Patent Description:
Fastener driving tools include devices for driving fixation elements or fasteners, such as a nail or a staple, designed to be anchored in a material composing a work surface. A known tool is generally illustrated in <FIG>, including a housing <NUM> with a handle <NUM> for grasping and handling and shooting, on which is mounted a trigger <NUM>. The tool is gas-powered, i.e. the housing <NUM> is provided with an internal combustion engine <NUM> to generate a driving force for propulsion of a piston designed to drive a nail into the work surface. The engine <NUM> includes at least one combustion chamber <NUM> adapted to contain a mixture of fluids suitable for combustion. Igniting the mixture by an internal ignition device provides a driving force, thereby propelling the piston to drive the nail through the exit of a guide tip <NUM>. Ignition of the ignition device is initiated by the user depressing the trigger <NUM> so as to generate an electric arc in the combustion chamber.

A combustible fluid mixture, typically an air and fuel mixture, is provided to the combustion chamber <NUM> for ignition. Fuel, such as a combustible gas or liquid, is moved into the combustion chamber <NUM> by way of injection from a gas cartridge <NUM> retained in the housing <NUM>. Air may be drawn into the combustion chamber <NUM> from the surrounding atmosphere by an electric fan. Some examples of fastener driving tools are known from <CIT>, <CIT> or <CIT>.

Another known tool, which operates in substantially the same way as described above, is disclosed in earlier patent document <CIT>.

A known problem of such fastener tools is that combustion is often not optimized, thus, reducing tool efficiency, which leads to a loss of power in the tool and therefore to poor fastening quality, or even having no explosion. Also, currently available tools are not capable to adapt to different environmental conditions (e.g. varying atmospheric pressure and/or temperature) leading to a potentially ineffective and poor performance.

It is therefore an object of the present disclosure to provide a fastener driving tool with improved combustion efficiency.

In particular, it is an object of the present disclosure to provide a tool configured to allow to monitor the quality of the ignition and of the combustion of the mixture of fluids within such a tool.

According to a first aspect of the present disclosure, there is provided a fastener driving tool, comprising:.

The ionization current measurement mechanism according to the present disclosure enables the detection of anomalies in the combustion by measuring the ionization current in the chamber under compression and after the spark, as well as the detection of the type of anomaly, for example a misfire corresponding to the failure of a combustion, or soot generated by the ignition device (for instance a spark plug) or occurrence of ringing within the combustion chamber.

According to an aspect of the present disclosure, said mechanism to measure a ionization current within the combustion chamber comprise a ionization sensor.

Advantageously, the fastener driving tool comprises a mechanism to generate a signal representative of an information measured by the ionization sensor.

According to an aspect of the present disclosure, said information measured by the ionisation sensor comprise any one of (i) a dysfunction of the ignition, and (ii) an improper use of said fastener driving tool by a user.

Advantageously, the sensor can detect dysfunction of the ignition such as ringing as well as misfiring and any other incorrect actuation.

Advantageously, the fastener driving tool further comprises:.

Advantageously, the fastener driving tool comprises a mechanism to deactivate the fan assembly, said mechanism to deactivate the fan assembly comprising a switch between the fan assembly and a power supply.

Advantageously, said first fluid is ambient air.

According to an aspect of the present disclosure, said second fluid is a combustible fuel.

Advantageously, the combustion chamber comprises an outlet port comprising a third actuator which is adapted to switch between an 'open state', in which combustion chamber is vented to the atmosphere, and a 'closed state' in which said combustion chamber (<NUM>) is prevented from venting.

Embodiments of the present disclosure are now described, by way of example only, hereinafter with reference to the accompanying drawings, in which:.

In the drawings, like reference numerals refer to like parts.

As used herein, the terms 'connected', 'attached', 'coupled', 'operated' are intended to include direct connections between two members without any other members interposed therebetween, as well as, indirect connections between members in which one or more other members are interposed therebetween.

Referring now to <FIG>, an example embodiment of a fastener driving tool <NUM> is shown according to the present disclosure. The fastener driving tool <NUM> includes a combustion chamber <NUM> with first and second inlet ports <NUM>, <NUM> for inputting respective first and second fluids into the combustion chamber <NUM>. The first fluid may be air, and the second fluid may be a standard fuel. The first inlet port <NUM> includes a first actuator <NUM>, and the second inlet port <NUM> includes a second actuator <NUM>. Each one of the first and second actuators <NUM>, <NUM> is adapted to switch between an open state, allowing the respective first or second fluid to move into the combustion chamber <NUM> at a respective first or second mass flow rate, and a closed state, in which respective first and second fluid is prevented from moving into the combustion chamber <NUM>. A controller (not shown) is configured to operate any one of the first and second actuators <NUM>, <NUM> and control the time interval of the 'open state(s)' based on at least one predetermined parameter in order to provide a predetermined mass ratio of the first and second fluids within the combustion chamber <NUM>.

