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US3023350A - Electrical switch means - Google Patents

Electrical switch means Download PDF

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Publication number
US3023350A
US3023350A US803282A US80328259A US3023350A US 3023350 A US3023350 A US 3023350A US 803282 A US803282 A US 803282A US 80328259 A US80328259 A US 80328259A US 3023350 A US3023350 A US 3023350A
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United States
Prior art keywords
thermally responsive
switch
motor
heater
responsive device
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
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US803282A
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English (en)
Inventor
William A Broadley
Edward P Jastram Jr
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Texas Instruments Inc
Original Assignee
Texas Instruments Inc
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Filing date
Publication date
Application filed by Texas Instruments Inc filed Critical Texas Instruments Inc
Priority to US803282A priority Critical patent/US3023350A/en
Priority to FR822929A priority patent/FR1252490A/fr
Priority to NL249998A priority patent/NL249998A/xx
Priority to GB11424/60A priority patent/GB952330A/en
Application granted granted Critical
Publication of US3023350A publication Critical patent/US3023350A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H61/00—Electrothermal relays
    • H01H61/002—Structural combination of a time delay electrothermal relay with an electrothermal protective relay, e.g. a start relay
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B31/00—Compressor arrangements
    • F25B31/006—Cooling of compressor or motor
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H37/00—Thermally-actuated switches
    • H01H37/02—Details
    • H01H37/32—Thermally-sensitive members
    • H01H37/52—Thermally-sensitive members actuated due to deflection of bimetallic element
    • H01H37/54—Thermally-sensitive members actuated due to deflection of bimetallic element wherein the bimetallic element is inherently snap acting
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K11/00—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection
    • H02K11/20—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection for measuring, monitoring, testing, protecting or switching
    • H02K11/25—Devices for sensing temperature, or actuated thereby
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2500/00—Problems to be solved
    • F25B2500/08—Exceeding a certain temperature value in a refrigeration component or cycle
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H37/00—Thermally-actuated switches
    • H01H37/02—Details
    • H01H37/32—Thermally-sensitive members
    • H01H37/52—Thermally-sensitive members actuated due to deflection of bimetallic element
    • H01H37/54—Thermally-sensitive members actuated due to deflection of bimetallic element wherein the bimetallic element is inherently snap acting
    • H01H2037/5463—Thermally-sensitive members actuated due to deflection of bimetallic element wherein the bimetallic element is inherently snap acting the bimetallic snap element forming part of switched circuit

Definitions

  • This invention relates to the protection of electric motors, and more particularly, to means providing protection against overheating of electric motors which are subject to the heat-transfer influence of the convective flow of a fluid medium and electric motors in environments wherein ambient temperature conditions vary widely.
  • thermally responsive device In protecting electric motors against overheating, it has been the practice to provide a thermally responsive device operatively connected to disconnect the motor electrically under fault conditions before the latter overheats.
  • a further object of the invention is the provision of an improved, sealed, thermally responsive protective device which is adapted to be responsive to changes in the heat-transfer influence of the convective flow of a fluid medium at substantially a. rate of response proportional to that of the means to be protected which is exposed to said convective flow.
  • a further object of the invention is the provision of such an improved sealed, thermally-responsive device which is relatively compact and inexpensive.
  • a further object of the invention is to provide an improved combination including at least one motor Winding exposed to the heat-transfer influence of the convective flow of a fluid medium and protected by a sealed, thermally responsive device which is adapted to be responsive to said influence at a rate substantially the same as that at which said motor winding is responsive.
  • FIG. 1 is a schematic view of an electrical circuit having portions disposed within a compressor unit, all according to a first embodiment of the invention
  • FIG. 2 is an elevational view in section of a thermally responsive device sealed Within a casing and having a heater wire wrapped about the outside of the casing, corresponding parts being included schematically in FIG. 1;
  • FIG. 3 is a sectional view taken along line 33 in FIG. 2;
  • FIG. 4 is a bottom plan view of the structure shown in FIG. 3;
  • FIG. 5 is a schematic view of an electrical circuit according to a second embodiment of the invention.
  • FIG. 6 is an elevational view with parts broken away of a thermally responsive switch having three electric heaters wrapped about the outside of the casing thereof, corresponding parts being included schematically in FIG. 5;
  • FIG. 7 is a schematic view of an electrical circuit according to a third embodiment of the invention.
  • FIG. 8 is an elevational view in section of a thermally responsive device sealed within a casing and having a heater wire wrapped about the outside of the casing, corresponding parts being included schematically in FIG. 7;
  • FIG. 9 is a sectional view taken along line 9-9 in FIG. 8;
  • FIG. 10 is a sectional view taken along line 10-10 in FIG. 8;
  • FIG. 11 is a schematic view of an electrical circuit according to a fourth embodiment of the invention.
  • FIG. 12 is a top plan view of a thermally responsive switch, corresponding parts being included schematically in FIG. 11;
  • FIG. 13 is an elevational view thereof
  • FIG. 14 is a sectional view taken along line 1414 in FIG. 13;
  • FIGS. 15 and 16 are sectional views taken along lines 1515 and 1616, respectively, in FIG. 14.
  • the situation whereby the motor winding or windings are subject to the heat-transfer influence of the convective flow of a fluid medium arises not infrequently in a number of different installations.
