AUTOMATIC MACHINE FOR CUTTING SEALS AND MEMBRANES FROM RUBBER OR PLASTICS TUBE

Abstract: The machine comprises: one mandrel (11) which supports a workpiece, a corresponding clamp unit (17) which is integral in rotation with the mandrel of means (19.1, 19.2, 19.3, 12.2) for causing rotation of the mandrel, means (20, 21, 22, 24, 25, 26) for controlling axial translational movement of said clamp unit with respect to the mandrel between a withdrawn and a forward position, a cutting member (34) which can move between an advanced position in which it performs cutting of the workpiece, and a withdrawn resting position in which the free end of the workpiece can be caused to move forward with respect to the cutting member.

Description: "AUTOMATIC MACHINE FOR CUTTING SEALS AND MEMBRANES FROM RUBBER OR PLASTICS TUBE" This invention relates to an automatic machine for cutting seals and membranes from rubber or plastics tube. The principal purpose of the invention is to provide a machine as specified, which makes it possible to obtain seals and membranes of a predetermined thickness with a very much reduced margin of dimensional error. Another purpose is to provide a machine as indicated which makes it possible to produce seals and membranes having a high degree of surface finish. Yet another purpose is to provide a machine as specified which is suitable for quality control systems with automatic management of control to 100%. A further purpose is to provide a machine as stated which is structurally simplified, functionally reliable and of high productivity. With these purposes in view this invention provides an automatic machine for cutting seals and membranes from rubber or plastics tube whose essential feature forms the sub ect-matter of the principal claim. Further advantageous features are specified in the dependent claims. The abovementioned claims are to be regarded as being reproduced in full here. The invention is more particularly described in the following detailed description with reference to the appended drawings, provided only by way of example, in which: Figure 1 is a plan view from above of the automatic machine for cutting seals and membranes from rubber or plastics tube in accordance with one embodiment of the invention, illustrated in the preparatory phase, in which corresponding intact rubber or plastics tubes are inserted and secured on its two workpiece-holding mandrels, from which a plurality of seals or membranes will be obtained by transverse cutting, - Figure 2 is a view similar to that in Figure 1, in which however each mandrel bearing a corresponding rubber or plastics tube is retracted at the end of the preparatory stage into the position in which the working cycle starts, - Figure 3 is a view in frontal elevation in the direction of arrow III in Figure 1, Figure 4 is a view in rear elevation in the direction of arrow IV in Figure 1, - Figures 5.1 and 5.2 are views on an enlarged scale and in cross section along the line V-V in Figure 2, showing the front part (Figure 5.1) and the rear part (Figure 5.2) respectively of a workpiece-holding mandrel unit with a corresponding pneumatic clamp unit with the clamp in the closed position, while a unit controlling translational movement of said pneumatic clamp unit is also illustrated in part (in Figure 5.2), - Figure 6 is a view on a magnified scale and in cross section along the line VI-VI in Figure 3, - Figure 7 is a detailed view, on an enlarged scale, of detail VII in Figure 3 illustrating a cutting unit with a cutting blade in the advanced position at the start of the cutting of a tubular rubber or plastics body, - Figure 8 is a view similar to that in Figure 7, in which however said cutting unit is illustrated with the cutting blade in the advanced position at which cutting is complete, - Figure 9 is a view in partial cross section along the line IX-IX in Figure 10, illustrating a part of the workpiece-holding mandrel in accordance with Figure 5.1, in which however the corresponding pneumatic clamp unit is located in the open clamp position, - Figure 10 is a view in cross section along the line X-X in Figure 9, - Figure 11 is a view in cross section along the line XI-XI in Figure 5.2, Figures 12 and 13 show in elevation two seals obtained by cutting a rubber or plastics tube by means of the machine according to the invention, - Figure 14 is a view in cross section along the line XIV-XIV in Figure 13, Figures 15, 16 and 17 show in elevation respectively three variant embodiments of a jaw for a pneumatic clamp unit for the machine according to the invention, - Figures 18 and 19 are partial detail views in axial cross section illustrating respectively two variant embodiments of the forward end (head) of a workpiece-holding mandrel of the machine according to the invention, - Figure 20 shows in elevation a seal or membrane obtained by cutting a rubber or plastics tube using the machine according to the variant embodiment of the invention illustrated in Figure 18 or Figure 19, - Figure 21 is a view in cross section similar to that in Figure 5.1, but illustrating a variant embodiment of said workpiece-holding mandrel unit. With reference to the drawings, 1 (Figures 1, 2) indicates as a whole the automatic machine for the cutting of seals and membranes from rubber or plastics tube in accordance with a simplified embodiment of this invention. Said machine 1 comprises a bench 2 (Figure 3) having a horizontal supporting table 3 on which are