Method and Apparatus for Braking a Bobbin Chuck and for Releasing a Bobbin Tube Thereon

This invention relates to a method and apparatus for braking a bobbin chuck and for releasing a bobbin tube thereon.

Various types of devices have been known for braking bobbin chucks and for holding and releasing bobbin tubes on the bobbin chucks. For example, Swiss Patent 495,907 U.S. Pat. No. 3,701,492 describes a structure in which a bobbin chuck is pivoted against a brake lever which, in turn, is pivotable about a fixed axis to activate a switching function. The bobbin chuck is pivoted in such a manner that a braking force component is generated to prevent a pivoting movement of the brake lever which would activate the switching function until the bobbin chuck is brought to a standstill. After braking to a standstill, the brake lever is pivoted under the influence of the contacting force of the bobbin chuck in such manner that the switching function of the brake lever is effected along with a release of a bobbin tube clamped on the bobbin chuck. In this arrangement, if fast bobbin changes are effected, hard and undampened shocks are generated which detrimentally influence the bobbin package and the bearings. Furthermore, this arrangement is not satisfactory if automatic bobbin change devices are used (which use is increasingly widespread today) because, in addition to a reliable bobbin braking action, an extremely precise positioning of the bobbin chuck axis is required. However, this cannot be achieved by using a device of the previously known type as the position of the bobbin chuck axis depends on the degree of wear of the brake linings.

Also, at increased delivery speeds, or at increased winding speeds of winding devices, the downtime for the bobbin change process must be kept as low as possible if expensive waste of already processed threads is to be avoided.

Accordingly, it is an object of the invention to effect a soft contact shock of the bobbin chuck on the brake lining and to bring the bobbin chuck into a precisely predetermined position, combined with a reliable braking action to a complete standstill before the bobbin tube is released.

It is another object of the invention to provide a simple reliable procedure for braking bobbin chucks to a standstill and for releasing bobbin tubes clamped thereon after stopping.

It is another object of the invention to use the braking momentum of a bobbin chuck to control a bobbin release operation.

Briefly, the invention provides an apparatus and method in which a bobbin chuck is braked to a standstill before a releaseable bobbin tube holding means of the chuck is activated to release a bobbin tube thereon.

The apparatus provides a combination of elements including a rotatable bobbin chuck having a means for releasably holding a bobbin tube thereon, a brake shoe having a brake lining facing a cylindrical surface of the bobbin chuck, means for pivotally mounting the brake shoe about a pivot axis coaxial of the bobbin chuck when the chuck is in braking engagement with the brake shoe, means for guiding the brake shoe radially of the pivot axis when the bobbin chuck comes into contact with the brake shoe, a pneumatic system connected to the bobbin tube holding means over the brake shoe for pneumatically operating the holding means to release a bobbin tube, and a control means in the brake shoe for controlling delivery of pressure medium to the holding means.

The means for pivoting the brake shoe may be in the form of a lever which is mounted to pivot on the pivot axis of the brake shoe while the means for guiding the brake shoe radially of this axis may include a dependent piston on the lever and a cooperating pressure chamber in the brake shoe by which the brake shoe may slide on the piston.

The pneumatic system includes a suitable means which communicates the pressure chamber with a source of pressurized gas, such as air, and a connection, including a bore, in the brake shoe which communicates the pressure chamber with the bobbin tube holding means. The control means is in the form of a piston slidably mounted in a slide chamber located in a side of the brake shoe so that the piston is disposed in the direction of brake shoe rotation, i.e. in the direction in which a rotating bobbin chuck rotates. This piston cooperates with an abutment outside the brake shoe and with the bore so as to close the bore and, thus, the connection to the bobbin tube holding means, when in a retracted position and to open the bore, and thus the connection when in an extended position.

In accordance with the method of the invention, a rotating bobbin chuck is moved in a first direction against the brake lining. The engaged brake shoe and bobbin chuck are then moved in the same direction during continued movement of the brake shoe. This causes the pressure in the pressure chamber of the brake shoe to increase due to the plunger effect of the piston therein. Also, during this time, as the bobbin chuck is being braked to a standstill, the brake shoe is pivoted about the remote pivot axis under a braking force component perpendicular to the first direction of movement which is applied to the brake lining. This braking force component is sufficient to overcome the pneumatic force on the piston in the side of the brake shoe. As a result, the piston remains in a retracted position in the side of the brake shoe and closes the connection to the bobbin tube holding means. This prevents release of a bobbin tube. Thereafter, when the braking force disappears, the brake shoe is pivoted in the opposite direction under the pneumatic force generated in the pressure chamber so as to open the connection to the bobbin tube holding means and thus simultaneously impose the pneumatic force on the holding means to release a bobbin tube.

