CN102173089B - Medium and small-sized hydraulic machine and die change device thereof - Google Patents

Abstract

The invention discloses a mold changing device, which comprises a workbench, a supporting plate, and a frame arranged under the supporting plate. The mold is installed in the working platform and supported on the supporting plate; the mold changing device also includes a guide rail bracket and a hydraulic cylinder; The fixed part of the cylinder runs through the frame from front to back and is fixedly supported on the frame. The movable part of the hydraulic cylinder is connected to the workbench through a connector; The sides are fixedly connected to the supporting plate, the height of the top surface of the supporting beam is equal to the height of the top surface of the supporting plate, and the bottom ends of the supporting legs are supported on the ground. The mold changing device can safely and quickly pull out and push the workbench out of the machine body to facilitate the replacement of hydraulic press molds. The invention also discloses a medium and small hydraulic press, which includes a machine body, an electric control system and a hydraulic control system; the machine body adopts the above-mentioned mold changing device, and the mold changing device is connected to the bottom of the machine body. The hydraulic press should also have corresponding technical effects.

Description

A Medium and Small Hydraulic Press and Its Die Changing Device

technical field

The invention relates to the technical field of hydraulic presses, in particular to a mold changing device for medium and small hydraulic presses. The present invention also relates to a hydraulic machine comprising the above-mentioned mold changing device.

Background technique

A hydraulic press is a machine that uses liquid as the working medium and is made according to Pascal's principle to transmit energy to realize various processes. According to the type of liquid that transmits pressure, hydraulic presses are divided into two categories: hydraulic presses and hydraulic presses. The total pressure produced by the hydraulic press is relatively large, and it is often used for forging and stamping.

In addition to being used for forging and forming, hydraulic presses can also be used for straightening, pressing, packing, briquetting and pressing. The usual hydraulic press mainly consists of three parts: mechanical structure, hydraulic transmission and electrical control. Put the upper mold and the blank on the top, use the principle of electric control and hydraulic transmission to make the slider drive the upper mold to punch down, so that the blank can be plastically deformed, so as to obtain the shape and size matching the mold.

At present, in the use of hydraulic presses, especially in the production of multiple varieties and small batches, a large number of different molds need to be replaced frequently. For large-scale hydraulic presses, a complete set of mold changing devices that are relatively independent from the body of the hydraulic press is usually required, such as a mold changing trolley that can move by itself to complete the mold changing work. For small and medium-sized hydraulic presses, the use of mold changing trolleys will increase production costs. Therefore, when changing the template, the workbench is usually pulled out from the hydraulic press body, the existing mold placed on the workbench is taken out, replaced with a new mold, and finally the workbench is pushed back into the hydraulic press body to start the forging process of the new product.

When changing the formwork of the known small and medium-sized hydraulic presses at present, the work of pulling out and re-pushing the workbench from the hydraulic machine body mainly depends on the operator's manual work, which not only has low work efficiency, but also has no guarantee for the personal safety of the operator.

Therefore, how to combine the structure of the body of the existing hydraulic press to design a mold changing device so that it can quickly and safely pull out and push the workbench out of the body, and realize accurate positioning during the process of pulling out and pushing in , to facilitate the replacement of hydraulic press molds, is a technical problem that those skilled in the art need to solve urgently at present.

Contents of the invention

The technical problem to be solved by the present invention is to provide a mold changing device for small and medium-sized hydraulic presses, which can safely and quickly pull out and push the workbench out of the machine body, and realize Precise positioning facilitates the replacement of hydraulic press molds. Another technical problem to be solved by the present invention is to provide a small and medium-sized hydraulic press including the above-mentioned mold changing device.

In order to solve the above-mentioned technical problems, the present invention provides a mold changing device, which includes a workbench, a pallet, and a frame arranged under the pallet, and the mold is installed in the workbench and supported on the pallet; The mold changing device also includes a guide rail bracket and a hydraulic cylinder; the fixed part of the hydraulic cylinder runs through the frame from front to back and is fixedly supported on the frame, and the movable part of the hydraulic cylinder is connected to the workbench through a connecting piece. Connection; the guide rail bracket is arranged on one side of the movable part, including a support beam and legs, one side of the support beam is fixedly connected to the pallet, and the height of the top surface of the support beam is equal to that of the support The height of the top surface of the board, the bottom ends of the legs are supported on the ground.

