Abstract:
The present invention provides a reversing valve assembly for selecting the direction of a motor that rotates in a forward direction and a reverse direction. The reversing valve assembly includes a push button that extends outwardly from the tool in a first position, and self-locks when depressed towards the tool in a second position. When it is desirable to return to the forward direction, the reverse valve assembly is releasable from the second position by further depressing the push button towards the tool and releasing the push button, thus controlling the direction of the motor by depressing and releasing the single push button.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application is a continuation-in-part of pending U.S. Ser. No. 09/903,026, filed Jul. 11, 2001. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    This invention relates to pneumatic tools. More specifically, it relates to a reverse mechanism for pneumatic tools that enables the user to control the direction of rotation of the tool by toggling a single push button.  
           [0003]    Pneumatic tools, such as impact wrenches, are well known in the prior art. High pressure air drives a motor as the air moves from a high pressure inlet, through the motor and is exhausted to a low pressure exhaust. The air travels by the path of least resistance as it moves from high pressure to ambient pressure. An impact wrench, for example, includes an air driven motor having an air inlet port and an air exhaust that vents to the atmosphere. These tools are commonly used in an industrial setting, where a common source of pressurized air may be used to power a number of individual units. In such a setting, impact wrenches are particularly useful, because a number of different bits, sockets or attachments may be used to perform a variety of tasks with a single motor unit.  
           [0004]    Frequently, these tools are used to remove screws, bolts or nuts as well as install them, so the tool drive must be able to rotate in both forward and reverse directions. Impact wrenches, for example, generally change the direction of the motor utilizing valves to change the airflow within the motor housing, thus changing direction of the rotation. Prior art impact wrenches have a “reverse bar” that causes the motor to rotate in one direction when the bar protrudes in the forward position, near the trigger switch. When the bar is positioned so that the button protrudes toward the endcap of the tool, the motor turns in the opposite direction.  
           [0005]    Use of the reverse bar of the prior art is inconvenient when the user is working in a confined space, where there is little or no room to turn the tool in order to see the location of the bar or to push it from the front of the tool. Car mechanics, for example, sometimes work in tight places under a car or under its hood, installing or removing parts. The front end of the tool, that holds the interchangeable bits, sockets and the like, is often in a small space while working. If the position of the tool is particularly tight, there may not be enough space to get a hand around to the front of the tool with enough leverage to push the reverse bar. When it is necessary to change direction of the tool, the mechanic must take the tool out of the small space, see the position of the reverse bar, turn the tool to reach for the bar, push the bar in the other direction, and reposition the tool in the confined space.  
           [0006]    Even if able to do so, it may be preferable not to put hands or fingers where there may be a safety hazard. In other situations, the user may be wearing work gloves that would reduce tactile sensitivity, making it difficult to detect or change the position of the switch merely by feel. Further, it is inconvenient and takes time to ascertain the position of the reverse bar so that the user knows where to reach in order to change direction.  
           [0007]    It is, therefore, an object of this invention to provide an improved reverse switch for pneumatic tools where the user can control direction of the motor from one position.  
           [0008]    It is another object of this invention to provide an improved reverse switch for pneumatic tools that can be operated with a single finger.  
           [0009]    It is still another object of this invention to provide an improved reverse switch for pneumatic tools that does not require access to the front of the tool to change the motor direction.  
         SUMMARY OF THE INVENTION  
         [0010]    These and other objects are met or exceeded by the present invention, which features a single button reverse switch for pneumatic tools. The reversing assembly of the present invention allows the user to consistently reach for the same position, without having to think about and decide when to push, or have to move to a second location if the button in the first location was previously aligned. The single button offers convenience to the user, since the same button changes direction of the motor drive from forward to reverse, as well as from reverse to forward.  
           [0011]    More specifically, the present invention provides a reversing valve assembly for selecting the direction of a motor that rotates in a forward direction and a reverse direction. The reversing valve assembly includes a push button that extends outwardly from the tool in a first position, and self-locks when depressed towards the tool in a second position. When it is desirable to return to the forward direction, the reverse valve assembly is releasable from the second position by further depressing the push button towards the tool and releasing the push button, thus controlling the direction of the motor by depressing and releasing the single push button.  
