US3737821A - Electrical contactors - Google Patents

Abstract

A solenoid operated contactor is disclosed which provides a larger than armature travel air gap, higher contact pressures and rolling or wiping action of the main contacts, by providing a conductive strap supporting the main moving contact, which strap is coupled intermediate its ends to the solenoid armature and has alternative fulcra, one nearer and one more distant from the armature-strap junction.

Description

United States Patent [1 1 Morton et al. 1451 June 5, 1973 54] ELECTRICAL CONTACTORS 3,345,476 /1967 Russell .....200/67 DA 3,076,073 1/1963 Townsend ..335/200 [751 Hazel 3,135,841 6/1964 Miller ..200/67 1) Marple; 3,550,049 12/1970 Blanc-Tailleur ..33s/195 Graham Spencer Thexton, Marple Budge of England Primary Examiner-Harold Broome [73] Assignee: Cableform Limited, Romiley, Attorney-Richard E. Sughrue, Gideo Franklin Stockport, England Rothwell, John H. Mion et al.

p [22] Filed: Sept. 24, 1971 I [57] ABSTRACT- [211 Appl' l83489 A solenoid operated contactor is disclosed which provides a larger than armature travel air gap, higher con- Foreign Application Priority Data tact pressures and rolling or wiping action of the main Sept 25 1970 Gm Britain 709/ contacts, by providing a conductive strap supporting the main moving contact, which strap is coupled inter- 521 U.S. c1 ..335/133, 200/166 .l 335/200 mediate ends mature and has 51 Int. "110111 1/12 and mm m fmm 58 Field 61 Search ..335/133, 192,200, the armature-Strap junction- 335/; 200/166 J, 67 DA, 67 D [56] References Cited 9 Claims, 5 Drawing Figures UNITED STATES PATENTS 3,623,150 il/i97i Minns ..335/l92 ELECTRICAL CONTACTORS This invention relates to electrical contactors for making and breaking thesupply of electrical current to a load.

Two main types of contactors are presently in use, the attracted armature or clapper type and the solenoid operated type. Of these .two, the attracted armature type is much more widely used, although it tends to be larger and more expensive, as its geometry is more convenient for incorporating arc blow out devices, wiping or rolling actions on the main contacts and larger air gaps between main contacts for a given air gap in the magnetic circuit. To achieve this larger air gap it is necessary to have a velocity ratio which has the disadvantage of giving the lowest of the two or more reactions to the armature force at the main contact and therefore less contact pressure for a given force on the armature.

A solenoid contactor has the advantage that it can be constructed in a smaller volume and with less parts but in general rolling or wiping action on the main contacts is not available nor is the facility for are blow out, greater air gaps between main contacts than armature travel or a greater air gap between main contacts than armature travel and yet still maintaining the largest reaction to the armature force on the main contact.

An object of the present invention is to provide an improved solenoid operated contactor in which the above mentioned disadvantages are obviated or mitisat According to the invention, a solenoid operated contactor comprises a fixed contact and a co-operating moving contact, the latter being carried at or towards one end of a conductive strap which is coupled intermediate its end to the solenoid armature, the strap in the portion beyond the armature-strap coupling remote from the moving contact having alternative fulcra of different spacings from the armature-strap coupling, the arrangement being such that when the solenoid is tie-energized the fulcrum nearer the armature-strap coupling is operative and when the contactor is fully operated the fulcrum more distant from the armaturestrap coupling is operative. I

Preferably the strap is electrically connectedto the more distant fulcrum by a flexible conductor .which as will be explained latter providesmeans enabling thereduction of duration of contactbounce for a given mass of moving components and closing'velocity.

Embodiments of the invention will now be described, by way of example, with reference 'to the accompanying drawing, in which:

FIG. 1 is a diagrammatic representation of the contact assembly in the closed condition, in accordance with the invention,

FIG. 2 is a similar representation to thatof FIG. 1 but showing the open condition,

FIG. 3 is a similar representation of a change-over contact assembly,

FIG. 4 is a part-sectional view of a contactor in accordance with the invention, and

FIG. 5 is a view at right angles to, that of FIG. 4.

