Automatic Anti-slanting Adjusting Roller for Belt Conveyor Disclosed is a type of automatic anti-slanting adjusting roller for belt conveyor, comprising rubber rolls (1), rubber cover (2), and wobbler mechanism (3); wherein said rubber rolls (1) are two rubber rolls arranged symmetrically at left and right sides, and said wobbler mechanism (3) is located between these rubber rolls and consists of screws (31), bearing cover (32). seal ring (33), rolling bearing (34), inner sleeve (35), central sleeve (36), outer sleeve (37), cylindrical pin (38), and central pendulum shaft (39). In the device of embodiments of this invention, since key motion mechanism is concentrated in the wobbler mechanism and the seal ring and rubber cover are used, protection against dust and water is more reliable, making this automatic anti-slanting adjusting roller applicable to sites of severe environment. Further more, by replacing rubber rolls, requirements for belt conveyers of different sizes can be satisfied, making said wobbler mechanism in embodiments easy to service, replace, and manufacture. Description Technical field This invention relates to a type of special device used to automatically correct wander of conveying belt of belt conveyer during conveying of material using the principle of automatic balancing. Background of the invention Each document, reference, patent application or patent cited in this text is expressly incorporated herein in their entirety by reference, which means that it should be read and considered by the reader as part of this text. That the document, reference, patent application or patent cited in this text is not repeated in this text is merely for reasons of conciseness. The following discussion of the background to the invention is intended to facilitate an understanding of the present invention only. It should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was published, known or part of the common general knowledge of the person skilled in the art in any jurisdiction as at the priority date of the invention. In the industries of China that use conveyer, due to wander of conveying belt of belt conveyer during conveying of materials, conveying capacity is lowered, material leaks, and even the machine needs to be shutdown for maintenance, thus seriously wasting labor, materials, and financial resource. Embodiments of the present invention seek to solve or mitigate these problems, or at least provide the consumer with a useful or commercial choice, and can be widely used for industries of cement, metallurgy, chemical engineering, coal, electric power, mining, coking, and iron and steel etc.
For conveying of materials (e.g. coal and ore), existing industries such as cement, metallurgy, chemical engineering, coal, electric power, mining, coking, and iron and steel etc. normally adopt belt conveyers. In such case, wander of conveying belt is common. To solve this problem, many manufacturers have designed many types of wander adjustment devices. For example, one existing technique adopts a type of anti-slanting roller of conveyer that adjusts its center, used to guide conveying belt during operation so that it runs on central path. This roller includes an adjusting roller (comprising a central regular cylindrical zone and two end conical zones) inside which the internal structure of the roller (comprising sleeve, bearing, and shaft pin) is installed. However, for different sizes of belt conveyer, support rollers of different sizes are required, and such anti-slanting rollers of existing technique are not easy to adjust. Further, during actual use of such rollers, assembling, maintenance, production, and replacement are not convenient. The present invention has been developed in this background. Summary of the invention According to a principal aspect of the present invention, there is provided an anti-slanting roller used for belt conveyer that automatically corrects wander, comprising rubber rolls, rubber cover, and wobbler mechanism; wherein said rubber rolls are two rubber rolls arranged symmetrically at left and right sides, and said wobbler mechanism is located between these rubber rolls; and wherein said wobbler mechanism comprises screws, bearing cover, seal ring, rolling bearing, inner sleeve, central sleeve, outer sleeve, cylindrical pin, and central pendulum shaft; said central pendulum shaft penetrates said inner sleeve and said cylindrical pin penetrates said inner sleeve, said central sleeve, and said central pendulum shaft at the same time, so that said central pendulum shaft can wobble around said cylindrical pin, said rolling bearing is pressed in between said inner sleeve and said outer sleeve, said seal ring is placed in said bearing cover, and said screws are used to fix said bearing cover on said outer sleeve. Embodiments of the invention make use of the principle of automatic balancing: In case of wander of conveying belt of belt conveyer, belt central plane will deviate from anti-slanting roller central plane (for installation of this anti-slanting roller, these central planes shall coincide, refer to Figure 1). Since the anti-slanting roller loses balance as driven by the belt, wobbling will occur (i.e. rubber roll I wobbles relative to central pendulum shaft 39, so that shaft 39 and rubber roll I do not have the same axis, refer to Figure 2 and Figure 3), so that the roller is in unstable status. To restore to stable status, the anti-slanting roller needs to wobble in the opposite direction, to achieve balance again. This generates automatic wander correction. In an embodiment of the invention, there is provided a new type of anti-slanting roller used in belt conveyer that can automatically correct wander, comprising rubber rolls 1, rubber cover 2, and wobbler mechanism 3; wherein said rubber rolls 1 are two rubber rolls arranged symmetrically at left and right sides, and said wobbler mechanism 3 is located between these rubber rolls and consists of screws 31, bearing cover 32, seal ring 33, rolling bearing 34, inner sleeve 35, central sleeve 36, outer sleeve 37, cylindrical pin 38, and central pendulum shaft 39. 