Method and apparatus for the transfer of, in particular, construction elements onto a transportation bed

Method and apparatus for the transfer of, in particular, construction elements onto a transportation bed

The present invention relates to a method in accordance with the preamble of claim 1 for the transfer of a plate-shaped product from two parallel storage stands or equivalent onto a transportation bed.

Generally speaking, the method is carried out by stacking the plate-shaped products onto two parallel storage stands, driving the transportation bed to underneath the goods to be transferred, and inclining the supports of the stands in their transverse direction until they are dumped and the goods are transferred onto the bed.

The invention also relates to a storage stand in accordance with the preamble of claim 5 for carrying out the method.

At present, construction materials are generally transferred by road transportation from factories or stores to construction sites. In order to maintain tight schedules, especially the deliveries of construction elements must take place at the right time and in the correct sequence. During the busiest seasons of construction, this may lead to congestion at the element factories and stores. The bottleneck of deliveries has proved to be the loading of transportation veohiiies. Loading is generally arranged so that the elements are transferred either from the store or directly from production, using a separate crane onto the transportation bed, typically on the platform of a truck or trailer. Thus, only so many elements can be loaded as there are available cranes, or a separate crane for each truck to be loaded is required. This factor has tended to increase loading and material handling costs at stores and factories.

The object of the invention is to simplify the handling of construction materials and to provide a novel method for transferring plate-shaped goods, especially concrete panels, from the storage premises onto a transportation bed. Effective utilization of the invention even includes the minimization of construction costs at the construction site by precisely maintaining delivery schedules. The inflexibility of deliveries from the production factory to the construction sites often generates excessive additional costs at the construction site. For operations at the construction site, the exact maintaining of the delivery time and correct loading method of elements are the principal factors in element deliveries. To avoid unnecessary on- and off- loading, the system operates so that the construction site gives the factory instructions each day for the delivery needs of the next day. This ensures a flexible system for the construction site, for instance, by taking into account such factors as weather conditions at the construction site and the rate of progress in fixed-fee operations which often bring changes in the plans.

At the construction site, an inflexible system often causes either waiting periods at unloading, or additional temporary storage or unloading. If the effective operating efficiency of element mounting personnel or crane machinery is thus decreased, also other indirect costs are created in addition to the costs mentioned above, such as the heating and fixed costs caused by the lengthening of the construction time. When these costs are taken into account, it is clear that the most advantageous method for the operation of the entire system is to deliver construction elements to the construction site exactly according to the time schelude expressed by the construction site.

Due to weather conditions and coinciding delivery times to different sites, the need of transportation equipment usually varies greatly from day to day. Consequently, the storage, load, dispatch, and transportation operations must be grossly overdimensioned at the factory compared to the average loading degree of these functions. Furthermore, these factor cause additional wage costs and heavy investments (in the form of several cranes required, large storage premises, working outdoors). All this can be avoided by applying the storage system in accordance with the invention.

The starting point of this invention is the storage of products in ready-packed bundles (=loads). The prerequisite for the operation of this system is an exact installation order of elements, received from the construction site, to enable correct sequential bundling of the loads.

In practice, the system.control is handled by a computer program. The input data is transferred after processing within the element design CAD program to the CAM program of the production factory. At this stage, the file is complemented with element delivery times and element mounting order according to instructions from the construction site.

When defining the production program, the CAM program takes into account the mounting schedules and mounting order requirements of the construction site to allow immediate compilation of loads when the products are received from the production line. Then, the products are continuously bundled straight from the production line without temporary storage or intermediate transfers. At the same time, the loading operations are transferred indoors, avoiding wasted time caused by weather changes and minimizing corrosion load on equipment located outdoors. Because the packing of load bundles is done on-line and the load data for the bundles is continuously available from the production program, the operation is performed in a controlled manner, leading to a lower need for investments and personnel for the loading equipment.

However, the essential invention of the storage system is the storage stand. When the load bundle has been transferred forth from the factory to a storage area onto the storage stand, the transportation vefhide driver can transfer the load onto the truck bed alone at his convenience. Thus, this method almost totally eliminates the conventional manning for storage and loading as well as the need for crane equipment. Furthermore, the system requires only one load bundler in the factory and a transfer vehicle driver for transferring the bundles to the outdoors area.

The system achieves a high flexibility of delivery times compared to the size of construction site and, consequently, offers savings in construction costs and disposes of storage lifts and all loading personnel at the factory. Simultaneously, the system also diminishes transportation costs because the load bundle can be tranfferred onto the transportation vehicle at any time convenient for the driver.

