IL31941A - Metering and dispensing apparatus - Google Patents

Description

A metering and dispeaeiag apparat s lCROCSDIO STSTBHS Cs-30259 This invention ia concerned with apparatus for metering and dispensing liquids· Such apparatuses of this kind are known: they are mainly used in test laboratories, e.g. biochemical and clinical laboratories, and are intended either to deliver a pre-determined volume of a liquid to be analysed (i.e. operating as a metering apparatus), or to deliver successively several metered quantities, all ofidentical volume, of the same liquid (1·β· operating as a dispensing apparatus), or else to deliver simultaneously both a volumetrically predetermined metered quantity of a liquid having to be analysed and a metered quantity, also volume rically predetermined but not necessarily of same volume as the liquid to be analysed, of a diluting liquid or of a reagent (i.e. operating as a diluting apparatus), The use of these apparatus is becoming more and more widespread as the demand for chain testing increases. However, the known apparatuses are often of low accuracy, inasmuch as the volumetric quantities they meter lack accuracy and are not readily reproducible, particularly when these volumetric quantities are small. This defect is largely due to the fact that, in these known forms of apparatus, adjustment of the metered quantity is not "digitalized" ; indeed adjustment is, as it were, continuous and such adjustment is often affected by errors in the reading of scales, these being human errors attributable to distraction, inattention or tiredness on the part of the operators. Moreover many of the known forms of metering apparatus operate in a rather brutal ways first an abrupt suction action occurs, then an abrupt stoppage of the suction action and finally an abrupt discharge of the metered 30259/2 T 5 " in breaks in the columns of liquid (hydraulic hammering effects) or in the formation of drops, both bei g a source of material errors* If it is desired to reduce the extent of these errors, this can only be achieved, with these known forms of metering and dispensing apparatus, by having them handle relatively large quantities of liquid, this: of course is a major drawback when it- is required to carry out a large number of different tests on a liquid from one source since, in order to do this, a corresponding number of samples of the liquid is usually required and this means that quite a sizeable starting quantity will be needed. The only way in which this need for a sizeable starting quantity of the liquid can be avoided is to reduce to the greatest possible extent the volume of each sample. Hence the desirability of minimizing all possible causes for inaccuracy in metering, This is particularly important in haematolog where it is often desired to carry out a large number of tests withou having to draw off large quantities of blood from the patients» One of the most relevant examples is in pediatric haematolog « The apparatus of the invention is capable of metering with considerable accuracy very small volumes of liquids* Accordingly the invention provides an apparatus for metering and dispensing liquids comprising a piston pump of adjustable predetermined stroke, reciprocable in a cylinder thereby alternately to take in and discharge an adjustable predetermined volume of liquid through a valved inlet and outlet respectively, wherein, in use, the piston undergoes 30259/2 interrupted sinusoidal reciprocation (as hereinbefore defined) having a pause wherein the interruption comprises a pause at the end of each stroke during which the inlet and outlet are opened and closed as appropriate* For the purposes of this specification and claims, by sinusoidal reciprocating is meant reciprocation such that a graph of displacement against time gives a sine curve.

Preferably the apparatus of the invention also includes a drive mechanism (a) for continuously transmitting drive for operating a valve "to open and close the inlet and outlet (b) for intermittently transmitting drive to a variable , throw crank mechanism, included in the drive mechanism, which in turn transmits drive to the piston and causes it : ~ intermittently to reciprocate in a sinusoidal manner, the extent of the throw determining the length of the piston stroke* She variable throw crank mechanism in the devices of the invention preferably includes &. rot&table member which, upon rotation of the crank, imparts reciprocating sinusoidal motion to a follower and which is moveable along the axis of . rotation of the variable throw crank mechanism to vary the throw of the crank and thereby the amplitude of stroke of the follower and wherein the movement along the axis of rotation of the crank is controlled by a micrometer screw and the valve preferably comprises two abutting relatively rotatable valve members so shaped as to allow communication between the cylinder and the inlet at one stage of relative rotation and between the cylinder and the outlet at another stage of relative rotation. .... : - - 5"-- r In the preferred devices of the invention, the micrometer screw is associated with a touch detent system capable of indicating to a human operator the rotation of the sc ew through one incremen ; and a display means capable of displaying to an observer a number indicative of the amplitude of the stroke and the. volume of the metered liquid* „ 7 One device according to the invention comprises a motor, a first motion translating means adapted to translate rotary motio into sinusoidal reciprocal motion, power transmitting meahs peratively-connecting the motor and the motion translating means, at least one removable pump having a piston and cylinder chamber, two ports, adapted to be in communicatio with the same end of the cylinder chamber, a valve, capable of alterately connecting the cylinder chamber' with the ports, a valve switching means operatively connecting to the valve, a second motion translating means operatively associated with he valve switching means arid th© power traasisti-iltix^ me«uis and adapted to translate the rota* tional movement of the power transmitting means into .movement of said valve switching means and operative to position said valve means in a predetermined position between strokes of t&e piston, a piston activating member, the member, connected to the first -motion translating means and the piston and adapted to translate the sinusoidal reciprocal motipn of said first motion translating means to said piston, said first motion translating means having an adjustment assembly adapted to vary the amplitude of the reciprocal sinusoidal motion, the 30259/2 stroke length can be adjusted externally of the apparatus* f e apparatus of the invention may be so constructed as to allow interchangeability of, for example, the pistons and/or cylinder and/or valves. By interchanging piston pumps of different capacities the range of amounts which the apparatus is capable of dispensing can be varied© Furthermore, the interchangeability assists servicing and cleaning* Although various parts of the apparatus can be made of a variety of suitable materials such as, for example, metal, glass, rubber or plastics, the cylinder is preferably made of glass, the piston of metal and any caps or plugs of a hard synthetic material such ae polytetrafluoro-ethylene or fluoroohloroethylenee Preferred embodiments of the invention will now be partio ularly described, f or the purposes of illustration only, with reference to the accompanying drawings in which: Fig, 1 is a side view, in a cross-section of a first a paratus according to the inventions Fig, 2 is a front sectional view of this first apparatus, taken along line II-II of Figure 1$ Fig, 3 is a rear sectional view of the first apparatus* taken along line III-III of Figure 1; Fi β 4 is a plan view of the first apparatus? ig* 5 is a front elevatlonal view of the first apparatus5 Figs* 6 and 7 are detail sectional views taken along 30259 2 - 7 - lines VI-VI and II-VII, respectively of Figure 4 on a somewhat enlarged scale; Figure 8 illustrates a further detail, partly in section,, of the first apparatus o a substantially enlarged scale; Fig, 9 shows three graphs illustrating the operation of the first apparatus; Fig, 10 shows a substantially enlarged scale and in a more detailed manner a portion otf Fig, 1; Fig, 11 shows the eleotrical wiring for the first apparatus; Fig, 12 is a side view, in cross-section of a second apparatus according to the invention; Fig. 13 is a front sectional view of the second apparatus, taken along the line XIII-XIII of Figure 12; Fig, 14 is a rear sectional view of the second apparatus, takek along line XIY-XIV of Figure 12; Fig, 15 is a top sectional view of the second apparatus, taken along line XV-XV of Figure 12; Fig, 16 is a front elevational view of the second apparatus Figs* 17 and 18 are detail section views taken along lines XVII-XYII and XVIII-XVIII respectively of Figure 12; Fig, 19 shows three graphs illustrating the opera» tlon of the second apparatus and lge, 20 shows on a substantially enlarged scale and in a more detailed manner a portion of Figure 12« Bach of the embodiments hereinafter described contains 30259/2 - 8 - two piston pump and valve mechanisms and can be used to provide, at the same time, samples of the same or of different liquids, depending on the arrangement of the inlets and outlets associated with each pump cylinder* As will be apparent, corresponding apparatus according to the invention having only one, or having three or more piston pumps can readily be designed* The liquid metering and dispensing apparatus shown in Figs. 1 to 5 comprises a pair of suction and forcing pumps la. and lb, a pair of switching Valves 2a. and 2b,, a pair of drive mechanisms 3a and 3b (powered however by a singls common motor 4 through a single common speed-reducing gear), a pair of adjustment means 6a. and %, a pair of display means 7j| and 7b, but a single control means comprising an automatic cut-out switch 8 and cam-actuated switch 9· Of each of the dual members only one will be described, the components of each such member being identified by three-figure re ere/iJii Minerals so chosen that their first figure corresponds to the reference numeral of the member to which they belong. Thus* all of the components forming part of -each pump, whether it be pump la or pum lb, will be identified by numerals ranging from 101 to 199» all those 2a or valve forming part of each valve, whether it be valve/2b» will be identified by numerals ranging from 201 to 299» and so forth. In view of the constructional symmetry of the dual members, the letter symbol that distinguishes one member from the other within a pair will be, omitted*, 30259/2 - 9 «· .

