US2893173A

US2893173A - Means for forming the teeth of spur gear wheels or the like

Info

Publication number: US2893173A
Application number: US510314A
Authority: US
Inventors: Bateman William Henry
Original assignee: Wickman Ltd
Current assignee: Wickman Ltd
Priority date: 1954-05-24
Filing date: 1955-05-23
Publication date: 1959-07-07
Anticipated expiration: 1976-07-07
Also published as: GB788158A; FR1125251A; CH342820A; BE538404A

Description

y 1959 w. H. BATEMAN 2,893,173

MEANS FOR FORMING THE TEETH OF SPUR GEAR-WHEELS OR THE LIKE Filed. May 25,1955 v s Sheets-Sheet 1 i. I v I 32 8: 1 k is I Fife 1 1 I I 1 28 E1 s 1 1 I] i 24 E z i R t l Fig.1

July 7, 1959 I w. H. BATEMAN 2,893,173

MEANS FOR FORMING THE TEETH OF SPUR GEAR WHEELS OR THE LIKE Filed May 25, 1955 3 Sheets-Sheet 2 July: 7, .1959 w. H. BATEMAN 2,893,173

- MEANS FOR FORMING THE TEETH OF SPUR GEAR WHEELS OR THE LIKE Filed May 23, 1955 5 Sheets-Sheet 3 United States Patent MEANS FOR FORMING THE TEETH 0F SPUR GEAR WHEELS OR THE LIKE William Henry Bateman, Overstream, Loudwater, Rickmansworth, England, assignor to Wickman Limited, Coventry, England Application May 23, 1955, Serial No. 510,314

Claims priority, application Great Britain May 24, 1954 4 Claims. (CI. 51-95) This invention relates to the forming of the teeth of spur gear wheels, shaft splines, or like parts of analogous work pieces, by means of the kind wherein the forming is effected by a rotary grinding or cutting tool having a helically shaped periphery, and wherein the workpiece is rotated during the forming operation at a rate such as would result by meshing the workpiece with a worm of the same pitch as the tool.

A disadvantage of the means hitherto employed for the purposes above mentioned has been the need for providing complex mechanism for enabling the wear of the tool to be uniformly distributed over the axial length of the tool, thereby obviating localisation of the wear.

The object of the present invention is to enable the desired distribution of wear of the tool to be effected in a simplified manner.

The invention consists of a means of the aforesaid kind, wherein the relative feed movement of the workpiece and tool is effected in a direction which is inclined to the rotation axis of the workpiece, and wherein the rotation axis of the tool is inclined to the direction of the feed movement and sensibly at a right angle to the rotation axis of the workpiece.

The invention also comprises a means as defined in the preceding paragraph wherein the means for imparting rotational movement to the workpiece include a pair of interengaging gear members one of which is slidable relatively to the other.

Moreover the invention comprises a machine substantially as hereinafter described for effecting the operations above defined.

In the accompanying drawings, Figure 1 is a sectional front elevation, Figure 2 a sectional side elevation, and Figure 3 a plan illustrating a machine in accordance with the invention in this example for grinding the teeth of a plain spur wheel.

Referring to the drawings, there is provided on a base 1, a guide 2 for carrying a horizontally movable slide 3, the latter being movable along the guide by any convient mechanism such as a hydraulic cylinder 40 provided with a reciprocal piston 41 connected to the slide 3 by the rod 42 and operated by reversing pump 43, which may be controlled manually or otherwise according to the requirements. On the bed is formed or secured a bracket 4 on which is provided a vertical guide 5, and on this guide is carried a slide 6 on which is mounted an electric motor 7 for rotating the helical grinding wheel 8, which latter is secured to one end of the rotary spindle 9 of the motor. Any convenient means (not shown) is combined with the guide for raising and lowering the slide 6.

On the slide 3 is mounted a spindle 10 to which is secured the workpiece 11, the spindle 10 being supported at one end by a bearing 12 and at the other end by a tail stock 13. The spindle 10 is connectible by a clutch 14 to a spindle 15 which preferably is embraced by a friction brake 16 for damping transient fluctuations in 2,893,173 Patented July 7, 1959 ice the movements of the spindle, and this spindle is connected by a train of change-speed gear wheels 17 to another spindle 18.

