FR2531147A1 - IMPROVED ARRANGEMENT OF A MEMBRANE PUMP DRIVEN BY A DIRECT CURRENT MOTOR - Google Patents

Abstract

THE INVENTION RELATES TO A DEVICE FOR REDUCING TORQUE Ripples INDUCED BY THE LOAD AND IMPROVING THE EFFICIENCY OF A DIAPHRAGM PUMP 20 DRIVEN BY A CONTINUOUS CURRENT MOTOR 12. THE PUMP IS ACTUATED BY A ROD 38 CONNECTED BY ITS TWO ENDS RESPECTIVELY TO THE MEMBRANE 34 AND TO AN ECCENTRIC 18 OF THE MOTOR SHAFT 16. A HELICOIDAL SPRING 56 IS CONNECTED BY ITS TWO ENDS RESPECTIVELY TO A FIXED POINT 60 OF THE MOTOR CRANKCASE AND TO ECCENTRIC 18. WHEN THE PUMP IS OPERATING, THE SPRING EXPANDS TO ACCUMULATE ENERGY WHEN THE MOTOR IS MOVING. ROD 38 TOWARDS THE TOP OF THE INTAKE PHASE, THE ENGINE LOAD IS THEN RELATIVELY LOW. WHEN THE ROD IS DRIVEN DOWN DURING THE COMPRESSION PHASE, THE SPRING RELEASES ITS ENERGY TO ASSIST THE ROD MOVEMENT DOWN. THUS, THE LOAD-INDUCED TORQUE Ripples which would occur in the absence of the spring are greatly reduced, and the load exerted on the direct current motor tends towards a constant torque. THIS ALLOWS THE PUMP TO RUN WITH SIGNIFICANTLY LOWER INPUT POWER FOR INCREASED PUMPING PRESSURES.

Description

The output of a low speed DC motor is generally

  assumed to be constant However, the actual torque often oscillates measurably beyond and

  below an average torque value This is general-

  due to the switching of the switch, but sometimes to the reluctance torque of the armature The ripple of the torque induced in this way is generally a very low

  percentage of nominal output torque and does not generally create

No problems whatsoever.

  However, when a DC motor is used to drive a mechanism such as a pump in which the load varies in large proportions between the low-load intake portion of the cycle and the compression, or setting portion pressure, of the cycle, this variation of the load can subject the motor to

  direct current at a substantial torque ripple.

  To achieve high pumping pressures,

  In reality, it uses motors whose char-

  entry age is relatively high A substantial percentage

  tiel of this input power was used to compensate for the load-induced torque ripple caused by

  the acceleration and deceleration of the armature.

  In applications in which the size of the pump is an important factor, in particular in portable assembly applications, in which a battery or an accumulator and the pump must both be carried by a person, a heat sink or a receiver requiring a larger accumulator than necessary is quite disadvantageous Such an application of a pump driven by a DC motor is found in itinerant blood pressure control devices, in which the motor actuates the diaphragm pump for provide the pressure necessary to pressurize the sleeve used for controlling blood pressure The use, according to the present invention, of a coil spring device greatly reduces the load supported by an accumulator, and simultaneously allows the pump generate higher operating pressures than can be achieved

  bare without the use of a coil spring.

  The invention is described below with reference to the accompanying drawings, in which:

  Fig 1 is a perspective view shown

  both a diaphragm pump and DC motor assembly equipped with a coil spring device according to

  the present invention, and functionally connected thereto

  ci, Fig 2 is a side view of Figure 1, partially in section along lines 2-2 of Fig 1, in which the base part of the pump is shown in cross section, Fig 3 is a graph of the load current as a function of the pumping pressure, which illustrates the operation of the pump with and without the coil spring device, for a direct current motor with a nominal voltage of twelve volts driven under a direct current of seven volts , and Fig 4 shows the curves of the load current as a function of the pumping pressure of the same motor driven by a direct current of six volts with and without the

helical spring.

  In Fig 1 is shown an assembly 10 to

  DC drive motor with diaphragm pump

  which can be used for portable applications, such as mobile traffic control devices

  blood pressure Motor 12 has a block of ac-

  coupling 14 mounted on its output shaft 16, block on which is mounted eccentrically a lug 18 The diaphragm pump 20 is supported by feet 22, and comprises an external casing 24 which covers and houses the pump The motor is carried by the support 26 which extends upwards from the upper surface 28 of the housing of the

  diaphragm pump The screws 32 support the motor in carrier

  overhang from the rear surface of the support 26.

