two-speed screwing-unscrewing device with floating crown

Abstract

The present invention relates to a screwing device comprising: a casing; a motor provided with a rotor; an output member capable of rotating a drive element of an element to be screwed; a transmission connecting said rotor to said output member, said transmission comprising at least one additional gear train capable of being engaged / disengaged, said at least one additional gear train comprising at least one epicyclic train provided with an internal toothed crown;said device comprising means for engaging said at least one additional gear train, capable of taking at least: an engaged state, and a disengaged state, the reduction ratio of said transmission being different depending on whether said additional gear train is engaged or not, said crown is mounted to move in translation along the axis of said rotor inside said casing between at least: a free position, taken when said engaging means are in said disengaged state, and in which said crown is movable in rotation relative to said casing so that said at least one additional gear train is disengaged, and a locked position, taken when said engaging means are in said engaged state, and in which said crown is locked in rotation relative to said casing so that said at least one additional gear train is engaged.;

Description

Title of the invention: two-speed screwing-unscrewing device with floating crown 1. Field of the invention

[0001] The field of the invention is that of the design and manufacture of portable tools intended to be used to carry out screwing / unscrewing operations.

[0002] More specifically, the invention relates to a screwing / unscrewing device offering several screwing / unscrewing speeds. This device is more particularly intended for continuous tightening screwdrivers whose torque exceeds 150 Nm (high torque screwdrivers). 2. Prior art

[0003] Screwing devices are commonly used in various industrial sectors to carry out screwing and / or unscrewing operations on assemblies.

[0004] A screwing operation generally comprises two successive phases, namely: - a pre-screwing phase during which the element to be tightened is driven at a rapid speed until a certain level of pre-tightening torque is reached, then - a slower tightening phase until a target tightening torque and / or target tightening angle are reached.

[0005] Electric motor-driven screwdriving devices are conventionally associated with control means and comprise a tightening torque and / or tightening angle sensor.

[0006] These control means make it possible to program screwing strategies, i.e. the parameters of the pre-screwing and tightening phases, in particular the rotation speeds of the motor in the pre-screwing and tightening phases, as well as the target torque and / or angle value at the end of tightening. Thus, during the performance of a screwing operation, the control means control the motor to drive the element to be tightened at the pre-screwing speed during the pre-screwing phase and then at the tightening speed during the tightening phase until the target torque and / or angle are reached.

[0007] Continuous tightening screwdrivers, that is to say screwdrivers which apply an uninterrupted and increasing torque to the screw during tightening, incorporate a transmission between the motor and the output member driving the screw. This transmission generally consists of one or more epicyclic gear trains. These epicyclic gear trains make it possible to have sufficient tightening torque available on the output shaft. This torque is the result of multiplying the engine torque by the reduction ratio of the transmission and its efficiency.

[0008] To be able to achieve high tightening torques, for example greater than 150 Nm, screwdriver manufacturers are therefore required to have a high reduction ratio by having several epicyclic gear trains in the transmission. This has the disadvantage that the rotation frequency of the screwdriver output shaft becomes relatively low, resulting in a long screwing time, which penalizes productivity.

[0009] Thus, manufacturers of high-torque screwdrivers have imagined having a device integrated into the transmission allowing one of the epicyclic gear trains to be disengaged during pre-screwing. The reduction ratio implemented during pre-screwing therefore becomes lower than in the increase in torque during tightening with the benefit of a high rotation frequency during pre-screwing and a high torque during the increase in torque during tightening. This epicyclic gear train capable of being engaged or disengaged is called an additional gear train.

[0010] The pre-screwing and tightening speeds applied during the pre-screwing and tightening phases therefore require the implementation of an additional engageable-disengageable gear train which makes it possible to define different reduction ratios between the rotor and the output member depending on whether it is engaged or not. Thus, the additional gear train is not engaged in the pre-tightening phase so that the pre-screwing speed is fast. Conversely, the additional train is engaged during the tightening phase so that the tightening speed is slower and the tightening torque achievable by the screwing device is higher.

[0011] The additional gear train is automatically mechanically engaged at the end of the pre-tightening phase. For this purpose, in the state-of-the-art solutions, the transmission incorporates an elastic element which allows, when the tightening torque reaches, during the pre-tightening phase, a predetermined speed change torque threshold, to automatically engage the additional gear train.

[0012] This type of mechanism is advantageous in that it allows for simple and efficient automatic screwing speed change. However, this type of technology can still be improved.

