US3598508A

US3598508A - Precision fluid dispenser

Info

Publication number: US3598508A
Application number: US814072A
Authority: US
Inventors: John D Reid; William M Sheppard
Original assignee: Hamilton Co Inc
Current assignee: Hamilton Co Inc
Priority date: 1969-04-07
Filing date: 1969-04-07
Publication date: 1971-08-10
Anticipated expiration: 1988-08-10

Abstract

An apparatus is described for repeatably dispensing precise quantities or amounts of liquid. An actuator operates a reciprocable syringe plunger for drawing liquid into the syringe and discharging same. A valve controls the inflow and outflow of the syringe and spaced permanent magnets hold the movable member of the valve in a position for connecting the syringe either with a source of liquid or in a position for connecting the syringe with a conduit for conveying discharged liquid, until the syringe plunger has been moved by the actuator to the respective ends of its stroke.

Description

United States Patent lnventors John D. Reid Monrovia; William M. Sheppard. Whittier. both of, Calif. Appl. No 814,072 Filed Apr. 7, 1969 Patented Aug. 10, 1971 Assignee Hamilton Company Whittier, Calif.

PRECISION FLUID DISPENSER 10 Claims, 6 Drawing Figs.

US. Cl. 417/400, 91/216 Int. Cl ..F04b 17/00, FOlb 15/00 Field of Search 103/227,

[56] References Cited UNITED STATES PATENTS 2.645.208 7/1953 Hardesty 91/216 2,791,]80 5/1957 Gotham etal. l03/227XR Primary Examiner- Robert M. Walker Atlorney.|. C. Baisch ABSTRACT: An apparatus is described for repeatably dispensing precise quantities or amounts of liquid. An actuator operates a reciprocable syringe plunger for drawing liquid into the syringe and discharging same. A valve controls the inflow and outflow of the syringe and spaced permanent magnets hold the movable member of the valve in a position for connecting the syringe either with a source of liquid or in a position for connecting the syringe with a conduit for conveying discharged liquid, until the syringe plunger has been moved by the actuator to the respective ends ofits stroke.

PATENTED Am; I 01971 SHEET 2 [)F 3 (10%? Q Pemf mil/am M She om;

INVENTORS,

PRECISION FLUID DISPENSER BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to liquid dispensing apparatus for use in medical and chemical research laboratories and industrial applications, and relates more particularly to apparatus of this character for repeated discharge or dispensing of precisely measured quantities ofliquid.

2. Description of the Prior Art There are various prior art devices aimed at repeated reproducible dispensing of predetermined quantities of fluids, including liquids. Various problems are encountered in providing suitable apparatus of this character that is satisfactory in meeting the very exacting requirements of scientific research laboratories and industrial applications.

SUMMARY OF THE INVENTION The present invention comprises a syringe and actuating mechanism for reciprocating the plunger of the syringe. A valve having a movable valve member controls the flow of fluid to and from the syringe, said movable valve member having two positions. When in one position liquid is admitted to the syringe and when in the other position discharge liquid flows from the syringe.

The actuating mechanism is operated by fluid under pressure and has a longitudinally movable cylinder and a piston operable reciprocable therein, the piston being attached to a piston rod that extends outwardly of the cylinder and has a soft iron armature connected or attached thereto externally of the cylinder. The piston rod also has an operable connection with the movable valve member for moving it from one position to the other and vice versa.

The armature is movable between a pair of spaced permanent magnets.

There are stop means for limiting the longitudinal movement of the cylinder in both directions and when the cylinder is at one limit of movement the armature is held by one of the permanent magnets which holds the piston against movement in the cylinder. Pressurized fluid is then supplied to one end of the cylinder to cause it to move to the opposite limit of movement. When the cylinder reaches said opposite limit of movement and is brought to a stop thereat pressurized fluid still continues to exert pressure within the cylinder and effects sufficient pressure on the piston to pull the armature from the permanent magnet on which it has been held and move the piston rod and armature and bring the armature into engagement with the other permanent magnet. At the same time the piston rod moves the movable valve member to its other position. Pressurized fluid is then applied to the opposite end of the cylinder and reverse action occurs. Thus the valve is not operated from one position to the other until the plunger of the syringe has reached one end or the other of its range of movement.

