US 3854521 A
Metal die casting apparatus including three abutting plates of which the outside plates are movable relative to the center plate. The casting is formed in one plate and the gate for leading the molten metal to the casting is formed in the other plates. After forming the casting, the gate is broken off and ejected by movement of one end plate. The casting is then ejected by movement of the other end plate. The novel plate apparatus and the method of degating provides a pinhole break-off point so that trimming of the cast part is unnecessary.
Description (OCR text may contain errors)
United States Patent 1191 Hannes Dec. 17, 1974  Assignee: Coats & Clark, Inc., New York,
 Filed: July 25, 1972  Appl. No.: 274,910
52 11.5.01 164/347, 164/70, 164/131, 64/264z 12 4/3103, .6 ./.26 LQ/ 2 l6 51 Im. c1 ..B22d 1/00  Field of Search 164/113, 69, 303, 70, 347, 164/347 US, 265, 264, 262, 131, 344, 404,
3,627,023 12/1971 Clark 164/264 Primary Examiner-J. Spencer Overholser Assistant Examiner-V. K. Rising 5 7 ABSTRACT Metal die casting apparatus including three abutting plates of which the outside plates are movable relative to the center plate. The casting is formed in one plate and the gate for leading the molten metal to the casting is formed in the other plates. After forming the casting, the gate is broken off and ejected by movement of one end plate. The casting is then ejected by movement of the other end plate. The novel plate apparatus and the method of degating provides a pinhole break-off point so that trimming of the cast part is unnecessary.
8 Claims, 6 Drawing Figures 1 SELF CONTAINED METAL CASTING DIES BROAD STATEMENT OF INVENTION DESCRIPTION OF THE PRIOR ART In the prior art the casting of metal parts is effected by injecting the molten metal from a nozzle into a runner or gate that leads to the recess for forming the cast part. After casting, the part and the gate form an integral unit, and the gate has to be broken off before the cast part is further treated. The gate can be broken off by various procedures, such as a special tool or tumbling, but this results in a rough surface that must be later smoothed, trimmed or otherwise treated. Accordingly, it would be desirable in metal casting to be able to break off the gate without the necessity for the trimming or tumbling operation.
DESCRIPTION OF THE INVENTION The present invention provides a metal die casting apparatus including three abutting die plates of which the outer two are movable for separation of the attached gate from the cast part.
In the present invention metal die casting apparatus is provided which includes three abutting plates with the casting formed in one outer plate and the gate in the other two plates, separation of the gate from the cast part being effected by movement of one outer plate.
A further provision of the present invention isv a metal die casting apparatus having three abutting plates in which the cast part is formed in one plate and the other two plates are configured to provide a conical gate with a break-off tip.
There is further provided by the present invention a metal die casting apparatus having three abutting plates in which the cast part and attached gate are formed to be separately degated and ejected by pins sliding through the outside plates.
There is also provided in the present invention a method of metal die casting in which plates are positioned in abutting relationship within which a cast part and attached gate are formed, the part and gate being separately ejected by movement of the outer plates.
A further provision of the present invention is a method of metal die casting in which abutting plates having a cast part and attached gate formed therein are sequentially moved relative to each other, and the plates include pins that slide therein to separately eject the cast part and the gate.
In a preferred embodiment of the die casting apparatus three plates are placed in abutting position so that molten metal can be injected therein. One of the outside plates includes a recess in which the part is cast, and the center plate includes a through opening while the other outside plate includes another recess. The opening and the other recess form the gate during casting. Each of the outside die plates is movable relative to the center plate. The opening in the center plate is conically shaped and tapers to a small opening at the end abutting the recess where the part is cast. After the molten metal solidifies, the outside plate including part of the gate is moved away from the center plate thereby breaking off the gate from the part. A pin is slidably mounted within this movable plate and projects therefrom so that when it strikes a fixed part of the machine, the gate which has been broken off from the cast part is then ejected by the sliding ejection pin. It is to be noted that the gate is conically formed tapering to its smallest size where it contacts the cast part so that breakage is easily effected at this contact point. Moreover, the part of the gate in the first movable plate is larger in size than the rest of the gate to insure that the breakage occurs at the cast part. The other outside plate including the cast part is then moved relative to the center plate and includes a sliding ejection pin that ejects the cast part when it strikes a fixed part of the apparatus. This sequential ejection of the gate and cast part provides a pinhole break-off point and ejection of the part whereby trimming in unnecessary.
