NOZZLE TOUCH SPRUE BUSHING DEVICE

Abstract: A nozzle touch sprue bushing device for a unit-type injection metal mold which includes a molding body such as a metal mold including an inner mold element which is re­ movably mounted on an outer frame mounted on an injecting molding machine, wherein a sprue bush (1) has a nozzle touch (11) provided at a rear end thereof for fitting with an end of a nozzle (7) of an injecting machine, and has a front end (12) formed in such a fitting configuration as to allow fitting engage­ ment thereof with a material admitting portion of a metal mold.

Description: This invention relates to a nozzle touch sprue bushing device to be provided at an introducing and connecting portion for a plastic material such as a synthetic resin provided on an outer frame in a unit-type injection metal mold or the like wherein a molding element body such as the metal mold or the like includes an inner mold element which is removably mounted on the outer frame mounted on an injection molding machine. Description of the Prior Art In an injection molding machine which injects a molten plastic material at a high temperature and at a high pressure to mold at one stroke, if connection of a material introducing path is incomplete even a little, leakage of resin will take place so that not only articles may fail but also there is the possibility that a danger may be caused in operation. Thus, conventionally the introducing paths of an injecting machine and a molding element are formed as an integral single material introducing path except at a nozzle touch between the injecting machine and the molding element, and contacting connection between the introducing paths cannot be anticipated. However, in order to change the type of articles to be molded, the entire metal mold must be exchanged, which is very uneconomical. Thus, in order to cope with this problem, an improvement has been proposed wherein a metal mold is divided into an inner mold element and an outer frame so that the type of articles to be molded element. In such an arrangement, interconnection between the introducing paths of the inner mold element and the outer frame relies upon the accuracy of a mirror face working of mutually contacting faces of the inner mold element and the outer frame and also upon a positioning and fixing technique depending upon lapping upon fitting of the inner mold element into the outer frame. In this instance, the steps at which a highest skill is required for contacting connection of the introducing paths are to finish contacting faces of both elements in which the relay introducing paths are provided so that they may have surfaces of a very high accuracy and to position the contacting faces in parallel to each other and contact them closely to each other. If the accuracy in such surface finish is low, this will cause a problem that leakage of a resin material may take place so that unacceptable molded articles may be produced. Incidentally, in molding of a plastic material, molten plastic material is injected at a high pressure of 2,000 kg/cm² to 1,500 kg/cm² in the case of engineering plastics and of at least 300 kg/cm² in the case of plastics for toys and so on which require a very high accuracy. US-A-4299791 discloses apparatus according to the preamble of claims 1 and 3. The sprue bush is movable, but biased toward the nozzle, and acts as a piston when the nozzle is removed, any excess moulding material being taken up by the expanding piston chamber. A practically identical apparatus is disclosed in JP-A-60-168619. SUMMARY OF THE INVENTION It is an object of the present invention to provide a nozzle touch sprue bushing device wherein an end of a sprue bush having a nozzle touch formed thereon for fitting with an end of a nozzle of an injecting machine and a material admitting portion of a metal mold can be automatically fitted with each other so that resin injecting and introducing paths of an inner mold element and an outer frame of the metal mold and the injecting machine may be automatically interconnected without requiring a high skill. Accordingly, the invention provides a nozzle touch sprue bushing device according to claim 1, and according to claim 3. The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a vertical sectional side elevational view of a nozzle touch sprue bushing device according to a first embodiment of the present invention before an introducing path for a resin material or the like is connected thereto; Fig. 2 is a similar vertical sectional side elevational view of the nozzle touch sprue bushing device of Fig. 1 after the introducing path for a resin material or the like is connected thereto; Fig. 3 is a vertical sectional side elevational view of a nozzle touch sprue bushing device according to a second embodiment of the present invention before an inner mold element is mounted; and Fig. 4 is a similar vertical sectional side elevational view of the nozzle touch sprue bushing device of Fig. 7 after an inner mold element is mounted. DETAILED