WO2005060726A1

WO2005060726A1 - Insert-molded synthetic resin spade and method of manufacturing the same

Info

Publication number: WO2005060726A1
Application number: PCT/KR2004/003414
Authority: WO
Inventors: Man Tae Kim
Original assignee: Jkmt Korea Co., Ltd.
Priority date: 2003-12-23
Filing date: 2004-12-22
Publication date: 2005-07-07
Also published as: KR20040041081A; KR100547905B1

Abstract

The present invention provides a spade, wherein the grip and the helve are with inserts embedded within the synthetic resin and also provides a method of manufacturing the insert-molded synthetic resin spade, comprising an insert placing step of placing inserts in a filling chamber of a mold for the grip with a transverse half of the filling chamber; an insert fixing step of inserting pins into the mold a synthetic resin filling step of causing the inserts to be embedded in the synthetic resin; a synthetic resin pressurizing step of compensating for volume reductions of the synthetic resin; a synthetic resin plasticizing step of solidifying resin a molded product separating step of separating a molded product form the mold an a finished product completing step of coupling the molded product by means of bolts or the like. According to the present invention, there are advantages in that the spade does not readily rot and cannot be easily broken, a user does not get splinters in his/her hand by means of the method of the present invention.

Description

INSERT-MOLDED SYNTHETIC RESIN SPADE AND METHOD OF MANUFACTURING THE SAME

Technical field The present invention relates to a spade comprising a grip, a helve and a scoop, and more particularly, to a spade with the strength of a grip and a helve reinforced by insert injection molding the grip and the helve integrally out of a synthetic resin, and a method of manufacturing the same.

Background Art Generally, a spade is a tool for use in moving or removing soil, sand, snow or the like. Referring to Fig. 1, which is a perspective view showing an example of a conventional spade 10, the spade can be roughly divided into three parts: a grip 11, a helve 12 and a scoop 13. The grip 11 is a short cylindrical wooden part, and the helve 12 is a generally Y-shaped wooden part in which an upper end is V-shaped and a lower portion formed integrally with the V-shaped upper end takes the shape of a long cylinder. The scoop 13 is constructed of a steel plate or plastic such that the center thereof is slightly recessed, one side thereof is partially provided with a blade-like edge to come into contact with soil, sand, snow or the like, the other side thereof is provided with a circular tube type coupling portion 15 protruding by a certain length to be coupled to the helve 12, and portions of the scoop on both sides of the coupling portion 15 are formed with ledges of a certain height for allowing the use of a user's foot in work while preventing soil, sand, snow or the like from coming out from the scoop. The grip 11 is interposed between both tips of the V-shaped upper end of the helve

12 and coupled thereto by means of bolts or rivets 14. An end of the cylindrical lower portion of the helve 12 is fitted into the coupling portion 15 of the scoop 13 and coupled thereto by means of bolts or rivets 16. The conventional spade has a problem in that the bolts or rivets for coupling the grip to the helve may loosen or come out when the spade is used over a long period of time so that the spade loses its function. Further, since the grip and the helve of the conventional spade are made of wood, there are problems in that coupling holes for the bolts or rivets therein are enlarged so that the coupling of the grip to the helve is loosened, a user may get splinters in his/her hand during use, and they may readily rot over a long period of time under natural conditions so that the service life thereof is shortened or the helve is easily broken.

