise temperature as in thecase where the thermally responsive switch is positioned within heating proximity of a device to be monitored and'the control network is responsive to any loverheating of such device to initiate corrective action.
  • thermally responsive switches provide consistent operation at precise temperatures. This requirement places stringent standards upon switch design and confactured switches are actuable at the same preselected temperature. It is therefore desirous to provide a method of making thermally responsive switches ,struction techniques especially where mass-production I techniques are employed in order that all of the manuwhereby the switches are, accurately calibrated during manufacture thereby eliminating the need for calibration of the assembledswitches and assuring reliable and accurate operation of the finished product.
  • U.S. Pat. Nos. 2,745,924, 3,148,258 and 3,230,607 is generally cognizant of electrical'switches which are calibrated during manufacture.
  • U.S. Pat. No. 2,745,924, for example discloses a switch in which a pair of contact elements are placed in a multiple section housing with the contact ends held in a fixed position by a spacer'23 as illustrated in FIG. 8. .
  • a base material 24 is molded about the contactelements and is cured at the operating temperature of the switch. Thereafter, spacer 23 is removed to complete the assembly.
  • 3,148,258 is generally similar to the previously described patent wherein contact elements 1 and 2 are placed in a multisectioned housing and are held, by structure not shown, during the curing of a plastic mass 24.
  • U.S. Pat. No. 3,230,607 pertains to a switch in which a cylindrical post is axially movable by a bimetallic contact element during the curing of a thermosettingmaterial.
  • thermally responsive switch being generally characterized as including a unitary container having an open end and a closed end defining a pair of parallel slots, a pair of elongated fiat contact elements including at least one bimetallic element, each of thecontact elements having a supportable portion opposite acontacting end and a protruding stop mediately formed adjacent the supportable portion, each of the stops abutting an edge of one of the slots with the supportable portions of the contact elements disposed interiorly of the container, a mass of thermosetting material disposed in the container surrounding the supportable portions of the contact elements and cured at a particular temperature while the distal ends of the contact elements are held in a fixed predetermined relationship, the unitary container and the mass of material interacting to form an integral support base for the contact elements whereby the contact elements assume such predetermined relationship upon being heated to the particular temperature.
  • the present invention has a further object in that a unitary container interacts with a mass of thermosetting material to form an integral support base for a pair of contact elements of a thermally responsive switch.
  • An additional objectof this invention is to construct an accurate thermally responsive switch by a simple and inexpensive method.
  • This invention has a further object in that a pair of switch contact elements are precisely positioned within an integral support base during assembly thereby increasing reliability and decreasing cost.
  • Some of the advantages of the present invention reside in its simplicity of construction, accuracy in operation, effectiveness in providing precise calibration, and ability to accurately position a pair of contact elements during manufacture without damaging the electrical contacts carried thereon or varying the switch calibration.
  • FIG. 1 is a plan view of a detail of a plurality of base containers in strip form for use in making a thermally responsive switch according to the present invention
  • FIG. 2 is a sectionalview taken on line 2-2 of FIG. 1;
  • FIG. 3 is a side elevational view of a detail of a contact element for use in a thermally responsive switch according to the present invention
  • FIG. 4 is a front elevational view of the contact element of FIG. 3;
  • FIG. 5 is a sectional view of a preferred embodiment of a thermally responsive switch according to the present invention with a cover member partially installed;
  • FIG. 6 is a sectional view similar to FIG. 5 illustrating a completed thermally responsive switch according to the present invention
  • FIG. 7 is a side elevational view of a support sleeve for supporting the switch assembly of FIGS. 5 and 6 during manufacture;
  • a preferred embodiment of a thermally responsive switch is generally designated at 20 and includes a cylindrical base mold or container 22 having a bottom end closed by a wall 24 having an annular shoulder 26 formed upon the bottom surface thereof.
  • Bottom wall 24 also defines a pair of centrally located, spaced parallel slots 28 having inclined, outwardly divergent, side walls best illustrated in FIG. 2.
