CA1132696A - Thermal relays particularly for starting single-phase asynchronous motors - Google Patents
Thermal relays particularly for starting single-phase asynchronous motorsInfo
- Publication number
- CA1132696A CA1132696A CA316,216A CA316216A CA1132696A CA 1132696 A CA1132696 A CA 1132696A CA 316216 A CA316216 A CA 316216A CA 1132696 A CA1132696 A CA 1132696A
- Authority
- CA
- Canada
- Prior art keywords
- resistor
- relay
- motor
- housing
- contact means
- 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
Links
Classifications
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H11/00—Apparatus or processes specially adapted for the manufacture of electric switches
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Thermally Actuated Switches (AREA)
- Motor And Converter Starters (AREA)
- Thermistors And Varistors (AREA)
- Compressor (AREA)
Abstract
Abstract of the Disclosure A motor starting relay particularly adapted for use in starting single phase asynchronous motors comprises a re-sistor element of positive temperature coefficient of resistivity which is compactly arranged within a housing and engaged by electrical contact and terminals means of particular structure and of a material of relatively high thermal resistance in a novel way such that power dissipation or loss by the resistor is reduced to a very low level after it has performed its motor starting fuction but so that, at the same time, the resistor is adapted to cool more rapidly after interruption of motor opera-tion to permit prompt motor restarting.
Description
~z~
IMPRoVEMENT IN THERMAL REL~YS PARTICULARLY FOR STARTING
SINGLE-PHASE ASYNC~RCNCUS MOTORS
The present invention relates to improved thermal relays, particularly for use in starting single phase, asynchronous electrical motors in refrigerator compressors and the like. In particular, the invention relates to solid state thermal relays embodying a wafer of a material with a - ;
positive temperature coefficient of electrical resistivity (PTC) of the type well-known to those skilled ln the art.
The invention includes a process for assemblying the relays.
In motor starting, a resistor element of positive 10 temperature coefficient of resistivity is conventionally ~ ~
arranged in series with the start winding of a refrigerator ~ -compressor motor or the like to permit a high initial current in the start winding for starting the motor. The resistor element heats up and stabilizes in a high resistance condition during running of the motor so that the start winding current is reduced to a very low le~el when the start winding has completed its motor starting function. When motor operation is thereafter interrupted by actuation of a motor protector or otherwise, the resistor element cools tores~tfor subsequent restarting of the motor. In that arrangement, th~ operating efficiency of the motor is affected -- to some extend at least --by power dissipation in the resistor element during normal running operation of the motor. Further, if motor restarting is attempted beore the resistor element has sufficiently cooled, the condition of the resistor element may interfere -~ with proper restartiny. It would be desirable to reduce such power dissipation in the resistor element to a very low level and, at the same time, to adapt the resistor to be rapidly cooled after interruption of motor operation to permit prompt restarting of the motor if such restaxting should be desired a short time a~ter the interruption in motor operation has occured.
In accordance with one aspect of the present invention there is provided a motor starting relay for a single-]~o phase motor having star-t and run windings comprising a resistor embodying a material of positive temperature coefficient of resistivity which displays a sharp increase in resistivity when heated above a selected temperature level, a housing of thermally insulating material for the resistor, and a pair of resilient electrically conductive metal contact means electrically engaging respective opposite sides of the resistor for connecting the resistor in series with the start -~ winding of a motor, characterized in that, the contact means are disposed between the housing and the respective opposite sides of the resistor holding most of the resistor surfaces spaced from the houging to retard heat transfer from the resistor directly to the housing, the contact means have at least some electrically conductive metal portions thereof of a material of relatively high thermal resistance to retard heat transfer from the resistor to the housing and from the resistor exteriorly of the housing through thè contact means, and the housing is compact and generally ball-shaped and is proportioned to substantially enclose and closely surround the resistor and substantial portions of the contact means for restricting the thermal mass of the relay as well as the surface to volume ratio of the housing to cooperate with the thermal conductivity characteristics of the contact means so that the relay i.s adapted to li.mit curren-t in the star-t winding of the motor after starting the motor has been completed and - la-Z69~
heat dissipation from the relay is minimized during running of the motor for enhancing operating efficiency of the motor while the cool down period of the relay is also minimized to permit prompt motor restarting if operation of the motor is interrupted.
In accordance with a second aspect of the invention there is provided a method for assembling a motor starting relay comprising the steps of continuing advancing a plurality of thermally insulating open-ended housing cases in sequence relative to each other, to an assembly station, continuously advancing a plurali.ty of terminal means and a plurality of spring means toward each other in sequence in each of two lines and securing the terminal means to respective spring means in each of the lines to form a plurality of contact means, advancing the contact means in each of the two lines to the assembly station to dispose pairs of the contact means within respective housing cases with the spring means thereof in facing relation to each other advancing a plurality of resistor wafers of positive temperature coefficient of resistivity in sequence to the assembly station to dispose respective wafers between pairs of contact means in each of the housing cases, and advancing a plurality of housing lids in the sequence to the assembly station and securing the lids to the respective housings for enclosing the resistor wafers and contact means withln the housings.
`I
lb -`h ~
...
`~ ~13ZB9~
.
.
It is an object of this invention to provide a novel and improved thermal relay for starting electrical motors; to provide such a relay whicll is particularly adapted for starting asynchronous motors for refrigerator compressors; to provide such an improved relav incorporating a resistor elemer.t of positive temperature coefficient of resistivlty wherein the power dissipation as loss in the resistor element during running operation of the motor is reduced to a very low level and wherein the resistor element is also adapted to cool rapidly after interruption of motor operation for promptly resetting the relay for restarting OL the motor; to provide such an improved thermal relay which is adapted for economical assembly; and to provide a novel and improved method for assembling such a relay.
. The present invention will now be described with reference to preferred embodiments of the invention, the description referring to the attached drawings wherein:
Figure 1 shows a top view of the thermal relay according to the invention with the lid removed;
Figure 2 shows a cross sectional view along section
IMPRoVEMENT IN THERMAL REL~YS PARTICULARLY FOR STARTING
SINGLE-PHASE ASYNC~RCNCUS MOTORS
The present invention relates to improved thermal relays, particularly for use in starting single phase, asynchronous electrical motors in refrigerator compressors and the like. In particular, the invention relates to solid state thermal relays embodying a wafer of a material with a - ;
positive temperature coefficient of electrical resistivity (PTC) of the type well-known to those skilled ln the art.
