MXPA97005241A - Control system for the detection and trigger desujetadores for mechanical tools impulsoras de subjectado - Google Patents

Abstract

The present invention relates to a power tool constructed to drive a driving blade in response to energy from a power supply source so that it hits a fastener and pushes it into a workpiece, which comprises: a box; of combustion defined within the box, mechanisms for supplying fuel to the combustion chamber, mechanisms distributed within the combustion chamber for the ignition of the fuel supplied to the combustion chamber, a driving blade placed inside the box to drive a fastener within the workpiece a tip operatively connected to the casing, mechanisms defining an opening within the tip to accept a fastener, and mechanisms for guiding an end of the driving blade to be impacted with the fastener; a supply assembly of the fastener operatively connected to the box to supply fasteners inside the pu Detector-optical mechanisms for detecting the presence and absence of a fastener within a portion of the supply path of a fastener defined by the fastener supply assembly and the tip, to generate signals indicating the presence and absence of a fastener within of the portion of the fastener supply path, and mechanisms that activate and deactivate combustion which respond to the signals of the optical detector mechanisms to activate the mechanisms of ignition of the fuel when the optical detectors detect the presence of a fastener inside the portion of the fastener supply path, the manner in which tool operation and fastener drive can be carried out, and to deactivate the fuel ignition mecha- nisms when the optical detec- tor mechanisms detect the absence of a fastener within the portion of the supply path of the subject or to prevent the activation of a blanking shot of the tool

Description

CONTROL SYSTEM FOR THE DETECTION AND TRIGGER OF FASTENERS FOR MECHANICAL TOOLS DRIVER OF FASTENERS This document is the continuation, in part, of the copending application with serial number, filed with date, and the priority of it is claimed in accordance with 35/120 of the Code of the United States of America.

BACKGROUND OF THE INVENTION The present invention relates in general to the improvements made to portable mechanical tools driving fasteners, such as tools driven by explosion of gunpowder and tools driven by internal combustion engines, and specifically, it refers to the improvements made in the detection of fasteners, the disabling of the firing system when the absence of a fastener is detected, and the notification to the operator when the absence of a fastener is detected. The tools driven by internal combustion engines that are used to drive fasteners into the workpieces are commonly described in the patents assigned to Ni olich, United States of America Patent Number 32,452, and the Patents of the United States of America. United States of America with Registration Numbers 4,552,162; 4,483,473; 4,483,474; 4,403,722; and 5,263,439; all of which are incorporated herein by reference. Bolt and staple driving tools driven by similar type combustion engines are commercially available at IT -Paslode of Lincolnshire, Illinois, under the trademark IMPULSE®. Said tools, generally incorporate a gun-shaped tool housing, which encloses a small internal combustion engine. The engine is powered by a pressurized fuel gas tank, also called a fuel cell. An electronic power distribution unit powered by batteries, produces the spark needed for ignition, and a fan placed inside the combustion chamber, provides an efficient combustion inside the chamber, as well as facilitates consumption, including the expulsion of the residual products of combustion. The motor includes a reciprocating piston having an elongated rigid blade disposed within the piston chamber of a cylinder body. A valve cover is axially reciprocal to the cylinder and, through a connecting element, is displaced to close the combustion chamber when a contact work element which is at the end of the connecting element is pressed against the workpiece. job. In addition, the pressure action causes the activation of a fuel metering valve to introduce a specific volume of combustible gas into the closed combustion chamber, coming from the fuel cell. The measuring valve can take the form of a solenoid valve, which is driven by the battery, or it can be a purely mechanical valve. From the moment the trigger switch is operated, which causes the ignition of a gas charge inside the combustion chamber of the engine, the piston and the impeller blade are fired down to impact with a fastener placed in their position, and direct it to the inside of the work piece. While the piston is driven in a downward direction, a displacement volume enclosed within the chamber and below the piston is forced out through one or more exit ports located at the lower end of the cylinder. After the impact, the