Stock sensing device

#This invention relates to workholding chucks as used on automatic turning machines. Automatic turning machines generally utilize long bars for work feed stock which extend through the spindle of the head stock of the machine out of the front of the spindle and though a work holding chuck. As a workpiece is finish-machined and cut off from the parent bar stock, the grip of the workholding chuck can be relaxed and the bar is fed outward to present new material for machining. Many types of bar feeder attachments are used to increment stock through the work spindle. There are pushers which urge the workstock forward from the rear of the headstock and there are pull type attachments which grab a part and withdraw it from the front of the chuck. It is with this latter type of attachment that the present invention can be used most advantageously.

#After withdrawing additional stock through the chuck for the next successive machine operation the chuck reclamps on the workstock. At this time, it is imperative that there be sufficient clamping stock present within the clamping area. If this condition is not met and there is not sufficient clamping stock present in the clamping area, a real and active danger exists, in that as the workpiece is rotated and a cutting tool is engaged against the workpiece, it may be "cammed" out of the clamping position due to forces generated by the cutting action. Additionally, in the absence of sufficient clamping stock, the chuck may not be operating at its proper design forces and may tend to have overstressed points which could operate to the detriment of the chuck assembly and cause failure of the components. For example, if a jaw type chuck is used for clamping the work stock and there is not sufficient stock to cover the clamping face of the jaws, high unit stresses will be developed over the zone of the clamp and high bending stresses may be developed in the jaw bodies as well. Since the jaws are normally subjected to great stresses because of the fly-away tendencies of centrifugal action, the internal stresses are compounded and may cause failure of the jaws.

#Most prior art devices for sensing the presence of stock to allow adequate clamping have also included cumbersome mechanical devices which reach through the headstock spindle and touch the end of the workpiece. These devices, however, are impractical to use and function. Similarly, stock feelers have been contained within a chuck body which necessitates having a complex chuck unit and feedback sensing control. Many of these disadvantages have been alleviated by the stock sensing device disclosed in applicant's U.S. Pat. No. 3,982,085. The present invention, likewise, alleviates many of these prior art problems with further elimination of mechanical features and increased simplicity. It provides an alternative method of stock sensing with additional cost savings.

#FIG. 1 is a front elevational view of a turning machine utilizing a form of the present invention.

#FIG. 2 is a front elevational view of the turning machine of FIG. 1 with the housing removed for clarity of illustration.

#FIG. 3 is a front elevational view, partially in cross-section, of the rotary union and quick disconnect coupling utilized in the embodiment of FIG. 1.

#Referring to the drawings and to FIGS. 1 and 2 in particular, a turning machine 1 having a rotating workholding chuck 2 is shown holding a workpiece 3. The chuck 2 is mounted to a face of a spindle 4 for rotation therewith. A draw tube 5 (shown in cross-section views of FIGS. 5 and 6) extends from the chuck 2 and beyond the housing 6 within the spindle 4. The draw tube 5 terminates in a rotating hydraulic cylinder 7 where it is axially moved by a piston 8 (FIG. 4) contained within the cylinder 7. An extension 9 from the cylinder 7 is capped by a quick disconnect coupling 10 which is connected to a rotary union 11. A fluid supply pipe 12 is joined in fluid communication with rotary union 11 and supplies a pressurized fluid, preferably air, to a channel 13 extending from the end of extension 9 through coupling 10, hydraulic cylinder 7, draw bar 5, and chuck 2 to the ambient atmosphere. A plastic liner 14 (FIGS. 3-5) lines substantially all of channel 13 and extends from the chuck 2 to the coupling 10.

#As shown most clearly in FIGS. 4 and 5, the draw tube 5 transmits a linear force to several pivoted levers 15 in the chuck 2 which convert the linear force to a radial force for radial movement of a plurality jaw slides 16, in unison, to grip the workpiece 3. This linear force is imparted to the draw tube 5 by the conventional rotating hydraulic cylinder 7.

#The hydraulic cylinder 7 (FIG. 4) is of conventional design and composed of two sections, a stationary section or stator 17 and a rotating section or rotor 18. An internal bore 19 extends through the spindle 4, stator 17 and the rotor 18 and receives the draw tube 5 within the rotor 18 where it is threadably connected to the piston 8. The piston 8 is axially movable about the periphery of plastic liner 14 within the rotor 18 in accordance with hydraulic pressure communicated to the piston surfaces through ports 20 and 21 contained in the stator 17 and defines a portion of the bore 19. Extending from the stator 17 is a rotor extension 9 which is supported by a plurality of cam rollers 22 (only one of which is shown in FIG. 3) which are in turn supported by an outboard support assembly 23. The rotor extension 9 terminates beyond the support assembly 23 and is capped on its end by a quick disconnect coupling 10 and rotary union 11.