Preferably, the supporting plate is provided with a guide mechanism on both sides perpendicular to the hydraulic cylinder, and a guide block is provided inside the guide mechanism, and the guide block is in contact with the outer wall of the workbench.

Preferably, the guide block is specifically a guide wheel, and the guide mechanism includes a trough structure with an opening facing the workbench and a cover plate connected above the trough structure, and the middle part of the cover plate is connected with a vertical The pin shaft is covered with the guide wheel.

Preferably, it also includes a pressing device, the pressing device includes a first stopper provided at the rear end of the pallet and a second stopper provided at the rear end of the workbench, the lower slope of the first stopper and the upper slope of the second stopper.

Preferably, the pressing device further includes a third stopper provided on the front side of the pallet and fourth stoppers provided at both ends of the front side of the workbench, the lower slope of the third stopper and the The upper slope of the fourth stop fits.

Preferably, the top surface of the pallet is provided with a groove extending back and forth, and a floating guide rail device is provided in the groove; the floating guide rail device includes a guide rail and a lifting component, and the guide rail is provided with a roller column at the top, When the lifting member is lifted up and down, the roller surface at the upper end of the roller column is higher or lower than the top surface of the supporting plate.

Preferably, the lifting component is specifically an upper piston and a lower piston vertically penetrating through the guide rail, the upper piston is fixedly connected to the guide rail, and an oil passage extending forward and backward is also provided in the guide rail, and the oil passage An oil chamber connected between the upper piston and the lower piston.

Preferably, the top surface of the guide rail bracket is also provided with the groove, and the floating guide rail device is also arranged in the groove.

Preferably, the mold changing device further includes a positioning plate, the upper part of the positioning plate is fixedly connected to the front side of the workbench, the bottom end of the positioning plate is lower than the top surface of the supporting plate, and the positioning plate The inner side of the plate is attached to the front side of the workbench and the front side of the pallet.

The present invention also provides a medium and small-sized hydraulic press, including a machine body, an electrical control system and a hydraulic control system; the machine body adopts the above-mentioned mold changing device, and the mold changing device is connected to the bottom of the machine body.

The mold changing device provided by the present invention includes a rail bracket and a hydraulic cylinder; the fixed part of the hydraulic cylinder runs through the frame and is fixedly supported on the frame, and the movable part of the hydraulic cylinder is connected to the workbench through a connecting piece; the rail bracket is arranged on One side of the movable part includes a support beam and a leg, one side of the support beam is fixedly connected to the supporting plate, the height of the top surface of the support beam is equal to the height of the top surface of the supporting plate, and the bottom end of the supporting leg is supported on the ground.

With this structure, when the hydraulic machine needs to replace the mold, the pressure oil of the hydraulic cylinder can be controlled to drive the movable part of the hydraulic cylinder to extend outward, and drive the worktable connected with the movable part to move outward from the bottom of the machine until the workbench is completely Move to the guide rail bracket and stop; at this time, take out the existing mold from the workbench and install a new mold; control the pressure oil in the hydraulic cylinder to retract the movable part inward, and drive the workbench connected to it to move inward. Until the workbench is completely moved to the supporting plate, return to the working position and start a new forging operation.

It can be seen that, with the above-mentioned mold changing device, the workbench can be pulled out and pushed in from the machine body quickly and smoothly by controlling the pressure oil of the hydraulic cylinder. The height of the top surface of the pallet enables the workbench to be stably supported on the support beam after it is detached from the pallet, which facilitates the replacement of molds. Compared with the prior art, this mold changing device greatly improves work efficiency and ensures that operators safety.

Since the above-mentioned mold changing device has the above-mentioned beneficial technical effects, the hydraulic press including the mold changing device should also have corresponding technical effects, which will not be repeated here.

Description of drawings

Fig. 1 is a schematic structural view of a specific embodiment of the mold changing device provided by the present invention;

Fig. 2 is the right view of Fig. 1;

Fig. 3 is the top view of Fig. 2;

Fig. 4 is a schematic structural view of the pressing device and the guide device in Fig. 1;

Figure 5 is a top view of Figure 4;

Fig. 6 is a schematic structural view of the floating guide rail device in Fig. 1;

Fig. 7 is a schematic structural view of a specific embodiment of the hydraulic machine provided by the present invention.

