US3053950A

US3053950A - Snap-acting switch

Info

Publication number: US3053950A
Application number: US833425A
Authority: US
Inventors: Michael J Dobes
Original assignee: National Acme Co
Current assignee: Devlieg Bullard Inc
Priority date: 1959-08-13
Filing date: 1959-08-13
Publication date: 1962-09-11
Anticipated expiration: 1979-09-11
Also published as: GB931991A; DE1440029B2; DE1440029A1

Description

Sept. 11, 1962 M. J. DOBES SNAP-ACTING swrrcn 3 Sheets-Sheet 1 Filed Aug. 15, 1959 Sept. 11, 1962 M. J. DOBES 3,053,950

SNAP-ACTING SWITCH Filed Aug. 13, 1959 3 Sheets-Sheet 2 M E /lQ/MISQ m\ ylzsfiugmgl ag -3 MICHAEL J.D OBES I03 I09 1M FIG. 4 m.

Sept. 11, 1962 M. J. DO BES 3, 5 0

SNAP-ACTING SWITCH Filed Aug. 13, 1959 5 Sheets-Sheet 5 I45 INVENTOR.

MICHAEL J. DOSES I (wa United States Patent 3, 53,959 SNAR-AQITING SWITCH Michael J. Dobes, fieveiand Heights, Ohio, assignor to The National Acme Company, a corporation of Ohio Filed Aug. 13, 1959, Ser. No. 833,425 8 Claims. (1. 2118-78) The invention relates in general to electrical switches and more particularly to snap-acting switches of the heavy duty type.

This application is a continuation in part of my copending application Serial No. 722,318, filed March 18, 1958, now Patent No. 2,958,747, issued November 1, 1960.

The prior art has known many forms of switches including both slow-acting and snap-acting and in general slow-acting switches require fewer parts and are thus easier to manufacture and in general more reliable. However, such switches are subject to considerable pitting and burning of the contacts because of the slow make and break of the contacts and; hence, such switches generally are not usable on anything but light current applications such as control circuits. For heavy duty applications wherein large currents are to be switched, the snap-acting variety of switch is practically mandatory. Such switches have in the past had a poorer reputation for reliability than the slow-acting type because of their greater number of parts and the operating characteristics during the life of the switch has been inconsistent. The wear on the several parts has caused them to change the operating point and; hence, to try to use such snap-acting switches as precisionlimit switches has generally been unsatisfactory.

Accordingly, an object of the invention is to provide a snap-acting precision-limit switch of the heavy duty type.

Another object of the invention is to provide a snapacting switch which will handle heavy currents and which may be precisely controlled as to the operating point and which operating point will remain constant throughout life.

Another object of the invention is to provide a precisionlimit switch which may be mounted on a machine for control of a machine function thereof and wherein electrical connections may be made to the switch without disconnection of the switch from the machine on which mounted.

Another object of the invention is to provide a heavy duty snap-acting switch which may have a variety of adjusted positions and which also may have a variety of internal electrical connections and also a variety of different forms of contact arrangements capable of being substituted therein.

Still another object of the invention is to provide a heavy-duty snap-acting switch which is shock proof or jar proof as well as capable of being oil, water, and dust tight.

Other objects and a fuller understanding of this invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is an exploded isometric view, partly in section, of the present switch;

FIGURE 2 is a top view of the switch;

FIGURE 3 is a sectional view on line 3-3 of FIG- URE 4;

FIGURE 4 is a longitudinal, vertical, sectional view of the switch;

FIGURE 5 is a bottom view with the cover removed;

FIGURE 6 is a view similar to FIGURE 5, but showing the switch in a slightly different position;

FIGURE 7 is a partial view of a modification of the switch;

FIGURE 8 is view similar to FIGURE 7, but showing the switch in a different position; and

Patented Sept. 11, 1962 FIGURES 9 and 10 are partial top views of the switch contacts corresponding to FIGURES 7 and 8, respectively.

The snap-acting switch of the present invention has been illustrated as a double-throw switch and used as a precision-limit switch. The switch may be readily connected for use either as a normally closed or a normally open type or as a combination of both.