  • the fluid medium may be at a higher or lower temperature than the winding or windings of the motor when under quiescent conditions and may even fluctuate between such higher and lower temperatures.
  • the convective flow of the fluid medium may result directly or indirectly from operation of the motor or may be totally independent of operation of the motor.
  • the instant invention is applicable in all of these cases.
  • the term sealed as employed throughout the specification is intended to include sealing against entry of at least one or more of the following, individually or in combination: moisture, refrigerant fluids, impregnating media such as varnishes, resins or the like and their vapors, lubricants and fuels and their vapors and other deleterious substances.
  • FIG. 1 in which an arrangement according to a first embodiment of the invention is shown, the two sides of a single-phase, electrical current supply source are indicated by the reference numerals 20 and 22.
  • the circuitry of FIG. 1 includes an on-off switch 24 and a contactor which may take the form of an electromagnetic relay generally indicated by the reference numeral 26.
  • Contacts 28 and coil 30 of relay 26 are electrically connected in parallel circuit arrangement with respect to each other and in series circuit relation to switch 24.
  • bridging member 32 thereof movesinto engagement with and electrically connects contacts 28.
  • One terminal 34 of an electric heater 36 is connected in series with contacts 28 of the relay, and the other terminal 38 of heater 36 is electrically connected in series with each of windings 40 and 42 of an electric motor 43.
  • Motor 43 may be of the split-phase type, winding 40 being the main winding and winding 42 being the auxiliary or start winding. It will be understood that a displacement of the phase angle between windings 40 and 42 can be effected in any desired manner such as by the use of capacitors, inductors, etc.
  • Start winding 42 is disposed in series with a start winding switch means 44 which may be in the form of a centrifugal switch or a starting relay to de-energize the start winding 42 as the motor comes up to speed.
  • Motor winding 40 is connected to the other side 22 of the current supply source as is start winding 42 through switch means 44.
  • Thermally responsive switch 46 includes a thermally responsive device 48 operatively connected through a motion-transfer member 50 to effect opening and closing of a switch 52.
  • electric heater 36 is disposed in heat-transfer relation to thermally responsive device 48.
  • Thermally responsive switch 46 includes a pair of terminals 54 and 56, the former being connected to side 20 of the current source through relay coil 30 and switch 24 and the latter being connected to side 22 of the current source.
  • thermally responsive switch 46 includes a cup-shaped casing member 58 formed of a material having a comparatively high heat conductivity such as, for example, copper or steel. Cup-shaped casing member 58 is provided with an internal, inwardly-directed shoulder 60 about its inner periphery.
  • Thermally responsive device 48 of the thermally responsive switch 46 takes the form of a conventional thermostatic disc.
  • Disc 48 is formed in a well-known manner with at least two layers or components, one having a higher coefiicient of thermal expansion than the other so that upon heating thereof the disc snaps from one position of stability to another. Upon cooling thereof, the disc will snap back to the opposite position of stability.
  • the high expansion layer or component of disc 48 as viewed in FIG.
  • cup-shaped member 62 is disposed within cup-shaped member 58 and is snugly fitted therein so as to prevent relative movement therebetween.
  • Cupshaped member 62 is formed of one of the conventional, electrically insulating plastics.
  • the outer peripheral surface portion of cup-shaped member 62 adjacent shoulder 60 of cup-shaped member 58 is spaced from this shoulder for the reception of the radially outer marginal portions of disc 48.
  • Cup-shaped member 62 is provided with an aperture 64 through which transfer pin 50 extends.
  • Transfer pin 50 includes a reduced-diameter portion 66 which extends through an aperture 68 in a movable contact-carrying arm 70 of the switch generally indicated by the reference numeral 52. Transfer pin 50 interfits sufiiciently loosely with apertures 64 and 68 to prevent jamming of the transfer pin in either of these apertures.
  • Contact-carrying member 70 is supported at one end in cantilever fashion by a member 72 having a distal or outer end terminating in an electrical terminal 56.
  • Member 70 carries a movable contact 76 for engagement with a stationary contact 78 supported by a member 80 which terminates at its distal or outer end with an electrical terminal 54.
  • Contact-carrying member 70 is inherently resiliently biased to the contacts-open position shown in broken lines in FIG.
  • Thermally responsive switch 46 further includes a header or casing cover member 82.
  • a section of glass 84 is bonded to the mutually adjacent portions of header member 82 and to each of members 72 and 80 thereby to support members 72 and 80 within apertures 86 and 88, respectively, of header member 82 with a conventional glass-to-metal seal.
  • Header member 82 provides an internal shoulder 90 about its inner periphery for the seating of the adjacent or open end of cup-shaped members 58 and 62.
  • the mutually engaged portions of cup-shaped member 58 and header member 82 are sealed to each other by soldering, brazing or welding or the like to provide a sealed casing including cupshaped member 58, header member 82 and glass sections 84.
  • the casing of thermally responsive switch 46 may include a thin layer of electrical insulating material 92 such as fish paper or Mylar (the latter being a registered trademark for a film of polyethylene terephthalate resin) wrapped about and in engagement with the exterior surface of cup-shaped member 58 and portions of header member 82; this insulating layer being of a relatively small thickness so as to offer as little resistance to the flow of heat therethrough as conveniently possible.
