US3096686A

US3096686A - Automatic hob shifter

Info

Publication number: US3096686A
Application number: US189660A
Authority: US
Inventors: Davenport Granger; Joseph E Van Acker
Original assignee: Norton Co
Current assignee: Saint Gobain Abrasives Inc
Priority date: 1962-04-12
Filing date: 1962-04-12
Publication date: 1963-07-09
Anticipated expiration: 1980-07-09

Description

July 9, 1963 G. DAVENPORT ETAL 3,096,686

AUTOMATIC HOB SHIFTER Original Filed July 5, 1957 4 Sheets-Sheet 1 g N E; (\l

INVENTORS 9 GRANGER DAVENPORT El By JOSEPH E. VAN ACKER AQWKM ATTORNEY July 9, 1963 G. DAVENPORT ETAL 3,096,586

AUTOMATIC HOB SHIFTER Original Filed July 5, 1957 4 Sheets-Sheet 2 mdE v RR.

T R m 00K TP C m? um X m0 V R E r P E MS em Y B WV 2 b. 5% 66C wn mw ATTORNEY y 1963 G. DAVENPORT ETAL 3,096,686

AUTOMATIC HOB SHIFTER Original Filed July 5, 1957 4 Sheets-Sheet 3 y 1963 G. DAVENPORT ETAL 3,

AUTOMATIC HOB SHIFTER 4 Sheets-Sheet 4 Original Filed July 5, 1957 o 0 a W m\ 2 mm m um um:

ATTORNEY a-ssasss United States Patent Ofifice 3,096,686 AUTOMATIC HOB SHIFTER Granger Davenport, Montclair, and Joseph E. Van Acker,

New Vernon, N.J., assignors to Norton Company,

Worcester, Mass., a corporation of Massachusetts Qontinuation of application Ser. No. 670,200, July 5, .1957. This application Apr. 12, 1962, Ser. No. 189,660

13 Claims. (Cl. 90-4) .Thepresent invention relates to bobbing machines and more particularly to an improved method and means for periodically shifting the hob axially precise increments or multiples thereof whereby to bring unused teeth of the hobintocuttin-g relation with the work blank, eventually to utilize all of the teeth of the hob before it is necessary to remove and resharpen the hob.

This application is a continuation of my prior copending application, Serial Number 670,200, filed July 5, 1957, now abandoned.

A primary aim of the invention is to render available a :hobbing machine in which the hob-spindle bearings of a shiftable hob remain firmly clamped to the swivel head during the cutting operations, and in which the mechanism provided for shifting the hob unit distances at preselected times during a run of work incorporates means automatically operable to vunclamp the hob-spindle bearings before effecting the shift, and to reclamp the hobspindle bearings firmly to the swivel head following each shift movement of the hob. It is proposed further to provide hob-shifting means in which the errors, if any, in the increments of shift are noncumulative in effect on the total shift. Moreover, the instant invention provides a device with inherent flexibility and versatility that will enable an operator to initially zero the hob on a tooth or a space, and thereafter to obtain minute but exact increments of shift, or if desired, only approximately correct increments of shift.

Another aim ofthe invention is to provide built-in hob-shifting means whose incremental shifts may be precisely controlled to suit the lead and tooth spacing of the hob and which may be operated to shift the hob progressively selectively in either axial direction with means available for operation at the end of the total shift toreturn the hob spindle relatively rapidly to its initial starting position for removal and replacement by a sharp one.

,Another aim of the invention is to provide a selfcontained and protected hob-shifting mechanism for hobbers which will perform automatically .to effect hob-shifting movements after one or a selected number of feed cycles have been concluded, and which is operative automatically to register the cycles and record the shifts and to impart a signal to the operator when the hob has been advanced incrementally a preset distance, usually the full distance that a given hob is capable of being advanced.

.Still another ,aim of the invention is to provide hobshifitinge means that is completely automatic in its action following an initial setting-up operation, to the end of relieving-the operator of all manual control or supervision in order that'he may devote his attention exclusive to other operations and functions of the machine.

A further aim of the invention is to render available a hob-shifting mechanism that is failure-safe, i.e., a mechanism that operates automatically to stop the machine should there be a failure in the power source relied upon to effect hob clamping.

A further objective of the invention is the provision of an improved hob-shifting mechanism that is substantially entirely enclosed and embodies a minimum of exposed parts "likely to become damaged or fouled by cutting Fatented July 9, 1953 chips or coolant liquids, or by being accidentally struck when mounting or removing the work.

In carrying forward the objectives of this invention it is proposed to mount the spindle bearings for lateral movement in the hob-swivel-head unit and to equip the head with built-in protected means operable to maintain the hob-spindle bearings firmly clamped except when it is desired to shift the hob at which time the bearings are unclamped. To effect shifting of the spindle bearings, driving and driven elements such as a rack and pinion or an equivalent screw and not are employed, the driven element being fast to one of the spindle bearings, and the driving element being actuated in a forward or reverse direction by means of an adjustable-stroke fluid-actuated power cylinder and intermediate gearing including a ratchet mechanism, stroke-modifying change gears, and a direction-reversing gear cluster. The stroke of the piston of the power cylinder is made variable by means of a graduated stop operative to normally aiford shift increments from .010 to .080 in. in steps of .010 in. For exact increments of shift which do not coincide with the .010 in. steps, provision is made for the insertion of pick off gears in the train between the ratchet device and the spindle bearing so that a movement of the power cylinder Which would normally impart an exact shift in increment steps of .010 in. will result in increment steps of .010 in. times the ratio Driver/Driven. For example, a powercylinder movement which normally would result in an exact .OSO-in. shift will with a 44-tooth gear driving a 46- tooth gear produce an equally exact shift increment of .07652 in. Larger shift movements may be imparted to the hob in accordance with this invention by the incorporation of a shift-increment multiplying element that functions automatically to cause the power cylinder to recycle its operation a selected number of times so that the total shift per cycle becomes a multiple of the previously determined unit increments.