provided: a) at the front, two side-by-side units 10 each provided with a mandrel 11 holding the workpiece (tube) which is to be cut, in which the corresponding mandrels are arranged with their axes (Y-Y) horizontal and parallel to each other, b) at the rear, a unit 20 controlling the simultaneous translational movement of the corresponding pneumatic clamp units which are integral with said mandrels 11, c) two cutting units 30, supported by said bench 2 in a position in front of said workpiece-holding mandrel units 10, one for each mandrel 11. Each workpiece-holding mandrel 10 comprises (Figures 5.1, 5.2) a corresponding box-like supporting body 10.1, fixed to table 3 in which a substantially cylindrical through cavity 10.2 is provided in said body (Figure 5.1), which is open at the front and rear. In said cavity 10.2 a tubular shaft 12.1 having a horizontal axis Y-Y is rotatably mounted on a pair of front radial ball bearings 11.1 and a rear radial ball bearing 11.2. These bearings are fixed to supporting body 10.1 by suitable front and rear bush means 11.3. A driven pulley 12.2 is keyed to said shaft 12.1 by means of key 12.3. Integrally with said tubular shaft 12.1 there rotate: - a coaxial front outer centring ring 13.1 and support for a workpiece (tube) W which is to be cut, which ring is fixed to shaft 12.1 by means of a coaxial front end bush 13.2, - a rear bush 14.1, fixed to shaft 12.1 by a rear end sleeve 14.2, - an axial rod 15 centring the workpiece (tube) W which is to be cut. Said rod 15 passes axially through tubular shaft 12.1 and has a frustoconical rear end 15.1. This end 15.1 is fixed by means of an interference fit into a corresponding axial hole passing through said rear bush 14.1 and is extended beyond said bush by means of an integral coaxial extension 15.2, which is threaded on the outside. Said extension 15.2, and therefore rod 15, is fixed to rear bush 14.1 by means of a corresponding sleeve 15.3. Said rod 15 has an axial hole 15.4, which is blind at the front and open at the rear through said extension 15.2. In addition said rod 15 is extended at its free front or head end beyond centring ring 13.1 and has an arrangement of through radial holes 15.5, which open to the exterior and which are in pneumatic communication with said axial hole 15.4. A rigid straight tubular pneumatic conduit 16 is inserted axially in said blind hole 15.4 without obstructing said radial holes 15.5 and extends to the rear through said extension 15.2 and said sleeve 15.3. Convenient sealing means ensure a pneumatic seal between the parts. In addition to this, within said tubular shaft 12.1 there is mounted a pneumatic clamp unit 17 for securing the workpiece (tube) W which is to be cut, which rotates integrally with the shaft and which moves in translation axially with respect to it. Said pneumatic clamp unit 17 comprises, in a coaxial arrangement with respect to axis Y-Y: a first bush 17.1 which can move axially maintaining a pneumatic seal (seal means 17.2) against the inside surface of said tubular shaft 12.1, - a second bush 17.3, which is proximal to centring ring 13.1 with respect to first bush 17.1, which is also fixed so that it can move axially maintaining a pneumatic seal (seal means 17.4) against the inside surface of said tubular shaft 12.1, - a sleeve 17.5 which can move axially maintaining a pneumatic seal (seal means 17.6) against the inside surface of said tubular shaft 12.1 and is fixed to said second moving bush 17.3, being correspondingly threaded for this purpose, - an axial sleeve 17.7 which is fitted so as to move on said axial rod 15 and abuts against said sleeve 17.5 with respect to which it is fixed by means of an annular support 17.8 which supports four tilting jaws J of clamp 17, which are substantially offset by 90° with respect to each other (Figure 10), - an axial bush 17.9, fitted on sleeve 17.7 and fixed with respect to annular support 17.8 by internal centring with respect to clamp unit 17 for the workpiece (tube) W which is to be cut, an annular spacer 17.10 located between said second bush 17.3 and said sleeve 17.5. Said spacer 17.10 forms a pneumatic seal with respect to bush 17.3 through ring seal means and with respect to sleeve 17.5 through an annular elastic membrane 17.11. The centre surface of said membrane 17.11 is placed against an annular chamber 17.12 (Figure 9) formed in sleeve 17.5. Within chamber 17.12 a coaxial ring 17.13 is located so as to move in an axial direction. Said ring 17.3 abuts against one end of four rods 17.14, movably housed in corresponding axial through holes provided through said sleeve 17.5 and said support 17.8. Said rods 17.14 are substantially offset by 90° with respect to each other (Figure 10) . It will be noted that a pneumatic passage 17.17 which opens against the surface of said annular membrane 17.11 opposite annular chamber 17.12 is formed through said first bush 17.1, said second bush 17.3 and said annular spacer 17.10. Suitable sealing means ensure a pneumatic seal between the parts. Each tilting jaw J is substantially L-shaped (lateral view, Figures 5.1, 9). One limb J.l (Figures 9, 10) is pivoted at its free end on a corresponding pin 17.18 to tilt between a working position (Figure 5.1) in which its other limb J.2 bears against the extreme rear end of workpiece W which is to be cut, securing it, and a resting position (Figure 9) in which said other limb J.2 does not bear against workpiece W which is to be cut, releasing