CA2025004A1

CA2025004A1 - Manually controllable lathe

Info

Publication number: CA2025004A1
Application number: CA002025004A
Authority: CA
Inventors: Franz Rechberger; Peter Meiser; Siegfried Grauli
Original assignee: Individual
Current assignee: Voest-Alpine Steinel GmbH
Priority date: 1989-09-11
Filing date: 1990-09-10
Publication date: 1991-03-12
Also published as: HU905845D0; RU1829982C; EP0418213A3; PL163393B1; YU170490A; PL286825A1; HU205728B; EP0418213A2; HUT55657A; KR910009372A; AT394509B; DD297581B5; KR940005394B1; ATA212489A; DD297581A5; CN1052443A

Abstract

ABSTRACT
MANUALLY CONTROLLABLE LATHE

A lathe is disclosed which permits of a simple manual control although the transmissions, clutches, brakes and change gears usually required for a manual control have been omitted. This is acocmolished in that the feed drives for the longitudinal slide and the cross-slide consist of respective variable-speed reversible three-phase a.c. motors, which serve to drive the associated screws, which consist of ball screws, the handwheels for controlling the movements of the tool carriage are operable to adjust respective electric synchro generators, each of which is connected to a control-ler for the associated three-phase a.c. motor, and a control unit is preferably mounted on the tool carriage and comprises manual data input means for input data indicating the prese-lectable transmission ratio between the rotation of each handwheel and the rotation of the associated screw or the associated three-phase a.c. motor and display means for indi-cating the input data and data representing the actual posi-tions of the slides.

Description

~ i~ 2 ~
M~NUALLY CO~JTROLLA~LL LATHE
RAC~G~OUND OF THE INVENTIG~
Field of the Invention This invention relates to a manually controll-able lathe comprising a machine bed provided with guideways for guiding a tool carriage, ~hich comprises at least one lonoitudinal slide and at least one cross-slide, a main drive for the ~lork spindle, a longitudinal feed drive comprising a lead screw and a feed screw for the longitudinal slide, a eross-feed drive comprising a cross-scre~ far the cross-slide, and two handwheels, which are mounted on the tool car-riage and operable to control the movements of the longitu-dinal slide and the cross-slide, respectively, along the asso-eiated screws.

Deseription of the Prior Art In the conventional lathes whieh can be manu-ally controlled the work spindle is driven by a multiple-speed main transmission, which is adapted to be driven at a eonstant speed by a three-phase a.c. motor and the drive for the tool carriage is derived from that main drive via a se-eandary transmission, which is operatively connected to the lead and feed screw for the lonyitudinal slide of the tool earriage. An apron is connected ta the longitudinal slide and is operable to drive a cross-screw for imparting a cross-Feed movement to the cross slide. P manually shiftable trans-mission is pravided for the longitudinal and cross-feed move-ments. In addition to said feed dri\/es which are provided on the tool carriage and driven by the main transmissian, hand-wheels may be provided, which are meehanically connected to the longitudinal slide and cross-slide and operable to drive said slides. It is apparent that the feed drives with their ~2~
Z

tr3nsmissions,clutches, brakes and shiftable gears involve a very high structural expenditure, particularly because close tol-rances must be complied with.
In addition to such manually controllable lathes, numerically controlled lathes are in operatian, in which the feed drives for the tool carriage are constituted by variable-speed reversible three-phase a.c. motors, which are controlled by a suitably programmed computer whereas there is no need for transmissions, clutches and brakes involving a substantial structural expenditure. Such computer-controlled lathes can hardly be used to machine individual workpieces but are used in series production because the control program mu3t be al-tered to conform to changing machining requirements and skilled operators are required for such alteration.

Summary oF the Invention It is an object of the invention so to improve a lathe which is of the kind described first hereinbeforz that the advantages of numerically controlled lathes as regards simolicity of structure and infinite control of the feed drives can be utilized whereas the conventional simple control which is desirable for the machining of individual workpieces is re-tained.

That object is accomplished in accordance with the invention in that the feed drives for the longitudinal slide and the cross-slide consist of respective variable-speed reversible three-phase a.c. motors, which serve to drive the associatzd screws, which consist of ball screws, the hand-wheels for contralling the movementa of the tool carriage are operable to adjust respective electric synchro generators, each of which is connected to a controller for the associated three-phase a.c. motor7 and z control unit is preferably mounted on the tool carriage and comprises manual data input means for input data indicating ~he preselectable transmission ratio between the rotation of each handwheel and the rotation of the assaciated screw or the assDciated three-ohase a.c. motor and display means for indicating the input data and data re-presenting the actual positions of the slides.

