Patent Publication Number: US-2006002775-A1

Title: Parallel-serial bevel and hypoid gear generating machine

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a parallel-serial bevel and hypoid gear generating machine.  
      2. Description of Related Art  
      Typical bevel and hypoid gear generating machines include a machine base and separate supports resting on the base for mounting a work gear and a rotating tool. The tool support is arranged to carry a rotary tool in the machine plane, which represents an imaginary gear positioned to mesh with the work gear. A machine cradle is journaled in the tool support so that its axis of rotation represents the axis of the imaginary gear. A rotary tool, having stock removing surfaces that represent one teeth in the imaginary gear, is supported on the front face of the cradle. In particular, the rotary tool is mounted on a tool spindle, which is journaled in a tilt mechanism carried by the cradle. The tilt mechanism is used to adjust the angular position of the rotary tool axis with respect to the cradle axis so that the stock removing surfaces of the tool are oriented to appropriately represent the position of gear teeth on the theoretical generating gear.  
      The work gear support generally includes means for adjusting the mounting position of the work gear so that the work gear will fit into mesh with the imaginary gear represented by the tool support. The work gear is journaled for rotation in the work support and means for rotating the work gear interconnect with means for rotating the machine cradle so that the work gear may be rotated in a timed relationship with the rotation of the cradle. Tooth sides are generated in the work gear by imparting a relative rolling motion between the tool and work gear as though the work gear were in mesh with another gear member (i.e. the theoretical generating gear) having an axis of rotation coincident with the machine cradle axis and mating tooth surfaces represented by the stock removing surfaces of the tool. The rotary tool may be arranged to represent a single tooth in a generating gear or may include a number of stock removing surfaces, which are specially positioned on the tool body for timed rotation with the work gear to represent a generating gear with a plurality of teeth. For purposes of additional background, it may be appreciated that for a number of years, advances in the computer and electronics industry have been routinely applied to machine tools. In fact, most state-of-the-art machine tools now include some sort of computer control. Such machines are referred to in the industry as computer numerically controlled (CNC) machines. It is well known, for example to use computers to control both machine operation and setup. Computers also enable a series of machines performing separate functions to work together in a system to perform many different operations on work pieces and to produce a number of different work pieces without requiring substantial manual intervention.  
      Although conventional bevel and hypoid type gear generating machines have been recently fitted with computer controls, mainly for monitoring and controlling machine operation, much of the set up of these machines still requires manual intervention. For example, U.S. Pat. No. 3,984,746 discloses a “master-slave” servo-system for replacing certain gear trains in a conventional bevel and hypoid gear generating machine which control relative machine motions during use. However, much of the setup of the modified machine still requires substantial manual intervention. Conventional bevel and hypoid gear generating machines require nine or more machine settings for appropriately positioning the tool with respect to the work gear. These settings include: (a) an angular setting of the cradle, (b) three angular settings of the tilt mechanism, (c) a rectilinear feed setting between the tool and work supports, (d) a rectilinear setting of work gear height above the machine base, (e) an angular setting of the work gear axis, and (f) a rectilinear setting of the work gear along its axis. These settings are difficult to make to required accuracy and are time consuming. Most of these settings are accomplished manually because the large number of settings and their often congested locations render computer control of these settings extraordinarily complex and/or prohibitively expensive.  
