US2689896A

US2689896A - Shock resistant electric switch

Info

Publication number: US2689896A
Application number: US258586A
Authority: US
Inventors: Clarence W Kuhn; Theodore F Rosing
Original assignee: Cutler Hammer Inc
Current assignee: Cutler Hammer Inc
Priority date: 1951-11-28
Filing date: 1951-11-28
Publication date: 1954-09-21
Anticipated expiration: 1971-09-21

Description

P 21, 1954 c. w. KUHN ETAL ,689,896

saocx RESISTANT ELECTRIC SWITCH 7 Filed Nov. 28, 1951 4 Sheets-Sheet 1 P 1954 C. w. KUHN ETAL suocx RESISTANT ELECTRIC SWITCH 4 Shee'ts-Sheet 2 Filed Nov. 28, 1951 M l m \\\\\\\\\\\\\\\\\A\\\\\\\\\\\\\\\\\\ INV EN TORS [Vere/Ice id. Xxx/1n BY jieaabrf ,7 Pas/12y p 21, 1954 c. w. KUHN ETAL SHOCK RESISTANT ELECTRIC SWITCH 4 Sheets-Sheet 5 Filed Nov. 28, 1951 INVENTORS'. fi/erem'e d! Ail/ BY 766010;! 7 @507 7 II: a

VIA

p 21, 1954 c. w. KUHN EI'AL 2,689,896

snocx RESISTANT ELECTRIC swr'rcu Filed Nov. 28, 1951 4 Sheets-Sheet 4 Patented Sept. 21, 1954 SHOCK RESISTANT ELECTRIC SWITCH Clarence W. Kuhn, Wauwatosa, and Theodore F. 1 Rosing, Whitefish Bay, Wis., assignors to Cutler-I-Iammer, Inc., Milwaukee, Wis., a corporation of Delaware Application November 28, 1951, Serial No. 258,586

16 Claims.

This invention relates to electric switches, and more particularly to a manually operable shock resistant starter switch.

An object of the invention is to provide a starter switch constructed to remain in either open or closed switching position until manually actuated to the opposite position, said switching positions being maintained despite the occurrence of high intensity percussion such as results from large explosions and the like.

Another object is to provide a compact switch of a construction permitting overload current responsive devices to be incorporated therein in a unitary manner for minimized possibility of misalignment due to shock, and permitting said overload devices to be reset by the manually operable switch actuating means.

Another object of the invention is to provide a switch embodying a shock resistant combination of balanced lever type latch means to insure maintenance of the switch in a first circuit controlling condition and spring loaded actuating means to effect unlatching operation of the latch means and operation of the switch to a second circuit controlling condition.

A further object is to provide means to achieve a predetermined wear allowance in the contactors of the switch regardless of variations in the construction of the switch as a result of manufacturing tolerances.

The switch, in general, comprises an electrical contact assembly, a link system movable to effect shifting of the contact assembly to various switching positions, and a balanced lever system including latch portions adapted to latch the link system and contact assembly in predetermined positions regardless of extraneous forces such as percussive shock. The balanced lever system and latch portions are adapted to be actuated to unlatching position both by manual means and by devices responsive to the flow of an overload current in a circuit controlled by the contact assembly, so that shifting of the link system and contact assembly may be effected either manually or automatically. In order to facilitate achievement of the proper wear allowance in the movable contactor elements of the contact assembly, indexing and adjusting means are provided to permit a predetermined initial adjustment of the stationary portions of the contact assembly relative to the frame on which the link system is mounted.

Other objects and advantages of the invention will be set forth more fully in the following description of an embodiment of the invention illustrated in the accompanying drawings.

In the drawings:

Figure 1 is an enlarged front elevation illustrating the switch in closed position, with portions being broken away to better illustrate the structure;

Fig. 2 is a vertical section taken generally along line 22 of Fig. 1;

Fig. 3 is a section on line 3-3 of Fig. 1;

Fig. 4 is a sectional view taken along line 4-4 of Fig. 1 and looking in the opposite direction from Figs. 2 and 3;

Fig. 5 is a partial horizontal section taken generally along line 55 of Fig. 1;

Fig. 6 is a side elevational view, partially schematic and partially in section, showing the positions of the parts after actuation thereof to circuit opening position by the left current responsive overload device in Fig. 1;

Fig. '7 is an enlarged detail view, primarily in horizontal section, illustrating the ratchet and solder elements of one of the overload devices;

Fig. 8 is an enlarged detail view showing the relation between a ratchet member and the corresponding lever member of the left overload device;

Fig. 9 is a rear elevation showing the switch in closed position, with portions broken away to illustrate the contact and contactor elements; and

Fig. 10 is a sectional view taken on line |c m of Fig. 9, showing the switch in closed position and illustrating the shim adjustment and reference means utilized to achieve the proper wear allowance in the contactor means.

Referring to the drawings and particularly to Figs. 1 and 10 thereof, the various operating components of the starter switch are mounted on and within a frame which is illustrated as comprising a generally rectangular base or mounting plate 6, a pair of spaced parallel side plates 2 projecting upwardly vertically from the base plate I and secured thereto as by screws 3 provided through outwardly extending flange portions 4 of the side plates, and a channel member 5 capped over the upper edges of the side plates 2 and connected thereto by suitable screws. The frame and all of the elements mounted thereon are adapted to be covered by a casing, not shown, which serves to protect the switch from dripping water and other harmful conditions which may be encountered in service.

As best shown in Figs. 1 and 6, the various elements I, 2 and '5 of the frame form a rectangular chamber adapted to contain intermediate or link means which operably connects a pair of switch actuating members c and l with an electrical contact assembly The front actuating member comprising a vertical arm bar 9 having a push button in at the upper end thereof, is adapted when manually depressed to effect actuation of the contactassenibly 8 to stop or ci cuit opening position, whereas the similarly constructed rear actuating member 1 serves when depressed to effect actuation of the contact assembly to start or circuit closing posi tion.

The intermediate or link means connecting the actuating elements and l with contact assembly 8 includes a vertically disposed pair of generally disc shaped cam plates l i and! 2 and a horizontal lever member 13 (Fig. 3), the latter being associated through cam means with the cam plates H and i2 and serving to operate the contact assembly it upon forward and reverse rotation of the cam plates by the actuating members it and I. The carn plates are pivotally mounted at approximately their centers on a principal axle rod M which extends between the mid portions of the side plates 2 and is secured by cotter pins against axial shifting movement. In order to rigidly interconnect the left cam plate l I (Fig. l) with the right cam plate l2 and maintain the same in spaced parallel relation, three members l5, l6 and ll, respectively, are provided between the plates H and 12 secured thereto by riveting.

