GB1565062A

GB1565062A - Apparatus for generating spherical surfaces by machining

Info

Publication number: GB1565062A
Application number: GB2055976A
Authority: GB
Original assignee: Dunbar & Cook Ltd
Current assignee: Dunbar & Cook Ltd
Priority date: 1977-06-27
Filing date: 1977-06-27
Publication date: 1980-04-16

Description

(54) APPARATUS FOR GENERATING SPHERICAL SURFACES BY MACHINING (71) We, DUNBAR & COOK LIMITED, a British Company of New John Street, Aston, Birmingham B6 4LF, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the followmg statement: This invention relates to an apparatus for generating spherical surfaces by machining.

An object of the invention is to provide new and improved apparatus for generating spherical surfaces easily and to a high degree of accuracy.

According to the present invention we provide an apparatus for generating spherical surfaces comprising a rotatable support for a workpiece, a first cutting tool head which is traversable along an arcuate path about an axis to the axis normal of rotation of the workpiece and a honing tool rotatable about an axis which is normal to the axis of rotation of the workpiece and which is fed to the workpiece along its own rotational axis.

The axis of rotation of the honing tool may be parallel to or lie in a plane defined by the arcuate path of travel of the cutting edge of the first cutting tool head.

The plane may contain the axis of rotation of the workpiece.

The workpiece may be provided with a through bore in which is received the means for mounting the workpiece on the support and in such a case it is desirable to bevel the surface of the workpiece where the external spherical surface meets the bore.

Accordingly a pair of further cutting tool heads may be provided each having a cutting tool adapted to act on the surface of the workpiece where said surface and a through bore in the workpiece meet in order to form a bevel on the workpiece at said location.

Fluid operated, preferably hydraulic, means may be provided to produce the traversing movement of the first cutting tool head and the feed movement for the honing tool and, when provided, said further cutting tool heads.

The first cutting tool head may be provided with two cutters movable alternatively into cutting relation with the workpiece; preferably in use the two cutters are mounted one vertically above the other and there being fluid operated means to move the cutters vertically up and down into respective cutting relationship with the workpiece.

The axis of rotation of the workpice, the axis of rotation of the honing tool and the direction in which the further cutting tool heads may be advanced towards the workpiece into cutting relationship therewith may all be parallel to or lie in the plane defined by the arcuate path of travel of the first cutting tool head.

The invention will now be described in more detail by way of example with reference to the accompanying drawings wherein: Figure 1 is a diagrammatic plan view of an apparatus embodying the invention, Figure 2 is a transverse cross sectional view on the line 2-2 of Figure 1, Figure 3 is a longitudinal cross sectional view on the line 3-3 of Figure 1, and Figure 4 is a fragmentary cross sectional view, illustrating the bearing arrangement for the first cutting tool head of the apparatus shown in Figures 1 to 3.

Referring now particularly to Figure 1, there is illustrated an apparatus for generating a spherical surface comprising a base part 10 on which is rotatably mounted an expandable mandrel 11 carried on spindle 12 rotatably mounted on a head part 13 of the apparatus and driven, through suitable variable speed means by an electric motor not shown. A centre 14 is received within a conical recess 15 in the end of the spindle 12 in order to support the spindle 12, the centre 14 being rotatably mounted on a tail part 16 of the apparatus.

The expandable mandrel 11 is of conventional construction and is adapted to secure a blank 17 to the spindle 12 by being engaged within an internal cylindrical passage 18 formed in the blank.

A first cutting head 20 is mounted on an arm 21 which slides on a track 19 and which as best shown in Figure 4, is attached by bolts 22 to a flange 23 at the upper end of a relatively massive shaft 24 which is mounted by taper bearings 25 and ball races 26 on the base part 10 of the apparatus.

Secured to the shaft 24 by means of a key connection 27 is a gear 28 engaged by a rack 29 whereby movement of the rack 29 by a double acting hydraulic ram, not shown, causes rotation of the shaft 24 and hence traversing of the first cutting tool head 20 along an arcuate path. The axis of rotation of the shaft 24 is arranged to lie vertically and to precisely intersect the axis of rotation of the spindle 12. Hence rottion of the shaft 24 causes traversing movement of the first cutting head 20 along an arcuate path which lies in a horizontal plane the centre of curvature of which is coincident with the axis of rotation of the spindle 12 and hence of the workpiece 17.

