초록 ▼

A linear portable actuator including a direct current electric motor (2) rotationally driving a screw with the aid of a reduction element, wherein the motor (2) is controlled by an electronic module (5) comprising means (12) for the acquisition of instantaneous intensity of a supply current for the

A linear portable actuator including a direct current electric motor (2) rotationally driving a screw with the aid of a reduction element, wherein the motor (2) is controlled by an electronic module (5) comprising means (12) for the acquisition of instantaneous intensity of a supply current for the motor. Further, the electronic module (5) also comprises means (13) for calculating the differential coefficient in relation to supply-current intensity time, which are connected to means (14) for comparing the differential coefficient to a first predetermined value, and a comparing means controlling means (15) for switching off the supply current it the differential coefficient is greater than the first predetermined value.

대표청구항 ▼

The invention claimed is: 1. A portable linear actuator comprising: a DC electric motor delivering rotary drive to a screw via a stepdown gearbox; an electronics module for controlling said DC electric motor, said electronics module including current acquisition means, derivative calculation means

The invention claimed is: 1. A portable linear actuator comprising: a DC electric motor delivering rotary drive to a screw via a stepdown gearbox; an electronics module for controlling said DC electric motor, said electronics module including current acquisition means, derivative calculation means and comparator means; and interrupter means, wherein said current acquisition means acquires an instantaneous current value of a power supply current supplied to said DC electric motor, wherein said derivative calculation means calculates a time derivative of values of the power supply current, said derivative calculation means being connected to said comparator means, wherein said comparator means compares the calculated time derivative with a first predetermined value, and wherein said comparator means controls said interrupter means to interrupt the power supply current when the calculated time derivative is greater than the first predetermined value. 2. A portable linear actuator according to claim 1, wherein said current acquisition means includes sampling means for sampling the instantaneous current value at regular intervals, said current acquisition means being connected to storing means for storing the samples of the instantaneous current value over a moving time window of a predetermined duration, and wherein said derivative calculation means includes difference calculating means for calculating a difference between a value of a most recent sample sampled by said sampling means and a value of an oldest sample sampled by said sampling means in the time window, and includes comparator means for comparing the difference calculated by said difference calculating means with the first predetermined value. 3. A portable linear actuator according to claim 1, wherein said electronics module further comprises second comparator means for comparing a value of the power supply current with a second predetermined value, and for controlling said interrupter means when the value of the power supply current is greater than the second predetermined value. 4. A portable linear actuator according to claim 1, wherein said electronics module further comprises timer means that activates said interrupter means only after a predetermined time has elapsed after the portable linear actuator has been started. 5. A portable linear actuator according to claim 1, further comprising end-of-stroke sensors for sensing a stroke of the screw and being connected to said electronics module, such that said interrupter means is activated when said end-of-stroke sensors sense that the screw is at an end of a stroke. 6. A portable linear actuator according to claim 1, wherein the screw includes an anti-rotation pin at one end thereof, and one end of the anti-rotation pin carrying a magnet, and wherein the portable linear actuator includes Hall effect sensors detecting a passage of the magnet and being positioned such that the passage of the magnet indicates that the screw is at an end of a stroke. 7. A portable linear actuator according to claim 6, wherein said Hall effect sensors are positioned on an electronics card having a plurality of locations for positioning sensors that are adapted, to different displacement strokes of the screw. 8. A portable linear actuator according to claim 1, wherein the screw is a recirculating ball screw and said DC electric motor is powered by a battery. 9. A portable linear actuator according to claim 1 being used in a machine-part puller for bearings, or used in a tool for working on tubes by expanding the tubes. 10. A method of controlling an electric motor of a portable linear actuator in order to limit a maximum force generated from the electric motor, the method comprising: acquiring a value of a power supply current supplied to the electric motor at regular intervals; calculating a derivative of the value of the power supply current as a function relative to time; and comparing the calculated derivative to a first predetermined value and, when the calculated derivative is greater than the first predetermined value, interrupting the power supply current supplied to the electric motor. 11. A method according to claim 10, wherein the value of the power supply current is acquired at regular intervals, and wherein the calculating of the derivative is approximated by calculating a difference between the value of the power supply current from a most recent acquisition by the acquiring of the value and the value of the power supply current from an oldest acquisition by the acquiring of a value in a moving time window. 12. A method according to claim 10, farther comprising: comparing the acquired value of the power supply current with a second predetermined value; and subsequently interrupting the power supply current when the value of the power supply current is greater than the second predetermined value. 13. A method according to claim 10, wherein the calculating of the derivative and the comparing are activated only after a predetermined time has elapsed after the electric motor has staffed. 14. A portable electromechanical tool for working on tubes, said portable electromechanical tool comprising: a portable linear actuator according to claim 1; first fastener means; a first working head adapted to perform a first task on a tube; and a second working head adapted to perform a second task on a tube, the second task being different from the first task, wherein the first working head and the second working head include second fastener means, wherein the first fastener means and the second fastener means of the first working head and the second working head are adapted to co-operate to fasten the first working head and the second working head to the portable linear actuator such that the portable linear actuator generates movement in translation of a predetermined portion of the first working head and the second working head fastened to the portable linear actuator. 15. A portable electromechanical tool according to claim 14, wherein the first working head and the second working head are adapted to perform at least one of the following tasks: radial expansion of a tube; axial expansion of a tube; cutting a tube; in-line axial press fitting; orthogonal axial press fitting; and radial press fitting of a tube. 16. A portable electromechanical tool according to claim 15, wherein the first working head and the second working head are each adapted to perform only one task of the first task and the second task. 17. A portable electromechanical tool according to claim 15, wherein one of the first working head and the second working head is adapted to perform axial press fitting of a tube in a movement that is orthogonal to the movement in translation generated by the portable linear actuator. 18. A portable electromechanical tool according to claim 17, wherein the one working head adapted to perform the axial press fitting includes a T-shaped stationary support having as a foot the second fastener means and having in a body thereof a bore suitable for allowing the screw to slide therein and defining a displacement plane for movable means suitable for transforming movement in translation generated by the screw along the body of the stationary support into movements in rotation of two jaw-carrier arms about two pins perpendicular to the displacement plane and positioned at ends of the one working head, and includes means for holding two jaws in parallel during the movements of the two jaw-carrier arms. 19. A portable electromechanical tool according to claim 18, wherein the movable means are symmetrical about the displacement axis of the screw and comprise first elements moving in translation along the body of the stationary support and secured to the screw, the movable means being connected via first rotary pins to second elements, the second elements being connected by second rotary pins to third elements mounted to pivot about rotary pins of the one working head, and wherein the two jaw-carrier arms are hinged about third rotary pins of the third elements, the two jaw-carrier arms including camming ramps that co-operate with cam followers carried by said second elements in order to maintain the jaws in parallel during the movements of the two jaw-carrier arms. 20. A portable electromechanical tool according to claim 14, wherein the first fastener means include a sliding catch for sliding along an axis perpendicular to the movement in translation of the screw, the catch being adapted to be inserted in an annular groove of the second fastener means so as to fasten the first working head and the second working head to the portable linear actuator while enabling the first working head and the second working head to rotate freely about the screw. 21. A portable electromechanical tool according to claim 20, wherein the sliding catch comprises an annulus urged towards an eccentric position so as to be inserted in the annular groove.