Incremental Dose Dispenser

Abstract

A dispenser is provided for use in conjunction with syringes and is capable of accurate, rapid dispensing of small incremental doses and rapid and convenient refilling of the syringe. The dispenser comprises an elongated plunger for engaging and advancing the piston of the syringe to expell liquid doses therefrom. The plunger is threaded along at least a portion of its longitudinal, peripheral surface. A drive wheel is provided for advancing the plunger; the drive wheel having its peripheral surface divided into alternate threaded sections and longitudinal separating grooves. The threaded sections engage the threaded portions of the plunger advancing the same to rapidly dispense the incremental doses. The longitudinal grooves provide a clearance between the plunger and drive wheel thereby leaving the plunger disengaged for rapid refilling of the syringe.

Description

This invention concerns liquid dispensers and particularly those designed to be used in conjunction with syringes and capable of dispensing accurate, incremental doses, each of which is only a small fraction of the total capacity of the syringe. Such dispensers are especially useful in laboratory work where a task frequently involves the rapid and accurate dispensing of many small incremental doses of a reagent from a storage supply such as a prefilled syringe. In such work, it is frequently necessary to refill the syringe after the supply is depleted and then continue to dispense the small accurate doses. Heretofore, no device has been available to smoothly perform the transition between accurate, rapid dispensing of small doses and rapid and convenient refilling of the syringe.

In accordance with this invention, a liquid dispenser is provided for use with a syringe having a liquid-containing cartridge, open at one end, and a piston, generally slidably mounted in the cartridge, for expelling the liquid out of the open end. The opening is usually fitted with a cannula for accurately directing the flow of liquid to the desired delivering point.

The dispenser of this invention comprises a housing and, mounted thereon and in reciprocating relationship thereto, an elongated plunger having means at one end for engaging the piston of the syringe so as to advance it and expell liquid therefrom. The plunger is threaded along at least a portion of its elongated peripheral surface. A cylindrical drive wheel, for advancing the plunger, is rotatably mounted to the housing. The drive wheel is threaded along its peripheral surface, the threads being interrupted by radially spaced grooves cut into the peripheral surface and extending parallel to the axis of the drive wheel. Thus, the peripheral surface presents a plurality of alternating threaded sections and separating grooves. The drive wheel is mounted on the housing, relative to the plunger, so that it may be rotated to, alternatively, bring the threaded sections and the separating grooves into register with the threaded portion of the plunger. Further, the threaded section of the drive wheel and the threaded portion of the plunger engage when they are in register and advance the plunger as the drive wheel is rotated. The grooves, on the other hand, are of sufficient depth to provide a clearance between the plunger and drive wheel when they are in the register. Actuating means are provided for rotating the drive wheel through a preselected degree of rotation, the degree of rotation, however, selected so as to always terminate with a groove of the drive wheel in register with the threads of the plunger (i.e., with the plunger disengaged from the drive wheel by virtue of the clearance between the threaded section of the plunger and the drive wheel).

In operation, as the drive wheel passes through a degree of rotation corresponding to one threaded section in engagement with the plunger, the plunger will advance reciprocally a discrete incremental distance. This, in turn, will advance the piston of the syringe the same incremental distance and hence dispense a controlled incremental dose of liquid. By preselecting the degree of rotation of the drive wheel to correspond to any number of threaded sections, the plunger may be advanced a desired multiple of increments and a dose, of the size corresponding to multiple increments, may be delivered.

In accordance with this invention, the preselected degree of rotation always terminates with the threaded portion of the plunger in register with a groove on the drive wheel. Thus, by virtue of the clearance between the groove and the plunger, the dispenser is always in a disengaged state after each dose has been dispensed, i.e., the plunger free to move, reciprocally to any extent with-out having to actuate the rotating mechanism. A user may, therefore, dispense any number of doses, each of a preselected size, and then, after a series of dose dispensing, the user may freely move the plunger, so as to fill or empty the syringe.

A better understanding of the invention will be had by referring to the appended drawings, illustrating a specific embodiment of the invention, as taken together with the following description.

Referring now to the drawings:

FIG. 1 is a perspective view of a dispenser embodying this invention as used in conjunction with a syringe;

FIG. 2 is a longitudinal, partial section taken along line 2--2 of FIG. 1;

FIG. 3 is a transverse, partial section taken along line 3--3 of FIG. 2; and

FIG. 4 is an exploded, perspective view of a portion of the dispenser and syringe shown in FIG. 1.

