Patent Publication Number: US-8985425-B2

Title: Fluid supply control device and gas combustion type nailer

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     The present application claims the benefit of priority of Japanese Patent Application No. 2010-167136, filed on Jul. 26, 2010, the disclosure of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a fluid supply control device and a gas combustion type nailer including the fluid supply control device. 
     BACKGROUND 
     A gas combustion type nailer is configured to send gas fuel from a fuel gas can to a cylinder of a striking mechanism and to ignite and combust the gas fuel, thereby driving a piston inside the cylinder by a combustion pressure to strike a fastener such as a nail (see, e.g., Japanese Patent No. 2956004 B2). To send the gas fuel to the cylinder with a constant amount per strike, a gauging chamber is connected to an ejection nozzle of the fuel gas can. A certain amount of gas fuel from the fuel gas can is charged in the gauging chamber, is sent to the cylinder via a solenoid valve. The solenoid valve is arranged between an inlet and an outlet of the gauging chamber, i.e., between the inlet through which the gas fuel is introduced from the fuel gas can and the outlet from which the gas fuel is supplied to the cylinder. When the solenoid valve opens the outlet of the gauging chamber, the fuel gas inside the gauging chamber is sent to the cylinder. When the solenoid valve closes the outlet of the gauging chamber, the certain amount of fuel gas is charged in the gauging chamber from the inlet. 
     Also in other related art, a fluid supply control device using a solenoid valve is configured in a similar manner (see, e.g., Japanese Patent No. 3063983 B2). 
     According to the fluid supply control device described above, when the solenoid valve closes the outlet of the gauging chamber, a certain amount of fluid is charged in the gauging chamber. However, when the solenoid valve opens the outlet of the gauging chamber, the fluid in the gauging chamber is discharged from the outlet, and at the same time, a subsequent fluid flows into the gauging chamber from the inlet. Therefore, the fluid is supplied slightly more than the certain amount. This error is related to a driving speed of the solenoid valve and a flow velocity of the fluid. The flow velocity is related to the pressure and viscosity of the fluid. For example, a temperature change causes a change in vaporization pressure of the fuel gas, and accordingly, a change in the flow velocity of the fuel gas. Further, the driving speed of the solenoid valve is influenced by the flow velocity of the fuel gas, and is not always the same. Therefore, for example, in the gas combustion type nailer described above, striking force of the gas combustion type nailer becomes unstable. 
     SUMMARY 
     Illustrative aspects of the present invention provide a fluid supply control device capable of supplying an accurate amount of fluid and a gas combustion type nailer including the fluid supply control device. 
     According to an illustrative aspect of the present invention, a fluid supply control device is provided. The fluid supply control device includes a gauging chamber configured to be charged with a fluid from a fluid supply source, an inlet port through which the fluid flows into the gauging chamber, an outlet port through which the fluid flows out from the gauging chamber, a first valve element arranged inside the gauging chamber to close the inlet port, a second valve element arranged inside the gauging chamber to close the outlet port, an electromagnetic biasing structure configured to electromagnetically bias the first valve element and the second valve element, and an elastic biasing structure configured to elastically bias at least one of the first valve element and the second valve element. The first valve element and the second valve element are configured and arranged such that the first valve element and the second valve element are independently movable and are actuated with a time difference. 
     According to another illustrative aspect of the present invention, a gas combustion type nailer is provided. The gas combustion type nailer includes the fluid supply control device described above, a combustion chamber to which fuel gas from a fuel gas can is supplied through the fluid supply control device, and a striking mechanism driven by a combustion of the fuel gas in the combustion chamber. 