  • the upper end of container 22 is open and has a pair of frangible fingers 30 radially extending from either side to a pair of outside runners 32. Fingers 30 have a tapered cross-section with the narrow end or apex attached to an upper peripheral edge of the container such that the fingers will be sheared off when pushed into a cover for the switch assembly, as will be more fully described below.
  • the containers 22 may be used singly or in strip form, as illustrated in FIG. 1, depending upon the contemplated production techniques to be employed. In either case, the runners 32 facilitate rapid handling of the containers thereby reducing time and costs during assembly of the switch. It is important to note that the containers are constructed as a unitary structure and are preferrably molded as such from a suitable plastic material. The unitary construction assures proper positioning of the contact elements of the switch assembly and precludesthe possibility of container leakage during manufacture. In this manner, additional manufacturing steps formerly required in carefully assembling and aligning sectioned containers are effectively eliminated.
  • Thermally responsive switch 23 further includes a pair of identically constructed elongated, flat contact elements 34.
  • Each of the contact elements has a diagonal contact 36 formed near one end thereof by any suitable means such as by swaging with the contact face paralleltothe flat surface of the element as shown in FIGS. 3 and 4.
  • the diagonal positioning of the contacts is preferred since it permits the use of identical contact elements for lower cost while assuring positive contact in the event of slight misalignment.
  • the contact end of elements 34 is also preferably rounded to enable cooperation with a calibration jig as willbe described more fully below.
  • a protruding stop 38 in the form of a dimple, tab, step or the like, is provided in the flat surface of the contact elements to assure proper positioning of the elements in base container 22 during calibration.
  • the portion of the contact elements above stop 38 is angularly offset, as illustrated in FIG. 3, and serves as a supporting means for the element.
  • the supporting portion defines a pair of centrally located apertures 40 which serve to rigidly lock each element in position after assembly. It should be understood that the contact elements could also be provided with serrated or cutout edges in addition to or in place of apertures 40, if desired.
  • Each of the contact elements 34 further defines a centrally located hole 42 in a rounded terminal end with the lateral sides 44 of the hole arcuately offset from the plane of the contact elements so as to receive the bare end of one of a pair of lead wires 45 for the switch.
  • theoffset wides 44 of hole 42 act to laterally support the lead wires 45 and provide an increased area to which the wires may be soldered.
  • a mass of a suitable thermosetting material 46 such as epoxy resin, in its uncured, liquid or semi-liquid form is poured into the container surrounding the supportable portions of the contact elements to secure the same within the base.
  • a suitable thermosetting material 46 such as epoxy resin
  • the completed switch assembly is inserted into a cylindrical cover, indicated generally at 48 in FIG. 5, having a rounded closed end.
  • the cover 48 has a lower portion 50 interconnected with a slightly larger diameter upper portion 52 at an inclined annulus 54.
  • Annulus 54 cooperates with shoulder 26 and the lower peripheral edge of container 22 to position the container, and thus the contact elements, in the cover as seen in FIG. 6.
  • Cover 48 is preferably made of a metal or metal alloy since such materials exhibit good thermal conductivity characteristics, but may be made of any other suitable material, such as plastic or glass, as desired.
  • the active portion of the bimetal contact elements 34 is enclosed within the lower portion 50 of the cover with the space between the elements filled with air or gas. Sufficient clearance is provided in this area to permit the elements to operate over a wide temperature range without contacting the cover wall.
  • a cylindrical aligning plug'68 is slidably disposed in the lower half of sleeve 60 and defines a conical bore 70 in an upper surface thereof.
  • Plug 68 is-fbiased upwardly by a low-rate spring 72 mounted interiorly of sleeve 60 between the bottom of plug 68 and 'tabs- 62.
  • a plurality of inwardly directed dimples 74 in the wall of sleeve 60 serves as stops to retain plug 68 within the sleeve and define its upper limit of movement.
  • FIGS. 9-12 The method of assembling and calibrating the thermally responsive switch 20 of the present invention is illustrated in FIGS. 9-12.
  • contact elements'34 are inserted from their terminal ends up into slots 28 of container 22 as illustrated in the exploded view of- FIG. 9.
  • the container carrying the bimetals 34 is then inserted into the open upper end of sleeve 60 whereupon the rounded contact end of the contact elements 34 engage conical bore 70 of plug 68.