[0013] Indeed, in the solutions described in the state of the art, the predetermined tightening torque threshold for changing speed from which the additional train engages automatically is not configurable insofar as it depends on the dimensioning of the elastic element integrated into the transmission. Consequently, this type of technology does not make it possible to provide versatile screwdrivers adaptable to different screwing operations requiring a change of speed after reaching a pre-tightening threshold of different values.

[0014] To overcome this drawback, the Applicant has designed a technique making it possible to choose the moment at which the additional train is triggered so as to adapt this engagement according to the needs of the screwing operation to be carried out.

[0015] Patent document EP-A1-4 205 907, filed in the name of the Applicant, describes in this sense a technique making it possible to engage an additional train, independently of the tightening torque, by acting only on the engine acceleration level.

[0016] Such a solution therefore constitutes a major improvement to the solutions previously described in the prior art.

[0017] The solutions described in this patent document are particularly effective. However, it is still possible to improve them. 3. Objectives of the invention

[0018] The invention aims in particular to provide an effective solution to at least some of these different problems.

[0019] In particular, according to at least one embodiment, an objective of the invention is to improve the screwing devices making it possible to ensure the engagement-disengagement of an additional gear train.

[0020] In particular, the invention aims, according to at least one embodiment, to provide such a screwing device in which the engagement of an additional train is done independently of the tightening torque and as a function of the acceleration of the motor.

[0021] Another objective of the invention is, according to at least one embodiment, to provide such a screwing device which is simplified.

[0022] In particular, an objective of the invention is, according to at least one embodiment, to simplify the manner in which the crown of the additional epicyclic gear train can be locked-unlocked in rotation relative to the casing of the screwing device to engage-disengage the additional gear train could be simplified.

[0023] Another objective of the invention is, in at least one embodiment, to reduce the number of components implemented.

[0024] Another objective of the invention is, according to at least one embodiment, to provide a solution which can be easily integrated into various screw / unscrew devices.

[0025] Another objective of the invention is, according to at least one embodiment, to provide a solution which is reliable and / or robust and / or economical. 4. Presentation of the invention

[0026] For this, the invention proposes a screwing device comprising: - a casing; - a motor equipped with a rotor;

[0027]

[0028]

[0029]

[0030]

[0031]

[0032] - an output member capable of rotating a drive element of an element to be screwed; - a transmission connecting said rotor to said output member, said transmission comprising at least one additional gear train capable of being engaged / disengaged, said at least one additional gear train comprising at least one epicyclic train provided with an internal toothed crown; said device comprising means for engaging said at least one additional gear train, said engaging means being able to take at least: - an engagement state in which said at least one additional train is engaged, and - a disengaged state in which said at least one additional gear train is not engaged, the reduction ratio of said transmission between said rotor and said output member being different depending on whether or not said additional gear train is engaged. According to the invention, said crown is mounted to move in translation along the axis of said rotor inside said casing between at least: - a free position, taken when said engagement means are in said disengaged state, and in which said crown is rotatable relative to said casing such that said at least one additional gear train is disengaged, and - a locked position, taken when said engagement means are in said engagement state, and in which said crown is locked in rotation relative to said casing such that said at least one additional gear train is engaged. Thus, the invention proposes a screwing and / or unscrewing device making it possible to ensure the engagement-disengagement of an additional gear train, in particular a simple one, having a reduced number of parts, the engagement-disengagement mechanism of which is easily integrated into the tool. According to a possible characteristic, a screwing device according to the invention comprises means for controlling said motor, said means for controlling said motor being configured to generate a predetermined acceleration or deceleration of said rotor, said predetermined acceleration or deceleration acting on said engagement means to make them pass from one of their states to the other. The invention thus provides a screwing device in which the engagement of an additional train is done independently of the tightening torque and as a function of the acceleration of the motor.

[0033] According to a possible characteristic, said internal toothed crown comprises a first locking portion and said casing comprises a second locking portion, said first and second locking portions being complementary to one another and shaped to ensure rotational locking of said crown relative to said casing when they cooperate with each other, said first and second locking portions cooperating with each other in said locked position of said crown and not cooperating with each other in said free position of said crown.

[0034] According to a possible characteristic, said first and second locking portions are of truncated cone shape.

[0035] According to a possible characteristic, a screwing device according to the invention comprises elastic return means acting on said crown to tend to maintain it in said blocked position.

[0036] According to a possible characteristic, a screwing device according to the invention comprises means for driving said crown in translation from one to the other of its locked and unlocked positions, said translational driving means comprising at least one cam path formed on said crown and at least one locking member linked in rotation to said rotor, said at least one locking member being movable between at least: - an inactive position in which said locking member is not in contact with said cam path so that a rotation of said rotor relative to said crown does not induce translation of said crown, and - an active position in which said locking member is in contact with said cam path so that a rotation of said rotor relative to said crown induces a translation of said crown along the axis of said rotor.

