Handle for a hydraulically driven tool with heat transmission reducing properties

A handle for a hydraulically driven tool is provided reduces the amount of heat transmitted to the user of the tool as a result of the high temperature fluid flowing through the inner body of the handle. The inner body is formed of a heat transmissive material which has at least one channel through which the fluid flows. The handle has a number of properties which reduces heat transmission to the user, including standoffs, ribs and fastener receiving extensions.

FIELD OF THE INVENTION

The present invention particularly relates to a handle for a hydraulically driven tool, such as a wrench or a drill, which reduces the amount of heat transmitted to the user of the tool.

BACKGROUND OF THE INVENTION

Existing hydraulic tools, such as hydraulic wrenches, generate heat as result of the use of high temperature hydraulic fluid passing through the tool. The user grips a grip which surrounds a metal valve body through which the high temperature hydraulic fluid passes. It is desirable to prevent the transfer of this heat to the user's hand. The prior art insulates the metal valve body with a PVC-based dip, which tends to be inadequate to prevent the passage of heat generated by the high temperature hydraulic fluid. In addition, the PVC-based dip is not very durable and is not easy to replace if the tool becomes damaged.

Prior art tools have controlled flow in a circuit, and thus output motor torque in the circuit. A control for setting the torque to two discrete settings has been used in the prior art. This presents a disadvantage in that only two settings are provided. Other prior art tools have used a pressure compensated flow control mechanism with an infinite adjustment setting. Pressure compensated flow control mechanisms are costly to manufacture.

A hydraulically driven tool is provided herein which provides improvements to existing tools and which overcomes the disadvantages presented by the prior art. Other features and advantages will become apparent upon a reading of the attached specification, in combination with a study of the drawings.

SUMMARY OF THE INVENTION

A handle for a hydraulically driven tool, such as a wrench or a drill, which reduces the amount of heat transmitted to the user of the tool is disclosed. The tool has a body formed of a heat transmissive material which has at least one channel through which a high temperature fluid flows. Heat is generated as a result of the fluid. The body includes a plurality of fastener receiving passageways therethrough; each passageway has a countersink provided at each end thereof. The handle is non-conductive and generally surrounds the body. The interior surface of the handle has a plurality of spaced apart standoffs extending therefrom. The standoffs contact the body and an air gap is formed between the interior surface and the body at locations where standoffs are not provided. This provides for a minimal amount of surface contact between the metal valve body and the non-conductive grip housing which reduces the amount of conduction from the heat transmissive body to the non-conductive handle, and thus to the user's hand which surrounds this area. In addition, the air gap allows air flow between the body and the handle for convection cooling of the body. The interior surface has a plurality of fastener receiving extensions, each having an aperture therethrough, which align with the respective passageways. The fastener receiving extensions seat within the countersinks and the fastener receiving extensions are smaller than the countersinks. As a result, the fastener receiving extensions do not contact the body to aid in minimizing the amount of heat transmitted to the handle.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

While the invention may be susceptible to embodiment in different forms, there is shown in the drawings, and herein will be described in detail, a specific embodiment with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that as illustrated and described herein. Therefore, unless otherwise noted, features disclosed herein may be combined together to form additional combinations that were not otherwise shown for purposes of brevity.

A fluid-operated tool20, such as a hydraulic wrench or drill, includes a fluid control system which provides for variable limitation of power output. The fluid control system provides multiple flow paths to provide for, among other things, selectable diversion of a portion of flow to a work unit assembly22of the tool20, and reversing the direction of the work unit assembly22. The tool20may be used by professional linemen who work outdoors under a variety of conditions, including blistering heat and intense cold.

The tool20is a two piece design formed of the work unit assembly22and a grip assembly24. The work unit assembly22has a series of ports26,28,30, seeFIG. 17, which align with ports32,34,36, seeFIG. 5, in the grip assembly24. O-rings38seal the connections between the ports26/32,28/34,30/36.

The work unit assembly22includes an impact mechanism housing40, a motor housing42attached to the impact mechanism housing40, a gear motor44mounted in the motor housing42, and a chuck46attached to the gear motor44by a rotary impact mechanism47. A bit or other tool (not shown) is mounted to the chuck46. A plurality of channels48,50,52,54,56,58, seeFIGS. 19-21, are provided in the impact mechanism housing40to supply the gear motor44with hydraulic fluid as discussed in further detail herein. A motor reversing spool assembly62,FIGS. 21-24, is mounted within channel50as discussed herein.

