two-speed screw-unscrewing device with floating crown

Abstract

The present invention relates to a screwing device comprising: a housing; a motor equipped with a rotor; an output member capable of rotating a drive element of a screwing element; a transmission linking 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 gear train equipped with a toothed inner ring;said device comprising engagement means, of 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 ring is mounted movable 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 ring is movable in rotation 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 engaged state, and in which said ring is locked in rotation relative to said casing such that said at least one additional gear train is engaged.;

Description

Title of the invention: Two-speed screw-unscrewing device with floating crown 1. Scope 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 particularly intended for continuous tightening screwdrivers with a torque exceeding 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 screwdriving devices are classically associated with control means and include a tightening torque and / or tightening angle sensor.

[0006] These control means allow for the programming of tightening strategies, i.e., the parameters of the pre-tightening and tightening phases, in particular the motor rotation speeds during the pre-tightening and tightening phases, as well as the target torque and / or angle at the end of tightening. Thus, during the execution of a tightening operation, the control means drive the motor to drive the element to be tightened at the pre-tightening speed during the pre-tightening 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, screwdrivers which apply an uninterrupted and increasing torque to the screw during tightening, incorporate a transmission between the motor and the output shaft driving the screw. This transmission generally consists of one or more planetary gear trains. These planetary gear trains ensure sufficient available tightening torque at the output shaft. This torque is the result of multiplying the motor torque by the transmission's reduction ratio and its efficiency.

[0008] To achieve high tightening torques, for example above 150 Nm, screwdriver manufacturers are therefore led to use a high reduction ratio by employing several epicyclic gear trains in the transmission. The drawback of this is that the rotational speed of the screwdriver's output shaft becomes relatively low, resulting in a long tightening time that negatively impacts productivity.

[0009] Thus, manufacturers of high-torque screwdrivers have devised a device integrated into the transmission that allows one of the planetary gear sets to be disengaged during pre-tightening. The reduction ratio used during pre-tightening is therefore lower than during the torque ramp-up during tightening, with the benefit of a high rotational speed during pre-tightening and high torque during the torque ramp-up during tightening. This planetary gear set, which can be engaged or disengaged, is called an additional gear set.

[0010] The pre-tightening and tightening speeds applied during the pre-tightening and tightening phases therefore require the use of an additional, switchable gear train that allows different reduction ratios to be defined between the rotor and the output member depending on whether it is engaged or not. Thus, the additional gear train is not engaged during the pre-tightening phase so that the pre-tightening speed is high. Conversely, the additional gear train is engaged during the tightening phase so that the tightening speed is slower and the tightening torque achievable by the tightening device is higher.

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

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

[0013] Indeed, in the solutions described in the prior art, the predetermined torque threshold for gear change, at which point the additional gear automatically engages, is not adjustable because it depends on the dimensions of the elastic element integrated into the transmission. Consequently, this type of technology does not allow for the provision of versatile screwdrivers adaptable to different screwdriving operations requiring a gear change after reaching a pre-tightening threshold of varying values.

[0014] To overcome this drawback, the Applicant has designed a technique allowing the moment at which the additional train is triggered to be chosen 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 regard a technique for engaging an additional train, independently of the tightening torque, by acting only on the level of acceleration of the engine.

[0016] Such a solution therefore constitutes a major improvement over 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 enabling 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 engine acceleration.

[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 way in which the crown of the additional epicyclic gear train can be locked-unlocked in rotation relative to the housing of the screwing device in order 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 used.

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

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

[0026] To this end, the invention proposes a screwing device comprising: - a crankcase; - a motor equipped with a rotor;

[0027]

[0028]

[0029]

[0030]

[0031]

[0032] - an output member capable of rotating a drive element of a screw-on element; - a transmission linking 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 gear train equipped with a toothed inner ring; said device comprising means for engaging said at least one additional gear train, said engagement 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 said additional gear train is engaged or not. According to the invention, said crown is mounted to move in translation along the axis of said rotor inside said housing between at least: - a free position, taken when said engagement means are in said disengaged state, and in which said crown is mobile in rotation relative to said housing in such a way that said at least one additional gear train is disengaged, and - a locked position, taken when said engagement means are in said engaged state, and in which said crown is locked in rotation relative to said casing in such a way that said at least additional gear train is engaged. Thus, the invention proposes a screwing and / or unscrewing device enabling the engagement-disengagement of an additional gear train, in particular a simple one, having a reduced number of parts, whose engagement-disengagement mechanism of the additional gear train is easily integrated into the tool. According to one possible feature, a screwing device according to the invention includes control means for said motor, said control means for 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 to the other of their states. 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 engine acceleration.

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

[0034] According to one possible feature, said first and second blocking portions are of frustoconical shape.

