GB2352198A - Non_circular profile cutting - Google Patents

Abstract

A device and method for cutting non-circular profiles in or on a workpiece comprises a rotatable drive shaft 16 securable in use to drive means, a non-rotatable cam profile 30 and an elongate toolholder 80 having first and second ends, the first end being suitable for holding a cutting tool 84 and the second end having a cam follower 92 provided thereon. The toolholder is pivotally and non-rotatably mounted about a point 98 intermediate its first and second ends on the drive shaft, the cam follower being disposed so as to follow the cam profile in use causing the toolholder to pivot about the point, and the cutting tool to thereby cut the shape of the cam profile in said workpiece.

Description

2352198 BORING AND OVERTURNING DEVICE The present invention relates to a

device for use in boring and overturning applications. More particularly, it relates to a boring device capable of boring non-circular bores, and 5 cutting non-circular external profiles on a workpiece (overturning).

Non-circular bores, for example elliptical, oval, square, hexagonal or other polygonal shapes are used in engineering in a wide variety of applications. The heads of bolts for use with allen keys provide a well known example. If such bores are to be mass produced, metal forming processes such as cold or hot impact extrusion are generally used.

If, however, bores are to be produced in smaller numbers, tooling up for these processes is not usually cost effective, and an alternative forming method must be used. Common methods include broaching, erosion machining, as well as interpolation using a milling cutter. However, these methods are generally time consuming to carry out, and in many cases the tools wear quickly and are costly to replace.

It is known from US 5 542 324 to Hormannsdorfer to produce a boring device comprising a drive shaft, a fixed housing and a toolholder, in which the toolholder and drive shaft are rotatably mounted in the housing. The drive shaft transmits a rotational force to the toolholder, and the toolholder, by means of a multiple cam and follower arrangement, is simultaneously deflected in a radial plane to cut a non-circular bore, The shape of hole bored is controlled by the shape of the cams. This device contains two or more cam rings which must be changed in order to alter the cam profile to be bored. Furthermore, angular positions of the cam rings must be assembled with the correct relative angular displacements in order for the device to operate as desired. Therefore, changeover from boring one hole type to another may be time consuming. Additionally, the range of hole sizes which may be bored are limited for a given size of device.

2 The present invention seeks to overcome, or at least mitigate the problems of the prior art.

According to the first aspect of the invention there is provided a device for cutting non circular profiles in or a workpiece, which device preferably comprising a rotatable drive shaft securable in use to drive means, a non-rotatable cam profile and an elongate toolholder having first and second ends. Preferably the first end may be suitable for holding a cutting tool and the second end having a cam follower provided thereon. The toolholder may be pivotally and non-rotatably mounted about a point intermediate its first and second ends on the drive shaft. The cam follower may be disposed so as to follow the cam profile in use causing the toolholder to pivot about the point, and the cutting tool to thereby cut the shape of the cam profile in said workpiece.

According to an optional feature of the first aspect of the invention the cam surface may be interchangeable in order that different shaped holes may be bored.

According to another optional feature of the first aspect of the invention biasing means may maintain contact between the cam and cam follower.

According to a further optional feature of the first aspect of the invention the pivot point may be located at a position substantially one third of the distance from the cam follower to the tip of the boring tool.

According to yet a further optional feature of the first aspect of the invention, the device may be adapted to cut non-circular bores in a workpiece. Alternatively, the device may be adapted to cut a non-circular exterior profile on a workpiece.

According to another optional feature of the first aspect of the invention means may be provided to set the orientation of the cam profile relative to the workpiece to be cut.

3 According to yet another optional feature of the first aspect of the invention the device may further comprise a fixed outer housing having an axial bore provided therein in which the drive shaft fits wherein the cam profile is provided on the surface of the bore.

According to yet another optional feature of the first aspect of the invention the device may the second end may comprise a bearing mounted on an off-centre spigot arranged so as to follow the cam.

