Patent GB-1211456-A (GB)
Title: Spindle orienting and drawbolt malfunction sensing machine tool control system
Inventor: WOHLFEIL JACK ALVIN
IPC: B23Q15/26
Filed: 1968-04-10
Abstract: 1,211,456. Programmed control of machine tools. GIDDINGS & LEWIS, Inc. April 10, 1968 [April 10, 1967], No. 17121/68. Heading G3N. [Also in Division B3] In a machine tool, having an electrically actiable spindle-locking mechanism, a control system slows down a spindle drive and locks the spindle in accordance with a varying signal, from a commanded transducer coupled to the spindle, whose instantaneous values are uniquely identifiable with corresponding rotary orientation positions of the spindle. Control system A machine tool has an arrangement for automatically changing a work tool in a spindle 21, Fig. 1, by arresting it in a particular rotary position and releasing a drawbolt 26, securing a toolholder 25 in the spindle, by a 45 degree rotation relative to the spindle. The spindle is driven by a motor 22 through an electrically disengageable clutch 23, electrically controlled multi-speed transmission 24 and a gear 108. The drawbolt is actuated by a hydraulic motor 27. The rotary position of the spindle and drawbolt is determined by a two-phase resolver 28, Fig. 10, the stator of which is energized from a sinecosine transformer 33. The rotor 31 of the resolver is driven by the spindle and the position signal from a winding 36 is fed to a discriminator 43 and an amplitude switch 53. The discriminator determines the polarity of the signal and, through direction switch 51, controls relays SP, SM. The amplitude switch controls a relay SAS. The position signal from a quadrature winding 37, through a discriminator 44 and a direction switch 52 controls relays SQP, SQM. It is shown in the specification, by reference to the waveforms from the windings of resolver 28, that the simultaneous de-energization of relay SP, SM, SQP identifies a band about the 360 degree orientation position, the width of which is determined by the setting of the threshold levels. Similarly, the energization of relays SM, SMQ, SQP identified a 90 degree creep speed check point and the energization of relay SQP and de-energization of relay SAS identifies a 180 degree intermediate speed check-point. The selective response to the actuations of the relays is determined by a logic circuit, Fig. 15 (not shown), whereby the transmission 24 is changed to give a two step speed reduction before the orientation position is reached and the clutch 23 disengaged. The logic circuit also controls the energization of electrically actuated hydraulic valve controlling the engagement or release of a shot-pin in a recess 75 Fig.1 of the spindle and the lock or release of the tool-holder in the spindle by a draw-bolt 26 and a draw-bolt actuating mechanism 27 comprising a breech-lock connection between a tool-holder end 165 and a drawbolt end 168 driven by sequentially actuated rotary hydraulic motors. A switch is actuated by the shot-pin to provide an interlock with the draw-bolt actuating mechanism. The desired orientation of the spindle is stated to be set in manually or from a programme control system of the machine tool. Mechanical details of spindle The spindle 21 is supported, for rotation and translation, in a headstock 102 by a spindle sleeve 103 and has a flared socket 104 to receive a tapered shank 105 of the tool holder 25. In a machining mode the spindle 21 is clamped within the sleeve 103 by an arrangement comprising spring stacks which, by axial force, act as a toggle mechanism. The spindle is axially translated, when unclamped, by a ram 141 displaced through a double rack-andpinion 145-147 by a piston 142 incrementally controlled by multiple valves 144.