Patent GB-1232916-A (GB)
IPC: B24B33/10
Filed: 1969-03-20
Abstract: 1,232,916. Grinding. CITROEN S.A. 20 March, 1969 [26 March, 1968], No. 14617/69. Heading B3D. [Also in Division G3] A honing machine tool comprises a hollow spindle 8, Fig. 2, which is mounted for rotational and axial movement, a honing tool 20 driven by the spindle, an expander rod 31, if the tool is expandable, mounted for axial movement within the spindle, means for rotating the spindle, means for moving the spindle axially, a torque detector 19 interposed between the tool and the spindle and operable in response to the torque reaction of the tool to control the pressure of a fluid in a first passage 95, Fig. 1, and means responsive to the pressure of the fluid in the passage 95 for imparting axial motion to the spindle or the expander rod. The pressure responsive means comprise a valve 100 having two relatively movable components one of which includes a second passage 106 and the other of which includes a member 104 movable relative to the passage 106 to close the passage. The tool also includes means for moving one of the valve components according to the fluid pressure in passage 95, e.g. a bellows 102, means for moving the other component according to a set pressure prevailing in an auxiliary passage 109, e.g. a bellows 108, a servo-mechanism for axially moving the expander rod 31 or the tool 20, and means for controlling the servo-mechanism according to the positions of the two components. The arrangement is such that the tool operates at substantially constant torque. In the tool described the spindle 18 is rotated by an hydraulic motor 30, and the rod 31 is moved axially of the spindle by an hydraulic motor 46. The spindle is movable axially by a piston 12, Fig. 2, in a cylinder 11, and the cylinder 11 and motors 30 and 46 are mounted on a vertically movable support 2. Operation of the machine commences with the support 2, Fig. 1, in its uppermost position in which a microswitch 7 is operated, contacts 89 are closed, and the tool is collapsed. In this situation electromagnets 52 and 61 are energized so that valves 51, 59 respectively are opened and fluid under pressure is supplied to motor 30 and to a cylinder 3 to cause the spindle 18 to rotate and support 2 to be lowered. When the support 2 reaches its lowest position it operates a switch 8. This causes an electromagnet 69 of a valve 68 to be energized so that fluid under pressure is supplied to a servo-valve 64 which in turn causes reciprocation of the piston 12 and hence of the tool. The switch 8 also causes energization of an electromagnet 126 of a valve 124 which allows fluid under pressure to be supplied to a servovalve 117. Simultaneously, electromagnet 114 of valve 113 is energized to reduce the reference pressure in bellows 108 so that the operating torque is lowered. Also an electromagnet 121 of a valve 118 is energized so that one bellows 116a of a pair of bellows linked to valve 117 is vented to atmosphere. As a result motor 46 is driven and the tool is expanded rapidly. As the rod 31 moves downwardly valve means carried by it causes a contact 81 to be operated to de-energize the electromagnet 121 and energize a first delay relay. This reduces the rate of expansion. The tool operates at low torque until the relay operates to de-energize the electromagnet 114 so that the reference pressure in bellows 108 returns to its normal value. The workpiece is then machined at normal torque. If the torque becomes excessive the valve 100 opens to vent the passage 106 to atmosphere which results in stoppage of the motor 46. When the desired workpiece size is reached, i.e. when a predetermined expansion is attained, valve means carried by the rod 31 cause contact 85 to close, thus causing valve 124 to close and motor 46 to stop. The tool then operates at reduced torque to smooth the workpiece until the torque reaches a predetermined minimum value. At this value contact 98 is closed to cause a valve 115 to be reversed and a second delay relay to be energized. When this relay closes valve 124 is opened and servo-valve 117 and valve 118 operated so that motor 46 runs in reverse to raise rod 31. At the same time electromagnet 69 is de-energized to stop reciprocation of the tool and valve 51 is operated to cause the support 2 to be raised. As the rod 31 rises valve mechanism carried by it causes contact 89 to operate to de-energize electromagnet 61 and stop rotation of the spindle. Simultaneously valve 124 is closed to stop the motor 46 and valve 115 is returned to its initial position. Finally micro-switch 7 is operated to return the valve 51 to its neutral position. To compensate for wear of the tool the valve mechanism carried by rod 31 is adjustable by a wheel 90 which moves a cylinder 76 relative to a piston 75 carried by the rod 31, the piston having passages which act as valve parts. In a second embodiment having a non- expanding tool the valve 100 controls the reciprocation of the support 2 during grinding.