EP0927305A1

EP0927305A1 - Piston pump

Info

Publication number: EP0927305A1
Application number: EP98924218A
Authority: EP
Inventors: Egbert Frenken
Original assignee: Gustav Klauke GmbH
Current assignee: Gustav Klauke GmbH
Priority date: 1997-07-19
Filing date: 1998-04-25
Publication date: 1999-07-07
Anticipated expiration: 2018-04-25
Also published as: ATE231217T1; US6206663B1; AU7649598A; WO1999004165A1; EP0927305B1; JP2001504909A; TW401484B; DK0927305T3; JP4138897B2; ES2187973T3

Abstract

The invention relates to a piston pump (1) for delivering a fluid at low pressure and high pressure, there being a greater delivery rate in a pump cycle at low pressure than at high pressure. The inventive piston pump comprises a low pressure delivery piston (4) which is moved in a pump cylinder (2) and which impinges on a pressure chamber (7) in its end delivery position under prestress, a high pressure delivery piston (11), an inlet valve and an outlet valve (9, 10), a fluid delivery channel (5) being configured between said inlet valve and outlet valve (9, 10). The low pressure delivery piston (4) can be moved back into a delivery starting position against its prestress. The aim of the invention is to achieve efficient delivery at both low pressure and high pressure with the simplest possible construction. To this end, the fluid delivery channel (5) passes through the low pressure delivery piston (4), a valve (6) which locks when the low pressure delivery piston (4) moves into the delivery starting position is located in said low pressure delivery piston (4), the high pressure delivery piston (11) and the low pressure delivery piston (4) work in a common pressure chamber (7) and the high pressure delivery piston (11) moves the low pressure delivery piston (4) towards its prestress.

Description

00001 piston pump

00002

The invention relates to a piston pump for delivery

00004 of a fluid at low pressure and at higher pressure,

00005 with a high in a pump cycle at low pressure

00006 re delivery rate is given than at higher pressure, with

00007 a moved in a Purap cylinder, under tension

00008 in its delivery end position of a pressure chamber

00009 struck low-pressure delivery piston, a high-pressure delivery

00010 the piston and an inlet and an outlet valve,

00011 being further between the inlet and outlet valves

A fluid delivery path is formed and the Nieder¬

00013 pressure delivery piston against its bias in one

00014 initial movement position is to be moved back.

00015

Such piston pumps are used, for example, in manual

00017 or motor-driven hand tools. This is about

00018 to a prior art according to the US patent specification

00019 ten 432,107, 5,195,354 and 2,688,231.

This state of the art relates to motor-driven hand

00021 tools for crimping cable lugs or cable

Connect 00022. Furthermore, the subject of the invention

00023 but also meaning with regard to Sche¬, for example

00024 ren, such as cable shears. This is about the German

00025 utility model 94 16 535 and the not pre-published

00026 published German patent application 196 49 932

00027 points. In addition, such pumps

00028 also used in other areas of technology. It

For example, U.S. Patent No. 2,845,033 and

00030 674.381.

00031

00032 Frequently, especially for the drive of hydraulic

00033 tools used pumps that have two pressure levels

00034. These deliver up to a certain limit

00035 pressure, which is 5% of the maximum pressure, for example 00036 significantly higher oil volume than at maximum pressure. In order to

