Patent GB-512297-A (GB)
Title: Improvements in machines for dressing cylindrical surfaces
IPC: B24B33/02
Filed: 1938-11-24
Abstract: 512,297. Grinding. BURGESS, A. F. (Barnes Drill Co.). Nov. 24, 1938, No. 34204. [Class 60] A machine for honing internal or external cylindrical surfaces comprises a number of honing tools adapted to operate on a number of work pieces simultaneously, means for effecting relative rotation and reciprocation of the tools and work pieces, means for expanding or contracting the tools simultaneously into operative engagement with the work, and means for independently varying the pressure exerted on the work pieces by the respective tools. In the machine shown, for honing internal surfaces, a pair of rotary tool spindles 13 and 14 are carried by a reciprocating head 11 guided on a pillar 9 of the machine, the work pieces 45 .being held stationary. The spindles 13, 14 are rotated by a variable-speed hydraulic motor 16 through gearing and a splined shaft 17, the motor being supplied with pressure fluid from a pump 21 driven by an electric motor 22a. Reciprocation of the head 11 is effected by a piston 23 connected thereto by a rod 24 and operating in a cylinder 25 carried by the pillar 9. Pressure fluid is supplied to either end of the cylinder 25 from a pump 26, driven by an electric motor 27, under the. control of a stop valve V-2 and a reversing valve V-3. Expansion and collapse of the tools 15 and 15a mounted on the spindles 13 and 14 is effected through rods 34 and 34a extending axially through the spindles, by pistons operating in cylinders 33 and 33a carried by the head 11. Pressure fluid is supplied to either end of the cylinders 33 and 33a through telescopic connections 35 and 36 under the control of a reversing valve V-4. Individual control valves 37 and 37a, associated with pressure gauges 38 and 38a, are provided for independently controlling the fluid pressure admitted to the upper end of the cylinders 33 and 33a, so as to provide for varying the pressure exerted by either tool on its work piece. A circular table 42 secured to the upper end of a shaft 43 is equipped with three holders 46 for the work pieces 45. When the table is set, one holder is in a first working position below the tool 15, which is constructed for rough honing, a second holder is in a second working position below the tool 15a, constructed for finish honing, and the third holder is clear of the tools and a clamping device so that a work piece may be loaded thereon or unloaded therefrom. Rotation of the table through 120 degrees brings the first holder below the tool 15a, the second holder to the unloading position, and the third holder below the tool 15. Such indexing of the table is effected by a piston 51 operating in a cylinder 52 and having a rod 53 formed with rack teeth engaging a gear 55 loose on the shaft 43. A pawl 57 pivoted on the gear 55 is urged by a spring 61 into engagement with one of three recesses 60 in the shaft 43, so that outward movement of the piston 51 produces 120 degree rotation of the shaft. To permit return movement of the gear without the shaft, a plunger 62 is projected to depress the fail of the pawl so as to disengage its head from the recess 60. The plunger is operated from a crank arm on a shaft 65 which is rocked by a piston 67 operating in a cylinder 68, the piston rod 73 having rack teeth meshing with a pinion 72 secured on the shaft 65 and also having a conical end adapted to engage in one of three conical recesses 74 formed in the shaft 43, so as to lock the latter. Clamping mechanism for the two work pieces disposed in the working positions comprises a bridging member 86 secured to brackets 83 integral with a slide 81 in which the shaft 43 is journalled and which is adjustable on a slideway 82 formed on the pillar 9. The member 86 has apertures in which are secured members 87 having downwardlyextending work-engaging portions. 88, while a bushing 90 in each member 87 acts to guide the tool. These two work pieces are each adapted to be lifted from its holder and clamped against the corresponding member 87 by a piston 91 operating in a cylinder 92 carried by the brackets 83. A sheet-metal pan 95 Carried by the brackets serves to collect the cooling fluid directed over the tools, whence it is discharged through pipes to a sump. Pressure fluid is supplied to the cylinders 52 and 92 by a pump 98a driven by the motor 27. Prior to operation of the machine, the motor 27 is started, the various elements and valves being in the positions shown diagrammaticaly in Fig. 5 and a new work piece having been loaded on the free work-holder. The operating cycle is now started by momentary closure of a "start" switch. The electrical control system is such that a solenoid VS-6 is first energised to operate a valve V-6, whereby fluid from the pump 98a passes to the upper ends of the cylinders 92 so as to unclamp the work pieces. When the pistons 91 reach the bottom, pressure builds up until a pressure-operated valve PV-1 opens and admits fluid to the inner end of the cylinder 68 to withdraw the rod 73 so as to unlock the tabfe 42 and withdraw the plunger 62. As the piston 67 reaches the end of its stroke, it uncovers a port which admits fluid to the outer end of the cylinder 52. The piston 51 thus moves to index the table. When the piston 51 reaches the end of its stroke, its rod 53 operates a switch S-4 which causes the solenoid VS-6 to be de-energised and the valve V-6 to return to normal position. Fluid is now directed into the outer end of cylinder 68 to move the rod 73 so as to lock the table and to advance the plunger 62 to disengage the pawl 57. As the piston 67 reaches the end of its stroke, it uncovers a port which admits fluid to pressurecontrolled valves PV-2 and PV-3. Valve PV-3 is set to open at a predetermined pressure so as to admit fluid to the lower end of the cylinder 92, whereby the work pieces are reclamped. Pressure builds up until the valve PV-2 opens to direct fluid to the inner end of cylinder 52, whereby piston 51 is retracted. The rod 53, during this return movement of the piston 51, momentarily operates a switch S-5 which energises a solenoid VS-2 to operate the valve V-2 so as to start the reciprocation of the head 11. As the tools enter the. work pieces, a cam 103 on the head closes' a switch S-9 which starts the motor 22a to drive the pump 21 and thus operate the motor 16 to rotate the tools. The switch S-9 also causes energisation of a solenoid VS-4 to operate the reversing valve V-4 whereby fluid is directed into the upper ends of the cylinders 33 and 33a from the low-pressure pump 26 so as to expand the tools into light engagement with the work pieces: As the head 11 approaches its lower limit, a projection 29 thereon engages a stop 30 on a control rod 28 whereby the latter is moved down to operate a pilot valve PV which causes hydraulic operation of valve V-3 so as to reverse the direction of movement of the head. At the upper end of the working stroke, the projection 29 engages a stop 31 on the rod and again causes reversal. The switch S-9 also sets in operation an electrically-driven timing device which, after a predetermined time, energises a solenoid VS-5 to operate a valve V-5 so as to switch over the tool expanding mechanism from the low-pressure pump 26 to the high-pressure pump 21, and also sets in operation a second timing device. This latter, after a predetermined time, de-energises the solenoid VS-4 to permit the valve V-4 to return to normal position and cause collapse of the tools, and also sets in operation a third timing-device which, after a predetermined time, energises a solenoid PS which rocks the rod 28 so as, to move the stop 31 out of the path of the projection 29. Thus the head 11 is permitted to move upwards beyond its normal stroke, withdrawing the tools from the work and co-operating with a stop 30a on the rod 28 to move the valve PV. When the head reaches its upper position, the cycle is ended by the opening of a cam-operated switch S-6. Means are also provided whereby the direction of rotation of the motor 16 may be controlled automatically or manually. Thus, if a manually-operable switch is moved to one position, an electrically-operated device is set into operation to energise solenoids VS-1 and VS-1a alternately whereby a valve V-1 is operated to reverse the motor 16 intermittently. If the switch is moved to a second position, the automatic reversal is rendered inoperative, while further manually-operated switches'are provided to reverse the motor as desired.