US3816995A

US3816995A - End mill grinder

Info

Publication number: US3816995A
Application number: US00267437A
Authority: US
Inventors: E Borchert
Original assignee: OMARK WINSLOW CO
Current assignee: OMARK WINSLOW AEROSPACE TOOL CO US; OMARK WINSLOW CO
Priority date: 1972-06-29
Filing date: 1972-06-29
Publication date: 1974-06-18
Anticipated expiration: 1991-06-18

Abstract

A production type machine is designed to grind end mills at a high rate while maintaining rigid standards of accuracy of dimension. Adjustments are quickly and easily made for different profiles of the ground face, the number of flutes on the mill, the size of the end mill, and so on. The machine will selectively grind either a curved cutter face, or an angular primarysecondary relief form thereon. Operation of the apparatus is fully automatic once the grind cycle is started, after necessary adjustments are made, as only the loading and unloading operations are manually performed.

Description

United States Patent 1191 Borchert, III June 18, 1974 END MILL GRINDER 1 Primary Examiner-Al Lawrence Smith [75] Inventor. Ernst Borchert, III, Pomona, Calif. Assistant Examiner NicholaS P. Godici s gne -Winslow Aerospace Tool Attorney, Agent, or Firm-Wolfe, Hubbard, Leydig,

Co., Portland, Oreg. Voit & Osann, Ltd. [22] Filed: June 29, 1972 21 Appl. No.: 267,437 [57] TM A production type machine is designed to grind end mills at a high rate while maintaining rigid standards [52] US. Cl 51/96, 51/225, 51/234 of accuracy of dimension Adjustments are quickly [51] Int. Cl B241) 3/06, B24b 7/02, B24b 9/00 and easily made f different profiles of the ground [58] new of

Search

51,96 124 219 face, the number of flutes on the mill, the size of the 5 1/234 16578 end mill, and so on. The machine will selectively grind either a curved cutter face, or an angularprimary- [56] References C'ted secondary relief form thereon. Operation of the appa- UNITED STATES PATENTS ratus is fully automatic once the grind cycle is started, 2,853,994 9/1958 Ronches 125/11 AT after necessary adjustments are made, as y the 3,318,050 5/1967 Leckington... 5l/96 loading and unloading operations are manually per- 3,623,277 ll/l97l Bottcher et a 5l/l24 R X formed, 3,680,262 8/!972 Aydelott et al. 51/96 3.719.459 3/1973 Southland 51/96 7 Clams, 40 Drawmg Flgures PATENTEflJunam 3.818995 sum 01 or 12 PATENTEDmw an sum ion or 12 SHEEI 05 0F 12 PATENTEDJun w an mmmmmm 3816395 sum can; 12

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10 or 12 PATENTEDJuu 18 I914 1 END MILL GRINDER BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to automatic grinding machines for end mills, and particularly to improvements in a grinding machine, such as disclosed in US. application Ser. No. 140,972, of John Robert Southland, converting this machine to offer two optional capabilities, first, an arcuate relief grind, and second, an angular primary and secondary relief grind. The arcuate relief grind, made by the machine of US. application Ser. No. 140,972, now U.S. Pat. No. 3,719,459, has certain advantages, but the angular, primary/secondary grind retains at the present time a preponderance of adherents. The general purpose of the invention is therefore to furnish the original grinding machine referred to hereinabove with a novel alter- 2 natively selective cycle of movements, differing from that of application Ser. No. 140,972, now US. Pat. No. 3,719,459, and with certain additional features, whereby a grind of the angular, primary/secondary relief type may be produced.

2. Summary The grinding machine of the invention includes a suitable frame, with a powered grinding wheel thereon. A holder is provided for the end mill, and the holder is mounted on a movable workhead. The workhead is mounted on the machine frame for movements in either of two selective basic sequences, differing both in kind and in sequence, to grind the end mill to either a continually curved form, or an angular form consisting of two angularly related primary and secondary faces. For the first grind, the end mill is advanced toward the grinding wheel, then swung relative to and along the grinding wheel on a predetermined axis, to obtain the desired arcuate shape on the end mill cutter, then retracted and swung back to its initial position and thereafter indexed to bring the next end mill cutter face into position, whereupon the cycle is repeated. The present invention is selectively operable to carry out a modified cycle, according to which the end mill is fed straight into and against the grinding wheel, while disposed at a selected secondary relief angle to the direction line of feed. A plunge grind at the secondary relief angle is thus made. The end mill is then retracted, then swung to the selected primary relief angle, and then fed back in, at this primary angle, to effect a second plunge grind, this time at the selected primary angle. The end mill is then retracted and thereafter rotated on its axis to index for the next cutter face. The invention includes adjustable stops and coacting arrangements for positioning the end mill at the selected primary and secondary angles for the specific grind desired.

BRIEF DESCRIPTION OF THE DRAWINGS Reference is now made to the following description and to the annexed drawings, in which:

FIG. 1 is a front and side perspective view of an end mill grinder embodying the present invention;

FIG. 2 is a fragmentary perspective of the end of an end mill blank;

FIG. 3 is a fragmentary perspective showing the relative position of the blank and the grinding wheel during start of the first face grind on the blank;

FIGS. 4 and 5 are diagrammatic views showing different shapes of surfaces ground on an endmill, only one longitudinal half of the end mill being shown;

FIGS. 6A to 6F are successive diagrammatic views showing the relative movement of the end mill during a cycle of operations for grinding at one flute to produce a known arcuate grind such as shown in FIG. 4;

FIGS. 6G to 6N are successive diagrammatic views showing a different operation, to produce the primary, secondary grind of FIG. 5;

FIGS. 7A, 7B and 7C are three side elevations of the discs comprising the flute selector means illustrating different relative positions of the two discs, according to the number of flutes on the end mill being ground;

FIG. 8 is a fragmentary vertical longitudinal section approximately on line 8-8 of FIG. 1 showing in side elevation the workhead for holding an end mill, the section passing through both the swing axis for the workhead and the grinding wheel axis;

