Core holder for a winder
BACKGROUND 
     The invention relates to a core holder for a winder for the centerless winding of webs, having a motor-driven spindle for the axial displacement of the core holder which is rotatably mounted on a sliding shaft mounted in a quill, a travel limiting means being provided to limit the axial movement of the core holder. 
     In the centerless winding of webs in a winding machine in which the roll is cradled between two supporting cylinders, the roll is held axially by the core holders set into the opposite ends of the roll. To change rolls it is necessary that at least one of the core holders be able to be axially shifted over a distance of, for example, 50 mm. For this displacement, a motor-driven spindle is provided, which engages the sliding shaft of a core holder. Several means are known for limiting the length of axial travel. In a first known travel limiting means a counter is provided which receives counting pulses produced by the rotation of the spindle and operates the drive motor according to the counting pulses received. A second, purely mechanical travel limiting means consists of two abutments engaging the sliding shaft. 
     In the event that the winder has to be reset for a smaller size, i.e., for a shorter distance between the core holders, it is necessary to extend the core holder on the sliding shaft beyond the position set by the travel limiting means. To make this possible, the electrical control means in the case of the first travel limiting means is so constructed that the stop pulse given to the motor by the counter when the one position is reached can be inactivated. The numerical value set at the counter for limiting the movement is preserved, however, so that, when the new core holder position is reached, the control means can act with the counter as a travel limiting means the same as it did at the former position. The changeover to another size in the case of the second, purely mechanical travel limiting means is, however, substantially more complicated. In this case it is necessary to loosen from the sliding shaft a pawl which cooperates with the abutments, so that it can be displaced axially on the sliding shaft. Not until the core holder has reached its new position can the pawl be locked axially again on the sliding shaft. 
     THE INVENTION 
     It is the object of the invention to create a core holder for a winder for the centerless winding of webs, whereby repositioning for a smaller size will be possible without complicated adjustments. 
     This object is achieved in accordance with the invention in that a control shaft for the travel limitation is coupled with the motor through a reduction gearing and a slip coupling, the control shaft bearing trippers for the limit switches associated with the motor and bearing a cam in whose path an abutment is disposed, and in that the reduction gearing has such a ratio that no more than one full rotation of the control shaft corresponds to the predetermined travel. 
     In the invention, the motor for the displacement of the core holder serves not just for gripping and releasing the roll, but also for repositioning. Upon a changeover to a smaller size, the stop signal given to the motor by the limit switch when the associated position of the core holder is reached is rendered inactive in a simple manner, for example by by-passing the limit switches or interrupting the signal conductor, depending on what type of control is used. The length of travel previously set is retained. Furthermore, the trippers are moved to the one end position simultaneously with the repositioning, so that any further adjusting work is unnecessary. 
    
    
     The invention will be explained hereinafter with reference to the drawing which presents a diagrammatic representation of an embodiment thereof, wherein 
     FIG. 1 is an axial cross section through a core holder in a winder with corresponding adjusting means, and 
     FIG. 2 is an axial cross section on line I--I of FIG. 1 through a portion of the adjusting means. 
    
    
     A roll of material 2 wound on a core 1 is cradled between a driven pair of cylinders 3. To hold the roll 2 in place axially, a core holder 4 is inserted into the core 1. The core holder 4 is rotatably mounted in a shaft 5 which is mounted for axial displacement in a quill 7 carried by the machine frame 6. The shaft 5 is held against rotation within the quill 7 by a rectilinear guide means consisting of the slot 8 and the key 9. The shaft 5 is hollow at the end opposite the core holder and contains a nut 10 borne on a threaded spindle 11 extending into the hollow of the shaft. The spindle 11 is driven by a motor 12. 
     With the winder described up to this point, it is possible to shift the sliding shaft 5 axially back and forth by operating the motor in one or the other sense of rotation. 
     On the spindle 11, or in the present case on the motor shaft 13, there is mounted a worm 14 which drives a worm gear 16 mounted on a control shaft 15. The worm gear 16 is mounted on a sleeve 17 disposed for co-rotation with the control shaft 15, this sleeve having a flange 18 against which the worm gear 16 is urged by a spring 20. Between the confronting faces of the worm gear 16 and of the flange 18 there is provided a clutch facing 19. In this manner, the worm gear 16 is therefore connected with the control shaft 18 by a slip coupling. The sleeve 17 furthermore bears a cam 21 into whose path extends a fixed abutment 22. Lastly, two trippers 23 and 24 are mounted on the control shaft 15 for co-rotation therewith, and with them there are associated limit switches 25 and 26 controlling the motor. The trippers 23 and 24 and/or their associated limit switches 25 and 26 can be moved about for the adjustment of a particular length of axial movement. The trippers 23 and 24 and their associated limit switches can be in the form of elements operating without physical contact. 
     The worm drive 14-16 has such a ratio that no more than one full rotation of the control shaft 15 corresponds to the maximum sliding shaft displacement. In any case, the relationship between cam 21 and the contact 23 controlling the left end position and the limit switch 25 is made such that, in the event of a stop signal given by the limit switch 25, the cam 21 will just come in contact with the abutment 22. With this relationship, it is then possible, once the core holder 4 has been driven to the new position, for the core holder to be shifted back and forth within the preset distance without further adjustments. 
     It will be understood that the specification and examples are illustrative but not limitative of the present invention and that other embodiments within the spirit and scope of the invention will suggest themselves to those skilled in the art.