Patent GB-898634-A (GB)
Title: Machine tool construction to eliminate effect of expansion in members
IPC: B24B49/14
Filed: 1960-03-10
Abstract: 898,634. Grinding. CINCINNATI MILLING MACHINE CO. March 10, 1960 [May 18, 1959], No. 8457/60. Class 60. A machine tool has a workpiece forming tool and supporting structure to hold a workpiece for forming by the forming tool, the supporting structure including a workpiece supporting member to hold the workpiece on an axis, a base member, and one or more intermediate positioning members between the base member and the workpiece supporting member, the members defining a plurailty of separating boundaries between the base and the workpiece supporting member so that the workpiece supporting member can be moved relative to the base, all of the separating boundaries having a single locating line about which expansion or contraction occurs, the locating lines and the workpiece axis intersecting a plane through the tool along a straight line in the plane when the members are positioned to hold a workpiece in a predetermined position for forming by the forming tool. A grinding wheel 16 is carried in a wheelhead 20 movably mounted on the rear portion 12 of the machine base 10 for transverse movement by a power-actuated shaft 21, engagement of which with a stop member 22 mounted in the base determines the final forward position of the grinding wheel. Coolant is supplied to the grinding zone through a nozzle 23 connected to the wheelhead. A workpiece 19 is supported by headstock 17 and tailstock 18 which are adjustably clamped on a swivel table 15 carried by a table 14 movable longitudinally on the forward portion 11 of the base 10. The table 14 may be reciprocated longitudinally by a hydraulic cylinder 44 connected to the table 14, the pistor 45 having rods extending through each end of the cylinder and connected to the base portior 11. Manual movement of the table 14 is effected by handwheel 47 operatively connected to gear 48 meshing with rack 49 on the table 14. The base portion 11 has a flat way 25 and a V-way 26 both extending longitudinally and receiving, respectively, a flat slide and a V-slide of the table 14. As the table 14 is located transversely on the base solely by the V-way 26 and V-slide transverse expansion or contraction of the table 14 relative to the base will occur about a locating line A extending longitudinally in the apex of the V. Mounted in the table 14 is a pivot pin 31 having a head received in a recess 30 in the swivel table 15 To eliminate play in the pivot connection the head of pin 31 is engaged by a rod 32 carried in the swivel table 15 and adjusted axially by screw 33. Swivelling is effected by a screw 15a journalled in a bushing 15b mounted in the swivel table 15, the screw engaging a nut 14a mounted in the table 14. The swivel table 15 is clamped in desired position by clamp 29 bolted to the table 14 and engaging a flange 15c on the swivel table 15. As there is play in the screw and nut mechanism 15a, 14a, the swivel table 15 is transversely located relative to the table 14 solely by the clamp 29 and pin 31 and these lie on the locating line B, on the top surface of table 14 and parallel to V-way 26, about which transverse expansion or contraction of the swivel table 15 relative to table 14 will occur. The swivel table 15 has a dovetail 34. A rigid depending portion 17b of the headstock 17 has a surface 36 in mating engagement with the shoulder 35 of the dovetail 34 and held thereagainst by clamp 37 secured on stud 38 by nut 39. As the headstock 17 is transversely located on the swivel table 15 by the surface 36 and shoulder 35, transverse expansion or contraction of the headstock 17 relative to the swivel table 15 will occur about a locating line C extending longitudinally at the upper end of the shoulder 35. The tailstock 18 is clamped to, and located by, the shoulder 35 of the swivel table 15 in the same manner as the headstock. The headstock and tailstock have centres 41, 42 on axis D defining the axis about which the workpiece 19 is rotated by dog 43 engaged with the headstock spindle 17a. When the swivel table 15 is adjusted for the grinding of a cylindrical workpiece, the locating lines A, B, C and axis D all lie in a common plane E in which all displacement of the workpiece axis relative to the base due to expansion or contraction of the workpiece mounting members 14, 15, 17, 18 will occur. The rear portion 12 of the base has a V-way and a flat way 50 extending perpendicular to ways 25, 26, upon which the wheelhead 20 is mounted for movement towards and away from the workpiece 19. A central portion 51 of the wheelhead 20 depends between the ways and carries a sleeve 52 in which is rotatably mounted a nut 53 internally threaded to engage the forward end 21a of lead screw 21. The nut 53 is secured against axial movement relative to the portion 51 by a thrust bearing 55 held against the portion 51 by a flange 57 on the nut and by a thrust bearing 56 held against the portion 51 by a collar 58 threadedly engaged with the nut. Inside a skirt portion 59 of the flange 57 is a backlash nut 60 threaded on a lead screw 21. A spring 62 received in the backlash nut engages a terminal plate 61 connected to the rear portion of the skirt portion 59 of the nut. The lead screw 21 is held in proper centered relation in the nut 53 by sleeves 63, 64. During automatic feed the lead screw is not rotated but is shifted axially by a power actuating unit connected by bracket 69 to the base member 70. As the lead screw is shifted forwardly the forward end extends through guard 71 connected to the base and the forward terminal surface of the lead screw abuts against stop member 22 mounted in the base portion 12 to determine the final position of the grinding wheel. This arrangement minimizes the effect of the heat expansion, in the direction parallel to the lead screw, on the final position of the grinding wheel, because it is only the portion of the lead screw between the nut and forward terminal surface whose expansion is effective and is offset by expansion of the wheelhead between the grinding wheel axis and the depending portion 51 in the direction parallel to lead screw 21. To accommodate workpieces of different sizes the position of nut 53 on lead screw 21 can be manually adjusted; a gear 73 pinned to the nut 53 is connected, through idler gear 77, with a gear 76 integral with a sleeve 75 rotatably mounted in the wheelhead portion 51. A shaft 80 is received in and keyed to sleeve 75 and a cap 82 is pinned on one end of the sleeve. The cap has a ring 83 slotted to receive the key and the ring can be rotated, by screw 84, relative to the sleeve to clamp the key in the sleeve and eliminate backlash therebetween. The shaft 80 is journalled in bushing 88 in the forward base portion 11 and has a gear 85 operatively connected to handwheel 86. In a modification, Figs. 4 and 5, line A<SP>1</SP> represents the locating of table 114 on base 111, line B<SP>1</SP> represents the locating of swivel table 115 on table 114 and line C<SP>1</SP> represents the locating of headstock 117 and tailstock on swivel table 115. The lines A<SP>1</SP>, B<SP>1</SP>, C<SP>1</SP> intersect a plane F<SP>1</SP> passing through the swivel pin 131, the points of intersection lying on a line G. The plane F<SP>1</SP> is parallel to the plane F of the grinding wheel 116 and for plunge cut grinding the table 114 is adjusted to align the plane F<SP>1</SP> with the plane F. A coolant passage 87 is provided through the base. A modified form of the machine is shown in Fig. 7.