As shown inFIGS. 1-4, the grip assembly24includes an inner valve body64, an outer grip housing66a,66b, generally surrounding the inner valve body64, a trigger spool assembly68and a bypass spool assembly70. A plurality of channels72,74,76,78,80a/80b,82,84are provided in the inner valve body64as discussed in further detail herein. The grip assembly24is attached to a supply (not shown) which provides hydraulic fluid to the tool20.

The inner valve body64is formed of heat transmissive material, such as metal, preferably sand cast aluminum. The outer grip housing66a,66b, which the user grips with his/her hand, is formed of a non-conductive material, preferably nylon, and includes first and second halves66a,66b.

As shown inFIG. 6, the inner valve body64is formed of an elongated portion86which has a trigger spool platform88formed at the top end thereof, and a bypass valve platform90extending from the upper end of the trigger spool platform88. An axis92is defined through the centerline of the trigger spool platform88and extends from a front end94to a rear end96of the trigger spool platform88.

As shown inFIG. 2, a pressure/pump port98and a return/tank port100are provided in the bottom end of the inner valve body64. An inlet channel72extends from the pressure/pump port98to a trigger spool channel74in which the trigger spool assembly68is mounted to provide for the flow of hydraulic fluid from the supply to the trigger spool channel74. An outlet channel76extends from the trigger spool channel74to the return/tank port100to provide for the flow of hydraulic fluid from the trigger spool channel74to the supply. The tool20is typically used in utility applications and is connected to a hydraulic power unit or auxiliary circuit in a boom truck or tractor via the ports98,100. When the ports98,100are not connected to the supply, suitable caps99,101cover the ports98,100.

The trigger spool channel74extends along the axis92through the trigger spool platform88. The trigger spool channel74is generally cylindrical and extends from the front end94of the trigger spool platform88to the rear end96of the trigger spool platform88. A C-clip receiving groove102,FIG. 9, is provided in the wall forming the trigger spool channel74proximate to the front end94. An enlarged O-ring receiving groove104is provided in the wall forming the trigger spool channel74proximate to the rear end94. The wall of the trigger spool channel74has an enlarged fluid chamber106provided at the junction between the trigger spool channel74and the inlet channel72; an enlarged fluid chamber108provided at the junction between the trigger spool channel74and the outlet channel76; and an enlarged fluid chamber110provided between and spaced from the enlarged fluid chamber106and the enlarged fluid chamber108.

A bypass spool channel78extends parallel to the axis92through the bypass spool platform90. The bypass spool channel78is generally cylindrical and extends from a rear end112of the bypass spool platform90forwardly a predetermined distance.

A transfer supply channel80a/80bhas a first portion80awhich connects the enlarged fluid chamber110of the trigger spool channel74to the bypass spool channel78and a second portion80bwhich connects the bypass spool channel78to the outlet port32in the upper end of the grip assembly24. The outlet port32supplies fluid to the work unit assembly22of the tool20.

A return transfer channel82connects port34to the enlarged fluid chamber108of the trigger spool channel74(seeFIG. 4); return transfer channel84connects port36to the enlarged fluid chamber108of the trigger spool channel74(seeFIG. 4). Ports34,36receive fluid from the work unit assembly22as described herein. The bypass spool channel78is connected to the return transfer channel82at port116.

As shown inFIG. 6, the inner valve body64has a pair of spaced apart fastener receiving passageways118extending through the trigger spool platform88, and another fastener receiving passageway118extending through the elongated portion86proximate to the bottom thereof. A countersink121is provided in each side of the inner valve body64at each end of the respective fastener receiving passageway118.

The first and second halves66a,66bof the grip housing are the mirror image of each other. The halves66a,66bare designed to minimize the amount of heat transfer to the user of the tool20which results from the use of high temperature hydraulic fluid passing through the tool20. Halve66bis shown inFIGS. 7 and 8. Each half66a,66bhas a wall120which mirrors the shape of half of the inner valve body64. Each wall120has an interior surface122which faces the inner valve body64and an exterior surface124which the user grasps with his/her hand. First, second and third fastener receiving extensions126extend from the interior surfaces122and each has an aperture127provided therethrough. A plurality of spaced apart standoffs128extend from the interior surfaces122. The standoffs128are preferably cross-shaped, however, other shapes are within the scope of the present invention. A plurality of spaced apart ribs130extend from the interior surfaces122at an upper end thereof. Each half66a,66bcan be formed by injection molding.

