Electrical generator or motor structure – Dynamoelectric – Linear
Patent
1998-10-19
2000-08-08
Ramirez, Nestor
Electrical generator or motor structure
Dynamoelectric
Linear
310 20, 310 80, H02K 706
Patent
active
061006092
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention concerns an electric linear actuator of the type comprising an electric motor, a tubular body comprising a piston and connecting means between the motor and the piston (commonly known as a jack).
Electric linear actuators used until now have been driven by an electric motor disposed outside the body of the linear actuator rotating a screwthreaded rod through a gear, the rod driving the piston of the linear actuator.
Linear actuators of the above kind are bulky, permeable because they are not sealed and fragile because the force is transmitted to the piston by a screwthreaded rod. There is a risk of the rod buckling when the linear actuator is operating in compression with a long travel.
Sealing against dust, inclement weather and moisture is difficult because the linear actuator is in two parts.
SUMMARY OF THE INVENTION
An aim of the invention is therefore to propose an electric linear actuator in which the above drawbacks are eliminated.
In accordance with the invention, the piston of the linear actuator is a tube mounted to slide in the body, the motor is housed inside the piston and the aforementioned connecting means cooperate with the inside wall of the body to move the piston in thrust or in traction.
Placing the motor inside a tubular piston of the linear actuator means that the linear actuator can be made in one compact unit of considerably reduced overall size.
In a preferred embodiment of the invention, the body and the piston being cylindrical, the motor is a gear motor one end of which is attached to the piston and an output shaft of which is adapted to rotate a nut provided with an external screwthread meshing with a complementary internal screwthread on the inside wall of the body.
In this way the electric gear motor transmits its rotation to the nut at the end of the gearbox and bearing directly on the screwthread in the linear actuator body.
A structure of the above kind therefore eliminates the screwthreaded rod for transmitting the force of the linear actuator and the associated risk of the rod buckling, because it is the tubular body of the linear actuator that receives the reaction forces.
BRIEF DESCRIPTION OF THE DRAWINGS
Other features and advantages of the invention will become apparent during the following description given with reference to the accompanying drawings which show two embodiments by way of non-limiting example.
FIG. 1 is a perspective view of a first embodiment of the electric linear actuator of the invention, shown with the piston deployed.
FIG. 2 is a view of the linear actuator from FIG. 1 in axial longitudinal section with the piston retracted inside the body.
FIG. 3 is a view in cross-section taken along the line 3--3 in FIG. 2, the gear motor having been removed.
FIG. 4 is a partial view in elevation to a larger scale on the line 4--4 in FIG. 3.
FIG. 5 is a part-sectional view to a larger scale of a detail from FIG. 2.
FIG. 6 is a view similar to FIG. 2 of a second embodiment of the electric linear actuator of the invention.
FIG. 7 is a half-sectional view taken along the line 7 in FIG. 6.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The electric linear actuator shown in the drawings comprises an electric gear motor 1 disposed inside a tubular piston 2 coaxial with the longitudinal axis XX of the piston. The cylindrical piston 2 slides along the axis XX inside a tubular body 3.
The piston 2 is closed at one end by a transverse flange 4 to which an end face of the gear motor 1 is fixed. Its opposite end is closed by a stopper 5 through which passes a bore 6 to receive an attachment (not shown).
One end 8 of the output shaft of the gear motor 1 passes axially through the flange 4 and is attached by a key 8a to a nut 9 which can therefore be rotated by the shaft end 8. The nut 9 includes a central sleeve 9a surrounding the shaft 8 and has an external screwthread 11 meshing with a complementary internal screwthread 12 on the inside wall of the cylindrical body 3 over a distance corresponding to the intended trav
REFERENCES:
patent: 3751998 (1973-08-01), Vasilatos
patent: 3788261 (1974-01-01), Colin
patent: 4428423 (1984-01-01), Koehler et al.
patent: 4496921 (1985-01-01), Carrera
patent: 5117700 (1992-06-01), Trechsel
patent: 5619082 (1997-04-01), Chei
Jones Judson H.
Ramirez Nestor
Wernest
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