           [0012]    In a preferred embodiment, the present invention provides for a pneumatic tool having a housing with an end cap, a motor area including a motor, a pressurized air inlet and an air exhaust port. The reversing valve assembly includes a reverse bushing that houses a reversing assembly within it. The reverse bushing also includes an air inlet opening, an air exhaust opening, a first air channel, a second air channel, and one of a cam track with at least one groove and a cam sized and configured to engage with the groove. The reversing assembly is biased toward the end cap and includes a push button that projects through the end cap; at least a first and second reverse valve; a rotating device; a spin ring having the other of the cam and the cam track; and an end support.  
           [0013]    When the push button is pushed, a first activation causes movement of the reversing assembly toward the end support, causing the reversing assembly to rotate by engaging the rotating device. Rotation causes the cam to engage the groove, aligning the first reverse valve between the air inlet opening and the first air channel and causing the second reverse valve to align between the second air channel and the air exhaust port, turning the motor in a forward direction. A second activation of the push button causes a downward movement of the reversing assembly, causing the reversing assembly to rotate by engaging the rotating device. The second rotation causes the cam to disengage the groove, aligning the first reverse valve between the first air channel and the air exhaust port and causing the second reverse valve to align between the second air channel and the air intake, turning the motor in a reverse direction.  
           [0014]    This reversing apparatus is particularly suitable for use with pneumatic tools because it provides a more convenient means of reversing direction of the drive mechanism. The push button of this invention acts as a toggle switch, changing the direction of the drive either to a forward motion from a reverse motion or from a reverse motion to a forward motion. There is no need for space to rotate the tool or reach around the tool. If it is necessary to determine the direction of rotation, the look or feel of the push button will instantly inform the user whether the button is in the retracted or extended position, thereby indicating the direction of motion of the drive mechanism. 
       
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is a perspective view of a pneumatic tool, with a portion of the housing cut away to show the reversing valve assembly of the present invention;  
         [0016]    [0016]FIG. 2 is an exploded perspective view of the reversing valve assembly of the present invention;  
         [0017]    [0017]FIG. 3 is a longitudinal cross section of the reversing valve with the push button in the first position; and  
         [0018]    [0018]FIG. 4 is a longitudinal cross section of the reversing valve with the push button in the second position.  
         [0019]    [0019]FIG. 5 is a perspective view of a second embodiment of a pneumatic tool. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    Referring to FIG. 1, a reversing valve assembly, generally designated  10 , for a pneumatic tool, generally designated  12 , is shown. Preferably, this reversing assembly is designed for use with an impact tool that uses pressurized air to turn the motor, and provide power for the accessories. The assembly  10  is designed to be used with a pneumatic tool having a housing  14 , an end cap  16 , and a motor area  18 , including a motor (not shown). Pressurized air flows into the motor area  18  through an inlet  20  and exits through exhaust port  22 .  
         [0021]    Referring to FIGS. 3 and 4, the tool  12  is driven by vanes (not shown) on the motor that are propelled by the pressurized air as it moves across a pressure drop between at least a first and a second air channel  24 ,  26 . Essentially, the vanes are connected between the first and second air channels  24 ,  26 . Direction of motion is controlled by the direction that the pressurized air flows past the vanes. High pressure air that enters through the first air channel  24  pushes the vanes as it moves toward the lower pressure second air channel  26 , causing the motor to turn in one direction. Redirecting the high pressure air through the second air channel  26  pushes the vanes, and therefore the motor, in the opposite direction as the air moves to the first air channel  24  at a lower pressure. The reversing valve assembly  10  of the present invention is designed to direct the flow of the pressurized air through the first and second air channels  24 ,  26  to control direction of the tool motor.  
