GB2151955A - Grinding machines - Google Patents

Abstract

A grinding machine (1) for accurate finishing of a processed workpiece (W) comprises a Y-table (8) which can freely move in the Y-axis direction mounted on an X-table (5) which can freely move in the X-axis direction on a base plate (3), and a slide table (9) for supporting the workpiece (W) mounted on the Y-table (8) so that it can freely move in any horizontal direction and freely revolve. A grinding lapping or the like tool (93) adapted to engage with the portion of the workpiece (W) to be worked is supported to a machining head (53) disposed above the slide table (9) so that it can move vertically and freely vibrate horizontally, the amplitude of the horizontal vibration being adjustable. <IMAGE>

Description

SPECIFICATION Improvements in or relating to grinding machines This invention relates to improvements in or relating to grinding machines and, in particular, to a grinding machine which is suitable for finishing a workpiece, that is to say, effecting precise grinding or polishing of a portion of the workpiece which has already been processed elsewhere, such as a groove, concavity, hole or the like.

Generally, metal moulds and the like having a portion such as a hole, groove or the like of complex shape and finished extremely accurately after they have been worked using an electrical discharge machine. The finishing is conventionally performed manually using an ultrasonic abrasion machine. However, this method of finishing is relatively inefficient and tends to result in lack of uniformity in the finished product. Furthermore, in conventional grinding machines, if there is any misalignment between the portion of the workpiece to be worked and the grinding tool, the workpiece is ground wrongly.

It is an object of the present invention to enable the provision of a grinding tool whereby the above disadvantage may be obviated or at least mitigated.

Accordingly, the present invention provides a grinding machine which comprises means for supporting a grinding tool and for effecting vibration thereof in a direction having a horizontal component and means for supporting a workpiece, the arrangement being such that, in use, the grinding tool andlor the workpiece is/are horizontally movable in response to vibration of the grinding tool in contact with the workpiece so as to reduce any misalignment between the grinding tool and the workpiece.

In a preferred aspect, the invention provides a grinding machine for finishing a workpiece, comprising a rotary slide table for receiving a workpiece, a grinding tool arranged to engage with a portion of the workpiece and to vibrate horizontally, a machining head disposed above the workpiece for holding the grinding tool, a first table supporting the slide table and a second table supporting the first table, the first and second tables being horizontally movable in mutually perpendicular directions.

The present invention enables the provision of a grinding machine which can perform finishing efficiently and precisely and automatically correct any misalignment between the portion of the workpiece to be worked and the grinding tool.

The invention also enables the provision of a grinding machine in which the amplitude of vibration of the grinding tool is adjustable in accordance with the magnitude of the clearance between the portion of the workpiece to be worked and the grinding tool.

The invention further enables the provision of a grinding machine in which the grinding tool is vertically and periodically movable to improve grinding efficiency.

The invention further enables the provision of a grinding machine in which a workpiece can be moved smoothly in a horizontal direction over large distances.

In particular, the present invention enables the provision of a grinding machine in which a grinding tool attached to a machining head disposed above a base plate can freely vibrate horizontally, and in which a workpiece having a portion which is to be processed by the grinding tool is placed on the base plate so as freely and smoothly to move in any horizontal direction. The grinding tool is preferably constructed so that the amplitude thereof can be adjusted by means of an eccentric system and so that the grinding tool can freely vibrate vertically. Advantageously, a table supporting the workpiece is disposed so as freely to move in mutually perpendicular horizontal directions over relatively large distances.

For a better understanding of the present invention, and to show how the same may be put into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure l is a front elevational view, partly in section, of a grinding machine in accordance with the present invention; Figure 2 is a top plan view of the grinding machine of Figure 1, Figure 3 is an enlarged cross sectional view of a holder of the grinding machine of Figure 1; Figures 4(a) and (b) illustrate the interaction between a workpiece and the machining tool of the grinding machine of Figure 1; Figure 5 is a simplified partly sectional view of an alternative spindle construction for the grinding machine of Figure 1; and Figure 6 is a simplified partly sectional view of an alternative supporting rod construction for the grinding machine of Figure 1.

