GB2183513A - Apparatus for grinding or polishing - Google Patents

Abstract

Apparatus for grinding or polishing a metallographic specimen has a rotatable disc 94 with a flat surface 96 against which the specimen is held by a rotatable specimen holder 80 driven by a drive member 48 which extends axially through a piston-cylinder device 54, 52 which applies a force to the holder so as to vary the contact pressure as required between the specimen and the rotatable disc. The specimen holder 80 is removably fixed to the drive member 48 by balls 100 which can be urged by a cam ring 84 into engagement with a groove in a coupling stud 86 on the holder. <IMAGE>

Description

SPECIFICATION Apparatus for grinding or polishing This invention relates to apparatusforgrinding or polishing. The invention relates particularly although not exclusively to apparatus for polishing metallographic specimens.

Apparatus for polishing metallographicspeci- mens is known. According to one example, metallographic specimens are mounting on or carried by a rotatable specimen holder and are brought into con tactwith an abrading surface, which isfixed, by moving the specimen holder in the direction of its rotation axis. One convenient way of effecting this movement is by a piston-cylinder device, but one disadvantage of prior arrangements is that off-centre forces are applied to the rotating holder. This is be causethepiston-cylinderdevice had to be located off-centre ofthe rotation axis of the holder due to the need to transmit the rotary drive to the disc.It is also known to apply a downward force to the top ofthe rotating shaft which carries a specimen holder, buta disadvantageofthisarrangementisthatthelocation of a piston-cylinder device above the shaftgivesthe apparatus extra height, which is undesirable.

It is an aim of the present invention to overcome or at least gradually mitigate these disadvantages.

According to the present invention, in one aspect, there is provided apparatus for grinding or polishing an article or a specimen, herein called an articlefor the sake of brevity, in which a rotatable specimen holder has provision for holding the articleforthe purpose of grinding or polishing it, characterised in that the holder is driven by a drive memberwhich extends axially through a piston-cylinder device, the device being arranged so that it can apply a force to the holder so astovarythecontactpressurebetween the article and an abrading surface located adjacent to the rotatable specimen holder.

In a preferred version of the invention, the abrading surface is a surface of a rotatable wheel, disc or plate, herein called a grinding wheel for brevity, although it will be understood that such a wheel may also be used for polishing. The specimen holder and the grinding wheel are preferably both rotatable with their rotation axes coaxial and vertical, the grinding wheel being lowermost. Other configurations may be employed without departing from the invention.

Also according to the present invention, in another aspect, there is provided apparatusforgrinding or polishing an article or a specimen, in which a rotatable specimen holder has provision for holding an article for grinding or polishing, characterised in that the rotatable specimen holder is removably fixed to a drive member by a coupling stud having a shaft portion in the outer surface of which is located a peripheral groove, and in which the coupling stud cooperates with a drive boss which can be fixed to the drive member, the boss being associated with a retaining ring having internal cam surfaces which in use urge balls within the ring into the groove in order to connect the boss to the stud and provide axial re- tention ofthe stud within the boss.

In a preferred embodiment of the invention, the piston-cylinder device has annular seals of U-shaped cross-section at each of its ends.

The piston-cylinder device is preferably air- or gasactuated and single-acting with spring return.

In one preferred example ofthe invention, the piston-cylinder device is provided with annular seals of U-shaped cross-section at each of its ends. The apparatuswill normally but need not necessarily include a source of air or gas under pressure; means for conveying the air or gas to the interior ofthe piston-cylinder device are provided.

In one specific embodiment ofthe invention,the rotatable specimen holder may have holes there through forthe receipt ofspecimensto be polished or ground. Such holes may be partcircularwith a tapering portion whosewider part merges with the part circular portion.