  The diaphragm 34 of the pump is connected by the connector 36 to the lower end of the movement rod.

  alternative 38, the upper end of which delimits a compartment

  ment 40 receiving the eccentric pin 18 Thus, during the rotation of the motor shaft, the pump is actuated by the reciprocating movement of the connecting rod 38 and, when the eccentric pin 18 is at the highest point of its displacement, at A ,

  the volume of chamber 42 is at its maximum, and the atmospheric air

  aspheric is sucked through the tube 46 'and the inlet valve 46 At this time, the outlet valve 48 is

  closed During the stroke to the top of the connecting rod 38, di '.

  point B towards point A, the motor is subjected to a relatively weak load Tle If one defines a value of average torque rour the whole cycle, then the race towards the top of the rod between points B and A corresponds to a torque lower than the average value During the downward stroke of the connecting rod 38, from point A to point B,

  the torque load on the DC motor increases

  te significantly to exceed the average value on the cycle when the piston is driven down to compress the gas contained in the chamber 42 The outlet valve 48 is then opened to allow the air to be

  put in communication, through the tube 50, with a device

  reil receiver such as uln-disposi- pressure sleeve

  itinerant tif of blood pressure control, in which the pressure must accumulate The c 1 after entry 46 is then closed Prior to the present invention, this cyclic operation of the diaphragm pump actually produced a significant ripple torque, whereby the load of the load torque was reduced during the stroke up the connecting rod, and significantly increased during the stroke down This caused continuous acceleration of the motor armature for half the cycle, and a deceleration of the motor during the other half of the cycle The forces generated by these repeated accelerations and decelerations of the armature caused the loss of a substantial quantity of the energy supplied, so that this one did not contribute when the desired pressure is established The input current is supplied to the DC motor 12 via the wires 52 and 54, from an accumulator In a traveling contiguous device role of blood pressure, it is desirable to keep the dimensions of the accumulator as small as possible and, therefore, it is desirable to use an accumulator which does not operate at more than about six, six volts direct current for supply the supply current through

sons 52 and 54.

  A DC motor and diaphragm pump device suitable for supplying fluid under

  pressure to a mobile voltage monitoring device

  arterial pressure, which substantially resembles the pump and motor device described with reference to FIGS. 1 and

  2, can be purchased without the layout of this information

  vention Such a motor and pump device is sold in

  the trade under the name of Roméqa, model 080 In a dis-

  positive itinerant blood pressure control, it is desirable to keep the battery voltage at a low value, of the order of 6 volts DC A motor device and pump whose motor has a nominal voltage of 6 volts will be therefore conventionally used with a 6 volt accumulator Using a motor with a nominal voltage of 6 direct volts to generate pressures exceeding 200 mm of mercury in a sleeve

  blood pressure measurement, relative consumption

  High current draw from the accumulator is necessary.

  For example, with the motor and pump of nominal voltage

  6 Volt DC Romea rating, model 080, it takes 4.5 watts of power to generate a pressure of 260 min of mercury This same motor and pump device consumes 2.7 watts of power at idle speed This consumption at relatively high idle is necessary for the engine to reach its service output torque under the load of the pump to reach the

desired pressure.

  The invention makes it possible to reduce the power at idle and to reduce the current consumption on the accumulator, since this does not contribute to the pumping efficiency of the device. To achieve this, a DC motor is chosen whose operating voltage is

  significantly higher than the battery voltage.

  For example, if you choose a motorized device and pump

  eg Romega, model 080, with a nominal voltage of 12 volts

  DC, powered at 6 volts, the power

  this consumed at idle will only be 0.6 watts.

  tight, the idling speed will be reduced, but this is of no consequence as long as the desired operating pressure

  is reached The Romega motor and pump device, model-

  080, with a nominal voltage of 12 volts DC supplied

  tee under 6 volts, without the assistance facilities of the cou-

  ple of the present invention, can generate a pressure of 210 mm of mercury in a sleeve of a portable blood pressure control device with a power dissipation of the order of 2.4 watts. Thus, when the desired pumping pressures are relatively low, using a DC motor with a higher rated voltage to drive the diaphragm pump

  will significantly decrease power dissipation and increase

will lie about performance.

  However, in the mobile devices of

  blood pressure control, it is sometimes desired to

  table of obtaining pressures above about 260 mm of mercury For example, pressures up to 500 to 600 mm of mercury may be desired Without them

  assistance arrangements for the couple of the present invention

  tion, a Romega model 080 motor with a nominal voltage of 12 volts DC will not be able to operate at 6 volts and still generate operating pressure

  significantly greater than 300 mm of mercury, despite the di-

  desired reduction in power dissipation which results from the use of a 12 volt DC motor under 6 direct volts. Prior to the present invention,

  obtaining high operating pressures required the use of

  reading of a motor whose nominal voltage was that

  of the 6 volt battery, for example, despite the increase

  tation of its power dissipation in service, and the

  corresponding higher idle power.

