Abstract:
A tool changer for a machine tool having a toolhead assembly including a spindle with means for detachable securing a tool thereto, generally consisting of at least one means for holding a tool detachably securable to the spindle, pivotally connected to the assembly and angularly displaceable in a plane including the axis of the spindle between a retracted position and an extended position for transferring a tool between the tool holding means and the spindle; and means for angularly displacing the tool holding means between such retracted and extended positions.

Description:
[0001]    This invention relates to CNC machine tools and more particularly to a tool changer for such machines. The invention further contemplates a novel automatic tool changer operable to reduce the cycle times of machining parts requiring the use of different tools to perform various machining operations.  
         BACKGROUND OF THE INVENTION  
         [0002]    In many machining operations performed by conventional CNC machine tools used in the woodworking, plastic and airframe industries, multiple tasks are required to be performed, requiring the use of different tools. Initially, tool changes were performed manually, simply by having the operator interrupt the operation of the machine, change out the tool and then resume operation. Because of the time consuming aspect of manual tool changes, automatic tool changes were developed which generally have involved moving the toolhead to a tool changer positioned on or adjacent the machine or moving the tool changer to the toolhead assembly to effect the tool change. In either of such arrangements, considerable machine motion and time has been required, resulting still in undue cycle times and less than optimal productivity. It thus has been found to be desirable and therefore the principal object of this invention to provide a tool changer for a CNC machine tool in which tool changes may be performed with minimal movement and rapidly, thereby reducing cycle times and correspondingly increasing productivity.  
         SUMMARY OF THE INVENTION  
         [0003]    The present invention overcomes the disadvantages of prior art automatic tool changers by providing a tool changer mountable on the toolhead assembly of a CNC machine tool generally consisting of an array of tool holders pivotally connected to the toolhead assembly and spaced apart relative to the axis of the toolhead spindle, with each of the tool holders being selectively angularly displaceable in a plane including the axis of the spindle between a retracted position and an extended position aligning the tool holder for loading or unloading a tool with respect to the spindle. Through the use of the collet on the end of the toolhead spindle, various tools may not only be loaded and unloaded unto and off of the spindle but may be transferred between the tool holder assembly mounted on the toolhead assembly and tool holders either mounted on other components of the machine or on separate equipment. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]    [0004]FIG. 1 is a perspective view of a CNC machine tool embodying the present invention, illustrating a portion of a conventional bulk tool changer which comprises a component of another embodiment of the invention;  
         [0005]    [0005]FIG. 2 is a top plan view of the machine tool and bulk tool changer shown in FIG. 1, having portions thereof broken away;  
         [0006]    [0006]FIG. 3 is a side elevational view of the machine tool shown in FIGS. 1 and 2;  
         [0007]    [0007]FIG. 4 is an enlarged top plan view of a gripper section of a tool holder comprising a component of the embodiment shown in FIGS. 1 through 3;  
         [0008]    [0008]FIG. 5 is a cross sectional view taken along line  5 - 5  of FIG. 4;  
         [0009]    [0009]FIG. 6 is an enlarged, top plan view of the tool changer shown in FIGS. 1 through 3, embodying the present invention, having portions thereof broken away;  
         [0010]    [0010]FIG. 7 is an enlarged cross sectional view taken along line  7 - 7  in FIG. 6;  
         [0011]    [0011]FIG. 8 is an enlarged, vertical cross sectional view of the spindle assembly forming a component of the toolhead assembly shown in FIGS. 1 through 3; and  
         [0012]    [0012]FIG. 9 is and enlarged view of the view shown in FIG. 8, designated by the reference numeral  9 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0013]    Referring to FIGS. 1 through 3, there is illustrated a CNC machine tool  10  adapted to perform various machining functions on workpieces positioned thereon including routing, drilling, sawing, sanding and the like, and a bulk tool changer  11 . The machine generally consists of a base member  12 , a movable workpiece support table  13 , a gantry  14 , a toolhead support assembly  15  and a toolhead assembly  16 . The base member includes a lower section  17 , a pair of longitudinally disposed, transversely spaced boxed beam sections  18  and  19  and a set of longitudinally disposed, transversely spaced guideways  20  and  21 . Table  13  is supported and displaceable longitudinally or along an x-axis or line of travel on guideways  20  and  21 , and includes a rectangularly configured workpiece support surface  22 .  
