DE1761078A1 - DEVICE FOR THE REMOVAL OF PLAY IN PRESSES - Google Patents

Description

PATENT Attorney DIPL.-ING. HARRY ROEVER

68 MANNHEIM - FEUDENHEIM · AM BOGEN 23 ■ POST BOX 124

November 17, 1969 R / C

Miller Printing Machinery Co. Hol Reedsdale Street,

Pittsburgh, Pennsylvania / U.S.A.

Device for eliminating backlash in printing presses

Priority of the USA patent application

dated November 11, 1967 .., ___

No. 685 Io5 Γ- "Γ-" * rf " ³ ^ iT ^p '? ^F

; ._; _; ■ 'U -: "be lurking

The invention relates to a device for eliminating the Tooth backlash that takes place with a pair of gears in one engaged gear train (gear chain) is connected and a positive force on the engaged Gear teeth exercising in the direction of gear rotation. In particular, the invention relates to a backlash elimination shaft unit for use in rotary printing presses that rait separate gears in the press cylinder drive 'gear train is connected. This control shaft unit is used in addition, a positive torque through a torque at a controlled level

{At. 7 31 rtbs. 2 Mr. χ set 3 d4s A * n * runr) sg3s. v. 4. 9.

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OcPl 79 H 24 ■ BANK: DEUTSCHE BANK KÖLN 126 8218 · POSTSCHECK: COLOGNE 497 29

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Stress or positive pressure on the engaged exercise standing teeth.

! Rotary printing presses, especially multi-color sheet-fed printing

jpressen comprise a first printing unit and a second ; Printing unit with a transfer cylinder in between. In sheet-fed rotary printing machines with perfecting, the first unit has one I feed roller drive, one impression cylinder and one

transfer cylinder. The cylinders and the feed roller drive are for the purpose of timed, coordinated movement by a permanently engaged Gear train connected to each other. This gear train includes: a gear connected to the intermediate transfer cylinder, the

commonly called the second transfer cylinder, between

the first and the second printing unit is connected. The second printing unit similarly has a printing cylinder,

a transfer cylinder and a sheet delivery mechanism.

pin continuously engaged gear train connects the various cylinders and the sheet delivery mechanism of the

^ wide printing unit with each other for the purpose of coordinated and timed rotary movement. The intermediate transfer cylinder has a second gear meshing with the gear train that includes the cylinders and the sheet delivery mechanism the second printing unit connects to one another. A main drive motor is with the gears on the

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Intermediate transfer cylinder operatively connected and forms the drive for the gear trains of the first printing unit and the second printing unit.

The various cylinders include cam actuated Sheet transport devices such as sheet gripping devices and suction devices. At high printing speeds it is assumed that the cam actuated Devices generate periodic torsional stresses in the various shafts connected to the cylinders. These torsional stresses in the cylinders associated with them Trowels cause the drive gears to vibrate and temporarily disengage them standing driving and driven teeth and thereby an irregular drive of the printing cylinder. This separation and irregular loading of the gear teeth as a result the external forces that occur are referred to below as "Kahnspiel". Because the respective gears are rigid are attached to the cylinders connected to them, causes the gear movement caused by the vibration also a corresponding movement or movement of the associated Cylinder. A deviation from the desired, coordinated, chronologically coordinated rotary movement of the printing cylinder leads to registration difficulties »It is also assumed that an unbalanced load of the various Phases in a polyphase electric motor, or an out-of-phase relationship between the three phases to an uneven, pulsating twisting of the

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lead by this electric motor driven gears and can also result in backlash.

The problem of backlash caused by deviations from the optimal distance between the gears of the forme cylinder and the impression cylinder is caused has been recognized earlier. U.S. Patent 2,948,215 is one Device disclosed, which comprises a series of gears with a cup-shaped ring gear, which has an internal and a Has external teeth. It is indicated that this cup-shaped ring gear is a means of reducing the Tooth backlash effects on the forme and impression cylinder of a printing pair, which is an eccentrically mounted Has adjusting device.

