EP0351529B1 - Adjustable grid for the opener arm of a bale-opening machine - Google Patents

Description

The present invention relates to an adjustable grate for the removal arm of a bale removal machine for adjusting the penetration depth of drivable fiber removal elements which extend between the grate bars arranged transversely to the longitudinal direction of the removal arm. An adjustable grate of this type is known from European patent application, publication number 199 041 or from US Pat. No. 3,381,341.

It is common nowadays to use a bale removal machine for opening the bale, the bales being placed in a row one behind the other and parallel to the direction of travel of the bale removal machine. Experience has shown that there are harder bales and softer bales and the density of the bale layer to be removed also changes with the degree of opening of the bale. This different density of the bale layers makes it necessary to change the penetration depth of the fiber removal elements of the bale removal machine. The penetration depth is defined as the distance by which the fiber removal elements protrude at most below the grating sliding over the surface of the bale. It differs from the infeed depth, which is a measure of the vertical adjustment of the entire removal arm of the bale removal machine before moving again along the row or group of bales.

The previously proposed mechanisms for adjusting the penetration depth by adjusting the grate are relatively complex. For example, in US Pat. No. 3,381,341 there are several bevel gears for adjustment of the grate used, which are relatively expensive in themselves. In order to adjust the grate at both ends, either an additional complex gear arrangement is required or two separate drive motors for the corresponding bevel gears arranged at both ends of the grate, it then being necessary to ensure the synchronization of the two motors. In the arrangement shown, it is also not possible to adjust the inclination of the grate.

The arrangement shown in EP 199 041 allows adjustment of both the penetration depth and the inclination of the grate, but ultimately also requires four drive motors which have to be synchronized with one another at least in pairs.

The present invention has for its object to provide an adjustable grate, which is inexpensive to manufacture, can be adjusted precisely, is mechanically stable and requires at least one or only one actuating motor on conventional removal arm lengths, so that any synchronization costs are eliminated. The grate should also be designed so that the angle of inclination can be adjusted without significant additional effort.

To achieve this object, in the case of an adjustable grate of the type mentioned in the introduction, it is provided that the grate bars are mounted at their two ends on respective pivot axes extending in the longitudinal direction of the removal arm, and that at least one axis extends around a second axis parallel to the first axes rotatable lever device provided is to raise or lower the grate bars at at least one of their two ends, and that in an advantageous embodiment the grate bars are supported at least at one end in a longitudinally displaceable manner, that is to say they are displaceable transversely to the longitudinal direction of the removal arm.

By using a lever device, the grate bars are therefore raised or lowered at least at one end, which changes the penetration depth. The rotary movement of the lever device can be brought about by a single actuating motor, the ends of all grate bars being adjusted by at least essentially the same amount due to the construction specified. In order to avoid that the grate bars are moved in operation in the horizontal direction, transversely to the longitudinal axis of the removal arm, in order to maintain the selected setting of the penetration depth, the grate bars must then be guided at at least one corresponding vertical stop, if only in one direction of travel fiber flakes are removed from the removal arm. However, if fiber flakes are removed in both directions of travel, the above-mentioned horizontal displacement of the grate bars in both directions must be prevented by one stop each.

After lifting or lowering only one end of the grate bars leads to a shortening of the horizontal distance between the two stops of the grate bars, the distance between the abovementioned stops can be made variable. However, this is not necessary if the shortening is practically negligible. In special embodiments, the grate bars are at least at one end supported in a longitudinally displaceable manner, ie so supported that the end in question can be displaced transversely to the longitudinal direction of the removal arm.

The lever device can comprise a lever which is pivotally connected to a connecting bracket, the lever being fixedly connected to a pivot shaft and the connecting bracket pivotably connected to a pivot axis which pivotally supports the grating ends. Such a lever device can be provided for both grate bar ends, so that both lever ends can be raised or lowered by the same or a different amount. The lever device preferably comprises an eccentric drive, since in this way a good leverage effect can be achieved with a space-saving arrangement.

In the simplest case, the eccentric drive can be an eccentric bushing, which extends through circular bores at one end of the grate bars. In this case, the eccentric bushing forms the lever which is firmly connected to the pivot shaft via the eccentric bore of the bushing. The penetration depth can be adjusted by turning the eccentric bushing, which is possible with an actuating motor in such a way that all grate bars are adjusted by the same amount.