         [0014]    Gantry  14  includes a pair of leg sections  23  and  24  disposed astride table  13 , rigidly connected at their lower ends to base section  17 , and a bridge section  25  secured to the upper ends of leg sections  23  and  24 , spaced above table  13  and disposed transversely. The front face of bridge section  25  is provided with a pair of transversely disposed, vertically spaced guideways  26  and  27  on which there is mounted and guided, toolhead support assembly  15  for displacement transversely along a y-axis or line of travel. Toolhead assembly  16  similarly is mounted and guided vertically along a z-axis or line of travel on a pair of vertically disposed, transversely spaced guideways mounted on a front face of the toolhead support assembly.  
         [0015]    The toolhead assembly includes a support frame  28  and a spindle assembly  29 , a DC servomotor  30  and a tool changer assembly  31  mounted on the support frame. The spindle assembly is best illustrated in FIGS. 8 and 9 and is driven through a belt drive by servomotor  30 . Tool changer assembly  31  is best shown in FIGS. 4 through 7. In addition to servomotor  30 , the machine is provided with a number of additional DC servomotors for displacing the table along the x-axis, displacing the toolhead support assembly along the y-axis and displacing the toolhead assembly along the z-axis. Such motors are operated by a controller (not shown) pursuant to the execution of a program loaded into the controller in the conventional manner.  
         [0016]    As best shown in FIGS. 4 through 7, tool changer assembly  31  includes a support bracket  32  secured to support frame  28 , and a plurality of arcuately spaced tool holders  33  pivotally connected to the support bracket. The support bracket includes a base section  32   a  mounted on the side of the support frame by means of a set of bolts or other suitable means, and disposed longitudinally, extending beyond the front end of the toolhead assembly, and a transversely disposed section  32   b , spaced from and extending across the front of the assembly, substantially at a right angle relative to the base section. Each of the tool holders consists of an arm section  34  and a gripper section  35 . Each arm section  34  has a j-shaped portion  34   a  pivotally connected to bracket section  32   b , as at  34   b  and an arcuate portion  34   c  formed integrally on the end of the J-shaped portion. As best seen in FIGS. 4 and 5, gripper section  35  includes an arcuate portion  35   a  mounted on and secured to arcuate arm portion  34   c  by means of a set of bolts  35   b , and arcuately spaced sets  35   c  of finger portions extending into the space in arcuate arm portion  34   c  and yieldably biased to engage a tool  36  therebetween as shown in FIG. 3. Each of the tool holders is provided with an air actuated cylinder assembly  37  for pivoting the tool holder between a retracted position as shown in solid lines in FIG. 7 and an extended position as shown in phantom lines in FIG. 7 in which tool gripper section  35  is disposed coaxially with and below a spindle of the toolhead assembly for yielding or accepting a tool relative to the spindle. Each cylinder assembly consists of a cylinder member  37   a  pivotally connected adjacent its rod end to transverse section  32   b  of the support bracket as at  37   b , and an extendable rod member  37   c  pivotally connected to the arm section of a tool holder as at  37   d . The various cylinder assemblies are operated by the controller pursuant to the execution of a software program loaded into the controller to selectively extend and retract selected tool holders for loading and unloading tools with respect to the spindle. The configuration of the arm sections and gripper sections of each of the tool holders permits each of the holders to hold and maintain a tool in a retracted position clear of the lower end of the spindle so as not to interfere with any machining operation of the spindle, and an extended position in which the collet of the spindle may grip or release a tool held by the holder. The inwardly biased fingers  35   c  of the gripping portion of each tool holder will yieldingly grip and hold a tool in the tool holder permitting the tool to be retained in the extended position for storage purposes, and displaced from the retracted to the extended position and easily be released or gripped in attaching and detaching the tool with respect to spindle.  
