Fuel-operated firing device and method for operating a firing device of this type

Abstract

The invention relates to a fuel-operated firing device for driving securing elements into a substrate, comprising at least one main combustion chamber for a fuel, a driving piston that can be driven out of the main combustion chamber in a firing direction by expandable gases, and a pre-chamber with which an ignition device is associated and in which a pressure acting on the main combustion chamber can build up prior to a fuel-air mixture being ignited in said main combustion chamber. In order to improve the efficacy and/or functionality during the driving in of securing elements using the fuel-operated firing device, the pre-chamber has at least two venting connections which are mutually spaced in an axial direction and which have passages that can be exposed conjointly in order to facilitate rapid venting of the pre-chamber.

Claims

1. A fuel-operated firing device for driving securing elements into a substrate, comprising at least one main combustion chamber for a fuel; a driving piston which can be driven out of the at least one main combustion chamber in a firing direction by expandable gases; and, a pre-chamber with which an ignition device is associated and in which a pressure acting on the at least one main combustion chamber can build up prior to a fuel/air mixture being ignited in said at least one main combustion chamber, wherein the pre-chamber has at least first and second venting connections spaced apart from one another in an axial direction and having through openings to enable rapid venting of the pre-chamber, wherein the at least first and second venting connections are provided with a non-return valve device.

2. The fuel-operated firing device according to claim 1, wherein the first venting connection in the axial direction is spaced further apart from the at least one main combustion chamber than the second venting connection.

3. The fuel-operated firing device according to claim 2, wherein the first venting connection is arranged in a vicinity of a stop and/or damping element for the driving piston.

4. The fuel-operated firing device according to claim 3, wherein each of the first and second venting connections comprise a series of through openings in a pre-chamber cylinder.

5. The fuel-operated firing device according to claim 4, the first and second venting connections comprise through openings in a control sleeve which, in an open position of the control sleeve, are made to overlap the through openings of the pre-chamber cylinder in order to expose the venting connections.

6. The fuel-operated firing device according to claim 5, wherein the control sleeve is combined with a non-return valve device for the first and second venting connections which opens if a positive pressure is present in the pre-chamber if the control sleeve is in the open position.

7. The fuel-operated firing device according to claim 6, wherein the non-return valve device comprises closing elements made of a spring steel material.

8. The fuel-operated firing device according to claim 2, wherein each of the first and second venting connections comprise a series of through openings in a pre-chamber cylinder.

9. The fuel-operated firing device according to claim 8, the first and second venting connections comprise through openings in a control sleeve which, in an open position of the control sleeve, are made to overlap the through openings of the pre-chamber cylinder in order to expose the venting connections.

10. The fuel-operated firing device according to claim 9, wherein the control sleeve is combined with a non-return valve device for the first and second venting connections which opens if a positive pressure is present in the pre-chamber if the control sleeve is in the open position.

11. The fuel-operated firing device according to claim 10, wherein the non-return valve device comprises closing elements made of a spring steel material.

12. The fuel-operated firing device according to claim 1, wherein each of the first and second venting connections comprise a series of through openings in a pre-chamber cylinder.

13. The fuel-operated firing device according to claim 12, the first and second venting connections comprise through openings in a control sleeve which, in an open position of the control sleeve, are made to overlap the through openings of the pre-chamber cylinder in order to expose the first and second venting connections.

14. The fuel-operated firing device according to claim 13, wherein the control sleeve is combined with the non-return valve device for the first and second venting connections which opens if a positive pressure is present in the pre-chamber if the control sleeve is in the open position.

15. The fuel-operated firing device according to claim 14, wherein the non-return valve device comprises closing elements made of a spring steel material.

16. The fuel-operated firing device according to claim 12, wherein a pre-chamber inlet is provided on an end of the pre-chamber cylinder remote from the at least one main combustion chamber.

17. The fuel-operated firing device according to claim 13, wherein a pre-chamber inlet is provided on an end of the pre-chamber cylinder remote from the at least one main combustion chamber.

18. The fuel-operated firing device according to claim 1, wherein the through openings of the first and second venting connections can be closed and exposed to enable rapid venting of the pre-chamber.

19. A method for operating a fuel-operated firing device according to claim 1, the method comprising venting the pre-chamber through the first and second venting connections.