Referring to FIGS. 1 and 2, the contact assembly comprises a strap carrying a moving contact 11 cooperating with a fixed contact 12. The strap is coupled to a solenoid armature (not shown) at 13 so that the strap experiences the force F when the solenoid is energized and a spring return force F 1 when it is dethe fulcrum B by a flexible conductor 15 in the form of braid. The clearance in the direction of the solenoid axis is so arranged that when the solenoid is energized the contacts close (positions 2) and the solenoid continues to travel until the other end of the conducting strap closes on to the fulcrum B (Position 1), thus causing the moving contact 11 to roll on the fixed contact 12.

In this closed position the reaction on the main contact is R (Fd2/dl d2) i.e., being larger than the reaction when fulcrum E is operative.

When the solenoid is de-energized the conducting strap moves from position '1 to position 2 (the effect being to roll'the contacts) due to the throw off spring. It then continues up to position 3 at which point the vertical movement of the strap is arrested at the fulcrum E. The solenoid then continues through distance X up to its fully open position, throughout this latter movement theconducting strap pivots about fulcrum E and theatre air gap between the contacts that is obtained during this movement is Z (X dl d4/d4) Current begins to flow through the contactor when the contacts touch, the current path being through the flexible conductor 15 which shorts the moving contact assembly to the cable terminal, fulcrum B. The velocity of the moving contact assembly only undergoes a small change at this moment due to a slight change in direction, the velocity of the whole assembly being relatively unaffected. The assembly continues to travel until the moving contact assembly is brought into contact with the fulcrum B. The velocity of the moving contact assembly now undergoes a major change and oscillation of the moving contact assembly with respect to the fulcrum B now takes place.

However, it can be seen that the flow of current through the contactor is only interrupted if the moving contact assembly is lifted to beyond the level position thus opening the contacts 11 and 12. This required amplitude of oscillation, if reached at all, is only present for a small period of time compared with the time required for the exponential decay of the oscillation. Also since fulcrum B is of a conducting material it can be seen that when the contactor is in the closed position the current flow is diverted from the flexible conductor 15 which allows the flexible conductor to be smaller in cross sectional area and therefore more flexible and still not limit the thermal rating of the contactor.

Referring to FIG. 3, there is shown diagrammatically a similar contact assembly with the exception that contacts 16 and 17 are provided at the fulcrum E and projection 14. As can be seen from FIG. 1 and 2 contact between fulcrum E and projection 14 is open when contacts 11 and 12 are closed and closed when contacts l1 and 12 are open. Thus a change-over contact assembly is provided, the movement between the position 3 and 4 shown in FIG. 2 providing a very positive wiping action for the contacts 16 and 17.

Referring to FIGS. 4 and 5 there is shown a completely assembled contactor in accordance with the invention. The contactor comprises a solenoid 20 having an operating coil 21 and a plunger 22 from which extends an operating rod 23 carrying an insulating collar 24 which is urged upwards by a coil spring 25 bearing on a base plate 26. Collar 24 supports the conductive strap 10 carrying the moving contact 11 co-operating with the fixed contact 12 mounted on a terminal assembly 27 which is secured to the base plate 26 by bolt 28. Strap 10 is held on the collar 24 by a light blade spring 29 and retaining ring assembly 30. Strap 10 is provided with the L-shaped projection 14 which co-operates with fulcrum E which is an extension from a terminal assembly 31 which is mounted on base plate 26 and also provides fulcrum B. The flexible conductor 15 extends from a lug 32 on terminal assembly 31 to the end of strap 10. The operation of the contactor is as already described in relation toFlGS. 1 and 2.

An arc chute assembly 33, 34 provided with permanent magnets 35, 36 is positioned adjacent the contacts 11, 12 to act as an arc blow out device. The magnets are positioned to achieve maximum flux density across the contact gaps to pull the are out as quickly as possible. The are chute assembly serves to locate the assem bly of the moving contact and the overtravel spring to the desired position relative to the fixed contact.

What is claimed is:

1. A contactor operated by a solenoid having an armature, said contactor comprising a fixed contact,

a conductive strap which is coupled intermediate its ends to said solenoid armature,

a moving contact carried on said conductive strap at a point remote from the point of said coupling and positioned to enable it to cooperate with said fixed contact,

a first fulcrum positioned for contact with said conductive strap at a point on the opposite side of the point of said coupling from the point at which said moving contact is carried,

a second fulcrum, also positioned for contact with said conductive strap at a point on the opposite side of the point of said coupling from the point at which said moving contact is carried, but at a point more distant from the point of said coupling than the point at which said first fulcrum is positioned,

said first and second fulcra being operatively associated with said conductive strap so that, when the solenoid is d e-energized, said first fulcrum is operative and,'when the contactor is fully operated, said second fulcrum is operative.