In that arrangement the handwheels for con-trolling the movement of the carriage in the longitLJdinal and transverse directions serve to adjust a synchro generator, which indicates to the control unit the desired value for the finite angular movement to be performed hy the associated screw and the associated three-phase a.c. motor can properly be operated in consideration of the preselected transmission ratio between the rotation of the handwheel and the rotation of the screw so that the slide that is to be moved is adjusted in response to an angular movement of the handwheel by a manual control which is similar to that reauired in conven-tional carriage control means comprising manually operable drive wheels. The actual position of each slide will be dis-played by the cantrol unit, which for that purpose is desirab-ly mounted on the tool carri2ge. The handwheels for controll-inq the movements of the slides may be mounted on the tool carriage at the same locations as in conventional lathes of the present kind so that the requirements for manual operation are the same. For instance it will be desirable to mount the handwheel for controllinq the adjustment of the cross-slide at a location which is axially aligned with the transverse screw provided for that purpose so that the lathe operator gets a visual indication that that handwheel controls the ad-justment of the cross-slide. The operational requirements differ from those of conventional lathes only in that the se-veral feed rates are not selected by associated transmissions but are preselected by the input data for the contrcl unit.

~2~
l, Special program~ing knowledoe is not required for inputt-ing such data, particularly because the data which have been input can be read from the display.

A relatively small torque will be sufficient for adjusting a synchro generatDr. In order to ensure that the rotation of the handwheels wheel is opposed by the re-sistances which customarily oppose the adjustment of the tool carriage in the longitudinal and transverse directions, a brake for controlling the resistance opposing the rotation of each handwheel may be provided so that conditions regard-ing the operation of the handwheels are also comparable to those arising in conventional lathes.

Conventional lathes for manual control comprise a control switch, which is provided adjacent to the apron and consists of a four-way intermediate switch, which via associated clutches controls the feed drives for the move-ments alon~ the longitudinal and transverse axes in both di-rections of movement in dependence on the position of the switch. The tool carriage of the lathe in accordance with the invention may also be provided with such a control switch for controlling the two feed drives by means of the control unit.

If the control unit is provided with desired-sDeed input means for the contral of the main drive and with a control signal output for the main drive consisting of a controllable three-phase a.c. motor and a manually shiftable two-speed transmission, the control unit can also be used to control the drive of the work spindle so that the control of the feed drives in dependence on the drive of the work spindle will be simplified. In that case, conventional operating re-quirements will have to be met in that respect iF the tool carriage carries for the control of the energization of the main drive a switch which i9 operatively connected to the control - 5 ~

unit and can be operated to initiate an ooeration of the work spindle in one sense or the other after an input of data which determine the speed desired for the work spindle.

Brief Description of the nrawina The drawing is a diagrammatic top plan view showing an illustrative embodiment of a manually controllable lathe in accordance with the invention and i9 also a block circuit diagram representing the control system.

Detailed Descriotion of the Preferred Embodiment The illustrated lathe comprises a machine bed 1, hich in the usual manner carries a~headstock 2, a ~ork spindle 3 mounted in the headstock, a tailstock 4 and a tool carriage 5. The tool carriage 5 comprises a longitudinal slide 7, which is movable alonq longitudinal guideways 6 of the machine bed 1, and a cross-slide B, which is movably mounted on transverse guideways on the longitudinal slide 7.
The work spindle 3 is driven by a variable-speed reversible three-ohase a.c. motor 9, which together with a manually shiftable two-speed transmission 10 constitutes the main drive of the lathe. The longitudinal feed drive for the longi-tudinal slide 7 consists of a variable-speed reversible three-phase a.c. motor 11 for driving a lead and feed screw 1Z, which consists of a ball screw that is provided with a bia-sed nut 13 for moving the longitudinal slide 7 without a backlash. Similarly, the cross-feed drive far the cross-slide 3 consists of a variable-speed reversible three-phase a.c.
motor 14 for driving the cross-feed screw 13, which again con-sists of a ball screw provided with a biased nut 16.

~ or the control of the three-phase a.c. motors 9, 11 and 14 the tool carriage 5 is provided with a control unit 17, which is provided with data input means 1~ for a manual input of data indicating the desired feed rates and transmission ratio, and with a display 19 for indicating the selected desired values anr! the instantaneous actual positions of the slides of the tool carriage 5. The manual control of the three-phase a.c. motors 9, 11 and 14 is effected by means of manual contrDls which are Drovided on the tool carriage 5 and are operable under conventional conditions. For instance, the main drive is controlled by means of a control switch Z1, which is operable by a handle 20 and delivers suitabla con-tral commands to the control unit 17 for the operation of the work spindle 3 at the speed which has been selected by the data input means 13. The actual speed of the work s,oindle 3 is detected by an incremental angle encoder Z2, by which corresponding feedback data are delivered to the control unit 17. The sense of rotation of the work spindle is determined by the sense of the rotation which is imparted to the handle Z0, which is mounted for rotation about an axis which is pa-rallel to the axis of the work spindle 3.