     Other aspects and advantages of the present invention will be apparent from the following description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a longitudinal sectional view of a fluid supply control device according to an exemplary embodiment of the present invention, illustrating a standby condition of the fluid supply control device; 
         FIG. 1B  is another longitudinal sectional view of the fluid supply control device of  FIG. 1A , illustrating the fluid supply control device in operation; 
         FIG. 1C  is yet another longitudinal sectional view of the fluid supply control device of  FIG. 1A , illustrating the fluid supply control device supplying a fluid; 
         FIG. 2A  is a longitudinal sectional view of a fluid supply control device according to another exemplary embodiment of the present invention, illustrating a standby condition of the fluid supply control device; 
         FIG. 2B  is another longitudinal sectional view of the fluid supply control device of  FIG. 2A , illustrating the fluid supply control device in operation; 
         FIG. 2C  is yet another longitudinal sectional view of the fluid supply control device of  FIG. 2A , illustrating the fluid supply control device supplying a fluid; 
         FIG. 3A  is a longitudinal sectional view of a fluid supply control device according to another exemplary embodiment of the present invention, illustrating a standby condition of the fluid supply control device; 
         FIG. 3B  is another longitudinal sectional view of the fluid supply control device of  FIG. 3A , illustrating the fluid supply control device in operation; 
         FIG. 3C  is yet another longitudinal sectional view of the fluid supply control device of  FIG. 3A , illustrating the fluid supply control device supplying a fluid; 
         FIG. 4A  is a longitudinal sectional view of a fluid supply control device according to another exemplary embodiment of the present invention, illustrating a standby condition of the fluid supply control device; 
         FIG. 4B  is another longitudinal sectional view of the fluid supply control device of  FIG. 4A , illustrating the fluid supply control device in operation; 
         FIG. 4C  is yet another longitudinal sectional view of the fluid supply control device of  FIG. 4A , illustrating the fluid supply control device supplying a fluid; 
         FIG. 5A  is a longitudinal sectional view of a fluid supply control device according to another exemplary embodiment of the present invention, illustrating a standby condition of the fluid supply control device; 
         FIG. 5B  is another longitudinal sectional view of the fluid supply control device of  FIG. 5A , illustrating the fluid supply control device in operation; 
         FIG. 5C  is yet another longitudinal sectional view of the fluid supply control device of  FIG. 5A , illustrating the fluid supply control device supplying a fluid; 
         FIG. 6A  is a longitudinal sectional view of a fluid supply control device according to another exemplary embodiment of the present invention, illustrating a standby condition of the fluid supply control device; 
         FIG. 6B  is another longitudinal sectional view of the fluid supply control device of  FIG. 6A , illustrating the fluid supply control device in operation; 
         FIG. 6C  is yet another longitudinal sectional view of the fluid supply control device of  FIG. 6A , illustrating the fluid supply control device supplying a fluid; 
         FIG. 7A  is a longitudinal sectional view of a fluid supply control device according to another exemplary embodiment of the present invention, illustrating a standby condition of the fluid supply control device; 
         FIG. 7B  is another longitudinal sectional view of the fluid supply control device of  FIG. 7A , illustrating the fluid supply control device in operation; 
         FIG. 7C  is yet another longitudinal sectional view of the fluid supply control device of  FIG. 7A , illustrating the fluid supply control device supplying a fluid; 
         FIG. 8A  is a longitudinal sectional view of a fluid supply control device according to another exemplary embodiment of the present invention, illustrating a standby condition of the fluid supply control device; 
         FIG. 8B  is another longitudinal sectional view of the fluid supply control device of  FIG. 8A , illustrating the fluid supply control device in operation; 
         FIG. 8C  is yet another longitudinal sectional view of the fluid supply control device of  FIG. 8A , illustrating the fluid supply control device supplying a fluid; 
         FIG. 9  is a longitudinal sectional view of a gas combustion type nailer having one of the fluid supply control devices of  FIGS. 1A to 8A ; and 
         FIG. 10  is a timing chart illustrating operations for preventing a nailer from being actuated without a fuel gas being mounted; 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1A  is a longitudinal sectional view of a fluid supply control device according to an exemplary embodiment of the present invention. A fluid is not particularly limited, and for example, a liquid is suitable. 
     The fluid supply control device is arranged on a passage between a fluid supply source A and a supply target B. A device body  1  includes a hollow coil receiving part  1   a  and a metallic valve seat block  1   b  covering an upper opening of the coil receiving part  1   a . An electromagnetic coil  2  (an example of an electromagnetic biasing structure) is accommodated in the receiving unit  1   a , and a magnetic body  3  is disposed above the electromagnetic coil  2 . A core  5  is provided in a lower region of a hollow portion of the device body  1 . The core  5  has a first valve seat  4   a , and an inlet port  6  is formed inside the first valve seat  4   a . The valve seat block  1   b  has a second valve seat  4   b , and an outlet port  7  is formed at the center of the second valve seat  4   b . A cylindrical gauging chamber  8  is formed between the inlet port  6  and the outlet port  7 . In the gauging chamber  8 , a first valve element  10  and a second valve element  11  are arranged so as to be slidable in a vertical direction, such that the first valve element  10  opens and closes the inlet port  6 , and the second valve element  11  opens and closes the outlet port  7 . An inflow pressure from the fluid supply source is constantly applied to the inlet port  6 . 
     The first valve element  10  and the second valve element  11  are made of iron (a soft magnetic body) and both are biased to move down by electromagnetic force when the electromagnetic coil  2  is excited. A seal member  12  is provided at the center of the lower end of the first valve element  10  to close an opening end of the inlet port  6 . An annular spacer  13   a  is formed on the lower end of the second valve element  11 . A seal member  14  is provided at the center of the upper end of the second valve element  11 . Further, a flange  15  is formed along a circumference of the upper end of the second valve element  11 . An annular recess  16  is formed in the valve seat block  1   b  at a position corresponding to the upper portion of the second valve element  11 , and a spring  17  (an example of an elastic biasing structure) is arranged in the recess  16 . The upper end of the spring  17  is coupled to the flange  15  of the second valve element  11 , and as a result, the second valve element  11  is constantly biased toward its top dead point. 
