GB2184889A

GB2184889A - Quick-break switch

Info

Publication number: GB2184889A
Application number: GB08628932A
Authority: GB
Inventors: Edwin Czarnetzki
Original assignee: Alfred Teves GmbH
Current assignee: Continental Teves AG and Co oHG
Priority date: 1985-12-21
Filing date: 1986-12-03
Publication date: 1987-07-01
Also published as: GB2184889B; FR2592209B1; GB8628932D0; FR2592209A1; DE3545670A1

Abstract

The switch comprises a contact pair (20, 21) electrically connected by a contact plate (10) which can be disengaged from the contacts by means of an abutting swivel arm (3). A snap switch mechanism formed by a tension spring (4) fastened between the swivel arm (3) and a part (19) formed fast with the housing communicates with an actuating member (5) to effect rapid switching as the actuating member is moved against the spring. The swivel arm is returned by the spring on removal of the actuating force. <IMAGE>

Description

SPECIFICATION Quick-break switch This invention relates to a quick-break switch with a contact pair and with a contact plate which establishes a current-carrying contact between the contacts of the contact pair and which can be disengaged from the contacts by means of a swivel arm, the swivel arm communicating via a snap switch mechanism with an actuating member which is guided within the housing and which, caused by a change in its geometrical position relative to the swivel arm, effects the quick change-over.

A quick-break switch e.g. is known from our prior West German patent application P 35 32 055.9. In said switch the quick changeover operation is effected by the relative movement of an actuating device relative to a switching arm which the actuating device is connected to by means of a snap switch mechanism. While the actuating device is formed by an actuating rod as well as by a sliding element screwed on top thereof, the snap switch mechanism consists of a tension spring, one end of which is fastened at the switching arm and the other end of which is fastened at the sliding element.

The relatively complicated design of this known switch and the thence resulting relatively high number of individual components are to be considered disadvantageous in this switch.

A further disadvantage of such switches consists in that there switching behaviour does not only depend on the distance travelled by the actuating device but also, in a way, on the friction existing between a printed circuit board arranged at the contact surface of the switching arm and the contacts to be connected. This complicates the adjustment of the correct switch points and thus of the differential distance of the switch, too.

It is thus an object of the present invention to provide a switch of the type referred to above where the above-mentioned disadvantages will be avoided. At the same time, the switch is to have a simple design and to be easily manufactured and to allow serial manufacture. It is to allow simple adjustment or regulation and to consist of components to be manufactured at low cost. Further, the number of the required individual components is to be reduced.

According to the present invention there is provided a quick-break switch with a contact pair and with a contact plate which establishes a current-carrying contact between the contacts of the contact pair and which can be disengaged from the contacts by means of a swivel arm, the swivel arm communicating via a snap switch mechanism with an actuating member which is guided within the housing and which, caused by a change in its geometrical position relative to the swivel arm, effects the quick change-over, characterised in that the snap switch mechanism is formed by a tension spring fastened between the swivel arm and a part formed fast with the housing.

The inventive switch having a simple and reliable design achieves a switching behaviour characterised by a hysteresis. This means, that in a first relative position of the actuating member relative to the swivel arm, said position corresponding to the distance travelled by the actuating member, the switch will change over while, upon a subsequent movement of the actuating element in the opposite direction, it will not switch back when said first position is passed but will rather be switched back only when a second position has been passed.

According to an advantageous further development of the inventive subject matter the arrangement of the actuating member and of the tension spring is such as to ensure that, upon the discontinuation of the actuating force, the return of the swivel arm is effected by a force component resulting from the elastic deformation of the tension spring upon the actuation by the actuating member. This measure enables a considerable reduction in the number of individual components as both the return spring required in the known switch is omitted and the actuating member can be designed considerably simpler.

A further preferred embodiment provides that the contact plate is carried by a leaf spring whose elastic bias generates a constant contact force. At its end facing the contact arrangement, the swivel arm of this embodiment is provided with a plane surface as well as with a there-adjoining arched surface having linear contact with the leaf spring in the operating position of the switch. Thanks to this particular measure, a change-over operation will be achieved which will largely be frictionless.

A particularly advantageous embodiment provides that the swivel arm's end averted from the contact arrangement forms a knifeedge support together with a recess provided at a carrier formed fast with the housing. This measure especially simplifies assembly of the inventive switch.

A further feature of this invention, finally, consists in that a stop is provided for the swivel arm, said stop being adjustable from the outside. Thence, there results a particularly simple method of regulating and adjusting the desired differential distance, that is the distance between the switch change-over points.

An embodiment of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a section through an embodiment of switch, said switch being in its "ON" position, Figure 2 is the switch in its "OFF" position, Figure 3 is a plan view of the arrangement of the contact pair with the contact plate, Figure 4 is a graphical representation of the switch's switching behaviour characterised by a hysteresis.

The switch shown in Figures 1, 2 and 3 comprises a housing 1 wherein a contact arrangement 2, 10, a swivel arm 3, as well as a snap switch mechanism are arranged. In the illustrated example, said snap switch mechanism is formed by a tension spring 4. The tension spring 4 is hooked with one of its ends to a suitable connection piece 18 of the swivel arm 3, which is arranged near the swivel arm's 3 end facing the contact arrangement 2, 10. The other end of the tension spring is hooked to a part 19 formed fast with the housing 1.

Co-operating with tension spring 4 is an actuating member 5 which is slidingly guided within a guide 30 of the right-hand housing wall (as seen in the drawing) and which can be acted upon by a force acting from the outside.

