GB2172528A - Telescopic drill leg for roof bolter - Google Patents

Abstract

The leg has a base and telescopic legs, 7, 8, 14, 15 of a laminated plastics material. The telescopic legs of the invention are made to desired tolerances whereby machining by conventional methods is avoided. The device of the invention avoids ignition problems and is less hazardous. Furthermore, the device has good strength and low water absorbence and thus does not swell and seize in use. A detachable head piece is fitted around the base leg 7 and sealed by O-rings, an end plug 3 being sealed and held in the base leg by a gearbox adaptor plate bolted to the head piece. <IMAGE>

Description

SPECIFICATION Improvements in roof bolting legs This invention relates to the manufacture of a telescopic drill leg and basefora roof bolter.

In mining there is a need for roof bolting to reinforce and consolidate the roof whereby props etc., are eliminated to a large extent. This technique requires drilling a long thin hole e.g. 180 cm to 240 cm by 2.5 to3 cm in the min roof and then inserting a frangible cartridge and long metal bolt and runninga nut up the bolt to secure and consolidate the strata.

The means of drilling the hole isto use atelescopic ram apparatus attached to an air drill motor.

In prior art manufacture, the apparatus has been made in aluminium and machined to the desired tolerance. However devices of aluminium and ferrous metals cause ignition problems and have been deemed hazardous and outlawed in many places.

As a result attempts have been madeto use other materials of construction. Nylon has proved to be unsuccessful despite its good strength properties because itswaterabsorbence causes swelling and consequent seizing in use.

Hence a need exists for a suitable material.

Surprisingly, I have found thatthe above disadvantages are overcome by using a device composed of a laminated plastics material.

In a preferred form the device of my invention comprises a base and unitary leg and one or more telescopic legs.

The invention will become clearer when regard is given to the drawings.

Figure lisa schematic sectional view of a drill leg.

Figure 2 is an elevational view ofthe leg; and Figure 3 is an end view of the leg.

It is pointed outthatthe drawings are merely illustrative and by no means limitative ofthis invention.

In manufacture, the outer leg and base, a mandrel and lathe are coated with a release coat, a coating of Gel coat of suitable thickness is applied to the mandrel. Upon gelation (afterabout45 minutes), resin impregnated fibre (i.e. fibre glass) is applied in a rotary helical action to the required build up say2to 5 mm of gelation after 56 hours the twin laminators and mandrel are positioned in a mould and injected with a urethane resin into the gap in the mouldto ensure a layer of about 3to 5 mm; this is substantially de-aired by vacuu m and al lowed to cure (about 48 hours). (Note the base is included and the bulk of it is urethane). All air. passages and the like may be moulded bya lostwaxprocess.

The telescopic legs are formed in a similar manner to desired tolerances whereby machining by conventional methods is avoided.

The product is readily serviced through the bottom of the base by a removable O-ring plug.

In the preferred design the end stroke keeper of the telescopic legs will have an inter-marrying taper witch its associated cylinder to reduce the side movement and thethruston sealing ringswhichinpriorart apparatuses are orthogonal to the longitudinal axis of the cylinder.

With second and successive legs, the outer laminate need not bathe same type of plastics material but e.g.cou id bea polyepoxywhich has good wearing properties and which does not need shock absorber properties as the base leg requires in practice as it is subject to abuse in use, the tolerance achieved may be of the order of 0.001 mm.

The mandrel used is preferably a remeltablewax e.g. a microcrystal li ne wax of m.p. circa 84"C whereby undercuts and grooves can be achieved in the moulding process thereby ameliorating or even obviating further machining.

Bearing the foregoing in mind, in the manufacture actually carried out, the following commercially available materials may be used.

(a) a Ciba-Geigy gel coat resin identified as araldite *SV 41 O/Hardener HY410 (*trademark).

(b) a Ciba-Geigy product araldite LC 261 with hardener HY837 LC 226.

(c) A Ciba-Geigy product being a rigid polyurethane elastomer marketed as Ureol Kit 6414.

In the drawing herewith, (Figure 1)1 denotes the drill leg proper; 2the base plate (retaining); 3the base plug (sealing); 3a the rubber seal; 4the inlet holeforpressure; 5thebase; 6the base maintaining holes; 7the base cylinder; 8 No. 1 piston; 9theraisec lip; lOthe circlip; lithe sealing ring; 12 the lip; 13th rubber sealing ring; l4the No.2 piston; l5the No.3 piston; 16thethreaded bolt and 17 the nut.

Turning to the drawings, (Figs. 2 and 3), numerical 1 designates a detachable head piece which is sealec by "0" rings to outer cylinder. Numeral 2 is an outer cylinder being moulded with a boss corresponding ii diameter and length of the counterbore in head piece see item 1. Item 3 is the cylinder end plug with "0" ring seal.

Item 4 designates the universal motorofthe gearbox adaptor plate and also functions as a lock uF plate with the through bolts thereby forming a rigid unit. Water and air passages can be provided through the pin and side wall orthrough the adaptor plate and end plug.

It is emphasised that the invention is to be given a broad connotation and is not confined to the specific illustration depicted.

1. A roof bolting drill leg having a base and unitary leg and one or more telescopic legs at least in part being composed of laminated plastics material characterized in thatthe said drill leg has a detachable head piece.