Entrance of chips or other foreign matter to the shifting mechanism is prevented by enclosing all moving parts within the swivel head and by controlling the operation thereof by valves and switches externally located.

In conjunction with the foregoing, manual means may be provided to select the direction of the automatic power shifting as well as to effect the shifting manually. Additional control means have been so arranged that the cutting cycles between shifts may be selected, the hobshift movements may be counted singly or in multiple, and a signal given when a count indicative of a full complement of shifts for a given hob has been reached. The device described herein also includes control means operable to efiect a succession of shifts, i.e., to impart a traverse movement to the hob in one direction or the other.

A further aim of the invention is to provide means for automatically effecting a hob-shifting movement at a point in the bobbing cycle in which such hob shifting can be carried out safely without requiring the operators attention.

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 prefer-red 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:

FIG. 1 is a side view of a representative hobbing machine embodying the invention.

FIG. *2 is a detailed view of a hob-shift control panel used with this invention.

FIG. 3 is a front view of the hob swivel head illustrating more clearly portions of the spindle-bearing mounting and clamping means.

FIG. 4 is an enlarged sectional view taken substantially along line 4-4 of FIG. 3.

FIG. 5 is a sectional view of portions of the bearingshifting gear train.

FIG. 6 is a sectional view of a preferred form of power cylinder and associated mechanism. provided to effect the power shifting.

FIG. 7 is a vertical sectional view of a preferred form of ratchet mechanism responsive to the strokes of the power cylinder.

FIG. 8 is a plan view of a portion of the head illustrating portions of the change-gear drive to the spindle-bearing-shifting rack.

FIG. 9 is an elementary diagram of the pneumatic and hydraulic system provided to actuate the hob-shifting mechanism and the bearing clamps.

FIGS. 10, 10A, and 10B are elementary diagrams of the electrical-control system.

Referring more particularly to FIGS. 1 and 3 of the drawings, the hobbing machine illustrated comprises a base 56 that provides bearings for a rotary work spindle 51, and a support for an upstanding stanchion 52. The forward face of the stanchion is provided with vertical guides 53 on which is mounted a vertically movable hob slide 54. The hob slide in turn carries an angularly adjustable hob swivel head 55 which supports laterally adjustable hob-

spindle bearings

56 and 57. A hob spindle 59 is journaled in the

bearings

56 and 57 and is adapted to mount a hob H in clamped position between suitable sized solid spacer collars 60, including, if desired, a micrometer-type adjustable-thickness spacer 60a to enable initial settings to be made more conveniently.

The letter W designates a stack of gear blanks that have been partially hobbed by the hob H. The blanks are mounted upon a suitable work-holding fixture secured to the rotary table WT, and in a normal hobbing cycle both the work and the hob are rotated in synchronisrn as the hob is fed axially of the gear blanks. M designates the main-drive motor which is connected by suitable gearing to drive the work and the hob. T is a traversing motor selectively connectable to propel the hob slide up or down on the stanchion, and C is a coolant motor that operates a pump to supply a coolant lubricant to the hob and Work during the hobbing operation. The several transmissions alluded to have not been illustrated in all their detail on the drawings for they may be of conventional design and per se form no direct part of the instant invention.

With reference more particularly to FIGS. 3, 4, and 5, which illustrate features of the hob swivel head in larger detail, it will be seen that the hob-

spindle bearings

56 and 57 are semi-circular and cradled in complementary shaped finished cavities 61 and 62 in the swivel-head casting and that their longitudinal marginal edges are overlaid by

clamp straps

63, 64, 65, and 66. The upper set of straps 63 and 64 are normally secured in a fixed position, whereas, the lower set of straps 65 and 66 are relieved at their undersides to form a toe portion 67 (in FIG. 4) that bears against the spindle bearings and a power-receiving end 69. A plurality of strap-mounting studs 70 pass through the clamp straps 65 and 66 at regions intermediate the toe portion 67 and the powerreceiving end 69 and function as aligned fulcrum points about which the straps may be tilted so as to bring pressure upon the spindle bearings for clamping or to relieve the pressure thereon to permit the bearings to be shifted. The clamp straps 65 and 66 are given a slight crown in their outer surface to make the fulcrums effective under the stud nuts.

One of the bearings, preferably the inner bearing 56,

is relieved at its rear to receive a section of a rack 71 which is secured to the bearing and meshed by a pinion 72 out on a transversely extending shaft 73, as shown in FIG. 5. The shaft 73 is journalled in the hob-swivelhead casting 55. The inner end of pinion shaft 73 has gear teeth 74 cut thereon adapted to be meshed by the teeth of a worm 75 on a vertical shaft 76 that is also journalled Within the hob-swivel-head casting, as shown in FIG. 5. Bevel gears 98 and 77 connect the shaft 76 with a stub shaft 79 that projects to the front of the head and terminates in a clutch end 78 designed to receive a removable hand crank. When the clamp straps 65 and 66 are released, the hand crank may be applied to the clutch end of the stub shaft 79 and a turning thereof will effect a shifting of the hob-

spindle bearings

56 and 57 and, as well, the hob spindle 59 and the hob mounted thereon.

In accordance with this invention it is proposed to axially move the hob preselected precision amounts by means of an air-operated cylinder 80 built into the swivelhead casting 55. FIGS. 6, 7 and 8 illustrate a preferred construction of power cylinder in which the piston rod 81 extends from the cylinder and is provided with rack teeth '82 that continuously mesh with the teeth of a pinion gear 83. The pinion '83 is mounted to revolve freely on a ratchet shaft 86 and carries a spring-loaded radial pawl 91 positioned to engage teeth 86:: on the ratchet shaft 86. A similar pawl 92 radially movable in a relatively fixed member 92a, retains the ratchet shaft during the reset strokes of the power cylinder. The angular movement imparted to the ratchet shaft 86 during the forward strokes of the power cylinder is transmitted to gear 87 removably splined to the shaft 86, and thence through change gears 88 and 89 to a vertical shaft 76a that is coaxial with the worm shaft 76. The intermediate gear 88 of this train is mounted upon a normally fixed but adjustable arm 90 that is pivoted on the ratchet shaft 86. By rearranging these gears or by substituting others, the ratio of power-cylinder movement to the movement of the coaxial shaft 76a may be modified and precisely determined.