The object of the invention is to create a device to eliminate the backlash by which the meshing teeth of the various gears in the gear train are held in abutment against one another, so that the externally caused vibrations the coordinated, laterally coordinated rotary movement of the various cylinders do not have any appreciable effect. It is therefore lurch the invention a device for eliminating the Eahnspiels can be created in a series of continuously meshing gears in a printing press l by generating a positive force on the engaged

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standing gear teeth in the driving direction of the gears. The device according to the invention is intended to be a controlled Change this positive force acting on the engaged standing gear teeth in gear train is exercised, be possible. It should go through certain gears of the gear train a shaft unit in which a torque of a controlled amount is present so as to be positive To generate force on the meshing gear teeth.

These and other objects, features, and advantages of the invention are described and explained below and result from the following description and drawings and the claims.

Fig. 1 is a partially schematic side view a first printing unit and a second printing unit with an intermediate transfer cylinder and with e'er Device for eliminating gear backlash for each printing unit.

Fig. 2 is a section along line 2-2 in Fig. 1 showing the means for removing backlash for the first printing unit.

FIG. 3 is a section along line 3-3 in FIG. 1 and z ^ Lgt the device for eliminating backlash

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for the second printing unit.

In Fig. 1, the rotary printing preamble, which was selected for the purpose of the illustration, is a sheet-processing offset lithographic press, with which two-color printing or front and back printing can be carried out can print. The printing press, denoted overall by Io, has a first printing unit 12 and a second printing unit 14} between the two printing units there is an intermediate transfer cylinder 16. The gears for the first printing unit 12, the second printing unit 14 and the one in between Transfer cylinders 16 are shown achematically in FIG. 1, the direction of rotation of the individual cylinders being indicated by directional arrows is specified

The transfer cylinder 16 has a pair of coaxial gears 18 and 2o (Figures 2 and 3), which sit on a common shaft and the printing units 12 and 14 with the one in between Connect transfer cylinder 16. The gear 2o of the transfer cylinder s can be released from its support shaft to a Rotation of the cylinders of the first printing unit relative to the cylinders of the second printing unit for the purpose of adjusting the press To enable two-color printing or face-to-face printing. In Fig. 1, the gear with 2o is shown schematically as an outer gear. It should be noted, however, that the gear

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2o the gear 18 is superimposed and that the gear 2o connects the transfer cylinder 16 with the second printing unit 14.

The first printing unit 12 has a gear 22 on the first transfer cylinder, which with the gear 18 on intermediate transmission cylinder 16 is engaged «The printing cylinder of the The first printing unit has a gear 24 which meshes with the gear 22 on the first transfer cylinder · Hn gear 26, which drives the cam operated feed roller, meshes with the gear on the impression cylinder 24 of the first printing unit 12.

The second printing unit 14 has a gear wheel 2x on the third transmission cylinder, which with the outer gear 2o on the between the transfer cylinder If is in Ilagriff. That Gear 3o, which is on the printing cylinder in the "wide Draakelahelt 14 Is attached, is in engagement with the gear wheel 2t on the third transfer cylinder of the second Draokeinhelt 14 «NIt is connected to the sheet delivery mechanism a gear wheel 32, which is connected to the The gear wheel 3o on the printing cylinder is in engagement Gear 18 connected, and the gear 18 in turn drives the gear 2o via a suitable clamping or tensioning device · At In this arrangement, the rotary motion of the Zanrlder 18 and 2o is transmitted to the respective gearwheels which are in engagement therewith, so *

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that a drive is formed for the first printing unit 12 and the second printing unit 14 and the gears in the first printing unit 12 form a gear train and the gears in the second printing unit 14 form a further gear train which is separate therefrom. It should be mentioned, however, that these gear trains are connected to one another during the pressing and thus as a single one Gear train act to ensure the desired timed rotational movement of all elements of the entire printing press 10. A suitable system for driving the gears 18 and 20 on the intermediate transfer cylinder 16 is in the

; U.S. Patent 2,757,610. Other propulsion systems for the coordinated drive of the two printing units 12 and 14 can also be used.

A first mechanism for eliminating play is provided, which is shown in FIGS. 1 and 2 and indicated at 34 as a whole is designated; it serves to eliminate the backlash of the gears in the first printing unit 12. A second such mechanism 36 is shown in Figures 1 and 3 and is used to eliminate the backlash in the second printing unit. It will though Referring to the first and second printing units 12 and 14, however, the drive includes gear train for these units also the gears 18 and 20 on the intermediate transfer cylinder 16. The gears on this second »intermediate transfer cylinder 16 are part of the drive unit.

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chain for these pressure units, and the associated mechanisms 34 and 36 for eliminating the backlash are with the gears this intermediate transmission cylinder 16 is connected.

