MXPA97003107A - Piston retention device for combused tools - Google Patents

Abstract

The present invention relates to a tool propelled by combustion to drive a fastener in a workpiece, comprising: a compartment with a nozzle part disposed at one end of the compartment, a cylinder body disposed within the compartment and having a first end adjacent to the nozzle part of the compartment, and a second end disposed opposite the first end, a combustion chamber disposed adjacent to the second end of the cylinder body, a piston reciprocally disposed within the cylinder body, an elongated booster blade attached to the piston, an annular groove defined within an inner side wall portion of the cylinder body, a radially deployable and retractable member disposed within the annular groove defined within the inner sidewall portion of the cylinder body; defined retention on the piston and the radially deployable member and retracta useful to cooperate with each other so that the piston is retained in a position prior to firing into the second end of the cylinder body by a retaining force that accommodates the weight of the piston when the tool is disposed in a pre-firing mode, but where the force can be superimposed to release the piston when the tool is fired

Description

PISTON RETENTION DEVICE FOR TOOLS OPERATED BY C0MBU8TIÓN BACKGROUND OF THE INVENTION The present invention relates, in general, to the improvements made in the combustion-driven tools, and specifically, to the type of tools that have a piston retention device to be used in the handling of relatively harder fastening bolts. , in steel, concrete, and other hard substrates. The portable combustion-driven tools that are used to handle fasteners within the workpieces are described in the United States patent commonly assigned to Nikolich U. S. Pat. Re. No. 32,452, and the U.S. Patent Nos. 4,552,162; 4,483,473; 4,483,474; 4,403,722; and 5,263,439; which are incorporated herein by reference. Similar nail and staple handling tools are available on the market manufactured by IT -Paslode of Lincolnshire, Illinois, under the IMPULSE® brand. Such tools generally incorporate a gun-shaped compartment, which contains a small internal combustion motor driven by a container of pressurized fuel gas. A powerful battery-powered spark plug unit produces the spark necessary for ignition, and a fan located inside the chamber provides efficient combustion within the chamber, as well as facilitating consumption, including the expulsion of waste products from the combustion. The motor includes a piston that is reciprocal with respect to an elongated rigid blade disposed within a cylinder body. A valve cover is axially reciprocal to the cylinder and, through a joint, moves to close the combustion chamber when a contact work element at the end of the joint is pressed against the workpiece. The pressure action causes a fuel metering valve to introduce a specific volume of fuel into the closed combustion chamber. From the moment the trigger switch is actuated, which causes the ignition of a gas charge inside the combustion chamber, the piston and the impeller blade are fired down to impact a fastener placed in its position, and direct it into the work piece. Then, the piston returns to its original or "ready" position, by means of differential gas pressures inside the cylinder. The fasteners are placed in a lens holder in which they are held in an appropriate position orientation to receive the impact from the driving blade.

The combustion-driven tools of the current generation are used to handle fasteners and introduce them into wood and concrete surfaces. In general, the momentum force developed in such tools is insufficient to introduce fasteners into harder surfaces, such as hard concrete or steel. In the same way, until now, these last types of applications have continued to rely on the use of Powder Activated Technology (PAT) tools. In order to increase the output efficiency of conventional combustion powered tools, one can increase the input power, use the existing output energy more efficiently, or both at the same time. In practical terms, these principles are applied by determining the appropriate combination between piston speed and piston mass, which varies with each particular application. In some applications, such as the fastening of metallic roofing materials over steel lattice joists, operators have developed a preference for a thinner fastening bolt, which does not produce the same damage in the relatively thin lattice girders as in case of the thicker bolts used previously. Nevertheless, the thinnest bolts used recently need relatively higher impact speeds in order to achieve adequate penetration of the steel lattice joists. It has recently been discovered that increased piston speeds can be achieved by lengthening the cylinder body of the tool. Such increased speeds are desirable for introducing the fasteners into relatively thin metal workpieces, such as the lattice girders mentioned above. Furthermore, by means of lengthening the cylinder body and / or increasing the mass of the piston, sufficient output energy can be developed within a combustion-driven tool, in order to introduce the fasteners into harder surfaces. However, in practice, the fact of adding mass to the piston and lengthening