FIGURE 1 shows an exploded isometric View of the entire snap switch 10 which includes generally a main housing 11 having open upper and lower ends which are adapted to be closed by top and

bottom covers

12 and 13 sealed by gaskets, not shown for clarity. Screws maintain the covers in place upon the housing. An intermediate wall 14 divides the housing 11 into top and

bottom compartments

15 and 19, respectively, and forms a bottom wall for each such compartment. Located at one end of the housing 11 is a cam mechanism 16 which includes first and

second parts

17 and 18, respectively. The cam mechanism 16 is rotatively carried by a shaft 21 which is journalled in one end of the housing 11. The cam first part 16 includes a cam member 21 provided with first and second cam portions or low and

high surface portions

23 and 24, respectively. First and second crossed slots 27 and 28, respectively, are provided in the end of the second part 18. The first part 17 includes raised wall portions 34 which are adapted to reside in either one of the slots 27 or 28 to non-rotatively connect together the first and

second parts

17 and 18 of the cam mechanism 16. A cam mechanism return torsion spring 36 surrounds the second part 18 and has two ends engaging either side of a projection 38 formed as an integral part of the housing 11. The second part 18 of the cam mechanism is provided with a finger 39 which extends between the two ends of the spring 36. This construction permits the cam mechanism to turn in either direction with the spring 36 exerting a returning force acting against the turning force, so as to return the cam mechanism to the neutral position as shown in FIGURE 1. The shaft 21 comprises generally pivot means for rotatively mounting the cam mechanism 16.

The cam first part 17 axially slides on the shaft 21 and a compression spring 3'25 held by a snap ring 37 in a groove in the shaft 21 urges the cam first part 17 toward the second part 18'. This assures engagement of the raised wall portions 34 in the slots 27 and 28. A rim 40 on the first part 17 provides a finger hold, with the bottom cover 13 removed, so that the cam first part 17 may be grasped, pulled outwardly, turned a quarter-turn and released to reengage the wall portions 34 with the slots 27 and 28. The cam 21 thus has a different position relative to the cam follower, described below.

An operating lever 42 is connected to the shaft 21 by a clamping screw 43 and is located outside the housing 11. An engagement roller 44 is journalled at the outboard end of the lever 42 and is positioned in the path of movement of a movable mechanism 46, see FIGURES 5 and 6. This moving mechanism may be any actuating means, for example, it may be a movable part such as a movable slide of a machine. The operating lever 42 and cam mechanism may be referred to as being in a first position in FIGURE 5 and may be referred to as being in a second position in FIGURE 6.

The end of the housing 11 opposite the cam mechanism 16 is provided with a threaded opening 50 communicating with the top compartment 15 to receive an electrical conduit or the like through which external conductors extend. These conductors may be connected to an external circuit (not shown) which may be used to control the movement of the moving mechanism 46. A terminal block 55 is secured to the intermediate wall 14 of the housing 11 by any suitable means, such as screws 56 which extend into bosses 57. The terminal block 555 is constructed of insulating material such as a plastic material and has a longitudinal recess or slot 6% extending lengthwise along the upper surface thereof, and this slot communicates at one end portion with the threaded opening 51 First and second pairs of terminals 52 and 63, respectively, are located on first and second end portions, respectively, of the terminal block 55. A terminal of each pair is located on either side of the longitudinal slot 60. First and second pairs of blade type

fixed contacts

65 and 66 are connected to the

terminals

62 and 63, respectively. The construction of the blade type contacts is best seen in FIGURES 1 and 4 of the drawings. A blade type contact of each of the pairs also resides on either side of the longitudinal slot 60.

A contact carrier 81 is supported on the intermediate wall 14 and positioned below the terminal block 55 and is movable between first and second positions. The first position is shown to the right as viewed in FIGURES 1 and 4. The contact carrier 81 carries movable blade type contacts 33 and 84, respectively. The contact carrier is constructed of insulation material, such as plastic material. The

movable contacts

83 and 84 are electrically connected together and are formed from two identical blades 85 urged together by springs 86 mounted on posts 87 and held by caps 88. The caps may be depressed and turned a quarter-turn to release the springs 86 and blades 85 from the posts.

A latchable channel member 9% is carried in the bottom compartment 19 immediately below the intermediate wall The latchable channel 9% includes a back member 92 which has first and second pairs of spaced leg members or

projections

93 and 94 respectively, integrally connected thereto at opposite end portions. All leg members extend generally perpendicularly to the back member 92. Carrier pins 97 fasten together the latchable channel member and the contact carrier 81 and extend through a slot 98 in the intermediate wall 14. A latch release channel ltll is movable between first and second positions, with the first position being to the right as viewed in FIGURES 1 and 4. This latch release channel is also movable relative to the spaced leg members as will hereinafter he described. The latch release channel 101 at an intermediate portion thereof, houses first and second relatively movable lugs 103 and 104 and a lug spring or resilient means 105 is positioned between these two lugs and urges them apart. The function of the first lug 103 is to engage the first pair of spaced members 93 and urge them and as a result urge the latchable channel 95 to the second position when the latch release channel moves to the second position. A return spring 107 is positioned at one end of the latch release channel 101 and urges same to its first position. A cam follower roller 108 is journalled on the other end of the latch release channel 101 and is adapted for engagement with the cam member 20 and alternatively engages the first and