Savings in on-loading time remarkably increase the mileage perfomance of the truck fleet, allowing the expensive fleet to be used mostly for effective transportation instead of waiting in a queue for unloading, as is customary.

The system can be described with the following concise features:

• - The store size is not limited because the staging yard need not be located within the operating range of a crane.
• - The fleet quantity is not bound to on-loading time; therefore an unlimited quantity of trucks can be on road simultaneously.
• - The on-loading time is short, eliminating truck waiting times at the factory.
• - The truck driver is capable of handling the on-loading alone.
• - The storage can be operated unmanned, without idling periods or weather associates problems.
• - The elements are sequentially bundled in the load, in their correct installation order.
• - The elements will not be broken during storage.
• - The on-loading is not limited by the operating time, availability, operating radius, or operational loading of the staging yard crane.

The invention will be examined in detail in the following:

• The invention is based on the idea that the elements are stored upon one another on such storage stands that will allow the elements to be transferred onto a desired platform by inclining the stands, for the purpose of which the leg parts of the stands are properly formed to enable this operation. Such a leg member preferably consists of a vertical support member and a beam such that the lower end of the vertical support member, essentially at the joint of the vertical support member and the horizontal beam, is provided with a tilting joint. More specifically, the method in accordance with the invention is characterized by what is stated in the characterizing part of claim 1. In practice, the method in accordance with the invention may be put into practice, for instance, as follow:
• The plate-shaped products, preferably one or several concrete panels, are stacked one by one by means of a crane onto two parallel storage stands so that the elements remain as supported at both ends by the stands. The elements with the stands are hereafter transferred to the storage area, for example, by using such a transportation veOhFile which is provided with hydraulically adjustable lifting means.

When the elements are supposed to be transferred from the stands onto a transportation bed, the transportation bed is first driven to underneath the elements, preferably in the longitudinal direction of the elements, whereby the transportation bed is also, at the same time, driven underneath both horizontal beams of the stands supporting the load. Next, a force is directed at the load to be transferred in its longitudinal direction, for instance, by coupling one of the storage stands with a pulling chain or equivalent to the transportation bed or to the vehicle and by pulling the load placed on the stands forwards in this manner. The force can also be directed in a similar manner directly at the load to be transferred. Owing to said force, the goods to be transferred are brought into a movement which is directed in the longitudinal direction of the elements forwards and downwards. To attenuate the movement, the storage stand can be attached to the vehicle with a pull bar which at the beginning of the transfer phase initiates the inclination of the stands, but at the final stage resists too fast inclination, regulating the tilt in a controlled manner according to the forward movement of the truck. In this method, the panels are transferred by a controlled movement onto the transportation bed when the storage stands are inclined.

According to a preferred embodiment of the method, the goods remain on the transportation bed, supported by the transverse beams of the stands. Thereby,.the leg members of the stands must be detached from the transverse beams before the panel load can be dispatched. The leg members can be attached to another transverse beam and used again in the storage and loading operations according to the method.

In the following, a preferred construction of storage stands intended for carrying out the method will be examined more closely with the aid of the attached drawings.

• Figure la shows a storage stand in accordance with the invention as a side view and Figure 2 correspondingly as a front view, i.e., as viewed in the transverse direction of the stand. Figures lb and lc show some details of the stand in the transverse direction.
• Figures 3...5 are illustrations of principle of the use of the stand described above for carrying out the method in accordance with the invention.
• Figure 6 shows an alternative embodiment of the invention from the side as a partial cross sectional view.
• Figure 7 shows a third alternative embodiment of the invention from the side.

The storage stand comprises two identical leg parts or members 1, 7 which are connected at their upper ends by a transverse beam 6. The transverse beam 6 is a so-called H profile beam in this case, but its cross section may as well be square or even circular. In a preferred embodiment of the method, when the goods remain on the transportation bed supported by the transverse beam 6, the cross-sectional shape of this beam is preferably a lying H or square.

Figure 1 shows the construction of one of the leg members. It comprises a vertical support member or stilt 1, perpendicular to said transverse beam 6, of metal or equivalent material, preferably of steel, e.g. of stainless steel, or of aluminium. The support 1 is connected at its upper end perpendicularly to a round tube 3. The tube 3 is fitted inside a second round tube 4 of slightly larger diameter, preferably so that it may revolve freely inside this larger tube. Furthermore, the tube 4 is connected with a suitable method, for instance by welding, to the transverse beam 6. At its lower end the support 1 is connected to the beam 7 via a pivotal shaft 8, 9. In practice, this is carried out by securing, e.g. by welding, a bushing to the lower part of support 1, said bushing being fitted around a shaft 8, attached to the beam 7 as shown in Figure lb. The upper surface and the sides of the beam 7 are provided with notches so that the stand 1 may incline, supported by the ends of the bushing 9, by an angle of about 5...60°, preferably about 30°, referenced to the vertical position, as shown by the dashed lines in Figure la. A locking brace element 10 is pivotally attached to the beam 7 and the support 1. The brace is provided with pivots 11 and 12. The brace is locked to the beam 1 with a locking means, such as a lock pin 13, when the load is supported by the storage stands. The foot of the locking brace 10 is fitted to move in a gliding slot 14, fabricated into the side of the stand 1. When desired, into the support 1 can be fitted a spring 15, which is attached at its one end to the support 1 and at its other end to the locking brace 10, preferably at the end which is fitted into the glide slot 14. Instead of the spring 15 another suitable damping element, such as a shock absorber, may also be used.