the cylinder body, causes a rise in operating problems that must be solved. The heavier, faster-moving pistons of larger combustion-driven tools do not tend to remain in the proper firing position at the top of the cylinder. The above can cause the tool to make a bad shot, or not shoot at all. In most applications, larger combustion-driven tools are used with a cylinder that is held in a vertical position. In conventional combustion-driven tools, the friction forces between the piston and the cylinder wall, and the driving blade and its guide, are sufficient to hold the piston in the proper firing position. However, with a heavier piston, the force of gravity acting on the piston can overcome the frictional forces and, when the tool is obtained in vertical position, the piston can begin to slide towards the bottom of the cylinder. With the piston removed because of its displacement towards the bottom of the cylinder, the combustion chamber stretches unintentionally. The added volume inside the combustion chamber reduces the compression of the incoming fuel mixture, resulting in inefficient combustion when the tool is fired. This leads to a lower power printed on the piston and the attached driving blade, and to a lower energy released to introduce the fastening bolt inside the work piece. Increasing the length of the cylinder body causes a similar problem. With an increased stroke length, the piston experiences much higher return speeds after inserting the fastener bolt into the workpiece. The piston stop impact on the top of the cylinder can cause the piston to bounce back toward the rear of the cylinder, away from the proper firing position, increasing, again unintentionally, the chamber volume of the piston. combustion. In addition to the above, when using a higher speed piston, it is necessary to have elements to stop the piston in a resilient manner in the upper part of the cylinder, and to keep the piston in the proper firing position. The elongation of the cylinder body can also create a problem to guide the piston up and down inside the cylinder. When the cylinder body is extended, the cylinder becomes longer than the impeller blade attached to the piston. When the piston is raised towards the upper end of the cylinder, the lower end of the driving blade freely hangs from the bottom of the piston. The lengthening of the impeller blade to compensate for this spatial difference adds extra mass to the piston and increases the length of the objective piece and the tool, both conditions being completely undesirable. Because the tamper must travel along the total length of the cylinder, any intervention mechanism for guiding the impeller blade towards the objective piece to properly impact the fastening bolt, could interfere with the trajectory of the piston. It is of critical importance that the piston travels in a straight line towards the bottom of the cylinder to ensure proper alignment of the driving blade and the objective piece. A general objective of the present invention is to provide an improved heavy-duty, combustion-driven tool for introducing fastening bolts into harder surfaces such as concrete and steel. Another object of the present invention is to provide an improved combustion tool, which has an increased output power released through a relatively heavier and / or faster moving piston. Another object of the present invention is to provide an improved combustion driven tool in which the piston is held in position in the upper part of the cylinder until the tool is fired. Another object of the present invention is to provide an improved combustion driven tool, having a self-guiding piston which ensures that the driving blade attaches between appropriately in the nosepiece when the tool is fired. Another object of the present invention is to provide a self-guided piston for use in combustion-driven tools in the manner described above, having integrally formed stabilizing members configured to physically engage the cylinder wall. A further object of the present invention is to provide an improved combustion driven tool having a piston retention device mounted on the cylinder wall, which is capable of releasably engaging with the piston, when the piston is in the piston. shooting position. Yet another objective of the present invention is to provide an improved combustion driven tool with a relatively larger speed piston. Said tool preferably provides a system for resistive stopping of the piston in the upper part of the cylinder, and for holding the piston in the proper firing position. A further object of the present invention is to provide an improved combustion driven tool having a high speed piston and a piston retention device in the form of a compressible pin which engages a cam lock which lies on the inner surface of the piston. . The plug also acts to absorb the return impact of the high speed piston. Another object of the present invention is to provide an improved combustion driven tool having a piston retention device that is capable of holding the piston in position until a short time before the tool is fired, long enough to allow it to obtain a higher combustion pressure before releasing the piston. When the piston retainer finally releases the piston, the higher combustion pressure gives the piston a higher speed.

