JPS6318036B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to pressure boosters for fluids. The device of the invention is particularly useful in the field of chromatography, where liquids must be delivered at high pressures and at precise flow rates without pulsation. A typical chromatography device utilizes a packed column to separate solutes from a liquid sample. To reveal specific components in solutes,
Detectors analyze the effluent flow from the packed tower. Many chemical components have similar elution characteristics and therefore exit the packed column almost simultaneously. Therefore, in order to perform accurate analysis, the liquid sample must be smoothly forced through the packed column continuously and at a constant flow rate. Conventional liquid chromatography devices employ positive displacement high-pressure pumps to force a liquid sample through a packed column. Piston or similar type pumps produce an output flow that is pulsed in nature. By using a double-acting piston pump with overlapping cam characteristics, it was possible to reduce the occurrence of pulsation to some extent, but in order to further suppress pulsation, it was necessary to perform sophisticated feedback control. . Regarding this technique, reference may be made to U.S. Pat. No. 3,917,531, which discloses a flow feedback device that uses a flow transducer to vary the motor speed of a pump in accordance with a feedback signal.
Further, US Pat. No. 3,398,689 discloses a control device for chromatography that uses a motor speed feedback system as a method of changing the pumping speed of a liquid. Furthermore, U.S. Pat. No. 3,932,078 measures the pressure while one piston is pumping and converts this pressure into a reference pressure for a second piston operating under an overlapping cam mechanism. A control device is used to convert the Thus, all of the devices in the prior art require complex high pressure control pumps and feedback controllers that are precisely constructed and require many adjustment operations as an additional measure for the properties of liquids operating at high pressures. It was. Therefore, prior art precision solvent control pumps are expensive to manufacture;
Otherwise, it was significantly less reliable than other components of the liquid chromatography device. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a system that can reliably feed high-pressure fluid at an accurate flow rate without requiring a complex high-pressure control pump or feedback controller. According to the invention, an injection member for delivering a selected relatively low pressure output flow fluid; an accumulator having an output flow and storing fluid from said relatively low pressure injection member; an accumulator for this fluid; a sensing member for sensing the amount of fluid in the accumulator for a selected value of the amount of fluid that can be accommodated therein and for generating a signal indicative of the amount of fluid in the accumulator; a fluid pressure booster comprising: a high pressure pump member for receiving as input and generating an output flow fluid at a high pressure; and a control member for regulating the flow rate from the high pressure pump member according to a fluid volume signal received from the sensing member; provided. The booster of the present invention utilizes an injection device to deliver a relatively low pressure flow output, and the injection device can operate at low pressures, thereby virtually eliminating problems such as pulsation associated with high pressure control pumps. I won't wake you up. This injection device consists of a single pump,
Alternatively, it may consist of a plurality of pumps cooperating with each other to pump one or more solutions. The output of the injection device is supplied to a device for storing fluid. Such a member may consist of a fluid container with a resilient diaphragm portion. Thus, as the volume of fluid within the fluid storage device increases, an outward pushing action occurs, pushing the diaphragm portion of the container in the same direction and vice versa. The device also includes a component for sensing the fluid volume converted within the fluid storage device with respect to fluid volume reference values (volume, concentration, pressure, and the like) established in the fluid storage device. There is. The output flow from the fluid storage device flows to a relatively high pressure pumping device which then increases the precisely measured and controlled rate of the input flow to a relatively high pressure output flow rate to accurately control the fluid flow. to maintain measured and controlled characteristics. The high pressure pumping device is regulated by a control member that regulates fluid flow from the sensing member to account for the difference between the volume in the fluid storage device and a reference value. In this way, the fluid storage device (accumulator) is a connection branch point (node) both mechanically and in the feedback control system.
fulfill the role of The control member can be electrical, mechanical, pneumatic or use other well known signal transmission media. The invention will be explained in more detail below with reference to the accompanying drawings. The entire apparatus of the present invention is designated by the numeral 10 in FIG. Apparatus 10 includes as an element an injection member 12, shown in FIG. 1, which is used to deliver a stream of solvent. The injection member 12 includes a motor 14 which operates a gear mechanism (not shown) within a gearbox 16. motor 14
rotates the shaft 18 at a predetermined rotational speed. A joint 20 connects the shaft 18 to a shaft 22 that rotates at the same speed as the shaft. The bearing 24 with the flange 26 is attached to the shaft 2
2 is extended to the cam 28. As shown in FIG. 1, cam 28 has cam followers 30 and 3.
