GB2097303A - Cutting machines - Google Patents

Abstract

A spindle assembly (8) for a cutting machine comprises a spindle (10) and a cutting head (22), from which a cutting tool (24) projects radially. In operation, an hydraulic force is applied between the cutting head 22 and the spindle (10) (specifically a flange (20) to which the cutting head (22) is secured, and a housing (26) mounted on the spindle (10)) to cause the longitudinal axis of the cutting head (22) to become inclined to the longitudinal axis L/A. of the spindle (10). Thus the cutting head (24) circumscribes a circle of larger radius; when the cutting operation is concluded, said force is removed, returning the cutting head (22) to a condition of colineality with the spindle (10), wherein the cutting tool (24) circumscribes a circle of smaller radius and can be withdrawn. <IMAGE>

Description

SPECIFICATION Improvements relating to cutting machines Description of Invention This invention is concerned with improvements relating to cutting machines, particularly of the kind (hereinafter referred to as being of the kind specified) used to provide a workpiece with an internal or an external cylindrical surface.

For example, whilst the rough boring of holes into workpieces presents little difficulty, problems are encountered in the provision of an existing hole with a smooth surface finish of an accurately predetermined diameter.

Conventionally used in such operations is a machine comprising a cutting head which mounts a radially extending cutting tool, means to secure the workpiece on the longitudinal axis adjacent to the cutting tool, means to cause relative rotation between the workpiece and the cutting tool on said longitudinal axis, and means to cause relative movement of approach between the workpiece and the cutting tool so that the cutting tool enters the hole, the cutting tool travelling along the hole while such relative rotation is effected, and cutting a small quantity of material to provide a smooth and accurate surface finish to the hole.

However on completion of the boring stroke, retraction of the workpiece from the cutting head tends to cause the tool to score the workpiece, producing a draw back line or scrole.

To overcome this problem, it is common practice to mount the cutting tool of the head for retractive movement, so that on completion of the cutting operation the tool may be moved towards the longitudinal axis prior to retraction of the tool from the workpiece.

However such arrangements tend to be complicated, and the inevitable reduction in rigidity which is produced tends to limit the accuracy which can be attained, and causes problems of wear.

Analogous problems may be encountered in certain circumstances, in the provision of an existing external cylindrical surface with a smooth surface finish of an accurately predetermined diamter.

It is one of the objects of this invention to provide a cutting machine in which problems encountered in existing arrangements are reduced or overcome.

According to this invention there is provided a spindle assembly for a cutting machine of the kind specified, said assembly comprising a spindle having a longitudinal axis, a cutting head adapted to carry a cutting tool and having longitudinal axis, and which is secured or adapted to be secured to the spindle in a manner in which the longitudinal axis of the cutting head is co-linear with the longitudinal axis of the spindle, and operating means which is operative between the spindle and the cutting head, or parts secured thereto, to cause the longitudinal axis of the cutting head to become inclined to the longitudinal axis of the spindle.

Thus, in the use of the cutting machine of which the spindle assembly forms part, on actuation of said operating means to cause the longitudinal axis of the cutting head to become inclined to the longitudinal axis of the spindle, the cutting tool will circumscribe a larger radius, producing a finished bore of larger diameter, than would otherwise have been achieved, had said means not been so actuated. On completion of the boring stroke and prior to the retraction stroke, said means may be rendered inoperative allowing the longitudinal axis of the cutting head to return to its position of colineality relative to the longitudinal axis of the spindle, and withdrawal of the cutting tool from the bore may be effected without the production of any draw back line or scrole.

Advantageously the spindle assembly comprises a deflection member having a first portion secured rigidly to the spindle and a second portion secured rigidly to the cutting head, the operating means being operative between the spindle and said second portion to cause deflection of an intermediate portion of the deflection member.

Advantageously the operating means is operative against said second portion at one or more positions spaced from the longitudinal axis of the cutting head.

Advantageously the operating means comprises one or more fluid, preferably hydraulic, operating devices.

Preferably the spindle assembly comprises a stop, which may be adjustable, which is operative between the second portion and the spindle to limit deflection of the intermediate portion, preferably the stop being positioned generally diametrically opposite to the position or positions at which the operating means is operative.

