Abstract:
A pipe end thread cutting apparatus includes three milling cutter heads mounted on a support wall which is vertically movable with the heads mounted symmetrically about a central axis in use; a gripping chuck for holding a pipe end is mounted on a rotatable shaft carried on a support member which is movable toward and away from the milling cutter heads and motor drives are provided for each cutter head.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to thread milling devices, especially thread milling devices for forming threads and the like in the periphery of a pipe end for connecting and retaining the pipe to a coupling or other fluid conducting member. A particular example of the present invention relates to forming threads and the like in a pipe end to make a pipe nipple. In past practice in the fluid conduit field, threads were cut in the ends of pipes to enable connection to other elements of a system such as valves, joints and the like. Equipment for cutting straight threads (i.e., threads that lie a uniform radial distance from the axis of the pipe) has been in widespread use for many years.  
           [0002]    However, the advantages of forming tapered threads (i.e., threads that vary in radial distance from the axis of the pipe) on pipe ends have become apparent, but equipment for forming tapered threads is difficult to set up, slow to operate, and expensive to acquire. An example of a pipe nipple having tapered threads is illustrated in FIG. 5 at  70 . Since the desirable characteristics of tapered thread nipples have increased demand for these types of pipe ends, there exists a need for an improved apparatus for quickly and accurately forming tapered threaded pipe ends that can be threaded into associated conduit elements to assure fluid tight seals. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0003]    [0003]FIG. 1 is a side view of an apparatus provided in accordance with the principles of the present invention;  
         [0004]    [0004]FIG. 2 is an enlarged side view of the apparatus illustrated in FIG. 1;  
         [0005]    [0005]FIG. 3 are end views of opposing portions of the apparatus according to the present invention;  
         [0006]    [0006]FIG. 4 is a plan view of a dual apparatus according to the present invention; and  
         [0007]    [0007]FIG. 5 is a side view of an exemplary conventional pipe nipple having tapered threads formed on a periphery thereof.  
         [0008]    [0008]FIG. 6 is an enlarged sectional view of two of the thread forming cutters used in the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0009]    Referring to FIG. 1, a thread cutting apparatus for cutting threads in pipe nipples is shown, generally indicated at  10 , provided in accordance with the principles of the present invention. Reference to the term “thread” or “threads” herein is meant to include, without limitation, both a helical structure for permitting rotational engagement (like a screw, for example) and one or more circumferentially extending structures for permitting axial press-fitting between members.  
         [0010]    The apparatus  10  includes a pipe holding portion, generally indicated at  11 , and a milling head portion, generally indicated at  13 .  
         [0011]    The milling head portion includes a thread milling head, generally indicated at  12 , mounted on a vertical platform  14 . The thread milling head  12  includes thread milling cutters  18 . Three thread milling cutters  18  are illustrated (see, for example, FIG. 3) strictly by way of example, and the number of thread milling cutters  18  that may actually be provided may vary as needed. Each thread milling cutter  18  is constructed in a known way to form a desired thread on the end of a pipe held in pipe holding portion  11  (as discussed below). Each thread milling cutter  18  is arranged to rotate about an associated shaft  42  (having axis of rotation  43 ) in the direction of arrow D (see, for example, FIGS. 2 and 3). The thread milling cutters  18  rotate in the same rotational direction and may be driven to rotate in a known manner, including, without limitation, being independently driven (for example, by a conventional motor housed in respective housings  20 ), and being synchronously driven, such as by one or more drive belts (not shown) engaged with the respective thread milling cutters  18  and with a single conventional drive motor (not shown). The motor (or motors) provided may be a servo motor controllably driven in a known manner using computer numeric control (CNC) methods.  
         [0012]    In addition, the thread milling head  12  (including the provided thread milling cutters  18 ) may be rotatably mounted about axis  52  with respect to platform  14 . Thread milling head  12  may be supported by a bearing structure, such as that shown schematically in FIG. 2 at  51 . Thread milling head  12  may be driven to rotate about axis  52  by drive motor (not shown) in a known manner, such as by way of a timing belt engaged therebetween similar to that shown on the left hand side of holding portion  11 .  
         [0013]    In an example of the present invention, thread milling cutters  18  are mounted so that their axes of rotation  43  are not parallel with axis  52 . In a particular example of the present invention, the axes of rotation of the respective thread milling cutters  18  are arranged so as to intersect at substantially the same point along axis  52 . The angle between axes  43  and axis  52  may be selectively adjustable in order to, for example, accommodate pipes of different diameters, or to selectively move the thread milling cutters  18  between a first position in which the pipe is arranged to be worked on and a second position in which the thread milling cutters are placed into position relative to the pipe for forming the desired threads.  
