CA1177629A - Thermally actuatable electrical switches - Google Patents
Thermally actuatable electrical switchesInfo
- Publication number
- CA1177629A CA1177629A CA000404605A CA404605A CA1177629A CA 1177629 A CA1177629 A CA 1177629A CA 000404605 A CA000404605 A CA 000404605A CA 404605 A CA404605 A CA 404605A CA 1177629 A CA1177629 A CA 1177629A
- Authority
- CA
- Canada
- Prior art keywords
- lead
- end plug
- skiving
- plug
- skived
- 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
- H01H37/00—Thermally-actuated switches
- H01H37/74—Switches in which only the opening movement or only the closing movement of a contact is effected by heating or cooling
- H01H37/76—Contact member actuated by melting of fusible material, actuated due to burning of combustible material or due to explosion of explosive material
- H01H37/764—Contact member actuated by melting of fusible material, actuated due to burning of combustible material or due to explosion of explosive material in which contacts are held closed by a thermal pellet
- H01H37/765—Contact member actuated by melting of fusible material, actuated due to burning of combustible material or due to explosion of explosive material in which contacts are held closed by a thermal pellet using a sliding contact between a metallic cylindrical housing and a central electrode
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Combustion & Propulsion (AREA)
- Fuses (AREA)
- Switch Cases, Indication, And Locking (AREA)
Abstract
A B S T R A C T
A method of making a thermally actuatable electrical switch involves the locking of a conductive lead, passing in a bore through an end plug of a housing of the switch, to the end plug by skiving the lead and compacting the skived part of the lead against one end of the end plug so as to render the lead immovable in a direction towards the other end of the end plug, as well as immovable rotationally. A contact on the lead, abutting the other end of the end plug, will thus be securely fixed in position relative to the end plug.
When the skived part is being compacted against the one end of the end plug, a portion of the skived part may be caused to enter the lead-carrying bore in the end plug to center the lead in the bore and to augment the locking effect.
Further augmentation of the locking effect may be achieved by applying a hard-setting sealing compound, such as an epoxy resin, over the compacted skived part so as to extend over respective portions of the end plug and the lead on opposite sides of the compacted skived part, whereby some of the sealing compound prior to setting will seep into the bore by capillary action to engage the portion of the skived part therein and some will fill recesses produced on the lead by the skiving step. The thermally actuatable electrical switch itself is unique by virtue of having a skiving of its conductive lead interlocked with an end of the end plug, a portion of which skiving may be interlocked with the wall of the lead-carrying bore in the end plug and with sealing compound in the bore, which compound may be inter-locked with recesses in the lead outboard of the bore, as well as with the skiving which is locked to the end of the end plug.
A method of making a thermally actuatable electrical switch involves the locking of a conductive lead, passing in a bore through an end plug of a housing of the switch, to the end plug by skiving the lead and compacting the skived part of the lead against one end of the end plug so as to render the lead immovable in a direction towards the other end of the end plug, as well as immovable rotationally. A contact on the lead, abutting the other end of the end plug, will thus be securely fixed in position relative to the end plug.
When the skived part is being compacted against the one end of the end plug, a portion of the skived part may be caused to enter the lead-carrying bore in the end plug to center the lead in the bore and to augment the locking effect.
Further augmentation of the locking effect may be achieved by applying a hard-setting sealing compound, such as an epoxy resin, over the compacted skived part so as to extend over respective portions of the end plug and the lead on opposite sides of the compacted skived part, whereby some of the sealing compound prior to setting will seep into the bore by capillary action to engage the portion of the skived part therein and some will fill recesses produced on the lead by the skiving step. The thermally actuatable electrical switch itself is unique by virtue of having a skiving of its conductive lead interlocked with an end of the end plug, a portion of which skiving may be interlocked with the wall of the lead-carrying bore in the end plug and with sealing compound in the bore, which compound may be inter-locked with recesses in the lead outboard of the bore, as well as with the skiving which is locked to the end of the end plug.
Description
l 177629 This invention relates to a method of making a thermally actuatable electrical switch and to a switch made according to the method.
It is known to provide a thermally actuatable electrical switch of the kind having a housing carrying an electrically insulating end plug provided with an opening passing therethrough in which a portion of a conductive lead is disposed 80 that opposed ènds of the lead extend beyond opposed ends of the end plug and respectively define a fixed contact inside the housing and a terminal outside the housing.
The lead is ~nterlocked with the end plug to prevent axial movement of the lead into the housing by means of an integral p~t of the terminal extending outboard of the opening and disposed against the respective opposed end of the end plug adjacent the terminal.
For example, see Figs. 8 and 9 of U.S. Patent No. 3,180,958 wherein the lead 118 is crimped at 119 and Figs, 3, 4 and 5 of Japanese Patent No. 54-5743 wherein in Fig, 3 it appears that the lead 2 is crimped at 13, in Fig.
4 it appears that the lead 2 is split at 14 to provide abutments 15, and in Fig. 5 it appears that the lead 2 is lanced at 16 to provide opposed tabs 17.
Another known means for interlocking the lead to the end plug involveæ forming tha portion of the lead that is disposed in the opening of the end plug with a plurality of radially disposed reliefs in a manner to prevent each re-lief from extending araund the circumference of the lead so that a sealing compound can enter the reliefs and harden ..
