OF VARYING LENGTHS

TECHNICAL FIELD

This invention relates to the removal of object from a moving belt. Of particular interest are fla belts used for transporting raw material, especiall mixtures in which both larger and smaller solids ar present.

BACKGROUND ART

Prior to this invention a trough was formed i the belt by the use of idlers that were placed nea the edges of the belt, with the outer end of eac idler being disposed upwardly. With the idlers s positioned, the edges of the belt formed lips whic prevented the material on the conveyor from falling of inadvertently. However, these lips hindered efforts dislodge oversized objects from the moving belt. Wh devices were employed to deflect such objects sideway for instance, the devices had to be capable of exerti

a large side force just to move them past the raised belt lip. But forces of the magnitudes required tended to damage both the material and the belt itself.

DISCLOSURE OF INVENTION The object of the present invention is to facili¬ tate removing oversized objects traveling on a conveyor belt after these objects have been deflected sideways and dislodged from the main body of the burden carried by the conveyor. The dislodging impact may be imparted to such objects by one or more rakes rotatably mounted above the belt. In the preferred embodiment, side kick rakes described by Wilson in U.S. Patent No. 4,541,532 are employed.

A further object of the present invention is to provide an apparatus which can be used in conjunction with a series of side kick rakes as described by Wilson to reduce the amount of force which otherwise needs to be applied by these rakes to remove large, heavy ob¬ jects (such as a stone weighing a ton) from a conveyor belt.

According to the present invention, a short sec¬ tion of a moving conveyor belt is partially supported by an array of idlers placed perpendicular to the longitudinal axis of the belt. Each of the idlers is rotatably mounted in a horizontal position and is disposed parallel to and spaced apart from the other idlers. These idlers have varying lengths, the shortest

idler being approximately one-half the length of the longest. The two longest idlers, each of which is approximately equal in length to the width of the belt, are disposed at the extreme ends of the array and centered on the belt. The shorter idler are offset with respect tc the belt centerline. In each of the shorter idlers, the end which is closest to this centerline lies in an arc with the general shape of a "C" which opens towards one edge .of the belt. The overall placement of the idlers in the array is such that a crescent-shaped soft spot is provided in the moving conveyor belt. At any given instant, this soft spot is positioned between the two longest idlers.

When large objects in the burden on the conveyor are deflected onto the soft spot and toward the belt edge, the short section of the belt not only flattens but also sags. Thus the belt where it is partially supported by the array forms a chute which appears when needed reducing the amount of force which would otherwise be required to dislodge an oversized object from the belt.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a perspective view of the apparatus according to the present invention, showing a fragmen- tary section of the conveyor belt; the rakes which are employed to deflect oversized objects sideways being shown in dashed lines;

FIG. 2 is a plan view in which the placement of the idlers and of the belt according to the present invention is shown schematically, the belt and the rakes being shown in dashed lines; FIG. 3 is a side elevational view on an enlarged scale along the line 111—111 in which the position of the burden is shown in dashed lines; and

FIG. 4 is a side elevational view on an enlarged scale taken along the line IV-IV in which the position of the burden is shown in dashed lines, the view being taken when an oversize object is situated atop the soft spot on the belt.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to FIGS. 1-4, an apparatus incorporating the present invention comprises an array

10 of rotatably mounted flat impact idlers 21, 31 over which a conveyor belt 11 travels. In most applications, the belt 11 travels at speeds between 350 feet and 1200 feet per minute. Each idler 21, 31 includes a roller 22, 32 on a shaft 23, 33 that turns in bearing blocks

24, 25; 34, 35 about an axis disposed perpendicularly to the belt centerline 12.

As best seen in FIGS. 2-4, each of the idlers 21,

31 is unpaired and disposed horizontally. The length of each of. the idlers 21 is approximately equal to the width of the belt 11 (FIG. 2). The length of each of the idlers 31, on the other hand, is substantially less

the idlers 21. The shorter idlers 31 are situated between the longest idlers 21 which are centered on the belt 11. In the shorter idlers 31, which are offset with respect to the belt centerline 12, one end of each idler lies along an imaginary arc 14 which opens towards an outer edge 15 of the belt 11. The overall placement ^' of the idlers 21, 31 in the array 10 is such that a cresent-εhaped soft spot 16 is formed. The soft spot 16 is disposed within the portion of the belt 11 lying directly above the arc 14 and within the edge 15 at any particular instant of time.

Both upstream and downstream of the array 10, pairs of idlers 41, 42 slope downwardly toward each other on either side of the belt centerline 12. A shaft 43, 44 within each of the idlers 41, . 42 is rotatably mounted on bearing blocks 47, 45, respectively, and disposed at an angle to the horizontal which measures by way of example, 20 degrees (FIGS. 3 and 4). Supported by the paired idlers 41, 42, the belts 11 resembles a trough, the walls of which are useful in retaining the burden 18 on the conveyor. Passing over the array 10, with its horizontally disposed idlers 21, 31, the belt 11 flattens abruptly. But in situations in which, all of the =>..orter idlers 31 are replaced by longer idlers 21, some lip remains along the edges 13, 15 of the belt 11, hindering the removal of oversized

objects when they are forced over the sides of the belt.

The soft spot 16 is sized and situated so that any burden 18 carried by the conveyor tends to remain on it unless a force is specifically applied to deflect objects within the burden laterally. When a large, heavy object 17, 17' in the burden 18 carried by the conveyor is deflected onto the soft spot 16 and towards the belt edge 15, the belt 11 sags, forming a temporary chute 19. In order to help keep an object 17, 17' as it exits the chute 19 away from the conveyor, a fixed chute 40 is preferably attached to structure (not shown) beneath points where the chute 19 can form.

INDUSTRIAL APPLICABILITY The apparatus according to the present invention can be used in conjunction with a series of side kick rake 51, 52, 53, 54, with the wheels being employed to deflect oversized objects 17, 17' from the belt 11. The construction and operation of suitable rake wheels is disclosed by Wilson in U.S. Patent No. 4,541,532. In the preferred embodiment illustrated in FIG. 2, the longest idlers 21 are positioned, by way of example, approximately 12 inches upstream of the leading edge of the first wheel 51 and approximately 12 inches downstream of the trailing edge of the last wheel 54. The space between these two longest idlers 21 is then divided into the same number of generally equal

portions as there are rake wheels. Preferably, the furthest downstream shorter idler 31 is also placed close behind the leading edge of the furthest down¬ stream wheel 54 to provide good support for the belt 11. A small overlap of the leading edge of the wheel 53 and the idler 31 is acceptable. In addition, the first paired set of idlers 41, 42 is mounted at a distance which measures no more than 4 feet downstream of the trailing edge of the wheel 54 and no more than 4 feet upstream of the point at which the axis of rotation of the wheel 51 lies directly above the edge 13 of the belt 11.

It is apparent from the foregoing that a new and improved apparatus for use in the removal of objects from moving belts has been provided. While only the presently preferred embodiment of the invention has been disclosed, as will be apparent to those familiar with the art, certain changes and modifications can be made without departing from the scope of the invention as defined by the following claims.