US3773387A

US3773387A - Tool with sweeping movement for a continuous boring or cutting machine

Info

Publication number: US3773387A
Application number: US00152839A
Authority: US
Inventors: M Montacie
Original assignee: BLANZY OUEST UNION INDLE
Current assignee: BLANZY OUEST UNION INDLE; UNION INDUSTRILLE BLANZY OUEST FR
Priority date: 1968-08-13
Filing date: 1971-06-14
Publication date: 1973-11-20
Anticipated expiration: 1990-11-20
Also published as: DE1938818A1; NL6911182A; SE352124B; ES376348A2; FR1597434A; CH510197A; GB1270276A; BE736847A; NL160051C; NL160051B; ES369719A1

Abstract

A plurality of individual tools mounted on a rotating head of a continuous drilling machine are each supported by a tool holder which is angularly oscillated at constant amplitude about an axis perpendicular in space to that of the rotating head. The oscillating axis for each tool is at the same radius with respect to the axis of the rotating head, and the oscillatory movement of each tool holder is circumferentially offset with respect to the other tool holders to insure the simultaneous sweeping of four concentric zones corresponding to the advance of conical form of the cutting front. Means are provided to exert periodic forces to produce a discontinuous advance of the tool upon each change in the direction of movement of the tool holder.

Description

1 United States Patent 11 1 Montaci 1 Nov. 20, 1973 TOOL WITII SWEEPING MOVEMENT FOR A CONTINUOUS BORING OR CUTTING MACHINE Related U.S. Application Data [63] Continuation-impart of Ser. No. 848,013, Aug. 6,

1969, abandoned.

[30] Foreign Application Priority Data Aug. 13, 1968 France 68162825 52 U.S. c1 299/86, 299/56, 299/61 51 1m. 01. EOlq 3/04, EZIC 27/24 [58] Field of Search 299/61, 80, 85, 86

[56] References Cited UNITED STATES PATENTS 9,774 6/1853 Talbot 299/86 X 14,483

3/1856 Wilson 299/86 Primary Examiner-Emest R. Purser Attorney-Richard C. Sughrue [57] ABSTRACT A plurality of individual tools mounted on a rotating head of a continuous drilling machine are each supported by a tool holder which is angularly oscillated at constant amplitude about an axis perpendicular in space to that of the rotating head. The oscillating axis for eachtool is at the same radius with respect to the axis of the rotating head, and the oscillatory movement of each tool holder is circumferentially offset with respect to the other tool holders to insure the simultaneous sweeping of four concentric zones corresponding to the advance of conical form of the cutting front. Means are provided to exert periodic forces to produce a discontinuous advance of the tool upon each change in the direction of movement of the tool holder.

11 Claims, 10 Drawing Figures PATENTEDrmvzo 1975 3.773387 SHEET 10F 5 INVENTOR MARCEL MONTACIE BY Zia f ATTORNEYS PAIENIEIIIIIIY 20 I975 SHEET 4 [IF 5 FIG. II)

I48 EL TOOL WITH SWEEPING MOVEMENT FOR A CONTINUOUS BORING OR CUTTING MACHINE CROSS-REFERENCE TO RELATED APPLICATION This is a continuation-in-part of application Ser. No. 848,013, filed Aug. 6, 1969, and now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to a tool for a continuous boring or cutting machine and is concerned more particularly with the mounting of this tool on a tool holder which carries out a sweeping movement in relation to the rotating head of such a machine. Such tools may be used, for instance, in drilling tunnels in rock.

It is .known that the conventional machines are equipped with one or two rotating heads disposed at the front and provided with tools mounted on fixed tool holders and that a thrust exerted on the rear enables the tools to bite into the rock.

In such machines, the biting tools or cutters arranged at a fixed position on the head are only displaceable when the said machine is stopped, either for carrying out operations forreplacing the cutter, or for reducing the'space occupied by the machine during the withdrawal of .the latter..

, SUMMARY OF THE INVENTION The object of the present invention is to reduce the mounting these tools on tool holders, then driven in rotation, but in addition given a movement in a plane passing through theaxis of rotation of the said head, permitting them to sweep over a larger zone of the cutting front than if they remained fixed.

The total surface of the operational front of the tunnel is thus swept over by one or more tools which, in establishing the two movements to which they are subjected, describe approximately a spiral trajectory, the pitch of which corresponds to the spacing between the concentric circles described by the tools of the conventional machines.

