ZA200503385B

ZA200503385B - Extensible mast

Info

Publication number: ZA200503385B
Application number: ZA200503385A
Authority: ZA
Inventors: Roger R Briggs
Original assignee: Transbor Pty Ltd
Priority date: 2004-03-23
Filing date: 2005-04-14
Publication date: 2006-12-27

Description

n 2005/0306 35

BACKGROUND OF THE INVENTION

[0001] This invention relates to a directly extensible mast which is suitable for use on a drilling machine or drill rig.

[0002] The invention is concerned particularly with a mast of relatively simple construction which is directly extensible by means of a piston and cylinder assembly wherein a piston rod of the assembly can be fully extended while providing adequate stabilisation for the rod.

SUMMARY OF INVENTION

[0003] The invention provides an extensible mast for a drilling machine which includes a column, a piston and cylinder assembly adjacent the column, at least one connection between the column and the cylinder which permits the piston and cylinder assembly to be telescopically retracted or extended with the cylinder moving relatively to the column, and a carriage, for a drill head, which is mounted to the cylinder and which is movable together with the cylinder between lower and upper limiting positions as the piston and cylinder assembly is respectively telescopically retracted and extended.

[0004] An outermost end of the piston may abut a support adjacent a foot of the column.

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[0005] The column may be pivotally mounted to support structure and be pivotally movable between a horizontal storage position and a vertical operative position.

[0006] The mast may include at least one support device which braces the piston in a direction which is transverse to its longitudinal axis. The device may be movable in the longitudinal direction as the piston and cylinder assembly is telescopically retracted and extended. When the assembly is fully extended the device may be positioned at a point which is midway along the length of the piston. The device may be slidingly engaged with the column.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The invention is further described by way of example with reference to the accompanying drawings in which:

Figure 1 is a side view of an extensible mast according to the invention, mounted to a carrier vehicle, in a retracted position;

Figure 2 is a view similar to Figure 1 but with the mast in an extended position;

Figure 3 is a cross sectional view of the mast taken on a line 3 —- 3 in Figure 1;

Figure 4 is a side view of a carriage of the mast viewed in a direction of an arrow 4 in Figure 2;

Figure 5 shows in perspective a portion of the mast, detached from a vehicle; and

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= 2064574558035

Figure 6 illustrates the construction at a lower end of the mast.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0008] Figures 1 to 4 of the accompanying drawings illustrate an extensible mast 10 according to the invention which is used in a drilling machine. The mast includes a column 12, a piston and cylinder assembly 14 which is adjacent the column, a sliding joint or connection arrangement 16 which is used to secure the assembly 14 to the column and a carriage 18, to which is mounted a drill head (not shown), which is mounted to the cylinder near a lower end thereof.

[0009] The piston and cylinder assembly 14 includes a cylinder 22 with a piston which is located inside the cylinder and from which extends a piston rod 24. The assembly 14 is oriented so that the piston rod 24 extends downwardly and a lower end of the piston rod, designated 26, is connected to a foot piece 30. The construction of the foot piece is described hereinafter with particular reference to Figure 6.

[0010] In this example the mast 10 is mounted to a load bed 34 of a vehicle 36. The foot piece 30 is secured to a lower end 40 of the column and is mounted at a point 42 to the load bed 34 for pivotal movement.

[0011] Figure 3 illustrates the mast and the connection arrangement 16 in cross section taken on a line 3-3 in Figure 1. The column 12 includes a hollow section 44 of rectangular configuration of appropriate dimensions

P.20156/jes calculated to carry the loads and stresses to which the mast is exposed during use and two channel sections 46 and 48 respectively which are welded to opposed respective outer sides of the section 44 and which define an enclosure 50 in which the assembly 14 is positioned.

[0012] Two spaced feet 52 and 54 are fixed to the cylinder 22. The feet have respective flanges 56 and 58 which are bolted to upper and lower angle iron cross pieces 60 and 62 respectively — see Figure 4. As is shown in Figure 3 strips 64 of low friction wear material are secured to surfaces of the feet and cross pieces which oppose flanges 66 and 68 of the channel sections 46 and 48. Plates 70, which are faced with wear strips 64A, are bolted to the cross pieces and thereby secure the cross pieces, and thus the feet and the cylinder, to the column 12 in a manner which permits the cylinder to slide parallel to, and relatively to, the column. It is possible to make use of rollers, in place of the strips of wear material, at the interfaces of the relatively movable components of the mast.

