Feed hopper for a material processing device

A feed hopper for a material processing device, in particular for a crusher (10), having two side walls (21) and a rear wall of the hopper (22), wherein the side walls (21) are directly or indirectly coupled to a machine support (12.1) in a swiveling manner and can be converted from a set-up work position to a folded-down transport position and back, wherein a feed area is formed between the side walls (21), and wherein at least one of the side walls (21) is supported relative to the machine support (12.1) in the set-up work position by a supporting device (30). A support lever (31), which in the work position is supported directly or indirectly in relation to the machine support (12.1) by a detachable form-fit connection, wherein the form-fit connection prevents the side wall (21) from folding down, projects into the feed area in the folded-down transport position. In this way, a space-saving design is also achieved in the folded-down transport position.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to a feed hopper for a material processing device, in particular for a crusher, having two side walls and a rear wall of the hopper, wherein the side walls are directly or indirectly coupled to a machine support in a swiveling manner and can be converted from a set-up work position to a folded-down transport position and back, wherein a material feed area is formed between the side walls, and wherein at least one of the side walls is supported relative to the machine support in the set-up work position by means of a supporting device.

Description of the Prior Art

From EP 2 730 459 A2 (U.S. Pat. No. 9,242,803) a rock crusher unit having a feed hopper is known. Such feed hoppers are used in material processing devices such as rotary impact crushers, jaw crushers, cone crushers or in screening stations. A transport device, for instance a conveyor chute or belt conveyor, is assigned to the feed hopper in the area of the bottom of the hopper chamber, which is designed as a feeding area. The feed hopper is used to fill the material to be crushed and to fed it onto the transport device. Typically, excavators, wheel loaders or shredding or screening plants are used to fill feed hoppers.

The overall height of the material processing device has to be dimensioned such that it can be transported on flat-bed trucks. The overall height of the machine can be reduced by means of the fold-down side walls. A set-up aid is used to facilitate the work, to easily convert the machine.

In the set-up aid according to EP 2 730 459 A2 (U.S. Pat. No. 9,242,803), the hopper chamber is delimited by two side walls, to which a wall extension is hinged via a first swivel bearing. The set-up aid has a hydraulic cylinder as an actuator, which is coupled to the side wall in a swiveling manner. Furthermore, a support is used, which is also connected to the side wall in a swiveling manner. The support itself is connected to a lever via a second swivel bearing. The lever is coupled to the wall extension in a swiveling manner. The piston rod of the actuator engages with the area between the coupling points of the lever to the wall extension or the support. In this mechanism, the articulated shafts of the first and second swivel bearing are aligned with each other in the folded-down position of the wall extension. This allocation of articulated shafts is maintained until the wall extension reaches its set-up position. To secure the set-up position, the hydraulic cylinder must be further telescoped such that the articulated shaft of the second swivel bearing is displaced in relation to the articulated shaft of the first swivel bearing. This mechanism has the disadvantage that, due to manufacturing tolerances, it is very difficult to align the two articulated shafts of the first and second swivel bearing with each other. Accordingly, compensating mechanisms must be provided in the gear arrangement to ensure functionality. For instance, slots or the like may be provided in the area of the articulating points. However, such slots or other compensating mechanisms have the disadvantage that they result in an unstable motion sequence. In the arrangement known from EP 2 730 459 A2, the gear arrangement passes over a dead-center position, in which the wall extension performs an uncontrolled motion at least in part of the swivel motion because of the compensating mechanisms. Furthermore, the known arrangement requires a lot of cost and effort in parts and assembly.

From EP 2 949 397 B1 (U.S. Pat. No. 9,833,787) a feed hopper for a rock crusher is known, which has two hinged side walls and a rear wall of the hopper. The side walls can be locked to the rear wall of the hopper in the unfolded operating position. In addition, a linkage can be used to support the side walls. The linkage requires a lot of cost and effort in parts and assembly.

GB 2496522 A discloses a design similar to EP 2 949 397 B1. The feed hopper known from this publication again uses bipartite side walls equipped with a wall extension. The side walls can be uniformly folded down in conjunction with the attached wall extension about a horizontal swivel axis. In the unfolded position, linkages secure the position of the side wall.

DE 10 2016 119 797 B3 (CA 3035402) reveals a rock crusher having a feed hopper, which has side walls and a rear wall of the hopper. Hydraulic cylinders can be used to bring the side walls into their unfolded operating position. In the unfolded position, the side walls can be secured by means of support struts. They are attached to the side walls and the machine chassis at the attachment points provided.

