MXPA00004854A - Combustion powered tool with combustion chamber delay - Google Patents

Abstract

A combustion powered tool has a power source 16 for driving a driver blade (66) to drive a fastener into a workpiece. The tool includes a combustion chamber (36) and a cylinder (58). A valve member (50) is disposed to close the combustion chamber. A piston (64) is associated with the driver blade for movement within the cylinder between start and driving positions. A nosepiece (26) has a workpiece contact element (52) movable relative thereto for causing the valve member (50) to close the combustion chamber (36). A delay apparatus (104) is provided for delaying the opening of the combustion chamber (36) by the valve member (50) until the piston (64) returns to the start position after driving the fastener.

Description

PROPELLED TOOL FOR COMBUSTION WITH DELAY FOR COMBUSTION CHAMBER RELATED APPLICATION This application is a partial continuation of the application of the EE.OTJ. with serial number 08 / 961,811, registered on October 31, 1997 and entitled TOOL FOR PROPULSED BY COMBUSTION WITH INSURANCE FOR COMBUSTION CHAMBER. BACKGROUND OF THE INVENTION The present invention is generally related to improvements in portable tools driven by bolts driven by combustion, and specifically with improvements related to the delay of post-combustion opening of the combustion chamber, to allow the piston to return appropriately to the starting position. Portable combustion-driven tools, or known as IMPULSE® brand tools that are used to drive bolts to a workpiece, are described in U.S. Pat. with registration number 32,452 and with numbers 4,552,162, 4,483,473, 4,483,474, 4,403,722 and 5,263,439, assigned jointly to Ni olich, all of which are hereby referenced. Similar tools driven by combustion and driving nails and staples are commercially available from IT -Paslode of Lincolnshire, Illinois, USA, with the IMPULSE® brand. These tools incorporate a tool compartment with a general pistol shape in which an internal combustion engine is housed. The engine is powered by a pressurized fuel gas tank, also called a fuel compartment. A powerful electronic power distribution unit, activated by battery, produces the ignition spark, and a fan located in the combustion chamber provides efficient combustion inside the chamber, and facilitates sweeping, including the escape of byproducts from the combustion chamber. combustion. The engine includes a reciprocating piston with an elongated and rigid driving blade disposed within a cylinder body. A valve sleeve is axially reciprocating about the cylinder and, by a hinge, moves to close the combustion chamber when a contact element of the workpiece at one end of the hinge is pressed against the workpiece. The contact element with the work piece is designed to reciprocate with respect to a tip piece, which is fixed with the compartment. This pressing action also initiates a fuel metering valve to introduce a specified volume of fuel to the closed combustion chamber. By pulling an initiating trigger, which causes the ignition of a gas charge in the combustion chamber of the engine, the piston and the driving blade are fired down to exert impact on a bolt placed and push it towards the work piece. The piston then returns to its original position, or "primed" by differential gas pressures inside the cylinder. The fasteners are fed to the tip piece, where they are held in an appropriately positioned orientation to receive the impact of the driving blade. One of the design criteria for conventional propulsion tools is that the trigger can not be operated until the point piece is pressed against the workpiece. This feature retards ignition until the combustion chamber is closed. In the U.S. patent No. 4,483,474 a suitable trigger safety mechanism is disclosed, which is incorporated herein by reference. In the patent 74, a cam and lever mechanism prevents depression of the trigger until the tip piece is pressed against the work piece, closing the combustion chamber. When firing, the combustion chamber can not be opened until the trigger is released. A recent development in combustion tools is the creation of high-energy tools that produce more force to drive the bolts into the piece of job. In some such tools, additional force is obtained by using an extended cylinder through which a piston travels, thereby providing a longer stroke to the piston. In other high-energy designs, the volume of the combun chamber is increased. In these designs, an attempt is made to minimize the increase in the surface area of the combun chamber, while the area of the cylinder surface may be the same. There is more combun energy, although equivalently there is no more surface area to cool and create the differential pressure to return the piston to the starting position. Consequently, the piston returns more slowly. For longer tools, the time required for the return of the piston increases as the length of the cylinder increases. It was found that in some relatively recent high-energy combun tools, the piston requires about twice as much time to return to its starting position as in conventional combun tools that have a relatively shorter stroke. Obviously, the tool should not be fired until the piston is fully back to the starting position. In the combun tools equipped as described above, in the event that the trip switch is released and the tool is lifted from the work piece before the piston returns to its starting position, the valve hinge allows the combun chamber to open, from this way destroying the differential pressures of gas that help the return upwards of the piston. In order to obtain consistent shots, the size of the combun chamber must always be the same. Another design criterion for combun tools of this type is the desire of operators working in construction sites to practice what is commonly called "push shot". This is a procedure for quick firing of the tool so that the operator uses the recoil of firing a first bolt to lift the tool and quickly place it in position for the next shot. In this way, there is a shorter period of time in which the tool is held with the tip piece and the contact element with the work piece pressed against the workpiece. To prevent tripping errors, the tool must be allowed to recover between shots, allowing the piston to return to the start position before subsequent ignition. For proper return of the piston, the combun chamber must remain sealed until the piston reaches the starting position.

