US2039711A - Grinding machine and method - Google Patents

Description

May 5, 1936. s. EINSTEIN GRINDING MACEINE AND METHOD Filed Oct. 26, 1931 2 Sheets-Sheet 1 Zhmentor Gttormg Patented May 5, 1936 PATENT OFFICE ammo. MACHINE AND METHOD Sol Einstein, Cincinnati, Ohio, assignor, by mesne assignments, to The Heald Machine Company,

Worcester, Mass,

a chusetts corporation of Massa- Application October 26, 1931, Serial No. 571,028

3 Claims.

This invention relates to improvements in machine tools and especially to improvements in grinding machines for, and in a method of grinding irregularly shaped work pieces.

An object of this invention is the provision of a grinding machine for the centerless grinding of the bore of hollow 'work pieces whose outer surface is not cylindrical or not concentric with the axis of the bore to be ground.

Another object of the invention is the provision of a grinding machine for grinding the bore orhole of irregularly shaped articles concentric with a predetermined axis. 1

A further object of the invention is the pro- :15 vision of an improved internal grinding machine adapted to grind or generate the hole or bore of work pieces normally diflicult to handle together with improved means for supporting such work pieces and effecting their rotation.

Other objects and advantages of the present invention will be readily apparent by reference to the following specification taken in connection with the accompanying drawings and it will be understood that any modification may be made 25 in the'speciflc structural details there illustrated within the scope of the appended claims without departing from or exceeding the spirit of the invention.

In the drawings:

Figure 1 is a front elevation of a grinding machine embodying this invention.

- Figure 2 is a fragmentary view of certain parts of the machine in elevation as particularly seen. from'line 2-2 of Figure 1.

- Figure3 is a sectional view taken on line 8-3 of Figure 1.

Figure 4 is a sectional view taken on line 4--4 of Figure 2, illustrating in section one form of work holding means.

Figure 5 is anelevation of a modified work holding means.

Figure 6 is a sectional view taken on line 6-4 of Figure 5.

Figure 7 is an elevation of a further modifica- 45 tion of a work holding means.

Figure 8 is a sectional view on line 8-8 of Figure 7.

Figure 9 is an enlarged elevation of one of the reversing dogs for the table.

Throughout the several views of the drawings similar reference characters are employed to denote the same or similar parts.

In the past work pieces of an irregular shape or contour have been mounted in suitable chucks 5 mounted on rotating shafts or spindles in line with a small diameter or internal grinding wheel. By reason of the inability to remount a. work piece a second time in the chuck in the same position with the axis of the bore being ground precisely concentric to the axis of rotation of the chuck, such irregular work pieces must be completely ground at one operation by a single grinding wheel which is generally a compromise between a roughing and finishing wheel and does not necessarily provide the desired finish. Recently work pieces have been ground internally by the centerless method which consists in rotating the work on a previously ground external surface thereby grinding or generating a bore precisely concentric with the axis of the external surface. This invention pertains primarily to the apparatus and method for grinding irregularly shaped objects by the same centerless machines as those in which cylindrical work pieces are now being ground.

The machine for accomplishing this purpose corresponds to the usual precision centerless grinding machine and comprises a bed In having formed on its upper surface ways II on which a wheel head I2 is movable. This head comprises a slide l3 movable on the ways I I and supporting a spindle housing M in which is journaled a wheel spindle IS. The slide l3 also carries a prime mover or motor 16 belted or otherwise connected with the spindle l5 through suitable mechanism enclosed within a housing H. The motor I6 isadapted to drive the spindle l5 at a high rate of speed for correspondingly rotating the small diameter or internal grinding wheel [8 secured thereto at a suitable speed for grinding. On a lateral extension IQ of the bed there is mounted a base plate 2| supporting the cross-slide 23 on which the work piece 20 is mounted. A dovetailed guideway 22 on the base plate 2| provides for guiding said cross or transverse slide 23 which carries the work supporting and rotating mechanism. This work supporting and rotating mechanism comprises a spindle 24 journaled in a suitable housing 25 integral with or secured to the slide 23 and forming part of the workhead. A worm wheel 26, Fig. 3, is secured to the spindle 24 intermediate its ends and the spindle 24 can'les on its free end a friction drive or work regulating gear 3| having a sleeve 32 which is suitably journaled in a bearing 33 integral with and depending from the guide bracket 34 of the housing 25. The sleeve 32 of the gear 3| has a sliding splined connection with a countershaft 35 journaled in a bracket 36 carried by the base plate 2|. Secured to the shaft 35 is a cone pulley driven by a belt or the like from any suitable source.

