CONVEYING SYSTEM

Abstract: The present invention relates to a conveying device comprising two parallel conveyor tracks, each having a stationary supporting member (48, 49) with a support surface for bearing a load and a lifting slide (44) which is displaceable along the conveyor track, which lifting slides having a lifting surface are displaceable between a release position situated beneath the support surface and a lift position situated above the support surface, as well as a first drive mechanism for displacement of the lifting slides along the respective conveyor track and a second drive mechanism for displacement of the lifting surface between the release position and the lift position. The lifting slides are preferably of pneumatic construction and comprise a U-shaped profile (50) having two side walls and, suspended between them, a running wheel, a cap embracing the U-shaped profile, and a flexible fluid line, lying between the cap and the profile, for the expansion-induced mutual displacement of the cap and the profile. With the conveying device according to the present invention, a large number of different loading and unloading operations can be executed rapidly and efficiently for the loading and unloading of lorries, containers or other loading spaces.

Description: Conveying system. The invention relates to a conveying system comprising two parallel conveyor tracks, each having a supporting member with a support surface for bearing an object and a lifting slide which is displaceable along the conveyor track, which lifting slides having a lifting surface are displaceable between a release position situated beneath the support surface and a lift position situated above the support surface, as well as a first drive mechanism for displacement of the lifting slides along their respective conveyor track and a second drive mechanism for displacement of the lifting surface between the release position and the lift position. The invention additionally relates to a conveying device for use in such a conveying system. A conveying device of this type can be obtained, for example, from the company Rolamat Ltd., Hampshire, UK, under the designation "Rolaload". This known conveying device for loading and unloading lorries comprises two parallel rails in which the lifting slides are mounted such that they are movable in the longitudinal direction. Situated between the rails is a rotary slat conveyor. At the ends of the rails there is a coupling device to which the rear of a semitrailer can be coupled and aligned relative to the rails. In the loading process, the load is brought by the slat conveyors to the ends of the rails, after which the lifting slides are brought into a lift position so that the load is lifted free from the slat conveyors. The lifting slides are next slid over the rails and brought into the loading space, so that the advanced load is transferred into a semitrailer, for example. In the loading space, the lifting slides run through aluminium chutes and, upon reaching the rear wall of the loading space, are withdrawn in these chutes to beneath the floor of the loading space to their release position. The load is thereby supported on the floor of the loading space and the lifting slides are able to be withdrawn from the loading space. The known device has the drawback of being relatively complex through the use of two different conveying systems in the form of the traversable lifting slides and the rotary slat conveyor. With the known device, furthermore, it is not possible to position the goods of the load one to another on the conveying device and to group them. In addition, the known device is not suitable for conveying a stream of goods which is advanced transversely to the conveying device. 2 An object of the present invention is to provide a conveying device in which these drawbacks are eliminated. To this end, the conveying device according to the present invention is characterized in that the support surfaces are of stationary construction and in that the device is provided with a control unit which is connected to the first and the second drive mechanisms and which is set up to execute cyclically the following steps: a activation of the second drive mechanism for placement of the lifting slides into the lift position, b activation of the first drive mechanism for displacement of lifting slides along the conveyor tracks over a first length of displacement which is relatively small in relation to the length of the conveyor track, c deactivation of the second drive mechanism for placement of the lifting slides into the release position, d activation of the first drive mechanism for displacement of the lifting slides in an opposite direction to the direction of displacement in step b, over a virtually equal distance, and the control unit possibly being set up, after a number of cycles a to d: e to activate jointly the first and the second drive mechanisms for the displacement of the lifting slides over a second length measuring at least three times the length of displacement of step b. In the conveying system according to the prior art, the lifting slides are not operative when the load is supported on the support