These and other objects and advantages of the invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 illustrates a schematical side view of a winding device according to the invention;

FIG. 2 illustrates a longitudinal sectional view of a bobbin chuck with a brake shoe according to the invention;

FIG. 3 illustrates a cross-sectional view of a detail of the brake shoe taken on line III -- III of FIG. 2 in a position during the winding process; and

FIG. 4 illustrates a view similar to FIG. 3 but after the standstill of the bobbin chuck.

Referring to FIG. 1, the winding device includes a thread traversing device 1 which moves a delivered thread 2 to and fro according to a desired traversing motion in such manner that the thread 2 contactingly moves on a driven friction drive drum 3 until being wound upon a bobbin package 4 which contacts the friction drive drum 3. The bobbin package 4 is wound onto a detachable bobbin tube 5 which in turn is placed on a bobbin chuck 6 which is supported by a pivotable arm 8 (FIG. 1) pivotally mounted on the frame and pivotably connected with a lift-off device 7.

Referring to FIG. 2, during operation, the bobbin tube 5 is held on the bobbin chuck 6 by a releasable holding means, such as an expandable clamping ring 9 which is pressed radially towards the outside by a cone 10 under the influence of an axially acting spring force. Other bobbin tube holding means and release mechanisms may also be used such as those described in U.S. Pat. Nos. 3,820,739 and 3,554,455. The opposite end of the bobbin chuck 6 carries a cylindrical surface in the form of a cylinder 11 for contacting a brake shoe 12 lined with a brake lining 13.

The brake shoe 12 is pivotally mounted by a means such as a pivotable element or support 15 which can pivot about a fixed hub 14 in the winding device frame. In addition, the brake shoe 12 is guided radially of the hub 14 by means of a piston 16 which is rigidly connected to the pivotable element 15 in dependent fashion. To this end, the brake shoe 12 includes a cylindrical space 17 to slideably receive the piston 16 which space 17 also acts as a pressure chamber.

A pneumatic system is connected to the releaseable bobbin tube holding means over the brake shoe 12 for pneumatically operating the holding means to release the bobbin tube 5. This pneumatic system includes a passage 35 in the brake shoe 12 which communicates the pressure chamber 17 with a permanent source of compressed air Q via a suitable conduit 36 containing a control valve 37. In addition, the pneumatic system includes a connection to the bobbin chuck which includes a bore 18 in the side of the brake shoe 12 which is connected to the pressure chamber 17 via a duct 20, a pressure chamber 21 within the bore 18, a bore 22 in the side wall of the bore 18 which communicates with a connecting hose 23 on the exterior of the brake shoe and a bore 24 defined by a sleeve extending through the hub 14. The bore 24 is disposed on an axis which is coaxial with the axis of the bobbin chuck 6 when the chuck 6 engages the brake shoe 12. To this end, an annular nozzle 28 of rubber material is mounted on the sleeve defining the bore 24 to form a counter-piece to an end piece 29 on the bobbin chuck 6 containing a bore. An axial bore 30 in the bobbin chuck 6 connects a chamber 31 with the end piece 29 in such a manner that during the winding operation the pressure of the surrounding atmosphere prevails in the chamber 31. The chamber 31 is sealed at one end of the bobbin chuck by a piston 32 which is connected via a piston rod 33 with the cone 10. During the winding operation, a coil spring 34 presses the cone 10 into the expandable clamping ring 9 to expand the ring 9 against the bobbin tube 5 in such a manner that the tube is held fixed.

Referring to FIG. 3, a control means in the form of a push-off piston 19 is mounted in the bore 18 to slide between a retracted position and an extended position (FIG. 4). The piston 19 cooperates with one abutment 26 of a pair of abutments 26, 27 which serve to limit rotation of the brake shoe 12 about the pivot axis, i.e. about the hub 14. As shown, the bore 18 acts as a slide chamber for the piston 19 while the pressure chamber 21 is located between the duct 20 and piston 19. In addition, in the retracted position, the piston 19 closes the bore 22 while in the extended position, the piston 19 opens the bore 22 to the pressure chambers 20, 17.

