This invention relates to an improved vertical prop with high setting load useful for supporting mine & tunnel roofs.
This invention particularly relates to an improved vertical prop with high axial & setting load capacity alongwith remote withdrawal device useful for supporting underground mine roofs.
In the mining industry props with high setting loads to support the underground roadways and galleries and the depillai— ing zones are required. The device of the present invention can be used in conventional mines as regular support as it is much cheaper than the presently available props which can provide high setting load and the whole operation can be made manually. It does not require any sophisticated equipment operation or any critical maintenance procedure.
There are mainly three types of props with high setting load being used presently.
Most of them are open circuit hydraulic props which can provide 10 tonne setting load. Open circuit hydraulic props are energised by a hydraulic power pack which is very costly. The prop is made of mainly two steel tubes as cylinder and pistons and gets filled by fluid in both the tubes when energised by the setting gun from a power pack. Hydraulic props are also very costly (more than Rs 20,000/- per unit presently) and have got some sensitive parts within them which are prone to get damaged and therefore not suitable for a blasting face. These props can

not be withdrawn remotely. For the full extension of the prop, about 9 litres of liquid is required, which gets discharged at the time of withdrawal of the prop.
Closed circuit hydraulic props are also available but those do not have the capacity to provide setting load of more than 5 tonne and can retain less than that. Within the prop there is a pump which can be operated from outside the prop and thus it can be set in a gallery but more than 5 tonne setting load can not be achieved by the system. It is also very costly, each costing around Rs 25,000/- today.
There is a mechanical support called friction prop which is mainly made of two telescopic steel tubes hold by a friction clamp. Though it is claimed by the manufacturer that it can provide 5 tonne setting load but in reality it can not retain more than 3 tonne setting load. It is heavy and costly (more than Rs 15,000 each ) and can not be withdrawn remotely.
There are also props which can be set by mechanical setting device-like screw props, wedge set props and others. But those cannot provide more than 3 tonne setting load. In underground mines, for withstanding blasting effect in front of a working face, it is required to retain a setting load of atleast 5 to 6 tonne for any vertical single prop used as immediate front roof support (IFRS).
The presently available props have got drawbacks that they are very costly or/and they cannot provide sufficient setting
load. In case of hydraulic props, the setting load is not retained permanently. These props are required to be reset regulai— ly at an interval. The3e props involve costly maintenance and are comparatively heavier. As they got sensitive parts, they are not suitable to be used at the goaf edge (the fully extracted area in a working panel of a coal seam is called goaf) or in front of the blasting face. Friction prop and screw prop can not provide more than 3 tonne setting load, which can not withstand the effect of blasting, being very near to the face.
The mining industry has long been facing the problem of supporting the sensitive roofs in underground workings, particularly for the immediate roof in front of the blasting face, for the goaf edges in depillaring areas, for the BG panel (Blasting Gallery method is a process of extraction of thick coal seam proposed by CdF of France) galleries and longwall gate roads, where they need supports with high setting load and higher axial load capacity.
Most of the roof falls occur under the freshly exposed roof in an underground mine and 60% of total accidents occur under the green roof. Therefore, it calls for quick supporting immediately after the exposure. Rather before any exposure is made, it should be pre-supported by vertical supports nearest to the working face. Thus it requires high setting load characteristics for the support such that it does not dislodge at the time of blasting the face. Generally face advancement is done by blasting in coal mines.
In our copending patent application no. 629/Del/92 we have described and claimed on improved prop with high setting load useful for supporting mine roofs. The device is illustrated in Fig. 1,2 & 3 of the drawings accompanying this specification.
This device is a vertical prop consisted of mainly two cylindrical tubes (j & n). The top tube (n) having external threads can move freely inside the bottom tube (j). The bottom tube has get a main clamp (1) on its top to hold the top tube by the inside threads of the two halves of the clamp. There are two studs (k) on both side of the bottom tube to fix up the bottom jack holder plate (r) on which the setting device twin jack would be placed alongwith the top jack holder plate (t) to set the prop with required load. The top jack holder plate has got threads inside its both clamps to match with the threads of the top tube (n). At the time of installation of the prop the twin jack (s) placed in between two plate3 (r & t) is pumped with a setting load of 10 tonne or more. Then the two halves of main clamp (1) are closed and tightened to hold the top tube with its external threads by the help of wedge (v). The setting device (r,s & t) are withdrawn after the installation. The top tube (n) has got a crown (o) to hold a piece of wood to set with the roof and the bottom tube (j) has got bottom plate with prongs (i) to set with the floor. The main clamp (1) has got a mechanism with a rotating lever (u) and a knotted rope (m) to withdraw the prop from remote distance. If the wedge (v) is taken out and the knotted rope (m) is pulled from a distance by a tirfor/puller, it would open the two halves of the clamp and the top tube would get inside the
bottom tube and thus by realising the load over prop the prop can be easily withdrawn.