surface, which in this case is formed by the rotary slat conveyor. In contrast, the support surfaces according to the present invention are of stationary construction. Periodic lifting motion of the lifting slides, displacement of the lifting slides with a small stroke and the re-withdrawal to the release position allow the step-by-step displacement of differently shaped goods such as, for example, paper rolls, barrels, rolling containers, closed-bottomed pallets, open-bottomed pallets, etc. Once a complete load has been placed on the lifting slides, it can be brought into the loading space by a long stroke of the lifting slides. With the conveying system according to the present invention, goods which are advanced with interspaces, for example over a roller conveyor, transversely to the direction of conveyance can be placed one against the other and can be loaded, in mutual contact, into a loading space. It is likewise possible to group the goods of the 3 load one to another with predetermined interspaces and to place the grouped load in its entirety into a lorry, for example. In addition, goods which have been placed one against the other are spaced apart as they are unloaded and are transported away transversely to the direction of conveyance. With the conveying system according to the present invention, a vast amount of freedom in conveyance operations is obtained, using a reliable and simple conveying device. The conveying system according to the invention preferably comprises at least one conveyor situated transversely to the conveyor tracks and having an end part, of predetermined width, extending between the lifting slides, each lifting slide comprising at least a first and a second segment, the second segments lying close to the conveyor and, in terms of length, at least matching the width of the conveyor, the first and the second segments each being provided with separate and independently operable second drive mechanisms. With the aid of the short and long segments which are displaceable in mutual independence between a lift position and a release position, goods of a load which have been placed one against the other, such as pallets, for example, can be spaced apart and delivered one by one to the cross-conveyor. The short and long segments are moved jointly to and fro in the direction of conveyance. For the loading or unloading of a loading space and for the supply or removal of a number of goods, placed one against the other, respectively to and from the cross- conveyor, the control unit according to the invention is set up to execute cyclically the following steps. For the loading of goods into the loading space: f placement of both segments into the release position and displacement of the segments to the conveyor, g placement of one of the segments into the lift position and displacement of both segments from or to the conveyor until the article to be taken over or taken over from the conveyor butts against the following article on the lifting slides, and h placement of both segments into the lift position and joint displacement from the conveyor. For the unloading of goods from the loading space: i placement of both segments into the lift position and displacement of the segments to the conveyor, j placement of one of the segments into the release position and displacement of 4 both segments from or to the conveyor until a free space has been formed between the article lying closest to the conveyor and the following article, and k placement of both segments into the release position and joint displacement from the conveyor. In the loading process, the short segment is used to bridge the mutual spacing of the products of the load in the direction of conveyance, before pushing the abutting load jointly along the conveyor track to inside the loading space in a single step. In the unloading process, the short segment is used to individualize the abutting load and to free the foremost goods from the products behind before transferring them to the cross-conveyor. A further device according to the invention comprises a lifting slide which is constructed as a downwardly open U-shaped profile having two side walls and, suspended between them, a running wheel, a cap embracing the U-shaped profile, and a flexible fluid line, lying between the cap and the profile, for the expansion-induced mutual displacement of the cap and the profile. In this way, a simple and robust lifting slide is formed. By virtue of a relatively large diameter of the running wheel, such as, for example, at least 70 mm, the displacement thereof is relatively insensitive to dirt and small particles on the running surface. By using the flexible fluid line, such as, for example, a 2 inch fire hose, a powerful lifting motion of the cap relative to the running wheel can be realized. Furthermore, the cap and the profile are preferably each provided with a stop for a force- limited lifting stroke of the cap of 25 mm, for example, relative to the U-shaped profile. The stop of the U-shaped profile can be bevelled, so that the stop of the cap, by being tilted, can be manually displaced along the stop of the U-shaped profile. The simple detachability of the cap by a simple