SUMMARY OF THE INVENTION The present invention achieves and / or achieves the aforementioned objectives by providing an improved combustion driven tool for introducing fastening bolts into concrete and steel. The present combustion-driven tool has a relatively heavier piston and a longer cylinder body than conventional combustion-driven tools. A feature of the present invention is a piston retention device which is located at the upper end of the cylinder to hold the piston in its position until just after the tool has been fired, by means of which it prevents the The piston slides towards the bottom of the cylinder, also avoiding the unintentional lengthening of the combustion chamber, as well as achieving a higher combustion pressure to be applied to the piston before it is released. Another feature of the present invention is that the mass added to the piston by means of integrally formed stabilizing members, which are disposed on the upper surface of the piston, or at the outer ends of a nut-shaped fastening member. The stabilizing members are configured to physically mate with the cylinder wall, and to guide the piston when it is fired into the cylinder. The stabilizing members ensure that the piston remains aligned during its travel through the cylinder. In addition, the attached impeller blade will be properly aligned to enter the nosepiece part to directly impact the fastener. In a first embodiment, the piston stop mechanism is formed by a compressible annular member which is disposed in a rim inside the cylinder wall near the upper part of the cylinder body. The annular member has a flanged surface shaped to engage releasably with a similar, but opposite surface, found in the piston stabilizing members. A spring that finds located between the rear wall of the rim and the annular member, provides a radially diagonal force towards the interior, which increases the friction between the annular member and the stabilizing members of the piston. More specifically, an improved combustion driven tool for introducing fastening bolts into workpieces including a main compartment that, at least partially, contains a cylinder and an adjacent combustion chamber. A objective piece to make contact with the work pieces, is subject to said compartment at the opposite end to the combustion chamber, and holds the fastening bolts that are going to be introduced in the work piece. A reciprocating piston is mounted inside the cylinder, and is attached to an elongated driving blade, and said driving blade is used to impact the bolts and insert them into the workpiece. The retainer is strong enough to accommodate the weight of the piston, but is designed to be exceeded when the tool is fired. A second embodiment of the present invention shows a combustion-driven tool with a high-speed self-guided piston and an even longer cylinder body. This second embodiment provides a piston retention device in the form of a compressible plug which engages a cam lock located on the upper surface of the piston. The plug also serves the double function of absorbing part of the force when the piston is hit against the top of the cylinder during the higher speed up stroke. In the above embodiment of the present invention, two different piston designs are contemplated. The first design incorporates stabilizing members formed integrally similar to those described above. However, in this case the inner surfaces of the stabilizing members cooperate with the retaining pin to form the stop of the piston.

Generally, the pin is conical, with a flange inclined and directed inward approximately to half its length. The internal surfaces of the stabilizing members have inclined flanges that protrude inwards, which form a cam lock. The cam lock engages with the inclined flange on the dowel to prevent the piston from sliding back down until the tool is fired. The retaining pin can also be configured as a spring loaded in the manner of a bullet shaft. In this case, while the pin enters the cam lock, the spring loaded with bullets is compressed to allow the pin to enter, but immediately extends once the pin has passed the retention portion of the cam lock. In this way, the plug resists being removed from the cam lock. When the piston returns to the top of the cylinder at high speed, the pin engages with a spindle-shaped diverticulum formed on the top of the piston. While the plug, which opens gradually, is forced, more and more, towards the diverticulum in the form of a spindle, the pin is compressed, absorbing the momentum of the returning piston. In this way, the plug acts as a device for the resistive stop of the high-speed piston, as well as as a stop device for holding the piston on the top of the cylinder. The second piston design incorporates a simple piston stabilizer that extends around the total circumference of the piston. The outer profile of the stabilizer is similar to that of the stabilizing members described above; however, since the stabilizer extends around the total circumference of the piston, the stabilizer physically engages the total circumference of the cylinder wall. The inner portion of the stabilizer is generally hollow, and forms a cup-shaped structure in the upper part of the piston. A threaded end of the impeller blade extends through the bottom of the piston and into the hollow region, and a clamp nut is then screwed into the impeller blade to hold the impeller blade and the piston together. In this design, the clamping nut adds mass to the piston / drive blade assembly, and provides the cam lock for engagement with the retention pin. The internal structure of the clamping nut, which forms the cam lock, is similar to that of the stabilizing members mentioned above.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a sectional fragmentary view of a combustion driven tool according to the first embodiment of the present invention.