A further provision of the present invention is a method of metal die casting wherein three die plates are first placed in abutting relation so that molten metal injected therein will form a cast part in one outside plate and an attached gate that is partly within the inside plate and partly in the other outside plate, the gate within the center plate being conically shaped and tapering toward the cast part. The outer plate including part of the gate is then moved away from the center plate for degating causing the gate to break off from the cast part at the small conical tip, and a sliding ejection pin then knocks the gate out of the die plate. Subsequently, the other outside die plate including the cast part is moved relative to the center plate and a sliding pin mounted therein operated to eject the cast part from the die plate.
The nature of the present invention will become more clearly apparent and better understood from the following description and accompanying drawings in which:
FIG. 1 is a front elevational view illustrating a die cast element and its attached gate as formed by a prior art procedure;
FIG. 2 is a schematic view, partly in section, showing the die plates of the present invention in abutting relation;
FIG. 3 is a view similar to FIG. 2 showing a displaced movement of one of the die plates;
FIG. 4 is a view similar to FIG. 3 showing a further step in the operation of the present invention;
FIG. 5 is a view similar to FIG. 3 showing a displacement of the other outside die plate; and
FIG. 6 is a view of the gate formed in the present invention.
In FIG. 1 a cast part 10 is shown which may be a metal slider element of a zipper. In the prior art when this slider is die cast of metal, the molten metal is introduced to a runner or gate 12 which has a fan-shaped part 14 where the metal flows into the mold or recess forming cast part 10. After solidification, cast part 10 is thereby attached to gate 12, and it is necessary to degate part 10. This has been done in the prior art by a special tool or by tumbling the assembled part and attached gate, but it is then necessary to trim part 10 since the surface is rough where fan-shaped part 14 breaks off.
In the present invention as shown in FIGS. a5 a novel arrangement of die plates and method of degating is presented resulting in an improved break-off arrangement so that trimming is no longer necessary. It is understood that the die casting apparatus would include the usual support with a power drive and cam actuation to provide for the movement of the parts. Since such elements are all conventional, they are not shown for purposes of clarity, and only the novel die plates and associated features are illustrated.
Three die plates constitute the primary novel feature and includes a center plate 16 which is substantially fixed with respect to the apparatus and outside plates 18 and 20 which are relatively movable with respect to center plate 16. In FIG. 2 the die plates are shown in the normal casting position in abutting relation with the recesses and opening described hereinafter ready to receive for the injection of the molten metal, such as zinc. Outside plate 20 is shown as a first die plate and includes a first recess 22 which is formed on the side abutting center plate 16 and in which the cast part is formed. A sliding ejection pin 24 is mounted within plate 20 and located so that it can slide into recess 22.
Center plate 16 includes a through opening 26 which is generally conically shaped. One end includes a small opening 28 in alignment with the approximate center of recess 22 and enlarging therefrom at a predetermined conical angle for approximately Va of the thickness of plate 16. Opening 28 continues to enlarge therefrom at a smaller angle and terminates in enlarged opening 30 at the'other end of plate 16 where it abuts plate 18.
Outside plate 18 includes a second recess 32 having a special configuration and generally aligned with opening 30. The configuration of recess 32 has a transverse dimension parallel to the surface of plate 18 which is greater than the corresponding transverse dimension of opening 30. As shown in FIG. 2 a top surface of recess 32 extends generally perpendicular to the surface and continues on to form a concave curved portion 34 of the plate to connect with a base surface 36. It is understood that concave curve 34 extends around the peripheryof recess 32 which is generally circular in shape, and a convex curved portion 38 of the plate 18 connects the lower part of base curve 34 with the outer abutting edge as shown in FIG. 2. This convex curvature 38 is an important feature of the invention, and although the exact curvature is not critical, it must be of a convex nature as will be explained hereinafter.
As shown in phantom at the top of FIG. 2, a nozzle 40 injects molten metal into a conduit 41 thereby forming a runner 42 (see FIG. 4) so that the molten metal flows into opening 26 and recesses 22 and 32.
As seen in FIG. 3, a cast part 44 has been formed in recess 22. An attached gate 46 was formed by the molten metal with part of the gate in inner plate 16 and part of the gate in outer plate 18. Originally cast part 44 is formed integral with gate 46, but FIG. 3 shows a step in the breaking off of gate 46. As a feature of the present invention, the outer plate 18 is first moved in a direction perpendicular to the surface of plate 16 and away from fixed plate 16 to the position shown in FIG. 3. Since the attaching connection between part 44 and gate 46 is smaller than any other part of gate 46, breakoff occurs at the abutment of plates 16 and 20. This can be considered a pinhole break-off point since the opening 28 is sufficiently small so that the break-off leaves a small-mark in the nature of a pinhole that does not require trimming as in the prior art. In fact, it is possible to design the location of the opening 28 so that the attachment of cast part 44 and gate 46 occurs at a re cessed area, the pinhole marking being scarcely visible and causing no problem as to any rough surface.
Plate 18 includes a pin 33 slidable therein that is positioned in the casting position shown in FIG. 2 to have one end abutting recess 32. In FIG. 3 plate 18 has been moved to the right and it will be noted that ejection pin 33 is approaching a fixed part 48 of the apparatus. Pin 33 is mounted so that it can slide within gate 18, and in FIG. 4 pin 33 is seen to strike a fixed part 48 whereby it is slid into recess 32 to eject gate 46. In FIG. 4 gate 46 is in the process of being ejected to fall into the space between plates 16 and 18.
In FIG. 5 the next step of the operation is shown where outer plate 20 is moved to the left relative to fixed center plate 16. An ejection pin 24 is mounted to slide within plate 20 in the same manner as pin 33 is mounted in plate 16. Accordingly, when pin 24 strikes a fixed part 50 of the apparatus, the end of pin 24 slides into recess 22 so that die cast part 44 is ejected therefrom and falls into the space between plates 16 and 20.
From the above description it is clear that a sequence of steps provides the novel method features of the invention, and the plate arrangement with the novel configuration thereof provides the gate with the pinhole break-off point. The gate itself is formed in a particular configuration as shown most clearly in F Ig. 6 so that the movement of die plate 18 allows the desired break-off and particular ejection to take place.
As mentioned previously part of gate 46 is formed in the center die plate 16 and part of the gate is formed in movable outer plate 18. Since recess 26 has larger end 30 opposite smaller end 28 which abuts recess 22, gate 46 is formed with a generally conical shape having a tip 52 of smallest size as compared to the rest of gate 46 and therefore the weakest strength to insure that breakage will occur at that tip point when die plate 18 is moved away from die plate 16. Since recess 32 has a larger transverse dimension, an undercut portion 54 is formed as part of gate 46. An intermediate area 56 between end 52 and undercut portion 54 provides a change in the angular conical form. A greater angle is provided between end 52 and intermediate area 56, and a smaller conical angle is provided from area 56 to undercut portion 54.
A critical feature of the invention is a concave area 58 in the gate that is formed due to convex surface 38 in die plate 18. The large or head area of gate 46 includes rounded surface 60 formed by the curved surface 34.
Since the concave area 58 is held in plate 18, and since point 52 is of such small size, it is clear that movement of die plate 18 to the right (FIG. 3) will cause gate 46 to be broken off at point 52 and be retained within die plate 18 as shown in FIG. 3.
A further important feature of the invention is the location of sliding pin 33 in the upper part of recess 32 as shown in FIG. 2. When one end of pin 33 strikes fixed part 48, the other end is caused to strike an upper part of gate 46 remote from concave area 58. This is shown in phantom in FIG. 6. Since pin 33 strikes this upper part of gate 46, a pivoting action by gate 46 takes place on curved surface 38, and the gate 46 is ejected in a pivotal manner from die plate 18 as indicated by the arrow 62 in FIG. 4.
The above description is a preferred embodiment of the subject novel die casting apparatus for forming and ejecting metal parts so that trimming is not necessary. Further modification is possible within the scope of the invention. For example, the die cast part may be formed with part in plate 20 and part in plate 16. In such case the draft angle would be different in the plates to insure that the die part would be retained in plate 20 upon the movement away from fixed plate 16. Corresponding modification would then be made in the through opening 26. It is also possible to change the shape of gate 46 as long as the smallest or pinhole point is retained at the end attached to the cast part and a concave portion is provided at the other end to provide for a retention within the movable plate and then for pivotal ejection.