manual tilting along one side makes the maintenance of the parts between the cap and the profile very simple. The U-shaped profile is further provided with a space for receiving/accommodating electric leads and/or of a fluid supply line connected to the fluid line. The electric leads can be connected, for example, to a pressure sensor located at the end of the lifting slides to determine when the continuous motion of the lifting slides has been blocked, for example by them having reached the end of the loading space. The U-shaped profile can further be provided on a side wall with a slot lying parallel to the side wall, the profile being fastened, close to the top part of the slot, to 5 a chain running through the slot, and the device comprising a chain wheel engaging on the chain and reaching into the slot. Furthermore, guide members reaching into the slot can be fitted along the conveyor tracks to ensure an accurate horizontal position of the lifting slides. The guide members can be formed, for example, from right-angled pro- files, one arm of which forms a running surface for running wheels of the lifting slides. The conveying device can further be provided with a motor as the first drive mechanism, having a drive shaft lying perpendicular to the conveyor track, with thereupon a chain wheel, a roller or pulley with a continuous belt or chain around it, the motor being fastened by spring elements to a mounting and containing a stop, the motor being displaceable relative to the mounting, in the direction of the conveyor track, until the stop butts against the mounting. The spring-fastening of the motor allows an axial displacement of the motor reduction gearbox, for example, which displacement is equal to the distance between two links of chain wheels gripping the drive chain. An alignment facility of this nature is important if a plurality of drive motors are used along the conveyor track and if the narrowly tolerated engagement of the chain wheels over large lengths, which can amount, for example, to three times the total length of the conveying device, cannot be achieved through synchronization or electronic control systems. Finally, it is possible mutually to connect two parallel lifting slides at their end faces to a hinged connecting member for mutual stability. The connecting member can be of hollow construction and can comprise electric leads and a fluid line. In order, however, to be able to make the lifting slides reach beneath an open-bottomed pallet and to allow the supply of goods via the end face of the device, the cross-connection can be tilted downwards along a hinge point so that the end parts of the lifting slides can reach between the supporting beams of a pallet or can reach beneath an object advanced along the end face. The various aspects of the conveying system according to the present invention will hereinafter be described in detail, by way of example, with reference to the appended drawing, in which: Figures la and lb show respectively a side and top view of a conveying device according to the present invention, which is constructed as a combined unloading and loading system, 6 Figure 2 shows a lateral cross section along the line II-II in Figure lb, Figure 3 shows a cross section through an alternative conveying device in which the ends of the lifting slides are supported on the rollers of the cross-conveyor, Figure 4 shows a partial side view of a fold-away end part of the conveying device, Figure 5 shows a cross section through a lifting slide according to the present invention, Figure 6 shows the removal of the cap of the U-shaped profile of the lifting slide, Figure 7 shows a lifting slide provided with alignment means, Figure 8 shows a schematic top view of a lifting system having lifting slides with short and long segments to be placed independently into a lift position, Figures 9a and 9b show two alternative ways of loading using a conveying device according to Figure 8, Figures 10a and 10b show two alternative ways of unloading using a conveying device according to Figure 8, Figure 11 shows a pneumatic plan of a conveying device, the lifting slides comprising a short and a long segment, Figures 12a to 12c show the application of the system according to the present invention in the conveyance of roller containers, and Figure 13 shows a partial cross sectional view of a spring-supported drive mechanism of a conveying system according to the present invention. Figure la shows a side view of a conveying device 1 having a frame 2 over which goods 3 are displaceable in a loading and unloading direction L. The goods 3 can comprise a load carrier 4 such as, for example, a pallet or a slipsheet bearing products 5 packed in boxes or foil. The goods 3 can likewise be formed by roller containers or other load carriers which are commonly used in transportation. On the front side 7 of the conveying device 1 there is an alignment member 6, in which a coupling piece of a semitrailer can be placed. The alignment member 6 is provided with a slope, so that a semitrailer of this type is lifted out of its springs and can be stably positioned on the front side 7 of the device. As shown in Figure lb, the device 1 which