The swivel arm 3, one of the ends of which forms a knife-edge support 17 together with a recess 8 provided in a carrier 7 formed fast with the housing, has a plane surface 14 at its other end, said plane surface 14 being adjoined by an arched surface 12. On the one hand, a stationary stop 15 which e.g. may be designed in one piece together with a housing wall and, on the other hand, an adjustable stop 16 formed by a set screw screwed into a threaded bore in another housing wall serve to limit the swivelling movement of the swivel arm 3. Upon actuation of the switch, the actuating member 5 will move along the guide 30 within the housing 1, on its axis two switch points X1, X2 are lying, which switch points are important for the operation of the switch, the meaning of said points will be explained in more detail below.The contact arrangement 2, 10 consists of a contact pair 2 formed by two lugs 20, 21 as well as of a contact plate 10 which, on its part, is carried by a prestressed bow-type spring 11 whose elastic bias generates a constant contact force FK.

in the following, the mode of operation of the inventive switch will be explained in connection with Figure 4 illustrating the switch's switching behaviour characterised by a hysteresis, reference being made to the diagrammatical illustration of the dependence of the contact force FK on the distance SB travelled by the actuating member 5.

These explanations start from the rest position of the system which is shown in Figure 1. The swivel arm 3 is in its first end position corresponding to the "ON" position of the switch.

The contact plate 10 establishes an electri cally conducting contact between the lugs 20, 21 and the swivel arm 3 is kept at the stationary stop 15 by the action of a retaining force which equals the component of the spring force of the prestressed tension spring 4, which acts in this direction. If, at the actuating member 5, the advancing movement thereof is initiated to the left along the guide 30 the angle enclosed between the central axis of the tension spring 4 and the central axis of the swivel arm 3 will diminish until that moment when the central axis of the tension spring 4 and that of the swivel arm 3 will coincide (first switch point X1) when the swivel arm 3 will abruptly change its position and come to abut the adjustable stop 16.

Due to the co-operation of the swivel arm's 3 plane surface 14 and arched surface 12 with the contact-plate-10-carrying bow-type spring 11 the contact plate 10 will be caused to lift off upwards, thereby the electrically conducting contact of the lugs 20, 21 is interrupted. As during this change-over operation there will be no friction between the swivel arm 3 and the bow-type spring 11 co-operating therewith, the first switch point X1 lies at the point of intersection of the swivel arm's 3 central axis with longitudinal axis of the actuating member 5.

Because of the sudden separation of the contact plate 10 from the contact pair 2 the contact force FK will also change to its minimum value FKm,n = O (section 1--22--3-X, in Figure 4). Now the swivel arm 3 will support itself on the adjustable stop 16 whose position determines the switch's second end position ("OFF" position) represented in Figure 2.

Upon the discontinuation of the actuating force acting on the actuating member 5 from the outside, the change-over will occur analogously due to the action of a force constituent resulting from the elastic deformation of the tension spring 4 upon the actuation by the actuating member 5. The swivel arm 3 again will reach its original first end position at that moment when the central axis of the tension spring 4 intersects the longitudinal axis of the actuating member 5 in the second switch point X2. As is evident from Figure 2 in this case the second switch point X2 will not coincide with point of intersection B of the central axis of the swivel arm 3 with the longitudinal axis of the actuating member 5, but will be offset by a slight amount to the right. This offset position of the second switch point X2 is due to the friction existing between the arched surface 12 and the bow-type spring 11.

By using the adjustable stop 16 it is possible to change the switching hysteresis of the switch, said hysteresis corresponding to the differential distance, i.e. to the distance between the switch points X1, X2. As the set screw is advanced into the interior of the housing 1 there will be a change in the position of the second switch point X2 which will approach the first switch point X, and thus will diminish the differential distance.

Claims

1. A quick-break switch with a contact pair and with a contact plate which establishes a current-carrying contact between the contacts of the contact pair and which can be disengaged from the contacts by means of a swivel arm, the swivel arm communicating via a snap switch mechanism with an actuating member which is guided within the housing and which, caused by a change in its geometrical position relative to the swivel arm, effects the quick change-over, characterised in that the snap switch mechanism is formed by a tension spring (4) fastened between the swivel arm (3) and a part (19) formed fast with the housing.

2. A switch as claimed in claim 1, characterised in that the arrangement of the actuating member (5) and of the tension spring (4) is such as to ensure that, upon the discontinuation of the actuating force, the return of the swivel arm (3) is effected by a force component resulting from the elastic deformation of the tension spring (4) upon the actuation by the actuating member (5).

3. A switch as claimed in claim 1, characterised in that the contact plate (10) is carried by a bow-type spring (11) whose elastic bias generates a constant contact force (FK).

4. A switch as claimed in claim 3, characterised in that, at its end facing the contact arrangement (2, 10), the swivel arm (3) is provided with a plane surface (14) as well as with a there-adjoining arched surface (12) having linear contact with the bow-type spring (11) in the operating position of the switch.

5. A switch as claimed in any of the preceding claims, characterised in that the swivel arm's (3) end averted from the contact arrangement (2, 10) forms a knife-edge support (17) together with a recess (8) provided at a carrier (7) formed fast with the housing.

6. A switch as claimed in any of the preceding claims, characterised in that a stop (16) is provided which is adjustable from the outside and which serves to adjust the differential distance, that is the distance between switch change-over points.

7. A quick-break switch substantially as herein described with reference to and as illustrated in the accompanying drawings.