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
  • B24B23/00—Portable grinding machines, e.g. hand-guided; Accessories therefor
  • B24B23/02—Portable grinding machines, e.g. hand-guided; Accessories therefor with rotating grinding tools; Accessories therefor
  • B24B23/028—Angle tools
• • 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
  • B24B23/00—Portable grinding machines, e.g. hand-guided; Accessories therefor
  • B24B23/04—Portable grinding machines, e.g. hand-guided; Accessories therefor with oscillating grinding tools; Accessories therefor

Definitions

• the present invention relates to an excentric grinding device comprising a rotatable tool holder, which on a first side is equipped with an axial drive and fastening means, e.g. a pin. with which the holder can be connected to a drive means, e.g. an angled hand-piece.
• an axial drive and fastening means e.g. a pin. with which the holder can be connected to a drive means, e.g. an angled hand-piece.
• This type of excentric grinding device is in the first instance intended to be used together with a rotating tool, such as grinding equipment ofthe type which is used during surface machining in the precision engineering field.
• a rotating tool such as grinding equipment ofthe type which is used during surface machining in the precision engineering field.
• it can, for example, be a question of grinding, polishing, lapping or the like machining of sur ⁇ faces or surface regions in difficult-to-reach places, such as in confined spaces or in, or alongside, concave corners.
• Such surface machining equipment is used, e.g. during the polishing treatment of difficult-to-reach flat resp. curved surfaces in moulds or precision-manufactured machine parts/machine elements, where there is a high requirement for flatness resp. shape accuracy and surface finish.
• Excentric grinding equipment of the type in question can, for example, comprise a drive unit in the form of an electrically powered micromotor unit, which can be combined with different sorts of exchangeable hand-pieces, such as straight hand- pieces or angled hand-pieces.
• rotatable tool holder is meant, according to the invention, an externally usually cylindrical holder part, which is intended to carry, on an excentrically fastenable disc or plate therein, a stock-removal tool means, e.g. in the form of a grinding disc or another type of grinding means, and which has combined drive and fastening means with which the holder part is mountable in, or in some other way connectable to.
• a drive output on a drive unit such as an angled hand-piece.
• rotational driving rotation-producing torque
• the excentric grinding device is based upon the known principle that the rotational movement of the tool holder is transformed into an oscillating movement ofthe holder which supports the actual tool means, i.e. in the above mentioned case the grinding disc, polishing cloth or the grinding means/polishing means which is used.
• a primary object ofthe invention is to produce a new type of excentric grinding arrangement which is suitable for grinding, polishing resp. lapping, which permits mobile and inclinable suspension or adjustment ofthe grinding material carrier carrying the grinding means or the grinding disc in relation to the tool holder drivingly fastened in the driving means or in its handpiece, without the grinding function of the grinding equipment being unfavourably affected.
• excentric grinding device should be so constructed that the grinding material carrier (grinding disc) can be changed in seconds without the need to use any tool.
• the excentric grinding arrangement should be so designed that it is possible to grind or polish right up to adjoining edges or edge walls, respec ⁇ tively out over slits and holes, without any sinking occurring at the edges.
• the in ⁇ vention also aims to produce an excentric grinding device which is so constructed that no torque is transferred to the grinding material carrier (grinding disc), whereby e.g. a grinding material carrier or grinding disc with rectangular, disc-shaped supporting parts for the grinding means surface can be used in order to reach into concave corners or to access other difficult-to-reach places/spaces.
• the excentric grinding device should furthermore be so constructed that the bearing is naturally securely axially fastened in the tool holder but even so is simple to remove in order to be changed when needed, with the help of only a simple tool.
• the main grinding work takes place around the periphery ofthe carrier.
• a torque is required which often is too great for the more common micromotors.
• the grinding material carrier must work at a relatively low rotational speed so that the grinding paste is not thrown off the carrier by centrifugal force.
• the "moment arm” will not be greater than the distance between the drive shaft and the central axis of the grinding material carrier, independently ofthe diameter ofthe grinding material carrier.
• the excentricity usually is not more than a millimeter, the required torque is low and a high rotation ⁇ al speed can be chosen without the disadvantages which follow with a rotating grinding material carrier.
• the bearing supports a grinding material carrier which has an axial fastening pin whereby the support is so removably fastened in the re ⁇ ceiving opening in the bearing that a certain inclination of the grinding material carrier is possible in relation to the fastening means ofthe tool holder.
