BENDING MACHINES

Abstract: A bending machine comprising a plurality of bending units (10) arranged to make bends in a common plane, the bending units being mounted so that the separation thereof is adjustable, and apparatus (20) for holding and turning a workpiece (13) about a predetermined axis (18) mounted so that said predetermined axis is aligned or alignable with said common plane; said apparatus comprising a plurality of jaw members (24,25), movable in unison about the predetermined axis; wherein each jaw member is axially open ended, has a central socket (28) and a mouth (27) extending from said socket to interrupt the periphery of the jaw member, and wherein said jaw members are interconnected and mounted so that- (a) they are rotatable in unison about the predetermined axis (18) when at least one thereof is driven by driving means (45), (b) one (25) thereof is arcuately movable relative to the other or others between an open position, in which the mouths are aligned to admit a workpiece into the sockets, and a clamping position in which said mouths are not aligned to trap the workpiece in the sockets, and (c) in said clamping position the socket of said one thereof is eccentric to the other or others of the sockets to exert a clamping force on the trapped workpiece.

Description: This invention concerns apparatus for holding and turning elongate workpieces, and bending machines incorporating such apparatus. In German Patent Specification No. DE-A-330106l there is disclosed apparatus for holding turning an elongate workpiece of a kind comprising a jaw member which has an axially open ended central socket and a mouth extending radially from the socket to interrupt the periphery of the jaw member, wherein the jaw member is peripherally toothed and is engaged by drive means comprising primary and secondary driving gears which mesh with the peripheral teeth of the jaw member at engagement locations which are spaced peripherally of the jaw member by an arc greater than the arcuate extent of the mouth. In this apparatus the single jaw member is provided with hydraulic cylinders to thrust clamping devices into the central socket for holding a workpiece coaxial with the jaw member. The applicants have produced a different form of a bending machine, which comprises two base units, each of which carries a bending unit, and, between the base units, an apparatus for holding and turning a tubular workpiece about a predetermined axis passing through the bending units. Said apparatus comprises a clamping jaw member disposed between two abutment jaws members, which jaw members are coaxial with said predetermined axis. The periphery of each jaw member is near circular, is interrupted to provide a mouth and is provided with outwardly projecting gear teeth to serve as an interrupted ring gear. Within each jaw member the mouth leads to a part-circular socket, coaxial with said axis to receive a tubular workpiece of predetermined diameter. In the clamping jaw member there is a protruding wedge which extends inwards into a part of the socket adjacent to the mouth. The jaw members are mounted in a body and are engaged by respective toothed hydraulically driven racks actuable to move the jaw members through a restricted arc of a circle about said axis. The rack engaging the clamping jaw member can be moved, firstly, independently of the other racks to move the mouth of the clamping jaw member between an open position (in which the mouths are aligned) and a clamping position displaced from the open position so as thus to ram the wedge against the workpiece; and, secondly, in unison with the abutment jaw members. This apparatus is intended to hold and turn the workpiece about said axis to permit the planes between the bends made by the bending units to be varied angularly, but several problems have arisen, from limitations inherent in this apparatus, including damage to the workpieces, imprecise angular adjustment or location of the workpieces and difficulties in loading the workpiece into the sockets in respect of some forms of tubing. Further problems have arisen because the apparatus cannot accommodate certain requirements for bending workpieces rapidly, for turning the workpieces through some ranges of angles and for accurate initial orientation of the workpieces. The apparatus has, however, many advantages which make it particularly effective for use in massproducing relatively complex shapes from constantsingle-diameter workpieces provided that the angles between the planes of adjacent bends lie within certain limited ranges and need to be only approximately accurate to within a few degrees, e.g. for producing wheelbarrow chassis. An object of the