GB2122520A

GB2122520A - Process and apparatus for producing a fluted operative surface of a cam

Info

Publication number: GB2122520A
Application number: GB08312123A
Authority: GB
Inventors: Bernardo Voglino
Original assignee: Fiat Auto SpA
Current assignee: Fiat Auto SpA
Priority date: 1982-05-07
Filing date: 1983-05-04
Publication date: 1984-01-18
Also published as: FR2526349B1; IT1155188B; DE3316662C2; FR2526349A1; JPS5930659A; DE3316662A1; GB8312123D0; JPH0615146B2; IT8267601A0; GB2122520B

Abstract

A process for producing a fluted surface extending around a straight longitudinal axis and serving as the operative surface of a cam 3 comprises providing a grindstone 1 which rotates around an axis and has a cylindrical working surface, placing such surface in contact with the fluted surface 4 of the cam blank, rotating the cam 3 around its axis Y, imparting thereto an angular oscillatory motion around an oscillation axis V of fixed direction, imparting to the grindstone a displacement adapted to move the grindstone working surface in a rectilinear direction F, and also impart- to the axis of the cam a second angular oscillatory motion about a second oscillation axis Z and a second displacement of the grindstone in a predetermined rectilinear direction G. Control means link the angular oscillatory motions of the cam and the displacements of the grindstone, so that, in all the operative positions of the cam, that segment 5, 6 of its fluted surface 4 which is in contact with the grindstone working surface is disposed parallel to the grindstone axis. <IMAGE>

Description

SPECIFICATION Process and apparatus for producing a fluted operative surface of a cam The invention relates to processes for producing by grinding a fluted surface extending around a straight longitudinal axis and serving as the operative surface of a cam, and to machines for performing such process.

The invention relates more particularly to a process and apparatus of the kind disclosed in the Applicants' earlier United Kingdom Patent Application No. 8305717.

The process according to said earlier application is of the kind comprising the steps of providing a grindstone which rotates around an axis and has an annular working surface, placing such surface in contact with the fluted surface of the cam blank rotating the cam around its axis, imparting thereto an angular oscillatory motion around an oscillation axis of fixed direction, imparting to the grindstone a displacement adapted to move the grindstone working surface in a predetermined rectilinear direction, and providing control means which so associate in a predetermined relationship cam rotation about its axis, oscillation of the cam axis and grindstone displacement as always to maintain the working surface of the grindstone in contact with the fluted surface of the cam.

Similarly, the apparatus according to said earlier application is of the kind comprising: a workpiece head so supported by the stationary structure of the apparatus as to be rotatable around an oscillation axis which is of fixed direction and on which a workpiece slide is disposed, the cam blank being disposed thereon for rotation around its longitudinal axis; a grindstone upright on which a tool spindle for carrying a grindstone coaxially of itself is disposed for rotation around its axis, such upright being movingly mounted in the stationary structure of the apparatus to permit displacement of the grindstone rotational axis along a predetermined straight path; and control means for producing a predetermined relationship between rotation of the cam around its longitudinal axis, angular movement of the workpiece head around the oscillation axis and the displacement of the movable spindle-bearing grindstone upright, the latter predetermined relationship being such that the working surface of the grindstone is always in contact with the fluted surface of the cam.

The process and apparatus of the kind just specified require in the prior art the use of a plane grindstone-i.e., one having a working surface belonging to a plane.

It is the object of this invention to provide a process and apparatus for producing by grinding a fluted surface extending around a straight longitudinal axis and serving as the operative surface of a cam, the process and apparatus being of the kind outlined and using a cylindrical grindstone having a working surface forming part of a constant crosssection cylinder.

Accordingly, the invention relates to a process of the kind specified wherein the annular working surface of the grindstone is a cylinder which is of constant circular cross-section and whose axis is the rotational axis of the grindstone, and the process comprises the further steps of imparting to the axis of the cam a second angular oscillatory motion about a second oscillation axis and of imparting to the grindstone a second displacement in a predetermined rectilinear direction, control means being provided which link the second angular oscillator motion of the cam axis with the first oscillatory motion thereof and the second displacement of the grindstone with the first displacement thereof, the action of the control means being such that, in all the operative positions of the cam, that segment of its fluted surface which is in contact with the grindstone working surface is disposed parallel to the grindstone axis, so that contact between the last-mentioned surface and the fluted surface of the cam extends over the whole of such segment.