00037, the working speed of the hydraulic equipment

00038 te considerably because with many tools,

00039 such as Crimping tools for crimping cable

00040 shoes, first a certain idle stroke

Must be 00041 before the workpiece is touched and the

00042 actual work process with high power requirements

00043 follows. At idle stroke only the force of the

00044 piston return spring of the tool hydraulic cylinder

00045 can be bridged. A low oil pressure is sufficient for this

00046. 00047

00048 There are numerous types of two-stage pumps

00049 knows. It is e.g. possible to use two different pumps

00050 pen designs to combine with each other and simultaneously

00051 to drive, e.g. a gear pump for the low

00052 gene pressure range and a piston pump for the high

00053 print area. As soon as the required outlet pressure reaches the

00054 working pressure of the low pressure pump is exceeded

00055 whose flow through a pressure relief valve in the tank

00056 returned. 00057

00058 are especially for hand-operated hydraulic tools

00059 two-stage piston pumps are common, both for

00060 the low as well as for the high pressure sub-piston pumps

00061 can be used. One type is widespread

00062 of the two pistons in the form of a pump tappet with two

00063 different diameters are combined. The hy

00064 drastically effective area is in the low pressure part

00065 the circular area between the two diameters

00066 and for the high pressure piston it is the entire cross

00067 cutting surface of the small diameter. Both

00068 and high pressure pump each have one with the

00069 tank connected inlet and one connected to pressure side

00070 denes exhaust valve. In addition there is a pressure relief valve 00071 required for the low pressure stage, through which 00072 the oil flows back into the tank after the pressure of the low pressure 00073 stage has been exceeded. The US-PS 4,492,106 relates to a lever-operated hand00076 tool in an embodiment for pressing 00077 cable lugs. Here, a pump device is proposed, which has a high-pressure delivery piston and a 00079 low-pressure delivery piston. The low-pressure För00080 derkolben consists of a spring-supported Rohrab- 00081 cut with a tube plate, which forms the piston plate 00082. The low-pressure delivery piston is displaced by a 00083 continuation of the high-pressure delivery piston against the spring 00084, whereby hydraulic fluid is sucked in from a storage container. Then the extension of the high-pressure delivery piston moves back in 00086 and the 00087 low-pressure delivery piston conveys the hydraulic fluid 00089 drawn into the working space due to the spring acting on it. The funding stops as soon as the 00090 pressure in the delivery chamber can no longer be overcome by the spring force 00091. Then only the high-pressure piston works in the known 00092 pump. 00093 00094 Starting from the above-mentioned state of Tech00095 nik, the invention deals with the technical 00096 problem of specifying a piston pump for conveying a fluid 00097 ids at low pressure and at higher pressure, 00098 which is an effective pumping system with the simplest possible structure enables. 00100 00101 This technical problem is first and essentially solved in the subject matter of claim 1, 00103 being based on the fact that the fluid delivery path passes through the 00104 low-pressure delivery piston, that in the low-pressure delivery piston in 00005 when moving in the direction of delivery 00106 blocking valve is arranged and that the high pressure

00107 delivery piston in the pressure chamber of the low-pressure delivery piston

00108 bens works. It's just a common pressure room for

00109 the low-pressure delivery piston and for the high-pressure delivery

00110 the piston available. The low pressure delivery piston will

00111 forcibly pushed back, namely by the

00112 pressure delivery piston. According to the invention, a simplified

00113 te execution of the piston pump first thereby

00114 is sufficient for the low-pressure delivery piston and the high-pressure

00115 pressure delivery pistons work in the same pressure chamber. It

00116 there is only one pressure chamber or pump chamber. The

00117 Losses due to throttling processes are minimized or

00118 no longer given. Next is the fluid delivery path

00119 passed through the low-pressure delivery piston,

00120 with a when moving the low pressure delivery piston in

00121 Direction of blocking valve. This means

00122 the same that when the low-pressure delivery

00123 piston against the conveying direction fluid in the pressure

00124 flows around, the pressure in the pressure chamber not

00125 is larger than in the inflow direction before the low pressure

00126 delivery piston. Rather, there is usually

00127 pressure rather than in the inflow direction before the low pressure

00128 delivery piston, reduced by the force of one on the

00129 Low pressure conveyor piston acting spring. When open

00130 valve in the low pressure delivery piston is the pressure

00131 on both sides of the low-pressure delivery piston

00132 same table. The embodiment advantageously has

00133 few items. In addition to the inlet and outlet

00134 running valve is only the valve in the low pressure

00135 delivery piston required. In addition, the design

00136 simplified. There is only one pressure room left for both

00137 given the low pressure level as the high pressure level. in the

00138 further it is provided that the movement of the lower

00139 pressure delivery piston against its bias

00140 the high pressure delivery piston. The high pressure conveyor 00141 the piston can in particular directly on the surface

