GB2041022A

GB2041022A - Workpiece Positioning Apparatus

Info

Publication number: GB2041022A
Application number: GB8003206A
Authority: GB
Original assignee: British United Shoe Machinery Ltd
Current assignee: Noxet UK Ltd
Priority date: 1979-02-01
Filing date: 1980-01-30
Publication date: 1980-09-03
Also published as: GB2041022B; ES488828A0; JPS55103614A; CA1136926A; FR2447990B1; FR2447990A1; KR830002093A; KR840000303B1; IT1193897B; ES8102603A1; IT8019523A0; JPH024819B2; DE3003292A1

Abstract

Apparatus for positioning a workpiece, e.g. in a sewing machine, relative to an operative tool comprises a motor 40 for moving a frame 22,24 and a motor 66 for moving a carriage 18 which holds the workpiece on the frame. The two motors are both mounted on a fixed base of the apparatus and the two axes of movement, 29,21 respectively, both lie in the same plane. This arrangement reduces the vibrations which may occur in the apparatus when operating at high speed. <IMAGE>

Description

SPECIFICATION Positioning Apparatus This invention is concerned with positioning apparatus for use in positioning a workpiece relative to an operative tool comprising a frame mounted for movement along a first axis, a carriage mounted on said frame for movement along a second axis and arranged to support a workpiece, first moving means operable to drive the frame along the first axis, and second moving means operable to drive the carriage along the second axis.

Positioning apparatuses as described above are used, for example, in automated sewing machines where the operative tool is a cyclically operating needle and the workpiece may be a number of separate pieces that require joining or a separate piece requiring a decorative pattern.

The positioning apparatus of a sewing machine is required to operate rapidly in the intervals when the needle is disengaged from the workpiece. In such positioning apparatus, the first and the second axis are usually transverse to each other but lie in different planes and the second moving means is mounted on the frame for movement therewith.

Because the positioning apparatus must stop and start very rapidly to enable the machine with which it is associated to achieve a high production rate, it is frequently found that vibrations are set up in the positioning apparatus causing inaccuracies in the operation on the workpiece and this problem is particularly acute where the workpiece is flexible and itself susceptible to vibration.

It is an object of the present invention to provide a positioning apparatus in which vibration is minimised.

The invention provides positioning apparatus for use in positioning a workpiece relative to an operative tool comprising a frame mounted for movement along a first axis, a carriage mounted on said frame for movement along a second axis and arranged to support a workpiece, first moving means operable to drive the frame along the first axis, and second moving means operable to drive the carriage along the second axis, wherein the first and the second axes lie in the same plane.

In order to reduce inertia, the first and the second moving means are both mounted on a fixed base of the apparatus and are not moved during operation of the positioning apparatus.

In order to further reduce vibration by preventing the workpiece from swinging about either of said axes, the carriage is preferably arranged to support a workpiece in the plane in which the first and the second axes lie.

In order to further reduce vibration by enabling use of lighter weight frame, the frame preferably comprises an L-shaped structure having a first beam extending in the direction of the first axis and a second beam extending in the direction of the second axis. The frame also comprises a Yshaped bracing member having one end portion connected to the first beam and two end portions connected to the second beam.

A positioning apparatus which is illustrative of the invention is described in detail below and is shown in the accompanying drawings. The illustrative apparatus has been selected for description by way of example and not of limitation.

In the drawings: Figure 1 is a perspective view of a sewing machine incorporating the illustrative positioning apparatus; Figure 2 is a perspective view with parts broken away of the illustrative positioning apparatus; Figures 3 and 4 show portions of the illustrative positioning apparatus; and Figure 5 is a plan view of the illustrative positioning apparatus.

Figure 1 shows a sewing machine 10 arranged to operate on a workpiece 14 held by a clamping mechanism 12. The clamping mechanism is attached to an arm 1 6 of the illustrative positioning apparatus and the arm 16 is in turn attached to a carriage 18 thereof. The carriage 18 is mounted for movement along the length of a cylindrical axis member 20 of the apparatus.

Referring to Figure 2, the axis member 20 is attached to a beam 22 of an L-shaped lightweight frame of the apparatus comprising the beam 22, a beam 24 extending normally to the beam 22, and a Y-shaped bracing member 26 having one end portion thereof connected to the beam 24 and two end portions connected to the beam 22. The frame is made out of lightweight material such as aluminium.

The frame is mounted for movement along a first axis 29 of the apparatus provided by the central axis of a cylindrical guide member 28 mounted on a relatively massive fixed base 30 of the apparatus. The carriage 18, being mounted on the beam 22, is mounted on said frame for movement along a second axis provided by the central axis 21 of the axis member 20. The axes 21 and 29 are normal to one another and lie in the same plane and the beams 22 and 24 respectively extend in the directions of the axes 21 and 29.

