Improved tensioning assembly for vibratory screens

#The present invention relates generally to vibratory material screening apparatus employed in the classifying of solid particulate matter and, more particularly, to such screening apparatus which employs a rotatable tensioning assembly for tensioning of the screen in such apparatus.

#Vibratory screening decks have been widely employed in the past for the classification and separation of particulate solids of varying particle sizes and compositions, such as limestone, coal and other ores. Such screening decks have typically comprised a generally rectangular frame which is suspended in operation and which has one or more screens in the frame upon which the materials to be classified are deposited. The frame and screening deck are suspended at an angle, and either the entire frame with the screen or the individual screens are vibrated to cause the solid particulates to move down the screen deck. As the materials move down the vibrating screen or screens, solids of smaller mesh size pass through the screen as "unders", and solids of larger dimensions are discharged from the lower end of the screen as "overs."

#One form of such screening deck is disclosed in U.S. Letters Pat. No. 4,732,670. In the screening deck disclosed therein one or more wire cloth screens having a predetermined mesh size to permit the passage therethrough of material are anchored at opposite ends of the screens to members extending transverse to the frame walls. In such screening deck one end of the screen is stationarily anchored over its width, and the other end of the screen is anchored to a rotatable tensioning assembly which, when rotated, adjusts the tension across the width of the screen.

#In the course of this description, reference will frequently be made to the attached drawings in which:

#FIG. 1 is an overall perspective view of a classifying apparatus incorporating a preferred embodiment of improved tensioning assembly in accordance with the principles of the present invention, and in which the screen deck has been partially cut away to show the components of the deck that underlie the screens;

#FIG. 2 is a partially cut away end view of the classifying apparatus as viewed substantially along lines 2--2 of FIG. 1;

#An overall perspective view of a vibratory screen classifying apparatus 10 incorporating the principles of the present invention is shown in FIG. 1. Generally, the classifying apparatus 10 comprises a vibrating screening deck 12 mounted within a rigid frame 14. The classifying apparatus as shown in FIG. 1 is similar to that shown in the aforementioned U.S. Letters Pat. No. 4,732,670 and, as such, the apparatus 10 will be described in general terms only, the specific details of the screening apparatus disclosed in the aforementioned application being incorporated herein by reference. It will be understood that apparatus other than that shown generally in the drawings may be selected by persons skilled in the art without departing from the principles of the invention.

#The classifying apparatus 10 includes a pair of longitudinally extending, rigid frame sidewalls 16, 16', such as channel beams as shown in FIG. 1. The elongate sidewalls 16 are spaced apart in generally parallel relationship to each other by vibrating tappet assemblies 18 beneath the screening deck as shown in FIG. 1. The tappet assemblies 18 include spaced tappet bars 20 extending transversely between the frame sidewalls 16, 16' and vibrators 22 for vibrating the tappet assemblies 18 and the screening deck 12 which lie upon the tappet bars and are supported by them. The details of the tappet assemblies 18 and their functions are fully described in U.S. Pat. No. 4,444,656, the disclosure of which is incorporated herein by reference. It will be understood that mechanisms for vibrating the screens other than those shown in the drawings may be employed in the invention.

#The frame walls 16, 16' are held in rigid spaced apart relationship by mounting tubes 24 which may provide the additional function of assisting in the suspension of the frame in angular relationship to a corresponding conveyor unit (not shown) which delivers the solid particulate matter to the top of the screening deck 12. Such suspension may be by way of suspension arms or cables 26, also as shown in FIG. 1. The suspension cables or arms 26 may be adjusted to change the angle of inclination of the vibrating screening deck 12 depending upon the particulate solids to be classified. Again, the manner of suspending the screening deck in the tappet assembly construction may take other various forms and do not form a principal part of the present invention per se.