OBJECTS AND ADVANTAGES OF THE INVENTION It is an object of the invention to provide a precision liquid dispenser that is extremely accurate in reproducibility of precise quantities of liquid repeatedly discharged.

It is another object of the invention to provide a dispenser of this character that has means for controlling the admission of fluid to a syringe and the discharge of fluid therefrom by valve means that is held in respective operation positions until the plunger of the syringe has reached respective ends of its range of movement.

It is still another object of the invention to provide a liquid dispenser of this character having magnetic means for holding the movable valve member of the valve in one or the other of its operative positions until the plunger of the syringe has reached respective ends of its range of movement.

It is a further object of the invention to provide a liquid dispenser of this character that is relatively simple in construction and operation.

A further object is the dispensing of very small volumes of liquids.

The characteristics and advantages of the invention are further sufficiently referred to in connection with the following detailed description of the accompanying drawings which represent one embodiment. After considering this example, skilled persons will understand that many variations may be made without departing from the principles disclosed and I contemplate the employment of any structures, arrangements or modes of operation that are properly within the scope of the appended claims.

Referring to the drawings, which are for illustrative purpose only:

FIG. 1 is a front elevational view of a liquid dispenser embodying the invention, a portion of the upper end being shown in section to show the armature or valve operating block of the magnetic mechanism in its upper position;

FIG. 2 is a side elevational view of the same;

FIG. 3 is a view similar to the upper end portion as shown in FIG. I with the armature or valve operating block in its lower position;

FIG. 4 is a sectional view taken on line 4-4 of FIG. 1;

FIG. 5, (a), (b), (c) and (d), diagrammatically shows various stages of a cycle of operation. In these views the right hand side is to be considered as the top of the mechanism while the left hand side is to be considered its bottom thereof; and

FIG. 6 is a view similar to FIG. 3 showing an alternative arrangement.

Referring more particularly to FIGS. 1 to 4 of the drawings, there is shown a body, indicated generally at 10, of any suitable material, preferably a nonmagnetic material such as aluminum for example. Body 10 has a back part 12 upstanding at right angles from the rear ofa base 14 which has a lug 16 upstanding therefrom atone side and integral with said base and the back part 12.

At the upper end of the back part 12 is a forwardly projecting block, indicated generally at 18, having horizontal upper and

lower parts

20 and 22 spaced vertically apart to provide a space, indicated generally at 24. Space 24 has a part 26 at one side, from the inner end of which is a portion 28 of reduced width and from which extends a further reduced width part 30.

Horizontal upper and

lower parts

20 and 22 of the block 18 have aligned

vertical holes

34 and 36 in which respective

permanent magnets

38 and 40 are disposed and secured in place by respective set screws 42. The inner faces of the

magnets

38 and 40 are flush with the top and bottom surfaces of the space 26, except when additional magnetic force is required as in the use of large volume syringes or pumps. FIG. 6 illustrates the application of two

additional magnets

38a and 40a cemented to the armature and aligned to meet

magnets

38 and 40 now recessed into upper and

lower parts

20 and 22. These magnets may be of any suitable type but those used are alnico magnets.

There are also axially aligned

vertical openings

44 and 46 in the respective upper and

lower parts

20 and 22 of the block 18. In each of the

openings

44 and 46 is a bearing or bushing 48 and 50 respectively.

