Perforated spiral pipe

Abstract

An improved filter pipe is disclosed, and also an improved apparatus is disclosed for making the improved filter pipe. The apparatus is meant for perforating, forming and cutting spirally formed pipe, particularly spiral pipes having a diameter of approximately one inch or more. The filter pipe has a unique corrugated or fluted configuration that adds section modulus to the pipe, potentially allowing for the use of thinner sheet metal in manufacturing such pipes and in filters made from such pipes. A machine for manufacturing the spiral pipe may include special machinery for forming the unique corrugated or fluted configuration.

What is claimed is:  
     
         1 . An apparatus for forming spiral pipe from a metal strip, the apparatus comprising: 
 forming rollers for forming lateral edge portions of the metal strip;    a forming head having a lateral bore;    a forming tool extending into the lateral bore of the forming head;    a closing assembly for coupling and compressing lateral edge portions of the metal strip into a lockseam of a pipe; and    rollers for perforating the metal strip and driving the metal strip around the forming tool, against an interior surface of the forming head, and in an axial direction, wherein the lateral edge portions of the strip mate and are coupled and compressed to form a lockseam and provide a continuous spiral pipe.    
     
     
         2 . The apparatus of  claim 1 , wherein the rollers for perforating yield perforations selected from the group consisting of square and rectangular perforations.  
     
     
         3 . The apparatus of  claim 1  wherein the rollers for perforating the metal strip and driving the metal strip comprise a first set and a second set of rollers.  
     
     
         4 . The apparatus of  claim 1  wherein the forming tool extending into the lateral bore of the forming head is a mandrel and the closing assembly includes at least one roller protruding through an opening in the top of the forming head.  
     
     
         5 . The apparatus of  claim 1  wherein the forming tool is a boom extending into the lateral bore of the forming head and the closing assembly includes a support roller inside the forming head and a clinching roller.  
     
     
         6 . The apparatus of  claim 1 , further comprising a cutting assembly for cutting a pipe section from the spiral pipe.  
     
     
         7 . An apparatus for forming spiral pipe from a strip of metal, the apparatus comprising: 
 rollers for forming edge portions of the strip;    a forming head for providing an external guide for the metal strip, the forming head having an entrance for the metal strip and an interior surface which has a predetermined radius of curvature;    a mandrel rotatable about its centerline, positioned inside the forming head, the mandrel providing a guide for an interior surface of the metal strip and a compression surface for forming a lock seam;    rollers for perforating and driving the metal strip into the forming head entrance, around the mandrel, against the interior surface of the forming head, and in an axial direction, wherein the edges of the strip mate to form a spiral cylinder, the rollers for perforating and driving only contacting the metal strip prior to entry into the forming head entrance; and    a closing assembly external to the mandrel for deforming and coupling the mated edges of the strip to form a lockseam in a spiral pipe.    
     
     
         8 . The apparatus of  claim 7 , wherein the rollers for perforating yield perforations selected from the group consisting of square and rectangular perforations.  
     
     
         9 . The apparatus of  claim 7  wherein the rollers for perforating and driving the metal strip comprise a first and a second set of rollers, each of the sets of rollers for performing one of perforating and driving the metal strip.  
     
     
         10 . The apparatus of  claim 7 , further comprising a cutting assembly for cutting a pipe section from the spiral pipe.  
     
     
         11 . A method of forming a filter pipe, the method comprising: 
 drawing a strip of sheet metal into a forming machine;    forming seal forms on a first edge and a second edge of the sheet metal;    drawing the metal and forming perforations in the sheet metal after the seal forms are formed;    forming the strip into a spiral;    sealing the first and second edge of the sheet metal into a lockseam; and    cutting a filter pipe from the formed strip.    
     
     
         12 . The method of  claim 11 , wherein the perforations are substantially in the form selected from the group consisting of a rectangle and a square.  
     
     
         13 . The method of  claim 11 , wherein the perforations are severed from the sheet metal.  
     
     
         14 . The method of  claim 11 , wherein the perforations are retained on the sheet metal and are raised from a surface of the sheet metal to a height of from about one to about three times a thickness of the sheet metal.  
     
     
         15 . The method of  claim 11 , wherein the perforations are from about thirty percent to about seventy percent of a surface area of the filter pipe.  
     
     
         16 . The method of  claim 11 , wherein a thickness of the sheet metal is from about 0.010 inch to about 0.030 inch (from about 0.25 mm to about 0.76 mm).  
     
     
         17 . The method of  claim 11 , wherein the step of perforating the metal is completed before the step of drawing the metal.  
     
     
         18 . A punch for perforating sheet metal, the punch comprising: 
 a roller having a plurality of protrusions radially extending from the roller, the protrusions arranged in at least two circumferential rows on the roller, the at least two circumferential rows staggered on a circumference of the roller, wherein the protrusions cause at least one of openings, perforations and corrugations in the sheet metal.    
     
     
         19 . A combination of the punch according to  claim 18  and a die, the die comprising a roller and at least two grooves for mating with the protrusions.  
     
     
         20 . The combination of  claim 19 , further comprising a drive gear on at least one of the punch and the die.  
     
     
         21 . The punch according to  claim 18 , wherein the at least two circumferential rows are staggered at an angle of from about ten degrees to about thirty degrees.  
     
     
         22 . The punch according to  claim 18 , wherein the protrusions form at least one of openings, perforations and corrugations in the sheet metal, but does not sever scrap from the sheet metal.  
     
     
         23 . The punch according to  claim 18 , wherein the protrusions form at least one of openings, perforations and corrugations in the sheet metal, and do sever scrap from the sheet metal.  
     
     
         24 . The punch according to  claim 18 , wherein the plurality of protrusions have sharp edges on two sides and radiused edges on two sides.  
     
     
         25 . The punch according to  claim 18 , wherein a depth of the punch is from about two to about four times the thickness of the sheet metal.  
     
     
         26 . A filter pipe, comprising: 
 sheet metal having a first edge and a second edge, and also having a first end and a second end;    a lock-seam formed by locking the first edge to the second edge, in forming a spiral-shaped pipe; and    a plurality of perforations in the filter pipe allowing communication between an inside of the filter pipe and an outside of the filter pipe, at least one side of the perforations forming an angle from about ten to about forty degrees to a plane of the sheet metal.    
     
     
         27 . The filter pipe of  claim 26 , wherein an outside diameter of the pipe is from about 0.5 inches to about 1.5 inches.  
     
     
         28 . The filter pipe of  claim 26 , where the perforations are about thirty percent to about sixty percent of a surface area of the filter pipe.  
     
     
         29 . The filter pipe of  claim 26 , wherein the perforations are substantially in a form selected from a group consisting of a rectangle and a square.  
     
     
         30 . An oil filter further comprising the filter pipe of  claim 26.