As illustrated more clearly in FIG. 4, the unidirectional movement imparted to the shaft 76a is transmitted to worm shaft 76 through the medium of a motion-reversing clutch mechanism consisting essentially of a shiftable clutch spool 96 that is keyed to the shaft 76a and a group of three

bevel gears

97, 98, and 77.

Gears

97 and 98 are provided with clutch teeth complementary to the teeth of the shiftable clutch spool. Gear 97 is loose on the coaxial shaft 76a, gear 98 is part of or may be secured to worm shaft 76, and the intermediate bevel gear 77 is keyed to the manually actuated stub shaft 79. Clutch spool 96 is annulalrly grooved to receive a shifting fork 100 on a spring-centered shaft 101 (FIG. 6) whose upper end is grooved to receive an eccentric pin 102 projecting from the end of a manually operable shaft 103. The shaft 103 extends to the front of the swivel head and is provided with a control knob 104 by means of which the shaft may be turned to cause the eccentric pin to operate the clutch shifter shaft 101 up or down from neutral, which in turn operates the motion-reversing clutch from a neutral position to a hobshift-left position or to a hob-shi'ft-right position. Means in the form of a ball-and-dentent mechanism 105 associated with the shaft 103 is provided to retain the clutch in any one of its three operative positions, i.e., manual shift, power-shift left, or power-shift might.

Through the transmission just explained, it will be seen that any given stroke of the power cylinder 80 and its rod 81 may be caused to shift the hob-spindle bearings a precise distance depending upon the selection of change gears 87, 89, and in either direction depending upon the setting of the direction control knob 104. The extent of axial-shift movement imparted to the hob may also be varied by varying the operating stroke of the power cylinder and its rod 81. In the embodiment illustrated in the drawings, it is intended that the piston of the power cylinder always move on its power stroke to the end of the cylinder and comet to a dead stop. At that time a limit switch 161.8, forming part of the control circuit, is engaged and actuated by the piston rod and the piston is caused automatically to return. The extent of the return movement of the piston is made a variable distance by means of an adjustable increment rod 110. The rod 110 is tubular in form and externally threaded so as to be moved axially within a rotatable gauging nut 111 journalled in the swivel-head casting. One side of the increment rod is flattened andgraduated as at 110a in uniform spaces indicative of the hob-shift distances, e.g., .010, .020, .030 and up to .080 in. when the ratio change gears 87-89 are 1:1. The rod 110 is adjusted in or out of the power cylinder to adjust the length of the stroke and this movement is then translated into increment steps of .010 in. by reason of the rack teeth 82 rotating the pinion $3 back so as to cause the pawl 91 to pass an integral number of teeth 86a on the ratchet shaft 86. Each tooth 86a passed on the reset stroke will result in a basic .010-in. shift during the forward stroke. The increment rod adjustment accuracy need only be such as topick up the desired number of ratchet teeth. The outer end of the tubular increment rod is capped and carries a limit switch 17LS whose operating plunger is adapted to be actuated by an extension rod 112 secured to the piston of the power cylinder and operative within the increment tube 110. The switch 17LS also forms a part of the control circuit that controls the flow of compressed air through lines .113 and 114- connected with the ends of the power cylinder 80.

Compressed air from any suitable source may be valved to the power cylinder by a system shown diagrammatically in FIG. 9. Air under pressure enters line 115 connected with a solenoid-operated reversing valve 119 of standard design commercially available. Normally the valve 119 is biased to the left position shown in FIG. 9 and pressure air is directed to the rod end of the cylinder 80 through line 114 to hold the piston retracted and to avoid creep. When, however, solenoid 121 is energized, the valve is shifted to the right and pressure air is directed to the large end of the cylinder through a restricting needle valve 117 and line 113 and the piston moves, thereby advancing rack bar 82 and turning pinion gear 83 of the bearing-shifting ratchet. Forward movement of the piston and rack bar continues until the piston of the power cylinder stops at the end of the cylinder whereupon limit switch 16LS is operated to de-energize valve solenoid .121 and the piston retracts.

Reference number 117a in the line around the restricting valve 117 is a bypass valve that is opened when shifting the hob uphill and the weight of the spindle assembly is against the pressure.

A further important feature and function of the hobshift mechanism is its flexibility in affiording an infinite variety of accurately measured shift increments. Briefly, the limit switches 16LS and 17LS and the solenoid 121 of the air valve 119 are elements of a control circuit that includes stepping switches and counters whereby the hobshift mechanism may be caused to function at the end of one or a selected number of bobbing cycles, to count the number of shifts made so that the hob may be replaced when fully used, and increase the extent of hob shifting by making exact integer multiples of exact increments when desired. As to this last-mentioned feature the following will serve as an example: Assuming the increment rod be set with relation to the end face of the nut 111 on line .050 and with change gears 87-89 of 1:1 ratio, the distance the hob will be shifted on any one shift cycle will be .050 in. However, if the shift-cycle multiplier switch ZTS is set on #2, the shift cycle is auto matically repeated and the extent of hob shift will be exactly .100 If the multiplier is set on #3 the shift increment will be repeated 3 times, giving a total-shift of .150 in. in any one shift cycle. The flollowingttableishows the rangeof shift increments made possibleby this invention:

Standard Hob-Shift Increments Automatic H0b-Sliift Attachment Increment Rod Multi- Increment Rod Multi- Setting plier Setting plies 010 l 060 5 020 1 080, 4 030 l 0 70 5 040 1' 060 6' 050 l 080 5 060 1 070' 6 070 '1 050 9 .080 l osn gs 030 3 070 7 050 2 050 10 060 2 0501 '0 070 2 080 i 7 050 3 060 10 080 2 070 9 060 3 080- i 8 050 a 070 10- 070 3 .080 '9' 080 3 I080 10 050 5 The above table is based upon the use of change-gears 87-89, giving a 1:1 ratio of movement. If, however, the shift increment desired in the preceding example were to be .0446 in. instead of 1050 in., ratio'change gears are installed that produce this fraction of the .050 setting indicated by the increment rod. Such fractions may be multiplied when desired by use of'the shift multi plier above explained to obtain any exact imfltip'I'e 0fthe selected fraction.

