US2567606A - Switch contact construction - Google Patents

Description

Sept. 11, 1951 J. J. KOJIS 2,567,605,

SWITCH CONTACT CONSTRUCTION Filed April 29, 1950 2 Sheets-Sheet 1 52 INVENTOIR'.

JQ/Q/Z J 501% BY Sept. 11, 1951 Filed April 29, 1950 J. J. KOJlS SWITCH CONTACT CONSTRUCTION 2 Sheets-Sheet 2 INVENTOR.

Lima

BY W W Patented Sept. 11, 1 951 SWITCH CONTACT CONSTRUCTION John J. Kojis, Chicago, Ill., assignor to S & Electric Company, Chicago, 111., a corporation of Delaware Application April 29, 1950, Serial No. 159,025

9 Claims. 1

This invention relates generally to electric switches and it has particular relation to the construction of contacts therefor. It constitutes an improvement over the switch construction disclosed in copending application Serial No. 41,597, filed July 30, 1948, and assigned to the assignee of this application.

Among the objects of this invention are: To reduce the force required to move the contacts of a switch to the closed position where a relatively great contact pressure is exerted; to provide a stepped application of force to the contacts on closing thereof; to reduce the likelihood of improper operation of switch contacts resulting from the presence of foreign materials such as dirt, oxides, ice, etc., in and around their relatively movable parts; to absorb heat generated by extremely high current flow under short circuit conditions and to prevent welding together thereby of the current carrying parts of the switch contacts; to interconnect switch members by employing a pair of pear shaped contact fingers rockably mounted on the ends of a U-shaped inner spring clip and arranged for the smaller ends to engage opposite sides of a switch blade or contact tongue under pressure and the larger ends to engage relatively heavy contact pads under pressure; to loosely mount the pear shaped contact fingers at their larger ends on the inner spring clip; to mount the contact pads on the ends of a U-shaped outer spring clip nested with the inner spring clip; and to shape the contact fingers to that ice accumulated thereon when the switch is closed is readily sheared oif and ice between the nested spring clips does not interfere with the opening movement of the contact fingers.

Other objects of this invention will, in part, be obvious and in part appear hereinafter.

This invention is disclosed in the embodiment thereof shown in the accompanying drawings and it comprises the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereinafter set forth and the scope of the application of which will be indicated in the appended claims.

For a more complete understanding of the nature and scope of this invention, reference may be had to the following detailed description, taken together with the accompanying drawings, in which:

Figure 1 is a View, in side elevation, of a high voltage load interrupter type of switch in which the present invention is embodied;

Figure 2 is a detail sectional view, at an enlarged scale, taken generally along the line 2--Z of Figure 1 and showing only the details of construction of the main contacts for the switch;

Figure 3 is a View, similar to Figure 2, showing the relative positions of the stationary and movable switch contacts just prior to contact engagement; and

Figure 4 is a view, similar to Figure 3, showing the relative positions of the contacts as they are being operated to the fully closed position.

Referring now particularly to Figure 1 of the drawings, it will be observed that the reference character In designates, generally, a high voltage switch which can be employed either as a unit or in combination with two like switches for connection in an electric power system. The particular switch construction In is intended for use on circuits operating at a voltage of 34.5v kv. This figure is mentioned for illustrative purposes only, it being understood that the present invention can be embodied in switches operating at higher or lower voltages.

The switch I I) includes a channel base I I which carries stationary insulators I2 at its ends. The channel base II also carries a centrally located rotatable insulator I3 which is journaled in a suitable bearing construction I4. An arm I5 extends from the pin supporting the insulator I3 to adapt the switch In for remote and gang operation. At its upper end the rotatable insulator I3 carries a clamp I6 which, as shown, is arranged to grip a switch blade I that preferably is in the form of a tube of good conducting metal such as copper. The switch blade I1 is illustrated in the switch closed position. For opening the switch it will be understood that the insulator I 3 is rotated about its longitudinal axis to swing the switch blade I! from its position shown in the plane of the drawing to a position at right angles thereto. While the channel base I I is illustrated as being mounted in a horizontal position with the insulators I2 and I3 thereabove, it will be understood that the channel base II can be mounted in a vertical direction or that it can be inverted so that the insulators I2 and I3 depend therefrom.

