GB2251817A - A boring head unit - Google Patents

Abstract

The unit comprises a boring head including a shaft, a machining unit including preferably two tools radially displaceable relative to the shaft of the head, gearing actuated by a stepping motor for automatic readjustment of the tools in operation, and electric circuitry for controlling the stepping motor. The gearing comprises a planetary system including satellite gears (106) carried by a satellite gear carrier (109) mounted on the boring head shaft, the carrier being provided with a gear ring (116) meshing with a setting gear (110) for controlling the tool feed via a motion screw (115). The shaft of the setting gear is coupled with the output shaft of the stepping motor associated with a power element of the electric controlling circuitry which is bidirectionally connected with a control unit. The control unit can be constituted by a machine NC control system, software equipment of a personal computer, or a control desk with connections of the corresponding functions. <IMAGE>

Description

1 A BORING HEAD UNIT The invention relates to a boring head unit h'ning

and designed especially for finishing mac... comprising a boring head, a machining unit including at least one tool, radially movable relative to the axis of the head, gearing actuated by a stepping motor for automatic readjustment of the machining unit in operation, and electric circuitry for controlling the stepping motor. As is well known, such heads can perform a variety of operations including turning outside and inside diameters, recessing, necking, undercutting, facing and others.

Known boring heads, apart from -he common principle of the arrangement of a rotary body in a stationary box, comprise variously embodied gearings C) J -ools.

for the radial displacement on readjustment of 4. The kind and number of gear sets used in such gearing -he boring head correspond to the purpose for which t may serve. Thus, -for instance, boring head according 58 allowing only the to the German Patent No. 1,652,6rl manual displacement of tools in operation, comprises bevel. wheel sets with palloid gearing, and worm wheel C C, sets. The same fundamental gearings are used with the boring head according to the US Patent 'No.

4,489,629, which can be automatically rearranged.

similar gearing structure is also used with the boring head according to the German Published Application No. 2,151,045 which, by providing additional gearings, enables the revolution rate be 7() controlled in dependence on the a radial tooi motion.

A common drawback of all of the boring head designs as hereinabove referred to resides in the mutual arrangement of the gearing elements. This arrangement requires the use of bevel wheels with A 2 palloid gearing as well as worm wheels which are relatively very expensive and do not enable plays in the assembled system to be adjusted. The plays are substantially determined in the manufacture by axial spacings. With systems improving the fundamental structural embodiment, it is the demand after ever increasing floor areas that is disadvantageous.

The abovementiond drawbacks have partially been eliminated by the boring head according to German Published Application No. 2,940,827 in which 4 relatively simple and Lnexpensive spu." gears have been applied. it is admitted that the arrangement of.he gearing so as to form a plurality of planetary gearings together with additional coupling elements, enables rapid movement of tools but the overall i 1 4 complexity of gearing system is prohib Lve. A considerable disadvantage can be seen in that the maximum radial movement of the too! does not even correspond to the most frequent diameters of holes to be bored, if considering the given boring head diameter. Depending upon the production plan, the user may therefore be obliged to use a plurality of boring heads with various diameters so that the cost of purchasing such tools is relatively very high. This drawback holds for all of the types of the boring heads as hereinabove referred to.

Another problem encountered with boring heads equipped with a servodriive of radial 'Uool readjustment lies in the complexity of thei-r design, since their gearings that comprise all elements necessary eg for the selection of tool motion speed, rapid retrotraverse and other operations, are equipped with a servo-drive which, however, simulates' only the manual control of operations of mechanical 4 35) gearing and Ls not adapted to the actual boring head 3 - structure. This is why the size of t'l-le boring head becomes so large as to impair the head clamping. This problem has partly been solved by providing a boring head (European Patent Application No. 2114 583) wherein a motor is received in the boring head interior and directly functionally coupled with a planetary gear. However, the expensiveness of such a specific structure corresponds to the abovementioned high price of the said embodiments -to which a servodrive has simply been added and whose price has simply risen.

he boring heads as herenbefore referred to have practically been used excl-,sively in connection with NC machine control system which, however, is ex-oloited for controlling the machine to a very reduced extent and, actually, is substantially blocked by this function. A better situation may be observed with special control systems for digitalized servo-drives which, however, have not been designed for the purpose of the present invention.

