DE19811338A1 - Automatic sliding door with emergency opening or closing - Google Patents

Abstract

The automatic sliding door has a main operating drive with an electric motor for movement of at least one door panel (1a, 1b) along a sliding runner and an auxiliary drive for emergency operation of the sliding door, provided by an energy store, e.g. a rubber band, acting on the drive coupling between the electric motor and the door panel. The energy store has a guide element (8) locating in a guide parallel to the door panel movement upon release of the stored energy and provided with a friction brake.

Description

The invention relates to a sliding door with an emergency opening or emergency closing direction with the features of the preamble of claim 1.

DE 195 33 153 describes such an emergency opening device for a preferably automatic two-leaf sliding door with a spring formed energy store. On the one hand, the spring is fixed in place in a bearing spans and on the other hand free in an electromagnetic holding device anchored anchorable. In normal operation of the sliding door, the spring is pre-tensioned ineffective. Only in an emergency, e.g. B. in the event of fire or power failure gives the hard keep the spring free, whereupon this is discharged with the stored in it energy interacts with the roller carriage of the sliding door and the Sliding sash moved to the full open position. A disadvantage of this version tion is that depending on the position of the sliding sash the spring after its release a connected driver hit the roller carriage hard and suddenly len. With frequent use, this can damage the Rol and the suspension of the sliding sash.  

The object of the invention is in a drive of the type mentioned, a To develop emergency opening or closing device, which has a high loading has drive safety.

The object is achieved by the subject matter of the To saying 1.

The brake prevents a hard and sudden impact of the preferably axially movable energy storage within the running rail or with the Energy storage connected guide part on a wing-fixed part, for. B. on the Roller carriage. The guide part connected to the energy accumulator can be used as be a sled. Provided the energy storage device or the slide is at its release by the holding device is not in contact with the wing fixed part or the roller carriage, as is partially or completely ge opened sliding sash is the case that is connected to the energy accumulator Guide part or the slide through the energy accumulator in the direction of the wing or the roller carriage moved and braked. Only after hitting on the wing or roller carriage is braked by a roller carriage arranged control device solved, so that then the entire in the power spit Stored force can act on the roller carriage, causing the sliding wings are moved into their open position under the effect of the energy accumulator.

The guide part of the energy accumulator is at the time of release riding at the ready with the wing or the roller carriage, as is the case with closed If the sliding sash is the case, the brake is already activated by the control unit solved and from the beginning the full force of the energy store acts on the Roller carriage and the sliding sash.

The brake is preferably a friction brake with two Brake shoes, which interact with the running rail. The brake shoes are arranged on the outside of two brake levers, which in scissors-like a preferably common pivot point stored within the carriage are. Under the action of a spring arranged between the brake levers preferably the compression spring applies the brake levers to the braking position.  

When hitting the roller carriage, the free ends of the brake levers moved apart along bevelled control surfaces of the control device and thereby the brake shoes under compression of the compression spring from the barrel rail released.

In normal operation of the door, the carriage is locked in a holding device d. H. the auxiliary drive remains cocked. In a preferred embodiment, the Festhal teeinrichtung a stationary electromagnet arranged in the track on. The electromagnet interacts with an anchor plate, which is attached to one rotatably mounted holding arm is articulated. When the elec tromagneten the anchor plate is attracted by the electromagnet and the Holding arm blocked in its holding position. When the electromagnet is de-energized ten detaches the anchor plate from the magnet, preferably by holding the arm under the action of the slide and the energy accumulator in its release position lung are pivoted.

The front end of the guide part of the energy accumulator or the slide has a projection with an upward locking lug. In finding position engages behind a downward-facing one located on the locking arm Locking nose this locking nose of the carriage and blocks it against one Axial movement. After switching off the electromagnet, the locking arm can Swing up freely and release the catch of the slide. The The auxiliary drive can then move the sliding sash to the open position.

If the emergency is eliminated, the elastic band will be the first time the door is closed Prestressed sliding door and reconnected to the holding device, that is held in the biased position.

In the case of modified, correspondingly constructed versions, the auxiliary person can driven instead of the emergency opening can also be used for emergency closing, whereby the above for the emergency opening in a corresponding manner for the Emergency closure applies.

Further details of the invention are set out in subclaims 2 to 20 leads.  