it. The free end of each rod 17.14 is in contact with the rear surface of limb J.l of corresponding tilting jaw J. Permanent magnet means 17.19 (Figure 9), which are fixed with respect to support 17.8, draw back said tilting jaws J of clamp 17 and retain them in the resting position by magnetic action. Figures 15 to 17 illustrate variant embodiments of an oscillating jaw for clamp unit 17. A pair of straight rods 18.1 which extend parallel to the axis Y-Y of shaft 12.1 are fixed at one end with respect to first bush 17.1 of pneumatic clamp unit 17. Said rods 18.1 pass freely through corresponding holes provided in rear bush 14.1 of tubular shaft 12.1 and are fixed at the other end with respect to a rotating disc body 18.2 (Figure 5.2) which is supported coaxially and integrally in rotation with respect to shaft 12.1. Said disc body 18.2 has an integral axial shaft 18.3 mounted so as to rotate freely in a pair of radial ball bearings 18.4 supported coaxially on axis Y-Y in a corresponding seat in a pedestal 21.1, with respect to which they are fixed by bush means. Pedestal 21.1 is fixed on a slide 21 of said unit 20 controlling the translational movement of pneumatic clamp units 17 of mandrels 11. Disc body 18.2 and corresponding shaft 18.3 are axially drilled so as to form an axial chamber through which there extends said rigid pneumatic conduit 16 providing a pneumatic seal, leaving a free pneumatic cavity 18.5, which is in pneumatic communication with a radial hole 18.6 formed in said disc body 18.2, in a part of said chamber. A rigid straight tubular pneumatic conduit 19 is fixed at one end with respect to said disc body 18.2 in leaktight pneumatic communication with said hole 18.6. Said conduit 19 extends freely through a corresponding hole through said rear bush 14.1 of shaft 12.1, parallel to its axis Y-Y, and is fixed at the other end with respect to said first bush 17.1 of pneumatic clamp unit 17 so as to provide leaktight pneumatic communication (by means of suitable seals) between said pneumatic cavity 18.5 and said pneumatic passage 17.17 of pneumatic clamp unit 17. At the free end of axial shaft 18.3 there are fixed two pneumatic valves, VI, V2, which are in leaktight pneumatic communication (by means of suitable seals), valve VI with said cavity 18.5 and then through hole 18.6 and pneumatic conduit 19 with pneumatic passage 17.17 in pneumatic clamp unit 17, and respectively valve V2 with the pneumatic cavity formed by hole 15.4 in axial rod 15 through pneumatic conduit 16. Figure 11 illustrates the arrangement of rods 18.1 mutually offset by 120° and tubular conduit 19 with respect to disc body 18.2, while their lengths, which are identical, make it possible for pneumatic clamp unit 17 to perform an axial movement within tubular shaft 12.1 between an extreme rear position close to rear bush 14.1 and an extreme forward position close to centring ring 13.1. This axial travel of pneumatic clamp unit 17 is brought about through said rods 18.1 and said conduit 19 by corresponding travel of slide 21 of unit 20 which is integral in translational movement with respect to said disc body 18.2. Said slide 21 is mounted so as to move in corresponding straight guides 22 (Figures 1, 2) which are fixed with respect to supporting table 3 and parallel to the axis Y-Y of shaft 12.1 of each mandrel 11. In the posterior end portion of said table 3 there is fixed a portal structure 23 (Figure 4) which supports a reversible electric motor/reduction gear unit 24 which through transmission members causes the rotation of a manoeuvring screw 25 (Figure 1) which is supported by said table 3 with an axis parallel to axis Y-Y of shafts 12.1 of mandrels 11. Said manoeuvring screw 25 is engaged in a corresponding nut 26, which is fixed with respect to said slide 21, by means of a helicoidal coupling. Another electric motor/reduction gear 19.1, which causes the rotation of a drive pulley 19.2 and two driven pulleys 12.2, respectively integral with shafts 12.1 of mandrels 11, by belt transmission means 19.3, is supported in a mounting 19 (Figures 1-4) fixed to table 3 and lying above workpiece-holding mandrel unit 10. Bench 2, in the position in front of each workpiece- holding mandrel unit 10, provides cantilever support for a corresponding table 4 (Figures 1-3, 7, 8) inclined by approximately 30° with respect to the horizontal plane which runs downwards towards the median vertical longitudinal plane of table 3. Each table 4 supports a corresponding cutting unit 30, corresponding to one workpiece-holding mandrel unit 10. On said table 4 is mounted a base plate 4.1, which supports a carriage 31 (Figure 6) which can move with respect to a straight central guide 31.1. Said guide 31.1 is fixed to plate 4.1 (by means of a suitable fixed support 4.2) and extends parallel to the plate, while it is orientated along a plane substantially normal to the axis Y-Y of shaft 12.1 of corresponding workpiece-holding mandrel 11. A reversible electric motor/reduction gear 32 which causes the rotation of a manoeuvring screw 32.1, supported by said support 4.2, whose axis is orientated parallel to said straight guide 31.1, is fixed to the end of each table 4 distally from corresponding workpiece-holding mandrel unit 10. Said manoeuvring screw 32.1 is engaged in a corresponding nut 32.2 (Figure 6) fixed to said carriage 31 by means of a helicoidal coupling. A fixed circular blade 34, which lies substantially in a plane normal to said axis