Referring particularly to Figs- 1 and 3, the horizontal lever i3 is formed of two generally arcuate side members it having their forward ends pivoted to a suitable fulcrum pin :9 which is mounted between the frame side plates 2 forwardly of the lower cam plate edges. From the fulcrum pin 13, the side members [3 extend rearwardly between the lower portions of the cam plates H and 12 for insertion into the contact assembly 8, with a roller 20 being journalled at the rear ends of the side members 18 for the purpose of engaging a slide barportion 2| of the contact assembly. The roller 2t! additionally serves, together with a cam pin 22 and with a spacer member 23 on fulcrum pin it, to hold the side members l8 of lever [3 in spaced relation.

The cam pin 22 is disposed at the relatively elevated central portion of lever l3 and is shaped with a thick center portion located between side members [8 and with two relatively thin end portions extending laterally through the side members in the manner of a trunnion. Each of the end portions of the cam pin is inserted through one of a pair of corresponding arcuate cam slots 24 in the lower portions of cam plates H and 12. The slots 24, as best shown in Fig. 3, slant upwardly and forwardly so that the cam pin 22 is elevated to effect upward pivot of lever I3 when the plate members H and i2 are rotated forwardly, or clockwise in Fig. 3, and is lowered to effect downward pivot of lever I3 upon reverse rotation of the plate members.

As previously indicated, the necessary forward and reverse rotation of the cam plates H and it to cause upward and downward pivot of lever I3 is efiected, respectively, by the front and rear actuating members 6 and i. For this purpose one of the rivet members which connect the cam plates is located forwardly of axle member I4 and passes through a vertical slot 25 in the arm bar 9 of front actuating member 6. Another rivet member 16, located diametrically opposite memher [5, passes through the lower end of the arm bar 9 of rear actuating member l. The third rivet member I! is located between the upper portions of the cam plates and serves, in addition to its spacing function, to stabilize the plates H and [2 against wobbling. Suitable spacing washers, not shown, are provided between the respective arm bars9 and the cam plates to hold the bars in position.

With the described construction wherein the arm 9 of front actuating member 5 is slotted to receive rivet member l5, a lost motion connection is provided which effects forward rotation of cam plates l l and [2 only when the front arm 9 is in engagement with rivet [5 at the upper end of-the slot 25. The purpose of the lost motion connection is to permit the front actuating member 6 to be employed, as will be described in detail subsequently, to reset a pair of overload current responsive devices and 21 after operation thereof. Since it performs no resetting function, the rear actuating member 1' is connected to rivet member it without lost motion and is substantially shorter than the front member 6.

Although the front and rear actuating members Band 7 are adapted to effect actuation of the lever l3 and contact assembly 8 as previously set forth, it is a principal feature of the invention that i and compression springs are provided between the respective actuating arms ii and button members lfl'for spring loading and lost motion action as will be described hereinafter.

The balanced lever assemblies 23 and 29 which lock the switch in the desired positions are substantially identical to each other and are mounted in reversed manner on axle member It so that the left assembly 28 may serve to latch the switch in circuit opening position and the right assembly 29 in circuit closing position. Referring to Fig. 2 wherein the right balanced lever system 29 is illustrated, each system comprises upper and lower horizontal lever links 3| and 32, a main horizontal lever 33 including two spaced parallel tapered members pivotally mounted at their centers on'axle member l4, and forward and rear vertical link bars 34 and 3'5 which operably associate the

horizontal lever links

32 and 3| with main lever 33. The-

vertical link bars

34 and 35 are pivotally connected, respectively, to the centers of the

horizontal lever links

32 and 31 and to the centers of the forward and rear arms of main lever 33. In addition, the outer ends of the

lever links

31 and 32 are pivoted on studs 36 which project inwardly from the associated frame side plate 2. In order to improve the stability of the

lever systems

28 and 29 under shook conditions, each horizontal lever link is formed, similarly to the case of main lever 33, of two components which are held in spaced parallel relation by a pivot stud 3G and also by an end of the associated vertical link bar.

The lever links 3| and 32, as Well as main lever 33 and the vertical link bars 34 and. 35, are balanced with respect to weight, shape, size, and lever ratiosso as to form two portitons of substantially the same shock susceptibleness. Accordingly, if a shock wave is traveling, for example, in a downward direction in Fig. 2 it will strike one such portion comprising the upper lever link 3 I, the rear vertical bar 35, and the left or rear arm of the main lever 33 and will tend to pivot the latter counterclockwise. The same shock wave, however, will also strike the second such portion comprising the right arm of lever 33, the forward vertical bar 34, and the lower lever link 32 and will tend to pivot the main lever 33 in a clockwise direction. Since the various members are balanced, the pivotal forces acting on main lever 33 will cancel each other and the resulting movement in the system will be zero.

According to the invention, each shock resistant balanced lever system has associated therewith a latch pin or lug 31 mounted at the inner end of the upper lever link 3| opposiite pivot stud 36. Each of the latch pins 31, which are secured as by riveting to the two components of the lever link, projects inwardly into either a circumferential slot 38 in the associated cam plate I I or l2 or into a communicating radial slot 39 or 46! therein, depending, as shown in Figs. 3 and 4, upon the relative positions of the cam plates and lever systems. The circumferential slots 38 of the two cam plates I l and [2 are correspondingly located a slight distance from the upper edges of the plates. The

radial slots

39 and 40 on the other hand, do not correspond in location but instead extend radially to the extreme cam peripheries from opposite ends (Fig. 6) of the circumferential slots 38 with which they communicate.

As shown in Fig. 3, the radial slot 40 in the right cam plate [2 is located at the forward end of the associated circumferential slot 38. Since the cam plates are illustrated in Fig. 3 as being in reverse or counterclockwise rotated position effecting closing of the switch, the radial slot 40 in right cam plate [2 is shown as registering with the latch "pin 37 of the right balanced lever assembly 29. In order to bias the pin 31 into latching position within radial slot 40 once such registry is attained, a pair of helical tension springs M (Fig. 2) are provided, respectively, between the pivot studs 33 and pins 42 extending between the components of main horizontal lever 33 at the opposite tapered ends thereof. The tension springs ll cooperate in effecting clockwise pivot of the main lever 33 and consequent counterclockwise pivot of upper lever link 3! and elevation of latch pin 31 into radial slot 33. Additional undesired elevation of latch pin 31 is prevented by the engagement of inwardly extending pairs of vertically spaced stop arms 43, one of the pairs being formed integral with the forward vertical link bar 34 and the other pair with the rear vertical link bar 35.

t the same time that the latch pin 31 of the right balanced lever system 29 is in the latching position shown in Fig. 3, the latch pin 31 of the similarly constructed left balanced lever system 28 (Fig. l) is in an unlatching position at the opposite end of the associated circumferential slot 38 in left cam plate H from radial slot 39 therein. This is because the left and right balanced lever systems 23 and 29 are reversed relative to each other, and because the radial slot 33 of left cam plate H is at the opposite end of its associated circumferential slot 38 from the radial slot 30 of right cam plate l2. When the left balanced lever system 28 is in unlatching position as shown in Fig. 4, the latch pin 31 thereof is depressed and the lever system 28 pivoted against the bias of tension springs M to space the stop arms 43 of link bars 34 and 35 from each other.

