Compression molded double-walled blocks for pallets and related methods

Abstract

The compression molding system includes a first extruder that outputs molten plastic and a second extruder downstream from the first extruder that mixes the molten plastic with wood chips to output a composite material. A transfer valve alternates the composite material between an inner block die and an outer block die. Each inner block die has an inner block press associated therewith for pressing the composite material into a desired shaped inner block having an opening on one side. Each outer block die has an outer block press associated therewith for pressing the composite material into a desired shaped outer block having an opening on one side. A press assembly presses one of the inner blocks into the opening of one of the outer blocks to form a double walled block.

Description

[Technical Field]

[0001] Related Applications This application claims the benefit of U.S. Provisional Application No. 63 / 239,501, filed September 1, 2021, which application is incorporated herein by reference in its entirety.

[0002] Technical Field The present disclosure relates to the field of pallets, and more particularly to double-walled blocks for pallets and related methods for manufacturing the same. [Background technology]

[0003] background A conventional pallet is typically made of wood and includes a lower deck and an upper deck separated by support blocks that form a gap between the lower and upper decks to accommodate lifting members, such as the tines from a forklift or pallet jack.

[0004] The top deck is typically multi-layered, with end deck boards assembled onto connector boards that span the entire length or width of the pallet. The end deck boards are nailed to support blocks via the connector boards to form the main structure of the pallet. The end deck boards are also known as lead boards. Intermediate deck boards are placed between the end deck boards. The base layer is typically a single layer, with the end deck boards not overlapping the connector boards. Summary of the Invention [Problem to be solved by the invention]

[0005] To move a pallet with a load on it, the tines from a forklift or pallet jack are inserted into the gap between the lower and upper decks. Depending on the forklift or pallet jack operator, the tines may contact the support blocks while aligning with the gap. If the force is significant, the support blocks may break.

[0006] The support blocks are typically solid wood. Solid wood support blocks offer superior strength and durability. Depending on their size, solid wood support blocks can be heavy, adding to the final weight of the pallet. The cost of each solid wood support block is typically based on its volume and the type of wood used. [Means for solving the problem]

[0007] summary The compression molding system includes a first extruder that outputs molten plastic, a second extruder downstream from the first extruder configured to mix the molten plastic with wood chips to output a composite material, and a transfer valve downstream from the second extruder that alternately routes the composite material between an inner block output and an outer block output associated with the transfer valve.

[0008] The at least one inner block assembly includes at least one inner block mold that receives the composite material from an inner block output associated with the transfer valve and at least one inner block press aligned with the at least one inner block mold for pressing the composite material in the at least one inner block mold into at least one inner block of a desired shape having an opening on one side. The at least one outer block assembly includes at least one outer block mold that receives the composite material from an outer block output associated with the transfer valve and at least one outer block press aligned with the at least one outer block mold for pressing the composite material in the at least one outer block mold into at least one outer block of a desired shape having an opening on one side.

[0009] A press assembly is downstream from the at least one inner and outer block assembly and presses one of the at least one inner block into an opening in one of the at least one outer block to form a double-walled block.

[0010] The compression molding system may further include an inner block carousel and an outer block carousel. The at least one inner block assembly may include a plurality of inner block assemblies spaced apart on the inner block carousel. The at least one outer block assembly may include a plurality of outer block assemblies spaced apart on the outer block carousel. The inner and outer block carousels are configured to rotate, and the composite material is alternately deposited onto the at least one inner and outer block mold as the at least one inner and outer block mold becomes available on the respective inner and outer block carousels.

[0011] The compression molding system may further include an inner block cooling system and an outer block cooling system, the inner block cooling system circulating a coolant through each inner block mold when the composite material in the inner block mold is compressed by at least one inner block press associated with the inner block mold, and the outer block cooling system circulating a coolant through each outer block mold when the composite material in the outer block mold is compressed by at least one outer block press associated with the outer block mold.

[0012] The inner and outer block molds can be cooled while pressure is applied, allowing the composite material to stabilize so that the inner and outer blocks can be removed from their respective inner and outer block molds without softening or sagging.

[0013] The compression molding system may further include a robot arm disposed between the inner block mold assembly and the outer block mold assembly and configured to alternately grasp the at least one inner block and the at least one outer block as they exit the at least one inner block mold and the at least one outer block mold. The inner block conveyor is disposed between the robot arm and the press assembly and receives the at least one inner block from the robot arm. The outer block conveyor is adjacent to the inner block conveyor and is disposed between the robot arm and the press assembly and receives the at least one outer block from the robot arm. The press assembly may receive the at least one inner block and the at least one outer block from the inner and outer block conveyors.