-- is an object of the present invention to IV eliminate the drawbacks of prior as hereinabove set forth and to reduce the boring head manufacturing costs while maintaining all of the head functions. Another object is to provide such a gearing structure wherein the radial tool motion, at a given boring head diameter, is extended. The purpose of both said objects is to reduce the price of this too! for the users. While ef-fecting the automatic readjustment of -uools by means of a servo-drive there has to be eliminated the necessity of using NC machine control system but the use of NC machine control system has to be enabled. Another object is to provide such a structure of servo-drive active or power element - ie stepping motor - which makes it possible to modify in 4 an easy way some parameters such as the step number, start, stop, mode- of control, or the like.

According to the invention, the gearings of Uhe boring head comprise a planetary gearing, whose carrier of satellite gears which is mounted for rotation on the shaft of the boring head, is provided with a toothed ring meshing with an output gear for controlling the tool feed, and with the axis of the output gear there is coupled, either directly or via 10 a gear, the output shaft of the steppging motor siruated perpendiculrly to the shaft of the boring head, the electric controlling circuitry comprising a power element attached to the stepping.motor and electrically connected in both directions to a 15 control unit.

The planetary gearing comprises a driving gear _"1xedly attached to an output gear of a smur gearing for reversing the direction of rotation, L further an input gear firmy attached to the shaft of the boring head, said input gear meshing with a first intermediate gear and through the latter and a second intermediate gear with the output gear, said, driving gear meshing with the satellite gears arranged on the carrier, the satellite gears being simultaneously in mesh with a driven gear of the planetary gearing which mesh with a driving gear of tool feed ixedly attached mechanism, said driving gear being f to a motion screw.

The radial tool motion is effected by turning the toothed ring due to the rotation of the output gear, whose shaft is coupled with the either builtin or separate power element which is provided with a connection into four parallel branches, of which each comprises a separating circuit, a shaping the circuit and a teminal circuit. The out-Dut oL separating circuit of each branch is connected to the -he input of said shaping circuit, the output of t latter being connected to the input of the terminal circuit. The output of the terminal circuit in the first branch is connected, via a first winding of the stepping motor, to the output of the terminal circuit in the second branch, the output of terminal circuit in the third branch is connected, via a cond winding of the stepping motor, with the out-out of terminal circuit in the fourth branch, and the middle of the -ed, via first winding of the stepping motor is connect a first voltage dropping resistor, to the second t of a feeding DC source connected through a output second voltage dropping resistor to the middle of the second winding of the stepping motor, while to the first output of said feeding DC source there are connected feeding inputs of all the four shaping " the four terminal circuits. By circuits and all of such a connection mode, in combination with the L rings 'or various feed rates, the suructure of gea, -L rapid tool reverse as well as other operations are enabled, since the stepping motor assumes the functions performed with different heads by additional gearing systems. The power element of the stepping motor is electrically connectd to the control unit which can be constituted by a machine NC control system and its respective programme, or a personal computer equipped with similar software. Most prelerably, however, the control unit comprises a control desk built together with the power element in a common box and provided with a single-chip microcomputer. 'The first gate of the latter is connected to the first input of a block of inputoutput circuits while its zero gate is bidirectionally connected, via a second bus-bar to 6 first input of a controller, zero input of a second gate of the microcomputer is connected via second irst output of second gate input of the controller, f of the microcomputer is connected to the third input of the controller, second up to seventh output of -9 the microcomputer are bidirectionally second gate o. connected to selection inputs of said block of input- -he microcomputer output circuits. Reading putput of t is connected to fourth input of the controller, recording output of the microcomputer is connected to -imer oupul of the Lth input of the controller, and 4V U microcomputer is connected to sixth input of the controller, the first ouput of the controller being U -L connected to first interrumiling, inDut of the microcomputer while to column input o^ the controller and to line input of the same there being connected, via third and fourth gate, a matrix of switches, and to second output of the controller there being connected, through fifth bus-bar, controlling input of a displaying unit. 1For controlling of all of the functions it is sufficient when the control desk is -'-ch for ' feed, a provided with a first main swiL, Uool.

second main switch for tool reverse motion, a block for fixing the feed rate by pushbuttons corresponding to the individual -feed rates and with usual STARTSTOP-ENTER elements. Preferably, it can be equipped with comparing or reference displays of which one is associated with the electronic adjustment and the other with the actual mechanical tool adjustment.

