US2196832A - Switch contact - Google Patents

Description

R- B. HUNTER SWITCH CONTACT Filed July 23, 19

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' UNITED STATES PATENT OFFICE? I SWITCH CONTACT' Richard B. Hunter, Shorewood, Wis., assignor to Cutler-Hammer, Inc., Milwaukee Wia, a

corporation of Delaware Application July 23, 1937, Serial No. 155,212

2 Claims. (01. 200-171) This invention relates to switch contacts and more particularly to contacts of the type employed in connection with drum controllers, although it late be understood thatcontacts of the character herein disclosed may be employed I in other electrical devices.

' aforementionedcharacter which is positively held against rotary movement with respect to the finger to which it is secured.

Another object is to provide a contact tip of the aforementioned character having an embedded securing element, wherein the embedded portion of the securing element is sufflciently removed from the contact surface of the tip to provide an adequate amount of wear allowance.

Another object s to provide a contact tip in which the securing element is rigidly held and supported in a novel and efi'ective manner.

.Another object is to provide a readily removable and replaceable contact tip which is simple in construction and which can be produced economically. v

Other objects and advantages of the invention will hereinafter appear.

Various forms of contact tips have heretofore been proposed, which individually possess certain advantages which are of vvalue depending upon their application. Those contact tips which are adapted to be permanently'secured to contact fingers, as by riveting, are satisfactory for use in drum controllers, for instance, which are employed in such relatively light service that wear and burning of the contact tips'is negligible.

- However, controllers which are employed for relatively heavyduty service, such as requires fre quent commutation of circuits carrying heavy currents, and in which high contact pressures are required, necessitate frequent replacement of the contact tips due to'relatively-rapld wear'and burning thereof. It is obvious that a permanently secured contact tip is undesirable where frequent replacement is necessary, and in recognition of the need for an easily removable and attachable contact tip various forms thereof have heretofore been proposed.

In drum controllers the engagement of the contact tip with the cooperatingcontacts carried by the rotary drum is Preferably effected with a maximum width of the contacting areas, and accordingly a necessary feature of such a tip is to provide means whereby the same is non-rotatably held with respect to the contact finger. Such means, heretofore proposed, include such devices 5 asan abutment formed at one end of the contact tip to cooperate with the outer end of the finger, the abutment however, preventing reversible attachment of the tip. Other tips are formed with recesses requiring specially formed projection 10 on the contact finger, or a separate element carried by the finger and having a projection to cooperate with a recess or recesses in the tip.

The present invention provides the aforementioned feature of non-rotatable securement in a novel manner and other desirable features as set forth in the foregoing objects, and the advantages of such features will be apparent from the following description with reference to the single embodiment of the invention illustrated, in the accompanying drawing; it-belng understood that the embodiment illustrated is susceptible of modification in respect of certain details of construction thereof without departing from the scope of the appended claims.

Inv the drawing, Figure l is a side elevational view, with parts thereof shown in vertical section, of a contact finger having secured thereto a form of contact tip embodying my invention;

Fig. 2 is a top plan view of the contact finger shown in Fig. l;

Fig. 3 is a perspective view, in separated relation, of the improved contact tip shown in Fig. 1 and the outer end .portion of the contact finger, showing a preferred form of the latter and indicating the manner-of cooperation of the parts; and. i

Fig. 4 is a plan view of the contact tip.

Referring now more particularly to Fig. 1 of the drawing, the numeral designates a segmental contact mounted on a. rotary drum in a position to engage the contact tip 2 secured to the outer endportion of a contactfinger I. The romember 5 formed of suitable insulating material. as

' Contact finger 3 is secured to supporting rod 4 by clamping means comprising a clamping member 3 having arms 1 and 3 formed at a rightangle to each other to engage two sides of the rod 4. Ann I also forms a supporting base plate for the contact mechanism. Cooperating with clamping member 8 is a second clamping member 3 having arms l0 and Ii formed at a right-angle to each other to engage the other two sides of rod 4. The clamping members 6 and 3 are firmly held in clamping engagement with supporting rod 4 by b0lts,i2 and i3 and nuts l4.

Contact finger 3 is provided adjacent to the inner end thereof with an opening to freely receive the reduced portion of bolt l2. A coiled compression spring I! encircles portion 15 and is held under compression between the outer surface of contact finger 3 and theinner surface of a cup washer I? which is retained on portion l5 by a cotter pin i8. The extreme inner end of contact finger 3 is bent downwardly and is formed in a manner to provide a bearing edge or surface i3 which seats within a Saddle or open bearing formed on the outer face of arm I of clamping member 6.

One end portion of a flexible conductor or pigtail 2! is secured to the inner end portion of contact finger 3, the other end of said conductor being secured on bolt l3 between nuts l4 and 22 together with a solder lug 23 of well known form.

