EP2147891A1

EP2147891A1 - Platform with scissor lift

Info

Publication number: EP2147891A1
Application number: EP09009426A
Authority: EP
Inventors: Livio Romano; Maurizio Benedetti; Marco Piu
Original assignee: Acr Di Romano Livio & C SNC
Current assignee: Acr Di Romano Livio & C SNC
Priority date: 2008-07-23
Filing date: 2009-07-21
Publication date: 2010-01-27
Also published as: ITUD20080173A1; IT1391626B1

Abstract

Scissor-type lifter comprising a base (2), a platform (3) movable with respect to said base and a plurality of pairs of scissor-like arms (7,8,10,11), each arm of each couple being hinged at the intermediate position with respect to its longitudinal development to the other arm forming said couple, said plurality of arms including at least one couple of upper arms (10,11) and one couple of lower arms (7,8), one couple of which being hinged on one side in a not-sliding way to said base and on the other side in a sliding way to said base and the other couple being hinged on one side in a not-sliding way to said platform and on the other side in a sliding way to said platform and comprising at least one intermediate frame (5) with respect to said base (2) and to said platform (3), said intermediate frame (5) including hinging means (20) not sliding with respect to the frame itself for said couple of lower arms (6) with respect to said intermediate frame (5), hinging means (21) not sliding with respect to the frame itself for said couple of upper arms (9) with respect to said intermediate frame (5), slideable means (17) with respect to the frame itself, said slideable means (17) comprising hinging means (19) for said couple of upper arms (9) with respect to said intermediate frame (5) and hinging means (18) for said couple of lower arms (6) with respect to said intermediate frame, said plurality of arms being arranged on each side of said base, and the lifting system being of the electro-mechanical type with rigid chains (23).

Description

Technical field

The present invention relates to a lifter of the scissor or pantograph type according to the characteristics of the pre-characterizing part of claim 1.

Definitions

In the course of the present description to indicate the scissor-type lifter also the term pantograph lifter will be used by which said product is also commonly known. As used herein the terms "scissor-type lifter" and "pantograph lifter" have to be considered perfectly equivalent.