In order to rotate the interconnected left and right cam plates H and I2 from the reverse rotated or circuit closing positions'illustrated in Figs. 3 and 4 to the forward rotated or circuit opening positions shown in Fig. 6, it is first necessary to depress the latch pin 31 of the right balanced lever system 29 into the circumferential slot 38 of right cam plate [2. This moves the pin 31 out of the path of the end of an arm member 44, the latter forming the portion of cam plate I2 outwardly of circumferential slot 33. The cam plates are then free to rotate forwardly, either as the result of manual depression of the front actuating member 6 or of operation of the

overload devices

26 and 21 as will be described subsequently. During such forward rotation the latch pin 3'! of right balanced lever system 29 rides along the under edge of arm 44, as a result of the bias of tension springs 4i, and the corresponding pin 3'! of left balanced lever system 2i? similarly rides along the under edge of a corresponding and oppositely extending arm 45 of left cam plate I I. After the cam plates have been rotated to their forward position, latch pin til i left balanced lever system 28 is in registry with radial slot 39 of left cam plate H and is actuated outwardly by tension springs ll to the locking position illustrated in Fig. 6. The left and right balanced lever systems and cam plates have thus in effect exchanged positions, so that the left balanced lever system 23 is shifted to latch the plates in forward rotated position whereas the right balanced lever system 28 is shifted to unlatching position.

The necessary depression of the latch pins 3? to permit forward and reverse rotation of cam plates H and i2 is accomplished by means of a pair of lug members 46 and ll which extend inwardly from the respective front and rear switch actuating members 3 and l. The lug 43 associated with front actuating member 3 is disposed above a pair of cars 33 formed integral above the latch pin 3'! of right balanced lever system 29 with the components of the upper lever link 3! thereof. Correspondingly, the lug 41 asso ciated with rear actuating member I is disposed above similarly located ears 43 of the left balanced lever system 28. The lug members 36 and ii are formed integral, respectively, with a pair of plate-like mounting members which are secured by screws to the undersides of the push buttons I U.

The push buttons l0, which are preferably formed of a plastic insulating material, are each shaped with a hollow generally cylindrical portion 5!! adapted to extend upwardly through a corresponding aperture in frame channel member 5, and with forwardly and rearwardly extending mounting portions 52 adapted to receive the screws securing the associated mounting member 56 in position. As shown in Figs. 1 and 3, the cylindrical chamber within each button portion 5! serves to receive one of the springs 35], the latter being compressed between the upper button end and an upright cup 53 which is slidably mounted within the chamber.

Each cup 33 is secured as by welding to the upper end of a vertical arm bar 9, there being a slot in mounting member 50 through which the arm bar 9 projects. A lost motion and spring loading arrangement is thus provided whereby the manual depression of a push button i 3 causes the button to move relative to its associated cup 33 and arm bar 9 and additionally compress spring 33. Such compressing action continues,

for examplein' the set of elements shown in Fig. 3, until the lug member engages ears 4B to depress latch pin 31 and move the same out of latching engagement with the" end of arm 44. Immediatelyupon the occurrence of unlatching, that is to say as soon as pin 31 is depressed into circumferential slot 38; the cam plates H and 12 are snapped forwardlydue to the sudden release of the energy stored in spring 3D'during the initial button movement prior to unlatching. The front vertical arm bar'9, through which the energy of the spring 301s transferred via rivet member to the unlatched cam plates, is thus depressed from the elevated position shown in Fig. 3 to a position lower than that of the arm bar of the rear actuating member "I.

In addition to their function of providing snapaction shifting, the spring portions of the front and rear actuating members 6 and 1 serve, together with the

balanced lever systems

28 and 29, to prevent-unlatching of the cam plates as the result of shock. This is because any shock actuation of push buttons I0 and lugs 46 and 41 is completely stopped by springs 30 prior to the unlatching engagement of

cars

48 and 49. After the shock, therefore, the buttons Ill snap back to the desired positions as the result of the energy stored in springs 30, there having been no switching action performed.

As mentioned previously, the switch is constructed to be operated not only by the front and rear actuating members 6 and 1 but by a pair of assemblies-26 and 21 connected to respond to the flow of overload currents in the circuits controlled by contact assembly 8. The overload devices each comprise a generally rectangular base 54 which is secured by the screws 3 to the upper surface of a side plate flange 4, and a thermal responsive means including a ratchet wheel 55 arranged at the inner face of the base 54 and a solder element 56 disposed in the communicating recessed outer portion thereof.

Referring particularly to Figs. '1 and 10, each solder element 56 includes a small sleeve or cylinder 51 which is non-rotatably connected to a base 54 as by interlocking with a bracket member 58 mounted on the base. A piston or core member 59, mounted at the outer end of cylinder 51 within a non-rotatable cup therein, is connected by a rod 6| to the ratchet wheel 55, there being a retainin ring interposed to prevent axial shifting of the core 59 and ratchet member. Suitable solder, not shown, is provided between the core 59 and cup 60 to lock the ratchet wheel 55 against rotation at all times except when the solder is melted. Such melting is performed by a heating coil, not shown, which is connected into a circuit controlled by contact assembly 8 and is coiled around the cylinder 51. The construction of the solder element is such that the solder does not flow out of place when melted but instead remains between the piston 59 and cup 60, so that the ratchet wheel is again locked against rotation upon cessation of the flow of overload current in the heating coil.

As best shown in-Figs. 1, 6 and 8, the normally locked ratchet wheels 55 are associated by means of pawls 62 with a pair of

levers

63 and 64 which are pivotally mounted outwardly adjacent side plates 2 on a fulcrum pin 65 extending between and through the lower'rear portions of the side plates. The pawls are secured, respectively, on the outerfaces of the

levers

63 and 64 and extend rearwardly to engage with their downwardly hooked end portions the teeth of ratchet wheels 55. Contraryto. thecase of the base member 54 and levers 63': and 64 which aremolded of an insulating plastics material, the pawls 62 are formed of a suitable spring metal.

In order to bias the

levers

63 and 64 upwardly, or-counterclockwise in Fig. 6, a pair of compression springs 66 are mounted, respectively, between lug portions 61 formed at the-lower edges of the levers forwardlyof fulcrum pin 65 and vertical studs 68 provided on base plate I. Each stud 68 extends into a large opening69 out both in the vertical portions of side plates 2 and in the hori zontal flanges 4 thereof.

