US2374258A - Infeed control for worm gear hobbing machines - Google Patents

Description

April 24, 1945. e. DAVENPORT INFEED CONTROL FOR WORM GEAR HOBBING MACHINES Filed Aug. 15, 1941 2 Sheets-Sheet l INVENTOR WZW ATTORNEY 2 Sheets-Sheet 2 G. DAVENPORT Filed Aug. 15, 1941 INVENTOR ATTORNEY INFEED CONTROL FOR WORM GEAR HOBBING MACHINES April 24, 1945.

hunted Apr. 24, 1945 INFEED CONTROL FOR WORM GEAR HOBBING MACHINES Granger Davenport, Montclalr, N.- J., assignor to Gould & Eberhardt, Newark, N. J., a corporation of New Jersey Application August 15, 1941, Serial No. 406,955

14 Claims. (01. 90-4) This invention relates to improvements in machine tools and concerns more particularly an improved method and means for bringing one or more movable members of the machine to a stop at a. precise point in the power travel thereof and thereupon to render the power drive inoperative until the movable member being controlled is physically uncoupled from the drive.

The invention is of special advantage and utility in controlling cutter infeed motions in a worm gear hobbing machine, but may, as will hereinafter become apparent, perform an equally important service in other environments where similar conditions obtain. Hitherto it has been customary to utilize adjustable dogs in combination with mechanical clutches to disconnect the power feed or to disconnect the main driving clutch of the machine at the apprdximate point whereat it was desired to stop the feed movement. Such devices were not, however, satisfactory in use for a number of reasons, chief among which was the difliculty experienced in setting such mechanical devices to trip out and stop the movement at a precise point. Frequently supplemental adjustments by hand were necessary if a predetermined distance of feed movement was required, viz. the correct center distance between the hob and the blank, in worm gearing. Another disadvantage existing in the prior constructions was the inability to reset large and heavy trip mechanisms, which of necessity are bulky and strongly constructed to overcome the powerful action of mechanical clutches, to suit minute refinements in adjustment that may be necessary after a test run. Moreover, such prior structures are not adapted to efiect or of permitting the tool to eiIect a continuation of its tooling motion while engaged with the work blank so that a finishing cut may be taken without further infeed movement.

The present invention overcomes the difliculties above mentioned and undertakes to render available an infeed control which may be set and accurately adjusted to stop the power movement at a selected point within a fraction of a thousandth part of an inch from the absolute dimension. The invention further aims to render available a control mechanism which may be relatively light in weight and construction and which will require but a minimum of force to operate, to the end that coacting elements of the device may be structurally light and therefore capable of minute and precision settings.

A further aim of the invention is to provide in a control capable of being set for fine precision adjustments a means for providing without damage to itself, a reasonable amount of overtravel of the movable member in emergencies, and a device that is fully protected against injury should the overtravel at any time be greater than antici- D ted.

Still another objective of the invention is to provide a simple control that is consistent and reliable in its. operation, easy and quick to install on existing machines and a control which remains unailected by the action of cutter lubricants, oil, water, etc. over long periods of usage.

In attaining the objectives, this invention proposes a partly electric and partly mechanical control for the motions of the shiftable member. A preferred manner of realizing such a control is to provide a sensitive auxiliary switch in the pilot circuit of the particular driving motor of the part to be stopped at a selected point, and to mount the sensitive switch means, or coacting elements thereof, on one of the relatively movable members propelled by the motor. The complementary part for actuating the sensitive switch ismounted adjustably but normally in fixed spacial relation on another relatively movable part. In the present embodiment of this invention one of the relatively movable parts is an infeed clutch control shaft. When the propelled member is power shifted to the point where the sensitive switch is actuated by its complementary part, the pilot circuit to the motor control is opened and the driving motor stops and so long as the feed clutch stays coupled (in position effective for infeeding) the motor cannot again be started.