         [0017]    Referring to FIGS. 8 and 9, the toolhead assembly includes a spindle assembly  40  generally consisting of a housing  41 , a spindle  42  mounted in the housing and a cylinder assembly  43 . The housing is provided with a lower section  41   a  and an upper section  41   b . Housing section  41   a  is provided with a cylindrical bore  41   f  therethrough having a first enlarged section  41   c  at a lower end thereof, a second enlarged section  45  and a third enlarged section  46  at the upper end thereof. Enlarged bore section  41  cprovides a bearing seat including an annular wall  41   d  and an annular seat  41   e . Enlarged section  45  similarly provides a bearing seat including an annular side wall  45   a  and an annular seating surface  45   b . Provided in enlarged section  41   c  is a cylindrical sleeve  47  having the outer cylindrical surface thereof adhesively bonded to annular wall  41   d  of the housing. A pair of roller bearings  48  and  49  are seated in enlarged bore section  41   c  with the outer surfaces of the outer races thereof engaging the inner annular surface of cylindrical sleeve  47  and an annular end surface of outer race  48  engaging annular surface  41   e  of enlarged bore section  41   c . Similarly, a cylindrical sleeve  50  is disposed in enlarged bore section  45  with the outer cylindrical surface thereof adhesively bonded to the annular side wall surface  45   a  of enlarged bore section  45 . Disposed within cylindrical sleeve  50  and axially displaceable relative thereto is roller bearing  51 . The inner races of bearings  48  and  51  are maintained in axially spaced relation by means of a spacer tube  52 . A spring washer  53  is provided between the outer race of bearing  51  and annular surface  45   b  of enlarged bore section  45 .  
         [0018]    Spindle  42  has a generally tubular configuration and is journaled in lower bearings  48  and  49  and upper bearing  51 . Outer cylindrical surface  60  is provided with a recessed cylindrical section  61  providing an annular shoulder on which the inner race of bearing  49  is seated, and an upper threaded portion  62 . It further is provided with an axially disposed bore  63  having a lower, first enlarged section  64  and a second enlarged section  65  opening into an end portion  66  provided with a diverging, conically configured wall  67  adapted to receive an upper portion  68  of a tool  36 , provided with a complimentary conical surface relative to surface  67 . The upper end of the tool is provided with a neck portion  70  and a head portion  71  received within enlarged bore section  64  of the spindle. The upper end of axial bore  63  is provided with an enlarged section  72 .  
         [0019]    The bearings and the spindle journaled in the bearings are retained within the housing with the bearings seated within enlarged bore sections  41   c  and  45  by means of a lower cover plate  80 , a bearing washer  81  and a jam nut  82 . Cover plate  80  has an annular configuration and is secured to the bottom end of housing  11  by a set screws. An inner end of plate  80  engages the outer race of bearing  49  and is provided with a seal  83  engaging the spindle about the periphery thereof Bearing washer  81  also has an annular configuration and has a depending, annular portion which engages the inner race of bearing  51 . Jam nut  52  is provided with an axial bore  84  having an enlarged, threaded section  84   a  threaded onto the upper threaded end of the spindle so that it engages bearing washer  81  which bears on the inner race of bearing  51 . Outer annular surface  84   b  of the jam nut is provided with an annular recess  84   c  which is adapted to receive a pair semi-circular retaining flanges  85 .  
         [0020]    Upper housing section  41   b  has a cylindrical configuration and is adapted to seat on and be secured to the upper end of lower housing section  41   a  by means of a set of bolts  86 . Such section is axially aligned with axial bore  41   f  of lower housing section  41   a . Mounted within upper housing section  41   b  is a floating cylinder mount  90  provided with an axially disposed bore  90   a  aligned axially with lower housing bore  41   f  and spindle  42 , having a lower enlarged section  90   a  which receives the upper end of jam nut  82 . Axial displacement of the cylinder mount is restricted relative to the spindle by means of retainer plates  85  which are secured to the underside of the cylinder mount by means of a set of screws, and project into annual grove  84   c  of jam nut  82 .  
         [0021]    Axially displaceable in spindle bore  63  is a draw bar  100  having a lower enlarged section  101  disposed in enlarged spindle bore section  64  and an upper enlarged section  102  received in an upper enlarged section  64   a  of spindle bore  63 . A collet  103  is provided on the lower end of enlarged draw bar section  101  having a set of fingers which are adapted to cam inwardly when the draw bar is urged in an upward direction to grip head portion  71  of the tool, and to spring apart when the draw bar is moved in a downward direction to release the head portion of the tool. The draw bar is urged into the upper position by means of a set of spring washers  105  disposed between an annular shoulder provided by enlarged spindle bore section  64   a  and a lower cylindrical surface of enlarged draw bar section  102 .  