An advantage of extensive use of spur gears is above the price-reducing of all boring head. Thus the number of bevel gears having exclusively linear teeth is limited to a minimum. Another advantage can U be seen in the omission of worm wheel system which is ordinarily used with existing boring head types. Due 7 - to a new arrangement of gearings, and particularly of mechanical part thereof, it is made possible to raise the radial feed rate of each tool to at least 550 per cent diameter with evey boring head size.

Another advantage consists in that the required mode of controlling radial readjustment of tools by means of a servo-drive has been complied with. In this way it is made possible to attain the independence upon software of the machine NC control system and to provide the possibility of easily introducing changes of all of the controllable parameters. Also t-he most preferable control mode by means of a control desk as well as the i-erconnection thereof with the power element of 'he nt stepping motor belong to the advantages of the -erna-4ve of present invention. Nevertheless, the alt U- controlling the boring head either by a computer, or by a machine NC control system remains unaffected.

The invention makes it possible to eliminate idle times in small-lot and piece production, and to include the boring head into an automated flexible production sustem with selectable workpiece flow. In case of automated production it is important that the -" the hole to be bored need not be s+ dimension o. Vored but once, without any corrections until the tool exchange. Advantageously there exists a possibility of a variable arrangement of individual boring head nodes which can be combined with one another. Thus, for instance, head and servodrive and power element cable machine NC control system, or head and servodrive - cable - power element and control desk or the like, as desired.

The invention relates particularly to boring heads of big sizes for boring holes of from 600 to 1400 mm diameter, whrein an accuracy of 0.01 8 - 1 5 2 15 mm or even less is to be attained.

The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which:

Figure 1 is a general view of a boring head controlled by a control desk; Figure 2 shows gearings of the boring head; Figure 3 is a wiring diagram of the power element; Figure 4 is a wiring diagram of one of the branches as shown in PSigure 3; Figure 5 shows the arrangement of controlling and displaying elements of the control box; and -rol Figure o is a wiring diagram of the cont box.

As can be seen in the drawings, and particularly in Figures 1 and 2 thereof, the boring =1 - S and a rotat head comprises a stationary part able part R. The stationary part S is in use firmly connected to a machine tool (not shown) and comprises a box with gearing 100. The box also contains a stepping motor 117 undirectionally connected to a power element 200 which, in turn, is bidilrectionally connected to a control desk 350. The rotatable Dart -ed in use eg by means of a R has a shaft A connect 1 " the machine UaDer M to the sDindle (not shown) ot tool and comprises a machining unit including at least one tool T, preferably two tools T, radially adjustable relative to the axis of the head, ie the axis of the shaft A.

The gearing 100 (Figure 2) comprises a spur gear train 101-104 for changing the direction of rotation and planetary gear train 105-107. The spur 9 gear train includes an input gear 101 f irmly attached to the head shaft onto which a torque from the spindle of a machine tool (not shown) is transmitted. Rotation is transmitted from the input gear 101 to an output gear 104 through a first intermediate gear 102 and a second intermediate gear 103 which mesh with each other and are coaxial with the head. Since -ached to a driving gear 105 the gear 104 is firmly att 4 of the planetary gear train,the latter, being in a differential gear ratio to the main boring head shaft, is driven by said gear 105. Satellite gears C) supported on a carrier 109 mesh with the riving gear 105, and simultaneously with a driven gear 107 of said planetary system. The driven gear 107 meshes with a feed gear 108 of a tool feed mechanism; the gear 108 is firmly attached to the shaft of a motion screw 115 provided with a nut (not shown) directly coupled with the tool feed mechanism. The carrier 109 of the satellite gears 106 is provided with a toothed ring 116 engaging with a setting gear 110 driven by the output shaft of the stepping motor 117 and serving for controlling the tool feeding.

