Tool driving or impacting – Impacting devices – Selective axial direction of impact
Reexamination Certificate
2001-08-20
2002-10-22
Smith, Scott A. (Department: 3721)
Tool driving or impacting
Impacting devices
Selective axial direction of impact
C175S019000, C175S296000
Reexamination Certificate
active
06467554
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to boring tools for underground boring, and more particularly, it relates to pneumatic impact operated boring tools for use with horizontal boring machines during horizontal boring operations for placement of utility lines and the like.
BACKGROUND OF THE INVENTION
Pneumatic impact-operated boring tools are well-known in the art. U.S. Pat. No. 3,756,328 issued to Sudnishnikov et al. discloses one such device. Typically, pneumatic impact-operated boring tools are used for burrowing holes in soil, particularly horizontal or near horizontal passages for installation of utility lines when trenching is undesirable. An example of such usage would be for the installation of services underneath an existing structure, such as a driveway or highway, where installation of the line by traditional open cut methods would be impractical. In this situation, the pneumatic impact-operated boring tool is launched from a pit on one side of the structure and is advanced to a receiving pit on the opposite side of the structures.
As the name implies, such boring tools function by impact. The tools possess a striking member (striker) slidable within a cylindrical housing. The striker delivers impacts on a surface at the front end of the housing. This impacting motion within the tool itself causes the soil around the tool to compact away from the nose of the housing, thus forming a hole. The tools are typically driven by a compressed air source. As the compressed air flows through the tool, the striker will be driven in a reciprocal motion generating a series of rapid impacts against the front of the tool housing, causing it to be driven through the ground.
Utility service lines to be installed may either be inserted into the hole formed by the piercing tool, or may be pulled into the hole behind the tool as it operates. Alternatively, pneumatic piercing tools have also been used to install rigid service lines such as steel lines by driving the steel line into place.
It is occasionally desirable to retract the piercing tools from the borehole being formed. For example, if the piercing tool encounters an obstruction in the soil such as a rock or stone or deviates from the desired path or is damaged in any way, quick withdrawal of the tool from the borehole may be necessary. Most tools are designed to facilitate this retraction by having a mode wherein the striker impacts the rear of the tool causing a retrograde progression of the tool within the borehole.
Thus, reversible impact-operated boring tools are also well-known in the art. U.S. Pat. No. 4,683,960 issued to Kostylev et al. discloses such a device. The prior art discloses various means for accomplishing the reverse motion. In the older designs, the shift from the forward operation mode of the tool to the reverse/withdraw mode is accomplished in any one of the following ways. Some require interrupting the pressurized fluid supply. Others require manipulation of the hose supplying the pressurized fluid to the tool, either by rotating the hose or by pulling it back. Still others require both the interruption of the pressurized fluid supply and the manipulation of the hose.
However, there are several disadvantages associated with these processes. For example, when the pressurized fluid supply is interrupted and the tool is therefore momentarily shut off, the tool may not restart when the pressurized fluid supply is recommenced. In tools requiring hose manipulation, when the hose is flexible, it is often difficult to relate the degree of rotational motion of the hose at the surface to the degree of rotational motion at the tool itself, which may be some distance away. In addition, cave-ins of the hole wall can bind the hose, making it difficult to rotate the hose, or preventing it altogether. Consequently, it is often difficult to reverse the operation of the tool, or to be certain of the direction of operation.
In the more recent designs, the mechanism of shifting the pneumatic tool from forward to reverse is somewhat simplified. U.S. Pat. No. 5,172,771 ('771 patent) and U.S. Pat. No. 5,327,636 ('636 patent), both issued to Wilson and both incorporated fully herein by reference, disclose such a device. In Wilson's '771 patent, a second air hose was added to act as a control mechanism for switching the tool from forward to reverse. Pressurizing the control hose caused a valve mechanism in the tool to move to a forward position, creating the forward movement of the pneumatic tool. Releasing the pressurized air from the control hose caused the valve mechanism to move to a rearward position, resulting in a reverse/withdrawal movement of the tool. However, the valving mechanism in the tool of the '771 patent is complex, and difficult to assemble, requiring assembly of several parts such as a pre-load spring, snap ring, etc. for valve containment. Additionally, the valving mechanism of the '771 patent is rigid in terms of deflection perpendicular to the longitudinal axis of the tool body. This inherent rigidity of the valving member makes the tool more prone to stalling if the tool body is deflected along its longitudinal axis by contact with an underground obstacle.
Due to the complexity presented by the current means for the reversing operation of impact-operated boring tools, and the increased labor and time associated with servicing the various component parts, an alternate simpler mechanism for switching a pneumatic piercing tool from forward to reverse operation is needed.
SUMMARY OF THE INVENTION
In one aspect, the invention relates to an impact-operated, ground-penetrating tool powered by a primary supply of pressurized fluid, and controlled between a forward operating mode and a reverse operating mode by a second supply of pressurized fluid. The tool comprises a housing, a striker, a manifold, a primary inlet tube, a valve chamber, and a control sleeve. The housing has a front end, a rear end, and body. The body of the housing defines an interior operating chamber with an inner surface, an exhaust conduit to provide fluid communication between the operating chamber and the outside of the tool, a forward striker surface, and a rearward striker surface.
The striker is reciprocally supported within the operating chamber of the housing between the forward and rearward striker surfaces. The striker has a forward end, a rear portion terminating in a rear end, and a striker body defining an interior striker chamber. The rearward portion of the striker sealingly engages the inner surface of the operating chamber to divide the operating chamber into a forward operating chamber and a rearward operating chamber. The rearward operating chamber is continuous with the exhaust conduit. Whereas, the striker body has at least one striker port to provide fluid communication between the forward operating chamber of the housing and the interior striker chamber.
The manifold is located near the rear end of the housing and comprises a primary conduit connectable to the primary fluid supply and a secondary conduit connectable to the secondary fluid supply. A primary fluid inlet tube extends from primary conduit of the manifold. Additionally, the valve chamber is in fluid communication with the secondary conduit in the manifold.
The control sleeve has a rear portion, a front portion, and an interior sleeve chamber defining a passage between the rear portion and the front portion. The front portion of the control sleeve is slidably and sealingly supported inside the rear portion of the striker. Whereas, the rear portion of the control sleeve is slidably and sealingly supported on the primary fluid inlet tube at least partially inside the valve chamber. The control sleeve provides continuous fluid communication between the primary fluid inlet tube and the striker chamber, so that in response to supply of primary fluid the striker reciprocates between a forward position and a rearward position. In the forward position, the striker port is open between the interior striker chamber and the fo
McKinney & Stringer, P.C.
Smith Scott A.
The Charles Machine Works, Inc.
LandOfFree
Quick reverse mechanism for pneumatic boring tool does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Quick reverse mechanism for pneumatic boring tool, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Quick reverse mechanism for pneumatic boring tool will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2930377