LIFTING DEVICE FOR LIFTING AND/OR LOWERING AN ORDERED STACK OF ARTICLES

Abstract: Lifting device for lifting and/or lowering an ordered stack (S) of articles (V), which lifting device is intended for cooperating with an unstacking and/or stacking device and with a stack-feeding and stack-discharging conveyor respectively, the stacking device comprising first lifting means (1) and second lifting means (2), which first lifting means and second lifting means cooperate such that the device continuously keeps the uppermost article (Vt) of a stack (S) located in the lifting device at a fixed, desired level.

Description: Title: Lifting device for lifting and/or lowering an ordered stack of articles . The invention relates to a lifting device for lifting and/or lowering an ordered stack of articles, which lifting device is intended for cooperating with an unstacking and/or stacking device and with a stack-feeding and stack- discharging conveyor respectively. The device is particularly intended for an unstacking and/or stacking device in which the articles to be fed and discharged respectively are fed and discharged respectively from above. That stacks that are unstacked or, conversely, formed in the lifting device, are moved to the lifting device by a stack-feeding conveyor, respectively discharged from the lifting device by a stack-discharging conveyor. A problem involved in known lifting devices intended for cooperating with unstacking and/or stacking devices is that the unstacking and/or stacking process is interrupted when a complete stack has been unstacked or formed in the lifting device and a new stack is to be fed into the lifting device, or the stack formed is to be removed from the lifting device. In the known devices, during the feed or discharge of a complete stack to or from the lifting device, it is not possible to already continue the unstacking or stacking process for stacking or forming a next stack of articles. As a consequence, in the known lifting devices, the discharge of the articles removed from a stack, or the feed of a articles to be added to a stack to be formed cannot take place in a continuous manner. Such discontinuous discharge or feed of articles is generally undesired. The object of the invention is to provide a lifting device without the above-mentioned drawbacks. To this end, the lifting device of the type mentioned in the preamble is characterized in that the lifting device comprises first lifting means and second lifting means, which first lifting means and second lifting means cooperate such that the device continuously keeps an uppermost article of a stack located in the lifting device at a fixed, desired level. Due to the particular cooperation of the first lifting means and the second lifting means, the uppermost article of a stack located in the lifting device can, when the lifting device cooperates with an unstacking device, in each case be removed from the same place in a continuous manner. In this context, 'continuous' must at least be understood to mean 'at a fixed rhythm' . As soon as an article has been removed from the stack, the lifting means will move the stack located in the lifting device slightly upwards, causing a next uppermost article to be located at the fixed, desired level, whence that next article can then be removed again by the unstacking device. When the lifting device according to the invention cooperates with a stacking device, it applies that in each case, a next article can be placed onto the uppermost article of a stack located in the lifting device, which next article subsequently forms the uppermost article and which, by lowering the lifting means slightly, is brought to the fixed, desired level again. As the lifting device possesses first lifting means and second lifting means, a completely formed stack and a partially formed stack can simultaneously be located in the device. As a result, when the lifting device cooperates with an unstacking device, a second complete stack can be fed to the lifting device and received by the first lifting means, while the second lifting means support an already partially unstacked first stack, so that an uppermost article of this first stack is always kept at the desired fixed level. As soon as the first stack has been unstacked completely, the uppermost article of the second stack is moved to the desired fixed level, so that the unstacking procedure can be continued without interruption. In the meantime, the second lifting means can, after a passage of time, take over the second stack from the first lifting means, after which the first lifting means are moved into a position in which they are ready to receive a third stack. When the lifting device cooperates with a stacking device, the second lifting means can, after the formation of a complete stack located on the first lifting means, be moved into a po'sition in which they can receive the lowermost article of a second stack to be formed. In the meantime, the first stack