piston returns to its original or "ready" position, by means of the action of differential gas pressures experienced inside the cylinder. The fasteners are fed to the objective piece by means of a supply assembly, such as a supply or breech conduit (loader), in which they are held in a suitable position orientation to receive the impact coming from the driving blade. A high-speed tool driven by an internal combustion engine of the same type, which has an elongated piston chamber or cylinder, is the subject of the copending US Patent Application Serial Number 08 / 536,854. The elongated cylinder increases the stroke force of the piston, which allows to obtain an increased piston speed, and to transfer the force of the impeller blade to the fastener. In one embodiment, the extended length also allows the operator to remain generally upr while the fasteners are being driven, which is done at the floor level. The fasteners are loaded into the supply duct at the operator's level, and are placed in their firing position within the objective piece. Details about the load-supply conduit at the operator's level, as well as about the associated objective piece, are described in U.S. Patent No. 5,199,624 commonly assigned to Dewey et al., Which is incorporated in the present description. as reference. A drawback associated with combustion-driven tools is the need to replace the fuel cell. The fuel cells used in the combustion-driven tools can be used for a certain number of combustions before they become empty, at which time, the replacement of the same is necessary. Convenience is improved when a fuel cell lasts for a greater number of shots before it needs to be replaced. On some occasions, the supply assembly that introduces the fasteners into the objective piece may get stuck or become empty. While such a condition can be easily solved, an operator may attempt to fire the tool before realizing that the fastener is not placed in the proper position within the objective piece. Such "blank shots" reduce the number of fasteners that are driven by each fuel cell, necessitating a more frequent replacement of the fuel cell. In addition to the above, due to blank shots, the total number of fasteners driven before the tool itself needs to be subjected to service processes is reduced. Between the parts that experience wear or rupture with the passage of time, is the piston. In each shot, the piston is violently hit against a damper that is placed at the bottom of the cylinder. Over time, such contact may cause premature failure of the piston, if blank shots are allowed to occur. In this way, the useful life of the tool is also reduced because of the blank shots, since a smaller number of fasteners are driven before the service of the tool is necessary.

Similar problems are detected in the Powder Actuated Tools (PAT) drive tools. Various types of PAT-type fastener driving tools are described, for example, in U.S. Patent Nos. 5,199,625 to Dewey et al. And 4,824,003 to Almeras et al., Which are incorporated herein by reference. PAT-type tools are commercially available at the Prospecting Societé et d'Inventions Techniques de Valence, France, a subsidiary of Illinois Tool Works, Inc., of Glenview, Illinois. In contrast to tools powered by internal combustion engines, PAT-type tools incorporate a chamber style loaded with a gunpowder cartridge located inside the combustion chamber. Similar to combustion tools, the efficiency of PAT-type tools is diminished by blank shots. Certainly, given that a simple gunpowder cartridge is used to make combustion in PAT-type tools, the blank shots represent a degree of inconvenience and waste even greater than that presented in the tools driven by internal combustion engines, in which the fuel cell is useful for many shots. According to the above, an object of the present invention is to provide a tool driven by improved internal combustion, which extends the useful life of the fuel cell and of the tool itself. Another object of the present invention is to provide a tool driven by improved internal combustion, in which the firing is prevented when the number of fasteners within the supply conduit of the breech is reduced to a predetermined number. A further object of the present invention is to provide an improved internal combustion driven tool, in which the operator is notified when the number of fasteners within the breech supply conduit is reduced to a predetermined number. A further object of the present invention is to provide an internal combustion driven tool that includes an optical detector for detecting the moment when the number of fasteners within the breech supply conduit is reduced to a predetermined number. A further object of the present invention is to provide an improved PAT type tool, in which the operator is notified at the time when the number of fasteners within the breech supply conduit is reduced to a predetermined number.

