Implements or apparatus for applying pushing or pulling force – Rack and pinion
Reexamination Certificate
1999-11-29
2001-05-01
Watson, Robert C. (Department: 3723)
Implements or apparatus for applying pushing or pulling force
Rack and pinion
Reexamination Certificate
active
06224037
ABSTRACT:
The present invention relates to a column for lifting loads designed to transmit vertical thrust forces and enabling loads to be lifted over large distances.
A column of this type is particularly well suited to erecting platforms although this application is not restrictive.
More specifically, the present invention relates to a device enabling loads to be lifted over large distances, which is simple to manufacture and implement and which furthermore consists of only a limited number of components.
To this end, the present invention relates to a lifting device designed to transmit vertical thrust forces, characterised in that it comprises a housing fitted with two rotary pinions driving an articulated lifting column having a horizontal arm and a vertical arm separated by an elbow part, the lifting column comprising two parallel articulated sides joined by means of transversely oriented connecting shafts co-operating with the driving pinions.
For the purposes of the invention, each side comprises two contiguous rows of essentially rectangular plates placed end to end in a same row and longitudinally offset one row from another.
Each plate has, on the one hand, two main faces provided with holes for receiving the connecting shafts, by means of one of which the plates of one row are applied against the plates of the contiguous row, and on the other hand, four edge faces, namely two longitudinal edge faces, one internal and the other external relative to the elbow part of the lifting column, and two side edge faces defining a front active face and a rear active face which bear respectively against the rear and front active faces of the adjacent plates of a same row when the section of the lifting column comprising these plates is vertically extended.
The function of the lifting column based on this design is to transmit vertical thrust forces whilst the housing transmits the power and retains the plates, subjected to vertical compression forces.
The operating principle of the device proposed by the invention is therefore based on converting a rotary movement into a movement in translation; this device can therefore be likened to an articulated bar.
A system based on this principle takes up less space for a longer distance of travel than jack-operated lifting systems known from the prior at.
The device proposed by the invention is also distinctive because of its reliability and safety in the event of incidents.
By preference, the plates proposed by the invention are all identical and are offset at a pitch equal to half their length from one row to the contiguous row.
This is a particularly advantageous feature of the invention since it means that only one cutting tool is needed for all the plates, regardless of their position on the lifting column; this simplification represents a significant reduction in the cost price of the lifting column.
Clearly, the dimensions of the plates and the pitch of the lifting column must be optimised for each situation and for a given length in order to reduce the cost price for a given length; in practice, the greater the pitch, the fewer the number of parts needed but the greater the space requirement of the housing.
It should be pointed out that as a general rule, this pitch is in the order of 100 mm.
Another advantage of the device proposed by the invention resides in the fact that the lifting column has a “closed” section, defined on the one hand by its two articulated sides (due to the presence of the two contiguous rows of plates) and on the other by the connecting shafts which are “trapped” between the two articulated sides of the lifting column; this guarantees better stability of the unit.
By virtue of one preferred feature of the invention, each plate has three holes for receiving three connecting shafts arranged respectively in the layout of an isosceles triangle.
These holes are subdivided into a driving hole contiguous with the external longitudinal edge face centred on the transverse axis of the plate and two articulation holes arranged symmetrically on either side of this axis and contiguous with the internal longitudinal edge face.
The articulation holes of the plates of the two contiguous rows of a same side of the lifting column are arranged in pairs one above the other.
The connecting shafts of the two sides of the lifting column are in turn subdivided on the one hand into articulation shafts which are inserted through the articulation holes arranged in pairs one above the other in the plates of the two respective contiguous rows and, on the other hand, driving shafts which are inserted alternately through the driving holes of the plates of one or other of the two contiguous rows.
The number of connecting shafts and their triangular layout improves distribution of the thrust force.
As a result of another feature of the invention, the side edge faces of the plates are provided with essentially semi-circular notches which form a releasable enclosure enabling the driving shafts to be inserted therein when these faces move to bear one against the other.
The presence of these notches is indispensable in enabling the active faces of the plates to be applied one against the other in line with the driving shafts.
By virtue of another feature of the invention, the internal longitudinal edge faces of the plates are bevelled at their ends.
This configuration permits articulation of the lifting column on a level with its elbow part.
As a result of another feature proposed by the invention, the driving pinions are fixed to the bottom part of the vertical arm of the lifting column, on the external face thereof, and co-operate with the driving shafts of the plates.
This particular positioning of the driving pinions is another essential feature of the device proposed by the invention since it produces a better “locking” effect, thereby enhancing the stability of the lifting column.
It should be pointed out that the rollers mounted on the external face of the column (pinion side) act as a drive for the latter whilst the rollers mounted on the internal face act as a guide thereof.
REFERENCES:
patent: 2574657 (1951-11-01), Pierce
patent: 3719291 (1973-03-01), Redan
patent: 3831455 (1974-08-01), Patrignani
patent: 4406096 (1983-09-01), Matsutani
patent: 4830337 (1989-05-01), Ichiro et al.
patent: 5156574 (1992-10-01), Gai
patent: 2 659 714 (1991-03-01), None
Knuth Randall J.
Serapid France
Watson Robert C.
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