EP2634426B1 - Two-stage pump - Google Patents

Description

The invention relates to a two-stage pump according to the preamble of patent claim 1.

Such two-stage pumps are used, for example, in manual or motor-driven hand tools, for example for pressing cable lugs, cable connectors, press fitting systems, also for shears such as cable shears and the like .. The two pumping elements deliver up to a certain limit pressure, which is a fraction of the maximum pressure of for example 700 bar can be, together a much higher flow rate than when the limit pressure is exceeded to the maximum pressure, for example, to cover an idle stroke of a tool quickly before the actual work process with high power requirements, ie high working pressure occurs.

Thus, it is known to combine a low-pressure gear pump with the larger flow rate and a high-pressure piston pump for the lower flow rate. As soon as the outlet pressure, which corresponds to the working pressure, exceeds the limiting pressure of the low-pressure pumping element, its delivery flow is conducted into the tank via a changeover valve, and the two-stage pump only supplies the delivery flow of the high-pressure pumping element.

At one off US 4,850,828 A known two-stage pump, the low-pressure and high-pressure conveying spaces are not separated from each other, but connected to each other via the suction valve of the high pressure delivery chamber, so that the flow from the Niederdruc delivery chamber to the pressure outlet takes the flow path through the high-pressure delivery chamber and the pressure valve of the high-pressure delivery chamber. Thus, the high-pressure and low-pressure pumping elements share a common pressure valve, which must be designed inordinately large, now also with the combined flow rates of high-pressure and low-pressure pumping elements to cope. The chamber of the changeover valve communicates with the pressure outlet downstream of the single pressure valve via a housing channel. The low pressure reciprocating piston is connected to the high pressure reciprocating piston. Both reciprocating pistons are biased together via a return spring of a pneumatic drive in each case in the suction direction.

At one off US 4,840,554 known two-stage pump are the high-pressure and low-pressure delivery chambers, the plunger of different cross-sections driven by a common eccentric, associated with their own suction and pressure valves.

Out DE 197 43 747 A a two-stage pump is known in which the two pumping elements have reciprocating piston, which operate linearly and reciprocally in a common delivery chamber with only one suction valve and only one pressure valve, the reciprocating piston of the low-pressure pumping element dividing the delivery chamber, and the high-pressure piston is driven. In the low-pressure reciprocating piston, a check valve is included, which opens in the flow direction to the high-pressure delivery chamber part dependent on pressure or positively controlled. The volumetric efficiency is low. The reciprocating piston are subject to heavy wear.

The invention has for its object to provide a two-stage pump of the type mentioned, which is structurally simple, reliable and easy to drive, works with high volumetric efficiency, and allows accurate adjustment of the limit pressure.

The stated object is achieved with the features of claim 1.

The two reciprocating pump elements with their separate reciprocating pistons, separate delivery chambers, and their own pressure and suction valves, work completely independently of each other and with high partial efficiencies. Their different flow rates are combined up to the limit pressure before the working pressure at the pressure port actuates the switching valve, so that from then on the flow of the low-pressure pump element loss is passed to the tank, the pressure in the pressure outlet, the pressure valve of the low-pressure pump element keeps closed, so that no portion of the delivery flow of the high-pressure pump element is lost via the pressure valve of the low-pressure pump element and then subsequently via the actuated changeover valve to the tank. The pressure valves are connected to each other via a housing channel connected to the pressure outlet. The housing channel leads into the chamber containing the switching valve. Thanks to the structural separation of the reciprocating pump elements, their reciprocating pistons can be driven efficiently in a structurally simple manner. In the common housing short and low-loss flow paths to the pressure outlet are possible in particular for the high-pressure stage. Overall, despite structural simplicity results in a high volumetric efficiency and can select the limit pressure exactly.

In an advantageous embodiment, the pressure valves are placed laterally of the delivery chambers and the suction valves in the reciprocating stroke direction in extension of the pumping chambers, which can be achieved with compact housing dimensions low-loss and short pressure-side flow paths, and the switching valve can be integrated to save space.

