EP0117396B1 - Security switch with an un authorised-closure provision - Google Patents

Description

The invention relates to a safety switch with fail-safe protection.

In particular, it is assumed that such a safety switch comprises a switch housing with a switch enclosed by it, a plunger guided through the wall of the switch housing and a control roller articulated to the plunger via toggle levers, which is pivotably arranged on a shaft in a control housing and on their circumference has a sector-like recess into which an actuating bracket assigned to the control housing, inserted through a slot in the control housing, can engage with its front free end, which is designed as a crosspiece in front of a window, in order to twist the control roller.

Such a safety switch has already become known, albeit with a differently designed operating bracket.

Even that safety switch could not be actuated by unauthorized persons with a simple aid, for example a screwdriver, but required a specially designed actuating element in the form of a claw, which, inserted into the slot in the control housing, was able to with the bent free end in to engage a recess of a control roller and to twist it so that a plunger connected to the control roller inevitably closes the contacts of an adjacent switch or, conversely, inevitably returns the roller when the actuating claw is removed and thus inevitably opens the contacts.

Increased security requirements against unauthorized use then led to further development. There, instead of the actuating claw, an actuating bracket was provided which, at its front free end, had a crosspiece for pivoting the control wing of a control roller and behind it a window for receiving a deflector wing of this control roller. This switch could also not be operated by simple tools, for example a screwdriver, but was also safe against operation by unauthorized persons who made an actuating claw from a correspondingly angled sheet metal strip and thus tried to operate the switch described above.

This safety switch can also be operated by unauthorized persons, provided they have a certain level of craftsmanship and make an operating bracket from a correspondingly strong wire, with which they can then turn the control roller and at least briefly switch on the switch. While in general the aforementioned safety switch already has increased security against tricking, the requirements for security against tricking may be screwed up even higher for certain applications. If the known safety switch described above should then no longer be considered sufficient with regard to securing against tampering, a further developed safety switch with a fail-safe device is described and claimed below, which no longer permits actuation with the aid of tools which have been produced for this in a reasonable amount of time.

The invention is accordingly based on the object of providing the known safety switch described above with a faulty closing device which prevents actuation by unauthorized persons with such aids which can be produced in a short time.

For the sake of explanation, however, it is noted that there is as little a safety switch with incorrect locking protection that cannot be operated by unauthorized persons at all, as there is a safety lock that offers absolute security against opening by qualified burglars. Ultimately, the technical possibilities of the unauthorized person and the time available to him decide whether he can be successful in his efforts or not.

To achieve the above object, it is proposed that the control roller is assigned at least one freely pivotable locking disk which, at its end projecting into the slot in the control housing, has a radially projecting control lug and also a cam slot for receiving the plunger of the switch with the toggle levers Axis.

The cam slot includes a in the starting position (rest position) of the locking disc receiving the axis and holding it before closing the contacts of the switch shorter slot part and a longer slot part connected to this by a central guide part, which receives the axis in the working position of the locking disc and allowing their further movement under the influence of the control roller until the contacts of the switch close.

If the locking disc remains in its initial position and the control roller is rotated further and the toggle levers are moved in the direction of the switch, the axis that connects these toggle levers with the plunger of the switch inevitably comes into the shorter cam slot of the locking disc, the length of which is dimensioned in this way is. that the movement of the axis is stopped before the contacts. of the switch can be closed. A further pivoting of the roller and a further movement of the plunger of the switch caused by this are then no longer possible.

Provided, however, the locking disk is pivoted from its starting position into its working position was, before the control roller is pivoted further, said axis reaches the longer slot part of the cam slot, which allows a much longer path of the axis and thus the plunger moving the contact bridge of the switch. With a subsequent movement of the control roller, the toggle levers and the axis and thereby the plunger of the switch are moved so far that the contacts of the switch are finally closed.

It should be emphasized that the middle guide part of the cam slot results in an inevitable resetting of the locking disk from its working position into the starting position for the inevitable readiness to lock again to prevent incorrect locking.

