Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B21/00—Machines or devices using grinding or polishing belts; Accessories therefor
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B19/00—Single-purpose machines or devices for particular grinding operations not covered by any other main group
  • B24B19/08—Single-purpose machines or devices for particular grinding operations not covered by any other main group for grinding non-circular cross-sections, e.g. shafts of elliptical or polygonal cross-section
  • B24B19/12—Single-purpose machines or devices for particular grinding operations not covered by any other main group for grinding non-circular cross-sections, e.g. shafts of elliptical or polygonal cross-section for grinding cams or camshafts
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B27/00—Other grinding machines or devices
  • B24B27/0076—Other grinding machines or devices grinding machines comprising two or more grinding tools

Definitions

• This invention relates to improvements in or relating to workpiece grinding apparatus.
• a method of workpiece grinding comprising the steps of:
• modified profile is meant an approximation to the final profile obtained using a grinding wheel so that a minimum of stock is left on non re-entrant parts of the profile but more stock may be left in regions of re-entrant parts of the profile.
• the abrasive belt is employed in accordance with the invention to remove the remaining stock from the parts of the workpiece having the modified profile including the stock in any re-entrant parts of the profile which cannot be removed- by a grinding wheel.
• a conventional grinding machine for grinding a workpiece such as a camshaft by a grinding wheel
• the workpiece is mounted between a headstock and a footstock which define a grinding station.
• the headstock and/or tailstock also rotate the workpiece in a conventional and controlled manner about an axis through the workpiece.
• a wheelhead mounts the grinding wheel and controls a reciprocating wheelhead feed to provide an action which puts the grinding wheel in the correct position during the rotation of each section of the workpiece being ground, to thereby generate the desired profiles therealong and to remove the grinding wheel therefrom.
• a profile is reduced in size in a controlled manner towards its finished size.
• the belt is similarly advanced and retracted in a reciprocal manner with a feed, to finish the workpiece as required.
• apparatus for grinding a workpiece comprises a grinding station having a grinding wheel mounted for rotation and reciprocal movement as aforesaid for producing a modified profile on the workpiece and associated therewith is an abrasive belt grinding facility adapted to finish grind the modified profile to the final profile whilst the shaft is still located between the same headstock and footstock in the grinding station.
• the belt grinding facility may be mounted for grinding with movement along the same abrasive axis as the grinding wheel at the grinding station, or along a different abrasive axis, which may be laterally spaced from the wheel abrasive axis, or opposite to but aligned with the abrasive axis of the wheel or in the same plane as the wheel but angled relative to the wheel abrasive axis.
• the headstock and footstock are mounted on a carriage which can be moved relative to the abrasive axis or axes of the wheel and belt, to present different regions of a workpiece in succession to the grinding station, the whole workpiece may be finished by way of a succession of separate wheel and belt grindings in the same machine.
• the grinding wheel and abrasive belt grinder and their respective drives and controls are incorporated in the wheelhead.
• the grinding wheel and abrasive belt assembly are both mounted on the wheelhead in such a manner that by rotating the wheelhead, typically through 180° about a vertical axis, either the grinding wheel or the abrasive belt can be presented to the workpiece.
• the abrasive belt may be driven independently by its own drive means or from the grinding wheel drive means.
• the drive means may to advantage be electronically and/or microprocessor controlled to control speed, direction of rotation, acceleration and deceleration as may be required to control the abrasive action of the wheel and belt. Where a single drive means is employed provision may be made to disconnect the drive to the grinding wheel and/or the belt by for example, a clutch such as an over-running clutch, or simply by controlled belt slackening.
• the wheelhead is separate from but mounted on an underslide which supports and guides the mechanism which determines the reciprocating axis of the wheel and belt, and indexing means is provided by which the wheelhead may be rotatably indexed to present one grinding device or the other and means is provided for locking the wheelhead when in either grinding position.
• indexing is incremental to allow for fine positioning of the wheelhead.