The present invention has for its object a tool for a rotating head of a continuous boring or cutting machine, characterized in that the tool is placed on a tool holder given a sweeping movement in a plane passing through the axis of rotation of the rotating head on which it is mounted and the tool holder is driven in this movement by a means disposed on the rotating head and fed with energy through the axis of rotation of the latter.

One result of the invention is to reduce the total thrust to be exerted on the head of a boring machine and necessary for its operation. Actually, the individual thrust to be exerted on each tool remains the same under identical working conditions. The total thrust is thus proportional to the reduced number of tools, and this number can in the limiting case be reduced to one. Now it is known that it is this total thrust which, for mechanical reasons and particularly when working in hard ground, limits the possibilities of number of tools to be positioned on the head, by I at a lower cost, in view of the smaller investment expenses and reduced working costs which it involves.

Generally speaking, an identical power. supplied by a higher speed of rotation of the tool head according to the invention and subjected to a smaller thrust. will produce an identical advance of the machine.

Conversely, for a given total thrust, it is possible to make available for each tool, their number being reduced, an increased individual thrust value whichimproves their efficiency. 7

Another object of this invention is to accomplish the constant penetration of the tool, enabling it to operate at constant torque owing to the actions of a thrust which will then be regular. To accomplish this, the machine is advanced by jolts at each end of the oscillation of the tool holders, both toward the outside and toward the inside, that is to say, at the moment there is a change in the direction of movement and, of course, to obtain this result, the tools mounted on the rotatin, head must arrive at the end of the run at the same time, i.e., they must be synchronized, some being in position near the axis of rotation of the head and the others being in a further removed position so as to balance the torques due to the various tools in the best possible way.

To simplify the control of the inversion of the oscillating movement direction of the tool holders, the jacks for causing each tool holder to oscillate are supplied with fluid through a turning joint facilitating the use of a fixed control device placed in a safety position behind the machine and inversion control is accomplished by a timer providing a given periodicity for the movements, independent of the variations in the oscillation of the tool holders around their average value.

This invention, therefore, involves a tool for a rotating head for a continuous drilling or working machine, mounted on a tool'holder attached to the rotating head and moving in a rotating sweeping movement in a plane that runs through the axis of rotation of the rotating head, and on which means associated with thrust jacks exert periodic forces producing a discontinuous advance of the tool upon each change in the direction of movement of the oscillation of the tool holder.

BRIEF DESCRIPTION OF THE DRAWINGS A simple sweeping movement is obtained by mounting a tool holder to oscillate about an axis arranged perpendicular to that of the rotating head, and in order to make apparent the objects and advantages of the present invention, a head with an oscillating tool holder is described in conjunction with the drawings, wherein:

FIG. 1 is a diagram showing the principle of boring a tunnel by means of a machine having four oscillating tools;

FIG. 2 shows the a rotating head;

FIG. 3 is a front view of a boring head equipped with four oscillating tools;

FIGS. 4, 5, 6 and 7 represent diagrammatically the respective mountings of the tools in FIG. 3;

FIG. 8 shows the mounting of a drilling head with oscillating tool holders and with fixed hydraulic control device, acting through a turning joint;

FIG. 9 shows the hydraulic circuit of the sweeping device of a tool holder; and

mounting of an oscillating tool on FIG. shows the hydraulic circuit of a device for advancing the tool by jolts and for the control of the thrust.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, the boring head 1, which is driven so as to rotate in the direction of the arrow 2 about its axis 3, is equipped with tools according to the invention mounted on tool holders such as 4, which oscillate about a shaft 32 carried by a support 5, to which is also fixed the driving jack 7 ensuring the oscillating movement of the tool holder 4. The shaft 32 is orthogomil in space to the axis 3.

The face being cut in the cylindrical tunnel 8 during the boring thereof is of toroidal form about the axis 3 and of half cross-section; e.g., the circular sector 9.

The head represented comprises four oscillating tools which respectively sweep over four equal arcs indicated by the arrowed arcs 10, 11, 12 and 13 outside these latter. The tools are indicated diagrammatically in the top position by arrowed straight lines 14, l5, l6 and 17, respectively, which indicate the axes of the tool holders, while the respective arrows 14a, 15a, 16a and 17a indicate the direction of their movement, from this top position, in order to sweep over their corresponding sector.

