GB2137542A

GB2137542A - Grinding wheel assembly

Info

Publication number: GB2137542A
Application number: GB08404475A
Authority: GB
Inventors: Masakazu Miyashita; Junichi Yoshioka; Fukuo Hashimoto; Akira Kanai; Kiochi Koizumi; Michimasa Daito; Takashi Hasebe
Original assignee: Nissin Machine Works Ltd
Current assignee: Nissin Machine Works Ltd
Priority date: 1983-03-02
Filing date: 1984-02-21
Publication date: 1984-10-10
Also published as: IT8412414A0; IT1180411B; NL183339C; SE8400225D0; CH658423A5; GB2137542B; SE454422B; IT8412414A1; NL8304490A; SE8400225L; DE3406667C2; DE3406667A1; GB8404475D0; NL183339B

Abstract

A grinding wheel assembly 27 comprising an outer wheel part 22 and an inner sleeve 26 which has an inner peripheral surface forming a mounting reference surface 23 by means of which the grinding wheel 27 is mounted for rotation on a shaft 29. The outer peripheral surface of the part 22 has an abrasive layer 21 and the outer peripheral surface of the sleeve 26 is formed with a pulley part 25 through which the grinding wheel is rotated. The grinding wheel assembly is mounted on a machine base 30 by clamping both ends of the fixed shaft 29 in split support arms 30 min . By this arrangement the assembly can be transferred between machines without introducing errors in the mounting position of the grinding wheel 27. <IMAGE>

Description

SPECIFICATION Grinding wheel/grinding wheel assembly The present invention relates to a grinding wheeli grinding wheel assembly.

Conventionally grinding wheels are dressed on wheel dressing machines separate from the processing machines (grinding machines). The transfer of the grinding wheel from one machine to another must be effected without changing the mounting position of the grinding wheel if radial runout of an accurately dressed grinding wheel is to be avoided when the grinding wheel is returned to a processing machine.

Up to now it has been the practice to use an arrangement in which a spindle is rotatably mounted on the mchine and the grinding wheel is secured to the spindle for rotation therewith. Each machine may have its own spindle on which the grinding wheel is releasably clamped. Alternatively, the spindle and grinding wheel secured thereon may form an assembly together with the spindle bearings which is transferred from one machine to another.

Although in such arrangements the grinding wheel is fixed to the spindle we have found that this does not prevent radial runout occurring.

More particularly, when each machine has its own spindle, differences between the mounting portions ofthe spindles and/orthe grinding wheel will produce changes in the mounting position. Similarly, when the spindle and grinding wheel is transferred as an assembly, any displacement between the spindle and its bearings will produce changes in the mounting position.

Accordingly it is an object of the present invention to provide a grinding wheel and a grinding wheel assembly in which the accuracy of a surface finish obtained on a dressing machine can be maintained and reproduced on a processing machine.

According to a first aspect of the present invention there is provided a grinding wheel having an inner peripheral surface defining a rotation/mounting reference surface by means of which the grinding wheel is adapted to be rotatably mounted on a fixed shaft and an outer peripheral surface provided with an abrasive layer and means for rotating the grinding wheel in use thereof.

By utilising a common surface to provide both the mounting and the rotation reference surface for the grinding wheel, accuracy in the mounting position of the grinding wheel on different machines is assured.

Preferably the grinding wheel comprises an outer ring providing the abrasive layer and an inner sleeve providing the rotation/mounting reference surface and the rotation means.

Conveniently the rotation means comprises a pulley part formed integrally on the outer surface of the sleeve and an endless belt extends between the pulley part and a pulley driven by a motor for rotating the grinding wheel.

The outer ring is preferably integral with the sleeve, for example the outer ring may be an interference fit or welded to the sleeve.

According to a second aspect of the present invention there is provided a grinding wheel assembly comprising the grinding wheel of the first aspect rotatably mounted on a fixed shaft.

By providing an assembly in which the grinding wheel is rotatably mounted on a shaft, the grinding wheel is supported during transfer from one machine to another and the shaft can be secured with a high rigidity and without any mounting error thereby further ensuring accuracy in the mounting position of the grinding wheel.

Preferably the grinding wheel is set on the shaft by a thrust bearing engaging an end face of the grinding wheel, the thrust bearing being located by an annular collar on the shaft.

Conveniently the grinding wheel is rotatably mounted through hydrostatic bearings.

In use, the shaft may be fixed by clamping both ends of the shaft in support arms of a machine base on which the assembly is to be mounted.