[0037] According to a possible characteristic, said at least one locking member, when it is in said active position, is configured to move against said cam path, during a relative rotational movement of said rotor with respect to said crown, between: - a first extreme position in which said crown is in said free position, and - a second extreme position in which said crown is in said blocked position.

[0038] According to a possible characteristic, a screwing device according to the invention comprises means for connecting in rotation said crown and said rotor, said means for connecting in rotation comprising said at least one locking member and at least one element forming a stop secured to said crown, said element forming stop being arranged in such a way that said locking member bears against said stop-forming element when said locking member is in said active position and in said first extreme position.

[0039] According to a possible characteristic, said cam path comprises a conformation capable of at least partially housing said locking member when it is in its first extreme position, said conformation being configured to reversibly maintain said locking member in said first extreme position.

[0040] According to a possible characteristic, said engagement means comprise a selection member movable in rotation relative to said rotor between at least: - an engagement position of said additional gear train, and - a disengagement position of said additional gear train,

[0041] said selection member acting on said at least one locking member to: - in said engaged position, place said locking member in its inactive position; - in said disengaged position, place said locking member in its active position.

[0042] According to a possible characteristic, said selection member comprises a cam surface in contact with said locking member, said cam surface acting on said locking member to allow its movement from one to the other of its active and inactive positions.

[0043] According to a possible characteristic, said locking member is held in abutment against said cam surface by an elastic return means, said elastic return means acting on said locking member to tend to move it towards its active position.

[0044] According to a possible characteristic, said locking member is movable in translation between its active and inactive positions along an axis orthogonal to the axis of rotation of said rotor.

[0045] According to a possible characteristic, a screwing device according to the invention comprises a support element linked in rotation to said rotor, said at least one locking member being integral in rotation with said support element and mounted to be movable relative to the latter between its active and inactive positions, said selection member being mounted to be movable in rotation relative to said support element between its engagement and disengagement positions, said support element comprising stop elements against which stop elements of said selection member are capable of coming to bear, said stop elements defining said engagement and disengagement positions of said selection member. 5. Description of figures

[0046] Other characteristics and advantages of the invention will appear on reading the following description of particular embodiments, given as a simple illustrative and non-limiting example, and the appended drawings among which:

[0047] [Fig-1] [Fig.l] illustrates a partial longitudinal sectional view of a device according to the invention with the additional train engaged;

[0048] [Fig.2] [Fig.2] illustrates a detail view of [Fig.l];

[0049] [Fig.3] [Fig.4] Figures 3 and 4 illustrate two views of a crown of the device of [Fig.l] and 2;

[0050] [Fig.5] [Fig.6] Figures 5 and 6 illustrate two views of a selection member of the device of [Fig.l] and 2;

[0051] [Fig.7] [Fig.7] illustrates a partial longitudinal sectional view of a device according to the invention with the additional train engaged;

[0052] [Fig.8] [Fig.8] illustrates a section along the axis BB of [Fig.7];

[0053] [Fig.9] [Fig.9] illustrates a section along axis AA of [Fig.7];

[0054] [Fig. 10] [Fig. 10] illustrates a partial longitudinal sectional view of a device according to the invention with the additional train disengaged;

[0055] [Fig. 11] [Fig. 11] a section along the axis BB of [Fig. 10];

[0056] [Fig. 12] [Fig. 12] illustrates a section along axis AA of [Fig. 10];

[0057] [Fig. 13] [Fig. 13] illustrates a detailed view of the device of [Fig.l] in a being intermediate between engagement and disengagement;

[0058] [Fig. 14] [Fig. 14] illustrates a detail view of [Fig. 13];

[0059] [Fig. 15] [Fig. 15] illustrates a longitudinal sectional view of a device according to the invention.

[0060] 6. Description of particular embodiments 6.1. Architecture

[0061] An example of an embodiment of a screwing device according to the invention is presented in relation to Figures 1 to 15.

[0062] Such a screwing device can make it possible to carry out screwing and / or unscrewing operations.

[0063] As shown, such a screwing and / or unscrewing device conventionally comprises a casing 10. This is a pistol-grip type casing in which the axis of the handle 11 forms an angle with the axis of the output member 12. Alternatively, it could be a casing in which the axis of the handle coincides with the axis of the output member.

[0064] The casing 10 houses an electric motor 13 comprising a stator 130 and a rotor 131 provided with a motor shaft 132. In this embodiment, the rotor is external. In variants, it could be internal.