SUMMARY OF THE INVENTION The aforementioned objectives are achieved or overcome by the improved fastener driving tool driven by internal combustion of the present invention, which prevents the firing when the content level of the supply conduit is reduced to a number previously. determined. A sensing element that is positioned along the path of the fastener determines whether or not there is a fastener present. When a fastener is detected, the switches are activated to allow the entry of fuel from the fuel cell, into the combustion chamber, and also allowing the spark to ignite the fuel. If a fastener is not detected, the switches can proceed to deactivate the fuel supply and ignition of the fuel, or either of the two mechanisms separately. In the preferred embodiment of the present invention, an extended body tool includes an optical sensor [a Hall effect sensor], which functions as an element for the detection of the fastener. The placement of a fastener in any previously determined part of the fastener supply path, causes [Hall effect] that the optical sensor enables the fuel supply and ignition circuits. The tool may also include an indicator to notify the operator at the time a fastener is not detected. The indicator may be visible, such as a light emitting diode (LED), and / or audible. An alternative element to the use of the optical sensor is a Hall effect sensor. Various features of the present invention can also be applied to PAT-type tools. The use of a fastener and indicator detector in a PAT type tool, in accordance with the present invention, provides the operator with the necessary notification that fasteners must be loaded before firing. A specific embodiment of the present invention provides a mechanical tool arranged to drive a driving blade that impacts against the fastener. A compartment includes a main chamber that houses a power source. One end of the driving blade is accepted within an opening formed within the objective piece associated with the compartment. The opening accepts a fastener, and guides the end of the impeller blade to the point of impact with the fastener. The fasteners are supplied to the interior of the objective piece by means of a fastener supply conduit associated with the compartment. A fastener sensing element detects the presence or absence of a fastener within a portion of the fastener supply path defined by the supply conduit. In response to the signal supplied by the detector, an indicator issues a notification signal to the operator at the moment when the fastener detector detects the absence of a fastener.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a fragmentary side view of an extended stroke internal combustion driven driving tool in accordance with the present invention. Figure 2 is an enlarged cross-sectional view of the power source of the fastener driving tool of Figure 1. Figure 3 is a combustion disablement and fastener detecting circuit constructed in accordance with the present invention to be used with a Hall effect sensor. Figure 4 is a combustion disablement and fastener detector circuit constructed in accordance with the present invention for use with an optical fastener sensor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to Figure 1 and Figure 2, the preferred embodiment of an extended-body, high-velocity internal combustion driven fastener tool suitable for practicing the present invention is generally designated with the number 10. A main compartment 12 of the tool 10, houses an internal self-contained power source 16, which is shown in detail in Figure 2. The power source includes a combustion chamber 20 communicating with a cylinder 22 A piston 24 is disposed within the cylinder 22, and is connected to the driving blade 28. In the preferred embodiment of the present invention, the cylinder 22 is of the extended body type, and as such, is considerably longer than the impeller blade 28. Upon pressing trigger element 30, an operator induces combustion of a measured amount of propellant F, such as MAPP gas, inside the combustion chamber 20. The propellant F is agitated by a fan 31 to help accelerate combustion. In response to combustion, the piston 24 is urged towards the terminal end 32 of the cylinder 22. Once the piston 24 reaches the terminal end 32, the impeller blade 28 will be guided towards the interior of the objective holder part 34, and will be impacted. with the fastener (not shown), held on the work piece by means of the objective piece. Although it is contemplated that the tool of the present invention will be used with fasteners of multiple types, it is preferable that the fasteners used are of the so-called bolt type, described in more detail in U.S. Patent No. 5,199,625. The impact of the driving blade 28 drives the fastener into the interior of the workpiece, or substrate. As a safety feature, and in order to regulate the use of the fuel, the firing of the tool will not take place, unless the objective piece 34 is pressed against the workpiece, or substrate. Said placement causes a connecting rod 35 to be pushed upwards, which displaces the valve cover 36, to seal the combustion chamber 20. The details related to the sealing process of the combustion chamber 20, and of the mechanisms to this, they can be found in the previously mentioned Nikolich patents. From the ignition of the propellant F inside the combustion chamber 20, the piston 24 is urged towards the terminal end 32 of the cylinder 22. A damper (not shown), is disposed inside the cylinder 22 at its terminal end 32 , and defines the end of the path of the piston 24 towards the terminal end 32, while the differential gas pressures cause the piston to return to the combustion chamber 20 after