  • the electric heater 36 as shown in FIGS. 2-4 may, as one example, take the form of a coil of electrical insulation coated wire having a significant electrical resistivity so as to be heated upon the passage of electrical current therethrough.
  • the terminals 34 and 38 of electric heater 36 as well as terminals 54 and 56 of thermally responsive switch 46 as shown in FIGS. 2 and 4 are adapted for electrical connection as shown in the diagrammatic circuit of FIG. 1.
  • Heater 36 is disposed in thermally conductive juxtaposition against the casing of thermally responsive switch 46 such as, for example, wrapped thereahout so as to he in heat-transfer relation to thermally responsive device 48.
  • thermally responsive device 48 is in heat-transfer relation with the casing 58 of thermally responsive switch 46 and the latter is in heat-transfer relation with heater 36. Accordingly, upon heating of heater 36, heat will be transferred therefrom through the layer of electrical insulating material 92, through and along cup-shaped member 58, to thermally responsive device 48.
  • the heater for this could be in the form of a length of insulation coated electrically conductive foil wrapped about or otherwise disposed in thermally conductive juxtaposition against the outside of the casing of the thermally responsive switch in heat-transfer relation to the thermally responsive device.
  • cup-shaped member 58 can be soldered, brazed, welded or the like to a supporting strap or plate 94 within an interfitting aperture 96 therein. It will be understood that thermally responsive switch 46 may be mounted against windings 40 and 42 of the motor or otherwise in good heat-transfer relation therewith such as, for example, by being mounted against the end bell of the motor.
  • thermally responsive switch 46, heater 36 and motor 43, along with a pump 100, are disposed within the housing 162 of a compressor unit generally designated by the reference numeral 184.
  • start winding switch 44 will be located outside housing 102 rather than inside as shown in FIG. 1, but this feature does not form a part of and has no bearing on the instant invention.
  • the electric motor is operatively connected for driving pump 100 to effect the flow of a fluid medium which may take the form of a refrigerant from an inlet 106 in housing 102 through the housing and past an outlet 168 in the housing.
  • Motor windings 40 and 42 are exposed to and lie in the path of the refrigerant flow through the housing.
  • the refrigerant being generally at a substantially lower temperature than the motor windings, takes heat from the windings and by convection carries this heat out of the housing.
  • This arrangement significantly increases the allowable current rating of the motor as compared with the corresponding allowable current rating of the motor when it is not so cooled by the convective flow of refrigerant.
  • Thermally responsive device 48 which along with switch 52, is disposed within a casing which is sealed to prevent the entry of moisture, refrigerant, etc., and is therefore not exposed to this convective flow. Consequently, thermally responsive device 43 is cooled very slowly by the convective flow of refrigerant through the housing. Thermally responsive device 48 is heated, in large part at least, by electric heater 36 and since this heater lies in the path of and is exposed to said convective flow of refrigerant, the cooling effect on the heater is reflected substantially as rapidly on the heater and in turn on the thermally responsive device as on the motor windings. This is not to imply, of course, that thermally responsive device 48 must heat or cool at the same rate as one or more of the motor windings.
  • relay coil 30 In operation, switch 52 being normally closed, relay coil 30 will be electrically energised upon closing of switch 24.
  • thermally responsive device 48 upon motor windings 40 and 42 approaching the condition of the overheating due to a fault, thermally responsive device 48 will be heated to its tripping temperature whereupon the latter trips to the broken-line position shown in FIG, 2 thereby to open contacts 76, 78 which in turn de-energize relay winding 30 to effect dropout of relay 26 and de-energization of windings 40 and 42 along with heater 36.
  • heater 36 in series with start winding 42 of the motor as well as with main winding 40, the heat-transfer effect of the convective flow on the start winding as well as on the main winding will be reflected upon the rate at which the heater 36 heats thermally responsive device 48 during starting of the motor as well as during a locked rotor condition or upon failure of switch 44 to open when the motor comes up to speed.
  • heater 36 could be electrically connected in parallel circuit relation with start winding 42 (while still in series with main winding 40) so as not to carry the start winding current.
  • a compressor unit 104 as set forth herein is adapted for operative connection in a cooling system including a condensor and an evaporator (along with other accouterment) in a number of different installations such, for example, as refrigerators, freezers, air conditioners, etc.
  • a cooling system including a condensor and an evaporator (along with other accouterment) in a number of different installations such, for example, as refrigerators, freezers, air conditioners, etc.
  • the cooling effect of the convective flow of refrigerant on the motor windings would, ordinarily at least, be substantially less during operation as a heating apparatus than during operation as a cooling apparatus due, for the most part, to the lower rate of flow and higher temperature of the refrigerant.
  • the invention is equally applicable to this condition because a change in the heat-transfer effect of the convective fiow is reflected on the thermally responsive device substantially as fast as it is on the motor windings whether the change is due to reversal of the refriger ating cycle or otherwise.
  • Some examples of other conditions which would result in changes in the heat-transfer effect of the convective flow would be an increase or de crease in the temperature of the convective flow and an increase or decrease in the quantitative rate of the flow (including stoppage of the convective flow)
  • Thermally responsive switch 122 includes a thermally responsive device 124 operatively connected through a motiontransfer member 126 to open and close a switch 128.