[0035] According to one possible feature, a screwing device according to the invention includes elastic return means acting on said crown to tend to maintain it in said locked position.

[0036] According to one possible feature, a screw-driving device according to the invention comprises means for translating said crown from one of its locked and unlocked positions to another, said means for translating and driving said crown comprising at least one cam track formed on said crown and at least one locking member rotationally linked 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 track so that a rotation of said rotor relative to said ring does not induce a translation of said ring, and - an active position in which said locking member is in contact with said cam track such that a rotation of said rotor relative to said ring induces a translation of said ring along the axis of said rotor.

[0037] According to one possible feature, said at least one locking member, when in said active position, is configured to move against said cam track, during a relative rotational movement of said rotor with respect to said ring, 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 one possible feature, a screw-screwing device according to the invention comprises means for rotationally connecting said crown and said rotor, said means for rotationally connecting said at least one locking member and at least one stop element integral with said crown, said stop element stop being arranged in such a way that said locking member is in contact with said stop element when said locking member is in said active position and in said first extreme position.

[0039] According to one possible feature, said cam track includes a conformation suitable for housing at least partially said locking member when it is in its first extreme position, said conformation being configured to maintain, reversibly, said locking member in said first extreme position.

[0040] According to one possible feature, said engagement means comprise a movable selection member that rotates relative to said rotor between at least: - an engagement position for said additional gear train, and - a disengagement position for said additional gear train,

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

[0042] According to one possible feature, said selection member includes 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 one possible feature, said locking member is held in contact with 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 one possible feature, 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 one possible feature, a screwing device according to the invention comprises a support element rotationally linked to said rotor, said at least one locking member being rotationally fixed to said support element and mounted movable relative to it between its active and inactive positions, said selection member being mounted 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 bearing, said stop elements defining said engagement and disengagement positions of said selection member. 5. Description of the figures

[0046] Other features and advantages of the invention will become apparent from the following description of particular embodiments, given by way of simple illustrative and non-limiting example, and the accompanying drawings, among which:

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

[0048] [Fig.2] [Fig.2] illustrates a detailed view of [Fig.1];

[0049] [Fig.3] [Fig.4] Figures 3 and 4 illustrate two views of a crown of the device of [Fig.1] and 2;

[0050] [Fig.5] [Fig.6] Figures 5 and 6 illustrate two views of a selection organ of the device of [Fig.1] and 2;

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

[0052] [Fig.8] [Fig.8] illustrates a section along the BB axis 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 cross-sectional view of a device according to the invention with the additional train disengaged;

[0055] [Fig. 11] the [Fig. 11] a section along the axis BB of the [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. 1] in a being intermediate between switching on and switching off;

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

[0059] [Fig. 15] [Fig. 15] illustrates a longitudinal cross-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 allow screwing and / or unscrewing operations to be carried out.

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

[0064] The housing 10 contains an electric motor 13 comprising a stator 130 and a rotor 131 equipped with a motor shaft 132. In this embodiment, the rotor is external. In variants, it may be internal.

[0065] The device includes an output member 12 located at the end of the housing 10. This output member 12 is capable of rotating a drive element of a screw-on element, in particular a screw socket or other.

[0066] The device includes 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 includes a two-speed mechanism 14 comprising two transmission chains having different gear ratios. For this purpose, the transmission T includes an additional gear train capable of being engaged / disengaged. As will be described in more detail later, this additional gear train comprises an epicyclic gear train which can be disengaged by allowing its inner toothed ring to rotate freely or engaged by locking its ring gear against rotation.

[0068] The two-speed mechanism 14 includes means for engaging the additional gear train, these means being able to take at least: - an engagement state in which the additional 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 differs depending on whether the additional gear train is engaged or not; the reduction ratio is higher when the additional gear train is engaged. In some variants, the reduction ratio may be higher when the additional gear train is engaged. In this way, for a given rotor speed, the output member's speed is higher when the additional gear train is not engaged and lower when it is engaged, so that the clamping torque that can be 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 for rotation within the housing 10 along the axis of the rotor 131. At one end, it is fixed to the drive shaft 132 in such a way that it is rotationally linked to the rotor 131. The assembly of the support element 15 and the drive shaft 132 can be achieved for this purpose by means of splines 151. At its other end, it comprises a sun pinion 152. The drive shaft 132 and the support element 15 could, in one embodiment, constitute a single piece.

[0071] The engagement means comprise a selection member 16. This selection member 16 is mounted to rotate about the axis of the rotor 131 on the support element 15, for example by means of plain bearings or roller bearings 161, between at least two extreme positions, namely: - an engagement position for 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 rotationally linked to the support element 15 by means of rotational linkage. For this purpose, the support element 15 is traversed by a transverse bore 153 formed along an axis perpendicular to its longitudinal axis. This bore 153 houses an elastic return means which, in this embodiment, comprises a compression spring 17. At each end of the compression spring 17 is placed a locking element. In this embodiment, these locking elements are formed by locking balls 18.

