Suction table apparatus for supporting and retaining a sheet of glass

Abstract: Assembly (80) for supporting and retaining sheets of glass (2), particularly in a machine (1) for machining said sheets of glass (2); the assembly (80) possesses a support structure (8), a plurality of suckers (45) carried by the support structure (8) to hold the sheet of glass (2) in an unambiguous reference position on a horizontal plane (11) and, for each sucker (45), a corresponding actuator (47) for vertically displacing said suckers (45) between a raised position and a lowered position.

Description: The present invention relates to an assembly for supporting and retaining sheets of glass, particularly for a machine for machining said sheets of glass such as those disclosed in US-A-5 094 282, EP-A-0 507 033 and EP-A-1 090 718. The document US-A 5 094 282 is regarded as being the closest prior art. In machines for machining sheets of glass, particularly in grinding machines, it is known practice to hold the sheets of glass in an unambiguous reference position during machining using a retention assembly comprising a plurality of sucker bodies which are arranged manually on a support surface def ined by the machine base, their positions being modified whenever required as a function of the dimensions and type of the glass sheets to be machined. Retention assemblies of the known type described above are not very satisfactory when it is necessary to machine a succession of sheets of glass whose dimensions differ from each other, not only because it takes a relatively long time to arrange the sucker bodies manually each time in the appropriate positions, but more importantly because of the obvious need to ensure that the machining tools do not interfere with the base or with the members used to support, position and retain t he sheets of glass, independently of the dimensions and shape of said sheets. It is an object of the present invention to provide an assembly for supporting and retaining sheets of glass, particularly in a machine for machining said sheets of glass, by which the problems described above can be solved in a simple and economical manner. The present invention provides an assembly for supporting and retaining sheets of glass comprising the features of claim 1. The invention will now be described with reference to the attached drawings, which illustrate a nonlimiting embodiment of it, in which: figure 1 illustrates in perspective and schematically a preferred embodiment of the assembly for supporting and retaining sheets of glass, particularly for a machine for machining said sheets of glass, produced in accordance with the present invention; and figure 2 is a plan view, with parts removed for the sake of clarity, of a detail of the supporting and retaining assembly shown in figure 1. In figure 1, 1 indicates a grinding machine for machining sheets 2 of glass (partially illustrated), comprising respective rectangular perimeter edges 5 to be ground, which have dimensions which can optionally be different from one another. The machine 1 comprises a base 8, which supports a conveyor unit 9, which, in particular, comprises a plurality of drive belts 10, in order to transfer the sheets 2 in succession one after another, along a horizontal plane 11, in a longitudinal horizontal straight direction A, from a loading station 12, towards an unloading station 13, through a work station 14. With reference to figure 2, the station 14 contains two straight longitudinal guides 15, which are disposed on opposite sides relative to the direction A, and are integral with the base 8, and four beams 20, 21, 22, 23, which extend in a horizontal direction B, which is at right-angles to the direction A, in positions which are adjacent to one another. The beam 20 is unmovably connected to the base 8, in a position adjacent to the station 13, whereas the beams 21, 22, 23 are connected to the guides 15, such as to slide in the direction A, between the beam 20 and the station 12, and are actuated by a movement unit 24, which is controlled by an electronic command and control unit 25 (illustrated schematically). The unit 24 comprises a motorized shaft 26 and an idle shaft 27, each of which can rotate around its own axis, parallel to the direction B, and at its ends supports two sets of three wheels 30, 31, 32, which are keyed in fixed positions, coaxially relative to one another, on the corresponding shaft 26, 27, and have respective radii which increase from the wheel 30 to the wheel 32, in order to define ratios of transmission which are different from one another. The unit 24 also includes two sets of three belts 34, 35, 36, which extend in the lateral portions 37 of the base 8, are each wound around a pair of wheels 30, 31, 32, and comprise respective sections 38, 39, 40, which are each connected integrally to the corresponding beam 21, 22, 23. Each of the