US3339048A

US3339048A - Switch having improved multiple blade assembly

Info

Publication number: US3339048A
Application number: US495807A
Authority: US
Inventors: Edward G Haderer
Original assignee: Texas Instruments Inc
Current assignee: Texas Instruments Inc
Priority date: 1965-10-14
Filing date: 1965-10-14
Publication date: 1967-08-29
Anticipated expiration: 1984-08-29
Also published as: GB1158119A; FR1496311A; DE1590757B1

Description

1967 E. e. HADERER 3,339,048

SWITCH HAVING IMPROVED MULTIPLE BLADE ASSEMBLY Filed Oct. l4, 1965 FIG.I FIG. 3

INVENTOR. EDWARD G. HADERER ATTORNEY United States Patent 3,339,048 SWITCH HAVING IMPROVED MULTIPLE BLADE ASSEMBLY Edward G. Haderer, Plainville, Mass., assignor to Texas Instruments Incorporated, Dallas, Tex., a corporation of Delaware Filed Oct. 14, 1965, Ser. No. 495,807 20 Claims. (Cl. 200-166) This invention relates to electrical switches, and in particular to electrical switches which are snap acting and of small size.

In the manufacture of snap-acting electrical switches, and particularly as to such switches which are made in very small sizes, it has been found desirable but difficult to construct switches which are able to withstand relatively high temperatures, have high current carrying capacity in relation to their size, and yet which at the same time have a relatively low resistance in order to minimize the voltage drop across the switch. Hitherto, attempts have been made to do this by using a high temperature-resistant metal for the snap-acting blade which serves as a switch arm in such devices, but high temperature-resistant metals ordinarily have a relatively high electrical resistance. As a result, the voltage drop across the switch is higher than that desired.

Therefore, in order to minimize the voltage drop by utilizing a switch blade that has a low resistance, the blade has been made thicker in order to increase its crosssection. However, the use of a single relatively thick snap-acting blade leads to an increase in stress level and sluggishness in operation, and these are undesirable features.

This invention overcomes these problems, particularly where snap-acting elements are used, by the use of a of an electrical snap-acting switch which has a crisp snapaction even though made of relatively high temperatureresistance material, and also has low electrical resistance; the provision of a snap-acting switch of classes stated A above in which'the switch blades are fastened together at plurality of snap-acting blades lying in face-to-face relationship, and attached together. By doing this, the crosssectional area of the composite blade is increased, thus lowering the resistance of the blade to current passage and thus also lowering the voltage drop across the switch. In addition, because the blades makes up the composite structure are permitted to slide slightly on each other during snapping, the crisp snap-action of a single blade is mostly retained, thus leading to a desirable operation of the switch. Since the overall resistance of the assembly is low due to the use of multiple blades through which the current passes in parallel, high temperature-resistant material for each individual blade can be used without adversely increasing the total lengthwise resistance of the assembly to an undesirable point.

In addition, the current carrying capacity of the switch is increased, because of the greater cross-sectional area and attendant smaller heating of the blades because of the passage of current therethrough.

In the use of multiple blades, a difliculty is experienced in that if the blades are attached together throughout their lengths, the aforementioned sluggish action will occur. To solve this, it has been found that if the blades are attached at one point only, this sluggishness of action is avoided. This invention, therefore, is also concerned with a means of fastening blades together which will provide simultaneously a single place of attachment and a means of good electrical conduction of current into all the blades. Additionally, the means of fastening is such as not to distort the blade material at the place of fastening, or stress the material unduly with resultant shortening of its life during repeated cycling.

V Therefore, among the several objects and provisions of this invention may be noted the provision of an electrical switch having as. a switch blade a plurality of individual switch blades fastened together; the provision of a snapone point by a novel fastening means; the provision of an electrical switch of the last named class in which the fastening means minimizes distortion of the switch blade material at the point where the blades are fastened, and also minimizes high stresses and strains in the switch blade material at the point of fastening; and the provision of a snap-acting electrical switch which is adaptable to be made economically in small sizes, and in mass production. Other objects and advantages of the invention will be in part obvious and in part pointed out hereinafter.

