EP0371176A1

EP0371176A1 - Multi-boost synchronized hydraulic pump

Info

Publication number: EP0371176A1
Application number: EP88311330A
Authority: EP
Inventors: Shojiro C/O Aioi Seiki Inc. Takeshima
Original assignee: Aioi Seiki Inc
Current assignee: Aioi Seiki Inc
Priority date: 1988-11-30
Filing date: 1988-11-30
Publication date: 1990-06-06
Anticipated expiration: 2008-11-30
Also published as: DE3887150D1; EP0371176B1; DE3887150T2

Abstract

The disclosed multi-boost synchronized hydraulic pump comprises a plurality of piston-type pumping means installed in series, a common connecting shaft (4) connecting these pumping means and a driving means for synchronously driving a plurality of pistons (3) through this connecting shaft (4), and is configurated in a manner capable of supplying pressurized liquid of equal pressure and equal flow rate from a plurality of pumping means.

Description

The present invention relates to a multi-boost synchronized hydraulic pump, and specifically relates to a multi-boost synchronized hydraulic pump which is optimum to synchronously drive a plurality of hydraulic cylinders by supplying these hydraulic cylinders or the like with hydraulic fluid of equal pressure and equal flow rate.
Conventionally, in the case of driving, for example, a plurality of hydraulic cylinders in a synchronized manner by hydraulic fluid supplied from a single hydraulic supply source, generally a hydraulic supply piping is branched and a flow control valve or a variable throttle valve is inserted in each branch piping and a hydraulic cylinder is connected to each branch piping, and thereby the flow rate of hydraulic fluid supplied to each cylinder is adjusted to become equal.
On the other hand, a synchronized hydraulic pump has been put in practical use which supplies hydraulic fluid of equal pressure and equal flow rate from each hydraulic operation chamber by synchronously driving plungers inserted slidably into a plurality of the hydraulic operation chambers installed in parallel by a driving piston. In this conventional synchronized hydraulic pump, a plurality of plunger holes are installed in parallel in a housing, and each plunger is inserted into each plunger hole, and these plungers are connected integrally to the driving piston at the end of the side opposite to the hydraulic operation chambers, and synchronized driving is performed by a common driving means.
In the previous utility model application (Japanese Utility Model Provisional Publication No. 63-106904), in order to eliminate defects of the synchronized hydraulic pump, there was proposed a multi-connected synchronized hydraulic pump which is configurated in a manner that a large-diameter piston is fitted slidably into a cylindrical casing, and a plurality of annular hydraulic operation chambers are formed which are concentric with this piston and are opened to one end surface of the piston, and an annular plunger projecting from one end wall of the casing is inserted slidably into each hydraulic operation chamber, and liquid (oil) in each hydraulic operation chamber is pressurized by driving the piston, and oil path formed in each plunger corresponding each hydraulic operation chamber is connected to each oil supplying piping.
In the known hydraulic pump using variable throttle valves or the like, adjustment of the degree of opening one throttle valve affects the control of flow rate of the other throttle valves, and therefore it is very difficult to adjust a variable throttle valve inserted in each branch piping, and problems exist that consideration is required on setting the length and the bent part of the branch piping to each hydraulic cylinder equal whenever possible, no stable operation is obtainable because of variation in flow rate due to variation in open air temperature and the number of parts such as pipes and valves of the piping system is increased.
In the known synchronized hydraulic pump, the ends of a plurality of plungers installed in parallel are connected integrally to the driving piston, and therefore if the load of each plunger is not equal, a moment exerts on the driving piston, and it is put in the inclined state and does not operate smoothly or stops. Resultingly, this synchronized hydraulic pump has a problem of difficulty in synchronized driving of a plurality of cylinders having different loads.
In the multi-connected synchronized hydraulic pump in the previous utility model application (Japanese Utility Model Provisional Publication No. 63-106904), a plurality of hydraulic operation chambers are formed in a shape of concentric circles, and therefore operation is performed relatively smoothly. However, problems exist such as various difficulties in machining a plurality of concentric circular shaped plunger inserting grooves on the piston side and in machining a plurality of concentric annular shaped plungers, and a very high manufacturing cost.
The first object of the present invention is to provide a multi-boost synchronized hydraulic pump which reliably performs synchronized operation, and thereby supplies pressurized fluid of equal pressure and equal flow rate even if loads of a plurality of hydraulic operation chambers are not uniform.
A second object of the present invention is to provide a multi-boost synchronized hydraulic pump which can be manufactured easily at a low cost and wherein the number of the hydraulic operation chambers can be varied as required.
A third object of the present invention is to provide a multi-boost synchronized hydraulic pump wherein the discharging pressure and discharging rate can be set freely only by partly replacing parts.
A multi-boost synchronized hydraulic pump comprises a casing, cylinder chambers formed in series in the casing, a piston installed in each cylinder chamber, an intake port installed in a hydraulic operation chamber of each cylinder chamber, a discharge port which is independent from or in common with each intake port, a connecting shaft connecting a plurality of pistons in an integral fashion, and a driving means for synchronously driving a plurality of pistons through the connecting shaft.
Drawings show embodiments in accordance with the present invention.

