US2345318A

US2345318A - Radial precision tapping machine

Info

Publication number: US2345318A
Application number: US461565A
Authority: US
Inventors: Harding F Bakewell
Original assignee: Individual
Current assignee: Individual
Priority date: 1942-10-10
Filing date: 1942-10-10
Publication date: 1944-03-28
Anticipated expiration: 1961-03-28

Description

March 1944- H. F. BAKEWELL RADIAL PRECISION TAPPING MACHINE Filed Oct. 10', 1942 4 Shee.ts-Sheet 1 .HIED/(VG f BAKEWELL,

INVENTOR.

BY W W ATTORNEY.

March 1944- H. F. BAKEWELL I RADIAL PRECISION TAPPING MACHINE Filed Oct. 10, 1942 4 Sheets-Sheet 2 .FAew/ve KBAKEWEL 1.,

INVENTOR.

BY A;

ATTORNEY.

March 28, 1944. BAKEWELL 2,345,318

RADIAL PRECISION TAPPING MACHINE Filed Oct. 10, 1942 4 Sheets-Sheet s JZflED/NG I. BAKEWE'LL,

' INVENTOK ATTORNEY.

March '28, 1944.

H. F. BAKEWELL RADIAL PRECISION TAPPING MACHINE Filed 001;. 10, 1942 4 Sheets-Sheet 4 .Hheows E 3A Mews/.1. Y INVENTOR.

ATTORNEY.

Patented Mar. 28, 1944 UNITED STATES PATENT OFFICE RADIAL PRECISION TAPPIN G ,MACHI NE Harding F. Bakewell, San Marino, Calif. Application OctoberlO, 1942, Serial No. 461,565

Claims.

conditions such that thework to be operated upon.

may be moved about relativeto the power tool which is employed to effect the desired operation, which materially restricts the utility of i the machine. The device of the present invention is of the so-called radial type, provided with a relatively large work-receiving bed or table portion, and in which the tool member is suspended above such table portion in such manner as to be capable of movement over substantially; the full area of such table portion so that the desired operation may be carried out upon substantially any portion of the work which is mounted on such table. It is a common, and generally preferable practice, in such radial type machine tool, to mount the driving means (such as, an electric motor or the like) inrelatively fixed relation to the tool which isto be used in performing the desired operation, thereby rendering the drive mechanism of maximum simplicity.

In view of the above, therefore, one of the particular objects of this invention is to provide a radial, typeof precision machine tool provided with a work-supportingtable member, and an overhead tool structure adapted for pivotal movement over a substantial proportion of the area of suchwork-supporting member.

A further object of the invention is to provide a device ofthecharacter described, in which the Work-performing member is mounted for. pivotal movement with respect to a relatively fixed support arm, and is provided with a drivemeans adapted to eifect the desired operation of the work-performing member, together with means for interlocking the pivotally movable part whenever such drive means is placed in operation, whereby the torque effect or the starting reaction of such drive means is prevented from reacting upon the. work-performing member.

A further object of-the invention is to provide a precision machine tool having a work-supporting table member, and an overheadtool structure mountedon an improved form of hydraulic ele-. vatormeans.

A further object of the invention is to provide a radial type of precision machine tool having a.

work-supporting table .member and anv overhead tool structure adapted; for pivotal movement over a substantial proportion ofthearea ofsuch worksupporting member, in which the overhead. tool structure is comprised of; a plurality of support portions which are pivotally interconnected and the structureis provided withan improved formof hydraulic elevator means, the hydraulic elevator means, and the tool portions defining the axes of pivotal; movement of -th e, overhead tool structure being of tubular construction whereby electrical conduit means may be extended through the elevator constructionand. within the tubular members defining the pivotal axes from,

the'base portion of the device adjacentthe worksupporting table member to the machine toolcarried by the overhead tool stru .cture.