The backlash-eliminating mechanism 34 has a shaft unit 38 which comprises aligned shafts 40 and 42 which are connected to one another at one end by a coupling 44. The shaft 4o is rotatably mounted in pillow block bearings 46 and 48 which are attached to a plate 5o, which in turn is fastened to the feed frame 52 in a suitable manner. This plate 5o has an opening 54 through which a shaft journal 56 extends. The shaft 56 is carried at one end by a bearing 58, which is seated in the opening 54 of the plate 5o, and at the other end by a bearing 6o. The bearing 6o is seated in a second plate 62 which is also fastened to the press frame 52. A pinion 64 is fixed non-rotatably on the shaft 56 between the bearings 58 and 6o? it is in engagement with the gearwheel 26 of the feed roller drive in the printing unit 12, a bevel gearwheel 66 is fixed non-rotatably at the end of the shaft 56; it is in engagement with a further bevel gear 68 which is non-rotatably fastened to the free end of the shaft 4o.

The shaft 42 is supported in the vicinity of its end in a pillow block bearing 7o which is fastened to a plate 72 which in turn is fastened to the press frame 52 by means of screws 74. The plate

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72 has an opening 76 through which a shaft 78 extends. By means of a bearing 8o, the shaft 78 is in the opening ' 76 of the plate 72 rotatably mounted. The opposite end of the shaft 78 is mounted in a bearing 82 which is seated in a bearing opening 84 in the frame 52 Spring connection connected? it meshes with an intermediate gear which is suitably supported on a shaft 9o which is indicated in Fig. 2 only schematically by a dash-dotted line «This intermediate gear 88 stands with the gear 18 of the intermediate transmission cylinder 16 in Intervention. An electric motor (not shown) is connected to and drives shaft 78. So the motor rotates the shaft 78 and the gearwheel 86 connected to it in a non-rotatable manner. The drive from the gearwheel 86 to the shaft 78 is via the gearwheel 88 to the gearwheel 18 transferred.

A bevel gear 92 is non-rotatable at the end of the shaft 78, beyond the Plate 72, fastened and is in engagement with a conical edge 94, which is also non-rotatable on the shaft 42 of the shaft unit 38 is attached, so that the rotation of the shaft 78 via the bevel gears 92 and 94 on the shaft 42 and also on the gears 86 and 88 is further transmitted to the gear 18 on the intermediate transfer cylinder 16.

The coupling 44, which connects the ends of the shafts 40 and 42 to one another, has a first element 96 with an end face 98 and a continuous longitudinal bore loo. The end of the wave 4o extends through this hole loo and is not rotatable in it

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attached, for example by means of a pin or a wedge bolt Io2. The element 96 has a plurality of threaded bores Io4, which run parallel to the axial bore loo at the same distance. The coupling 44 has a second, similar element Io6 rait a longitudinal bore Io8, in which the end of the shaft 42 is fixed by means of a pin or spline bolt Ho. The element Io6 has an end face 112 which rests against the end face 98 of the element 96; the element also has a plurality of longitudinal bores 114 which are aligned with the threaded bores Io4 in the other element 96. Screws 116 { which are screwed into the threaded bores Io4 in element 96 go through the bores 114 in the element Io6. The longitudinal bores 114 in the element Io6 are larger than the shank of the screws 116 and can optionally also be arcuate if a greater torque is desired in the shafts, as will be explained in more detail below.

Each of the elements 96 and Io6 has a radial bore 118 and 119, as shown in FIGS. 1 and 2. A torque can be exerted on the shaft unit 38 by means of the coupling 44 are made by rotating the elements 96 and Io6 in the directions indicated by arrows in FIG. 1 and by fastening in the twisted position by tightening the screws 116 and thus non-rotatable fastening of the elements 96 and

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106 to each other. Levers are inserted into the radial bores 116 and 119 of the elements 94 and 106 and moved in opposite directions, specifically in the direction of the arrows, until the desired torque is exerted on the shaft unit. The bright ones; As indicated by the arrows in FIGS. 1 and 2, 40 and 42 are rotated in mutually opposite directions, whereby a torque is exerted on the shaft unit 38. The magnitude of the torque exerted on the shaft unit 38 is determined by the amount of mutual rotation of the elements 96 and 106 in opposite directions. The Wellenein- ■ helt 38 of the device 34 is to eliminate backlash at one end with the gear 26 of the feed roller drive and at the other end via the toothing 86 and 88, with the ^v inner gear 18 of the intermediate transfer cylinder 16 is connected.