According to this invention there is also provided a cutting machine comprising a machine frame defining a longitudinal axis, a cutting head which is adapted to cary a cutting tool, a work holder adapted to carry a workpiece, drive means to cause relative rotational movement between the cutting head and the work holder on said longitudinal axis, advancement means to cause relative movement of advance and retraction between said cutting head and said work holder along said longitudinal axis, and operating means which is operative in the operation of the machine to deflect the cutting head relative to the longitudinal axis.

Conveniently the cutting head is mounted on a forward end portion of an elongate deflection member, and on actuation of the operating means a force is appled to deflect said forward end portion of the deflection member from the longitudinal axis. Where the cutting head is mounted for rotation, conveniently the elongate member is afforded by or secured to a driven spindle which is mounted for axial rotation in the machine frame.

Conveniently the cutting head is deflected from the longitudinal axis by fluid pressure means, preferably hydraulic, into engagement with a stop, which ensures an accurate determination of the degree of deflection, and hence accuracy of the diameter of the finished bore produced by the machine.

The stop may be positionally adjustable, whereby the degree of deflection may be adjusted, as is required.

According to this invention there is also provided a method of providing a workpiece with a smooth internal or external cylindrical surface, involving the use of a machine which comprises a spindle carrying a cutting head from which a cutting tool projects radially, and wherein the workpiece and the cutting head are subjected to relative rotation about an axis co-axial with said cylindrical surface, and linear movement of approach and separation along said longitudinal axis, wherein during an initial stage of the operation of the machine the cutting head or a part to which it is secured is subjected to a force to cause the cutting head to be deflected relative to said longitudinal axis, and during a final stage in the operation of the machine the cutting head is restored to is original position.

The invention may be utilised in a boring machine adapted to provide an existing hole, (which may be bored, cast or otherwise formed) with a smooth interior cylindrical surface of an accurately predetermined diameter.

The invention is conveniently utilised, as is described hereinafter in detail, in a boring machine of the kind in which the work holder is rotationally stationary and the cutting head rotates.

However the invention may also be utilised in machines of the kind in which the cutting head is rotationally stationery on the longitudinal axis and the work holder rotates.

Additionally the invention may be utilised in the provision of an existing external cylindrical surface with a smooth exterior surface finish of an accurately predetermined diameter.

There will now be given a detailed description, to be read with reference to the accompanying drawings, of a boring machine which is a preferred embodiment of this invention, and which has been selected for the purposes of illustrating the invention by way of example.

In the accompanying drawings: Figure 1 is a front elevation of the machine which is the preferred embodiment of the invention; Figure 2 is a side elevational view of the machine, part being in part section; Figure 3 is an enlarged sectional view of part of the machine taken on the line 3-3 of Fig. 1; and Figure 4 is a sectional view taken on the line 4-4 of Fig. 1.

The machine which is the preferred embodiment of this invention is specifically adept in the finishing of holes previously formed in a workpiece, and comprises a spindle assembly 8, which is also illustrative of the invention, and which comprises a spindle 10 mounted for rotation in bearings about a longitudinal axis L/A and a cutting head 22 secured to the spindle 10. The cutting head 22 has a longitudinal axis which when the machine is at rest is aligned with the longitudinal axis L/A. The machine also comprises a work holder (not shown) to which a workpiece may be securely clamped in a position in which a hole thereof which is to be finish bored lies on the longitudinal axis L/A.

The spindle 10 is provided with a central bore 12, through which an elongate member 14 extends. An elongate deflection member 16 is secured at a first rearward end portion thereof to the member 14, a central portion 18 of the member 16 being reduced in diameter. A second outer end portion of the deflection member 16 is provided by a radially extending lange 20, and the cutting head 22 secured to the flange, extending axially therefrom. A cutting tool 24 may be secured to the cutting head with the cutting tool projecting radially outwardly from the longitudinal axis of the cutting head.