Fig. 1 is a cross-sectional view of a multi-boost synchronized hydraulic pump of a first embodiment.
Fig. 2 is a plan view of the hydraulic pump as shown in Fig. 1.
Fig. 3 through Fig. 5 are cross-sectional views of major parts of modifications of the hydraulic pump as shown in Fig. 1, respectively.
Fig. 6 is a side view of a lubricant supply pump of a second embodiment.
Fig. 7 is a cross-sectional view of a major part of modification of the lubricant supply pump as shown in Fig. 6.
Fig. 8 is a cross-sectional view of a multi-boost synchronized hydraulic pump of a third embodiment.
Fig. 9 is a cross-sectional view of a major part of a multi-boost synchronized hydraulic pump of a fourth embodiment.

First, description is made on a configuration, function, advantages and the like of the present invention without referring to drawings.
A multi-boost synchronized hydraulic pump in accordance with the present invention comprises a casing, a plurality of cylinder chambers formed in a series in the casing, a piston installed slidably in each cylinder chamber, an intake port for supplying liquid to a hydraulic operation chamber formed on at least one side of the piston in each cylinder chamber, a discharge port for discharging pressurized liquid of each hydraulic operation chamber which is formed independent from or in common with each intake port, a connecting shaft integrally connecting a plurality of the above-mentioned pistons, and a driving means for synchronously driving a plurality of pistons through the connecting shaft.
Hereinafter, detailed description is made on a configuration of each part.
This casing may be formed in an integral fashion, and, for example, may be formed in a divided manner corresponding to each cylinder chamber.
In the case of forming a plurality of cylinder chambers in series in the integrally formed casing, for example, a cylindrical hole is formed in the casing, and partition walls sectioning each cylinder chamber and sleeves configurating an inner peripheral wall of each cylinder chamber between the both partition walls have only to be inserted alternately into this hole in the casing.
Also, in the case of forming the casing in a divided fashion corresponding to each cylinder chamber, for example, the portion of the casing corresponding to each cylinder chamber may be configurated with a partition wall portion sectioning one end of each cylinder and a peripheral wall portion of each cylinder connected continuously to this portion, or may be formed in a manner of dividing into the partition wall portion sectioning one end of each cylinder chamber and a portion corresponding to the peripheral wall of each cylinder chamber. These portions formed in a divided fashion may be combined in a manner capable or incapable of disassembling. For the structure of combining in a manner capable of disassembling, for example, a structure of connection by screws, a structure of connection by a common through bolt or the like has only to be adopted. In addition, it is reasonable to install a sealer for preventing leakage of pressurized liquid at the junction part of each portion of the casing formed in a divided fashion as required.
Basically, the configuration is made in a manner that the inner diameters of a plurality of cylinder chambers and the pressing areas of the pistons are formed equally, and thereby pressurized liquid of equal pressure and equal flow rate can be supplied from a plurality of hydraulic operation chambers. However, it is also possible to supply pressurized liquid of different pressures and flow rates from a plurality of hydraulic operation chambers by setting the pressing areas of a plurality of pistons to be different values.
The above-mentioned intake port for taking liquid into the hydraulic operation chamber may be dependent from the discharge port for discharging pressurized liquid from the hydraulic operation chamber, or may be an intake/discharge port which is used in common with the discharge port.
In the case of using this hydraulic pump as a multi-boost synchronized booster, the intake/discharge port is installed, and in the case of using this as a multi-boost synchronized pump or distributor, the intake port and the discharge port are formed independently from each other.
The piston inserted into each cylinder chamber is required to be connected integrally with the connecting shaft. This means that each piston may be formed integrally with the connecting shaft, or may be fixed integrally in a manner that a plurality of pistons are sequentially fitted to the connecting shaft consisting of one through bolt and are tightened with nuts. In this case, the interval between pistons is set through a spacer formed integrally with this piston or a spacer formed separately from the piston.