     The first valve element  10  receives the inflow pressure of the fluid to open the inlet port  6 . The second valve element  11  receives the spring force of the spring  17  and the inflow pressure to close the outlet port  7 . By the electromagnetic force of the electromagnetic coil  2 , the first valve element  10  is biased in a direction to close the inlet port  6  against the inflow pressure, and the second valve element  11  is biased in a direction to open the outlet port  7  against the spring force and the inflow pressure. 
     The spring force of the spring  17  is smaller than the electromagnetic force of the electromagnetic coil  2 . 
     Inside the gauging chamber  8 , a certain amount of fluid is charged in a space other than the first valve element  10  and the second valve element  11 . The gauging chamber  8  includes the recess  16 . Outer diameters of the first valve element  10  and the second valve element  11  are smaller than an inner diameter of the gauging chamber  8 , whereby a gap  18  is formed to allow the fluid to flow from the inlet port to the outlet port. 
     The first valve element  10  and the second valve element  11  are actuated with a time difference by the electromagnetic force of the electromagnetic coil, the spring force, and the inflow pressure of the fluid from the fluid supply source. For example, the first valve element  10  closes the inlet port  6 , and thereafter, the second valve element  11  opens the outlet port  7 . The second valve element  11  closes the outlet port  7 , and thereafter, the first valve element  10  opens the inlet port  6 . A distance between the first valve element  10  and the electromagnetic coil  2  is different from a distance between the second valve element  11  and the electromagnetic coil  2 . The first valve element  10  is placed between the second valve element  11  and the core  5 , and placed closer to the electromagnetic coil  2  than the second valve element  11 . Moreover, the second valve element  11  is biased upward by the spring  17 . As a result, the electromagnetic force of the electromagnetic coil  2  that acts on the first valve element  10  is stronger than the electromagnetic force of the electromagnetic coil  2  that acts on the second valve element  11 . Therefore, when the electromagnetic coil  2  is energized, the first valve element  10  on which the strong magnetic action acts is actuated to close the inlet port  6 , and thereafter, the second valve element  11  is actuated to open the outlet port  7 . When current to the electromagnetic coil  2  is shut off, the second valve element  11  closes the outlet port  7 , and thereafter, the first valve element  10  opens the inlet port  6 , by the spring force of the spring  17  and the inflow pressure of the fluid. 
     The spacer  13   a  of the second valve element  11  is made of a nonmagnetic material. Since a space is formed between the first valve element  10  and the second valve element  11  by the spacer  13   a , the first valve element  10  is placed closer to the electromagnetic coil  2  than the second valve element  11 . 
     According to the above configuration, in the standby condition, the first valve element  10  opens the inlet port  6  and the second valve element  11  closes the outlet port  7 , as shown in  FIG. 1A . Therefore, the fluid from the fluid supply source A is sent into the gauging chamber  8  from the inlet port  6  at a constant pressure. Since the outlet port  7  is closed, a certain amount of fluid is charged in the gauging chamber  8 . 
     To supply the fluid to the supply target B, the electromagnetic coil  2  is energized. By the electromagnetic force of the electromagnetic coil  2 , the first valve element  10  is actuated downward to close the inlet port  6  as shown in  FIG. 1B , and thereafter, the second valve element  11  is actuated downward against the spring force of the spring  17  to open the outlet port  7 , as shown in  FIG. 1C . When the first valve element  10  closes the inlet port  6 , the inflow of the fluid into the gauging chamber  8  through the inlet port  6  is stopped. Thereafter, when the second valve element  11  opens the outlet port  7 , the second valve element  11  lands on the upper end of the first valve element  10 . The fluid in the gauging chamber  8  moves upward through the longitudinal groove  18 , and is sent out from the outlet port  7  in a vaporized state. Accordingly, when the outlet port  7  is opened, the first valve element  10  closes the inlet port  6 , and as a result, the fluid from the fluid supply source A does not flow into the gauging chamber  8 . Therefore, the fluid charged in the gauging chamber  8  is accurately supplied to the supply target B with a certain amount. 
     When the supply of current to the electromagnetic coil  2  is shut off, the second valve element  11  is actuated by the spring  17  to close the outlet port  7 , as shown in  FIG. 1A . Thereafter, since the first valve element  10  moves upward by the inflow pressure from the fluid supply source A, the inlet port  6  is opened and the fluid is supplied into the gauging chamber  8  from the inlet port  6 . A certain amount of fluid is charged in the gauging chamber  8 , and a next supply actuation is prepared. 
