Patent Application
20240051100
The field of the invention is that of the design and manufacture of impact screwing/unscrewing devices, more commonly known as impact wrenches.
An impact wrench is a tool conventionally used to tighten and loosen elements such as nuts or screws, without causing torque feedback to the hand of the operator using them. Such a tool comprises an electric or pneumatic motor and an impact mechanism, the input whereof is connected to the rotor of the motor and the output whereof comprises an output square capable of rotating a screwing tool. The impact mechanism typically comprises a flywheel which can be rotated by the motor and which carries a mass, more typically referred to as a hammer, which is capable of striking the output square, which acts as an anvil, and thus rotate it to transmit a torque to the element to be tightened-loosened. The striking mechanism thus transforms the kinetic energy of a rotating mass (driven by the motor) into impact energy. There are several types of impact mechanism but they all have the common feature of having one or more hammers that strike the output square.
Different types of impact mechanisms exist, such as Twin hammer, Two jaws or Pin clutch mechanisms, etc. which all have the common feature of systematically generating a determined number of impacts per revolution, which number is generally equal to one, sometimes two. The number of impacts per revolution is linked to the kinematics of the impact mechanism and cannot be changed.
All impact mechanisms operate on the same principle, i.e. a multitude of impacts are required to gradually reach the tightening torque. The tightening torque of an impact wrench is thus dependent on the number of impacts and the amount of energy transmitted to the anvil during each impact. It is generally claimed that the tightening torque of an impact wrench corresponds to the torque reached after 10 seconds of screwing.
To reach a high tightening torque quickly, the energy transmitted to the output square during each impact must be high. This can be achieved by increasing the rotational speed of the impact mechanism before impact. This requires implementing a more powerful motor, which is a drawback, in particular in terms of overall dimensions, weight and cost.
Another solution involves running the impact wrench idle, i.e. by keeping the hammers in a non-engaged position where they cannot collide with the anvil, until the motor reaches a predetermined speed, and then placing the hammers in an engaged position wherein they are capable of colliding with the anvil to generate a high-power impact.
This technique is of interest, but requires implementing an actuator independent of the motor, in order to move the hammers from one of either the engaged or non-engaged position to the other. This type of impact wrench is thus structurally complex.
Impact wrenches can thus be further improved to enable them to quickly reach a high tightening torque.
An exemplary embodiment of the invention proposes an impact screwing/unscrewing device comprising:
According to the invention, a variation of said command instruction supplied to said motor by said means for controlling triggers the passage of said at least one hammer from one of the positions thereof to the other.
Thus, according to this aspect of the invention, a simple variation of the instruction supplied to the motor allows the hammers to be moved from one of their positions to the other without the need to implement an actuator to allow this movement to take place. This makes the device according to the invention very simple in design, but nonetheless allows high tightening torques to be reached quickly by making it possible to activate the striking mechanism when the motor is running fast enough.
According to one possible feature, said device comprises a flywheel coaxial to said rotor.
According to one possible feature, said means for controlling of said motor allow said device to be implemented in order to carry out a screwing or unscrewing operation comprising carrying out a series of successive impact cycles during each of which the hammers collide with the anvils, said means for controlling being capable of transmitting a command instruction to said motor, said means for controlling being capable of generating, during each impact cycle, a variation of said command instruction supplied to said motor by said means for controlling, said variation triggering the passage of said at least one hammer from one of its positions to the other.
According to one possible feature:
According to one possible feature:
According to one possible feature, said angular range is bounded by two end positions of said drive shaft relative to said flywheel in which said flywheel and said drive shaft are rotatably linked and said at least one hammer is in the non-engaged position thereof.
According to one possible feature, said at least one hammer is capable of rotating, between the engaged and non-engaged positions thereof, along an axis parallel to the axis of rotation of said motor.
