SE535460C2 - Compressed air powered tool with integrated voltage generating device - Google Patents

Abstract

Abstract. Pneumatic power tool comprising a housing a motor(14), (19), (17) (10), an accumulator a pressure air inlet passage and an exhaust outlet passage (22), both passages (17, 22) being connected to the motor, a throttle valve (12)located in the inlet passage(25), (18) (17), and an electric energy consuming device wherein an electric voltagegenerating device is arranged to deliver a voltage for energising the electric energy consuming device (25). The(19) (25), electric accumulator is connected to the electric consuming device and a charging controlling circuitryconnects the accumulator to the electric voltage generating(18). (18) device The voltage generating device (40) comprisesconnected to the air (20) an air turbine, a generator turbine, and an air feed passage (34) connecting the air turbine to the pressure air inlet passage (17) wherein a charge level indicating device is connected to an accumulator (19), and a shut-off valve (21) is located in the feed passage(20) and arranged to interrupt the pressure air supply to the air turbine (34) as the charge level indicating device indicates a certain charge level of the accumulator (19).

Description

Pneumatic tool with integrated voltage generating device The invention relates to a pneumatic tool having an integrated voltage generator. In particular, the inventionconcerns a pneumatic impulse wrench wherein the electric voltage is generated by a turbine driven generator.

Pneumatic tools of the above mentioned type are predominant tools like power wrenches, grinders etc. but are frequently used also in process industry. In many applications thereis a demand for obtaining accurate and precise informationof the motor operation and/or the actual status of themotor unit or status of work performed. Preferably, this isaccomplished by using electrically actuated operationmonitoring or controlling means for obtaining data of theand/or means for motor speed, the power shut off etc. indicating accumulated operation time, motor temperatureetc. Such operation and status monitoring means is dependent on signals from signal emitting sensors on themotor unit. Using sensors of this type is no problem inelectrically powered tools where electric power is alwaysaccessible, but using sensors and transferring data inpneumatic tools is not possible unless there is especiallyprovided electric voltage, either via a cable connection with an external electric power source.

In some applications it is not practical or suitable to usecables, routed separately or in connection with a pressureair conduit, for supplying electric power to the motorunit. This means that in such applications there has to beprovided a voltage generating means integrated in the motor unit itself.

An alternative to supply electric power via a cable wouldbe to provide the motor unit with an onboardbattery/accumulator.

However, accumulators are rather space demanding, and a battery of small enough dimensions wouldhave a restricted service life and would neither be able toprovide peak currents of magnitudes required for powering sensors and/or wireless communication equipments.

An example on pneumatic tools with an integrated voltage generating means is described in US Patent 6,840,723. Thisknown motor unit forms a part of a milling tool spindle andcomprises a pneumatic turbine, wherein the turbine rotor isprovided with a permanent magnet arranged to cooperate witha stationary coil to form a voltage generating means. Themagnitude of the voltage generated by this device is speeddependent and is used for activating a speed governing air inlet valve.

This prior art device is disadvantageous in that itrequires a specific design of the turbine rotor forattaching the magnet since the voltage generating device isintegrated on to the tool main air motor. Anotherdisadvantage is that the location of the coil is restrictedto a well defined disposition relative to the main motorrotor. Yet another disadvantage of this tool is that thegenerator only can supply the tool circuit board with a voltage when the tool is actually being used.

It is an object of the invention to provide a pneumatictool which comprises a motor with a voltage generatingmeans of a compact and durable design, wherein the locationof the voltage generating means is not restricted to a specific disposition relative to the air motor rotor.

Another object of the invention is to provide a pneumatictool having a more reliable electric voltage source inorder to facilitate use of the tool during different stages of operation.

Further objects and advantages of the invention will appear from the following specification and claims.

A preferred embodiment of the invention is described below in detail with reference to the accompanying drawing.

In the drawing Fig. 1 shows a shortened side view, partly in section, of apneumatic power wrench comprising a voltage generatingdevice according to the invention.

Fig. 2 shows on a larger scale, an exploded view of thevoltage generating device according to the invention.Fig. 3 shows a section view of the voltage generatingdevice according to the invention.

