US2405550A

US2405550A - Profile milling machine

Info

Publication number: US2405550A
Application number: US513552A
Authority: US
Inventors: Benjamin S T Bishop; Frank A Bicknell
Original assignee: Leland Gifford Co
Current assignee: Leland Gifford Co
Priority date: 1943-12-09
Filing date: 1943-12-09
Publication date: 1946-08-13
Anticipated expiration: 1963-08-13

Description

Aug. 13, 1945. 2,405,550

B. S. T. BISHOP ET AL PROFILE MILLING MACHINE Filed Dec. 9, 1943 7 Sheets-Sheet l V/AV 46 72 94. as 62 32 92 M 54 as 58 a as 55 3 1L1 T L'- jnvj ni omi I I If 7 Maw 13, 1946- s. s. T. BISHOP ET AL ,405,550

PROFILE MILLING MACHINE Filed Dec. 9, 1943 '7 Sheets-Sheet 2 l l 'l l I 71 venior's.

Maw

g- 13, 1946- B. s. T. BISHOP ETAL PROFILE MILLING MACHINE 7 Filed Dec. 9, 1943 7 Sheets-Sheet 4 Aug. 13, 1946.

B. S. T. BISHOP ET AL PROFILE MILLING MACHINE Filed Dec. 9, 1943 7 SheetsSheet 5 v 1 a 5 Q Gm m? fl. M nfla ma J I J m Q am ml www 55R \\\\\\\\\\\\\\\\\\\L /N\ Aug. 13, 1946. B. s. T. BISHOP ET AL PROFILE MILLII IG MACHINE Filed Dec. 9, 1943 7 Sheets-Sheet 6 Aug. 13, 1946. as. T. BISHOP ET AL I 2,405,550

PROFILE MILLING MACHINE Filed Dec. 9, 1943 Sheets-Sheet 7 Patented Aug. 13, 1946 PROFILE MILLING MACHINE Benjamin S. TwBiShOP, Shrewsbury, and Frank A. Bicknell, Worcester, Mass, assignors to Leland-Gifford Company, Worcester, Mass, a corporation of Massachusetts Application December 9, 1943, Serial No. 513,552

18 Claims. 1

This invention relates to improvements in milling machines. More particularly it provides a milling machine which can mill irregularly shaped profile surfaces of work pieces, such as the profile edges of balancing webs of crank shafts, for example.

It is among the objects of the present invention to greatly increase the speed and efficiency of machining the profile edges of crank shaft webs and comparable surfaces as compared with prior procedures. Heretofore, the balancing webs of crank shafts have been machined on shapers or planers involving a multiplicity of cutting strokes in direction parallel to the axis of the crank shaft which makes the machining of an entire web profile relatively slow. The machine of the present invention steps up production several times what has been customary and feasible according to shaper and planer methods of profiling. A rotating milling cutter is carried on a vertically movable carriage and does the profiling as the work is moved toward and in contact therewith, the cutter carriage bein guided in its vertical movements by a cam whose cam surface corresponds to the desired profile of the web that is undergoing machining. A feature is that the cutting is done by the periphery of the milling cutter held in cutting relation to the work by the action of gravity acting on the cutter car riage and maintaining a cam roller thereon in contact with the cam surface.

Approximately one-half of the edge contour of a crank shaft web may be profiled by a single travel of the work carriage past the cutter. Then the crank shaft is turned over and the other half of the same web is similarly profiled, either in the same machine with suitable interchange of work holding jig and cam or, preferably, in a substantially duplicate machine having the proper work jig and cam thereon which conveniently may be associated with the first machine, on a common bed. For crank shafts having two balancing webs requiring profiling, an efficient set up is to have four of the duplex machines, two for rough profiling of the two balancing webs and the other two for finish profiling of the same two webs. Provision of a milling machine having the features and capabilities as described is a further object of this invention.

Another object is to provide for approximately uniform cuttin speed notwithstanding that the web profile may include ne or more relatively sharp inclines and one or more relatively long gradual inclines. According to the invention the speed of feed of the work to the cutter automatically reduces substantially when the cutter is working on a steep incline as compared with the feed of the work when the cutter is workin on a gradual incline. An electric motor havin at least two speeds is employed for driving the work carriage and mechanism is effective for shifting automatically from one motor speed of say 1200 R. P. M. to another which may be 600 R. P. M., when the cutter is working on a steep incline, and for shifting automatically back to the first speedwhen a, more gradual incline is reached. The provision of mechanism for accomplishing this automatic change of speed of work feed constitutes a further object of the invention.

' Still another object resides in a pneumatic control for the vertical cutter carriage. Provision is made for pneumatic lifting of the cutter carriage in response to operation of a hand valve, thereby to condition the machine for loading and unloading.

A further object of the invention is to provide an automatic safety control which is operative to stop the work feed if and when the speed of the cutter drops below a predetermined minimum, as when the cutting load may be too great. A centrifugal governor operated from the tool spindle is adapted to cause opening of the circuit to the work feed motor if and when the cutter speed drops below a predetermined minimum.

