Abstract:
A casting rollover apparatus includes a cage supporting a casting mold and a slide coupled to the cage for advancing the mold into and out of engagement with a molten metal discharge nozzle. A spindle is carried on the slide and coupled to the cage for rotating the cage. A clamp cylinder is carried on the cage for clamping the mold in the closed position. A single transducer is mounted on one of a pair of pressurized fluid drive cylinders on the slide to detect the position of the slide. Electrical plug connectors are coupled to the transducer and the cylinder control elements. Thrust bearings are mounted on the spindle and apply a pre-load to the spindle. A digital proportional valve is coupled to a drive cylinder for controlling the deceleration of the spindle. A position detector switch is mounted in the path of angular rotation of the spindle to initiate spindle deceleration. The clamp cylinder carries a tubular member coupled to the piston and movable with respect to the clamp cylinder housing. An end of the tubular member is formed as a scrape surface to remove debris from the sidewall of the clamp cylinder.

Description:
CROSS REFERENCED TO CO-PENDING APPLICATION 
     This application claims the benefit of the filing date of provisional patent application Ser. No. 60/245,759 filed Nov. 3, 2000 in the name of Robert H. Spangler, III and Michael H. Kaubasta and entitled “Casting Rollover Apparatus,” the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     In casting work pieces, such as engine blocks, from various metals, it is well established that with certain metals, such as aluminum, the molten metal contains impurities which, if cast into the workpiece, could result in imperfections or weak areas in the workpiece. To address this problem, the assignee of the present invention previously devised a multiple-station rollover device, shown in FIG. 1, which receives the mold cores, moves the mold cores, after the cores are clamped in a non-movable position, into engagement with a molten metal discharge nozzle for the discharge of molten metal into the mold cores, and, finally, moves the filled core to an unload station. While the molten metal in the mold cores is still molten, the prior apparatus uniquely turned the mold cores over approximately 180°. This caused any impurities in the molten metal to rise to the rotated top of the mold cores. Specially designed, elongated runners or cavities in what was originally the bottom of the mold cores, received the molten metal and the impurities as the impurities rise to the top of the molten metal in the runners thereby essentially removing the impurities from the molten metal actually forming the workpiece. After solidification, the runners are separated from the cast work piece thereby removing the impurities from the workpiece. 
     The Assignee&#39;s prior casting rollover apparatus makes use of multiple stations of a base mounted on the rotary table, a slide mounted in the base for movement relative to the base to bring the mold cores into and out of engagement with the molten metal discharge nozzle, and a spindle carried on the slide which is capable of rotating the entire mold core and a surrounding support cage and clamps. 
     In operation, the rotary table advances one of the cages carrying a closed mold core to the molten metal pump station. The slide is advanced to move the spindle and the workpiece clamp cage from a retracted position to an extended position wherein the mold core is disposed in fluid communication with the molten metal discharge nozzle. The molten metal, typically aluminum, is then pumped through the nozzle into the mold core. 
     While the molten metal is still molten in the mold core, the spindle rotates the cage and the mold cores 180° causing any impurities which may be present in the molten metal to rise to the top of the inverted mold core and solidify in the runners which are subsequently separated from the main workpiece. The slide is then reversed to retract the spindle and the cage away from the discharge nozzle. The rotary table then brings the filled mold core to an unload station where the mold core is removed from the cage. 
     While the Assignee&#39;s prior casting rollover apparatus has proven effective over many years of operation, it is believed that certain improvements could be made to the casting rollover apparatus to improve its reliability, to reduce manufacturing costs, and to simplify the replacement or changeover of certain parts of the apparatus. 
     SUMMARY 
     The present invention is an improved casting rollover apparatus which provides improved performance and reliability over previously devised casting rollover apparatus. 
     In one aspect, the casting rollover apparatus of the present invention includes a cage supporting an openable and closable casting mold, an extensible and retractable slide coupled to the cage for moving the cage and the casting mold into and out of engagement with a molten metal discharge nozzle, a spindle carried on the slide and coupled to the cage for rotating the cage, and a clamp cylinder carried on the cage for clamping the mold in the closed position. 