The above-mentioned driving means is not limited particularly provided that it can synchronously drive a plurality of pistons through the connecting shaft, and it is possible to use a conventional reciprocating driving means, for example, a return-spring-loaded type single-acting pneumatic cylinder or hydraulic cylinder, a double-acting type pneumatic cylinder or hydraulic cylinder, a solenoid type actuator, a motor and a cam driven by this motor, and a motor and a crank mechanism driven by this motor.
Description is made on the function of the above-mentioned multi-boost synchronized hydraulic pump.
A plurality of cylinder chambers are formed in series in the casing, and the pistons installed respectively in these cylinder chambers are connected integrally with the connecting shaft, and the hydraulic operation chamber is formed on one side of each cylinder chamber, and therefore by synchronously driving a plurality of pistons to the hydraulic operation chamber side by the driving means through the connecting shaft, liquid in each hydraulic operation chamber is pressurized, being discharged through the discharge port.
By forming equally the pressing areas of a plurality of these pistons, pressurized liquid of equal pressure and equal flow rate is discharged from a plurality of hydraulic operation chambers, and therefore by supplying pressurized liquid from each hydraulic operation chamber to each external hydraulic actuator, a plurality of actuators can be synchronously operated at an equal speed, can be synchronously operated with an equal stroke, or can be operated at an equal output.
Since a plurality of pistons are connected integrally with the connecting shaft, all of the pistons perform reliable synchronized operation even if loads exerting on the pistons in the hydraulic operation chambers are not uniform across a plurality of pistons.
Also, in the case of supplying pressurized liquid from a plurality of hydraulic operation chambers to a common actuator through change-over valves with relief function, the operating stroke of this actuator can be controlled stepwise.
Also, different discharging pressures can be produced by different pressing areas of the hydraulic operation chambers by means of different inner diameters of the cylinder chambers or different outer diameters of the connecting shaft portions corresponding to each piston or spacers fitted thereto.
Description is made on advantages of the multi-boost synchronized hydraulic pump. As described above, this pump can reliably discharge pressurized liquid in a synchronized fashion from a plurality of hydraulic operation chambers, and therefore a plurality of hydraulic actuators can be reliably driven synchronously.
This means that since a plurality of pistons are connected integrally with the connecting shaft, each piston is free from moments caused by loads exerting on the other pistons, and operates smoothly in the cylinder chamber, and thereby poor operation or disabled operation can be prevented.
By forming equally the pressing area of the piston of each hydraulic operation chamber, pressurized liquid of equal pressure and equal flow rate can be discharged from each hydraulic operation chamber, and, for example, a plurality of hydraulic cylinders can be synchronously operated at an equal speed, with an equal stroke, or at an equal output. Also, pressurized. liquid discharged from each hydraulic operation chamber is made to selectively join together and is supplied to the common hydraulic cylinder, and thereby, for example, the amount of protrusion of the hydraulic cylinder can be controlled stepwise.
Also, in accordance with the present invention, different discharging pressures can be produced by different pressing areas of the hydraulic operation chambers by means of different inner diameters of the cylinder chambers or different outer diameters of the connecting shaft portions corresponding to each piston or spaces fitted thereto.
Since a plurality of cylinder chambers are formed in series in the casing, the casing can be formed with a structure of connecting divided units of casing corresponding to the respective cylinder chambers, and the piston can also be configurated with divided units corresponding to the respective cylinder chambers, and in this case, by increasing or decreasing the number of the divided units of casing, the number of the cylinder chambers and the discharging pressure can be set freely according to the purpose, and elements other than the connecting shaft and the driving means can be configurated with a plurality of divided units of casing and pistons of the same kinds having relatively small-sized simple structures, and therefore the manufacturing cost can be remarkably reduced by mass-producting effect where a large number of pumps are manufactured.
Hereinafter, description is made on a plurality of specific embodiments in accordance with the present invention with reference to drawings.

