EP1457437A2

EP1457437A2 - Load spreaders

Info

Publication number: EP1457437A2
Application number: EP04250888A
Authority: EP
Inventors: Patrick John Gorner
Original assignee: Mercol Products Ltd
Current assignee: Mercol Products Ltd
Priority date: 2003-03-08
Filing date: 2004-02-19
Publication date: 2004-09-15
Also published as: EP1457437A3; GB2399334A; GB0305367D0; GB0403695D0

Abstract

A load spreader for use for example on air cargo transport comprises a plank member (10) of rigid polyurethane material. The plank 10 has tubular reinforcing members 11 through which are passed locating cables 15. A locking device 16, 17 is provided to clamp the plank 10 to the cables including a compressible inner member 17 which can clamp on the cable in one rotational position within an outer member 16 which compresses the inner member 17 in one rotational position thereof, and allows release thereof in an alternative position.

Description

This invention relates to improvements in load spreaders, for use in facilitating the transportation of goods, particularly of air cargo.
Air cargo is usually transported within the hold of aircraft supported upon lightweight aluminium sheets in place of pallets. The sheets are intended to bridge between ribs supporting the outer skin of the lower part of the aircraft fuselage, as the skin itself does not have the strength to support loads exerting high pressures. The aluminium sheets themselves however lack rigidity and load bearing capability and thus it is necessary to make use of load spreaders. In current practice these are timber planks which are laid on the aluminium sheets and are sufficiently long to bridge the spaces between at least adjacent pairs of fuselage ribs and are sufficiently strong to support the weight of cargo items, and transfer the load to the ribs without affecting the skin panels of the aircraft fuselage.
Being of timber, such load spreaders are moisture absorbent, prone to splitting, cracking and also warping due to the response of timber to changes in temperature and humidity, so that they have generally short operating life. Further, timber is also liable to be stolen for use as firewood or building material, particularly in less developed countries. Replacement of timber planks due to degradation and pilferage is thus a regular requirement and whilst individual planks are not expensive, the requirement for regular replacement over a relatively short life cycle imposes a significant operational cost to air cargo operations.
It is an object of the invention to provide a load spreader which comprises a plank like member fabricated from a rigid synthetic material.
The invention provides a load spreader comprising a plank member characterised in that the plank member is fabricated from a low density rigid polyurethane.
The material is preferably a low density polyurethane including a filler which provides a feel and density close to that of timber.
The polyurethane material may comprise a blend of low and high molecular weight polyurethane resin, an aliphatic or aromatic polyisocyanate based system, and a low density filler. Pigment and water may also be included.
The plank member advantageously includes at least one longitudinally extending reinforcing member, and the reinforcing members may comprise two or more hollow tubes embedded within the member. The reinforcing members are preferably each adapted to allow a cable or cord to be passed through the reinforcing member.
Each reinforcing member preferably has a locking device at one or both ends thereof, to fix the position of the plank member on the cable. Each locking member may comprise a rotatable inner member having a part with a longer width and a shorter width and is arranged to be rotatable through at least a quarter turn within an outer fixed member received in an end part of the reinforcing member, the outer fixed member having recesses to receive the longer width of the inner member in one rotational position of the inner member.
The inner member may comprise a wider end part having a flattened profile and a circular cross section shank part, the end part having a slit which allows a degree of compressibility to the end pat to clamp the cable and the outer member may have a corresponding wider end part and a narrower part, the wall of the wider end part being split at each side to enable expansion thereof to free the cable and having the recess disposed between the splits, for example at 90° rotational angle.
The inner member preferably has an axial passage for the cable or cord.
A preferred embodiment of load spreader member in accordance with the invention will now be described by way of example, with reference to the accompanying drawings wherein:-

Fig. 1: is a perspective view of a load spreader according to the invention in use in an aircraft cargo hold environment;
Fig. 2: is a cross sectional view of a load spreader according to the invention;
Fig. 3: is a fragmentary longitudinal sectional view of one end region of a load spreader according to the invention;
Fig. 4a-4b: show different rotational positions of a locking device shown in Fig. 3
Fig. 5: is a sectional view of an outer part of the locking device;
Fig. 6: is a sectional view of an inner part of the locking device; and
Fig. 6a: is an end view of the inner part of the locking device from the direction X in Fig. 6.

Referring first to Fig. 1, a load spreader according to the invention comprises a plank member 10, having a plurality of reinforcing cores 11, of aluminium tube, of square cross-section.
The plank member 10 is shown laid upon a sheet 12 of aluminium, which is in turn. laid upon ribs 13 forming reinforcing structure of the floor of an aircraft fuselage, with skin panels 14 between and outside of the ribs 13.
Because the skin panels 14 have effectively no load-bearing capacity, the sheet 12 and the plank member 10 bridge at least two adjacent ribs 13. Further, the sheet 12 also has only a low load-bearing capacity, and thus any load is carried by two or more of the plank members 10 which act as load-spreaders and apply the weight of the load at two or more points of the aircraft frame.
Fig. 2 is a cross-section taken transversely of the plank member 10, and showing three square cross-sectioned core members 11 extending longitudinally therethrough.
The body of the plank member is moulded about the core members 11 from a low density rigid polyurethane material including a high percentage of filler, reckoned on a volume basis, for example between 50 and 80%.