An actuator means, indicated generally at 54, is provided and comprises a cylinder 56 in which is disposed a piston 58 carried by an actuator shaft 60 which extends outwardly ofthe upper end of the cylinder through a bushing or seal 62 of an end wall, not shown, thereby preventing actuating pressurized fluid from escaping from the upper end of the cylinder, the opposite end of the cylinder being closed by a wall, also not shown, which includes a lug 64 having a fluid passage therein but not shown, a fitting 66 being provided for said fluid passage to which a pressurized fluid conduit 68 is attached to supply pressurized fluid to the lower end of the cylinder through said fluid passage. Adjacent the upper end of the cylinder is a fitting 70 to which a conduit 72 is attached to supply pressurized fluid to the upper end of the cylinder. Shaft 60 has an enlarged upper end portion 74 slidable in the

bearings

48 and 50 of the block 18.

A relatively flat cylinder bracket, indicated generally at 78, is attached to the cylinder 56. There is an opening 80 in said bracket in which the cylinder 56 is disposed, one side of the opening 80 being defined by a strap 82. From the hole 80 there is aslot 83 to the adjacent edge of the bracket thus providing a somewhat resilient tongue 84 at the end of the strap 82. Tongue 84 has a hole 86 therethrough in alignment with a tapped bore 88 in that portion of the bracket opposite the tongue, there being a screw 90 disposed in said hole and screwed into the tapped bore 88 to tighten the strap 84 on the cylinder and secure the cylinder in its opening 80.

The bracket 78 also has a vertical tapped bore, not shown, which is provided with screw threads, not shown, and in which is screwed a bushing 92 of suitable friction reducing material such as Teflon, for example, Teflon being the trademark of the Du Pont Company for their fluorocarbon resins. The bushing may be externally knurled to facilitate screwing into the tapped bore in the bracket. Bushing 92 has a longitudinally extending bore therethrough for reception of adjustment nut 94 on which said bushing is slidable so that the cylinder bracket is movable upwardly and downwardly and is guided by said nut 94 which has an enlarged knurled part 95. Nut 94 has a tapped bore extending longitudinally there through and said nut is screwed onto an externally threaded adjustment shaft 96 which has a lower end portion screwed into a tapped bore, not shown, provided therefor in the lug 16. Rotation of the part 95 of the adjustment nut effects upward or downward movement of the nut 94 and there is a lock nut 100 on the adjustment shaft'below the part 95 for securing the adjustment nut in adjusted positions. The part 95 of the adjustment nut provides a stop for downward movement of the cylinder bracket and hence for the cylinder 56. Shaft 94 is upstanding from lug 16 and its axis is parallel to the axis of the actuator means 54.

A three port, two position valve, indicated generally at 110 has a part 112 from which an externally threaded part 114 extends. The part 112 is received in an opening 113 provided therefor in a housing portion 116 of a valve mounting plate 118 secured to the front side of the block 18 by screws 119. Housing portion has a bore 120 extending from the inner end and axially aligned with the opening 113. Within the bore 120 is a valve adapter 122 having a bore therein with an annular inturned flange having threads for threaded reception of the threaded part 114 of the valve 110. Thus the valve is held in position by the adapter 122. Valve 110 may be of any suitable well known character but as shown by way of example is of the type disclosed in the application of Clark H. Hamilton, for a VALVE, Ser. No. 403,223, filed Oct. 12, 1964, the valve 110 however being of such character as to have two operative positions as will be described hereinafter.

Within the valve adapter 122 is a valve actuator 126 operably connected to the movable valve member, not shown, of the valve 110. Valve actuator 126 has a flange 128 thereon and at its inner end said valve actuator has a flattened part with a notch therein, said flattened part being received in a notch 130 ofa valve shaft 132. There is a gear 136 with an integral collar 138 secured to the valve shaft 132 by means ofa pin 140. Gear 136 is disposed in the space 30 and on said valve shaft 132 is a bushing 142 disposed in a bore 144 extending from the rear of the body 10. Bushing 142 is retained in position by an external flange at its inner end which engages the area of the rear wall of space 30 about the bore 144. The end ofthe collar 138 opposite the gear abuts against the inner end ofsaid bushing or hearing 142.