However, an arrangement is preferred which is characterized in that the grate bar end is not arranged such that it can be pivoted directly on the eccentric bushing, but rather a lever which in turn is pivotally connected to a pivot axis which is used for pivotably receiving the grate bar end serves. Such an eccentric / lever device can also be used for both grate bar ends.

This arrangement has the particular advantage that the space required for the removal of the removed fiber flakes in the circumferential area of the rotatable fiber removal elements is less restricted by the lever device than by the previously mentioned lever device with two levers and is more flexible than the aforementioned eccentric drive directly in the grate bar end.

In this arrangement, an operating lever is provided which engages one of the eccentrics or on the pivot shaft in order to rotate the eccentrics at the same time.

In the special arrangements discussed, at least the pivot axis facing away from the pivot shaft is preferably guided so as to be displaceable in slot guides of the removal arm. There are several options for the slot guides. They can extend in the horizontal direction or they can be inclined upwards, or they can also have a curvature.

If the slot guides extend in the horizontal direction, an adjustment of the lifting or lowering ends of the grate bars by a vertical distance x leads to a change in the penetration depth of approximately x: 2 if the grate bars are arranged symmetrically. Through the use of slot guides which are inclined upwards (or possibly downwards), the ends of the grate bars, which can be raised or lowered directly by the lever device, can be moved up and down, which also leads to a horizontal movement of the grate bars leads, so that the other ends of the grate bars are raised or lowered. By using curved slot guides, one can even ensure that the two ends of the grate bars are raised or lowered by exactly the same amount.

Another possibility of the special arrangements to ensure the necessary displaceability of the grate bars is to provide a second pivot axis which extends parallel to the first pivot axis facing away from the pivot shaft and is connected to this via at least two pivotable connecting straps distributed over the length of the pivot axes .

An arrangement of this type is particularly preferred, which is characterized in that the two pivotable connecting straps between the second pivot axis and the first pivot axis assigned to it are designed in accordance with the connecting strap extending between the pivot shaft and the first pivot axis assigned to it and also on which second pivot axis arranged eccentrics are stored.

The eccentrics arranged on the second swivel axis are preferably also fastened on this second swivel axis and a further actuating lever is provided which is fastened on one of these eccentrics or on the second swivel axis. This means that the mechanical arrangements on the left and right ends of the grate bars are of the same design.

With such a design, the first axes should be guided in slot guides which extend at least substantially in the vertical direction in order to limit the horizontal displaceability of the grate bars. However, these slot guides must be somewhat wider in the horizontal direction than the diameter of the first axes in order to allow the longitudinal movement of the grate bars due to the eccentric or lever action.

An arrangement of this type is preferably characterized in that the pivot shaft and the second pivot axis are at a greater distance from one another than the two first pivot axes and are arranged above the first pivot axes. As a result, the space below the usually rotatable fiber removal elements is optimally adapted to the rotating circle of these elements, so that the mechanical arrangements do not restrict the space available for the removal of the fiber flakes.

In the case of an arrangement with a lever device at the two ends of the grate bars, the possibility is created of setting the grate bars for both directions of movement of the stripping machine along the rows of bales in such a way that a positive angle of attack is present in each direction of travel, which makes it much easier for the grate bars to slide over the bales to be removed .

The or each actuating lever can preferably be actuated by a motor and is movable between two switching positions, at which switches are provided, which stop the motor and limit the lever stroke. Even when using two actuating levers and therefore two actuating motors, ie one Motor for each side of the adjustable grate, no synchronization of the two motors is required.

The drive provided for the or each actuating lever is preferably designed such that it cannot be reversed by pressure on the grate bars; e.g. a spindle drive that engages the actuating lever with a nut can be used. This prevents the penetration depth from being adjusted by pressure on the grate bars.

The grate bars themselves preferably have integrated spacers at their ends, with the spacers sitting directly next to one another after the grate bars have been arranged on the first axes. Loose spacers are hereby avoided and the arrangement consists of a large number of identical grate bars, which can then be manufactured inexpensively, preferably as castings made of aluminum, e.g. Die-cast aluminum.

The size of the spacers should be chosen so that the distance between adjacent grate bars is somewhat larger than the amplitude of the preferably tumbling movement of the fiber ablation elements. Furthermore, the grate bars can be inclined somewhat upwards at the ends in side view, so that they function like a kind of skids for both directions of movement of the removal arm.

