GB2072949A

GB2072949A - Electrical switches

Info

Publication number: GB2072949A
Application number: GB8108400A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1980-03-29
Filing date: 1981-03-18
Publication date: 1981-10-07
Also published as: IT8120782A0; DE3012354A1; DE3012354C2; DE8008801U1; JPH0142454B2; FR2479555B1; GB2072949B; JPS56152131A; FR2479555A1; IT1136875B

Abstract

A fixed contact (19) of an electromagnetic switch is adjusted into a desired position by providing at least one indentation (22) in a region (20c) of a contact angle bracket (20) having a bottom end (20b) secured to a support plate (11) and a top end (20a) bent at right angles and carrying the fixed contact (19), the indentation (22) being formed for the purpose of elongating that region (20c) of the contact angle bracket. A support (26) is introduced at one side of the contact angle bracket (20) and the indentation (22) is stamped in the contact angle bracket (20) by a stamping die (23). A backstop for the armature may be adjusted in a similar manner. <IMAGE>

Description

SPECIFICATION Improvements in or relating to electrical switching elements, preferably electromagnetic switches and methods of adjusting them The present invention relates to electrical switching elements, preferably electromagnetic switches, and methods of adjusting them.

One form of electrical switching element comprises a contact angle bracket whose bottom end is secured to a support plate and is provided with an electrical connection, and whose top end is bent at right angles and carries a fixed contact which cooperates with a switching contact of a movable member. In one such electrical switching element which is an electromagnetic relay the distance between the contact is adjusted by rebending the angled upper end having the fixed contact. Since the contact angle bracket yields resiliently in the first instance when the contacts are adjusted in this manner, a check measurement has to be made after each bending operation.

Thus, this method is expensive and cannot be readily automated. The bending operation is effected on the contact angle bracket and might have to be repeated several times in order to bring the contact into a desired position. Moreover, the contact can readily assume a sloping position when this method is used, thus leading to increased burning or pitting of the contacts.

According to one feature of the present invention an electrical switching element, preferably an electromagnetic switch having a magnetic core, an excitation winding and a movable magnetic armature, comprises a contact angle bracket whose bottom end is secured to a support plate and is provided with an electrical connection, and whose top end is at right angles and carries a fixed contact which cooperates with a switching contact of a movable member, and, in order to adjust the fixed contact into a desired position, that region of the contact angle bracket which is below the top end bent at right angles is provided with at least one indentation for the purpose of elongating this region.

An electrical switching element embodying the present invention has the advantage that after springing of the fixed switching contact is virtually eliminated by elongating the contact angle bracket. The adjustment of fixed switching contacts and of predetermined distances between the contacts can then be fully automated and thus substantially simplified.

It is particularly advantageous to dispose several smaller indentations adjacent to one another, whereby to elongate the contact angle bracket by a predetermined small amount with each indentation.

According to another feature of the present invention there is provided a method of adjusting a fixed contact of an electrical switching element in which a support is introduced at one of the sides of a contact angle bracket, and at least one identation for elongating the contact angle bracket is then stamped in that side of the contact angle bracket which is remote from the support by means of a stamping die having at least one cutting edge.

The invention will be further described by way of example with reference to the accompanying drawing which is an elevational view of a power delay, drawn to an enlarged scale, and illustrating a method adjusting a fixed switching contact fully automatically by a stamping die.

A power relay which can be used for, for example, switching the glow plugs of a diesel engine, is designated 10 in the drawing. A magnetic angle bracket 12 is secured to a support plate 11 of the relay 10 and carries a magnetic core 1 3 (indicated by broken lines) having an excitation winding 14. A magnetic armature 1 5 is pivotably secured to the top end of the magnetic angle bracket 12 and carries a leaf spring 1 6 having a first switching contact 1 7.When in its normal or rest position, the magnetic armature 1 5 is raised from the magnetic core 13 by a tension spring 1 8. A fixed switching contact 1 9 cooperates with the first switching contact 1 7 and is located on a top end 20a, bent at right angles, of a contact angle bracket 20 whose bottom, bent end 20b is secured to the support plate 11 and is provided with an electrical connection 21.

In order to adjust the fixed switching contact 1 9 into a desired position, that region 20c of the contact angle bracket 20 which is located below the angled top end 20a is provided with a plurality of indentations 22 which are located adjacent to one another and which extend over the entire width of the contact angle bracket 20. The indentations 22 are produced by a stamping die 23 and elongate the region 20c of the contact angle bracket 20. The end face of the stamping die 23 incorporates two cutting edges 24 which are located adjacent to one another and which dig into the material of the contact angle bracket 20 when the stamping die is advanced in the direction of the arrow 25.Astable support 26 is inserted at that side of the contact angle bracket 20 which is remote from the indentations 22 and absorbs the pressure of the stamping die 23. The stamping die 23 is operated by a stamping device 27 which is illustrated diagrammatically.