formed can be discharged from the lifting device while the formation of the second stack is continued in a continuous manner. After the partial formation of the second stack, this stack is taken over from the second lifting means by the first lifting means, so that directly after the complete formation of the second stack, the second lifting means can be moved into a position in which they are ready to receive the lowermost article of a third stack. Summarizing, it can be stated that the presence of the first lifting means and the second lifting means enables a continuous unstacking and/or stacking process, which unstacking and/or stacking process need not be interrupted for feeding or discharging a complete stack of articles . In accordance with a further elaboration of the invention, it is particularly favorable when the first lifting means are constructed as a vertically adjustable lifting table and the second lifting means are constructed as lifting frames, the lifting table engaging a first area of a lower side of a lowermost article of the stack, the lifting frames in folded-down position engaging a second area of the lower side of the lowermost article of the stack, while the first area and the second area do not coincide, and the lifting frames in a folded-up position can pass a stack in vertical direction. Such embodiment of the lifting device can be realized in a relatively simple manner and can hence be manufactured in an economical manner. As the lifting frames can be brought from a folded-down position into a folded-up position, the lifting frames can pass an entirely or partially formed stack in vertical direction, which is important for causing the unstacking and/or stacking process to take place in a continuous manner. Further elaborations of the invention are described in the subclaims and will be specified on the basis of an exemplary embodiment, with reference to the accompanying drawings. Fig. 1 is a front view of an exemplary embodiment of the device in a first condition; Fig. 2 is a front view similar to Fig. 1, in a second condition; Fig. 3 is a front view similar to Figs. 1 and 2, in a third condition; Fig. 4 is a top plan view of the device shown in Figs. 1-3; and Fig. 5 is a left-side view of the lifting device shown in Figs. 1-3. The lifting device shown in Figs. 1-5 is intended for lifting and/or lowering an ordered stack S of articles V. In the present case, this concerns trays filled with eggs. However, it may also concern boxes of eggs or other articles to be stacked having a substantially rectangular section. The lifting device is in particular intended for cooperating with an unstacking and/or stacking device and with a stack-feeding and stack-discharging conveyor respectively. The lifting device comprises first lifting means constructed as a vertically adjustable lifting table 1 and second lifting means constructed as lifting frames 2. These lifting frames can likewise be adjusted upwards and downwards and can moreover assume a folded-down and folded- up position. The lifting table 1 engages a first area of the lower side of a lowermost article Vb of a stack S . In a folded-down position, the lifting frames 2 engage a second area of the lower side of the lowermost article Vb of the stack S, while the first area and the second area do not coincide. In the folded-up position, the lifting frames 2 can pass a stack S in vertical direction. As Fig. 4 clearly demonstrates, the lifting table 1 and the lifting frames 2 are of a construction such that the first area is formed by a central part of the lower side of the lowermost article Vb, while the second area is formed by a part of the lower side of the lowermost article Vb which part surrounds the central part . The lifting device according to the present exemplary embodiment comprises first drive means 3, 4 intended for adjusting the height of the lifting table 1 and second drive means 5, 6 intended for adjusting the height of the lifting frames 2. The first lifting means comprise a drive cam 3 controlling the position of the lever 4. The cam 3 is driven by a drive motor 7. The lever 4 has one end 4a thereof pivotally and/or slidably connected to a part which is fixedly connected to the lifting table 1. Rotation of the cam 3 causes a pivotal movement of the lever 4, which pivotal movement in turn results in a height adjustment of the table 1. The second drive means 5, 6 likewise comprise a cam 5 determining the position of a pivotally bearing- mounted lever 6. The lever 6 has one end 6a thereof pivotally and/or slidably connected to a part which is fixedly connected to the lifting frames 2. The position of the lever 6 and, accordingly, the vertical position of the lifting frames 2 is determined by the rotative position of the cam 5, which rotative position is in turn determined by the drive motor 7. The two cams 3 , 5 are mounted so as to be restrained from rotation on a common shaft 10 driven by a chain or belt 11, which is in turn driven by