FIG. 9 is a front and top perspective, with enclosure removed, of the workhead and mounting means therefor viewed from the left in FIG. 8, the lower portion being in section;

FIG. 10 is a vertical median section through the workhead on line 10l0 of FIG. 9;

FIG. 10a is an enlarged fragment of FIG. 10 with the tool holder removed;

FIG. 11 is a fragmentary combined elevation and section showing the mounting means for the end mill locator;

FIG. 12 is a vertical transverse section taken substantially on line 12-12 of FIG. 10;

FIG. 13 is a fragmentary horizontal section on line l313 of FIG. 12 showing the drive from the hydraulic motor to the ring gear of the workhead;

FIG. 14 is a fragmentary vertical section substantially on line l4l4 of FIG. 13 showing the output shaft from the hydraulic motor for the workhead;

FIG. 15 is a fragmentary horizontal section through the mounting means for the workhead taken substan tially on line 15-15 of FIG. 9 or FIG. 12;

FIG. 16 is a fragmentary vertical section through the flute indexing mechanism taken substantially on line l6-16 of FIG. 9, FIG. 10 or FIG. 17;

FIG. 17 is a fragmentary vertical section taken on line l717 of FIG. 9 or FIG. 16;

FIG. 18 is a fragmentary perspective of the means for moving the workhead;

FIG. 19 is a longitudinal median section through the tool holder;

FIG. 20 is a schematic of the electric circuit;

FIGS. 21A and 21B taken together comprise a schematic drawing showing the air-hydraulic control system and the component parts operated and controlled thereby, the pneumatic logic units being shown symbol ically according to the legend on the figures;

FIG. 22 is an operating diagram showing the movements of the various parts during a sub-cycle grinding of a single face on the end mill;

FIG. 23 is a diagram similar to .FIG. 22 but showing the events when the machine produces an angular primary/secondary type grind.

DESCRIPTION OF A PREFERRED EMBODIMENT The end mill grinder has a frame F on which is mounted a workhead H in which the tool to be ground is placed. To effect the desired movement of this workhead and the tool therein, support and actuating means S are provided on the frame. To effect automatic control of the duration and sequence of the various motions of the machine required to successively grind cutter faces on the tool, one for each flute on the end mill, there is provided an air-hydraulic control system which includes pneumatic logic units interconnected appropriately for the functions to be carried out. Such a system is shown schematically in FIGS. 21A and 21B. In each of these figures are pneumatic lines ending at terminals such as 1, 2, 3, and the system is complete when the like terminals of FIGS. 21A and 21B, such as 1,1, 2,2, 3,3, etc. are connected together. The pneumatic lines of these figures are also identified by the numerals of the terminals to which they are connected. In FIG. 21A, hydraulic lines, which carry the hydraulic fluid from the various hydraulic work cylinder and piston assemblies are distinguished by heavy lines with arrows thereon designating flow directions, while lines without arrows are pneumatic control lines and these are in circuit with the pneumatic logic circuit (FIG. 21B).

GENERAL OPERATION Assume first that a curved face grind (FIG. 3) is to be produced. In FIG. 2 is shown a fragment of a four fluted end mill blank B which has an end face to be sharpened or ground, in this case with a corresponding number of arcuate end cutting faces 30a. Grinding is accomplished by bringing face 30 on the ene mill into contact with the periphery of a grinding wheel 31 normally thereto (FIG. 6B), and with its longitudinal axis 58 substantially in the plane of the top surface of the grinding wheel, so that the peripheral grinding surface will be tangent to only the lower half of the end of the blank B. As indicated in FIGS. 6A and 6B, the end mill approaches the grinding wheel with its axis 58 parallel to but laterally offset from a plane 47 that is at right angles to the grinding wheel, and that passes through the grinding wheel axis. The end mill is then swung in a horizontal plane on an axis 32 which is in the plane 47, and is parallel to the grinding wheel axis, so as to move to the position of FIG. 6C. Thereby is produced arcuate end face 30a, sweeping away from the beginning radial line of the grind on a downward or inward arcuate curve, and producing a radial cutting edge or lip e for the next succeeding face 30a to be ground. The end mill, after termination of such a grind by swinging movement about axis 32, is shown in FIG. 3 (corresponding to FIG. 6C), with face 30a ground, and a radial lip e formed. The end mill is indexed, by rotation through 90, for example, for a four flute end mill, following each face grind, so there will be one cutting edge or lip e and face 30a for each flute on the end mill. The shape in profile of the ground face 30a (to provide clearance) may be smoothly curved, as shown in FIG. 4. By certain changes, under selective control, the face may be ground to have instead a substantially flat, angular, primary relief area 3012 adjacent the lip e, at a primary relief angle Q5, and therebeyond a second steeper area 300 disposed at a secondary relief angle 9 (FIG.

5). This latter grind is known as a primary/secondary relief grind.

FIGS. 6A-6F show the sequence of movements to accomplish the arcuate grinding face form of FIGS. 3 and 4.

First, the end mill blank B is hand loaded into the workhead and properly positioned, as shown schematically in FIG. 6A. Next, the end mill feeds in endwise toward the grinding wheel to engage the wheel as shown in FIG. 68 after which one face grind forming a cutting lip e is supplied by swinging the end mill as shown in FIG. 6C about the swing axis 32. The swing axis 32 is vertical and parallel to the axis 35 of the grinding wheel. It is also offset laterally from axis 58, in a vertical plane 47 parallel with axis 58 and substantially through grinding wheel axis 35.

After the grinding pass, the end mill is retracted FIG. 6D), and it then swings back about the swing axis to its position at FIG. 6E, following which the end mill blank is indexed as at FIG. 6F by rotating is around its longitudinal axis 58 to bring it into position for grinding another arcuate face 30a and lip e on the end face 30. The grind sub-cycle shown in FIG. 22 for the various positions of FIGS. 6A to 6F is then repeated according to the number of flutes on the mill with an indexing rotation taking place between each two grinding subcycles, except that after the last grind, the grind cycle is terminated.

