MXPA06008685A - Exhaust system for combustion-powered fastener-driving tool - Google Patents

Abstract

A combustion-powered fastener-driving tool (10) includes a combustion powered power source (14) including a cylinder (20) defining a path for a reciprocating piston (22) and an attached driver blade (24), the piston (22) reciprocating between a pre-firing position achieved prior to combustion and a bottom out position. Upon combustion in the power source (14), the cylinder (20) includes at least one exhaust valve (52) configured for releasing combustion gases from the cylinder (20). The at least one exhaust valve (52) is dimensioned so that sufficient gas is released to reduce post-combustion pressure in the cylinder (20) to approximately one atmosphere in the time available for the piston (22) to travel past the at least one exhaust valve (52) and return to the at least one exhaust valve (52).

Description

DOWNLOAD SYSTEM FOR A DRIVER DRIVE TOOL POWERED BY COMBUSTION RELATED REQUEST The present application claims priority according to 35 USC 120 from US Serial No. 60 / 543,053 filed on February 9, 2004.

BACKGROUND The present invention relates generally to fastener driving tools used to drive fasteners within workpieces and, specifically, to fastener driving tools powered by combustion, also referred to as combustion tools. The combustion-powered tools are known in the art and the exemplary tools produced by Glenview Illinois Tool Works; IL, are known as IMPULSE® brand tools for use in driving fasteners into workpieces, are described in the commonly assigned Nikolich patents, U.S. Patent No. Ref. No. 32,452, and Patents of the U nited States of North America N o. 4, 522, 162; 4,483,473; 4,483,474; 4,403,722; ,197,646; 5,263,439 and 6,145,724, all of which are incorporated herein by reference. Said tools incorporate a tool housing, generally in the form of a gun, enclosing a small internal combustion engine. The engine is powered by a metal container of pressurized fuel gas, known a fuel cell. A battery-powered electronic power distribution unit produces a spark for ignition, and a fan located in a combustion chamber provides efficient combustion within the chamber, while facilitating auxiliary processes for the combustion operation of the device. Such auxiliary processes include: inserting the fuel into the combustion chamber; mix the fuel and air inside the chamber; and removing, or debugging, combustion byproducts. The motor includes an alternating piston with a rigid, elongated drive blade positioned within a single cylinder body. A valve sleeve is axially reciprocable around the cylinder and, through a link, moves to approach the combustion chamber when a working contact element at the end of the link is pressed against a work piece. The pressure action also activates a fuel metering valve to introduce a specified volume of fuel into the closed combustion chamber. By pulling a trigger switch, which causes the spark to ignite a gas charge in the combustion chamber of the engine, the combined piston and the driving blade are forced down to impact a fastener placed and driven into the workpiece . The pump returns to its original position, or pre-trip, through differential gas pressures inside the cylinder. The fasteners are fed in the feeder style within the nozzle, where they are held in a properly positioned orientation to receive the impact of the driving blade. The combustion-powered tools that are currently offered in the market are sequentially operated tools. The tool must be pressed against the work, collapsing the work or the work piece contact element (WCE) before the trigger is pulled for a tool to unload a nail. This contrasts with the tools that can be triggered in what is known as repetitive cycle operation. In other words, these latter tools will fire repeatedly when a tool is pressed against the workpiece, if the trigger