CA1076416A - Pump and drive assemblies - Google Patents

Abstract

IMPROVEMENTS IN AND RELATING TO PUMP AND DRIVE ASSEMBLIES

A B S T R A C T

A pump assembly for use e.g. in analysis apparatus of the type described in U.S. Patent No. 3923463 comprises a cylinder and piston slidable in the cylinder and defining therewith a pump chamber. The chamber is defined between opposed corresponding conical surfaces of the end wall of the cylinder and a face of the piston and communicates with a passage opening into the chamber at the apex of the cone in the end wall. The end wall of the cylinder is provided by an end member separate from the cylindrical part of the cylinder and may be integral with the movable member of a valve assembly for connecting the passage to a selected one of a plurality of inlet/outlet passages.
The drive for sample containers used in the apparatus of the above U.S. Patent may comprise a drive assembly comprising two motors each connected to drive a respective first bevel gear, which gears are coaxial and mesh with a freely rotatably mounted second bevel gear arranged with its axis perpendicular to the axis of the first gears and coupled to an annular member coaxial with the first gears, and means for preventing rotation of the respective first gears such that with one first gear stationary and the other first gear being rotated, the annular member will rotate in one direction and at a speed related to the speed of the motor driving the other first gear and with the other first gear stationary and the one first gear driven the annular member will be rotated in the opposite direction and at a speed related to the speed of the motor driving the one first gear.

Description

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The present invention relates to improvements in pump assemblies and drive assemblies particularly but not exclusively for use in analysis machines of the type described in U.K. patent No. 1,451,449.
In that specification there is disclosed an analysis machine which requires that accurately metered small volumes of liquid be withdrawn from and dispensed into containers. The containers are located in racks in cassettes which are moved from one module of the machine to the next. The racks in a cassette when located in a module are circulated round the cassette past a liquid dispensing or liquid withdrawing head. Each cassette is divided into two compartments and the racks of tubes are arranged in two banks, one in each compartment, and are ` 15 moved intermittently up each compartment and the front rack in one compartment is moved to the back of the other compartment. The drive for moving a rack from one compart-ment to the other compartment conveniently includes an index pin which engages the end of the rack and moves it forwards. When the rack has been moved to its correct position in the other compartment, the index pin returns to its initial position to engage the next rack. Two such drives are provided operated synchronously for moving the racks between -the compartments. There are in addition separate drives for pushing the racks along the compart-ments and which are actuated during the idle return move-ment of each index pin.
In accordance with one aspect of this invention there is provided a pump assembly for liquid comprising a 3Q cylinder comprising a cylindrical body having a longitu- -dinal axis and an end member closing one end of said : ,: . , .

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cylindrical body, a piston slidable within said cylin-drical body and defining with said body and said end member a pump chamber, said end member defining passage means opening in said pump chamber for liquid flowing to and Erom said pump chamber, and a valve assembly for connecting said passage means to a selected one of a plurality of inlet/ou-tlet means, said valve assembly including a stationary valve body defining said inlet/
outlet means and a movable valve member fast with said end member for connecting said passage means with said selected one of said inlet/outlet means, said valve member being angularly movable about said axis of said cylindrical body, wherein said valve member is generally/
- frusto-conical, tapering in the direction of said end member, and defines passage means connected to said passage means in said end member and opening in the cir-.cumferential surface of said valve member, said valve body is annular and has a corresponding frusto-conical inner circumferential surface in which said inlet/outlet means open and against which said valve member seats.
According to another aspect of the present invention there is provided a pump assembly for pumping liquid comprislng a cylinder defining a longitudinal axis, a ~.