Referring to Fig. 1, a grinding machine 1 in accordance with the present invention is shown, in which a pair of guide rails 4 which extend in the Xaxis direction (the right to left direction in Fig. 1) is mounted to a base plate 3 of the grinding machine 1, and an X table 5 is slidably supported on the guide rails 4. On the upper surface of the X table 5, a pair of guide rails 6 which extend in the Y-axis direction perpendicular to the direction of the movement of the X table 5 is mounted, and a Y table 8 is likewise slidable supported on the guide rails 6. A first discoid slide table 7 is mounted on this Y table 8 so as to move horizontally and to freely rotate. A second discoid slide table 9 is similarly mounted on this first slide table 7 so as to move horizontally and to freely rotate.A number of balls 11 are rollably interposed between the Y table 8 and the first slide table 7 and between the first slide table 7 and the second slide table 9 for extremely smooth movement and rotation, and each ball 11 is held with a proper interval by discoid retainers 13. A radial bearing 15 extending in a central hole 13a of each retainer 13 mentioned above is rotatably supported at the central portions of the above-stated first and second slide tables 7 and 9.

Therefore, when each retainer 13 comes into contact with the radial bearing 15, the movement of each of the slide tables 7 and 9 becomes hard since each ball 11 changes from the rolling state to the sliding state. Consequently, the smooth movement of each slide table is secured in the range where no radial bearing 15 contacts with each retainer 13. However, since the slide tables 7 and 9 are supported on the X and Y tables 5 and 8, it is possible to smoothly move the slide tables even in the case of largely moving them to change the work position of the workpiece material, and the positional relationship between the first and second slide tables 7 and 9 and each retainer 13 can be maintained without affecting their accurate location so largely.

An annular cover 17 surrounding and enclosing the first slide table 7 and the like is fixed by bolts or the like on the bottom surface of the abovementioned second slide table 9. An annular plate 21 is attached on the lower surface of this cover 17 through an annular spacer 19. Thus, the intrusion of dust or dirt into the first and second slide tables 7 and 9, etc. is prevented. A plurality of radial Tshaped grooves 23 are formed in the upper surface of the second slide table 9. Therefore, it is possible to fix the workpiece W on the upper surface of the second slide table 9 through a fixing tool such as T bolts or the like so that the workpiece thus fixed on the second slide table 9 can freely and smoothly move in any horizontal direction and freely rotate.

A cylindrical guide post 25 is vertically fixed near one side portion of the aforementioned base plate 3 by a plurality of bolts, and a supporting rod 27 is mounted in this guide post 25 so that the vertical location can be freely adjusted. Namely, a threaded portion 27a is formed in the lower end portion of this supporting rod 27, and sleeve nuts 31 are threadably engaged with this threaded portion 27a, these sleeve nuts being supported in a gear box 29 mounted on the lower surface of the base plate 3 so as to only rotate freely. A worm wheel 33 is fixed to these sleeve nuts 31 in a body and a worm gear 35 which is suitably connected to a motor and the like engages this worm wheel 33. A key number 37 fixed on the upper end portion of the above-mentioned guide post 25 engages a key groove 27b which is formed vertically in the body of the supporting rod 27.Therefore, the proper rotation of the worm gear 35 allows the supporting rod 27 to be moved up and down.

A pipe member 41 is rotatably supported at the upper end portion of the supporting rod 27 through a plurality of bearings 39. A cover pipe 43 which is slidably surrounding the guide post 25 is attached on the lower surface of this pipe member 41 in a body. Ribs 47 for reinforcement are fixed along opposite edges of the upper face of this plate-like arm 45, and a rotation driving apparatus 51 such as a motor is mounted to the rear end portion through a bracket 49. A machining head apparatus 53 is mounted to the edge portion of the arm 45. Thus, the machining head apparatus 53 and the like moves vertically in a body depending upon the ascent or descent of the above-mentioned supporting rod 27.