This prop ha3 some limitations in its mechanism which create problems in the field use.
The drawbwcks are as follows :
1. The main clamp has got inside threads which are supposed to match with the outer threads of the top tube, but it takes much time to fix the clamps properly with the outer threads and some times it does not at all match with the threads mutually because of the different workmanship.
2. The top clamp for holding the twin jack is also having two halves threaded inside. Those are also supposed to set with the outer threads of the top tube to hold it properly, but those also many times do not set with the outer threads of the top tube. This type of mismatching occurs due to the different manufactures of the prop & setting device. The chance of slightly variation with the size of threads is very common in mines. The operators face difficulties in the underground.
3. The withdrawal mechanism in the device is given by a rotating
lever and a small knotted rope. If the rope is pulle4i#ltflinger
rotates and gets the clamp open. But to pull the ropof
a tirfor/puller of 5 tone capacity, which is not available in
mines always. Again, the use of puller/tirfor for every prop is a
cumbersome practice for the workers, because they do not need to
withdraw the prop from a great distance for which the tirfor is useful, rather they need to withdraw it from only a distance of 3m or so. Again there is chance of theft or damage of the tirfor in underground mines. Therefore, this is a limitation and calls for further modification for smooth use of the prop in the field.
4. The bottom plate of the bottom tube is having 4 prongs evenly placed at its lower side to accommodate with the floor of mines. But it is found that existence of the prongs creates more problem for hard floors of the mines. These extended prongs do not suit to the rocky floor and therefore some times they do not touch the floor evenly, may be only one or two prongs are in touch of floor, the rests are in the air, creating unequal distribution of load on the prop and certainly diminishing its efficiency. It needs suitable modification for its wide use in underground mines.
The main object of the present invention is to provide an improved vertical prop with high setting load useful for supporting mine & tunnel roofs which overcomes the drawbacks of available props.
Another object of the present invention is to provide an improved prop which provides high and assured setting load and has got more than 40 tonne vertical load bearing capacity, along-with remote withdrawal device.
In the drawings accompanying this specification Fig. 4 (a&b) shows the schematic diagram of the prop, figures 5 & 6 depict the clamp, Figures 7,8 & 9 show the schematic diagram of setting
According to the present invention there is provided an improved vertical prop for supporting the mine 8s tunnel roofs, which comprises two cylindrical steel tubes (2,9), bottom tube (2) having a smooth internal surface, provided with a plate (1) at bottom end of the tube for support on the mine floor, the other end of the tube (2) being open and having an extended rim around its top periphery, bottom tube (2) also being provided at its upper portion with two studs (3) placed diametrically opposite to each other, tube (9) having an external diameter less than the internal diameter of tube (2) such that it is capable of sliding inside tube (2) telescopically, tube (9) being provided with threads on its outer surface, tube (9) also being provided with crown (10) at its top end for supporting the mine/tunnel roof, tube (2) being provided on its upper rim with a clamp (5) having two halves of the clamp (5) being circular in shape, the other end of both halves of the hinged clamp (5) having elongated portion provided with locks (11,12) and wedge (6) for locking the clamp (5) around tube (9) by pins (4,13), said clamp being provided for opening the clamp (5) remotely through a rod with hook (22) and a
handle (23), a platform (18) having locking member (19) being removably fixed on studs (3) of tube (2) for placing twin jacks (14), top tube (9) being provided with a threaded locknut (7) and a flat nut (8) above the locknut fitted onto the outer threads with help of its matching inside threads, a tube holder plate (20) having two halves with locking members (21) being provided for removably fixing on tube (9) under the flat nut (8), the tube holder (20) being provided with matching dimensions for accommodating the rams of the twin jacks (14), the twin jacks (14) having pressure gauge (16) and interconnecting rod (15) being connected with an in-built hydraulic pump (17).
The prop of the present invention is a mechanical telescopic device having two cylindrical steel tubes. A wide range of telescopic extension (600 mm to 1000mm) is possible with this device. Setting device is a separate hydraulic twin jack. By the setting device, a setting load of more than 10 tonne can be provided against the mines roof. A clamp is attached with the bottom tube which is used to retain the setting load with the help of a lock nut upon it. When setting device is withdrawn, the prop can retain around 10 tonne setting load. An arrangement is made with the prop such that setting load achieved is assured and does not decay with the passage of time. The prop can be withdrawn remotely. A threaded bolt is fixed with one half of the clamp such that if it is rotated
by a hooked rod from a distance.
it gets into the clamp and push two halves to move apart and thus the clamp is widely opened and the top tube gets inside down the bottom tube. Thus it does not require any person to be very n&ar the prop for withdrawal when there is load over it. The prop has got sufficient load bearing capacity as well, with least maintenance cost.