present invention is to enable said problems to be overcome or reduced, and to improve said advantages. According to the present invention there is provided apparatus for holding and turning an elongate workpiece comprising a jaw member which has an axially open ended central socket and a mouth extending radially from the socket to interrupt the periphery of the jaw member, wherein the jaw member is peripherally toothed and is engaged by a single drive means comprising primary and secondary driving gears which mesh with the peripheral teeth of the jaw member at engagement locations which are spaced peripherally of the jaw member by an arc greater than the arcuate extent of the mouth and characterised in that: (a) a pair of said jaw members are mounted for rotation about a predetermined axis and a clamping jaw member is mounted between the pair of said jaw members so as to be rotatable relative to said jaw members about a clamping axis which is parallel to and offset from the axis; (b) the drive means is arranged, firstly, to drive said jaw members so that they rotate in unison about said predetermined axis for rotating a workpiece, and, secondly, to produce differential rotation between the clamping jaw member and the pair of jaw members by rotating the clamping jaw member about the offset clamping axis relative to the pair of jaw members between a position in which the mouths are aligned and no clamping is produced and a position in which the mouth of the clamping jaw member is offset arcuately from the mouths of the pair of jaw members and clamping of the workpiece is effected; and (c) it comprises means to restrict the relative rotation between the clamping jaw member and the pair of jaw members to a maximum arc, defined by said two positions. Each socket is preferably provided with a replaceable part-cylindrical insert to engage the workpieces, and has abutment means which extends axially of the socket, prevents rotation of the insert in the socket, and permits the insert to be slid axially into the socket from one axially open end of the socket. Said one open end may be partially restricted by removable retaining means to retain the insert in the socket. At least one of the inserts is preferably of a material which is harder and more rigid than the material from which another of the inserts is made. The drive means preferably includes brake means to halt movement of the clamping jaw member for causing relative rotation. A stop may be provided to limit the arcuate extent of said relative rotation. A sensor is preferably provided to determine when the jaw members or at least one thereof is or are in a predetermined angular position. The invention includes a bending machine comprising a plurality of bending units arranged to make bends in a common plane, the bending units being mounted so that the separation thereof is adjustable, and apparatus of the invention mounted so that said predetermined axis is aligned or alignable with said common plane. The mounting of the apparatus preferably permits said predetermined axis to be moved horizontally and vertically relative to the bending units. The invention will be described further, by way of example, with reference to the accompanying drawings, wherein:- FIGURE 1 shows parts of a bending machine and apparatus of the invention in front elevation; FIGURE 2 is a part sectional side-elevation of apparatus of the invention; FIGURE 3 is a cross-sectional view of the apparatus; FIGURE 4 is an enlarged cross-sectional diagram of a clamping unit incorporated in the apparatus. FIGURE 5 shows part of the clamping unit in side elevation; and FIGURE 6 shows part of an eccentric bearing member incorporated in the clamping unit. The bending machine comprises two bending units 10 carried by slides 11 and movable by respective motor driven screws 12 (only one of which is represented) to control the movement and positions of the bending units along the slides 11; together with apparatus 20 for holding and rotating a workpiece, e.g. a tube 13 shown in broken lines. The apparatus 20 comprises a clamping unit 21 mounted rotatably on a body 22 which is in turn mounted on a mounting 23 provided with adjustment means 24 to move the body 22 and unit 21 vertically relative to the units 10 and further adjustment means 24A to move the body and unit forwards and backwards relative to the units 10, so that the axis of the unbent tube 13 held in the unit 21 can be brought into and adjusted for height in the plane in which the units 10 make bends so as to be accurately aligned with the bending tools 14 and 15 provided for the units 10. The tools 15 are movable by the units 10 as indicated by the arrows 16 to make bends 17 in