Patent Application
20090136614
The present invention relates to injection molding equipment and more particularly, relates to a plug insert for a hot runner manifold for injection molding of thermally sensitive resins.
Externally heated hot runner manifolds with internally drilled passages are typically used with injection molding machines when injecting resins into multi-cavity molds. Different types of resins from different resin sources may be mixed together in the manifolds prior to being inserted in the mold. Moreover, plastic molding requires the distribution of the resin to multiple locations, thus necessitating multiple passages or runners within the manifold.
Plastic resin injected into a manifold must flow against the manifold runner walls or passages. One problem that exists is that the thermal properties of the resin can be affected as the resin flows through the manifold. The amount of time the resin spends in the mold and the temperature of the resin in the mold will have an effect on the properties of the finished product.
It is well known that as resin is forced through the manifold system, a temperature differential develops in the resin between the temperature of the resin in the center of the channel and the temperature of the resin along the wall of the manifold due to shear within the resin itself. Some prior art manifold plugs have been designed to deal with this temperature differential caused by shear layers within the melt stream. One such prior art plug is shown in U.S. Pat. No. 5,683,731 assigned to the assignee of the present invention. Such manifold plugs are designed to serve a very specific purpose and a very complicated to manufacture given that the channel in the manifold plug must go from the exterior of the manifold plug to receive holder resin along the manifold wall to the center of the manifold or runner to remakes the colder resin along the manifold wall with the warmer resin at the center of the manifold or runner system.
Generally, manifolds are produced which are somewhat generic or general in design having an internal runner system with two or more runner passages which intersect at one more various points within the manifold. At the points of intersection, a hole is provided into which may be inserted a specially designed manifold plug. Each specially designed manifold plug is provided with internally drilled passageways specifically designed to link selected runner passageways within the manifold based on the resin sources needed for a particular molding. The prior art manifold plugs with internal passageways are created by drilling the manifold plug. This creates undesirable sharp corners and edges within the hot runner system. It is the sharp corners and edges that typically cause problems within the manifold by creating more sheer layers within the resin distribution system.
It is well known that thermally sensitive resin is sheared and thus overheated when injected under pressure over sharp corners or edges found within the manifold system. Sharp corners or edges occur whenever two or more passages intersect within the hot runner manifold especially within the manifold plugs.
Accordingly, what is needed is a system and method for providing hot runner manifold plugs that avoid the sharp corners and edges normally found in internally bored hot runner manifold plugs and wherein such manifold plugs are able to generally completely turn and distribute the volume of resin found in the source manifold.
The present invention features a manifold plug for a hot runner manifold of an injection molding system. The manifold plug includes a generally circular shaped outer surface. The generally circular shaped outer surface includes a channel extending along at least an arc in the outer surface of the circular shaped manifold plug. The manifold plug is configured for insertion into a generally circular shaped opening in the hot runner manifold. The hot runner manifold includes at least first and second unconnected runner passageways. The first and second unconnected hot runner passageways provide a passageway for flowable material.
The first and second unconnected runner passageways terminate in the generally circular shaped opening in the hot runner manifold. The channel or passageway in the generally circular shaped outer surface of the manifold plug is configured for fluidly connecting at least the first and second otherwise unconnected runner passageways. The channel in the generally circular shaped outer surface of the manifold plug extends only partially through and not completely through a cross-section of the manifold plug.
The channel in the generally circular shaped outer surface of the manifold plug is sized to generally accommodate the flow of material, such as resin, in the passageways of the manifold. In one embodiment, the channel alone accommodates generally the same flow as the manifold. In another embodiment, a channel in the outer surface of the generally circular shaped manifold plug cooperates with a channel on the inner surface of the generally circular shape hole in the manifold which accommodates the manifold plug to allow for sufficient flow to matched that of the flow in the manifold.
In the preferred embodiment, the generally circular shaped opening in the hot runner manifold and at least a portion of the manifold plug include an alignment keyway, for facilitating alignment of the manifold plug in the circular shaped opening in the hot runner manifold.
The manifold plug may also include a head portion having a circumference which is greater than a circumference of the generally circular shaped outer surface of the manifold plug. The head portion is sized and configured to frictionally engage with a corresponding shoulder region located in the generally circular shaped opening of the hot runner manifold.
These and other features and advantages of the present invention will be better understood by reading the following detailed description, taken together with the drawings wherein:
The present invention features a novel manifold plug 10,
A manifold plug 10 in accordance with the teachings of the present invention includes at least one channel 18 machined, milled or otherwise provided in the outer circular shaped surface 20 of the manifold plug 10. The channel 18 is located to appropriately interconnect with two or more passageways 14 located in the hot runner manifold as will be explained in greater detail below, and sized to accommodate generally the same resin flow volume as that carried by passageway 14 in the manifold plug. Channel 18 made carry this volume either alone, or in combination with a similarly shaped channel in the circular shaped sidewall 21 of the manifold 12. The channel 18 does not extend completely through the manifold plug 10 but rather, is disposed only on the outer surface 20 of the manifold plug. In this manner, the channel 18 may be milled, etched or otherwise provided in the outer surface of the manifold plug without any sharp edges or tight bends which would impact on the resin or other material flowing through the runners 14.
The manifold plug 10 includes a head portion 22 that is sized to press fit into a shoulder region 24 located in the manifold 12. In addition, the manifold 12 as well as the head portion 22 of the manifold plug may each include a keyway or other similar element 26 which facilitates and ensures proper orientation of the manifold plug within the opening 16 of the manifold 12 to guarantee that a proper flow path is established between two or more unconnected passageways 14 in the manifold which terminate in the opening 16 of the manifold.
As shown in
In another embodiment of the manifold plug 10,
Accordingly, the present invention provides a novel manifold plug for a hot runner manifold system for use with an injection molding machine which eliminates a sharp corners and edges found in the prior art manifold plugs which are drilled through the plug to interconnect runners or passageways. Most importantly, the present invention provides a novel manifold plug that is easy to manufacture and provides a resin flow passageway channel which can carry generally the same volume of resin as can be carried in passageway 14 in the manifold plug 12. thus the present invention is not used simply to carry a small volume of resin as in the prior art, to makes resins of different temperatures but rather, all of the directional change of the entire volume of the resin flowing to the manifold is accomplished by an easy to manufacture, low cost manifold plug.
It is important to note that the present invention is not intended to be limited to a system or method which must satisfy one or more of any stated objects or features of the invention. It is also important to note that the present invention is not limited to the preferred, exemplary, or primary embodiment(s) described herein. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention, which is not to be limited except by the allowed claims and their legal equivalents.