With removal arms of the usual lengths, it is sufficient to provide an operating lever for each side of the grate, the operating lever preferably being arranged in the middle of the removal arm, which makes possible Inaccuracies due to twisting of the second or third axes are kept to a minimum. Finally, the eccentrics can each have a slot and be attached to the pivot shaft or second pivot axis by means of a clamping screw.

• Fig. 1 eine Seitenansicht eines einzelnen, erfindungsgemässen bewegbaren Roststabes,
• Fig. 2 eine Draufsicht auf einen Abtragarm einer Ballenabtragmaschine mit einem anders ausgebildeten Mechanisms für die Bewegung der Rostsäbe, wobei die Abtragorgane der Darstellung halber weggelassen sind und der Arm verkürzt dargestellt ist,
• Fig. 3 eine Frontansicht des Ballenabtragarmes entsprechend den Pfeilen III-III in Fig. 2,
• Fig. 4 eine Seitenansicht von Fig. 2 mit einem einselnen bewegbaren Roststab, um die Verstellung dieses Roststabes zu verdeutlichen,
• Fig. 5 eine Seitenansicht ähnlich der Fig. 4, wobei jedoch gezeigt wird, wie der Anstellwinkel des Roststabes geändert wird,
• Fig. 6 eine Seitenansicht eines Roststabes bei einer etwas abgewandelten Ausführung,
• Fig. 7 eine Seitenansicht des linken Endes eines einzelnen Roststabes, um die für die Verstellung des Roststabes vorgesehenen Betätigungsmechanismen zu verdeutlichen,
• Fig. 8 eine Seitenansicht einer weiteren Ausführung eines Roststabes,
• Fig. 9 eine Seitenansicht entsprechend der Fig. 8, jedoch von einer etwas abgewandelten Ausführungsform,
• Fig. 10 eine Seitenansicht entsprechend den Fig. 8 und 9, jedoch mit einer weiteren Abwandlung, und
• Fig. 11 eine Seitenansicht einer weiteren abgewandelten Ausführungsform eines Roststabes eines verstellbaren Rostes,
• Fig. 12 eine Seitenansicht einer Variante eines erfindungsgemässen Roststabes.

The invention is explained in more detail below on the basis of exemplary embodiments with reference to the drawing. In this shows:

• 1 is a side view of a single movable grate bar according to the invention,
• 2 shows a plan view of a removal arm of a bale removal machine with a differently designed mechanism for the movement of the grate bars, the removal elements being omitted for the sake of illustration and the arm being shown in shortened form,
• 3 is a front view of the bale removal arm according to the arrows III-III in Fig. 2,
• 4 is a side view of FIG. 2 with a single movable grate bar to illustrate the adjustment of this grate bar,
• 5 is a side view similar to FIG. 4, but showing how the angle of attack of the grate bar is changed,
• 6 is a side view of a grate bar in a somewhat modified embodiment,
• Fig. 7 is a side view of the left end of a individual grate bar in order to clarify the actuation mechanisms provided for the adjustment of the grate bar,
• 8 is a side view of a further embodiment of a grate bar,
• 9 is a side view corresponding to FIG. 8, but of a slightly modified embodiment,
• Fig. 10 is a side view corresponding to FIGS. 8 and 9, but with a further modification, and
• 11 is a side view of a further modified embodiment of a grate bar of an adjustable grate,
• Fig. 12 is a side view of a variant of a grate bar according to the invention.

Fig. 1 shows a single grate bar 11, which is movably received at both ends by a lever device 100. In this case, the lever device 100 comprises a lever 101, which on the one hand is fixedly connected to a pivot shaft 102 and on the other hand is pivotably connected to a connecting bracket 103, which in turn is pivotally connected to a first pivot axis 104 receiving the grate bars 11.

The pivot shaft 102 is mounted in a removal arm 16 which will be described in more detail later in the directions of rotation R and can be driven.

Furthermore, at least two levers 101 are provided in a removal arm per pivot shaft 102, which in turn are connected by a second pivot axis 105, by means of which the levers 101 and the connecting straps 103 are pivotally connected to one another. The levers 101 are essentially perpendicular, as seen in FIG. 1, to the connecting straps 103, the connecting straps 103 being arranged essentially vertically, which is not essential to the invention, since an oblique arrangement has the same purpose, only with different force ratios , would meet.

