Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation of U.S. patent application Ser. No. 10/339,514 now U.S. Pat. No. 6,757,949 filed on Jan. 9, 2003, which claims the benefit of U.S. Provisional Application Ser. No. 60/367,795, filed on Mar. 27, 2002. The disclosures of the above applications are incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The present invention generally relates to component manufacture methods, machinery and tooling and more particularly to an improved gear manufacture method, tooling and machinery. 
   BACKGROUND OF THE INVENTION 
   Mass production of components, such as gears and the like, typically includes a series of machines integrally linked in a production line. Such machines may include cutters, grinders, shavers, heat treat and the like. Generally, a raw component is loaded at the beginning of the line and each machine performs a specific manufacturing process on the raw component, ultimately producing a finished product. Each step of the process includes an associated cycle-time. The cycle-time is the amount of time it takes a particular machine to perform its process, including loading and unloading of a component. The cycle-time translates directly into manufacturing costs and thus component price. 
   In addition to cycle-times, each machine has associated costs. The initial cost is the capital investment required to purchase the machine. Other costs are incurred throughout the life of the machine. These on-going costs include maintenance, replacement parts, general running costs (electricity, lubricant, etc.) and the like. 
   Gear hobbing is one of a variety of methods employed for manufacturing gears and is generally used in mass production for rough cutting teeth in gear blanks. In gear hobbing, the cutting tool is termed a “hob”. Generally, hobs are cylindrical in shape and are greater in length than in diameter. The cutting teeth of a hob extend radially from the cylindrical body and follow a helical path about the hob, along the length of the hob. Hobbing is a continuous process in which the hob and gear blank rotate in timed relation to one another. The cutting action is continuous in one direction until the gear is complete. 
   The hob is fed across the circumferential face of a gear blank at a uniform rate. As the hob moves across the circumferential face of the gear blank, both the hob and the gear blank rotate about their respective axes. As the hob cuts the gear blank, tooth profiles gradually form within the circumferential face of the blank and the teeth gradually take shape across the gear face. 
   Accuracy and production requirements dictate the type of hob to be used. Hob types vary from single-thread to double-thread or more in multiple. A single-thread hob makes one revolution as the gear being cut rotates the angular distance of one tooth and one space. For example, for producing a spur gear having 49 teeth, a single-thread hob rotates 49 times for one revolution of the gear blank. Similarly, when using a double-thread hob, the hob rotates 49 times for two revolutions of the gear blank. Multiple threads increase the rotational speed of the gear blank accordingly. However, certain limitations are inherent in using multiple-thread hobs. 
   The number of threads is a function of the intended purpose. Although not efficient for mass production, single-thread hobs may be used for both roughing and finishing. Multiple-thread hobs are commonly used for roughing. As a result of the multiplication effect of multiple-thread hobs, speed increases, thus providing savings in cycle-time. However, compared to single-thread hobs, multiple-thread hobs leave much larger feed marks on the tooth profiles of the gear teeth. For example, using a single-thread hob, each tooth of the hob cuts every tooth space in the gear blank. A double-thread hob contacts every other tooth space during any single revolution of the gear blank. 
   Various feed directions of the hob, relative to the gear blank, are employable and are dependent upon the type of gear to be cut. The hob feed directions include axial, oblique, infeed (or plunge) and tangential. Generally, the hob is fed into contact with the gear blank as opposed to the gear blank being fed into contact with the hob. Axial hob feeding includes the hob being fed into the gear blank along a path that is parallel to the axis of rotation of the gear blank. In oblique hobbing, the hob path is at an angle relative to the axis of rotation of the gear blank. In this manner, the cutting action is distributed along an increased length of the hob as it is fed across the gear blank. In infeed hobbing, the hob is fed radially inward into the gear blank. With tangential hobbing, the hob is fed tangentially across the gear blank. 
   Besides rough forming of gear teeth, other forming processes may be required for a particular gear design. For example, typical gear designs dictate that a chamfer be formed on each side of the individual gear teeth. To achieve this, a second roughing process is required using additional tools and machines. Generally, a chamfering tool is used and includes a circumferential face having a set of mating gear teeth recessed between chamfer forming faces. The rough gear and tool are pressed into engagement with one another, wherein the rough gear blank meshes with the mating gear teeth of the chamfering tool and both the tool and the rough gear rotate in unison. As the rough gear and chamfering tool rotate, the chamfer forming faces displace material at each side of the individual gear teeth, thus forming a chamfer on each side of the individual gear teeth. 