The prop of the present invention, the clamp arrangement, the setting device and the withdrawal arrangement as shown respectively in Figures 4 (a&b), 5, 6, 7, 8, 9 & 10 of the drawings accompanying the specification are described below. The prop consists of a bottom tube (2), top telescopic tube (9), clamp (5) and crown (10). The top tube can freely move within the bottom tube. The setting device consists of a hydraulic pump (17) with a pressure gauge (16) & a twin jack (14), with two accessories- a bottom jack holder plate (18) and a top jack holder plate (21).
Operation of the device is very simple. Initially, the roof height is measured and the telescopic tube is extended accordingly and the locknut (7) is placed properly and the main clamp is kept locked by the wedge (6). Then the prop is lifted and erected vertically. The bottom jack holder plate (18) is fixed with the bottom tube with the help of two locking arrangement (19)on both sides, around the two welded studs (3) on both sides of tube (2) below the clamp (5). Then the twin jack (14) is placed over the jack holder plate (18) and the telescopic tube holder plate (20)
is placed over the rams of the twin jack and kept tightened with the top tube (9) below the round nut (8). The lower portion of the top tube about 1 m from the bottom is threaded which helps the telescopic extension of the prop upto a height of about 0.75 m when it is fully extended. When the top holder plate (20) is set with the top tube under the ring nut (8) and rest over the jack (14) properly, the main clamp (5) is kept locked though it allows free movement of the top tube (9) through it. The jack is extended by pumping the hydraulic pump (17). The top tube (9) with its crown (10) is then pressed against the roof. When the load shows 10 tonne by the gauge (16), the locknut (7) is tightened with clamp (5) by rotating it downward. Now the prop is set with setting load and the setting device the jack (14), the top and bottom holder plates (18 & 20) are to be opened.
At the time of withdrawal, one person has to go near to the prop and the wedge (6) of the clamp (5) to be opened. When the wedge is taken out, the prop is intact with the load over its locknut (7) and clamp (5). A hooked rod (22) and a threaded pin (4) are used for withdrawal of the prop. The threaded pin which has a flat head with hole is fixed within the one half of the clamp (5). Now the hook of the rod is fixed within the hole of the pin (4) and then it is rotated by holding at other end. The two halves thus are opened and the top tube (9) gets ilnsid© the bottom tube (2) through the clamp (5). Thus the prop i* Ldftfcl and can be taken out by pulling the same rod from a distance df 10 feet or more. The setting time is around 10 minutes for each prop and withdrawing of this prop is safe.
The advantages of the improved prop are:
1) This prop has got high vertical load bearing capacity of the order of 40 tonnes.
2) It can provide higher setting load of the order of 10 tonnes or more and does not delay over time.
3) It can be used as Immediate Front Roof Support and can
be set at a distance of 1 m in front of a blasting face.
4) It involves low maintenance cost and it has no sensitive
parts which may be damaged due to handling or by blasting.
5) The prop is comparatively lighter; it can be carried in
two separate members.
6) It can be withdrawn remotely from a distance, with the help of a tirfor/puller.
7) Running cost of this prop is almost nil, it does not require any costly equipment to run the operation of the prop.
8) It is cheap compared to existing props and has longer useful life and can be used as general roof support for mines.

WE CLAIM:
An improved vertical prop for supporting the mine & tunnel roofs, which comprises two cylindrical steel tubes (2,9), bottom tube (2) having a smooth internal surface, provided with a plate (1) at bottom end of the tube for support on the mine floor, the other end of the tube (2) being open and having an extended rim around its top periphery, bottom tube (2) also being provided at its upper portion with two studs (3) placed diametrically opposite to each other, tube (9) having an external diameter less than the internal diameter of tube (2) such that it is capable of sliding inside tube (2) telescopically, tube (9) being provided with threads on its outer surface, tube (9) also being provided with crown (10) at its top end for supporting the mine/tunnel roof, tube (2) being provided on its upper rim with a clamp (5) having two halves of the clamp (5) being circular in shape, the other end of both halves of the hinged clamp (5) having elongated portion provided with locks (11,12) and wedge (6) for locking the clamp (5) around tube (9) by pins (4,13), said clamp being provided for opening the clamp (5) remotely through a rod with hook (22) and a handle (23), a platform (18) having locking member (19) being removably fixed on studs (3) of tube (2) for placing twin jacks (14), top tube (9) being provided with a threaded locknut (7) and a flat nut (8) above the locknut fitted onto the outer threads with help of its matching inside threads, a tube holder plate (20) having two halves with locking members (21) being provided for removably fixing on tube (9) under the flat nut (8), the tube holder (20)
being provided with matching dimensions for accommodating the rams of the twin jacks (14), the twin jacks (14) having pressure gauge (16) and interconnecting rod (15) being connected with an in-built hydraulic pump (17).
An improved vertical prop for supporting the mine & tubbel roofs, substantially as herein described with reference to fig. 4 to 10 of the drawings accompanying this specification.
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