Prior art

In the field of the construction of lifters, the so called "scissor-type titter" or "pantograph liter" has a particular relevance.
The most simple lifters essentially consist of a base supporting a platform by means of at least two couples of arms, the arms of each couple being reciprocally hinged in a fulcrum located at an intermediate position with respect to each of the two arms, one arm of each couple having the lower end hinged at a fixed point of the base and the upper end hinged on a guide and sliding on said platform, the other arm of the same couple having the lower end hinged on a guide and sliding on said base and the upper end hinged at a fixed point of the platform, each pair of arms performing a reciprocal movement similar to the one of the scissors, said reciprocal movement of one of the two couples of arms occurring on a plane which is parallel to the plane on which the reciprocal movement of the other couple of arms occurs. The scissor-type movement of the couples of arms occurs in a reciprocally coordinated way and is translated in the lifting / lowering action of the platform with respect to the base. The lifting corresponds to the reciprocal approaching action of the two lower ends of the arms forming each couple and corresponding reciprocal approaching of the two upper ends of the arms forming each couple. However, said simple system, commonly identified as single scissor-type system, does not allow to reach high heights.
Solutions are present for lifters in which the platform is supported and raised by a system based on a vertically placed piston. However, said system is applicable only in the case in which the maximum height of the platform is limited, therefore not solving the problem of reaching strokes with a greater height of the platform itself.
To overcome the limitation relative to the maximum reachable height, more complex lifters with double, triple, quadruple, etc. scissor have been made, in which the platform is supported by means of at least one couple of lever systems, each lever system consisting of a sequence of couples of arms, each couple of arms consisting of two arms reciprocally hinged in a fulcrum located at an intermediate position with respect to each of the two arms, each end of each arm being provided with a hinging point intended to be hinged either with said base or with said platform or with a corresponding end of another arm belonging to a couple of lower or upper arms, the hinging on said base and on said platform occurring on one side in a not-sliding way, and at the opposite side with respect to the axis connecting the central fulcrums of said arms in a sliding way.
Solutions are also known in which the lifter is also provided with means intended to tilt the platform with respect to the base, in the case in which said tilting is required.
GB 1423749 discloses a jack comprising a rectangular base on each side of which are two pairs of cross-pieces pivoted at their centres. One cross-piece of each pair is pivoted at near the end of the base, the other cross-piece resting on the base via a roller. The cross-pieces support a platform, one being pivoted to it, the other bearing a roller in a rail. Pneumatic bellows between the base and the platform can be inflated to raise the platform. At least one further platform can be supported from the platform in a similar manner. A safety device is provided to prevent collapse of the jack should the bellows be accidentally deflated. This device comprises a stop member in the form of a bar pivoted to one of the cross-pieces at its lower end with the roller. Abutment faces on block are provided to engage the lower ends of the other crosspieces adjacent their rollers. The bar may be disengaged by a lever, the lever being automatically returned to its inactive position by a lug on the bar when the jack is lowered. The bar automatically comes into action as the jack is raised as the blocks are bevelled on their non-abutment ends. In a modification (not shown) the safety bar is pivoted to the base of the jack.
EP 1571083 describes an aircraft loading platform having a lower frame and an upper frame linked by a scissor-jack. The ladder on the upper frame is linked to that on the lower frame by a third ladder.
DE 9013231 describes an equipment to change wheels of railway vehicles with an elevating platform moved over a sheared linkage, characterized by a sheared linkage for the entire vertical lift, whereby the sheared linkage between the linkage beginning and the linkage end is provided with a guide, a table being present in the sheared linkage with one fixed articulation and a sliding articulation. Both scissors are articulated with one another and with an intermediate table. The intermediate table possesses a frame structure and it is movable guided between pillars. The pillars consist of sheet metals having a suitable thickness, which are welded with one another to a steel metal angle. The pillars are fixed to a sole construction and/or sub-construction. Above on the pillars an electric motors is present, provided with an upstream gear box and longitudinally moving vertical spindles in the pillars. The spindles cooperate with suitable nuts (spindle locks) in the intermediate table. Thus each spindle leads, depending upon direction of rotation, to a stroke movement.
US3341042 describes an elevator for transporting cargo to and from aircrafts where the elevator has titling means for tilting the upper supporting surface of the elevator as the aircraft fuselage pitches in response to changes in load distribution.
FR1479687 discloses an elevator of the type comprising a movable foot characterized in that the elevator element consists of a plurality of reciprocally articulated deformable parallelograms causing with their deployment the rise of the elevator element, the parallelograms folding involving a considerable reduction of the volume of the elevator facilitating its displacement. The deployment of the various parallelograms is obtained by the deployment of one hinged support point. Each end of hinges is connected to a second arm whose second end is secured with a plate on which parallelograms are secured. One second series of deformable parallelograms is secured on an intermediate plate. The support point of each tiltable hinge consists of a rotatable roller, on which the aforementioned hinge can slip. Each series of parallelograms constituting the elevator element is secured at its base on the bottom of the movable foot.
FR2470751 discloses an elevator composed by at least two pairs of articulated arms one on the other one between a base plate and a vertically movable carrying plate above the base plate, one of the ends of each arm of each pair being pivotally mounted on the base plate, the other end of each arm of each pair being sliding mounted in slides formed on the base plate. Engine means are provided to ensure the vertical displacement of the movable carrying plate with respect to the base plate. The engine means consists of a chain perpendicularly pushed laid between the base plate and the movable carrying plate and whose reciprocally articulated links comprise abutment surfaces shifted on a side of the chain compared to the plane of the articulation pins of these links. The abutment surfaces are one against the other when the chain is straight, the chain supporting the movable carrying plate at one of its ends.

Problems of the prior art

The maximum reachable lifting is limited by various factors:

length of the arms constituting the couples of arms, wherein the greater is the length of the arms, the greater is the height to which it is possible to lift the platform;
static stability of the structure in the maximum height position, which is reduced as the height increases, because, as previously explained, the ends of the arms constituting each couple are progressively reciprocally approached with a movement that in the limit condition of maximum approaching would correspond to reciprocal overlapping of the arms each other for each of the two couples of arms, this involving the presence of two supporting points only of the platform located in an eccentric position with respect to the platform itself, said limit condition being absolutely unreachable due to safety reasons;
static stability of the structure in the intermediate positions between the one corresponding to the maximum height and the one corresponding to the minimum height;
dynamic stability of the structure during the lifting / lowering movement to ensure the safety of people and/or things moved by means of said platform.