[0013] The assembly 14 is substantially parallel to the longitudinal axis of the column and is telescopically movable, with the connection arrangement 16 sliding along the flanges 66 and 68, by the application of hydraulic fluid to the piston and cylinder assembly. This aspect is known in the art and for this reason is not further described herein.

[0014] The carriage 18, shown from the side in Figure 4, includes the upper and lower cross pieces 60 and 62 respectively and the plates 70 secured to

P.20156/jes the cross pieces so that a drill head, not shown, can be attached to the carriage. Hydraulic fluid connections 72, of a kind known in the art, are used to power the drill head and the piston and cylinder assembly.

[0015] Two opposed shaped plates 74A and 74B respectively, are fixed to ends of the cross pieces and sides of the plates 70, and provide support for a motor plate 76 to which a drill motor, not shown, is attached. The motor is conventional and therefore is not further described herein.

[0016] When the mast 10 is in the Figure 1 configuration the piston and cylinder assembly 14 is fully retracted and the connection arrangement 16 is at, or near to, a lower end of the column 12. The mast 10 is then in a storage or transport mode and can be pivoted downwardly over the load bed 34 of the vehicle, as is indicated by means of an arrow 77 in Figure 1, to a substantially horizontal position which allows easy transport of the mast.

[0017] When the mast is to be used it is placed in a desired orientation, e.g. vertical or angled, with the drill in a ground-engaging position. Figure 2 shows the drill in a vertical position. The assembly is then extended. The extension results directly from the actuation of the cylinder which rises along the length of the piston rod. The connection arrangement is thereby moved along the column 12 to its highest position, as is shown in Figure 2.

[0018] The length of a typical drill rod, not shown, is of the order of 6m. The position of the drill rod, which extends from the drill head on the carriage, is indicated by a line 78. Thus the stroke of the assembly 14 should be at least

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6m, say 6,8m. The length of the carriage 18 depends inter alia on the nature of the drill head with which the mast is used and may, for example, range from 1m to 2m. The column 12 has a length which is slightly greater than the sum of the lengths of cylinder and the carriage 18 and, for the given figures which are cited only by way of example, the length of the column 12 is from 8m to 9m. This means that when the assembly is extended, as shown in Figure 2, it is possible for a drill rod to be attached to the drill head. Drilling can then take place. The drilling force, also known as the “pull-down” force, is equal to the sum of the mass of the drilling arrangement and the force which is exerted in a downwards direction by hydraulic fluid applied to the assembly 14.

[0019] As the assembly 14 is retracted the drilling head is moved downwardly together with the cylinder whereupon the piston rod 24 moves into the cylinder 22 with the assembly then moving to the position shown in

Figure 1.

[0020] It is apparent that the pull-down force is directly dependent on the force which can be applied by the assembly 22 and that the lift-out force, generated when drill rods are to be extracted from a borehole, is also directly dependent on the rating of the assembly. The cylinder thus transfers full force directly to the carriage and operates at the same speed as the carriage.

[0021] The mast of the invention has a particularly simple construction. Use is made of standard components which are available off-the-shelf from a steel mill or steel merchant, and a minimum amount of fabrication is therefore

P.20156/es required in order to make the mast. The cylinder 22 is securely stabilised, again in a non-complex manner, as the cylinder assembly is extended or retracted.

[0022] In the construction described thus far, in connection with Figures 1 to 4, the piston rod 24, when fully extended, could be prone to buckling, depending on the load applied to the rod. This means that a long rod can only be used at a low hydraulic pressure, a factor which lowers the efficiency of the system. The use of higher pressures requires the cylinder to be made oversized and the piston rod also to be made bigger and heavier. This increases the cost and the piston and cylinder assembly then no longer “matches” the rest of the hydraulic system which is at a higher pressure and lower hydraulic flow.

[0023] The calculation of the parameters applying to buckling of an elongate slender object such as a piston rod is notoriously imprecise. Consequently it is normal to work on a 4 : 1 safety factor.