Disclosure of Invention Accordingly, the present invention is conceived to solve the aforementioned problems in the prior art. An object of the present invention is to provide a spade with a better tactile sensation and improved durability by insert injection molding a grip and a helve integrally out of a synthetic resin so that inserts are embedded in the synthetic resin, and a method of manufacturing the same. To achieve the object, the present invention provides a spade with a grip, a helve and a scoop, wherein the grip and the helve are injection molded integrally out of a synthetic resin with inserts embedded within the synthetic resin. In the spade of the present invention, the inserts may be made of any one of wood, metal and nonmetal. Further, the present invention provides a method of manufacturing a spade with a grip, a helve and a scoop, comprising an insert placing step of placing a grip insert and a helve insert in a filling chamber of a mold for the grip and the helve constructed of a fixed mold half and a movable mold half each of which is formed with a transverse half of the filling chamber; an insert fixing step of fixing the inserts by inserting fixing pins into the mold from the outside to determine relative positions of the inserts with respect to the filling chamber, after the insert placing step; a synthetic resin filling step of filling a synthetic resin into the filling chamber to cause the inserts to be embedded in the synthetic resin, after the insert fixing step; a synthetic resin pressurizing step of withdrawing the fixing pins from the mold and pressurizing the synthetic resin to compensate for volume reductions due to contraction produced during cooling of the synthetic resin, after the synthetic resin filling step; a synthetic resin plasticizing step of solidifying the synthetic resin while cooling the mold, after the pressurizing step; a molded product separating step of separating a molded product of an integral grip and helve from the mold by means of an ejector while the movable and fixed mold halves are separated from each other, after the plasticizing step; and a finished product completing step of coupling the molded product to a separately manufactured scoop by means of fasteners, including bolts, after the separating step. In the method of the present invention, the inserts may be made of any one of wood, metal and nonmetal.

Brief Description of the Drawings Fig. 1 is a perspective view of a conventional spade. Fig. 2 is a perspective view of a spade of the present invention. Fig. 3 is a longitudinal sectional view of a grip and a helve with inserts embedded therein in the spade of the present invention. Fig. 4 is a cross sectional view of a portion with the embedded insert in the spade of the present invention. Fig. 5 is a flowchart illustrating steps of a process of the present invention. Fig. 6 is a view showing the configuration of a filling chamber of a movable mold half in the present invention. Fig. 7 is a view showing a state where inserts are placed in a fixed mold half in the present invention. Fig. 8 is a view showing a state where fixing pins are used in the present invention.

