Portable Electric Power Tool for Bending Elongate Objects

This application claims priority from European Patent Application No. 24171074.8, filed Apr. 18, 2024, the disclosures of which is incorporated herein by reference in its entirety.

This specification relates to portable electric power tools for bending elongate objects such as rebar or linear conduits such as pipes or tubes.

Rebar is a term used for steel reinforcement bars around which concrete is poured during construction. The presence of rebar embedded within concrete improves the integrity of a concrete structure. Prior to concrete pouring rebar is arranged in a predetermined manner. Rebar is generally provided in the form of straight rods, to enable mass production, making it incumbent on construction workers to bend such rods into required shapes. Hydraulic rebar bending tools are known. This specification addresses the issue that sometimes a piece of rebar may be bent too much during a bending operation requiring an operator to discard the bent rebar and try to bend a new piece of rebar to the required extent.

BRIEF SUMMARY OF THE INVENTION

According to the invention there is provided a portable electric power tool for bending elongate objects according to claim, wherein optional features thereof are defined in claimsto.

shows a side cross-sectional view of a portable electric rebar bending power tool. The toolhas a housingpart of which is formed of a plastic clam shell type constructionhaving two halves which are fastened together. A batteryis releasably connected to the baseof the handlevia a battery attachment feature. The toolhas a bend mechanismfor bending rebar in use. A support portionof the bend mechanismis fixed relative to the tool housing, specifically to a metal partof the housing. A bias portionof the bend mechanismis moveable relative to the tool housing.

shows that the support portionhas an upper frame portionand a lower frame portion. A first abutment portionand a second abutment portioneach extend between the upper and lower frame portions,. Optionally the first abutment portionand the second abutment portionare arranged so as to be rotatable relative to the upper and lower frame portions,. The first and second abutment portions,are separated by a gapand a notional axisextends between the first and second abutment portions,. The bias portionhas a fingerwhich supports a third abutment portion.

show that the first, second and third abutment potions,,each have a circumferential depression,,. The first, second and third abutment potions,,are arranged so that the circumferential depressions,,are in the same plane so that in use rebar is received in such depressions for enhancing stability of rebar during a bending operation.

As will be explained in detail, the bias portionis operatively coupled to an electric motor of the rebar bending power toolso that the third abutment portioncan be linearly moved relative to the first and second abutment portions,along a direction (denoted B-B in) perpendicular to the notional axisfor causing the first to third abutment portions,,to bend a piece of rebar.

shows a piece of rebarplaced on the fingerso it lies in the same plane as the circumferential depressions,,provided on the first to third abutment portions,,. The first and second abutment portions,are located on a first side of the rebarand the third abutment portionis located on a second, opposite, side of the rebar.

Upon pulling a triggerof the toolthe bias portionof the bend mechanismis movably driven relative to the support portionof the bend mechanismas shown in. More specifically the third abutment portionis forced axially along a direction (denoted B-B in) perpendicular to the notional axis, whereby the third abutment portionis moved towards the gapextending between the first and second abutment portions,.

During such movement the third abutment portionexerts a force Fon the rebar, the first abutment portionexerts a force Fon the rebarand the second abutment portionexerts a force Fon the rebar; in the embodiment described the force Farises from pulling the bias portionand thus retracting the fingerinto the toolwhereas the forces Fand Fare reaction forces arising due to the rebarbeing pressed against the first and second abutment portions,.

It will be appreciated that interaction of the rebarwith the first to third abutment portions,,and the forces F, F, Fexerted thereby on the rebarcause the rebarto bend. The further the third abutment portionis moved relative to the first and second abutment portions,the more the rebaris bent.

shows that the third abutment portioncan be moved through the gapbetween the first and second abutment portions,. The extent to which the rebaris bent can thus be selectively controlled by a user of the portable rebar bending power tool. Naturally, moving the third abutment portionin the reverse direction releases the rebar.

Internal features of the portable electric rebar bending power toolwill now be described with reference towhich shows a side cross-sectional view of such power tool.

The toolhas a controllerfor determining that the triggerhas been pulled. In response to the controllerdetermining that the triggerhas been pulled the controllergenerates a signal to activate an electric motor, which is a DC brushless motor. Persons skilled in the art will be able to select a suitable electric motor, however, an example of a suibale electric motoris the BL41 DC brushless motor designed by Stanley Black & Decker Inc. and used in some commercially available DEWALT® branded power tools. The motoris located in the handleand has a motor output shaft.