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~64~6 piston slidable in said cylinder, and end wall closing one end of said cyllnder, said end wall having a generally conical surface and defining with said cylinder and a face of said piston a pump chamber, said face of said piston opposite said end wall having a generally conical shape corresponding to that of said surface of said end wall, and passage means for liquid flowing into and out of said chamber, said passage means communicating with said pump chamber through an opening in the apex of said conical end wall surface.
In a preferred embodiment, the end wall of the cylinder is provided by an end member separate from the cylindrical wall of the cylinder and made of a material different from that of the cylindrical wall. Preferably, the end member and the body of the piston are made of PTFE
and the cylindrical wall is made of a transparent material, e.g. glass, so that the correct operation of the pump can be visually checked.
The pump may include a valve assembly connected to the pump chamber opening and having a movable valve member for connecting the opening to one of two outlet/inlets.
Preferably the valve body is fixed to or formed integrally - with the end member of the cylinder.
According to another-aspect of the present invention there is provided a pump assembly for liquid comprising a cylinder comprising a cylindrical body having a longitudinal axis and an end member closing one end of -said cylindrical body, a piston slidable within said cylindrical body and defining with said body and said end member a pump chamber, said end member defining passage '' , ~' means OpCII illg i.n said pulnp chamber for li.qu:id flowin$ ~
to ~nd from sa:Lcl pllmp cllnmber, and a valvc asselnbly .
for connectinS sn:id pass~lse meclns to a qelocted one of i n plurality of inlet/outlet me~ns~ sa.id valve assembly including a stationary valve body defining said inlet/
outlet means and a movable valve member fast with said end member for connecting said passase means with said selccted one of said inlet/outlet means, said valve member being movable in rotation about said axis of said cylindrical body.
Aceording to another aspect of the present invention there is provided a pump assembly for liquid comprising a cylinder, a piStOJl slidable ~ithin said cy~inder and defining therewith a pump chamber, passage means connected to said pump chamber for liquid flowing to and from said chamberj a valve assembly connected to ~: said passage means and defining a plurality of inlet/outlet means and comprising a valve member movable to connect said passage means to a selected one of said inlet/outlet means, and drive means for reciprocating said piston - and moving said valve member in synchronism, said drive . `
, ~ means comprising a single motor and two independent : cam assemblies for controlling reciprocation of said piston and movement of said valve member respectively.
According to a further aspect o~ *he present invention there is provided a drive assembly for providing oscillatory movement comprising: a first motor and a second - motor, means connect1nS said first motor to rotate a first bevel gear; mcans connecting said second motor to rotate R
second bevel ~ear identical with and coaxi.al with said : ~ , -1(~t76~
firs~ bevel ~oar, a third bevel sear freely rot~tably mounted with its axis perpendicular to said axes of said first and second bevel sears and meshins with said first and socond bevel gears, aJI annular member coaxial wit~i said first bcvel genr; means coup:Ling sald annular member to said third beve] gear for rotation about said axis of said first bevel gear, and means for independently preventinS
rotation of said first and second bevel gears such th~t when said first bevel gear is stationary and said second bevel gear is rotated by said second motor said annular member is rotated by said second motor in one direction and at a speed related to the speed of said second motor, and when said second bevel sear is stationary and said first bevel gear is rotated by said first motor said annular member is rotated by said first motor in a direction - opposite said one direct~on and at a speed related to the speed of said first motor.
In the preferred embodimentt the annular member is externally toothed and is coupled to provide reciprocal movement of a drive member.
In use of the above described drive assembly - in an analysis machine as described above, two axially spaced annular members are provided~ each having oppositely directed helical teeth mes~ing with a helical gear axially fast with a shaft such that the shafts are rotated in ~pposite directions at the s,ame speed. ~ach shaft carries a gear meshins with a toothed rack on which a drive member -~ is mounted.
The present inventioll will be morc fully understood from the following ~escription of embodiments thereof, given by w.ly of exa~ple onl~, rith reference to the accompanyillS
drawingsO

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F.;~ure 1 is a vcrticlll section tllrou~h an ~mboditl~cllt o~ a pump ns4embly in acco~-danco with tho proscnt invantion;
.I Figurc 2 is a porspoctive view of a stop a~solnbly for use ~Yith the pump of Fisure 1;
. Fi~lre 3 is a section on the line III-III of Figur e 1;
Fisures 4 and 5 are plan views showing two state~ of a mechanism for operating a valve assembly - ' ... ' ~ "' . . ..