     As described above, the difference in intensity of the electromagnetic forces of the electromagnetic coil  2  with respect to the first valve element  10  and the second valve element  11  is caused by a difference in distances from the electromagnetic coil  2  to the first valve element  10  and the second valve element  11 . By forming the space between the first valve element  10  and the second valve element  11 , the second valve element  11  is placed further away from the electromagnetic coil  2  than the first valve element  10 . Accordingly, since the distances from the electromagnetic coil  2  to the first valve element  10  and the second valve element  11  are different from each other, the first valve element  10  receives the magnetic action of the electromagnetic coil  2  more strongly than the second valve element  11  when the electromagnetic coil  2  is energized. Therefore, the first valve element  10  and the second valve element  11  are actuated with a time difference, such that the first valve element  10  is first actuated to close the inlet port  6  to create an airtight condition of the gauging chamber  8 , and thereafter, the second valve element  11  is actuated to open the outlet port  7 . Therefore, while the fluid in the gauging chamber  8  is discharged from the outlet port  7 , the fluid does not flow into the gauging chamber  8  from the inlet port  6 . That is, only the fluid inside the gauging chamber  8  is discharged toward the supply target B. When the energization is shut off, the second valve element  11  is first actuated by the force of the spring  17  to close the outlet port  7  and thereafter, the first valve element  10  is actuated to open the inlet port  6 . As a result, a certain amount of fluid is charged in the gauging chamber  8 , whereby a next supply actuation is prepared and the fluid supply control device is in a standby condition. 
     Accordingly, the first valve element  10  and the second valve element  11  are sequentially actuated. As a result, a certain amount of fluid is charged in the gauging chamber  8  and only the charged fluid is supplied from the outlet port  7  of the gauging chamber  8  to the supply target B. Therefore, an accurate amount of fluid can always be supplied to the supply target B. 
     The spacer causing the difference in the distance to the electromagnetic coil  2  is not limited to the annular spacer  13   a . For example, as shown in  FIG. 2A , an intermediate member  13   b  made of an electrically insulating material may be provided between the first valve element  10  and the second valve element  11 . Also by this configuration, when the electromagnetic coil  2  is energized from the standby condition, the first valve element  10  receives the magnetic action of the electromagnetic coil  2  more strongly than the second valve element  11 , and as a result, the first valve element  10  and the second valve element  11  are actuated with a time difference. That is, the first valve element  10  is first actuated to close the inlet port  6 , and thereafter, the second valve element  11  is actuated to open the outlet port  7 , as shown in  FIGS. 2B and 2C . Therefore, while the fluid in the gauging chamber  8  is discharged from the outlet port  7 , the fluid does not flow into the gauging chamber  8  from the inlet port  6 , and only the fluid in the gauging chamber  8  is discharged. When the energization is shut off, the second valve element  11  is first actuated by the force of the spring  17  to close the outlet port  7 , and thereafter, the first valve element  10  opens the inlet port  6 , as shown in  FIG. 2A . As a result, a certain amount of fluid is charged in the gauging chamber  8 , whereby a next supply actuation is prepared and the fluid supply control device is in a standby condition. 
     In  FIG. 2A , the same reference numerals refer to the same elements as  FIG. 1A . This similarly applies to the figures following  FIG. 3A . 
     The difference in distances to the electromagnetic coil  2  between the first valve element  10  and the second valve element  11  may be achieved by making the length of the first valve element  10  to be longer than the length of the second valve element  11 , as shown in  FIG. 3A . 
     Also in this case, when the electromagnetic coil  2  is energized from the standby condition, the first valve element  10  receives the magnetic action of the electromagnetic coil  2  more strongly than the second valve element  11 , and as a result, the first valve element  10  and the second valve element  11  are actuated with a time difference. That is, the first valve element  10  is first actuated to close the inlet port  6  and thereafter, the second valve element  11  is actuated to open the outlet port  7 , as shown in  FIGS. 3B and 3C . Therefore, while the fluid in the gauging chamber  8  is discharged, no fluid flows into the gauging chamber  8  from the inlet port  6 , that is, only the fluid inside the gauging chamber  8  is discharged. When the energization is shut off, the second valve element  11  is first actuated by the force of the spring  17  to close the outlet port  7 , and thereafter, the first valve element  10  is actuated to open the inlet port  6 , as shown in  FIG. 3A . As a result, a certain amount of fluid is charged in the gauging chamber  8 , whereby a next supply actuation is prepared and the fluid supply control device is in a standby condition. 
     The difference in intensity of the magnetic action of the electromagnetic coil  2  on the first valve element  10  and the second valve element  11  may also be achieved by other means. 
