CHUCK STRUCTURES

Abstract: A chuck (l0) for a filament winder comprises integral cantilever (package-holding) and bearing portions (l4, l2). The cantilever portion (l4) is hollow and provides both a structural member and a casing for packaging re­ taining means. Advantageous forms of package retaining elements (44,48) and bobbin tube locating elements (34) are also described.

Description: The present application relates to chuck structures for use in winding machines, particularly but not exclusively in high speed winding machines for take-up of synthetic plastics filament. In this context, "high speed" refers to speeds in excess of 3000 m/min. and especially to speeds in excess of 5000 m/min. Prior Art Filament winders designed for take-up of synthetic plastics filament can be classified into two types - those intended for take-up of relatively coarse (heavy denier or heavy titre) filaments and those intended for take-up of relatively fine filaments. The coarser filaments are normally used for industrial purposes, in tire cord and in carpet yarn; the finer filaments are generally used for textile purposes. The coarser filaments have a much greater breaking strength than the finer filaments. The difference in the breaking strength of the two filament types has in the past exerted a substantial influence on the design of chuck (also called "spindle" or "mandrel") for use in continuous or wasteless winders. Examples of such winders can be seen from European Patent Specification No. 73930 and United States Patents 4298l7l; 40l4476 and 4l86890. Examples of chucks for such winders can be seen from United States Patents 43369l2 and 4460l33. As will be seen from the specifications referred to above, a continuous winder comprises at least two chucks, one of which is held on standby while a package is formed on the other chuck. When the package is complete, a changeover is effected in the course of which the thread being wound is transferred to the "incoming" chuck while the "outgoing" chuck is moved to a doffing position. In the latter, the completed package can be removed and replaced by a fresh bobbin tube, ready for an other changeover when the ongoing package winding operation is completed. In continuous winders it is necessary to catch the thread on the incoming chuck and to sever the thread between the incoming and outgoing chucks. For finer filaments it has been possible to provide catching slots in the bobbin tubes and to rely upon tearing of the filament between the incoming and outgoing chucks after catching of the filament on the incoming chuck. For coarser filaments, however, it has been necessary to incorporate catching and severing devices in the chuck structure, for example as described in United States Patents 4l067ll; 4477034; 43369l2 and 4460l33 and in European Patent No. 470. Chucks designed for use with finer filaments have included a tube functioning simultaneously as an outer casing (or shell) of the chuck and the major structural element thereof providing both the strength and stiffness of the cantilever-mounted chuck in use. This tube has been secured at one end to a hollow stubshaft cooperating with bearings in the cantilever mounting for the chuck in the winder. However, the join between the stubshaft and the tube inevitably reduces the space available within the end portion of the tube and production of an adequate join can also give rise to problems. The space within the tube is always important for the design of the bobbin tube clamping and locating systems carried within the tube in use. A different chuck design is used for coarser filaments. In this alternative design, the major structural element providing strength and stiffness to the chuck is a longitudinal "core" tube. The thread-catching and severing structures, and the bobbin tube clamping systems are carried on the exterior of this core tube, and the assembly is partially enclosed in a surrounding casing. The latter has, however, no structural function, and it is interrupted to enable access of the thread to the catching and severing structures. For given materials in the load bearing tube, and a given proportion of the chuck cross section allocated to that tube, a chuck of the second type will be neither as strong nor as stiff as a chuck of the first type. Furthermore, the externally mounted elements are not as securely retained as corresponding elements in a chuck of the first type. EP-B1-78 978 shows a chuck structure comprising a main structural element having a rear portion supported in a pair of bearings and a front portion which carries elastic bobbin holding members and an operating system for those members. The operating system comprises a piston and cylinder unit provided at the front end of the structure and a "spacer" in the form of a sleeve extending back over the front portion. A tube to be held on the chuck structure is fitted over the outwardly facing surfaces provided by the spacer while the latter is operated to allow the elasticity of the bobbin holding members to retract the operative ends thereof sufficiently to enable mounting or removal of a bobbin tube. DE-C2-30 39 064 shows a chuck structure comprising an inner sleeve mounted by ball bearings on a support arm fixed to the machine frame and carrying an outer sleeve. A bobbin tube clamping and releasing system is provided between the inner and outer sleeves. US-C-3,030,039 shows a chuck structure comprising a central spindle and an outer sleeve which receives bobbin tubes to be held on the chuck structure. The outer sleeve is secured by screws to "support rings". Each support ring is provided with a set of three locking pins which can be urged outwardly to grip an associated bobbin tube at its mid-length. The sets of locking pins are said to be operable independently of each other, this independence being provided by a compression spring transferring operating force from the "expander" for one set to the "expander" for the other set. It is nowhere apparent from the description or the drawings how the outer sleeve should be secured relative to the spindle. The description states (at column 6, lines 13 to 15) that the support ring assemblies are secured to the spindle, but this connection is not illustrated in the drawings or further described in the text. The description also refers to connection of the outer sleeve with the support rings by means of screws (column 6, lines 32 to 35) "to hold the sleeve in place on the support rings". The tubular sleeve is closed by a "spring stop" (column 6, line 63) at the outboard end and a "stop or positioning member" (column 7, line 54) at the inboard end. There is no description of the manner in which these elements are mounted in the chuck structure. All three publications discussed in the immediately preceding paragraphs are of the type in which strength is provided by a central support element or shaft. The outermost (bobbin tube receiving) element performs at most an auxiliary operating function or acts simply as a casing or as a support for auxiliary elements of the structure. The Invention It is the object of this invention to provide a chuck which, within the confines defined by given tube (package core) sizes, enables improved utilisation of space within the hollow chuck shell while nevertheless providing adequate strength for practical operations. The solution to this problem is set out in the characterising clause of claim 1. Preferably both the first and second portions are made of steel. The second portion may be provided at its end remote from the first portion with a coupling enabling transmission of a pressure medium, preferably air, to the interior of the chamber in the first portion via the hollow interior of the second portion. A chuck according to the invention may be provided with a tube engaging element for movement radially of the chuck between an operating position engaging the interior of a bobbin tube and an inoperative position releasing the tube. The element may comprise a head portion having a surface adapted to engage the tube, a hollow body portion and a foot portion having a surface adapted to slide on a wedging member for moving the element between the operative and inoperative positions. The foot portion may have projections preventing the element from passing through an opening in a casing portion of the chuck. The hollow body portion may be open at the foot end thereof. The surface adapted to slide on the wedging member may then comprise a rim at the foot end of the body portion together with the surfaces on the projections. The element is preferably made in one piece from a light weight material such as a plastics material. An element of this type has a low mass compared to a solid element, and thus is subjected to a relatively low centrifugal force in use. A chuck design incorporating such elements can therefore be arranged to ensure that, in use, the