US2423422A

US2423422A - Thread grinding machine

Info

Publication number: US2423422A
Application number: US585048A
Authority: US
Inventors: Turrettini Fernand
Original assignee: Genevoise Instr Physique
Current assignee: Societe Genevoise dInstruments de Physique
Priority date: 1944-08-23
Filing date: 1945-03-27
Publication date: 1947-07-01
Anticipated expiration: 1964-07-01

Description

July 1, 1947. F. TURRETTINI 2,423,422

THREAD GRINDING MACHINE Filed March 27, 1945 5 sheets-sheet 1l mmm, mm QN QW E July 1, 1947. F. TURRETTLNI THREAD GRINDING MACHINE Filed March 27, 1945 3 Sheets-Shea? 2 July 1, 1947. F.-TURRETT|N| 2,423,422

TEREAD GRINDING MACHINE Filed March 27, 1945 5 Sheets-Sheet 3 Ilz/U @12:60.21 Twzr e tte/@ZL Patented July 1, 1947 UNITED STATES ATENT OFFICE THREAD GRINDING MACHINE Fernand Turrettini, Geneva, Switzerland, as-

sgnor to Societe Genevoise DInstruments De Switzerland, a Iirm of Physique, Geneva, Switzerland 6 Claims. l

The present invention relates to thread grinding machines, and in Iparticular to machines of the type comprising a grinding wheel mounted on a carriage slidable at a right angle to the axis of the work piece under the action of a first adjusting device, a truing tool mounted retractably in front of the grinding wheel on a rst support mounted rotatively on said carriage around an axis parallel to the direction of motion of the latter, the grinding wheel being carried by a second support mounted rotatively around the axis of rotation of the first support and slidably along this common axis, and a second adjusting device inserted between the first and the second support for moving the grinding wheel in a direction parallel to that of said carriage, with the object that the distance from the cutting edge of the grinding wheel to the axis of the work piece remains permanently determined by the indications of the first adjusting device, independent from the quantity of abrasive removed from the grinding wheel.

The advantage of this machine is that the operator can carry on its thread grinding work without the necessity of frequently interrupting it for measuring the workpiece, the micrometric adjustment of the wheel supporting carriage giving always an accurate reading of the position of the wheels cutting edge in respect with the workpiece, independently from the wear of the wheel.

The annexed drawing represents by way of example one constructional form of the machine according to the invention.

The machine according to the invention, of the type mentioned above, eliminates all these diiculties. It is characterized in that the truing device, which operates in front of the grinding wheel, is retractably arranged on a first support enabling to clear the grinding Wheel, said support being borne by a carriage in such a manner as 'to be dependent on the latter in the direction of the travel of this carriage and, in the same time, rotating on itself in order to adjust the inclination of the plane in which the truinghas to be performed, the grinding wheel being carried by a second support concentric with the first one and arranged to rotate on itself in such a manner that the grinding wheel may be adjusted tangentially to the helices of the thread to be ground and that it also may move in a direction parallel axis ci the work piece remains permanently determined by the indications of the first adjusting device, independent from the quantity of abrasive removed from the grinding wheel.

The annexed drawing represents by way of example one constructional form of the machine according to the invention. The Fig, l is a transverse section; the Fig. 2 is a section through II-II and the Fig. 3 a section through III-III of the Fig. l. The Fig. 4 is a front elevation.

In all these figures, I is the bed of the grinding machine comprising a slide 2 extending at right angle to the longitudinal slides 3 and 3a of the bed; the slide 2 extends towards the rear of the machine and bears the carriage 4. The table is and the axis of the work piece to be ground is the work piece itself being 6. The work piece moves with the table on the bed by means of the spindle 1, as well as by means of other members not shown.

The grinding wheel is 8, its axis is 9; the latter is being driven by the pulley I0. The truing diamond is II, its point of contact with the grinding wheel is on the horizontal axis A-A at right angle to the axis of the Work piece to be ground and passing through the centre of the grinding wheel. The arm I2, carrying the diamond, is fixed on trunnion -pin I3. The diamond II trues-up the two anks of the active face of the grinding wheel by an oscillatory movement of small amp-litude about said trunnion pin. The oscillatory movement is produced by means not shown on the drawing.

