Patent Publication Number: US-6655033-B2

Title: Pneumatic hand tool with improved control valve

Description:
FIELD OF THE INVENTION 
     The present invention relates to pneumatic hand tools and more particularly to pneumatic hand tools having user operated control valves for governing the flow of operating air to the tool. 
     BACKGROUND OF THE INVENTION 
     Pneumatic hand tools having an air powered motor with a user-operated control valve for governing the flow of operating air to the motor are known. Among the various tools that fall within this category are, for example, drills, grinders, meat trimming knives, and skiving, or skinning knives. The knives are used in the meat industry and feature rotating, or oscillating blades that are driven by air motors. Conventionally these tools are connected to a source of high pressure air via a flexible conduit. Their operation is controlled by a user-actuated valve that is opened and closed to start and stop the drive motor. 
     For safety purposes these tools are often designed so that the user must open the control valve and manually maintain it opened so long as the tool is operated. The valve automatically closes if the user no longer maintains it in its open condition. This minimizes the possibility of tool operation when undesired, which might otherwise result in injury to the user or others. Some tools have handles that house the drive motor and/or the control valve. The user grips the handle and in so doing depresses a valve operating plunger to open the control valve. When the plunger is released the valve closes. 
     Even though the prior art tools were equipped with control valves of the type referred to, undesired tool operation could sometimes occur. For example, where a tool and/or its source of operating air were improperly maintained, the control valve could be fouled or damaged so that it failed to completely close when the tool was not operating. Consequently, air from the source bled past the valve to the air motor inlet. If the leak has sufficient volume, the air motor will run continuously as long as the air volume remains sufficient. The unintended tool operation was a potential source of workplace injury. 
     The present invention provides a new and improved pneumatic hand tool that is so constructed and arranged that unintended tool operation is avoided even though the tool motor control valve fails to fully close when the tool is not operating and air from a pressure source bleeds past the valve. 
     SUMMARY OF THE INVENTION 
     A pneumatic hand tool constructed according to the invention is connected to a source of pressurized operating air and comprises a tool body communicable with the source, a pneumatic motor supported by the tool body, and a control valve for controlling the flow of air from the source to the motor. 
     The motor has an inlet that is communicable with the source via the control valve so that when the control valve is in an open condition the motor is operated from the pressure source and drives the tool. When the control valve is in its closed condition the motor is not operated. 
     The control valve comprises a valve body defining a delivery port through which air is supplied to the motor, a seat surrounding the port, and a valving member movable relative to the seat to open and close the port. The valving member is biased toward engagement with the seat to block flow through the port. In its open condition the control valve is stationed relative to the tool body in a first position where the valve body port communicates directly with the motor inlet and the valving member is spaced from the seat so that air from the source is communicated to the motor. In the closed condition the valving member is in a second position where the valving member engages the seat for blocking flow from the pressure source through the control valve and the valve body delivery port communicates with air at ambient atmospheric pressure so that any source air leaking from the control valve delivery port is vented away from the motor inlet passage. 
     The disclosed control valve body comprises a tubular projecting end that surrounds the delivery port and the tool body comprises a seal member which seals the projecting end when the valve body is in the first position so that the port and the inlet passage are directly communicated. The valve member projecting end is spaced away from the seal member when the valve body is in the second position. 
     In the disclosed embodiment a spring biases the valving member toward engagement with the seat. 
     A valving member actuator is fixed with respect to the tool body for unseating the valving member when the control valve is in its open condition. 
     In an illustrated embodiment a hand grippable lever is provided for enabling a tool user to easily maintain the control valve in its first position. The lever is movable relative to the tool body between a gripped position where the lever maintains the control valve in the first position to a released position where the control valve shifts to its second position. 
     The illustrated hand tool is connected to the source by a conduit and the control valve is connected to the conduit and extends into a receptacle formed by the tool body. 