Accordingly, it is an object of the present invention to provide an improved combun driven tool that extends the sealing condition in the combun chamber until the piston returns to its pre-combun starting position. Another object of the present invention is to provide an improved combun-driven tool that is characterized by a mechanism that keeps the combun chamber closed until the piston returns to its starting position. A further objective of the present invention is to provide an improved combun-driven tool, where the combun chamber is kept closed until the piston returns by a mechanism that delays the release of the trigger switch and, by a connection with the safety mechanism , ultimately delays the opening of the combun chamber. Yet another object of the present invention is to provide an improved combun-driven tool characterized by a trigger switch that is relatively easier to push or activate than to return to its initial position and not activated. Yet another objective of the present invention is to provide an improved combun-driven tool that is characterized by a closing mechanism that it temporarily prevents the movement of the contact element with the workpiece relative to the tip piece, and consequently keeps the combustion chamber in the closed position until the piston returns to the starting position. SUMMARY OF THE INVENTION The objectives described above are met or exceeded by this an improved tool powered by bolt combustion, which is characterized by a delay device for delaying the opening of the post-combustion combustion chamber until the piston returns to its starting position. In a first embodiment, the tool is provided with a mechanism for securing the combustion chamber operated by a trigger that prevents undesired opening of the combustion chamber until the trigger is released after firing. The delay device retards the movement of the trigger from the on position to the off position, thereby providing additional time for the piston to return to the starting position. In another embodiment, the delay device prevents unwanted premature opening of the combustion chamber by preventing movement of the valve member. The valve member is controlled by temporarily closing the contact element with the workpiece relative to the tip piece until the piston returns to the starting position.

More specifically, the present invention provides a combustion-driven tool having a self-sufficient source of internal combustion energy constructed and arranged to create a combustion to drive a driving blade to impact with a bolt and propel it into the workpiece. The tool includes a compartment constructed and arranged to house the power source, a combustion chamber defined at an upper end of the compartment and a cylinder arranged in the compartment to be in fluid communication with the combustion chamber. A valve member is disposed in the compartment to periodically open and close the combustion chamber. A piston is associated with the driving blade and is configured for a reciprocal movement within the cylinder, between a starting position located at a first end of the cylinder and a driving position located at the second end of the cylinder. Also included in the tool is a tip piece that has a contact element with the work piece connected to the valve member and configured to make contact with the workpiece on which the bolt will be driven. The contact element with the work piece is movable relative to the tip piece, and upon such contact, the movement of the contact element with the work piece causes the valve member to close the combustion chamber. A device Delay may be joined with the contact element with the workpiece and the joint to delay the opening of the combustion chamber by the valve member until the piston returns to the starting position after driving the bolt. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a fragmentary side view of a tool for bolts driven by combustion, according to the present invention, shown with the combustion chamber open and the trigger of the off position, where the tool is partially cut for the purpose of giving more clarity. Figure 2 is a fragmentary side view of the combustion-driven bolt tool of Figure 1, shown with the combustion chamber closed and the trigger in the firing position, where the tool is partially cut for the purpose of clarity . Figure 3 is an enlarged and partially cut away view of the trigger assembly and pneumatic delay valve of the present invention shown in the off position. Figure 4 is an enlarged and partially cut-away view of the trigger assembly and pneumatic retard valve of Figure 3, shown in the on position.