According to the invention, the actuating bracket has a projection at its free end, that is to say in front of the crossbar, or, if two locking disks are provided, two projections which are arranged and dimensioned such that they engage a control lug when the actuating bracket is inserted into the slot in the control housing of the respective lock washer. This control lug protrudes into the path of the actuating bracket and is acted upon by the respective projection when it is inserted, so that the locking disk is finally pivoted out of the starting position into the working position.

You can basically get by with a single locking disk, which is then arranged on one side or the other of the control roller. Preferably, however, one will provide a locking disk on each side of the control roller and accordingly also arrange two projections at the ends of the crossbar of the actuating bracket, since this increases the effect of the incorrect locking device.

The length of the projections on the actuating bracket is of course dimensioned such that the locking disks are already pivoted into their working position before the control roller has already inserted the axis that articulates the toggle lever with the plunger of the switch into the shorter slot part of the cam slot.

If an unauthorized person wanted to try to close such a safety switch according to the invention with a mishandling device with simple means, then he could think about making a bracket bent from strong wire to actuate the control roller, with which he tries to pivot the control roller. At about the same time, however, he would have to bring the two locking disks into their working position and, for this purpose, insert an appropriately dimensioned pin on each side of the slot in the control housing, which pin hits the control lug of the respective locking disk and moves it.

Such manipulation can be considered practically impossible, if only because the person concerned would have three hands to operate the three different parts of the switch, and it is also difficult to insert the three parts into the slot.

If you disregard the theoretical possibility that an unauthorized person can procure a suitable operating bracket for this switch or laboriously produce it yourself, then you can safely address the safety switch according to the invention with a fail-safe device as tamper-proof.

In a further development it is provided that the shorter slot part in the or each locking disk also has a short part which extends in the direction of the shaft of the control roller. This configuration furthermore makes it difficult to manipulate the switch with individual rods or the like inserted through the slot. If you hit the two locking disks with one or two tools and want to swivel them in the desired direction before you pivot the actuating wing of the control roller a little from its rest position, the axis that can be moved in the slot of the or each locking disk comes into it Part of the slot and prevents further pivoting of the locking disc (s).

It is preferably provided that the central guide part of the cam slot in the or each locking disk is designed such that it brings about the inevitable return of the locking disk from the working position to the starting position.

This curve slot configuration is normally sufficient to guarantee a reliable return of the locking disk.

In addition, however, it is proposed that a spring means is assigned to the or each locking disk, which holds the locking disk in the starting position. Such a spring means ensures that the locking disk is reset reliably in any position of the safety switch.

In principle, all conceivable spring means can be used as spring means for the locking disks. Preferably a. such spring means, however, is formed by a spring arm which is fixedly connected to the respective locking disk, protrudes approximately radially therefrom and is biased against an inner wall of the control housing.

In particular, it is provided that the locking disk and spring arm are made in one piece from a highly elastic thermoplastic. Since the spring arm does not have to absorb large forces or have to carry out paths because only the frictional forces acting on the respective locking disk can be overcome, the spring arm can be designed in such a way that it is practically fatigue-free and has a practically unlimited service life.

The safety switch can not only, as described in detail above. can be switched by inserting an operating bracket into a slot in one of the two side walls of the control housing, but also through a slot which is located in the bottom wall of the control housing, that is to say in the wall facing away from the switch housing. In this case too, with the correct arrangement and design of the control roller and the locking disks, actuation can only be effected by the associated actuating bracket, but not by manipulations with other tools.

• Figur 1 eine perspektivische Darstellung eines erfindungsgemäßen Sicherheitsschalters mit Fehischließsicherung, einschließlich eines dazugehörigen Betätigungsbügels ;
• Figur 2 eine vergrößerte Ansicht auf die Vorderseite des Steuergehäuses, mit abgenommener, jedoch strichpunktiert angedeuteter, den Schlitz zur Einführung des Betätigungsbügels enthaltender Kappe, gesehen in Richtung des Pfeiles 11 in Fig. 3 ;
• Figur 3 einen Längsschnitt durch das in Fig. 2 dargestellte Steuergehäuse, im gleichen Maßstab ;
• Figur 3a die Ansicht einer Sperrscheibe ;
• Figur 4 bis Figur 7 Schnitte ähnlich Fig. 3, in verschiedenen Schaltzuständen ;
• Figur 8 eine Darstellung ähnlich Fig. 3a einer abgewandelten Sperrscheibe und
• Figur 9 einen Schnitt ähnlich Fig. 4 durch ein Steuergehäuse mit Bodenschlitz und dort eingeführtem Betätigungsbügel.