Pump In the present embodiment, each suction and forcing pump consists of a cylinder 101 in which can move a piston 102 having a cap 103 and mounted at the end of a rod 10j» Cylinder 101 is closed off by a plug 105 formed at its top end with a nipple 106 by means of which it communicates with the switching valvee $he cylinder is kept in place by an ^-shaped element 107 which, in conjunction with a spring blade 108, holds it tight against the switching valve, with the nipple 106 of its plug 105 engaged in a recess (not marked in the drawing) formed for that purpose in the valve* She rod 104 extends through a slot formed in the short arm of the L-shaped element 101 and its free end portion is connected near to the free end of a lever 339 (which is part of the drive means described hereinafter)* 2* Switching . Valve Bach switching valve comprises a stationary body 201 which is fitted into a stationary socket 202, and a rotary valve member 203 which is fitted into a rotary socket 204· She valve body and the valve member are held together by an assembly sleeve 205 which fits into an opening 206 formed in a front wall 10 of the apparatus frame* 'She valve is kept in place in this opening by a 7 releaaable holding device which oonsists of a plate 207 and of two Curled-headed tightening screws threaded Mo holes formed- in the front wall 10 of the apparatus frame, When in position, the valve fits by means: of two holes formed in the base of the rotary socket 204, on. to two driving pins 302 and 30259/2 • to - described below* In this way, the valve member 203 can be plugged onto the driving pins. Because of its design and of its manner of attachment, the switching valve can be exchanged aa a unit, with the valve member and the valve body remaining connected together by means of the assembly sleeve 205» and such changes are exceedingly easy to perform, this being an advantage for servicing* The valve body 201 is formed (see Figure 6) with an axial passage 210 which communicates with a recess 211 into which is inserted the nipple 106 of pump 1 and with two lateral passages 212 and 213 which communicate with recesses 214 and 215 adapted to receive, respectively, one end of a flexible intake tube 11 and one end of a flexible discharge tube 12· e intake tube 11 communicates with an outside reservoir (not shown) from which the apparatus is required to draw off metered quantities of a liquid contained therein) the discharge tub© 12 communicates with an outside receptable (not shown) to which thene metered quantities are to be discharged or with a nozzle 31 fitted to a handle 30 enabling the metered quantities being discharged to be delivered at a desired location, ΐο one of these handle-nozzle assemblies is attached a container 27 (whose function will be explained later). In other embodiments such as an embodiment having no handle-noasle assembly the container may be located in another convenient place, e.g. it may be a footswitch on the floor, S e valve member 203 is formed, in its face adjacent valve bod 201 with a channel 216 havin the a roximate shape of an anchor (see Figure 7)» which depending on the angular position of the valve member, causes the axial passage 210 in body 201 to communicate with either one or the other of the two lateral passages 212 and 213 in the; body. Thus, upon rotation of the valve membe 203 in. relation to the stationary valve body 201, the pump successively communicates with the intake tube and with the discharge tube. This communication lasts for as long as it takes the arcuate portion 217 to channel 216 to sweep past the orifice of one or other of the lateral passages 212 and 213» which length of time is dependent, for a given speed, on the length (In, degrees) of the arcuate portion 217· fhe length of portion 217 is of course less than 180° to avoid the possibilit of direct communication between these two lateral passagess 3:*' . Drive Means The drive means are powered by one motor through a common speed-reducing gear. She motor, identified as 4 is preferably synchronous and the speed- educing gear,, identified as 5, comprises an output shaft 13 which carries a. plriion; 14; Pinion 14 is coupled to shaft 13 through a fractional torque-limiting device 15 (see Figure 8) and meshes with the first gear-wheel of each of the two drive . means 3& and ¾. Al hough only drive means 3a will be described, it will of course be understood that what is about to be said oh connection with drive means 3a is also true of drive means 3b since these are identical to 3&· Pinion 14 thus meshes with a toothed wheel 301 which carries the 30259/2 - 12 two pins 302, 303 mentioned earlier (Figure 2). The latter extend through a flanged disc 304 and project, as already stated, into recesses formed in the base of the rotary socket 204 holding the rotary valve member^ of the switching valve* Disc 304 forms, in conjunction with a spring 305» a resilient axial abutment which presses, through opening 206 and inside sleeve 205» the valve member 203 against the valve body 201· Wheel 301 drives a toothed wheel 306 secured to the input shaft 321 of a variable throw crank mechanism, .320. Along two portions of the periphery of toothed wheel 301, the teeth have their axial length reduced by about half by means of milled arcuate recesses 307 and 307*· ¾e axial length of the teeth on the toothed wheel 306 is less than the depth of the recesses 307 and 307' (see Figures 1 and 2). Moreover, wheel 306 ia located in the plane of these recesses. Consequently, wheel 301 only drives wheel 306 during those portions of its rotation which ooincide with the action of the non-recessed portions 308 of i s periphery. ¾heel 306 is mounted on a hub which carries a pair of radial arms 310 spaced from wheel 306 and dimensioned to cooperate alternately with two pins 311 and 311* projecting from the side of wheel 301. Arms 310 and pins 311 and 311' are so positioned that, upon engagement they cause the teeth of wheels 301 and 306 to mesh as the leading end of one or other of the non-recessed portions 308 is about to engage the wheel 306. The peripheral length of the non-recessed portions 308 an is equal to half the circumference 30259/2 «· 13 » of wheel 306 so that for each half turn of the wheel 301,. wheel 306 carries out one h¾lf turn followed by a pause corresponding to the passage of one or other of the recessed portions 307 and 307*. The wheel 301 and 306 thus together form an intermitten drive able to convert the continuous rotation of *heel 301 into an intermittent rotary motion on the par of vheel 306 while leaving the latter free to rotate when either of the recessed portions 307 and 3Q7* lies opposite thereto* She variable throw crank mechanism 320 comprises a first rotary member 322 which is secured to the input shaft 321 and which is formed with a diametral slot 32 in which cam slide islally' throw-setting member consisting of a blade 32 whose edges 325 and 326 are oblique in relation to the rotation axis 327 Of the rotary member 322. fhe latter Is. positioned opposite a second rotary member 328 which is also formed with a diametral slot 329 enabling motion of the blade 324 along the rotational axis of member 3 · Slide members 330 and 331» mounted in a slideway 332, are provided to guide movement of the bladee Blade 324 extends into, and contacts the sides of, an annulus formed by the inner race of a b il bearing 333» this inner race carries, on the radially inner surface thereof, two spur-like elemtns 334 and 335 which engage the edges 325 and 326 of blade 324 and which project from opposite sides of the race into the diametral slots 323 and 329 of rotary members 322, and 328 whereby this inner race can rotate with the latter, Ihisbaltl bearing 333 can be off-set in relation to the axis 327 to a extent determined by the axial position of blade 324 and this 30259/2 - 14 - axial position is governed by a micrometer screw 601 which forms part of the adjustment means hereinafter described.

