192 clutches and power-stop control – Vortex-flow drive and clutch – With brake
Patent
1996-04-10
1998-06-16
Bonck, Rodey H.
192 clutches and power-stop control
Vortex-flow drive and clutch
With brake
188134, 192144, B66F 308, F16H 2520
Patent
active
057656681
DESCRIPTION:
BRIEF SUMMARY
The present invention refers to a drop protection device at actuator devices, of the type intended to displace a load linearly. Actuator devices since long time constitute a well tested mechanical component, which is used to convert rotational motion into linear motion. Its main parts is a drive motor, the power of which via a gear is transferred to a spindle or a screw provided with a screw thread, which cooperates with a ball nut or a slide nut with a low degree of self-braking, which nut at rotation of the screw will be displaced axially along this.
Actuator devices of this type are used in a great number of applications such as for raising and lowering a load resting thereon or suspended therefrom. In many such cases it is important that the load is not allowed to drop uncontrolled, if, for example a breakdown in the gear would occur, whereby the spindle might rotate freely. Even if this is rare, very serious consequences would be the result if the falling load is constituted by goods which at a drop might be damaged or itself could cause damage to peripheral equipment and staff. For example a field of application where the damage risk is obvious at rapid, uncontrolled drop of the load, is in the field of nursing, where such vertically or almost vertically mounted actuator devices frequently are used in patient lifts of different types.
The purpose of the invention is to provide a drop protection device, by means of which the risk that such free drops might happen is eliminated,
In the following the invention will be further described with reference to two embodiments shown in the accompanying drawings.
FIG. 1 shows in section an actuator device with a drop protection device according to the invention.
FIG. 2 shows in larger scale a portion of the actuator device with a drop protection device according to FIG. 1, and
FIG. 3 is a view corresponding to FIG. 2 of a modified embodiment of the invention.
The actuator device 10 shown in FIGS. 1 and 2 incorporates an electric motor 11 connected to a gear housing 12, containing a worm-gear, which via a worm-screw 14, provided on the motor shaft, transfers rotation to a spindle 16 provided with threads along a major part of its length and journalled in the housing 12, via a worm-wheel 18 fitted on the spindle. The threaded part of the spindle or the screw 16 is provided with a first nut 20 arranged thereon, in the embodiment shown, a ball nut 20, which has very low friction and which at rotation of the screw is displaced axially along this. Fitted to the nut 20 is an actuator tube 22, which surrounds and encases the screw 16, and which by displacement of the ball nut along the screw is brought to project different distances beyond the screw end. The actuator tube 22 at its free end 24 is intended to be interconnected with a not shown forward or upper attachment, intended to carry the load or a support, which supports this load. The screw 16, the ball nut 20 and at least a part of the actuator tube 22 is enclosed in a protecting tube 26 attached to the housing 12, which protects the screw and by means of seals 28 prevents contaminations from reaching the surface of the screw. The gear housing 12 has a rear or lower attachment 30.
If for example, such an actuator device which is mounted vertically or almost vertically and supports a. load, should be exposed to a breakdown in the worm-gear, the screw 16, under actuation of the load, would be brought into a very rapid rotation, and fragile goods, patients and others handled by the actuator device, will be injured or damaged by the motion resulting from this, which can be regarded as equal to free fall.
For preventing this the screw 16, in accordance with the invention, at the proximity of its end facing the gear housing 12 is provided with a sleeve shaped member, in the embodiment shown in the shape of a second nut 32 provided with an annular contact surface 34 facing the gear housing. This second nut 32 is arranged to follow the normal rotation of the screw. At the rapid acceleration, to which the screw is subject
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Hasselberg Par-Olof
Olofsson Dag Arne
Bonck Rodey H.
SKF Specialty Products AB
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