GB2150099A

GB2150099A - Conveyor assemblies

Info

Publication number: GB2150099A
Application number: GB08331804A
Authority: GB
Inventors: William Peter Billington
Original assignee: National Research Development Corp UK
Current assignee: National Research Development Corp UK
Priority date: 1983-11-29
Filing date: 1983-11-29
Publication date: 1985-06-26
Also published as: GB8331804D0; GB2150099B

Abstract

The driven sprockets 11 of a soil-separating web 8 are powered from the output shaft 15 for a Hooke's joint 17. The input shaft 19 of the joint 17 is inclined to shaft 15 at an angle of other than 180 DEG so that a constant speed drive to shaft 19 will result in the output shaft 15 accelerating and decelerating about some mean value which determines the overall conveying speed of the web. The resulting component of in-plane vibratory motion superimposed on the overall conveying motion of the web 8 gives the assembly a good soil-separating performance. The desired in-plane variation in the web motion may be achieved alternatively by means of a freewheel device and oscillating drive member. <IMAGE>

Description

SPECIFICATION Conveyor assemblies The present invention relates to conveyor assemblies e.g. soil-separating assemblies for use in or with a root-crop harvester.

With any root crop harvesting system that lifts relatively large quantities of soil with the crop, it is highly desirable to remove unwanted soil as quickly as possible once it enters the machine. The primary elevator is a convenient area to start cleaning and separating and the conventional method is to vibrate the primary web in a plane normal to its surface by supporting the web on elliptical sprockets. There are three major problems with this system: (i) the frequency of vibration is dependent on the web speed and is limited because the web loses contact with the sprockets as the speed increases; (ii) vibration in the plane normal to the web is the least effective in relation to soil removal; and (iii) vibrating in this plane is the most damaging to the crop.

The most effective way to remove soil from a root crop and also to reduce damage to that crop is now thought to be to vibrate the web in the plane of its direction of movement and UKPA 8226156 (NRDC) and GB 2077626 (NRDC) describe ways of doing this in which either the supporting frame or just the websupporting elements are vibrated in the desired fashion.

It is an object of the present invention to provide an assembly whereby in-plane vibration of a moving conveyor surface is provided by varying the rotary drive to the surface rather than by vibrating the surface independently of this drive. The ivention has practical advantages not only in its application to the primary webs of root crop harvesters but also in its application to other forms of conveyor (including elevators etc.) where surface agitation is desirable.

According to the present invention, a conveyor assembly for providing the in-plane vibration referred to above comprises an endless conveyor surface supported on a rotary support and drive means for periodically accelerating and/or decelerating the rotary motion of the support about some mean value.

A characteristic of a Hooke's joint is that when used to connect two shafts set at an angle of other than 180 to one another, the relative angular velocities of the two shafts will be continuously varying as the joint rotates, the ratio of the output shaft speed to the input shaft speed passing through two maxima and two minima in each revolution of the joint. This fact is made use of in a preferred first embodiment of the present invention where the rotary support for the conveying surface is driven from the output shaft of a Hooke's joint, the input shaft of which is arranged to rotate at a substantially constant speed about an axis lying at an angle of other than 180 to the rotation axis of the output shaft.

Although, as above explained, the Hooke's joint will superimpose an in-line oscillating motion on the overall conveying movement of the conveyor surface, it will be appreciated, nevertheless, that the overall surface speed of the conveyor will in this case be the same as if it were driven by an in-line joint with no speed variation.

In this preferred embodiment, the frequency of vibration can be varied by changing the speed of the input shaft to the Hooke's joint and/or the amplitude of vibration can be varied by changing the relative inclination between the two shafts.

It should be noted that in the context of the present invention, the term "conveyor surface" should be broadly interpreted to include any load-supporting moving surface capable of carrying the load from a first location to a second location while the term Hooke's joint should be interpreted as a device comprising two shaft-accepting members interconnected by a coupling member which is pivotally coupled to one of the shaft-accepting members about a first pivot axis and to the other one of the shaft-accepting members about a second pivot axis intersecting the first pivot axis and lying at right angles to the first pivot axis.

In an alternative embodiment, the drive means comprises a substantially constant speed rotary drive shaft connected with the rotary support via a first freewheel device allowing a freewheeling motion of the support relative to the drive shaft only in a first direction and a drive member arranged for oscillating rotary motion about the rotation axis of the rotary support to which it is connected via a second freewheel device allowing a freewheeling motion of the drive member relative to the rotary support only in the opposite direction to said first direction.

Conveniently, in this latter case, said first direction is the direction of rotation of the drive shaft and the drive member operates to periodically accelerate the rotation of the rotary support above the rotation speed otherwise imposed on it by the drive shaft.

Conveniently, the, or at least one of the two freewheel devices in a spragg Reynolds clutch, a rachet mechanism or any other suitable known freewheel device.