Opposite to the regulating wheel 21 is a pressure roller 38 rotatably journaled in the upper end of an arm 39 secured at its other end to a shaft 40 extending lengthwise of the wheel head 2|) and terminating in a pinion 4| enclosed within cylinder housing 42. Axially slidable through the cated intermediate the axis of the shaft 46 and spindle 24. Said bracket 61 carries a work support in the form of a blade 68 having an active supporting surface inclined in the direction of the operative face of the regulating wheel and forming between said wheel and blade a work-receiving trough, into which a work piece is normally urged by the pressure roller.

The work piece illustrated in Figures 2 and 4 is a bevelled pinion having the bore 46 therein, on which the grinding operation is to be performed. As shown in Figure 4 the pinion 46 is mounted against a locating plate 41 which has projecting from it three lugs 48, Fig. 2, of a pitch equal to the pitch of the gear 45 and adapted to enter the space between certain of the pinion teeth for properly centralizing the pinion relative to the plate 41. From this it will be seen that the work piece is centralized relative to the plate 41 in accordance with the pitch circle thereof. The plate 41 is held by means of screws or the like 49 against cap member 50 which is in turn secured by means of screws 5| to a drum or thimble 52 having a cylindrical outer surface. The drum or thimble 52 has its axis absolutely coaxial with the axis of the cap 59 and locating plate 41. Consequently, the pinion 45, when centralized relative to the locating plate 41 as above described, has the center of the pitch circle coinciding precisely with the axis of the cylindrical outer surface of a thimble.

The thimble 52 is provided with a flange 53 depending from the interior wall thereof and form'- ing a bearing for a clamp nut 54. The clamp nut 54 is held against axial movement relative to the thimble 52 by means of the flange 53 and a plate 55 fastened to the rear end of the thimble 52. Nut 54 has a threaded connection with the shank 56 of a clamping head 51 which terminates in flange or head 58 to which are pivoted, at equally spaced points, such as 59, arms 60 which extend through openings 6| formed in thethimble cap 56 and locating plate 41. The arms 66 terminate in hook fingers 62 adapted to engage with the face of the work. The arms 60 are further provided on their outer surfaces with cam faces 63 adapted to co-operate with camsurfaces 64 formed at the end of the openings 6| formed in late each arm 60 in a counter-clockwise direction about pivot 59 thereby maintaining contact between the upper surface of the arm 60 and the upper surface of the opening 6 I.

The operation of the work holding mechanism? is as follows: The nut 54 is rotated by means of. a suitable spanner wrench cooperating with sockets 66 formed in the clamp nut 54 for shifting the clamp head 51 to the right as seen in Figure- 4. As soon as the arms 60 have been projected through the openings 6| a distance to permit cam faces 63 and 64 to clear one another, the spring pressed plunger 65 actuates said arm outwardly thereby freeing the work piece from the clamp? ing pressure. An unfinished work'piece is then' substituted for the one previously finished whereupon the clamp nut 54 is actuated in the opposite direction for drawing the clamp head 51 to the left, as seen in Figure 4, carrying with it the arms 60 which through the interengagement of cam faces 63 and 64 are actuated against the resist ance of spring pressed plunger 65 for clamping; the work against the locating plate 41, withtho center of the pitch circle of the gear precisely concentric to the axis of the cylindrical outer sur-' face of the thimble.

With the work now clamped in position in the thimble 52 with the axis of the pitch circle of the gear coaxial with the axis of said thimble 52, the latter is positioned in the above described work-j head for rotation on its cylindrical outer sur face. The thimble, in grinding position, engages with the regulating wheel and the supporting blade 68 and the pressure roller 38 tends to force the thimble 52 against the surface of the regu: lating wheel 21 whereby rotation of the said regu-J lating wheel effects rotation of the thimble 52 and all parts carried thereby about the axis of the said finished exterior surface of the thimble. It will be apparent that the rotation of the thimble by this workhead procures a rotation of the work piece therein about an axis coinciding with the center of the pitch circle of the gear teeth on said work piece. 7

