Abstract:
A pair of frame members are connected in laterally spaced, parallel relation; and, when mounted on a molding machine, the frames extend perpendicularly to the centerline of the machine&#39;s mandrels. A major center portion of each frame is excised to provide a pair of aligned window-like openings surrounded by perimetric portions of the frames. Actuators are secured between the spaced frame members and have extensible piston rods attached to mold segments for advancing and retracting the same within the openings. Movement of a machine platen occurs along an axis which penetrates the openings; and, piston rod movement is generally normal to movement of the platen.

Description:
TECHNICAL FIELD  
         [0001]    This invention pertains generally to an apparatus for molding single-piece foam patterns used in lost foam pattern casting. More particularly, the invention relates to an improved base for mounting pattern forming tools on a molding machine.  
         BACKGROUND OF THE INVENTION  
         [0002]    Tools for making foam patterns and their application are well understood by tool designers, tool makers, and pattern molders and need not be described herein in great detail; however, the general characteristics of currently used tools will be briefly set forth to provide an understanding of how they differ from the present invention.  
           [0003]    Typical foam pattern tools include at least the following structural elements:  
           [0004]    1. Plural mold segments having machined or cast recesses which coact when closed together to define a molding cavity for receiving expandable pattern material such as polystyrene beads and for shaping such material to the exact configuration of the cavity.  
           [0005]    2. Wall portions of each mold segment extend rearwardly from its pattern-forming front face to define an integral chest for receiving molding process fluids including steam, cooling water and air.  
           [0006]    3. A generally flatback plate is removably secured over the open back side of the chest to close and seal the same.  
           [0007]    4. Each of the backplates employed for sealing the chest of the individual mold segments is, in turn, secured to a baseplate mountable on a molding machine.  
           [0008]    5. Associated with the mold segments, the backplates and the baseplates are various alignment pins and pin bushings which interfit to insure that the mold segments align correctly when closed and clamped by the molding machine or by auxiliary fluid-actuated cylinders.  
           [0009]    6. Bead injection conduits leading from air-actuated bead filling guns usually extend through one or more of the aforesaid chests and then penetrate the molding cavity wall to fill the same with partially expanded pattern material.  
           [0010]    7. Various venting devices are placed in the walls of the mold segments to vent air from a closed molding cavity as it fills with pattern material.  
           [0011]    8. The chests defined by the back surfaces of the mold segments and coacting backplates are provided with service fittings and connectors for pattern forming media, i.e. foam beads, steam, water and air.  
           [0012]    The enumerated tool components are structurally arranged and assembled to provide an individual foam pattern making assembly known as a self-contained tool. In its simplest form, a self-contained, single-axis tool having only two mold segments somewhat resembles the opposed halves of a box. The mold segments are mounted on the movable and stationary platens of a molding machine for sequentially opening, closing and clamping the segments during the molding operation. The molding machine not only supports the box-like tool, but also carries the cavity filling equipment and service lines and drains which are respectively connected to the molding cavity and to the utility chests defined by the box halves.  
           [0013]    In more complex self-contained tools, provision is made for opening and closing opposed mold segments by means other than single-axis motion of the platens of the molding machine. For example, known tools for forming the molding cavity for a cylindrical pattern may employ three sets of opposed mold segments which operate normally to each other. The cylindrical exterior wall of the mold cavity is defined by two opposed sets of concave cylindrical quadrants; and, the top and bottom walls of the molding cavity are established by opposed cylindrical mandrels which are movable between the quadrants perpendicularly to the direction of quadrant opening and closing. A complex three-axis, six-segment tool may be largely contained within the walls of a substantially closed box-like housing supported on a molding press. In this tool configuration, each of a first set of opposed mold segments has baseplates respectively fixed to the stationary platen and movable platen of the molding machine. Each of the four remaining mold segments or pulls is enclosed within the box-like tool housing and is operable for opening and closing reciprocation by means of fluid operated actuators connecting the baseplate of each segment to an adjacent box wall.  
           [0014]    Self-contained foam pattern tools of the more complex, multiple-axis type require substantial time and expense to design, build, install and maintain. Nevertheless, such greater expenditures of money and time are economically justifiable by increases in pattern design flexibility and quality as well as the ability of complex tools to produce large quantities of consistently acceptable patterns at high production rates. In designing a self-contained tool, primary consideration must be given to the precise configuration, close dimensional tolerances, and surface finish of the pattern to be produced; however, many other tool design considerations can directly affect the pattern-forming operation performed within the tool&#39;s mold cavity. For example, means providing efficient cavity alignment and filling; proper locations and connections for utilities, vents and drains; the operating and service capabilities of the molding machine; and, means for inter-connecting the mold cavities, the tool base, and the molding machine structure all importantly define the tool&#39;s molding capabilities and effectiveness. Because tools must incorporate structural and operational features responsive to many design demands, individual patterns, except those of the most simple configuration, require a different molding tool comprising a one-of a-kind assemblage of component parts.  
           [0015]    For pattern molders, the singular nature of each self-contained tool has presented long-recognized, but heretofore unsolved problems, namely: Modification of an existing tool for the purpose of producing a differently sized or configured pattern requires that most, if not all, of its interdependent elements be redesigned and rebuilt at substantial expense and with accompanying delay. Furthermore, the cost entailed in owning and maintaining a minimal inventory of different self-contained pattern tools must be either absorbed by the molder or passed on to his customer as an increase in the price of the finished pattern. An unavoidably large investment of capital in unproductive pattern tools can seriously limit the profitability and growth potential of a molding concern.  
           [0016]    Even if a variety of pattern tools are available from the molder&#39;s tool inventory, the interchange of a pattern tool from inventory for another mounted on a molding machine is an arduous, time-consuming task usually performed by specially trained work crews. Molding machine downtime due to long tool change-out times and accompanying pattern production losses also increase the production cost of each pattern piece in the following significant regards: To reduce the frequency of tool changes, minimum production runs of each pattern are usually made with excess patterns being stored at the molder&#39;s expense until paid for and delivered to the user. Molding machine downtime reduces the molder&#39;s total molding capacity without reducing overhead expense; and, downtime may also require him to invest in additional molding equipment and shop floor space. Profit opportunities presented by short production runs are not available unless a molder can absorb or pass on the aforenoted downtime costs occasioned by frequent tool changes. Frequent tool replacements inevitably increase wear and tear on the tools elements and the tool supports of the molding machine.  
           [0017]    Besides the cost problems attributable to machine downtime, other problems are encountered each time a complex tool is replaced. Many of these other problems are directly attributable to the bulk and weight of three-axis tools employed for molding large patterns and multi-cavity patterns. In the three-axis tools in use today, the four backplates of two opposed sets of mold segments are attached to extendable piston rods of actuators which are, in turn, mounted on the baseplates associated with the backplates. The backplates of the remaining two mold segments are attached to associated baseplates which, in turn, are respectively connected to the stationary and movable platens of the molding machine. The aforedescribed six baseplates are structurally joined to form the walls of a six-sided structure which houses the molding segments of the tool and serves as a mounting base for the complete tool for attaching the same to some supportive molding machine structure. The connected baseplates forming the box-like tool base are necessarily of substantial length in order to provide the actuators which they support with adequate piston travel for opening the mold segments sufficiently for removal of finished patterns. These elongated baseplates are likewise quite thick in order to provide tool strength and stability; therefore, the total tool weight, even where lightweight metal, such as aluminum, is used extensively for the molds, backplates and baseplates, may reach several hundred pounds. Thus, the weight and bulk of a tool mounted on a press by means of a conventional box-like tool base is such that tool change out crews have difficulty in installing and removing these unwieldly tools. Special lifting and positioning devices are often required to set up or change-out such tools. Moreover, personnel performing this task must be specially trained and closely supervised to minimize risk of personal injury and molding machine damage.  
           [0018]    Additional time-consuming procedures are usually encountered in mounting and connecting a complex three-axis tool to a typically configured molding machine. For example, numerous tool-to-machine alignment and locking devices must be installed and carefully adjusted to assure mold segment stability and alignment accuracy for correct cavity closure. A myriad of conduits and connectors must be routed and secured between all utility services and the inlet fittings of mold cavities, mold chests and mold segment actuators. The box-like nature of conventional tools greatly reduces access to interior components and hampers the installation and subsequent maintenance and repair of such tools.  
           [0019]    The foregoing recitation of problems that molders of foam patterns often encounter in altering the molding cavity of a pattern tool or in removing a tool from a molding machine and replacing it with another, highlights the need for a means for exchanging a tool&#39;s mold segments while the remainder of the tool itself remains mounted on the machine.  
         SUMMARY OF THE INVENTION  
         [0020]    The general object of this invention is to provide a solution to the hereinabove recited problems commonly associated with the design, construction and use of prior art foam pattern molding tools.  
           [0021]    Another broad object is to provide a tool base which is simpler, lighter in weight and adaptable for a broader range of uses than the box-like bases described above. To this end, a base according to this invention essentially comprises an open frame which encircles, but does not enclose, the elements of a pattern tool supported thereon. More particularly, such a base includes an open frame which affords great flexibility in the orientation of various types of mold segments and their associated actuators in order to meet the requirements of highly complex pattern designs.  
           [0022]    To obviate other shortcomings of known tool bases, this invention contemplates a tool base having these key features: Firstly, different sets of mold segments can be interchangeably mounted on a single base without alteration of other tool elements carried by the base. Secondly, one set of mold segments can be changed out with another set while the tool base remains mounted on a molding press and stays connected to various service lines. In many cases, easily accessible, light weight mold segments can be quickly exchanged through the effort of a single workman.  
           [0023]    Another important aspect of this invention is the provision of a highly adaptable tool base which serves as a common structural interface between a molding machine and a number of interchangeable sets of mold segments thereby facilitating the production of a series of patterns which are generally similar in shape and graduated in size. Tool bases having this capability can be used to great advantage for producing patterns required for cast parts such as housings for electric motors and cylinders for air compressors.  
           [0024]    A further object is realized by an improved tool base which provides the functions of a conventional box-like base yet weighs less than one half as much thereby dramatically reducing the physical effort, time and expense heretofore involved in installing and exchanging self-contained tools in a molding machine.  
           [0025]    In basic form, the tool base of this invention includes at least one metal plate having a window therethrough defined by a perimetric frame. Plural mold segments and actuators therefore are carried by the frame with the cavity-forming recesses of the segments directed toward the window opening.  
           [0026]    The following detailed disclosure of illustrative embodiments of the invention will show that the tool base may include a pair of frame members connected in spaced, parallel relation; and, when mounted on a molding machine, these frames extend perpendicularly to the centerline of the machine&#39;s mandrels. A major center portion of each frame is excised to provide a pair of aligned window openings surrounded by perimetric portions of the frames. Fluid powered actuators are secured between the spaced frame members and have extensible piston rods attached to mold segments for advancing and retracting the same. Movement of the machine platen occurs along an axis which passes through the window opening; and, piston rod movement is usually normal to movement of the platen.  
           [0027]    Still another object of this invention is the provision of a base for a pattern tool wherein the base includes an open frame having a separable portion that is selectively movable for repositioning such portion and a finished pattern piece attached thereto to permit removal of the finished piece from the tool.  
           [0028]    These and other advantages and objects of this invention and the manner of obtaining them will become apparent and the invention will be best appreciated and fully understood by having reference to the following detailed description taken in conjunction with the accompanying drawings. 
