US3424882A - Switching device - Google Patents

Description

.im 2s, 1969 K. .1. sToKEs SWITCHING DEVICE Sheet Filed April 14 1967 A TTU/may Jm 2s, 1969 I K, J, STOKES 3,424,882

swITcHING DEVICE Filed April 14, 1967 sheet Z of 2.

INVENTOR.

KEA/,vf rf/ L/ Sra/(fs WM l? s/U7 4 r Tam/EY United States Patent O 3 Claims ABSTRAQT F THE DISCLOSURE A switching device includes a frame member which supports a pivotally-mounted handle and a pivotallymounted contact arm. The curved edge of the frame provides an arcuate cam surface for a roller. The contact arm includes an elongated slot, providing upper and lower cam surfaces, in which the roller is disposed. The handle is connected to the roller by a tension type operating spring and operation thereof causes the roller to be moved along the cam track with an overcenter or snap action. The action of the roller on the cam surfaces is such as to wedge between the contact arm and the frame to positively lock the contact in closed position and prevent blowing open of the contacts.

Background of invention This invention relates to a switching device, and particularly to a snap-acting switching device including a movable contact carried by a contact arm and means for compensating for contact erosion to maintain adequate contact pressure.

Snap-acting switching devices, wherein a pivotallymounted contact arm is moved rapidly between open and closed circuit positions, are well known in the art. Switching devices of the prior art, such as that described in U.S. Patent No. 3,134,880, Murphy, and assigned to the same assignee as the present invention, have utilized a two-toggle linkage arrangement to effect the snap action of the switch. In such devices an actuating handle is connected by means of a tension type operating spring to the pivotal connection of two-toggle members. An end of one toggle member is pivotally supported on a suitable frame. The end of the other toggle operatively engages a central section of a pivotally-mounted contact arm carrying a movable contact. The toggle linkage is adapted to be moved between collapsed and straightened positions, with the aforementioned snap action, by action of the operating spring when the handle member is moved. Such linkage movement acts, thereby, to move the contact arm between open and closed positions.

In another recent Patent, 3,171,929, Iencks et al., assigned to the same assignee as the present invention, a circuit breaker is provided with an improved releasable cam type switching mechanism. The circuit breaker includes a pivotally-supported movable contact member and a pivotally-supported, normally latched, releasable support member. The releasable support member is provided With an arcuate cam surface so arranged and disposed that a cam follower roller member, which is operated by a handle through a pair of tension-type springs, moves from one point to another on the cam surface of the releasable member with an overcenter or snap action. The movable contact member is provided with a convex slot, establishing upper and lower cam surfaces, whereby the action of the cam follower roller as it moves along the cam surface of the releasable member is transmitted to the movable contact member to move it between open and closed circuit positions.

Heretofore, the switching mechanism shown in the Jencks patent has not been adapted to a switching device ICC per se because of the complexity of parts and their interrelation in a circuit breaker and the expense that would be involved in producing such a device. This is because the individual parts, while being operatively connected, are generally individually supported and the whole assembly is so large that adaptation for a simple switching device has not been feasible. Additionally, the switching mechanism shown in the Jencks patent is subject to decrease of contact pressure when erosion of the contacts occurs from extended use. As a result, a compression spring is required to maintain suicient pressure to keep the contacts in a closed position. Also, the spring does not completely prevent against contact bounce upon closing, which could result in undesirable arcing between the contacts, or blowing open of contacts on high currents, with subsequent welding of the contacts when they come together again. Y

It is therefore, an object of this invention to provide a simplified snap-acting switching device including a cam type switchin g mechanism.

It is another object of this invention to provide a snapacting switching device utilizing a cam type switching mechanism which compensates for contact erosion to maintain adequate Contact pressure.

It is a further object of this invention to provide a snapacting switching device utilizing a cam type switching mechanism which effectively prevents contact bounce when the switch is closed and blowing open on shortcircuit.

