Abstract:
Incoming tubes are turned and fed into a pilger mill by use of a single gearbox using a rotating dual track drive system. The dual track system holds the incoming tube while tube reducing (metal tube forming) occurs by the pilger tooling. When the pilger tooling is free of the incoming tube product, the dual track drive moves the tube into the pilger tooling by feeding an incremental amount of tube product. The dual track drive also indexes the incoming tube at the correct time and at a pre-determined amount. Additionally, the gearbox sub-assembly bumps the tube at a pre-determined time while the tube is free from the tooling.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    One of the existing methods of producing medium to large quantities of metal tubing is through the use of pilger mills, also known as tube reducers. Another method to produce metal tubing is cold drawing but it is typically only used for small quantities of tubing. Pilger mill machines have been producing metal tubing since 1880 and are considered to be an efficient manufacturing process for significant quantities. The fundamental methods to form tubing from the pilger mill is with the use of an upper and lower die, rolling back and forth over a mandrel. This method was established in 1880 by the Mannesmann brothers of Germany when they patented a hot working of tubes. 
         [0002]    In 1896, an American engineer patented the first cold pilger mill. The process principle has not changed since then but the supporting mechanisms have changed over the years many times. Many patents have been issued using new technology to support the same pilger principle. As the pilger principles utilize tooling to reduce the tube products, supporting mechanisms within the current day process are vital and crucial to the updated functions. 
         [0003]    In general, each pilger machine has a major drive mechanism that provides a linear motion to the tooling, known as a stroke. Many of the machines in use today use a crankshaft for the linear movement. As the tooling consists of an upper &amp; lower die that rolls back and forth over the tube product. A stationary rotating mandrel is located within the tube inside diameter. 
         [0004]    Both top &amp; bottom dies have a pre-shaped groove which forms or re-shapes the tube product smaller on each stroke. As the top &amp; bottom dies form the outside diameter of the tube to a smaller size, the mandrel and the dies together also work the tube wall into a smaller size. As the dies roll back &amp; forth, the tube product is fed into the dies and over the stationary rotating mandrel. While the tube is reduced in size of outside diameter and inside diameter, the tube also becomes elongated. 
         [0005]    The supporting mechanisms that provide the vital functions on today&#39;s pilger mills are done thru the use of various gearboxes. All of these current gearboxes provide 3 basic functions directly to the incoming tube for the typical pilger process. They provide tube turning (or indexing), incremental feeding, and bumping of the incoming tube over the rotating mandrel. The stationary mandrel rotation is also provided by two of the gearboxes and is mechanically driven from within the gearboxes. 
         [0006]    Current pilger mill machines perform these three functions, along with pilgering (forming) the tube, for a continuous operation. A continuous operation means that the pilger machine operates without stopping the machine to load new incoming tubes. Older generations of pilger mills have to stop and load one tube and then operate for that one tube, then stop to load the next incoming tube. 
         [0007]    As a continuous pilger mill operation, many of these machines have 4 gearboxes that service the previously mentioned functions, turning, feeding and bumping. One gearbox, referred to as an upper gear train gearbox, transfers the rotary motion from a crankshaft, or other rotary drive, to three other gearboxes via a line shaft mechanism. A second gearbox, as driven by the line shaft, transfers the rotary motion into turning of the incoming tube and mandrel lock. The third gearbox, as driven by the line shaft, transfers the rotary motion into turning of the incoming tube. Also, this third gearbox provides feeding and bumping of the incoming tube as well as operating a mandrel lock. The forth gearbox, as driven by the line shaft, transfers the rotary motion into turning of the incoming tube. Also, this forth gearbox provides feeding of the incoming tube. 
         [0008]    As described in U.S. Pat. No. 5,035,132 by Josef Gerretz, multiple gearboxes were used in order to achieve a continuous operation of the pilger mill. These multiple gearboxes provided the necessary feeding and turning of the incoming tubes. Other related patents enhance this continuous mill operation. The disadvantage to this patent is that it does not perform any of the necessary bumping of the tube products which is very important to many of the pilger processes. Also, this patent fails to describe how the device grips the tube product. 
         [0009]    As described in U.S. Pat. No. 6,257,040, by Michael Beansch, Wolfgang Ernhardt, Bernhard Gromada, Ernst Holler, Horst Mattes, the inventors replaced the older mechanical drives of the 1960s with updated technology. The improved controls of the hydraulic drives, are an improvement to the pilger process. These drives still provide the same necessary feeding and turning of the incoming tubes in all of the gearboxes. The disadvantage of this patent effort is it still requires multiple gearboxes. 
