Abstract:
A linear broaching machine for machining rotating parts wherein a plurality of tooling carriages are mounted upon a moving chain and broach type tools are supported by the carriages wherein the tools are moved in a linear path into engagement with a rotating workpiece to remove metal from the workpiece and form an accurately sized cylindrical surface concentric to the workpiece axis of rotation. The tool carriages are spaced from each other providing non-machining access durations wherein the workpiece may be loaded or unloaded from its rotating support spindles.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention pertains to the machining of rotating workpieces by the use of broaching tools sequentially brought into engagement with the workpiece for removing metal therefrom. 
     2. Description of the Related Art 
     It is known to mount a plurality of workpieces on a moving chain and move the workpieces past a fixed tool such as shown in U.S. Pat. Nos. 2,088,119 and 2,191,193. Further, it is known to mount a tool upon a moving chain, such as in a power chain saw, and attention is directed to U.S. Pat. Nos. 1,244,789 and 2,523,301. 
     However, the advantages of mounting a plurality of tools in such a manner as to permit the tools to be sequentially moved past a rotating workpiece in order to permit rapid metal removal from the workpiece and yet accurately control such removal and sizing of the workpiece has not been previously appreciated. It is this concept of the linear movement of broach type workpieces past a rotating workpiece with which the invention deals. 
     OBJECTS OF THE INVENTION 
     An object of the invention is to provide a broach machine tool system for use with a rotating workpiece wherein a high rate of production can be achieved at a high level of accuracy. 
     Another object of the invention is to provide a broach type machine tool for removing metal from a rotating workpiece wherein the tool moves in a linear path while engaging the workpiece. 
     A further object of the invention is to provide a broach type machine tool capable of removing metal from a rotating workpiece wherein a plurality of broach type tools are mounted upon a chain in a spaced manner wherein workpieces may be loaded and unloaded from supporting spindles intermediate machining operations. 
     SUMMARY OF THE INVENTION 
     In the practice of the invention, the linear broach machine includes a frame having spaced opposed rotating spindles defining a workpiece axis of rotation. One or both of the spindles can be powered by a controlled drive unit, and each of the spindles includes clamping mechanism whereby the workpiece may be accurately supported at each end. The machine of the invention was created particularly for heavy duty turning, such as turning the main bearings for internal combustion engine crankshafts. However, it will be appreciated that the invention may be utilized in any turning operation and is particularly suitable in those situations where it is desired to remove a considerable amount of metal in a relatively short time under high conditions of accuracy and tool life. 
     In the preferred embodiment of the invention, a combination of sprockets are located in a triangular relationship whereby the tool carriers may be mounted upon spaced parallel chains guided by the sprockets wherein the carriers will move through a triangular path. It is possible to only use two combinations of chain sprockets in the broad concept of the invention, but the use of three combinations of sprockets permits a greater length of chain to be used permitting a greater number of tool carriers to be mounted upon the chain, thereby providing increased flexibility of tool carrier spacing and the rate of chain movement. 
     Two of the chain sprocket combinations are spaced in such a relationship as to cause the tool carriers mounted upon the chains to move in a path of movement transverse, normally perpendicular, to the axis of workpiece rotation. In this manner, broaching tools mounted upon the tool carriers will move past the workpiece in a tangential manner. Preferably, the two chain sprocket combinations positioning the tool carriers during a cutting action are vertically spaced wherein the tool carriers and tools are moving in a downward direction during cutting. 
     Usually, two or more broaching turning tools are mounted upon a tool carrier, each subsequent tool being located closer to the axis of workpiece rotation wherein the last cutting tool will produce the finished diameter. With some turning operations, the broaching and turning tools necessary to make an entire cut may be located on adjacent tool carriers if it is necessary that three or four tools are required for a machining operation. 
     The tool carriers may be spaced along the chain as desired, and usually, sufficient spacing will exist between the carriers necessary to perform a workpiece operation, and the rate of tool carrier movement is such, that after turning, the workpiece spindles may be stopped, the finished workpiece removed from its supporting spindles, and a new workpiece mounted upon the spindles such that the next series of tools will engage the new workpiece and the turning cycle repeated with a new set of tools without stopping the tool carriage movement. The chain mounting of the tool carriers and tools permits a high rate of production with minimal wear upon any given tool, and turning machines constructed in accord with the invention are capable of high production turning operations for extended periods of time between tool replacement. 