is held in the oppressed mode. These differences are manifested in the number of fasteners that can be fired per second for each type of tool. The mode is substantially faster than the sequential firing mode; 4 at 7 fasteners per second can be triggered in repetitive cycle compared to only 2 to 3 fasteners per second in sequential mode. The effective and complete return of the piston to the pre-firing position after combustion is required for the operation that depends on sequential firing combustion tools as well as repetitive cycle combustion tools. An important factor limiting the combustion powered tools of sequence operation is the manner in which the drive piston is returned to the initial position after the tool is fired. The combustion powered tools make use of the self-generating vacuum to perform the return function of the piston. The return of the vacuum type piston requires significantly more time than that of the tools that use positive air pressure from the supply line for the return of the piston. With combustion-compensated tools of the type disclosed in the patents listed above, by means of the tripping and control regime of the valve sleeve, the operator controls the time interval provided for the return of the vacuum-type piston. The formation of the vacuum occurs immediately after the combustion of the mixture and the discharge of the high pressure burned gases. With the high temperature waste gases inside the tool, surrounding aluminum components of lower temperature cool and collapse the gases, thereby creating a vacuum. In many cases, the operating cycle regime of the tool is slow enough, such as in finishing applications in which vacuum return operates consistently and reliably. However, for those cases where a tool is operated at a much higher cycle rate, the operator can open the combustion chamber before removing the tool from the work piece, allowing the valve sleeve to return to its position of rest, causing the loss of the vacuum. Without vacuum to move it, the displacement of the piston stops before reaching the top of the cylinder. This leaves the driving blade within the guide channel of the nozzle, thus preventing the nail strip from advancing. The net result is that there is no nail inside the firing channel and the nail is not fired at the next shot. Conventional combustion tools using the sequential firing mode ensure adequate closed dwell time of the combustion chamber with a locking mechanism of the chamber that is linked to the trigger. The mechanism keeps the combustion chamber closed until the operator releases the trigger, thus taking into account the operator's relatively slow response time. In other words, the physical release of the trigger consumes enough time from the firing cycle to ensure the return of the piston. It is disadvantageous to keep the chamber closed beyond a minimum time to return the piston, since cooling and purging of a tool is avoided. The return of the piston in the vacuum return combustion tools is the simple process with the longest duration in the motor cycle of the tool, which is defined as the time from when the ignition occurs and the piston is returned to the position of the piston. pre-shot The piston return times can vary from 75 or even above 100 milliseconds. These times are controlled by the regime and magnitude of the vacuum formation. When the tool is operated in a repetitive cycle mode, a fastener cycle time is desired and thus less time is available to achieve the proper return of the piston. A piston that does not return completely will prevent the tool from being fired properly in a later cycle. Therefore, there is a need for a combustion-powered fastener tool provided with an improved piston return that is capable of operating in a repetitive cycle mode, and also that is capable of improving the operation of combustion-powered tools. sequentially fired.