Fig. 2 is an enlarged fragmentary cross sectional view of the tool, taken in the same plane as in FIG. 1, which shows the upper end of the cylinder body and the piston. Fig. 3 is a sectional view of the cylinder body and together with the piston, taken along line 3-3 of Fig. 2 and in the generally indicated direction. Fig. 4 is an enlarged cross sectional view taken along the same plane of Fig. 2, showing a compressible annular member and a compressed radial spring within a notch in the wall of the cylinder body by means of the surface piston outside when the piston is near the top of the cylinder. Fig. 5 is an enlarged cross sectional view taken along the same plane as in Fig. 2, showing the compressible annular member and the inwardly expanded spring, so that the ridged surface of the annular member home with a Recess cavity that is on the external surface of the piston when the piston is in its position in the upper part of the cylinder body. Fig. 6 is a partial sectional view of a combustion driven tool, in accordance with an alternative embodiment of the present invention. Figs. 7 through 9 are fragmentary cross-sectional views of the tool taken along the same plane as in Fig. 6, showing the coupling sequence of the piston with the upper end of the cylinder body. Fig. 10 is a cross sectional view of another alternative embodiment of the present invention, of a piston suitable for use with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED MODE Referring now to Fig. 1, a combustion-driven tool of the type suitable for use with the present invention is designated, in general, with the number 10. The tool 10 has a compartment 12 that includes a main chamber 14 of sufficient dimensions to receive an internal source of self-contained combustion energy, a fuel cell chamber 16 which is generally parallel to the adjacent main chamber 14, and a handle portion 18 extending from one side of the fuel cell chamber and in the opposite direction to the main chamber. A piece of objective poles 20 hanging from the lower end 22 of the main chamber 14, and a battery (not shown) that is releasably housed within a tubular compartment (not shown) located on the opposite side of the portion of handle 18. The use of the terms "lower" and "upper" in the present description is made in relation to the tool 10 in its operating position, as shown in Fig. 1; however, it should be understood that the present invention can be used in a variety of orientations, depending on the application. A cylinder head 40 is disposed at the upper end 24 of the main chamber, and extends into the fuel cell chamber 16, defining a fuel cell opening 32. The cylinder head 40 also defines the end upper of the combustion chamber 42, and provides a mounting point for the main switch, a spark plug, and a sealing ring (0-ring), which are not shown, and an electric fan motor 44. The fan 46 is subject to the motor armature 44, and located within the combustion chamber 42. The fan 46 reinforces the combustion process and facilitates cooling and consumption. A reciprocating valve device 48, generally cylindrical, is displaced within the main chamber 14 by means of a workpiece locating member 50, using a joint in the manner known per se. The side walls of the combustion chamber 42 are provided by means of the valve device 48. The lower portion 52 of the valve device 48 circumscribes the cylinder body 54, which is generally cylindrical. Within the cylinder body 54 there is a reciprocating piston 56, to which is attached a driving blade 58 which is rigid and elongated, which is used to drive the fastening bolts and the nails, which are positioned in a manner suitable in the objective piece 20, towards the work piece. In the preferred embodiment, the fasteners used are relatively heavy duty fastening bolts, of the type commonly used with PAT tools. A first lower end of the cylinder body 54 provides a seat 60 for a damper 62, which defines the lower travel limit of the piston 56. The present combustion-driven tool 10 differs from conventional tools in that the cylinder body 54 is axially elongated to increase the power and / or the speed of the driving blade. Now, referring to Figs. 2 and 3, the piston 56 has a lower portion 64, which is similar to the piston configuration used in conventional combustion powered tools. The lower portion 64 contains an annular groove (not shown), to accept the piston ring according to the process known in the art. The upper surface 66 of the lower portion 64 defines the lower end of the combustion chamber 42 when the piston 56 is raised to the second upper end 57 of the cylinder body 54. At least three integrally formed stabilizing members 68 are attached to the upper surface 66 of the piston 56. In the preferred embodiment, the three stabilizing members 68 are evenly spaced around the circumference of the piston 56, and they extend radially outwards. Each stabilizing member 68 has an upper portion 70, which forms an outward arc, away from the central axis of the piston 56, and has an outer curved surface 72. In the configuration, the stabilizing members 68 are oriented toward each of the outer surfaces 72, and will physically engage the inner wall 74 of the cylinder body 54. The stabilizing members 68 tend to keep the piston 56 aligned during its up and down travel along the