Torque from the motor output shaftis transferred via a transmissionto an input pinionof a bevel gear arrangement. The transmissioncomprises at least one planetary gear arrangement for reducing output speed while increasing torque. The motor output shaftdrives an input sun gearof the first stage of the transmission. The input sun gearmeshes with a plurality of first stage planet gearswhich mesh with a stationary outer ring gearand are coupled to a first stage carrier. An axial extension of the first stage carrieris the input sun gearof the second stage of the transmission. The input sun gearmeshes with a plurality of second stage planet gearswhich mesh with the stationary outer ring gearand are coupled to a second stage carrier. An axial extension of the second stage carrieris rotationally fixed to the input pinionof the bevel gear arrangement.

The input pinionof the bevel gear arrangementthus rotates at a lower speed than the motor output shafthowever with an increased torque relative to the motor output shaft.

The motor output shaft, transmissionand input pinionof the bevel gear arrangementare aligned along a first axis A-A which extends along a longitudinal length of the handle. By also locating the battery attachment feature (and thus battery) on the first longitudinal axis A-A weight distribution of the toolis improved, whereby the toolfeels balanced in a users hand.

By locating the motor, the transmissionand the batteryon the same axis A-A extending along the length of the handleimproves weight distribution of internal features of the tool. Also by providing the motorwithin the handleleaves more space available within the tool housingabove the handle, whereby there is more freedom to position features of the toolin positions which improve weight distribution of internal features of the tool.

It will be appreciated that there is some design freedom in the transmissionbetween the motor output shaftand the input pinionof the bevel gear arrangement. In particular the number of planetary gear stages, and its (or their) configuration, forming the transmissiondepends on the required gear ratio to be achieved between the motor output shaftand the input pinion.

Given that it is well known that planetary gear stages step down rotation speed while stepping up torque persons skilled in the art, based on the disclosure given herein, will be able to decide upon a suitable transmission arrangement which achives the required gear ratio for thier tool to function; wherein the appropriate gear ratio depends on multiple factors including maximum achieveble motor output torque, pitch of the ball screw arrangement described below, friction between moveable features within the tooland the maximum permissible bending force (such as up to 100 kN). It will be appreciated that for some toolsa suitable transmisisonmay only have a single planetary gear stage, whereas for other tools a suitable transmisisonmay have a plurality of planetary gear stages arranged in series.

Continuing with reference toa bevel gearof the bevel gear arrangement, which is meshed with the input pinionfor receiving torque therefrom, is provided. An axial extension of the bevel gear, hereafter the driving sleeve, is rotationally fixed relative to an input sleeveof a ball screw arrangement. The driving sleeveand input sleeveare fixed relative to each other due to a friction fit arrangement. An internal surface of the input sleevecomprises a threaded surface. The outer surface of the input sleeveis supported by bearingswhich enable rotation of the input sleevewith respect to the housing. In a radial direction the bearingsare located between the input sleeveand the inner surface of the housing, whereas in an axial direction the bearingsare located between the driving sleeveand a bearing engagement sleevewhich is rotatably fixed to the input sleevevia a friction fit engagement; part of the bearing engagement sleevelips around the outer edge of an axial bearingfor preventing the axial bearingfrom touching the inner side of the housing. A threaded rodis mounted within the input sleeve, which extends through the input sleeve. A plurality of balls, such as metal ball bearings, ride in the opposing threaded surfaces of the input sleeveand threaded rod, thereby defining a ball screw arrangement.

When the input sleeveis rotatably driven by the driving sleevethis causes axial movement of the threaded rod. In other words, torque from the electric motoris transferred through the transmission, through the bevel gear arrangementto the input sleeve, whereby rotation thereof causes axial movement of the threaded rod. The threaded rodis configured to move along a second longitudinal axis B-B of the tool. The threaded rodcan move forwards or backwards along the axis B-B depending on the motor driving direction, whereby the bias portionmoves with the threaded rod.

shows that an anti-rotation baris engaged with the threaded rodin a manner whereby the anti-rotation baris axially and rotationally fixed to the threaded rod. As the input sleeveis rotated the anti-rotation barcooperates with the threaded rodand slots,within the housingfor causing the threaded rodto move axially along the axis B-B. The anti-rotation baris rotationally fixed with respect to the housingso it slides relative to the housingthrough the slots,during axial movement of the threaded rod.

The anti-rotation barcomprises a central holewith a threaded inner surface which is tightly threadably engaged with a reciprocal threaded portionat an end of the threaded rodas shown in.

