KR20180027219A - Non-Powered Hydraulic metallic mold lifting system of plastic working device and Plastic working device containing the same - Google Patents

Abstract

Disclosed are a non-powered hydraulic mold lifting/lowering system of a plastic working device, which does not use a separate pressure source, and a plastic working device including the same. According to one embodiment of the present invention, the hydraulic mold lifting/lowering system elastically supports movement in the predetermined direction of a holder with respect to a base of a lower mold in a plastic working device including upper and lower molds paired by corresponding to upper and lower sides. The system comprises: a hydraulic spring of a hydraulic cylinder structure to elastically support the holder with respect to the base of the lower mold; an energy storage unit to temporarily store high pressure oil, which exits from the hydraulic spring to be supplied through a hydraulic hose, when the hydraulic spring is contracted, and to return the temporarily stored high pressure oil to the hydraulic spring by self-restoration force when an external force is removed; a pressure control valve installed in an intermediate portion of the hydraulic hose forming a supply path to maintain an internal pressure of the hydraulic spring at a set pressure; and a check valve installed in a hydraulic hose forming a return path between the energy storage unit and pressure control valve to allow only movement of the oil towards the hydraulic spring through the return path. Accordingly, a system to lift/lower the holder corresponding to lifting/lowering of the upper mold without using a separate pressure source, such as a hydraulic pump, during a plastic work, such as forming and drawing, is able to be constructed.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-powered hydraulic mold lifting system of a plastic working apparatus, and a plastic working apparatus including the same.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-powered hydraulic mold lifting system of a plastic working machine and more particularly to a non-powered hydraulic mold lifting and lowering system of a plastic working machine that does not require a separate pressure source such as a hydraulic pump, The present invention relates to a plastic working apparatus including the above-

Among various machining methods, a plastic working method such as forming or drawing means a processing method in which a plate-shaped material is put in a certain mold and pressed to form a certain shape. This method is widely used because it can be mass-produced in a large amount of products having a relatively high shape accuracy while processing the material by plastic deformation by applying a force to the material by using a punch and a pad.

Equipment used in plastic forming such as forming or drawing is generally referred to as a press. The press consists largely of a top mold and a bottom mold, and comprises a mechanism for hitting the lower mold with a predetermined force in a state where the plate to be processed is positioned between the upper mold and the lower mold, thereby molding the plate located therebetween to a desired shape.

Fig. 1 shows a schematic view of a conventional press used for forming or drawing.

Referring to FIG. 1, the press comprises largely a top mold 100 and a bottom mold 200. The upper die 100 includes a die 110 having a forming surface corresponding to the intended shape and a pad 120. The lower die 200 is provided with a punch having a forming surface corresponding to the forming surface of the upper die 110 And a lifting plate 110 having a holder 210 surrounding the punch and moving up and down on the base 240 in conjunction with lifting and lowering of the upper mold 100.

An elastic body 300 is installed on the lower mold 200 between the base 240 and the holder 210. The elastic body 300 elastically supports the lifting plate 110 and the holder 210 so that the lifting plate 110 and the holder 210 are lowered together when the upper mold 100 strikes the lower mold 200, 100 are separated from each other, the holder 210 provides a restoring force so as to return to the original height. As such an elastic body 300, a compression coil spring is conventionally used.

However, the compression coil spring has a limited durability. That is, there is a problem that the fatigue is accumulated in proportion to the number of times of hitting and the elastic strength is lowered accordingly. If the elasticity of the spring falls below the initial setting value due to the accumulation of the number of times of use, the pressing force of the upper die against the holder of the upper die is not uniform, and the shape accuracy of the product is lowered.

Therefore, a technique of using a hydraulic cylinder instead of a coil spring has been proposed. The technique of replacing the spring with a hydraulic cylinder controls the flow of the high-pressure oil supplied from a pressure source, for example, a hydraulic pump, to the directional control valve to control the lifting and lowering of the hydraulic cylinder. Therefore, it is very unlikely that the stroke distance will change even when the number of strikes is accumulated. Therefore, the quality uniformity of the molded product can be maintained even for a long time.