     To ensure accuracy, the tool carriers are held upon a rigid bedway mounted on the machine frame during cutting. The tool carriers include guide surfaces firmly held against bedway guide surfaces (bearings) and as the bedway is well lubricated, it is possible to support the tool carriers on the bedway during cutting in a relatively movable relationship and yet hold the necessary tolerances to achieve accurate tool removal without chattering. 
     It will be appreciated that the aforedescribed machine meets all of the objects of the invention as set forth above. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The aforementioned objects and advantages of the invention will be appreciated from the following description and accompanying drawings wherein: 
     FIG. 1 is a front elevational partially broken away view of a linear broach machine in accord with the invention, 
     FIG. 2 is a top plan view of the machine of FIG. 1, 
     FIG. 3 is an elevational view, partially broken, illustrating the machine of FIG. 1 as taken from the right side thereof, 
     FIG. 4 is a detail plan view, partially in section, illustrating the workpiece spindles and bedway construction as taken along Section  4 — 4  of FIG. 3, and 
     FIG. 5 is an elevational detail sectional view as taken through a tool carrier along Section  5 — 5  of FIG.  4 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The machine of the invention includes a frame whose basic component is the frame plate  10  which constitutes the base for the spindle support cabinet  12  and the chain support structure  14 . Spindle housings  16  and  18  are mounted upon the spindle support  12 , and these housings rotatably support spindles  20  and  22 , respectively. The spindle  20  supports the workpiece chuck  24  while the workpiece chuck  26  is mounted upon the spindle  22 . The spindle  20  is rotated by the controlled drive unit  28 , FIG. 2, drivingly connected to spindle  20  by the power transmission component  30 . 
     The workpiece  32  is affixed between the chucks  24  and  26  for rotation by the controlled drive unit  28 . The workpiece  32  defines the axis of rotation of the apparatus. In the drawings, the workpiece  32  constitutes a crankshaft for internal combustion engines having main bearings  34  which are concentric to the axis of rotation. It will be understood that the particular configuration of the workpiece  32  constitutes no part of the invention as any workpiece to be shaped by turning may be supported upon the chucks  24  and  26 . 
     Behind the spindle support  12 , a pair of spaced parallel vertically extending sprocket supporting plates  36  are affixed to and arise from the frame base  10 . The sprocket plates  36  constitute the support for the three chain sprockets, each sprocket actually constituting a pair of axially aligned sprockets rotatably mounted upon an axle, the upper sprocket is designated at  38 , the lower sprocket  40  is located directly below sprocket  38 , and the rear sprocket  42  is located behind the sprocket  40 , and these relationships will be appreciated from FIG.  3 . Each of the sprocket sets includes the usual chain links which intermesh with the teeth of the sprockets as the chain passes thereover. An controlled drive unit  44  through a transmission  46  and transmission drive shaft  48 , FIGS. 2 and 3, rotates the rear sprocket set  42 . 
     A pair of heavy duty link chains  50  extend over the sprockets  38 ,  40  and  42 , and the chains  50  include a downwardly moving portion  52 , an upwardly moving portion  54 , and a rearward moving portion  56  between the sprockets  40  and  42 . 
     A plurality of tool carriers  58  are attached to and between the chains  50  by a pin or rod stud structure  59 , FIG.  4 . In this manner, a plurality of tool carriers  58  are affixed to the chains  50  in any spacing arrangement desired. Usually, the separation between adjacent tool carriers is substantially the same, but under certain conditions, it may be desired to stagger the tool carrier spacing for reasons later apparent. 
     Movement of the tool carriers  58  during the cutting action is controlled by a pair of spaced bedway guides  60 , FIG. 4, rigidly affixed to the machine frame. The bedway guides each define oppositely positioned flat guide surfaces  62  whose planes are parallel to the axis of rotation. Also, the bedway guides  60  include inner end surfaces  64 . 
