Conveyor belt with improved rod to link attachment

Metal working – Method of mechanical manufacture – Assembling or joining

Reexamination Certificate

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Details

C198S848000, C029S523000

Reexamination Certificate

active

06195868

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to conveyor belts generally comprising a support surface, and connective rods and connective links which are affixed to one another without manual welding as is necessary with conventional components and assembly methods.
BACKGROUND OF THE INVENTION
Wire and plastic conveyor belt systems are widely used in a great variety of industrial fields. A wire mesh or plastic overlay can be used with the rods to provide a support surface of a conveyor belt. The wire or plastic components of the overlay are intermeshed together by connecting rods which extend transversely across the width of the belt. Typically the intermeshed overlay components are connected to one another by the connecting rods. Alternatively, the support surface provided by the rods can be used without an overlay. The ends of the rods are inserted into connective links and the rods and links are welded together. The connective links may serve as tractive links around a sprocket wheel.
In conventional conveyor belts, a weld is typically placed at the exterior sides of the link legs to attach the link to the rod. This weld serves two purposes. Firstly, it achieves positive fixation of the link to the outermost portion of the rod. This is important because the connective links at the outer edges of a belt are used for driving interface with the drive sprockets so that any transverse or lateral movement of the connective link along the rod will result in misalignment with the sprockets. This will lead to damage to the sprockets, belt and the system. Secondly, the weld prohibits the connective links from rotational movement that leads to “tenting” of the link on the rod. Tenting refers to the rotational movement of the link relative to the rod when the rods move together causing a link to tilt upward about its rod apertures, and is illustrated schematically in FIG.
16
. This movement normally occurs on the inside edge of the belt during its collapsed state of operation in a spiral system, and causes the belt to jam during operation resulting in belt and system damage, as well as downtime.
The weld holding the link to the rod is a main area of perceived failure and real failure for conveyor belts since the weld is subjected to numerous stresses during operation. The biggest contributors to weld failures include normal fatigue caused by belt tensions above the allowable limit including lateral deflection of the legs of the connective links and rod buckling. These stresses on the links cause cracks to form in the welds. Even after a weld fails, however, it continues to function to hold the connective links in a fixed position which allows the belt to operate. It has been observed that the weld deposits on the rod act as barriers that trap the connective link in place allowing for proper sprocket and drive engagement. In addition, while tenting has been observed where welds have failed, in general the ragged edges of the fractured welds continue to prevent rotational movement of the connective link.
A conveyor belt with fractured welds is acceptable and operational as long as the system is running under allowable tension limits, however, the problem of perceived failure of the belt arises whenever some of the welds are cracked. Even though a belt with cracked welds is still able to function effectively under normal operating conditions, users who have been repeatedly warned by belt manufacturers that broken welds are precursors to real failure have perceived the broken welds as a failure in and of themselves. There has been a need to structurally affix the links on the rods to prevent their rotation about the rods. This engagement would eliminate this perceived problem with conventional belts that raises user complaints and warranty issues.
Besides showing the first signs of fatigue stress, the conventional welds between the links and rods also require a time-consuming manual welding step during manufacture. As can be seen from
FIGS. 12-14
, the conventional methods require that the connective links be individually welded to the rods. This step is inefficient and expensive.
In conveyor belts used to move consumable material through processing machinery, such as coating, freezing, cooking, etc., sanitation is a concern particularly in conveyor systems which present a variety of crevices into which the material can be deposited and spoil. In conventional conveyor systems, the belts must be cleaned periodically, particularly in the welded area.
Therefore, there exists a need for a conveyor belt with structural features that will eliminate the time consuming welding step and thereby eliminate perceived and real weld failure, decrease the chances of tenting of the links, and presents a conveying surface with less crevices for sanitary operating conditions. There also exists a need for streamlining the manufacture of conveyor belts by eliminating the current methods of attaching the connective links to the rods.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides connective links and rods for a conveyor belt and its manufacture which overcomes many of the problems associated with the prior art.
The present invention pertains to a conveyor belt comprising rods that are resistance welded within the connective link apertures. During assembly, electrodes are applied to rods to provide the necessary energy for the rods to undergo a controlled deformation which results in the formation of an annular protrusion or swell. Such a protrusion is formed on either side of each leg of the link to constrain the link from lateral movement on the rod. At the ends of the rods, a similar process is used to form an upset or button head. In this way a button head can be thought of as a type of protrusion. By varying the position of an electrode on the rod during manufacture, the location of the protrusion can be chosen. The resistance weld and the protrusions constrain the link to the rod and eliminates the additional fixation steps used in conventional belt manufacture and simplifies production. In this manner, the conventional manual welds and their attendant problems such as fatigue cracks are eliminated altogether.
One aspect of the invention is the use of rods with stepped ends which provide for control of the expansion and swelling of the rod to fix the link onto the rod and prevent its lateral movement.
Another aspect of the invention is the use of rods of uniform diameter which can be made to swell into the desired shape and size by controlling the shape of the apertures and slots in the link, and by careful placement of the forming electrodes along the rod.
Yet another aspect of the present invention is that the button head and inside weld seals the rod-link interface eliminating any crevices between the rod and the aperture in the link which provides a more sanitary edge without the necessity for repeated cleaning of the belt.
An additional aspect of the present invention is the provision of a structural feature to prohibit rotational movement of the link relative to the rod and thus eliminate the tenting problem.
These and other features and advantages of the invention may be more completely understood from the following detailed description of the preferred embodiments of the invention with reference to the accompanying drawings.


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