Vacuum belt conveyor for plates

The present invention refers to a vacuum conveyor for plates, particularly for glass plates. Such conveyor is particularly adapted to be used in industries and with machinery for working glass.

In such industries, glass plates having different sizes, shapes and thicknesses are subjected to side grinding, and drilling and grinding workings along any direction that is parallel or not with respect to the advancement direction of the plates.

For every type of working that provides for a removal of material or equivalent workings, the currently-used machinery comprise belt conveyors, operating in a position that is substantially horizontal, vertical or slanted with respect to the ground, on which the plates are placed and dragged due to the friction between plate itself and material (usually special rubber) of which the belts are composed. Given the high efforts to which the plates are subjected during their working, it is necessary that they are further unmovably held in position on the belts: for such purpose, currently pressing means are provided, that are preferably composed of a plurality of rollers around which rubber rings or rubber tracks are placed, that press against the plates themselves from above, namely from the plate side that is opposite to the one resting onto the conveyor belts.

Even if rubber rollers and rings are provided in order to keep the surface in contact with glass as small as possible, however, in order to carry out some pressure, it is anyway necessary to provide a series of contact points that almost always create glass scoring problems, since the glass, when working, is covered by rather abrading dust and glass chips. Moreover, with the evolution of the glass product, nowadays plates are provided that are equipped with an upper film that is nicked and ruined by the contact with pressing means (so-called "LOW-E" - "low emission" glasses)

US-A-3389908 discloses a device for transferring flat or sheet products according to the pre-characterising part of Claim 1.

US-A-5648140 discloses a conveyor for continuous vacuum lamination according to the pre-characterising part of Claim 1.

Object of the present invention is solving the above prior-art problems, by providing a belt conveyor that does not need any more any type of pressing means and that exerts onto the moving plates a force that is equal to, if not greater than the holding force so far provided by the pressing means, in order to allow working the plates along any direction with respect to their moving direction.

A further object of the present invention is providing a belt of the above-mentioned type that is of simple construction, high reliability, is not subjected to problems deriving from the difficult working environment in which it will have to operate, and allows providing an holding force onto the plates with high efficiency (up to 80% or more), but also when its holding efficiency is much smaller (down to 40%).

The above and other objects and advantages of the invention, as will appear from the following description, are obtained by a belt conveyor as claimed in Claim 1. Preferred embodiments and non-trivial variations of the present invention are claimed in the dependent Claims.

The present invention will be better described by some preferred embodiments thereof, given as a non-limiting example, with reference to the enclosed drawings, in which: <ul id="ul0001" list-style="dash" compact="compact"><li>Figure 1 is a perspective view of an embodiment of the belt conveyor of the present invention, in one of its operating positions;</li><li>Figure 2 is a bottom perspective view of the conveyor in Fig. 1;</li><li>Figure 3 is a perspective view of the belt conveyor of Fig. 1, in another of its operating positions;</li><li>Figure 4 is a bottom perspective view of the conveyor in Fig. 3;</li><li>Figure 5 is an exploded perspective view of the three main components of the belt conveyor of the present invention;</li><li>Figure 6 is a partial top perspective view of the conveyor belt of the present invention;</li><li>Figure 7 is a partial top view of the belt in Fig. 6;</li><li>Figure 8 is a side sectional view of the belt in Fig. 6;</li><li>Figure 9 is a partial bottom perspective view of the belt in Fig. 6;</li><li>Figure 10 is a perspective view showing the inside of the supporting means in Fig. 5;</li><li>Figure 11 is a perspective view that shows the inside of the guiding means in Fig. 5; and</li><li>Figure 12 is a detailed view of a moving and cleaning arrangement for the conveyor belt of the present invention.</li></ul>

With reference to the Figures, a preferred embodiment of the belt conveyor of the present invention is shown and described, referred to the field of transporting glass plates (with any shape, size and thickness). It will be immediately obvious to the skilled people in the art that numerous variations and modifications (for example related to shape, sizes and parts with equivalent functionalities) could be made to the described conveyor without departing from the scope of the invention as claimed in the enclosed Claims.

With reference to the Figures, a preferred embodiment of the belt conveyor 1 of the present invention is shown, applied (in a non-limiting way) to the transport of glass plates 2 having various sizes.

Such conveyor 1 operates using the vacuum obtained through common circuits and, for example, a liquid loop pump or a multi-stage ejector pump: such circuits (and other ones equivalent thereto) are known in the art and will not be described in detail herein below. Suffice it to say that the vacuum realised by such circuits (with a reduced cost and that can be easily realised and applied to the conveyor of the invention) is enough high to guarantee an unmovable holding of the plates 2 during their transport and their working, and such holding is much higher than the one currently obtained by the top holding means that have the above-mentioned problems.

Moreover, the vacuum circuit applied to the invention can reach efficiencies that are equal to 80% or more (in spite of the fact that the belt conveyor components are not mutually connected with high seals), but a low efficiency even down to 40% is enough to guarantee an holding force onto the plates 2 that is more than enough to transport and work them. This allows applying the vacuum only to part of the conveyor 1 when moving the plates 2, in a progressive way according to the advancement of the plates 2 themselves, without worrying that the vacuum leakages, due to the application of vacuum to a part of the conveyor 1 where the plate 2 has still not passed, or to a part of the conveyor 1 where the plate 2 has already passed, reduce the final holding efficiency of the conveyor itself.

The inventive conveyor 1 is realised in order to exert, when the plates 2 are worked along any direction with respect to their advancement direction, an holding force onto the plates 2 themselves that operates only on one of the major surfaces of the plates 2 that is not subjected to working, thereby avoiding to damage the moste delicate surface ("LOW-E") of the plates 2 in contact with working scraps.