The anti-rotation barcomprises a first armand a second arm. The first and second arms,are mounted in first and second slots,within the housing. When the threaded rodmoves along the second longitudinal axis B-B, the first and second arms,slide along the first and second slots,. The first and second slots,extend along longitudinal axes which are parallel to the second longitudinal axis B-B.

With continued reference tothe fingerof the moveable bias portionis fixed to the threaded rodby a connector, wherein suitable connectors will be apparent to persons skilled in the art.

The threaded rodextends through an openingdefined by the housing, specifically through an openingdefined by the metal partof the housing.shows an axial bearingprovided inside the housingfor supporting the threaded rod. The ingress of dirt and moisture through the openingand into the housingis blocked by a flexible bellowprovided between the front rim of the openingand the connector(the flexible bellowis omitted fromfor purposes of illustration). The flexible bellowcontracts and expands in length depending on the extent to which the threaded rodis retracted into the tool.

The exterior of the section of the metal tool housing partdefining the openingis threaded and forms a threaded connection with a frame support. The frame supportis part of the support portionand carries the upper frame portionand the lower frame portion, which can be formed integrally with the frame supportor be fixed thereto. In view of the foregoing it will be apparent that during tool use, when the threaded rodis caused to move along the second longitudinal axis B-B, the fingerand third abutment portionare caused to move within the space defined between the upper and lower frame portions,. A volumeis provided within the housingfor accommodating the threaded rodwhen retracted into the tool.

Designers are free to select a suitable way for the controllerto control operation of the motorin use to implement a bending operation. In other words designers are free to select a suitable way for the controllerto determine when the bend mechanismhas been actuated sufficiently for rebarto be bent by a predetermined angle, in other words designers are free to select a suitable way for the controllerto determine when the third abutment portionhas been moved far enough linearly relative to the first and second abutment portions,for rebarto be bent by a predetermined angle.

For example, in a starting configuration of the portable electric rebar bending power toolshown in, the third abutment portionis located in front of the first and second abutment portions,so that a user can place a piece of rebarbetween said features as already described. In this starting configuration the bias portionis located in a home position, which is a predetermined starting position along the second longitudinal axis B-B relative to the support portion. Upon the controllerdetermining that the triggeris pulled the controllercauses the electric motorto rotate in a forward rotational direction for causing the third abutment portionto be linearly moved along the second longitudinal axis B-B towards the first and second abutment portions,whereby the rebaris bent. In some embodiments users are required to manually judge when their rebar is bent enough and thus are required to release the triggerwhen their rebarhas been bent a required amount, wherein upon the controllerdetecting that the triggeris released it causes the motorto drive in a reverse direction for causing the bias portionto be returned to its home position thereby releasing the bent rebar.

As a safety mechanism a mechanical switch may be provided within the power toolfor causing a reset operation upon the threaded rodbecoming retracted into the toolby a predetermined amount. During a bending stage of operation the threaded rodis retracted into the tool. If the user does not release the triggereventually an arm,of the anti-rotation barwill engage a mechanical switch, whereby upon the controllerdetecting that the mechanical switch is activated it causes the motorto reverse direction and returns the bias portionto the home position; a user must then release the triggerbefore a subsequent bending operation can be implemented. In some embodiments instead of a mechanical switch an optical sensor can be used for detecting the presence of the anti-rotation baror threaded rodfor initiating a reset operation.

Furthermore, in some embodiments a magnetic sensor is provided for detecting the presence of a magnet carried by the anti-rotation barfor initiating a reset operation.

Alternatively in some embodiments the controlleris configured to receive user input via a user interface of the toolwhich is indicative of the thickness of the rebarand the required bend angle, wherein based on this user input the controllerdetermines the extent to which the bias portionshould be retracted upon pulling the trigger. During a bending operation, while the triggerremains pulled the controllerwill cause movement of the bias portionfor bending the rebar the required amount and then will reverse motor direction and return the bias portionto the home position, whereby the triggermust be released before a subsequent bending operation can be performed. At any time during a bending operation if the triggeris released the controllerwill cause reverse movement of the motorand will return the bias portionto the home position.

