REPEATING DETONATION DEVICE

Abstract: A purging and recharging system improves the repeating of detonations from a detonation device 10 having a detonation chamber 20 separated from an ignition chamber 25 by a detonation plate 22 having an opening 23 through which a flame jet can pass from ignition chamber 25 to detonation chamber 20. A differential piston 30 driven by a detonation in a differential cylinder 31, 32 around detonation chamber 20 affords a fluid passageway between differential piston 30 and detonation chamber 20. On a power stroke, differential piston 30 compresses recharging air and draws in cooling and exhaust purging air to surround detonation chamber 20. On a return stroke, differential piston 30 forces cooling and purging air into detonation chamber 20 and then admits com­ pressed recharging air into detonation chamber 20. A check valve 55 on the detonation side of the opening in detonation plate 22 admits fluid and flame from ignition chamber 25 into detonation chamber 20 during ignition and blocks backflow of fluid or flame from detonation chamber 20 into ignition chamber 25 during detonation.

Description: A repeating detonation device The present invention relates to a repeating detonation device according to the preamble of claim 1 and to a method of purging and recharging a detonation chamber of a repeating detonation device according to the preamble of claim 8. A repeating detonation device of that kind is known from US-A-4 599 861. This known repeating detonation device comprises a detonation chamber, a valved exhaust passageway from said detonation chamber and a recharging system using a differential free piston driven by a detonation for reciprocation within a differential cylinder. By this known device it is possible to rapidly burn a charge of fuel and air and to use the energy of that detonation to drive, e.g., a hand-operated fastener tool. A drawback of this known detonation device, however, lies therein that the power output of each detonation is not efficient. It therefore is the object of the present invention to improve a detonation device according to the preamble of claim 1 and to improve a method of purging and recharging a detonation chamber according to the preamble of claim 8 in such a way that efficiency of detonations can be improved. According to the present invention this object is achieved by the advantageous measures indicated in the characterizing portions of claim 1 and 8, respectively. These advantageous measures provide for a very high efficiency of detonation, so that the power output of each detonation can be increased without increasing fuel consumption. The invention will now be discussed in more detail in the following description with reference to the accompanying drawings in which: Fig.1 is a partially schematic, elevational, cross-sectional view of a preferred embodiment of the invention as applied to a hand-operated fastener driving tool; and Figures 2-4 are enlarged bottom views of a detonation plate suitable for the device of FIG. 1 and showing alternative preferred check valve arrangements. Tool 10, as shown in FIG. 1, is a hand-held fastener driving tool that conveniently illustrates a preferred way of applying the present invention to a practical purpose. However, the invention is not limited to fastener tools and applies to detonation devices used for other purposes. A detonation in detonation chamber 20 of device 10 is accomplished by an ignition chamber 25 as explained more fully below. But for some fuels and some circumstances, a detonation in chamber 20 can be initiated by a spark or flame not produced by ignition chamber 25. Tool 10 has a housing 11, a handle 12, a trigger 13, a fastener driver 14, and a fuel supply 15, all of which are schematically or partially illustrated as conventional components of a fastener driving tool. The improvement lies in a purging and recharging system using a differential piston 30 and associated valving and passageways that cooperate to accomplish effective purging and recharging for rapidly repeating detonations of improved efficiency. Differential piston 30 is a free piston and moves in a differential cylinder having a smaller bore 31 and a larger bore 32. Differential piston 30 also includes upstanding sidewalls forming a cylinder, as it were, within the piston. This inner cylinder or expansion chamber surrounds and is spaced from the wall 21 of detonation chamber 20. An inside bottom surface 33 of differential piston 30 forms a power piston that is driven downward by a detonation from chamber 20. A one-way seal 34 around an outer surface of differential piston 30 moves in smaller cylinder 31 to operate as a pump piston. Air is admitted to smaller cylinder 31 via an opening 35 covered by a one-way check valve 36 that lets air flow into cylinder 31 and blocks air outflow. As pump seal 34 moves downward on a power stroke, air in smaller cylinder 31 is compressed and escapes past seal 34 toward a plenum 16 in handle 12 where the compressed air is stored for recharging purposes. On a return stroke, as differential piston 30 moves upward, pump seal 34 draws more air into smaller cylinder 31 via passageway 35 and check valve 36. At the upper end of differential piston 30, a seal 37 runs in larger cylinder 32. Above seal 37 is a displacer piston surface 38, and below seal 37 is a return surface 39. When differential piston 30 is moving downward on a power stroke, displacer 38 draws in purging air via an air inlet opening 40 and a one-way seal 41. This purging air is drawn into larger cylinder 32 around the outside of detonation chamber wall 21 where it absorbs some heat transmitted through wall 21. A seal 42 engaging the inside of differential piston 30 cooperates with seal 37 around the outside of differential piston 30 so that purging air drawn into larger bore 32 on a power stroke of differential piston 30 is pumped