• the excentric grinding device according to the invention is preferably intended to be able to be used in all types of hand tools, especially those with 3 mm or 6 mm chucks. If the working conditions permit, it could often be simpler and more com ⁇ fortable to work with a 90° angled piece.
• the grinding material carrier being movably and inclinably suspended in the cavity in the tool holder, the actual hand tool can be held at an angle in relation to the surface which is to be ground, without the grinding function being influenced detrimentally.
• the bearing results in no turning movement being transferred from the rotating tool holder to the grinding material carrier, whereby even a carrier with a rectangular, disc-shaped supporting part for the grinding means or the grinding means surface can be used, for example, to be able to grind in con ⁇ cave corners or along concave edges. Consequently, the grinding material carrier does not rotate but works with an oscillating movement as a consequence ofthe excentric mounting of the bearing in the rotatable tool holder.
• the fastening pin of the grinding material carrier is preferably formed with a conical tapering in the direction towards the cavity in the tool holder and is equipped, at its inner end situated inside the cavity, with retaining means which limit the axial free- dom of movement of the pin in relation to the bearing without thereby limiting the permitted inclination of the fastening pin.
• the taper ofthe fastening pin of the grinding material carrier is suitably so large that the pin can be inclined at least 5 - 6°, which means that the top angle for the conical shape of the fastening pin therefore amounts to 10 - 12°.
• the retaining means at the inner end ofthe fastening pin of the grinding material carrier has the task of preventing the grinding material carrier from coming loose from the tool holder during normal handling and use ofthe excentric grinding equipment.
• the retaining means shall, however, at the same time be so designed that it is easy, by hand, without any special tools, to attach the grinding material carrier in the receiving opening in the bearing, respectively to remove the grinding material carrier from the tool holder, for example, in order to change to another grinding material carrier with another grinding disc or another grinding means.
• the retaining means functions as a locking arrangement which prevents the grinding material carrier unintentionally coming loose from the tool holder but which locking effect evenso is not so large that it cannot be overcome for the intentional removal of the grinding material carrier from the tool holder.
• the retaining means is formed from a circumferen ⁇ tial groove in the fastening pin ofthe grinding material carrier, in the region ofthe inner end ofthe pin, and an O-ring engaged in this groove.
• the O-ring made of resilient material, is placed so that it does not affect the inclining movement (tipping movement) of the fastening pin.
• the O-ring is dimensioned with such an outer dia ⁇ meter that the ring prevents the fastening pin ofthe grinding material carrier from coming loose out ofthe receiving opening in the bearing, but the outer diameter must, however, not be so large that the O-ring, and therewith the fastening pin of the grinding material carrier, cannot be easily inserted into the receiving opening in the bearing during mounting of the grinding material carrier.
• the fastening pin of the grinding material carrier is axially slit at its inner part and this inner part is equipped with one or more radially projecting shoulders, preferably two diametrically opposing shoulders, which thereby form the retaining means.
• the shoulders are so dimensioned that they reach out a small amount radially outside the inner diameter of the receiving opening in the bearing.
• the actual slit in the fastening pin causes the two separate half sides ofthe inner part ofthe fastening pin separated by the slit and equipped with shoulders to have a certain radial resilient capacity so that the grinding material carrier can easily be mounted, respectively be moved, by hand in/from the receiving opening in the bearing.
• the grinding material carrier suitably comprises a disc-shaped supporting part (also called grinding disc or grinding plate) to support an attachable grinding disc or grinding means surface fastenable thereupon, whereby the fastening pin ofthe grinding material carrier is rigidly joined to this bearing part at its central part.
• the grinding material carrier suitably has a ring-shaped surface region, which forms the contact surface against the bordering parts of the inner ring ofthe bearing.
• the disc-shaped supporting part ofthe grinding material carrier does not need to be circular but can, for example, be rectangular or quadratic when seen in plane view.
• the bearing comprised in the excentric grinding arrangement according to the invention is suitably a roller bearing, preferably a ball bearing, of standard type.
• This roller bearing is suitably axially fixed in an axially outer part of the cavity in the tool holder, whereby the inner ring of the roller bearing forms a contact surface with the grinding material carrier at one end ofthe inner ring and, at the opposite other end, forms a contact surface for the existing retaining means at the inner end of the fastening pin ofthe grinding material carrier.
• the axial fixing of the roller bearing in the cavity in the tool holder can be achieved in various ways known per se.