The above and other objects of the invention will be apparent from or will be brought out specifically in connection with the ensuing description of a preferred embodiment of the invention illustrated in the accompanying drawings, in which:

Fig. 1 is a partly broken away end elevation of a radial tapping machine according to this invention;

Fig. 2 is a plan view thereof;

Fig. 3 is a sectional detail of the device, a taken on line 33 in Fig. 2;

Fig. 4 is a transverse section taken on line 4-4 in Fig. 3;

Fig. 5 is a further section taken online 55 in Fig. 4;

Fig. 6 is a. vertical section taken along line 6-,6 in Fig. 2, on somewhat enlarged scale;

Fig. '7 is a transverse detail thereof taken on line 'I! in Fig. 6; and

Fig. 8 is a schematic wiring diagram which may be employed for operation of the above illustrated machine tool, utilizing the features of thisv invention.

Referring, to the drawings, Figs. 1, 2 and 6 in particular, the device is shown as provided with a base portion I having a horizontal work-bed 2 and an. elevated articulated tool-carrying structure 3 comprising a support arm 4 constituting a mainframe member, a pivot arm 5 pivotally mounted to the support arm 4 for rotation about a vertical axis 6 and constituting a secondary frame member, and a combined spindle-frame andmotor-carrying member 1 pivotally mounted at the forward end of the arm 5 for rotation about a vertical axis indicated at 8; The elevated structure 3 is provided with a downwardly extending tubular pisto member-9 slidablymounted within a cylinder member 10 secured to the base I in any suitable manner as through the agency of a flanged portion Illa and screws lob. Interiorly of the tubular piston member 9 I provide a tubular internal cylinder wall made integral with the outer cylinder H! as by welding to a cross plate member II. A suitable cup member, of annular shape, is provided as at |3 for the lower end of the tubular piston member 9, and fluid is supplied to or withdrawn from the cylinder space l5 through a'line l6 communicating with a suitable fluid pressure device, suchas a gear pump or the like, driven by an electric motor under the control of the operator.

be of any of the types which are well known in the art, and is not illustrated herein. It will be appreciated that the tubular. piston member. 9 may be freely rotated within the outer cylinder HI, so as to change support arm 4, and I preferably provide means for locking the assembly in' any desired angular position, as by s'plitti'ng the upper end ll of the outer cylinder H) as at 13,- and extending a threaded bolt type of lock therethrough, as indicated at Hi. The inner-cylinder defined'by the wall member will-define apassage 26a with the tubular piston member 9, through which passage {an electrical conduit 20bmay' extend for supply of currentto the tooldriving' means.

As shown more particularly in Fig. 6, the arm member 5 may be" pivotally' mounted upon the relatively fixed support arrn or mainframe member 4 through the agency of forwardly extending

upperand lowerarm portions

4a and 4b through which a shaft member-2|- rigidly attached to the arm portion-5 is extended. Suitable upper and lower bearings are provided as at 22 and 23, and the shaft member 2| being secured in place through the agency of a'lock nut 24 provided with-a lock screw 25. 1

The spindle-frame and motor-carrying member is similarly mounted on the forward end of the support arm orsecondary frame portion 5 through the agency of a shaft member 3| mounted within upper and lower projecting arm portions 511 and 5b of-the member 5 through the agency of upper and-lower bearings 32 and 33 and lock nut 34, which is held in position through the agency of a lock screw 35. The shaft members 2| and 3| are preferably of tubular construction whereby the conduit 261) may be carried through the device up to the position of the drive motor, for example, to eliminate any tendency for the conduit to become twisted or entangled upon pivotal movement of the articulated tool-carrying structure.

The fluid pressure supply means for the structure may the angular position of the In order to provide the desired breaking effect 7 to render the

members

4, 5 and substantially rigid with respect to one another when the drive motor 36 is turned on or reversed in direction, I preferably provide a clamp member 4| mounted on the member Sand adapted to immobilize and interlock the members 4, Sand 1 against pivotal movement about the

axes

6 and 8. V For this purpose the clamp or braking member 4| is providedwith a shoe portion 42 concentric with the shaft 2| and adapted to bear against the lower face of the arm'portion 4b.of the support. arm 4, as at 43. Thebuter end: of the arm 5 carries the vrotatably disposed shaftv 3|, and the brake member 4| is adapted to engage'the shaft 3| to immobilize the member 1.. For thisipurposei I provide a circular sleeve member 44 at the lower end of the shaft 3| whichiisconstrained to rotate with such shaft, the memberi44beingprovided 54 of a solenoid 55.