When the halves66a,66bare assembled with the inner valve body64, the halves66a,66bsubstantially cover the sides of the inner valve body64. The user grasps the area of the outer grip housing66a,66bwhich surrounds the elongated portion86of the inner valve body64. The respective apertures127and passageways118align with each other such that the fastener receiving extensions126seat within the countersinks121, however, the fastener receiving extensions126are smaller than the countersinks121such that the fastener receiving extensions126do not contact the metal inner valve body64. The halves66a,66bare assembled with the inner valve body64by a plurality of fasteners132, such as bolts, which pass through the apertures127and passageways118. The ribs130and the standoffs128contact the inner valve body64, and an air gap129is formed between the walls120and the inner valve body64at the points between the ribs130and the standoffs128. Preferably, the air gap129provides a spacing of 0.10″ between the walls120and the inner valve body64. Therefore, a minimal amount of surface contact is provided between the metal valve body64and the non-conductive grip housing66a,66bwhich reduces the amount of conduction from the metal valve body64to the non-conductive grip housing66a,66b, and thus to the user's hand which surrounds this area. In addition, the air gap129allows air flow between the inner valve body64and the grip housing66a,66bfor convection cooling of the inner metal valve body64.

A soft grip material67preferably surrounds the halves66a,66bof the grip housing. The soft grip material67helps to insulate the user from the heat generated by the hydraulic fluid.

As shown inFIGS. 3, 11 and 12, the trigger spool assembly68includes a trigger spool134mounted in the trigger spool channel74, a spring assembly136for sealing the trigger spool134to the wall forming the trigger spool channel74and for biasing the trigger spool134, a trigger138attached by C-clips to the trigger spool68which extends from the trigger spool channel74, and a system adjusting spool assembly140provided in a rear end of the trigger spool134. The trigger138can be depressed by the user to move the trigger spool134backward and forward along the axis92in the trigger spool channel74.

The trigger spool134is generally cylindrical. A first cylindrical section146of the trigger spool134extends rearwardly a predetermined distance from the front end142. An aperture148is provided through the first section146proximate to the front end142for connection of the trigger spool134to the trigger138. The first section146has a predetermined outer diameter which is smaller than the inner diameter of the trigger spool channel74. A flange150extends from the first section146at a position spaced from the front end142. The flange150has an outer diameter which is approximately the same as the inner diameter of the trigger spool channel74. A second section152extends from the rear end of the first section146. The second section152has an outer diameter which is approximately the same as the inner diameter of the trigger spool channel74. A third section154extends from the rear end of the second section152. The third section154has an outer diameter which is approximately the same as the first section146and thus is smaller than the inner diameter of the trigger spool channel74. A fourth section156extends from the rear end of the third section154. The fourth section156has an outer diameter which is less than the diameter of the second section152, but greater than the outer diameter of the third section154. A fifth section158extends from the rear end of the fourth section156. The fifth section158has an outer diameter which is approximately the same as the inner diameter of the trigger spool channel74, and is larger than the diameter of the fourth section156.

A central bore160,FIG. 3, extends from the rear end of the trigger spool134and extends axially forwardly through the fifth, fourth, third and second sections158,156,154,152. The central bore160terminates in the second section152. The central bore160has a forward portion162, an intermediate portion164and a rearward portion166. The forward portion162extends through the second and third sections152,154and is smaller in dimension than the intermediate portion164which extends through the fourth section156and part of the fifth section158. As a result, a seat168is formed between the forward and intermediate portions162,164of the central bore160. A first set of four spaced apart passageways170extend radially outwardly from the forward portion162of the central bore160through the second section152of the trigger spool134. A second set of four spaced apart passageways172extend radially outwardly from the intermediate section164of the central bore160through the fourth section156of the trigger spool134. The rearward portion166of the central bore160is threaded and extends through the fifth section158of the trigger spool134. The rearward portion166of the central bore160is larger in dimension than the intermediate portion164of the central bore160, and as a result, a seat173is formed between the intermediate and rearward portions164,166. The rear end144of the central bore160is open and thus is accessible to the user.

The trigger spool134is mounted in the trigger spool channel74such that the front end of the trigger spool134extends outwardly from the front end of the tool20and connects to the trigger138. The spring assembly136seats between the flange150and the front end94of the trigger spool platform88. The spring assembly136includes a C-clip174which seats within the corresponding C-clip receiving groove102in the trigger spool channel74, a washer176which seats against the C-clip174, a spring178seated between the washer176and the flange150, and a rubber O-ring180which seats around the first section146between the flange150and the second section152. The trigger spool74can move axially along the trigger spool channel74by compressing the spring178.