Y-Y, is fixed to carriage 31 by means of an adjustable support 33. Said carriage 31 bears three integral fixed contact members 35.1 each designed to act together with a corresponding microswitch 35.2 fixed with respect to said support 4.2. The two end microswitches 35.2 identify the extreme travel positions for said carriage 31 for safety purposes while intermediate microswitch 35.2 identifies the "0" for resetting the machine. Preparation of machine 1 All the operations of machine 1 are controlled on the basis of a program recorded in a central electronic processing and calculation unit (computer) which can be programmed through a suitable control panel 5 (Figures 3, 4). In Figures 1 and 2 this panel is omitted for reasons of clarity of illustration. In addition, each of pneumatic valves VI, V2 is leaktightly connected by means of corresponding pneumatic circuits (shown diagrammatically as PI and P2, Figures 3, 4) alternately with a source of compressed air or a vacuum pump (which is in itself known and not illustrated) . The operation of these pneumatic devices is also controlled by a program recorded in said central electronic processing and calculation unit. When a working cycle is complete, slide 21 and therefore each pneumatic clamp unit 17 is at the end of its working travel - the extreme forward position of the clamp unit with respect to the corresponding shaft (or in the condition illustrated in Figure 1, in which however new intact tubular members Wl are also illustrated already fixed to mandrels 11 of the machine) . In the pneumatic circuit formed by a valve VI, pneumatic cavity 18.5, hole 18.6, conduit 19 and pneumatic passage 17.17, negative pressure is created so that elastic membrane 17.11 is deformed from the flat resting condition as illustrated in Figure 9. In this condition rods 17.14 are withdrawn into their corresponding holes and tilting jaws J of pneumatic clamp means 17 are tilted and secured in the resting position (by means of magnets 17.19) as illustrated in said Figure 9. That is, pneumatic clamp 17 is open. Any terminal residue of tube W (Figure 5.1) is released by clamp 17 and discharged from the machine. In cutting units 30, each slide 31 with a fixed cutting blade 34 is withdrawn into the corresponding resting position distal from corresponding mandrel 11. A corresponding tubular body Wl of rubber or plastics, which may be joined end to end, is inserted end-on and coaxially onto each mandrel 11 (Figure 1), in such a way as to cover the terminal end, on inner central axial bush 17.9 of the mandrel and the head of rod 15. Outer centring ring 13.1 cooperates to ensure correct positioning of said tubular body Wl . The head of axial rod 15 slidably penetrates the cavity in said end of tubular body Wl and its radial holes 15.5 are thus positioned opposite its internal surface. The pneumatic circuit formed by valve V2, pneumatic conduit 16, pneumatic chamber (hole) 15.4 and said radial holes 15.5 is placed under negative pressure, thus exerting a suction action on said tubular body Wl, securing it in position. At the same time, in the other pneumatic circuit formed by valve VI, pneumatic cavity 18.5, hole 18.6, conduit 19 and pneumatic passage 17.17, air is delivered under pressure so as to bring about corresponding elastic deformation of membrane 17.11, which expands in opposite pneumatic chamber 17.12 (occupying it as illustrated in Figure 5.1). This causes movable ring 17.13 to move forward axially in said chamber and corresponding movement of rods 17.14 which, by extending with respect to their seats, cause corresponding tilting jaws J to tilt into the closed working position. Pneumatic clamp 17 thus securely grips the terminal end of tubular body Wl, which is held secured in this way until the last membrane or seal has been cut from the piece. Motor/reduction gear 24 is caused to rotate and so therefore is manoeuvring screw 25 with respect to nut 26 to move slide 21 back along guides 22 to the start of the working travel (Figure 2) . The two pneumatic clamp units 17 move backwards with slide 21 in their corresponding tubular shafts 12.1, again to the start of the working travel (extreme withdrawn position of the clamp unit with respect to the corresponding shaft) . Each tubular body Wl then runs along corresponding axial rod 15 and is positioned within shaft 12.1 of corresponding mandrel 11, leaving only the free front end projecting, which is protected a little beyond the corresponding cutting blade 34, as illustrated in Figure 2. Shaft 12.1 of each mandrel 11 is then caused to rotate by means of motor/reduction gear 19.1 and so integrally with it is each tubular body Wl, and these are kept continually in rotation until the last membrane or seal has been cut off from the workpiece. Each motor/reduction gear 32 is set in rotation so as to determine the working travel of carriage 31 of each cutting unit 30. Carriage 31 therefore bears corresponding cutting blade 34 to perform the cutting of workpiece Wl in a plane normal to the axis Y-Y of the corresponding mandrel, separating the first off-cut from the free end of the workpiece. Corresponding carriage 31 and corresponding blade 34 are returned to the withdrawn resting position by reverse rotation of each motor/reduction gear 32 (Figures 3 and 7) . WORKING CYCLE OF MACHINE 1 During the working cycle of machine 1, slide 21 is caused to advance stepwise (from said starting position for its working travel) axially along