GB2073070A - The dressing of workpiece surfaces by a rotatary tool - Google Patents

Abstract

In a method of dressing a cylindrical surface (such as 26) of a workpiece e.g. a tool an image (5Im) of the workpiece is projected on to a screen (20), in a position such that the center of the arc of a circle corresponding to the surface (26) coincides with the crossing point of crossed index lines (21) provided on the screen (20). This crossing point of the index lines (21) coincides with the trace, on the screen (20), of an axis of rotation (Z), in endwise view, of a support of a dressing grinding wheel (7) mounted on the frame of a machine. Then, said support is rotated about said axis of rotation (Z) to cause the dressing wheel (7) to effect a rotatary movement, during which its cutting point (28) traverses a circular trajectory. The dressing tool is movable relative to the support in two mutually perpendicular directions, perpendicular to the axis (Z). These directions are marked on the screen and are used for adjusting the dressing tool for dressing straight parts of the workpiece. <IMAGE>

Description

SPECIFICATION Method for the dressing of surfaces by means of a rotatary cutting tool and machine for carrying out this method The present invention relates to a method for dressing surfaces by means of a rotatary cutting tool, using a machine in which a support of the tool is arranged in such a manner as to be able to move in two mutually perpendicular directions, and in which said support can moreover rotate around an axis which is perpendicular to the plane containing said mutually perpendicular directions.

The machine further comprises an optical device operative to project onto a screen a magnified image of the workpiece viewed in a direction parallel to the axis of rotation of the tool support.

The invention also provides a machine for carrying out the foregoing method, comprising the rotatary cutting tool the support of which is arranged in such manner as to be capable of movement in two directions which are mutually perpendicular, and in which said support can moreover rotate around an axis perpendicular to the plane containing said mutually perpendicular directions, and an optical device operative to project onto a screen a magnified image of the workpiece viewed in a direction parallel to the axis of rotation of the support of the tool.

The above-mentioned method and a machine by which it can be performed are known per se.

This machine is the subject of Swiss Patent No.

600,987.

The method and machine of the invention serve, mainly, for the dressing of surfaces of cutting tools employed in turning operations. In this machine, displacements of the rotatable cutting tool in one of said mutually perpendicular directions, parallel to the axis of rotation of the tool, are effected by movement of a tool-carrying carriage to effect dressing of plane surfaces. The displacements of the tool in the perpendicular direction provide the approach or withdrawl of the tool with respect to the surface being dressed and thus determine the depth of cut.So far as rotatary movement of the tool support about the axis perpendicular to said mutually perpendicular directions of displacement are concerned, their purpose is to enable the first of said directions of displacement to be brought parallel to the surface to be dressed so as to avoid the necessity for the dressing operation to be effected by a double carriage movement, which is always a difficult procedure.

The circular cylindrical surfaces of the workpiece have, up to now, not been dressed by means of a machine of the type forming the subject of Swiss Patent No. 600,987, such a known machine not being capable of performing the method of the present invention.

The main object of the latter is to permit precise dressing of such circular cylindrical surfaces, this object being achieved by the means as claimed.

The invention provides, for the screen of the optical device of the machine, a reference mark indicating the trace on the screen of said axis or rotation of the tool support, in endwise view. This adjunct to the machine enables the method of the invention to be performed using the machine.

The various features of the invention will be apparent from the following description, drawing and claims, the scope of the invention not being limited to the drawing itself as the drawing is only for the purpose of illustrating a way in which the principles of the invention can be applied. Other embodiments of the invention utilising the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention and the purview of the appendant claims.

The accompanying drawing shows, by way of example, one preferred embodiment of the invention. In the drawing: Fig. 1 is a diagrammatic perspective view of a machine operative for dressing the surface of a cutting tool; Fig. 2 illustrates the geometrical axes of displacement of the rotatary working tool possible with the construction of the machine of Fig. 1; and Figs. 3, 4 and 5 are respectively three views of the projection screen of the machine of Fig. 1 as it appears at different stages during the operation of this machine.

The machine illustrated comprises a stationary frame 1 on which is mounted a stationary disc 2 carrying a column 3 on which is secured a bracket 4 intended to receive the workpiece. The latter will be constituted, most generally, by a cutting tool for use in turning operations and the surfaces of which require to be dressed. This cutting tool, designated by reference 5, is clamped on the bracket 4 by means of a locking handle 6.

The cutting tool of the machine as described and illustrated is constituted by a rotatary grinding wheel 7 rotatably driven by a motor 8 mounted on a support comprising two elements 9 between which the said motor is firmly clamped by means of a locking handle 1 0. The axis of the motor 8 and the wheel 7 will prefereably be horizontal, as shown in Fig. 1, but an arcuate slot 11, provided in each of the elements 9 and only one of which is visible in the drawing, permits adjustment of the motor between the elements 9 so that the axis can be slightly inclined, in a vertical plane, if necessary. An angular adjusting movement of the axis of the motor of the grinding wheel in the horizontal plane can also be made when a locking handle 12 is slackened off.

The two elements 9 of the support of the motor 8 of the wheel 7 are carried by a base 13 able to move in a direction indicated by the axis X of Fig.

2, the displacements of this base in this X direction being produced by a lead screw mechanism (not illustrated) operated by a control hand wheel 14. The base 13 slides on a carriage 1 5, which is itself displaceable in the direction indicated by the axis Y of Fig. 2, which is perpendicular to the X displacement direction of the base 1 3. Displacement of the carriage 1 5 in the Y direction are produced by a lead screw mechanism (not illustrated) operated by a control hand wheel 16.