[A first embodiment (Fig. 1 through Fig. 5):]

Fig. 1 shows a multi-boost synchronized booster of one embodiment in accordance with the present invention, and this booster is suitable for applications to the hydraulic apparatuses, for example, for a carrying cart having lifting function, a metal mold fixing apparatus of press machine, injection molding machine or the like, a positioning apparatus of metal mold of press machine or work to be machined, and press shearing apparatus.
This multi-boost booster comprises a casing 1, four cylindrical cylinder chambers 2 formed in series inside this casing 1, a piston 3 installed slidably in each cylinder chamber 2, a connecting shaft 4 integrally connecting the four pistons 3, and a driving means 5 for synchronously driving the four pistons 3 reciprocatively through the connecting shaft 4.
The casing 1 is formed with four divided units of casing 1A corresponding to the respective cylinder chambers 2, and each divided unit of casing 1A is configurated integrally with a partition wall part 1a configurating the top end wall of the cylinder chamber 2 and a peripheral wall part 1b configurating the peripheral wall of the cylinder chamber 2. These four divided units of cylinder 1A are stacked upward, and as shown in Fig. 2, being tightened to a casing 10 of the driving means 5 with four through bolts 22. In addition, an inner diameter D₁ of four cylinder chambers 2 is formed equally, and the length thereof is formed also equally.
A hydraulic operation chamber 6 is sectioned on the upper side of the piston 3 in each cylinder chamber 2, and each hydraulic operation chamber 6, a hydraulic path 7 connected thereto and a pressure receiving chamber 23a of a cylinder 23 at the end of the hydraulic path 7 are all filled with oil. An intake/discharge port 8 making the hydraulic path 7 communicate with the hydraulic operation chamber 6 penetrates through the peripheral wall part 1b of each cylinder chamber 2, and opens to the top end of the inner peripheral surface of the hydraulic operation chamber 6. Also, the portion sectioned on the lower side of the piston 3 in each cylinder chamber 2 communicates with the open air through an air passage hole 9 formed on the partition wall part 1a of the cylinder chamber 2 to prevent the inner pressure from decreasing when the piston 3 ascends.
In addition, a top end wall 10a of the casing 10 of the driving means 5 is used also as a bottom end wall of the casing 1, and the air passage hole 9 of the lowermost cylinder chamber 2 is formed on this top end wall 10a.
On the top surface of each piston 3, a spacer 11 defining the interval between pistons 3 is formed integrally with each piston 3. The thickness and the outer diameter D₁ of four pistons 3 and the length (height) and the outer diameter D₂ of the spacers 11 are formed equal respectively. The top end of each spacer 11 penetrates through the partition wall la of the cylinder chamber 2 and is fitted into a recess formed on the bottom surface of the piston 3 on the upper side thereof. Shaft holes 4a are formed in the center parts of four pistons 3 and spacers 11 along the whole length, and the connecting shaft 4 consisting of a long through bolt is inserted into the shaft holes 4a, and the bottom part of this connecting shaft 4 is inserted into a piston 12 of the pneumatic cylinder 5 and a spacer 13 defining the interval between the piston 12 and the piston 3 in the lowermost cylinder chamber 2, and is tightened together with a nut 14, and thereby the four pistons 3 and spacers 11, the spacer 13 and the piston 12 are connected integrally and coaxially.
The driving means 5 comprises a cylindrical casing 10 the top and bottom ends of which are closed and which configurates a single-type pneumatic cylinder provided with a compressed spring 17 for restoration, a cylinder chamber 15 formed inside this, a piston 12 installed slidably in this cylinder chamber 15, a pressure receiving chamber 16 sectioned on the lower side of this piston 12 in the cylinder chamber 15, and a compressed spring 17 installed on the upper side of the piston 12. The portion sectioned on the upper side of the piston 12 in the cylinder chamber 15 communicates with the open air through an air passage hole 18 penetrating the peripheral wall of the casing 10, and a compressed air supply/exhaust apparatus 19 is connected to the pressure receiving chamber 16 through an intake/discharge port 19a.
This compressed air supply/exhaust apparatus 19 is configurated in a manner that when the control sequence is started manually or automatically, it supplies compressed air of a predetermined pressure to the pressure receiving chamber 16, drives the piston 12 upward, drives four pistons 3 upward through the piston 12 and the connecting shaft 4, and lifts them to the position where a limit switch 20 is turned to ON through the connecting shaft 4 and stops them at that position, and when the control sequence is ended manually or automatically, the pressure of the pressure receiving chamber 16 is released.
In addition, the position of the limit switch 20 can be adjusted by an adjust screw 21.