1 177~9
It is known to provide a thermally actuatable electrical switch of the kind having a housing carrying an electrically insulating end plug provided with an opening passing therethrough in which a portion of a conductive lead is disposed 80 that opposed ènds of the lead extend beyond opposed ends of the end plug and respectively define a fixed contact inside the housing and a terminal outside the housing.
The lead is ~nterlocked with the end plug to prevent axial movement of the lead into the housing by means of an integral p~t of the terminal extending outboard of the opening and disposed against the respective opposed end of the end plug adjacent the terminal.
For example, see Figs. 8 and 9 of U.S. Patent No. 3,180,958 wherein the lead 118 is crimped at 119 and Figs, 3, 4 and 5 of Japanese Patent No. 54-5743 wherein in Fig, 3 it appears that the lead 2 is crimped at 13, in Fig.
4 it appears that the lead 2 is split at 14 to provide abutments 15, and in Fig. 5 it appears that the lead 2 is lanced at 16 to provide opposed tabs 17.
Another known means for interlocking the lead to the end plug involveæ forming tha portion of the lead that is disposed in the opening of the end plug with a plurality of radially disposed reliefs in a manner to prevent each re-lief from extending araund the circumference of the lead so that a sealing compound can enter the reliefs and harden ..
1 177~9
-2-into blocks that tend to prevent axial movement of the lead into the housinq as well as to tend to prevent rotational movement of the lead relative to the end plug. For example, see U.S. Patent No. 4,060,787.
However, according to the teachings of the present invention, the conductive lead of a thermally actuatable electrical switch construction can be formed in another unique manner to interlock with the end plug so as to be effective in preventing axial movement of the lead in the opening of the end plug in a direction that would be into the housing that carries the end plug.
In particular, according to the invention, there is provided a method of making a thermally actuatable electrical switch of the kind having a housing carrying an electrically insulating end plug provided with an opening passing therethrough in which a portion of a conductive lead is disposed so that opposed ends of the lead extend beyond opposed ends of the ènd plug and respectively define a fixed contact inside the housing and a terminal outsidethe housing the lead being interlocked with the end plug to prevent axial movement of the lead into the housing by means of an integral part of the terminal that extends outboard of the opening and is disposed against the respective opposed end of the end plug adjacent the terminal, comprising the steps of skiving the part from the lead and compacting the skived part against the respective opposed end of the end plug.
We also provide a thermally actuatable electrical switch of the kind having a housing carrying an electrically insulating end plug provided with an opening passing there-through in which a portion of a conductive lead is disposed80 that opposed ends of the lead extend beyond opposed ends of the end plug and respectively define a fixed contact inside the housing and a terminal outside the housing, the lead being interlocked with the end plug to prevent axial movement of the lead into the housing by means of an integral part of the terminal extending outboard of the opening and disposed against the respective opposed end of the end plug ~ .,, I 177~2~
~3--ad~acent the terminal, wherein the integral part of the terminal comprises a skiving of the terminal.
Preferably, the integral part of the termirlal has a portion thereof disposed in the opening adjacent the respective end of the end plug. The integral part may be covered by a sealing compound disposed on the respective end of the end plug and extending onto the terminal outboard of the integral part, and the integral part may have a con-figuration that interlocks with the sealing compound in a manner to pre~ent rotational movement of the terminal relative to the end plug.
In order that the invention may be fully understood, it will now be described with reference to the accompanying drawings, wherein:
Fig. 1 is a perspective view of an embodiment of the improved thermally actuatable electrical switch of this invention.
Fig. 2 is an enlarged cross-sectional view of the thermally actuatable electrical switch embodiment of Fig. 1 and is taken substantially on the line 2-2 of Fig. 1.
Fig. 3 is a cross-sectional view taken on line 3-3 of Fig. 2.
Fig. 4 is a cross-sectional view taken on line 4-4 of Fig. 2.
Fig. 5 i8 an axial cross-sectional view schemati-cally illustrating an example of how the method of this invention may be implemented for forming a sub-assembly that is utilized in forming the thermally actuatable electrical switch embodiment illustrated in Figs. 1-4.
Fig. 5' and Fig. 5" are enlarged fragmentary views similar to Fig. 5 and illustrate the method and apparatus of Fig. 5 in various stages of the operation thereof.
Fig. 6 is a view similar to Fig. 5 and illustrates the completed sub-assembly that was made by the method and apparatus of Fig. 5 or Fig. 7.
Fig. 7 is a view similar to Fig. 5 and illustrates another example of how the method of this invention may be `~ 1177~2~
implemented for forming the sub-assembly of Fig. 6.
Fig. 8 is an end view of the sub-assembly of Fig.
6 and is taken in the direction of the arrows 8-8 of Fig. 6.
Fig. 9 is an enlarged cross-sectional view taken on line 9-9 of Fig. 6.
Referring now to Figs. 1 and 2, the improved ther-mally actuatable electrical switch is generally indicated by the reference numeral 10 and, with the exception of the interlocking arrangement for its end plug and the lead passing therethrough, is substantially of the same type and construction as the thermally actuatable electrical switch disclosed in U.S. Patent No. 3,519,972. Therefore, it is only necessary to describe certain details of the thermally actuatable electrical switch 10 to understand the features lS of this invention.