         [0022]    Referring back to FIG. 1, a common source of pressurized air is often used to provide air for multiple tools, as in a machine shop or automotive garage. The high pressure air generally travels through a hose  30  from the common source, and enters the individual tool  12  through an inlet valve  32  of a handle area  34 . This position is not critical, but is preferred because it places the hose  30  in a position that it is less likely to interfere with the user. It minimizes interference with the grip of the user, the user&#39;s view of the workpiece, ability to get the tool  12  into small places, and to freely move the tool as needed to accomplish a task.  
         [0023]    The reversing assembly  10  is housed in a reverse bushing  40 , best seen in FIGS. 3 and 4. Assembly of the component parts of the reversing assembly  10 , and the limited amount of space available within the tool housing  14 , suggests that a long, narrow shape is preferred for the reverse bushing  40 . Most preferably, the bushing  40  is generally tubular in shape. Preferably, the reverse bushing  40  is aligned such that the longitudinal axis of the tube is generally perpendicular to the end cap  16  of the tool housing  14 , as shown in FIG. 1. A first end  42  is located closest to the end cap  16 , while a second end  44  is at the end of the tube opposite the first end  42 .  
         [0024]    Preferably, the reverse bushing  40  should be constructed of a material that is sufficiently strong to hold the parts of the reversing assembly  10  in place, but should not be overly costly or heavy. Suitable materials include metals, polymers or wood. Both natural materials, such as rubber, and synthetics, such as polyethylenes, polyimides, polyisoprenes, semi-rigid or rigid nylons, are suitable for construction of the reverse bushing, as well as many other polymers and polymer blends.  
         [0025]    Referring to FIGS. 3 and 4, at least one air inlet opening  46  and air exhaust opening  48  are located in a wall  50  of the bushing  40 , allowing air to flow to and from an interior area  52  within the exhaust bushing. The air inlet opening  46  allows pressurized air from the inlet valve  32  in the handle area  34  to enter the reversing assembly  10  for control of the motor direction. The air exhaust opening  48  allows the air to exit the reverse bushing  40  of the tool  12 . A first channel opening  60  and a second channel opening  62  allow the air to pass between the interior  52  (FIG. 2) of the reverse bushing  40  and either the first channel  24  or the second channel  26 , respectively. It is contemplated that there could be openings for a plurality of air inlet openings  46  and/or air exhaust openings  48 . Preferably, there is an air exhaust opening  48  for each channel opening  60 ,  62 , such as a second air exhaust opening  64 .  
         [0026]    A push button  66  is sized and configured to fit inside the reverse bushing  40 . The push button  66  has a front end  68  and a back end  70 , and is preferably cylindrical. A sleeve  72  surrounds the back end  70 , preventing the push button  66  from sliding out of the reverse bushing  40  at the first end  42 . Suitably, the push button  66  protrudes from the first end  42  of the reverse bushing  40 , through the end cap  16 , and through a regulator lever  74  with sufficient length that the front end  68  is accessible for engagement by the user when in a depressed position.  
         [0027]    Preferably, the front end  68  of the push button  66  has a slot  76 . A prong  78  on the regulator lever  74  is designed to engage the slot  76 , allowing the push button  66  to move in and out relative to the reverse bushing  40 , without rotating as it does so.  
         [0028]    A biasing device spring or the like  79 , may optionally be used to help the reverse assembly move smoothly along the longitudinal axis when the push button  66  is activated. It is preferably installed over the push button  66 , between the sleeve  72  and the end cap  16 .  
         [0029]    A reverse valve  80  is located next along the longitudinal axis of the reverse bushing  40  away from the end cap  16 . This valve  80  is a suitable shape that allows it to rotate within the reverse bushing  40  and move back and forth from the first end  42  to the second end  50  within the reverse bushing. Preferably, the reverse valve  80  is cylindrical, with at least one spiral-shaped end  81 . The end  81  spirals in the axial direction so that the amount of air allowed to pass through the inlet  46  varies as the valve  80  is rotated by the regulator lever  74 .  
