BACKGROUND OF THE INVENTION 
   The present invention relates to belt scrapers for conveyor belts. 
   Scraper blades are often used to clean conveyor belts on the return side of the belt. Such devices typically include a shaft that is positioned transverse to the direction of conveyor belt travel and one or more scraper blades are mounted on the shaft. When the shaft is rotated, the scraper blade is forced into engagement with the conveyor belt such that the blade will scrape adherent material from the belt. The scraper blade wears down during use, with the result that the shaft has to be further rotated to maintain the blade in contact with the belt. Various tensioning and biasing devises have been proposed for maintaining contact between the blade and the belt, as shown for example in U.S. Pat. Nos. 5,378,202; 5,727,670; 5,845,761; and 5,826,700. 
   Nonetheless, there remains a need for a belt scraper and tensioning device that is reliable and which is user friendly and cost efficient to manufacture, install, and operate. 
   SUMMARY OF THE INVENTION 
   According to at least one example of the invention there is provided a conveyor belt scraper tensioning device including a support member mounted to at least partially rotate about a first axis, the support member being radially spaced apart from the first axis and having a scraper blade bracket for securing a scraper blade thereto. The device also includes a torsion bar located substantially along the first axis for imparting a torsional bias to the support member, the torsion bar having a first portion connected to the support member and a further portion spaced apart from and at least partially rotatable relative to the support member. A lever member is connected to the further portion of the torsion bar at a location spaced apart from the first portion for imparting torsional bias on the torsion bar. 
   According to a further example of the invention, there is provided in combination with a conveyor belt system having a conveyor belt mounted to a support frame, a scraper blade support device including a tubular member mounted at opposite ends to the support frame and at least partially rotatable about an axis that is substantially transverse to a direction of: travel of the conveyor belt. A scraper blade extends outward from the tubular member arid has an end for engaging the conveyor belt for removing material therefrom. A torsion bar extends along the axis inside the tubular member, the torsion bar having a first portion rigidly attached to the tubular member for imparting a torsional bias thereto and a further portion partially rotatable relative to the tubular member. A lever member is connected to the further portion of the torsion bar remote from the first portion for imparting a torsional bias to the torsion bar. 


   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Example embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein: 
       FIG. 1  is a side view of a belt scraper installed on a conveyor belt; 
       FIG. 2  is a side view of the belt scraper; 
       FIG. 3  is a perspective view of the belt scraper; and 
       FIG. 4  is an end view, with cut-away sections, of the belt scraper device. 
   


   Like reference numerals are used throughout the Figures to denote similar elements and features. 
   DETAILED DESCRIPTION 
     FIG. 1  shows a belt scraper device, indicated generally by reference  10 , according to example embodiments of the invention, installed on a conveyor system, generally indicated by  12 , which includes a conveyor belt  14  supported by a conveyor frame  16 . The belt scraper  10  is mounted to structural members of the conveyor frame  16  and maintains a scraper blade  20  in contact with the conveyor belt  14  for cleaning adherent material from the return side of the conveyor belt. 
   With reference to  FIGS. 1-3 , the belt scraper  10  includes a scraper blade support  18  that extends substantially transverse to the direction of travel of the conveyor belt  14 . The scraper blade support  18  includes an elongate tubular member  26  that is rotatably supported at its opposite ends by first and second mounting brackets  22 ,  24 , that are rigidly secured to the conveyor frame  16 . In an example embodiment, the scraper blade  20  is removably mounted to a scraper blade bracket  28  provided on the tubular member  26 . With reference to  FIG. 4 , the scraper blade support further includes an elongate internal torsion bar  30  that passes through, and is co-axial with, the tubular member  26 . As will be explained in greater detail below, the torsion bar  30  imparts a torsional bias on the tubular member  26 , which in turn transmits the torsional bias onto scraper blade  20  to maintain it in contact with conveyor belt  12 . The tubular member  30  is a substantially cylindrical wall having a circular cross-section in the illustrated example embodiment, however other configurations could also be used for tubular member. 
