Patent Application
20160102552
The present disclosure relates to a temporary roof support system for a roof bolter machine, and more particularly, to a temporary roof support system including a locking tube assembly to prevent rotation of the roof support system during operation.
Roof bolting is a common process to stabilize roofs in underground coal mines and tunnels. It involves inserting conventional, cable or resin bolts by drilling directly into the rock strata using a roof bolter machine. The roof bolter machine generally includes a temporary roof support system for installing multiple bolts simultaneously in a roof to make it self-supporting. Typically, the temporary roof support system includes a crossbar mounted on a hydraulic cylinder. The crossbar has rocker pads at either end to support the roof while drilling holes in the rock strata, and subsequently introducing bolts in these holes. The hydraulic cylinder not only provides enough pressure to lift the crossbar but to support the temporary roof support system as well.
When the hydraulic cylinder is pressurized to lift the crossbar, the hydraulic cylinder develops an inherent rotary motion. This rotary motion tends to undesirably rotate the crossbar, which subsequently changes position of the rocker pads. Currently, rectangular multistage covers are used to prevent the rotation of the crossbar due to locking by diagonals of the rectangular multistage covers. Consequently, the rectangular multistage covers have to be very heavy and thick, in order to provide necessary force for preventing the rotation of the cylinder. This adds excess weight to the temporary roof support system.
U.S. Pat. No. 4,284,368 discloses a temporary support system for a mine roof. The temporary support system includes a base, a telescopic column mounted on the base, and a crossbar connected to the top of the column. The system further includes two expandable hydraulic jacks, each hydraulic jack mounted on each side of the column. One end of each of the jacks is connected to the base and the other end of each of the jacks is connected to the crossbar for expanding and retracting the temporary roof support system. Though, the temporary support system prevents the rotation of the crossbar, the temporary support system uses multiple jacks, which adds complexity to the system. Also, the jacks are single stage hydraulic cylinders, which are used to operate the same actuator, and are needed to be operated in unison otherwise they tend to pull and push each other, in turn, leading to in efficient operation of the temporary roof support system. Moreover, a difference in minimum height of the crossbar and the maximum height of the crossbar is dependent on stroke length of the jacks. Since jacks are single stage hydraulic cylinders, the difference and thus, the height to which the crossbar can be raised is limited. Thus, there exists a need of a simpler design with less number of components for the temporary roof support system to restrict the undesirable rotation of the crossbar.
In one aspect of the present disclosure, a temporary roof support system is provided. The temporary roof support system includes a base, a multistage hydraulic cylinder, a multistage telescopic cover assembly, a crossbar and a locking tube assembly. The multistage hydraulic cylinder has a first end and a second end, and multistage hydraulic cylinder is mounted on the base at the first end. The multistage hydraulic cylinder is extendable along a vertical axis. The multistage telescopic cover assembly encompasses the multistage hydraulic cylinder, and is coupled to the multistage hydraulic cylinder at the second end. The multistage telescopic cover assembly further includes a first plurality of cylinders of successively differing diameters disposed coaxially within the multistage telescopic cover assembly. The multistage hydraulic cylinder is coupled to the crossbar at the second end using a pivot joint at a center of the crossbar. Further, the locking tube assembly has a first pivot end and a second pivot end. The locking tube assembly includes a second plurality of cylinders including an outermost cylinder and an innermost cylinder. The second plurality of cylinders is coaxially disposed and having successively differing diameters. The locking tube assembly further includes a first mounting eye at the first pivot end and a pair of mounting eyes at the second pivot end. The first mounting eye is coupled to the innermost cylinder of the locking tube assembly and the pair of mounting eyes is coupled to the outermost cylinder of the locking tube assembly. The second pivot end of the locking tube assembly is coupled to the crossbar and the first pivot end of the locking tube assembly is coupled to the base such that a length of the locking tube assembly is parallel to the vertical axis.
Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.
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Further, the locking tube assembly 32 includes a second plurality of cylinders 58 including an outermost cylinder 60 and an innermost cylinder 62, the second plurality of cylinders 58 are coaxially disposed within the locking tube assembly 32 and have successively differing diameters. The first mounting eye 38 is coupled to the innermost cylinder 62 of the locking tube assembly 32. The pair of mounting eyes 40 is coupled to the outermost cylinder 60 of the locking tube assembly 32. The locking tube assembly 32 has the length L1. When the multistage hydraulic cylinder 48 is extended along the vertical axis 1-1′, the second plurality of cylinders 58 of the locking tube assembly 32 also extends along the length L1 such that the length L1 of the locking tube assembly 32 is parallel to the vertical axis 1-1′. Since the first pivot end 34 of the locking tube assembly 32 is connected to the base 22, the locking tube assembly 32 can only extend and contract along the length L1, but can't rotate about axis 1-1′. Thus it allows the crossbar 26 along with the multistage telescopic cover assembly 24 to lift up and down but arrests its inherent rotation alone.
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When the crossbar 26 supports uneven roof levels at both sides, the crossbar 26 needs to be inclined at an angle to the horizontal. At this stage, the pins 46 allows the locking tube assembly 32 to adjust this deflection on its own by extending and contracting of the locking tube assembly 32, and by pivoting of the first pivot end 34 and the second pivot end 36 of the locking tube assembly 32. This key movement allows the locking tube assembly 32 to adjust its vertical orientation. Thus, the crossbar 26 is able to freely rotate along the axis of the pivot joint 30.
Roof bolting is a common process to stabilize roofs in underground coal mines and tunnels using a roof bolter machine. The roof bolter machine generally includes a temporary roof support system for installing multiple bolts simultaneously in a roof to make it self-supporting. Typically, the temporary roof support system includes a crossbar mounted on a hydraulic cylinder. The crossbar has rocker pads at either end to support the roof while drilling holes in the rock strata, and subsequently introducing bolts in these holes. When the hydraulic cylinder is pressurized to lift the crossbar, the hydraulic cylinder develops an inherent rotary motion. This rotary motion tends to undesirably rotate the crossbar, which subsequently changes position of the rocker pads. To prevent the rotation of the crossbar, rectangular multistage covers are used. However, such rectangular covers add an excess weight and a lot of complexity into the temporary roof support system.
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Further, the temporary roof support system 20 does not require the multistage telescopic cover assembly 24 to prevent the rotation of the multistage hydraulic cylinder 48, therefore, the multistage telescopic cover assembly 24 need not be rectangular in design. Also, as the multistage telescopic cover assembly 24 does not need to prevent rotation of the crossbar 26, the multistage telescopic cover assembly 24 is light in weight, reducing the overall weight of the roof support system 20. Also, the multistage telescopic cover assembly 24 is cylindrical in design, therefore, there is very less rubbing action between the first plurality of cylinders 54 of the multistage cover assembly 24, thereby, very less friction is generated. Consequently, the need for lubrication and use of wear pads are not required, thereby reducing the overall manufacturing costs of the roof bolter machine 10.
Further, in an extended position of the multistage cover assembly 24, the outermost cylinder 56 covers a top of the inner cylinders, leaving no space for the debris to enter the multistage cover assembly 24. The outermost cylinder 56 of the multistage telescopic cover assembly 24 is coupled to the crossbar 26 via the pivot joint 30. Due to this design of the multistage telescopic cover assembly 24, there are less chances of dirt to stick and retain in the cylindrical covers and thereby, the maintenance requirements are reduced and consequently, idle time of the roof bolter machine 10 is reduced.
While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.