the motor 7. To provide that a complete stack S is completely supported when it is being slid into or out of the lifting device, a supporting element 8, 9 is preferably located on either side of the lifting table 1, at the level of the lowermost position of this lifting table 1. In the present exemplary embodiment, these supporting elements 8, 9 are designed as endless conveyors 8, 9 whose feed ends 8a, 9a are intended to connect to a stack-feeding and stack-discharging device respectively, such as for instance a conveyor belt. In the present exemplary embodiment, the drive of these endless conveyors 8, 9 is also connected to the drive motor 7, via chain wheels or pulleys and chains or belts cooperating therewith. It is thus effected that all movements of the lifting table 1, the lifting frames 2 and the endless conveyors 8, 9 are intercoupled. It is observed that instead of the endless conveyor belts 8, 9 as supporting elements, plate parts may also be used, extending on either side of the lifting table 1 so as to provide, with the lifting table 1, a supporting surface which fully supports the entire stack. When intended for cooperating with the unstacking device, the operation of the lifting device is as follows: When a first stack of articles is being fed into the lifting device, the lifting table 1 is in a lowermost position. If necessary, the lifting frames 2 can support the last article or the last few articles of a preceding stack and the lifting frames are virtually in the uppermost position. This position is shown in Fig. 1, in which the lifting table 1 is in the lowermost position and the lifting frames 2 are in an uppermost position, in folded- down condition. When the last article Vt of the preceding stack has been removed from the lifting frames 2, the lifting frames 2 are folded up and the lifting table 1 is moved upwards stepwise, so that in each case the uppermost article Vt can be removed from the stack S and it is provided that the uppermost article Vt of the stack S is always at the same fixed level. The meanwhile folded-up lifting frames 2 are moved to a level below the lifting table 1. This condition is shown in Fig. 2. Next, the lifting frames 2 can be folded down and moved up again for taking over the support of the stack S. This condition is shown in Fig. 3. In Fig. 3, the stack S is still supported by the lifting table 1, but the lifting frames 2 are about to take over the support of the stack S. Next, the lifting table 1 is moved down to the lowermost position, to be ready for receiving a next stack of articles, while the lifting frames 2 move up stepwise. The stepped upward movement of the lifting frames 2, too, takes place such that the uppermost article Vt of the stack S is always at the same fixed level at the right moment for the desired duration. In this condition, the lifting device is ready to repeat the above-described procedure for a next stack. When the lifting device is intended for cooperating with a stacking device, the lifting frames 2 are moved into an uppermost position in which they are brought into a folded-down condition while the lifting table 1 is in a lowermost position for discharging an already completely formed first stack S from the lifting device. Next, the lifting frames 2 are moved down stepwise, each time receiving an article V to form the second stack S. After the second stack S has been partially formed or during that process, the lifting table 1 is moved into an at least partially lifted position for taking over, at that location, the partially formed second stack S from the lifting frames 2. Subsequently, the lifting table 1 moves down stepwise to reach the lowermost position when the second stack S has been formed completely, while at the same time, the lifting frames 2 are brought into the folded-up condition and moved to an uppermost position and, at that location, brought into the folded-down condition as soon as the second stack S has been formed completely. From this moment onwards, the above method can be repeated for forming a third stack. It is readily understood that the invention is not limited to the exemplary embodiment described, but that various modifications are possible within the framework of the invention. For instance, the drive may also take place by means of two motors which, via a gear wheel and a gear rack, engage movable frame parts mounting the lifting frames 2 and the lifting table 1. Also, the lifting frames 2 and the lifting table 1 may have a different shape and the manner of feeding and discharging a stack S to and from the lifting device may be varied. One may for instance think of a pusher plate pushing a stack from or into the lifting device. It is essential that the lifting device be provided with first and second lifting means, causing the uppermost article of an uppermost stack located in the lifting device to be always at the same level, so that the stacking and/or unstacking process can take place in a continuous manner.