The machining head apparatus 53 is constructed as follows. Namely, a rotary tube 57 is supported so as to only rotate in a sleeve 55 which is fixed of the edge of the arm 45 through a plurality of bearings and a pully 59 is attached in a body to the upper portion of this rotary tube 57. A belt 63 installed around a driving pulley 61 which is equipped to the aforementioned rotation driving apparatus 51 is installed around this pulley 59. A spindle 65 piercing vertically through the rotary tube 57 up and down is further supported to the rotary tube 57 so that it can freely slide in only the axial direction. Namely, an axial key groove 65a is formed in the body of the spindle 65, and a key 67 formed on the rotary tube 57 engages this key groove 65a. Therefore, the spindle 65 rotates together with the rotary tube 57 in a body and it can freely move solely in the axial direction.

A tubular cap 69 is attached to the upper end portion of the spindle 65 through a plurality of bearings so as to only rotate. A coupling plate 75 which is pivotally mounted to a swinging lever 71 through a pin 73 (refer to Fig. 2) is connected to this cap 69. The body of the above swinging lever 71 is pivtoally mounted to a bracket 77 which is vertically attached to the above-mentioned arm 45.

A spring member 83 such as a balance spring which serves to balance with the weight of the afore-stated machining head apparatus 53 is attached between the rear end portion of this swinging lever 71 and a threaded rod member 81 which is supported so as to freely adjust the vertical location thereof relative to a bracket 79 fixed to the above-stated guide post 25. Thus, the spindle 65 is always lifted upward by a function of the spring member 83, and it goes down by operating the swinging lever 71 against the biasing force of the spring member 83. In this case, it is possible to pull the spindle 65 downward against the biasing force of the spring member 83 by suitable hanging down a plurality of weights or weights having different weights (not shown) to the edge of the swinging lever 71.

A cam-follower 87 is rotatably attached through a pin 85 to a proper position of the swinging lever 71. A cam 91 contacts rotatably with the lower side of this cam-follower 87, this cam 91 is connected to the output shaft of a rotation driving apparatus 89 such as a motor which is attached to the aforementioned arm 45. Thus, when the cam 91 rotates by the rotation driving apparatus 89, the swinging lever 71 repeates the vertical driving apparatus 89, the swinging lever 71 repeates the vertical motion periodically, so the spindle 65 moves vertically in association with this; therefore, suitable control of the rotation of the rotation driving apparatus 89 provides the suitable control of the cycle or period of the vibration. It is possible to change the amplitude of the vertical motion and the location of the bottom dead point of the spindle 65 by disposing detachably or removably either of the cam-follower 87 or the cam 91 or both of them in a conventional manner, thereby coping with the variations of the thickness of the workpiece and the depth of the groove or the like of the work portion.

The mechanism for vertical moving the spindle 65 is not limited to the construction described previously; however, for instance, it is possible to interpose the cylindrical cam or the like between the pulley 59 and the sleeve 55 mentioned before, or other various constructions may be employed. The rotation driving apparatus 51 can be also used as a driving source for moving the spindle 65.

A holder 93 is attached to the lower end portion of the spindle 65. This holder 93 serves to hold a grinding tool comprising a grindstone or an appropriate tool steel or a chuck such as a collet chuck which holds the grinding tool. The construction of this holder 93 is shown in Fig. 3. That is, a flange 95a is formed horizontally in the lower portion of a sleeve 95 fixed in a body to a lower end portion of the spindle 65 by using set screws and the like, and arcuate holes 95b are formed in a plurality of portions of this flange 95a. An eccentric hole 95c is formed in the center of the lower face of the sleeve 95 with a slight eccentricity relative to the axial center of the spindle 65.An eccentric disc 99 is attached to the lower face of the sleeve 95 through a plurality of bolts 97 piercing through the aforementioned arcuate holes 95b so that the rotation position of the disc 99 can be freely adjusted. An eccentric height 99a engaged with eccentric hole 95c is formed on the upper portion of this eccentric disc 99. Thus, the eccentric disc 99 is attached with an eccentricity relative to the axial center of the spindle 65, it is possible to adjust the location of the axial center of the eccentric disc 99 relative to the axial center of the spindle 65 by suitably rotating the eccentric disc 99 after the above-mentioned bolts 97 have been loosened.

