Description
BACKGROUND OF THE INVENTION
1. Technical Field
The invention is directed to a flexible joining device for use with conveyor belts.
2. Prior Art
Conveyor belts are used in various industries for carrying materials and matters, generally, but not necessarily, in bulk form. Most often these conveyor belts are made up of a flexible material, having a certain elasticity, at least in the longitudinal direction, and they require the junction of the two ends, to constitute an endless conveyor belt, which passes around rollers, at least one of them being a driving roller the other one being generally a free roller known as idle roller.
In what concerns the methods of joining these conveyor belts, two main families are known hitherto.
A first family consists in sticking or vulcanizing the conveyor belt ends, when the band or the belt contains a large proportion of rubber. The operating conditions for presenting these ends and the operating conditions for carrying out the sticking or the vulcanization of these ends, one to the other, are well known by the men of the art.
The other family of joining methods makes use of joining devices consisting in a series of rigid metallic staples, usually U-shaped, each comprising two fixing lugs and an eyelet at their internal concave part, thus forming a so-called knuckle, similar to hinges. The fixing lugs of these rigid staples are attached to one end of the conveyor belt, one of them being fixed on one of the end faces of the conveyor belt, the other one on the other end face of the conveyor, by means of rivets or by means of spikes, often dual type spikes the sharp-pointed free ends of which are turned down after crossing matching holes, one of the lugs, the band and the other lug, then projecting from this latter.
The first family of joining methods, suffers of the major inconvenience resulting from the length of the operations, requiring a rather long shut-down, which may last up to 24 hours, and on the other hand from the difficulty often encountered in the hard running conditions (prevailing in transport of materials, and certain production industries) detrimental to a proper performance of the preparation of the ends. Furthermore, these junctions are not detachable. The possibility of carrying out a disconnection is useful, if a conveyor belt device has to be lengthened, which is often the case in mines, in quarries and in public works, along with the advance of the mine working face, the quarries works of the public works. Also, an easy disconnection enables an easy replacement of a piece of worn or damaged belt, the remaining pieces being usable.
In the case of the second family of joining methods, the operation can be faster and require a less careful preparation of the conveyor belt ends. However these junctions present major drawbacks which consist essentially in two problems. The first one lies in the fact that the linking and hinging axis is worn by the staples which are hinged upon it, and rotate with respect to it, during the running of the conveyor belt. This is unavoidable owing to the inherent design of the joining devices. Some corrective measures have been envisaged in order to obviate such wear, but these measures are either inefficient, or they increase considerably the cost, while they are far from totally effective.
The second problem encountered with the method of joining according to the second family, results from tears in the belt ends caused by the nails or points positioned rather close to the extremity of the belt ends. Due to their stiffness, the fixing lugs of the staples must be short in order to match more or less with the curve of the belt when the latter moves over a roller (either driving or idle), thus requiring as mentioned hereabove the location of the points or the rivets, rather close to the ends of the belt. Moreover, owing to this stiffness, the points are submitted to hard tensions, the path of the lug located on the roller side being shorter than the path of the lug located on the external side. The hard tensions which are supported by the points owing to the stiffness of the fixing lugs, cause the slow tear of the conveyor belt by the rivet or spike stem which crosses through the belt, and the failure of the junction.
OBJECT AND SUMMARY OF THE INVENTION
The object of the present invention is a joining device having all the advantages of both families and none of their inconveniences, i.e.
It is to be noted that the properties aimed at by the invention, concerning the novel method of joining, are properties found partly in the known joining devices of the first family and partly of those of the second family, although the devices according to both of the known families, do not present the whole of the properties which are incompatible within the same known family.