SUMMARY OF THE INVENTION

The invention addresses the task of providing a feed hopper of the type mentioned above, which permits an effective securing of the side walls in the unfolded operating position with a minimum of cost and effort in parts and assembly and which, in the folded-down transport position, is accommodated in a space-saving manner.

This problem is solved by the support device having a support lever, which, in the work position, is supported directly or indirectly in relation to the machine support by means of a detachable form-fit connection, wherein the form-fit connection prevents the side wall from folding down, and the support lever projects into the material feed area in the folded-down transport position. As used herein the term “form-fit connection” means a connection that transmits force by positive engagement of one part against another such that force is transferred by one part bearing against another. This is contrasted for example with a frictional connection where the force is transmitted through the connection by friction between the two parts, or a bonded connection where the two parts are glued, welded or soldered together

The support lever can be designed as a simple component, and can be attached directly to the side wall, for instance. This results in a significantly lower number of parts than for the state of the art, which in particular uses complex linkages. In the unfolded operating position, the support lever rests against the machine support based on a detachable form-fit connection. In this way, the operating position of the side wall is reliably and easily secured. If the side wall is now to be moved into the transport position, the detachable form-fit connection is a convenient way for the user to release the lock of the side wall. It can now be swiveled into the folded-down transport position. The support lever is then accommodated in a space-saving manner by swiveling into the material feed area formed between the side walls. In this way, the support lever does not affect the overall width of the material processing device and can also be integrated in the feed area in such a way that the overall height of the machine is not affected.

According to a preferred variant of invention, provision may be made that the support lever has a blocking seat, on or in which in a blocking position a lock bar rests or is inserted to form the form-fit connection, that the lock bar is coupled to an actuating element, that an actuating unit can be used to move the actuating element in the unlocking direction between the blocking position and a release position, in which the lock bar and the blocking seat are disengaged. The machine operator can easily use the actuating unit to establish or override the form-fit connection. In particular, a remote-control device can be used for this purpose to perform the actuation outside of the danger zone. The lock bar reliably secures the form-fit connection.

If provision is made to attach the support lever to the side wall and the actuating element to the machine support, this results in a wear-optimized design. The actuating element and in conjunction, the actuating unit, are then assigned to the machine support and not to the side wall, which is exposed to strong impact-like forces.

According to a preferred invention variant, provision may be made to form the actuating unit of a hydraulic cylinder and to form the actuating element of a piston rod of the hydraulic cylinder, and to orient the direction of motion of the piston rod transversely to the direction of action of the form-fit connection. By the “direction of action” of the form-fit connection it is meant the direction in which force is transferred by the form fit connection. In the operating position, the piston rod and the hydraulic cylinder are then exposed to no or only slight lateral forces, because these forces are dissipated via the form-fit connection. This results in a long service life of the hydraulic cylinder.

It is particularly preferred that the hydraulic cylinder is designed as a double-acting hydraulic cylinder, which preferably has a greater actuating force in the unlocking direction than in the opposite closing direction. The machine operator can use such a hydraulic cylinder to both establish and override the form-fit connection by remote control. Because a greater actuating force can be exerted in the unlocking direction, i.e. when the form-fit connection is overridden, the high stiction acting in the form-fit connection can be reliably overcome.

A variant of invention can be characterized in that the support lever has a locking section, which is preferably formed at the end facing away from the side wall, that the locking section in the work position is assigned to a retaining part of a blocking piece, wherein the retaining part is coupled to the machine support, that the retaining part has a form-fit element, and that the lock bar in the work position rests in a form-fit manner both against the form-fit element and against the blocking seat of the support lever transversely to the swivel direction of the side wall. In this arrangement, the supporting force required to support the side wall can be reliably transferred in the form-fit connection via the coupling point formed between the lock bar and the retaining part.

If additionally provision is made to arrange the locking section of the support lever in the work position between two retaining parts, each of which has a form-fit element, and for the lock bar to rest against the form-fit elements of the two retaining parts and against the blocking seat of the locking section, then the lock bar can be reliably released from the blocking position. This is possible in particular because the locking section is enclosed between the two retaining parts. This minimizes the risk of the lock bar becoming jammed.