The direction of the gear wheels of the first printing unit 12 Exerted drives is indicated in Fig. 1 by directional arrows. The gear 18 rotates clockwise and is in engagement with the gear 22 of the first transmission cylinder in the first printing unit 12 and rotates the transfer cylinder 22 counterclockwise. The gear wheel 24 on the printing cylinder is in engagement with the gear wheel 22 on the transfer cylinder and is driven by the gear 22 in the clockwise direction. The feed roller gear 26 meshes with the impression cylinder gear

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24 and is driven by this counterclockwise.

! I.

; In this gear train, the gear 18 rotates on the transmitted

I -!

• supply cylinder 16 in the opposite direction as that with the | Pinch roller drive connected gear 26. The torque in the The shaft unit 38 presses the gear 18 of the intermediate transfer cylinder 16 in the same direction as the drive direction, and also presses that with the feed roller drive ! connected gear 26 in the direction that corresponds to the direction of rotation is opposed by the drive mechanism. On this i

Way, the backlash elimination mechanism 34 presses the rait-

mutually engaging teeth of the respective gears in the \ gear train in mutual contact and switches any play j j between the pressure side of the drive teeth and the teeth of the other! with meshing gear.

The backlash eliminating mechanism 34 rotates due to its teeth H. wheel connection in the same way as the permanently engaged

existing gear chain 18, 22, 24 and 26 and represents a second Ver j connection between the gears 18 and 26. This second Ver i

j binding between the gears 18 and 26 includes the inter-tooth! ξ wheel 88, the gear 86 on the shaft 78, the bevel gear 92 * x * on you I shaft 78, the bevel gear 94 engaged therewith on the white ' ! len unit 38 and the bevel gears 68, 66,

ι the shaft 56 and the bevel pinion 64, which is connected to the gear 26 of the ! The feed roller drive is engaged. This second connection

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is, however, under a torque which the meshing teeth of the gears 18, 22, 24 and 26 are in contact with one another presses and exerts a pressure or a force on the gear teeth such that they remain in contact with each other when on the Gears a vibration force is exerted against the drive direction.

The mechanism 34 for eliminating the backlash also includes a generally designated 12o cylinder adjustment mechanism, which serves to rotate the cylinder of the first printing unit 12 when the gear 2o from the shaft of the intermediate Vbertragungszylinders 16 is released to the cylinder of the first printing unit 12 on perfecting or two-color printing to move. The cylinder adjustment mechanism includes a shaft 122 which passes through an opening in the plate 5o and is rotatably mounted in the frame 52. On the shaft 122 iat a gear 124 fixed non-rotatably, which with a gear 126 is engaged. This gear 126 sits on a shaft 128 and is firmly connected to a gear 13o, which is connected to the gear 22 of the transfer cylinder of the first printing unit in engagement is. The shaft 122 has a stepped portion 132 and an in Flg. 2 handle 134 indicated schematically with dash-dotted lines. When this tape handle 134 is rotated, the Shaft 122, the gears 124, 126, 13ö and the gear 22 rotated on the transfer cylinder of the first printing unit, so that

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the cylinder of the entire first printing unit rotated and thus be adjusted relative to the cylinders of the second printing unit.

The mechanism 36 for switching off the game is in many relationships! gene similar to the corresponding mechanism 34; it has a shaft unit 136, the two axially aligned shafts; 138 and 140 includes. The shaft 138 is mounted in pillow blocks 142 and 144, which are attached to a plate 146, which their- {

on the other hand is fastened to the printing press frame in a suitable manner. A coupling 148 connects the ends of shafts 138 and 140, thereby forming shaft assembly 136. The shaft 140 is mounted in the vicinity of its end in a pillow block bearing 150 which is fastened to a plate 152 which in turn is attached to the press frame; 50 is attached. The plate 152 has an opening 154 through which a shaft 156 extends which is rotatably supported at one end by means of a bearing 158 in the press frame 50 and also by means of a bearing 160 in the opening 154. At the end of the shaft 156 a bevel gear 162 is attached, while between the plate 152 and the press frame 50 on the shaft 156 an intermediate!

gear 164 is fixed non-rotatably. The gear 164 is engaged with the gear 32 engages which is connected to the Bogenauslegemechanismus. On the shaft 140, a bevel gear is non-rotatably fastened 166, AAMT meshed with the bevel gear 162 in engagement so that the ¹ connected to the gear 32 with the Bogenauslegemechanismus Wells

140 is connected via the gear reduction described above.