  • Thermally responsive switch 122 is or may be substantially identical with thermally responsive switch 46 of the embodiment of FIGS. 1-4 described above. Refer ring to FIG. 6, thermally responsive switch 122 may be mounted on a supporting member 130 in a manner similar to that described with respect to the preceding embodiment.
  • each of heaters 132, 134 and 136 are provided, each of which if desired, can be covered with a coating of electrical insulation and each of which is disposed in heat-transfer relation to the thermally responsive device 124 of the thermally responsive switch 122.
  • each of heaters 132, 134 and 136 is disposed in thermally conductive juxtaposition against the sealed casing of the thermally responsive switch 122 such as, for example, wrapped thereabout so as to transfer heat to thermally responsive device 124 in the manner described above with respect to the embodiment of FIGS. l-4.
  • heater 132 is connected in series circuit relation with a first three-phase motor winding 138 and spaced contacts 140 of relay 118 to line 110; heater 134 is connected in series with motor winding 142 and spaced contacts 144 of relay 118 to line 112 and heater 136 is connected in series with motor winding 146 through spaced contacts 148 of relay 118 to line 114.
  • the three-phase motor 149 which includes windings 138, 142 and 146 is operatively connected to drive pump 150 for pumping a convective How of refrigerant from inlet 152 of the housing 154 of a compressor unit generally designated by the reference numeral 156, through the housing in heat-transfer relation to motor windings 138, 142 and 146 as well as to heaters 132, 134 and 136, and out of housing 154 through outlet 158 therein.
  • thermally responsive device 124 is heated, in large part at least, by heaters 132, 134 and 136, with the latter exposed to and lying in the path of the same convective flow as motor windings 138, 142 and 146, changes in the heat-transfer effect of the convective fiow will be reflected on the thermally responsive device substantially as rapidly as on the motor windings.
  • heating and cooling of the thermally responsive device 124 take place at a rate substantially proportional to that which heating and cooling of the motor windings take place.
  • Thermally responsive switch 122 as well as each of the thermally responsive switches of each of the other embodiments, may be disposed in heat-transfer relation with the motor windings of the associated motor so as to transfer a significant amount of heat from the motor windings to the thermally responsive device 124.
  • thermally responsive elements 48 and 124, respectively, of the thermally responsive switches 46 and 122, respectively No electric current is carried by the thermally responsive elements 48 and 124, respectively, of the thermally responsive switches 46 and 122, respectively, according to the two embodiments previously described.
  • the thermally responsive switches of the two embodiments subsequently to be described differ in that the respect ve thermally responsive device carries the current flowing through the motor winding or windings with which it and one or more respective heaters are respectively connected in series circuit relation.
  • reference numerals 160 and 162 designate the two sides of a single-phase electrical current supply source.
  • a terminal 164 of a thermally responsive switch generally designated by the reference numeral 166 is connected through an on-ofi switch 168 to side 162 of the current supply source.
  • the other terminal 170 of thermally responsive switch 166 is connected to an electric heater 172, the latter being disposed in heat-transfer relation to a thermally responsive device 174 of thermally responsive switch 166 as will later be described more in detail with respect to FIGS. 8-10.
  • Heater 172 is electrically connected in series circuit relationship with each of main winding 175 and auxiliary or start winding 176 of a split-phase electric motor 177; windings 175 and 176 being connected in parallel relationship with each other.
  • a start-winding switch means 178 is connected in series with start winding 176 for deenergizing the latter as the motor comes up to speed.
  • Main winding 175 is connected to the other side 160 of the current supply line as is start winding 176 through switch means 178.
  • thermally responsive switch 166 includes a generally rectangular, cup-shaped casing member 180 formed of a material having a high heat conductivity such as, for example, copper or steel.
  • the open end of casing member 180 is closed by a header or cover member 182, flanges 184 and 186 provide respectively by these casing members being sealed together as by welding to provide a sealed casing.
  • a section of glass 188 is bonded to the mutually adjacent portions of header member 182 and each of terminals 164 and 170 thereby to support these terminals within apertures 190 and 192, respectively, of header member 182 with a conventional glass-to-metal seal.
  • a cup-shaped member 194 formed of a conventional material such as moldable, electrically insulating material is disposed within the casing of thermally responsive switch 166.
  • a pair of headed studs 196 and 198 extend through interfitting apertures in cup-shaped member 194. Stud 196 is welded at one end to a strap 200 and stud 198 is welded at one end to a strap 202. Straps 200 and 202 are welded to terminals 164 and 170, respectively, thereby to support cup-shaped member 194 and the parts fixed with respect thereto within the casing of thermally responsive switch 166 and electrically to connect each of studs 196 and 198 to a respective terminal 164 and 170.
  • each of studs 196 and 198 Threadedly engaged with a tapped hole 209 in cup-shaped member 194 is a post 208 which is secured in adjusted relation to cup-shaped member 194 by means of a lock nut 210.
  • Post 208 includes a reduced-diameter portion 212 extending loosely through an aperture 214 in thermally responsive device 174.
  • Thermally responsive device 174 is loosely confined between a flange 216 and a headed over portion 218 provided by thepost 208.