Among them, the corresponding relationship between reference signs and component names in Fig. 1 to Fig. 7 is: 1 workbench; 2 pallet; 3 frame; 4 guide rail bracket; 5 hydraulic cylinder; 8 floating guide rail device; 9 positioning plate; 41 supporting beam; 42 outrigger; 51 fixed part; 52 movable part; Block; 72 second block; 73 third block; 74 fourth block; 81 guide rail; 82 lifting components; 811 roller; 812 oil passage;

Detailed ways

The core of the present invention is to provide a mold changing device for small and medium-sized hydraulic presses, which can quickly and safely pull out and push the workbench out of the machine body, thereby greatly improving the efficiency of mold replacement. Another core of the present invention is to provide a hydraulic press including the above-mentioned mold changing device.

In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Please refer to Fig. 1, Fig. 2 and Fig. 3, Fig. 1 is a schematic structural view of a specific embodiment of the mold changing device provided by the present invention; Fig. 2 is a right view of Fig. 1; Fig. 3 is a top view of Fig. 2 .

In a specific embodiment, as shown in Fig. 1, Fig. 2 and Fig. 3, the mold changing device provided by the present invention includes a workbench 1, a pallet 2, a frame 3, a hydraulic cylinder 5 and a guide rail support 4; The mold is installed in the workbench 1, which is an important working part of the hydraulic press; the supporting plate 2 is arranged under the working platform 1 and supports the working platform 1; The workbench 1 and the supporting plate 2; the hydraulic cylinder 5 is arranged on the frame 3, and its fixed part 51 runs through the frame 3 front and back and is fixedly supported on the frame 3; its movable part 52 is connected to the workbench 1 through a connecting piece 53; The support 4 is arranged on one side of the movable part 52 of the hydraulic cylinder 5, and includes a support beam 41 and a leg 42. One side of the support beam 41 is fixedly connected to the pallet 2, and the height of the top surface of the support beam 41 is equal to the top of the pallet 2. The bottom of the leg 42 is supported on the ground.

With this structure, when the hydraulic machine needs to replace the mold, the pressure oil of the hydraulic cylinder 5 can be controlled to drive the movable part 52 of the hydraulic cylinder 5 to extend outward, and drive the workbench 1 connected with the movable part 52 to move outward from directly below the machine body , until the workbench 1 is completely moved to the guide rail bracket 4 and stops; at this time, the existing mold is taken out from the workbench 1, and a new mold is installed; the pressure oil in the hydraulic cylinder 5 is controlled to make the movable part 52 retract inwardly, driving The workbench 1 connected with it moves inward until the workbench 1 is completely moved onto the supporting plate 2, and returns to the working position to start a new forging operation.

It can be seen that, by using the above-mentioned mold changing device, the workbench 1 can be pulled out from the machine body quickly and smoothly by controlling the pressure oil of the hydraulic cylinder 5 and then pushed in. When the workbench 1 is pulled out, due to the support beam 41 The height of the top surface is equal to the height of the top surface of the supporting plate 2, so that the workbench 1 can be stably supported on the supporting beam 41 after it is separated from the supporting plate 2, which is convenient for the replacement of the mold. Compared with the prior art, this mold changing device is greatly improved. Improve work efficiency and ensure the safety of operators.

It should be noted that the length of the above-mentioned guide rail support 4 in the front-to-back direction is preferably not less than the length of the workbench 1 in the front-to-back direction, which can increase the stability of the workbench 1 placed on the support beam 41; the stroke of the hydraulic cylinder 5 needs to be large enough , so as to ensure that the workbench 1 can be completely moved onto the support beam 41 of the guide rail bracket 4 .

The above-mentioned connecting piece 53 can be specifically a bent arm, and the bent arm can include a 90-degree bent structure, the horizontal arm of the bent structure is fixedly connected to the workbench 1, and the bottom end of the vertical arm is fixedly connected to the hydraulic cylinder 5 The movable part 52 of the movable part adopts such a connecting piece 53. When the hydraulic cylinder 5 extends outward, the horizontal arm on the upper part of the curved arm pulls the workbench 1 completely horizontally, which makes the force of the workbench 1 stable and reliable in operation. , and the curved arm has the characteristics of simple structure and convenient manufacturing. Of course, the above-mentioned connecting piece 53 can also adopt other structures, for example, it can be specifically a U-shaped arm that falls down. The unit 52 can realize the same function.

