Drill Boom With Feed Direction Sensing And Control

Abstract

A drill boom consisting of a telescopically extendable boom leg, which is pivotably mounted on a rotatable bracket. A rock drill is attached to a pivotable boom head at the opposite end of the boom leg. The boom head is pivotable about an axis which is parallel to the pivot axis of the boom leg. The rock drill is fed by a pivoting force and a length changing force simultaneously acting on the boom. A control system is provided to continuously sense and correct the rock drill position during drilling whereby the corrections is accomplished by adjusting of the composite feeding force direction.

Description

This invention relates to a drill boom for mechanized positioning and feeding of a rock drill, said boom being extendable and pivotably connected to a boom supporting bracket at its rear end.

A conventional drill boom, supporting a feed shell at its forward end, constitutes together with the feed shell a rigid unit for guiding the rock drill. In order to establish a thorough guiding of the rock drill this unit must be very rigid, which necessitates a very solid and heavy drill boom. The purpose of the invention is to eliminate the fixed rock drill guide so as to reduce the rigidness requirements. Such a drill boom can be made slender and light and because of that specially suitable for working in narrow drifts and tunnels.

The invention will be more closely described with references made to the accompanying drawings, in which

FIG. 1 is a perspective view of a drill boom according to the invention.

FIG. 2 is an elevational view of the drill boom shown in FIG. 1 and is schematically illustrating two alternative positions of the same.

FIG. 3 is a top plan view of the forward end of the boom.

FIG. 4 is a longitudinal section of the forward end of the boom and shows the components of a control system attached to the boom.

FIG. 5 is a cross sectional view along line V--V in FIG. 4.

FIG. 6 shows schematically the drill boom and its control system.

FIG. 7 is a longitudinal section of a locking device for a drill boom supporting leg.

FIGS. 8-10 show a drill boom according to another embodiment of the invention, whereof FIG. 8 is a longitudinal elevation section of the forward end of the boom and shows the components of the control system. FIG. 9 is a sectional view along line IX--IX in FIG. 8 and FIG. 10 shows schematically the drill boom and its control system.

As being appearent from FIGS. 1 and 2, the drill boom consists of a telescopically extendable leg 1, the rear end of which is pivotally mounted on an axle 2 on a boom supporting bracket 3. The boom supporting bracket 3 is rotatably arranged on a frame 4, which is intended to be mounted for instance on a mobile base. (Not shown.) Between an attachment 5 on the boom leg 1 and the boom supporting bracket 3 there is provided a hydraulic cylinder 6 by means of which the boom is pivotable relative to the boom supporting bracket. The boom leg 1 is telescopically extendable and consists, as as shown in FIG. 6, of three telescopic tubes 1a, 1b, 1c which are slidably arranged relative to each other. Extension of the boom leg 1 is accomplished by compressed air whereas damping of the boom leg extension movement as well as contraction of the boom leg is accomplished hydraulically. Alternatively, the extension movement could be accomplished hydraulically too. At the forward end of the boom leg 1 there is mounted a boom head 7 which is pivotable about a transverse stub axle 8 for pivoting in the same plan as the boom. Upon the boom head 7 there is rigidly attached a rock drill 9. The pivoting movement of the boom head 7 relative to the boom leg 1 is controlled by a parallel movement establishing device which constitutes an integral part of the control system. The parallel movement establishing device consists of two flow connected hydraulic cylinders 10 and 11, one of which is attached between the boom leg 1 and the boom supporting bracket 3, constituting pilot means 10, whereas the other one is attached between the boom leg 1 and the boom head 7, constituting slave means 11. The advantage obtained by this device is that the rock drill 9 is always moved parallelly when the boom leg 1 is pivoted about the stub axle 8 on the boom supporting bracket 3. However, the rock drill may be positioned in different angles relative to the rotation axis of the boom supporting bracket 3 for drilling of slanted holes and is always retaining this angle relative to said axis when pivoting the boom. (This angle-setting of the rock drill will be described herebelow in connection with the control system.)

The rock drill is arranged to be fed along a certain boring axis by a feeding force which consists of pivoting and extension forces applied to the boom leg. Hereby, the rock drill movement is controlled by continuous sensing of the rock drill position relative to the boring axis. Corrections of this position are carried out by changing the direction of the composite feeding force. In the embodiments of the invention described herein changes in the feeding force direction is accomplished by keeping the extension force constant and increasing or decreasing the pivoting force so that the rock drill is being fed linearly along the boring axis. The control system comprises not only the parallel movement establishing device but also means for sensing of the rock drill position relative to the boring axis and means for correcting this position in accordance with the impulses given by the sensing means. The control system which is shown in FIGS. 4 and 6 comprises a sensing device 12 which is mounted on the boom head 7. In the described embodiment of the invention this sensing device consists of a pneumatic valve. Alternatively, there can be used different types of pneumatic valves, air stream contacts, electrical limit switches and photocells.