According to yet another optional feature of the first aspect of the invention, the device may the cam profile may be provided on an outer surface of a fixed elongate member and the follower rotates around said outer surface.

According to an optional feature of the first aspect of the invention said means may comprise a resiliently biased engagement member provided in the outer housing and preferably arranged, in use, to engage an aperture provided on the drive means. Preferably, the engagement member further may comprise a projection arranged to engage the drive shaft and prevent relative rotation of the housing and drive shaft when the device is not in use.

According to another optional feature of the first aspect of the invention, the means may comprise an eccentric projection fixed to the cam surface, and preferably arranged to engage a hole provided in the workpiece.

According to another optional feature of the first aspect of the invention the fixed elongate member may be moveable longitudinally relative to the drive shaft. Preferably, biasing means may urge the elongate member away from the drive shaft.

According to another optional feature of the first aspect of the invention the cam follower may be adjustably mounted on the toolholder.

4 According to another aspect of the device there is provided a method of cutting a noncircular profile on a workpiece using a cutting device including a drive shaft, a toolholder and a cutting tool, preferably comprising the steps of selecting an appropriate non-circular cam profile, setting the diameter of the profile to be cut, orientating the cam profile in the desired position relative to the workpiece, applying rotary motion to the cutting tool via the drive shaft, wherein the cutting tool follows the shape of the cam profile, and advancing the workpiece towards the cutting tool.

According to a third aspect of the invention, the use of a device to cut a non-circular 10 profile on a workpiece is provided.

Embodiments of the present invention will now be described, by example only, with reference to the accompanying drawings, in which:

FIGURE I is a partial longitudinal cross-section through a device according to one embodiment of the invention; FIGURE I A is a partial longitudinal cross-section through a device according to a second embodiment of the invention; 20 FIGURE 2 is a cross- section through the device along the line "A"-"A" of Figure 1; FIGURE 3 is a longitudinal cross-section through a device according to a second embodiment of the invention; and 25 FIGURE 4 is a cross-section through the device of the third embodiment of the invention along the line "A"-"A" of Figure 3.

Referring to Figure 1, a boring device 10 is shown comprising an outer housing 12, a 30 drive shaft 16, and a toolholder 20.

In this embodiment, the housing comprises two parts, a main housing 14 having a bore 18 provided therein, and a secondary housing 20 having a catch mechanism 40, and a second bore 22 co-axial with the first bore 18. The main housing and secondary housing are secured together using bolts 38 or other suitable means known in the art. In a preferred embodiment, the two bores 18 and 22 are of differing diameters to aid the axial positioning of the drive shaft 16 within the housing. In alternative classes of embodiment, the housing may be manufactured in one piece.

In this embodiment catch mechanism 40 comprises an engagement member, for example, a button 48 mounted partially within a recess 46 provided on the secondary housing 20.

The button 48 is urged outwardly by resilient biasing means such as a helical spring 44. This causes projection 42 to engage within one of a plurality of slots provided on a collar 62 of the drive shaft 16. When the projection 42 is engaged, relative rotation between the drive shaft 16 and housing 12 is prevented. 15 Within the main housing 14, there is provided a counter bored portion 24 in which a sleeve 26 fits. The sleeve preferably comprises a cylindrical outer surface, and an inner surface, a portion of which is cylindrical 28 and another portion of which has a cam surface 30 with a profile corresponding to the desired shape of the bore to be machined by 20 the device. Figure 2 illustrates in transverse cross- section, an embodiment with a sleeve 26 having an ellipsoidal cam surface 30. A lip 32 is preferably provided at one end of the sleeve to allow bolts 34 to secure the sleeve 26 to the housing 12. In other classes of embodiments, alternative securing means known in the art may be used. In alternative embodiments, sleeves having polygonal and curved profiles, other than ellipses may be 25 used.