In accordance with this invention, one of the switch parts is mounted on an infeed clutch control member in such relation that the only way the motor may again be started (to take finishing cuts for example) is to actuate the control member to a position elfecting physical uncoupling of the motor from the propelled member. In the present embodiment, such disconnecting of the power automatically restores or resets the sensitive switch to a. circuit closed position whereupon the drive motor may be again started in the usual way. The restarting of the motor if effected in this manner does not, however, produce any further infeed movement of the propelled member, for the only elements then driven are those connected in branch trains that receive or are connected to the power source ahead of the clutch above mentioned. In machines of the hobbing character, it is often desirable to continue the cutter rotating and work rotating movements, without feed, so as to allow delicate or final finishing cuts to be taken. With the aid of this invention the operator may so operate the machine and continue cutter and work move-.-

ments without fear of inadvertent further infeed' The electrical mechanical interlocking herein set forth alsodefinitely guards against inadvertent infeed by rotating of the feed screw by hand after the main drive motor is automatically stopped, for the reason that so long as the power lnfeed clutch remains engaged and the reduction gearing between the motor-and feed screw remains effective, the propulsion of the stanchion by hand cannot be conveniently accomplished. Manual propulsion of the stanchion may, however, be easily eifected by first dise'ngiwin the power infeed clutch, and this extra operation is sufficient to remind the operator and so prevent accidental stanchion shifting unless such subsequent hand shifting is intended for a particular purpose or reason. On the other hand should the operator back the stanchion (and cutter) away from the work and restart the cutter drive, a recoupling of the power to the infeed mechanism automatically restores complementary parts of the precision stop mechanism to a position effective to discontinue the infeed movement at the previously set point.

Other objects and advantages will be in part indicated in the following description and in part rendered apparent therefrom in connection with the annexed drawings.

To enable others skilled in the art so 'fully to apprehend the underlying features hereof that they may embody the same in 'the various ways contemplated by this invention, drawings depicting a preferred typical construction have been annexed as a part of this disclosure and, in such drawings, like characters of reference denote corresponding parts throughout all the views, of which:

Figure 1 is aside elevation of a bobbing machine incorporating the precision stopping con trol of this invention.

Fig. 2 is a diagrammatic line diagram (in developed form) of the drive gearing and control of the machine illustrated in Fig. 1.

Fig. 3 is an enlarged view of a portion of the precision control means.

Figs. 4 and 5 are transverse sectional views taken along lines [-4 and 5-5 of Fig. 3.

Fig. 6 is a detail view of a portion of the infeed mechanism.

The drive mechanisms for the entire machine are illustrated schematically by Fig. 2 of the drawings. Power derived from the main drive motor l enters the machine through a chain drive mechanism II and main power clutch l2 and drives a transverse shaft IS. The shaft II extends across the machine and by means of pick-off speed change gears l4 and bevel gears l drives a horizontally extending splined shaft I. That portion of shaft l6 which extends to the left of bevel gears l5 drives the cutter I! through bevel gears it, splined vertical shaft l9, bevel gears and worm gearing 2i journaled in the tool slide A, bevel gears 22, gearing 2t and cutter mandrel 24. Thru this mechanism the worm cutter I1 is designed to be driven at a speed determined by the pick-off gears I I selected for the purpose.

To the right of bevel gears It, the cutter drive shaft l6 transmits power through index change speed gearing to a table drive shaft 20 that also extends along the base of the machine parallel to splined shaft II. A worm 21 secured to the either the tool slide A or its supporting stanchion B. The power flow is from bevel gears II,

:to shaft 3|, worm gearing 3|. to shaft 31, thence through changeable speed feed gearing It to a feed shaft 34, provided, however, that a main feed clutch 35 is engaged. Feed shaft It has a second clutch Ii thereon which, in this disclosureof the invention, is in the form of a sliding gear. when the clutch gear 36 is in the position illustrated in Figs. 2 and 6, the feed power is from gear 38 through idler gears 31, to a gear 38 splined to a rotatable screw shaft 39. The screw shaft 39 is rotatably ioumaled to the underside of the stanchion B and is threadably engaged by'a stationary nut 40. that is secured to the gear box. Through this infeed mechanism the stanchion and all parts carried thereby including the worm cutter Il may be fed by power toward the work blank. I