The invention includes a process for assemblying the relays.
In motor starting, a resistor element of positive 10 temperature coefficient of resistivity is conventionally ~ ~
arranged in series with the start winding of a refrigerator ~ -compressor motor or the like to permit a high initial current in the start winding for starting the motor. The resistor element heats up and stabilizes in a high resistance condition during running of the motor so that the start winding current is reduced to a very low le~el when the start winding has completed its motor starting function. When motor operation is thereafter interrupted by actuation of a motor protector or otherwise, the resistor element cools tores~tfor subsequent restarting of the motor. In that arrangement, th~ operating efficiency of the motor is affected -- to some extend at least --by power dissipation in the resistor element during normal running operation of the motor. Further, if motor restarting is attempted beore the resistor element has sufficiently cooled, the condition of the resistor element may interfere -~ with proper restartiny. It would be desirable to reduce such power dissipation in the resistor element to a very low level and, at the same time, to adapt the resistor to be rapidly cooled after interruption of motor operation to permit prompt restarting of the motor if such restaxting should be desired a short time a~ter the interruption in motor operation has occured.
In accordance with one aspect of the present invention there is provided a motor starting relay for a single-]~o phase motor having star-t and run windings comprising a resistor embodying a material of positive temperature coefficient of resistivity which displays a sharp increase in resistivity when heated above a selected temperature level, a housing of thermally insulating material for the resistor, and a pair of resilient electrically conductive metal contact means electrically engaging respective opposite sides of the resistor for connecting the resistor in series with the start -~ winding of a motor, characterized in that, the contact means are disposed between the housing and the respective opposite sides of the resistor holding most of the resistor surfaces spaced from the houging to retard heat transfer from the resistor directly to the housing, the contact means have at least some electrically conductive metal portions thereof of a material of relatively high thermal resistance to retard heat transfer from the resistor to the housing and from the resistor exteriorly of the housing through thè contact means, and the housing is compact and generally ball-shaped and is proportioned to substantially enclose and closely surround the resistor and substantial portions of the contact means for restricting the thermal mass of the relay as well as the surface to volume ratio of the housing to cooperate with the thermal conductivity characteristics of the contact means so that the relay i.s adapted to li.mit curren-t in the star-t winding of the motor after starting the motor has been completed and - la-Z69~
heat dissipation from the relay is minimized during running of the motor for enhancing operating efficiency of the motor while the cool down period of the relay is also minimized to permit prompt motor restarting if operation of the motor is interrupted.
In accordance with a second aspect of the invention there is provided a method for assembling a motor starting relay comprising the steps of continuing advancing a plurality of thermally insulating open-ended housing cases in sequence relative to each other, to an assembly station, continuously advancing a plurali.ty of terminal means and a plurality of spring means toward each other in sequence in each of two lines and securing the terminal means to respective spring means in each of the lines to form a plurality of contact means, advancing the contact means in each of the two lines to the assembly station to dispose pairs of the contact means within respective housing cases with the spring means thereof in facing relation to each other advancing a plurality of resistor wafers of positive temperature coefficient of resistivity in sequence to the assembly station to dispose respective wafers between pairs of contact means in each of the housing cases, and advancing a plurality of housing lids in the sequence to the assembly station and securing the lids to the respective housings for enclosing the resistor wafers and contact means withln the housings.
`I
lb -`h ~
...
`~ ~13ZB9~
.
.
It is an object of this invention to provide a novel and improved thermal relay for starting electrical motors; to provide such a relay whicll is particularly adapted for starting asynchronous motors for refrigerator compressors; to provide such an improved relav incorporating a resistor elemer.t of positive temperature coefficient of resistivlty wherein the power dissipation as loss in the resistor element during running operation of the motor is reduced to a very low level and wherein the resistor element is also adapted to cool rapidly after interruption of motor operation for promptly resetting the relay for restarting OL the motor; to provide such an improved thermal relay which is adapted for economical assembly; and to provide a novel and improved method for assembling such a relay.
. The present invention will now be described with reference to preferred embodiments of the invention, the description referring to the attached drawings wherein:
Figure 1 shows a top view of the thermal relay according to the invention with the lid removed;
Figure 2 shows a cross sectional view along section
2-2 of Figure 1,.with the lid mounted;
~32~
-` Figure 3 shows a cross-sectional view along plane
~32~
-` Figure 3 shows a cross-sectional view along plane
3-3 of ~igure 1, wi th the lid mounted;
Figure 4 shows a top view of the lid partially shown in Figures 2 and 3;
Figure 5 shows a cross section along sec-tion 5-5 of Figure 4;
Figure 6 shows a bottom vlew of the lid of Figure 4;
Figure 7 shows a cross-sectional view along section 7-7 of E'igure 6;
Figure 8 shows a detail of the electric contacts of the relay according to the invention;
Figures 9a and 9b show in detail one of the retention and contact springs with the thermosensitive wafer (PTC) of the relay according to the invention;
Figures 10a, 10b, and 10c show three circuit arrange-ments for the relay according to the invention;
Figures lla, llb and llc show various mechanical forms for mounting the relay according to the invention, and Figure 12 shows schematically an assembly line for the relay according to the invention.
Referring to the drawings, particularly to Figure thereof, the thermal relay 50 according to the invention includes a case 1 of electrically and thermally insulating material inside of which is disposed a wafer 2 of a material with a positi~e coefficient of temperature (PTC) of a type well known to the skilled in the ar-t. ~See for example U.S.
Patents 3,750,082 to P. Peterson et all. issued ~uly 13, 1973 and U.S. Patent 3,842,1~38 to P. Peterson issued October 15, 1974). Preferably the wafer size is relatively small while being sufficient to achieve the desired start winding performance.
~ 1!J~ ~" /~J~
3Z6~6 Where the PTC material comprises a conven-tional doped barium titanate ceramic material having a 130C. Curie temperature, the waEer typically has a diameter of about 0.700 inches and a mass of about 5 yrams for 220 volt motors and smaller, for example 3 grams when adapted for starting 120 volt motors.