GRINDING WHEEL ASSEMBLY The grinding wheel 31 is rotatably mounted on the frame by spindle 33 joumalled in bearing housing 34. SPINDLE 33 mounts the grinding wheel to turn about vertical axis 35 and is driven from motor 36 by one or more belts 37 which pass from the output shaft of the motor to a drive pulley mounted on an extension of spindle 33. Spindle housing 34 and motor 36 are mounted on adjustable block 38 on frame F.

WORKHEAD workhead H has upper and lower trunnions shown at 45 in FIG. 10 and 46 in FIG. 8, respectively. These trunnions are mounted in the upper and lower arms 45a and 45b of carriage which is in the form of a yoke, and they establish the vertical swing axis 32 about which the workhead and the end mill swing. Axis 32 is parallel to grind wheel axis 35 and the two axes preferably lie in or close to a common plane indicated at 47 in FIGS. 4 and 5.

To adapt the workhead to hold end mills of different dimensions, the end mill blank is placed in a removable tool holder 48 illustrated in detail in FIG. 19. The external housing of the tool holder remains constant in size in order that the holder may be held firmly in the workhead, but the holder has an internal sleeve 49 which engages collet 50 that is replaceable in order to provide a collet of the proper size, to hold end mills of different diameters and lengths. The inner sleeve 49 is springbiased by a spring 49a to urge collet 50 to the left in FIG. 19 and into a closed or gripping position, but the end mill can be released by grasping handles 51 and manually bringing them together to relieve the pressure of spring 49a and sleeve 49 on collet 50.

Tool holder 48 is held within the workhead by a chuck comprising a pair of spaced bearing

sleeves

53 and 54 which receive the tool holder with a snug-sliding fit. Between sleeves S3 and 54 is collet 55 which can be closed by movement of an hydraulically actuated piston 56 (to the right in FIG. to firmly grip the exterior of tool holder 48.

As may be seen better in FIG. 10A, hydraulic fluid under pressure is admitted to the lefthand face of piston 56 through fluid passage 56.1 in the head and an annular distribution passage 56.2 in the periphery of sleeve 54. The force exerted by the fluid moves piston 56 to the right against spring 56.3 which normally urges the piston to the position of FIG. 10 in which the collet is open. Movement of the collet to the right closes the collet, by engagement with inclined surface 56.4, to grip tool holder 48.

When collet 55 is released, the tool holder isfree to move axially or rotationally about longitudinal axis 58, which is also the longitudinal axis of blank B when mounted in holder 48. Workhead H establishes axis 58 at a known position with respect to grind wheel 31.

The location of longitudinal axis 58 is indicated in FIGS. 4 and 5 from which it will be noticed that this axis is laterally offset from and is parallel to plane 47 which passes through swing axis 32 and wheel axis 35. The spacing or offset between plane 47 and axis 58 is variable by means to be described. The magnitude of this offset affects the shape of the ground surface 30a of the end mill and consequently is closely controlled. Typically, the magnitude of the offset varies between 0 and 0.200 inches.

The Workhead is divided into front and rear halves H, and H respectively, more or less along a vertical transverse plane 60 illustrated in FIG. 10. The two halves are relatively rotatable to one another on an axis 62, bur firmly clamped together by an annular clamping band 61 which is provided with screw 61a by which it can be tightened to firmly hold the two halves of the head in adjusted positions. It will be seen by reference to FIG. 12 that the geometric center 62 of the two halves of Workhead H is above axis 58, that is, it is eccentric with respect to axis 58. Consequently, when the front half H,, or face plate, in which the tool holder 48 is held, is rotated about the geometric center 62 with respect to the rear half H of the Workhead, the tool holder 48 moves in a short horizontal arc and thereby the longitudinal axis 58 of the tool can be moved toward or away from plane 47 in order to establish the desired magnitude of the offset between plane 47 and axis 58.

The amount of this offset is indicated by a graduated scale 63 on the front of the Workhead (FIG. 9) and a pivoted index arm 64 actuated by link 65 connected to the arm and to the front half of the Workhead. Adjustment is accomplished with clamping band 61 released by backing off screw 61a.

The rear half H of the workhead carries the

trunnions

45 and 46 and consequently is fixed relative to v the aforementioned Workhead carriage or yoke 120,

except for rotation about vertical axis 32.

Recessed and rotatable in the forward face of the rear half H of the Workhead is ring gear 66 (FIGS. 10 and 12). The periphery of the ring gear is smooth and provides a bearing surface for the gear as it turns. It is provided with internal teeth which, as shown in FIG. 12, mesh with three

spur gears

67, 68 and 78. The lower one of these spur gears 67 comprises teeth out on the periphery of bearing sleeve 54 whereby rotation of the ring gear turns bearing sleeve 54 and tool holder 48 when collet 55 is tightened since the collet frictionally 6. locks the tool holder to the front bearing sleeve 53 and the two

sleeves

53 and 54 are connected by pins (not shown) to transmit torque from one sleeve to the other.

Ring gear 66 is rotated by a second spur gear 68 on a short horizontally extending shaft. 70 mounted in suitable bearings in the rear half of head H. Shaft 70, shown in FIG. 13, also carries a second gear 71 which meshes with worm gear 73 driven by shaft 74 from the output shaft of hydraulic motor 75. Hydraulic motor 75 may be of any suitable design, a gear or lobe type positive displacement motor having a rotary output member being preferred.

FIG. 12 shows the Workhead substantially as it would appear if the front half of the head were removed. From this view, it is apparent that as ring gear 66 rotates, for example in a clockwise direction, gear 67 likewise rotates clockwise about axis 58. This rotates tool holder 48 with the blank B to index the blank by the angle between successive flutes. The sequence and control of this movement will be discussed later.