When the clutch gear 36 is shifted to the left (in Figs. 2 and 6) out of engagement with gears 31 and into engagement with a tool slide feed shaft ll axially aligned therewith, the feed power from the clutch is through bevel gears 42, vertical shaft .3, gears 44 to a tool slide feed screw 45. The screw 45 is secured at one end it to the vertically movable tool slide A and travels therewith. When the nut is in operation, the

slide and cutter is propelled up or down as when 40 the inner end of shaft 48 a reversing clutch mechanism is' provided to effect forward or reverse rotations at a rapid rate to the common feedshaft l4. Clutches 49 and 35 are interlocked, as will later be described to prevent incompatible operations. Hand feeding of the stanchion may be effected through a crank or hand wheel 50, shaft ii and bevel gears 62 journaled in the stanchion. One of the bevel gears 52 is keyed to the feed screw 39 and all move together as the stanchion is shifted. The power feed clutch I! should he disengaged before hand propulsion is attempted thereby to avoid back driving of normally non-reversible gearing.

Manual operation of the master clutch l2, feed clutch 35, and rapid traverse clutch 49, is effected by means'of levers a, b, 0, respectively, situated adjacent the operator's normal work station. Lever a, is'splined to a control shaft 5| that extends to the rear of the machine and operates a load-and-flre clutch shifting mechanism 52a operatively associated with the main drive clutch l2.

Lever b is splined to a shaft '53 that also extends to the rear of the machine and operates feed clutch 35 through gears 54 and shaft 55 and a similar load-and-fire clutch shifting mechanism 56 operatively associated with the feed clutch.

Lever c is splined to a third shaft 51 and operates the rapid traverse reversing clutch mechanism-l9 through gears 58 and shaft 59. As above mentioned, however, the rapid traverse and feed clutches are interlocked, and this interlocking is effected, in this instance, at the levers c and b. Lever c carries a segment I (see Fig- 4) provided menace with a single detent I! located in its periphery midway its ends. Lever b carries a rigid pawl 68 which. when lever c is in an intermediate or neutral position, may enter the detent in the segment secured to said lever c. When the pawl 63 is actuated to enter the detent, the feed clutch I! is engaged. Should the operator thereafter. operate the rapid traverse lever c from neutral in either direction, such movement automatically throws the pawl 63 out of the detent and disengages the slow feed clutch 35. On the other hand, should the rapid traverse clutch be already engaged, the detent 62 is out of phase with the pawl 63, and feed control lever b cannot be actuated to a feed clutch engaging position.

Safety rapid traverse power throw-out cams B4 and 65 are adjustably secured to the control shaft 51 to throw the rapid traverse clutch 49 to neutral at extremes of stanchion travel should the operator neglect to operate the lever c to neutral at or before the limit of travel is reached. Lugs 56 and 61 carried by the stanchion -B are arranged to engage and to rotate the cams 64 and 65 at the selected points.

- The foregoing briefly explains the operation and control. commonly provided on hobbing machines of the character to which this invention is applicable and with the exception of the power infeed mechanism, further description and explanation of the conventional machine may be had, if desired, by referring to the patents to W. F. Zimmermann Nos. 1,707,546 and 2,008,740.

The power infeed mechanism, as represented herein, is provided for the purpose of enabling an otherwise conventional gear hobber to be used for the production of worm gears by the infeed method of cutting. In such cutting, the hob I1 is brought to the center of the plane of the blank W to be finished as a worm gear and is thereafter fed slowly radially in that plane as the tooling progresses. Extreme precision in the radial in feed of the cutter is of paramount importance and unless great accuracy in the point of stopping is achieved, the worm gear being cut is finished either oversize or undersize. Heretofore, it has been the customary practice to manually stop the power infeed some distance short of the desired depth of cut, and then feed the rest of the way by hand by means of a hand feed mechanism such as 50, 5|, and 52. Operation of that character, however, slows production time materially and, in addition, leaves the hobbing cutter running an indefinite period of time on a fraction of the not fully finished teeth of the worm gear while other teeth of the same gear were not similarly treated. Such stopping and restarting of the infeed by manual operation, even neglecting errors due to the human element, causes a portion of the worm gear teeth to be finished in infinitesimally small steps, whereas, other teeth of the same gear (due to the gears slow rotation during the cutting and hence not necessarily affected throughout its periphery by the stopping of the infeed) are finished without steps. The above presupposes, however, that the operator infeeds by hand at precisely the same rate as the power infeed. If he does not, the non-uniformity in worm gear tooth profiles become still more exaggerated.