     For example, a magnetic property of the first valve element  10  may be different from a magnetic property of the second valve element  11 . Specifically, the first valve element  10  and the second valve element  11  may be formed by using materials having different magnetic permeability. In an example shown in  FIG. 4A , the first valve element  10  is made of a material having high magnetic permeability (e.g., stainless steel) and the second valve element  11  is made of a material having low magnetic permeability (e.g., stainless steel). 
     According to the above configuration, to supply the fluid to the supply target B, the electromagnetic coil  2  is energized. As shown in  FIG. 4B , first, the first valve element  10  having high magnetic permeability moves downward to close the inlet port  6  and stops the flowing in of the fluid into the gauging chamber  8 . Thereafter, when the second valve element  11  moves downward against the spring  17  to open the outlet port  7 , the second valve element  11  lands on the upper end of the first valve element  10 , as shown in  FIG. 4C . The fluid in the gauging chamber  8  moves upward and is sent out from the outlet port  7 . Accordingly, while the outlet port  7  is opened, the first valve element  10  closes the inlet port  6 , and as a result, the fluid does not flow into the gauging chamber  8  from the fluid supply source A. Therefore, the fluid charged in the gauging chamber  8  is accurately supplied to the supply target B with a certain amount. 
     When the supply of current to the electromagnetic coil  2  is shut off, the second valve element  11  is actuated by the spring  17  to close the outlet port  7 , as shown in  FIG. 4A . Thereafter, since the first valve element  10  moves upward by the inflow pressure from the fluid supply source A, the inlet port  6  is opened and the fluid from fluid supply source A is supplied into the gauging chamber  8  through the inlet port  6 . A certain amount of fluid is charged in the gauging chamber  8  and a next supply actuation is thus prepared. 
     According to the exemplary embodiments described above, the time difference actuation of first valve element  10  and second valve element  11  can be achieved with a simple structure and low cost. 
     The time difference actuation of the first valve element  10  and the second valve element  11  is not limited to the time difference actuation by the difference in intensity of the magnetic action of the electromagnetic coil  2  on the first valve element  10  and the second valve element  11 . For example, the time difference actuation of the first valve element  10  and the second valve element  11  may be achieved by a difference between a spring load (spring force) to the first valve element  10  and a spring load to the second valve element  11 . 
     For example, as shown in  FIG. 5A , the electromagnetic coil  2  is connected to a power supply device  19 , and the first valve element  10  and the second valve element  11 , each having a plate shape and made of magnetic material, are arranged above the electromagnetic coil  2  is a vertically movable manner. One end of the first valve element  10  is pivotably supported on the device body  1  and the other end of the first valve element  10  is biased upward by a first spring  17   a . One end of the second valve element  11  is pivotably supported on the device body  1  and the other end of the second valve element  11  is biased upward by a second spring  17   b . The spring force of the first spring  17   a  is smaller than that of the second spring  17   b . The outlet port  7  is formed in the upper part of the device body  1  and the inlet port  6  is formed on the lateral side of the device body  1 . The first valve element  10  moves upward to open the inlet port  6  and moves downward to close the inlet port  6 . The second valve element  11  moves upward to close the outlet port  7  and moves downward to open the outlet port  7 . 
     According to the above configuration, to supply the fluid to the supply target B, the power supply device  19  is switched on to energize the electromagnetic coil  2 , thereby exciting the electromagnetic coil  2 . As shown in  FIG. 5B , first, the first valve element  10  moves downward to close the inlet port  6  against the first spring  17   a  having the smaller spring load and stops the flowing of the fluid into the gauging chamber  8 . Thereafter, as shown in  FIG. 5C , the second valve element  11  moves downward against the second spring  17   b . As a result, the fluid in the gauging chamber  8  moves upward and is sent out from the outlet port  7 . Accordingly, while the outlet port  7  is opened, the first valve element  10  closes the inlet port  6 , and as a result, the fluid does not flow into the gauging chamber  8  from the fluid supply source A. Therefore, the fluid charged in the gauging chamber  8  is accurately supplied to the supply target B with a certain amount. 
     When the supply of current to the electromagnetic coil  2  is shut off, the second valve element  11  is actuated by the second spring  17   b  having the larger spring load to close the outlet port  7 , as shown in  FIG. 5A . Thereafter, the first valve element  10  is actuated by the first spring  17   a  having the smaller spring load, such that the inlet port  6  is opened and the fluid from the fluid supply source A is supplied into the gauging chamber  8  through the inlet port  6 . A certain amount of fluid is charged in the gauging chamber  8  and a next supply actuation is thus prepared. 
     Also in this exemplary embodiment, the time difference actuation of the first valve element  10  and the second valve element  11  can be achieved with a simple structure. 
     According to another exemplary embodiment, the first valve element  10  and the second valve element  11  are actuated with a time difference by attracting the first valve element  10  and the second valve element  11  by different electromagnetic coils. 