[0073] The selection member 16 is traversed 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 rotationally linked position in which the balls 18 are housed in two diametrically opposed locking recesses 162 such that the support element 15 and the selection member 16 are rotationally linked, and - a release position in which the balls 18 are not housed in any of the locking housings 162, but are in the groove 163, so that the support element 15 and the selection member 16 are not rotationally bound.

[0075] When the selection member 16 is in its position for engaging the additional gear train, the locking balls 18 are housed in the first two of the opposite housings 162. When the selection member 16 is in its position for disengaging the additional gear train, the balls 18 are housed in the other two 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 selector member 16 are able to transmit a predetermined limiting torque Cl, beyond which the balls move to their release position in which the support element and the selector 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 recesses 162, and the groove 163. This torque can be conventionally determined by calculation or empirically.

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

[0078] The device conventionally includes motor control means 19. These means allow the motor to be controlled, in particular by controlling its electrical supply. They may be located wholly or partially inside the housing or outside of it.

[0079] The motor control means 19 allow, by acting on the acceleration / deceleration of the rotor 131 of the motor 13, to move the engagement means from one to the other of their states, i.e. to move the selection member 16 from one to the other of its positions 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 maximum torque Cl transmissible by the rotating linkage means divided by the inertia Jos of the selector member about its axis of rotation. This acceleration / deceleration is called the gear-change acceleration / deceleration insofar as it allows the engagement / disengagement of the additional gear train and thus changes the reduction ratio of the transmission between the rotor and the output member.

[0081] During a screwing / unscrewing operation, the motor typically produces accelerations and variations in acceleration, particularly at start-up. Therefore, the acceleration / deceleration that causes the switching means from one state to the other must be sufficiently significant, i.e., far removed from and, more precisely, greater than the accelerations that are typically likely to occur, for example, at start-up or stopping, so as not to cause unintentional switching of the switching means from one state to the other.

[0082] The transmission comprises an epicyclic gear train including the sun gear 152 fixed in rotation to the support element 15, a planet carrier 20 fixed in rotation to the output member 12, and an internal toothed ring 21 meshing with planets 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 a cascade of epicyclic gear trains, the output of which will be linked in rotation to the output member 12.

[0083] The crown 21 is mounted to rotate freely inside the housing by means of a bearing 23.

[0084] The crown 21 has, at one of its ends, a truncated cone-shaped blocking portion 210.

[0085] The housing 10 has a frustoconical blocking portion 100.

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

[0087] The crown 21 is mounted to move in translation inside the housing 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 ring 21 is mobile in rotation relative to the housing in such a way that the additional gear train is disengaged: in this position, the locking portions 210 and 100 are separated from each other; - a locked position, taken when the engagement means are in the engaged state, and in which the ring 21 is locked in rotation relative to the housing 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 ring 210 in rotation relative to the housing 10.

[0088] A compression spring 24 is interposed between a bearing surface 250 of a base 25 in which the ring 21 is mounted to move in translation between its two extreme positions. This compression spring 24 acts on the ring 21 to tend to hold 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 that thickens from a recess 212 towards the end of the ring 21 oriented towards the support element 15. A stop element 213 is provided at the thickest end of each cam track 211. The connection area between each cam track 211 and each stop element 213 comprises a conformation 214.

[0091] The support element 15 is traversed 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 within 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 track 211 of the ring 21, so that a rotation of the rotor 131 relative to the ring 21 does not induce a translation of the ring 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 track 211 of the ring 21 so that a rotation of the rotor 131 relative to the ring 21 induces a translation of the ring 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 track 211 of the ring 21, during a relative rotational movement of the rotor 131 with respect to the ring, between: - a first extreme position in which the crown is in its free position; the locking members 26 are then in contact with 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 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 mechanisms in their inactive position; - in its disengaged position, place the locking mechanisms in their active position.

[0096] Each locking member 26 includes a guide housing 261 provided 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 recesses 261 of the locking members 26 by fitting into them. These cam surfaces 164 have a thin end from which they tend 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 contact with 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 designed 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 clearer from the description of the operation of a According to the device of the invention, these stops make it possible to stop the rotation of the selection member 16 relative to the support element 15 without going 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 elements 213 of the crown 21 are arranged in such a way that the locking members 26 bear against these stop 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 a 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 locking elements ensure a rotational connection of the crown with the rotor.

