Patent Application
20140072372
The present invention is directed toward an improved tandem plate for use with friction rock stabilizers and, more particularly, toward a tandem plate (sometimes referred to as a butterfly plate) that can easily be attached to a bearing plate of a rock stabilizer when desired so that a miner can handle the entire assembly with two hands.
Ground support, especially in the mining industry, is an important safety factor that must be taken into consideration during any type of excavating activity. Rock stabilizers, or rock bolts, have been used for many years to support exposed rock during mining operations. A number of types of rock bolts are used depending on the situation, such as ground conditions, costs, personal preferences, etc. There are three primary types of rock bolts. The first is an expansion shell type bolt where a screw threaded steel bar is inserted into a drilled hole in the rock. The bolt has a “shell” at its tip. Once the bolt is inserted into the drilled hole and is turned, the shell expands to the sides of the hole and grips the rock so that the steel bar can then be tensioned. This results in bolting the rock strata layers together.
Grouted bar type stabilizers are also known. These include a ribbed bar which is inserted into a drilled hole and which hole is then further filled with a specialized cement or resin-based grout. This type of support depends directly on the bond between the rock and the grout and the grout and the steel bar and acts like a reinforcing bar.
Another effective anchoring system that is currently used is commonly referred to as a Split Set available from International Rollforms, of Deptford, N.J. A Split Set is a brand of a friction rock stabilizer that includes an elongated tube and a bearing plate. The tube is typically made from resilient steel and has a slit along its length so that the tube will be compressed during insertion into a pre-drilled bore in a mine roof or wall. One end of the tube is tapered and the other end has a ring flange. In order to install the split set, the bearing plate is placed over the end of the tube so as to engage the ring flange and the tapered end of the tube is then driven into the drilled hole in the rock. As tube slides into place, the slot narrows, exerting radial pressure against the surface over its full contact length and provides plate load support. The result is a tight grip brought about by the friction generated between the outer steel wall of the tube or cylinder and the inner side wall of the bore in the wall. Such systems are described, for example, in U.S. Pat. No. 5,295,768 to Buchhorn et al., U.S. Pat. No. 4,652,178 to Kates et al., U.S. Pat. No. 4,445,808 to Arya, and U.S. Pat. No. 4,382,719 to Scott.
Bearing plates, such as mentioned above, can be use with substantially any of these rock bolts or friction rock stabilizers. The purpose of the bearing plate is to distribute the load applied by the stabilizer against the surface of the rock. That is, the bearing plate transfers the weight load of the rock face to the bolt.
In some applications, an additional plate, commonly referred to as a tandem plate is used in combination with a bearing plate. The tandem plate placed on the bearing plate and the bolt is then threaded through the two plates. The tandem plate is larger in size than the bearing plate and is usually made of a much lower gauge steel material so that it can conform to some degree to the rock face of the mine roof surrounding the bolt. The primary purpose of the tandem plate is to inhibit fretting of the rock face about the bolt. That is, the tandem plate supports loose material or rocks and prevents them from falling.
When utilizing a tandem plate in addition to the bearing plate, it is normally just placed over the bolt along with the bearing plate and is allowed to simply move freely. This creates problems when the bolt is being driven into place as the plate may not line up properly. In particular, with prior art tandem plates, both plates are free to rotate as the bolt is hammered into the hole. The bearing plate should seat into the square pocket in the tandem plate, but as the two plates can rotate freely, they may not seat properly as the bolt installation is completed, thereby crushing the tandem plate.
One solution to this problem is to weld the tandem plate to the bearing plate such as shown in U.S. Pat. No. 5,628,587 to Lesslie or to interconnect a tandem plate and a bearing plate by crimping them together to essentially form a single plate such as shown in U.S. Pat. No. 5,791,828 to Fergusson. Such combinations, however, are not satisfactory for several reasons. Most significantly, not all bolts require both a bearing plate and a tandem plate. Thus, workers would have to carry both the combined plates such as taught by Lesslie or Fergusson and bearing plates without the tandem plate attached.
There is, therefore, a need for a tandem plate for use with friction rock stabilizers that can easily and quickly be applied to a bearing plate in the field if such is ever deemed to be necessary or beneficial.