Further details and advantages of the invention will be apparent from the following description taken in conjunction with the accompanying drawings wherein: Figure 1 is a longitudinal sectional front elevational view of a conventional grinding wheel assembly having a wheel spindle supported at both its ends; Figure 2 is a partially sectional view of a conventional grinding wheel assembly having a wheel spindle supported at only one end thereof; Figure 3 is a longitudinal sectional view of a grinding wheel in acordance with the first aspect of the present invention; Figure 4 is a longitudinal sectional view of a grinding wheel assembly in accordance with the second aspect of the present invention secured on a mounting base;; Figure 5 is a side elevational view of a wheel dressing machine for use with the grinding wheel/ grinding wheel assembly of Figures 3 and 4; Figure 6 is a plan view of the wheel dressing machine shown in Figure 5; Figure 7 is an enlarged frontelevational view of part of the wheel dressing machine shown in Figure 5 with the dressing tool shown in a first position; Figure 8 illustrates the positional relationship between the dressing tool in the first position shown in Figure 7 and a grinding wheel; Figure 9 is an enlarged front elevational view of part of the wheel dresing machine shown in Figure 5 with the dressing tool shown in a second position normal to the first position shown in Figure 7; Figure 10 illustrates the positional relationship between the dressing tool in the second position shown in Figure 9 and a grinding wheel; and Figure 11 illustrates the positional relationship between the dressing tool in a third position in which the tool is inclined at an acute angle relative to a grinding wheel.

In the following description two conventional grinding wheel assemblies will first be described with reference to Figures 1 and 2 respectively. A grinding wheel and grinding wheel assembly according to the first and second aspects of the present invention will then be described with reference to Figures 3 and 4 respectively. Finally a wheel dressing machine for use with the grinding wheel/ grinding wheel assembly of Figures 3 and 4 will be described with reference to Figures 5 to 11.

Referring to Figure 1, a first known grinding wheel assembly is shown comprising a wheel spindle 1 and a grinding wheel a. The spindle 1 is rotatably mounted on a machine base 4 through bearing housings 3 provided at both ends of the spindle. The spindle 1 is coupled at one end to an intermediate shaft 6 through a coupling 5 and is supported at the other end by a thrust bearing 7. The grinding wheel a has an abrasive layer on the outer peripheral surface and the inner peripheral surface is a clearance fit on the outer peripheral surface of the spindle 1. The grinding wheel a is secured to the spindle 1 for rotation therewith by means of a threaded fastener 2.

In the assembly thus described, the mounting reference surface of the grinding wheel a is constituted by the inner peripheral surface thereof and the mounting reference surfaces of the assembly are constituted by the outer peripheral surfaces of the bearing housings 3 and the confronting surfaces of the machine base 4.

In the case where the abrasive layer is constituted by super abrasive grains such as diamond and the required surface finish is provided by a wheel dressing machine, it is necessary to transfer the assembly having the bearing housings 3 set on the spindle 1 between the dressing mchine and the processing machine (grinding machine). In transfer the positional relationship between the spindle 1 and the bearing housings 3 may change with possible consequential change in the acuracy of the mounting reference surfaces between the bearing housings 3 and the machine base 4. More particularly, even if the surface finish obtained on the dressing machine is accurate, the grinding wheel a may have a radial runout when the assembly is returned to the base 4 of the processing machine due to a change in the mounting position or clamping.It is disadvantageously difficult to move and reset the spindle 1 accurately to avoid this problem.

Referring now to Figure 2, a second known grinding wheel assembly is shown comprising a wheel spindle 1' and a grinding wheel 9. The spindle 1' is rotatably mounted on a machine base 4 through a bearing housing 3 provided at or adjacent one end of the spindle. The other end of the spindle 1' has a tapered portion 11 terminating in an externally threaded portion. The grinding wheel 9 has a diamond-bonded abrasive layer on the outer peripheral surface and the inner peripheral surface is a clearance fit on the outer peripheral surface 8' of an annular insert 8 to which the grinding wheel 9 is secured by means of a threaded fastener 2'. The insert 8 has a stepped bore provided with a tapered portion 10 complementary to the tapered portion 11 on the spindle 1'.The insert 8 having the grinding wheel 9 secured thereto is mounted on the tapered portion 11 of the spindle and clamped for rotation therewith by means of a releasable lock nut 12 mounted on the threaded end portion of the spindle 1' and engaging an annular shoulder in the spindle bore.

In the assembly thus described, the mounting reference surface of the grinding wheel is constituted by the tapered portions 10,11 of the insert and spindle.

In the case where the required surface finish on the abrasive layer is provided by a wheel dressing machine, it is necessary to transfer the insert 8 and grinding wheel 9 between tapered spindles 1' of the dressing machine and the processing machine (grinding machine). In transfer, the positional relationship between the spindle 1' and the insert 8 may change from one machine to another with possible consequential change in the accuracy of the mounting of the insert 8 on the spindle 1'. More particulary, even if the surface finish obtained on the dressing machine is accurate, the grinding wheel 9 may have a radial runout on the processing machine due to possible differences between the tapered portions 11 of the spindles 1' on the dressing machine and processing machine and/or between the tapered portions 11, 10 of the spindles 1' and the insert 8.This grinding wheel assembly is therefore not suitable for precision grinding. Moreover, since the securing of the grinding wheel 9 to the insert 8 is also effected through a mounting reference surface, there is a possibility of displacement of the grinding wheel 9 due to a repetition of starts and stops or an impact load.