As shown inFIG. 3, the system adjusting spool assembly140is mounted within the trigger spool134. The system adjusting spool assembly140includes an adjusting spool182which seats within the intermediate and rearward sections164,166of the central bore160and is sealed thereto by a rubber O-ring183. A C-clip184seats within a sloped recess186provided in the wall forming the rearward section166. A user can adjust the position of the adjusting spool182by screwing the adjusting spool182forward to move the adjusting spool182along the trigger spool channel74until ball194seats on seat168, or can be screwed in reverse until the adjusting spool182backs onto C-clip184. The C-clip184holds the adjusting spool182in position and prevents the removal of the adjusting spool182from the central bore160. A rubber O-ring190and back up ring192seat around the fifth section158and seat within the enlarged O-ring receiving groove104. The system adjusting spool assembly140includes a ball194which seats within the fourth and fifth sections156,158of the central bore160. The ball194abuts against the forward end of the adjusting spool182. The ball194is moved by the user adjusting the position of the adjusting spool182. The ball194can be moved to seat against the seat168, thus closing the fluid communication between the forward portion162and the intermediate portion164(and thus the radial passageways172), or can be moved away from the seat168, thus opening the fluid communication between the forward portion162and the intermediate portion164(and thus the radial passageways172).

When the trigger138is not depressed, the first set of passageways170are in alignment with the inlet channel72to receive hydraulic fluid. If the tool20is to be operated in an open-center configuration, the system adjusting spool assembly140is adjusted to move the ball194away from the seat168. As a result, the hydraulic fluid can continuously flow from the supply, through the inlet channel72, through the first set of passageways170, through the forward portion162of the central bore160, past the seat168, into the intermediate section163of the central bore160, through the second set of passageways172and into the return channel76. If the tool20is to be operated in a closed-center configuration, the system adjusting spool assembly140is adjusted to move the ball194against the seat168. As a result, the hydraulic fluid cannot flow into the intermediate section163of the central bore160and through the second set of passageways172.

The bypass spool channel78is generally cylindrical and extends from a front end196of the bypass spool platform90to a rear end198of the bypass spool platform90. The front end of the bypass spool channel78is closed by an adjusting spool200as shown inFIG. 16. The rear end of the bypass spool channel78is open.

The bypass spool assembly70, seeFIGS. 13 and 14, includes a bypass spool202which is seated in the bypass spool channel78, and a knob204. The bypass spool202is generally cylindrical and has first and second opposite ends206,208. The second end208of the bypass spool202extends outwardly from the bypass spool channel78and the knob204is mounted thereon by suitable means. A central bore210extends rearwardly from the first end206of the bypass spool202a predetermined distance. The open end of the central bore210is in fluid communication with the transfer channel80a,80b. First and second passageways212,214,FIGS. 14 and 15, extend radially outwardly from the central bore210proximate to, but spaced from, the first end206thereof. The passageways212,214are perpendicular to each other. The first passageway212has a smaller diameter than the second passageway214. The bypass spool202is sealed to the bypass spool channel78by a pair of spaced apart O-rings216. The bypass spool202can be rotated to be in one of three discrete positions within the bypass spool channel78by a user grasping the knob204and rotating it. In a first position, neither radial passageway212,214aligns with the port116(which connects the bypass spool channel78to the return transfer channel82) and hydraulic fluid does not flow through the central bore210to either radial passageway212,214. This configuration provides for high revolutions per minute (rpm) of the gear motor44as the all of the hydraulic fluid flows to the work unit assembly22. In the second position, radial passageway212aligns with the port116, and hydraulic fluid flows through the central bore210, to the first, smaller radial passageway212, through port116, through the return channel82, through enlarged chamber108, and into return channel76. This configuration provides for medium revolutions per minute (rpm) of the gear motor44as most of the hydraulic fluid flows to the work unit assembly22, but some of the hydraulic fluid is diverted to the return channel76. In the third position, radial passageway214aligns with the port116, and hydraulic fluid flows through the central bore210to the second, larger radial passageway214, through port116, through the return channel82, through enlarged chamber108, and into return channel76. This configuration provides for low revolutions per minute (rpm) of the gear motor44as most of the hydraulic fluid is diverted to the return channel76, and some of the hydraulic fluid flows to the work unit assembly22. The work assembly unit22, is connected to the rotary impact mechanism47. Therefore, the hydraulic motor work assembly revolutions per minute (rpm) will govern the output torque of the tool20.

As a result of this structure, the bypass spool assembly70is formed from a movable bypass spool202which form a valveless conduit. The bypass spool202is adapted for diverting a portion of the inlet flow from entering the work unit22directly to a return flow from the work unit22. The bypass spool202is movable about an axis generally orthogonal to an axis of movement of a motor reversing spool230discussed herein.

