METHOD AND DEVICE FOR FEEDING A CABLE

Abstract: A method and a device for controlling the tension in a cable, band, line or the like (4) when storing it in a plurality of loops over a first, substantially stationary set of wheels (9) and a second movable set of wheels (10) during continuous running of the cable or the like and exchange of drums in the unwind stand (2) or the take-up stand (3), the second set of wheels (10) being movable along a beam system (8) by means of a drive unit (12). The novelty of the invention resides in that at least one of the wheels of the first set of wheels (9) is displaceable towards or away from the second set of wheels (10) under the influence of a change in the balance between the tension in the cable or the like and a constant pressure pro­ duced by an operating mechanism (13) connected to the displaceable wheel or wheels of the first set of wheels, said constant pressure being directed away from the second set of wheels (10), and in that a sensor (23) sensing the displacement of said displace­ able wheel or wheels is arranged to supply a correcting signal corresponding to the displacement, to the drive unit (12) for controlling the tension in the cable or the like (4) by moving the second set of wheels (10) towards or away from the first set wheels (9), and/or a correcting signal to the unwind stand (2) or the take-up stand (3) for controlling the tension in the cable or the like (4) by correcting the speed of rotation of the unwind stand or the take-up stand.

Description: The present invention relates to a device for storing a cable, band, line or the like with controlled tension during continuous running of the cable and exchange of the drum in an unwind stand or in a take-up stand, comprising a first, substantially stationary set of wheels and a second movable set of wheels over which the cable or the like passes in a plurality of loops, said second set of wheels being movable along a beam system by means of a drive unit. Also, the invention relates to a method in connection with the storing of a cable, band, line or the like in a plurality of loops over a first, substantially stationary set of wheels and a second movable set of wheels, for controlling the tension in the cable or the like during continuous running of the cable and exchange of the drum in an unwind stand or a take-up stand. Cable stores for storing av cable or the like are previously known and allow continuous production of a cable, also while the drums are exchanged in the unwind stand and the take-up stand. A commonly used cable store comprises a stationary and a movable set of wheels. The cable runs in loops between the two sets of wheels, and at least one cable store is provided between the unwind stand and the take-up stand for either paying out or taking up the cable when the drum of the unwind stand or the take-up stand is exchanged and the other drum is driven at a constant speed. When the drum of the take-up stand is exchanged, the store is thus supplied with cable and when the drum of the unwind stand is exchanged, the store is paying out cable. The movable set of wheels is located adjacent the stationary set of wheels when the store is empty, and the distance between the two sets of wheels is maximal when the store is full. The tension in each run of the cable is normally controlled by applying a predetermined constant tensile force to the movable set of wheels by means of a chain assembly connected to an electric motor, the tensile force applied being adjusted by means of a potentiometer. With this arrangement, it is not possible to apply small tensile forces. The tensile force applied to the movable set of wheels cannot be made less than 0 (i.e. the motor assists in contracting the store), since there are no means provided for checking the tension in the cable. Thus, when the store should be emptied, this must be effected by means of the tensile forces in the cable runs. These forces must than overcome all frictional forces in the device, e.g. frictional drag between the chain and the frame, friction and loss of efficiency occasioned by the geared motor being forced to rotate backwards etc. Compensators for controlling the tension in cables and the like in connection with cable winding are preciously known from U.S. patent specifications 2,834,556, 2,978,196 and 2,981,491. The compensators are mounted in association with the winding machines and comprise a sensing mechanism consisting of a lever (dancer) biased by a tension spring. One end of the lever carries guide pulleys for only one cable loop, and the lever is mounted on a shaft connected to a sensor for sensing the angular movement of the lever. The signals from the sensor control either the unwinding speed of the cable or the take-up speed of the cable. EP-A-0 114 365, which is considered to reveal the closest prior art, is directed to a device for controlling the tension in a cable during continuous running of the cable. The device includes a stationary and a movable set of wheels, which sets of wheels are not adapted to move towards or away from each other in such an extent, that any significant alteration of the length of the cable will occur, as is the case of the device of present invention, during exchange of drums in the unwind stand or the take-up stand. A spring applies a tensile force to the movable set of wheels and the displacement of this set of wheels is sensed and regulates the rotary speed of the unwinder in order to control the tension in the cable. Thus, none of the sets of wheels is used to control the tension in the cable but only to sense