US2060438A - Grinding machine - Google Patents

Description

Nov. l0, 1936. s, J, HARLEY GRINDING MACHINE Filed March 22, 1935 9 Sheets-Sheet l Nov. 10, 1936. s- J. HARLEY GRINDING MACHINE Filed March 22, 1955 9 Sheets-Sheet 2 Nov. 10, 1936. s. J. HARLEY 2,060,438

GRINDING MACHINE Filed March 22, 1935 9 Sheets-Sheet 3 Nov. 10, 1936. s. J. HARLEY GRINDING MACHINE 9 Sheets-Sheet 4 Q2 my Filed March 22, 1935 New. 1Q, 1936. s. J. HARLEY GRINDING MACHINE Filed March 22, 1955 9 sheets-sheet 5 Nov. w, 1936. s, J HARLEY GRINDING MACHINE Filed Maron 22, 1935 '9 sheets-sheet e Nov. 10, 1936. s. J. HARLEY GRINDING MACHINE Filed March 22, 1935 9 Sheets-Sheet 7 s. L HARLEY 2,060,438

GRINDING MACHINE Filed March 22, 1935 9 Sheets-Sheet 8 Nov. 10, 1936. s. J. HARLEY GRINDING MACHINE Filed March 22, 1935 9 Sheets-Sheet 9 mmm'a a 'non mmm Wo u

Patented Nov. 10, 1936 PATENT yOFFICE 2,060,438 Gm'NDmG MACHINE stanley Jana nai-ley, suvlcnau, Coventry, England Application March 22, 1935, Serial No. 12,475 In Great Britain March 21, 1934 5 Claims.

This invention relates to an improved grinding machine in which a formed grinding wheel is employed for producing screw threads from the solid material, or for finishing existing screw threads, and has for itsobject to provide a machine for this purpose. by means of which screw threaded work can `be rapidly produced or iinished with a high degree of accuracy.

The improved machine is electrically driven, the equipment comprising a main driving motor, a pair of generators and an exciter, driven thereby, a motor for the grinding wheel driven by one of said generators, and a motor for the workhead driven by the other generator.

The electrical equipment also includes a system oi. speed control for the grinding wheel and for the feed and rotational movements of the Workhead.

Constructionally, the improved machine is characterized by a number of features including means for grinding taper work and for relieving purposes when grinding taps. Provision is also made whereby the peripheral speed of the work and of the feed movement thereof can be temporarily accelerated each time the flute of a tap passes the grinding wheel. Other features hereinafter described include means for effecting rapid Withdrawal of the grinding wheel head when grinding shouldered work and for adjusting the said head to accommodate the helix angle of the thread to be ground. Means are also incorporated in the machine whereby the formed periphery of the grinding wheel can be accurately retrued without disturbing the setting-of the ma chine. A lateral setting device for the work-head is also provided whereby the dead centre can be advanced or retarded so that existing threads on the Work can be readily set relatively to the grinding wheel with the aid of a microscope incorporated in the machine.

In the accompanying drawings,

Figures 1 and 2 are front elevational and end views respectively of one form of the improved grinding machine.

Figures 3 and 4 are two views showing the arrangement of the main motor, generators and exciter.

Figure 5 shows the means employed for adjusting the position of the grinding wheel head in relation to the work.

Figure 6 shows the manner in which the wheel head is mounted to provide adjustment for the helix angle of the thread.

Figures 7 and B are side and end views o1.' the (Cl. 51--94l machine when adapted for producing or' finishing screw threads on fiuted or taper work.

Figures 9 and 10 are side and transverse sectional views of the tailstock showing the wheel truing device.

Figure 11 is a schematic diagram of the electrical equipment.

Figure 12 shows means for accelerating the work for gap-jumping or the like purposes.

The main constructional features of the improved machine comprise a fixed bed, 2, a horizontal slide 3 mounted on the bed and adapted for movement longitudinally thereof, a work-head 4 and a tailstock 5 mounted on said slide, and a grinding wheel head 6 mounted upon the said bed and capable'of adjustment towards and away from the centre line of the work-head and tail stock.

The electrical equipment comprises a main driving motor ID, a pair of generators Il, l2 and an exciter I3, all driven by the main motor, a motor 8 for driving the grinding Wheel energized by one of said generators, and motor 9 for driving the slide 3 and work-head 4 energized by the other generator. The grinding wheel motor 8 is 25 carried on the wheel head 6 and drives the wheel by means of a belt I6.

