KR20070032028A - A check valve with a spiral coil seal - Google Patents

Abstract

The present invention relates to a seal for a check valve for a metal forming machine. The seal is provided by a combination of a peripheral groove in the outer surface of the check valve and a spirally wound coil in the groove. The spirally wound coil is expandable to sealingly engage the cylindrical wall of the molding machine. The spirally wound coil may laterally move between the melt channel open position and the melt channel closed position in a groove to open or seal the melt channel.

Check valve, spiral coil, groove, flow path, sealing ring, engagement surface

Description

CHECK VALVE WITH A SPIRAL COIL SEAL

The present invention relates to check rings and seals for injection molding machines, and more particularly to check rings and seals for metal injection molding machines and die casting machines.

Prior art includes US Pat. No. 3,578,803 to Huhn, May 18, 1971, which discloses the use of a helical spring to press the seal ring towards the counter-ring to form a seal on the shaft.

US Patent No. 3,655,206, issued to Durametallic Corp. on April 11, 1972, is a helical seal that is pressed against a wedge surface to apply radially inward and axial compressive forces to the seal ring to form a seal around the shaft. The use of the ring is disclosed. The sealing ring is composed of a multilayer graphite material. The sealing ring is designed to hold the seal around the shaft.

US patent application 2002/0100507, published August 1, 2002 by Hauser et al., Discloses a check valve for a piston pump in an automatic braking system. The check valve is formed as a single piece consisting of a helical coil having a base ring at one end and a closing disk at the other end. Movement of the base ring provides opening and closing of the check valve. Helical springs provide opening and closing movement of the valve. The outer surface of the helical spring is not used as a closing or sealing surface.

US Patent Application 2004/0001900, published January 1, 2004 by Dominka, discloses a check valve for an injection system. The valve has a shutoff pin, a spring guide member, and a helical spring. The helical spring is compressed by the guide member to close the flow path by pressurizing the pin and decompressed so that the flow path can be opened. The surface of the helical spring is in contact with the flow path but does not provide either a closed or sealed surface.

None of the prior art suggests the use of helical coils to substantially seal the flow channel.

There is a need for a reliable wear resistant seal to seal the flow path through a check valve in an injection molding machine.

In injection molding of plastics, it is common to employ any sealless check valve and rely on the relatively large gap and high viscosity of the melt to create a complete seal. Metals used in metal injection molding do not have the high viscosity of plastic and will therefore leak through the gaps normally employed in plastic injection molding. In addition, the high corrosion resistance of the metal and the high temperatures required for injection also make it difficult to use plastic injection molding sealing devices for metal injection molding. Thus, effective seals for metal injection molding are required to have tight gaps and tolerances and to withstand high temperature and corrosive environments. The present invention provides such a seal using a helical coil.

The present invention provides a seal for an injection molding machine that will prevent backflow of the molten metal in the check valve, reduce wear at the barrel and check valve, and operate reliably even in the presence of significant wear. The invention is achieved by providing a helical coil to seal the channel. The spiral coil can also serve as a check ring for opening and closing the melt path.

The present invention provides a seal for a check valve for a metal forming machine. The seal includes a peripheral groove in the outer surface of the check valve and a spirally wound coil in the groove. The spirally wound coil is expandable to hermetically engage a cylindrical wall of the forming machine.

The present invention also provides a check valve for a metal forming machine. The valve has a spiral wound coil. The coil seals on the check valve and slides on the cylinder of the check valve to open and close the flow path through the valve. The first turn of the coil has a surface that mates to the engagement surface to close the valve when in contact with the engagement surface on the cylinder. The outer circumferential surface of the coil mates with the cylinder wall surrounding the check valve to provide an axial seal to the check valve.

The invention also provides an injection unit for an injection molding machine comprising an injection screw, a nozzle body on one end of the injection screw and a check valve on the nozzle body. The check valve has a sealing ring. The sealing ring includes a spirally wound coil slidable between a first position surrounding the nozzle body and opening the nozzle and a second position in which the nozzle is closed. The first turn of the coil is sealingly engaged with the shoulder on the nozzle body when the coil is in the closed position.

DETAILED DESCRIPTION Exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

1 is an end view of a barrel assembly for a metal injection molding machine.

Figure 1A illustrates a barrel assembly of a conventional injection molding system in which the present invention may be used.

