DE9401016U1 - Electrical switching device for safety-relevant machines - Google Patents

Description

PATENT ATTORNEYS .: * *.** .1. ..* &Ggr;

DIPL.-ING. R. LEMCKE
DR.-ING. HJ BROMMER
DIPL.-ING. F. PETERSEN

BISMARCKSTRASSE 16

76133 KARLSRUHE

TELEPHONE (0721) 912800

FAX (0721) 21105

21 January 1994 16 040 Bl/Wa

Description

The invention relates to an electrical switching device for switching on or interrupting the power supply of safety-relevant machines such as shredders, circular saws, etc., whereby the switching device automatically interrupts the power supply when certain machine and housing parts are opened and in the event of an overload, and whereby manual operation is carried out by an external actuator connected to the switching device.

Such switching devices are not only mandatory in Germany for the operation of the machines mentioned for safety reasons, as they can eliminate significant sources of danger, especially for the machine operator. For example, the feed hopper of a shredder is connected to the switching device, so that when the feed hopper is removed

- which exposes the intake and shredding tools

- an immediate interruption of the power supply is caused by the switching device.

Such switching devices consist, on the one hand, of an actuator in the form of a rotary electrical switch, which establishes the power supply via various locking and lever connections when the rotary switch is moved to the I position or interrupts it again when it is turned in the opposite direction to the O position. On the other hand, the electrical switching device has connectors for the connected machine parts and an electrical overload protection device in the form of a bimetal. Both the connectors and the overload protection device are attached to another lever, which acts on the electrical switch via an additional locking connection. Removing a connected machine part - such as the above-mentioned shredder feed hopper - or activating the overload protection device leads to a lateral deflection of the attached lever, which in turn unlocks the additional locking connection and thus interrupts the power supply.

The disadvantage here, however, is that such a lateral deflection of the lever and the associated interruption of the power supply have no effect on the position of the rotary switch. Rather, although the power is interrupted, it remains in the I position and thus does not indicate that the switching device has interrupted the power supply.

It is now the object of the present invention to provide an electrical switching device in which the position of the actuator corresponds to the state of the electrical switching device.

This object is achieved according to the invention in that the actuator and switching device are connected by a gear that is effective in both switching directions. This direct coupling means that the actuator is returned to the O position when the power supply is interrupted due to the opening of certain machine parts or due to an overload by the gear. This makes it easy to see the state of the electrical switching device at a glance, which makes troubleshooting after a power interruption much easier: If the actuator is in the I position and the power supply is interrupted, an overloaded motor or an open machine part can be ruled out as the reason for the power interruption, and therefore the only possible source of the error is a defect outside of these elements.

It is particularly advantageous if the transmission is designed as a gear transmission. Such a gear transmission consists either of a gear connected to the actuator and a rack coupled to the switching device or of two gears in mutual engagement, whereby the first gear is operatively connected to the actuator and the second gear is operatively connected to an electric switch which can be actuated by a toggle switch. The second gear is expediently in positive contact with the toggle switch, which ensures that switching movements of the toggle switch are transferred directly to the second gear and from there via the first gear to the actuator.

Such a coupling using a gear transmission is not only cost-effective, but also - given the high number of switch operations expected - represents a reliable device for the mechanical transmission of movements.

In addition, the use of a gear transmission according to the invention offers the advantage that the adjustment paths can be increased or reduced by selecting the gear ratio of the two gears. In the present invention, it is advantageous if the transmission works in the direction of reduction based on the movement of the actuator, whereby a very small feed movement of the toggle switch can be converted into a relatively large swivel movement of the actuator. This makes it easier to distinguish the 0/I positions of the actuator, as is also required to obtain an operating license for such a switching device. This means that only by using the reduction gear can the feed swivel movement of the toggle switch of approx. 30° be converted into a swivel movement of more than 90° of the actuator, which then results in a much clearer display of the actuator.