The invention is explained in more detail in an exemplary embodiment with reference to the drawing. Show:

• Figure 1 is a perspective view of a safety switch according to the invention with incorrect locking device, including an associated operating bracket;
• FIG. 2 shows an enlarged view of the front of the control housing, with the cap removed, but indicated by dash-dotted lines and containing the slot for introducing the actuating bracket, viewed in the direction of arrow 11 in FIG. 3;
• 3 shows a longitudinal section through the control housing shown in Figure 2, on the same scale.
• 3a shows the view of a locking disk;
• Figure 4 to Figure 7 sections similar to Figure 3, in different switching states.
• FIG. 8 shows a representation similar to FIG. 3a of a modified locking disk and
• FIG. 9 shows a section similar to FIG. 4 through a control housing with a bottom slot and an operating bracket inserted there.

- The safety switch 1 shown in Fig. 1 with a mishandling device comprises a switch housing 3 and a control housing 4 connected to it. In the front wall 12a of the control housing 4 there is a rectangular slot 13 through which an associated actuating bracket 2 can be inserted. This operating bracket has a crossbar 14 at the front end and a window 15 behind it. At the rear end of the operating bracket 2 there is a base plate 16 with holes 17, by means of which the operating bracket can be attached to a door, a movable machine part or the like.

From the crosspiece 14 at the free end of the operating bracket protrusions 10a and 10b protrude on both sides, which assume a special switching function to be described below.

Details of the control housing 4 can be seen from FIGS. 2 and 3. As can be seen in particular from FIG. 3, a control roller 8 is pivotally arranged in this housing on a shaft 6, which has a control wing 5 to be acted upon by the crossbar 14 of the actuating bracket 2, a sector-like recess 28 and a deflector wing 9. The crossbar 14 comes into the sector-like recess 28 when the actuating bracket is inserted.

If a closed plate, a rod or the like were used instead of a windowed operating bracket, then a complete insertion thereof would be prevented by the deflector wing 9 pivoting into the path of the operating bracket.

In the control roller 8, behind the control wing 5, facing away from the sector-like recess 28, there is an axis 18 which projects beyond the control roller 8 on both sides and on which a toggle lever 7a or 7b is pivotally mounted. These toggle levers located on both sides of the control roller have at their other ends facing the switch housing a continuous shaft 19 on which the plunger 20 (only partially shown) of the switch, which carries the contact bridge (not shown), is pivotably mounted.

When the control roller is rotated counterclockwise (in FIG. 3), the axis 19 and with it the plunger 20 are guided in the direction of the switch housing 3 and, if the path is sufficiently long, the switch is finally closed.

Such pivoting of the control roller by the actuating bracket 2 and thus closing the switch are only possible if the two locks explained below are released approximately simultaneously.

These locks are formed by two locking disks 21 a and 21 b, the shape of which can be seen from Fig. 3a. The two locking disks are arranged on both sides of the control roller 8 so that they can pivot on their shaft 6 and, in their starting position, as shown in FIG.

In this case, the spring arm 23 of each locking disk is placed under prestress on the inside of the front wall 12a and thereby ensures that the locking disk remains in the starting position.

In each locking disk there is a cam slot which comprises a shorter slot part 22, which extends approximately radially to the shaft 6, a longer slot part 25, also approximately radially to the shaft 6, and a central guide part 24 connecting these two slot parts.

The arrangement, as can be seen from FIG. 3, is such that when the locking disks are in their starting position, the shorter slot part 22 runs parallel with the central plane connecting the shaft 6 with the axis 19.

The further movement processes are now explained with reference to FIGS. 4 to 7.