[0014] The compression molding system may further include a first cooling spray adjacent to the inner block conveyor and the outer block conveyor and configured to cool the at least one inner block and the outer block as the at least one inner block and the outer block travel on the respective inner block conveyor and outer block conveyor to the press assembly.

[0015] The compression molding system may further include a single conveyor for receiving the double-walled blocks from the press assembly. A second cooling spray may be adjacent to the single conveyor to cool the double-walled blocks as they travel on the single conveyor.

[0016] The temperature of the outer block of the double-walled block is greater than the temperature of the inner block of the double-walled block, and as the outer block cools, it contracts onto the inner block, creating a seal at the interface between the inner and outer blocks.

[0017] The composite material may be about 50% plastic and about 50% wood. The double-walled block may be formed with a hollow center. The inner block may be configured as a five-sided block with openings on the remaining sides, and the outer block may be configured as a five-sided block with openings on the remaining sides. The inner and outer blocks may be oriented so that the opening in the inner block faces the opening in the outer block.

[0018] Yet another aspect is directed to a compression press including a frame, a movable lid carried by the frame and having an opening therethrough, and an enclosure including a core carried by the frame and movable between a retracted position and an extended position, the core being aligned with the opening in the lid.

[0019] The first hydraulic stage is carried by the frame and configured to move the core from a retracted position to an extended position so that the core in the extended position extends through an opening in the lid, and then move the lid and core to the extended position so that the lid and core contact a mold having a cavity in which material is deposited. When pressure is applied to the lid and core in the extended position within the cavity, the pressure causes the material to expand and form an object having a desired shape within the mold. The second hydraulic stage is carried by the frame and configured to apply additional pressure to the lid and core in the extended position within the cavity.

[0020] Other aspects are directed to methods of operating the above-described compression molding system and to methods of operating the above-described compression press. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a perspective view of a compression molded inner block according to the present disclosure. [Figure 2] FIG. 1 is a perspective view of a compression molded outer block according to the present disclosure. [Figure 3] FIG. 3 is a perspective view of the compression molded inner and outer blocks shown in FIGS. 1 and 2 aligned. [Figure 4] FIG. 3 is a perspective view of the compression molded inner and outer blocks shown in FIGS. 1 and 2 pressed together to form a double-walled block. [Figure 5] FIG. 3 is a cross-sectional side view of the compression molded inner and outer blocks shown in FIGS. 1 and 2 aligned. [Figure 6] FIG. 3 is a cross-sectional side view of the compression molded inner and outer blocks shown in FIGS. 1 and 2 pressed together to form a double-walled block. [Figure 7] FIG. 5 is a cross-sectional side view of the double-walled block shown in FIG. 4. [Figure 8] FIG. 3 is a block diagram of a compression molding system for forming the compression molded inner and outer blocks shown in FIGS. 1 and 2. [Figure 9] 3A and 3B illustrate the operation of a multi-stage compression press used to form the inner and outer blocks shown in FIGS. 1 and 2. [Figure 10] 3A and 3B illustrate the operation of a multi-stage compression press used to form the inner and outer blocks shown in FIGS. 1 and 2. [Figure 11] 3A and 3B illustrate the operation of a multi-stage compression press used to form the inner and outer blocks shown in FIGS. 1 and 2. [Figure 12] 3A and 3B illustrate the operation of a multi-stage compression press used to form the inner and outer blocks shown in FIGS. 1 and 2. [Figure 13] 3A and 3B illustrate the operation of a multi-stage compression press used to form the inner and outer blocks shown in FIGS. 1 and 2. [Figure 14] 14A-14C illustrate the operation of a robotic arm used to remove an inner block from the multi-stage compression press shown in FIG. 13. [Figure 15] 10A-10C illustrate the operation of how composite material is deposited into the respective inner and outer block mold cavities. [Figure 16]10A-10C illustrate the operation of how composite material is deposited into the respective inner and outer block mold cavities. [Figure 17] 10A-10C illustrate the operation of how composite material is deposited into the respective inner and outer block mold cavities. [Figure 18] 10A-10C illustrate the operation of how composite material is deposited into the respective inner and outer block mold cavities. [Figure 19] FIG. 1 is a perspective view of a double-walled block with a logo formed during a compression molding process. [Figure 20] 7 is a flow diagram of the operation of the compression molding system shown in FIG. 6. [Figure 21] FIG. 14 is a flow chart of the operation of the compression press shown in FIGS. 9-13. DETAILED DESCRIPTION OF THE INVENTION

[0022] Detailed Description This description is made with reference to the accompanying drawings, in which exemplary embodiments are shown. However, many different embodiments may be used, and therefore the description should not be construed as being limited to the specific embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. Like numbers refer to like elements throughout, and prime notation is used to indicate like elements in different embodiments.