At each end of the switch blade N there is a blade tip that is indicated, generally, at 2|], Figure 2. Each blade tip 20, which is formed of suitable material such as cast brass, is arranged to cooperate with a stationary contact and load interrupter mechanism, shown generally at 2I in Figure 1. These mechanisms are described in detail in the copending application referred to as indicated at 4|.

. inch and a length of 1% inches.

above and, since they form no part of the present invention, no further description thereof is considered to be necessary herein. These mechanisms are carried by suitable mounting brackets 22, preferably brass castings, which have terminal pads 23 formed integrally therewith and carried by the upper ends of the stationary insulators 12. The terminal pads 23 are employed for connection to the circuit conductors in accordance with conventional practice.

Each of the mechanisms 2| includes a load interrupter device 24 in which the circuit is finally interrupted and any arc drawn is extinguished. For operating each of the load interrupter devices 24, each of the blade tips 20 is provided with a tail extension 25 and an operator 26 which are cast integrally with the blade tip 20. The manner in which they cooperate with the load interrupter devices 24 is set forth in the copending application above referred to.

Each blade tip 28 also has a contact tongue 2'! formed integrally therewith. The contact tongue 21 is arranged to cooperate with a stationary contact assembly, shown generally at 28. The contact tongue 27 and the stationary contact assembly 28 are arranged to carry the load current between each end of the'switch blade H and the mounting brackets 22. However, they are not intended to interrupt any current when they are separated, this function being taken care of by the load interrupter devices 24. The present invention has to do particularly with the construction of the contact tongue 2! and of the stationary contact assembly 28. While they are intended specifically for use in the high voltage switch l shown in Figure 1, it will be understood that their use is not so limited. Since the stationary contact assembly 28 at each end of the switch blade I? is a duplicate of the other,

it is necessary to describe herein only one of them.

Each stationary contact assembly 28 is secured by bolts 29 to an L-shaped bracket 30. As shown in Figure 2, the bracket 30 has tapped mounting bolt holes 3| for receiving mounting bolts to permit its being fastened to the sides of the mounting brackets 22 opposite from the terminal pads 23.

The stationary contact assembly 28 includes a generally U-shaped inner relatively strong spring clip that is illustrated, generally, at 36. The spring clip 36 is formed of suitable resilient good electrically conducting material such as beryllium copper. It may be formed of a strip of this material which has a length of 11% inches before it is bent to the configuration shown. The strip may have a width of 1% inches and a thickness of .125 inch. As shown, the end portions 3! of the spring clip 36 converge and are bifurcated to provide arms 38. The portions 39 of the arms 38 extend generally normal to the end portions 31 and are wrapped around the ends of transversely extending hinge pins 40. In order to permit the arms 38 to grip frictionally the ends of the hinge pins 40, they are serrated The hinge pins 40 may be formed of copper rod having a diameter of The serrations 4i extend about /4 inch from each nd.

Between'the arms 38 of the bifurcated ends of the portions 31 are loosely mounted generally pear shaped contact fingers 44. Each contact finger 44 is formed preferably from extruded copper bar and, after final finishing is silver plated.

' Generally centrally located in the larger ends of the contact fingers 44 are openings 45. In order that the contact fingers 44 shall fit loosely on the hinge pins 40 each opening 45 has a diameter of .437 inch. This provides a clearance of about .062 inch, the purpose of which will be described presently.

The smaller ends 46 of the pear shaped contact fingers 44 are arranged to engage opposite sides of the contact tongue 21. As shown in Figure 2 the contact tongue 2'! has a wedge shaped end 47 for entering between the smaller ends 46 of the contact fingers 44. These smaller ends 46 are arranged to interfit with recesses 48 in opposite sides of the contact tongue 21 and to bear against the rear end surfaces 41 of the wedge shaped end 41 for locking the contact tongue 2! in the switch closed position. When the switch blade I! is swung to the open position, the contact fingers 44 are rocked outwardly of the contact assembly 28 by the interaction between the smaller ends 48 and the rear end surfaces 4? of the wedge shaped end 41. Preferably the contact surfaces of the recesses 48 are formed of silver in order to reduce contact resistance to a minimum.

Extending from opposite sides of the contact tongue 27 are flanges 49. When the contact tongue 2'! is moved to the switch closed position, the smaller ends 45 of the contact fingers 44 are engaged by the forward faces of the flanges 49, as illustrated in Figure 4, to rock the contact fingers 44 from their inclined switch open position, as shown in Figure 3, with respect to a plane, indicated by the broken line 58, between the pivot axes of the contact fingers 44, to a position inclined to the plane 58 on the opposite side in the switch closed position as shown in Figure 2. The action which takes place when the switch is closed will be described in more detail presently.