As shown inFIGS. 2 and 18, the gear motor44includes a pair of gears218,220which drive a shaft222that drives the chuck46by known means. The gears218,220seat within a gear chamber224formed between the impact mechanism housing40and the motor housing42. The gears218,220intermesh with each other and can be driven clockwise or counterclockwise in order to drive the chuck46in a clockwise or counterclockwise direction. First and second motor ports226,228feed hydraulic fluid into the gear chamber224as discussed herein.

As shown inFIG. 3, the impact mechanism housing40has a pressure supply channel48which extends from the inlet port26to a reversing spool channel50in which the motor reversing spool assembly62is mounted. As shown inFIGS. 19 and 20, the impact mechanism housing40further has a first transfer channel52extending from the reversing spool channel50to the first motor port226, and a second transfer channel54extending from the reversing spool channel50to the second motor port228. A first return channel56extends from the reversing spool channel50to the port28and connects with port34and first return transfer channel82in the grip assembly24. A second return channel58extends from the reversing spool channel50to the port30and connects with port36and second return transfer channel84in the grip assembly24.

The motor reversing spool assembly62, which is shown inFIGS. 22-24, includes a reversing spool230having first and second ends232,234and a central bore236extending from the first end232a predetermined distance, a spring biased relief valve assembly238mounted within the central bore236, a first handle239provided at the first end232of the reversing spool230which closes the open end of the central bore236, and second handle241provided at the second end234of the reversing spool230. Rubber O-rings and back-up rings240,242seal the reversing spool230to the wall that forms the reversing spool channel50. The relief valve assembly238limits the torque of the gear motor44, and always dumps flow to port30when the relief valve assembly238is activated.

The reversing spool230is generally cylindrical. A first section244extends from the front end232and has a predetermined outer diameter which is smaller than the inner diameter of the reversing spool channel50. A flange246extends from the first section244at a position spaced from the end232to provide a means for attaching the handle239. A second section248extends from the rear end of the first section244. The second section248has an outer diameter which is approximately the same as the inner diameter of the reversing spool channel50. A third section250extends from the rear end of the second section248. The third section250has an outer diameter which is less than the diameter of the second section248and thus is smaller than the inner diameter of the reversing spool channel50. A fourth section252extends from the rear end of the third section250. The fourth section252has an outer diameter which is the same as than the diameter of the second section248. A fifth section254extends from the rear end of the fourth section252. The fifth section254has an outer diameter which is the same as the third section250. A sixth section256extends from the rear end of the fifth section254. The sixth section256has an outer diameter which is the same as than the diameter of the second section248and the fourth section252. A seventh section258extends from the rear end of the sixth section256. The seventh section258has an outer diameter which is the same as the third and fifth sections250,254. An eighth section260extends from the rear end of the seventh section258. The eighth section260has an outer diameter which is the same as than the diameter of the second, fourth and sixth sections248,252,256. The eighth section260has a groove261therein into which an O-ring is seated. A ninth section263extends from the eighth section260and has a flange265extending therefrom at a position spaced from the end234to provide a means for attaching the handle241.

A first portion262of the central bore236extends from the first end232of the reversing spool230and extends axially forwardly through the first, second, third and fourth sections244,248,250,252. A second portion264of the central bore236starts at the end of the first portion262and extend through the fifth portion254. The first portion262is larger in dimension than the second portion264. As a result, a seat266is formed between the first and second portions262,264. A first set of diametrically opposed passageways268a,268bextend radially outwardly from the first portion262through the third section250. A set of four spaced apart passageways270extend radially outwardly from the second portion264through the fifth section254. The reversing spool230is mounted in the reversing spool channel50such that the ends232,234, and thus the handles239,241, extend outwardly from the sides of the tool20.

The spring biased relief valve assembly238is mounted in, and extends substantially the entire length of, the first portion262of the central bore236. The spring biased relief valve assembly238includes a spring272sandwiched between a pair of pins274,276. Pin274abuts against the handle239and against a first end278of the spring272. Pin276abuts against a second end280of the spring272. Pin276has a shaft282which seats within the coils of the spring272and an enlarged cone-shaped head284which extends outwardly from the second end280of the spring272. A front surface285of the cone-shaped head284can be biased via the spring272to be in engagement with the seat266of the central bore236. A rear surface287of the cone-shaped head284is in engagement with the second end280of the spring272. The front surface28mated with seat266, and the rear surface287each define an area. Instead of being cone-shaped, other forms may be provided, for example, a stepped shape.