Referring to FIG. 2, when the pivoting arm 8 is in a pivoted-up position, i.e. during the braking process (position indicated with dash-dotted lines in FIG. 1), the bobbin chuck 6 is placed coaxial with the hub 14 on the brake; a stop 25 rigidly arranged on the frame of the winding device ensuring the coaxiality of the hub 14 and the bobbin chuck 6. The pivoting movement of the pivotable element 15, or of the brake shoe 12 respectively, is limited by the two laterally provided stops 26, 27.

A bobbin change is effected in the following manner.

During the package build of the bobbin package 4, the pressure chamber 17 of the brake shoe 12 is connected with the source Q of compressed air and the brake shoe 12 is placed in a moved out position A (FIG. 3). The effective surface F of the push-off piston 19 is dimensioned in such a manner that the force of the push-off piston 19 is smaller than the force component of the brake shoe 12 acting in the same direction. Thus, the piston 19 remains pressed against the stop 26 and thus remains in the retracted position during the winding operation owing to the greater force of the brake shoe 12. The brake shoe 12 also rests against the stop 27 on the side opposite to the push-off piston 19.

As the lift-off device 7 is activated, the bobbin chuck 6 including the bobbin tube 5 and the full bobbin package 4 are lifted off the friction drive drum 3 and are pivoted towards the brake lining 13, the pivoting movement of the bobbin chuck 6 being limited by the stop 25. As the cylinder 11 engages the brake lining 13, the brake shoe 12 is moved upwardly as viewed along the guide piston 16 radially of the pivot axis of the brake shoe 12. The compressed air in the pressure chamber 17 is then repressed into the pressure source Q. However, owing to the reaction of the braking force, acting in the circumferential direction, a braking force component generates a momentum M which acts on the pivotable element 15 in such a manner that the push-off piston 19 in the bore 18 of the brake shoe 12 remains in the retracted position. The relation M = P .times. a prevails, where P is the friction force (i.e. braking force component) and a is the distance between the pivot axis of the pivotable element 15 and the point of action of the force P, N being the normal force of the cylinder 11 acting on the brake shoe 12. The braking shoe 12 thus takes the position B as indicated in dash-dotted lines in FIG. 4.

Simultaneously with the pivoting movement of the bobbin chuck 6 to the braking position, the end piece 29 is brought into coaxial position with the nozzle 28 and an airtight connection between the two elements 28, 29 is established (FIG. 2). As the bobbin chuck 6 comes to a complete standstill, the braking momentum M acting onto the brake shoe 12 disappears. The push-off piston 19 can now be pushed outwards, i.e. extended relative to the slide chamber 18, by the pressure prevailing in the chambers 21, 17 in such a manner that the pivotable element 15 is pivoted against the abutment 27 into the position C indicated with solid lines in FIG. 4. The bore 22 is thus uncovered and a connection is established between the pressure chamber 17 via the duct 20 and the opening 22 with the chamber 31. The increase of the pressure in the chamber 31 pushes the piston 32 including the piston rod 33 and the cone 10 towards the right hand side as viewed in such a manner that the expandable clamping ring 9 releases the bobbin tube 5.

After the full bobbin package is doffed and a new bobbin tube is donned, the pivoting arm 8 again moves the bobbin chuck 6 towards the friction drive drum 3. As the bobbin chuck 6 pivots away from the brake shoe 12, the supply of compressed air to the chamber 31 is interrupted and the bobbin tube 5 again is fixed on the bobbin chuck 6 by the spring 34 and the cone 10.

The invention thus provides a system in which a brake shoe is radially shifted under the influence of the contacting force of a bobbin chuck and, at the same time, is subject to a first rotational movement in the direction of the braking momentum by the generated braking momentum in order to prevent release of a bobbin tube and in which a second rotational movement of the brake shoe in the opposite direction is effected by compressed air after the braking momentum has disappeared, the same compressed air also effecting the release of the bobbin tube clamping action after the bobbin chuck has come to a complete standstill.

The brake shoe 12 permanently supplied with compressed air from the source Q of compressed air has proven especially advantageous. For example, no hard shock and no high momentaneous deceleration act on the bobbin package 4 while the bobbin 6 is rapidly pivoted to the brake lining 13, which could otherwise shift the bobbin package 4 in itself or on the bobbin tube 5. By varying the pressure of the source Q of compressed air, the braking momentum can easily be adjusted to the type of package build, to the fiber material processed and to the brake lining material used. Further, the degree of wear of the brake lining 13 does not influence the correct function of the apparatus.