• the axial fixing of the bearing is achieved by means of an O-ring, which is arranged in a circumferential groove in the wall to the outer part ofthe cavity in the tool holder.
• the O-ring is in this case radially clamped between the bottom ofthe groove and the outside ofthe outer ring ofthe roller bearing and serves in this way as a retaining means for the bearing in the tool holder.
• the bearing can, when required, easily be drawn out of the cavity in the tool holder with the help of a simple tool, such as an L-shaped hook which is introduced through the receiving opening in the bearing and is placed against the inner ring, whereafter axial outwardly directed force on the inner ring can be made to easily overcome the retaining friction force from the O-ring which acts on the outside ofthe outer ring ofthe bearing.
• the bearing can, without difficulty, be drawn out ofthe cavity in the tool holder. It is a clear advantage that the bearing can without difficulty be removed from the tool holder as the bearing is the part of the excentric grinding device which is subjected to wear in use and which therefore eventually needs to be replaced.
• Fig. l shows a first embodiment of an excentric grinding device according to the invention, wherein the cylindrical tool holder is partially shown in longitudinal section;
• Fig. 2 shows, on a larger scale, the retaining means at the inner end ofthe fastening pin of the disc holder according to the embodiment of Fig. 1 :
• Fig. 3 shows, in the same sort of view as in Fig. 1 , a second embodiment with an alternative embodiment ofthe retaining means;
• Fig. 4 shows, in the same sort of view as in Fig. 1, a third embodiment with a lengthened fastening pin (motion transmitting pin) for the grinding means carrier;
• Figs. 5 - 7 finally show some alternative embodiments ofthe pivoting connection of the grinding material carrier to the motion transmitting pin.
• the excentric grinding device comprises a rotatable, cylindrical tool holder 2. which on a first side is provided with an axially projecting drive and fastening pin 4, with which the holder 2 can be mounted, in a (not shown) driving arrangement, e.g. an angle piece.
• the tool holder 2 On the other side, opposite to that provided with pin 4, the tool holder 2 is equipped with a cavity 6 with a radially widened, axial outer part 8, wherein a ball bearing 10 is mounted against an annular shoulder 12.
• the cavity 6 in the tool holder 2 is dimensioned suitably so that the quantity of material which is machined away as much as possible corresponds to the weight of the bearing assembly with grinding material carrier, in order to minimize resulting inbalance vibrations.
• the ball bearing 10 comprises an outer ring 14, an inner ring 16 and between these rings a number of ball bearing balls 18.
• the ball bearing 10 is axially retained in the outer part 8 ofthe cavity 6 by means of an elastic O-ring 20, which is placed in a circumferential groove 22 in the wall ofthe outer part 8 ofthe cavity.
• the O-ring 20 is consequently clamped between the bottom ofthe groove 22 and the outside ofthe outer ring 14 of the ball bearing, and serves as a retaining means which ensures that during normal use the ball bearing 10 does not come out of the cavity 6 in the tool holder 2.
• the cylindrical cavity 6 in the tool holder 2 is, as can be seen, excentrically placed in relation to the drive and fastening pin 4 of the tool holder.
• the widened outer part 8 of the cavity 6 is coaxial with the inner part of the cavity, which means that the bearing 10 is excentrically mounted in the tool holder 2 in relation to the centrally placed pin 4.
• the central receiving opening 24 in the inner ring 16 of the bearing is consequently also excentrically situated in relation to the fastening pin 4 through which the tool holder 2 imparts its rotational motion from the power output in the angled hand-piece or the equivalent in which the excentric grinding device according to the invention is drivingly fastened.
• the ball bearing 10 supports a grinding material carrier 26, which has a conically tapered, axial fastening pin 28 by means of which the carrier is so dismountably fastened in the receiving opening 24 in the bearing that a certain inclination or sloping ofthe fastening pin 28 ofthe grinding material carrier - and by that the grinding material carrier 26 itself- is possible in relation to the central axis A of the bearing and thus also in relation to the central axis B, parallel but displaced to one side of axis A, for the tool holder's 2 own fastening pin 4.
• the maximal slope or inclination of the conical fastening pin 28 ofthe grinding material carrier 26 is in Fig. 2 illustrated through the angle ⁇ shown between the central axis A ofthe receiving opening 24 and the inclinable fastening pin's 28 own central axis C.