is herein described is provided with a pair of cross-conveyors 8, 9 in the form of driven roller conveyors which are dis- 7 posed on the front side 7 and on the rear side 10 of the device. The device 1 comprises two pairs of parallel-disposed conveyor tracks 12, 13, 12', 13'. Each conveyor track 12, 13, 12', 13' comprises a U-shaped chute and one or more lifting slides which are displaceable to and fro in the chute. The vertical rims of the chute form a station- ary support surface, whilst the lifting surface of the lifting slide can be displaced to above or below the support surface. The cross-conveyor 8 is driven by a motor 14 in the direction of the arrow TI. The lifting slides of the conveyor tracks 12, 13; 12', 13' are driven by a motor 15 in a direction of the arrow T2, as well as in a direction opposite thereto. The cross-conveyor 9 is driven by a motor 16 in the direction of the arrow T3. The lifting motion of the lifting slides of the conveyor tracks 12, 13, 12', 13' is driven by a drive mechanism 17, for example in the form of a compressor and a pneumatic gate. The motors 14, 15 and 16, as well as the gate of the compressor 17, are operated by a control unit 18, which determines the direction and the displacement stroke of the lifting slides of the conveyor track 12, 13, 12', 13' parallel to the direc- tion T2, as well as the height of the lifting stroke of the lifting slides and the phase of the lifting motion relative to the longitudinal displacement. With the device according to the present invention shown in Figures la and lb, the load 20 can be unloaded from a lorry which is docked onto the front side 7 against the device 1. To this end, the lifting slides of the conveyor tracks 12, 13, 12', 13' are slid in their lowest release position past the front side 7 of the device until they are extending fully into the loading space of the lorry. The lifting slides are subsequently activated by means of the compressor 17 and are withdrawn until the load 20 is at the position, represented by a dashed line, on the rear side 10 of the device. Step-by-step displacement, to and fro, of the lifting devices of the conveyor tracks 12, 13, 12', 13' allows the load 20 to be delivered row by row to the cross-conveyor 9 and to be transported away in the direction of the arrow T3. At the same time, the load 21 can be advanced by means of the cross-conveyor 8 and then placed on the device 1 and the emptied lorry 7 can subsequently be loaded with the new load 21 by placing the lifting slides of the conveyor tracks 12, 13; 12', 13' fully within the loading space of the lorry. Although the device in Figures la and lb is described with reference to a combined loading and unloading system having a pair of cross-conveyors 8, 9, it is likewise possible for the system according to the present invention to be constructed 8 with a single cross-conveyor 8 on the front side 7 or with a single cross-conveyor 9 on the rear side 10. Furthermore, it is likewise possible according to the invention to use the device with supply conveyors present in the continuation of the conveyor tracks 12, 13, 12', 13'. The automatic loading or unloading according to the present invention results in many working hours being saved, whilst there is no need, moreover, to employ expensive tools such as forklift trucks and the like. The automatic handling of the goods serves to prevent any damage to the products. Furthermore, the waiting time for the lorries and drivers is shortened and a high throughput can be achieved, so that a factory or warehouse can work with fewer conveying devices for processing the same quantity of goods, thereby enabling savings to be made on costs and buildings. Figure 2 shows a cross sectional view, transversely to the direction of conveyance T2, of the conveyor tracks 12, 13 in Figure lb. As is apparent from Figure 2, all conveyor tracks 12, 13 comprise a chute 25 having vertical rims 26, 27, the top surfaces 28, 29 of which form a support surface for the load, which in this case is formed by a pallet 30. The lifting slide 23 present within the chute 25 is shown in its release position situated beneath the support surfaces 28 and 29, whilst the lifting slide 24 is shown in a lift position situated above the support surfaces 28, 29. As is apparent from Figure 2, the rollers 31 of the cross-conveyor 9 extend between the conveyor tracks 12 and 13. This means that when the lifting slides 23, 24 are placed into the lift position, the pallet 30 can be lifted above the rollers 31. By bringing the lifting slides 23, 24 into the release position, as is represented on the left-hand side of Figure 2, the pallets 30 are able to be supported on the rollers 31 and are transported away transversely to the direction of conveyance in the direction of the arrow T3. The arrangement of the conveyor tracks 12, 13 according to Figure 2 is suitable for the displacement of closed-bottomed objects, such as pallets. For the displacement of open-bottomed objects such as Europallets 32, for example, as shown in Figure 3, different pairs of lifting slides 34, 35 and 36 are disposed so as to fall between the chocks of the pallets 32. In view of the fact that the Europallets 32 cannot be displaced by means of the rollers 37 of the cross-conveyor, a chain 38 is provided to displace the pallets in the direction of the arrows T3. The distance between mutually opposing parts of the chain 38 is somewhat smaller than the diameter of the rollers 37. Recessed in the rollers 37 are circumferential slots, in which the chain 38 is situated. 