  • the contact elements 34 are forced into the container until stops 38 engage the inclined walls of slots 28; additional movement of the container 22 causes plug 68 to be moved down against the biasing force of spring 72 until the container 22 is seated within the sleeve 60 as shown in FIG. 10.
  • the conical bore 70 in plug 68 cooperates with contact elements 34 under the influence of low-rate spring 72 to maintain both elements 34 in proper longitudinal alignment with each other and with container 22, to assure proper positioning of the contact elements within the container 22 by forcing the elements upwardly such that stops 38 abut the walls of slots 28, and to exert a small inwardly directed force near to and behind contacts 36 so as to hold the contacts together without stressing the same during assembly.
  • stop 38 of contact elements 34, the slotted base containeror mold the supportable portions of the contact elements34,
  • thermosetting material 46 is selected to have a curing temperature range within which the desired operating temperature of the switch lies such that as the material is being cured, the contact elements 34 will assume and maintain a flexedshape corresponding to their desired calibrated positions.
  • the divergent walls of slots 28 allow free movement or flexure of the contact elements such that the contact elements are not subjected to stresses which would otherwise adversely affect the switch calibration.
  • the flexure of the contact elements 34 may be seen from a comparison of FIG.
  • FIG. 10 illustrating the assembly prior to heating
  • FIG. 12 showing the assembly during the curing step.
  • the plastic container 22 interacts with the mass of material 46 to provide a hardened integral support base for contact elements 34 which increases the durability of the completed assembly.
  • a removable mold may be utilized in place of container 22' in which case the molded base assembly would be so sized as to cooperate with the cover member to provide a proper fit.
  • the heat source is removed and the calibration jig separated from the calibrated switch sub-assembly including the bimetal elements 34 and the integral support base formed of container 22 and the cured mass of material 46.
  • the lead wires 45 aresoldered to the terminal ends of contact elements 34 and the subassembly is inserted into cover member 48 as shown in FIG. 5.
  • the fingers 30 will be sheared off and the unit maybe subsequently sealed as shown in FIG. 6.
  • the contacts 36 of the completed switch assembly 20 will remain closed until the calibrated operating temperature is reached at which point the contact elements will assume the shape in which they were maintained during the cure cycle, with contacts 36 just touching. Upon being heated above this temperature, the contacts will move apart to provide an electrical open circuit. After the switch is again cooled to the calibrated temperature, the contacts will contact each other, as before, to provide an electrical closed circuit. In this manner, the switch effectively operates at the preselected operating temperature at which the switch sub-assembly was cured.
  • the present invention enables the simple, rapid and inexpensive manufacture of thermally responsive switches on a mass-production basis with each of the switches having a precise operating temperature and being durably and accurately constructed for reliable operation.
  • each of said contact elements having a supportable portion opposite a contacting end thereof and a protruding stop mediately formed adjacent the supportable portion
  • each of said protruding stops of said contact elements abutting an edge of a respective one of said slots
  • a cover member open at one end
  • said unitary container being constructed of a plastic material and having a plurality of protrusions extending outwardly from an upper peripheral edge thereof, said container being mounted interiorly of said cover-member with said protrusions cooperating with the walls of said cover member to secure said container therein.
  • a thermally responsive switch comprising a unitary container having an open end and a closed end with a pair of parallel slots extending therethrough,
  • each of said pair of elongated flat contact elements comprises a bimetal having a diagonally disposed contact formed on the contacting end thereof.
  • a thermally responsive switch comprising a unitary container of plastic material having an open end and a closed end with a pair of parallel slots extending therethrough,
  • a pair of elongated flat contact elements including at least one bimetallic element, each of said contact elements having a supportable portion and a contacting end portion,
  • each of said slots being defined by a pair of divergent walls facilitating lateral movement of said contact elements and each of said contact elements including a protruding stop abutting one of said divergent walls to locate said contact elements in their respective slots,
  • tainer is disposed in said opened end.