In accordance with the multi-boost synchronized booster configurated as described above, when the operation of the compressed air supply/exhaust apparatus 19 is started manually or automatically, compressed air is supplied to the pressure receiving chamber 16 of the pneumatic cylinder 5, and the piston 12 is lifted, and the four pistons 3 are synchronously driven upward through the connecting shaft 4. Then the oil filling each hydraulic chamber 6, the hydraulic path 7 and the hydraulic cylinder 23 is pressurized, being supplied to the pressure receiving chamber 23a of each cylinder 23. Here, the inner diameter D₁ of four cylinder chambers 2 and the outer diameter D₂ of spacers 11 of four pistons 3 are formed equal respectively, and the four pistons 3 are connected integrally through the connecting shaft 4, and resultingly the stroke L thereof becomes the same, and therefore hydraulic fluid of equal pressure and equal flow rate is supplied to the hydraulic path 7 from the four hydraulic operation chambers 6 respectively in a synchronized manner, and is supplied to the pressure receiving chamber 23a of the cylinder 23, and the protruding speeds and the amounts of protrusion of the piston rods become accurately the same. When the protruding operation of the piston rod of the cylinder 23 is stopped, by releasing the pressure of the pressure receiving chamber 16 of the driving means 5, the four pistons 3 are synchronously lowered by elastic force of the spring 17 through the piston 12 and the connecting shaft 4, and each cylinder 23 is synchronously restored while hydraulic fluid of equal amount is returned from the pressure receiving chamber 23a of the cylinder 23 to each hydraulic operation chamber 6 with the same pressure.
A load applied from the outside through each cylinder 23 acts on each piston 3, and the load exerting on each piston 3 exerts in the direction of the axial center thereof, generating no moment to the other pistons 3.
Accordingly, an external load exerts on each cylinder 23 as a deviated load, and even if the loads shared by the respective pistons 3 become uneven, there is no fear of causing a poor operation or disabled operation, and a smooth operation can be performed.
In this case, by increasing or decreasing the numbers of the divided units of casing 1A and the pistons 3 with the spacer 11 in the interior thereof and replacing the connecting shaft 4 and the bolt 22, the number of hydraulic operation chambers 6 of the multi-boost booster can be set freely.
In addition, the divided unit of casing 1A and the piston 3 with the spacer 11 of the same kinds can be mass-produced at low costs, and therefore the manufacturing cost of the multi-boost booster can be reduced to a great extent.
In the above-mentioned embodiment, the casing 1 is formed in a manner that the divided units of casing 1A corresponding to each cylinder chamber 2 are connected in series, and therefore by increasing or decreasing the number of the divided units of casing 1A and the number of the pistons 3 and the spacers 11, this embodiment is applicable also to the case where the number of cylinders 23 of the driven side differs.
In the above-mentioned embodiment, the casing 1 is formed in a divided manner corresponding to the cylinder chambers 2, but it is also possible to form the casing 1 integrally. In this case, a plurality of cylinder chambers 2 are formed in the casing 1, and therefore, for example, as shown in Fig. 3, a cylindrical hole 1c is formed in the casing 1, and the partition wall parts 1a sectioning each cylinder chamber 2 and sleeves 31 configurating the inner peripheral wall of each cylinder chambers 2 between the partition wall parts 1a have only to be inserted alternately into the casing through this hole 1c. In addition, here, the pressing area of each hydraulic operation chamber 6 is made to differ by means of different inner diameters of the sleeves 31, and thereby the discharging pressure of hydraulic fluid from each hydraulic operation chamber 6 is made to differ.
Also, as shown in Fig. 4, the above-mentioned divided unit of casing 1A can be further divided into a partition wall portion la configurating the end wall of the cylinder chamber 2 and a peripheral wall portion 1b configurating the peripheral wall of the cylinder chamber 2.
Also, as shown in Fig. 4, it is also possible to form the piston 3 and the spacer 11 in a separate manner.
Furthermore, as shown in Fig. 5, the connecting shaft 4 and each piston 3 may be configurated in a manner that each piston 3 is clamped by the stepped surface 4a formed on the connecting shaft 4 and a nut 32 screwed to the connecting shaft 4. In this case, the position of the piston 3 is defined by the stepped surface 4a, and therefore the spacer 11 may be omitted. Also, in this case, by forming the connecting shaft 4 in a stepped manner to have different diameters, the hydraulic force of each piston 3 differs on a hydraulic operation chamber 6 basis. In this case, to make the discharging pressure of the hydraulic operation chamber 6 equal, although not illustrated, the cross-sectional area of each hydraulic operation chamber 6 is required to be made equal by fitting the sleeves having the same outer diameter to the connecting shaft 4 for the respective pistons 3.