2. A contactor as claimed in claim 1 wherein said conductive strap is electrically connected to said second fulcrum by a flexible conductor and said second fulcrum has an extension forming a terminal of the contactor.

3. A contactor as claimed in claim 1 wherein said conductive strap has a main member which carries said moving contact and which co-operates with said second fulcrum and I a generally L-shaped projection which co-operates with said first fulcrum, said first fulcrum extending into the space between the remote leg of said L- shaped projection and said main member.

4. A contactor as claimed in claim 3 wherein the part of said first fulcrum nearer to the point of said coupling is an extension from a part of said first fulcrum more distant from the point of said coupling.

5. A contactor as claimed in claim 1 wherein a first additional contact is mounted on said conductive strip at the point where it contacts said first fulcrum and a second additional contact is mounted on said first fulcrum,

whereby said first and second additional contacts are closed when said first fulcurm is operative and open when said second fulcurm is operative.

6. A contactor as claimed in claim 4 wherein said second additional contact forms said first fulcrum.

7. A contactor as claimed in claim 1 wherein the point of said coupling is approximately midway between the point at which said moving contact is carried on said conductive strap and the point at which said conductive strap contacts said second fulcurm.

8. A contactor as claimed in claim 1 wherein said solenoid armature is coupled to said conductive strap via an insulating collar which also serves as an abutment for one end of a throw-off coil spring, said conductive strap being steadied on said insulting collar by a blade spring.

9. A contactor as claimed in claim 1 further comprising an arc chute including permanent magnets adjacent said fixed contact and said moving contact, the arc chute serving to locate the assembly of said moving contact and said conductive strap to the desired position relative to said fixed contact.

Claims (9)

1. A contactor operated by a solenoid having an armature, said contactor comprising a fixed contact, a conductive strap which is coupled intermediate its ends to said solenoid armature, a moving contact carried on said conductive strap at a point remote from the point of said coupling and positioned to enable it to cooperate with said fixed contact, a first fulcrum positioned for contact with said conductive strap at a point on the opposite side of the point of said coupling from the point at which said moving contact is carried, a second fulcrum, also positioned for contact with said conductive strap at a point on the opposite side of the point of said coupling from the point at which said moving contact is carried, but at a point more distant from the point of said coupling than the point at which said first fulcrum is positioned, said first and second fulcra being operatively associated with said conductive strap so that, when the solenoid is deenergized, said first fulcrum is operative and, when the contactor is fully operated, said second fulcrum is operative.

2. A contactor as claimed in claim 1 wherein said conductive strap is electrically connected to said second fulcrum by a flexible conductor and said second fulcrum has an extension forming a terminal of the contactor.

3. A contactor as claimed in claim 1 wherein said conductive strap has a main member which carries said moving contact and which co-operates with said second fulcrum and a generally L-shaped projection which co-operates with said first fulcrum, said first fulcrum extending into the space between the remote leg of said L-shaped projection and said main member.

4. A contactor as claimed in claim 3 wherein the part of said first fulcrum nearer to the point of said coupling is an extension from a part of said first fulcrum more distant from the point of said coupling.

5. A contactor as claimed in claim 1 wherein a first additional contact is mounted on said conductive strip at the point where it contacts said first fulcrum and a second additional contact is mounted on said first fulcrum, whereby said first and second additional contacts are closed when said first fulcurm is operative and open when said second fulcurm is operative.

6. A contactor as claimed in claim 4 wherein said second additional contact forms said first fulcrum.

7. A contactor as claimed in claim 1 wherein the point of said coupling is approximately midway between the point at which said moving contact is carried on said conductive strap and the point at which said conductive strap cOntacts said second fulcurm.

8. A contactor as claimed in claim 1 wherein said solenoid armature is coupled to said conductive strap via an insulating collar which also serves as an abutment for one end of a throw-off coil spring, said conductive strap being steadied on said insulting collar by a blade spring.

9. A contactor as claimed in claim 1 further comprising an arc chute including permanent magnets adjacent said fixed contact and said moving contact, the arc chute serving to locate the assembly of said moving contact and said conductive strap to the desired position relative to said fixed contact.

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