The present invention generally relates to a conveyor frame assembly for use with a plastic chain conveyor belt. More specifically, the present invention relates to a conveyor assembly that reduces the catenary sag of the lower run of the conveyor belt downstream from the drive roller.
In many conveyor applications, a plastic chain conveyor belt is utilized to move materials throughout a facility. The plastic chain conveyor belt includes individual links that run across the width of the conveyor belt such that the conveyor belt can assume a flat transporting condition yet can transition over both a drive roller and an idler roller to create the upper and lower runs of the conveyor belt.
Since plastic chain conveyor belts can be used to move a large number of products throughout a facility, the weight of the products on the plastic belt and the wear of the belt links cause the belt to “stretch” when the belt is under load. When the belt is placed under a larger load, the “stretching” of the conveyor belt increases the length of the belt, which creates a sag in the lower run of the conveyor belt following the drive roller. This “loop” of chain hangs down immediately following the drive sprockets and is referred to as catenary sag. Since there is nearly zero tension on the chain immediately following the drive sprockets, the lower run of the conveyor belt sags beneath the lowermost edge of the spaced side rails of the conveyor assembly to create the catenary sag.
During conveyor design, the amount of catenary sag is calculated and the conveyor is designed to incorporate the catenary sag. Although the catenary sag allows the conveyor to compensate for the stretching of the conveyor belt under tension, the catenary sag oftentimes extends beneath the lower edge of the conveyor frame assembly. This causes many problems, including allowing the conveyor belt to be contacted by personnel in the area surrounding the conveyor frame assembly and greatly expanding the overall height of the conveyor.
Therefore, a need exists for a conveyor frame assembly that addresses the problems created by the catenary sag beneath the lower edge of the conveyor frame assembly. Further, a need exists for a conveyor assembly that allows for the stretching of the plastic belt while still addressing the cantenary sag of the lower run of the conveyor belt.
The present invention generally relates to a conveyor assembly used in connection with a conveyor belt formed from individual link sections, preferably each made from plastic. More particularly, the invention relates to a conveyor assembly that includes an enclosed area within the side frame members that allows the conveyor assembly to compensate for the stretching of the conveyor belt during use of the conveyor belt with a load.
During use of a conveyor belt under tension, the individual plastic links are pulled, which causes the plastic conveyor belt to stretch and increase in length. Typically, such increase in length is compensated for by a catenary sag in the lower run of the conveyor belt. However, in accordance with the present invention, an enclosed retaining cavity is created within the spaced side frame members that allows the individual links of the conveyor belt to “tent” to take up the increased length in the conveyor belt. The “tenting” of the individual links of the conveyor belt decreases the overall linear length of the conveyor belt, thus compensating for the stretching that occurs during use of the conveyor belt in a loaded condition.
Each side frame member of the conveyor frame assembly includes a retaining cavity having a height greater than the thickness of the conveyor belt. The height of the retaining cavity allows the conveyor belt to tent within the retaining cavity and eliminates the catenary sag of the lower run of the conveyor belt.
The drawings illustrate the best mode presently contemplated of carrying out the invention. In the drawings:
As can best be seen in
Referring back to
Referring now to
As can be seen in
As described previously, the plastic chain conveyor belt 35 shown in the Figures stretches as the belt undergoes loading due to products being transported. Since the conveyor frame length is designed for the belt under no load, the stretching of the belt must be compensated for in the design of the conveyor assembly. As previously described, one method of compensating for the increase in length of the conveyor belt is to allow the conveyor belt to create a catenary sag in the lower run of the conveyor belt following the drive sprocket. In past conveyor assemblies, the catenary sag allowed the conveyor belt to sag beneath the lowermost edge 56 of the side frame member.
In the embodiment of the invention shown in
An exit end 51 of the guide channel 41 is aligned with the retaining channel 60 to guide the side edges of the conveyor belt into the retaining channel 60. As illustrated in
The retaining channel 60 is a continuous channel that extends along the entire length of each of the side frame members 14 to prevent the catenary sag anywhere along the entire length of the side frame members 14. The retaining channel thus prevents the lower run of the conveyor belt from extending below the lower edge of the side frame members 14 at any point.
Referring now to
Referring now to
As illustrated in the embodiment shown in
In the embodiment of the invention shown, the conveyor assembly includes a series of wear strips 77 that extend lengthwise between the cross supports 79. The wear strips 77 are formed from a durable material, such as UHMW, that contacts the moving conveyor belt to limit the amount of tenting of the conveyor links. Preferably, the wear strips 77 extend only near the drive end of the conveyor assembly since the tenting of the conveyor belt occurs only near the drive end.
As can be understood in
The present application is based on and claims priority to U.S. Provisional Patent Application Ser. No. 60/950,659 filed on Jul. 19, 2007.
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Number | Date | Country | |
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20090020397 A1 | Jan 2009 | US |
Number | Date | Country | |
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60950659 | Jul 2007 | US |