A portion of the current is carried by the U-shaped inner spring clip 36, because it rockably mounts the contact fingers 44 at its outer end. It is also desirable that an additional current path be provided between the contact fingers 44 and the bracket 30, which, of course, is formed of good conducting material such as copper. For this purpose a generally U-shaped outer relatively weak spring clip 52 is employed. As shown in Figures 2, 3 and 4 of the drawings, the spring clip 52 is nested with the spring clip 35 and together they are held firmly to the bracket 38 by the bolts 29. The spring clip 52 is formed of resilient good electrically conducting material such as beryllium copper. It may have an initial length of 7% inches, a width of 1% inches, and a thickness of .078 inch. At the outer ends of arms 53 of the spring clip 52 relatively thick contact pads 54 are secured by rivets 55. Each of the contact pads 54 is formed of a length of copper bar having a length of 2% inches, a width of 1% inches, and a thickness of inch. Preferably each contact pad 54 is silver plated to reduce contact resistance. The relatively thick contact pads 54 are employed to provide a relatively large mass of good conducting metal for the purpose of absorbing heat that is generated under conditions of high current density, such as during a short circuit. This prevents overheating of the parts and welding of the outer spring clip 52 to the contact fingers 44 under these conditions.

In the switch closed position, as shown in Figure 2, the inner sides of the contact pads 54 have contact engagement under pressure with convex smooth inner contact surfaces 56 of the contact fingers 44. In the switch open position, as shown in Figure 3, the inner surfaces of the contact pads 54 are juxtaposed to fiat surfaces '1 on the contact fingers 44 which constitute a continuation of the convex contact surfaces 56. The interaction between the contact pads 54 and the fiat surfaces 5'! acts to locate the contact fingers 44 in the position shown in Figure 3 inclined to the plane 55 where they are ready to receive the wedge shaped end 41 of the contact tongue 21 therebetween when the switch is to be closed. In order to limit the outward swinging movement of the contact fingers 44 detents 58 are formed integrally therewith at the outer ends of the fiat surfaces 51. It will be understood that the detents 58 are arranged to cooperate with the outer ends of the contact pads 54 and thus limit the outward rocking movement of the contact fingers 44. The inward rocking movement of the contact fingers 44 is limited by tongues 59 which are formed as integral extensions of the end portions 31 of the inner spring clip 36. As illustrated in Figures 2, 3 and 4 of the drawings, the tongues 59 are located in the space between the arms 38 and, as shown in Figure 2, limit the inward rocking movement of the contact fingers 44.

In describing the operation of the contact construction disclosed herein, reference first will be had to Figure 3 of the drawings. The positions that the contact fingers 44 occupy in the switch open position are here illustrated. They are inclined forwardly away from the plane 50 which extends through the pivot axes of the contact fingers 44. In this position the relatively weak spring clip 52, acting through the contact pads 54 urges the contact fingers 44 generally toward each other so that the clearance 6! between the openings 45 in the contact fingers 44 and the hinge pins 45 will appear on the inner sides of the latter. As described hereinbefore, the contact fingers 44 are held in this position by the interaction of the contact pads 54 and the fiat surfaces 51.