It is, moreover, our purpose and object generally to improve the structure and efficiency of milling machines.

In the accompanying drawings:

Figure 1 is a front elevation of a duplex milling machine embodying features of the present invention, a mid part of the bed being broken away;

Figure 2 is a cross-sectional view on line 22 of Figure l;

Figure'3 is a detail elevation of one of the columns or heads on which the tool carriage is mounted for vertical movement;

Figure 4 is a cross-sectional View on line 44 of Figure 1;

Figure 4a is a detail cross-sectional view on line la-4a of Figure 4;

Figure 5 is a front elevation of the cam and its supporting means;

Figure'fi is a top plan view of the cam bracket;

Figure 7 is an end elevation of'the cam and its bracket and showing the means for adjusting the cam relative to the cam roller on the tool carriage;

Figure 8 is an elevation of the cam-adjusting screw;

Figure 9 is a top plan View of the work holding J Figure 10 is a side elevation of th'e work 31% showing the manner of its mounting on the work carriage;

Figure 11 is a front end elevation of the work Figure 12 is an elevation of a crank shaft of the general type whose balancing Webs may be profiled in the present machine;

Figure 13 is a front elevation of the work carriage and its driving means, a mid portion of the bed of the machine being broken away for conservation of space;

Figure 14 is a cross-sectional view on line i l-54 of Figure 13;

Figure 15 is a detail face view of the feed nut cam;

Figure 16 is a cross-sectional view on line lt-it of Figure 13;

Figure 17 is a cross-sectional view on line fie-i? of Figure 13, the motor being shown in elevation;

Figure 18 is a cross-sectional view on line 55-48 of Figure 1;

Figure 19 is a cross-sectional view through the motor-speed-s'nifting mechanism, on line [9-49 of Figure 2;

Figure 20 is a diagrammatic view showing the electrical connections; and

Figure 21 is an elevation looking at the end of a crank shaft and showing the general profile of a balancing web thereof.

Referring to the drawings, the machine shown in front elevation in Fig, l is in reality two identical but reversed profiling machines mounted on a common bed l0. Each has a column or head 92, I 2 adapted to be fixed at their respective ends of the bed, and each has a work carriage 14, I 4' and separate feed screw shafts IE, IS driven by separate motors i8, i8 mounted on opposite'ends of the bed H1. Inasmuch as the structure and operation of both profiling machines is the same, only the left hand half of the complete machine of Fig. l is shown in detail in the drawings and only that half will be described, it being understood that the description applie-sequally to both profiling machines which are in opposed conveniently spaced apart relation on bed I0 so that one half of a balancing web of a crank shaft, for

example. may be profiled by one profiling machine, after which the crank shaft will be transferred to the other machine for profiling of the other half of the web.

The bed it has the pair of spaced guide ways 20 extending horizontally from one end to the other of the bed, and the base of column [2 has complementary grooves 22 in its under face for slidably mounting the column or head on the ways 20. However, after the column has been positioned as desired along the bed I B, it is fixed to the bed by any suitable means (not shown). Retaining plates as on the under face of the column base and engaging under the ways 20 hold the column on the ways as by the screws 26 (Fig. 3).

A tool carriage 28 is slidably mounted on the vertical dove-tail guide 30 of column l2 and is operated thereon by means later tobe described. Mounted on the carriage 28, or formed integral therewith, is the housing 32 within which is mounted in suitable bearings 33 an upper horizontal shaft 34 (Fig. 4) having the pinion gear so keyed thereon. The rear end of shaft 34 proiects out of the housing and has a pulley 38 keyed thereon by which, through belt 40, shaft 34 is driven from the motor 42 which in Fig. 1 is shown mounted on the column l2 and around whose pulley it the belt M1 is trained. The forward end of shaft 34 project through the front wall of housing 32 and into the lower portion of a governor housing 46 which is mounted on the front wall of housing 32 as by the screws 48. Within the governor housing 46, the shaft 34 extends through suitable bearings and has on its extreme forward end a bevel gear 52. Gear 52 meshes with a bevel gear 54 on the lower end of governor shaft 55 which is vertically disposed within the upstanding portion of the governor housing 46. Vertical shaft 56, mounted in lower bearings 58 and upper bearing 60 within the housing, has the pivoted, weighted governor arms 62 thereon, the position of which under centrifugal force controls an electric switch 64 for a purpose later to be described. As shown in Fig. 4, the horizontal shaft 34 is in two parts to facilitate assembly, with a driving inter-engagement 0f the two parts at 66.

A second horizontal shaft 68 is mounted in the combined radial and thrust bearings 10 in housing 32, below the shaft 34, This shaft 68 has a spur gear 12 keyed thereon and meshing with the pinion gear 36 on shaft 34. It constitutes a spindle for receiving and driving the tool shaft 14, for which purpose it has an axial hole extending from end to end, the forward tapering portion 15 of which receives the tapered portion 15 of the tool shaft, and the rearward portion '18, of smaller diameter, receiving the draw-bolt Whose forward end is screw-threaded into the end of tapered part 1-5 of the tool shaft and whose head engages the rear end of the spindle 68. A nonround flange 82 on. the tool shaft fits into a complementary socket 84 in the front face of the spindle and provides a drive connection between spindle and shaft, maintained by the drawbolt B0. The tool shaft extends forwardlythrough a bearing 86 on bracket-88 which is adjustably mounted on the vertical carriage 28 as b the bolts 90. These bolts have their heads slidably engaged in the horizontal T-slots 92 in the vertical carriage 28 and their shanks extending out of the slot-s and through the base of bracket 88, with nuts 9 screwed on their ends for clamping the bracket in any adjusted position'thereof.