For the safe functioning of the electrical switching device, it is also recommended that a second actuator be provided which operates the switching device in the interruption direction independently of the gearbox. This second actuator can be activated by opening mechanically.

mechanically coupled machine parts, by manual operation of an emergency stop switch or by a bimetal that deforms in the event of an overload. To do this, the second actuator is expediently held in operative connection with the first actuator by a spring element or the like when the electrical switching device is switched on. If this operative connection is canceled by one of the three activation types mentioned above, the spring force causes the first actuator to spring back into the O position. Of course, manual operation of the first actuator from the O position to the I position and back also leads to the operative connection between the first and second actuators being established and canceled again.

The fact that the active connection between the two actuators is cancelled when the second actuator is activated has the great advantage that the interruption in the current would cause the first actuator to move to the O position, but would otherwise occur independently of the position of the first actuator. This means that the second actuator would interrupt the current supply even if the first actuator were held in the I position. After the first actuator was released, it would immediately jump back to the O position due to the spring force, so that in this case too a reliable position indication of the actuator corresponding to the state of the switching device would be guaranteed.

The first actuator is expediently designed as a rotary knob, as this allows the clearest position display to be produced using simple means. In order to be protected against unintentional or accidental actuation, for example by handling branches to be chopped, it is particularly advantageous if the rotary knob is recessed relative to the housing surrounding it, i.e. the rotary knob and housing tops are flush with each other.

In addition, it is recommended that the rotary knob for interrupting the power supply in emergency situations also functions as an emergency stop switch, whereby activation takes place by pressing the rotary knob in a direction perpendicular to the plane of rotation, which in turn affects the second actuator. In this way, the advantage of rapid, targeted switching off, which is otherwise only possible with a conventional pushbutton switch, is transferred to the rotary switch according to the invention.

Further advantages and features of the present invention will become apparent from the following description of an embodiment based on the drawings;

Figure 1 shows a switching device according to the invention in plan view;

Figure 2 the switching device also in plan view, but with the housing cover removed;

Figure 3 The switching device in a partially sectioned front view;

Figure 4 an electrical switch for establishing or interrupting the power supply with an open contact;

Figure 5 the electrical switch with closed contact

Figure 1 shows a switching device 1, consisting of a first actuator 2 in the form of a rotary switch which can be rotated between an O position which interrupts the power supply to a machine (not shown) and an I position which establishes the power supply. The rotary switch 2 consists of a disk-shaped base plate 3 and a web 4 which tapers in the direction of the position to be indicated. The rotary switch 2 is recessed into a circular opening 5 in a housing cover 6 of the switching device so that the top of the web 4 is flush with the top of the housing cover, and is rotatably mounted in the housing cover 6 by means not shown.

Referring to Figure 1, an extension 7 extending into the plane of the page is formed on the rotary switch 2 and runs in the direction of a first gear 8 located underneath, shown in Figure 2, with which it is also firmly connected. (The exact connection conditions can be seen in section in Figure 3 and will be explained later.

explained in more detail). Through this fixed connection, the operation of the rotary switch 2 is transmitted directly to the first gear 8. Since the first gear 8 is in engagement with a second gear 9, this rotary operation is passed on to the second gear 9 in accordance with the relative reduction ratio of the two gears.

As can also be seen in Figure 2, the second gear 9 is in positive contact with a conventional toggle switch 12 via two bolts 10 and 11 shown in dashed lines and arranged below the gear, which acts on an electrical switch 13 shown only schematically (the electrical switch is shown in more detail in Figures 4 and 5). It is therefore obvious that a rotation of the rotary switch 2 in a clockwise direction causes a pivoting movement of the toggle switch 12 in an anti-clockwise direction.

Figure 3 shows the switching device 1 in a front view, with the rotary switch 2 and the two gears 8 and 9 shown cut away along the center line III-III from Figure 2. Here, the guide openings formed in the housing cover 6 for receiving the first gear 8 connected to the rotary switch 2 via the extension 7 and the second gear 9 can also be seen, which is mounted in the housing cover 6 via a guide cylinder 14.