corresponding guides 22 by corresponding control of the rotation of motor/reduction gear 24. In machine 1 the thickness of each membrane or seal which is to be cut from tubular member Wl is directly dependent on the size of each axial step in the advance of slide 21, to which there corresponds an identical axial advance of the free end of each body Wl with respect to adjacent cutting blade 34. Therefore the magnitude of this advance or step is recorded in the central processing and calculation unit as a fraction of the angular rotation of manoeuvring screw 25 with respect to nut 26, controlled by motor/reduction gear 24 for each working cycle. At the beginning of the cycle the forward movement of slide 21 along guides 22, and therefore the forward movement of tubular bodies Wl is determined by motor/reduction gear 24 in accordance with a first axial step corresponding to the predetermined thickness of the membrane or seal which is to be cut. Once this axial step has been completed each motor/reduction gear 32 is caused to rotate so as to determine the working travel of carriage 31 for each cutting unit 30 and therefore that of corresponding fixed blade 34 which cuts a circular crown slice from the free end of adjacent tubular body Wl along a plane normal to the axis Y-Y of shaft 12.1, forming a corresponding flat seal or membrane G (Figure 12) of a desired thickness. When cutting is complete the rotation of each motor/reduction gear 32 is stopped and carriages 31 stop in the forward working position (Figure 8). It will be noted that, when cutting is complete, pressurized air is delivered through the pneumatic circuit formed by valve V2, pneumatic conduit 16, pneumatic chamber (hole) 15.4 and said radial holes 15.5, thus exerting a blowing action on each seal G cut from said tubular body Wl in order to assist its expulsion from machine 1. In addition to this, reliable separation between the inner surface of workpiece Wl and the head of rod 15 is ensured in this way, thus assisting subsequent axial advance of the workpiece with respect to mandrel 11. Carriages 31 and corresponding fixed blade 34 are returned to their withdrawn resting position by reversing the rotation of each motor/reduction gear 32 (Figure 7 ) . There then begins a new identical working cycle and so on until each pneumatic clamp unit 17 reaches its predetermined end of forward travel position with respect to corresponding shaft 12.1 (extreme forward position of the clamp unit close to front centring ring 13.1). The automatic operation of machine 1 is then stopped to permit the residual waste of tubular bodies Wl to be expelled. It will be noted that in each cutting unit 30, base plate 4.1 is attached to table 4 in a manner such that it can be orientated about an axis Z (Figures 7, 8) lying in a plane substantially at right angles to the axis Y-Y of corresponding mandrel 11. This arrangement makes it possible to orientate each fixed cutting blade 34 about said axis Z so as also to achieve cutting of tubular body Wl which is not parallel to said plane, so as to obtain substantially frustoconical seals or membranes Gl, as illustrated in Figures 13 and 14. A number of variant embodiments will be described below with reference to Figures 18 to 21. In these figures parts similar to those illustrated in Figures 1 to 17 will be indicated using the same reference numbers . In Figure 18, an axial rod 15' of a mandrel 11' supports a fitted coaxial head 41, which is substantially disc-shaped and drilled axially. Said disc head 41 has an integral hollow axial rod 42. An axial screw 42.1 provides a pneumatically leaktight attachment (through suitable sealing means) between this head 41 and rod 15', the axial cavity 15.4 of which is open at the front and correspondingly threaded. The shank of this screw has a blind axial hole 42.1 which provides leaktight communication with axial hole 15.4 of rod 15' and through a plurality of radial holes with corresponding radial holes 43 in said disc-shaped head 41. Said radial holes 43 are open to the exterior. In addition to this, disc-shaped head 41 has two axial peripheral holes 44 communicating with the outside environment and with said radial holes 43. Through radial holes 15.4' are provided in rod 15' and communicate with its axial hole 15.4. A tubular body W2 of rubber or plastics, having relatively flexible walls, which is to be cut is fitted coaxially onto mandrel 15' . Head 41 is located within this tubular body W2, substantially corresponding to cutting blade 34 and in such a way that its radial holes 43 lie opposite the inside face of the body. Nitrogen gas at low temperature is delivered through the pneumatic circuit formed by valve V2, conduit 16, axial hole 15.4 and radial holes 15.4' of rod 15', axial hole 42.1 and radial 43 and axial 44 holes of attached head 41, and this cools the head region of rod 15' and spreads within tubular body W2, freezing it. This renders tubular body W2 substantially rigid in the cutting zone, despite its flexible walls, and dispenses with the presence of centring means outside the body (such as ring 13.1 described above with reference to mandrel 11) . Means for blowing hot air and/or heating the cutting blade (which are in themselves known and not illustrated) are located in the cutting zone to four of the seals or membranes as soon as they have been cut from said tubular body. Figure 19 illustrates an arrangement which is wholly similar to that illustrated in Figure 