US3526736A

US3526736A - Sliding contact

Info

Publication number: US3526736A
Application number: US785227A
Authority: US
Inventors: Joseph M Ramrath
Original assignee: Allis Chalmers Corp
Current assignee: Allis Chalmers Corp
Priority date: 1968-12-19
Filing date: 1968-12-19
Publication date: 1970-09-01
Anticipated expiration: 1987-09-01

Description

p 1, 1970 J. M. RAMRATH 3,526,736

SLIDING CONTACT Filed Dec. 19, 1968 United States Patent 3,526,736 SLIDING CONTACT Joseph M. Ramrath, Mattapan, Mass., assignor t0 Allis- Chalmers Manufacturing Company, Milwaukee, Wis. Filed Dec. 19, 1968, Ser. No. 785,227 Int. Cl. H01h 1/34; H01n 1/54 US. Cl. 200-166 6 Claims ABSTRACT OF THE DISCLOSURE A sliding contact for engagement with a cylindrical bayonet type contact having a central opening and a plurality of pivotal contact fingers radially disposed around the opening so that one end of each contact finger can make sliding engagement with the side of the bayonet contact when the latter enters the opening. Current flow, from the bayonet contact to the sliding contact, follows a looped path and generates a magnetic field which aids in forcing the contact fingers against the bayonet contact.

SUMMARY OF THE INVENTION This invention relates generally to electrical contacts. More particularly, it relates to sliding contacts which engage with relatively movable bayonet contacts.

Sliding contacts employ a plurality of contact fingers, either linearly or radially disposed, which engage a relatively movable bayonet contact. Sliding contacts presently available are satisfactory for their intended purposes but could be improved on. For example, in one type of sliding contact, the individual spring biased contact fingers or segments are radially disposed around a bayonet contact but tend to move laterally out of position when subjected to high peak currents and attendant electromagnetic forces. Furthermore, these electromagnetic forces tend to lift the contact fingers off of the bayonet contact thereby causing severe burning and scoring at the lift-off points. These electromagnetic forces also cause lateral shifting of the contact fingers so that they touch each other thereby causing irregularly shaped current paths which cause additional burning and scoring between the contact fingers. Accordingly, it is desirable to provide an improved sliding contact which overcomes the aforesaid disadvantages and has other advantages.

In accordance with the present invention, there is provided a sliding contact for engagement with a relatively movable bayonet contact. The sliding contact comprises an electrically conductive base member having an opening for accommodating the bayonet contact. The base is provided with an electrically conductive flange adjacent said opening and the flange is provided with a groove on the side thereof away from the opening. A plurality of C-shaped contact fingers or segments are arranged on the base near the opening. One end of each contact finger pivotably engages the groove in the flange on the base member. The other end of each contact finger is adapted to pivot toward the opening for engagement with the bayonet contact. Insulating means are provided on the base to physically support the contact fingers, to prevent direct electrical contact between them, and to limit pivotal movement of the contact fingers. Biasing springs are disposed between the insulating means and the contact fingers for biasing the contact fingers toward the opening. Each contact finger, the flange and the base are shaped 3,526,736 Patented Sept. 1, 1970 so as to provide a looped path for current flowing from the bayonet contact, through the contact finger, flange and the base. The electromagnetic forces associated with the looped current path tend to move each contact finger tightly against the bayonet contact.

OBJECTS It is an object of the present invention to provide improved sliding contacts having contact fingers which are prevented from making direct electrical contact with each other.

Another object is to provide sliding contacts of the aforesaid character having contact fingers which are individually supported and electrically insulated from each other.

Another object is to provide sliding contacts of the aforesaid character wherein each contact finger is pivotably mounted on a flange on the base and wherein each contact finger, the flange, and the base form a current loop which generates an electromagnetic field which causes increased pressure between the contact finger and the flange and the bayonet contact as current flow increases.

Another object is to provide sliding contacts of the aforesaid character wherein current flow from the bayonet contact radiates outward through individual contact fingers in straight line paths with respect to the axis of the bayonet contact.

