Self-cleaning Bucket for Hydraulically Operated Trench Diggers

New Zealand Journal of Agriculture, Volume 87, Issue 3, 15 September 1953, Page 273

Self-cleaning Bucket for Hydraulically Operated Trench Diggers

HYDRAULICALLY operated diggers or power shovels are becoming increasingly popular and there are now several makes on the market. Driven by any medium-horsepower tractor they have many uses on the farm, but this article by J. R. Chapman, Assistant Drainage Advisory Officer, Massey Agricultural College, Palmerston North, is confined to discussion of the use of the back hoe assembly for trenching, more especially for digging narrow trenches suitable for field tiles. EXPERIENCE has shown that in anything but a free-running soil the operator of a trench digger has difficulty in emptying the bucket. This difficulty may not be very apparent when a wide bucket, say 24in., is being ? ■ —— used, but it becomes accentuated when a narrower bucket is used. The farmer considers it desirable to use as narrow a bucket as possible to reduce not only the cost of digging but also the amount of material to be backfilled. Various methods were tried to overcome this difficulty, including the use of skeleton buckets, but eventually it became clear that some positive way of ejecting the spoil was necessary. A method was evolved whereby the movement between the boom and the bucket arm was used and, by appropriate linkage, transferred to a swinging ejector. The ejector consists basically of a pair of levers cranked to conform to the construction of the bucket and swung on lugs so positioned on the bucket frame that they cause the ends of the levers to sweep, as nearly as possible, the arc of the

back of the bucket. These levers are joined by a steel plate which forms the scraper, cleaning the bucket after each working stroke. The point of attachment to the. bucket frame becomes the fulcrum and the levers project to link with the connecting arms. Care was taken to make the whole ejector very rigid and to provide an ample bearing surface at the fulcrum point. The connecting arms, designed to take compressive as well as tensile stress, are hinged to a yoke attached to the boom. , ~ Action of the Ejector The action of the ejector assembly is entirely automatic and requires no modification of the normal controls or change in the work cycle. When the digging stroke has been completed and the bucket traversed clear. of the trench the emptying stroke takes place as shown in the diagram on page 273. The whole assembly has been outlined in both loaded and empty positions, and arcs show the movement of the ejector linkage in the course of the stroke. During the emptying stroke the ejector fulcrum point moves along an arc centred at A from Di to D. At the same time the point at which the ejector is linked to the connecting arms travels from Ci to C along an arc centred at B. As these arcs have different centres, a movement of C about D is caused. In this way the application of force to C operates the ejector. During the digging stroke the ejector action is reversed, allowing the bucket to be filled to capacity. The position of the boom yoke and dimension of the connecting arms and ejector must be suited to the particular make of machine and the size of bucket to be used. Acknowledgment The help and advice of A. A. D. McGregor, Head of the Engineering Department, Massey Agricultural College, in the design and manufacture of the prototype are acknowledged.