IThe trunnion pin I3 revolves in a head Ill dependent on a shaft I5 which may, by rotating in a bearing Iii, describe the angle a comprised between the flanks of the active face of the grinding wheel. The bearing I formspart of an arm i? rigidly fixed by screws IS and I9 on extensions 28 and 2l of a hollow cylinder 22 rotating in bearings 23 and 24 belonging to a sleeve 25 iixed to the carriage 4.

This rotary motion, obtained by the action of a worm screw 26 engaging a toothed sector 26 fixed to the sleeve 25, serves to adjust the plane of inclination in which the diamond I I has to carry out the truing-up. The worm screw 25 rotates "i bearing 2l and 28 dependent on the arm Il. The group consisting of pieces I6, Il, 2d, 2| and 22 forms the rst support which moves with the carriage i with respect to the axis 6 and the work piece t through the action of a handle 29 dependent on a graduated wheel 36; the latter is fixed on a shaft 3I comprising at its extremity a threaded portion 32 engaged with the nut 33 dependent on the carriage 4.

A second support is arranged concentrioally with the hollow cylinder 22; it is formed by the tube 34 ending at the extremity facing the work piece by a ange 35 xed rigidly on the tube and carrying the bearing 3S containing the axis 9 of the grinding wheel S. The tube 34 bears at its rear a flange 31 on which is fixed the motor 38 driving the grinding wheel.

The second support 34 may rotate about the axis A--A under the action of a toothed sector 33 with straight teeth engaging with a circular rack formed by a tube 4S provided with parallel grooves 4l showing the profile of a rack.

The tube 45 is fixed axially on a shaft 42 on which it may freely rotate due to the ball bearings li and 44. The shaft 4:2 may move axially by means of a screw l5 engaging with a not 46 fixed in a recess il on the shaft 42. The rotation of this screw is eifected by the action of a wheel 43 provided with a handle 49 and with a graduation 55. The group consisting of

pieces

39, 4I, 42, 55, 45, 49 and 55 has the object of adjusting the grinding wheel tangentially to the helices of the thread to be ground on the piece 6. The tube 34 with all the pieces which it carries (second support) has to move axially in the hollow cylinder 22 (first support) in order to bring the grinding wheel 8 in contact with the diamond ll in such a manner that the truing operation re-conditions the profile of the active edge of the grinding wheel. This axial movement is obtained by means of a second adjusting device formed by a handle 5| dependent on a shaft 52', meshing by the gear 53 with a shaft 54, the bearing 54 of which is dependent on the arm il. The shaft 54 transmits its rotary motion to the gear 55 by means of universal joints 56 and 5l. The shaft of the gear 55 is provided with an extensible part 55a to allow for the rotation of support 34 around the axis A-A. The rotation of 55 drives the pinion 58 dependent on a screw 59 forming part of a shaft 5D, which is supported on one hand by a bearing 5l fixed as well as the nut 62 on the flange 31 and consequently on the tube 34 and the grinding wheel 3 which it carries, and on the other hand, by a ball bearing 53 arranged in a piston IB4 which moves in the tube 34 and resting at 65 on a rod 55 housed 67 and 68 in the hollow cylinder 22.

A spring 69 thrusting on one hand on a circular abutment li! arranged to rotate in the piston G4, and, on the other hand, on a lid 1I xed to the tube 34, constantly forces the grinding wheel towards the diamond. The adjusting screw 59 is opposed to the pressure exerted by the spring because it indirectly thrusts on the hollow cylinder 22, which is fixed axially. The rotation of the shaft B0 thus enables bringing the grinding wheel in contact with the diamond.

It is by no means necessary that the amplitude of the travel imparted to the grinding wheel by the second adjusting member to be taken into consideration, measured or checked in any way in a machine working according to the invention. This travel may be of any length, provided that it is sufficient to bring again the profile of the grinding wheel into contact with the diamond in such a manner that the action 0f the latter reconditions the surface of the grinding wheel.