00142 Act low pressure delivery piston. The high pressure conveyor

00143 the piston preferably has a smaller one

00144 of the Purπpens effective cross-sectional area as the Nieder-

00145 pressure delivery piston. The relationship can, for example,

00146 lent the surface of the low pressure delivery piston to the

00147 area of the high-pressure delivery piston 4: 1. Practically

00148 good values are also with ratios from 6 to 7: 1

00149 reached. In a further preferred embodiment

00150 also provided that the high pressure delivery piston in

00151 arranged the low-pressure delivery piston valve

00152 when the low-pressure delivery piston moves in the delivery

00153 direction locked, actuated. Because the high pressure

00154 Delivery piston when the low-pressure delivery piston moves

00155 in the conveying direction not on the low-pressure delivery pistons

00156 must be a continuation of this idea

00157 in construction very simple valve, namely a

00158 plate valve, arranged in the low-pressure delivery piston

00159 be net. The valve in the low pressure delivery piston

00160 further preferably has a stylish extension

00161 or the piston head of the low-pressure delivery piston

00162 penetrating actuation end. About this actuation

00163 can end an actuation of the valve in the described

00164 NEN done by the high pressure delivery piston.

00165 The preload of the low pressure delivery piston in his

00166 end position is advantageously by a

00167 spring, more preferably by a coil spring

00168 (compression spring) reached. With regard to that in the

00169 valve contained low pressure delivery piston can in particular

00170 special also be provided that the low pressure

00171 conveyor piston acting spring the valve in the

00172 biased locking position. Furthermore, it is

00173 causes the volume of fluid in the piston pump, i.e. on

00174 the inlet side of the low pressure delivery piston and in

00175 pressure space is as small as possible. In one embodiment 00176 is provided for this that the low-pressure delivery piston

00177 ben has a stylish extension on the back, for

00178 reduction in the fluid volume between the inlet valve

00179 til and the low pressure delivery piston. In the same way

00180 can also be a rear-side projection in the

00181 the low-pressure delivery piston receiving cylinder

00182 may be provided or a combination of these measures.

00183 In a further embodiment, to achieve a high

00184 ease of maintenance, it is also provided that the

00185 pump cylinder on an operationally disclosed floor

00186 points. Because the pump cylinder bottom is operational

00187 is evident, it is possible, for example, in a simple manner

00188 with the spring and / or the low-pressure delivery piston

00189 valve to be replaced or serviced.

00190 For this, the pump cylinder Bo¬ can in further detail

00191 to be screw-fastened in the pump housing. It emp¬

00192 is also missing that the pump cylinder bottom

00193 is designed like a pot overall, with a single

00194 screw thread on a pot edge outer wall. It is

00195 in combination or alternatively also possible that the

00196 Guide the high pressure delivery piston and possibly a part

00197 of the adjacent piston crown in this way

00198 screws and is interchangeable.

00199

The invention is further based on the

00201 attached drawing, which, however, is only an embodiment

00202 example, explained. Here shows:

00203

00204 Fig. 1 is a schematic cross-sectional view of a

00205 piston pump;

00206

00207 Fig. 2 in the representations a, b and c the sequence of a

00208 delivery cycle at low pressure;

00209 00210 Fig. 3 in the representations a, b and c the sequence of a

00211 delivery cycle at high pressure;

00212

00213 Fig. 4 is a schematic view of a piston pump

00214 of a second embodiment, ^•

00215

00216 Fig. 5 is a schematic cross-sectional view of a

00217 motor-operated hand-held device with a piston

00218 pump according to FIG. 4;

00219

00220 FIG. 6 shows an embodiment modified from FIG.

00221 form; and

00222

00223 Fig. 7 shows another embodiment in which the

00224 actuated with a hand lever.