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nssociated ~Yith thc pump a~selr1bly of Figur0 l;
Fig~e 6 is a ~ction throus1l an embodiment of ~ drive a~se111bly in uccordance with the pre~ont invention and taken on the line VI-VI Or Figure 7;
Figure 7 i9 A Vi0W ill elevatlon of the drive assembly of ~isure 6;
Figurc 8 is a ~ide view of part of a drive mechani~m driven by the drive assembly of Figure 6~ and ~i~ures 9 and lO are sections on the lines IX-IX and X-X of ~igure 8.
Ag shown in Figure 1, the pump assembly com-prises a cylinder l and a piston 2, one end of the cylindar being closed by an end wall 3 and definin~ with the pi~ton 2 a pump chamber 4. The piston 2 is pro~ided by a cylindrical member 5, e.g. of glass, closed at ona ` end by an end member 6 providing the end wall 3 for the pwr.p chamb6r, which end wall is conical. The inlet/
outlet opening 7 for the pwnp chamber 4 is provided at the apex of the cone in the end member and communicates with an L-shaped passage 8 in member 6. Cylinder 5 is - held by rings 9a, lOa, e.g. of PTFE, between two fixed members 9~ lO, e.~. of stainless steel, which are bolted together~ member 9 being fixed to tne ~ramework.
The pi3ton 2 has an end face ll whlch is conical and corresponds in shape to the shape of the end - wall 3 of the chamber. The piston 2 is fixed to a piston rod 12 which is sulded in a bu3hing 13 closing th~
other 0nd of the cylinder 50 A vent 14 is pro~-ided at the other end of th0 cylinder.
Th~ end me~b~r 6 has a lo~er cylindrical part 6a .
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which fits into the ond of cylinc'er 5 and 30als elgainst '. thc wall~ of the cylindor, and ha~ an uppcr co~lical part 6b which i~ receiv~d in ~ con.ical reces~ in m~mber 9 ~n~l is bias.qcd into ~ontac-t with the rece~s ~ by ~ ~prin$ 15 oxtendin~ between the metnber 6 and ~n end plate 16~
In use, the cylinder 5 is arranged with its a~is vertical and end membe.r 6 uppermost~ Wall 3 of member G and face 11 of piston 2 are shaped as described 10 above so as to encour'age the movement of any gnq bubble~
forming in the pwnp chamber upwardly to the opening 7.
Additionall~, thc end part of the piston 2 providing face 11 is made of a material, e.g. stainleqs steel~ .-which inhibitq the attachment of gas bubbles thereto.
'l`he body oP the piston 2 is made of PTFE.
The end of piston rod 12 is received in a .
~leeve 17 which is retained on the rod by circlips 18.
. 1`he sleeve 17 is externally thre&ded and screwed into a .
threaded bore in a bar or bridge 19 which is attached to rods 20 extend.ing between~ and a~ially slida~le relative to ~ members of the frame and is biassed downwardly by springs 21 around the bars 20. Brid~e 19 carrie~ a cam .
follower ?2 (Figure 3) which runs on the periphery of a cam 23 which is rotated by a motor (not shown) about the ~ :
a~is of shaft 24 of the cam. The periphery of the c~m is.
:~ shaped to move the piston 2 ~ro.. its lo~rmost to it~
uppermost positions in the cylinder. At the uppermo~t .
po~ition, the cam is provided with a flat surface so that - the piston 2 has a ~hor~ dwell at this timeO In operation, - 30 *h~ volume of the ~troke of the pump~ i~e. t}lC ef'fective '. ' ~.:
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~07f~6 lowermo3t position of the piston in ~he cylinder, is detormined by a stop 24 against which thc bridgo 19 abut~ at thc ond OL the required downward tra~el of the piston. Thus the pi~ton 2 also has a short dwell ~t lt~
effective lowermost position whilc the bridge 19 rests on the stop ~4 and before the cam follower again con-tacts the cam 23. The effective lowermost position of the piston may be varied manually or automatically.
Preferably a plurality of stops 24a, 24b, 24c ...
(Figure 2) are provided on a rotatable di~c 25 which may be rotated manually, for example by providing the shaft of the disc with a knurled knob, or automaticaily. For automatic operation, the periphery of the disc 25 may be toothed and the disc arranged to be in mesh ~th a gear wheel driven by a stepping motor which is operated when the volume of the pump stroke is to be changed.
` Where the pump i8 only to be used to take up - and discharge liquid along the same path, pas~age o in end member 6 communicatas with a single radial passage (not shown in Figure 1) in member 9. Where the pump i8 to be used to take up and discharge liquid through different paths, the end member 6 forms the body of a valve assenlhly and is rotated n ~.enber 9 abo~t *hc axi~
of the c~linder 5 between two positions, shown in Figures 4 a~d 5, in each of whlch passage 8 communicate3 with a radial pas~age 26 or 27 in member 9. As shown, rotation of metnber 6 is effected by engagemcnt betwean a m~mber 28 in tha form of a sector of a circle which is fixed to the end of a sha~t 29 coaxial with member 5 and fixed to membcr 6, and a pair of followcr rod~ 30, 31 pi~otcd hy th~ir end~ at 32 to a frame mcmber. The rods 3O, 31 ~re parallel and ec-ch bears ~ projection 33 ~hich ensages th~ inncr ~urface 3l~ o~ an invorted cup~ aped CUIIl 35. The inner ~urfAco of the cam 35 is part circular witll a flRt~ In operation wlth the cam 35 rotating, when a projection 33 comes into contact with the ~lat the follower rod a~sociated therewith i8 moved to~ards the axis of the cam to cause the member 28 to pi~rot. The cam 35 i~ arranged to be rotated through gearin~ by the motor drivins cam 23 so that the two cams rot&te at the same specd. In the preferred embodi-mert, the shaft 2l~ of th0 cam is extended upwardly and provided with a gear which is in mesh with a gea~ on the shaft of c~m 35 The cams 35 and 23 are so arran~ed that when the pisto~ reaches either the top of its stroke or the bottom of its stro~e and dwells there, duxing the period of dwell the valve member 6 is rotated from one positio~
to the othe~ po~sition.
~O There is thus provided a pump assembly which may include a valve assembly, the total a~sembly being easy to demcunt and replace simply by removing the bolts connecting plate 16 to the framework and unscrew-ing the sleeve 17 from the bridge 19. In replacin~ the pump, no adjustment of the stop 24 is required since this abuts the - brldge 1~ and does not act directly on the piston o~ the pump.
There i3 shown in Figure~ 6 and 7 a drive i mechani~m for providing o~cillatory drive movementl The 3~ mechanisln compri~es a irst ar.d a ~econd motor 51, 52 : ` , .