[0065] The device comprises an output member 12 placed at the end of the casing 10. This output member 12 is capable of driving in rotation a drive element of an element to be screwed, in particular a screw socket or other.

[0066] The device comprises a transmission T connecting the shaft 132 of the rotor 131 to the output member 12 so as to drive the latter in rotation.

[0067] The transmission T comprises a two-speed mechanism 14 which comprises two transmission chains having different transmission ratios. For this, the transmission T comprises an additional gear train capable of being engaged / disengaged. As will be described in more detail later, this additional train here comprises an epicyclic train which can be disengaged by making its inner toothed crown free to rotate or engaged by locking its crown in rotation.

[0068] The two-speed mechanism 14 comprises means for engaging the additional gear train, these means being able to take at least: - an engagement state in which the additional gear train is engaged, and - a disengagement state in which the additional gear train is disengaged.

[0069] The reduction ratio of the transmission between the rotor and the output member is different depending on whether or not the additional gear train is engaged, the reduction ratio being higher here when the additional gear train is engaged. In variants, the reduction ratio may be higher when the additional gear train is engaged. In this way, for a given rotation frequency of the rotor, the rotation frequency of the output member is higher when the additional gear train is not engaged and slower when it is engaged, so that the tightening torque capable of being delivered by the device is higher when the additional gear train is engaged.

[0070] The engagement means comprise a support element 15. This support element 15 is mounted to rotate in the casing 10 along the axis of the rotor 131. At one of its ends, it is secured to the motor shaft 132 in such a way that it is linked in rotation to the rotor 131. The assembly of the support element 15 and the motor shaft 132 can for this purpose be achieved by means of splines 151. At the other of its ends, it comprises a sun gear 152. The motor shaft 132 and the support element 15 could in a variant constitute a single piece.

[0071] The engagement means comprise a selection member 16. This selection member 16 is mounted to move in rotation along the axis of the rotor 131 on the support element 15, for example by means of plain bearings or rolling bearings 161, between at least two extreme positions, namely: - an engagement position of the additional gear train, and - a disengagement position for the additional gear train.

[0072] In each of these two extreme positions, the selection member 16 is connected in rotation to the support element 15 by rotational connection means. For this, the support element 15 is crossed by a transverse bore 153 arranged along an axis perpendicular to its longitudinal axis. This bore 153 houses an elastic return means which comprises in this embodiment a compression spring 17. At each end of the compression spring 17 is placed a locking element. These locking elements are in this embodiment produced by locking balls 18.

[0073] The selection member 16 is crossed by an internal bore 160 housing the support element 15. Two pairs of diametrically opposed locking housings 162 are provided at the periphery of the internal bore 160. The locking housings 162 of each pair are connected by a peripheral groove 163.

[0074] The locking balls 18 are movable along an axis orthogonal to the axis of the support element 15, against the effect of the elastic return means 17, between at least: - a rotational connection position in which the balls 18 are housed in two of the diametrically opposed locking housings 162 so that the support element 15 and the selection member 16 are rotationally connected, and - a release position in which the balls 18 are not housed in any of the locking housings 162, but are located in the groove 163, so that the support element 15 and the selection member 16 are not linked in rotation.

[0075] When the selection member 16 is in its position for engaging the additional gear train, the locking balls 18 are housed in two first of the opposite housings 162. When the selection member 16 is in its position for disengaging the additional gear train, the balls 18 are located in two other of the opposite housings 162.

[0076] When the balls 18 are in their rotationally locked position, the means for rotationally connecting the support element 15 to the selection member 16 are able to transmit a predetermined limit torque C1 beyond which the balls pass into their release position in which the support element and the selection member are no longer rotationally connected and can no longer transmit torque. This predetermined torque depends in particular on the stiffness of the spring 17, the size of the balls 18, the geometry of the locking housings 162 and the groove 163. This torque can be conventionally determined by calculation or empirically.

[0077] The device conventionally comprises means for measuring the tightening torque delivered by the device at the output member. These measuring means can for example, include a torque sensor placed in the transmission between the rotor and the output device or a current sensor consumed by the motor.

[0078] The device conventionally comprises means 19 for controlling the motor. These means make it possible to control the motor by controlling in particular its electrical power supply. They can be totally or partially located inside the casing or outside it.

[0079] The control means 19 of the motor make it possible, by acting on the acceleration / deceleration of the rotor 131 of the motor 13, to switch the engagement means from one of their states to the other, i.e. to switch the selection member 16 from one of its positions to the other relative to the support element 15.