         [0010]    Other related patents continue to promote or enhance the continuous pilger mill operation using two or more gearboxes to support the necessary feeding &amp; turning of the tube into the pilger tooling. The disadvantage of the use of multiple gearboxes is the large cost of operation and maintenance that is required to maintain the necessary supporting functions of feeding &amp; turning. A large percentage of the initial cost of investment into a pilger mill is in the complex gearboxes. Also, the maintenance cost of two or four gearboxes is staggering over time as the machine experiences normal wear. 
         [0011]    Accordingly, there is a need for a pilger mill device that performs the necessary functions of indexing, feeding, bumping and mandrel rotation with fewer gearboxes. The present invention satisfies this need and provides other related advantages. 
       SUMMARY OF THE INVENTION 
       [0012]    The present invention allows the necessary pilger mill supporting functions of feeding, turning and bumping to be performed in one gearbox only, therefore replacing anywhere from two to four gearboxes in prior art devices. The cost savings on the initial machine investment, as well as the saving on the long term maintenance of the gearboxes is extremely large. 
         [0013]    The present invention is directed to a single gearbox for providing feed, index and bump motion of tube product in a pilger mill. The gearbox includes a sub-assembly that comprises a track drive including a linearly rotating track for feeding the tube product along a longitudinal axis of the sub-assembly. The sub-assembly also includes an end support attached to an end thereof for rotating the sub-assembly about the longitudinal axis, thereby indexing the tube product. The sub-assembly also includes a hydraulic ring cylinder attached to an end thereof for shifting the sub-assembly along the longitudinal axis, thereby bumping the tube product. 
         [0014]    The track drive comprises a dual track drive having two linearly rotating tracks, wherein each track is comprised of a looped series of segmented clamps contoured to the shape of the tube product. The track drive further includes a slide-wedge assembly for forcing a portion of the linearly rotating track against the tube product. With two linearly rotating tracks, the slide-wedge assembly forces opposing portions of the tracks against the tube product. The end support may comprise a pair of end supports attached to opposite ends of the sub-assembly. Further, a rotary union is attached to an end of the sub-assembly for providing a point of connection for an external pneumatic or hydraulic source to the sub-assembly. The pneumatic or hydraulic source being for actuating a cylinder acting on the slide-wedge assembly. 
         [0015]    An electrical slip ring is attached to an end of the sub-assembly for providing a point of connection for an external electrical source to the sub-assembly. The electrical source for powering a servo motor acting on the track drive. A ring bearing is disposed proximate to a longitudinal midpoint of the sub-assembly, the ring bearing being operatively connected to a gearbox casing to facilitate rotating of the sub-assembly about the longitudinal axis. The ring bearing may comprise a pair of ring bearings uniformly spaced about the longitudinal midpoint of the sub-assembly. Further, a servo drive may be included on the gearbox casing for acting on the end support to rotate the sub-assembly. 
         [0016]    Other features and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The accompanying drawings illustrate the invention. In such drawings: 
           [0018]      FIG. 1  illustrates the dual track drive of the present invention; 
           [0019]      FIG. 2  illustrates one of the segmented clamps of the dual track drive; 
           [0020]      FIG. 3  is an end view of the dual track drive of the present invention; 
           [0021]      FIG. 4  shows the dual track drive with the servo drive motor and transfer gears on drive and idler shafts; 
           [0022]      FIG. 5  shows the dual track drive with the slide-wedge assembly in each of the linearly rotating tracks; 
           [0023]      FIG. 6  shows the pneumatic or hydraulic cylinder to actuate slide-wedge assembly on the dual track drive; 
           [0024]      FIG. 7  shows the end supports and the base plate on the sub-assembly of the present invention; 
           [0025]      FIG. 8  shows the end supports and the base plate on the sub-assembly of the present invention; 
           [0026]      FIG. 9  shows the end supports with the rotary union, the electrical slip ring and hydraulic ring cylinder; 
           [0027]      FIG. 10  shows the mounting of two ring bearings and the upper base plate on the sub-assembly; 
           [0028]      FIG. 11  illustrates how the use of ring bearings facilitate the rotation of the sub-assembly in the gearbox casing; and 
           [0029]      FIG. 12  shows the sub-assembly mounted in the complete gearbox casing. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0030]    As shown in the accompanying drawings, for purposes of illustration, the present invention is directed to a new device for feeding and turning metal tube products within a tube reducer or pilger mill. For ease of understanding, the drawings illustrate the piecewise assembly of the inventive gearbox, generally referred to by reference numeral  10 . This described “assembly” of the gearbox  10  is only for purposes of describing a sub-assembly  11  and is not intended to limit the manner in which the gearbox  10  is manufactured. 