The slide ways of the carriage 1 5 are carried by a rotatable table 17 the axis of rotation of which, corresponding to the axis Z of Fig. 2, is perpendicular to both the directions of displacements along line X and along line Y respectively. This axis of rotation is vertical in the case of the machine illustrated in Fig. 1. The rotatary movements of the table 17 are produced by a lead screw mechanism and a tangential gear wheel (not illustrated) operated by a control hand wheel 18.

The machine comprises moreover an optical projection device, only a tubular mounting element 1 9 of which has been shown, which operates to project, onto a screen 20, a magnified image of the workpiece 5 as viewed in a direction parallel to the axis of rotation Z of the table 1 7.

The enlarged image such as it appears on the screen 20 has been represented in Figs. 3, 4 and 5 where it is designated by 5,,.

The screen 20 carries crossed index lines 21 the crossing point of which, designated by Z, is situated at the position of the trace, on this screen, of the axis of rotation Z of the table 1 7, in endwise view.

The dressing of a plane surface of the workpiece 5 such as the face 22 (Fig. 3) is effected by bringing, by rotation of the table 17, the X displacement axis of the tool parallel to said face 22. An approach movement of the wheel 7 to this face is produced by displacement along the axis Y by means of the control hand wheel 14, following which the operation of traversing of the face by displacement of the tool parallel to the axis X, in the direction of the arrow 23 of Fig. 3, is effected by means of the control hand wheel 1 6.

The dressing of another plane surface, such as the face 24 of the member 5 (Fig. 4), is effected in exactly the same way, the table 17 having however been rotated to bring the X axis parallel to said face 24. The traversing movements of the carriage are then effected in the direction of the arrow 25.

It is to be noted that the foregoing operations relating to the dressing of the plane faces 22 and 24 of the workpiece 5 are effected while there is placed on the screen 20 a drawing on linen of the magnified workpiece, the scale of which corresponds to the magnification ratio of the optical projection device 19. This drawing is placed to coincide, on the screen 20, with the projected image of the workpiece, thus enabling the operator to check at any time the precision of the dressing operation being performed.

It is also to be noted that the operator could also effect the dressing of plane surfaces of the workpiece without necessarily bringing them parallel to the X axis direction of displacement of the tool. However, this would necessitate, for dressing each plane surface, the production of a double movement of the carriage which is always a difficult procedure and preferably avoided.

So far as the dressing of cylindrical surfaces of the workpiece is concerned, such as, for instance, the surface 26 (Fig. 5), it is effected by using a drawing on linen of the magnified workpiece on which is marked the center of the circular arc representing said cylindrical surface. This drawing is positioned on the screen 20 so that the center of the cylindrical surface to be dressed coincides with the point Z of the screen indicated by the intersection of the two crossing index lines 21, and the workpiece 5 is positioned so that its image on the screen 20 coincides with the drawing, the latter representing the workpiece profile to the same scale as the magnification ratio of the projection device 19.The tool 7 is then brought, by a displacement in the direction X, into contact with the workpiece, followed by rotation of the table by means of the control hand wheel 18, which imparts to the tool a rotatary movement indicated by the arrow 27 of Fig. 5 such that its cutting point, designated by reference 28, follows a circular trajectory producing the requisite dressing of the cylindrical surface 26.

It is further to be noted that, to facilitate positioning of the drawing on the screen and its remove therefrom, the glass of the screen is preferably slidably mounted on the frame of the apparatus. Hence, with such a construction, it is not useful to trace the crossing index lines 21 directly onto the glass, but it is preferable to provide the screen with a second glass, preferably hinged to the frame of the apparatus in such manner that it can be lifted up to a rest position or turned down to its working position, this second glass carrying the index lines 21 the position of which is thus exactly determined when said second glass occupies its turned down working position.

Claims (5)

1. A method for dressing surfaces by means of a rotatary cutting tool, using a machine in which the support of the tool is arranged in such manner as to be movable in two mutually perpendicular directions, and in which said support can moreover rotate around an axis which is perpendicular to the plane containing said mutually perpendicular directions, said machine comprising an optical device operative to project onto a screen a magnified image of the workpiece as viewed in a direction parallel to the axis of rotation of said tool support, wherein an enlarged drawing of a workpiece to be dressed is placed on said screen with the center of a circular cylindrical surface to be dressed coinciding with a reference mark provided on the projection screen, said reference indicating the trace on said screen of the axis of rotation of the support of the tool in endwise view, the workpiece is positioned so that its projected image coincides with the showing of the workpiece on said drawing, and said circular cylindrical surface is then dressed by rotation of the support of the tool about said axis, which causes the cutting point of the tool to traverse a circular trajectory.

2. A machine for carrying out the method as claimed in claim 1, comprising a rotatary cutting tool, a support for the tool which is arranged in such manner as to be movable in either of two mutually perpendicular directions, said support also being rotatable about an axis perpendicular to a plane containing said mutually perpendicular directions, and an optical device operative to project onto a screen a magnified image of the workpiece as viewed in a direction parallel to the axis of rotation of said support for the tool, wherein said screen is provided with a reference mark indicating the trace, on said screen, of said axis of rotation of said tool support in endwise view.

3. A machine according to claim 2, wherein said screen comprises two glasses onto one on which the image of the workpiece is projected and the other of which is provided with said reference mark, said other glass being hinged on the frame of the machine so as to be able to occupy either of two positions, namely a working position in which it is superposed on said one glass and a resting position, in the latter of which it is lifted up, thus uncovering said one glass.

4. A method for dressing cylindrical surfaces by means of a rotatary cutting tool, substantially as herein described and exemplified in the accompanying drawings.

5. A machine for dressing cylindrical surface, constructed and arranged substantially as herein particularly described with reference to the accompanying drawings.