FIG. 2 is a cross-sectional view of the barrel assembly of FIG. 1 taken along the dividing line 2-2 of FIG. 1, showing the helical seal provided by the present invention.

FIG. 3 is a detailed view of the portion of FIG. 2 showing the check valve with the helical seal in the closed sealing position, taken along the dividing line 3-3 of FIG.

FIG. 3A is a detailed view of the circle portion A of FIG. 3 showing a closer view of the relationship between the spiral shape and the groove.

4 is an end view of the check valve of FIG.

5 is a perspective view of the check ring of the present invention.

5A and 5B are cross sectional and end views, respectively, of the check ring shown in FIG.

6 is a perspective view of a helical coil to be fitted to the check ring of FIG. 5 to seal the check ring.

6A and 6B are sectional and end views, respectively, of the spiral coil shown in FIG.

Fig. 7 is a cross sectional view taken along the dividing line 7-7 of Fig. 8 showing a check valve having a spiral coil serving as a seal and a check ring.

8 is an end view of the check valve shown in FIG.

Figure 9 illustrates another embodiment of the present invention in which a spiral coil is combined as a check ring and a seal.

Fig. 10 is a cross sectional view taken along the dividing line 10-10 of Fig. 11, showing another embodiment of the present invention having a wear ring between the spiral coil and the check valve.

FIG. 11 is an end view of the check valve shown in FIG.

The structure and operation of the present invention is hereinafter referred to as an improvement in the function and durability of a check valve configured for use in a barrel assembly of an injection molding system for forming a metal alloy, such as magnesium, in a semisolid (ie thixotropic) state. This will be explained in terms of. A detailed description of the structure and operation of some of these injection molding systems can be obtained with reference to US Pat. Nos. 5,040,589 and 6,494,703. However, even if such are not intended, the general use of the check valve of the present invention or its affinity with other metal alloys (eg, aluminum, zinc, etc.) is not intended to be limited to them.

The barrel assembly of a conventional injection molding system is shown in FIG. 1A.

The barrel assembly 138 has an elongate cylindrical barrel 140 through which an axial cylindrical bore 148A is formed. The barrel assembly is connected to a stationary platen 16 of a clamping unit (not shown). Bore 148A is disposed therein for processing and transporting the metal feedstock, and is configured to cooperate with screw 156, which is a means for accumulating melt of the injection material during its injection and subsequently channeling. Screw 156 has a helical flight 158 disposed around the elongate cylindrical body portion 159. The rear portion of the screw (not shown) is configured to engage the drive assembly (not shown), and the front portion of the screw 156 is configured to receive the check valve 160 in accordance with one embodiment of the present invention. The operating portion of the check valve 160 is disposed in front of the front engagement surface or shoulder 32 of the screw 156. The barrel assembly 138 has a barrel head 2A positioned midway between the mechanical nozzle 144 and the front end of the barrel 140. A melt passage 10 is formed through the barrel head 2A, which connects the barrel bore 148A with the complementary melt passage 148C formed through the machine nozzle 144. The melt passage 10 penetrating through the barrel head 2A has a portion tapered inside such that its diameter is transferred to the narrower melt passage 148C of the machine nozzle 144. The central bore 148A of the barrel 140 has a lining 12A made of a corrosion resistant material, such as Stellite ™, to protect the barrel substrate typically made of a nickel-based alloy such as Inconel ™ from the corrosion characteristics of hot metal melts. Have Other portions of the barrel assembly 138 in contact with the melt of molding material may have similar protective linings or coatings. The barrel 140 is also configured to connect with a source of pulverized metal feedstock through a feed throat (not shown) disposed through the top-rear portion (not shown) of the barrel 140. . The feed throat directs the feedstock into the bore 148A of the barrel 140. The feedstock is then processed sequentially into the molding material by its mechanical work, by the cooperative action of the barrel bore 148A and the screw 156, and by its controlled heating. Heat is provided by a series of heaters (not shown) and heaters 150 along the machine nozzles 144 disposed along a substantial portion of the length of the barrel assembly 138.