20. A fuel-operated firing device for driving securing elements into a substrate, comprising at least one main combustion chamber for a fuel; a driving piston which can be driven out of the at least one main combustion chamber in a firing direction by expandable gases; and, a pre-chamber with which an ignition device is associated and in which a pressure acting on the at least one main combustion chamber can build up prior to a fuel/air mixture being ignited in said at least one main combustion chamber, wherein the pre-chamber has at least first and second venting connections spaced apart from one another in an axial direction and having through openings to enable rapid venting of the pre-chamber, wherein the driving piston travels over the second venting connection and discharges combustion gases from the at least one main combustion chamber through the second venting connection.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

(1) Further advantages, features and details of the invention are apparent from the following description in which various embodiments of the invention are described in detail with reference to the drawings. In the drawings:

(2) FIG. 1 shows a plan view of a fuel-operated bolt firing device in an unpressed initial state during scavenging of a main combustion chamber;

(3) FIG. 2 shows a longitudinal section of the bolt firing device from FIG. 1,

(4) FIG. 3 shows a plan view of the bolt firing device from FIGS. 1 and 2 in a pressed state with a closed main combustion chamber;

(5) FIG. 4 shows a longitudinal section of the bolt firing device from FIG. 3,

(6) FIG. 5 shows a perspective representation of the bolt firing device from FIGS. 3 and 4;

(7) FIG. 6 shows a longitudinal section of the bolt firing device from FIGS. 1 to 5 during ignition in the main combustion chamber with opened venting connections;

(8) FIG. 7 shows a longitudinal section of the bolt firing device from FIGS. 1 to 6 during thermal return of a driving piston with closed venting connections;

(9) FIG. 8 shows a perspective representation of a control device from FIGS. 1 to 6;

(10) FIG. 9 shows a plan view of the control device from FIG. 8;

(11) FIG. 10 shows a perspective representation of a non-return valve device which is integrated into the control device of FIGS. 8 and 9, and

(12) FIG. 11 shows a perspective representation of the control device from FIGS. 8 and 9 without the non-return valve device which is shown alone in FIG. 10.

DETAILED DESCRIPTION OF THE INVENTION

(13) FIGS. 1 to 7 show a highly simplified longitudinal section of a firing device 1 in different operating states and views. The firing device 1 shown in FIGS. 1 to 7 can be operated with a fuel gas or with a vaporizable liquid fuel. The firing device 1 comprises a housing 3 with a main cylinder 5 which delimits a main combustion chamber 6. The main combustion chamber 6 can be supplied with gas and/or air by means of an inlet device 8. Furthermore, an ignition device 9 is associated with the main combustion chamber 6.

(14) In FIGS. 1 to 7 a driving piston 10 is guided movably back and forth in the housing 3 of the firing device 1. The driving piston 10 comprises a piston rod 11 which extends from a piston head 12. A firing end 14 of the piston rod 11 remote from the piston head or piston plate 12 is arranged in a bolt guide which serves for operating securing elements which are also designated as bolts. In FIG. 7 is the firing end 14 of the piston rod 11 of the driving piston 10 is shown truncated.

(15) The bolt guide with the piston rod 11 of the driving piston 10 arranged therein is also designated as a firing unit. By means of the firing unit a securing element, such as a nail, bolt or the like, can be driven into a substrate (not shown). Before the firing of a securing element, the firing device 1 with its bolt guide is pressed onto the substrate and triggered. A switch (not shown) which is also designated as a trigger switch serves, for example, for triggering a firing operation. The switch is provided, for example, on a handle (likewise not shown) of the firing device 1.

(16) A firing device is indicated by an arrow 15 in FIGS. 1 to 7. During the firing of a securing element, the driving piston 10 with the piston rod 11 is greatly accelerated in the firing direction 15 in order to drive the securing element into the substrate. During the firing operation, the driving piston 10 is moved out of its starting position shown in FIG. 1, which corresponds to an upper or rear dead center, into an end position which corresponds to a lower or front dead center.

(17) A movement of the driving piston 10 towards the right in FIGS. 1 to 7 is delimited by a piston stop 16 fixed to the housing. The upper dead center of the driving piston 10 is defined by the piston stop 16. The piston stop 16 can be combined with a magnet device 17. The magnet device 17 serves, for example, to hold the driving piston 10 with a predetermined holding force in its starting position shown in FIG. 1.

(18) A movement of the driving piston 10 towards the left is delimited by stop and/or damping elements 28, 29. The stop and/or damping elements 28 constitute a buffer 110. The piston head 12 comprises a first piston surface 21 which faces the main combustion chamber 6. A second piston surface 22, which faces away from the main combustion chamber 6, delimits a pre-chamber 25 in a pre-chamber cylinder 24.

(19) The pre-chamber 25 constitutes a pre-combustion chamber with which an ignition device 26 and an inlet device 27 are associated. Furthermore, the stop and/or damping elements 28, 29 are arranged in the pre-chamber 25. A gas/air fuel mixture, which is ignited with the aid of the ignition device 26 in the pre-chamber 25, is supplied to the pre-chamber or pre-combustion chamber 25 by means of the inlet device 27.

