GB2046106A - Manufacture of target boards for darts or archery - Google Patents

Abstract

A circular target board is made by joining two semi-circular hemp boards of equal thickness, tightly pressed together with a joining device. The semi-circular hemp boards are obtained by cutting a tightly pressed, semi-cylindrical hemp bundle into plurality of semi-circular disc like boards of equal thickness. The tightly pressed, semi-cylindrical hemp bundle is formed directly from a large bunch of suitable quantity of hemp fibers with a forming press device. <IMAGE>

Description

SPECIFICATION Method and equipment for manufacture of target boards for darts or archery A conventional method of manufacture of the target boards popularly used in darts games or archery is described as follows: As shown in Fig.1 first of all, a property quantity of hemp fibers are wrapped tightly with PVC tapes Bto become a bundle A (approximately 5-7 cm in diameter) prior to the press-forming process, then the hemp bundle wrapped with PVC tape A is cut with a knife into plurality of small cylindrical parts C-C of equal thickness as that of target board.Next, as shown in Fig.1A, a suitable number of the small cylindrical parts C-C (just enough to constitute a target board) are laid and tightly arranged on a joining device and are forced thereby inwardly to become a disc-like, shrunk circular board, and then a circular plate d (usually a wooden plate) is attached manually thereon with glue, and finally, a protection ring E is put around the shrunk circular board to become a completed target board.Upon reviewing aforesaid conventional manufacturing process, one could easily find out many disadvantages as follows: (1) According to the conventional method, first of all it is necessary to wrap PVC tapes around the small bunch of hemp fibers to become a tightly wrapped hemp bundle, which is then cut into small cylindrical parts of the same thickness as the target board, the process is time consuminy and also there is a lot of waste of material.Therefore it is costly. (2) As each small cylindrical part is wrapped with PVC tapes, the internal cohesion as a whole unit is lacking when the group of small cylindrical parts are pressed inwardly, therefore the completed target board is lacking in tightness and uniformity. (3) The cross section of each small cylindrical parts after inward pressing shows irregular contacts with the neighboring parts, which lead to such an essential defect as uneven surface F that requires many times of glue coating to make flat and even before the circular plate D can be attached smoothly, therefore, it is obvious that the completed target board is not strong enough. Furthermore, because of aforesaid reason the quality is poor and the productivity is low.

Summary of the Invention The main object of this invention is to provide a new method and equipment for manufacture of the target boards for darts or archery, in order that aforesaid difficulties and disadvantages with the conventional manufacturing method can be thoroughly eliminated, and thus the productivity can be increased, the cost, reduced, and the process, simplified. It is another object of this invention to provide a new method and equipment for darts or archery with reduced cost to put the manufactures in favorable position with regard to export business for earning foreign exchange.

The method of manufacture according to this invention has several special features and advantages as follows: (1) According to this invention a large bunch of hemp fibers are directly placed in a press-forming device and pressed tightly to become a semi-cylindrical hemp bundle, which eliminates the need of wrapping PVC tapes around the hemp fiber bunch prior to the pressing process, sewing material and labor. (2) The target board manufactured according to this invention has better uniformity, internal cohesion and contraction that that manufactured according to conventional method as the heml;; fibers are more tightly and uniformly pressed with the method of this invention. (3) The target board manufactured according to this invention is made from two semi-circular hemp boards tightly pressed and joined together, the semi-circular hemp boards being obtained by cutting with sewing machine a tightly pressed, large hemp bundle into disc-like boards, therefore the surface of the target board is flat, even and smooth which will not be badly affected during the other process of manufacture.

In comparision, the target board manufactured according to the conventional method is made from small hemp bundles that are obtained by cutting a slender hemp bundle into small parts of same thickness as the target board before pressing together to become a board, thus taking more processing labor. (4) There are no wrinkles or trace of wrinkles on the surface of the target board manufactured according to this invention as the hemp fibers joined therein are evenly and uniformly distributed and also tightly pressed, thus it gives beautiful appearance. In comparison, wrinkles or trace of wrinkles always appear, though insignificantly, on the surface of the target board manufactured according to the conventional method.This is because of the edges of PVC tapes wrapped around on each small hemp bundle, which make appearance bad even after coating with paint. (5) The method of manufacture according to this invention is simple and fast, thus it improves the productivity. The inventor's experiments reveal a fact that the productivity with the method of this invention has been raised three times over that with the conventional method, and that the quality of the product is better, and the cost, less. This proves that this invention is of high practical and economical value.