The cutting tool 96 is mounted on the reduced portion 14a of the tool shaft, being keyed to the shaft'by the ends of pins 93 projecting from the forward face of spindle T4 and engaging in sockets If!!! in the rear end face of the tool 96. A retaining nut H32 screws on the reduced portion 14a of the shaft for holding the tool in keyed engagement with the key pins 98. The extreme forward end of shaft 14, further reduced as at Mb, has a bearing ISM in a second bracket I06 which is adjustable along a horizontal T-slot 1838 in a forwardly projecting part 29 of the bracket 88, with the bolts H0 and nuts I I2 for clamping the bracket in adjusted positions. This adjustable bracket I06 facilitates mounting and removal of a cutting tool. The bracket may be loosened and drawn forward to permit a tool to be slipped on or off the shaft after removal of the retaining nut I02.

When the machine is in operation for cutting a profile on a work piece, the vertical carriage 28, carrying the housings 32, 45 and the

shafts

34, 55, 68 and 14 mounted therein, rests by gravity on a profile cam H4 mounted on the work carriage l4, and the vertical carriage 28, with itsappurtenances including cutter 95 is caused to rise and fall according to the contour of the cam as the latter moves with the work carriage I4 in direction along the bed I of the machine. For this purpose, a roller H6 is mounted in bearings H8 in an under part of the housing 32 directly over the cam H4, and rides on the top profile surface of the cam. The roller is vertically under but set rearward of the milling cutter 96, and is of the same diameter as the cutter. Preferably, as illustrated, the roller has a slight taper and the cam surface has a complementary inclination, so that a slight adjustment of the cam in direction along the axis of the tapered roller II6 can effect a slight vertical adjustment of the cutting tool 96.

Cam H4 is in the nature of a heavy plate as best seen in Figs. and '7. It is secured by bolts I20 on the front face of an upstanding cam bracket I22 whose base has the slots I24, I26 for securement of the bracket as by bolts I28 in adjusted positions on a rearward part of the work holding jig, indicated generally at I30, and mounted on work carriage I4 in a manner later to be described. An adjusting screw I32 loose in lug I34 of bracket I22 threadedly engages a rear upstanding part of the work holding jig I30. The head of the screw may be in the form of a graduated dial I36 for micro-adjustment of the bracket and cam in directions along the axis of the cam roller I I6, thereby to adjust the tool 96 slight amounts, as to compensate for wear of the cutting edges of the tool.

The work which is to be machined by tool 96 may be mounted on the work carriage in any suitable work holding jig. As illustrated in the drawings, and more particularly in Figs. 2, 9, and 11, a jig is represented for mounting crank shafts whose balancing webs are to be profiled by the tool 96, which in the present case is a milling cutter, the cutting edges of which at its generally cylindrical side act on the work, as distinguished from milling operations in which the machining is an end-milling accomplished by the end of a milling cutter.

The jig as shown has a base I38 resting on work carriage I4 and adjustable on the carriage in directions longitudinally of the machine by reason of the bolts I40 whose head ends engage in longitudinal T-slots I42 in the carriage I4 and whose shanks extend thence through the base of the jig and have nuts I44 threaded on their ends for clamping the jig to the carriage in adjusted positions therealong. A key plate I46 on the under side of the jig engages in a longitudinal groove I48 in the carriage I4 for maintaining a precise predetermined alignment of the jig on the carriage.

A crank shaft such as that shown in Fig. 12 whose endmost balancing webs are to be profiled in the machine, is disposed crosswise of the machine with its opposite ends engaging in forward and rear half-round cradle bearings which upstand from the jig base respectively at I50 and I52. The rear bearing I52 may be capped by a half-round bearing piece I54 which may be secured in place by screws I55. The forward bearing I 50, however, preferably has a half-round bearing cap'piece I56 which is pivoted at I58 at one end and has a swingable bolt and nut securement at its other end. As seen in Figs. 9-11, the bolt I60 is pivoted at I62 in a groove in the forward upstanding cradle bearing I50 and is swingable into and out of a groove I64 in the cap piece, with a nut I66 on the end of the bolt for clamping the cap piece over the end of; a crank u the cutter.

shaft. This structure facilitates insertion and removal of crank shafts in that by merely loosening nut I66 the bolt I60 may be swung out of engagement with the cap so that the cap may be swung to open position about its pivot I58. The rear end of the crank shaft fits nicely in the rear cradle bearing and can be withdrawn axially when the front cradle cap piece is opened, to remove a crank shaft. To insert a crank shaft in the jig, the rear end is thrust axially into the rear cradle bearing and the forward end is laid in the front cradle bearing, after which .the hinged cap piece is closed and clamped by the bolt and nut I60, I66.