[0023] Referring first to Figures 1 and 2, as will be described in more detail below, compression molding is used to form inner and outer blocks 20 and 30 for use in pallets. Inner block 20 is a five-sided block with an opening 22 on the remaining side. Similarly, outer block 30 is a five-sided block with an opening 32 on the remaining side. Immediately after inner and outer blocks 20, 30 are formed, inner block 20 is inserted into opening 32 in outer block 30 to form compression molded double-walled block 40, as shown in Figures 3 and 4. Compression molded double-walled block 40 may also be referred to as a double-walled block or a support block.

[0024] Depending on the orientation of the inner block 20, the double-walled block will have four or five double-walled sides. When the inner block is placed within the outer block so that the cavity of the inner block is exposed, a five-sided double-walled block results. The fifth double wall will be on the other side of the opening. Pallets with double-walled blocks 40 with hollow centers reduce the weight of the pallet compared to using solid wood blocks, while also providing durability and strength.

[0025] In one configuration, the inner block 20 and the outer block 30 can be oriented so that the opening 22 in the inner block 20 faces the opening 32 in the outer block 30, as shown in Figure 5. A side view of the inner block 20 and the outer block 30 includes dashed lines 24, 34 indicating the wall thickness of the respective blocks. In this configuration, the double-walled block 40 has four sides with double walls.

[0026] Immediately after the inner and outer blocks 20, 30 are formed, and while they cool, the inner block 20 is inserted into the opening 32 in the outer block 30 to form the double-walled block 40, as shown in FIG. 6. As explained in more detail below, the inner block 20 is pre-cooled before being inserted into the warmer outer block 30. After the double-walled block 40 is formed, a cooling spray continues to cool the warmer outer block 30, causing it to shrink onto the inner block 20 while creating an airtight seal.

[0027] In other configurations, the orientation of the inner block 20 may be rotated 90 or 180 degrees before being inserted into the opening 32 of the outer support block 30. This allows the double-walled block 40 to have five sides with double walls, providing improved durability.

[0028] The compression molding system 50 used to form the double-walled block 40 will now be described with reference to FIG. 8. The compression molding system 50 includes a pair of extruders. The first extruder is a plasticizing extruder 60 that receives recycled thermoplastic and melts the plastic. While recycled thermoplastic is cost-effective, non-recycled (i.e., virgin) thermoplastic can alternatively be used. The molten plastic is then transferred to a second extruder, a mixing extruder 70. The mixing extruder 70 mixes the molten plastic with wood chips received from a wood filler hopper 80 to form a composite material. The output of the mixing extruder 70 sends the composite material to a transfer valve 90.

[0029] There are advantages to plasticizing the recycled thermoplastic before adding the wood chips. The problem with simultaneously plasticizing the recycled thermoplastic and wood chips is that the temperatures required to plasticize the recycled thermoplastic can cause the wood chips to burn. A temperature of approximately 370°F is required to melt the plastic. If the wood chips are added before the plastic is melted, the wood chips reduce the efficiency of the extruder.

[0030] In the mixing extruder 70, wood chips are added to the molten plastic before it enters the compression section of the mixing extruder 70. The wood chips then act as a coolant, lowering the temperature of the molten plastic to an optimum temperature for compression molding. The temperature of the molten plastic is reduced from about 370°F to about 300°F. At this reduced temperature, the composite material is mixed and the fully wetted wood fibers are bonded together at a temperature before gassing begins.

[0031] Two carousels 100, 120 are used to enable a continuous compression molding process: inner block carousel 100 for inner blocks 20 and outer block carousel 120 for outer blocks 30. Transfer valve 90 alternately routes composite material between an inner block output associated with transfer valve 90 to inner block molds 102 on inner block carousel 100 and an outer block output associated with transfer valve 90 to outer block molds 122 on outer block carousel 120.