The connection in the power element 200 (Figure 3) is in the form of four identical parallel branches each of which comprises a separating circuit 201, a shaping circuit 202 and a terminal power circuit 203, each of said circuits being earthed. Each of the separating circuits 201 is provided with a pair of input terminals d6signed for connection with one of four parallel outputs of a compuer (not shown). In each of said parallel branches, the output of the separating circuit 201 is connected to the input of the shaping circuit 202 whose output is connected to the input of the terminal circuit 203. 'he output of the terminal circuit 203 in the first branch is connected, via a first winding 204 of the stepping motor 117 (not shown in Figure 3), with the outut of the terminal circuit 203 in the second branch while the output of the terminal circuit 203 in 'he third branch is connected, via second winding 205 of the stepping motor 1117, with the output of the terminal circuit 203 in the fourth branch. T11 h e middle of the first winding 204 is connected, via a first voltage dropping resistor 206, to the second output of a feeding DC source 208 connected, via a second voltage dropping resistor 207, to the middle o the second winding 2205.

To the first, output of the earthed feeding DC source 208 there are connected feeding inputs of all -- Jng circuit Pour shapJ -Us 202 and 7our ' 4 all -IL Uerminal circuits 20-- Figure 4 shows the wiring diagram of one of the branches of 'he power element 200. The separating circuit 201 contains an optical element 20Q. comprising a diode and two transistors (NPN) in Darlington connection. Tnput terminals of said separating circuit 201 are by-passed by the diode of the optical element 209 and interconnected collectors of the two transistors are connected to 'he output of the separating circuit 201, the emitter of the second Uransistor being earthed. The input of the shaping circuit 202 is connected, on the one had, to the base of an input transistor 210 and, on the other hand, via a third resistor 211, to the feeding input of the he emit' shaping circuit 202. T Uer of said input transistor 210 is connected, on the one hand, to the first outlet of a fourth resistor 214 and, on the 12' a fourt other hand, to the first outlet o-I h resistor 214 and, on the other hand, to the first outlet of a fifth resistor 215. The second outlet of said fourth resistor 214 is connected, on the one hand, to earth and, on the other hand, through a capacitor 217, to -L U the output of the shaping circuit 202. To the 'atter there is also connected the second outlet of a sixth resistor 216 whose first outlet is connected to the second outlet of said fifth resistor 215. The collector of the input transistor 210 is interposed, via a first gate 212 and with it series-connected second gate 213, between the fifth and the sixth resistor 215 and 216, respectively. The input of the terminal circuit 203 is connected to the base of its switching PNP transistor 218. The emitter oil said switching transistor 218 is connected, on the one hand, via a seventh resistor 219, to the feeding input of the terminal circuit 203 and, on the oti-ler hand, to the base of a first one of a pai-- of NPN J- uransj4s-U"ors in Darlington connection. This pair -age 220 of the termi- nal circuit constitutes a power st 203. The emitter of the second transistor of the pair of transistors of said power stage 220 is connected, on the one hand, to the collector of the switching transistor 218, and, on the other hand, to earth as well- as to the anode of a Zener diode 221, t bhe cathode of which is connected, on the one hand, to the interconnected collectors of the two transistors of power stage 220, and, on the other " the terminal circuit 203.

hand, to the output o--IL As can be seen in Figures 5 and 6, the f the electric controlling circuitry consists ocontrol desk 350 which constitutes one o he alternatives of a control unit 300, and a fundamental component of which is the connection of a single-chip microcomputer 301. To a resetting input 312 of said microcomputer 301 there is connected a resetting circuit 302. A first hour input 313 of the - output of microcomputer 301 is connected to the first an hour signal source 303 whose second outDuU is connected to a second hour input 314 of the microcomputer 301. To a second interrupting input 317 of the microcomputer 301 there is connected a first output of a block 304 of separating circuits, a -ing second output of which is connected to a count input 316 of said microcomputer 301.