     Additional features and advantages of the invention will become apparent from the following detailed description of an embodiment of the invention and the accompanying drawings that form part of the specification. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational view of a hand tool, constructed according to the invention, connected to a source of high pressure operating air; 
     FIG. 2 is an enlarged fragmentary cross sectional view of the hand tool of FIG. 1 with a valve illustrated in a closed, non-operating position; 
     FIG. 3 is an enlarged fragmentary cross sectional view of the hand tool of FIG. 1 with the valve illustrated in an open, operating position; 
     FIG. 4 is a view similar to FIG. 3 with the hand tool and air supply conduit separated; 
     FIG. 5 is an elevational view of part of the hand tool illustrated in FIG. 1; 
     FIG. 6 is a cross sectional view seen approximately from the plane indicated by the line  6 — 6  of FIG. 2; 
     FIG. 7 is a cross sectional view seen approximately from the plane indicated by the line  7 — 7  of FIG. 2, with parts removed; and, 
     FIG. 8 is a cross sectional view seen approximately from the plane indicated by the line  8 — 8  of FIG.  7 . 
    
    
     DESCRIPTION OF THE BEST MODE CONTEMPLATED FOR PRACTICING THE INVENTION 
     A pneumatically operated hand tool  10  constructed according to the invention is illustrated in FIG. 1 of the drawings connected to a high pressure source of operating pressure, not illustrated. The hand tool  10  is illustrated as comprising a tool body  14 , a pneumatic motor assembly  16  supported by the tool body  14 , and a control valve  18  for controlling the flow of air from the source to the motor assembly  16  and a drive transmission assembly  19  for transmitting drive from the motor to a tool element. 
     The hand tool  10  is illustrated and described as connected to the source via a flexible conduit  20  that permits the tool user to move about and manipulate the tool freely. The conduit  20  may be of any conventional or suitable construction and is illustrated as an assembly of flexible rubber-like hoses  22 ,  24  that are respectively connected, at one end, to the source and a vent path to atmosphere by a suitable coupling, not illustrated, and detachably connected, at the opposite end, to the tool body  14 . In the illustrated embodiment, the hoses  22 ,  24  are coextensive, with the hose  22  illustrated as disposed loosely within the hose  24 . The hose  22  communicates the source pressure to the motor assembly  16 . The hose  24  vents air from within the tool body  14  (e.g. air exhausted from the motor assembly  16 ) to an exhaust manifold and sound attenuating muffler (not illustrated) and to atmosphere remote from the tool body adjacent the connection to the pressure source. 
     The motor assembly  16  comprises a stator  16   a  fixed in the tool body and a rotor  16   b  disposed within the stator. The rotor  16   b  has a drive shaft  16   c  projecting from one end and a support shaft  16   d  projecting from the opposite end. Bearing assemblies  16   e ,  16   f  support the shafts  16   c ,  16   d , respectively. The rotor and stator may be of any suitable or conventional construction and therefore are not described in further detail. 
     For purposes of illustration and description the hand tool  10  is disclosed as an industrial meat trimming knife. The tool element is illustrated as an annular blade  30  that is supported for rotation about its central axis by a blade housing  32 . The blade and blade housing are supported by a head assembly  36  attached to the tool body  14  by means of a connector which in the disclosed embodiment is a screw. The tool body  14  is illustrated as a tubular handle assembly that the tool user grips while using the knife. The blade  30  is driven about its axis by the motor assembly  16  via the drive transmission  19 . 
     The drive transmission  19  provides a gear reduction between the motor assembly and the knife blade. The transmission is illustrated as an epicyclic gear train disposed within the tool body  14 . As shown, the output shaft  16   c  has gear teeth formed on its periphery and forms a sun gear  19   a  that rotates within a ring gear  19   b  fixed in the tool body  14 . Planet gears  19   c  surround the sun gear and run in mesh with the sun and ring gears to rotatably drive the planet carrier  19   d  at speeds that are greatly reduced from the rotational speed of the rotor  16   b . The planet carrier  19   d  is supported by bearing assemblies  19   f ,  19   g . The planet carrier  19   d  drives an output pinion gear  19   h  that is mounted in the head assembly via a drive shaft  19   i . In the illustrated knife, the blade  30  is formed with gear teeth around its perimeter at its axial end opposite the blade edge. The blade gear runs in mesh with the pinion driving gear  19   h.    