In particular, the thermally actuatable electrical switch 10 includes an electrically conductive casing or housing means 11 formed of metallic material and having an open end 12 and a closed end 13 secured to an electrically conductive lead or terminal 14 while another electrically conductive lead 15 is carried in an opening 16 of an electrically insulating end plug 17 secured in the open end 12 of the casing or housing means 11 by having one end 18 of a cylindrical portion 19 thereof abutting a shoulder 20 of the casing 11 and the other end 21 being held by a turned over end 22 of the casing 11 whereby the end plug 17 is fixed in the open end 12 of the casing 11 and is hermetically sealed thereto by a suitable epoxy resin 23 being disposed on the exterior of the casing 11 at the turned end 22 thereof and over a projecting cone portion 24 of the end plug 17 and onto a terminal means or end 25 of the lead 15 that projects beyond the adjacent end 26 of the end plug 17 as illustrated whereby the uncovered part of the end 25 of the lead 15 provides a terminal structure for the thermally actuatable eleatrical switch 10 to be interconnected into the desired electrical circuit.
The lead 15 has an enlarged arresting head 27 that ~" l 177~2~
pro~ects beyond the end 28 of the end plug 17 and bears against the same outboard of the opening 16 to define a fixed contact within the casing 11 that i5 normally engaged by a movable disc-like contact member 29 that has outer peripheral resilient fingers 30 disposed in sliding and electrical contact with the internal peripheral surface 31 of the con-ductive casing 11 as illustrated, the movable contact 29 normally being held in conductive contact with the fixed contact 27 b~ a compression spring 32 normally held in the compressed condition illustrated in Fig. 1 by a temperature sensitive member 33 that remains in the solid condition illustrated in Fig. 2 as long as the same is sensing a tem-perature below a predetermined temperature. However/ when the temperature sensed by the member 33 exceeds the pre-determined temperature thereof, the member 33 melts and thereby permits the compression spring 32 to expand so that a weaker compression spring 34 disposed between the end plug 17 and the movable contact member 29 can expand and move the movable contact 29 out of contact with the fixed contact 27.
Therefore, it can be seen that as long as the tem-perature sensing member 33 is in the solid condition illus-trated in Fig. 2, an electrical circuit can be completed between the terminals 14 and 25. However, once the tempera-ture sensitive member 33 melts, the force of the compression ~pring 34 now moves the movable contact 29 out of contact with the fixed contact 27 and holds the same out of contact with the fixed contact 27 so that the electrical circuit between the terminals 14 and 25 is permanently interrupted by the thermally actuated electrical switch construction 10.
As set forth in the aforementioned U.S. Patent No. 4,060,787, it is desired to prevent someone from attempting to push axially inwardly on the lead lS, after the thermally actuatable switch 10 has been thermally actuated in the manner previously described, and break the bond be-tween the epoxy resin 23 and the lead 15 so as to move the lead 15 into the casing 11 to again contact the fixed con-tact 27 against the movable contact 29. This could be .
1 177~29 accomplished by the person pushing inwardly on the lead 15 with sufficient force to break the bond between the epoxy resin 23 that has seeped into the bore or opening 16 around the inner portion 35 of the lead 15 or by that person first tending to rotate the lead 15 relative to the end plug 17 and thereby breaking such bond so as to thereafter push axially inwardly on the lead 15.
It is a feature of this invention to provide unique interlocking means between the lead 15 and the end plug 17 to tend to prevent such axial inward movement of the lead 15 into the casing or housing 11.
In particular, it was found that an integral part of the lead 15 can be formed to interlock the lead 15 with the end plug 17.
This unique interlocking means comprises an integral part 36 of the lead 15 that is formed so as to be disposed outboard of the opening 16 and against the end 26 of the end plug 17 so as to tend to prevent movement of the lead 15 into the housing 11 of the thermally actuatable electrical switch construction 10.
One example of how the method of this invention may be carried out, thereby to form the part 36 of the lead 15, is generally indicated by the reference numeral 37 in Fig.
S which depicts a pair of opposed skiving knives 38 and 39 which are adapted to be brought toward each other to indent slightly into the opposed sides of the lead 15 after the lead 15 has been disposed in the opening 16 of the end plug 17 with its enlarged fixed contact means 27 disposed against the end 28 of the end plug 17. The skiving knives 38 and 39 initially engage into the lead 15 at the respective points 40 and 41 thereon which are spaced from the end 26 of the end plug 17 a distance sufficient to subsequently form the part 36 from the resulting skived or shaved material of the lead 15 when the skiving knives 38 and 39 in the indenting position are subsequently moved toward the end plug 17 while the lead 15 is held in the position illustrated in Fig. 5 so that the skived material being skived or shaved from the opposed -` I t7762~
, sides of the lead 15, as illustrated in Figs. 5' and 5", will respectively be compacted and reshaped against the end 26 of the end plug 17 to form two tab-like portions 42 and 43 respectively disposed against the end 26 of the end plug 17, as illustrated in Fig. 6, and respectively extending radially outwardly from the opposed sides of the lead lS, as illustrated in Fig. 8.