'In the particular arrangement shown, the spindle 9 of the motor is disposed at an angle of relatively to the longitudinal centre line of the slide 2, the axis of the work-carrying spindle It) being arranged at a nominal right angle to the axis of the spindle 9.

The spindle 15 is coaxial with the spindle 10, and the spindle 18 is parallel with the spindle 15.

In the bed of the machine is mounted a long helically toothed wheel 19 carried by a spindle 20. Its axis is parallel with the longitudinal centre line of the guide 2, and in this example, its teeth are inclined at 10 to its axis. Engaging with this pinion is a corresponding helical pinion 21 carried by a spindle 22 on the slide 3, the spindle 22 being connected to the above mentioned spindle 18 through a pair of bevel pinions 23.

The helically toothed wheel 19 is driven by an electric motor 24 through worm reduction gearing 25 and a change-speed train of gear wheels 26. Preferably a flywheel 27 is combined with the said worm gearing to minimise transient fluctuations of motion.

The two motors 7 and 24 are synchronous alternating current motors, and to prevent relative movements of their rotors the latter are interconnected by

coaxial spindles

28, 29, a clutch 30 and bevel pinions 31, 32.

In brief, the mode of action of the machine is such that by linear movement of the slide 3 the whole length of the workpiece is subjected to the action of the grinding wheel, and by reason of the inclination of the axis of the workpiece relatively to the direction of motion of the slide the workpiece has a component of motion parallel with the axis of the grinding wheel, the amount of this component being such as will cause the workpiece to move across the whole of the axial length of the grinding wheel, thereby ensuring uniform wear of the whole length of the helix of the grinding wheel.

The kinematics involved in the actions of the machine will now be explained more fully. Let it be supposed that the grinding wheel is replaced by an identically similar worm, and that a finished workpiece is mounted in position, but free from engagement with any of the associated gearing above described, the slide 3 being stationary. It will be obvious that on rotating the worm a corresponding rotation will be imparted to the workpiece. Now let it be supposed that the worm is held stationary, and that a linear movement is imparted to the workpiece. It will be equally obvious that this will result in a rotational movement of the workpiece, this movement being termed the compensatory rotation. From this it follows that when the worm is rotated, and the workpiece is simultaneously given a linear movement relatively to the Worm, the workpiece will have imparted to it not only the above mentioned rotational movement but also the additional compensatory rotational movement.

For the purpose of the invention it is required that during linear movements of the slide 3, the workpiece shall have imparted to it not only a normal rotational movement such as would be imparted to it (when stationary) by a worm corresponding to the grinding wheel, but also the above mentioned compensatory rotational movement, and this latter requirement is satisfied by the inclination of the teeth of the helical wheel 19.

It will be understood, however, that the angle between the two

spindles

9 and 10 will depend to some extent on the helix angle of the grinding wheel. With a grinding wheel initially of about 12' diameter and having a helix angle of about 1.5 degrees, the said angle between the

spindles

9 and 10 could be precisely and the small lack of parallelism between the helix of the grinding wheel and the teeth of the workpiece would be of no practical consequence. But with reduction of diameter of the grinding wheel resulting from wear and repeated trimmings to, say, the consequent increase of the helix angle may necessitate the adoption of a compromise angle between the

spindles

9 and 10 which could bring the helix of the grinding wheel into sufliciently close parallelism with teeth of the workpiece throughout the normal life of the grinding wheel. It follows that the angle between the

spindles

9 and 10 may differ by a few degrees from 90 to accommodate the obliquity of the helix of the grinding wheel.

Thus the inclination of the workpiece axis to the direction of feed is invariable, i.e., is substantially at right angles and is referred to herein, and in the claims, as at a fixed angle, which may be only modified slightly (as explained'in the previous paragraph) to accommodate the lead of the helix of the grinding wheel periphery.