[0032] The inner block carousel 100 includes a plurality of inner block assemblies spaced apart on the inner block carousel. As described in more detail below, each inner block assembly includes at least one inner block mold 102 for receiving composite material from an inner block output associated with a transfer valve 90, and at least one inner block press aligned with the at least one inner block mold 102. The at least one inner block press is configured to press the composite material in the at least one inner block mold 102 into at least one inner block 20 of a desired shape having an opening 22 on one side.

[0033] Similarly, outer block carousel 120 includes a plurality of outer block assemblies spaced apart on the outer block carousel. As described in more detail below, each outer block assembly includes at least one outer block die 122 for receiving composite material from an outer block output associated with transfer valve 90, and at least one outer block press aligned with at least one outer block die 122. The at least one outer block press is configured to press the composite material in at least one outer block die 122 into at least one outer block 30 of a desired shape, having an opening 32 on one side.

[0034] As the inner block carousel 100 rotates and an inner block mold 102 becomes available, the transfer valve 90 directs a predetermined amount of composite material to be deposited into the inner block mold cavity 104. The inner block mold cavity 104 is then closed using its associated inner block compression press. The inner block compression press forces the floating core into the inner block mold cavity 104. This causes the composite material to flow into the desired shape of the inner block 20.

[0035] After the floating core is pressed into the inner block mold cavity 104, the inner block carousel 100 rotates. As the outer block carousel 120 rotates and an outer block mold 122 becomes available, the transfer valve 90 sends a predetermined amount of composite material to be deposited into the outer block mold cavity 124. The outer block mold cavity 124 is then closed using its associated outer block compression press. The outer block compression press presses the floating core into the outer block mold cavity 124. This causes the composite material to flow into the desired shape of the outer block 30.

[0036] After the cores are pressed into the outer block mold cavities 124, the outer block carousel 120 rotates. During rotation, the transfer valve 90 delivers a predetermined amount of composite material to be deposited into the next available inner block mold cavity 104. The alternating deposition of composite material into the inner and outer block mold cavities 104, 124 is a continuous process as inner and outer block molds 102, 122 become available on the respective carousels 100, 120.

[0037] The compression molding system 50 is configured to consistently form the inner block 20 and the outer block 30. This is due to many interdependencies between materials, equipment, and processes.

[0038] The ratio of plastic to wood used to form the inner and outer blocks can vary. In one example, the composite material from the mixing extruder 70 is about 50% plastic and about 50% wood. The ratio can be balanced to meet the desired nail holding power of the double-walled block. In another example, the wood ratio in the composite can vary between 30-50%, while the corresponding amount of plastic can vary between 70-50%. These example ratios are for illustrative purposes and not limiting.

[0039] The temperature of the composite material from the mixing extruder 70 is about 300° F. This allows the composite material to flow well into the respective inner and outer die cavities 104, 124 and have a good mixture with good consistency.

[0040] Cooling of the composite material after it is deposited into the inner and outer molds 102, 122 is also a factor. Cooling the inner and outer molds 102, 122 while under pressure allows the composite material to harden and set (i.e., stabilize) sufficiently to remove the inner and outer blocks 20, 30 from their respective molds without softening or sagging.

[0041] The inner block carousel 100 and the outer block carousel 120 are sized based on the coolant 106, 126 to allow sufficient time for the inner blocks 20 and outer blocks 30 to cool as they are rotated. The coolant 106, 126 is, for example, chilled water that is circulated through the inner block molds 102 and outer block molds 122. The number of molds on each carousel is determined by how long it will take for the composite material to cool sufficiently so that the inner and outer blocks 20, 30 can be removed from their respective molds 102, 122.

[0042] In the illustrated compression molding system 50, the inner block carousel 100 has 14 molds 102 and the outer block carousel 120 has 14 molds 122. The molds on each carousel are grouped into seven stations, each station having two molds. Both molds per station are filled with composite material simultaneously.

[0043] When the inner block molds 102 are rotated, the floating cores from the inner block compression presses associated with each inner block mold 102 remain within the inner block mold cavities 104. Similarly, when the outer block molds 122 are rotated, the floating cores from the outer block compression presses associated with each mold 122 remain within the outer block mold cavities 124.

[0044] After a pair of inner block molds 102 in a station on the inner block carousel 100 reaches a certain point in its rotation, the respective floating cores from the compression mold press are removed from the inner block mold cavities 104, which then pull the inner blocks 20 from the cavities. As the inner blocks 20 cool, they tend to shrink onto their respective cores. As a result, when the cores are removed from the inner block mold cavities 104, the inner blocks 20 remain on their respective floating cores.