As illustrated in both FIGS. 10 and 12, there also meshes with ring gear 66 a third spur gear 78which is driven by movement of the ring gear. This gear is an input to the flute selector mechanism which is adjusted manually by the machine operator in order to index automatically the tool as required according to the number of flutes on the blank being ground. The flute selector mechanism is generally indicated at 80 and is shown in detail in FIGS. 16 and 17.

Spur gear 78 is attached to shaft 81 (FIG. 10) which is rotatably mounted in the rear half of Workhead H and which carries at its rear end bevel gear 82. Bevel gear 82 meshes with a second bevel gear 83 mounted on shaft 84. Shaft 84 is mounted in suitable bearings, as shown in FIG. 16, in a housing constituting part of the Workhead structure. Shaft 84 extends forwardly beyond the housing and carries at the outer exposed end knob 85 which is preferably provided with an index mark 86 as shown in FIG. 9.

Mounted on shaft 84 to rotate therewith is a first selector disc 87. Adjacent disc 87 is a second selector disc 88 mounted coaxially of disc 87 on a hub89 which surrounds the extension of shaft 84 and carries on its outer free knob 90. Knob 90 carries indicia which cooperate with index 86 to indicate to the machine operator the relative positions of the two

discs

87 and 88.

One of the discs, typically disc 87, carries a fixed pin 91 which can be located in aselected one of a plurality of openings 93 in disc 88. In order to locate pin 91 in a selected opening 93, disc 88 is mounted for axial slid ing movement on shaft 84; but it is biased by spring 94 to the position shown in engagement with disc 87, thereby keeping pin 91 in a selected opening 93. To change the location of the hole in which pin 91 is placed, the operator can grasp knob 90, pull it outwardly on shaft 84 thereby compressing spring 94 and freeing disc 88, and turning the knob to bring another hole into registration with pin 91. Release of knob 90 then allows the pin to enter the newly selected hole under the biasing action of spring 94.

The relationship to eachother of the two

discs

87 and 88 of the flute selector mechanism is shown schematically in FIGS. 7A to 7C which illustrate three different positions of the discs.

Since end mills are nonnally provided with two, three, or four flutes, provision has been made in the preferred embodiment for only these numbers of flutes, but it will be understood that in the broad sense the invention is not so specifically limited. Referring now to FIGS. 7A to 7C, it will be noticed that disc 87 has around its periphery a plurality of notches 87a. Likewise, disc 88 has around its periphery a series of notches 88a. These notches in the peripheries of the two discs are so located that various combinations of the notches are brought into registration with each other by relative rotation of the discs with respect to each other. Two notches in registration form a gate.

For example, in FIG. 7A, two pairs of notches 87a and 88a, spaced 180 apart around the discs, are brought into registration when pin 91 is in the center one of the three holes 93 in disc 88. This is the condition existing when it is desired to index the tool for two flutes, it being necessary to rotate the tool 180 between contacts with the grinding wheel.

When the tool has three flutes, disc 88 is shifted to the position of FIG. 7B in which three pairs of notches 87a and 88a spaced 120 apart around the periphery of the discs are in registration, as shown.

In the case of a four-flute mill, the two discs can be rotated to the position in FIG. 7C in which four pairs of notches are in registration, as shown. The relative positions of the two discs are displayed to the operator by the cooperation of index 86 and markings on knob 90 which are shown schematically in FIGS. 7A, 7B, and 7C.

The object of this arrangement of the two selector discs is to present to a subsequently described indexing control pin 96 a number of gates in the form of peripheral indentations, equal to the number of end mill flutes and equally spaced around the periphery of the combined discs. Entry of the control pin into the peripheral gate results in delivery of a signal for the later mentioned control system (FIGS. 16, 17, 20 21A and 2113). The control system can be any capable of carrying out the necessary programmed sequence of machine operation, and a suitable alternative could be supplied readily by those skilled in the art. For simplification, therefore, the present control system is described generally but details of some unclaimed components, particularly the logic circuit, are left to illustration in drawings which can readily be understood by those skilled in the art.

In general, with the

disks

87 and 88 rotating during an indexing period, a pneumatic signal produced by the entry of control pin 96 into a peripheral gate provided by a pair of notches 87a and 88a in mutual registration conveys the information to the control system that the rotating tool B is now approaching a new position at which the machine is to perform again the grind subcycle of operation illustrated in FIGS. 6A to 6F. How ever, in order to terminate the grinding operation after one complete revolution of

discs

87 and 88, representing a complete revolution of tool B, one gate, for example, the one at the upper right portion of FIG. 7A, is made radially deeper than all others. Upon entry into the deeper gate, the greater radial inward movement of the control pin 96 conveys to the control system the additional information that all faces of the particular end mill blank in the machine have now been ground.

Control pin 96 is mounted on swinging link 98 which is pivotally connected to one end of spool 99 in hydraulic valve 100. Also connected to link 98 is bell crank 101 which is pivoted at 102 to a fixed portion of the frame. One arm is pivoted at 103 to spool 104 of pneumatic control valve 105 while the other arm of bell crank 101 is coupled to link 98 by pin 196 sliding in a slot in link 98 allowing relative movement between the pin and the link 98. Movement of pin 96 radially of

selector discs

87 and 88 causes bell crank 101 to swing about its fixed pivot 102 and thereby shifts spool 104 longitudinally of valve 105.

When indexing an end mill blank, shaft 84 and the

selector discs

87 and 88 turn in a counterclockwise direction viewed in FIG. 17. During this movement, control pin 96 rides against the circumference of one or both

discs

87 and 88, under a force applied as later described.