The pneumatic power wrench shown in Fig. 1 comprises ahousing 10 with a handle 11 and a throttle valve 12. In thehousing 10 there is supported a rotation motor 14, and anoutput shaft 13 is coupled to the motor via a non-illustrated hydraulic impulse generator. The handle 11 isalso provided with a connection 16 for a pressure airsupply hose, a pressure air inlet passage 17 and an exhaustair outlet passage 22 for directing exhaust air to theatmosphere. The inlet passage 17 connects the pneumatic tool, via the hose to a pressure air source. An electricvoltage generating device 18 comprising of a turbine 34 being connected to a generator 40 is arranged to deliver a voltage for energising an electric energy consuming device25. An air feed passage 20 is provided for connecting theair turbine 34 to the pressure air inlet passage 17. In thepreferred embodiment is the feed passage 20 arranged,upstream of the throttle valve 12, between the pressure airinlet passage 17 and the exhaust outlet passage 22. Thelocation of the feed passage 20 is chosen so as to providethe electric voltage generating device 18 with a continuesair pressure, even when the tool is not in use.The electric energy consuming device 25 comprises ofdifferent electronic process control circuits/units. Anelectric accumulator 19 is provided which is connected tothe electronic process control units. An accumulatorcharging device, with a charge level sensing and charging controlling circuitry, is located in the tool. The circuitalso has a means for rectifying the voltage so as toprevent the voltage from flowing back to the generator. Inthis latter case the generator could start to act as a motor instead.

The air feed passage 20 is furthermore provided for with anshut-off valve 21 that is arranged to interrupt thepressure air supply to the air turbine when the chargelevel sensing circuitry indicates that a certain charge level of the accumulator has been obtained.

The electric energy consuming device 25 comprises of anintegrated electronic process control circuits. Theelectrical circuit has several functions. The first is tostore the power so that the generator system does not needto be active at all time and to control the power storage so that the generator system can be activated or deactivated and to regulate the charge level to a certainlevel. The electrical circuit also has a voltage addressingso as to prevent that the voltage from flowing back to thegenerator. In this latter case the generator could start toact as a motor instead. Further the control unit 25 isprogrammable to be able to make the pneumatic tool carryout screw joint tightening operations according to desiredtightening strategies.

Fig. 2 shows on a larger scale a exploded view of theelectric voltage generating device 18 according to theinvention, comprising of a turbine wheel 31, enclosed by a turbine band 32 with an integrated generator 40. The sizeof the generator 40 has to be small in order to fit intothe handle of the pneumatic tool but still big enough todeliver the necessary power to energise the energy consuming device 25. The generator part comprises of abrushless DC motor with a rotor 35, comprising permanentmagnets, and is on its outer periphery connected to theturbine wheel 31. The generator stator 37 is supported bythe outlet plate 38 of the turbine housing 39. Thegenerator 18 in this embodiment is specified for a power of7 W.

The diameter of the generator 18 is 12 mm, where the rotor is 4 mm wide and weights 3,3 g. The motor is furtherspecified to have 2700 rpm/volt, which for 5 V corresponds to 13500 rpm.

The turbine wheel 31 is adapted to match the recommendedrotation rpm speed of the generator in order to avoid unnecessary use of gearings. The turbine used in thepreferred embodiment is a single stage axial-flow impulseturbine. The single stage turbine is recommended due to its size, since the effect requirements are limited, in this case less than 10 Watt. The turbine wheel 31 and the fixed nozzle 33 are dimensioned for the turbine. The specificdesign of the turbine parts are known per se and does not form part of this invention.

The feed passage 20 which provides the turbine withpressurised air is further provided with a shut-off valve21. The shut-off valve 21 is adapted to be actuated bymeans of an electric current acting on an electric coilThe actuation of the valve is element, not shown. controlled by the controller 25 on the circuit board.