As the skived material 42 and 43 is being formed and reshaped against the end 26 of the end plug 17 by the skiving knives 38 and 39 moving to the left in Fig. 5 to the position illustrated in Fig. 6, portions 44 and 45 of the skived material 42 and 43 actually enter into the opening 16 of the end plug 17 to not only cause centering of the lead 15 in the opening 16 of the end plug 17 for a purpose here-inafter described, but also to provide means for interlockingwith the epoxy resin 23 as will be apparent hereinafter.
Thus, it can be seen that the method and apparatus 37 indicated in Fig. 5 is adapted to provide a self-contained sub-asse'mbly in Fig. 6 that comprises the lead 15 and the end plug 17 and is generally indicated by the reference numeral 46 in Fig, 6, the end plug being sandwiched between the contact 27 of the lead 15 and the portions 42 and 43 compris-ing the part 36 of the lead 15.
The skiving knives 38 and 39 respectively have the skiving surfaces 47 and 48 thereof formed in such a unique manner that the same skive the lead 15 to provide opposed recesses 49 and 50 on the terminal portion 25 of the lead which do not join with each other as they only extend around the circumference of the substantially cylindrical lead 15 at a distance that is less than 180 as fully illustrated in Fig. 9. This feature permits the skived material 42 and 43 that is disposed outboard of the opening 16 and against the end 26 of the end plug 17 to not cover substantial por-tions of the opening 16 as represented by the reference numerals 51 and 52 in Fig. 8. In this manner, the portions 51 and 52 of the opening 16 readily permit the epoxy resin or sealing compound 23 to flow into the opening 16 by capil-, .
~ l 177~2~
--8--lary action to completely surround the portion 35 of the lead 15 in the manner illustrated in Figs. 2 and 3 to seal the opening 16 as well as to interlock with the portions 44 and 45 of the skived material 42 and 43 to tend to prevent rota-tional movement between the lead 15 and the end plug 17, theportions 44 and 45 when formed having centered the portion 35 of the lead within the opening 16 to substantially insure that the epoxy resin 23 can flow completely around the portion 35 of the lead 15 in the opening 16.
In addition, when the sub-assembly 46 is disposed in the open end 12 of the casing 11 to form the thermally actuatable electrical switch 10 and has the epoxy resin 23 subsequently disposed on the end 24 of the end plug 17 as illustrated in Fig. 2, the epoxy resin 23 fully covers the skived portions 42 and 43 as illustrated in Fig. 2 and extends onto the lead 15 beyond the recesses 49 and 50 as illustrated in Fig. 2. In this manner, the shape of the recesses 49 and 50 as well as the confiquration of the skived tab-like members 42 and 43 interlock with the epoxy material 23 when the same subsequently hardens so as to prevent rotational movement between the lead 15 and the end plug 17.
The self-contained sub-assembly 46 can be made by another example of the method of this invention generally indicated by the reference numeral 37A in Fig. 7.
As illustrated in Fig. 7, the skiving knives 38A
and 39A are adapted to respectively come together and initially dig into the lead 15 at the points 40A and 41A on the opposed sides of the lead 15 at a location spaced from the contact 27 of the lead 15 which is exactly the same dis-tance that the skiving knives 38 and 39 of the example 37 initially make contact at the points 40 and 41 with the lead 15 of Fig. 5.
However, in the example 37A of Fig. 7, it can be seen that the lead 15 is moved to the right in the end plug 17 while the skiving knives 38 and 39A are held stationary in their inwardly indented position so that subsequently the rightward moving lead 15 has the contact 27 impacted against - l t77B2~
g the end 28 o~ the end plug 17 so that the resulting skived material will be impacted and reshaped against the other end 26 of the end plug 17 when the parts are in the position illustrated in Fig. 6 whereby the resulting sel-contained sub-assembly 46 is identical to the self-contained sub-assembly 46 produced by the example 37 of Fig. 5.
Therefore, it can be seen that it is relatively simple, according to the method of this invention, to form the integral part 36 of the lead 15 to interlock against the end 26 of the insulating end plug 17 to tend to prevent axial movement of the lead 15 relative to the end plug 17 in one direction while the contact 27 prevents axial move-ment in the opposite direction.
Thereafter, it can be seen that it is relatively lS simple to assemble the sub-assembly 46 into a casing or housing means 11 to form the thermally actuatable electrical switch 10 of this invention because once the end plug 17 has been secured in place by turning over the end 12 of the casing 11 to hold the cylindrical part 19 of the end plug 17 between the shoulder 20 and the turned end 12, as illustrated in Fig, 2, the subsequent application of the epoxy resin 23 to the device 10 causes the epoxy resin 23 to enter by capillary action through the portions 51 and 52 of the opening 16 to completely surround the portion 35 of the lead 15 to seal the opening 16 as well as to interlock with the portions 44 and 45 of the skived parts 42 and 43 of the lead 15, the skived parts 42 and 43 and recesses 49 and 50 also interlocking with the epoxy resin 23 as illustrated to tend to prevent rotational movement between the lead 15 and the device 10.
While this invention is not to be limited to specific dimensions, one typical thermally actuatable electrical switch 10 made by the method of this invention comprised a lead 15 of No. 18 AWG electrolytic tough pitch copper wire approximately 0.0403 of an inch in diameter and having a flash silver plating thereon of approximately 0,000020 of an inch thick. The longitudinal length of the .