00225

00226 is shown and described, initially with reference to

00227 Fig. 1, a piston pump 1 for delivering a fluid

00228 at low pressure and at higher pressure. The piston pump

00229 pe 1 can be used in a very wide variety of ways

Find 00230. With simple, manually operated pumps, the

00231 high-pressure delivery piston operated by a hand lever

00232 and those already mentioned above

00233 motor-driven handheld devices just by a motor,

00234 like an electric motor. It is essential that first, without

00235 load, an overdrive is desired, accordingly

00236 a high flow rate per stroke, and then under load

00237 and higher pressures must be applied (with low pressure

00238 lower flow rate per stroke).

00239

00240 The piston pump 1 has a pump cylinder 2, in

00241 which against the bias exerted by a spring 3

00242 ung a low-pressure delivery piston 4 is movable. The

00243 low-pressure delivery piston 4 also has a Durch¬

00244 path 5 for the hydraulic fluid, which here 00245 is pumped. The fluid passageway 5 is through a

00246 valve 6 designed as a check valve closes

00247 sen. The valve 6 locks when the low pressure För¬

00248 the piston 4 moves in the conveying direction and can

Open 00249 when the low-pressure delivery piston 4 moves away

00250 moved towards its conveying direction.

00251

00252 The low-pressure delivery piston 4 works on a pressure

00253 room 7. The valve 6 opens accordingly only when

00254 if the pressure in the pressure chamber 7 is less than

00255 the inlet side in an inflow space 8 of the low pressure

00256 delivery piston 4.

00257

00258 Furthermore, the piston pump 1 has an inlet valve 9 and

00259 an outlet valve 10. The inlet valve 9 is in

00260 a line connection to a fluid storage room

00261 arranged. The outlet valve 10 is in a line

00262 Connection to an Ar¬ not shown in Fig. 1

00263 arranged work room (see also fluid storage room 26

00264 and work space 27 in Fig. 5).

00265

00266 A high-pressure conveyor continues to work in the pressure chamber 7

00267 piston 11, which is fundamentally different, in Fig.

00268 1 ways not shown to be driven

00269 can. For example, one with an electric motor

00270 connected eccentric drive, by a manual drive

00271 or another, generate back and forth movements

00272 the drive. The freedom of movement of the high-pressure conveyor

00273 derkolbens 11 is by the dashed line

00274 indicated.

00275

00276 The high-pressure delivery piston 11 has a lower one

00277 effective cross section than the low pressure delivery piston

00278 4. The ratio here is about 4: 1 (low pressure

00279 delivery piston to high pressure delivery piston). 00280 The function of the piston pump 1 is with reference to the

00281 FIGS. 2 and 3 explained in further detail. In Fig.

00282 2 a is in low pressure operation, i.e. at low pressure

00283 in the work area, the end position of the low

00284 pressure delivery piston 4 shown. The spring 3 is still practicing

00285 a pretension, which can be

00286 corresponds to a value of 10 bar. The high pressure

00287 delivery piston 11 is at its farthest

00288 retracted position, in the embodiment

00289 it closes approximately flush with a (lower)

00290 cylinder wall 12 (of the pressure chamber 7). 00291

00292 It is shown in FIG. 2b that the high-pressure conveying

00293 the piston 11 in - face - plant on the low

00294 pressure delivery piston 4 and this against the

00295 kung the coil spring 3 moved back. At this

00296 Back movement, valve 6 is open. From the related

00297 loaned the low-pressure delivery piston 4 on the rear

00298 flow space 8 fluid flows through the fluid delivery path 5 in

00299 the pressure chamber 7. As the volume of the pump

00300 (inflow space 8 and pressure space 7) by the incoming

00301 high-pressure delivery piston 11 is continuously reduced

00302 also opens the outlet valve 10 and flows fluid in

00303 the work area. 00304

00305 In FIG. 2c the delivery stroke of the low-pressure delivery piston

00306 bens 4 shown. Due to the effect of the screw

00307 spring 3, the low-pressure delivery piston 4 after

00308 the high-pressure delivery piston 11 started its return movement

00309 NEN has in the direction of its end-of-conveyance position

00310 Fig. 2a moves. The valve 6 is closed

00311 and on the inflow side is due to resulting

00312 negative pressure via the opening inlet valve 9

00313 fluid from the reservoir into the inflow space

00314 sucks. At the same time, the fluid from the pressure chamber 7 00315 opened exhaust valve 10 displaced in the work space.