         [0031]    The inventive gearbox  10  includes a dual track drive  12  that is more efficient and provides quality delivery of metal tube product  14  to the tooling of a pilger mill or tube reducing machine (not shown). The gearbox  10  provides for a continuous machine operation without work stoppage. The feeding and turning functions of the gearbox  10  are both infinitely adjustable with the use of computer controls to variable drive motors. The inventive device results in a reduction of the number of gearboxes needed to perform the task of feeding and turning the incoming tube  14  to the pilger mill tooling. Comparatively, for prior art pilger mill machines that perform the same functions, the number of gearboxes is reduced from three or four gearboxes to only one gearbox. 
         [0032]      FIG. 1  shows the dual track drive  12  and how the motion of a dual track system feeds a tube in a forward direction (arrows) towards the pilger mill. Preferably, the dual track drive  12  includes two linearly rotating tracks  16  positioned opposite one another. However, the track drive  12  may include only a single track  16  positioned opposite a surface that permits the tube product to slide thereon, i.e., essentially frictionless. Each track  16  has a drive sprocket  18  which drives the track  16 . An idler sprocket  20  is also used to complete the circular motion of the track  16 . The track  16  consists of a plurality of segmented or individual clamps  22 , as illustrated in  FIG. 2 , joined in a loop by linkage and pins  23  which have the same or similar shape or contour  24  as the metal tube product  14 . 
         [0033]      FIG. 3  shows an end view of the dual track drive  12  and the contour  24  of the track segments  22 . The segment contour  24  makes contact with the outside diameter of the tube  14  spanning approximately half of the tube circumference. Several sequential segments  22  of the track  16  are in contact with a linear section of the tube  14  in order to have a large amount of surface contact with the tube  14 . The segments  22  of the oppositely positioned tracks  16  surround the tube  14 , providing improved gripping. 
         [0034]    A servo motor  26 , as shown in  FIG. 4 , is used to provide power or rotational motion to the dual track drive  12 . The servo motor  26  rotates transfer gears  28 , which rotate the drive sprockets  18  and in turn move the tracks  16  and segments  22 . The tube product  14  is shown and the direction of the material flow within the track drive  12  is shown by the arrows. The motion of the track drive  12  may be stopped or held by a disk break (not shown) located inside or near the servo motor  26 .  FIG. 4  clearly shows the drive sprockets  20  that are driven by the servo motor  26  and the idler sprockets  20  that complete the loop or circular motion of each of the two tracks  16 . 
         [0035]    Within each of the tracks  16 , is a slide-wedge assembly  30  which forces contact of several opposing segments  22  of each of the tracks  16  to the tube product  14 .  FIG. 5  shows the placement of the slide  32  and wedge  34  in each track  16 . Clamping of the tube product  14  is achieved through the use of linear motion, as provided from a cylinder  36  to the slide-wedge assembly  30 . As seen in  FIG. 6 , as the cylinder  36  moves inward against the wedges  34 , the wedges  34  force each slide  32  against the adjacent segments  22 . This clamping movement from both slides  32  forces contact between the track segments  22  and the tube product  14 . Therefore, there is direct contact between the track drive segments  22  and the tube product  14  while the servo motor  26  turns the sprockets to rotate the tracks  16  and move the tube product  14  in the material flow direction. The slides  32  and segments  22  are configured such that one slides over the other even under the pressure exerted by the slide-wedge assembly  30 . The track drive segments  22  release the tube product  14  when the cylinder releases the wedge  34  and the force upon the slides  32  and the tube product  14 . 
         [0036]    The track drive assembly  12  is mounted on two base plates  38 . For viewing purposes, only one plate  38  and how the assemblies are located on the plate is shown in  FIGS. 7 ,  8  and  9 . The second base plate  38  is positioned on the opposite side of the track drive  12  as shown in  FIG. 10 . Also, as shown in  FIGS. 7 and 8 , there are two end supports  40  mounted on each end of the plates  38 . The end supports  40  provide a mount for active components as described below. 
         [0037]      FIG. 9  shows the sub-assembly  11  of the gearbox  10  without a housing (shown below). Support bearings  42  are mounted on the end supports  40  in order to allow for full 360 degree rotation of the sub-assembly  11 . 
         [0038]    Also mounted on an end support  40  is a rotary union  44  providing pneumatic or hydraulic pressure to the gearbox  10 . The rotary union  44  allows for pressure to be transferred from a stationary, external source (not shown) to the rotating sub-assembly  11  upon which the cylinder  36  is mounted. As described, the cylinder  36  operates the slide-wedge assembly  30 . A hole  46  is provided in the rotary union  44  for a pneumatic or hydraulic line (not shown) to be attached and provide a source of pressure to the cylinder  36 . 
         [0039]    Also mounted on an end support  40  is an electrical slip ring  48  which allows electrical current to be transmitted from a stationary, external source (not shown) to the rotating sub-assembly  11  upon which the servo motor  26  is mounted. As described, the servo motor  26  drives the track drive  12  of the sub-assembly  11 . 