connected to links member 4| to the position The solenoid 55 may be secured to the arm 5 as at its lower end with a conical face 45 adapted to be engaged by a coactingly shaped seat 46 formed in the outer end of the brake member 4|. The brake member 4|, in the braking action, is required to be moved upwardly into engagement with the area 43 and the face 45 at the inner and outer ends, of the support arm 5, respectively, and this movement is conveniently effected through the agency of a pull rod ,1 slidably mounted as at 48 on the arm 5, the pul1 rod 41 being connected through

links

43 and 5| to a pull link 53 connected to the movable armature The link 5| which is pivotally 49 and 53 is conveniently mounted for pivotal movement as at 52, whereby upon upward movement of the armature 54 to the position shown, the counterclockwise rotation of the link 5| will lift the link 49 and the thereto-connected pull rod 41, lifting the braking illustrated in Fig. 6.

at 56 and 51. e

In Figs. 3, 4 and 5 I have illustrated a control mechanism which may be employed to control the operation of the solenoid 55 with respect to the operation of the motor 36. This control mechanism is mounted at one side of the spindleframe 6| carrying a spindle 62 provided with a pulley 63 which may be belt-connected to a pulley 64 mounted on the drive shaft of the motor 36.

A suitable frictionclutch means is indicated at 65 which acts as an'overlo'ad release device in the event that the tool carried by the spindle 62 is overloaded for some reason, thereby preventing damage to the tool or the work;

The spindle-frame 6| is provided with a conventional rack-and-pinion elevating and de pressing device, the pinion shaft 66 therefor terminating in a hand wheel 61. mechanism for operating the solenoid 55 comprises a plurality of switches which are in part under the control of 66. Referring to Fig. 3 a thumb switch 63 is'provided in convenient position for access by the operator for controlling the initial operation of the electric motor. Associated with the switch 68 are three switch members 69, H, and 12, which may be of the so-called micro-switc type, mounted on a housing portion 13 forming a part of the spindle frame 6|. As shown in Fig. 3, the switch 69 will be employed as a solenoid-actuating switch, the switch II will be employed as a reversing switch for the motor 36, and the switch 12 will be employed as a disconnecting or limit switch which will interrupt the operation of the motor 36 when the spindle has been returned to its upper or inoperative position. Actuating means for securing operation of the switches 69, II, and 12 are provided on the pinion shaft 66, the actuating member for the switches 69 and II being indicated at 14, and the actuating member for the switch 12 being indicated at 15. The

solenoid and reverse control mechanism for the motor 36 is adapted to energize the motor 36 in its normal or cutting direction at the start of an operation, after which the operation of the tool carried by the spindle 62 is carried to a complete cycle without further attention on the part of the operator. As described in connection with my above-mentioned patents, when the drive motor 36 is energized a clamp member 16 is closed upon a lead screw 11 which carries a tap memher or the like not shown. The lead screw 11 has a lead threadupon it which corresponds to the The control the operator and in part directly actuated by rotation of the pinion shaft 2, 345,318.: thread oftheztap withywhichit: is associated, and

before, the motor 36 is energized and released'as; soon as the motor is brought up to speed. Simi larly, when the motor'is reversed-at the lowermost position of the tap, the stopping of themotor andre-startinginthe reverse direction will tend to produce a swinging of the support arm assembly; and the magnetic brake is, againactuated to render the. structure rigid. at this moment.

Referring. to Fig. 3, when the shaft 66 isrotated in a-clockwise direction .the actuating member 75 will fall off the roller 12a of the switch 12.

and the actuating. member 14- will approach the position of the roller. 69a which is mountedon the actuating arm of theswitch B9. Asingle roller 69a maybe employed to actuate boththe switches wand 7|, the switch. 69 being adapted to operate first, followedby the operation of the switch H. spaced angularly in such a position that it will operate the switch fifiwhen the tap is about one threadfromthe bottom of itslowermost position, and the reversing switch 7.! ,willthenbe actuated immediately thereafter. The immediate. reversal of. thernotor 36 thenwill rotatetheshaftfifi. in. a counter-clockwise position, backing thev actuating member Hi. off. the roller 6.9a, de-actuating the switchfifl; and when the spindle 6.2 has been raised to it uppermost, positio.n,,the actuating member 15 will engage the roller 12a and actuate the switch 12, stopping. the motor 3.6; The switch 2 thus constitutes a limit switch and is for that reason marked L on the drawings. Similarly, the switch 59 is the braking switchand is markedB and the switch H isthe reversing switch, and is marked R.