Embodiments of the invention will now be described, by way of example only with reference to the accompanying drawing in which: Figure 1 is a partially diagrammatic plan view of a conveying assembly according to the present invention; and Figure 2 is a partially diagrammatic perspective view of part of a second embodiment.

Thus referring first to Fig. 1, the primary web 1 8 of a carrot harvester or the like is supported on two pairs of sprockets 10, 11 the driven sprockets 11 of which are mounted on the output shaft 1 5 of a Hooke's joint 1 7.

The input shaft 19 of the joint 1 7 is driven at constant speed e.g. 300 r.p.m. from a hydraulic motor (not shown) also mounted on the harvester frame 21 or from the towing tractor p.t.o. shaft. Two digger shares 23 are provided at the front of the harvester.

In the situation shown, the input shaft 1 9 has been set at 45' to the output shaft 1 5 and as the joint 1 7 rotates, the ratio of varying output speed to constant input speed of the shafts varies between 0.7 at the minimum ratio and 1.4 at the maximum ratio with two maxima and minima occurring every revolution. With the shafts inclined at 20 , say, the value of these ratios would change to 0.8 at the minimum to 1.25 at the maximum. In this latter case, a typical input speed for shaft 1 9 would be 500 r.p.m. corresponding to a belt speed of 1 to 2 metres per second.

In a modification (not shown) of this embodiment, variations in the amplitude of vibration can be achieved for a given mean web surface speed by changing the drive ratio from the output shaft of the Hooke's joint to the web shaft 15.

Alternative vibratory drive means for the conveyor which can be used instead of the Hooke's joint 1 7 include that shown in Fig. 2 where reference numerals 30, 31 indicate two freewheel mechanisms such as a spragg Reynolds clutch, a ratchet mechanism or any other suitable freewheel device. For convenience, only a diagrammatic representation of these two devices is shown in the drawings.

In this embodiment, the primary device comprises a substantially constant speed input drive shaft 33 connected with the sprocket shaft 1 5 via the first freewheel device which allows a freewheeling motion of the shaft 1 5 relative to the shaft 33 only in the clockwise direction of rotation of the input shaft 33.

An oscillating crank 35 is arranged for oscillating rotary motion about the rotation axis of the sprocket shaft 1 5 to which it is connected via the second freewheel device 31. This latter item allows a freewheeling motion of the crank 35 relative to the sprocket shaft only in the anti-clockwise direction. The free end of the crank 35 is conveniently driven in the desired motion by an appropriate crankshaft e.g. a rotating eccentric shaft.

In operation, the free end of of the crank 35 is driven downwardly as above described at a greater angular speed than the shaft 1 5 thereby periodically to accelerate the rotation speed of the shaft 1 5 above the value otherwise imposed on it by the input shaft 33.

During the upward return motion of the crank 35, the freewheel device 31 operates to allow the inward end of the crank to move in the opposite direction to the shaft 1 5 until the crank is back is position in readiness for the next downstroke.

Claims

1. A conveyor assembly comprising an endless conveyor surface supported on a rotary support and drive means for continuously accelerating and/or declerating the rotary motion of the support about some mean value.

2. An assembly as claimed in Claim 1 in which the drive means includes a Hooke's joint, the rotary support being driven from the output shaft of the Hooke's joint and the input shaft to the Hooke's joint being arranged to rotate at a substantially constant speed about an axis lying at an angle of other than 180' to the rotation axis of the output shaft.

3. An assembly as claimed in Claim 2 including means for varying the speed of the input shaft for the Hooke's joint and/or the relative inclinations between the input and output shafts for the Hooke's joint.

4. An assembly as claimed in any of Claim 2 or Claim 3 including means for changing the drive ratio between the output shaft of the Hooke's joint and the rotary support for the conveyor surface.

5. An assembly as claimed in Claim 1 in which the drive means comprises a substantially constant speed rotary drive shaft con necked with the rotary support via a first freewheel device allowing a freewheeling motion of the support relative to the drive shaft only in a first direction and a drive member arranged for oscillating rotary motion about the rotation axis of the rotary support to which it is connected via a second freewheel device allowing a freewheeling motion of the drive member relative to the rotary support only in the opposite direction to said first direction.

6. An assembly as claimed in Claim 5 in which said first direction is the direction of rotation of the drive shaft and the drive member operates to periodically accelerate the rotation of the rotary support above the rotation speed otherwise imposed on it by the drive shaft.

7. An assembly as claimed in Claim 5 or Claim 6 in which the or at least one of the two freewheel devices is a spragg Reynolds clutch, a rachet mechanism or any other suitable known freewheel device.

8. A conveyor assembly substantially as hereinbefore described with reference to, and/or as illustrated in, Fig. 1 or Fig. 2 of the accompanying drawing.