A bearing sleeve 101 is fixed in a body on the lower face of the eccentric disc 99 through a plurality of bolts, and a holder block 105 is rotatably supported in this bearing sleeve 101 through an eccentric bearing 103. The above eccentric bearing 103 is so constructed that the axial center of the inner hold of the inner race is slightly eccentric relative to the axial center of the eccentric disc 99.

Therefore, the axial center of the holder block 105 is eccentric relative to the axial center of the eccentric disc 99. A holder machine 107 for holding the grinding tool and the like is attached in a body through a plurality of bolts to the lower face of this holder block 105. A pin 109 projection horizontally in the radial outward direction is fixed to the lower end portion of the holder block 105. This pin 109 engages slit 111a formed vertically on the lower end portion of a tubular cover 111 which is supported roatably to the sleeve 95 through a bearing.

The above cover 111 is also formed with a protruding pin 113 (refer to Fig. 1) projecting horizontally, and this protruding in 113 engages a vertical slit 115a of a bracket 115 which depends from the previously mentioned arm 45. Consequently, the rotation of the cover 111 and the holder block 105 around the spindle 65 and the like is restricted.

In the above construction, assuming that the axial centers of the spindle 65, the eccentric disc 99, and the holder block 105 are designated by letters O, P and 0, respectively, the interval between the axial centers 0 and 0 is adjusted by adjusting the location of the eccentric disc 99 relative to the spindle 65, so that it is possible to adjust the radius (amplitude of the microvibration) of the eccentric rotation of the holder block 105 upon rotation of the spindle 65.

In operation, a workpiece W is fixed on the second slide table 9; a work tool corresponding to the work portion such as a hole or the like of the workpiece is installed to the holder 93; the work tool is brought into engagement with the work portion of the workpiece by operating the swinging lever 71 and at the same time a lapping agent is supplied therein as required; the spindle 65 is rotated by the rotation driving apparatus 51 and then the rotation driving apparatus 89 is rotated; hereby the work tool starts the rotation (microvibration) with a radius equivalent to a micro-eccentric amount and at the same time it moves vertically.

Therefore, as shown in Figs. 4(a) and 4(b), when the work tool R performs the eccentric rotation with a micro-radius counterclockwise as indicated by the arrow A, and in the case where a part of the work tool R does not coordinate with the work portion Wa of the workpiece W but they abut at a point B to each other, the workpiece W is automatically rotated in the direction indicated by the arrow C so that the directions of the work tool R and the work portion Wa of the workpiece W coincide, thereby providing an automatic and accurate coordination. Due to this, even in the case where the work tool R is not precisely directed to the work portion Wa of the workpiece W at the initial setting, it is automatically adjusted and the correct coordination can be obtained.

For example, in case of grinding the rectangular groove by using the work tool having the cross section of square shape, the deviation of the work tool in the direction perpendicular to the longitudinal direction of the groove is absorbed since the workpiece moves in a body, consequently the work tool microvibrates in the longitudinal direction and vertically of the above groove for the workpiece and at the same time it periodically moves. Therefore, by moving the workpiece to the longitudinal direction of the groove, the groove is precisely ground by the work tool. When moving the workpiece to the longitudinal direction of the groove, even if the workpiece has been introduced to the direction which will cross the longitudinal direction of the groove, the workpiece is slightly rotated as described before to correctly coordinate the groove with the work tool.In this way, it is possible to extremely easily perform the precise grinding of the work portion of the workpiece.

The above explanation has been made with respect w the case where the workpiece W along with the table in a body moves horizontally and rotates; however, the similar functional effects as described previously can be derived by supporting the work tool so that it can freely move horizontally and slightly rotate. That is to say, for instance, as shown in Fig. 5, the spindle which can move vertically is divided into the upper spindle 65a and a lower spindle 65b; these upper and lower spindles 65a and 65b are coupled with each other through a proper flexible coupling 117 such as a coil spring; and the lower spindle 65b is mounted to the upper spindle 65a such that the lower spindle 65b changes its location slightly and can freely twist.The lower spindle 65b depends from the arm 45 and is supported through balls 121 by a supporting member 119 which is suitably mounted so as to move vertically, so that the lower spindle 65b can freely move horizontally and rotates (twists) slightly.