BRIEF DESCRIPTION OF THE INVENTION The above listed needs are met or exceeded by the present fastener driving tool powered by repetitive cycle combustion that overcomes the limitations of current technology. Among other things, the present tool incorporates an exhaust valve sized to increase the return of the piston facilitating the release of exhaust gases from the combustion chamber, thus accelerating the creation of the vacuum responsible for the return of the piston. More specifically, the present combustion-powered fastener tool includes a combustion-powered energy source that includes a cylinder defining a frayecforia for a reciprocating footwell and a driving blade attached, the reciprocating footplate engages a pre-position. shot achieved anís of the combustion and a position when reaching the bottom. Upon combustion of the power source, the cylinder includes at least one exhaust valve configured to release the combustion gases from the cylinder. At least one exhaust valve is dimensioned so that sufficient gas is released to reduce the combustion pressure within the cylinder to approximately atmospheric pressure at the time available for the piston to move past at least one exhaust valve and return to at least one exhaust valve.

BRIEF DESCRIPTION OF THE DIFFERENT VIEWS OF THE DRAWINGS FIGURE 1 is a perspective view of a suitable combustion tool to incorporate the present discharge system; and FIGURE 2 is a fragmentary vertical transverse section of a fastener driving tool incorporating the present unloading system.

DETAILED DESCRIPTION Referring now to FIGS. 1 and 2, a combustion-powered fastener driving tool embodying the present invention is generally designated 10 and preferably is the general type described in detail in the paediaires disabled with anorexia and incorporated medianie reference in the present request. A housing 12 of the tool 10 encloses a source of open-end energy 14 of a main housing chamber 16. As with conventional combustion tools, the power source 14 is powered by an internal combustion and includes a combustion chamber. 18 communicating with a cylinder 20. A foot 22 reciprocatingly positioned within the cylinder 20 is connected to the upper end of a driving blade 24. As shown in FIGURE 2, an upper limit of the reciprocal displacement of the footplate 22 is referred to as a pre-trip position, which was present at the time of firing, or the ignition of the combustion gases that initiates the downward impulse of the driving blade 24 to impact a fastener (not shown) to drive it into a workpiece . Through the oppression of the winch 26, an operator induces the combustion of the combustion chamber 18, causing the driving blade 24 to be driven forced downwards through a jet 28. The nozzle 28 guides the driving blade 24 to move a fastener that has been supplied from the nozzle through a fastener feeding device 30. Included in the nozzle 28 is a workpiece conjoint element 32, which is provided by the nozzle 28. connected, through a coupling or upper probe 34 to a reciprocating valve sleeve 36, an upper end of which partially defines the combustion chamber 18. The tightness of the housing 12 of the tool against the part conical element of the Fig. 32 in a downward direction (other operational orientations are considered as they are known in the art), causes the work piece conical element to move from a rest position to a pre-trip position (Fig. 2). This movement exceeds the orientation normally deviated downwards of the workpiece contact element 32 caused by a spring 38 (which is shown in the blank in FIGURE 1). It is considered that the position of the spring 38 can be varied to fit the application, and sites displaced beyond the nozzle 28. In the pre-firing position (FIGURE 2), the combustion chamber 18 is sealed, and is defined by the foot plate 22, the valve sleeve 36 and a cylinder head 42 , which accommodates a chamber injector 44 and a spark plug 46. In a preferred embodiment of the present tool 10, the cylinder head 42 is also the point of departure for a cooling fan 48 and a fan motor 49 which powers the winder. of cooling, the venfilator and at least a portion of the engine are exhausted within the combustion chamber 18 as is known in the art. The shot is triggered when an operator presses the item-of-work item element 32 to a piece of paper. This action exceeds the deflecting force of the spring 38, causes the valve sleeve 36 to move upwardly relative to the housing 12, and to seal the combustion chamber 18 and to aggravate the chamber inerror 44. This operation also induces a potentiality. measure of combusible that will be released from the combustion chamber 18 from a metal container of combusible 50 (fragmented mosirado) At the fraction of the trigger 26, the spark plug 46 is energized, igniting the mixture of fuel and air in the chamber of combusible. combustion 18 and sending the piston 22 and the driving blade 24 downward in the direction of the standby fastener As the piston 22 moves down the cylinder, it pushes a flow of air that is discharged through at least one reigning valve or palisades 52 and at least one ventilation hole 53 or located beyond the piston displacement (FIGURE 2). In the case of the pisíón race or the disienza of maximum displacement of the pisíón, the pisíón 22 impacted a head of shock elásíico 54 as it is known in the technique. With the piston beyond the discharge relief valve 52, the gases at high pressure exit from the cylinder 20 where conditions close to atmospheric pressure are obtained and the check valve 52 is closed. Due to the internal pressure differentials in the cylinder 20, the piston 22 is returned to the pre-firing position shown in FIGURE 2. As described above, one of the issues facing designers of combustion-powered tools of this type is the need for a return Fast piston 22 had the pre-firing position and the chamber conirol 18 improved before the next cycle. Although a problem with sequentially powered combustion tools is often triggered, this need is especially critical if the tool will be fired in a repeating cyclic mode, where ignition occurs each time the item of workpiece element 32 is reused, and last longer. whose time gaíillo 26 is sustained conininely in the fraction or compressed position. To accommodate these design concerns, the present tool 10 preferably incorporates an optional locking device, generally designated 60, configured to prevent alternation of the valve sleeve 36 from the closed or firing position until the piston 22 returns to the pre-trigger position. This maintenance or closing function of the locking device 60 is operative for a specified period required for the piston 22 to return to the pre-trip position. For example, the operator who uses the tool in a repetitive cyclic mode can raise the tool from the work piece where a fastener was recently driven, and start relocating the tool for the next cycle of work. Shooting.