second surface portions

23 and 24 of this cam member. Movement of the cam follower roller 168 from engagement with the first surface portion 23 of the cam to engagement with the second surface portion 24 causes the latch release channel 101 to move from its first to its second position. This progressive movement is best seen in FIGURES and 6.

An unlatching stud or abutment means 169 is fixedly secured to the latch release channel 101 and is adapted to travel therewith between the first and second positions of the channel 101.

A latch plate 111 is located near the bottom cover 13 and is secured to the housing by means of screws 112 at bosses 113. The latch plate 111 serves to confine the latch release channel 101 and the latchable channel member 90 within the bottom compartment of the housing 11. Inte gral guides 114 on the plate 111 serve as a guideway for sliding movement of the latch release channel 101 and resist any side thrust on the latch release channel 101 as exerted by the cam 20 acting on the cam follower roller 108. The latch plate 111 is provided with slots 115 which receive the

leg members

93 and 94 of the latchable channel 913. The latch plate 111 also has an opening 116 which receives the unlatching abutment 109. First and second pairs of latch members or

levers

118 and 119, respectively, are pivotallyconnected by meansof pins 120 near the center of the latch plate. Each of these latch members 118 and 1119 has a latch shoulder 1122 with which the

leg members

93 and 94 are engageable and springs 124 and 125 urge the latch members of a respective pair laterally toward each other to be urged into engagement with the

leg members

93 and 94. The latch shoulder 122 of the first pair of latch members 118 is adjacent the left edge, as viewed in FIGURES 1 and 5, of the leg members 93 when the latch release channel 101 is in the first position shown in these figures. Each of the latch members is provided with an actuating surface 126 which is engageable with the unlatching abutment 109.

Operation The snap switch 10 may be used in many different environments and one typical environment is as a precision-limit switch as actuated by an actuating means in this case shown as a moving mechanism 46. The snap switch 10 has precision construction permitting it to be precisely actuated from one switch condition to another at a precise point of movement of the moving mechanism 46, and to have this switch actuation precisely repeated each time the moving mechanism 46 moves to that particular point in its path of movement. External conductors may be connected to either

terminals

63 or 62 to provide either normally closed or normally open switching functions. Assuming that the moving mechanism 46 is traveling in a downward direction indicated by the arrow 129, then engagement of the mechanism 46 with the engagement roller 44 causes the cam mechanism and the cam member 20 to rotate in a clockwise direction as viewed in FIGURES 5 and 6. Rotation of the cam member 20 causes the cam follower roller 108 on the latch release channel 101 to travel from engagement with the first surface portion 23 to the second surface portion 24 of the cam member 20. This action initially causes movement of the latch release channel 101 from the first toward the second position and also causes the first lug 103 to engage the first pair of spaced leg members 93 which urges the latchable channel 90 toward the second position. The latchable channel, however, is initially held from movement toward the second position because the latch shoulders 122 on the first pair of latch members 118 engage the left side of the first pair of leg members 93 and prevent movement of the latchable channel 90. During this period when the latchable channel 90 is held against movement, the latch release channel 101 is moving toward the left, and the first lug 103 which engages the first pair of leg members 93 compresses the lug spring 1G5. This construction, therefore, in the initial movement of the latch release channel 101, permits relative movement between this latch release channel and the latchable channel 90. The movement of the latch release channel 101 causes movement of the unlatching abutment 109 which engages the actuating surface 126 on the first pair of latch levers 118 and continues to urge the first pair of latch levers against the urging of the spring 124. Upon sufiicient longitudinal movement of the latch release channel 101, the unlatching abtument 109 forces the first pair of latch levers 118 sufficiently far apart so that the latch shoulders 122 release the first pair of leg members 93, at which time the compressed lu-g spring 1E5 by way of the first lug 103 rapidly moves the latchable channel 90 to the second position. Since the contact carrier 81 is operatively connected to the latchable channel Q0, this contact carrier also travels rapidly from the first to the second position. This rapid movement is transmitted to the

movable contacts

83 and 84 which rapidly break electrical connection between the second blade type contacts '66 and then make electrical connection between the first pair of blade type contacts 65. Overtravel downwardly of the mechanism 4-6 is permitted by the cam mechanism 20 and torsion spring 36.