In addition, the orientation word "front" in this article refers to the direction from the back of the hydraulic press to the front of the hydraulic press, that is, the direction from left to right in Figure 1, and the orientation word "rear" refers to the direction from the front of the hydraulic press to the back of the hydraulic press. That is, the direction from right to left in FIG. 1 , it should be understood that the appearance of these orientation words is established based on the accompanying drawings, and their appearance should not affect the protection scope of the present invention. Of course, the above-mentioned embodiment does not limit whether the movable part 52 of the hydraulic cylinder 5 is located at the front end or the rear end of the frame 3. In fact, no matter whether the movable part 52 is located at the front end or the rear end of the frame 3, all the activities of the hydraulic cylinder 5 One side of the part 52 is provided with a guide rail support 4 to ensure that the mold change device that can be placed on the guide rail support 4 after the workbench 1 stretches out should belong to the protection scope of the present invention.

The specific structural form of the above-mentioned mold changing device can also be further set.

Please refer to FIG. 4 and FIG. 5 , FIG. 4 is a structural schematic diagram of the pressing device 7 and the guiding device in FIG. 1 ; FIG. 5 is a top view of FIG. 4 .

In another specific embodiment, as shown in Figure 4 and Figure 5, the above-mentioned supporting plate 2 is provided with a guide mechanism 6 on both sides perpendicular to the hydraulic cylinder 5, and a guide block 61 is arranged inside the guide mechanism 6. The guide block 61 is in contact with the outer wall of the table 1 . By setting such a guide mechanism 6, when the workbench 1 protrudes forward with the movable part 52 of the hydraulic cylinder 5, the guide blocks 61 on both sides are in frictional contact with the two outer walls of the workbench 1, so that the workbench 1 moves along the The predetermined trajectory moves forward in a straight line, which plays a very good guiding role. Here, two above-mentioned guide mechanisms 6 can be arranged in the front and back directions of the frame 3, that is, four guide mechanisms 6 are arranged symmetrically on both sides of the workbench 1, which can play a more accurate guiding role. Of course, the above-mentioned mold change The device can also comprise other numbers of guide mechanisms 6 .

In a specific solution, the above-mentioned guide block 61 can be specifically a guide wheel, and the guide mechanism 6 can include a trough structure 62 with an opening facing the workbench 1 and a cover plate 63 connected above the trough structure 62. The middle part of the cover plate 63 is connected with Vertical pin shaft 64, pin shaft 64 outer sleeves are provided with guide wheels. Here, the guide block 61 is set as a guide wheel, the sliding friction between the guide block 61 and the worktable 1 can be changed into rolling friction, and the wear is further reduced without weakening the guiding effect, thereby enhancing the service life of the guide block 61 , reducing the production cost of the mold changing device.

Of course, the above-mentioned guide block 61 is not limited to guide wheels, and can also be other structures such as guide plates; the above-mentioned guide block 61 can be a guide block 61 of wear-resistant material, which can further enhance its service life; the above-mentioned groove structure can be specifically Three vertical plates are welded, of course, the trough structure can be other structures, as shown in Figure 4 and Figure 5, the above-mentioned trough structure 62 can be specifically composed of three vertical plates, two parallel set The vertical plates are vertically fixed on the supporting plate 2 by bolts, and a horizontal vertical plate is also vertically fixed on the supporting plate 2 by bolts. Trough structure. Of course, the horizontal vertical plate can also have a bent structure, and the inner surface of the bent part can be attached to one of the two vertical plates, wrap the vertical plate from the outside and be fixedly connected with it, thereby forming a trough structure Such a trough structure can enhance the strength of the trough structure when the workbench 1 runs back and forth, and prevent the trough structure 62 from tilting forward and backward due to excessive friction between the workbench 1 and the guide wheels. Of course, the bonding surfaces between the inner side of the above-mentioned horizontal vertical board and the outer side of the two vertical boards can be parallel to the outer wall of the workbench 1, and can also be arranged at a certain angle with the outer wall of the workbench 1.

Other specific structures of the above-mentioned mold changing device can also be further provided.

In another embodiment, as shown in Fig. 4 and Fig. 5, the above-mentioned mold changing device may also include a pressing device 7, and the pressing device 7 includes a first stopper 71 arranged at the rear end of the pallet 2 and a The second stopper 72 at the rear end of the table 1, the lower slope of the first stopper 71 and the upper slope of the second stopper 72 fit together. Using such a pressing device 7, when the mold changing device pushes the workbench 1 back onto the supporting plate 2, the first stopper 71 and the second stopper 72 gradually come into contact until they fit together completely, so that the workbench 1 can be tightly pressed. It is tightly pressed on the supporting plate 2 to achieve a good positioning effect.

