Abstract:
A rotary drive system is provided that can rotate any object or a die holding assembly up to 270 degrees of rotation that uses both air and oil along with a oil/air pressure transferring device to smooth out each rotary cycle. The rotary drive system also utilizes a combination of air and oil in combination with a flow control device and an oil recovery reservoir to provide an impact cushion at the end of each rotational cycle.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    In the metal foundry business there is a need for cores that can be placed in the molds which produce voids in the castings as the molten metal is poured into molds. The cores generally are made from a sand and resin mixture that is forced into heated dies. The heat causes the sand-resin mixture to solidify producing the core. Dr. Johan Croning developed the phenolic resin process during WWII in Germany. The Germans gravity fed and hand rammed the resin sand around heated plates and contoured dies to make mortar and artillery shells. The American government brought the process to the United States and promoted it in 1947.  
           [0002]    In the 1950&#39;s Dependable foundry made its first machine to pneumatically inject phenolic resin, phenolic flake, and hexa catalyst into heated dies. Hence the first shell core machine was born.  
           [0003]    Generally there are two types of cores; solid cores and shell cores which are hollow on the inside.  
           [0004]    A variety of machines have been developed to manufacture these cores. In general cores are manufactured in a heated die that is held by a die holder. A sand resin mixture is forced into a fill opening while the fill opening is in an upward position.  
           [0005]    When solid cores are made, the entire core hardens. After the core has a final cure, the die holder and die are opened up and the solid core is extracted. After the solid core is extracted, the die holder and die are closed and the cycle is repeated.  
           [0006]    When shell cores are made, a sand resin mixture is forced into a fill opening while the fill opening is in an upward position. As the outer layer of resin-sand mixture cures or hardens to a die specified shape and utility thickness, the die holder carriage and die must be rotated so that the fill opening is in a downward position and the die holder is rocked back and forth so that any of the resin-sand that is unhardened will be shaken out of the die. This results in the formation of a hollow or shell core. After the uncured sand is shaken out the die, the die is rotated so that the fill opening is in a 90 degree position (facing the operator). After the core has a final cure, the die holder and die are opened up and the shell core is extracted. After the core is extracted the die holder and die are closed and the cycle is repeated.  
           [0007]    There are several different designs of core machines and shell core machines. There are also several methods used to rotate and shake the die holder and die. One design requires the rotating of the die holder carriage and die manually by hand. A second design uses cylinders and pneumatic power to rotate the die holder carriage and die. A third design uses cylinders and hydraulic power to rotate the die holder carriage and die. A fourth design uses an electric motor along with a gear reducer and roller chain to rotate the die holder and die.  
           [0008]    The most productive shell core machine has been the pneumatic powered machine. This machine however, has been very problematic. The machine is constantly in need of adjustment.  
           [0009]    These machines can produce a wide range of sizes and shapes of shell cores by using different dies in the die holder. Dies for different cores can vary from a few pounds to hundreds of pounds. Sand demand for cores can vary from a few ounces to tens of pounds. Every time a different die is placed into the die holder to make a different part, a lengthy process of changing flow controls and cams and limit switches is required to provide the optimum cycle for producing each different shell core design.  
           [0010]    During each short core making cycle the drive system must rotate the heavy die holder carriage, dies, and sand hopper. Because some of the individual components in the drive system are poorly designed, the stresses and strains and impact and inertia changes resulting from rotating the heavy die holder, dies, and sand hopper causes the various components to fail. This results in expensive repairs and much unproductive down time.  
           [0011]    Another problem with the pneumatic drive system is that the rotational cycle usually has a jerky motion and does not rotate at a constant high rate of travel through each production cycle.  
           [0012]    Another problem with the pneumatic drive system is that the rotational cycle of 270 degrees has a 180 degree portion and a 90 degree portion. The 180 degree portion is where the die front rotates from “top dead center to bottom dead center” or from zero degrees to 180 degrees. The 90 degree rotation is when the die front rotates from facing the operator at a horizontal to a bottom dead center position. (90 degrees to 180 degrees. The inertia of the 180 degree rotation is greater than the inertia of the 90 degree rotation. The machine can be set for smooth rotation in only one of the rotational portions. In other words, if the machine is set for smooth rotation in the 90 degree portion it will not have smooth rotation in the 180 degree portion and vise versa. The operation manual even states that machine “cannot be properly set for both conditions!” 
