US2407577A - Device for dressing grinding disks - Google Patents

Description

S p 10, 1946. A. RICKENMANN 2,407,577 DEVICE FOR DRESSING GRINDING DISKS Filed Deb. 17, 1943 3 Sheets-Sheet l IIIIIh Jar/er; z'ar' red fiz'dfenmann a E a a: H 4 5 52.: .E: -I

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flfrgdfiz'afenmnm Sept. 10, 1946 A. RICKENMANN' 2,407,577

DEVICE FOR DRESSING GRINDING DISKS Filed Dec. 17, 1945 :5 Sheet-Sheet 3 Patented Sept. 10, 1946 orrics DEVICE FOR DRESSING GRINDING DISKS Alfred Rickenmann, Zurich, Switzerland Application December 17, 1948, Serial No. 514,589 In Switzerland December 28, 1942 10 Claims. 1

The invention relates to an improved device for accurately forming the profiled working face of a grinding disk for use in grinding and truing screw threads.

One object of the invention consists in the provision of a device by means of which even not high grade diamonds of any suitable shape may 7 be used for dressing the grindingwheel and to produce thereon ridges of perfect profile for ac-- curately grinding screw threads.

Another object consists to provide means to automatically adjust the dressing tool with reference to the grinding disk in conformity to the wear thereof and to compensate the same.

I attain these and other objects by means of a simple device which may be brought in and out of operation either by hand or by automatic governing devices in a predetermined sequence of operations.

In the accompanying drawings the new device is shown in a diagrammatical manner by way of an example in connection with screw thread grinding wheels of any of the well known constructions.

Fig. 1 shows in a side elevation a thread grinding machine parts being shown in section.

Figs. 2 to 8 are cross-sections taken respectively on the lines 2-2; 33; i-t; 5-5; 6-5; 'i'l; and 8-8of Figs. 1 and 2.

Figs. 9 and 10 are sections on the lines ll-9 and liiil of Fig. 8.

Figs. 11 to 14 are a front view, a sid view, a back View and a top view of the cam plate actuating the dressing tool.

Fig. 15 illustrates the manner of the operation of the diamond.

Fig. 16 shows a detail of construction.

On a base i of a screw thread grinding machine a carriage 2 is slidably mounted. On the carriage 2 a headstock 3 and a tailstock d are arranged in the usual manner adapted to receive the work piece. 5 between their centres. The driving spindle 6 is journalled in the headstock 3, it is positively driven by a worm it and a worm wheel Mwhich is keyed to spindle ii. The worm i3 is driven by a-shaft 12 which is connected to the worm shaft by universal joint l2! and by another universaljoint with shaft ii. The latter is driven by bevel gears Iii from a shaft Hll journalled in a gear box "i. On the shaft llll a sleeve "32 is slidably mounted on a key thereof, it may be brought in engagement either with toothed gear IE3 or with gear Hit; The shaft I0! is driven by the motor 8 and the gear W5 meshing with gear I04 or by change gears )6 driving iii by the intermediary change gears [01 the toothed gear I63.

The carriage 2 is moved in the well known manner by a lead screw H9 and a set of change speed gears 19 interconnecting spindle 5 and lead screw Hi3. By bringing the clutch member in engagement with one or the other gear [03 or ass the travel of the carriage 2 and the direction of rotation of spindle B and therewith of the work piece 5 is reversed.

The clutch member 9 is actuated by a lever 23 which is connected by a link 23I to the rod 22 of a piston 12! slidably arranged in a cylinder 26. The latter is provided with ports 2M, 25'2 communicating with the casing of a piston valve IS. The valve casing communicates by a pipe 263 with a hydraulic pump P and is provided with two exit ports 204, 205. The piston valve i9 is connected by a linklel with the armature l8l of two electromagnets i8. By exciting the electromagnets iii the armature l8! shifts thepi'ston valve l9 to allow oil under pressure to pass on either side of piston 2|. The circuits in which the electromagnets I8 are arranged are opened and closed by a reversing switch I! which is actuated by the dogs l5, It adjustably mounted on the carriage 2.

