Geometrical instruments – Gauge – Collocating
Reexamination Certificate
2002-04-30
2003-07-29
Bennett, G. Bradley (Department: 2859)
Geometrical instruments
Gauge
Collocating
C033S645000, C405S303000
Reexamination Certificate
active
06598309
ABSTRACT:
BACKGROUND OF THE INVENTION
Rock bolters, independent of whether they are platform- or turret-type bolters, employ mechanisms to sequentially bring a drill and a bolt driver into alignment with a work axis which corresponds to the axis of the hole to be drilled and the bolt to be positioned therein. These mechanisms can be either a platform transfer device, such as taught in U.S. Pat. Nos. 5,114,279 and 5,690,449 or, alternatively, a turret transfer device such as is taught in U.S. Pat. Nos. 4,473,325 and 4,497,378. In either case, the drill is first aligned with the work axis and advanced to bore a hole into a desired location on a rock surface. The drill is withdrawn, and the bolt driver is then aligned with the work axis to advance the bolt into the hole. The bolt typically has a bolt plate associated therewith which is brought into contact with the rock surface when the bolt is fully inserted into the hole.
To assure that the bolt is accurately aligned with the axis of the drilled hole, a bolt centralizer, while not a necessity, is highly desirable. While a centralizer is desirable, the use of a centralizer does increase the complexity of the rock bolter. The centralizer should be, at least in part, positioned in close proximity to the hole and requires a bolt-directing element having a passage therethrough which needs to be in close proximity to the rock surface into which the hole is drilled. The introduction of a bolt centralizer presents two problems. The centralizer must not interfere with either the bolt driver or the bolt plate as the bolt driver is advanced, and the centralizer must have its bolt-directing element be retractable when the bolt is partially driven so that the bolt plate can be advanced to the rock surface.
The '378 patent teaches a rock bolter which does not employ a centralizer, but instead relies on a pair of grippers for holding the bolt as it is transferred from a bolt magazine into alignment with the hole, these grippers apparently also serving to guide the bolt into the hole bored in the rock. The grippers are described as being pivotably mounted, and thus presumably pivot out of the way as the bolt driver and the bolt plate are advanced, allowing the bolt plate to be advanced into contact with the rock surface. Accurate alignment of the bolt with the hole has been found problematic with such devices, frequently requiring the operator to adjust the position of the rock bolter visually to insert the bolt into the hole. Even when bolts having a tapered bolt tip to assist in inserting the bolt into the hole are employed, accurate alignment of the bolt with the hole is problematic.
The '325 patent, assigned to the same assignee as the '378 patent, teaches the use of a centralizer in combination with the rock bolter described in the '378 patent. The centralizer has a bolt-directing assembly with a bolt plate holder which positions the bold plate to allow the bolt plate to serve as the bolt-directing element. This approach requires the bolt plates to reside in close proximity to the rock surface, limiting the ability to store multiple bolts with the bolt plates residing thereon in a magazine when the rock bolter is intended for use in mines where the footprint of the front surface of the bolt magazine needs to be minimized to avoid interference with the surrounding rock surface during the bolt-setting operation. Also, since there are various configurations of bolt plates which are commonly used, a different holder would need to be used for different types. This would require alteration of the rock bolter when the plate type is changed, which is undesirable.
The '279 patent, which is for a platform-type rock bolter, employs an arm to help transfer the bolt to the work axis and may also use the arm to direct the bolt into the hole. The arm has a hydraulic cylinder that causes it to grip the bolt and a second hydraulic cylinder that pivots the arm about an axis parallel to the work axis. The '279 patent does not discuss how the arm is moved to allow the bolt plate to pass thereby. The use of two hydraulic cylinders to operate the arm complicates both the structure and the operation of the rock bolter.
Applicant's assignee has overcome the problem of centralizing the bolt for most situations with the use of a combination stinger/centralizer, as taught in U.S. No. Pat. 5,556,235 and U.S. Pat. No. 6,413,019, for both of which the present Applicant is a co-inventor. The stinger/centralizer has two mating heads which form the centralizer, and which can be separated and withdrawn to allow the bolt plate to be advanced therepast. While the stinger/centralizer has been advantageously employed in many situations, the use of a stinger/centralizer may not be practical when clearances are severely limited, as the stinger/centralizer increases the overall height of the rock bolter. Additionally, when the rock surface is extremely friable, it is preferred to use the bolts to secure a screen material to the rock surface to stabilize it, and the presence of a stinger/centralizer may result in interference with the apparatus for handling such screen material.
Thus, there is a need for a centralizer structure for maintaining alignment of a bolt with respect to a pre-drilled hole which is suitable for use in limited clearance situations and for use with a screen handling apparatus.
SUMMARY OF THE INVENTION
The present invention is for a bolt centralizer that has utility in rock bolters which have frames and employ either platforms or turrets attached to the frames to move a rock drill and a bolt driver onto and off of a work axis. The work axis is defined as the axis which is traversed by a drill steel while being advanced by the rock drill to form a hole at a desired location on a rock surface and the axis along which a bolt is advanced when the bolt is being driven into the hole by the bolt driver. Further descriptions of these rock bolters are found in U.S. Pat. Nos. 5,556,235 and 5,690,449, and in U.S. patent application Ser. No. 09/691,736, all of which are assigned the assignee of the present application.
The bolt centralizer of the present invention has an arm terminating in an arm first end and an arm second end. The arm first end is connected to the frame of the rock bolter. A bolt-directing hand having a hand first end and a hand second end is provided. The bolt directing-hand is pivotably attached to the arm second end so as to pivot about a hand pivot axis. This hand pivot axis is preferably normal to the work axis to allow the hand to pivot in an arc which is coplanar with the work axis.
A pair of fingers is pivotably attached to the hand second end such that the fingers pivot with respect to each other about a finger pivot axis between a closed position, where they are in a bolt-gripping relationship with respect to each other, and an open position, where they are in a bolt-releasing relationship. A spring is provided to bias the pair of fingers to the closed position. Preferably, the fingers are both pivotably mounted to the hand second end and share a common finger pivot axis that is positioned so as to swing through a plane which contains the work axis when the bolt-directing hand is pivoted about the hand pivot axis.
A recess is provided in each of the fingers and these recesses are configured and positioned such that, in combination, they form a centralizer passage when the fingers are in the closed position. The centralizer passage is sized to slidably engage the bolt when the bolt is positioned in the recesses and the fingers are in the closed position. Alternatively, when the fingers are in the open position, they are sufficiently separated as to allow the bolt to be passed into and out of the recesses.
Means for rotating the bolt-directing hand about the hand pivot axis are provided, and serve to rotate the bolt-directing hand between a first hand position, where the centralizer passage is alignable with the work axis, and a second hand position, where the hand and fingers are positioned so as not to obstruct the
Bennett G. Bradley
Oldenburg Cannon, Inc.
Sempreben Jeffrey E.
Weins Michael J.
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