There is also a bearing 148 similar to bearing 142 disposed on valve shaft 132 at the opposite side of the gear 136, said bearing extending into the bore of the valve adapter and having its flange engaging the adjacent end of the valve adapter and being engaged by the adjacent side of the gear 136. A spring 150 is disposed within the bore of the valve adapter 122 and reacts between the bearing 148 and the flange 128 of the valve actuator, and urge these parts apart. There is a sufflcient clearance between the valve actuator and the valve shaft so that there will be no binding and the valve readily actuated with rotative movements of the gear.

Within the

spaces

26 and 28 is a traveling block or armature 156 having a vertical bore 158 therethrough for reception of the upper end portion 74 of the actuator shaft 60, said traveling block being secured to said shaft portion 74 by means of a set screw 160 disposed in a tapped bore provided therefor. The bore 158 is disposed in a part of the traveling block that is of reduced width and disposed in the space portion 28. The traveling block or armature is of any suitable magnetic material such as low carbon steel and is illustrated in FIG; 6 and described on line 25 pages 5 and 6.

Means for actuating the gear 138 comprises a rack 162 disposed in a notch provided therefor at the free end of the reduced width part of the traveling block, said rack being secured in said notch by a screw 164. Rack 162 has teeth 166 operably engaging the teeth of the gear 136 and adapted to rotate said gear with vertical movements of said traveling block 156 which in turn is actuated upwardly and downwardly with corresponding movements of the actuator shaft 60. The traveling block 156 moves between the

magnets

38 and 40.

A syringe, indicated generally at 170, has a transparent barrel 172 and a plunger 173 on a plunger rod 174 having a flange 176 at its outer, free end. The syringe may be of any well known type for handling liquids or gases and is removably attached to the valve 110 by any well known means. For example, a luer lock is used and includes a female part 178 on the valve 110 and a male part 180 on the forward end of the syringe barrel. Thus the forward or upper end of the syringe is securely held in position.

The plunger rod is secured to the cylinder bracket by placing the pressure member or flange 176 in a recess 178 in the cylinder bracket. There is also a notch 180 to accommodate the adjacent part of the plunger rod so that there is proper alignment of the parts of the syringe, said flange being held in position by a thumb screw 182 disposed in a tapped opening provided therefor in the portion of the cylinder bracket below the recess 178. The syringe may, of course, be installed in the mechanism or removed therefrom and various types and size of syringes may be used. l

A conduit 186 connects the valve 110 with a source offluid to be measured and there is a conduit 188 connected to said valve for discharged fluid.

Actuator cylinder may be operated by any suitable fluid under pressure but air under pressure is a convenient and satisfactory fluid.

Conduits

68 and 72 connect the lower and upper ends of the cylinder 56 with a valve mechanism, indicated generally at 190, which receives air under pressure by means of a conduit 192 connected to a source of air under pressure, not shown. Valve 190 is shown as being manually operated and may be of any suitable two position type. Pressurized fluid is supplied to the valve 190 from a suitable source of such pressure by way of conduit 192. This fluid is directed to the upper end and the lower end respectively of the cylinder 56 by proper positioning of the valve 190. When fluid pressure is supplied to one end of the cylinder the fluid at the other end is returned to the valve and vented therefrom by means of an atmospheric vent port, not shown. This arrangement is well known and need not be further described.

It is to be understood that while the valve 190 is manually operated it may be automatically operated by suitable mechanism of any well known type.

ln the operation of the apparatus or mechanism, it is to he understood that the cylinder moves upwardly and downwardly and is carried or supported by the shaft 60 which also moves upwardly and downwardly under certain conditions which are described hereinbelow. Movement of the cylinder is limited at the bottom by engagement of the cylinder bracket 78 with the adjustment nut part 94 and is limited in its upward movement by engagement of the bushing or seal 62 with the under side of the block 18, it being noted that the diameter of the seal or bushing 62 is greater than the diameter of the bore 46 so that said bushing or seal will not enter said bore but will engage the area of the bottom of said block 18 immediately about the lower end of said bore 46. With the syringe installed as illustrated in FIG. 5a, the cylinder bracket 78, cylinder 56, and syringe plunger 174, are adjusted to the zero point on the syringe scale 172. With the cylinder bushing 62, pressing the underside of block 18, and the plunger at zero, the cylinder bracket 78, is secured by clamping screw 90.