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1(~76~6 havins ~iff~Ient angular OUtpllt speed~, e.g. of 15 r.p.m.
j ~nd 60 r.p.ll~., and each a~f30cinted with an electrically actuat~d brake. The output sha~ts 53, 5l~ of the Inotors aro coaxLal and each has mounted thcreon for rotation therewith a bev~l gear 55 whichl aq shown, is a mitre gear, 56. The mitro gears 55, 56 mesh with two bevel gears 57, 58 ~hich~ as shown, are mitre gears arranged with their axes at risht angles to the axes of the gears 55~ 56 and freely rotatably mounted on a common shaft 59.
The ends of shaft 59 are received in a ring or cage 60 coaxial with shafts 53, 54 and to which is fixed a drive transmitting member 61.
In operatioII of the above described assembly, ~ith one motor driving ~nd the other motor braked~ the members 60~ 61 are rotated in one direction at half the speed of the one motor, or a speed related thereto i~ the gears are other than mitre gears. ~Yith the other motor driving9 the members 60, 61 are rotated il~ the other direction at half the speed of that motor or a 2V speed related thereto.
~or use in a machine as described in the abovG
; referred to specification where two synchronised recipro-cating drives are required, the above described assembly includes two drive transmitting members 61 fixed to the cage 60 and axially spaced apart. The members 61 are provided on their external peripheral ~llrfacef3 with helical teeth~ one having le~t-hand teeth and the other having right~hand teeth. Each member 61 i~ in mesh with a gear 62 provided Wit}l corresl)onding helical teeth arld 3V fafit -~ith a shart 63 e~tending perpelldicu ar to the sh~t`t~