In addition, the pressing device 7 can also include a third stopper 73 arranged on the front side of the pallet 2 and a fourth stopper 74 arranged at both ends of the front side of the workbench 1, the lower slope of the third stopper 73 and the The upper slope of the fourth block 74 fits together. The function of the first stopper 71 and the second stopper 72 is the same as that of the above-mentioned first stopper 71 and the second stopper 72. When the workbench 1 is pushed back onto the pallet 2, the third stopper 73 and the fourth stopper 74 are completely fitted together, which can further enhance the work The positioning accuracy of table 1 and pallet 2.

Other specific structures of the above-mentioned mold changing device can also be further provided.

Please refer to FIG. 6 , which is a schematic structural diagram of the floating rail device in FIG. 1 .

In another specific embodiment, as shown in Figure 6, the above-mentioned mold changing device can also include a floating guide rail device 8; the top surface of the pallet 2 is provided with a groove extending forward and backward, and the floating guide rail is arranged in the groove Device 8: Floating guide rail device 8 includes guide rail 81 and lifting part 82, guide rail 81 is provided with roller column 811 at the top, when lifting part 82 lifts, the upper end roller surface of roller column 811 is higher than or lower than the top surface of supporting plate 2.

Specifically, the lifting member 82 can vertically penetrate the upper piston 821 and the lower piston 822 of the guide rail 81, the upper piston 821 is fixedly connected to the guide rail 81, and the guide rail 81 is also provided with an oil passage 812 extending forward and backward, and the oil passage 812 communicates with the An oil chamber 823 between the upper piston 821 and the lower piston 822 .

With this floating guide rail device 8, when the workbench 1 works normally, the elevating member 82 is in a descending state, and the upper end roller surface of the roller column 811 on the guide rail 81 is lower than the top surface of the workbench 1; when the workbench 1 needs to be pulled When it is pushed out or pushed back, the oil circuit system is started, and the pressure oil is passed into the oil passage 812, and the pressure oil flows into the oil chamber 823 between the upper piston 821 and the lower piston 822. As the pressure oil gradually increases, the upper piston 821 rises upwards. lift up, thereby driving the guide rail 81 fixedly connected to it to rise upwards, so that the upper end of the roller 811 is higher than the top surface of the workbench 1, so that the mold changing device can work in the process of pulling out and pushing into the workbench 1. The bottom surface of the table 1 forms rolling friction with the upper end roller surface of the roller column 811 of the floating guide rail device 8, so that the push in and pull out of the worktable 1 can be realized with a relatively small thrust force, which greatly saves the driving force and reduces the replacement cost. The production cost of the mold device. Of course, in addition to the lifting part 82 formed by the upper piston 821 and the lower piston 822, the above-mentioned floating guide rail device 8 can also adopt other structures. The floating guide rail device 8 on the top surface of the pallet 2 should all fall within the protection scope of the present invention.

Of course, the above-mentioned embodiment does not limit the specific quantity of the floating guide rail device 8. According to the size and weight of the workbench 1, four grooves can be arranged in parallel on the supporting plate 2, and four guide rails 81 can be built in. Of course, other numbers can also be used. , each floating rail device 8 can also be provided with several lifting parts 82 according to the front and back length of the workbench 1, so as to ensure that the weight of the workbench 1 can be fully supported.

In another embodiment, the above-mentioned groove is also provided on the top surface of the above-mentioned guide rail bracket 4, and the above-mentioned floating guide rail device 8 is also arranged in the groove. In this way, when the workbench 1 moves to and from the guide rail support 4, it can also form sliding friction with the top of the support surface of the guide rail support 4, thereby reducing the thrust during mold change and further reducing the cost.

The specific structural form of the above-mentioned mold changing device can also be further set.

In another specific embodiment, the mold changing device can also include a positioning plate 9, the upper part of the positioning plate 9 is fixedly connected to the front side of the workbench 1, and the bottom end of the positioning plate 9 is lower than the top surface of the supporting plate 2, The inner side of the positioning plate 9 is attached to the front side of the workbench 1 and the front side of the supporting plate 2 .

With such a structure, when the workbench 1 is pushed back onto the supporting plate 2 from the front side, when the positioning plate 9 installed on the front side of the workbench 1 touches the front side of the supporting plate 2, the workbench 1 stops moving. It further plays the role of accurate positioning when the workbench 1 is pushed back.