As best shown in FIG. 1, a dispenser 10 is provided with a gun-shaped housing 12 having an arm 14 for supporting a syringe 16. The syringe comprises a cartridge 18 for containing a supply of a liquid, the cartridge terminating in an opening 20 having, fitted therein, a cannula 22 for accurately directing the flow of liquid to the desired delivery point. Externally accessible, depressible means, illustrated in the drawing, by a trigger 24, is provided for actuating the dispenser, and a selection wheel 26 is provided for selecting the size of the dose corresponding to one full actuation, i.e., one full depression of the trigger. The housing 12 is also provided with an arm 28 for supporting a plunger (not shown in FIG. 1) which engages the piston of the syringe (also not shown in FIG. 1). The arm 28 has a slot 30 running longitudinally therewith through which a projection 32, integral with the plunger, extends for manually repositioning the plunger. In operation, the size of a given dose is preselected, by rotating the selection wheel. The trigger is then depressed, activating the dispenser and advancing the plunger and the piston of the syringe so as to dispense the preselected dose.

Referring now to FIGS. 2, 3, and 4, the plunger 34 as illustrated, reciprocally mounted to the housing 12, and provided with means for engaging the piston 36, said piston being slidably mounted in the cartridge 18 of the syringe 16 so as to be capable of advancing and expelling liquid contained within the cartridge through the cannula 22. The engagement means shown comprise a small projection 38 extending collinearly from the end of the plunger and having a circumferential bead 40 for snap-fitting into a corresponding bore 42 provided in one end of the piston 36.

The plunger comprises an elongated member having threads 44 on a portion of its longitudinal peripheral surface. As best shown in FIGS. 2 and 3, surfaces of the plunger 46, and 48 are preferably flattened and contained against corresponding surfaces 46', and 48' of the housing to prevent rotation of the plunger in operation and to limit movement of the plunger to reciprocal motion. Thus, as assembled, the plunger, the piston and the syringe cartridge are each co-aligned and collinear with the reciprocating motion of the plunger.

A drive wheel 50, for advancing the plunger is rotatably mounted to the housing and is provided with threads 52, cut into its peripheral surface. These threads are interrupted by radially spaced grooves 54, extending parallel to the axis of the drive wheel. Thus, as best viewed in cross-section in FIG. 3, and in perspective in FIG. 4, the peripheral surface of the drive wheel displays a plurality of radially spaced, alternating threaded and grooved sections.

The drive wheel is rotatably mounted in the housing so that the threaded sections 52 may be rotated into register and engage the threaded portion of the plunger. In this position of engagement, the plunger can only be advanced by rotation of the drive wheel, the extent of the advance being determined by the degree of rotation of the drive wheel and the pitch length of the threads. For example, when the threads of the drive wheel have a pitch length equal the the threads of the plunger, the plunger will move reciprocally one pitch length per thread-engaged revolution. On the other hand, if the wheel is rotated through only one fifth of the revolution, the plunger will advance a distance equal to 0.2 times the pitch length. For the specific embodiment illustrated in the drawings, the drive wheel comprises five equal, radially spaced, grooves 54. The pitch length is chosen so that rotation of the drive wheel through one threaded section will advance the plunger and hence, the engaged piston of the syringe, a distance equivalent to one incremental dose. A rotation of the drive wheel through two threaded sections will deliver a dose equal to two increments. Similarly, a three, four and five incremental dose may be delivered by corresponding rotation of the drive wheel through a corresponding number of threaded sections. As will be more fully described below, means are provided for actuating the device to rotate the drive wheel through a pre-selected number of thread sections per actuator and hence deliver a preselected dose size per actuation.

Irrespective of the number of threaded sections selected to be rotated in engagement with the plunger per actuation, at the end of each actuation, the drive wheel rotation terminates with a longitudinal groove in register with the threads of the plunger. As best viewed in FIG. 3, the longitudinal grooves are cut to a depth sufficient to provide a clearance 56 between the threads of the plunger and the drive wheel when the grooves and the plunger are in register. By virtue of this clearance, the plunger is then free to move reciprocally after every rotation. Thus, in accordance with this invention, the drive wheel may be actuated repeatedly to deliver repeated doses, each of a pre-selected size. At the end of each delivery, the plunger is completely disengaged from the drive wheel and may be manually repositioned by gripping the projection 32 and sliding the plunger. Thus, for example, at any time the syringe may be refilled and the plunger will be immediately ready to deliver further incremental doses. To insure that the threads will mesh, as the threaded section of the wheel is rotated into engagement with the threads of the plunger, bearing plate 58 is provided, urged into contact with the plunger by a spring 60.