9 During the displacement of the pallets in the direction of the arrow T3, the lifting slides 34, 35 and 36 are withdrawn in the direction lying out of the plane of drawings. The chutes of the conveyor tracks do not extend above the rollers 37 of the cross-conveyor. Once the pallets 32 are in a correct position, the lifting slides 34, 35 and 36 are displaced over the rollers 37, into their release position, and brought to beneath the pallets. The lifting slides are next brought into their lift position and the pallets are able to be conveyed perpendicular to the plane of drawing. A lateral displacement of the conveyor tracks and a height- adjustment of the cross-conveyor such that the lifting slides 34, 35 and 36 are situated above the rollers 37 or fall there or in- between enables the system to be used for loading and unloading both closed-bottomed articles and open-bottomed articles. As shown in Figure lb, the lifting slides are mutually connected on the rear side 10 by means of a connecting member 40 in order to increase the lateral stability of tne lifting slides. Should the lifting slides 34, 35 and 36 need to be introduced between chocks of the pallets 32, as shown in Figure 3, the connecting member 40 has to be hinged downwards. Furthermore, the connecting member 40, comprising a sleeve, for example, allows connecting lines for power supply and pneumatics or hydraulics to be laid for each conveyor track 12, 13, 12', 13'. As shown in Figure 4, the conveyor tracks 12, 13, 12', 13' are provided on the rear side 10 with a hinge point 41 for folding away the connecting member 40. This hinged construction is also useful whenever the pallets are advanced to the top side of the device instead of transversely to the direction of conveyance as shown in Figure lb. Figure 5 shows a cross section, on enlarged scale, of a conveyor track 42 according to the present invention, having a chute 43 in which a lifting slide 44 is displaceably disposed. The chute 43 is provided with a bottom which forms a running surface for the running wheel 45 of the lifting slide 44. The two vertical side walls 46, 47 form with their top sides 48, 49 a support surface for the stationary supporting of articles to be displaced. The lifting slide 44 comprises a U-shaped profile 50, in which the axle 51 of the running wheel 45 is mounted. Over the U-shaped profile 50 is placed a movable cap 52, a top side of which forms a lifting surface 53 for engaging on the bottom side of the goods to be conveyed. Between the cap 52 and the top side 54 of the U-shaped profile 50 lies a fluid line 55, such as, for example, a 2 inch fire hose. Through the pressurization of the fluid line 55, the cap 52 is displaced with a 10 stroke of 2.5 centimetres, for example, relative to the U-shaped profile 50. Fitted to the bottom side of the cap 52 is a stop 56, which in the maximum height position of the cap butts against a stop 57 on the outer wall of the U-shaped profile 50. The profile 50 further comprises on the left side a space 58, on the top side a chamber being formed in which a chain 59 is situated. The U-shaped profile 50 is fastened firmly to the chain 59. A chain wheel 60 reaches into the space 58 and engages on the chain 59 for displacement of the lifting slide 44. On the bottom side, the U-shaped profile 50 is provided with two flanges 61, 62, which reach beneath cams 63, 64 on the side walls 46, 47. A stable vertical posi- tioning of the U-shaped profile 50 in the chute 43 is thereby obtained. Recessed in the U-shaped profile 50 are spaces for receiving/ accommodating electric cables 65,66 and for an air hose 67. Along the electric cables 65, 66, signals originating from a pressure sensor present on the front side 7 can be fed, for example, to the control unit 18. Furthermore, different segments from which the lifting slides are able to be constructed are able to be provided with compressed air by means of the air hose 67. Figure 6 shows that the cap 52 of the lifting slide 44 can easily be removed by being manually tilted. To this end, the stop 57 is provided with a bevel 70 along which the stop 56 can be moved, when the cap 52 is tilted around the stop 56', once the latter butts against the stop 57' of the U-shaped profile 50. In this way, access is gained to the fluid line 55, as well as to the electric leads 65 and 66, which, in the embodiment shown in Figure 6, are somewhat different from in the embodiment according to Figure 5. Finally, Figure 7 shows an embodiment in which the slot 58 of the U-shaped profile 50 receives a guide member 71 in the form of a right-angled profile, one arm of which serves as a running surface 72 for the running wheel 45 of the lifting slide 44. The running wheel 45 can be formed, for example, by a standard pallet roller which, by virtue of its design and small structural height, can absorb a