In order to prevent the grate bars 11 from being displaced in the horizontal direction U, stops 106 and 107 are provided. These stops can be continuous over the entire length of a removal arm or can also be distributed individually, but at least the outermost grate bars should find a hold on such stops.

The game shown in Fig. 1 Y.1 respectively. Y.2 should only be so large that the grate bars between the stops 106 and 107 are well guided, but not clamped.

If the grate bars 11 are to change their position during operation, the swivel shafts 102 are rotated in a manner described for the variants described later, so that the levers 101 are swiveled in the swivel direction R, which, depending on the direction, causes the grate bars to be lifted up or down be moved.

For example, the lever 101 on one side pivoted more or in a different direction than that on the other side of the grate bars, so the game increases Y.1 or. Y.2, but this is practically negligible.

As further shown in Fig. 1, the individual grate bars have upwardly inclined regions 12 and 13 at their ends which, in operation, function as a kind of skid to ensure that the grate slides along the row of bales, the two regions 12 and 13 being these Allow sliding in both directions.

The grate bars made of die-cast aluminum are provided at their ends, as shown in FIG. 2, with integrated spacers 14 and 15, so that when installed in a removal arm 16, for example as shown in FIG. 2, the grate bars can be arranged directly next to one another without that intermediate pieces are required.

FIG. 2 shows a further lever device designed according to the invention, which is further illustrated in FIGS. 4 to 7. The removal arm 16 of FIG. 2 is only provided with eight such grate bars, in practice there are many more, but the number of grate bars has been reduced for the sake of simplicity. The removal arm 16 has at its upper end in FIG. 2 a continuous plate 17 which can be attached to the tower of a bale removal machine. At its lower end in FIG. 2, the removal arm 16 has a shield or plate 18, which can be seen in FIG. 3. The plate 18 and the plate 17 are connected to one another via frame parts 19 and 21 to form a cuboid rigid frame. The wave extends within this arm Bale removal device which is provided with fiber removal elements arranged in the manner of a swashplate. These organs are not visible in the drawing according to FIG. 2, but they are known per se from the European patent application with the publication number 199 041. The circulation circles of the swashplate-like fiber ablation elements are, however, shown in FIGS. 4 to 7 and identified by the reference number 22. The arrangement is such that a swashplate-like organ lies between two adjacent grate bars, the working tips of the organ being at the lowest point below the underside of the grate bars, the distance between these working tips and the underside of the grate bar at the deepest point being the penetration depth T is designated. In operation, it is necessary to adjust this penetration depth T between two values T _min and T _max (see, for example, FIG. 4), the difference T _min -T _{max being} approximately 7 mm.

The purpose of the arrangement just described is to simultaneously adjust the penetration depth for all grate bars of the grate formed by these grate bars by the same amount. For this purpose, two pivot axes 23 and 24 extend through the bores at the two ends of the grate bars. The pivot axes 23, 24 extend parallel to the longitudinal direction of the support arm 16 and penetrate the plates 17 and 18, which terminate the removal arm 16 at the opposite ends. The openings in the end plates of the removal arm which receive the pivot axes 23, 24 are designed as guide slots 25 and 26, as can be seen from FIG. 3. To avoid sagging of the axes, on the left and right side of the removal arm in Fig. 2 screwed to the respective frame parts 19 and 21 respective supports 27 and 28, respectively. The guide slots 25 and 26 are dimensioned somewhat wider in width than the diameter of the pivot axes 23 and 24 to have enough width even if the grate bars 11, as described earlier, are not raised or lowered while maintaining the horizontal position. The length of these slotted slots is sufficiently long that the desired adjustment range for the penetration depth is possible. The end view of FIG. 3 shows in the middle the bearing housing 29 for the shaft of the fiber ablation elements, the housing being fastened to the plate 18 by means of screws 31. A further storage can be provided on the plate 17.

To adjust the grate bars, a first pivot axis 32 and a second pivot axis 33 extend to the left or right of the removal arm 16, which are rotatably mounted in the bearing bores 34 and 35 of the end plate 18. Corresponding bearing bores are arranged in the end plate 17 and in the two supports 27 and 28. On the first pivot shaft 32, three eccentric bushes 36, which are all of the same design, are clamped, and this is done in that each eccentric bushing has a slot 37, a clamping screw 38 being able to extend and be tightened through the material on both sides of the slot 37 to clamp the eccentric bushing.