When the moving mechanism 46 moves upwardly from the position shown in FIGURE 6, the cam mechanism return spring 36 causes the cam member 20* to move in a counterclockwise direction from the position in FIGURE 6 to the position in FIGURE 5. While this movement is taking place, the return spring 107 moves the latch release channel 101 from the second position to the first position. This movement causes the snap switch '10 to function in much the same way only in reverse to that described above. The initial movement of the latch release channel 101 from the second toward the first position causes the second lug 104 to engage the second pair of leg members 94 to urge the latchable channel 90 to the first position along with the latch release channel 101. The second pair of latch levers, 119, however, engage the right edge of the second pair of leg members 94 and prevent the latchable channel member 90 from moving to the first position,

which causes the lug spring 105 to be compressed. Upon further movement of the latch release channel 101 toward the first position, the unlatching abutment 109 forces the second pair of latch levers 119 far enough apart to release these latch levers from the second pair of leg members 94. This permits the force which has been built up by compressing the lug spring 105 to act upon the latchable channel member 90 to rapidly move the same to the first position. This rapid movement is transmitted to the movable contacts carried by the contact carrier 81 and provides a quick break at the first contacts 65 and a quick make at the fixed contacts 66.

To change the rotational direction of operation of the switch or the switch position, for example, if the mechanism 46 were located at the lower right-hand corner of the switch (FIGURE 5) rather than at the upper righthand corner, it is only necessary to remove the bottom cover 13 and pull out and rotate the first part 17 of the cam mechanism 16 substantially ninety degrees so that the raised wall portions 34 interfit with the alternate slots 27 and 28. The bottom cover is then re-positioned and fastened in place. The operation of the switch is the same as described hereinabove, except now the latch release channel 101 is actuated to the second position by a counter clockwise rotation of the cam 20. It will be seen that this permits greater latitude in selecting the operational positions of the switch. The operating lever may also be adjusted relative to the shaft 21 by means of the clamping screw 43.

The blade type contacts on both the movable and fixed contacts permit the entire switch to be shock proof or jar proof so that it will Withstand stresses in all directions yet the contacts will remain established in the position to which they have been actuated. Also, the blades 85 of the

movable contacts

83 and 84 are urged by the springs 86 so that these movable contacts 83 and 84- make a sliding or wiping action with the fixed

contacts

65 and 66 to assure continuously clean contacts for sure electrical switching. As the

movable contacts

83 and 84 slide onto a pair of the fixed contacts, the movable contacts are forced apart slightly to compress the springs 86 to thus assure a positive contact pressure. Also, since the

movable blade contacts

83 and 84 are urged together by the springs 86 in a direction generally perpendicular to the direction of travel of the contact carrier 81, this means that the

movable contacts

83 and 84 move the same distance as the contact carrier 81 so that provision for overtravel of the contact carrier 81 relative to the

movable contacts

83 and 84 is not necessary.

The FIGURES 7-9 show a modification of the invention and show only partial views of the switch 10 wherein components are changed. FIGURES 7 and 8 are partial views similar to FIGURES 5 and 6 showing the latching mechanism, and FIGURES 9 and 10 are partial views of the fixed terminals and contact carrier similar to the view of FIGURE 3, but with the upper part of the terminal block removed.

In FIGURES 9 and 10 the fixed terminals 62 have connected thereto a first pair of fixed contacts 140 of the butt- 5 type and the second pair of terminals 63 have connected thereto a second pair of fixed butt-type contacts 141. A modified contact carrier 81A is provided which carries first and second

movable contacts

142 and 143, respectively. These

contacts

142 and 143 abut shoulders 144 in the contact carrier 81 and are urged thereagainst by a compression spring 145.

FIGURES 7 and 8 show the latching mechanism including the same latch plate 111 pivotally mounting first and second pairs of latch levers 151 and 152, respectively. The unlatching stud 109 engages actuating surfaces 126 on these levers, the same as in FIGURES l6=. Each latch lever has inboard and outboard shoulders 153 and 154-, respectively, for engagement with the

legs

93 and 94 of the same latchable channel member 90. A rotatable cam A has a small radius portion 23 and a large radius portion '24 plus an intermediate radius portion 156. This cam 20A again cooperates with the cam follower roller 108. In this embodiment the torsion spring 36 shown in FIGURE 1 would be mounted to urge the cam 20A so that the intermediate radius portion 156 engaged the roller 108. This establishes the latch release channel 101 in an intermediate position and; hence, the unlatching stud 109 is in an intermediate position as shown in FIGURE 7.