The grinding wheel carriage I2 is now actuated to the left as seen in Figure 1, to position the grinding wheel within the bore of the work piece} by any suitable or desirable means such as the mechanism disclosed in co-pending application of Einstein, Booth and Haas, Serial Number 374,556 filed June 28, 1929. This mechanism terminates in a pivoted lever 10 for reverselyf actuating a suitable hydraulic control valve of any well-known construction as, for example, the

valve disclosed in Patent No. 1,582,468, granted April 27, 1926 to Heald and Guild. The lever 16 is secured to a pivot shaft 1| which has depend-t ing from it the arm 12. Dogs 13 and 14 co-operate with the upper end of the lever 16 for reversing the movement of the wheel head at each end of its stroke, as is the usual practice with this type if grinding machine and as shown in the co-pendin'g application above referred to, thus providing for a reciprocation of the grinding wheel over thl surface of the work piece. After the grinding wheel has entered the bore of the work. the slide 23 is shifted transversely on the bed along deway 22 to relatively feed the work and wheel and effect the desired stock removal from thework. This is accomplished by the arm 12 which is pivoted as at 15 to one end of a link 16 which has its other end pivoted at 11 to an arm 18 keyed or otherwise secured to an oscillatable stub shaft 19. The shaft 19 is journaled in the walls of a box or casing 84 secured to the forward face of the 75 aoaonn bed l8 and enclosing the intermittent feeding mechanism now to be described.

Secured to the shaft I9 interiorly of the casing 88 is a wedge shaped cam 8I adapted to engage the roller 82 rotatably carried by a bell crank lever 83 pivoted at 84. The lever 83 is actuated in one direction about its pivot 84 by means of a spring 85 having its opposite ends secured respectively to an anchor within the casing 88 and the bell crank lever 83. The free end of arm 86 of lever 83 is furcated as at 81 and receives therein the pin 88 projecting from the rod 89 on bell crank 98. The bell crank 98 carries on its other arm a pawl 9| co-operating with a ratchet 92 of any suitable cross feed mechanism for'actuating the pinion 93, Fig. 3, on the end of a cross feed screw 94. The screw 94 is threaded into a nut 95 depending from the under surface of the slide 23.

It will be noted that the reversing dog I4 is pivotally mounted on a movable core 96 of solenoid 9'I adjustably carriedwby the wheel head slide I3. The dogs I3 and I4 determine the normal reciprocatory stroke of the wheel head while the grinding wheel is within the work for breaking up grinding lines on the work. This stroke does not permit the wheel head to carry the wheel outside of the work which is necessary in order to replace the finished work piece with an unfinished one. The dog I4 is therefore withdrawn from the path of the lever 18 at the conclusion of the grinding operation, and is effected by energizing the solenoid 91 through electrical means. The means for this purpose may reasonably take the form of a suitable electrical circuit with a switch member 98, Fig. 3, in the circuit, the'latter being closed by the gear 4I during retraction of the pressure roller 38 from contact with the thimble 52. This retraction of the reversing dog I4 permits an extended stroke of the wheel head which continues until thethird dog 99 on the slide I3 engages with and. actuates the reversing lever I8, thereby reversing the hydraulic control valve, above mentioned, for returning the wheel head to its grinding position. The time limit during which the extended stroke takes place is suilicient to permit the replacement of the thimble in the worksupporting structure by another thimble having an unfinished work piece positioned therein. It will be noted that the slide I3 may be brought to rest when the grinding wheel is withdrawn from the bore of the work piece by manual operation of the lever III.

The operation of the grinding machine is as follows: The work piece is first properly centralized and clamped within the thimble 52 .whereupon it is placed on the work rest blade 88 and in engagement with the regulating wheel 21. The piston 43 is then actuated in the proper direction for oscillating the arm 39 and urging the pressure roller 38 into contact with the thimble 52 forcing the same into the work receiving trough formed by the inclined edge 59 of the blade 88 and the active face of the wheel 21. The wheel 21 being constantly rotated effects the rotation of the thimble and work carried thereby. The lever 18, which has been in mid-position in which position the slide carrying the grinding wheel is supported against movement from the inoperative position of Fig. 1 in the usual manner, is then manually actuated to effect movement of the slide I3 to the left which causes the grinding wheel I8 to enter the bore in the work. The wheel head I2 is automatically reciprocated in operative relation to the work at the end of its initial stroke to the left into operative position and then operates the feeding mechanism as above described for eflecting the relative cross feed between the work and grinding wheel to reduce said work to the desired size.

It will be noted that the work piece is rotated about the axis of the pre-formed cylindrical outer surface of the thimble 52 which has the work properly centralized therein so that the axis of the hole or bore in the work is co-axial with the said pre-formed surface of the thimble. This insures absolute rotation of the work about the desired axis.