element is contacted at all times by the wedging member and can be centered by that member relative to the chuck. The first tubular portion may have at least one pair of openings and an associated tube-positioning member with first and second arms. The member is arranged in the chamber for movement between a first position, in which the first arm passes through one opening of the pair to project beyond the outer circumference of the first tubular portion while the second arm is located within that outer circumference, and a second position in which the second arm passes through the other opening of the pair to project beyond the outer circumference of the tubular portion while the first arm is located within that outer circumference. The tube-positioning member may have a generally part-circular configuration. Means can be provided within a chamber to urge the tube positioning member into one of the positions. In comparison with known types of tube positioning members, for example as disclosed in United States Patent Specification No. 4056237, the arrangement defined above provides substantially improved guidance and retention of the member in the tubular portion. Embodiments of the invention By way of example some embodiments of the invention will now be disclosed in further detail with reference to the accompanying diagrammatic drawings, in which Fig. 1 is a sectioned side elevation of a chuck according to the invention, Fig. 2 is a sectioned side elevation of the bearing part of a chuck according to the principles described with reference to Fig. l, Fig. 3 is a side elevation of the junction region between the bearing part shown in Fig. 2 and a cantilever part shown in Fig. 4, Fig. 4 is a sectioned side elevation of a part of the chuck containing bobbin tube gripping and locating elements, Fig. 5 is a sectioned side elevation of the free end of the chuck shown in Figs. 2 to 4, Fig. 6 is a sectioned side elevation of a bobbin tube engaging element suitable for use in a system as shown in Fig. 4, Fig. 7 is a plan view of the element shown in Fig. 6 Fig. 8 is a front elevation of the element shown in Figs. 6 and 7 Fig. 9 is a diagrammatic side elevation showing the combination of an element as illustrated in Figs. 6 to 8 with an operating system as shown in Fig. 4, Fig. l0 is a diagram similar to Fig. 4 and showing additional detail of part of that Fig. Fig. ll shows an axial section of a detail taken from Fig. l0 Fig. 12 shows a series of diagrams representing various positions of a part shown in Figs. 10 and 11, Fig. 13 is a sectioned side elevation of a further detail taken from Fig. 10, Fig. 14 shows an axial section of the detail shown in Fig. 13. The chucks referred to below in the description of the drawings are intended for use in filament winding machines as disclosed in US Patent No. 4298171 and European Patent No. 73930. The function of the chucks in use assumed to be known from those prior specifications and will not be specifically disclosed herein. It will be clear to persons skilled in the art that chucks based on the relevant principles could be used in other winder designs. Chuck 10 shown in Fig. 1 comprises a bearing part indicated at 12 and a cantilever part indicated at 14. Bearing part 12 comprises a stationary casing 16 enclosing bearings 18 defining an axis of rotation 20. The rotational structure of the chuck comprises a single, integral (one-piece) load-bearing element which is made up of a first tubular portion 22 in the cantilever part 14, and a second tubular portion 24 extending from the first portion 22 into the bearing part 12 to be carried by the bearings therein. The outer surface of tubular portion 22 is cylindrical and the diameter of the section is such that the chuck can receive and support bobbin tubes such as those indicated in dotted lines at 26, 260. These tubes are normally specified by the end users of the machines. They should be a smooth sliding fit on the cylindrical outer surface of portion 22 so as to enable interference free donning of tubes and doffing of completed thread packages formed thereon as indicated in dotted lines at 28. For convenience of illustration and description of the principles involved, all drawings show or refer to a chuck designed to carry two bobbin tubes in use to wind two packages from two delivered threads. The chuck is designed to be cantilever-mounted and the bobbin tubes are "donned" by moving them axially along the chuck from the free end thereof. When the chuck is ready for use, therefore, it carries an "inboard" bobbin tube 26 (near the chuck support) and an "outboard" bobbin tube 260 (near the free end of the chuck). The invention is not limited to use with only two bobbin tubes, but except where specifically indicated to the contrary, all of the features to be described for a "two-bobbin" chuck are applicable without alteration in a chuck carrying more than two bobbin tubes. The expressions "upper" and "lower" are used hereinafter in the description of the drawings; it will be understood that these expressions apply merely to the dispositions of the parts as they happen to be illustrated in the Figures and have no significance in relation to the operation of the illustrated parts. The hollow interior of tubular portion 22 defines a chamber 30 extending axially over almost the whole length of portion 22 and opening onto the free end of the chuck. The chamber is closed in use by a cap 32 secured to portion 22 by any suitable means (not shown). Mounted within chamber 30 are devices for securing and centering each bobbin tube 26 relative to tubular portion 22 for rotation with that portion about axis 20. These devices have been indicated only in block diagrammatic form in Fig. l; suitable embodiments of such devices will be described later with reference to subsequent Figures, and further devices are already known in the filament winding art. Taking the inboard device (that is, the device nearest bearing section l2) by way of example only, the device comprises a plurality of tube engaging elements 34 passing through respective openings in portion 22. These openings are equiangularly spaced around axis 20. There are commonly 6 or 8 such openings with a corresponding number of tube engaging elements. The elements are movable radially between radially inward (withdrawn) positions in which they do not interfere with doffing and donning of bobbin tubes, and radially outward (extended) positions in which they secure the respective bobbin tube relative to portion 22. For each bobbin tube there are two sets of elements 34 located adjacent the inboard and outboard ends respectively of the bobbin tube when the latter is correctly axially located relative to tubular portion 22. For each set of elements 34 there is a respective moving means, the inboard moving means being indicated at 36. Each moving means is operable to move the elements 34 of its respective set from the withdrawn to the extended positions, and to enable return of the elements to the withdrawn position. The moving means are selectively operable by an energising means generally indicated at 38, extending axially along the central portion of chamber 30. A suitable form of energising means will be disclosed later with reference to Fig. 4. Communication with the energising means 38 can be established via a passage 40 extending axially of tubular portion 24. Correct axial location of the inboard bobbin tube relative to tubular portion 22 is assured by an axial abutment 42 adjacent the inboard end of portion 22. The inboard bobbin tube can be pushed along portion 22 into engagement with abutment 42. Correct location of the outboard bobbin tube 260 is ensured by a locating element 44 which is caused to project through a suitable opening in portion 22 after donning of the inboard bobbin tube 26. When moved to its extended position, element 44 acts as an abutment limiting movement of outboard tube 260 towards the inboard end of portion 22. As shown in Fig. l, the arrangement is such that a gap 46 is left between the adjacent ends of correctly located tubes 26, 260. A catching and severing element 48 can be caused to move into this gap after donning of the tubes. Elements 44 and 48 are carried by a common support ring 50 within tubular portion 22. A suitable form of ring 50 will be described later in this specification. A ring 52 similar to the ring 50 is provided adjacent the outboard end of the outboard tube 260. However, ring 52 carries only thread catching and severing elements 54, since the outboard tube is axially located by the element 44 at the inboard end thereof. The various components disposed within tubular portion 22 are assembled therewith by insertion through the open, free end of the tubular portion, which is thereafter closed by cap 32. Before turning to details of practical embodiments based upon the principles illustrated in Fig. l, attention