Operation The latch release channel 101 is adapted to have the intermediate position as well as the first and second positions as in the embodiment of FIGURES 16. The intermediate position is as shown in FIGURES 7 and 9 and the second position is to the left as shown in FIGURES 8 and 10. The first position would be similar to that shown in FIGURES 1 and 5, whereat the movable contacts 143 would be to the right to engage the fixed contacts 141. With the switch in the position shown in FIGURES 7 and 9; namely, the intermediate position, the latch levers 151 and 152 are positioned so that the outboard shoulders 154- are adjacent and ready to engage the leg members 03 and 94- therefore this holds the latch able channel member 90 in an intermediate position to also hold the contact carrier 81A in the intermediate position; hence,

movable contacts

142 and 143 are out of engagement with all fixed contacts. If the cam member 20A is rotated clockwise, as shown in the transition from FIGURE 7 to 8, this urges the cam follower roller 108 to the left and hence, the unlatching stud 109 is moved to the left. First this compresses the lug spring 105 as seen in FIGURE 1 to urge the latchable channel member 90 to the left, but such movement is prevented because the outboard shoulders 154 of the latch levers 151 engage the leg members 93. Upon suificient movement, the unlatching stud 10% engages the actuating surfaces 126 to move outwardly the latch levers 151 and unlatch the channel member 90. The stored energy in the lug spring 105 is released to quickly move the contact carrier 81A and to move the movable contacts 142 into engagement with the fixed contacts 140. The spring 125 urges the latch levers 152 inwardly so that the inboard shoulders 153 are adjacent the leg members 94. Consequently, upon return movement of the unlatching stud 109 to the right,

5 such as upon the occurrence of counterclockwise rotation of the cam 20A from the position shown in FIGURE 8, the latchable channel member 90 is prevented from movement to the right because the inboard shoulders 153 engage the leg members 94. Thus, energy is stored in,

the lug spring 105 until the unlatching stud 109 has separated the latch levers 152 sufliciently that the leg members 94 slide off the inboard shoulders 153. This then restores the switch to the condition shown in FIGURES 7 and 9 which means that the movable contacts 142 have broken engagement with the fixed contacts 140. If the cam member 20A is rotated counterclockwise from the position shown in FIGURE 7, then the return spring 107, FIGURE l, urges the cam follower roller 103 and unlatching stud 109 to the right from the position shown in FIGURE 7 and this causes a switch actuating movement similar to that described above, wherein the outboard shoulders 154 of the levers 152 are released from the leg members 94; hence, the movable contacts 143 engage the fixed contacts 141 with a snap action.

It will be seen that the modification of FIGURES 7-9 provides a switch which has not only first and second alternative switch conditions, but also an intermediate or neutral ofi condition wherein no fixed conditions, but also an intermediate or neutral oh condition wherein no fixed contacts are closed. Thus by changing the type of contacts from blade type to butt type, changing the latch levers to ones with two shoulders and providing an intermediate radius portion on the cam member 20A, one is able to achieve greater flexibility in the switch 10 by providing a different form of switching function. It will be noted that the butt-

type contacts

142 and 143 may be used on the switch construction of FIGURES 1-6 if desired, and also two or

more contact carriers

81 or 81A may be actuated by the latchable channel member 90 if multiple switching functions are desired.

It will thus be seen that a snap action switch has been provided wherein the quick movement of a movable switch contact relative to a fixed contact is eitected by building up a force tending to move the movable contact while latching this contact from movement. After a predetermined force has been built up, the movable contact is unlatched and the force which is built up can be effectively used at once to bring about a quick action. This reduces sparking between the contacts and resultant burning and pitting of the same. It necesarily follows that the life of the contacts is greatly increased. The action of the springs 86 provides a definite contact pressure between the switch contacts giving a positive electrical connection. The use of the upper and lower compartments and '19 permits the switch 10 to be mounted where desired, and then the external wiring connected to the switch by removing the top cover 12, and without need to remove the switch to connect the wiring. The construction of the cam mechanism which includes the first and second par-

ts

17 and 18 offers a switch construction which can be easily adjusted to provide either right or left-hand operation of the switch.

