US3651294A

US3651294A - Contact assembly with an unchangeable switching state at the instant of welding

Info

Publication number: US3651294A
Application number: US14524A
Authority: US
Inventors: Heinz Dames; Gerhard Furtwaengler
Original assignee: Siemens Corp
Current assignee: Siemens AG; Siemens Corp
Priority date: 1969-03-10
Filing date: 1970-02-26
Publication date: 1972-03-21
Anticipated expiration: 1989-03-21
Also published as: DE1912077C2; YU56970A; DE1912077B1; ES377093A1; CH504094A; SE372998B; ZA701569B; GB1257141A; FR2037906A5; PL71265B1; NL7002851A; DK123195B; JPS4919897B1; YU33030B; NO127997B; NL154358B; BE747138A; AT303180B

Abstract

A contact arrangement such as a relay having at least a pair of substantially stationary contact springs and a movable contact spring which are mounted with the movable contact spring disposed between the pair of stationary springs characterized in that the substantially stationary contact springs have a portion extending at an angle of at least 10* to the movable contact spring so that a welding of the movable contact spring to either one of the stationary contact springs caused by arcing therebetween provides a rigid triangular structure to prevent movement of the movable contact spring into engagement with the other stationary contact spring and a short circuiting between the two stationary contact springs. Preferably the movable contact spring is moved by an actuating means having an operating member forming a connection with the movable contact spring which is either a conical slot or a ball shaped slot receiving an end of the movable contact member to guide the movable contact spring without play. To further resist movement of the substantially stationary contact springs, in a direction toward the other stationary contact spring, a support plate is provided for each of the stationary contact springs.

Description

United States Patent Dames et al.

[4 Mar. 21, 1972 CONTACT ASSEMBLY WITH AN UN CHANGEABLE SWITCHING STATE AT THE INSTANT OF WELDING [72] inventors: Heinz Dames; Gerhard Furtwaengler, both of Munich, Germany [73] Assignee: Siemens Aktiengesellschaft, Berlin and Munich, Germany 22 Filed: Feb. 26, 1970 [21] App1.No.: 14,524

Primary Examiner-H. 0. Jones Attorney-Hill, Sherman, Meroni, Gross & Simpson [57] ABSTRACT A contact arrangement such as a relay having at least a pair of substantially stationary contact springs and a movable contact spring which are mounted with the movable contact spring disposed between the pair of stationary springs characterized in that the substantially stationary contact springs have a portion extending at an angle of at least 10 to the movable contact spring so that a welding of the movable contact spring to either one of the stationary contact springs caused by arcing therebetween provides a rigid triangular structure to prevent movement of the movable contact spring into engagement with the other stationary contact spring and a short circuiting between the two stationary contact springs. Preferably the movable contact spring is moved by an actuating means having an operating member forming a connection with the movable contact spring which is either a conical slot or a ball shaped slot receiving an end of the movable contact member to guide the movable contact spring without play. To further resist movement of the substantially stationary contact springs, in a direction toward the other stationary contact spring, a support plate is provided for each of the stationary contact springs.

10 Claims, 6 Drawing Figures BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is directed to a contact assembly in particular a contact assembly used as a relay assembly.

2. Prior Art Contact assemblies of the conventional construction have a movable contact spring disposed between a pair of substantially stationary contact springs with each of the contact springs being approximately parallel to one another. The as sembly is provided with actuating means such as an armature which shifts the movable contact from one switching step or position of engagement with one of the stationary contact springs to another switching stage with engagement with the other of the pair of stationary contacts. To minimize the distance of travel of the movable contact spring, the distance between the two stationary contact springs is at a minimum and each of the stationary contact springs is flexible to allow a slight movement upon engagement by the movable contact spring to prevent chattering of the contact or relay assembly. lf arcing occurs as the movable contact engages one of the stationary contact springs, the two contact springs will become fused or welded together. With a subsequent switching signal, the welded contact springs will move into engagement with the other stationary contact spring to cause an undesirable circuit connection between the two stationary contact springs. Such a circuit connection often causes damage to the elements of the circuit connected to each of the stationary contacts. One solution proposed to prevent the formation of the short circuit between the two stationary contact springs after welding has occurred is the provision of a racket or support plate for each of the stationary contacts which plate increases the resistance of the stationary contact spring to movement towards each other. However, the support plates will also be deflected by movement of the actuating means during a switching change and flex or be deflected a sufficient amount to allow formation of the short circuit between the two stationary contact springs.