In this particular example, the first actuator is a fan assembly <NUM> that is configured to switch between an open and a closed state. When in the 'open state' the fan assembly <NUM> is activated so as to draw in air from the ambient atmosphere and move it into the combustion chamber <NUM>. According to an aspect of the present disclosure, the fastener driving tool <NUM> comprises a mechanism to deactivate the fan assembly <NUM> when in said first 'closed state'. Advantageously, the fastener driving tool <NUM> comprises a mechanism to activate and/or deactivate the fan assembly <NUM>. When in the 'closed state', the fan assembly <NUM> is deactivated. Activation and deactivation of the fan <NUM> may simply be provided by a switch between the fan assembly <NUM> and its power supply.

The second actuator may be a valve assembly <NUM> configured to switch between an 'open state' and a 'closed state'. The valve assembly <NUM> is operably connected to a fuel source, for example, in the form of a pressurised cartridge adapted to provide combustible fluid at constant, elevated pressure. When in the 'open state', the valve assembly <NUM> allows combustible fluid to move into the combustion chamber <NUM> from the fuel source. When in the 'closed state' the fuel source is isolated from the combustion chamber <NUM>.

Furthermore, the combustion chamber <NUM> is provided with an outlet port <NUM> having a third actuator <NUM> that is adapted to switch between an 'open state', in which combustion chamber <NUM> is vented to the atmosphere, and a 'closed state' in which the actuator <NUM> prevents venting.

The fastener driving tool <NUM> is further provided with a cylinder <NUM> extending between the combustion chamber <NUM> at a proximal end of the cylinder <NUM> and an exit <NUM> at a distal end. The exit <NUM> leads to a guide tip on the front of the fastener driving tool <NUM> adapted to direct a fastener (e.g. nail) into a work surface. A piston <NUM> is provided in the cylinder <NUM>, adapted to move from the proximal end towards the distal end under a driving force provided from within the combustion chamber <NUM>. The piston <NUM> is designed to drive a fastener (not illustrated) into a work surface.

An ignition device <NUM>, such as, for example, a spark plug <NUM>, is provided within the combustion chamber <NUM>, adapted to generate an electric arc (i.e. a spark) in order to ignite within the combustion chamber <NUM> the mixture of said first fluid and said second fluid. The spark plug <NUM> ignites the combustible fluid mixture within the combustion chamber <NUM>. Ignition is typically initiated by the user depressing a trigger of the fastener driving tool <NUM>. The fastener driving tool <NUM> further comprises a mechanism to measure a ionization current (e.g. an ionisation sensor) <NUM> within the combustion chamber <NUM>. Said mechanism to measure a ionization current within the combustion chamber <NUM> comprises an ionization sensor <NUM>.

The ionisation sensor <NUM>, as the one used for this present disclosure, is one as known in the art and is suitable for a spark plug or ignition system of a combustion system. In particular, the ignition system comprises, inter alia, an inductor or solenoid having a primary and secondary coil. The ionisation sensor <NUM> may be provided by operably coupling the secondary coil to the spark plug, as well as, a measurement circuit for measuring the ionisation current. The measurement circuit may comprise an amplifier for amplifying the ionisation current and a converter for converting the ionisation current into voltage signal.

The tool <NUM> further comprises a mechanism to generate a signal representative of an information measured by the ionization sensor <NUM>.

Preferably, the information measured by the ionisation sensor may comprise information of any one of a dysfunction of the ignition and the improper use of the tool <NUM> by an operator.

The ionisation current measured within the combustion chamber <NUM> can be utilised as an indication of the quality of the ignition within the tool <NUM>.

Thus, the present disclosure allows for (i) the detection of potential anomalies within the combustion chamber <NUM> by simply measuring the ionization current within the combustion chamber <NUM> under compression and after the spark ignition, as well as, (ii) the detection of the type of anomaly, for example, a misfire corresponding to failure of combustion, or soot generated by the ignition device (i.e. the spark plug) or the occurrence of ringing noise (knocking) within the combustion chamber <NUM>.

The operation of the fastener driving tool <NUM> will now be described with further reference to <FIG> which shows a simplified schematic illustration of the control system <NUM>. In particular, the control system <NUM> is provided with a controller <NUM> configured to provide independent digital output signals to first and second power drivers <NUM>, <NUM>.

Further, the control system <NUM> is configured to control and power the spark plug <NUM>, as well as, the ionisation sensor <NUM> and comprises a mechanism to process at least an information measured by the ionisation sensor <NUM>.