As mentioned above, means are provided for actuating the device by rotating the drive wheel through a preselected degree of rotation. Such means comprise the trigger 24, for depressing once per actuation and a spring 62, to thereafter return the trigger to its original, undepressed position. Translating means are provided for translating the reciprocating motion of the depressing trigger into a rotary motion for rotating the drive wheel. The translating means comprise a cam pin 64 mounted to the trigger and hence adopting the reciprocating motion of the trigger when depressed. The cam pin cooperates with a cam barrel 66, rotatably mounted to the housing and having cut therein, a helical camway 68 in which the cam pin travels reciprocally and, by cam action, rotates the cam barrel. Transmitting means are provided for transmitting the rotary motion of the cam barrel to the drive wheel. These transmitting means comprise, in serial, coaxial alignment: a cam barrel drive shaft 70; integral therewith, the driving element 72 of a two-element ratchet; and, integral with the drive wheel 50, the driven element 74 of the ratchet. The cam barrel, the cam barrel drive shaft and the driving element of the ratchet all rotate when the trigger is either depressed or repositioned by the action of spring 62. The two elements of the ratchet co-engage by means of teeth 75, slanted so as to cause the driving element, when rotated, as when the trigger is depressed, to rotate the driven element 74 in a direction corresponding to the advancement of the plunger. On the other hand, when the driving element is rotating in the opposite direction, as when the trigger is repositioned by the action of the spring 62, the teeth 75 will slip past each other and the driven element 74 will not rotate. To allow for such slippage, the driving element 72 of the ratchet is mounted on the end of the cam barrel drive shaft 70 so as to be limitedly slidable, with a spring 76 provided to supply sufficient tension to urge the teeth of the two elements to co-engage when the trigger is depressed, the spring also being sufficiently yieldable to allow the driving element to slide back on the cam barrel drive shaft when the trigger returns to the undepressed position by the action of the spring 62.

As described above, the size of the dose delivered per actuation of the device, i. e., per depression of the trigger, is determined by the degree of rotation of the drive wheel. Stated in other words, the dose size is determined by the number of threaded sections of the drive wheel rotated in engagement with the thread plunger. Because of the coaxial alignment of the cam barrel, cam barrel drive shaft, ratchet and drive wheel, the degree of rotation of the drive wheel is determined by the degree of one full rotation of the cam barrel; rotation of the cam barrel in the advancing direction of the plunger will produce a full rotation of the drive wheel. The degree of rotation of the cam barrel, in turn, is a function of the extent of travel of the cam pin in the cam way. In the embodiment illustrated in the drawings, means are provided for setting the travel of the cam pin to a preselected limit and hence preselecting the size of the dose per actuation. These means comprise a limiting pin 78 mounted on the trigger and projecting therefrom in the direction of trigger travel. The limiting pin cooperates with a selection barrel 80, rotatably mounted on the housing and having a face 82 opposing, and spaced apart from, the limiting pin. The selection barrel is provided, on the face of the barrel opposing the limiting pin, with a series of radially spaced bores 84 of varying depth. Each of the bores may be selectively brought into register for receiving the limiting pin by rotating the selection barrel.

When any one of the bores is brought into register, the extent of travel of the trigger when fully depressed is limited to the distance between the projecting end of the limiting pin and the bottom of the bore. Accordingly, by rotating the selection barrel into register with a selected bore, the degree of travel of the trigger, the degree of rotation of the drive wheel and hence, the dose size may be selected. In the embodiment illustrated in the drawings, the depth of the shallowest bore is sized to correspond to a degree of rotation of the drive wheel equal to rotating the drive wheel through one threaded section 52 from one longitudinal groove 54 to the next. Accordingly, when selectively registering the shallowest bore, the device will dispense a dose of an incremental size equivalent to the plunger and piston advancement resulting from rotating the one threaded section 52 of the drive wheel in engagement with the threads of the plunger. The deepest bore corresponds to rotating the drive wheel through one full rotation, i. e., five threaded sections 52, and hence by registering this bore, the device will dispense a five-fold incremental dose. Stated generally, the selection barrel is provided with a bore of a depth limiting the degree of trigger travel, to that corresponding to a rotation of the drive wheel through a preselected number of threads sections on the drive wheel.

