EQUIPMENT WITH RACKS

Abstract: Equipment with racks, in particular pallet racks, comprising a stacker crane (1) with a transfer wagon (3), a mast (2) on the transfer wagon and on this a lifting table (10) or other load carrier, an aisle along the warehouse, drive means (7, 11) comprising separate motors for the transfer wagon and for the load carrier so as to move the transfer wagon in the aisle and so as to raise and lower the load carrier on the mast, and also controls to guide the load carrier to the desired place in the warehouse (5) during movement of the transfer wagon and the load carrier. According to the invention the mast slopes from a foot point on the transfer wagon over or near one of the carrier wheels of this inwards over the transfer wagon. The controls comprise individual pulsators (14, 15) for the transfer wagon and for the load carrier arranged to emit pulses related to the transfer wagon's movements in the longitudinal axis in the aisle or to the load carrier's movements in both the longitudinal and the height axis on the sloping mast and also pulse counters which give information about the load carrier's actual position, that is to say the position's actual value. Further there is a computer so as to compare the actual value with the nominal value which corresponds to the desired place in the warehouse and also so as to regulate the drive motors of the transfer wagon and the load carrier, so that the transfer wagon and/or load carrier moves till its actual value co-incides with the current nominal value.

Description: Equipment with racks TECHNICAL FIELD The invention concerns equipment with racks, particularly pallet racks, comprising a stacker crane with a transfer wagon, a mast on the transfer wagon with a lifting table or other load carrier that can be raised and lowered, and aisle along the warehouse, drive means for the transfer wagon and for the load carrier comprising separate motors for moving the transfer wagon in the aisle and for raising and lowering the load carrier on the mast, and also controls for guiding the carrier to the desired place in the warehouse during movement of the transfer wagon and the load carrier. BACKGROUND ART Racks, such as pallet racks, are often very large and especially very high. Modern pallet racks are generally more than 20 metres high and there are warehouses which are even up to 40 metres high. This makes very high demands on the loadhandling equipment. To-day's stacking cranes are generally of conventional design with the mast placed on the transfer wagon halfway between the carrier wheels. This means that when the crane moves along with the load carrier (lifting table or similar) in the highest position on the mast, that is to say at a height which perhaps exceeds 20 metres, and brakes so as to take up the desired position the mast bends outwards simultane¬ ously with the transfer wagon beam. The sum result of these bendings -I makes the mast sway for a while after braking. So that the load carrier may be able to move forward to the desired place in the warehouse a waiting time must be inserted in the automatic regulation equipment so that the swing has time to cease. Another factor that makes load handling relatively slow is positioning system in the existing art, which is based on the fact that a number of so-called "flags" (detectors) is arranged along the aisle, corres¬ ponding to the racks in * the warehouse, and that the identity of these detectors is recognised by transmitters on the crane. Corresponding detectors are also arranged in the height member so as to position the load carrier too. These detectors or corresponding devices are used for rough positioning. In order subsequently to fine position the load carrier in against a certain carrier beam in the rack a reflex tape on the carrier beam is generally used, as an alternative to the use of photo-electric cells. The latter alternative has, however, the dis¬ advantage that photo-electric cells cannot recognise all colours. Therefore to-day almost exclusively reflex tape is used in combination with four photo-electric cells on the load carrier. When these photo¬ electric cells touch the outer edges of the tape the load carrier is in the right position. The system is slow. First one has to rough position, then one has to wait until its oscillations have ceased, and finally one must adjust inwards to the tape. Particularly the latter can take a long time for response since the carrier beam in some racks is bent downwards a few degrees depending on the loading and the distribution of the load. This positioning system also entails one having to use a vertically placed mast, which is conventionally placed in the middle of the transfer wagon. DISCLOSURE OF THE INVENTION The aim of the invention is to offer an improved rack equipment, particularly with pallet racks. More precisely the aim is to offer a system which enables a faster positioning of the load carrier than the existing system. One aim is also to offer a system which is particu¬ larly suitable for very high stores. Another aim is to be able to eliminate the so-called "flags" (detectors) and similar positioning aids which are used in accordance with known technology and which can easily be damaged mechanically. These and other aims can be achieved through the fact that the mast slopes from a foot point on the transfer wagon over or near one of its bearer wheels inwards over the transfer wagon, and that the afore¬ mentioned controls comprise individual pulsators for the crane and for the load carrier arranged to emit pulses related to the movements of the transfer wagon in the longitudinal axis in the aisle or to the load carrier's movements in both the longitudinal and the height axis on the sloping mast, pulse counters which give information about the load carrier's actual position, that is to say the actual value of the position, and also a computer to compare the said actual value with the nominal value which corresponds to the desired place in the warehouse and to regulate the drive motors of the transfer wagon and the load carrier so that the transfer wagon and/or load carrier moves till its actual value co-incides with the current nominal value. Through the fact that the mast slopes and