2. A drill leg as claimed in claim 1 wherein the heac piece is sealed by "0" rings to an outer cylinder.

3. A drill leg as claimed in claim 1 wherein the heac piece is sealed by "0" rings to an outer cylinder which is moulded with a boss corresponding in diameter and length of a counterbore in the head piece.

4.A drill leg as claimed in claims 1 and 2 provided with a gearbox adaptor plate which also functions ac a lock up plate and has through boltswherebyarigic unit is formed.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in roof bolting legs This invention relates to the manufacture of a telescopic drill leg and basefora roof bolter. In mining there is a need for roof bolting to reinforce and consolidate the roof whereby props etc., are eliminated to a large extent. This technique requires drilling a long thin hole e.g. 180 cm to 240 cm by 2.5 to3 cm in the min roof and then inserting a frangible cartridge and long metal bolt and runninga nut up the bolt to secure and consolidate the strata. The means of drilling the hole isto use atelescopic ram apparatus attached to an air drill motor. In prior art manufacture, the apparatus has been made in aluminium and machined to the desired tolerance. However devices of aluminium and ferrous metals cause ignition problems and have been deemed hazardous and outlawed in many places. As a result attempts have been madeto use other materials of construction. Nylon has proved to be unsuccessful despite its good strength properties because itswaterabsorbence causes swelling and consequent seizing in use. Hence a need exists for a suitable material. Surprisingly, I have found thatthe above disadvantages are overcome by using a device composed of a laminated plastics material. In a preferred form the device of my invention comprises a base and unitary leg and one or more telescopic legs. The invention will become clearer when regard is given to the drawings. Figure lisa schematic sectional view of a drill leg. Figure 2 is an elevational view ofthe leg; and Figure 3 is an end view of the leg. It is pointed outthatthe drawings are merely illustrative and by no means limitative ofthis invention. In manufacture, the outer leg and base, a mandrel and lathe are coated with a release coat, a coating of Gel coat of suitable thickness is applied to the mandrel. Upon gelation (afterabout45 minutes), resin impregnated fibre (i.e. fibre glass) is applied in a rotary helical action to the required build up say2to 5 mm of gelation after 56 hours the twin laminators and mandrel are positioned in a mould and injected with a urethane resin into the gap in the mouldto ensure a layer of about 3to 5 mm; this is substantially de-aired by vacuu m and al lowed to cure (about 48 hours). (Note the base is included and the bulk of it is urethane). All air. passages and the like may be moulded bya lostwaxprocess. The telescopic legs are formed in a similar manner to desired tolerances whereby machining by conventional methods is avoided. The product is readily serviced through the bottom of the base by a removable O-ring plug. In the preferred design the end stroke keeper of the telescopic legs will have an inter-marrying taper witch its associated cylinder to reduce the side movement and thethruston sealing ringswhichinpriorart apparatuses are orthogonal to the longitudinal axis of the cylinder. With second and successive legs, the outer laminate need not bathe same type of plastics material but e.g.cou id bea polyepoxywhich has good wearing properties and which does not need shock absorber properties as the base leg requires in practice as it is subject to abuse in use, the tolerance achieved may be of the order of 0.001 mm. The mandrel used is preferably a remeltablewax e.g. a microcrystal li ne wax of m.p. circa 84"C whereby undercuts and grooves can be achieved in the moulding process thereby ameliorating or even obviating further machining. Bearing the foregoing in mind, in the manufacture actually carried out, the following commercially available materials may be used. (a) a Ciba-Geigy gel coat resin identified as araldite *SV 41 O/Hardener HY410 (*trademark). (b) a Ciba-Geigy product araldite LC 261 with hardener HY837 LC 226. (c) A Ciba-Geigy product being a rigid polyurethane elastomer marketed as Ureol Kit 6414. In the drawing herewith, (Figure 1)1 denotes the drill leg proper; 2the base plate (retaining); 3the base plug (sealing); 3a the rubber seal; 4the inlet holeforpressure; 5thebase; 6the base maintaining holes; 7the base cylinder; 8 No. 1 piston; 9theraisec lip; lOthe circlip; lithe sealing ring; 12 the lip; 13th rubber sealing ring; l4the No.2 piston; l5the No.3 piston; 16thethreaded bolt and 17 the nut. Turning to the drawings, (Figs. 2 and 3), numerical 1 designates a detachable head piece which is sealec by "0" rings to outer cylinder. Numeral 2 is an outer cylinder being moulded with a boss corresponding ii diameter and length of the counterbore in head piece see item 1. Item 3 is the cylinder end plug with "0" ring seal. Item 4 designates the universal motorofthe gearbox adaptor plate and also functions as a lock uF plate with the through bolts thereby forming a rigid unit. Water and air passages can be provided through the pin and side wall orthrough the adaptor plate and end plug. It is emphasised that the invention is to be given a broad connotation and is not confined to the specific illustration depicted. CLAIMS

1. A roof bolting drill leg having a base and unitary leg and one or more telescopic legs at least in part being composed of laminated plastics material characterized in thatthe said drill leg has a detachable head piece.

2. A drill leg as claimed in claim 1 wherein the heac piece is sealed by "0" rings to an outer cylinder.

3. A drill leg as claimed in claim 1 wherein the heac piece is sealed by "0" rings to an outer cylinder which is moulded with a boss corresponding in diameter and length of a counterbore in the head piece.

4.A drill leg as claimed in claims 1 and 2 provided with a gearbox adaptor plate which also functions ac a lock up plate and has through boltswherebyarigic unit is formed.

5. A roof bolting drill leg constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.