     For example, as shown in  FIG. 6A , a first electromagnetic coil  2   a  and a second electromagnetic coil  2   b  are connected to the power supply device  19 , a plate-shape magnetic first valve element  10  is arranged above the electromagnetic coil  2   a , and a plate-shape magnetic second valve element  11  is arranged above the electromagnetic coil  2   b . The first valve element  10  and the second valve element  11  are vertically movable. One end of the first valve element  10  is pivotably supported on the device body  1  and the other end of the first valve element  10  is biased upward by the first spring  17   a . One end of the second valve element  11  is pivotably supported on the device body  1  and the other end of the second valve element  11  is biased upward by the second spring  17   b . The outlet port  7  is formed in the upper part of the device body  1  and the inlet port  6  is formed on the lateral side of the device body  1 . The first valve element  10  moves upward to open the inlet port  6  and moves downward to close the inlet port  6 . The second valve element  11  moves upward to close the outlet port  7  and moves downward to open the outlet port  7 . 
     In the above configuration, to supply the fluid the supply target B from the standby condition of  FIG. 6A  in which the fluid from the fluid supply source A is charged in the gauging chamber  8  through the inlet port  6 , the first electromagnetic coil  2   a  is energized. As shown in  FIG. 6B , by electromagnetic attraction force of the electromagnetic coil  2   a , the first valve element  10  moves down to close the inlet port  6  against the spring force of the first spring  17   a  and stops the flowing of the fluid into the gauging chamber  8 . Thereafter, as shown in  FIG. 6C , when the second electromagnetic coil  2   b  is energized, the second valve element  11  moves downward against the spring force of the second spring  17   b  by the electromagnetic attraction force of the electromagnetic coil  2   b  to open the outlet port  7 , and the fluid in the gauging chamber  8  is sent out through the outlet port  7 . While the outlet port  7  is opened, the first valve element  10  closes the inlet port  6 , and as a result, the fluid does not flow into the gauging chamber  8  from the fluid supply source A. Therefore, the fluid charged in the gauging chamber  8  is accurately supplied to the supply target B with a certain amount. 
     When the supply of current to the electromagnetic coil  2   b  is shut off, the second valve element  11  is actuated by the second spring  17   b  to close the outlet port  7 . Thereafter, when the supply of current to the electromagnetic coil  2   a  is shut off, the first valve element  10  is actuated by the first spring  17   a , such that the inlet port  6  is opened and the fluid from the fluid supply source A is supplied into the gauging chamber  8  through the inlet port  6 . A certain amount of fluid is charged in the gauging chamber  8  and a next supply actuation is thus prepared. 
       FIG. 7A  shows another exemplary embodiment in which the first valve element  10  and the second valve element  11  are actuated with a time difference by attracting the first valve element  10  and the second valve element  11  using different electromagnetic coils. As shown in  FIG. 7A , the first electromagnetic coil  2   a  and the second electromagnetic coil  2   b  are connected to the power supply device  19 , the plate-shape magnetic first valve element  10  is arranged above the electromagnetic coil  2   a , and the plate-shape magnetic second valve element  11  is arranged above the electromagnetic coil  2   b . One end of the first valve element  10  is pivotably supported on the device body  1  and the other end of the first valve element  10  is biased upward by the first spring  17   a . One end of the second valve element  11  is pivotably supported on the device body  1  and the other end of the second valve element  11  is biased upward by the second spring  17   b . The spring force of the first spring  17   a  and the spring force of the second spring  17   b  may be the same. The electromagnetic force of the first electromagnetic coil  2   a  and the electromagnetic force of the second electromagnetic coil  2   b  may also be the same. The inlet port  6  and the outlet port  7  are formed in the upper part of the device body  1 . The first valve element  10  moves upward to close the inlet port  6  and moves downward to open the inlet port  6 . The second valve element  11  moves upward to close the outlet port  7  and moves downward to open the outlet port  7 . 
     In the above configuration, to supply the fluid to the supply target B from the standby condition of  FIG. 7A  in which the inlet port  6  and the outlet port  7  are closed, only the electromagnetic coil  2   a  is energized first. As shown in  FIG. 7B , by the electromagnetic attraction force of the electromagnetic coil  2   a , the first valve element  10  moves downward to open the inlet port  6  against the spring force of the first spring  17   a  to charge the fluid into the gauging chamber  8 . Thereafter, as shown in  FIG. 7C , the supply of current to the electromagnetic coil  2   a  is shut off, and the electromagnetic coil  2   b  is energized. The second valve element  11  moves downward against the spring force of the second spring  17   b  by the electromagnetic attraction force of the electromagnetic coil  2   b  to open the outlet port  7 , and the fluid in the gauging chamber  8  is sent out from the outlet port  7 . While the outlet port  7  is opened, the first valve element  10  closes the inlet port  6 , and as a result, the fluid does not flow into the gauging chamber  8  from the fluid supply source A. Therefore, the fluid charged in the gauging chamber  8  is accurately supplied to the supply target B with a certain amount. 
