LIFTING DEVICE

Abstract: The present invention relates to an apparatus for lifting and moving articles, comprising at least one arrangement (12) with a cavity (14), hereafter called vacuum chamber, which is connected to an arrangement (40) which is capable of producing negative pressure in said vacuum chamber, the underside of said lower plate (16) being provided with an elastic airtight bottom (18) and also being provided with a number of first through-passages (20) to said vaccuum chamber. The invention is characterized in that each first passage (20) is of cylindrical design with a diameter reduction in the part which is connected to the vacuum chamber, forming a shoulder (22) in the passage, in that the passage contains a body (30) arranged movably in said passage, in that said body, in planes which are at right angles to the centre line of the passage, has a greatest diameter which is only slightly smaller than the diameter of said first passage (20), and in that said first passage is provided with a second passage (24) with a considerably smaller diameter than the first passage (20), said body (30) being capable of essentially blocking said first passage (20) when a negative pressure is obtained in the vacuum chamber (14) with the exception of a given air flow in said second passage (24).

Description: L I FT I NG DEVI CE TECHNICAL FIELD The present invention relates to an apparatus for lifting and moving articles, coirjprising at least one arrangement with a cavity, hereafter called vacuum chamber, which is connected to an arrangement which is capable of producing negative pressure in said vacuum chamber, the underside of said lower plate being provided with an elastic airtight bottom and also being provided with a number of first through-passages to said vacuum chamber. The invention also relates to a lifting arrangement comprising said apparatus. BACKGROUND OF THE INVENTION In handling equipment for lifting and moving articles, use has long been made of negative pressure as a gripping function. The basic problem with negative pressure is that the lifting arrangement must close tightly against the article in order to obtain a lifting effect and that air must not be allowed to be sucked into the system anywhere else as otherwise the lifting capacity is lost. For lifting individual articles, this is not a major problem if the lifting arrangement can be designed so that it encloses the article. The problem is major, on the other hand, if a lifting arrangement and a negative-pressure source are to be used to lift many articles at the same time. A number of arrangements are known, which take the form of a lifting plate with a vacuum chamber comprising a number of passages out to the surface against which the article to be lifted bears. Some of these plates have some form of blocking arrangement for the individual passages so, in order that negative pressure is not lost, the passages and the articles must be orientated in relation to one anodier so that all passages are covered so that a proper lifting negative pressure can be established. This involves laborious arrangement of the articles and also special adaptation of the lifting plates to the specific articles to be lifted. A further disadvantage is that if an article comes loose during the lift, then the negative pressure and all the articles are lost. Certain plates have blocking arrangements for each passage, either in the form of mechanical valves or light balls which are sucked firmly against a seat and block the passage if it is not covered by an article. Known vacuum plates therefore have a relatively complicated design and construction and/or handling in order for the blocking arrangements to function correctly and have thus far not been really effective for lifting and handling many articles at the same time and different types of article with die same design and functioning of the vacuum plate. DESCRIPTION OF THE INVENTION The object of the present invention is to provide an effective lifting arrangement based on negative pressure and also a simple and cost-effective construction. This object is achieved according to one aspect of the invention by die apparatus mentioned in the introduction above being characterized in that each first passage is of cylindrical design with a diameter reduction in the part which is connected to the vacuum chamber, forming a shoulder in the passage, in mat the passage contains a body arranged movabry in said passage, in that said body, in planes which are at right angles to the centre line of the passage, has a greater diameter which is only slightly smaller than the diameter of said first passage, and in mat said first passage is provided with a second passage with a considerably smaller diameter than the first passage, said body being capable of essentially blocking said first passage when a negative pressure is obtained in the vacuum chamber with the exception of a given air flow in said second passage. According to another aspect of the invention, a lifting arrangement comprising said apparatus is provided, characterized in that it comprises arrangements capable of moving the arrangement vertically and horizontally and also towards die articles to be lifted, with the underside of the vacuum plate parallel to die plane which is formed by die surfaces of die articles facing the plate, and also members which, on contact with die articles to be lifted, are capable of angling the plate in relation to said plane. Further aspects and advantages of die invention will emerge from die detailed description of a possible embodiment and also from the subsequent patent claims. BRIEF DESCRIPTION OF THE FIGURES In die following description of a preferred embodiment, reference will be made to the attached drawings, in which Fig. 1 shows a perspective view of an embodiment of die lifting arrangement according to the invention, Fig. 2 shows a detailed view in cross-section of a vacuum plate forming part