The teeth of the ratchet wheels 55of both left and

right overload devices

26 and 21 are formed in a manner-to permit downward pivot of the left and

right levers

63 and 64 but to prevent upward pivot thereof. are normally maintained in a depressed position against the bias of springs 66 until melting of the solder in solder elements 56 permits turning ofthe ratchetwheels 55 and upward pivot oi The levers 63'and 64 may be resetthe levers. to downward pivoted position merely by depressing the same, the ratchet teeth then being inoperative to :prevent movementof the pawls 62relative thereto;

Referring to Figs. 1, 2 and 5 wherein the lever 64 of the right overload device 21 is shown, a portion lfl of lever 64 is shaped to extend inwardly through aside plate opening 69 for actuating engagement with the right balanced lever system29. For this purpose a horizontal shelf 1i is provided on 'the lever portion 10 beneath a pair of ears-12; the latter being integral with the components of'the lower lever link 32 of the right=lever-system 29. Assuming that the cam plates II and are in their rearward pivoted positions as shown in Fig. 3, so that the right balanced lever system 29 is in latching condition and the contact assembly 8 'is in circuit closing position, theupward pivotof the right overload lever 64 resulting from melting of the solder in the associatedsolder element 56 will cause the shelf 1| to engage and actuate the right car 12 upwardly. The lower lever link 32 will thus rotate clockwise, which operates through balanced

lever system members

33, 34 and 35 to pivot the upper lever link 3| clockwise and depress the latch lug 31 into unlatching position in circumferential slot 38. In order to pivot the cam plates H and I2 forwardly to effect opening of the circuits controlled by contact assembly 8 once such unlatching is accomplished, a spring 13 (Figs. 1 and 3) is provided between the cam plates on a spacer on axle member 14. The spring 13, which is coiled around the spacer, is hooked at one end over the front rivet member l5 and is hooked atthe other end under a pin 14 extending between the front upper portions of side plates 2.

Referring to Figs. 1, 4, and 5, the left overload lever 63 is adapted to similarly efiect forward pivot of the cam plates II and I2 and consequent shifting of thecontact assemblyB to circuit opening condition for cessation of the flow of overload current. For this purpose the lever 63 is provided with a portion 15 which extends inwardly through an opening 69 and terminates in a small cylindrical lug 16. The lug 16 is inserted through a corresponding aperture in one arm 11 of a generally 'U-shaped lever member 18 which is pivoted on fulcrum pin 65, so that upward pivot'of the overload lever 63 causes upward pivot of the lever 18. As best shown in Accordingly, the levers Fig. 5, the base or rear portion I9 of the U- shaped lever 18 extends laterally behind fulcrum pin 65 to interconnect the arm 11 with a corresponding forwardly extending arm 80 disposed on the right side of the switch. The arm 88 terminates at its forward end, generally opposite lug 16, in a raised shelf portion 8| disposed beneath the left ear I2 of right balanced lever system 29 adjacent shelf H of right overload lever 64. Accordingly, the right balanced lever system 29 may be actuated to unlatching position by the shelf portion 8| of U-shaped lever E3 in the same manner as by the shelf l: of right overload lever 64.

In order to more rigidly interconnect the arms H and til of U-shaped lever 18, and also to brace the lever against shock, a horizontal pan portion 82 is provided between the lower and rear edges of the arms H and 80 and along the lever base is. The pan 82 is shaped with a slot 83 to receive an angle bracket 863 which is mounted on base plate I and adapted to reinforce fulcrum pin 65 against bowing unde shock conditions.

The construction, mounting, and operation of the

overload devices

26 and 21 and associated parts is such that the possibility of undesired unlatching of the cam plates H and I2 and consequent operation of the contact assembly 8 is minimized. A percussive shock for example, would not shift shelf H or shelf 8! to actuate the right balanced lever system 29 to unlatching position since the shelves are effectively locked in place by the solder elements 55 acting through the pawl and ratchet assemblies and through levers 63, 6d and f8. Also, the fact that the overload devices 2i: and 2'! act through a balanced lever system 29 results in a shock resistant remote control arrangement permitting the overload devices to be rigidly mounted as a unit with the lower frame portions of the switch, where they do not interfere with manual snap-action switch operation and where they may be easily reset by the front switch actuating member 8 will next be described.

The left and

right overload devices

26 and 21 are adapted to effect unlatching of the cam plates II and i2 either in cooperation with each other or independently, depending upon the manner in which the heating coils which melt the solder in solder elements 56 are connected. In Fig. 6 for example, the left overload lever fit is illustrated as having effected actuation of the cam plates to forward or clockwise pivoted position whereas the right lever 64 is still in a de pressed position. In order to either simultaneously or separately reset the overload levers to depressed positions, a resetting lever 85 is pivotally mounted on fulcrum pin 65 between the arms ll and 80 of U-shaped lever f8.

Referring to Figs. 3 and 5, the lever 85 which is utilized to reset the overload levers 63 and $4 to their depressed positions is constructed with a pair of spaced parallel side members 86 having their rear ends pivoted on pin 65 and their relatively narrow forward ends formed integral with inwardly bent overlapping portions 8'! which are welded together to connect the side members. A channel bar 238 is secured transversely above the mid portions of the members, for example by welding to opposed inwardly extending tabs thereon, and is adapted to engage the upper edges of both arms Ti and 8B of U-shaped lever '13. In addition, the right end of the channel bar 83 is disposed to engage a second shelf portion 88 of right overload lever 64, the shelf 89 being to the rear and beneath the first shelf 10 of said lever. To insure that the channel bar 88 and other resetting elements remain in the proper lateral positions, suitable spacing cylinders are provided along fulcrum pin 55 as shown in Fig. 5, and a laterally extending portion Eli) is formed integral with the left side member 86 of resetting lever and shaped to bear against the left arm 11 of lever 18.

The overlapping front portions 8'! of resetting lever 85 are disposed (Fig. 3) beneath the lower end of the relatively long arm bar 9 of front actuating member 6, there being a portion out out of the lower front portion of the arm to permit depression thereof to engage resetting lever portions 8"! without interference by the fulcrum pin I9 and the associated lever sides It between which the bar 9 passes. When the resetting lever portions 87 are engaged upon downward movement of front arm bar 9, the resetting lever is pivoted downwardly to depress channel bar 38. The overload levers 63 and 64 are thus pivoted downwardly and reset, either directly as in the case of right lever 84 which is engaged at shelf 89 by the channel bar 88, or indirectly as in the case of left lever 63 which is reset by the channel bar acting through U-shaped lever 13.