         [0022]    Cylinder assembly  43  includes a cylinder  110  retained in a frame  111  secured to the upper end of cylinder mount  90  and a rod member  112  which extends through bore  90   b  of the cylinder mount in axial alignment with draw bar  100 . When rod member  112  is in the retracted position, it will be out of engagement with enlarged draw bar section  102  so that spring washers  105  will urge the draw bar into an upper position causing the fingers of the collet to be cammed inwardly and grip head portion  71  of the tool and correspondingly secure the tool to the spindle for performing a machining function. When the rod member is extended as shown in FIGS. 8 and 9, the rod member will engage and downwardly displace the draw bar against the biasing action of spring washers  105 , allowing the fingers of collet  103  to spring apart and thus release the head portion of the tool, allowing it to be removed from the lower end of the spindle. The detachment of rod member  112  from draw bar  100  permits the draw bar to rotate as part of the spindle assembly during machining operations.  
         [0023]    In the normal operation of the spindle assembly to perform a machine function, the tool will be received in the lower end of the spindle and firmly gripped by the collet formed on the lower end of draw bar, and the spindle with the tool will be free to rotate relative to the housing, the cylinder mount and the cylinder assembly. When it is desired to change the tool, the spindle drive is discontinued, suitable controls are operated to supply air under pressure to the base of the cylinder  110 , to extend rod member  112  into engagement with the draw bar against the biasing actin of spring washers  105 , thus causing the collet to displace downwardly and permit the gripping fingers thereof to spring outwardly, releasing the tool. A new tool then may be inserted into the lower end of the spindle and the cylinder assembly operated to allow the draw bar to displace upwardly under the biasing action of the spring washers thus causing the gripping fingers of the collet to be cammed inwardly and grip the upper end of the tool.  
         [0024]    Most machining operations on a particular workpiece have been found not to require more than five tools to perform the desired machining operation. Accordingly, up to five tools required by a particular software program to be run may be inserted in one or more of the tool holders carried by the toolhead assembly to perform the desired machining operation. Once the appropriate number of tools have been loaded on the tool changer as described, and the appropriate program has been loaded into the controller of the machine, the controller will execute the program to load and unload the proper tools with respect to the spindle and in the appropriate sequence, the spindle will be stopped and started as required and the toolhead assembly will be displaced along the x, y and z axes to perform the programmed machining operation. Whenever a tool on the spindle is to be changed, the spindle will be stopped, a selected air cylinder will be operated to angularly displace a selected tool holder from the retracted to the extended position below and in axial alignment with the tool attached to the lower end of the spindle to grip the tool, the tool head assembly will be displaced downwardly along the z-axis to position the attached tool in the aligned tool holder permitting the spring biased fingers of the tool holder to grip the tool, cylinder assembly  43  will be operated to extend the draw bar of the spindle assembly to cause the fingers of collet  103  to spring outwardly and release the tool, and the air cylinder for such a tool holder is operated to displace the tool holder from the extended position shown in phantom lines in FIG. 7 to the retracted position as shown in solid lines therein. The machine is then ready to receive another tool carried by the tool changer. Such loading occurs simply by the operation of the cylinder assembly for the other selected tool whereby the tool holder of the selected tool will be caused to be angularly displaced from its retracted position to its extended position, positioning the selected tool below the spindle in axial alignment therewith. The selected tool is then attached to the lower end of the spindle by operating cylinder assembly  43  to allow the collet at the lower end of the spindle to move upwardly, camming the fingers thereof inwardly to grip and thus retain the head portion of the selected tool. The tool head assembly may then be displaced along the z-axis as well as the x and y-axes to continue the machining operation.  
         [0025]    Each of tool holders  33  mounted on support bracket  32  is operable to be angularly displaced in a plane including the axis of spindle  42  so that when displaced from its retracted to its extended position, its gripper section  35  will be positioned below and in axial alignment with spindle  42  to permit the relinquishment or receipt of a tool. Such tool changing operation can be performed as the toolhead assembly is displaced along the x, y and/or z-axis of the machine, moving from one coordinate to another. By being capable of effecting a tool change while the toolhead assembly is repositioned, the cycle time of the machining operation being performed is substantially reduced. Furthermore, because of the simple and lightweight construction of the tool holders, the dynamics in the displacement of the toolhead assembly are negligently effected.  
         [0026]    In a sense, tool holders  33  resemble and function like the arms of an early typewriter in which an arm corresponding to a certain key would angularly displace and strike a platen upon the key being pressed.  