A further requirement to be satisfied is that the same machine shall be capable of dealing with workpieces of different diameters. It will be evident that the rate of rotation that can be imparted to :a workpiece by a given worm depends on the diameter of the workpiece. It will be also evident that the compensatory movement to be imparted to all workpieces must be in inverse proportion to their diameters when expressed in degrees of rotation, and uniformly in terms of length along their circumferences. Consequently it is necessary to make provision whereby the rate of rotation of the workpiece to be treated'by the grinding wheel can be varied in a manner appropriate to the diameter of the workpiece. This requirement is met by combining with the

Wheels

19, 21, a changeable wheel train 26 for driving the wheel 19, and another changeable wheel train 17, for transmitting motion from the wheel 19 to the spindle 10.

Moreover, the invention is not limited to a means for treating gear wheels, as it may be applied also to forming shaft splines, or performing other analogous grinding or cutting operations by means of a helical grinding wheel or cutting tool.

In the illustrated example, the grinding wheel 8 is considered as being of such diameter and the thread thereof of such pitch that the lead angle of the thread is so slight as to admit of the axis of the work-carrying spindle 10 being at substantially a right angle to the axis of the spindle 9. This angle, however, is referred to herein and in the claims as being nominal, inasmuch as this may vary through an angular range, say, of

substantially 80 to 100 to accommodate various pitch angles of the grinding wheel thread (in a right or in a left hand direction) such as might occur where a grinding wheel of smaller diameter is used with correspondingly greater pitch angle for any given pitch.

It will be apparent, of course, that such variation of the nominal right angle between the axes of the spindle 10 on the spindle 9 would be accompanied by the appropriate ratio of compensatory gearing hereinbefore referred to, to properly meet the requirements of the angular relationship between the work-carrying spindle 10 and the spindle 9.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. In a machine for grinding the teeth of spur gear wheels, splines and similar non-helical workpieces in which the teeth lie in the direction of their lengths parallel with the axis of the workpiece by a grinding wheel having an operative peripheral surface of helical form, the combination of a grinding wheel spindle, a work spindle, a work spindle supporting table, means for irnparting linear movement to said table in a direction inclined to the axis of the work spindle and at a fixed angle to the axis of the grinding wheel spindle whereby planes containing the axes of both spindles together with the direction of movement of the table form a triangle, interengaging gear members for inter-connectingly transmitting rotation from a driving source to the grinding wheel spindle and the work spindle including a gear slidable with the said table parallel with the axis of another gear in meshing engagement, thereby providing relative rates of rotation of the grinding wheel spindle and the work spindle corresponding to rates which would result if a workpiece derived its rotation from the grinding wheel throughout movements of the said table.

2. A machine as claimed in claim 1, which includes a changeable train of gear wheels for imparting motion from a source to one of the pair of interengaging gear members, and which includes another changeable train of gear wheels for transmitting motion from the other of the interengaging gear members to the workpiece.

3. A machine as in claim 1, wherein one of the interengaging gear members is mounted for rotation only and is of increased length relative to the slidable interengaging gear member.

4. In a machine for forming the teeth of spur gears, splines and similar workpieces wherein the teeth lie in a direction parallel with the axis of the workpiece, a grinding wheel having an operative peripheral surface of a helical form, a work spindle, a grinding wheel spindle, a work spindle supporting table, a work table slide movably relatively to the grinding wheel along a line which is inclined at a fixed angle relatively to the rotation axis of the grinding wheel, and gearing connecting the grinding wheel and work spindles, said gearing including a pair of relatively slidable and inter-engaging helical wheels, the sliding movement of one of which wheels is effected by the work-table slide, and change speed gear wheels for varying the rate of rotation of the workpiece spindle.

References Cited in the file of this patent UNITED STATES PATENTS 2,424,191 Rickenmann July 15, 1947 2,449,354 Wickman Sept. 14, 1948 2,528,242 Praeg Oct. 31, 1950 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION- Patent No. 2,893.11?) July 7 1959 William Henry Bateman It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2 line 69 for "12" read 12" --g column 3, line 13, for "workpiece" read grinding wheel Signed and sealed this 4th day of October 1960.

(SEAL) Attest:

KARL H. AXLI NE Attesting O flicer ROBERT C. WATSON Commissioner of Patents