         [0014]    In order to further control the position of the thread milling head  12  relative to the pipe holding portion  11 , the vertical position of the thread milling head  12  may be controlled, for example, by a servo motor  19  which may operate a screw feed to raise or lower the platform  23  slidably mounted on column  23   a.    
         [0015]    The pipe holding portion  11  holds a pipe segment being operated on. The pipe holding portion  11  is provided on a support  13 . The support  13  in the form of a plate and is in turn laterally movable relative to the platform  14  by way of, for example, a precision slide mechanism  36  (see, for example, FIG. 2). The lateral position of support  13  (with pipe holding portion  11  provided thereon) relative to platform  14  may be automatically controlled by motor  40  connected to support  13  by a known linkage, such as a ball screw mechanism. In an example of the present invention, motor  40  may be a CNC servo motor to provide precise control of the position of pipe holding portion  11  relative to platform  14 .  
         [0016]    Pipe holding portion  11  also includes a housing  30  that contains a chuck, spindle, or other mechanism  54  for selectively retaining a pipe segment therein during the process of thread cutting. The chuck  54  is arranged so as to hold a pipe segment (not shown) therein substantially coaxial with axis  52  of the milling head  12  (see, for example, FIG. 2). The chuck  54  may be either manually actuable, automatically actuable, or both, in accordance with known practices.  
         [0017]    Chuck  54  is mounted on a rotatable shaft  60 . Shaft  60  is mounted within housing  30  so as to be rotatable (for example, on one or more rotational bearings provided within housing  30  and not shown here). A pulley  62  is fixedly mounted on shaft  60 . Pipe holding portion  11  also includes a drive motor  15  arranged to drive a pulley  17  in rotation. Pulleys  17  and  62  are engaged in a known manner, such as by a belt  16  extending therebetween. Therefore, drive motor  15  is operable to drive shaft  60 , and in turn, chuck  54 , in rotation. Drive motor  15  may be a CNC servo motor.  
         [0018]    As best shown in FIG. 6, the thread milling cutters  18  are arranged about axis  52  to receive the end of a pipe segment therebetween and to cut threads in an exterior periphery of the pipe segment. Each thread milling cutter  18  carries multiple, generally circumferentially extending teeth  60  for cutting threads in the periphery of a pipe segment upon simultaneous rotation of the milling cutters  18  about their associated shafts, and rotation of the entire thread milling head  12  about axis C. The thread milling cutters  18  can be changed for cutting tapered or straight threads. In FIG. 3, the end of the pipe holding portion  11  facing the milling head portion  13  is illustrated schematically to simplify the drawing. In FIG. 3, the pipe holding portion  11  and milling head portion  13  are illustrated as being placed on an inclined surface as is sometimes done in the field of milling. However, it is not necessary to provide the apparatus on an inclined surface.  
         [0019]    In this regard, certain structural parameters can be varied as desired, depending on the degree of tapering in the threads, the pitch of the threads, etc. For example, the teeth of a thread milling cutter  18  may be provided on a frusto-conical surface. Therefore, for example, one or both of the angles between the frusto-conical surface and respective axis  43 , and the angle between axis  43  and axis  52  can be varied.  
         [0020]    [0020]FIG. 4 illustrates an embodiment of the present invention for forming threads on both ends of a pipe segment. As seen in FIG. 4, two apparatuses  10 ,  10 ′ according to the description set forth herein are provided. Apparatus  10  is provided in reverse orientation from apparatus  10 ′ (i.e., the relative positions of the pipe holding portion  11 ,  11 ′ and milling head portion  13 ,  13 ′ are reversed. With this reversed arrangement, a thread can be formed at one end of a pipe segment in apparatus  10 . Then the pipe segment can be moved to apparatus  10 ′ to form a thread in the other end of the pipe segment, while at the same time, a second pipe segment is processed in apparatus  10 . With this arrangement, therefore, manufacturing throughput can be desirably increased.  
         [0021]    It can be appreciated that the pipe segment in chuck  54  effectively acts as a “sun gear,” the thread milling cutters  18  act as “planet carriers,” and the housing  20  can be considered the “ring gear” of the planetary arrangement described above.  
         [0022]    Thus, the apparatus provides a self-contained, coaxial thread milling head using multiple cutters with multiple teeth for very high speed thread cutting with low chip load per tooth.  
         [0023]    As mentioned above, motors  15 ,  19 ,  20 , and  40  may, for example, be CNC servo motors. Thus, in an example of the present invention, the motors may be all controlled collectively (such as by a control computer) in order to automate the manufacturing process.  
         [0024]    The foregoing preferred embodiments have been shown and described for the purposes of illustrating the structural and functional principles of the present invention, as well as illustrating the methods of employing the preferred embodiments and are subject to change without departing from such principles. Therefore, this invention includes all modifications encompassed within the spirit of the following claims.