The injection mold has at least one molding cavity (not shown) formed in closed cooperation between complementary molding inserts shared between the mold cold half (not shown) and the mold hot half 125. The mold cold half has a core plate assembly with at least one core molding insert disposed therein. Mold hot half 125 has a cavity plate assembly 127 disposed therein with at least one complementary cavity molding insert and mounted to one side of runner system 126. The runner system 126 connects the melt passageway 148C of the machine nozzle 144 with at least one molding cavity and provides a means for filling it. As is known, runner system 126 may be an offset or multi-drop hot runner, cold runner, cold sprue, or any other known melt dispensing means. In operation, the core and cavity molding insert cooperate in a mold closed and clamped position to form at least one mold cavity for receiving and forming a melt of molding material received from runner system 126.

In operation, the mechanical nozzle 144 of the barrel assembly 138 is coupled to the sprue bushing 55 of the injection mold while the melt is injected into the mold (ie, acting against the reaction forces generated by the injection of the melt). do).

The molding process generally comprises the following steps.

(i) introducing a metal feedstock into the rear end of the barrel 140;

(Ii) a. The feedstock / melt is moved along the length of the barrel 140 via the cooperation of the screw flight 158 and the axial bore 148A, past the check valve 160 to the accumulation site formed in front of the check valve 160. The action of the screw 156 (i.e., rotation and retraction) to

b. By heating as the feedstock material moves along a substantial portion of the barrel assembly 138,

Processing (ie, shearing) and heating the metal feedstock to form thixotropic melt of the molding material;

(Iii) closing and clamping the injection mold half;

(Iii) injecting the accumulated melt into the injection mold through the machine nozzle 144 by forward translation of the screw 156;

(v) optionally, filling (ie, packing) the void remaining at least in the molding cavity by application of a sustained injection pressure;

(Iii) opening the injection mold if the molded part solidifies through cooling of the injection mold;

(Iii) removing the molded part from the injection mold, and

(Iii) optionally, servicing (eg, applying a release agent) the injection mold for subsequent molding cycles.

Preparing a large amount of melt for subsequent injection (i.e. steps (i) and (ii)) is known as "recovery" and packing at least one mold cavity [i.e., steps (i) and ( v)] is known as "injection".

The check valve 160 allows the molten metal to move forward to the accumulation site in front of the barrel 140, while preventing the backflow during the injection of the molten metal. The proper functioning of the check valve 160 depends on the pressure difference between the melts on both sides (i.e. the valve rear is higher during withdrawal and the front higher during injection). The construction and operation of conventional check valves for use in metal injection molding is shown in US Pat. No. 5,680,894.

1 and 2, there is shown generally a spiral coil used in accordance with a preferred embodiment of the present invention. 1 shows a coil used as a seal.

In FIG. 2, the barrel 2 with the barrel liner 4 supports a screw (not shown) to which the check valve 20 is attached by a thread 28. A bolt (not shown) connects the barrel head 6 to the barrel 2 through the bolt hole 8. Sprue bushings (not shown) and the like are attached to the barrel head 6 by bolt holes 9. When the check valve 20 is in the open position shown in FIG. 2, the screw rotates and the melt is transferred into the melt passageway 10 in front of the check valve 20 through the check valve in a manner known in the metal molding art. do.

When filling the melt passage 10, the melt exerts a force on the inclined surface 32 to move the check ring 24 forward and open the flow path between the inclined surfaces 32, 34. Surface 40 constrains the forward movement of ring 24. During forward movement the helical coil is only slightly pressured from the melt and will hardly resist the forward movement of the ring.

When the melt passage 10 is filled with melt, the rotation of the screw stops and the melt injection into the mold cavity (not shown) begins. The forward movement of the screw during injection forces the front face of the check ring to move backwards, which causes the inclined surfaces 32 and 34 to contact and seal the melt path.

In addition, the opening 12 (shown in FIG. 3) in the side wall of the ring 24 may press the inner wall of the spiral coil with melt to make sealing contact with the barrel liner 4, thereby allowing the length of the barrel during the injection cycle. It is possible to seal the leakage along.

As shown in FIG. 3, the check valve 20 is composed of a main stem 22, a check ring 24, and a spiral coil 26. The stem 22 is attached to the end of the injection screw by a thread 28. The shoulder 30 is fixed to the end of the injection screw.

