FIELD OF THE INVENTION

The invention relates to apparatus for collecting and discharging agglomerations of miscellaneous matter for example as is to be found in form of municipal rubbish and floating detritus on a water surface.

Such matter may include cans and bottles, articles of wood or cardboard or plastics material, ropes and cordage, weeds, textile waste, rotting substances such as household refuse and dead fish and birds and, also viscous liquids such as bunker oils and tars.

BACKGROUND OF THE INVENTION

Apparatus for collecting and discharging waste material is known utilising two cooperating sets ^' of moving toothed structures, each being provided with plate-like teeth lying in parallel planes parallel to the direction of motion, and spaced, on each structure, at intervals perpendicular to those planes. The teeth of both structures are mutually intercalated in a collection zone where they are both moving in the same direction and, at positions remote from the collection zone, both structures interact with stationary combs comprising sets of blades which lie between adjacent lines of teeth, closely fitting against the sides of the teeth and their separating means to remove matter trapped between the teeth or adhering to the sides thereof. Means are also provided whereby the toothed structures, together with their comb assemblies, may become separated to permit the passage of matter which is too tough or bulky to be shredded by the teeth.

Both toothed structures may take the form of rotatably mounted shafts carrying assemblies of thin metal discs with circumferentially formed teeth, the discs being separated by relatively thick plain discs of diameter somewhat less than that at the tooth roots, all members being clamped together so that the assembly rotates as an integral unit.

Alternatively, one of the structures may be a shaft assembly as described and the other a belt type conveyor bearing lines of teeth at intervals across its width. Although teeth of almost any conceivable shape may be used to create an entrapment and collecting action, difficulties arise with the prior art apparatus as the spoil enters the separating scraper zone because of the generation of a biting action on the material developed between the disc teeth and separator combs as the teeth move relative to the combs. If the parts are not sufficiently robust or the driving force is inadequate, this biting action will defeat the objective of the separator combs and result in either the machine breaking or jamming even when dealing with soft materials such as cordage or plastic bags.

SUMMARY OF THE INVENTION

It is one object of the invention to provide apparatus of the above type although not necessarily incorporating the two intercalated sets of toothed structures, wherein the cooperating teeth of the discs and separator combs are designed such that the possibility of matter becoming trapped and jamming the machine by the cutting action between the teeth and combs, if the matter is too robust to be sheared, as would be the case with, for instance, wire or thick metal objects,

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is obviated. The necessity, as in the prior art, for providing a machine which is very powerful and furnished with hardened and ground teeth and combs is thereby eliminated.

According to the invention there is provided apparatus for collecting and discharging waste material comprising at least one rotatable shaft, a series of peripheral rows of teeth arranged on the or each shaft, the teeth in each row having side flanks delimiting a leading tooth face which is presented to the material to be collected by the teeth as the shaft rotates, material-clearing elements between said rows, the elements having material-clearing blade edges defining a series of slits respectively between which a said one of the peri¬ pheral rows of teeth passes with the flanks in closely spaced adjacent relationship to the blade edges such that the material collected between the rows of teeth is removed for passage to a discharge zone, said elements and said teeth being configured such that the angle formed at any time between the edges of the leading tooth face of each advancing tooth and an adjacent blade edge of a respective slit through which the teeth pass is of a magnitude necessary to ensure that the cooperating teeth and material-clearing elements do not act to bite or cut into the waste material to such an extent as to prevent said material passing smoothly to said discharge zone.

With this arrangement the biting action set up between the slits and the rotating teeth, is never sufficient to induce the required amount of frictional engagement in relation to the material being handled by the machine, so that the waste material being collected does not therefore, become caught between the teeth and the material-gathering elements but is passed

smoothly by these elements to the discharge zone.

In a preferred form cylindrical separators are between the peripheral rows of teeth of the material-gathering elements in the form of flat scraper blades having rectilinear blade edges, which rest tangentially on the separators. The leading faces of the rotating teeth are then configured to lie on the involute of a base circle being the generatrix of the rotating cyclindrical separators. In this case the angle between the scraper blade edges and the edges of o the leading faces of the rotating teeth is always 90 . Other features and advantages of the invention will become clear from the following detailed description of preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described by way of example with reference to the accompanying drawings wherein:

Figure la is a front elevation of apparatus for collecting and discharging waste material as seen from the direction from which spoil is being accepted, provided with teeth bearing collector discs and waste material removing scraper blades according to one form of the invention:

Figure lb is a sectional view of the apparatus of Figure la taken along the line A-A:

Figure lc is a view of the machine of Figure la taken along the line

B-B of Figure lb: Figure 2 illustrates one way of determining the curvature of the leading face of the teeth of the collector discs interacting with a scraper comb blade of rectilinear form.