The valve 19 controls moveover the flow of oil from the pump P to a cylinder 48 by the pipes 38, 39. The piston M of cylinder 4a is provided with a rack (Figs. 1, 2) meshing with a toothed gear 42 rotatably mounted on a shaft 55 journalled in the base On the hub of gear 42 an arm 43 is keyed carrying a spring actuated pawl 44 engaging a ratchet wheel 45 fast on shaft 55 (Figs. 2, 16). A pawl M4 (Fig. 16) engaging ratchet wheel 45 retains same in its position. On the shaft 55 a rotary distributing valve 3? is arranged within a casing 31! (Figs. '2 to 5) controlling the flow of pressure oil through pipes 35, 36 (Figs. 1, 2) to a cylinder 32 fast on a slide 3! (Figs. 1, 8, 10) of the carriage 25 in which the grinding disk 26 is journalled the edge of which is to be trimmed.

The carriage 25 is slidably mounted on the base i. A weight 353 (Fig. 2) fixed to a band 33] and running over a pulley 302 tends to draw thecarriage 25 and therewith the grinding disk 26 away from the work piece 5. To the carriage 25 a nut 29 is fastened with which a screw threaded shaft 2a is in engagement. The latter is journalled in the base I and carries a hand wheel 2'! by turning of which the carriage 25 maybe adjusted by hand. The shaft 28 co-op'erates moreover with the shaft 55 by means of a cam 5'! keyed to shaft 3 55 (Figs. 2, 6). With the cam 51 contacts an arm 6| of a sleeve 6| rotatably mounted on shaft 28. A coiled spring 53 (Fig. 6) keeps the tooth 62 of the arm 6| in contact with cam 51 which when turning with shaft 55 rocks the arm 6| and therewith the sleeve 6| i. On a second arm 6|: of sleeve 5|! a pawl E54 is mounted (Fig. 6) engaging a ratchet wheel 65 (Figs, 2, 6) keyed to shaft 28. By turning shaft 55 by means of piston 4| say for an angle a and by setting thereby the distributing valve 31 th ratchet'wheel 65 is also turned and therewith the shaft 28. The carriage 25 is moved with reference to the work piece 5 as will be explained hereinafter. The way of piston 4| and therewith the angle about which the shaft 55, the distributing valve 31 and the shaft 28 may be turned may be limited by any one of a plurality of pins 45 (Figs. 1', '7).

The pins 46, 46!, 462, 463, 464, 465, 466 are fastened-to the face of a toothed gear 49 journalled in the base The pins 46, to 456 are all of different lengths each one may be brought in the path of piston 4| by turning the gear 49 by means of a toothed gear 5|] fast on a shaft 5 The latter is journalled in the base it may be rotated by a knob 52. A scale 53 indicates which one of the pins 45 is in its operative position. The travel of piston 4| is limited at its other end by an abutment 41 (Fig. 1) fixed to cylinder 4! The shaft 55 and therewith shaft 28 may further be turned by hand by means of ashaft 59 carrykey 134. The casing 13 is provided with 2. lu 15 (Fig. 9) and in the path of lug 15 project two stop screws 15, l! adjustably mounted in the slide 3|. The stops 15, ll limit the movement .of casing 13 when the latter is reciprocated by the piston 33 and the rack 688 of sleeve 68. The rocking movement of casing 13 differs While the stroke of the piston 33 is always a full stroke; Between a shoulder of piston rod 34 and'a nut |i8| of sleeve 38 a spring 13 is arranged. The nut 68| rests on a washer 682 fastened to the piston rod 34. Th spring it which is under tension allows a movement oftheslide 53 with reference to piston rod 34. The piston 33 may perform therefor a full stroke whatever the-way of the casing 13 will be.

ing a hand wheel 65 and a toothed gear 58 mesh- 7 ing with a gear 56 keyed to shaft 55 (Fig. 2).