The outer race of the ball bearing 333 is secured to a radial push-rod 336 which is connected, by means of a ball 337 held in socket 338, to a rooking lever 339 of which one end is pivotally mounted on a pin 340 mounted in the casing of the apparatus and of which the other end carries a tightening clamp 341 in which is held, by means of a knurled-headed screw 342» the lower end of the piston rod 104 of the pump described earlier. It will thus be appreciated that the ball race and associated spur-like elements and push rod together make up a follower for the blade* The drive means are thus able both to drive the switching valve 2 ih^ continuous manner, thereby to place the pump 1 cyclically -in communication with the suction tube 11 and with the discharge,tube 1 , and to drive the variable throw crank mechanism 320 in an intermittent manner, whereby its output member 336, which is connected to pump 1» can have imparted thereto a intermittent reciprocating motion h¾ving a regul&table amplitude* Wheels 301 and .306 are so keyed in relation to the valve member 203 and to the input shaft 321 of variable throw crank mechanism 320 as to achieve between these various movements the phasing illustrated by the graphs of Figure 9· In this Figure, curve trates. the operation of the switching valve, curve "EeM represents the motion of the input shaft of the variable throw crank mechanism and curve "Po" illustrates the operation of the pump. Cycle I consists, as regards the valve, of a portion "Asp" during which the pump communicates with the intake on suction tube, a portion "C" during which switching occurs and during which communication of any. kind is interrupted, and a portion "Exp" during which the pump communicates with the discharge tube (graph "Vc" ). As regards the input shaft of the variable throw crank mechanism, cycle I consists of a portion "^" during which this shaft rotates through 180°, a portion "R" during which it is at rest, and a portion '^" during which it completes its revolution (graph "Ee"). As regards the output member of the variable throw crank mechanism, i.e. , as regards the pump, cycle I consists of a suction phase "Asp" during which the pump carries out a suction or intake stroke, a pause "P" during which the pump remains stationary, and a phase "Ref" during which the pump discharges the' liquid it has sucked in during the "Asp" phase. Pause "P", during which the pump is idle, overlaps portion "C" of the valve operation, i.e. the portion during which switching takes place. Curve "Po" in Figure 9 further illustrates the intermittent sinusoidal nature of the pump's motion, the effect of this sinusoidal motion being progressively to set the liquid in motion -and progressively to bring it to rest, thereby avoiding any hydraulic hammering effect. In this graph "Po", there has also been sketched in the extent to which the amplitude of the stroke of piston 102 can be varied, such variation enabling the metering of liquid to be freely varied between a maximum quan-tity Dmax and a minimum quantity Dmin' with the possibility of this latter quantity being nil if the axial position of blade 324 is such that the roller bearing 333 is made concentric with axis 327 of the variable throw crank mechanism. 4. Adjustment Means Each adjustment means comprises a micrometer screw 601 v/hich co-operates with a nut 602 formed by one of the ends of a stationary element 603 whose other end 604 acts as a bearing for the second rotary member 328 of variable throw crank mechanism 320. Element 603 is kept stationary by a set screw 605 driven into a socket 606 fixed to the rear wall 16 of the apparatus frame. The micrometer screw 601 is formed with a smooth, push-rod forming, portion. 607 having a rounded tip which co-operates with the slide member 331 of the throw setting member 324 of the variable throw crank mechanism. Rotation of the screw 601 is controlled by a knurled knob 603, which is rigidly secured to th outside end of a socket 609 which projects out of the casing wall and which, at its inner, open end, fits over the stationary element 603. Socket 609 carries a sprocket 610 whose function will be explained further on. This sprocket 610 (see Figure 10) is provided with a pin 611 which projects into a longitudinal groove 612 formed in the outer face of socket 609. In this way, socket 609 can slide axially through the sprocket while remaining angularly solid therewith. Socket 609 extends also through a setting disc 613 which lies on the outside of sprocket 610 and which is formed with two diametrically opposite recesses 614 and 614'. In these two recesses are movably housed balls 615 and 615' against which act springs 616 and 616'. The function of these balls is to signal tac-tually to the operator the passage of the groove 612 there-past; these balls thus in effect form spring-loaded detents which enable the operator called upon to actuate the knurled adjustment knob 608 to feel when he has rotated screw 601 by half a turn. Setting disc 613 is immobilized by lugs through which extend screws 617 and 618 (see Figure 3) and its function is to aid in the calibration of the display means. More specifically, the removal of screws 617 and 618 allows the setting of the zero. ■ . Disnlay Means Each display means comprises a revolution counter 701 whese input shaft has secured thereto a sprocket 702 connected by chain 703 to the previously referred to sprocket 610. This revolution counter is formed with a window 704 (Figure 4) through which sn be seen a set of figures indicating the number of rotations made by its input shaft. This number is directly related to the rotation carried out by the knurled, throw adjusting, knob 608 and the use of a sprocket chain 703 helps to maintain this relationship by preventing any slip between the wheels 610 and 702. The diameters of the wheels 610 and 702, the slope.of the -edges 325 and 326 on the throw setting blade 324 and the ratio between the arms of lever 339 are so chosen that the volume of the quantity of liquid being metered and discharged can directly be determined by multiplying the number displayed in the window 704 by a calibration figure indicative of the maximum capacity of the pump cylinder and which is inscribed on the cylinder. Further, the ratio between the sprockets 610 and 702 is 2 to 1 so that sprocket 702 will perform one whole turn for every half-turn of the sprocket 610, and hence of the micrometer screw 601. Moreover, the angular position of the setting disc 613 is so chosen that each desent made by the spring-loaded detent can cause the number visible in window 704 to vary by one unit or increment. Since the operator will, when making an adjustment, always stop at a detent, the number displayed in window 704 is always a full number.