Three identically designed eccentric bushes 36 are also clamped on the second pivot shaft 33. Levers 41 are pivotably arranged on the cylindrical outer surfaces 39 of the eccentrics, the arrangement left and right of the removal arm is mirror-symmetrical. The mentioned pivotability of the levers 41 results from a first cylindrical bore 42 which is rotatably mounted on the cylindrical outer surface 39 of the associated eccentric bushings 36. At their ends 43 facing away from the bores 42, the levers 41 have a second cylindrical bore 44, in which the pivot axes 23 and 24 are pivotably guided. These bores 44 are dimensioned as large as the cylindrical bores 56 (FIG. 1) in the two ends of the grate bars 11. From FIGS. 4 to 7 it can be seen that the eccentric bushes 36 have a bore 45 eccentric to their cylindrical outer surfaces 39 through which the first pivot shaft 32 and the second pivot shaft 33 extend.

2 that the first cylindrical bores 42 of the levers 41 have a considerable length. This design was chosen to avoid jamming of the levers on the cylindrical surface of the respective eccentric. One can immediately see that all levers, all eccentric bushings or all grate bars, whether they are to the left or right of the axis of symmetry of the removal arm, are of the same design.

The adjustment of the grate bars via the lever 41 is effected with an operating lever 46, which can only be seen in FIG. 7. This actuating lever 46 is arranged on the pivot shaft 32 and 33 in a rotationally fixed manner (not shown). The free end 47 of the actuating lever 46 facing away from the eccentric bushing 36 is pivotably connected via a joint pin 48 to a joint part 50 with an internal thread, the joint part 50 receiving a threaded rod 49 which is the shaft of an electric motor 51. By operating the motor 51, the joint part 50 is moved away or closed by the threaded rod 49 from the fixed motor 51. In addition, two limit switches 52 and 53 are provided, which are switched in the two end positions 461 and 462 of the actuating lever 46 by this actuating lever and interrupt the power supply to the electric motor 51. FIG. 7 shows only the arrangement on the left side of the removal arm 16 in FIG. 2. A similar arrangement is also provided on the right side.

As can be seen in particular from FIGS. 4 and 7, a movement of the actuating lever leads to a rotation of the first pivot shaft 32 and. the second pivot shaft 33 and thus to a rotation of the two eccentric bushes 36 at the ends of the removal arm 16. This rotation of the eccentric bushes leads to an increase in the end 43 of the lever 41 and via the pivot axis 23 to an increase in the ends of the left in FIG Grate bars 11.

Fig. 4 shows the simultaneous adjustment of the two ends of the grate bars 11 by the motors 51 left and right of the removal arm 16, whereby the penetration depth can be varied between T _min and T _max . Intermediate positions are also easily possible.

FIG. 5 shows that different adjustments of the left and right ends of the grate bars 11 are possible by correspondingly controlling the respectively assigned motors 51, wherein the angle of attack of the grate bars 11 can be changed, if desired, without a simultaneous adjustment of the average penetration depth . The possibility of Changing the angle of the grate bars is particularly favorable, since this can increase the skid effect of the grate bars.

As FIG. 6 shows, it is not absolutely necessary to adjust the two ends of the grate bars in order to change the penetration depth. Instead, the right end of the grate bar 11 shown in FIG. 6 can simply be articulated on the pivot axis 24, in which case it is not necessary to ensure that the axis 24 can also be displaced. Although the change in the angle of attack of the grate that can be achieved by moving the left end of the grate bar is limited, this does not necessarily have to be disadvantageous, e.g. with a bale removal machine, which always removes in the same removal direction.

However, it is also possible to effect an adjustment of the two ends of the grate bars 11 with only one actuating motor. This is shown by the embodiments according to FIGS. 8, 9 and 10. It must be said in advance that in the different embodiments of FIGS. 8, 9 and 10 the axes are guided in elongated slots 261, 262 and 263, which in turn are in the end plates 17th and 18 or the support 28 are provided. In this arrangement, the eccentric bushes are arranged in a different angular position, so that rotation of the eccentric bush 361 leads to a pronounced displacement of the grate bars 11 in their longitudinal direction. This can be seen in particular from FIG. 8, where the relative displacement of the axis 24 is shown with half an adjustment movement of the eccentric 361. This large displacement movement of the grate bars can now be achieved by using an inclined slot guide 262, as shown in FIG. 9, or by using a curved slot guide 263, as shown in FIG. 10, to bring about the raising or lowering of the right end of the grate bar and therefore of the grate.