maximum load and is also low on maintenance. The running surface of the running wheel 45 is inci- sion-proof and has a low rolling resistance. Figure 8 shows a schematic representation of a system according to the present invention for loading and unloading a lorry 73, in which the lifting slides 74 and 75 are each divided into a first segment 76 and a second segment 77. Displacement of the 11 lifting slides of both segments 76 and 77 in the direction of conveyance L is effected simultaneously by means of a single drive motor 78, commanded by the control unit 79. Furthermore, each segment 76 and 77 is driven separately in the direction of lift H, for example by separate compressors 80, 81 or by means of a single compressor and a controlled gate. Furthermore, the cross-conveyor 83 is driven in the direction of conveyance T by means of a drive motor 84. The length of the short segments 77 essentially matches the width of the cross-conveyor 83. Figure 9a shows a first way in which the control device 79 commands the lifting slides of the short segment 77 and of the long segment 76 in the direction of lift H and in the direction of displacement L in order to load a lorry 73. The goods are fed over the cross-conveyor 83 to the short segments 77. As is shown in step 1 of Figure 9a, both segments 77 and 76 are brought into a lift position and subsequently conveyed to the right. The product I is thereby brought to the position as shown in step 2 of Figure 9a. The stroke of the displacement is in this case somewhat greater than the length of the shorter segment 77. A new product II is aligned by the conveyor 83 with the conveyor tracks of the lifting slides 74 and 75. From position 2 in Figure 9a, both the short and the long segment 77 and 76 are brought into a release position and moved back to the left, as represented in position 3 of Figure 9a. The short segment 77 is subsequently brought into its lift position, so that the product II lifts up from the support surface. After this, the long segment 76 and the short segment 77 move jointly to the right until the product II butts against the product I. The long segment 76 is next brought into its lift position, so that the mutually abutting products I and II are conveyed jointly to the right. As shown in step 6 of Figure 9a, a new product III is next aligned with the conveyor tracks of the lifting slides 74 and 75. The steps 2 to 6 of Figure 9a are subsequently repeated until the number of products on the conveyor tracks matches the length of the loading space of the lorry 73. Once this is so, all abutting products are displaced jointly to the right with one large stroke of both segments 77 and 76, so that all products are brought jointly into the loading space of the lorry 73. After this, both segments are returned to the release position and fully with- drawn, after which the process can be repeated. Figure 9b shows an alternative way of loading a lorry 73, in which the long segment 76 and the short segment 77, in step 1, both move to the right into the lift position so that a new product II can be brought into a conveying position, as shown 12 for position 2 of Figure 9b. Both segments 76, 77 are subsequently placed into the release position and moved to the left. After this, in step 4 of Figure 9b, the long segment 76 is brought into its lift position and both segments are subsequently moved to the left until the goods I and II butt one against the other, as shown in position 5 of Figure 9b. From this state, the short segment 77 is next brought into its lift position and the products I and II are conveyed jointly to the right as far as the starting position 6, where a new product III is placed into a conveying position. The steps 2 to 6 of Figure 9b are subsequently repeated. Figure 10a shows a first embodiment of a method for unloading a lorry 73 as shown in Figure 8. First of all, the goods I-III are brought out of the loading space of the lorry 73, both segments 76 and 77 being in their lift position and being displaced to the left with a relatively long stroke. As shown in step 2 of Figure 10a, the short segment 77 is next brought into the release position and both segments 76, 77 are subsequently displaced to the right, as shown in step 3. The released product I can subsequently be transported away via the cross-conveyor 83, as shown in Figure 8. The two segments 76, 77 are placed beneath the following products II, III as shown in position 4 and are subsequently placed back into a lift position as shown in position 5 of Figure 10a. After this, the segments are displaced to the left as far as the starting position as shown in step 6 of Figure 10a and steps 2 to 6 are repeated again until all products have been transported away. In the unloading procedure which has been described here, the control device 79 can drive the conveyor 83 such that this is energized at the moment of step 3 of Figure 10a. The conveyor 83 can thus be driven intermittently. Figure 10b shows a following embodiment for unloading a loading space of a lorry 73, in which the cross-conveyor 83 can be driven continuously. In step 1, all products I-III are first removed from the loading space 73, butting one against the