the nominally vertical bending plane. The unit 21 is rotatable about a predetermined axis 18 (FIGURE 4) and holds the tube 13 co-axial with said axis, to enable the tube to be rotated so that the planes of consecutive bends may be mutually inclined at any desired angle. The unit 21 comprises three jaw members, namely two abutment jaw members 24 and a clamping jaw member 25 therebetween assembled together to form a replaceable assembly. Each member 24 or 25 is substantially circular, and has a toothed periphery 26 interrupted by a mouth 27 which leads to a central socket 28, the mouth and socket being open at the axial ends or sides of the member so that when the mouths are aligned a tube can be inserted therethrough into the sockets to extend axially centrally through the unit. The internal surface of each jaw member is provided with abutment means comprising two axially extending near-diametrically opposed recesses 29, at the junction of the mouth and the socket, to receive protuberances 30 at each end of an almost semi-circular insert or liner 31 or 32 (not shown in FIGURE 4), which recesses 29 are longitudinally aligned when the mouths are aligned to allow the liners 31 and 32 to be slid into or out of the unit from one or either end. The radial thickness of the liners is selected so that the internal radius of each liner is commensurate with the tube radius. The outside axial ends of the jaw members 24 are engaged and supported by main bearing members 34 supported on a forwardly extending part of the body 22, so that the entire unit 21 is bodily rotatable about the axis 18, the members 24 and 34 being concentric with said axis. Each bearing member 34 has a fixed mouth 35 leading to a central recess which is partially closed by a retaining means comprising detachable end plates 36 (FIGURE 2 only) releasably secured to the jaw members 24 to retain the liners 31 and 32 in the unit 2l. The clamping jaw member 24 has an axis 40, referred to as "the clamping axis". The inside ends of the members 24 and both ends of the clamping jaw member 25 are circularly recessed or slotted to engage offset bearing means comprising stepped partcircular friction bearing members 37 and 38 each of which has a crescent shaped land 39 which is eccentric to the remainder and fits co-axially into the respective jaw member 24. Said remainder is coaxial with the clamping axis 40 of the member 25 so that the member 25 is arcuately movable, relative to the members 24, about said clamping axis 40. The members 37 and 38 serve as frictional engagement means between the jaw members to entrain the member 25 to move with the members 24 when the latter are rotated without a workpiece in the unit. The members 24 and 25 are slotted and recessed to receive, fixedly or slidably, metal pins 41 which serve as stops to prevent unwanted relative movements between the members 24, 25, 37 and 38 and to restrict the arcuate movement of the member 25 relative to the members 24 to a maximum arc, e.g. to 180 from an open position, in which all the mouths are aligned (FIGURES 1, 2 and 4) to a clamping position, as shown in FIGURE 5. The clamping axis 40 is offset from the axis 18 in a direction towards the sockets in the members 24 (downwards in FIGURES 4 and 5) by an amount which is predetermined by the radial maxima of the lands 39 to suit the nature of the liners and the workpieces, and said offset will commonly be about 0.1 mm, but could well be varied within a wide range, e.g. from about 0.05 to 1 mm depending upon the clamping compression to be produced when a workpiece, of overall radius equal to the internal radius of the liners, is held in the unit. In the clamping position the liners 31 are on a circle continued in broken lines 42 in FIGURE 5, whereas the liner 32 is eccentric to the circle as indicated in FIGURE 5 which eccentricity is equal to the maximum amount of clamping compression. The liners 31 are preferably of steel or a like hard material, whereas the liner 32 is preferably of a plastics material, such as nylon, which: a) is more compressible than steel, b) provides a smooth non-abrasive surface, and c) is hard wearing and resistant to tearing, cracking and splintering. The internal shape of the liners 31 may be noncircular, e.g. to conform to part of a non-circular workpiece to accept and support the workpiece so that it, firstly, lies radially inwards beyond the inner surface of the liner 32 in said open position, which surface has the position shown in chain-broken lines 44, and, secondly, extends to or to close to said continuation 42 indicated in broken lines for clamping by the liner 32 in the clamping position indicated in Fig. 5. The body 22 carries drive means 