If according to a variant of invention provision is made for the blocking seat of the support lever to have an orientation flank and the lock bar to have a mating surface assigned to the orientation flank, wherein the orientation flank and/or the mating surface is/are arranged inclined with respect to the motion direction of the lock bar, and that when the lock bar is moved in the direction of its locking position, the orientation flank runs up against the mating surface, then the side wall can be accurately oriented when the lock bar is moved to the locking position in the work position. Because the orientation flank runs up against the mating surface, the support lever is moved into the accurate work position.

If provision is made to use a swivel bearing to couple the lock bar to a connecting piece of the actuating element, positional tolerances can be compensated. In that way, provision may not only be made to use the swivel bearing to compensate angle differences. It is also conceivable to provide a clearance within the swivel bearing to compensate for linear misalignment.

In a further variant of the invention provision is made to provide a support piece having a bracket, to which the actuating unit is attached by means of a fastener, that the retaining part(s) is/are attached to the support piece or to the bracket, and that the bracket is detachably or permanently connected to the machine support. In this way a pre-assembled unit can be formed, which can be connected to the machine support. This unit can then be oriented exactly opposite from the machine support such that the lock bar coupled to the actuating unit and the support lever are allocated to each other in a matching manner. The unit is then fixed in place.

If provision is made that the side wall has an inner wall facing the feed area and, at the rear on the side facing away from the inner wall, is equipped with a bracing structure having at least one bracing strut, and that the integral support lever is attached, preferably welded, to the bracing structure; then a lightweight structure is provided for the side wall, wherein the support lever is nevertheless reliably supported and can reliably transfer the forces occurring during the rough operation of a construction site.

A preferred variant of invention is such that the rear wall of the hopper has lateral edge sections assigned to edge sections of the side walls in the work position, that interlocking elements are arranged in the area of the edge sections of the side walls and counter-lock bar elements are arranged in the area of the edge sections of the rear wall of the hopper, that the interlocking elements and the counter-lock bar elements are used to lock the side walls to the rear wall of the hopper in the work position, and that the support lever is preferably arranged in the area of the end of the side wall facing away from the edge section. Locking the side walls to the rear wall of the hopper results in an additional securing of the side walls and also of the rear wall of the hopper in the work position. If the support levers are arranged such that they are located in the area of the end of the side wall facing away from the edge section, this results in particularly high stability of the support of the side wall.

For a stable support of the side wall, provision may in particular also be made that the side wall has two bearing sections, which are arranged at a distance from one another and by means of which the side wall is swivel connected to the machine support using swivel bearings, and that the support lever is arranged in the area between the two bearing sections.

DETAILED DESCRIPTION

FIG. 1shows a material processing plant, namely a mobile crusher10, as it is typically used for crushing recycling material, rocks or other mineral material. This mobile crusher10has a machine chassis supported by two crawler tracks11.

The crusher10is equipped with a feed unit20, which has a feed hopper. This feed hopper has two side walls21and a rear wall of the hopper22. The feed unit20is supported by a boom12of the machine chassis. The boom12has a machine support12.1. This machine support12.1is formed by a longitudinal beam extending in the longitudinal direction of the crusher10.

This feed unit20can be used to fill the crusher10with the material to be crushed. The feed unit20has a transport device at the bottom, which in particular has a feed chute. This conveyor device is used to feed the material to be crushed to a screening unit13. A vibration exciter18is assigned to the feed unit20, which vibration exciter can be designed as an eccentric drive. This vibration exciter18can be used to vibrate the feed unit20to feed the material conveyed in the conveying direction V to the screening unit13. The fed material is subjected to a screening process in the screening unit13. The plant design can be selected such that the vibration exciter18causes not only the feed chute but also the screening unit13to vibrate for transport purposes. In particular, in conjunction with the inclined arrangement of the feed chute and/or one or more screen decks, a transport effect similar to that of a vibratory conveyor is achieved as well.

AsFIG. 1shows, the screening unit13feeds the coarse rock fraction, which is not screened-out, to a crusher unit14(transfer area19). The crusher unit14is designed to have the shape of a jaw crusher. This crusher unit14has two crushing jaws14.2,14.3that form a converging gap. The material to be crushed is fed into this gap area. The crusher unit14has a stationary crushing jaw14.2and a movable crushing jaw14.3; the movable crushing jaw14.3is driven by an eccentric drive14.1.

