GB2387116A

GB2387116A - Safety syringe

Info

Publication number: GB2387116A
Application number: GB0207951A
Authority: GB
Inventors: Wu-Shun Huang
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-04-05
Filing date: 2002-04-05
Publication date: 2003-10-08
Also published as: FR2838970B1; FR2838970A1; GB0207951D0; DE10219234A1

Abstract

A safety syringe includes a hub (3) that is inserted in a neck portion (12) of a barrel (1) with a shoulder portion airtightly abutting on an internal stepped surface (13) of the neck portion (12) and is therefore prevented from forward separating from the neck portion (12). The neck portion (12) has a reducing diameter inner wall surface (121) corresponding to a respective outer wall surface (361) of the hub (3), so that the two surfaces mutually contact with each other in an airtight manner. The safety syringe also has a plunger (2) having a grooved cone (22) provided at a front end thereof for engaging with the hub (3), so that the used hub could be backward pulled into the barrel (1) via the plunger (2). The groove (23) on the cone (22) allows medical liquid remained in a front end of the barrel (1) to flow into the hub (3) without generating a resistance to the plunger (2).

Description

23871 1 6

SAFETY SYRINGE

BACKGROUND OF THE INVENTION

5 In the medical practices of early days, a used syringe would be thoroughly sterilized for repealed use later.

Any incomplete sterilization would dangerously cause a second time infection of a patient and/or any other people. To avoid such second time infection, 10 disposable syringe for use only once was developed.

Although the disposable syringe avoids the problem of second time infection due to incomplete sterilization of conventional syringes, it does not include any protective means for a used and discarded cannula that 15 tends to unexpectedly stab nursing or cleaning personnel to result in another type of infection and injury. To solve this problem, various types of safety syringes are developed. US Patent Nos. 5899887, 603385, and 5569203 all disclose a safety syringe 20 having barrel and hub connected in a special manner to allow pulling of the hub and used cannula into the barrel before the used syringe is discarded, lest the used syringe should unexpectedly stab other people to cause undesired infection and injury.

However, all the safety syringes of prior art developed

to improve the conventional syringes have drawbacks

in the structure for backward pulling the hub and the used cannula. It is understood that a safety syringe mustmeet three basic but very important requirements: (a) the hub is firmly connected to the barrel, (b) the 5 hub of the used syringe can be pulled into the barrel, and, the most important one, (c) the joint of the hub and the barrel is highly airtight. A common problem encountered by manufacturers in designing the safety syringe is, when the requirements of firmly connected 10 hub and barrel as well as highly airtight joint of the hubandthebarrelareparticularlyemphasized,itmight be difficult for the hub of used syringe to be easily pulled backward) and, on the other hand, when the requirement of easily backward pullable hub of used 15 syringeisemphasized, the firmand airtight connection of the hub to the barrel wouldinevitably tee sacrificed.

Please refer to Figs. 1A to 1C that show three different conventionalsafetysyringeshavingabackwardpullable 20 hub. These syringes alsoincludeabarrelanda plunger having a forward projected cone provided at a front end thereof for engaging with the hub, such that the plunger may backward pull the hub into the barrel of the syringe when it becomes engaged with the hub. In 25 practical use of these conventional safety syringes, when the plunger is pushed close to a front end of the barrel with the projected cone in initial contact with

a rear end of the hub, a front head of the projected cone closes a passage via which a medical liquid is sent from the barrel to the hub and a closed space is formed between the plunger and the front end of the 5 barrel. At this point, a part of the medical liquid that is remained in the closed space is stopped from entering into the hub and forms a resistance to a further engagement of the cone with the hub. An increased push is therefore needed to achieve such engagement and 10 inevitably results in vibration during injection with the syringe and accordingly discomfort to the patient.

In a worse condition, the cone does not engage with the hub at all.

15 Fig. 1C shows the safety syringe disclosed in US Patent No. 5569203, of which the cone is prevented by residual medical liquid in the barrel from engaging with the hub. Figs. 1A and 1B show the safety syringes disclosed in US Patent Nos. 5899887 and 6033385, respectively, 20 as improvements to US Patent No. 5569203. As can be seen from Figs. 1A and 1B, the illustrated safety syringes include a hub being provided on its rear peripheral wall with cone-receiving holes and on its inner wall surface with radially inward inclined tabs.

25 However, a syringe with such a design is almost impossible from the terms of injection molding with plasticmaterial. Even if such syringe is successfully

molded, it does not include any means between the cone and the tabs for preventing error engagement of the cone with the hub. Therefore, it is very possible the plunger is undesirably engaged with the hub when it 5 is pushed forward to expel air from the barrel before drawing the medical liquid into the barrel for injection. It is therefore tried by the inventor to develop an 10 improvedsafetysyringetoeliminatedrawbacksexisting in the conventional safety syringes.

SUGARY OF THE INVENTION

15 A primary object of the present invention is to provide a safety syringe, a hub and a barrel of which are connected to each other in a firm manner that prevents the hub from separating from a front end of the barrel onceitis backwardinsertedinto the barrel and ensures 20 an airtight joint of the hub and the barrel.