The machine comprises operating means which is provided by deflector mechanism, adapted to deflect the deflection member 16, and hence the longitudinal axis of the cutting head 22, a short distance from the longitudinal axis L/A of the spindle. A housing 26 is bolted to a forward end of the spindle 10 by four bolts 27, said housing 26 comprising a stem 28 which extends into an axial recess in the spindle 10 and which extends around the deflection member 16. The deflector mechanism comprises two fluid-operated (specifically hydraulic) piston/cylinder devices 32, each comprising a cylinder 34, afforded by a recess in an upper and radially outer portion of the housing 26, the two cylinders 34 being arcuately separated, as is shown in Fig. 1.

Extending from each cylinder 34 through the stem 28 of the housing is a bore 36, said bores extending to a circumferential reservoir 38 afforded between the stem and the deflection member 16 (Fig. 3). Mounted within each cylinder 34 is a piston 39, a nose 40 of which bears against an inner side of the flange 20 of the deflection member 16.

The deflector mechanism also comprises a stop device 41, comprising a recess 42 afforded in a lower part of the housing 26, in which an inner V-block 43 is secured. Se cured in a recess 45 to a lower portion of the flange 20 at a position by bolts 44a and pins 44b opposite the recess 42, by bolts 45a and pins 45b is an outer V-block 46, the block 46 projecting a short distance into the recess 42, a roller member 48, affording a stop, being located between the two V-blocks.

Secured to the periphery of the housing 26, and sealingly engaging the periphery of the flange 20, is a circumferential sealing member 52.

The member 14 is provided with an axial bore 60, which opens into a space 62 between the leading end of the bar and a recess in the deflection member 16 within which said leading end of the member 14 extends.

A radial bore 64 extends through the deflection member 16 from said space 62 to the reservoir 38.

At its rear end, the member 14 is connected to a rotary union 66, by which hydraulic fluid at constant pressure may be fed through an inlet thereof into the axial bore 60 of the bar.

The machine also comprises a drive motor 70, operative to rotate the spindle 10 on said longitudinal axis L/A through a belt 72.

The machine which is the preferred embodiment of this invention is one in which the cutting tool is rotated about the longitudinal axis of the machine, whilst the workpiece is maintained axially stationary by the work holder, and advanced onto the rotating cutting tool. However the invention may be utlised in machines of other kind, such as those in which the cutting tool is maintained rotationally stationary, the work holder serving to rotate the workpiece, and/or in which the cutting tool advances axially into engagement with an axially stationary workpiece.

In the use of the machine which is the preferred embodiment of this invention, in carrying out a method which is also illustrative of certain aspects of the invention, with the drive motor running under rest conditions (i.e.

no fluid applied to the rotary union 66), the member 14, the spindle 10, the deflection member 16, the cutting head 22 and cutting tool 24 rotate about the longitudinal axis L/A, with the cutting tool travelling around a circle Xl (Fig. 3). However on the application of fluid under pressure to the rotary union, such fluid is applied, by way of the axial bore 60 in the bar, the space 62, the radial bore 64, reservoir 38, and bores 36, to the two cylinders 34, causing the pistons thereof to move outwardly, and the noses 40 to move into engagement with the flange 20 of the deflection member 16, causing the deflection member 16 to deform or deflect at its central, reduced portion 1 8. Such deflection of the member 16 causes the portion of the flange 20 which is generally opposite to the two piston/cylinder devices 32 to move towards the housing 26 of the deflector mechanism, and the outer V-block 64 to move further into the recess 42, into engagement with the roller member 48, such engagement limiting the degree of deflection effected. The longitudinal axis of the cutting head 22 is thus moved out of alignment with the longitudinal axis L/A of the spindle 10 and thus on by operation of the drive motor 70, the cutting tool 24 will circumscribe a circle whose radius is X2 (Fig.

3).

In the use of the machine, with the deflection member 16 so deflected, the machine is used to finish a previously formed hole in a workpiece, to a radius X2. On conclusion of the boring stroke, and prior to initiation of a retraction stroke, the application of fluid under pressure to the cylinders 34 is releaxed, allowing the deflection member 16 to adopt its undeflected position, and allowing the cutting tool 24 to return to the circle whose radius is X1. In this manner, the cutting tool may be retracted from the finished bore, without touching the sides of the bore and producing any scoring or draw back line.