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53, 5l~. Tl~e cn(ls of e;lch shat 63 are carried in bCnrillSs in rralllC mclnbors (llOt sho~Yn) and ~t one end of cnch shaft th(3rc is l rovided a gcar 6l~ (~isurcs 8 to 10) an~ rly fz~st with tho sl~aft and meshins with a 5 raclc 65. Gcar~ 6l~ and raclcs 65 r.re arransed one on each sido of each reces~; of each module for receiving a cassette~ Each rack 65 slides along a rod 66 whicb i:3 received in openings in supports 67 for the rack Each - rack 65 also carries a drive member or index pin 68 for lC~ engasing a rack of containers in a cassette.
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It will be appreciated that the drive assembly may be differently arransed relative to the racks and the racks differently arranged relative to the supports -and drive members in dependence on the space available ~5 around the module recess. For example shafts 63 maybe connected by sears to drive other shafts provided with~
the gears 64.
- In operation of the above described assembly, each rack 65 and index pin 68 is moved in one direction at a speed related to the speed of one motor and in the - other direction at a speed related to the speed of the other motor.
In the particular application of the machine of the above referred to specification~ the forward movclllent Or the rack is stepped and slow and the return movcme~lt of the rac1c is fast. Control of the forward stepped movcment is obtained by providing on one rack 65 a plelte 69 havin~ sp~ced apertures 70 at intervals correspondi~-g I
to the dis~ance between eac}l step. Tlle aperturcq 70 are ~0 sensed by a photoelectric sencor ~ hic~ con~rols t;hc brakin~

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of the forward dr:ive motor. The ends of t:ravel of the index pin are sensed by other photoelectric sonsors sensing an ond rnomber 71 wh:ich cont:rols braking of the other motor for the return movement.
There is thus provi.ded a drive asserllb].y which can provide oscillatory movement, which can be converted -. into reciprocal movement, simply and easily and which can provide synchronised reciprocal drives. While the assembly has been described with m otors associated with brakes, it will be appreciated that the basic requirement of means for braking the shafts of the gears 55, 56 could be obtained by other means~ e.g.
- declutching of the motors and braking of the gears 55, 56.

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Claims (11)

CLAIMS:

1. A pump assembly for liquid comprising a cylinder comprising a cylindrical body having a longitudinal axis and an end member closing one end of said cylindrical body, a piston slidable within said cylindrical body and defining with said body and said end member a pump chamber, said end member defining passage means opening in said pump chamber for liquid flowing to and from said pump chamber, and a valve assembly for connecting said passage means to a select-ed one of a plurality of inlet/outlet means, said valve assembly including a stationary valve body defining said inlet/outlet means and a movable valve member fast with said end member for connecting said passage with said selected one of said inlet/outlet means, said valve member being angularly movable about said axis of said cylindrical body, wherein said valve member is generally frusto-conical, tapering in the direction of said end member, and defines passage means connected to said passage means in said end member and opening in the circumferential surface of said valve member, said valve body is annular and has a corres-ponding frusto-conical inner circumferential surface in which said inlet/outlet means open and against which said valve member seats.

2. An assembly as claimed in claim 1, wherein said valve member is integral with said end member and defines passage means connected to said passage means in said end member.

3. An assembly as claimed in either claim 1 or claim 2, comprising drive means for reciprocating said piston and for moving said valve member in synchronism, said drive means comprising a single motor and two independent cam assemblies for controlling reciprocation of said piston and movement of said valve member respec-tively.

4. A pump assembly as claimed in claim 3, wherein said cam assembly controlling reciprocation of said piston is adjustable to vary the stroke of said piston.

5. A pump assembly as claimed in either claim 3 or claim 4, wherein said cam assembly controlling recipro-cation of said piston is adapted to hold said piston stationary at each end of its stroke during movement of said valve member.

6. An assembly as claimed in claim 1, wherein said end member provides an end wall closing the one end of said cylinder, said end wall having a generally conical surface, the face of said piston opposite said end wall has a generally conical shape corresponding to that of said surface of said end wall, and said passage means in said end member opens into said pump chamber through an opening in the apex of said conical end wall surface.

7. An assembly as claimed in claim 6, wherein said face of said piston is made of a material inhibiting the attachment of gas bubbles thereto.

8. An assembly as claimed in claim 7, wherein said cylinder is made of a transparent material, said end member is made of PTFE and said piston comprises a body made of PTFE and a surface part providing said conical face of said piston made of stainless steel.

9. An assembly as claimed in claim 1, wherein said end member extends into an end of said cylindrical body.

10. An assembly as claimed in claim 9, wherein said end of said cylindrical member seats on said valve body.

11. An assembly as claimed in any of claims 1, 2 or 3, wherein said frusto-conical valve member is spring biased into abutment with said valve body.