it. Due to the fact that all wheels of the set are displaceable and not only one, two or three of the wheels the device has a rather large inertia. The device requires more time to sense a change in the tension of the cable when all of the loops are involved compared to sensing a change in the tension of one or a few loops. The control of the tension is performed by controlling the rotary speed of the unwinder. This control requires more time compared to controlling the tension by moving one of the sets of wheels towards or away from the other set of wheels as in present invention. Thus, the design of the device according to the invention offers a faster and more accurate control of the tension in the cable besides greater compactness. One object of the present invention is to provide a method and a device for controlling the tension in a cable in a cable store of optional size during continuous winding and exchange of drums. A further object is to provide a space-saving sensing mechanism which is integrated with the cable store and by means of which the tension in one or more cable runs can be sensed and controlled, and by means of which a quick response can be obtained upon a change in tension. Yet another object is to provide a reliable sensing mechanism which has few components, is capable of exerting a constant adjustable pressure, is relatively inexpensive to manufacture and can be accommodated in the cable store. According to the invention, these objects are achieved by a device as above, wherein at least one of the wheels in the first set of wheels is displaceable towards and away from the second set of wheels under the influence of a change in the balance between the tension in the cable or the like and a constant pressure produced by an operating mechanism connected to the displaceable wheel or wheels of said first set of wheels, said constant pressure being directed away from the second set of wheels, and wherein a sensor sensing the displacement of said displaceable wheel or wheels is arranged to supply a correcting signal corresponding to said displacement, to the drive unit for controlling the tension in the cable or the like by correcting the basic speed of the second set of wheels or by moving the second set of wheels towards or away from the first set of wheels. The method according to the inventions is characterized in that changes are sensed in the balance between the tension in the cable or the like and a constant pressure, counteracting said tension, from the displaceable wheel or wheels of the first set of wheels, the control of the tension in the cable or the like being effected by correcting the basic speed of the second set of wheels or by moving the second set of wheels towards or away from the first set of wheels. Further developments of the invention will appear from the subclaims. Preferred embodiments of the invention will now be described by way of examples with reference to the accompanying drawings, in which Fig. 1 is a side view schematically showing an unwind stand and a take-up stand, as well as a device for storing a cable according to the invention, with a preferred drive unit for the movable set of wheels, Fig. 2 is a side view on a larger scale showing an alternative device for storing the cable according to the invention, with the operating mechanism completely enclosed in the cable store, and Fig. 3 is also a side view showing a further alternative device for storing a cable according to the invention where the store is vertically oriented. The device for storing a cable according to the invention is generally designated 1 and is shown together with an unwind stand 2 and a take-up stand 3 as schematically illustrated in Fig. 1. The unwind stand 2 and the take-up stand 3 each have a drum for the cable, band, line or the like 4, and a tachometer 5, 6. The tachometers 5, 6 may be mounted on guide rollers which are connected to the unwind stand and the take-up stand, respectively, but which, for greater clarity of Fig. 1, are shown integrated in the unwind stand and the take-up stand. The cable 4 is unwound from the unwind stand 2 at a substantially constant speed in the direction of the arrow, runs through the store 1 where a variable length of the cable is taken up, and is wound at a substantially constant speed onto the drum of the take-up stand. Alternatively, two or more stores 1 may be arranged successively after each other between the unwind stand and the take-up stand. The device 1 for storing the cable 4 comprises a frame 7 with a beam system 8 consisting of one or two pairs of parallel beams which are horizontally oriented in Figs. 1 and 2, and vertically oriented in Fig. 3. Further, the device 1 has a first, substantially stationary set of wheels 9 and a second movable set of wheels 10. Each set of wheels 9, 10 consists of a plurality of rotatably mounted wheels or guide rollers over which the cable 4 passes in a plurality of loops between the two sets of wheels 9, 10 in a conventional manner, as appears from Figs. 1-3. The wheels of the second set 10 are preferably mounted on a common shaft supported by a carriage 11 which is movable along the beam system 8 towards and away from the first set of wheels 9 by means of a drive unit 12 in a manner which will be described in more detail below. The wheels of the first set 9 may all be mounted on a common shaft connected to an operating mechanism 13. Alternatively, only one, two or an optional number of wheels (less than the total number of wheels) are connected to the operating mechanism by a common shaft while the other wheels of the