With the syringe installed as shown in FIGS. 1 and 2 and the cylinder 56 in its lower position the cylinder bracket 78 is adjusted by means of the enlarged part 94 of the adjustment nut to bring the forward end of the syringe plunger to the quantity of discharge required and indicated on the syringe scale.

With this adjustment made, the operation ofthe mechanism or apparatus will be best understood by referring to FIG. 5. As shown at (b) of FIG. 5 the traveling block 156 is in engagement with the lower magnet 40 which magnetically holds the block in its lower portion whereat the valve 110 is in the fill position. Cylinder 56 is in its upper position and ready to move downwardly when supplied with pressurized operating fluid by positioning the valve 190 to supply pressurized fluid to the lower end of said cylinder by way of the conduit 68; that is, pressure is applied at I while pressure above the piston 58 is relieved through the conduit 72 and the atmospheric vent port ofthe valve 190.

Since the piston 58 in cylinder 56 is held stationary by magnet 40 pressurized fluid in the lower end of the cylinder 56 acts against the lower end wall of the cylinder to force said cylinder downwardly to the position shown in (c) of FIG. 5. Since the valve 110 is at the fill position, downward movement of the plunger 173 in the syringe barred draws fluid into said barrel by way of the conduit 186.

Downward movement of the cylinder 56 is halted when the cylinder bracket 78 contacts the adjustment nut. Continued supply of pressurized fluid to the lower end of the cylinder forces the piston 58 upwardly against the magnetic attraction of the magnet 40 causing the traveling block to move upwardly into engagement with the magnet 38. The upward movement of the traveling block 56 causes the rack 162 to rotate the gear 136 and this in turn causes the valve 110 to be actuated to thedischarge position. The parts are now in the position shown at (d) of FIG. 5. Because the piston 58 and hence the traveling block 156 do not move until the cylinder has reached one or the other end ofits stroke as limited by engagement of the bearing 62 with the block 18 or by engagement-with the adjustment nut part 98 and there is a pressure build up sufficient to overcome the magnetic attraction of one or the other of the

magnets

38 and 40 the valve 110 is not actuated from one operative position to the other until there has been a complete filling of the syringe or a complete discharge thereof. Consequently the amount of liquid repeatedly discharged by the syringe is consistently the same. The apparatus or mechanism is extremely accurate as required in scientific research.

After the traveling block 156 has been moved to the position shown in (d) of FIG. 5, the valve mechanism 190 is operated to cut off the pressure to the lower end of the cylinder, that is P and supply pressurized fluid to the upper end of the cylinder, as at P The cylinder 56 then moves upwardly to its upper limit of movement, as shown at (e) of FIG. 5, which is identical to (a) of FIG. 5. As the cylinder moves upwardly, with the valve 110 in the discharge position, fluid is discharged from the syringe.

With the air pressure still applied to the upper end of the cylinder 56 and the piston 58 is forced downwardly to cause the traveling block 156 to move from engagement with magnet 38 to engagement with the magnet 40.

The foregoing is a description of the cycling of the apparatus and after the discharge movement of the cylinder while the traveling block is held by magnet 38, the operating of the mechanism or apparatus starts over at (a) of FIG. 5. It should be noted that the valve mechanism 190 may be the simplest manual valve control or any automatic mechanism defined by the use requirements for automatic liquid dispensing.