A first gate 319 of the microcomputer 301 is connected via a first busbar, bidirectionally to a first in-outu 328 of an input-output block 305, and a J' the microcomputer 301 is zero gate 320 o bidirectionally connected, via a second bus-bar, to a first input 3,31 of the controller 306. A zero output 321 of a second gate of the microcmpu+.e-r -501 is 4connected to the second input 332 of the controller 306, and the first output 322 of the second gate of the microcomDuter 301 is connected to a third input 333 of the controller 306. A second outUPu. 323 of the second gate of the microcomputer 301 up to the -he seventh output 324 of the second gate of IV microcomputer 301 are bidirectionally connected to selection inputs 330 of the input-output circuit block 305. The reading output of the microcomputer 'ourth input 334 of the 301 is connected to a f controller 306 while a recording output 326 of the Ith 4-nPut 335 microcomputer 301 is connected to a fi L f the of 'he control 306. A timing output 327 oj microcomputer 301 is connected to a sixth input 336 of the controller 306, and a first outDut 337 of the control'Ler 306 is connected to first interputing input 315 of the microcomputer 301. To column inputs 3-48 of the controller 306 there is connected, via a lihird bus-bar, a first output of a switch matrix 308, a second ou-put of which is connected, via a fourth bus-bar, to line OuPuts 339 of the controller 306. A second output 341 of the controller 306 is connected, via a fifth bus-bar, to a controlling input 343 of a displaying unit 307.

A feeding input 310 of the resetting 9 circuit 302, a feeding input 311 of the separating circuit block 304, a feeding input 318 of the micrcomputer 301, a feeding input 329 of the input output circuit block 305, a feeding input 340 of the controller 306, and a feeding input 342 of the displaying unit 307 are connected to an output of a feeding cur-rent source 309.

A first main switch 351 for tool ffeed as well as a second main switch 352 for tool reverse motion are designed to be at-tlended to by the operator. Feed rates are given through a pushbutton block 348 the feed speed by pushbuttons S1 to S4.

The preset values can be read off displays 355, 3556.

For starting, stopping and data inserting, START STOP-ENTER elements 354 are designed.

The individual nodes of the boring head operate as follows:

For boring without any tool readjustment, the torque is transmitted from the rotating head shaft by the input gear 101 to the spur gear train for reversing the direction of rotation, wherein, due to the transmission through the first and the second intermediate gears 102 and 103, respectively, there is obtained, with the output gear 104 and consequently with the driving gear 105 of the planetary system, rotation opposite to the rotation of the shaft of the boring head. Because of the absence of tool readjustment, the carrier 109 together with the toothed ring 116 meshing with the setting gear 110 for controlling the tool feed rate, is at standstill so that due to the operation of the satellite gears 106, the rotation of the driven gear 107 relative to the driving gear 105 is reversed. The driven gear 107 meshing with the feed gear 108 of thefeed mechanism, rotates therefore in the same direction as the shaft of the boring head and at the same speed, including the shaft of the feed gear 108 which is also out of operation. in this way no motion of the screw 115 and no readjustment of the tools occur.

The tool readjustment effected during the head oDeration will hereinafter be described for the case of enlarging the hole diameter. For the sake of C) simplicity, on-Ly changes relative to the above torque -;on will be described.

transmiss.

If the shaft of the setting gear 110 is rotated by the stepping motor 1 '17 to the right the " its standstill and carrier 109 is brought out oL turns also the right. Due to this turning of the carrier 100,, the axes of satellite gears 106 are angularly readjusted about the roating head shaft, and since together with the usual rotation of the boring head shaft to the right, the driving gear 105 meshing with the satellite gears 100 rotates to the 3' rotation of the satellite gears left the speed o-E W 106 increases due to this meshing so that also the driven gear 107 is accelerated whereby the rotation of the feed gear 108 of' the tool feed mechanism controlling the motion screw 115 is caused. The rotation of the motion screw 115 causes the motion of the nut (not shown) which is directly coupled with the bearing of the tool to be readjusted, which means ^ the - in this case - radially away from the shaft oL boring head.

Naturally, the opposite or reverse readjustment will be effected under the same - conditions by turning the shaft of setting gear 1 10 in the oppoiste direction. The desired direction of rotation is not decisive for controlling the feed "rom the rate, since it will result, for instance, 4. character of a spur gearing (not shown) interposed between the setting gear 110 and the stepping motor 117, from the direction of rotation of the output shaft of said stepping motor 117, from the thread of the motion screw 115, or the like, and can be standardized without any problems. What is decisive, Ct4 however, are the gearing nodes where a dire Lon of rotation is changed to the opposite, Which depends - of ind4vidual bevel upon the relative arrangement gears with straight teeth and spur gears with helical teeth in the embodiment as described. It has been proved in practice that the assumption of eliminating the problem of plays was correct with the types of gears as described and with the described arrangement thereof.