AsFIG. 1shows, the coarse rock material is crushed in the converging gap. On the bottom side, the crushed and broken rock material exits the crusher unit14in the area of a feed opening14.4of the converging gap and falls onto a crusher discharge belt16due to gravity. The crusher discharge belt16can, as in the present case, be designed as an endlessly circulating conveyor belt.

The crusher discharge belt16discharges the crushed rock material and piles it up behind crusher10.

A magnetic separator16.1can be provided in the area of the crusher discharge belt16at the crusher10. It is arranged above the material flow, which is routed on the crusher discharge belt16. Magnetic or magnetizable metal parts in the material flow are magnetically attracted by the magnetic separator16.1and separated from the material flow.

As the drawing shows, the material coming from the feed unit20is passed through a pre-screen13.1(e.g. top screen deck) in the screening unit13. In the process, part of the rock material is singled out. These are pieces of rock which, due to their size, do not have to be sent through crusher unit14, as they already have a size that corresponds approximately to the rock size that results from crushing by the crusher unit14. As the drawing shows, a part of this singled-out rock fraction is fed directly to the crusher discharge belt16in a bypass of the crusher unit14.

AsFIG. 1shows, there may now be a further lower screen deck13.2in the screen unit13below the pre-screen13.1. This lower screen deck13.2screens-out a further, fine partial fraction from the material already screened-out. It is now partly desired to separate this particularly fine partial fraction, for which a side discharge belt15is used. The fine partial fraction is fed onto this endlessly rotating side discharge belt15, is conveyed out of the working area of crusher10and piled up, as shown inFIG. 1.

However, discharging the fine sub-fraction is not always desired. Rather, the machine operator wants to have the choice of feeding it separately or conjointly with the coarser screened material directly onto the crusher discharge belt16. An adjustable flap chute17is used for this purpose.

As mentioned above, an excavator or the like is used to feed the material to be crushed into the crusher10in the area of a feed unit20.FIG. 2shows the feed unit20in more detail. As this illustration shows, the feed unit20has two side walls21. These side walls21are essentially oriented in the conveying direction V. At the rear, the feed unit20has a rear wall of the hopper22. A feed area is formed between the set-up side walls21and the rear wall of the hopper22. The material to be crushed can be fed into this feed area. At the bottom, the feed area closes off with the above-mentioned conveyor unit, i.e. the conveyor chute or the conveyor belt.

The two side walls21can preferably be designed as mirror images of each other.

The side walls21have an inner wall21.1, which is formed by a sheet metal blank. The inner wall21.1forms an angled edge21.2at the top. A chamfer21.3adjoins the upper edge21.2. The upper edge21.2and the chamfer21.3are used to brace the upper part of the side wall21. The inner wall21.1has a bracing structure on its side facing away from the feed area. This bracing structure is formed by bracing struts21.4.

AsFIG. 3shows, the side walls21have edge sections21.5in their areas facing the rear wall22of the hopper. Interlocking elements21.6are provided at these edge sections21.5. The interlocking elements21.6can, for instance, take the form of protruding lugs, which protrude from the edge section21.5and have an opening. The edge sections21.5may also be referred to as rear edge sections of the side walls21.

The design of the rear wall of the hopper22is similar to that of the side walls21. Correspondingly, the rear wall of the hopper22has an inner wall22.1, which may be formed of a sheet metal blank. An upper edge22.2protrudes beyond the outside of the inner wall22.1and is adjoined by a chamfer22.3. The upper edge22.2and the chamfer22.3are used to brace the upper part of the rear wall of the hopper22.

AsFIG. 2shows, the crusher10has a machine chassis having a machine support12.1. A machine support12.1in terms of the invention can be considered to be any component, which is part of the machine chassis or which is directly or indirectly coupled to the machine chassis and which is sufficiently strong to support at least one of the side walls21in the operating position shown inFIG. 2.

AsFIG. 2shows, the crusher10has the boom12. This boom12has two longitudinal beams which are oriented in the direction of the longitudinal extension of the crusher10. These two longitudinal members each form a machine support12.1. At the rear, the two machine beams12.1are interconnected by a cross beam12.2.

The two side walls21can, for instance, be attached to the machine supports12.1based on the same design. The explanations below therefore apply to the two side walls21.