Hob-Spindle-Bearing Clamping (FIGS. 3, 4, and 9 The spindle bearings of the present construction are clamped preferably by a hydraulic-fluid pressure system comprising lower clamp straps 65 and 66 of the spindle bearings. The rod end of the piston element 130 in each cylinder bears directly on the power receiving end 69 of the respective clamp straps. Pressure fiuidfor acmating the pistons outwardly to effect a: rocking of the straps about the fulcrum points afiorded' by the mounting studs 70, whereby to efiect clamping of the spindle bearings, is derived from an air-operated booster pump or intensifier illustrated diagrammatically in FIG. 29-.- The intensifier unit consists essentially of an airoperated pump section that drives an hydraulic pumpsection 12 1. Pressure air from the line 115 after passing a; pres-- sure regulator valve 122 is directed to' the air motorhydraulic pump section 120. The hydraulicpumptakes fluid from a reservoir R and passes it under. relatively high pressure through a nonreturn valve 123' to a sole noid-operated spring-returned valve 124. In the position shown in FIG. 9 the valve is biased to tlieleft and high-pressure fluid is passed through a disconnect coupling 126 to line 127 Where it branchesinto-five: separate lines leading to the respective clamp'cyhnders 12'8. When the solenoid ofthe valve is energized the valveRshifts to the right against its spring and the fluid within each clamp cylinder back flows through the'valve tothe'reservoir R. A cup-shaped spring 128a within each clamp cylinder assists the back flow of fluid and assures release 0; the clamp straps so that the spindle bearings may s ift.

Hob-Shift Limiting Stops (FIGS. 3 and 4) Shifting of the hob to the right or to the left an'excessive distance may be prevented by providing one of the hob-spindle bearings, preferably the main hob-spindle bearing 56, with a stop pin arr-anged'to'operate between sets of adjustable collars 136' and 137 mounted upon a rod 138. Rod 138 is secured at itsends in-em tensions of the upper-main-bearihg strap'63 and is therefore relatively fixed. Accordingly, if the attendant fails to change the hob at the end of the total shift movement determined by presetting the collars 136, '137, the pin 135 that travels with the main hearing will come up against one of the sets of collars and stop the shifting movement. When that occurs the power cylinder will not complete its stroke, limit switch 16LS will not be.

actuated, and subsequent functions of the machine will not be instituted.

Control (FIG. I)

This invention further proposes novel means for effecting incremental hob shifts selectively automatically and manually, the automatic means including in part the electrical switching means provided to control the hobbing cycle. trated, this includes in part a pair of spring-balanced switch-operating rods 140 and 141 mounted along the stanchion for limited vertical movement.

dogs 142 each adapted to be engaged by a slide-carried latch 145 to eifect lifting or lowering of the rod 140. Movement of the rod 140 in an upward direction eifects actuation of limit switch 3LS, and movement in a downward direction effects actuation of limit switch 418. Trip rod 141 mounts adjustable dog 147 and

extreme limit dogs

146 and 148 adapted to be engaged by another slide-carried latch 149 and movement of the rod 141 vertically actuates limit switch 1LS. The limit switches lLS, 3L8, and 4LS are mounted in an enclosure 150 and are instrumental in controlling the cycle of operation of the machine and of the hob-shifting mechanism including a cycle-counting means located in a control panel 167 illustrated at the right end of the machine adjacent the housing which contains the pneumatic and hydraulic equipment previously explained and the electrical-control panel and circuitry now to be explained.

Electrical System (FIGS. 10, A, 10B) MOTOR CONTROL In the diagrams FIGS. 10, 10A, and 10B, the letters M, T, C, and D designate the mainadrive motor, traverse motor, coolant motor, and chip-conveyor motor, respectively, each of which is controlled by a

magnetic starter

1M, 2M, and 4M connected to heavy-duty power lines L1, L2, and L3. The main power lines L1, L2, and L3 are fed through a circuit breaker CB connected as indicated in FIG. 10. A transformer 150 connected across lines 1L1 and IE3 supplies lower voltage to the control circuit that is fed by lines 151 and 152. The main-control circuit for the motor starter initiates at line 152 and current is supplied through normally closed STOP pushbutton 153 and normally closed COUNT switch 216 to the RUN-TOG switch 154. When switch 154 is turned to RUN and thereby closed, a circuit is completed through DOWN button 156 and UP button 157 and normally closed limit switch lLS to coil M1 of the starter of the main-drive motor M. If the COOLANT: OFF- ON switch 159 is ON a parallel circuit is completed to coil M3 of the coolant-motor starter.

When the main-motor contactors close, a holding circuit around the RUN button is completed through contactor switch M1. Should the operator turn the switch 154 to its 106 position and press the button, the holding circut becomes ineffective.

The traverse-motor control circuit starts at STOP button 153, and after passing normally closed limit switch 2LS and the TRAVERSE switch 155, assuming the latter to be closed on the RUN side, a pressing of the UP button -7 completes a circuit to the reverse coil 2R of the traverse starter through limit switch 3L8, and opens the circuit to coils M1 and M3 of the main and coolant motors M and C. When coil 2R is energized a holding In the vertical-feeding bobbing machine illus-' Rod 140 mounts

adjustable dogs

143, 144, and two extreme limit 8. circuit is completed through contacts 2R around the UP button.

When the DOWN button 156 is pressed, a similar circuit is completed through limit switch 4L8 to the forward coil 2F of the traverse-motor starter, and as before a holding circuit will be completed around the DOWN button through contacts ZF and the circuit to main and traverse motor coils Md and M3 will be interrupted. The establishment of a holding circuit is necessary in each instance, because UP button 157 and DOWN button 156 are of the momentary contact type.