The thimble may be arranged for holding work pieces other than the gears or pinions shown in Figures 2 and 4. A modified showing is illustrated in Figures 5 and 6 in which the cap or cover plate I88 is provided with a depression or seat I 8| conforming substantially with the contour of the work. In this construction a hook or clamp member I82 is provided which is carried by the head I83 and actuated by the clamp nut 54 for holding the formed work I84 within the seat I8I. In this construction the seat IN is so formed as to have the axis of the hole or bore to be ground will be located coaxially with the axis of the cylindrical outer surface of the thimble body 52.

Figures 7 and 8 show a further modification for clamping formed work pieces to the thimble 52. This modification again consists of a head I85 having an openingIOB formed therein substantially to the contour of the work piece to be operated upon. Interiorly of the body portion of the thimble there is mounted a ring I8'I supporting a plate I88 against which the work piece rests. In this modification the head I89 has pivoted thereto a pair of clamp arms II8 forholding the work against the base plate I88. The head and plate I89 and I88 are provided with central apertures III and H2 co-axially aligned with the axis of the outer surface of the thimble. The said apertures receive therein the reduced portion 3 of a centralizing and positioning pin II4 having an enlarged portion I I 5 adapted to enter the bore or hole in the work and thereby centralize the work relative to the cylindrical outer surface of the thimble 52. In other words, the work piece has a bore or hole therein substantially equal to the enlarged portion II 5 of the pin on which it is mounted and then the work piece and pin are positioned in the thimble so that the reduced portion 8 of the pin passesvthrough the apertures III and H2 in the clamp head and plate respectively whereupon the clamp nut 54 is actuated for causing the clamp finger IIII to secure the work against the base plate I88. With this constructionv the work is centralizedin the thimble 52 whereupon it may be mounted on the work rest blade with the assurance that the work will rotate about the axis of the bore which is co-axial with the axis of the thimble.

If desired a similar centralizing and positioning mechanism may be employed with the modification shown in Figures 2 and 4, or in the modification of Figures 5' and 6.

What is claimed is:

1. In a centerless internal grinding machine the combination with a grinding wheel, and means for supporting and rotating a cylindrical member on its cylindrical outer surface, said means and wheel having a relative transverse movement for a cross-feed between said wheel and said means. said supporting and rotating means including a regulating wheel having its ads substantially in the plane of the cross-feed movement, a work-support spaced from said regulating wheel, both said regulating wheel and support being engageable with the cylindrical outer surface of said member, and a pressure 7 member also engageable with the cylindrical outer surface for holding said cylindrical member against'the regulating wheel and work-support, of a thimble having a cylindrical outer surface' and adapted to'be removably positioned in said supporting and rotating means with its cylindrical outer surface engaging with the regulating wheel, the work-support and the pressure member, and, means within said thimble for clamping a work piece therein with the axis of the surface of the work piece to be ground coincident with the "axis'of the cylindrical outer surface of the thimble,

the latter providing for the rotation of the work piece by the supporting and rotating means during a grinding'o'peration on said work piece, said regulating wheel by its rotation procuring a rotation of the thimble.

2. In a centerless internal grinding machine, the combination with a grinding wheel and a centerless work-supporting structure, said wheel and structure having a relative transverse movement for a cross-feed movement therebetween, said work-supporting structure comprising spaced work-supporting and rotating members engageable with the cylindrical outer surface of an annular member for supporting and rotating the same, the axis of rotation of one of said members being in substantial alinement with the plane of the cross-feed movement for backing up the annular member, of a thimble having a cylindrical-outer surface, and means within said thimble for clamping a work piece therein with the axis of the surface to be ground coincident with the axis of the cylindrical surface of the thimble, said thimble being removably positioned within the work-supporting structure with its cylindrical outer surface engaging with the supporting.

and rotating members and being rotated by the rotation of one of said members.

3. A work-holding and rotating mechanism for non-cylindrical or formed work pieces for use in connection with internal grinding machines in which there is provided a cross-feed movement between the grinding member and the worksupporting member, said mechanism comprising a centerless work-supporting structure including a rotating regulating wheel having its axis substantially in the plane of the cross-feed movement, a work-support spaced from said wheel and a pressure member spaced from said wheel and support, said wheel support and member each being engageable with the cylindrical outer surface of a member positioned therebetween, a thimble having an exteriorly finished surface of revolution and adapted to be positioned within said supporting structure with its finished surface engaging with said regulating wheel and work-support and being held in engagement therewith by the pressure member whereby said thimble is supported and rotated on its exteriorly finished surface, said thimble being positively rotated by the rotation of the regulating wheel, and means within said thimble for supporting and clamping a work piece in said thimble with the axis of the bore of the work piece coincident with the axis of the surface of revolution of the thimble.

' SOL EINSTEIN.

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