Conventional contact arrangements such as relays are also provided with an operating member attached to the actuating means and connected by a slot arrangement with the movable contact spring. Due to the size of the slot, a lost motion connection is formed which provides play between the member of the actuating means and the movable contact which is undesirable.

SUMMARY OF THE INVENTION The present invention is directed to a contact assembly in which the stationary contact springs are provided with a portion extending at an angle of at least to the movable contact spring so that upon welding of the movable contact spring to the stationary spring a triangular arrangement or bracing is formed to prevent movement towards the other stationary contact spring and to prevent an inadvertent formation of a circuit between the two stationary contact springs. In the preferred embodiment support plates or brackets are provided to increase the rigidity of each of the stationary contact springs and to increase the rigidity of the triangular configuration. The present invention also contemplates providing connecting means between an operating member of the actuating means and the movable contact to guide the movable contact spring without play. In the preferred embodiments, the connecting means is the provision of a conical or tapered slot receiving an end of the contact spring or a ball-shaped slot both of which provide contact engagement with the contact spring while enabling relative pivotal movement therebetween.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a contact assembly of the conventional construction for the purpose of explaining the problems in accordance with the invention.

FIG. 2 is the contact assembly of the present invention.

FIG. 2a is an enlarged partial view of a'connection between the operating member and movable contact spring of FIG. 2.

FIG. 2b is an enlarged partial view of an embodiment of the connection.

FIG. 20 is an enlarged partial view of another embodiment of the connection.

FIG. 2d is a partial view of an embodiment of the contact assembly of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT To aid in the description of the preferred embodiments of the present invention, a conventional electromagnetic relay is illustrated in FIG. 1, and includes an actuating means illus trated as an electromagnetic system of an iron core 1 disposed in an exciter coil 2 with the core and coil mounted on a yoke 3. A contact assembly 4 is mounted on a portion of the yoke by appropriate means such as the attachment screw 4a. The actuating means also includes an armature 7 having the armature arm 8 supporting an operating member 9. The armature 7 is supported for pivotal motion on the yoke 3 to move between the rest position illustrated and a position where the armature 7 in contact with the core 1 when an electrical current is passed to the exciter coil 2.

The contact assembly 4 has a plurality of

contact springs

40 and 4d supported in a substantially parallel arrangement in a stack by a mounting means 10 which is illustrated as comprising a plurality of blocks or members of an insulation type material held together by the screw 4a. As illustrated, contact spring 4d is a movable contact spring which is disposed between a pair of spaced substantially stationary contact springs 40. Each of the

contact springs

4c and 4d are flexible to prevent chattering of the relay during a switching change as the moveable contact spring 4d moves into engagement with either one of the stationary contact springs 40. To provide additional support for the substantially stationary contact spring 40, support brackets or plates 4b are provided for each of the stationary contact springs and are supported in the mounting means 10.

To connect the movable contact spring 4d to the actuating means, the operating member 9 is provided with a slot or opening 9a which receives an end or a portion of the end of the movable contact spring 4d to form a connection. Due to the size of the slot 9a, the connection is a lost motion connection having considerable play in transferring the motion of the armature 7 to the movable contact 4d.

In operation, with the electromagnetic system deactivated, the armature 7 assumes the rest position, as illustrated, to provide a rest switching position with the movable contact 4d in contact with the lower stationary contact 4c. When electrical current is received by the exciter coil 2, the armature 7 is moved toward the core I with a pivotable movement and applies a force to the movable contact 4d to disengage it from the lower stationary contact 40 and engage the upper stationary contact 40 of the contact assembly 4. As mentioned hereinabove, the spacing between the two stationary contacts 40 is at a minimum to reduce the necessary travel of the movable contact 4d during shifting of the switching state, and to prevent relay chatter, the stationary contact springs 40 are flexible and can yield when engaged or contacted by the movable contact 4d.

In operation, if an arcing occurs during the formation of an engagement or contact between the movable contact 4d and one of the stationary contacts 40, the resulting heat causes fusion of the two contacts to weld the movable contact spring to one of the stationary contacts 40 to form a weld arrangement. When the switching state of the assembly changes due to a change in the input to the electromagnetic system, the welded arrangement of the movable contact 4d and a stationary contact will move to engage the other stationary contact and create a short circuit between the two stationary contact springs 4c. The provision of the support brackets or plates 4b offer resistance to the movement of the welded arrangement,

however due to the size of the contact spring 4c and the support brackets 4b and their parallel arrangement, the force causing the shifting in the switching state can overcome the resistance allowing sufficient movement to create the short circuit.