Between the forward and rear cradle bearings of the jig, an upstanding part I68 is shaped at its upper portion to engage and position .a mid Web of the crank shaft so that the outermost web will be properly positioned for profiling by the milling cutter 96. Also a longitudinal screw I10 has its rear end carrying a clamping element I12 which coacts with the fixed clamp element I14 on the jig for engaging and holding the rearmost web of the crank shaft.

Hence, assuming that cam II4 has its top edge shaped to provide the desired profile of approximately one-half of the balancing web of the crank shaft, movement of the work carriage to the left in Fig. 1 moves the crank shaft and the cam as a unit, with the cam roller I I6 of the tool carriage riding on the cam and causing the milling cutter to rise and fall according to the contour of the cam as the crank shaft balancing web which is being profiled moves past and in contact with When approximately one-half the periphery of a web has been profiled, the work carriage I4 is moved back to the right in Fig. 1, and the crank shaft is transferred to the other profiling machine for a similar profiling of the other half of the same web. Then with the proper work holding jigs on another machine like that of Fig. 1, or substituted on the same machine, the other balancing web may be similarly profiled.

The means for manually moving the work carriage I4 and for controlling its automatic screw feed are best seen in Figs. 2 and 14-16. As shown, carriage I4 has a hollow depending apron I16 between which and the front wall of bed I0 the feed screw shaft I6 extends from its inner end bearing at I18 on the bed I0 longitudinally to the left end of the machine where it passes through bearing I on bed I0 and thence into gear housing I82 suitably mounted at the end of the bed. Within housing I82 (Fig. 1'1) the shaft I6 has keyed thereon a worm gear I84 which meshes with worm I86 keyed on shaft I88 of electric motor I8. The motor is mounted on the end of bed I0 as by the screws I90, and its shaft I88 extends into housing I82 and has bearings I92 in the housing on opposite sides of worm I86. Hence, so long as motor I8 is running, screw shaft I6 is rotated thereby for automatic feed of the work carriage I4 if and when the carriage is operatively connected to the feed screw I1. Motor I8 has at least two speeds for a purpose which later will appear. Work carriage I4 may be connected to or disconnected from the feed screw I1 by a mere partial rotation of a handle I94 at the front of carriage apron I16. The hollow nature of the apron provides front and rear apron walls, the rear one of which is provided with vertical ways I96 on which the two half nuts I98 are mounted for vertical movement on opposite sides of feed screw I1. Each half nut has a screw 200 therein whose head projects forward between the apron walls forengagementv in cam slots 202 in the rear face of an enlargement. 204. of the shaft of handle I94, said shaft. being horizontally disposed in a suitable bearing 206 in the front wall of apron I16. The cam slots, as seen in Fig. 15, are such that when handle I94 is turned counter-clockwise, the half nuts I98 will be drawn into en-. gagement with the feed screw to provide automatic feed of the work carriage I4. Turning of the handle I84 in clockwise direction will spread the half nuts out of engagement with the feed screw leaving the work carriage at rest and in condition for manual movement thereof.

Manual control of carriage I4 may be effected by rotation of hand wheel 208 which is mounted at the front of apron I 1.6 on shaft 2I8. Referring to Fig. 16', the hand wheel shaft 2H1 is mounted on the front wall of the carriage apron, project'- i g through that wall and having on its inner end a pinion gear 212. The pinion meshes with a spur gear M4 on a shaft 2I6, the inner end of which shaft is formed with gear teeth as at 2I1 which mesh with a gear rack 2I8 secured as at 220 at an under forwardly projecting part of bed I 0. Whenever the automatic feed is disconnected, the. carriage I4 may be manually moved in either direction by rotation of hand wheel 288.

The vertically movable tool carriage 28, during milling of a crank shaft web, rests by gravity on the cam II4. In order to raise it for loading and unloading, there is provided on the topof column I2, above. the vertical carriage, a cylinder 222 (Figs. 1, 2 and 18) wherein a piston 224 is vertically operable. The piston rod 226 extends through suitable packing 221 at the bottom of the cylinder and has its end adjustably secured as at 228 to a bracket 23.0 on the tool carriage 28 so that the carriage and the piston move as a unit in vertical directions. A pipe 232 leads from a suitable source of compressed air and opens into cylinder 222 on the under side of the piston, a suitable two-way valve 234 in the pipeline providing for manual control of' the compressed air. Hence, in Fig. 2, with the handle 236 of valve 234 in. the upper position as shown, air is directed into cylinder 222 elevating the piston 2 24 therein. Tool carriage 28 is correspondingly elevated as a result. of its connection at 228, 238 to the piston. Movement of the valve handle to its lowermost position closes the passage from the air source and opens cylinder 222 through the valv to atmosphere so that the carriage can descend into working position by gravity with the piston tending to cushion its descent. Also, because the cylinder 222 continues open to. atmosphere during milling operations of the machine, the piston 224 isfree to move in the cylinder in response to vertical movements imparted to the tool carriage by ngagement of cam roller I16 with cam H4.