   At one end  31 , the torsion bar  30  is rigidly connected to the tubular member  26 —by way of example, in one embodiment, a disc-like connector  32  rigidly connects the torsion bar end  31  to an inner surface of the tubular member  26 , although other connector configurations, for example a connector comprising one or more radially extending spokes, can be used. Other than connected end  32 , the remainder of the torsion bar  30  is permitted to have a degree of rotational movement relative to the tubular member  26 , and a lever arm  36  is rigidly connected to the opposite end  33  of the torsion bar  30  for imparting a torsional bias to the torsion bar  30 . 
   In one embodiment, one or more bushings  34  are provided along the length of the torsion bar  30  to maintain the correct spacing between, and the co-axial alignment of, the torsion bar  30  and the tubular member  26 . In the illustrated embodiment, bushing  34  is a disk-like member rigidly connected at its center to the torsion bar  30  to rotate therewith, and having an outer surface that rotatably engages the inner surface of the tubular member  26 . Other bushing configurations can also be used, for example the bushing could rigidly engage the tubular member  26  rather than the torsion bar  30 , or could rigidly engage neither the tubular member or the torsion bar. 
   As best seen in  FIGS. 1 and 2 , the lever arm  36  has a first end  38  and a second end  40  located on opposite sides of the lever arm pivot axis, which is the point at which the lever arm is connected to torsion bar  30 . The first end  38  functions as a handle that a human operator can apply pressure to and adjust the torsion applied to torsion bar  30 . An opening  42  is provided through the second end  40  of the lever arm for cooperating with a selected one of a plurality of openings  44  provided through the first bracket  22 . A securing cotter pin  46  (see  FIGS. 2 and 4 ) is placed through the lever arm opening  42  and an aligned one of the bracket openings  44  to maintain the lever arm in a selected position once the operator has applied a desired torsional force to the torsion bar  30 . As the scraper blade  20  wears down, the position of the lever arm  36  can be periodically adjusted by an operator by aligning the lever arm opening  42  with a subsequent bracket opening  44  and inserting the pin  46  therethrough. FIG.  2  and  FIG. 1  show the lever arm  36  in two different positions. Although the lever arm opening  42  is shown near the second end  40  of the lever arm  36 , it could alternatively be located elsewhere, such as on the handle side of the lever arm pivot axis, for example, with bracket openings  44  being located in corresponding locations. In the place of a cotter pin and cooperating openings configuration, other known securing configurations could also be used to lock the lever arm  36  in a selected position to the bracket  22 , such as a ratchet teeth and pawl configuration, for example. The lever arm  36  could take various forms—for example, it could be replaced by a wheel or knob or other type of lever device. 
   In an example embodiment, a stopper plate  48  is rigidly attached to and extends outward from the tubular member  26 . The stopper plate  48  is configured to prevent the blade from being dragged under the belt  14  if it wears down too far. In particular, if the blade  20  wears down a predetermined distance, the stopper plate  48  rotates sufficiently to engage a stop member  78  (shown in phantom in  FIGS. 1 and 2 ) that protrudes inwardly from bracket  22 , thereby preventing further rotation of the outer tubular member  26 . 
   In an example embodiment, outward projecting first and second cylindrical connectors  50  and  52  are provided on the first and second brackets  22 ,  24 , respectively. A first weld plate  54  is pivotally and slidably mounted to the first connector  50  and a second weld plate  56  is pivotally mounted and slidably mounted to the second connector  52  such that, prior to installation on a conveyor system  12  each weld plate  54 ,  56  can be slid inwards and outwards along its respective connector  50 ,  52 , (as indicated by arrow  70  in  FIG. 3 ) and rotated about its respective connector (as indicated by arrow  68 ). When the belt scraper  10  is to be mounted to a conveyor system  12 , the spacing between the weld plates  54  and  56  is adjusted as required for attachment to the specific conveyor frame, and the weld plates  54  and  56  welded to the frame. Additionally, the weld plates  54 ,  56  are rotated about and then rigidly welded to their respective connectors  50 ,  52  at the appropriate angle to correctly position the scraper blade support relative to the conveyor belt  14 . It will thus be appreciated that the combination of connectors  50 ,  52  and weld plates  54 ,  56  allow the belt scraper to be secured to a variety of conveyor belt frames that have differing configurations and sizes. 