     While a particular construction is illustrated and described, the blade, blade housing, head assembly, and gear drives may be of any suitable or conventional constructions. It should be noted that although an industrial knife exemplifies the hand tool  10  in this disclosure, other kinds of pneumatically operated hand tools may be constructed according to the invention. 
     Referring to FIGS. 1-4, the illustrated tool body comprises a tubular housing  42 , an ergonomic handle sleeve  44  surrounding the housing  42 , and end pieces  46 ,  48  that are fixed in the housing  42  and secure the motor assembly and drive transmission between them. The housing  42  is generally cylindrical while the sleeve  44  is irregularly shaped to conform with the shape of the tool users hand. The end piece  46  is fixed in the head end of the housing  42  and is formed by a generally cylindrical, tubular body that abuts the bearing assembly  19   f  at one of its ends and abuts the head assembly  36  at its opposite end. The end piece  46  has internal threads that receive the head assembly mounting screw. The end piece  48  is illustrated as fixed in the housing  42 , fixed with respect to the stator  16   a  and abutting the rotor supporting bearing assembly  16   f . The illustrated end piece  48  is formed by a generally circular port plate  50  that defines an air inlet port, or passage,  52  and an exhaust port, or passage,  54  each communicating with the motor assembly (see FIGS.  7  and  8 ). 
     The control valve  18  communicates the rotor  16   b  with the conduit  22  via the inlet port  52 . When the control valve  18  is in an open condition (FIG. 3) the motor assembly  16  is operated from the pressure source and drives the tool. The outlet port  54  delivers exhaust air from the motor assembly  16  to the vent hose  24 . When the control valve  18  is in its closed condition (FIG. 2) the motor  16  is not operated. 
     The illustrated control valve  18  comprises a tubular valve body  60  defining a delivery port  62  through which air is supplied to the motor  16  from the air source, a seat  64  surrounding the port  62 , and a valving member  66  movable relative to the seat to open and close the port  62 . The valving member  66  is biased toward engagement with the seat  64  to block flow through the port  62 . In its open condition the control valve  18  is stationed relative to the tool body  14  in a first position where the valve body port  62  communicates directly with the motor inlet port  52  and the valving member  66  is spaced from the seat  64  so that air from the source is communicated to the motor for driving the rotor  16   b . In the closed condition the valving member  66  is in a second position where the valving member engages the seat  64  for blocking flow from the pressure source through the control valve  18  and the valve body delivery port  62  communicates with air at ambient atmospheric pressure so that any source air leaking from the control valve delivery port is vented away from the motor inlet passage and into the exhaust hose  24 . 
     In the illustrated hand tool the control valve  18  is axially shiftable relative to the tool body between a first position (see FIG. 3) where the valve is in its open condition and a second position (FIG. 2) where the valve is in its second, closed condition. In its first position the valve body sealingly engages the tool body in such a way that the delivery port  62  and the motor inlet port  52  are in direct communication so that source air is delivered to the rotor  16   b  for operating the motor. The disclosed control valve body  60  comprises a tubular projecting end  70  that surrounds the delivery port  62 . When the valve  18  is in its first position, the projecting end  70  is in sealing engagement with the motor inlet port so that air delivered from the delivery port  62  is channeled directly to the motor. Air that is exhausted from the motor assembly flows from the rotor through the exhaust port  54  and into the space surrounding the valve body  60  and from there to the atmosphere via the vent hose  24 . 