' The cylinder 32 (Figs. 2, 8 to 15) with piston 33 which operates the dressing tool "14 (Fig. 8)

is arranged on the slide 3| which may be vertically adjusted with reference to the grinding disk 26 by means'of a screw threaded spindle 93 screwed in a nut 94 of the carriage 25. The shaft93 carries a hand wheel 95 and a ratchet wheel 92 with which a pawl 9| is kept in engagement bya spring 9|! (Fig. 10). The pawl 9| may be withdrawn from the ratchet wheel 92 by a knOb'SB. The pawl 9| is arranged in a, casing 9|0 which is rockingly mounted in the slide 3| and which may be rocked by a pin 89 actuated by the rod 34 of the piston 33 of cylinder 32.

"The pawl 8| turns wheel 92 and shaft 93 on each stroke ofpiston 33 and feeds the slide 3| and therewith the tool'14 towards the grinding wheel 26. The piston 33 is provided with an annular groove 33| (Fig. 10) into which enters one of two catches 91 or 91! as soon as thepiston 33 comes to bear on the'abutment 66 or on the lid 61 of cylinder 32. The catches '91, SH are brought in engagement with the piston 33 by springs 98 and 98! and are brought out of engagement therewith by oil pressure acting on the faces 99 and 99| of the catches B1, 91!. In the position of piston 33 shown in Fig. 10 oil under pressure enters by pipe 36, the catch 59| has released piston 33, the latter moves to the .left and actuates by its rod 34 and a bevelled face 342 the pin 89and therewith the feed screw 93. On the return stroke of piston 33 the bevelled face 343 of piston rod 34 actuates said pin 8B again. The faces 342, 343 areapart for-a distance equal to 34L the feeding of the slide 3| and the tool 14 is timely distanced and coordinated to'other functions which the piston 33 is to perform. On the piston rod 34 a sleeveGB is slidingly mounted being provided with a rack 688 engaging a pinion I! (Fig. 8) keyed to a shaft 12. The latter is journalled' in the slide 3| and carries on its free end a casing 13, by a The piston rod 34 is provided with a tooth B3 projecting through a slot of sleeve 58 and co- 7 operating with a cam plate 18 (Figs. 8 to 14) rockingly mounted on a shaft 79 of slide 3|. The reciprocating piston rod 34 forces the tooth 65 over thecams 18] to 785 formedon theone face of lever 18. On the other face the camlever E8 is provided with a segmental row of teeth |l3|. A pin Bel of a block 863 is in engagement with said row of teeth |18|, the block 8?! being slidably mounted in the casing 73.

33 is in engagement on which a spring84 is acting tending to keep pin 80! in contact with lever 18 andthe latter in contact with tooth 69; Any movement of the pin Bill is transmitted to shaft 36 on the face of which a pointed diamond piece I4 is eccentrically mounted adapted to work the flanks of the grinding disk 26 (Figs. 8, 15).

The shaft may be adjusted in axial direction by a nut 81 screwed on th screw threaded portion 'i'3| of the casing 13. The nut 81 acts on a ball bearing 833 fixed to shaft 85 by a screw 85 and displaces the shaft 86 against the action of a,

spring BM.

The piston rod 34 oscillates by means of rack 688 and toothed gear the casing 13. The pin 8ll| passes thereby over the toothed segment '|8| mounted on shaft 19 of the casing 3| and transmits a vibratory movement to the tool 14 depending on the number and the height h (Fig, 14) of the teeth l'l8l. In addition thereto the cam plate i8 is rocked about shaft l9 and the Pin 8M displaced. Shaft 85 is turned by the tooth dle 93 makes a part rotation, adjllsting'the slide.

3| towards the grinding disk 26. While the tooth 69 passes over the portion 733 of the cam 18 the latter remains stationary and only a vibratory motion is imparted to the tool '14 by the teeth |8|. The tool 14 performs oscillating movements I-I (Fig, 15) While the casing 13 is rocking about axis X--X of shaft 12 from one stop 16. to stop 1! or vice-versa the tool 14 passes over the centre line (3- 0 15) of the grinding disk 26. r

The latter is rounded offthe radius R' corresponds to the radial distance of the working point of the tool 14 from the axis of rotation Ii -X" denoted by r in Fig. 8.