beams 20, 21, 22, 23 supports a row of suckers 45, which have an upper surface 46 to support the sheet 2 to be ground, constitute part of a retention unit 44, which is controlled by the unit 25, in order to retain the sheet 2 itself on the surface 46 during grinding, and are connected to a suction pump (not illustrated) by means of respective pneumatic control valves (not illustrated). Each sucker 45 supports a lower rod, which is connected to a pneumatic cylinder, which is integral with the corresponding beam 20, 21, 22, 23, and defines together with the corresponding rod an actuator 47 (illustrated schematically), which is controlled by the unit 25, in order to displace the suckers 45 between a raised position, in which the sheet 2 is disposed in a position spaced from the belts 10 in order to be ground, and a lowered rest position, in which the sheet 2 is disposed on the belts 10, in order to be transferred from and to the station 14 on the plane 11. The station 14 accommodates a positioning unit 50, which is controlled by the unit 25, in order to dispose each sheet 2 to be processed in a reference position on the plane 11, relative to the base 8, and comprises a retractable reference stop (not illustrated) of a known type, which is supported by the base 8, and an alignment device 51, which is supported by the lateral portion 37. In particular, the device 51 comprises a thrust unit 52, which is delimited by a surface 53, parallel to the direction A, and is actuated by an actuator 54, by means of interposition of a four-bar chain lever system 55, in order to displace the surface 53 parallel to itself in the direction B, against one side 5b of the sheet 2, thus aligning the side 5b itself in the direction A. As illustrated in figure 1, the station 14 contains a frame 56, which supports four grinding heads 74, 75, 76, 77. The grinding heads 74, 75, 76, 77 are actuated by respective motors (not illustrated), which are independent from one another, are accommodated in the frame 56, and are controlled by the unit 25, in order to displace the heads 74, 75, 76, 77 themselves simultaneously along respective transverse paths which are incident relative to one another, defined by respective guides, such as to grind respective sides 5a, 5b, 5c, 5d of the edge 5, which are transverse relative to one another, and consecutive. In use, the sheets 2 are loaded one after another on the station 12, by setting on the unit 25 the parameters relative to the perimeter dimensions to be obtained for the sheets 2 to be processed. The parameters can be set manually for each of the sheets 2, or they can be entered together with the number of consecutive sheets 2 which have the same dimensions, or they can be taken from a data base which is stored and resident in the unit 25, or in a remote computer (not illustrated), which is connected to the unit 25 itself. It is understood that the machine 1 comprises sensors (not illustrated), which allow the unit 25 to detect the type of sheet 2 present on the station 14, and check the accuracy of the parameters set. During transfer of the sheet 2 to be processed, towards the station 14, the unit 25 controls actuation of the shaft 26, in order to make the belts 34, 35, 36 run at different linear speeds from one another, and such as to move the beams 21, 22, 23 apart from one another progressively, on the basis of the dimensions of the sheet 2, keeping the beams 20, 21, 22, 23 equally spaced. When the sheet 2 reaches the station 14, the unit 25 firstly controls the unit 50, in order to position the sheet 2 in an unambiguous reference position, and then the unit 44, in order to actuate only the suckers 45 covered by the sheet 2. Subsequently, the unit 25 actuates the actuators 47 associated with the suckers 45 which are retaining the sheet 2, such as to bring the sheet 2 itself into the raised machining position. Whilst these operations are being carried out on the sheet 2, the unit 25 commands positioning of the head 75, 74, 76, 77 with respect to the base 8 in respective corresponding points for commencement of machining, each at a vertex of the edge 5, in order to adapt the grinding cycle to the dimensions of the sheet 2. Simultaneously, the configuration of the grinding wheels of each head 74, 75, 76 , 77 is regulated by the unit 25, on the basis of the thickness of the sheet of glass 2 to be ground. During the grinding operations, the heads 74, 75, 76, 77 are displaced in an unambiguous direction of travel or advance of the edge 5, following one another without interfering with one another. The point or vertex of completion of machining of each head 74, 75, 76, 77 coincides with the point or vertex of commencement of machining of the following side 5a, 5b, 5c, 5d. When the grinding has been completed, the actuators 47 are controlled such as to take the suckers 45 into their lowered position, and the suckers 45 themselves