  • the thermally responsive device 174 is formed in a conventional manner of two or more layers or components having respectively different coefficients of thermal expansion so as to be snappable from a first position of stability to a second position of stability upon being heated to a predetermined temperature and snappable back to said first condition upon being cooled to a predetermined temperature.
  • Thermally responsive device 174 carries a pair of movable contacts 220 and 222, these movable contacts being engaged with stationary contacts 204 and 206 when the thermally responsive device is in said first condition in the solid line position in FIG. 10 and being spaced from and electrically disconnected from contacts 204 and 206, respectively, when in said second condition as shown by the dashed-line position in FIG. 10.
  • Thermally responsive device 174 includes opposed ears 221 and 223 as clearly shown in FIG. 8, respectively, which interfit loosely with grooves 225 and 227 provided by member 194 thereby preventing substantial rotation of the thermally responsive device about post 208.
  • cup-shaped member 180 as in the species of FIGS. l-4 may be wrapped with or may otherwise have disposed thereabout a layer of electrical insulating material 224 such as fish paper or Mylar which is of a minimum thickness so as to offer as little resistance to the flow of heat therethrough as is conveniently possible.
  • Electric heater 172 is coated with a thin layer of electrical insulation and is disposed in heat-transfer relation to thermally responsive device 174 through the casing such as, for example, by wrapping the electric heater about and disposing it in engagement with the outer surface of the casing.
  • thermally responsive device 174 The layers or components of which thermally responsive device 174 is formed can be and most often are of a significant electrical resistance so as to be heated in part by the flow of current therethrough.
  • electric motor 177 is operatively connected to drive a pump 226 for pumping the refrigerant of a refrigerating system from an inlet 228, through the housing 230 of a compressor unit generally designated by the reference numeral 232, and past an outlet 234 in the housing.
  • Windings and 176 as well as heater 172 lie in the path of and are exposed to the flow of refrigerant through the housing.
  • the heat transfer effect of the convective flow of refrigerant will be reflected upon heater 172 substantially as rapidly as upon windings 175 and 176 so as to have a proportional cooling effect on the thermally responsive device 174.
  • switch 168 is closed to energize main winding 175 and start winding 176, it being noted that both the main and start winding currents flow through heater 172 and thermally responsive device 174.
  • the thermally responsive device will be heated, in part, to
  • thermally responsive device 174 Upon either or both of windings 175 and 176 approaching the condition of overheating, thermally responsive device 174 will snap from the contacts-closed position to the contacts-open position electrically to deenergize windings 175 and 176 as well as heater 172, which snap-action will take place regardless of changes in the heat-transfer effect of the convective flow of refrigerant. As with the embodiment of FIGS.
  • heater 172 could be disposed so as to be in parallel circuit relation with start winding 176 (while still in series with main winding 175), if desired.
  • the provision of the external heater or heaters wrapped around and in heat-transfer relation to the casing of the sealed thermally responsive switching means 46 and 122, 166 described above additionally has the advantage of enabling production of a protective sealed device which is smaller, more compact and less expensive than that which would be possible with a sealed protective device having such heaters sealed internally therein.
  • a three-phase on-off switch generally designated by the reference numeral 241 includes three pairs of mutually spaced contacts 242, 244 and 246, respectively.
  • a first terminal 248 of a thermally responsive switch generally designated by the reference numeral 250 is disposed in series circuit relation with an electric heater 252 and a three-phase motor winding 254 through contacts 244 to line 238.
  • Another terminal 256 of thermally responsive switch 250 is electrically connected in series circuit relationship with an electric heater 258 and a three-phase motor winding 260 through contacts 246 to line 240.
  • thermally responsive switch 250 is electrically connected in series circuit relationship with a third three-phase motor winding 264 through contacts 242 to line 236.
  • No electric heater is included in the current flow path between terminal 262 and contacts 242 for the reasons described above with respect to the embodiment shown in FIGS. and 6.
  • Such a third electric heater could be added if a neutral, fourth wire to ground were added or if otherwise desired.
  • the thermally responsive switch according to the invention may be provided with internal heating means and may include one or more internal heaters sealed within the casing along with the thermally responsive device.
  • Thermally responsive switch 250 as schematically shown in FIG. 11, includes three internal heaters 266, 268 and 270, each electrically connected to a stationary electrical contact 272, 274 and 276, respectively.
  • Thermally responsive switch 250 further includes a thermally responsive device 312 carrying three movable contacts 273, 275 and 277, for engagement respectively with stationary contacts 272, 274 and 276.
  • thermally responsive switch 250 includes a cup-shaped casing member 280 formed of a material having a comparatively high thermal conductivity.
  • Casing member 280 provides an internal shoulder 282 for the reception of a radially outer marginal portion of a header or casing cover member 284.
  • the mutually contiguous portions of cup-shaped member 280 and header 284 are sealed to each other such as by welding.
  • a section of glass 286 is bonded to the mutually adjacent portions of header member 284 and each of terminals 248, 256 and 262 thereby to support these terminals within apertures 288, 290 and 292, respectively, of the header member with a conventional glass-to-metal seal.
  • Cup-shaped member 294 Disposed within the casing provided by casing member 280 and header 284 is a generally cup-shaped member designated by the reference numeral 294.
  • Cup-shaped member 294 is formed of a conventional moldable electrical insulating material and is provided with a plurality of apertures 295, 297, 299 and adjacent shoulders 295a, 297a, 299a.