A flange286,FIG. 3, is retained by the underside of the impact mechanism housing40and extends into bypass spool channel78to prevent the removal of the bypass spool202from the bypass spool channel78, when connected to grip assembly24.

Now that the specifics of the components of the tool20have been described, the method of using the tool20will be described.

As discussed above, the tool20can be used in an open-center configuration or a closed-center configuration. To operate the tool20in an open-center configuration, the system adjusting spool assembly140is adjusted to move the ball194away from the seat168. As a result, the hydraulic fluid can continuously flow from the supply, through the inlet channel72, through the first set of passageways170, through the forward portion162of the central bore160, past the seat168, into the intermediate section164of the central bore160, through the second set of passageways172and into the return channel76even when the trigger138is not depressed. If the tool20is to be operated in a closed-center configuration, the system adjusting spool assembly140is adjusted to move the ball194against the seat168. As a result, the hydraulic fluid cannot flow into the intermediate section164of the central bore160and through the second set of passageways172.

The user must then determine whether the tool20is be used to rotate the chuck46in a clockwise direction (thus using motor port226), or a counterclockwise direction (thus using motor port228). The motor reversing spool assembly62controls the direction the gear motor spins by diverting flow to either motor port226,228. The motor port226,228which is not pressurized dumps flow to one of ports28,30, depending upon which motor port226,228is pressurized.

Operation of the tool is first described with the tool20placed into the configuration to rotate the chuck46in a counterclockwise direction, thus using motor port226as the supply to the gear chamber224. To do so, the reversing spool230is pushed until the handle239contacts the side of the impact mechanism housing40. Supply channel48aligns with the fifth section254of the reversing spool230and the radial passageways270. The fifth section254of the reversing spool230also aligns with transfer channel52which feeds fluid into motor port226. Motor port228feeds fluid into transfer channel54.

In either the open-center configuration or the closed-center configuration, when the trigger138is depressed, the trigger spool134moves axially along the trigger spool channel74toward the front end of the tool20. The third section154of the trigger spool134aligns with the inlet channel72(the radial passageways170are moved out of alignment such that fluid cannot flow through the trigger spool134), and the third and fourth sections154,156span between the enlarged fluid chambers106and110to allow fluid communication between the enlarged fluid chambers106and110. The fifth section158aligns with the enlarged fluid chamber108and the return channel76.

The hydraulic fluid flows from the supply, through port98, through the supply channel72, into enlarged fluid chamber106, between the third and fourth sections154,156of the trigger spool134and the wall of the supply channel72, and then into enlarged fluid chamber110, through transfer channel80a, into bypass spool channel78, into transfer channel80b, through ports32and26, into supply channel48, and into reversing spool channel50. In the configuration to rotate the chuck46in a counterclockwise direction, transfer channel52aligns with radial passageways270; transfer channel54aligns with radial passageways268a,268b. As a result, hydraulic fluid flows from supply channel48, around the fifth section254of the reversing spool230and through the radial passageways270and the second portion264of the central bore236, through transfer channel52and through motor port226to supply hydraulic fluid to the gear chamber224to rotate the gears218,220, and thus the chuck46. Hydraulic fluid flows out of the gear chamber224, through motor port228, through transfer channel54, around the third section250of the reversing spool230and through the radial passageway268ainto first portion262of the central bore260and through the radial passageway268b, to the return channel58. Hydraulic fluid then flows through ports30,36, into return transfer channel84, into fluid chamber108, around fifth section158of trigger spool134, into return channel76, through port100to return to the supply.

The relief valve assembly238is provided within the reversing spool230and limits the torque of the gear motor44. When resistance is seen by the gear motor44, the pressure from the hydraulic fluid builds in the second portion264of the central bore236. When enough pressure builds, the head284of the pin276unseats from seat266and fluid flows past the head284into the first portion262of the central bore236and out the radial passageways268a,268b, to the return channel58(that is, the fluid flows from the pressure side of the reversing spool230to the side exposed to the return channel58). The pressure at which hydraulic fluid will be diverted by is determined by the force of the spring272and pressure in the return channel58.

Therefore, when the reversing spool230is set to drive the tool20in reverse (counterclockwise), the rear surface287of the head284of the relief valve assembly238is exposed to the channel54from the gear chamber224. The channel54usually has some residual back pressure built up as a result of being used to return hydraulic fluid through the circuit to the supply. This pressure built up in the channel54acts on the rear surface287which creates a force. The pressure side force on the front surface285of the head284created by the pressure on that side must counteract this pressure on the rear surface287to unseat the head284and relieve the pressure. After leaving the area around the third section250of the reversing spool230, fluid flows to the trigger spool134where the fluid is drained out of the tool20. Once the pressure is relieved, the spring272expands to reseat the head284against the seat266. The relief valve238can be activated and closed as many times during operation as is necessary.

