Patent Description:
Two main applications are identifiable in railway constructions:.

The assembly or disassembly of the truck wheels consists of screwing or unscrewing the fixing nuts of the wheel in the horizontal position.

The work listed above is physically demanding and repetitive and requires postures, which can quickly tire the worker's muscles. Operations of screwing and unscrewing result in considerable acoustic noise and mechanical vibrations due to the percussion mechanism, the internal combustion engine, the reduction mechanism and interaction with friction of the bolts, nuts and screws with components to be screwed or unscrewed. Furthermore, using the wrench in varying climatic conditions and immediately at the ballast of the railway line, at times in a position resting directly thereon, at times in a vertical position, not only expose the wrench to intense mechanical stress, but also to humidity, drops and water sprays, stones and metal powders, which are inevitably present at the railway sleepers.

The noise and vibrations, combined with the weight of the wrench and also the exhaust gases of the combustion engine, create wearing conditions for the worker.

Furthermore, the mechanical vibrations and exposure to dust and humidity contribute to the deterioration of the mechanical and electrical/electronic parts of the wrench.

The heating of the wrench motor must be limited by means of forced ventilation to prevent the motor and electrical/electronic components from overheating, and to protect the operator. This requirement applies both to combustion engines and to electric motors. However, the forced ventilation sucks dust, humidity and drops of water into the housing of the wrench, thereby increasing the risk of damage to the electrical and electronic components.

Finally, the vibrations of the motor, the reducer, and the percussion mechanism move and wear out juxtaposed interfaces of the housing of the wrench and further promote the inlet of humidity, drops of water and dust into the wrench.

<CIT> describes a tool according to the preamble of claim <NUM>. It is therefore the object of the present invention to provide an improved impact motor-wrench, having features such as to overcome at least some of the stated drawbacks with reference to the prior art.

Such object is achieved by means of an impact motor-wrench according to claim <NUM>. Dependent claims relate to preferred and advantageous embodiments.

To better understand the invention and appreciate the advantages thereof, some nonlimiting examples of embodiments will be described below with reference to the accompanying figures, in which:.

With reference to the figures, a motor wrench (hereinafter, wrench) is globally denoted with reference numeral <NUM> and comprises a tool-holder shaft <NUM>, adapted to support a bush or similar tool for engaging the nuts or heads of the screws to be screwed, unscrewed. The tool-holder shaft <NUM> is arranged on a front side F of the wrench <NUM> and rotatably supported about a rotation axis R.

A motor unit <NUM>, e.g., an electric motor <NUM>', preferably a brushless motor, powered by two electric batteries (rechargeable) <NUM>, may be arranged in a central region, or on a rear side P of the wrench <NUM> opposite to the front side F and is adapted to produce the kinetic energy, in particular, the rotary motion and the couple needed for screwing/unscrewing operations. The motor unit <NUM> is operable and controllable by means of a manual actuation member, e.g., a button or trigger operating switch <NUM>.

The wrench <NUM> further comprises a transmission unit <NUM> with a percussion mechanism <NUM> arranged between the motor unit <NUM> and the tool-holder shaft <NUM>. Such transmission unit <NUM>, e.g., a reducer mechanism, interacts with the motor <NUM>' and the tool-holder shaft <NUM> so as to transmit the rotary motion (transforming the angular speed thereof and the couple) from the motor <NUM>' to the tool-holder shaft <NUM> for rotating the latter about the rotation axis R.

The motor unit assembly <NUM>, the transmission unit <NUM> and the percussion mechanism <NUM> form a base body <NUM> of the wrench <NUM>, which substantially develops along the rotation axis R.

The wrench <NUM> further comprises two gripping handles <NUM>, <NUM> secured to the base body <NUM>. The gripping handles <NUM>, <NUM> both have an elongated shape and are transversely spaced apart from each other with respect to the longitudinal extensions thereof or, in other words, they are not arranged along the same straight line. Advantageously, the two gripping handles <NUM>, <NUM> are oriented so as to define a gripping plane A, which is substantially tangential to both gripping handles <NUM>, <NUM> and transversal, preferably perpendicular, to the rotation axis R. The actuation member <NUM> of the motor <NUM>' may be associated with one of the two gripping handles <NUM>, <NUM>.

