CONVEYOR BELT

Abstract: The conveyor belt 3 particularly suitable for use in the cylindrical form in cross-section includes upper, 4, and lower, 5, cover rubber layers, a core layer 6 embedded between the upper and lower cover rubber layers. The core layer is integrally formed with thinned portions 6a, at both sides of a thickened central portion 6b of the core layer and the stepped shoulder portions 6c formed between the thickened central portion and the thinned portions are located on the upper side of the core layer, so that the belt is easily rolled into the cylindrical form by pinching the belt from the sides by means of pinching rollers by virtue of the thinned portions at both sides of the central thickened portion.

Description: DESCRIPTION CONVEYOR BELT The present invention relates to a conveyor belt, and more particularly to improvements in a conveyor belt suitable for use in a belt of a so-called cylindrical belt conveyor. The cylindrical conveyor for transporting mainly poer-like or granular materials in which the bel± of the conveybr is pinched from both sides by means of a plurality of pinching rollers so as to roll the belt into the cylindrical form in cross-section has advantages in that the materials to be transported by the conveyor belt are effectively prevented from scattering out of the conveyor belt and from getting wet by rain and water, while it can transport the materials effectively even though the transporting line is inclined. Such a conveyor belt is required to possess a property permitting the belt to be quickly rolled into the cylindrical form by means of the pinching rollers, while it can be restored to the original flat form by removal of the pinching force; However, as the diameter of the cylindrical form in cross-section of the belt increases, the thickness of the belt and, particularly, the thickness of the core layer thereof for reinforcing the strength of the belt necessarily increase, so that it is made difficult or impossible for the belt to be rolled into the cylindrical form b the action of the pinching rollers and to restore its original flat form by the removal of the pinching action of the pinching roliers, while, as described layer, the overlapping end edge portions of the belt when it is rolled into the cylindrical form in cross-section will yield to the gravitational force acting thereon so as to collapse'inwardly, thereby causing permanent deformation in the overlapping end edge portions of the belt which makes it difficult to supply the materials onto the belt after it is- restored to its flat form and, in the extreme instance, the restoration of the belt to its flat form is made impossible. The present invention aims at avoiding the above described disadvantages of the prior art conveyor belt. It is an object of the present invention to provide a novel and useful conveyor belt which positively avoids the above described disadvantages of the prior art conveyor belt. In order to achieve the above object, the conveyor belt constructed in accordance with a feature of the present invention which includes an upper cover layer, a lower cover layer and a reinforcing core layer embedded between the upper and lower cover layers is characterised in that the core layer is integrally formed with thinned portions at both sides of a thickened central portion of the core layer with the stepped shoulder portions formed between the central thickened portion and the thinned side portions being located on the upper surface of the core layer thereby providing a flat surface to the entire lower surface of the core layer. The upper and lower cover layers are resilient preferably rubber. With the belt constructed as described above, it is easily rolled into the cylindrical form by pinching the belt from both sides thereof by means of the pinching rollers, while the uniform surface pressure is maintained in the lower surface of the belt thereby reducing the wear and fatigue cf the lower surface of the belt contacting with the guide pulleys. in accordance with a further feature of the present inxientioll, the belt may be provided with stiffened sections located widthwise of the belt in symmetry to each other with respect to the centre line of the belt and extending lengthwise thereof, which serve to prevent collapsing of the overlapped end edge portions of the belt inwardly by the gravitational force acting thereon tending to generate permanent deformation at the collapsing portions or to make it difficult to supply materials onto the belt after it is restored to the flattened state for the transport of the material. Various other objects, features and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description when considered in connection with the accompanying drawings in which like reference characters designate like or corresponding parts throughout the several views and wherein: Fig=l is a cross-sectional view showing the conditions under which a prior art conveyor belt is operated; Fig.2 is a cross-sectional view showing an embodiment of the conveyor belt