WO2005042227A1

WO2005042227A1 - Mold device for manufacturing hand-car type pallet

Info

Publication number: WO2005042227A1
Application number: PCT/KR2004/002786
Authority: WO
Inventors: Younghwan Choi
Original assignee: Younghwan Choi
Priority date: 2003-11-01
Filing date: 2004-11-01
Publication date: 2005-05-12
Also published as: KR100436695B1

Abstract

Disclosed herein is a mold device for use in the manufacture of a hand-car type pallet which is formed at a bottom surface thereof with wheel-protraction holes for the installation of casters. The mold device comprises locking means for achieving air-thightness in order to prevent molten resin from leaking from the device in the manufacture of the pallet, thereby being capable of preventing generation of burrs on the resulting pallet and damage to the mold device caused when the leaked resin sticks to the device.

Description

[DESCRIPTION] [Invention Title]

MOLD DEVICE FOR MANUFACTURING HAND-CAR TYPE PALLET

[Technical Field] The present invention relates to a mold device for use in the manufacture of a hand-car type pallet, and more particularly to a mold device for use in the manufacture of a hand-car type pallet which comprises locking means for achieving air-tightness in order to prevent molten resin from leaking from the device in the manufacture of the pallet, thereby being capable of preventing generation of burrs on the resulting pallet and damage to the mold device caused when the leaked resin sticks to the device.

[Background Art]

A pallet is a device for use along with a forklift for allowing the forklift to easily convey heavy or bulky cargo or freight disposed on the pallet. For this, the pallet has plural fork insertion through-holes. Recently, when the cargo or freight should be manually conveyed across a relatively short distance or a narrow space disabling the use of the forklift, there has been increasingly used a hand-car, which is formed at a front side thereof with the same forks as those of the forklift and at the bottom thereof with casters. Fig. 4 is a perspective view illustrating a conventional hand-car type pallet, and Fig. 5 is a side sectional view illustrating the usage of the pallet shown in Fig. 4. As shown in Figs. 4 and 5, the pallet comprises a relatively thin rectangular body 1, fork insertion through-holes 11 perforated through the entire length of the body 1, and wheel- protraction holes 12 perforated at a lower surface of the body 1 to communicate with the fork insertion through-holes 11. With such a configuration, forks 21 of a hand car 2 are inserted into the fork insertion through-holes 11, and the hand car 2 is supported by means of front casters 22 formed at a distal end of a respective one of the forks 21 and rear casters 23 formed at a body of the hand car 2. In such a state, the pallet can be manually moved using a handle 24 of the hand car 2. In the above described hand-car type pallet, differently from other kinds of conventional pallets, the wheel-protraction holes 12 are perforated through the lower surface of the pallet to be positioned adjacent to the fork insertion through-holes 11. Generally, in the case of the pallet configured to allow the forks of the hand car to be inserted in all directions, the wheel-protraction holes 12, having a square form, are symmetrically formed at the lower surface of the pallet in all directions. Figs. 6 and 7 are a sectional view and a partially enlarged sectional view, respectively, illustrating a conventional mold device for use in the manufacture of the conventional hand-car type pallet. The mold device comprises a upper mold 3 having an upper core 31 fixed at a lower surface thereof, and a lower mold 4 having a lower core 41 fixed at an upper surface thereof. The upper and lower molds 3 and 4 are coupled to upper and lower coupling plates 32 and 42, respectively, to form a predetermined space 100 therebetween, i order to supply molten resin into the space 100, at least one molten resin feeding channel 5 extends from an upper surface of the upper coupling plate 32 to the space 100. The mold device further comprises slide cores 6 and an insert core 7. The slide cores 6 are located at opposite sides of the space 100 and are adapted to form fork insertion through-holes as they are slidably moved by means of their first hydraulic cylinders 61. The insert core 7, used to form wheel-protraction holes, includes a second hydraulic cylinder 71, which is fixed at a lower surface thereof to the lower coupling plate 42 in a vertically reciprocable manner. Upon upward movement of the second hydraulic cylinder 71, the insert core 7 is correspondingly moved upward through the lower mold 4. In such an upwardly moved state, in order to enable the insert core 7 to come into close contact with the lower mold 4 to keep the space 100 air-tightness, the insert core 7 has a rectangular longitudinal sectional shape having a tapered upper portion. With such a sectional shape, the insert core 7 can come into close contact with the lower mold 4 under operation of the second hydraulic cylinder 71. However, even if the insert core 7 achieves the air-tightness as stated above, since the second hydraulic cylinder 71 is liable to move upon receiving a pressure generated in injection molding, there always exists the risk of leakage of the molten resin. Further, due to structural defects of the second hydraulic cylinder 71, a hydraulic fluid contained in the second hydraulic cylinder 71 maybe compressed upon receiving an external force even though the degree of compression is slight. Furthermore, the second hydraulic cylinder 71 has a limitation in transmission of the hydraulic fluid, and suffers from various problems, such as minor expansion of a cylinder body. For the above described several reasons, the second hydraulic cylinder 71 tends to slightly move, and such an unintentional movement of the cylinder 71 causes the leakage of the molten resin. This is especially fatal to the mold device for manufacturing a bulky pallet having a complicated molten resin channel and requiring a high injection pressure. That is, the leakage of the molten resin prevents the acquisition of the pallet having a dense composition, resulting in a deterioration in the structural reliability of the pallet. Further, the leakage of the molten resin increases the usage of material and impedes downward movement of the second hydraulic cylinder 71 since the leaked resin sticks to the mold device, resulting in sudden stop of the mold device. If the stuck, solidified resin is not removed frequently, it increases operational load and interferes with accurate movement of the cylinder. [Disclosure] [Technical Problem]

Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a mold device comprising means for securing a hydraulic cylinder, used to vertically move an insert core, at its final uppermost position, thereby being capable of preventing leakage of molten resin. It is another object of the present invention to provide a mold device which can prevent generation of burrs on the resulting pallet caused by leaked molten resin. It is yet another object of the present invention to provide a mold device which can prevent malfunction and contamination thereof due to the leakage of molten resin.

[Technical Solution]

In accordance with an aspect of the present invention, the above and other objects can be accomplished by the provision of a mold device for use in the manufacture of a hand-car type pallet comprising: an upper mold having an upper core fixed at a lower surface thereof, the upper mold being coupled at an upper surface thereof to an upper coupling plate; a lower mold having a lower core fixed at an upper surface thereof, the lower mold being coupled at a lower surface thereof to a lower coupling plate, thereby defining a predetermined interior space along with the upper mold coupled to the upper coupling plate; at least one molten resin feeding channel extending from an upper surface of the upper coupling plate to the interior space in order to supply molten resin into the space; slide cores located at opposite sides of the space and adapted to form fork insertion through-holes as they are slidably moved by means of their first hydraulic cylinders; and an insert core having a second hydraulic cylinder fixed at a lower surface thereof to the lower coupling plate and adapted to vertically move so as to perforate wheel- protraction holes, the insert core being upwardly moved through the lower mold upon upward movement of the second hydraulic cylinder, wherein the mold device further comprises: a locking bar connected to one of the first hydraulic cylinders used to operate the slide cores so as to be synchronized in movement with the first hydraulic cylinder, the locking bar accessing and coming into close contact with the lower surface of the second hydraulic cylinder upon the upward movement of the second hydraulic cylinder.

[ Advantageous Effects ]

As apparent from the above description, the present invention provides a mold device for use in the manufacture of a hand-car type pallet, which comprises a locking bar capable of preventing unintentional movement of a hydraulic cylinder of an insert core, thereby achieving air tightness between the insert core and an interior space defined in the mold device even if a high pressure is applied thereto during injection molding. Further, according to the present invention, it is possible to prevent the leakage of molten resin, thereby completely preventing generation of burrs on the resulting pallet. This has the effect of eliminating consumption of labor and time required for the removal of the burrs, and hence preventing quality degradation due to the burrs. Furthermore, according to the present invention, it is possible to prevent malfunction and contamination of the mold device due to the leaked molten resin, and thus eliminate consumption of labor and time required for the removal of the leaked, solidified molten resin.

[Description of Drawings]

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: Fig. 1 is a partial sectional view illustrating a mold device for use in the manufacture of a pallet in accordance with an embodiment of the present invention; Fig. 2 is a perspective view illustrating a locking bar in accordance with the embodiment of the present invention; Figs. 3 a and 3b are a sectional view and a front sectional view, respectively, illustrating the mold device for use in the manufacture of a pallet in accordance with the embodiment of the present invention; Fig. 4 is a perspective view illustrating a conventional hand-car type pallet; Fig. 5 is a side sectional view illustrating the usage of the pallet shown in Fig. 4; Fig. 6 is a sectional view illustrating a conventional mold device for use in the manufacture of the conventional hand-car type pallet; and Fig. 7 is a partially enlarged sectional view illustrating the mold device shown in Fig. 6.

[Mode for Invention]