Associated with contact finger 3 is a contact pressure adjusting device comprising a polygonal headed screw 24 the shank of which is threaded into a tapped opening in the contact finger and is adapted in the inactive position of said finger to engage the upwardly offset extension 25 of arm I. Adjustment of screw 24 effects variation of the initial position of contact tip 2 and provides for correct inactive positioning of tip 2 as the latter wears down. A reflexed or substantially U-shaped spring element 26 is provided with an upwardly bent fiat projection 21 which-is adapted to yieldably engage any one of the fiat sides of the head of screw 24 to effect retention of the latter in any adjusted position against displacement by vibration. One of the legs of spring element 26 engages the outer surface of contact finger 3 while the other leg engages the inner surface of the head of screw 24, said legs having armed, relatively large openings to freely receive the shank of screw 24 and to provide a degree of longitudinal movement of spring element 26 to permit adjustment of screw 24.

When the rotary drum is of sufficiently large diameter to presen the danger of arcing between the segmental contacts carried thereby and the metal clamping members of the contact mechanism supporting means, a shield 23 formed of suitable insulating material is preferably mounted on the extension 29 of clamping member 9 by a screw 30, as shown in Fig. 1.

The contact tip 2 comprises essentially a suitably shaped body of metal, preferably copper, having embedded therein the head 3i and a .portion of the threaded shankof a securing element or stud 32, which is preferably made of steel. The stud and the contact tip are assembled in a well known manner;the head 3| being inserted in a recess in the tip formed to receive it and the metal then pressed or flowed and shaped around it as by swaging or hot forging of the copper to positively lock the stud in position in the tip. ,The stud head 3| is illustrated in the drawing as being of fiat circular form, the peboss or projection 34 formed on said surface.

Projection 34 is adapted to be accommodated within an elongated opening formed in the forward end of contact finger 3, the walls of said opening closely engaging the periphery of said projection to positively and non-rotatably interlock the contact tip with said finger. By means of a nut 35 which is threaded on stud 32 and a.

lock washer 31 which is interposed between said nut and the upper surface of contact finger 3, the contact tip 2 is rigidly secured to said contact finger.

As best shown in Fig. 4 the width of the projection 34 corresponds substantially with the diameter of stud 32, this width being preferred to a lesser width to avoid specially forming the opening 35 to accommodate the shank of stud 32. Moreover, the width of projection 34 should be sufficient to present a relatively large peripheral wall surface for cooperative engagement with the walls of opening35 and also to provide an adequate body of metal to prevent shearing of the projection by a wall of said opening when the nut 36 is turned to tighten the tip in position. On the other hand, a projection substantially larger than that shown is objectionable as it would require an opening 35 of such size as to materially weaken the contact finger.

It should be noted that the projection 34 is preferably arranged longitudinally with respect to the body of the contact tip 2, that is, in line with the direction of movement of the segmental contacts of the drum, and that the opening 35 is likewise preferably arranged longitudinally with respect to the contact finger 3. By this arrangement the shank of stud 32- is well supported by projection 34 in the direction of thrust, whether the drum is being rotated in one direction or the other.

The advantages of the aforedescribed arrangement are particularly evident when it is pointed out that if the projection 34 were arranged transversely of the contact tip the desired support for the shank of stud 32 in the direction of thrust would not be provided unless the projection were made substantially wider; and further, if the opening 35 were arranged transversely with respect to contact finger 3, the latter would be materially weakened unless it in turn were made wider to accommodate an opening so arranged. However, it iausnally desired to make drum controllers of as small size as is practically possible to conserve materials and reduce the cost thereof, and obviously if the contact fingers were required to be made wider than is necessary to serve their purpose, the center-to-center spacing of the fin-- gers would be greater, thus materially increasing the size of the drum controller. I

The character and arrangement of projection 34 serves a further and important purpose. In

order to obtain the maximum amount of wear from the contact tip the stud head 3| should be embedded in the tip as far removed from the contact surface as possible. As best shown in Fig. 1 the projection 34 provides an added thickness of metal enabling the head II to be located dad in said body of relatively soft metal closely relatively close to the surface 33 of the contact tip 2 without danger of the stresses incurred during tightening of nut 32 or the stresses incident to operation of the drum resulting in displacement of the stud from its embedded position. What I claim as new and desire to secure by Letters Patent is:

1. A contact tip comprising an integral body of relatively soft metal having surfaces for engagement with 'a cooperating contact and for engagement with a supporting finger, and having on the latter surface for interlock with such supporting finger a projection which is relatively low and of elongated form with parallel fiat sides,

and further comprising a securing-member hav-- ing a threaded shank terminating in a relatively thin wide head, such securing member being of relatively hard metal and having its head embedadjacent the finger engaging surface of said body for preservation of depth of the portion of said body subjected to. wear and said projection on the finger engaging surface of said body being formed to overlie the head of said securing meming a flat surface for engagement with saidsupporting member, the contact tip having a projection formed on said fiat surface, said projection being adapted for interlocking non-rotatable and non-slidable engagement with the walls of said opening, and a-securing element of a relatively harder metal having a head embedded in said tip closely adjacent to said flat surface to provide a wearing portion of maximum depth and having a threaded shank extending exteriorly of said tip substantially through the center of said projection, said element being adapted to assist in providing for securement of said tip to said supporting member. l

RICHARD B. mm.

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