When one of the gates passes under index control pin 96, the control pin enters the gate and moves a short distance with the discs, link 98 moving toward the upper left in FIG. 17, thus shifting spool 99 of the valve 100 upward. This valve is a two-position valve and is in series with the supply of hydraulic fluid to motor 75. In the lower position, the valve is open and allows full flow of hydraulic fluid to the motor to accomplish indexing rotation of the end mill. In the upper position (full lines in FIG. 210), the valve 100 reduces the flow and decelerates motor 75 but does not shut off hydraulic fluid flow entirely. The motor 75, however, is stopped by a presently described locking pin 107. Motion of pin 96 is also transferred by link 98 to pin 106 which in turn acts through bell crank 101 to shift spool 104 of valve 105 between three later described positions to control flows of air in a suitable control system, such as shown schematically in FIG. 21A and 21B.

The final position of the end mill B after each indexing rotation is determined by lock pin 107 FIG. 21A) which is reciprocated toward and away from chuck sleeve 53 by pressure of air or hydraulic fluid on one of pistons 108 and 108a, moving within cylinder 109 on the workhead. Check sleeve 53 has around its periphery a plurality of notches 53a any one of which may be entered by locking pin 107 when aligned with the pin and the pin is pressed down. When pin 107 is in the raised or retracted position, it is out of the notches 53a and check sleeve 53 is free to turn under torque imparted to it from ring gear 66 driven by motor 75.

Locking pin notches 53a correspond in number and location to the gates provided by

discs

87 and 88. When control pin 96 is out of a gate and spool 104 is in its lowermost position (FIG. 17), valve 105 signals the control system to withdraw the plunger 107, which permits indexing of the end mill blank. In the proper position in the angular movement of the chuck, pin 107 is moved toward chuck sleeve 53 by air pressure applied to piston 108 and enters the appropriate notch 53a in the sleeve, as will be further described.

When pin 107 enters into a notch 53a, the hydraulic motor stops turning. Fluid supply to hydraulic motor 75 is reduced but not entirely shut off so that the motor urges the chuck against plunger 107 thus eliminating any backlash or play in the system and bringing the end mill blank accurately to the desired grind position.

The full indexing operation, following swing back of the head FIG. 615), is as follows;

Hydraulic pressure is applied at the end of swing back to the end of piston 1040 of valve spool 104 through valve W under control of the logic circuit pneumatic line identified by terminals 4 (FIGS. 21A and 21B). This pressure application, which initiates indexing, results from coaction of functions in the logic circuit of FIG. 21B owing to actuation of later described pneuamtic swing and feed end limit pneumatic switches V2 and V4 for the workhead (FlG. 21A) as the workhead returns to the position of FIG. 6E. Spool 104 then shifts to the right, to the full line position in FIG. 17, lifting pin 96 out of a gap in

discs

87, 88 by means of bell crank 101 pivoted at 102. At this time also constant system air pressure (from constant pressure source terminal 8) on piston 100a acts to shift spool 99 of valve 100 together with link or lever 98 and pin 96 to the right pin 96 moving a distance equivalent to about 15 of arc of the

discs

87 and 88. The air lines through

terminals

5 and 6 from the logic circuit are then open to atmosphere through valve 105 (FIG. 7), with the effect of conditioning or signalling the logic circuit to act through its line 7 to operate valve Hy to send hydraulic pressure fluid to the underside of piston 1080, thereby elevating locking pin 107 out of a notch 53a in chuck sleeve 53. At this time, with the valve spool 99 in the position of FIG. 17, held there by application of pressure fluid received from line 8, hydraulic fluid flows through valve 100 to hydraulic motor 75, rotating it, the chuck sleeve 53 and the end mill through an indexing interval.

The hydraulic pressure to piston 104a is, after a short delay, then shut off through operation of a timer in the logic circuit and the control circuit line 4 leading to valve W. The constant air pressure from line 8, under piston 104a then acts through valve spool 104 and bell crank 101 to cause pin 96 to bear against the periphery of

discs

87 and 88, awaiting the next gap; and when the next gap reaches the pin 96, which in this case is one of the shallow gaps, the pin is forced therein. The air pressure on the underside of the piston head 104a then coacts with the pin 96 engaged in the gap in the rotating disks to shift valve spool 104 to the left, to the intermediate position indicated in phantom lines in F 1G. 17, and to carry the pin 96 counterclockwise through about of arc.

At this time, the intermediate piston 1040 of spool 104 closes the port exhausting air from line 5 to atmosphere, and opens line 5 to pressure line 8, sending pressure to the logic circuit via line 5. This in turn acts through the logic circuit, line 7 and valve Hy to remove the hydraulic pressure from the underside of piston 108a. This allows the constant air pressure applied to the top side of piston 108 to push the locking pin 107 against the chuck sleeve 53.

The described motion of the pin 96 entered into a gap in the rotating disks has also carried the link 98 and the valve spool 99 toward the left, and the lower piston of spool 99 then nearly, but not quite, closes the flow passage for supplying the hydraulic motor, which then slows down to a low speed.

As the chuck sleeve notch 53a aligns with locking pin 107, said pin 107 enters therein, locking the motor from rotation, and completes the index sub-cycle.

As the locking pin 107 enters chuck sleeve notch 53a, piston 108 shifts downward in valve 109, applying pressure from line 8 to line 16, which is sent to the logic circuit and signals it to start the next series of operations to grind the next face on the end mill.

After all end mill faces have been ground, the next following indexing rotation of the

discs

87, 88, results in the pin 96 dropping into the deep gap therein, causing the spool 104 to move to an extreme upper position (not shown) with its piston 104a against stop 104a (FIG. 17). This connects open line 6 to pressure line 8 (as may be understood from FIG. 21A). The rise in pressure in line 6 acts in the logic circuit to cancel all further turning and feed motions, and controls the workhead via line 12 and valve U, and the hydraulic piston 53 and the elevating cylinder 133, respectively, to release the collet and rise to the: load position, completing the cycle.