Finally, FIG. 11 shows a further, somewhat modified embodiment, in which the eccentric bush 362 again has the rotational position of the eccentric bush 36 of FIGS. 1 to 7, but the right end of the grate bar is articulated on a connecting lug 55, the connecting lug 55 on their bores 57 and 58 at both ends. The pivot axis 24 is rotatably received in the bore 57 and the second pivot shaft 33 in the bore 58.

In this embodiment, the guide slots 25 and 26 are not necessary.

12 shows a further variant, in which an eccentric bush 363 is provided in both ends of a correspondingly adapted grate bar 11.1. The eccentric bushings in the left end 108, as seen in FIG. 12, of the grate bar 11.1 are firmly connected to the first pivot shaft 32 and in the right end 109 are firmly connected to the second pivot shaft 33.

Furthermore, both eccentric bushes 363 are connected to one another by an overdrive 110, which essentially consists of a crank lever 111 being fastened to each eccentric bush 363, and that these crank levers 111 are pivotably connected to a connecting bracket 112.

Accordingly, it is only necessary to use one of the to drive two pivot shafts 32 and 33 by means of the actuating lever 46 and the elements described.

In order to allow the overdrive 110 to act in a favorable force ratio, the crank levers 111 are offset by an angle of approximately 90 ° to the pivot shafts 32 and 33. Furthermore, the eccentric bushes 363 are not arranged in mirror image, as is shown in FIGS. 4 and 5, but are aligned in order to have the possibility of evenly lowering or raising the grate bars 11.1 with both ends.

Of course, here too there is the possibility of arranging the crank levers in a different position in the respective eccentric bushings on the left and right ends of the grate bars 11.1, so that, for example, the right end 109 is lower than the left end 108, or vice versa. For this purpose, it is only necessary to provide one of the two crank levers 111 on the respective eccentric bushing which can be moved and locked, which can be achieved, for example, with an annular sliding groove (not shown) in the cross-sectional area of the eccentric bushing 363, in which the corresponding crank lever 111 is guided and lockable.

Legend

11

Grate bar

12/13

End area on grate bar 11

14/15

Spacers

16

Removal arm

17/18

Plate or shield

19th

Frame part

20th

21

Frame part

22

Fiber removal organ

23/24

Swivel axes

25th

Guide slot

26/261/262/263

Guide slot

27/28

Support

29

Bearing housing

30th

31

Screws

32

first swivel shaft

33

second pivot shaft

34

35

36/361/362

Eccentric bushing

37

slot

38

Clamping screw

39

cylindrical outer surface of the eccentric bush

40

41

lever

42

first cylindrical. Hole on lever 41

43

Lever end

44

second cylindrical. Hole on lever 41

45

cylindrical bore of the eccentric bush 36

46

Operating lever

47

free end of the operating lever 46

48

Hinge pin

49

Threaded rod

50

Joint part

51

Electric motor

52/53

Limit switch

54

55

Tab

56

cylinder no. Hole in the grate bar 11

57/58

Holes

100

Lever device

101

lever

102

Swivel shaft

103

Connecting strap

104/105

Swivel axes

106/107

attack

108

left end of the grate bar 11.1

109

right end of the grate bar 11.1

110

Exaggeration

111

Crank lever

112

Connecting strap

Claims (19)

1. Adjustable grid for the extraction arm of a bale extraction machine for setting the penetration depth of driveable fibre extraction members extending through between the grid bars arranged transversely to the longitudinal direction of the extraction arm, characterised in that the grid bars (11) are mounted at each of their two ends on swivelling axes (23 or 24 or 104) extending in a longitudinal direction of the extraction arm, that at least one lever device (41 or 100), which is rotatable by means of a swivel shaft (32 or 102) extending parallel to the swivelling axes (23 or 104), is provided in order to raise or lower the grid bars (11) at at least one of their two ends, and that the grid bars (11) are supported by stops (106, 107 or 25, 26) at least at one end against longitudinal displaceability, i.e. displacement transversely to the longitudinal direction of the extraction arm (16).