Accordingly, the invention comprises the elements and combinations of elements, features of construction, arrangement of parts, and methods and steps of construction, which will be exemplified in the structures and methods hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings in which are illustrated several embodiments of the invention:

FIG. 1 is a plan view of a plurality of individual switch blades, with a portion of one blade broken away to show the use of an exemplary two-blade construction;

FIG. 2 is a cross-section of a portion of an end of the blades of the FIG. 1 embodiment, taken in the direction of sight lines 22 thereon;

FIG. 3 is a sectional view of a hermetically sealed switch using the blade assembly of FIGS. 1 and 2;

FIG. 4 is a cross-sectional view, similar to FIG. 2, but showing another embodiment of the invention;

FIG. 5 is a plan view of a plurality of individual blades of another embodiment of the invention, again with a portion of one blade broken away to show an exemplary two-blade construction.

FIG. 6 is a plan view of a snap-acting switch using the FIG. 5 bade assembly;

FIG. 7 is a view similar to FIG. 2, another embodiment of the invention;

FIG. 8 is a view similar to FIG. 2, but showing still another embodiment of the invention; and

FIG. 9 is a schematic cross-section of apparatus showing a method of assembling the structures of FIGS. 1, 4, 5, 7, and 8.

Throughout the drawings, similar reference characters illustrate corresponding parts of the several embodiments. The various drawings are in some instances enlarged in order to show detail with greater clarity; and for the same reason, the relative dimensions of certain parts have been exaggerated.

Referring now to FIGS. 1, 2 and 3, generally indicated by numeral 2 is an assembly of individual switch blades, these blades being normally flat, and the assembly being fastened together by, and acting as a supporting structure for, an electrical contact which will be described later. In this exemplary embodiment, the assembly consists of the two

individual blades

4 and 6, a portion of blade 4 being broken away to show blade 6. Each of

blades

4 and 6 may be the same, and examples of such individual blades are described in United States Patent 2,777,032, dated Jan. 8, 1957, with full details and a description of operation thereof being set forth in such patent. The teaching of said patent is therefore incorporated herein but showing yet by reference. Briefly, each of

blades

4 and 6 comprises three legs, namely, a pair of outer legs 8 and 10, and a center leg 12. At one end of these legs, they are attached by a connecting member or web 14, (all as described in said patent), and the other ends are free.

The free ends of the legs are provided with

holes

16, 18 and 20, the

holes

16 and 20 constituting mounting means (as will be described later) for the ends of the two outer legs, and the hole 18 constituting a means now to be described for attaching the blades together at the ends of the center legs 12.

It will be noted that the holes 18 are approximately of the same size, and when the

blades

4 and 6 are placed in alignment in face-to-face relationship, the holes 18 are substantially co-axial.

A pair of substantially identical

electrical contacts

22 and 24 are provided, each of the

contacts

22 and 24 being a so called button-type contact well-known in the electrical switch industry. Each button comprises a face 26 of precious metal such as silver and a layer 28 of base metal which is adapted for a welding operation. In addition, as is customary, each of the contacts is provided with an extension or projection 30' extending from the base metal side of the contacts.

The diameter of the projections 30 at their back ends is made the same as the holes 18 or just slightly less, for the purpose of accurately locating the contact buttons in position on the blades. If the hole 18 in one blade is larger or smaller than in the other blade, then the corresponding projection for the respective contact is made to fit the hole. The shape of the projections is not material but it is preferred that they be so shaped that when fitted into the holes 18, there be a small space left to receive the flash from the welding operation described below. That is, the volume of the hole 18 must be equal to or preferably greater than the volume of the projections 30 to receive the flash from the welding operation. The length of the projections 30 is such that when the

contacts

22 and 24 are located on each side of the combined

blades

4 and 6, the backing materials of these contacts are separated slightly from the surfaces of the

blades

4 and 6. Reference to FIG. 9 indicates such a preliminary assembly, and shows contact 24 placed in a suitably provided recess in a welding electrode 34, in customary fashion. The other contact 22 is likewise located in a suitable recess in a top welding electrode 36, and it will be noted that when so positioned, the innermost ends of each of the projections 30 touch, the length of the

projections

22 and 24 providing the above mentioned spacing 37.