, 1 177~g skived rece3ses 49 and 50 therein were approximately 0.045 of an inch and approximately 0.003 of an inch deep at the point of greatest depth thereof. The length of the end plug 17 is approximately 0.057 of an inch and the diameter of the opening 16 therein is approximately 0.045 of an inch. It was found that the resulting self-contained sub-assembly 46 when assembled in the device 10 provided substantial resistance to inward axial movement of the lead 15 relative to the device 10 even after the epoxy resin material 23 had been completely melted off of the same. In addition, it was found that the recesses 49 and 50 in the lead 15 do not adversely reduce the strength of the lead 15 between such areas so as to cause breaking of the lead 15 between the recesses 49 and 50.
Also, it has been found that when tabs are merely lanced from the lead to interlock with the end of the end plug, such lanced tabs tend to merely fold back into place when the lead is heated and is axially pushed into the end plug, whereas with the skived tabs, sufficient material from the lead has been plowed or shaved in advance of the skiving knives to cause a jamming with the end plug when the lead is heated and an axial force is imposed on the lead in a direc-tion toward the end plug. In this manner, the skived tabs provide a greater resistance to an axial force tending to move the respective lead into the thermally actuatable electrical switch construction than is provided by the lanced tabs.
However, according to the teachings of the present invention, the conductive lead of a thermally actuatable electrical switch construction can be formed in another unique manner to interlock with the end plug so as to be effective in preventing axial movement of the lead in the opening of the end plug in a direction that would be into the housing that carries the end plug.
In particular, according to the invention, there is provided a method of making a thermally actuatable electrical switch of the kind having a housing carrying an electrically insulating end plug provided with an opening passing therethrough in which a portion of a conductive lead is disposed so that opposed ends of the lead extend beyond opposed ends of the ènd plug and respectively define a fixed contact inside the housing and a terminal outsidethe housing the lead being interlocked with the end plug to prevent axial movement of the lead into the housing by means of an integral part of the terminal that extends outboard of the opening and is disposed against the respective opposed end of the end plug adjacent the terminal, comprising the steps of skiving the part from the lead and compacting the skived part against the respective opposed end of the end plug.
We also provide a thermally actuatable electrical switch of the kind having a housing carrying an electrically insulating end plug provided with an opening passing there-through in which a portion of a conductive lead is disposed80 that opposed ends of the lead extend beyond opposed ends of the end plug and respectively define a fixed contact inside the housing and a terminal outside the housing, the lead being interlocked with the end plug to prevent axial movement of the lead into the housing by means of an integral part of the terminal extending outboard of the opening and disposed against the respective opposed end of the end plug ~ .,, I 177~2~
~3--ad~acent the terminal, wherein the integral part of the terminal comprises a skiving of the terminal.
Preferably, the integral part of the termirlal has a portion thereof disposed in the opening adjacent the respective end of the end plug. The integral part may be covered by a sealing compound disposed on the respective end of the end plug and extending onto the terminal outboard of the integral part, and the integral part may have a con-figuration that interlocks with the sealing compound in a manner to pre~ent rotational movement of the terminal relative to the end plug.
In order that the invention may be fully understood, it will now be described with reference to the accompanying drawings, wherein:
Fig. 1 is a perspective view of an embodiment of the improved thermally actuatable electrical switch of this invention.
Fig. 2 is an enlarged cross-sectional view of the thermally actuatable electrical switch embodiment of Fig. 1 and is taken substantially on the line 2-2 of Fig. 1.
Fig. 3 is a cross-sectional view taken on line 3-3 of Fig. 2.
Fig. 4 is a cross-sectional view taken on line 4-4 of Fig. 2.
Fig. 5 i8 an axial cross-sectional view schemati-cally illustrating an example of how the method of this invention may be implemented for forming a sub-assembly that is utilized in forming the thermally actuatable electrical switch embodiment illustrated in Figs. 1-4.
Fig. 5' and Fig. 5" are enlarged fragmentary views similar to Fig. 5 and illustrate the method and apparatus of Fig. 5 in various stages of the operation thereof.
Fig. 6 is a view similar to Fig. 5 and illustrates the completed sub-assembly that was made by the method and apparatus of Fig. 5 or Fig. 7.
Fig. 7 is a view similar to Fig. 5 and illustrates another example of how the method of this invention may be `~ 1177~2~
implemented for forming the sub-assembly of Fig. 6.
Fig. 8 is an end view of the sub-assembly of Fig.
6 and is taken in the direction of the arrows 8-8 of Fig. 6.
Fig. 9 is an enlarged cross-sectional view taken on line 9-9 of Fig. 6.
Referring now to Figs. 1 and 2, the improved ther-mally actuatable electrical switch is generally indicated by the reference numeral 10 and, with the exception of the interlocking arrangement for its end plug and the lead passing therethrough, is substantially of the same type and construction as the thermally actuatable electrical switch disclosed in U.S. Patent No. 3,519,972. Therefore, it is only necessary to describe certain details of the thermally actuatable electrical switch 10 to understand the features lS of this invention.