is supported by one or more struts sloping in the opposite direction and/or by a grid, the weight of the mast, load carrier and load is distributed over a plurality of wheels of the transfer wagon, that is to say in the normal case over the two wheels which are set at the two ends of the transfer wagon. Preferably the distance from the foot point of the mast on the transfer wagon to the perpendicular from the top of the mast to the transfer wagon equals a number of whole rack partitions, particularly one rack position (compartment). The reason is that when one has a very high rack one always has a place where one fetches and leaves loads in front of the rack, and when the crane stands in this position it must be able to reach the highest compartment without moving. Then the crane does not steal any geometry either in relation to the rack. In other words one is using optimally the extent of the rack in the premises.' The sloping mast is made possible by the fact that one has a complete¬ ly different positioning system from that of conventional load hand¬ ling equipment. As mentioned above, pulsators are used, which give a measurement of the position both in the longtitudinal axis (herein¬ after called x axis) and in the height axis (hereinafter called y axis). This entails in principle that one calculates forward in the warehouse from a point of origin, that is to say a zero point, at the end of the warehouse. The pulse distribution can most suitably correspond to a length of approx. 1.5 mm. Pulsators are fitted on non-driving wheels on the transfer wagon and in the mast. One can also imagine fitting a chain along the whole length of the warehouse and a chain wheel with pulsators. The same principle can be used also in the y axis with a chain wheel on the drive motor. In the computer's memory each load place (it is the same with the pallet place in a pallet rack) has a definite x co-ordinate and a definite y co-ordinate. This is called the position's nominal value, which is a mathematically calculated value. The data programme is also arranged to control the acceleration and deceleration curves of the drive motors. If for example there are used DC motors, which are recommended according to the invention, then it is possible to control the motor with great precision according to a preprogrammed acceleration curve, so that one can land with the load carrier with great exactitude at the x/y co-ordinate envisaged without having to finish the move with a time wasting creep movement, as with existing systems. In practice an accuracy of + 1.5 mm is attained in this manner. It is also seen that the load carrier's vertical and horizontal movements are carried out simultaneously. The whole time the pulses are counted in the x axis and the y axis, at the same time as the position in the computer is compared with the nominal value. Depending on this comparison the speed of the drive motors can be increased or reduced. If the desired position is passed before the load carrier comes completely to a halt this is recognised in comparison between the actual and nominal values, after which the transfer wagon and/or the load carrier is moved back as far as is required so as to stop in the desired posi- tion. There can also be suitably carried out in the computer according to one aspect of the invention a pure stress calculation of the loading on the carrier beams in the warehouse. This presupposes that the load weights are noted in a warehouse account in the computer's memory. From the warehouse account there is received according to the data programme information as to whether there is any load on the beam or not, and how any existing load is distributed in the rack. These various combinations are combined in their turn with the different calculation formulae for different cases of loading for calculation of the downwards bending of the beam. This downwards bending is converted by the computer into a number of pulses for the different load places in the rack and these pulse counts are subtracted in the computer from the original nominal value for the load place in question. Further characteristics and aspects of the invention become clear from the appending patent claims and also from the following description of a preferred embodiment. DESCRIPTION OF PREFERRED EMBODIMENT In the following description of an embodiment of the invention reference is made to the attached drawing which constitutes a perspec¬ tive view of a stacker crane 1 with a sloping mast 2 on a transfer wagon 3, which can move on a rail 4 in an aisle along a pallet rack 5. The slope of the mast corresponds to one pallet rack partition. The pallet rack consists of a large number of storage compartments (parti¬ tions) 6. In each compartment 6 there is room for two or three load pallets beside each other on the carrier beams 17. Each such pallet place has allocated to it according to the invention an x and y co-ordinate corresponding to the nominal value of the pallet place in a computer memory in the computer which forms part of the equipment. The transfer wagon 3 consists in principle of a strong beam with a wheel at each end. The back wheel is driven by a first DC motor 7. The sloping mast 2 is supported by a sloping head support 8 and a strut 9. The support 8 has its foot point on the transfer wagon 3 over the back drive wheel. A lifting table 10 can be raised and lowered along the mast 2 with the aid of a second DC motor 11 via a chain 12 with lower and upper turning wheels. The stacker crane 1 is usually manoeuvred in the normal automatic manner but can also be manoeuvred manually. For this purpose there is a cabin 13 which accompanies the lifting table 10 at the side of the mast 2. The front wheel of the transfer wagon 3 is fitted with a first pulsator 14, and a second pulsator 15 is connected to the drive wheel which drives the chain 12. In a control cabinet 16 there are pulse counters, computer and controllers for the two DC motors. Regarding the function of the above described equipment, referene is made to the preceding disclosure of the invention. CLAIMS 1. Equipment with racks, in particular pallet racks, comprising a stacker crane (1) with a transfer wagon (3), a mast (2) on the transfer wagon and on this a