Referring now to Figures 3 and 4, a grinding wheel and a grinding wheel assembly according to the first and second aspects respectively of the present invention, are shown.

The grinding wheel 27 comprises an outer ring 22 and an inner sleeve 26. The outer ring 22 has an abrasive layer 21 on the outer peripheral surface and the inner peripheral surface is an interference fit on the outer peripheral surface of the sleeve so as to be integral therewith. For example, the ring 22 may be integrally mounted on the sleeve 26 by applying a low temperature shrinkage to a jointed portion thereof. One end of the sleeve extends axially beyond the ring and is formed on the outer peripheral surface thereof with a pulley part 25. The other end of the sleeve defines an end reference surface 24 for a thrust bearing. The inner peripheral surface of the sleeve defines a mounting/rotation reference surface 23 for the grinding wheel.

The grinding wheel assembly is provided by the grinding wheel 27 above-described rotatably mounted on a fixed shaft 29 through hydrostatic bearings so as to be radially positioned. The shaft 29 has pockets 28 formed by planarly notching the shaft and the grinding wheel is positioned in the direction of thrust by parts related to the shaft 29. The grinding wheel further has a rotation guide formed thereby.

The assembly is rigidly mounted on a machine base 30 through split support arms 30' which clamp the shaft 29 at both ends and the grinding wheel is rotated on the fixed shaft 29 through an endless belt (not shown) connecting the pulley part 25 to a motor (not shown).

in the grinding wheel assembly according to the present invention thus described, the shaft 29 is fixed and the grinding wheel 27 is rotatable thereon in a set position. Consequently, the assembly can be moved from one machine to another without any possibility of change in the positional relationship between the fixed shaft 29 and the grinding wheel 27. In this way the accuracy of the grinding surface obtained on the dressing machine is maintained on transfer of the assembly to the processing machine and radial runout is avoided. In addition, since the assembly is secured by clamping the shaft 29, a high rigidity can be obtained. Moreover, the grinding wheel 27 is supported on the fixed shaft 29 through the bearings, with the sleeve inner peripheral surface defining a rotation/mounting reference surface 23.Therefore, a reliable mounting can be effected, and the grinding accuracy can be increased.

It will be understood that the invented grinding wheel/grinding wheel assembly is not limited to the embodiments above-described. For example the outer ring 22 and inner sleeve 26 could be integrally connected by any suitable means such as welding.

Alternatively, the outer ring 22 and inner sleeve 26 could be formed in one piece. The grinding wheel 27 may be positioned on the shaft 29 by any suitable means.

Referring now to Figures 5 to 11, a wheel dressing machine is shown in combination with the grinding wheel/grinding wheel assembly above-described with reference to Figures 3 and 4 and, where appropriate, in the following description like reference numerals are used to indicate corresponding parts.

The wheel dressing machine includes a body 31 of rectangular shape in plan view mounting at one end a base 30 on which the grinding wheel assembly is rigidly mounted through two split support arms 30' which clamp the shaft 29 at both ends. A motor 32 housed within the body 31 has an output shaft carrying a pulley and an endless belt 33 extending between the pulley and the pulley part 25 of the grinding wheel 27 transmits the drive for rotating the grinding wheel 27 at low speed e.g. several tens of revolutions per minute.

The body 31 further mounts a first table 36 connected to a feed screw 35 driven by a motor 34 to advance or retract the first table in a direction normal to the longitudinal axis of the fixed shaft 29. The table 36 mounts a second table 37 connected to a feed screw 39 driven by a motor 38 to reciprocate the second table 37 in a direction parallel to the longitudinal axis of the fixed shaft 29.

A mounting plate 40 is rotatably mounted on a shaft 41 secured to the second table 37. The mounting plate 40 is guided for rotation by two bolts 43 mounted on the second table 37 which pass through an arcuate slot 42 formed in the mounting plate and having its centre of curvature coaxial with the axis of rotation of the mounting plate. Lock nuts 44 mounted on threaded parts of the bolts 43 allow the mounting plate 40 to be clamped at any selected one of a range of positions between the limits defined by the engagement of the bolts 43 with the ends of the slot 42.