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Oils plate 146 (Flg. 3) has a through opening 168 in which a bearing 170 is seated, in which the central part of the shaft 172 is supported. The end of the shaft 172 is supported in a bearing 174, j which sits in an opening 176 in the press frame 50. Another \ ! ί

I shaft 178 is arranged parallel at a distance from shaft 172 and in I bearings 180 and 182 stored. On the shaft 172 is a pinion gear

184 fixed non-rotatably, the with a pinion 186 on the Shaft 178 is engaged. There is also a on shaft 178

Pinion 188 non-rotatably attached, which is connected to the gear 20 of the intermediate transfer cylinder 16 is engaged. At a bevel gear 190 is attached to the shaft 172 which meshes with a bevel gear 192 which is attached to the shaft 138 of the shaft

unit 136 is attached. As a result of this arrangement, the gear is

32 of the sheet deposit mechanism is connected to the gear 20 of the intermediate transfer cylinder 16.

The clutch 148 is similar to the clutch 44; she has a first Element 194 and a second element 196 with aligned bores 198 and 200, in which the ends of shafts 140 and 138 are fixed so that they cannot rotate. The element 196 has a plurality of threaded bores 202 which are equidistant from the j

j ■ j

Axial bore 200, parallel to this, run. In the element 194 is a plurality of enlarged through holes 204

provided with threaded bores 202 in element 196

ifluchten. Screws 206 are screwed into the bores 202.

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The size of the bores 204 is larger than the diameter of the;

Shank portion of the screws 206, so that a relative ver- j Rotation to a limited extent between the elements 194 and 196 can also take place when the screws extending through the aligned bores 202 and 204 are screwed into the bores 202. The coupling elements 194 and 196 have receiving openings 208 and 210 for the insertion of levers with which the shaft unit 136 is inserted Torque can be exerted. The screws 206 are loosened so that a mutual relative rotation between the Coupling elements 194 and 196 becomes possible, and levers are inserted into the openings 208 and 210 and into one another moving in opposite directions, as indicated by the arrows is shown in Figures 1 and 3. As soon as the desired torque is exerted on the shaft unit 136, the Screws 206 are tightened and the torque remains in the;

Shaft unit 136 back. The torque in the shaft unit 136 tries to return the shaft unit 136 to the de-energized position, and as a result exerts a force or a pressure on the gear teeth of the gears 32 and 2o in the direction of gear rotation, so that a positive pressure; or a positive force 1n in the direction of rotation on the in Meshing teeth of the gears 20, 28, 30 and 32 comprehensive gear train is exercised.

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The basic principles, preferred construction and operation of the invention have been explained above, and FIG what has been illustrated and described is what is considered the best embodiment for the tent. However, the invention can, within the scope of the patent claims, also be realized in other ways than this Has been shown and described in detail 1st.

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Claims (7)