One of the objectives of this invention is to render worm gears cut by the infeed method free of error due to stopping the power infeed short of the desired depth and continuing by hand, and of the error due to over and under hand feedingof the cutter stanchion. To achieve the objective of the invention, it is proposed to stop the entire machine at the precise point of infeed desired, and to render it impossible to restart any portion thereof unless and until the power infeed clutch has been disengaged. Inadvertent restarting of the machine and the consequent damage to the gear blank is by this method of operation and control entirely eliminated.

Trip dogs and like mechanical contrivances for tripping out the power infeed clutch have not proved satisfactory, one reason being that such expedients were lacking in sensitivity and could not be relied upon to stop the power infeed at a precise point. Moreover, mechanical trip mech anisms are necessarily cumbersome and bulky by reason of the heavy duty performed in thedisengaging of a power clutch, and are not only diflicult to adapt to a machine of this character but also exceedingly difficult to manipulate and to set.

The disadvantages of the prior devices are overcome by the present invention in incorporating a highly sensitive limit switch in the pilot circuit of the magnetic starting switch of the main drive motor. The sensitive switch just mentioned is micro-sensitive in its operation, i. e., it'is designed and adapted to operate from a fully closed to opened position (or conversely) with a movement of its control button of only .001 part of an inch. Such sensitivity in action in combination with other features of the control herein explained, provides a means for stopping the entire machine within exceptionally fine or close limits, without fear of over-run or underrunning the required distance.

Stopping the main drive at a precise point in the travel of the movable member is not alone the solution to the problem encountered in the cutting of worm gears by the infeed method, for

a the power infeed should be rendered definitely the precise point of infeed required, and to hold that circuit open and the main switch ineffective until the power infeed clutch has been physically disengaged. When the latter event occurs, the sensitive switch is again automatically closed and the main drive may be restarted in the normal way.

Figs. 2 and 3 of the drawings illustrate a preferred arrangement for accomplishing these objectives, which includes mounting the sensitive switch 10 on the movable stanchion member B or on an extension thereof, and an adjustable switch actuating abutment H on the feed clutch control shaft 53. Normally the abutment H, which extends laterally to one side of the axis of the shaft 53, is in the path of movement of the limit switch 10 and will operate the latter to its open position when the cutter stanchion has been fed toward the gear center the requisite distance. Such opening of the sensitive switch stops the main drive, but as soon as the power infeed control is operated to disengage the infeed clutch 35, the abutment H is rotated out of ensagement with the switch II, and the pilot circuit of the magnetic starter is slain in condition to be energized by pressing the regular start button.

In Fig. 2, the mechanism MS represents the magnetic switch and includes main contactsj and operating coil I, and auxiliary contacts I forming part of a holding circuit. "The mechanism S represents a conventional start and stop control switch of the .push button type, and is connected in series with the sensitive switch 10.]

' I- from the start switch st leads to the solenoid coil 8', and line connects with the other side of the ausiliary'switch 9, v

To start the machine, the stanchion B and saunas because of the prior opening of the infeed clutch 3|. A subsequent attempt to re-engage the power infeed clutch causes abutment II, which has a cam like surface II, to 're-engase switch II and stopping the entire cutter infeed stopping may be elected by ren A line sensitive switch II will be normally some distance removed from the abutment H, andswitch II will be closed. Current, flows from L1 thru line I, switch 10, line 2, stop switch sp, line 3, start switch st, which is pressed closed by the operator, line I, coil 8, lines I, 6, and I toreturn line Ls. Coil I is thereby energized and closes main and auxiliary contacts 8 and 9, and the main drive motor I. is started. L

Closing of the auxiliary contacts 3, completes a holding circuit across the start switch st, through line 3,.switch 9, lines 6, 6, and 1 and it becomes unnecessary to hold switch st closed. Any time that the stop switch sp is actuated to its open position, the holding circuit is broken,

as well as the starting circuit, and coil 8 is denergized.