The invention is explained in more detail in the figures. It shows:

Figure 1 shows the schematic diagram of a sliding door drive with emergency opening device.

Fig. 2 shows a detail in Figure 1 with a representation of the Notöffnungseinrich device. a) in side view, b) in top view;

3 shows a cross section through the runner taken along line III-III in Fig. 1.

Fig. 4 is a detailed representation of the brake in Fig. 1; a) in side view, b) in top view;

FIG. 5 shows a detailed illustration of the electromagnetic holding device in FIG. 1; a) in side view, b) in top view;

Fig. 6 shows a detailed illustration of the roller carriage in Fig. 1; a) in side view, b) in top view;

FIG. 7 shows a detailed illustration of the bearing in FIG. 1; a) in side view, b) in top view.

Fig. 1 shows an automatic sliding door system with two door leaves 1 a, 1 b and a sliding door drive 2 with a drive box 21st Each of the two Türflü gel 1 a, 1 b is provided with two carriages 5 and slidably guided in a stationary horizontal track 4 . The running rail 4 is arranged in the drive box 21 integrated.

The door wings 1 a, 1 b and are driven via a toothed belt 34 , which is driven by a drive motor 3 via a drive pulley 31 and is guided in a circumferential manner via a deflection roller 32 . Drive disc between the drive motor 3 and 31 to a coupling, not shown, is disposed, which the drive wheel 31 automatically decoupled in egg nem failure of the drive motor 3 from the motor. A driver 33 b connected to the right door leaf 1 b is fastened to the upper run of the toothed belt 34 , while a driver 33 a located on the left door leaf 1 a is connected to the lower run of the toothed belt 34 .

The emergency opening device has an auxiliary drive 6 , which is designed as an elastic band. Both ends of the elastic band 6 are attached to a fixed bearing 9 on the left end of the running rail 4 . The elastic band 6 is guided inside half of the running rail 4 , it being guided in the recesses 55 ( FIG. 3) of the running rollers 53 a, 53 b for the sake of saving space in the area of the roller carriage 5 . The extreme right end of the elastic band 6 is connected to a slide 8 which is axially displaceable in the running rail 4 . The carriage 8 has a locking lug 85 ( FIG. 4a) with which it interacts with a holding device 7 arranged in a fixed manner in the running rail 4 .

The right front side of the right roller carriage 5 b on the left door leaf 1 a forms a stop surface for the carriage 8 , whereby this together with the roller lenwagen 5 after an accident or when the door leaf 1 a, 1 b is first closed after the installation of the emergency opening device in it Holding position is brought to the holding device 7 .

In the event of a power failure or other emergency situations, the holding device 7 releases the carriage 8 . This moves under the action of the prestressed elastic band 6 to the left until it meets the roller carriage 5 b. Only when the door wings 1 a, 1 b are closed is the carriage 8 already at the ready with the roller lenwagen 5 b.

An arranged in the carriage 8 brake prevents an unbraked on impact of the carriage 8 on the roller carriage 5 b after release by the holding teeinrichtung 7th The movement of the carriage 8 , which occurs under contraction of the elastic band 8 , is braked by frictional force. Only after the braked impact on the roller carriage 5 b, the brake of the carriage 8 is released by a control device 56 ( FIG. 6) attached to the roller carriage 5 b, so that, in an emergency, the sliding sash 1 a, 1 b can be braked with the full force of the elastic band 6 can be opened. The auxiliary drive 6 is designed and preloaded so that in the event of an emergency, the door leaves 1 a, 1 b are pulled into the open position with certainty.

The biased elastic 6 remains anchored in the holding device 7 during normal operation of the door in a tensioned state. In an emergency situation such as B. power failure, the carriage 8 is released by the holding device 7 ben and comes to a stop with the roller carriage 5 , whereupon he moves it under contraction of the tensioned elastic band 6 in the open position.

Two-leaf versions are possible in which only one door leaf with egg nem auxiliary drive is provided. As soon as one of the sliding sashes goes through the Auxiliary drive is moved, the second sliding sash is automatically moved through the Forced coupling also moved over the driver and the toothed belt. In particular with sliding doors with large opening widths and heavy door leaves Both door panels can also be equipped with auxiliary drives, which are independent work from each other.

If the event of damage or the malfunction has been remedied, the elastic movement 6 is tensioned with the most closing movement of the door leaves 1 a, 1 b, the catch 85 of the carriage 8 engaging in the electromagnetic holding device 7 .