The continued movement of the contact tongue 2'! in the direction indicated by the arrow 60, Figure 3, causes the wedge shaped end 41 to enter between the smaller ends 45 of the contact fingers 44 and to spread them apart. Aside from this movement apart of the contact fingers 44, they are not rocked about the hinge pins 40 until the smaller ends 45 engage the forward sides of the flanges 49 as illustrated in Figure 4. Continued movement of the contact tongue 41 in the direction of the arrow 62 causes the contact fingers 44 to be rocked in the directions indicated by the arrows 63 and 54. The engaging surfaces of the smaller ends progress across the surfaces of the recesses 48 with a rolling wiping action which clears away oxides and provides a clean low resistance contact surface. However, since these contact fingers 44 are loosely mounted on the hinge pins 4!], their movement apart while they are being rocked in the directions indicated by the arrows 63 and 54 does not at this time cause the end portions 31 of the inner spring clip 36 to be moved apart. The clearance between the openings 45 and the hinge pins 40, indicated at 55, is shifted to the opposite sides of the hinge pins 45 from that shown in Figure 3. During this interval the contact fingers 44 are being swung from the position shown in Figure 3, a position of least mechanical advantage, to the position shown in Figure 4, where they are more closely alined with the plane 50. During this 6-. interval'only sufficient force need be exerted on the contact tongue 27 to spread the contact pads 54 apart against the relatively small force exerted by the relatively weak outer spring clip 52. Now, when the slack has been taken. up between the contact fingers 44 and the hinge pins 45, as illustrated in Figure 4, continued movement of the contact tongue 21 in the direction of the arrow 52 causes the end portions 3'! of the inner spring clip 35 to be spread apart. Since the spring clip 36 has a relatively great strength, there is a corresponding application of contact pressure between the convex surfaces of the smaller ends 45 and the contact surfaces of the recesses in the contact tongue 21. At the same time the convex contact surfaces 56 of the contact fingers 44 are rocked into engagement with the adjacent surfaces of the contact pads 54 and they are spread still further apart. There is then additional contact pressure exerted between the contact pads 54 and the convex contact surfaces 56 of the contact fingers 44. In the closed position of the contact fingers 44, as shown in Figure 2, these smaller ends 45 bear against the rear sides of the wedge shaped end 4'1 of the contact tongue 2? under the biasing action of the spring clip 35 and of the spring clip 52 and act to lock it in the closed position with an over center toggle action. The spring clip 52 acts through the con tact pads 54 along the plane 50 through the axis of the hinge pins 48 to assist the spring clip 35 in providing the locking toggle action. Unless the contact tongue 21 is forcibly withdrawn, it is held in the closed position by this toggle action.

In the event that the contact fingers 44 should be covered with ice when they are in the closed position, as shown in Figure 2, there is little interference with the proper opening of the switch. The ice which may have accumulated on the flat surfaces 5'! is sheared ofi as the contact fingers 44 are rocked in directions opposite to the arrows 63 and 64 by the outer ends of the contact pads 54. Any ice which may have collected between the inner sides of the contact pads 54 and the outer sides of the end portions 31 of the inner spring clip 35 will not interfere with the rocking movement of the contact fingers 44 since the contact surfaces 56 are formed at a radius extending generally from the center of the openings 45. The surfaces 55 are smooth so that it is unnecessary to crush any ice in their vicinity when the switch is opened.

Because of the loose mounting of the contact fingers 44 on the hinge pins 45 only the spring pressure exerted by the relatively weak outer spring clip 52 is active during that portion of the closing action of the switch Where there is the least mechanical advantage in the rocking movement of the contact fingers 44. Duringthe final closing stages, as illustrated in Figure 4, the mechanical advantage is greatly increased and then the heavier and greater pressure exerted by the relatively strong inner spring clip 35 is brought into action. This sequence of operations allows a substantial decrease in the force required to move the contact tongue 21 to the switch closed position in relationship to the contact pressure that is developed between the contact fingers and the contact surfaces of the recesses 48 and between the contact surfaces of the contact pads 54 and the contact surfaces 56 of the contact fingers 44.

A further advantage of this clearance between the hinge pins 40 and the contact fingers 44 is to make the bearing less susceptible to binding by allowing sufiicient clearance for dirt and oxides that may accumulate. Yet the construction provides a rolling and wiping action that cleans the bearing surfaces and provides good electrical contact engagement.

Since certain changes can be made in the foregoing construction and difierent embodiments of the invention can be made without departing from the spirit and scope thereof, it is intended that all matter shown in the accompanying drawings and described hereinbefore shall be interpreted as illustrative and not in a limiting sense.

What is claimed as new is:

1. In a switch, in combination, a pair of generally pear shaped contact fingers, a generally U-shaped inner spring clip loosely rockably supporting at its outer ends the larger ends of said contact fingers, a generally U -shaped outer spring clip nesting with said inner spring clip and bearing against the larger ends of said contact fingers, said contact fingers being rockable from one side of the plane through their axes of rotation away from said spring clips toward the other side thereof, a contact tongue arranged to enter the space between said smaller ends of said contact fingers when they are on said one side of said plane and to be engaged thereby for completing a circuit therethrough, and abutment means on said contact tongue reacting against said smaller ends of said contact fingers on continued movement of said contact tongue toward the switch closed position for rocking said contact fingers and causing the ends of said outer spring clip to be spread apart without simultaneously spreading apart the ends of said inner spring clip until the slack between them and said contact fingers is taken up whereupon continued movement of said contact tongue toward the switch closed position causes said ends of said inner spring clip to be spread apart and said ends of said outer spring clip to be spread further apart thereby causing relatively high contact pressure to be exerted between said outer contact clip and said contact fingers and between said contact fingers and said contact tongue.