45, which comprises brake means 46 and a stepping motor 47, for driving the clamping unit 21 and causing said relative arcuate movement between the jaw members. The electrically actuated stepping motor 47 drives the abutment jaw members 24 via a train comprising an input shaft 48 with a worm gear, an input spur gear 49 keyed to a primary shaft 50, paired primary driving gears 51 keyed to the shaft 50, paired idler gears 52 and paired secondary driving gears 53 keyed to a secondary shaft 54. The primary driving gears 51 engage the toothed periphery 26 at a primary location 55; and the secondary driving gears 53 engage the teeth 26 at a secondary location 56 which is separated angularly about said axis 18 by an amount which is greater than the angle through which the toothed periphery 26 is interrupted by the mouth. The shafts 48, 50 and 54 are adjustably mounted to permit backlash in said train to be removed. The brake means 46 comprises an electrically actuated brake 57 to halt the clamping jaw member 25 via a free running train comprising a brake shaft 59 having a keyed gear 60, an idler gear 61, a secondary brake gear 62 free running on the shaft 54, an idler gear free running on an adjustable shaft (not shown) which carries the gears 52, and a primary brake gear 63 free running on the shaft 50. The brake gears 62 and 63 engage the toothed periphery 26 of the jaw member 25 at said locations 55 and 56. The body also carries a sensor 64 to determine when the mouths are aligned with an opening 65 in the forwardly extending part of the body and the fixed mouths in the bearings. In use, when the brake is disengaged, drive is transferred from the motor via the drive means to the jaw members 24, and from the jaw members 24 to the clamping jaw member 25 to rotate the jaw members 24 and 25 in unison so that all the torque necessary to rotate the workpiece is transmitted by the abutment jaw members 24 to the workpiece, irrespective of the angular position of the abutment jaw members 24, thus preventing accidental opening of the unit. During such movement, the free running train is driven by the clamping jaw member 25 but the train is sufficiently free running not to exert a torque load upon the clamping jaw member which could alter the angular relationship between the jaw members 24 and 25. The bending machine is provided with an electronic control unit capable of being programmed to control a sequence of bends in a bending cycle which includes:- a) bringing the jaw members to, or ensuring that the jaw members are in, the open position in alignment with the opening 65 for insertion of a workpiece into the sockets, so as to be aligned with the tools 14 and 15; b) rotating the abutment jaw members 24 whilst holding the clamping jaw member 25 to clamp the workpiece in the sockets, and releasing the brake; c) moving the bend units 10 longitudinally of the slides to predetermined positions; d) actuating the bend units to make bends in said plane, and moving said units to the positions for the next bends; e) rotating the workpiece, by driving the members 24, through a predetermined angle if the next bend or bends is or are to be made in a different plane, during which rotation the brake is not engaged so that the jaw members rotate in unison; f) repeating steps d) e) and f) as needed to complete bending of the workpiece; and g) actuating the unit 21 to permit the bent workpiece to be removed. The step g) can be performed simply by engaging the brake, rotating the jaw members 24 to the open position, disengaging the brake and turning the jaw members 24 and 25 in unison into alignment with the opening 65. However, it may be beneficial to first bring the workpiece into a safe, convenient or otherwise desirable final angular position, e.g. to be taken up by tube handling apparatus for transfer to a subsequent workstation, prior to clamping being released by relative arcuate movement between the jaw members 24 and 25. Threaded fasteners are indicated by reference numeral 10 in FIGURE 2. The invention is not confined to details of the foregoing example, and many variations are possible within the scope of the invention. For example, the periphery of the jaw member 25 may be plain cylindrical and the brake may comprise a brake shoe actuable to engage frictionally upon said periphery, to obviate the braking train. The relative hardness of the liners may be reversed so that the liner 32 is harder than the liners 31. Instead of being of different materials, the liners may be of the same material, and may have different internal surface finishes. The unit 21 may be hydraulically instead of electrically operated, and may be releasably attached to the mounting 23.