In the closed position shown in FIG. 3, the inclined surface 32 on the check valve 20 and the inclined surface 34 on the shoulder 30 are ring 24 by the melt in the melt channel 36 in a manner known in the art. Pressurized by back pressure applied to the

The outer diameter of the helical coil 26 has a sufficient gap to allow easy assembly. The opening 12 allows the molten metal to enter the space 14 near the inner circumference of the spiral coil 26. During injection, the melt in the space 14 is axially and radially outward, which easily compresses and radially expands the highly flexible structure of the helical coil 26 until all gaps are removed and a seal is produced. The dead power is applied to the coil 26. When the injection pressure is lost, the force causing compression and expansion no longer exists and the helical coil 26 is relaxed. Once the plasticizing screw (not shown) starts turning to transfer new material to the front of the screw, the integral contact between the check ring 24 and the helical coil 26 results in a smaller outer seal diameter. Will be applied to torque twisting helical coil 26 so that the seal diameter disengages from the wall of the barrel liner and wear is reduced.

The end of the main stem 22 branches to form a finger 38 which creates a slot 42 in the melt channel 36 as shown in FIG. When the injection screw is retracted and rotated in a manner known in the art, the screw opens the valve 20 to move the check ring 24 forward so that the melt channel 36 can receive the melt from the rotating screw. to provide. As the melt channel 36 is filled with melt, the pressure in the channel slowly retracts the plasticizing screw to its full shot position. When the injection stroke begins, the closed volume of melt in front of the check ring returns the check ring 24 to the closed position shown in FIG. When the check ring 24 reaches the sealed position shown in FIG. 3, sufficient melt may be provided in the melt channel 36 to inject the next melt into the cavity. The rotation of the screw is stopped and the screw translates forward to press the melt into the mold cavity. The translational movement of the screw increases the pressure created by the melt, which ensures that the melt path 36 is sealed along the barrel surface near the coil 26 at the slopes 32, 34.

As shown more clearly in Fig. 3A, the coil 26 is almost rectangular in cross section. The outer circumferential surface of the coil is machined to high tolerances to make intimate contact with the walls of the associated barrel liner. The inner circumferential surface may be of other shapes, such as convex or concave. The only limitation to the shape of the inner circumferential surface is that it has a sufficient surface to ensure proper transfer of force to move the coil in sealing engagement with the barrel liner surface. The radial surface of each turn of the coil is also machined to large tolerances to ensure that adjacent turns of the coil are effectively sealed to each other. The outer radial surface of the outer coil and the surface where it contacts the check ring should also be machined to large tolerances to ensure good sealing.

The check ring 24 is shown more clearly in FIGS. 5, 5A, and 5B. Ring 24 has a circular slot 44 around it. Slot 44 is disposed near the middle of ring 24, but may be located near both ends if desired. The only limitation is that the wall sections 46, 48 near the slot must have sufficient strength to withstand the pressure exerted by the coil 26 when mounted in the slot 44.

Spiral coil 26 is shown more clearly in FIGS. 6, 6A, and 6B. As shown in these figures, the outer circumferential surface 66 is machined with large tolerances. The radial surface 68 is also machined to large tolerances. The inner circumferential surface 70 does not need to be manufactured with large tolerances because it contacts the melt during operation.

7 shows a check ring coil 50 that combines the action of opening and closing the check valve 52 with the action of sealing the melt channel 54. In this embodiment, the surface 56 of the outer coil of the coil 50 engages the inclined surface 34 to close the valve as shown. The circumferential surface of the turn of the coil 50 engages with the wall of the barrel to seal the wall so that no back flow of the melt occurs. The flexibility of the coil 50 turns ensures that the coil 50 provides a consistently reliable seal even if the barrel wears when the pressure of the melt against the inner wall of the coil 50 presses the outer wall of the coil against the barrel. . Thus, the seal along the wall will only begin to corrode when the barrel wears to such an extent that the expansion of the coil is insufficient to cover the wear gap.

For metal moldings, helical coils must be made of a material that is stable and corrosion-inert at high operating temperatures, such as 600 ° C. for magnesium molding. For example, when molding magnesium, nickel should not be present.

The stem 22 shown in FIG. 7 is essentially the same as the stem 22 shown in FIG. 3, and therefore similar reference numerals have been used to represent the same parts of the stem. The stem 22 need not be described further.

7A more clearly shows the machined surface of the coil 50.

FIG. 8 is an end view of the check valve 52 shown in FIG. 7 with a slot 42 that allows melt to flow into the injection cavity.