     Each of the tool carriers  58  includes bearing structure which slidably engages the guide surfaces of the bedway guides  60 . The tool carrier bearings  66  engage one of the guide surfaces  62 , while the tool carriage includes a guide surface  67  engaging the bedway guide surfaces  62  closest to the workpiece axis of rotation. End bearings  68  carried by the tool carriers  58  engage the flat bedway guide end surfaces  64 . Spring  70 , FIG. 4, bear against the bearings of the tool carriages, and upon the locking structure for the tool carriages&#39; bearings, not shown, being loosened, the springs  70  will bias the bearings against the bedway guide surfaces. In this manner, the tolerances between the bedway guide  60  and the bearings of the tool carriers can be controlled to prevent tool chattering, and the bearings  66  and  68  will be firmly held against the bedway guide surfaces  60  once they are firmly locked to the tool carrier by their threaded set screw arrangements, not shown. 
     As will be appreciated from FIG. 5, each of the tool carriers  58  supports a tool rest plate  72  and is affixed thereto by threaded fasteners, and the tool holder plate  74  is attached to the rest plate  72  by threaded fasteners or tool locking mechanism  76 . The tool holders  78  are mounted upon the tool holder plate  74  by bolts or any locking mechanism, and as will be appreciated from FIG. 5, sequential broach type tools  80 ,  82  and  84  are mounted upon the tool holders  78 , three of which are shown in the version of FIG.  5 . 
     In operation, the workpiece  32  is mounted in the chucks  24  and  26 , and upon energizing of the controlled drive unit  28 , the workpiece  32  will be rotated at the desired rate of speed in a counterclockwise direction as viewed in FIG.  5 . The motor  44  is energized which will drive the chains  50  in a counterclockwise direction of movement as viewed in FIG.  3 . Accordingly, as the tool carriers  58  move along the bedway guides  60 , the tools  80 ,  82  and  84  will come into sequential engagement with the workpiece  32  to remove metal from the main bearings  34  of the workpiece. As will be appreciated from FIG. 5, the tool  82  extends further toward the workpiece axis of rotation than the tool  80 , and thereby will remove metal from the workpiece in a second cut. As the tool  84  moves into engagement with the workpiece main bearing  34 , the fact that the finishing tool  84  is slightly closer to the axis of rotation than tool  82 , the tool  84  only needs to remove a small amount of metal from the workpiece to define the desired finished diameter of the workpiece bearing  34 . In most cases, the entire turning of the workpiece main bearings  34  can be accomplished by the three tools  80 ,  82  and  84 . 
     From the above description, it will be appreciated that the tools moving along the bedway guides  60  on their associated tool carrier function as a broach wherein each tooth removes the appropriate amount of metal during its cutting action, which is a turning process. 
     It is to be understood that the chains and tool carriers  58  are being moved downwardly by the controlled drive unit  44  and transmission  46  at a rather slow rate as to not overload the tool  80 , and the movement of the chains  50  is such that after the finishing tool  84  has properly sized the workpiece main bearing  34 , the spindle controlled drive unit  28  may be stopped and the workpiece  32  removed from the chucks  24  and  26  and a new workpiece inserted in the clamping area. During this time of removal and reloading of workpieces, the chains  50  can continue to move the subsequent tool carrier downwardly toward the newly positioned workpiece and the tools mounted upon the subsequent tool carrier will turn the main bearings of the newly installed workpiece, and the cycle repeated. 
     As will be appreciated from FIG. 4, a plurality of tools may be mounted upon a tool carrier wherein all of the main bearings of the workpiece may be simultaneously machined. In FIG. 4, five main bearings are being machined which, of course, requires five sets of tools  80 ,  82  and  84  to be mounted upon a common tool carrier  58 . 
     The linear broaching machine producing turning operations in accord with the aforedescribed structure is capable of the rapid machining of relatively large, yet complex, workpieces. As a different set of tools engages consecutive workpieces, the tools have adequate time to cool as the tools travel about the triangular configuration of the chains  50  as apparent from FIG.  3 . While the disclosed apparatus may require a relatively large number of tools, the high production rate of the machine, and the long tool life achieved, renders this type of machine economically feasible. 
     It is also to be appreciated that the inventive concepts could be employed by using only a single tool carrier having tools mounted thereon. In such instance, the controls for the chain controlled drive unit  44  would accelerate chain movement between the unloading and loading of workpieces so as to maintain the desired high production rate. However, preferably, a number of sets of tools and tool carriers are mounted upon the chains so that high production can be achieved while yet attaining a long tool life. 
     It is appreciated that various modifications to the inventive concepts may be apparent to those skilled in the art without departing from the spirit and scope of the invention.