The second support 34 has therefore to rotate and to slide in the iirst cylinder 22; it is important that these movements are effected with a minimum of friction in order not to reduce the sensibility of the adjustments. For this reason, the sets of balls 12 and T3 inserted between the hollow cylinder 22 and the tube 34 have to support and to guide the latter, the balls being able to roll in all directions enabling said pieces to carry out relativerotary and translatory movements. The sets of balls are arranged at the two extremities of the tube 34 and are formed by `two elements im and 72b (for the train 12) separated from each other by an angle b suiciently large to decompose the weight P of the tube 34 into two divergent components P1 and P2 which prevent any de-centrmg movement in the direction B-B. This arrangement of balls produces an eect similar to that of usual prismatic guide ways and has the advantage of enabling movements with a minimum of friction. The arm I2, which carries the diamond Il, may carry out an additional rotary motion about the trunnion pin I3 and thus may be brought into the retracted position when not in use, as shown on Fig. 4, in which position it enables the grinding wheel to come freely into contact with the work piece to be ground. The arm l2 may be maintained in this position by a retaining member 55.

If it is required to grind threads or taps, the axis C-C has to be vertically adjusted by means of the worm screw 25. Ii, on the other hand, milling cutters for gears have to be ground, where the characteristic profile is to be at right angle to the helices, the axis C-C has to be maintained in the same plane as that of the grinding wheel 8, plane which is tangent to the helices of the work piece to be ground. This result will be obtained by means of the worm screw 25 and the rotating rack 4).

The machine described enables maintaining the active edge of the grinding wheel immobile in space during the operation of truing-up carried out by a tool borne on a slide, the distance of which from the axis of the work piece being constantly controlled by means of an adjusting member 29, 3), dependent on the bed of the machine. The truing tool acts at the point of contact of the grinding wheel with the work piece, so that a definite relation of the position of the slide with respect to the axis of the work piece, when the latter will reach the prescribed dimensions, may be ensured. This relation will be given by the adjusting member mentioned above.

The movable parts Il, l2 of the truing member, which may form an obstable to the Contact of the work piece with the grinding wheel, may be retracted in order to permit such a contact.

Thus, the machine described does away with the necessity of measuring the work piece during the grinding operation; it further makes it pos sible to grind either threads with the characteristic profile being in a plane containing the axis of the work piece (in the case of screws and taps) or in a plane at right angle to the helix of the thread (in the case of gear milling cutters).

What I claim is:

1. A thread grinding machine comprising a grinding wheel mounted on a carriage slidable at a right angle to the axis of the work piece under the action of a first adjusting device, a truing tool mounted retractably in front of the grinding wheel on a first support mounted rotatively on said carriage around an axis parallel to the direction of motion of the latter, the grinding wheel being carried by a second support mounted rotatively around the axis of rotation of the first support and slidably along this common axis, and a second adjusting device inserted between the rst and the second support for moving the grinding wheel in a direction parallel to that of said carriage, with the object that the distance from the cutting edge of the grinding wheel to the axis of the work piece remains permanently determined by the indications of the first adjusting device, independent from the quantity of abrasive removed from K the grinding wheel.

2. Machine according to claim 1, characterized in that the truing tool is carried by an oscillating arm mounted on the rst support in such a manner that it is possible to bring it into a retracted position by an oscillation of sufficient amplitude.

3. Machine according to claim l, characterized by the fact that the second support comprises cylindrical parts passing through a cylindrical bearing of the rst support, sets of balls being inserted at these spots between the two supports in order to enable the second support to rotate and to travel axially in the rst one, without harmful friction, whereby the grinding wheel can be inclined in accordance with the lead of the thread to be ground.

4. Machine according to claim l, characterized by four sets of balls arranged by pairs at the extremities of cylindrical bearing surfaces between the first and the second support, the two sets of each pair being spaced apart from one another, in order to produce an eiTect of prismatic guiding excluding all radial or lateral play of the second support, by means of the action of its own weight.

5. Machine according to claim l, characterized by the fact that the rotary motion of the second support is obtained by means of a toothed sector dependent on said second support and which is engaged with a circular rack rotating freely on a shaft carried by the rst support-and which may travel axially by means of an adjusting member, determining the angle comprised between the plane of the grinding wheel and that in which the truing-up is carried out.

6. Machine according to claim 1, characterized in that the second support also carries the motor driving the grinding Wheel.

FERNAND TURRETTINI.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date y 1,564,670 Hanson Dec. 8, 1925 1,946,883 Tougas et al Feb. 13, 1934 2,087,662 Bysshe et al. July 20, 1937 2,292,875 Flanders Aug. 11, 1942 2,311,253 Stewart Feb. 16, 1943