By means of a conventional welding transformer 38 controlled by a switch 40 (each being indicated schematically) a projection weld is made at the touching end of projections 30. This weld is a fusion-bond, that is, the projection ends melt and fuse together. As the projections 30 melt, the electrodes squeeze the

contacts

22 and 24 tightly against the respective blade surfaces of

blades

4 and 6. Upon solidification of the fusion-bond between the projections 30, the projections cool from the welding temperature to room temperature. As this cooling takes place, what is now effectively a single fastening member in the holes 18 for the

contacts

22 and 24, that is the the joined projections, will contract due to the coefficient of thermalexpansion of the material of the projections, and this contraction holds the contacts even tighter against the

blades

4 and 6. It is to be noted that the materials of legs 4 and6 are not distorted by this attaching method. It is also to be noted that because of the additional pulling of the two

contacts

22 and 24 toward each other by the contraction of the fastening means in the holes 18, the contacts are still held tightly in engagement with the

blades

4 and 6, even though these parts may become heated during use of the blade assembly in a switch, such heat oc curring because of electrical current or from the ambient temperature. The amount of this heating will not approach the amount of heating used to make the fusion-bond, and as a result the

contacts

22 and 24 will remain tightly attached to the center leg 12. If, on the other hand, a rivet type of construction were used to hold one or both of the contacts to the center leg 12, then due to the springback of the material of the shank of the rivet, and also due to the thermal mismatch of the expansion characteristics of the rivet shank and blade because of heating of the blade and contact during use, the attachment of the contacts by means of a rivet has a tendency to loosen, with the result that there is an increase in the electrical resistance between the contacts and the material of the center legs 12. This increased resistance, in conjunction with the electrical current, develops more heat at the surfaces. When this happens, the surfaces may corrode and further increase the resistance. This build-up of resistance increases rapidly and eventually will destroy or deleteriously affect the engagement of the contacts with the center leg 12, and in some cases the ability of the rivet type electrical contact to transmit current into the switch blade. Thus, the use of the fusion-bond of this invention has another highly desirable advantage in that it will eliminate if not minimize such adverse corrosion.

As thus assembled, it will be noted that the

individual blades

4 and 6 are free to slide upon each other slightly through-out the rest of their configuration. This permits each blade to snap, jointly with the other, with a crisp, clean action when the combined assembly is used as unitary snap-acting assembly in a switch.

Referring now to FIG. 3 for an illustration of an exemplary use of the blade assembly of FIG. 1 and 2, there is shown an hermetically sealed snap-acting switch indicated generally by numeral 42. Switch 42 is illustrated and described both as to its construction and as to its method of operation in United States Patent 3,146,329, dated Aug. 25, 1964, the teaching of which is incorporated herein by reference.

Briefly, snap switch 42 comprises a container 44 sealed at the top by a flexible motion transmitting means, such as the diaphragm 46. An actuating button 48 is fastened to the outside of diaphragm 46. Inside the container 44 there is mounted a guide member comprising the rigid supporting plate 50 and the guide sleeve 52. A thrust pin 54 slides in sleeve 52 in position to transmit to the interior of the container the motion of the diaphragm.

On a metal plate 62 mounted within the container 44 on an electrically insulating base 56 as described in Patent No. 3,146,329 are the mounting

posts

58 and 60. Post 60 is firmly fixed in the supporting plate 62, but post 58 is a squeeze fit in a hole plate 62 so that the post 58 can be rotated. Each of

post

58 and 62 are provided with the mounting notches 64. Plate 62 is supported by a current carrying stud 66 which extends outwardly through the insulating base 56 to terminal for the flow of current to the secondary plate 62. A second stud of current carrying metal 68 is held by base 56 and at its inner end has a bent over contact arm 72 whose under surface carries a stationary top contact. A third stud 74 is likewise fastened in the insulating base 56, and at its inner end carries a bent over bottom contact arm 78, the top surface of which carries a bottom stationary contact. Each of

studs

68 and 74 extends through the plate 56- to form the

terminals

82 and 84, respectively.