In the operation of the resetting means, assume that the cam plates I l and i2 are in their rearward pivoted positions, so that the contact assembly 8 is maintained in circuit closing position by the connecting lever I3. Upon the occurrence of an overload one or more of the solder elements 55 will melt to release the associated

lever

63 or 64 for upward pivot under the bias of a spring 66 until ears E2 on right balanced lever system 29 are engaged and actuated. The associated right latch pin 31 will thus be depressed to permit forward pivot of cam plates II and if under the bias of spring '13, and the resetting lever 85 will be pivoted to its uppermost position (Fig. 6) due to lifting of channel bar 88 by one or more of the overload levers. Such forward pivoting of the cam plates II' and I2 and substantially simultaneous upward pivoting of the resetting lever 85 is possible because of the described lost motion connection between the front vertical arm bar 9 and the rivet member l5 connecting the cam plates.

Upon cessation of the overload condition the front actuating member 5 may be depressed, which operates through arm bar 9 thereof to pivot the lever 85 downwardly and reset the overload levers 63 and 64 to downward pivoted positions. The normal manual operation of the switch may then be resumed, for example by depressing the rear actuating member 7 to effect backward pivot of the cam plates I! and I2 and consequent operation of the contact assembly 8 to circuit closing position. Even if the overload condition has not been corrected, the switch may be maintained in circuit closing condition for emergency operation by manually maintaining the rear actuating member 1 in depressed condition. The continued depression of rear actuat ing member 1 prevents forward pivot of cam plates H and [2 under the bias of spring it after unlatching operation of the overload devices as a result of the overload.

The contact assembly 8, which is actuated between circuit opening and closing positions by the elements set forth heretofore, is substantially identical, except for adjustment and index means to be described subsequently, with the assembly illustrated and claimed in U. S. Patent 2,532,365

the upper'and lower walls of the aperture.

I for an Electric Switch, issued to HerbertE. Heller on December 5, 1950.

Referring to Figs. 9 and 10, the contact assembly comprises a housing or contact supporting member 9| which. is vertically mounted :at. the rear of the frame and is shaped with an internal guideway 92 in which the slide bar-2| is vertically movable.

Both the housing 9| and slide bar 2| are molded of a suitable insulating material, as is a cover member 93 which is secured over theflrear of the housing. The housing 9| servessas a support for three vertically spaced pairs of opposed stationary contact members 94 having terminal extensions-95 which project outwardlythrough openings in the housing. The means for securing. the contact members 94 to the housing may comprise screws 96 located mid- .way between the terminal extensions 95 and the inner or contact ends of the members 94.

The slide bar 2| is provided with three vertically spaced rectangular apertures 91 to receive transversely extending bridging contactor bars gagementwith the contact members 94 when the slide bar'2I is in its lower position, a helical com- I pressionspring 99 is mounted in each aperture 91 over centrally disposed vertical end projections I and. IOI which are formed, respectively, on The end projections are of elliptoid shape and extend lengthwise between the open ends of the apertures, so that each lower end projection IOI may project througha guide opening in the associated contactor bar.98 and maintain the same in the correct transverse position.

As shown inFig. '6, when the slide bar 2| is in elevated: position the contactor bars 98 are spaced fromthe stationary contact members 94 and are biased'downwardly by springs 99 against stop-portions I02 formed in'the apertures 91.

- Upon downward sliding of the bar 2| to the lower or circuit closing. position illustrated. in Figs. 9 and the respective contactors-98 engage the contact ends of contact members 94 and are relatively lifted off the stop portions I02 against the bias of springs 99. The shifting of the contactor I bar 2 Icbetween its upper or circuit opening positionand its. lower or circuit closing position is efiected' by the rear end of the connecting lever member I3 which'projccts through an opening in contact housing! and into a suitable recess I03 9 in the lower end of the slide bar 2|.

The slide bar recess I03 is only slightly larger than the roller which is mounted at the rear end of connecting lever I3, so that when the lever is locked in its upper or lower position by the latching and cam means previously described the slide bar may not be shifted, for example as the result of shock, to undesired switching positions. The precise upper or lower position of the lever I3, roller 20 and slide bar 2| relative to the frame of the switch varies between switches, however, as the result of manufacturing tolerances.

Because of the fact that the circuit opening and closing positions of the slide bar 2| relative to the frame of the switch vary from switch to switch due to tolerances in the manufacture of the switch components, it becomes necessary to provide means for obtaining a desired uniform wear allowance in .all switches manufactured in accordance with the invention. The wear allowance may be definedas the amount that the contacting. faces of. contactor bars 99, and also of contact members 194,"must wear or burn off before the bars'l98 engage thestop portions I02 of the slide bar 2| when the slide bar is in thelower or circuit closing position shown in Figs..9 and 10.

If the wear allowance is too small. that is to say if a new contactor bar 98 is only lifted a slight distance off a. stop portion I02 when the switch is closed, the contactor bar will engage stop I02 after only slightwear of the contact faces and the life of the contactor bar will be unnecessarily shortened. If, on the other hand, the wearallowance is too large, improper switchingwill result after the wearing off of an excessive amount of the contacting faces.

According to the invention, means are provided to initially adjust the contact housing, 9| relative to the frame of the switch and to indicate when such adjustment has produced the correct wear allowance in the contactor bars 99.

The adjustment means comprises-a plurality of horizontally stacked shims I04, which are disposed betweenan overhanging ledge portion I05 (FiglO) of the vhousing'ql and the upper rear portion of the framev channel member 5, and a pair of vertically elongated screw holes I06 provided through the lower corners of the housing. The holes I06, permit vertical adjustment of the housing 9| relative tomounting screws I01 which extend: forwardly through the holes and into vertical flanges I08 on the rear edges of frame portions4. The ledge portion I05 and shims are apertured to receive a pair of downwardly extending mounting screws I09 which are threaded into frame portion-*5.

In the adjustment of the contact assembly 8 for the desired'wear allowance, the switch is first operated to .its circuit closing position illustrated in Fig. 10. The screws I0! are then loosened and a sufiicient number of shims I04 are inserted to cause the lower edges of contactor bars to register with raised index or reference marks 0 which are formed at predetermined points on the sides of the slide bar 2 I. The screws |0'I are then tightened and the screws I09 are inserted: and tightened to rigidly lock the contact housing-9| in the correct position. With such an adjustment arrangement, variations between switches in the position of the slide bar2| relative to the frame are easily compensated for by corresponding-variations in the position of the contact supporting member 9| relative thereto.

The operation of the switch, after the same has been initially adjusted to the proper wear allowance as described, will next be summarized.