In Figs. 4 and 5 I have illustrated theconstruction of a control mechanism which can be employed to position the actuating members 14' and 15 in the correct angular relation to the rollers 69a and 72a for a given operationalproblem, and referring thereto the shaft 66- and'the handwheel 6'! shown as provided with a sleeve portion 8| keyed or otherwise secured to the shaft 66, the sleeve 81 being provided with a shoulder portion at its inner end at 82' andbeing threaded at its outer end at 83; The actuating .member 14 is mountedon pin. 84:; carried by a. disc- 8.5.2

rotatably mounted on the sleeve 8i and: adapted to bear'against the shoulder 82: The. actuating member 15 is mounted on a pin86 which;is carried by a disc 81. outwardly of the disc 85 I provide a locking sleeve 88 which is rotatably mounted on the sleeve. ill and. is keyed to the disc 85 throughthe agency of a, pin; or the like 89v extending. into an opening 9!. of the disc 85.

The locking sleeve 88 comprisesa hub portion. 884;. and a flange portion 651b, and thedisc-81 isprovided with ahub portion 81a bearing on the exterior of. the hub portion 88a of the locking sleeve 88. The axiallength of the hubportion 87a is suchthat when the flange portion88b ofthe locking sleeve 83. is forcedinwardly, thehub 81a. will be ecurely gripped betweenthe inner face of the flange 88b, and the outer face of,-.thev

The actuating member. 14 will be.

-mountedon the spindle-frame 6i.

di Q.:8.5.-'. The;lockine-slceye 88:isr orcedi wars ly" through; the agency of alock collar -92;threadedly mountedgonthe sleeve 8-1, and proyidedwith an; operating-lever or handle 93 It. will be apparent that :if the lock collar 92-is backed off, the threaded portion 83;. the;

parts

85, 81a and 8 8;w'ill'be fric-. tionally disengaged, whereupon, the disc or 81 may be rotated manually to any desired set.- ting, after whichthe lock collar-His tightenedand the partsare retainedin their established position: The disc is preferably provided with outer ylindrical surface portion -94 which may conveniently he graduated in inches, centimeters or the like, and a suitable marker or index mcmher (not shown) may be provided on the spindle frame 6|. Similarly the outer face of the disc B'lmay, be provided'with a scale, such asindicated at 95 in Fig. 5, and a coacting pointer may be provided'as at 96 on the;locking sleeve 88, which is-keyed to the disc 85. In adjusting thev device the tap may be run down'manually until'it is.

just-ready toenter the hole to be tapped, at which time thedisc B'lmay be set'to zero on the first mentioned pointer or index, member which is Assuming that the tap i to be run down into the hole a distance of 27/32", the pointer 96 will be set at the" position indicated in Fig; 5. The locking collar; 52: is then screwed up to establish discs. 8'! and85. in close frictional engagement with one another, and the control device is adapted, when set asabove, to actuate the switch B just beforereaching the 27/32." position, followedv by; an actuation of the switch R, followedby ade-actuationaof; the switch B. When the-spindle-is raised upto --the zero position correspondingto the top of the, hole, the switch L will be actuated and the-motor 35 deenergized;

Lhave-illustrated in Fig. 8; a; suitable electrical circuit whichmay be, employed for'the control of, the electrical motor circuit and the solenoid circuit. The switchesfiS, H and 12 are indicatedat B, R andL respectively; and the solenoid 5.5; is shownschematically. As above described, the

a motor 36 is ofaa reversing type, and is preferably 35 is illustrated. as being the three phase type,

provided with separate windings for the two peedsandtwo directionsof operation. Separate relays are provided for actuating the'motor in its two directions of operation, as at |0l and I02, the relay I01 being adapted to connect themotor'for downward movement of the spindle 52' and the relay Ill-2 being adaptedto' energize the motor for upward or return movement thereof.

