US1986222A - Electric switch - Google Patents

Description

.1. SACHS ELECTRIC SWITCH Jan. 1, 1935.

Filed July 30, 1932 fn enzi-ar 705,530]? 555/75 Patented Jan. 1, 1935 UNITED STATES PATENT OFFICE '5 Claims.

In electric switches and other electric circuit making-and-breaking devices difliculties have long been experienced due to the adhering or welding together of the relatively movable contacts under the action of heat produced by arcing or otherwise. This adhering or welding has sometimes prevented, or at least retarded, the separation of the contacts when breaking of the circuit became desirable or necessary.

In order to avoid the aforesaid tendency of the contacts to adhere to each other or to weld together it has heretofore been proposed and practiced to construct one or both of the contacts of specially constituted materials or compositions adapted to prevent or resist the said tendency. Contacts formed of some of these special materials 'or compositions have been quite satisfactory as to performance, but the cost of the contacts has been abnormally large and for some classes of devices has been practically prohibitive.

The principal object of the present invention is to provide a switch or other circuit makingand-breaking device adapted to effectively resist any tendency toward adhering or welding of the contacts, but nevertheless capable of being manufactured and maintained in use at'a low cost. 3 In accordance with the invention I utilize the well known properties of graphite for the prevention of welding and I ,also utilize the graphite for other purposes, and I accomplish these results at a minimum cost by locating the graphite in novel relationship to the metallic parts .of the device without however using any special or peculiar composition or mixture.

I vIn accordance with the invention at least one of the switch contacts has a graphite portion separate from the metallic portion thereof, and this graphite portion is so arranged that it not only serves to prevent welding, but also serves to effect lubrication of the contacts and constitutes an arcing contact to minimize the effects of arcing when the circuit is broken.

It will be understood that, while my invention is applicable to circuit making-and-breaking devices generally, it is particularly useful in conjunction with automatic circuit breakers. A manually operable switch not provided with automatic means for separating the contacts under overload conditions is ordinarily associated with 50 a fuse, the result being that in the event of a.

short circuit or other extreme overload condition, it is the fuse and not the switch which serves to break the circuit under excess current conditions, and the blowing of the fuse prevents the reestablishment or attempted reestablishment of the circuit under such conditions. With an automatic circuit breaker, however, the circuit must be broken at the contacts thereof even under the mostextreme conditions and the contacts may be momentarily reengaged with the overload or short circuit conditions still prevailing. For these reasons it is necessary, or at least highly-desirable, to provide automatic cir- ,-.cuit breakers with contacts especially adapted to resist the melting and welding tendencies resulting from overload and short circuit conditions. The invention will, therefore, be illustrated and described in conjunction with an automatic circuit breaker, but it is to be understood that it is not necessarily so limited.

In the accompanying drawing I have shown. two principal embodiments of the invention insofar as the contacts are concerned, together with certain variations thereof, and I have also shown an automatic circuit breaker mechanism for controlling the relative movement of the contacts. It will be understood that the drawing is intended for illustrative purposes only and that there may be ,wide variation from the structures shown, particularly as concerns the operating or controlling mechanism. The drawing is not to be construed as definingor limiting the scope of the invention, the claims forming a part of this specification being relied upon for that purpose.

Of the drawing:

Fig. 1 is a side view of a circuit making-andbreaking device incorporatingv the invention, the contacts being shown separated.

Fig. 2 is a view similar to Fig. 1, but showing the parts in the positions which they assume at the first engagement of the switch contacts.

Fig. 3 is a view similar to Fig. 1, but showing the parts in the positions which they assume when the switch contacts are fully engaged.

Fig. 4 is an enlarged fragmentary perspective view showing the switchcontacts in the same relative positions as in Fig. 2.

Figs. 5 and 6 are enlarged longitudinal sectional views showing alternative contact details.

Fig. '7 is a view similar to Fig.4, but showing an alternative embodiment of the invention.

Referring to the drawing, 1 represents as an entirety an approximately stationary electrical contact and 2 represents as an entirety another coacting electrical contact movable into and out of engagement with the said contact 1.

As to the means for supporting the said con tacts and efiecting relative movement between ,them there may be wide variation, but inorder that my invention may be clearly understood I have shown in detail one supporting and controlling means for the contacts which may be used if desired. The construction shown is similar in many respects to that shown and described in detail in my Patent No. 1,812,847 dated June 30, 1931. Reference may be had to the said patent for details of construction not herein fully shown and described.

The approximately stationary contact 1 is connected with an insulating base 3 by means of a resilient conducting strip 4 which is suitably secured to the base and which is electrically connected at 5 with a wire terminal.

The movable contact 2 is carried by a conducting arm or blade 6 which is pivoted at 7 to a conducting supporting bracket 8 secured to the base 3. A spring 9 tends to move the arm in the direction to carry the contact 2 away from engagement with the contact 1.