[0024] Figure 5 illustrates a modification to the arrangement which has been described in connection with Figures 1 to 4, which provides a simple and inexpensive means of preventing buckling.

[0025] The mast is designated 10A and includes a column 12A with a structure which is generally of the type shown in Figure 3. The piston and cylinder assembly is designated 14A and includes a cylinder 22A and a piston

P.20156/jes rod 24A which is telescopically mounted to the cylinder. A lower end of the piston rod is attached to a floating foot 80 at a lower end of the column 12A.

[0026] The drill head carriage is designated 18A. A drill motor which, in use, is attached to the carriage 18A, is not shown.

[0027] A support device 82, which is shown in an inset drawing (Figure 5(a)) in Figure 5, is made from any suitable material such as a hard nylon and is formed with a hole 84 through which the piston rod 24 extends. The hole 84 provides a substantial clearance, for example of the order of 15mm on radius, around the piston rod 24A. The device 82 is slidably engaged with the flanges 66 and 68 on the column. These flanges keep the device 82 captive on the column but allow for easy sliding movement of the device along the flanges.

[0028] A second device 90 (Figure 5(b)) is positioned on an opposing side of the drill head carriage 18A and is also engaged with the flanges 66 and 68.

[0029] Two elongate lift rods 92 and 94 respectively are positioned on opposing sides of the assembly 14A and interconnect the first device 82 to the second device 90. These rods pass with a loose fit through corresponding holes which are formed, as may be necessary, through structural components of the carriage or, for that matter, of the connecting arrangement 16, where appropriate. These holes, may, if necessary, be lined with rubber.

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[0030] The rods are square ended to ensure that the device 82 is heid true without jamming. The length of each lift rod is such that when the carriage 18A is at an uppermost position and the device 90 has been moved to an uppermost position along the column 12A the device 82, which is the lower device, sits at a point which is mid-way between the upper and lower ends of the column.

[0031] The device 90 includes a tie 90A which connects respective upper ends of the rods 92 and 94 to each other. The tie is only on an outer side of the cylinder, although it could alternatively be on an inner side of the cylinder, and it does not surround the cylinder. Its function is to restrict the upper ends of the elongate rods 92 and 94 from moving from side to side during operation of the mast i.e. it acts as an anti-rattle component. The tie does not contribute to the strength of the mast for, essentially, it is a non-load carrying member.

[0032] The device 82 and the lift rods 92 and 94 form an anti-buckling frame, for the piston rod, which is movable as the piston and cylinder assembly is expanded or retracted. The device 82, in particular, braces the piston rod. If the rod starts buckling its lateral motion is arrested by the device 82 and the forces which arise are transferred to, and then restrained by, the column 12A.

The device 82 which restrains the rod 24A in the middle of its length raises the anti-buckling capability of the rod by a factor of 4.

[0033] During road travel the drill head carriage 18A is at a lowermost position, ie. at the bottom of its stroke, and the device 82 is trapped at a lower

P.20156/jes end of the column. As the head rises the effect of gravity would normally be such that the device 82 remains at the lower end. Irrespective of whether this happens it is evident that the upper device 90 cannot move beyond the upper end of the column 12A. With the upper device at this position the device 82 is at a position mid-way along the length of the piston rod at which it provides optimum anti-buckling capability.

[0034] As the rod cannot buckle, and as the joints at opposed ends of the cylinder and piston rod are stabilised, a lower safety factor is demanded of the feed cylinder.

[0035] The construction of the foot piece 30 is shown in enlarged detail in two side views (Figures 6(a) and 6(b)) which are at a right angle to each other, in Figure 6.

[0036] The foot piece 30 has two spaced plates 100 and 102 respectively and a block 104 is positioned between the plates. Two circular guide rods 106 and 108 respectively are fixed to and extend between the plates and pass through corresponding holes 110 and 112 in the block 104.

[0037] The lower end 26 of the piston rod 24 is threaded and passes through a hole 114, in the block, which is at a right angle to the holes 110 and 112. A collar 116 on the piston rod abuts an upper side of the block while a nut 118 which is threadedly engaged with a protruding lower section of the piston rod keeps the rod captive to the block.

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[0038] In a first direction 120, shown by a double-headed arrow in Figure 6(a), there is minimal permitted play between the block and the rods.