An important feature of the invention i that the feed of the work past the milling cutter 96 can be at one speed during milling of a portion of the. profile and at a slower speed during milling of another portion of the profile. This is desirable to maintain the cutting speed substantially constant both when the milling cutter is working down the relatively steep incline, at A in Fig. 2 1, and when it is working up the relatively long and gradual incline at B in Fig. 21. Th invention accomplishes this substantially constant cutting speed by employing a motor I 8 having at least two speeds for feed of the work carriage I4. For example, motor I8 may have one speed of 1200 R. P. M; and another of 600 R. P. M., and means is. provided for automatically shifting from one motor speed to the other during a. profiling operation, so that. feed of the work carriage I4 and of the. work thereon may be slowed by one-half while the milling cutter 9.6 is working down the sharp. incline A and will. feed at the higher speed during other portions of the profiling operation.

Fig. 2, and more especially Fig. 19., and the diagrammatic. showing of. Fig. 2.0., illustrate the means for automatic control of the work carriage feed. Referring to. Fig. 19, a. switch casing 238 is mounted on a base part of the relatively fixed column or head I.2 at the. rear of the machine as viewed in Fig. 1. The long shaft 240 is slidably and non-rotatably mounted in the bearings 2.42, 244 of the end walls of the casing, extending in a horizontal plan generally longitudinally of the bed 18, of, the. machine. It projects at, both ends of, casing 236 and has its right hand end con.- nected as at- 246 to. a smaller diameter rod .248 which extends slidably through a bracket 250, uD- standing, from a rear part of work. carriage I4. T;W.o collars 252 are adjustably fixed on rod 248, by set screws 254, on opposite sides, of bracket 250, the collars being shown spaced apart a distance greater than the axial extent. of the bracket so that, there is lost motion as the bracket moves from engagement with one collar into engagement with the other. A tubular housing 25,6, mounted on casing 238, encloses substantial portions; of the shaft 248 and rod 248 where they extend to the right of the casing 238 in Fig. 19. Hence, it will be obvious that when the Work. carriage I4. moves to the left, as when advancing a piece of, work thereon to the action of. the milling cutter, shaft 248 will be moved to the left: by engagement of bracket 255) with the left hand collar 252 on rod 228. Movement of carria e, I4 to the right similarly will cause movement of shaft 248 to the right by engagement of the bracket with the right hand collar 252.

Within casing 238 are the two

switches

258, 268 connected in the electrical circuit of the machine as indicated diagrammatically in Fig, 20. Switch 258 is of a type whose switch element 262 (Fig.

- 20) is movable to cause shifting from one to another speed of motor I8. In Fig. 19 switch element 262 is shown shring-urged to its open position. A switch actuating member is pivoted at 264 on the switch housing and has one arm 266 engaging the end of the switch element and another arm 268 with a roller 218 on its end engaging the bottom of a longitudinal groove 212 in the shaft 242. A shorter groove 214 to the left of and aligned with groove 212 can similarly receive roller 218, a short non-grooved portion 216 of the shaftb-eing adapted to cam the roller in direction toward the switch when the shaft 248 i shifted to bring the non-grooved portion 216 opposite the roller, thus causing switch element 262 to be depressed to closed position. The

grooves

212 and 214 are so positioned that the roller will be riding on the periphery of; the non-grooved portion 216 of the shaftv when the milling cutter 96 is working down the relatively steep incline A of the profile of a crank shaft web, thereby to cause the feed of the work to be diminished one half in speed while the cutter traverses the incline. At the start of a milling operation, the roller will be in the left hand groove 214 so that the initial feed of the worktoward the cutter will be at the higher speed. When the roller reaches the right hand end of groove 214 it rides onto the non-grooved portion 216 and the work feed is dropped to the lower speed until the roller rides into the longer groove 212, to cause a return to the higher. speed of workfeed.

The switch 269 is a stop switch for stopping motor I8 when the work has been acted upon by the milling cutter and has passed beyond the cutter. Its switch element 218 is spring-urged to circuit closing position and continues closed during a complete milling operation. Its switch actuating member is pivoted at 289 on the switch housing and has arm 282 engaging the end of the switch element and arm 284 equipped with roller 286 riding in the bottom of groove 212 of shaft 249. This roller 286 continues in the same groove 212 throughout a milling'operation but rides out of the groove to open the motor circuit when shaft'249 has moved to the left an amount surficient to bring the right hand end of groove 212 into contact with the roller to cam it out of the groove with resulting opening of the switch 269.

Another feature of the invention is the provision for stopping the work feed in case the speed of the tool spindle drops below a predetermined speed, as from a too heavy cutting load. The governor within housing 46 accomplishes this automatic stoppage of the work feed in conjunction with th governor controlled switch 64, also in housing 46. This switch is connected in the secondary control circuit of motor I8 and is open whenever the tool spindle is at rest. It is closed whenever the tool spindle, driven by motor 42, is rotating above a predetermined speed, the weighted governor arms 62 acting under centrifugal force to elevate the switch element 64 to close the switch and hold it closed so long as the speed of the spindle is maintained. Any substantial drop in spindle speed, bringing it below the predetermined minimum, permits the switch element to open the control circuit of the motor I8 that drives the work carriage.