The wrench <NUM> can further comprise an elongated-shaped auxiliary grip <NUM>, arranged on an upper side S of the wrench <NUM>, and spaced apart from the gripping plane A along the rotation axis R in the direction of the front side F of the wrench <NUM>, and possibly extending parallel to the rotation axis R.

The two gripping handles <NUM>, <NUM> and, if provided, the auxiliary grip <NUM>, can form, together, a three-dimensional handlebar structure <NUM>, which is preferably connected and rigid in itself, and connected to the base body <NUM> of the wrench <NUM>, e.g., by means of screws and by means of interposing damper elements, e.g., bushing or rubber washers (so-called anti-vibration elements).

According to one aspect of the invention, the wrench <NUM> comprises a damping connection system <NUM> (in other words, an anti-vibration system), which mechanically connects a transmission housing <NUM> of the transmission unit <NUM> (reducer and percussion mechanism) with a main housing <NUM> of the motor unit <NUM> (only electric motor <NUM>' or with battery/batteries <NUM>) and the main housing <NUM> with the handlebar structure <NUM> and which comprises one or more first damper elements <NUM>, e.g. bushing or rubber washers, interposed between the transmission housing <NUM> and the main housing <NUM> and one or more second damper elements <NUM>, e.g. bushing or rubber washers, interposed between the main housing <NUM> and the handlebar structure <NUM>, so that:.

Furthermore, the wrench <NUM> is devoid of rigid mechanical connections between the transmission housing <NUM>, the main housing <NUM> and the handlebar structure <NUM> bypassing the first damper elements <NUM> and second damper elements <NUM>.

The damping connection system <NUM> realizes two anti-vibration barriers in series between the transmission housing <NUM> (where the striking hammer of the percussion mechanism <NUM> and the reducer generate the most important mechanical vibrations and knocks) and the handlebar structure <NUM>, which is gripped by the user, thereby protecting the user from harmful vibrations and allowing the use of the wrench <NUM> to be prolonged.

Furthermore, the damping connection system <NUM> exploits one of the two anti-vibration barriers as an anti-vibration barrier between the transmission housing <NUM> and the main housing <NUM>, protecting the motor <NUM>', the control electronics and the electrical power components, as well as the connection interfaces of single housing shells, possible displays, etc. from damage due to undesired mechanical movements, knocks and wear.

According to an embodiment, the damping connection system <NUM> comprises a central connection body <NUM>, e.g., a plate or a rigid frame (<FIG>, <FIG>), preferably made of metal (aluminum or steel), positioned between the motor unit <NUM> and the transmission unit <NUM>, and which forms:.

As an alternative to the third connection seats <NUM>, the central connection body <NUM> may be made in one piece with the main housing <NUM>.

According to an embodiment, the first connection seats <NUM> each comprise a hole for inserting a screw or a connection pin, and a cylindrical seat or flange for at least partially housing one of the first damper elements <NUM>, respectively.

Advantageously, there are provided three or more, preferably four, first connection seats <NUM> positioned about the and at a distance from the rotation axis R.

According to an embodiment, the second connection seats <NUM> each comprise a hole for inserting a screw or a connection pin, and a cylindrical seat or flange for at least partially housing one of the second damper elements <NUM>, respectively.

Advantageously, there are provided three or more, preferably four second connection seats <NUM> positioned about the and at a distance from the rotation axis R.

The second connection seats <NUM> are made at a distance from one another and from the first connection seats. Advantageously, the orientation (e.g., the screw/pin insertion axis) of the second connection seats <NUM> is transversal, preferably perpendicular, to the orientation of the first connection seats <NUM>. For example, the first connection seats <NUM> may be oriented parallel to the rotation axis R and the second connection seats may be oriented perpendicular to the rotation axis R (<FIG>).