It is a still further object of this invention to provide a snap-acting switching device utilizing a cam type switching mechanism which is more compact and less expensive than comparable prior art devices.

In accordance with my invention in one form thereof, I provide a switching device including a frame member which supports a pivotally-mounted handle and a pivotally-mounted contact arm carrying a movable contact. The frame includes a curved lower edge which provides an arcuate cam surface for a cam follower roller member. The operating handle is operatively connected to the cam follower roller through a tension-type operating spring so that the roller may be caused to ride along the cam track with a snap action in response to movement of the handle. The pivotally-mounted contact arm includes an elongated slot, providing upper and lower cam surfaces, in which the cam follower roller rides so as to move the contact arm with the aforementioned snap action between open and closed circuit positions. The action of the roller on the cam surfaces is such as to wedge between the contact arm and the frame to positively lock the contact in closed position and prevent blowing open of the contacts.

Description of drawings Other objects and advantages of my invention will better 'be understood by reference to the following detailed description when taken in connection with the accompanying drawings in which:

FIGURE 1 is a yfront elevation view of the `switch mechanism of the present invention in open position;

FIGURE 2 is a front elevation view of the switch mechanism in the closed position;

FIGURE 3 is a side elevation view of the switch mechamsm;

FIGURE 4 is an exploded perspective view of the switch mechanism of FIGURE 1;

FIGURE 5 is a View of another embodiment of the switch mechanism in the open position;

FIGURE 6 is a view of the switch mechanism of FIG- URE 5 in the closed position, and

FIGURE 7 is an exploded perspective View 0f the switch mechanism of FIGURE 5.

Detailed description FIGURE 1 shows the switching device 1 of the present invention. The switching device 1 includes a cam-type switching mechanism 2 supported on a generally rectangularly-shaped support plate or frame member 3. The frame 3 supports a contact arm 5 which is pivotally mounted thereon lby means of a pivot pin 7 at a lower corner portion of the support frame 3. The support frame 3 includes a lower arcuate cam surface or cam track 9. A cam follower is provided in the form of a pin or roller 11 which rides along the cam surface 9. The roller 11 is further disposed in an elongated slot 13 in the contact arm and is adapted to act upon upper and lower cam surfaces 15 and 17, respectively, of the slot 13 as it rides along the cam track 9. A handle member 19 is preferably pivotally mounted on the frame 3 by means of a pivot pin 21. An anchor pin 23 is rigidly positioned on the handle member 19 as a central portion thereof. A pair of tension type overcenter springs 25, are connected between the anchor pin 23 on the handle member 19 and the cam follower roller 11, one on each side of the frame member 3. It is to be understood that one overcenter spring on one side of a frame member is also contemplated 'by the present invention but `better `balance may Ibe obtained with two springs. Roller movement along the cam track 9 causes the contact arm 5 to rotate through an arcuate path so that a contact 27 carried by the contact arm 5 moves into and out of engagement with a stationary contact 29. The contact 29 may -be carried, if desired, by the support frame 3.

As shown in FIGURE 3, the handle 19 may comprise an elongated U-shaped member 20 having side portions 20A disposed on opposite sides of the frame 3 and connected by the pins 21 and 23, respectively. Similarly, the contact arm 5 comprises an elongated generally U-shaped member having side portions 6 disposed on opposite sides of the frame 3 and including the elongated slots 13 therein. The members 6 are integrally connected at the free end of the contact arm 5 and lform a support surface for the contact 27. The members 6 are connected `by the pivot pin 7 at the xed end of the contact arm 5. While the present switching device has 4been found to operate quite effectively with such a :balanced arrangement, the invention also contemplates the provision of a switch mechanism wherein a handle member and contact arm are provided on only one side of the frame member.

As seen in FIGURE 1, the switching mechanism 2 is shown in the fopen-circuit position. The handle member 19 has been rotated to its furthermost clockwise position. The overcenter springs 25 act upon the cam follower roller 11 so as to move it to the right along the cam track 9, thereby causing the roller 11 to move to near one end of the elongated slot 13 in contact arm 5 and exert an upward force ion cam surface 15 so as to maintain the contacts 27 and 29 separated.