   Having thus formed the chamfers, the displaced material must be removed from the rough gear in a process known as deburring. Deburring of the rough gear is typically achieved using a third process that implements a third tool for cutting away the displaced material. It is, however, known in the art to combine the chamfer forming and deburring tools. A single chamfer/debur tool is constructed similarly as described above for the chamfer tool, however, further includes cutters associated with the chamfer forming faces. The cutters remove the displaced material immediately after the corresponding forming face forms the chamfer. 
   To finish the gear, a finishing process is performed. Gear finishing processes are used for improving accuracy and uniformity of the gear teeth. The degree of accuracy and, thus, the finishing process required is dependent upon the functional requirements of the gear. 
   Gear shaving is the most commonly used method of finishing gear teeth prior to hardening. Gear shaving is a cutting process, whereby material is removed from the profiles of each gear tooth by a cutter. The cutter may vary in form, typically resembling a gear or rack depending upon whether a rotary or a rack gear shaving method is used. 
   Typical gear production lines include a series of machines for performing each of the above-described processes. As such, each machine requires an initial capital investment cost and the other associated costs described above. Furthermore, general production cycle-time of a production line, having multiple machines, includes transfer time between machines. Key elements of manufacturing costs include, but are not limited to, the number of machines required, the number of processes required, the set-up time between the processes and the overall cycle-time of each work-piece. As manufacturers seek to improve overall operational costs reduction in any one of these areas is sought. Manufacturers seek to reduce the amount of machines required for production, thereby reducing capital and maintenance costs, as well as reducing the cycle-time for producing each component, thus increasing the efficiency of the complete process. 
   A majority of state-of-the-art machine tools are computer numerically controlled machines or “CNC” machines. Such machines use computer control for both machine operation and set-up. Computers further enable a series of machines that perform separate functions to work in concert to perform several operations on a work piece and to mass produce final products. Each machine, however, must be independently programmed by an operator prior to processing a new work piece design. Because each machine is independently programmed, set-up time and thus, overall manufacture time is less efficient than desired. As a result, overall manufacture cost and product cost is higher than desired. 
   Therefore, it is desirable in the industry to provide improved machinery for producing components, such as gears. The improved machinery should limit the need for additional, supporting machines, reduce the overall capital investment and maintenance costs, as well as reduce the cycle time of component manufacture. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a gear manufacturing apparatus according to the principles of the present invention; 
       FIG. 2  is a plan view of a combination hob/shave tool of the gear manufacturing apparatus of  FIG. 1 ; and 
       FIG. 3  is a plan view of a combination chamfer/debur tool of the gear manufacturing apparatus of FIG.  1 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   With particular reference to  FIG. 1 , an exemplary embodiment of a four-process manufacturing apparatus  10  (the apparatus) is shown. The apparatus  10  of the exemplary embodiment is provided for the manufacture of gears. However, it should be noted that the apparatus  10  is preferably variable for manufacture of any one of a number of alternative components. The apparatus  10  and its related components, described in detail below, are preferably CNC controlled by any one of a number of controllers (not shown) commonly known in the art. The controller is programmable for manufacturing a variety of components and/or component designs. It is foreseen that the controller is also programmable to simultaneously control operation of the rectilinear movement of the various stocks described herein. 
   The apparatus  10  includes a generally rectangular, solid metal base  12  providing a solid support structure for the various apparatus components described herein. First and second stocks  14 ,  16  are included and are each slidably engaged with the base  12 . A third stock  18  slidably engages the first stock  14 . A fourth stock  20  is rotatably supported by the third stock  18  and operatively supports a combination hob/shave tool  22 . A fifth stock  24  is positioned between the first and second stocks  14 ,  16  and operatively supports a combination chamfer/debur tool  26 . The second stock  16  includes a retention device  28  for operably retaining a work-piece (not shown) during manufacture. Rectilinear movement of the various sliding stocks described above is achieved by respective drive motors that act through speed reducing gearing and recirculating ball screw drives. 