According to a further embodiment, the orientation of the second connection seats (<NUM>) is parallel to the orientation of the first connection seats (<NUM>), e.g., parallel to the rotation axis (R). Alternatively, the first connection seats (<NUM>) and/or the second connection seats (<NUM>) are oriented perpendicular to the rotation axis (R).

According to an embodiment, the third connection seats <NUM> each comprise a hole for inserting a screw or connection pin and preferably, they are oriented parallel to the rotation axis R.

The central connection body <NUM> may comprise stiffening ribbing <NUM> and lightening openings <NUM>.

According to a further embodiment, the damping connection system <NUM> comprises one or more third damper elements <NUM>, e.g., bushing or rubber washers, interposed between the central connection body <NUM> and the main housing <NUM>, so that:.

According to an embodiment, the third connection seats <NUM> of the central connection body <NUM> each comprise a hole for inserting a screw or a connection pin, and a cylindrical seat or flange for at least partially housing one of the third damper elements <NUM>, respectively.

According to an embodiment, the wrench <NUM> comprises a vibration sensor <NUM>, such as an accelerometer, placed and configured to detect the vibrations of the handlebar structure <NUM> and in signal connection with an electronic control system <NUM> of the wrench <NUM>.

Preferably, the vibration sensor <NUM> is positioned at one of the gripping handles <NUM>, <NUM>.

The electronic control system <NUM> is configured to generate notifications (e.g., symbolic, chromatic, alphanumerical, acoustic or numerical, residual usage time or permissible excess usage time), depending on the detected vibration values and the operation time to which the detected vibration values refer, as well as predetermined exposure limits.

For example, the electronic control system <NUM> is configured to:.

According to an embodiment, the electronic control system <NUM>:.

Preferably, the electronic control system <NUM> filters the detected vibration values, by excluding, from the processing, the frequency vibrations, which are higher than a predetermined threshold of harmlessness for the user.

According to a further embodiment, the electronic control system <NUM> compares features (intensity and/or frequency of the acceleration) of the detected vibrations with predetermined reference intervals, which are indicative for correct operation of the wrench <NUM> and, in the event of the features of the detected vibrations departing from the predetermined reference intervals, it generates a fault warning.

Advantageously, this comparison takes into consideration (e.g., by means of using different predetermined reference intervals depending on) the level of torque set by the user (for example, by means of the torque selection switch <NUM>, which will be described later on).

The screw-driver <NUM> comprises a cooling fan <NUM> for the motor <NUM>' configured to be activated together with the operation of the motor <NUM>', sucking ambient air through an inlet opening (grid) <NUM> formed in the main housing <NUM>, conveying the sucked ambient air through, or along the motor <NUM>' and expelling the air through an outlet opening (grid) <NUM> into the environment.

Advantageously, the cooling fan <NUM> is directly connected to a rotor of the motor <NUM>' on one side facing the rear side P of the wrench <NUM>.

Preferably, the inlet opening (grid) <NUM> is positioned on two opposite lateral sides of the main housing <NUM> and can comprise inlet guide surfaces <NUM>, which direct the sucked air flow inside the main housing <NUM> towards the rear side P of the wrench <NUM> and towards the separation wall (<NUM>).

Preferably, the outlet opening (grid) <NUM> is positioned on a front side of the main housing <NUM> facing towards the front side F of the wrench <NUM> and can have, for example, an annular-slit shape through which the cooling air flow is expelled in the front axial direction. In this way, the expelled air flow removes, from the main housing (<NUM>), the dust dispersed or the swarf scraped during the screwing/unscrewing.

According to one aspect of the invention, the motor <NUM>' is housed inside a special motor compartment <NUM> of the main housing <NUM> and at least one heat-sensitive part of the electronic control system <NUM>, in particular, an electronic control board, or substantially the whole electronic control system <NUM>, possibly together with the one or more electric batteries <NUM>, is housed inside a protected compartment <NUM>.