Should the operator desire to jog the traverse motor and inch the hob slide up or down the TRAVERSE switch is turned to JOG which cuts out the holding circuit made by contacts 2R and 2F.

Limit switch 2LS is located in the base of the machine and is actuated to :open position when the power-feed clutch-lever 160 is operated to engage the power feed to the hob slide that is driven from the main motor M through conventional bobbing-machine feed gearing (not shown).

Limit switches 1LS, 3L8 and 4LS are on the stanchion and are actuated in response to the vertical movements of the hob slide by means of the trip rods and dogs previously mentioned. Switch 1LS is actuated by rod 141 to stop the main motor M when the slide reaches its preset bottom position under power feed. Switches 3LS and -4LS are double-contact double-throw and are actuated by trip rod 140 to stop the traverse motor at the preset limits of the up-and-down traverse movements of the slide as well as to control the action of certain elements of the hob-shifting mechanisms and their control circuits as will now be explained.

HOB-SHIFT CONTROL In accordance with this invention, means and circuitry is provided to efiect the hob shifting automatically or manually, to elfect the shifting only after a preselected number of pieces have been cut by the hob, to effect the shifting either at the top or the bottom of hob-slide movement, and to .give warning and shut down the machine at the completion of the total shift movement for that hob.

The electrical elements which are located at the operators control station on the stanchion 52 and which are manually set to control the hob shift are a four-circuit selector switch 200 having its circuit closings controlled by a three-position cam, and a combination pushbutton and selector switch 201.

The electrical elements which are located at the electrical component enclosure and which are manually set are a multi-position selector tap switch 1TS, a shift-cycle multiplier switch ZTS, a predetermining counter 204, and a pushbutton switch 205.

In a hobbing machine equipped for radial feeding, the hob shift occurs always at the point Where the hob is withdrawn radially from the Work and in this case, the operator is relieved of the necessity for selecting the point in the bobbing cycle at which the hob shift will occur. However, in hobbing machines equipped for axial feeding only, it is necessary for the machine operator to select the point at which the hob will shift. For axial feeding up, hob shift preferably occurs when the hob slide 54 is returned to its lower-most position at the end of the cutting cycle, whereas for axial feeding down, hob shift preferably occurs when the hob slide 54 is raised to its upper-most position just prior to loading a new workpiece W. For this purpose, a selector switch 206 is furnished at the operators control station on the stanchion which permits him to select the shift point at the top or the bottom of the hob-slide movement.

The selector switch 200 has one position which closes a set of circuits which effects a continuous hob shifting to rapidly move the hob-

spindle bearings

56 and 57 to one extreme end of its movement, this switch position being labeled RE. (RETURN). A second position of this selector switch closes a circuit to directly energize solenoid 125 of valve 124, and also removes all forward power from the hob-shift power cylinder 80 via relay 20CR, this switch position being labeled UNCL. (UN- CLAMP). The third position closes a set of circuits which are normal for the operation of the hob shift and is labeled CL. (CLAP).

The combination pnshbutton and selector switch 201 has one position which closes a circuit which causes the hob shift to occur automatically at the correct point in the hobbing cycle, this position being labeled HOB shift: AUTO. The other position of this selector switch 201 allows the switch to operate as a pushbutton and when depressed, it initiates a hob-shift movement at a point other than during the hobbing cycle, this position being labeled HOB SHIFT: MANUAL.

Hobs do not always wear during the cutting of a single stack of gear blanks sufficiently to require the hob to be shifted. For this reason, selector tap switch [1T8 selects the number of stacks of gears to be cut before a hob shift occurs.

The control operation for automatic hob shifting is as follows:

The operator presets the selector switch 200 to the CLAMP position and the selector-pushbutton switch 201 to HOB SHIFT: AUTO position. He then sets the dial of the loads-per-shift selector switch -1TS at any desirable setting determined from his past experience with the amount of wear which results from cutting a stack of gears; for example, he may know that cutting one stack of largerdiameter gears of heat-treated steel results in enough Wear top-revent satisfactory cutting on the second stack, so he will then set the switch ITS at the #1 position. He also knows that the hob-tooth advance is exactly .090 in, so he sets increment rod 110 to the .030- in. graduation mark and sets the dial of multiplier switch ZTS' to #3 position. His machine may not be equipped for radial feed, and he may be feeding down, so he sets the selector switch 206 to automatically shift when the slide 54' is at its upper-most position.

The operator proceeds to out a gear. The slide feeds down and the gear is finished when the hob leaves the blank at the bottom. The operator unloads the gear from the machine and then causes the slide to traverse to its uppermost point so as to allow a new workpiece to be loaded. As soon as the slide in its upward movement forming relay SCR. This relay is operated by DC. and

has a heavy single-turn winding at the armature end of the core which effectively slows the movement of the armature and delays the opening of the relay contacts so that a pulse having a duration of about .050 second is formed. This pulse momentarily energizes the stepping relay coil STEP 2, which advances the stepping switch wipers 210 one step to contact terminal B1. and at the same time, the stepping switch off-normal contact ON. 2 closes. Considering the stepping switch of itself, each gear cut would cause the stepping switch wipers to progress from position B1 to B2 to 133, etc., while the offnormal contact ON. 2, closed only upon the initial step, remains closed until such time as the switch is advanced all the way forward to the normal or zero position when ON. 2 will open. However, since switch 1TS has been set to the #1 position where the wiper 211 contacts its terminal B1 (B1 identifying a wire not shown between the stepping switch. and tap switch 2T5) a circuit is set up .through ON. 2, to the stepping switch to terminals B1 to ITS wiper to relay 19CR to ground wire #2 via the motor starter contacts M1. (Motor starter contacts M1 prevent hob'shift during the period of cutting of the gear.) When relay 19CR isenergized, 19CR contacts bypass the stepping switch and tap switch and 19CR is thereby held energized even if the stepping switch should move off the contact which originally energized 19CR. At the same time, other 19CR contacts close a circuit through ON. 2 to the stepping switch self-interrupter contacts INT 2 to energize the coil of stepping switch. This mode of energization of the stepping switch causes the STEP 2 stepping switch to buzz, advancing its wiper forward rapidly until the wiper reaches the normal position at which ON. 2 opens the circuit and stops the stepping switch in its off position. In the process of advancing to the normal position, the stepping switch wiper passes over a few terminals 212 after B24 which momentarily closes a circuit through ON. 2, 17LS, 16LS, and relay 20CR. 20CR being energized closes contacts ZOCR which bypasses ON. 2, the stepping switch, and 17LS, and holds 20CR energized even after the stepping switch wipers move off the contacts which originally energized ZOCR. At the same time, this same 200R contact closes a circuit via 17LS limit switch to energize 21CR relay. 21CR relay contacts energize valve solenoid 125 which causes the hob-spindle bearings to be unclamped, and 20CR re lay contacts energize the hob-shift valve solenoid 121 which causes air to be exhausted from the rod end of the power cylinder and causes pressure air to be admitted to the large end of the cylinder through line 113. 20CR relay contacts also close in the circuit to the MINOR stepping switch coil circuit which causes the MINOR step wiper 213 to advance from its off position to the position Al and at the same time, the minor off-normal contacts MINOR O.N. close.