As shown in FIGS. 4 and 5 the boom head 7 is provided with a through channel 13 in which a direction indicating bar 14 is arranged. The forward end of the direction indicating bar 14 is kept in a predetermined position relative to the boring axis by means of a frame work 15. The direction indicating bar 14 is pivotably mounted about an axle 16 at the forward end of the frame work. At its forward end, the frame work 15 is provided with a drill rod centralizer 17 and a spur 18. The purpose of the drill rod centralizer is to keep the forward end of the frame work 15 at a predetermined distance relative to the drill rod. At its rear end, the frame work is fixed by a couple of telescopically extendable and to the boom supporting bracket 3 connected support legs 19. These legs 19 can be locked against changes in length by means of lock devices 20 which are adapted to be activated by compressed air. Such a locking device is shown in FIG. 7 and consists of a wedge means 21 which is disposed within the smaller telescopic tube and is arranged to force a number of balls 23 against the wider telescopic tube inner wall. The wedge means 21 is activatable by means of a piston 22. As the rock drill starts working, compressed air is supplied to the locking devices so as to fix the frame work 15 in its proper position. Another purpose of the legs 19 is to prevent twisting of the boom head 7 and the rock drill 9 about the longitudinal axis of the boom leg 1. Thus, the telescopic tubes of the boom leg do not have to be provided with any twist preventing means.

The direction indicating bar 14 as well as the side members of the frame work 15 are surrounded by the boom head 7. Between the frame work and the boom head 7 there is arranged a gap large enough to allow a slight transverse movement of the boom head relative to the boring axis. During such a movement the boom head 7 only has contact with the direction indicating bar 14 via a couple of backing rollers 24 and a fork 25 which is connected to the sensing device 12. Thus, the frame work 15 and the legs 19 have no positive guiding function for the rock drill during drilling but its only purpose is to constitute a supporting device for the direction indicating bar 14. During positioning of the rock drill, before the rock drill starts working, the frame work 15 is fixed relative to the boom head 7. This fixing is accomplished by wedge-formed guiding heels 26 and 27 and a latch 28 which are displaced at the rear end of the frame work and which means are cooperating with the boom head as the latter is withdrawn to its rear-most position. Thereby, the frame work is brought into a position parallel with the boring axis. The spur 18 is then resting against the rock surface. Just as the rock drill is started the legs 19 are axially locked. At the same moment the boom head 7 and the rock drill 9 are released and the control system starts working. The latch 28 is disengaged by means of a pneumatic cylinder 29 which is activated at the same time as the rock drill starts working (see schedule in FIG. 6). From now on the boom head 7 is in contact with the direction indicating bar 14 only.

The direction indicating bar 14 which is kept in its position by the frame work 15 and by the boom head 7 via the backing rollers 24 is parallel with the boom head channel 13 as the rock drill is positioned in alignment with the boring axis. However, the extension force applied to the boom tends continuously to displace the rock drill upwardly (see FIG. 2). By influence of the parallel movement establishing device such a displacement will always be parallel. When an upward displacement of the rock drill occurs, the direction indicating bar, the forward end of which is kept stationary at its original level, will at its rear end be displaced upwardly together with the rock drill. Accordingly, the direction indicating bar 14 will extend an angle relative to the boom head. As a result, the direction indicating bar is pivoted about the axle 16 and the rollers 24 and displaces the valve body of the valve 12 out of its neutral position by means of the fork 25. Thereby, the valve 12 allows compressed air to pass from a supply conduit 30 to a pneumatically shiftable hydraulic valve 31 which then opens to allow hydraulic fluid to flow from a pressure accumulator 32, FIG. 6, through a conduit 33 into the rear part of the cylinder 6 so as cause lowering of the boom. Though, the boom is lowered until the direction indicating bar has returned the valve body to its neutral position by means of the fork. The extension force acts constantly on the boom anyhow and will again displace the rock drill and the boom head upwardly causing the direction indicating bar to shift the valve body downwardly accomplishing another lowering of the boom. By means of suitable restrictions 34-35 put into the hydraulic conduits and by means of sensitive sensing means the above described step by step steering process will be rectified so that a substantially linear feeding of the rock drill is obtained.