The protected compartment <NUM> borders directly, but is not in communication, with the motor compartment <NUM> and is separated from the motor compartment <NUM> by means of a separation wall <NUM>. The cooling fan <NUM> conveys the cooling air flow into the only motor compartment <NUM> along the separation wall <NUM>, which forms a metal radiator (heat sink) <NUM> in relation of heat exchange with the heat-sensitive part of the electronic control system <NUM>, in particular, with the electronic control board in the protected compartment <NUM> (<FIG>, <FIG>).

In this way, it is possible to cool the motor <NUM>' and the heat-sensitive electrical and electronic components without the dust, humidity and possible drops of water carried with the cooling air flow, coming into contact with the electrical and electronic components of the electronic control system <NUM>. This ensures an elevated level of waterproofing and a reliable use of the wrench <NUM> also in unfavorable weather conditions and in the presence of dust.

Advantageously, the protected compartment <NUM> accommodates both the electronic board of the control system <NUM> and the one or more batteries <NUM> for the power supply therein.

According to an embodiment, the metal radiator <NUM> forms a plurality of cooling flaps <NUM> protruding into the motor compartment <NUM> and directly touched by the cooling air flow.

According to a further embodiment, the metal radiator <NUM> forms a plate-shaped protrusion <NUM> extending into the protected compartment <NUM> and in direct contact with the electronic board of the control system <NUM>.

According to a further embodiment, the main housing <NUM> forms said motor compartment <NUM> and said protected compartment <NUM> and comprises:.

A first gasket <NUM>, preferably made in a single piece, extends along the first contact interfaces <NUM> and along the radiator seat <NUM> (and about the metal radiator <NUM> accommodated therein).

A second gasket <NUM>, preferably made in a single piece, may be extended along the control seat <NUM> or at the control panel <NUM> accommodated therein.

A further gasket may be extended along the second contact interfaces <NUM>, but such further gasket is not essential, as the motor compartment <NUM> is nonetheless in communication with the external environment.

In this way, an elevated level of protection is obtained from dust, humidity and drops of water and the first contact surfaces <NUM>, in turn, are locally dampened and protected from the harmful effects of the mechanical vibrations.

Advantageously, the rear cover <NUM> is made of elastomeric material, or with an elastomeric edge, so as to be elastically fittable on a protruding edge of the rear access opening <NUM>.

The rear cover <NUM> may be unlosably hinged to the main housing <NUM>.

According to the present invention, the electric motor <NUM>', e.g., a synchronous brushless motor with permanent magnets and with an integrated control unit and battery powered <NUM> Volt DC, is simultaneously powered by two rechargeable batteries <NUM>, connected parallel to each other, e.g., lithium-ion batteries, voltage <NUM> V, 8Ah or higher, housed together in the protected compartment <NUM> of the main housing <NUM>.

The electronic control system <NUM> comprises a device for generating the current supplied to the motor <NUM>' (e.g., obtained by means of MOSFET) configured to utilize a first battery of the batteries <NUM> for generating a first phase, a second battery of the batteries <NUM> for generating a second phase, and both batteries <NUM> for generating a third phase of a three-phase current, wherein the ratio of the contributions of the first battery and the second battery to the generation of the third phase is determined depending on the residual charge state of the batteries <NUM>. In particular, the least charged battery contributes less to the generation of the third phase than the most charged battery.

The current supplied to the electric motor <NUM>' is greater than the current, which may be supplied by only one of the two batteries <NUM>.

In addition to the main supply contacts <NUM>, the batteries <NUM> comprise auxiliary contacts for controlling the battery operating conditions. The electronic control system <NUM> recognizes the type of battery used by detecting an electrical resistance between the auxiliary contacts.

The wrench <NUM> further comprises a display <NUM>, which can form part of the user control panel <NUM>, for displaying the state of charge of the batteries <NUM>. In order to prevent damage to the motor <NUM>' (stall) due to too low a level of the supply voltage, the control system <NUM> is configured to detect a flat battery state, e.g., by detecting a flat battery signal at the auxiliary contacts <NUM> or by detecting the battery <NUM> voltage and comparing the detected voltage with a predetermined minimum threshold value as a function of the type of battery used.