constructed in accordance with the present invention; Figs. 3 and 4 are perspective views each showing alternative embodiments of the conveyor belt of the present invention; and Fig.5 is a cross-sectional view showing the conditions under which the conveyor belt shown in Fig.4 is operated. With reference to Fig.l, the prior art conveyor belt 1 is shown rolled into the cylindrical form in cross-section by means of the pinching rollers 2 with the end edge portions la and Ib overlapping each other. As shown by the chain line in Fig.l, the overlapping end edge portions la and lb wiil yield to the gravitational force acting thereon so that they tend to collapse inwardly. Thus, a disadvantage of the prior art conveyor belt is that the overlapping end edge portions la and lb are subjected to permanent deformation, so that it is made difficult to safely supply the materials onto the belt after it is restored to its flat form for the transport of the materials or it is made impossible to restore the belt to its flat form. Referring now to Fig.2 showing an e.,.oodiment of the conveyor belt of the present invention, the belt 3 comprises an upper cover rubber layer 4, a lower cover rubber layer 5, a reinforcing core layer 6 embedded between the upper and lower cover rubber layers 4 and 5 and made of materials such as nylon canvas and steel cords and the like, and a pair of elongation-resisting reinforcing layers 7 embedded in the upper cover rubber layer 4 and abutting against or secured to the upper surfaces of the outer ends of the respective end edge portions 6a of the core layer 6. The reinforcing core layer 6 is made of materials such as laminated nylon or polyester canvas or nylon or steel cords having a high tensile strength and a high modulus of elasticity. The end edge portions 6a of the core layer 6 are made thinner than the central portion 6b in order to reduce resistance against bending widthwise of the belt 3, with the respective stepped shoulder portions between the thickened central portion 6b and the thinned side portions 6a being located on the upper side of the core layer 6 so as to maintain the lower surface thereof in the flat form thereby permitting the surface pressure generated by the guide pulleys supporting the belt 3 between the same and the pulleys to be kept uniform so that local fatigue or wear generated in the lower cover rubber layer 5 is kept to the minimum. \ The elongation-resisting reinforcing layers 7 serve to maintain the elongation'lengthwise of the respective end edge portions of the belt 3 to the minimum, thereby urging positively the outer overlapping end edge portion of the belt operated in the cylindrically rolled state against the inner overlapping end edge portion of the belt as described later in connection with Fig.5, so that the outer overlapping end edge portion of the belt 3 is prevented from moving or stripping apart from the inner overlapping end edge portion of the belt 3, because the elongation lengthwise of the outer end edge portion of the belt 3 is limited to the minimum by virtue of the provision of the elongation-resisting reinforcing layers 7 even in the position intermediate the neighbouring pinching rollers located in spaced relationship lengthwise of the belt 3, i.e. in positions spaced a substantial distance between the pinching rollers arranged in the longitudinal direction of the belt 3, while the cross-sectional configuration of the belt 3 is kept exactly in the cylindrical form with the overlapping end edge portions thereof held in contact with each other. Referring now to Fig,.3 showing the perspective view of another embodiment of the belt of the present invention, the belt 8 comprises in the similar manner as that shown in Fig.2 an upper cover rubber layer 9, a lower cover rubber layer 10, a reinrorcing core layer 11 embedded between the upper and lower cover rubber layers 9 and 10, and two pairs of reinforcing canvases 12a and 12b, each pair being embedded in the upper and lower cover rubber layers 9 and 10 at the upper side and the lower side of the core layer 11, respectively, at positions in accordance with the present invention as described hereinbelow. The reinforcing canvases 12a and 12b are preferably made of materials such as nylon, vinylon or polyester canvas or cords or steel cords and the like. The positions where the respective pairs of the reinforcing canvases 12a and 12b are embedded in the belt 8 are so determined that the positions of the reinforcing canvases 12a and 12b are symmetrical to each other with respect to the centre line of the conveyor belt 8 and the centre of each of the reinforcing canvases 12a and 12b is preferably set to the position spaced from the respective end edges of the belt 8 by about 9 where b-is the width of the belt 8, while the width 32 of each of the reinforcing canvases 12a and 12b is 1 1 preferably in the range of -17 b and -5b. Thus, when the belt 8 is rolled into the cylindrical form in crosssection by means of the pinching rollers, the reinforcing canvases 12a and 12b are positioned in