Conversely, when it is desired to place the switching mechanism 2 in a closed-circuit position, the handle member 19 is rotated to its furthermost counterclockwise position. Movement lof the handle 19 to this position causes the springs 25 to urge the cam follower roller 11 to the left, as viewed in FIGURE 2, near the other end of the slot 13 thereby acting on cam surface 17 to urge the contact arm 5 and associated contact 27 to a closed circuit position.

The movement of the handle member 19 from the open to the closed circuit position does not result in instantaneous movement of the roller 11. Instead, the roller 11 moves along the cam track 9 only when the action line of the spring 25 with respect to the cam surface 9 is such-as to cause movement. This occurs when the line of action of the spring reaches a position wherein it coincides with a radius line of the arc defining the arcuate cam surface at the point t0n which the cam follower roller 11 rests (see dotted line in FIG. l).

Movement of the handle 19 and the spring 25 beyond this position results in movement of the roller 11 quickly along the cam surface 9, with what can be characterized as an overcenter or a snap action, until the desired closed circuit position on the cam track 9 is reached. Since the contact arm 5 moves in response to the movement of the roller 11, the movement of the contact arm 11 and its associated contact 27 is also characterized by this snap action.

In switch mechanisms such as these, a certain amount of erosion of the contacts can he expected. Such contact erosion usually results in a decrease in contact pressure. However, with the switching device of the present invention, as the contacts 27 and 29 erode, the roller 11 will move along the cam track 9 further to the left, and further to the left in slot 13 of the contact arm 5, the slot being sufficiently long, so as to increase the pressure on the lower cam surface 17 of the contact arm 5 to compensate for the difference in gap. This action takes place because, as may be clearly seen from FIG. 2 of the drawings, the lower cam surface 17 of the contact arm 5 and the cam surface 9 of the frame 3 extend in converging relation in the direction of impending movement of the cam follower 11 at the points thereof engaged by the cam follower 11 when the contact arm 5 is in its closed circuit position as shown. The roller 11 also serves to wedge the contact arm 5 into the closed position through co-operation with the lower cam surface 17 of the contact arm 5 and the cam surface 9 of the frame 3 to provide a locking action which prevents the contacts 27 and 29 from being blown apart. This locking action alleviates the necessity for a contact pressure spring to provide uniform contact pressure. The locking action of the pin also prevents a certain amount of contact bounce which could result in unnecessary arcng between the contacts.

FIGURES 5-7 show a modification of the switching device of the present invention. The Switching device 45 includes a support frame comprising a plate member 51 which supports the switching mechanism 47. A handle member 53 is pivotally mounted by means of a pivot pin 55 at a central portion of the plate 51. A contact arm 57 including a contact 58 is pivotally mounted below the handle 53 by means of a pivot pin 59. The frame 51 includes a lower arcuate cam surface 62. A cam follower roller 63 is provided to ride along the cam surface 62. An elongated slot 65, providing upper and lower cam surfaces 67 and 69, respectively, is provided in the contact arm 57. Overcenter springs 71 are provided, connected between the cam follower roller 63 and a central portion of the handle member 53 on each side of the frame member 51. The springs 71 are connected to the handle 53 by means of a suitable arrangement such as pin 73.

The switching device 45 is shown in the open-circuit position in FIGURE 5 and in the closed circuit arrangement in FIGURE 6. The operation of the switch mechanism 47 is the same as that of the previously described switch mechanism, in that the roller 63 acts upon the upper and lower cam surfaces 67 and 69 of the contact arm slot 65 as it rides along the cam surface 62 of the frame 51 so as to move the contact 58 carried by contact arm 57 into and out of engagement with a stationary contact 75 which is carried by the support frame 51. However, in this embodiment, the Contact arm 57 is rotated upwardly into engagement with the stationary contact 75. In the closed position, the roller 63 moves further to the left upon any contact erosion to maintain adequate contact pressure. In accordance with one aspect of the invention in this form, the handle member 53 is provided with a projection 54 adjacent the pivot 55. When the handle member is moved from on to off position, if the contacts should stick or weld, the projection 54 engages the contact arm 57 and provides a means for forcibily separating the contacts and breaking such weld.