The electrical system of the machine is illustrated in simplified form in the diagram of Fig. 20. Both motors I8 and 42 are three phase induction motors connected in the high tension side of the system. This high tension circuit is controlled by switch 288 whose closing starts the spindle-driving motor 42.

In order to start motor 42, however, preparatory to the start of a work stroke, the switch 258 must be open with the roller 219 riding in the left hand roove 214 of the shiftable shaft 249, and the switch 269 must be closed with roller 286 riding in groove 212. Also a manually operable stop switch 299 will be closed, and a manually operable starting switch 292 will be open. Closing of the starting switch 292 energizes a relay 294 which draws armature 296 to the left in Fig. 20 to close the main motor control switch 288. Armature 296 also closes a switch 298 in a shunt circuit around the starting switch 292 so that relay 294 continues energized when starting switch 292 'is released and returns to open position.

Closing of switch 288 results in starting of motor 42. When it attains a predetermined cutting speed, the governor-controlled switch 64 closes. Then, by manually closing a feed off and on switch 399, motor I8 will be started and will operate at whichever of its two speeds has been determined by the position of shiftable shaft 249 relative to switch 258. In Fig. 20, rod 249 is in its position ready to start a work stroke to the left and both the primary and the secondary circuits are open. Hence motor I8 when started will operate at its higher speed of 1200 R. P. M.

Operation of motor I 8 is controlled by two relay operated switches, one in the low speed motor circuit as indicated at 392 in Fig. 20 and the other in the high speed motor circuit at 394. A relay 396 and armature 398 operate the low speed switch 392, and a similar relay 9I9 and armature 3I2 operate the high speed switch. Both of these armatures are shown as switch elements in the secondary circuit and both are normally closed until their respective relays become energized to open them. However, stil1 another relay 3I4 in the secondary circuit controlled by switch 258 has an armature 3I6 which normally closes a circuit through the relay 3I9 of the high speed motor control circuit so that, when motor 42 is op ting and switches 64 and 399 are closed, the relay 3I9 is energized to close the high speed motor switch 394, and motor I8 will operate'at the high speed so long as switch 258 remains open. When roller 219 rides up on the part 216 of shaft 249, however, switch 258 is closed to energize the relay 3| 4 which shifts armature 3| 6 from itsnormal position closing a circuit through high speed relay 3I9 toa position closing a circuit through the low speed relay 396. Hence high speed motor switch 394 opens and low speed motor switch 392 is closed by armature 398, and motor I8 operates at the low speed so long as roller 219 is on the part 216 of shaft 249. As soon as roller219 rides into'groove 212 of shaft 249, switch 258 opens to de-energize relay 3I4, which permits armature 3| 6 to move back to position closing a circuit through high speed relay 3 I 9 and opening'the circuit through low speed relay 396, thereby to cause a return to high speed operation of motor I8 until roller 286 rides out of groove 212 to stop motor I 8 by opening of switch 269. The carriage I4 then will be disconnected from the feed screw I! for manual return of the carriage to unloading position.

We claim as our invention:

1. In a milling machine having a rotatingcutter and a work holding carriage movable topresent work held thereon to the action of the cutter. the combination therewith of means for feeding the carriage in direction toward the cutter in. cluding a plural-speed electric motor, a track on the carriage extending longitudinally of the machine generally in the directions of travel of the carriage. electrical connections between the m0- tor and carriage including a speed-change switch constantly engaging said track and relative to which said track is bodily movable in the directions of its longitudinal extent. and means on said track for effecting a speed changing actuation of said switch and for maintaining the switch in the actuated position throughout only a predetermined distance of movement of said carriage.

2. In a milling machine having a rotating cut-- ter and a work holding carriage movable to present work held thereon to the action of the cutter, the combination therewith of means for feeding the carriage in direction toward the cutter including a plural-speed electric motor, means in the motor circuit for shifting from one motor speed to another, and an actuator having length at least equal to the travel of the work carriage in one direction and linearly movable with the work carriage and constantly engaging said speed shifting means and operative on said means for causing a shift from one motor speed to another at an intermediate point in the travel of the carriage, thereby to change the speed of feed of the carriage.

3. In a milling machine having a rotating cutter and a work holding carriage movable to present work held thereon to the action of the cutter, the combination therewith of means for feeding the carriage in direction toward the cutter including a plural-speed electric motor, a switch in the motor circuit normally connecting the motor for operation at one speed and movable toconnect the motor for operation at a different speed, and an actuator for said switch, said switch and actuator being longitudinally movable relatively generally in the directions of travel of the carriage in response to movements of the carriage andsaid actuator being-constantl-y engagedwith the switch and having a switch actuating portion operative to shift saidswitch at an intermediate pointin the travel of the carriage, thereby to change thespeed of the motor with resultingchange of speed of feed of the carriage.