(20) The pre-chamber cylinder 24 comprises through openings 31, 32 which, for example, enable the exhaust gases to exit the pre-chamber 25. The through openings 31, 32 can be closed as required by a control device 30. The control device 30 comprises a control sleeve 34 which has through openings 37, 38.

(21) If the through openings 37, 38 of the control sleeve 34 are made to overlap the through opening 31, 32, then the through openings 31, 32 are opened, as can be seen in FIG. 6. In FIGS. 1 to 5 and 7 the through openings 31, 32 are closed by the control sleeve 34. The control sleeve 34 has substantially the configuration of a straight circular cylindrical shell and is illustrated in detail in FIG. 11.

(22) Overflow openings 41, 42 are provided between the pre-chamber 25 and the main combustion chamber 6. A valve device 43, 44 is associated with each of the overflow openings 41, 42. The valve devices 43, 44 are, for example, valve flaps which enable a passage of an ignited air/fuel mixture from the pre-chamber 25 into the main combustion chamber 6.

(23) The control device 30 comprises a control pressure surface 45, which is connected to the main combustion chamber 6 for control pressure purposes. The control pressure surface 45 is designed as an annular surface 46 which faces the main combustion chamber 6 radially outside the pre-chamber cylinder 24. The control pressure surface 45 is coupled mechanically to the control sleeve 34 by means of a coupling element 48.

(24) The coupling element 48 is designed as a slider 50 which, in FIGS. 1 to 7, is guided movably back and forth in the horizontal direction on the pre-chamber cylinder 24. The control pressure surface 45 designed as an annular surface 46 is provided on a right-hand end 51 of the slider 50 in FIGS. 1 to 7. The control control sleeve 34 is fastened to a left-hand end 52 of the slider 50 in FIGS. 1 to 7.

(25) Furthermore, the control device 30 comprises spring devices 54, 55 which are designed, for example, as helical compression springs. Housing-mounted stops 56, 57 are in each case associated with the left-hand ends of the spring devices 54, 55 in FIGS. 1 to 7. The housing-mounted stops 56, 57 are provided on the pre-chamber cylinder 24.

(26) The spring devices 54, 55 are clamped between the housing-mounted stops 56, 57 and the right-hand end 51 of the slider 50 having the control pressure surface 45. Thus, the slider 50 is supported on the housing-mounted stops 56, 57 by means of the spring devices 54, 55.

(27) In FIGS. 1 and 2 the bolt firing device 1 is shown in an unpressed state. “Unpressed state” means that the firing end 14 of the driving piston 10 is not acted upon by a pressing force. When pressed, the bolt firing device 1 is pressed with the firing end 14 against the substrate.

(28) The main combustion chamber 6 is delimited by a combustion chamber sleeve 84 which can be moved to a limited extent in the axial direction in order to enable scavenging of the main combustion chamber 6. A fan 80 is arranged in the main combustion chamber 6.

(29) In FIG. 2 the position of the combustion chamber sleeve 84 is such that the fan 80 generates an air stream 81, 82, indicated by arrows, from the rear face of the device, that is to say the right-hand face in FIG. 2, through the main combustion chamber 6 into the environment. After a firing operation exhaust gases are transported out of the main combustion chamber 6 by the air stream 81, 82. Furthermore, the air stream 81, 82 ensures cooling of the main combustion chamber 6.

(30) In FIGS. 3 to 6 the bolt firing device 1 is shown in a pressed state. In the pressed state the tool tip of the bolt firing device 1 is pressed against a substrate. Due to the pressing movement the combustion chamber sleeve 84 is moved rearwards, that is to say towards the right in FIG. 4, as indicated by an arrow 83 in FIG. 4. The main combustion chamber 6 is closed off from the environment towards the rear by the movement 83 of the combustion chamber sleeve 84.

(31) As described below, fuel gas is injected into the pre-chamber 25 by means of the inlet device 27 and into the main combustion chamber 6 by means of the inlet device 8. During injection of the fuel gas into the pre-chamber 25 and into the main combustion chamber 6 the fan 80 rotates in the main combustion chamber 6.

(32) The ignition of the gas mixture is initiated by the ignition device 26 which is associated with the pre-chamber 25 and located in the vicinity of the buffer 110. After the ignition of the gas mixture in the pre-chamber 25, a flame front propagates, travelling from the side of the buffer 110 in the direction of the main combustion chamber 6, that is to say towards the right in FIG. 4. In this case the propagating flame front pushes uncombusted air/fuel mixture ahead of it at high pressure into the main combustion chamber 6.

(33) The overflow from the pre-chamber 25 into the main combustion chamber 6 takes place by means of the overflow openings 41, 42 with the valve devices 43, 44 open. The valve devices 43, 44 are, for example, designed as non-return valves which expose the overflow openings 41, 42, which are also designated as ignition openings, during propagation of the laminar flame front.