It is obvious that what is shown is diagrammatic, because the axes of the tool holders distributed on the boring head are .never simultaneously in the same cross-sectional plane; in addition, the bottom positions of these same axes, i.e., after rotation of the head 1 through half a revolution, are indicated in broken lines.

In FIG. 2, the cutter 18 of the upper tool turns on the fixed shaft 22 mounted in the bearing-supporting element 26 fixed to the end of the tool holder 4 oscillating about the shaft 32. The tool holder 4 is given an oscillatory movement by the double-action jack 7, which is mounted to oscillate by means of journals 31 on the support 5 formed of two side plates. The shaft 22 is or thogonal in space to the shaft 32. The rod 30, fast with the jack piston 7, drives the tool holder 4, formed of two sheet metal plates, by means of a shaft 33 which is disposed between the latter and turns freely, while two nuts 37 are screwed onto the threaded end of the rod 30 extending completely through a transverse cylindrical hole drilled in the shaft 33, these nuts ensuring the required rigidity.

Th rotating head 1 is of the type described in my earlier U.S. Pat. No. 3,545,81 l, issued Dec. 8, 1970, on an application filed Nov. 18, 1968. The head 1 rests on a fixed member 38 forming the front of the machine by means of two

roller bearings

39 and 40 which define the axis of rotation 3 of the said head.

A stop 41 transmits the thrust force during the operation of the machine, while a counter-stop 42 ensures that the head is held in position when the latter is not in contact with the cutting front. Finally, the supply means for fluid and electricity, which are necessary for the operation of the oscillating jacks which are rotated with the head, extend through the central hole 43.

FIG. 3 represents the positions of the four freely rotating

cutters

18, 19, 20, 21 forming operating tools and fixed to the oscillating

tool holders

4, 34, 35 and 36, respectively, which are pivotable about four shafts 31 disposed at an equal distance from the axis 3 of the head 1 and at 90 from one another in the plane perpendicular to the said axis. The oscillatory movement of the tool holders ensures that four concentric zones are swept over, these zones being represented diagrammatically by the sectors with criss-cross hatching 10a, 11a, 12a and 13a, respectively; the sector 13a terminates at a point situated on the axis of rotation of the head and corresponding to an advance of conical form of the cutting front.

The oscillation angle of each of the tool holders is of the order of 30.

The head 1 rotates in the direction of the arrow 2 and the buckets 44, as they travel at the lowest point through the rock debris 45, pick up a fraction 45a, which the bucket tips on to a discharge belt, while passing through the following top point, through the hole 46 formed opposite the said bucket in the barrel supporting it, and in the direction of the arrow 47, at the moment when this latter is in the vertical position, that is to say, before the position indicated in a part broken away in FIG. 3.

In FIGS. 4, 5, 6 and 7, each tool holder has been shown at the moment when its shaft passes into the plane of the Figure and the corresponding sectors which are swept over have been indicated by the arcs l0, 11, 12 and 13, indicated by arrows at their two ends. These sectors are shown contiguous, but it is obvious that, for operational safety, the sectors overlap at their ends. In the mounting and driving of the tools, all the parts are the same, except the tool holders themselves, indicated by 4, 34, 35 and 36, respectively, of which the shape is defined by the position in space to be given to the corresponding tool.

The oscillation of the tool holders about the shaft 32 is effected by mounting these holders on roller bearings which are able to withstand the strong force being used.

Each jack may be operated by the oil originating from a gear pump driven by an electric motor and installed on the rotating head. The reversal of the reciprocatory movement may be controlled by limit switches which are arranged on the tool holders and control the reversal of the running direction of the electric motor and consequently the direction in which the oil feeding the jacks is circulating.

By regulating the oil delivery, the pitch of the spiral described by the cutters on the cutting front is fixed.

It is to be understood that the foregoing description of the present invention is strictly by way of example and has no limiting character; consequently, all the modifications in construction which conform to the general definition as already given form part of the present invention.

In particular, the sweeping movement of the tool holder in the plane passing through the axis of the rotating head can equally well be a translatory movement as a rotational movement, with a true or virtual center, or a combination of these two simple movements, so that, in the plane, the axial section or generating curve of the surface of revolution forming the cutting rront, is a given curve which is suitable for the subterranean work to be carried out. Similarly, the number of tools to be mounted on a single head can be increased or reduced, depending on the conditions of the subterranean work to be carried out, the dimensions of the tunnel to be cut and the power to be used.