SUPPORT AND ACT UATION OF WORKHEAD The means or mechanism S for supporting and moving the yoke 120 and workhead carried thereby, and ultimately tne end mill held by the workhead, over a predetermined path is disclosed in detail particularly in FIGS. 8, 9 and 18. It involves or produces a compound movement of the workhead which has three major components: a vertical bodily lift and fall of the workhead and means S as a whole; movement (F IG. 6B) of the yoke 120 and workhead about a vertical axis 127 for causing feed and retraction of the mill blank relative to the grinding wheel; and swing and swing-back (FIGS. 6C and 6B) of the workhead only with respect to the yoke 120 about vertical trunnion axis 32.

The yoke arms 46a and 46b of the aforementioned yoke 120 are vertically spaced, and contain at their ends, the bearings for the

trunnions

45 and 46, respectively, which establish the swing axis 32. As seen best in FlG. 12, lower arm 46a of yoke is mounted, about midway of its length, on the upper end of a vertical inner sleeve 121, which is mounted for vertical reciprocation and angular oscillation in an external hearing sleeve 122. Bearing sleeve 122 contains a series of straight rows of ball bearings between the inner and outer sleeves. Bearing sleeve 122 is mounted within collar 124 which may be attached to the machine frame F by bracket 125.

Within the concentric of inner sleeve 121 is vertically extending shaft 126 whose longitudinal axis 127, which becomes the pivot axis for the yoke 120, is parallel to but laterally offset from the trunnion axis 32 of the workhead. Shaft 126 extends above and below inner sleeve 121; and the inner sleeve in turn extends below the bearing sleeve.

The lower end of inner sleeve 12:1 rests upon a yoke 130 which surrounds shaft 126. At one end, yoke 130 is pivoted to a fixed but adjustable pivot 131. The other end of yoke 130 is connected to piston rod 132 projecting down from a double acting hydraulic cylinder 133 which is mounted on collar 134 of the machine frame F. The lifting motion of the workhead and support structure is accomplished by introducing hydraulic fluid under pressure into cylinder 133 and raising the piston therein to raise rod 132, thereby swinging yoke 130 about pivot 131 to raise the blank B from the lower grinding position in FIG. 10 to the upper position in which it engages locator 110. The means to feed the end mill blank toward and retract it from the grinding wheel are as follows: Near the lower end of inner sleeve 121 is fastened collar which is shown in FIG. 18 as having two oppositely extending arms, 140a and 140)). Arm 140a has connected to it one end of helical spring 142, the other end of the spring being attached to a suitable stationary point, as a portion of frame F. The pull of spring 142 on arm 140a biases collar 140 and inner sleeve 121 to move in a clockwise direction, viewed from above, which is the direction of retract movement which moves the workpiece away from the grinding wheel.

The opposite arm 14Gb is moved counterclockwise to rotate the sleeve with the workhead in the counterclockwise direction, viewed from above. The means for so doing includes roller 143 which bears against arm 140b and is mounted on one arm of bell crank 144. The other outwardly extending arm of this bell crank is pivoted at 145 to a clevis on the upper end of rod 146. The pivot point is fixed, but preferably adjustable.

Bell crank 144 is pivotally mounted on eccentric 150 on rock shaft 151. Rock shaft 151 is rotatably mounted in suitable bearings in brackets 152 which are attached to suitable portions of the frame F. Rock shaft 151 has nonrotatably attached to it arm 154, the outer end of the arm being attached by linkage 155 to the upper end of vertically moving piston rod 156. Piston rod 156 is attached to a piston moving within double-acting hydraulic cylinder 157, this cylinder being referred to as the in-feed cylinder, since introduction of hydraulic fluid under pressure into the upper end of the cylinder lowers the piston within the cylinder, thereby dropping piston rod 156 and rotating rock shaft 151 in a clockwise direction, viewed from the righthand end thereof in FIG. 18. Such rotation of rock shaft 151 about its longitudinal axis rotates eccentric 150 and pushes bell crank 144 against collar arm 140b. The movement of the bell crank is essentially one of rectilinear translation since pin 145 moves only in a short are that is approximately horizontal. This motion of arm 14% is transmitted through inner sleeve 121 to the yoke 120 supporting the head H, thereby moving head H and the workpiece toward the grinding wheel.

When flow of hydraulic fluid is reversed through cylinder 157, reverse movement of yoke 120 in the grinding head to retract the workpiece from the grinding wheel is effected.

The third component of the compound movement of the workhead is a swinging movement of workhead H about trunnion axis 32. This swinging movement of the workhead is initiated by supplying hydraulic fluid under pressure to double-acting cylinder 160, the fluid moving piston rod 161 out of the cylinder. This motion of the piston rod is conveyed through link 162 to arm 163 which is fixed on inner shaft 126, as may be seen in FIGS. 9 and 18. The connection between arm 162 and shaft 126 preferably includes a spline or key 164 FIG. 9) in order to permit shaft 126 to move vertically relative to arm 163, as already described.

To the top of shaft 126 FIG. is attached an arm 166. The outer end of this arm 166 is pin-connected to link 167, the other end of the link being pin-connected to an arm 168 attached by screws 169 to trunnion 46 to which workhead H is connected.

Arms

166 and 168 are preferably parallel to each other, and the linkage is such that the workhead is swung counterclockwise, as viewed from above (FIG. 15 through an arc equal to the angular movement of shaft 126.

Return swing of the workhead about axis 32 is accomplished by reversing hydraulic fluid flow through swing cylinder 160. Spring 171 is attached at one end to arm 173 mounted on shaft 126 near arm 163, while spring 172 is attached at one end to the outer end of arm 168. Both of these return springs are attached at their other ends to suitable anchorages, as illustrated. The springs are to eliminate backlash.