Moreover designers are free to select a suitable way for the controllerto control operation of the motorto implement a reset operation. In other words designers are free to select a suitable way for the controllerto determine when the bias portion(and thus the third abutment portion) has returned to the home position at which point in time reverse movement of the bias portionis ceased. For example a mechanical switch may be provided within the tool. Following a bending operation, upon initiation of reverse movement of the motorfor causing a reset operation, the controlleris configured to detect output from the mechanical switch indicative that an arm,of the anti-rotation baractuates the mechanical swich, thereby indicating that the bias portion(and thus the third abutment portion) has returned to the home position. Alternatively an optical sensor may be provided within the toolwhich generates output based on the presence or absence of the anti-rotation baror threaded rodwherein based on output from the optical sensor the controllercan determine that the bias portion(and thus the third abutment portion) has reached the home position. In some embodiments a magnetic sensor is provided for detecting the presence of a magnet carried by the anti-rotation barfor generating output indicative that the bias portion(and thus the third abutment portion) has reached the home position.

show another embodiment of the portable electric rebar bending power tool, wherein corresponding features to the first embodiment described herein are labelled with like reference numerals increased by. The portable electric power toolis an inline version wherein the battery attachment feature (and thus battery), the electric motor, the transmission, the ball screw mechanismand the bend mechanismare arranged in axial sequence one after the other.

Looking atthe motor output shaftextends along the axis C-C and drives an input sun gearof the first stage of the transmission. The input sun gearmeshes with a plurality of first stage planet gearswhich mesh with a stationary outer ring gear(which extends along the axis C-C) and are coupled to a first stage carrier. An axial extension of the first stage carrieris the input sun gearof the second stage of the transmission. The input sun gearmeshes with a plurality of second stage planet gearswhich mesh with the stationary outer ring gearand are coupled to a second stage carrier. An axial extension of the second stage carrieris the input sun gearof the third stage of the transmission. The input sun gearmeshes with a plurality of third stage planet gearswhich mesh with the stationary outer ring gearand are coupled to a third stage carrier. An axial extension of the third stage carriercooperates with a drive sleeveof the ball screw mechanism, wherein such features are rotationally locked such that rotation of the third stage carrierrotatably drives the drive sleeve.

It will be appreciated that there is some design freedom in the transmissionbetween the motor output shaftand the drive sleeveof the ball screw mechanism. In particular the number of planetary gear stages, and its (or their) configuration, forming the transmissiondepends on the required gear ratio to be achieved between the motor output shaftand the drive sleeveof the ball screw mechanism.

Similarly as heretofore described in connection with the first embodiment the driving sleeveis fixed to an input sleevedue to a friction fit arrangement and an internal surface of the input sleevecomprises a threaded surface for cooperating with a threaded surface of the threaded rod. Moreover a plurality of balls, such as metal ball bearings, ride in the opposing threaded surfaces of the input sleeveand threaded rod, thereby defining a ball screw arrangement.

A metal inner housingsupports the ball screw arrangement. A first axial bearingis received between the internal surface of a first step portionof the metal inner housingand an external surface of a step portionof the drive sleeve. A second axial bearingis received between the internal surface of a second step portionof the metal inner housingand an end surface of the input sleeve. The input sleeveis thus axially supported between the second axial bearingand an inner surface of the drive sleeve. Additionally the input sleeveis supported in a radial direction by one or more bearingswhich permit rotation of the input sleeve. In a radial direction the (or each) bearingis (or are) located between the input sleeveand the inner surface of the metal inner housing, whereby an outer race of the (or each) bearingis friction fit with an inner surface of the metal inner housingand an inner race of the (or each) bearingis friction fit with the input sleeve. Looking atthe input sleeveis axially supported between the axial bearingand the bearing, wherein the input sleeveextends though an opening defined by the axial bearing. The input sleeverotates in use without touching the inner surface of the metal inner housing.

In use, torque from the electric motoris transferred through the transmissionto the input sleeve, whereby rotation thereof drives rotation of the driving sleevefor causing axial movement of the threaded rod. The threaded rodis configured to move along the longitudinal axis C-C of the tool. The threaded rodcan move forwards or backwards along the axis C-C depending on the motor driving direction, whereby the bias portionmoves with the threaded rodcausing actuation of the bend mechanism.

With continued reference tothe fingerof the moveable bias portionis fixed to the threaded rodby a connector, wherein suitable connectors will be apparent to persons skilled in the art. In particular the threaded rodis rotatably and axially fixed to the connectorand thereby to the finger. Since the bias portionand support portionof the bend mechanismmust permit movement relative to each other they are shaped and cooperate to enable axial movement between the bias portionand support portionbut restrict rotational movement of the bias portionand support portionrelative to each other; whereby in use the threaded rodis able to move axially within the toolbut is restricted from rotating.