[0045] The robot arm 130 is disposed between the inner block carousel 100 and the outer block carousel 120. The robot arm 130 is a swing arm for gripping a pair of inner blocks 20. Once the robot arm 130 grips the pair of inner blocks 20, a stripper plate from the inner block compression press descends and pushes the inner blocks 20 out of their respective floating cores. Next, the robot arm 130 places the inner blocks 20 onto the inner block conveyor 140.

[0046] Similarly, after a pair of outer block molds 122 in a station on the outer block carousel 120 reaches a point in its rotation, the respective cores from the compression mold press are removed from the outer block mold cavities 124, which then pull the outer blocks 30 from the cavities 124. A robotic arm 130 is used to grab the pair of outer blocks 30. Once the robotic arm 130 grabs the pair of outer blocks 30, a stripper plate from the outer block compression press lowers, pushing the outer blocks 30 from their respective cores. The robotic arm 130 then places the outer blocks 30 onto an outer block conveyor 150 adjacent to the inner block conveyor 140.

[0047] The inner block conveyor 140 and the outer block conveyor 150 are separated because they move at different speeds, the inner block conveyor 140 being slower than the outer block conveyor 150. This allows more time for the inner blocks 20 to cool.

[0048] As the inner block 20 and the outer block 30 move downstream on the inner block conveyor 140 and the outer block conveyor 150, they are cooled by cooling sprays 160. A press assembly 170 is disposed downstream of the inner block conveyor 140 and the outer block conveyor 150 and receives the inner block 20 and the outer block 30. The press assembly 170 is configured to press the inner block 20 into the opening 32 of the outer block 30, while the outer block 30 is pressed against the inner block 20.

[0049] After the inner block 20 and outer block 30 are pressed together to form the double-walled block 40, the newly formed double-walled block 40 moves downstream on a single conveyor 180. The double-walled block 40 is further cooled by a cooling spray 162. Because the outer block 30 is warmer than the inner block 20, as the outer block 30 cools, it contracts onto the inner block 20, creating a seal at the interface between the inner block 20 and the outer block 30.

[0050] 9-13, the inner and outer block compression presses described above for forming the compressed inner and outer blocks 20, 30 will be described in more detail. For purposes of explanation, the inner and outer block compression presses will be generally referred to as compression press 200. Compression press 200 is advantageously configured as a multi-stage compression press, and is identical for the inner block die 102 and the outer block die 122.

[0051] The compression press 200 includes a first hydraulic stage 230 and a second hydraulic stage 240, as shown in Figure 9. Both hydraulic stages are independently controlled by a hydraulic system 250.

[0052] In one embodiment, as shown, the first and second hydraulic stages 230, 240 are formed as a single unit. The first and second hydraulic stages 230, 240 share a single cylinder. Alternatively, the first and second hydraulic stages 230, 240 can be formed as separate units, with each stage having its own cylinder.

[0053] The inner block mold 102 is sized for a pair of inner blocks 20. Alternatively, a pair of inner blocks 20 may be formed using a pair of side-by-side inner block molds 102, with each inner block mold 102 sized for a single inner block 20. As mentioned above, each carousel 100, 120 is divided into stations, with each station being used to form a pair of inner blocks 20 or a pair of outer blocks 30.

[0054] The compression press 200 includes a frame 211 secured to a base 213. The base 213 may be, for example, part of the inner or outer block carousel 100, 120. A movable lid 210 is carried by the frame 211 and has a pair of openings therethrough. A pair of enclosures 215 are carried by the frame 211 and include a pair of cores 220 movable between a retracted position and an extended position. The pair of cores 220 are aligned with respective openings in the lid 210. The cores 220 may also be referred to as floating cores.

[0055] Next, as shown in Figure 10, a composite material 202 is deposited in the cavity 104 of the inner block mold 102. A first hydraulic stage 230 is carried by the frame 211 and is configured to move the pair of cores 220 from a retracted position to an extended position, as shown in Figure 11. When the pair of cores 220 are in the extended position, they extend through a pair of openings in the lid 210.