       
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
       [0029]    [0029]FIG. 1 is a perspective view of a molding machine of the type commonly employed to operate foam pattern molding tools;  
         [0030]    [0030]FIG. 2. is a top plan view of the tool with a fragment of the molding machine shown in phantom lines;  
         [0031]    [0031]FIG. 3 is a section of taken along lines  3 - 3  of FIG. 4;  
         [0032]    [0032]FIG. 4 is a side elevational view taken generally along lines  4 - 4  of FIG. 2;  
         [0033]    [0033]FIG. 5 is a top plan view similar to FIG. 3 showing a modified embodiment of the invention; and,  
         [0034]    [0034]FIGS. 6 and 7 are fragmentary views of the modified embodiment shown in FIG. 5. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0035]    The foam pattern molding tool  10  disclosed herein is mounted on and operated by a molding machine of a well-known type shown in outline in FIG. 1 and designated in its entirety by numeral  12 . The machine  12  not only supports the tool  10 , but is structurally stable, has smooth operation and has platens that move in parallel for dimensional accuracy. The machine  12  is generally U-shaped and has a bed  14 , a stationary platen  16  and a machinery area  18  including a hydraulically actuated ram the extensible piston  20  of which carries a movable platen  22 . The platen  22  is penetrated by bars or rods  24  fixed between the housing  18  and platen  16 ; and, such bars slidably support the platen  22  as it is advanced and retracted relative to platen  16  by the action of piston  20 . Conventional controls  26  for the machine  12  are operable to provide bead filling, to heat and cool the molding cavities of the tool  10  and to actuate various mechanisms which open and close these cavities. In a well understood manner, the controls  26  regulate the supply of foam beads to the tool cavities and the flow of steam and cooling water to the chests adjacent the cavities. Compressed air may be furnished to the cavities to eject finished patterns; and, hydraulic fluid or compressed air is directed to pressure fluid actuator devices for operating various mold pulls. The supply lines and control lines required to interconnect the sources of molding beads, steam, water, air and hydraulic pressure fluid to the molding machine  12  and to the tool  10  are not shown in the drawings since their structure and function are disclosed in the prior art relavant to molding machines and foam pattern tools.  
         [0036]    As best illustrated in FIG. 1, the tool  10  is mounted on the machine  12  intermediate the platens  16  and  22 . A hopper, not shown, containing a supply of foam beads may be conveniently mounted upon the upper surface of platen  16  with the hopper outlet connected to tool  10  in a manner to be described.  
         [0037]    The preferred embodiment of the invention depicted in the drawings comprises a base  28  which includes a pair of like plates  30   a ,  30   b  that are joined in spaced, parallel relation, as best shown in FIGS. 2 and 4. In lateral profile, the plates  30   a ,  30   b  resemble windows having open centers  32  surrounded by perimetric frames  34 ; and, the frames have continuous inner and outer perimetric edges indicated in FIG. 3 at  36  and  38 , respectively. At its four corners, the outer edge  38  of each frame is defined by a horizontal edge  40 , a vertical edge  42  and a connecting curved edge  44 . The parallel top and bottom edges  46  and  48  extend horizontally between spaced vertical edges  42  and the parallel side edges  50  and  52  connect spaced horizontal edges  40 . The inner edges  36  of the plates  30   a  and  30   b  define four angularly spaced recesses  54 ,  56 ,  58  and  60  which open toward one another and into the frame center  32 . The upper recess  54  is defined by spaced vertical edges  62  and horizontal edge  64  which are connected by curved edges  66 . The lower recess  56  is defined by spaced vertical edges  68 , horizontal edge  70  and curved edges  76 . One lateral recess  58  is defined by spaced horizontal edges  74 , vertical edge  76  and curved edges  78 ; and, the opposed lateral recess  60  is defined by horizontal edges  80 , vertical edge  82  and curved edges  84 .  
         [0038]    A principal function of the tool base  28  is to provide means for supporting the plural mold segments of tool  10  on the molding machine  12  in correct operating relation to one another and to the machine. One example of the manner in which mold segments are supported by the base  28  will be described in connection with an illustrative tool providing a molding cavity  86 , shown in broken lines in FIG. 2. Four angularly spaced mold segments  88   a,b,c,d  are vertically supported by four like backplates, two of which are shown at  90   a  and  90   c  in FIG. 3. The backplates for mold segments  88   a,b,c,d  are respectively secured to baseplates  92   a,b,c,d.  As best seen in FIG. 2, the mold segment  88   b  is attached to baseplate  92   b  which, in turn, is connected to movable platen  22  by intermediate mounting plate  94 . Mold segment  88   d  is attached to baseplate  92   d  which, in turn, is attached to the stationary platen  16  by intermediate mounting plate  96 .  