           [0013]    Another problem with the prior art drive system is that at both ends of each 270 degree cycle the drive piston hits the inside end of the piston drive cylinder to bring the heavy die holder carriage assembly to the ending position. Because of the repeated heavy impact between the piston and cylinder at the end of each cycle the drive piston and/or drive cylinder fail often.  
         Oil Between Air Drive System for Core Machine With End of Cycle Impact Cushion  
         [0014]    SUMMARY AND OBJECTS OF THE INVENTION  
           [0015]    It is a primary object of the invention to provide an improved drive system for a shell core machine that overcomes the above problems of the existing prior art.  
           [0016]    It is another object of the invention to provide a drive system that is more rugged and more dependable than the existing prior art drive systems.  
           [0017]    It is another object of the invention to provide a drive system design that spreads out the stresses and strains and loading and inertia and torsional forces that are the result of rotating the die holder, die, and sand hopper during each core making cycle.  
           [0018]    It is another object of the invention to provide a drive system design that uses more than one drive cylinder and piston along with a double ended lever with a drive shaft in a lever center location. This provides a mor evenly applied force across all drive components and allows for a greater applied pressure.  
           [0019]    It is another object of the invention to provide a drive system that rotates at a consistent high rate of travel, smoothly, through each production cycle rather than the jerky motion of the prior art drive system.  
           [0020]    It is another object of the invention to provide a drive system that uses both air and oil along with a oil/air pressure transducing device or a oil/air pressure transferring device. This smooths out each production cycle. Thus, the jerky motion of the prior art drive system is eliminated.  
           [0021]    It is another object of the invention to provide a drive system that provides a cushion at the end of each 270 degree rotation cycle. This minimizes the impact of the drive piston hitting the end of the piston drive cylinder.  
           [0022]    It is another object of the invention to provide a drive system that utilizes a combination of air and oil in combination with a metered port or a restricting orifice and check valve to provide a cushion at the end of each piston stroke. This minimizes the impact of the drive piston hitting the end of the piston drive cylinder.  
           [0023]    It is another object of the invention to provide a drive system that provides an end of cycle cushion that is adjustable.  
           [0024]    It is another object of the invention to provide a drive system with a cushion at the end of each 270 degree rotation cycle that has a long service life.  
           [0025]    It is another object of the invention to provide a drive system that provides a more rapid index of die carriage holder and die from start position to blow fill position. This can be up to 50% faster.  
           [0026]    It is another object of the invention to provide a drive system that requires very little or no adjustment to compensate for different sizes and weights of different dies that are used to make different cores in the shell core machine.  
           [0027]    It is another object of the invention to provide a drive system that requires very little or no adjustment so that there is a smooth rotation through the entire 270 degree rotation; both in clockwise rotations and counterclockwise rotations. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]    [0028]FIG. 1 is a drawing of the drive system of the existing prior art. This drive uses a single pneumatically powered drive cylinder and piston which is attached to a lever which is attached to a shaft which is connected to the die holder carriage, die and sand hopper.  
         [0029]    [0029]FIG. 2 is one of the components of the invention which essentially is an end of cycle impact cushion device. This drawing shows the oil recovery reservoir empty.  
         [0030]    [0030]FIG. 3 is end of cycle impact cushion device showing the oil recovery reservoir full. The objects and advantages of the invention will become apparent when the drawings are studied in conjunction with reading the following description.  
         [0031]    [0031]FIG. 4 is a mechanical and schematic layout of the present invention.  
         [0032]    [0032]FIG. 5 is a front view of the double ended lever of present invention.  
         [0033]    The objects and advantages of the invention will become apparent when the drawings are studied in conjunction with reading the following description.  