• the grinding material carrier 26 comprises, as can be seen, a disc-shaped supporting part or grinding plate 30 intended, on its in Fig. 1 downwardly facing plane outer side 32, to support e.g. a (not shown in the Figure) grinding disc or grinding means surface of conventional type.
• the fastening pin 28 ofthe grinding material carrier is rigidly joined or formed in one piece with the supporting part 30.
• the grinding mate ⁇ rial carrier 26 has an annular surface region 34, which forms a contact surface with adjacent surface regions of the inner ring 16 ofthe ball bearing 10. As is clear from Figs. 1 and 2.
• the, towards the cavity 6 conically tapered, fastening pin 28 o the grinding material carrier 26 is equipped with retaining means 36 at its inner end situated inside the cavity.
• These retaining means have the purpose of limiting the axial freedom of movement of the pin 28 in relation to the bearing 10, without thereby limiting the maximal permitted inclination ⁇ of the fastening pin.
• the retaining means 36 consists partly of a circumferential groove 38 in the fastening pin 28 in the region of the inner end of the pin and partly of an O-ring 40 received in this groove.
• the O- ring 40 is so dimensioned that its outer diameter somewhat exceeds the diameter of the receiving opening 24 in the inner ring 16 of the bearing 10. In this way, the O- ring 40 prevents the grinding material carrier 26 from coming loose out ofthe receiving opening 24 of the bearing.
• the O-ring 40 being manufactured of an elastic material, it is still possible, when necessary, without great axial force, to pull the grinding material carrier 26 out ofthe receiving opening 24. e.g. to exchange the actual grinding disc.
• the fastening pin 28 ofthe grinding material carrier 26 is equipped with a central, axial slit 42 in its part situated inside the cavity 6.
• the slit divides the fast ⁇ ening pin into two parallel halves which at their inner ends each are equipped with a radial projecting retaining shoulder 44.
• These two diametrically opposed shoulders 44 in this case form the retaining means 36, through the shoulders being so dimen ⁇ sioned that the "outer diameter measure" between the radially outermost parts of the shoulders somewhat surpasses the diameter of the receiving opening 24 in the inner ring 16 of the bearing 10. In this way, the grinding material carrier 26 is prevented from, by mistake, coming out of the receiving opening 24.
• the retaining means according to Figs. 1 - 2, i.e. the O-ring locking, and according to Fig. 3. i.e. the shoulder locking, respectively, are probably equally good, but from a manufacturing point of view, the O-ring locking should be preferred.
• One reason therefor is that the required special shaping of the inner end of the fastening pin 28 is simpler, and therefore cheaper to produce, with the design according to Figs. 1 - 2, which only requires the production of a circumferential groove 38.
• a somewhat stronger fasten ⁇ ing pin 28 is achieved than with the slitted solution shown in Fig. 3.
• the excentric grinding device according to the invention is especially usable with motor-driven grinding equipment for the precision engineering field.
• diamond grinding equipment for high-mirror finish polishing.
• the paste is not thrown outwardly, which is the case when using rota ⁇ ting tools instead of tools with oscillating movements as is the case according to the present invention.
• the drive and fasten ⁇ ing means 4 ofthe excentric grinding device can therefore be used, and it is easier to "drive" the paste forward during polishing.
• FIG. 4 This embodiment differs from that shown in Figs. 1 - 2 to the extent that the means which permit the inclination ofthe grinding material carrier 26 have been moved out from the cavity 6 ofthe tool holder 2 to the distal end 29 ofthe motion-transferring pin 28' removably fastened in the inner ring 16 of the bearing 10.
• the part ofthe pin 28' fastened in the bearing in this case is a cylindrical part 35, at the inner end of which there is the same type of retaining means 36 as in the embodiment shown in Figs. 1 - 2.
• the parts ofthe tool holder 2 which correspond to the embodiment shown in Figs.
• the motion- transferring pin 28' has a first shoulder part 31 which abuts against the inner ring 16 ofthe bearing 10, and a second shoulder part 33 which forms a support for the grinding material carrier 26.
• the pin 28' has a cylindrical part 37 between the shoulder parts 31 and 33.
• the shoulder part 33 is provided with a conical annular surface 39 and a holder pin 41 axially projecting therefrom and which, with a certain play, projects in through an opening 43 in a centrally outwardly curved part 45 of the grinding material carrier 26 made of sheet metal. Thanks to the conical annular surface 39 and the play between the pin 41 and the opening 43, the grinding material carrier 26 can be inclined at least 5° from its starting position at right angles to the central axis A.