lifting table (10) or other load carrier, an aisle along the warehouse, drive means (7, 11) comprising separate motors for the transfer wagon and for the load carrier in order to move the transfer wagon in the aisle and in order to raise and lower the load carrier on the mast, and also controls in order to guide the load carrier to the desired place in the warehouse (5) during movement of the transfer wagon and load carrier, c h a r a c t e r i s e d by the fact that the said controls comprise individual pulsators (14, 15) for the crane and for the load carrier arranged to transmit pulses related to the transfer wagon's movements in the longitudinal axis or to the load carrier's movements in both the longitudinal and the height axis on the sloping mast, pulse counters which give information about the load carrier's actual position, that is to say the posi¬ tion's actual value, and also a computer to compare the said actual value with the nominal value which corresponds to the desired place in the warehouse and also to regulate the drive motors of the transfer wagon and the load carrier, so that the tranfer wagon and/or load carrier moves till its actual value co-incides with the current nominal value. 2. Equipment as per claim 1, c h a r a c t e r i s e d by the fact that the"sloping mast is supported by one or more supports (8) sloping in the opposite direction and/or by a grid, so that the weight of the mast, load carrier and load is distributed over a plurality of the transfer wagon's carrier wheels. 3. Equipment as per claim 1, c h a r a c t e r i s e d by the fact that the distance from the foot point of the mast on the transfer wagon to the perpendicular from the mast top to the tranfer wagon corresponds to a number of whole rack partitions, particularly one rack partition. 4. Equipment as per claim 1, c h a r a c t e r i s e d by the fact that the drive motors of the transfer wagon and load carrier are DC motors (7, 11) . 5. Equipment as per claim 4, c h a r a c t e r i s e d by the fact that the said DC motors are arranged to be controlled by the computer depending on the actual positions of the transfer wagon and load carrier and on the desired position of the load carrier, so that the load carrier is guided with great accuracy to the intended position substantially without concluding creep movement of the transfer wagon and/or of the load carrier. 6. Equipment as per any one of the claims 1-5, c h a r a c t e ¬ r i s e d by the fact that the computer is arranged so as to compensate for the downwards bending of the carrier beam owing to loading from the load in the compartment which contains the current load place.

Claims: AMENDED CLAIMS [received by the International Bureau on 17 February 1987 (17.02.87); original claims 1—6 replaced by amended claims 1—5 (2 pages)] 1. Equipment with racks, in particular pallet racks, comprising a stacker crane (1) with a transfer wagon (3) with a first carrying wheel in one end thereof and a second carrying wheel in the other end thereof, a mast (2) on the transfer wagon and on this a lifting table (10) or other load carrier, an aisle along the warehouse, drive means (7, 11) comprising separate motors for the transfer wagon and for the load carrier in order to move the transfer wagon in the aisle and in order to raise and lower the load carrier on the.mast, and al--o c'-nt^ol means provided to guide the load carrier to the desired place in the warehouse (5) during movement of the transfer wagon and load carrier, " c h a r a c t e r i s e d by the fact that the mast (2) slopes from a foot point on the transfer wagon (3) over or adjacent to one of its carrying wheels in over the transfer wagon, that tne sloping mast is supported by one or more supports (8) sloping in the opposite direction and/or by a grid, so that the weight of the mast, load carrier and load is distributed over said first and second carrying wheels which are provided in the two ends of the transfer wagon, that the distance from the foot point of the mast on the transfer wagon to the perpendicular from the mast top to the transfer wagon corresponds to a number of whole rack partitions, and that the said control means comprise individual pulsators (14, 15) for the crane and for the load carrier arranged to transmit pulses related to the transfer wagon's movements in the longitudinal axis or to the load carrier's movements in both the longitudinal and the height axis on the sloping mast, pulse counters which give information about the load carrier's actual position, that is to say the position's actual value, and also a computer to compare the said actual value with the nominal value which corresponds to the desired place in the warehouse and also to regulate the drive motors of the transfer wagon and the load carrier, so that the transfer wagon and/or load carrier moves till its actual value co-incides with the current nominal value. 2. Equipment as per claim 1, c h a r a c t e r i s e d by the fact that the distance from the foot point of the mast on the transfer wagon to the perpendicular from the mast top to the transfer wagon corresponds to one rack partition. 3. Equipment as per claim 1, c h a r a c t e r i s e d by the fact that the drive motors of the transfer wagon and load carrier are DC motors (7, 11). 4. Equipment as per claim 3, c h a r a c t e i s e d by the fact that the said DC motors are arranged to be controlled by the computer depending on the actual positions of the transfer wagon and load carrier and on the desired position of the load carrier, so that the load carrier is guided with g>-eat accuracy to the intended position substantially without concluding creep movement of the transfer wagon and/or of the load carrier. 5. Equipment as per any one of the claims 1-4, c h a r a c t e r i ¬ s e d by the fact that each partition comprises a carrier beam (17), and that the computer is arranged so as to compensate for the downwards bending of tne carrier beam owing to loading from the load in the compartment which contains the current load place.

Inventors: LARSSON URBAN AOKE INGEMAR, WIKLUND BJOERN STURE, LARSSON, URBAN, AOKE, INGEMAR, WIKLUND, BJOERN, STURE
Applicants: MTH AB
Application year: 1986
Main classification: B65G1
IPC codes: B65G1, B66F9