It is to be noted that the shaft 24 and its bearing arrangement are arranged to be massive and accurate to ensure that the arcuate path of the first cutting head is precise.

The head 20 is slidably mounted on the arm 21 for movement towards and away from the workpiece. A double acting hydraulic ram. not shown, is provided to move the head into and out of position for cutting engagement with the workpiece. A stop is provided to limit inward movement of the head and the stop is adjustable to permit adjustment of the depth of cut.

As best shown in Figure 2 the first cutting head 20 has a tool holder 30 slidably mounted therein for movement in a vertical direction. The tool holder 30 is provided with a dove-tail guide, not shown, and a pair of hydro-pneumatic, not shown, cylinders are provided to clamp against the dovetail to secure the toolholder in an upper or lower position.

The toolholder is moved between the upper tnd lower positions by means of a piston rod 31 connected by bolts 32 to the holder 30. At its lower end the piston Irod 31 carries a piston 33 slidable within a cylinder 34 and there being suitable sealing means as well as further seals 36 being provided between the piston rod 31 and a sleeve 37 in which it is slidably mounted and a seal 36a between the sleeve 37 and the part of the head 20 in which the sleeve 37 is mounted.

The tool holder 30 carries a pair of cutting tools 38 and 39 which are clamped to the tool carrier, in conventional manner, by screws 40.

The tools 38 and 39 are of conventional configuration and the lower tool 38 is moved into cutting engagement with the workpiece 17 to form an initial cut in the workpiece when the toolholder 30 is moved by the piston 33 into its upper position, whilst the tool 39 is moved into cutting engagement with the workpiece 17 to provide a finishing cut when the toolholder 30 is moved into its lower position by the piston 33. Because in the lower position of the toolholder 20 the undersurface 20a of the holder engages the surface 20b and because the hydropneumatic clamps are in clamping engagement with the dove-tail the toolholder is located precisely hence permitting a very precise spherical surface to be formed on the workpiece.

A honing tool 41 comprising five carborundum sticks 42 mounted in a holder 43 is mounted on a spindle 44 rotatably mounted in bearings 45 in a support part 45a of the apparatus. The spindle 44 is drivtn by an electric motor 46 by a belt drive 47 and gears 48. The axis of rotation of the spindle 44 lies ;n a vertical plane which intersects the axis of rotation A-A of the workpiece.

The support part 45a is slidably mounted on the base 10 and a hydraulic double acting ram 49 is connected between the base and the support part 45a in order to move the honing head 41 towards and away from the workpiece.

Two further cutting heads 50 carrying bevel tools 51 are carried at the lower end of shafts 52 which are mounted in support heads 53 there being an adjustment device 54 provided whereby a vertical adjustment of the tools 51 is provided so as to accommodate different sizes of workpiece.

In use. a workpiece in the form of a generally spherical forging, casting or machined element is provided with a cylindrical axial bo -e and, if desired, a chordal slot or any other desired machined configuration depending upon the application of the workpiece. The workpiece is then mounted on the spindle 12 by means of the mandrel 11 and the spindle 12 caused to rotate. The first cutting head 20 is then caused to traverse from its extreme position adjacent head 16 to a further position adjacent the head 13, after. of course. bringing the tool 38 into cutting relationship with the workpiece. The head 20 is traversed whilst the workpiece rotates with the result that a spherical surface is formed on the workpiece. When the head 20 has reached the other extremity of its travel the other tool 39 is brought into operative relationship with the workpiece and the tool traversed back so that a fine cut is formed on the workpiece.

The bevelling tools are then brought into operative relationship with the workpiece by operation of the rams 56 and the desired bevel formed on the workpiece at the position of meeting between the external spherical surface and the bore 18.

Finally, the honing tool is caused to rotate by the motor 46 and the ram 49 is operated to bring the honing tool into pressure engagement with the surface of the workpiece whilst the workpiece is again rotate.

As honing continues the pressure applied to the workpiece by the honing tool is reduced and the speed of rotation of the workpiece is increased to provide a final finish of high quality. The speed of rotation of the workpiece and honing tool and the speed of feed or the various heads varies during operation of the machine to give a high quality finish and the machine may be provided with automatic control means whereby the machine performs the above described sequence of operations automatically.

