Plunger repositioning system

A tool for repositioning a plunger is formed from a pair of concentric and relatively rotatable shafts. The inner and tubular outer shafts respectively support enlarged forward and rear head elements. The shafts are relatively rotatable between a first position, in which the cross-sectional profiles of the head elements are aligned, and a second position, in which the cross-sectional profiles of the head elements are in skewed opposition. A ball detent mechanism at the interface between the forward and rear head elements permits accurate location of the first and second positions. The tool is used with a tubular collar element having a stem section and an enlarged flange section, and a disk-shaped platform element having a centrally disposed and internally threaded opening. The threaded opening in the platform element receives the externally threaded outer shaft of the tool.

SUMMARY OF THE INVENTION

A tool is formed from a pair of concentric and relatively rotatable shafts, including an elongate tubular outer shaft, and an elongate inner shaft. A head assembly is formed from adjacent coaxial head elements. The inner shaft supports a forward head element and the outer shaft supports a rear head element. The head elements have the same cross-sectional profiles and cross-sectional dimensions.

An assembly is formed from a plunger and a tool. The plunger has a longitudinally extending socket bore that opens into an enlarged internal chamber. The tool is formed from a pair of concentric and relatively rotatable shafts, including an elongate tubular outer shaft, and an elongate inner shaft. A head assembly is formed from adjacent coaxial head elements. The inner shaft supports a forward head element and the outer shaft supports a rear head element. The head elements have the same cross-sectional profiles and cross-sectional dimensions. The forward head element is positioned within the internal chamber of the plunger and the rear head element is positioned within the socket bore of the plunger.

A method of repositioning a plunger situated within a housing entails inserting a tool within the housing through a housing bore. The tool is formed from a pair of concentric and relatively rotatable shafts, including an elongate tubular outer shaft, and an elongate inner shaft. A head assembly is formed from adjacent coaxial head elements. The inner shaft supports a forward head element and the outer shaft supports a rear head element. The head elements have the same cross-sectional profiles and cross-sectional dimensions.

The plunger has a longitudinal socket bore that opens into an enlarged internal chamber. The forward head element of the tool is closely but clearingly receivable within the socket bore.

After the tool is inserted within the housing, the forward head element is positioned within the internal chamber and the rear head element is positioned within the socket bore. The cross-sectional profiles of the head elements are aligned during this step. Next, the inner and outer shafts are relatively rotated until the cross-sectional profiles of the head elements are in skewed opposition, thereby locking the plunger to the tool. The locked tool and plunger are then at least partially withdrawn from the housing.

DETAILED DESCRIPTION

A plunger repositioning system comprises a tool10, shown inFIGS. 1 and 2, having a first end12and an opposed second end14. The tool10is formed from a pair of concentric and relatively rotatable shafts, including an elongate inner shaft16, shown inFIGS. 3 and 4, and an elongate tubular outer shaft18, shown inFIGS. 5 and 6. The inner shaft16has a length that exceeds that of the outer shaft18and is extendable within the tubular outer shaft18.

As shown inFIG. 3, the inner shaft16has a first end20and an opposed second end22. Preferably, the inner shaft16is shaped as a cylindrical solid along the major portion of its length. At its first end20, the inner shaft16is provided with a pair of parallel faces24. The paired faces24facilitate gripping of the inner shaft16with a tool, in order to apply a rotational force.

A forward head element26is installed on an extremity of the inner shaft16at its second end22. The forward head element26is supported by the inner shaft16and is disposed in concentric relationship thereto. The forward head element26is characterized by a body28having a uniform cross-sectional profile. The body28is bounded laterally by a plurality of planar longitudinal side walls30, and features a centrally disposed axial bore32, shown inFIGS. 2 and 4, through which the inner shaft16extends.

Preferably, the body28is characterized by a polygonal cross-sectional profile. In the embodiment shown in the Figures, the forward head element26features an octagonal cross-sectional profile, with four major sides34of equal length, and four minor sides36of equal length. The ends of each adjacent pair of major sides34are joined by a minor side36. Opposed major sides34extend in parallel relationship, as do opposed minor sides36.