According to one possible feature, a device according to the invention comprises an indexing pin fixed to said drive shaft for rotation therewith and capable of bearing, in said at least one end position, against at least one stop, that is fixed to said flywheel for rotation therewith, so as to rotatably link said drive shaft and said flywheel.
According to one possible feature:
According to one possible feature:
According to one possible feature, said at least one hammer is capable of translating, between the engaged and non-engaged positions thereof, along an axis parallel to the axis of rotation of said drive shaft.
According to one possible feature, a device according to the invention comprises a secondary drive shaft fixed to said drive shaft for rotation therewith but free to translate, said secondary drive shaft being mounted such that it can translate and rotate relative to said flywheel along the axis of rotation of said drive shaft, said secondary drive shaft comprising at least one cam against which at least one guide pin rigidly connected to said flywheel is capable of moving, said at least one cam having a profile that is shaped to allow said secondary drive shaft to rotate relative to said flywheel over said angular range between said at least one end position and said predetermined position, and to allow for a translational movement of said secondary drive shaft relative to said flywheel during the movement thereof between said at least one end position and said predetermined position.
According to one possible feature, said at least one hammer is fixed to said drive shaft for translation therewith but not for rotation therewith, and is mounted such that it can translate relative to said flywheel so as to be moved between the engaged and non-engaged positions thereof by said drive shaft.
According to one possible feature, said motor comprises an internal stator provided with coils, said rotor being external, said at least one hammer being fixed to said rotor for rotation therewith and being mounted such that it can rotate relative to said rotor between the engaged and non-engaged positions thereof along an axis parallel to the axis of rotation of said rotor, the magnetic fields created by said coils acting on said at least one hammer:
According to one possible feature, said means for controlling are capable of:
According to one possible feature, said means for controlling are configured to:
According to one possible feature, said means for controlling are configured to maintain the rotation of said rotor at said predetermined speed until they detect at least one parameter signifying that said at least one hammer is in a predetermined angular position along the axis of rotation of said rotor relative to said at least one anvil before supplying said instruction to decelerate or not power said motor.
According to one possible feature, said motor comprises a sensor for measuring the angular position of said rotor, and said means for controlling are configured to determine and record the angular position of said at least one anvil at the end of each impact cycle based on the measurement made using said sensor, and to deduce therefrom, at a subsequent impact cycle, the angular position of said at least one hammer relative to said at least one anvil and the reaching of said predetermined angular position.
According to one possible feature, a device according to the invention comprises an output shaft rigidly connected to said at least one anvil, said device comprising a sensor for measuring the angular position of said output shaft, said means for controlling being configured to determine and record the angular position of said output shaft at the end of each impact cycle and to deduce therefrom, at the subsequent impact cycle, the angular position of said at least one hammer relative to said at least one anvil and the reaching of said predetermined angular position.
According to one possible feature, said means for controlling are capable of controlling said motor so as to stabilize the angular offset between said rotor and said flywheel in said predetermined angular position of said at least one hammer.
According to one possible feature, a device according to the invention comprises an angle sensor capable of measuring the angular position of said flywheel, said means for controlling being capable of calculating the angular position of said rotor relative to said flywheel.
Further features and advantages of the invention will become apparent on reading the following description of specific embodiments, which is given merely as a non-limiting example for illustration purposes, and the accompanying drawings, in which:
A first embodiment of a screwing/unscrewing device according to the invention, also referred to as an impact wrench, is shown with reference to
Such a device comprises a casing 1 housing an electric motor 2 comprising a stator 20 and a rotor 21. It comprises an actuating trigger 10.
The rotor 21 is provided with a drive shaft 3, at the end of which protrude two fins 4 extending away from one another along an axis perpendicular to the longitudinal axis of the drive shaft 3.
The end of the drive shaft 3 further comprises an indexing pin 5.
The device comprises an impact mechanism 6 comprising:
Each anvil 60 comprises two opposing collision surfaces 601.
The anvils 60 are rotatably linked to an output shaft 602, also referred to as an output square, which is capable of carrying a screwing/unscrewing bit in order to rotate an element to be screwed/unscrewed such as a nut or a screw.