         [0040]    Also shown in  FIG. 9 , is a hydraulic ring cylinder  50  that is mounted on an end support  40 . The hydraulic ring cylinder  50  provides small linear movement or bumping of the entire sub-assembly  11 . The amount of linear movement or bumping is adjustable and can be as much as ½ inch or nearly no movement at all. As described, bumping is used to release the tube product  14  from the tooling inside the pilger mill. 
         [0041]      FIG. 10  shows the complete sub-assembly  11 , including both the top and bottom base plates  38 . Also shown are two ring supports  52  around the assembly  11  which allow the entire sub-assembly  11  to be mounted on bearings  54 . The bearings  54  are mounted to the ring supports  52 . With bearings  54  located on the two ring supports  52  and the two end supports  40 , the entire sub-assembly  11  is able to rotate in a nearly frictionless manner about a longitudinal axis coinciding with the tube product  14 . Each of these four main bearings  54  is fit within a bronze sleeve that allows the entire sub-assembly  11  to be bumped by the hydraulic ring cylinder  50 . 
         [0042]    Alternatively, the ring supports  52  and related structures may be omitted and replaced by a plurality of stiffener bars. The stiffener bars run the length of the sub-assembly  11  and are positioned at the edges of the base plates  38 . The ends of the stiffener bars are attached to the end supports  40  and provide additional support to the entire sub-assembly  11 . With the ring supports  52  removed, the sub-assembly  11  rotates in the gearbox housing  58  solely upon the support bearings  42 . Such structure works best when the gearbox  10  is of a smaller design. 
         [0043]      FIG. 11  shows how the sub-assembly  11  is mounted into the lower gearbox housing  58 . A servo drive  60 , used to rotate the entire sub-assembly  11 , is located on the outside of the lower housing  58 . The rotation of the servo drive  60  is transferred to the sub-assembly  11  by gears  62 . One gear  62  is mounted onto a end support  40  and a transfer gear is mounted on the housing  58  to transfer the rotary motion from the servo drive  60  to the sub-assembly  11 . A disc brake (not shown) mounted internally or externally of the servo drive  60 , is used to stop the rotation of the sub-assembly  11  when needed.  FIG. 12  shows the completely assembled gearbox  10  with the upper housing  64  open so the sub-assembly  11  can be seen. 
         [0044]    The inventive gearbox  10  is used to provide turning and feeding of incoming tube products  14  into the tooling of a pilger mill. The pilger mill reduces or works the incoming tube  14  into a smaller size both on outer diameter and inner diameter. For purposes of understanding, the function of a pilger mill is briefly explained. 
         [0045]    As is common to pilger mills, this reduction of tube product  14  is accomplished by tooling of the pilger mill comprising a set of round dies and a mandrel. The outer diameter reduction of the incoming tube  14  is performed by dies which work the tube outer diameter when the dies rotate and travel. The incoming tube  14  inner diameter is formed by a mandrel while the dies reduce the tube outer diameter. The tube inner diameter and consequently the tube wall, is worked at the same time the tube outer diameter is reduced or formed. 
         [0046]    As the tooling performs the work or the metal reduction, the rotation and travel of the tooling is controlled by a saddle. The saddle is moved back and forth by means of a mechanical drive, via a single crankshaft, or a bull gear system, or a multiple crank system, or a multiple gear system or other similar devices. The single back and forth movement of the saddle is described as one stroke. This functionality is separate from the feeding, turning and bumping of the gearbox  10  described above. 
         [0047]    During the pilgering process, the incoming tube  14  is held or clamped in position momentarily by the gearbox  10  while the tooling reduces the tube product. After the pilger mill tooling has completed a stroke, the gearbox  10  incrementally moves the tube  14  forward a pre-determined amount, known as feeding. At the same time, the gearbox  10  indexes (rotates) the tube  14  a pre-determined amount. At the same time, the gearbox  10  bumps the tube  14  to release it from the mandrel. 
         [0048]    The clamping or holding of the tube  14  is achieved by holding the dual track drive  12  stationary such that the segmented clamps  22  which are in contact with a portion of the tube  14  and compressed by the slide-wedge assembly  30 , as described above, securely hold the tube  14 . The feeding and turning, as described, may occur either at one or both end positions of the stroke of the saddle as it is mechanically moved. These end saddle positions are known in the art as entry and exit positions. The tooling is not reducing or in contact with the incoming tube  14  at either the entry or exit positions, therefore the tube  14  is free to be fed and indexed. After each feeding and indexing of the incoming tube  14 , the tooling resumes the reduction process again on each stroke. 
         [0049]    Although an embodiment has been described in detail for purposes of illustration, various modifications may be made without departing from the scope and spirit of the invention. Accordingly, the invention is not to be limited, except as by the appended claims.