     When the supply of current to the electromagnetic coils  2   a  and  2   b  is shut off, the first valve element  10  and the second valve element  11  close the inlet port  6  and the outlet port  7  by the first spring  17   a  and the second spring  17   b , and a next supplying actuation is prepared. 
     According to the exemplary embodiment shown in  FIGS. 6A to 7C , the time difference actuation of the first valve element  10  and the second valve element  11  can be achieved only by an electrical timing control. Therefore, the time difference actuation can be performed accurately and reliably. 
       FIG. 8A  shows another exemplary embodiment in which the position of the spring  17  is changed. In the exemplary embodiment shown in  FIGS. 1A to 4C , the annular recess  16  is formed in the valve seat block  1   b  of the device body  1  and the spring  17  is disposed in the recess  16 . In contrast, according to the exemplary embodiment of  FIG. 8 , the spring  17  is arranged between the upper end of the core  5  and the lower-end of the first assembly body  10 . Specifically, the spring  17  is arranged between a shoulder portion of the core  5  formed around the inlet port  6  and the bottom surface of the first valve element  10 . The first valve element  10  and the second valve element  11  are constantly biased by the spring  17  toward their top dead points. 
     According to the above configuration, in the standby condition, by the inflow pressure of the fluid sent into the gauging chamber  8  from the inlet port  6  at a constant pressure and the pressure of the spring  17 , the first valve element  10  opens the inlet port  6  and the second valve element  11  closes the outlet port  7 , as shown in  FIG. 8A . Therefore, the fluid from the fluid supply source A is sent into the gauging chamber  8  through the inlet port  6  at a constant pressure, and a certain amount of fluid is charged in the gauging chamber  8 . 
     To supply the fluid to the supply target B, the electromagnetic coil  2  is energized. By the electromagnetic force of the electromagnetic coil  2 , the first valve element  10  moves downward against the spring force of the spring  17  to close the inlet port  6 , as shown in  FIG. 8B  and thereafter, the second valve element  11  moves downward to open the outlet port  7 , as shown in  FIG. 8C . When the first valve element  10  closes the inlet port  6 , the inflow of the fluid into the gauging chamber  8  is stopped. Thereafter, when the second valve element  11  opens the outlet port  7 , the second valve element  11  lands on the upper end of the first valve element  10  via the intermediate member  13   b . The fluid in the gauging chamber  8  moves upward through the longitudinal groove  18 , and is sent out from the outlet port  7  to the supply target B in a vaporized state. Accordingly, while the outlet port  7  is opened, the first valve element  10  is closed, and as a result, the fluid does not flow into the gauging chamber  8  from the fluid supply source A. Therefore, the fluid charged in the gauging chamber  8  is accurately supplied to the supply target B with a certain amount. 
     When the supply of current to the electromagnetic coil  2  is shut off, the first valve element  10  and the second valve element  11  move upward by the spring  17 , as shown in  FIG. 8A , such that the second valve element  11  closes the outlet port  7 . The first valve element  10  moves upward by the inflow pressure from the fluid supply source A, the inlet port  6  is opened, and the fluid from the fluid supply source A is supplied into the gauging chamber  8  through the inlet port  6 . A certain amount of fluid is charged in the gauging chamber  8  and a next supply actuation is thus prepared. 
     As described above, this exemplary embodiment can also provide similar advantages as the other exemplary embodiments. Further, because this exemplary embodiment does not include the recess  16  of the exemplary embodiment  FIGS. 1A to 4C , the overall height of the device body  1  can be reduced by an amount corresponding to the recess  16 , and as a result, the entire device can be downsized. 
     Next, a gas combustion type nailer including the fluid supply control device described above will be described. 
       FIG. 9  is a longitudinal sectional view of a gas combustion type nailer including the fluid supply control device. The nailer has a striking mechanism in a body  20 . The striking mechanism includes a cylinder  21 , a piston  22  accommodated inside the cylinder  21  in a vertically slidable manner, and a driver  23  integrally coupled to the piston  22 . A discharge nose portion  24  is formed below the body  20 . The driver  23  is provided to be slidable in the nose portion  24 . A magazine  25  is provided in the rear of the nose portion  24 . A front end of the magazine  25  is opened to the nose portion  24  and nails in the magazine  25  are sequentially supplied into the nose portion  24  from the magazine  25 . 
     A combustion chamber  26  is formed to be openable and closable in an upper part of the cylinder  21 . Fuel gas is injected into the combustion chamber  26  and the injected fuel gas is ignited and exploded. 