Clearly, the throw of variable throw crank mechanism 320 can only be adjusted by means of the micrometer screw 601 within certain limits; consequently the range within which can be selected the quantity of liquid which is to be metered and dispensed by the pump is determined by the maximum capacity of the cylinder used in the pump. Accordingly, in order to increase the range within which this quantity can be chosen, the apparatus is provided with cylinders a set of interchanneabie Or distributor pumping units or cylinders having diameters such that their maximum capacities will define a suitably stepped series to form the desired broad range, for' example: 0.2; 2; 5; 10; 20; and 50^1. 6. Control Means The control means comprises the switch 9 which consists of a microsv/itch and which is provided with a pushbutton 20 actuated by a cam formed by a pair of cavities 21 and 22 and in one of the members of the drive mechanism, e.g. in wheel 301 (Figures 1, 2 and 4). In the apparatus Shown in Figures 2 and 4 a second, spare . cam-activated switch ia provided- The switch is connected, as is shown by the electrical wiring diagram of Figure 11, so as to cut off the motor's supply whenever one of the cavities comes to lie opposite the push-button 20, i.e. tv/ice per revolution of wheel 301. It is therefore the cavities which cause the breaks "R" previously mentioned in connection with Figure 9. The control means also comprises the automatic cut-out switch 8, which, as can be seen from Figure 3, includes a contact blade 24 adapted to come into contact with a contact head 25 under the action of a thrust exerted by a push member or pjiston 26 pneumatically actuated by squeezing a flexible end resilient air container 27 which acts as a control pump adjacent handle 30 (see Figure 1) and which is connected by a conduit such asjjflexible tube 29 to a cylindrical chamber 28 wherein the push member 26 is slidably mounted. The contact blade 24 is arranged to lie, at rest, biased away from the head 25. Between the head of the push member 26 and its cylinder 23 there is provided some play' such that the push member will be propelled forward by a sudden increase in pressure brought about by squeezing the air container 27, but such that it will allow the air to leak out so that the pressure of the air is made to drop progressively until it is unable to counteract the bias of blade 24. This play is so chosen that the time taken by the switch 8 to open again, through push member 26 being forced back to its position of rest, is enough to enable the motor to rotate v/heel 301 by a sufficient angular extent to cause the cavity which had brought about actuation of the switch 9 to be moved past push-button 20. Since the switch 8 is connected in parallel with switch 9, the return of 8 to its "open" position will have no effect on the electric supply to the motor. The latter will therefore carry on rotating v/heel 301 until the next cavity comes to lie opposite push-button 20 to actuate switch 9. The electrical diagram of Figure 11 is self-explanatory in this regard.