is drawn to the following features; portion 22 is of constant wall thickness over substantially its whole length, that is chamber 30 is of constant cross section to a position close to or beyond the inboard end of the inboard bobbin tube 26, the load bearing element (portion 22) in the cantilevered, rotational structure also provides the casing for that structure, the cantilever and bearing parts l2, l4 of the rotational structure are strongly joined by the integral junction portion indicated at 56 in Fig. l. Fig. 2 shows the bearing part l2 of a chuck designed on the principles described with reference to Fig. l, but with additional detail of a practical embodiment. The support casing is again indicated at l6 and the bearings at l8. The smaller diameter portion of the rotating structure is again indicated at 24 with the axial bore 40 therein. A braking and driving unit 60 is secured to portion 24 at the end thereof remote from portion 22. This unit is conventional and will not be described in detail. The unit also provides a coupling 62 by way of which pressure fluid medium can be supplied to the interior of passage 40 in use. The purpose of this medium will become apparent from the description of Fig. 4 below. Fig. 3 shows the junction region 56 in greater detail. In particular, Fig. 3 shows that the inboard end of chamber 30 can be brought very close to the outboard bearing l8. A suitable taper is provided between the external diameter of portion 22 (determined by reference to the bobbin tubes to be used) and the external diameter of portion 24 (determined by the structure of the bearing part l2). The abutment 42 forms a projection on this taper and adjoins in this embodiment an additional projection 63 enabling provision of a thread catching groove 64. In the event any thread winding passes beyond the inboard end of inboard bobbin tube 26 it will be retained within groove 64. As also shown in Fig. 3, the outer end of passage 40 adjoins the inner end of a tube 66 which extends axially along the central portion of chamber 30. The purpose of this tube will be further explained below in the course of the description of Fig. 4. It provides the energising means referred to above in connection with Fig. l. Fig. 4 shows the greater part of the inboard bobbin tube 26 and the adjoining end of the outboard bobbin tube 260, each being correctly axially located relative to tubular portion 22. Various details shown in the upper half of Fig. 4 have been omitted from the lower half thereof. The latter is in practice a mirror-image of the upper half, the chuck being symmetrical about its central axis 20. Consider first the inboard bobbin tube 26 (to the left in Fig. 4) and in particular the devices within chamber 30 adapted to cooperate with that bobbin tube. Tube gripping system One important function of the devices to be described is securing of bobbin tube 26 to portion 22 for rotation therewith about axis 20. It is important that tube 26, and any thread package carried thereby, is secured against any movement relative to the chuck during rotation about axis 20. In particular, the systems to be described must prevent not only relative axial and circumferential movement between the package and the chuck, but also relative radial movement thereof. The latter can be caused, for example, if the devices in contact with tube 26 are not positively centered relative to portion 22. If that happens, unbalance can arise in the system and can lead to severe damage at very high rotational speeds. The tube engaging elements 34 referred to in the description of Fig. l are shown again in Fig. 4. There are two sets of elements 34 (inboard and outboard) for each bobbin tube. The elements of each set are equally spaced angularly around axis 20, being located in respective openings 72 indicated in the lower half of Fig. 4. The moving means 36 referred to in the description of Fig. l comprise in the embodiment of Fig. 4 an inboard device 68 and an outboard device 70 which is similar but in verted relative to device 68. The latter will be described first. Device 68 comprises a piston element 74 and a wedging cone 76. Piston element 74 is annular. At its outer edge it is a smooth sliding fit on the cylindrical internal surface of tubular portion 22. At its inner edge, it is a smooth sliding fit on the external cylindrical surface of the tube 66 already referred to in the description of Fig. 3. Element 74 therefore defines a pressurisable compartment 78 between itself and the axially facing end surface 80 (Fig. 3) of the chamber 30. Compartment 78 can be pressurised through the slight gap between the inboard end of tube 66 and the outboard end of passage 40 (Figs. 2 and 3) and also via radial openings 82 in the portion of tube 66 lying within the compartment 78. When compartment 78 is pressurised (with an adequate pressure) piston 74 is moved to the right as viewed in Fig. 4. Wedging cone 76 is a hollow, frusto-conical body, the smaller diameter end of which is mounted on an axial projection 84 which is integral with piston element 74. The outwardly facing conical surface of element 76 extends axially across the array of openings 72, and is engaged by the radially inner ends of each of the tube engaging elements 34. As clearly seen in Fig. 4, the ends of elements 34 are suitably profiled to enable them to slide smoothly on the wedging cone 76. As the latter is moved to the left as viewed in Fig. 4, the elements 34 of the device 68 are forced outwardly to engage and grip bobbin tube 26. As cone 76 is moved to the right as viewed in Fig. 4, elements 34 are permitted to retract (radially inwardly) to release tube 26. As already described, the latter movement can be caused by pressurising compartment 78. Normally, however, as will now be described, device 68 is biassed towards the left as viewed in Fig. 4, so that elements 34 are normally forced to their extended position. As will be described with reference to Figs. 6-8, each element 34 has a suitable retaining means (not shown in Fig. 4) to ensure that the element is retained within the chuck structure when device 68 is forced to its full leftward (inboard) position in the absence of a bobbin tube 26. The space between devices 68 and 70 is divided by a bulkhead 86 into two compartments, an inboard compartment 88 and an outboard compartment 90. Bulkhead 86 is secured against axial movement relative to tubular portion 22 by fixing screws 92 passing through suitable bores in portion 22. Bulkhead 86 is also annular, and carries at its inner edge a tube 94 closely encircling the tube 66 and extending in both axial directions from the bulkhead 86 into both the device 68 and the device 70. The inboard end of tube 94 provides an end stop for the rightward movement of piston element 74. The inboard end of compartment 88 is defined by an annular wall 96 integral with cone 76. The outer edge of wall 96 is a smooth sliding fit on the internal surface of tubular portion 22, and the inner edge of wall 96 is a smooth sliding fit on the external surface of the tube 94. Compartment 88 contains a biassing means adapted to generate a force urging device 68 to the left as viewed in Fig. 4. The biassing force is preferably generated mechanically. Various mechanical devices using springs have already been proposed for this purpose and one such arrangement is indicated highly diagrammatically in the lower half of Fig. 4 in the form of six ring-elements 87 arranged axially side by side in compartment 88 and in contact at their inner and outer edges. In practice, many more than six elements would be provided. Elements 87 are axially compressible in the axial direction and the group of elements is in a state of compression at all times in the assembled chuck structure (when confined between bulkhead 86 and wall 96). Expansion of compartment 88 (relaxation of the group of elements 87) is limited by the means limiting radially outward movement of tube gripping elements 34. It is an important feature of the illustrated chuck structure that all elements thereof are securely centered relative to axis 20 in order to avoid imbalance in use. In the case of the elements 87, such centering can be obtained either by secure contact of each element at its inner edge with the tube 94, or secure contact of each element at its outer edge with the internal surface of tubular portion 22. In this context, "secure contact" means that contact is established and maintained over a sufficient proportion of the periphery (either internal or external) of the ring-element 87 to ensure that that element is centered relative to axis 20. Since play is normally required to enable assembly of the elements, each element should be deformable in response to the axial compression load supplied thereto to ensure that the required secure contact is achieved after assembly is complete. An alternative, preferred biassing