A typical composition of the material from which the plank member 10 is made comprises:-

	Weight	% By Weight
Blend of low and high molecular weight Polyurethane Resin 803/75DFR	1371gm	45.58%
Aliphatic or aromatic Polyisocyanate Based System	1129gm	37.53%
Low Density Filler, ad lib	300gm	9.97%
Powder Colour Pigment	200gm	6.65%
Water	8gm	0.27%

The filler may be added to either the polyurethane resin or the polyisocyanate before mixing, or all the components may be blended in a single mixing step, or the filler may be added after mixing of the resin and polyisocyanate.
A suitable filler is sometimes supplied ready mixed with one of the precursor components, usually polyol or polyether containing components. The composition also includes a fire retardant and a UV stabiliser.
When the reaction and curing is completed, including of the effect of the water, which is included as a blowing agent, the resulting material has a specific gravity of about 0.2. The resulting material has tactile and other properties similar to timber, but does not share some of the disadvantages of timber, such as moisture and the ability to split, warp and burn.
Fig. 2 is longitudinal cross-section of an end part of the plank member 10. The reinforcing tube 11 has a cable or cord 15 extending axially therethrough, and a locking device, consisting of an outer member 16 and an inner member 17 is provided at both ends of the tube 11.
The locking member is described in more detail below, but serves to grip the cord 15 and the plank member 10 so that the plank member 10 will not be displaced along the cord, so that the plank member when in use as a load spreader will be maintained in place, and not be displaced for example by changes in slope of the cargo space floor when the aircraft is climbing, descending or manoeuvring.
Figs. 4-6a show the components and operation of the locking device in more detail.
The outer member 16 is shown in cross-section in Fig. 5, and includes a bore 18 which has a widened end part 19, and a narrower part 20. The locking device locates within tube 11. The wall of the widened end part 19 is split at each side at 21, so that the wall of the end part has some flexibility and resilience. The inner face of the wall of the widened end part is also provided with axially opposed recesses 22, which are set at 90° from the splits 21, but the wall is also thicker at these parts, making the interior cross-section elliptical.
The inner member 17 is received within the outer member 16 and comprises a flattened wide end part 23, a circular cross-section shank part 24, and a square cross-section protruding end part 25 which projects from the outer member 16. The cable or cord 15 extends axially through a passage 26 in the inner member 17. The wall of the flattened wide end part 23 has a slit 27 which extends from the passage 26 to one flattened face of the upper end part 23.
The parts cooperate as illustrated in Figs. 4a and 4b.
Fig. 4a shows the locking device in the unlocked position. The inner member 17 has the flattened wide end part 23 aligned with the splits 21 of the outer member, and with the greater internal diameter thereof. The outer wall is not stretched so that the splits 21 are closed and the end part 23 of the inner member 17 is not subject to compression, so that the slit 27 is open and the cable within passage 26 is not clamped so that relative motion is possible.
To lock the device in the cable, the inner member 17 is turned through 90° by means of a suitable spanner or lever acting in the square-sectioned end 25, to turn the end part 23 to the Fig. 4b position. Here the ends of the part 23 engage in the recesses 22, and are subject to pressure due to the reduced internal diameter along the minor axis of the elliptical inner bore, the outer wall of member 16 is expanded so that slots 21 are open, and the inner member end part 23 is subjected to compressive force so that slit 27 is closed and the cable or cord is clamped within the passage 26 and the inner wall of tube 11.
The locking device can thus be engaged and disengaged using a suitable spanner or lever on end 25, and the position of the plank member 10 on the cable 15 adjusted and fixed or released as required.
The plank member 10 may be of any suitable synthetic material which provides a strong load bearing member which is not prone to water absorption, warping, splitting, cracking or burning.
The cable and clamping system described although preferred is not essential, and other methods or means for locating the plank member may be adopted.
It is of course to be understood that the invention is not intended to be restricted to the details of the above embodiments which are described by way of example only.

Claims

A load spreader comprising a plank member (10) characterised in that the plank member (10) is fabricated from a low density rigid polyurethane.
A load spreader according to claim 1, characterised in that the material is a low density polyurethane including a filler and which provides a feel and density close to that of timber.
A load spreader according to claim 1 or 2 wherein the polyurethane material comprises a blend of low and high molecular weight polyurethane resin, an aliphatic or aromatic polyisocyanate based system and a low density filler.
A load spreader according to claim 1, 2 or 3 characterised in that the plank member (10) includes at least one longitudinally extending reinforcing member (11).
A load spreader according to claim 4 characterised in that the reinforcing members (11) comprise two or more hollow tubes embedded within the member.
A load spreader according to claim 5 characterised in that the reinforcing members (11) are each adapted to allow a cable or cord (15) to be passed through the reinforcing member (11).
A load spreader according to claim 6 characterised in that each reinforcing member (11) has a locking device (16, 17) at one or both ends thereof, to fix the position of the plank member (10) on the cable (15).
A load spreader according to claim 7, characterised in that each locking device (16, 17) comprises a rotatable inner member (17) having a part with a longer width and a shorter width and is arranged to be rotatable through at least a quarter turn within an outer fixed member (16) received in an end part of the reinforcing member 11, the outer fixed member having recesses (22) to receive the longer width of the inner member in one rotational position of the inner member (17).
A load spreader according to claim 8 characterised in that the inner member (17) comprises a wider end part (23) having a flattened profile, and a circular cross-section shank part (24), the end part (23) has a slit (27) which allows a degree of compressibility to the end part (23) to clamp the cable (15) and in that the outer member (16) has a corresponding wider end part (19) and a narrower part (20), the wall of the wider end part (19) is split at each side (21) to enable expansion thereof to release the cable (15) and has said recesses (22) disposed between the splits (21) at 90° rotational angle.
A load spreader according to claim 9 characterised in that the inner member (17) has an axial passage (26) for the cable or cord (15).