     In one aspect, the slide includes first and second pressurized fluid operable cylinders coupled to extend and retract the slide, and a single transducer mounted on one of the first and second cylinders for detecting the position of the slide. 
     Preferably, electrical plug connectors are used to electrically interconnect the transducer with the cylinder control elements, such as a control for and a solenoid. 
     In another aspect, the spindle includes a spindle housing surrounding the spindle, an end cap mounted on one end of the spindle housing, and thrust bearings mounted between the spindle and the end cap. The thrust bearings provide a pre-load force on the spindle. 
     In another aspect, the spindle further includes means, coupled to the spindle, for rotating the spindle, at least one pressurized fluid cylinder coupled to the rotating means to drive the rotating means, and a digital, proportional valve coupled to the cylinder for receiving a variable electric current from a controller to smoothly decelerate rotation of the shaft. Further, end-of-travel detectors cooperate with the spindle to generate output signals indicating the end of rotational travel of the spindle in one direction. At least one deceleration-initiating sensor is spaced angularly from one of the end-of-travel switches, the declaration initiating sensor generating an output to the controller to initiate decleration of the spindle. 
     In yet another aspect, the clamp cylinder includes a cylinder housing having a sidewall, a piston movably disposed in the cylinder housing and movable between first and second positions in response to the input and exhaust of pressurized fluid into the cylinder housing on opposite sides of the piston, and input and exhaust ports carried on an end of the cylinder housing for providing the intake and exhaust of pressurized fluid into the cylinder housing. 
     In this aspect, a tubular member has a sidewall, guide rods coupled between the piston and an end plate on the tubular member, and a spacer coupled to the tubular member and having through bores slideably receiving the guide members therethrough. 
     Further, the tubular member encloses one end of the cylinder housing. The tubular member is coupled to and movable with the piston. An end of the tubular member is concentrically disposed over the sidewall of the cylinder and defines a scraping surface with respect to the sidewall of the cylinder housing. 
     The casting rollover apparatus of the present invention provides many advantages over previously devised casting rollover apparatus of the same type. First, only a single transducer is employed to detect the position of the slide. This reduces a part count. The use of the single transducer, when coupled with removable electric plug connectors, simplifies the replacement and removal of the transducer by eliminating the need to remove the prior solder connections between the transducer and the controller or solenoid conductors. 
     The use of thrust bearings in the spindle simplifies the assembly of the spindle as well as enabling a pre-load force to be applied to the spindle. 
     The use of a digital proportional valve to control the electric current to the drive cylinder on the spindle enables the spindle to be smoothly decelerated to a “stop” position. Detector switches angularly spaced from the end of travel position detector switches on the spindle uniquely initiate the start of spindle decleration. 
     The unique clamp cylinder of the present invention has end ports which enable the port connections to be spaced a further distance from the mold to minimize any accumulation of mold flash or debris on the port connections. Further, the tubular member mounted on one end of the cylinder housing provides a scraping action over the sidewall of the housing to remove any debris or metal flash which may accumulate on the cylinder and which previously would interfere with the smooth operation of the clamp cylinder. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The various features, advantages and other uses of the present invention will become more apparent by referring to the following detailed description and drawing in which: 
     FIG. 1 is a side elevational view of a prior art casting rollover apparatus; 
     FIG. 2 is an end view of a slide for a casting rollover apparatus according to the present invention; 
     FIG. 3 is a side elevational view of the slide shown in FIG. 2; 
     FIG. 4 is an end elevational view of a spindle for a casting rollover apparatus according to the present invention; 
     FIG. 5 is a longitudinal, cross-sectional view of the spindle shown in FIG. 4; 
     FIG. 6 is an end elevational view of a cage used in the casting rollover apparatus according to the present invention; and 
     FIG. 7 is a longitudinal, cross-sectional view of the clamp cylinder shown in FIG.  6 . 
    
    
     DETAILED DESCRIPTION 
     The following description of the complete casting rollover apparatus will necessarily include components which appear in the above-described prior casting rollover apparatus. The improvements or new components will be described in detail where appropriate. 