of die lifting arrangement according to Fig. 1, Fig. 3 shows a detailed view from below of a passage formed in the vacuum plate, and Figs 4 and 5 show two different detailed views of how a cellular rubber plate mounted on the vacuum plate is shaped during use at different passage diameters. DESCRIPTION OF PREFERRED EMBODIMENT The arrangement according to die invention which is shown in Fig. 1 has die general reference number 10 and comprises a vacuum lifting body, here called the vacuum plate 12. The vacuum plate comprises a space, hereafter called die vacuum chamber 14, Fig. 2, which is enclosed by an upper plate 13, sides (not shown) and an essentially plane lower plate 16, hereafter called the vah/e plate. Mounted on the underside of the vah/e plate 16 is a plate 18 made of elastic airtight material, for example cellular rubber. A number of dirough-passages 20 are arranged in die vah/e plate 16. Each passage 20 is designed as a cylindrical hole with a considerable reduction in diameter close to the inlet to die vacuum chamber so that a shoulder 22 is formed. At the edge of the passage 20, a hole 24, hereafter called escape air hole, is arranged and extends parallel to the through-hole. As is shown in Fig. 3, the escape air hole 24 is orientated in such a manner tiat its centre line coincides witii the cylindrical surface of die passage. The escape air hole 24 has a considerably smaller diameter than die passage. More specifically, die diameter of die escape air hole 24 is less tiian 0.2 times the diameter of die passage 20 which means tiiat the ratio between die cross-sectional areas of die escape air hole 24 and of die passage 20 is less tiian 0.04. An elastic ring 26, for example an O-ring, is pressed into the passage and bears against die shoulder 22. A spherical body 30, a ball, is also located in die passage, which ball has a given own weight. The diameter of the ball is selected so as to be only slightly smaller than the diameter of the passage 20. This means that the ball can move in the passage but mat only a very small gap 27 is formed between the ball and ϋhe passage wall. Appropriately, the ball 30 has a diameter which is a maximum of 1.0, preferably a maximum of 0.5, and expediently a maximum of 0.2 mm smaller than the passage 20, which means mat die width of die gap 27 amounts to at most half said dimension. In principle, die ball 30 can be replaced by anotiier vah/e body which, in planes at right angles to die centre line of the passage 20, has a circular shape, for example a cylindrical shape, ellipsoidal shape, egg shape, or a shape which includes a cylindrical portion and a spherical end portion etc. The elastic plate 18 is provided widi tiuτjugh-holes 32 between its underside and die passages 20. Arranged between tie underside of die vacuum plate and die elastic cellular rubber plate is a filter 34 in die form of a net or the like, so that die filter covers the passages. An arrangement 40 capable of producing a negative pressure is provided for tie vacuum chamber 14. The arrangement 40 comprises a pump 42 and a pipe connection 44 between tie pump and the vacuum plate 12. The arrangement 40 is preferably capable of producing a relatively large flow and therefore die vacuum chamber 14 is designed to be relatively large and also the diameter of die connection pipe 44 is selected to be relatively great. According to an embodiment of the arrangement, Fig. 1, the latter is designed witii linear guides 60 in die vertical direction and also arrangements capable of moving tie vacuum plate 12 in die vertical direction, for example pneumatic or hydraulic cylinders or electric motors. Furthermore, die arrangement is designed with linear guides 62 in die horizontal direction and also arrangements capable of moving the vacuum plate in die horizontal direction. The arrangement is also provided with an arrangement so as to be capable of tilting tie plate in planes which deviate from die horizontal plane. This is effected for example by a pneumatic or hydraulic cylinder 64A-D at each comer of tie plate. The cylinders 64A-D can be actuated independently of one anotiier in order individually to move die selected comer in tie vertical direction. The arrangement functions as follows. Via die pipe connection 44, the vacuum pump 42 produces a negative pressure in the vacuum chamber 14 which means that die balls 30 in die passages 20 are sucked up against die O-ring 26 which bears against the shoulder 22 and thus seal die passages with die exception of a small air flow which passes through tie escape air holes 24. The articles to be lifted, for example a number of containers to be lifted from a pallet 66 to a filling line, are placed in die correct position. The lifting arrangement moves die vacuum plate 12 to die correct position in the lateral direction and lowers die vacuum plate 12 until the cellular rubber plate 18 bears against the upper edge of the articles. Contact with die articles gives rise to a pressure change in the passages 20, which are covered by tie articles, because of the escape air passages 24. whereupon die ball 30 drops from its seat against the O-ring, Fig. 4. The flow then increases considerably and a negative pressure is built up in both the passage 20, 32 and the article if die latter is not completely smooth and then sucks the article firmly. The passages which are not covered by an article continue to suck die ball firmly against die seat by negative pressure. In order to ensure that all die articles to be lifted come into contact whh the vacuum plate and are sucked firmly, for example if the base on which the articles stand should not be entirely plane, the tilting cylinders 64A-D are actuated, which independently raise and lower tie comers of the vacuum plate. More specifically, die tilting cylinders are actuated in order in a cyclical sequence around the vacuum suction plate 12, for example in a repeated 64A-64B- 64C-64D sequence one or more times, which