the piston 24 has finished its travel in the downward direction. The tool 10 shown in Figure 1 is a type of modality called an extended body cylinder. The embodiment of the extended body cylinder 22 illustrated in particular, allows the operator to stand upright to operate the tool 10 and drive the fasteners at floor level. An important additional feature of the extended body tool 10, is the increase of the stroke of the piston 24. By increasing the stroke, the piston speed is improved upon reaching the point of impact, as well as the efficiency of the energy transfer, when compared to other types of tools powered by combustion that have a shorter stroke. As is known in the industry, the PAT-type tools have an external configuration similar to the tool 10 of Figure 1, but their operation is supported by the explosion of a powder cartridge to drive the piston 24. Similar to how it happens in a firearm, the powder cartridge is deposited inside a combustion chamber, which is equivalent to the chamber 20 of the combustion driven tool 10, and which is placed on the piston, and is ignited by the impact of a hammer, in order to drive a driving blade into the interior of the objective part, and make the impact with a fastener. A fastener supply conduit 38 is the preferred applicable delivery assembly for both tools, i.e., for the combustion driven tool 10, and the PAT type tools. An upper end of the flexible supply conduit 38 is generally connected to the upper portion of the compartment 12, like the handle 40, while the lower end of the flexible supply conduit 38 is connected to the conduit of the objective part 42 The supply conduit 38 can be held at both ends by means of the appropriate clip 44. The fasteners 46 which are fed at an open end 48 of the supply conduit 38, descend by gravity towards the objective piece 34, and into the duct of the objective piece 42. When an operator presses the objective piece 34 against a work piece, the lowermost clip within the objective piece 34 is pushed by means of a shuttle block (not shown) connected to the joining unit 47, and is placed in position within the channel 48 of the objective part 34. In this position, a fastener can be er beaten by the driving blade 28. PAT-type tools, like combustion-driven tools, are used in areas that demand a rapid cyclic operation. Frequently, an operator restores the tool in its position and triggers the trigger quickly to facilitate production. When operating under these, or other conditions, there may be failures in that the operator realizes that the supply conduit 38 is empty. The positioning of the objective piece near the foot of the operator, as well as the opaque nature of the objective piece 34, are additional impediments to recognize the moment when the supply conduit 38 is empty. The opacity of the supply conduit 38, either because of the original design or because of the accumulation of dust and dirt from the workplace, similarly serves to reduce the visibility of the vacuum condition of the supply conduit 38. To import the reason why an operator fails to realize that the supply conduit is empty, this failure can lead to a blank shot of the tool 10, that is, to make a shot when a fastener it is not placed on the channel 48. The blank shot of the tool reduces the useful life of the same, since the wear associated with the firing of the tool is produced even when no fastener is driven. Additionally, the blank shot causes the cost of propellant. In a PAT-type tool, a blank shot causes the waste of a powder cartridge, causing the gun cartridge chamber to empty more quickly. In the combustion driven tool 10, the fuel cell 50 shown in Figure 2, includes the amount of propellant F sufficient to drive a certain number of cartridges, so that when the propellant is wasted during a blank shot, it is necessary to replace more frequently the fuel cell 50, by means of displacement, by the operator, of the lid 52. These and other inefficiencies associated with the performance of blank shots are alleviated in accordance with the present invention. Referring to Figure 1, the tool 10 in accordance with the present invention includes a fastener sensing sensor 54, which is disposed along the fastener supply path defined by the supply conduit 38 and the objective part. 34, including the duct of the objective piece 42. Preferably, the sensor 54 takes the form of [a Hall effect sensor] an optical sensor that responds to a light source. The optical detector and the source, such as a photodetector and a LED element arranged in pair, are mounted in a predetermined position on the fastener supply path defined by the supply conduit 38 and the objective part 34, so that the presence of a fastener will optically separate the detector and the light emitting source. The LED element and the photodetector can be mounted internally or externally in the supply path. External mounting requires that the previously determined position within the fastener supply path be transparent, to allow light from the LED element to reach the photodetector element; while the internal assembly must be done avoiding mechanical interference between the fasteners and the sensor components. External mounting is more convenient (easy to assemble) for existing tools, while (or) any of the assemblies, can be easily incorporated into the design of modified tools. An alternative to the arrangements of the optical sensor and the LED element is the Hall effect sensor 55, which itself has a proximity sensing capability that obviates the need to place a switch within the current fastener supply path. However, the use of the Hall effect sensor 55 requires a fine calibration, in addition to the fact that the sensor has a tendency to