The wafer 2 is positioned by ribs 3 made on the inside of the case 1 and by two leaf springs 4, S fastened to electrical connection means 6, 7 to be hereinafter described in greater detail. The springs 4, 5 have fins or arms 4a, 4b and 5_, 5b that make contact with the metallized surfaces 8, 9 respectively as conventionally provided on the wafer 2.
The elec-trical connection means 6, 7 are joined with upper "quick-connect" type terminals 10, 10', 11, 11' and with resilient, lower "plug-on" connectors 12, 13 arranged so as to be self-adjusting when inserted on the pins 51.1 on an airtight connector (fusite) of a refrigerator compressor, as denoted at 51 or on a suitable terminal board. Furthermore, the electrical connection means 6, 7 are held in position by projec-tions or ribs 14, 15 and 16, 17 made on the inside of case 1. On the outside of case 1, apertures 18, 19 are provided which engage detents or tongues ~ormed on the lid of the device. The said tongues are not shown in Figure 1.
Figure 2 shows a cross section along section 2-2 of Figure 1, showing lid 20 in position on case 1. The broken line 21 shows the course of the otherwise unillustra-ted part of lid 20. It can be seen there that the curved part 20a joins with a knurled fla-t part 20b so as to facilitate the insertion of the device of the invention of-the pins 51.1 of the airtight connec-tor 51 or other electrical connec~ion device.
~13Z6~
Figure 3 shows a cross section alony section 3-3 of Figure 1 wherein the device in question is shown separate from the airtight connector 51 (fusite) or other connection device.
In this Figure, the lid 20 is seen in position on case 1, ~"i-th the apertures 18, 19 engaged by the snap-action detents or tongues 22, 23 of the lid. The terminals 10, 11 are then adapted to be connected to pin cables 56. The other components have already been illustra-ted and will therefore not be repeated here.
Figure ~ shows a -top view of the lid illustrated partially in Figures 2 and 3. It shows a quadrangular flange element 24 provided with apertures 25, 26, 27, 28 for the con-nection terminals lOt 10', 11, 11' and the detents or tongues 22, 23 which engage with apertures 18, 19 o~ case 1. Figure 4 shows the curved part 20a and the knurled part 20_. Figure 5 shows a cross section along section 5-5 of Figure ~.
Figures 6 and 7 show respectively a bottom uiew of the lid shown partially in Figures 2 and 3 and a cross sectional view along sec~on7-7. The said Figures show the internal ribs 3.1, 3.2 o~ the lid -for the positioning o~ the PTC wa~er as indicated by broken line 2a in Fig. 7, arranged so as to enclose the PTC wafer and to minimize the thermal conduc-tion from the water to the case and thus minimize power losses once -the working or motor-running temperature of the PTC element is reached.
The configuration o-f -the case 1 and the lid 20 also coopera-te to - provide the relay with a generally ball-shaped outer housing configuration as shown in the drawings, thereby to minimize the sur~ace~to-volume ratio of the relay struc-ture to ~urther reduce power loss when the motor-running temperature oE the relay is reached-Figure 8 shows a detail o~ the elec-trica] contacts ~ or ~L3;~G~6 7 of the relay according to -the invention. The con-tact means 7, for example, has a body 29 on which terminals ll, 11' of the "quick-connect" type are disposed and a socket 13 of the "plug-on" -type is welded to the body 29 for joining to the so-called "fusite"
pin 51.1 or terminal board. On the central part of body 29, a thin retention and contact spring 5 for the PTC wafer is fastened, preferably spot welded to the body, as previously indicated by references 4, S in Figure 1.
~igures 9a and 9b show in detail one of the retention and contact springs 5 for the thermosensitive wa~er (PTC) of the relay according to the invention.
The spring 5 has a body 30 of a material oE suitable electrical conductivity and of a relatively high thermal resistance metal such as stainless steel, and has a central part 31 for fastening, pre-ferably by spot welding, to the body 29 of the electrical contact 7 of the relay. The sprlng body 30 has two fins 32, 33 with turned up and narrowed ends 34, 35 on each of which ends a layer 36 of electrically highly conducting material, such as silver, is applied for a good electrical contact with the conducting surfaces ~ or 9 of the PTC wafer 2. The silver coating is applied suitably by ; "top-lay", "plating", "tape weld" or similar techniques.
That is, the springs 4, 5 have limited hea-t-transfer engagement - with the PTC wafer 2, are formed of a ma-terial of high thermal resistance, and have relatively limited cross-sections, thereby to minimize thermal conduction from the PTC wafer 2 to the case 1 for further reducing power loss when -the motor-running temperature of the relay is reached. Thus the springs Eorm a thermal barrier between the PTC wa~er and the relay housing.
~ "
~3~6g~
Preferably, the springs ~, 5 have a thermal resistance RT
(se~oanldoriec ) on the order of 1000 or more for slgnificantly retarding heat dissipation from the PTC wafer 2.
There are finally provided from the mechanical point of view ribs 37, 38 for stiffening the fins 32, 33 so as to obtain an appropriate pressure agains-t the PTC wafer. Addi-tionally, slots may be provided (not shown) in the fins 32, 33 to impede conduction of heat through the spring. For instance a slot could be disposed intermediate ribs 37 and another intermediate ribs 38. Although the configuration of the spring 30 is the one actually preferred, helical springs could also be employed in the relay 50 of this invention.
In a preferred embodiment of this invention, the relay utillzes a PTC wafer of selected small size, has a generally ball-shaped outer configuration as noted, and has springs ~ and 5 of high thermal resistance as above described but so that lower dissipation by the relay at the motor running temperature of the relay is on the order of 2.0 watts or less in 120 or 220 volt motor applications while also being adapted to cool down for restarting the motor within a period on the order of 200 second or less after interruption of motor operation. That is, the rate of heat dissipation is retarded so that the PTC wafer 2 operates at very reduced current levels in its high resistance condition to minimize power loss in the relay but the relay structure as described has such small thermal mass that it is still adapted to cool down to reset within a relatively brief period of time after an interruption in motor operation.
.
3L3L32~
It should be noted that the configuration and the Coefficient K = De~ectlo-n- f -the spring are chosen so that the sys-tem ~rmed by the PTC wafer and the springs has a pro-per mechanical oscillation frequency far Erom the typical excitation ~requencies met with, for example, in motor compressors for refrigerators fed at 50 to 60 ~Iz. Preferably, the resonance frequency of the spring-wa~er system is made above 300 Hz.
