Abstract:
The auto/single functions selecting device of a grease gun includes a switch unit connected to the main body of the grease gun. When the user switches the switch unit to the first position, a single shot is available when pulling the trigger one time. When the user switches the switch unit to the second position, the grease is continuously supplied when keep pulling the trigger. The grease gun provides the function of single shot and the function of auto shot.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a pneumatic grease gun, and more particularly, to a pneumatic grease gun with auto/single functions selecting device. 
       BACKGROUND OF THE INVENTION 
       [0002]    Grease is added to the gear box or the transmission shaft for most of the heavy duty tools or vehicles so as to lubricate the gears and bearings and movable parts to reduce friction. The adding of the grease is made by using a grease gun  9  which is disclosed in  FIG. 9 . The grease stored in the grease can  92  is injected to the gear box or the transmission shaft via the outlet  93  of the body  91  of the gun  9 . 
         [0003]    The conventional pneumatic grease gun  9  is operated in single shot each time so that when a large amount of grease is needed, the user has to repeatedly pull the trigger  94 , and this is not convenient. TW-M279793 discloses a grease gun which provides a large amount of grease by one operation of the trigger to improve the shortcoming of the conventional pneumatic grease gun. 
         [0004]    However, when operating the grease gun that supplies a large amount of grease within one shot, the amount of the grease may be much more than needed. This becomes waste of the grease. 
         [0005]    The present invention intends to provide a grease gun with an auto/single functions selecting device which allows the user to choose desired function to get the desired amount of grease. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention relates to an auto/single functions selecting device of a grease gun. A pressurized air source is connected to the handle of the grease gun and the handle of the grease gun has a primary path, a return path, an air release path, a recess and a valve unit. By pulling the trigger, the valve unit changes the directions of the pressurized air to move the piston to control the grease to be supplied in the single mode of one shot at a time, or the auto mode of providing continuous grease. 
         [0007]    The auto/single functions selecting device comprises a switch unit connected to the main body of the grease gun. When the user switches the switch unit to the first position, a single shot is available when pulling the trigger one time. When the user switches the switch unit to the second position, the grease is continuously supplied when keep pulling the trigger. The grease gun provides the function of single shot and the function of auto shot. 
         [0008]    The present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a preferred embodiment in accordance with the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a cross sectional view of the grease gun with the auto/single functions selecting device of the present invention; 
           [0010]      FIG. 2  is an enlarged cross sectional view of the valve unit and the switch unit, wherein the switch unit is switched to the second position; 
           [0011]      FIG. 3  shows the pressurized air flowing through each of the paths of the auto/single functions selecting device of the present invention; 
           [0012]      FIG. 4  shows the movement of the piston when the grease gun is operated in single shot function; 
           [0013]      FIG. 5  shows that the piston is returned when the grease gun is operated in single shot function; 
           [0014]      FIG. 6  shows the first movement of the piston when the grease gun is operated in auto shot function; 
           [0015]      FIG. 7  shows that the piston is returned when the grease gun is operated in the auto shot function; 
           [0016]      FIG. 8  shows the following movement of the piston when the grease gun is operated in auto shot function, and 
           [0017]      FIG. 9  shows the conventional grease gun. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0018]    Referring to  FIGS. 1 and 2 , the auto/single functions selecting device of an auto/single functions selecting device of a grease gun comprises a main body  10  which is composed of a front part  13  and a rear part  11 . The main body  10  has a handle  111  connected to the rear part  11  and the main body  10  has a chamber  101  in which a piston  102 , a piston rod  103  and a spring  104  are received. The handle  111  has a recess  12  and a grease can holder  14  is connected to the front part  13  of the main body  10 . An air exit  131  is defined through the front part  13 . A valve unit  2  is located in the recess  12  by an end member  21  and the end member  21  has the air exit  131 . A primary path  3  is defined in the handle  111  and communicates between the chamber  101  and a pressurized air hose “A”. The primary path  3  is composed of a main air path  31 , a first air path  32  and a second air path  33 . The first air path  32  communicates with the recess  12  and the second air path  33  communicates with the chamber  101 . The recess  12  communicates with the mediate portion of the chamber  101 . An air release path  4  is defined in the handle  111  and communicates with the recess  12  and opens to the underside of the handle  111 . A return path  5  is partially defined in common with a section of the primary path  3  and communicates with the recess  12  via the valve unit  2 . The valve unit  2  controls the direction of the pressurized air in the primary path  3 , the air release path  4  and the return path  5 . A trigger  15  is pivotably connected to the main body  10  and contacts the valve unit  2 . An auto/single control path  6  is located between the second air path  33  and the recess  12 , and communicates with the recess  12  from the primary path  3 . The auto/single control path  6  is composed by the third air path  61  and the valve unit  2 . A switch unit  7  is located in the auto/single control path  6  and controls the auto and single functions. A pneumatic driving unit  8  has retractable tubes  81 , and a hose  82  is connected between the main air path  31 , the pressurized air hose “A” and the retractable tubes  81 . 
         [0019]    As shown in  FIGS. 2 and 3 , the valve unit  2  comprises a separation board  26 . A first room  121  and a second room  122  are defined by the separation board  26 , the end member  21 , the recess  12  and the first piston  222 . A third room  123  and a fourth room  124  are defined by the separation board  26 , the end member  21 , the recess  12  and the second piston  232 . 