DESCRIPTION OF THE PREFERRED EMBODINENTS Referring first to Figs. 1 and 2, there is shown a nozzle touch sprue bushing device according to a first preferred embodiment of the present invention. The nozzle touch sprue bushing device shown includes a sprue bush 1 having a nozzle touch 11 formed at a rear end thereof and having a spherical face 12 at a front end thereof. An injection route 13 is formed at and extends through the center of the sprue bush 1. The nozzle touch sprue bushing device further includes a plate bush 2 having a spherical face contacting recess 22 formed at a rear end thereof corresponding to the spherical face 12 of the sprue bush 1 and having a contacting face 21 formed at a front end thereof for contacting with a contacting face 6 of a material admitting portion of an inner mold element of a metal mold. An injection route 23 is formed at and extends through the center of the plate bush 2. A housing 8 is provided in an interposed portion 5 of an outer frame or the like which is interposed between an injecting nozzle 7 of an injecting machine and the contacting face 6 of the inner mold element of the metal mold, and a compression coil spring 3 is received in the housing 8 and extends between a flange 14 of the sprue bush 1 and another flange 24 of the plate bush 2. Consequently, the sprue bush 1 and the plate bush 2 are urged to move away from each other by the spring 3, and the sprue bush 1 is packed by a locating ring 4 so that an upper face of the flange 14 of the sprue bush 1 is resiliently pressed against a bottom face of the locating ring 4 while a bottom face of the flange 24 of the plate bush 2 is resiliently pressed against an upper face of a bottom plate of the housing 8. As the contacting face 6 around an introducing path 61 is contacted with the contacting face 21 of the plate bush 2 as a result of fitting of a molding element such as the inner mold element of the metal mold in position, the spring 3 is compressed as seen in Fig. 2 until the spherical face 12 of the sprue bush 1 and the spherical face contacting recess 22 of the plate bush 2 are contacted with each other, which constitute a universal coupling structure described hereinabove. Further, as the injection nozzle 7 is fitted with the nozzle touch 11 of the sprue bush 1, the injecting path 71, injection routes 13 and 23 and introducing path 61 are opened. Subsequently, operation of the nozzle touch sprue bushing device will be described. If the contacting face 6 of the inner mold element having the introducing path 61 therein is contacted obliquely with the contacting face 21 of the plate bush 2, the plate bush 2 is moved so that the spherical face contacting recess 22 thereof is brought into contact with and then slidably moved on the spherical face 12 of the sprue bush 1 until the contacting face 21 of the plate bush 2 is brought into a parallel position to the contacting face 6 of the inner mold element by the pressure thereupon from the contacting face 6 and compression of the spring 3 is averaged. The corresponding position of the plate bush 2 is corrected in this manner. When a material is to be injected, the injection nozzle 7 is advanced so that it is fitted with the nozzle touch 11 of the sprue bush 1 as seen in Fig. 2 and moves the sprue bush 1 while compressing the spring 3. In this instance, since the compression of the spring 3 has been already averaged by the pressure from the contacting face 6 of the inner mold element, the pressing force of the injection nozzle 7 is transmitted to the sprue bush 1 without causing any displacement of the sprue bush 1. Since the nozzle touch sprue bushing device of the first embodiment of the present invention has such a construction as described above, each of the communicating portions for the resin injecting introducing path can be automatically made into a hard metal touch without requiring a high skill, which will contribute to reduction in cost of the metal mold and enable coping with molding at a high injecting pressure. Referring now to Figs. 3 and 4, there is shown a nozzle touch sprue bushing device according to a second embodiment of the present invention. The nozzle touch sprue bushing device shown includes a sprue bush 1 having a nozzle touch 11 formed at a rear end thereof and having a convex fitting portion 32 formed at a front end thereof. The convex fitting portion 32 of the sprue bush 1 has such a shape as to allow the same to fit with a recess 31 formed in a material admitting portion 20 of an inner mold element of a metal mold, and injection route 13 penetrates the sprue bush 1 at the central portion thereof. While, the fitting shape of the convex fitting portion 32 and the recess 31 is not limited cylindrical shape but also rectangular one. An introducing path 61 is formed in a continuous relationship to the recess 31 at the center of the material admitting portion 20 of the inner mold element. The sprue bush 1 is fitted in an interposed portion 5 of an outer frame or the like which is interposed between an injection nozzle 7 