     In the illustrated tool the end piece  48  comprises a tubular projection  72  extending from the port plate  50  to form a receptacle with a central opening  73  into which the projecting valve body end  70  telescopes. The motor inlet port  52  opens through the port plate  50  into the opening  73  while the exhaust port  54  opens through the port plate radially outwardly of the projection  72  (see FIGS.  7  and  8 ). The region that surrounds the projection  72  is always at atmospheric pressure due to its communication with the vent hose  24 . The opening  73  has a cross sectional shape that conforms to and closely surrounds the projecting valve body end  70  when the valve body is in its open condition. A seal member  74  is disposed within the projection  72  and extends between the receptacle opening  73  and the projecting valve body end  70  to prevent the escape of source air from the projection  72  to the surrounding region when the valve  18  is open. In the illustrated tool the projecting valve body end  70  and the receptacle opening are cylindrical and the seal member  74  is a resilient O-ring that is seated in a circumferential receptacle wall groove, but other forms of seals could be employed if desired. 
     As the valve body  60  moves axially into the housing  42  to its first position (FIG.  3 ), the projecting valve body end  70  and the receptacle wall are sealed together as the valve  18  opens. The illustrated end piece  48  includes a valve actuator pin  76  that is anchored in the port plate and extends through the opening  73  in alignment with the valve port  62 . The actuator pin  76  engages the valving member  66  and shifts it off of the seat  64  to open the delivery port  62  when the valve  18  is in its open position. In the illustrated control valve the valving member is formed by a ball and is biased toward engagement with the seat by a helical spring  78 . The valving member, spring, and actuator could be constructed in other ways. For example, the valving member might have a different shape and/or carry the actuator pin so that as the valve body advances, the actuator pin engages the receptacle and unseats the valving member. 
     As the valve body  60  moves to its second position (FIG. 2) it is shifted generally away from the housing  42  and the projecting valve body end  70  is withdrawn from the receptacle opening  73  as the valving member  66  returns to its seat  64 . In its second condition the valve body end  70  is withdrawn from the seal member  74 . The receptacle wall at the distal end of the projection  72  is internally fluted so that any air leaking from the port  62  is vented out of the receptacle opening to the region radially outward of the projection  72  and to the vent hose  24 . If the valve  18  should leak when in its closed condition for any reason, the air leaking from the valve is vented to atmosphere rather than being directed into the motor inlet port. Consequently, it is not possible for undesired tool operation as a result of air flow from the control valve leakage. 
     In the illustrated tool  10 , the valve  18  is carried by a coupling assembly  80  that functions to detachably couple the tool  10  to the conduit  20  as well as to enable the tool user to shift the valve  18  between its open and closed conditions. The illustrated coupling assembly (see FIG. 4) comprises a central body member  82  that carries the valve  18 , a coupling collar  84  carried by the body member  82  for attaching the assembly to the tool  10 , and a tool user grippable lever  88  for maintaining the valve  18  in its open condition. 
     In the illustrated coupling assembly  80 , the body member  82  surrounds and supports the valve body  60 . As shown in FIG. 3, the valve body  60  is a two part structure formed by generally cylindrical, tubular elements  60   a ,  60   b  that are sealed and screwed together at their juncture (the disclosed valve body  60  is so constructed to enable assembly of the valving member and biasing spring  78  inside the valve body). The element  60 b has a projecting, barbed nipple-like end  89  (FIG. 4) that extends into the pressure hose  22  to fix and seal the valve body and pressure hose together. A hose clamp  90  surrounding the hose  22  and projecting element end assures a sealed connection. 
     The illustrated coupling body member  82  is a two part member formed by elements  82   a ,  82   b  that are hermetically secured together as a unit. A first member element  82   a  supports the valve body element  60   a  and is constructed to telescope into the tool body when the conduit  20  is attached to the tool. As shown, the element  82   a  has a cylindrical skirt-like projecting end  91  that fits closely within the end of the tool body housing  42 . The second member element  82   b  supports the projecting end of the element  60   b  and is hermetically fixed to the exhaust hose  24 . As shown, the element  82   a  has a projecting end that extends within the exhaust hose  24 . A hose clamp  93  surrounds the hose end and the element projecting end to secure them together. 