The forward head element26may be secured to the inner shaft16by welding, or by any other method that maintains forward head element26in an axially and radially fixed position at the second end22of the inner shaft16. More preferably, forward head element26is secured to the inner shaft16by a roll pin (not shown) that extends through a radially-extending rectilinear passage (not shown) formed in the inner shaft16and an aligned rectilinear passage38formed in the forward head element26.

The inner shaft16carries a floating annular spacer element40that is positioned immediately adjacent the forward head element26. In one embodiment, the spacer element40is formed from bronze.

As shown inFIGS. 5 and 6, the outer shaft18is an elongate tubular structure having a first end42, an opposed second end44and an internal bore46extending along its entire length. The outer shaft18preferably is cylindrical in shape along the major portion of its length, and is provided with external threads48. Preferably, the threads48are Acme threads.

At its first end42, the outer shaft18preferably includes a tubular upper section50having a polygonal cross-sectional profile. More preferably, the cross-sectional profile of the upper section50is hexagonal. Such an external shape facilitates gripping of the outer shaft18with a tool, such as crank138, in order to apply a rotational force. A centrally disposed longitudinal bore (not shown) extends through the upper section50. The bore is sized to allow the upper section50to closely but clearingly receive the inner shaft16adjacent its first end20. The upper section50thus serves to maintain the inner shaft16in a central and axial position within the outer shaft18.

A bushing52is installed within the outer shaft18at its second end44. A centrally disposed longitudinal bore54extends through the bushing52. The bore54is sized to allow the bushing54to closely but clearingly receive the inner shaft16. The bushing52cooperates with the upper section50to maintain the inner shaft16in a central and axial position within the outer shaft18.

A rear head element56is installed on an extremity of the outer shaft18at its second end44. The rear head element56is supported by the outer shaft18and is disposed in concentric relationship thereto. The rear head element56is characterized by a body58having a uniform cross-sectional profile. The body58is bounded laterally by a plurality of planar longitudinal side walls60, and features a centrally disposed axial bore (not shown), through which the outer shaft18closely but clearingly extends. The rear head element56is characterized by the same cross-sectional profile and cross-sectional dimensions as the forward head element26.

The rear head element56may be secured to the outer shaft18by welding, or by any other method that maintains rear head element56in an axially and radially fixed position at the second end44of the outer shaft18. More preferably, the rear head element56is secured to the outer shaft18by one or more set screws (not shown), each of which extends through a radially-extending rectilinear passage (not shown) formed in the outer shaft18and an aligned rectilinear passage62formed in the rear head element56. In one embodiment, two such set screws are used to secure the rear head element56to the outer shaft18.

The inner shaft16is coaxially inserted at its first end20into the second end44of the outer shaft18. The inner shaft16is extended coaxially through the outer shaft18, and positioned in concentric relation to the outer shaft18. Extension continues until the rear head element26engages the spacer element40, which maintains separation between the forward and rear head elements26and56.

After the inner shaft16has been installed concentrically within the outer shaft18, the shafts16and18are secured against relative longitudinal movement by a fastener. The fastener is installed adjacent the first end of the tool10, as shown inFIG. 1, and preferably comprises a tubular cap element64.

The cap element is provided with an internal bore (not shown) through which the inner shaft16is closely but clearingly received. The cap element64is secured to the inner shaft16by a roll pin (not shown) that extends through a radially-extending rectilinear passage (not shown) formed in the inner shaft16and an aligned rectilinear passage66formed in the cap element64.

The cap element64engages the outer shaft18at its second end44. The cap element64has maximum cross-sectional dimensions that exceed those of the internal bore46within outer shaft18. Because the cap element64cannot enter the bore46, it maintains the inner and outer shafts16and18in longitudinally fixed relationship. Alternately, the fastener may comprise a snap ring installed in a circumferential groove formed adjacent the upper end of the inner shaft.

When the inner and outer shafts16and18are assembled, the coaxially disposed head elements26and56form a head assembly68.

By relative rotation, the inner and outer shafts16and18may be moved between a first position and a second position. Preferably, such relative rotation is carried out by applying a rotational force to the inner shaft16at its first end20, while the outer shaft18remains static.