The blade assembly 2 is mounted on the

posts

58 and 60 by forcing the free ends of the outer legs 8 and 10 toward each other until the

holes

16 and 20 will slide over the posts and come into engagement with the mounting notches 64. The effect of forcing these free ends together as described in said United States Patents 2,777,- 032 and 3,146,329 is to warp the assembly of blades until the composite center leg 12 moves downwardly (as drawn) to bring the contact 24 into engagement with the stationary bottom contact 78. In the position of the center leg 12 thus described, it will be noted that current may flow through the switch and the assembly 2 as follows;

from terminal 80 to stud 66-, plate 62, mounting

posts

58 and 60, outer legs 8 and in parallel, center leg 12, contact 24, the bottom contact on contact arm 78, contact arm 78, mounting stud 74 and terminal 84.

Positioned above the blade assembly 2, as described in Patent 3,146,329, is an actuating arm 86 which is position to be engaged by the thrust pin 54. Upon pushing the actuating arm 86 downwardly, the blade assembly 2 will be caused to warp with a snap action in a downward direction, thus causing the center leg 12 to reverse its position with a snap action so that contact 22 will then engage the top stationary contact on arm 72. In this position, current may pass into the switch to the end of the center leg 12 as described above for the FIG. 3 position, and then it will pass out of the switch via the top stationary contact, contact arm 72, mounting stud 68, and terminal 82.

It will be noted that since the outer legs 8 and 10 are at an angle to the mounting notches 64, there will be resulting forces tending to displace slightly the ends of these outer legs laterally relative to one another. The fact that these ends are not rigidly fastened to each other permits this sliding, and thus there is no such binding action as would be the case if these ends were rigidly fastened together. Likewise, since the whole blade structure 2 warps in causing the snap action of the center leg 12, the other parts of the individual blades are relatively free to slide or displace slightly relative to one another with resulting minimizing of any binding action, and thus leading to a crisp snap action of the assembled structure.

Turning now to FIG. 4 for another embodiment of the invention, the embodiment is the same as the FIG. 1 embodiment except for the means of attaching the movable contacts to the end of the center leg 12. That is, the

blades

4 and 6 are provided and the holes 18 in the ends of the center legs 12. In this instance,however, the contacts are made differently, but again are identical to each other. In each instance the

contacts

88 and 90 are provided with the aforesaid silver faces 92, the layers 94 and the projections 96. In this instance, however, coating the surfaces of the backing layers 94, including particularly the surfaces of the projections 96, is a layer of solder 98.

Such buttons are fastened to the blades as was described for the assembly of the buttons of the FIG. 1 embodiment as illustrated by FIG. 9, and when electrical current is passed through the contacts from one to the other, the solder layers 98 are melted. When the heating current is stopped, the solder layers cool and fuse together. Upon cooling, a contraction again occurs as described for the FIG. 1 embodiment with its attendant advantages. As in the FIG. 1 embodiment, the assembly of the projections 96 with the fused solder layer therebetween constitutes a fusion-bond between the contacts, and this assembly constitutes a fastening means within the holes 18 holding the contacts 92 together. Turning now to FIG. 5 for yet another embodiment of the invention, there is shown another blade 100 adapted to be used in a snap-acting switch. The blade assembly 100 comprises (in this instance) two identical snap-acting 'blades of the kind shown in United States Patent 2,630,504 dated Mar. 3, 1956, whose teaching is incorporated herein by reference. In the exemplary embodiment illustrated there are two substantially identical blades in alignment and lying in face-to-face relation. Briefly, each of the

identical blades

102 and 104 making up the structure 100 comprises a unitary plane structure having a pair of oppositely extending

loops

106 and 108. These loops have a common leg 110 which constitutes the longer side of each loop, and two

shorter legs

112 and 114. Short leg 112 has a laterally extending extension 116 attached thereto for mounting purposes, and at the end of the sections 116 of each blade there is provided the mounting holes 118. At the end of each of the short legs 114 is likewise provided the mounting holes 120. A contact arm 122 extends outwardly of the closed end of loop 108 at a substantial angle to the common leg 110.

At the end of the contact arm 122 of each blade of the composite structure there is provided a mounting hole 124 similar to the contact mounting holes provided in the FIG. 1 and FIG. 4 embodiments. At these holes 124 there is mounted, as described for the FIG. 1 or the FIG. 4 embodiments, a pair of electrical contacts 126 and 128 (the latter not being shown).