Another object of the present invention is to provide a safety syringe having a cap closed onto a hub thereof with a rear edge of the cap defining anoptimalposition 2S for the hub to connect to a barrel of the syringe in a firm and airtight relation.

A further object of the present invention is to provide a safety syringe, a barrel of which has a front neck portion, and a hub of which is shaped and dimensioned for tightly fitting in the neck portion of the barrel 5 to ensure an airtight contact of an outer wall surface ofthehubwithaninnerwallsurfaceoftheneckportion. A still further object of the present invention is to provide asafetysyringe, aplungerofwhichis provided 10 at affront end with a grooved cone, and a hub of which is provided with a receiving hole for the cone of the plunger to engage therewith, such that when the plunger is pushed forward with the cone initially closing a rear end of the hub, medical liquid remained in a front 15 end of the barrel between the plunger and the hub can still be forced into the hub via the groove provided on the cone, allowing the plunger to move forward smoothly and the cone to engage with the receiving hole on the hub.

A still further object of the present invention is to provide a safety syringe, a hub of which is provided atapositionsomedistanceinfrontofa rear end thereof witha receivinghole,and aplungerofwhichis provided 25 atafrontendwithaconeforengagingwiththereceiving hole on the hub, such that when the plunger is pushed forward to expel air from a barrel of the syringe before

drawing medicalliquid into the barrel, the cone would first touch the rear end of the hub that provides a warning for an operator to stop pushing the plunger any further. Error engagement of the cone with the hub 5 can therefore be avoided.

BRIEF DESCRIPTION OF THE DRAWINGS

The structure and the technical means adopted by the 10 presentinventionto achieve theaboveandotherobjects can be best understood by referring to the following detailed description of the preferred embodiments and

the accompanying drawings, wherein 15 Fig. 1A is an exploded perspective view of a first conventional safety syringe; Fig. 1B is an assembled sectional view of a second conventional safety syringe; Fig. 1C is an exploded perspective view of a third conventional safety syringe; Fig. 2 is a partially exploded perspective view of a 25 safety syringe according to the present invention; Fig. 3 is a sectional view showing the hub with cap

and the barrel of the safety syringe of the present invention before being assembled to each other; Fig. 4 is a sectional view showing the hub covered with 5 a cap end the barrelof the safety syringe of the present invention have been assembled to each other; Fig.5 shows the cap for the safety syringe of the present inventionis removed from the assembled hub end barrel; 1 0 Fig. 6 shows the plunger of the safety syringe of the present invention is fully pushed forward to engage a cone thereof with the hub; and 15 Fig.7showsthehubwithusedcannulaisbackwardpulled into the barrel by the plunger of the safety syringe of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Please refer to Fig. 2 that is a partially exploded perspective view of a safety syringe according to the presentinvention. Asshown,the safety syringemainly includes a barrel 1, a plunger 2 movably received in 25 the barrel 1, a hub 3 connected to a front end of the barrel 1, and a cap 4 closed onto the hub 3.

Please also refer toFig.3. The front end of the barrel 1 is diametrically reduced to provide a neck portion 12, arimofwhichisradiallyinwardinclinedtoprovide a beveled annular surface 11. Moreover, a rear end of S the beveled annular surfacellradiallyinward projects from an inner wall surface 121 of the neck portion 12 to provide a stepped surface 13. It is to be nosed that theinnerwallaurfacel21Of the neck portionl2 defines a variable-diameter bore, diameters of which gradually 10 reduces from top to bottom.

The plunger 2 is a long member disposed into the barrel 1 from a rear end of the barrel 1. The plunger 2 is provided at a front end thereof with a piston 21, from 15 an end surface of which a cone 22 forward projects.

A groove 23 is provided to extend across a top of the cone 22.

The hub 3 is designed to hold a cannula 31 to a front 20 end thereof. An annular shoulder portion 32 is formed at a predetermined position on the hub 3. A receiving hole 33 is provided at a rear portion 36 of the hub 3 a distance behind the annular shoulder portion 32 and a distance in front of a rear end of the hub 3 to 25 diametrically extend through the hub 3. It is to be noted the rear portion 36 of the hub 3 extended between the annular shoulder portion 32 and the rear end has

a variable-diameter outer wall surface361. Itis also to be noted the variable-diameter outer wall surface 361 of the hub 3 has a configuration corresponding to that of the variable-diameter inner wall surface 121 5 of the neck portion 12 of the barrel 1, and dimensions slightly larger than that of the variable-diameter inner wall surface 121, The cap 4 is dimensioned to removably close onto the 10 hub to cover the entire cannula 31 therein. A rear portion of the cap 4 has a reduced wall thickness, so that a stepped surface 41 is formed on an inner wall surface of the cap 4 at a predetermined position close to a rear end of the cap 4, and an inner diameter of 15 the rear portion of the cap 4 is adapted to tightly fit around a front portion of the hub 3 in front of the annular shoulder portion 32.