A third relay I03 is provided for control of the operation of the solenoid 55.. The relays l0| and H12 are adapted to supply current to the respective fields of the motor 36. when they are energized, and the relay I03 is adaptedto supply current to the solenoid 55. when it is; deenergized; The main three-phase power supply lines are indicated at I04. The relay [0i may'bea fourpole single-throw relay, three poles, of which are connected to the, respective leads of the; p0wer supply lines I04 and the fourth pole and armar ,ture member of which isemployed to mai t i 4, the relay in energized condition after its closing motion has been instituted through the agency of the thumb or finger switch 68. The finger switch 68 is a two-pole double-throw switch providing a normally closed circuit defined by the contacts I04 and I and a normally open circuit defined by the contacts I06 and I01. A transformer I08 is provided for the supply of local operating current for the relays IOI, I02 and I03, and current is normally supplied to the coil of relay I03 from one side of this transformer through the contacts I04 and the switch B thence back through line I09 to the opposite side of the transformer I08. In this normally energized condition of relay I03 the contacts thereof are held in open position, interrupting the current supply circuit for the solenoid 55. With the switch 68 in the position illustrated in the drawings, which would be the normal or rest position of the switch, the relays IM and I02 are deenergized, and the relay I03 is energized. In this condition the motor 36 is deenergized, and the circuit to the solenoid 55 is held open. When the operator pushes in the thumb button of the switch 68 the circuit between I04 and I05 is broken, deenergizing the relay I03 and allowing the associated contacts to close, closing the circuit to the solenoid 55. In this condition the magnetic brake 4| is brought securely up against the support arm 4 and the arm 5, locking the radial overhead arm assembly securely in the position which has been established by the operator. When the operator presses the thumb button of the switch 68, moving such switch to its inner position, shorting the contacts I06 and I01, current is supplied from the one side of the transformer I 08 across the contacts I 06 and I01 thence through line IIO, through the coil of the relay IOI thence back through line III to armature I I2 of the relay I02 thence through contact II3 to the other side of the transformer I08. Thecircuit for the coil of the relay IN is thus closed, actuating this relay, energizing the motor 36 in one direction of rotation, and supplying current directly from the one side of the transformer I08 to the armature II4 from line II5 to the coil of the relay IOI thence through line III through armature IIZ, contact II3 to the other side of transformer I08. This serves'to hold the relay IOI in actuated or energized condition, maintaining the current supply to the motor 36. Upon release of the switch 68 by the operator, the circuit for the coil of the relay I03 is again energized, and the solenoid 55 is deenergized, releasing the clamp member 4|. In this condition the tool-supporting assembly may float as the tap or other tool progresses downwardly into the work.

Operation of the device and the accompanying clockwise rotation of the shaft 66 as shown in Fig. 3 resulting from downward travel of the spindle 62 will bring the actuating member I4 upwardly into engagement with the roller 69a, as above described, when the tap is about one thread from the bottom of the hole. Actuation of the roller 69a will cause the circuit for the relay I03 to be broken at the switch B, the switch B being a normally closed switch. The deenergization of the coil of the relay I03 thus causes a reenergization of the solenoid 55, in the same manner as described in connection with the first part of the operation of the switch 68, and the magnetic brake M is clamped into position. As the motor 36 continues to rotate, rotating the actuating member 14 further ahead in a clock- I05, thence through wise direction, the roller 69a will be pressed outwardly a sufficient distance to cause actuation of the switch 'II (indicated at R). The switch R is a normally open switch, and the actuation thereof will cause a completion of the'circuit to the coil of relay I02 in the following manner: connection from the one side of the transformer I08 is made through the switch L (which is a normally closed switch) thence through line I I6 to one side of the coil of the relay I02 thence to the switch R through line II'I thence to line I09 through lead H8 and through to the other side of the transformer I08. Upon operation of the relay I02 the circuit for is immediately broken by separation of the armature II2 from the contact H3. The deenergization of the relay IOI, breaking the circuit to the motor 36 precedes slightly the closing of the three-pole contact group of the relay I02 which supplies current from the leads I04 to the other field coil of the motor 36. The motor is thus immediately reversed upon completion of the opera tion of the relay I02, and the return circuit for the coil of the relay I02 which had gone through. the switch R. thence to the other side of the transformer I08 is now established directly through branch line II9, armature I20 and contact I2I. As soon as the actuating member It is backed away from the roller 69a a sufficient distance to close the switch B, the circuit for the coil of the relay I03 is reestablished, opening the contact in the power circuit for the solenoid 55 thus releasing the magnetic brake 4|. As the shaft 86 is rotated counter-clockwise, bringing the actuating member I5 toward the roller 12a of the switch L, the tap is backed out of the threaded hole which was previously formed. When the actuating member I5 actuates the switch I2, which is a normally closed switch, the current supply through switch L and line IIB to. the coil of the relay I02 is interrupted, thus deenergizing the coil I02 and opening the circuit to the motor 36.