Best Mode for Carrying out the Invention Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. Referring to Fig. 2, which is a perspective view of a spade 20 of the present invention, the spade 20 can be roughly divided into three parts: a grip 21, a helve 22 and a scoop 23. However, since the grip 21 and the helve 22 are integral with each other and the scoop 23 is separately manufactured and then coupled to the helve, the spade is substantially divided into two parts. The grip 21 is a short cylindrical part, and the helve 22 is a generally Y-shaped part in which an upper end is V-shaped and a lower portion formed integrally with the V- shaped upper end takes the shape of a long cylinder. Both the grip 21 and the helve 22 are injection molded integrally out of a synthetic resin 26 using a mold comprising a fixed mold half 27-1 and a movable mold half 27-2 each of which is formed with a transverse half of a filling chamber 29. As shown in Fig. 7, which is a view illustrating a state where inserts are placed in the fixed mold half in the present invention, a grip insert 24 is placed in a portion of the filling chamber 29 of the movable mold half 27-2 or the fixed mold half 27-1, which corresponds to the grip 21, and a helve insert 25 is placed in a portion of the filling chamber 29 of the mold half, which corresponds to the helve 22, before the injection molding. The movable mold half 27-2 is brought close to and into close contact with the fixed mold half 27-1, and fixing pins 30 are then inserted into the mold from the outside to support the inserts, so that relative positions of the inserts with respect to the filling chamber 29 are determined. The inserts are fixedly placed at the center of the filling chamber 29 while maintaining constant gaps with the inner wall of the mold half defining the filling chamber. After the inserts are fixed, injection molding is performed using the synthetic resin 26, resulting in the integral grip 21 and helve 22 with the inserts embedded in the synthetic resin 26. In the integral grip 21 and helve 22 with the embedded inserts in the present invention, as shown in Fig. 3 that is a longitudinal sectional view of a portion of the integral grip 21 and helve 22 with the embedded inserts in the spade of the present invention and Fig. 4 that is a cross sectional view of a portion with the embedded insert in the spade of the present invention, the diameter and length of the helve insert 25 are smaller than the outer diameter and length of the helve 22 and takes the shape of a cylinder. The diameter and length of the grip insert 24 are smaller than the outer diameter and length of the grip 21 and takes the shape of a cylinder. Thus, the inserts are embedded in the synthetic resin 26 constructing the grip 21 and the helve 22. The inserts may be made of any one of wood, metal and nonmetal. Meanwhile, the scoop 23 is constructed of a steel plate or plastic such that the center thereof is slightly recessed, one side thereof is partially provided with a blade- like edge to come into contact with soil, sand, snow or the like, the other side thereof is provided with a circular tube type coupling portion protruding by a certain length to be coupled to the helve 22, and portions of the scoop on both sides of the coupling portion are formed with ledges of a certain height for allowing the use of a user's foot in work while preventing soil, sand, snow or the like from coming out from the scoop. A cylindrical lower end of the integral grip 21 and helve 22 with the embedded inserts is fitted into the coupling portion of the scoop 23 and then coupled thereto by mean s of bolts or rivets, resulting in the spade of the present invention. Since the grip 21 and the helve 22 of the spade of the present invention are obtained by covering the inserts with the synthetic resin 26, a user feels a smooth tactile sensation upon contact of his/her skin therewith, they do not readily rot over a long period of time under natural conditions, the strength thereof is improved due to the inserts so that they cannot be easily broken, and the user does not get splinters in his/her hand. Further, since the grip 21 and the helve 22 are formed integrally with each other in the present invention, there is no phenomenon in which bolts or rivets for use in coupling the grip 21 to the helve 22 may loosen or come out. Therefore, there is an advantage in that they are not separated from each other or the coupling thereof is not loosened. As shown in Fig. 5, which illustrates procedures of a method of manufacturing the spade according to the present invention, the method comprises the following sequential steps: an insert placing step, an insert fixing step, a synthetic resin filling step, a synthetic resin pressurizing step, a synthetic resin plasticizing step, a molded product separating step, and a finished product completing step. Specifically, the insert placing step is a step of placing the grip insert 24 and the helve insert 25 within the filling chamber 29 of the mold, as shown in Fig. 7 which is a view illustrating a state where the inserts are placed in the fixed mold half. As shown in Figs. 6 and 7, the mold comprises the fixed mold half 27-1 that is formed with the filling chamber 29 recessed from the surface of the fixed mold half to correspond to transverse halves of external appearances of the grip 21 and the helve 22, and the movable mold half 27-2 that is formed with the filling chamber 29 recessed from the surface of the movable mold half to correspond to the transverse halves of the external appearances of the grip 21 and the helve 22 and is installed to be brought close to and incorporated with the fixed mold half 27-1 or to be taken away therefrom. The reason why the mold is divided in the transverse direction is that dividing the mold into the movable mold half 27-2 and the fixed mold half 27-1 in a direction orthogonal to the transverse direction makes the design of the mold inconvenient or impossible due to the V-shape of the helve 22, 21 is coupled. The mold is provided with a circular, semicircular or trapezoidal runner 28 in the vicinity of the V-shaped upper end of the helve 22 to introduce molten resin, which has been injected from a nozzle, into the filling chamber 29. However, the position of the runner 28 is not limited thereto since it can be determined again in consideration of the lengths and materials of the inserts and a cooling rate of the synthetic resin 26 depending on a filling amount thereof. The insert placing step is performed by placing the grip insert 24 within the portion of the filling chamber 29 corresponding to the grip 21 and the helve insert 25 within the portion of the filling chamber 29 corresponding to the helve 22 in the movable or fixed mold half 27-2 or 27-1. Here, the fixed mold half 27-1 is secured on a main body of an injection molding machine, whereas the movable mold half 27-2 is normally separated from the main body of an injection molding machine but is brought close to and into close contact with the fixed mold half 27-1 in operation. In the integral grip 21 and helve 22 with the embedded inserts in the present invention, as shown in Fig. 3, which is a longitudinal sectional view of a portion of the integral grip 21 and helve 22 with the embedded inserts in the spade of the present invention and Fig. 4, which is a cross sectional view of a portion with the embedded insert in the spade of the present invention, the diameter and length of the helve insert 25 are smaller than the outer diameter and length of the helve 22 and takes the shape of a cylinder. The inserts may be