Assume that the switch is .in its closed position, as illustrated in Figs. 1-4, 9 and 10. The cam plates I and I2 are then in their reverse rotated positions, that is to say counterclockwise rotated in Fig. .3, and the lever member I9 is pivoted downwardly to hold the slide bar 2| in a depressed condition and cause the contactors 98 to be in engagement with contact members 94. In addition, the right balanced lever system 29 is in latching condition with the latch pin 31 thereof in the radial slot 40 of right cam plate I2.

In order to manually actuate the switch to circuit opening position, the operator presses downwardly on the push button I0 of front actuating member- 6. This moves the button relative to the associated arm bar 9 until the lug member, 46 engages cars 49 todepress the same and force right latch pin 31 downwardly to unlatching position against the bias of tension springs 4|. Immediately upon completion of suchunlatching movement, the cam plates II and I2 are snapped forwardly due to the sudden release of energy stored in the front spring 39 during unlatching, with the spring acting on the cam plates via front arm bar 9 Which engages at the upper end of slot 25 the rivet member l5. During the forward pivot of the cam plates, the connecting lever [B is pivoted upwardly as the cam pin 22 thereon rides in the cam slots 24 of the plates I! and I2, so that the slide bar 2| is lifted to disengage the contactors 98 from contact members 94 and open the switch.

At the completion of the forward pivot of the cam plates, the latch pin 31 of left balanced lever system 28 is actuated upwardly by tension springs 4! thereof to latching position within the radial slot 39 of left cam plate ll. As shown in Fig. 6, additional upward movement of the left latch pin 31 past the end of arm member 45 is prevented due to the engagement of the stop arms 13 of forward and rear vertical

lever system members

34 and 35 with each other.

To actuate the switch to closed position the button it! of rear actuating member I is depressed, causing lug member 4'! thereon to engage the ears 49 of left balanced lever system 28 and force the latch pin 31 thereof into the associated circumferential slot 38. As in the case of the operation of the switch to open position, the cam plates H and 12 are then snapped rearwardly because of the sudden release of the energy of rear spring 30 upon unlatching of the left balanced lever system. This rearward motion, effected by the pivotal connection between rear vertical arm Q and rivet member [6, causes downward pivot of connecting lever l3 due to the movement of cam pin 22 within cam slots. 2 3. Slide bar 2| is thus snapped downwardly to its lower position, shown in Figs. 9 and 10, at which time the contactors 98 are in biased engagement with contact members 94. The right balanced lever system 29 then being in latching position as before, the switch tends to remain in closed condition despite the effects. of percussive shock.

When the switch is in this circuit closing position, an overload condition may occur in the circuits controlled by contact assembly 8, which will cause one or more of the overload devices 26 and 271 to actuate the switch to circuit opening position in the following manner. Referring to Figs. '1, 5, 7, 8 and 10, the flow of overload current in a circuit controlled by contact assembly 8 may cause, depending upon how the overload devices are connected, a heating coil, not shown, to melt the solder of the solder element 56 of left overload device 26. The melting of the solder will release the associated ratchet wheel 55 for rotational movement, so that it becomes inoperative to prevent upward movement of the pawl 62 engaged therewith under the bias of the left compression spring 66 acting on the left lever member 83. As the left lever 63 snaps to its upper position, shown in Fig. 6, the U-shaped lever member 18 is also moved upwardly due to the mounting of lug 16 through the aperture in the left arm ll of lever 18. As the U-shaped lever l8 approaches its uppermost position, the shelf portion 8! thereof engages an ear 12 of right balanced lever system 29 and actuates the same upwardly. This in turn effects downward actuation of the latch pin 31 of the right balanced lever system into unlatching condition within circumferential slot 38 of right cam. plate l2, the cam plates H and I2 then being free to pivot forwardly or clockwise in Fig. 3 under the bias of spring l3 acting on forward rivet member i5. Since the cam plates H and I2 are pivoted forwardly, the connecting lever I3 is operated to its upper position to lift the slide bar 2i and open the switch, as in the case of manual operation of the switch through the depression of front actuating member 8.

Similarly to the case of the left overload device Et, the right overload device 21 is responsive to an overload condition in its circuit, which results in the melting of the solder element 55 thereof and consequent freeing of the right I ratchet wheel to permit upward pivot of right overload lever member 64 under the bias of the spring 86 therebeneath. The horizontal shelf ll of the right lever member 64 is thus engaged with an ear 12 to unlatch the switch. for move ment to circuit opening position as in the case of actuation of an car 12 by the shelf ill of U- shaped lever 58.

As one or the other of the left and right overload levers 53 or 64 pivot upwardly to effect opening of the switch, the channel bar 88 of resetting lever 35 is lifted due to engagement thereof by shelf 89 of the right overload lever 66 or by the arms El and 30 of the uhaped lever '78 operated by the left overload lever 63. The vertical arm 9 of front actuating member 6 is thus maintained in its elevated position, shown in Fig. 6, due to engagement of the resetting lever portions 87 with the lower end thereof. Since the front actuating arm 9 is maintained stationary while the cam plates II and l2 pivot forwardly, the rivet member 15 moves downwardly relative to the vertical slot 25 in the arm bar.

In order to reset the actuated

overload device

26 or 27, it is merely necessary to depress front actuating member 6 and thus pivot the resetting lever downwardly. The channel bar 38 will then depress the overload levers G3 and M, and they will remain in depressed condition due to the locking of their associating p-awls 62 by the ratchet wheels 56, the ratchet wheels then being locked in position due to freezing of the solder in elements 53 upon cessation of the flow of overload current. Regardless of whether the solder is melted and the overloads actuated, the switch may be maintained in circuit closing position for emergency operation by holding the rear actuating member 6 in a depressed position.

The invention provides a compact switching unit which is constructed for maximum resistance to percussive shocks, and which is both manually operable and operable in response to overloads in the circuits controlled thereby. Because of the fact that a balanced lever system is employed as a shock resistant remote control means by which the current responsive devices effect unlatching operation upon the occurence of an overload, the current responsive devices may be conveniently and rigidly mounted a substantial distance from the members which latch the switch in its open and closed positions.

Although the invention has been shown and described with the pushbuttons and contact structure in a vertical position, it should be understood that this was done for ease of description only. Under normal circumstances the switch will be mounted so that the pushbuttons and contact structure are in horizontal position.

Various embodiments of the invention may be employed within the. scope of the "following claims.

We claim:

1. In a shock resistant starter switch, contact means, shifting means operatively connected with said contact means, said shifting means being movable between a first position effecting a first circuit controlling condition in said contact means and a second position effecting a second circuit controlling condition therein, a i

balanced lever system including a latch portion adapted to latch said shifting means in said first position and thus insure maintenance of contact means in said first circuit controlling condition, and means for effecting unlatching operation of said balanced lever system and movement of said shifting means from said first position to said second position.