Furthermore, the means to be used for driving the tools relatively to the rotating head can be other than the hydraulic jack which has been described and can,

for example, be electromechanical or even strictly mechanical.

Finally, the tool mounted on the tool holder is a disc rotating freely on itself, but can also quite well be formed of a tricone type of cutter, or on the contrary it can be fixed and have the form of a pick or a cutter, the choice of the said tool being dictated by the nature of the ground to be operated upon.

FIGS. 8-10 disclose one example of means for driving the rotating head 1 and the.

tool holders

4, 34, 35 and 36 at individual cyclic speeds. As shown in FIG. 8, the boring head 1 rotates in the direction of the arrow 2 and is secured to the shaft 3.

The jacks 7 are connected to a fixed assembly 1 13 for hydraulic control by means of a turning joint 114, whose. fixed portion 115 is connected by fixed tubes 1 16 to assembly 1 13 and where the turning portion 1 17 receives the tubes 118 mounted on the boring head 1 and connected to jacks 7, each of these tubes 118 being connected to the corresponding tube 116 so as to constitute the hydraulic circuit for the individual controls of the jacks 7. p

, The axes of shafts 32, around which the

tool holders

4, 34, 35 and 36. oscillate, are perpendicular, in terms of space, to the rotation axis of shaft 3 which carries the boring head 1 and, in terms of space, are situated at an equal distance from the shaft. Likewise, the

shafts

31 and 33 are perpendicular to shaft 3 and the plane of symmetry of tool carrier 4 constantly passes during the latters oscillation through the rotation axis of shaft 3 and containsthe rotationaxis of shaft 22 around which tool 18 turns freely.

As hereinbefore described, tunnel 8 with the toric working face 9 is dug by the four

tools

18, 19, 20, 21, each so arranged as to define a cut with a spiral shape in sectors, respectively, 9a, 9b, 9c and 9d, swept by them in the course of their oscillation; on the other hand, in the absence of oscillation, the tools each describe a circular cut, as is known in machines with fixed mounted tools, directly forward of the turning head.

The tool 18 at the top in FIG. 8 describes the sector 9a and the tool 20 at the bottom describes the sector 9!), bothof them being shown in their positions furthest removedfrom the axis, that is to say, at the moment 0 change in the direction of oscillation.

In FIG. 9, a jack 7 is associated with its hydrauliccontrol circuit whose control oil comes in through tubes 1.16, and passes into tubes 118 after having traversed the turning joint 114. This is a double-action jack whose rod 30 of piston 12] ensures the oscillating "movement of the corresponding tool holder, not shown here. Each jack 7 is connected to a double-barreled pump, respectively, 122 and 123, whose cylinders correspond to the unequal volumes of chambers 124 and 12.5, respectively, the difference between the two volumes being due to the fact that rod 30 moves in chambe! 124-.

Shaft 126 of the double-action pump. is advantageously rotated along arrow 127 by an independent electric motor (not shown); the same electric motor can move all of the pumps of the various tool holders. It goes without saying that the double-action pump could be moved mechanically by the rotation of the head 1.

Between the pumps and jacks, there are placed fourway distributors 128', electrically controlled by coil 128a, in order to control the direction of circulation of the oil in the hydraulic circuit; thus, in FIG. 9, rod 30 enters the cylinder of jack 7 accordingto arrow" 129 in order to remove the corresponding tool-from the axis of the boring head owing to the action of the oil coming from the pump 122, traversing the distributor 128 along arrow 130, and circulating in tube 116 according to arrow 131. In themeantime, the oil comes from an oil tank 132, where it is subjected to a pressure-on the order of 1 bar, passing both through the central tube 133, through the no-return valves'134, and' through tube 135 and distributor 128; appropriatearrows indicate the direction of circulation of the oil.;Other noreturn valves and pressure limiters. or reducers 136 complete the hydrauliccircuit. The dotted tubes 133a serve to recover the oil that has escaped. When the direction of circulation is reversed, distributors 128 ensure the crossing of the hydraulic circuits, indicated symbolically by the oblique straight lines 137, provided with arrows at their ends, to indicatethe new direction of circulation.