Generally speaking, the device 60 includes a reciprocating energized solenoid-type retainer engaging the valve sleeve according to a designated timing sequence controlled by a main control unit of the tool. It will be understood that a variety of mechanisms can be provided to keep the combustion chamber sealed during this period, and the illustrated locking arrangement does not mean the only means in which the operation can be performed. Due to the shorter periods of the firing cycle inherent with the repeating cycle operation, the locking device 60 ensures that the combustion chamber 18 remains sealed, and the differential pressures of the gas maintained in such a manner that the piezo 22 will be re-fried towards up without a premature opening of the chamber 18, which would normally interrupt the return of the piston. With the present locking device 60, the return of the foot 22 and the opening of the combustion chamber 18 can occur while the tool 10 is being moved to the next level of the workpiece. It should be understood that the block device 60 is considered to be used with some types of tools powered by combustion, but a required component is not considered. The time required for the desired return of the piston is controlled by the degree to which the combustion gas escapes before the piston begins its return after having struck and bounced off the impact head. The construction of the typical combustion tool locates exhaust ports at a convenient disengagement above the impact head, so that the combustion gas can escape once the hole passes the holes and until it passes back into the hole. return race. It is usually desirable to place the holes near the impact head to gain the longest possible power stroke. This causes the escape time to be very short; ideally in the order of only a few milliseconds. Once the initial pressure of the tool equals atmospheric pressure, a check valve system closes the exhaust port, allowing the vacuum to form in the tool to begin the return of the piston. It has been found that the exhaust ports typically found in the combustion tools are too small for the combustion gas under pressure to be completely relieved. This causes the return time of the footing to be unnecessarily prolonged, or the footboard to bounce or oscillate from top to bottom, even to stop for a while, as the vacuum develops. The piston 22 that bounces away from the impact head or bounces away from the air cushion formed below the piston can cause such an oscillation. The air cushion is formed when the exhaust ports 70, associated with the vane valves 52, and the vent hole 53 around the shock head 54 do not effectively allow the stroke volume caused by the downward movement of the piston 22 be exhausted in a timely manner. In the cases where the foot 22 rebounded above the exhaust ports 70, the residual combustion residual pressure has been known to force the foot back down towards the shock head a second time. When it occurs, there is an idiosyncratic mark on the work as evidence of the "double strike," which is undesirable in finished job applications. It has been found that poor venting limited the speed of the tool cycle, especially in alpha speed applications. In the present tool 10, the desired short cycle times of the firing cycle in the repeating cycle mode are achieved in part by sizing the exhaust ports 70 (Figure 2) to equalize the volume of combustion gases that must be deficient as that the pressure inside the cylinder 20 is essentially reduced to an aosphere. Although it is tedious, it is considered that the appropriate orifice area can of course be found empirically for each specific case. During the development of the present tool 10, the inventors developed a rule that can be used once the available time of discharge is selected. The latter is defined by the location of the exhaust ports 70 in relation to the shock head 54, the stiffness of the shock head, the pressure of the air cushion, and the speed of the piston 22. The ratio of the volume to be discharged ( in cubic inches) with respect to the effective orifice area, in square inches it is approximately ten times the required exhaust time (in milliseconds). Ideally, it is desired that after combustion, the area of the cylinder 20 above the foot 22 is at the atmospheric pressure as the piston reaches the position upon reaching the bottom with the impact head 54. The differential pressure within of the cylinder 20 on either side of the piston 22 helps to return the piston back to the pre-firing position. It has been found that the above relationship can be expressed as V / A = 20 + 8.4Í, where V is the expandable volume of the combustion chamber, A is the effecive orifice area, V / A is the ratio of the exhaust volume the effecive hole area, and i is the time in milliseconds that the exhaust ports 70 allow fluid communication between the cylinder 20 and the atmosphere. In other words, the time "i" represented the interval you start when the piston 22 passes the exhaust holes 70, hits the shock head, and returns back to the combustion chamber and passes over the exhaust ports again. For the effective return of the piston, the value of "t" is approximately 4 milliseconds, although the available times may vary from 2 to 10 milliseconds. For a typical combustion-powered tool 10 with an exhaust volume of 655.5 cm3 (40 cubic inches), when applying the above formula, the available time varies from 2 to 10 milliseconds and requires a range of corresponding effective minimum orifice areas of 7,097. and 2.58 cm2 (1.1 and 0.4 square inches) respectively to achieve effective escape conditions. It has been found that the above relationships in the dimensioning of the exhaust holes 70 can be used to increase the performance of combustion tools of many types, including those designed for the repetitive cycle mode, in which a blocking device 60, as well as in combustion tools operating in a sequential firing mode, in which blocking devices are not normally required. Although a particular embodiment of the discharge system for a combustion-powered fastener tool has been described herein, those skilled in the art will appreciate that changes and modifications can be made thereto without departing from the invention in its broader aspects. and as set forth in the following claims.

CLAIMS 1. A combustion powered fastener tool, characterized in that it comprises: a combustion powered energy source including a cylinder defining a trajectory for a reciprocating piston and an attached driving blade; said reciprocating plunger between a pre-firing position obtained upon combustion and a position upon reaching the bottom, upon burning the power source, the cylinder includes at least one relief valve configured to release the combustion gases from the cylinder; at least one exhaust valve is dimensioned in such a way that sufficient gas is released to reduce the combustion pressure in said cylinder to approximately one atmosphere in the time available for the piston to move past the minus one exhaust valve and return to at least one valve. The tool according to claim 1, further characterized in that at least one exhaust valve is a check valve. 3. The tool according to claim 2, further characterized in that at least one exhaust valve is a vane valve. 4. The tool according to claim 1, further characterized in that the exhaust valve is an exhaust valve is dimensioned according to the formula V / A = 20 + 8.4Í. 5. The tool according to claim 1, further characterized in that the exhaust valve has an orifice area in the range of 2.58 to 7.097 cm2 (0.4 and 1.1 square inches). 6. The tool according to claim 1, characterized

Claims (1)

1. Because it also includes a valve sleeve locking device.