Another object is to provide sliding contacts of the aforesaid character which are relatively economical to manufacture and assemble and which have greater current carrying ability than known types of sliding contacts of comparable size.

Other objects and advantages of the invention will hereinafter appear.

DRAWINGS The accompanying drawing illustrates a preferred embodiment of the invention, but it is to be understood that the embodiment illustrated is susceptible of modifications with respect to details thereof without departing from the scope of the appended claims.

In the drawing:

FIG. 1 is a plan view with portions broken away of a sliding contact in accordance with the present invention; and

FIG. 2 is a cross sectional view taken along line -IIII of FIG. 1.

DESCRIPTION OF THE INVENTION Referring to FIGS. 1 and 2 of the drawing, the numeral 10 designates a sliding contact in accordance with the present invention. Sliding contact 10 is adapted to cooperate with an electrically conductive cylindrical bayonet contact 12. It is to be understood that the

contacts

10 and 12 are relatively movable with respect to each other and either could be the stationary or movable contact in a piece of electrical equipment. However, in the embodiment shown, sliding contact 10 is the fixed or stationary contact and bayonet contact 12 is the movable contact. Sliding contact 10 comprises an electrically conductive base member 14 which is provided with a central opening 16 for accommodating bayonet contact 12. Base member 14 is adapted for electrical and mechanical connection to an electrically conductive member 18 which is to be understood to be part of a piece of electrical equipment and which serves as a physical support for sliding contact and as an electrical connection thereto. Base member 14 is provided with a circular depression which is concentric with opening 16 and which is bonded on each side by

cylindrical flanges

21 and 22. The depression 20 further accommodates components hereinafter described. Preferably, depression 20 in base 14 is deeper nearer the inside thereof to afford clearance space as at 26 for movement of the contact fingers 28. Cylindrical flange 22 is disposed around and adjacent opening 16. Flange 22 is provided on the side facing away from opening 16 with a circular groove 24 which as FIG. 2 shows has a V-shaped cross section. However, groove 24 could have a curved cross sectional configuration.

Sliding contact 10 further comprises a plurality of electrically conductive contact fingers or segments 28 which are disposed on base 14 and adapted to cooperate with bayonet contact 12. In the embodiment shown,

sixteen radially disposed contact fingers 28 are provided but a greater or lesser number could be employed. Since all contact fingers 28 are identical, only one of them will hereinafter be described in detail.

As FIG. 2 shows, a contact finger 28 has a substantially C-shaped or U-shaped configuration. One end 30 of contact finger 28 is rounded and is disposed in groove 24 in flange 22 of base 14 so as to be pivotable therein and to make electrical contact with the flange. The other end 32 of contact finger 28 is also rounded and is adapted to make sliding contact with the side surface of bayonet contact 12, as hereinafter explained.

Means are provided on base 14 to physically support the contact fingers 28 in radial arrangement, to physically separate and electrically insulate each contact finger from another, and to control or limit pivotal move- I merit of the contact fingers. Such means comprise first and second

insulating plates

34 and 36, nespectively. As FIG. 1 shows, insulating plate 34 is provided with slots or notches 38 and each notch accommodates a contact finger 28. Insulating plate 36 is also provided with similar notches 40. The insulating segments 41 and 43 between the

notches

38 and 40 in the

plates

34 and 36, respectively, limit lateral movement of any contact finger 28 disposed therebetween and also prevent any contact finger 28 from making direct physical or electrical contact with any other contact finger. An insulating member 42 having notches 44 is disposed between the

plates

34 and 36 and serves to space them part, and cooperates therewith to define cavities which serve as spring retaining means. Each notch 44 in member 42 accommodates a biasing spring 46 which bears against the rear of the associated contact finger 28 and tends to bias its end 32 toward opening 16 in base 14 and its end 30 against flange 22. Under the action of its biasing spring 46, each contact finger 28 tends to pivot clockwise (with respect to FIG. 2) into tight engagement with bayonet contact 12, if the latter is disposed in opening 16. However, such pivotal travel of contact finger 28 is limited by means such as an insulating plate 50 which overlies insulating plate 34. The insulating

plates

34, 42, 36 and 50 are rigidly secured with respect to each other and with respect to base 14 by means of a plurality of bolts 52 which extend through appropriate holes in the insulating plates and into threaded holes (not shown) in base 14.