In accordance with this construction as shown in Fig. 5, since the work tool moves horizontally and rotates slightly to provide the coordination between the work portion of the workpiece and the work tool, it is possible to obtain the remarkable work effects even if the weight of the workpiece is very large.

Furthermore, such a construction as shown in Fig. 6 is also possible. Namely, a circular concavity member 123 is fixed on the upper portion of the supporting rod 27 and a pole 127 having a disc 125 is vertically mounted in a body downward of the lower portion of the arm 45. A discoid retainer 129 having a number of balls so as to roll freely is arranged to the bottom in the above-mentioned concavity member 123, and the disc 125 is supported on this retainer 129. An annular cover member 131 is fixed in a boxy above the concavity member 123, and an annular retainer 133 having a number of balls is sandwiched between this cover member 131 and the disc 125, so that the arm 45 can freely move in any horizontal directions and rotate, resulting in the same effect as the embodiment described previously. The spring member 83 serves to under load joint the pole 127 and the swinging lever 71.

As understood from the above-described embodiments, according to the present invention, even when the directions of the workpiece and the grinding tool do not coincide correctly, since the workpiece instantly conforms and goes with the deviation of the grinding tool to be automatically corrected, the correct coordination between the grinding tool and the work portion of the workpiece is assured, and it is possible to easily perform ultra-precision grinding finish-work with high accuracy. Therefore, the initial setting is not always necessary to be done accurately but relatively rough setting may be possible, which provides improvements in work efficiency. Moreover, it is possible to adjust the amplitude of the grinding tool according to, for example, the clearance or the like between the work portion of the workpiece and the grinding tool, this enables precise grinding finishwork under suitable condition.

Furthermore, since the work tool vertically and periodically move, the cutting ratio (worked area per unit time) is further improved and the work can be done efficiently. In addition, when the workpiece material is largely moved in order to change the work location thereof, since the X and Y tables are moved, it is possible to smoothly and largely move the workpiece.

Claims (13)

1. A grinding machine which comprises means for supporting a grinding tool and for effecting vibration thereof in a direction having a horizontal component and means for supporting a workpiece, the arrangement being such that, in use, the grinding tool and;or the workpiece is/are horizontally movable in response to vibration of the grinding tool in contact with the workpiece so as to reduce any misalignment between the grinding tool and the workpiece.

2. A grinding machine according to Claim 1, wherein the means for supporting a workpiece comprises a table which is horizontally movably mounted on a base plate and means for fixing the workpiece to the table.

3. A grinding machine according to Claim 1 or 2, wherein the means for supporting a grinding tool comprises a movable arm.

4. A grinding machine according to any one of the preceding claims, wherein the amplitude of vibration of the grinding tool is adjustable.

5. A grinding machine according to Claim 4, wherein the means for effecting vibration of the grinding tool comprises means for effecting eccentric rotation thereof and wherein the amplitude of vibration is adjustable by adjusting the eccentricity.

6. A grinding machine according to any one of the preceding-claims, further comprising means for effecting vertical movement of the grinding tool.

7. A grinding machine for finishing a workpiece, comprising a rotary slide table for receiving a workpiece, a grinding tool arranged to engage with a portion of the workpiece and to vibrate horizontally, a machining head disposed above the workpiece for holding the grinding tool, a first table supporting the slide table and a second table supporting the first table, the first and second tables being horizontally movable in mutually perpendicular directions.

8. A workpiece whenever processed using a grinding machine in accordance with any one of the preceding claims.

9. A grinding machine, substantially as hereinbefore described with reference to, and as shown in, Figures 1 to 4 of the accompanying drawings.

10. A grinding machine, substantially as hereinbefore described with reference to, and as shown in, Figures 1 to 5 of the accompanying drawings.

11. A grinding machine, substantially as hereinbefore described with reference to, and as shown in, Figures 1 to 6 of the accompanying drawings.

12. A grinding machine, substantially as hereinbefore described with reference to, and as shown in Figures 1 to 4 and 6 of the accompanying drawings.

13. Any novel feature or combination of features described herein.