(34) When the flame front has reached the non-return valves of the valve devices 43, 44, the flame can pass via the non-return valves into the main combustion chamber 6 for ignition, so that the main chamber combustion is initiated in the main combustion chamber 6. In FIG. 6 is the main chamber ignition in the main combustion chamber 6 is indicated by a symbol 86.

(35) During the main chamber ignition 86 the pressure in the main combustion chamber 6 rises and the control sleeve 34 is pushed forwards, that is to say towards the left in FIG. 6 as indicated by arrows 87, 88, against the force of the spring devices 54, 55 which are supported on the housing-mounted stops 56, 57. Two pressure relief connections 108, 109 of the pre-chamber 25 are opened by the movement 87, 88 of the control sleeve 34 forwards.

(36) The pre-chamber pressure escaping from the pre-chamber 25 by means of the opened venting connections 108, 109 is indicated by arrows 91 to 94 in FIG. 6. The pressure relief connections 108, 109 are also designated as exhaust outlets. The pre-chamber pressure can escape by means of the pressure relief connections or exhaust outlets 108, 109 at the main chamber ignition 86. At the main chamber ignition 86 the driving piston 10 moves at high speed and carries out a firing.

(37) In FIG. 7 the bolt firing device 1 is shown in longitudinal section during thermal return of the driving piston 10. After the driving piston 10 has reached the lower or front piston reversal point on the buffer 110, a main chamber residual pressure is discharged by means of the pressure relief connection 109. The consequence of this is that the main combustion chamber pressure in the main combustion chamber 6 drops to ambient pressure and the control sleeve 34 closes the exhaust outlets or pressure relief connections 108, 109 again in a pressure-controlled manner.

(38) After the firing a negative pressure is produced in the main combustion chamber 6 by cooling of the bolt firing device 1. This negative pressure in the main combustion chamber 6 leads to the driving piston 10 being retracted or drawn back into its starting position. In this case fresh air is sucked or drawn into the pre-chamber 25 of the bolt firing device 1 through a pre-chamber inlet 140 on the left-hand end of the pre-chamber cylinder 24 in FIG. 7. The drawing in of the fresh air is indicated by an arrow 141 in FIG. 7.

(39) A non-return valve on one side is advantageously associated with the pre-chamber inlet 140. The non-return valve comprises, for example, a relatively large spring lamella, which enables fresh air to be drawn into the pre-chamber 25, but in the reverse direction it prevents unwanted outflow of pressurized fuel/air mixture out of the pre-chamber 25 into the environment.

(40) When the bolt firing device 1 with the firing end 14, which is shown truncated in FIG. 7, is lifted off from the substrate, the combustion chamber sleeve 84 is moved again so that the main combustion chamber 6 can be scavenged with ambient air, as indicated by the arrows 81 and 82 in FIG. 2. Subsequently a new firing cycle can be started.

(41) The control device 30 is illustrated alone in different views in FIGS. 8 to 11. The control device 30 comprises the control sleeve 34 which is connected by means of the coupling element 48 to a coupling sleeve 100. The control pressure surface 45 designed as an annular surface 46 is provided on a free end of the coupling sleeve 100, that is to say the right-hand end of the coupling sleeve 100 FIG. 9.

(42) The coupling 100 is fixedly connected to a connecting flange 105 by means of slider rods 101, 102, 103 which partially constitute the slider 50. The connecting flange 105 connects the control sleeve 34 to the slider rods 101 to 103. On the other hand, the slider rods 101 to 103 are connected by means of a connecting flange 98 to the coupling sleeve 100. A spring device 54, 55 designed as a compression spring is associated with each slider rod 101 to 103. In the installed state of the control device 30 the spring devices 54, 55 are clamped between the connecting flange 98 and the housing-mounted stops 56, 57 on the pre-chamber cylinder 24.

(43) The control sleeve 34 serves to expose the through openings 31, 32; 117, 118 in the pre-chamber cylinder 24 as required, as indicated in FIG. 6 by the arrows 91 to 94. For this purpose the control sleeve 34 has the through openings 37, 38; 117, 118 which are made to overlap the through openings 31, 32; 111, 112 in the pre-chamber cylinder 24 for opening the venting connections 108, 109.

(44) In FIG. 10 it can be seen that the non-return valve device 120 comprises valve elements 121 to 123 which are connected to one another by a connecting ring member 124. Each of the valve elements 121 to 123 comprises two closing elements 127, 128, which are associated with through openings 37; 118 of the two pressure relief connections 108; 109. The valve elements 121 to 123 with the closing elements 127, 128 are formed integrally from spring steel. The production of the valve elements 121 to 123 with the closing elements 127, 128 takes place, for example, by laser beam cutting. The connecting ring member 124 can likewise be produced by laser beam cutting from a spring steel material.