18. In this case however a fitted disc-shaped head 45 with integral rod 46 does not instead have axial peripheral holes although it has radial holes 47 leaktightly communicating with the axial hole 15.4 of rod 15' and the outside environment. In a manner similar to that described with reference to Figures 5.1 and 5.2, negative pressure or a pressurized air feed is applied alternately through said radial holes 47 of fitted head 45 to bring about stable positioning of workpiece W2 or respectively expulsion of the cut seal or membrane when the cutting operation is complete. Figure 20 indicates a seal or membrane G3 which is obtained by cutting tubular member W2 with the machine according to Figure 18 or Figure 19. In Figure 21 an axial rod 15" is supported in a shaft 12.1 of a mandrel 11" fixed at its posterior end with respect to a rear bush 14.1. Said axial rod 15" is of short length and provides a cantilever support for a long straight metal tubular member 51, which is coaxial with said rod and welded to it at one end. Said tubular member 51 extends through the remaining part of shaft 12.1, beyond which it projects with its free end, which is supported by a front centring ring 52 fixed coaxially to said shaft 12.1. A pneumatic clamp unit 17 mounted to move axially within said shaft 12.1 and along said tubular member 51 comprises four tilting jaws J pivoted on an annular support 17.8 in an arrangement in which they are offset by 90°. Corresponding to each tilting jaw J said tubular member 51 has a through notch 53 extending for a substantial part of its length from its front end. This notch 53 permits free passage of the free end of a corresponding tilting jaw J of clamp unit 17. Through this arrangement the terminal end of a tubular body W3 of rubber or plastics having a wall of relatively large thickness and an outside diameter which is little less than the internal diameter of said tubular member 51 is inserted axially on the free front end of the tubular member, is secured by the tilting jaws J of clamp unit 17 and is then drawn by the unit, integral with slide 21, until it comes into contact with axial rod 15" . Then, following forward movement of slide 21, said tubular body W3 is drawn out axially stepwise with respect to the front end of tubular member 51, which is stationary with respect to pneumatic clamp unit 17, the free end being positioned with respect to cutting blade 34 at each step so that a corresponding seal or membrane can be cut off by cutting unit 30. Of course in practice numerous variants may be applied to what has been described and illustrated purely by way of a non-restrictive example without thereby going beyond the scope of the invention and therefore the protection of this industrial monopoly. Thus, for example, to simplify the machine, the hollow shaft in each mandrel can be integrated with a mandrel servomotor unit (motor spindle unit) . The motor may be of the "brushless" synchronous direct current type.

Claims: CLAIMS 1. Automatic machine for cutting seals and membranes from rubber or plastics tube, characterized in that it comprises : - at least one mandrel (11, 11', 11") which supports a workpiece which is to be cut (tubular body Wl, W2, W3) which is fixed coaxially (with respect to the axis Y-Y of the mandrel), - a corresponding clamp unit (17) which is integral in rotation with respect to said mandrel to secure one end of the workpiece until the cutting of seals or membranes from its other end, which projects freely as a cantilever with respect to said mandrel, is complete, - means (19.1, 19.2, 19.3, 12.2) for causing said at least one mandrel to rotate about its axis, - means (20, 21, 22, 24, 25, 26) for controlling the axial translational movement of said clamp unit with respect to said mandrel between an extreme withdrawn position and an extreme advanced position and vice versa, - cutting means (30, 31, 31.1, 32, 32.1, 32.2, 33) provided with a cutting member (34) positioned corresponding to said free end of the workpiece which can move between an advanced working position in which it performs the cutting of said workpiece in a plane substantially normal or inclined with respect to said axis, producing a corresponding seal or membrane (G, Gl, G3) from it, and a withdrawn resting position in which said free end of the workpiece can be made to advance with respect to the cutting member and vice versa, in that at least during the cutting operation said means imparting rotation keep said mandrel, said clamp unit and said workpiece which is to be cut in rotation, in that after each cutting operation, when said cutting member is in its said withdrawn resting position, said means for controlling translational movement cause said clamp unit to move forward with respect to said mandrel by an axial step so as to correspondingly extend said free end of the workpiece with respect to said mandrel so that the thickness of the membrane or seal subsequently cut from said piece corresponds to the magnitude of said axial step which defines corresponding axial forward movement of said free end of the workpiece with respect to the cutting member, and in that the axial forward movement of said clamp unit by one step with respect to said mandrel after each cutting operation is repeated sequentially from said extreme withdrawn position of the clamp unit in which it supports the intact workpiece to said extreme advanced position of said clamp unit in which it supports the terminal residue (W) of the workpiece after a plurality of seals or membranes have been cut from the workpiece. 