2 Said central pendulum shaft 39 penetrates inner sleeve 35 and said cylindrical pin 38 penetrates inner sleeve 35, central sleeve 36, and central pendulum shaft 39 at the same time, so that said central pendulum shaft 39 can wobble around cylindrical pin 38. Said rolling bearing 34 is pressed in between inner sleeve 35 and outer sleeve 37. Said seal ring 33 is placed in bearing cover 32. Said screws 31 are used to fix bearing cover 32 on outer sleeve 37. Beneficial effects of embodiments of the invention 1. In an embodiment of the invention, since key motion mechanism is concentrated inside the wobbler mechanism, and also owing to use of seal ring (sealing device is provided in the wobbler mechanism) and rubber cover (sealing device is provided between rubber roll and wobbler mechanism), more reliable protection against dust and water is provided, so that this anti-slanting roller can be used for sites of severe environment. 2. In an embodiment of the invention, since there are many sizes of belt conveyers, in order to satisfy them with this anti-slanting roller, just change the rubber rolls, and the wobbler mechanism may remain basically unchanged. This allows versatility and interchangeability of this anti-slanting roller. 3. In an embodiment of the invention, this anti-slanting roller concentrates required key motion mechanism in the wobbler mechanism, so as to facilitate maintenance, replacement, and organization of production. Description of drawing figures In order that the invention may be more fully understood and put into practice, preferred embodiments thereof will now be described with reference to the accompanying drawings in which: Figure l is a plane of installation position of the anti-slanting roller of an embodiment of this invention that automatically corrects wander with conveying belt shown. Figure 2 is a schematic of normal operation process of an embodiment of the anti-slanting roller of an embodiment of this invention that automatically corrects wander with conveying belt shown. Figure 3 is a schematic of wandering process of the anti-slanting roller of an embodiment of this invention that automatically corrects wander with conveying belt shown. Figure 4 is a structural schematic of the anti-slanting roller of an embodiment of this invention that automatically corrects wander. Figure 5 is a structural section of the anti-slanting roller of an embodiment of this invention that automatically corrects wander. Figure 6 is a structural outline of the anti-slanting roller of an embodiment of this invention that automati cal ly corrects wander. Figure 7 is an exploded view of the structure of the wobbler mechanism of an embodiment of this invention. 3 Figure 8 is a structural section of the wobbler mechanism of an embodiment of this invention. Figure 9 is a structural outline of the wobbler mechanism of an embodiment of this invention. In these figures, 1 is rubber roll; 2 is rubber cover; 3 is wobbler mechanism (central part); 4 is screw; 5 is spring pad; 7 is central plane; 8 is conveying belt; 9 is anti-slanting roller that automatically corrects wander; 31 is screw; 32 is bearing cover; 33 is seal ring; 34 is rolling bearing; 35 is inner sleeve; 36 is central sleeve; 37 is outer sleeve; 38 is cylindrical pin; and 39 is central pendulum shaft. Preferred embodiment The following further describes this invention in combination with the figures and a preferred embodiment. Refer to figures 4-6 for structural schematic of this preferred embodiment. The anti-slanting roller of this preferred embodiment that automatically corrects wander comprises rubber rolls 1, rubber cover 2, and wobbler mechanism 3; wherein said rubber rolls I are two rubber rolls arranged symmetrically at left and right sides, and said wobbler mechanism 3 is located between these rubber rolls. Rubber cover 2 is put on central pendulum shaft 39, and screw 4 and spring pad 5 are used to fix rubber roll 1 on wobbler mechanism 3. Perform the same assembling at the other side. Refer to figures 7-9 for structural schematic of wobbler mechanism 3 (central part). Central pendulum shaft 39 penetrates inner sleeve 35 and cylindrical pin 38 penetrates inner sleeve 35, central sleeve 36, and central pendulum shaft 39 at the same time, so that central pendulum shaft 39 can wobble around cylindrical pin 38. Rolling bearing 34 is pressed in between inner sleeve 35 and outer sleeve 37. Seal ring 33 is placed in bearing cover 32. Screws 31 are used to fix bearing cover 32 on outer sleeve 37. Use of the principle of automatic balancing: In case of wander of conveying belt of belt conveyer, belt central plane will deviate from anti-slanting roller central plane (for installation of this roller, these central planes shall coincide, refer to Figure 1). Since the anti-slanting roller loses balance as driven by the belt, wobbling will occur (i.e. rubber roll 1 wobbles relative to central pendulum shaft 39, so that shaft 39 and rubber roll I do not have the same axis, refer to Figure 2 and Figure 3), so that the roller is in unstable status. To restore to stable status, the anti-slanting roller needs to wobble in the opposite direction, to achieve balance again. This generates automatic wander correction. Refer to Figure 3. Although this invention is disclosed using above preferred embodiment, this preferred embodiment and the figures are not intended to limit this utility model, and anyone familiar with this art can make variations or touchup within the concept and scope of this invention, which fall in the scope of protection of this invention. Therefore, the scope of protection of this invention shall be determined according to the claims of this invention. Throughout the specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising" , will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. 4 Furthermore, throughout the specification, unless the context requires otherwise, the word "include" or variations such as "includes" or "including" , will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. Modifications and variations such as would be apparent to a skilled addressee are deemed to be within the scope of the present invention. 5