         [0030]    The wide cylindrical portion of the reverse valve  80  is a reverse valve  82 . Fit of the reverse valve  82  within the reverse bushing  40  is important, as the valve acts as a divider between a first air chamber  84  and a second air chamber  86 . The second air chamber  86  is defined by a cavity between the reverse valve  80  and an end piston  88 . Operation of the motor depends on a sufficient pressure difference between the air entering the motor area  18  and the air exiting the same area. If too much air leaks between the first air chamber  84  and the second air chamber  86 , the difference in pressure between the first and second air channels  24 ,  26  could be inadequate to drive the motor to a useful power level. Therefore, preferably, the diameter of the reverse valve  80  is large enough to maintain a useful power output from the motor, but small enough that the valve moves easily along the longitudinal axis of the reverse bushing  40 .  
         [0031]    A first separator rod  90  extends from the reverse valve  80 . It acts as a spacer between the reverse valve  82  and the sleeve  72 . The first separator rod  90  may be attached to the sleeve  72 , or the reverse valve  82 , or they can be individual units. The volume of the first air chamber  84  is determined by the length and diameter of the first separator rod  90 , and is suitably large enough that the flow of air through the first air chamber is not restricted.  
         [0032]    Length of the first separator rod  90  is be chosen to align the first channel opening  60  with either the air inlet opening  46  or the air exhaust opening  48 , depending on the position of the push button  66 . When the push button is in a first position, as shown in FIG. 3, the air inlet opening  46  is open to the first air chamber  84 , the first channel opening  60  and the first air channel  24 , allowing the pressurized air to flow from the inlet to the motor area  18  (FIG. 1) through the first air channel. In this position, the sleeve  72  around the push button  66  blocks flow to the air exhaust opening  48  from the first air chamber  84 , maintaining pressure of the incoming air. The pressurized air passes through the motor and returns through the second air channel  26 . It exhausts through the second air chamber  86  and air exhaust opening  64 .  
         [0033]    When the push button  66  is actuated and moves to a second position shown in FIG. 4, the entire reversing assembly moves along the longitudinal axis of the reverse bushing  40 , changing the orientation of the spaces and dividers within the bushing. In the second position, the reverse valve  82  moves toward the end cap  16 , blocking flow of air from the air inlet opening  46  to the first air chamber  84 . However, the sleeve  72  also moves to open the air exhaust opening  48  to the first air chamber  84 , so that air exhausting through the first air channel  24  flows through the first channel opening  60 , through the first air chamber and out the air exhaust opening. The length of the first separator rod  90  must be selected in cooperation with other elements to assure that when the first air inlet  46  is open to the first air chamber  84 , the air exhaust opening  48  is blocked from this chamber. Thus, the suitable length of the first separator rod  90  is one that allows movement of the reverse valve  82  from opening the air inlet opening  46  to the first air chamber  84  when the push button  66  is in the first position, to blocking air flow from the air inlet opening to the first air chamber when the push button is in the second position.  
         [0034]    A second separator rod  96  defines the volume of the second air chamber  86  and separates the end piston  88  from the reverse valve  82 . The diameter of the piston  88  is suitably large to prevent leakage of air from the second air chamber  86  to the air exhaust opening  64  when the push button  66  is in the second position. Air flow is directed by the position of the second air chamber  86  to and from the appropriate passages depending on the position of the push button  66 . As shown in FIG. 3, when the push button  66  is in the first position, air flows from the second air channel  26 , through the second channel opening  62  and the second air chamber  86  to the second air exhaust opening  64 . When the push button  66  is activated and moved to the second position shown in FIG. 4, the end piston  88  moves toward the end cap  16 , blocking flow to the air exhaust opening  64 . However, the reverse valve  82  has also moved, so that the air inlet opening  46  is open to the second air chamber  86 . This arrangement allows flow of high pressure air from the air inlet opening  46  into the second air chamber  86 , through the second channel opening  62  and into the second air channel  26 . Thus, a suitable second separator rod  96  will have a length sufficient to move the end piston  88  to provide the air flow described above, while blocking the exhaust opening  64 .  