2. Machine according to Claim 1, characterized in that said mandrel (11, 11' ) comprises: - a tubular shaft (12.1) which is mounted so as to rotate about its own axis (Y-Y) on bearings (11.1, 11.2), and an axial rod (15, 15') which passes axially through said shaft, with respect to which said rod is fixed at its posterior end (15.1), and in that said clamp unit (17) comprises: - an annular body (17.1, 17.3, 17.5, 17.8) which is integral in rotation with and can slide axially within said tubular shaft (12.1) and bears a plurality of tilting jaws (J) , said annular body being fitted so as to move axially (e.g. through a sleeve 17.7) with respect to said axial rod and supporting an axial bush (17.9) for internal centring of the terminal end of said workpiece (Wl, W2) with respect to said clamp unit, and - a plurality of straight rods (18.1) parallel to the axis of said shaft and fixed to said annular body at one end and at the other end to a disc-shaped body (18.2) which is supported so as to rotate (by means of a rod 18.3) coaxially and integrally in rotation with respect to said shaft by means of a slide (21) of said means controlling translational movement, which is slidably mounted on corresponding straight guides (22) extending parallel to said axis in such a way that for preparation of the machine the terminal end of an intact workpiece (Wl, W2) is inserted in said mandrel and secured by means of said clamp unit when said clamp unit is in its extreme forward position with respect to said shaft, subsequently through said slide said clamp unit is translated to an extreme withdrawn position with respect to said shaft, integral with said workpiece, which is also axially retracted with respect to said shaft and centred on the corresponding axial rod, which is introduced by means of its free end or head to the interior thereof over part of the length of the workpiece, which has its other end free and projecting from said mandrel, this being the starting working position of the machine, from which in order to cut seals or membranes from the workpiece said clamp unit is caused to advance together with the workpiece after each cutting operation through an axial step by means of corresponding forward motion of said slide along its guides. 3. Machine according to Claim 1, characterized in that said mandrel (11") comprises: - a tubular shaft (12.1) mounted to rotate about its own axis (Y-Y) on bearings (11.1, 11.2), - an axial rod (15") which is fixed with respect to said shaft at its posterior end, which in part it passes through, while at the other end it supports a straight fixed coaxial tubular member (51) which extends along the remaining part of said shaft, beyond which it projects with a free end, and in that said clamp unit (17) comprises: - an annular body (17.1, 17.3, 17.5, 17.8) which is integral in rotation with and moves axially within said tubular shaft and externally with respect to said tubular member and bearing a plurality of tilting jaws (J) which with their free ends penetrate said tubular member through corresponding axial through notches (53) which extend at least part way along the length of the tubular member itself, and - a plurality of straight rods (18.1) which are parallel to the axis of said shaft and fixed at one end to said annular body and at the other end to a discshaped body (18.2) which is supported (through a rod 18.3) so as to rotate coaxially and integral in rotation with respect to said shaft by means of a slide (21) of said means controlling translational movement, which is slidably mounted on corresponding straight guides (22) extending parallel to said axis in such a way that for preparation of the machine the terminal end of an intact workpiece (W3) is inserted axially into the free end of said tubular member and is secured by means of said clamp unit, the jaws of which engage the workpiece through said notches when said clamp unit is in its extreme forward position with respect to said shaft, subsequently through said slide said clamp unit is translated to an extreme withdrawn position with respect to said shaft, integral with said workpiece, which is also axially retracted with respect to said shaft and within said tubular member over a substantial part of the length of the workpiece, which has its other end free and projecting with respect to the tubular member and with respect to the mandrel, this being the starting working position for the machine, from which said clamp unit is caused to advance together with the workpiece for cutting seals and membranes from the workpiece by an axial step after each cutting operation by means of corresponding forward movement of said slide along its guides. 