[0056] 12, the lid 210 and the pair of cores 220 in the extended position are moved into contact with the pair of molds 102, each having a cavity 104 with material 202 deposited therein. When pressure is applied to the lid 210 and the pair of cores 220 in the extended position within the cavity 104, the pressure causes the material to expand within the pair of molds 102 to form an object having a desired shape (e.g., inner block 20). A second hydraulic stage 240 is carried by the frame 211 and configured to apply additional pressure to the lid 210 and the pair of cores 220 in the extended position within the cavity 104.

[0057] After the composite material 202 is deposited into each inner block cavity 104 of the inner block mold 102, the first hydraulic stage 230 extends or pre-moves the core 220 halfway past the lid 210 used to seal the inner block cavity 104. The floating core 220 extends through the lid 210.

[0058] The floating core 220 moves into the inner block cavity 104 with the composite material 202 therein. During this process, the composite material 202 is spread evenly within the inner mold cavity 104 to prevent flashing of the composite material 202. At this point in the process, the second hydraulic stage 240 continues to press down, and the lid 210 and floating core 220 remain pressed against the inner block mold 102.

[0059] As the inner block 20 cools within the inner block mold 102, the inner block 20 begins to shrink. To prevent this shrinkage, the floating core 220 is pressurized within the inner block mold cavity 104, forcing it back, and the steel walls that form the inner block mold cavity 104 also force the composite material 202 back.

[0060] This advantageously allows the dimensions of the inner block 20 to be approximately the same as the dimensions of the inner block cavity 104. In a typical compression molding process where a single hydraulic stage is used, the molded part typically shrinks within 5-8 percent of the mold dimensions. The inner block 20 shrinks by 2 percent or less of the inner block mold cavity 104 dimensions.

[0061] By controlling the shrinkage of the inner block 20, the compression molding system 200 can tolerate variations in the volume of the composite material 202 deposited within the inner block mold cavity 104. The volume of the composite material 202 can vary, for example, by up to 15%.

[0062] The multi-stage compression press 200 helps ensure the physical properties of the inner block 20. If enough shrinkage is introduced in the single-stage compression press, stress lines and other defects will begin to appear in the part.

[0063] After the first and second hydraulic stages 230, 240 engage and maintain pressure on the inner block mold 102 with the composite material 202 therein, as the inner block carousel 100 rotates, the inner block mold 102 is cooled by the coolant 106. In one embodiment, the coolant 106 is chilled water that circulates within the inner block mold 102 adjacent to the cavities 104 therein.

[0064] After each inner block mold 102 has been fully rotated on the inner block carousel 100, the inner block 20 is removed. The first and second hydraulic stages 230, 240 release pressure to remove the floating core 220 from the inner block mold cavity 104, as shown in Figure 13. Once the floating core 220 is removed, the inner block 20 is removed as it has shrunk onto the floating core 220.

[0065] To remove the inner blocks 20 from the floating core 220, the lid 210 acts as a stripper plate to disengage the inner blocks 20 from the floating core 220 so that the floating core can be fully retracted. Before the inner blocks 20 are disengaged by the lid 210, the robot arm 130 grabs a pair of inner blocks and places them on the inner block conveyor 140, as shown in FIG.

[0066] 15-18, the deposition of composite material into the respective inner and outer block mold cavities 104, 124 will be described in more detail. The transfer valve 90, described above, operates in conjunction with a composite material shuttle 300.

[0067] A composite material shuttle 300 shuttles between the inner block carousel 100 and the outer block carousel 120. The composite material shuttle 300 includes a pair of spaced heads 310, 320 for depositing composite material as needed. The heads 310, 320 may be referred to as the inner block output and the outer block output.

[0068] As shown in Figure 16, the head 320 associated with the inner block carousel 100 is aligned with the inner block mold 102. The head 320 is then moved over a pair of inner block mold cavities 104 to deposit the composite material 202, as shown in Figure 17.

[0069] After the composite material has been deposited, the head 320 is moved away from the inner block mold 102, as shown in Figure 18. The composite material 202 is now ready to be compressed using the multi-stage compression press 200, as described above.

[0070] 19, double-walled block 40 is configured with logo 43. Outer block mold cavity 124 is modified to have a raised surface in the shape of logo 43 on one or more side walls of cavity 124.

[0071] Another aspect of the present disclosure is directed to a method of operating the above-described compression molding system 50. Reference is now directed to flow chart 300 of FIG. 20. From the start (block 302), the method includes extruding molten plastic from a first extruder 60 at block 304, and then mixing the molten plastic with wood chips downstream of the first extruder using a second extruder 70 at block 306 to output a composite material. At block 308, the transfer valve 90 is alternately actuated to route the composite material between the inner block mold 102 and the outer block mold 122.