The power-cylinder piston starts to move and this move ment withdraws rod 112 and allows 17LS to open. 20CR relay contacts still hold 20CR energized, and the piston completes its movement, advancing the hob-spindle bearing .030 in., and at the end of its stroke, 16LS is operated which opens the circuit to 200R, which then opens its contacts. The MINOR switch coil releases its armature, and the valve solenoid 121 returns under its spring bias to reverse the directions of pressure and airflow to the power cylinder 80. MINOR O.N. contacts are still closed so that relay 21CR remains energized to hold the hob-spindle bearings unclamped. The power-cylinder piston starts its reset strokeand 16LS closes. 20CR contact and 17LS are both open, so that closing of 16LS only permits ZtiCR relay coil to be later energized. The piston completes its movement and rod 112 operates to close 17LS. This completes a circuit through MINOR O.N. to 17LS to 1618 to 20CR which closes the bypass circuit through 20CR contacts. 20CR being again energized causes the MINOR step wiper 213 to advance to position A2, and the valve solenoid 121 again to become energized to cause a second stroke of the power cylinder to advance the spindle hearings to .060 in. from its initial point. The reset stroke of the power cylinder acts the same as it did on the previous reset stroke, and the power cylinder starts on its third operating stroke. When 20CR is energized for this third operating stroke, the MINOR switch coil is energized and the MINOR step wiper advances to the position A3. 2TS tap switch is already set to the third (-A3) position for a 3 multiplier and this causes the MINOR reset coil to be energized.

The power cylinder completes its third stroke to advance the hob-spindle bearings .090 in. from its initial position and opens 16LS which de-energizes 20CR. 20CR contacts open, de-energizing the MINOR coil, and since the MINOR reset coil is energized, the wiper is returned to its off position. The MINOR switch wiper moving off the A3 position de-energizes the MINOR reset coiland upon reaching the off position, opens the MINOR O.N. off-normal contacts. This all occurs so rapidly that when the power-cylinder piston completes its third reset stroke and closes 17LS, the circuit previously closed via MINOR O.N. is open and no further shifting occurs. MINOR O.N. being opened also de-cnergizes 21CR which de-energizes valve solenoid 125 which returns to its normal position. High-pressure hydraulic fluid then operates to clamp the hob-spindle bearings. This entire three-stroke hob-shift cycle occurs in approximately one second. i

Each time valve solenoid 125 is energized to unclamp the hob-spindle bearings to permit shifting, a counter coil 204 COUNT 2 is also energized. This causes a predetermining counter 215 to record the number of times that the hob is shifted, and when the hob has been shifted a predetermined number of times, the counter trips a contact 216 which opens the starting circuit for the hobber. (The counter 215, in some respects, duplicates the function of the system of stops previously described and may be eliminated if visual recording is not desired.) At the same time, a signal light 217 indicates that the hob is worn out and must be changed. The operator must then remove the worn hob and replace it with a sharp one and then return the hob-spindle hearings to their starting position. To return the spindle bearings to their starting point, the operator turns the handle 104 to the opposite direction from that used for shifting, and then turns the HOB: RETURN-CLAMP-UNCLAMP selector switch 2% to the RETURN position. This closes the circuit to relay 21CR which causes the hob-spindle bearing to be unclamped, closes the circuit to 230R via 17LS and 16LS, and also opens the circuit to the MINOR stepping switch coil to prevent counting strokes or shifts. -The hob-shift power cylinder 81) then continuously recycles to rapidly move the hob-spindle bearings to the beginning point which is established by the stop nuts 136 mounted on range rod 138. The hob-spindle hearing has a short stub 135 projecting from its upper quarter which acts cooperatively with the stop nuts to limit the extent of movement. When this stub contacts the range-rod stop nuts, the power cylinder stalls with pressure still applied to the large end of the piston and all of the drive train will be under strain. It is now necessary that the operator return handle 164 to the normal shifting direction, but due to the strain on the drive train, this will not be possible until the air pressure is removed from the large end of the piston. To accomplish this, the operator turns the HOB: RETURN-CLAMP-UNCLAMP selector switch 200 to UNCLAMP which removes power from 200R relay which in turn de-energizes solenoid 121 of valve 119. Air pressure thereby removed from the power cylinder relieves the strain against the handle 104 and allows it to be turned to the direction required to shift the hob spindle.

When the handle 104 is turned in the proper direction, the HOB: RETURN-CLAMP-UNCLAMP switch 260 is turned to CLAMP. This causes the hob-spindle hearings to be clamped and places all circuits ready to shift. The operator then turns his HOB SHIFT: MANUAL-AUTO pushbutton selector switch 201 to MANUAL and momentarily depresses the pushbutton. This causes 20CR to be energized and causes the hob-spindle bearings to be shifted. This effectively removes all backlash from the drive train, and the operator then turns his selector switch 201 back to AUTO for the normal automatic operation.