Each hammer 61 comprises two opposing striking surfaces 610. Each hammer 61 further comprises two lugs 620 separated by a central recess 630 defining a ramp profile 640 against which the fins 4 of the drive shaft can move.
The hammers 61 are rigidly connected to a flywheel 7. The flywheel 7 forms a bell inside which the hammers 61 are placed. The hammers 61 are mounted such that they can rotate on shafts 70 fixed to the flywheel 7 such that they are stationary and which extend along axes parallel to the axis of rotation of the rotor.
The rotor, the drive shaft, the flywheel and the output shaft are coaxial.
A hole 71 passes through the center of the flywheel, at the periphery of which hole is formed a groove 72, of a larger outer diameter, which extends over an angular portion bounded by two stops 73. The implementation of two stops allows the device to operate both during screwing and unscrewing. The implementation of a single stop would allow the device to operate in only one or the other of these two directions.
The indexing pin 5 has a shape that complements that of the groove 72 so that it can move therein until it comes to bear against either of the stops 73 bounding the groove 72. The flywheel 7 is thus capable of rotating on the drive shaft 3 along the axis thereof over an angular range bounded by the two stops 73.
The flywheel is thus capable of rotating relative to the drive shaft over an angular range bounded by at least one end position, two end positions defined by the stops 73 in this embodiment, wherein the flywheel and the drive shaft are rotatably linked. When the indexing pin 5 is bearing against a stop 73, the flywheel 7 and the drive shaft 3 are rotatably linked in the direction for bringing the indexing pin closer to the stop.
Each hammer 61 is capable of rotating about the corresponding shaft 70 between at least:
The striking and collision surfaces are capable of hitting one another when the at least one hammer is in the engaged position thereof and when the at least one hammer is rotated by the motor.
The striking and collision surfaces are not capable of hitting one another when the at least one hammer is in the non-engaged position and when the at least one hammer is rotated by the motor.
The device comprising at least one actuating element acting on the at least one hammer in order to place it
The actuating element comprises the fins 4 which are fixed to the drive shaft 3 for rotation therewith and which are capable of moving against the ramps 640 of the lugs 620 of the hammers 61.
The fins 4 and the ramps 640 are shaped
When the indexing pin 5 is bearing against one of the stops 73, the fins 4 are housed inside the central recesses 630 in the hammers 61. The hammers are thus held in the non-engaged position thereof and the flywheel is rotatably linked to the drive shaft so that the motor can freely drive the hammers which rotate about the anvil without colliding therewith.
As the indexing pin 5 moves in the groove between the two stops 73, it takes a predetermined position wherein the fins 4 interact with the lugs 620 to bring the hammers into the engaged position and thus allow the striking surface thereof to collide with the collision surfaces of the anvils.
The device comprises means for controlling the motor, which means are capable of transmitting a command instruction to the motor.
These means for controlling comprise a user interface, such as a screen and/or a keyboard allowing the user to input, for example, a setpoint for a tightening torque or for a percentage of a maximum tightening torque.
The means for controlling comprise a controller for converting the user's instruction into a speed according to a pre-set control law. They allow a method to be implemented for controlling the device in order to work towards carrying out a screwing or unscrewing operation comprising carrying out a series of successive impact cycles during each of which the hammers collide with the anvils.
The angle sensor of the motor allows the controller to know the position of the rotor in real time and to calculate the speed thereof.
When the operator actuates the trigger of the impact wrench to trigger a screwing or unscrewing operation, the means for controlling transmit an instruction to the motor to bring it to a predetermined rotation frequency Vi. The device is in an ordinary state such as, for example, that shown in
The drive shaft moves inside the groove of the flywheel until it comes to bear against the stop 73 (passage from
When the rotor reaches the rotation frequency Vi, the means for controlling control the motor so that they remain at the rotation frequency Vi until satisfaction of a condition checking that the impact mechanism is in a suitable position prior to impact. It can be clearly seen from
In order to achieve this and according to a first alternative, an angular position sensor can be placed on the output shaft to which the anvils are rigidly connected.