  • Each set of apertures and shoulders 295, 295a; 297, 297a; and 299, 299a, respectively co-operatively interfits with and fixedly mounts an electrically conductive member 296, 298 and 300, respectively.
  • Members 296, 298 and 300 are in turn respectively connected to, as by welding or the like, and supported by terminals 248, 256 and 262.
  • Cup-shaped member 294 is provided with another set of apertures 301, 303 and 305 and shoulders 301a, 303a and 305a alternately spaced between said apertures 295, 297, 299 and shoulders 295a, 297a and 299a and at a lower elevation as seen in FIG. 14.
  • Each set of apertures and shoulders 301, 301a; 303, 3031:; and 305, 305a interfits with and receives respectively contact providing members 302, 304 and 306.
  • Each of members 302, 304 and 306 includes a turnedover portion providing respectively contacts 272, 274 and 276.
  • internal electric heater 266 electrically connects contact 272 with member 296, internal electric heater 268 electrically connects contact 274 with member 298, and internal electric heater 270 electrically connects contact 276 with member 300.
  • a post 308 is fixedly secured in threaded engagement with cup-shaped member 294 by means of a lock nut 310.
  • Thermally responsive device 312 provides a substantially centrally located aperture 314 within which is disposed a reduced diameter portion 316 of the post 308.
  • Thermally responsive device 312 is loosely confined between an adjacent shoulder 318 and a headed end 320 provided by the post. Substantial rotation of thermally responsive device 312 about the axis of post 308 is prevented by a plurality of ears 322 projecting radially outwardly from the disc and loosely interfitting with mating recesses 324 provided by cup-shaped member 294 as best seen in FIG. 15.
  • Thermally responsive device 312 is similar to the thermally responsive device of each of the preceding embodiments, and is formed of a plurality of layers or components having mutually different coefiicients of thermal expansion whereby the thermally responsive device snaps from the contacts-closed position as shown in full lines in FIG. 14 to the contacts-open position shown in broken lines in this figure upon being heated to a predetermined temperature, and snaps back to the full-line, contacts-closed position upon being subsequently cooled to a predetermined temperature. As in the embodiment of FIGS. 7-10, thermally responsive device 312 may, and most often does, have sufficient electrical resistance to cause heating thereof due to the flow of motor winding current therethrough.
  • the open end of cup-shaped member 294 is further provided with a shoulder 326 as seen in FIG. 14 for the reception of a circular member 328 formed of electrical insulating material and cemented in place about its periphery to shoulder 326.
  • a thin film 330 of electrical insulating material such as fish paper or Mylar may be wrapped about the outer surface of cup-shaped member 280.
  • External heaters 252 and 258 are covered with a thin layer of electrical insulation and are disposed in thermally conductive juxtaposition against the exterior of the casing of thermally responsive switch 250, such as by wrapping said heaters thereabout so as to dispose said heaters in heat-transfer relation to the thermally responsive device 312 through the casing.
  • three-phase electric motor 331 which includes windings 254, 260 and 264 is operatively connected to drive a pump 332 for pumping the refrigerant of the refrigerating system from an inlet 334 of the housing 336 of a compressor unit generally designated by the reference numeral 338, through the housing 336 and past the outlet 340 of housing 336, the latter also forming the outlet of pump 332
  • thermally responsive device 312 is enclosed within a sealed casing and is therefore not as rapidly cooled by the convective flow as are the motor windings or heaters 252 and 258. However, since heaters 252 and 258 are in heat-transfer relation with the thermally responsive device, changes in the heat-transfer efiect of the convective flow will be reflected on the thermally responsive device 312 substantially as rapidly as upon the motor windings.
  • an electric motor having at least one winding; said winding lying in the path of and being exposed to the convective flow of a fluid medium; electric heater means; an electric switch; said motor winding, heater means and switch being electrically connected in series circuit relation with each other; a thermally responsive device operatively connected for opening said switch upon reaching a predetermined temperature; and a sealed casing encompassing said thermally responsive device; said heater means being associated with said casing in heattransfer relation to said thermally responsive device and lying in the path of and being exposed to the convective flow of said fluid medium.
  • an electric motor having at least one winding, said winding lying in the path of and being exposed to the convective flow of a fluid medium; an electric heater electrically connected in the same electrical circuit as said winding, a thermally responsive device operatively connected for opening said electrical circuit upon reaching a predetermined temperature, and a sealed casmg encompassing said thermally responsive device, said heater being associated with said casing in heat-transfer relation to said thermally responsive device and lying in the path of and being exposed to the convective flow of said fluid medium.
  • a compressor unit for pumping the refrigerant of a refrigerating system; an electric motor having at least one Winding lying in the path of refrigerant flow through said unit; an electric heater and an electric switch electrically connected in series circuit arrangement with each other and with said winding; a thermally responsive device operatively connected for opening said switch upon reaching a predetermined temperature; and a sealed 12 casing encompassing said thermally responsive device, said heater being associated with said casing in heat transfer relation to said thermally responsive device and lying in said path of and being exposed to said refrigerant flow through said unit.
