GB2230985A - Auxiliary machining device and method - Google Patents

Abstract

The device is made up of a drive unit which includes an electric motor having a rotary output shaft, a speed controller for the motor whereby output shaft speed can be varied, output torque of the output shaft being substantially independent of output shaft speed at least at low motor speeds; a tool holder A, for a cutting tool, adapted to be driven by the drive unit so as to rotate a cutting tool retained in the holder; and a mounting chassis B for the drive unit and the toolholder. The chassis B enables the device to be secured to a conventional tool carrier 17 of a machine tool, such as a lathe, so that the device can be controllably displaced along three axes at right angle to one another by conventional tool carrier locating controls 15, 18 or adjustments on the machine tool. The chassis B includes adjustable locating means eg. an array of fixing holes whereby one of a predetermined plurality of fixed locations for the tool holder relative to a datum location on the chassis can be selected prior to securing the chassis to the machine tool. Preferably the drive unit incorporates a gear box or other speed ratio establishing means whereby one of two of more speed ratios between motor and tool holder can be established independently of the output shaft speed established by the speed controller. <IMAGE>

Description

AUXILIARY MACHINING DEVICE AND METHOD This invention relates to a device for and method of machining. It is particularly concerned with the provision of an auxiliary machining facility on an existing machine tool.

According to a first aspect of the present invention there is provided an auxiliary machining device comprising: 1 a drive unit including an electric motor having a rotary output shaft, a speed controller for the motor whereby output shaft speed can be varied, output torque of the output shaft being substantially independent of output shaft speed at least at low motor speeds; 2 a tool holder, for a cutting tool, adapted to be driven by the drive unit so as to rotate a cutting tool retained in the holder; and 3 a mounting chassis for the drive unit and the toolholder, whereby the device can be secured to a conventional tool carrier of a machine tool, such as a lathe, so as to enable the device to be controllably displaced along three axes at right angle to one another by conventional tool carrier locating controls or adjustments on the machine tool; the chassis including adjustable locating means whereby one of a predetermined plurality of fixed locations for the tool holder relative to a datum location on the chassis can be selected prior to securing the chpssis to a carrier as aforesaid.

In a preferred version of the first aspect of the present invention the drive unit incorporates a gear box or other speed ratio establishing means whereby one of two or more speed ratios between motor and tool holder can be established independently of the output shaft speed established by the controller.

In the present context the term cutting tool should be taken to include not only conventional tools used for turning, milling and slot cutting but also tools for material removal such as thread cutters and reamers.

According to a second aspect of the present invention there is provided a machine tool, such as a lathe, equipped with an auxiliary machining device according to the first aspect or the preferred version thereof.

According to a third aspect of the present invention there is provided a method of auxiliary machining on a machine tool (such as a lathe) comprising the steps of: 1 mounting on a tool support of a machine tool an auxiliary machining device, by way of a chassis incorporated in the device, according to the first aspect of the present invention or the preferred version thereof, the tool holder having been located at one of the plurality of predetermined positions relative to the chassis; 2 coupling a cutting tool to the tool holder; 3 utilising displacement controls of the machine tool to position the cutting tool at a workpiece machining location of the machine tool; and 4 causing the motor to drive the the cutting tool about a first axis by way of the transmission shaft so as to enable the cutting tool to act on a workpiece located at the workpiece machining position.

An exemplary embodiment of the invention will now be described with reference to the accompanying drawings which includes an auxiliary machining device of which: Figure 1 is a side elevation of a part of a lathe equipped with the device; Figure 2 shows a first part of the device of Figure 1 in more detail; and Figure 3 shows a second part of the device of Figure 1.

Figure 1 shows part of a lathe having a bed 11 extending from a headstock 12 and supporting a tool carriage 13. The headstock 12 incorporates a conventional chuck 14 whereby a workpiece W can be secured and rotated at a predetermined speed for a conventional turning operation.

The carriage 13 can be be displaced to any position along the bed in the direction of longitudinal axis X by way of control wheel 15. A cross-slide 16 (to which is secured a tool post 17) is carried on the carriage 13 and can be displaced relative to the carriage 13 by way of control wheel 18 in a direction perpendicular to the plane of the paper (that is to say in direction Y perpendicular both to axis X and a vertical axis Z.

Initial machining of the workpiece W is carried out by way of a conventional lathe tool secured in a known manner to the tool post 17. In this way the workpiece W can be conventionally turned, faced or threaded.

In the event that some further cutting action is required, such as the milling of slots, keyways or flats, the workpiece would usually need to be removed from the chuck 14 and either remounted in the lathe to expose a further face or on some other machine tool for the further operation to be completed. To obviate this need for relocating the workpiece the conventional tool is removed from attachment to the toolpost 17 by way of a conventional toolholder and replaced by the auxiliary machining device 20 clamped in a tool holder 21 of the Woods type which allows for a limited degree of movement of the device 20 in the direction of axis Z relative to the cross-slide 16 when initially mounting the device 20.

The device 20 is in two parts as will be described hereafter and adapted to be readily secured to the tool holder 21 so as to enable the device 20 to be moved, by way of the carriage and cross-slide controls 15, 18 of the lathe in the direction of, respectively axes X and Y and by operation of the tool holder 21 in the direction of axis Z.

Figures 2 and 3 show in more detail the device 20, broadly shown in Figure 1, which is in two parts: a powered section A described with reference to Figure 2, and a chassis section B described with reference to Figure 3.