By thusregulating the flow rate of the pumps, the theoretical time for one outgoing or one return trip of the piston 121 of jack 7 is regulated at a value T. With the'help of a timing device, I simultaneously invert distributors 128 of the assembly of

tool holders

4, 34, 35, 36 at time intervals T0= T+t; t here is a very short time with respect to T on the order of a second, which ensures the synchronization of oscillation of all of the tool holders, rods 30 being locked in the course of time t by means of pistons 121 which engage one of the rings 138. In the meantime, the pumps at this moment deliver through their pressure reducers 136. h

The timing device controls the inversion of the distributors 128 with the help of a contactor equipped with one contact per

tool holder

4, 34, 35, 36 to be controlled and selected either open or closed. Under these conditions, each contact respectively controls the cutoff and the supply of the coils 128a of the distributors 128 assigned to the hydraulic control circuit of one and the same tool holder so as to select the direction of oscillation of the tool holders, some of which approach the axis of rotation of the head along arrows 139a and 139b, while the others move away along 1390 and 139d, as shown in FIG. 8. As a matter of fact, it is essentially important that the furthest removed sectors 9a and 9b be simultaneously traversed in the same direction with respect to the axis of rotation of the tuming head.

Many variations in this hydraulic circuit are possible. Thus, one could use double-action pumps with axial pistons and the inversion of the oil flow would be accomplished by inverting the table or bed of the pump. In the case where we have pistons 12], equipped with a double rod, the volumes of chambers 124 and of jack 7 are the same and we can use a simple singleaction pump with axial'pistons. The inversion of the hydraulic flow can also be accomplished through mechanical inversion of the direction of rotation of the single-action or double-action pump, either through a mechanical inverter or directly, by inverting the direction of rotation of the movement motor.

The speed of rotation of the boring head is obtained on the basis of the intended design or construction and is in practice considered constant, in view of the inertia of the assembly and in view of the manner of movement by means of a motor with surplus power.

The average oscillation frequency of the tool holders is likewise obtained by intended design or construction and in relation to the angular rotation speed of the head, so as to make the tool describe, on the working face, a groove with a spiral shape and with an average given pitch. To take into account the various utilization parameters, especially the-hardness of the rock in the ground to be drilled, one can adapt the pitch to the work required by modifying the flow rate of the pumps that control jacks 7; but maintaining this pitch, that is to say, the ratio of the rotation speed of the head and the sweeping speed of the tool carriers, is not critical because the rotation speed is practically constant and because the sweeping speed is adjustable, which means that strict synchronization of these two movements is thus useless and that these movements can be obtained from independent movement means.

In FIG. 10, a hydraulic pump 140, with an adjustable flow rate of Q liters per second, is made to rotate in the direction of arrow 141 by an electric movement motor 142 and to discharge into a hydraulic accumulator 143 whose inflation pressure is greater than that necessary to make the drilling machine advance. Between accumulator 143 and thrust jacks 144, there is inserted a simple hydraulic distributor 145 with electric controls supplied by coil 145a and normally closed.

Jacks 144 are placed between the mobile structure supporting the turning head of the machine and the latters support points on the ground to be drilled so as to exercise the desired thrust upon the head.

Upon each inversion of the direction of oscillation of the tool holders, the timing mechanism for the control of the inversion of the direction of oscillation of the tool holders by four-way electric distributors 128 also controls, by means of timed relays, the opening of simple electric distributor 145 during a time period that can be adjusted from 2 to 4 seconds, thus enabling the oil stored in the accumulator 143 to pass entirely into jacks 144, thus ensuring the jolt-by-jolt advance.

With each inversion or return of the tool holders, the machine thus advances by a certain quantity, which is linked to the time T, for the duration of one half oscillation of the tool holders, and to the adjustable flow rate Q of pump 140.

When we are dealing with a working machine, the thrust on the boring head is accomplished by means of caterpillar tracks on which the machine is mounted; these tracks are moved by a hydraulic motor and the jolt-by-jolt advance of the machine is then obtained by supplying the hydraulic motor with oil from the accumulator 143 during the latters desired discharge time.

This hydraulic advance control system is equipped with a general oil tank 146 into which lead the various oil circuits of the device, equipped furthermore with pressure reducers 147, no-

return valves

149 and 150, and cut-off cocks 151 which serveto isolate the accumulator 143.