Attached to the mounting plate 40 are a bracket 47 and a motor 48. The bracket 47 supports a spindle 45 on which a dressing tool 46 and a pulley 49 are mounted for rotation therewith. The rotational axis of the tool 46 defined by the spindle 45 extends normal to the rotational axis of the mounting plate 40. The motor 48 has an output shaft carrying a pulley 50 and an endless belt 51 extending between the pulleys 49, 50 transmits the drive for rotating the spindle 45 and dressing tool 46 at high speed e.g. a peripheral speed of several hundred metres per minute.

As will now be apparent from the foregoing description, in operation, the dressing tool 46 is brought into contact with the abrasive layer 21 of the grinding wheel 27 by operation of motor 34 to advance the first table 36 and simultaneously is traversed to and fro across the width of the abrasive layer 21 by operation of motor 38 to reciprocate the second table 37. Furthermore, by adjusting the rotational position of the mounting plate 40 the contact between the abrasive layer 21 and the dressing tool 46 can be selected to provide any required surface finish.

More particularly, if, as shown in Figures 7 and 8, the mounting plate 40 is clamped in a first-position with the spindle 45 extending parallel to the longitudinal axis of the fixed shaft 29, line contact is obtained between the surfaces of the dressing tool 46 and the abrasive layer 21 to effect a fine dressing.

When the uneveness in height between the surfaces has been completely removed, the surfaces only slide on each other and dressing is no longer effected.

Next, if, as shown in Figures 9 and 10, the mounting plate 40 is clamped in a second position with the spindle 45 extending normal to the longitudinal axis of the fixed shaft 29, point contact is obtained between the surfaces of the dressing tool 46 and the abrasive layer 21 so that the dressing tool 46 intermittently comes into contact with the surface of the abrasive layer 21 and it becomes possible to continue the dressing further.

Moreover, if, as shown in Figure 11, the mounting plate 40 is clamped in a third position with the spindle 45 extending at an acute angle relative to the longitudinal axis of the fixed shaft 29, the surfaces of the dressing tool 46 and the abrasive layer 21 will have a relative peripheral speed difference corresponding to the inclination angle and, if this speed difference is made small, the bond portion is ground by the abrasive grains to effect a dressing.

After the required dressing has been effected, the ends of the fixed shaft 29 are released from the support arms 30' and the grinding wheel assembly, comprising shaft 29 and grinding wheel 27 is transferred to the processing machine.

The wheel dressing machine above-described is convenient, since, by changing the position of the dressing tool, the surface contact between the dressing tool and the grinding wheel can be varied to effect various dressings, such as rough, finish and surface dressings by a single wheel dressing machine. In addition, the construction is simple and the mounting space is reduced.

It will be understood that the dressing machine is not limited to the embodiment above-described, for example the guide means may be the mounting modified to provide the bolts on the mounting plate and the slot in the second table. Furthermore, any number of bolts may be used and these can be arranged together with the length of the slot to provide any range of rotational movement. Alternatively, any other suitable guide means for controlling rotational movement and securing the mounting plate at a selected position may be used. The dressing tool may be detachably mounted to facilitate removal and interchange of tools as necessary.

Finally it will be appreciated that the dressing machine above-described is not limited to use with the grinding wheel/grinding wheel assembly of Figures 3 and 4. Thus by appropriate modification of the base 30 the machine could mount the grinding wheel assembly of either Figure 1 or Figure 2 to effect various surface finishes on the grinding wheel by adjustment of the dressing tool as abovedescribed.

Claims

1. A grinding wheel having an inner peripheral surface defining a rotation/mounting reference surface by means of which the grinding wheel is adapted to be rotatably mounted on a fixed shaft and an outer peripheral surface provided with an abrasive layer and means for rotating the grinding wheel in use thereof.

2. A grinding wheel according to claim 1 wherein the grinding wheel comprises an outer ring providing the abrasive layer and an inner sleeve providing the rotation/mounting reference surface and the rotation means.

3. A grinding wheel according to claim 2 wherein the rotation means comprises a pulley part formed integrally on the outer surface of the sleeve.

4. A grinding wheel according to claim 2 or claim 3 wherein the outer ring is integral with the inner sleeve.

5. A grinding wheel substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings.

6. A grinding wheel assembly comprising the grinding wheel according to any one of the preceding claims rotatably mounted on a fixed shaft.

7. A grinding wheel assembly according to claim 6 wherein the grinding wheel is positioned on the shaft by a thrust bearing engageable with an end face of the grinding wheel and located by an annular collar on the shaft.

8. A grinding wheel assembly according to claim 6 or claim 7 wherein the grinding wheel is rotatably mounted through hydrostatic bearings.

9. A grinding wheel assembly according to any one of claims 6 to 9 wherein the shaft is fixed by clamping both ends of the shaft in support arms of a base on which the assembly is mounted in use.

10. A grinding wheel assembly substantially as hereinbefore described with reference to Figure 4 of the accompanying drawings.