Particularly useful is the switching valve, a spring-loaded seat valve. The spring preload, which determines the limit pressure for the low-pressure pumping element or the control pressure of the changeover valve, should be adjustable in order to select the limit pressure as needed. The seat valve construction also guarantees in the locked position leakage.

In order to ensure a clean response of the switching valve, it may be expedient to provide an aperture at least in the housing channel, which leads to the control valve to the switching valve.

In a favorable embodiment, in the chamber of the common housing, a seat for a poppet-closing member of the switching valve exhibiting sleeve insert is mounted sealed. This has a multiple function, since it separates entrances into the chamber from each other without leakage, and at the same time can form an abutment for a biasing spring of the seat valve closing member.

In view of compact design, high closing force, a favorable spring characteristic and high reliability, eg against breakage or fatigue, the biasing spring is a threaded onto a shaft of the seat valve closing member disc spring package.

In order to adjust the preload force and thus the limit pressure as needed, a spring abutment nut can be screwed onto the shaft. Thus, even after a long period of use, the spring preload is not changed uncontrollably, can be arranged, preferably, in the internal thread of the spring abutment nut against the free shaft end tensionable counter-Madenhohlschraube.

In order to ensure a low-loss and short Abströmweg to the tank, and to simplify the assembly of the components in the housing, or to provide a convenient way to change the bias pressure of the switching valve, in an open end of the chamber of the common housing a sleeve insert in the Chamber-positioning screw be used, which at the same time has a flow connection to the tank-forming passages, for example, open directly to a housing outside.

Also in terms of compact dimensions (axial height) and high reliability are the pressure and suction valves spring-loaded platelet valves appropriate.

Structurally simple, the high pressure pressure valve, preferably centric, placed in lying on a housing outside pressure outlet. The high-pressure pressure valve has lateral valve openings to the pressure outlet, where appropriate, where the housing channel opens into the pressure outlet and the low-pressure pressure valve connects to the pressure outlet.

The pressure outlet is, for example, a circular recess in the outside of the housing, so that there an O-ring can be mounted, which provides the necessary seal to the other hydraulic system at this interface.

To ensure that the change-over valve is opened exactly at the predetermined limit pressure, the seat valve closure member is expediently pressure-balanced with respect to the pressure from the low-pressure delivery chamber and acted upon exclusively by the pressure from the housing channel or the working pressure at the pressure outlet against the spring preload.

In an expedient embodiment, the reciprocating pistons are arranged parallel next to one another. They are available with their operating ends on the same outside of the housing, and are, for example, by a common eccentric or phase-shifted in the direction of rotation eccentrics, optionally even eccentrics of different eccentricity, one drive shaft or two drive shafts, actuated, in the latter case, not only the strokes out of phase, but also the speeds can be chosen either the same or different. The former case allows a simple drive with a common drive shaft whose torque substantially only after exceeding the limit pressure more is removed from the high-pressure pumping element, since the low-pressure pumping element runs "empty", so to speak.

In another embodiment, although the lifting pistons are arranged parallel next to one another. However, their actuating ends are on opposite sides of the housing to each eccentric on its own of two drive shafts. With this design, not only different strokes or stroke frequencies, but also any phase displacements between the strokes can be adjusted to achieve the highest possible degree of uniformity. As a rule, in all embodiments, the diameter of the reciprocating piston of the low-pressure pump element is greater than the diameter of the piston of the high-pressure pump element.

Such a two-stage pump with housing dimensions of about 32 x 32 x 36 mm, piston diameters <10.0 mm and strokes, for example, about 5 mm generated before exceeding the arbitrarily high selectable limit pressure, a flow rate, depending on the drive speed of about 0.35 to 1 , 4l / min, and after exceeding the limit pressure only a flow of about 0.2 to 0.5 l / min, in order to achieve a maximum working pressure at the pressure outlet, for example, 700 bar relatively quickly.