The cam memebr 20 may also be of any desired shape, and other than that shown in FIGURES 5 to 8. Such changes in shape of the cam member 20- can provide for dilterent operating points each of which, however, will be accurately predetermined so that the switch 10 is precisely operated in the same point in travel of the moving mechanism 46 for repetitive movement of the mechanism 46. For example, the cam mechanism 20 may have plural lobes :for alternative actuation of the switch contacts during continuous rotary movement of the cam mechanism 20. For such continuous rotary movement the torsion spring 36 would be removed.

Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

What is claimed is:

1. A snap action switch including, in combination, a housing having top and bottom compartments, 3. terminal block in said top compartment, fixed contacts on said terminal block, movable contacts located in said top compartment and engageable with said fixed contacts, a latchable channel in said bottom compartment movable between first and second positions, first and second leg members extending generally laterally from said latchable channel, means connecting together said movable contacts and said latchable channel for corresponding movement, a latch release channel located adjacent said leg members for movement between first and second positions, spring means in said latch release channel and acting on said first leg member and urging said latchable channel toward said second position on movement of said latch release channel toward said second position and acting on said second leg member and urging said latchable channel toward said first position on movement of said latch release channel toward said first position, unlatching stud means carried by said latch release channel, first and second latch levers pivotally connected relative to said housing, each said latch lever having a latch shoulder with which a leg member is engageable and having an actuating surface engageable by said unlatching stud means to move the same to an unlatched condition, each said latch lever being a bell crank lever having said latch shoulder and said actuating surface on difierent legs and with the leverage ratio establishing a ratio of movement of said latch shoulder relative to the movement of said actuating surface of greater than unity, and second spring means urging said latch levers toward a latched condition, said latch shoulder of said first latch lever engaging said first leg member in the first position of said latch release channel to prevent movement of said latchable channel toward said second position until said unlatching stud means unlatches said first latch lever, and said latch shoulder of said second lever engaging said second leg member in the second position of said latch release channel to prevent movement of said latchable channel toward said first position until said unlatching stud means unlatches said second latch lever.

2. A snap action switch including, in combination, a housing having top and bottom compartments, a terminal block in said top compartment, fixed contacts on said terminal block, a contact carrier movable between first and second positions in said top compartment, movable contacts carried by said contact carrier and engageable with said fixed contacts, a latch plate fixed in said bottom compartment, a latchable channel in said bottom compartment adjacent said latch plate and movable between first and second positions, a back member on said latchable channel and having first and second leg members extending generally laterally therefrom, means connecting said contact carrier and said latchable channel together for corresponding movement, a latch release channel located adjacent said leg members for movement between first and second positions and relative to said leg members, first and second lugs carried by said latch release channel, spring means acting on said first and second lugs, said first lug engaging said first leg member and urging said latchable channel toward said second position on movement of said latch release channel toward said second position, said second lug engaging said second leg member and urging said latchable channel toward said first position on movement of said latch release channel toward said first position, return spring means urging said latch release channel to said first position, an unlatching stud carried by said latch release channel, first and second latch levers pivotally connected to said latch plate, each said latch lever having a latch shoulder with which a leg member is engageable and having an actuating surface engageable by said unlatching stud to move the same to an unlatched condition, each said latch lever being a bell crank lever having said latch shoulder and said actuating surface on different legs and with the leverage ratio establishing a ratio of movement of said latch shoulder relative to the movement of said actuating surface of greater than unity, and spring means urging said latch levers toward a latched condition, said latch shoulder of said first latch lever engaging said first leg member in the first position of said latch release channel to prevent movement of said latchable channel toward said second position until said unlatching stud unlatches said first latch lever, and said latch shoulder of said second latch lever engaging said second leg member in the second position of said latch release channel to prevent movement of said latchable channel toward said first position until said unlatching stud unlatches said second latch lever.