cylinder body 54. above ensures that the attached impeller blade 58 will travel directly along the central axis of the cylinder body 54, and will be properly impacted with the fastening bolt that is in its position in the objective piece 20. An additional benefit of the stabilizing members 68 is the additional mass added to the piston. With reference to Figs. 4 and 5, a significant feature of the piston 56 of the present embodiment of the invention is that the external surfaces 72 of the stabilizing members 68 have a series of transverse inclined flanges. Said ridges form a cam lock profile along the outer surfaces 72 from the top to the bottom. In the preferred embodiment of the present invention, six consecutive linear segments form the profile of each of the outer surfaces 72. A first segment 76 extends from the top of the outer surface 72 to a second segment 78, and tilts slightly out from the top to the bottom. Between the first segment 76 and the third segment 80, the second segment 78 is generally parallel to the axis of the piston 56. The third segment 80 is between the second segment 78, and a fourth segment 82, and is sharply inclined inwards. Between the third segment 80 and the fifth segment 84, the fourth segment 82 extends generally parallel to the axis of the piston 56. The fifth segment 84 lies between the fourth segment 82 and the sixth segment 86, and is inclined slightly outwardly. Finally, the sixth segment 86 extends from the fifth segment 84 to the bottom of the outer surface 72, and is generally parallel to the axis of the piston 56. The region defined by the third, fourth, and fifth segments, 80, 82, and 84, respectively, forms an inclined recess of recess 88 within the outer surface 72 of each of the corresponding stabilizing members 68. Referring now to Figures 3, 4, and 5, an annular groove 90 is cut into the wall internal 74 of the cylinder body 54, near the lower end of the combustion chamber 42, or in the close proximity of the upper limit of the piston stroke 56. Included in the notch 90 is a rear wall 92 parallel to the axis of the body of cylinder 54, which normally extends the upper and lower walls 94, and 96, respectively. A compressible annular member 98 is disposed within the notch 90 to form a piston stop by frictional engagement of the outer surfaces 72 of the piston stabilizer members 68. It is preferable that the frictional force between the annular member 98 and the piston stabilizing members 68 are sufficient to support the piston 56 in the upper part of the cylinder body 54 until the tool is fired. A circular expander, or folded linear expander or spring 100 is disposed within the notch 90 between the rear wall 92 and the annular member 98. The spring 100 exerts a steering force directed radially inwardly against the annular member 98, whereby, the friction between the annular member 98 and the piston 56 increases. In the preferred embodiment, the outer surface of the annular member 98 has a notch 101 configured to accommodate the spring 100 when the piston 56 is in the position shown in Figure 4.

To further increase the clamping force of the piston stop device, a series of inclined segments are formed on the inner surface of the annular member 98. Taken in combination, these segments form a cam lock profile. The profile of the inner surface of the annular member 98 is similar, but opposite to, or inverse to, the profile of the outer surfaces 72 of the piston stabilizing members 68. Four consecutive linear segments form the profile of the inner surface of the annular member 98. The first segment 101 extends from the peripheral upper edge of the annular member 98, to the second segment 104, and is generally parallel to the axis of the cylinder body 54. The second segment 104 is between the first and the third segment 100. and 106, respectively, and is markedly outwardly inclined. Between the second segment 104 and the fourth segment 108, the third segment 106 extends generally parallel to the axis of the cylinder body 54. The fourth segment 108 extends from the third segment 106 to the bottom of the annular member 98, and is slightly inclined inland. An inclined ledge 110 is formed by the second, third, and fourth segments, 104, 106, and 108, respectively, and has a shape such that it engages in the inclined recess 88 of the outer surfaces 72 of the members. piston stabilizers 68. In addition, the piston stop device formed by the notch 90, the spring 100, and the annular member 98, is releasably engaged with the piston stabilizing members 68 when the piston 56 is located in the piston 56. upper end of the cylinder body 54. During operation, when the cylinder 56 returns to the upper limit of its stroke after driving a fastening bolt, the outwardly inclined segment 76 of the piston stabilizing members 68 will engage and depress momentarily, or they will radially displace the annular member 98. At this point, the orientation force of the spring 100 is temporarily overcome. Once the first segment 76 on the piston passes the opposed segments 106 and 108 of the annular member, the spring 100 will direct the member radially inwardly, so that the inclined segments 104 and 108 of the annular member 98 will engage with the inwardly inclined segments 80 and 84 of the corresponding piston 56. In this way the relatively heavy piston 