However the block, and the end 26 of the piston rod, can move in a second direction 122, which is transverse to the direction 120 and which is shown in

Figure 6(b). The degree of this movement is dependent on, and is allowed in order to compensate for, wear on the various wear strips 64 and 64A of the carriage arrangement (see Figure 3).

[0039] Thus, to a limited extent and in one direction 122, the lower end 24 of the piston rod can “float” to accommodate wear in the carriage wear strips.

The degree to which the lower end can move is greater than the expected wear of the wear strips. This characteristic helps to reduce stresses which would otherwise be imposed on the piston rod.

[0040] It will not normally be necessary for the lower end 24 to be able to “float”, or self-adjust, its position in the transverse direction 120, for the wear in this direction of the relative components of the carriage arrangement is relatively small.

[0041] A benefit of the construction at the foot piece 30 is that if it is necessary to service the cylinder 22, for example to replace a packing gland at the lower end of the cylinder, the nut 118 can be unthreaded, with the mast in situ, and the cylinder can then be accessed to carry out the desired maintenance or service work and there is no need to disengage the whole mast structure from the equipment to which it is mounted.

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[0042] The mast of the invention is of simple, yet effective, construction. The column 12, which is of unitary construction, is made from three elements comprising off-the-shelf sections, e.g. from a steel mill or steel supplier, which are inherently sound beam-torsion boxes. The mast is lighter and more compact than the masts of conventional equipment and the labour for fabrication and assembly is reduced accordingly. The cylinder is bolted directly through the feet to the carriage, and the mast does not use pull- down/puli-up (multiplier) chains.

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Claims

1. An extensible mast for a drilling machine which includes a column, a piston and cylinder assembly adjacent the column, at least one connection between the column and the cylinder which permits the piston and cylinder assembly to be telescopically retracted or extended with the cylinder moving relatively to the column, and a carriage, for a drill head, which is mounted to the cylinder and which is movable together with the cylinder between lower and upper limiting positions as the piston and cylinder assembly is respectively telescopically retracted and extended.

2. A mast according to claim 1 wherein an outermost end of the piston abuts a support adjacent a foot of the column.

3. A mast according to claim 1 or 2 wherein the column is pivotally mounted to support structure and is pivotally movable between a horizontal storage position and a vertical operative position.

4, A mast according to any one of claims 1 to 3 which includes at least one support device which braces the piston in a direction which is transverse to its longitudinal axis.

5. A mast according to claim 4 wherein the support device is movable along the length of the piston as the piston and cylinder assembly is telescopically retracted and extended.

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6. A mast according to claim 5 wherein, when the assembly is fully extended, the support device is positioned at a point which is substantially midway along the length of the piston.

7. A mast according to claim 4, 5 or 6 wherein the support device is engaged with the column thereby to restrict movement of the piston laterally relatively to the column.

8. A mast according to claim 4 wherein the support device is engaged with the piston at a location which is between the carriage and an outermost end of the piston and which includes a second device which is slidingly engaged with the column on an opposing side of the carriage, and at least one rod which connects the support device to the second device so that the support device and the second device are movable in unison.

S. A mast according to any one of claims 1 to 8 wherein an outermost end of the piston is fixed to a foot piece which allows limited movement of the piston end in at least one direction which is transverse to a longitudinal axis of the piston.

10. An extensible mast for a drilling machine which includes an elongate column, a piston and cylinder assembly mounted for telescopic movement of the cylinder relative to the column, a carriage, for a drill head, mounted to the cylinder, and a support device which is engaged

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3 2005/03585 with the column for restricting movement of the piston in a direction which is transverse to its longitudinal axis.

11. A support arrangement for use with a piston and cylinder assembly which includes an elongate column which is located adjacent the assembly, a support device which is slidingly engaged with the column and with the piston, a second device which is engaged with the column and which is movable relative to the column, at least when the assembly is extended, and at least one rod which connects the second device to the support device so that the second device and the support device are movable in unison.

12. A support arrangement substantially as hereinbefore described with reference to Figures 5(a) and 5(b) of the accompanying drawings.

13. An extensible mast substantially as hereinbefore described with reference to any one of the accompanying drawings. Dated this 14™ day of A Vv, y // McCALLUM, RADEMEYER & FREIMOND Patent Agents for the Applicant

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