Patent Publication Number: US-2015060514-A1

Title: Firing-operation totalizing device for a gas nail gun

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority of Taiwanese Application No. 102132018, filed on Sep. 5, 2013. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a counting device, and more particularly to a device for totalizing the number of the firing operations of a gas nail gun. 
     2. Description of the Related Art 
     Taiwanese Patent Publication No. 201242727 discloses a method for totalizing the number of the firing operations of a nail gun, in which a nail is struck by a high-pressure air produced due to explosion, and the number of the firing operations is totalized according to high-voltage discharge signals. 
     During operation of the gas nail gun, electricity is supplied from a battery set. However, since the gas nail gun includes a safety member for preventing misfiring, before a firing operation is performed, the electricity is supplied for activating the safety member if necessary. As such, the totalized number of the firing operations may be increased by one due to an inadvertent actuation of a trigger prior to operation of the safety member, or due to an actuation of the trigger prior to installation of a gas can. In other words, even if the nail gun is not fired, the totalized number of the firing operations may be increased due to unexpected high-voltage discharges, so that the number of the firing operations cannot be totalized accurately. 
     SUMMARY OF THE INVENTION 
     The object of this invention is to provide a device that can totalize accurately the number of the firing operations of a nail gun. 
     According to this invention, a firing-operation totalizing device for a gas nail gun includes two pressure areas, a pressure feedback unit mounted in a body, and an electric control unit. The pressure areas are constituted by an interior of a combustion chamber and an interior of a cylinder body. The pressure feedback unit outputs a pressure signal in response to each pressure change of at least one of the pressure areas. The electric control unit includes a control circuit that totalizes the number of the firing operations based on the pressure signals received thereby. As such, the totalized number of the firing operations is increased only when a pressure change of the at least one of the pressure areas occurs due to an explosion to totalize accurately the number of effective firing operations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of this invention will become apparent in the following detailed description of the embodiments of this invention, with reference to the accompanying drawings, in which: 
         FIG. 1  is a sectional view of a gas nail gun including the first embodiment of a firing-operation totalizing device according to this invention; 
         FIG. 2  is a fragmentary sectional view of the gas nail gun of  FIG. 1 ; 
         FIG. 3  is a fragmentary sectional view of a gas nail gun including the second embodiment of a firing-operation totalizing device according to this invention; 
         FIG. 4  is a fragmentary schematic view of a pressure feedback unit of the second preferred embodiment; 
         FIG. 5  is a front view of the gas nail gun, illustrating one modified alarm member of the firing-operation totalizing device, which is configured as a light emitting member; and 
         FIG. 6  is a front view of the gas nail gun, illustrating another modified alarm member of the firing-operation totalizing device, which is configured as a display. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Before the present invention is described in greater detail in connection with the embodiments, it should be noted that similar elements and structures are designated by like reference numerals throughout the entire disclosure. 
     Referring to  FIGS. 1 and 2 , the first embodiment of a firing-operation totalizing device according to this invention is used in a gas nail gun  2 . The gas nail gun  2  includes a body  22  defining a combustion chamber  21 , a cylinder body  23  disposed in the body  22 , a piston type impact member  24  contacting sealingly and extending outwardly from the cylinder body  23 , and a trigger unit  25  disposed on the body  22  and operable for activating the piston type impact member  24 . Upon an explosion in the combustion chamber  21 , the piston type  24  is movable along the cylinder body  23  to perform a nail-striking operation (i.e., firing operation). The firing-operation totalizing device includes first and second pressure areas (A, B), a pressure feedback unit  3 , and an electric control unit  4 . 
     The first and second pressure areas (A, B) are constituted by an interior of the combustion chamber  21  and an interior of the cylinder body  23 , respectively. 