The above operation assumes that the bypass spool202is in the position where no flow of hydraulic fluid is being diverted therethrough. In the situation where the bypass spool202is turned to the second position, radial passageway212aligns with the port116and hydraulic fluid flows through the central bore210, to the first, smaller radial passageway212, through port116, through the return channel82, through enlarged chamber108, and into return channel76. This configuration provides for medium revolutions per minute (rpm) of the gear motor44as most of the hydraulic fluid flows to the work unit assembly22, but some of the hydraulic fluid is diverted to the return channel76. In the situation where the bypass spool202is turned to the third position, hydraulic fluid flows through the central bore210to the second, larger radial passageway214, through port116, through the return channel82, through enlarged chamber108, and into return channel76. This configuration provides for low revolutions per minute (rpm) of the gear motor44as most of the hydraulic fluid is diverted to the return channel76, and some of the hydraulic fluid flows to the work unit assembly22. In this tool20, the bypass operation takes place in the line of flow before the hydraulic fluid reaches the motor reversing spool assembly62. The bypass valve assembly70connects the pressure side of the circuit to the return side of the circuit. The bypass valve assembly70regulates the revolutions per minute (rpm) of the gear motor44by diverting flow that would normally pass the motor reversing spool assembly62and power the gear motor44. By bypassing flow directly to the supply between the trigger spool assembly68and the motor reversing spool assembly62, the flow used to the power the gear motor44is reduced, thus reducing the revolutions per minute (rpm) of the gear motor44. In this tool20, speed regulates torque.

Operation of the tool is now described with the tool20placed into the configuration to rotate the chuck46in a clockwise direction, thus using motor port228as the supply to the gear chamber224. To do so, the reversing spool230is pushed until the handle241contacts the side of the impact mechanism housing40. Supply channel48remains aligned with the fifth section254of the reversing spool230and the radial passageways270. Since the position of the reversing spool230has been shifted, the fifth section254of the reversing spool230now also aligns with transfer channel54which feeds fluid into motor port228. Transfer channel52aligns with the seventh section258of the reversing spool230. The radial passageway268bremains aligned with the return channel58, but are not aligned with the channel54.

In either the open-center configuration or the closed-center configuration, when the trigger138is depressed, the trigger spool134moves axially along the trigger spool channel74toward the front end of the tool20. The third section154of the trigger spool134aligns with the inlet channel72(the radial passageways170are moved out of alignment such that fluid cannot flow through the trigger spool134), and the third and fourth sections154,156span between the enlarged fluid chambers106and110to allow fluid communication between the enlarged fluid chambers106and110. The fifth section158aligns with the enlarged fluid chamber108and the return channel76.

The hydraulic fluid flows from the supply, through port98, through the supply channel72, into enlarged fluid chamber106, between the third and fourth sections154,156of the trigger spool134and the wall of the supply channel72, and then into enlarged fluid chamber110, through transfer channel80a, into bypass spool channel78, into transfer channel80b, through ports32and26, and into supply channel48. Hydraulic fluid flows from supply channel48, around the fifth section254of the reversing spool230and through the radial passageways270and the second portion264of the central bore236, through transfer channel54and through motor port228to supply hydraulic fluid to the gear chamber224to rotate the gears218,220, and thus the chuck46. Hydraulic fluid flows out of the gear chamber224, through motor port226, through transfer channel52, around the seventh section258of the reversing spool230, to the return channel58. Hydraulic fluid then flows through ports30,36, into return transfer channel84, into fluid chamber108, around fifth section158of trigger spool134, into return channel76, through port100to return to the supply.

When resistance is seen by the gear motor44, the pressure from the hydraulic fluid builds in the second portion264of the central bore236. When enough pressure builds, the head284of the pin276unseats from seat266and fluid flows past the head284into the first portion262of the central bore236and out the radial passageways268a,268b, to the return channel58(that is, the fluid flows from the pressure side of the reversing spool230to the side exposed to the return channel58). The pressure at which hydraulic fluid will be diverted by is determined by the force of the spring272. Once the pressure is relieved, the spring272expands to reseat the head284against the seat266. The relief valve238can be activated and closed as many times during operation as is necessary.

