GB2106811A - Grinding wheel dressing machines - Google Patents

Abstract

The machine tool comprises: Support means (12 & 15) for the rotatable mounting of a grinding wheel (M) and drives means (13) adapted to rotate the grinding wheel (M); A member (6) movable along two coordinate axes (X & Y) and carrying a first dressing tool (19) and a second dressing tool (20) in respective static positions adjacent one another, the dressing tools being adapted to dress a first operative surface (M1) and the second operative surface (M2) respectively of the grinding wheel (M), the operative surfaces being axially opposite one another, and Means (23, 9 & 5) for controlling movement of the moving member (6) relatively to the grinding wheel (M) and for controlling the drive means (13) and adapted to move the dressing tools (19 & 20) along the two co-ordinate axes (X & Y) disposed in a plane parallel to the rotational axis of the grinding wheel (M) and intersecting the same, along the first operative path (C-D) on which the first dressing tool (19) engages said first operative surface (M1) of the grinding wheel (M) in a predetermined manner, and a second operative path (H-L) on which the second tool (20) engages the second operative surface (M2) of the grinding wheel (M). <IMAGE>

Description

SPECIFICATION Improvements in grinding wheel dressing machines This invention relates to a machine tool for dressing the surface of an abrasive grinding wheel having the shape of a solid of rotation and having at least a first operative surface and a second operative surface which are disposed axially opposite one another.

More particularly, the invention relates to a machine tool of the kind comprising: support means for the rotatable mounting of a grinding wheel; drive means adapted to rotate the grinding wheel; a moving member carrying at least one dressing tool having a diamond tip, and control means adapted to actuate the drive means to move the moving member nearthe grinding wheel in a predetermined manner so thatthe dressing tool carried by the moving member engages the operative surface of the grinding wheel to produce or restore the correct geometrical shape and cutting ability of such surface.

Machine tools of the kind specified are known wherein the control means are adapted to move the moving member, and therefore the dressing tool, along three co-ordinate axes relatively to the grinding wheel. In the known machines the moving member and the control means are adapted to produce movements of the dressing tool relatively to the grinding wheel along two cartesian co-ordinate axes (X & Y) perpendicular to one another and the concomitant rotation of the tool relatively to an around the grinding wheel. Machines of this kind require complex and expensive systems for checking the position and trajectory of the dressing tool along three co-ordinate axes if grinding wheels having a required profied and cutting ability are to be produced.The complication of the checking and control systems used in such machines derives virtually entirely from the need to have continuous checking of the position and trajectory of the tool on three co-ordinate axes. In order to reduce the complication of the checking and control systems needed by machine tools of the kind described, and thus to reduce theirfirst costs, dressing machines in which the position and the path of the dressing tool need to be checked only on two co-ordinate axes would be desirable.

This invention accordingly relates to a machine tool of this kind hereinbefore outlined, with the main feature that the moving member carries at least one first dressing tool and at least one second dressing tool in respective static positions adjacent one another, the tools being adapted to dress the first operative surface and the second operative surface respectively of the grinding wheel, and the control means are adapted to move the dressing tools along only two co-ordinate axes disposed substantially in a plane parallel to the rotational axis of the grinding wheel and intersecting the same along the first operative path on which the first dressing tool engages said first operative surface of the grinding wheel in a predetermined manner, and a second operative path on which the second dressing tool engages the second operative surface of the grinding wheel.

Other features and advantages of the machine tool in accordance with this invention will emerge from the following detailed description which is given with reference to the accompanying purely exemplary and non-limitative drawings wherein: Figure 1 is a perspective view of a machine tool in accordance with this invention; Figures 2 and 3 are perspective views showing parts of the machine of Figure 1 in two different operative positions, and Figure 4 is a diagrammatic view of a possible path followed by a moving tool carrier of the machine in accordance with the invention in the course of operation.

Referring to Figure 1, a machine tool in accordance with the invention comprises a base 1 carrying a vertical plate 2 whose top part forms a pair of wings or cheeks or the like 2a, 2b bent at right-angles and facing one another. Two horizontal cylindrical guide bars 3 extend parallel to one another from the cheeks 2a, 2b and a carriage 4 is slidable along the bars 3. An electric motor 5 is connected to the flange 2a on the side remote from the flange 26. Motor shaft 5a is externally screwthreaded and extends horizontally. Shaft 5a extends parallel to the guides 3 borne by the plate 2 and engages in a screwthreaded aperture 4a in carriage 4. Consequently, energization of motor 5 causes carriage 4 to move relative to plate 2 along an axis X in Figure 1.A moving member 6, basically comprising a cylindrical bar or rod, is arranged for axial movement through the carriage 4 along an axis Y which can be seen in Figure 1 and which is perpendicular to the axis X. The bottom part of member 6 extends to the exterior of carriage 4 by way of an aperture 4,5. The top end portion of member 6 is formed with an axial cylindrical screwthreaded aperture in which a screwthreaded rod 7 is recieved for rotation. Rod 7 is locked axially inside a casing 8 carried at the top of carriage 4. However, rod 7 can be rotated around its longitudinal axis by means of an electric motor 9 which is rigidly connected to casing 8 and which has a shaft 9a carrying a pulley 9b. By means of a transmission belt 10 the pulley 9b can rotate a similar pulley 11 rigidly secured to one end of rod 7.

When motor 9 is energized, rotation of rod 7 moves the member 6 along the axis Y. Disposed on a support frame 12 is an electric motor 13 to whose shaft a pulley 14 is rigidly secured. At the end remote from the motor 13 the frame 12 has an arm 12a carrying a shaft 15 which is rotatable but blocked axially. Secured to one end of a shaft 15 is a pulley 16 which is connected by a transmission belt 17 to a pulley 14 driven by motor 13. The longitudinal axis of shaft 15 extends parallel to the axis X.