made of any one of wood, metal and nonmetal. Although the helve 22 is circular in cross section, it is not limited thereto. The helve 22 may be hexagonal, octagonal, or the like in cross section. When the movable mold half 27-2 is brought close to and into contact with the fixed mold half 27-1 after the insert placing step, the insert fixing step is then performed. In this step, as shown in Fig. 8, which is a view illustrating a use state of the fixing pins, the fixing pins 39 pneumatically operated by air cylinders are preferably inserted into the mold from the outside between the movable and fixed mold halves 27-2 and 27-1 to determine the relative positions of the inserts with respect to the filling chamber 29 and to fix the inserts. By doing so, the inserts are placed at the center of the filling chamber 29 while maintaining the constant gaps with the inner wall of the mold half defining the filling chamber 29. The fixing pins 30 are withdrawn after the synthetic resin 26 has been filled in the next step, i.e. the synthetic resin filing step. Spaces produced in the synthetic resin 26 after the withdrawal of the fixing pins 30 are filled with the synthetic resin 26 in the next step, i.e. the synthetic resin pressurizing step. The positions of the fixing pins 30 are not limited only to positions between the movable and fixed mold halves 27-2 and 27-1 but may be limited only to the movable or fixed mold half 27-2 or 27-1. It is preferred that a pair of fixing pins 30 be used for the grip insert 24 and two pairs of fixing pins be used for the helve insert to keep the helve insert at a predetermined position in consideration of the long length of the helve insert. The reason why such fixing pins 30 are used is that the inserts are caused to be positioned at the center of the filling chamber 29. Thus, there is an advantage in that the molten resin is uniformly distributed around the inserts. After the insert fixing step, the synthetic resin filling step is performed. This step is a step of filling the filling chamber 29 of the mold with the molten resin so that the inserts are embedded within the synthetic resin 26. The molten resin injected from a conical nozzle of a molding machine passes through a conical sprue that is in contact with the nozzle of the molding machine and has a small width and a taper of 2 to 4 degrees to readily push cooled and solidified resin. Then, the molten resin flows through the runner 28 in the form of a short trough or passage with a circular or trapezoidal cross section. Subsequently, the molten resin flows into the filling chamber 29 via gates with circular or semicircular cross sections which are installed at blind positions with respect to a product to be molded, at positions where the molten resin can rapidly flow from an entrance of the filling chamber 29 to an opposite side, and at positions where twisting of the product to be molded does not occur. A pressurizing device comprising a screw of the injection molding machine or the like transfers the molten resin to fill the filling chamber 29 therewith. The molten resin flows from a heated cylinder to the filling chamber 29 via the nozzle, the sprue, and the gates, as described above. After the synthetic resin filling step, the synthetic resin pressurizing step is performed. This step is a step of pressurizing the molten resin to compensate for volume reductions produced due to contraction while the molten resin is cooled after the fixing pins have been withdrawn from the mold to the outside. In other words, this step is a step of applying pressure to the molten resin while the pressurizing device further advances after the filling chamber 29 has been filled with the molten resin and the fixing pins have been withdrawn from the mold. The volume contraction of about 25% produced when the molten resin is changed from a molten state to a solid state, i.e. volume reductions due to contraction during the cooling of the molten resin, is compensated and the spaces produced due to the withdrawal of the fixing pins are filled with the resin by means of pressurization. After the synthetic resin pressurizing and compensating step, the synthetic resin cooling and plasticizing step is performed. This step is a step of solidifying the synthetic resin 26 while cooling the mold. Heat of the molten resin is removed from the mold by passing cooling water through cooling holes or grooves formed in the molding machine or mold, and the molten resin is given plasticity, i.e., a property by which a material is permanently deformed under a stress above an elastic limit and thus cannot be restored to its original state. After the synthetic resin cooling and plasticizing step, the molded product separating step is performed. This step is a step of separating a molded product, i.e. an integral grip 21 and helve 22, from the mold by means of an ejector while the movable and fixed mold halves 27-2 and 27-1 are separated from each other. The molded product is separated from the filling chamber 29 by means of ejector pins that are fixed to an ejector plate and installed in the mold and can be advanced together with the ejector plate when the mold halves are separated from each other. After the molded product separating step, the finished product completing step is performed. This step is a step of inspecting the molded product and assembling an acceptable molded product with the scoop 23. Here, acceptable molded products are selected while rejecting inferior products, including those produced since the resin did not sufficiently flow throughout the mold and was cooled and solidified so that a portion of a molded product is lost due to lack of the resin, those with a flash phenomenon in which an excess molten resin portion is formed on a molded product, those with a silver streak phenomenon in which a bundle of fine streaks are formed on or near the surface of a molded product in a flow direction of the resin, those with a sink mark phenomenon in which a depression appears on the surface of a molded product, those with a jetting phenomenon in which a serpentine portion is formed on the surface of a molded product, and those with a weld mark phenomenon in which fine streaks are created at a portion where the molten resin was split into two streams and the streams then joined together in the filling chamber 29. Meanwhile, the separate scoop 23 is constructed of a steel plate or plastic such that the center thereof is slightly recessed, one side thereof is partially provided with a blade-like edge to come into contact with soil, sand, snow or the like, the other side thereof is provided with a circular tube type coupling portion protruding by a certain length to be coupled to the helve 22, and portions of the scoop on both sides of the coupling portion are formed with ledges of a certain height for allowing the use of a user's foot in work while preventing soil, sand, snow or the like from coming out from the scoop. When the cylindrical lower end of the molded product, i.e. the integral grip 21 and helve 22 with the embedded inserts, is fitted into the coupling portion of the scoop 23 and then coupled thereto by mean s of bolts or rivets, the method of manufacturing the insert-molded synthetic resin spade according to the present invention is completed. In the above method, since the fixing pins 30 are inserted into the mold from the outside during injection molding, the inserts can be easily placed in the mold. Thus, productivity can be improved and a uniform thickness of the synthetic resin 26 in the integral grip 21 and helve 22 with the embedded inserts can be ensured.