Figure 3 shows a situation in which the piece goods 18 are supported by the transverse beams 6 of the stands such that their leg members 4 form the contact faces against the base. driven A transportation bed 17 has been underneath the goods 18 in its longitudinal direction. whereby the bed 17 is also underneath the transverse beams 6.

A pulling bar 19 is attached to the leg member of one of the storage stands. Next, a force in the direction of arrow A is applied to the upper end of the stands via the pulling bar 19, moving the transportation bed forward in the direction of arrow A. Pivoting around the pivotal shaft 8, 9, the stands are inclined by about 30...40°, and under the influence of the pulling force, the goods 18, leaning on the stands, are forced into a movement directed forwards and downwards, the radius of curvature of the path of movement being the distance between the pivotal shaft 8, 9 and the upper surface of the transverse beam 6.

When the stands reach a position in which inclination of the goods proceeds in an accelerating manner (Fig. 4), the inclination speed is attenuated by braking the movement of the vehicle. Now, the braking force is transfered to the pull bar 19, connecting the load to the transportation bed 17, thereby preventing an accelerating inclination. By installing into the stand 1 of the storage support 1 a spring 15, the attenuation of the inclinational movement of the supports is assisted.

When the goods have reached the position shown in Figure 5 and thus have been transferred onto the transportation bed 17, the leg members are detached from the transverse beam by detaching the tube 3 from the tube 4. In a preferred embodiment of the stand, the tube 3 and the leg member connected to it is rotable relative the transverse beam 6, whereby a maximum contact face is maintained between the goods ;H and the transverse beam 6 throughout the entire transfer movement and it is ensured that the goods remain steadily in support on the transverse beams 6 on the transportation bed. The upper and lower surfaces of the transverse beam 6 are in this case preferably parallel and plane.

In the method in accordance with the invention, a stand shown in Figure 6 may also be used, having support 21 attached to a beam 22 via a pivotal shaft 23, 24 in the manner described above. The locking brace 25 is provided with a shock absorber or spring-loaded piston which is fitted into a cylinder. Also in this case the locking brace is attached at its both ends via pivots 26, 27 to the vertical suppport 21 and the beam 22, respectively. The brace 25 can be locked to its place by a locking pin 28. When a stand construction of this type is used, especially the initial phase of the inclination movement can be extremely effectively attenuated by a shock absorber or spring 29.

A third possible embodiment is shown in Figure 7 in which a vertical support 31 and one leg of a beam 32 are welded together, forming an L-shaped support as a side view. The other leg of the beam 32, which is located in the inclination direction, is attached to the support via a pivot 33. Said leg is shaped such that it is at least slightly curving upwards, and to ensure the stable standing of the support, the underside of the leg is provided with a wedge bushing 36. The part of the leg facing the L-shaped support is skew. The wedge-shaped slot between the support and leg is provided with a locking wedge 34. The wedge must be removed before the support is brought into the inclination movement.

The radius of curvature of the surface of the leg, which is rotated supported by the pivotal shaft, is preferably variable in order to prevent an accelerating inclination. When the support is inclined tilted in the manner shown in Figures 3...5, the curved leg operates as a rocking chair, and the stand transfers the load by a tilt, remaining, however, in a standing position after the tilt.

Without diverging from the scope of the invention, the method can be carried out in several different ways. Thus, the transportation bed may be driven to underneath the load in its transverse direction by driving the bed only under the load, not under the load-supporting transverse beams. By directing a pulling or pushing force to the load, as described above, the load can be shifted onto the transportation bed so that it remains transversely on the bed. In this case the storage stands are not left under the load and need not be dismantled for removal. The load may also remain on supports ready installed on the transportation bed, whereby, after the leg parts have been detached, the transverse beams can also be removed from the transportation bed.

A final reference should be made to point out the applicability of the invention to the storage and transfer of internationally standardized containers.