first set of wheels, as required, are fixed to the beam system by another, common shaft. To the beam system 8, there is fixed a chain assembly comprising one, two or more parallel, identically designed and identically mounted, endless chains 14 which are movable between a pair of sprockets 15, 16. The sprocket or sprockets 16 are connected by a gear 17 to an electric motor 18 or like means. The components of the drive unit 12 are only shown in Figs. 1 and 2, but a similar drive unit is preferably used in the alternative embodiment of the device according to the invention illustrated in Fig. 3. The second set of wheels 10 is fixed to the chain assembly and moved by the motor 18 via the chain assembly and the gear 17, the carriage 11 sliding along the beam system 8 towards or away from the first set of wheels 9 in dependence upon the direction and the speed of rotation of the motor. By operating the electric motor, it is possible to control both the length of the cable 4 in the store and the tension in the cable, which will be described in more detail further on. The operating mechanism 13 according to Figs. 1 and 3, which is connected to and capable of displacing one, two or more wheels is the first set of wheels 9, comprises an arm 22, a so-called dancer, at the free end of which the displaceable wheels are rotatably mounted. The other end of the arm is pivotally mounted in a bracket 19 fixed to the frame 7. Spaced from the bracket in the direction of the second set of wheels 10, a pneumatic cylinder 20 is pivotally mounted in the frame. The piston rod 21 of the cylinder is pivotally mounted in the arm 22, preferably midway between the bearing of the arm in the bracket and the bearing of the wheels in the arm. To the cylinder, which preferably is of the low friction type, there is connected a control device (not shown) of known design for setting and maintaining a selected pressure in the cylinder. In order to maintain the pressure in the cylinder constant, also with a high instantaneous load thereon, the control device comprises an instantaneous evacuation port. This adjustable pressure produces a force which is directed away from the second set of wheels 10 and directly proportional to the tensile force in the cable runs and is used for setting the desired tensile force in the cable as described below. At the end of the arm 22 which is pivotally mounted in the bracket 19, there is provided a sensor 23 which is connected to the arm in such a manner that it will sense the angular movements of the arm. The position of the displaceable wheel or wheels of the first set of wheels 9 can thus be instantaneously sensed by means of signals from the sensor. To avoid crowding of the drawings, the alternative embodiment of the invention according to Fig. 2 shows only those components which differ from the components used in the embodiment according to the Fig. 1, and are required for describing this alternative embodiment. Fig. 2 also shows the incoming and outgoing ends to the right in the Figure to indicate that the unwind stand 2 and the take-up stand 3 can also be located on the same side of the cable-storing device 1. In this case, too, it is possible to use two or more cable stores. The essential difference of the embodiments of Figs. 1 and 2 lies in the design of the operating mechanisms. In the embodiment according to Fig. 2, the operating mechanism 13 is completely enclosed in the cable store. The operating mechanism comprises a pneumatic cylinder 20 with a control device. These components are similar to the corresponding components used in the embodiment according to Fig. 1. One end of the cylinder 20 is fixed to bracket means 24 in turn fixed to the frame 7 and/or the beam system 8, e.g. by welds or bolts (not shown). Preferably, the fixing point of the cylinder in the bracket means is located on a straight line intersecting the centre axes of the two sets of wheels 9, 10. The piston rod 21 of the cylinder is connected in a suitable manner, e.g. by means of fork-shaped element (not shown), to the displaceable wheel or wheels of the first set of wheels 9. A position sensor 23, preferably provided at the cylinder 20 and connected to the piston rod 21, senses the movements of the displaceable wheel or wheels in the longitudinal direction of the beam system 8. The sensor may also, for example, consist of a load cell connected to the wheel or wheels for sensing very small displacements. The position of the displaceable wheel or wheels of the first set 9 can therefore be instantaneously sensed by means of the signals from the sensor. The non-displaceable wheels of the first set of wheels 9 are mounted on a common shaft, which by the intermediary of bracket means 25, is fixed to the frame 7 and/or the beam system 8, as in the embodiment according to Fig. 1. In Fig. 3, there is shown a further embodiment of the invention where the cable store is vertically oriented, i.e. the movable set of wheels 10 moves in a vertical plane instead of a horizontal plane as in the embodiments according to Figs. 1 and 2. The design of the frame 7 thus slightly differs from the design used in the previously described embodiments of the invention, especially in respect of the attachment to the floor, but since the frame per se is no part of the inventive object, this circumstance is here disregarded. However, the vertical orientation of the cable store necessitates a pair of additional guide pulleys 26, 27 provided at the lower end of the cable store (at the end of the store where the first set of wheels 9 is located), the incoming end of the cable passing over