Brief description of the drawing The method and equipment of this invention wili be more fully understood from the following description in detailed step by step taken in conjunction with the accompanying drawings, in which: Fig. 1, 1 A, 1 B and 1 C are simplified schematic views showing the conventional method; Fig. 2 is a perspective, composite view of the press-forming device of this invention; Fig. 3 is a sectional view of the upper and lower molds in press-form action; Fig. 4 is a schematic view of the holding bar holding the upper members of the clamps; Fig. 5 is a perspective, exploded view of the tightly pressed semi-cylindrical hemp bundle and the tightly pressed semi-circular hemp board separated therefrom; Fig. 6, 6A, 6B and 6C are schematic views of the joining device of this invention in action;; Fig. 7 is a perspective, schematic view of the circular target board body manufactured according to this invention; Fig. 8 is an oblique view of the complete product manufactured according to this invention, showing its appearance.

Detailed description of the invention The press-forming device of this invention is as shown in Fig. 2, mainly consisting of an upper mold is connected with a hydraulic plunger 11 which forces the upper mold to press downward.

The mold face 12 of said upper mold is a straight plane provided with plurality of straight grooves 13-13 equally spaced at the pitch which is equal to the thickness of the target board, a said straight grooves 1 3-1 3 being so designed to receive in each groove respectively a slender, rectangular upper clamp member 14-14 having the thickness equal to the depth of said groove 13-13, said upper clamp member having both ends protruding outwardly from the groove 1 3-1 3 and hooked onto the spring 1 5-1 5 provided at both sides of the upper mold.The lower mold 20 is provided with a large, semicylindrical cavity 21 having plurality of equally spaced semi-circular grooves 22-22 on the cavity wall, said semi-circular grooves 22-22 being so designed that each semi-circular groove 22-22 faces the corresponding straight groove 13-13 on the upper mold respectively, and that each semi-circular groove 22-22 receives therein, respectively, a semi-circular lower clamp member 23-23 having both sides protruding outwardly from each grove 22-22.

To operate the press-forming device, first of all, a large bunch of hemp fibers are placed in the large semi-cylindrical cavity 21 on the lower mold 20 till the mold is properly filled; them the hydraulic plunger 11 is actuated to force the upper mold 10 to more downward, whereby the hemp fibers in between the upper and lower molds are pressed tightly as the mold face 12 moves down to contact with the hemp fibers and continues to move down; as soon as the upper and lower molds 10, 20 close completely, i.e., the upper mold 10 completes its press-forming stroke, the hemp fibers are press-formed into a tightly pressed hemp bundle 30 as shown by the sectional view in Fig. 3. When the upper and lower molds close completely, the ends of each set of upper and lower clamp members come to coincide with each other.Then the springs on which the upper clamp members are hooked are detached and at the same time each pair of the ends of upper and lower clamp members coinciding each other are linked together with a sleeve 31 (having a hole 32 therein) at the projections 140,230 before the upper and lower molds are set apart in order to prevent the tightly pressed hemp bemdle 30 from loosening apart because of the opening of the clamp members when the upper and lower molds open.

The arrangement of the springs 15-15 on the sides of the upper mold for holding each upper clamp member may be replaced with such arrangement that comprises four brackets 1 6-1 6 wherein each bracket has a hole and is provided at each of the four corners of the upper mold in such manner that each two brackets face side to side each other and are provided a bar 17-17, respectively, which is put through the holes of said each two brackets and disposed in between, said bar 1 7-17 being arranged to hang the upper clamp members 14-14 on to the upper mold, keeping said upper clamp members 14--14 in the groove 1 4-14 as a substitute for the springs 1 5-1 5. In this case, however, the bars 17-17 can be removed as soon as the mold face 1 2 of the upper mold 10 comes in contact with the hemp fibers (at this moment the upper clamp members 14-14 will not fall off the grooves as they are already being supported by the hemp fibers), and then following the same procedure as described above, the sleeves 31 are put on the ends of the clamp members as soon as they coincide with each other when the upper and lower molds close.