Figure 3 shows a preferred construction of a scraper comb:

Figure 4 shows a further form of scraper comb, and

Figures 5a and 5b shows preferred arrangements for driving the machine of Figure la.

BEST MODES OF PERFORMING THE INVENTION

The apparatus for collecting and discharging waste material shown in the drawings, and more particularly in Figures la, lb and l£ comprises upper and lower rows 1 and 2 of peripheral teeth T arranged respectively on horizontal shafts 3 and 4.

The lower shaft 4 is journalled for rotation in fixed bearings 5 mounted at fixed positions 6, while the upper shaft 3 is mounted on bearings at the free ends of lever arms 7 which swing about pivots 8 attached to a fixed position 9. Positions 6 and 9 bear a fixed relationship to one another, as or _* instance, would be the case when the various parts are attached to a mounting framework. The rows 1 and 2 of teeth T are set apart in planar fashion by cylindrical spacers 10, and are mounted to have their respective rows of teeth T at least partially intercalated to form an entrapment zone Z for waste material as shown in Figure lb, as the shaft 3 and 4 rotate in contra-wise fashion as indicated by the arrows 11. End portions of scraper comb plates 12 having rectilinear blade edges 12' , are mounted between the rows 1 and 2 and press firmly against the separators 10, with their blade edges 12' in close fitting relationship to the side flanks of teeth T, the other ends being fixed by any convenient known method to the lever arms 7 for those on the upper shaft 3, and to the fixed location 6 for those on the lower shaft 4. The blade edges 12' of adjacent scraper blades 12 form slits between which the teeth T of each respective row pass as the shafts 3 and 4 rotate.

Material thus entering the zone Z is crushed, impaled or shredded depending on its nature. Viscous substances such as tars or heavy oils become convoluted around the teeth T of the discs and adhere strongly to the sides thereof. Objects which are too tough to be dealt with as described cause the upper shaft 3 to rise and ride over them, the teeth T then exerting a gripping function to permit this to happen.

After leaving the entrapment zone Z the spoil is stripped from the teeth T by the action of the scraper comb blades 12 as the teeth T pass through the slits S, for deposition in a collection chamber (not shown) fior feeding to any subsequent process.

Although not illustrated shafts 3 and 4 which need not neces¬ sarily rotate at the same speed, may be driven from a power source, of any known type by a transmission system such as hydraulic motors on the shaft ends connected by pipeline to a pump and motor unit. Chain and linkwork systems may also be used.

The teeth T of the discs in rows 1 and 2 are specially designed in accordance with the invention, so that, as described earlier, the biting action effected between the leading faces of the teeth T presented to the material being collected as the shafts 3 and 4 rotate and scraper comb blade edges 12' to cut and shear the material being gathered so causing clogging or breakdown, is eliminated.

This biting action will occur if the "attack" angle with respect to the material being gathered, formed at any time between the leading faces of teeth T and the edges 12' of the scraper comb blades 12 as the teeth pass through the slits S between them, is below a certain value, taking into account the roughness and sharpness of the interacting surfaces and the nature of the waste material in question.

The phenomenon is easily understood by considering the effect of scissor blades. If the blades are wide open to an angle of 90 or greater, they will not bite into a piece of paper however sharp they are. However, as the "attack" angle between the blades gradually decreases a biting and cutting action will ensue. It has been found for example that with teeth and scraper comb blades that have smooth surfaces, the undesired biting action did not occur with angle of attack fi _ greater than 70o. ^' The attack angle is of the required magnitude in the embodiment of the invention illustrated when the leading face of each tooth T lies on the involute 13 of the circle 14 , whose diameter is that of the cylindrical separators 10 as shown in Figure 2. The heavily lined portion 15 of the involute curve 13 in Figure 2, is the leading face of a representative tooth R, while the dotted portion 16 is the trailing face of tooth R. The attack angle at any time may be defined by the angle A formed between tangent on the curve 13 at the points of intersection of tangents to the circl 14 with the curve 13, the latter tangents being extensions of the scraper comb blades 12 (not shown in Figure 2) lying on the separators 10,if it be imagined for purposes of illustration,that the circle 14 rotates with respect to the curve 13.

Since the curve 13 is the involute of the circle 14, the angle of attack A in Figure 2, between the leading face of the tooth R and a fixed scraper blade, is always 90 as the tooth R rotates in practice, in the direction of the arrow 17 about the centre 18. If either of the shafts 3 and 4 are always rotated in one direction the shape of the trailing flank 16 is not important, and may

take the form of a straight line descending from the tooth crest to the root of the adjacent tooth.