In alternative embodiments, a spring balancer or another resilient body can also be provided instead of the elastic band 6 .

The illustrations in Fig. 2a and Fig. 2b show the emergency opening mechanism in an overview display with the omission of the running rail 4. All depicted th components with the exception of the suspension device 54 for the sliding sash 1 a, 1 b are arranged within the running rail 4 .

The auxiliary drive 6 , designed as a rubber band, is fixed with its two ends on the left side in a fixed bearing 9 . The bearing 9 also has a buffer 96 shown in FIG. 7, which in the event of an emergency opening dampens the impact on the left roller carriage 5 a on the rail end. A vertical bumper 58 , with which the roller carriage 5 a runs onto the buffer 96 , is screwed onto a bracket of the suspension device 54 .

The right roller carriage 5 b is in the illustrated closed position of the sliding sash 1 a, 1 b in abutment with a slide 8 which is axially movably guided in the running rail 4 . The elastic band 6 is passed through the carriage 8 and is tensioned or relaxed in accordance with the movement of the carriage 8 in the running rail 4 .

In normal operation of the sliding door system, the carriage 8 is fixed in a Festhaltein device 7 , ie the elastic 6 remains biased regardless of the movement of the door leaf 1 a, 1 b.

The roller carriage 5 a, 5 b is guided with its rollers 53 a, 53 b in a track 4 shown in section in FIG. 3. A suspension device 54 engages with a threaded screw 54 a in the roller carriage base body 51 .

The drive consists of a U-shaped running rail 4 , on the underside of which, between two lateral webs 4 a, 4 b, there remains a central opening for carrying out the suspension device 54 for the sliding leaf 1 a. About a threaded screw 54 a of the sliding sash 1 a with the underside of the roller carriage 5 a related party, the sliding sash 1 a with a bracket 54 c on the head of Ge threaded screw 54 a and secured there by a lock nut 54 b.

The webs 4 a, 4 b are designed as running surfaces for the roller carriage 5 , the left web 4 a in FIG. 3 having a running surface with a curved cross section and the right web 4 b having a running surface with a flattened cross section. Fittingly, the two left rollers 53 a of the roller carriage 5 have a curved tread and the right rollers 53 b have a flattened tread.

The rollers 53 b with a flattened tread each have a circumferential recess 55 within their tread. This recess 55 is used to measure and guide the elastic 6 , which causes the opening of the sliding sash 1 a, 1 b in emergency operation. The elastic strip 6 is on the one hand fixed in a rail 4 in the running guided slide 8 and the other part fixed in a stationary bearing. 9 It serves as an auxiliary drive 6 for emergency opening or closing of the sliding sash 1 a, 1 b in the event of failure of the sliding door drive. The elastic 6 runs in the area of the rollers 53 b within the recess 55 in the running surface. An undesirable mutual blocking or jamming of rollers dare 5 and elastic 6 is avoided.

In the webs 4 a, 4 b facing grooves 4 c are arranged for receiving sealing brushes. The upper region of the profiled rail 4 with the roller carriage 5 contained therein is thereby closed off and the penetration of dirt or foreign bodies is largely prevented.

FIG. 4a shows the operations in the running rail 4 slide 8. The carriage 8 consists of an elongated carriage body 81 , which has a horizontal projection 81 a with a locking lug 85 pointing upwards at a front end. The locking lug 85 cooperates with the electromagnetic holding device 7 shown in FIG. 5 to determine the slide 8 during normal operation of the door. The locking lug 85 has a first of the retaining means 7 facing flatter contact bevel 85 a and a second of the retaining means 7 facing away steeper stop bevel 85 b on.

At the opposite end of the carriage body, two brake levers 82 , 83 are mounted in a common pivot point 89 like scissors. One brake lever 82 rests on the top and the other brake lever 83 rests on the underside of the slide body. Between the two brake levers 82 , 83 , a compression spring 86 is received in the slide body, which biases the two lever arms 82 , 83 directed outwards. On the outward side of each brake lever 82 , 83 6 friction linings 84 are arranged on both sides of the rubber band, not shown, which cooperates with the running rail 4 in the event of braking under the contact pressure of the compression spring 86 . The brake levers 82 , 83 are arranged on the side of the flattened running surfaces 4 b ( FIG. 3) in the running rail 4 , so that the friction linings 84 cooperate with the flattened rail-side running surfaces 4 b.