As in the FIG. 1 and FIG. 4 embodiments, the individual blades of the composite structure 100 are free to slide on one another relatively, when the blade is warped, these individual blades being fastened together only by the contacts 126 and 128.

Referring now to FIG. 6, there is shown a switch in which the composite structure 100 is used. Reference is made to United States Patent 2,630,504 for a complete description of the construction and operation of such a switch using a single blade.

Briefly, a base 130 is provided having a tongue 132 struck upwardly therefrom. The composite structure 100 is mounted on this base by attaching extensions 116 with a rivet 134 to the tongue 132, and another rivet 136 is used to attach the short leg 114 to the end of the base. A stationary contact plate 138 is mounted on the base 130 and insulated therefrom by the insulation 140. A lead in wire 142 is soldered to the contact plate 138, and another lead in wire 144 is soldered to the plate 130.

If, now, the tongue 132 is slightly depressed, it will put tension on the composite structure and warp the same as explained in said Patent No. 2,630,504. The result of this warping is to cause the contact arm 122 to move downwardly until the contact on the end therefrom comes into electrical engagement with the contact plate 138. If now the end of the short leg 112 is pushed, for example at the point indicated by numeral 146, the composite blade structure or assembly will warp with a snap action to lift the contact arm 122 and its contacts away from the contact plate 138.

All of the advantages ascribed above in respect to the FIGS. l-3 embodiment are found also in this FIGS. 5 and 6 embodiment.

Referring now to FIG. 7, there is shown still another embodiment, and relating primarily to the method of attaching a contact to a contact supporting structure. In this instance, the contact supporting structure is again shown as a pair of

blades

4 and 6 as in the FIG. 1 embodiment, and an electrical contact 148 is provided having the silver face 150, a metal layer 152 attached thereto, and a projection 154 extending therefrom. Here, the projection 154 has a length just slightly greater than the combined thickness of the two

blades

4 and 6. A back-up member 156 is provided of metal, and when a welding current is passed through the contact 148 and the back-up member 156, using electrodes of suitable nature for this purpose, a fusion-bond indicated at numeral 158 will be made. With the bond thus made, when the materials of the electrical contact 148 and the projection 154 cool, the contraction of the projection 154 will occur, as described for the FIG. 1 embodiment, with the result that contact 148 is tightly clamped against the surface of the layer 4.

If desired, and as shown in FIG. 8, as an alternate embodiment, a contact 160 may be provided having the silver face 162 and a metal layer 164 joined thereto. However, in this instance, the back surface of the contact 160, that is, the surface of the layer 164 is flat. To go with this, a back-up member 166 is provided having the projection 168 thereon. The length of projection 168 is slightly longer than the combined thickness of the

blades

4 and 6. Again, as in the above described embodiments, when electrical current is passed through the contact 160 and the back-up member 166 sufficient to melt the junction between the end of the projection 168 and the surface of the layer 164, a fusion-bond indicated by numeral 170 will occur which, when it cools, will tightly clamp the contact 160 against the surface of the blade 4 and squeeze the two

blades

4 and 6 together between the aforesaid parts.

Throughout the description, reference has been made to making fusion-bonds, and it will be understood that these bonds can be bonds made by electrical welding, or by melting solder layers together. The important feature is that the joint between the contacts lying on each side of the

blades

4 and 6 in each instance, or the joint between a contact and a back-up member such as indicated by numeral 156 or numeral 166, is made while the joint is molten, and because of the heat thus engendered the projections or extensions in the hole will have expanded during the fusing because of their coefficient of thermal expansion. Then, upon cooling, contraction occurs to clamp the relative parts securely against the combined

blades

4 and 6. In all of the above embodiments, the electrical contacts have been shown as being composite in structure and comprising a silver face mounted or integrally attached to a metal layer. If desired, the additional metal layer can be omitted and the entire electrical contact can be made of one material, such as silver or other good contact material. If pure silver is used, suitable means for making the fusion-bonds or welds is commonly available, such as percussion welding apparatus. In the FIG. 9 illustration, it has been indicated that the attachment was made by spot welding. Again, if solder layers are used, then suitable electrodes can be provided and the proper amount of current passed through the contacts in order to melt the solder. Such means of melting a layer of solder on another body are well known in the art and no further description needs to be given here.