The principles of the present invention are best illustrated in FIG. 2 in which the contact arrangement 4 is mounted on a yoke 3 by a suitable fastener means such as 4a which yoke 3 supports the electromagnetic system which includes the core 1, the coil 2, and the armature 7 with its armature arm 8 which supports the operating member 9.

The contact assembly 4 includes the plurality of contact springs 40' and 4d which are supported in a mounting means 10'. Each of the substantially stationary contact springs 4c'has

parallel portions

11 and 12 with a portion 13 which extends therebetween at an angle P which is at least 10. When the contact springs are supported in the mounting means 10, the portions 11 are arranged to be parallel to the movable contact spring 4d so that the portion 13 of the stationary contact springs extends at the angle 7 with respect to the movable contact spring 4d. As illustrated, support brackets or plates 4b which extend substantially parallel to movable contact 4d are provided. The mounting means 10 is similar to the mounting means 10 with the addition of blocks 14 which are disposed between each support bracket or plate 4b and the parallel portion 11 of its respective stationary contact springs 4c. The portion 13 which extends at an angle to the movable contact spring 4 d enables the portions 12 to be spaced the same distance apart while the other parallel portions 11 are spaced a greater distance from the movable contact 4d.

When arcing occurs between the movable contact 4d and one of the stationary contacts 40 to form a welded arrangement, a triangular structure which has a leg equal to the spacing between portions 11 and contact spring 4d is formed which triangular structure increases the rigidity of the welded arrangement to prevent the inadvertent movement of the welded arrangement into electrical contact with the other stationary contact 4c and therefore prevents the inadvertent short circuiting between the circuits of the spaced stationary contacts 40. The provision of the support brackets or plates 4b increases the resistance of the movement of the contact spring 40' towards the other contact spring. While each of the support brackets or plates 4b is illustrated in FIG. 2 as extending parallel to the movable contact 4d, it may be desirable to have support brackets or plates 41; (FIG. 2d) formed with the same configuration as the spring contact 40 with a parallel portion and a portion extending at an angle 7 The preferred embodiment also contemplates a change in the connection between the movable contact spring 4d and the operating member 9. By providing a tapered or conical slot or opening 9a (FIG. 2a) for receiving the end of the contact spring 4d, the narrowest portion of the slot 9a engages both surfaces of the movable contact spring 4d while providing a pivot point to allow pivoting movement between the operating member 9 and movable contact 4d. Such an arrangement results in a connection between the operating member 9 and the movable contact spring 4d which guides the movement of the operating spring 4d without play. It is also contemplated that instead of using a slot 9a having a tapered or conical cross section a slot such as 9a (FIG. 2b) or 9a' (FIG. 20) having a ball shape with a circular cross section forming a narrow slot to provide pivot points for engaging the movable contact 4d can also be utilized to provide the desired guiding without play of the movable contact spring 4d during changes in the switching state.

Although minor modifications might be suggested by those versed in the art, it should be understood that we wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of our contribution to the art.

We claim as our invention:

1. ln a contact assembly having at least one movable contact spring and a pair of substantially stationary contact springs which are arranged in a mounting means with the movable contact spring disposed between the pair of stationary contact springs and with each of the springs having a portion gripped between insulating members in a parallel and spaced relationship, said assembly including an actuating means engaging a free end of the movable contact spring to selectively switch it from a position forming a contact with a free end of one of said pair of stationary contact springs to a position forming a contact with a free end of the other of said pair, the improvement comprising each of the stationary contact springs having a second portion extending at an angle to first mentioned portion from adjacent said insulating members to form an angle of at least 10 with the movable contact spring, said second portion having a length substantially equal to the length of the movable contact spring so that when the movable contact spring becomes welded to either of the pair of stationary contact springs, said movable contact spring, the second portion of the stationary contact spring welded thereto and the insulating member disposed therebetween form a rigid triangular configuration to prevent further movement of the movable contact spring during switching by the actuating means to prevent short circuiting of the pair of stationary contact springs.

2. In a contact assembly according to claim 1, wherein the actuating means includes an armature arm having an operating member carried thereon, said operating member engaging the movable contact spring forming a connection therewith to guide the movable contact spring without play during actuation of the armature arm.