The lever pads 82 a, 83 a opposite the friction linings 84 project horizontally beyond the slide body 81 and have beveled ends with an incline directed inwards. These lever ends 82 a, 83 a cooperate with a control device 56 shown in FIG. 6 to release the brake.

The elastic band 6 is passed through a recess 81 b in the carriage body 81 from the top to the bottom. The carriage 8 is, so to speak, "threaded" on the elastic 6 , the elastic 6 experiencing a deflection of 180 ° in the manner of a loop. In Fig. 4a, the elastic band 6 is only indicated by dashed lines. The two ends of the elastic band 6 are fixed in a fixed bearing 9 at the rail end. The elastic band 6 can be tensioned or relaxed by the movement of the carriage 8 in the running rail 4 .

In order to prevent the slide body 81 from tilting in the running rail 4 , a T-piece 88 is fastened to the side of the slide body 81 by a screw connection 87 , as shown in FIG. 4b. The T-piece 88 is supported with its T-leg on the rail wall opposite the brake levers 82 , 83 .

In normal operation of the sliding door system, the carriage 8 is held in the tensioned position of the elastic band 6 by an electromagnetic fixed holding device 7 shown in FIG. 5a in the running rail 4 . The holding device 7 is arranged within the running rail 4 and consists of a horizontal base body 71 which has a first vertical leg 71 a at one end and a second vertical leg 71 b is fastened at its other end by a screw connection 77 b.

In a vertical bore of the first vertical leg 71 a, a clamping screw 78 is received, through which the holding device 7 is fixed in place in the running rail 4 . At the free end of the second leg 71 b is a horizontally aligned, the carriage 8 facing arm 74 rotatably articulated in a pivot bearing 76 so that it can pivot up and down.

The free end of the retaining arm 74 is designed as a retaining lug 75 , which cooperates with the locking lug 85 of the carriage 8 . The court preparing downward retaining nose 75 has a facing to the carriage 8 flatter contact bevel 75 a on, and a slide 8 b the remote steeper stop bevel 75 miles.

Between the two vertical legs 71 a, 71 b and below the locking arm 74 , an electromagnet 72 is fastened to the base body 71 by a screw connection 77 a. Above the electromagnet 72 , an armature plate 73 is articulated centrally on the holding arm 74 . When the solenoid is energized, the armature plate 73 is attracted by the electromagnet 72 and the locking arm 74 is thereby blocked against deflection.

To determine the carriage 8 , this is moved when the door is closed by the roller carriage 5 b and comes into contact with the holding arm 74 determined by the electroma 72 . The flatter run-up slope 85 a of the locking lug 85 of the carriage 8 interacts with the flatter run-up slope 75 a of the holding lug 75 of the holding arm 74 . Due to the flat angle in which the locking lug 85 and the holding lug 75 meet, the forces exerted by the door drive are sufficient to lift the holding arm 74 together with the anchor plate 73 against the attractive force of the electromagnet 72 . The retaining arm 74 pivots clockwise upward, and the latch 85 can pass through the retaining nose 75 , whereupon the retaining arm 74 lowers towards the latch 85 and blocks it. The retaining arm 74 is now again fixed to the electromagnet 72 via the armature plate 73 .

During further operation of the door, the carriage 8 remains blocked in its locking position regardless of the movement of the roller carriages 5 a, 5 b. In this fixed position, the steeper ramp slope 75 b of the retaining lug 75 cooperates with the steeper ramp slope 85 b of the locking lug 85 . The force exerted by the pre-tensioned elastic band 6 on the carriage 8 is not sufficient to lift the holding arm 74 against the force of the electromagnet 72 . Only after the electromagnet 72 has been switched off can the holding arm 74 be pivoted upwards under the force of the elastic band 6 and thereby release the slide 8 .

Contraction of the tensioned elastic band 6 causes the carriage 8 to move to the left after being released in FIG. 2, the friction linings being pressed against the running rail 4 by the compression spring 86 at the same time. The carriage 8 thus moves only braked within the running rail 4 . If the carriage 8 is not in contact with the roller carriage 5 b at the time of release, for. B. because the door was already fully or partially open at this point, this prevents an uncontrolled acceleration of the carriage 8 and a hard impact on the roller carriage 5 b.