4. Machine according to Claim 2 or 3, characterized in that said annular body (17.1, 17.3, 17.5, 17.8) is mounted so as to move axially while maintaining a pneumatic seal (in 17.2, 17.4, 17.6) within said tubular shaft (12.1) and within the body of which there are provided: a pneumatic chamber (17.12) in which there is movably located a thrust member (17.13) opposite an end of a plurality of rods (17.14), one for each tilting jaw (J) , mounted so as to slide in corresponding seats which open corresponding to said tilting jaws (J), and an elastic membrane (17.11) located with a pneumatic seal between said pneumatic chamber and a pneumatic passage (17.17) provided through said annular body, and in that a pneumatic circuit (valve VI, cavity 18.5, hole 18.6, conduit 19) is provided and leaktightly connected to said pneumatic passage and through which alternately pressurized air is fed or negative pressure is created, in such a way that said membrane is correspondingly either deformed elastically and caused to expand in said pneumatic chamber so as to bring about forward movement of said thrusting member in said chamber and therefore corresponding movement of said rods which project with respect to their seats causing the corresponding tilting jaws to tilt into the closed working position so that said clamp unit firmly secures the terminal end of the workpiece (Wl, W2, W3), or said elastic membrane retracts to the flat resting state and in this condition said rods withdraw into their corresponding seats and said tilting jaws are tilted and secured in the resting position (e.g. through the attractive effects of permanent magnets 17.19) in such a way that said clamp unit is open and any terminal residue of the workpiece (W) is released and discharged from the machine. 5. Machine according to Claim 2, characterized in that said axial rod (15, 15' ) has a pneumatic passage (axial hole 15.4) in fluid communication with the outside environment through its free forward end or head (45) through a plurality of holes (15.5, 47) and in that through a pneumatic circuit (valve V2, conduit 16) leaktightly connected to said pneumatic passage and said holes in said rod negative pressure is created or a pressurized air feed is provided alternately in such a way that during the operation of the cutting of each seal or membrane from said workpiece (Wl, W2 ) there is created through negative pressure through said holes a momentary effect of adhesion between the inner wall of the workpiece and the free end or head of the axial rod which secures the workpiece in a stable position during cutting, or causes expulsion of the cut seal or membrane at the end of each cutting operation by means of a jet of compressed air through said holes and separation between the inner surface of the workpiece and said axial rod facilitating subsequent axial advance of the workpiece by one step with respect to said rod and therefore the mandrel. 6. Machine according to Claim 2, characterized in that said axial rod (15' ) has a pneumatic passage (axial holes 15.4, 42.1) in fluid communication with the outside environment through its free front end or head (41) through a plurality of holes (43, 44) and in that said pneumatic passage and said holes are leaktightly connected to a source of a low temperature fluid (e.g. nitrogen) through a fluid circuit (valve V2, conduit 16) in such a way that during the operation of cutting each seal or membrane from said workpiece (W2), said fluid is delivered through said holes, emerges in contact with the inner wall of the workpiece and by means of a freezing effect hardens the free end of the workpiece which can be then correctly cut without the need for corresponding means to retain it in position. 7. Machine according to Claim 1, characterized in that said means (19.1, 19.2, 19.3, 12.2) for causing said at least one mandrel (11, 11', 11") to rotate about its axis (Y-Y) comprise an electric motor/reduction gear (19.1) . 8. Machine according to Claim 1, characterized in that said at least one mandrel is incorporated into a mandrel servomotor unit. 9. Machine according to Claim 1, characterized in that said means (20, 21, 22, 24, 25, 26) for controlling axial translational movement of said clamp unit (17) with respect to said mandrel (11) comprise a reversible electric motor/reduction gear (24) which brings about the rotation of a manoeuvring screw (25) which has its axis parallel to the axis (Y-Y) of said at least one mandrel and which is engaged by means of a helicoidal coupling with a corresponding nut (26) which is fixed with respect to said slide (21), and in that the magnitude of each axial step in the forward movement of said clamp unit with respect to said mandrel corresponds to a fraction of the angular rotation of said manoeuvring screw with respect to said nut. 10. Machine according to Claim 1, characterized in that said cutting means (30, 31, 31.1, 32, 32.1, 32.2, 33) comprise a carriage (31) which supports said cutting member (34) and is mounted so that it can move with respect to at least one straight guide (31.1) which is stationary with respect to said at least one mandrel (11) and orientated in a plane substantially at right angles to the axis (Y-Y) of the mandrel, a reversible electric motor/reduction gear (32) which controls the rotation of a manoeuvring screw (32.1) which is stationary with respect to said mandrel and whose axis is orientated parallel to said at least one guide, said manoeuvring screw being engaged in a corresponding nut (32.2) which is fixed with respect to said carriage, through a helicoidal coupling. 11. Machine according to Claim 10, characterized in that said cutting member (34) can be orientated about an axis (Z) lying in a plane substantially at right angles to the axis (Y-Y) of said at least one mandrel (11), so as to effect cutting of the workpiece (Wl, W2) parallel or inclined with respect to said plane, obtaining flat (G) or frustoconical (Gl) seals or membranes respectively.

Inventors: RAIA GIUSEPPE, RAIA, GIUSEPPE
Applicants: RAIA GIUSEPPE, RAIA, GIUSEPPE
Application year: 1999
Main classification: B26D3
IPC codes: B23B3, B26D3, B26D7