[0080] To allow the engagement means to move from one position to the other, the acceleration / deceleration generated by the motor must be greater than the quotient of the limit torque Cl transmissible by the rotational connection means by the inertia Jos of the selection member along its axis of rotation. This acceleration / deceleration is called speed change acceleration / deceleration insofar as it allows the additional gear train to be engaged / disengaged and thus the reduction ratio of the transmission between the rotor and the output member to be modified.

[0081] During the performance of a screwing / unscrewing operation, the motor conventionally produces accelerations and variations in acceleration, in particular at start-up. It is therefore appropriate that the acceleration / deceleration which induces the switching of the engagement means from one state to the other be sufficiently discriminating, i.e. distant from and more precisely greater than the accelerations conventionally likely to occur, for example at start-up or stop-up, so as not to inadvertently cause involuntary switching of the selection means from one state to the other.

[0082] The transmission comprises an epicyclic gear train comprising the sun gear 152 integral in rotation with the support element 15, a planet carrier 20 integral in rotation with the output member 12, and an internal toothed crown 21 meshing with satellites 22 carried by the planet carrier 20. In variants, the planet carrier may be linked in rotation with the input of another epicyclic gear train or of a cascade of epicyclic gear trains, the output of which will be linked in rotation with the output member 12.

[0083] The crown 21 is mounted to move in rotation inside the casing by means of a bearing 23.

[0084] The crown 21 has, at one of its ends, a locking portion 210 of truncated cone shape.

[0085] The casing 10 has a truncated cone-shaped locking portion 100.

[0086] The locking portions 210 and 100 are of complementary shape and intended to cooperate with each other.

[0087] The crown 21 is mounted to move in translation inside the casing 10 along the axis of the rotor 131 between at least: - a free position, taken when the engagement means are in the disengaged state, and in which the crown 21 is movable in rotation relative to the casing so that the additional gear train is disengaged: in this position, the locking portions 210 and 100 are spaced from each other; - a locked position, taken when the engagement means are in the engaged state, and in which the crown 21 is locked in rotation relative to the casing 10 so that the additional gear train is engaged: in this position, the locking portions 210 and 100 are applied against each other to lock the crown 210 in rotation relative to the casing 10.

[0088] A compression spring 24 is interposed between a bearing surface 250 of a base 25 in which the crown 21 is mounted to move in translation between its two extreme positions. This compression spring 24 acts on the crown 21 to tend to maintain it in its locked position.

[0089] The crown 21 has, at one of its ends, two pairs of cam tracks 211.

[0090] Each cam track 211 has an inclined surface thickening, from a hollow 212 towards the end of the crown 21 oriented towards the support element 15. A stop element 213 is provided at the thickest end of each cam track 211. The connection zone between each cam track 211 and each stop element 213 comprises a conformation 214.

[0091] The support element 15 is crossed by a transverse bore 154. This bore 154 houses two locking members 26 mounted to slide in the bore 154 and in a diametrically opposite manner.

[0092] A compression spring 27 is interposed in the bore 154 between the two locking members 26 and tends to move them away from each other.

[0093] Each locking member 26 is movable in translation in the bore 154 between at least: - an inactive position in which the locking member 26 is retracted into the bore 154 so that it is not in contact with the cam path 211 of the crown 21 so that a rotation of the rotor 131 relative to the crown 21 does not induce translation of the crown 21, and - an active position in which the locking member 26 is deployed outside the bore 154 so that it is in contact with the cam path 211 of the crown 21 so that a rotation of the rotor 131 relative to the crown 21 induces a translation of the crown 21 along the axis of the rotor 131.

[0094] The locking members 26, when in their active position, are configured to move against the cam path 211 of the crown 21, during a relative rotational movement of the rotor 131 with respect to the crown, between: - a first extreme position in which the crown is in its free position; the locking members 26 are then in support against the stops 213 in the conformations 214; - a second extreme position in which the crown is in its locked position; the locking members 26 are then located in the hollows 212.

[0095] The selection member 16 is capable of acting on the locking members 26 to: - in its engaged position, place the locking members in their inactive position; - in its disengaged position, place the locking devices in their active position.

[0096] Each locking member 26 comprises a guide housing 261 arranged laterally.

[0097] The selection member 16 has, at its end oriented towards the locking members 26, cam surfaces 164 shaped to interact with the guide housings 261 of the locking members 26 by being housed therein. These cam surfaces 164 have a thin end from which it tends to extend radially to a thicker end.

[0098] These cam surfaces are capable of acting on the locking members to release their movement from their inactive position to their active position and to induce their movement from their active position to their inactive position.