The fixed switching contact 19 can be adjusted fully automatically relative to the switching contact 1 7 on the magnetic armature 1 5 if the power relay 10 is placed into a reception device after the relay 10 has been assembled. A gauge 28 of predetermined thickness is then introduced at the narrowest location between the magnetic armature 16 and the magnetic core 13. The support 26 is also introduced at that side or the contact angle bracket 20 which is remote from the indentations 22. The two switching contacts 1 7 and 1 9 are connected by way of the terminal 21 and a terminal 29 of the magnetic angle bracket 12 to an electrical circuit 30 which also includes the stamping device 27.The magnetic armature 1 5 is then pressed towards the magnetic core 1 3 by a force acting in the direction of the arrow 31, so that the gauge 28 is rigidly clamped between the magnetic armature 1 5 and the magnetic core 1 3. In the simplest case, the magnetic armature 1 5 is pulled in by applying a voltage to the excitation winding 14. The switching contact 17 on the magnetic armature thereby assumes a predetermined position in which it is not yet in contact with the fixed contact 19. Thus, the electrical circuit 30 is not yet closed. The first two indentations 22 are then stamped in the contact angle bracket 20 by means of the stamping die 23.The region 20c of the contact angle bracket 20 is thereby elongated to raise the switching contact 19 by a predetermined amount of, for example, 0.2 mm.

If the switching contact 1 9 has still not come in contact with the oppositely located switching contact 17 of the magnetic armature 1 5, the power relay 10 is then raised relatively to the stamping die 23 by twice the width of an indentation 22. The stamping die 23 is then actuated again by a further step in the direction of the arrow 25, and the cutting edges 24 stamp two further indentations 22 in the contact angle bracket 20. The electrical circuit 30 is closed as soon as the switching contact 19 comes into contact with the oppositely located switching contact 1 7 during the stamping operation. The switching contact 1 9 has then assumed its predetermined position and, with the closing of the electrical circuit, the stepwise operating stamping die is stopped by means of the stamping device 27.The gauge 28 and the support 26 are removed, and the adjusted power relay can be removed from the reception device.

The invention is not confined to the illustrated embodiment, since the switching contacts of other electrical switching elements can also be adjusted by the elongation, in accordance with a method embodying the present invention, of a contact carrier. It is essential that the indentations should be made in a region of the contact carrier which lies parallel to the axis of the switching contact, so that the switching contact is raised by the elongation of the contact carrier caused by the indentations. It is also possible to provide only one cutting edge on the end face of the stamping die 23. In this case, several indentations are stamped successively in the contact angle bracket by the stamping die 23, the depth of penetration being limited by the height of the cutting edge of the stamping die.When making the last indentations, closing of the electrical circuit prevents the cutting edge of the stamping die from being pressed fully into the contact angle bracket, so that the depth of penetration is less than the height of the cutting edge of the stamping die.

If it is desired to adjust the switching contact by only one stamping operation, the stamping die is preferably provided with a plurality of cutting edges of stepped height. When using a stamping die of this kind, the contact carrier is continuously elongated when stamping the indentations. The stamping operation is terminated as soon as the electrical circuit is closed, and the switching contact has then been adjusted to its desired position.

By way of example, a power relay having an advance or leading fixed contact can also be adjusted by indentations made by a method embodying the present invention, wherein, after the main fixed contact has been adjusted, indentations in the contact angle bracket of the advance fixed contact raise the advance fixed contact relative to the main fixed contact to an extent that the advance contacts lead the main contacts by a predetermined amount upon closing of the relay. The stop for the magnetic armature, which determines the distance between the contacts when the relay is switched off, can also be adjusted in a similar manner.

Claims

1. An electrical switching element, preferably an electromagnetic switch having a magnetic core, an excitation winding and a movable magnetic armature, comprising a contact angle bracket whose bottom end is secured to a support plate and is provided with an electrical connection, and whose top end is bent at right angles and carries a fixed contact which cooperates with a switching contact of a movable member, in which, in order to adjust the fixed contact into a desired position, that region of the contact angle bracket which is below the top end bent at right angles is provided with at least one indentation for the purpose of elongating this region.

2. A switching element as claimed in claim 1, in which the or each indentation extends transversely over the width of the contact angle bracket.

3. A switching element as claimed in claim 2, in which a plurality of indentations are located adjacent to one another.

4. A switching element as claimed in claim 1, 2 or 3, which is an electromagnetic switch and the movable member is a movable magnetic armature.

5. A method of adjusting a fixed contact of an electrical switching element as claimed in any of claims 1 to 4, in which a support is introduced at one of the sides of a contact angle bracket, and at least one indentation for elongating the contact angle bracket is then stamped in that side of the contact angle bracket which is remote from the support by means of a stamping die having at least one cutting edge.

6. A method as claimed in claim 5, in which several indentations are successively stamped in the contact angle bracket by the stamping die and their depth of penetration is limited by the height of the cutting edge or edges of the stamping die.

7. A method as claimed in claim 6, in which, in the case of the last indentation, the stamping die is pressed into the contact angle bracket only to an extent that the depth of penetration is less than the height of the cutting edge of the stamping die.

8. A method as claimed in claim 7, in which the switching contact of the movable member is first brought into a predetermined position, the two cooperating contacts are connected to an electrical circuit, and in which during the stamping of the indentations the electrical circuit is closed by said contacts when the fixed contact has reached the desired position.

9. A method as claimed in claim 8, in which stepwise operation of the stamping die is stopped in response to closure of said electrical circuit.

10. A method as claimed in claims 8 or 9, in which the switching element is an electromagnetic switch having a magnetic core, an excitation winding and a movable magnetic armature serving as said movable member, and in which a gauge of predetermined thickness is inserted at the narrowest location between the magnetic armature and the magnetic core before the indentations are stamped, and the magnetic armature is then pulled towards the magnetic core so that the switching contact on the magnet armature is thereby brought into a predetermined position.

11. An electrical switching element constructed and arranged and adapted to operate substantially as hereinbefore particularly described with reference to and as illustrated in the accompanying drawing.

12. A method of adjusting an electrical switching element, substantially as hereinbefore particularly described with reference to and as illustrated in the accompanying drawing.