6 Preferably, means such as a projection (not shown) on the sleeve 26 which engages with a slot (not shown) on the housing 12 is used to ensure that the sleeve 26 has the correct angular position relative to the housing 12 and, therefore, the orientation of the cam profile 30 relative to the housing is also known. Alternatively, some form of indication of the orientation of the cam profile 30 on a visible surface of the sleeve 26 when in position within the housing 12 may be used. Bearing means, such as roller bearings 74, 76,78 are preferably provided to rotatably mount the drive shaft 16 within the housing 12.

Turning now to the construction of the drive shaft 16, this comprises a portion 60 for use in engaging drive means (not shown) provided by a milling machine, for example, and has a standard configuration for secure releasable engagement with the drive means. A collar 62 is provided for engagement with the catch mechanism 40 as described in more detail above. The remainder of the drive shaft 16 is journalled into the housing 12 and comprises a cylindrical shoulder portion 64 of greater diameter than the cylindrical main body of the drive shaft 66. In this embodiment, the shoulder 64 fits into the wider bore on the secondary housing 20, and thus aids the accurate axial location of the shaft 16 in the housing 12.

A blind bore 68 extends into the body of the shaft from the cutting end of the device, to define a cylindrical wall 72 an aperture 70 being provided in the wall 72 adjacent the cam profile. Pivotally mounted within the bore 68 is the toolholder 80. One end thereof protrudes out of the bore 68 and has mounted thereon a known cutting tool 82, for example a known Wohlhaupter tool. The tool 82 preferably comprises a hardened tungsten carbide cutting tip 84 to cut the desired shape of bore within a workpiece (not shown), and adjusting means 86 which may be turned to set the position of the tip 84.

The type of tool may, however, be changed depending upon the running speed of the device and/or the material of the workpiece to be cut.

7 An off-centre spigot 90 is provided on the opposite end of the tool holder 80. A cam follower 92, provided in this embodiment by a roller bearing is mounted on the spigot, and is secured by suitable means, for example, a bolt and washer arrangement 94. In alternative classes of embodiments, the cam follower may simply be provided by an appropriately located surface having a low friction or hardened coating provided thereon, for example.

Suitable means such as a pin (not shown) may be used to pivotally, but non-rotatably mount the tool holder 80 onto the wall of the drive shaft 72 about point 98. The axis of pivoting is provided in a position off-set from the longitudinal axis of the spigot 90. In a preferred embodiment, the distance from the cam follower 92 to the pivot point 98 is half the distance from the pivot point 98 to the cutting tip 84 of the tool 82.

The tool holder is sized to provide a sufficient gap between itself and wall 72 to permit a sufficient amount of pivoting motion for the cam follower 42 to follow the cam profile 36. Resilient biasing means, for example coil spring 96, is provided between the wall of drive shaft 72 and the tool holder 80 to urge the cam follower into contact with the cam profile 36 on the sleeve through the window 70 in the wall 72. In alternative classes of embodiment, a leaf spring or other suitable resilient biasing means may be used.

Grease nipples and ducts (not shown) are preferably provided on the housing to permit grease to be supplied to the cam follower, pivot and bearings for lubrication. Seals are also preferably fitted at the ends of the housing to prevent the unwanted escape of grease.

In use, the desired sleeve 26 with the desired cam profile is selected and fitted to the counterbored section 24 of the main housing 14. The drive shaft 16 is them fitted to the drive means. When multiple devices are to be interchanged frequently on a single milling machine, the tools are generally stored on a carousel, so that the machine may be programmed to automatically fit and subsequently remove each device as required. In this case, the catch mechanism 40 prevents unwanted relative rotation between the drive shaft 16 and cam profile whilst the device is stored. Were relative rotation to occur, then 8 the orientation of the non-circular hole bored into the workpiece would be incorrect. When the device is fitted onto the drive means of the machine (not shown) the projection 42 is forced to disengage the slots provided on the device, and the button engages an aperture provided on the machine. In this way, the non-circular aperture will be maintained in the correct orientation relative to the machine, and hence relative to the workpiece which is secured directly or indirectly to the machine.