Adjustable swing limiters 176 and 177 (FIG. 15) are utilized, more particularly for the primary, secondary relief grind, (to be described hereinafter) to preselect and limit the angular swing of the workhead H and end mill positioned therein, and thus determine the primary and secondary relief angles for the grind of FIG. 5, but the limiter 177 is also useful for the grind of FIG. 4. As here shown, such limiters, or stops, 176 and 177, are in the form of two plungers FIG. 15), which are alternatively, or selectively, engageable by the opposite ends of the link 167. Each such plunger is movable longitudinally through, and screwthreaded within, a corresponding bushing 178 mounted in walls 179 of the hollow lower arm 46a of yoke 120, wherein are contained also the

arms

166 and 168, and link 167. A knob 18] on the outer extremity of each such plunger can be calibrated in suitable angular divisions to be read against indicia on the bushing 178. In grinding the arcuate type grind, sometimes referred to as form relief, the

limiter plungers

176 and 177 can be backed off, so as to have no limiting effect in making this grind. In such a case, the ends of the swing cylinder 160 set the end limits of swing. However, it is feasible and useful to use and set the limiter 177 to terminate the swing of the workhead H at the end of the grinding stroke (FIG. 6C). Both of these

limiters

176 and 177 are essential, however, to primary, secondary relief grinding as accomplished by the improvements of the present invention, and constitute component elements of the invention, as discussed below.

OPERATION CYCLE Assuming an arcuate form relief grind FIG. 4) to be used, limiter 177 is set to limit the swing of the workhead H to, for example, 30 and logic circuit selector switch SL is thrown to the position shown in full lines in FIG. 21A.

The flute selector is then set by means of knob to agree with the number of flutes on the mill to be ground. The blank shown in FIG. 2 has four flutes and so the two

discs

87 and 88 are set, as shown in FIG. 7C to provide four matching pairs of recesses or gates adapted to receive control pin 96.

The machine is now placed in standby condition by pressing the button of start switch 174 (FIGS. 1 and 20). This energizes the electrical circuit shown in FIG. 20 and starts motor Ml which drives the pump P FIG. 21A) to provide hydraulic fluid under pressure for the control system.

As soon as hydraulic pressure reaches a safe value, pressure switch lPS closes and grindwheel spindle drive motor 36 (M2 in FIG. 20) starts. At this time, the workhead is in the raised position, holding the end mill in the load position of FIG. 6A as a result of a swing back, an indexing rotation, and an elevation, which were the last operations of the preceding workhead swing cycle (FIGS. 6E and 6F). The hydraulic connections, fluid flow directions and position of valve SC for their last operations of the preceding cycle are shown in FIG. 21A, wherein hydraulic fluid flow is into the front end of swing cylinder 160 to withdraw plunger 161 and swing the workhead clockwise relative to the yoke (FIG. 6A). At the inner limit of this stroke, (whether by engagement of the plunger, with the cylinder bottom, or with a stop) rise of hydraulic pressure in the front end of cylinder to a predetermined level, conveyed to an air switch V2, switched an open 13 line D leading to logic circuit terminal 13 into communication with pressure line 8. The pin 96 is at this time in a deep selector disk gap, valve spool 104 is in its uppermost position (FIG. 21A); and in this condition, the

increase in pressure in the line D leading from the now closed valve V2 to the logic circuit via terminals 13 signaled the logic circuit FIG. 21B) via line 12to actuate valve U to send hydraulic fluid into the lower end of cylinder 133, raising the workhead to theloadinglevel.

After loading, cycle startvalve 179 is actuated, and initiates the automatic grinding cycle by supplying air from supply source S to the control system shown in FIGS. 21A and 21Band causing it to take overcontrol and perform automatically a programmed sequence of operations. First, the logic circuit (FIG. 21B) signals valve U via terminals 12 to send hydraulic fluid to the upper end of cylinder 133, thereby dropping the workhead to the grind level in which blank Bis inthe full line position shown in FIG. 10, and also, after. a short delay introduced by a timer in the logic circuit, to apply hydraulic fluid to the chuck cylinder for chuck clamp piston 56 to clamp the end mill. Also, at this time, the logic circuit signals the control valve F via terminals to supply hydraulic fluid from pump P to feed cylinder 157 to retract the plunger thereof. This FIGS. 15 and 18) rotates the workhead support yoke 120 counterclockwise on axis 127 to feed the blank in toward the grindwheel as indicated in FIG. 21A and FIG. 6B. At the predetermined limit of infeed, an air limit switch V3 is engaged and actuated to connect pressure line 8 to open logic circuit line 9. This signals the logic circuit to send a signal via line 11 to control valve SC to feed hydraulic fluid into the back end of swing cylinder 160, causing the plunger 161 thereof to extend to swing the workhead relative to yoke 120 in a counterclockwise direction about axis 32, so swingingthe blank B along grinding wheel 31 as shown in FIG. 6C. At the end of this swing, determined by the setting of limit stop 177 and which may be about 30, hydraulic pressure rises behind the plunger, and in the connection leading from the back end of cylinder 160 to switch V1 and operates said switch V1 to connect open air line D to pressure line 8, sending pressure air into line D leading to the logic circuit via terminals 14. This signals the logic circuit to act via line 15 to operate valve F to cause re verse flow through feed cylinder 157, which thereupon retracts the workhead and yoke 120, without swing back of the workhead, as indicated in FIG. 6D. As the retraction is completed, limit switch V4 is actuated and connects pressure lie 8 to line 10 to signal the logic circuit to reverse the flow of hydraulic fluid through swing cylinder 160, and send it again into the front end of said cylinder. This it does with a pneumatic signal through line 11 to valve SC. The workhead and end mill blank B are thereby swung back (clockwise) around swing axis 32 as shown in FIG. 6B; and upon this return, switch V2 is controlled to supply a pressure signal to line D and terminals 13 of the logic circuit, so as to initiate the indexing cycle.

This same sub-cycle is automatically repeated for each flute on a blank B. The control system is programmed by the flute selector to automatically grind an end face 30a with reference to each flute in exactly the same manner and in sequence. After the last grind set by the flute selector, pin 96 drops into the gate in the periphery of the selector discs which is deeper than the other gates, thereby producing the earlier described se-.

quence of operations which end thecycle, with the workhead elevated and collet :nreleased, so that the tool holder canbe manually removedand the: machine unloaded.