The disposi-tion of two "quick-connects" per each side of the PTC wafer makes possible a flexibility of application as illustrated in Figures lOa, lOb, lOc.
Figure loa shows the starting with only the PTC 2;
Figure lOb shows the starting with PTC 2 and with a parallel-connec-ted capacitor 55, and Figure lOc shows starting with the PTC 2 in series with a capacitor 56. These circuital arrange-lS ments are well known to one skilled in the art and thus need not be exp'lained in detail here.
When used in the Fig. lOa and lOb circuit con~igura-tions the relay is coupled to the "fusite" as shown ~or instance in Figs. 1 and 2 where two pins are electrically connected to the relay by being inserted therein~
When a series connected capacitor is used as shown in Fig. lOc one "-fusite" pin lS electrlcally connected to the relay and an auxiliary structural member is physically but no~ elec-trically connect~d ~o ano~h~r "~usite" pin to provid~ suppor~
for the relay.
Figures lla, llb, llc show three examples according to the invention ~or fastening the thermal relay ~0 on a three-pole airtight connector (fusite) 51 on an electrical mo-tor when the Fig. lOc circuit is employed.
/ J ~ , ~
~L3~69~
Figure lla shows the thermal relay 50 fastened to the "fusite" 51 by means of one of the plug-on 12, 13 and an auxilliary bracket 53. In Figure llb, the support or holder 5 is made directly on the case o~ the thermal relay 50. In S Figure llc, a variation of Figure llb is shown wherein the support or holder 5~ is placed in a different location.
Figure 12 shows, by way of example, an assembly line 56 with a circular course for the relay according to the inven-tion. The system according to the invention, as described further below, combines the assembly of the parts "on line" in synchronism with the assembly o~ the parts on a "revolving table". The operations are as follows:
The bodies of the terminals 6, 7 made in strip form are inserted in two assembly lines A, B, and A', s' which provide:
a) feeding the connector 12, 13, positioning of the same on the terminal 6, 7 and welding (A, A') b) feeding of the springs 4, 5 in strip ~orm, positioning oE the spring on the terminal, welding and separa-tion of the same from the strip (B, B').
There are thus obtained at the end of the said lines the terminals 6, 7 in s-trip form with the connectors 12, 13 and the springs 4, 5 mounted, ready to be inserted in the base 1.
The assembly phases are as follows:
The base is fed and guided by means of a vibrator in station C of the rotating table system 56. I'he s-tation provides for the transEer of the base 1 on a suitable fixture situated on the rotating table.
1~3~ 6 With a rotary movement of the table, the positioned base moves toward station D.
In the meantime, the above described subsidiary lines A, B and A', B' provide the stations D and E with terminals 6, 7 carrying connectors and springs, still in the form of strips.
The stations D and E first clamp and then separate a terminal with connector and spring mounted from the strip and subsequently inset it ~orcibly into the base 1.
At the exit of station E, the base positioned on the revolving table has the two complete terminals 6, 7 with connectors and springs mounted.
In station F, a transfer system inserts between the contacts (springs) ~, 5 the PTC wafer which is held in a force fit between the said contacts.
The thus mounted parts of components that make up the relay move, still by means oE the rotating table, towards station G where a vlbra-tor feeds and steers the liàs 20 in the station where the lid is mounted and fastened onto the base.
The completely assembl~d relay is ejected at station H and moved automatically toward the process lines J and K
which control and register the respective data for the above described device and system.
The drawings show a cons-truction o~ base or case and lid equipped with means of fastening by mechanical engagement.
However, the lid could also be fastened to the base by means of gluing or by the known ultrasonic bonding technique, or also by -thermal action.
L J . i), / ~ ~ J .; ., . . . ~ .,, ."., , ~L3Z696 Furthermore, although leaf srpings are mentioned for the PTC wafer, -the same could equally constitute helical or spiral springs.
Furthermore, from the elec-tromechanlcal point of view, mention was made of a thermal relay joined to an airtight con- -nector (fusite). The thermal relay could, however, just as well ~ .
be mounted on a separate terminal board. When desired or when required for purposes or complying with safety standards, the upper terminals "quick-connects" can be protected by a sheath by a extension of the lid.
The present invention has been described by way of a preferred form of realization. It is understood, however, that variations and modifications can be made in the same, without departing from the scope of -the present invention.
Figure 4 shows a top view of the lid partially shown in Figures 2 and 3;
Figure 5 shows a cross section along sec-tion 5-5 of Figure 4;
Figure 6 shows a bottom vlew of the lid of Figure 4;
Figure 7 shows a cross-sectional view along section 7-7 of E'igure 6;
Figure 8 shows a detail of the electric contacts of the relay according to the invention;
Figures 9a and 9b show in detail one of the retention and contact springs with the thermosensitive wafer (PTC) of the relay according to the invention;
Figures 10a, 10b, and 10c show three circuit arrange-ments for the relay according to the invention;
Figures lla, llb and llc show various mechanical forms for mounting the relay according to the invention, and Figure 12 shows schematically an assembly line for the relay according to the invention.
Referring to the drawings, particularly to Figure thereof, the thermal relay 50 according to the invention includes a case 1 of electrically and thermally insulating material inside of which is disposed a wafer 2 of a material with a positi~e coefficient of temperature (PTC) of a type well known to the skilled in the ar-t. ~See for example U.S.
Patents 3,750,082 to P. Peterson et all. issued ~uly 13, 1973 and U.S. Patent 3,842,1~38 to P. Peterson issued October 15, 1974). Preferably the wafer size is relatively small while being sufficient to achieve the desired start winding performance.
~ 1!J~ ~" /~J~
3Z6~6 Where the PTC material comprises a conven-tional doped barium titanate ceramic material having a 130C. Curie temperature, the waEer typically has a diameter of about 0.700 inches and a mass of about 5 yrams for 220 volt motors and smaller, for example 3 grams when adapted for starting 120 volt motors.