means will be referred to at the end of this specification. Device 70 is similar in structure to device 68 and will be described relatively briefly. It comprises a piston element 98, a wedging cone l00 and an annular end wall l02 slidable between tubular portion 22 and tube 94. In device 70, however, piston element 98 is at the outboard end of the device, and wall l02 at the inboard end adjoining compartment 90 which contains a non-illustrated mechanical biassing means similar to the biassing means described for compartment 88. A pressurisable compartment l04 is defined between piston element 98 and a carrier unit l06, (equivalent to the ring 50 in Fig. l) the structure and purpose of which will be described later with reference to Fig. l0. Radial openings l08 in tube 66 enable supply of pressure fluid from the tube to compartment l04 in order to move piston element 98 to the left as viewed in Fig. 4 until it engages an end stop provided by tube 94. Such movement of element 98, and hence of cone l00, enables the tube engaging elements 34 of device 70 to move radially inwards in their respective opening 72 and thereby release bobbin tube 26. Devices 68 and 70 are operated simultaneously by application of pressure to passage 40 (Fig. 2) and hence to tube 66. However, the movements of devices 68 and 70 are independent of each other. Tube 66 does not form a connection transmitting movement to the devices, but only a pressure-fluid transmitting lead. The mechanical biassing means in compartments 88 and 90 are separated by the bulkhead 86 which is fixed relative to tubular portion 24. Accordingly, each set of tube engaging elements 34 can be independently urged into contact with its respective "end" of the bobbin tube 26 to be gripped. This enables independent adaptation of each set of tube engaging elements to varying tube tolerances found in practice. For each bobbin tube carried by the chuck there is an inboard device 68 and an outboard device 70, each with a respective set of tube engaging elements 34 and each pressurisable via the common pressure-fluid supply tube 66. For each pair of devices 68, 70 there is a respective intermediate bulkhead 86 separating the mechanical biassing means acting on the respective devices. Where more than two bobbin tubes are to be carried on the chuck, a support unit l06 is provided in the region bridging the adjacent ends of each successive pair of tubes. The arrangement at the outboard end of the chuck will now be described with reference to Fig. 5. In this Figure, the open end of the tubular portion 22 is shown, together with the closure cap 32 secured to portion 22 by fixing screws ll0. Cap 32 has an axial projection ll2 extending into the open end of tubular portion 22 and locating at its inboard end a disc ll4, (equivalent to the ring 52 in Fig. l). The structure and purpose of which will be described later with reference to Fig. l0. The outboard end of tube 66 engages disc ll4. A pressurisable compartment ll6 is formed between the disc ll4 and the piston element 98 of the outboard device 70, and this compartment can be pressurised via radial openings ll8 in tube 66. Each bobbin tube must be secured against axial and circumferential slippage relative to tubular portion 24, and also against radial play. Such play must be prevented between each tube engaging element 34 and the facing internal surface on the bobbin tube, and between the radially inner end of engaging element 34 and the respective associated wedging cone 76 or l00. It is important in this respect that, as far as possible, each tube engaging element 34 is positively urged outwardly by its associated wedging cone 76 or l00. In this connection, centrifugal force acting on the element 34 at high rotational speeds represents a problem, since it tends to urge each element 34 outwardly away from its associated wedging cone 76 or l00. This increases the axial and circumferential gripping effect of element 34 on the associated bobbin tube, but reduces the centering effect. Accordingly, if the elements 34 in any one set thereof are no longer positively centered relative to axis 20, and significant imbalance arises in the system during formation of a thread package, then the resulting vibrations can cause serious damage to the chuck and, possibly, to the machine as a whole. The centrifugal force acting on any one element 34 is a function of the mass of that element. Figs. 6 to 8 show a design of tube engaging element of a relatively low mass compared with those currently in use so that there is less tendency for centrifugal force to create radial play between the radially inner end of such engaging elements and the respective wedging cone. The new elements, generally indicated at 34A in Figs. 6 to 8, each comprise a hollow cylindrical body portion l20 having a closed end l22 providing a tube-engaging head portion and an open-end providing a cone-engaging foot portion. The generally axially facing surface l24 at the open end of body l20 is shaped, as seen in Fig. 6 and Fig. 8, to lie on the corresponding frusto-conical surface of its associated wedging cone 76 or l00. Preferably, the wedging cones 76 and l00 have the same shape, so that all elements 34A can be substantially identical. Head portion l22 has an outwardly facing surface l23 which, as seen in Fig. 8, is convex as viewed axially of the chuck. The curvature corresponds to that of the internal surface of the bobbin tube. Surface l23 has an area A (not marked) which is further discussed later. Four outwardly extending projections l26 (Figs. 7 and 8) are provided at the foot portion of each element 34A. These projections act as retainers, preventing the element escaping from its respective opening 72 (Fig. 4) in tubular portion 22. Furthermore, the radially inwardly facing surface on each projection l26 is formed, as can be seen in Fig. 8, to engage and slide upon the associated wedging cone 76 or l00. The head portion l22 is provided with two chamfers l28 facing in opposite axial direction relative to the chuck, and with an end opening l30 permitting exit of air from the hollow interior. Each element 34A is made in one piece of a plastics material, for example polyacetal or polyoxymethylene (POM). This material is of low density relative to metal. Furthermore, the hollow structure of each element 34A reduces the mass thereof, so.that there is less tendency for centrifugal force to separate surface l24 from the corresponding wedging cone. Nevertheless, the columnar body l20 provides adequate compression strength to resist the forces applied axially thereto in firmly gripping the bobbin tubes. The head portion l22 provides an adequate zone of contact with the internal surface of the bobbin tube, enabling firm gripping thereof without causing undue tube damage by forcing of the gripping elements into the wall of bobbin tubes used therewith. By way of example only, Fig. 9 shows diagrammatically a system using tube engaging elements 34A suitable for gripping a bobbin tube of nominal internal diameter 75 mm. In Fig. 9, element 34A is shown engaging the internal surface of a tube 26 having exactly the nominal diameter 75 mm. The foot portion of the element is in firm engagement with the wedging surface l32 of the corresponding wedging cone 76 or l00. The wedging angle of surface l32 is indicated at α in Fig. 9. This is the angle between an imaginary line defined by the intersection of an axial plane with the surface l32 and a line in the same plane parallel to the axis of the cone, i.e., the half angle of the corresponding cone. Angle α may be about 42°. The line l34 in Fig. 9 represents an axially facing surface on the wall 96 or l02 (Fig. 4) of the associated device 68 or 70. Line l36 represents the axial surface, facing surface l34, on the corresponding piston element 74 or 98 (Fig. 4). The external diameter of element 34A in a plane at right angles to the axis of the cylindrical body l20 (Fig. 6) is shown at D in Fig. 9, the spacing of the body l20 from the surface l34 is indicated at s and the spacing of the body from surface l36 is indicated at d. The diameter D may be approximately l2 mm, and when element 34A is in its normal extended position (as illustrated, in contact with the internal surface of a tube of the specified internal diameter) spacing s may be approximately 4 mm and spacing d may be approximately 5 mm. The non-indicated internal diameter of the hollow body l20 in a plane corresponding to the diameter D may be approximately 8 to l0 mm. The resulting area A of surface l23 is approximately l00 mm², but areas in the range 80 to l20 are suitable. Line l38 in Fig. 9 represents the intersection of the axial plane referred to above with the internal surface of tubular portion 22 (Fig. 4) and line l40 represents the intersection of the same axial plane with the external surface of portion 22. The wall thickness of tubular portion 