The invention will be better understood from the following illustrative description of one example thereof, given with reference to the accompanying drawings in which: Figure 1 is a front elevation of one example of apparatus according to the invention; Figure2 is a plan view ofthe apparatus shown in Figure 1 but omitting a lubricantcontainerwhich is shown in Figure 1; Figure 3 is a side elevation, partly in section in the region of the piston-cylinder device, through the apparatus shown in Figures 1 and 2; Figure 4 is a plan view of one example of rotatable specimen holding disc; Figure 5 is a sectional view on the xx of Figure 4Of the disc shown in Figure 4; Figures 6-10 are a series of views of a drive boss by which the disc is connected to a drive member;; Figures 11-14 are a series of views of a retaining ring used in connecting and disconnecting a coupling stud to and from the drive member; Figures 15and 16 depict a retaining ring fastening screw; and Figures 17-19 illustrate a coupling stud used in connecting the rotating disc to the drive member, in conjunction with the retaining ring referred to.

Referringfirstlyto Figures 1-3 and in particularto Figure 1, the illustrated apparatus for grinding and polishing includes a base 20 having an upstanding post 22 upon which a housing 24 is vertically slid able. Aclamping mechanism 26 of any convenient kind known per se, operated bya rotatable handle 28, allows the housing 24to be clamped in any one of a number of chosen positionsrelativetothepost22.A supportcollar25fixed to the post 22 sets the minimum height of the housing 24. If desired, the collar 25 may be adjustable vertically relative to the post 22. In brief, the housing 24 is vertically adjustable re- native to the post 22. In brief, the housing 24 is vertically adjustable relative to the base 20. The housing 24 has a bracket 30 to which can be attached a support 32 for a lubricant container 34. This may contain lubricantforthe polishing operation and suitable tubing (not shown) is provided to conveythe lubricant from the containerto the polishing zone.

The housing 24 contains an electric motor36 (Figure 2) having an output shaft upon which is located a worm 38 which is in engagement with a worm gear40, mounted on a shaft 42. Also mounted on the shaft 42 is a gear 44, in driving engagement with a furthergear46.Thegear46issecuredtoarotary shaft48which is located within a piston tube 50. The gear 44 is axially extended in a vertical direction, as seen bestin Figure 3, in orderto permitthegears44 and 46 to remain in engagementovera rangeofvertical positions of the gear 46. An upper position is indicated in chain-dot at46A.As will be better understood from the following description, the gear 46, the shaft 48 and the parts including the rotating specimen holder carried indirectly by the shaft48 are arranged sothatthey can be moved vertically relat ive to the gear 44 and during this movementtheteeth of gear46 remain in engagement with gear44.

The arrangement of a rotary shaft according to the invention axially within a piston-cylinder device is best illustrated in the right hand portion of Figure 3, to which attention is now directed, this relative arrangement being of the essence of the present invention.

The illustrated piston-cylinder assembly includes an annular piston working within an annular space whose inner wall is constituted by the piston tube 50 and whose outer wall is constituted by a cylindrical sleeve 52. Within this cylinder slides a piston assembly constituted by a piston 54 and a fluid sealing arrangement including a U-ring type seal of suitable rubberorelastomeric material 56. The piston assembly 54 is connected to the tube 50 in any suitable way so that the tube 50 moves vertically with the piston assembly 54. A compression spring 58 is located between a surface 60 on the piston assembly and a surface 62 on a closure member 64 closing the lower end ofthe cylindrical sleeve 52, and there is meanswherebyairorotherfluid under pressure can be fed into an annularchamber66 located between the sleeve 52 and the piston tube 50.Compressed air will normally be employed. It is fed in, as illustrated, via athreaded hollow boss 68to which an airsupply tube (not shown ) may be secured. The hollow boss 68 is connected to a bore indicated at 70 leading into the chamber66. A rubber or elastomeric U-ring type seal 72 is located in a top closure member74and seals againstthe axially movable piston tube 50. As illustrated,the seals 56,72 are shaped so thatupon an increase of pressure intheannularchamber66, the seals make tighter sealing engagement with the piston tube 50 orthe cylindrical sleeve 52 as the case may be.