of an injecting machine and the material admitting portion 20 of the inner mold element of the metal mold, and the sprue bush 1 is fixed to the interposed portion 5 by means of a locating ring 4. A backing plate 2A similar to the plate bush 2 of the nozzle touch sprue bushing device of the first embodiment shown in Figs. 1 and 2 is fitted on the sprue bush 1 and normally urged toward the material admitting portion 20 of the inner mold element by a compression coil spring 3 received in a housing 8 provided in a casing 91. The packing plate 2A has such an inner peripheral face of a suitable configuration such as a tapered face that it may closely contact with an outer peripheral fitting portion 33 of the sprue bush 1. Subsequently, operation of the nozzle touch sprue bushing device of Figs. 3 and 4 will be described. If the convex fitting portion 32 at the front end of the sprue bush 1 is fitted into the countersunk recess 31 provided in the material admitting portion 20 of the inner mold element of the metal mold, the basic fitting position of the inner mold element with respect to the outer frame 5 is automatically determined, and when the inner mold element is fixed to a fixed side plate 5A of the outer frame 5, the packing plate 2A which is mounted for movement and urged toward the inner mold element by the spring 3 is pushed by the inner mold element being fitted so that it is ring-fitted with the sprue bush 1 under the guidance of the outer peripheral fitting portion 33 of the sprue bush 1 while it seals the circumference of the recess 31 of the material admitting portion 20 of the inner mold element by the pressure thereupon caused by a reactive force of the spring 3. Since the nozzle touch sprue bushing device of the third embodiment of the present invention has such a construction as described above, the sprue bush and the material admitting portion of the metal mold are contacted with each other not depending upon flat face contact which will readily cause leakage of a material but depending upon different specific contact which will little cause leakage of a material and will assure interconnection of injection routes. Further, when the inner mold element or the like is to be mounted, fitting of the fitting portions of the sprue bush and the material admitting portion of the inner mold element with each other automatically determines the basic mounting position of the inner mold element in the outer frame, which facilitates a mounting operation of the inner mold element or the like. Also, there are effects that leakage of a resin material can be prevented completely without the necessity of improving the accuracy in face machining very much, and so on.

Claims: A nozzle touch sprue bushing device, comprising a sprue bush (1) having a nozzle touch (11) provided at a rear end thereof for fitting with an end of a nozzle (7) of an injecting machine, said sprue bush (1) having a front end (12) formed in such a fitting configuration as to allow fitting engagement thereof with a material admitting portion of a metal mold, and characterized in that said engagement is effected via a plate bush (2), an end portion (21) of which forms a contacting structure for closely contacting with a connecting injecting path contacting face (6) of said metal mold. A nozzle touch sprue bushing device according to claim 1, wherein said end (12) of said sprue bush (1) is formed so as to have a convex spherical face while said plate bush (2) is formed so as to have a spherical recessed face (22). A nozzle touch sprue bushing device, comprising a sprue bush (1) having a nozzle touch (11) provided at a rear end thereof for fitting with an end of a nozzle (7) of an injecting machine, said sprue bush (1) having a front end (32,33) formed in such a fitting configuration as to allow fitting engagement thereof with a material admitting portion of a metal mold, and characterized in that said engagement is effected via a backing plate (2A) which is fitted in a ring contact with the end (33) of said sprue bush (1). A nozzle touch sprue bushing device according to claim 3, wherein said end (33) of said sprue bush (1) is formed so as to have a truncated convex conical face while said backing plate (2A) is formed so as to have a truncated concave conical face. A nozzle touch sprue bushing device according to claim 1 or claim 3, wherein said sprue bush (1) and said plate bush (2) or said backing plate (2A) are packed in a housing space (8) and said sprue bush (1) is urged toward said injecting machine while said plate bush (2) or said backing plate (2A) is urged toward said metal mold. A nozzle touch sprue bushing device according to claim 5, wherein said sprue bush (1) and said plate bush (2) or said backing plate (2A) are urged by a spring (3).

Inventors: NAKAMURA, HAJIME C/O SANKYO ENGINEERING CO., LTD., NAKAMURA, SUSUMU C/O SANKYO ENGINEERING CO., LTD., YOKOI, KOICHI C/O SANKYO ENGINEERING CO., LTD.
Applicants: SANKYO ENGINEERING CO. LTD.
Application year: 1988
Main classification: B29C45
IPC codes: B29C45