:4. In a milling machine having a rotating cutter and-.a work holding carriagemovable to present'work held thereon to the action of the cutter, the combination therewith of means for feeding the carriage in direction toward the cutter including-a pluralespeed electric motor,*mea ns in the motor circuit forshifting from one motor speed to another, and .an actuator for said means, said means and said actuator being bodily movable relatively with motion' of translation in response to movement of the carriage, and said actuator having. substantial extent inthe directions of. movement of the carriage and being constantly engaged bysaid Speedshiftingmeans, and having. a fixed cam portion operative on said: means at an intermediate pointin the travel of the carr-iage for causing a shift from one motor speed to another withresulting change of speed of 'feed' of the ,carriage.

5. In a milling machine having a rotatin cutter. and a work holding carriage movable to present work held thereon to the action of the cutter, the combination therewith ofwmeans for feeding the carriage indirection toward the cutter including a-plural-speed electricmotor, aswitch in the=motor circuit at a fixed=location on the machine,vsaid switch being movable between a position closing a circuit for operation of the motor at one speed'and a position closing a nilcuit for operation of the motor at another speed; a .bar slidably mounted on/the machine and 6X- tending generally in the direction of-travel of the carriage and connected to the carriage for bodily movement therewith, said bar-being constantly in engagement with saidiswitch and having means thereon .for camming engagement with said Switch, andconnection between said bar and the carriage whereby thebarmoves with the carriage and shifts said switch-at an intermediate-point in the travel of the carriage thereby to change the speedyof feed. of the carriage.

6. In a milling machine having a rotating cutter and a-.work holding carriage movable to present work held thereon to. the action of the cutter, the combination therewith of means for feeding th carriage in direction toward the cutter includ ing a plural-speed electric motor, a switch in the motor circuit ata fixed location on the machine, said switch being movable between a, position closing a circuit for-operation of the motor at one speed and a position closing a circuit for operation of the motor at another speed, means yieldably maintaining the switch in position for operation of the motor at-one speed, a bar slidably mounted on the machine adjacent to said switch and extending generally in the direction of travel of the carriage, said bar-constantly engagingsaid switch and having a portion thereof adapted to shift said switch when the bar is moved relative to the switch, and connection between the bar-and the carriage whereby the bar moves 12 with the carriage longitudinally past the switch to cause a shifting of the switch at'an intermediate point in the travel of the carriage, thereby to change the speed of feed of the carriage at said intermediate point in its travel.

'7. In a milling machin having a rotating cutter and a work holding carriage movable to present work held thereon to the action of the cutter, the combination therewith of means for feeding the carriage in direction toward the cutter including .a plural-speed,electricmotor, :a switch in the motor circuit ,yieldably urged to position connecting the motorf'or operation ate-one speed and movable to connecttheimotor for operation at a different speed, a second switch in the motor circuit 'yield'ably urged to closed'ci-rcuit position and movable to an open circuit position wherein it stops the'motona common actuator for both switches arranged adjacent to the switches and constantly inter-engaged with bothswitches, and mounted for sliding movement in the direction of travel of the carriage, andconnections between the actuator and the carriage whereby the actuator moves with the carriage, there being'means on the actuator for shifting the first saidvswitch at an intermediate point in the travel of the carriage thereby to change'the speed of feed of the carriage, and for shifting the-second said switch at a predetermined limit of travel of the carriage thereby to stop the feed of the carriage.

8. In a milling machine having a rotating cutter and a work holding carriage movable to present work held thereon to the actionof the cutter, the combination therewith of mean for feeding the carriage in direction toward the cutter including a plural-speede'lectric motor, means in the motor circuit responsive to movement of the carriage and operative to-shift from one motor speed to another at an intermediate point in the travel of the carriage thereby'to change the speed ofifeed of the carriage, said-means comprising a switch arm yieldably urged to position for operation of the motor atone speed, a grooved actuating bar adjacent to the .switchiarm' and "movable with the carriage, an'dwa bell crank .l'ever having one arm in position to engage 'theend of'the switch-arm and to depress it whenthe bellcrank lever is :rocked and having its other arm engaging in the-groove of the-bar, and adapted to be cammed out of the groove by an end wall of the groove thereby to rock th bell crank lever and shift saidswitch. for operation of the motor at a different speed, said end wall-of the groove being located to cause change of the motor speed at an intermediate point in the travel of the carriage.

9. In a machine tool, th combination of a tool support, awork support, a variable speed electric motor for drivingthe work support, a switch in the motor'circuit operative to cause a change from one motor speed to another thereby to change the rate of travel of the work support, an actuator for said switch, and means carried by said work-support movable therewith in a straight line past said actuator and constantly slidably engaging said actuator duringmovements of the work support, said means having a portion at an intermediate location therealong for causing an actuation of said switch and maintenance thereof in the actuated position throughout a predetermined intermediate distance of travel of the work support.