      For example, known tool tilt mechanisms on bevel and hypoid gear generating machines are associated with a number of particularly difficult settings. These settings are made to incline and orient the tool axis with respect to the cradle axis so that the stock removing surfaces of the tool are positioned to appropriately represent tooth surfaces of the theoretical generating gear. Three coordinated settings known in the art as “eccentric angle”, “swivel angle”, and “tilt angle” are usually required for this purpose. The tool drive that acts through the tilt mechanism also involves an extraordinary amount of complexity. This drive is required to impart rotation to the tool at variable angular orientations and positions with respect to the cradle axis. Thus, both the complex settings of the tool tilt mechanism and the tool drive at variable orientations take place within the space of the machine cradle that is rotatable. Accordingly, machine cradles tend to be quite large and cumbersome. The diameter of the theoretical generating gear represented by the tool support is also substantially determined by the diameter of the machine cradle. Thus, it may be readily understood that the just-mentioned slides may be used to move a tool axis to the same position otherwise effected by a cradle in non-generating machines. This general concept has also been proposed for bevel and hypoid generating machines in WO 02/066193, JP 62-162417 and JP 11-262816. However, neither of these proposed generating machines suggests any means for inclining the tool axis with respect to their intended representation of the customary cradle axis. In fact, even if a known tool axis tilt mechanism were to be added to either of the proposed machines, the arcuate translation of an inclined tool axis along the rectilinear slides of the proposed machines would not reproduce the rotational motion of the inclined tool axis about the cradle axis of a conventional machine. In other words, translation of an inclined axis about another axis to which it is initially inclined is not the same as rotation of the inclined axis about another axis. Thus, neither of the proposed generating machines disclosed in the patents just referred to above is appropriate for manufacturing the variety of gears traditionally produced by conventional bevel and hypoid generating machines which utilize large machine cradles and complex tilt mechanisms for appropriately positioning and operatively engaging a tool and work gear.  
      Furthermore, even when generating without any provision for tool axis tilt, neither of the proposed machines appears to account for the change in angular position of the tool about its axis which should accompany their respective translational representations of cradle axis rotation, and the lack of such a change in angular position would undesirably affect the required timed relationship between tool and work rotations during continuous indexing operations.  
      Another important consideration relating to the generation of longitudinally curved tooth bevel and hypoid gears is the determination of appropriate setup and operating parameters for such machines. Because of the complexity of tooth surfaces formed by conventional bevel and hypoid generators, such tooth surfaces can only be exactly defined geometrically by the machine motions that are used to produce them.  
      Further, little or no benefit would be derived from the large amount of existing know-how which relates such desired tooth geometry and mating characteristics to conventional machine settings. This is particularly true of “higher order” modifications that are expressed directly in terms of known machine motions or in terms of a theoretical generating gear.  
      To overcome the shortcomings, the present invention intends to provide an improved bevel gear generating machine to mitigate the aforementioned problems.  
     SUMMARY OF THE INVENTION  
      The primary objective of the invention is to provide an improved bevel gear generating machine. The machine configuration is greatly simplified with respect to bevel gear generating machines of the prior art and is readily adaptable to computer controls for automatically setting up and operating the machine.  
      The machine of the present invention has more freedom in rotation and minimum accumulated error so as to increase the precision of the machine.  
      Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view of a machine in accordance with the present invention;  
       FIG. 2  is a perspective view of the machine observed from a different angle;  
       FIG. 3  is a perspective view of the machine observed from still a different angle;  
       FIG. 4  is a perspective view of a rotary device of the present invention;  
       FIG. 5  is a schematic view showing the movement of the rotary device of the present invention;  
       FIG. 6  is a perspective view of a parallel device of the present invention;  
       FIG. 7  is a cross-sectional view of the parallel device shown in  FIG. 6 ; and  
       FIG. 8  is a schematic view showing the movement of the parallel device of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT  
      With reference to  FIGS. 1-3 , a bevel gear generating machine constructed in accordance with the present invention includes a main work platform  10 , an X-axis work platform  20 , a Y-axis work platform  30 , a rotary device  40  (as shown in  FIGS. 4 and 5 ), and a parallel device  50  (as shown in  FIGS. 6-8 ).  
      The main work platform  10  has a pair of first tracks  11  formed in the X-axis to correspond to a pair of second tracks  21  formed on the X-axis work platform  20  to form a sliding pair to provide the X-axis work platform  20  to slide thereon. The X-axis work platform  20  has a pair of Y-axis third tracks  22  to correspond to a pair of Y-axis fourth tracks  31  formed on the Y-axis work platform  30  to form a sliding pair to allow the Y-axis work platform  30  to slide thereon. The X-axis work platform  20  is driven at a side face  25  thereof by a first threaded bolt  24  in connection with a first motor  23  that is mounted on the main work platform  10 . Therefore, when the first threaded bolt  24  is driven by the motor  23 , the X-axis work platform  20  is able to move in the X-axis.  