Accordingly, during withdrawal of the drill rod from the drilled hole the direction indicating bar will be tilted, but as the contraction force acting on the boom is constant, the rock drill will be pulled backwardly and downwardly. (This position is shown in FIG. 4). Thereby, the direction indicating bar will shift the valve body upwardly so that the valve will supply hydraulic fluid to the forward end of the cylinder 6 via the pneumatically operated hydraulic valve 31 and the conduit 36 to raise the boom. As the boom is raised high enough the valve body will reoccupy its neutral position and the raising operation is interrupted. However, the contraction force of the boom pulls the boom head downwardly constantly whereby the valve body is displaced upwardly again and the boom is again raised. This step by step process is rectified too, so that a substantial linear withdrawal of the drill rod is obtained.

In FIGS. 8-10 there is shown a drill boom according to another embodiment of the invention. The drill boom according to this embodiment is specially adapted for drilling in connection with shaft sinking. This boom is intended to be mounted hanging from the frame 4 with a vertical rotation axis. This version of the drill boom is different from the above described embodiment as the frame work and the direction indicating bar is substituted by a longitudinal box-girder 114 (see FIG. 9). The forward end of this box-girder is provided with a spur 118 and a drill rod centralizer 117 and is connected to a couple of legs 119 at its rear end. The box-girder is surrounded by the boom head 107 and is adjustable relative to the latter by means of pneumatic press plungers 127 and 128. Such adjustment is made during positioning of the rock drill. Thus, these press plungers have the same purpose as the guide heels 26-27 and the latch 28 in the above described embodiment.

For sensing and correction of the rock drill position relative to the boring axis, the box-girder 114 is arranged to be pivoted about its forward end and thereby be displaced at an angle relative to the boom head 107 as the rock drill is parallelly displaced out of its proper position. (Compare the earlier described embodiment). At such a pivoting the box-girder also pivots about the rollers 124 of the boom head and acts upon one of the two sensing means 112a, 112b on the boom head. These means consist of pneumatic valves which acted upon are opened to let compressed air flow to a pneumatically shiftable hydraulic valve 131. Depending on which of the valves being actuated the hydraulic valve will be shifted to cause pivoting of the boom either to or from its vertical rotation axis. By such a continuous sensing and correction of the rock drill position relative to the boring axis there is obtained a substantial linear movement of the rock drill during feeding and withdrawal of the drill rod.

Moreover, the drill boom according to the invention is provided with manually operated control valves by means of which the boom is manually controlled. The control systems of the two described embodiments are identical (see FIG. 6 and FIG. 10). Yet, the drill boom according to the last described embodiment is provided with an extra control valve 180 for alternative supply of compressed air to the sensing means and the press plungers.

In positioning the rock drill for drilling along a certain boring axis the boom is pivoted about the axle 2 on the boom supporting bracket 3 by means of a cylinder 6 and is extended by movement of the boom leg telescopic device for positioning of the rock drill on the proper radius relative to the rotation axis of the boom supporting bracket 3. Moreover, the boom and the boom supporting bracket is rotatable for moving the rock drill along an arc the center of which is coincident with the rotation axis of the boom supporting bracket.

To establish manual pivoting of the boom about the boom supporting bracket there is provided pneumatic valves 37, 38. These valves can be opened for compressed air supply to the pneumatically shiftable hydraulic valve 31 and depending on which of these valves being opened the hydraulic valve supplies the cylinder 6 with hydraulic fluid via the conduits 33 and 36 establishing pivoting of the boom either to or from the rotation axis of the boom supporting bracket 3.

Manual operating of the extension and contraction movements of the boom leg is accomplished by a hydraulic valve 39. By means of this valve the forward facing piston surfaces of the telescopic device are alternatively connectable to a pressure fluid source or to the exhaust. The backward facing piston surfaces of the telescopic device are permanently connected to the compressed air source. Whereby the extension and contraction movements of the boom leg are controlled by regulating of the flow in the hydraulic circuit. This regulating is carried out by means of the valve 39. Moreover, the feeding force rate is changable by regulating the compressed air pressure in the telescopic device. Means for this regulating purpose are not shown.

The rotation of the boom is accomplished by two hydraulic cylinders 40 and 41 alternately acting on a crank pin 42 on the rotation axle of the boom supporting bracket 3. (See FIGS. 1, 6 and 10.) The alternating order of the hydraulic cylinders is controlled by two control valves 43, 44 which are acted upon by a cam disc 45 attached to the rotation axle. The hydraulic fluid supply to these valves and cylinders are controlled by a valve 46.

The drill boom according to the invention makes it also possible to position the rock drill for drilling holes which form angles with the rotation axis of the boom. This positioning possibility is obtained by changing the relationship between the hydraulic cylinders 10 and 12 of the parallel movement establishing device and is carried out by operating the valve 47.