What is claimed is: j

l. A continuous boring or cutting machine comprising:

a supporting means,

a rotating head mounted on said supporting means for rotation about a first axis;

a tool holder mounted on said rotating head for rotation about a second axis; and

a cutting tool mounted on said tool holder, said cutting tool having a cutting edge substantially perpendicular to a third-axis,

said third axis being orthogonal in space to said second axis and at an angle to said first axis which varies with the rotational motion of said tool holder about said second axis. 7v

2. A continuous boring or cutting machine as claimed in claim 1 wherein said second axis is orthogonal in space to said first axis.

3. A continuous boring or cutting machine as claimed in claim 1 wherein said cutting tool is a disc mounted for free rotation about said third axis.

4. A continuous boring or cutting machine as claimed in claim 1 wherein the rotation of 7 said tool holder about said second axis is an oscillatory sweeping movement over an arc. I

5. A continuous boring or cutting machine as claimed in claim 4 wherein a single cutting tool is mounted by itself on said rotating head and the angle subtending said are is equal to the total attack angle of the cutting front necessary for continuous working of said machine.

6. A continuous boring or cutting machine as claimed in claim 4 wherein the number of cutting tools is at least two and said machine further comprises:

means for limiting the angle of oscillation of each tool holder to an angle equal to or slightly greater than the total angle necessary for attacking the cutting front divided by the number of tools mounted on said rotating head and means for effecting said oscillatory sweeping movement of each tool holder such that the portion of the cutting front swept by each tool holder is circumferentially offset with respect to the portion of the cutting front swept by each of the other said tool holders, thereby causing multiple concentric poi'tions of the cutting front to be swept over by the cutting tools during the rotation of said rotating head about said first axis.

7. A continuous boring machine as claimed in claim 6 wherein said tool holders carried by said rotating head are distributed at equal angles circumferentially with respect to said rotating head to equalize the load thereon.

8. A continuous boring or cutting machine as claimed in claim 4 and further including means disposed on said rotating head for driving said tool holder in oscillatory sweeping movement and means for supplying energy to said driving means.

9. A continuous boring or cutting machine as claimed in claim 8 wherein said means for driving said tool holder in oscillatory sweeping movement comprises a double-acting hydraulic jack.

10. A continuous boring or cutting machine as claimed in claim 9 and further including a gear pump for delivering hydraulic fluid under pressure to said double-acting hydraulic jack and means for reversing the direction of rotation of said gear pump to cause reversal of movement of said hydraulic jack.

11. A continuous boring or cutting machine as claimed in claim 10 and further comprising:

a motor for driving said gear pump and means for reversing'the direction of rotation of said motor to reverse the direction of rotation of said gear pump.

l 1 I 4K

Claims

1. A continuous boring or cutting machine comprising: a supporting means, a rotating head mounted on said supporting means for rotation about a first axis; a tool holder mounted on said rotating head for rotation about a second axis; and a cutting tool mounted on said tool holder, said cutting tool having a cutting edge substantially perpendicular to a third axis, said third axis being orthogonal in space to said second axis and at an angle to said first axis which varies with the rotational motion of said tool holder about said second axis.

4. A continuous boring or cutting machine as claimed in claim 1 wherein the rotation of said tool holder about said second axis is an oscillatory sweeping movement over an arc.

5. A continuous boring or cutting machine as claimed in claim 4 wherein a single cutting tool is mounted by itself on said rotating head and the angle subtending said arc is equal to the total attack angle of the cutting front necessary for continuous working of said machine.

6. A continuous boring or cutting machine as claimed in claim 4 wherein the number of cutting tools is at least two and said machine further comprises: means for limiting the angle of oscillation of each tool holder to an angle equal to or slightly greater than the total angle necessary for attacking the cutting front divided by the number of tools mounted on said rotating head and means for effecting said oscillatory sweeping movement of each tool holder such that the portion of the cutting front swept by each tool holder is circumferentially offset with respect to the portion of the cutting front swept by each of the other said tool holders, thereby causing multiple concentric portions of the cutting front to be swept over by the cutting tools during the rotation of said rotating head about said first axis.

11. A continuous boring or cutting machine as claimed in claim 10 and further comprising: a motor for driving said gear pump and means for reversing the direction of rotation of said motor to reverse the direction of rotation of said gear pump.