CA2214468A1

CA2214468A1 - Syringe dose limiter

Info

Publication number: CA2214468A1
Application number: CA 2214468
Authority: CA
Inventors: Douglas C.V. Campbell
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-09-12
Filing date: 1997-09-12
Publication date: 1999-03-12

Description

SYRINGE DOSE LIMITER

The invention relates to syringes and in particular to disposable syringes.
Syringes are generally used to inject liquids into or extract fluids from a patient.
When injecting liquids, the amount injected is important. With many potent medicines, for exampl~, vaccines or narcotics, it is imperative that dosage administered be closely controlled. For this purpose, syringes are provided withvolume markings on the syringe barrel or are simply sized to carry only a limited volume of liquid when co""~l~tely filled. In the former case, the exact dosage control depends entirely on the diligence of the operator or user of the syringe, while the latter solution requires high capital expenditures for the manufacture and storage of a different syringe produced for each desired volume.
These disadvantages are now overcome with the dose limiter in accordance with the invention. It is an object of the invention to provide a syringe dose limiter which is universally adjustable to different syringe sizes and allows the use of the same size syringe barrel for different dosage amounts.
It is another object to reduce the manufacturing and storage costs in the production and distribution of disposable syringes.
These objects are achieved with a dose limiter for a syringe having a barrel from a piston sealingly movable in the barrel for aspirating liquid into and expelling liquid from the barrel and a plunger for manual displacement of the piston, the dose limiter including a limiter means for limiting a rearward movement of the plunger during aspiration, the limiter means being rigidly affixed to the plunger, and a stop means for limiting the rearward movement of the limiter means, the stop means and the limiter means being shaped and constructed to prevent movement of the limiter means past the stop means during aspiration, the maximum operating volume of thesyringe being controlled by the axial position of the limiter means on the plunger, i.e., the distance of the limiter means from the stop means in the fully inserted position of the plunger. The larger that distance, the larger the aspiratable volume.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Figure 1 of the drawing is an axial cross-section through a disposable syringe including a barrel 10, a piston 12 and a plunger 14 sealingly fitting and movable in the barrel. The dose limiter, in accordance with the invention, includes a limiter plate 16 secured to the plunger 14 and a stop shoulder 18 rigidly connected with the barrel wall and plCjE~,tillg into the path of the limiter plate 16. The stop shoulder 18 is preferably integrally molded with the barrel wall and made of the same material to reduce manufacturing costs. In a plefer,ed embodiment, the limiter plate 16 is directly molded onto the plunger 14. In another pl~fer,ed embodiment, the limiter plate 16 is manufactured separately from and installed onto the plunger 14 either during molding of the plunger or during assembly of the syringe. The location of the limiter plate 16 is prefe~dbly conl,olled by way-of annular plate receiving groove (not illustrated) in the plunger at the desired localiol, of the limiter plate. The limiter plate is constructed to be snapped into the groove on the plunger 14. By providing several grooves in the plunger 14 for locl~i,lg the limiter plate 16 in place in cor,espondence with the desired dosage sizes of the syringe, one barrel 10, piston 12 and plunger 14, in combination, can be used for a range of different dosage sizes. As shown in Figs.
2A and 2B, respectively illustrating the location of the limiter plate 16 relative to the stop shoulder 18 before and after assembly of the syringe, the respectively opposite surfaces of the limiter plate 16 and the stop shoulder 18 are ramped to facilitate passage of the limiter plate 16 past the stop shoulder 18 during assembly while preventing passage of the limiter plate 16 past the stop shoulder 18 when the plunger 14 is pulled backward in the fully assembled condition of the syringe, for example, for aspiration of a liquid.

Claims

1. A syringe dose limiter for a syringe having a barrel, a piston sealingly movable in the barrel for aspirating fluid into or expelling fluid from the barrel and a plunger for displacement of the piston, the dose limiter comprising a limiter means for limiting rearward movement of the plunger during aspiration, the limiter means being rigidly affixed to the plunger, and a stop means for limiting the rearward movement of the limiter means, the stop means and the limiter means being shaped and constructed so that movement of the limiter means past the stop means during aspiration of the syringe is prevented, the maximum operating volume of the syringe being controlled by the axial position of the limiter means on the plunger.

2. A syringe dose limiter as defined in claim 1, wherein the limiter means is integrally molded with the plunger and the stop means is integrally molded with the syringe barrel.

3. A syringe dose limiter as defined in claim 1, wherein the limiter means is manufactured separately from the plunger and rigidly affixed thereto during assembly of the syringe.