  • a compressor unit for pumping the refrigerant of a refrigerating system comprising an electric motor having at least one winding lying in the path of and being exposed to the convective flow of a fluid medium; electrical heater means; electric switch means; said motor winding; heater means and switch means being electrically connected in series circuit relation with each other; a thermally responsive device for opening and closing said switch means at predetermined temperature conditions, said thermally responsive device being enclosed within a sealed casing, said heater means being associated with said casing in heat-transfer relation to said thermally responsive device and lying in the path of and being exposed to the convective flow of a fluid medium.
  • a protective device for an electric motor having at least one winding electric heater means, said means and said winding; lying in the path of and being exposed to the convective flow of a fluid medium; electric switch means; said motor winding, heater means and switch means being electrically connected together in series circuit relation, said protective device including thermally responsive means for opening said switch means at predetermined temperature conditions, sealed casing means enclosing said thermally responsive means, said heater means being operatively associated with said casing means in heat-transfer relation to said thermally responsive means.
  • said motor comprises a main winding and a starting winding electrically connected in series circuit with each other and with said heater means and said switch means.
  • said electric motor comprises a main winding and start winding electrically connected to each other in parallel circuit relationship and in series circuit relationship with said heater means and said switch means.
  • thermally responsive device comprises a plurality of internal heaters enclosed with said thermally responsive device in said sealed casing.
  • a protective device adapted to be connected to an electric motor having at least one winding lying in the path of and being exposed to the convective flow of a fluid medium; said protective device comprising electric switch means; heater means for said switch means; said heater means, switch means and motor winding being electrically connectable together in series circuit relation; thermally responsive means associated with said protective device for opening said switch means at predetermined conditions; sealed thermally conductive casing means enclosing said thermally responsive means; said heater means being operatively associated with said casing means externally thereof and in heat-transfer relation to said thermally responsive means and exposed to the said convective flow of a fluid medium when elec- 13 trically connected in series circuit relation with said motor Winding.
  • a protective device adapted to be connected to an electric motor having at least one winding lying in the path of and being exposed to the convective flow of a fluid medium; said protective device comprising a thermally responsive means operative to control an electrical circuit for Said motor at predetermined conditions; said means being disposed within a switch housing; heater means for said thermally responsive means; said heater means, thermally responsive means and motor winding being electrically connectable together in series circuit relation; and said heater means being proximally disposed adjacent said switch housing externally thereof in heat-transfer relation to said thermally responsive means and directly exposed to the said convective flow of a fluid medium when electrically con- 5 nected in series circuit relation with said motor winding.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Protection Of Generators And Motors (AREA)
US803282A 1959-03-31 1959-03-31 Electrical switch means Expired - Lifetime US3023350A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US803282A US3023350A (en) 1959-03-31 1959-03-31 Electrical switch means
FR822929A FR1252490A (fr) 1959-03-31 1960-03-30 Dispositif de protection pour moteur électrique
NL249998A NL249998A (nl) 1959-03-31 1960-03-31 Inrichting voor het beschermen van elektromotoren tegen overhitting
GB11424/60A GB952330A (en) 1959-03-31 1960-03-31 Thermally-responsive electrical switch means

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US803282A US3023350A (en) 1959-03-31 1959-03-31 Electrical switch means

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US3023350A true US3023350A (en) 1962-02-27

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US (1) US3023350A (fr)
FR (1) FR1252490A (fr)
GB (1) GB952330A (fr)
NL (1) NL249998A (fr)

Cited By (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3192345A (en) * 1961-04-18 1965-06-29 Texas Instruments Inc Plural heater unit thermally responsive motor protector
US3219856A (en) * 1962-10-23 1965-11-23 Gen Electric Motor thermal protection system
US3240908A (en) * 1960-12-19 1966-03-15 Texas Instruments Inc Thermostatic switches
US3246104A (en) * 1961-03-06 1966-04-12 Texas Instruments Inc Electrical switch having an external wrap-around resistance heater
US3255397A (en) * 1962-10-29 1966-06-07 Texas Instruments Inc Motor protection
US3263049A (en) * 1964-04-13 1966-07-26 Texas Instruments Inc Miniaturized, vibration resistant, thermally responsive electrical switch
US3272943A (en) * 1964-02-06 1966-09-13 Calor App Electro Domestiques Electric shaver control assembly