[A second embodiment (Fig. 6 and Fig. 7):]

Fig. 6 shows a lubricating oil supply pump suitable for a rolling apparatus in accordance with the present invention.
In the casing 1 of this lubricating oil supply pump, the cylinder chambers 2 having the same diameter and the same length are formed in series, and the pistons 3 having the same thickness and the same outer diameter are installed slidable in the respective cylinder chambers 2. The four pistons 3 are connected integrally to the piston 12 of the driving means 5 through the connecting shaft 4 consisting of a through bolt likewise the case of Fig. 1. The above-mentioned driving means 5 is similar to the one in the above-mentioned first embodiment. The hydraulic operation chamber 6 sectioned on one side of the piston 3 in each cylinder chamber 2 is connected to an external lubricating oil supply source 34 through an intake port 8a, and each discharge port 8b installed independently from this intake port 8a is connected respectively to places to be lubricated in the rolling apparatus. Here, to obtain a pumping function, each intake port 8a is connected to the lubricating oil supply source 34 through an intake branch piping 36 wherein a check valve 35 is installed individually, and a check valve 38 is also installed in a discharge piping 37 connected to the discharge port 8b.
Also, in this lubricating oil supply pump, the outer diameter of the spacer 11 in the hydraulic pump 6 nearest to the driving means 5 is formed larger than the outer diameters of the spacers of the other hydraulic operation chamber 6, and the pressing area of that hydraulic operation chamber 6 is narrowed to generate a discharging pressure higher than those of the other hydraulic operation chambers 6. Also, the amount of hydraulic discharge from each hydraulic operation chamber 6 is controlled by controlling the stroke of the connecting shaft 4 likewise the first embodiment as shown in Fig. 1. However, in this embodiment, when the connecting shaft 4 is brought in contact with the limit switch 20, the pressure of the pressure receiving chamber 16 of the driving means 5 is released, and the piston 12 and the connecting shaft 4 are pushed back in the direction of increasing the volume of the hydraulic operation chamber 6 by the spring 17. Also, the position of the limit switch 20 is adjusted by automatically rotating the adjust screw 21 by a required amount by a motor 38.
In the lubricating oil supply pump configurated as described above, when compressed air is supplied from the compressed air supply/exhaust apparatus 19 to the pressure receiving chamber 16 of the driving means 5, the piston 12 moves to the casing 1 side, and each piston 3 is driven in the direction of reducing the volume of the hydraulic operation chamber 6. Then, the pressure lubricating oil is discharged from each hydraulic operation chamber 6 to the discharge piping 37. At this time, the discharged pressures from the three upper hydraulic operation chambers 6 are the same, and the amount of hydraulic discharge thereof are also the same. The discharging pressure of lubricating oil discharged from the hydraulic operation chamber 6 nearest to the driving means 5 is higher than those of lubricating oil discharged from the other hydraulic operation chambers 6, and the amount of discharge thereof is smaller than the amounts of discharge of the other hydraulic chambers 6.
To simplify the description, here, only the discharging pressure of one hydraulic operation chamber 6 differs from the discharging pressures of the other hydraulic operation chambers 6, but in the actual lubricating oil supplying apparatus, it is also possible to make the discharging pressure differ on a hydraulic operation chamber 6 basis.
In this embodiment, the hydraulic operation chamber 6 is installed on one side of the piston 3, but, for example, as shown in Fig. 7, it is also possible to form the hydraulic operation chamber 6 on the both sides of the piston 3. In this case, the driving means 5 is desirably configurated with a double-type pneumatic cylinder or hydraulic cylinder.