If an actuating bracket, as shown in FIG. 1 and described for this purpose, is inserted and brought into position 2 'according to FIG. 4, its transverse web 14' has touched the control wing 5 'and pivoted it slightly, so that the axis 19' also somewhat was raised, although it has not yet entered the short slot of the locking washers.

If the actuating bracket is then brought into the position 2 "shown in FIG. 5, the projections 10a and 10b come into the position 10a" or 10b "in which they meet the control lugs 27 of the locking disks and thereby the locking disks in their position shown in FIG 5. Swivel the working position shown in this working position longer slot part 25 approximately with the axis 19 and this, if the control roller is subsequently pivoted further, can enter the longer guide slot.

In Fig. 6, the end position is shown with the operating bracket fully inserted. The crossbar 14 of the actuating bracket has pivoted the control roller further and this has inserted the axis 19 into the long slot part 25; wherein the plunger 20 of the switch has reached its end position and the switch contacts (not shown) have closed.

In Fig. 7 is shown comparatively what happens in the control part of the safety switch when not a properly designed actuating bracket, but for example a flat sheet metal piece 26 is inserted into the slot 13 of the control housing. On the one hand, as can be seen from Fig. 7, the deflector wing of the control roller in the position 9 "" and thereby prevents further advancement of the sheet metal piece 26 and thus a further Ver .. pivoting the control roller. On the other hand, the sheet metal piece 26 has not moved the two locking disks out of their working position, so that the axis 19 has come into the short slot part and is held by it. The length of the short slot part is dimensioned so that the contacts of the switch are certainly not yet closed in this position.

Even if you were to use a bow-shaped tool that did not cause any problems with regard to the deflector wing of the control roller, the axis 19 would still get into the short slot parts of the locking disks and thereby further movement and thus closing of the switch would be prevented with certainty.

It should also be noted in relation to FIGS. 4 to 7 that, for the sake of clarity, the spring arm 23 of the locking disk 21b has not been shown, but has been broken off.

The channel located behind the slot 13 in the front wall 12a and intended for receiving the actuating bracket 2 extends through the control housing 4 and runs through the rear wall 12b thereof. The safety switch can then be designed by simply repositioning the control roller 8 and the two locking disks 21a and 21b in such a way that it can be actuated from the rear wall 12b by an actuating bracket. The arrangement of the moving parts inside the control housing 4 and their movements when actuated by the actuating bracket are mirror images of those described above with reference to the exemplary embodiment shown.

8 shows a modified locking disk 121 with spring arm 123 and control lug 127 and with slot parts 122, 124, 125. The cam slot of this embodiment, however, comprises, in addition to the locking disk shown in FIG. 3a, a further short slot part 128, opposite the slot part 122, which further increases the security against manipulation in the manner described below.

FIG. 9 shows an embodiment of the control housing in which the slot 130, which is provided for receiving the actuating bracket 102, is located in the bottom of the control housing, that is to say in the wall 111 facing away from the switch housing. The control roller 108 is here shaped and used that its actuating wing 109 is acted upon by the front transverse web 114 when inserting the actuating bracket 102. The two projections 110, which are also arranged on both sides of the crossbar 114 in this embodiment and protrude in the direction of insertion over this crossbar, meet the control lug 127 of each locking disk 121, as shown in dashed lines in FIG to rotate the spring clip 123 clockwise and thus guide the axis 119 via the slot part 124 of the cam slot into the longer slot part 125 of the slot. As can be seen from FIG. 9, this is only possible if the axis 119 is first lifted out of the short slot part 128. This can only happen if the crossbar 114 first pivots the control roller 108 somewhat clockwise. Then the axis 119 is moved out of the short slot part 128 via the toggle lever 107. A further forward movement of the crosspiece 114 would, however, now lead to the axis 119 being guided into the short slot part 122 lying above in FIG. 9 and being held there. So there must be an exact match between the movement of the control roller 108 and the movement of the two locking disks, so that the axis 119 is finally able to enter the slot portion 124 of the cam slot and then subsequently in the long slot portion 125. However, such a coordination is only possible if an actuating bracket 102 is used, in which the lateral projections 110 protrude a very specific amount beyond the front control surface of the crossbar 114.