For instance, such information may be a dysfunction of the ignition, such as, for example, a ringing or misfiring, but also any other faulty actuation. The information may also be based on an improper use of the fastener driving tool <NUM> by a user. Other information may be anomalies during the combustion by measuring the ionization current within the combustion chamber <NUM> under compression and after spark ignition, as well as, the detection of the type of anomaly, for example a misfire corresponding to the failure of a combustion, or soot generated by the ignition device (for instance a spark plug) or occurrence of ringing within the combustion chamber <NUM>.

Further, the control system <NUM> of the present disclosure comprises a mechanism configured to count and record any ignition dysfunction (or anomalies of the combustion) occurrences or any information representative of ignition dysfunction (or anomalies of the combustion) occurrences, and provide a signal representative of any one of the information extracted. The control system <NUM> is further adapted to transmit a signal to a remote network, to a user receiver, and/or to a display (e.g. a maintenance signal) or any other suitable user interface adapted to notify the user of an occurrence or fault in the tool (e.g. an LED lamp coupled to the tool for a visual indication of a fault or improper use).

During use, the output signal provided to the first power driver <NUM> causes the first power driver <NUM> to switch the fan assembly <NUM> between its 'open state' and 'closed state'. Thus, by varying the output signal to the first power driver <NUM>, the controller <NUM> is able to control the time intervals for respective 'open state' and 'closed state' of the fan assembly <NUM>.

At the same time, the controller <NUM> monitors (the controller comprises a mechanism to monitor the electric current consumed by the first actuator <NUM>) the electric current consumed by the fan assembly <NUM> via sensor <NUM> (the mechanism to monitor the electric current consumed by the first actuator comprise a sensor). This information can be used to generate a feedback signal from the sensor to the controller <NUM> via a signal convertor <NUM>. The controller <NUM> is thus able to determine the electric current consumed by the fan assembly <NUM> during its 'open state' or 'closed state'.

The output signal provided to the second power driver <NUM> causes the second power driver <NUM> to switch the valve assembly <NUM> between its 'open state' and its 'closed state'. In this way, the controller <NUM> controls the time interval of respective 'open state', as well as, 'closed state' of the valve assembly <NUM>. The controller <NUM> comprises a mechanism to control the time interval of respective 'second open state' and 'second closed state' of the valve assembly <NUM> (second actuator).

When the fastener driving tool <NUM> is in use, the combustion chamber <NUM> is prepared for a firing cycle by inputting a mixture of air and fuel to the chamber <NUM>. The controller <NUM> provides an output signal to the first power driver <NUM> causing the fan assembly <NUM> to switch to an 'open state' and thereby move air into the combustion chamber <NUM>. The controller <NUM> provides an output signal to the second power driver <NUM> causing the valve assembly <NUM> to switch into an 'open state' and thereby move fuel into the combustion chamber <NUM>. In the example shown, the controller <NUM> provides the output signals sequentially so that air is provided to the combustion chamber <NUM> before fuel. However, equally, the controller <NUM> may provide output signal(s) which provide the air and fuel in any suitable sequence, including wholly or partly within the same time period.

When in the 'open state', the fan assembly <NUM> draws air into the combustion chamber <NUM> at a first mass flow rate. The specific mass flow rate during an individual 'open state' is dependent on the characteristics of the ambient air itself at that time. In particular, the inventor has appreciated that the first mass flow rate depends on the ambient atmospheric pressure. Thus, when the atmospheric pressure is low, for example, if the fastener driving tool <NUM> is used at high altitude, then the air density is relatively low and the electrical current consumed by the fan assembly <NUM> is correspondingly lower (compared to a standard mass flow rate at standard environmental conditions). Conversely, when atmospheric pressure is high, for example, if the fastener driving tool <NUM> is used at low altitude, then the air density is higher and the electrical current consumed by the fan assembly <NUM> is correspondingly higher.

As the electrical current consumed by the fan assembly <NUM> is monitored by sensor <NUM> during any 'open state' and then fed back to the controller <NUM>, the controller <NUM> is able to determine the air mass flow rate and the mass of air inputted into the combustion chamber <NUM> for the upcoming firing cycle (e.g. interpolation from the performance data of the fan assembly at different electrical current consumptions).

When the valve assembly <NUM> is switched to the 'open state' by the controller <NUM>, the elevated pressure of the fuel source causes combustible fluid to move into combustion chamber <NUM> at a predetermined fuel mass flow rate. The time interval for the second 'open state' is determined by the controller <NUM> based on the feedback signal of the sensor <NUM> (i.e. the current air mass flow rate and the amount of air moving into the chamber) in order to adapt the mass of fuel moved into the combustion chamber <NUM>, so as to optimise the fuel/air mixture for optimal combustion. Therefore, an optimum fuel/air mixture is provided irrespective of the ambient atmospheric pressure or any other environmental parameter.