Fig. 1

einen Schnitt in der Schnittebene I - I in Fig. 2, einer Zweistufenpumpe für die Hochdruckhydraulik,

Fig. 2

eine Draufsicht auf die Zweistufenpumpe, in Fig. 1 von oben,

Fig. 3

einen weiteren Schnitt der Zweistufenpumpe in der Schnittebene III in Fig. 2,

Fig. 4

einen weiteren Schnitt der Zweistufenpumpe in der Schnittebene IV in Fig. 1,

Fig. 5

einen Schnitt eines Umschalt-Sitzventils der Zweistufenpumpe, in der Schnittebene I - I in Fig. 2, wobei in den Fig. 1 bis 5 eine Betriebsfase angedeutet ist, in der die Zweistufenpumpe gerade einen Saughub ausgeführt hat und das Umschaltventil sperrt,

Fig. 6

die Zweistufenpumpe in Form eines Blockschaltbildes, und

Fig. 6a

eine Detailvariante zu Fig. 6.

With reference to the drawings, embodiments of the subject invention will be explained. Show it:

Fig. 1

a section in the section plane I - I in Fig. 2 , a two-stage pump for high-pressure hydraulics,

Fig. 2

a plan view of the two-stage pump, in Fig. 1 from above,

Fig. 3

a further section of the two-stage pump in the sectional plane III in Fig. 2 .

Fig. 4

a further section of the two-stage pump in the sectional plane IV in Fig. 1 .

Fig. 5

a section of a switching seat valve of the two-stage pump, in the sectional plane I - I in Fig. 2 , where in the Fig. 1 to 5 a Betriebsfase is indicated, in which the two-stage pump has just performed a suction stroke and the switching valve locks,

Fig. 6

the two-stage pump in the form of a block diagram, and

Fig. 6a

a detail variant too Fig. 6 ,

Marriage on the constructive structure of one in the Fig. 1 to 5 is received in detail and shown in different sectional views two-stage pump P is based on the block diagram of the Fig. 6 explains its structure.

In a common block-shaped housing 1, for example made of steel, a low-pressure pumping element N with a larger flow rate and a high-pressure pumping element H with a smaller flow rate, for example, are accommodated parallel to one another. The housing 1 has a pressure outlet 2 to a hydraulic system connectable there and outlets 20 to a tank T, which may be formed by a housing containing the two-stage pump P (not shown) itself. The high-pressure pump element H is a piston pump element with its own delivery chamber 3, own pressure and suction valves 4, 5 and a reciprocating piston 16, the actuating end 18 protrudes on a housing outside. Also, the low-pressure pumping element N is a piston pump element with a reciprocating piston 17 in its own low-pressure delivery chamber 6, the own suction and pressure valves 8, 7 are assigned, and a portion 15 a of a housing channel 12 to a in the housing 1 (in a chamber 27, for example Fig. 1 ) integrated switching valve 9 is connected, which in turn can open to the tank T. A section 14 of the housing channel 12 leads to the low-pressure pressure valve 7, which is connected via a portion 15 b with the low-pressure delivery chamber 6 or inserted directly into this. The section 15a forms a branch of the housing channel 12, from which also a further branch 13 leads to a control side of the changeover valve 9, for example, contains a against a biasing spring 10 from the shutoff position shown in the open position to the tank T adjustable closing member 11.

Suitably, the switching valve 9 is a seat valve with leak-free shut-off (see Fig. 6a ). The housing channel 12 leads from the portion 14 of the low-pressure pressure valve 7 to the pressure outlet 2 at or downstream of the high-pressure pressure valve 4. In the branch 13 of the housing channel 12 to the switching valve 9, a diaphragm 28 may be included, for example, in FIG Fig. 4 is shown.

The two reciprocating pistons 16, 17 can be driven together or separately to and fro (not shown), for example via a common eccentric or separate eccentric drive shaft (in Fig. 3 indicated), or two drive shafts (not shown).