It is in contact with 2. Shaft 22 extends through a bearing 34 that includes a flange 36. Cam 38 moves cam followers 40 and 42. Shaft 22
is ultimately supported at its terminal end by a bearing 44. The operation of cam followers 30, 32, 40 and 42 will be described in detail below. Injection member 12 includes a first pump 46 and a second pump 48 . Referring to FIG. 1, cam 38
It is clear that the pumps operate the pump mechanisms of pumps 46 and 48. FIG. 2 shows pump 48 in more detail. The components of pump 48 are substantially similar to those of pump 46. Therefore, the description of pump 48 below also applies to pump 46 shown in FIG. Pump 48 includes the cam follower 32 described above. Washer 52 and plate 54 create a return spring 56 that acts to bias cam follower 32 toward cam 28. The end plate 54 is connected to the liquid head portion 6 of the pump 48.
0 constitutes one end of the housing. Washer 52 and plate 54 near the annular ring 50
This serves as a bearing surface for the spring 56. The cam follower 32 causes the piston 62 to reciprocate within the piston chamber 64 .
come into contact with. Cam follower 32 is supported by a guide member 66 that includes bearings 68 and 70. 2, it can be seen that the piston 62 extends through the bushing 72 and is held in place by the plate 52. Bearing member 74 supports and guides piston 62 independently of cam follower 32 . Bearing member 7
4 may be made of carbon such that the piston 62 is lubricated by this carbon material. This effectively prevents leakage from occurring. liquid head 60
includes an inlet 80 and an outlet 82. Inlet 80 and outlet 82 typically do not have check valves connected to the liquid chromatography device. Fastening member 8
8 holds the housing 58 to the plate 54 and holds the bushing 72 and seal member 76 in place. A first pump 46 surrounds an outlet tube 90 and an inlet tube (not shown). Shaft 2
2 operates the valve member 92 via the cam 38, which cam is connected to the first valve member 92 as shown in FIG.
valve 94 and a second valve 96. The aforementioned cam followers 40 and 42 are joined to valves 94 and 96, respectively. 3 depicts a second valve 96 which is substantially similar to the first valve 94. Valves 94 and 96 are shown as double two-way valves, model 201 manufactured by Alex Scientific, Inc.
-This is the same valve as 00. By way of example, the flow that is actuated by valve 96 and ultimately removed by pump 48 originates in a reservoir (not shown) and enters inlet tube 98 as indicated by arrow 100 in FIG. Enter. Cam follower 42 operates valve 96 so that flow is directed to valve housing 1
02 to the inlet tube of the liquid head 60. Flow also flows through inlet 80 into chamber 64 and piston 62 directs the flow out of outlet 82. Since the sliding mechanism of valve 96 is well known in the art, its operation will not be discussed in detail. Similarly, flow exiting the outlet 82 of the liquid head 60 flows through the outlet pipe 86, through the valve housing 102, into the outlet pipe 104 (in the direction of arrow 108) and into the accumulator 106 shown in FIG. . The return stroke of the piston 62 of the pump 48 is coincident with the movement of the inlet tube 98 of the valve 96 and the inlet tube 84 of the liquid head. The flow of fluid through the outlet tube 104 of the valve 96 and the outlet tube 86 of the liquid head 60 then corresponds to the forward travel stroke of the piston 62, which empties the chamber. Returning to FIG. 1, it can be seen that cam followers 42 and 40 actuate sliding mechanisms 110 and 112 of valves 94 and 96, respectively. Return springs 114 and 116 act on supports 118 and 120 to bias cam followers 40 and 42 into contact with cam 38. Cam 38 operates valves 94 and 96 such that valve 94 drains into accumulator 106 while valve 96 sucks in flow from the reservoir, and vice versa. Thus, the accumulator 106 receives a steady flow of relatively low pressure but very precisely measured fluid from the injection member 12. A fluid accumulator 106 (FIG. 4) directs the flow discharged by injection member 12 and valve member 92 to an outlet pipe 104 of valves 96 and 94 and another outlet pipe (not shown). It is received through connected inlet holes 115. Accumulator 106 includes a housing 117. Conduit 119 directs flow from valve 92 and directs the flow to chamber 121 . Magnetically actuated vane 122
The injection member 12 and injection member 139 (described later) by using a bipolar actuator 124
Mix the flows thoroughly. Entrance hole 115
The flow enters a portion of the communication chamber 126 located above the chamber 121, as shown in FIG.