  The torque assistance arrangements of the present invention are provided by the coil spring 56 which is elongated and acquires energy when the

  connecting rod 38 is driven upwards, eccentric pin 18 -

  moving from position B to position A The spring 56 then releases its energy to participate in the movement

  towards the bottom of the connecting rod 38, while the eccentric is moving

  place from position A to position B, when running

  compression of the pump The lower end of the spring has a hook 58 which engages on a loop located on the curved part 62 of an elongated rod

  64, which preferably also consists of a material

  elastic thread The ends 66 and 68 of the rod fix it on the upper surface 28 of the casing by means

  nuts 70 and 72 screwed onto threaded screws 71, 73 The former

  upper end of the spring 56 also includes a hook 74 which engages in a loop 76 located on a support member 78 The end of the support member

  78 is fixed in the housing 40 of the connecting rod 38, ma-

  this spring is elongated and compressed when it is moved

cement of the lug 18.

  The role of the extension and compression of the spring is to accumulate energy when the pump is driven in its intake phase, or expansion phase, of the cycle, thereby increasing the load during this part.

253 'H 47.

  of the cycle The spring then releases its energy when the pump is driven in its compression phase, thereby reducing the torque imposed on the motor during this part of the cycle Spring 56 thus tends to reduce the effect of torque ripple on the motor 12, which is induced by the load during the operation of the pump 20 With a Romega motor and pump device, model 080, with a nominal voltage of 12 direct volts, a helical spring of a state length can be used free of 1.65 cm T with an elastic wire diameter of 0.5 mm and a winding diameter of 0.47 cm Figures 3 and 4 illustrate the

  results of using such a spring with this arrangement

  tif with motor and pump when the spring is extended to approximately 2 cm when the eccentric pin 18 is at point B. the spring then being under a tension of approximately 0.5 kg, and the spring having a length of about 2.4 cm when the lug is at point A, the spring then being under a tension of about 0.77 kg The ratio between the tension

  maximum and the minimum voltage is therefore about 1.5.

  Figs 3 and 4 show the comparison between

  input currents as a function of millimeters of sea-

  cure generated by the pump 20, -for respective operations under continuous voltages of 7 volts and

  6 volts In Fig 3, curve 82 represents the function

  operation without the torque assist spring 56, tan-

  say that the curve 84 represents the operation with the spring In FIG. 4, the curve 86 represents the functions without the spring and the curve 88 represents the

  operation with the spring As shown in these figures

  res, the most important influence of the spring takes place beyond the points of intersection 90 and 92, where the pumping pressure is at least 200 mm of mercury Although the loop 58 of the spring 56 is represented as connected

  permanently to the loop 60 of the rod 64 when the res-

  fate is energized, it remains as part of this

  The invention of moving the curved part upwards, thereby relaxing the spring when the pump is operating under pressures located before the points of intersection, 92 If the pump has exceeded the pressures indicated by these points, the curved rartie 62 can be moved down to increase the tension of the spring 56, enough so that it absorbs and then releases its energy in the way

  described above, to suppress the undesirable effect of undu-

  lation of the torque induced by the load on the DC motor.

2531147.

Claims (8)

  1 Improvement to a DC motor and diaphragm pump device of the type comprising a connecting rod (38) connected at one end to the diaphragm (34) of the pump (20), and at its other end to an eccentric rotary member ( 14) coupled to the motor drive shaft (16) characterized in that it comprises elastic means (56) connected by a first end to a fixed point (60), and by a second end to said eccentric rotary member (14) from   so that said elastic means acquire energy   during the expansion phase of the operating cycle   of the pump, and release the energy acquired, during the pha-   compression of the pump operating cycle, in order to reduce the ripple effect of the torque induced by the   load on the motor, caused by the pump.   2 Device according to claim 1, character-   laughed at the fact that the elastic means consist of a spring helical (56).   3 Device according to claim 2, character-   rised in that the coil spring (56) has a ratio between its maximum tension and its minimum tension of about 1.5   over the entire operating cycle of the pump.   4 Device according to claim 2, character-   that the location of the fixed point (60) is adjustable   ble, so that the spring (56) is roughly subject   at no voltage before the pump outlet pressure   pe has reached a predetermined value.   Device according to claim 1, characterized in that a direct current motor (12) is used   supplied with a voltage significantly lower than its voltage nominal rating.   6 Device according to claim 5, character-   rised in that the DC supply voltage of the motor (12) is equal to approximately half of its nominal DC voltage.   7 Device according to claim 1, character-   risé in that the pump feeds the pressure sleeve of a   blood pressure monitor.   8 Device according to claim 7, charac-   terized in that such a voltage control device   arterial blood pressure is portable, and the motor is driven by a DC accumulator with a voltage of approx. 6 volt ron.   9 Device according to claim 8, charac-   characterized in that a constant current motor (12) is used   continuous with a nominal voltage of 12 volts.