   The base  12  includes a top surface  30 , to which the first and second stocks  14 ,  16  are slidably interfaced. The first stock  14  is slidable along a first axis X that runs along the length of the base  12 . The second stock  16  is slidable along a second axis Y that is generally perpendicular to the first axis X, running across the width of the base  12 . The base  12  includes a first pair of rails  32  disposed along a length of and extending upward from the top surface  30 . The first pair of rails  32  slidably engages a corresponding pair of rails  34  disposed on a bottom surface of the first stock  14 . Rectilinear movement of the first stock  14  is imparted by a drive motor  36  acting through a gear reduction unit  38  and a ball screw  40 . The drive motor  36  is controllable for selectively sliding and locating the first stock  14  along the axis X. The base  12  further includes a second pair of rails  42  disposed across a width of and extending upward from the top surface  30 . The second pair of rails  42  slidably engages a corresponding pair of rails  44  disposed on a bottom surface of the second stock  16 . Rectilinear movement of the second stock  16  is imparted by a drive motor  46  acting through a gear reduction unit  48  and a ball screw  50 . The drive motor  46  is controllable for selectively sliding and locating the second stock  16  along the axis Y. 
   The first stock  14  includes a front face  52  to which the third stock  18  is slidably attached. The front face  52  of the first stock  14  includes a pair of rails  54  extending therefrom that slidably engage a corresponding pair of rails  56  disposed on a back face of the third stock  18 . The third stock  18  is slidable along a vertical axis Z of the front face  52 . A drive motor (not shown) acting through a gear reduction unit (not shown) and ball screw (not shown) are provided for selectively sliding and locating the third stock  18  along the axis Z, relative to the second stock  16 . 
   The third stock  18  further includes a front face  64 , to which the fourth stock  20  is rotatably attached. The fourth stock  20  is selectively rotatable about a rotational axis A and includes first and second arms  66   a ,  66   b  extending therefrom, for operably retaining the combination hob/shave tool  22  therebetween. A positioning motor (not shown) is provided for rotationally positioning the fourth stock  20  about the rotational axis A. The hob/shave tool  22  is rotatably driven, by a drive motor  70 , about an axis B that is generally parallel to the front face  64  of the third stock  18  and is initially generally perpendicular to the axis A. The rotational position of the fourth stock  20  and the lateral position of the third stock  18  are controlled by the controller. 
   With reference to  FIG. 2 , the hob/shave tool  22  includes a hob  80  and a shaver  82  affixed to one another. It should be noted, however that detachment of the hob  80  and shaver  82  is anticipated, whereby a portion of the hob/shave tool  22  may be replaced if worn before the other portion. The hob  80  is generally cylindrical in shape and includes a plurality of hob teeth  84  radially extending from a circumferential surface. The hob teeth  84  follow a generally helical path along the length of the hob  80 . The shaver  82  is generally gear shaped including a plurality of gear teeth  86  and a clearance hole (not shown) through the base of each tooth  86 . The gear teeth  86  are serrated to provide a series of cutting edges  90 . The serrations extend from the tip of the tooth  86  into the clearance hole. The clearance holes provide channels for the flow of cutting fluid and material as the shaver operates. 
   With reference to  FIG. 3 , the chamfer/debur tool  26  is operatively supported by the fifth stock  24  and is rotatably driven by a drive motor (not shown) through a gear unit (not shown). With reference to  FIG. 3 , the chamfer/debur tool  26  is a generally gear shaped tool having a series of gear teeth  96  extending radially from an outside circumferential surface. At the ends of each of the gear teeth  96  is located a chamfer surface  98  that serves to displace material at the ends of gear teeth formed on the work-piece thereby producing a chamfer. Positioned adjacent each chamfer surface  98  is a cutting edge  100  that cuts away the displaced material for deburring the chamfer of the gear teeth. 
   As mentioned previously, the second stock  16  includes the retention device  28  for selectively holding a work-piece. It is foreseen that the work-piece may be either manually loaded, by an operator, or alternatively, an automated loading system (not shown) may be included for loading the work-piece into the apparatus  10 . The work-piece is held by the retention device  28  such that it is freely rotatable about a rotational axis C. The rotational axis C is generally parallel to the front face  64  of the third stock  18  and perpendicular to the top surface  30  of the base  12 . Rotation of the work-piece about the axis C is driven by the tools as described in further detail herein. It is also foreseen that the second stock  16  is rotatable about an axis D. The rotational position of the second stock  16  is controlled by a positioning motor (not shown). 