The housing 24 has a pressure gauge76 in itsfront surtace and thefront panel is also provided with a control knob 77 of a pressureregulatorwherebythe pressureofcompressedairfedtothechamber66 can be regulated. Its pressure value is displayed on the gauge 76. The front panel may have a switch (not shown) for switching on and off the compressed air supply.

The shaft48 extends downwardly and at its lower end carries a rotatable specimen holder. This is conveniently in theform of a disc 80, Figure 3. The disc 80 is supported on the shaft 48 by means of a drive boss 82, whose details are seen from Figures 6-10, a retaining ring 84, whose details are seen from Fig ures 11-14, and a coupling stud 86 whose details are seen from Figures 17-19. The retaining ring is maintained in position by a retaining ring screw 88 shown in Figures 15 and 16. The details of one possibleform ofthespecimen holderare illustrated in Figures4 and 5. The disc is circular and has a number,forexample 8 as illustrated, specially shaped holes therethrough.Each hole is bounded by part circularwall merging with two straight walls and a rounded end (as seen in plan) so providing a tapering space in which specimens of different sizes can be securely fixed. The disc has screw threaded bores extending thereinto from the outer periphery, these bores being aligned with the axis of symmetry of the associated hole. Referring to the hole 89, the axis of symmetry is shown at 90 and the threaded bore at 92. By tightening a fastening bolt orfastening screw (not shown) located in the bore 92, a specimen may be securelyfixedwithinthecorresponding hole 89.

A rotatable grinding wheel or circular plate 94 (Figure 3) is located belowthe specimen holder disc 80, and has an upper surface 96 upon which an abrading or polishing material can be placed. Alternatively, a fixed (non-rotatable) base may be employed. In operation, specimens mounted within the specimen holder 80 extend downwardly into contact with the surface 96 and are suitably polished or abraded as required, the contact pressure between the specimens and the surface 96 being adjustable by changing the pressure of fluid supplied to chamber 66. The downward force supplied by the pistoncylinder device is, in use, transferred to the specimen holderviaa downward-facing annularflatsurface95 which contacts the coupling stud 86.

The drive box 82 is fixed to the shaft 48 in any suitable manner, and has two diametrically opposed bores or holes 98 (Figure 8) which are dimensioned to accommodate corresponding ball bearings 100 (Figure 3). These ball bearings are free to move in radialy inward and outward directions (that isto say radially of the drive boss 82) fo r a reason which will shortly be explained. Acoupling stud 86 extends into the drive boss 82 and has a pair of holes 102 by which it can be bolted to the rotatable specimen holder 80.

The shaft 104 of the coupling stud has a peripheral channel l06therein,thischannel being intended to receive the balls 100 when they are urged radially inwardly so preventing axial removal of the stud 86 from the drive boss 82. A retaining ring 84surrounds the drive boss 82 and is made captive to it bythe retaining ring screw 88. The screw extends through a hole 100 in the retaining ring 84, as seen for example in Figures 11 and 12. Outwardly and downwardlyex- tending diametrically located lugs 118 on the drive boss 82 are dimensioned to extend into corresponding slots 120 in the coupling stud 86 in orderto transmit the rotational drive to the stud.

The inner surface 112 ofthe retaining ring 84 is shaped to provide an oval cam surface as bestseen in Figures 13 and 14. Consequently rotation of the retaining ring 84 by 90 relative to the drive boss, by virtue of the cam surface 112, effects an inward radial movement of the ball bearings so causing them to engage within the channel 106 and prevent axial re moval ofthe coupling stud from the drive boss 82.

As seen in Figures 7,8 and 10, the drive boss 82 has a peripheral groove 122 and one of the walls ofthe groove has two recesses 124which connect with the groove. The recesses are located at opposite ends of a diameter, and each is of a size to receivethe cylin- drical end 126 of the retaining ring screw 88. This screw has a threaded portion 128 which engages in a threaded bore 130, Figure 13, in the retaining ring 84.