[0072] Each inner block mold 102 has an inner block press associated with it for compressing the composite material into a desired shaped inner block 20 having an opening 22 on one side (block 310). Each outer block mold 122 has an outer block press associated with it for compressing the composite material into a desired shaped outer block 30 having an opening 32 on one side (block 312). At block 314, the press assembly 170 is operated to press one of the inner blocks 20 into the opening 32 of one of the outer blocks 30 to form a double-walled block 40. The method ends at block 316.

[0073] Yet another aspect of the present disclosure is directed to a method of operating a compression press 200 as described above. Reference is now directed to a flow chart 350 of FIG. 21 . From the start (block 352), a movable lid 210 is provided at block 354, carried by a frame 211 and having an opening extending therethrough. At block 356, an enclosure 215 is provided, carried by the frame. The enclosure 215 includes a core 220 that is movable between a retracted position and an extended position. The core 220 is aligned with the opening in the lid 210.

[0074] The method includes, at block 358, operating the first hydraulic stage 230 to move the core 220 from a retracted position to an extended position, with the core 220 in the extended position extending through an opening in the lid 210. The first hydraulic stage 230 then, at block 360, moves the lid 210 and core 220 into the extended position and into contact with the mold 102 having the cavity 104 with the material 202 deposited therein.

[0075] At block 362, pressure is applied by first hydraulic stage 230 to lid 210 and core 220 in the extended position within cavity 104, causing material 202 to expand and form object 20 having a desired shape within mold 102. The method further includes, at block 364, operating second hydraulic stage 240 to apply additional pressure to lid 210 and core 220 in the extended position within cavity 104.

[0076] At block 366, pressure is released by the first and second hydraulic stages 230, 240, removing the core 220 from the mold cavity 104. Once the core 220 is removed, the object 20 is also removed. At block 368, the lid 210 acts as a stripper plate to detach the object 20 from the core 220 so that the core can be fully retracted. The method ends at block 370.

[0077] Many modifications and other embodiments will occur to those skilled in the art having the benefit of the teachings presented in the foregoing description and the associated drawings. For example, the above-described compression molding system 50 including compression press 200 can be modified to form other types of compression molded parts. The other types of compression molded parts may take the form of, for example, more durable boards for use in pallets.

[0078] In this example, a board is placed into a mold. The board is not necessarily uniform in size. For example, the width of the board may vary from 4 inches to 3 inches. The board is lifted into the mold and a composite material is compressed around the board within the mold. The composite material may have a ratio of about 50% plastic and about 50% wood. The end result is a dimensionally uniform laminated board.

[0079] Therefore, it is to be understood that the above is not limited to the exemplary embodiments and that modifications and other embodiments are intended to be included within the scope of the appended claims.

Claims

1. 1. A compression molding system comprising: a first extruder configured to output molten plastic; a second extruder downstream from the first extruder configured to mix the molten plastic with wood chips to output a composite material; a transfer valve configured to alternately route the composite material between an inner block output and an outer block output associated with the transfer valve downstream from the second extruder; At least one inner block assembly, at least one inner block mold associated with the transfer valve for receiving the composite material from the inner block output; the at least one inner block assembly comprising: at least one inner block press aligned with the at least one inner block mold and pressing the composite material in the at least one inner block mold into at least one inner block of a desired shape having an opening on one side; at least one outer block assembly, at least one outer block mold associated with the transfer valve for receiving the composite material from the outer block output; the at least one outer block assembly comprising: at least one outer block press aligned with the at least one outer block mold and pressing the composite material in the at least one outer block mold into at least one outer block of a desired shape having an opening on one side; a press assembly downstream from the at least one inner and outer block assembly, the press assembly configured to press one of the at least one inner block into the opening in one of the at least one outer block to form a double-walled block.

2. 10. The compression molding system of claim 1, further comprising: an inner block carousel, the at least one inner block assembly comprising a plurality of inner block assemblies arranged at intervals on the inner block carousel; an outer block carousel, wherein the at least one outer block assembly comprises a plurality of outer block assemblies arranged at intervals on the outer block carousel; the inner and outer block carousels are configured to rotate, and the composite material is alternately deposited onto the at least one inner and outer block molds as they become available on their respective inner and outer block carousels.