CONTROL SYSTEM The various movement of the workhead required to grind each of the faces on the end of an end mill B could, of course, be carried out by hand. However, it is an objective of the present invention and one of its advantagesthat the sequence of the various operations be carried out automatically by a control system with greater speed, accuracy, and uniformity of product than is possible by manual operation. To control the various operations, there has been provided the airhydraulic system shown in detail in FIGS. 21A and 21B.

The major control functions are carried out in sequence by a network of conventional pneumatic logic elements, shown particularly in FIG. 21B. These logic elements are known valves with the character shown in the legend attached to FIG. 2113. In addition to the elements shown in the legend, there are a number of position sensors which are basically limit valves or switches actuated by the movement of parts of the workhead of the supporting structure therefor. These sensors are generally two-position valves, as shown diagrammatically in FIG. 21A in association with the component parts of the machine which actuate the sensors. The purpose of such sensors is to signal the completion of certain movements of the machine, thereby causing the control system to complete certain movements or to initiate other movements, as will bewell understood by those skilled in the art.

The construction of the logic circuit of FIGS. 21A and 21B is not described in greater detail since it, per se, is not claimed and since other controlsystems may be used, also because the art of pneumatic logic circuit control of sequencing of machine element movements is now so well understood that such circuits can be readily constructed as a routine matter by technitians skilled in the art to carry out any system of sequential operations from requirements stated.

PRIMARY/SECONDARY RELIEF GRIND The present invention incorporates means whereby either the arcuate, form relief grind of FIG. 4, or the primary, secondary relief grind of FIG. 5, can be ac complished.

To set the logic circuit for the primary/secondary grind, selector switch SL is thrown to its alternate position in FIG. 21A, thereby altering the control circuit of FIG. 218. With reference now to FIGS. 66 to 6N, the end mill blank B, which in this case is tobe ground to the primary/secondary relief form of FIG. 5, is returned at the end of each grind cycle to an angular position such as represented in FIG. 66. The plane 47 again passes through the rotation axis of the grinding wheel 31, and the pivot axis 32 again is substantially in this plane 47, and is parallel to the grindingwheel axis, or at least parallel to an element of the grinding surface. The end mill blank, instead of having been left at the end of the preceding cycle in a position with its axis 58 parallel to plane 47, is instead at an adjusted primary relief angle 4) of, for example, 15 relative to the plane 47. This angle, which may range as high as 20", is set

Claims

1. In a grinding machine for grinding end faces on an end mill, the combination of: a frame; a grinding wheel rotatably mounted on said frame; a workhead for holding the end mill with its longitudinal axis in predetermined relation to said grinding wheel; a workhead carriage movable on said frame to carry said workhead and end mill along a predetermined feed in path ending substantially normally to the grinding surface of said grinding wheel, so as to engage an end portion of said end mill with said grinding surface of said grinding wheel; means for imparting successive feed in movements to said workhead carriage to move said workhead along said path, a pivot mounting for said workhead on said carriage on an axis perpendicular to said path; adjustable stop means for limiting swing of said workhead about is pivot mounting on said carriage for establishing the longitudinal axis of said end mill at two preselected angular spaced end limit positions relative to said grinding surface; means for swinging the workhead to position it and thE end mill held thereby in one and then the other of said end limit positions in a timed sequence prior to successive feed in movements of the carriage along said predetermined path so that upon feed in movement at each position a predetermined different angular relief surface is formed on said end mill; and means for initiating feed in movements of the workhead carriage in response to arrival of the workhead at each said preselected end limit positions.

2. The subject matter of claim 1, including two manually and independently adjustable stops for setting said end limit positions of said workhead relative to said carriage.

3. The subject matter of claim 1, including a pivot mounting for said carriage on said frame, on an axis parallel to that of said workhead on said carriage, so arranged that said feed in path for said workhead is an arc approaching a grinding surface on said grinding wheel substantially normally thereto.

4. The grinding machine according to claim 3, wherein: the means for imparting feed in movements to the workhead carriage and the means for swinging the workhead each comprises a hydraulic cylinder and plunger assembly, and including means responsive to arrivals of the workhead at said end limit positions as moved thereto by one of said cylinder and plunger assemblies for activating the other of said cylinder and plunger assemblies to initiate feed in movements of the workhead carriage.

5. The grinding machine according to claim 2 in which one of said stops is adjustable to position the workhead and the end mill held therein such that feed in movement of said end mill against said grinding wheel at that position causes a primary relief surface to be ground on said ene mill at a predetermined angle with respect to the longitudinal axis of said end mill, and said other stop is adjustable to position said work head and the end mill held therein such that feed in movement of said end mill in that angular position causes a secondary relief surface to be formed on said end mill at predetermined angles with respect to said primary relief surface and the longitudinal axis of the end mill.

6. The grinding machine according to claim 1 in which said workhead includes at least one trunion mounted for relative rotational movement in said carriage, an arm member secured to said trunion for rotational movement with said trunion and workhead relative to said carriage, and a pair of stop members adjustably positionable in said carriage on opposite sides of said arm member for limiting rotational movement of said arm, trunion, and workhead between predetermined positions.

7. The grinding machine according to claim 3 in which said pivot mounting for said carriage includes a depending sleeve mounted for relative rotational movement within same frame, means for selectively imparting rotational movement to said sleeve in response to the arrival of said workhead at each of said preselected in limit positions, said workhead having at least one trunion mounted in said carriage for relative rotational movement, said means for swinging said workhead to said limits including a shaft extending coaxially through said depending sleeve, linkage means connecting one end of said shaft to said trunion whereby rotation of said shaft relative to said sleeve causes rotary movement of said trunion and workhead relative to said carriage, means for imparting rotary movement to said shaft in response to the arrival of said workhead at each of said preselected limit positions, and said stop means including a pair of threaded members adjustably mounted within said carriage for engagement by said linkage to limit rotational movement of said shaft and trunion between determined angular positions.