9 shows another embodiment of the present invention. In this embodiment, the melt flow channel 60 extends from the periphery of the check valve toward the interior of the barrel 64. The helical coil 66 acts as a check ring and seal for the check valve in a manner similar to that described above with reference to FIGS. 7 and 8.

10 and 11 show a further embodiment of the present invention. In this embodiment, a ring 72 is disposed between the seat 74 on the screw (not shown) and the helical coil 76. The ring 72 enables the use of a thin coil 76 and maintains the required flow path. The ring 72 moves back and forth with the coil 76.

It is to be understood that the foregoing is provided by way of example only and that various modifications in detail are included within the scope of the present invention.

Claims (17)

Seals for check valves for metal forming machines, The seal comprises a peripheral groove in the outer surface of the check valve and a spirally wound core in the groove, The spirally wound coil is expandable to sealingly engage the cylindrical wall of the forming machine. The seal of claim 1, wherein each turn of the coil has a flat radial wall, and adjacent turns of the coil contact each other to radially seal the coil. Check valve for metal forming machine, The valve comprises a peripheral groove in the outer surface of the check valve and a spirally wound coil in the groove, And the coil is inflatable to seal seal with the cylindrical wall of the forming machine. 4. The check valve of claim 3, wherein the spirally wound coil is laterally movable between a melt channel open position and a melt channel closed position. 4. The check valve of claim 3, wherein the coil turns are substantially rectangular in cross section. The check valve of claim 4, wherein adjacent surfaces of the turns of the coil are machined to a large tolerance to ensure sealing between adjacent turns when the coil is compressed. The check valve of claim 4, wherein the outer surface of the turn of the coil is machined to large tolerances to seal tightly against the wall when the coil is inflated. Check valve for metal forming machine, The valve has a spiral wound coil, The coil seals the check valve and is slidable on the cylinder of the check valve to open and close the flow path through the valve, The first turn of the coil has a surface that conforms to the engagement surface to close the valve when in contact with the engagement surface on the cylinder, An outer circumferential surface of the coil mates with a cylinder wall surrounding the check valve to provide an axial seal to the check valve. The check valve of claim 8, wherein each turn of the coil other than the first turn has a flat radial wall that provides a radial seal when compressed together. Injection unit for injection molding machine, An injection screw, a nozzle body on one end of the injection screw, and a check valve on the nozzle body, The check valve has a sealing ring, the sealing ring includes a spirally wound coil slidable between a first position surrounding the nozzle body and opening the nozzle and a second position in which the nozzle is closed, The first turn of the coil is sealingly engaged with a shoulder on the nozzle body when the coil is in the closed position. 12. The injection unit of claim 10, wherein each turn of the coil except the first turn has a flat radial surface and is sealingly coupled with the flat radial surface of the adjacent turns to provide a radial seal of the check valve. . Seals for check valves for metal forming machines, The seal includes a helical coil that can be inserted into a peripheral groove in the valve, the coil having an outer radial surface that is expandable to sealingly engage the cylinder wall when the inner radial surface of the ring is pressurized, The first turn has a axial surface that mates with an axial surface on the groove and provides an axial seal when the coil is subjected to an axial force. 13. The seal of claim 12, wherein each turn of the coil except the first turn has a flat axial surface and is sealingly engaged with the flat axial surface of an adjacent turn to provide an axial seal of the coil. It is a spiral coil in the check valve for metal forming machines, The coil seals the check valve and is axially translatable to open and close the flow path through the valve, The first turn of the coil has a surface that conforms to the engagement surface to close the valve when in contact with the engagement surface on the check valve body, An outer radial surface of the coil mating to a cylinder wall surrounding the check valve to provide a radial seal to the check valve. 15. The coil of claim 14 wherein each turn of the coil other than the first turn has a flat axial wall that provides an axial seal between each turn when subjected to axial force. Injection unit for metal forming machines, An injection screw and a check valve on one end of the injection screw, The check valve has a seal, the seal comprising a spirally wound coil axially translatable to enclose the check valve body and to open and close the flow path through the valve, The first turn of the coil has a surface that conforms to the engagement surface to close the valve when in contact with the engagement surface on the check valve body, An outer radial surface of the coil mating to a cylinder wall surrounding the check valve to provide a radial seal to the check valve. 17. The injection unit of claim 16, wherein each turn of the coil other than the first turn has a flat axial surface and is sealingly coupled with the flat axial surface of an adjacent turn to provide an axial seal of the check valve. .

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