When operating record both piston pump elements suck first on the suction valves 5, 8 hydraulic medium from the tank into their delivery chambers 3, 6, compress the sucked hydraulic medium, and promote this via their pressure valves 7, 4 with the larger flow of the low-pressure pumping element N and the added smaller flow of the high pressure pumping element H to the pressure outlet 2, wherein the switching valve 9 is in the leak-tight dense shut-off position. If, for example, at the pressure outlet 2, a set on the biasing spring 10 limit pressure reached, then the switching valve 9 is opened via the branch 13, which connects the low-pressure delivery chamber 6 via the branch or the section 15a directly to the tank T. From then the low-pressure pressure valve 7 is kept closed by the working pressure, so that the low-pressure pumping element N sucks on the low-pressure suction valve 8, but low-loss directly into the tank T promotes, while the smaller flow of the high-pressure pumping element H via the high pressure Pressure valve 4 is conveyed from the high-pressure delivery chamber 3 to the pressure outlet 2 until the maximum system pressure is reached.

The basis Fig. 6 explained components of the two-stage pump P can also be found in the Fig. 1 to 5 , The switching valve 9 is located in a chamber 27 of the housing 1, which in Fig. 1 better to see.

In the Fig. 1 and Fig. 3 are the reciprocating piston 16, 17 shown with the same effective length, but the low-pressure piston 17 and the delivery chamber 6 have a larger diameter than the high-pressure piston 16 and the delivery chamber 3. The stroke directions of the two reciprocating pistons 16, 17 are here, for example approximately perpendicular to the axis of the chamber 27, in which the switching valve 9 is mounted. The high-pressure suction valve 5, for example a spring-loaded platelet valve, is mounted directly in the end region of the high-pressure delivery chamber 3, while the high-pressure pressure valve 4, for example visible on a housing outside, can be mounted in the pressure outlet 2. The low-pressure pressure valve 7 is according to Fig. 4 mounted laterally of the low-pressure delivery chamber 6 behind a plug, while the low-pressure suction valve 8 according to Fig. 3 is mounted approximately in extension of the low-pressure delivery chamber 6 behind a lying on a housing outside, continuous and caulked insert. The high pressure suction valve 5 is in Fig. 3 positioned with a continuous ring insert, which is fixed by a continuous locking screw, so that suck both suction valves 5, 8 on the same outside of the housing. Both reciprocating pistons 16, 17 are acted upon in the suction direction of springs 19 and have approximately equal and aligned actuating ends 18, which in the embodiment of Fig. 1, 2 and 3 projecting on the same outside of the housing, and facing away from the outside of the housing, to suck the suction valves 8, 5.

From the housing channel 12 and its portions 15 a, 15 b, 14, 13 are in the Fig. 1 . 3 and 4 in each case the courses are recognizable. So shows Fig. 1 combined with Fig. 4 the branch 13 as a blind bore, which opens into an inner end of the chamber 27, shows Fig. 3 the portions 15a, 15b in the low-pressure suction valve 8, of which in Fig. 6 the section 15b to the low pressure pressure valve 7 and section 15a lead to another inlet in the chamber 27 (see also Fig. 4). Fig. 4 also illustrates how the low-pressure pressure valve 7 is connected via the portion 14 with the housing channel 12, the in Fig. 3 leads to the region of the pressure outlet 2 and is connected to this via a connection 24.

The pressure outlet 2 (interface) is in Fig. 3 For example, a circular recess 22 in a housing outside, where there may be an O-ring 23 may be arranged. The high-pressure pressure valve 4 has a spring-loaded plate 26 and lateral valve outlets 25 in the recess 22 of the pressure outlet 2.

In the Fig. 1 to 4 is the changeover valve 9 in its blocking position, the suction valves 8, 4 are open, and the pressure valves 5, 7 are closed (suction stroke). Fig. 4 shows the in the housing channel 12, for example, upstream of the branch 13 to the chamber 27, inserted aperture 28th

Fig. 3 indicates two different drive principles of the reciprocating piston 17, 16 via a here preferably common drive shaft 46, although separate drive shafts would also be possible. In the in Fig. 3 shown embodiment, the operating ends 18 of the two reciprocating pistons 16, 17, for example via roller bearings or plain bearings 44, supported on eccentrics 47, 45 of the drive shaft 46, wherein the eccentric 47, 45 are shown separately, but here have same rotational phases. Alternatively, the two eccentrics 47, 45 could be phase-shifted in the direction of rotation of the drive shaft 46 (not shown). Furthermore, it is conceivable to drive both actuating ends 18 of a common eccentric 45 'of the drive shaft 46.