22 is therefore indicated at t in Fig. 9 and may be approximately 8 mm for a steel tube. The radial spacing between the external surface of tubular portion 22 and the internal surface of the bobbin tube is indicated at ℓ in Fig. 9, and may be approximately l mm for a bobbin tube having the nominal internal diameter and maximum l.7 mm. Such a chuck can be driven in use at speeds up to about 24000 RPM. Bobbin tube positioning As shown in Fig. 4, and as already described with reference to Fig. l, a gap 46 is provided between the adjacent ends of axially successive bobbin tubes 26, 260. As can also be seen in Fig. 4, the gap 46 is bridged within tubular portion 22 by the support unit or "ring" l06 referred to very briefly above. This ring is fixed axially relative the tubular portion 22 by fixing screws l42. Support ring l06 carries at least one positioning element adapted to act as an axial stop for the inboard end of the outboard bobbin tube 260. The principle of such a positioning element is shown in U.S. Patent Specification 4056237, and the element shown in that patent could be used in the ring l06 if suitable openings were provided in the tubular portion 22. However, a preferred form of positioning element is shown in Fig. l0 and will now be described. Fig. l0 shows the support unit l06 drawn to a larger scale to show internal details thereof. Unit l06 comprises a pair of annular bulkheads l44, l46 respectively fixed to tubular portion 22 by the screws l42 referred to above. Each of these bulkheads is sealed at its outer edge to tubular portion 22 and at its inner edge to tube 66 so as to define a compartment l48 which is isolated from the pressure fluid in compartments 78 and l04 to either side of support unit l06. A ring l50 is mounted on tube 66 within compartment l48. Ring l50 has two radial slots l5l diametrically opposite each other and opening onto the circumference of the ring. A central end projection l53 on the ring carries a pair of arms l52 extending into respective slots l5l, only the lower arm l52 being illustrated in Fig. l0. The purpose of these springs will be explained below. Tubular portion 22 has two pairs of radial bores, one pair (indicated at l54 and l56 in Fig. l0) opening into one of the slots l5l, and the other pair (not indicated in Fig. l0 but diametrically opposite to the first pair) opening into the other slot l5l. Each slot contains a positioning element l58, only the lower element being seen in Fig. l0. Element l58 is equivalent to element 44 in Fig. l. Each element l58 comprises a first arm l60 located in the associated bore l54 and a second arm l62 located in the associated bore l56. The arms are joined by a connecting portion l64 within compartment l48. The detailed construction of element l58 will be described below with reference to Fig. ll. It will be seen from Fig. l0, however, that the connecting portion l64 has a slot l65 receiving a transverse bar (not indicated) on the associated spring l52. Spring l52 is effective to urge element l58 radially outwardly so that its arms are retained in the respective bores l54, l56. Simultaneously spring l52 tends to rotate the part-circular element l58 about an imaginary center in a direction urging the free end of arm l60 outwardly from the tubular portion 22; that is, for the element l58 actually illustrated in Fig. l0, in an anti-clockwise direction about its imaginary center. Connection portion l64 is seen in section in Fig. ll together with the arm l62. Portion l64 is of rectangular section, while arm l62 is of circular section, the transverse dimension of the arm being less than that of the connecting portion so that a shoulder l66 is formed at the junction of the arm with the connecting portion. A similar shoulder, indicated diagrammatically at l68 in Fig. l0, is formed at the junction of the arm l60 with the connecting portion l64. At its free end, arm l62 has a chamfer l70 and a surface l72 (Fig. l0) which faces axially of the chuck when element l58 is in the position shown in Fig. l0. As will be described later, surface l72 provides a tube stop. As seen in Fig. l0, the free end of arm l60 has oppositely facing, chamfered surfaces l74, l75. Surface l74 faces surface l70. The bores l54 and l56 are dimensioned to receive the respective arms l60, l62 but not the connecting portion l64. Accordingly, when appropriate forces are applied, each element l58 can be rotated about its imaginary center until either shoulder l66 (Fig. ll) or shoulder l68 (Fig. l0) engages the internal surface of tubular portion 22 adjacent the respective bore l54, l56. When shoulder l66 engages tubular portion 22 as shown in Fig. l0, surface l72 faces generally axially of the chuck and projects from bore l56 so as to provide an end stop for engagement by the outboard bobbin tube 260. When shoulder l68 engages the tubular portion, arm l62 lies wholly within the external surface of tubular portion 22, and does not interfere with axial movement of bobbin tubes. As will now be described with reference to Fig. l2, each spring l52 urges its associated element l58 towards a predetermined "starting" position, but the element can be forced away from this starting position and into a series of further possible positions by simple axial movement of bobbin tubes along the chuck. Fig. l2 is in the form of a series of diagrams representing the various positions of the upper element l58, the starting position being shown in Fig. l2a. In the starting position, the chuck is assumed to be at rest and does not carry any bobbin tubes. The free end of arm l62 projects from the external surface of tubular portion 22, whith surface l74 facing towards the free end of the chuck (to the right as viewed in Fig. l2a). The outer curved surface of arm l62 contacts the surface defining bore l54 at l77 on the inboard side of bore l54. Arm l60 lies within the external surface of tubular portion 22, or at least is withdrawn so far into its bore l56 that it will not interfere with movement of inboard bobbin tube 26 from right to left as indicated by the arrow. Accordingly, the end face on the inboard end of bobbin tube 26 will strike against surface l74 and "wedge" arm l62 radially inwardly into its bore l54. As movement of bobbin tube 26 to the left continues, the flat end surface on arm l62 passes into contact with the internal surface of tube 26 as shown in Fig. l2b. Spring l52 meanwhile continues to urge the outer curved surface of arm l62 into contact with the inboard side of bore l54. Both shoulders l66 and l68 are now spaced from the internal surface of tubular portion 22, and the generally radially outward force applied by spring l52 urges the free end of arm l60 also into engagement with the internal surface of bobbin tube 26. As soon as the outboard end of tube 26 moves to left beyond the free end of arm l60, spring l52 urges arm l60 still further radially outwardly until shoulder l68 comes in to contact with the internal surface of tubular portion 22. This is the position illustrated in Fig. l0, in which surface l72 is disposed as an end stop for the axial end of the outboard bobbin tube 260 as also shown in dotted lines in Fig. l2c. It will be noted, however, that at all stages of these movements, spring l52 urges element l58 in a generally inboard direction so that contact is maintained between the outer curved surface of arm l62 and the inboard side of bore l54. The zone of contact of course moves axially of the bore l54 and around the circumference of the part-circular element l58 as the element moves, but contact is nevertheless maintained as a main guidance and location means for the element l58. In addition, in the condition shown in Fig. l2c, contact will be made between the inner curved surface of arm l62 and the lower edge of bore l54 as indicated at l79. Assuming that inboard bobbin tube 26 is brought into contact with end stop 42 (Fig. l) and outboard bobbin tube 260 is correctly seated against stop surface l72, then axial gap 46 will be formed between the adjacent ends of the bobbin tubes. This gap will be of generally predetermined width, allowing for length tolerances on the inboard tube 26. The purpose of the gap will be described later with reference to Figs. l3 and l4. First, however, removal of bobbin tubes from the chuck will be described with reference to Fig. l2. Assume firstly that the bobbin tubes are removed from the chuck without performance of a winding operation, that is, no thread packages have been formed. At the start of the removal operation, the bobbin tubes and the positioning element l58 are in the positions shown in Fig. l2c. Removal of the outboard bobbin tube 260 has no effect upon the disposition of element l58. When inboard tube 26 is moved away from its end stop 42 (Fig. 3) it will first strike against the surface l70 on arm l60. Continued movement of tube 26 towards the free end of the chuck will wedge arm