However, the conventional technique of using a hydraulic cylinder as an elastic body is disadvantageous in that, since a separate pressure source requiring electricity is used, such as a hydraulic pump, the cost for maintaining the apparatus is high and the pressure source is normally If it is not driven, normal product molding can not be performed, and the operation is interrupted until the problem is solved, which leads to cost and time loss.

Korean Patent Publication No. 2014-0075342 (published on April 19, 2014)

SUMMARY OF THE INVENTION It is an object of the present invention to provide a non-powered hydraulic mold lifting system of a plastic working apparatus that does not require a separate pressure source such as a hydraulic pump while using a hydraulic cylinder, and a plastic working apparatus including the same.

According to an aspect of the present invention,

A hydraulic type metal elevating system for elastically supporting a movement of a holder in a specific direction with respect to a base of a lower mold in a plastic working apparatus composed of upper and lower pairs of upper and lower pairs,

The holder is elastically supported so that the workpiece between the lower and upper molds is plastic-worked at a predetermined constant pressure while being contracted while being interlocked with the lowering of the holder by the upper mold, A hydraulic spring of a hydraulic cylinder structure for providing a restoring force to return to the position;

Pressure oil that is temporarily stored by the self-restoring force when the upper mold is lifted is stored in the hydraulic spring by a force of an upper mold acting on the hydraulic spring through the holder, temporarily stores high-pressure oil supplied from the hydraulic spring through the hydraulic hose, An energy storage unit operable to return the energy storage unit;

And a control unit that is provided in the middle of a hydraulic hose forming a supply path to prevent a pressure drop so that an internal pressure of the hydraulic spring is maintained at a set pressure, and opens when the internal pressure exceeds a set pressure, Pressure control valve; And

A hydraulic pressure hose which is provided in a hydraulic hose forming a return path between the energy storage unit and the pressure control valve and which permits movement of the oil toward the hydraulic spring through the return path and restricts movement of the oil on the energy storage side through the return path; And a valve for controlling the movement of the mold in the non-powered hydraulic mold lifting / lowering system.

The hydraulic spring applied to the non-powered hydraulic type mold lifting system according to one aspect of the present invention is characterized in that a single variable hydraulic pressure chamber defined by an inner cylinder wall and a piston is formed in the inner side of the piston, It may be a single acting hydraulic cylinder structure in which a support surface for contacting a part of the lower surface of the holder is formed.

The energy storage unit may include a single-acting hydraulic cylinder-type pressure oil storage tank having a single variable hydraulic chamber defined therein by an inner cylinder wall and a piston, a pressure oil storage tank connected to the pressure oil storage tank so as to be interlocked, And an operating rod of the accumulator may be coaxially connected to the piston rod of the pressure oil storage tank.

At this time, the piston rod of the pressure oil storage tank is expanded in the direction of the accumulator by the high-pressure oil supplied during the contraction of the hydraulic spring due to the action of the external force (pressing force due to the descending of the upper mold) and the accumulator is compressed to store the pressure energy, When the external force due to the rise is removed, the accumulator is restored to its original state by the pressure energy, and the high-pressure oil filled in the pressure oil storage tank is returned to the hydraulic spring side again so that the hydraulic spring can be restored to its original state.

The non-powered hydraulic type mold lifting system according to one aspect of the present invention is also provided in the hydraulic spring or the hydraulic hose and measures the pressure of the oil moved in accordance with the expansion and contraction of the hydraulic spring to convert it into a digital value And outputting the digital pressure gauge.

In addition, the hydraulic springs may be installed in two or more pairs so as to be symmetrical with respect to each other with punches of the lower mold interposed therebetween at different positions, and the total capacity of the hydraulic springs is the same as the capacity of the pressure storage tank of the energy storage unit So that the plurality of hydraulic spring displacement widths can always be kept constant.

According to another aspect of the present invention, there is provided a non-powered hydraulic mold lifting / lowering system, comprising: an electronic control valve installed in a hydraulic hose between the pressure control valve and a check valve for controlling movement of oil toward a hydraulic spring under the control of a controller; .