Lodgment of the end 126 in one of the recesses 124 prevents relative rotation ofthe ring 84 and boss 82 and is arranged to occurwhen the "high" portions of the cam surface 112 are adjacentthe recesses 98.

This holds the balls 100 within the groove 106 so pre- Venting axial removal ofthe stud 86 from the drive boss 82. To detach the coupling stud, the ring 84 is liftedashortdistancetodisengagetheend 126from its recess 124,and is then rotated substantially 90'.

The "low" cam surfaces are then adjacent there cesses 98 and so the balls 100 can move out ofthe groove 106, releasing the coupling stud.

With the illustrated arrangement, it is possible to provide a readily removable connection which is not affected or loosened by the rapid rotation ofthe polishing disc 80, and yet to achieve a simple and easy manual disconnection between these parts, such as can be readily operated even by a junior or unskilled operator.

While the specimen holder has been described as a disc having specially shaped holes therein, other forms of specimen holder may be employed. For example, a triangular, square or pentagonal shaped plate may be employed with provision forfixing, clamping or bolting specimens to its peripheral flat surfaces. While a rotating specimen holder and a rotating abrading disc or plate have been disclosed, the invention may equally well be employed in an arrangmentwherethespecimen holder only is rotated. It will be understood that reliefvalves and con- trol valves would be provided as necessary in the pneumatic circuit by which air or gas is supplied to the piston-cylinder device. While a single acting piston-cylinderdevicewith spring return has been particularly described and illustrated, it will be appreciated that if desired a double acting pistoncylinder device could be employed instead. Other variations will occur two a man of average skill in this art, and the present invention is not considered to be limited to the details ofthe particular embodiment specifically described and illustrated.

Claims (9)

1. Apparatus for grinding or polishing an article or a specimen, herein called an articleforthe sake of brevity, in which a rotatable specimen holder has provision for holding the article forthe purpose of grinding or polishing it, characterised in that the holder is driven by a drive member which extends axi allythrough a piston-cylinderdevice,thedevice being arranged so that it can apply a force to the holder so as to vary the contact pressure between the article and an abrading surface located adjacent to the rotatable specimen holder.

2. Apparatus for grinding or polishing an article or a specimen, in which a rotatable specimen holder has provision for holding an article for grinding or polishing, characterised in that the rotatable specimen holder is removably fixed to a drive member by a coupling stud having a shaft portion in the outer surface of which is located a peripheral groove, and in which the coupling stud co-operates with a drive boss which can be fixed to the drive member, the boss being associated with a retaining ring having internal cam surfaces which in use urge balls within the ring into the groove in orderto connect the boss to the stud and provide axial retention ofthestud within the boss.

3. Apparatus according to claim 1 in which the piston-cylinder device has annular seals of U-shaped cross-section at each of its ends.

4. Apparatus according to claim 1 or3 including a source of air or gas under pressure and meansfor conveying the airorgasto the interior ofthe pistoncylinder device.

5. Apparatus according to claim 1 inwhichthe rotatable specimen holder is removably fixed to a drive member by a coupling stud having a shaft portion in the outer surface of which is located a peripheral groove, and in which the coupling stud cooperates with a drive boss which can be fixed to the drive member, the boss being associated with a retaining ring having internal cam surfaces which upon rotation of the ring relative to the boss urge balls within the ring into the groove in orderto connectthe boss to the stud and provide axial retention of the coupling stud and hence the dise while allo- wing easy disassembly.

6. Apparatus according to any preceding claim in which the rotatable specimen holder has holesthere throughforthereceiptofspecimensto be polished or ground.

7. Apparatus according to claim 6 in which the holes are part-circular with a tapering portion whose wider part merges with the part circular portion.

8. Apparatus substantially as herein described with reference to and as illustrated in the accompanying drawings.

9. Any novel combination or sub-combination disclosed and/or illustrated herein.