As can be seen from the length of the tooth flanks of the first gear 8 in the sectional view in Figure 3, the rotary switch 2 can simultaneously be used as

Emergency stop switch can function by being pressed perpendicular to the rotary switch's plane of rotation in the direction of the electrical switch. Before it comes into contact with the latter, however, it is supported by projections on the housing cover or on the second gear 9 that extend in the direction of movement. This closing movement causes a mandrel 15 that is firmly connected to the rotary knob 2 or its base plate 3 to be pressed downwards in relation to Figure 3 and causes its lower end to pivot an actuating lever 16 clockwise around a pivot point 17 that is firmly connected to the housing. Due to the outer contour of the actuating lever 16, this emergency shutdown and the associated pivoting of the actuating lever 16 into the position shown in dashed lines in Figure 3 causes a closing movement of a further dome 18 that runs into the electrical switch 13 (the mandrel 18 is only partially shown in Figure 3, the further course can be seen in Figures 4 and 5).

The same pivoting movement of the actuating lever 16 or the feed movement of the mandrel 18 is generated by opening a machine or housing part, whereby levers not shown in Figure 3, which interact with an extension 19 of the actuating lever 16, generate a pivoting of the extension 19 clockwise into the position shown in dashed lines in Figure 3. Thus, Figure 3 shows two of the three ways of activating the electric switch 13: firstly, by pressing the rotary switch 2 and thus transmitting a feed movement to the

Mandrel 15 and secondly by opening a machine or housing part and thus transmitting a swivel movement to the extension 19. The third possibility of interrupting the power supply is explained in connection with the description of Figures 4 and 5.

In Figures 4 and 5, the electrical switch 13, as sold by the company ETA, for example, is shown in a partially cutaway view - in Figure 4 with open contacts and thus interrupted power supply, and in Figure 5 with closed contacts and thus established power supply. The horizontally running mandrel 18 shown in the center of Figure 3 for manually actuating the electrical switch 13 can also be seen in the lower left half of Figure 4: It is guided so as to be displaceable in its longitudinal direction in a manner not shown and is located with its tip facing away from the actuating lever 16 in indirect contact with a second actuator in the form of an approximately L-shaped release lever 20. The release lever has a long leg 20a and a short leg 20b, which are approximately perpendicular to each other. A current-carrying bimetal 21 is arranged between the mandrel 18 and the long leg 20a of the release lever 20, which deforms in the event of an electrical overload. Just as the opening of a machine or housing part, as explained above, leads to a displacement of the mandrel 18 in the direction of the release lever 20, the bimetal 21 also presses in the direction of the release lever 20 due to its deformation in the event of an overload. Both operations - the manual

as well as the electrical one - lead to the release lever being pivoted anti-clockwise about a pivot point 22, which is arranged at the intersection point of its two legs 20a and 20b.

During this pivoting, the force of a spring 23 must be overcome, which acts on the long leg 20a of the release lever opposite the mandrel 18 and the bimetal 21 and ensures that the two actuating elements are securely positioned on the release lever. This spring also causes the release lever 20 to move back to its original position after being actuated by the mandrel 18 or the bimetal 21.

The toggle switch 12 is shown on the opposite right-hand end of the electrical switch in relation to Figure 4, via which the movements of the rotary switch 2 are transmitted to the electrical switch 13. The toggle switch 12 is arranged to pivot about a fixed pivot point 24, whereby it can pivot from the position shown in Figure 4 (corresponding to the O position of the rotary switch 2 in Figure 1) to the position shown in Figure 5 (corresponding to the I position of the rotary switch 2 in Figure 1). A guide pin is arranged on the edge area of the toggle switch 12 facing the inside of the electrical switch 13, which extends into the plane of the page in relation to Figure 4, parallel to the pivot axis of the pivot point 24. This guide pin 25 is guided in a guide groove 26 of an actuating element 27 and thus defines the pivot point of the actuating element 27. The actuating element 27 extends

is parallel to the plane of the sheet of Figure 4 below the inner edge area of the toggle switch 12 and is also arranged perpendicular to the axis of rotation 24 of the toggle switch 12 or to the guide pin 25.