l60 back into its bore l56 until the position shown in Fig. l2b is reestablished. Then, when the inboard end of tube 26 passes to the right (as viewed in Fig. l2b) beyond the free end of arm l62, spring l52 will return element l58 to the disposition shown in Fig. l2a, whereupon the element is ready for a repeat operation. When packages have been wound on the bobbin tubes 26 and 260, the situation differs only in that the bobbin tubes are compressed by the package windings against the external surface of tubular portion 22, as indicated by the dotted lines in Fig. l2b. Correspondingly, element l58 is pushed bodily radially inwardly of tubular portion 22, so that the outer curved surface of connecting portion l64 lies along the dotted line shown in Fig. l2b. Element l58 is, however, still spaced from the surface l49 defining the base of slot l5l. In other respects, the mode of operation is the same as that described for removal of bobbin tubes without packages. Where the chuck is designed to carry only two bobbin tubes, there is only one axial gap 46 and only one pair of positioning elements l58. When there are more than two bobbin tubes, however, an axial gap 46 must be formed between the neighbouring ends of each pair of successive bobbin tubes, and there must be a separate pair of positioning elements for each axial gap 46. For the inboard pair of positioning elements, operation during removal of bobbin tubes will be as described immediately above with reference to Figs. l2a to l2c. This will be true also for all the other positioning elements if all bobbin tubes are moved together, for example by engagement of a "push-off" shoe with the inboard end of the inboard bobbin tube. It will not apply to the other positioning elements, however, where the bobbin tubes are removed successively, starting with the outboard tube. In such a case, during removal of the second tube (the tube following the outboard tube) the outboard positioning elements l58 will return to the starting positions as shown in Fig. l2a, although at least one bobbin tube is still located further inboard on the chuck. Movement of such a tube past the outboard positioning elements l58 is illustrated in Figs. l2d, e and f. In Fig. l2d, the bobbin tube being moved off the chuck is indicated at 26A; it is assumed to bear a package, so that its internal surface is contact with the external surface of tubular portion 22; the tube is being moved to the right as viewed in the figure, towards the free end of the chuck and is approaching an outboard element l58 which is in its starting position as also shown in Fig. l2a. The outboard end of tube 26A rides onto the outer curved surface of arm l62 and from there onto the chamfered surface l75. In doing so, it drives arm l62 radially inwardly along its bore l54. In addition, however, it applies a turning moment to element l58 which prevents spring l52 from forcing arm l60 outwardly through its bore l56. Instead, the inner curved surface of arm l62 is forced into contact with the outboard side of bore l54, as indicated at l8l in Fig. l2e, while element l58 is forced bodily radially inwardly in its slot l5l. Spring l52 is, however, still effective to hold the outer curved surface of arm l62 in contact with the inboard side of bore l54, as indicated at l83 in Fig. l2e. The radially inward movement of element l58 continues until the outer curved surface of connector portion l64 comes into contact with the surface l49 in the slot, as indicated at l85 in Fig. l2e. With continued movement of tube 26A to the right, the flat end of arm l62 comes into contact with the internal surface of the tube as shown at Fig. l2f. In moving to this position from the position shown in Fig. l2e, arm l60 is forced radially outwardly along its bore l56, while sliding contact is maintained between the outer curved surface of connector portion l64 and surface l49 in the slot l5l. Contact may also be made between the outer curved surface of arm l60 and the outboard side of bore l56, as indicated at l87 in Fig. l2f. As before, spring l52 maintains contact between the outer curved surface of arm l62 and the inboard side of bore l54. As soon as tube 26A passes over the free end of arm l62, element l58 is free to return to its starting position as indicated in Fig. l2a under the influence of spring l52. It will be noted from Fig. l2e that arm l60 at no time leaves its bore l56, so that element l58 is always securely retained relative to tubular portion 22, although there may be some slight variation in the disposition of the elements from case to case because of play in the guidance and locating systems provided by bores l54, l56. Thread catching Angularly displaced from the bore pair l54, l56, tubular portion 22 has four further bores l76 (Fig. l3) communicating with the compartment l48. These bores (only one illustrated) are equiangularly distributed around axis 20. Ring l50 (Fig. l4) has four additional radial slots l55 aligned with respective openings l76. Each bore l76 receives a thread catching and severing device generally indicated at l78 in Fig. l3, and equivalent to elements 48 in Fig. 1. Each device 178 comprises a radially outer head portion 180, an intermediate body portion 182 and a radially inward foot portion 184. Head portion 180 comprises an axially projecting tooth 186 and a radially movable clamping pin 188 cooperable with the "underside" (radially inwardly facing surface) of the tooth 186 to form a clamping point. Pin 188 is radially movable in a suitable bore (not shown) in body portion 182 and is pressed outwardly against the underside of tooth 186 by centrifugal force when the chuck is rotating in use. The arrangement of the tooth 186 and its cooperation with clamping pin 188 are disclosed in U.S. Patent Specification No. 4106711. Details of the arrangement can be obtained from that specification. An alternative arrangment, which can be adapted to the system shown in Fig. 13, is shown in U.S. Patent Specification No. 4477034. As indicated by the double headed arrow in Fig. 13, device 178 is bodily movable in generally radial directions between an operating position (shown in Fig. 13) in which head portion 180 projects from the external surface of tubular portion 22, and a retracted position (not shown) in which head portion 180 lies within the external surface of tubular portion 22. As head portion 180 is drawn back into the opening 176, foot portion 184 and body portion 182 are drawn radially inwardly into the slot l55 in support ring l50. This radial inward movement of device l78 can be continued until head portion l80 lies within bore l76. Movement of device l78 in the radially outward direction is limited by shoulders l90 on foot portion l84 engaging the internal surface of tubular portion 22 as illustrated in Fig. l3. As seen in Fig. l4, foot portion l84 has flat side faces (facing in the circumferential direction relative to the chuck). These side faces slide smoothly on the side walls of the respective slot l55, which therefore provides guidance for the device l78 in its movement between the retracted and the operative positions. Tubular portion 22 has a circumferential groove l92 (Figs. l0 and l3, omitted from Fig. l2) axially spaced from the openings l76 on the outboard side thereof. As clearly seen in Fig. l0, this groove is aligned with the gap 46 when adjacent bobbin tubes 26, 260 are correctly located. Accordingly, during a thread catching operation, a thread extending substantially at right angles to the axis 20 can be laid in the groove l92, as indicated at l94 in Fig. l3, and can then be moved axially of the chuck into the head portion l80 (as indicated by the arrow l96 in Fig. l3). Once in the head portion l80, the thread will be caught in the clamping position provided by the engagement of pin l88 with the underside of tooth l86 (as described in U.S. Patent No. 4l067ll) and the thread portion downstream from the clamping point will be severed, as described in the same patent. Further axial movement of the thread upstream from the clamping point will then carry the thread over the tooth l86 onto the bobbin tube 26 inboard thereof, so that package winding can begin. In the illustrated embodiment device 178 is biassed radially inwardly towards the retracted position so that a radially outward force is required to carry it into the operating position. The retracting system comprises a carrier disc 198 (Figs. 10 and 13) mounted on the tube 66 and supporting four spring arms 200 extending axially from disc 198 into respective slots 155. The free end of each arm 200 engages in a groove 202 provided in the foot portion 184 of the associated device 178. Each spring arm is arranged to apply biassing force to its associated device 178 tending to draw the device radially inwardly. A means providing the outward force to overcome the bias applied by spring arms 200 has not been