'10. In a machine tool, the combination of a too1'support, a work support, a variable speed electric motor for driving the work support, a

switch in the motor circuit operative to cause a change from one motor speed to another thereby to change the rate of travel of the work support, a second switch in the motor'circuit operative to cause stopping of the motor, a separate actuator for each said switch, and means carried by said work support constantly slidably engaging each said actuator during movements of the work support, said means having a portion at an intermediate location therealong for causing an actuation of said speed change switch and maintenance thereof in the actuated position throughout a predetermined intermediate distance of travel of the work support, and having another portion located for causing actuation of said stop switch at the end of a travel of the work support in one direction.

11. In a machine tool, the combination of a work support, variable speed power means for driving the work support, power connections between said power means and the work support including means operative to cause a change from one to another speed of the power means thereby to change the rate of travel of the work support, linear means carried by the work support having substantial extent in the directions of travel of the work support, said means operative to cause a change from one to another speed being constantly in resilient engagement with said linear means carried by the work support, and the latter said means having a portion at a predetermined location along its linear extent for actuating said speed change means at an intermediate stage of travel of the work support in one direction, thereby to change the rate of travel of the work support.

12. In a machine tool, the combination of a work support, a variable speed electric motor for driving the work support, electrical connections between the motor and the Work support including a speed change switch operable between open and closed positions and constantly resiliently urged to one of said positions, means carried by the work support constantly engaging said switch and movable with the work support linearly past the switch and having an intermediate portion operative to cause operation of said switch from one of its said positions to the other and adapted to maintain it in the new position throughout a predetermined intermediate distance of travel of the work support.

13. In a profile milling machine, the combination of a vertically slidable milling cutter support, a horizontally movable work support, a profile guide track mounted on the work support and movable therewith, said tool support resting by gravity on said profile guide track, power means for lifting the tool support away from the profile guide track, a plural speed electric motor for driving the work support, electrical connections between the motor and the work support including speed-change means mounted stationariiy relative to the work support, means carried by the work support constantly inter-engaged with said speed-chan means, said means carried by the work support having an intermediate portion for causing actuation of said speed-change means to and holding of it in a speed-changing position throughout a predetermined intermediate distance of travel of the work support.

14. In a profile milling machine, the combination of a vertically slidable milling cutter support, a horizontally movable work support, a profile guide track mounted on the work upport and movabl therewith, said tool support resting by 14f gravity on said profile guide track, a plural speed electric motor for driving the work support, electrical connections between the motor and the work support including a speed-change switch mounted stationarily relative to the work support, a longitudinally grooved bar carried on the work support, actuating means associated with said switch and intervening between said switchand bar constantly urged resilientlyagainst the bar and having a portion engaging in the groove of the bar for riding therealong during movements of the work support, said bar having means thereon for displacing said actuating means out of said groove at an intermediate location in'the travel of the work support.

15. In a profile milling machine, a vertically slidable milling cutter support, a horizontally movable work support, a profile guide track mounted on the work support and having a relatively steep sloping portion, said cutter support resting by gravity on the track and riding thereon during movements of the work support, a. plural speed electric motor for driving the work support, electrical connections therefor including a speed-change switch stationarily mounted relative to the work support, means carried by the work support constantly slidably engaged with said switch and having an intermediate portion for causing actuation of the switch from one position thereof to another, and for causing return of the switch after a predetermined intermediate travel of the work support, said intermediate portion being positioned relative to said switch and said steep sloping portion of the guide track so that the speed of the motor is changed while the milling cutter support is riding on said steep sloping portion of the guide track.

16. In a machine tool having a rotating tool support and a work support, the combination therewith of means for feeding one of said supports in general direction toward the other on a working stroke, said means including a variable speed electric motor, a linear track mounted on one of said supports, electrical connections between the motor and the other of said supports including a speed-change switch having an actuator constantly engaging said track, said track and actuator having relative linear movement in response to movement of said one support toward the other and means on the track for effecting a speed-changing actuation of said switch and for maintaining the switch in actuated position throughout only a predetermined distance of movement of said one support toward the other.

17. In a machine tool having a rotating tool support and a work support, the combination therewith of means for feeding one of said supports in general direction toward the other on a working stroke, said means including a variable speed electric motor, a track fixed relative to one of said supports, electrical connections between the motor and one of said supports including a pair of switches each having an actuator constantly engaging said track, one of said switches being a motor-speed-change switch and the other being a motor-stop switch, means on the track for effecting a speed-changing actuation of said motor-speed-change switch at a predetermined intermediate location in a said working stroke, and additional means on said track for efiecting a motor-stopping actuation of said motor-stop switch at the end of a said working stroke.

18. In a machine tool having a rotating tool support and a work support, the combination therewith of means for feeding one of said supports: in general direction: toward. the other: on a working stroke; Vsaid meansrincluding :a variable speedT-electriomotor; attrack fixedreiativeto one ofgsaid supports, electricalconnections between.

the. motor and one of, said. supports including a, speed-change switch having; an; actuator constantlyengaging said track; means. on the track for; efiecting a speed-changing; actuation of:sa,id

switch; at a; predetermined intermediate. location,

means for, actuating saidtzsecond switch to stop one of said: motors whenzrotationzof thetool supportdrops belowa; predetermined speed.

BENJAMIN S; .T.' BISHOP; FRANK A. BICKNELI.1.-;