00316 It can be seen that the fluid quantity displaced in this case

00317 is dependent on the cross-sectional ratio of the

00318 low-pressure delivery piston 4 to the high-pressure delivery piston

00319 ben 11. The more fluid in the low pressure stage

00320 fe via the outlet valve 10 in the working area

00321 changes, the larger the - effective - cross-sectional ratio

00322 of the two pistons.

00323

00324 With reference to FIGS. 3a to 3c is a corresponding

00325 delivery cycle shown, in which it is assumed

00326 that the pressure in the work space is greater than that

00327 preload of the low-pressure delivery piston 4 in its

00328 Conveying end position. The pressure is said to be much greater

00329 as the initially mentioned pressure of approx. 10 bar.

The key is that the pressure in the work area is greater

00331 than that by the coil spring (compression spring 3) in the

00332 upper, maximum preloaded position of the low pressure

00333 delivery piston 4.

00334

In Fig. 3a is the delivery end position of the high-pressure piston

00336 bens 11 shown. The high pressure delivery piston 11 is

00337 maximally moved into the pressure chamber 7.

00338

00339 A state is shown in FIG. 3b in which

00340 the high-pressure delivery piston 11 on the return stroke

00341 is located. The outlet valve 10 is closed because of

00342 Pressure in the pressure chamber 7 only by the spring 3rd

00343 is determined. For example, this can be a pressure between

00344 be 10 and 20 bar. This pressure is therefore essential

00345 smaller than that in this state to be assumed to be high

00346 mende pressure in the work room. The falling pressure

00347 or the compensation, which is due to the moving out Hoch¬

00348 pressure delivery piston 11 resulting volume increase

00349 tion leads to a wake movement of the low pressure 00350 delivery piston 4. This is at the same time by the

00351 opening inlet valve 9 fluid from the storage container

00352 sucked into the inflow 8. The low-pressure delivery piston

00353 ben 4 does not reach the delivery end position

00354 according to FIG. 2a, but one in the conveying direction

00355 upstream position until a compensation of the volume

00356 part of the moving out part of the high-pressure conveyor

00357 the piston 11 is reached.

00358

3c is a point in time in the conveying stroke of the high

00360 pressure delivery piston 11 shown. The high pressure conveyor

00361 the piston 11 is not (yet) in contact with the Nieder¬

00362 pressure delivery piston 4. Due to the given

00363 pressure increase, the inlet valve 9 is closed. Dage¬

00364 gene, the outlet valve 10 is open because the pressure in

00365 the pressure chamber 7 due to the retracted Hoch¬

00366 pressure delivery piston 11 has increased so that the pressure

00367 in the work area.

00368

00369 With reference to Fig. 4 is another embodiment

00370 of the piston pump 1 shown. The reproduced Stel¬

00371 lung corresponds to Fig. 3a, this position itself

00372 here, however, on both a low pressure and one

00373 high pressure cycle.

00374

00375 The inlet valve 9, the outlet valve 10 and the Hoch¬

00376 pressure delivery pistons 11 are essentially unchanged.

00377

00378 However, the low-pressure delivery piston 4 points back here

00379 sided a step-like extension 13. This everyone

00380 if functional.

00381

00382 The stylish extension 13 is in fact one

00383 plate 14, which is part of the valve 6 here, ausgeb¬

00384 formed. The valve 6 or in the specific embodiment 00385 shape of the plate 14 also has a front

00386 actuation extension 15 on.

00387

00388 The stylish extension 13 leads to a minimal

00389 fluid volume in inflow space 8. This is desirable to

00390 to achieve certain flow velocities there.