A scale 198 may be provided for convenient resetting of the mechanism, said scale having a longitudinal slot 200 in its lower end for reception of a screw 202 screwed into a tapped opening provided therefor in front end of the lug 16. Thus the scale may be adjusted longitudinally. The scale is positioned adjacent the cylinder bracket so that one edge of the latter is operably positioned as an indicator with respect to said scale.

Relative to the magnet arrangement it will be apparent that in a broad sense the magnets function as a detent. There may be, of course, other detent arrangements to releasably restrain movements of the piston rod and hence actuation of the valve between the fill and discharge positions. By using a detent mechanism the valve 110 is not actuated from one position to the other until the syringe has been completely filled or completely discharged.

I claim:

1. A precision fluid dispenser, comprising:

A. an actuator mechanism including:

a. a cylinder part mounted for reciprocal longitudinal movements,

b. a piston operably disposed in said cylinder, said cylinder having means for connection at opposite sides of the piston with a source of pressure fluid,

0. a piston rod part to which said piston is secured,

' d. a pair of magnetic detent means mounted in spaced relation to each other, 7

. a traveling member secured to one of said actuator mechanism part, said traveling member being disposed and movable between said detent means and engageable therewith respectively, said detent means each restraining said traveling member with a limited force when said traveling member is engaged therewith;

and means for limiting reciprocating movements of one of said parts in both directions, the other part moving from one detent to the other when movement of said one part is stopped by said means for limiting reciprocal movement at a respective end of movement of said one part.

2. A precision fluid dispenser, comprising:

A. an actuator mechanism including:

a. a cylinder part mounted for reciprocal longitudinal movements.

b. a piston operably disposed in said cylinder, said cylinder having means for connection at opposite sides of the piston with a source of pressure fluid.

c. a piston rod part to which said piston is secured.

d. a pair of detent means mounted in spaced relation to each other.

e. a traveling member secured to one of said actuator mechanism parts, said traveling member being disposed and movable between said detent means and engageable therewith respectively, said detent means each restraining said traveling member with a limited force when said traveling member is engaged therewith;

f. and means for limiting reciprocating movements of one of said parts in both directions, the other part moving from one detent to the other when movement of said one part is stopped by said means for limiting reciprocal movement at a respective and of movement of said one part; and

B. a syringe operably connected to said other of actuator parts, movement of said one of said parts effecting filling and discharging of said syringe according to the direction of reciprocal movement of said one part; a valve; fluid connecting means for connecting the valve to said syringe, said valve having syringe filling and syringe discharging positions, said valve being operably connected to said other part and actuated thereby from one of said positions to the other when the respective detent means releases said other part and the latter moves the traveling member to the other detent means.

3. The invention defined by claim 2, wherein the cylinder is the one part and the piston rod comprises the other part; the detent means each comprises a magnet, said magnets being spaced apart; and the traveling member comprises a traveling armature block being of less thickness than the space between the magnets and being adapted to be magnetically held by either of said magnets depending upon the position of the traveling armature block, operative movements of the piston rod moving said armature block from one magnet to the other when cylinder movement is stopped by the means for limiting reciprocating movements of said cylinder and moving said valve from one position to the other.

4. The invention defined by claim 3, wherein the syringe comprises a barrel, a piston in said barrel, and a plunger to which said piston is attached, and wherein the valve is fixedly mounted, means for connecting the valve to the forward end of the syringe barrel for holding said forward end in position; and a cylinder bracket to which the cylinder is secured for effecting movements of said cylinder bracket with respective movements of said cylinder. the free end of the syringe plunger being secured .to said cylinder bracket for effecting longitudinal movements of the syringe plunger with respective movements ofthe cylinder bracket.

5. The invention defined by claim 4, wherein the means for connecting together the valve and the forward end of the syringe barrel comprises a pair of luer'parts attached respectively to the valve and the syringe barrel, said parts being removably connected together.

