US2945929A

US2945929A - Contact making devices

Info

Publication number: US2945929A
Application number: US767421A
Authority: US
Inventors: Howard J Calhoun; Jr Walter L Hinman
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1958-10-15
Filing date: 1958-10-15
Publication date: 1960-07-19
Anticipated expiration: 1977-07-19

Description

July 19, 1960 J, CALHOUN ETAL 2,945,929

' .CONTACT MAKING DEVICES Filed on. 15, 1958,

INVENTORS Howard J. Calhoun 8 Walter J. Hinmon BYZJJ ATTORNEY United States Patent CONTACT MAKING DEVICES Howard J. Calhoun, Sayreville, and Walter L. Hinman, Jr., Plainfield, N.J., assignors to WestinghouseElectric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 15, 1958, Ser. No. 767,421

8 Claims. (Cl. 200-87) This invention relates to contact making devices, and it has particular relation to electroresponsive relays having relatively movable contacts.

One of the problems present in the operation of relatively movable contacts involves contact bounce. When a movable contact is actuated into engagement with a fixed contact, any tendency of the movable contact to rebound may interfere with proper control of a circuit associated with the contacts.

In an effort to overcome the effects of contact bounce, the prior art has mounted a stationary contact for limited movement, the contact being biased in a predetermined direction by means of a spring. Although the resultant follow action of the stationary contact is helpful for high operating torques, it does not eliminate contact bounce for low operating torques. For example, if the stationary contact is permitted to move for a distance of the order of .015 inch, the torque level at which -nonbounce action is lost may be as high as 59 times the minimum pickup torque of the operating mechanism. This means that for torques betweenthe minimum pickup torque and 50 times the minimum pickup torque, substantial bounce of the movable contact may be encountered.

In accordance with the invention, a movable'contact is operated into engagement with a stationary contact through a friction coupling. The friction of the coupling increases as the movable contact is forced against the associated stationary contact. Preferably, the friction is created by an energy-absorbing material. With such a construction, the absorbed energy is no longer available to create contact bounce. The stationary contact is either of rigid construction or it may have a very small follow. The invention also contemplates a cam-operated movement of the movable contact which assures a positive wiping action between the movable and stationary contacts.

It is, therefore, an object of the invention to provide an improved contact making device.

It is a further object of the invention to provide a relay having a movable contact which is operated into engagement with a stationary contact through a coupling which develops increased friction and energy absorption as the movable contact is urged against the stationary contact.

It is also an object of the invention to provide operating mechanism for relatively movable contacts which assures improved wiping of the contacts.

Other objects of the invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which:

Figure 1 is a view in side elevation with parts broken away of a relay embodying the invention;

Fig. 2 is a view in top plan with parts in section of the rotor structure employed in the relay of Fig. 1; and

ice

making devices, it is particularly suitable for relays having relatively movable contacts. For this reason the invention will be described as applied to a relay of the type illustrated in the copending patent application of Gino J. Marieni, Serial No. 677,639, filed August 12, 1957, and assigned to the same assignee as the present patent application.

Referring to the drawing, Fig. 1 shows a relay having a rotor structure 1 which is associated with a stator structure 3. The rotor structure 1 includes a shaft 5 on which is mounted a hub 7 constructed of a suitable insulating material such as a phenolic resin. An electroconductive armature 9 in the form of a hollow cylinder has one end secured to the hub 7 in any suitable manner.

The shaft 5 is mounted for rotation relative to the stator structure 3 by means of suitable bearings 11 and 13 which form part of the stator structure. The stator structure includes windings 15 which may be energized to produce a rotating magnetic field which acts to pro duce a torque urging the armature 9 about its axis relative to the stator structure. The components of Fig. 1 which thus far have been specifically referred to may be similar in construction to the corresponding components of the aforesaid Marieni patent application.

