US2442500A - Relay contact system - Google Patents

Description

June 1, 1948. A. H. LAMB RELAY CONTACT SYSTEM Filed March 17, 1943 Patented June I, 1948 RELAY CONTACT SYSTEM Anthony H. Lamb, Hillside, N. J., assignor to Weston Electrical Instrument Corporation,

Newark, N. 1., a corporation of New Jersey Application March 17, 1943, Serial No. 479,518

1 Claim.

This invention relates to relay contact systems and particularly to contact systems for sensitive instrument type relays that develop relatively minute forces for effecting the contact engagement, the novel contact systems including multiple contacts for obtaining a plurality of successive wiping contact engagements to assure reliable contact closures when the relay has remained inoperative for a long time or when the relay is subject to atmospheric conditions that promote the formation of high resistance films on the contact elements.

An object of the invention is to provide a relay contact system including a relatively rigid contact arm and a. cooperating contact assembly having a plurality of contact members that are successively engaged by the contact arm, the initially engaged contact member or members being flexible to permit further movement of the contact arm to engage one or more additional contacts. An object is to provide a relay contact system including a relatively stationary contact assembly comprising a base supporting a plurality of contact members in positions for successive engagement by the relay contact arm as the initially engaged contact member flexes and is rubbed across by the contact arm in its continued movement to engage another contact member. An object is to provide a relay contact system including a base carrying a plurality of contact members that are successively engaged by a contact arm with a rubbing contact engagement to afford a reliable contact closure when dirt or high resistance films tend to prevent current flow through the relay contacts.

These and other objects and advantages of the invention will be apparent from the following specification when taken with the accompanying drawings in which:

Fig. l is a fragmentary perspective view, to an exaggerated scale, of a relay including a contact system embodying the invention;

Fig. 2 is a fragmentary plan view showing the movable contact arm adjacent the relatively stationary contact assembly;

Figs. 3 and 4 are fragmentary perspective views illustrating successive stages in the movement of the relay contact arm into engagement with the stationary contact assembly;

Fig. 5 is a fragmentary perspective view of another embodiment in which the contact arm includes a plurality of contact sections;

Fig. 6 is a perspective view of another form of duplex contact pointer; and

Fig. 7 is a perspective view of another multiple contact embodying the invention.

In the drawings the reference numeral l identifies the coil element of the moving system of an instrument type relay that includes a magnetic system, not shown, having an interpolar gap in which the coil is supported for pivotal movement. A pointer or contact arm 2 of relatively rigid design is mounted on the coil l for cooperation with one, or alternatively with two, relatively stationary contacts.

In accordance with this invention, the stationary contact or contacts each include a plurality of contact elements that are successively engaged by the contact arm 2 upon the angular displacement of the moving system into a contact-closing position. As shown in Figs. 1 to 4, the stationary contact comprises a conducting-base plate'3 in which three wires 4, 5, 0 are secured in upright position to extend into the path of movement of the contact arm 2. The contact wires are of varying stiffness and are progressively displaced from a radial line through the axis of the moving system and the initially engaged contact wire, the stiffness of the contact wires increasing with their displacement from the radial line of initial contact. The wires are preferably of the same metal or alloy, andthe varying stifiness is obtained by a selection of the size or diameter of the contact wires. For simplicity of construction, the contact wires are preferably all normally straight and parallel, but they maybe bent or bowed for greater flexibility or for other purposes.

The most flexible contact wire 4 is the inner contact element of the contact system shown in Figs. 1 to 4, but the relative arrangement of the contact wires may be reversed to locate the most flexible contact element at the outer side of the stationary contact assembly. The intermediate contact element 5 is of greater stiffness than the initial contact element 4, and the contact element 6 is of still greater stifi'ness but is preferably somewhat flexible to aiTord a resilient stop for the contact arm 2.