other, by means of a long displacement stroke of both segments 76, 77, which are in a lift position for this purpose. In step 2, the long segment 76 is next placed into its release position and, after this, both segments are brought to the left as shown in step 3. The product I is thereby placed above the cross-conveyor 83. The short segment 77 is next placed into its release position as shown in Figure 4, so that product I is supported on the rollers of the cross-conveyor 83 and is thereby removed. Both segments 77 and 76 subsequently withdraw into their release position to position 5 of Figure 13 10b. After this, they are both returned to the lift position and displaced to the left, as shown in position 6 of Figure 10b. It will be clear to the person skilled in the art that a large number of different loading and unloading operations can be effected by the correct programming of the command unit 79. By fitting a pair of cross-conveyors as shown in the construction according to Figures la and lb, as well as by having a shorter segment of the lifting slides present close to each cross-conveyor, it is thus possible, for example, to carry out a combined loading and unloading operation. It is further possible to divide the conveying device according to the invention into a plurality of segments which can all be moved independently between a release and a lift position. Figure 11 shows a pneumatic plan for operation of the long and short segments of a conveying device according to the invention, in which the lifting motion of the lifting slides is obtained with a short hose section 91 and a long hose section 92. Through a reducing valve 93, compressed air is fed to an electrically operated three/five gate 94. The three/five gate 94 is connected by a vent valve 95 to the long hose sections 92, 92' of each of the lifting slides situated along a conveyor track. Via a line 96, respective vent valves 97, 97' of the short sections 91, 91 ' are connected to the three/five gate 94. In the shown middle position of the gate 94, both the long and the short hose sections 91, 91 ', 92, 92' are ventilated via the respective lines 96 and 98. In the lowermost position of the gate 94, the line 96 is ventilated and the line 98 is connected to the reducing valve 93. The long hose sections 92, 92' are hereupon pressurized whilst the short hose sections 91, 91' are ventilated. In the uppermost position of the gate, the line 98 is ventilated and the line 96 is connected to the reducing valve 93, so that the short hose sections 91, 91 ' are pressurized and the long hose sections 92, 92' are ventilated. The position of the three/five gate 94 is in this case determined by the microcomputer in the control unit 18, 79. The operating pressures of the short and long sections 91 and 92 measure between 1 and 4 bar. Figures 12a to 12c show a conveying device according to the present invention, in which the lifting slides 100, 101 are displaced over running surfaces 102, 103 measuring virtually twice the length of the lifting slides. To this end, two motors 104, 105 are included in order to be able to displace the lifting slides 100, 101 along the entire path. Figure 12a shows how the system according to the present invention can be 14 used to transfer a load 106 of a first dock 107 to a second dock 108. The load 106 can here be formed, for example, by roller containers, which, on the front side 109, are displaced transversely to the direction of conveyance using, for example, a forklift truck 110. Figure 12b shows how the system according to the invention can be used to transfer a load to a waiting position. Figure 12c shows how, with the system according to the invention, a first load 110 can be brought into a loading space whilst on the stationary part of the conveying device a second load 111 is being grouped pending completion of the loading. Where a pair of drive motors 104, 105 are used, as shown in Figure 12a, the chain wheels of each motor 104, 105 need to engage precisely in the chains fastened to the lifting slides. The second drive 105 in Figure 12a has to take over driving the motor 104 once the lifting slides 100, 101 pass out of the range of the motor 104. In order to facilitate the engagement of the chain wheels on the links of the chain, the motor 105, as shown in Figure 13, is spring-fastened to a mounting 116. As is shown in Figure 13, the chain wheel 117 by which the lifting slide 118 is driven is fastened to the drive shaft 119, which is connected to the motor 105 by a reduction gearbox 111. The reduction gearbox 111 and the drive shaft 119 are connected by the spring elements 120, 121 and 122 to a respective mounting 116, 116'. The reduction gearbox 111 comprises a stop 123, which, whenever there is an angular twisting of the motor around the centre line of the drive shaft 119 equivalent to the distance between two successive links, butts against the mounting 116, after which the full drive force is applied to the shaft 119. It will be clear that the present invention is not limited to the examples described above and that various changes and modifications can be made by the person skilled in the art without breaching the scope of the present invention.