[0099] The locking members are held in abutment against the cam surfaces by the spring 27, this spring 27 acting on the locking members to tend to move them towards their active position.

[0100] The selection member 16 comprises diametrically opposed stop elements 165 intended to bear against stop elements 155 provided for this purpose on the support element 15. These stops 165, 155 define the engagement and disengagement positions of the selection member 16. As will become more clear from reading the description of the operation of a device according to the invention, these stops make it possible to stop the rotation of the selection member 16 relative to the support element 15 without passing through the locking members 26. This makes it possible to protect the locking members from shocks when the selection member 16 reaches its engagement and disengagement positions.

[0101] The stop-forming elements 213 of the crown 21 are arranged in such a way that the locking members 26 bear against these stop-forming elements 213 and are housed in the conformations 214 when the locking members 26 are in their active position and in their first extreme position.

[0102] The cam tracks of the crown and the locking members make it possible to ensure translational drive of the crown by transforming a rotational movement of the support element into a translational movement of the crown.

[0103] The crown stops and the locking members ensure a rotational connection of the crown with the rotor.

[0104] The conformations 214 of the crown 21 are capable of at least partially housing the locking member when it is in its first active position, this conformation being configured to reversibly maintain the locking member in the first extreme position.

[0105] In variants, one or more permanent gear trains, i.e. non-disengageable, for example epicyclic, may be arranged between the planet carrier 20 and the output member 12.

[0106] When the additional gear train is disengaged, the reduction ratio of the transmission is equal to 1 insofar as the support element 15 and the planet carrier 20 rotate at the same rotation frequency, or to the reduction ratio of the permanent gear train or to their product if several permanent trains are implemented.

[0107] When the additional gear train is engaged, the reduction ratio of the transmission is equal to the reduction ratio of the additional epicyclic gear train, or to its product with the reduction ratio(s) of the permanent gear train(s) where applicable implemented. 6.2. Operation

[0108] A screwing operation is described below comprising a pre-tightening phase at high speed followed by a tightening phase at slower speed.

[0109] Before starting a screwing / unscrewing operation, the operator in charge programs in the controller, for example by means of a touch screen, a keyboard, a smartphone or other, the value of the predetermined speed change torque threshold CchangementVitesse which, when reached at the output of the screwing device during a pre-screwing phase, causes a speed change and the transition to the tightening phase. This speed change torque can alternatively be automatically calculated by the tool based on the desired target torque rather than being set by the operator. This shift torque can be a percentage of the target torque. This percentage can be set by the operator or hard-set in the tool.

[0110] The operator can also program the value of the objective torque to which he wishes the assembly to be screwed to be tightened at the end of the tightening phase.

[0111] It is assumed that the screwing device has previously been implemented to carry out a screwing operation comprising a rapid pre-tightening phase and a slower tightening phase. Thus, the additional train is engaged.

[0112] When starting the screwing device in order to carry out such a screwing / unscrewing operation, the control means control the motor in such a way that it generates, in the screwing or unscrewing direction, a speed change acceleration W whose value is greater than the quotient of the predetermined limit torque Cl beyond which the balls 18 pass into their release position in in which the support element 15 and the selection member 16 are no longer linked in rotation, by the inertia Jos of the selection member. The balls then leave the pair of locking housings 162 corresponding to the engagement position of the selection member 16 to come and be housed in the other pair of locking housings 162 corresponding to the disengagement position of the selection member 16. In this way, the engagement means of the additional gear train are placed in their disengagement state. The control means then control the motor so as to rotate it in the screwing direction to disengage the additional gear train and carry out the pre-screwing phase.

[0113] When the engagement means are in the disengagement state of the additional gear train, the selection member 16 is in its disengagement position, in which it is held by the balls 18 which are located in the corresponding locking housings 161, its stops 165 bearing against the stops 155 of the support element 15.

[0114] The cam surfaces 164 of the selection member 16 act on the locking members 26 so as to release their movement into their active position in which they are placed and held under the effect of the spring 27. The cam surfaces 164 therefore do not move the locking members 26 into their active position. This makes it possible to prevent any blocking of the system during the transition from the engaged state to the disengaged state. Indeed, during this transition, it may be that at the moment when the locking members 26 are released and pushed by the spring 27 towards their active position, their end is in the extension of the inner surface 215 of the stops 213 of the crown 21. If the locking members 26 were at this moment pushed by the cam surfaces 164, they would come to bear against these internal surfaces 215 and would block the rotation of the moving parts. Because the cam surfaces 164 only allow to release, i.e. make possible, their movement in their active position under the effect of the spring 17, once they are no longer in the extension of the internal surfaces 215, the spring places the locking members 26 in their active position.