     
    
     DESCRIPTION OF THE PRIOR ART DRIVE SYSTEM  
       [0034]    Referring now to the drawings, the existing prior art drive system  10  is shown in FIG. 1. Die holder  11  and enclosed die have a Die Front Position 1 (DFP1) which is the starting, and ending position of every core making cycle. The die front position faces the operator at a 90 degree position from the top of the machine. A shaft  12  is connected to the die holder. Lever  13  connects the shaft to pivot coupling connection on drive shaft  15 . Seals  16  on drive piston make a tight fit between drive shaft and drive cylinder  17 . Pivot connection  18  of drive shaft allows movement through each core making cycle. Air line  19  is attached to drive cylinder at top connection  20 . Air line  21  is attached to drive cylinder at bottom connection  22 .  
         [0035]    At the beginning of a typical core making cycle the die front is facing the operator at a 90 degree angle from the top of the machine or “die front position 1” (DFP1). During a typical cycle the operator presses the start switch and air is forced into the top of the drive cylinder  17  which starts the die holder  11  rotating in a counterclockwise movement. The drive shaft  12  pulls the lever  13 , rotates shaft  12 , and the attached die holder  11  down to the 180 degree position. The control system then switches the control valve and air is forced into air line  21  at the bottom of the drive cylinder. This forces the continuation of the counterclockwise rotation a full 270 degrees so that the die front is at 0 degrees, or top dead center. The rotation of die holder assembly comes to the end of 270 degree rotation when the drive piston  15  hits the end of the drive cylinder  17 . This is “die front Position 2” (DFP2). At this point the sand/resin mixture is forced into the heated die cavity by compressed air (blow). The heated die causes the outer layer of the sand/resin mixture to harden (invest) and then the die holder assembly is rotated in a clockwise direction so that the die front is at bottom dead center, or 180 degrees. This is “die front position 3” (DFP3). In this position the control system causes the drive system to rock the die holder back and forth (rock drain.) This drains any unhardened sand from the center of the core, thereby producing a hollow core, or “shell core.” After a final cure period, the drive system continues the clockwise rotation of the die holder assembly into the ending/starting position. (DFP1) The rotation of die holder assembly comes to the end of 270 degree clockwise rotation when the drive piston  15  hits the end of the drive cylinder  17 . The die holder is unlatched (unlatch), the die is opened, and the core is extracted from the die. The die is closed and the cycle starts again.  
         [0036]    As can be seen in the drawing the lever rotates through a 270 degree arc starting at 45 degrees and ending at 315 degrees.  
         [0037]    This drive uses a single pneumatically powered drive cylinder and piston which is attached to a lever which is attached to a shaft which is connected to the die holder. The problems with this drive system have been described heretofore.  
       DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0038]    [0038]FIG. 2 is a mechanical and schematic layout of one of the embodiments of the present invention. This device provides an end of cycle cushion effect for the drive system. If this device were to be used on a prior art drive system such as shown in FIG. 1, oil/air line  23  would connect to upper drive cylinder  17  through air line  19 . Other components in this device include flow control device  24  which includes check valve  25  which allows free flow of air and oil into the top drive cylinder  17  and check valve  25  does not allow oil and air to flow freely through it in the opposite direction. When air and oil are being forced out of the top of drive cylinder  17 , it would enter air line  19  &amp;  24  and passes through flow restricting device  26 . Flow restricting device could be a restrictive orifice or a metered port or any device that restricts fluid flow. Oil/air line  27  connects into the bottom of oil recovery reservoir  28 . Air line  29  connects from the oil reservoir to a machine control valve (not shown). This end of cycle cushion device is explained in more detail further into the description of the preferred embodiments. This drawing shows the oil recovery reservoir empty.  
         [0039]    [0039]FIG. 3 is end of cycle impact cushion device showing the oil recovery reservoir full.  