In particular, the thermally actuatable electrical switch 10 includes an electrically conductive casing or housing means 11 formed of metallic material and having an open end 12 and a closed end 13 secured to an electrically conductive lead or terminal 14 while another electrically conductive lead 15 is carried in an opening 16 of an electrically insulating end plug 17 secured in the open end 12 of the casing or housing means 11 by having one end 18 of a cylindrical portion 19 thereof abutting a shoulder 20 of the casing 11 and the other end 21 being held by a turned over end 22 of the casing 11 whereby the end plug 17 is fixed in the open end 12 of the casing 11 and is hermetically sealed thereto by a suitable epoxy resin 23 being disposed on the exterior of the casing 11 at the turned end 22 thereof and over a projecting cone portion 24 of the end plug 17 and onto a terminal means or end 25 of the lead 15 that projects beyond the adjacent end 26 of the end plug 17 as illustrated whereby the uncovered part of the end 25 of the lead 15 provides a terminal structure for the thermally actuatable eleatrical switch 10 to be interconnected into the desired electrical circuit.
The lead 15 has an enlarged arresting head 27 that ~" l 177~2~
pro~ects beyond the end 28 of the end plug 17 and bears against the same outboard of the opening 16 to define a fixed contact within the casing 11 that i5 normally engaged by a movable disc-like contact member 29 that has outer peripheral resilient fingers 30 disposed in sliding and electrical contact with the internal peripheral surface 31 of the con-ductive casing 11 as illustrated, the movable contact 29 normally being held in conductive contact with the fixed contact 27 b~ a compression spring 32 normally held in the compressed condition illustrated in Fig. 1 by a temperature sensitive member 33 that remains in the solid condition illustrated in Fig. 2 as long as the same is sensing a tem-perature below a predetermined temperature. However/ when the temperature sensed by the member 33 exceeds the pre-determined temperature thereof, the member 33 melts and thereby permits the compression spring 32 to expand so that a weaker compression spring 34 disposed between the end plug 17 and the movable contact member 29 can expand and move the movable contact 29 out of contact with the fixed contact 27.
Therefore, it can be seen that as long as the tem-perature sensing member 33 is in the solid condition illus-trated in Fig. 2, an electrical circuit can be completed between the terminals 14 and 25. However, once the tempera-ture sensitive member 33 melts, the force of the compression ~pring 34 now moves the movable contact 29 out of contact with the fixed contact 27 and holds the same out of contact with the fixed contact 27 so that the electrical circuit between the terminals 14 and 25 is permanently interrupted by the thermally actuated electrical switch construction 10.
As set forth in the aforementioned U.S. Patent No. 4,060,787, it is desired to prevent someone from attempting to push axially inwardly on the lead lS, after the thermally actuatable switch 10 has been thermally actuated in the manner previously described, and break the bond be-tween the epoxy resin 23 and the lead 15 so as to move the lead 15 into the casing 11 to again contact the fixed con-tact 27 against the movable contact 29. This could be .
1 177~29 accomplished by the person pushing inwardly on the lead 15 with sufficient force to break the bond between the epoxy resin 23 that has seeped into the bore or opening 16 around the inner portion 35 of the lead 15 or by that person first tending to rotate the lead 15 relative to the end plug 17 and thereby breaking such bond so as to thereafter push axially inwardly on the lead 15.
It is a feature of this invention to provide unique interlocking means between the lead 15 and the end plug 17 to tend to prevent such axial inward movement of the lead 15 into the casing or housing 11.
In particular, it was found that an integral part of the lead 15 can be formed to interlock the lead 15 with the end plug 17.
This unique interlocking means comprises an integral part 36 of the lead 15 that is formed so as to be disposed outboard of the opening 16 and against the end 26 of the end plug 17 so as to tend to prevent movement of the lead 15 into the housing 11 of the thermally actuatable electrical switch construction 10.
One example of how the method of this invention may be carried out, thereby to form the part 36 of the lead 15, is generally indicated by the reference numeral 37 in Fig.
S which depicts a pair of opposed skiving knives 38 and 39 which are adapted to be brought toward each other to indent slightly into the opposed sides of the lead 15 after the lead 15 has been disposed in the opening 16 of the end plug 17 with its enlarged fixed contact means 27 disposed against the end 28 of the end plug 17. The skiving knives 38 and 39 initially engage into the lead 15 at the respective points 40 and 41 thereon which are spaced from the end 26 of the end plug 17 a distance sufficient to subsequently form the part 36 from the resulting skived or shaved material of the lead 15 when the skiving knives 38 and 39 in the indenting position are subsequently moved toward the end plug 17 while the lead 15 is held in the position illustrated in Fig. 5 so that the skived material being skived or shaved from the opposed -` I t7762~
, sides of the lead 15, as illustrated in Figs. 5' and 5", will respectively be compacted and reshaped against the end 26 of the end plug 17 to form two tab-like portions 42 and 43 respectively disposed against the end 26 of the end plug 17, as illustrated in Fig. 6, and respectively extending radially outwardly from the opposed sides of the lead lS, as illustrated in Fig. 8.
As the skived material 42 and 43 is being formed and reshaped against the end 26 of the end plug 17 by the skiving knives 38 and 39 moving to the left in Fig. 5 to the position illustrated in Fig. 6, portions 44 and 45 of the skived material 42 and 43 actually enter into the opening 16 of the end plug 17 to not only cause centering of the lead 15 in the opening 16 of the end plug 17 for a purpose here-inafter described, but also to provide means for interlockingwith the epoxy resin 23 as will be apparent hereinafter.