From the foregoing it will be seen that a novel hobshifting mechanism has become available that is not only unique in its action but exceptionally versatile in its ability to perform the important hob shifting function under a wide range of hobbing conditions. The mechanism disclosed is fully protected against damage by chips, coolants, or other abuse by being self-contained and fully enclosed within the swivel-head casting. The head carries no bulky units or mechanisms likely to interfere with an operators close observation as to whether the machine is setup for rightor for left-hand helical-gear hobbing or whether it is setup for cutting with or against the feed. The mechanism is readily adaptable to effect the hob shifting in noncumulative precision increments over the whole range, upon obtaining the initial hob zero position with the micrometer collar 60:: on the hob spindle and with the selection and installation of proper pick-01f gears 8'7, 88 and 8? of which a wide range is available. Provision is also made for incremental shifting in either direction and likewise provision is made for quickly returning the hob by power to its initial starting position.

When set for automatic operation the shifting is completely automatic, the shifts occurring without attention on the part of the operator after each stack of gears or after a given number of stacks have been hobbed. The device functions automatically to shut down the machine when the preset complement of shifts has been made and gives an appropriate signal should the operator fail to note or be unaware that it is time to change the hob.

During the hobbing periods between shifts, the hobspindle bearings are securely clamped; the machine may not be operated with the bearings unclamped. Should there be a failure in the air pressure that motivates the hydraulic clamping system of the instant embodiment, pressure switch PPS illustrated schematically in FIGS. 9 and 10A opens the entire control circuit and the machine stops. The entire system of controls is pushbutton and knob operated, all appropriated identified as to function, and requires a minimum of effort and skill on an operators part to manipulate.

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:

What is claimed is:

1. The combination of a translatable slide member, a hob spindle, means mounting said hob spindle for rotary and axial movement relative to the slide member, power-operated clamping means for said spindle-mounting means normally operative to retain the spindlemounting means in a preselected axially adjusted position, first power means for actuating said clamping means, second power means adapted when actuated to effect axial movement of said mounting means a preselected unit distance, selectively adjustable means to vary the preselected unit distance, independently operable control means for each of said first and second power means, and a coordinating system of controls responsive to translation of said slide member and operative normally to effect operation of said control means through one cycle including unclamping of said spindle-mounting means, then axial movement thereof, and then a reclamping of the spindle-mounting means to the slide member, and additional selectively operable means associated with said system of controls for causing said system of controls to repeat the axial movement portion of the cycle two or more times to thereby obtain two or more preselected unit distances of movement of the mounting means before reclamping of the spindle-mounting means.

2. In a hobbing machine having a rotary hob spindle adapted to support a hob and a rotary work spindle adapted to support a workpiece to be operated upon by the lhOb and means for rotating the hob spindle and the work spindle in timed relation and simultaneously effecting relative movement between the spindles in the direction of the teeth to be cut on the workpiece, the combination of means mounting the :hob spindle for axial displacement, clamp means normally operative to maintain the hob spindle in a preselected axially displaced position during the performance of a hobbing operation, power means operatively connected with said hob spindle adapted when actuated to effect axial displacement of said hob spindle a unit distance, said power means comprising an adjustable-stroke power cylinder having a movable piston and means comprising an adjustable abutment member positioned in;the path ofv movement of the piston for defining one end of the stroke of the piston whereby selectively and directly to control the unit distance said hob spindle is displaced on each operating cycle, and control means responsive to the said relative movement between the spindles for rendering said clamp means inoperative at a selected point in the said relative movement between the spindles and thereafter said power means operative to effect axial displacement of the hob spindle said unit distance.

3. The combination of claim 2 characterized by the inclusion of ratio varying means in the connections between the power cylinder and the displaceable hob spindle for modifying the effect of a preselected limited movement of the piston of the power cylinder on the extent of hob spindle displacement to obtain fractional units of axial displacement.

4. The combination of claim 2 in which said power means operatively connected with the hob spindle for effecting axial displacement thereof includes a one-wayoperating ratchet means connected to be driven from the piston of said power cylinder, and means selectively operable to render said ratchet means operable to effect hob-spindle displacement in either direction on a power stroke of the cylinder so that on repeated cycles of operation of the said clamp means and the said hob-spindle displacing means the hob spindle is displaced in successive increments in the selected direction, and means op erative on the displacement of the hob spindle through a pre-selected distance for rendering said power cylinder ineffective.

5. In a hobbing machine having a reciprocable slide member adapted to carry a rotatable hob spindle the combination of bearing means displaceable in the direction of the axis of the hob spindle for journalling the hob spindle to the slide member, bearing-clamping means housed in the slide member operative normally to clamp the hob-spindle bearing means in a preselected axially displaced position, power means also housed within the slide member and operatively connected with said bearing means and adapted when actuated to displace said bearing means from the said preselected position, means responsive to the reciprocatory movement of the slide member for counting the strokes thereof, and means operative when the slide strokes reach a selected count to effect cyclic actuation of said clamp means in a bearing unclamping direction and thereafter to effect actuation of said power means to effect the displacement of said bearing means, and means operative on the conclusion of the bearing displacement movement to again effect actuation of the bearing clamp means in a bearing clamping direction.

6. The combination set forth in claim 5 characterized by the inclusion in the combination of additional counting means responsive to a displacement movement of the bearing means for recording the bearing displacement cycles and operative when a predetermining count is reached to render said power means ineffective to produce further displacement of the said bearing means.

7. In a bobbing machine having a reciprocaible tool slide adapted to support a rotatable hob spindle in operative relation with a work blank, the combination of means mounting the hob spindle to the tool slide for displacement in the direction of its axis of rotation comprising shi-ftable hob-spindle bearing means, power means within the tool slide and connected with said bearing means adapted when actuated to shift said bearing means predetermined unit increments of shift whereby to effect axial displacement of the hob spindle a corresponding distance, control means for said power means responsive to the reciprocatory movements of the tool slide for rendering said power means effective, said control means including a first counting means and connections for rendering the power means ineffective until a preselected number of tool-slide reciprocations have. been. made, and a second counting means and connections operative to render said power means ineffective when said bearing means has been shifted a preselected number of" unit increments.