At this time, the controller outputs a control command to shut off the movement of the oil to the electronic control valve immediately after the upper mold is completely lowered, and outputs a control command allowing the movement of the oil to the electronic control valve Lt; / RTI >

According to another aspect of the present invention as a solution to the problem,

An upper die including a die and a pad vertically movable in the center of the die;

A punch disposed on the base in correspondence with a portion of the upper die and a pad; and a holder provided on the lifting plate to correspond to another portion of the die and surrounding the punch; And

And a plurality of hydraulic springs provided between the base and the holder to elastically support the lifting plate so that the lifting plate is lowered when the lifting plate is lowered and provide a restoring force to return the holder to its original position upon lifting the lifting plate, And a hydraulic mold lifting / lowering system according to the present invention.

According to the embodiment of the present invention, a hydraulic cylinder is used as an elastic body for elastically supporting a part of the lower mold so that the upper mold has a constant pressing force on the holder of the lower mold, but a separate pressure source such as a hydraulic pump is not required . Thus, it is possible to greatly reduce the cost of maintaining the apparatus, and there is no need to worry about problems caused by electrical problems or controller malfunctions.

In addition, even if there is a change in the restoring force of the hydraulic cylinder due to a slight leakage during use due to a load greater than the set value in the hydraulic cylinder or accumulation of the number of times of use, the oil may be additionally supplemented. Therefore, there is an advantage that the maintenance is very easy, and since the configuration is simple, the system can be easily constructed and the cost can be greatly reduced. That is, a low-cost and high-efficiency plastic working apparatus can be realized.

1 is a schematic view of a conventional press used for forming or drawing;
2 is a schematic perspective view of a non-powered hydraulic mold lifting system of a plastic working apparatus according to a preferred embodiment of the present invention.
3 is a schematic view of the hydraulic mold lifting system shown in Fig.
4 is a system schematic diagram showing another preferred embodiment of a hydraulic mold lifting system;
5 is a schematic view of a plastic working apparatus according to another aspect of the present invention.
FIG. 6 is an operational state view of a plastic working apparatus according to another aspect of the present invention, and shows a product molding process in sequence through a plastic working apparatus. FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. It is to be understood that the terms "comprises", "having", and the like in the specification are intended to specify the presence of stated features, integers, steps, operations, elements, components, or combinations thereof, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, parts, or combinations thereof.

Also, the terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

In addition, the terms " part, "" unit," " module, "and the like, which are described in the specification, refer to a unit for processing at least one function or operation, which may be implemented by hardware or software or a combination of hardware and software .

In the following description with reference to the accompanying drawings, the same reference numerals are given to the same constituent elements, and a duplicate description thereof will be omitted. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

FIG. 2 is a schematic perspective view of a non-powered hydraulic mold lifting system of a plastic working apparatus according to a preferred embodiment of the present invention, and FIG. 3 is a schematic view of the hydraulic mold lifting system shown in FIG.

The non-powered hydraulic mold lifting system of the plastic working apparatus according to the embodiment of the present invention is characterized in that in the plastic working apparatus composed of upper and lower pairs of upper and lower pairs corresponding to each other, So that the damping function can be continuously performed without using a separate pressure source such as a hydraulic pump while using a hydraulic cylinder as an elastic body for elastically supporting a part of the lower mold.

More specifically, a hydraulic mold lifting system that exhibits a damping function with respect to the movement of a holder in a specific direction with respect to the base of a lower mold, characterized in that it comprises a high pressure oil which is released from a hydraulic spring during an external force action And the hydraulic spring is restored to its original state by returning the oil to the hydraulic spring by self-restoring force when the external force is removed.

2 and 3, the hydraulic mold lifting system of the present invention mainly comprises a hydraulic spring 30, an energy storage unit 50, and a pressure control valve 40. The hydraulic spring 30 may be a hydraulic cylinder structure. The energy storage unit 50 temporarily stores the high-pressure oil discharged during the contraction of the hydraulic spring 30 and, when the external force is removed, the high- And returns to the hydraulic spring 30.

The hydraulic spring 30 is installed at any position of the base 24 constituting the lower mold 20 in the plastic working apparatus constituted by the upper and lower pairs of the upper and lower molds 10 and 20. The hydraulic spring 30 is contracted in conjunction with the lowering of the holder 21 by the upper die 10 so that the workpiece 5 between the lower die 20 and the upper die 10 is plastic- 21) at a constant force.