The conveyor 1, as shown in the Figures, substantially comprises: <ul id="ul0002" list-style="bullet" compact="compact"><li>at least one belt 3 equipped with at least one suction recess 4 comprising at least one through-hole 4';</li><li>supporting means 5 of the at least one holed belt 3, in which such supporting means 5 comprise at least one vacuum chamber 7; and</li><li>guiding means 9 of the at least one holed belt 3, in which such guiding means 9 are placed between the belt 3 and the supporting means 5 in order to close the at least one vacuum chamber 7, and in which such guiding means 9 are equipped with at least one opening 11 adapted to externally open the at least one vacuum chamber 7 since it is placed next to the chamber 7 itself.</li></ul>

As can be seen in Fig. 5, the guiding means 9 can be made separately from the supporting means 5 and are joined thereto through securing means (not shown). Even if this is the preferred embodiment, the guiding means 9 can be made integrally with the supporting means 5.

In order to perform the best holding onto the plates 2, the belt 3 (as shown in Fig. 6 to 9) is equipped with a plurality of suction recesses 4 with respective holes 4' that are obtained along its whole longitudinal extension: in this way, by applying vacuum to the conveyor, the suction recesses 4 will create a sort of suction chambers that will progressively operate onto the plate 2, that covers them when passing above them (also guaranteeing a certain airtightness for them), and that will be disabled (by progressively removing vacuum therefrom in a known way, through suitable adjustments supplied, for example, by an encoder that detects the movement of the plates 2) as soon as a plate 2 has passed them when moving forward. The suction recesses 4 are realised (Fig. 6 and 7) in an elongated and slanted way with respect to the longitudinal axis of the belt 3 in order to guarantee a continuous but progressive holding onto the plates 2 and in order to reduce the wear problems onto the belt 3, providing recesses 4 that progressively work onto the plates 2 themselves.

In a corresponding way to the above-described one, when the belts 3 are realised with a plurality of recesses 4, also the supporting means 5 are equipped with a plurality of vacuum chambers 7 and the guiding means 9 are equipped with a plurality of respective openings 11 each one corresponding to one of the vacuum chambers 7. Such chambers 7, supplied by correspondinig holes 30 connected to the upstream and downstream vacuum circuit, allow being progressively activated and deactivated (by respectively applying and removing vacuum to and from them) according to the advancement of the plates 2 over the chambers 7.

While the general vacuum circuit is preferably driven by a solenoid valve (not shown) that activates the vacuum itself, every chamber 7 is preferably equipped with a membrane valve (not shown because it is known in the art) driven by another solenoid valve in order to create vacuum in or remove vacuum from the chamber 7.

In order to allow its handling, the belt 3 is equipped with a plurality of dragging teeth 14 adapted to engage respective dragging grooves 16 of toothed wheels 18 for moving the conveyor 1 around the wheels 18 and corresponding idle rollers 18'.

Moreover, since, after a prolonged use, glass dust and other impurities are sucked inside the holes 4' of the belt 3, the conveyor 1 is equipped with at least one wheel 20 (Fig. 12) around which the belts 3 rotate, in which such wheel 20 is equipped with a plurality of projecting pins 22 adapted to engage and penetrate into the respective holes 4' of the belt 3 in order to clean them and detach therefrom possible foreign substances contained therein upon every complete rotation of the belt 3.

The inventive conveyor 1 is so flexible as to be realised in various versions and configurations, that are able to be mutually coupled and uncoupled, in order to allow moving and working plates having different shapes and sizes, even simultaneously on the same line. Figures 1 to 4 show one of these construction variations, in which three belt conveyors 3, 3', 3" are provided that are mutually connected and cooperating. A first belt 3 is fixed and is equipped with a plurality of bearing and working-reference rollers 26, while a pair of belts 3', 3" are provided that are placed on a support 24 that is movable with respect to the fixed belt 3 along a transverse direction with respect to the advancement direction of the plates 2. In this way, the distance between the fixed belt 3 and the two movable belts 3', 3" can be adjusted, in order to keep it variable to realise the support and holding of plates 2 with any transverse size. Moreover, these two movable belts 3', 3'', once having been placed with respect to the fixed belt 3, are adapted to be simultaneously or alternatively activated to provide a higher or lower grip onto the plates 2, to complete the operating flexibility of the inventive conveyor 1.

While Fig. 1 and 2 show the belts in an "open" position, namely with the belt 3' detached from the fixed belt 3, to realise an holding on plates 2 having big sizes, Fig. 3 and 4 show the belts in a "closed" position, namely with the belt 3' approaching the belt 3 for holding plates 2 having small sizes. Due to its configuration, it would even be possible to use a single belt 3 to obtain an efficient holding on many types of plates 2 having small sizes: it is however preferable to perform the holding with two belts 3 that engage respective ends of the plates 2 when they pass. As can be well seen in Fig. 1 and 3, it is obviously possible to also modify the distance between the two belts 3' and 3" by operating on the structure of the support 24.

Still more, Fig. 2 and 4 show the lower part of the support 24, where means 28 for moving the support 24 are better shown: such means are preferably composed of an electro-cylinder and/or suitable reducers.

With the constructive variation of the conveyor 1 shown in Fig. 1 to 4, a real conveyor system can thereby be realised for plates 2 having various sizes, such system being equipped with a plurality of conveyors 1 as described above, each one moving with a different speed with respect to the other ones. With this arrangement, by equipping a line, for example, having two series of transport rollers, with one, but preferably two pairs of conveyor systems, it is possible to simultaneously or disjointly work plates having different sizes and shapes that come into the working station from the two upstream series of rollers. Many other configurations of the inventive system and conveyor are obviously possible, due to the intrinsic flexibility with which its construction is equipped.