Industrial Applicability As described above, the spade of the present invention has advantages in that a , user feels a smooth tactile sensation upon contact of his/her skin with the spade, the spade does not readily rot over a long period of time under natural conditions, the strength thereof is improved so that it cannot be easily broken, and the user does not get splinters in his/her hand. Further, since a phenomenon in which bolts or rivets for coupling a grip to a helve in the spade loosen or come out does not occur in the present invention, the spade of the present invention has an advantage in that there is no possibility that the grip and the helve will be separated from each other or the coupling of them will be loosened. Moreover, the method of the present invention has advantages in that inserts can be easily placed in a mold, thereby improving productivity and ensuring a uniform thickness of a synthetic resin in the integral grip and helve with the embedded inserts.

Claims

1. A spade with a grip, a helve and a scoop, wherein: the grip and the helve are injection molded integrally out of a synthetic resm with inserts embedded within the synthetic resin.

2. The spade as claimed in claim 1, wherein the inserts are made of any one of wood, metal and nonmetal.

3. A method of manufacturing a spade with a grip, a helve and a scoop, comprising: an insert placing step of placing a grip insert and a helve insert in a filling chamber of a mold for the grip and the helve constructed of a fixed mold half and a movable mold half each of which is formed with a transverse half of the filling chamber; an insert fixing step of fixing the inserts by inserting fixing pins into the mold from the outside to determine relative positions of the inserts with respect to the filling chamber, after the insert placing step; a synthetic resin filling step of filling a synthetic resin into the filling chamber to cause the inserts to be embedded in the synthetic resin, after the insert fixing step; a synthetic resin pressurizing step of withdrawing the fixing pins from the mold and pressurizing the synthetic resin to compensate for volume reductions due to contraction produced during cooling of the synthetic resin, after the synthetic resin filling step; a synthetic resin plasticizing step of solidifying the synthetic resin while cooling the mold, after the pressurizing step; a molded product separating step of separating a molded product of an integral grip and helve from the mold by means of an ejector while the movable and fixed mold halves are separated from each other, after the plasticizing step; and a finished product completing step of coupling the molded product to a separately manufactured scoop by means of fasteners, including bolts, after the separating step.

4. The method as claimed in claim 3, wherein the inserts are made of any one of wood, metal and nonmetal.