• the sequence of grinding in accordance with the invention comprises rough grinding consecutively all the camshaft lobes on a workpiece using the grinding wheel to produce modified cam profiles at each cam position, indexing the wheelhead through the appropriate angle to present the abrasive belt to the workpiece and finish grinding consecutively all the modified profiles along the camshaft to the required size and shape.
• the finished component can be unloaded and a new workpiece put in place whilst the wheelhead indexes to present the grinding wheel to begin again the sequence as described above.
• the abrasive belt is mounted alongside the grinding wheel and the belt and wheel are movable towards and away from the workpiece so that when the abrasive belt is grinding the grinding wheel is clear of the parts of the workpiece being ground by the belt and when the grinding wheel is to be engaged, the abrasive belt can be retracted so that the grinding wheel can be presented to the workpiece without the abrasive belt making contact with the workpiece.
• the grinding sequence typically involves rough grinding a component using the grinding wheel and then finish grinding the same part of the component using the abrasive belt before the wheelhead assembly is moved to the next region of the component to be ground.
• the abrasive belt is adapted to be engaged with the workpiece to finish grind a modified profile whilst the grinding wheel is actively rough grinding another axially spaced region of the workpiece. In this way workpieces can be finish ground in virtually the same time as would be required to rough grind it prior to a finish grinding sequence.
• the method and apparatus of the invention can be applied to non re-entrant component grinding.
• Figure 1a is a schematic view of a cam lobe adjacent to a grinding wheel for rough grinding in accordance with the invention and Figure 1b is a cam lobe adjacent to an abrasive belt for finish grinding in accordance with the invention
• Figure 2 is an elevation and plan of a combined grinding wheel and abrasive belt machine tool showing the grinding wheel presented to the workpiece
• Figure 3 is an elevation and plan view of a combined grinding wheel and abrasive belt machine tool showing the abrasive belt presented to the workpiece
• Figure 4 is an elevation and plan view of a combined grinding wheel and abrasive belt machine tool showing the grinding wheel and belt fitted alongside each other
• Figure 5 is an elevation and plan view of a combined grinding wheel and abrasive belt showing the grinding wheel and abrasive belt incorporated in separate grinding heads.
• Figure 1a shows a section of a grinding wheel 10, rotating in the direction of arrow 22 about an axis of rotation (not shown) and reciprocably. in the direction of arrows 13 to move wheel 10 and its grinding surface towards and away from a cam lobe 14 to be ground.
• the surface of wheel 10 engages the surface of lobe 14 at an imaginary plane 12 diametrically passing through the axis of rotation of wheel 10 and the base circle axis of lobe 14 at a variable point 24 of cam lobe 14.
• Lobe 14 is rotating in a controlled manner around an axis 18 in the direction of arrow 16.
• the cam lobe 14 has a modified profile 20 which remains after the rough grinding step. Cam lobe 14 is rotated about axis 18 to facilitate its grinding. The controlled angular rotation of the cam lobe 14 is complemented by a controlled reciprocal movement of the grinding wheel in the direction of arrow 13 so that it is in the correct position relative to the angle position of the cam lobe.
• Figure 1b shows a section of an abrasive belt 26 moving in direction of arrow 28 over cylindrically curved shoe. face 30 of fixed guide shoe 32.
• the fixed shoe may be replaced by a roller 33 driven by passage of the abrasive belt over its periphery.
• the belt assembly is selectably securable along axis 34, in the direction of the arrow 36.
• Belt 26 and its grinding surface is also movable in the direction of arrow 36 to move its grinding surface towards and away from the surface of the cam lobe 40 to be ground.
• FIG. 2 shows an elevation 46 and plan view 48 of a dual purpose grinding machine wherein a grinding wheel 50 is conventionally mounted on a spindle (not shown) which rotates in the direction of arrow 51 in a wheel housing 52 about an axis 54 and is driven by a drive motor 56.
• the grinding surface of grinding wheel 50 is in contact with the surface of a cam lobe 58 of a cam shaft 60, which is fixed between a headstock 64 and a footstock 62.
• Headstock 64 rotates cam shaft 60 in a conventionally controlled manner about an axis -66 and is in turn driven by an electric motor (not shown) housed in headstock 64.
• An approximate cam profile can thus be produced by advancing the grinding wheel surface towards cam lobe 50 until the approximate cam profile is achieved.
• Footstock 62 is slidable and securable along axis 66 in the directions indicated by arrow 68.
• Adjacent to the headstock 64 is a conventional truing or dressing device 70 which is manoeuvred by sliding headstock 64 across the face of grinding wheel 50 or belt 72 with device 70 in contact therewith for truing the grinding wheel 50 or abrasive belt 72 prior to use.