Figure 5 is a fragmentary rear view of a tip piece of the tool of Figures 1 and 2, in which an alternative embodiment of the lock system is incorporated, where the tool is shown in the rest position. Figure 6 is a view of the tool shown in Figure 5, presented in the firing position. Figure 7 is a fragmentary perspective view of another alternative embodiment of the present insurance system. Figure 8 is a fragmentary, perspective and enlarged view of the system of Figure 7. Figure 9 is a front elevated view of the pivot shaft shown in Figure 8. Figure 10 is a section taken on the line -10 of Figure 9 and in the general direction indicated. Figure 11 is a planar top view of an external cam plate of the tool of Figure 7. Figure 12 is a planar top view of an internal cam plate of the tool of Figure 7. Figure 13 is a view flat top of a secure member of the driving blade of the tool of Figure 7. Figures 14A-F are schematic front views of the normal operation sequence of another mode of the present tool. Figures 14G-L are schematic front views of the abnormal operation sequence of the tool of Figures 14A-F. DETAILED DESCRIPTION OF THE PRESENT INVENTION Referring now to Figures 1 and 2, a combustion-driven tool of the type suitable for use with the present invention is generally designated 10. The tool 10 has a compartment 12 which includes a main power source chamber 14 whose dimensions are suitable for housing a self-sufficient internal combustion energy source 16, a fuel cell chamber 18, generally parallel and adjacent to the main chamber 14, and a portion of handle 20 extending from one side of the fuel cell chamber and opposite to the main chamber. Further, a bolt cartridge 22 is positioned to extend generally parallel to the handle portion 20 from a point of attachment with a tip piece 26, depending on a first or bottom end 28 of the main chamber 14. A battery is provided (not shown) for supplying electrical power to the tool 10, and is detachably housed in a tubular compartment (not shown) located at the opposite end of the compartment 12 with respect to the bolt cartridge 22. As used herein, the terms "lower" and "upper" are used to refer to the tool 10 in its operational orientation, as shown in Figures 1 and 2; however, it will be understood that the present invention can be used in a variety of orientations, depending on the application. Opposite the lower end 28 of the main chamber is a second or upper end 30, which is provided with a plurality of air intakes 32. In a preferred embodiment, an electromagnetic and solenoid type fuel metering valve is provided (not shown). sample), or an injector valve of the type described in U.S. Pat. No. 5,263,439, assigned jointly, to introduce fuel into the combustion chamber, as is known in the art. The previously identified patent No. 5,263,439 is hereby incorporated by reference. A liquid hydrocarbon fuel under pressure, such as MAPP, is contained within a fuel cell located in the fuel cell chamber 18 and pressurized by a propellant, as is known in the art. Returning to the main chamber 14, a cylinder head 34 is disposed at the upper end 30 of the main chamber, which defines an upper end of a combustion chamber 36, and provides a mounting point for a head switch 38, a spark plug 40, an electric fan motor 42 and a sealing ring 44. A combustion chamber fan 46 is attached to an armature 48 of the engine 42 , and is located inside the combustion chamber to increase the combustion process and to facilitate cooling and sweeping. The fan motor 42 is controlled by the head switch 38, as is more fully disclosed in the prior patents incorporated herein by reference. A generally cylindrical reciprocating valve member 50 is moved within the main chamber 14 by a workpiece contact member 52 on the tip piece 26 using a hinge 54 in a manner known in the art. The link 54 is considered as part of the work piece contact element 54. The valve member 50 functions as a gas control device in the combustion chamber 36, and the side walls of the combustion chamber are defined by a member of valve, whose upper end is joined, forming a seal, with the ring 44 to seal the upper end of the combustion chamber (as best seen in Figure 2). A lower portion 56 of the valve member 50 circumscribes a cylinder body of generally cylindrical shape, or cylinder, 58. An upper end of the cylinder body 58 is provided with an outer ring 60 that is joined with a corresponding portion 62 of the valve member 50 (as best seen in Figure 2) to seal a lower end of the combustion chamber 36. A piston 64 is disposed reciprocally within the cylinder body 58. a driving blade is attached 66 rigid and elongated that is used to drive bolts (not shown), being properly placed in the tip piece 26, to the workpiece (not shown). A lower end of the cylinder body defines a seat 68 for a stop 70 that defines the lower stroke limit of the piston 64. In. at the opposite end of the cylinder body 58, a piston stop retaining ring 72 is fixed to limit the upward travel of the piston 64. Located in the handle portion 20 of the compartment 12, are the controls for operating the tool 10. A trigger switch assembly 74 includes a trigger switch 76, a trigger 78 and a driven return member 80, which in the preferred embodiment is a coil spring. An electric control unit 82, under the control of the trigger switch 76, activates the spark plug 40. The operation of the trigger 78 between the off position (Figure 1) and the ignition position (Figure 2) is controlled by a cam interlock mechanism or trigger lock, generally designated as 84, which prevents activation of the trigger until the tool 10 is pressed against a work piece. This pressure causes the tip piece 26 to become depressed, causing the joint 54 move the valve member 50 upwards to close the combustion chamber 36 and seal it from the atmosphere. More specifically, and now referring to Figures 1 to 4, the lock mechanism 84 includes a trigger clamp 86 which is secured at one end with the trigger 78, and in the other has an angled arm 88 which is provided with a transverse pivot bolt 90. Attached to the bolt 90 is a triangular general-shaped release cam 92 provided with an open-ended groove 94 with dimensions suitable for slidingly engaging with the bolt 90. The cam 92 is also provided with a perforation 96 which coincidentally joins a pivot bushing 98 and a cam lobe 100. Referring now to Fig. 1, the cam lobe 100 is joined to one end of a roller with a general "U" 102 shape when the combustion chamber 36 is left open to the atmosphere. This connection prevents the depression of the trigger 78, thus preventing ignition. Now referring to Figure 2, since the U-shaped roller 102 is connected to the valve member 50, as the combustion chamber 36 is closed by the valve member, the roller 102 moves upwards with the valve member, which creates a space for the movement of the release cam 92 next to the roller.