In an alternative embodiment, the actuator ends 18 could protrude from two opposite sides of the housing, and be driven by a respective drive shaft, wherein also the stroke of each reciprocating piston 16, 17 could be selected individually, as well as the phase offset between the strokes. Also in Fig. 3 For example, the two eccentrics 45, 47 could be different from each other to produce different strokes.

That in the Fig. 1, 2 and 4 indicated switching valve 9 is based Fig. 5 explained. It is for example a seat valve according to Fig. 6a , which is mounted with a sleeve insert 29 in the chamber 27 of the common housing 1. The sleeve insert 29 is sealed on the outside in the chamber 27 twice (see Fig. 1 ), on the one hand to separate inlets into the chamber 27 from each other, ie the separation of the working pressure to the pressure in the low-pressure chamber 6, and on the other hand to separate the branch 15a from the tank T, ie the sealing of the pressure in the low-pressure delivery chamber 6 against escape into the Tank T. The sleeve insert 29 has there a circumferential groove, where the inlet of the branch 15a lies in the chamber 27, and transverse passages 30 from the circumferential groove to the sleeve insert 29 limited Inner space. Furthermore, the sleeve insert 29 forms a valve seat 31 for a seat valve closing member 33, for example, with the in Fig. 6a indicated valve member 11 corresponds.

The seat valve closure member 33 is here e.g. formed as a cone and has a shaft 34 which protrudes from the sleeve insert 29, and on which the biasing spring 10 is threaded in the form of a plate spring package 36. The shaft can serve as centering of the biasing spring. As a biasing spring 10 may also serve any other spring. The sleeve insert 29 forms a spring abutment 37 for the biasing spring 10. On the shaft 34, a spring abutment nut 38 is screwed, which adjusts the bias of the biasing spring 10, and may have a rotary handle 41 for adjustment. In the other end of the seat valve closing member 33 may also be formed a rotary handle 42 to be able to counteract when setting the spring preload can. The spring abutment nut 38 may be further secured by a counter-serrate hollow screw 39 which has an internal rotary handle 40 and is tightened against the free end of the shaft 34. Finally, the seat valve closing member 33 has a sealing surface 43 which cooperates with the valve seat 31 in the sleeve insert 29, wherein the effective diameter D of the poppet valve closing member 33 with the diameter of the valve seat 31 almost coincides, so that the poppet valve closure member 33 with respect to the pressure is pressure-balanced in the branch or the portion 15a, and on the effective diameter D exclusively from the pressure in the branch 13 in the direction of control, ie Lifting direction of the sealing surface 43 is acted upon by the valve seat 31 against the biasing spring 10.

The sleeve insert 29 is positioned in the chamber 27 by a closure screw 32 which includes flow passages 20 to the tank T, which may also be used, for example, in FIG Fig. 2 you can see. Furthermore, the closure screw 32 limit the poppet valve in its stroke to achieve a defined maximum opening cross-section, and also limit the stroke of the plate spring package to a predefined stroke, which positively affects its life.

In the illustrated embodiment, the bias of the biasing spring 10 can be adjusted only after removing the switching valve 9 from the chamber 27. However, it would be conceivable to provide a clearance to be cleared at the other end of the chamber 27 in order to be able to change the pretension in the installed state of the changeover valve 9. The effective diameter D of the seat valve closing member 33 is for example about 4 mm, while its opening stroke may be about 0.5 mm.

Claims (14)