Claims: CLAIMS 1. A lifting device for lifting and/or lowering an ordered stack (S) of articles (V) , said lifting device being intended for cooperating with an unstacking and/or stacking device and with a stack-feeding and stack- discharging conveyor respectively, the lifting device comprising first lifting means (1) and second lifting means (2) , said first lifting means (1) and second lifting means (2) cooperating such that the device continuously keeps an uppermost article (Vt) of a stack (S) located in the lifting device at a fixed, desired level. 2. A lifting device according to claim 1, characterized in that the first lifting means (1) are constructed as a vertically adjustable lifting table (1) and the second lifting means (2) are constructed as lifting frames (2), the lifting table (1) engaging a first area of a lower side of a lowermost article (Vb) of the stack (S) , the lifting frames (2) in a folded-down position engaging a second area of the lower side of the lowermost article (Vb) of the stack (S) , while the first area and the second area do not coincide, and the lifting frames (2) in a folded-up position can pass a stack (S) in vertical direction. 3. A lifting device according to claim 2, characterized in that the lifting table (1) and the lifting frames (2) are of a construction such that the first area is formed by a central part of the lower side of the lowermost article (Vb) , while the second area is formed by a part of the lower side of the lowermost article (Vb) which part surrounds the central part . 4. A lifting device according to claim 2 or 3 , characterized in that it comprises first drive means (3, 4) intended for adjusting the height of the lifting table (1) and second drive means (5, 6) intended for adjusting the height of the lifting frames (2) . 5. A lifting device according to claim 4, characterized in that the first and the second drive means each comprise a cam and/or rod system (3, 4; 5, 6), the two cam and/or rod systems (3, 4; 5, 6) being driven by a common motor (7) , causing the position of the two cam and/or rod systems (3, 4; 5, 6) to be coupled. 6. A lifting device according to any one of the preceding claims, characterized in that a supporting element (8, 9) is located on either side of the lifting table (1) , substantially at the level of the lowermost position of the lifting table (1) , so that during the feed or discharge of a stack (S) into or from the lifting device respectively, said stack (S) is supported over substantially the entire lower side of the lowermost article (Vb) thereof. 7. A lifting device according to claim 6, characterized in that the two supporting elements (8, 9) located on either side of the lifting table (1) are designed as endless conveyors (8, 9) whose feed ends (8a, 9a) are intended to connect to said stack-feeding and stack- discharging device respectively. 8. A lifting device according to at least claim 2, characterized in that when said lifting device is intended for cooperating with the unstacking device, the drive of the lifting table (1) and the lifting frames (2) is such that when a first stack (SI) of articles (V) is being fed into the lifting device, the lifting table (1) is in a lowermost position, the lifting table (1) being subsequently moved upwards stepwise until a number of articles (V) have been removed from the first stack (SI) , the lifting frames (2), located at a level below the lifting table or being moved thereto, being subsequently folded down and moved up for taking over the support of the stack (SI) of articles (V) , after which the lifting table (1) is subsequently moved down to the lowermost position, to be ready for receiving a second stack (S2) of articles (V), while the lifting frames (2) move up stepwise, the stepped upward movement of both the lifting table (1) and the lifting frames (2) taking place such that the uppermost article (Vt) of the stack (S) is always at the same fixed level . 9. A lifting device according to at least claim 2, characterized in that when said lifting device is intended for cooperating with the stacking device, the drive of the lifting table (1) and the lifting frames (2) is such that for forming a complete, second stack (S2) in the lifting device, the lifting frames (2) are moved into an uppermost position in which they are brought into a folded-down condition while the lifting table (1) is in a lowermost position for discharging an already completely formed, first stack (S) from the lifting device, the lifting frames (2) subsequently moving down stepwise while each time receiving an article (V) to form the second stack (S) , while after the second stack (S) has been partially formed, or during that process, the lifting table (1) is moved into an at least partially lifted position for taking over, at that location, the partially formed second stack (S) from the lifting frames (2), the lifting table (1) subsequently moving down stepwise into the lowermost position when the second stack has been entirely formed, while at the same time, the lifting frames (2) are brought into the folded-up condition and moved into an uppermost position and, at that location, are brought into the folded-down condition as soon as the second stack (S) has been formed completely, the stepped downward movement of both the lifting table (1) and the lifting frames (2) taking place such that the uppermost article (Vt) of the stack (S) is always at the same level.

Inventors: DOORNEKAMP MARTIN, VAN WALDERVEEN BART, DOORNEKAMP, MARTIN, VAN WALDERVEEN, BART
Applicants: DOORNEKAMP MARTIN, FOOD PROCESSING SYSTEMS, WALDERVEEN BART VAN, DOORNEKAMP, MARTIN, FPS FOOD PROCESSING SYSTEMS B.V., VAN WALDERVEEN, BART
Application year: 1998
Main classification: B65G1
IPC codes: B65G1, B65G57, B65G59