As will be seen in Fig. 3, the two piston/ cylinder devices are spaced so as to produce maximum effect to the flange 20 on one side of a diameter, whilst the stop device 41 is located medially on the opposite side of the diameter, to produce maximum accuracy. The degree of deflection permitted may be varied by adjustment of the position of the outer Vblock 46.

By the use of the invention, the effective radius of the cutting tool may, by application of fluid under pressure to the deflector mechanism, be increased by up to 0.015 inches, to a high degree of accuracy.

However, in practice, a deflection of between 0.002 inches and 0.010 inches is sufficient depending upon the diameter of the hole being drilled, and upon the materials being used. In a typical operation, a deflection capability of 0.007 inches was used.

Claims (17)

1. A spindle aasembly for a cutting machine of the kind specified, the assembly comprising a spindle having a longitudinal axis, a cutting head adapted to carry a cutting tool and having a longitudinal axis and which is secured or adapted to be secured to the spindle in a manner such that the longitudinal axis of the cutting head is co-linear with the longitudinal axis of the spindle, and operating means which is operative between the spindle and the cutting head, or parts securd thereto, to cause the longitudinal axis of the cutting head to become inclined to the longitidinal axis of the spindle.

2. A spindle assembly according to Claim 1 comprising a deflection member having a first portion secured rigidly to the spindle and a second portion secured rigidly to the cutting head, the operating means being operative between the spindle and said second portion to cause deflection of an intermediate portion of the deflection member.

3. A spindle assembly according to Claim 2 wherein said operating means is operative against said second portion at a position spaced from the longitudinal axis of the cutting head.

4. A spindle assembly according to Clam 3 wherein the operating means is operative at two positions spaced circumferentially around the longitudinal axis of the cutting head.

5. A spindle assembly according to any one of the preceding claims wherein the operating means comprises one or more fluid operating devices.

6. A spindle assembly according to any one of Claims 1 to 5 comprising a stop operative between the cutting head and the spindle to limit the degree to which the longitudinal axis of the cutting head becomes inlined to the longitudinal axis of the spindle.

7. A spindle assembly according to Claim 6, as appendend to any one of Claims 2 to 5, wherein the stop is positioned generally diametrically opposite to the position or positions at which the operating means is operative.

8. A cutting meachine comprising a machine frame defining a longitudinal axis, a cutting head which is adapted to carry a cutting tool, a work holder adapted to carry a work piece, drive means to cause relative rotational movement between the cutting head and the work holder on said longitudinal axis, advancement means to cause relative movement of advance and retraction between said cutting head and said work holder along said longitudinal axis, and operating means which is operative in the operation of the machine to deflect the cutting head relative to the longitudinal axis.

9. A machine according to Claim 8 wherein the cutting head is mounted on a forward end portion of an elongate deflection member, and on actuation of the operating means a force is applied to deflect said forward end portion of the deflector member from the longitudinal axis.

10. A machine according to any one of Claims 8 and 9 wherein the cutting head is mounted for rotation, and the elongate member is afforded by or secured to a driven spindle which is mounted for axial rotation in the machine frame.

1-1. A machine according to any one of Claims 8 to 10 wherein the cutting head is deflected from the longitudinal axis by fluid pressure means into engagement with a stop.

12. A machine according to Claim 11 wherein said stop is adjustable.

13. A method of providing a workpiece with a smooth internal or external cylindrical surface, involving the use of a machine which comprises a spindle carrying a cutting head from which a cutting tool projects radially, and wherein the workpiece and the cutting head are subjected to relative rotation about an axis which is coaxial with said cylindrical surface, and linear movement of approach and separation along said longitudinal axis, wherein during an initial stage in the operation of the machine the cutting head or a part to which it is secured is subjected to a force to cause the cutting head to be deflected relative to said longitudinal axis, and during a final stage in the operation of the machine the cutting head is restored to its original position.

14. A spindle assembly for a cutting machine of the kind specified, constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.

15. A machine of the kind specified, constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.

16. A method of providing a workpiece with a smooth internal or external cylindrical surface, when carried out substantially as hereinbefore described with reference to the accompanying drawings.

17. Any novel feature or novel combination of features hereinbefore described and/or shown in the accompanying drawings.