Claims
- 1. A pit prop assembly for use in a mine having a floor, a roof, and a face, said assembly comprising: a pair of pit props having parallel elongated floor-engaging bases each with a front end adapted to be turned toward said face and a rear end turned away from said face and spaced in the longitudinal direction of the respective base from the respective front end, a roof-engaging arm pivoted on each of said bases at the respective rear end thereof, and means between each of said arms and the respective base for pressing the respective arm against said roof; a longitudinal hydraulic ram extending in said direction and having one end operatively connected to one of said bases and another end operatively connected to the other of said bases, whereby longitudinal contraction or extension of said ram displaces said bases relative to each other in said direction; and means including an element of variable length between said bases for varying the spacing transverse to said direction therebetween.
- 2. The assembly defined in claim 1, further comprising a pair of members telescoped in each other, a pivot defining a longitudinal pivot axis between each of said ends of said one base and one of said members and between one of said ends of said other base and the other member, said ram being connected between said members.
- 3. The assembly as defined in claim 2 wherein said means includes a transverse ram operatively connected between the other end of said other base and said other member.
- 4. The assembly defined in claim 2 wherein said one of said elements is of nonround section and the other element has a passage of similar nonround section.
- 5. The assembly defined in claim 2 wherein each of said pivots includes a part having a throughgoing hole of hyperboloidal shape and a pin of generally cylindrical shape received in said hole and limitedly cantable therein.
- 6. The assembly defined in claim 1 wherein said means is a transverse ram operatively engaged between said rear ends.
- 7. The assembly defined in claim 1 wherein said means includes a flexible element having an outer end secured to said one base and an inner end at said other base, and a hydraulic ram on said other base connected to said inner end.
- 8. The assembly defined in claim 1 wherein said ram lies between said bases.
- 9. The assembly defined in claim 1, further comprising a guide on said one base defining a pivot axis generally parallel to said direction, a pivot on said other base, a traverse extending transverse to said direction carried on said pivot and extending toward said one base, and an axle extending from said transverse in said direction along said axis and lying in said guide, said ram having its said one end connected to said traverse and its said other end connected to said one base.
- 10. The assembly defined in claim 9 wherein said guide lies within said one base, said means being a transverse ram engaged between said rear ends of said bases.
Priority Claims (1)
| Number |
Date |
Country |
Kind |
| 2522111 |
May 1975 |
DT |
|
CROSS REFERENCE TO RELATED APPLICATIONS
This application is related to my copending patent applications Ser. No. 477,084 (now U.S. Pat. No. 3,949,562), Ser. No. 543,369 (now U.S. Pat. No. 3,959,976), Ser. No. 618,212 (now U.S. Pat. No. 3,961,487), and filed June 6, 1974, Jan. 23, 1975, Sept. 30, 1975, and now commonly herewith, respectively.
The present invention relates to a pitprop assembly. More particularly this invention concerns such an assembly used to hold up the roof of a mine during working of the face thereof.
In a conventional mine, a face conveyor or a guide for a coal plow or the like is normally secured to a succession of pit props which are braced between the floor and roof of the mine and serve to prevent the roof from caving in. As the face is dug away and the useable coal or ore is displaced out of the mine with the waste or tailings displaced backwardly behind the pit props, it is necessary to move these pit props toward the face. In most common arrangements each pit prop is connected via a respective hydraulic cylinder to the face conveyor. Thus the ram which presses the roof shield against the mine roof is relaxed and the displacement ram itself is operated in order to drag the pit prop toward the conveyor. During such displacement of one pit prop the other props are maintained tightly in place to hold the conveyor stationary in order that it provide a solid pulling support for the prop being moved. In this manner it is possible to move the props forward one-by-one.
