GB2110648A

GB2110648A - An elevating platform with scissors linkage

Info

Publication number: GB2110648A
Application number: GB08234141A
Authority: GB
Inventors: Graaf Clemens Adrainus Wilh De
Original assignee: NIERSTRASZ NV
Current assignee: NIERSTRASZ NV
Priority date: 1981-11-30
Filing date: 1982-11-30
Publication date: 1983-06-22
Also published as: GB2110648B; NL8105415A

Abstract

An elevating platform with scissors linkage comprises a base frame 1, a lifting platform 30, a plurality of pairs of scissors 5-8 in each of the group vertical planes interconnected by cross bars 17-20, with pivotal connections at 29 and 24 to the platform and base respectively, and sliding connections at 31 and 21, the scissors arms being opened by a jack 35 connected between the cross bars 18, 19 and arranged midway between the said two vertical planes. <IMAGE>

Description

SPECIFICATION An elevating platform with scissors linkage The invention relates to an elevating platform with scissors linkage comprising a base frame, a lifting platform, a plurality of pairs of scissors interconnected through cross bars, one pair of scissor arm ends being connected in stationary pivotal relationship and the associated pair of scissor arm ends in slidable pivotal relationship to the base frame and the lift platform, respectively, and the other scissor arm ends being connected pivotally to linked scissor arm ends, and drive means for the scissors comprising at least one jack member.

In such known elevating platforms with scissors linkage, the drive means are formed by a plurality of hydraulic cylinders of relatively small dimensions. These cylinders are positioned in such a way that they are present between the pairs of pivots when the scissors are contracted.

To this effect, the cylinders are positioned, whether or not groupwise, engaging cross bars between\the scissors and/or auxiliary arms provided in the scissors. Such a positioning of the cylinders, however, results in adverse bending loads on the cylinders and hence a heavier design thereof. Besides, the supply of fluid to the various cylinders and the control thereof may create problems, in particular in case of a non-groupwise positioning of the cylinders. The application of auxiliary arms provided in the scissors-may again create problems in connection with the pivot attachment thereof, i.e. an extremely tolerance-responsive positioning of a link rod in a link parallelogram, and a proper force transmission onto the scissors, which then, at least partly, is to take place via the auxiliary arms.

It is the object of the invention to improve an elevating platform with scissors linkage of the above described type in such a way that the above drawbacks are inexistent.

This is achieved according to the invention when the drive means have a joint axis coinciding substantially with the line of intersection of the median perpendicular plane between the pairs of scissors and the plane comprising the axes of the central shafts of the successive scissors. Through these features, such a central positioning of the drive means is obtained that these can no longer be subjected to bending loads, but need only take up compressive forces. Likewise, such a positioning entails that problems concerning the connection to the scissors, as well as a proper force transmission thereto can be avoided in a simple manner, in particular if, according to a preferred embodiment of the invention, the drive means comprise a centrally arranged, hydraulic cylinder engaging in situ of the axes of the central shaft of successive scissors.

A compact building method, even with working heights to e.g. 14 m, can be achieved if according to a further embodiment of the invention said two scissors are linked to a further scissor connected to the base frame and the lifting platform, respectively, in that in contracted condition of the elevating platform with scissors linkage, parts of the central cylinder may be present in the space between said additional scissors, which appears sufficient in practice to receive the cylinder in the space between the scissors without the necessitv for the parts thereof to project to underneath the underside of the base frame or to above the underside of the lifting platform.In order to optimally use the space occuried by the contracted apparatus, it is recommendable according to a further embodiment of the invention that all scissor arms have the same length, which from the viewpoint of forces and transmission of forces, does not create problems when centrally positioning the lifting cylinder. If, moreover, the lengths of base frame, lifting platform and scissor arms are chosen substantially equal, there will be obtained a highly compact, block-shaped construction, it being likewise possible that all scissors have an identical design, which is advantageous from the viewpoint of manufacture and maintenance.