US3352986A (en) * 1962-11-30 1967-11-14 Texas Instruments Inc Vibration resistant construction for thermally responsive electrical switches
US3370201A (en) * 1965-03-29 1968-02-20 Task Corp Overload protective circuit for electrical machinery
US3445725A (en) * 1967-02-02 1969-05-20 Whirlpool Co Solid state lock-out circuit for compressor
US3489976A (en) * 1966-01-03 1970-01-13 Texas Instruments Inc Self-protected time delay relay
US3496511A (en) * 1968-01-15 1970-02-17 Elmwood Sensors Thermostatic switch for small electrical appliances
US3530419A (en) * 1968-03-21 1970-09-22 Fasco Industries Thermostat
US3649943A (en) * 1970-04-21 1972-03-14 Victor G Matto Thermal switch
US3963962A (en) * 1973-12-18 1976-06-15 Texas Instruments Incorporated Motor protector
US4034265A (en) * 1973-06-18 1977-07-05 Essex International, Inc. Electric motor protector
US5509786A (en) * 1992-07-01 1996-04-23 Ubukata Industries Co., Ltd. Thermal protector mounting structure for hermetic refrigeration compressors
EP0890967A2 (fr) * 1997-07-10 1999-01-13 Texas Instruments Incorporated Dispositif pour le démarrage et la protection d'un moteur
US5973587A (en) * 1997-06-26 1999-10-26 Hofsaess; Marcel Temperature-dependent switch having a contact bridge
US5986535A (en) * 1998-01-20 1999-11-16 Texas Instruments Incorporated Low cost thermostat apparatus and method for calibrating same
US20070294929A1 (en) * 2006-02-27 2007-12-27 Battenfeld Technologies, Inc. Containers for carrying firearm accessories and/or supporting firearms
EP2352160A1 (fr) * 2008-11-05 2011-08-03 Ubukata Industries Co., Ltd. Dispositif de protection de moteur triphasé
FR3006127A1 (fr) * 2013-05-22 2014-11-28 Valeo Equip Electr Moteur Machine electrique tournante comprenant un module de protection thermique

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1292731B (de) * 1964-08-27 1969-04-17 Licentia Gmbh Thermischer Schnappschalter
US3538379A (en) * 1968-05-06 1970-11-03 Irving Berlin Photo-electric light-activated switch apparatus
GB9107778D0 (en) * 1991-04-12 1991-05-29 Electrolux Northern Fan-cooled electric motor arrangement

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2169989A (en) * 1936-10-29 1939-08-15 Gen Motors Corp Refrigerating apparatus
US2354529A (en) * 1942-06-03 1944-07-25 Edison Inc Thomas A Control device

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2169989A (en) * 1936-10-29 1939-08-15 Gen Motors Corp Refrigerating apparatus
US2354529A (en) * 1942-06-03 1944-07-25 Edison Inc Thomas A Control device

Cited By (26)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3240908A (en) * 1960-12-19 1966-03-15 Texas Instruments Inc Thermostatic switches
US3246104A (en) * 1961-03-06 1966-04-12 Texas Instruments Inc Electrical switch having an external wrap-around resistance heater
US3192345A (en) * 1961-04-18 1965-06-29 Texas Instruments Inc Plural heater unit thermally responsive motor protector
US3219856A (en) * 1962-10-23 1965-11-23 Gen Electric Motor thermal protection system
US3255397A (en) * 1962-10-29 1966-06-07 Texas Instruments Inc Motor protection
US3352986A (en) * 1962-11-30 1967-11-14 Texas Instruments Inc Vibration resistant construction for thermally responsive electrical switches
US3272943A (en) * 1964-02-06 1966-09-13 Calor App Electro Domestiques Electric shaver control assembly
US3263049A (en) * 1964-04-13 1966-07-26 Texas Instruments Inc Miniaturized, vibration resistant, thermally responsive electrical switch
US3370201A (en) * 1965-03-29 1968-02-20 Task Corp Overload protective circuit for electrical machinery
US3489976A (en) * 1966-01-03 1970-01-13 Texas Instruments Inc Self-protected time delay relay
US3445725A (en) * 1967-02-02 1969-05-20 Whirlpool Co Solid state lock-out circuit for compressor
US3496511A (en) * 1968-01-15 1970-02-17 Elmwood Sensors Thermostatic switch for small electrical appliances
US3530419A (en) * 1968-03-21 1970-09-22 Fasco Industries Thermostat
US3649943A (en) * 1970-04-21 1972-03-14 Victor G Matto Thermal switch
US4034265A (en) * 1973-06-18 1977-07-05 Essex International, Inc. Electric motor protector
US3963962A (en) * 1973-12-18 1976-06-15 Texas Instruments Incorporated Motor protector
US5509786A (en) * 1992-07-01 1996-04-23 Ubukata Industries Co., Ltd. Thermal protector mounting structure for hermetic refrigeration compressors
US5973587A (en) * 1997-06-26 1999-10-26 Hofsaess; Marcel Temperature-dependent switch having a contact bridge
EP0890967A3 (fr) * 1997-07-10 1999-06-16 Texas Instruments Incorporated Dispositif pour le démarrage et la protection d'un moteur
EP0890967A2 (fr) * 1997-07-10 1999-01-13 Texas Instruments Incorporated Dispositif pour le démarrage et la protection d'un moteur
US5986535A (en) * 1998-01-20 1999-11-16 Texas Instruments Incorporated Low cost thermostat apparatus and method for calibrating same
US20070294929A1 (en) * 2006-02-27 2007-12-27 Battenfeld Technologies, Inc. Containers for carrying firearm accessories and/or supporting firearms
EP2352160A1 (fr) * 2008-11-05 2011-08-03 Ubukata Industries Co., Ltd. Dispositif de protection de moteur triphasé
EP2352160A4 (fr) * 2008-11-05 2012-12-05 Ubukata Ind Co Ltd Dispositif de protection de moteur triphasé
CN102203894B (zh) * 2008-11-05 2014-03-26 株式会社生方制作所 三相电动机的保护装置
FR3006127A1 (fr) * 2013-05-22 2014-11-28 Valeo Equip Electr Moteur Machine electrique tournante comprenant un module de protection thermique

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GB952330A (en) 1964-03-18
NL249998A (nl) 1964-04-10
FR1252490A (fr) 1961-01-27

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