Machine element or mechanism – Mechanical movements – Reciprocating or oscillating to or from alternating rotary
Patent
1997-06-17
1999-07-06
Herrmann, Allan D.
Machine element or mechanism
Mechanical movements
Reciprocating or oscillating to or from alternating rotary
29456, 29516, 744248R, 74459, 403281, 403359, 411361, F16H 2524
Patent
active
059185058
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a linear actuator comprising a driven spindle having a nut which is connected to the expelling rod of the actuator. An actuator of this type is for instance known from EP-B1-0 531 247 and EP-A1-0 577 541. The invention also relates to a method of manufacturing the actuator.
2. The Prior Art
Linear actuators that, e.g., are used for raising and lowering movements on hospital beds can be relatively heavily loaded. For instance, an actuator can be loaded with up to 15000 N axially and torques to the size of 25 Nm.
The spindle, the expelling rod as well as the nut of the actuator are made of metal, and the nut is secured to the hollow expelling rod by threaded insertion into the inner thread of the rod and prevented against turning, e.g., by welding.
It is of upmost importance that the nut and the expelling rod are rigidly connected to each other, as the aforementioned axial and torque forces must be transferred from the nut to the expelling rod.
It is not enough that the forces must be transferred in a sufficiently secure manner; there are also in certain cases demands for low friction, life time lubrication, low noise level, low production and service costs. Linear actuators are attractive because they easily can be incorporated in an electrically control and also are relatively inexpensive.
SUMMARY OF THE INVENTION
By the present invention it is realized that the nut, that is to cooperate with the metal spindle, can be made of an elastomeric material for obtaining a lubrication free connection with a minimal friction as the nut and the expelling rod are joined to each other by intermeshing embossings for the transfer of axial forces as well as torques.
In an embodiment the actuator is provided with a safety nut of metal connected to the main nut by breakable entrainment means so that the safety nut follows the main nut as a slave nut, whereby the safety nut takes over the function of absorbing the load.
By a method according to the invention a safe fastening of the nut in the tube is achieved by providing a nut that in one end has a thread and in the other end is provided with axially orientated grooves and where the tube in that part that is intended for receiving said aforementioned grooves is extended in a funnel shape which allows the nut to be screwed into an internal thread in the tube and where the funnel internally is provided with axially orientated grooves intended for engagement with the aforementioned grooves in the nut, and where the funnel section of the tube after the insertion of the nut is clamped together until the grooves in the tube and the grooves in the nut are brought in close engagement with each other.
Hereby is an assembly obtained that can resist both axial and rotational forces and the axially orientated grooves prevent rotation of the nut.
The invention is described in detail in the following with reference to the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a longitudinal sectional view of an actuator according to the invention,
FIG. 2 is a perspective view of the nut and the expelling rod of the actuator according to the invention, and
FIG. 3 is a perspective view of the nut and the expelling rod of the actuator in an embodiment with a safety nut.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
As mentioned in FIG. 1 of the drawings, a longitudinal sectional cutaway view is shown through an actuator that comprises a spindle 10 with a nut 12 of plastic. To the nut is fastened a tubular expelling rod 14. The spindle is driven by an electric motor 16 via a gearing 18. FIG. 2 shows the end of the expelling rod 14 and the nut 12 in an enlarged scale. As it appears, the nut has an inner thread 18 for the spindle 10 and an outer thread 20. The nut 12 comprises also in the shown embodiment a collar 22 and between the collar 22 and the thread 20 a number of axially oriented grooves 24.
A metal tube 14 comprises an inner thread 26 and is at the extreme end extended to a cone sha
REFERENCES:
patent: 3464472 (1969-09-01), Reynolds
patent: 4644811 (1987-02-01), Tervo
patent: 4872903 (1989-10-01), Periou
patent: 4934203 (1990-06-01), Bailey et al.
patent: 4939945 (1990-07-01), Ryder et al.
patent: 4983084 (1991-01-01), Gray
patent: 4983085 (1991-01-01), Gray
patent: 5366331 (1994-11-01), Erbes
Herrmann Allan D.
Linak A/S
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