The main motor, generators and exciter, Figures 3 and 4, are all arranged at the rear of the machine and enclosed in a louvered guard I4. 30

The grinding Wheel head 6 complete with its motor 8 is enclosed in a louvered guard I 4a and is mounted on rollers running in oil baths in the bed of the machine and is guided by a V-section rib and groove engagement with the bed. Ad- 35 justment of the wheel for depth of cut, Figure 5, is obtained by a precision screw 20 and nut 2| controlled by means of a large hand wheel 22 located in front of the machine. Two rates of wheel adjustment are provided one being direct from the hand wheel 22 and the other through epicyclic reduction gear 23, the change from one ratio tothe other being controlled by the knob 24 which puts the member 24a either into direct driven relationship with the hand wheel or, as

. shown, into gear with the sun wheel 24b of the epicyclic gear, the planet pinlons 24 rolling around the pinion 24d on the spindle of the screw 20, which is thereby rotated at a proportionately lower ratio. 50

A-quck return movement of the wheel head away from the work can be effected by means of a hand lever 25 which is iixed to one end of an externally screw threaded sleeve 25* mounted loosely on the spindle 20 of the screw 20 and working ina fixed nut 25b on the machine frame 2. By turning the lever in a clockwise direction the other end of the sleeve is caused to abut against a shoulder 25c on the spindle and to move the latter bodily toward the left hand in Figure 5.

For screw-threading shouldered work the quick return movement of the wheel head is carried out automatically, a projection 21b (see Figures 1 and '7) adjustably mounted in the slide 3 carrying the work-head being arranged so that as the latter reaches a predetermined point in its traverse movement said projection 21b depresses a plunger 21 to release a trip-lever 2111. Normally said triplever 21'L engages with a shoulder 25d (see Figures 5 and 1) on the hand-lever 25 whereby said handlever 25 is held against displacement along the axis of the spindle 20, such displacement being due to the feed-forward of said hand-lever 25 on rotation. Depressing the plunger 21 by the projection 21b disengages the trip-lever 21El from the shoulder 25d, sleeve 25* and hand-lever 25 are then free to rotate in a clockwise direction under the influence of a spring 25e attached to the collar 25f carried by the sleeve 25a. Such rotation moves the wheel-head away from the work as previously described, the spindle 20a and its adjustable mechanism moving with it.

To accommodate the helix angle of the thread to be ground or finished, the wheel head is arranged, as shown in Figure 6, so that it can be adjusted angularly in a plane parallel with the rotational axis of the wheel for which purpose the wheel head is made in two parts, a lower part 6 sliding on the machine bed 2 formed on its upper side with a spherical seating 6a and an upper part 6b carrying the wheel spindle 1 and having a spherical under part 6c adjustably mounted in said seating. The grinding wheel 1 itself may be of the multiple rib type shown or of the single rib type.

Where the machine is intended solely for use in producing or finishing screw threads on plain cylindrical worli the work-head 4 and tail-stock 5 are both mounted directly on the slide 3, as shown in Figures 1 and 2. For taper and uted work such. as taps, however, the work-head 4 and tail-stock 5, Figure '1, are mounted on a bar 30 which is free to rock about a longitudinal axis on trunnions mounted in bearings 32 at the ends of the slide 3. The slide, like the grinding wheel head, is mounted on rollers 33, Figure 2, rotating in oil baths 34 in the bed 2 of the machine and is guided by a rib and groove engagement 35 with the bed.

'I'he slide 3 and work-head 4 are both driven by the motor 9, the former by a lead screw 40 from a gear box 4| at the left-hand end of the machine, and the latter through gearing housed within the work-head 4 and driven from the gear box 4|. The direction of rotation of the lead screw 40 and of the work-head 5 for right and left hand threaded work is changed by means of tumbler gear within the gear box operated by a lever 42 having forward, neutral and reverse positions.

For flute relieving purposes the bar 30 carrying the work-head and tail-stock is adapted to be rocked about the axis of the trunnions to move the work toward and away from the wheel for backing the thread by means of a cam 43 carried by a longitudinal shaft 44 mounted in bearings in the work-head.