The threaded rodextends through an openingdefined by the inner metal housing. An exterior section of the metal inner housingforms a threaded connection with the frame support. The frame supportis part of the support portionand carries the upper frame portion and the lower frame portion, which can be formed integrally with the frame supportor be fixed thereto. A volumeis provided for accommodating the threaded rodwhen retracted into the tool. The ingress of dirt and moisture through the openingand into the metal inner housingis blocked by a flexible bellowprovided between the front rim of the openingand the connector. The flexible bellowcontracts and expands in length depending on the extent to which the threaded rodis retracted into the tool. Comparing, these drawings illustrate the same toolhowever differ by the axial position of the threaded rodand thereby the consequential configuration of the bend mechanism.

Designers are free to select a suitable way for the controllerto control operation of the motorin use to implement a bending operation. In other words designers are free to select a suitable way for the controllerto determine when the bend mechanismhas been actuated sufficiently for rebar to be bent by a predetermined angle, in other words designers are free to select a suitable way for the controllerto determine when the third abutment portionhas been moved far enough linearly relative to the first and second abutment portions,for rebar to be bent by a predetermined angle.

For example, in a starting configuration of the portable electric rebar bending power toolshown in, the third abutment portionis located in front of the first and second abutment portions,so that a user can place a piece of rebar between said features as already described. In this starting configuration the bias portionis located in a home position, which is a predetermined starting position along the longitudinal axis C-C relative to the support portion. Upon the controllerdetermining that a trigger of the toolis actuated the controllercauses the electric motorto rotate in a forward rotational direction for causing the third abutment portionto be linearly moved along the longitudinal axis C-C towards the first and second abutment portions,whereby the rebar is bent. In some embodiments users are required to manually judge when their rebar is bent enough and thus are required to release the trigger when their rebar has been bent a required amount, wherein upon the controllerdetecting that the trigger is released it causes the motorto drive in a reverse direction for causing the bias portionto be returned to its home position thereby releasing the bent rebar.

As a safety mechanism a mechanical switch may be provided within the power toolfor causing a reset operation upon the threaded rodbecoming retracted into the toolby a predetermined amount. During a bending stage of operation the threaded rodis retracted into the tool. If the user does not release the trigger eventually the threaded rod(or a feature provided thereon) will engage a mechanical switch, whereby upon the controllerdetecting that the mechanical switch is activated it causes the motorto reverse direction and returns the bias portionto the home position; a user must then release the trigger before a subsequent bending operation can be implemented. In some embodiments instead of a mechanical switch an optical sensor can be used for detecting the presence of the threaded rodfor initiating a reset operation. Furthermore, in some embodiments a magnetic sensor is provided for detecting the presence of a magnet carried by the threaded rodfor initiating a reset operation.

Alternatively in some embodiments the controlleris configured to receive user input via a user interface of the toolwhich is indicative of the thickness of the rebar and the required bend angle, wherein based on this user input the controllerdetermines the extent to which the bias portionshould be retracted upon actuating the trigger. During a bending operation, while the trigger remains actuated the controllerwill cause movement of the bias portionfor bending the rebar the required amount and then will reverse motor direction and return the bias portionto the home position, whereby the trigger must be released before a subsequent bending operation can be performed. At any time during a bending operation if the trigger is released the controllerwill cause reverse movement of the motorand will return the bias portionto the home position.

Moreover designers are free to select a suitable way for the controllerto control operation of the motorto implement a reset operation. In other words designers are free to select a suitable way for the controllerto determine when the bias portion(and thus the third abutment portion) has returned to the home position at which point in time reverse movement of the bias portionis ceased. For example a mechanical switch may be provided within the tool. Following a bending operation, upon initiation of reverse movement of the motorfor causing a reset operation, the controlleris configured to detect output from the mechanical switch indicative that threaded rod(or a feature provided thereon) actuates the mechanical swich, thereby indicating that the bias portion(and thus the third abutment portion) has returned to the home position. Alternatively an optical sensor may be provided within the toolwhich generates output based on the presence or absence of the threaded rodwherein based on output from the optical sensor the controllercan determine that the bias portion(and thus the third abutment portion) has reached the home position. In some embodiments a magnetic sensor is provided for detecting the presence of a magnet carried by the threaded rodfor generating output indicative that the bias portion(and thus the third abutment portion) has reached the home position.

Another embodiment of the portable electric rebar bending power toolwill now be described with reference towherein corresponding features to those heretofore described will be denoted with like reference numerals increased by.