Rotation of the shaft 5 is employed for actuating a movable contact 17 into and out of engagement with a stationary contact 19. To this end, the hub 7 is provided with a projection or boss 21 having a substantially cylindrical cross section. By inspection of Fig. 2, it will be noted that the boss 21 is eccentric relative to the hub 7. For example, the axis of rotation of the hub 7 is represented in Fig. 2 by a point 23 whereas the axis of the boss 21 is represented by a point 25. The purpose of this eccentricity will be pointed out below. The boss 21 may be provided with flanges 27 and 29 between which a ring 31 is mounted for rotation about the boss 21. If desired, the hub 7, the boss 21 and the flanges 27 and 29 may be molded as a unit from suitable insulating material such as phenolic resin.

To facilitate mounting of the ring 31, it may be of split construction. To this end a support for the movable contact 17 may be constructed of a strip 33 of electroconductive material which has a semicylindrical portion 35 forming one-half of the ring 31. A second strip 37 has a semicylindrical portion 39 constituting the remainder of the ring 31. By inspection of Fig. 2, it will be noted that the strip 37 has a lip 41 which extends through an opening 43 in the strip 33 and underlies the strip 33. A machine screw 45 is provided for securing the right-hand ends of the

strips

33 and 37 to each other.

Preferably, the movable contact 17 is rigidly secured to the ring 31. In order to provide rigidity with minimum weight, a brace member 47 is secured to the portion of the ring 31 formed by the strip 33 and to the lefthand end of the strip 33 to form a rigid truss. A stop 49 secured to the stator structure limits movement of the movable contact 17 in a counterclockwise direction, as viewed in Fig. 2. A counterweight 51 may be employed for balancing the structure supporting the movable contact 17.

The rotor structure 1 is biased in a counterclockwise direction as viewed in Fig. 2 by means of a spiral control spring 53 which has its outer end secured to the stator structure and which has its inner end secured to a lug 55 which forms part of the strip 33.

The ring 31 and the boss 21 are configured to provide a tapered or wedge-shaped space therebetween. Such a space may be readily provided by forming a flat surface 57 on the boss 21 which terminates at a step 59. An element is disposed in this space for the purpose of providing a wedging action between the ring 31 and the boss 21 as the movable contact 17 is forced against the stationary a 3 contact 19 To this end a rib 61 is secured to the semicylindrical portion 35 and is located in the tapered space formed by the flat surface 57 and the step 59.

The surface of the boss 21 which engages the ring 31 preferably is of a material offering low friction to rotation of the ring 31 relative to the boss. The portion of the boss which engages the rib 61 preferably is of a material which absorbs energy. Although the entire boss may be constructed of a material suitable for these purposes preferably a surface layer is applied to the boss which provides the desired properties. To this end a strip of material, such as a superpolyamide, may be positioned on the surface of the boss 21. Such a material is available on the market under the trade name nylon. Preferably, however, the strip 63 is a polytetrafluoroethylene. Such a material is available under the trade name Teflon. it offers low friction to rotation of the ring 31 and forms a sink capable of absorbing substantial energy as the rib 61 wedges against the strip 63. Preferably, the strip 63 is located in position by the boss 21 and the ring 31 and is not cemented or secured to either of these parts. This construction enhances absorption of energy produced by relative movement of the boss and the ring.

Preferably, the stationary contact 19 is of rigid construction. However, if desired, the stationary stop con tact may be spring mounted in a conventional manner to permit a very small deflection thereof as the movable contact 17 is forced against the stationary contact. The movement of the stationary contact under these conditions preferably should not exceed about .006 inch, the preferred maximum movement being about .004 inch.

In operation, the movable contact 17 is held against the stop 49 by the bias developed by the control spring 53 or by a restraint torque or by both the bias and the restraint torque. Such a bias and a restraint torque are well known in the relay art. Under these conditions, the rib 61 is held against the step 59 and the mechanism is ready for a contact making operation.