In the first position of the shafts, shown inFIG. 2, the cross-sectional profiles of the head elements are aligned. In the second position of the shafts, shown inFIG. 7, the cross-sectional profiles of the head elements are in skewed opposition. The second position is offset from the first position by a central angle having an apex that coincides with the longitudinal axis of the tool10. This central angle is preferably 45 degrees.

As shown inFIG. 8, a mechanism70is formed at the interface between the inner and outer shafts16and18. The mechanism70is adapted to resist relative rotation of the inner and outer shafts16and18at their second position, and preferably at their first position as well. The mechanism70comprises a passage72formed within the rear head element56and outer shaft18. The passage terminates in an opening74in the outer shaft18. Installed within the passage72is a ball76that is urged into a compact first depression78by a spring80. A plug82engages the spring80and closes the passage72opposite opening74.

The first depression78is formed in the exterior side of the inner shaft16near its second end22, as shown inFIG. 4. The position of the first depression78is selected so that it aligns with the opening74when the shafts16and18are in their second position.

When the ball76is urged into the first depression78, the mechanism70resists, but does not block, relative rotation of the shafts away from their second position. This resistance allows a user of the tool10to accurately locate the second position of the concentric shafts16and18, even when the head assembly68is not visible. When sufficient relative rotational force is applied to the concentric shafts16and18, they may be moved away from their second position.

The mechanism70preferably further comprises a compact second depression84, having the same size and shape as the first depression78. The second depression84is formed in the exterior side of the inner shaft16at the same longitudinal position as the first depression78. The position of the second depression84is selected so that it aligns with the opening74when the shafts16and18are in their first position.

When the ball76is urged into the second depression84, the mechanism70resists, but does not block, relative rotation of the shafts away from their first position. This resistance allows a user of the tool10to accurately locate the first position of the concentric shafts, even when the head assembly68is not visible. When sufficient relative rotational force is applied to the concentric shafts, they may be moved away from their first position.

As shown inFIG. 4, the depressions78and84are offset by a central angle86having an apex that coincides with the longitudinal axis88of the inner shaft16. The central angle86is equal to the angular offset of the first and second positions, and is preferably 45 degrees.

In one embodiment, components of the tool10are formed from a strong and durable material, such as mild steel. The inner shaft has a length of 15.5 inches and a diameter of 0.5 inches. The outer shaft has a length of 13 inches, and is provided with an Acme thread having a diameter of 1.25 inches. The length of the head assembly68, including both head elements, is 2.07 inches. The bushing52is 1 inch long and its internal bore has a diameter of 0.5 inches.

The tool10is adapted to reposition a plunger90, shown inFIGS. 9-11. The plunger90has a generally cylindrical shape, with a first end92and opposed second end94. Formed in the first end92of plunger90is a longitudinally extending socket96. The socket96is characterized by an externally-opening socket bore98and an enlarged internal chamber102.

The socket bore98is characterized by plural planar side walls100. Opposite its external opening, the socket bore98opens into the internal chamber102. Preferably, the socket bore98has a cross-sectional profile that is complementary to those of the forward and rear head elements26and56.

The internal chamber102is bounded by an upper wall104and a parallel lower wall106. The internal chamber102should have maximum cross-sectional dimensions that exceed those of the socket bore98. Preferably, the internal chamber102is characterized by a cylindrical shape.

An internally threaded bore is formed in the second end94of the plunger90. Within this bore, a threaded connection is formed between plunger90and a coaxial rod108, shown inFIG. 19.

In one embodiment, the length of the plunger90is 12.563 inches, and its diameter is 3.0 inches. The total depth of socket96is 2.07 inches, and the length of socket bore98is 1.42 inches. The maximum cross-sectional dimension of socket bore98is 1.57 inches, while the diameter of internal chamber102is 1.938 inches.

FIGS. 12 and 13show the head assembly68of the tool10in an inserted position within the socket96of plunger90. The cross-sectional shape and cross-sectional dimensions of the forward head element26are selected so that it may pass closely, but clearingly, through the socket bore98during insertion. When insertion is complete, the forward head element26of the tool is fully contained within the internal chamber102. At this point, the rear head element56is lodged closely, but clearingly, within the socket bore98, while remaining entirely outside of internal chamber102. The dimensions of the head elements26and56are chosen so as to enable the tool10and plunger90to assume this configuration.

