Centering apparatus for injection mold machine

#This invention relates to a centering mechanism for use with injection mold systems and in particular to a centering mechanism utilizing a threaded rod to connect and maintain proper spacing of mold plates in the injection mold system.

#It is well known in the art of injection molding to use opposing faces of adjacent mold plates, one defining a cavity, the other including a mold core which mates with the cavity, creating a cavity therebetween. These plates are brought together and molten plastic is injected between adjacent mating plates. Mold plates are cooled to cause solidification of the plastic. The plates are then separated and the finished plastic article ejected. In order to achieve high volume production, a stack mold is often used, wherein two or more sets of molds are interspersed in sequence in which rows of mold cores and mold cavities (often referred to as mold levels or mold sets) are stacked in a single machine. In conventional stack molds, typically, a central, first mold plate is provided, for holding the mold cavities of the respective stacks of molds. Typically, the central plate comprises two or more abutting plates, and is connected to cooling lines and the like for cooling of the injected molten plastic.

#Two outer, second mold plates are located on either side of the central plate, with the entire system opening and closing during the molding process. One of the outer, second mold plates is affixed to a stationary platen of a conventional molding machine, while the other outer mold plate is attached to the moveable platen, so this other outer, second mold plate and the central first mold plate move in the opening and closing process of molding.

#FIG. 1 is a perspective view of a stack mold and the preferred embodiment of the centering apparatus in accordance with this invention in a closed position;

#FIG. 2 is a perspective partly broken away view of a stack mold and a preferred embodiment of the centering apparatus in accordance with this invention showing a rod outer portion separated from the rod central portion;

#FIG. 3 is a perspective view, with portions broken away, of an embodiment of the centering apparatus in accordance with this invention in a closed position;

#Referring to FIGS. 1 to 5, a preferred embodiment of a centering apparatus according to the present invention is generally indicated by reference 10. The mold centering apparatus 10 controls relative movement between the mold plates in an injection stack mold apparatus, generally indicated by reference 100. The features of the stack mold 100 are conventional and as such will not be discussed in further detail below. Shown in the FIGS. 1 and 2, the stack mold used with the invention includes a first mold plate assembly 12 positioned between a pair of second mold plates 14. The first mold plate assembly 12 is connected to the second mold plates 14 by the centering apparatus of the invention 10. The mold plates are movable along a mold axis, the direction of which is indicated by arrow 120. The first plate assembly includes mold faces 16 on opposite sides thereof. The second plates 14 include second plate faces 18 designed for mating with the faces 16 such that in the closed position, as shown in FIG. 2, molten plastic may be injected between the first 16 and second 18 plate faces, for producing mold plastic products. Such molten plastic is injected between the first and second mold plate faces in a known manner, typically through sprues extending through the first plate to nozzles leading through the plate faces.

#As shown in FIGS. 1 to 4, the centering apparatus includes an elongate threaded rod member 24 having a central portion 26, and two oppositely extending, outer portions 28 extending from the central portion 26 parallel to the mold axis 120 toward each of the second plates. The central portion 26 is attached to a peripheral portion 40 of the first plate, preferably by means of a connector block 36 defining an opening 38 therethrough for accepting said rod central portion 26. Preferably the central connector block 36 is releasably securable to the first plate peripheral portion 40 by means of screws inserted therethrough. The connector block may be comprised of two separate parts 46, abutting each other. The rod central portion (and as will be discussed below, the rod member when the portions of the rod member are secured together) is axially rotatable within said connector block 36 and thus with respect to the first plate. Preferably axial rotation is facilitated by bearings 72 positioned within the connector block opening. The rod member 24 is prevented from axial movement relative to said first plate. Preferably the rod central portion includes an annular flange 44 and a pair of such bearings 72 are positioned on either side of the annular flange 44. The two separable parts 46 may be inserted over opposite ends of the central portion 26 and abut each other at the position of the annular flange 44.

#Each outer portion 28 includes a threaded portion 30. As shown in FIG. 3, the threaded portions of each outer portion having the same thread pitch and count but are in opposite orientation to each other.