         [0040]    [0040]FIG. 4 is a mechanical and schematic layout of several embodiments of present invention. Generally at  30  is the die holder assembly connecting to a bearing supported hollow drive shaft and a double ended lever. Generally at  32  is a top drive rod, piston and cylinder, and generally at  34  is a bottom drive rod, piston and cylinder. Generally at  36  is a oil/air pressure transducer that has air on one side and oil on the other side. Generally at  38  is an oil reservoir and a check valve in combination with a restricting orifice and generally at  40  is a four way, three position control valve.  
         [0041]    Die holder assembly  41  is connected to Shaft  42  which is fastened at the other end to double ended lever  44 . Shaft  42  is held by bearing support  43 . The die holder carriage assembly includes burner manifolds, a die holder, a die and a sand hopper which are together can weigh up to 900 pounds.  
         [0042]    Double ended lever  44  is made from ductile iron to make it very rugged, and is connected at one end to pivot connection  46  between upper drive cylinder  60 . Double ended lever  44  has an “H” shape as can be seen in FIG. 5. The other end of double lever is connected to pivot connection  48  of lower drive rod  50 . Drive rod  50  has piston  51  and has seals  54  inside drive cylinder  52 . Drive cylinder  52  has pivot connection  34  and  48 . Lower cylinder has a lower oil line connection  56  and an upper air line connection  58 .  
         [0043]    Upper drive cylinder  60  has a lower flow control device  94  and an upper air/oil inlet/outlet connection  62 . Upper drive cylinder,  8  rod and piston  64  has seals  65  and pivot connection  66  and  46 .  
         [0044]    Oil/air line  70  connects to upper drive cylinder  60  and has a flow control device  71  which allows free flow of air and oil into the top drive cylinder and restricted flow in the opposite direction. Flow control device includes check valve  72  and a flow restricting device  73 . When air and oil are being forced out of the top of drive cylinder  60 , it would enter air line and pass through restricting device  73 . Flow restricting device  73  could be a restricting orifice or a metered port or any device that restricts fluid flow. Oil/air line  74  connects into the bottom of oil recovery reservoir  76 . An oil deflector/diffuser  78  is located inside the oil recovery reservoir which helps retain the oil while allowing the air to exhaust. An oil reservoir/diffuser or accumulator could have a wide variety of designs. One way to provide a diffuser/accumulator inside a reservoir could be a copper mesh material. Oil fill line  80  terminates in an opening with a plug  82  which is in a normally closed configuration. Air line  84  connects from the oil reservoir to the machine control valve  120  at air connection  85 .  
         [0045]    Air line  87  makes a “T” connection  86  into air line  84 . Alternately, air line  87  could connect directly into control valve  120 . Air line  87  connects into air connection  58  of lower drive cylinder.  
         [0046]    Upper cylinder has a restricting orifice  94 . The restricting orifice produces a dampening effect in the drive system during a piston upstroke (in cylinder vacuum) and a cylinder downstroke (in cylinder compression).  
         [0047]    Oil line  96  connects from the lower drive cylinder oil connection  56  and to the oil connection  100  of the oil side  104  of the oil/air pressure transducer  105 . Oil line  96  has a “T” connection  97  which leads to an oil drain port and cap  98  which is in a normally closed position. Oil line  96  also has a “T” connection  99  which leads to an oil fill port and cap  102  which is in a normally closed position.  
         [0048]    The oil/air pressure transducer  105  has an oil reservoir side  104  and an air reservoir side  106 . Between the two sides of the oil/air pressure transducer is a rubber diaphragm  108  which stretches toward the oil side or the air side which ever side has a higher pressure. In this embodiment there is one pressure transducer, however, two or three, or more pressure transducers could be hooked up in parallel rather than using one, to assure enough volume of oil to drive cylinder piston through full cylinder stroke.  
         [0049]    Additionally, other pressure transducing devices could be used also.  
         [0050]    Air line connection  110  and air line  112  connect to pressure regulator  114  which regulates the input air pressure between o and 150 psi. Air line  116  connects the pressure regulator to an air fitting  118  on the machines  4  way  3  position control valve  120 .  
         [0051]    Compressed air supply line  122  is connected by air line  124  into an air fitting  126  on machine control valve  120 . Machine control valve  120  has exhaust ports  128  and  129 .  