When the relay is to engage the

contacts

17 and 19, the energy supplied to the windings 15 produces a torque urging the shaft in a clockwise direction as viewed in Fig. 2. When the movable contact 17 engages the stationary contact 119, the shaft 5 continues to rotate. As an example of suitable parameters, the clearances may be such that a force in the range of two to ten grains acting against the movable contact surface sufiices to cause the ring 31 to slip relative to the boss 21. Because of the eccentric mounting of the boss 21 relative to the shaft 5, a lateral motion is imparted to the movable contact 17 which forces the movable contact to move sideways as viewed in Fig. 2 to provide a positive wiping action against the stationary contact 19. This Wiping action punctures any film which otherwise might prevent the making of a good contact, and it also acts to break any'minutewelds which could be caused by arcing of the contacts.

As the shaft 5 continues its rotation, the rib 61 is wedged against the strip 53 to bring the shaft 5 to a gradual stop. During this Wedging action, the strip 63 acts to absorb the energy produced by the relative movement of the ring 31, and the boss 21 and the shaft 5 come to rest without rebound of the contacts.

Some improvement in the operation of the relay may be effected by introducing small spacers between the ring 31 and the adjacent strip. For example, the spacers may be produced by forming one or more discontinuities, dimples or projections in the material of the ring. As shown clearly in Fig. 3, the semicylindrical portion 35 of the strip 33 has two

small dimples

65 and 67 which are spaced from each other in a direction parallel to the axis of the ring and which project slightly from the semicylindrical surface towards the strip 63. These dimples introduce a space which prevents the boss Zll and strip 63 from rolling up the surface of the ring 31. Specifically, the dimples prevent a side force from being developed against one member of the truss and thereby causing the member to bend in response to the force and then rebound upon removal or reduction of the force.

Engagement of the

contacts

17 and 19 may be employed for controlling a circuit in a mannerwell understood in the relay art.

Although the invention has been described with reference to certain specific embodiments, numerous modifications are possible, Therefore, the illustrations and description herein presented are to be construed in an illustrative rather than in a limiting sense.

We claim as our invention:

1. In a relay device for controlling an electrical circuit, a stator structure including a fixed electrical contact, a rotor structure mounted for a first revolution relative to the stator structure about a first axis, a movable contact, and mounting means mounting the movable contact on the rotor structure for actuation by the rotor structure into and out of engagement with the fixed electrical contact, said mounting means mounting the movable contact for revolution about an axis relative to the rotor structure, and said mounting means including friction means for increasing the friction acting between the movable contact and the rotor structure as the rotor structure revolves about the first axis in contact-engaging direction.

2. In a relay device for controlling an electrical circuit, a stator structure including a fixed electrical contact, a rotor structure mounted for a first revolution relative to the stator structure about a first axis, a movable contact, and mounting means mounting the movable contact on the rotor structure for actuation by the rotor structure into and out of engagement with the fixed electrical contact, said mounting means mounting the movable contact for revolution about an axis relative to the rotor structure, and said mounting means including friction means for increasing the friction acting between the movable contact and the rotor structure as the rotor structure revolves about the first axis in contact-engaging direction, said mounting means including means for limiting revolution of the movable contact relative to the rotor structure as the rotor structure revolves about the first axis in contact-disengaging direction.

3. In a relay device for controlling an electrical circuit, a stator structure including a fixed electrical contact, a rotor structure mounted for a first revolution relative to the stator structure about a first axis, a movable contact, and mounting means mounting the movable contact on the rotor structure for actuation by the rotor structure into and out of engagement with the fixed electrical contact, said mounting means mounting the movable contact for revolution about an axis relative to the rotor structure, and said mounting means including friction means for increasing the friction acting between the movable contact and the rotor structure as the rotor structure revolves about the first axis in contact-engaging direction, said friction means comprising a friction device and a driving part coacting to form a friction coupling, one of said parts being formed of energy-absorbing material, said parts being shaped to produce a wedging action therebetween as the rotor structure rotates in contact-engaging direction.