The energization of the feed drives for the movements along the longitudinal axis and the transverse axis can similarly be controlled by a contral switch 23, which consists of a four-way intermediate switch and which in res~
ponse to an actuation in a direction which is parallel to the lead and feed screw 12 will cause the control unit 17 to energ,ize the three-~h~se a.c. motor 11 for a rotation in a sense dependino on the direction of the movement of the con-trol switch 23 and for effecting a feed movement at the in-stantaneously selected feed rate or at a rapid feed rate. An actuation of the control switch Z3 in a plane which is at right angles ta the lead and feed screw 1Z will similarly control the energizatian of the three-phase a.c. motor 14 for the movement along the transverse axis.

- 7 - 2~ 3~

In addition, the longitudinal slide 7 and the cross-slide a can be moved under the control of handwheels 24 and Z5, respectively, each of which is connected for that purpose to an associated electric synchro generator 25 so that a desired value of the angular movement to be imparted to each of the screws 1Z and 15 can be indicated to the con-trol unit hy the synchro generators 26 in dependence on the preselected transmission ratio between the rotation of the handwheel and the rotation of the screw. In this manner the handwheels 24 and 25 can control the movements of the tool carriage 5 along the longitudinal and transverse axes and the actual positions of the resoective slides will be fed back to the control unit 17 by incremental angle encoders, which are associated with the three-phase a.c. motors 11 and 14 or the screws 1Z and 15, and will be indicated by the display 19.

It is aoparent that the illustrated lathe can be used for all machining operations which can be performed by conventional lathes and the operational requirements are the same as usual and the advantases are afforded which are due to the use of variable-speed reversible three-phase a.c.
motors in the feed drives. This will not only result in a higher economy but also in a higher accuracy of the machining operation, e.g., because the drives can infinitely be con-trolled.

Claims

1. In a manually controllable lathe comprising a machine bed provided with longitudinal guide-ways, a tool carriage mounted on said machine bed and comprising a longitudinal slide, which is in sliding contact with and movable along said longitudinal guideways and is pro-vided with transverse guideways extending transversely to said longitudinal guideways, said tool carriage also com-prising a cross-slide, which is mounted on said longitudinal slide to move in unison therewith along said longitudinal guideways and is in sliding contact with and movable along said transverse guideways, a work spindle mounted on said machine bed for rotation about a longitudinal axis which is parallel to said longitudinal guideways, main drive means for rotating said work spindle about said axis, a longitudinal feed drive comprising a first lead and feed screw for imparting to said longitudinal slide a longitudinal feed movement along said longitudinal guideways, a cross-feed drive comprising a second feed screw for imparting to said cross-slide a cross-feed movement along said transverse guideways, a first handwheel, which is rotatably mounted on said machine bed and is manually rotatable to control said longitudinal feed drive, and a second handwheel, which is rotatably mounted on said machine bed and is manually rotatable to control said cross-feed drive, the improvement residing in that said longitudinal feed drive comprises a first variable-speed reversible three-phase a.c. motor for rotating said first screw, siad cross-feed drive comprises a second va-riable-speed reversible three-phase a.c. motor for rotating said second screw, each of said first and second screws consists of a ball screw, first and second synchro generators are opera-tively connected to said first and second handwheels, re-spectively, and adapted to deliver output signals depending on the rotation of said handwheels, first and second motor controllers are provided and arranged to control said first and second motors, re-spectively, in response to said output signals of said first and second synchro generators, respectively, for a rotation of the associated screw at a preselectable transmission ratio between said screw and the associated one of said handwheels, and a control unit is provided, which comprises data input means for a manual input of input data indicating de-sired feed rates for said longitudinal feed and cross-feed movements and desired values for said transmission ratios, and display means for indicating said input data and the ac-tual positions of said longitudinal slide and cross-slide along said longitudinal and transverse guideways.

2. The improvement set forth in claim 1, wherein said control unit is mounted on said tool carriage.

3. The improvement said forth in claim 1, wherein a brake is associated with each of said handwheels and pre-sents a predetermined resistance opposing the rotation of said handwheel.

4. The improvement set forth in claim 1, in which a four-way intermediate switch is provided, which is mounted an said tool carriage and operable to control the energization of said first and second motors for effecting said longitudi-nal feed movement and said cross-feed movement at the feed rates indicated by said input data.

5. the improvement set forth in claim 1, wherein said main drive comprises a manually shiftable two-speed transmission and a third variable-speed three-phase a.c. motor for rotating said work spindle via said trans-mission, said data input means comprise speed input means for inputting desired-speed data indicating a desired speed of said work spindle, and said control unit is provided with a control output connected to said third motor and is operable to con-trol said third motor via said control output in dependence on said desired-speed data.

6. The improvement set forth in claim 5, wherein said tool carriage comprises a switch, which is provided with a handle and is electrically connected to said control unit and serves to control the energization of said third mo-tor.

7. The improvement set forth in claim 1, wherein said first and second motor controllers are arranged to con-trol said first and second motors, respectively, in response to said output signals of said first and second synchro gene-rators, respectively, for a rotation of the associated screw at a preselectable transmission ratio between said motor and the associated one of said handwheels.