[A third embodiment (Fig. 8):]

As shown in Fig. 8, a multi-boost synchronized hydraulic pump is used wherein the intake port 8a and the discharge port 8b which are independent from each other are installed in place of the intake/discharge port 8 of each hydraulic operation chamber 6 of the multi-boost booster as shown in Fig. 1, and a hydraulic fluid supplying apparatus 39 is connected to each intake port 8a of this hydraulic pump through the intake branch piping 36 wherein the check valve 35 is installed, and each discharge port 8b is connected to a single-type cylinder 23A through a branch piping 37a having a cross valve 40 and a gathering piping 37 where four branch piping 37a having a cross valve 40 and a gathering piping 37 where four branch pipings 37a join. The remaining port of the cross valve 40 of each branch piping 37a is connected to a drain piping 41, and the end of this drain piping 41 is opened to an oil tank 42 of a hydraulic fluid supplying apparatus 39. Change-over of connection of each cross valve 40 is controlled by a controlling circuit (not illustrated).
In accordance with the hydraulic pump configurated as described above, by sequentially changing-over the cross valves 40, the amount of oil supplied to the pressure receiving chamber 23a of the cylinder 23A can be controlled stepwise, and the stroke of that cylinder 23A can be controlled stepwise.

[A fourth embodiment (Fig. 9):]

In another embodiment of the present invention, configuration is made in a manner that the stroke of each piston 3 in the casing 1 differs.
This means that, as shown in Fig. 9, between the piston 3 second from the top (upper piston 3) and the piston 3 on the lower side of this, a gap 43 wherein the upper piston 3 can slide in the direction of connecting shaft 4 is formed, and the upper piston 3 is fitted to the connecting shaft 4 in a manner slidable in the direction of the axial center thereof, and a compressed spring 44 preventing an idle motion of the upper piston 3 is inserted, and thereby the strokes of the two upper pistons 3 can be made shorter than the strokes of the other pistons 3.
In this case, by setting the spring constant of the spring 44 weak, the pistons 3 lower from the spring 44 are driven by ascending movement of the connecting shaft 4, and the four pistons 3 are synchronously driven upward after contraction of the spring 44.
Also, by setting the elastic force of the spring 44 larger than the hydraulic force of the piston 3, first the four pistons 3 are synchronously driven attending on ascending movement of the connecting shaft 4, and only the two lower-side pistons 3 are driven upward after a movement by the stroke L₁.
In addition, when the discharging pressure is made to differ by means of a different cross-sectional area of each hydraulic operation chamber 6, the stroke of each piston 3 is made to differ as described above, and thereby the amount of discharge of pressurized liquid having different discharging pressures which is discharged from each hydraulic operation chamber 6 can be made equal, and a plurality of cylinders receiving a different load can also be synchronously driven at an equal speed.
The multi-boost synchronized hydraulic pump in accordance with the present invention is applied to a booster supplying pressurized liquid to a plurality of hydraulic actuators or a pump or distributor supplying pressurized liquid intermittently, and for a booster, it is applied, for example, to a carrying cart having a lifting function, a stationary lifting apparatus, a positioning apparatus of metal mold of press machine or work to be machined, a metal mold fixing apparatus of press machine or injection molding machine and a hydraulic apparatus such as a press machine and a shearing apparatus. Also, for a pump or distributor, it is applied, for example, to a lubricating oil supply pump of a rolling mill.