• headstock 64 is slid back and secured so as to secure workpiece 60 in position, so that truing device 70 is free of the grinding wheel 50 and belt 72.
• a wheelhead 92 also incorporates the abrasive belt assembly 76 which includes the belt 72. Conventional rotational indexing of the wheelhead through 180° about an axis 108 presents abrasive belt 72 instead of wheel 50 to workpiece 60.
• Wheelhead 92 is mounted on an underslide 106 which supports and guides wheelhead 92 for rotation about axis 108, so that wheelhead 92 can be rotatably indexed and rigidly locked (by locking means not shown) when in either grinding position.
• Wheelhead 92 is mounted on underslide 106 and driven backwards and forwards on slide 134 by a feed member 107 so that the abrasive belt 72 or grinding wheel 50 can be advanced or withdrawn from the workpiece as required at the beginning and ending of a grinding step and reciprocated so as to respond to the changing component profile during rotation of the latter and to readjust position for the next workpiece.
• Slide 134 is conventionally supported on the machine tool base 136.
• FIG 3 shows the grinding machine of Figure 2 with the abrasive belt in contact with the cam lobe.
• the belt mechanism comprises an abrasion belt tensioning pulley 78 attached by means of arm 80 to a securing member 84.
• the arms are attached to the securing member by means by pivot bearings 81, and to the body of the wheelhead 92 by means of a pneumatic cylinder 200.
• the pneumatic cylinder is retractable allowing the arm to swing down for fitting new belts.
• the pneumatic cylinder can then be extended at a controlled rate and pressure to correctly tension the abrasive belt 72.
• the abrasive belt is driven around a larger pulley 86 which is rotated by a belt drive 90 via drive motor 88.
• the larger pulley 86 is carried by the securing member 84 and the abrasive belt drive motor 88 is secured to the body of the wheelhead 92 via a vibration absorbing platform 94.
• the abrasive belt 72 also passes around two belt guide pulleys 96 and 98 which are also carried by securing member 100 so that they are equidistant from the guide shoe 102 and shoe supporting grooved member 104.
• the guide pulleys are located behind the guide shoe 102 so that the belt passing over the guide shoe protrudes forward of the guide mechanism enabling grinding of the workpiece 105 by the abrasive belt.
• Figure 4 shows plan 112 and elevation 114 of an embodiment of the machine wherein the abrasive belt mechanism and grinding wheel mechanism are adjacent to each other and wherein the abrasive belt extends forwardly of the abrasive wheel when the abrasive belt supporting grooved arm 116 has been lowered into the position shown in Figure 4(a).
• Alternation between abrasive mechanisms is by retraction of the abrasive belt shoe by rotation of supporting arm 116 around axis 118, so that the abrasive belt mechanism is now displaced behind the grinding wheel surface when viewed from the side.
• rotation of the arm 116 allows alternative abrasive wheel rough grinding and abrasive belt finish grinding operations, without the non grinding device interfering with the workpiece while the other is active.
• the abrasive belt 120 and the abrasive wheel 122 are located on separate wheelheads 124 and 126 on either side of the machine tool mounting 128. Both wheelheads are slidable over respective support members 130 and 132 and the abrasion mechanism is essentially as hereinbefore described except that in this embodiment it is possible to grind a workpiece from both sides.
• one part of the grinding wheel 122 is retracted and the abrasive belt 120 is advanced and engaged for finish grinding the same part, before the workpiece is axially advanced to present another region for rough grinding.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
• Grinding And Polishing Of Tertiary Curved Surfaces And Surfaces With Complex Shapes (AREA)
• Grinding Of Cylindrical And Plane Surfaces (AREA)
• Constituent Portions Of Griding Lathes, Driving, Sensing And Control (AREA)

Priority Applications (4)

Applications Claiming Priority (4)

Publications (1)

Family

ID=26302211

Family Applications (1)

Country Status (7)

Cited By (4)

Families Citing this family (1)

Citations (6)

• 1993
  • 1993-12-16 AT AT94902880T patent/ATE169543T1/de not_active IP Right Cessation
  • 1993-12-16 EP EP94902880A patent/EP0675780B1/de not_active Expired - Lifetime
  • 1993-12-16 AU AU57055/94A patent/AU5705594A/en not_active Abandoned
  • 1993-12-16 CA CA002151400A patent/CA2151400C/en not_active Expired - Fee Related
  • 1993-12-16 WO PCT/GB1993/002569 patent/WO1994014571A1/en active IP Right Grant
  • 1993-12-16 ES ES94902880T patent/ES2120003T3/es not_active Expired - Lifetime
  • 1993-12-16 DE DE69320368T patent/DE69320368T2/de not_active Expired - Fee Related

Patent Citations (6)

Non-Patent Citations (1)

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