4. In a relay device for controlling an electrical circuit, a stator structure including a fixed electrical contact, a rotor unit mounted for a first revolution relative to the stator structure about a first axis, a movable contact unit and mounting means mounting the movable contact unit on the rotor unit for actuation by the rotor unit into and out of engagement with the fixed electrical contact, said mounting means comprising a cylindrical part secured to a first one of the units and having an axis parallel to the first axis, a tubular part secured to a second one of the units for rotatably receivingsaid'cylindrical part, one of said parts having an axially-extending notch defining. a Wedge-shaped space between the two parts and the other of the parts having a rib projecting into the space, said space tapering in a direction such that the rib is gradually wedged against the notch surface as the rotor unit rotates in contact-engaging direction.

5. In a relay device for controlling an electrical circuit, a .stator structure including a fixed electrical contact, a rotor structure mounted for a first revolution relative to the stator structure about a first axis, a movable contact and mounting means mounting the movable contact on the rotor structure for actuation by the rotor structure into and out of engagement with the fixed electrical contact, said mounting means comprising a cylindrical part secured to the rotor structure and having an axis parallel to the first axis, a tubular part secured to the movable contact for rotatably receiving said cylindrical part, one of said parts having an axially-extending notch defining a wedgeshaped space between the two parts and the other of the parts having a rib projecting into the space, said space tapering in a direction such that the rib is gradually wedged against the notch surface as the rotor structure rotates in contact-engaging direction, said part having the notch being provided with a surface formed of lowfriction, energy-absorbing material.

6. In a relay device for controlling an electrical circuit, a stator structure including a fixed electrical. contact, a rotor structure mounted for a first revolution relative to the stator structure about a first axis, a movable contact and mounting means mounting the movable contact on the rotor structure for actuation by the rotor structure into and out of engagement with the fixed electrical contact, said mounting means comprising a cylindrical part secured to the rotor structure and having an axis parallel to the first axis, a tubular part secured to the movable contact for rotatably receiving said cylindrical part, said cylindrical part having an axially extending notch in its surface defining a wedge-shaped space between the two parts, said tubular part having a rib projecting into said space, and having spacer means engaging the cylindrical surface of the part to space such part slightly from the tubular part at a position spaced from the notch, said cylindrical part having at least a surface layer of low-friction, energyabsorbing material, said space tapering in such a direction that the rib is gradually wedged against the notch surface as the rotor structure rotates in contact-engaging direction, and stop means limiting movement of the movable contact in contact-disengaging direction.

7. In a relay device for controlling an electrical circuit, a stator structure including a fixed electrical contact, a rotor unit mounted for a first revolution relative to the stator structure about a first axis, a movable contact unit and mounting means mounting the movable contact unit on the rotor unit for actuation by the rotor unit into and out of engagement with the fixed electrical contact, said mounting means comprising a cylindrical part secured to a first one of the units and having an axis parallel to the first axis, a tubular part secured to a second one of the units for rotatably receiving said cylindrical part, one of said parts having a small projection extending radially towards the other of said parts to introduce a small spacing between such parts adjacent the projection.

8. In a relay device for controlling an electrical circuit, a stator structure including a fixed electrical contact, a rotor unit mounted for a first revolution relative to the stator structure about a first axis, a movable contact unit and mounting means mounting the movable contact unit on the rotor unit for actuation by the rotor unit into and out of engagement with the fixed electrical contact, said mounting means comprising a cylindrical part secured to a first one of the units and having an axis parallel to the first axis, a tubular part secured to a second one of the units for rotatably receiving said cylindrical part, one of said parts having an axially-extending notch defining a wedge-shaped space between the two parts and the other of the parts having a rib projecting into the space, said space tapering in a direction such that the rib is gradually wedged against the notch surface as the rotor unit rotates in contact-engaging direction, and a plurality of small spacers located between small areas of said parts to space said parts radially from each other adjacent the spacers, said spacers being spaced from each other in a direction substantially parallel to said axes.

References Cited in the file of this patent UNITED STATES PATENTS 1,660,197 Holte Feb. 21, 1928 2,422,861 Skrobisch June 24, 1947 2,499,632 Coake Mar. 7, 1950 2,661,404 Wasserman Dec. 1, 1953