illustrated in this application. Correspondingly, the part of foot portion 184 radially inwardly of groove 202 has been omitted. The present invention is not in any case limited to a specific means to move the devices 178 to their opening positions. For example only, by suitable modification of the system disclosed in European Patent Specification No. 470, movement of the outboard bobbin tube 260 shown in Figs. 10 and 13 to its positioning engagement with stop surface 172 (Fig. 10) could be made to apply a mechanically derived force to urge the devices 178 to their extended positions. Alternatively, support ring 150 could include a pressurefluid operated device for applying the required force to the device 178 to drive it to the radially outward position against the bias applied by arm 200. The device could be pressurised from tube 66 but would have to be controlled to operate in the inverse mode relative to the tube engaging elements 34, since those elements have to be forced radially outwardly at the time when the devices 178 have to be withdrawn to their retracted positions. In a further alternative, the biassing systems could be reversed so that the spring bias is effective to urge devices 178 to their operative positions, and a pressure-fluid operated device is provided to withdraw them to the retracted positions. In this case, withdrawal of devices 178 could be effected in synchronism with the release of the gripping systems for the bobbin tubes 26, generally as described in US Patent 4336912. At the free end of the chuck, shown in Fig. 5, a support ring 114 has been illustrated. This ring seals with the internal surface of tubular portion 22 to close off compartment 116. In addition, ring 114 is provided with slots (not shown) receiving catching and severing elements identical with those shown in Figs. 13 and 14. Tubular portion 22 is provided with corresponding bores (not shown) to permit a radially outward movement of these elements for cooperation with the outboard end of the outboard tube 260 in operation. Ring 114 is not, of course, provided with tube positioning elements similar to those shown in Figs. 10 and 11. Modifications It is not essential to provide a chuck according to the invention with catching and severing elements moving through bores therein. Where the chuck is to be used in winding of packages of relatively fine threads, whick break easily, the threads can be caught in slots in the bobbin tubes and can be severed between incoming and outgoing bobbin tubes simply by tensile forces created in the length of thread between them. Even where a specifically designed catching and severing structure is required, it may not be incorporated in the chuck structure, but may be provided in rings mounted on the structure between successive bobbin tubes thereon, for example as described in U.S. Patent Specification No. 4477034. In the latter case also, no bobbin tube positioning devices are required, since the bobbin positioning function is performed by the rings which provide the catching and severing devices. In the embodiment shown in Fig. 4, the arrangement is such that the mechanical biassing systems (not specifically illustrated) urge the wedging cones 76, 100 away from each other, while the pressurisable compartments 78, 104 can be pressurised to urge the wedging cones towards each other. This enables each compartment 88, 90 containing the mechanical biassing means to be of substantial length relative to the associated pressurisable compartments 78, 104. This will usually be the most desirable arrangement, but could be reversed if adequate axial force could be derived from a relatively short mechanical biassing means. In the preferred arrangement, all parts within tubular portion 22 are centered by reference to the internal surface of that portion. This is true of both the pistons 74, 98 and walls 96, 102 associated with the wedging cones 76, 100 respectively. Accordingly, each piston is preferably separable from its corresponding wall, being joined thereto by way of the axial projection, for example projection 84 shown on piston 74 in Fig. 4. This enables separate insertion of the piston and wall elements into the chuck assembly, thus facilitating the assembly of the complete tube gripping structure with the tube engaging elements 34 engaging the cones 76, 100 and located in their respective bores in tubular portion 22. Separate formation of the piston and cone portions may not, however, be necessary if centering of the assembly by the piston alone is adequate, or if the assembly can be centered on both the internal surface of tubular portion 22 and the external surface of the central tubular structure constituted in Fig. 4 by tubes 66 and 94. As already described, each tube engaging element 34 is preferably made of a synthetic plastics material. The preferred material is polyoxymethylen or polyacetal. The particularly important characteristics of this material are its form stability, even when subjected to moisture, sliding capacity and wear resistance. Other materials having adequate properties in this regard could also be used, however. The characterising feature of the invention, requiring a "one piece" or "integral" tubular body for the chuck, implies that this tubular body, when made of metal, is made from a single pre-formed blank. The use of two pre-formed blanks joined together is excluded, even where an intimate join is made between the bodies of metal by joining techniques such as welding. The pre-form to be used depends upon the manufacturing technique employed. For example, a bar-preform could be machined to provide the reduced diameter end portion and bored to provide the passage 40 and the chamber 30. Alternatively, a tubepreform could be swaged or forged on a suitable die to give the two required tubular portions. The invention enables optimum structural design (strength, stiffness etc.) of both parts of the tubular body without necessitating compromises in the operating functions which are associated with the parts in use (bearing design, including lubrication; thread package gripping and centering etc.). As previously referred to, the devices 68 and 70 preferably operate independently of each other. Where total independance is not required, the bulkheads 86 can be eliminated and a "common" biassing means can be provided for both devices. As also referred to above, the preferred arrangement is one in which each individual element of the biassing means is firmly centered relative to axis 20, and this is preferably effected by ensuring centering contact of each element with the internal surface of the tubular portion 22. For this purpose, the outer edge of each individual element 87 may have a sufficient axial extent (dimension) to ensure the required centering contact referred to above for all assembled conditions in use. The system as described immediately above is generally conventional. In a preferred embodiment, however, the biassing means comprises a body of resiliently compressible material extending between axial end members provided in the illustrated embodiment by bulkhead 86 and wall element 92 defining the ends of compartment 88. The body of resilient material can be arranged to fill, or substantially fill, the volume of the compartment, and the material should be chosen to have a high degree of volume compressability and low degree of compression set. The body can be made of a plurality of elements, for example rings, with the axially facing surfaces arranged in face to face contact with each other. Means may be provided to ensure return of the clamping elements 34 radially inwardly as the wedging cones are moved by pressurisation of chambers 78 and l04 (Fig. 4) and ll6 (Fig. 5). For example, a bias spring could be made to act between the legs l26 (Fig. 5) and the internal surface of the part 22. Alternatively, a spring similar to springs l52 could be provided to act on legs l26 to draw the elements radially inwardly. As a further alternative, the legs l26 could themselves be made resiliently deformable to provide a radially inward bias when pressed against part 22. The expression "cantilever-mounted" (where used in this specification) refers to the free extension of the "first tubular portion" (the package-holding portion) away from the bearings supporting the "second tubular portion". The expression does not refer in any way to the structure in which those bearings are mounted. In a continuous (or "wasteless") winder, the support structure may be provided by a rotatable head carrying two such chucks (a "revolver head"), or there may be an independent swing arm for each chuck - or any other suitable support. In a single chuck winder, the support structure may be fixed or movable relative to the machine frame. The expression does not exclude the possibility of temporary support for the "free" end of the chuck during a winding operation.