Such a system has the considerable disadvantage that it places a considerable strain on the face conveyor, guide or other element functioning as a support which is provided at the face. In particular, it is not a rare occurrence that the pit prop being moved becomes jammed so that it cannot move and instead the conveyor or support is pulled toward the jammed pit prop, thereby damaging this element. It has been suggested to use a separate support beam that extends between three or more such pit props so as to eliminate this potential damage to the conveyor, but such an arrangement only increases the cost and complexity of the system.
Another considerable disadvantage of this system is that it usually establishes a fixed spacing between the pit props. Thus it is impossible to compensate for local conditions by varying the prop spacing. Furthermore, each prop can only be displaced when connected to a support or when winched or pushed into place by means of a tractor. Another disadvantage of the known systems is that it is impossible to move the pit props in a direction parallel to the face without the use of a separate winch or tractor.
It is therefore an object of the present invention to provide an improved pit prop assembly.
Another object is the provision of such an assembly which can move without stressing the face conveyor or other support.
A further object is to provide a pit prop assembly which can move to at least a limited extent parallel to the face.
These objects are attained according to the present invention in an arrangement wherein a pair of pit props each comprising a floor-engaging base and a roof-engaging arm are interconnected by a hydraulic ram which extends in the longitudinal direction of the bases, that is perpendicular to the face, and has one end connected to one of the bases and another end connected to the other base. Such a ram can therefore be contracted or expanded to displace one of the props relative to the other toward or away from the face.
In accordance with another feature of this invention means is provided to maintain the front or the rear ends of the bases at a predetermined lateral spacing while permitting relative longitudinal displacement of them, and means is provided at the opposite end of these bases for varying the spacing between them. This makes it possible to cant the one base relative to the other and, therefore, to walk the pit prop in a direction parallel to the face.
With the system according to the present invention it is therefore readily possible to couple a power hose to a pit prop assembly comprising a pair of props and have it move itself independently of any other structure in the mine. Simple straightforward and backward movement is effected by bracing one prop between the roof and floor and then expanding or contracting the longitudinal ram to displace the other prop in the appropriate direction parallel to the fixed prop, and then to reverse this procedure with the other prop. In order to go around a corner the transverse ram is actuated to cant the two props relative to each other while the one prop is fixed so that the bases can be aligned in the desired direction before longitudinal displacement is effected. In this manner it is indeed possible to turn the prop completely around in a relatively small area without the necessity of providing external winches or using a tractor.
According to further features of the present invention a pair of telescope members are provided, one of which is connected by a pair of pivots defining a longitudinal pivot axis to one of the base and the other of which is connected only by one pivot to the other base. The longitudinal displacement ram is effective between these two members and the transverse displacement ram is effective between the other member and the other base.
The pivot interconnecting these various elements and, indeed, connecting the transverse ram to the other member and the other base may be formed as a ball-and-socket joint in order to permit limited canting of the various elements relative to each other or may be formed of one part having a throughgoing hole of hyperboloidal or double-flared shape in which fits another element of generally cylindrical shape. Thus with this system it is possible for the one base to lie above or below the other or even at an angle to the other.
In accordance with yet another feature of this invention a guide is provided on one base defining a pivot axis generally parallel to the longitudinal base direction and a pivot is provided on the other base. A traverse extending transverse to the direction is carried on this pivot and extends toward the one base and an axle extends from this transverse in the longitudinal direction along the axis through the guide. The ram therefore has its one end connected to this traverse and its other end connected to the one base so that by expansion or contraction it can displace the two bases relative to each other in the longitudinal direction.
According to yet another feature of this invention a flexible element such as a cable or chain has one end connected to one of the bases and another end passing over a deflecting roller or sprocket and connected to a ram on the other base. The contraction of this ram can therefore pull the corresponding ends of the bases together. These ends can be rushed apart by means of hydraulic cylinders provided on the arms of the base which are used for positioning of the roof shield.
The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of the specific embodiments when read in connection with the accompanying drawings.
US Referenced Citations (7)
Foreign Referenced Citations (1)
| Number |
Date |
Country |
| 2,013,634 |
Nov 1970 |
DT |
Patent Grant
4008578