[0104] The conformations 214 of the crown 21 are suitable for housing at least partially the locking member when it is in its first active position, this conformation being configured to maintain, reversibly, 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 rotational 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) implemented where applicable. 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 the predetermined torque threshold value for speed change, CchangementVitesse, into the controller, for example using a touchscreen, keyboard, smartphone, or other device. Reaching this threshold at the output of the screwing device during a pre-screwing phase triggers a speed change and the transition to the tightening phase. This speed change torque can alternatively be The torque is calculated automatically by the tool based on the desired target tightening torque, rather than being set by the operator. This speed change torque can be a percentage of the target tightening torque. This percentage can be set by the operator or hard-programmed into the tool.

[0110] The operator can also program the target torque value at which he / she wants the screw assembly to be tightened at the end of the tightening phase.

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

[0112] When the screwing device is started to perform such a screwing / unscrewing operation, the control means drive the motor in such a way that it generates, in the direction of screwing or unscrewing, 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 selector member 16 are no longer rotationally bound by the inertia Jos of the selector member. The balls then leave the pair of locking slots 162 corresponding to the engagement position of the selector member 16 and move into the other pair of locking slots 162 corresponding to the disengagement position of the selector member 16. In this way, the engagement means of the additional gear train are placed in their disengaged state. The control means then command the motor to rotate it in the screwing direction to disengage the additional gear train and perform 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 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 selector member 16 act on the locking members 26 so as to release them into their active position, in which they are placed and held by the spring 27. The cam surfaces 164 therefore do not displace the locking members 26 into their active position. This prevents the system from jamming during the transition from the engaged to the disengaged state. Indeed, during this transition, it is possible that, at the moment the locking members 26 are released and pushed by the spring 27 towards their active position, their ends are aligned with the inner surface 215 of the stops 213 of the ring 21. If the The locking members 26 were at that moment pushed by the cam surfaces 164; they would then bear against these inner surfaces 215 and block the rotation of the moving parts. Since the cam surfaces 164 only allow, i.e., enable, their movement into their active position under the effect of the spring 17, once they are no longer aligned with the inner surfaces 215, the spring places the locking members 26 into their active position.

[0115] Rotation of the engine induces a displacement of the locking members 26 against the cam tracks 211 of the crown 21, causing a translational displacement of the crown 21, against the effect of the compression spring 24, from its locked position to its free position, which is reached when the locking members 26 are abutted against the stops 213 of the crown. They are then housed in the supports 214 which hold them in position.

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

[0117] The ring 21 drives the sun gear 151 in rotation via the satellites 22. The sun gear and the ring 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 the motor. Thus, the output member 12 is driven in rotation in the direction of high-speed screwing.

[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 torque threshold for speed change CchangementVitesse.

[0119] When the control means detect, by means of the torque sensor, that this threshold has been reached, the control means brake the motor to generate a gear change deceleration whose value is greater than the quotient of the predetermined limit torque Cl divided 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 come to occupy its engagement position in which its stops 165 are in contact with 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 tracks 211 of the crown 21 until they reach their thinnest end and come to rest in the hollows 212 so that the crown translates progressively from its free position to its locked position in which it is held immobile in rotation relative to the housing.

[0122] The control means then drive the motor so that it reaches its nominal rotational speed, however generating an acceleration W lower than the acceleration of the gear change in order to ensure 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 command the motor so as to rotate it in the direction of screwing to carry out the tightening phase at a slower speed.

[0123] In the state of engagement of the additional gear train, when the rotor turns in the screwing direction, the output member 12 is driven in rotation at a different speed than that of the motor insofar as the satellite carrier 20 rotates at a different speed than that of the motor since the ring is no longer free in rotation but blocked in rotation in the housing.

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

[0125] The torque sensor can be a current measurement. It could be envisaged to trigger the engagement and disengagement of the auxiliary train based on a pattern other than the torque measurement, for example a time measurement.

[0126] Any other motive aimed at 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 certain torque, time, etc.) or at the operator's request (pressing a button, etc.).

[0127] When the target torque is reached, the control means preferentially brake the motor with a deceleration lower than the deceleration during gear changes until the motor's rotational speed reaches zero. However, braking with a stronger deceleration would have no effect, given that the sliding torque of the selector member 16 relative to the support element 16 is significantly higher when the balls no longer have the opportunity to pass through a groove 163.

[0128] At equal motor rotational speed during the rapid pre-tightening and slow tightening phases, the difference in speed of the output element is due to the fact that during During the pre-tightening phase, the ring gear is free to rotate, whereas it is stationary during the tightening phase. In other words, the additional gear train is disengaged during the pre-tightening phase but engaged during the tightening phase. Therefore, the transmission chains stressed during these two phases have different gear ratios.

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

[0130] If an acceleration is required for the selection means to move from their state of disengaging the additional gear train to their state of engaging the additional gear train, a deceleration will be required to move from their state of disengaging the additional gear train to their state of engaging the additional gear train to their state of disengaging the additional gear train to their state of disengaging the additional gear train, 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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