     A gas can receiving portion  28  is provided between a grip  27  provided in the rear of the body  20  and the magazine  25 . A gas can  29  charged with the fuel gas is accommodated in the gas can receiving portion  28 . When a front nozzle  30  of the gas can  29  is received in the gas can receiving portion  28 , the front nozzle  30  is connected to one end of a fuel pipeline  31  provided in the body  20 . The other end of the fuel pipeline  31  is opened to the combustion chamber  26 . A solenoid valve device  32  is provided in the middle of the fuel pipeline  31 . An ignition plug  33  is attached to the combustion chamber  26 . The ignition plug  33  is sparked by an ignition device  34  provided in the grip  27 . 
     The ignition device  34  and the solenoid valve device  32  are actuated by pushing a contact arm  35  provided on the front end of the nose portion  24  onto the workpiece. 
     When striking a nail, first, the lower end of the contact arm  35  is pushed onto the workpiece, whereby the combustion chamber is closed and the solenoid valve device  32  is actuated, such that a certain amount of fuel gas is supplied from the gas can  29 . The gas fuel is ejected into the combustion chamber from the ejection nozzle through the fuel pipeline  31 , and is mixed with air. 
     Thereafter, by pulling a trigger  36 , a circuit connected to the ignition plug  33  is switched on by the ignition device  34  and the mixed gas in the combustion chamber  26  is ignited. The mixed gas is combusted and explosively expanded. The pressure of the combustion gas acts on the top surface of the piston  22  to impulsively drive downward the piston  22 , such that the piston  22  strikes the nail supplied in the nose portion  24  to strike the nail into the workpiece. 
     When the trigger  36  is released and the nose portion  24  is separated from the workpiece, the nailer is restored to the standby condition and the combustion chamber is opened to discharge the combustion gas to the atmosphere. A certain amount of fuel gas is supplied to the solenoid valve device  32  and a next striking is prepared. 
     The solenoid valve device  32  includes any one of the fluid supply control devices shown in  FIGS. 1A to 8C , and controls the flow of the fuel gas so as to supply only a certain amount of fuel gas from the gas can  29 . 
     That is, the solenoid valve device  32  includes a gauging chamber in which the fuel gas (fluid) of an amount to be supplied to the combustion chamber  26  per strike is charged from the fuel gas can  29 , a first valve element closing the inlet port of the gauging chamber, and a second valve element closing the outlet port of the gauging chamber. The first valve element and the second valve element are actuated with a time difference by the electromagnetic force of the electromagnetic coil and the spring force. A certain amount of fuel gas is charged in the gauging chamber from the inlet port, and is supplied to the combustion chamber  26  from the outlet port of the gauging chamber. 
     According to the above configuration, the fuel gas is always supplied to the combustion chamber  26  by a certain amount. Therefore, insufficient striking of nails is prevented, thereby enabling a stable striking of the nails. 
     When a fluid supply control device according to one of the exemplary embodiments shown in  FIGS. 1A to 6A  and  FIGS. 8A to 8C  is used as the solenoid valve device  32 , the fuel gas for one strike is charged in the gauging chamber  8  of the solenoid valve device  32  in the standby condition. Therefore, when the contact arm  35  is pressed and the trigger  35  is pulled after removing the gas can from the nailer, the fuel gas for one strike remaining in the solenoid valve device  32  is still supplied to the combustion chamber and ignited. In the manner, a nail may be erroneously discharged. 
     Therefore, as shown in  FIG. 10 , a sensor switch that senses whether or not the gas can is present is provided in the gas combustion type nailer and when the sensor switch is in an off state, the gas combustion type nailer may be configured to prevent the ignition of the gas in the combustion chamber. When the sensor switch is in the off state, a fan motor may also be prevented from being driven. 
     According to the above configuration, when the gas can is mounted, the sensor switch is turned on. As a result, when a fan switch is turned on by pushing the contact arm onto the workpiece, the fan motor is driven and the solenoid valve of the solenoid valve device is opened to supply the fuel gas into the combustion chamber and agitated by a fan. Thereafter, by pulling the trigger, the mixed gas in the combustion chamber is ignited by an igniter discharge to actuate the nailer. In contrast, when the gas can is not mounted, the sensor switch is turned off. Therefore, even if the fan switch is turned on by pushing the contact arm onto the workpiece, the fan motor is not driven and a spark by the igniter discharge is not generated. Even if the trigger is pulled, the mixed gas in the combustion gas is not combusted, and thus, the nailer is not actuated. When the contact arm is moved away from the workpiece, the fan switch is tuned off and the combustion chamber is opened, so that the internal mixed gas is discharged to the atmosphere. Accordingly, it is possible to prevent a nail from being erroneously discharged by the fuel gas remaining in the solenoid valve device  32 .