The beam 22 has a downwardly extending portion 31 which has two cylindrical rollers 32 and 33 mounted thereon which engages top and bottom surfaces of a guide rail 34. The guide rail 34 is mounted on two vertical supports 36 and 38 mounted on the base 30. The rail 34 provides support and guidance for the frame.

The carriage 18 is arranged to support a clamped workpiece 14 in the plane in which the first axis 29 and the second axis 21 lie and the connection between the carriage 18 and the arm 16 is arranged accordingly.

A motor 40 mounted on the base 30 provides first moving means of the apparatus operable to drive the frame along the first axis 29. The motor 40 is contained in a housing 42 mounted on an elevated base 44 fixed to the base 30. Gearing 46 (Figure 2) is driven by the motor 40 and drives a pinion 48 which in turn drives a rack 50. The rack 50 is maintained in engagement with the pinion 48 by a roller 52 mounted on a bracket carried by the base 30. The rack 50 is connected to the beam 22 so that operation of the motor 40 moves the frame along the axis 29.

The carriage 18 includes a rack 54 which engages a pinion 56 and is maintained in engagement by a roller 57 mounted on the beam 22. The pinion 56 is driven by a spline shaft 58.

The spline shaft 58 extends parallel to the first axis 29 and is rotatable in a bearing mounted on a lower portion 60 of the beam 22 of the frame.

The spline shaft 58 is also rotatably mounted on a mounting 62 secured to the base 30.

Gearing 64 at the end of the spline shaft 58 is driven by a motor 66 which thus provides second moving means of the apparatus operable to drive the carriage 18 along the second axis 21. The motor 66 is fixedly mounted on the base 30.

The mounting of the spline shaft 58 with the lower portion 60 will now be further described.

The shaft 58 is suspended within a cylindrical collar 68 (Figure 3) by a plurality of ball bearings 70 and 80. When viewed in transverse crosssection (Figure 4), the cylindrical collar 68 can be seen to comprise three evenly-distributed recesses 72. 74 and 76, each of which contains a set of paired ball bearings 70 and 80. Each set of ball bearings is maintained in its recess by a retaining ring 82. The shaft 58 comprises three separate splines 84, 86 and 88 which are respectively supported by the sets of paired ball bearings. Thus, rotation of the shaft 58 rotates the collar 68 and, as the collar 68 is keyed to a casing 90 by a key 92 and the casing 92 includes the aforementioned pinion 56, the pinion 56-is also rotated moving the carriage 18 along the axis 21. The casing 90 rotates on bearings 94 and 96 on the lower portion 60. The shaft 58 is thus rotatable in a bearing 94 and 96 mounted on the frame and the bearing is slidable with the frame along the shaft 58 when movement of the frame takes place, this movement being allowed by the ball bearings 70 and 80. With this arrangement, simultaneous movement along the axes 21 and 29 can readily take place.

Since the motors 40 and 66 of the positioning apparatus are both mounted on a fixed base 30 of the apparatus, vibrations caused by the operation of the motors are absorbed by the base 30 and not transmitted to the workpiece 14.

Furthermore, as neither motor is moved, the inertia of the system is minimised reducing the possibility of vibration. Also, because the axes are in the same place, vibrations about these axes are also minimised. Accordingly, the positioning apparatus is able to operate accurately at high speed.

Claims

1. Positioning apparatus for use in positioning a workpiece relative to an operative tool comprising a frame mounted for movement along a first axis, a carriage mounted on said frame for movement along a second axis and arranged to support a workpiece, first moving means operable to drive the frame along the first axis, and second moving means operable to drive the carriage along the second axis, wherein the first and the second axes lie in the same plane.

2. Positioning apparatus according to claim 1 wherein the first and the second moving means are both mounted on a fixed base and are not moved during operation of the positioning apparatus.

3. Positioning apparatus according to either one of claims 1 and 2 wherein the carriage is arranged to support a workpiece in the plane in which the first and the second axes lie.

4. Positioning apparatus according to any one of claims 1, 2 and 3 wherein the frame comprises an L-shaped structure having a first beam extending in the direction of the first axis and a second beam extending in the direction of the second axis.

5. Positioning apparatus according to claim 4 wherein the frame also comprises a Y-shaped bracing member having one end portion hereof connected to the first beam and two end portions connected to the second beam.

6. Positioning apparatus according to any one of claims 1, 2, 3, 4 and 5 wherein the second moving means is connected to the carriage via a shaft extending parallel to the first axis and rotatable in a bearing mounted on the frame, the bearing also being slidable along the shaft when movement of the frame takes place.

7. Positioning apparatus according to claim 6, wherein the carriage is driven by means of a pinion rotatable by the shaft which is maintained in engagement with a rack connected to the carriage.

8. Positioning apparatus for use in positioning a workpiece relative to an operative tool substantially as hereinbefore described with reference to and as shown in the accompanying drawings.