The above specific example of a wiring diagram for use in connection with the construction of the present invention will be appreciated as being given only by way of example. Other useful circuits will be visualized by one skilled in the art, and I do not choose to be limited to the specific arrangement of electrical parts and circuits which I have illustrated. Similarly the control mechanism illustrated in Figs. 3, 4 and 5 will not be considered as peculiar to the apparatus of this invention, but rather as illustrative of a suitable control means which is useful in connection therewith. For the above and other reasons, therefore, I do not choose to be limited to the specific embodiments of the invention herein delineated and described, but rather to the scope of the subjoined claims.

Iclaim:

l. A radial type machine tool which comprises: a base portion provided with a work-supporting table member; an articulated overhead toolcarrying structure pivotally mounted on said base portion and provided with a pivotally mounted outer frame portion carrying a tool member and rotative drive means therefor arranged in such relation to the axes of pivotal movement of said articulated structure as to inherently cause an inertia reaction tending to produce movement of said articulated structure and displacement of said tool member upon initiation of the rotation of said drive means, said rotative drive means the coil of relay I0l comprising an electric motor; brake means adapted to engage the articulated portions of said overhead tool-carrying structure including said outer frame portionand renderthe isame rigid at the position of the axes'of pivotal move-- ment; brake actuating means operatively connected to said brake means and control means adapted' to cause operation of said actuating means to bring said brake means into such engagement immediately prior to the energization of said electric motor.

2. Aradial type machine tool which comprises: a base portion providedwith a work-supporting table member; an articulated overhead toolcarrying structure mounted on said base portion and comprising a main frame member, a secondary frame member pivotally mounted on said main frame member for movement about one axis, and an outer frame portion pivotally mounted on said secondary frame member for movement about another axis and carrying a'tool member and rotative drive means therefor arranged in such relation to said axes as to inherently cause an inertia reaction tending to produce movement of said articulated structure and displacement of said tool member upon initiation of the rotation of said drive means; brake means mounted on said secondary frame member and movable into and out of position to engage said main frame member and said outer frame portion to thereby rigidly interlock said articulated structure against pivotal movement at both of said axes; and actuating means operable to move said brake means to said position.

3. A radial type machine tool as set forth in claim 2, said rotative drive means comprising an electric motor, and said tool comprising in addition control means adapted .to cause operation of said actuating means immediately prior to the energization of said electric motor.

4. In a radial type power tool provided with a relatively fixed main frame member, a relatively movable secondary frame member pivotally mounted on said main frame member, and a frame portion pivotally mounted on said secondary frame member, said frame portion carrying a tool member and rotative drive means therefor arranged in such relation to the axes of pivotal movement of said tool structure as to inherently cause an inertia reaction tending to produce a displacement of said tool member upon initiation of the rotation of said drive means, a brake means adapted to render such pivotal mounting rigid, which comprises: a clamp member mounted on said secondary frame member and adapted for movement between two positions with respect thereto, said clamp member being provided with portions adapted to engage said main frame member and said frame portion when located in one of said positions with respect to said secondary frame member, and to move out of engagement with said main frame member and said frame portion when moved toward the other of said positions.

5. A radial type machine tool which comprises: a base portion provided with a work-supporting table member; means defining a hydraulic elevator secured to said base portion and provided with a movable piston member; a support arm secured to'said piston member; a pivot arm pivotally mounted to said support arm for rotation about a vertical axis; a frame member carrying a tool member and rotative drive means therefor, said frame member being pivotally mounted on said pivot arm for rotation about asecond vertical axis; a clamp member secured to .said ipivotiarm and adapted for movement between two positions with respect thereto, said clamp member being provided with portions adapted to frictionally engage said supportarm and said frame member when in one of said positions with respect to said pivot arm and to move out of engagement with said support arm and said frame member when moved out of said one position toward the other I of said positionaand actuating means adapted said actuating means immediately-prior-to the energization of said electric motor.