The machine supports12.1have a bearing bracket12.4and a bearing support12.7. The bearing bracket12.4bears two lugs12.5with aligned drilled holes. In the same way, the bearing support12.7also has two lugs12.8having aligned drilled holes. These drilled holes are aligned with the drilled holes of bearing sections25,26. The bearing sections25,26are attached to the external bracing structure of the side wall21. Bearing pins can pass through the aligned drilled holes to form a swivel bearing12.6,12.9. The swivel axis of the two swivel bearings12.6,12.9are aligned with each other. Accordingly, the side wall21can be moved about this common swivel axis between the work position shown inFIG. 2and the folded-down transport position shown inFIG. 3.

As shown inFIG. 2, the lateral bracing in25.2,26.2can be used to couple the bearing section25and/or the bearing section26to the side wall21. These bracings25.2,26.2not only increase the stiffness of the bearing sections25,26but also that of the side wall21in this heavily stressed area.

AsFIG. 2further shows, the machine supports12.1are equipped with brackets12.3. One actuator12.10each can be swivel-mounted to these brackets12.3. The actuator12.10is formed by a hydraulic cylinder. Accordingly, the actuator12.10has a cylinder12.11and a piston, which can travel therein. A piston rod12.12is connected to the piston. At its free end, the piston rod12.12is connected to a support section24of the side wall21in a swiveling manner. This detail is shown more clearly inFIG. 4. As this illustration shows, the support section24bears a bracket24.1. The piston rod12.12has a head12.15at its free end. This head12.15has a drilled hole, which is aligned with drilled holes in the bracket24.1. A pin24.2can be inserted through the aligned drilled holes to form a swivel bearing. This swivel bearing is at a distance from the swivel bearings12.6and12.9, wherein this eccentric assignment creates a support distance.

The rear wall of the hopper22has the bearing section22.5, as described above. This bearing section22.5has bearing shoulders, which are assigned to two bearing brackets12.13. The bearing brackets12.13are fixed to the cross beam12.2. The bearing brackets12.13also have drilled holes that are aligned with the bearing shoulders of the bearing section22.5. Swivel bearings12.14are formed here using bearing pins. The rear wall of the hopper22can be swiveled about the aligned articulated shafts of these two swivel bearings12.14between the work position shown inFIG. 2and the transport position shown inFIG. 3.

FIG. 3illustrates that the rear wall of the hopper22also has edge sections22.6. The edge sections22.6may be referred to as lateral edge sections of the rear wall. In the operating position shown inFIG. 2, these edge sections22.6are assigned to the edge sections21.5of the side walls21. The counter-lock bar elements22.7shown inFIG. 3are arranged in the area of the edge sections22.6. These counter-lock bar elements22.7may, for instance, be formed by movable pins. These movable pins engage with the openings of the interlocking elements21.6of the side walls21when the latter are in the operating position. The form-fit interlock formed in this way secures the operating positions of the side walls21and of the rear wall of the hopper22.

AsFIGS. 2 and 3illustrate, a support device30is arranged on each of the two side walls21. This support device30comprises at least one support lever31. The support lever31is designed as a rigid integral lever.

The support lever31has a fastening segment34. This fastening segment34is used to attach the support lever31to the side wall21. Preferably the fastening segment34is mounted on the outside of the inner wall21.1and further preferably in particular on at least one of the bracing struts21.4of the bracing structure. The fastener is preferably formed by a material bond, in particular a welded joint.

The integral lever-shaped locking section33adjoining the fastening segment34projects from the side wall21. The locking section33has a blocking seat32. This blocking seat32can, as in this exemplary embodiment, be formed by an opening, which is inserted into the locking section33.

AsFIG. 3shows, the support lever31is arranged in the area between the bearing bracket12.4and the bearing support12.7. The arrangement is such that the support lever31is located in the area of the end of the side wall21facing away from the rear wall of the hopper22to provide stable support for the side wall21.

AsFIG. 3shows, the support lever31projects into the feed area in a space-saving manner if the side walls are in the folded-down position, which they assume in the transport position. In the upright operating position, as shown inFIG. 2, the locking section33of the support lever31is assigned to a blocking piece27. This can be more clearly seen inFIG. 4.

AsFIG. 4shows, the blocking piece27has two retaining parts27.1, which are spaced apart from each other. The retaining parts27.1can be formed by plate-shaped elements. Every retaining part27.1has a form-fit element27.2. As the drawings illustrate, this form-fit element27.2can be formed by a breakthrough in the retaining parts27.1. The openings in the two retaining parts27.1are aligned with each other. The retaining parts27.1are attached to a support piece28.7. The support piece28.7may be designed to be plate-shaped. It is connected to a bracket28.6, wherein the connection between the bracket28.6and the support piece28.7is preferably formed by a welded joint. In the same way, the retaining parts27.1can be connected to the bracket28.6or to the support piece28.7, for instance by welding. The locking piece27also bears an actuating unit28.4. In this example a fastener28.5is used to attach the actuating unit28.4to the support28.7. The actuating unit28.4is formed by a hydraulic cylinder. This hydraulic cylinder also comprises a piston rod, which forms an actuating element28.3. A connecting piece28.2is provided at the end of the actuating element28.3. A lock bar28is connected to the connecting piece28.2via a swivel bearing28.1. The actuating unit28.4may also be referred to as an actuator.

The blocking piece27forms a pre-assembled unit in conjunction with the bracket28.6, the support piece28.7, the actuating unit28.4and the lock bar28. Bolts28.8can be used to connect this pre-assembled unit to a flange12.16of the machine support12.1. The assignment to the machine support12.1is such that in the operating position shown inFIG. 4, the support lever31comes to rest between the two retaining parts27.1. In particular, the blocking receiver32of the support lever31is aligned with the two form-fit elements27.2of the retaining parts27.1. AsFIG. 4shows, the lock bar28secures this operating position. The lock bar28passes through the aligned form-fit elements27.2and the blocking seat32. In this way, a form-fit connection is formed, wherein a form fit is formed transverse to the swivel direction of the side wall21. In this way, the side wall21is blocked against the machine support12.1in a form-fitting manner. Preferable the form-fit connection acts in both the unfolding and the fold-down direction. In this way a secure immobilization of the side wall21is achieved. However, this is not mandatory in accordance with the invention. In particular, it may only be provided that the form-fit connection is effective in the fold-down direction.

To move the side walls21from the operating position shown inFIGS. 2 and 4to the transport position shown inFIG. 3, first the connection between the rear wall of the hopper22and the side walls21(interlocking element21.6and counter-lock bar elements22.7) is released. Then, suitable devices, for instance of an actuator not shown in the drawings, can be used to move the rear wall of the hopper22into the folded-down transport position shown inFIG. 3.

Simultaneously or afterwards, the side walls21can be swiveled. To this end, first the actuating unit28.4is activated and then the actuating element28.3is retracted. In this way, the lock bar28and the blocking seat32of the support lever31are disengaged. Consequently, the support lever31is released and no longer connected to the blocking piece27. Now the actuator12.10can be activated, wherein the piston rod12.12is retracted. This causes the side wall21to swivel about the swivel axis formed by the swivel bearings12.6and12.9. During this swivel motion, the locking section33of the support lever31inFIG. 4moves backwards ‘into the image’ out of the fitting formed between the two retaining parts27.1. As a result of the swiveling motion of the side wall21, the support lever31also swivels until it reaches the position shown inFIG. 3and comes to rest in the feed area between the two side walls21.

Stops22.4and25.1can be provided to limit the swinging motion of both the rear wall of the hopper22and/or the side walls21. The stop22.4can, for instance, be provided on the bearing section22.5of the rear wall of the hopper22. The stop25.1can, for instance, be provided at the bearing section25of the side wall21. These bearing sections25offer a stable coupling point for the stop22.4or25.1.

To set up the side walls21or the rear wall of the hopper22from the transport position shown inFIG. 3to the operating position shown inFIG. 2, the operating procedure described above has to be followed in reverse order.

As explained above, the lock bar28passes through the blocking seat32of the support lever31and the aligned form-fit elements27.2of the retaining parts27.1. Accordingly, the force is transferred from the support lever31into the retaining parts27.1via the lock bar28, in particular via the form-fit connections formed there. The direction of force is transverse to the actuating direction of the piston rod (actuating element28.3). The piston rod is thus at least largely free from transverse forces permitting a low-stress operating mode of the actuating unit28.4. In particular, any bending of the piston rod is prevented.

It may also be provided that the lock bar28has a wedge-shaped geometry. If it is then inserted into the blocking seat32of the support lever31, an orienting flank of the wedge-shaped geometry of the lock bar28runs up against a mating surface of the blocking seat32. In this way the support lever31can be oriented exactly opposite from the blocking piece27. This orientation then makes for an exact orientation of the side wall21in the operating position.