InFIG. 12, the shafts16and18are in their first position, so that the cross-sectional profiles of the head elements26and56are aligned. In this configuration, the head assembly68may be freely inserted into and removed from the socket96of plunger90.

InFIG. 13, the shafts16and18are in their second position, so that the cross-sectional profiles of the head elements26and56are in skewed opposition. In this configuration, axial removal of forward head element26from internal chamber102is blocked by interference between the upper surface110of forward head element56and the upper wall104of the internal chamber102. As a result, the tool10is locked to the plunger90, and the two components can move together as a unit. These two components may be unlocked by returning the shafts16and18to their first position.

The tool10may rotated while its head assembly68is within the socket96of plunger90. When such rotation of the tool10occurs, the planar side walls60of the rear head element56engage the facing side walls100of the socket bore98. This causes the plunger90to rotate about its longitudinal axis. Such rotation can be used to unthread the second end94of the plunger90from its connecting rod108.

The plunger repositioning system further comprises a tubular collar element112, shown inFIGS. 14-16, having a first end114and an opposed second end116. An enlarged annular flange section118is formed at the first end114of the collar element112. Axially extending external threads120are formed on the side walls of the flange section118, which features a planar and annular face122at first end114. Fastener openings124are formed in the face122.

The flange section118is joined to a concentric stem section126, which terminates at second end116. The stem section126is preferably cylindrical in external shape, and has maximum cross-sectional dimensions that are less than those of the flange section118. Preferably, the flange section118and stem section126are formed as a single piece of material.

The collar element112features an internal collar bore128that extends its entire length, through both the flange section118and stem section126. The collar bore128is characterized by a uniform and preferably circular cross-sectional profile. The dimensions of the collar bore128are selected so that it may closely but clearingly receive the plunger90.

In one embodiment, the collar element112is formed from 6061-T6 aluminum alloy. The length of collar element112is 6 inches. The length of the flange section118is 2.03 inches, and its diameter is 5 inches. The length of the stem section126is 3.97 inches and its diameter is 3.475 inches. The diameter of the collar bore is 3.01 inches. The collar element112is anodized and coated with Teflon.

The plunger repositioning system further comprises a disc-shaped platform element130, shown inFIG. 17. The platform element130is adapted for coaxial engagement with the collar element112at its flange section118. The platform element is preferably characterized by a circular cross-sectional profile, and features a centrally disposed axial platform bore132extending therethrough.

The platform bore132is sized to closely but clearingly receive the outer shaft18of tool10. Internal threads134formed within the platform bore132mate with the external threads48formed on the outer shaft18. Fastener openings136formed in platform element130register with the fastener openings124formed in the annular face122of the collar element112.

In one embodiment, the platform element130is formed from 6061-T6 aluminum alloy. It has a diameter of 4.9 inches and a height of 1.25 inches. The platform element130is anodized and coated with Teflon.

The plunger repositioning system further comprises a crank138, shown inFIG. 18. The crank138is adapted to apply a rotational force to the tool10, at the upper section50of outer shaft18.

FIG. 19shows a plunger90situated within the fluid end140of a pump142having a housing144. The plunger90is connected at its second end94by internal threads to a rod108that is mechanically engaged with the power end (not shown) of the pump142. The rod108may comprise a pony rod.

Under power, the plunger90reciprocates within a longitudinal plunger bore146formed within the housing144. Positioned within the plunger bore146is a stuffing box148through which the plunger90can move. The stuffing box148forms a seal between the fluid end140and the power end of the pump142.

The plunger bore146opens into a pump chamber150formed within the housing144. A housing bore152is formed in the housing144and aligns with the plunger bore146. The housing bore152is internally threaded and features an external opening154. In one embodiment, the housing bore152is 5 inches in diameter and provided with a 45°/7° buttress thread. The housing bore152is normally closed by an externally threaded cover (not shown) that is installed within the housing bore152through opening154.