       Operation  
       [0052]    Die holder assembly  41  and enclosed die have a Die Front Position 1 (DFP1) which is the starting, and ending position of every core making cycle. The die front position faces the operator which is a 90 degree position in a counter clock wise direction with top dead center being zero degrees. At the beginning of a core making cycle the die is in a latched or closed position.  
         [0053]    To start a core making cycle the operator presses the start switch which opens control valve  120  which allows air to be forced into air line  84  and into the top of oil reservoir/accumulator  76  which forces oil therein to flow through check valve  72  and then into the top rod side of piston of drive cylinder  60 . Air and oil flowing into the top drive cylinder  60  causes drive piston  64  and rod  63  to retract which causes drive lever  44  and die holder assembly  41  to begin to rotate in a counterclockwise direction. At the same time air is forced into air lines  84 , air is also being forced into air line  87  into air line  90  and then into the top of bottom drive cylinder  52 . The air being forced into the top of the drive cylinder  52  also exerts a force on lever  44  which starts lever  44 , shaft  42 , and the die holder assembly  41  rotating in a counterclockwise movement.  
         [0054]    In this preferred embodiment rather than having a single drive piston, there are two drive pistons and cylinders utilized with a double ended lever with the shaft  42  at central pivot position. This two cylinder design helps achieve equal force rod extend or rod retract. Additionally, the double ended lever with a fixed central pivot spreads out the stress and strains and resulting wear and tear of the components caused from rotating the heavy die holder assembly. The double ended lever is made from ductile iron which makes it very rugged as opposed to the steel lever of the prior art drive.  
         [0055]    As the die holder assembly continues to rotate in the counter clockwise direction, air is forced out of the bottom of top drive cylinder  60  through restricting orifice  94  which provides a dampening effect.  
         [0056]    Additionally, as the die holder assembly continues to rotate counterclockwise, oil is forced out of the bottom of bottom drive cylinder  52 , through oil line  96  and into the oil side of air/oil pressure transducer. Rubber diaphragm  108  flexes toward the air side  106  of the device which provides a dampening and smoothing effect in the drive system. As oil is forced into the oil side  104  air/oil transducer, air is forced out of the air side  106  and into air lines  112  and  116  and through 4-way, 3-position control valve  120  and exhausted to ambient.  
         [0057]    The drive system continues to rotate the die holder assembly in a counterclockwise direction until the drive cylinder rods are in a fully retracted position. At this point bottom drive shaft pivot  48  is at bottom dead center or 180 degrees. At this point the lever and cylinders are perfectly vertical. At this point the control system directs control valve  120  to switch positions and directs air into air line  116  through pressure regulator  114 , into air line  112  and into the air side  106  of air/oil pressure transducer  105 . As pressurized air enters the air side  106  of air/oil transducer  105  the diaphragm  108  is deflected in the opposite direction and oil is forced out of the oil side  104  and into oil line  96 . Oil continues through oil line  96  and into the piston side of bottom drive cylinder  52 . The oil entering drive cylinder  52  pushes the drive piston upward and causes the drive lever  44  and die holder assembly  41  to continue rotating in a counter clockwise direction. Oil continues to flow into lower drive cylinder  52  and continues the rotation. As the rotation nears the end of the full 270 degrees the die front is approaching the 0 degrees position, or “die front position 2” (DFP2).  
         [0058]    As the die holder assembly  41  rotates in a counterclockwise rotation, air has been flowing out of the drive cylinder  60  and through restricting orifice  73  at a high flow rate. As the drive system nears the ending position of the 270 degree cycle, cylinder rod  63  is approaching the last few inches of drive cylinder  60 , the few ounces of oil that are in the top of cylinder  60  begin to flow out of drive cylinder  60  and then into air/oil line  70  and then the flowing oil hits restricting orifice  73 . As the oil hits restricting orifice  73  the rate of oil flow is slowed dramatically compared to the rate of flow of air through the restricting orifice  73  because the oil has a higher viscosity than the air. Also air is compressible and liquids are not compressible. Flow rate of fluids traveling through the flow control device goes from rapid flow to moderate flow to slow flow as piston approaches the end of working stroke.  