the guide pulley 26 and the outgoing end of the cable passing over the guide pulley 27. Also, the control device of the pneumatic cylinder 20 is compensated, for instance, for the weight of the wheel set 9, the arm 22 and the piston rod 21. Although the operating mechanism 13 has been shown in the foregoing with a pneumatic pressure cylinder, it is of course also possible to use other, similar devices. However, it is not compatible with the principles of the invention to use spring assemblies since they would produce a varying force, whereas not a constant force which is of decisive importance for ensuring the desired function of the invention, which will be described in greater detail hereinbelow with reference to Fig. 1. During continuous running of a cable 4 from a drum in the unwind stand 2, through the cable-storing device 1, to a drum in the take-up stand 3, the substantially constant speed of the cable is sensed at the unwind stand (V in ) and at the take-up stand (V out ) by the tachometers 5, 6 provided at the unwind stand 2 and the take-up stand 3. The signals from the tachometers are supplied to a per se known control circuit (not shown) for the electric motor 18. If the number of cable runs in the cable store is n, the displaceable set of wheels will have a basic speed (V g ) according to the following equation: Thus, if the speed of the cable at the unwind stand is equal to the speed of the cable at the take-up stand, i.e. V in = V out , the basic speed is zero, which means that the second set of wheels 10 is stationary and that the speed and the tension of the cable in the store are substantially constant. When exchanging the drum at the unwind stand, the end of the cable entering the cable store is decelerated, i.e. V in < V out , the second set of wheels 10 being moved to the right in the Figure at a speed according to the above equation, and the relative distance between the wheel sets 9, 11 decreases, i.e. the cable store is being emptied. When exchanging the drum at the take-up stand, the end of the cable leaving the cable store is decelerated, i.e. V in > V out , the second set of wheels being moved to the left in the Figure, i.e. the cable store is being filled. This control of the movements of the second set of wheels 10 is however not sufficiently accurate or rapid at the required speed (preferably up to 400 m/min.) and for the tensile tolerance of the cable, especially in the cable store. To compensate for insufficient control of the movements of the second set of wheels, non-linearity in the control system, manufacturing tolerances of the different components in the system and of the cable, and for the "travelling" movement of the second set of wheels etc., the tension of the cable in the cable store is instantaneously sensed. The tension in the cable is controlled for maintaining a predetermined value by correcting the movement of the second set of wheels. The pneumatic cylinder 20 of the operating mechanism 13 can be set for maintaining a constant pressure which is transmitted as a tensile force to the cable loop or loops in the store running over the displaceable wheel or wheels of the first set 9, whereby the desired tension in the cable 4 is set. Upon a change in the balance between the tension in the cable and the constant pressure, counteracting said tension, from the displaceable wheel or wheels of the first set of wheels, the arm 22 of the operating mechanism is pivoted from its neutral (vertical) position to the right in the Figure upon a decrease of the tension in the cable, or to the left upon an increase of the tension. The sensor 23 then produces a signal corresponding to the angular movement of the arm from its neutral position and, hence, to the change of tension in the cable. The signal is supplied to the control circuit of the electric motor 18 which, via the drive unit 12, moves the second set of wheels to the left in the Figure upon a decrease of the tension in the cable or to the right upon an increase of the tension. In the embodiment according to Fig. 3, the arm 22 is pivoted downwards in the Figure upon a decrease of the tension in the cable or upwards upon an increase of the tension. Otherwise, the function is identical with that described above. In the embodiment according to Fig. 2, the movement of the piston rod 21 is sensed by the sensor 23, and the signal generated is supplied to the control circuit of the motor as described above. When the drum is exchanged in the unwind stand or in the take-up stand, V in differs from V out , but also in these cases the tension in the cable is obtained as a function of the basic speed of the second set of wheels and of the pressure in the cylinder, it being possible to maintain the tension in the cable constant also when filling or emptying the cable store by correcting the basic speed of the second set of wheels as described above. One characteristic feature of the present invention is that the movement of the displaceable wheel or wheels in the first set of wheels is used for correcting the tension in the cable. The correcting signal can be used, to the same end, for correcting the speed of rotation of the unwind stand and the take-up stand, especially if they are located adjacent the cable store. Another characteristic feature of the invention is that the control device is integrated with the cable store, which simplifies the path of travel of the cable. The invention is not restricted to the embodiments described above and illustrated in the drawings, but may be modified in various ways within the spirit and scope of the accompanying claims.

