GB2035178A

GB2035178A - Apparatus for supporting workpieces on turning machines

Info

Publication number: GB2035178A
Application number: GB7937735A
Authority: GB
Original assignee: Mannesmann AG
Current assignee: Vodafone GmbH
Priority date: 1978-11-23
Filing date: 1979-10-31
Publication date: 1980-06-18
Also published as: GB2035178B; FR2442095B1; FR2442095A1; DE2850984A1

Abstract

In order to permit longitudinally profiled sleeves or pins for oilfield pipes to be machined and exchanged rapidly a device (15) mounted on a workpiece support chuck (3) is provided at the front spaced from the chuck with a plurality of claws (13) around the workpiece (12) and an inclined fluidic piston-cylinder drive (16) on the chuck for each claw (13) for moving the claw so that the workpiece can be lifted out when the claws (13) are in the retracted position. The claws accept radial loads during workpiece parting-off. <IMAGE>

Description

SPECIFICATION Apparatus for supporting workpieces on turning machines This invention relates to apparatus for supporting workpieces on turning machines.

In a known apparatus for supporting workpieces which are clamped only at their ends, more particularly longitudinally profiled sleeves or pins for oilfield pipes at a spacing from a chuck in a turning machine a backrest for supporting the workpiece is provided between the chuck and the workpiece support. A backrest is suitable only for workpieces which are outwardly adapted for abutment on the backrest and are positioned in a precisely concentric position. These conditions are not met in the case of workpieces which have to be machined and exchanged rapidly in the large-scale production of, for example, longitudinally profiled sleeves or pins for oilfield pipes. Moreover, it is a complicated operation to ensure that the sliding conditions in the backrest are always maintained and to fold the backrest after each machining operation on a workpiece.

French Patent Specification No. 929,184 discloses a chuck which performs the function of a support in the apparatus according to the invention, which already comprises a chuck.

The aim of the invention is to provide an apparatus for supporting the workpieces which does not require a sliding mounting and does not necessitate accurate centering of the support point.

According to the invention the apparatus as set forth above is characterised in that a clamping device mounted on a chuck is provided at the front with a plurality of claws enclosing the workpiece and a displacement drive on the chuck so that the workpiece can be lifted out when the claws are in the retracted position.

In a preferred embodiment of the apparatus the clamping device comprises at least two rods mounted to as to be movable in an inclined direction relative to the workpiece axis.

Preferably the rods are constructed as piston rods which takes into account the special task of the support apparatus according to the invention, i.e. to be capable of being advanced and moved back particularly rapidly. The synchronism of the rod movement is not important, as there is no centering apparatus involved.

An embodiment of the apparatus according to the invention will now be described by way of example, with reference to the accompanying drawings, in which: Figure 1 is a longitudinal section through a chuck with a support apparatus in a turning machine for machining the pins for oilfield pipes.

Figure 2 shows a cross section taken along the line Il-Il of the apparatus shown in Figure 1.

Referring now to the apparatus in detail a thickwalled tube 1 is clamped in a turning machine having a chuck 2. The end of the tube 1 emerging towards a second chuck 3 makes contact with a stop plate 4 and at its outermost end 5 it is located for a short distance between three clamping jaws 6 which are driven by means of a hydraulic cylinder 7.

The portion of the tube 1 located between the two chucks 2 and 3 is the workpiece. A longitudinal contour 8 has already been produced on the workpiece by turning. The next operation to be carried out is to cut off the workpiece at the point 9 shown by chaindotted lines, using a cutting tool 10, shown in its position of readiness, on a support 11 which is movable in the direction of the arrow.

The short section clamped by the jaws 6 is put under very great stress when, at the last moment of cutting with the tool 10, it has to absorb the transverse force of the end which has been cut off. The following apparatus is proposed in order to relieve this stress: On the portion 12 of the tube 1 which is to be cut off, namely the blank for a pin for an oilfield pipe, three claws 15 are arranged on the circumference at a spacing A, and are angularly offset relative to the clamping jaws 6. The claws 13 are attached to the ends of cylindrical rods 15 by means of screws 14.

Each rod 15 is constituted by the piston rod of a cylinder 16 which passes through the housing of the chuck3 in an inclined position, is provided with a flange 17 at the front end is fixed with this flang in the housing. The cylinder 16 may be hydraulically or pneumatically operated. When the rod 15 is in the fully inserted position the claw 13 assumes the position 13' shown by the chain-dotted lines.

In the position of the apparatus shown in the drawing, the cutting off at the point 9 then takes place. At the instant when this cutting is about to end the claws 13 absorb the transverse forces produced, so that the clamping jaws 6 are completely freed from stress. To this end, the dimension A should be as large as possible, so that the claws 13 are located relatively near the cut-off point 9, but the practically limited length of the piston rod results in a small diameter A, i.e. more or less the dimension shown in the drawing.

After the workpiece 12 has been severed from the tube 1, the three rods 15 rapidly move into their respective cylinders 16, with the result that the claws assume the positions 13'. A lifting tool may engage on the workpiece 12. Whilst the support 11 travels back slightly, the jaws 6 release the workpiece 12 so that it can be lifted out. The chuck 2 is then opened and the tube 1 is pushed forwards, by means of a device (not shown), until it abuts on the plate 4. The chucks 2 and 3 then re-engage and the production of the next longitudinal contour8 starts. Beforeth cutting tool 10 is brought into engagement again with the workpiece, the holders of the claws 13, i.e. the piston rods 15, are moved out in an inclined direction until they reach the position shown. The piston force is such that in the inclined position given a predetermined force component is exerted radially on the workpiece 12. This latter movement occurs whilst the machining steel (not shown) is rapidly reciprocating towards the cutting tool 10 shown.