During a normal power infeed movement of the cutter stanchion, the sensitive switch ll gradually approaches the adjustable abutment H and when contact is made therewith, a further movement of .001 part of an inch or less, opens the switch and the pilot circuit of the magnetic starter MS is broken and the main switch U opens, stopping the power drive. By virtue of the 'many reducing gears forming part of the infeed drive from the motor, the drive motion from the motor It to the cutter stanchion is considerably reduced in speed, and the slight motor coast, following opening of the main switch, is barely perceptible on the distance the cutter stanchion moves.-;1

Such slight additional movement may be compensated for and extreme accuracy in the actual distance of infee'd' attained by first making a trial setting of the abutment II and then refining its adjustment, as will later be explained, to take care of motor coast."

The opening of switch ll renders the pilot circuit permanently ineffective, as will be clear from the diagrams, and the main drive may not,be

inadvertently restarted. To restart the main drive the power infeed clutch 35 must be dis- Il. The outer end of the stem 'Il carries a jam nut H". The adjustable dog |,l is keyed to the control shaft I! and'is adapted to be clamped in position thereon by a relatively light knurled screw H'. Major adjustments of the button Il may be effected by shifting the dog along the control shaft and exceedingly fine adjustments -thereafter effected by loosening the jam nut ll and unwinding the abutment H a fraction of a turn and again tightening the jam nut.

To facilitate the making of the flne adjustment of a definite amount the head end of the abutment 1| may be calibrated as at H, the graduations thereof being proportioned with relation to the pitch of the. thread on the stem 1| to give an adjustment in thousandths or fractions of thousands of an inch. A zero mark II is applied-to the arm of the dog 1| in cooperative relation with the graduations on the abutment.

Fig. 5 shows in full lines the relative angular positions of the switch III and its cooperating abutment II when the machine is set for power infeeding. The dotted line position of the dog 1l illustrates the position assumed thereby when the feed control lever b has been actuated to a position that disengages the power infeed clutch 35. It is only when the feed clutch has been disconnected that the microswitch i restored to its initial circuit closing position after being actuated by the abutment 1 I. In this way a definite safety against inadvertent further infeed is afforded.

As hereinabove explained the microswitch 10 is arranged to be thrown from its closed to its open position by a movement of approximately one-thousandth part of an inch of its control button 'llland thereafter to afford a slight overtravei without injury to the switch mechanism. However, should the actual overmovement of the stanchion, from one cause or another, exceed the overtravel provided in the switch, a positive" stop 10" is secured to the moving part, in this case the stanchion member B. The forward end of the stop 10' lies adjacent the switch button 10* in a position to be engaged by the abutment H before the limit of overtravel of the button 10 has been reached thereby definitely stopping further movement of the switch button and preventing damage to the switch itself. The purpose of the relatively light clamp screw II is to provide an additional safety in allowing the dog I la to slip longitudinally of the control shaft in cases of emergency.

The entire control is, however, relatively delicate in its construction and operation and lends itself eminently suitable for the making of fine precision adjustments of the character herein demanded.

Where necessary or advisable the microswitch I. may be of the water and 011 proof type available to protect same against the action of coolants and lubricants used about the machine.

From the foregoing description taken in conthe precision infeed control and mechanical interlock do not function as such when the machine disclosed is set up and used as a conventional gear hobber. In the latter event the clutch gear 88 (Figs. 2 and 6) is unlocked from the shaft 34 and shifted to the left and relocked to shaft 34 and also to shaft M. A pair of set screws 36 and trio of holes 36" equally spaced (illustrated more clearly in Fig. 6 are provided to effect the conversion. When the clutch gear 36 is shifted to a position illustrated in dotted lines in that ligure, it no longer drives gear units 31 and 38 and the infeed screw 39.