     Referring now to FIGS. 2 and 3, there is depicted a detailed view of the slide  20  of the casting rollover apparatus  10 . The slide  20  includes a base formed of a weldment containing a base plate  22  and two upstanding side plates  24  and  26 . Bearing blocks  28  and  30  are mounted on the upper ends of the side plates  24  and  26 , respectively, for sliding engagement with movable bearings  32  and  34 . The bearing blocks  28  and  30  and the movable bearings  32  and  34  are part of a commercially available linear bearing assembly. A saddle or platen  36  is fixedly mounted to the movable bearings  32  and  34  for longitudinal extension as described hereafter. 
     As shown in FIG. 3, which depicts a side view of the slide  20  with the left side plate  24  removed, there is depicted the two end plates  38  and  40  which are fixed to opposite ends of the side plates  24  and  26  as well as to a base extension  42 . 
     The slide  20  is provided with the capability of a predetermined amount of linear travel, such as four inches, by example only. The slide  20  is also devised to create a force on the molten metal discharge nozzle, not shown, to form a seal between each mold core mounted in the cage, as described hereafter, and the molten metal machine discharge nozzle. 
     A pneumatic or air cylinder  50  and a hydraulic fluid cylinder  52  are mounted on the end plate  38 , with fluid connections extending through the end plate  38  to the various ports on the cylinders  50  and  52 . The cylinders  50  and  52  work in conjunction with a die spring  55 . 
     Specifically, a cylinder rod  54  extensibly projects from one end of the pneumatic cylinder  50 . One end of the rod  54  is threadingly secured to a bracket  56 . The rod  54  also extensibly projects through a second bracket  58  which is fixed to one end of the air cylinder  50 . 
     The other end of the second bracket  58  receives a threaded end of a cylinder rod  60  projecting from the hydraulic cylinder  52 . The second bracket  58  also receives a threaded end of an interconnecting rod  62  which slidably extends through the upper portion of the first bracket  56 . The first bracket  56  is fixedly secured by bolts to the saddle or platen  36 . The die spring  55  is mounted over one end of the interconnecting bracket  62 . 
     Energization of the B return port of the pneumatic cylinder  50  pulls the bracket  56  solidly into contact with the bracket  58 . This enables elimination of the use of the spring  55  for force control and turns the slide  20  into direct hydraulic force control. Energization of the B port of the hydraulic cylinder  52  will result in the advance feed of the platen  36  to the right which, in a machine orientation, is toward the molten metal discharge machine nozzle. At a predetermined set point (set point one) defined by a predetermined distance between the inlet of the mold cores and the molten metal discharge nozzle, which is measured by a sensor, such as a proximity switch mounted on the side plate  24 , the pneumatic cylinder  50  return port exhausts to atmosphere. 
     This allows the brackets  56  and  58  to move independent of each other. With the B port of the hydraulic cylinder  52  still energized, the mold core comes in contact with the molten aluminum discharge nozzle. Once the mold core contacts the molten aluminum discharge nozzle, the brackets  56  and  58  start to separate which begins the collapse of die spring  55 . The collapse of die spring  55  generates a spring force pushing the platen  36  to the right in FIG. 3, or toward the molten aluminum discharge nozzle. At the same time the brackets  56  and  58  are separating, the rod  54  of the pneumatic cylinder  50  starts to extend, which translates into movement of the linear transducer mounted inside pneumatic cylinder  50 . The pneumatic cylinder  50  extends to a predetermined set point “mold secure”, set point two. Once set point two is made, the proper amount of sealing force between the mold core and the molten aluminum discharge nozzle has been achieved. 
     According to the present invention, only a single position sensor or linear transducer, which is disposed through the center of the pneumatic cylinder  50 , is used to detect when the platen  36  reaching the mold secure or set point two position. Previously, separate sensors or linear transducers were employed on both cylinders  50  and  52 . The present invention eliminates the linear transducer on the cylinder  52 . 