V The block 85] is provided with a rack 8| meshingwith a'toothed gear 82 on a shaft 86. With the gear SZarack The length of the straight portion 183 of the cam '58 corresponds to the greatest angle through which the casing 13 may swing, the said angle corresponds to the greatest possible angle a, Fig.

i5, enclosed by the flanks E, F of thegrinding disk 2%. When the casing 13 comes to bear either on stop it or on stop ll the cam plate It cannot any further about the axis of shaft E2 the oscillatory movement of the tool it is in terruptedv The piston rod 34 moves on and the tooth $3 co-operates now with one of the portions i812 or 564% of the cam plate 78. The latter is rocked about the shaft l9 by the combined action of the tooth B9 and of the spring 84. Each portion 182 and F84 has three flanks over which the tooth 69 passes successively rocking thereby the plate (8 about the shaft 19. The plate I8 moving in one direction transmits its movement over the members Sal, 85),. 8|, 82 to shaft 85 and. to tool It against the action of spring 84. The tool M is swung over the flank E or F. The spring 86 returns the plate is and keeps the same in contact with tooth (it. The tool It swings three times over the flank E or F while the tooth 69 passes over the portion it?! or ltd of plate 18. It may happen that the pintfil comes to rest on the ground or on the top of a tooth of the segment i8? and in such a case the tool M would not be rocked far enough to work the flank E or F of grinding disk 25 on its whole breadth. To obviate thisdrav back the edge 88 is slightly above and the edge 85! slightly below the plane of the centre portion 2 After the tooth 89 has passed the portions 132 or it the piston rod 34 still moves on the tooth 69 passing over the end portions H8! or Hit. By passing these portions I8! and I85 the tool H- is brought out of contact with the disk 26.

With the tool it in this position the bevelled por- V tions $42 or 343 actuate the pin 39 and feed the tool "i l towards the grinding disk 26. After eachstroke of the piston rod 34 the tool 14 is advanced towards the grinding disk 2 6. The infeed of the slide 3! towards disk 25 is equal to the infeed of the carriage 25 towards he work piece 5 by means of the cam disk 51. The piston 33 remains stationary at its end position as long as the oil exerts pressure on it. 'To (prevent the piston to leave this end position accidentally, for instance by stopping the machine, the above described catches ill. Sill are provided for. The

catches are brought out of their catching position as soon as the oil pressure on the faces 99 Sill attains a certain hight sufficient to overcome the pressure of the springs 9B, 98!.

By starting the machine. the motor 8 drives the spindle 6 and work piece '5 and table 2 moreover oil is supplied by pump P and pipe 283 to cylinder Ez'l and to the distributing valve 31. The table 2 actuates by its dogs 15, it switch ll' electro magnets it, the valve is and the reversing gear. lvloreover oil under pressure is brought to reciprocate the piston ll which turns step by step the distributing valve 31. The latter governs th flow of oil to the cylinder 32 by the pipes 35, 36 to opcrate the piston 33 and therewith the cam plate 53 and the tool 54. The valve 3! reverses the stroke of piston 33 when completing half a turn. Therefore the tool M is set to work only when the valve 3? has been turned by piston M by half a fullrotation. The way of piston Al may be varied by placing one of the several stop pins 46 in its path. The pins it are positioned by turning the gear all by knob 52. By making a full stroke the piston ll turns the valve 31 for half a full turn, by placing any of the pins Mil to 466 in the path of piston Ill the latter has to perform several strokes to turn the valve 31 for half a fullxturn. Each reversal of piston ll corresponds to a reversal of piston 2i andtherefore tothe reversal of direction of rotation of work piece Eand table 2 as the piston 21 commands the reversing clutch 9. By placing a certain stop pin Mil to 566 in the way of piston M by :nob 52 the number of strokes of table 2 and ofreversals of the shaft 6 may be determined until the piston. 33 makes a stroke and sets the tool Hi to work on the grinding disk 26. The valve 3! may be set by hand by means of knob Gil (Fig. 2) on shaft 59 on which the gear 53 is keyed meshing with gear 56 fast on shaft 55.

