Conveyors: fluid current – Conduit – Having changing cross section
Reexamination Certificate
1999-02-04
2001-05-08
Ellis, Christopher P. (Department: 3651)
Conveyors: fluid current
Conduit
Having changing cross section
C406S086000
Reexamination Certificate
active
06227770
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to improved apparatus for the delivery of particulate material, which apparatus is specially adapted for use with an agricultural pneumatic conveyance device such as an air seeder.
BACKGROUND OF THE INVENTION
Seed and fertiliser products are distributed from a hopper or aircart to a delivery tool via a pneumatic conveyor tube. The travel path is initially substantially lateral over the first part of the distance from the supply hopper to the delivery tool. Then, the conveyor tube is provided with a substantially vertical orientation and its upper end connects with a flow dividing header. The header directs the air-entrained product into a number of conduits connected with the ground openers and delivery tools. In some cases the conduits of the header communicate with secondary headers before distributing the product to individual delivery tools. It is important to achieve an even distribution of product to each conduit from the header to apply equal amounts of product in each furrow. An uneven distribution results in inefficient soil and fertiliser usage, and affects the uniformity of the produce growth. A term commonly used is the coefficient of variation (CV) which is a measure of the uniformity of distribution across the distribution apparatus. A CV of 15% or greater is deemed unacceptable. A CV below 5% is considered very good.
The variation in distribution is effected by a number of factors. For instance, grain travelling in the conveyor tube tends to travel along the inside surface, particularly following any bend for redirection to vertical. The outlet of the conveyor tube delivers the material to a spreader in the distribution header which separates the material into channels arranged circumferentially about the header. Thus, if the product material is more heavily concentrated at one side of the conveyor tube, distribution will not be even. To deliver the product more evenly into the header, a number of designs have been proposed to create turbulence in the conveyor tube forcing the product away from the inside surface, and to centre the stream of product entering the header.
U.S. Pat. No. 4,717,289 issued to S. Popowich in 1988 discloses a corrugated delivery tube for use with a horizontal distribution head. Corrugations tend to direct material from the side walls in a substantially horizontal system with gravity also affecting the stream. In a substantially vertical orientation, many materials may follow the corrugated surface without experiencing enough turbulence to achieve the desired result.
A vertical header system allows a larger number of separation channels to be arranged circumferentially, without constricting the size of the channels which constriction would increase the pressure requirements and potentially cause more damage to the seed.
Canadian Application No. 2,111,611 to G. Bourgault published in June 1995 discloses the use of a central baffle to divide the material into two streams as it is redirected through a 90 degree bend and centering deflector rings. This is a relatively complicated structure to manufacture. Further, the seed and other material is exposed to a plurality of deflecting surfaces and since they are travelling at high speed this increases the possibility of damaging the seed in particular.
The use of a dimpled distribution tube is disclosed in Canadian Patent 1,167,704 issued to D. Kelm in 1984. A regular pattern of dimples, or interior projections, creates turbulence within the material flow. This design includes a number of variations in an attempt to improve the uniformity of distribution. Both cylindrical and conical tube sections are disclosed having regularly spaced dimples. An alternative embodiment places a dimpled section between two 45 degree bend sections to act on the material more gradually. This design improves the distribution of material considerably over the previous designs. However, the CV results of the Kelm device are somewhat inconsistent depending on the product used and the rate of delivery.
Various product materials, e.g. peas, wheat, canola and fertilisers exhibit different responses to turbulent flow. The objective is to provide a uniform stream of material to the dividing spreader of the header. Since any number and combination of materials may be distributed by the same equipment, it is desirable to find an optimised median system suitable for the full range of products to provide the necessary versatility.
Kelm identified that changing the placement of the dimpled tube section within the conveying system has an effect on the CV from the distribution head. However, it is not practical to reconfigure the conveying system for different products or application conditions.
The distribution head design also has a substantial effect on the CV. The prior art has provided a wide variety of distribution heads. Some heads promote turbulence in the flow while others make attempts to reduce turbulence in the head. Reference may be had to Kelm CA 1,097,149; Weiste AU 437,160; EP 211,295; Wurth SU 1,496,668; Gillespie U.S. Pat. No. 3,189,230; Oberg et al U.S. Pat. No. 4,191,500; Smith et al U.S. Pat. No. 4,413,935; Widmer et al U.S. Pat. No. 4,562,968 and Memory CA 2,073,237-A among others. Although several of these designs were partially successful it is the opinion of those skilled in this field that there is room for improvement insofar as effect on CV is concerned.
SUMMARY OF THE INVENTION
It is an objective to provide improved conveyor tubes and distribution heads for producing more even product distribution despite changing variables including product size, shape, density and mixture.
The present invention in one aspect relates generally to a conveyor tube for use in a distribution system for conveying air-entrained material between a first location to a distribution head, which has an interior surface with a plurality of inwardly directed spaced apart projections, said projections forming a plurality of spaced annular rows which extend around a lengthwise axis of the tube for creating controlled turbulence in the flow of material.
According to one feature of the invention, the space between at least some of the annular rows of projections decreases from one end toward another end of the conveyor tube.
According to another aspect of the invention the space between said annular rows of projections decreases in the direction of flow of the material through the conveyor tube from an inlet portion to an outlet portion thereof. Stated differently, annular rows nearer an end of the conveyor tube which is closest to the distribution head, when in use, are preferably more closely spaced than the rows closest to the first location. This helps provide adequate turbulence and acceptable CVs for a wide range of products.
According to another preferred feature the projections forming the plurality of annular rows may be arranged such that projections forming one row are angularly offset about the lengthwise axis of the tube with respect to the projections of an adjacent row. This helps to ensure that all particles of the material being conveyed are subjected to turbulence.
The conveyor tube advantageously includes a straight section of uniform diameter adapted to be vertically positioned when in use and having said rows of projections formed therein, said projections being of uniform depth and having their inner extremities concentrically positioned about the central lengthwise axis of the tube.
Further preferred features include a smoothly curved elbow section leading into an inlet portion of said straight section with said straight section having a first space devoid of projections between the elbow section and a first row of said projections at said inlet portion and a second space devoid of projections between the last row of said projections and an outlet end of the straight section.
Preferably said second space is not less than about 2 to 3 inches long, the total length of said straight section preferably being about 12 to 16 inches.
Advantageously said elbow section has a
Kydd Hughie Douglas
Memory Russell James
Poncelet Robert
Summach Montgomerie Blair
Dillon, Jr. Joe
Ellis Christopher P.
Flexi-Coil Ltd.
Miller Larry W.
Stader John William
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