After hitting the roller carriage 5 b, the brake of the carriage 8 is released by a control device 56 . Fig. 6a and Fig. 6b show the Rol lenwagen 5 b and b formed on the roller carriage 5 controller 56.

The roller carriage 5 b consists, as shown, of an elongated, quaderörmi gene base body 51 , in which two continuous, one behind the other horizontal axes 52 are mounted. Each of the axes 52 carries two external de, different shaped rollers 53 a, 53 b.

A horizontal control arm 56 is fastened on the side of the roller carriage 5 b facing the carriage 8 by a screw connection 57 on the roller carriage base body 51 . The control arm 56 is arranged transversely to the running direction of the roller carriage 5 b and has a wedge-shaped control surface with a lower slope 56 b and an upper slope 56 a. The control arm 56 projects into the movement path of the slide 8 . When the carriage 8 strikes the roller carriage 5 b, the two bevels 56 a, 56 b interact with the bevelled ends 82 a, 83 a of the two brake levers 82 , 83 , one brake lever 82 on the upper bevel 56 a and the other Brake lever 83 hits the lower slope 56 b. Along the bevels 56 a, 56 b, the ends of the brake levers 82 a, 83 a are moved apart and, at the same time, the opposite ends of the brake levers 82 , 83 are brought together under compression of the compression spring 86 . The braking effect of the friction surfaces 84 is canceled, and the roller carriage 5 b is moved into the open position with the slide 8 under the action of the elastic band 6 without braking.

Fig. 7a shows a side view of the stationary bearing 9 and the buffer 96 at the end of the rail. The bearing 9 consists of a flat base body 91 , onto which a vertical leg 92 is screwed by means of two fastening screws 93 . The vertical leg 92 has two vertical bores 92 a for receiving clamping screws 94 . The bearing 9 is inserted from the rail end into the running rail 4 and fixed there by means of the two clamping screws 94 .

The front of the vertical leg 92 has a recess 92 b for receiving a compression spring 95 . A buffer element 96 is placed on the compression spring 95 and , when the rail end is reached, serves as a stop for a bumper 58 connected to the left roller carriage 5 a ( FIG. 2a). A front panel 97 is screwed onto the front of the vertical leg 92 and has an opening in the area of the buffer 96 . The buffer 96 protrudes in the horizontal direction over the front panel 97 , but is fixed by the front panel 97 with axial play within the recess 92 b.

Fig. 7b shows the laterally on the vertical leg 92 with a fastening screw 99 screwed bearing block 98 for the elastic 6th The bearing block 98 has two axial bores 98 a arranged parallel to one another, through which the ends of the rubber band 6 , not shown, are passed. Behind the implementation 98 a, the ends of the elastic band 6 are knotted after setting the desired pretension or fixed by a clamping device.

Reference list

1

a,

1

b Door leaf, sliding leaf

2nd

Sliding door drive

21

Drive box

3rd

Drive motor

31

Traction sheave

32

Pulley

33

a,

33

b carrier

34

Drive belt

4th

Track

4th

a,

4th

b bridges

4th

c grooves

5

Roller carriage

5

b Right roller carriage

51

Basic body

52

axes

53

a,

53

b casters

54

Suspension, suspension device

54

a threaded screw

54

b Lock nut

54

c bracket

55

Recess

56

Control arm

56

a,

56

b slant

57

Screw connection

58

Buffer

6

Auxiliary drive

7

Holding device

71

Basic body

71

a,

71

b vertical bar

72

Electromagnet

73

Anchor plate

74

Holding arm

75

Holding nose

75

a flat slope

75

b steep slope

76

Pivot bearing

77

a,

77

b screw connection

78

Clamping screw

8th

carriage

81

Basic body

81

a lead

81

b recess

82

upper brake lever

82

a lever end

83

lower brake lever

83

a lever end

84

Friction lining

85

Latch

85

a flatter slope

85

b steeper slope

86

Compression spring

87

Screw connection

88

Tee

89

pivot point

9

camp

91

Basic body

92

vertical bar

92

a hole

92

b recess

93

Fastening screw

94

Clamping screw

95

Compression spring

96

buffer

97

Front panel

97

a screw fastening

98

Bearing block

98

a hole

99

Fastening screw

Claims (20)