2. A switch comprising, in combination, a pair of relatively movable switch members for opening and closing an electric circuit; one of said switch members including a pair of generally pear shaped contact fingers, a generally U- shaped inner spring clip having bifurcated end portions each loosely pivotally supporting the larger end of one of said contact fingers therebetween, a generally Ushaped outer spring clip nested with said inner spring clip for engaging the larger ends of the associated contact fingers, said contact fingers in the switch open position being inclined outwardly away from the plane joining their axes of rotation; the other switch member including a contact tongue arranged to enter said one switch member between the smaller ends of said contact fingers in the switch open position, and flanges extending from opposite sides of said contact tongue for cooperating with said smaller ends of said contact fingers when said other switch member is moved toward the switch closed position to rock the same toward said plane and simultaneously therewith cause them to engage the ends of said outer spring clip and spread the same apart against the force exerted thereby without at the same time spreading said ends of said inner spring clip apart until the slack between said bifurcated end portions of said inner spring clip and said contact fingers is taken up whereupon continued closing movement of said other switch member and rocking or" said contact fingers toward said plane spreads the ends of said inner spring clip apart and the ends of said outer spring clip further apart thereby causing relatively high contact pressure to be exerted between the latter and said larger ends of said contact fingers and between said smaller ends of said contact fingers and said sides of said contact tongue.

3. A switch comprising, in combination, a pair of relatively movable switch members for opening and closing an electric circuit; one of said switch members including a pair of generally pear shaped contact fingers, a generally U- shaped relatively strong inner spring clip having a bifurcated end portions each loosely pivotally supporting the larger end of one of said contact fingers therebetween, a generally U- shaped relatively weak outer spring clip nested with said inner spring clip for engaging the larger ends of the associated contact fingers, said contact fingers in the switch open position being inclined outwardly away from the plane joining their axes of rotation; the other switch member including a contact tongue arranged to enter said one switch member between the smaller ends of said contact fingers in the switch open position, and flanges extending from opposite sides of said contact tongue for cooperating with said smaller ends of said contact fingers which said other switch member is moved toward the switch closed position to rock the same toward said plane and simultaneously therewith cause them to engage the ends of said outer spring clip and spread the same apart against the'relatively weak force exerted thereby without at the same time spreading said ends of said inner spring clip apart until the slack between said bifurcated end portions of said inner spring clip and said contact fingers is taken up whereupon continued closing movement of said other switch member and rocking of said contact fingers toward said plane spreads the the ends of said inner spring clip apart and the ends of said outer spring clip further apart thereby causing relatively high contact pressure to be exerted between the latter and said larger ends of said contact fingers and between said smaller ends of said contact fingers and said sides of said contact tongue.

4. A switch comprising, in combination, a pair of relatively movable switch members for opening and closing an electric circuit; one of said switch members including a generally U-shaped relatively strong inner spring clip having bifurcated end portions, hinge pins carried by the arms of the end portion, a generally pear shaped contact finger loosely carried at its larger end by each hinge pin, a generally U-shaped relatively tweak outer spring clip nested with said inner spring clip for engaging the larger ends of the associated contact fingers, said contact fingers in the switch open position being inclined outwardly away from the plane joining their axes of rotation; the other switch member including a contact tongue arranged to enter said one switch member between the smaller ends of said contact fingers in the switch open posi tion, and flanges extending from opposite sides of said contact tongue for cooperating with said smaller ends of said contact fingers when said other switch member is moved toward the switch closed position to rock the same toward said plane and simultaneously therewith cause them to engage the ends of said outer spring clip and spread the same apart against the relatively weak force exerted thereby without at the same time spreading said ends of said inner spring clip apart until the slack between said hinge pins and said contact fingers is taken up whereupon continued closing movement of said other switch member and rocking of said contact fingers toward said plane spreads the ends of said inner spring clip apart and the ends of said outer spring clip further apart thereby causing relatively high contact pressure to be exerted between the latter and said larger ends of said contact fingers and between said smaller ends of said contact fingers and said sides of said contact tongue.