     Using only one transducer also simplifies the replacement of the transducer by using a insertable plug connector for the wiring connections between the transducer, the cylinder actuation solenoids and the external controller. Previously, protective dust covers were employed on both cylinders  50  and  52  to protect the position sensor or linear transducers mounted therein as well as the electrical connections to the linear transducers. The wire terminals were soldered to a connector mounted on the dust cover which required difficult assembly and disassembly of the solder connections during replacement of the transducer. 
     While the dust covers provided the desired protection from the ambient environment, replacement of the transducers due to damage, wear, or inoperability was time consuming due to the need to first remove the dust cover and then disconnect each soldered electrical connection. The use of the plug-in connector enables all the connections to be made or disengaged at one time in a quick and easy plug-in action. 
     Referring now to FIGS. 4 and 5, there is depicted the spindle  80  according to the present invention. The spindle utilizes a rotary actuator  82 , such as a Parker (M) series rotary actuator Model No. 150M-1803C-XXIV-B63. This rotary actuator  82  utilizes two spaced, parallel, rotatable racks  84  and  86  having a rotatable pinion  88  therebetween. Simultaneous activation of the racks  84  and  86  causes opposite linear movement of the racks  84  and  86  and a rotation of the pinion  88 . As shown in FIG. 5, the pinion  88  is connected to one end of an elongated shaft  90  which is rotatably mounted by means of a first bearing assembly  92  at one end, and a second bearing assembly  94  at an opposite end of a housing  96  which is fixedly mounted on the platen  36 . 
     The second bearing assembly  94  is preferably a conventional ball bearing assembly which supports one end of the shaft  90 . The first bearing assembly  92  is improved over Assignee&#39;s prior casting rollover apparatus in that it includes a unique arrangement of thrust bearings which are mountable in the housing  96  in a simplified assembly process. 
     In the prior spindle, it was necessary to first bolt the spindle together, drop the suit plate over the spindle, force the spindle through the bearings, lower the housing over the spindle and then bolt the assembly together. In the present invention, due to the orientation of the thrust bearings in the first bearing stack  92 , the bearings  92  can move in and out of the spindle housing  96  after removal of an end cap  102 . This significantly reduces the time required to assemble the spindle  80  and may actually reduce the assembly time up to half of that required for the spindle in Assignee&#39;s prior casting rollover machine. 
     It should also be noted that lowering the housing  96  over the spindle shaft  90  squeezes the outer races of the bearing  92  against the inner races of the bearing  92  thereby trapping the inner races in a non-separable position with respect to the housing  94  and the spindle shaft  90 . This arrangement of the bearings  92  also provides a pre-load on the spindle shaft  90  which prevents longitudinal movement of the spindle shaft  90 . 
     The spindle  80  is also provided with a unique run switch  97  which, when made, provides an indication of “okay to run.” When the switch  97  is not made, it is not okay to run the casting apparatus or to rotate the spindle. 
     Finally, the spindle  80  utilizes pressurized, fluid-operated cylinders  104  and  106  to drive the racks  84  and  86  to rotate the spindle shaft  90  via the pinion  88 . Previously, the rack drive cylinders were provided with cushions which operated to bleed off cylinder pressure at the end of cylinder rod travel. This was used to decelerate the rotation of the spindle shaft  90  at the end of either bi-directional rotation. 
     The present spindle employs a digital proportional valve and two new switches, such as proximity switches  108  and  110 , which are mounted on the end of the spindle  80 . The switches  108  and  110  are located angularly ahead of the end of travel switches  112  and  114  and are used to generate an external control signal to the spindle controller, typically a programmable logic controller (PLC), which, in turn, generates external trigger signals to vary the current to the proportional valves to thereby smoothly decelerate the rotation of the spindle shaft  90  until it reaches its end of rotation position. 
     Referring now to FIGS. 6 and 7, there is depicted a unique pressurized fluid/or air operated cylinder  120  which is used in the cage  122  to operate a clamp fixture used to hold the mold core  124  in the cage  122 . As shown in FIG. 6, the cylinder  120  is mounted in the top portion of the cage  122  by a bracket or mount  121  and has an end plate  162 . The end plate  162  is fixed to the bracket or mount  121  on the cage  122 . 