The position of the cutting tip 84 is then set using by rotating adjusting means 86 using an allen key or the like which will thereby set the diameter of the hole to be bored.

The boring operation may then commence. As the drive shaft 16 rotates, the spring biasing means 96 urges the cam follower 92 into contact with the cam profile 36 on the inner face of the sleeve. This causes the tool holder 80 to swivel about the pivot point, forcing the cutting tip 84 to follow the locus of the cam follower 180' out of phase.

As mentioned above, in a preferred embodiment, the distance from the pivot point 98 to the tip 84 is twice that from the cam follower 92 to the pivot point. This causes the amplitude of the movements in the cutting tip 84 to be twice those of the cam follower 92 and thus reduces the amount of eccentricity in the movement and, therefore, the inertia loadings on the cam follower 92. In alternative embodiments the length from the pivot point 98 to the tip 84 may be increased to further increase the amplitude of the tip movement for a given cam profile.

For a given cam profile 30 and tool holder 80, the preferred method of varying the average diameter of the hole to be bored is to radially adjust the position of the cutting tip 84 in relation to the axis of the tool holder using the adjusting means 86 with the standard sized device, this permits the average diameter to be adjusted in 5 micron increments between 3) mm and 32 mm. Naturally, if the size of the overall device is changed, then non-circular holes of practically any desired average diameter may be bored.

9 Turning to Figure I A, there is shown a second embodiment of the invention. The second embodiment is essentially a modification of the first and, therefore, only the relevant altered portions will be discussed in detail and are indicated with the suffix "a".

By reducing the depth of the main and secondary housings 12a and 20a, and adjusting the configuration of the sleeve 26a such that is secured to approximately half way along its length to the main housing. The overall length of the device I Oa, as well as the amount of materials required in its manufacture, have been reduced in comparison with the device 10 of the first embodiment.

In order to accommodate a larger cam follower 92a and/or greater pivoting movement of the tool holder 80a, the window 70a has been increased in size and it is preferred that when the tool holder 80a is in its neutral position (i.e. in line with the axis of the drive shaft) the cam follower 92a is in contact with the widest part of the non-circular cam surface 30a.

The tool holder has been further altered in comparison with the first embodiment by the inclusion of a ball bearing 97a in the resilient biasing means, and the inclusion of four 0rings 93a fitted in recesses 81 a provided in the body of the tool holder 80a. The O-rings 80a serve to dampen any unwanted vibrations that may be induced during the use of the device, as well as providing a seal to minimise the escape of grease supplied to the cam arrangement via grease nipple 77a. It is envisaged that in alternative embodiments, the number of O-rings 93a may be increased or decreased according to particular operational requirements.

Turning now to Figures 3 and 4 which illustrate a third embodiment of the invention which operates on a similar principle to the first, with a cam follower 192 being attached to a cutting tool 184 via a pivoting arrangement. Like numerals have, where possible, been used for like parts with the addition of the prefix " I 5 Referring in particular to Figure 3, the device, in this embodiment, comprises a rotatable drive shaft 116 to which a tool holder 180 is pivotally secured. The drive shaft 116 comprises a first portion 160 for use in engaging drive means (not shown) provided by a milling machine, for example. Secured thereto by bolts, or other suitable means known in the art, is the second portion 166. A bore 168 is preferably provided along the axis of the drive shaft, and has a substantially circular elongate member 126 rotatably mounted therein on bearings 176 and 178. In alternative embodiments, the aperture may be blind, with the drive means end 160 being closed off. A portion of the elongate member has a cam profile 1330 provided thereon, preferably intermediate the two bearings 176 and 178 15 to minimise the bending stress on the elongate member 126. The end face of the elongate member proximate the drive means of the device is advantageously provided with a grease nipple 212, and duct 214 which allow grease to be pumped into the preferably hollow interior 216 of the elongate member 126. Further ducts 218, 220 are then preferably provided to allow grease to be supplied to the bearings 176, 178. In this 20 embodiment, the bore 168 allows grease to be supplied to the elongate member 126 without disassembling the device. The elongate member 126 is slidable within the bore 168 in the drive shaft 116 and has mounted on the end proximate the drive means resilient means such as a helical spring 25 200 which urges the elongate member 126 out of the bore 168. A stop 202 prevents the entire removal of the member 126. One end of the spring 200 is rotatably mounted on the drive shaft 116 using a roller bearing arrangement 222 for example such that the drive shaft 116 may rotate whilst the elongate member 126 remains stationary.