1. Apparatus for supporting workpieces which are clamped only at their ends, more particularly longitudinally profiled sleeves or pins for oilfield pipes at a spaying from a chuck in a turning machine,

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Apparatus for supporting workpieces on turning machines This invention relates to apparatus for supporting workpieces on turning machines. In a known apparatus for supporting workpieces which are clamped only at their ends, more particularly longitudinally profiled sleeves or pins for oilfield pipes at a spacing from a chuck in a turning machine a backrest for supporting the workpiece is provided between the chuck and the workpiece support. A backrest is suitable only for workpieces which are outwardly adapted for abutment on the backrest and are positioned in a precisely concentric position. These conditions are not met in the case of workpieces which have to be machined and exchanged rapidly in the large-scale production of, for example, longitudinally profiled sleeves or pins for oilfield pipes. Moreover, it is a complicated operation to ensure that the sliding conditions in the backrest are always maintained and to fold the backrest after each machining operation on a workpiece. French Patent Specification No. 929,184 discloses a chuck which performs the function of a support in the apparatus according to the invention, which already comprises a chuck. The aim of the invention is to provide an apparatus for supporting the workpieces which does not require a sliding mounting and does not necessitate accurate centering of the support point. According to the invention the apparatus as set forth above is characterised in that a clamping device mounted on a chuck is provided at the front with a plurality of claws enclosing the workpiece and a displacement drive on the chuck so that the workpiece can be lifted out when the claws are in the retracted position. In a preferred embodiment of the apparatus the clamping device comprises at least two rods mounted to as to be movable in an inclined direction relative to the workpiece axis. Preferably the rods are constructed as piston rods which takes into account the special task of the support apparatus according to the invention, i.e. to be capable of being advanced and moved back particularly rapidly. The synchronism of the rod movement is not important, as there is no centering apparatus involved. An embodiment of the apparatus according to the invention will now be described by way of example, with reference to the accompanying drawings, in which: Figure 1 is a longitudinal section through a chuck with a support apparatus in a turning machine for machining the pins for oilfield pipes. Figure 2 shows a cross section taken along the line Il-Il of the apparatus shown in Figure 1. Referring now to the apparatus in detail a thickwalled tube 1 is clamped in a turning machine having a chuck 2. The end of the tube 1 emerging towards a second chuck 3 makes contact with a stop plate 4 and at its outermost end 5 it is located for a short distance between three clamping jaws 6 which are driven by means of a hydraulic cylinder 7. The portion of the tube 1 located between the two chucks 2 and 3 is the workpiece. A longitudinal contour 8 has already been produced on the workpiece by turning. The next operation to be carried out is to cut off the workpiece at the point 9 shown by chaindotted lines, using a cutting tool 10, shown in its position of readiness, on a support 11 which is movable in the direction of the arrow. The short section clamped by the jaws 6 is put under very great stress when, at the last moment of cutting with the tool 10, it has to absorb the transverse force of the end which has been cut off. The following apparatus is proposed in order to relieve this stress: On the portion 12 of the tube 1 which is to be cut off, namely the blank for a pin for an oilfield pipe, three claws 15 are arranged on the circumference at a spacing A, and are angularly offset relative to the clamping jaws 6. The claws 13 are attached to the ends of cylindrical rods 15 by means of screws 14. Each rod 15 is constituted by the piston rod of a cylinder 16 which passes through the housing of the chuck3 in an inclined position, is provided with a flange 17 at the front end is fixed with this flang in the housing. The cylinder 16 may be hydraulically or pneumatically operated. When the rod 15 is in the fully inserted position the claw 13 assumes the position 13' shown by the chain-dotted lines. In the position of the apparatus shown in the drawing, the cutting off at the point 9 then takes place. At the instant when this cutting is about to end the claws 13 absorb the transverse forces produced, so that the clamping jaws 6 are completely freed from stress. To this end, the dimension A should be as large as possible, so that the claws 13 are located relatively near the cut-off point 9, but the practically limited length of the piston rod results in a small diameter A, i.e. more or less the dimension shown in the drawing. After the workpiece 12 has been severed from the tube 1, the three rods 15 rapidly move into their respective cylinders 16, with the result that the claws assume the positions 13'. A lifting tool may engage on the workpiece 12. Whilst the support 11 travels back slightly, the jaws 6 release the workpiece 12 so that it can be lifted out. The chuck 2 is then opened and the tube 1 is pushed forwards, by means of a device (not shown), until it abuts on the plate 4. The chucks 2 and 3 then re-engage and the production of the next longitudinal contour8 starts. Beforeth cutting tool 10 is brought into engagement again with the workpiece, the holders of the claws 13, i.e. the piston rods 15, are moved out in an inclined direction until they reach the position shown.The piston force is such that in the inclined position given a predetermined force component is exerted radially on the workpiece 12. This latter movement occurs whilst the machining steel (not shown) is rapidly reciprocating towards the cutting tool 10 shown. CLAIMS

1. Apparatus for supporting workpieces which are clamped only at their ends, more particularly longitudinally profiled sleeves or pins for oilfield pipes at a spaying from a chuck in a turning machine, in which a clamping device mounted on the chuck is provided at the front with a plurality of claws enclosing the workpiece and a displacement drive on the chuck so that the workpiece can be lifted out when the claws are in the retracted position.

2. Apparatus according to Claim 1, in which the clamping device comprises at least two rods mounted so as to be movable in an inclined direction relative to the workpiece axis.

3. Apparatus according to Claim 2 in which the rods are constructed as piston rods.

4. Apparatus for supporting workpieces which are clamped only at their ends substantially as herein described with reference to the accompanying drawings.