The actuating element 27 is guided by a further guide element 32, shown only schematically, in the form of a pin-groove arrangement connected to the housing. As a result, the actuating element 27 is simultaneously displaced slightly downwards - in relation to Figure 4 - when pivoting about the pivot point 25 in an anti-clockwise direction, for example, whereby the pivoting and sliding movements overlap.

The actuating element 27 can be brought with its lower end region in relation to Figure 4 into contact with another leaf spring 28, at the lower end of which a contact pair 29 is arranged; with the other end of the actuating element 27, this can be brought into contact with the short leg 20b of the release lever 20, whereby the operative connection between the second actuating element and the first actuating element, i.e. between the release lever 20 and the rotary switch 2, can be established.

The leaf spring 28 has a preload in the direction of the actuating element 27, through which it and its contact pair 29 can be brought out of contact with another contact pair 30 that is fixedly arranged in the housing. If the two contact pairs 29 and 30 are in contact with each other, the current flow is established. This can be seen in Figure 5, where the current would therefore flow through the electrical switch.

Figures 4 and 5 also show a further leaf spring 31 acting on the toggle switch 12, which presses the toggle switch into the position shown in Figure 4 through its spring force. Thus, in order to establish the flow of current, both the force of the leaf spring 28 and the force of the further leaf spring 31 must be overcome manually when operating the rotary switch 2.

To ensure that the toggle switch remains in the position shown in Figure 5, which corresponds to the I position of the rotary switch 2 in Figure 1, the groove guiding the pin 25 of the toggle switch 12 is approximately L-shaped with a short leg area that is approximately perpendicular to the much longer leg of the groove 26. This short leg serves to lock the toggle switch 12 in the position shown in Figure 5 by locking the guide pin 25 in this short leg area. The locking is achieved by the leaf spring 28 pushing the actuating element in the direction of the toggle switch 12 after the rotary switch 2 has been moved to the I position, which does not, however, impair the contact between the two contacts 29 and 30, and the flow of current is therefore maintained.

Flipping the toggle switch 12 from the position shown in Figure 5 to the position shown in Figure 4 causes the guide pin 25 to be moved back into the area of the long leg relative to the guide groove, whereupon the spring forces of the leaf spring

28 and the further leaf spring 31 can take effect, which finally return the switch to the position shown in Figure.

Since the long leg of the guide groove 26 is slightly inclined in the direction of the pivot point 24, turning the toggle switch 12 from off to on (i.e. from the position in Figure 4 to the position in Figure 5) causes the actuating element 27 to be pressed away from the toggle switch 12 in the direction of the leaf spring 28 and the short leg 20b of the release lever 20 and to be moved almost parallel. If the pin 25 is at the apex of the groove 26 or in the area of the short leg, the actuating element rests with one side on the short leg 20b of the release lever 20 and with its other side on the leaf spring 28 and presses these and thus also the contact pair 29 in the direction of the contact pair 30. The current flow is thereby established and the two actuators are in operative connection with one another. The spring force of the leaf spring 28 is transmitted via the actuating element 27 and its pivot point 25 to the short leg 20b of the release lever 20, whereby the operative connection between the two elements is also maintained by the leaf spring 28.

The interruption of the power supply by the three activation types listed above now takes place as follows: The mandrel 18 or the bimetal 21 pivots the long leg 20a of the release lever 20 in an anti-clockwise direction, which also causes the short leg 20b to pivot in an anti-clockwise direction.

is pivoted counterclockwise. As a result, the release lever 20 and the actuating element 27 resting against it are no longer connected and the leaf spring 28 also pivots the actuating element 27 counterclockwise around the guide pin 25, which acts as the axis of rotation, whereby the actuating element is pivoted with its upper end past the short leg. This opens the contact and interrupts the power supply. The schematically indicated guide element 32 also pushes the actuating element downwards relative to the guide pin when pivoting - based on Figure 5 - so that the guide pin comes into the area of the long leg of the guide groove 26 and thus out of the engaged position, whereby the further leaf spring 31 pushes the toggle switch 12 back into the off position (corresponding to Figure 4).