With the cam 92 remaining free to move, the trigger 78 can be depressed to cause ignition. This insurance mechanism 74 is described in greater detail in the patent of the USA No. 4,483,474, assigned jointly. When the trigger 78 is pulled, a signal is generated from the central electrical distribution and control unit 82, to produce a spark plug discharge 40, which ignites the fuel injected into the combustion chamber 36 and vaporized or fragmented by the fan 46. This ignition forces the piston 64 and the driving blade 66 to lower down the cylinder body 58, until the driving blade comes into contact with a bolt and urges it towards the substrate, as is well known in the art. The piston then returns to its original or "starting" position by differentials in the gas pressures inside the cylinder, which are partly preserved by the sealed condition of the combustion chamber. If the combustion chamber 36 is opened before the piston returns to its starting position, as can be seen in Figures 1 and 2, then this differential ratio in the gas pressures is destroyed, which interferes with the return of the piston. It was found that in high-energy combustion powered tools equipped with a relatively longer cylindrical body 58, or larger combustion chamber, additional time is required for the piston 64 to return to the starting position, as can be seen in FIG. Figures 1 and 2. In these models there is the potential, when the trigger 78 is released, so that the combustion chamber opens prematurely. It can be seen in Figures 1 and 2 that as long as the trigger 78 is depressed, the U-shaped roller 102 can not move downward to release the valve member 50 from its sealing position in the combustion chamber. However, once the trigger 78 is released, the cam 92 moves to the position of Figure 1 and allows the roller 102 to move downwards, opening the combustion chamber. As described above, it is important that the combustion chamber 36 does not open before the piston returns to the starting position. Accordingly, an important feature of the present invention is to provide a delay device for delaying the opening of the combustion chamber. In a preferred embodiment, this is achieved by delaying the release of the trigger 78 from its depressed or firing position until the piston 64 returns fully.

Referring now to Figures 3 and 4, the delay device of the present invention is generally designated 104 and, in the preferred embodiment, is characterized by a pneumatic check valve configured to retard the action of the driven return member or helical spring 80 which returns trigger 78 to the released or off position shown in the Figure 3. The pneumatic check valve includes a cavity 106 defined by a generally cylindrical inner wall 108 located within the trigger 78. A plunger 110 is fixed at the base end 112 to a support formation in the compartment 12 by an accessory of friction, a bolt with rope or any other known fastening technology. At the opposite end or tip 114, the plunger 110 coincidentally joins the cavity 106. In the preferred embodiment, the plunger 110 is equipped with a sealing member 116 secured within an annular groove 118 located near the tip 114. It can be used a friction fitting or chemical adhesives to secure the sealing member 116 in place. The sealing member 116 is preferably what is known as a "U" seal, which has an external projection 120 that projects at an oblique angle with respect to the longitudinal axis of the plunger 110 to form a spike or arrowhead configuration. Accordingly, the projection 120 is slidably joined with the inner wall 108 of the cavity 106, and creates a friction that counteracts the action of the driven back member 80 and delays the return of the trigger 78 to the off position. In other words, the sealing member 116 is disposed on the plunger -110 so that it is easy to pull the trigger to the on position (Figure 4), but it is slower on its return to the off position (Figure 3). When the trigger 78 is depressed, the movement of the trigger on the plunger 110 drives a substantial amount of residual air from the cavity 106, creating a relative vacuum in the region 122 of the cavity behind the sealing member 116. Due to imperfections inherent in the sealing member 116, which is preferably made of buna-N, butyl rubber or equivalent, this vacuum is not complete and, as a result of the force applied by the driven return member 80, air will slowly leak to region 122, of this mode allowing spring 80 to push trigger 78 to return to the off position. Those skilled in the art will appreciate that the sealing member 116 should not be made to create a total seal, since it would create a vacuum that would prevent the return of the trigger 78 to the off position. In some applications, the protrusion 120 may be coated with grease so that it slides more easily into the cavity 106. In the preferred embodiment, the plunger 110 and the The cavity 106 has dimensions such that the vacuum created in the region 122 is sufficient to delay the trigger 78 to reach the off position until the piston 64 returns to the starting position. It was found that incorporation of the present delay device 104 into the tool 10 generally doubled the time required for the trigger 78 to return to its off position as compared to conventional combustion driven tools. When equipped with the present delay device, the time required for the trigger 78 to reach the off position from the on position is approximately 200 milliseconds. Referring now to Figures 5 and 6, an alternative embodiment for the tool 10 is generally designated 130, and shared components are designated with identical reference numbers. Figures 