         [0035]    The valves are held in place using a rotating means  100  that turns a cam follower  100  within a cam track  102 . Any rotating device may be used that translates the linear motion of the push button  66  into a rotational motion. Preferably, rotation is caused by a cam roll  104 , that turns a spin ring  108 .  
         [0036]    Shown best in FIG. 2, the cylindrical cam roll  104  provides an sloped surface  110  that causes the spin ring  108  to turn. Any suitable diameter of the cam roll  104  is used that allows it to move freely within the reverse bushing  40 . One end of the cam roll  104  closest to the end cap  16  optionally includes an extension  111  that matingly engages with a corresponding depression in the end piston  88  (FIGS. 3 and 4). In the preferred embodiment, when all elements of the reversing assembly  10  align along a common longitudinal axis, this extension  111  helps keep the cam roll  104  in line with other elements.  
         [0037]    At the opposite end of the cam roll  104  is a serrated edge  114 , having a plurality of teeth  116  around the outside diameter. Each tooth  116  has at least one of the sloped surfaces  110 , so that as the entire reversing valve assembly  10  moves along the longitudinal axis of the reverse bushing  40 , rotational motion is imposed on the spin ring  108  by engagement of at least one spin projection  112  with the sloped surface of the teeth. Other rotational means are contemplated for use with this invention that translate linear motion to rotational motion. For example, a projection could be used to engage a spiral ramp.  
         [0038]    The interior  52  of the reverse bushing  40  also has a cam track  102  with at least one groove  118 , a stop position  122  and first and second angular surfaces  124 ,  126 . As the spin ring  108  rotates, the spin projections  112 , which extend closer to the reverse bushing  40  than the body of the spin ring, engage the features of the cam track  102 . When push button  66  is in the first position, as in FIG. 3, a forward edge  120  of the spin projection  112 , closest to the end cap  16 , rests on the cam track  102  at a stop position  122 . The stop position  122  is located between the first angular surface  124  and the second angular surface  126 . When the spin projection  112  is in the stop position  122 , the spin projection aligns with the slope of the tooth  116  on the cam roll  104 . If the push button  66  is depressed, the reversing valve assembly  10  is pushed away from the end cap  16 . Initially, there is no rotational motion while the spin projection  112  is engaged against the stop position  122 . However, when depression of the push button  66  extends far enough that the spin projection  112  disengages the stop position  122 , the spin projection  120  slides to the bottom of the tooth  116 . By so doing, rotation of the spin ring  108  aligns the spin projection  112  with the second angular surface  126  of the cam track  102 . As the depressed push button  66  is released, rotation continues as the spin projection  112  slides down the second angular surface  126  and into the groove  118 . The biasing force  134  pushes the spin projection  112  deep into groove  118  as the push button  66  moves to the second position.  
         [0039]    Similarly, when the push button  66  is depressed again, the tooth  116  of the cam roll  104  pushes upward on the spin projection  112  until the spin projection  112  clears the top of the groove  118 . When released, the spin projection slides down the tooth  116  of the cam roll  104  until it stops at the bottom of the tooth. This begins rotation of the spin ring  108  and positions the spin projection  112  over the first angular surface  124  of the cam track  102 . As the depressed push button  66  is released, the spin projection  112  contacts the cam track  102  and slides down to the stop position  122 , leaving the push button  66  in the first position.  
         [0040]    In the preferred embodiment, the cam roll  104  also includes one or more stabilizers  128 . The stabilizers  128  are preferably shaped as a bar or a pin that engages the end  129  of the long groove  126  closest to the end cap  16 . Engagement of one of the stabilizers  128  in the end of long groove  129  also helps keep the cam roll  104  and the spin ring  108  aligned so that the spin projections  112  properly engage the teeth  116  to provide a consistent rotational motion.  