At the end of each impact, this sensor measures the angular position of the output shaft and thus that of the anvils, which remains unchanging until the subsequent impact. During the subsequent impact cycle, the position of the anvils is thus known (it corresponds to that measured at the end of the previous impact cycle), whereas that of the hammers is deduced from that of the rotor measured by the angle sensor of the motor. The relative position of the hammers to the anvils can thus be known, and the deceleration of the motor can be controlled so as to place the hammers in the engaged position thereof only when the angular position thereof relative to the anvils allows them to pass from the non-engaged position to the engaged position thereof without interfering with the anvils.
According to a second alternative, the angular position of the anvils can be determined without implementing an angle sensor on the output shaft. In such a case, the angular position of the anvils is determined using the angle sensor of the motor upon each impact. More specifically, when a sharp drop in the rotation frequency of the motor is detected, following the occurrence of an impact in the impact mechanism, the means for controlling record the position of the rotor which corresponds to that of the anvils. At the subsequent impact cycle, the relative position of the anvils, which position is that recorded during the previous cycle, and of the hammers, which corresponds to that measured in real time by the angle sensor of the motor, can thus be known. The relative position of the hammers to the anvils can thus be known, and the deceleration of the motor can be controlled so as to place the hammers in the engaged position thereof only when the angular position thereof relative to the anvils allows them to pass from the non-engaged position to the engaged position thereof without being hindered by the potential positioning of the hammers facing the anvils.
According to this alternative, at least one impact must take place before being able to deduce the initial position of the anvils. The screwing cycle will thus begin with a first impact at a low speed, for which the motor braking instruction will begin as soon as the desired speed is reached, without any other condition.
Once the relative position of the hammers to the anvils is such that it allows the hammers to move from the non-engaged position to the engaged position thereof, the motor can be controlled so as to place the hammers in the engaged position thereof.
For the hammers to be in the engaged position thereof, the angular offset between the drive shaft and the flywheel must be equal to a predetermined value α.
Once the relative position of the hammers to the anvils is suitable, the motor is thus decelerated by the means for controlling so that the angular offset between the flywheel and the drive shaft reaches the predetermined value α in which the hammers are in the engaged position thereof.
Just before the engine is decelerated, the drive shaft and the flywheel rotate at the speed Vi. When the engine is decelerated, the flywheel continues to rotate at the speed Vi due to its inertia. The angular position thereof can thus be known from its speed and the position it occupied just before the motor was braked, this position being that of the rotor measured by the angle sensor of the motor at the time when the motor was decelerated. Alternatively, the angular position of the flywheel can be known by using an angle sensor placed on the flywheel. The position of the drive shaft, which corresponds to that of the rotor, can also be known in real time. By taking these data into consideration, the time at which the offset between the flywheel and the drive shaft reaches the predetermined value α in which the hammers are in the engaged position thereof (see
When this time is detected, the means for controlling re-accelerate the motor to the speed Vi such that the angular offset between the drive shaft and the flywheel is maintained at the predetermined value a in which the hammers are in the engaged position thereof.
The speed Vi is maintained until the means for controlling detect a rapid drop in the speed of the motor following the time at which the hammers collide with the anvils to rotate the output shaft and thus the element to be screwed.
The position of the output shaft is measured at the end of the impact and then a new impact cycle is carried out. The impact cycles are repeated in series until the desired tightening torque is reached.
A screwing operation typically comprises two successive phases:
The approach phase is carried out by producing a multitude of small impacts.
A second embodiment of an impact wrench according to the invention is shown with reference to
Only the differences between the first embodiment and the second embodiment are described hereinbelow.
In this second embodiment, the device comprises at least one driven gear 8 which is fixed to each of the hammers 61 for rotation therewith.