Claims: Apparatus (20) for holding and turning an elongate workpiece (13) comprising a jaw member (24, 25) which has an axially open ended central socket (28) and a mouth (27) extending radially from the socket to interrupt the periphery of the jaw member, wherein the jaw member is peripherally toothed and is engaged by a single drive means (45) comprising primary and secondary driving gears (51 and 53) which mesh with the peripheral teeth of the jaw member at engagement locations which are spaced peripherally of the jaw member by an arc greater than the arcuate extent of the mouth and characterised in that:- (a) a pair of said jaw members (24) are mounted for rotation about a predetermined axis (18) and a clamping jaw member (25) is mounted between the pair of said jaw members (24) so as to be rotatable relative to said jaw members (24) about a clamping axis (40) which is parallel to and offset from the axis (18); (b) the drive means (45) is arranged, firstly, to drive said jaw members (24,25) so that they rotate in unison about said predetermined axis (18) for rotating a workpiece, and, secondly, to produce differential rotation between the clamping jaw member (25) and the pair of jaw members (24) by rotating the clamping jaw member about the offset clamping axis (40) relative to the pair of jaw members (24) between a position in which the mouths are aligned and no clamping is produced and a position in which the mouth of the clamping jaw member is offset arcuately from the mouths of the pair of jaw members and clamping of the workpiece is effected; and (c) it comprises means (41) to restrict the relative rotation between the clamping jaw member (25) and the pair of jaw members (24) to a maximum arc, defined by said two positions. Apparatus as claimed in Claim 1 wherein said axes (18,40) pass substantially centrally through the sockets (28) and are separated by a distance of less than one millimetre. Apparatus as claimed in Claim 1 or 2 wherein both of said jaw members (24) are peripherally toothed and are engaged by respective ones of primary and secondary driving gears (51,53) at engagement locations which are spaced peripherally of the jaw members (24) by an arcs greater than the arcuate extents of the mouths (27); and the clamping jaw member (25) is rotatable about said predetermined axis (18) by said jaw members (24). Apparatus as claimed in Claim 1, 2 or 3 wherein the clamping jaw member (25) is carried by the jaw members (24) by means of offset bearing means (37,38) and said jaw members (24,25) are peripherally assembled together to form a clamping unit (21) mounted on bearings (34) co-axial with said predetermined axis (18), said bearings (34) being part circular and interrupted by fixed mouths (35). Apparatus as claimed in Claim 4 wherein a stop (41) is provided to limit the arcuate extent of said relative rotation between the jaw members (24,25). Apparatus as claimed in any preceding claim wherein the drive means includes brake means (46) to halt movement of the clamping jaw member (25) by the jaw members (24). Apparatus as claimed in Claim 6 wherein the brake means comprises a brake which acts on the periphery of the clamping jaw member, either directly or via brake gears (62,63). Apparatus as claimed in any preceding claim wherein each socket (28) is provided with a replaceable part-cylindrical insert (31 or 32) to engage the workpieces, and has abutment means (29) which prevents rotation of the insert relative to the socket, and permits the insert to be slid, longitudinally of the axis, into the jaw member (24 or 25). Apparatus as claimed in Claim 8 at least one of the inserts (31,32) is of a material that is harder and more rigid than the material from (32 or 31) which another of the inserts is made. A bending machine comprising apparatus (20) as claimed in any preceding claim and a plurality of bending units (10) arranged to make bends in a common plane, the bending units (10) being mounted so that the separation thereof is adjustable; and the apparatus (20) is mounted so that said predetermined axis (18) is aligned or alignable with said common plane, and wherein the mounting of the apparatus (20) permits said predetermined axis (18) to be moved horizontally and vertically relative to the bending units (10). A bending machine as claimed in Claim 10 wherein the apparatus (20) is as claimed in Claim 6 or 7, and incorporating an electronic control unit capable of being programmed to control a sequence of bends in a bending cycle which includes:- (a) bringing the jaw members (24,25) to, or ensuring that the jaw members are in, the open position in alignment with an opening (65) for insertion of a workpiece into the sockets, so as to be aligned with tools (14) and (15) of the unit (10); (b) rotating the jaw members (24) whilst holding the clamping jaw member (25) to clamp the workpiece in the sockets, and releasing the brake; (c) moving the bend units (10) longitudinally of the slides to predetermined positions; (d) actuating the bend units to make bends in said plane, and moving said units to the positions for the next bends; (e) rotating the workpiece, by driving the members (24), through a predetermined angle if the next bend or bends is or are to be made in a different plane, during which rotation the brake is not engaged so that the jaw members rotate in unison; (f) repeating steps (d) (e) and (f) as needed to complete bending of the workpiece; and (g) actuating the unit (21) to permit the bent workpiece to be removed, by engaging the brake, rotating the jaw members (24) to the open position, disengaging the brake and turning the jaw members (24 and 25) in unison into alignment with the opening (65).

Inventors: LANGLEY, GEOFFREY THOMAS
Applicants: LANGBOW LIMITED
Application year: 1987
Main classification: B21D7
IPC codes: B21D7, B21F1