In view of the above, it will be seen that the several objects of the invention are achieved, and other advantageous results attained.

As many changes could be made in the above constructions, and in the above methods of attachment, without departing from the scope of the invention, it is intended that all matter contained in the above description, or shown in the accompanying drawings, shall be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. A switch comprising a base, a first contact mounted on said base, a snap-acting member mounted on said base, said snap acting member comprising an assembly of a plurality of snap-acting elements lying together in face-toface juxtaposition and aligned with each other, and a second contact carried by said snap-acting member, said second contact being adapted to cooperate with said first contact to make and break an electrical circuit, and said elements fastened together solely in proximity to said second contact, the remainder of any one element being slidable on its adjacent element.

2. A switch comprising a base, a first contact mounted on said base; a support member mounted on said base, said support member having a flat portion and having a hole extending through said flat portion from one face of said support member to the other face; a second contact carried by said support member and overlying said hole on one side of said support member, said second contact being adapted to cooperate with said first contact to make and break an electrical circuit; a backing member carried by said support member and overlying said hole on the other side of said support member; and a fastening member having a volume not greater than the volume of said hole in said support member, said fastening member positioned in said hole and having its ends attached to each of said second contact and said backing member, said fastening member attached to at least one of said backing member and said second contact with a fusion-bond, thereby to pull said second contact and backing member toward each other to clamp said flat portion tightly between said backing member and said second contact.

3. The switch of claim 2 in which said backing member comprises a third contact.

4. The switch of claim 2 in which said backing member and said second contact each comprises a head portion overlying said hole and a projection attached at one end to a face of said head portion and extending outwardly therefrom, the other ends of said projections meeting in said hole and fusion-bonded together, said projections thereby constituting said fastening member.

5. The switch of claim 2 in which said backing member and said second contact each comprises a buttontype contact having a head portion and a projection integrally formed thereon, said head portion having on one side a layer of precious metal for electrical contact purposes, and on the other side a second layer of base metal for attachment purposes, said projection formed at least in part from said second layer; and in which the head portion of each contact overlies said hole and the projections extend into said hole, the ends of said projections meeting within said hole and fusion-bonded together, said projections thereby constituting said fastening member.

6. The switch of claim 2 in which said support member comprises an assembly of a plurality of resilient normally flat blades, each blade having spaced apart outer legs and a center leg joined thereto by one of its ends with its other end being free and extending therebetween, said blades lying together in face-to-face relation and in alignment, each center leg provided with a said hole at the free end thereof and all said holes coaxially aligned; and in which said fastening member extends through said holes with said second contact and said backing member overlying said holes and in tight engagement with the outer surfaces of the center legs of said assembly, thereby holding the end portions of said center legs together; means supporting the free ends of said outer legs and drawing the free ends of one set of said outer legs toward the free ends of the other set of said outer legs, thereby to distort said assembly; a fulcrum engaging one side of the center legs near the base portion thereof; and said means for causing relative movement between said first and second contacts being means for reversing the distortion of said assembly.

7. The switch of claim 6 in which said backing member and said second contact each comprises a button-type contact having a head portion and a projection integrally formed thereon, said head portion having on one side a layer of precious metal for electrical contact purposes, and on the other side a second layer of base metal for attachment purposes, said projection formed at least in part from said second layer; and in which the head portion of each contact overlies said holes and the projections extend into said holes, the ends of said projections meeting within said holes and fusion-bonded together, said projections thereby constituting said fastening member.

8. The switch of claim 2 in which said support member comprises an assembly of a plurality of unitary normally plane structures lying in face-to-face relation and substantially in registration, each structure including a pair of oppositely extending loops having a common leg constituting the longer side of each loop, the other shorter legs of the loops terminating adjacent the middle of said common leg, and an arm extending outwardly of the closed end of a loop at a substantial angle to the longitudinal axis of said common leg, said legs having a high width to thickness ratio; the free end of each said arm provided with said hole and all of said holes coaxially aligned; said fastening member extending through said holes with said second contact and said backing member overlying said holes and in tight engagement with the outer surfaces of the arms of said assembly, thereby holding the free ends of said arms together; means on said base for supporting said assembly in tension by the ends of said shorter loops thereby to warp said assembly;

and said means for causing relative movement between said first and second contacts being means for reversing the warping of said assembly.

