JP7748637B2 - Hollow sprue - Google Patents

Description

The present invention relates to a hollow sprue used in the casting process of metalworked products.

Conventionally, the manufacturing process for metal processed products (typically dental prostheses and jewelry, hereafter referred to as metal prostheses) produced by casting has typically been as follows:

(Step A1) A dental technician (typically a dental technician or jewelry manufacturing technician) creates a dental prosthesis (hereafter referred to as a wax prosthesis) using wax as the material. In the case of dental prostheses, it is common to first create a plaster model (called an intraoral model) by taking a mold of the patient's oral cavity, and then create the wax prosthesis on top of the intraoral model.

(Step A2) The wax prosthesis is placed on the wax base via a sprue. A sprue is a solid rod-shaped jig made of a material such as plastic that can be completely incinerated. As shown in Figure 1, the end face E of a conventional sprue is cut off so that the angle α relative to the center line X of the sprue is approximately a right angle. The technician applies a small amount of melted wax (wax that acts as an adhesive) to one end face of the sprue to bond it to the prosthesis (so-called surface bonding), and then embeds the other end face of the sprue into the base. At this time, an appropriate amount of melted wax is piled up in a mound shape (build-up) around the connection points between the sprue and the prosthesis, and around the connection points between the sprue and the base, to increase the adhesive strength.

(Step A3) The wax base, sprue, and wax dental prosthesis are embedded in plaster. After the plaster hardens, it is heated to dissolve or vaporize the wax base, sprue, and wax dental prosthesis inside the plaster. This creates a continuous cavity inside the plaster that is modeled after the shapes of the base, sprue, and wax dental prosthesis.

(Step A4) Molten metal is poured into the cavity formed in the plaster that corresponds to the former base site. The cavity that corresponds to the former sprue site acts as a flow channel, and the molten metal flows into the cavity that corresponds to the former wax prosthesis site.

(Step A5) After the metal has hardened, the plaster is peeled off to obtain a metal product that integrates the metal prosthesis, sprue, and base. The sprue is cut from the metal prosthesis, and finally the metal prosthesis is polished to complete the final product, the metal prosthesis. When separating the metal prosthesis and sprue, the cut is made so that some of the buildup and sprue end remain on the metal prosthesis side. Any buildup remaining on the surface of the metal prosthesis is then removed by polishing. This prevents the metal prosthesis from being damaged during cutting.

As explained in step A5, during the manufacturing process of metal prostheses, it is necessary to remove any buildup or sprue ends remaining on the metal prosthesis by grinding. However, the prices of precious metals used as raw materials for metal prostheses have risen in recent years, and the cost of raw materials lost in this grinding process has now become non-negligible.

The present invention was made to solve these problems, and aims to provide a hollow sprue that increases the adhesive strength between the wax dental prosthesis and the sprue during the metal prosthesis manufacturing process, while also reducing the amount of metal used as a raw material for the metal prosthesis.

According to one embodiment, the hollow sprue is a sprue used in casting metal crafts, and is characterized in that it has a tubular body, and at least one end E1 of the body has a cutting surface S formed thereon that is inclined with respect to the axis X of the tube.
According to one embodiment, the hollow sprue is characterized in that a molten adhesive material is attached to a tip portion T formed on the cut surface S of one end E1 of the main body, and the tip portion T is penetrated into the wax prosthesis, thereby causing the molten adhesive material to flow into the internal cavity of the main body.
According to one embodiment, a method of using a hollow sprue is characterized by having a tubular body, at least one end E1 of the body having a cut surface S inclined with respect to the axis X of the tube, and includes the steps of applying a molten adhesive material to the end E1 of the hollow sprue and penetrating a tip T formed on the cut surface S of the end E1 into a wax dental prosthesis.
According to one embodiment, the method of using the hollow sprue further includes a step of planting multiple hollow sprues in a plate-shaped base, and in the planting step, the length of the hollow sprue is longer the closer it is to the center of the base.
According to one embodiment, the base is a plate-shaped base on which a plurality of hollow sprues are planted, and the longer the hollow sprues are planted, the closer they are to the center of the base.
According to one embodiment, the base has a multi-layer structure including a first layer and a second layer made of wax that is softer than the first layer.

The present invention makes it possible to provide a hollow sprue that increases the adhesive strength between a wax dental prosthesis and a sprue during the manufacturing process of a metal dental prosthesis, while also reducing the amount of metal used as a raw material for the metal dental prosthesis.

FIG. 1 is a diagram showing the structure of a conventional sprue. FIG. 2 is a perspective view of a hollow sprue 1. FIG. 2 is a front view of the hollow sprue 1. FIG. 2 is a rear view of the hollow sprue 1. FIG. 2 is a plan view of the hollow sprue 1. FIG. 2 is a bottom view of the hollow sprue 1. FIG. 2 is a left side view of the hollow sprue 1. FIG. 2 is a right side view of the hollow sprue 1. FIG. 2 is a cross-sectional view of a hollow sprue 1. 10A and 10B are diagrams showing how a dental prosthesis is connected to a hollow sprue 1. FIG. 1 is a cross-sectional view showing how a dental prosthesis is connected to a hollow sprue 1. FIG. 1 is a diagram showing an example of a wax dental prosthesis W into which a hollow sprue 1 has been inserted. FIG. FIG. FIG. 10 is a diagram showing the embedding process. FIG. 1 is a diagram showing an example of a casting CA produced in a casting process. FIG. 10A and 10B are diagrams showing an example of a metal technical work D produced in a cutting step. 10 is a flowchart showing an example of a method for using the hollow sprue 1.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. <Structure>
The structure of the hollow sprue 1 according to the embodiment of the present invention will be described with reference to FIGS.

Figure 2 is a perspective view of the hollow sprue 1, Figure 3 is a front view of the hollow sprue 1, Figure 4 is a rear view of the hollow sprue 1, Figure 5 is a plan view of the hollow sprue 1, Figure 6 is a bottom view of the hollow sprue 1, Figure 7 is a left side view of the hollow sprue 1, Figure 8 is a right side view of the hollow sprue 1, and Figure 9 is a cross-sectional view of the hollow sprue 1.

The hollow sprue 1 is a tubular structure. That is, it is a columnar object formed by extruding a doughnut-shaped cross section C along an orthogonal axis X. There are no restrictions on the length L, outer diameter R1, or inner diameter R2 (< R1) of the hollow sprue 1, but for example, when producing dental prostheses, it is convenient to use it if the following relationships are approximately 7 mm < L < 30 mm, 1 mm < R1 < 3 mm, and 0.1 mm < wall thickness (= R1 - R2) < 0.3 mm.

The material of the hollow sprue 1 is typically a plastic that can be completely incinerated, that is, a plastic that completely melts or vaporizes during the heating process. However, it is not limited to such plastics; any other material that is solid at room temperature, easy to process, and melts or vaporizes when heated may be used. However, the melting point of the material must be lower than that of the mold material, such as plaster, described below, and higher than that of the molten wax used as an adhesive for wax dentures.

At least one of the ends E1, E2 of the hollow sprue 1 is cut off so that a cut surface S is formed that is inclined relative to the axis X. For example, in the example shown in Figure 9, end E1 is cut off at an angle to form a cut surface S with a sharp tip T.

<Manufacturing method>
A typical method for manufacturing the hollow sprue 1 will now be described.
(Manufacturing Method 1) A hollow plastic rod of length LL (>L) is cut into pieces of length L. The cut surfaces are not perpendicular to the axis X of the hollow plastic rod, but are inclined at an angle. This allows the manufacture of a hollow sprue 1 with cut surfaces S formed at both ends E1 and E2.

(Manufacturing Method 2) A hollow plastic rod of length LL (>L) is cut into lengths of 2L. The cut surfaces may be perpendicular to the axis X of the hollow plastic rod. Next, the hollow plastic rod cut into lengths of 2L is cut at the length L position. The cut surfaces are not perpendicular to the axis X of the hollow plastic rod, but are inclined. This allows the production of a hollow sprue 1 in which a cut surface S is formed at one end E1 and a conventional perpendicular cut surface is formed at the other end E2.

<How to use>
A typical method of using the hollow sprue 1 will be described with reference to the flowchart of FIG.

(Step B1) A technician (typically a dental technician or jewelry manufacturing technician) molds a wax prosthesis using wax. In the case of dental prostheses, it is common to first create a plaster model (called an intraoral model) by taking a mold of the patient's oral cavity, and then mold the wax prosthesis onto the intraoral model.

(Step B2) The wax dental prosthesis is placed on a wax base via a hollow sprue 1. First, the wax dental prosthesis and hollow sprue 1 are bonded together, and then the hollow sprue 1 is implanted into the wax base (implantation process).

Figures 10 and 11 show how to connect the wax dental prosthesis and hollow sprue 1. The technician inserts the tip T of the cut surface S formed at the end E1 of the hollow sprue 1 into the wax dental prosthesis W. As shown in Figure 11, it is preferable to insert the cut surface S so that only a portion, not all, of it is embedded in the wax dental prosthesis W. This ensures that the area of the surface where the wax dental prosthesis W and hollow sprue 1 intersect is smaller than the area of cross section C.

When inserting the hollow sprue 1 into the wax prosthesis W, a small amount of preheated molten wax M is applied to the tip T of the hollow sprue 1 before the insertion. At this time, as shown in Figure 11, the molten wax M flows into the cavity inside the hollow sprue 1. At the same time, a small amount also adheres to the outer periphery of the hollow sprue 1, forming a buildup. The molten wax M gradually cools and hardens, bonding the wax prosthesis W and the hollow sprue 1 together.

In conventional sprues, the sprue is primarily supported by a buildup of molten wax M adhering to the outer periphery. In contrast, in the hollow sprue 1, the molten wax M also supports the hollow sprue 1 in the inner cavity, allowing for a stronger bond between the hollow sprue 1 and the wax prosthesis W. Furthermore, in the hollow sprue 1, the contact area between the molten wax M and the hollow sprue 1 is greater than in conventional sprues, resulting in a stronger adhesive force. In particular, in this embodiment, the cutting surface S is inclined relative to the direction of travel of the hollow sprue 1 (axis X direction), allowing more molten wax M to flow into the interior than when the cutting surface S is perpendicular to the axis X. This makes it easy to achieve a strong adhesive force.

As such, in this embodiment, the area of the surface where the wax prosthesis W and the hollow sprue 1 intersect is smaller than in the case of conventional sprues (the area of cross section C). Therefore, the size of the buildup formed around it can also be smaller than in conventional cases. Furthermore, because the molten wax M penetrates into the interior of the hollow sprue 1 and exerts adhesive force, the size of the buildup can be further reduced.

Figure 12 shows an example of a wax prosthesis W into which a hollow sprue 1 has been inserted. In this example, several types of hollow sprues 1 with different lengths L are used. Preferably, the color of the hollow sprues 1 may be changed depending on the length L. For example, if there are three types of hollow sprues 1 with lengths L1, L2, and L3, the hollow sprues 1 with length L1 are colored red, the hollow sprues 1 with length L2 are colored yellow, and the hollow sprues 1 with length L3 are colored green. This makes it easy to distinguish between hollow sprues of different lengths L.

Figure 13 shows the process of implanting multiple hollow sprues 1 into a wax base B. The wax base B has a plate-like shape, and in this example, it is disk-shaped. Preferably, the disk-shaped base B has a multi-layer structure including a first layer made of a relatively hard wax and a second layer made of a softer wax than the first layer. The hollow sprues 1 are implanted on the surface of the second layer. This allows the first layer to ensure the rigidity of the base B, while the flexibility of the second layer makes it easy to implant the hollow sprues 1, thereby efficiently progressing the implantation process. Furthermore, if the second layer is preheated before starting the process, the surface of the second layer will soften, further improving workability.

In the implantation process, the longest hollow sprue 1 is first implanted near the center of the disk. Subsequently, other hollow sprues 1 are implanted. At this time, as shown in the cross-sectional view of Figure 14, it is preferable to implant hollow sprues 1 with longer lengths L closer to the center of the disk and hollow sprues 1 with shorter lengths L further away from the center. For example, consider a case where the hollow sprues 1 are colored differently depending on their length L, with the hollow sprue 1 of length L1 being red, the hollow sprue 1 of length L2 being yellow, and the hollow sprue 1 of length L3 being green (L1 > L2 > L3). In this case, the red hollow sprue 1 is first implanted in the center of the base B, then the yellow hollow sprues 1 are implanted around the red hollow sprue 1, and finally the green hollow sprues 1 are implanted around the yellow hollow sprue 1. This facilitates the subsequent cutting process (the process of separating the metal prosthesis from the sprue).

(Step B3) The wax base, hollow sprue 1, and wax dental prosthesis are embedded in plaster (embedding process). Figure 15 shows the embedding process. First, the wax base with the hollow sprue 1 embedded therein is placed in a stainless steel casting ring CR. Next, liquid plaster is poured into the casting ring to embed it.
After the plaster hardens, it is heated to dissolve or vaporize the wax and plastic therein, thereby forming a series of cavities within the plaster that are molded to the shape of the base, the hollow sprue 1, and the wax dental prosthesis.

(Step B4) Molten metal is poured into the cavity formed in the plaster that corresponds to the site of the base (casting process). The cavity that corresponds to the site of the hollow sprue 1 becomes a flow path, and the molten metal flows into the cavity that corresponds to the site of the wax prosthesis.

(Step B5) After the metal has hardened, the plaster is peeled off, resulting in a metal product (casting CA) that integrates the metal prosthesis, sprue, and base (Figure 16). The technician uses a circular saw SW or similar tool to separate the metal prosthesis D from the casting CA (cutting process), and finally polishes the metal prosthesis (polishing process), completing the final metal prosthesis.

As shown in FIG. 17 , it is recommended to start work on the metal prosthesis D installed on the outer periphery of the base and then work on the metal prosthesis D installed closer to the center of the base. In the installation process of this embodiment, a hollow sprue 1 was used that was shorter toward the outer periphery of the base and longer toward the center. Therefore, even if the sprue (more precisely, the portion of the casting CA corresponding to the hollow sprue 1 trace) is left on the base after the metal prosthesis D installed on the outer periphery is separated, this does not interfere with the cutting of the metal prosthesis D installed closer to the center with the circular saw SW. If all the hollow sprues 1 were the same length, the outer sprues would get in the way when cutting the central metal prosthesis D with the circular saw SW. Therefore, the outer sprues from which the metal prosthesis D was separated are first removed from the base before the cutting process for the central metal prosthesis D is performed. Alternatively, the cutting process for the central metal prosthesis D must be performed while tilting the circular saw SW so as to avoid the sprue on the outer periphery from which the metal prosthesis D has been cut. In the former case, the number of steps increases, resulting in reduced work efficiency. In the latter case, the cutting process for the central prosthesis D is limited in accuracy, resulting in excess metal remaining on the metal prosthesis D. This excess metal is lost in the polishing process, resulting in waste of expensive metal material. However, according to this embodiment, as shown in FIG. 18 , the metal prosthesis D can be cut out while leaving the sprue on the base. In other words, there is no need to remove the sprue from the base, significantly improving work efficiency. Furthermore, the circular saw SW can easily access the metal prosthesis D embedded in the center of the base and perform high-precision cutting, thereby reducing waste of metal material.

When separating the metal prosthesis and sprue, the cut is made so that some of the buildup and the end of the sprue remain on the metal prosthesis side. Any buildup remaining on the surface of the metal prosthesis is then removed by grinding. This prevents the metal prosthesis from being damaged during cutting.

In this embodiment, a cut surface S is formed on at least one end E1 of the hollow sprue 1 body, inclined relative to the axis X of the hollow sprue 1. This allows the area of the surface where the wax dental prosthesis and the hollow sprue 1 intersect and the amount of buildup to be smaller than in the past. This means that less buildup and hollow sprue 1 debris remains on the surface of the metal dental prosthesis than in the past. This reduces the amount of metal lost during the polishing process compared to the past, making it possible to reduce the manufacturing costs of metal dental prostheses.

In addition, in this embodiment, when multiple hollow sprues 1 are planted into a disc-shaped wax base, the longer the hollow sprues 1 are used the closer they are to the center of the base. This eliminates the need to remove the sprues from the base during the cutting process, thereby improving work efficiency.

If a dome-shaped base is used instead of a disk-shaped base, the same effect can be achieved even when multiple hollow sprues 1 of the same length are installed. However, the task of installing hollow sprues 1 vertically is much easier with a disk-shaped base. Furthermore, if all hollow sprues 1 are installed approximately vertically, the angle of the circular saw can be kept approximately constant during the cutting process, allowing for the metal prosthesis to be separated one after another, improving workability. On the other hand, when installing hollow sprues 1 on a dome-shaped base, the hollow sprues 1 are likely to tilt. If the installation angles of the hollow sprues 1 are inconsistent, the circular saw must be applied at different angles to each sprue during the cutting process, which can reduce workability and result in wasted metal material.

1 Hollow sprue E, E1, E2 Ends X Axis L Distance between cutting surfaces of sprue R1 Outer diameter of sprue R2 Inner diameter of sprue S Cutting surface of sprue end α Angle between cutting surface S and axis X T Tip of cutting surface S W Wax dental prosthesis M Molten wax B Base

Claims (7)

A sprue used in casting metal crafts,
It has a tubular body,
At least one end E1 of the body has a cut surface S inclined in one direction with respect to the axis X of the tubular body ,
A hollow sprue, characterized in that an opening is formed on the cut surface S that is inclined with respect to the axis X. A method for using a hollow sprue having a tubular body, wherein at least one end E1 of the body has a cut surface S inclined in one direction with respect to an axis X of the tubular body , and an opening is formed on the cut surface S inclined with respect to the axis X ,
applying a molten adhesive material to the end E1 of the hollow sprue;
and a step of penetrating a tip portion T formed on the cut surface S of the end portion E1 into a wax dental prosthesis. The penetrating step causes the molten adhesive material to flow into an internal cavity of the body.
A method for using the hollow sprue according to claim 2. In the penetrating step, only a part of the cut surface S is embedded in the wax dental prosthesis.
A method for using the hollow sprue according to claim 2. The method further includes a step of planting a plurality of the hollow sprues on a plate-shaped base,
The method for using a hollow sprue according to claim 2 , wherein in the step of planting, the length of the hollow sprue is longer as it approaches the center of the base. A plate-shaped base on which a plurality of hollow sprues according to claim 1 are planted,
A base in which the hollow sprues are planted so that the closer they are to the center of the base, the longer they are. The base according to claim 6 , wherein the base has a multi-layer structure including a first layer made of wax and a second layer made of wax that is softer than the first layer.