In assembling the safety syringe of the present 20 invention, the cap 4 is first put onto the hub 3 and the cannula 31 with the stepped surface 41 in the cap 4 abutting on the front end of the hub 3. At thispoint, the rear portion of the cap 4 is tightly fitted around the front portion of the hub 3 with the rear end of 25 the cap 4 located a distance above the annular shoulder portion 32, as shown in Fig. 3. Thereafter, the hub 3 with the cap 4 closed thereon is connected to the

: barrel 1 by inserting the rear portion 36 of the hub 3 into the neck portion 12 of the barrel 1 until the rear end of the cap 4 abuts on the rim, that is, a front end of the neck portion 12, as shown in Fig. 4. At this 5 point, the rear portion 36 of the hub 3 is located in the neck portion 12 with the annular shoulder portion 32 just passing the beveled annular surface 11 to abut onthesteppedaurface13,forming anoptimalconnection of the cap 4 and the hub 3 to the barrel 1 and providing 10 a first airtight joint 34 between the stepped surface 13 and the annular shoulder portion 32. The hub 3 with the annular shoulder portion 32 abutted against the stepped surface 13 is not forward separable from the neck portion 12. Meanwhile, since the 15 variable- diameter outer wall surface 361 of the rear portion 36 Of the hubs has a configuration corresponding to that of the variable-diameter inner wall surface 121 Of the neck portionl2Of the barrel 1 and dimensions slightly larger than that of the latter, and since the 20 two surfaces 361 and 121 are designed to taper from front to rear end within optimal length and at optimal gradient, the rear portion 36 of the hub 3 is actually received in the neck portion 12 of the barrel 1 in a manner of compression fit with a certain position 25 between the inner wall surface 121 of the neck portion 12 and the outer wall surface 361 of the rear portion 36 of the hub 3 forming a second airtight joint 35.

With the first and the second airtight joints 34, 35, the safety syringe of the present invention completely meets one of the mostimportant requirements for safety syringes. To use the safety syringe of the present invention, the cap4 ispulledina direction opposite to the barrel 1, i.e., pulled forward to expose the cannula 31 for giving an injection, as shown in Fig. 5. Then, the 10 plunger 2 is pushed forward until the cone 22 on the piston 21 is engaged with the receiving hole 33 in the hub 3,as showninFig.6. When the cone22 isin initial contact with and thereby substantially closes the rear end of the hub 3, as shown in Fig. 5, the groove 23 15 provided on the top of the cone 22 allows medical liquid remained in the barrel 1 between the piston 21 and the hub 3 to keep flowinginto the hub 3 without generating aresistancetotheplunger2. Thus, theplunger2could still be smoothly pushed forward without causing any 20 vibration during injection or resulting in jetted medicalliquid from the cannula 31. When theinjection is completed, simply pull the plunger 2 backward and the hub 3 together with the used cannula 31 are rearward moved out of the neck portion 12 into the barrel 1, 25 as shown in Fig. 7.

With the above arrangements, the safety syringe of the

present invention fully meets the three basic and most important requirements of firm connection of the hub to the barrel, rearward pullable hub and used cannula, and absolute airtightness at the joint of the hub and 5 the barrel.

Claims

What is claimed is:

1. A safety syringe, comprising: 5 a barrel, a front end of which teeing a diametrically reduced neck portion having a rim radially inward inclined to provide a beveled annular surface, a rear end of said beveled annular surface radially inwardprojecting from en inner wall surface of said 10 week portion to provide a stepped surface, and said inner wall surface of said neck portion defining a variable-diameter bore, diameters of which gradually reducing from top to bottom; 15 a plunger being movably received in said barrel behind said neck portion; a hub holding a cannula to a front end thereof and being provided at a predetermined position with an 20 annular shoulder portion, and at a predetermined position on a rear portion a distance behind said annular shoulder portion with a receiving hole diametrically extended through said rear portion; and said rear portion being extended between said 25 annular shoulder portion and a rear end of said hub and having a variable- diameter outer wall surface gradually tapered rearward; and

a cap for removably closing said hub and entire said cannula,and haying a rear portion with reduced wall thickness, so that a stepped surface is formed on an inner wall surface of said cap at a predetermined 5 position close to a rear end thereof; and said hub being inserted in said neck portion of said barrel in such a manner that said annular shoulder portion is abutted on said stepped surface in said 10 neck portion to prevent said hub from forward separating from said barrel and to form a first airtight joint of said hub with said barrel, and that said rearward tapered variable-diameter outer wall surface of said rear portion of said hub is 15 receivedin said rearward taperedinner wall surface of said neck portion in a relation of compression fit to form at a certain contacted position a second airtight joint of said hub and said barrel.

20

2. The safety syringe as claimed in claim 1, wherein said plunger is a long member disposed into said barrel via a rear end of said barrel, said plunger being provided at a front end with a piston, at a front end of which a forward projected cone having 25 a groove extended across a top thereof is provided for engaging with said receiving hole on said hub.

3. A safety syringe constructed substantially as hereinbefore described with reference to the accompanying drawings.