Claims: A chuck structure for a high speed winding machine, said structure having a first elongated portion (22) formed as a tube, with an external cylindrical surface adapted to receive one or more bobbin tubes (26, 260) with a small radial spacing to permit interference-free donning of tubes and doffing of completed thread packages (28), and a second elongated portion (24), the first and the second portions (22, 24) having a common longitudinal axis (20), means (12) cooperating with the exterior of the second portion (24) for mounting said structure cantilever-fashion in said winder so that the portions (22, 24) are rotatable about their common axis, bobbin tube engaging elements (34) extendable through openings (72) in said first tubular portion (22) to secure and center each bobbin tube (26, 260) for rotation with the first tubular portion about the chuck axis (20) and means (36, 38; 68, 70) within the first tubular portion operable to extend said elements (34) through said openings (72) and to permit retraction thereof, characterised in that the second portion (24) is also tubular, being of reduced external diameter relative to the first portion (22), and the first elongated tubular portion (22) and second portion (24) being joined by an intermediate portion (56) that is formed integrally with both the first and second tubular portions, so that the first, second and intermediate portions form a one-piece chuck. A chuck as claimed in claim 1 characterised in that the first and second portions (22, 24) are made of steel. A chuck as claimed in claim 1 or claim 2 characterised in that the second portion (24) is provided at its end remote from the first portion (22) with a coupling enabling transmission of a pressure medium, preferably air, to the interior of a chamber (78, 104) in the first portion (22) via the hollow interior of the second portion (24). A chuck as claimed in any preceding claim characterised in that the first tubular portion (22) has an internal cylindrical surface defining a chamber (30) receiving said means (36, 38; 68, 70) for causing extension of said elements (34), whereby the first tubular portion (22) provides both a load-bearing portion of the chuck and a casing for operating elements thereof. A chuck as claimed in claim 4 characterised in that the first tubular portion (22) is of constant wall thickness over substantially its whole length such that the chamber (30) is of constant cross section to a position close to or beyond the inboard end of the inboard bobbin tube (26). A chuck as claimed in claim 4 or claim 5 characterised in that the means (36, 38; 68, 70) for causing extension of said elements (34) comprises at least one member (36; 74, 96; 98, 102) slidable on the internal cylindrical surface of the first tubular portion (22). A chuck as claimed in any one of claims 4 to 6 characterised in that the means (36, 38; 68, 70) for causing extension of said bobbin tube engaging elements (34) comprises resilient members (87) adapted to generate a biasing force urging said elements (34) into a tube securing condition, said resilient members (87) being centered relative to the chuck axis (20) by engagement with the internal cylindrical surface of the first tubular portion (22). A chuck as claimed in any preceding claim characterised by a plurality of sets of elements (34), one set being provided for each end of each bobbin tube carried by the chuck in use, and a corresponding plurality of independently operable means (36, 38; 68, 70) for causing extension of the elements (34), one such independently operable means (36, 38; 68 70) being provided for each set of elements (34), said independently operable means (36, 38; 68, 70) being separated by at least one member (86) secured to said first tubular portion (22). A chuck as claimed in claim 8 characterised in that the elements (34) of each set engage on a respective conical surface on a wedging member (76, 100) forming part of said means (68, 70) for causing extension of the elements. A chuck as claimed in claim 9 and claim 6 characterised in that said wedging member (76, 100) is connected to said member (96, 102) slidable on the internal cylindrical surface of the first tubular portion (22). A chuck as claimed in claim 3 characterised in that said means (36, 38; 68, 70) for causing extension of said elements (34) comprises means (74, 98) operable by said pressure medium to urge said means (36, 38; 68, 70) for causing extension of the elements (34) to a bobbin tube releasing condition. A chuck as claimed in claim 11 and claim 4 characterised in that said means (74, 98) operable by said pressure medium is slidable on said internal cylindrical surface defining the chamber (30). A chuck as claimed in claim 3 and claim 4 characterised in that a central tube (66) extends along the chamber (30) to feed pressure medium from said second portion (24) to selected points spaced along the length of the chuck and defined by openings (82, 108) in said tube (66). A chuck as claimed in claim 12 and claim 13 characterised in that said means (74, 98) operable by said pressure medium is also slidable on said tube (66). A chuck as claimed in any preceding claim characterised in that said elements (34), are radially movable between an operating position engaging the interior of a bobbin tube (26, 260) and an inoperative position releasing the tube, each element (34) comprising a head portion having a surface adapted to engage the tube, a hollow body portion and a foot portion having a surface adapted to slide on a member (76, 100) for moving the element (34) between the operative and inoperative positions. A chuck as claimed in claim 15 characterised in that the foot portion of the element (34) has projections for engaging said first tubular portion (22) to prevent the element (34) from passing through the opening (72). A chuck as claimed in claim 16 characterised in that the hollow body portion of the element (34) is open at the foot end thereof and the surface adapted to slide on the wedging member (70) comprises a rim at the foot end of the body portion together with the surfaces on the projections. A chuck as claimed in any preceding claim characterised in that said first tubular portion (22) has at least one additional opening and an element (44) movable through said additional opening to provide an abutment limiting movement of an outboard bobbin tube (260) towards an inboard bobbin tube (26). A chuck as claimed in claim 18 characterised in that at least one pair of additional openings (154, 156) is provided in said first tubular portion (22), and said element (44) movable through said additional openings (154, 156) comprises a tube-positioning element (158) with first and second arms (160, 162), the element (158) being arranged for movement between a first position, in which the first arm (162) passes through one opening (154) of the pair to project beyond the outer circumference of the first tubular portion (22) while the second arm (160) is located within that outer circumference, and a second position in which the second arm (160) passes through the other opening (156) of the pair to project beyond the outer circumference of the first tubular portion (22) while the first arm (160) is located within that outer circumference. A chuck as claimed in claim 19 characterised by means (152) within the chamber urging the tube-positioning element (158) to the first position. A chuck as claimed in any preceding claim characterised in that the first tubular portion (22) has at least one further opening (176) and a thread catching and severing device (178) is provided within the first tubular portion (22) and is radially movable between an operating position in which a head portion (180) of said thread catching and severing device (178) projects beyond the external surface of the first tubular portion (22) and a retracted position in which the head portion (180) lies within the external surface of the first tubular portion (22). A chuck as claimed in claim 21 and claim 18 characterised in that a plurality of additional openings (154, 156) and a plurality of further openings (176) are equiangularly spaced around the axis (20) of the chuck.

Inventors: BUSENHART, PETER, FLUEELI, ADOLF, HOLBEIN, ERWIN, MAIER, HANSUELI, SCHNEEBERGER, RUEDI, WIRZ, ARMIN, Flüeli, Adolf
Applicants: MASCHINENFABRIK RIETER AG
Application year: 1986
Main classification: B65H54
IPC codes: B65H54