Chamber 126 is divided by a diaphragm 132 into a flow section 128 and a volume section 130 of the device. Fluid pumped by injection member 12 impinges on diaphragm 132 before entering outlet conduit 134 and outlet hole 136. Generally, the actuating vane 12
2 can be made of non-reactive materials such as Teflon, Kel-F, or the like. Referring to FIG. 10, another injection member 13
9 (schematically shown) directs another fluid flow to the inlet hole 138 of the fluid accumulator 106. The injection member 139 has a similar structure to the injection member 12. The preferred solvent composition or variation thereof is determined by the relative flow rates of the fluids from injection members 12 and 139. Thus, fluid accumulator 106 can accommodate multiple fluid flows for multiple injection members. The mixing chamber 121 allows the output streams of the injection members 12 and 139 to mix, which in the case of liquid chromatography gradients is accomplished by a distinct solvent stream. FIG. 4 also shows a member 140 for sensing the amount of fluid within the accumulator 106. Diaphragm 132 has as one element a conduit section 142 with an electrical ground connection. Diaphragm 132 is held between housing 117 and member 144 by fastening member 146 . Detection member 140 includes a capacitive electrode 148 fixed to the bottom surface of printed circuit board 150 .
Circuit components 152 and 154 and connector 156 are mounted on top of circuit board 150 (FIG. 5).
Details of the electrical components of device 10 will be discussed subsequently in this specification. However, the series of fluids impinging on the diaphragm creates various capacitive effects between conductive portion 142 and capacitive electrode 148. Therefore, the change in the amount of fluid appearing in the accumulator 106 is detected by the detection member 1.
Detected by 40. As shown in the preferred embodiment, the total amount of fluid is converted to a volume of volume. However, optical or mechanical structures can also be used to achieve the same effect as the capacitor described above. Flow through the accumulator 106 enters the high pressure pump 158 shown in FIGS. 6-9, as shown in the preferred embodiment, where the high pressure pump member 158 is a piston driven diaphragm pump. Other types of high pressure pumps, such as solenoid driven diaphragm pumps, dual piston pumps, or the like, may be employed to increase the pressure of fluid exiting the accumulator 106. For example, the pressure of the fluid can be increased from just a few positive absolute pressures to pressures of over 700 kilograms per square centimeter. Pump 158 pumps chamber 1
64 includes a housing 160 having a receptacle 152 forming a housing 152. The chamber 164 is the oil tank 166 in FIG.
The lubricating oil is held by the member shown as .
Usually used variable speed motor M-10 (Fig. 12)
causes shaft 168 to rotate at a speed determined by control member 242. Shaft 16
8 is supported by a bearing 170 before the shaft extends through the opening 172 of the housing 162. Seal member 174 prevents oil from escaping from chamber 164 while allowing shaft 168 to rotate. The end of the shaft 168 is the chamber 1
It is supported by a needle bearing positioned inside 64. The cam 176 is the fastening member 17
8 to the shaft 168, and the cam rotates with rotation of the shaft 168. Cam follower 180 is shown in rotational engagement with the surface of cam 176. Cam follower 180 is attached to cam follower shaft 182 by a fastening member 184. The shaft 182 has a bearing 186
and is in contact with the piston 188.
The housing 162 has a shelf 189, as shown in FIG. 7, which engages a guide roller 192.
Guide roller 192 prevents cam follower shaft 182 from rotating. Pump member 158 is connected to liquid head 1 bolted to housing 162 by bolt member 194.
It has 90 structural units. Returning to FIG. 8, fill plug 19 with screen 198 for ventilation
6 is located in the refilling hole 200. In this way, the liquid level in the oil tank 166 is easily maintained.
Piston 188 reciprocates within guide member 202 . Hole 204 ensures that piston chamber 206 always contains oil. piston 188
The stroke of the piston 188 is performed over the bore 204 (shown in phantom) while the forward pumping stroke is made past the bore 204 (shown in phantom) to seal it.