Claims: 15 Claims 1. Conveying system comprising two parallel conveyor tracks, each having a supporting member with a support surface for bearing an object and a lifting slide which is displaceable along the conveyor track, which lifting slides having a lifting surface are displaceable between a release position situated beneath the support surface and a lift position situated above the support surface, as well as a first drive mechanism for displacement of the lifting slides along their respective conveyor track and a second drive mechanism for displacement of the lifting surface between the release position and the lift position, characterized in that the support surfaces are of stationary construction and in that the conveying device is provided with a control unit which is connected to the first and the second drive mechanisms and which is set up to execute cyclically the following steps: a activation of the second drive mechanism for placement of the lifting slides into the lift position, b activation of the first drive mechanism for displacement of lifting slides along the conveyor tracks over a first length of displacement which is relatively small in relation to the length of the conveyor track, c deactivation of the second drive mechanism for placement of the lifting slides into the release position, d the activation of the first drive mechanism for displacement of the lifting slides in an opposite direction to the direction of displacement in step b, over a virtually equal distance, and the control unit possibly being set up, after a number of cycles a to d: e to activate jointly the first and the second drive mechanisms for the displacement of the lifting slides over a second length measuring at least three times the length of displacement of step b. 2. Conveying system according to Claim 1, characterized in that the relatively small length of displacement in step b matches a dimension of an object to be dis- placed and the second length of displacement in step e matching the dimension of a loading space to be loaded. 3. Conveying system according to Claim 1 or 2, characterized in that it comprises at least one conveyor situated transversely to the conveyor tracks and having an end 16 part, of predetermined width, extending between the lifting slides, each lifting slide comprising at least a first and a second segment, the second segments lying close to the conveyor and, in terms of length, at least matching the width of the conveyor, the first and the second segments each being provided with separate and independently operable second drive mechanisms. 4. Conveying system according to Claim 3, characterized in that the control unit is set up to execute cyclically the following steps: For the loading of goods into a loading space: f. placement of both segments into the release position and displacement of the segments to the conveyor, g. placement of one of the segments into the lift position and displacement of both segments from or to the conveyor until the article to be taken over or taken over from the conveyor butts against the following article on the lifting slides, and h. placement of both segments into the lift position and joint displacement from the conveyor, and for the unloading of goods from a loading space: i. placement of both segments into the lift position and displacement of the segments to the conveyor, j. placement of one of the segments into the release position and displacement of both segments from or to the conveyor until a free space has been formed between the article lying closest to the conveyor and the following article, and k. placement of both segments into the release position and joint displacement from the conveyor. 5. Conveying device for use in a conveying system according to one of the pre- ceding claims, the lifting slide comprising a downwardly open U-shaped profile having two side walls and, suspended between them, a running wheel, a cap embracing the U- shaped profile, and a flexible fluid line, lying between the cap and the profile, for the expansion-induced mutual displacement of the cap and the profile. 6. Device according to Claim 5, characterized in that the profile on an external surface of the side walls and the cap on an internal surface are each provided with a stop, which stops butt against each other whenever an outermost lift position of the cap is attained. 7. Device according to Claim 6, characterized in that the stop of the U-shaped 17 profile is bevelled, so that the stop of the cap can be manually displaced along the stop of the U-shaped profile by tilting of the cap. 8. Device according to Claim 5, 6 or 7, characterized in that in the profile a space is made for receiving electric leads and/or a fluid supply line connected to the fluid line. 9. Device according to Claim 5, 6, 7 or 8, characterized in that the U-shaped profile is provided on a side wall with a slot lying parallel to the side wall, the profile being fastened, close to the top part of the slot, to a chain running through the slot, and the device comprising a chain wheel engaging on the chain and reaching into the slot. 10. Device according to Claim 9, characterized in that guide members reaching into the slot are fitted along the conveyor tracks. 11. Device according to Claim 10, characterized in that the guide members comprise a right-angled profile, one arm of which forms a running surface for the running wheel of the lifting slide. 12. Device according to one of Claims 5 to 11, characterized in that the lifting slides are provided at their end with a pressure sensor, connected to the control unit, for switching off the first drive mechanism whenever the control unit receives a pressure sensor signal. 13. Device according to one of Claims 5 to 12, characterized in that the first drive mechanism comprises a motor having a drive shaft lying perpendicular to the conveyor track, with thereupon a chain wheel, a roller or pulley with a continuous belt or chain around it, characterized in that the motor is fastened by spring elements to a mounting and contains a stop, the motor being displaceable relative to the mounting, in the direc- tion of the conveyor track, until the stop butts against the mounting. 14. Device according to one of Claims 5 to 13, characterized in that the two parallel lifting slides are mutually connected at their ends by a connecting member situated transversely to the conveyor tracks, each lifting slide comprising, close to the connecting member, a hinge point for tilting downwards an end part of the lifting slides, which end part is coupled with the connecting member.

Inventors: VAN LEEUWEN CORNELIS JOHANNES, VAN LEEUWEN, CORNELIS, JOHANNES, LEONARDUS
Applicants: LEEUWEN CORNELIS JOHANNES LEON, VAN LEEUWEN, CORNELIS, JOHANNES, LEONARDUS
Application year: 1999
Main classification: B65G67
IPC codes: B65G1, B65G25, B65G67