2. Adjustable grid according to claim 1, characterised in that the lever device (100) comprises a lever (101) firmly connected to the swivel shaft (102) and a connecting bracket (103) pivotably connected to the lever (101) and likewise pivotably connected to the appropriate one of the two swivelling axes (104).

3. Adjustable grid according to claim 1, characterized in that the lever device (41) comprises an eccentric bush (36; 361, 362) which is connected eccentrically relative to its peripheral surface (39) and non-rotatably to the swivel shaft (32 or 33) and on whose peripheral surface (39) is pivotably disposed a connecting bracket (41), the other end of which is pivotably connected to the appropriate one of the two swivelling axes (23 or 24).

4. Adjustable grid according to claim 3, characterized in that provided at the end of the connecting bracket (41) associated with the swivel shaft (32) is a first cylindrical bore (42) in which the eccentric bush (36) fixed on the first swivel shaft (32) is rotatably disposed, and that the connecting bracket (41) has on its end opposite the first bore (42) a second bore (44) through which the swivelling axis (23) associated with the second swivel shaft (32) rotatably extends.

5. Adjustable grid according to claim 3, characterized in that an operating lever (46) is provided which acts upon the first swivel shaft (32) in order simultaneously to rotate the eccentric bush (36).

6. Adjustable grid according to one of the preceding claims, characterized in that at least the swivelling axis remote from the first swivel shaft (32) is displaceably guided in guide slots (26; 261; 262; 263) of the extraction arm serving as stops.

7. Adjustable grid according to claim 6, characterized in that the guide slots (261; 262; 263) extend in a horizontal direction or are inclined obliquely upwards or are curved.

8. Adjustable grid according to one of claims 1 to 5, characterized in that a second swivel shaft (33) extends parallel to the swivelling axis (24) remote from the first swivel shaft (32) and is connected to said swivelling axis by way of a lever device (41 or 100).

9. Adjustable grid according to one of claims 1 to 8, characterized in that at least two lever devices (41 or 100) are provided per first and second swivel shaft (32 and 33).

10. Adjustable grid according to claim 7, characterized in that a further operating lever (46) is provided which is fastened rotatably on the second swivel shaft (33).

11. Adjustable grid according to one of the preceding claims, characterised in that the swivelling axis (23) facing the first swivel shaft is also guided in guide slots (25) of the extraction arm (16) serving as said stops in order to limit said horizontal displaceability of the grid.

12. Adjustable grid according to claim 8, characterized in that the first swivel shaft (32) and the second swivel shaft (33) are a greater distance apart from one another than the two swivelling axes (23, 24) and are disposed above the swivelling axes (23, 24).

13. Adjustable grid according to one of the preceding claims, characterized in that the operating lever or each operating lever (46) is actuable by a motor (51) and is movable between two switching positions (461, 462), at which are provided switches (52, 53) which stop the motor (51) and limit the movement of the grid bars (11).

14. Adjustable grid according to one of the preceding claims, characterized in that the drive provided for the operating lever or for each operating lever (46) is so designed that the pressure upon the grid bars is non-reversible.

15. Adjustable grid according to one of the preceding claims, characterized in that the grid bars (11) have on their ends integrated spacers (14, 15) which are seated directly adjacent to one another on the swivelling axis or on each swivelling axis (23, 24).

16. Adjustable grid according to one of the preceding claims, characterized in that the fibre extraction members are disposed in a swashplate manner on a driven shaft and that the distance between adjacent grid bars (11) is slightly greater than the amplitude of the swashplate-like movement of the fibre extraction members.

17. Adjustable grid according to one of the preceding claims 2 to 16, characterized in that the eccentric bushes (36, 361, 362) are non-rotatably fastened by clamping means (37, 38) to the first or second swivel shaft (32 or 33).

18. Adjustable grid according to claim 1, characterized in that the lever device comprises an eccentric bush (363) in either end (108, 109) of each grid bar (11.1), that the eccentric bushes are connected to one another by a transmission (110), that one eccentric bush is driven, and that the eccentric bushes are disposed aligned in the same direction in said ends.

19. Adjustable grid according to one of the preceding claims, characterized in that the motor (51) steplessly adjusts the penetration depth T in a range of, for example, 0 - 10 mm by means of a programmable timing element or a displacement monitoring device (neither of which is shown).

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