5. A switch comprising, in combination, a pair of relatively movable switch members for opening and closing an electric circuit; one of said switch members including a generally Ushaped inner spring clip having bifurcated converging end portions, hinge pins carried by the arms of each end portion, said arms extending outwardly generally normal to their respective end portions and around said hinge pins and frictionally gripping the same, a generally pear shaped contact finger loosely carried at its larger end by each hinge pin, a generally U-shaped outer spring clip nested with said inner spring clip, a relatively thick contact pad carried by each end portion of said outer spring clip for engaging the larger end portion of the associated contact finger, said contact fingers in the switch open position being inclined outwardly away from the plane joining their axes of rotation and in the switch closed position being inclined inwardly away from said plane; the other switch member including a contact tongue arranged to enter said one switch member between the smaller ends of said contact fingers in the switch open position, said contact tongue being recessed on opposite sides for receiving said smaller ends of said contact fingers in interlocking engagement in the switch closed position, and fianges extending from opposite sides of said contact tongue for cooperating with said smaller ends of said contact fingers when said other switch member is moved toward the switch closed, position to rock the same toward said plane and simultaneously therewith cause them to engage said contact pads and spread the same apart against the force exerted by said outer spring clip without at the same time spreading said ends of said inner spring clip apart until the slack between said hinge pins and said contact fingers is taken up whereupon continued closing movement of said other switch member and rocking of said contact fingers toward said plane spreads the ends of said inner spring clip apart and said contact pads further apart thereby causing relatively high contact pressure to be exerted between said contact pads and said larger ends of said contact fingers and between said smaller ends of said contact fingers and said recessed sides of said contact tongue.

6. A switch comprising, in combination, a pair of relatively movable switch members for opening and closing an electric circuit; one of said switch members including a generally U-shaped relatively strong inner spring clip having bifurcated end portions, hinge pins carried by the arms of each end portion, a generally pear shaped contact finger loosely carried at its larger end by each hinge pin, a generally U-shaped relatively weak outer spring clip nested with said inner spring clip, a relatively thick contact pad carried by each end portion of said outer spring clip for engaging the larger end of the associated contact finger, said contact fingers in the switch open position being inclined outwardly away from the plane joining their axes of rotation; the other switch member including a contact tongue arranged to enter said one switch member between the smaller ends of said contact fingers in the switch open position, and flanges extending from opposite sides of said contact tongue for cooperating with said smaller ends of said contact fingers when said other switch member is moved toward the switch closed position to rock the same toward said plane and simultaneously therewith cause them to engage said contact pads and spread the same apart against the relatively weak force exerted by said outer spring clip without at the same time spreading said ends of said inner spring clip apart until the slack between said hinge pins and said contact fingers is taken up whereupon continued closing movement of said other switch member and rocking of said contact fingers toward said plane spreads the ends of said inner spring clip apart and said contact pads further apart thereby causing relatively high contact pressure to be exerted between said contact pads and said larger ends of said contact fingers and between said smaller ends of said contact fingers and said sides of said contact tongue.

'7. A switch comprising, in combination, a pair of relatively movable switch members for opening and closing an electric circuit; one of said switch members including a generally U-shaped relatively strong inner spring clip having bifurcated end portions, hinge pins carried by the arms of each end portion, a generally pear shaped contact finger loosely carried at its larger end by each hinge pin, a generally -U-shaped relatively weak outer spring clip nested with said inner spring clip, a relatively thick contact pad carried by each end portion of said outer spring clip for engaging the larger end of associated contact finger, said contact fingers in the switch open position being inclined outwardly away from from the plane joining their axes of rotation and in the switch closed position being inclined inwardly away from said plane; the other switch member including a wedge shaped contact tongue arranged to enter said one switch member between the smaller ends of said contact fingers in the switch open position, said contact tongue being recessed on opposite sides for receiving said smaller ends of said contact fingers in interlocking engagement in the switch closed position, and flanges extending from opposite sides of said contact tongue for cooperating with said smaller ends of said contact fingers when said other switch member is moved toward the switch closed position to rock the same toward said plane and simultaneously therewith cause them to engage said contact pads and spread the same apart against the relatively weak force exerted by said outer spring clip without at the same time spreading said ends of said inner spring clip apart until the slack between said hinge pins and said contact fingers is taken up whereupon continued closing movement of said other switch member and rocking of said contact fingers toward said plane spreads the ends of said inner spring clip apart and said contact pads further apart thereby causing relatively high contact pressure to be exerted between said contact pads and said larger ends of said contact fingers and between said smaller ends of said contact fingers and said recessed sides of said contact tongue.