2. In a shock resistant starter switch, contactor means, intermediate means operative-1y associated with said contactor means and movable to shift the same between first and second circuit controlling positions, a balanced lever system comp 'ising portions of substantially equal shock susceptibleness balanced on opposite sides of a fulcrum and including latch means adapted when said lever system is in a given position to latch said intermediate means against shifting movement, and means to actuate said latch means and balanced lever system to an unlatching position and to move said intermediate means for shifting of said contactor means between said first and second positions.

3. In a shock resistant starter switch, contact means, intermediate means operatively associatod with said contact means and movable to shift the same between first and second circuit controlling positions, balanced lever means havlatch means adapted when said balanced lever means is in a given position to latch said intermediate means and thus prevent shifting of said contact means, and manually operable "dating means to actuate latch means to unlatching position and to more said intermediate means for shifting of said contact means between said first and second positions, said actuating means including a lost motion and spring loading portion effecting snap-action movement of said intermediate means and contact means upon operation of said latch means to unlatching position.

4. A shock resistant starter switch, comprising electrical contact means, intermediate means connected to said contact means and movable to shift the same to a plurality of circuit controlling positions, a balanced lever system including a latch portion adapted to latch said intermediate means against shifting movement, manual means adapted to actuate said balanced lever system on one side of the principal fulcrum thereof to thereby effect unlatching operation of said latch portion and permit shifting movement of said intermediate means, and current responsive means adapted to actuate said balanced lever system on the opposite side of said principal fulcrum thereof to similarly effect unlatching operation of said latch portion in the event of an overload in the circuit controlled by contact means.

5. In a starter switch, electrical contact means, intermediate means operably associated with said contact means and movable between a first position effecting closing of said contact means and a second position effecting opening of said con- .tact means,,.meanstolatch said intermediate as means in each of saidpositionsand manually operable-means to effect -unlatching operation of said latch means andhto move said intermediate means between said first and second positions for opening and closing of said contact means.

6. A shock resistant switch, comprising electrical contacts, intermediate means connected with said contacts and movable between a first position effecting closing of said contacts and a second position effecting openingthereof, a first balanced lever system havinga latchportion adapted to latch said intermediate means in said first positionya second balanced lever system having a latch portion adapted to latch said intermediate means in said second position, first manuallyoperable means to effect unlatching operation of'said second balanced lever system and shift said intermediate means to said first position, and second manually operable means to effect unlatching operation of said first balanced lever systemrandshift said intermediate means to said second position.

'7. A shock resistant starter switch, comprising electrical contact means, intermediate means operably associated with said contact means and movable between a first position effecting closing of said contact means and a second position efiecting opening thereof, balanced lever means, means on saidi balanced lever means and intermediate means to alternately latch said intermediate means-in said first and second positions, a pair of actuating arms operably associated with said intermediate means to move the same between said positions, a pair of manually operable members mounted, respectively, at the ends of said actuating arms and movable relative thereto, said manually operable members being disposedto actuate said balanced lever means and latch means to unlatching condition. after predetermined movements relative to said actuating arms, and ,a pair of springs mounted, respectively, between said actuating arms and manually operable members for loading during said predetermined movements, said balanced lever means and said springs serving to prevent undesired actuation. of said latch means to .unlatching condition as a result of percussive shocks.

8. A starter switch,. comprising a frame, an intermediate member rotatably mounted on said frame, electrical contact means mounted on said frame, a lever pivotally connected to said frame and operably associated with said contact means to shift the same between open and closed conditions, means interconnecting said intermediate member and said lever and effecting operation of said lever to open said, contact means upon rotation of said intermediate member to a first position and to close saidcontact means upon rotation of said intermediate member to a second position, means to latch said intermediate member in at least one of said positions, and manually operable means to effect unlatching operation of said latch means and to rotate said intermediate member to the other ,of said positions.

9. A shock resistant switch, comprising a frame, a cam plate mounted in said frame for rotation about an axis transverse to said cam plate, electrical contact means mounted on said frame, a connecting lever associated with said contact means to shift the same between open and closed conditions, cam means interconnecting said cam plate and said lever and effecting operation of said lever. taopen said contact means .upon rotation of said plate member to a first position and to close said contact means upon reverse rotation of said cam plate to a second position, a lever system comprising corresponding portions of substantially equal shock susceptibleness balanced on opposite sides of a fulcrum, a latch member mounted on said lever system and adapted to extend into a radial opening in said cam plate to latch the same in one of said positions, and an actuating arm adapted firstly to actuate said lever system and effect movement of said latch member out of said radial opening and secondly to actuate said cam plate to the other of said positions.

10. A shock resistant starter switch, comprising a frame, a plate member mounted on said frame and rotatable about an axis transverse to said plate member, an electrical contact assembly mounted adjacent said frame, a connecting member operatively associated with said contact assembly, said connecting member being operated by said plate member and effecting shifting of said contact assembly to one circuit controlling condition upon rotation of said plate member to a first position and shifting of said contact assembly to another circuit controlling condition upon reverse rotation of said plate member to a second position, first and second balanced lever systems including latch portions adapted, respectively, to latch said plate member in said first and second positions, first and second actuating members associated with said plate member and manually operable, respectively, to shift the same to said first and second positions, first and second button means associated, respectively, with said first and second actuating members and movable relative thereto, said first button means being adapted after a predetermined initial movement relative to said first actuating member to actuate said second balanced lever system to unlatching condition, said second button means being adapted after a predetermined initial movement relative to said second actuating member to actuate said first balanced lever system to unlatching condition, and compression spring means interposed, respectively, between said first and second button means and said first and second actuating members to effect snap action shifting of said plate member after operation of said balanced lever systems to unlatched condi tions by said button means, said spring means and said balanced lever systems insuring maintenance of said contact assembly in the desired circuit controlling condition until manual actuation of said button means by the operator of the switch.

11. A shock resistant switch, comprising a frame, a cam element mounted on said frame for rotation about an axis normal to said cam element, an electrical contactor assembly mounted on said frame, a connecting lever associated with said contactor assembly to shift the same between open and closed conditions, cam means interconnecting said cam element and said lever and effecting operation of said lever to open said contactor assembly upon rotation of said cam element to a first position and to close said contactor assembly upon rotation of said cam element to a second position, first and second balanced lever systems mounted on said frame adjacent said cam element, said lever systems each comprising portions of substantially the same of a principal fulcrum, a first latch means interconnecting said first balanced lever system and said cam element to latch said cam element in said first position, second latch means interconnecting said second balanced lever system and said cam element to latch said cam element in said second position, first manual means to actutae said first balanced lever system and first latch means to unlatching condition for shifting of said cam element to said second position, second manual means to actuate said second balanced lever system on one side of the principal fulcrum and effect unlatching operation of said second latch means for shifting of said cam element to said first position, and a solder type overload device mounted on said frame and connected to respond to the flow of overload current in a circuit controlled by said contactor assembly, said overload device being disposed to actuate said second balanced lever system on the opposite side of the principal fulcrum thereof from the point of actuation of said second manual means and to similarly effect unlatching operation of said second latch means for shifting of said cam element to said first position and opening of said contactor assembly.