The hydraulic spring 30 also provides a restoring force for returning the holder 21 to its original position upon removal of the external force due to the lifting of the upper mold 10. The restoring force is compressed to a predetermined pressure when the hydraulic spring 30 is retracted, is forced out of the hydraulic spring 30 and is temporarily stored in the energy storing part 50, By means of a force stored in the form of pressure energy.

The hydraulic spring 30 may preferably be a single acting hydraulic cylinder structure having a single variable hydraulic chamber defined therein by an inner cylinder wall and a piston. The upper end of the piston rod 32 extending out of the cylinder in the piston of the hydraulic spring 30 is provided at the lower end of the lower portion of the holder 21 which is lowered by the strike of the upper mold 10 on the base 24 of the lower mold 20 A supporting surface 320 is formed.

An external force (hitting force) transmitted through the holder 21 when the upper mold 10 is lowered and struck the holder 21 of the lower mold 20, preferably the lower mold 20, And is contracted in the direction in which the piston rod 32 is drawn into the cylinder by an external force inputted to the support surface 320. [ Accordingly, the oil filled in the hydraulic chamber of the hydraulic spring 30 is instantaneously compressed, and the pressure control valve 40 is opened and moved to the energy storage unit 50 through the hydraulic hose.

A slight load may be generated during use due to a momentarily large load applied to the hydraulic cylinder than the set load by the pressure control valve (40) or accumulation of the number of times of use. If oil leakage occurs, the stroke of the hydraulic cylinder is shortened and the pressing force of the workpiece 5 may be changed. An injection port (not shown) may be formed at an appropriate position in the hydraulic cylinder or the energy storage unit 50 to supplement the oil.

The energy storage unit 50 is connected to the energy storage unit 50 when the hydraulic spring 30 is contracted by an external force acting on the hydraulic spring 30 through the holder 21 (force that the upper die 10 hits the lower die 20) (30) and temporarily stores high-pressure oil supplied through the hydraulic hose. And returns the high-pressure oil temporarily stored by the self-restoring force to the hydraulic spring 30 when the upper mold 10 is lifted.

The energy storage unit 50 preferably includes a hydraulic oil storage tank 52 in the form of a hydraulic cylinder in which the piston rod 520 is extended to an oil pressure supplied through a hydraulic hose when the hydraulic spring 30 is contracted by an external force, And an accumulator 54 interlocked with the storage tank 52 and storing the reaction energy with respect to the pressure of the oil acting on the pressurized oil storage tank 52 in the form of pressure energy.

The pressurized oil storage tank 52 may be a single acting hydraulic cylinder structure having a single variable hydraulic pressure chamber defined by an inner cylinder wall and a piston and the accumulator 54 may be connected to the pressurized oil storage tank 52 And the inside is filled with pressure gas. Preferably, the pressurized oil storage tank 52 and the accumulator 54 may be coaxially arranged as shown in the drawing.

That is, the piston rod 520 of the pressure oil storage tank 52 and the operation rod 540 of the accumulator 54 are coaxially connected. However, it is not limited thereto. The pressure oil storage tank 52 and the accumulator 54 are arranged in a parallel structure in different axes and are connected to each other via an interlocking link that rotates around a central hinge, And the accumulator 54 in a linkable manner.

The piston rod 32 of the pressure oil storage tank 52 is extended in the direction of the accumulator 54 and the accumulator 54 is compressed by the oil forced out of the hydraulic spring 30 due to the contraction of the hydraulic spring 30 The pressure energy is stored. When the external force is removed, the accumulator 54 is restored to its original state by the pressure energy, and the high-pressure oil filled in the pressure oil storage tank 52 is returned to the hydraulic spring 30 side again The hydraulic spring 30 is restored to its original state.

The pressure control valve 40 is installed in the middle of the hydraulic hose forming the supply path L1. The pressure control valve 40 prevents the oil from moving toward the energy storage part 50 through the supply path L1 so that the internal pressure of the hydraulic spring 30 is maintained at the set pressure when the external force does not act, And is opened when the internal pressure exceeds the set pressure due to an external force action to allow movement of the oil toward the energy storage part 50.