Figure 2 shows powered sectiop A housing an electric motor 22 having a power supply lead 23. The motor 22 drives output shaft 24 by way of a mechanical gear box 25 which enables the output shaft 24 to be driven at one of two speed ranges depending on the position of a selector 26. The speed of shaft 24 is established by way of a speed controller incorporated in the motor and governed by a speed control 27. Using selector 26 to engage the lower speed range enables the speed control 27 to be used to provide any output speed for shaft 24 between 0 and 950 rpm. With the higher speed range engaged by selector 26 any output speed between 0 and 2400 can be provided by appropriate rotation of of speed control 27.The motor 22 is of a type and has a control system which provides that the torque output of the machine fed to output shaft 24 is substantially independent of motor speed at least over the low speed end of the motor speed range. This ensures that an effective cutting torque is available despite having to use a relatively low cutting speeds such as would be required with a large diameter cutter for a given cutting speed.

A suitable drive unit is provided by a Metabo (RTM) drill identified by the model number EDV 1000 Signal6.

The output shaft 24 is coupled by way of a bevel drive 29 to a hollow tubular transmission shaft transmission shaft 28 whose output end incorporates a collet 31 providing for the retention of a cutting tool 32 so that it can be rotated about axis T. The collet is clamped and released by way of a tube spanner inserted through port P and passing through the shaft 28 to engage the collet Figure 3 shows the chassis section B of the device 20 which includes a block 35 whereby the device is secured in place on tool carrier 21 as shown in Figure 1. The chassis enables the device 20 to be positioned to appropriately locate axis T of a cutting tool in the collet 31 relative to axis X, Y and Z when clamping the device 20 by way of block 35 in tool holder 21.Movement of the mounted device 20 in the direction of axes X and Y is readily carried to virtually any desired extent by the lathe controls. The amount of movement available from the lathe tool carrier in the direction of axis Z is not so extensive as in axies X and Y and the chassis section shown in Figure 3 provides a means for enabling the device to be initially positioned in a wide range of positions. To this end the chassis section B incorporates a demountable second part of the chassis in the form of a back plate 40. This is provided with threaded holes 41 whereby the back plate 40 can be secured to the driving section A and the clamping block 35 in a number of ways so as to enable one of a wide range of predetermined alignments for the axis T relative to the axis of block 35 prior to clamping the device 20 in the tool holder 21.The clamping block 35 can be secured to any one of a pair of holes in the back plate 40 with the axis T parallel either to the longitudinal axis of block 35 or to the longitudinal axis of block 40. This ability to vary the alignment of the powered section A relative to the clamping block 35 and the block 40 and the further ability to raise and lower the mounting of the device on the tool post and to rotate the tool holder about the tool post of the lathe enables the work piece W to be machined by the device along any axis parallel to axes X, Y, Z or at virtually any angle thereto.

Once the device is clamped in place on the lathe the lathe controls 15, 18 are used to displace the device along axes X and Y, and by adjustment of the Woods tool holder a limited amount of motion along axis Z so that cutting tool 32 can be appropriately positioned relative to that part of the workpiece W which is to be machined. In this case a set of flats are to be machined on workpiece W to provide a hexagonal section on it.

The range of operating speed of the device 20 is established by means of the selector 25 in the light of factors such as the geometry and the material of the tool and workpiece. The lathe displacement controls 15, 18 and any others required are used to position the cutting tool 32 relative to the workpiece W and the motor 22 started. Speed control 26 is used to establish the appropriate tool speed. Once the cutting operation is completed the lathe controls are used to withdraw the tool 32 to enable the chuck and workpiece to be rotated sufficiently to present the next part of the workpiece W which is to be machined. Once the necessary machining steps on the workpiece have been completed the device 20 is removed and a conventional parting tool used to separate the workpiece from the remaining stock gripped in the chuck.

In this particular case the cutting tool 32 is a milling cutter but any rotatable cutting or material removing tool can be used including reaming or thread cutting tools. It will be apparent that the ability to provide a substantial torque at low motor speeds advantageously enables the device to be used with a wide range of cutting tool sizes and materials including those of relatively large diaeter where the rotary speed has to be kept low to provide a suitable cutting speed on a given work piece material.

Claims (6)

CLAIMS An auxiliary machining device comprising: 1 a drive unit including an electric motor characterised by a rotary output shaft, a speed controller for the motor whereby output shaft speed can be varied, and an output torque of the output shaft which is substantially independent of output shaft speed at least at low motor speeds; 2 a tool holder, for a cutting tool, adapted to be driven by the drive unit so as to rotate a cutting tool retained in the holder; and 3 a mounting chassis for the drive unit and the toolholder, whereby the device can be secured to a conventional tool carrier of a machine tool, such as a lathe, so as to enable the device to be controllably displaced along three axes at right angle to one another by conventional tool carrier locating controls or adjustments on the machine tool; the chassis including adjustable locating means whereby one of a predetermined plurality of fixed locations for the tool holder relative to a datum location on the chassis can be selected prior to securing the chassis to a carrier as aforesaid. 2 An auxiliary machining device as claimed in Claim 1 wherein the drive unit incorporates a gear box or other speed ratio establishing means whereby one of two of more speed ratios between the output shaft and the tool holder can be established independently of the output shaft speed established by the controller. 4 A method of auxiliary machining on a machine tool (such as a lathe) comprising the steps of

1 mounting on a tool support of a machine tool an auxiliary machining device, by way of a chassis incorporated in the device the tool holder having initially been located at one of the plurality of predetermined positions relative to the chassis;

2 mounting a cutting tool on the tool holder;

3 utilising displacement controls of the machine tool to position the cutting tool at a workpiece machining location of the machine tool; and

4 causing the motor to drive the cutting tool about a first axis by way of the transmission shaft so as to enable the cutting tool to act on a workpiece located at the workpiece machining position.

5 An auxiliary machining device as hereinbefore described with reference to the accompanying drawings.

6 A machine tool, such as a lathe, equipped with an auxiliary machining device as claimed in Claim 1, Claim 2 or Claim 5.