         [0020]    As shown in  FIG. 3 , the primary path  3  is composed of the main air path  31 , the first air path  32  and the second air path  33  in sequence, and eventually communicates with the chamber  101 , when the primary path  3  is opened, the piston  102  is moved forward. The pressure in the main air path  31  applies a right push force P 4  to the second valve  23 . The path of the air release path  4  starts from the chamber  101 , the second air path  33 , the first air path  32 , the recess  12  and then communicates with the first air release path  41 . When the air release path  4  is opened, the spring  104  returns the piston  102  to its initial position, and the air pressure behind the piston  102  is released from the main body  10 . The return path  5  starts from the main air path  31 , the recess  12 , the second inlets  231  of the second valve  23 , the second space  233 , the first inlets  221  of the first valve  22 , the first passage  224  and then reaches the third room  123 . The pressure applies a left push force P 1  to second piston  232 . The auto/single control path  6  starts from the third air path  61 , the air intake hole  711  and the transverse hole  712  of the switch rod  71  and to the through hole  212  of the end member  21 . When the auto/single control path  6  is opened, the air pressure is introduced from the second air path  33  and enters into the air intake hole  711  and the transverse hole  712  of the switch rod  71 , the through hole  212  of the end member  21  and then enters into the first room  121 . The pressure applies a left push force P 2  to the first piston  222 . 
         [0021]    Referring to  FIGS. 1 ,  3  and  4 , when using the single function, the pressurized air hose “A” is connected to the grease gun  1 , the pressurized air is introduced into the retractable tubes  81  of the pneumatic driving unit  8  so that the grease  143  in the grease can  142  enters the first path  132  via the grease outlet  141 . 
         [0022]    The user rotates the knob  73  to the first position as shown in  FIG. 4 , the switch rod  71  moves into the third air path  61  and compresses the assistance spring  72  to close the auto/single control path  6 . When the pressurized air passes through the return path  5 , a left push force P 1  is applied to the second piston  232  which also receives a left push force P 3  from the second spring  24 . The sum of the left push force P 1  and the left push force P 3  is larger than the right push force P 4 , so that the second valve  23  moves left and seals the primary path  3  while the air release path  4  is opened. Therefore, the piston  102  does not act to inject the grease or return. 
         [0023]    As shown in  FIGS. 3 and 4 , when the trigger  15  is pulled, the elongate member  151  pushes the rod  25  into the first space  223  to seal the return path  5  so that the left push force P 1  is disappeared. The second piston  232  is only applied by the left push force P 3  from the second spring  24 . The left push force P 3  is smaller than the right push force P 4  from the second valve  23 , so that the second valve  23  moves right. The primary path  3  is opened and the piston  12  is moved forward. There is no air released from the air exit  131 , the grease  241  in the first path  132  is ejected from the grease gun  1 . When the user releases the trigger  15 , the rod  25  is moved right by the pressure in the return path  5 . The return path  5  is opened and the rod  25  is pushed right and the left push force P 1  is formed again to move the second piston  232  left. The primary path  3  is sealed while the air release path  4  is opened, the spring  104  in the chamber  101  returns the piston  102 , and the air in the chamber  101  is released from the air release path  4 . 
         [0024]    Referring to  FIGS. 2 and 3 , when the switch unit  7  is switched to the second position, the transverse hole  712  is located in alignment with the auto/single control path  6  which is opened and the pressure in the auto/single control path  6  applies the left push force P 2  to the first piston  222 . As shown in  FIGS. 3 ,  6 , when the user holds the trigger  15  to eject the grease, the left push force P 2  generated by the auto/single control path  6  pushes the first piston  222  left. The return path  5  is opened and the left push force P 1  is formed again, and the second piston  232  is moved left and seals the primary path  3 , while the air release path  4  is opened as shown in  FIGS. 3 and 7 . The spring  104  in the chamber  101  returns the piston  102  and the air in the chamber  101  is released from the grease gun to finish the first injection of the grease. 
         [0025]    As shown in  FIGS. 3 and 7 , when the first time inject is completed and the piston returns while the trigger  15  is still held, because the air in the auto/single control path  6  is released from the auto/single control path  6  and the primary path  3 . The left push force P 2  applied to the first piston  222  is disappeared, the first valve  22  moves right as shown in  FIGS. 3 and 8 . The return path  5  is sealed and the left push force P 1  is disappeared. The second valve  23  moves right because of the right push force P 4  so that the primary path  3  is opened and the grease  143  is injected. The auto/single control path  6  is opened and the pressure enters into the first room  121  and the left push force P 2  is formed which is applied to the first piston  222 . The first valve  22  is moved left to open the return path  5 . The left push force P 1  is formed and the second piston  232  returns left to seal the primary path  3  and open the air release path  4 . This returns the piston  102  and the air in the chamber  101  is released from the grease gun to complete the second inject of the grease. The steps are repeated to proceed the third time injection, the fourth time inject and so on until the trigger  15  is released. The piston  102  is eventually returned to its initial piston, the auto function is then stopped. 
         [0026]    While we have shown and described the embodiment in accordance with the present invention, it should be clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.