The pressure control valve 40 may be a known relief valve having two input and output ports (P1 and P2 ports) and one drain port (T port) The oil return path L2 connecting the P2 port to the hydraulic spring 30 in the pressurized oil storage tank 52 is connected to the oil return path L2 A hydraulic hose can be connected.

Before the internal pressure of the hydraulic spring 30 reaches the set pressure of the pressure control valve 40 (before the pressure control valve 40 is opened to allow oil movement to the energy storage portion 50 side) The oil can be moved to the energy storing portion 50 side even with a small external force equal to or less than the set pressure through the hydraulic hose that forms the oil passage L2. A check valve 60 may be installed in the hydraulic hose forming the return path L2.

That is, the check valve 60 is installed in the hydraulic hose forming the return path L2 between the energy storage part 50 and the pressure control valve 40 so that the hydraulic spring of the oil through the return path L2 30 side movement is permitted and the movement of the oil through the return path L2 to the energy storage portion 50 is restricted. Since the check valve 60 has a known configuration, a detailed description thereof will be omitted.

A pressure gauge (not shown) may be installed in the hydraulic spring 30 or the hydraulic hose described above. The pressure gauge may be a digital pressure gauge that measures the pressure of the oil moved in accordance with the expansion and contraction displacement of the hydraulic spring 30, converts the measured value into a digital value, Of course, the present invention is not limited to this, and a known analog type pressure gauge can also be used.

4 is a system schematic diagram showing another preferred embodiment of a hydraulic mold lifting system according to an aspect of the present invention, wherein the hydraulic mold lifting system may further include an electronic control valve. The electronic control valve 70 may be installed in the hydraulic hose between the pressure control valve 40 and the check valve 60 and controls the movement of the oil toward the hydraulic spring 30 under the control of the controller 80 .

In another embodiment where the electronic control valve 70 is applied, the controller 80 outputs to the electronic control valve 70 a control command to shut off the movement of the oil immediately after the upper mold 10 is completely lowered, The holder 21 of the lower die 20 is raised at the same time as the upper mold 10 is elevated by outputting a control command allowing the movement of the oil to the electromagnetic control valve 70 at an arbitrary time after the rising of the upper die 10, So as to prevent the deformation of the workpiece 5 due to the deformation.

Hereinafter, the operation of the plastic working apparatus according to another aspect of the present invention will be described in more detail.

The above-described hydraulic springs 30 may be installed in two or more pairs so as to be symmetrical with each other with punches 22 of the lower die 20 interposed therebetween at different positions. At this time, the total capacity of the hydraulic springs 30 is set to be equal to the capacity of the pressure storage tank 52 of the energy storage unit 50, so that the displacement widths of the plurality of hydraulic springs 30 can be always kept constant .

Next, a plastic working apparatus according to another aspect of the present invention having a hydraulic mold lifting system according to one aspect will be described with reference to the accompanying drawings.

5 is a schematic view of a plastic working apparatus according to another aspect of the present invention.

5, the plastic working apparatus mainly comprises a hydraulic mold lifting system according to the above-described one aspect including the upper mold 10, the lower mold 20, and the plurality of hydraulic springs 30. [ Since the hydraulic mold lifting system has been described in detail above, a duplicate description thereof will be omitted. Hereinafter, the configuration and overall operation of the plastic working apparatus will be mainly described.

The upper die 10 includes a die 11 and a pad 12 which is vertically movable in the center of the die 11. The die 11 may be attached to a lift base 10 that presses the lower die 20 by a lift cylinder (not shown) or performs a linear movement away from the lower die 20, 11) a linear movement independent of the die 11 (movement of pushing the punch 22 of the lower die or moving away from the punch 22) is carried out by a separate lifting cylinder along the center guide hole.

The lower die 20 includes a punch 22 mounted on the base 24 to correspond to a part of the die 11 and the pad 12 and another part of the die 11, And a holder (21) provided on the lifting plate (23) so as to surround the punch (22). The die 11 of the upper die 10 is provided with a molding surface corresponding to the intended shape of the product and the punch 22 of the lower die 20 is provided with the corresponding upper die 10, Is formed.

In the figure, the upper die 10 has a die 11 and the lower die 20 has a punch 22 corresponding to the die 11. However, the present invention is not limited thereto. The punch 22 may be formed in the upper die 10 and the die 20 corresponding to the punch 22 may be formed in the lower die 20. The punch 22 and the die 11 ) Of the product forming surface of the product may also be changed in accordance with the intended product shape.

The above-described hydraulic spring 30 is installed between the base 24 of the lower die 20 and the holder 21. The hydraulic spring 30 resiliently supports the holder 21 so that the hydraulic spring 30 is lowered together with the lifting plate 23 when the upper mold 10 is lowered and the resilient force is applied to the holder 21 to return the holder 21 to its original position . At this time, the hydraulic springs 30 are symmetrically arranged to pair with each other with the punch 22 constituting the lower die 20 interposed therebetween to support the holder 21.

FIG. 6 is an operating state diagram of a plastic working apparatus according to another aspect of the present invention, and is a diagram showing a product molding process in sequence through a plastic working apparatus. A hydraulic mold lifting / lowering system (see FIG. 4) employing an electronic control valve 70 is applied as an example.

Referring to FIG. 6 and FIG. 4, a workpiece 5 to be molded is placed between the upper die 10 and the lower die 20. In this state, the upper die 10 descends toward the lower die 20 The die 11 and the pad 12 of the upper die 10 strike the punch 22 and the holder 21 of the lower die 20 with a predetermined force. At this time, the holder 21 of the lower die 20 is moved downward together with the die 11 of the upper die 10, so that the plate material is deformed in a shape corresponding to the molding surface of the die 11 and the punch 22 (Figs. 6 (a) to 6 (d)).

The hydraulic spring 30 for holding the holder 21 is contracted simultaneously with the descent of the holder 21 by an external force acting on the holder 21 (force of the die 11 hitting the holder 21) The oil filled in the hydraulic spring 30 is instantaneously compressed and the pressure control valve 40 is opened to be moved to the energy storage part 50 through the hydraulic hose. Of course, in this case, the electromagnetic control valve 70 is kept switched to the side which allows the movement of the energy storage portion 50 of the oil.

Immediately after the upper mold 10 is completely lowered, the controller 80 outputs a control command to the electromagnetic control valve 70 to shut off the movement of the oil, thereby further stopping the movement of the oil. In this state, the die 11 of the upper die 10 is moved upward, and the pad 12 is lifted with a slight time difference. At this time, the electromagnetic control valve 70 blocks the flow of the oil, so that the holder 21 remains lowered even after the upper mold 10 is completely lifted (Fig. 6 (e) to (f)).

Thereafter, a control command is inputted to the electronic control valve 70 to allow the movement of the oil at a predetermined time difference after the upper mold 10 is fully raised. Accordingly, the oil passage is opened, and the oil is again moved to the hydraulic spring 30 by the restoring force of the energy storing portion 50 storing the reaction energy against the pressure of the oil in the form of pressure energy. The hydraulic spring 30 and the holder 21 are restored to their original state (Fig. 6 (g)).

If the hydraulic spring 30 is restored and the holder 21 is raised in a state where the die 11 is raised as shown in FIG. 6E but the pad 12 is still pressing the plate material, Undesirable deformation of the plate material 5 can not be avoided. Therefore, if the pad 12 is lifted with a predetermined time difference from the die 11 as shown in the drawing, a holder 21 locking mechanism for delaying the return of the oil through the electronic control valve 70 is necessarily required .

In the foregoing detailed description of the present invention, only specific embodiments thereof have been described. It is to be understood, however, that the invention is not to be limited to the specific forms thereof, which are to be considered as being limited to the specific embodiments, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. .