Furthermore, the solution in which the platform is supported by lever systems reciprocally fixed at the ends, though allowing to reach greater heights of the platform with respect to the base, in addition to the above mentioned stability problems of the structure, also has side torsion problems of the lever systems and circular torsion problems of the platform with respect to the base.
No less important are the problems concerning the oscillations which can be generated during the movement, as well as in the final position with said lever systems even in a partial extended position.
All the above mentioned stability, torsion and oscillation problems of the structure result in heavy limitations from the point of view of the maximum height reachable by the platform, as well as from the point of view of the maximum load that said platform can lift.
In the case of platforms supported by couples of lever systems, each lever system lying on a parallel plane with respect to the plane on which the other lever system lies, some of said problems are solved by means of the application of orthogonal reinforcing cross-pieces with respect to said planes, each cross-piece connecting two corresponding arms, one arm belonging to a lever system and the other arm belonging to the other lever system parallel to the previous one, said cross-pieces being able to be applied both in correspondence of the central fulcrum between couples of arms, and in correspondence of the ends of the arms. Said cross-pieces, though partially solving the torsional stability problems of the structure, make the space totally unusable between the platform and the base in any extended position even in an intermediate extended position. This can be a disadvantage in many applications which need said space for different reasons, as, only by way of example, lifters for motor vehicles intended to allow the access to the underside of the vehicle, lifters for motor vehicles able to allow the parking of another vehicle or even to allow only the passage below the lifted vehicle, movement platforms of vehicles from a plane to another one in which the passage below the platform must be ensured while it is in a raised position, applications in which the access to the platform in the raised position must be ensured by a trapdoor located on said platform, said access being possibly made by a lifting system similar to the one of the platform itself and located internally to the lifting system of the platform.
In the case of stationary installations some of said problems are solved by means of guides anchored to one or more vertical walls developing parallel to the movement direction of the platform, but it will be apparent that a wall to which said guides are anchored is not always available, or, in the case in which said wall can be built, the cost of the installation increases.
For example concerning GB 1423749 , at least one pair of scissors is present, a first scissor having one arm hinged in a not-sliding way at one side of the base and the other arm hinged in a sliding way at the same side and a second scissor arranged in a similar way on the same side of the base, the two sliding arms of the couple of scissors being sliding one toward the other to lower the platform and moving away from each other to lift the platform. The pair of scissors must lay on the same plane because a common safety device is provided to prevent the collapsing of the platform. Moreover the lifting occurs by pneumatic bellows between the base and the platform which can be inflated to raise the platform. So the solution proposed by GB 1423749 fails in allowing enough lateral space on the side where the scissors are present in order to have a free access to the space below the platform. Moreover being the sliding arms of the pair of scissors sliding on the same side of the platform the width of the platform relative to the side where the pair of scissor is mounted must be considerably increased to allow the retraction of the two sliding arms when the platform is lowered because the sliding arms will lay approximately horizontally at the base the one after the other. Moreover the solution proposed by GB 1423749 suggests the use of pneumatic bellows between the base and the platform, this necessarily involving the use of the internal space of central column defined by the frame supporting the platform which for this reason is not free, in any case being it inaccessible for the above stated reasons.
In EP 1571083 , as for its description, all of the sliding hinges of the scissors are connected to corresponding sliding hinges of the scissors on the other side of the frame by means of reinforcing yokes, that is orthogonal reinforcing cross-pieces which follow the movements of the sliding hinges during rising and lowering operations of the platform, so that the space below the platform is not free and the access to the central column defined by the frame must be precluded for safety reasons. Moreover the solution does not allow to install a second smaller platform in the free internal space of central column, the rising/lowering movement of the second smaller platform being independent from rising/lowering movement of the first bigger platform. The installation of the second smaller platform is not allowed because of the reinforcing yokes.
The solution provided by DE 9013231 is based on the presence of a couple of pillars guiding the entire vertical lift of the sheared linkage, a table being present in the sheared linkage with one fixed articulation and a sliding articulation. The pillars consist of sheet metals having a suitable thickness, which are welded with one another to a steel sheet metal angle. The pillars are fixed to a sole construction and/or sub-construction. Above on the pillars an electric motors is present, provided with an upstream gear box and longitudinally moving vertical spindles in the pillars. The presence of the pillars limits the access to the internal space of central column defined by the frame supporting the platform. Moreover the solution does not allow to install a second smaller platform in the free internal space of central column, the rising/lowering movement of the second smaller platform being independent from rising/lowering movement of the first bigger platform. The installation of the second smaller platform is not allowed because the pillars of the second smaller platform would preclude the lowering movement of the of the first bigger platform, said pillars being fixed and not collapsing together with the lowering of the second smaller platform.
Also in US3341042 the space below the platform is not free and the access to the central column defined by the frame must be precluded for safety reasons because of the presence of reinforcing yokes, that is orthogonal reinforcing cross-pieces and because of the presence of the lifting mechanism. The installation of the second smaller platform is not allowed.
Also in FR1479687 the space below the platform is not free and the access to the central column defined by the frame must be precluded for safety reasons because of the presence of reinforcing yokes, that is orthogonal reinforcing cross-pieces and because of the presence of the lifting mechanism. The installation of the second smaller platform is not allowed.
In FR2470751 the presence of the lifting mechanism internally to internal space of central column precludes the access to it. Moreover the solution does not allow to install a second smaller platform in the free internal space of central column, the rising/lowering movement of the second smaller platform being independent from rising/lowering movement of the first bigger platform.