The cam bears upon a roller 45 carried by a vertical bar 4B mounted in guides on the slide 3 and resting at its lower end on a sine bal.' 4.7 which is adapted to be moved into various inclined positions or into horizontal position according as may be selected in accordance with the work to be performed and locked in such adjusted position by the screws 48 and 49 and is adapted to take the thrust produced by the rocking of the workhead 4 and tail-stock 5. For flute relieving purposes when operating on a work-piece of the same cross-sectional size from end to end of that portion which is being ground the sine bar 41 will be adjusted to, and locked in. horizontal position. 'I'he arrangement is such that at the proper times during the rotation of the work the cam as it turns causes the work head to be moved toward the grinding wheel to give the required amount of relief at the flutes.

For gap-jumping purposes when forming or finishing screw threads on fiuted work, such as taps, a cam 99 (see Fig. 12) carried by a longitudinal shaft 44 mounted in the work-head 4 and adapted to be driven from the motor 9 through the gear-box 4| and bevel-gearing |00 is provided. This cam is timed to operate a tappet IDI while a ute is passing the grinding wheel so as to close a switch which short circuits a resistance in the eld of the appropriate generator thereby momentarily increasing the speed of the work-head motor and in consequence the rotational speed of the work. The tappet |01 is housed in a member |04 which is longitudinally movable by an adjusting screw |03 so as to adjust the position of said tappet on the face of the cam 99, whereby the time during which the switch 80 is closed may be altered to suit the different sizes of tap flutes.

For screw threading taper work the work-head, which, as already stated is in this case mounted on the rocking bar 30, is gradually tilted towards the wheel as the work traverses across the face of the wheel. For this purpose the cam 43 on the longitudinal shaft is rendered inoperative and the inclination of the sine bar 41 is adjusted by the screws 48, 49 according to tthe angle of taper required, so that as the slide traverses the bed of the machine the foot of the vertical bar 46 slides along the inclined sine bar 41 and in doing so tilts the Work-head gradually toward the wheel.

Where it is desired to relieve a tapering workpiece it will be understood that the proper form of cam 43 will be selected, and will be driven at the proper speed with relation to the longitudinal movement of the slide 3 to result in relieving the work-piece at the proper points, and the sine bar 41 will be adjusted to, and locked in, the

inclined position necessary to the exact degree of taper involved. Of course also it will be understood that by using a grinding wheel with a differently formed operative face the machine may be used for form grinding generally.

The acting peripheral face of the grinding wheel is preferably formed in the manner described in my co-pending application Serial No. 651,597, the wheel truing and forming device being in this case permanently associated with the tail-stock so that there is no need to remove or disturb the work when truing up the wheel.

'I'he said device, Figures 9 and 10, comprises a cam 50 driven from a spindle 5| through gearing 5| c the outer end of said spindle 5| being adapted for driving connection with the work-head 4 by means of the splined shaft 5|b in the housing 5 la. The cam bears against a diamond holder 52 carried by a slide 53 which reciprocates between adjustable ball bearing guides 54 against the action ot springs II. The cam operates to move the diamond towards and away from the axis of the grinding wheel at-the same time that the slide I carrying the work-head 4 and tail-stock listraversedbytheleadscrewacrossthe face of the wheel, the two movements being correlated and relatively adjustable to give the desired form to the acting peripheral face oi the wheel.

Referring now to the schematic diagram, Pigure ll, of the electrical equipment it will be seen that the shunt fields l, 9' and II', I2l of the motors 8, 9 and generators II, I2 are each separately excited, the supply of current thereto from the exciter I3 being regulated by variable resistances II", and I2", I2 of the potentiometer type so that whilst the voltage output of the generators can be varied at will 'the torque of the motors respectively driven therefrom remains constant throughout the whole of the speed range.

By suitable regulation of the resistance IIb the speed of the grinding wheel motor 8 and hence the peripheral speed oi the wheel itself can be readily varied in ilne gradations between a speed as low as 730 feet per minute for economical wheel truing and forming purposes and a speed as high as 6500 feetper minute thereby enabling the most suitable grinding speed to be obtained for any class of work. 'I'he wheel motor 8 is started up by closing the push-button switch 93 which completes the circuit of the exciting coil 94 of a contactor controlling switches 95, 96 in the shunt ileld and armature circuits of the generator Il.