It will be apparent to one skilled in the art that the actual volume of a single incremental dosage, i. e., a dosage equivalent to rotating the drive wheel through one threaded section, is a function of such factors as the pitch length selected for the threads, the number of threaded sections per revolution, and the volume displaced in the syringe by a limited length of piston travel. The device may be designed to delivery any of a wide range of incremental dose sizes. For example, a device dispensing a one micro-litre incremental dose may be designed by using a syringe having an inside diameter of 1/8-in. in combination with a drive wheel, threaded with five sections and using a pitch length of 0.025 inches for both the threads on the drive wheel and the threads on the plunger. With this combination, the device is capable of alternatively delivering doses of 1, 2, 3, 4 or 5 microlitres per actuation.

The dispenser of this invention may be made from various materials of construction known to those skilled in the art and limited only by such economic considerations as the cost of raw material, the ease of manufacture, and the durability of parts, when taking into consideration the repeated usage of the dispenser. For example, a preferred method of manufacture is the well-known injection molding technique using various materials and composites such as ABS (acrylonitrude, butadiene and styrene), Noryl (polycarbonate), or reinforced nylon. Metals, capable of being machined, such as aluminum, stainless steel or brass are also suitable.

While the dispenser of this invention and the methods for making and using the same have been described in terms of specific embodiments and illustrations, it will be apparent to one skilled in the art that various changes may be made in form, construction and arrangement of parts without departing from the scope and spirit of the invention. Accordingly, the scope and spirit of the invention should not be restricted except as defined in the accompanying claims.

Claims

1. A dispenser for delivering a controlled dose of liquid from a syringe having a liquid containing cartridge open at one end and a piston for expelling the liquid through the open end of the cartridge, said dispenser comprising:

a. a housing;

b. an elongated plunger, reciprocally mounted on said housing, having means at one end for engaging said piston, and being threaded along at least a portion of its longitudinal peripheral surface;

c. a cylindrical drive wheel for advancing said plunger, rotatably mounted to said housing, said drive wheel being threaded along its peripheral surface, said threads being interrupted by radially spaced grooves cut into the peripheral surface and extending parallel to the axis of said drive wheel and separating said threads into radially spaced threaded sections;

d. said drive wheel being mounted, relative to said plunger, so that it may be rotated to alternatively bring said threaded sections and said grooves into register with said plunger, the threaded sections when brought into register with said plunger, engaging the threads of said plunger and the grooves when brought into register with said plunger providing a clearance between said drive wheel and said plunger; and

e. actuating means for rotating said drive wheel through at least one threaded section and from registry with one separating groove to registry with any separating groove, thereby advancing said plunger and said piston, said rotation ending with said plunger disengaged from said drive

2. The dispenser of claim 1 provided with preselecting means for selecting the number of threaded sections through which said actuating means will

3. The dispenser of claim 2 wherein said preselecting means comprise:

a limiting pin mounted on said depressible element and projecting therefrom in the direction of depression;

a cylindrical section barrel, rotatably mounted on said housing, and having a face opposing and spaced apart from said limiting pin when said depressible element is in the undepressed state;

said opposing face provided with a plurality of radially spaced bores;

said selection barrel being mounted with respect to said limiting pin so that each of said bores may be selectively brought into register for receiving said limiting pin by rotating said selection barrel, whereby the degree of reciprocal travel of said depressible element is limited by the depth of each bore, each bore having a depth limiting the degree of said depressible element travel to corresponding to a rotation of said drive

4. The dispenser of claim 1 wherein said actuating means comprise:

a depressible element, reciprocally mounted to said housing;

translating means for translating the reciprocating motion of said depressible means to rotary motion; and

5. The dispenser of claim 4 wherein said translating means comprise:

a cam pin mounted on said depressible element and adopting the reciprocal motion thereof;

a cam barrel, rotatably mounted on said housing and having a helical cam way cut therein for receiving said cam pin and, by cam action, converting the reciprocating motion of said cam pin into rotary motion of said cam

6. The dispenser of claim 5 wherein the transmitting means comprise:

a cam barrel drive shaft, integral with said cam barrel;

a driving element of a two-part ratchet, integral with said drive shaft; and

the driven element of the two-part ratchet, integral with said drive wheel;

said cam barrel, said drive shaft, said driving element, said driven element, and said drive wheel all being coaxially aligned.