         [0039]    [0039]FIGS. 3 and 4, show in broken lines, upper and lower cylindrical mandrels  98  and  100  which respectfully define the inner cylindrical walls  102   a  and  102   b  of mold cavity  86 . The enlarged base  98   a  of mandrel  98  is attached first to backplate  104  and then to baseplate  106 ; and, enlarged base  100   a  of mandrel  100  is attached first to backplate  108  and then to baseplate  110 .  
         [0040]    The various backplates, baseplates, and mounting plates mentioned above may be detachably secured to one another by suitable fasteners, not shown, which facilitate the rapid interchange of sets of mold segments and/or mandrels.  
         [0041]    The drawings depict the aforedescribed mold segments and mandrels in their closed condition wherein the cylindrical outer wall  112  of the mold cavity  86  is defined by the contiguous concave faces  88   e,f,g,h  of the mold segments  88   a,b,c,d;  the cylindrical inner walls  102   a  and  102   b  of the cavity  86  are defined by the vertically aligned outer walls of the mandrels  98  and  100 ; and, the top and bottom of the cavity  86  are respectively closed by the enlarged bases  98   a  and  100   a  of the mandrels.  
         [0042]    The manner in which the frame  28  provides a base for the operating components of tool  10  and mounts the tool on the molding machine  12  will now be set forth in detail.  
         [0043]    The bars  24  bear against the curved frame edges  44  allowing the frame  34  to project beyond the bars which allows an increase in the size of the frames and of the tool  10  mounted thereon. Such bar-to-frame engagement supports the weight of the tool  10  while maintaining the verticality of the frame and concentricity of the frame relative to the piston  20 . The frame plates  30   a ,  30   b  are rigidly held in spaced parallel relation by means of four fluid powered actuators  114   a,b,c,d  fixed between the plates at 90° intervals about the frame&#39;s perimeter. The elongated housings of these actuators have opposed flat side surfaces which bear against the inwardly turned sides of the plates  30   a ,  30   b  in the manner best seen in FIGS. 2 and 4. Any suitable mounting bracket or strap, not shown, may be utilized to removably secure individual actuators between the plates at the midpoints of each edge  46 ,  48 ,  50  and  52 . As best shown in FIG. 3, the actuators  114   a,b,c,d  have extensible pistons or piston rods  114   e,f,g,h  which, when extended, project inwardly into frame recesses  54 ,  56 ,  58 ,  60  respectively. The baseplate  106  for the upper mandrel  98  is fixed to the piston  114   e  and is supported thereby within the recess  54  in spaced relation to the adjacent frame edges  62  and  64 . Similarly, the baseplate  110  for the lower mandrel  100  is fixed to the piston  114   f  and is supported thereby within the recess  56  and in spaced relation with adjacent frame edges  68  and  70 . The baseplate  92   a  for the mold segment  88   a  is fixed to the piston  114   g  and is supported thereby within the recess  58  and in spaced relation with adjacent frame edges  74  and  76 . The baseplate  92   c  for the mold segment  88   c  is fixed to the piston  114   h  and is supported thereby within the recess  60  in spaced relation with adjacent frame edges  90  and  82 . Additional mold segment stabilizing rods, not shown, may extend from their points of attachment to the baseplates  92   a ,  92   c ,  106  and  108  through cylindrical slide bearings, not shown, mounted between plates  30   a ,  30   c  on both sides of the four power actuators  114   a,b,c,d.    
         [0044]    In the positions shown in FIG. 2 of the drawings, the actuators  114   c  and  114   d  have been operated to extend their pistons and the platen  22  is fully extended whereby the mold segments  88   a,b,c,d  are closed in abutting relation and the mold faces  88   e,f,g,h  join to form the cylindrical outer cavity wall  112 . The actuator pistons  114   e  and  114   f  have fully inserted the mandrels  98  and  100  thereby forming the cylindrical inner cavity walls  102   a  and  102   b  and closing the cavity at its top and bottom, as best shown in FIGS. 3 and 4.  