When the reversing spool230is positioned to drive the tool20forward (clockwise) the fluid return channel switches and therefore, motor44does not drain fluid behind the relief valve238. The fluid drains directly to the return channel56and proceeds to enlarged fluid chamber108. Since there is a pressure drop (Δp) from the loss of energy of the fluid between these locations, the pressure around the trigger spool134in chamber108is less than the pressure in the area around the reversing spool230in channel56. The channel58is exposed to the rear surface287of the pin276on the opposite end of the reversing spool230. Since fluid does not pass behind the pin276from the motor44, the pressure behind the pin276is the same as the pressure in the chamber108around the trigger spool134.

The above operation assumes that the bypass spool202is in the position where no flow of hydraulic fluid is being diverted therethrough. In the situation where the bypass spool202is turned to the second position, radial passageway212aligns with the port116and hydraulic fluid flows through the central bore210, to the first, smaller radial passageway212, through port116, through the return channel82, through enlarged chamber108, and into return channel76. This configuration provides for medium revolutions per minute (rpm) of the gear motor44as most of the hydraulic fluid flows to the work unit assembly22, but some of the hydraulic fluid is diverted to the return channel76. In the situation where the bypass spool202is turned to the third position, hydraulic fluid flows through the central bore210to the second, larger radial passageway214, through port116, through the return channel82, through enlarged chamber108, and into return channel76. This configuration provides for low revolutions per minute (rpm) of the gear motor44as most of the hydraulic fluid is diverted to the return channel76, and some of the hydraulic fluid flows to the work unit assembly22. In this tool20, the bypass operation takes place in the line of flow before the hydraulic fluid reaches the motor reversing spool assembly62. The bypass valve assembly70connects the pressure side of the circuit to the return side of the circuit. The bypass valve assembly70regulates the revolutions per minute (rpm) of the gear motor44by diverting flow that would normally pass the motor reversing spool assembly62and power the gear motor44. By bypassing flow directly to the supply between the trigger spool assembly68and the motor reversing spool assembly62, the flow used to the power the gear motor44is reduced, thus reducing the speed output of the gear motor44.

Therefore, the same relief valve238is capable of being activated to relieve pressure when the gear motor44is being operated to drive the tool20in reverse (counterclockwise) and to drive the tool20forward (clockwise). In reverse, a higher pressure is provided behind the head284of the relief valve238because the head284is exposed to the pressure of the fluid as it directly leaves the channel54. In the forward operation, the relief valve238is not exposed to the return flow from the gear motor44. Therefore, the rear surface287of the relief valve238is only exposed to pressure in the channel58which is equal to pressure in chamber108since it is not exposed to channel54. Since the pressure on the channel58is less in forward operation than in reverse, the orientation for reverse operation causes the relief valve238to have a higher pressure on the rear surface287than in the forward orientation. This provides a higher force on the rear surface287in that orientation and therefore, a higher pressure is needed in second portion264of the central bore236to open the relief valve238. When the reversing spool230is positioned to drive the tool20forward (clockwise), the pressure needed to unset the pin276is less than in the reverse (counterclockwise). This is done by exposing the dumping side of the relief valve238to different pressures, thus in the reverse (counterclockwise) rotating position, more pressure works on the rear area of the pin276. Thus, more pressure must work on the front surface28to unseat the pin276. This is useful when hydraulic motor torque differential settings are needed in forward and reverse.

As a result of the structure of the tool20, the trigger spool assembly68is downstream of the inlet port98and controls the flow of fluid to the work unit22. The bypass valve assembly70is disposed downstream of the trigger spool assembly68. The motor reversing assembly62is disposed downstream of the bypass valve assembly70.

While several components are referred to as a “spool” in the preferred embodiment disclosed herein, the spools may be any component, such as, in non-limiting embodiments, a valve, that otherwise provides for the functions described herein. Similarly, other “spools” disclosed herein may be suitably replaced by other components, such as other types of valves.

In addition to the foregoing aspects of the fluid control system described, it is within the teachings herein to include diversion from the flow of oil at selected locations for other purposes. That is, in addition to the features above, the fluid control system1may contain bleeder valves or other features that provide oil supply for such purposes as tool lubrication.

One skilled in the art will recognize that the invention disclosed herein is not limited to use in a variable torque impact wrench. For example, the fluid control system disclosed herein may be used in wrenches, grinders, drills, chain saws, pole saws, circular saws, pruners, tampers, and other tools having similar power requirements. As another example, features of the present invention could be used in a pneumatic tool rather than a hydraulic tool. Therefore, it is within the teachings contained herein to use this invention, and variations thereof, in other applications.

While a preferred embodiment of the present invention is shown and described, it is envisioned that those skilled in the art may devise various modifications of the present invention without departing from the spirit and scope of the appended claims.