The cam 5's (Figs. 2 ant. 6) and the valve 3'! fastened on the same shaft 55. The position of the active flank G of cam at with reference to the point 52 of the lever E! in Fig. 6 corresponds to the position of the valve 31 with reference to the ports of the pipes 35, in Fig. 4. While the valve 3? turns about angle [3 the 5! turns about a like angle or. The change of pressure in the sipes 35 and 56 takes place while the cam 51! passes the angle on. The cam Ell therefore shifts the ratchet wheel 65 and turns therewith the shaft 2? and advances the carriage 25 at that moment at which the pressure in the pipes 35, 35 and therewith on the side of the piston 33 changes and that timely co-incides with its positions'at one of the ends of. cylinder. 32, that is when the tooth E53 free off the cam plate 58 and with the tool it out of contact with the grinding disk 2%. A part rotation of cam 5'5 equal to angle on will compensate the Wear of the grinding disk This compensation takes place positively but only after the piston 33 has performed a stroke thereby initiated the dressing oi the grinding disk 25.

What I wish to claim by United States Letters Patent is:

1. In a screw thread grinding machine, the combination of a reciprocable work carriage and a tool carriage mounted for cross-feed movement in a direction transverse to the path of reciprocation of said work carriage, manually operable means to adjust'said tool car iage, power actuated means for reciprocating said work carriage, a grinding disk rotatably mounted in said tool carriage about an substantially parallel to said path of reciprocation of said work car- Triage, a slide mounted on said tool carriage for movenient thereon at a right angle with respect to. the movement of said tool carriage, a housin which is arranged a grinding disk dressing tool. housing mounted for oscillatory movement on said slide, a second manually operable for adjustir said slide to bring said dressing tool into operative position with respect to grinmng disk, means in said slide oscillating said housing and said dressing tool, means operated by said oscillating mean for rotating said dressing tool in said housing, whereby said vmessing tool is moved once over the grindin face of the grinding disk during each cs atlng movement of said housing, and means at dated by said power actuated operat g oscillating means in timed relation to overnent of said work carriage, namely when the latter ohangesits direction of movement.

11in a screw thread grinding machine, the combination of a reciprocabie Work carriage and a tool carriage mounted for cross-feed movemerit in a direction transverse to the path of reciprocation of said work carriage, manually V operable means to adjust said tool carriage, power actuated means for reciprocating said work carriage, a grinding disk rotatably mounted in said tool carriage about an axis substantially parallel to said path of reciprocation of said work carriage, a slide mounted on said tool carriage for movement thereon at a right angle with respect to the movement of said tool carriage, a housing in which is arranged a grinding disk dressing tool, said housing being mounted'ior oscillatory movement on said slide, a second manually operable means for adjusting saidlslide to bring said dressing tool into operative position with respect to said grinding disk, means in said slide for oscillating said housing and said dressing tool,

' means operated by said oscillating means for rotating said dressing tool in said housing, whereby said dressing tool is moved once over the grinding face of the grinding disk during each oscillating movement of said housing, means actuated by said power actuated means for operating said oscillating means in timed relation to the movement of said work carriage, namely when the latter changes its direction of movement, and means for automatically operating said first mentioned manually operable means to ad- Vance the tool carriage toward the path of movement of the Work carriage a distance which compensates for the amount of wear caused by the dressing tool on said grinding disk, said auto matic'a'dvancing means being operated by said power actuated means.