In the embodiments of the invention shown in the drawings the pressure fluid source of the drill boom hydraulic systems consists of a hydraulic pump 48 which is driven by a pneumatic motor 49. The hydraulic circuit is, however, not directly connected to the hydraulic pump 48. In this circuit there is a pressure accumulator 42 the purpose of which is to extend the working intervals of the pump. Principally, this pressure accumulator consists of a piston-cylinder device one end of which is connected to the hydraulic pump. At the other end of the accumulator there is enclosed a gas volume which acts as a spring means. Thus, the accumulator is loaded by the hydraulic pump and is drained by means of the expansion force of the enclosed gas volume. Compressed air is supplied to the control system through a conduit 50.

The invention is not limited to the described embodiments but can be freely varied within the scope of the claims. For instance, the boom may be designed for establishing a longer feed movement by increasing its pivot range. According thereto the boom is pivotable from a rear start position in which the boom leg is constituting an obtuse angle with the boring axis. During the initial part of the feed movement the boom leg will be contracted and, having passed its perpendicular position relative to the boring axis, the boom leg starts to extend. The length changing of the boom is controlled by the control system so that the rock drill will be fed linear along the boring axis when the boom is pivoted about the boom supporting bracket.

Claims

What I claim is:

1. An extendable drill boom for positioning and feeding a rock drill along predetermined boring axis pivotally connected to one end of the boom, the other end of the boom being pivotally supported on a base comprising:

a. a boom head carried by said drill boom for supporting the rock drill and being pivotally mounted to rotate about an axis which is parallel to the pivot axis of the drill boom;

b. force means for producing an extending force component and a pivoting force component on said drill boom during the feeding operation;

c. a control system responsive to a sensing device carried by said boom head for sensing the position of the rock drill relative to the boring axis and being effective upon said force means to adjust the two force components and correct deviations of the rock drill from its boring axis.

2. An extendable drill boom according to claim 1 in which the control system further includes means for moving the rock drill parallel to the movement of the drill boom as the latter is pivoted relative to its base.

3. An extendable drill boom for positioning and feeding a rock drill along predetermined boring axis pivotally connected to one end of the boom, the other end of the boom being pivotally supported on a base comprising:

a. a boom head carried by said drill boom for supporting the rock drill and being pivotally mounted to rotate about an axis which is parallel to the pivot axis of the drill boom;

b. force means for producing an extending force component and a pivoting force component on said drill boom during the feeding operation;

c. a control system responsive to a sensing device carried by said boom head for sensing the position of the rock drill relative to the boring axis and being effective upon said force means to adjust the two force components and correct deviations of the rock drill from its boring axis;

d. said sensing device comprising a direction indicating bar slidably engaging said boom head.

4. A drill boom according to claim 3 characterized in that when the rock drill (9) is moved parallelly out of alignment with the boring axis, the direction indicating bar (14) is arranged to be pivoted about its forward end and thereby be displaced in an angle relative to the rock drill and the boom head so as to act on a sensing device (12) which is attached to the boom head (7).

5. A drill boom according to claim 3 characterized in that the forward end of the direction indicating bar (14) is connected to a frame work (15) which is substantially parallel to said direction indicating bar and to the rear end of which is connected a couple of telescopically extendable and length-wise lockable legs (19).

6. A drill boom according to claim 5 characterized in that the boom head (7) surrounds the direction indicating bar (14) as well as the frame work (15), and means (26-28) are provided to fix the frame work (15) relative to the boom head (7) during positioning of the rock drill.

7. A drill boom according to claim 6 characterized in that the fixing means (26-28) are arranged to be disengaged at the same moment as the rock drill starts working, whereby the frame work (15) is released from the boom head (7), permitting working of the control system.

8. A drill boom according to claim 3 characterized in that the direction indicating bar (14) consists of a box-girder (114) which is provided with a spur (118) and a drill centralizer (117) at its forward end and which is connected to a couple of legs (119) at its rear end.

9. A drill boom according to claim 8 characterized in that the boom head (7) is provided with pneumatic press plungers (127, 128) by means of which the box-girder (114) is arranged to be fixed relative to the boom head (7) during positioning of the rock drill (9).

10. A drill boom according to claim 9 characterized in that the press plungers (127 and 128) are arranged to be disengaged at the same moment as the rock drill starts working, whereby the box-girder (114) is released from the boom head (7), permitting working of the control system.

11. A drill boom according to claim 5 characterized in that the boom supporting base (3) is rotatably mounted on a shaft, which is provided with a crank pin (42) upon which are alternately acting two hydraulic cylinders (40, 41) for making the base rotate.