BACKGROUND OF THE INVENTION

Field of the Invention

The field of the invention relates to bushings for facilitating the engagement of a mix head to a mold.

Brief Description of the Prior Art

The manufacture of molded articles generally include the injection of a polymeric material into a mold. The material is allowed to harden, and the resulting article separated from the mold. The injection of the polymeric material may be accomplished by a device known as a mix head. Depending upon the material to be injected, the mix head mixes two or more materials prior to injection.

It is important that the mix head form a good seal with respect to the mold in order to avoid drawing air within the mold cavity. Potential leakage is also avoided. Forming a good seal becomes relatively difficult if the mix head is out of alignment or if other irregularities are present.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a good seal between a mix head and a mold.

It is another object of the invention to provide a mix head bushing which facilitates sealing engagement with mix head.

In accordance with these and other objects of the

invention, a mix head bushing is provided which includes a body portion having a flange extending radially outwardly therefrom and an inner wall defining an opening extending through the body portion. A resilient coating is adhered to the inner wall of the body portion. The coated inner wall defines a passage which includes a conical portion. The passage is preferably conical throughout its length. A second flange preferably extends radially inwardly from the body portion and over a selected portion of the passage. The body portion and both flanges are preferably annular in configuration. The inner surface of the second flange is preferably flush with the outer surface of the coating. The body portion preferably includes an upper surface which is coplanar with the upper surface of the radially inwardly extending flange.

In use, the mix head bushing is attached to the mold. The radially outwardly extending flange preferably includes openings extending therethrough for facilitating such attachment.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is an exploded perspective view of a mix head bushing and a fixturing assembly for allowing an elastomeric coating to be applied to the mix head bushing;

Fig. 2 is a side elevation view of a molding plug shown in Fig. 1;

Fig. 3 is a front end view thereof;

Fig. 4 is a rear end view of a molding cap shown in Fig. 1;

Fig. 5 is a sectional view thereof taken along line 5-5 in Fig. 4;

Fig. 6 is a rear end view of the mix head bushing;

Fig. 7 is a sectional view of the mix head bushing taken along line 7-7 in Fig. 6, and showing a mix head in phantom partially inserted therein;

Fig. 8 is a front elevation, schematical view of a molding apparatus;

Fig. 9 is a perspective view of a mold receptor; and

Fig. 10 is a top perspective view of a bathtub shell

DETAILED DESCRIPTION OF THE INVENTION

A mix head bushing 10 is provided for engagement wit a mix head as the latter injects a polymeric material, such as an expandable foam, into a mold. The bushing is attache to the mold when in use. The mix head, which has an end configuration corresponding to the inner configuration of the mix head bushing, is insertable within the mix head bushing. It is important that a good seal be formed betwee the mix head and mix head bushing so that air is not drawn into the mold during the injection of the polymeric material. The mixture of air with the injected, hardenable material causes the production of a defective product.

Referring to Fig. 1, the mix head bushing 10 is sho as part of an exploded assembly including the fixturing which is used to provide a coating of selected thickness upon the inner wall 12 of the body portion 14 thereof. Th mix head bushing 10, which is preferably made from aluminu includes an annular flange 16 extending radially outwardly from the body portion 14. Four holes 18 extend through th flange 16, each of which is separated from two adjacent holes by ninety degrees. The walls defining the holes are preferably chamfered, as best shown in Fig. 6.

The inner wall 12 of the body portion 14 defines a substantially conical passage 20 which is coaxial with the axis of the annular flange 16. A second annular flange 22 extends radially inwardly from the body portion 14 and over a portion of the relatively narrow end of the conical passage 20. The inwardly extending flange 22 includes a substantially planar outer surface which is substantially coplanar with one of the end surfaces of the body portion 14. Both the inner wall 12 defining the passage 20 and the inner edge 24 of the inwardly extending flange 22 extend at acute angles with respect to the axis 26 of the mix head bushing 10. This acute angle is preferably, though not critically, about fifteen degrees.

An annular groove, and/or one or more indentations, are preferably formed within the inner wall 12 of the body portion. Such a groove 28 is shown in Fig. 7. The groove may be semicircular in cross section as shown. It helps maintain a polymeric coating 30 within the passage 20 as the mix head (not shown) is inserted and withdrawn from the passage.

The coating 30, which should be at least about one quarter of an inch in thickness, is applied to the inner wall 14 when the mix head bushing 10 is mounted to the fixturing assembly shown in Fig. 1. Such a thickness insures that sufficient resiliency is provided. The outer surface of the coating 30 extends at the same fifteen degree angle with respect to the axis 26 of the mix head bushing as the inner edge 24 of the inwardly extending flange 22.

The fixturing assembly includes a molding plug 32 and a molding cap 34. The molding plug and molding cap may be secured to each other by a head cap screw 36 which extends through a flat washer 38, the molding cap, and threadably engages the molding plug.

Referring to Figs. 2-3, the molding plug 32 includes

a cylindrical body 40 having a generally conical end portio 42. The relatively narrow end of the conical end portion 4 includes a rim 44 which projects radially slightly beyond the outer surface thereof. A threaded bore 46 extends through the conical end portion 42 and into the cylindrical body 40. The bore 46 is coaxial with the longitudinal axis of the molding plug 32.

The molding cap 34, shown in Figs. 1, 5 and 6, includes a substantially cylindrical body 48 having an axial bore 50 extending therethrough. One end of the body 46 includes a shallow recess 51 which is defined in part by an annular rim 52. A forty-five degree bevel is formed betwee the rim and the bottom surface of the recess.