• The, in this case disc-shaped, grinding material carrier 26 and the end 29 of the motion-transferring pin 28' can be designed in other ways than that shown in Fig. 4.
• Figs. 5 and 6 show a pair of such alternate embodiments.
• the end 29 of the pin 28' has a conical indentation 47 which cooperates with a spheric ⁇ ally curved ball-joint part 49 on the upper side ofthe grinding material carrier 26, and according to Fig. 6.
• the end 29 ofthe pin 28' has an axial support pin 41 * . of which the end surface rests against the bottom of a hole 51 in the middle of a cylindrical central part 53 on the upper side ofthe grinding material carrier 26.
• FIGS. 4 - 6 show two alternative embodiments ofthe "joint connection” formed between the end 29 of the pin 28' and the respective grinding material carrier 26, which permit the inclination ofthe grinding material carrier 26.
• All of the grinding material carriers shown in Figs. 4 - 7 are on the underside (grinding side) equipped with a central "chamber" 55, 55' resp. 55", in which a suitable grinding medium, e.g. diamond paste, can be introduced before the grinding, polishing or lapping is started.
• a suitable grinding medium e.g. diamond paste
• the grinding material carrier in this case is made of a suitable plastic material, i.e. a material with a certain elasticity.
• the motion-transferring pin 28' has at its lower end a shoulder part 33" in the form of a spherical joint ball 58, which is pivotably received in a cavity 60 in the central shoulder part 62 ofthe grinding material carrier 26.
• the cavity 60 which also forms the joint socket for the joint ball 58.
• the shoulder part 62 has at the upper side 64 ofthe shoulder part 62 an orifice opening diameter, which is only that much smaller than the diameter of the joint ball such that the grinding material carrier 26 formed as a grinding disc, without difficulty, can still be pressed firmly onto the ball 58 by hand, respectively be removed by hand from the ball.
• the difference in diameter is sufficiently large so that the grinding material carrier 26 will remain firmly on the ball 58 during the performance of grinding, i.e. during use.
• a grinding material carrier of metal e.g. copper or some other inelastic but still formable material
• metal e.g. copper or some other inelastic but still formable material
• the orifice edge of the cavity must then instead at the upper side 64 be made in such a way that it "closes in” the ball 58 in the cavity 60.
• the grinding disc in this case will not be attachable to, respectively removable from, the ball of the ball joint, but the combined unit formed ofthe motion-transferring pin 28' and the grinding disc 26 can still be quickly exchanged through being simply removed from the bearing 10.
• the excentric grinding device according to the invention is not only usable during the grinding of plane surfaces but has also proven to be usable during grinding of concave and convex curved surfaces, and in this case particularly spherical surfaces.
• the grinding material carrier surface e.g. with the grind ⁇ ing means chamber 55
• the grinding disc 26 it is possible to use it also on sur ⁇ faces for which it is required that the spherical shape is retained during grinding or polishing work.
• the risk of making unintentional indentations during grinding is considerably reduced during use of an excentric grinding device according to the invention compared to when using some other conventional polishing technique.
• the excentric grinding device according to Figs. 4 - 7 can advantageously be used especially during grinding and polishing of small surfaces, and in particular when the respective surface is limited by raised edges.
• a grinding material carrier 26 formed as a small grinding disc, according to Figs. 4 - 7, is preferable to the larger one according to Figs. 1 - 3.
• the grinding disc 26 can either be pivotally fastened to the pin end 29 or loosely attached to it. whereby the complete equipment is held in the intended working position before the start and until the rotation of the tool holder 2 has finished after completion ofthe grinding.
• a lengthened motion-transferring pin 28' adapted to fit inside the inner ring 16 of the ball bearing 10, according to Figs.
• the grinding discs or grinding material carriers 26 naturally do not need to be designed as round discs, as according to Figs. 1 - 7, but can equally well be quadratic, triangular or have some other suitable, multi- sided shape, in particular so that in this way it will be easier to reach into corners.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Polishing Bodies And Polishing Tools (AREA)
• Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (2)

Cited By (3)

Citations (6)

• 1996
  • 1996-01-25 SE SE9600274A patent/SE507850C2/sv not_active IP Right Cessation
• 1997
  • 1997-01-17 WO PCT/SE1997/000075 patent/WO1997027027A1/en active Application Filing

Patent Citations (6)

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