Without further analysis, the foregoing will so fully reveal the gist of this invention that others can, by applying current knowledge, readily adapt it for various utilizations by retaining one or more of the features that, from the standpoint of the prior art, fairly constitute essential characteristics of either the generic or specific aspects of this invention and, therefore, such adaptations should be, and are intended to be, comprehended within the meaning and range of equivalency of the following claims:

Having thus revealed this invention, I claim as new and desire to secure the following combinations and elements, or equivalents thereof, by Letters Patent of the United States:

1. A machine tool combining a main drive motor, a member to be shifted thereby, power connections between said motor and member to efi'ect such shifting, said connections including a clutch adapted when actuated to connect and disconnect the drive selectively, means for operating said clutch including a non-shiftable control element, a control for the drive motor including a part mounted upon said shiftable member and a complementary actuating part mounted upon said non-shiftable control element in relative positions to engage one another when the shiftable member reaches a preselected position in its travel, the engagement of said complementary parts effecting operation of the motor control and stopping the motor; and means for restarting said motor in the same direction subsequent to the engagement of said complementary parts without disturbing the position of the said shiftable member.

2. In a machine tool the combination of a tool carrying member arranged to be power fed toward the workpiece, a main drive motor, a magnetic starting switch for the motor, a transmission between the motor and said member including a clutch, a normally closed microswitch operatively connected with said magnetic starting switch and adapted when actuated to a circuit breaking position to open said magnetic switch and stop motor movement, a switch actuating abutment positioned and arranged to actuate said microswitch when the tool carrying member has been power fed a predetermined distance toward the work, and means interlocking said actuating abutment with said clutch to necessitate opening of the clutch prior to a restarting of said motor in the same direction after the tool carrying member has been power fed toward the work said predetermined distance.

3. A machine for producing gears by the infeed method of cutting comprising a shiftable hob carrier, a rotatable hob journaled therein, power means for rotating the hob and for shifting the carrier including a main drive motor and a clutch in the drive to the carrier adapted when acmated to connect or disconnect the motor from nection with the drawings, it will be apparent that the carrier, a switch for starting and stopping said motor, cooperative means carried in part by said shiftable carrier and in part by a nonshifting part of the machine for eilecting'actuation 01' said switch to an open position when the hob carrier has been power fed to a predetermined position thereby to stop said motor, hob, and further power feed, means for actuating said clutch as to disconnect the motor from the carrier, a connection between said clutch actuating means and said cooperative means automatically operative to render said cooperative means ineffective on said switch when the motor is disconnected from the carrier, and additional means operative thereafter to effect a closing of said switch to thereby effect motor operation solely for hob rotating.

4. The combination set forth in claim 3 characterized by the provision of means for efiecting minute precision adjustments in the point or stopping of the hob carrier and for compensating for motor coast following the opening of said switch.

5. A hobbing machine combining a rotatable cutter, a shiftable stanchion, a motor and connections for feeding said stanchion by power toward the workpiece and connections for rotating said cutter, a clutch and control means therefore in the connections for feeding the stanchion, a main control means for starting and stopping the motor, auxiliary control means for actuating said main control means to effect stopping of said motor, means adjustably mounting said auxiliary control means to the machine normally in a position to be actuated when the stanchion has been power fed to a preselected position, said means for mounting the auxiliary control including a part interlocked with said clutch control means for maintaining said relative positions of 40 the parts constant until said clutch control is actuated to disconnect the stanchion from the motor, means thereupon operative to restart the motor in the same direction to effect further power rotation of the cutter without effecting further Dower feed of the stanchion.

6. A precision control for stopping movement of a propelled member of an electric motor driven machine combining a main switch for starting and stopping motor operation, a control circuit for the main switch including manual start and stop'switches and a micro-sensitive switch in series with the said manual switches, a transmission for transmitting motive power from the motor to the member of the machine to be propelled including a clutch mechanism for rendering the power drive selectively eilective and ineffective; control means for said clutch; a switch actuating element, and means mounting said micro-sensitive switch on the said propelled member and said actuating element on said clutch control means in positions to coact with one another and open said control circuit when said clutch is engaged and when the member propelled by the motor reaches a given position, and means automatically restoring said micro-sensitive switch to its circuit closing position upon disengaging said clutch whereby said motor may again be started by operating said start switch but without effect upon said propelled member.