8. The combination of claim 7 including shift-multiplying means operatively connected with said control means for the power means to selectively render the power means effective to shift the spindle-bearing means two or more of said unit increments in any one bearingshiftin-g cycle.

9. The combination of claim 7 in which means are also provided electively to vary the increment of bearing shift imparted to the bearing means by the said power means to a selected fraction of the normal whole unit increment.

10. The combination of claim 7 including means for varying the increment of bearing shift imparted by said power means to a selected fraction of the normally-available whole-unit of shift and including a shift-multiplying means operatively connected with the said control means for the power means to selectively render the said power means effective to shift the spindle-bearing means two or more of said fractional increments in any one bearingshifting cycle.

11. The combination of a reciprocable slide member adapted to support a rotary hob-carrying spindle, bearing means mounting the rotary spindle for axial movement relative to said slide member, a rack section mounted to said bearing means, a pinion journalled for rotation in said slide member and meshing with said rack section effective when rotated to impart axial movement to said bearing means and to the spindle supported thereby, a power cylinder mounted fixedly relative to said slide enclosing a reciprocably mounted piston and supporting an externally adjustable calibrated stop means arranged to coact with said power cylinder to limit the stroke of the power cylinder piston to a selected predetermined distance, operative connections including a ratchet mechanism between said power cylinder piston and said pinion for actuating said pinion upon the power stroke of said power cylinder piston, said stop means being so calibrated that adjustment of said stop means to each setting produces a different predetermined integer displacement of said ratchet mechanism, means for reciprocating said slide member to cause the hob to perform the hobbing operation, means responsive to slide movement for initiating a power stroke of said power cylinder piston and thence a predetermined displacement of said ratchet mechanism to effect a predetermined precise axial movement of the bearing means, and quick change gears in the connections between the power cylinder piston and said pinion selectively adjustable to modify the effect of a unit stroke of the power cylinder piston on the axial movement imparted to the bearing means to a precise predetermined extent for any given setting of said stop means, whereby different predetermined precise axial movements of the spindle may be produced.

12. The combination including a reciprocable slide member, a rotatable hob-carrying spindle, bearing means supporting said spindle for rotation about its axis, of rotation, bearing displacement means mounted upon said slide member operable to displace said bearing means and the spindle supported thereby axially of the spindle relative to said slide member, a reversible unidirectional intermittent motion device operatively connected to said bearing displacement means and effective therethrough to produce precise, predetermined successive displacements of said spindle in a given direction, cyclically operable actuator means, stop means selectively adjustable to determine the desired distance through which said actuator means is operable in a given cycle to produce a predetermined precise integer displacement of said in termittent motion device, said actuator means being auto: matically operable to displace said intermittent motion device a predetermined precise amount according to the setting of said stop means, and quick change gears interposed between said intermittent motion device and said bearing displacement means, said quick change gears being selectively adjustable to different ratios to achieve desired fractional modification of the precise predetermined displacements of said spindle effected by said actuator means at a given setting of said stop means, where- 'by said spindle may be advanced axially by successive substantially identical precisely predetermined amounts.

13. A device as described in claim 12, including dis- 1 6 placement multiplying means selectively operable to determine the number of successive uninterrupted operating cycles for said actuator means.

References Cited in the file of this patent UNITED STATES PATENTS 1,618,668 Mikaelson Feb. 22, 1927 2,484,856 Purvin Oct. 18, 1949 2,516,750 Brower July 25, 1950 2,690,701 Zirnmermann et al. Oct. 5, 1950 2,697,382 Petrie Dec. 21, 1954 2,714,838 Scone Aug. 9, 1955 2,897,728 Vasselli Aug. 4, 1959

Claims

1. THE COMBINATION OF A TRANSLATABLE SLIDE MEMBER, A HOB SPINDLE, MEANS MOUNTING SAID HOB SPINDLE FOR ROTARY AND AXIAL MOVEMENT RELATIVE TO THE SLIDE MEMBER, POWER-OPERATED CLAMPING MEANS FOR SAID SPINDLE-MOUNT ING MEANS NORMALLY OPERATIVE TO RETAIN THE SPINDLEMOUNTING MEANS IN A PRESELECTED AXIALLY ADJUSTED POSITION FIRST POWER MEANS FOR ACTUATING SAID CLAMPING MEANS, SECOND POWER MEANS ADAPTED WHEN ACTUATED TO EFFECT AXIAL MOVEMENT OF SAID MOUNTED MEANS A PRESELECTED UNIT DISTANCE, SELECTIVELY ADJUSTABLE MEANS TO VARY THE PRESELECTED UNIT DISTANCE, INDEPENDENTLY OPERABLE CONTROL MEANS FOR EACH OF SAID FIRST AND SECOND POWER MEANS, AND A COORDINATING SYSTEM OF CONTROLS RESPONSIVE TO TRANSLATION OF SIAD SLIDE MEMBER AND OPERATIVE NORMALLY TO EFFECT OPERATION OF SAID CONTROL MEANS THROUGH ONE CYCLE INCLUDING UNCLAMPING OF SAID SPINDLE-MOUNTING MEANS, THEN AXIAL MOVEMENT THEREOF, AND THEN A RECLAMPING OF THE SPINDLE-MOUNTING MEANS TO THE SLIDE MEMBER, AND ADDITIONAL SELECTIVELY OPERABLE MEANS ASSOCIATED WITH SAID SYSTEM OF CONTROLS FOR CAUSING SAID SYSTEM OF CONTROLS TO REPEAT THE AXIAL MOVEMENT PORTION OF THE CYCLE TWO OR MORE TIMES TO THEREBY OBTAIN TWO OR MORE PRESELECTED UNIT DISTANCES OF MOVEMENT OF THE MOUNTING MEANS BEFOR RECLAMPING OF THE SPINDLE-MOUNTING MEANS.