         [0041]    At the end of the reverse bushing  40  is a cap  130  to hold the reversing valve assembly  10  together. The cap  130  preferably frictionally engages the reverse bushing  40  to hold it in place. At least one biasing device  134  holds the assembly together and encourages movement along the longitudinal axis of the reverse bushing  40 . Preferably the biasing device  132  is a spring  134 . The spring  134  is preferably located between the cap  130  and the spin ring  108 , and prevents the sleeve  72 , the separating rods  90 ,  96 , the reverse valve  82 , the end piston  88 , the cam roll  104  and the spin ring from separating. Biasing of the reverse valve assembly  10  toward the push button  66  is also performed by the device  134 , so that when the push button moves from the first position to the second position, the entire assembly  10  moves with it. Preferably, the cap  130  also includes a spring support  136  to hold the spring  134  in an appropriate position.  
         [0042]    Operation of the reverse valve assembly  10  will now be described. Starting from the first position shown in FIG. 3 where the tool is operating in a forward direction, when the push button  66  is activated, the reverse valve assembly  10  moves away from the end cap until the spin projection  112  disengages with the long groove  126  and begins rotation of the spin ring  108 . As the push button  66  is released, biasing device  132  pushes the spin ring  108 , cam roll  104 , end piston  88 , reverse valve  82 , first and second separating rods,  90 ,  96 , the sleeve  72  and the push button  66  toward the end cap  16 . Rotation allows the spin projections  112  within the short groove  124 , allowing the reverse valve assembly  10  to move toward the end cap  16  and shifting the push button  66  toward the second position.  
         [0043]    As the reverse valve assembly  10  moves toward the end cap  16 , the end piston  88  shifts to cover the air exhaust opening  48  from the second air chamber  86  and the reverse valve  82  shifts to cover access to the air inlet opening  46  from the first air chamber  84 . The reverse valve assembly  10  continues to move toward the end cap  16 , pushing the sleeve  77  and opening the air exhaust opening  48  to the first air chamber  84 . At the same time, the reverse valve  82  moves across the air inlet opening  46 , allowing high pressure air to flow into the second air chamber  86 . When fully pushed to the second position by the biasing force  134 , shown in FIG. 4, the high pressure air enters the second air chamber  86  through the inlet air opening  46  and flows through the second chamber opening  62  and into the second air channel  26 . The air then flows to the motor where it pushes against the vanes, turning the motor in a reverse direction. Air flows from areas of high pressure to areas of low pressure, and in this case, will seek the path to the air exhaust opening  48 . After turning the motor, the spent air flows through the first air channel  24 , through the first channel opening  60 , the first air chamber  84  and into the air exhaust opening  48 .  
         [0044]    Depressing the push button  66  from the second position, shown in FIG. 4, the push button pushes against the sleeve  72 , the first separator rod  90 , the reverse valve  80 , the second separator rod  90 , the end piston  88 , the cam roll  104 , the spin ring  108  and the biasing force  134 . As these elements move away from the end cap  16 , the sleeve  72  shifts to block access to the air exhaust opening  48  and the reverse valve  82  moves past the inlet air opening  46 , opening it to the first air chamber  84 . When the spin projections  112  have cleared the short groove  124  (FIG. 2), the spin ring  108  rotates, allowing the spin projection  112  to drop into a long groove  126  releasing the push button from the depressed position.  
         [0045]    A second embodiment  212  of the tool, currently the preferred embodiment, is shown in FIG. 5. In this embodiment, the reverse valve assembly is oriented so that a push button  266  is positioned at the front of the tool  212 , instead of at the rear of the tool. Rather than protruding through the end cap  16 , the push button  266  is accessed through the housing  214 . Preferably, the push button  266  is located above and moving parallel to the trigger  215 . Internally, the channels and openings are aligned as described above so that air flow is correctly diverted through the valves. Linear movement of the reversing assembly will be rotated 180° from the above description. For example, motion of the reversing assembly previously described as moving toward the end cap  16  will now move away from the end cap. The biasing force  134  now acts to push the reversing assembly away from the end cap. Other minor adjustments needed to place the push button  266  toward the front of the tool  212  will be obvious to an artisan skilled in this field.  
         [0046]    While a particular embodiment of the reversing valve assembly for a pneumatic tool has been shown and described, it will be appreciated by those skilled in the art that changes and modifications may be made thereto without departing from the invention in its broader aspects and as set forth in the following claims.