         [0045]    Following operation of the molding machine controls  26  to close the molding cavity  86 , foam beads are supplied by air-operated guns to the cavity  86  and process fluids are sequentially communicated to the usual chests, not shown, defined by the rear surface of each mold segment and a backplate attached thereto. The various baseplates which provide surfaces upon which the backplates can be readily attached and detached also have internal passages which function as conduits for interconnecting the interior of the mold segment chests and supply lines for pressurized steam, water and compressed air. In proper sequence and for required durations, the molding machaine operates valves which open and close the supply lines for the beads and for the various utilities required to fill the cavity, to heat and fuse the beads, and to cool and stabilize the finished pattern.  
         [0046]    To prepare for removal of a completed pattern from the tool  10 , the molding machine communicates pressure fluid to the actuators  114   a,b,c,d  through suitable lines to effect retraction of the actuator pistons  114   e,f,g,h  whereby the baseplates  92   a ,  92   c ,  106 , and  108  are drawn into the recesses  54 ,  56 ,  58 , and  60 . Also, the machine&#39;s movable platen  22  is drawn away from stationary platen  16 . These machine controlled actuations cause the mold segments  88   a,b,c,d  and the mandrels  98  and  100  to separate sufficiently for removal of the pattern from the tool by a mechanism for pushing the pattern from the cavity  86 , by compressed air directed against the pattern surface or, alternatively, by hand.  
         [0047]    A modified version of the frame  28  is shown in FIGS. 5, 6 and  7 . In the first-described embodiment of the tool  10  shown in FIG. 3, for example, the maximum vertical displacement of the mandrel  98  is limited by the length of travel of the actuator piston  114   e  and/or by the vertical clearance between the top surface of baseplate  106  and the lower edge  64  of frame  28 . If a longer mandrel is required for a particular pattern, the length of available vertical displacement for such a mandrel could be increased by first providing a frame  28  having a recess  54  with longer vertical walls  62  and then replacing actuating cylinder  114   a  with another having longer piston travel. However, such modifications may be undesirable due to the resulting increase in the vertical projection of the frame above the molding machine and less stable alignment and movement of the tool. By means of the modifications of frame  28  about to be disclosed, a mandrel longer than depicted mandrel  98  can be employed to form the inside cavity wall  102   a  yet such a mandrel, even with a finished cylindrical pattern still attached, is laterally separable from the remainder of tool  10  without first withdrawing the mandrel from the pattern. This is accomplished by providing a separable and independently movable top segment  28   a  of the frame  28  which may be selectively coupled to the platen  22  for lateral movement therewith. Such lateral movement of the segment  28   a  and the mandrel attached thereto is made possible by separating inverted U-shaped segments  116   a  and  116   b  from the frame plates  30   a  and  30   b  as best shown in FIG. 6. Four elongated rods  118   a,b,c,d  are secured to the machine platen  22  by means of the mounting plate  94  and extend toward the stationary platen  16  in parallel with the tool-mounting bars  24 . The rods  118   b  and  118   c  penetrate aligned apertures  120  and  120   c  in the inverted legs  122   a  and  122   b  of the U-shaped segments  116   a  and  116   b . The rods  118   c  and  118   d  penetrate aligned apertures  124   a  and  124   b  in the frame  28 . All of these rods penetrate openings, not shown, through the mounting plate  96  and the stationary platen  16  and extend well beyond the platen  16 .  