For manually operating the switch arm 6 and the contact 2 thereon there is provided a handle member 10 pivoted at 11 to a bracket 12 secured to the base 3. A spring 13 tends to move the handle member to its open-circuit position as shown in Fig. 1. Interposed between the handle member 10 and the switch arm 6 are two toggle links 14 and 15. The link 14 is pivoted to the handle member 10 at 16, and the link 15 is pivoted to the switch arm 6 at 1'7, and the two links are pivoted to each other at 18. An extension 19 on the link 15 normally engages the link 14 and normally holds the links in the relative positions shown in Fig. 1, the links ordinarily functioning as a single link to transmit motion from the handle 10 to the switch-arm 6.

When the handle member 10 is moved in the clockwise direction the switch arm 6 is also moved in the clockwise direction, the result being that the contact 2 is brought into initial engagement with the contact 1 as shown in Fig.

2. Continued movement of the handle member 10 to the position shown in Fig. 3 brings the contact 2 into its final position with respect to the contact 1 and the pivotal axis at 16 'is brought below a straight line connecting the axes 11 and 17. The before-mentioned spring 9 is much stronger than the before-mentioned spring 13 and the result is that, with the parts in the relative positions shown in Fig. 3, the force of the spring 9 transmitted through the links 15 and 14 holds the handle member in its upper position and thus holds the contact 2 in engagement with the contact 1. However, the handle member 10 can be manually moved at any time to the open-circuit position as shown in Fig. 1, thus separating the contacts and breaking the circuit.

In order that the circuit may be broken automatically in the event of an overload there is provided a U-shaped bi-metallic strip 20 which is connected in the circuit between the conducting bracket 8 and a lower wire terminal at 21. The bi-metallic strip 20 carries a rod ,22 which extends upward into close proximity to an extension 23 on the link 14. In the event of an overload the bi-metallic strip becomes heated and it is deflected upward carrying the rod 22 with it. The rod 22 engages the extension 23 and moves the pivot 18 sufficiently to break the toggle whereupon the parts, are automatically moved to the position shown in Fig. 1, the swtich arm 6 being moved by the spring 9 and the handle member 10 being moved by the spring 13.

As shown more clearly in Fig. 4 one of the contacts, as for instance the contact 1, in composite and includes a portion 1 consisting of copper or other suitable metal, and a portion 1 comprising graphite. While I have referred to the portion 1 as comprising graphite it will be understood that it may include other substances, it merely being essential that there be suflicient graphite to provide the desired advantageous results as hereinafter set forth. The contact surfaces of these two portions are preferably in register, or substantially in register, with each other. The movable contact 2 is preferably so formed as to have a convex contact surface at 2 providing a transverse line contact with the contact 1.

The means for relatively moving the contacts,

whether constructed in detail as before described or otherwise, is of such construction that it serves to effect the initial circuit-making engagement between the contacts at the portion 2 of the contact 2 and at the said graphite portion 1 of the contact 1 and to then by a relative sliding motion eifect metalr-to-metal engagement between the contacts, that is, between the portions 2 and 1. It will be observed that with the particular construction shown and described the contact surface of the contact 1 is at an acute angle to the path of movement of the contact 2, this path of movement being indicated by a dot-and-dash line in Fig. 1. As already stated the contact 1 is resiliently mounted. As the result of the said resilient mounting and the said acute angle between the contact surface of the contact 1. and the line of movement of the contact 2 there is effected a relative sliding movement, the contact surface 2 first engaging the graphite portion 1 of the contact 1 as shownin Fig. 2 and then sliding into engagement with the metal portion 1 of the said contact as shown in Fig. 3.

As the result of the sliding or wiping action shown and described a very thin film of graphite is formed on the metallic surfaces 2 and 1, this film being formed as the result of adherence of graphite to the surface 2 and its subsequent transfer to the surface 1. The said graphite film serves to lubricate the contacts and effectively resist any tendency that might otherwise exist toward a welding action between the metals forming the said surfaces 2 and 1. By reason of the wiping action described this graphite film is constantly renewed at each action of the switch.

Not only is there provided the described graphite film which prevents any possible welding action, but the graphite body at 1 serves as an auxiliary contact to minimize arcing when the circuit is broken. It will be apparent that when the circuit is about to be broken either manually or automatically, there is a relative sliding motion between the contacts from the position shown in Fig. 3 to the intermediate position shown in Fig. 2. When actual separation begins, any arcing that may occur takes place between the metallic portion 2 and the graphite portion 1*, the said graphite portion effectively resisting any tendency to burn or melt. When the circuit is reestablished the initial engagement is at the graphite portion 1 as already described.

As already suggested the danger of welding or other injury to the contacts is particularly great when an attempt is made to re-close the circuit after an automatic opening thereof and while the overload or short circuit conditions portion 24 still prevail. It will be apparent that in the construction shown the circuit would be first reestablished with the contacts in the relative positions illustrated in 'Fig. 2, the excess current responsive device, such as 20, becoming immediately energized. The automatic re-opening of the circuit would immediately follow and might take place before the fully closed position shown in Fig. 3 was reached, and even if it did not so take place the before-described fi m of carbon between the contact surfaces at 1 and 2 would prevent any welding or melting of the metal of the contacts.