Please refer to FIG. 7 , which is a schematic structural diagram of a specific embodiment of the hydraulic machine provided by the present invention.

As shown in Figure 7, the present invention also provides a medium and small-sized hydraulic press, including a body, an electrical control system and a hydraulic control system; the body adopts the above-mentioned mold changing device, and the mold changing device is connected to the bottom of the body. Since the above-mentioned mold changing device has the above-mentioned beneficial technical effects, the hydraulic press including the mold changing device should also have corresponding technical effects, which will not be repeated here.

The above is a detailed introduction of a medium and small-sized hydraulic press and its mold changing device provided by the present invention. In this paper, specific examples are used to illustrate the principle and implementation of the present invention, and the descriptions of the above embodiments are only used to help understand the method and core idea of the present invention. It should be pointed out that for those skilled in the art, without departing from the principle of the present invention, some improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims (7)

1. a mould changing device, comprise workbench (1), supporting plate (2), and the frame (3) of being located at described supporting plate (2) below, in described workbench (1), mould is housed and is supported in described supporting plate (2); It is characterized in that, described mould changing device also comprises rail brackets (4) and hydraulic cylinder (5); Run through described frame (3) before and after the fixed part (51) of described hydraulic cylinder (5), and be fixedly supported to described frame (3), the movable part (52) of described hydraulic cylinder (5) is connected with described workbench (1) by connector (53); Described rail brackets (4) is located at a side of described movable part (52), comprise supporting traverse (41) and supporting leg (42), one side of described supporting traverse (41) is fixedly connected on described supporting plate (2), the apical side height of described supporting traverse (41) equals the apical side height of described supporting plate (2), and the bottom of described supporting leg (42) is supported in ground;

Described supporting plate (2) is provided with guiding mechanism (6) in the both sides perpendicular to described hydraulic cylinder (5), is provided with guide pad (61) in described guiding mechanism (6), and described guide pad (61) contacts with the outer wall of described workbench (1);

Described guide pad (61) is specially directive wheel, described guiding mechanism (6) comprises opening towards the trench structure (62) of described workbench (1) and is connected in the cover plate (63) of described trench structure (62) top, described cover plate (63) middle part is connected with vertical bearing pin (64), is set with described directive wheel outside described bearing pin (64);

Also comprise hold down gag (7), described hold down gag (7) comprises the first block (71) of being located at described supporting plate (2) rear end and is located at second block (72) of described workbench (1) rear end, the ramp laminating of the lower inclined plane of described the first block (71) and described the second block (72).

2. mould changing device according to claim 1, it is characterized in that, described hold down gag (7) also comprises the 3rd block (73) of being located at described supporting plate (2) front side and the 4th block (74) of being located at described workbench (1) two ends, front side, the ramp laminating of the lower inclined plane of described the 3rd block (73) and described the 4th block (74).

3. mould changing device according to claim 1, is characterized in that, the groove extended before and after the end face of described supporting plate (2) is provided with, be provided with floating guide rail device (8) in described groove; Described floating guide rail device (8) comprises guide rail (81) and Lift Part (82), described guide rail (81) is provided with roller (811) on top, during described Lift Part (82) lifting, the upper end roll surface of described roller (811) is higher or lower than the end face of described supporting plate (2).

4. mould changing device according to claim 3, it is characterized in that, described Lift Part (82) is specially upper piston (821) and the lower piston (822) that vertically runs through described guide rail (81), described upper piston (821) is fixedly connected on described guide rail (81), the oil duct (812) extended before and after described guide rail (81) also is provided with, described oil duct (812) is communicated in the oil pocket (823) between described upper piston (821) and described lower piston (822).

5. mould changing device according to claim 4, is characterized in that, the end face of described rail brackets (4) also is provided with described groove, also is provided with described floating guide rail device (8) in described groove.

6. mould changing device according to claim 1, it is characterized in that, described mould changing device also comprises location-plate (9), the top of described location-plate (9) is fixedly connected on the front side of described workbench (1), the bottom of described location-plate (9) is lower than the end face of described supporting plate (2), and the leading flank of the medial surface of described location-plate (9) and the leading flank of described workbench (1), described supporting plate (2) is fitted.

7. a medium-small hydraulic press, comprise body, electric control system and hydraulic control system; It is characterized in that, described body adopts as the described mould changing device of claim 1-6 any one, and described mould changing device is connected in the bottom of described body.

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