3. 10. The compression molding system of claim 1, further comprising: an inner block coolant system configured to circulate coolant through each inner block mold when the composite material in the at least one inner block mold is pressed by the at least one inner block press associated with the at least one inner block mold; an outer block coolant system configured to circulate coolant through each outer block mold when the composite material in the at least one outer block mold is compressed by the at least one outer block press associated with the at least one outer block mold.

4. 4. The compression molding system of claim 3, wherein cooling the inner and outer block molds while under pressure allows the composite material to stabilize such that the inner and outer blocks may be removed from the respective inner and outer block molds without softening or sagging.

5. 10. The compression molding system of claim 1, further comprising: a robot arm disposed between the inner block mold assembly and the outer block mold assembly and configured to alternately grasp the at least one inner block and the at least one outer block as they exit the at least one inner block mold and the at least one outer block mold; an inner block conveyor disposed between the robot arm and the press assembly and configured to receive the at least one inner block from the robot arm; an outer block conveyor positioned adjacent to the inner block conveyor and between the robot arm and the press assembly, the outer block conveyor configured to receive the at least one outer block from the robot arm; a press assembly configured to receive the at least one inner block and the at least one outer block from the at least one inner block conveyor and the at least one outer block conveyor.

6. 6. The compression molding system of claim 5, further comprising a first cooling spray adjacent to the inner block conveyor and the outer block conveyor and configured to cool the at least one inner block and the at least one outer block as they move on the inner block conveyor and the outer block conveyor, respectively, to the press assembly.

7. 10. The compression molding system of claim 1, further comprising: a single conveyor for receiving the double-walled blocks from the press assembly; a second cooling spray adjacent to the single conveyor and configured to cool the double-walled blocks as they move on the single conveyor.

8. 8. The compression molding system of claim 7, wherein the temperature of the outer block of the double-walled block is greater than the temperature of the inner block of the double-walled block, and as the outer block cools, the outer block contracts onto the inner block, creating a seal at the interface between the inner and outer blocks.

9. 10. The compression molding system of claim 1, wherein the composite material is approximately 50% plastic and approximately 50% wood.

10. 10. The compression molding system of claim 1, wherein the double-walled block is formed with a hollow center.

11. 11. The compression molding system of claim 10, wherein the inner block is configured as a five-sided block with an opening on the remaining side, and the outer block is configured as a five-sided block with an opening on the remaining side, and the inner block and the outer block are oriented such that the opening in the inner block faces the opening in the outer block.

12. A compression press, comprising: The frame and a movable lid carried by said frame and having an opening therethrough; an enclosure carried by the frame, the enclosure including a core movable between a retracted position and an extended position, the core aligned with the opening in the lid; a first hydraulic stage carried by the frame, the first hydraulic stage comprising: moving the core from a retracted position to an extended position, wherein the core in the extended position extends through the opening in the lid; the first hydraulic stage configured to: bring the lid into contact with a mold having a cavity in which material has been deposited; and move the lid and the core to an extended position to position the core within the cavity, wherein pressure applied to the lid and the core in the extended position within the cavity causes material to expand within the mold and form an object having a desired shape; a second hydraulic stage carried by the frame, the second hydraulic stage configured to apply additional pressure to the lid and the core in the extended position within the cavity.

13. 13. The compaction press of claim 12, further comprising a hydraulic system configured to independently control the first and second hydraulic stages.

14. 13. The compression press of claim 12, wherein a predetermined amount of material is deposited in the cavity of the die, and the pressure applied by the first hydraulic stage prevents flashing of the deposited material.

15. 13. The compression press of claim 12, wherein the additional pressure applied by the second hydraulic stage reduces shrinkage of the formed body as the body cools.

16. 13. The compression press of claim 12, wherein the mold is cooled by a coolant while the first and second hydraulic stages apply pressure to the lid and core, respectively, in the extended positions within the cavity.

17. 13. The compression press of claim 12, wherein the first and second hydraulic stages further comprise: Releasing the pressure applied to the lid and the core while they were in the extended position within the cavity; and and moving the lid and core away from the cavity while in the extended position, with a formed object remaining attached to the core.

18. 18. The compression press of claim 17, wherein the lid functions as a stripper plate to strip the object from the core before the core is returned to the storage position.

19. 13. The compression press of claim 12, wherein the material deposited in the cavity is a composite material comprising plastic and wood.

20. 13. The compression press of claim 12, wherein at least one sidewall within the cavity is configured with a raised surface in the shape of a logo to form the logo on the object.

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