     The pressure feedback unit  3  is mounted to the body  23 . In this embodiment, the pressure feedback unit  3  includes an air conduit  30  in fluid communication with and extending outwardly from the second pressure area (B), and a pressure sensor  31  connected to the air conduit  30 . The pressure sensor  31  measures a pressure (V) of air in the second pressure area (B) via the air conduit  30  to output a pressure signal. Alternatively, the air conduit  30  may be in fluid communication with and extend outwardly from the first pressure area (A), and the pressure sensor  31  is used to measure a pressure of air in the first pressure area (A) via the air conduit  30 . 
     The electric control unit  4  is mounted to the body  22 , and includes a control circuit  41  electrically connected to the pressure sensor  31 , and an alarm member  42  electrically connected to the control circuit  41 . The control circuit  41  has a preset threshold pressure value (V 0 ), and a preset number value (S 0 ), and totalizes the number (S) of the firing operations, which corresponds to the total number of the pressure signals. In this embodiment, the alarm member  42  is an audio warning device that can produce a warning message. In this embodiment, the message is a sound. 
     When the trigger unit  25  is actuated, the gas in the combustion chamber  21  is ignited to create an explosion. Upon explosion, the piston type impact member  24  is moved along the cylinder body  23  for striking a nail. Hence, air in the cylinder body  23  is compressed until the nail striking operation is completed. 
     When the trigger unit  25  is actuated, the pressure sensor  31  detects a pressure (V) and a pressure change in the second pressure area (B), so as to output the pressure signal to the control circuit  41 . When receiving the pressure signal, the control circuit  41  judges whether or not the pressure (V) is greater than the preset threshold pressure value (V 0 ). If yes, the pressure change must be created due to one effective firing operation. At this time, since one effective firing operation is identified by the control circuit  41 , the totalized number (S) of the firing operations is increased by one. When the totalized number (S) reaches the preset number value (S 0 ), the warning sound is produced by the alarm member  42  so that the user realizes that the totalized number (S) has reached the preset number value (S 0 ). 
       FIGS. 3 and 4  show the second embodiment of a firing-operation totalizing device according to this invention. Similar to the first embodiment, the second embodiment includes first and second pressure areas (A, B), a pressure feedback unit  3 , and an electric control unit  4 . Unlike the first preferred embodiment, the pressure feedback unit  3  includes a movable member  32 , and a trigger switch  33  disposed outside the second pressure area (B) and electrically connected to the control circuit  41 . The pressure feedback unit  3  further includes a seat body  121  connected to the air conduit  30 . The movable member  32  is configured as a piston rod that is movable on the seat body  321  to contact the trigger switch  33 . The trigger switch  33  may be a proximity switch or a microswitch, which outputs a pressure signal when contacted. 
     When the pressures in the first and second pressure areas (A, B) increase as a result of explosion in the combustion chamber  21  and movement of the piston type impact member  24 , the piston rod  32  is driven by compressed air in the second pressure area (B) to move to thereby contact the trigger switch  33  for outputting the pressure signal. Consequently, each pressure signal corresponds to one effective firing operation, so that the number (S) of the firing operations can be totalized accurately. 
     It is worth noting that, the alarm member  42  of each abovementioned embodiment may be a light emitting member (see  FIG. 5 ), or a display (see  FIG. 6 ). In this case, when the number (S) of the firing operations reaches the preset number value (S 0 ), the control circuit  41  controls the alarm member  42  to emit light or produce an image (e.g., of numerals) for warning. 
     To sum up, the firing-operation totaling device of this invention has the following advantage: 
     This invention takes pressure changes in the first and second pressure areas (A, B) as judgment source of the number (S) of the firing operations. Since pressures in the first and second pressure areas (A, B) can change only when explosions occur in the combustion chamber  21  to move the piston type impact member  24 . As a result, the number (S) of the firing operations can be totalized accurately. 
     With this invention thus explained, it is apparent that numerous modifications and variations can be made without departing from the scope and spirit of this invention. It is therefore intended that this invention be limited only as indicated by the appended claims.