Abstract:
A compression assembly for applying consistent pressure to the material being formed into a continuous tube. The pressure is applied to at least one of a pair of forming rolls of a tube mill during the operation thereof.

Description:
[0001]    This application claims the benefit of U.S. provisional patent application Serial No. 60/285,563, filed Apr. 20, 2001. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates generally to the production of continuous seam-welded tubes or pipes and, more particularly, to a compression assembly to cause the forming rolls of a tube mill to apply consistent pressure across the surface of the material being formed such as, for example, a continuous strip of steel.  
           [0004]    2. Description of the Prior Art  
           [0005]    Roll forming machines or tube mills are well known in the art for use in manufacturing seam-welded tubes. The tube forming process involves the shaping of flat stock into a tube with a substantially cylindrical cross section and applying pressure to the circumferential walls of the tube to form the final product. The material being formed is “cold worked” to produce a material of desired diameter and wall thickness.  
           [0006]    Cold working has the undesirable effect of increasing the yield point of the tube material resulting in work hardening. For normal uses, work hardening is an acceptable side effect of the tube manufacturing process. With the increased popularity of hydroforming in the vehicle manufacturing area, however, work hardening has become an undesirable side effect. Hydroforming is a process where water is used to pressurize the tubing during the final bending processes, thereby reducing wall thinning and wrinkling. Tubing which is bent through the utilization of the hydroforming process is typically used for complex shapes requiring strong structural characteristics such as automobile frames. Hydroforming requires a lower yield point material in order to be capable of being bent into the complex shapes. If an increase in the yield point occurs during the tube forming process, hydroforming becomes more difficult.  
           [0007]    Roll forming machines or tube mills currently used are comprised of means for applying pressure to the material being formed. The pressure is applied by hydraulic or spring pressure conveying devices that operate independently of one another. Because of the independent interaction, uneven pressure is often applied to the material being worked resulting in excessive cold working of that portion of the material. Therefore, the uneven application of pressure results in an increased yield point in the tubing material.  
           [0008]    An object of the present invention is to produce a compression system that reduces the effect of increasing the yield point in the material being formed.  
           [0009]    Another object of the invention is to produce a system for tube mills for applying consistent pressure to the forming rolls during the process of producing continuous seam welded tubes.  
         SUMMARY OF THE INVENTION  
         [0010]    The above, as well as other objects and advantages of the invention, may be readily achieved by a tube mill including a forming roll section having at least one pair of cooperating forming rolls including a rear stand; a front stand spaced from the rear stand; an upper forming roll; an upper spindle supporting the upper forming roll; a lower forming roll cooperating with the upper forming roll; a lower spindle supporting the lower forming roll; a first bearing means for rotatingly supporting the upper spindle; a second bearing means for rotatingly supporting the lower spindle; and means for mounting the first bearing means and the second bearing means on the rear stand and the front stand and applying constant pressure between the upper forming roll and the lower forming roll. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The objects and advantages of the invention will become readily apparent to those skilled in the art from the following detailed description of an embodiment of the invention when read in the light of the accompanying drawings, in which:  
         [0012]    [0012]FIG. 1 is an elevational end view partially in section of the rear and front stands of a forming roll section of a tube mill;  
         [0013]    [0013]FIG. 2 is a right side elevational view of the forming roll section illustrated in FIG. 1; and  
         [0014]    [0014]FIG. 3 is a schematic view of a hydraulic system for controlling the pressure fluid applied to the forming rolls illustrated in FIGS. 1 and 2. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0015]    Referring to the drawings, there is illustrated a compression assembly for forming rolls, incorporating the features of the invention More specifically, there is illustrated in FIGS. 1 and 2 a rear stand assembly  10  and a front stand assembly  12  of a typical forming roll section of a tube mill of the type wherein a continuous length of strip stock, generally referred as skelp, is introduced at the inlet end of the mill and is caused to be passed through a series of sections of cooperating rolls which function to gradually form the flat strip of metal into a tube wherein the abutting edges of the formed strip are resistance welded to form a continuous tube. The continuous tube is finally cut into predetermined lengths and off-loaded from the mill for subsequent shipment to the ultimate users.  
         [0016]    The diameter and wall thickness of the finished tube is determined by the gauge and width of the skelp being formed as well as the diameter and cross-sectional configuration of the cooperating rolls of the mill. The section of the mill illustrated in FIGS. 1 and 2 is generally referred as the forming section where the skelp is introduced after being broken down or formed slightly in a breakdown section. The forming section employs at least one section of a cooperating pair of forming rolls  14  and  16 . The forming roll  14  is referred to as the upper forming roll and the lower forming roll  16  is referred to as the lower forming roll. As clearly apparent from FIG. 1, the upper forming roll  14  has a convex cross section, while the lower forming roll  16  has a concave cross section. The skelp  18  is shown between the cooperating outer surfaces of the forming rolls  14  and  16 .  
         [0017]    The upper forming roll  14  and the lower forming roll  16  are mounted on separate power drives for the upper and lower spindles  20  and  22 , respectively. The opposite ends of the spindles  20  and  22  are journaled in suitable bearings in the rear stand  10  and the spaced apart front stand  12 . One end of the upper spindle  20  is journaled in a bearing  24  which, in turn, is mounted in the rear stand  10 , and the other end is journaled in a bearing  26  which, in turn, is mounted in the front stand  12 . One end of the lower spindle  22  is journaled in a bearing  28  which, in turn, is mounted in the rear stand  10 , and the other end is journaled in a bearing  30  which, in turn, is mounted in the front stand  12 .  
         [0018]    In order to apply the desired pressure to the forming rolls, the bearings  24  and  26  which support the upper spindle  20  and the associated upper forming roll  14  are affixed to pressure fluid actuated cylinders  32  and  34 , respectively. The cylinders  32  and  34  are suitably mounted to the rear and front stands  10  and  12  as illustrated in FIGS. 1 and 2. Further, the cylinders  32  and  34  are provided with depending piston rods  36  and  38 , respectively, which, in turn, are provided with suitable fittings connected to respective bearings  28  and  30 .  
         [0019]    The bearings  28  and  30  are adjustable in a vertical direction independently of the cylinders  32  and  34  and the respective piston rods and fittings. The adjustment is effected by suitably positioned rack and pinion assemblies  40  and  42 . The rack and pinion assembly  40  for effecting movement of the bearing  28  is mounted to the rear stand, and the rack and pinion assembly  42  for effecting movement of the bearing  30  is mounted to the front stand. Concommitant movement of the bearings  28  and  30  to accept forming roll members of different diameters is achieved by coupling the pinions of the assemblies  40  and  42  by a connecting shaft  44 .  
         [0020]    While there are a number of various systems that could be used to apply pressure fluid to the cylinders  32  and  34 , the system illustrated in FIG. 3 has been found to be satisfactory. It will be noted that in the illustrated system pressure fluid is uniformly introduced from a power source to the cylinders  32  and  34  to selectively cause the associated pistons to move in unison. Also, other types of pressure transducers may be use, such as for example, springs. The objective of the transducers is to consistently transmit energy from one system to another and finally to the strip stock being formed.  
         [0021]    In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be understood that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.