Thus, it can be seen that the method and apparatus 37 indicated in Fig. 5 is adapted to provide a self-contained sub-asse'mbly in Fig. 6 that comprises the lead 15 and the end plug 17 and is generally indicated by the reference numeral 46 in Fig, 6, the end plug being sandwiched between the contact 27 of the lead 15 and the portions 42 and 43 compris-ing the part 36 of the lead 15.
The skiving knives 38 and 39 respectively have the skiving surfaces 47 and 48 thereof formed in such a unique manner that the same skive the lead 15 to provide opposed recesses 49 and 50 on the terminal portion 25 of the lead which do not join with each other as they only extend around the circumference of the substantially cylindrical lead 15 at a distance that is less than 180 as fully illustrated in Fig. 9. This feature permits the skived material 42 and 43 that is disposed outboard of the opening 16 and against the end 26 of the end plug 17 to not cover substantial por-tions of the opening 16 as represented by the reference numerals 51 and 52 in Fig. 8. In this manner, the portions 51 and 52 of the opening 16 readily permit the epoxy resin or sealing compound 23 to flow into the opening 16 by capil-, .
~ l 177~2~
--8--lary action to completely surround the portion 35 of the lead 15 in the manner illustrated in Figs. 2 and 3 to seal the opening 16 as well as to interlock with the portions 44 and 45 of the skived material 42 and 43 to tend to prevent rota-tional movement between the lead 15 and the end plug 17, theportions 44 and 45 when formed having centered the portion 35 of the lead within the opening 16 to substantially insure that the epoxy resin 23 can flow completely around the portion 35 of the lead 15 in the opening 16.
In addition, when the sub-assembly 46 is disposed in the open end 12 of the casing 11 to form the thermally actuatable electrical switch 10 and has the epoxy resin 23 subsequently disposed on the end 24 of the end plug 17 as illustrated in Fig. 2, the epoxy resin 23 fully covers the skived portions 42 and 43 as illustrated in Fig. 2 and extends onto the lead 15 beyond the recesses 49 and 50 as illustrated in Fig. 2. In this manner, the shape of the recesses 49 and 50 as well as the confiquration of the skived tab-like members 42 and 43 interlock with the epoxy material 23 when the same subsequently hardens so as to prevent rotational movement between the lead 15 and the end plug 17.
The self-contained sub-assembly 46 can be made by another example of the method of this invention generally indicated by the reference numeral 37A in Fig. 7.
As illustrated in Fig. 7, the skiving knives 38A
and 39A are adapted to respectively come together and initially dig into the lead 15 at the points 40A and 41A on the opposed sides of the lead 15 at a location spaced from the contact 27 of the lead 15 which is exactly the same dis-tance that the skiving knives 38 and 39 of the example 37 initially make contact at the points 40 and 41 with the lead 15 of Fig. 5.
However, in the example 37A of Fig. 7, it can be seen that the lead 15 is moved to the right in the end plug 17 while the skiving knives 38 and 39A are held stationary in their inwardly indented position so that subsequently the rightward moving lead 15 has the contact 27 impacted against - l t77B2~
g the end 28 o~ the end plug 17 so that the resulting skived material will be impacted and reshaped against the other end 26 of the end plug 17 when the parts are in the position illustrated in Fig. 6 whereby the resulting sel-contained sub-assembly 46 is identical to the self-contained sub-assembly 46 produced by the example 37 of Fig. 5.
Therefore, it can be seen that it is relatively simple, according to the method of this invention, to form the integral part 36 of the lead 15 to interlock against the end 26 of the insulating end plug 17 to tend to prevent axial movement of the lead 15 relative to the end plug 17 in one direction while the contact 27 prevents axial move-ment in the opposite direction.
Thereafter, it can be seen that it is relatively lS simple to assemble the sub-assembly 46 into a casing or housing means 11 to form the thermally actuatable electrical switch 10 of this invention because once the end plug 17 has been secured in place by turning over the end 12 of the casing 11 to hold the cylindrical part 19 of the end plug 17 between the shoulder 20 and the turned end 12, as illustrated in Fig, 2, the subsequent application of the epoxy resin 23 to the device 10 causes the epoxy resin 23 to enter by capillary action through the portions 51 and 52 of the opening 16 to completely surround the portion 35 of the lead 15 to seal the opening 16 as well as to interlock with the portions 44 and 45 of the skived parts 42 and 43 of the lead 15, the skived parts 42 and 43 and recesses 49 and 50 also interlocking with the epoxy resin 23 as illustrated to tend to prevent rotational movement between the lead 15 and the device 10.
While this invention is not to be limited to specific dimensions, one typical thermally actuatable electrical switch 10 made by the method of this invention comprised a lead 15 of No. 18 AWG electrolytic tough pitch copper wire approximately 0.0403 of an inch in diameter and having a flash silver plating thereon of approximately 0,000020 of an inch thick. The longitudinal length of the .
, 1 177~g skived rece3ses 49 and 50 therein were approximately 0.045 of an inch and approximately 0.003 of an inch deep at the point of greatest depth thereof. The length of the end plug 17 is approximately 0.057 of an inch and the diameter of the opening 16 therein is approximately 0.045 of an inch. It was found that the resulting self-contained sub-assembly 46 when assembled in the device 10 provided substantial resistance to inward axial movement of the lead 15 relative to the device 10 even after the epoxy resin material 23 had been completely melted off of the same. In addition, it was found that the recesses 49 and 50 in the lead 15 do not adversely reduce the strength of the lead 15 between such areas so as to cause breaking of the lead 15 between the recesses 49 and 50.