3. A snap action switch including, in combination, a housing having top and bottom compartments, a cam mechanism rotatively mounted in said housing, an operating lever operatively connected to partially rotate said cam mechanism and residing outside said housing, a spring member urging said cam mechanism to a first position, a terminal block in said top compartment, terminals on said terminal block for connection with external conductors, a fixed contact on each said terminal, a contact carrier movable between first and second positions and located in said top compartment, movable contacts carried by said contact carrier and engageable with said fixed contacts, a latch plate fixed in said bottom compartment, a latchable channel in said bottom compartment adjacent said latch plate and movable between first and second positions, a back member on said latchable channel and having first and second leg members extending generally laterally therefrom, means connecting said contact carrier and said latchable channel together for corresponding movement, a latch release channel located adjacent said leg members for movement between first and second positions and relative to said leg members, first and second lugs carried by said latch release channel, a spring between said first and second lugs urging them apart, said first lug engaging said first leg member and urging said latchable channel toward said second position on movement of said latch release channel toward said second position, said second lug engaging said second leg member and urging said latchable channel toward said first position on movement of said latch release channel toward said first position, return spring means urging said latch release channel toward said first position, an unlatching stud carried by said latch release channel, a cam follower carried by said latch release channel and residing adjacent and engageable with said cam mechanism, first and second latch levers pivotally connected to said latch plate, each said latch lever having a latch shoulder with which a leg member is engageable and having an actuating surface engageable by said unlatching stud to move the same to an unlatched condition, spring means urging said latch levers toward a latched condition, said latch shoulder of said first latch lever engaging said first leg member in the first position of said latch release channel to prevent movement of said latchable channel toward said second position until said unlatching stud unlatches said first latch lever, and said latch shoulder of said second latch lever engaging said second leg member in the second position of said latch release channel to prevent movement of said latchable channel toward said first position until said unlatching stud unlatches said second latch lever.

4. A snap action switch including, in combination, a housing having top and botom compartments closed by top and bottom covers, respectively, an intermediate wall in said housing forming a bottom of each said compartment, a cam mechanism rotatively mounted in said housing, an operating lever operatively connected to partially rotate said cam mechanism and residing outside said housing, means permitting angular adjustment of said cam mechanism, a spring member urging said cam mechanism to a first position, a terminal block in said top compartment, terminals on said terminal block for connection with external conductors, a fixed contact on each said terminal, a contact carrier movable between first and second positions and located in said top compartment, movable contacts carried by said contact carrier and engageable with said fixed contacts, a latch plate fixed in said bottom compartment spaced from the bottom thereof, a latchable channel supported by said latch plate and disposed between said latch plate and said intermediate wall and movable between first and second posi tions, a back member on said latchable channel andhaving first and second leg members extending generally laterally therefrom, means connecting said contact carrier and said latchable channel together through a slot in said said first position on movement of said latch releasew channel toward said first position, return spring means urging said latch release channel toward said first position, an unlatching stud carried by said latch release channel, a cam follower carried by said latch release channel and residing adjacent and engageable with said cam mechanism, first and second latch levers pivotally connected to said latch plate, each said latch lever having a latch shoulder with which a leg member is engageable and having an actuating surface engageable by said unlatching stud to move the same to an unlatched condition, spring means urging said latch levers to a latched condition, said latch shoulder of said first latch lever engaging said first leg member in the first position of said latch release channel to prevent movement of said latchable channel toward said second position until said unlatching stud unlatches said first latch lever, and said latch shoulder of said second latch lever engaging said second leg member in the second position of said latch release channel to prevent movement of said latchable channel toward said first position until said unlatching stud unlatches said second latch lever.

5. A snap action switch including, in combination, a housing having top and bottom compartments closed by top and bottom covers, respectively, an intermediate wall in said housing forming a bottom of each said compartment, a cam mechanism rotatively mounted in one end of said housing, an operating lever operatively connected to partially rotate said cam mechanism and residing outside said housing, means permitting angular adjustment: of said cam mechanism, said operating lever having an engagement roller on an end portion thereof to transmit movement from a mechanism to move said cam mech anism from a first to a second position, a spring member urging said cam mechanism to a first position, a terminal block fastened in said top compartment, terminals on said terminal block for connection with external con-- ductors and accessible with said top cover removed, a

blade type fixed contact on each said terminal, an electrically insulated contact carrier movable between first and second positions and located in said top compartment between said terminal block and said intermediate wall,

movable blade type contacts carried by said contact carrier and enageable with said fixed contacts, a latch plate fixed in said bottom compartment spaced from the bottom thereof, a latchable channel supported by said latch plate and disposed between said latch plate and said intermediate wall and movable between first and second positions, a back member on said latchable channel and having first and second pairs of leg members extending generally laterally therefrom toward said bottom cover, a longitudinal slot in said intermediate wall, means connecting said contact carrier and said latchable channel to-- gether through said slot in said intermediate wall, a latch release channel located between said leg members for movement between first and second positions and relative to said leg members, first and second lugs carried by said latch release channel, a spring between said first and second lugs urging them apart, said first lug engaging said first pair of leg members and urging said latchable channel to said second position on movement of said latch release channel toward said second position, said second lug engaging said second pair of leg members and urging said latchable channel to said first position on movement of said latch release channel toward said first position, return spring means urging said latch release channel to said first position, an unlatching stud carried by said latch release channel, a cam follower carried by one end of said latch release channel and residing adjacent and engageable with said cam mechanism, said latch plate having slots for the reception of said leg members of said latchable channel and having an opening for the reception of said unlatching stud, first and second pairs of latch levers pivotally connected to said latch plate, each said latch lever having a latch shoulder with which a leg member is engageable and having an actuating surface engageable by said unlatching stud to move the same to an unlatched condition, spring means urging said latch levers to a latched condition, said latch shoulders of said first pair of latch levers engaging said first leg members in the first position of said latch release channel to prevent movement of said latchable channel to said second position until said unlatching stud unlatches said first latch levers, and said latch shoulders of said second pair of latch levers engaging said second leg members in the second position of said latch release cha. nel to prevent movement of said latchable channel to said first position until said unlatching stud unlatches said second latch levers.