3. In a screw thread grinding machine, the combinationof a reciprocable work carriage and a tool carriage mounted for cross-feed movement in a direction transverse to the path of reciproccation oisaid work carriage, manually operable means to adjust said tool carriage, power actuated means for reciprocating said work carriage,

,a grinding disk rotatably mounted in said tool carriage about an axis substantially parallel to said path of reciprocation of said work carriage, a slide mounted on-said tool carriage for movement thereon at a right angle with respect to the movement of said tool carriage, a housing in which is arranged a grinding disk dressing tool,

said housing being mounted for oscillatory movement on said slide, a second manually operable means for adjusting said slide to bring said dressing tool into operative position with respect to said grinding disk, means in said slide for oscillating said housing and said dressing tool, means actuated by said power actuated means for operating said oscillating means in timed relation to the movement of said work carriage, namely when the latter changes its direction of movement, and means for automatically operating said second'manually operable means to feed the dressing tool toward the grinding disk, said last named means being operated by said means oscillating said housing and said dressing tool.

4. In a screw thread grinding machine, the combination of a reciprocable work carriage and a tool carriage mounted for cross-feed movement in a direction transverse to the path of reciprocation of said work carriage, manually operable means to adjust said tool carriage, poweractuated means for reciprocating said work carriage,

carriage about an axis substantially parallel to said path of reciprocation of said work carriage, a slide mounted on said 'tool carriage for movement thereon at a right angle with respect to the movement of said tool carriage, a housing in which is arranged a grinding disk dressing to said grinding disk, means in said slide for oscillating said housing and said dressing tool, means actuated by said power actuated means for operating said oscillating means in timed a grinding disk rotatably mounted in said tool relation to the movement of said work carriage, namely when the latter changes its direction of movement, means for automaticallyv operating said first mentioned manually operable means to advance the tool carriage toward the path of movement of the work carriage a distance which compensates for the amount of wear caused by the dressing tool on said grinding disk, said automatic advancing means being operated by said power actuated means, and means for automatically operating said second manually operable means to feed the dressing tool toward the grinding disk, said last named means being operated by said means oscillating said housing and'said dressing tool. a V

5. In a screw tlxead grinding machine, as claimed in claim 1, in which said means for oscillating said housing and dressing tool in clude a power actuated piston mounted for reciprocable movement in said slide, a piston rod secured to said piston and supporting a member provided with rack teeth, a shaft having gear teeth meshing with said rack teeth and supported by said slide, said housing being attached to said shaft to oscillate with the latter, a cam plate pivotaily mounted within said slide and engaged by a lateral extension on said piston rod, said dressing tool being rotatably mounted in said housing, and an operative connection between said cam plate and said dressing tool for rotating the latter: about-an axis at a right angleto the axis of said shaft when said housing is"being oscillated, whereby said dressing too-1 is caused to progressively engage first one flank of the grinding disk, then the apex of the a teeth, a cam face on said piston rod adapted to V actuate said second manually operable means to automatically feed the slide, and therewith the dressing tool toward the grinding disk one step during each reciprocating movement of said pis-' ton, a shaft having gear teeth meshing with said rack teeth and supported by said slide, said housing being attachedto said shaft to oscillate" with the latter, a cam plate pivotally mounted within said slide and engaged by a lateral extension on said piston rod, said dressing tool being rotatably mounted in said housing, and an operative connection between said cam plate and said dressing tool for rotating the latter about an axis 7 at a right angle to the axis of said shaft when said'housing is being oscillated, whereby said dressing tool is caused to progressively engage first one flank of the grinding disk, then the apex of-the same and finally the otherfiank of said disk during each movement of said'pist'on in one direction. a