In order to take up any clearance and tolerances without problems, it is recommendable according to a further embodiment of the invention that the drive means are connected to the scissors via Cardan joints, thus avoiding advantageously that the lifting cylinder could be subjected to bending loads as a result of clearance and/or elastic deformations.

One embodiment of the elevating platform with scissors linkage according to the invention will now be described, by way of example, with reference to the accompanying drawing in which: Fig. 1 shows the elevating platform in extended condition; Fig. 2 shows the platform in contracted condition; and Fig. 3 shows the suspension of the lifting cylinder.

The elevating platform with scissors linkage shown in Figs. 1 and 2 is provided with a substantially rectangular base frame 1, which is movable through a plurality of wheels 2. At a place of use, the base frame 1 can be stopped by means of a plurality of jacks 3, e.g. one at each angular point of the base frame 1. For the purpose of a stable arrangement, the jacks 4 are to be installed on arms extensible relative to the base frame 1, diagrammatically indicated in Fig. 2 by numeral 4. The jacks 4 can be so designed as to lift the base frame 1 from the group to the extent that the wheels 2 become freely suspended.

On the base frame 1 there are successively disposed four pairs of scissors 5, 6, 7 and 8, each scissor consisting of a pair of arms 9 and 10; 11 and 12; 13 and 14; 15 and 16, respectively, which pair of arms is interconnected via a pivot pin 17, 18, 19, 20, respectively. The one end of an arm 9 is connected via a roller bearing 21 to the base frame 1 in such a way that said end of the arm 9 is adapted to swivel relative to the base frame 1 and likesise to be moved horizontally along the base frame 1, while forces can be taken up vertically, The other end of the arm 9 is connected via a pivot 22 to the one end of an arm 12. Similarly, the one end of the arm 10 is connected via a pivot 23 to the one end of the arm 11, while the other end of the arm 10 is connected via a pivot 24 for exclusive swivelling movement to the base frame 1.The other ends of the arms 11 and 12 are connected for swivelling movement via pivots 25 and 26 to the one ends of the arms 14 and 13, the other ends of which, in turn, are again connected to the one ends of the arms 15 and 16 via pivots 27, 28. The other end of the arm 15 is connected via a pivot 29 for exclusive swivelling movement to a lifting platform 30, while the other end of the arm 1 6 is connected via a roller bearing 31 to the platform 30 similarly as the connection between the one end of the arm 9 and the base frame 1.

The lifting platform 30 is fitted with a frame beam 32, a floor 33 (see Fig. 3) and a railing 34.

The operation of the pairs of scissors 5-8 is done by means of a three-stage hydraulic cylinder 35. The activation and supply means (not shown) for the hydraulic cylinder 35 are disposed substantially on the base frame 1, while in and along the arms lines may be provided; the operating panel for the cylinder 35 is normally present on the platform 30.

With reference to Fig. 3, the suspension of the cylinder 35 within the pairs of scissors 5-8 will now be further discussed.

The elevating platform is in the contracted position, as also shown in Fig. 2. As shown in Figs. 1 and 3, the cylinder 35 is positioned centrally within the scissor pairs 5-8. The hydraulic cylinder 35 thereby engages the pivot pins 1 8 and 19 of the intermediate scissor pairs 6 and 7.

Cylinder portion 36 is connected via Cardan joint 37 to the shafts 18. The Cardan joint is composed of four plates 38 and 39 welded together to one tube of square cross-section, each being provided with a substantially V-shaped recess 40 whose apex angle is rounded for accommodating a shaft. The opening direction of the V-shaped recesses 40 in the plates 39 is opposite to that in the plates 38. The shafts 1 8 find support in the thus formed nests in the plates 39, while stub shafts 41 attached to the cylinder portion 36 find support in the nests in the plates 38. For the purpose of horizontal locking, the stub shafts are fitted with a shoulder 42 of increased diameter. A vertical locking is ensured by a buffer plate 43. The locking of the shafts 1 8 relative to the plates 39 is not shown, but can take place in a similar or other conventional.manner.