To this end, the invention also relates to an apparatus of the kind specified wherein the grindstone has a cylindrical working surface which is of constant circular cross-section and which is disposed coaxially of the tool spindle, the same being disposed for rotation on a tool slide movingly mounted in the grindstone upright to permit a second displacement of the grindstone rotational axis along a predetermined straight path; and the workpiece slide on which the cam blank is rotatably mounted is supported by a retaining plate which is articulated to the workpiece head for movement around an oscillation axis, control means being provided for linking the angular movement of the workpiece slide with the angular oscillation motion of the workpiece head and the displacement of the tool spindle slide with the displacement of the grindstone upright so that in all the operative positions of the cam that segment of the fluted surface of the cam which is in contact with the working surface of the grindstone is disposed parallel to the grindstone axis, so that contact between the last-mentioned surface and the fluted surface of the cam extends over the whole of such segment.

The invention will be described hereinafter with reference to a preferred practical embodi ment illustrated in the accompanying purely exemplary and non-limitative drawings wherein Figures 1 to 4 are perspective diagrammatic views of the cam blank and of the grindstone in various consecutive steps of the process according to the invention; Figure 5 is a plan view corresponding to Fig. 1; Figure 6 is a side view looking in the direction of an arrow Vl in Fig. 5 parallel to the grindstone axis; Figures 7 and 8, 9 and 10 and 11 and 12 are figures similar to Figs. 5 and 6 and relate to Figs. 2, 3 and 4 respectively;; Figure 13 is a view parallel to the axis of the grindstone showing the same and the cam in a further phase of the process according to the invention, and Figure 14 is a perspective view of apparatus for performing the process according to the invention.

A cylindrical grindstone 1 rotates around an axis X. The grindstone 1 has a working surface 2 which is cylindrical, of constant crosssection and coaxial with the axis X. The axis X can be displaced in the direction indicated by an arrow F. A cam 3 has an operative surface 4 in the form of a fluted surface-i.e., embodied by a number of rectilinear segments.

The cam 3 is rotatable around an axis Y and its operative surface 4 has a shape varying continuously along the axis Y. The cam 3 is rotatable around a first axis V perpendicular to the grindstone axis X and is also rotatable around a second axis Z perpendicular to the axes Y and V. A plane A is tangential to cam surface 4 along a straight segment 5. A generatrix 7 generates the cylindrical surface 2 disposed in the plane bounded by the grindstone axis X and the direction F of its displacement. In Figs. 1, 5 and 6 the generatrix 7 is parallel to the segment 5 and is aligned relatively to the latter in the direction F.

Consequently, when the grindstone 1 is moved in the direction F the generatrix 7 moves until coinciding with the segment 5. A plane B is tangential to the cam surface 4 along a straight segment 6 and is angularly offset from the plane A around the axis Y by an angle H. In Figs. 2, 7 and 8 the cam 3 has been turned from the position previously shown through the angle H around the axis Y in the direction indicated by an arrow H 1. The plane B is therefore perpendicular to the plane bounded by the grindstone axis X and the displacement direction F. In Figs. 3, 9 and 10 the cam 3 has been turned from its position shown in Figs. 2, 7 and 8 through an angle K around the axis Z in the direction indicated by an arrow K1. Because of the rotation K the segment 6 is placed parallel to the plane bounded by the grindstone axis X and its direction F of displacement.In Figs. 4, 11 and 12 the cam 3 has been turned from the position shown in Figs. 3, 9 and 10 through an angle L around the axis V in the direction indicated by an arrow L1. Consequently, the segment 6 is placed parallel to the grindstone axis X and has therefore moved relatively to the plane bounded by the axis X and the direction F by an amount E. In Fig. 13 grindstone 1 has moved from its position shown in Figs. 4, 11 and 12 by the amount E in the direction indicated by an arrow G perpendicular to the direction F. Because of this second displacement the grindstone generatrix 7 is aligned with the segment 6 in the direction F. Consequently, when the grindstone 1 is moved in the direction F, the generatrix coincides with the segment 6.The description of the process according to Figs. 1 to 13 is as follows: In Figs. 1, 5 and 6 the grindstone 1 is so moved in the first displacement direction F as to engage with the segment 5, whereafter the cam 3 is rotated around its own axis Y simultaneously as the cam position is altered by angular movements of the cam around the axes Z and V, the grindstone being moved one way and/or the other in the directions F and G. The cam and grindstone movements are numerically controlled by known control means (not shown), so that, in all the relative positions of the cam 3 and grindstone 1, the grindstone generatrix 7 is in contact with a particular segment of the fluted surface 4 of the cam 3. This operation is shown in the remaining Figs. 2 to 13.In these figures, and with reference to a generic plane B tangential to the surface 4, the correct operating position of the grindstone 1 and cam 3 is set up by means of the rotations H, K, L of the cam 3 and the grindstone displacements F, G. If the profile required for the cam surface 4 is known, it is possible to work out for every tangential plane B the corresponding values of the angles of rotation of the cam 3 and the units of displacement of the grindstone 1. Fig.

14 shows an apparatus 10 for performing the process hereinbefore described. The apparatus 10 comprises a base 11 on which a workpiece head 12 is mounted for rotation around a stationary axis V. A retaining plate 13 is so borne by head 12 as to be rotatable around an axis Z perpendicular to the axis V. A workpiece slide or carriage 14 is movingly mounted on the plate 13 and a cam shaft 15 is rotatably mounted on the slide 14. The shaft 15 is rotatable around an axis X perpendicular to the axes Z and V and is rotated by a motor 16. A grindstone upright or column 17 is so disposed on the base 11 as to be movable in a displacement direction F perpendicular to the rotational axis V of the head 12.

The moving mounting of the column 17 is provided by means of a dovetail guide 18. A tool spindle slide 19 is so disposed on the column 17 as to slide in the displacement direction G, the same being perpendicular to the direction F. The slide 19 has a spindle and disposed thereon coaxially thereof is a grindstone 1 having a cylindrical working surface which is of a constant circular crosssection and coaxial with the rotational axis X of the grindstone 1. The axis X is perpendicular to the axis V and to the directions F, G.

Drive means (not shown) rotate the grindstone 1. The apparatus 10 operates as follows. The camshaft 15 is rotated by the motor 16 around the axis Y in the direction indicated by the arrow HI. Simultaneously, numerically controlled drive means (not shown) rotate the plate 13 around the axis Z in the direction indicated by the arrow K1 and the workpiece head 12 around the axis V in the direction indicated by the arrow L1. Also simultaneously, through the agency of numerically controlled drive means (not shown) the column 17 is moved in the direction F and the slide 19 is moved in the direction G. The effect of such combined movements is to ensure that the grindstone 1 is at all times in engagement with the nearby cam 3 of the camshaft 15 along one of the segments forming the fluted operative surface of the cam 3.

The practical embodiments and details can of course vary widely from what has been described and shown without for that reason departing from the scope of this invention. For instance, since the motions hereinbefore described are effective as relative motions and not as absolute motions for the purpose of achieving correct operative engagement between the grindstone 1 and the cam 3, some of the movements performed by the cam can be performed by the grindstone and vice versa, and the displacement movements of the grindstone can be performed by the cam.

Claims

1. A process for producing by grinding a fluted surface extending around a straight longitudinal axis, and serving as the operative surface of a cam, the process comprising the steps of providing a grindstone which rotates around an axis and has an annular working surface, placing such surface in contact with the fluted surface of the cam, rotating the cam around its axis, imparting thereto an angular oscillatory motion around an oscillation axis of fixed direction, imparting to the grindstone a displacement adapted to move the grindstone working surface in a predetermined rectilinear direction, and providing control means which so associate in a predetermined relationship cam rotation about its axis, oscillation of the cam axis and grindstone displacement as always to maintain the working surface of the grindstone in contact with the fluted surface of the cam, characterised in that the working surface of the grindstone is a cylinder which is of constant circular crosssection and whose axis is the rotational axis of the grindstone, and the process comprises the further steps of imparting to the axis of the cam a second angular oscillatory motion about a second oscillation axis and of imparting to the grindstone a second displacement in a predetermined rectilinear direction, control means being provided which link the second angular oscillatory motion of the cam axis with the first oscillatory motion thereof and the second displacement of the grindstone with the first displacement thereof, the action of the control means being such that, in all the operative positions of the cam, that segment of its fluted surface which is in contact with the grindstone working surface is disposed parallel to the grindstone axis so that contact between the last-mentioned surface and the fluted surface of the cam extends over the whole of such segment.

2. A process according to Claim 1 characterised in that the fluted operative surface of the cam consists of side-by-side straight segments each disposed in a corresponding plane passing through the cam longitudinal axis.

3. A process according to Claim 1 or 2, characterised in that the first oscillation axis and the second oscillation axis around which the first oscillatory motion and the second oscillatory motion of the cam rotational axis occur are perpendicular to one another.

4. A process according to Claim 3, characterised in that the first oscillation axis of the cam is perpendicular to the rotational axis of the grindstone.

5. A process according to Claim 3 or 4, characterised in that the first displacement and the second displacement of the grindstone occur along straight paths perpendicular to the grindstone rotational axis.

6. A process according to Claim 5, characterised in that the first displacement and second displacement of the grindstone occur along straight paths perpendicular to one another.

7. An apparatus for producing by grinding by the process according to Claim 1 a fluted surface which is the operative surface of a cam, the apparatus comprising: a workpiece head so supported by the stationary structure of the apparatus as to be rotatable around an oscillation axis which is of fixed direction and on which a workpiece slide is disposed, the cam blank being disposed thereon for rotation around its longitudinal axis; a grindstone upright on which a tool spindle for carrying a grindstone coaxially of itself is disposed for rotation arounds its axis, such upright being movingly mounted in the stationary structure of the apparatus to permit displacement of the grindstone rotational axis along a predetermined straight path; and control means for producing a predetermined relationship between rotation of the cam around its longitudinal axis, angular movement of the workpiece head around the oscillation axis and the displacement of the movable spindle-bearing grindstone upright, the latter predetermined relationship being such that the working surface of the grindstone is always in contact with the fluted surface of the cam, characterised in that the grindstone has a cylindrical working surface which is of constant circular cross-section and which is disposed coaxially of the tool spindle, the same being disposed for rotation on a tool slide movingly mounted in the grindstone upright to permit a second displacement of the grindstone rotational axis along a predetermined straight path; and the workpiece slide on which the cam blank is rotatably mounted is supported by a retaining.

plate which is articulated to the workpiece head for movement around an oscillation axis, control means being provided for linking the angular movement of the workpiece slide with the angular oscillation motion of the workpiece head and the displacement of the tool spindle slide with the displacement of the grindstone upright so that in all the operative positions of the cam that segment of the fluted surface of the cam which is in contact with the working surface of the grindstone is disposed parallel to the grindstone axis, so that contact between the last-mentioned surface and the fluted surface of the cam extends over the whole of such segment.

8. An apparatus according to Claim 7, characterised in that the fluted operative surface of the cam is embodied by side-by-side straight segments each disposed in a corresponding plane passing through the cam longitudinal axis.

9. An apparatus according to Claim 7, or 8, characterised in that the oscillation axis of the workpiece head and the oscillation axis of the retaining plate are perpendicular to one another.

10. An apparatus according to Claim 9, characterised in that the oscillation axis of the workpiece head is perpendicular to the rotational axis of the grindstone spindle.

11. An apparatus according to Claim 9 or 10, characterised in that the two displacement motions of the grindstone occur along straight paths perpendicular to the rotational axis of the grindstone spindle.

12. An apparatus according to Claim 11, characterised in that the two translational motions of the grindstone occur along straight paths perpendicular to one another.

13. A process as claimed in Claim 1 substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

14. An apparatus as claimed in Claim 7 substantially as hereinbefore described with reference to, and as shown in the accompanying drawings.