1. Two-stage pump (P), comprising a drivable high pressure pump element (H) for a smaller discharge flow and a drivable low pressure pump element (N) for a higher discharge flow, a common pressure port (2), and a switchover valve (9) arranged between the low pressure pump element (N) and a tank (T), the switchover valve (9) being controlled to open to the tank (T) depending on the pressure in the pressure port (2), wherein both pump elements (H, N) are piston pump elements with reciprocating pistons (16, 17) spring loaded in suction direction in high pressure and low pressure discharge chambers (6, 3) comprising separate suction valves (5, 8) and at least one pressure valve (4, 7), the reciprocating pistons (16, 17), the suction and pressure valves (5, 8; 4, 7) and the switchover valve (9) being arranged in a chamber (27) and sharing a common housing (1) characterised in that the high pressure and low pressure discharge chambers (3, 6) are separately arranged in the housing (1) and comprise respective pressure valves (4, 7), and that the pressure valves (4, 7) are connected with each other downstream via a housing channel (12) connected with the pressure port (2) and branching into the chamber (27).
2. Two-stage pump according to claim 1, characterised in that the pressure valves (4, 7) are placed sidewards of the discharge chambers (3, 6), that the suction valves (5, 8) are placed in the piston stroke direction in prolongation of the discharge chambers (3, 6), and that the chamber (27) accommodating the switchover valve (9) is placed in the region of the suction valves (5, 8), and, preferably, communicates separately with the low pressure discharge chamber (6) and the pressure port (2) of the housing channel (12).
3. Two-stage pump according to claim 1, characterised in that the switchover valve (9) is a spring loaded seat valve, and that, preferably, the spring load determining the opening control pressure towards the tank (T) and defining the limit pressure of the two-stage pump (P) is adjustable.
4. Two-stage pump according to claim 1, characterised in that an aperture (28) is provided in at least one flow path (13) branching off from the housing channel (12) to the chamber (27).
5. Two-stage pump according to claim 2, characterised in that a sleeve insert (29) is mounted in sealed fashion in the chamber (27), the sleeve insert (29) comprising a seat (31) for a seat valve closure member (11, 33) of the switchover valve (9), that the sleeve insert (29) separates ports to the chamber (27) which ports are connected to separate flow paths to the chamber (27), and, preferably, constitutes a retainer (37) for a pre-loading spring (10).
6. Two-stage pump according to claim 5, characterised in that the pre-loading spring (10) is a belleville spring package (36) threaded onto a shaft (34) of the seat valve closure member (11, 33).
7. Two-stage pump according to claim 6, characterised in that a spring retainer nut (38) is threaded on the shaft (34) and that, preferably, a hollow locking set screw (39) is arranged in an interior thread of the spring retainer nut (38) so as to be tightened against the free end of the shaft (34).
8. Two-stage pump according to claim 5, characterised in that for positioning the sleeve insert (29) in the chamber (26), a closure screw (32) is inserted into an open end of the chamber (27) the closure screw (32) comprising openings (20) forming a flow connection to the tank (T), preferably openings (20) which open freely in an outer side of the housing.
9. Two-stage pump according to claim 1, characterised in that the pressure and suction valves (4, 7, 5, 8) are spring loaded disk valves.
10. Two-stage pump according to claim 1, characterised in that the high pressure pressure valve (4) is placed, preferably centrally, in the pressure port which is situated in an outer side of the housing and comprises sideward valve openings (25) to the pressure port (2) at a location, where as well the housing channel (12) opens into the pressure port (2), the housing channel being connected to the low pressure discharge chamber (6) via the low pressure pressure valve (7).
11. Two-stage pump according to claim 10, characterised in that the pressure port (2) is a circular recess (22) in an outer side of the housing and contains an O-ring (23).
12. Two-stage pump according to claim 5, characterised in that the seat valve closure member (33) is pressure balanced in relation to the pressure in the low pressure
    discharge chamber (6) and is actuated in opening control direction counter to the pre-loading spring (10) solely by pressure in the housing channel (12).
13. Two-stage pump according to at least one of the claims 1 to 12, characterised in that the reciprocating pistons (16, 17) are arranged parallel and side by side, protrude with their actuation ends (18) beyond the same outer side of the housing and are actuated by a common eccenter or separated in-phase eccenters (45, 47) or by eccenters having a phase shift in rotational direction, respectively of a single driving shaft (46) or of two driving shafts.
14. Two-stage pump according to at least one of claims 1 to 12, characterised in that the reciprocating pistons (16, 17) are arranged parallel and side by side and protrude with their actuation ends (18) beyond opposite outer sides of the housing towards a respective eccenter of a separate one of two drive shafts, arranged at both opposite sides of the housing (1).

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