5 and 6 show elevated, posterior, fragmentary and enlarged views of the tip piece region of the tool 130. In this embodiment, the tip piece 26 is provided with an axial notched rail 132 that slidably receives the driving blade 66 when reciprocating with each shot. An important differentiating feature of the tool 130 is that the tip piece 26 is provided with a device for securing the contact element with workpiece 52 relative to the tip piece until the piston 64 reaches the starting position. In the preferred embodiment, this device takes the form of at least one, and preferably two cams 134 joined by a pivot in the tip piece 26. Each cam 134 has a first or external lobe 136 for joining with the contact element with part of work 52, and a second or internal lobe 138 for joining with the driving blade 66. Both cams 134 are freely secured by pivoting with the tip part 26 by bolts 140. Both cams 134 need to have such dimensions to be sufficiently wide to join the lobes 136 and 138 with the appropriate component 52 and 66. Another differentiating feature of the tool 130 is that the work piece contact element 52 is provided with at least one and preferably a pair of tabs 142 configured to join with the lobes 136 such that, when joined, the contact element 52 can not move relative to the tip piece 26 until the lobes 136 are separated from each other. the flanges 142. Since the contact element 52 is connected to the valve member 50 by the link 54, this connection prevents the valve member 50 from opening until the piston 64 reaches the starting position. More specifically, the flanges 142 each have an angled guide edge 144 that rests on an opposing surface 146 of the lobes 136. The dimensions of the lobes have sufficient radii to increase the relative sliding action between the flanges 142 and the lobes when released when the driving blade 66 passes. The cams 134 are configured in such a way that, once the flanges 142 are joined on the surfaces of the arms. lobes 144, as the driving blade 66 descends on the rail 132 and joins with the lobes 138, a wedge arrangement is created by which the cams 134 prevent the work piece contact element 52 from moving and the valve member 50 opening the combustion chamber, until the The driving blade retracts or rises beyond the cams 134. In operation, in a rest position shown in Figure 5, the work piece contact member 52 is disposed in an extended position with respect to the tip part. 26, which means that the combustion chamber 36 is open because the valve member 50 is connected to the extended element 52 by the link 54. Furthermore, the driving blade 66 is in a fully retracted position because the piston 64 is in its starting position. It will be appreciated that the flanges 142 are disposed below the cams 134 which, in this position, do not unite with the flanges 142 or the driving blade 66, and are freely pivoted. Referring now to Figure 6, the operator presses the tool 130 against the workpiece 147, in preparation for the shot. In this manner, a lower end 148 of work piece contact member 52 is in contact with the work piece 147, and a lower end 150 of the tip piece 26 is closely adjacent to the end 148. This means that the joint 54 caused the valve member 50 to move upwardly relative to the compartment 12, closing the combustion chamber 36. At the same time, the flanges 142 on the work piece contact member 52 moved from a position below the cams 134 (as best seen in Figure 5) to a position on the cam lobes 136 and 138 (as will be better seen in Figure 6). The tool 130 can then be fired, as described above in relation to the tool 10. Upon firing, the piston 64 is pushed downward, causing the edges of the driving blade 66 to be slidably connected with the internal lobes 138. This union creates a wedge relationship between the driving blade 66, the cams 134 and the flanges 142, forcing the angle guide edge 144 of the flange 142 to closely match the cam surface 146. In this position, if the tool 130 is raised from the work piece 147, as in the case of thrust firing, the valve member 50 can not open the combustion chamber 36 because the contact element with workpiece 52 can not move at all. This insured condition keeps the combustion chamber sealed 36 until the piston 64 can return to the starting position due to differential pressures of gases created within the tool. Once the piston returns to the starting position, represented by the highest position of the driving blade 66, the driving blade is no longer attached to the inner lobes 138, and the pivoted cams 134 are free to move away from the eyelashes 142 at the work piece contact element 52. The valve member 50, which is spring driven to the open position, pushes the outer lobes 136 inward, allowing the valve member to open, so that the chamber of combustion 36 be purged of exhaust gases and prepare for another shot. Referring now to FIGS. 7 and 8, yet another alternative embodiment of the tool 10 is generally designated 160, with shared components designated with the same reference numerals. In general, the tool 160 incorporates the same feature of the tools 10 and 130, in the sense that the combustion chamber 36 can not be opened until the piston 64 returns to the starting position. Like the tool 130, the tool 160 achieves this goal by securing the contact element with the workpiece with respect to the piece of tip 26 until the driving blade 66 is fully retracted. More specifically, the workpiece contact element 162 is formed at an angle of 90 °, and has a first panel .64 to which the valve link 166 is attached, and a second panel 168 provided with a lock tab. with an angled upper portion 172.