are deactivated in order to release the sheet 2, which is then transferred towards the station 13. The subsequent sheet 2 is already on the station 14, in particular in the case in which the sheet 2 which is being processed is smaller than the station 14 itself, and is transferred such as to initiate a new cycle on the basis of the parameters entered in the unit 25. It will be clear from the above that the base 8, the suckers 45, the actuators 47 and the units 24, 25 and 50 are part of a supporting and retaining assembly 80 that is extremely flexible since it is capable of holding sheets 2 of dissimilar dimensions firmly and precisely and machining the sheets 2 without difficulties, independently of their dimensions. This is due to the fact that the raising, by the suckers 45, of the sheet 2 to be ground prevents interference of the heads 74, 75, 76, 77 against the base 8 and with any suckers 45, or with other devices for positioning the sheets 2, which are positioned outside of the projection of the edge 5 onto the plane 11. Moreover, the unit 24 makes it possible to adapt the position of the suckers 45, and to render stable the positioning and retention of sheets 2 which have dimensions different from one another. Lastly, owing to the features of its construction, the assembly 80 is extremely simple and compact. Finally, it is apparent from the foregoing that modifications and variants can be made to the assembly, as defined by the appended claims. In particular, the units 24 and 50 could be different from those illustrated and described, and the assembly 80 could be used in a glass-sheet machining machine different from the machine 1 described and illustrated by way of example.

Claims: Assembly (80) for supporting and retaining sheets of glass (2), particularly for a machine (1) for machining said sheets of glass (2); the assembly comprising a support structure (8) and retention means (45) carried by said support structure (8) to keep said sheet of glass (2) in an unambiguous reference position with respect to said support structure (8) on a plane; said assembly also comprising actuator means (47) for displacing said retention means (45) between a raised position and a lowered position perpendicularly to said plane (11), said retention means (45) consisting of a plurality of retention members (45) distributed in said plane (11), said assembly also comprising means (25) for displacing said retention members (45) perpendicularly to said plane (11), said retention members (45) being disposed in a plurality of parallel rows arranged transversally with respect to an advancement direction of said sheet of glass (2), said rows being supported by parallel beams (20, 21, 22, 23), the assembly (80) characterised in that the beam (20) is unmovably connected to the support structure (8), whereas the beams (21, 22, 23) are connected to belt transmission means (34, 35, 36), which are wound around wheels (30, 31, 32), which are keyed in fixed positions, coaxially relative to one another on a shaft, and have respective radii, which increase from the wheel (30) to the wheel (32), the rows being controllable by said means for displacing (25) in order to displace the rows apart from one another progressively and at different linear speeds, on the basis of the dimensions of the sheet (2), while keeping the rows equally spaced, the displacement of each one of said rows of retention means (45) being always in a fixed ratio and being always different from the displacement of another one of said rows of retention means (45). Assembly according to Claim 1, characterised in that said actuator means (47) comprise one actuator (47) for each of said retention means (45). Assembly according to Claim 1, characterised in that it also comprises movement means (24) for varying the relative positions of said retention members (45) in said plane (11). Assembly according to Claim 1, characterised in that said belt transmission means (34, 35, 36) comprise a plurality of belt transmission units (34, 35, 36), which have transmission ratios which differ from one another, and are each interposed between a corresponding one of said mobile rows and a single actuation unit (26). Assembly according to Claim 1, characterised in that it comprises conveyor means (9) for advancing said sheets of glass (2) on said plane (11) along a direction of advance through a work station (14), said direction of advance being parallel to a direction of regulation (A). Assembly according to Claim 1, characterised in that it also comprises positioning means (50) for arranging said sheet of glass (2) in said unambiguous reference position on said plane (11) with respect to said support structure (8).

Inventors: GARIGLIO DAVIDE, GARIGLIO, DAVIDE
Applicants: FORVET S R L, FORVET S.R.L.
Application year: 2001
Main classification: B23Q1
IPC codes: B24B9, B24B41, B24B27, B23Q1, B25B11, B23Q7