         [0027]    To expand the number of tools that may be used to perform a particular machining operation, the tool changer as described may be used in conjunction with a conventional tool bar  120  mounted on the machine or a conventional bulk tool changer  121  as best shown in FIG. 2. The bar tool changer typically consists of a base plate  122  mounted on the rear edge  123  of the machine table, and a number of transversely spaced tool grippers  35   a  which are comparable in construction and function to tool grippers  35 . By displacement of the machine table along the x-axis and the displacement of the toolhead assembly along the y and z-axes, spindle  42  may be positioned in axial alignment with a selected one of tool grippers  35   a  to relinquish and receive a tool in the manner as described in connected with tool changer assembly  31 . Furthermore, through the use of the collet arrangement on spindle  42 , tools may be transferred between any of tool grippers  35  and tool grippers  35   a.    
         [0028]    Bulk tool changer  11  consists of a separate apparatus which may be positioned adjacent to the machine and operated in cooperation with the toolhead assembly by the controller to accept tools from and provide tools to the spindle of the toolhead assembly. It consists of a base member  30  which is adapted to be positioned adjacent a side of a machine table, close to the gantry, and a carriage  131  mounted on the base member and displaceable longitudinally. Journaled at each end of the carriage is a vertically disposed shaft  132  having a gear  133 . An endless chain  134  is trained about each of gears  133  and is provided with a plurality of tool grippers  35   b  spaced along the length thereof. Each of tool grippers  35   b  is similar to each of tool grippers  35  of tool changer assembly  31  and tool grippers  35   a  of bar tool changer assembly  120 , and may be positioned below and in axial alignment with spindle  42  of the toolhead assembly. The bulk tool changer is provided with various drives for longitudinally displacing the carriage thereof and rotating a gear shaft  132  to index the tool grippers, thus permitting a selected one of tool grippers  35   b  to be positioned at a location where spindle  42  of the toolhead assembly may be positioned in axial alignment therewith.  
         [0029]    The toolhead assembly may be used in conjunction with the bulk tool changer assembly to either change a tool as between spindle  24  and the bulk tool changer or transfer one or more tools between the bulk tool changer and toolhead mounted tool changer  31 . This is accomplished merely by operating the controls of the bulk tool changer to displace the carriage thereof and index the chained conveyor to position a selected tool thereon to a selected position, and then operating other machine controls to displace the toolhead assembly so that spindle  42  may be displaced to a position above and in axial alignment with a tool retained by a tool gripper of the bulk tool transfer assembly at the selected position. The cylinder assembly of the spindle may then be operated to cause the collet component of the spindle to grip the selected tool in the manner previously described. If the tool thus retrieved from the bulk tool changer assembly is to be transferred to a tool holder of tool changer assembly  31 , the selected one of the tool holders of such assembly is then operated to transfer the tool from the spindle to the selected tool holder.  
         [0030]    Tool changer assembly  31  may be used independently or in conjunction with one or both of bar tool changer assembly  120  and bulk tool changer assembly  121  to provide a greater availability of tools and a minimum amount cycle time in the performance of a machining operation. The arrangement further permits a program used to operate the machine to be devised in a manner whereby prior to the execution of the machining function with respect to a particular workpiece, the machine will be caused to select the appropriate tools from either or both of the bar or bulk tool changer assemblies and mount them on the toolhead mounted tool changer assembly. Such preliminary routine would be repeated upon each new machining procedure.  
         [0031]    To minimize the effects of the additional mass possibly adversely affecting the dynamics of the movement of the toolhead assembly, the components of a tool changer assembly  31  are formed of a lightweight materials such as aluminum, plastic and perhaps lightweight composite materials. Any form of gripping device may be utilized allowing for the proper gripping, retaining and releasing of the various tools used with the assembly.  
         [0032]    Although the invention has been described in the context of a CNC machine tool utilizing a moveable table and a stationary gantry, it is contemplated within the scope of the invention may be used with a CNC machine provided with a stationary table and a moveable gantry. In either of such arrangements, it further is contemplated that the toolhead mounted tool changer assembly as described may be used independently or in conjunction with either or both a bar tool changer assembly and a bulk tool transfer assembly as described.  
         [0033]    From the foregoing detailed description, it will be evident that there are a number of changes, adaptations and modifications of the present invention which come within the province of those persons having ordinary skill in the art to which the aforementioned invention pertains. However, it is intended that all such variations not departing from the spirit of the invention be considered as within the scope thereof as limited solely by the appended claims.