I I In order to prevent the elongate member 11.6 from rotating, it is secured to the Xvorkpiece W preferably by drilling a pilot hole eccentric to the rotational axis of the drive shaft 116 through which eccentric projection 204 mounted on the exterior end of elongate member 126 may fit.

The tool holder 180 may be provided with a cranked portion 206 shown in Figure 3), the offset of which may be altered to vary the size of the non-circular hole to be drilled. The toolholder 180 is pivotally mounted on portion 166 of the drive shaft 116 about pivot point 198 using a pin or other suitable means known in the art. Referring in particular to Figure 4, one end of the tool holder 180 has a threaded aperture 224 provided therein in line with a second aperture 226 provided in the drive shaft 116 and the cam profile 130 on the elongate member 126. A cam follower 192 is advantageously screwed into the aperture so as to project through the second aperture 226 and contact the cam profile surface 130. A replaceable wearing sleeve 228 with a low friction coating is preferably provided in the second aperture 226 to prevent the drive shaft 116 itself becoming wom as.

A known cutting tool 184 is mounted on the opposite end of the tool holder 180 from the cam follower 192. In this embodiment, the tool lacks the adjustment means of the first embodiment, as adjustments are carried out by screwing the cam follower 192 in or out within the aperture 224, or by replacing the tool holder 180 with a different cranked offset. In an alternative embodiment, a tool such as the adjustable tool 82 of the first embodiment may be fitted for the end of the tool holder 180. Rough adjustment may then be achieved using the cam follower 192, and fine adjustment using the adjusting means 86 of the tool 82. This alternative embodiment is, therefore, particularly applicable for applications in which greater cutting accuracy is required.

12 The cam follower 192 is biased into contact with the cam surface 130 by resilient means such as helical spring 196 held in place by spring holder 208. Detachable securing means such as one or more bolts 2 10 allow the spring holder 208 to be removed in order to allow the tool holder 180 to be changed, for example, for one with a differently offset cranked portion 206 for the reasons explained above.

It can be seen that, in order for boring to take place, a hole of the required depth must already be provided within the workpiece W, either by drilling a pilot hole or by casting a hole into the workplece. The hole will then be machined out further to the required profile by the tool 184.

In use, the required elongate member 126 including the cam profile 130 will be selected and is then fitted by separating portions 160 and 166 of the drive shaft 116 by undoing bolts (not shown) or other fixing means provided. Additionally, the required tool holder for a particular size of aperture will be selected and will be fitted by securing it onto portion 166 of the drive shaft and fitting spring holder 208 in place using bolt 210, Fine adjustment of the cutting diameter can then be achieved by adjusting the depth of the cam follower 192. Portion 160 of the drive shaft 116 is then secured to the milling machine and protrusion 204 is located within the hole provided on workpiece W.

Drive shaft 116 is then rotated whilst the elongate member remains stationary 126, and as the cam follower 192 follows the cam profile 130 the pivoting action causes the rotational movement of the tool to follow the cam 180' out of phase. Workpiece W is advanced towards the cutting tool 184 against the action of spring 200 causing the non-circular profile to be cut into workpiece W. The cam follower simultaneously traverses across cam profile 13)0 which will normally remain identical along its axial length. In some classes of embodiments, however, the cam profile 130 may be progressively altered along its length so that the profile cut in to the workpiece W may alter according to depth. For example, the hole may be caused to taper inwardly at increasing depths. To prevent the device I 10 being damaged in any way, stop 202 is positioned to impinge on surface 230 of the drive shaft before the cam follower 192 traverses the full length of cam profile 130.

