Abstract:
A syringe for controlling the amount of material or medical fluid in a syringe body which is expelled therefrom upon depression of a plunger in the syringe body. The syringe includes a syringe body having a chamber and a discharge end portion and an open opposite end portion, with a plunger received in the syringe body. A measuring ring having an inner thread in mesh with an outer thread on the plunger, with latch means for setting and holding the measuring ring and plunger and thus, permit an exact volume to be expelled from said chamber.

Description:
The invention generally relates to a syringe and in particular, the invention relates to a syringe having a plunger and barrel with a ring engaged on the plunger for dispensing controlled amounts of a fluid in the barrel. 
     BACKGROUND OF THE INVENTION 
     The prior art syringe is described in U.S. Pat. No. 4,153,056, issued May 8, 1979. A related patent is U.S. Pat. No. 3,563,240, issued Feb. 17, 1971. The prior art syringe includes a cylinder having a chamber and having a cannula with a core at a first end thereof, and having an open second end thereof, the cylinder has exterior finger flanges disposed adjacent the open second end, a plunger having a piston head with a ring seal disposed in the cylinder for sealing the chamber at a first end of the plunger and having a stem with four ribs in a cruciform shape fixedly connected to the piston head and having a thumb engaging flange fixedly connected to the four ribs at a second end of the plunger, each of the ribs having an Outer edge with a set of spaced notches forming an exterior thread, and a measuring ring having an interior thread in mesh with the exterior thread notches formed on the stem flanges for measuring and setting a selective volume in the chamber and bore for holding a selective volume of medical fluid. One problem with the prior art syringe is that it is sometimes difficult for operator to set the measuring ring at a selective angle relative to the plunger for setting an exact desired volume in the chamber and core. 
     SUMMARY OF THE INVENTION 
     According to the present invention, a syringe is provided with a cylinder having a chamber and a cannula with a bore at a first end thereof and having an open second end thereof, the cylinder having exterior finger flanges disposed adjacent to the open second end, a plunger having a piston head with a ring seal disposed in the cylinder for sealing the chamber at a first end of the plunger and having a stem with first and second and third and fourth ribs in a given cross shape fixedly connected to the piston head and having a thumb engaging flange fixedly connected to the four ribs. At a second end of the plunger, the ribs have respective outer edges with first, second, third and fourth sets of notches forming an exterior thread, and a measuring ring having an interior thread in mesh with the exterior thread notches formed on the ribs permitting a predetermined volume of fluid in the chamber to be dispensed by the plunger. The interior thread on the ring has a pair of detents projecting radially inwardly of the first, second, third and fourth sets of rib thread notches, each of which have minor thread diameters, wherein the first, second and third sets of stem flange thread notches have a uniform selective minor thread diameter for allowing clearances in a radial direction from the pair of detents, and wherein the fourth set of rib thread notches have a selective minor thread diameter which is larger than the uniform selective minor thread diameter whereby the pair of detents do not have any clearance in a radial direction from the pair of detents when adjacent thereto, so that the measuring ring is latched to the plunger upon disposition of the pair of detents on opposite sides of the fourth set of rib thread notches. 
     By using the measuring ring thread detents an operator can set a desired volume of fluid which may be expelled from the syringe. The angle of the threads on the ribs and the measuring ring may be changed to permit a change in the volume to be expelled from the syringe for each revolution of the measuring ring. 
     A principal object of the present invention is to provide a syringe which will expel predetermined accurate volume of fluid for each revolution-of the measuring ring. 
     One object of the present invention is to avoid the difficulty for an operator in setting the measuring ring at a selective angle relative to the plunger or setting exactly a desired volume in the chamber and the bore for holding a selective volume of medical fluid. 
     These and other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational view of the syringe according to the invention; 
     FIG. 2 is a longitudinal sectional view of the syringe shown in FIG. 1; 
     FIG. 3 is an enlarged partial sectional view of an edge portion of the plunger piston and seal arrangement of the present invention; 
     FIG. 4 is a partial perspective view illustrating the threaded stem of the plungers; 
     FIG. 5 is a sectional view as taken along line 5--5 of FIG. 1; and 
     FIG. 6 is a sectional view as taken along line 6--6 of FIG. 5. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings wherein like reference characters designate like or corresponding parts throughout, there is illustrated in FIG. 1, a variable dosage syringe generally designated by reference numeral 10 which has an axis 11 and includes a hollow syringe body or cylinder 12 formed of a synthetic plastic material, or the like, and includes an elongated tubular cannula 14 having a tapered end portion 16 that is electively closed by a removable cap 18. As seen in FIG. 2, the cannula 14 has a bore 20 formed therein which communicates with an internal chamber 22 of the syringe body 12. This chamber is adapted to receive a pharmaceutical preparation or the like which is intended to be dispensed from the chamber 22 through the bore 20 of the cannula 14. 