     The coupling member  82  is generally cylindrical and has two elements  82   a ,  82   b . These elements have cylindrical outer sections and a plurality of radially inwardly projecting spokes  96  that support the valve body  60  along the axes of the member  82  (see FIG.  6 ). The openings between the spokes  96  provide exhaust air flow passages between the is exhaust port  54  in the port plate  50  and the exhaust conduit  24 . 
     In the illustrated tool the valve body  60  clamps the coupling member elements  82   a ,  82   b  together. The valve body element  60   b  has radially outwardly extending flange  100  that abuts the coupling member element  82   b  and defines a series of wrench flats along its periphery. A radially outwardly extending shoulder  102  on the valve body element  60   a  engages the coupling member element  82   a . The coupling member elements  82  are assembled to the valve body  60  and the flange  100  is turned to screw the valve body elements together. The flange  100  and the shoulder  102  trap the elements  82   a ,  82   b  between them and firmly clamp the elements together as the valve body elements are screwed together. A flange  104  on the coupling member element  82   b  is moved into overlying relationship with the outer periphery of the coupling element  82   a  when the elements  82   a ,  82   b  are clamped together. An O-ring seal element  106  retained within the flange  104  and sealingly engages both elements  82   a ,  82   b  when they are clamped together. 
     The coupling collar  84  functions to detachably secure the tool body to the conduit. The collar  84  has an annular body  110  that surrounds the element  82   a  and the end of the tool body housing  42  and an axially projecting, semi-cylindrical section  112  that closely surrounds the outer periphery of the element  82   a . The inner periphery of the annular body  110  carries diametrically opposed pins  114  (FIG. 4) that project radially inwardly. The end of the tool body housing  42  forms radially outwardly opening cam slots  116  (see FIG. 5) that receive the pins  114 . The collar  84  is slid onto the tool body housing  42  so that the pins  114  enter the cam slots  116 . The collar is turned so that the pins follow, and are captured in, the cam slots. This action secures the conduit  20  to the tool  10  with the valve  18  in its closed position (FIG. 2) so that the tool is not supplied with motor operating air from the pressure source. 
     When the tool user wishes to operate the motor the user pushes the coupling member  82  axially into the tool body  14  (FIGS.  1  and  3 ). The member  82  slides axially into the tool body housing carrying the valve  18  along with it. A seal ring  118  stationed in the tool body housing inner periphery sealingly engages the projecting end  91  of the coupling member element  82   a  as the valve  18  moves to its open position. At the same time the valve body  60  enters the receptacle opening  73  and the valving member  66  is unseated by the actuator pin  76  resulting in high pressure air being supplied to the motor. 
     In the illustrated tool  10  the user manually maintains the operating airflow to the motor by gripping the lever  88  and holding it in juxtaposition with the handle. The illustrated lever  88  is connected to the coupling body element  82   a  by a clamp  120  and associated pivot pin, or pintle,  122  that are secured to the element  82   a . The lever  88  is illustrated as a stamped sheet metal member comprising a pivot bearing section  130 , a grip section  132  and a camming bight section  134 . When the valve  18  is in its open position (FIGS.  1  and  3 ), the tool user grips the grip section of the lever  88  so that it is moved adjacent the tool handle. The camming bight section  134  of the lever engages the annular collar body  110  to maintain the valve open. Because of the length of the grip section  132 , minimal tool user gripping force is required to maintain the lever in its FIGS. 1 and 3 position. User hand fatigue is thus avoided. If the lever is released by the tool user, the force of the valve spring  78  and the air pressure acting on the valving member  66  urge the coupling assembly  80  axially away from the tool. The collar body  110  reacts against the lever bight section  134  shifting the lever aside and allowing the valve  18  to close (FIG.  2 ). 
     While a single embodiment of the invention has been illustrated and described in detail, the invention is not to be considered limited to the precise construction disclosed. Various adaptations, modifications and uses of the invention may occur to those skilled in the art to which the invention relates. The intention is to cover all such adaptations, modifications, and uses that fall within the scope or spirit of the claims.