If the window already described is present behind the crosspiece 114, the deflector wing 105 of the control roller 108 can enter this window and the movement can continue until the axis 119 finally over the (not shown in Fig. 9) plunger Switch in the switch housing. use 3 (see Fig. 1).

The control housing according to FIG. 9 can be used as desired for actuation from the left or from the right or, as shown in FIG. 9, from below, in which case one or the other slot is used in each case. As shown in FIG. 9, the slots are expediently closed by break-out parts. One can then break out one or the other part as desired and use the housing for such a type of actuation. Of course, the locking disks and the control roller must then be shaped and used accordingly.

Claims (8)

1. Security switch with an unauthorised-closure provision, which comprises a switch housing (3) with a switch enclosed by the latter, a plunger (20) guided by the wall of the switch housing, and a control roller (8 108) which is connected in an articulated manner to the plunger via toggle levers (7: 107) and is arranged pivotably on a shaft (6 ; 106) in a control housing (4), and which has on its periphery a sector-like recess (28), into which an actuating bar (2 ; 102) assigned to the control housing and inserted through a slot (13 ; 130) in the control housing (4) can engage by means of its front free end designed as a crossmember (14: 114) in front of an aperture (15), in order to rotate the control roller, characterised in that the control roller (8; 108) has assigned to it at least one freely pivotable detent disc (21 ; 121) which, at its end projecting into the slot (13; 130) in the control housing (4), has a radially projecting control nose (27; 127) and also a cam slot (22, 24, 25 ; 122, 124, 125, 128) for receiving an axle (19; 119) connecting the plunger (20) of the switch to the toggle levers (7 ; 107) in an articulated manner, the cam slot comprising a shorter slot part (22 ; 122) which, in the initial position of the detent disc (21 ; 121 receives the axle (19 ; 119) and which retains it before the contacts of the switch are closed, and a longer slot part (25 ; 125) which is connected to the said shorter slot part (22 ; 122) by means of a middle guide part (24 ; 124) and, in the working position of the detent disc (21 ; 121), receives the axle (19 ; 119), and which allows it to move further under the effect of the control roller (8 ; 108) until the contacts of the switch are closed, and the actuating bar (2; 102) having, at its free end, a projection (10; 110) which is assigned to the detent disc (21 ; 121) and, when the actuating bar (2 ; 102) is introduced into the slot (13 ; 130) in the control housing (4), comes up against the control nose (27 ; 127) of the associated detent disc (21 ; 121) and, during further introduction, pivots the detent disc out of the intial position into the working position.

2. Security switch according to Claim 1, characterised in that two detent discs (21a, 21 b) are provided.

3. Security switch according to Claim 1 or 2, characterised in that the middle guide part (24 ; 124) of the cam slot (22, 24, 25; 122, 124, 125, 128) in the or in each detent disc is designed so that it ensures the forced return of the detent disc from the working position into the initial position.

4. Security switch according to Claim 3, characterised in that the shorter slot part (122) in the or in each detent disc (121) also has a short part (128) extending in the direction of the shaft (106) of the control roller (108).

5. Security switch according to one of Claims 1 to 4, characterised in that the or each detent disc (21 ; 121) has assigned to it a spring means which holds the detent disc in the initial position.

6. Security switch according to one of Claims 1 to 5, characterised in that the spring means assigned to the or to each detent disc (21 ; 121) is a spring arm (23 ; 123) which is connected firmly to the detent disc and projects radially from it and which is laid under prestress against the inside of that wall (12 ; 111) of the control housing (4) provided with the slot (13 ; 130).

7. Security switch according to Claim 6, characterised in that the detent disc or detent discs (21 ; 121), together with the spring arm (23 ; 123), is or are produced in one piece from a highly elastic thermoplastic.

8. Security switch according to one of Claims 1 to 7, characterised in that the slot (130) for receiving the actuating bar (102) is located in that wall (111) of the control housing (4) which faces away from the switch housing (3).

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