6. A snap action switch including, in combination, a housing, relatively fixed contact means in said housing, movable contact means engageable with said fixed contact means, a latchable member in said housing movable between first and second positions, a leg member extending generally laterally from said latchable member, means connecting together said movable contact means and said latchable member for corresponding movement, a latch release channel located adjacent said leg member for movement between first and second positions, spring means in said latch release channel and acting on said leg member and urging said latchable member toward said second position on movement of said latch release channel toward said second position, unlatching stud means carried by said latch release channel, latch lever means pivotally connected relative to said housing and having a-latch shoulder with which said leg member is engageable and having an actuating surface engageable by said unlatching stud means to move the same to an unlatched condition, said latch lever means including a bell crank lever having said latch shoulder on one leg and having said actuating surface on the other leg and with the relative lengths of said legs establishing a ratio of movement of said latch shoulder relative to the movement of said actuating surface of greater than one to one, and second spring means urging said latch lever means toward a latched condition, said latch shoulder of said latch lever means engaging said leg member in the first position of said latch release channel to prevent movement of said latchable member toward said second position until said unlatching stud means unlatches said latch lever means.

7. A snap action switch including, in combination, a housing, relatively fixed contacts in said housing, movable contacts engageable with said fixed contacts, a latchable channel in said housing movable between first and second positions, first and second leg members extending generally laterally from said latchable channel, means connecting together said movable contacts and said latchable channel for corresponding movement, a latch release channel located adjacent said leg members for movement between first and second positions, spring means in said latch release channel and acting on .said first leg member and urging said latchable channel toward said second position on movementofsaid latch release channel toward saidsecond position and acting on said second leg member and urging said latchable channel toward said first position on movement of said latch release channel toward said first position, unlatching stud means carried by said latch release channel, first and second latch levers pivotally connected relative to said housing, each said latch lever having a latch shoulder with which a leg member is engageable and having an actuating surface engageable by said unlatching stud means to move the same to an unlatched condition, each said latch lever being a bell crank lever having said latch shoulder and said actuating surface on difierent legs and with. the leverage ratio establishing a ratio of movement of said latch shoulder relative to the movement of said actuating surface of greater than unity, and second spring means urging said latch levers toward a latched condition, said latch shoulder of said first latch lever engaging said first leg member in the first position of said latch release channel to prevent movement of said latchable channel toward said second position until said unlatching stud means unlatches said first latch lever, and

said latch shoulder of said second latch lever engaging said second leg member in the second position of said latch release channel to prevent movement of said latchable channel toward said first position until said unlatching stud means unlatches said second latch lever.

8. A snap action switch including, in combination, a housing, first contact means in said housing, movable contact means engageable with said first contact means, a latchable member in said housing movable between first and second positions, means connecting together said movable contact means and said latchable member for corresponding movement, a latch release channel movable between first and second positions, spring means urging said latchable member toward said second position on movement of said latch release channel toward said second position, unlatching stud means carried by said latch release channel, latch lever means pivotally connected relative to said housing and having a latch shoulder with which said latchable member is engageable and having an actuating surface engageable by said unlatching stud means to move the same to an unlatched condition, said latch lever means including a bell crank lever having said latch shoulder on one leg and having said actuating surface on the other leg and with the relative lengths of said legs establishing a ratio of movement of said latch shoulder relative to the movement of said actuating surface of greater than unity, and said spring means urging said latch lever means toward a latched condition, said latch shoulder of said latch lever means engaging said latchable member in the first position of said latch release channel to prevent movement of said latchable member toward said second position until said unlatching stud means unlatches said latch lever means.

References Cited in the file of this patent UNITED STATES PATENTS