8. A switch comprising, in combination, a pair of relatively movable switch members for opening and closing an electric circuit; one of said switch members including a generally U-shaped relatively strong inner spring clip having bifurcated converging end portions, hinge pins carried by the arms of each end portion, said arms extending outwardly generally normal to their respective end portions and around said hinge pins and frictionally gripping the same, a generally pear shaped contact finger loosely carried at its larger end by each hinge pin, a generally U-shaped relatively weak outer spring clip nested with said inner spring clip, a relatively thick contact pad carried b each end portion of said outer spring clip for engaging the larger end of the associated contact finger, said contact fingers in the switch open position being inclined outwardly away from the plane joining their axes of rotation and in the switch closed position being inclined inwardly away from said plane; the other switch member including a wedge shaped contact tongue arranged to enter said one switch member between the smaller ends of said contact fingers in the switch open position, said contact tongue being recessed on opposite sides for receiving said smaller ends of said contact fingers in interlocking engagement in the switch closed position, and flanges extending from opposite sides of said contact tongue for cooperating with said smaller ends of said contact fingers when said other switch member is moved toward the switch closed position to rock the same toward said plane and simultaneously therewith cause them to engage said contact pads and spread the same apart against the relatively weak force exerted by said outer spring clip without at the same time spreading said ends of said inner spring clip apart until the slack between said hinge pins and said contact fingers is taken up whereupon continued closing movement of said other switch member and rocking of said contact fingers toward said plane spreads the ends of said inner spring clip apart and said contact pads further apart thereby causing relatively high contact pressure to be exerted between said contact pads and said larger ends of said contact fingers and between said smaller ends of said contact fingers and said recessed sides of said contact tongue.

9. A switch comprising, in combination, a pair of relatively movable switch members for opening and closing an electric circuit; one of said switch members including a generally U-shaped relatively strong inner spring clip having bifurcated end portions with a tongue projecting from each end between the arms of each bifurcated end portion, said end portions converging with the tongue of each constituting a projection thereof, hinge pins carried by said arms of each end portion, said arms extending outwardly generally normal to their respective end portions and around said hinge pins and frictionally gripping the same, a generally pear shaped contact finger loosely carried at its larger end by each hinge pin, each contact finger having a detent on its outer side and a generally convex smooth inner surface joining a generally flat surface extending to said detent, a, generally U-shaped relatively weak outer spring clip nested with said inner spring clip, a relatively thick contact pad carried by each end portion of said outer spring clip and engaging said convex surface of the associated contact finger in the switch closed position and said flat surface of the associated contact finger in the switch open position and having its outer end in the path of said detent whereby the outward rocking movement of each contact finger is limited, rocking movement of said contact fingers in the opposite direction being limited by the tongue on said inner spring clip associated therewith, said contact fingers in the switch open position being inclined outwardly away from the plane joining their axes of rotation and in the switch closed position being inclined inwardly away from said plane; the other switch member including a wedge shaped contact tongue arranged to enter said one switch member between the smaller ends of said contact fingers in the switch open position, said contact tongue being recessed on opposite sides for receiv ing said smaller ends of said contact fingers in interlocking engagement in the switch closed position, and flanges extending from opposite sides of said contact tongue for cooperating with said smaller ends of said contact fingers when said other switch member is moved toward the switch closed position to rock the same toward said plane and simultaneously therewith cause said convex surfaces thereof to engage said contact pads and spread the same apart against the relatively weak force exerted by said outer spring clip without at the same time spreading said ends of said inner spring clip apart until the slack between said hinge pins and said contact fingers is taken up whereupon continued closing movement of said other switch member and rocking of said contact fingers toward said plane spreads the ends of said inner spring clip apart and said contact pads further apart thereby causing relatively high contact pressure to be exerted between said contact pads and said convex surfaces of said contact fingers and between said smaller ends of said contact fingers and said recessed sides of said contact tongue.

JOHN J. KOJIS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,560,165 Johnson Nov. 3, 1925 1,868,482 Austin July 26, 1932

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