In the preferred embodiment, the lower end 148 of the work piece contact element 162 is disposed in the first panel 164, but it is also contemplated that the element 162 be configured so that the lower end 148 is located in the second panel 168. A mounting plate 174 is configured to be mountable on a lower end of the compartment 12, and also has at least four loosely spaced eyelets 176. The eyelets 176 each have a perforation 178, and the perforations are in register with each other . A connector shaft 180 (which can best be seen in Figures 9 and 10) is non-circular in cross section and is configured to rotatably receive in each of the perforations 178. Connected to the shaft 180 is a driving blade securing member, generally flat, 182 (which can be better appreciated in Figure 13) which has a first end 184 with a non-circular perforation 186 configured to coincide coincidently with the axis 180 and for it to rotate there, and an opposite second end 188 with an enlarged formation 190 to be joined with the driving blade 66. The driving blade securing member 182 is preferably located between a pair of eyelets 176, so that when the blade drive 66 descends to join with a bolt, the enlarged formation 190 joins the driving blade and rotates by pivoting on (and with) the shaft 180, moving away from the driving blade as reflected by the arrow 192 (Figure 7). Referring now to Figures 7, 8, 11 and 12, a flange lock 194 is disposed between a second pair of eyelets 176 and is joined on the axle 180 to move with the axle when the driving leaf insurance member 182 joins the driving leaf 66. Four major components form the tab 194: a pair of identical cam external plates 196 and 198, an internal cam plate 200 and a helical spring 202. Each of the external cam plates 198, 198 (which can be best seen in Figure 11) it is generally triangular in shape, with a non-circular perforation 204 configured to coincide coincident with the axis 180, an arched spring opening 206 and an eyelet for connection with the spring 208. In the preferred embodiment, the eyelet for joining with the spring 208 projects laterally on one side of the plate, generally on the arc defined by the opening arched spring 206, but other configurations are contemplated, depending on the application. The internal cam plate 200 is similar in its general configuration to the external cam plates 196 and 198, but differs in two main aspects. First, a perforation 210 is circular, and as such will rotate independently of the axis 180, with which it joins. Second, instead of an attachment eyelet with the spring 208, the internal cam plate 200 has a projection 212 extending from the edge of the opposite side of the plate to the eye 208. A spring opening 206 is also provided to the inner cam plate 200. The spring 202 is disposed in the spring opening 206 of the cam plate. internal 200, so that the ends 214 of the spring are joined with the edges 216 of the opening 206. In the preferred embodiment, the spring 202 has a diameter dimensioned so that when the plates 196, 198 and 200 are assembled in sandwich form (which can be better appreciated in Figure 7), with the internal cam plate disposed between the two outer cam plates, the spring will extend toward the respective spring openings 206 of both outer cam plates. In its rest position, the spring 202 will basically extend from end to end in each of the openings 206 to drive the inner cam plate 200, and particularly the projection 212, towards the latch 170. In case a load on the projection 212, as will be described later, which causes the inner cam plate 200 to pivot relative to the outer cam plates 196 and 198 in the direction towards the driving blade 66, the spring 202 will be compressed, and will force to the internal cam plate to return to its original position when the load is released. A return spring 218 (which can best be seen in Figure 14A) is connected at one end with both eyelets for connection to the spring 208, and at another end with a pin 220, which depends on the mounting plate 174. spring 218 is configured to return the cam plates 196, 198 and 200 to their "resting" position, separate from the latch tab 170 on the workpiece contact member 162 as the driver blade 66 retracts once the piston reaches the starting position. In operation, and now referring to Figures 14A to F, tool 160 is initially shown in the starting position (Figure 14A), with the driving blade 66 retracted and the piston (not shown) in the starting position. . The return spring 218 pulls the tab lock 194, including the plates 196, 198 and 200 to separate them from the lock tab 170, and the spring 202 holds the plates 196, 198 and 200 in register, or in general alignment with each other . In addition, it should be noted that the insurance tab 170 is shown under the projection 212 on the internal cam plate 200, which means that the work piece contact element 162 is in the extended position, indicating that the combustion chamber 36 is open. In the arrangement on the mounting plate 175, the securing member of the driving blade 182 and the flange latch 194 are disposed one relative to the other so that the securing member of the driving blade 182 can be attached to the blade drive 66, and flange lock 194 can be joined with lock tab 170. Referring now to Figure 14B, the operator presses tool 160 against the work piece, so that the work piece contact element moved upwards (see the new position of the flange 170) and the combustion chamber 36 was sealed by the valve member 50. Note that the flange 170 is completely above the protrusion 212. The tool 160 is now ready for shoot. Referring now to Figure 14C, the tool 160 was fired, and the driver blade 66 descended to join a bolt. In its descent, the driving blade 66 was joined with, and was pushed, by the flared formation 190 of the driving blade securing member 182, and consequently caused the rotation of the member 182, the shaft 180 and the flange lock 194 in direction of the hands of the watch, as can be seen by arrow 222. This position will now be designated as displaced or rotated position of member 182 and lock 194. Note that, in its rotated position, flange 212 of flange lock 194 prevents any downward