The diameter of the rim 44 of the molding plug 32 is substantially the same as the diameter of the passage 20 as measured at the inner edge 24 of the inwardly extending flange 22. The exterior surface of the rim 44, like that o the inner edge 24 of the flange 22, forms about a fifteen degree angle with the longitudinal axis of the molding plug. The diameter of the recess 51 is larger than that of the small end of the passage 20.

Once the mix head bushing 10 is locked into position between the molding plug 32 and the molding cap 34, the molten seal material is poured into the conical recess formed between the inner wall 12 of the mix head bushing an the outer surface of the conical end portion 40 of the molding plug 32. The seal material, preferably a polyurethane elastomer, is allowed to harden. As shown in Figs. 1 and 7, the inner edge 24 of the second annular flange 22 remains uncoated, thereby allowing the steel mix head to engage the aluminum flange. A small step 30A is formed in the coating 30 just beneath the flange 22 due to the rim 44 of the molding plug 32. The inside diameter of the coated bushing is slightly smaller than the outside diameter of the conical end of the mix head to be inserted

therein, except at the step 30A where the diameters are equal. The molding plug 32 is detached from the molding cap 34 by removing the cap screw 36 from the threaded bore 46 once the coating 30 has hardened.

The mix head bushing 10 may be employed in a molding apparatus 54 as shown in Fig. 8. The apparatus 54 includes a platform 56 onto which a mold receptor 58 is mounted. A mix head 60 is positioned below the platform 56 for injecting polymeric foam through a conduit in the platform 56 and into the mold receptor 58. The mix head 60 includes a tapered end, as shown in Fig. 7. The tapered end of the mix head is inclined at the same angle with respect to the axis 26 of the mix head bushing as the surfaces of the coating 30 and the inner edge 24 of the inwardly extending flange. The mold receptor 58 shown in Fig. 8 is adapted for receiving a bathtub shell 64, leaving a void between the non-finish side 66 of the shell and the upper face 68 of the mold receptor 58. The bathtub shell 64 is placed within the mold receptor with its apron 76 positioned along the front mold receptor face 74.

A male mold closing member 70 has a rubbery elastomeric surface which fits snugly within the bathtub shell 64 on the finish side 65 thereof, sealing the shell 64 to the mold receptor 58 and forming a closed cavity between the mold receptor face 68 and the shell's non-finish side 66. The closing member 70 also helps to minimize warp, bowing and distortion of the bathtub shell 64 during the injection molding process.

A hydraulically operated system 72 lowers and retains the male mold closing member 70 against the bathtub shell 64 and mold receptor 58 during the molding process. As illustrated in Figs. 8-10 and discussed briefly above, the mold receptor 58 includes a mold receptor face 74 for forming a void between it and the non-finish side of the bathtub shell apron 76. The mold receptor 58 also includes

a front apron door 78 which is covered with an elastomeric material to sealably engage and hold the apron 76 of the bathtub shell to the mold receptor 58 during the injection molding process. Two side doors 80, each covered with elastomeric material are also incorporated as parts of the mold receptor 58. Each includes channels 80A and 80B for molding of the polymeric foam surrounding the small brace 8 and a relatively large brace 84, respectively, within the finished product. As with the apron door 78, side doors 80 sealably engage and hold the bathtub shell to the mold receptor 58 during the injection molding process.

An aperture 86 in the mold receptor 58 communicates with the mix head 60 for introducing the hardenable polymeric foam into the void between the mold receptor face 68 and the bathtub shell 64. The mix head bushing 10 is mounted to the mold receptor 58 such that the passage 20 is aligned with this aperture 86.

A plurality of ejectors 88 are positioned in the mol receptor 58 and serve to separate and eject the molded bathtub from the mold receptor 58 after the molding process has been completed. Preferably, the ejectors are cylindrical rods which are hydraulically activated from a recessed position to an ejected position (shown in Fig. 9) and vice versa.

In operation, a bathtub shell 64 is positioned withi the mold receptor. The bathtub shell is preferably constructed from steel which has been coated with enamel at least on the finish side 65 thereof. The shell 64 sealingl engages the mold receptor 58 by lowering the male mold closing means 70. The two side doors 80 are closed to form sealed molding channels about the small and large braces 82 84 of the shell. The front door 78 sealably engages the finish side of the apron 76 and seals against the rim of th male mold closing means 70.

The hardenable polymeric foam is introduced from the mix head 60 through the aperture 86 in the bottom of the mold receptor 58. The mix head bushing 10, being secured to the bottom of the mold receptor 58 by screws or bolts extending through the holes 18 in the flange portion 16 thereof, allows the tapered end of the mix head 60, as shown in Fig. 7, to sealingly engage and slightly compress the conical inner surfaces of the mix head bushing defined by the polyurethane elastomeric coating 30. The inclined inner edge 24 of the inwardly extending flange 22 is also engaged by the mix head upon full insertion within the passage 20. Such a seal will be formed even if the mix head is slightly misaligned or worn. This allows the foam to be injected without the danger of drawing air within the molding cavity.

Once the foam has cured, the front and side doors 78, 80 are opened and the male mold closing member 70 retracted. The molded bathtub, which is formed by the shell and the hardened foam adhered thereto, is lifted partially out of the mold receptor 58 by the hydraulic ejectors 88. It may then be removed entirely from the receptor by manual or mechanical means. The mix head bushing 10 may be removed from the mold receptor and cleaned. The inwardly extending flange 22 protects the polyurethane elastomer coating 30 as the top surface of the bushing is scraped clean.

Although illustrative embodiments of the present invention have been described herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various other changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention.