Mold for tile

Abstract

 A mold for a tile composed of a frame mold (2), a front mold (4) which is inserted into the frame mold from the front side thereof, and a rear mold (6) which is inserted into the frame mold from the back side thereof. The rear mold is composed of a plurality of plungers (5).
A back pressure is applied to each plunger by the corresponding hydraulic cylinder mechanism (7, 8, 9, 10). The hydraulic cylinder mechanisms are connected to each other in such a manner that a fluid can pass through each mechanism. When the fluid pressure within each hydraulic cylinder mechanism is equal, the back pressure applied to each cylinder by the corresponding hydraulic cylinder mechanism is equal.

Description

[0001] The present invention relates to the structure of a mold for a tile which is capable of uniformly pressing the whole surface of the tile and, more particularly, to a mold for a tile having a rugged pattern.

[0002] A tile is press-molded by pressing a plastic body as a material (hereinunder referred to as "body material") with which a cavity surrounded by a frame mold is filled. The frame mold is provided with a front mold for molding the top surface of a tile and a rear mold for molding the back surface of the tile.

[0003] In such a conventional mold, the pressure applied to the body material for press molding is constant over the entire surface. Therefore, although the mold is suitable for press-molding a flat tile having a uniform surface, when a tile having a rugged pattern is molded, the pressure is locally different, so that it is impossible to press-mold a tile with the whole surface uniformly pressed. The formed tile is sometimes deformed, or the speed of water absorption of the tile is also locally different due to the locally different pressure at the time of press molding, which results in nonuniform glazing on the tile surface.

[0004] Accordingly, it is an aim of the present invention to eliminate the above-described problems in the related art and to provide a mold which is capable of molding a tile with a uniform pressure over the entire surface and, hence, preventing the deformation of the formed tile and nonuniform glazing on the tile surface even if the tile has a rugged pattern.

[0005] To achieve this aim, a mold for a tile according to the present invention comprises: a frame mold; a front mold having a rugged molding surface; and a rear mold having a plurality of plungers which can protrude from the molding surface.

[0006] A back pressure is applied to each plunger by the corresponding hydraulic cylinder mechanism. The hydraulic cylinder mechanisms are connected to each other in such a manner that a fluid can pass through each mechanism. When the fluid pressure within each hydraulic cylinder mechanism is equal, the back pressure applied to each plunger by the corresponding hydraulic cylinder mechanism is equal. This means that all the plungers press the plastic body in the mold with the same pressure. In other words, the same pressing force is applied to the plastic body in the mold at any part by each plunger. The density of the formed tile is therefore substantially the same at any part.

[0007] The molding surface (the surface facing the cavity) of the rear mold is preferably composed of the end surfaces of the plungers. In this case, the upper surface of each plunger can slide on the lower surface of the adjacent plunger. The upper or lower surface of a plunger disposed along the inner peripheral surface of the frame mold can slide thereon.

[0008] A cylinder bore is preferably formed in the rear end surface of each plunger, and the corresponding hydraulic cylinder is slidably inserted into the bore. A passage for passing a fluid therethrough is formed in each cylinder in such a manner that the forward end thereof opens toward the forward end of the cylinder and the rear end thereof communicates with a common tank. A fluid is supplied from the tank to the bore of a cylinder through the corresponding passage, thereby advancing the corresponding plunger. When the fluid in the bore is returned to the tank, the corresponding plunger is withdrawn.

[0009] The above and other objects, features and advantages of the present invention will become clear from the following description of the preferred embodiment thereof, taken in conjunction with the accompanying drawings.

[0010] An embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawings, in which:-

FIG. 1 is a sectional view of an embodiment of a mold for a tile according to the present invention before press molding;

FIG. 2 is a sectional view of the embodiment of a mold for a tile according to the present invention filled with a body material; and

FIG. 3 is a sectional view of the embodiment of a mold for a tile according to the present invention during press molding.

[0011] An embodiment of a mold for a tile according to the present invention will be explained in the following with reference to the accompanying drawings.

[0012] FIGs. 1 to 3 serially show the steps of molding a tile using an embodiment of a mold for a tile according to the present invention. As shown in FIG. 3, this embodiment is used for molding a tile 1 having a rugged pattern on the surface.

[0013] The mold is composed of a frame mold 2, a front mold 4 having a rugged molding surface 3 so as to mold the rugged pattern on the surface of the tile 1, and a rear mold 6 composed of a plurality of plungers 5.

[0014] A cylinder bore 7 is formed in the rear end surface of each plunger 5. A cylinder 8 is slidably inserted into the corresponding bore 7. A passage 9 for passing an oil therethrough is provided in each cylinder 8. The forward end of each passage 9 opens toward the forward end of the corresponding cylinder 8 and the rear end of the passage 9 communicates with a tank 10. When the oil in the tank 10 is supplied to the bore 7 through the passage 9 of the cylinder 8, the corresponding plunger 5 is advanced. When the oil in the bore 7 is returned to the tank 10, the corresponding plunger 5 is withdrawn.

[0015] FIG. 1 shows the positional relationship of the mold before press molding. At the initiation of press molding, the forward end surface of the frame mold 2 and the molding surface of the rear mold 6 (i.e, the forward end surfaces of the plungers 5) are in the same vertical plane, and the same hydraulic pressure is applied to each plunger 5.

[0016] The plungers 5 are then withdrawn to predetermined positions in the frame mold 2 so that a cavity 11 defined by the molding surface of the rear mold 6 and the inner peripheral surfaces of the frame mold 2 is formed, as shown in FIG. 2, and the cavity 11 is filled with a body material 12 as a material of a tile.

[0017] When the cavity 11 is filled with the body material 12, the front mold 4 is withdrawn by, for example, a front mold reciprocating mechanism (not shown). As a result, each plunger 5 is pressed in the direction of withdrawal (downward in FIG. 3) by the body material 12.

[0018] At the initial stage of press molding, the pressure applied to the plunger 5a which faces the most concave portion 3a of the molding surface 3 by the body material 12 is smaller than the pressure applied to the plunger 5b which faces the most convex portion 3b of the molding surface 3 by the body material 12. The pressure applied to the plunger 5c which faces an intermediate portion by the body material 12 is intermediate between the pressures applied to the plungers 5a and 5b by the body material 12. Consequently, the plunger 5b is withdrawn farther than any other plunger, and the oil in the bore 7 into which the plunger 5b is inserted flows back to the tank 10. Then the oil in the tank 10 flows into the bore 7 into which the plunger 5a is inserted. The oil in the bore 7 into which the plunger 5c is inserted hardly flows and remains as it is.

[0019] In the state of the mold in which the front mold 4 is sufficiently advanced, as shown in FIG. 3, the oil in each bore 7 does not communicate with each other and remains as it is. In this state, the pressure applied to each plunger 5 by the oil in each bore 7 is the same, as is clear from the Pascal's law. That is, the entire part of the body material 12 in the mold is uniformly pressed by the plungers 5.

[0020] In this way, a tile 1 having a rugged pattern which is uniformly pressed is produced. The speed of water absorption of the molded pattern is the same at any part. It is therefore possible to uniformly glaze the surface.

[0021] Although the back surface of the formed tile 1 having a rugged pattern is also rugged, since it is not necessary that the tile 1 has a flat back surface, the product has no particular problem.

[0022] While there has been described what is at present considered to be a preferred embodiment of the invention, it will be understood that various modifications may be made thereto, and it is intended that the appended claims cover all such modifications as fall within the true spirit and scope of the invention.

Claims

1. A mold for a tile comprising:
   a frame mold (2);
   a front mold (4) inserted into said frame mold from the front side thereof; and
   a rear mold (6) inserted into said frame mold from the back side thereof characterized in that
   said rear mold includes a plurality of plungers (5) which can protrude from the molding surface of said rear mold and which are respectively provided with hydraulic cylinder mechanism (7, 8, 9, 10) for applying a back pressure thereto, and
   said hydraulic cylinder mechanisms being connected to each other.

2. A mold according to claim 1, wherein the entire part of the molding surface of said rear mold is composed of the end surfaces of said plungers.

3. A mold according to either of claims 1 and 2, wherein each of said plungers is provided with a cylinder bore (7) formed in the rear end surface thereof, and a cylinder is inserted into each of said cylinder bores.

4. A mold according to claim 3, wherein each of said cylinder is provided with a passage (9) for passing a fluid therethrough in such a manner that the forward end thereof opens toward the forward end of said cylinder and the rear end thereof communicates with a common tank (10).

Drawing