Now, preferred embodiments of the present invention will be explained in detail with reference to the accompanying drawings. Fig. 1 is a partial sectional view illustrating a mold device for use in the manufacture of a pallet in accordance with an embodiment of the present invention. As shown in Fig. 1, the mold device for use in the manufacture of a hand-car type pallet in accordance with the present invention basically comprises upper and lower molds, slide cores and an insert core. The upper mold has an upper core fixed at a lower surface thereof, and the lower mold has a lower core fixed at an upper surface thereof. The upper and lower molds are coupled to upper and lower coupling plates, respectively, to form a predetermined space therebetween. In order to supply molten resin into the space, at least one molten resin feeding channel extends from an upper surface of the upper coupling plate to the space. The slide cores, designated as reference numeral 6, are located at opposite sides of the space and adapted to form fork insertion through-holes as they are slidably moved by means of their first hydraulic cylinders 61. The insert core, designated as reference numeral 7, includes a second hydraulic cylinder 71, which is fixed at a lower surface thereof to the lower coupling plate in a vertically reciprocable manner. Upon upward movement of the second hydraulic cylinder 71, the insert core 7 is correspondingly moved upward through the lower mold, thereby serving to perforate wheel drawing holes, hi the present invention, the mold device further comprises a locking bar 8. The locking bar 8 is connected to the first hydraulic cylinder 61, used to operate the slide core 6, and is synchronized in movement with the first hydraulic cylinder 61. Further, in response to the upward movement of the second hydraulic cylinder 71, the locking bar 8 accesses and comes into close contact with the lower surface of the second hydraulic cylinder 71, serving to prevent the second hydraulic cylinder 71 from downwardly moving upon receiving an injection pressure. Although a separate member for fixing the locking bar 8 may be realized in an easy manner, it is preferable in view of ease of manufacture and maintenance to horizontally access the locking bar 8 to the second hydraulic cylinder 71 by means of the first hydraulic cylinder 61 in the same manner as the slide core 6. Fig. 2 is a perspective view illustrating the locking bar 8 in accordance with the embodiment of the present invention. As shown in Fig. 2, the locking bar 8 has a tapered tip portion which partially forms an inclined flat surface 82 extending in an advance direction thereof. The inclined flat surface 82 is preferably configured to completely prevent movement of the second hydraulic cylinder 71 to thereby maximize the operational efficiency of the locking bar 8. Further, the inclined flat surface 82 enables the locking bar 8 to easily access the second hydraulic cylinder 71 in its initial stage and effectively push the cylinder 71 upward in contact with it. In this way, the insert core 7 can improve the air-tightness thereof. Figs. 3a and 3b are a side sectional view and a front sectional view, respectively, illustrating part of the mold device, more particularly, detailed components used to mount the locking bar 8, in accordance with the embodiment of the present invention. Referring again to Fig. 1, the locking bar 8 has a horizontally movable frame 81 connected to an end of the first hydraulic cylinder 61. That is, the horizontally movable frame 81 is coupled at an upper end thereof to the slide core 6 and at a lower end thereof to an end of the locking bar 8, and is adapted to horizontally move the locking bar 8. In this case, it is preferable to provide guide means for achieving smooth horizontal movement of the frame 81. Under operation of the horizontally movable frame 81, the locking bar 8 is moved along a guide groove formed at the lower coupling plate 42. Meanwhile, the insert core 7 of the present invention further includes a vertically movable rod 72 installed on the second hydraulic cylinder 71, and fixed frames 73 fixedly connected to the vertically movable rod 72 to extend downward therefrom to the guide groove. The fixed frames 73 serve to prevent the movement of the second hydraulic cylinder 71 as their lower ends come into close contact with the locking bar 8. In this case, it is preferable that at least two fixed frames 73 are installed at diagonally symmetric positions around the rod 72 to keep balance, and that the lower ends of the fixed frames 73 are connected to an auxiliary frame 74 and in turn, a lower surface of the auxiliary frame 74 comes into close contact with the inclined flat surface 82 of the locking bar 8. It should be clearly understood that, without being limited to the above described embodiment, another means for accessing a lower surface of the vertically movable rod 72 in order to prevent downward movement of the insert core 7 may be realized within the technical scope of the present invention.

[Industrial Applicability]

Claims

[CLAIMS]

[Claim 1 ] A mold device for use in the manufacture of a hand-car type pallet comprising: an upper mold having an upper core fixed at a lower surface thereof, the upper mold being coupled at an upper surface thereof to an upper coupling plate; a lower mold having a lower core fixed at an upper surface thereof, the lower mold being coupled at a lower surface thereof to a lower coupling plate, thereby defining a predetermined interior space along with the upper mold coupled to the upper coupling plate; at least one molten resin feeding channel extending from an upper surface of the upper coupling plate to the interior space in order to supply molten resin into the space; slide cores located at opposite sides of the space and adapted to form fork insertion through-holes as they are slidably moved by means of their first hydraulic cylinders; and an insert core having a second hydraulic cylinder fixed at a lower surface thereof to the lower coupling plate and adapted to vertically move so as to perforate wheel- protraction holes, the insert core being upwardly moved through the lower mold upon upward movement of the second hydraulic cylinder, wherein the mold device further comprises: a locking bar connected to one of the first hydraulic cylinders used to operate the slide cores so as to be synchronized in movement with the first hydraulic cylinder, the locking bar accessing and coming into close contact with the lower surface of the second hydraulic cylinder upon the upward movement of the second hydraulic cylinder.

[Claim 2] The device as set forth in claim 1, wherein the locking bar has a tapered tip portion which partially forms an inclined flat surface extending in an advance direction of the locking bar.

[Claim 3] The device as set forth in claim 1, wherein the locking bar further has a horizontally movable frame connected to an end of the first hydraulic cylinder, so that the horizontal transfer frame is coupled at an upper end thereof to one of the slide cores and at a lower end thereof to an end of the locking bar so as to horizontally move the locking bar. [Claim 4] The device as set forth in claim 1 or 3, wherein the locking bar moves along a guide groove formed at the lower coupling plate, and wherein the insert core further has a vertically movable rod installed on the second hydraulic cylinder, and fixed frames fixedly connected to the vertically movable rod to extend downward therefrom to the guide groove, whereby lower ends of the fixed frames come into close contact with the locking bar, preventing movement of the second hydraulic cylinder.