movement of the lock tab 170. Referring now to Figure 14D, the operator lifted the tool 160 from the surface of the workpiece, in a motion called "push shot" to quickly move the tool to the next shooting position. . As such, the work piece contact element 162 is no longer constrained by the workpiece, and attempts to return to the rest position of Figure 14A. However, the protrusion 212 prevents such movement by joining with an edge 213 of the latch tab 170, which also keeps the combustion chamber 36 sealed by preventing unwanted movement of the valve member 50. In Fig. 14E, the driver blade 66 is fully retracted, and the locking member of the driving blade 182 then returns to its starting position by the return spring 218, which, by moving the latch lock 194, also moves the driving blade securing member. by means of the shaft 180. Next, the contact element with workpiece 162 is free to move downwards, thereby opening the combustion chamber 36 to allow the purge of the combustion gases of the combustion chamber (Figure 14F).

Figures 14A and 14F are identical, and tool 160 is now ready for another shot. Referring now to Figures 14G to 14L, it can be seen that the - ^ tool 160 is designed to prevent clogging by the operation of the tab lock 194. In Figure 14G, the driver blade 66 appears in the start position, but the contact element with the work piece 162 has not yet reached the fully retracted or closed position, so that the projection 212 was joined to a side surface 224 of the lock tab 170. As can be seen in Figure 14H, still when the combustion chamber 36 is not fully closed, the tool 160 was fired, causing the driving blade 66 to push the driving blade lock member 182 to move it away, and also move the latch lock 194 in a clockwise direction due to the connection through the shaft 180. However, the connection of the protrusion 212 with the surface 224 prevents the flange latch from reaching its full movement in the direction of the flanges. the clock If there is no releasing mechanism, the impeller blade would be prevented from freely descending to drive the bolt, as well as properly returning to the starting position. Accordingly, to remedy this situation, the internal cam plate 200 is movable relative to the cam plates external 196 and 198, because it has the circular perforation 210 (which can be better appreciated in Figure 12). In addition, the spring 202 compresses, allowing the driving blade 66 to properly clear the safety member 182. A related problem is set forth in Figure 141 where, due to the lack of an appropriately closed combustion chamber during firing, there are differentials of Insufficient and even non-existent gas pressure that normally allows the piston to return to the starting position. By compression of the spring 202 shown in Figure 14H, the lock tab 170 may pass the protrusion 212 and descend, a movement facilitated by the angled upper portion 172 of the flange 170. Referring now to Figures 14J and 14K , the tool 160 can not be fired again, since the driving blade 66 is already in the lowered position. To restart the tool, which is not jammed, but simply the parts is not in its proper position, the operator presses the tip piece 26 and the contact element with work piece 62 against the work piece 147. This action pushes the contact element with workpiece 162 upwards, but since the driver blade 66 is at the bottom, the flange latch 194 remains in the displaced or rotated position, and the contact element with the driver part is in the displaced or rotated position. work can not do all its journey up. To allow element 162 to pass the outgoing 212, the angled portion 172 of the latch tab 170 initiates a camming action that compresses the spring 202. With further downward pressure exerted by the operator, the latch tab 170 sufficiently compresses the spring 202 to move the nose 212 and the nose. internal cam plate 200 in a counterclockwise direction until sufficient space is provided to allow the work piece contact element 162 to pass projection 212. Referring now to Figure 14L, it can be seen that the tab 170 of the contact element with workpiece 162 has already passed the projection 212, and the valve member 50 has reached the start position where the combustion chamber 36 is typically closed. However, the chamber is not closed in this instance, because the piston 64 remains in its lower or fired position, and has not yet returned to the starting position because the combustion chamber is open. Since the driving blade 66 is depressed, the locking member of the driving blade 182 and the locking latch 194 remain in the rotated or displaced position. To prepare the tool 160 for firing, the operator restarts the driving blade 66 with a screwdriver or tool similar by pushing the pusher blade up and towards compartment 12, until it reaches the starting position (which can be better appreciated in Figure 14A). At that time, the lock member 182 and the tab lock 194 will be pulled to the position of Figure 14A by the return spring 218. The tool 160 can be fired again once the tool is placed on a workpiece. 147 and is depressed to close the combustion chamber, as shown in Figure 14B. Accordingly, it will be appreciated that the present delay mechanism, in the form of the trigger delay 104, the pivot cams 134 or the combination of the driving leaf insurance member 182 and the flange lock 194, ultimately retards the opening of the latch. the combustion chamber 36 until the piston 64 reaches the starting position. Consequently a more reliable operation of the tool is achieved, and the operator can manipulate the tool more efficiently when shooting with push when desired. It will be appreciated that other mechanisms known to those skilled in the art can be used to keep the combustion chamber closed until the piston reaches the starting position, and still remain within the scope of the present invention. While a particular mode of the combustion chamber delay was shown and described for a In the tool of the present invention, those skilled in the art will appreciate that changes and modifications can be made without departing from the present invention in its broader aspects, as described in the appended claims.