into detonation chamber 20 on a return stroke. This is possible because of a fluid flow passageway 43 formed between chamber wall 21 and the inside of differential piston 30 and passageways 44 arranged inside of seal 42 and having check valves 45. A return stroke of differential piston 30 is caused partly by a vacuum that occurs after a detonation in chamber 20 and partly by recharging air that is compressed in plenum 16 during a power stroke. The compressed recharging air exerts force on return surface 39 to lift differential piston 30 to its uppermost position where seal 37 enters into port 47 and disengages from larger cylinder 32. This opens a passageway around seal 37 and over displacer surface 38 so that compressed recharging air flows around seal 37 in port 47 and follows the purging air down through passageway 43, passages 44, and check valves 45 to flow into detonation chamber 20. Such an arrangement also allows the compressed recharging air to fill chamber 20 with air at more than atmospheric pressure, which can substantially increase the force of a detonation. An exhaust system cooperates with differential piston 30 for exhausting burnt gases and some of the purging air to keep chamber 20 adequately cool, fully exhausted, and fully recharged with fresh air. Exhaust valve 50 controls an exhaust passageway 51 and is operated by a diaphragm 52 that is subject to the pressure of the compressed recharging air in plenum 16 as shown by the broken line arrow. It has been found that it is desirable to open exhaust valve 50 rapidly at the end of a power stroke so as to vent exhaust gases and residual heat as quickly as possible. Using the rising pressure of the recharging air that is compressed in plenum 16 on a power stroke to open exhaust valve 50 toward the end of a power stroke accomplishes this. When exhaust valve 50 opens, a pin 53 extending downward from exhaust valve 50 opens a check valve 55 covering opening 23 in detonation plate 22. This opens an exhaust route through valve 55, opening 23, ignition chamber 25, and exhaust passageway 51, venting both detonation chamber 20 and ignition chamber 25 to exhaust. Check valve 55 is loosely mounted on screws 54 and blocks any backflow of fluid or flame from detonation chamber 20 through opening 23 during a detonation. This improves the force and efficiency of a detonation. It is believed that this is due to the fact that ignition in chamber 25 forces some unburned fuel/air mixture into detonation chamber 20 ahead of a flame jet injected through opening 23. Then when the flame jet detonates the fuel/air mixture in detonation chamber 20, the force of the detonation slams check valve 55 closed over opening 23, trapping all the available fuel and air in chamber 20 for a more forceful detonation. Also, blocking any escape route through detonation plate 22 by the closure of check valve 55 forces the full detonation energy through the output from chamber 20 against power piston surface 33. Another function of check valve 55 is to divert a flame jet from ignition chamber 25 through opening 23 so that the flame spreads radially outward along detonation plate 22 toward the periphery of detonation chamber 20. There, a deflector surface 56 directs the radially spreading flame axially of detonation chamber 20 for an effective ignition. An alternative check valve arrangement as shown in FIG. 3 uses three reed valves 57 overlapping each other and covering opening 23 in detonation plate 22. Reed valves 57 not only cooperte to serve as check valves over opening 23, but also divide an incoming flame jet into three radial segments flowing in the spaces between reed valves 57 and deflected axially of detonation chamber 20 by peripheral deflector surfaces 58. Another reed check valve arrangement for detonation plate 22 as shown in FIG. 4 uses three reed valves 59 covering three openings 24 formed around the periphery of detonation plate 22. As reed valves 59 are forced open by flames injecting into the detonation chamber through openings 24, reed valves 59 deflect each flame jet from an axial path and make the flame jets swirl helically around the periphery of detonation chamber 20 for a fast and effective initiation of a detonation. Reed valves 59 also check any backflow of fuel or flame through openings 24 during a detonation. Piston 60 can be moved in handle 12 by knob 61 for manually pumping up the pressure of recharging air in plenum 16 for an initial detonation after which detonations can be repeated automatically and indefinitely. Air enters through opening 35 and check valve 36 as this occurs. Trigger 13 delivers a spark to spark plug 17 in ignition chamber 25 as schematically shown by a broken line arrow. An arrangement not shown injects fuel from container 15 into ignition chamber 25, also as schematically shown by a broken line arrow. The purging and recharging accomplished by differential piston 30 and its associated valves and passageways assures that adequate air is forced through detonation chamber 20 and ignition chamber 25 to purge exhaust gases and prevent heat build-up. The rapid action of the exhaust system in response to compressed recharging air cooperates to help make this possible. The recharging air pumped in by differential piston 30 and compressed during a power stroke also provides piston return force and ensures an adequate volume of recharging air, which can be compressed above atomospheric pressure to improve performance in detonation chamber 20. Fuel injection and spark ignition then ready tool 10 for an automatically repeatable detonation. Check valving the flame injection opening through detonation plate 22 not only cooperates with the exhaust system, but also increases the force of a detonation. This cooperates with the purging and recharging system to produce a large driving force from a small detonation chamber to increase the efficiency of the device.