         [0059]    This cushion effect or shock absorbing effect causes the entire drive system and attached die holder assembly to slow down and minimizes the impact as the heavy die holder assembly moves into the end of cycle position. This innovative device effectively absorbs the forces caused by the rotational inertia and momentum of the 900 pound die holder assembly rotating through a 90 or 180 or 270 degree rotation in a few seconds.  
         [0060]    As the oil continues to flow through the restricting orifice it is collected in oil recovery reservoir  76 . A coil of copper mesh  78  is located inside the oil reservoir which diffuses and accumulates the oil while allowing the air to escape. Other devices that could be utilized other than copper mesh might include other metal meshes, stacked perforated plates, plastic beads, fiber sponge, or combinations thereof.  
         [0061]    When the die front is at zero degrees or “die front Position 2” (DFP2), the sand/resin mixture is forced into the heated die cavity by compressed air (blow). Shortly thereafter, the heated die causes the outer layer of the sand/resin mixture to harden (invest).  
         [0062]    Next, the control system and control valve switches position forcing air into air lines  84  and  87  into the tops of the two drive cylinders. This causes the die holder assembly  41  to begin rotating in a clockwise motion and continues to rotate until the die front is positioned downward or 180 degrees. This is “die front position 3” (DFP3). In this position the control system and control valve causes the drive system to rock the die holder back and forth (rock drain) which drains any unhardened sand from the center of the core. This produces the hollow core, or “shell core” 
         [0063]    After a final cure period, the drive system rotates the die holder in a clockwise motion toward the starting position. (DFP1) This motion is accomplished as described earlier by the control valve directing air through airline  118  into the air side of oil/air pressure transducer thereby forcing oil out of the pressure transducer and into oil line  96  and into lower drive cylinder  52 .  
         [0064]    As the die holder assembly  41  rotates in a clockwise rotation air has been flowing out of the top drive cylinder and through restricting orifice  73  at a high flow rate. As the drive system nears the ending position of the clockwise cycle, drive piston  64  is approaching the end of drive cylinder  60 , the few ounces of oil that are in the cylinder begin to flow out of drive cylinder  60 , then into air/oil line  70 , then to restricting orifice  73 . As the oil hits restricting orifice  73  the rate of flow is slowed dramatically compared to the rate of flow of air through the restricting orifice because of the higher viscosity of the oil compared to the viscosity of the air. The flow rate of fluids traveling through the flow control device goes from rapid flow to moderate flow to slow flow as piston approaches the end of working stroke. This cushion effect or shock absorbing effect causes the entire drive system to slow down and minimizes the impact as the heavy die holder assembly moves into the start or end of cycle position. Again, this innovative device effectively absorbs the forces caused by the rotational inertia and momentum of the 900 pound die holder assembly near both ends of its 270 degree cycle which takes only a few seconds.  
         [0065]    Similar to the other end of the 270 degree cycle, the oil continues to flow through the restricting orifice  73  and is collected in oil accumulator reservoir  76 . Different designs for the oil reservoir/deflector could be utilized as long as they perform the same function.  
         [0066]    Again, in the prior art drive system, cycle comes to an end when the drive piston hit the end of the drive cylinder. This repeated high impact is cause of the prior art drive cylinder to fail often.  
         [0067]    To complete the core making cycle, the die holder is unlatched (unlatch), the die is opened, and the core is extracted form the die. The die is then closed and latched and the core making cycle starts again.  
         [0068]    As can be seen in the drawing the double ended lever rotates through a 270 degree arc starting at 45 degrees and ending at 315 degrees.  
         [0069]    This invention having been described in its presently contemplated best mode, it is clear that it is susceptible to numerous, variations, modifications, modes and embodiments within the ability of those skilled in the art and without departing from the true spirit and scope of the novel concepts or principles of this invention. It should be understood that this drive system could have widespread use in applications other than for manufacturing cores. Accordingly, the scope of the invention is defined by the scope of the following claims.