9. The switch of claim 8 in which said backing member and said second contact each comprises a buttontype contact having a head portion and a projection integrally formed thereon, said head portion having on one side a layer of precious metal for electrical contact purposes, and on the other side a second layer of base metal for attachment purposes, said projection formed at least in part from said second layer; and in which the head portion of each contact overlies said hole and the projections extend into said hole, the ends of said projections meeting within said hole and fusion-bonded together, said projections thereby constituting said'fastening member.

10. A switch comprising a base; a stationary contact mounted on said base; a movable contact arm on said base; and a second contact carried by said contact arm and movable therewith to cooperate with said stationary contact to make and break an electrical circuit; said contact arm comprising an assembly of a plurality of individual contact arms with each individual arm having a flat portion with a hole in a said portion thereof, the holes of the arms being aligned; a fastening member positioned in said holes and attached at one end to said second contact; a backing member carried by said assembly in position overlying said holes and fastened to the other end of said fastening member; and means on said base for moving said contact arm to cause relative motion between said stationary contact and said second contact; said fastening member joined to at least one of said backing member and said second contact with a fusion-bond, thereby to pull said second contact and said backing member toward each other to clamp the flat portions of said individual arms tightly together.

11. An article of manufacture comprising an assembly of a plurality of individual springy sheet metal blades superimposed on one another with the edges of the blades approximately in registration, each of said blades provided with a hole through a portion thereof, all of such holes being in axial alignment, and fastening means in the holes for clamping said portions tightly together solely at said hole, the remainder of any one blade being slidable on its adjacent blade.

12. The article of claim 11 in which said fastening means comprises an electrical contact overlying said hole on one side of said assembly, a backing member overlying a corresponding hole on the other side of said assembly, and means within said holes connecting said contact and said backing member, said means attached to at least one of said contact and said backing member with a fusion-bond.

13. The article of claim 12 in which said backing member comprises another electrical contact.

14. The article of claim 12 in which each of said electrical contact and said backing member consists of a button-type contact having as an integral part thereof a projection extending from a face thereof, the end of the projection on one contact abutting within said holes the end of the projection of the other contact, said ends fusion-bonded together.

15. The article of claim 12 in which each of said blades has spaced apart outer legs and a center leg joined thereto by one of its ends with its other end free, said hole in each blade being located in proximity to said free end, and said blades fastened solely at the free ends of the center legs.

16. The article of claim 12 in which each of said blades includes a pair of oppositely extending loops having a common leg constituting the longer side of each loop, the other shorter legs of the loops terminating adjacent the middle of said common leg, and an arm extending outwardly of the closed end of a loop at a substantial angle to the longitudinal axis of said common leg and having one end free, said legs having a high width to thickness ratio, said hole in each blade being located in proximity to the said free end, and said blades fastened together solely at the free ends of the said arms.

17. The method of fastening together an assembly of a plurality of current carrying blades each having a hole therein comprising aligning the holes of each blade, providing an electrical contact having a head portion greater in diameter than said holes and a projection thereon adapted to enter said holes, placing said contact over said holes at one side of said assembly with said projection in said holes, positioning a backing member over said holes at the other side of said assembly and touching the end of said projection, heating said projection sufiiciently to melt its end and a portion of said backing member to fuse together the end of said projection and said backing member while applying a force to squeeze said blades together between said contact and said backing member, and maintaining said force until the joint between the projection, and the backing member has solidified.

18. The method of claim 17 in which said backing member is an electrical contact having a head portion greater in diameter than said holes and has a projection thereon adapted to enter said holes and meet the projection of the other electrical contact, and in which the 1einils of said projections are fused together within said 19. The method of claim 17 in which the fusing step is a welding step.

20. The method of claim 17 in which is a soldering step.

References Cited UNITED STATES PATENTS the fusing step 2,509,021 5/1950 Settle 200-166 2,777,032 1/1957 Burch 200--113 3,023,287 2/1962 Epstein 200-113 3,113,196 12/ 1963 Spooner et al 200-166 ROBERT K. SCHAEFER, Primary Examiner. H. O. JONES, Assistant Examiner.