Conveyors: power-driven – Conveyor section – Endless conveyor
Reexamination Certificate
1998-11-03
2002-02-12
Walsh, Donald P. (Department: 3651)
Conveyors: power-driven
Conveyor section
Endless conveyor
C198S852000
Reexamination Certificate
active
06345715
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is concerned with modular plastic conveyor belts, and in particular relates to retention of connecting rods in such belts.
Examples of modular plastic conveyor belts are shown in U.S. Pat. Nos. 4,742,907, 4,901,844, 5,069,330, 5,181,601 and 5,224,583. The conveyor belts are shown formed of plastic modules having sets of link ends or projections extending in fore and aft directions, for interdigiting with similar preceding and succeeding modules. The interdigited projections have transverse openings through which pass connecting rods, typically also of plastic. Each module row includes one or more modules side by side, and the belts can be made up in virtually any length and width, within practical limits.
The connecting rods of belts such as disclosed in the above referenced patents, and those of other belts of the same general type, must be retained against lateral movement so as to prevent them from extending transversely out of the belt, which would allow the belt to separate between succeeding modules. This need has been addressed in several different ways. U.S. Pat. No. 4,904,844 describes the use of recesses in end members of the integral plastic modules or in separate side plate members at the outside of the belt, to receive connecting rod heads in countersunk relationship. Such rod heads can be formed in the ends of assembled rods by deformation of the rod end, sometimes called “buttoning”.
U.S. Pat. No. 5,181,601 describes a different approach wherein a connecting rod has an integral, enlarged collar or interference ring on the rod, to be forced into and engaged with the inside of a bore in a plastic module, the bore having a slightly smaller diameter than the interference ring. This creates a positive press fit engagement between the rod and module, so that the rod is tightly retained relative to one module. Rod heading could be eliminated. The same patent also disclosed the use of three separate connecting rod sections serving as a connecting rod for each pair of adjacent modules, with the two outer rod sections retained by the interference fit described above, and a middle rod section floating between the ends of the outer rod sections.
Other conveyor belts have employed rod heads, on a one-piece connecting rod, to retain the rod in the belt.
Further approaches to retaining connecting rods without rod heads have been suggested. One approach is a spring clip inserted into a receptacle in an edge link end, as in U.S. Pat. No. 5,123,524. Other approaches have sometimes involved an integrally molded tab or flange at the outside edge of a belt module, positioned to require forcing of the length of the rod past the somewhat flexible tab or flange (or manually holding back the tab), with the tab then springing back to an undeformed position when the rod has been fully inserted. The intention is then for the tab or flange to prevent outward movement of the rod by interfering with its path of movement. See, for example, U.S. Pat. Nos. 4,925,016, 5,058,732, 5,156,262 and 5,156,264. Another approach has not involved a movable tab, but simply a bending path through which the rod must be pushed at the edge of the belt, so that once forced into position past the bend, the rod tends not to migrate out from the belt. The latter type of headless rod retention is shown in U.S. Pat. No. 5,372,248 and a similar arrangement is shown in U.S. Pat. No. 5,598,916, where an off-axis hole is provided in a module edge member. See also U.S. Pat. No. 5,573,106. Examples of other forms of headless rod retention are shown in U.S. Pat. Nos. 4,993,544 and 4,893,710.
Some types of headless connecting rod retention cause excessive wear against the belt module or against a retaining element or the rod itself, both in radius and linear travel belts.
Removal of retaining rods in general has often required the cooperation of at least two technicians, one to pull the rod from one side of the belt and the other to push or strike or otherwise manipulate the rod from the other side of the belt, which can be impractical.
It is an object of this invention to overcome problems of excessive module or rod wear caused by the rod retention system employed, both in radius and linear travel belts, while also providing a simple and easily used arrangement for engaging the rod retention and further for releasing the rod retention when desired. Another object, in a specific embodiment of the invention, is to facilitate release of the retaining rod by a single person operating from only one side of the conveyor belt.
SUMMARY OF THE INVENTION
A connecting rod retention system in according with the invention, for straight or radius type modular conveyor belts, avoids the need for rod heads or any form of movable flange or tab for locking the rod in place. In addition, the invention in one preferred embodiment allows a connecting rod to be freely and easily pushed into the assembled position through two sets of interdigited projections of successive module rows, without interference or force required for assembly. Wear of the rod, the rod retention device and the modules due to the rod retention arrangement is minimized, in part because the rod is free to rotate and a retention device on the rod preferably is free to rotate relative to the rod and is not squeezed or ground between modules.
In one embodiment, a rod retention system for a modular plastic conveyor belt of the character described above includes a groove or slot in the surface of a connecting rod, located so as to be between two of the adjacent interdigited projections from the two successive modules which the rod is to connect. At this narrow location, the groove or slot defines a smaller diameter or dimension on the rod than the outside diameter of the rod. A clip, preferably flat in profile, on its side surfaces, is provided for engaging over the slot or groove area of the retaining rod, between the adjacent interdigited projections. The clip is dimensioned so as to allow it to be forced over the rod at the groove, with the clip yielding due to its inherent flexibility, and to be retained on the rod unless a substantial and deliberate force is applied to remove the clip.
In a preferred embodiment, the groove or slot is a generally circumferential groove around the rod, and the clip comprises a generally C-shaped clip with an open end which is dimensioned to snap over the groove on the rod, and thence to be freely rotatable on the rod.
In one preferred embodiment the connecting rod is formed of plastic material, and the retaining clip is also formed from a plastic material, which may be acetal (although a steel rod or steel clip may be used). The retention system of the invention avoids wear between the conveyor module itself and the retention means, while also allowing fast and easy assembly using tools already available for brass or steel ring retainers used in other fields. Further, by firmly holding the belt, one can remove any of the rods with a punch and hammer, which provides sufficient force to dislodge and pop the retaining clip off the rod and out of the belt.
The retention device cannot escape by itself provided the material utilized for the retaining clip is one with a good memory, such as the plastic material acetal; this allows the C-shaped clip to be forced open for assembly, while quickly returning to its original configuration after being positioned in the rod groove.
In some embodiments of the invention, the modular plastic conveyor belt utilizes discontinuous connection rods such as disclosed in U.S. Pat. No. 5,181,601. Such a discontinuous connection rod may include a free-floating middle section and two opposed edge or side rod sections. With the retention system of the present invention, the two outer rod sections each have the retention device of the invention, with a groove and the clip engaged over the groove; or one end of the belt is closed and the clip is on the rod section at the opposite end.
In some belts, particularly radius type belts, the faces of adjacent interdigited link ends betwe
Freiburger Thomas M.
KVP Falcon Plastic Belting, Inc.
Ridley Richard
Walsh Donald P.
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