The present invention is designed to overcome the deficiencies of the prior art discussed above. It is an object of this invention to provide a new tandem plate for a friction rock stabilizer that has advantages over prior art plates.
It is a further object of the present invention to provide a new tandem plate that is relatively simple to install.
It is a still further object of the present invention to provide a new tandem plate that can simply and quickly be applied to a bearing plate in the field whenever desired.
In accordance with the illustrative embodiments demonstrating features and advantages of the present invention, there is provided a tandem plate for use with a friction rock stabilizer of the kind that includes an elongated metal tube adapted to be driven into a bore drilled in a rock wall and a second end adapted to engage a bearing plate. The tandem plate is comprised of a substantially planar sheet of metal having an upper surface and a lower surface and an overall dimension which is larger than the size of the bearing plate. An opening adjacent the center allows the tube to pass therethrough. The lower surface is adapted to engage the rock wall while the upper surface of the tandem plate engages the bearing plate. A plurality of tabs on the upper surface, that are formed by punching and bending parts of the planar sheet from which the tandem plate is made, engage the bearing plate prior to installation forming one unitized assembly. This assembly can then be installed with the tube being driven into said bore. A plurality of ribs is formed on the tandem plate for increasing the strength thereof.
Other objects, features, and advantages of the invention will be readily apparent from the following detailed description of the preferred embodiments thereof taken in conjunction with the drawings.
For the purpose of illustrating the invention, there is shown in the accompanying drawings one form which is presently preferred; it being understood that the invention is not intended to be limited to the precise arrangements and instrumentalities shown.
Referring now to the drawings in detail wherein like reference numerals have been used throughout the various figures to designate like elements, there is shown in the figures a tandem plate constructed in accordance with the principles of the present invention and designated generally as 10.
The tandem plate 10 is intended to be used with a friction rock stabilizer system that includes an elongated metal tube 12 having a first end 14 that is adapted to be driven into a bore drilled in a rock wall of a mine or the like. The second end 16 of the tube 12 includes a flange 18 formed thereon. The friction rock stabilizer system also includes a bearing plate 20 having a raised conical center portion 22 that effectively increases the strength of the bearing plate 20. The conical center portion rises from a flatter base portion 23. An opening 24 adjacent the center of the bearing plate 20 allows the tube 12 to pass therethrough but is smaller than the flange 18 so that the flange 18 will engage the bearing plate 20.
The friction rock stabilizer system thus far described is, per se, well known in the art and, as mentioned above, is commonly referred to as a “Split Set” friction rock stabilizer” available from International Rollforms, of Deptford, New Jersey. These systems are also described, for example, in U.S. Pat. No. 6,257,802 to Vosbikian.
Tandem plate 10 of the present invention is intended to be used with the friction rock stabilizer described above. As will be apparent to those skilled in the art, however, the tandem plate 10 could also be used with other similar systems.
The tandem plate 10 is comprised essentially of a planar sheet of metal 26 which is, preferably, steel. The sheet of metal 26 includes an upper surface 28 and a lower surface 30. As can be seen, the overall dimension of the tandem plate 10 is larger than the size of the bearing plate 20. An opening 32 is formed adjacent the center of the bearing plate and is of a size to allow the tube 12 to pass therethrough. Obviously, the opening 32 is substantially smaller than the overall size of the bearing plate 20.
In order to increase the strength of the tandem plate 10, ribs 34 and 36 are formed thereon. These can be formed by stamping and bending the sheet metal from which the tandem plate is made. While two such ribs are shown, it should be readily apparent to those skilled in the art that any number of ribs can be formed. Furthermore, the ribs can extend in different directions.
A pair of spring tabs 38 and 40 is formed in the upper surface 30 of the tandem plate 10. This is preferably accomplished by simply stamping out a portion of the sheet metal 26 from which the tandem plate 10 is made and then bending the tabs 38 and 40 to the shape shown.
As can be seen most clearly in
As should be readily apparent to those skilled in the art, when it is desired to connect the tandem plate 10 to the bearing plate 20, all that is needed is to slide the base 23 of the bearing plate 20 under the tabs 38 and 40. This is done before the two plates are passed over the end 14 of the tube 12.
As can be seen from
The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and accordingly, reference should be made to the appended claims rather than to the foregoing specification as indicating the scope of the invention.