I have thus described a switching device including a frame member which supports a switching mechanism ina cluding a pivotally-mounted Contact arm and a pivotallymounted handle member. The frame includes an arcuate surface which provides a cam track for a cam follower roller. The handle operatively engages the roller through a tension type operating spring. Movement of the handle results in movement of the roller along the cam track with a snap action. The roller, which also rides in an elongated slot in the Contact arm, moves the contact arm with the aforementioned snap action between open and closed circuit positions.

While the present invention has ben described with specificity, it is the aim of the appended claims to include all such modifications and variations as come within the true spirit and scope of the foregoing disclosure.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A switching device comprising:

(a) a stationary contact;

(b) a movable contact;

(o) a frame having an arcuate cam surface;

(d) a contact arm having said movable contact mounted at one end thereof and pivotally supported at the other end thereof on said frame for movement to move said movable contact into and out of engagement with said stationary contact;

(e) said contact arm having an elongated slot therein establishing upper and lower cam surfaces;

(f) an actuating handle movable between open and closed positions for operating said contact arm between open and closed circuit positions and pivotally supported on said frame member;

(g) a cam follower riding on said cam surface of said frame and disposed in said elongated slot of said contact arm; and

(h) at least one tension type operating spring connecting said handle and said cam follower, motion of said handle from said open toward said closed position causin-g said cam follower to ride along said frame cam surface with a snap action and simultaneously to act upon said lower cam Surface of said contact arm to cause said contact arm to rotate from said open toward said closed circuit position with a snap action, said lower cam surface of said contact arm and said cam surface of said frame extending in converging relation at the points thereof engaged by said cam follower when said contact arm is in said closed circuit position, said cam follower acting between said frame cam surface and said lower cam surface of said contact arm to lock said contact arm in said closed circuit position with a wedging action.

2. A switching device comprising:

(a) a stationary contact;

(b) a movable contact;

(c) a frame having an arcuate cam surface;

(d) a contact arm having said movable contact mounted at one end thereof and pivotally supported at the other end thereof on said frame for movement to move said movable contact into and out of engagement with said stationary contact;

(e) said contact arm having an elongated slot therein establishing upper and lower cam surfaces;

(f) an actuating handle for operating said contact arm between open and closed circuit positions and pivotally supported on said frame member;

(g) a cam follower riding on said cam surface of said frame and disposed in said elongated slot of said contact arm;

(h) at least one tension type operating spring connecting said handle and said cam follower, whereby motion of said handle causes said cam follower to ride along said frame cam surface with a snap -action and simultaneously to act upon said cam surfaces of said contact arm to cause said contact arm to rotate between said open and closed circuit positions with a snap action, said cam follower acting between said frame and said contact `arm to lock said Contact arm in said closed lcircuit position; and

(i) said contact arm comprising a channel-shaped member including a pair of side portions disposed on either side of said frame and including elongated slots therein, said contact arm carrying said movable contact at one end thereof and being pivotally supported at the other end thereof on said frame for movement to move said movable Contact into and out of engagement with said stationary contact.

3. The switching device as recited in claim 2 wherein said handle comprises a channel-shaped member including a pair of side portions disposed on opposite sides of said frame, said handle being pivotally supported on said frame at one end thereof.

References Cited UNITED STATES PATENTS 3,171,929 3/1965 Jencks et al.

FOREIGN PATENTS 717,662 2/ 1942 Germany. 772,651 8/1934 France.

ROBERT K. SCHAEFER, Prmwry Examiner.

D. SMITH, JR., Assistant Examiner.

U.S. Cl. X.R.

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