This is done in such a way as to open up the Guide member 202
is held in place by a plate 208, which is configured as part of the housing 162. A spring member 21 is attached to the plate 208.
A surface 210 is provided to bias 2 and 214. Spring member 212 acts to bring cam follower shaft 182 into contact with cam 176 . For this purpose, the cam follower shaft 182 includes a fixed collar 216. As a result, spring member 212 biases cam follower shaft 182 away from surface 210 of plate 208 . Similarly, piston 188 includes a collar 218 secured to piston 188 by ring member 220. As is clear from the above structure, the spring member 214 is connected to the piston 18.
8 into continuous contact with the end 222 of the cam follower shaft 182. Piston chamber 206
terminates at one end in a relatively rigid member 224 with porosity for oil pumped by piston 188. Adjacent porous member 2
Adjacent to 24 is a relatively flexible diaphragm 226 or membrane that is impermeable to the oil being pumped. The diaphragm 226 is connected to the liquid head 1
One side of the fluid chamber 228 is formed within the fluid chamber 90 . A diaphragm return spring 230, shown in FIG. 9, is wedged in place within chamber 228. Liquid head 190 includes an inlet 232 and an outlet 234. Inlet 232 receives fluid outlet hole 136 of accumulator 106 . Inlet 232 and outlet 234 include check valves well known in the art to direct fluid flow in the direction of the arrows in FIG. Fluid entering inlet 232 flows into passageway 236 and, as a result, fluid chamber 2
It flows into 28. At this point, movement of the diaphragm driven by the pumping action of the piston causes the volume of fluid chamber 228 to contract and direct fluid into passageway 238 . Fluid then passes from passageway 238 through outlet 234 to the feed terminal port requiring flow. In the case of a liquid chromatography device, the outlet stream from outlet 234 enters a sealed column 240, shown schematically in FIG. When the check valve is removed, porous member 224 supports diaphragm 226 against rupture. Referring to FIG. 10, apparatus 10 is schematically illustrated. First and second pumps 46 and 48
Injection member 12 made up of valves 94 and 96
and/or similarly configured injection member 139 directs fluid to fluid accumulator 106 . The combined fluid flow is transferred to the high pressure pump member 15
8 and then flows to column 240.
Sensing member 140 senses the amount of fluid within accumulator 106 and generates a signal that is sent to control member 242 indicative of the amount of fluid sensed. Control member 24
2 compares this signal with a reference signal and then generates an error signal that regulates the flow rate of the high pressure pump member 158. Such regulation of the high pressure pump member 158 maintains the amount of fluid contained within the accumulator 106 at a reference value. In the illustrated embodiment, the flow rate of the high pressure pump member 158 is controlled by the amount of voltage applied to the motor to rotate the shaft 168. Thus, the flow rate of fluid exiting the high pressure pump member is equal to the flow rate of fluid pumped by injection member 12 and/or any other injection member. Control member 268 can determine the composition and/or component gradient of the solvent delivered by the plurality of injection members. Sample injection member 270 mixes the sample to be analyzed with the solvent stream exiting high pressure pump member 158 . FIG. 11 further depicts a particular embodiment of control member 242. FIG. As already mentioned, the detection member 14
The fluid volume signal from 0 is received by control member 242 and converted into a signal that regulates the flow rate of high pressure pump member 158. Control member 242 includes an oscillator 244 that generates a frequency signal 252;
The frequency signal is inversely proportional to the capacitance between capacitance electrode 148 and conductive portion 142 of diaphragm 132. Frequency signal 252 is converted to a voltage signal by frequency-to-voltage converter 246.
Voltage signal 253 is accepted by summing amplifier 248. Reference voltage generator 250 also sends a voltage signal 256 indicative of the value of the reference quantity for fluidic accumulator 106 to summing amplifier 248, which in turn controls the speed of an activation member connected to high pressure pump member 158. A voltage signal 258 is sent. It should be noted that such a starting member may be a simple DC motor as is well known in the art. Therefore, as the pumping speed of the injection member 12 increases, the amount of fluid in the fluid accumulator 106 increases. Detection member 140 detects this increase and signals this change to control member 242, which increases the pumping speed of high pressure pump member 158. High pressure pump member 15
By increasing the flow rate of 8, the amount of fluid seen within fluid accumulator 106 will be reduced. The null circuit previously described in conjunction with the control member 242 makes the high pressure pump member 158 a slave member to the master injection member 12 or 139, or both. FIG. 12 shows the detection member 140 and the control member 24.