The wafer 2 is positioned by ribs 3 made on the inside of the case 1 and by two leaf springs 4, S fastened to electrical connection means 6, 7 to be hereinafter described in greater detail. The springs 4, 5 have fins or arms 4a, 4b and 5_, 5b that make contact with the metallized surfaces 8, 9 respectively as conventionally provided on the wafer 2.
The elec-trical connection means 6, 7 are joined with upper "quick-connect" type terminals 10, 10', 11, 11' and with resilient, lower "plug-on" connectors 12, 13 arranged so as to be self-adjusting when inserted on the pins 51.1 on an airtight connector (fusite) of a refrigerator compressor, as denoted at 51 or on a suitable terminal board. Furthermore, the electrical connection means 6, 7 are held in position by projec-tions or ribs 14, 15 and 16, 17 made on the inside of case 1. On the outside of case 1, apertures 18, 19 are provided which engage detents or tongues ~ormed on the lid of the device. The said tongues are not shown in Figure 1.
Figure 2 shows a cross section along section 2-2 of Figure 1, showing lid 20 in position on case 1. The broken line 21 shows the course of the otherwise unillustra-ted part of lid 20. It can be seen there that the curved part 20a joins with a knurled fla-t part 20b so as to facilitate the insertion of the device of the invention of-the pins 51.1 of the airtight connec-tor 51 or other electrical connec~ion device.
~13Z6~
Figure 3 shows a cross section alony section 3-3 of Figure 1 wherein the device in question is shown separate from the airtight connector 51 (fusite) or other connection device.
In this Figure, the lid 20 is seen in position on case 1, ~"i-th the apertures 18, 19 engaged by the snap-action detents or tongues 22, 23 of the lid. The terminals 10, 11 are then adapted to be connected to pin cables 56. The other components have already been illustra-ted and will therefore not be repeated here.
Figure ~ shows a -top view of the lid illustrated partially in Figures 2 and 3. It shows a quadrangular flange element 24 provided with apertures 25, 26, 27, 28 for the con-nection terminals lOt 10', 11, 11' and the detents or tongues 22, 23 which engage with apertures 18, 19 o~ case 1. Figure 4 shows the curved part 20a and the knurled part 20_. Figure 5 shows a cross section along section 5-5 of Figure ~.
Figures 6 and 7 show respectively a bottom uiew of the lid shown partially in Figures 2 and 3 and a cross sectional view along sec~on7-7. The said Figures show the internal ribs 3.1, 3.2 o~ the lid -for the positioning o~ the PTC wa~er as indicated by broken line 2a in Fig. 7, arranged so as to enclose the PTC wafer and to minimize the thermal conduc-tion from the water to the case and thus minimize power losses once -the working or motor-running temperature of the PTC element is reached.
The configuration o-f -the case 1 and the lid 20 also coopera-te to - provide the relay with a generally ball-shaped outer housing configuration as shown in the drawings, thereby to minimize the sur~ace~to-volume ratio of the relay struc-ture to ~urther reduce power loss when the motor-running temperature oE the relay is reached-Figure 8 shows a detail o~ the elec-trica] contacts ~ or ~L3;~G~6 7 of the relay according to -the invention. The con-tact means 7, for example, has a body 29 on which terminals ll, 11' of the "quick-connect" type are disposed and a socket 13 of the "plug-on" -type is welded to the body 29 for joining to the so-called "fusite"
pin 51.1 or terminal board. On the central part of body 29, a thin retention and contact spring 5 for the PTC wafer is fastened, preferably spot welded to the body, as previously indicated by references 4, S in Figure 1.
~igures 9a and 9b show in detail one of the retention and contact springs 5 for the thermosensitive wa~er (PTC) of the relay according to the invention.
The spring 5 has a body 30 of a material oE suitable electrical conductivity and of a relatively high thermal resistance metal such as stainless steel, and has a central part 31 for fastening, pre-ferably by spot welding, to the body 29 of the electrical contact 7 of the relay. The sprlng body 30 has two fins 32, 33 with turned up and narrowed ends 34, 35 on each of which ends a layer 36 of electrically highly conducting material, such as silver, is applied for a good electrical contact with the conducting surfaces ~ or 9 of the PTC wafer 2. The silver coating is applied suitably by ; "top-lay", "plating", "tape weld" or similar techniques.
That is, the springs 4, 5 have limited hea-t-transfer engagement - with the PTC wafer 2, are formed of a ma-terial of high thermal resistance, and have relatively limited cross-sections, thereby to minimize thermal conduction from the PTC wafer 2 to the case 1 for further reducing power loss when -the motor-running temperature of the relay is reached. Thus the springs Eorm a thermal barrier between the PTC wa~er and the relay housing.
~ "
~3~6g~
Preferably, the springs ~, 5 have a thermal resistance RT
(se~oanldoriec ) on the order of 1000 or more for slgnificantly retarding heat dissipation from the PTC wafer 2.
There are finally provided from the mechanical point of view ribs 37, 38 for stiffening the fins 32, 33 so as to obtain an appropriate pressure agains-t the PTC wafer. Addi-tionally, slots may be provided (not shown) in the fins 32, 33 to impede conduction of heat through the spring. For instance a slot could be disposed intermediate ribs 37 and another intermediate ribs 38. Although the configuration of the spring 30 is the one actually preferred, helical springs could also be employed in the relay 50 of this invention.
In a preferred embodiment of this invention, the relay utillzes a PTC wafer of selected small size, has a generally ball-shaped outer configuration as noted, and has springs ~ and 5 of high thermal resistance as above described but so that lower dissipation by the relay at the motor running temperature of the relay is on the order of 2.0 watts or less in 120 or 220 volt motor applications while also being adapted to cool down for restarting the motor within a period on the order of 200 second or less after interruption of motor operation. That is, the rate of heat dissipation is retarded so that the PTC wafer 2 operates at very reduced current levels in its high resistance condition to minimize power loss in the relay but the relay structure as described has such small thermal mass that it is still adapted to cool down to reset within a relatively brief period of time after an interruption in motor operation.
.
3L3L32~
It should be noted that the configuration and the Coefficient K = De~ectlo-n- f -the spring are chosen so that the sys-tem ~rmed by the PTC wafer and the springs has a pro-per mechanical oscillation frequency far Erom the typical excitation ~requencies met with, for example, in motor compressors for refrigerators fed at 50 to 60 ~Iz. Preferably, the resonance frequency of the spring-wa~er system is made above 300 Hz.