During operation of the pump142, reciprocation of the plunger90causes the seals within the stuffing box148to wear. In order to keep the pump142operating efficiently, these seals must be replaced periodically. Such replacement cannot occur until the plunger90is repositioned, by disconnecting it from rod108and withdrawing it from the stuffing box148. Only then can the stuffing box148be accessed through service port156.

FIG. 20shows the first stage of repositioning the plunger90. The cover has been removed from housing bore152, and collar element112has been installed within the housing bore152. Installation of the collar element112is carried out by first inserting the stem section126into external opening154, and then extending it through the housing bore152and into the pump chamber150. The connected flange section118is then rotated until it is engaged within the housing bore152. The external threads120on flange section118mate with the internal threads134formed within the housing bore152.

The flange section118has the same depth as the housing bore152, and is fully contained within the housing bore152when installed. The installed stem section126cantilevers within the pump chamber150, and aligns with the plunger bore146.

The tool10is next inserted, head assembly68first, through the collar bore128and into the pump chamber150. The shafts16and18are preferably in their first position when this step is performed.

As shown inFIG. 21, the head assembly68is next inserted into the socket96formed at the first end92of plunger90. While the shafts are in their first position, the forward head element26is positioned within the internal chamber102and the rear head element56is positioned within the socket bore98.

The shafts16and18are next relatively rotated to their second position, so that the cross-sectional profiles of the head elements26and56are in skewed opposition. As a result, the plunger90is locked to the tool10. This configuration of the head elements is shown inFIG. 12.

A user of the tool10cannot see the forward head element26within the pump chamber150, and thus cannot visually confirm that the shafts16and18have reached their second position. However, the resistance to rotation provided by the mechanism70allows the second position to be reached accurately without need for visual access.

As shown inFIGS. 20 and 21, platform element130is carried on the outer shaft18of the tool10. Preferably the platform element130is threaded onto the outer shaft18before the tool10is inserted into pump chamber150. The platform element130should not be secured to the collar element112until after the head assembly68has been inserted into the plunger90, and the forward head element26positioned within the internal chamber102of the socket96.

The platform element130is next rotated on threaded outer shaft18until it is disposed in face-to-face engagement with the collar element112, at the face122of flange section118. The platform element130is secured in place with fasteners158that extend through the aligned fastener openings124and136. This configuration is shown inFIG. 21. The fasteners158may comprise bolts.

When the platform element130is secured to the collar element112, the outer shaft18is securely supported in coaxial alignment with the housing bore152and the plunger bore146. The plunger90is in turn securely locked to outer shaft18by the head assembly68.

Rotational force is next applied to the tool10at outer shaft18, preferably using crank138at upper section50. This rotational force disconnects the locked plunger90from rod108. Although considerable force may be required to break the threaded connection between plunger90and rod108, the plunger90remains securely supported on outer shaft18as the connection is broken. As a result, the plunger90does not fall into the pump chamber150, nor does it strike the housing144or other components of the pump142. Either occurrence can produce plunger damage that can interfere with efficient operation of the pump142.

Once the connection with rod108has been broken, the outer shaft18is further rotated to at least partially withdraw the locked tool10and plunger90from the housing144. This stage of the repositioning process is shown inFIG. 22. If desired, the plunger90may next be fully withdrawn from the pump142by disconnecting the platform element130from collar element112and withdrawing the locked tool-plunger assembly.

Alternately, the platform element130may be maintained in engagement with collar element112, and the outer shaft18rotated until the plunger90is positioned outside the stuffing box148. Access to the stuffing box148may then be conveniently gained through service port156while the plunger90remains suspended on outer shaft18within the pump chamber150.

The plunger90is reinstalled within plunger bore146and reconnected to rod108by reversing the steps just described.

Any two or more of the components described herein, aside from the plunger90, pump142and its components, may be collected to form a kit. Such a kit may include one or more of the tool10and its components, the collar element112, the platform element130, and the crank138. Kit components may be unassembled, partially assembled or fully assembled.

Changes may be made in the construction, operation and arrangement of the various parts, elements, steps and procedures described herein without departing from the spirit and scope of the invention as described in the following claims.