means mat the plate as it were moves in a wave pattern or "wanders" over all the articles which then come into full contact with tie plate. The vacuum plate is men lifted up and moved in die lateral direction to the setting-down place 68. The articles are lowered and die negative pressure is discontinued, eidier by die pump being stopped or by die connection to die vacuum plate being closed. The articles are released then and the plate can collect another set of articles. Thanks to die vacuum plate being provided with die balls in tie passages, on tie one hand not all the passages have to be covered in order for die plate to be able to lift articles and on the other hand there is no danger if an article should come away or break so that the passage is exposed. The negative pressure in the vacuum chamber does not decrease as the changed pressure difference in the opened passage causes the ball to be sucked up against die seat and seal the passage. Thanks to the escape air passage, the negative pressure arrangement can be in operation die whole time while articles are being sucked firmly because mere is constantly a given flow dirough the passages. If the escape air passage were not present, no pressure change would take place when the plate comes into contact with the articles, as a result of which tie ball would continue to be sucked firmly against the seat. The only way to suck articles firmly would dien be to have tie vacuum pump shut off when the plate descends against the articles and to set it in operation after that. The passages covered by articles would dien receive such a negative pressure that the articles would be sucked firmly at the same time as die passages not covered by articles would suck the balls up against the seat. Another advantage of die arrangement according to die invention is that the balls in the passages have a given own weight. When articles with a relatively great space of their own are to lifted, such as open containers and the like, the weight of die ball ensures that it is not sucked up before appropriate negative pressure has been obtained in the space of the article. The considerable own weight of the ball also ensures that it does not stick in die passage which moreover means that mere can be a relatively narrow gap between the ball and tie passage without risk of tie ball sticking. The filter 34 provided for the passage 30 between die cellular rubber plate 18 and die lower plate 16 furthermore ensures that no refuse, dust or other particles are sucked into the arrangement. The filter 34 also serves as the lower limit of the movement of the ball 30 and means that die ball does not he and press against the cellular rubber plate. The O-ring in the passage affords on the one hand good sealing against the ball and on the other hand a relatively soft stop surface when die ball is sucked up against the shoulder. By virtue of the design with tie O-ring covering a part of the escape air passage, the latter can be drilled witi a larger drill which makes manufacture easier. The cellular rubber plate preferably has relatively great elasticity and, by varying the size of the passages 32 through it and also its thickness, different characteristics can be obtained for different articles to be lifted. If a large number of articles are to be lifted at tie same time, such as for example glass containers, aluminium containers, Fig. 4, it is an advantage if the diameters of the passages are relatively small, on die one hand because the containers themselves contain a volume in which negative pressure is built up and holds the container firmly, and on die other hand in order to avoid die passages falling outside the edge of the container in some cases. If plane articles are to be lifted, such as for example sheets or planks, the passages 32 in die cellular rubber plate can advantageously be made greater and a thicker plate can also be selected. With this design, a space is obtained, in which negative pressure can be built up. Thanks to tie elasticity of the cellular rubber plate, this space becomes even greater when tie article is sucked firmly as the edges of die passage in die cellular rubber are drawn inwards towards die passage, as shown in Fig. 5. Although die invention has been described in connection witii an arrangement for lifting a number of articles located on a plane surface using a plane vacuum plate, it is to be understood that die invention can be designed in many ways for many articles to be lifted. For example, it is possible to envisage lifting wood products such as planks, laminated flooring and similar elongate articles, and dien to design the vacuum plate, or plates, in the appropriate manner. Instead of an elongate plate, h is possible to envisage having a number of smaller plates and also appropriate arrangements for manoeuvring the plates for positioning, lifting and moving. It is also possible to envisage lifting non-plane articles or otiier articles which cannot be connected to a plane surface, for example lying bottles or articles widi more irregular shape. In this case, the elastic plate can be profiled in a corresponding manner, tiiat is to say provided with recesses in its underside with a shape adapted to the shape of die article in question so tiiat the latter, when it is orientated in the recess, can be sucked firmfy therein. By using a vacuum plate according to die invention, very effective lifting of a multitude of articles is achieved without risk of losing die lifting negative pressure if some passages should not be covered by articles. Compared with vacuum plates according to die prior art, much simpler design and manufacture are also obtained, as is cheaper construction without arduous special machining of tie plate or parts thereof It is to be understood that the invention is not lirnited to the embodiment described above and shown in die figures of the drawings, but can be modified widiin the scope of the following patent claims.