7. In a machine tool the combination of a shiftable member, a control for stopping the movement of the member at a precise point in the travel thereof, including an electric motor, a main switch for starting and stopping motor operation, a control circuit for the main switch into open the control circuit to the main switch and stop the motor when the device carried by the propelled member reaches the device mounted on the clutch control means; and means for disengaging said devices to restore said control cir-- cult to operable condition without readiusting the position or the propelled member.

8. A machine tool combining a shiitable member; power means and connections for shifting said member, said connections including a device for physically uncoupling the shiitable member from the power means; means for rendering said power means operative, additional means for rendering the power means inoperative at a given point in the travel 0! said shiitable member; and means interlocking said last named means with the uncoupling device in the said connections for insuring the continuing of said power means in a state of inoperativeness until said device is actuated to a position to uncouple the drive connection between the said power means and the shiftable member.

9. A machine tool combining a shiitable member; power means and connections for shifting said member, said connections including a clutch mechanism; control means for the power means including a master switch, an auxiliary sensitive switch for controlling the effective operation of the master switch, means for actuating said auxiliary sensitive switch at a given point in the travel of said shiftable member whereby to eilect actuation of the master switch to a position stopping the power means, and means interlocking said last named means with said clutch mechanism for rendering said master switch inoperative to restart the power means until said clutch is actuated to a position to disconnect the shiitable member therefrom.

10. The combination set forth in claim 9 characterized by the embodiment of means for protecting the said auxiliary sensitive switch in the event of undue overrun or the shiftable member.

11. Control means for a machine tool embodying a movable part; a source or power including a power transmission for propelling said part; a power clutch in said transmission adapted when actuated selectively to engage and disengage said source of power from said movable part; a control means for said clutch comprising a member normally stationary relative to the movement or said movable part; control means for said power source comprising two normally aligned cooperating elements one of which is mounted upon said asvasss movable part and the other or which is mounted upon said clutch control member, said last named means being constructed and arranged when actuated to stop the operation of said power source: and means for moving one or said cooperating elements out of said aligned position and opening said power clutch thereby to render said source of power operable but ineiiective to propel said movable part.

12. Control means for a machine tool embodying a shiitable part; a source of power including power transmitting elements for propelling said part and a power clutch adapted when actuated selectively to engage and disengage said source or power from said shiitsble part: control means for said clutch comprising a member normally stationary relative to the movements of said shiitable part; control means for said power source comprising two cooperating elements one of which is mounted upon said shiitable part and the other of which is mounted upon said relatively stationary clutch control member. said elements being normally operative when juxtaposed to control the further operation of said power source when the shiitable member reaches a preselected position; and a handle means for moving one of said cooperating elements out of said Juxtaposed position to thereby restore said control means for the power source to operative condition and simultaneously to open said power clutch.

13. Control means for a machine tool power trion combining a source or power: a transmission connected with said source of power and arranged to propel two elements of the machine; a clutch in said transmission operable to connect and disconnect said source of power from one or the said two elements of the machine; control means for said source of power; control means for said clutch; and means interconnecting said two control means selectively operative to render said source of power operable but ineflective to drive the said one element oi the machine situate on the side of said clutch away from said source of power.

14. Control means for a machine tool power transmission combining a source of power; a first machine element adapted to be actuated by said source, and a second machine element adapted to be actuated by said source, and a third machine element adapted to be actuated by said source. power transmission means connected between said source and each of said elements including a clutch in the transmission to but one or said elements operable to connect and disconnect the said source of power therefrom; control means for said source of power; control means ior said clutch: and means interconnecting said two control means operable to condition said source or power for operation to effect actuation of two of said machine elements and automatically rendering said power source ineflective to actuate the said one of said elements on the machine side of said clutch.

GRANGER DAVENPORT.

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