Abstract:
A control valve for ejecting rivet pieces of a rivet gun has an adapter, a bushing, a first valve member and a second valve member. The adapter has cavity and a mounting hole. The bushing is mounted in the mounting hole of the adapter and has a through hole. The first and second valve members are mounted respectively on front and rear ends of the bushing into the through hole. An internal air space is defined between the first and second valve members. Changing the size of the internal air space adjusts an airflow rate inside the control valve so that the moving speed of a rivet piece through the control valve can be controlled.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a control valve, and more particularly to a control valve that is mounted in a rivet gun and capable of ejecting rivet pieces such as core pins of a rivet toward a collector on a rear end of a barrel of the rivet gun. The control valve adjusts the ejection speed of the pieces to prevent excessive impact of the rivet pieces to the collector probably damaging the collector and noise incurred thereby. 
         [0003]    2. Description of Related Art 
         [0004]    Conventional rivet guns are used for mounting rivets on at least two pieces so that the rivets securely hold the pieces together. A rivet has a cap and a core pin. The cap is T-shaped and has an enlarged end and a mounting end. The core pin is mounted longitudinally through, protrudes out of the cap and has two ends and a ball formed on one end and adjacent to the mounting end of the cap. 
         [0005]    A conventional rivet gun comprises a barrel, a handle, a trigger, a pin collector and a pneumatic cylinder. 
         [0006]    The barrel has a front end, a rear end and a vise assembly that may vise and pull a core pin of a rivet on the front end into the barrel. The handle is mounted perpendicularly on the barrel and has air passageways. The collector is a jar mounted on the rear end of the barrel to collect the ejected core pins. The pneumatic cylinder is mounted movably under the handle and capable of activating the vise assembly through pneumatic and hydraulic means. Furthermore, the pneumatic cylinder may be connected to a high-pressure air source such as an air bottle to implement the ejection of the core pin. 
         [0007]    When the rivet gun is used to rivet two pieces such as boards or plates together, a rivet is mounted through the pieces. The enlarged end of the cap of the rivet abuts an inside piece and the front end of the barrel of the rivet gun abuts the enlarged end. The trigger is pulled to activate the vise assembly to pull a core pin on the cap into the barrel. The ball on the core pin longitudinally compresses and radially expands the mounting end of the cap into T-shape so that the expanded mounting end hooks on an outside piece to complete the riveting process. Then, the air output by the high-pressure air source flows through the barrel from the front end to the rear end and sucks the broken core pin vised by the vise assembly backward into the collector 
         [0008]    A casing of the pneumatic cylinder is formed integrally and manufactured by insert-molding processes to ensure good airtight/watertight properties thereof. However, disassembling the integrally formed casing is not easy, which raises the difficulty of repairing or replacing components inside the pneumatic cylinder. Therefore, the whole pneumatic cylinder is frequently replaced even though only few inside components are damaged. Maintaining the rivet gun is expensive. 
         [0009]    To overcome the shortcomings, the present invention provides a control valve for ejecting rivet pieces of a rivet gun to mitigate or obviate the aforementioned problems. 
       SUMMARY OF THE INVENTION 
       [0010]    The main objective of the invention is to provide a control valve that is mounted in a rivet gun and capable of ejecting rivet pieces such as core pins of a rivet toward a collector on a rear end of a barrel of the rivet gun. The control valve adjusts the ejection speed of the rivet pieces to prevent excessive impact of the rivet pieces to the collector probably damaging the collector and noise incurred thereby. 
         [0011]    A control valve for ejecting rivet pieces of a rivet gun in accordance with the present invention comprises an adapter, a bushing, a first valve member and a second valve member. The adapter has cavity and a mounting hole. The bushing is mounted in the mounting hole of the adapter and has a through hole. The first and second valve members are mounted respectively on front and rear ends of the bushing into the through hole. An internal air space is defined between the first and second valve members. Changing the size of the internal air space adjusts an airflow rate inside the control valve so that the moving speed of a rivet piece through the control valve can be controlled. 
         [0012]    Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a cross sectional perspective view of a control valve for ejecting rivet pieces of a rivet gun in accordance with the present invention; 
           [0014]      FIG. 2  is a cross sectional side view of the control valve and the rivet gun in  FIG. 1 ; 
           [0015]      FIG. 3  is a perspective view of the control valve in  FIG. 1 ; 
           [0016]      FIG. 4  is another perspective view of the control valve in  FIG. 1 ; 
           [0017]      FIG. 5  is an exploded perspective view of the control valve in  FIG. 3 ; 
           [0018]      FIG. 6  is another exploded perspective view of the control valve in  FIG. 3 ; 
           [0019]      FIG. 7  is a cross sectional side view of the control valve in  FIG. 1  omitting the adapter; and 
           [0020]      FIG. 8  is an operational cross sectional side view of the control valve in  FIG. 7  omitting the adapter. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0021]    With reference to  FIGS. 1 and 2 , a control valve  1  for ejecting rivet pieces of a rivet gun in accordance with the present invention may be mounted on a rivet gun  90 . The rivet gun  90  has a barrel  91 , a handle and a pin collector  93 . The barrel  91  has a rear end on which the control valve  1  is mounted and an air passageway  92  defined longitudinally. The handle is mounted under the barrel  91 . The pin collector  93  is mounted behind the control valve  1  to collector core pins of rivets. 