Attention is however directed to the advantage that such a pneumatically actuated automatic cut-out switch has for the operator's safety in view of the risks that are inherent in handling electrical equipment in premises where it would be exposed to splashing by conductive liquids such as water. Since the present metering and dispensing apparatus is in fact meant to be used in laboratories where such risks do exist, the advantage of this pneumatically actuated sv/itch will be obvious.

This safety feature enables the control means 27 for the contact-maker 8 to be mounted adjacent the handle 30 by means of which the operator holds the nozzle 31 at the end of the discharge conduit 12.

The apparatus hereinbefore described thus provides the following advantages: - because of the intermittent sinusoidal motion of the pump, the liquid can be metered smoothly, the drav.'ing off of a metered quantity and its discharge beginning and ending in progressive manner; - the adjustment of a metered quantity is achieved ■by means of a micrometer screw and is accordingly highly accurate; - the determination of the volume-of a metered quantity is achieved by means of a touch-detent system thereby helping to increase the accuracy of a metering op¬ ed in rises 18b_, a single, ducing of means 8 and dual of each ts, being osen that eral of component e drive mechanism 3a or drive mechanism 3b_, will be identified by numerals ranging from 301 to 399, all of those forming part of the adjustment means, whether they be adjustment means 6a_ or adjustment means 6b, will be identified by reference numerals ranging from 601 to 699, and so forth. The only exceptions to this rule are the distributor pumping units 18a and 18b whose components will be identified by reference numerals ranging from 100 to 199 (for one part of these components) and from 200 to 299 (for another part of these components). In view of the constructional symmetry of the dual members, the letter symbol that distinguishes one member from the other within a pair will be omitted. 1. Distributor Pumping Uni Each distributor pumping unit comprises a holder consisting of two tubular casings 130 and 131, fixedly screwed to one another, which enclose a suction and forcing pump and a switching valve, the suction and forcing pump consisting of a cylinder 132, of a plug 133 and of a piston 134 which is provided with a cap 135 and which is mounted at the end of a rod 136, and the switching valve including a stationary valve body 230 and a valve member 231 housed in a rotary socket 232. The holder, is provided with a bayonet connection having studs 151 which engage in slots 152 formed in a Gim- bal ring 153 which is pivotally mounted, in relation to a fixed portion 154 of the apparatus frame, on a pair of pins (not visible) lying at riqht angles to .the studs 151 and to the plane of the paper'. Socket 232, which houses valve men~ ber 231, is rendered angularly solid, by means of a pair of pins 251, with a drive transmission member 252. The top end of transmission member 252 is formed with a crenellated crown 253 defining ratchet teeth of triangular shape (saw-toothed). When the distributor pumping unit is in place, the crenellated crown 253 of member 252 co-operates with driving pins 351 forming part of the drive means and a spring-loaded abutment ball 155 exerts an axial force on the centre of member 252, this force being, transmitted through member 252 and socket 232 to the valve member 231 thereby pressing the latter against the valve body 230 to ensure fluid tightness. A spring 156 is provided between the transmission member 252 and the socket 232 so as to maintain this fluid tightness when the distributor pumping unit is removed from the apparatus.

The valve body 230 is formed, in its operative face adjacent valve member 231, with a central orifice 233 (Figure 17), which communicates, via an axial passage, with the interior of the cylinder 132, and two lateral orifices 234 and 235 wnich com unicate, via further passages, with conduits 236 and 237. These lateral orifices or ports lie on a circle 238 which is concentric with central orifice 233, and are spaced from one another by an angular distance of 135°. The valve member 231 is formed, in its operative face adjacent valve body 230, with four radially extending link channels 239 to 242 (Figure IS) which lie at right angles to one another and which serve to put the central orifice 233 of valve body 230 in communication v/ith either one or the other of the two lateral orifices 234 and 235j in a first -- -- - - condition, that shown in Figure 18, it is lateral orifice 235 which is made to communicate by the valve member 231 with the central orifice 233 and, in a second condition, which is reached when the valve member 231 has rotated through 45°, it is lateral orifice 234 which is made to communicate with the central orifice.

Consequentl , every time valve member 231 rotates through 45°, the valve changes over from one condition to the other. It will thus be observed that with this arrangement of radial link channels, the valve must be driven in an intermittent manner and is required to r.otate through 45° at each step, whereas, in the first embodiment, the valve was driven in a continuous manner , the valve member in this latter case being formed with an anchor-shaped arrangement of link channels. 2. Drive Means Each drive means comprises a first intermittent drive made up of a driving toothed wheel 301 meshing with a driven toothed wheel 306. This intermittent drive is identical to that in the first embodiment and will therefore not be described again here. Suffice it to say that the teeth of wheel 301 are of reduced axial length along two portions of its periphery so that, during each half turn of wheel 301, wheel 306 also carries out one half turn followed through by a pause which lasts, the length of time taken by one set of axially shortened teeth to travel past wheel 306 and during which the teeth of the latter are disengaged from the teeth of wheel 301, and to say that studs 311 and 311' on wheel 301 and spoke 310 on wheel 306 are provided to facilitate re-engagement of the teeth of these tv/o wheels at the end of the above-mentioned pause.

Each drive means further comprises a second intermittent drive which is made up of a driving wheel 352 which is mounted on the same shaft as toothed wheel 301 and which carries a diametral arm 353, end of a driven wheel 354 whose axis lies at right angles to that of driving vmeel 352 and coincides with that of valve member 231 in the distributor pumping unit. The driven vmeel 354 carries eight radial arms 355 which are spaced 45° apart, and it is on this driven wheel that are secured the pins 351 that serve to rotate valve member 231. With this arrangement, the driven wheel 354 is rotated by 45° at each half turn of the driving wheel 352 whereupon it becomes completely disengaged from the latter.

The position of the radial arms 355 is so chosen that each rotational step of the intermittently driven wheel 354 will cause the switching valve of the distributor pumping unit to pass from the first to the second of the above- mentioned conditions, then back to the first, and so on, cyclically.