drift during the operation phase. In addition, the Hall effect sensor 55 responds only to fasteners made of soft magnetic materials, while the optical sensor will operate independently of the material used to manufacture the fastener. With either of the two types of sensor configuration described above, the presence or absence of a fastener adjacent the sensor 54 is communicated to the fastener sensing circuit within the circuit portion 56 of the compartment 12, by means of the guides 58 Other sensors such as an optical sensor or a contact sensor can also be used, instead of the preferred optical sensor (Hall effect). However, the operating medium contributes to making the optical sensor and the contact sensor less reliable than the preferred Hall effect sensor. In addition, the contact sensor necessitates undesirable modifications of the fastener supply conduit 38, to allow contact between the (pin-type) fastener and the sensor, in addition to representing a potential risk of mechanical interference. However, such alternative sensors should be used with fasteners that are not made of soft magnetic materials, because this type of fasteners will not produce a response in the Hall effect sensor. In PAT-type mechanically driven tools, as well as in combustion-driven tools that have a mechanical fuel metering valve, the warning signal is sent to the operator when the sensor 54 detects the absence of a fastener in the portion of Adhesive supply path of adjacent fasteners. The warning signal is also preferably provided in the combustion driven tool 10, which includes an electrically controlled fuel metering solenoid valve, which can be emitted in the form of a light 60 placed within the line of sight of the operator , and / or a grid 62 for an audible signal, or some other suitable type of alarm system, sufficient to notify the operator when the sensor 54 detects the absence of a fastener. From the moment in which the notification is sent by means of the grid 62 or by means of the light 60, the operator proceeds to load the additional fasteners in the opening 48 of the supply conduit 38, in order to avoid the realization of firings in White. In tools that include electrical components within the firing system, blank shooting can also be avoided, and firing, when no fastener is detected. In addition, the waste of propellant can be avoided if the propellant is normally supplied, through the use of electrical fuel measuring components. Taking advantage of the electrical components incorporated in the combustion driven tool 10, the present invention contemplates the disabling of the fuel ignition of the combustion driven power tools when the sensor 54 detects the absence of a fastener in the supply conduit portion of fasteners adjacent to the sensor 54. Referring to Figure 2, the propellant F is introduced into the combustion chamber 20 through the fuel pipe 64, under the control of a solenoid valve assembly for fuel measurement 66. Electric power for the valve assembly 66, the fan 31, and the spark coil 68, is provided by at least one battery 69 (shown extensively in FIG. Figure 1). In conventional combustion driven tools, the introduction of the propellant F under the control of the valve assembly 66 occurs in response to the pressure of the objective piece 34 against a workpiece. The movement of the fan 31 to agitate the propellant F also occurs in response to the pressure exerted on the objective piece. Thus, the trip occurs when the spark coil 68 turns on the propellant F in response to activation of the trigger 30 by the operator. In a conventional mechanical tool driven by combustion, the process can be carried out even when the fastener supply conduit 38 is empty. In accordance with the present invention, the combustion process is disabled when the sensor 54 detects the absence of a fastener in the portion of the adjacent fastener supply path. Both the spark coil 68 and the fuel metering valve assembly 66, or either of the two separately, can be deactivated to prevent a trip when the presence of a fastener is not detected. The deactivation or disqualification of the fuel supply just mentioned is not possible if the fuel measuring valve assembly 66 is completely mechanical, but it is preferable when a solenoid valve or other type of electromechanical valve is used within the assembly. valve 66, because an additional benefit can be obtained in terms of fuel savings. Referring to Figure 2, if a blank shot is prevented only by disabling the spark coil 68, the propellant remains inside the combustion chamber 20, after the valve cover 36 it closes by the action of the connecting rod 35. An operator who has been prevented from firing the tool 10 by means of disabling the spark coil 68, must lift the tool to restart the firing process, so that the it realizes the reopening of the combustion chamber 20 at the moment in which the valve cover 36 moves downward, releasing the propellant that was introduced into the interior of the chamber. This waste of propellant is avoided by means of disabling the electromechanical solenoid valve assembly for the preferred fuel measurement 66, when the sensor 54 detects that no fastener is present. Referring to Figure 3, a preferred embodiment of a combustion alarm and disablement circuit 70, constructed in accordance with the present invention, is shown to be used in cases where the sensor 54 comprises a Hall effect sensor 55. Generally, the circuit includes an oscillator section 72, a sensor section 74, an alarm section 76, and a disabling section 78. The oscillator section 72, including the resistors R1-R2, the capacitor Cl, the diode DI, and the gate NAND Al, produce pulses of energy, preferably at a low level to reduce the