When the control system <NUM> determines the "flat battery" state, it controls the wrench <NUM> to complete a potential ongoing screwing cycle and prevents successive operations, or it prevents any further operation until establishing sufficient electrical voltage (after replacing or recharging the batteries <NUM>).

According to an embodiment, the wrench <NUM>, preferably, the user control panel <NUM> formed at the main housing <NUM>, comprises an electric torque selection switch <NUM> in connection with the control system <NUM>, for allowing the selection of a plurality of, for example, <NUM> values or levels of torque in the range of torque transmissible by the wrench <NUM>. For example, the maximum torque transmissible may be equal to <NUM>. The control system <NUM> controls the rotational speed of the motor <NUM>' as a function of the torque level or value selected. The rotational speed of the motor <NUM>' determines the rotational impact intensity of the percussion mechanism <NUM> and, consequently, the transmissible torque.

The torque selection switch <NUM> can comprise a rotational switch, possibly with Hall sensor and digital coding of the angular selection position.

The wrench <NUM>, preferably, the user control panel <NUM>, further comprises a main switch <NUM>, e.g., an unstable balancer, in connection with and for switching on and off the control system <NUM>.

The wrench <NUM> further comprises a direction selection switch <NUM>, e.g., a switch with a stable slide, with two positions, in connection with the control system <NUM>, for selecting the direction of rotation of the motor <NUM>' for screwing and unscrewing. Advantageously, the direction selection switch <NUM> is positioned at one of the gripping handles <NUM>, <NUM>.

The wrench <NUM> further comprises an operating switch <NUM>, e.g., an unstable switch, with a button or a trigger, in connection with the control system <NUM>, for activating the rotation of the motor <NUM>'. Advantageously, the operating switch <NUM> is positioned at the same gripping handle <NUM>, <NUM> to which the direction selection switch is connected <NUM>.

In order to reduce the risk of an accident to a minimum, the electronic control system <NUM> is configured to automatically brake the motor <NUM>', e.g., by means of electromagnetic braking, upon releasing the operating switch <NUM>.

Claim 1:
An impact screw/bolt driver (<NUM>) comprising:
- a motor unit (<NUM>) with a motor (<NUM>') accommodated in a main housing (<NUM>) of the screw/bolt driver (<NUM>) and adapted to produce a rotary motion, as well as an operating switch (<NUM>) for operating the motor (<NUM>'),
- a tool-holder shaft (<NUM>) which is rotatable about a rotation axis (R),
- a transmission unit (<NUM>) with a percussion mechanism (<NUM>) connected between the motor unit (<NUM>) and the tool-holder shaft (<NUM>),
- an electronic control system (<NUM>), containing at least one electronic control board, connected to two electric batteries (<NUM>) and to the operating switch (<NUM>),
wherein the transmission unit (<NUM>) interacts with the motor (<NUM>') and with the tool-holder shaft (<NUM>) so as to transmit the rotary motion from the motor (<NUM>') to the tool-holder shaft (<NUM>) for rotating the tool-holder shaft (<NUM>) about the rotation axis (R),
characterized in that
the impact screw/bolt driver (<NUM>) comprises a handlebar structure (<NUM>) with two gripping handles (<NUM>, <NUM>) for manually gripping the wrench (<NUM>),
wherein the electric motor (<NUM>') is simultaneously powered by two rechargeable batteries (<NUM>) connected in parallel to each other and accommodated together in the main housing (<NUM>), wherein the electronic control system (<NUM>) comprises a device for generating the current supplied to the motor (<NUM>'), configured to use a first battery (<NUM>') of the batteries (<NUM>) for generating a first phase of a three-phase current, a second battery (<NUM>") of the batteries (<NUM>) for generating a second phase of the three-phase current, and both first and second batteries (<NUM>', <NUM>") for generating a third phase of the three-phase current,
wherein the ratio of the contributions of the first battery (<NUM>') and second battery (<NUM>") to the generation of the third phase is determined depending on the residual charge state of the batteries (<NUM>', <NUM>"),
wherein the least charged battery (<NUM>'; <NUM>") contributes less to the generation of the third phase than the most charged battery (<NUM>"; <NUM>').