The movements of the work-head in feeding the work across the face of the grinding wheel are controlled by means of a pair of limit switches 60, 6I which open and close the circuits of the exciting coils 62, 63 -of contactors governing the direction of rotation of the generator I2 supplying current to the work-head motor 9. 'I'he said switches are operated by a trip lever 64 pivoted in the bed of the machine and arranged between a pair of adjustable stops 65, 66 on the slide 3. The arrangement is such that when the work-head reaches the end of its feed movement the lever 64 is moved by the stop 66 to close limit switch 60 and open limit switch 6I.. 'I'he eiect produced is to complete the circuit o f the contactor exciting coil l63 and to break the circuit of the contactor exciting coil 64, respectively, and hence to close the switches 61 and open switches 68 in the armature circuit of the motor 9 thereby reversing the direction of rotation of the latter.

At the same time the closing of contacter energized by coil 62 also opens switch 69 and closes switch 10 in the eld circuit of the generator I2 thus short circuiting the greater part of the controlling resistances I2", I2c and increasing the speed of the motor so that the work-head is given a quick return movement. At the end of the return movement the trip lever 64 is moved in the opposite direction by the second stop 65 to open limit switch 60 and close limit switch 6I the effect of which is to break the circuit of the exciting coil 63 controlling switches 68, and 10 and to close the circuit of the exciting coil- 62 thereby closing switches 61 and 69.

The work-head will now move forward on its feed movement at a speed which is set by adjustment of the regulating resistances I 2b, I 2 in the ileld circuit of the generator I2.

When the work speed is required to be the same in both directions a change-over switch 1I can resistances I2, I2.

be introduced in the ileld circuit of the generator I2 in which case the connecting link 12 previously necessary will be removed;

The armature oi the change over switch 1I is connected to that part ot the ileld circuit of generator I2 containing switch 69 and is adapted to make contact with one. or the other of terminals 13, 14 connected respectively with one end of re-l sistance I2e and with the amature circuit of the exciter I3 respectively. Iny this case when the work-head is moving in one direction switches 61, B9 are closed and switches 68 and-18 are open and the speed of the motor is controlled by the When the work-head is moving in the other direction switches t1, 69 are open and switches 68, 10 are closed and the armature of the change over switch 1I makes contact with terminal 13 so that the speed of the motor is again controlled by resistances I2", i2.

For producing or finishing left-hand threads the operation of the limit switches 60, 6I has the reverse effect, that is to say, by means of a second changeover switch 16, which may be conveniently operated by the tumbler gear lever 42 aforesaid, the said limit switches and excitingcoils 62, 63 are cross-connected so that when the workfhead reaches the end of its feed movement in the lefthand direction the resultant operation of the trip lever 64 on the said switches 60, 6I is to reverse the direct-'on of rotation of the motor and accelerate its speed to give a fast return of the work.

For flute jumping purposes' the link 11 is removed and connections made as shown in dotted lines in Figure ll. A separate contactar is pro vided, the circuit of the excit'ng coil 'I8 of which when closed by the hand switch 19 is controlled by a cam-operated switch (see Fig. 12). The

cam 99 is arranged to close this switch during the the latter across the circuit of the armature of the exciter I3, as shown in dotted lines, so that the speed of the motor is accelerated. When the ilute has passed the wheel the cam allows the switch 80 to cpen thus breaking the circuit` of the exciting coil 18 of the contacter controlling,

switch 8 I The switch panel is arranged at the front of the machine and conveniently carried by the door of a housing in the bed of the machinev for the resistances and contactors. The said panel comprises starting and stopping switches 9I of the press button type for the main motor and similar switches 93 and 94 for the motors for the wheel and work-head respectively, as well as speed control hand wheels 91, 98 for the variable resistances IIb, I2' in the field circuits of the generators. A safety switch may also be provided and arranged so that when the door of the housing is opened the machine is rendered inoperative.