Each drive means comprises, moreove , a special crank mechanism of variable throw. It is special inasmuch as it enables asymmetric (described below) adjustment of its throw. It includes a rotary member 356 rigidly secured to an input shaft 321 on which is keyed 'the driven v/heel 306 of the first intermittent drive. Into this rotary member 356, which is cup-shaped,.extends an axially moveable - - 30259/2 of the cone by the above plane. Since the crank-pin slides in relation to the runner, the diameter of this circle varies but since the crank-pin, lies, in its "uppermost" position, parallel to the axis of its rotational drive, the topmost point of this circle occupies an invariable position. Consequently, any variation of throw brought about by axial displacement of the crank-pin is asymmetric as opposed to variable throw crank mechanism wherein the crank-pin describes a cone having an axis which coincides with the rotational driving axis and never having its generatrix lying parallel to this rotational driving axis. In order that the crank-pin 357 can be moved to an axial position such that the apex of the cone comes to be located at the centre of runner 367 , thereby to cause all motion on the part of runner 367 to cease, ball 361 is off-set in relation to the axis of the crank-pin 357. In apparatus where it is not necessary for the motion of runner 367 to be caused to cease, ball 361 could of course be centered on the crank-pin axis.

I A yoke 370, of which only a lower portion can be seen in Figure 12, connects the slide 368, through the intermediary of a hinge 371, to a lever 373 pivotally mounted at one end on a stationary pin 374. There is thus imparted to lever 373 a reciprocating motion having an amplitude which can be made to vary asymmetrically. The opposite, free end of lever 373 is connected to the piston rod 136 extending out of the distributor pumping unit, by a play-free, readily releasable, coupling which is constructed as follows: The lower corner of the free end of lever 373 is •~~rr cut away at right angles and the vertical face of the resulting notch has driven thereinto a supporting stud 383. · In the upper, unnotched, part of the free end of the lever is formed a recess in which is held a ball 384 caused to project by a spring 385, housed in the recess, towards stud 383. As for the piston rod 136, it carries at its free end a slotted socket 157 through which extends a pin 158 having a diameter such that when socket 157 is fitted on the the free end of lever 373, pin 158 comes to be trapped at the bottom of the notch, above stud 383, by the action of the spring-loaded ball 384 which it will have lifted on the way in.

The variable throw crank mechanism is provided with an arrangement of spring-loaded detents 375 and 376 mounted on opposite sides of the casing 364 so as to cooperate with a longitudinally extending slot 377 on the out side of rotary member 356. These detents are so positioned in relation to the slot as to be actuated each time crank- pin 357 passes through its "uppermost" and "lowermost" positions. Their purpose will be explained further on.

Head 363 is secured to a screw 378, preferably a precision micrometer screw, which co-operates with a nut 379 formed at one end of a tubular casing 372 adapted to be rotated by a knurled knob 380 whereby the axial position of head 363 may be changed by actuating knob 380. In so doing, the amplitude of the reciprocating movement of the variable throw crank mechanism output member formed by yoke 370, and hence the stroke of the pump piston 134 can be varied and the fact that crank-pin 357, in its "uppermost" position, always lies parallel to the rotational drive aicis, causes this variation to be asymmetrical, i.e. that the top dead point of piston 134 is alv/ays at the same place v.'hatever the length of its stroke. The interest of such asymmetry for stroke variation purposes, by resorting to a variable throw crank mechanism of asymmetrically variable throw, will become apparent later on.

To avoid the difficulties that could arise, as regards accuracy of adjustment, with misalignments of the axes of rotary member 356, of the cylindrical space inside casing 364, and of screw 378, the tubular casing 372 formed with nut 379 is preferably mounted in an elastic bearing, consisting, in the present instance, of three spring wires arranged to form a triangle and engaging more or less tangentially in a groove formed in the periphery of the tubular casing (in Figure 12 only two of these wires can bje seen, to wit wires 381 and 382).

I ■ As in the first embodiment, the electric motor drives, through a speed-reducing gear 5 and a frictional torque-limiting device 15 (Figure 8), a single pinion 14 <y which rotates both driving wheels 301 by meshing with the uncut portions of their teeth. 3. Adjustment I•loans In addition to the screw 378 and its nut 379, which, in fact, belong to the variable throw crank mechanism, the adjustment means each comprise a setting disc 613 (Figure 20) having balls 615 which co-operate, under - - ("Asp" or "Ref", curve Po, Figure 19). These movements together constitute half an operational cycle, such a half- cycle either being an intake half-cycle (if the pump has performed a suction stroke, i.e. if piston 134 has moved ' downwardly), or being a discharge half-cycle (if the pump has performed a frcing stroke, i.e. if the piston 134 has moved upwardly). The Operator can then take whatever time he needs to change the containers into which dip the ends of conduits 236 and 237 and once this is done he can then 0 trigger off, by means of switch 8, the next half-cycle (interruption "Int", Figure 19).

It will thus be observed that this second embodiment, constructed as has just been described, operates in much the same way as the first embodiment; it has, however, in relation to the latter the following distinctive features: - eac. pump and its valve, through being grouped together ,19.8468 to form a distributor pumping unit which can readily be removed without any form of dismantling, can easily be exchanged (for instance to alter the range within which 0 the volume of a metered quantity can be varied by re- sorting to a cylinder of different maximum capacity); - the separate sterilization of the pump and of the valve, involving subsequent reassembly under sterile conditions, can be replaced by sterilization of the distributor pump5 ing unit as a whole (including even, -conduits 236 and 237); - since each half-cycle starts off with the actuation of the valve there is no need to take any particular steps, when putting the distributor pumping unit back in place, to set the valve member in the correct position as this will be done automatically, and the saw-toothed outline of the crenellated crown 253 helps to achieve smooth inter-engagement of the teeth and the driving pins 351; each valve can readily be moved by the operator- from one of its operative conditions to the other by acting on the radial arms that project from the front portion 154 of the apparatus frame: this possibility enables · the roles assigned to conduits 236 and 237 to be reversed, so that either can selectively be used for drawing off liquid or for discharging liquid; any change in volume of a metered quantity by rotating knurled knob 380 (which, by changing the axial position of crank-pin 357 causes the throw of tne variable throv; crank mechanism, and hence the stroke of piston 134, to be varied) does not cause the piston to move at all when the crank-pin lies in its "uppermost" position, and hence does not cause any movement of liquid in the conduits: this is an important advantage afforded by the use of a variable throw crank mechanism of asymmetrically variable eccentricity. 30259/2 - 34 °