Means are provided whereby the speed of rotation of feed and sequence of operations can be adjusted manually if desired. In the present example the workpiece may be rotated at a speed lying in the range 136 513 rpm and the honing tool at a speed in the range 196 - 1175 rpm. The actual speeds used are selected in relation to the workpiece size, type and specification of the honing tool.

The apparatus is capable of producing a surface with no more than plus or minus 0.0005" deviation from a true sphere and with a surface finish of up to about 4 cla.

The machine described in the example is capable of handling work-pieces up to about 1'in diameter but similar machines made to a larger scale can deal with spheres up to 30" in diameter.

WHAT WE CLAIM IS: 1. An apparatus for generating spherical surfaces comprising a rotatable support for a workpiece, a first cutting tool head which is traversable along an arcuate path about an axis normal to the axis of rotation of the workpiece and a honing tool rotatable about an axis which is normal to the axis of rotation of the workpiece and which is fed to the workpiece along its own rotational axis.

2. An apparatus according to Claim 1 wherein the axis of rotation of the honing tool is parallel to a plane defined by the arcuate path of travel of the cutting tool edge of the first cutting tool head.

3. An apparatus according to Claim 1 wherein the axis of rotation of the honing tool lies in a plane defined by the arcuate path of travel of the cutting edge of the first cutting tool head.

4. An apparatus according to claim 2 or claim 3 wherein the plane contains the axis of rotation of the workpiece.

5. An apparatus according to any one of the preceding claims wherein a pair of further cutting tool heads are provided each having a cutting tool adapted to act on the surface of the workpiece where said surface and through a bore in the workpiece meet in order to form a bevel on the workpiece at said location.

6. An apparatus according to any one of the preceding claims wherein fluid operated means are provided to produce the traversing movement of the first cutting tool head and the feed movement for the honing tool and, when provided, said further cutting tool heads.

7. An apparatus according to any one of the preceding claims wherein the first cutting tool head is provided with two cutters movable alternatively into cutting relation with the workpiece.

8. An apparatus according to Claim 7 wherein in use the two cutters are mounted one vertically above the other.

9. An apparatus according to Claim 8 wherein fluid operated means are provided to move the cutters vertically up and down into respective cutting relationship with the workpiece.

10. An apparatus according to any one of the preceding claims wherein the axis of rotation of the workpiece, the axis of rotation of the honing tool and the direction in which the further cutting tool heads when provided, may be advanced towards the workpiec'e into cutting relation therewith all be parallel to or lie in the plane defined by the arcuate path of travel of the first cutting tool head.

11. An apparatus substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

12. A workpiece when produced on an apparatus as claimed in any one of the preceding claims.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the workpiece and the tool traversed back so that a fine cut is formed on the workpiece. The bevelling tools are then brought into operative relationship with the workpiece by operation of the rams 56 and the desired bevel formed on the workpiece at the position of meeting between the external spherical surface and the bore 18. Finally, the honing tool is caused to rotate by the motor 46 and the ram 49 is operated to bring the honing tool into pressure engagement with the surface of the workpiece whilst the workpiece is again rotate. As honing continues the pressure applied to the workpiece by the honing tool is reduced and the speed of rotation of the workpiece is increased to provide a final finish of high quality. The speed of rotation of the workpiece and honing tool and the speed of feed or the various heads varies during operation of the machine to give a high quality finish and the machine may be provided with automatic control means whereby the machine performs the above described sequence of operations automatically. Means are provided whereby the speed of rotation of feed and sequence of operations can be adjusted manually if desired. In the present example the workpiece may be rotated at a speed lying in the range 136 513 rpm and the honing tool at a speed in the range 196 - 1175 rpm. The actual speeds used are selected in relation to the workpiece size, type and specification of the honing tool. The apparatus is capable of producing a surface with no more than plus or minus 0.0005" deviation from a true sphere and with a surface finish of up to about 4 cla. The machine described in the example is capable of handling work-pieces up to about 1'in diameter but similar machines made to a larger scale can deal with spheres up to 30" in diameter. WHAT WE CLAIM IS:

1. An apparatus for generating spherical surfaces comprising a rotatable support for a workpiece, a first cutting tool head which is traversable along an arcuate path about an axis normal to the axis of rotation of the workpiece and a honing tool rotatable about an axis which is normal to the axis of rotation of the workpiece and which is fed to the workpiece along its own rotational axis.