Once the optimal fuel/air mixture has entered the combustion chamber <NUM>, the firing cycle commences igniting the mixture by the ignition device, generating a driving force to propel the piston and drive a fastener into a work surface.

After firing and combustion is complete, the combusted fluids are purged from the combustion chamber <NUM> in readiness for preparing the next firing cycle. Thus, the third actuator <NUM> is switched to an 'open state', via a third power driver(not shown), by the controller <NUM> to allow the combusted fluids to be vented into the atmosphere. In order to accelerate the venting, the controller <NUM> switches the fan assembly <NUM> into an 'open state' to simultaneously draw fresh air into the combustion chamber <NUM> and displace the combusted fluids vented through the outlet port <NUM>. With the combusted fluids purged, the controller <NUM> is ready to initiate preparation for the next firing cycle.

In the example embodiment the controller <NUM> bases the time interval of the valve assembly 'open state' on the electrical current consumed by the fan assembly <NUM> during preparation for the firing stage. In other words, the electrical current consumed by the fan assembly <NUM> when the outlet port <NUM> is closed.

Alternatively, the controller <NUM> may base the time interval on the current consumed by the fan assembly <NUM> when the third actuator <NUM> is open. In other words, the controller <NUM> may respond to feedback from the sensor <NUM> when the fan assembly <NUM> is providing air to displace combusted fluids in the combustion chamber. To this extent, when controlling a time interval, the controller <NUM> may evaluate, whether the third actuator <NUM> is in an 'open state' or 'closed state', in order to determine its response to the feedback of the sensor <NUM>.

Additionally, it is understood by the person skilled in the art that the control system <NUM> may base a time interval ('closed state' and/or 'open state') of either one of the first or second actuator <NUM>, <NUM> on any other indicator signal suitable for determining the ambient atmospheric pressure. The indicator may be a direct measurement, for example, from a pressure sensor directly coupled to the control system <NUM>, or a pressure measurement from a pressurised fluid source. Further, the indicator signal may be provided by one or more indirect measurement, such as, for example, the rotational speed of the fan assembly <NUM>, or a flow rate measurement device suitably positioned e.g. at the inlet port of the fan assembly <NUM>. The indicator signal may also be provided from a remote sensor, for example, atmospheric data provided from another device over a suitable wired or wireless connection, e.g. a mobile phone application.

Additionally, or alternatively, the control system <NUM> may base the time interval of the 'open state' of any one of the first or second actuator <NUM>, <NUM> on any other data suitable to derive the amount of air and/or fuel mass moved into the combustion chamber <NUM> at a predetermined time interval, e.g. ambient temperature or relative humidity.

Any indicator signal, data or measurement provided to the control system <NUM> may be provided directly or via a suitable intermediary module, for example an analogue-to-digital convertor or wireless receiver.

Any suitable actuators capable of providing fluids to the combustion chamber may be used, in any appropriate combination. For example, pumps or injectors, or any other device or apparatus capable of selectively inputting fluids for a time interval controlled by the controller. Any such devices or apparatus may include or exclude additional features required to enable them to function with a fastener driving tool.

In example embodiment of <FIG> and <FIG>, the control system <NUM> controls the time interval of the second actuator <NUM> based on a parameter associated with the first actuator <NUM>, so that the time interval of the constant pressure fuel source is controlled depending on a variable characteristic of the ambient atmospheric air. However, other mechanism of control are possible, which allow either one (or both) of the time intervals to be controlled based on characteristics of one or both fluids. For example, the time interval of the actuator inputting a fluid with a variable characteristic, such as air, may be based on the fixed pressure and time interval of a fluid provided from a pressurised fluid cartridge. Thus, many variations and combinations of parameters and controls may be adapted in order that the final mixture of fluids within the combustion chamber contains an optimum mass ratio for the specific fluids being used.

Claim 1:
A fastener driving tool (<NUM>), comprising:
a combustion chamber (<NUM>) having a first inlet port (<NUM>) for inputting a first fluid having at least one variable fluid characteristic, and a second inlet port (<NUM>) for inputting a second fluid;
a piston (<NUM>) configured to drive a fastener into a work surface;
an ignition device (<NUM>) adapted to generate an electric arc within the combustion chamber (<NUM>) in order to ignite within the combustion chamber (<NUM>) a mixture of said first fluid and said second fluid;
characterised in that the fastener driving tool further comprises means to measure an ionization current (<NUM>) within the combustion chamber (<NUM>).