13 In an alternative embodiment the shape of the toolholder 180 may be altered, for example by manufacturing the crank in the opposite direction and placing the tool 184 on the opposite face of the tool holder 180, such that the device may be used to cut non-circular profiles on the outer faces of workpieces (overturning). 5 It is envisaged that numerous changes may be made within the scope of the invention. For example, the axial length of the cam profile may be increased to allow holes of greater depth to be bored. Additionally, the length of the tool holder 180 and/or the position of the pivot point 198 may be adjusted in order to alter the amplitude of the path 10 traced by the cutting tool 184 during rotation.

Claims (20)

14 CLAIMS

I A device for cutting non-circular profiles in or on a workpiece, which device comprises a rotatable drive shaft securable in use to drive means, a non-rotatable cam profile and an elongate toolholder having first and second ends, the first end being suitable for holding a cutting tool and the second end having a cam follower provided thereon, wherein the toolholder is pivotally and non-rotatably mounted about a point intermediate its first and second ends on the drive shaft, the cam follower disposed so as to follow the cam profile in use causing the toolholder to pivot about the point, and the 10 cutting tool to thereby cut the shape of the cam profile in said workpiece.

2. A device according to claim I wherein the cam surface is interchangeable in order that different shaped holes may be bored.

3. A device according to claim I or claim 2 wherein biasing means maintains contact between the cam and cam follower.

4. A device according to any preceding claim wherein the pivot point is located at a position substantially one third of the distance from the cam follower to the tip of the 20 boring tool.

5. A device according to any preceding claim which is adapted to cut noncircular bores in a workpiece.

6. A device according to any one of the claims I to 14 which is adapted to cut a noncircular exterior profile on a workpiece.

7. A device according to any preceding claim wherein means is provided to set the orientation of the cam profile relative to the workpiece to be cut. 30

8. A device according to any preceding claim further comprising a fixed outer housing having an axial bore provided therein in which the drive shaft fits wherein the I cam profile is provided on the surface of the bore.

9. A device according to any preceding claim wherein the second end comprises a bearing mounted on an off-centre spigot arranged so as to follow the cam.

10. A device according to any one of claims I to 7 wherein the cam profile is provided on an outer surface of a fixed elongate member and the follower rotates around said outer 10 surface.

11. A device according to claim 7 wherein said means comprises a resiliently biased engagement member provided in the outer housing and arranged, in use, to engage an aperture provided on the drive means. 15

12. A device according to claim I I wherein the engagement member further comprises a projection arranged to engage the drive shaft and prevent relative rotation of the housing and drive shaft when the device is not in use.

13. A device according to claim 7 wherein the means comprises an eccentric projection fixed to the cam surface, and arranged to engage a hole provided in the workpiece.

14. A device according to any one of claim 10 wherein the fixed elongate member is 25 moveable longitudinally relative to the drive shaft.

15. A device according to claim 14 wherein biasing means urges the elongate member away from the drive shaft.

16. A device according to any one of claims 10 or 13 to 15 wherein the cam follower is adjustably mounted on the toolholder.

16

17. A method of cutting a non-circular profile on a workpiece using a cutting device including a drive shaft, a toolholder and a cutting tool, comprising the steps of selecting an appropriate non-circular cam profile, setting the diameter of the profile to be cut, orientating the cam profile in the desired position relative to the workpiece, applying rotary motion to the cutting tool via the drive shaft, wherein the cutting tool follows the shape of the cam profile, and advancing the workpiece towards the cutting tool.

18. The use of a device according to any one of claims I to 16 to cut a non-circular profile on a workpiece. 10

19. A device substantially as hereinbefore described.

20. A device substantially as hereinbefore described with reference to Figures I and 2 or 3 and 4 of the drawings.