Patent GB-500907-A (GB)
Title: Improvements in or relating to spindle mountings for boring, grinding and like machines
IPC: B23B47/04
Filed: 1938-02-17
Abstract: 500,907. Grinding internally. HEALD MACHINE CO. Jan. 11, 1938, Nos. 890 and 891. Convention dates, April 9, 1937 and Sept. 15, 1937. [Class 60] [Also in Groups XXII and XXXIV] In a boring-head for a grinding or like machine, the spindle is mounted in rocking shoe bearings of the Michell type so that during rotation the spindle floats centrally for cutting, but on stoppage of the rotation the spindle may be moved laterally in the bearings to relieve the cutter from the work during withdrawal. In a modification, the work is carried by a spindle mounted in Michell bearings. In one modification the housing 1, Fig. 1, has pivoted pads 3 forming bearings for the spindle 2 carrying a cutter 8. Springs 27 in a ring 23 splined on the spindle press against a ring 25 secured to the spindle and the ring 23 abuts on a loose flange 21 engaging the end surface of the housing so as to tend to draw the spindle rearwardly. The flange 21 and a similar flange 20 engaging the other end of the housing prevent escape of oil from the bearings. The oil is supplied by a gravity or pressure pipe 28 and a bleed passage in a plug 35 allows accumulated air to escape. Passages 29, 30 allow oil leakage to escape. The pivoted pads 3 have inner surfaces of greater radius than the spindle 2 and outer surfaces of smaller radius than the housing 1 so that they can rock about their locating pins 12, 15, Fig. 2, the pins 15 being adjustable. A radial plunger 39 in the pindle is pressed outwards by a spring 40 and engages the bore of the housing through a pad 41 so as to tend to press the spindle laterally in a direction to cause the cutter to leave the work. When the spindle is rotating the oil drawn into the bearings maintains the spindle in a central position for cutting, but when rotation is stopped the oil pressure under the pads falls and the spring 40 is enabled to move the cutter out of contact with the work. The plunger 39 and pad 41 are counterbalanced by an arcuate plate 42 attached to the spindle. In a modification the plunger 39 engages a ring loosely encircling the spindle and rotating therewith, and when the spindle carries the rotating work the plunger is mounted in the housing, in line with the stationary cutter, and engages a stationary ring loose on the spindle. The boring-head or the work may be fed axially. In a modified construction, the spindle 54, Fig. 8, is mounted in Michell bearings 55, 56 in a housing 53 attached to a support 52. Flanged collars 82, 94 loose on the spindle carry piston rings forming a slidable oil seal with the bore of the housing and springs 87 in a ring 85 splined to the spindle engage an annular disc 88 thereon to draw the spindle rearwardly relatively to the housing. A ring 98 keyed to the spindle has a projecting bevelled portion 101 in line with the cutter 60 which, in the rearward position of the spindle, in free from the housing and allows the spindle to rotate centrally for boring. When rotation of the spindle is discontinued, however, and a fluid pressure brake is applied to bring the spindle to rest, oil from the brake cylinder passes through a pipe 110 to lift a plunger 109 and raise the pressure in the lubricating oil supplied to the housing by a pump 107 and a pipe 106. This increased pressure acts on the collar 94 to overcome the pressure of the springs 87 and move the spindle forwardly, the bevelled ring 98 then coacting with the housing to move the spindle laterally and free the cutter from the work. The weight of the spindle is balanced by a spring plunger 76 in the housing pivotally engaging a pad 73 bearing on the spindle. The bearing pads 62, Fig. 9, of the bearings 55, 56 are freely pivoted on pins 64 and the remaining pads 62a are pivoted on pins 69 adjustable by screw plugs 67 locked by screws 71. The housing 53 is cooled by radiating fins 112 thereon and air currents passing through openings 119, 120 in the support 53. The spindle and housing are preferably made of material having the same co-efficient of thermal expansion and the housing is mounted on the support by means of a machined flange 116 in line with the spindle axis so that the position of the latter will not be affected by temperature changes in the housing or support. The support 52 is preferably made of low thermal expansion material and the housing 53 of cheaper material which is more readily machined. Pads 121 are provided on the sides of the support so that a number of them may be mounted together to form a multiple-spindle machine, the flanges 116 of the housing being spaced inwardly from the pads 121 so that thermal expansion of the housings will not affect the spacing of the spindles.