      The Y-axis work platform  30  is driven at a side face  36  thereof by a second motor  34  mounted on the X-axis work platform  20  via a second threaded bolt  35  such that when the second threaded bolt  35  is driven by the second motor  34 , the Y-axis work platform  30  is able to move in the Y-axis. A first bearing seat  32  and a second bearing seat  33  are mounted on the Y-axis work platform  30  (as shown in  FIG. 4 ) to respectively receive therein a first rotary shaft  41  and a second rotary shaft  47 . The first rotary shaft  41  is in combination with a drive motor  42 , which in turn securely engages with a third threaded bolt  43  parallel to the X-axis. The second rotary shaft  47  is combined with a workpiece seat  46  having therein a rotary motor  49  to rotate a workpiece  48  securely mounted on an end of the workpiece seat  46 . A third rotary shaft  45  extends out from opposite sides of the workpiece seat  46  to be coupled with a frame  44  which is threadingly connected to the third threaded bolt  43 . The main work platform  10 , the X-axis work platform  20  and the Y-axis work platform  30  are connected to each other in series so that the combination of the Y-axis work platform  30 , the third threaded bolt  43 , the frame  44  and the workpiece seat  46  is able to move in both the X and Y axes. Preferably, the rotary motor  49  is able to connect to the third threaded bolt  43  and rotate the workpiece  48  directly without the workpiece seat  46 .  
      The rotary device  40  is pivotally connected to the first bearing seat  32  via the first rotary shaft  41  and the third threaded bolt  43  is connected to the frame  44  to allow the frame  44  to pivot relative to the Y-axis work platform  30 . The frame  44  is pivotally connected to the workpiece seat  46  via the third rotary shaft  45  to allow the workpiece seat  46  to pivot relative to the frame  44 . The second rotary shaft  47  is pivotally received in the second bearing seat  33  and connects to the workpiece seat  46 . Thus a rotary device  40  is formed. Therefore, when the drive motor  42  is activated to drive the third threaded bolt  43  to rotate, the workpiece  48  received in the workpiece seat  46  is able to pivot to an angle required. In alternating embodiment, the drive motor  42  is able to drive the frame  44  directly and still achieve the same goal, which is shown in  FIGS. 4 and 5 .  
      The parallel device  50 , as shown in FIGS.  7  an  8 , of the present invention is fixed on the main work platform  10  via a casing  51 . The casing  51  has three pairs of sliding tracks  52  (shown in  FIG. 3 ), three pairs of sliding seat  53  in corresponding to the sliding tracks  52  and three motors  54  each with a fourth threaded bolt  55  in connection with a corresponding one of the sliding seats  53  such that when each of the motors  54  is activated to drive the fourth threaded bolt  55  to rotate to force the sliding seats  53  to move along the Z-axis, the sliding seats  53  is able to pivot about a first pin  56  connecting the sliding seat  53  to a linkage  57  which in turn connects to a universal joint  59  via a second pin  58 . The universal joint  59  is fixed on a tool seat  5   a  (as shown in  FIG. 6 ) and has a third pin  5   b  sandwiched between the linkage  57  and the universal joint  59  to allow the universal joint  59  to pivot in two different directions and thus the three sliding seats  53  are able to control the position of the tool seat  5   a.  The tool seat  5   a  has a driving motor  5   c  inside the tool seat  5   a  to control the rotation of the tool  5   d  formed on the tool seat  5   a.    
      Another embodiment of the present invention is that the position of the workpiece seat  46  of the rotary device  40  and the tool seat  5   a  of the parallel device  50  may be switched and thus the tool seat  5   a  is coupled to the frame  44  and the workpiece seat  46  is connected to the linkages  57  inside the parallel device  50 .  
      From the aforementioned description, it is noted that the rotation angle of the device of the present invention is increased and the accumulated error is decreased in the production of bevel gear, which are the most advantageous aspects of the present invention.  
      Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.