10: image 11: die
12: pad 20: bottom
21: holder 22: punch
23: lifting plate 24: base
30: Hydraulic spring 40: Pressure control valve
50: energy storage unit 52: pressure oil storage tank
54: accumulator 60: check valve
70: Electronic control valve 80: Controller
L1: supply path L2: return path

Claims (9)

A hydraulic type metal elevating system for elastically supporting a movement of a holder in a specific direction with respect to a base of a lower mold in a plastic working apparatus composed of upper and lower pairs of upper and lower pairs,
The holder is elastically supported so that the workpiece between the lower and upper molds is plastic-worked at a predetermined constant pressure while being contracted while being interlocked with the lowering of the holder by the upper mold, A hydraulic spring of a hydraulic cylinder structure for providing a restoring force to return to the position;
Pressure oil that is temporarily stored by the self-restoring force when the upper mold is lifted is stored in the hydraulic spring by a force of an upper mold acting on the hydraulic spring through the holder, temporarily stores high-pressure oil supplied from the hydraulic spring through the hydraulic hose, An energy storage unit operable to return the energy storage unit;
And a control unit that is provided in the middle of a hydraulic hose forming a supply path to prevent a pressure drop so that an internal pressure of the hydraulic spring is maintained at a set pressure, and opens when the internal pressure exceeds a set pressure, Pressure control valve; And
A hydraulic pressure hose which is provided in a hydraulic hose forming a return path between the energy storage unit and the pressure control valve and which permits movement of the oil toward the hydraulic spring through the return path and restricts movement of the oil on the energy storage side through the return path; And a valve for controlling the movement of the mold in the non-powered hydraulic mold lifting / lowering system.
The method according to claim 1,
The hydraulic spring includes:
A single variable hydraulic chamber defined by an inner cylinder wall and a piston and a support surface contacting a part of a lower surface of the holder is formed on an upper end of a piston rod extending out of the cylinder in the piston, Characterized in that the non-powered hydraulic mold lifting system of the plastic working apparatus.
The method according to claim 1,
The energy storage unit may include:
A single-acting hydraulic cylinder structure having a single variable hydraulic chamber defined by an inner cylinder wall and a piston therein;
An accumulator connected to the pressure oil storage tank in an interlocked manner and filled with pressure gas,
Wherein the piston rod of the pressurized oil storage tank and the operating rod of the accumulator are coaxially connected to each other.
The method of claim 3,
The piston rod of the pressure oil storage tank is expanded in the direction of the accumulator by the high-pressure oil supplied during the contraction of the hydraulic spring, the accumulator is compressed to store the pressure energy,
The pressure accumulator is restored to its original state by the pressure energy when the external force is removed due to the rise of the upper mold, and the high-pressure oil filled in the pressure oil storage tank is returned to the hydraulic spring side again so that the hydraulic spring is restored to its original state Non - powered hydraulic mold lifting system of plastic forming machine.
The method according to claim 1,
And a digital pressure gauge installed in the hydraulic spring or the hydraulic hose for measuring the pressure of the oil moved in accordance with the expansion and contraction of the hydraulic spring and converting the measured pressure into a digital value so that the user can recognize the pressure externally, Hydraulic mold lifting system.
The method according to claim 1,
Wherein at least two of the hydraulic springs are symmetrically arranged at a plurality of positions with a punch of the lower die interposed therebetween,
Wherein the total capacity of the hydraulic springs is equal to the capacity of the pressure storage tank of the energy storage unit.
The method according to claim 1,
And an electronic control valve installed in a hydraulic hose between the pressure control valve and the check valve for controlling the movement of the oil toward the hydraulic spring under the control of the controller.
8. The method of claim 7,
The controller outputs a control command to shut off the movement of the oil to the electronic control valve immediately after the upper mold is completely lowered,
Wherein the control means is configured to output a control command to allow movement of the oil to the electronic control valve at an arbitrary time after the rise of the upper mold.
An upper die including a die and a pad vertically movable in the center of the die;
A punch disposed on the base in correspondence with a portion of the upper die and a pad; and a holder provided on the lifting plate to correspond to another portion of the die and surrounding the punch; And
And a plurality of hydraulic springs installed between the base and the holder to elastically support the lifting plate so that the lifting plate is lowered when the lifting plate is lowered and provide a restoring force to return the holder to its original position upon lifting the upper lifting plate, And the hydraulic type mold lifting system according to any one of claims 1 to 8.

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