   With reference to the Figures, a method of manufacturing a gear and the corresponding operation of the apparatus  10  will be described in detail. Manufacturing of a gear includes the steps of: loading a gear blank (work-piece), hobbing rough gear teeth into the work-piece, chamfering and deburring the rough gear-teeth, finishing the gear teeth via shaving, and unloading the finished work-piece. 
   Initially, a work-piece, in the form of a cylindrical gear blank, is loaded into the retention device  28  of the second stock  16 . Once locked in position, the controller initiates the hobbing step, whereby the hob/shave tool  22  is rotatably driven and fed into contact with the work-piece for forming rough gear teeth in the work-piece. The preferred feeding method of the present invention is infeed or plunge. The hob/shave tool  22  is infed via forward movement of the first stock  14  along the axis X, relative to the second stock  16 . As the hob/shave tool  22  contacts a circumferential surface of the work-piece, the hob teeth  84  begin cutting corresponding teeth into the circumferential surface. As the hob teeth  84  cut, the helical pattern of the gear teeth cause the work-piece to rotate about the axis C. In this manner, the gear teeth are cut into the complete circumferential surface of the work-piece. The number of revolutions of the hob/shave tool  22 , and thus the work-piece, is dependent upon the number of threads of the hob/shave tool  22 . Upon completion of rough gear tooth formation, the hob/shave tool  22  is withdrawn through reverse movement of the first stock  14  along the axis X, relative to the second stock  16 . 
   After the hob/shave tool  22  has been withdrawn, the chamfer/debur tool  26  is brought into meshed engagement with the work-piece. Specifically, the gear teeth of the chamfer/debur tool  26  engage the rough gear teeth of the work-piece. Initially, the chamfer/debur tool  26  is rotatably driven in a first direction whereby the chamfer surfaces  98  displace material at both ends of the rough gear teeth and the displaced material is cut away by the corresponding cutting edge  100 . As the chamfer/debur tool  26  rotates, the meshed engagement with the work-piece causes corresponding rotation of the work-piece. The rotation of the chamfer/debur tool  26  then ceases and changes direction, rotating in a second direction. In this manner, chamfers are formed at the ends of each of the rough gear teeth about the circumference of the work-piece and excess material is cut away on both sides of each gear tooth. Upon completion of the chamfer/debur process, the chamfer/debur tool  26  is withdrawn from the work-piece. 
   During operation of the chamfer/debur tool  26  on the work-piece, the fourth stock  20  is concurrently repositioned on the third stock  18  to prepare the hob/shave tool  22  for a subsequent shaving process. The fourth stock  20  rotates approximately 90° on the front face  64  of the third stock  18 , whereby the rotational axis B is positioned generally parallel to the rotational axis C and generally perpendicular to the top surface  30  of the base  12 . In this manner, the shaver  82  is properly aligned for engagement with the work-piece. Concurrent repositioning of the fourth stock  20  helps to reduce overall cycle time of the manufacturing process. 
   Once the chamfer/debur tool  26  is completely withdrawn, the first stock  14  again moves forward along the axis X and the third stock  18  is concurrently adjusted on the Z axis whereby the shaver  82  of the hob/shave tool  22  is aligned for meshed engagement with the work-piece. The serrated teeth  86  of the shaver  82  engage the rough gear teeth of the work-piece. The hob/shave tool  22  is initially driven in a first rotational direction by the fourth stock  20 , whereby the work-piece is correspondingly caused to rotate, due to the meshed engagement therebetween. Similar to the chamfer/debur tool  26 , the shaver  82  stops and rotates in a second direction opposite that of the first. This “reversal” process is repeated twice more for a total of six times, three in each direction. As the shaver  82  and work-piece rotate together, each of the serrated gear teeth  86  of the shaver  82  act upon the rough gear teeth of the work-piece for finishing both sides of each gear tooth of the work-piece. Upon completion of the shaving process, the hob/shave tool  22  is withdrawn and the finished gear is unloaded from the retention device  28 . 
   As initially noted, the apparatus of the present invention includes four manufacturing processes. By performing four-processes, only a single machine need be purchased to produce a finished gear. Thus, significant savings are realized in initial capital investment costs. Additionally, a single machine occupies less floor space, requires less maintenance attention and less running costs, than multiple machines. Therefore, additional savings are achieved throughout the lifetime of the machine. Further, overall cycle-time is significantly reduced because a component is only loaded and unloaded once and there is no transfer time present between machines. The reduced cycle-time translates into further cost savings. 
   The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.

Technology Category: 4