The disposi-tion of two "quick-connects" per each side of the PTC wafer makes possible a flexibility of application as illustrated in Figures lOa, lOb, lOc.
Figure loa shows the starting with only the PTC 2;
Figure lOb shows the starting with PTC 2 and with a parallel-connec-ted capacitor 55, and Figure lOc shows starting with the PTC 2 in series with a capacitor 56. These circuital arrange-lS ments are well known to one skilled in the art and thus need not be exp'lained in detail here.
When used in the Fig. lOa and lOb circuit con~igura-tions the relay is coupled to the "fusite" as shown ~or instance in Figs. 1 and 2 where two pins are electrically connected to the relay by being inserted therein~
When a series connected capacitor is used as shown in Fig. lOc one "-fusite" pin lS electrlcally connected to the relay and an auxiliary structural member is physically but no~ elec-trically connect~d ~o ano~h~r "~usite" pin to provid~ suppor~
for the relay.
Figures lla, llb, llc show three examples according to the invention ~or fastening the thermal relay ~0 on a three-pole airtight connector (fusite) 51 on an electrical mo-tor when the Fig. lOc circuit is employed.
/ J ~ , ~
~L3~69~
Figure lla shows the thermal relay 50 fastened to the "fusite" 51 by means of one of the plug-on 12, 13 and an auxilliary bracket 53. In Figure llb, the support or holder 5 is made directly on the case o~ the thermal relay 50. In S Figure llc, a variation of Figure llb is shown wherein the support or holder 5~ is placed in a different location.
Figure 12 shows, by way of example, an assembly line 56 with a circular course for the relay according to the inven-tion. The system according to the invention, as described further below, combines the assembly of the parts "on line" in synchronism with the assembly o~ the parts on a "revolving table". The operations are as follows:
The bodies of the terminals 6, 7 made in strip form are inserted in two assembly lines A, B, and A', s' which provide:
a) feeding the connector 12, 13, positioning of the same on the terminal 6, 7 and welding (A, A') b) feeding of the springs 4, 5 in strip ~orm, positioning oE the spring on the terminal, welding and separa-tion of the same from the strip (B, B').
There are thus obtained at the end of the said lines the terminals 6, 7 in s-trip form with the connectors 12, 13 and the springs 4, 5 mounted, ready to be inserted in the base 1.
The assembly phases are as follows:
The base is fed and guided by means of a vibrator in station C of the rotating table system 56. I'he s-tation provides for the transEer of the base 1 on a suitable fixture situated on the rotating table.
1~3~ 6 With a rotary movement of the table, the positioned base moves toward station D.
In the meantime, the above described subsidiary lines A, B and A', B' provide the stations D and E with terminals 6, 7 carrying connectors and springs, still in the form of strips.
The stations D and E first clamp and then separate a terminal with connector and spring mounted from the strip and subsequently inset it ~orcibly into the base 1.
At the exit of station E, the base positioned on the revolving table has the two complete terminals 6, 7 with connectors and springs mounted.
In station F, a transfer system inserts between the contacts (springs) ~, 5 the PTC wafer which is held in a force fit between the said contacts.
The thus mounted parts of components that make up the relay move, still by means oE the rotating table, towards station G where a vlbra-tor feeds and steers the liàs 20 in the station where the lid is mounted and fastened onto the base.
The completely assembl~d relay is ejected at station H and moved automatically toward the process lines J and K
which control and register the respective data for the above described device and system.
The drawings show a cons-truction o~ base or case and lid equipped with means of fastening by mechanical engagement.
However, the lid could also be fastened to the base by means of gluing or by the known ultrasonic bonding technique, or also by -thermal action.
L J . i), / ~ ~ J .; ., . . . ~ .,, ."., , ~L3Z696 Furthermore, although leaf srpings are mentioned for the PTC wafer, -the same could equally constitute helical or spiral springs.
Furthermore, from the elec-tromechanlcal point of view, mention was made of a thermal relay joined to an airtight con- -nector (fusite). The thermal relay could, however, just as well ~ .
be mounted on a separate terminal board. When desired or when required for purposes or complying with safety standards, the upper terminals "quick-connects" can be protected by a sheath by a extension of the lid.
The present invention has been described by way of a preferred form of realization. It is understood, however, that variations and modifications can be made in the same, without departing from the scope of -the present invention.
Claims (12)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A motor starting relay for a single phase motor having start and run windings comprising a resistor embodying a material of positive temperature coefficient of resistivity which displays a sharp increase in resistivity when heated above a selected temperature level, a housing of thermally insulating material for the resistor, and a pair of resilient electrically conductive metal contact means electrically engaging respective opposite sides of the resistor for connecting the resistor in series with the start winding of a motor, characterized in that, the contact means are disposed between the housing and the respective opposite sides of the resistor holding most of the resistor surfaces spaced from the housing to retard heat transfer from the resistor directly to the housing, the contact means have at least some electrically conductive metal portions thereof of a material of relatively high thermal resistance to retard heat transfer from the resistor to the housing and from the resistor exteriorly of the housing through said contact means, and the housing is compact and generally ball-shaped and is proportioned to substantially enclose and closely surround the resistor and substantial portions of the contact means for restricting the thermal mass of the relay as well as the surface to volume ratio of the housing to cooperate with said thermal conductivity characteristics of the contact means so that the relay is adapted to limit current in the start winding of the motor after starting the motor has been completed and heat dissipation from the relay is minimized during running of the motor for enhancing operating efficiency of the motor while the cool down period of the relay is also minimized to permit prompt motor restarting if operation of the motor is interrupted.
2. A motor starting relay as set forth in claim 1 wherein the contact means include terminal portions to be connnected in an electrical circuit for connecting the resistor in series with the start winding of said motor and relatively thin spring portions secured to said terminal portions to resiliently engage said opposite sides of the resistor, and said thin spring portions are formed of said metal of said high thermal resistance to provide a thermal barrier between the resistor and the terminal portions and housing.
3. A thermal relay as set forth in claim 1 further characterized in that said contact means include relatively thin spring portions formed of said metal material having said high thermal resistance to provide a thermal barrier between the resistor and housing, the thin spring portions being formed of stainless steel to be disposed in firm electrical engagement with the opposite sides of the resistor while forming said thermal barrier.