The problems of the prior art methods are solved by means of a joining device for conveyor belt presenting linking elements aligned on the external edge of each one of the two halves of the joining device, each one being solidly attached to a respective end of a conveyor belt: the linking elements are arranged to receive linking stems transversally threaded alternately, across a linking element belonging to one half of the joining device they then cross a linking element belonging to the other half of the joining device and so on. The halves of the joining devices are brought close together in order to interleave the linking elements belonging to one half of the joining device, to the linking elements belonging to the other half of the joining device. The joining device according to the invention is characterised by the fact:
According to a preferred embodiment of the invention, each linking element is provided with one single passage or through hole for one linking stem. This through hole has no round transversal cross section, for instance of a "race-course" shape. The linking stem has a transversal cross-section of complementary shape, with a slight gap therebetween. This no round shape is aimed to prevent the operation of the joining device as a hinge, as in the case of the devices comprising stiff staples, according to the prior previous art, since these staples are quickly worn out. Other no-round shapes could be envisaged provided they prevent the rotation of the linking elements with respect to the linking stem during the operation of the conveyor belt. Although the joining device, according to the invention, is not hinged at the linking elements, this shortcoming is compensated by the flexibility and the elasticity of the material and by that of the frame surrounding the passages.
According to another preferred embodiment of the invention, each linking element is provided with two or several through holes, the link being obtained by means of two or several linking stems. In this case, the linking stems may have either a round shaped or a non-round shaped transversal cross-section, since the provision of at least two stems prevents the hinge effect, even with round shaped transversal cross-section stems. The through holes may be shifted in the longitudinal direction as well as in the direction perpendicular to the general plane of the joining device. The through holes are advantageously surrounded by parts of the frame of the joining device, in order to transmit the tensions to the frame and therefrom to the whole of the joining device and to the conveyor belt solidly attached to the joining device.
In what concerns the solid attachment of the joining device to the conveyor belt ends, two main methods are envisaged according to the invention. The first method of solid attachment to the conveyor belt according to the invention consists in the fact that each one of the halves of the joining device constitutes a single unit with the conveyor belt end, the frame of the joining device being the extension in the joining device of at least a part of the conveyor belt frame. These joining devices are obtained by overcasting or overvulcanization at least a part of the conveyor belt frame projecting beyond the conveyor belt and arranged adequately in a mould.
According to a second method for a solid attachment each half of the joining device is provided with two wings, a lower wing and an upper wing with the frame extending therebetween. These wings, formed as a single unit with the part of the joining device comprising the linking elements, are flexible and elastic, particularly in the longitudinal direction, on account of the elasticity of their constituents and of those of the frame. For fixing the said wings on one end of the conveyor belt, the wings are arranged on each side of the conveyor belt end which is thus located between the two wings. Rivets or spikes are forced into holes formed in the said fixing wings by crossing through the end of the conveyor sandwiched between the two fixing wings.
The holes, which are advantageously lined by means of washers, are distributed over the fixing wings, in such a way as the rivets or spikes are not arranged in longitudinal alignment, or if such is the case they should be set apart along a large distance.
It has to be underlined that since the wings of the joining devices, according to the invention, are flexible and extend over the whole width of the joining devices, they can largely extend in the longitudinal direction without hampering the operation of the device. This arrangement enables the setting of the rivets or spikes largely apart from each other, this being quite different from the prior art, where rigid individual staples are used, with necessarily short fixing lugs, which in spite of that, and due to their stiffness cause tears to the conveyor belt end, because of the difference of radius, during the passage of the joining device over the idle rollers of the conveyor belt, between the upper face and the lower face of the joining device.
Advantageously, the frames are trimmed to the washers located inside the holes used for the passage of the rivets or spikes for fixing the halves of the joining devices. These washers could be replaced by small plates provided with openings, in particular at the free ends of the wings. These small plates, in which the frames are wedged, are advantageously folded externally, in order to form a tapered edge. These tapered edges are useful for protecting the ends of the wings against the attacks of the scrapers when these latter are used for clearing the conveyor belt from the material wastes. Effectively, without this tapered edge, the end of the wing projects from the plane of the corresponding surface of the conveyor belt, due to the thickness of the wing.