The stop push button for the grindlng'wheel'- motor may be interlocked with thecorresponding button of the work-head motor so that if the wheel is stopped the work is also stopped and cannot be restarted until the wheel is again set in motion. e

1. A grinding machine comprising a fixed bed,

a driven grinding wheel, means for moving' said wheel transversely of said bed, a slide mounted in said bed for reciprocation longitudinally thereof a bar extendingflongitudinally of said bed and rockably mounted on said slide, work-holding means mounted on said bar to present the workpiece to the operative face of said grinding wheel, a drive gearing, and means driven by said gearing for reciprocating said slide, in combination with a cam mounted in said work-holding means, a longitudinally extending sine bar mounted on said bed, means for adjusting said sine bar to a horizontal and to various inclined positions and for locking it in a selected position of adjustment, guides carried by said slide, a rod working in said guides and traveling with saidslide, said rod engaging said cam with one end and slidably engaging said sine bar with its other end and moving endwise in its guides in accordance with the degree of inclination of said sine bar as said slide moves longitudinally whereby said bar will be caused to rock correspondingly about its axis, and means driven by said gearing in denite relation to said slide reciprocating means for rotating said cam to by its engagement with said rod cause an independent cyclic oscillatory movement of said bar and the work-piece.

2. A grinding machine comprising a xed bed, a driven grinding wheel, a slide mounted in said bed for reciprocation longitudinally thereof across the operative face of said grinding wheel, a bar extending longitudinally of said bed and rockably mounted on said slide, work-holding means mounted on said bar to present the work piece to the operative face of said grinding wheel, and means for reciprocating said slide, in combination with a cam mounted in said work-holding means, a longitudinally extending sine bar mounted on said bed, means for selectively ad- Justing said sine bar to a horizontal and to,

various inclined positions, guides carried by said slide, a rod working in said guides and traveling with said slide, said rod engaging said cam with one end and slidably engaging said sine bar with its other end and moving endwise in its guides in accordance with the inclination of said sine bar as said slide moves longitudinally whereby said bar is caused to rock correspondingly about its axis, and means for rotating said cam to by its engagement with said rod cause an independent oscillatory movement of said bar and work-piece.

3. A grinding machine comprising a xed bed, a driven grinding wheel, a slide mounted in said bed for reciprocation longitudinally thereof across the operative face of said grinding wheel, a bar extending longitudinally of said bed and rockably mounted on said slide, work-holding means mounted on said bar to present the workpiece to the operative face of said grinding wheel, and means for reciprocating said slide, in combination with a'cam mounted in said work-holding means, a longitudinally extending sine bar mounted on said bed, means for selectively adjusting said sine bar to a horizontal and to various inclined positions, guides carried by said slide, a..

rod working in said guides and traveling with said slide, said rod engaging said cam with one end and slidably engaging said sine bar with its other end and moving endwise in its guides in accordance with the degree of inclination of said sine bar as said slide moves longitudinally whereby said bar will be caused to rock correspondingly about its axis, means adapted to rotate said cam to by its engagement with said rod cause supplementary oscillatory movement of said bar and the work-piece, and means for rendering the last mentioned means inoperative.

4. A grinding machine comprising a fixed bed, a driven grinding wheel, a slide mounted in said bed for reciprccation longitudinally thereof `across the operative face of said grinding wheel,

a bar extending longitudinally of said bed and rockably mounted on said slide, work-holding means mounted on said bar to present the workpiece to the operative face of said grinding wheel, and means for reciprocating said slide, in combination with an abutment carried by said workholding means, a longitudinally extending sine bar, means for selectively adjusting said sine bar to various inclined positions, guides carried by said slide, and a rod working in said guides and traveling with said slide, said rod engaging said abutment with one end and slidably engaging said sine bar with its other end and moving endwise in its guides in accordance with the degree of inclination of said sine bar as said slide moves longitudinally whereby said bar will be caused to be rocked correspondingly about its axis.

5. A grinding machine comprising a fixed bed, a driven grinding wheel, a slide mounted in said bed for reciprocation longitudinally thereof across the operative face of said grinding wheel, a bar extending longitudinally of said bed and 'rockably mounted on said slide, work-holding means mounted on said bar to present the workpiece to the operative face of said grinding wheel, and means for reciprocating said slide, in combination with a cam mounting in said workholding means, abutment means engaged by said cam throughout the range of movement of said slide, said abutment means being rigid with said bed, and means for rotating said cam for causing a cyclic oscillatory movement of said bar and work-piece throughout the longitudinal movement of said slide.

STANLEY JAFFA HARLEY.

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