         [0048]    After a pattern has been molded by a tool  10  which incorporates the modifications just described, the mold segments  88   a  and  88   c  are retracted and the lower mandrel  100  is withdrawn vertically from the completed pattern. Next, mold segment  88   b , the upper mandrel, the completed pattern and the frame segment  28   a  are moved as a unit in response to retraction of machine piston  20 . This machine controlled movement separates segment  28   a  from the frame  28  thereby drawing the upper mandrel  98  and the surrounding pattern away from the stationary mold segment  88   d  and between the retracted mold segments  88   a  and  88   c . The rods  118   a,b,c,d  are drawn through the platen  16  and the mounting plate  96  as the separable frame segment  28   a , mold segment  88   b , mandrel  98  and pattern are all transported with the platen  22 . When sensors incorporated in machine  12  detect that the lower perimetric edge of the pattern has cleared the baseplate  110  sufficiently, the frame segment  28   a  is automatically decoupled from the platen  22  and locked against further movement. A final increment of machine controlled platen movement will draw the rods  118   b  and  118   c  through the now stationary frame segment  28   a  as the mold segment  88   b  is drawn away from the finished pattern.  
         [0049]    At this point in the molding operation, the tool  10  and machine  12  are idled while the finished pattern remains suspended on mandrel  98  from which it may be readily removed in the downward direction by a push-off mechanism, by compressed air or by manually pulling the same from the upper mandrel. Various position sensors, latches, couplers and the like are incorporated in the molding machine  12  and in the tool  10  for operating the modified tool in the described fashion; however all such electronic, electrical and mechanical devices are commercially available and their applications in this invention are entirely conventional.  
         [0050]    In accordance with the illustrative embodiment, the molding tool actuators are attached to frame  28  at four evenly spaced locations about its perimeter; and, the diametrically opposed pairs of cavity forming tools carried by these actuators move along two axes which pass through the centerpoint of the frame&#39;s open center. The frame  28  is mounted on machine  12  so that the centerline of the machine&#39;s piston  20  also passes through the frame&#39;s centerpoint and is perpendicular to the actuator axes. However, this invention also contemplates a tool frame which may be differently shaped and sized from frame  28  for mounting an odd or even number of mold-segment actuators appropriate for forming very complex cavities. Furthermore, the extension and retraction of an individual actuator may occur at any desired angle with respect to that of any other actuator mounted on the frame or with respect to the axis of travel of a machine platen. Moreover, the tool  10  may be mounted on the machine  12  with the plates  30   a  and  30   b  tilted at an angle to the centerline of the machine piston  20  nor must the piston centerline coincide with the centerline of the frame opening  32 . While the frame  28 , as shown, is made up of a pair of spaced, parallel plates  30   a  and  30   b  having actuators  114   a,b,c,d  attached between and joining these plates, the advantages attributalbe to the open frame structure of this invention can be provided by a single plate having any size opening displaying any perimetric outline. The actuators could be removably attached to the single frame plate by any suitable clamp or fastener.  
         [0051]    Other desirable structural variations of the frame element  28  of tool  10  are possible and can be achieved without sacrificing the quintessential structural feature of this invention; namely, an open-centered frame which encircles but does not enclose the cavity forming elements of the pattern tooling. The significance of this key feature of the molding tool  10  will be understood and appreciated by tool designers who will be able to devise multiple-axis molding tools using open-center frames, as taught by this invention, that are specially configured for mounting a plurality of cavity forming segments on a molding machine in unique spatial relationships and orientations required to mold highly complex patterns. Pattern molders will appreciate that the various backplates which mount mold segments inside the open frame become readily accessable to workemen when the mold-operating platens and actuators are retracted. Such accessability makes it possible to change out mold segments without demounting the tool from the molding maching merely by exchanging those backplates which attach the old and new segments to associated baseplates and possibly reconnecting bead supply lines to the new mold cavities. A single workman can manually detach and exchange relatively light weight mold segments while the tool remains mounted on the molding machine in a fraction of the machine down time entailed in the exchange of closed, box-like tools of the kind described above in the Background Of The Invention.  
         [0052]    The foregoing description of the embodiments of the invention shown in the drawings is illustrative and explanatory only; and, various changes in the size, shape and materials, as well as in specific details of the illustrated construction, may be made without departing from the scope of the invention. Therefore, we do not intend to be limited to the details shown and described herein, but intend to cover all changes and modifications which are encompassed by the scope and spirit of the appended claims.