This pivoting movement of the switch is transmitted via the pins 10 and 11 to the second gear 9 and from there to the first gear 8, which is connected to the rotary switch 2. Thus, activation of the second actuator, i.e. the trigger lever 20, not only leads to an interruption of the power supply, but also to the rotary switch 2 being moved from the I to the O position, whereby the rotary switch 2 accurately reflects the state of the switching device at all times.

Of course, errors outside the switching device or the mechanically coupled machine or housing parts do not affect the position of the rotary

switch is off, so an interruption of the power supply, e.g. by removing the plug connection from the socket, has no effect on the switch position.

But even if the rotary switch 2 or the toggle switch 12 is manually held in the on or I position while the second actuator is activated, the power supply is still interrupted: only the second and first actuators are decoupled from each other: Similar to the above case, the actuating element 27 is pivoted counterclockwise by the leaf spring 28, whereby the mutual contact of the two contact pairs 29 and 30 is canceled and the power supply is thus interrupted. The pin 25 is now already in the area of the long leg of the guide groove 26, but due to the manual locking of the toggle switch 12, the force of the further leaf spring 31 cannot take effect to push the pin 25 into the end area of the guide groove 26. Only when the switch is released does the spring force cause the toggle switch 12 to return to the off position and thus the rotary switch 2 to return to the O position. This shows that even attempts to manipulate the switching device have no effect on safe functioning.

Claims (1)

Protection claims 1. Electrical switching device for switching on or interrupting the power supply of safety-relevant machines such as shredders, circular saws, etc., whereby the switching device automatically interrupts the power supply when certain machine or housing parts are opened or in the event of an overload, and whereby manual operation is carried out by an external actuator connected to the switching device, characterized in that that the connection between the actuator (2) and the switching device (1) is made by a gear (8,9) which is effective in both switching directions. 2. Electrical switching device according to claim 1, characterized in that that the transmission is designed as a gear transmission (8,9). Electrical switching device according to claim 2, characterized in that the gear transmission (8,9) consists of two mutually engaging gears (8,9), the first gear (8) being operatively connected to the actuator (2) and the second gear (9) being operatively connected to an electric switch (13). ia 4. Electrical switching device according to claim 3, characterized in that the electrical switch (13) is actuated by a toggle switch (12). 5. Electrical switching device according to claim 1, characterized in that the gear mechanism acts in the reduction direction based on the movement of the actuator (2). 6. Electrical switching device according to claim 1, characterized in that a second actuator (20) is provided which independently of the transmission actuates the switching device (1) in the interruption direction. 7. Electrical switching device according to claim 6, characterized in that the second actuator (20) can be activated by opening mechanically coupled machines or housing parts or by manually actuating an emergency stop switch. 8. Electrical switching device according to claim 6, characterized in that the interruption of the power supply in the event of an overload is carried out by a bimetal (21) which activates the second actuator (20). 9. Electrical switching device according to claim 6, characterized in that the second actuator (20) in the switched-on • Φ·· ··* ΦΦ State of the electrical switching device (1) is kept in operative connection with the first actuator (2) by a spring element (28), and that by activation of the second actuator (20) this operative connection can be canceled. 10. Electrical switching device according to claim 1, characterized in
that the actuator (2) is designed as a rotary knob. 11. Electrical switching device according to claim 10, characterized in that that the rotary knob (2) is recessed relative to a surrounding housing (6). 12. Electrical switching device according to claim 10, characterized in that the rotary knob (2) simultaneously functions as an emergency stop switch, whereby activation occurs by pressing the rotary knob (2) in a direction perpendicular to the rotation plane.