3. In a contact assembly according to claim 11, which further includes a bracket plate associated with each of the stationary contact springs, each of said bracket plates being gripped in the mounting means and having a portion extending out of the mounting means to engage its respective stationary contact spring adjacent to the free endthereof to provide support for the stationary contact spring and to increase the resistance of the stationary contact spring against movement in a direction towards the movable contact spring.

4. In a contact assembly according to claim 3, wherein said bracket plates extend parallel to the movable contact spring and are disposed in said mounting means in spaced relationship to the first mentioned portion of their respective stationary contact springs.

5. In a contact assembly according to claim 3, wherein the bracket plates have the configuration of the stationary contact springs.

6. A contact assembly according to claim 3, wherein said actuating means includes an armature arm carrying an operating member having a connection with the movable contact spring formed by a conical slot receiving the free end of the movable contact spring to guide the movement of the movable contact spring without play.

7. In a contact assembly according to claim 3, wherein said actuating means includes an armature arm carrying an operating member having a ball-shaped slot receiving the free end of the movable contact spring forming a connection therewith for guiding the movable contact spring without play.

8. In a contact assembly having at least one movable contact spring and a pair of substantially stationary contact springs which are arranged in a stack by mounting means with the movable contact spring disposed between the pair of stationary contact springs and with each of the springs having a portion gripped between insulating members in a parallel and spaced relationship, said assembly including an actuating means engaging a free end of the movable contact spring to selectively switch it from a position forming a contact with a free end of one of said pair of stationary contact springs to a position forming a contact with a free end of the other of said pair, the improvement comprising each of the stationary contact springs having a second portion extending at an angle to first mentioned portion from adjacent said insulating members to form an angle of at least 10 with the movable contact spring and said actuating means including an operating tact springs.

9. A contact assembly according to claim 8, wherein the connection between the operating member and the movable contact spring comprises a conical slot receiving the free end of the movable contact spring.

10. In a contact assembly according to claim 8 wherein the connection between the operating member and the movable contact spring comprises a ball-shaped slot receiving the free end of the movable contact spring.

Claims

1. In a contact assembly having at least one movable contact spring and a pair of substantially stationary contact springs which are arranged in a mounting means with the movable contact spring disposed between the pair of stationary contact springs and with each of the springs having a portion gripped between insulating members in a parallel and spaced relationship, said assembly including an actuating means engaging a free end of the movable contact spring to selectively switch it from a position forming a contact with a free end of one of said pair of stationary contact springs to a position forming a contact with a free end of the other of said pair, the improvement comprising each of the stationary contact springs having a second portion extending at an angle to first mentioned portion from adjacent said insulating members to form an angle of at least 10* with the movable contact spring, said second portion having a length substantially equal to the length of the movable contact spring so that when the movable contact spring becomes welded to either of the pair of stationary contact springs, said movable contact spring, the second portion of the stationary contact spring welded thereto and the insulating member disposed therebetween form a rigid triangular configuration to prevent further movement of the movable contact spring during switching by the actuating means to prevent short circuiting of the pair of stationary contact springs.

3. In a contact assembly according to claim 11, which further includes a bracket plate associated with each of the stationary contact springs, each of said bracket plates being gripped in the mounting means and having a portion extending out of the mounting means to engage its respective stationary contact spring adjacent to the free end thereof to provide support for the stationary contact spring and to increase the resistance of the stationary contact spring against movement in a direction towards the movable contact spring.

8. In a contact assembly having at least one movable contact spring and a pair of substantially stationary contact springs which are arranged in a stack by mounting means with the movable contact spring disposed between the pair of stationary contact springs and with each of the springs having a portion gripped between insulating members in a parallel and spaced relationship, said assembly including an actuating means engaging a free end of the movable contact spring to selectively switch it from a position forming a contact with a free end of one of said pair of stationary contact springs to a position forming a contact with a free end of the other of said pair, the improvement comprising each of the stationary contact springs having a second portion extending at an angle to first mentioned portion from adjacent said insulating members to form an angle of at least 10* with the movable contact spring and said actuating means including an operating member having means engaging the free end of said movable contact spring to guide its movement without play during switching so that when the movable contact spring becomes welded to either of the pair of stationary contact springs, said movable contact spring, the second portion of the stationary contact spring welded thereto and the insulating member disposed therebetween form a rigid triangular configuration to prevent further movement of the movable contact spring and the operating member during switching by the actuating means to prevent short circuiting of the pair of stationary contact springs.