The method of operation of the relay contact system will be apparent from an inspection of the drawings. The initial contact engagement is between the contact arm 2 and the most flexible contact element 4 of the stationary contact assembly, as illustrated in Fig. 2. A good contact closure of low resistance may be obtained by this initial contact engagement to energize the controlled relay circuit but, if it is not, the further displacement of the moving system will result in a flexing of the contact element 4 to effect a further closure oi. the contact arm 2 upon the contact element 5, see Fi 3. The contact arm 2 rubs across and along the initial contact element 4 during this movement of the pointer 2, and tends to scrape dirt and any high resistance films from the engaged contacts. Further displacement of the moving system increases the flexing of contact element 4 and flexes the intermediate contact element 5 to permit a closure of the contact arm 2 upon the contact element 6.. The sequence of contact action is a closure of contact arm 2 on contact element 4, a rubbing of the engaged surfaces as contact element 4 flexes, a closure of contact arm 2 on the contact element 5, a rubbing of contact arm 2 on contact elements 4 and 5 as contact element 5 flexes, and a closure of contact arm 2 on contact element 6. When the contact element 6 or the contact arm 2 is somewhat flexible under the pressures developed by current flow through the coil I, there is a further rubbing of the contact arm 2 across all of the contact elements of the stationary contact assembly. The

- successive contact closures, the rubbing engagement of the closed contacts and the movement of different portions of the cooperating contacts'into engagement will afford reliable low resistance contact closures in spite of dirt or fllms that may be present on the contacts when the relay is not operated for long periods.

The number of contact and rubbing engagements may be increased by substituting a contact arm or pointer with multiple contact sections for the usual single element pointer 2 of Figs. 1 to 4. A satisfactory pointer construction, as shown in Fig. 5, comprises a U-shaped wire having a longer leg I secured to the cross arm 8, for example by welding. and a shorter leg 'I' located below the longer leg, 1. e., between the contact sectionl and the base I that carries the contact elements 4, 5, 6. The leg I has suflicient rigidity to bend the contact wires 4 and 5 upon increasing current flow through the relay coil, and the leg I has a lesser rigidity in view of the U-bend connection or the contact sections of the pointer. The contact section I therefore engages and rubs against the stationary contact elements but it does not deflect them out or engagement with the upper contact section I of the pointer.

An alternative construction for a duplex pointer comprises a pair of wires 9 secured to the cross arm 8 and having outer contact portions spaced apart to engage the contact elements 4, '5, 6 at different distances from their supported ends.

In the embodiment illustrated in Fig. 7, the base 5 ll carries a flexible contact wire l2 that extends '4 4 through the loop It at the upper end or a rela' tively stifl wire II that is mounted on the base I l. The size of the loop I! is preferably such that the contact wire 12 does not engage the inside of the loop when flexed by the contact arm of the relay moving system. This adjustment or the stiflness of contact wire l2 to the loop size is not critical when the base plate I l is metallic and the contact elements l2 and H are electrically in parallel in the same relay controlled circuit.

The invention also contemplates relay contacts in which the base plate 3 or II is of insulating material and the several contact elements are included in diflerent controlled circuits. The flexible contact wire 8 should not engage the loop 13 or the stiiI wire il in this embodiment of the invention, and the function 01 the loop I! is to protect the flexible wire from permanent deformation from heavy mechanical shocks during shipment and installation or during normal use.

It is to be understood that the invention is not limited to the particular constructions herein illustrated and described as various modifications that may occur to those familiar with the desi n and construction or sensitive relays fall within the spirit of my invention as set forth in the following claim.

I claim:

A contact assembly for use with the movable and relatively rigid pointer contact of a sensitive instrument type relay, said contact assembly including a base member supporting a plurality of flexible contact wires positioned for successive engagement by the relay pointer contact, the contact wires being of diflerent stiffness and flexing under the pressure exerted thereon by the pointer contact to eflect rubbing engagement of the engaged surfaces upon further movement 0! the pointer contact after the initial contact engagement, one or said contact wires including a loop portion extending around and spaced from a more flexible contact wire.

ANTHONY H. LAMB.

'- nnrmencns crrnn The following references are of record in the flle of this patent:

UNITED STATES PATENTS Number Name Date 1,179,389 Austin Apr. 18, 1916 2,076,115 Benit Apr. 6, 1937 2,324,265 McMaster July 13, 1943

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