As to the details of the mechanical construction of the contact 1 there may be wide variation, but I have shown the metallic portion of the contact formed with a transverse recess having a dovetail 1 therein, and I have shown the graphite body 1 as shaped to fit the recess and as having a transverse groove therein adapted to receive and fit the dovetail. The graphitebody 1 may be separately formed or it may be molded in place.

In Fig. 5 I have shown an alternative contact 25 which may be substituted for the contact 1. In lieu of the dovetail 1 for holding the graphite body 25 in place the metallic part of the contact is provided with one or more round holes at 25 into which the graphite body projects.

In Fig. 6 I have shown another alternative contact 26 which may be substituted for the contact 1. As shown in Fig. 6 the graphite body 26 fits a transverse undercut recess in the metal 26 of the contact. It will be understood that the contact 26 is so mounted in relation to the coacting contact that the initial engagement and the final disengagement takes place at the graphite body 26 exactly as heretofore described.

In Fig. 7 I have shown a construction similar to that already described, but differing in that each contact is composite and is formed with a graphite portion anda metal portion. The contact 1 is or may be exactly as already described, but in lieu of the contact 2 there is provided a contact 24 having a metallic portion 24 similar to the before described portion 2 of the contact 2. In addition, the contact 24 has a graphite portion 24 immediately adjacent the The parts are so constructed and so positioned that when engagement is first effected the two graphite portions 24 and l engage with each other as shown by full lines in Fig. 5. The parts then slide relatively so that in their final position the metallic portion 24=*contacts with the metallic portion 1 as shown by dotted lines in Fig. 5.

The construction shown in Fig. 7 has the ad vantage that there are two bodies of graphite to provide the required graphite film between the metallic contact surfaces, and it has thefurther advantage that when the contacts are separated or engaged arcing takes place between the two graphite bodies, thus completely eliminating all possibility of any burning or melting of the metallic portions of the contacts.

Throughout the foregoing specification I have referred to graphite as the material used for preventing welding, for effecting lubrication and for constituting an arcing contact. understood, however, that this term is used in a generic sense and is intended to include other equivalent substances capable of producing the same or similar results.

It will be What I claim is:

1. In an electric circuit making-and-breakin device, the combination of a contact consisting at least in part of metal, another contact which is composite and has at its contacting surface a portion comprising graphite and another portion consisting of metal, means for resiliently supporting one of the contacts, and means for moving one of the contacts into and out of engagement with the other contact along a fixed path at a substantial angle to the contacting surface of the composite contact, the last said means serving by reason of the resilient supporting means and the said angular relationship to cause the metal of one contact to relatively slide from the graphite portion of the composite contact to the metal portion thereof during movement into engagement and to relatively slide oppositely during movement out of engagement.

2. In an electric circuit maklng-and-breaking device, the combination of a movable contact consisting at least in part of metal, a substantially stationary composite contact having at its contacting surface a portion comprising graphite and another portion consisting of metal, means for resiliently supporting one of the contacts, and means for moving the movable contact into and out of engagement with the composite contact along a fixed path at a substantial angle to the contacting surface of the latter, the last said means serving by reason of the resilient supporting means and the said angular relationship to cause the metal of the movable contact to relatively slide from the graphite portion of the composite contact to the metal portion thereof during movement into engagement and to relatively slide oppositely during movement out of engagement.

3. In an electric circuit making-and-breaking device, the combination of a movable contact consisting at least in part of metal, a substantially stationary resiliently supported composite contact having at its contacting surface a portion comprising graphite and another portion consisting of metal, and means for moving the movable contact into and out of engagement with the composite contact along a fixed path at a substantial angle to the contacting surface of the latter, the last said means serving by reason of the said resiliency of support and the said angular relationship to cause the metal of the movable contact to relatively slide from the graphite portion of the composite contact to the metal portion thereof during movement into engagement and to relatively slide oppositely during movement out of engagement.

4. In an electric circuit making-and-breaking device, the combination of a contact consisting at least in part of metal, another contact which is composite and has at its contacting surface a portion comprising graphite and another portion consisting of metal, means for resiliently supporting one of the contacts, and means including toggle links for moving one of the contacts into and out of engagement with the other contact along a fixed path at a substantial angle to the contacting surface of the composite contact, the last toggle links serving by reason of the resilient supporting means and the said angular relationship to cause the metal of one contact to relatively slide from the graphite portion of the composite contact to the metal portion thereof during movement into engagement and to relatively slide oppositely during movement out of engagement and the said toggle tionary contact along a fixed path at a substantial angle to the contacting surface of one of the contacts, the last said means serving by reason of the resilient supporting means and the said angular relationship to cause the metal of each contact to relatively slide from the graphite portion of the other contact to the metal portion thereof during movement into engagement and to relatively slide oppositely during movement out of engagement.

JOSEPH SACHS.

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