00391 In the further also to a (high pressure) delivery stroke

00392 as little receding as possible due to

00393 the hydraulic fluid given elasticity

Reach 00394. In general, however, it is essential that for

00395 the pump uses a fluid that is essentially

00396 is incompressible. The usual - oil-based -

00397 tige - hydraulic fluids.

00398

00399 In further detail, the coil spring 3 is in the

00400 embodiment of FIG. 4 surrounding the cylinder arti¬

00401 gene extension 13 arranged.

00402

00403 In the piston crown 17 of the low-pressure delivery piston 4

00404 through-flow openings 18 are formed, which at

00405 of this embodiment form the fluid delivery path 5.

00406 As can be seen by system contact between one

00407 end face 19 of the high-pressure delivery piston 11 and the

00408 actuation extension 15 of the valve 6 an opening of the

00409 valve 6 reached so that through the openings 18 in

00410 the piston crown 17 of the low-pressure delivery piston 4

00411 fluid flows from the inflow space 8 into the pressure space 11.

00412 The valve 6 of the embodiment according to FIG. 4 is thus

00413 not pressure operated, but positively controlled.

00414

00415 In further detail, it is important that the

00416 embodiment of FIG. 4, the piston crown 31 as Ein¬

00417 screw part is formed. It has side wall

00418 tig an external thread 33 with a corresponding

00419 cooperates with the internal thread of the pump housing 32. Here- 00420 is a simple exchange or a

00421 Ease of maintenance given.

00422

00423 In the embodiment of FIG. 6 it is shown that

00424 both the piston guide for the high pressure delivery piston

00425 11 as the piston crown for the low-pressure delivery piston

00426 4 are designed to be screwed in. It is preferred only

00427 the piston guide for the high pressure delivery piston 11

00428 to be screwed in.

00429

00430 It is also important that in this embodiment

00431 form in the low-pressure delivery piston 4, namely the

00432 cylindrical extension, a flow path out

00433 forms, in which a conventional check valve

00434 is arranged. This makes it possible, on the one hand

00435 still in the compressed position of the spring 3

00436 to keep the given volume as small as possible,

00437 on the other hand in particular also such a stream

00438 training path that always relatively high flow

00439 speeds are ensured. Is essential

00440 also that the construction is such that

00441 little or no dead spaces are given.

00442

00443 With reference to FIG. 5 is a hand-operated motor

00444 tool with a piston pump according to the above

00445 illustrated embodiment Fig. 4 shown.

00446

00447 In the hand-operated power tool 20 is an electric

00448 motor 21 arranged, the reduction gear 22nd

00449. The reduction gear 22 acts via a

00450 shaft 23 on an eccentric 24, which in turn over

00451 a roller bearing 25 on the high-pressure delivery piston 11

00452 acts.

00453 00454 In the manner explained above, the

00455 fluid storage space 26 fluid in the working space 27 ge

00456 pumps and thereby a working piston 28 against the

00457 effect of a return spring 29 in its working end

00458 position moved. The return movement of the working piston

00459 28 takes place via the return spring 29 if - what here

00460 is not shown in detail - a drain valve

00461 of the work space 27 is open, via which the

00462 fluid can then flow back into the storage space 26.

00463 The drive of the electric motor 21 takes place in another

00464 Detail about a battery or an accumulator 30.

00465

00466 In the embodiment of FIG. 7, the high-pressure

00467 delivery piston 11 directly by a hand lever 34

00468 operated. The high pressure piston 11 is for this purpose in detail

00469 NEN with a coaxially aligned connector 35

00470 connected, which by means of a hook formation 36

00471 coupled a driving pin 37 of the hand lever 34

00472 is. The hand lever is independent of this

00473 pivot pin 38 mounted on the housing 39.

00474

00475 Otherwise the piston pump 1 behaves when it is

00476 management form of Figure 7 in the same way as that

00477 piston pump 1 of the embodiment described above

00478 men, so that reference is made to this.