12. A shock resistant starter switch, comprising electrical contact means, intermediate means connected to said contact means and movable to a first position effecting opening of said contact means and a second position effecting closing thereof, first and second balanced lever systems including latch portions adapted, respectively, to latch said intermediate means in said first and second. positions, manual means including a spring loading and lost motion portion operable to actuate said second balanced lever system on one side of the principal fulcrum thereof to unlatch said intermediate means, said manual means being operable to effect snap-action shifta ing movement of said intermediate means after unlatching thereof, and current responsive means adapted to actuate said second balanced lever system on the opposite side of said principal fulcrum thereof to similarly unlatch said intermediate means in the event of an overload in the circuit controlled by said contact means, said current responsive means being adapted to be reset to normal position by said manual means.

13. A shock resistant switch, comprising a frame, an axle member mounted in said frame, a pair of rigidly interconnected spaced parallel cam plates mounted on said axle member for pivotal movement thereabout, an electrical contact assembly mounted on said frame and including a contactor bar slidable between circuit opening and circuit closing conditions, a lever member having one end disposed in a corresponding recess in said slidable contactor bar and extending between said cam plates for pivotal connection at its other end to said frame, a cam pin mounted transversely of said lever member and extending into cam slots in said cam plates, said cam pin and cam slots effecting pivot of said lever member to actuate said contactor bar to circuit opening condition upon rotation of said cam plates to a first position and effecting pivot of said lever member to actuate said contactor bar to circuit closing condition upon reverse rotation of said cam plates to a second position, first and second balanced lever systems mounted on said axle member adjacent the outer surfaces of the respective cam plates and being reversed relative to each other, a first latch lug mounted on said first balanced lever system and adapted to alternately extend into a circumferential slot in one of said cam plates and into a communicating radial slot in said one cam plate depending upon the rotated position thereof, a second latch lug mounted on said second balanced lever system and adapted to alternately extend into a corresponding circumferential slot in the other of said cam plates and into .a communicating radial slot in said other cam plate depending upon the rotated position thereof, said radial slots being at opposite ends of said corresponding circumferential slots, spring means to bias said first balanced lever system in a direction eifecting latching location of said first latch lug in the associated radial slot upon rotation of said cam plates to said first position and to bias said second balanced lever system in a direction effecting latching location of said second lug in the associated radial slot upon reverse rotation of said cam plates to said second position, a first actuating arm extending between said cam plates and 'pivotally connected thereto on one side of said axle member, a first spring loaded push button mounted for movemen-t relative to said first actuating arm, means on said first push button to engage said first balanced lever system adjacent said first latch lug and effect movement of said lug .to unlatching position within the associated circumferential slot and free said cam plates for shifting to said second position, a pair of spring biased ratchet type current responsive devices mounted on said frame and adapted to engage said second balanced lever system on the opposite side of said axle member from said second latch lug and effect movement of said lug to unlatching position within the associated circumferential slot, spring means to rotate said cam plates to said first position upon unlatching thereof by said current responsive devices, a second actuating arm extending between said cam plates and pivotally connected thereto by a lost motion connection disposed on the opposite side of said axle member from said first actuating arm, a second spring loaded push button mounted for movement relative to said second actuating arm, means on said second push button .to engage said second balanced lever system adjacent said second latch lug and effect movement of said lug to unlatching position within the associated cir cumferential slot and free said cam plates for shifting to said first position, and a resetting lever pivotedly connected to said frame and having portions disposed for actuation by said second actuating to reset said current responsive devices to the normal positions thereof.

14. A shock proof starter switch, comprising a frame, a contact housing mounted adjacent said frame, a plurality of electrical contacts rigidly mounted in said housing and movable therewith, a slide bar mounted in said housing and slidable relative thereto, a plurality of electrical contactors movably mounted on said slide bar and disposed, respectively, in engagement with said contacts when said slide bar is in circuit closing position and out of engagement with said contacts when said slide bar is in circuit opening position, spring means disposed, respectively, between said contactors and slide bar to .bias said contactors against said contacts when said slide bar is in circuit closing position, s ide bar actuating means mounted on said frame and operatively associated with said slide bar to actuate the same between circuit opening and circuit closing positions, balanced lever type latch means mounted on said frame and adapted to latch said actuating means at a position effecting location of said slide bar at said circuit closing position, said circuit closing position varying relative to said frame in accordance with the manufacturing, tolerances of the slide bar actuating means and latch means, index means provided on said slide bar, and means to adjust the position of said contact housing relative to said frame for correlation of the positions of said contactors and said index means when said slide bar is in said circuit closing position, said index means and adjusting means making possible the achievement of a predetermined wear allowance in said contactors despite said variations in the circuit closing position of said slide bar.

15. A shock resistant actuating mechanism comprising, in combination, a movable element, means movable to first and second positions adapted for moving said element, said means including a pair of rotatably mounted rigidly interconnected spaced parallel plates; first and second balanced lever systems concentrically mounted adjacent the outer surfaces of the respective cam lates and being reversed relative to each other; a first latch pin mounted on said first balanced lever system and adapted to al-- ternately extend into a circumferential slot in one of said plates and into a communicating radial slot in said one plate depending upon the rotated position thereof; a second latch pin mounted on said second balanced lever system and adapted to alternately extend into a corresponding circumferential slot in the other of said plates and into a communicating radial slot in said other plate depending upon the rotated position thereof, said radial slots being at opposite ends of said corresponding circumferential slots;

spring means biasing each of said latch pins toward said radial slots; and actuating means for moving said balanced lever systems to unlatching position and to move said plates to effect movement of said movable element.

16. A shock resistant actuating mechanism according to claim 15, wherein said actuating means comprises a pair of actuatin arms .operably associated with said movable means to move the same between said positions; a pair of manually operable members mounted, respectively, at the ends of said actuating arms and movable relatively thereto, said manually operable members being disposed to actuate said balanced lever means to unlatching condition after predetermined movements relatively to said actuating arms; and a pair of springs mounted, respectively, between said actuating arms and manually operable members for loading during said predetermined movements, said balanced lever systems and said springs serving to prevent undesired actuation .of said latch means to unlatching condition by percussive shocks.

References Cited in the .file of this patent UNITED STATES PATENTS Number Name Date 1,912,109 Van Valkenburg et al. May 30, 1933 2,248,387 *Rosing et a1. July 8, 1941 2,276 085 Pearson Mar. 10, 1942