Claims (1)

1. CLAIMS 1 · An apparatus for metering and dispensing liquids comprising a piston pump of adjustable predetermined stroke, reciprocable in a cylinder thereby alternately to take in and discharge an adjustable predetermined volume of liquid through a yalyed inlet and outlet respectively, wherein upon ^actuation, the piston executes single stroke of reciprocation with a pause at one end thereof during which ; pause the inlet and outlet are opened and, closed as appropriate* being a stroke the stroke/of sinusoidal reciprocation (a8 hereinbefore defined). 2» An apparatus as claimed in Claim 1 which also includes a drive mechanism (a) for continuously transmitting drive for operating a valve to open and close the inlet and outlet and (b) for intermittently transmitting drive through a variable throw crank mechanism, included in the drive mechanism, to the piston and causing the piston to execute the stroke of reciprocation, the extent of the throw determining the length of the piston stroke, with the pause at one end thereof. 3· An apparatus as claimed in Claim 2 wherein the variable throw crank mechanism includes a rotatable member which, upon rotation of the crank, imparts reciprocating sinusoidal motion to a follower and which is movable along the axis of rotation of the variable throw crank mechanism to vary the throw of the crank and thereby the amplitude of the stroke of. the follower and wherein the movement along the axis of rotation of , the crank is controlled by a micrometer screw. 4· An apparatus as claimed in Claim 2 or 3» wherein the valve comprises two abutting relatively rotatable valve merabers so shaped as to allow communication between the cylinder and the inlet at on© stage of relative rotation and b ween the cylinder and the - 55 - 30259/2 5· An apparatus as claimed in Claim 3 hich also includes a touch detente system associated with the micrometer screw and capable of indicating to a human operator the rotation of the screw through one increment; and a display means capable of displaying to an observer a number indicative of the amplitude of the stroke and the volume of the metered liquid. 6· An apparatus as claimed in Claim 1, (a) in which the piston pump is an interchangeable suction and forcing piston pump able, during each suction stroke, to draw off a predetermined volume of liquid and, during a subsequent forcing stroke, to discharge this liquid. (b) which contains a switching valve associated with the pump for alternately opening into communication with the pump first one and then the other of two conduits forming the inlet and outlet, (c) which contains a drive mechanism able to operate the valve and to cause the piston to execute the stroke of sinusoidal reciprocation, the mechanism being such that suction strokes of the pump occur when the inlet is open and forcing strokes of th* pu-ap ou vhea the outlet is open and such that between each suction and forcing stroke there is a pause during which the valve switches, (d) which contains adjustment means for selectively adjusting the volume of the predetermined quantity of liquid by varying the length of the stroke of the pump piston, and (e) which contains display means for displaying to a human observer a number which is helpful in the determination of the volume; and a motor coupled to the drive meshaniam a© that it drives this mechanism and control means for controlling the motor* ' 7* An a aratus as claimed in Claim 6 wherein the switchin - 36 - 3w259/2 with a rotary valve member driven by the drivemechanism, the valve body and the valve member having mutually cooperating operative surfaces, with the operative surface of the valve body having therein a central orifice communicating with the pump and a pair of lateral orifices communicat ng with the two conduits respectively and with the operative surface of the valve member having channels formed therein so arranged as to put said central orifice in communication with one of the lateral orifices for a length of time corresponding substantially to one half-turn of the valve member and with the other of the lateral orifices for a length of time corresponding substantially to the other half-turn of the valve member, so that rotation of the valve member periodically causes the valve to switch. 8. An apparatus as claimed in Claim 6 or 7» wherein the drive mechanism includes an intermittent drive having a member for receiving drive from the motor and whioh drives the switching valve, and having a member for transmitting drive to a variable throw crank mechanism which in turn has a member fo transmitting the drive to the pump piston causing it to execute the stroke of sinusoidal reciprocation, the extent o thethrow determining the length of the piston stroke. 9·,' An apparatus as claimed in Claim 8 wherein the variable throw crank mecha ism has an asymaetrieally variable throw whereby one of the. two dead points corresponding to the ends of the piston stroke through which passes the member which transmits drive to the pump piston, is a fixed point whose poslticn is independent of variations in the amplitude of motion of that ipember. 10, An apparatus as claimed in Claim 6, 7, 8 or 9 wherein the adjustment means include a micrometer screw so arranged as to adjust accurately the throw of the variable throw crank mechanism 30259/2 - 37 - counter having a window and connected to the micrometer screw via a non-slip transmission whereby the number appearing i the window o said revolution-counter canbe in direct relation to the angle through which the screw is rotated, wherein the adjustment means further include a touch detent system associated with the micrometer screw whereby a huma operator actuating the micrometer screw can feel hen the screw passesthrough predetermined angular positions, the angular motion of the screw from one detent to another corresponding to a variation of one unit in the number displayed in the window pf the revolution-counter* If · An apparatus as claimed in Claim 8, wherein the motor is electrical and the control means is adapted to activate at will half an operational cyole, the half cycle being either an intake half cycle, including a suction stroke of the pump piston, or a discharge half cycle, including a forcing stroke of the pump piston and the control means include a switch actuated b acaia driven from the intermittent .drive, the switch and the cam being .arranged to cut off the electrical supply of the »« every time the intermittent drive has rotated through an angle eorresponding to a half operational cycle, and an automatic cut-put switch connected in parallel with the cam actuated switch and adapted to provide for the supply of the motor, when being started»for a predetermined length of time which is substantially less than the time taken to complete one operational half-cycle and greater than the time taken by the cam to render . said cam actuated switch inoperative. 