2 represents an embodiment of an electrical circuit that is connected to 2 and performs zero operation. The table below provides comparative values for the building blocks identified in FIG.

【table】

[Table] VC-10 or detection member 160 serves as a summing node sensor. As shown in FIG. 12, VC-10 is connected to amplifier Z-10 and resistor R.
-10, R-12, and R-14, which form part of the oscillator 244. Output signal 252 is a square wave signal with a frequency of 1 to 10 kilohertz. Frequency signal 252 is received by integrated circuit Z-12, which includes charge pump 260. Integrated circuit Z-12 serves as part of a frequency-to-voltage converter 246 with frequency doubling characteristics. Capacitor-C-12 and C-1
4, and resistors R-14 and R-18 form a two-pole low-pass filter.Signal 25
4 flows into integrated circuit Z-14. C-10
is the charging pump 2 at each axis intersection of the signal 252.
Determine the magnitude of the charge emitted from 60. R
-22 biases the output transistor in a differential amplifier located within Z-12. R-16,
R-20 and R-26 determine the voltage input to the operational amplifier section of Z-12. R-16 and C-26
creates a zero point that increases the gain of the Z-12 differential amplifier. R-20 helps stabilize the feedback loop. Passive structural unit C-1
6, R-28 and R-30, R-24, R-26
and CR-10 are coupled to Z-16 and cause the DC residual voltage signal 256 to produce a triangular wave signal 262, the output of the reference voltage generator 250. Z-14
compares signal 254 with signals 262 and 256 to produce a signal 258 with a modified pulse width that is directly proportional to voltage signal 254. Thus Z-14 acts as a summing amplifier 248. Q-10, Q-12, Q-14, and Q-16
is “on” at an extremely fast speed for Q-18,
Causes "off" operation. R-38 acts as a pull-up resistor for Z-14 while C-
20 filters the power supplied thereto. R-40 limits the peak current through Q-10. Q-10 and Q-12 continuously rotate on and off. High positive signals with pulse width converted are CR-12, C-22, R-42, R
-44, forces the current through Q-14 and to the base of Q-16. Q-14 bypasses any excess current received from Q-10 to ground through CR-16. The current through R-44 is not bypassed and conducts to the base of Q-16, turning it on. The limited activation of Q-14 prevents Q-16 from being over-driven when the system begins to operate, so that Q-16 is more quickly turned off. After C-22 is charged, R-42 limits the drive current through Q-10 and prevents Q-14 from bypassing measurable current to ground after the C-22 charging time. The collector of Q-18 reaches a low value some time after the start of activation. After the pulse width modulated signal reaches a low value, Q-12 is turned on and Q-10 is turned off, causing the voltage at the emitter of Q-12 to reach a low value. C
-22 provides negative bypass and large current, Q
-16 and Q-18 base through CR20 and eliminated at very high speed. As a result, Q-16 and Q-18 turn off very quickly, allowing the voltage across their collectors to rise. This continuous "on-off", high-low operation occurs at relatively high frequencies, eliminating the need for large heat sinks to dissipate heat from the Q-18. The schematic also shows the current limiting component of Q-18 using current sensing resistors R-50 and Z-18 and the circuitry connected thereto. Z-18 is R-32, R-34 and R-36
Compare the reference voltage sourced from C-18 with the signal voltage developed across C-18. Such a signal voltage changes the voltage drop across the current sensing resistor R-50,
Double time constant averaging from R-46, R-48 and R-18. For example, the voltage drop at R-50 is lower than the voltage at C-18, and CR-1
8 are oppositely biased to determine the time constants in which R-46 and R-48 are related to C-18. Signal voltage is comparator (comparator) Z
Once the reference voltage at Z-18 is exceeded, the output of comparator 18 is superimposed on the pulse width converted signal from Z-14 and shuts off the driver portion of the circuit. R-36 drops the reference voltage to a low level to maintain the driver section in the off position for a set period of time. When the signal from C-18 is issued lower than the reduced reference signal, Z
-14 causes the driver part of the circuit to operate again. The on/off operation of this current limiter is performed at a predetermined frequency. L-10 and C-24 are combined to create a low pass filter, which slowly reacts to the voltage converter from the driver portion of the circuit. The signal whose pulse width has been converted by this member is converted into a DC signal that is supplied to M-10 (DC motor that drives the high-pressure pump 158). R-52, Q-20 and
The CR-24 constitutes a dynamic brake to prevent the M-10 from overspeeding. In other words, when CR-24 is biased forward, Q-20 is turned off and L-10, CR-
22 low pass filters control the M-10. However, when the DC voltage produced by motor M-10 exceeds the DC voltage supplied to C-24, CR-24 applies a reverse bias causing Q-20 to turn on. This short circuit conduction applies damping to M-10. Diode CR-22 is Q-16 and Q
- the voltage on the collector of 18 to 35 volts (voltage source 2
64 voltage), but at this time Q-18 is in the OFF position. Returning to FIG. 1, it will be seen that the motor 14 provides power to the injection member 12. motor 14
The motor may be a stepping motor such as a Copal SP45. The control member 266 is the motor 14
and determining the selected speed of the injection member 12.