6. The invention defined by claim 3, wherein the valve has a valve actuator and the connection between the traveling armature block and the valve includes a gear connected to said valve actuator and a rack connected to said traveling armature block, said rack having teeth engaging the teeth of the gear for effecting rotative movement of the gear with movements of the traveling armature block from one magnet to the other.

7. The invention defined by claim 4, including means for adjusting the cylinder relative to the cylinder bracket.

8. The invention defined by claim 3, wherein at least one of the means for limiting reciprocal movements of the cylinder is adjustable.

9. The invention defined by claim 1, including means for controlling the supply of pressure fluid to the respective ends of the cylinder and relieving pressure at the respective ends of the cylinder opposite the end to which pressure fluid is supplied.

10. The invention defined by claim 9, wherein the means for controlling the supply of pressurized fluid to the cylinder comprises a valve.

Claims

1. A precision fluid dispenser, comprising: A. an actuator mechanism including: a. a cylinder part mounted for reciprocal longitudinal movements, b. a piston operably disposed in said cylinder, said cylinder having means for connection at opposite sides of the piston with a source of pressure fluid, c. a piston rod part to which said piston is secured, d. a pair of magnetic detent means mounted in spaced relation to each other, e. a traveling member secured to one of said actuator mechanism part, said traveling member being disposed and movable between said detent means and engageable therewith respectively, said detent means each restraining said traveling member with a limited force when said traveling member is engaged therewith; f. and means for limiting reciprocating movements of one of said parts in both directions, the other part moving from one detent to the other when movement of said one part is stopped by said means for limiting reciprocal movement at a respective end of movement of said one part.

2. A precision fluid dispenser, comprising: A. an actuator mechanism including: a. a cylinder part mOunted for reciprocal longitudinal movements, b. a piston operably disposed in said cylinder, said cylinder having means for connection at opposite sides of the piston with a source of pressure fluid, c. a piston rod part to which said piston is secured, d. a pair of detent means mounted in spaced relation to each other, e. a traveling member secured to one of said actuator mechanism parts, said traveling member being disposed and movable between said detent means and engageable therewith respectively, said detent means each restraining said traveling member with a limited force when said traveling member is engaged therewith; f. and means for limiting reciprocating movements of one of said parts in both directions, the other part moving from one detent to the other when movement of said one part is stopped by said means for limiting reciprocal movement at a respective end of movement of said one part; and B. a syringe operably connected to said other of actuator parts, movement of said one of said parts effecting filling and discharging of said syringe according to the direction of reciprocal movement of said one part; a valve; fluid connecting means for connecting the valve to said syringe, said valve having syringe filling and syringe discharging positions, said valve being operably connected to said other part and actuated thereby from one of said positions to the other when the respective detent means releases said other part and the latter moves the traveling member to the other detent means.

3. The invention defined by claim 2, wherein the cylinder is the one part and the piston rod comprises the other part; the detent means each comprises a magnet, said magnets being spaced apart; and the traveling member comprises a traveling armature block of material attracted by magnetic force, the armature block being of less thickness than the space between the magnets and being adapted to be magnetically held by either of said magnets depending upon the position of the traveling armature block, operative movements of the piston rod moving said armature block from one magnet to the other when cylinder movement is stopped by the means for limiting reciprocating movements of said cylinder and moving said valve from one position to the other.

4. The invention defined by claim 3, wherein the syringe comprises a barrel, a piston in said barrel, and a plunger to which said piston is attached, and wherein the valve is fixedly mounted, means for connecting the valve to the forward end of the syringe barrel for holding said forward end in position; and a cylinder bracket to which the cylinder is secured for effecting movements of said cylinder bracket with respective movements of said cylinder, the free end of the syringe plunger being secured to said cylinder bracket for effecting longitudinal movements of the syringe plunger with respective movements of the cylinder bracket.

5. The invention defined by claim 4, wherein the means for connecting together the valve and the forward end of the syringe barrel comprises a pair of luer parts attached respectively to the valve and the syringe barrel, said parts being removably connected together.