Mechanical-hydraulic radial feed system for a lathe

#The invention relates to lathes, and more particularly, to a mechanical-hydraulic radial feed system for a lathe having a plurality of tools which can be selectively operated in the radial direction to cut a workpiece in the form of wire or rod which is carried by a headstock for rotation and axial movement therewith.

#In known lathes there are provided a plurality of tool slides capable of movement in the radial direction of the workpiece and which are operated by corresponding profile cams mounted on a common control shaft and which in turn act through strongly spring biased lever mechanisms. In automatic lathes, lever mechanisms having different lengths constitute the path for transmission of force from the associated cams to the respective tool slides, so that the transmission loss resulting from the rigidity of levers and the joint between the levers as well as the relative magnitude of such loss are of a great consequence. An automatic lathe having an increased length of the transmission path is inadequate for a high precision machining, and additionally presents inconveniences because of varying machining precision associated with different tool slides. The preparation of a plurality of cams applicable to the respective tool slides and their positioning in predetermined orientations on the common control shaft also represent a troublesome operation.

#The above described disadvantages can be overcome in part by driving the tool slides with corresponding hydraulic cylinder units. A construction of this type is disclosed in Japanese Patent Publication No. 15,356/1970 which is based on its counterpart application in West Germany filed Dec. 21, 1965. In the disclosed arrangement, each tool slide is connected with a piston rod of an associated hydraulic cylinder unit, so that the path of transmission mentioned above can be minimized. However, the motion of the tool slides is controlled by a switching of control valves which are connected between the cylinder units and a pump. As a result, in contrast to the forced drive transmitted through the lever mechanisms mentioned above, alignment with the cams is not assured. In addition, a variation in the consistency of the working fluid resulting from temperature changes gives rise to a deviation, requiring resort to a manual adjustment of screw stops in determining the amount of feed.

#FIG. 1 is a side elevation of the mechanical-hydraulic radial feed system for a lathe according to the invention, as viewed in the axial direction of the workpiece;

#FIG. 2 is an enlarged cross section taken along section line 2--2 shown in FIG. 1;

#FIG. 3 is an enlarged cross section taken along the line 3--3 shown in FIG. 1;

#FIG. 1 shows the essential part of a mechanical-hydraulic radial feed system for a lathe according to the invention which is mounted on a machine table, not shown. The lathe on which the system is used includes a bed 10 from which extends a rigid vertical frame 11, which is integral therewith. A support bushing 12 is fixedly mounted in an opening 16 which is formed in the frame 11. Since a support bushing is well known in the art, it is not shown in detail. However, the support bushing 12 used in the present invention may be either of the type which is in sliding contact with a workpiece 13 or the type which rotates with the workpiece 13. As will be clear from FIG. 2, the workpiece 13 is held by a headstock 14 of a lathe which includes a chuck 15, and is adapted to be driven by the headstock 14 for rotation and axial movement. A feed arrangement incorporating such a headstock is also well known in the art, and in the embodiment, it is arranged on the back side of the vertical frame 11. Instead of providing the support bushing 12, the arrangement shown may be modified by advancing the location of the chuck 15 into the opening 16, together with the headstock 14.

#A plurality of tool slides 17, which are five in the example shown, are slidably mounted on the front surface of the vertical frame 11 so as to be movable in the radial direction of the workpiece 13. Each tool slide 17 has an identical construction, and the slides are distributed in a single vertical plane. Each tool slide 17 has a tool holder 18 mounted thereon, on which a tool 19 is firmly held by set screws 20 so as to be at a given spacing from the workpiece 13 when the slide 17 is in its inoperative position. In order to hold the tool 19 in a given orientation, the tool holder 18 is adjustable with respect to the tool slide 17. More specifically, referring to FIG. 4, the holder 18 is mounted on a pair of stems 21, 22 which are secured to the slide 17. A screw 23 threadably engaging the holder 18 in turn threadably engages a threaded bore in the stem 21, thus making the holder 18 adjustable lengthwise of the stem 21. A pair of screws 24, 25 (see FIGS. 1, 3 and 4) threadably engage the holder 18 through the opposite walls and have their inner end in abutting relationship against the opposite sides of the stem 22 which extends through a transverse bore 26 in the holder 18, thus making it adjustable in a direction along a line which joins the screws 24, 25. In this manner, the holder 18 enables the tool 19 to be movable in the radial direction of the workpiece 13 in a vertical plane. Once the adjustment is made during the assembly, the orientation is maintained for a prolonged period of use.

#Each tool slide 17 is formed with a dovetail groove 27 (see FIG. 3) which extends radially of the workpiece 13, and a dovetail guide 29, secured to the front face of the vertical frame 11 by means of a threaded bolt 28, slidably engages the groove 27, whereby the tool slide 17 is movable between its inoperative position and its maximum advanced position. The guide 29 is formed with a relatively large slot 30, which communicates with a slot 31 formed in the vertical frame 11. The tool slide 17 carries an arm 32 extending in a direction parallel to the length of the workpiece 13 to the opposite side of the vertical frame 11 and which has a flange 33 which is in turn firmly attached to the slide 17 by means of threaded bolts 34. The arm 32 is made of a material having a high rigidity, and carries a roller 38 at its end which is pivotally connected, through a bearing, with a forked end 37 of a piston rod 36 received in a hydraulic cylinder unit 35. The cylinder unit 35 has a first and a second port 40, 41, and when a hydraulic pressure is supplied through the port 40 while a hydraulic pressure is released through the port 41, the piston rod 36 is driven to its lowermost position, as viewed in FIG. 2. At this time, the piston rod 36 acts through the arm 32 to drive the tool slide 17 to its maximum advanced position, which is lowermost as viewed in FIG. 2. When the hydraulic pressure is released through the first port 40 and simultaneously the hydraulic pressure is supplied through the second port 41, the reverse is true. Thus the piston rod 36 is driven to its uppermost position as viewed in FIG. 2, and in turn drives the tool slide 17 to its inoperative or uppermost position. The control of movement of the piston rod 36 between these two extreme positions will be more fully described later with reference to FIG. 7.