However, it will sometimes be desirable to regurgitate or disgorge the collected spoil by reversing the rotation of the shafts 3 and 4, an oppositely facing set of scraper blades at some other point • on the circumference being used to disgorge the spoil. In such a case, the tooth flank 16 should then be the reverse of the original shape leading flank 15 as shown.

The necessary shape of the flanks of teeth T having a constant, but different attack angle, may be found with the assistance of the formula:

L = R x tanA x (e & ^" /tanA - 1)

Where L = Length of tangent to generating circle. <_9~ = Angular distance of tangent point from the start point of the curve.

R = Radius of base circle

A = Attack angle.

Curve 19 shown in Figure 2, is calculated from this formula with an attack angle 20 of 70 . This smaller attack angle is some- times of advantage in that, for a given desired height, the tooth is narrower and more may be used around the circumference. A composite curve having an attack angle which varies with the tooth height, but is nowhere less than the minimum requirement may also sometimes be of value. It is, in practice, usually possible to approximate the mathematically correct curve with a portion of a plain circular arc, for which it is easier to arrange manufacture.

Figure 3 shows a modified form of scraper comb blade in the form of a continous metal band 21 which loosely engages the circumference of the separators 10 and also a stationary reaction rod 22 which spans the entire machine longitudinally of the shafts 3 and 4. To form the band 21, the ends of a metal strip may be welded together or any known convenient type of end joint may be used at some indifferent position, such as, for instance, a bolt and nut in rear of the rod 22.

Figure 4 shows a further modified form of scraper comb blade in the form of a plastics material moulding 23 such as nylon is provided with an open-ended slot to engage the reaction rod 22 as before. The moulding 23 is provided with a circular opening 24 accommodating the separators 10 which are of smaller diameter owing to the curvature of the sides of the type of scraper blade 23 the attac angle A is increased and this will sometimes be useful when it is desirable to use disc teeth which would have a smaller attack angle against a straight scraper blade.

Both the types shown in Figures 3 and 4 may be used for regur¬ gitating types of machine in which disgorgement occurs on reversal of rotations of the shafts 3 and 4.

Figure 5 shows a method of driving the machine for collecting and discharging waste material so as to obtain the necessary contra¬ riwise rotation of the upper and lower shafts 3 and 4 and the rise and fall motion of the upper assembly by means of a single chain and which depends upon the convenient property of being able to engage sprockets at both sides of the chain.

Dashed lines 25 are representations of upper and lower toothed disc assemblies being driven in the directions of arrows 26 to accept

spoil arriving in the direction of arrow 27, the shafts of the assemblies being attached to chain sprockets 28.

In Figure 5a the sprockets 28 are shown as the same size as is also a sprocket 29 which is in a fixed position and powered to rotate in the direction shown. A single endless chain C is routed as shown by the dashed line C so as to provide the rotations required. The lever arm 7 carrying the upper shaft disc assembly 3 is shown in the extreme up and down positions which occur during rise and fall motion. Although strict mathematical accuracy is not obtainable, it is possible to select a length of lever arm 7 and the position of its pivot in relation to the size and extreme positions of the upper shaft sprocket so that the total length of the chain C in the system remains constant from a practical point of view, the need for a heavily biassed jockey sprocket to take up slack being thereby avoided. » In a case when the two driven sprockets are to be of differing size to provide differing shaft speeds and/or when it is desirable to take advantage of the ability of a chain-drive system to provide a speed reduc¬ tion ratio relative to the driving sprocket it will not always be possible to use the simple system of Figure 5a so that the oppositely moving parts of the chain remain clear of each other. The difficulty may be overcome by adopting the more complicated arrangement of Figure 5b. In this diagram the two main driven sprockets 28 are shown in different sizes. Two small sprockets 30 are shown in fixed positions, power being delivered to either of them and the other acting as an idler to permit the necessary chain clearances to be obtained. The chain is routed as shown, but in this case the lever arm 7 must be pivoted forward of the shaft assembly centres instead of in rear. The advantage of sensibly invariant chain length may be realised as before.

Although a preferred embodiment of the invention has been described with reference to a machine incorporating two sets of inter¬ calating toothed structures, it is equally applicable to a machine employing a single set, and this is reflected in the appended claims. Moreover additions and modifications to the disclosed embodi¬ ments will be apparent to one skilled in the art but such will be withi the scope of the claims which follow. For example to achieve the results of the invention, it is not essential that the scraper comb blades be rectilinear and the co-operating leading faces of the rotatingteeth be curved, so long as the required angular relation¬ ship between them is preserved.

Thus the leading faces of the teeth (or face edges thereof) may be rectilinear and the scraper blade edges curved, or aiternatively the leading faces (or face edges thereof) and blade edges may be of curved profile as appropriate.