The actuating element in this case comprises a drive gear 9 fixed to the drive shaft 3 for rotation therewith and engaged with the driven gear of each hammer 61.
A relative motion of the drive shaft 3 to the flywheel 7 allows the at least one hammer to be moved between the engaged and non-engaged positions thereof.
The means for controlling and the way of controlling the motor are the same as for the first embodiment.
A third embodiment of an impact wrench according to the invention is shown with reference to
In this third embodiment, said at least one hammer is capable of translating, between the engaged and non-engaged positions thereof, along an axis parallel to the axis of rotation of said drive shaft.
In this embodiment, the device comprises a secondary drive shaft 9 which is fixed to the drive shaft 3 of the rotor 21 for rotation therewith but free to translate.
The secondary drive shaft 9 is mounted such that it can translate and rotate relative to the flywheel 7 along the axis of rotation of the drive shaft 3.
The secondary drive shaft 9 comprises at least one cam 90 against which at least one guide pin 91 extending perpendicular to the axis of rotation of the flywheel, and rigidly connected to the flywheel 7, is capable of moving.
The cam 9 is bounded by two stops 73 bounding an angular range in which the flywheel is free to rotate relative to the secondary drive shaft between two end positions.
The at least one cam 90 has a profile that is shaped to allow the secondary drive shaft 9 to move rotationally relative to the flywheel over said angular range between the end positions and a predetermined position in the angular range, and to allow for a translational motion of the secondary drive shaft relative to the flywheel during the movement thereof from either one of the end positions and the predetermined position.
The hammers 61 are shafts that are mounted such that they can translate inside guide ramps 700 of the flywheel along axes parallel to the axis of rotation thereof. Each hammer has a groove 650 inside which an edge of a washer 100 fastened to the end of the secondary drive shaft 9 is housed so as to translationally link the hammers with the secondary drive shaft so as to move them between the engaged and non-engaged positions thereof.
Resilient return means, such as compression springs 11, act on the hammers to bias them to return to the non-engaged position thereof.
The means for controlling and the way of controlling the motor are the same as for the first embodiment.
A fourth embodiment is shown with reference to
In this embodiment, the motor comprises an internal stator 20 provided with coils 200, the rotor 21 being external.
The external rotor forms a flywheel.
The hammers are fixed to the rotor for rotation therewith, and are mounted such that they can rotate relative to the rotor along axes parallel to the axis of rotation thereof between the engaged and non-engaged positions thereof.
In the engaged position thereof, the striking surfaces 610 of the hammers 61 protrude from the periphery of the rotor to collide with the anvils.
In the non-engaged position thereof, the striking surfaces 610 of the hammers 61 do not protrude from the periphery of the rotor so as not to collide with the anvils.
In this embodiment, the magnetic fields created by the coils act on the hammers:
The means for controlling are thus able to transmit to the motor:
Resilient return means, such as compression springs, and/or centrifugal force, allow the hammers to be moved into the engaged position thereof when the power to the coils is cut off.
In
One or more exemplary embodiments of the invention aim to provide an effective solution to at least some of the various problems of the prior art.
In particular, an exemplary embodiment provides an electric impact wrench that allows a high tightening torque to be quickly reached.
An exemplary embodiment provides such an impact wrench with a simple design.
An exemplary embodiment provides such an impact wrench that is both reliable and robust.
An exemplary embodiment provides such an impact wrench that is cost-effective.
Although the present disclosure has been described with reference to one or more examples, workers skilled in the art will recognize that changes may be made in form and detail without departing from the scope of the disclosure and/or the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014124 | Dec 2020 | FR | national |
This application is a Section 371 National Stage Application of International Application No. PCT/EP2021/087549, filed Dec. 23, 2021, which is incorporated by reference in its entirety and published as WO 2022/136662 A1 on Jun. 30, 2022, not in English.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/087549 | 12/23/2021 | WO |