7. In a screw thread grinding machine as claimed in .claim 1', in which. said means for oscillating said housing and dressingtool include a power actuated piston mounted for reciprocable movement in said slide, a piston rod secured to said piston and supporting a member provided with rack teeth, a shaft having gear teeth meshing with said rack teeth and rotatably supported in said slide, said housing being non-rotatably attached to said shaft to oscillate with the latter, a cam plate pivotally mounted within said slide about an axis parallel to said piston rod, said cam plate having a cam surface on one of its sides engaged by a lateral projection on said piston rod, said dressing tool being rotatably mounted in said casing by being attached eccentrically to the end face of a shaft journalled in said casing, said last named shaft carrying a pinion engaging a rack slidably mounted in said casing, said rack being urged lengthwise in yielding engagement with the other side of said cam plate to be slidably moved when said cam plate is moved about its pivot by the lateral projection on said piston rod when the latter is reciprocated to oscillate said housing, whereby said dressing tool is caused to progressively engage first one flank of the grinding disk, then the apex of the same and finally the other flank of said disk during each movement of said piston in one direction.

8. In a screw thread grinding machine as claimed in claim 1, in which said means for oscillating said housing and dressing tool include a power actuated piston mounted fer reciprocable movement in said slide, a piston rod secured to said piston and supporting a member provided with rack teeth, a shaft having gear teeth meshing with said rack teeth and rotatably supported in said slide, said housing being non-rotatably attached to said shaft to oscillate with the latter, a cam plate pivotally mounted within said slide about an axis parallel to said piston rod, said cam plate having a cam surface on one of its sides engaged by a lateral projection on said piston rod, said dressing tool being rotatably mounted in said casing by being eccentrically attached to the end face of a shaft journalled in said casing, said last named shaft carrying a pinion engaging a rack slidably mounted in said casing, said rack being urged lengthwise in yielding engagement with the other side of said cam plate to be slidably moved when said cam plate is moved about its pivot by the lateral projection on said piston rod when the latter is reciprocated to oscillate said housing, whereby said dressing tool is caused to progressively engage first one flank of the grinding disk, then the apex of the same and finally the other flank of said disk during each movement of said piston in one direction, and means on that side of the cam plate which engages said rack for causing the latter and therewith said dressing tool to vibrate 10 ment in a direction transverse to the path of reciprocation of said work carriage, manually operable means to adjust said tool carriage, power actuated means for reciprocating said work carriage, a grinding disk rotatably mounted in said tool carriage about an axis substantially parallel to said path of reciprocation of said work. carriage, a slide mounted on said tool carriage for movement thereon at a right angle with respect to the movement of said tool carriage, a housing in which is arranged a grinding disk dressing tool, said housing being mounted for oscillatory movement on said slide, a second manually operable means for adjusting said slide to bring said dressing tool into operative position with respect to said grinding disk, means in said slide for oscillating said housing and said dressing tool,

means operated by said oscillating means for rotating said dressing tool in said housing, whereby said dressing tool is moved once over the grinding face of the grinding disk during each oscillating movement of said housing, means actuated by said power actuated means for operating said oscillating means in timed relation to the movement of said work carriage, namely when the latter changes its direction of movement, and stop means on said slide for positively limiting the extent of the oscillatory movement of said housing in both directions.

10. In a screw thread grinding machine, the combination of a reciprocable work carriage and a tool carriage mounted for cross-feed movement in a direction transverse to the path of reciprocation of said work carriage, manually operable means to adjust said tool carriage, power actuated means for reciprocating said work carriage, a grinding disk rotatably mounted in said tool carriage about an axis substantially parallel to said path of reciprocation of said work carriage, a slide mounted on said tool carriage for movement thereon at a right angle with respect to the movement of said tool carriage, a housing in which is arranged a grinding disk dressing tool, said housing being mounted for oscillatory movement on said slide, a second manually operable means for adjusting said slide to bring said dressing tool into operative position with respect to said grinding disk, means in said slide for oscillating said housing and said dressing tool, means actuated by said power actuated means for operating said oscillating means in timed relation to the movement of said work carriage, namely when the latter changes its direction of movement, means for automatically operating said first mentioned manually operable means to advance the tool carriage toward the path of movement of the work carriage a distance which compensates for the amount of wear caused by the dressing tool on said grinding disk, said automatic advancing means being operated by said power actuated means, and means for rendering said automatically operating means inoperative at will.

ALFRED RICKENMANN.

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