56 is prevented from failing to return to the cylinder body 54 prior to the spark plug firing. In addition, the dimensions of the combustion chamber are now more uniform due to the fact that the piston returns to a specific position each cycle. Upon ignition of the fuel within the combustion chamber 42, the combustion force will urge the piston 56 downwards, and the segments 80 and 82 will momentarily overcome the force of the spring 100, and temporarily retract the annular member 98 to release the piston. Referring now to Figure 6, a second embodiment of the invention is generally designated as 150. Those components of tool 150 that correspond to their counterparts of tool 10 have been designated with the same reference numbers. In the present embodiment of the invention, the combustion-driven tool 150 has a still longer cylinder body 152, to increase the speed of the piston 154. The fundamental difference between the first and second embodiments of the present invention, in addition to the Cylinder body length 152, is the system used to hold the piston 154 in the proper firing position at the top of the cylinder. While in the first embodiment a retention device of the piston embedded within the wall of the cylinder is used, the present embodiment of the invention rests on a retention pin 168, which is suspended from a support 170 that is inside the body of the cylinder 152. The retaining pin 168 engages with a cam lock 166 which is located on the upper surface of the piston 154, to hold the piston in the proper firing position at the top of the cylinder 152. Two independent piston designs are considered for the present embodiment, and both are described individually below. Referring to Figures 6 to 9, the second embodiment of the present invention is shown using a first piston design. As in the first embodiment of the invention, the piston 154 is formed by at least three integrally formed stabilizing members 156, attached to the upper surface. Here, however, the outer surfaces of the stabilizing members 158 are smooth and run at the same level against the inner wall 160 of the cylinder body 152. Between the stabilizing members 156, a spindle-shaped diverticulum 162 is formed within the surface upper of the piston 154, along the central axis of the piston. In the preferred embodiment, the diverticulum 162 is a separate insert threaded into an axial hole 163 of the piston 154. Near the top of each of the stabilizing members 156, an inclined ledge 164 is formed on the inner surface of the stabilizing member. on the spindle-shaped diverticulum 162. The inclined shoulders 164 mentioned above form a cam lock 166 in the opening of the spindle-shaped diverticulum, the cam lock 166 cooperates with the resilient stop pin 168 which is fixed to the upper end. of cylinder body 152, to form a piston stop device.

A sloping cover 169 retains the pin 168 in the mounting bracket 170, which extends across the upper part of the cylinder body 152. The stop pin 168 hangs from the support 170 towards the interior of the cylinder body 152. A groove axial 171 is defined between at least two legs 172 of pin 168, to allow compression of the pin in a manner similar to safety clothing pins, when the pin is forced into the spindle-shaped diverticulum 162 This compressibility of the legs 172 also creates a radial tilt force that generates friction between the pin 168 and the piston 154. In the preferred embodiment, the eternal profile of the pin 118 is in the shape of an arrow. A narrower arrow portion 174 of each leg 172 extends from the mounting flange 170 towards the interior of the cylinder body 152. Approximately half the length of each leg 172 is formed at the lower end of the interior of the head 176, having a generally inverted conical configuration. A generally inclined base portion 178 of the head portion has a larger diameter than the arrow portion 174. A spindle-shaped portion 180 is similar in shape to the shape of the spindle-shaped diverticulum 162 on the piston. 154. During the complete firing cycle of the tool 150, the pin 168 undergoes three separate compressions. When the tool is ready to be fired, as shown in Figure 8, the base portion 178 of the head portion 176 of the pin 168 engages within the cam lock 166 to secure the piston 154. Referring to FIG. Figure 7, when the tool is fired, the downward force of the piston 154 is more than sufficient to compress the legs 172 of the pin 168, and the cam lock 166 slides over the base portion 178 of the pin. The piston 154 is triggered through the elongated cylinder body 152, is struck against the fastener at a very high speed, and returns to the upper part of the cylinder body. Then, the pin 168 undergoes a second compression when the cam lock 166 is forced onto the pin in the return stroke. Referring now to Figure 8, once the base portion 178 passes the cam lock 166, the legs 172 decompress and act to slow the rising stroke of the piston. It will be noted that the base portion 178 exerts a radial force against the interior surfaces of the stabilizing member 156 to assist in the process of slowing the stroke speed of the piston 154. However, referring to Figure 9, the piston retained 154 it has sufficient momentum to pass upwards to a point where the tip portion 180 is compressed towards the inside of the closed end of