4. A thermal relay as set forth in claim 1 wherein the housing is formed of a thermally insulating material and substantially encloses the resistor, the housing having a generally ball-shaped outer configuration restricting the surface to volume ratio of the relay to retard heat dissipation from the relay.
5. A thermal relay as set forth in claim 1 wherein the contact means have upper and lower terminal means thereon extending from opposite sides of the housing.
6. A thermal relay as set forth in claim 5 wherein the lower terminal means comprise resilient socket means for facilitating mounting of the relay on electrical connector pins refrigerator compressor motor.
7. A thermal relay as set forth in claim 5 wherein the housing comprises an open-ended case receiving the resistor therein, the contact means are fitted between the case and respective opposite sides of the case for positioning the resistor in the case, and the housing further comprises a cap-shaped lid disposed over the open case end for substantially enclosing the resistor, the lid having means releasably engaging the case holding the relay in assembled relation.
8. A motor starting relay according to claim 1 wherein the contact means include terminal portions and relatively thin spring portions secured to said terminal portions, said thin spring portions of the contact means being formed of stainless steel.
9. A motor starting relay as set forth in claim 8 wherein said spring portions have silver coatings on ends thereof electrically engaging the resistor.
10. A motor starting relay as set forth in claim 6 wherein the contact means have a thermal resistance of at least about 1000 sec. °C/calorie and the relay is adapted to dissipate less than about 2 watts during normal running operation of the motor.
11. A motor starting relay as set forth in claim 10 wherein the relay is proportioned with a sufficiently small thermal mass for normally permitting cooling and resetting of the relay within about 200 seconds or less after interruption of motor operation.
12. A method for assembling a motor starting relay comprising the steps of continuously advancing a plurality of thermally insulating open-ended housing cases in sequence relative to each other, to an assembly station, continuously advancing a plurality of terminal means and a plurality of spring means toward each other in sequence in each of two lines and securing the terminal means to respective spring means in each of the lines to form a plurality of contact means, advancing the contact means in each of said two lines to the assembly station to dispose pairs of the contact means within respective housing cases with the spring means thereof in facing relation to each other, advancing a plurality of resistor wafers of positive temperature coefficient of resistivity in sequence to the assembly station to dispose respective wafers between pairs of contact means in each of the housing cases, and advancing a plurality of housing lids in sequence to the assembly station and securing the lids to the respective housings for enclosing the resistor wafers and contact means within the housings.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IT51821A/77 | 1977-11-15 | ||
| IT5182177A IT1112068B (en) | 1977-11-15 | 1977-11-15 | IMPROVEMENT IN THERMAL RELAYS, IN PARTICULAR FOR STARTING ASYNCHRONOUS SINGLE-PHASE MOTORS |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1132696A true CA1132696A (en) | 1982-09-28 |
Family
ID=11275795
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA316,216A Expired CA1132696A (en) | 1977-11-15 | 1978-11-14 | Thermal relays particularly for starting single-phase asynchronous motors |
Country Status (13)
| Country | Link |
|---|---|
| JP (2) | JPS54113081A (en) |
| AR (1) | AR217336A1 (en) |
| AU (1) | AU525907B2 (en) |
| BR (1) | BR7807484A (en) |
| CA (1) | CA1132696A (en) |
| DE (1) | DE2849584A1 (en) |
| DK (1) | DK158689C (en) |
| ES (1) | ES475049A1 (en) |
| FR (1) | FR2408907A1 (en) |
| GB (1) | GB2015823B (en) |
| IT (1) | IT1112068B (en) |
| MX (1) | MX146622A (en) |
| NL (1) | NL189103C (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2845965C2 (en) * | 1978-10-21 | 1983-01-20 | Fritz Eichenauer GmbH & Co KG, 6744 Kandel | Electric resistance heating element |
| JPS5598851A (en) * | 1979-01-23 | 1980-07-28 | Matsushita Refrig Co | Semiconductor device with elastic terminal |
| JPS57106002A (en) * | 1980-12-23 | 1982-07-01 | Murata Manufacturing Co | Positive temperature coefficient thermistor |
| IT1147231B (en) * | 1981-05-20 | 1986-11-19 | Necchi Spa | STARTING RELAY OF THE RESISTANCE TYPE WITH POSITIVE TEMPERATURE COEFFICIENT IN MOTOR-COMPRESSORS FOR REFRIGERATING SYSTEMS |
| JP3036453B2 (en) * | 1997-01-22 | 2000-04-24 | 日本電気株式会社 | Disk support device |
| DE19816809C2 (en) * | 1998-04-16 | 2001-10-18 | Thermik Geraetebau Gmbh | Temperature-dependent switch |
| KR100852047B1 (en) | 2001-01-12 | 2008-08-13 | 마츠시타 덴끼 산교 가부시키가이샤 | Disc cartridge |
| US6910219B2 (en) | 2001-07-06 | 2005-06-21 | Matsushita Electric Industrial Co., Ltd. | Disc cartridge |
| US7038896B2 (en) * | 2002-12-13 | 2006-05-02 | Texas Instruments Incorporated | Solid state motor protector |
| DK1828693T3 (en) * | 2004-12-20 | 2008-08-04 | Angelantoni Ind Spa | Energy saving climate test chamber and operation method |
| JP2007014071A (en) | 2005-06-29 | 2007-01-18 | Sanyo Electric Co Ltd | Starting relay |
Family Cites Families (21)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB628567A (en) * | 1945-07-30 | 1949-08-31 | Philips Nv | Improvements in or relating to resistances having a negative temperature coefficient |
