Patent GB-953563-A (GB)
Title: Improvements in or relating to automatic grinders for small diameter bores
IPC: B24B33/02
Filed: 1961-07-13
Abstract: 953,563. Chucks; grinding. GUISEPPE MINGANTI & C. S.p.A. July 13, 1961 [July 16, 1960], No. 25409/61. Headings B3B and B3D. An automatic grinder for small diameter bores in which the work is arranged with the bore axis vertical comprises a base, cylindrical vertical guides carried by the base, a grinding- wheel, a grinding-wheel spindle for the grinding- wheel, said wheel spindle being carried by the guides, a work spindle carried by the guides, a motor associated with the wheel spindle for rotating the wheel spindle, a drive unit for effecting horizontal translatory displacement of the wheel spindle, a second motor associated with the work spindle for rotating the work spindle, a second drive unit for vertically reciprocating the work spindle, means sensitive to the diameter of the bore being worked for disengaging said two drive units when the bore diameter attains a predetermined value, members actuated by said forging means for effecting the immediate removal of the grinding-wheel from the finished workpiece and members provided for the setting and adjusting of the feeds and of the frequency of rotation and vertical reciprocation. General.-A machine comprises a base 1, uprights 2, 3 and a beam 4. Cylindrical guides 5, 6 extending between the base 1 and beam 4 support a wheelhead 7, a workhead 8 and a size gauging device 9. Wheelhead.-The wheelhead 7 comprises a high-speed motor rotating the grinding-wheel 12 at 90,000-150,000 r.p.m. A cooling system maintains the temperature within predetermined limits. The wheelhead 7 is carried by a slide 24<SP>1</SP> mounted by rollers 26 for horizontal movement on a support 15a rigid with a cylinder 15 movable relatively to a double-acting piston 16 secured to the guide 5. The wheelhead 7 is vertically moved by the cylinder 15 at the beginning and end of each cycle to permit unloading of a finished workpiece 10 and loading of a fresh workpiece, these operations being performed automatically by mechanism the drive for which is contained in the upright 3. Feed.-A lever 19 pivoted at 20 to the upright 2 and biased by a spring 19<SP>1</SP> has a shoulder 21 co-operating with a rod 24 for moving the slide 24<SP>1</SP> against the bias of a spring 23. The rod 24 comprises two coaxial portions 24<SP>11</SP>, 24<SP>111</SP> having therebetween a trapezoidal piece 24a adjustable by a knob 24b to vary the overall length of the rod 24. A cam 18 driven by a motor, e.g. hydraulic, co-operates with a part 19d of an element 19b pivoted at 19c on the lever 19. The element 19b is rendered rigid with the lever 19 when an electromagnet 19<SP>11</SP> mounted on the latter is energized, whereupon the cam 18 effects feeding of the wheelhead 7. The value of the feed can be adjusted from a minimum of 0.0001 mm. to a maximum of 0.01 mm. for every stroke of the workhead, different values being selected for rough grinding and for finishing. A rapid rotation returns the cam 18 into its initial position when the wheelhead is removed at the end of the cycle. Workhead.-The workhead 8 comprises a high-speed motor for rotating the workpiece 10 at 2,500-10,000 r.p.m. The motor stator 28 is rigid with a slide 29 mounted by rollers 31 for vertical movement of parts 32. The motor rotor 33 is mounted by bearings 34 and can be braked by a plate 35<SP>1</SP> bearing friction material and actuated by an electromagnet 35; alternatively the plate may be actuated pneumatically. A tube 36 rigid with the rotor 33 is provided with blocks 38, 38 against which the workpiece 10 is clamped by a jaw 39 which, when the tube 36 rotates, is forced against the workpiece 10, against the action of a spring 44, by centrifugal action on a part 40 of the jaw 39, the latter being pivoted at 41, to the tube 36. Traverse.-To reciprocate the workhead 8 vertically a motor, e.g. hydraulic, oscillates a lever 45 pivoted at 46 and carrying at one end pins 48, 48 connected to slides 50, 50 located in guides 51, 51 in the slide 29. The stroke and frequency may be varied according to the size of the workpiece. Size gauging.-When the workpiece 10 is at bottom end of its stroke the diameter of the bore is gauged by the ends 53 of arms 56 of the gauging device 9 which is mounted on a base 57. For replacement of the ends 53 when worn the base 57 is lowered by means 58. The base 57 is secured in operative position on the guides 5, 6 by clamping screws. Cycle.-A workpiece 10 is loaded into the workhead 8, whereupon rotation and reciprocation of the workpiece commence. The wheel head 7 is lowered into operative position, and the cam 18 rotates to feed the wheelhead 7 for rough grinding. When a certain size of bore is reached, the gauging device 9 permits a change to finish grinding with appropriate grinding- wheel feed and frequency of reciprocation of the workpiece. When a further certain size of bore is reached, the gauging device 9 permits the stopping of feed, so that " sparking out " takes place, the reciprocation of the workpiece remaining unaltered. When the bore attains the desired size, the gauging device 9 permits reverse feed of the grinding-wheel away from the workpiece, raising of the wheelhead 7, cessation of the reciprocation of the workhead 8, and of rotation of the workpiece, and movement of the gauge arms 56 towards each other to facilitate unloading of the finished workpiece. Specification 953,562 is referred to.