'7. The construction set forth in .claim '5, said hydraulic elevator, being defined by two concentric tubular members defining an annular hydraulic cylinder, and said piston member being of tubular shape and slidably disposed within said cylinder, the inner one of said two concentric tubular members defining with said tubular piston member an elongated passage extending from within said base member toa position exteriorly 'of said piston member.

- 8. The construction set forth in claim 15, .said

hydraulic elevator being defined by two concentric tubular members defining an annular ,hy--

draulic cylinder, said piston member being of tubular shape and slidably disposed within said cylinder, the inner one of said two concentric tubular members defining With said tubular piston member an elongated passage extending from 1 within saidbase member-to a positionexteriorly of said piston member, said rotative ,drive means comprising an electric motor, and saidiconstruction comprising in addition conductor means providing current supply for said electric motor extending through said elongated passage from within said base member to said electric motor means.

9. The construction set forth in claim 5, said vertical axes being defined by tubular members and said hydraulic elevator being defined by two concentric tubular members defining an annular hydraulic cylinder, and said piston member being of tubular shape and slidably disposed within said cylinder, the inner one of said two concentric tubular members defining with said tubular piston member an elongated passage extending from within said base member to a position exteriorly of said piston member.

10. The construction set forth in claim 5, said pivot arm being mounted on said support arm by means of a tubular shaft and said frame member being mounted on said pivot arm by means of a second tubular shaft, said vertical axes being defined by said tubular shafts, and said hydraulic elevator being defined by two concentric tubular members defining an annular hydraulic cylinder, and said piston member being of tubular shape and slidably disposed within said cylinder, the inner one of said two concentric tubular members defining with said tubular piston member an elongated passage extending from within said base member to a position exteriorly of said piston member, and said rotative drive means comprising an electric motor, the construction further comprising conductor means defining current supply means for said electric motor extending from within said base member through said elonf gated passage thence downwardly through the .tubular member defining said first-named vertical axis thence upwardly through the tubular member defining said second-named tubular axis.

11. A radial type precision machine tool which comprises: a base member provided with a worksupporting table portion; two concentric tubular members secured to said base member and-defining an annular hydraulic cylinder; a tubular piston member slidably disposed within Said cylinder; an overhead tool structure securedto said piston member and provided with a tool member and rotative drive means therefor; and fluid pressure supply means associated with said cylinder.

12... A construction set forth in claim 11, said rotative drive means comprising an electric motor,

and the inner one of said two concentric tubular members defining with said tubular piston member an elongated passage: extending fromuwithin saidbase member to a positionexteriorly of said piston member, and comprising in addition conductor means extending within said passage from within saidba'se member to said electric motor means.

13. A radial type power tool which comprises:

; a relatively fixed main frame member; a relatively gagement upon energization; first switch means associated with said drive means and adapted to cause energization thereof, and second switch means in cooperative relation to said first switch means and adapted to cause energization of said actuating means prior to the energization of said rotative drive means resulting, from operation of means mounted on said frame portion; a clamp member movably mounted on said secondary frame member in position to engage said'main frame member and said frame portion to interlock the same against relative movement 'e1ectroresponsive actuating means adapted to'eiiect movement of said clamp member into engagin position upon energization; cooperating switch means controlling the energization of said electrio motor means and said actuating means. said switch means being adapted to cause'energization of said actuating means slightly in advance of the energization of said electric motormea ns, and being further adapted to deenergize said actuating means slightly after the energization of said electric motor means.

15. The structure set forth in claim 14, said switch means further comprising reversing switch means adapted to cause rotational reversal'of said electric motor means upon axial movement of Said axially movable member to a given position, and being further adapted to cause energization of said actuating means slightly in advance ,of the reversal of such motor means, and to cause deenergization of said actuating means slightly after such reversal.

HARDING F. BAKEWELL.