Determine the selected pump operating speed. The control member 266 may consist of a drive transducer such as a Copal DM402X linked to a PG-01 pulse generator. The drive transducer and pulse generator may be controlled by a single variable resistor or "pot" with a level value of about 500 kilohms. This allows the user to set a pot to control the speed of stepping motor 14. Such controls can be programmed automatically. In operation, the user sets the speed of stepping motor 14 via controller 266. The pumping speed of injection member 12 can be selected to provide a pressure value necessary to force fluid through liquid chromatography column 240. Motor 14 rotates shaft 18 which in turn rotates valves 94 and 9 of accumulator 106.
6, pumps 46 and 48 have a carefully metered and controlled flow of low pressure fluid. Fluid passes through the accumulator 106 and into the high pressure pump member 158
Enter. The fluid accumulator 106 also serves as a connection node for a feedback system that controls the speed of the actuating member for the motor M-10 and the high pressure pump 158. The sensing member 140 and the control member 242 are comprised of a null circuit, thereby providing the high pressure pump 158 with the appropriate pump operating speed. The output therefrom then flows to liquid chromatography column 240. The fluid pressure booster according to the invention is adapted to direct fluid from an injection member delivering a low-pressure fluid flow output through an accumulator to a high-pressure pump member, the accumulator being connected mechanically and in a feedback system. Because it is used as a node, high-pressure fluid can be reliably delivered at a precise flow rate without the need for complex high-pressure control pumps or feedback controllers. Although the above description has described embodiments in detail to better disclose the invention, those skilled in the art will appreciate that various changes can be made without departing from the principles of the invention. Will.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the injection member of the present invention.
FIG. 2 is a cross-sectional view taken along line 2--2 in FIG. FIG. 3 is a partial cross-sectional view taken along line 3--3 in FIG. FIG. 4 is a partially cutaway cross-sectional view of the fluid accumulator. FIG. 5 is a plan view of the fluid accumulator. FIG. 6 is a partially cutaway sectional view of the high-pressure pump. Figure 7 shows the line 7-- in Figure 6.
FIG. 7 is a partial cross-sectional view at FIG. FIG. 8 is an enlarged view of the right portion of the high pressure pump shown in FIG. 6; FIG. 9 is a cross-sectional view taken along line 9--9 in FIG. FIG. 10 is a general block diagram of a pressure booster device for fluids. FIG. 11 is a block diagram of the booster speed control device. FIG. 12 is a schematic wiring diagram of the pressure booster. Explanation of symbols: 12: injection member, 106: accumulator, 140: detection member, 158: high pressure pump member, 242: control member.

Claims (1)

Claims: 1 a. An injection member 12 for delivering a selected relatively low pressure output flow fluid; b. an accumulator 10 having an output flow and storing fluid from said relatively low pressure injection member 12.
6; c. sensing for sensing the amount of fluid in the accumulator for this fluid relative to a selected value of the amount of fluid that can be accommodated in the accumulator and for generating a signal indicative of the amount of fluid in the accumulator; member 140; d high pressure pump member 158 for receiving as input an output flow of fluid from said accumulator and generating a high pressure output flow fluid; and e high pressure pump member 158 for receiving a fluid volume signal from said sensing member 140. a control member 242 for adjusting the flow rate from; a fluid pressure booster;