- 19 -patent claims 1. Printing press with a device for eliminating backlash, with a gear train consisting of several continuously meshing gears for transmitting the Rotary movement on the individual parts of the press and a device for eliminating the backlash for this permanently engaged gear train, marked by a pair of axially aligned shafts (4o, 42; 138, 14o) which are connected to one another by a coupling (44; 148), whereby a shaft unit (38; 136} is formed, one end of the shaft unit (38; 136) with one (18; 20) of the gears of the continuously engaged gear train and the other end of the Shaft unit (38; 14o) with another (26; 32) this permanently engaged gear train is connected, these two gears in each other opposite Rotation directions run, and the clutch (44; 148) has two elements (96, 106; 194, 196), which for the purpose of exercising a torque on the shaft unit (38, 136) rotatable relative to one another and against mutual relative rotation by locking devices (116; 206) are lockable so that the shaft unit (38; 136) on the gears in the permanently engaged Gear train a force in the direction of rotation of the 509812/0385 Gears this gear train exerts, which is proportional to the torque in the shaft unit (38; 136). 2. Printing press according to claim 1, characterized in that for the connection of one shaft end of the shaft unit (38; 140) to this a bevel gear (94; 192) is fixed non-rotatably, which with a second bevel gear (92; 19o) is engaged, which is non-rotatably attached to a first intermediate shaft (78; 172) which is at right angles to the shaft unit 38; 136) runs and over a Transmission is connected to one of the gears (18; 2o) of the gear train, so that the torque in the shaft unit (38; 136) via these bevel gears 94, 92; 192, 19o), the intermediate shaft (78; 172) and the gear on this a gear (18; 2o) of the gear train is transmitted. 3. Printing press according to claims 1 and 2, characterized in that the transmission has a third, on the first Intermediate shaft (78; 172) non-rotatably attached gear (86; 184) and an intermediate gear (88; 186, 188) with this third gear (86; 184) and with the a gear (18; 20) of the continuously engaged gear train is in engagement. b09812 / 0385 4. Printing press according to claim 2 or according to claims 2 and 3, characterized in that for the connection of the other end of the shaft unit (38; 136) on this non-rotatably a third bevel gear (68; 166) is attached, which is connected to a fourth bevel gear ( 66; 162) is in engagement, which is non-rotatably attached to a second intermediate shaft (56; 156) which is mounted perpendicular to the shaft unit (38; 136) and via a gear with another gear (26; 32) of the permanent in Engaging standing gear train is connected, so that the torque in the shaft unit (38; 136) via these bevel gears (68, 66; 166, 16 * 2), the second intermediate shaft (56; 156) and the gear on this other gear (26 , 32) is transmitted in the gear train. 5. Printing press according to one or more of claims 1 to 4, characterized in that the coupling (44; 148) has a first Element (96; 196) with an end face (98) and a plurality of shafts (4o, 42; 138, 14o) at a radial distance to these extending threaded bores (Io4; 2o2) and a second element (Io6; 194) with an end face (112) and with a plurality of radial to the shafts (4o, 42; 138,14ο) lying, with the threaded bores (Io4; 2o2) in the first Element (96; 196) has aligned openings (114; 2o4), the end faces of the first element (96; 196) and the 509812/0385 1761-78 second element (Io6; 194) bear against each other and through the openings (114; 2o4) 1n through the second element (Io6; 194) Screws (116; 2o6) run into the aligned with it Threaded bores (Io4; 2o2) in the first element (96; 196) inserted-ι are screwed, the transverse dimension of the through openings (114; 2o4) in the second element is greater than that of the threaded bores (104; 2o2) in the first element (96; 196), so that the at the elements (96, Io6; 196, 194) of the coupling (44; 148) with screws screwed into the threaded bores (Io4; 2o2) (116; 2o6) are rotatable relative to one another for the purpose of exerting a torque on the shaft unit (38; 136). 6. Offset printing press with a device for eliminating the Backlash, and with a gear train to transfer the rotary motion to the individual elements of the printing press, thereby characterized in that the gear train has a first rotatable gear (26), a printing cylinder gear (24) which is in engagement with this, a gear (22) which is in engagement with the printing cylinder gear (24) for the first transfer cylinder and a gear which is in engagement with the latter (18) for the second transfer cylinder (16), while the device for eliminating gear backlash consists of two axially aligned shafts (4o, 42), which are connected to one another by a coupling (44) to form a shaft unit (38) 5Ü9812 / 0385 are connected to the other, one end of which is connected by a connecting device to the gear wheel (2o) of the second transfer cylinder (16), while its other end is connected by a second connection means is connected to the first rotatable gear (26), the clutch (44) having two Elements (96, Io6) with adjacent end faces which are rotatable relative to one another for the purpose of generating a torque in the shaft unit (38) and can be locked against relative rotation to one another by locking devices (116), so that the shaft unit (38) and the first and second connecting means exert a force on the intermeshing gears in the drive direction of the gears which is proportional to the Torque in the shaft unit (38). 7. Offset printing press according to claim 6, with a second gear train for transmitting rotary motion to the elements of the Printing press, characterized by a second, gear (2o) on the second transfer cylinder (16), a gear (28) in engagement therewith on the third transfer cylinder, with the a gear (3o) is engaged on the second pressure cylinder, which in turn engages a second rotatable gear (32), wherein by a second device (36) for Elimination of the backlash a force on these meshing gears of the second gear train in the direction of rotation these gears is exercised. 50981 2/0385 Blank page