The tightly pressed hemp bundle 30 taken off the press-forming device after the press-forming process becomes a semi-cylindrical hemp bundle as shown in Fig. 5, which is then out apart with sewing machine (not shown) along the middle in between each two adjacent pairs of clamp members into plurality of tightly pressed semicircular boards of predetermined thickness as 33 with each pair of the clamp members remaining on in order to prevent the board 33 from deformation.Then, referring to Fig. 6, two pieces of tightly pressed semi-circular boards 33-33 are placed in between the two joining devices 40-40, each having inner mold 41 and outer mold 42, said inner mold being slided in the outer mold 42, said out mold having semi-circular mold face profile 43--43 to fit the semi-circular profile of the tightly pressed semi-circular board.In the joining operation, first, the two tightly pressed semi-circular board 33-33 are clamped by the outer molds 42-42 as shown in Fig 6A, and then with the two semi-circular board held together by the molds 42 42 the sleeves 31 linking the upper and lower clamp members are removed, and next, the upper clamp members are pulled off, then the outer molds 42-42 are further forced inwardly to press the two semi-circular boards together harder (see Fig 6B). With the upper clamp members pulled off, the two semi-circular boards are then joined together as the hemp fibers at the junction are forced to bind together, a circular target board body 44 being thereby constituted. Then with the board still held by the mold, glue is applied to the upper surface of the circular target board body 44 and a reinforcing plate 45 of the same diameter as the circular target board body 44 is attached thereon.

The two outer molds 42--42 are released as soon as the glue is cured and the reinforcing plate 45 is bonded securely on the circular target board body 44 (as shown in Fig. 6C), and then the two lower clamp members 23-23 are removed. Then referring to Fig. 6D, to facilitiate the fixing of protecting ring 47 on the periphery of the circular target board body 44 the two inner molds 41-41 are pushed toward the mold faces, said protecting ring 47 being constituted by two semi-circular metal plates secured together by means of rivets.

Meantime, two pieces of metal strips 46A6 (to be used as a protecting ring) are placed in between the circular target board 44 and the molds, and then both of the inner and outer molds are forced to move inwardly and press on the circular target board body 44, forcing to fix the protecting the ring 47 on the periphery of the circular target board body 44. Finally, the decoration covering is put on the surface of the target board body to become the completed product of nice looking target board for darts or archery.

The operation of aforesaid joining device has been given in precise detail in order that the operation is fully and clearly understood, however, in the actual operation the whole process can be performed in a very short period of time, and furthermore, it is much faster and easier than the conventional method. It has therefore proven and testified that the method of this invention not only improves the productivity, but also eliminates the waste of PVC tapes, also beautifies the appearance of the target board for darts or archery and thus increased the effedtiveness of application; it also has proven that the target board manufactured according to this invention is stronger, and lasts longer without any worry of deformation.

Claims (2)

1. A method of manufacture of the target boards for darts or archery, with which a target board for darts or archery is made from a tightly pressed circular hemp board, said tightly pressed circular hemp board being made by joining two semi-circular hemp boards of equal thickness with a joining device, said semi-circular hemp boards of equal thickness being obtained by cutting a tightly pressed, semi-cylindrical hemp fiber bundle into plurality of tightly pressed, semi-circular board of equal thickness, said tightly pressed semi-circular hemp fiber bundle being obtained from a large bunch of suitable quantity of hemp fibers through a direct press-forming process with a pressforming device.

2. A press-forming device for manufacture of target boards for darts or archery, comprising an upper mold and a lower mold, the upper mold being provided with plurality of equally spaced, straight grooves on the mold surface, said mold surface being a straight plane, said straight grooves being designed to receive freely in each groove a slender, rectangular upper clamp member having the thickness which is equal to the depth of said groove and the ends protruding outward from the groove; the lower mold being provided with a large, semi-cylindrical cavity facing the upper mold face, said lower mold having on the cavity wall plurality of semi-circular grooves each facing each of the corresponding straight groove on the mold face of the upper mold, said semi-circular grooves being so desighted to receive freely in each groove a semicircular lower clamp member having the thickness which is equal to the depth of said semi-circular groove and the ends protruding outward from the groove, said ends of the upper and lower clamp members being so arranged that they coincide with each other when the upper and lower molds close completely, and that they are linked together with a sleeve at the point where they coincide.