Aim of the invention

The aim of the present invention is to supply a lifter of the scissor or pantograph type solving the above-mentioned problems of the prior art, that is a lifter being stable in the position corresponding to the maximum extension in height, as well as in the lifting / lowering phases, at the same time ensuring the space inside the lifting pantograph system to be free from reinforcing cross-pieces either to use said space with the platform in the raised position or to pass below the platform with the platform in the raised position or to access the platform in the raised position, the space between of the platform and the base being available when the platform is in an even partially raised position with respect to the base and being completely free, said free space allowing the installation of a second smaller platform in the free internal space of central column defined by the frame of the first platform, the rising/lowering movement of the second smaller platform being independent from rising/lowering movement of the first bigger platform.

Concept of the invention

The aim is reached with the characteristics of the main claim. The dependent claims represent advantageous solutions.

Advantageous effects of the invention

The proposed solution according to the present invention presents advantages from the point of view of the:

static stability of the structure in the position corresponding to the maximum height;
static stability of the structure in the intermediate positions;
dynamic stability of the structure during the lifting / lowering steps;
reduction of the side torsion of the structure;
reduction of the circular torsion of the platform with respect to the base;
liftable mass;
reduction of the oscillations;
availability of the space between the platform and the base when the platform is in an even partially raised position with respect to the base.

Description of the drawings

An embodiment of the invention is now described with reference to the accompanying drawings to be considered as a not limitative example of the present invention in which:

Fig. 1 represents the lifter made according to the present invention in an isometric three-dimensional view with the platform in a raised position with respect to the base.
Fig. 2 represents the lifter made according to the present invention in an isometric three-dimensional view with the platform in a lowered position.
Fig. 3 represents the lifter made according to the present invention in a schematic plan view.

Description of the lifter with reference to the drawings

The scissor or pantograph type lifter (1) object of the present invention (Figs. 1 and 2) consists of a base (2) and a platform (3) supported by a series of at least two reciprocally superimposed couples of arms, respectively the couple of lower arms (6) consisting of a first lower arm (7) and a second lower arm (8) and the couple of upper arms (9) consisting of a first upper arm (10) and a second upper arm (11). Interspersed between said couples of reciprocally superimposed arms is a quadrangular intermediate frame (5) consisting of four beams orthogonal to one another intended to supply some intermediate supporting points for said arms. The couple of lower arms (6) is therefore hinged on the lower part in correspondence of the base (2) and on the upper part in correspondence of said intermediate frame (5), while the couple of upper arms (9) is hinged on the lower part in correspondence of said intermediate frame (5) and on the upper part in correspondence of said platform (3). Each arm of each couple is hinged to the other arm constituting said couple by means of the central fulcrum (12) in an intermediate position with respect to the overall longitudinal development of the arm itself.
With regard to the couple of lower arms (6), the first lower arm (7) is hinged on the lower part on said base (2) by means of the not-sliding pin with respect to the base (13) and it is hinged on the upper part in correspondence of the lower sliding pin (18) which is present on a support of the central pins (17) which is slidable on a guide (22) with respect to said intermediate frame (5). The second lower arm (7) is hinged on the lower part on said base (2) by means of the sliding pin with respect to the base (14) on a guide (22) and it is hinged on the upper part on said intermediate frame (5) by means of the not-sliding lower pin (20).
In a similar way, with regard to the couple of upper arms (9) corresponding to the couple of the previously described lower arms (6), the first upper arm (10) is hinged on the upper part on said platform (3) by means of the not-sliding pin (15) with respect to the platform and it is hinged in correspondence of the upper sliding pin (19) which is present on said support of the central pins (17) which is slidable on a guide (22) with respect to said intermediate frame (5). The second upper arm (11) is hinged on the upper part on said platform (3) by means of the sliding pin with respect to the platform (16) on a guide (22) and it is hinged on the lower part on said intermediate frame (5) by means of the not-sliding upper pin (21).
In the Figs. 1 and 2 the arrows indicate the sliding directions of said slidable pins.
In the illustrated embodiment, the same configuration is repeated on all of the four perimetrical sides of said base (2), said platform (3) and said intermediate frame (5), but it will be apparent to those skilled in the art that, in a different embodiment, said configuration can be repeated only on three perimetrical sides or only on two opposite perimetrical sides.
The sliding of said slidable pins occurs, in the illustrated embodiment, by means of a system consisting of a guide and a trolley sliding on said guide, the hinging point being obtained on said trolley.
It will be also apparent to those skilled in the art that, though in the illustrated embodiment an essentially double superimposed scissor system is represented with an intermediate frame, other configurations are possible as, by way of example only, with triple scissors with double intermediate frames, quadruple scissors with three intermediate frames, and so on.
Advantageously (Fig. 3) each of the four not-slidable pins (21) (of which in the figure only the upper ones have been represented relative to the intermediate frame (5)), is located in correspondence of a different corner of said intermediate frame (5), the sliding of each of the slidable pins (19) (of which in the figure only the upper ones have been represented relative to the support (17)), occurring along the corresponding side of said base in an approaching movement to the corresponding not-sliding pin (21), so that, also in the limit situation in which the sliding would occur until the two pins are brought into reciprocal contact, said platform is advantageously supported in correspondence of each of the four corners. This constitutes a considerable advantage with respect to the systems of the prior art, in which, at the maximum theoretically possible approaching limit, only two supporting points are present for the platform located in an eccentric position with respect to the platform itself, said limit condition being absolutely unreachable due to safety reasons.
More than allowing the reaching of higher heights, this solution constitutes an undoubted benefit from the point of view of the static stability in any position, terminal or intermediate position, because the platform (3) is always supported in correspondence of four points corresponding to the ends of the platform (3) and in four points each of which in an intermediate position with respect to two of the four supporting ends.
Moreover the dynamic stability is also improved in the lifting / lowering phases of the platform (3) with respect to the base (2) and the oscillations of the platform (3) with respect to the base (2) are also reduced.
Not least an effective reduction occurs of the circular torsion of the platform (3) with respect to the base (2), because said intermediate frame (5) acts as structural stiffening system of the lifter.
All of this is translated on the one hand in an increased safety of the lifter (1) but also in a consequently increased load capacity, both for the presence of a greater number of perimetrical supporting points, and for the presence of the intermediate frame stiffening the overall structure.
Moreover the lifter (1) object of the present invention does not need any structural stiffening cross-piece connecting arms on opposite sides, this involving the absence of encumbrances internally to the space defined by the arms themselves and, for example, it makes it possible to use a central trapdoor (4) with respect to the platform (3), said trapdoor (4) being accessible by the internal space defined by said arms, said trapdoor being able to include in turn a lifter similar to the represented one and centrally located with respect to the latter.
For the aims of this invention, the lifting system (23) of the platform is considered, as known in the art and therefore it will not be disclosed in details, possibly being of the hydraulic type, of the electro-mechanical type with rigid chains, etc.
It will be also apparent to those skilled in the art that the lifter (1) object of the present invention will include all the necessary elements to ensure the operative safety, as, by way of example only, mechanical standing locking means and antifall mechanical guards able to intervene at any height level of the platform.
The description of this invention has been made with reference to the enclosed figures showing a preferred embodiment of the invention itself, but it is evident that many alterations, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Thus, it should be understood that the invention is not limited by the foregoing description, but it embraces all such alterations, modifications and variations in accordance with the spirit and scope of the appended claims.

Used nomenclature

With reference to the identification numbers reported in the enclosed figures, the following nomenclature has been used:

1. Lifter
2. Base
3. Platform
4. Trapdoor
5. Intermediate frame
6. Couple of lower arms
7. First lower arm
8. Second lower arm
9. Couple of upper arms
10. First upper arm
11. Second upper arm
12. Central fulcrum between the arms
13. Not-sliding pin on the base
14. Sliding pin on the base
15. Not-sliding pin on the platform
16. Sliding pin on the platform
17. Sliding intermediate pin support
18. Lower pin on sliding intermediate pin support
19. Upper pin on sliding intermediate pin support
20. Lower not-sliding pin on intermediate frame
21. Upper not-sliding pin on intermediate frame
22. Guide
23. Lifting system

Claims

Scissor-type lifter comprising a base, a platform movable with respect to said base and a plurality of arms forming couples of vertically extensible arms with a scissor-like movement, each arm of each couple being hinged at the intermediate position with respect to its longitudinal development to the other arm forming said couple, said plurality of arms including at least one couple of upper arms and one couple of lower arms, one couple of which being hinged on one side in a not-sliding way to said base and on the other side in a sliding way to said base and the other couple being hinged on one side in a not-sliding way to said platform and on the other side in a sliding way to said platform characterised in that it includes at least one intermediate frame (5) with respect to said base (2) and to said platform (3), said intermediate frame (5) including:
- hinging means (20) not sliding with respect to the frame itself for said couple of lower arms (6) with respect to said intermediate frame (5);

- hinging means (21) not sliding with respect to the frame itself for said couple of upper arms (9) with respect to said intermediate frame (5);

- slideable means (17) with respect to the frame itself, said slideable means (17) comprising: hinging means (19) for said couple of upper arms (9) with respect to said intermediate frame (5) and hinging means (18) for said couple of lower arms (6) with respect to said intermediate frame.
and being further characterized in that:
- said plurality of arms is arranged on each side of said base

- for adjacent pairs of arms, the hinging point, not-sliding with respect to the support whereon said point is fixed, being placed in correspondence of a different corner of said support with respect to the corner near which there is the hinging point not-sliding with respect to the support of the adjacent couple of arms.

- for opposite pairs of arms, the hinging point not-sliding with respect to the support whereon said point is fixed is placed in correspondence of an opposite corner of said support with respect to the corner near which there is the hinging point not-sliding with respect to the support of the opposite couple of arm.

- it includes a rising system of the electro-mechanical type with rigid chains.
Scissor-type lifter according to the previous claim characterised in that it includes a plurality of said intermediate frames (5), subsequent pairs of intermediate frames (5) being reciprocally connected and supported by at least one couple of vertically extensible arms with a scissor-like movement, each arm of said couple being hinged at the intermediate position with respect to its longitudinal development to the other arm forming said couple at the fulcrum (12), each pair of arms being hinged on one side by means of hinging means not-sliding with respect to said frame (5) and being hinged at the opposite side with respect to the vertical axis which passes through said fulcrum (12) by means of hinging means slideable with respect to said frame (5).
Scissor-type lifter according to any of the previous claims 1 to 2 characterised in that the sliding of said hinging point occurs by means of a system made of a guide (22) and of a trolley sliding on said guide, said trolley comprising said hinging points.
Scissor-type lifter according to any of the claims 1 to 3 characterised in that said plurality of arms is arranged at three sides of said base.
Scissor-type lifter according to any of the previous claims 1 to 4 characterised in that it includes suitable means for the mechanical locking in standing positions.
Scissor-type lifter according to any of the previous claims 1 to 5 characterised in that it includes suitable means for the fall-prevention mechanical locking.