12. An apparatus as claimed in Claim 1 , wherein the automatic cut-out switch is pneumatically actuated and includes a stationary 30259/2 cal chamber, a control pump and a conduit connecting the pump to the cylindrical chamber, the control pump, the conduit and the cylindrical chamber together forming a pneumatic circuit in which the control pump can set up a pressure able to actuate the piston to move the movable contact into engagement with the stationary contact against the bias, the pneumatic circuit including a leak, so calibrated that, after actuation of the control pump, there occurs in the circuit a drop in pressure to a value enabling the bias to force the movable contact away from the stationary contact and the piston back in the cylindrical chamber, the time taken for the pressure in the circuit to drop corresponding to the predetermined time* 13· An apparatus as claimed in any of Claims Θ to 12, wherein the variable throw crank mechanism has an asymmetrically variable throw whereby one of the two dead points, corresponding to the ends of the piston stroke through which the intermittent member which transmits drive to the piston passes, is a fixed point whoa© position is independent of the varations of the amplitude of motion of that member and said intermittent drive mechanism includes a driving wheel' having two disusetrically opposed toothed segments arranged to mesh with a circuaferentially toothedtiriven wheel having arms to actuate the variable throw crank mechanism, each toothed segment having a length equal to half thecircumference of the toothed driven wheel and being each followed by a recessed segment so that each half turn of the driving wheel causes the driven wheel to rotate through 180° and then to pause for a length of time corresponding to the passage of one of the recessed seg« ments, wherein the cam and the variable throw crank mechanism are so arranged that the end of one operational half cycle coincides 30259/2 - 39 - recessed segments of the driving wheel and the dimensions of the actuating arms are so chosen that, during a pause at the end of an operational half-cycle, the driven wheel can be freely rotated whereafter further rotation reverses th© direction of the next movement of the member transmitting drive to the piston. 14» An apparatus as claimed in any of Claims 2 to 13» wherein the drive mechanism, includes an intermittent drive drivingly connected to the motor and switching valve and the switching valve includes a stationary body associated at one axial end thereof with rotary valve member driven by the drive mechanism, the valve body and the vaL ve member having mutually cooperating operative surfaces, with the operative surfaces of the valve body having therein a central orifice, communicating with the pump and a pair of- radially spaced orifices, respectively communicating with the two conduits, which lie on a circle concentric with the central orifice and which are spaced from one another by an angular distance of 135°, and with the operative surface of the valve member having channels formed therein, the channels including four radially extending arms which have a length at least equal to the radius of the circle and which lie at right angles to one another to put the central orifice in coxnmunication with either one or the other of th© two radially spaced orifices every time the rotary valve member comes to occupy one of eight particular angular positions, so that the valve will not switch when. -said rotary valve member is at a stop in any one of said angular ~ ositions, .,: 15· An apparatus as claimed in Claim 14, wherein the piston pump and the switching valve are housed in a common easing to form a distributor um in unit removabl mounted on the a aratus 30259/2 - 40 -pumping unit is put in place, thes itching valve is automatically coupled to the drive mechanism, the pisto rod of the pump being connected to the drive mechanism through a releasable coupling, and wherein the drive mechanism includes a second intermittent drive is between the motor and the rotary valve member of the switching valve and causes the rotary member to move in angular steps of 459» the second Intermittent drive being so associated with the first intermittent drive that the switching valve can pass from one of its two conditions to the other during a first part of each of the op rational half-cycles, while the pump piston is stationary, and that the switching valve can remain stationary in either of its two conditions during a second part of eaeh of the operational half-cycles, while the pump piston is moving. 16· An apparatus as claimed in Claim 15» wherein the second intermittent drive includes a first driving wheel drivingly connected to the motor and carrying a diametral arm, arid a seoond driven wheel drivingly connected to the valve and carrying-eight radial arms spaced 45° apart, the wheels having their axes orthogonally disposed and so set in relation to one another that the arms of the diametral arm carried b the first driving wheel engage, during one quarter of each half turn thereof, the radial arms carried by the second driven wheel. to cause the latter to move by angular steps of 45°· while remaining disengaged therefrom during the remainin three quarters of each half-turn, 17· An apparatus as claimed in Claim 1 or 6 comprising a motor, a first motion translating means adapted to translate rotary motion into sinusoidal reciprocal n&tiort, power transmitting means operatively connecting the motor and the motion a 1 30259/2 41 alternately connecting the cylinder chamber with the ports, a valve switching means operatlvely connected to the valve, a second motion translating means operatively associatedwith the valve switching means and thepower transmitting means and adapted to translate the rotational movement of the power transmitting means into movement of said valve switching means and operative to position said valve means in a predetermined position between strokes of the piston, a piston activating member, the member connected to the first motion translating means and the piston and adapted to translate the sinusoidal reciprocal motion of said first motion translating means to said piston, said first motion translating means having an adjustment assembly adapted to vary the amplitude of the reciprocal sinus-soidal motion, the adjustment assembly having control means whereby the piston stroke length can be adjusted externally of the apparatus. 18· An apparatus as claimed in Claim 17 including a display means for indicating" he setting of the adjustment assembly and thereby the volumetric capacity of the pump for a given stroke length of said pieton. 19. An apparatus as claimed in Claim 17 or 18 wherein the valve means comprises a generally cylindrical member mounted on the cylinder chamber and having a passage in communication with the chamber and having channels therein adapted, upon a predetermined movement of the member, to place one of the ports in communication with the chamber. 20. An apparatus as claimed in any of Claims 17 to 19 ? wherein the first motion translating means comprises a housing, a member mounted for non-rotary longitudinal movement within said housing, a linkage 30259/2 - 42 - of said housing and means, associated with said linkage means and connected to said reciprocating arm, to convert the rotary movement into reciprocal movement, 21, An apparatus as claimed in Claim 10, wherein the piston pump comprisee a piaton and calibrated cylinder the calibration being inscribed on the cylinder and the piston and cylinder being removably mounted whereby it can be exchanged for another piston and cylinder. 22· An apparatus for metering and dispensingliquids substantially as hereinbefore described with reference to the accompanying drawings* For the Applicants DR. RBIWHOLD COHN AND PARTNERS