consumption of the energy coming from the battery 69, by means of the activation of the emitting diode of light 60 (D2), during short periods of pulsation. Of course, the same technique is preferably used to generate an audio alarm (which is not shown in Figure 3), which is used in addition to, or instead of, the light emitting diode 60. Although the circuit values can be chosen to configure some particular application, the illustrated values produce a pulse oscillation of approximately 1 ms / s. The sensor section includes a stable voltage source 80 for activating the Hall effect sensor (54) 55, and for providing a selectable voltage to the voltage tracking comparator Cl, through a voltage divider comprising two resistors R8 and R9, and a variable resistor VR1. The voltage output from the Hall effect sensor (54) 55 is followed by the output of the comparator C2. When the Hall effect sensor (54) 55 detects a fastener, the voltage output from the comparator C2 exceeds the voltage output from the comparator Cl, to make the output of the comparator C3 high. The above causes the output of the NAND gate A2 to be low, so it disables the diodes D2 and D3, which, in turn, produce signals, respectively, to disable the spark coil 68, and the valve assembly fuel measurement 66. In addition, the output of low electrical potential from the NAND gate A2, disables the NAND gate A3 through the NAND gate A4, to prevent the pulses from the oscillation circuit section 72 from activating the diode light emitter 60. The modification of the alarm and disabling circuit 70 for PAT-type tools (and for combustion-driven mechanical tools) simply requires the omission of the disabling circuit section 78, since there is no system electric that allows to disable combustion in conventional type PAT tools. The exact placement of the Hall effect sensor (54) 55 along the fastener supply path determines the time at which disabling combustion or emitting the alarm signal occur. In the position shown in Figure 1, disabling occurs when two fasteners 46 remain inside the objective piece 34, including the duct of the objective piece 42. This represents a convenient positioning position for mounting the Hall effect sensor (54). ) 55, although other positioning positions can be used. The displacement of the Hall effect sensor (54) 55 to a lower portion of the fastener supply path could reduce the previously determined number of fasteners which activates the disablement and alarm mechanisms, from one to zero. The number of fasteners can be equally high, by moving the sensor 54 or 55, upwards, in the direction of the fastener supply conduit 38. The exact positioning of the sensor 54 will depend on the shape of the fastener used, and this should be aligned to produce the most intense response possible. As an example, we would say that the bolt-type preferred fasteners produced the most intense response when the Hall-effect sensor (54) 55 was placed along the supply path, aligning it with the washer portion of the fastening bolt. For purposes of reliability and ease of manufacture, the Hall effect sensor (54) 55, preferably has an output that is proportional to the magnetic field generated by a magnet attached to the back of the sensor, when it is mounted on the sensor. fastener supply conduit 38. Out of the presence of a magnet, the output of the Hall effect sensor (54) 55 will generally be a given multiple of the voltage supplied by the voltage source section 80., for example 1/2. This will be increased once the magnet is clamped, and also increases when a fastener is close to the Hall effect sensor (54) 55. However, there may be some variation in the amount of the increase produced by the magnet, depending on the the properties and the exact size of the magnet used. Instead of providing more exact tolerances for the magnet, the variations in the produced magnetic field are accounted for during the manufacturing process of the tool, by means of the adjustment of the voltage in the terminal 82, depending on the voltages with presence of fastener and absence of clamp measured in terminal 84. Using the logic applied in the mode of Figure 3, the output of C2 (terminal 84), should be smaller than that which is represented by Cl (terminal 82), when no fastener is found. next to the Hall effect sensor 55. In the presence of a fastener, the voltage presented by C2 should exceed the voltage presented by Cl. Preferably, the voltage present in the terminal 82 is established during the manufacturing process, by adjusting the variable resistor VR1, to be the midpoint between the voltages with the presence of a fastener and in the absence of a fastener, measured at terminal 84. This adjustment can be carried out at any time subsequent to the coupling of the Hall effect sensor (54) 55, and its magnet. This process also confirms that the polarity of the magnet is properly aligned with respect to the Hall effect sensor (54) 55. When the polarity of the magnet is oriented in the proper direction, the presence of a fastener causes an increase in the voltage present in terminal 84. If the polarity is reversed, a reduction is observed. These calibration difficulties are overcome by the use of a sensor 54 that includes an optical sensor (sensor) and a source, such as a photodetector 86 and an LED element 88, as shown in Figure 4. The photodetector element 86 and the LED element 88 are configured so as to allow passage of a light pulse through the portion of the supply path at the location where the sensor 54 is mounted, in the absence of a fastener; and said luminous pulse is blocked when a fastener is present. An oscillator circuit 90 generates a pulse of 2 ms every second, which causes the activating transistor Qll