Disposed at that end of shaft 15 which is nearthe moving member 6 are conventional securing means, not shown in detail, for securing to the shaft 15 an abrasive grinding wheel M whose operative surface it is required to dress. In operation, energization of motor 13 causes grinding weel M to rotate around an axis parallel to the axis X, the drive being by way of the belt 17 and pulleys 14 & 16.

Releasably secured to the bottom end of moving member 6 is a tool carrying head 18 carrying a first dressing tool 19 and a second dressing tool 20 which are both of known kind and which each have a diamond tip.

The motors 5, 9 & 13 are connected by connecting wiring to a numerical control unit 23 adapted in known mannerto co-ordinate the operation of the motors so that the moving member and the tools 19 & 20 move in predetermined manners which will be described hereinafter.

A machine tool of the kind hereinbefore described can be used to dress the operative surface of an abrasive grinding wheel M of the kind for instance, having the shape visible in Figure 4. The grinding wheel shown has the shape of a solid of rotation and has a first operative surface M1 and a second operative surface M2, the two surfaces being axially opposite to one another.

As previously stated, each tool 19 & 20 has a diamond tip 19a & 20a respectively (Figures 2 and 3).

The tools 19 & 20 are supported on the tool carrier head 18 in respective static positions adjacent one another. More particularly, the longitudinal axis of the tip 19a is preferably at an inclination to the axis Y, the amount of such inclination being somewhere between the inclinations to the axis Y of the straight lines perpendicular to the steepest portion and to the less steep portion of the operative surface M1 of the wheel M. Similarly, the longitudinal axis of the tip 20a has an inclination somewhere between the inclinations to the axis Y of the straight lines perpendicular to the steepest portion and to the less steep portion of the second operative surface M2 of the wheel M.

Preferably, the tools 19 & 20 are so connected to the head 18 that the longitudinal axes ofthetips 19a & 20a are disposed in a single plane which extends parallel to the axis X and which intersects the wheel M.

In operation, as will be explained hereinafter, tip 19a is adapted to dress the operative surface M1 and tip 20a to dress the other operative surface M2.

The operation of the machine tool in accordance with the invention and shown in Figures 1 - 3 will now be described with reference to Figure 4, which shows in diagrammatic form one possible path for the head 18.

After a grinding wheel M which it is required to dress has been secured to the shaft 15, motor 13 is switched on to rotate the wheel M. Initially the control unit 23 acts by way of the motors 5 and 9 to move the moving member 6 into a position such that the head 18 is positioned relative to the wheel M in the position A in Figure 4. The moving member 6 is then lowered to being the head 18 into position B, whereafter the member 6 is moved horizontally along the axis X until the diamond tip 19a of the tool 19 engages the radially most inward portion of the operative surface M1 of the wheel (position C).The unit 23 then causes the moving member 6 to move along axes X & Y so that the tool 19 rises along the profile of the operative surface M1 of the wheel and engages such surface in order to impart or restore to it a predetermined geometric shape, until position D is reached. The head 18 then moves to position E.

The moving member 6 again moves horizontally towards position F, then moves down parallel to the axis Y to bring head 18 into position G. In this position the control unit 23 causes the member 6 to move horizontally towards position H in which the diamond tip 20a of tool 20 is in contact with the radially most inward portion of the operative surface M2 of the wheel. The moving member 6 then moves along the axes X & Y so that the tip 20a rises along the profile of the operative surface M2, engaging the same to give it the required shape. The cycle is complete when the tool 20 reaches position L in Figure 4 - i.e., when the tip 20a has reached the top of the operative surface M2. The member 6 then moves the head 18 into position N, then back to the initial position A.

Throughout the complete cycle of operations all the movements of the head 18 take place in a plane parallel to the axes X & Y. Consequently, the machine tool in accordance with the invention has the advantage of requiring merely a supervisory and control system for controlling the movements of the member 6 along just two co-ordinate axes. The machine tool in accordance with the invention therefore has the substantial advantage of greater simplicity.

The forms of actuation and more particularly of construction may of course vary widely, without prejudice to the underlying idea of the invention, from what has been described and illustrated purely by way of non-limitative example and without for that reason departing from the scope of this invention.

Claims (4)

1. A machine tool for dressing the surface of an abrasive grinding wheel having the shape of a solid of rotation and having at least a first operative surface and a second operative surface which are disposed axially opposite one another, the machine comprising: support means for the rotatable mounting of a grinding wheel; drive means adapted to rotate the grinding wheel; a moving member carrying at least one dressing tool having a diamond tip and control means adapted to actuate the drive means to move the moving member near the grinding wheel in a predetermined manner so that the dressing tool carried by the moving member engages the operative surface of the grinding wheel to produce or restore the correct geometrical shape and cutting ability of such surface;; characterised in that the moving member carries at least one first dressing tool and at least one second dressing tool in respective static positions adjacent one another, the tools being adapted to dress the first operative surface and the second operative surface respectively of the grinding wheel, and the control means are adapted to move the dressing tools along only two co-ordinate axes disposed substantially in a plane parallel to the rotational axis of the grinding wheel and intersecting the same along a first operative path on which the first dressing tool engages said first operative surface of the grinding wheel in a predetermined manner, and a second operative path on which the second dressing tool engages the second operative surface of the grinding wheel.

2. A machine tool according to Claim 1, characterised in that the first and second dressing tools are so connected to the moving memberthatthe longitudinal axes of the respective diamond tips are substantially coplanar.

3. A machine tool according to Claim 2, characterised in that the first and second dressing tools are releasably secured to the moving member.

4. A machine tool for dressing the operative surface of an abrasive grinding wheel, substantially as described and illustrated and for the purposes specified.