| US3153769A (en) * | 1962-02-14 | 1964-10-20 | Electro Diagnostics Inc | Electrical temeperature indicator |
| DE2129587C3 (en) * | 1971-06-15 | 1973-11-29 | Danfoss As | Device for holding and contacting thermally loaded ceramic resistors |
| US4083336A (en) * | 1971-08-10 | 1978-04-11 | Texas Instruments Incorporated | Condition responsive control device |
| JPS499957U (en) * | 1972-05-06 | 1974-01-28 | ||
| US3750082A (en) * | 1972-06-15 | 1973-07-31 | Danfoss As | Plug assembly with resistor |
| JPS4930429A (en) * | 1972-07-04 | 1974-03-18 | ||
| DE2255664C2 (en) * | 1972-11-14 | 1974-11-28 | Danfoss A/S, Nordborg (Daenemark) | Device for holding and contacting thermally loaded ceramic resistors in a housing |
| JPS5250350Y2 (en) * | 1973-07-20 | 1977-11-15 | ||
| US3925748A (en) * | 1973-11-08 | 1975-12-09 | Thermo Electronics Inc | Resistance device for use in energizing the starting winding of a split phase induction motor |
| US3914727A (en) * | 1974-01-02 | 1975-10-21 | Sprague Electric Co | Positive-temperature-coefficient-resistor package |
| AT351611B (en) * | 1974-01-07 | 1979-08-10 | Siemens Bauelemente Ohg | PLASTIC HOUSING FOR A COLD CONDUCTOR OR FOR A COLD CONDUCTOR COMBINATION |
| US3958208A (en) * | 1974-06-05 | 1976-05-18 | Texas Instruments Incorporated | Ceramic impedance device |
| US4037316A (en) * | 1974-09-23 | 1977-07-26 | General Electric Company | Method of assembling temperature responsive resistance member |
| US3955170A (en) * | 1974-11-29 | 1976-05-04 | Texas Instruments Incorporated | Solid state switch |
| US3921117A (en) * | 1974-11-29 | 1975-11-18 | Texas Instruments Inc | Solid state electrical switch |
| JPS5522723Y2 (en) * | 1975-04-16 | 1980-05-30 | ||
| US3988709A (en) * | 1975-05-12 | 1976-10-26 | Eugene T. McKinnon | Electric motor controlling relay |
| JPS5219669A (en) * | 1975-08-08 | 1977-02-15 | Ono Pharmaceut Co Ltd | Preparation of tetrazole derivatives and acid addition salts thereof |
| JPS568162Y2 (en) * | 1976-03-19 | 1981-02-23 | ||
| JPS5332271U (en) * | 1976-08-27 | 1978-03-20 |
-
1977
- 1977-11-15 IT IT5182177A patent/IT1112068B/en active
-
1978
- 1978-11-02 NL NL7810915A patent/NL189103C/en not_active IP Right Cessation
- 1978-11-06 AU AU41358/78A patent/AU525907B2/en not_active Expired
- 1978-11-14 ES ES475049A patent/ES475049A1/en not_active Expired
- 1978-11-14 CA CA316,216A patent/CA1132696A/en not_active Expired
- 1978-11-14 GB GB7844357A patent/GB2015823B/en not_active Expired
- 1978-11-14 MX MX17560878A patent/MX146622A/en unknown
- 1978-11-14 DK DK506178A patent/DK158689C/en active
- 1978-11-14 BR BR7807484A patent/BR7807484A/en unknown
- 1978-11-14 JP JP13948378A patent/JPS54113081A/en active Granted
- 1978-11-15 AR AR27445578A patent/AR217336A1/en active
- 1978-11-15 DE DE19782849584 patent/DE2849584A1/en active Granted
- 1978-11-15 FR FR7832286A patent/FR2408907A1/en active Granted
-
1991
- 1991-08-21 JP JP3209567A patent/JPH06105581B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| GB2015823A (en) | 1979-09-12 |
| JPS6318817B2 (en) | 1988-04-20 |
| NL189103C (en) | 1993-01-04 |
| IT1112068B (en) | 1986-01-13 |
| NL7810915A (en) | 1979-05-17 |
| GB2015823B (en) | 1982-06-16 |
| JPH06105581B2 (en) | 1994-12-21 |
| MX146622A (en) | 1982-07-15 |
| AU525907B2 (en) | 1982-12-09 |
| JPH0515178A (en) | 1993-01-22 |
| DE2849584C2 (en) | 1989-06-15 |
| ES475049A1 (en) | 1979-12-01 |
| NL189103B (en) | 1992-08-03 |
| DK506178A (en) | 1979-05-16 |
| AU4135878A (en) | 1979-05-24 |
| BR7807484A (en) | 1979-07-17 |
| JPS54113081A (en) | 1979-09-04 |
| DK158689B (en) | 1990-07-02 |
| DE2849584A1 (en) | 1979-05-17 |
| FR2408907B1 (en) | 1984-03-23 |
| DK158689C (en) | 1991-02-25 |
| FR2408907A1 (en) | 1979-06-08 |
| AR217336A1 (en) | 1980-03-14 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4241370A (en) | Thermal relays particularly for starting single-phase asynchronous motors | |
| CA1132696A (en) | Thermal relays particularly for starting single-phase asynchronous motors | |
| EP0104809B1 (en) | Motor protector | |
| JP3231843B2 (en) | Motor control parts mounting device | |
| CA1131300A (en) | Combination starter-protector device | |
| US5936510A (en) | Sealed case hold open thermostat | |
| US4499517A (en) | Motor protector particularly suited for use with compressor motors | |
| US4086558A (en) | Motor protector and system | |
| EP0177652A2 (en) | Motor protector particularly suited for use with compressor motors | |
| US4237510A (en) | Electrical switching apparatus | |
| US4224591A (en) | Motor protector with metal housing and with preformed external heater thereon | |
| US5870014A (en) | Thermally actuatable auxiliary electrical switch apparatus | |
| US4458231A (en) | Protector apparatus for dynamoelectric machines | |
| US4299026A (en) | Method of assembling a motor starting relay | |
| US5014035A (en) | Bimetallic circuit breaker with insulated terminal assembly | |
| EP0375261A1 (en) | Combination motor protector and starter apparatus | |
| KR19990037415A (en) | NTC thermistor | |
| US4926542A (en) | Method of making a surface mount wirewound resistor | |
| US4327481A (en) | Method of assembling an electrical device | |
| US4414530A (en) | Miniature motor protector apparatus and method for assembling thereof | |
| US4754251A (en) | Thermostatic electric switch and thermal biasing assembly therefor | |
| US4241494A (en) | Method of assembling an electrical device | |
| US5734312A (en) | Overtemperature protection assembly for an appliance | |
| CA1041162A (en) | Ignition breaker point arrangement | |
| CN210925877U (en) | Novel indirect heating type thermal protector |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |