Elevator – industrial lift truck – or stationary lift for vehicle – Having specific load support drive-means or its control – Includes gear on support mating with stationary rack or chain
Reexamination Certificate
2001-01-17
2003-07-29
Ellis, Christopher P. (Department: 3652)
Elevator, industrial lift truck, or stationary lift for vehicle
Having specific load support drive-means or its control
Includes gear on support mating with stationary rack or chain
C187S250000, C187S268000, C074S424600, C182S142000
Reexamination Certificate
active
06598708
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to driving apparatus, and more particularly to the driving apparatus using an endless screw having tapered rollers spacedly arranged along a helical line and rotatably engaging related projection surfaces mounted on the driven device.
BACKGROUND OF THE INVENTION
In driving mechanisms, it is well known to use a gear and rack type of assembly, especially when the driven part of the assembly is substantially heavy such as a work platform of scaffolding or an elevator cage. In some situations the load is so high, 1000 pounds and more, that a lot of drag torque will be caused by the friction between the gear and the different teeth of the rack. This drag torque might even be increased by dust depositions on the rack teeth.
To enhance the efficiency of the driving mechanism by smoothing the interface between the gear and the rack teeth is already known as shown in U.S. Pat. No. 4,541,297 granted on Sep. 17, 1985 to Fujita and U.S. Pat. No. 5,636,705 granted on Jun. 10, 1997 to St-Germain.
St-Germain shows a driving mechanism where the endless screw
80
engages with a plurality of equally spaced studs
50
forming the rack portion of the assembly, each stud
50
having a roller bearing mounted at its extremity.
Fujita shows an opposite driving mechanism where the endless screw is made with a cylindrical shaft proper
1
having a plurality of rollers
7
spaced along a helical line H mounted thereon. The rollers
7
engaging spaced projection
12
surfaces
13
representing the rack portion of the assembly.
Both of these mechanisms have a similar problem. Since the rollers have a certain thickness, they obviously have a large portion of their thickness that slides onto their respective engaging surface during the movement because of the varying radius from the axis of the endless gear, or shaft proper, of each engaging region between the roller and its engaging surface (or line). The sliding tends to deteriorate the surface of the weaker engaging material, thus considerably limiting the life of the driving mechanism. Also, the bearings being generally expensive, one would like to limit the replacement frequency of these, if they have the weaker engaging material. On the other hand, the replacement of either the endless screw or the rail projections of the driven structure is also an expensive situation.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide a driving apparatus for linearly moving a structure that will obviate the above-noted disadvantages.
It is another object of this invention to provide a driving apparatus having at least two rollers simultaneously engaging projection surfaces.
It is also another object of this invention to provide a driving apparatus having the capability to drive its driven device into both directions of a linear movement.
It is a further object of this invention to provide a driving apparatus being driven by a hydraulic system that includes two hydraulic motors for increased load capabilities.
It is yet an object of this invention to provide a lifting driving apparatus being driven by a hydraulic system which includes a manual backup valve allowing for a safe and smooth descending movement upon failure of the hydraulic system.
It is yet another object of this invention to provide a structure including at least two lifting driving apparatus each being driven by an independent hydraulic system.
Other objects of the present invention will become apparent from a careful reading of the detailed description provided herein, with appropriate reference to the accompanying drawings.
SUMMARY OF THE INVENTION
According to an aspect of the present invention, there is provided a driving apparatus that comprises:
a roller screw member including a main shaft, a plurality of roller shafts projecting radially outwardly from the main shaft and arranged at equally spaced intervals along a helical line around the main shaft and, a plurality of rollers rotatably mounted on the roller shafts, the rollers including a bearing means for mounting the rollers on the roller shafts, the rollers being tapered to an angle, the rollers being oriented onto the roller shafts with the tapering inwardly to the main shaft; and
a rail member adjacent and axially oriented with the main shaft of the roller screw member, the rail member including a plurality of equally spaced projections having inclined upper surfaces adapted for radial engagement with a bottom region of the tapered surfaces of the rollers, the inclination of the projection upper surfaces being equal to that of the helical line of the roller shafts of the roller screw member;
one of the roller screw and rail members being adapted for axial movement and the other of the roller screw and rail members being fixed against axial movement, the rotation of the main shaft providing the movable member to move in the axial direction of the main shaft with the bottom regions of the tapered surfaces of the rollers rotatably engaging the projection upper surfaces, the angle of the tapering being determined to have a projected extension of the tapered roller bottom regions intersecting an axis of their respective roller shaft on the axis of the main shaft, thereby providing a sliding free engagement between the roller surfaces and the projection upper surfaces during.
Preferably, the roller shafts projecting radially outwardly and upwardly at the angle from the radial direction from the main shaft thereby providing each roller with the bottom region of its tapered surface being generally perpendicularly oriented with the axis of the main shaft.
Alternatively, the projections of the rail member further having inclined lower surfaces adapted for radial engagement with a top region of the tapered surfaces of the respective rollers, the inclination of the projection lower surfaces being equal to that of the helical line of the roller shafts of the roller screw member, the opposite rotation of the main shaft providing the movable member to move in the opposite axial direction of the main shaft with the top regions of the tapered surfaces of the rollers rotatably engaging the projection lower surfaces, the angle of the tapering being determined to have a projected extension of the tapered roller top regions intersecting the axis of their respective roller shaft on the axis of the main shaft, thereby providing a sliding free engagement between the roller surfaces and the projection lower surfaces during opposite movement, the spacing between a projection upper surface and the facing lower surface of the adjacent projection being adapted to essentially freely receive the rollers thereby providing a smooth transition between the movements of the movable member along the axial direction and the opposite axial direction of the main shaft.
Preferably, the bearing means comprises roller bearings.
Preferably, the roller tapered surfaces are made of a material selected from the group consisting of metal, rubber and thermoplastics.
Preferably, the roller screw member is adapted for axial movement and the rail member is fixed against axial movement.
Alternatively, a second rail member adjacent the opposite side and axially oriented with the main shaft of the roller screw member.
Preferably, at least two rollers are being simultaneously rotatably engaging the projection upper surfaces at all time.
Preferably, the driving apparatus further comprises a structure member fixedly attached to the roller screw member, the structure member including a means for rotating the main shaft around its axis.
Alternatively, the means for rotating the main shaft being an electrical motor, the structure member further including a power source means connected to and a means for controlling the electrical motor whereby a user controllably operates the movement of the driving apparatus.
Preferably, the means for rotating the main shaft being a hydraulic motor located at one end of the main shaft, the structure member further including a hydraulic system linked to and a means for controlling the h
St-Germain Andre
Tessier Luc
Les Produits Fraco Ltee
Tran Thuy V.
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