Upon reaching of a certain charge level of the electricaccumulator, the controller 25 activates the coil thatcauses the shut-off valve 21 to close the air feed passage20. As the airflow is stopped the turbine will cease torotate which will stop the electric voltage generation. Theshut-off valve will stay closed until the accumulatorvoltage level has reached a certain minimum level. Theclosed valve will prevent the pressurised air from flowingtowards the exhaust outlet passage 22. The tool willconsequently not consume any pressurized air while theaccumulator 19 has a certain acceptable voltage level. Onthe other hand will the tool always be fit for use evenwhen the tool has not been used for a prolonged period oftime.Fig. 3 shows on a larger scale a section view A-A of theelectric voltage generating device 18 according to theinvention, comprising the turbine wheel 31, enclosed by the turbine band 32 with the integrated generator 40, the rotor35 and stator 37. The stator is supported by the outlet plate 38 of the turbine housing 39, which also provides the exhaust passage from the turbine. The feed passage 20provides the turbine with pressurised air is provided with a shut-off valve 21.

The preferred embodiment as sated above is not limited tothis. The generator 40 could also comprise of another typeof generator. The generator could e.g. be located at adistance from the turbine, but preferably still with acommon axis. This would enable a larger capacity of thegenerator. The turbine could also be a multi step turbinewhile the shut of valve could also be chosen to be of anysuitable type in order to obtain the same function asdescribed above. The air feed passage 20 could beconfigured in differently. The main requirement is that thefeed passage 20 is continuously supplied with pressurizedair when the tool is connected to the pressurized airsource. The electric voltage generating device 18 could also be provided in an exhaust passage of the tool.

The electric voltage generating device 18 could also beprovided as a module, to be release-ably connected to a tool. In such a configuration, the module contains aconnection for pressure air supply which communicates airto the air feed passage 20 of the voltage generating device18, and a passage which is connected to the air inletpassage 17 of the connected tool. The module furthercomprises electrical cables for connecting to the connectedtool. The charging and activation of the shut-off valve 21 follow the same principals as described above.

The above described embodiment of the invention isdescribed in connection with a pneumatic power wrench, but the invention is not at all restricted that application.

Claims (6)

1. Claims.1. Pneumatic power tool comprising a housing (10), a(14), (17)(17, 22)(12) motor a pressure air inlet passage and an exhaust outlet passage (22), both passages being connected to the motor, a throttle valve located in the inlet passage (17), (25), and an electric energy consumingdevice (18) wherein an electric voltage generating deviceis arranged to deliver a voltage for energising the electric energy consuming device (25),c h a r a c t e r i z e d (18) in that the voltage generating device comprises an air turbine, a generator (40) connected to the air turbine, (20) (34) and an air feed passageconnecting the air turbine (17). to the pressure air inletpassage

2. Pneumatic tool according to claim 1, wherein an(19)(25), electric accumulator is connected to the electric consuming device and a charging controlling circuitryconnects the accumulator to the electric voltage generatingdevice (18).

3. Power tool according to claim 1 or 2, wherein the air feed passage (20) (17) is connected to the air inlet passage at a point upstream of the throttle valve (12).

4. Power tool according to claim 3, wherein a charge level indicating device is connected to the accumulator (19), and a shut-off valve (21) is located in the feed passage(20) and arranged to interrupt the pressure air supply to the air turbine (34) as the charge level indicating device indicates a certain charge level of theaccumulator (19).comprising a housing (10), (17)

5. Pneumatic power tool, (14), a pressure air inlet passage and an(22) (12) a motorexhaust outlet passage both being connected to thelocated in the inlet passage (25), motor, a throttle valve (17), and an electric energy consuming device wherein an electric voltage generating device (18) is arranged todeliver a voltage for energising the electric energyconsuming device (25),c h a r a c t e r i z e d (18) in that the voltage generatingcomprises an air turbine (34), (34), device and a generator (40) wherein the air (22) connected to the air turbine turbine (34) is located in the exhaust oulet passage and arranged to be energised by the exhaust air flow from the motor (14).

6. Power tool according to claim 5, wherein anaccumulator (19) is connected to the electric energy (25), and a charging controlling circuitry (19) consuming device connects the accumulator to the voltage generating device (18).