Claims (12)

1. CLAIMS 1. A combustion powered tool that has a self-sustaining internal combustion energy source built and arranged to create a combustion to drive a driving blade to impact against a bolt and drive it into a work piece, comprising: a constructed compartment and arranged to house the power source; a combustion chamber defined at an upper end of the compartment; a cylinder arranged in the compartment to be in fluid communication with the combustion chamber; a valve member disposed in the compartment for periodically opening and closing the combustion chamber; a piston associated with the driving blade and configured for reciprocal movement with the cylinder between a starting position located at a first end of the cylinder and a driving position located at a second end of the cylinder; a tip piece having a contact element with workpiece connected to the valve member and configured to make contact with a workpiece in which a bolt will be driven, where the contact element with workpiece is movable relative to the workpiece. to the tip piece and when contacting the movement of the contact element with workpiece causes the valve member to close the combustion chamber; and a delay device that joins the contact element with piece of working to retard the opening of the combustion chamber by the valve member until the piston returns to the starting position after driving the bolt. The tool defined in claim 1, wherein the delay device includes a trigger switch assembly in the compartment, which has a trigger that operates between an ignition position and an off position, wherein the delay device includes a safety mechanism operatively connected between the valve member and the trigger, and which is configured to retard movement of the trigger from the ignition position to the off position until the piston returns to the starting position. The tool defined in claim 2, wherein the trigger switch assembly includes the trigger, a trigger switch, a driven return member and a pneumatic check valve configured to retard the action of the driven return member. . The tool defined in claim 3, wherein the pneumatic check valve includes a cavity with internal walls located on the trigger, a plunger fixed to the compartment and coincidentally joined in the cavity, wherein the plunger has a sealing member to be slidably attached to the walls internal so that the union of the sealing member with the cavity creates friction which counteracts the action of the driven back member and retards the return of the trigger to the off position. The tool defined in claim 1, wherein the delay device includes securing devices configured to secure the contact element with workpiece relative to the tip piece until the piston reaches the start position. The tool defined in claim 5, wherein the lock device includes at least one cam linked by pivoting with the tip piece, and having a first lobe for joining the contact element with a workpiece and a second lobe to join with the driving blade. The tool defined in claim 6, wherein the contact element with the workpiece includes at least one tab for joining with the corresponding one and at least one first lobe. The tool defined in claim 5, wherein the insurance device includes a lock tab on the work piece contact element, a first lock member that joins the drive leaf when descending to impact the pin , and a second insurance member configured to move with the first insurance member and to join with the insurance tab to prevent the valve member from moving to open the valve. combustion chamber until the piston reaches the starting position. 9. The tool defined in the claim 8, wherein the first insurance member is a driving blade insurance member that joins the driving blade when descending to make an impact with the bolt, and the second insurance member is an insurance tab configured to join with a driving edge. the lock tab to prevent the valve member from moving to open the combustion chamber until the piston reaches the starting position. 10. The tool defined in the claim 9, where 'the tab tab is configured to possess an overload characteristic supplied by a pair of external cam plates and an internal cam plate having a projection for joining with the securing tab, where the internal cam plate is sandwiched between the external cam plates, and that is tilted towards the locking tab. The tool defined in claim 10, wherein the internal cam plate is configured so that when joined with one side of the safety tab, the inner plate can move against the inclination and toward the flange and retract, allowing the passage of the driving blade without clogging the tool. 12. The tool defined in the claim On the other hand, the plates move away from the safety tab, so that when the piston reaches the starting position, the cam plates move away from the safety tab.