Conveyors: power-driven – Conveyor section – Endless conveyor
Reexamination Certificate
2000-01-19
2001-01-16
Ellis, Christopher P. (Department: 3651)
Conveyors: power-driven
Conveyor section
Endless conveyor
C198S806000, C198S808000
Reexamination Certificate
active
06173830
ABSTRACT:
BACKGROUND TO THE INVENTION
This invention relates to a tracking or training idler assembly which is typically although not exclusively adapted to track a trough shaped belt.
It is well known that conveyor belts tend to drift or creep sideways as they travel along their intended paths. The problem is exacerbated where the belt is particularly long, carries a high load, or is a particularly heavy belt. The problem is further compounded on the load carrying side of the belt where the load is not centrally located on the belt. The load carrying side of the belt is often configured in a trough cross-sectional configuration so as to contain material loaded onto the belt.
To try and keep the belts centrally located (central tracking) it is known to adjust the alignment of either the drive roller or the return roller or both, and thereby keep the path travelling down its central path. However, if the belt is unevenly loaded, or if the belt stretches or wears in use, achievement of central tracking becomes more and more of a problem. A further problem is that it is often found that one part of the belt will tend to track centrally but other parts of the belt along its length tend to drift laterally to one or other side. For this reason it is standard practice to have an operator continuously adjusting the belt or the idlers over which the belt travels to try and achieve central tracking of the belt. High cost automatic pneumatic or hydraulic adjustors are known, but these are not always appropriate to use, particularly in high load mining operations.
To avoid this continual adjustment of the end idlers it is also known to install tracking idlers, which are also know as training idlers, along the length of the conveyor belt which will automatically slew about a vertical axis as the belt moves out of alignment to steer the belt back into its central path. Many different types of idlers of this type are known for tracking flat belts but that tracking or training of trough shaped belts constitutes more of a problem. The following patents indicate attempts to achieve tracking of trough shaped belts:
U.S. Pat. No. 2,815,851
U.S. Pat. No. 1,963,099
U.S. Pat. No. 2,561,641
U.S. Pat. No. 2,109,925
U.S. Pat. No. 1,705,558
The abovementioned patents all basically disclose an arrangement in which three idlers, which are mounted on a sub-frame in a normal trough-like configuration, are mounted so as to lie substantially transverse to the length and direction of travel of the belt. The sub-frame itself is mounted on a pivot axis which is perpendicular to the plane of the belt. Some mechanism is provided towards each edge of the assembly which the edge of the belt will contact as it shifts to one or other side of the assembly. By contacting the mechanism will cause the sub-frame to pivot on its pivot axis and thereby steer the belt back to its central position. Various problems exist, to a great or lesser extent with the different known systems. One problem, for example, is that the mechanism used to pivot the sub-frame has to be contacted by the edge of the belt in order to cause the necessary pivoting. The engagement of the edge of the belt against the mechanism tends to damage the edge of the belt, or the mechanism. Also, the manner in which the sub-frame is mounted to the main structure of the conveyor installation often means that adaptations are needed to be made to the conveyor installation which is undesirable.
A further problem with the tracking assemblies described in the abovementioned patents is that as the assembly pivots, the edge or “wing” idlers tend to move somewhat into the path of the belt which places significant strain on the assembly and decreases the efficacy of the tracking action.
It is desirable that where a training idler is to be installed, this can be done with a minimum of interruptions to the operation where the belt is located. It is also desirable that the training idler assembly is relatively expensive and uncomplicated in operation so that no special maintenance or skilled operator is required to install and maintain the training idler.
SUMMARY OF THE INVENTION
According to a first aspect of the invention there is provided a tracking assembly adapted to be mounted to a support frame of a conveyor belt installation in order to keep the conveyor belt which travels thereon centrally aligned, the tracking idler assembly comprising:
a sub-frame adapted to be mounted to a support frame of a conveyor belt installation;
at least one independently rotatable idler mounted for rotation on the sub-frame, the idler adapted to support a belt of the installation in position, the idler being aligned generally transverse to the length of the belt;
the idler including a support shaft, an outer drum rotatably supported on the shaft, and a pivot assembly located within the drum defining a pivot axis about which the drum is pivotable relative to the shaft, the pivot axis being perpendicular to the belt which in use travels on the idler;
contact means on at least one side of the idler adapted to be contacted by an edge region of a conveyor belt which has travelled from its central position towards that one side;
the contact means being arranged to cause the drum of the idler to pivot about the pivot axis to steer the belt back to its central position.
There is preferably a contact means on each side of the idler. The contact means may form part of, or be detached from the drum.
According to another aspect of the invention there is provided a tracking assembly for mounting to a support frame of a conveyor belt installation, the tracking assembly comprising:
a sub-frame adapted to be mounted to the support frame of a conveyor belt installation;
a plurality of independently rotatable idlers mounted for rotation on the sub-frame, the idlers adapted to support a belt of the installation in position, the idlers being aligned generally parallel to each other spaced apart from each other across the width of the belt, the sub-frame and idlers being mounted to the support frame generally transverse to the length of the belt;
each of the idlers including a support shaft, an outer drum rotatably supported on the shaft, and a pivot assembly located within the drum defining a pivot axis about which the drum is pivotable relative to the shaft, the pivot axis being perpendicular to the belt which in use travels on the idler;
adjacent idlers being linked together via link means adapted to transmit pivotal movement from one idler to the idler adjacent thereto in such a manner that as one idler pivots through a particular angle the idler adjacent thereto will be caused to pivot through substantially the same angle.
The axis of rotation of the idlers need not be co-incident. In one form of the invention the idlers are mounted to the support frame in a troughed configuration comprising at least one centre idler and a pair of side idlers on opposite sides of the centre idler or idlers, the side idlers being inclined relative to the centre idler to define a trough shape support arrangement for a belt. An alternative arrangement will be for the assembly to comprise a pair of idlers mounted in a V-shaped configuration, said link means connecting the two idlers together.
Each of the idlers may include an inner sleeve located co-axially with the drum and a pair of bearing assemblies located on opposite sides of the pivot axis providing for relative rotation between the drum and the sleeve, the pivot assembly connecting the shaft to the sleeve.
The link means may itself be pivotally connected to the sub-frame and will in any event be pivotally connected to each of the idlers. The link means may comprise a rigid bar and it may further include a lost motion facility on one or both ends thereof.
The idler assembly includes contact means for causing the idlers to pivot through a selected angle when the belt which travels over the idler assembly moves off its central path of travel. The means for causing the idlers to pivot may include a reduced diameter end portion on the two outer idlers which comprise the plurality
Cumberlege John P.
Savage Paul A.
Ellis Christopher P.
McGuire Woods LLP
Ridley Richard
Tru-Trac Roller (Proprietary) Ltd.
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