00479

00480 All disclosed features are essential to the invention. In

00481 the disclosure of the application is hereby also the

00482 disclosure content of the associated / attached priori

00483 full documents (copy of pre-registration)

00484 Lich included, also for the purpose of characteristics of this

00485 documents in claims of the present application

00486 record.

Claims

00487

00488 AN S P RU C H E

00489

00490 1. Piston pump (1) for delivering a fluid at niede¬

00491 rem pressure and at higher pressure, whereby at lower

00492 pressure in a pump cycle countered a higher delivery rate

00493 ben than at higher pressure, with one in a pump

00494 cylinder (2) moved, under tension in its För¬

00495 of the end position acting on a pressure chamber (7)

00496 low-pressure delivery piston (4), a high-pressure delivery piston

00497 ben (11), an inlet and an outlet valve (9, 10),

00498 being further between the inlet and outlet valves

00499 (9, 10) a fluid delivery path (5) is formed and the

00500 low-pressure delivery piston (4) against its preload in

00501 is to move back to a starting position, da¬

00502 characterized in that the fluid delivery path (5)

00503 low-pressure delivery piston (4) penetrates that in the

00504 low-pressure delivery piston (4) when moving into the

00505 arranged delivery position blocking valve (6)

00506 is that the high-pressure delivery piston (11) and the Nieder¬

00507 pressure delivery piston (4) in a common pressure chamber

00508 (7) and that the high-pressure delivery piston (11)

00509 the low-pressure delivery piston (4) against its Vor¬

00510 tension moves.

00511

00512 2. Piston pump according to claim 1 or in particular da¬

00513 according to, characterized in that the high-pressure conveyor

00514 piston (11) has a smaller cross section than

00515 the low pressure delivery piston (4).

00516

00517 3. Piston pump according to one or more of the previous

00518 ilenden claims or in particular according thereto, thereby ge

00519 indicates that the high-pressure delivery piston (11)

00520 low-pressure delivery piston (4) against its preload

00521 move.

00522 4. Piston pump according to one or more of the preceding00523 claims or in particular according thereto, characterized gekenn00524 in that the valve (6) is a pressure actuated check valve 00525. 00526 00527 5. Piston pump according to one or more of the preceding00528 claims or in particular according thereto, characterized in that the valve (6) is a positively controlled 00530 valve. 00531 00532 6. Piston pump according to one or more of the preceding00533 claims or in particular according thereto, characterized in that the high pressure delivery piston (11) actuates the Ven00535 valve (6). 00536 00537 7. Piston pump according to one or more of the preceding00538 claims or in particular according thereto, characterized in that the valve (6) is designed as a plate valve. 00541 00542 8. Piston pump according to one or more of the preceding00543 claims or in particular according thereto, characterized in that the valve (6) has an actuating end (15) penetrating the piston crown (17) 00545 of the low-pressure delivery piston (4). 00547 00548 9. Piston pump according to one or more of the preceding00549 claims or in particular according thereto, characterized in that the preload is achieved by a spring (3) 00551. 00552 00553 10. Piston pump according to one or more of the preceding claims or in particular according thereto, characterized in 00555 that the spring (3) biases the valve (6) in the 00556 closed position.

00557 11. Piston pump according to one or more of the preceding claims or in particular according thereto, characterized 00559 in that the low-pressure delivery piston (4) 00560 has a stem-like extension (13) on the back, 00561 for reducing the fluid flow path (volume) 00562 between the inlet valve (9) and the low-pressure För00563 the piston (4). 00564 00565 12. Piston pump according to one or more of the preceding claims or in particular according thereto, characterized in that ge00567 that the Purap cylinder (2) has a pump cylinder base (31) which is operationally visible. 00569 00570 13. Piston pump according to one or more of the preceding claims or in particular according thereto, characterized ge00572 that the pump cylinder base (31) is screw-fastened in a 00573 pump housing (32). 00574 00575 14. Piston pump according to one or more of the preceding claims or in particular according thereto, characterized ge00577 in that the pump cylinder base (31) is pot-shaped 00578, with a screw-in thread (33) on 00579 of an outer rim wall.