Claims: A repeating detonation device comprising a detonation chamber (20), a valved exhaust passageway (51) from said detonation chamber, and a recharging system using a differential free piston (30) driven by a detonation for reciprocation within a differential cylinder (31, 32), characterized in that [a] said differential cylinder (31, 32) is surrounding said detonation chamber (20) with an annular space therebetween; [b] the top of said differential free piston (30) is having upward sidewalls extending into said annular space, thereby defining an expansion chamber which is communicating via a restricted opening with said detonation chamber (20) and which is disposed for reciprocation relative to said detonation chamber (20), said sidewalls affording a fluid passageway (43-45) around the periphery of said detonation chamber (20), and said differential free piston (30) being driven by a detonation from said detonation chamber (20); [c] said differential free piston is further comprising [c1] a pumping surface with a valving arrangement (34) which is compressing recharging air from an extension (31) of said differential cylinder being disposed below said detonation chamber (20); [c2] a displacer piston surface (38) at the top of said upward sidewalls which is drawing cooling and exhaust purging air into said annular space surrounding said detonation chamber (20) via a valving arrangement at the top of said differential cylinder (31, 32); and [c3] a return surface which, on a return stroke of said differential free piston (20) biased by compressed recharging air, is forcing said purging air through said fluid passageway (43-45) into said detonation chamber (20) and which, upon completion of said return stroke, is providing combustion air for the next power stroke via an enlarged part (47) of said differential cylinder (31, 32). A repeating detonation device according to claim 1, characterized in that said detonation chamber (20) is separated from an ignition chamber (25) by a detonation plate (22) which comprises an opening (23) through which a flame jet can pass from said ignition chamber (25) toward a peripheral region of said detonation chamber (20). A repeating detonation device according to claim 2, characterized by a check valve (55) which is arranged for diverting said flame jet from said ignition chamber (25) toward a peripheral region of said detonation chamber (20). A repeating detonation device according to claim 2, characterized in that said detonation chamber (20) comprises a plurality of openings (24) for admitting a plurality of said flame jets into said detonation chamber (20). A repeating detonation device according to claim 4, characterized by a check valve system (57; 59) which is arranged for permitting said flame jets to flow through said openings (24) during ignition, and to block backflow of fluid and flame from said detonation chamber (20) through said openings (24) to said ignition chamber (25) during detonation. A repeating detonation device according to claim 5, characterized in that said check valve system (57; 59) is arranged for diverting said flame jets from said ignition chamber (25) toward a peripheral region (56) of said detonation chamber (20). A repeating detonation device according to one of the preceding claims, characterized in that an exhaust valve (50) in said valved exhaust passageway (51) includes a diaphragm (52) which is controlling the opening of said exhaust valve (50) and means for communicating said compressed recharging air with said diaphragm (52) for controlling said exhaust valve. A method of purging and recharging a detonation chamber (20) of a repeating detonation device which comprises a valved exhaust passageway (51) from said detonation chamber, and a differential piston (30) driven by a detonation for reciprocating within a differential cylinder (31, 32), characterized by the following steps: [a] flowing fluid through an inlet passageway between said detonation chamber (20) and said differential piston (30) for purging and recharging said detonation chamber (20); [b] operating a valving system which cooperates with surfaces of said differential piston (30) and said differential cylinder (31, 32) in such a way that [b1] on a power stroke wherein said differential piston (20) is driven by a detonation from said detonation chamber (20), one side of said differential piston (20) compresses recharging air and another side of said differential piston (20) draws in purging air; [b2] on a return stroke of said differential piston (20) biased by compressed recharging air, said purging air is forced through said inlet passageway and into said detonation chamber (20); and [b3] upon completion of said return stroke, said compressed recharging air flows through said inlet passageway and into said detonation chamber (20) for recharging said detonation chamber (20) with air. A method according to claim 8, characterized by the step of opening an exhaust valve in said exhaust passageway from said detonation chamber (20) in response to compression of said recharging air during an end portion of said power stroke. A method according to claim 8 or 9, characterized by the step of initiating said detonation by injecting a flame from an ignition chamber (25) through a detonation plate (22) into said detonation chamber (20). A method according to claim 10, characterized by the step of diverting flame passing through said detonation plate (22) toward a peripheral region (56) of said detonation chamber (20).

Inventors: ADAMS, JOSEPH S.
Applicants: ADAMS, JOSEPH S.
Application year: 1987
Main classification: F02B71
IPC codes: B25C1, F02B71