     As shown in FIG. 6, the cage  122  is formed of a framework of tubular members carrying a base  134  at a lower end. The mold core  124  is mounted on the base  134  at a load station and is removed from the base  134  at an unload station on the rotary table shown in FIG.  1 . 
     When a new mold core  124  is loaded in to the cage, the clamp cylinder  120  is activated causing movement of a piston  148  to either an extended or a retracted position. 
     The cylinder piston head  130  is formed of a tubular member having a sidewall  132  and a hollow internal chamber  135  which is closed at one end by the end cap  162 . The opposite end of the sidewall  132  is concentrically disposed within a movable tubular housing  136  having an inner diameter slightly larger than the outer diameter of the piston sidewall  132 . The tubular member  136  is closed at an opposite end by an end cap  138 . A clamp plate  128  is attached to the end cap  138  and causes an RF transmitter  128  which generates mold fill signals. 
     The clamp cylinder employed in the prior casting rollover apparatus employed a more conventional cylinder having an extensible and retractable rod projecting from one axial end of the cylinder housing. The rod was prone, however, to the deposit of casting material which could interfere with the smooth extension and retraction of the piston rod from the cylinder and lead to a gradual breakdown of the cylinder seals. 
     One unique feature of the cylinder  120  is a plurality of guide rods  140  and  142  which are fixed at one end by means of fasteners, such as screws, to the end plate  138  and extend through the tubular member  136  to a sealed connection via o-ring  144  and a countersunk threaded bolt  146  in the piston  148 . A spacer  150  is fixedly mounted in the tubular member  136 , with the guide rods  140  and  142  sliding therethrough in spaced bores. 
     The cylinder  120  uniquely has end porting in which the advance and return pressurized air connection ports  152  and  154 , respectively, are uniquely mounted in the end plate  162  rather than on the side of the cylinder as in Assignee&#39;s prior clamp cylinder or as is conventional in air operated cylinders. This arrangement places the air connections further away from the molten metal in the mold core as well as enabling the sidewalls  132  of the piston head  130  to remain smooth, for reasons which will become more apparent hereafter. 
     As shown in FIG. 7, the advance port  152  communicates with the interior chamber  135  in the piston head  130 . The return port  154  extends through an elongated bore  156  through the piston head  130  to a second chamber  158  disposed between the spacer  150  and the piston  148 . 
     In operation, pressurized air applied to the chamber  135  through the advance direction port  152 , while the return port  154  is open to exhaust, applies force against one surface of the piston  148  to move the piston  148  and the tubular member  136  in a direction away from the stationary end cap  162  to the fully advanced position shown in FIG.  7 . 
     When it is desired to unclamp the mold, the advance port  152  is connected, typically by valves, not shown, to exhaust and pressurized air is applied to the return port  154 . The bore  156  communicates the pressurized air to the chamber  158  whereby causing force to be generated on the opposite surface of the piston  148  resulting in sliding movement of the piston  148  to the right in the orientation shown in FIG. 7 until the tubular member  136  reaches a return position which spaces the clamp plate  128  further away from the mold core to allow loading and unloading of the mold core  124  to and from the cage  122 . 
     During the extension or retraction movement of the piston  148  relative to the piston head  130 , it can be seen that the end  160  of the tubular member  136  which is disposed in proximity with the outer surface of the sidewall  132  of the piston head  130  has a sharply pointed end which acts as a scraper to remove any debris, solidified molten metal, etc., from the exterior surface of the sidewall  132  of the piston head  130  thereby assuring smooth, sliding movement of the tubular member  136  relative to the piston head  130 . This scraping action defines a unique feature of the cylinder  120  and is possible due to the end porting of the advance and return ports  152  and  154  on the end plate  162  rather than porting along the sides of the cylinder  120  as would be typical in pressurized fluid cylinder designs. 
     The cylinder  120  also has a modular design construction in that the cylinder  120  can be provided with any stroke or piston head advance length by merely changing the length of one or both of the sidewalls  136  and  132 , and the length of the guide rods  140  and  142 .