the side wall portions of the cylindrically rolled belt 8 extending lengthwise thereof with the overlapping end edge portions of the belt 8 extending upwardly and inwardly toward each other so as to form the cylindrical form. It is of course possible to provide only a single reinforcing canvas at each side of the belt 8 above or beneath the core layer 11. Fig.4 shows a further embodiment of the conveyor belt of the present invention. In this embodiment, the belt 8' is provided with a pair of high hardness rubbers 13a and 13b each having a width generally equal to that of the reinforcing canvases i2a, 12b and embedded in the belt 8' in place of the reinforcing canvases 12a and 12b shown in Fig.3 at positions corresponding to those where the reinforcing canvases 12a, 12b are located. The high hardness rubbers 13a and 13b have a Shore hardness of 75 or higher, and they can be prepared by adding suitable amount of phenol resin to the mass of rubber, or by blending 80 parts or more of carbon black with 100 parts of rubber, or by adding polymers such as high stylene and other like substance to the mass of rubber. Fig.5 shows the conditions under which the belt 8' shown in Fig.4 is operated in the cylindrical form in cross-section by using a plurality of pinching rollers 2 arranged around the periphery of the belt 8'. The high hardness rubbers 13a and 13b are located in the side wall portions of the belt 8' as shown and the centre angle subtended by the high hardness rubbers 13a, 13b is about 60 - 900. The centre angles subtended by the overlapping end edge portions 8'a and 0 8'b is about 50 . The restoring force for restoring the overlapping end edge portions 8'a and 8'b to their original flat form is given by the high hardness rubbers 13a, 13b so that the overlapping end edge portions 13a and 13b of'the belt 8' are positively prevented from collapsing inwardly by the action of the gravitational force acting thereon or from being subjected to permanent deformation thereby making it possible to maintain exact cylindrical form in cross-section of the belt 8' and safe transport of the materials M held in the cylindrical form of the belt 8'. It is clear that the belts shown in Figs. 2 and 3 can also exhibit the above described performance. With one feature of, the conveyor belt constructed in accordance with the present invention, it can be easily rolled into the cylindrical form in cross-section by using the pinching rollers by virtue of the fact that the central portion of the reinforcing layer is made thicker in comparison with both side portions integral thereto. Further, since the lower surface of the core layer is made flat without any stepped shoulder portions, the uniform surface pressure is maintained over the lower surface of the belt contacting with the guide pulleys thereby reducing local fatigue nd wear in'the lower surface of the belt. In case the elongationresisting reinforcing layers are provided at the end portions of the core layer, the elongation of the end edges of the belt is positively limited to the minimum so that the exact cylindrical form in cross-section of the belt is maintained without causing stripping of the outer overlapping end edge portion of the belt from the inner overlapping end edge portion even at positions spaced apart from the position at which the belt is pinched by the pinching rollers, i.e. even at positions where the belt is not pinched by the pinching rollers. Further, with the conveyor belt of the present invention which is provided with locally stiffened portions extending lengthwise of.the belt, the collapsing of the belt rolled into the cylindrical form in crosssection is positively prevented, while permanent deformation at the collapsing portions of the belt is positively prevented from occurring.

Claims: CLAIMS CONVEYOR BELT 1. A flexible conveyor belt comprising an upper cover layer, a lower cover layer and a reinforcing core layer embedded between said upper and lower cover layers, characterised in that said core layer 6 is integrally formed with thinned portions 6a at both sides of a thickened central portion 6b of said core layer with the stepped shoulder portions 6c formed between said central portion and said thinned side portions being located in the upper surface of said core layer. 2. A conveyor belt as claimed in claim 1, further comprising stiffened sections 12a, 12b, 13a, 13b having a bending-resisting strength located widthwise of said belt in symmetry to each other with respect to the centre line of said belt in at least cne of the upper side and the lower side of said core layer. 3. A conveyor belt as claimed in claim 2, wherein said stiffened sections 13a, 13b are foamed of high hardness rubber. 4. A conveyor belt as claimed in claim 1, 2 or 3, further comprising a pair of elongation-resisting reinforcing layers 7, each located along the respective end edge of said core layer.

Inventors: FUJITA, MAMORU, SUMINO, SHINICHI
Applicants: BRIDGESTONE TIRE KABUSHIKI KAISHA
Application year: 1981
Main classification: B65G15
IPC codes: B65G15