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  • Manufacture Of Switches (AREA)
  • Thermally Actuated Switches (AREA)
US00323616A 1971-02-17 1973-01-15 Thermally responsive switch Expired - Lifetime US3825868A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
AU39040/72A AU458613B2 (en) 1971-02-17 1972-02-16 Thermally responsive switch and method for making thesame
GB725472A GB1357044A (en) 1971-02-17 1972-02-16 Thermally responsive switch and method of making the same
FR7205217A FR2125521B1 (enExample) 1971-02-17 1972-02-16
CA134,866A CA956682A (en) 1971-02-17 1972-02-16 Thermally responsive switch and method for making the same
US00323616A US3825868A (en) 1971-02-17 1973-01-15 Thermally responsive switch
US00323617A US3816910A (en) 1971-02-17 1973-01-15 Method for making thermally responsive switches

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US11618571A 1971-02-17 1971-02-17
US00323616A US3825868A (en) 1971-02-17 1973-01-15 Thermally responsive switch

Publications (1)

Publication Number Publication Date
US3825868A true US3825868A (en) 1974-07-23

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ID=26813963

Family Applications (1)

Application Number Title Priority Date Filing Date
US00323616A Expired - Lifetime US3825868A (en) 1971-02-17 1973-01-15 Thermally responsive switch

Country Status (5)

Country Link
US (1) US3825868A (enExample)
AU (1) AU458613B2 (enExample)
CA (1) CA956682A (enExample)
FR (1) FR2125521B1 (enExample)
GB (1) GB1357044A (enExample)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4395694A (en) * 1982-06-23 1983-07-26 Portage Electric Products, Inc. Thermostat construction employing aramide insulation
US4486733A (en) * 1982-09-29 1984-12-04 Eaton Corporation Thermal mechanism with ambient compensating bimetal providing trip force
USD278050S (en) 1982-10-25 1985-03-19 Leviton Manufacturing Co. Inc. Thermal detector
CN105308710A (zh) * 2013-04-19 2016-02-03 泰科电子日本合同会社 保护装置
US20170062167A1 (en) * 2013-08-26 2017-03-02 Tyco Electronics Japan G.K. Protective Device

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2563812A (en) * 1948-08-30 1951-08-14 Jefferson Electric Co Thermal time lag fuse
US3033960A (en) * 1959-05-11 1962-05-08 West Bend Co Thermostatic switch
US3148258A (en) * 1961-09-26 1964-09-08 Dales George Franklin Thermostat with bimetal set in plastic

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1799651A (en) * 1928-11-27 1931-04-07 Bell Telephone Labor Inc Electrical switching apparatus
US2925599A (en) * 1958-07-29 1960-02-16 Alton R Wells Probe type thermostat
GB1060626A (en) * 1963-06-28 1967-03-08 Vitramon Inc Improvements in or relating to a temperature responsive switch
GB1094735A (en) * 1966-01-18 1967-12-13 Ass Elect Ind Improvements in electric thermal switches

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2563812A (en) * 1948-08-30 1951-08-14 Jefferson Electric Co Thermal time lag fuse
US3033960A (en) * 1959-05-11 1962-05-08 West Bend Co Thermostatic switch
US3148258A (en) * 1961-09-26 1964-09-08 Dales George Franklin Thermostat with bimetal set in plastic

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4395694A (en) * 1982-06-23 1983-07-26 Portage Electric Products, Inc. Thermostat construction employing aramide insulation
US4486733A (en) * 1982-09-29 1984-12-04 Eaton Corporation Thermal mechanism with ambient compensating bimetal providing trip force
USD278050S (en) 1982-10-25 1985-03-19 Leviton Manufacturing Co. Inc. Thermal detector
CN105308710A (zh) * 2013-04-19 2016-02-03 泰科电子日本合同会社 保护装置
US20160086753A1 (en) * 2013-04-19 2016-03-24 Tyco Electronics Japan G.K. Protection Device
CN105308710B (zh) * 2013-04-19 2018-08-07 泰科电子日本合同会社 保护装置
US10283295B2 (en) * 2013-04-19 2019-05-07 Littelfuse Japan G.K. Protection device
US20170062167A1 (en) * 2013-08-26 2017-03-02 Tyco Electronics Japan G.K. Protective Device

Also Published As

Publication number Publication date
AU458613B2 (en) 1975-02-06
FR2125521B1 (enExample) 1975-10-24
AU3904072A (en) 1973-08-23
FR2125521A1 (enExample) 1972-09-29
CA956682A (en) 1974-10-22
GB1357044A (en) 1974-06-19

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AS Assignment

Owner name: BANKERS TRUST COMPANY, NEW YORK

Free format text: SECURITY INTEREST;ASSIGNOR:ROBERTSHAW CONTROLS COMPANY A CORP. OF DELAWARE;REEL/FRAME:005758/0075

Effective date: 19900730