A step of the stepping motor 117 and consequently a desired rotation of its output shaft (not shown) is caused by signals released by the control desk 350 to the inputs or windings 204, 205 -icu'arly via of said stepping motor 117, and part separating circuits 201 of the power element 200; the signals are then transmitted to the shaping circuits 202 and given a rectangular.shape. From the outputs -ed signals are of said circuits 202, the adjust transmitted to the terminal circuits 203 of which each assumes the function of a two-stage amplifier; the first stage is constituted by the switching transistor 218 while the second by the power stage 220 together with the protective voltage reference or Zener diode 221.

Signals for the power element 200 are - 16 produced in the control desk 350 as follows: in the computer program are stored modes of operator's communication with this unit, insertion of data, commands or the like by means of the switch matrix 308 in the form of, for example, a bidimensional matrix keyboard field of singlep-ole pushbutton switches where individual lines and columns are connected to the controller 306. Stored data - as together with the respective responses of the unit eg indication signs, error reports, checking data -c are shown about the present boring head operation et on the displays 355, 356 (Figure 5) or on the displaying element 307 (Figure 6) eg of LED type. These elements are connected to the controller 306 of the displaying element 307 and of the switch matrix 308. The controller 306 (eg a standard product of the firm INTEL) comprises an integrating circuit (not shown) complemented with a selector of lines and -P the d4 columns of the keyboard field and o splaying elements as well as of their individual segments. I t further comprises separating circuits (not shown) in the form of a switch transistor field. The integrating circuit of the controller 306 is connected to the microcomputer 301 in such a way that data are supplied through the zero gate 320 of the microcomputer 301, the resetting signal of the controller 306 is supplied thereto from the zero outut 321 of second gate of the microcomputer 301, the signal of activation of the controller 306 is supplied from the first output of second gate of the microcompter 301, the reading signal is supplied from the reading output 325, the recording signal is supplied from the recording output 326 of the microcomputer 301, the timing signal is supplied from the timing output 327 of the microcomputer 301, and 9 the interrupting singal is supplied from the integrating circuit of the first interrupting input 315 of the microcmputer 301. The power element 200 is connected to the first (eight-bit) gatue 319 of the microcom-outer 301 over an addressable boundary in the _P b' form of the input-output circuiU Lock.05 and of 4 optical elements (not shown). The flow dLrection is selected by means of correspond _4 ng connecting 0 in-put elements. For extending the number of Us/outputs to more than eight, the individual boundary modules are addressed by means of a six-bit bus-bar formed by the second output 327 up to seventh Output 32A of 2' the microcomputer 301. By means of second gate o.4 or4 such two-state inputs/outputs the b Lng head --s not onlycontrolled but also its state or condition or fo r Uhe like can be checked. Thus, for instance, f monitoring critical siuations, it is made possible to apply two inputs separated from each other by means of separating circuit block 304 of the microcom-Duter '301, and comprising the counting input 316 and the second interrupting input 317 of the microcomputer -er.701 is 301. The initial state of the microcomiDut I adjusted by means of the resetting circuit 302.

Finally, the source 303 of the hour signal Js constituted by a crystal (1.2 to 12 MHz frequency) and the current feeding source 300 supplying the unit with 5 V voltage, can be a part of the control desk, or can form a separate unit.

When holes of repeated diameters are to be bored, the operator need not but set up the dimension of the first hole on the control desk 350. 3Y depressing the first main switch 351, a positive feed keeping per dLameter is by 0.01 mm greater, since ii 4 the switch 351 depressed, the feed rate rses.

Similarly, by depressing the second main switch 352, 18 the radial adjustment of tools is reduced by 1.0 min, since if the switch 352 is kept depressed, the tools may, for example, move even up to their initial position. By means of the pushbutton block 343 it is possible to set up digitally the feed rate that is shown on the display 355. The other display 356 shows then the actual. tool readjustment value which can be stored in the program by depressing the STOP pushbutton 354. Simultaneously it is possible to "eed rate by one of the pushbuttons S1 to select the J. S3, or the rapid traverse by the pushbutton S4.