1. sliding door with an automatic drive and an auxiliary drive for emergency opening or closing,
with at least one ver via a drive motor in a sliding rail driven wing
and with an energy accumulator as an auxiliary drive which, in the event of a failure of the drive motor or of a transmission part between the drive motor and the door leaf, brings the door leaf into the open or closed position,
wherein the energy accumulator or a guide part connected to the energy accumulator is fixed in normal operation of the door on a fixed or wing-fixed bearing and can be released via a holding device,
wherein when the force accumulator or the guide part connected to the force accumulator is released, it is guided in a guide device running parallel to the direction of movement of the wing, characterized in that the force accumulator or the guide part ( 8 ) connected to the force accumulator has a brake ( 82 , 83 , 84 ) having. 2. Device according to claim 1, characterized in that the brake ( 82 , 83 , 84 ) is effective as a function of the wing position. 3. Apparatus according to claim 1 or 2, characterized in that the brake ( 82 , 83 , 84 ) via a control device ( 56 ) can be switched on and off, preferably switched off when the energy accumulator or the guide part ( 8 ) connected to the energy accumulator. on the wing or a wing-proof part, e.g. B. roller carriage comes in plant. 4. Device according to one of claims 1 to 3, characterized in that the control device ( 56 ) on the roller carriage ( 5 b) is arranged. 5. The device according to claim 4, characterized in that the control device ( 56 ) has a preferably wedge-shaped end face ( 56 a, 56 b) which cooperates with the guide part connected to the energy storage, preferably with the slide ( 8 ). 6. Device according to one of the preceding claims, characterized featured, that the guide device is stationary, preferably in the area or as part the running rail is formed or is designed as the running rail. 7. Device according to one of the preceding claims, characterized in that the brake ( 82 , 83 , 84 ) cooperates with the guide device. 8. Device according to one of the preceding claims, characterized in that the guide part connected to the energy accumulator, preferably the slide ( 8 ) in the guide device, preferably the running rail ( 4 ), in which the sliding sash ( 1 a, 1 b) with roller carriages ( 5 a, 5 b) are guided, axially displaceably mounted. 9. The device according to claim 8, characterized in that the guide part connected to the energy accumulator, preferably the carriage ( 8 ) has two brake levers ( 82 , 83 ), which preferably in a common pivot point ( 89 ) within the carriage ( 8 ) are stored like scissors. 10. The device according to claim 8 or 9, characterized in that on the outer sides of the brake lever ( 82 , 83 ) friction surfaces ( 84 ) are net angeord, which cooperate with the profile of the running rail ( 4 ). 11. Device according to one of claims 8 to 10, characterized in that the brake levers ( 82 , 83 ) via a compression spring ( 86 ) or the like are acted upon in the braking position. 12. The device according to one of claims 8 to 11, characterized in that the brake levers ( 82 , 83 ) are acted upon in cooperation with the control device ( 56 ) against the force of the compression spring ( 86 ) in the release position. 13. Device according to one of the preceding claims, characterized in that the holding device ( 7 ) is arranged stationary in the running rail ( 4 ), preferably fastened by a clamp connection ( 78 ). 14. The apparatus according to claim 13, characterized in that the holding device ( 7 ) has an electromagnet ( 72 ), which cooperates with a preferably rotatably mounted holding arm ( 74 ). 15. The apparatus of claim 13 or 14, characterized in that the locking arm (74) is determined at the energized electromagnet (72) and released upon de-energized electromagnet (72). 16. The device according to one of claims 13 to 15, characterized in that the retaining arm ( 74 ) with the carriage ( 8 ), preferably with a locking device ( 85 ) of the carriage ( 8 ) cooperates. 17. Device according to one of the claims, characterized in that the auxiliary drive ( 6 ) on the running rail ( 4 ), preferably at the front end of the running rail ( 4 ) is fixed in a fixed bearing ( 9 ). 18. The apparatus according to claim 17, characterized in that the fixed bearing ( 9 ) is arranged within the running rail ( 4 ). 19. Device according to one of the preceding claims, characterized in that the auxiliary drive ( 6 ) is guided within the running rail ( 4 ), vorzugwei se within recesses ( 55 ) of the rollers ( 53 b) of the roller carriage ( 5 a, 5 b) . 20. Device according to one of the preceding claims, characterized in that the auxiliary drive ( 6 ) is designed as an elastic band, spring or the like.