   In one example embodiment, the scraper blade bracket  28  is a plate that extends outward from the tubular member  26 , and which has a plurality of mounting holes  58  (see  FIG. 4 ) provided therethrough for receiving bolts  62  to secure the scraper blade  20  to the scraper blade bracket  28 . The scraper blade  20  includes a row of openings  62  for receiving bolts  62 . In and example embodiment, the scraper blade  20  is bisymmetrical about the row of openings  62 , and has two useable scrapping edges  64  and  66 . When one edge is suitably worn down, the blade  20  can be detached from scraper blade bracket  28 , turned around 180 degrees, and remounted so that the opposite scrapping edge is located adjacent the conveyor belt  14 . The scraper blade  20  can be made out of a number of materials, and in an example embodiment is made of a tough resilient material such as rigid urethane, and the belt scraper device  10  is generally constructed of steel components. As seen in  FIGS. 1 and 2 , the scrapping edges  64  and  66  of the blade  20  are angled. 
   The operation of belt scraper  10  will now be described. With the scraping end of scraper blade  20  engaging the conveyor belt  14 , an operator applies pressure to the handle end  38  of lever arm  36 , causing a torsional force to be applied to torsion bar  30 , which in turn applies a torsional bias to the tubular member  26  that is transferred to scraper blade  20 , biasing the blade  20  against the conveyor belt. When a desired bias is applied, the lever arm  36  is secured in place by inserting locking pin  46  through the lever arm opening  42  and into a selected bracket opening  44 . When the lever arm  36  is moved into its desired position, the end  33  of the torsion bar  30  rotates relative to the tubular member  26 , whereas the opposite end  31  of the torsion bar that is fixed to the tubular member does not, thereby storing bias energy in the torsion bar  30  so that force between the blade  20  and the conveyor belt  14  is maintained as the blade  20  wears down. Such a configuration maintains a relatively, consistent bias pressure between the blade  20  and the belt  14  throughout a range of blade wear as such pressure is proportional to the torsional force applied by torsion bar  30  and inversely proportional to the length of the blade  20 —thus the decreasing length of the blade and the resulting decrease in torsional force applied by the torsion bar counterbalance each other to an extent. After the blade wears down a predetermined amount, an operator can adjust the position of lever arm  36  and lock it into the new position. 
   In some embodiments, mounting brackets  22  and  24  are omitted, with blade support  18  being mounted to brackets integral to conveyor frame  16  and the lever arm  36  being securable in selected positions relative to the conveyor frame  16 . Scraper blade bracket  28  could take a number of configurations other than as shown. For example, it could include a slot for receiving an end of the blade therein. In some embodiments, a plurality of blades  20  are positioned side-by-side across the tubular member  26 , rather than just a single blade. Although shown as having an uninterrupted outer surface, in some embodiments tubular member  26  could include slots or other openings along its length. 
   The above-described embodiments of the present invention are intended to be examples only. Alterations, modifications and variations may be effected to the particular embodiments by those skilled in the art without departing from the scope of the invention, which is defined by the claims appended hereto.
A conveyor belt scraper tensioning device including a support member mounted to at least partially rotate about a first axis, the support member being radially spaced apart from the first axis and having a scraper blade bracket for securing a scraper blade thereto. The device also includes a torsion bar located substantially along the first axis for imparting a torsional bias to the support member, the torsion bar having a first portion connected to the support member and a further portion spaced apart from and at least partially rotatable relative to the support member. A lever member is connected to the further portion of the torsion bar at at location spaced apart from the first portion for imparting torsional bias on the torsion bar.