Depending on the application of the boring head as eg with coordinate drilling, milling or NC machines, or the like, the individual nodes of the boring head are arranged either in a complex, or separately.

19 -

Claims (5)

1. A boring head unit comprising a boring head including a shaft, a machining unit including at 1 least one tool radially displaceable relative to the shaft of the boring head, gearing actuated by a stepping motor for automatic readjustment of the machining unit in operation, and electric circuitry 1 L.or controlling the stepping motor, wherein the gearing comprises a planetary gear train including satellite gears carried by a carrier which is mounted o for rotation on the boring head shaft and is provided wi-'.h a gear ring meshing with a setting gear for controlling the displacement of the tool, the output shaft of the stepping motor, which is situated perpendicularly to the boring head shaft, being coupled, either directly or via a gear, with the ^t of the setting gear, the electric controlling shat circuitry comprising a power element associated with the stepping motor and electrically connected in both directions with a control unit.

2. A boring head unit according to Claim 1, further comprising a spur gear train for reversing the direction of rotation, the spur gear train including an input gear which is firmly attached to the boring head shaft, and an output gear, connected to the input gear via intermediate gear means, wherein the planetary gear train comp.rises a driving gear, which is firmly attached to said output gear, and a driven gear, said driving gear meshing with the satellite gears arranged on the carrier, the satellite gears being simultaneously in mesh with said driving gear which meshes with a feed gear firmly attached to a motion screw of a tool motion mechanism.

3.

A boring head unit according to '.!-aim 1 or - 20 Claim 2, wherein the Dower element is provided with a connection into four parallel branches of wh ich each comprises a separating circuit, a shaping circuit and a terminal circuit while in each of said branches the output of said separating circuit is connected to the input of said shaping circuit, 'he output of the latter being connected with the input of the terminal circuit, and wherein the output of said terminal circuit in the first branch is connected, via a first -put of winding of the stepping motor, with the out -he said terminall circuit in the second branch, t - in the 'Uhird branch is output of terminal circuit connected, via a second winding of the stepping motor, -with the output of terminal circuit in the -Pour' Uh branch, and the middle of the fi-st winding of Dp4 the ste Lng motor is connected, via a first voltage dropping resistor, with the second output of a feeding DC source connected through a second voltage dropping resistor also with the middle of the second winding of the stepping motor, while to the first output of said feeding DC source there are connected feeding inputs of all the four shaping circuits and all of the four terminal circuits.

4. A boring head unit according to any one of Claims 1, 2 or 3, wherein the control unit comprises a control desk including a single-chip microcomputer connected via a first gate with the first input of a block of input-output circuits, wherein the ?;ero gate of said microcomputer is bidirectionally connected, with a first input of a controller, a zero output of a second gate of the microcoputer is connected with a second input of the controller, a first output of the second gate of the microcomputer is connected with a third input of the controller, a second output up to seventh output of the second gate of the 1 1, 21 -ed with microcomputer are bidirectionally connect selection inputs of said block oil input-output circuits, a reading output of the microcomputer is connected with a fourth input of said controller, a recording output of the microcomputer is connected with a fifth input of the controller, and a timer output of the microcomputer is connected with a sixth input of the controller, and wherein a first output of the controller is connected with a first I U4 -er while wit interrup Lng input of the microcomput Uh a column input of the controller and wi-th a 1-4ne input of the controller there is connected, via a third and a fourth gate, a matrix of switches, and with a second output of the controller there is connected a controlling input of a displaying unit.

5. A boring head unit according to Claim 4, wherein the control desk is provided with a first main switch for tool feeding, a second main switch for tool reverse motion, a block for fixing the feed rate by pushbuttons, pushbuttons corresponding to the individual feed rates, and a pushbutton for rapid tool traverse, the control disk being further provided with a display and a display for visually representing the electronic tool adjustment -and -ool values corresponding to the mechanical t adjustment, respectively.

A boring head unit constructed, arranged and adopted to operate substantially as here-in described with reference to, and as shown in, the accompanying drawings.