Claims

1. A multi-boost synchronized hydraulic pump comprising:
a casing (1),
a plurality of cylinder chambers (2) formed in series in said casing (1),
a piston (3) installed slidable in each cylinder chamber (2),
an intake port (8, 8a) for supplying liquid in a hydraulic operation chamber (6) formed at least on one side of the piston (3) of each cylinder chamber (2) and a discharge port (8, 8b) for discharging pressurized liquid of each hydraulic operation chamber (6) which is formed independently from or in common with said intake port (8, 8a),
a connecting shaft (4) connecting a plurality of said pistons (3) in an integral fashion, and
a driving means (5) synchronously driving a plurality of said pistons (3) through said connecting shaft (4).

2. A multi-boost synchronized hydraulic pump according to claim 1, wherein pressing areas of a plurality of said pistons (3) are formed equal.

3. A multi-boost synchronized hydraulic pump according to claim 1 or 2, wherein said casing (1) is configurated by connecting in series divided units (1A) of said casing (1) consisting of a peripheral wall part (1b) of each cylinder chamber (2) and a partition wall part (1a) which is connected integrally to one end of said peripheral wall part (1b) and closes one end of said cylinder chamber (2).

4. A multi-boost synchronized hydraulic pump according to claim 1, 2 or 3 wherein a cylindrical spacer portion (11) which extends toward said hydraulic operation chamber (6) and contacts the piston (3) of the adjacent cylinder chamber (2) is formed integrally on said each piston (3), and said connecting shaft (4) is installed in a manner of penetrating a plurality of said pistons (3) and said spacer portions (11).

5. A multi-boost synchronized hydraulic pump according to claim 1, 2, 3 or 4 wherein said casing (1) is configurated with a common outer cylinder member covering a plurality of said cylinder chambers (2), partition wall members (1a) partitioning between said cylinder chambers and sleeves (31) which form respectively the peripheral wall portion of each cylinder chamber (2) and define the positions of said partition wall members (1a).

6. A multi-boost synchronized hydraulic pump according to claim 1, 2, 3, 4 or 5 wherein a casing portion forming each cylinder chamber (2) of some of said cylinder chambers (2) is configurated with a cylinder member (1b) and a partition wall member (1a) separate therefrom.

7. A multi-boost synchronized hydraulic pump according to any preceding claim wherein said driving means (5) comprises a pneumatic cylinder with a return spring (17) and a compressed air supply/exhaust apparatus (19) which supplies and exhausts compressed air to and from said pneumatic cylinder.

8. A multi-boost synchronized hydraulic pump comprising:
a casing (1),
a plurality of cylinder chambers (2) formed in series in said casing (1),
a piston (3) installed slidably in each cylinder chamber (2),
an intake port (8, 8a) for supplying liquid to a hydraulic operation chamber (6) formed at least on one side of the piston (3) of each cylinder chamber (2) and a discharge port (8, 8b) for discharging pressurized liquid of each hydrauiic operation chamber (6) which is formed independently from or in common with said intake port (8, 8a),
a connecting shaft (4) connecting a plurality of said pistons (3) through compressed springs (44) inserted between at least one pair of the adjacent pistons (3) among a plurality of said pistons (3), and
a driving means (5) for driving a plurality of said pistons (3) through said connecting shaft (4).