Claims: A device for storing a cable, band, line or the like (4) with controlled tension during continuous running of the cable and exchange of the drum in an unwind stand (2) or in a take-up stand (3), comprising a first, substantially stationary set of wheels (9) and a second movable set of wheels (10) over which the cable or the like passes in a plurality of loops, said second set of wheels (10) being movable along a beam system (8) by means of a drive unit (12), characterized in that at least one of the wheels in the first set of wheels (9) is displaceable towards and away from the second set of wheels (10) under the influence of a change in the balance between the tension in the cable or the like and a constant pressure produced by an operating mechanism (13) connected to the displaceable wheel or wheels of said first set of wheels, said constant pressure being directed away from the second set of wheels (10), and that a sensor (23) sensing the displacement of said displaceable wheel or wheels is arranged to supply a correcting signal corresponding to said displacement, to the drive unit (12) for controlling the tension in the cable or the like (4) by correcting the basic speed of the second set of wheels (10) or by moving the second set of wheels (10) towards or away from the first set of wheels (9). Device as claimed in claim 1, characterized in that all the wheels of the first set (9) are displaceable and mounted on a common shaft. Device as claimed in claim 1 or 2, characterized in that the second set of wheels (10) is fixedly connected to a chain assembly comprising at least one endless chain (14) which is movable between a pair of sprockets (15, 16), one (16) of which is connected by a gear (17) to a motor (18) or equivalent means. Device as claimed in claim 3, characterized in that both the unwind stand (2) and the take-up stand (3) comprise a tachometer (5, 6) adapted to supply signals corresponding to the speed of the cable or the like (4) in the unwind stand and the take-up stand, to a control system for the motor (18), these signals, together with the signal from the sensor (23), being adapted to operate the motor (18). Device as claimed in any one of the preceding claims, characterized in that the displaceable wheel or wheels of the first set of wheels (9) are mounted at the free end of an arm (22) of the operating mechanism (13), the other end of which is pivotally mounted in a bracket (19), that a cylinder assembly (20, 21) is fixed approximately at the centre of the arm (22) and that the pivotally mounted end of the arm is connected to the sensor (23) adapted to sense the angular movements of the arm. Device as claimed in any one of claims 1-4, characterized in that the displaceable wheel or wheels of the first set of wheels (9) are mounted at one end of the operating mechanism (13) and that the other end of the operating mechanism is fixed to a support (24) disposed between the two sets of wheels (9, 10). Device as claimed in any one of the preceding claims, characterized in that the operating mechanism (13) comprises a pneumatic cylinder assembly (20, 21) provided with control means for setting and maintaining a selected pressure in the cylinder assembly. A method in connection with the storing of a cable, band, line or the like (4) in a plurality of loops over a first, substantially stationary set of wheels (9) and a second movable set of wheels (10), for controlling the tension in the cable or the like during continuous running of the cable and exchange of the drum in an unwind stand (2) or a take-up stand (3) as claimed in claim 1, characterized in that changes are sensed in the balance between the tension in the cable or the like (4) and a constant pressure, counteracting said tension, from the displaceable wheel or wheels of the first set of wheels (9), the control of the tension in the cable or the like being effected by correcting the basic speed of the second set of wheels (10) or by moving the second set of wheels (10) towards or away from the first set of wheels (9). Method as claimed in claim 8, characterized in that the speed of the cable or the like (4) from the unwind stand (V in ) and its speed to the take-up stand (V out ) are sensed, and the tension in the cable is obtained as a function of the basic speed ((V in -V out )/the number of cable runs) of the second set of wheels (10) and said pressure, the change sensed in said balance being used for correcting the basic speed of the second set of wheels (10) and, hence, for controlling the tension in the cable or the like. Method as claimed in any one of claims 8 and 9, characterized in that the force controlling the tension in the cable or the like is adjustable.

Inventors: JOHNSSON, OLA
Applicants: NOKIA-MAILLEFER HOLDING S.A.
Application year: 1987
Main classification: B65H59
IPC codes: B65H51, B65H59