to produce an equally short pulse of light in the LED element 88. If no fastener is present, the light pulse is received by the photodetector element 86. A signal from the photodetector element 86 is amplified by the amplifier element 92, which is formed by a damping stage and two stages of coupled gain capacitors. The coupling of the capacitors eliminates direct current (DC) voltages. The peaks in the amplified signal of the LED are detected by a peak detector circuit 94, and are used to determine the presence or absence of a fastener, by means of a comparator C4, which has a reference voltage applied to its output investment. When no fastener is present, comparator C4 produces an output capacitor to NAND gate A5, whereby the oscillator circuit is allowed to pulse LED 60 (also shown in FIG. 1). When applied to a combustion driven tool, diodes D4 and D5 are preferably used to provide signals that disable the spark coil 68 and the fuel metering valve assembly 66. Of course, when a fastener is found present, the NAND gate is deactivated so that the LED 60 is not pressed, and deactivation signals are not provided by the diodes D4 and D5. The modification of the circuit of Figure 4 for tools of the PAT type is carried out by leaving the outputs of the diodes D4 and D5 disconnected, or by omitting, completely, the diodes and the outputs. According to the description made above in relation to the drawings, the features of the present invention provide the notification to the operator when the number of fasteners has been reduced to a predetermined number in the PAT type tools and in the combustion-driven mechanical tools. , as well as providing the necessary elements to deactivate the combustion in the tools operated by combustion, in cases in which the same condition mentioned above occurs. All, or some, of the features of the present invention, could be applied to other tools, such as pneumatic tools. In addition, although a particular embodiment of the control system for the detection and firing of fasteners for combustion-driven mechanical tools and PAT-type tools of the present invention has been shown and described, it should be apparent to those skilled in the art, the fact of that changes and modifications may be made thereto, without departing from the spirit and scope of the invention in its broadest aspects, as set forth in the following claims.

Claims (8)

1. CLAIMS 1. A mechanical tool driven by combustion, built to drive a driving blade in response to energy from a power supply source, to impact a fastener and push it into a workpiece, which comprises the following: A compartment having a main chamber housing the aforementioned power supply source. A nose piece associated with the aforementioned compartment, which has a defined opening for accepting a fastener and guiding one end of said driving blade toward the point of impact with the aforementioned fastener. A fastener supply assembly associated with the aforementioned compartment for supplying the fasteners to the interior of the aforementioned nose piece. A fastener sensing element for detecting the presence or absence of fasteners within a portion of the fastener supply path defined by the aforementioned fastener supply assembly and nose piece. An indicator that responds to the aforementioned fastener detector signal, to notify the operator when the fastener detector detects the absence of a fastener.
2. 2. A tool in accordance with claim 1, characterized in that said tool is a mechanical tool driven by combustion further comprising the following: A combustion chamber configured to communicate the combustion force to the aforementioned driving blade. A fuel cell that is placed inside the aforementioned compartment to supply a predetermined amount of fuel into the combustion chamber. An ignition element to ignite the fuel that is inside the combustion chamber to drive the aforementioned driving blade. An element for combustion disablement configured to prevent combustion within the combustion chamber when the fastener detector detects the absence of a fastener in the aforementioned supply path portion.
3. 3. A tool according to claim 2, wherein the combustion disablement element comprises a circuit that responds to the aforementioned detector signal, and said circuit activates the ignition element when the detecting element detects a bra.
4. 4. A tool in accordance with claim 3, which also comprises the following: An element for the supply of fuel, which regulates the supply of fuel from the aforementioned fuel cell to the interior of the chamber of combustion. A fuel supply switch within the aforementioned circuit, which activates the fuel supply elements when the detector detects a fastener.
5. 5. A tool according to claim 2, which also comprises the following: Fuel supply elements that regulate the fuel supply coming from the aforementioned fuel cell towards the interior of the combustion chamber. A fuel supply switch within the aforementioned circuit, which activates the fuel supply elements when the detector detects a fastener.
6. 6. A tool according to claim 1, wherein the aforementioned fastener detector comprises a Hall effect sensor (subject a) located in the lower portion of the aforementioned fastener supply assembly.
7. 7. A tool according to claim 1, wherein the fastener detector comprises an optical source and an optical detector located in the lower portion of the fastener supply conduit such that a fastener is present in the fastener supply conduit. said lower portion of the fastener supply assembly prevents a signal from the aforementioned light source from reaching the light detecting element.
8. 8. A tool according to claim 1, wherein the indicator comprises a light.