[0115] A rotation of the motor induces a movement of the locking members 26 against the cam paths 211 of the crown 21 inducing a movement of the crown 21 in translation, against the effect of the compression spring 24, from its blocked position to its free position which is reached when the locking members 26 are in abutment against the stops 213 of the crown. They are then housed in the conformations 214 which hold them in position.

[0116] In this state, the motor shaft 132 drives the support element 15 and the locking members 26 in rotation, which in turn drive the crown 21 in rotation at the speed of the motor shaft 132.

[0117] The crown 21 rotates the sun gear 151 via the satellites 22. The sun gear and the crown 21 then rotate at the same speed, which forces the satellite carrier 20 to rotate at the same speed as well. The output member 12 therefore rotates at the same speed as that of the motor. Thus, the output member 12 is rotated in the screwing direction at high speed.

[0118] The control means control the motor in such a way that the output member is driven in rotation at high speed during the pre-screwing phase until the tightening torque delivered by the screwing device reaches the predetermined speed change torque threshold CchangementVitesse.

[0119] When the control means detect by means of the torque sensor that this threshold is reached, the control means brake the motor in order to generate a speed change deceleration whose value is greater than the quotient of the predetermined limit torque Cl by the inertia Jos of the selection member. In this way, the selection means are moved into their state of engagement of the additional gear train.

[0120] When this deceleration is generated, the balls 18 come out of their housings 162 to circulate in the groove 163 until they are housed in the other locking housings 162 of the selection member 16. In doing so, the selection member 16 rotates relative to the support element 15 so as to occupy its engagement position in which its stops 165 are in abutment against the stops 155 of the support element 15.

[0121] During this movement of the selection member 16, its cam surfaces 164 act on the locking members 26 so as to return them to their position. inactive. During their movement from their active position to their inactive position, the locking members 26 move along the cam paths 211 of the crown 21 until they reach their thinnest end and come to be housed in the hollows 212 so that the crown translates progressively from its free position to its blocked position in which it is kept immobile in rotation relative to the casing.

[0122] The control means then control the motor so that it reaches its nominal rotation frequency while generating, however, an acceleration W lower than the speed change acceleration in order to guarantee that the selection means remain in their state of engagement of the additional gear train; in other words, the acceleration W must be such that < The control means then control the motor so as to make it rotate in the screwing direction to carry out the tightening phase at a slower speed.

[0123] In the state of engagement of the additional gear train, when the rotor rotates in the screwing direction, the output member 12 is driven in rotation at a speed different from that of the motor insofar as the satellite carrier 20 rotates at a speed different from that of the motor since the crown is no longer free to rotate but locked in rotation in the casing.

[0124] The control means thus control the motor until they detect, by means of the torque sensor, the reaching of the objective tightening torque at which it is desired to tighten the assembly being screwed.

[0125] The torque sensor may be a current measurement. It could be envisaged to cause the engagement / disengagement of the additional train on the basis of a reason other than the torque measurement, for example a time measurement.

[0126] Any other reason for switching from the high speed / low torque state to the low speed / high torque state (and vice versa) can be considered. This can be done automatically (reaching a torque, a time, etc.) or at the request of the operator (pressing a button, other...).

[0127] When the target torque is reached, the control means brake the motor preferentially with a deceleration lower than the speed change deceleration until the rotation frequency of the motor becomes zero. However, braking with a stronger deceleration would have no effect given that the sliding torque of the selection member 16 relative to the support element 16 is significantly stronger when the balls no longer have the opportunity to pass into a groove 163.

[0128] At equal rotation frequency of the motor during the rapid pre-tightening and slow tightening phases, the difference in speed of the output member is due to the fact that during the pre-screwing phase, the crown is free to rotate while it is immobile in rotation during the tightening phase. In other words, the additional gear train is disengaged during the pre-screwing phase but engaged during the tightening phase. Thus, the transmission chains stressed during these two phases have different transmission ratios.

[0129] In this embodiment, the motor rotates counterclockwise for a screwing operation and non-clockwise for an unscrewing operation as seen from the output member towards the rear of the screwdriver. These directions could be reversed.

[0130] If acceleration is required for the selection means to move from their additional gear train disengagement state to their additional gear train engagement state, deceleration will be necessary to move from their additional gear train disengagement state to their additional gear train engagement state to their additional gear train disengagement state to their additional gear train disengagement state, and vice versa.