     The chamber 22 has a uniform diameter from one end to the other and is open at an end 24 thereof opposite the cannula 14. Laterally extending handles or finger flanges 26 are provided adjacent this end of the syringe body 12 in a conventional manner. 
     The medicament is expelled from the chamber 22 through the bore 20 by a plunger 28 having a stem portion or an integral body formed of a plurality of radially extending ribs 29, 30, 31, 33, in a cruciform array. The plunger 28 has a first or inner end portion 32 which includes an integral or snap on seal piston 34 formed thereon and adapted to be inserted through an open end 24 of the syringe body 12. The opposite end of the plunger 28 has an integral palm or thumb engaging base or flange 42 formed thereon in a conventional manner. 
     The piston 34 includes an integral annular seal or flange 36 surrounding the piston 34 and having a diameter which is greater than the maximum diameter of the ribs 29, 30, 31, 33 of the plunger 28. As shown in FIG. 3, the flange 36 is connected to the piston 34 by an integral annular web 38 which is formed in the piston 34 by an annular V-shaped notch 40, so that the web 38 has a reduced thickness as compared to the flange 36 and is flexible, to permit the flange 36 to serve as a wiping seal along the interior surface of the syringe body 12. 
     A plunger limiting nut or ring 44 is provided on the plunger 28. The ring may be rotated to be properly located along the length of the plunger so that to permit a proper dosage of the material in the chamber to expelled through cannula 14. Thus by adjusting the distance of the annular ring 44 from the finger flanges 26, more or less material from the syringe 10 can be expelled. 
     As shown in FIG. 5, the ring 44 has an inner surface 46, which has a horseshoe shaped segmental rib or inner thread 48, that has an inner face 49. The thread 48 has a first latch 50 and a second latch 52, which are located 180 degrees apart. The latch 50 has a first and second detent or projection 54,56. The latch 52 also has a third and fourth detent or projection 58, 60. The detents 54, 56, 58, 60 are made of a resilient conventional plastic material and each extends from the inner face 49 in a radially inward direction. The detents 54, 56, and 58, 60 respectively are disposed on the peripherally opposite sides of the ribs 29 and 31, in the latched condition as shown in FIG. 5. 
     As illustrated in FIG. 2 and FIG. 6, the flanges 29, 30, 31, 33 have along their outer edges respective sets of axially spaced notches 62, 64, 66, 68, which receive the inner thread 48. The three sets of notches 64, 66, 68, of the respective fibs 31, 32, 33 have a uniform similar minor thread diameter and radius 67. The fourth set of notches 62 of the rib 29 has a minor thread diameter and radius 69 which is slightly larger than the uniform minor thread diameter and its radius 67. Thus, the latch 50 or 52 can only engage the plunger 28 on the fourth set of notches 62 of the stem flange 29. It should be noted that the minor thread diameter and radius extends to the valley or root of the notch and in a typical example, the axial width of each of the notches 62, 64, 66, 68 is slightly larger than the corresponding axial width of each of the detents 54, 56, 58, 60 and also larger than the corresponding axial width of the inner thread 48. Thus, the tip portions of the detents 54, 56, or 58, 60 act to latch or hold the sides of one notch in the set of notches 62, adjacent to the root of the notch. 
     In this embodiment 10, the ring 44 has an outer surface with a pair of ribs 70,72. Ribs 70, 72 which are respectively disposed radially outwardly of the latches 50, 52 in order to aid the operator to line up the ring 44 with the contacting flange 29 of the plunger 28. In an alternate embodiment (not shown), painted markings or raised arrows may be used in place of the ribs 70, 72. In another alternate embodiment (not illustrated), the ring 44 may have a rough finish or rippled finish in place of the smooth finish on its outer surface; or the ring 44 may have a plurality of equally angularly spaced ribs on its outer surface, in addition to the ribs 70, 72 which have a painted marking. 
     In this embodiment ring 44 is adjustable relative to the ribs 29, 30, 31, 33 by an angular displacement of the ring 44, and a half turn of the ring 44 may provide a two cubic centimeters (cc) volume change or dose in the chamber 22, including the bore 20. In alternate embodiments, other doses may be accommodated by changing the pitch angle of the thread such that a single turn of the ring 44 can produce one cc or another pitch angle of the thread would produce 3 cc with a single turn of the ring 44. The advantage of the syringe 10 is that the operator avoids the difficulty in setting measuring ring 44 at a selective angle relative to the plunger 28, for exactly setting a desired volume in the chamber. 
     It should be understood that the foregoing relates only to a limited number of preferred embodiments of the invention which have been by way of example only, and that is intended to cover all change and modifications of the examples of the invention herein chosen for the purposes of the disclosure which do not constitute departures from the spirit and scope of the invention.