Claims: PATENT CLAIMS 1. Apparatus for lifting and moving articles, comprising at least one arrangement (12) with a cavity (14), hereafter called vacuum chamber, which is connected to an arrangement (40) which is capable of producing negative pressure in said vacuum chamber, the underside of said lower plate ( 16) being provided widi an elastic airtight bottom (18) and also being provided with a number of first through-passages (20) to said vacuum chamber, characterized in that each first passage (20) is of cylindrical design widi a diameter reduction in die part which is connected to the vacuum chamber, forming a shoulder (22) in die passage, in that die passage contains a body (30) arranged movabry in said passage, in that said body, in planes which are at right angles to the centre line of the passage, has a greatest diameter which is only slightly smaller than the diameter of said first passage (20), and in diat said first passage is provided with a second passage (24) with a considerably smaller diameter than tie first passage (20), said body (30) being capable of essentially blocking said first passage (20) when a negative pressure is obtained in the vacuum chamber (14) with the exception of a given air flow in said second passage (24). 2. Apparatus according to Claim 1, characterized in tiiat die second passage (24) extends along tie edge of the first passage (20) over its entire length. 3. Apparatus according to Claim 1, characterized in tihat said body (30) is manufactured from a material which gives it a given considerable own weight. 4. Apparatus according to Claim 3, characterized in tiiat die body (30) is manufactured from steel or another metal, and in tiiat it is preferably homogeneous, ώat is to say not hollow. 5. Apparatus according to any one of Claims 1-4, characterized in that die body (30) consists of a spherical ball 6. Apparatus according to Claim 1, characterized in tihat the first passage (20) is provided with an elastic ring (26) mounted against the shoulder (22). 7. Apparatus according to Claim 6, characterized in diat the elastic ring (26) partly covers the second passage (24). 8. Apparams according to Claim 1 , characterized in that the first passage (20) is provided widi a filter (34) mounted between the vacuum plate ( 12) and the elastic plate ( 18). 9. Apparatus according to Claim 1, characterized in that the vacuum chamber ( 14) is designed as a relatively large space and in that die arrangement (40) for producing a negative pressure is capable of generating a considerable flow in the arrangement. 10. Lifting arrangement comprising the apparatus according to Claim 1, characterized in that it comprises arrangements (60, 62) capable of moving the arrangement vertically and horizontally and also towards the articles to be lifted, with the underside of the vacuum plate (12) parallel to the plane which is formed by the surfaces of the articles facing die plate, and also members (64) which, on contact with tie articles to be lifted, are capable of angling the plate in relation to said plane. 11. Lifting arrangement according to Claim 10, characterized in that said angling of tie plate is brought about in a cycle in which, in order, one of die comers of die plate is moved an additional distance towards said articles while the other comers are not acted on. 12. Lifting arrangement according to Claim 10 or 11, characterized in that said movement takes place with die aid of piston/cylinder arrangements.

Inventors: PERSSON CURT, PERSSON, CURT
Applicants: PERSSON CURT, TEPRO MACHINE & PAC SYSTEM AKT, PERSSON, CURT, TEPRO MACHINE & PAC-SYSTEM AKTIEBOLAG
Application year: 1997
Main classification: B66C1
IPC codes: B65G47