Also, it has been found that when tabs are merely lanced from the lead to interlock with the end of the end plug, such lanced tabs tend to merely fold back into place when the lead is heated and is axially pushed into the end plug, whereas with the skived tabs, sufficient material from the lead has been plowed or shaved in advance of the skiving knives to cause a jamming with the end plug when the lead is heated and an axial force is imposed on the lead in a direc-tion toward the end plug. In this manner, the skived tabs provide a greater resistance to an axial force tending to move the respective lead into the thermally actuatable electrical switch construction than is provided by the lanced tabs.
Claims (5)
1. In a method of making a thermally actuatable electrical switch construction having a housing means carrying an electrically insulating end plug provided with an opening means passing therethrough and in which a por-tion of a conductive lead is disposed so that opposed ends of said lead extend beyond opposed ends of said end plug and respectively define a fixed contact means inside said housing means and a terminal means outside said housing means, said lead having means interlocking with said end plug to tend to prevent axial movement of said lead into said housing means, said means of said lead that interlocks with said end plug comprising an integral part of said terminal means that extends outboard of said opening and is disposed against the respective opposed end of said end plug that is adjacent said terminal means whereby said lead and said part thereof comprise a one-piece member, said switch construction having a sealing compound dis-posed on said respective end of said end plug so as to extend onto said terminal means outboard of said part there-of whereby said compound covers said part, said compound extending into said opening from said respective end of said end plug and surrounding said portion of said lead within said end plug, the improvement comprising the steps of skiving said part from said lead, and compacting said skived part against said respective opposed end of said end plug, said steps of skiving and compacting comprising the step of forming said part to comprise a plurality of circumferentially spaced apart tab-like members extending substantially radially from said terminal means against said respective opposed end of said end plug and respective-ly having portions disposed in said opening in said end plug in circumferentially spaced apart relation to tend to center said portion of said lead in said opening of said end plug and to interlock with said compound in said open-ing to tend to prevent rotational movement of said lead relative to said end plug.
2. A method of making a thermally actuatable electrical switch construction as set forth in claim 1, wherein said steps of skiving and compacting comprise the steps of indenting into said terminal means of said lead with skiving knife means in a direction substantially transverse to the longitudinal axis of said lead and at a plurality of point means each longitudinally spaced from said fixed contact means thereof and circumferentially spaced from each other, and thereafter, and while said knife means are in such indented position, causing relative movement between said lead and said knife means in a direction substantially parallel to said longitudinal axis of said lead to shave or plow said skived part from said terminal means from said point means toward said fixed contact means until said skived part is compacted against said respective opposed end of said end plug between said respective opposed end of said end plug and said skiving knife means, said steps of skiving and compacting compris-ing the step of creating a plurality of recesses in said terminal means each of which is many times longer in a longitudinal direction thereof than the transverse depth thereof at the point of the greatest depth of the respective recess.
3. A method of making a thermally actuatable electrical switch construction as set forth in claim 1, wherein said terminal means has a generally circular trans-verse cross-section configuration and wherein said steps of skiving and compacting said part of said terminal means causes said part to comprise a pair of said tab-like members extending substantially radially from opposed sides of said terminal means.
4. A method of making a thermally actuatable electrical switch construction as set forth in claim 2, wherein said conductive lead has a diameter of approxi-mately 0.0403 of an inch and wherein said step of creating said recesses creates each said recess to have a depth of approximately 0.003 of an inch at the point of greatest depth thereof and to have a longitudinal length of approxi-mately 0.045 of an inch.
5. A method of making a thermally actuatable electrical switch construction as set forth in claim 1, wherein said steps of skiving and compacting take place before said end plug and its interlocked lead are assembled with said housing means.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US27764781A | 1981-06-26 | 1981-06-26 | |
| US277,647 | 1981-06-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1177629A true CA1177629A (en) | 1984-11-13 |
Family
ID=23061788
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000404605A Expired CA1177629A (en) | 1981-06-26 | 1982-06-07 | Thermally actuatable electrical switches |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS5844631A (en) |
| CA (1) | CA1177629A (en) |
| DE (1) | DE3222660A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3605421A1 (en) * | 1986-02-20 | 1987-08-27 | Thomson Brandt Gmbh | DATA EXCHANGE METHOD BETWEEN A FIRST AND A SECOND PROCESSOR |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2016146C3 (en) * | 1970-04-04 | 1979-12-13 | Opti-Patent-Forschungs- Und Fabrikations- Ag, Glarus (Schweiz) | Zipper with knitted straps |
-
1982
- 1982-06-07 CA CA000404605A patent/CA1177629A/en not_active Expired
- 1982-06-16 DE DE19823222660 patent/DE3222660A1/en not_active Withdrawn
- 1982-06-21 JP JP10662382A patent/JPS5844631A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| DE3222660A1 (en) | 1983-02-03 |
| JPS5844631A (en) | 1983-03-15 |
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| MKEC | Expiry (correction) | ||
| MKEX | Expiry |