Sliding contact 10 operates as follows. Assume first that bayonet contact 12 is withdrawn from opening 16. Under such circumstances each biasing spring 46 forces its associated contact finger 28 to pivot clockwise with respect to FIG. 2 as far as insulating plate 50 will permit. Thus, a portion of end 32 of each of the contact fingers 28 extend into opening 16 in base 14 and into the path that bayonet contact 12 will eventually traverse. When bayonet contact 12 enters opening 16 in base 14 axially, it engages the ends 32 of all of the contact fingers 28 and forces them back against the bias of their associated springs 46 thereby assuring that a good electrical connection exists between the side surface of bayonet contact 12 and contact fingers 28. Current flowing from bayonet contact 12, through each contact finger 28, through flange 22, through base 14 and through member 18 follows a looped path, as shown by an arrow 54 in FIG. 2. The current path depicted by the arrow 54 is looped and generates an electromagnetic field which forces its contact finger 28 to move in a clockwise direction (with respect to FIG. 2). Thus, the action of the biasing springs 46 and the action of the electromagnetic forces cause all contact fingers 28 to tightly engage bayonet contact 12. As current flow increases, the magnetic forces increase, thus insuring an even tighter electrical connection The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a sliding contact for cooperation with a bayonet contact,

an electrically conductive base having an edge past which said bayonet contact is adapted to move, said base having a flange adjacent said edge and said flange having a groove therein on the side away from said edge, at least one contact finger, one end of said contact finger disposed in said groove and pivotable therein and the other-end of said contact finger extending over said flange and toward said edge and adapted to engage said bayonet contact when the latter is disposed adjacent said edge, insulating means on said base for supporting said contact finger and for limiting pivotal movement thereof, and biasing means disposed in a recess in said insulating means between said insulating means and said contact finger for biasing said contact finger in said groove and for pivoting it toward said edge, said base, said flange and said contact finger forming a current path which, during current flow there through, generates an electromagnetic field which forces said contact finger against said bayonet con tact and said flange.

2. A sliding contact according to claim 1 wherein said insulating means is provided with a slot wherein said contact finger is disposed, and being further provided with a recess wherein said biasing means in the form of a spring is located, said insulating means having a portion overlying said slot for limiting pivotal movement of said contact finger.

3. A sliding contact according to claim 2 wherein said insulating means comprises a pair of contact supporting members, a spring retaining member disposed between said contact supporting members, and a stop member overlying one of said contact supporting members to limit pivotal movement of said contact finger, said contact supporting members being slotted to accommodate said contact finger and prevent substantial lateral movement thereof, and said spring retaining memher being slotted to provide a recess to accommodate said spring.

4. A sliding contact according to claim 2 wherein said base has an opening therethrough which defines said edge and wherein a plurality of contact fingers, slots,

and recesses are provided, at least some of said contact fingers, slots and recesses being disposed on different sides of said opening.

5. A sliding contact according to claim 4 wherein said contact fingers, slots and recesses are radially disposed.

6. A sliding contact according to claim 3 comprising a plurality of contact fingers, slots and recesses disposed in radial arrangement, and wherein said contact sup porting members and said spring retaining members are 5 6 provided with central openings from which the slots 3,137,778 6/ 1964 Barr 200-166 XR radiate. 3,328,550 6/1967 Miller 200166 References Cited 3,381,105 4/ 1968 Morte-nson 200-166 XR UNITED STATES PATENTS HERMAN 0. JONES, Primary Examiner 2,180,155 11/1939 Leopold 200--166 5 2,751,471 6/1956 Wills 200-166 US. Cl. X.R. 3,127,492 3/1964 Date 200-166 200-170