Claims

1. Claims Screwing device comprising: - a casing; - a motor equipped with a rotor; - an output member capable of rotating a drive element of an element to be screwed; - a transmission connecting said rotor to said output member, said transmission comprising at least one additional gear train capable of being engaged / disengaged, said at least one additional gear train comprising at least one epicyclic train provided with an internal toothed crown; said device comprising means for engaging said at least one additional gear train, said engaging means being able to take at least: - an engagement state in which said at least one additional train is engaged, and - a disengaged state in which said at least one additional gear train is not engaged, the reduction ratio of said transmission between said rotor and said output member being different depending on whether or not said additional gear train is engaged, characterized in that said crown is mounted to move in translation along the axis of said rotor inside said casing between at least: - a free position, taken when said engagement means are in said disengaged state, and in which said crown is rotatable relative to said casing such that said at least one additional gear train is disengaged, and - a locked position, taken when said engagement means are in said engagement state, and in which said crown is locked in rotation relative to said casing such that said at least one additional gear train is engaged, said device further comprising means for controlling said motor, said means for controlling said motor being configured to generate an acceleration or deceleration of said predetermined speed change rotor, said predetermined acceleration or deceleration of speed change acting on said engagement means to cause them to pass from one to the other of their states, said engagement means comprising means for driving in translation of said crown from one to the other of its locked and unlocked positions, said drive means being configured to transform a rotation of said rotor into a translation of said crown following the generation of said predetermined acceleration / deceleration by said means for controlling said motor.

2. A screwing device according to claim 1 wherein said internal toothed crown comprises a first locking portion and said casing comprises a second locking portion, said first and second locking portions being complementary to one another and shaped to ensure rotational locking of said crown relative to said casing when they cooperate with each other, said first and second locking portions cooperating with each other in said locked position of said crown and not cooperating with each other in said free position of said crown.

3. A screwing device according to claim 2 wherein said first and second locking portions are of frustoconical shape.

4. Screwing device according to any one of claims 1 to 3 comprising elastic return means acting on said crown to tend to maintain it in said blocked position.

5. Screwing device according to any one of claims 1 to 4 wherein said translational drive means comprise at least one cam path formed on said crown and at least one locking member linked in rotation to said rotor, said at least one locking member being movable between at least: an inactive position in which said locking member is not in contact with said cam path such that a rotation of said rotor relative to said crown does not induce a translation of said crown, and - an active position in which said locking member is in contact with said cam path such that a rotation of said rotor relative to said crown induces a translation of said crown along the axis of said rotor.

6. Screwing device according to claim 5 wherein said at least one locking member, when in said active position, is configured to move against said cam path, during a relative rotational movement of said rotor with respect to said crown, between: - a first extreme position in which said crown is in said free position, and - a second extreme position in which said crown is in said blocked position.

7. Screwing device according to claim 6 comprising means for rotationally connecting said crown and said rotor, said rotational connecting means comprising said at least one locking member and at least one stop-forming element secured to said crown, said stop-forming element being arranged in such a way that said locking member bears against said stop-forming element when said locking member is in said active position and in said first extreme position.

8. Screwing device according to claim 6 or 7 wherein said cam path comprises a conformation capable of at least partially housing said locking member when it is in its first extreme position, said conformation being configured to reversibly maintain said locking member in said first extreme position.

9. Screwing device according to any one of claims 5 to 8 wherein said engagement means comprise a selection member movable in rotation relative to said rotor between at least: - an engagement position of said additional gear train, and - a disengagement position of said additional gear train, said selection member acting on said at least one locking member to: - in said engagement position, place said locking member in its inactive position; - in said disengagement position, place said locking member in its active position.

10. A screwing device according to claim 9 wherein said selection member comprises a cam surface in contact with said locking member, said cam surface acting on said locking member to allow its movement between its active and inactive positions.

11. A screwing device according to claim 10 wherein said locking member is held in abutment against said cam surface by an elastic return means, said elastic return means acting on said locking member to tend to move it towards its active position.

12. Screwing device according to any one of claims 5 to 11, in which said locking member is movable in translation between its active and inactive positions along an axis orthogonal to the axis of rotation of said rotor.

13. A screwing device according to any one of claims 10 to 12 comprising a support element rotatably connected to said rotor, said at least one locking member being integral in rotation with said support element and mounted to be movable relative to the latter between its active and inactive positions, said selection member being mounted to be movable in rotation relative to said support element between its engagement and disengagement positions, said support element comprising stop elements against which stop elements of said selection member are capable of coming to bear, said stop elements defining said engagement and disengagement positions of said selection member.

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