         [0022]    With further reference to  FIGS. 3 to 6 , the control valve comprises an adapter  10 , a bushing  20 , a first valve member  30  and a second valve member  40 . 
         [0023]    The adapter  10  is mounted on the rear end of the barrel  91 , has a front end, a rear end  12 , a cavity  11  and a mounting hole  13  and may have a front outer thread  101  and a rear outer thread  102 . The cavity  12  is defined in the front end of the adapter  10 . The mounting hole  13  is defined in the rear end of the adapter  10 , communicates with the cavity  11  and may have an inner surface and an internal thread formed on the inner surface. The front outer thread  101  and rear outer thread  102  are formed respectively on the front end and rear end  12  of the adapter  10  and are connected respectively to the rear end of the barrel  91  and the pin collector  93 . 
         [0024]    With further reference to  FIGS. 7 and 8 , the bushing  20  is mounted in the mounting hole  13  of the adapter  10 , extends out from the rear end of the adapter  10  and has a front end, a rear end, a through hole  21 , a first inner thread  25 , a second inner thread  26  and at least one air channel  215  and may further have an outer flange  22  and an external thread  23 . 
         [0025]    The through hole  21  is defined longitudinally through the bushing  20  and has an inner surface. 
         [0026]    The first inner thread  25  is formed on the inner surface of the through hole  21  adjacent to the front end of the bushing  20 . 
         [0027]    The second inner thread  26  is formed on the inner surface of the through hole  21  behind the first inner thread  25 . 
         [0028]    The at least one air channel  215  is defined longitudinally in the front end of the bushing  20  and communicates with the through hole  21 . The at least one air channel  215  may have a front opening and a rear opening. The front opening is defined at the front end of the bushing  20 . The rear opening is defined at the inner surface of the through hole  21 . 
         [0029]    The outer flange  22  is formed on and protrudes radially from the front end of the bushing  20 , is mounted in the cavity  11  of the adapter  10  and presses against an inside wall of the rear end  12  of the adapter  10 . 
         [0030]    The external thread  23  is formed on the bushing  20  and engages with the internal thread of the mounting hole  13  of the adapter  10 . 
         [0031]    The first valve member  30  is mounted in the through hole  21  through the front end of the bushing  20  and has a front end, a rear end, a first air hole  31  and a first outer threaded element  35  and may further have a tapered section  32 . 
         [0032]    The first air hole  31  is defined longitudinally through the first valve member  30  and may allow a core pin of a rivet to pass therethrough. 
         [0033]    The first outer threaded element  35  is formed on the first valve member  30  and engages with the first inner thread  25  of the bushing  20  so that rotating the first valve member  30  longitudinally moves the first valve member  30  in the through hole  21  of the bushing  20 . 
         [0034]    The tapered section  32  is formed on the rear end of the first valve member  30 . 
         [0035]    The second valve member  40  is mounted in the through hole  21  through the rear end of the bushing  20 , has a front end, a rear end, a second air hole  41  and a second outer threaded element  46  and may further have a funneled opening  42 , a stopper  45 , an annular groove  47  and an O-ring  48 . 
         [0036]    The second air hole  41  is defined through the second valve member  40  and may allow a core pin of a rivet to pass therethrough. 
         [0037]    The second outer threaded element  46  is formed on the second valve member  40  and engages with the second inner thread  26  so that rotating the second valve member  40  longitudinally moves the second valve member  40  in the through hole  21  of the bushing  20  to change a distance between the rear end of the first valve member  30  and the front end of the second valve member  40 . An internal air space S is defined between the rear end of the first valve member  30 , the front end of the second valve member  40  and the inner surface of the through hole  21 , communicates with the first air hole  31  and the second air hole  41  and may communicate with the rear opening of the at least one air channel  215 . The internal air space S changes according to the variation of the distance between rear end of the first valve member  30  and the front end of the second valve member  40 . 
         [0038]    The funneled opening  42  is defined in the front end of the second valve member  40  and corresponds to the tapered section  32  of the first valve member  30 . 
         [0039]    Preferably, the internal air space S is an annular passageway that is defined between the tapered section  32  of the first valve member  30  and the funneled opening  42  of the second valve member  40 . 
         [0040]    The stopper  45  is formed on and protrudes radially from the rear end of the second valve member  40  and selectively presses against the rear end of the bushing  20  to prevent the second valve member  45  from excessively extending into the through hole  21 . 
         [0041]    The annular groove  47  is defined radially in the second valve member  40   
         [0042]    The O-ring  48  is mounted in the annular groove  47  and hermetically contacts the inner surface of the through hole  21  of the bushing  20 . 
         [0043]    The internal air space S between the first valve member  30  and the second valve member  40  changes depending on the distance therebetween. When the internal air space S is reduced, the flow rate of air from the at least one air channel  215  to the internal air space S is lowered. The core pin of a rivet in the first air hole  31  suffers a lower suction force and moves toward the second air hole  41  at a lower speed. When the intern air space S is enlarged, the flow rate of the air from the at least one air channel  215  to the internal air space S is raised. The core pin in the first air hole  31  suffers a higher suction force so moves toward the second air hole  41  at a higher speed. Therefore, the control valve may adjust and lower the speed of the core pin to prevent excessive impact to the pin collector  93 . 
         [0044]    Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only. Changes may be made in the details, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.