the spindle-shaped diverticulum 162. Furthermore, the final compression of the pin 168 occurs when the piston 154 reaches the most extreme part of the cylinder portion 152. By forcing the pin 168 into the spindle-shaped diverticulum 162, the return shock of the piston 154 is absorbed. In case more damping is required during the deceleration of the piston 154, an energy absorber (not shown) can be mounted between the pin 168 and the mounting flange 170. Additionally, the pin 168 and the cam lock 166 form a piston stop device for supporting the self-guided piston 154 at the end of the extended-length cylinder body 152. The piston stop device is sufficient to support the weight of the piston 154, but is easily overcome when the tool is shot. Pin 168 has the characteristic of a second function, since it acts as an impact absorption element for the deceleration of the returning piston. The foregoing helps to ensure the prevention of a premature uncoupling when the piston 154 strikes the upper end of the cylinder 152 at the end of the return stroke. Now, referring to Figures 6 and 10, there is shown an alternative piston design for use with a second embodiment of the present invention, and is generally designated with the reference number 181. Here, instead of having three individual stabilizing members , a single piston stabilizer member 182 extends around the total circumference of the piston 183, which is equivalent to the piston 154 of Figure 6. The outer profile of the piston stabilizer 182 is similar to that of the piston stabilizer members described above, wherein the outer surface 184 of the stabilizer is configured to engage with the wall of the cylinder 152. The inner region of the stabilizer is hollow, and defines a cup-shaped recess 186 on the upper end of the piston. In the present design, the upper end 188 of the driving blade 58 is threaded and extends through the piston 183 and into the recess 186 defined by the stabilizer 182. A nut-shaped fastening member 190 is threaded into the driving blade to firmly hold the piston / impeller blade assembly. The ends of the fastening member 186 can be enlarged as necessary, to add mass to the assembly. In the preferred embodiment, the fastening member is made of steel for greater durability and heat resistance. However, the use of other materials is contemplated depending on the application. A cam lock 192 is formed internally on the fastener member 190, and is configured to engage the latch pin 156 as described above (see in detail in Figure 7). The threaded portion of the driving blade defines a spindle-shaped diverticulum 94, which communicates with the cam lock 192 when the piston 183, the driving blade 58, and the holding member 190 are assembled. During operation, the cam lock 192, the pin 156, and the spindle-shaped diverticulum 194 function in the same manner as described above in relation to Figures 7 to 9. While the particular embodiments of the self-guided piston with a Piston retention device for combustion driven tools of the present invention has been shown and described, it will be evident to those skilled in the art, that these can undergo changes and modifications without departing from the spirit of the present invention in its broader aspects, and according to what is established in the following claims.

Claims (7)

1. CLAIMS 1. A combustion-driven tool for driving a fastening bolt into a workpiece, comprising a compartment, a cylinder body arranged longitudinally, at least partially, inside said compartment, and the cylinder body has a first end adjacent to a nose piece and a second end opposite the first end mentioned above; a combustion chamber adjacent to the second cylinder body; a self-guided piston disposed reciprocally within the cylinder body; an elongated driving blade attached to the piston, and elements for retaining the piston at the second end of the cylinder body, said retaining elements being sufficient to accommodate the weight of the piston, but are exceeded when the tool is fired.
2. 2. A combustion driven tool, according to claim 1, characterized in that the cylinder body has an annular groove placed in the second end of the cylinder body, and the retaining elements are disposed within the groove.
3. 3. A combustion-driven tool, according to claim 2, characterized in that it also includes a steering member placed between the internal wall of the notch to provide a radially obliquely directed impulse inwards against the retaining elements.
4. 4. A combustion driven tool, according to claim 2, characterized in that the retaining elements also include an annular member placed within the aforementioned notch, so that the annular member is coupled to the piston by means of the friction when the piston is positioned in its position at the second end of the cylinder body.
5. 5. A combustion-driven tool, according to claim 4, characterized in that the annular member also includes an inner surface having a protruding transverse flange.
6. 6. A combustion driven tool, according to claim 1, characterized in that the piston also includes at least one stabilizing member.
7. 7. A combustion driven tool, according to claim 6, characterized in that each stabilizing member includes at least one outer surface having a portion configured and arranged to slidably engage with the cylinder.