It will be understood that still further changes and modifications may be made by those skilled in the art in the particular features of the apparatus and method which has been described above for illustrative purposes without departing from the scope of the invention as defined by the following claims.
What I claim is:
1. Die casting apparatus having a plurality of die plates for forming a metal cast part and attached gate part therein comprising a first outer die plate having a first recess in which said cast part is formed by injecting molten metal therein;
a second die plate positionable in abutment with said first die plate during casting and having an opening therethrough in communication with said first recess to permit said molten metal to flow through said opening into said first recess;
said second die plate being mounted in a substantially fixed position within said apparatus, and said first die plate being movable with respect thereto;
a third outer die plate having a second recess therein,
said second recess and said opening in communication with each other when said second and third plates are in abutment and adapted to form the gate part when the molten metal is injected therein, said third plate being in abutment with said second plate during casting and being movable relative thereto,
said second recess being open at the surface of said third die plate and including at one end a portion which extends beyond the area of the recess open at the surface of the third die plate and thus constitutes an undercut portion of said third die plate, said undercut portion including a convex surface extending inwardly from the surface of the third die plate and terminating at a concave surface portion of said third die plate within said second recess, said convex and concave surface portions being shaped to permit removal of said gate part only by pivotal movement about said convex surface portion; and means mounted on said first and third plates for ejecting said cast part and said gate part respectively from said die plates. 2. Die casting apparatus according to claim 1 in which said opening has an enlarged end on that part of said second die plate abutting said third die plate, and
the end of said opening abutting said first die plate is substantially smaller than said enlarged end.
3. Die casting apparatus according to claim 2 in which the surface of said opening is substantially coneshaped.
4. Die casting apparatus according to claim 2 in which said second recess has a dimension across the face of said third die plate abutting said second die plate that is greater than the dimension of said enlarged end of said opening adapted to be aligned therewith.
5. Die casting apparatus according to claim 1 in which said ejecting means comprise pins slidably movable within said first and third plates to accomplish the ejection when said die plates move away from said second plate and said pins contact a fixed portion of the apparatus.
6. A die casting apparatus for forming a metal cast part and attached gate part therein, comprising: a dirst die member provided with a surface, a second die member provided with first and second opposite surfaces, and a third die member provided with a surface, a first recess in said first die member extending to said surface thereof, said first recess being shaped to form said cast part, an opening in said second die member extending between said first and second opposite surfaces thereof, and a second recess in said third die member extending to said surface thereof, siad die members being movable to a casting position with the first surface of said second die member abutting said surface of said first die member and the second surface of said second die member abutting said surface of said third die member with said first and second recesses in communication by way of said opening, saidopening and said second recess forming a recess for said gate part, a dimension of said opening in the plane of said second surface being larger than the dimension thereof in the plane of said first surface, and a dimension of said second recess in the plane of said surface of said third die member being greater than the corresponding dimension of the opening in the plane of said second surface, said second recess being open at the surface of said third die member and including at one end a portion which extends beyond the area of the recess open at the surface of the third die member and thus constitutes an under cut portion of said third die member, said undercut portion including a convex surface extending inwardly from the surface of the third die member, and terminating at a concave surface portion of said third die member within said second recess, said convex and concave surface portions being shaped to permit removal of said gate part only be pivotal movement about said convex surface portion, whereby cast metal breaks at said first surface upon separation of said first and second die parts and whereby said gate part is retained in said second recess upon relative separation of said second and third die members, and means for ejecting said cast part and said gate part from said first and third die members respectively.
7. The apparatus of claim 6 wherein said means for ejecting said gate part from said third die member comprises a pin mounted in said third die member to slidably extend through said third die member into said second recess for pivotally ejecting said gate part about said convex portion.
8. The apparatus of claim 7 wherein said pin extends through said third die member offcenter of said second recess on the side thereof away from said convex portion.
I UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,854,521 Dated December 17, 1974 Inventor(s) KARL I-IANNES It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
Column 1, line l, after "METAL" add DIE Column 2, line 66, change "a-S to 2 5 Column 6, line 18, change "dirst" to first line 27, change "siad" to said Signed and sealed this 10th day of June 1975.
C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks