GB2105625A - Method and machine for crown-shaving the tooth flanks of a toothed workpiece - Google Patents

Abstract

In a gear-shaving machine with a toothed workpiece 16 held non- displaceably and in mesh with a shaving wheel 9, a tool carrier 5, 15 holding the shaving wheel performs a reciprocating feed movement, for which purpose it is guided in a part 4 which is pivotable about an axis 11 lying transverse to the feed direction 8 and guided by a guide bar 21 in a slotted guide 24 of a stationary part 3. In order to produce crowned tooth flanks on the workpiece 16 the distance between the guide bar 21 and the tool carrier 5 is altered as a function of the cycle of the reciprocating feed movement, and the guide bar is held in the pivotable part 4 constantly parallel to the guide 13 of the tool carrier 5. <IMAGE>

Description

SPECIFICATION Method and machine for crown-shaving the tooth flanks of a toothed workpiece The invention relates to a method of crownshaving the tooth flanks of a toothed workpiece, and to a machine suitable therefor.

The invention is based upon a machine for finemachining gearwheels, as described in our UK Patent Specification No 2058627. When using a straight guide bar, the crowing of the tooth flanks which may be produced with the known machine is variable only over a narrow range. The use of curved guide bars is limited for reasons of design and costs.

The object of the invention is therefore to provide a method and machine by means of which the size and the shape of the crowning can be selected with the greatest possible choice and can be altered without a great deal of complication.

The object is attained with a method according to the characterising feature of Claim 1 which may be advantageously supplemented by the feature of Claim 2. A machine suitable for performing the method has the features of Claim 3. In order to produce crowned tooth flanks, the shaving wheel must be inclined relative to the workpiece in accordance with the desired degree of crowning.

The degree of inclination necessary in each case may be altered according to the invention as a function of the cycle of the reciprocating feed movement by varying the distance between the feed slide and the guide plate, e.g. by way of a pulse generator which is connected to the - for example digital -- control of the machine and which effects a change in the distance as a function of the feed path covered. In order to obtain satisfactory shaved products it is desirable for the shaving wheel always to be orientated perpendicularly to the respective portion of the workpiece tooth. This requirement is met by the guide plate always being held parallel to the guide of the feed slide in the guide carrier, i.e. parallel to the feed movement.

One embodiment of the invention is explained in greater detail below with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of the arrangement of the shaving head, the feed slide and the guide bar, Fig. 2 is an elevation of the same parts, Figs. 3 to 5 illustrate the course of movement in different positions of the feed slide, and Fig. 6 is a diagrammatic view of the tool in different positions in the case of normal crowning.

A setting slide 2 which essentially consists of three parts movable relative to one another - a pivoting plate 3, a guide carrier 4 and a feed slide 5 - is arranged on a vertically adjustable vertical slide 1 of a gear-shaving machine (not shown in greater detail (Figs. 1 and 2)). The pivoting plate 3 is held in a pre-stressed circular guide 6 in the vertical slide 1 in such a way as to be pivotable about a vertical axis 7 and lockable. In this way the feed direction 8, 8', 8" of the shaving wheel 9 may be set as desired for parallel, diagonal or underpass shaving.The guide carrier 4 is suspended on a pin 10 on the pivoting plate 3 in such a way as to be tiltable about a horizontal axis 1 The feed slide 5 is held in a prestressed longitudinal guide 1 2 on the underside of the guide carrier 4. A shaving head 1 5 rotatable about a vertical axis 14 is held, with the shaving wheel 9, on the underside of the said feed slide 5 in a circular guide 13 for adjusting the axial crossing angle. The longitudinal guide 12 is orientated transversely to the axis 1 The devices for displacing the feed slide 5 as well as the devices for rotatably setting the pivoting plate 3 or the shaving head 1 5 are known and are not described here. They have also not been provided with a reference numeral.The workpiece 1 6 is held in known devices -- not shown -- beneath the shaving wheel 9 and in mesh engagement therewith in such a way as to be rotatable but non-displaceable. One end of the feed slide 5 is provided with an upwardly directed, longitudinally displaceable arm in the form of a threaded spindle 19, which engages in a spindle nut 1 8 and at whose free end a guide bar 21 is arranged in a head 20. The guide bar 21 is pivotable about a horizontal axis 22, which is orientated parallel to the tilting axis 11, and may be locked to the head 20. The pivoting plate 3 is provided with an arm 23, at the free end of which a slotted guide 24 is hinged so as to be freely pivotable. The guide bar 21 is guided in this slotted guide.A servomotor 26 is arranged on a carrier 25 connected to the head 20 and drives the threaded spindle 1 9 rotatingly by way of a belt drive - not shown - in the carrier 25. The servomotor 26 is connected to the control system of the shaving machine by way of a known pulse generator.

In the normal or intermediate position of the shaving wheel 9 the length of the threaded spindle 19 is set in such a way that the feed slide is horizontal. The guide bar 21 is likewise horizontal at a distance 28 therefrom (Figs. 2 and 3). If the feed slide is moved to the left or right (arrow X) it moves in a plane parallel to the axis of the workpiece. In order to produce crowned teeth on the workpiece 16, the threaded spindle 1 9 is moved in such a way as to reduce the distance between the feed slide 5 and the guide bar 21 during the feed movement to the left.In this way a slight anti-clockwise pivoting movement about the axis 11 is imparted to the feed slide 5 and the guide carrier 4, the guide bar 21 is inclined in the direction Y and the shaving wheel 9 is given an inclination (or a slope) a relative to the workpiece 1 6. As the distance continues to be reduced during the feed movement to the left the shaving wheel moves along an arcuate curve (Fig. 6) having the rise H. At the end of the feed path it then has its greatest inclination a and at the same time the distance 28 is reduced to its minimum (28' in Fig. 4).In the subsequent reversal of the feed direction X the distance between the feed slide 5 and the guide plate 21 is increased again by reversing the direction of rotation of the servomotor 26 or the threaded spindle 1 9, and the inclination a of the shaving wheel 9 is reduced.

When the starting position according to to Fig. 3 Is reached again, the shaving wheel is vertical again so that as the feed movement is continued towards the right and the distance 28 continues to be increased, caused by the corresponding slight clockwise pivoting movement of the feed slide 5, the shaving wheel is inclined towards the other side. At the end of the feed path it again has its greatest inclination a and at the same time the distance 28 has reached its maximum (28" in Fig. 5).

The rotating movement of the threaded spindle 1 9 is controlled by a pulse generator which is connected to the general control, e.g. an analogue control, of the machine and which switches on, switches off and reverses the servo-motor 26 in the cycle of the reciprocating feed movement and as a function of the feed path covered in each case or other criteria which may be varied in accordance with the respective requirements. The curved path described by the shaving wheel 9 may be further varied by a movement of the setting slide -- superimposed upon the feed movement X - in the direction Z, i.e. in the sense of a reduction or an increase in the axial distance.

Therefore a, H, H, B =f(X,Y,Z).

It is also possible of course to begin to alter the distance 28 between the feed slide and the guide plate 21 only when part of the feed path B has been covered. In this case only the ends of the teeth would be crowned. Alternatively, the alteration of the distance 28 is ended before the entire feed path B is covered. The ends of the teeth then terminate conically. In each case, however, it is important that a change in distance in one feed direction must be matched by an exactly opposite change in distance at the respective point on the feed path in the opposite feed direction.

The invention is not restricted to the example of embodiment of a shaving machine with a shaving wheel disposed above the workpiece, as described here, but may be used in all shaving machines and machines for comparable gearwheel finemachining processes in which the workpiece is held stationary and all the necessary movements are performed by the tool.

Claims (6)

1. A method of crown-shaving the tooth flanks of a toothed workpiece, which is mounted rotatably, but non-displaceably, in a gear-shaving machine having a shaving wheel which is held so as to be driven rotatingly in a shaving head which is disposed on a feed slide so as to be rotatably adjustable about an axis perpendicular to the workpiece axis whereby the shaving wheel can be set with its axis crossing that of the workpiece, which feed slide is a) displaceably guided in a guide carrier for reciprocating feed motion, the guide carrier being mounted to pivot about an axis to the feed direction on a pivoting plate which can be pivoted about an axis perpendicular to the axis of the workpiece and may be locked at a selected pivot angle, and b) guided by a guide bar by way of a slotted guide or the like on the pivoting plate, and having means for altering the distance between the axes of the shaving wheel and the workpiece, characterised in that the distance between the guide bar and the feed slide is altered as a function of the cycle of the reciprocating feed movement and the guide bar is held constantly parallel to the guide of the feed slide in the guide carrier.

2. A method according to Claim 1, characterised in that in addition the distance between the axes of the shaving wheel and the workpiece is altered as a function of the cycle of the reciprocating feed movement.

3. A machine for finishing the tooth flanks of a toothed workpiece, comprising means for rotatably but non-displaceably supporting a workpiece, a tool carrier for rotatably supporting a toothed tool, driving means for rotating the tool and workpiece in mesh with each other in operation of the machine, the tool carrier being angularly adjustable about an axis perpendicular to the workpiece rotation axis for setting the tool and workpiece axes at a desired relative angle, a guide carrier on which the tool carrier is mounted for reciprocating movement for longitudinal tool feed motion, a support for the guide carrier on which the guide carrier is pivotable about an axis transverse to the feed motion and which is angularly adjustable about an axis perpendicular to the workpiece rotation axis for setting the tool feed direction, and a rocker mechanism for causing the tool carrier to rock about the said horizontal axis in the course of the said horizontal axis in the course of the said reciprocating movement, which rocker mechanism comprises a guide bar on, and parallel to the feed motion of, the guide carrier, a stationary guide element in guiding engagement with the guide bar, and means for moving the guide bar laterally towards or away from the guide carrier as a function of the feed motion cycle.

4. A machine according to Claim 3, characterised in that the guide bar and the feed slide are connected together by way of a threaded spindle with a spindle nut and the spindle can be driven by a servomotor controlled by a control system of the machine.

5. A method of crowning gear teeth substantially as herein described and illustrated in the accompanying drawings.

6. A gear-shaving machine substantially as herein described with reference to the accompanying drawings.