Piston rod 44 is pivotally connected at its free end via a shaft 45 to a crosshead 46 fitted with a pair of shaft journals 47, while the other end of the rod 48 is pivotally connected to one of the shafts 19. The axes of the journals 47 parallel those of the shafts 19, so that crosshead 46 is rockingly suspended so to speak. The axis of the shaft 45 is perpendicular to the plane through the axes of the journals 47 and shafts 19, so that again, a kind of Cardan joint construction is realized.

Due to this suspension and the central positioning, the hydraulic cylinder 35, in operation, will only be subject to a compressive load, which enables an optimally light construction. Besides, the suspension and design of the hydraulic cylinder 35 enables to accommodate the same in vertical position between the scissor pairs 5-8 in contracted condition thereof, without the cylinder 35 projecting to underneath the base frame 1 or to above the floor 33 of the platform 30.

Exclusively for the sake of illustration, it is observed that such an elevating platform with a total length of about 3.80 m, a width of about 2.00 m and a contracted height of about 1.65 m (exclusive of the height of the railing) can be extended to a platform height of about 12.20 m, which means a maximum working height of about 14.00 m. A cylinder of the dimensions diamgrammatically shown in Fig. 3 allows to obtain a lifting capacity of 700 kg.

It stands to reason that many modifications and variants are possible within the scope of the invention. For instance, naturally any other number than four scissors can be used, while in such case more than one lifting cylinder can be applied, provided the axes thereof are coextensive and are positioned centrally relative to the scissors. Besides, it is possible to design the suspension of the cylinder via a bridge construction, e.g. if the free lengths of the shafts 1 8 and 19 between the scissors and the cylinder are deemed too large. In that case, two bridge shafts 49 and 50 are disposed e.g. between the arms 12 at the left and the right beside the cylinder 35 (as diagrammatically shown in Fig. 1), which both extend from the one arm 12 to the other arm 12. From the shaft 49 to the shaft 50 then extend (at the left and at the right beside the cylinder 35 in Fig. 3.) two bridge portions, each being provided with a stub shaft, e.g. similar to the stub shaft 41, which find support in the nests in the plates 39. The axes of said stub shafts should then coincide with those of the shafts 1 8.

A similar bridge construction with bridge shafts 49 and 50 (again diagrammatically shown in Fig.

1) can be applied for the suspension of the crosshead 46, in which case the rods 48 attached via bridge portions between the shafts 49 and 50, may be connected to the scissor pairs.

Claims

1. An elevating platform with scissors linkage, comprising a base frame, a plurality of pairs of scissors interconnected through cross bars, one pair of scissor arm ends being connected in stationary pivotal relationship and the associated pair of scissor arm ends in slidable pivotal relationship to the base frame and the lifting platform, respectively, and the other scissor arm ends are connected pivotally to adjacent scissor arm ends, and drive means for the scissors comprising at least one jack member, characterized in that the drive means have a joint axis substantially coinciding with the line of intersection of the median perpendicular plane between the pairs of scissors and the plane comprising the axes of the central shafts of the successive scissors.

2. An elevating platform with scissors linkage according to claim 1, characterized in that the drive means comprise a centrally positioned hydraulic cylinder engaging in situ of the axes of the central shafts of two successive scissors.

3. An elevating platform with scissors linkage according to claim 2, characterized in that said two scissors are linked to a further scissor which is connected to the base frame and the lifting platform, respectively.

4. An elevating platform with scissors linkage according to any one of the preceding claims, characterized in that all scissor arms have the same length.

5. An elevating platform with scissors linkage according to claim 4, characterized in that all scissors are identically designed.

6. An elevating platform according to any one of the preceding claims, characterized in that the drive means are connected to the scissors via Cardan joints.