Patent Publication Number: US-2023158245-A1

Title: Syringe with brake means

Description:
The present invention relates generally to syringe and particularly, although not exclusively, to a syringe of the type comprising a tube/barrel/body and a plunger/piston. 
     A syringe is a simple reciprocating pump consisting of a plunger/piston that fits tightly within a cylindrical tube (often called a barrel). The plunger can be linearly pulled and pushed along the inside of the tube, allowing the syringe to take in and expel liquid or gas through a discharge orifice at a front end of the tube. 
       FIGS.  1  and  2    illustrate analysis of a syringe  10  conducted by the present inventors. It appears that, with constant pressure, the speed of the piston  20  within the barrel  30  accelerates at the end of the stroke (indicated by box B) compared to the initial part of the stroke (illustrated by box A) due to a different tightening between the piston and body in these areas. This can result in a “spray effect” at the end of the stroke. 
     The present invention seeks to provide improvements in or relating to syringes. 
     An aspect of the present invention provides a syringe comprising a barrel having an outlet and a piston movable along the inside of the barrel to take in or expel fluid from the outlet, the syringe comprising brake means for influencing movement of the piston. 
     The goal of some embodiments is to reduce/eliminate the spray effect at the end of use. 
     The brake means may be effective to slow insertion of the piston over at least part of the stroke. 
     The brake means may be effective to slow insertion of the piston over only part of the stroke. 
     The brake means may slow the piston as it approaches the end of the insertion stroke. 
     The brake mean may be effective to decelerate insertion of the piston towards the end of the stroke; for example during the final approximately 1%, 5%, 10%, 15%, 20%, 25% or 30% of the stroke. 
     Brake means may be provided on or by the piston. Alternatively or additionally brake means may be provided on or by the barrel. 
     Brake means may be provided at or towards an end of the piston distal to the barrel outlet. 
     The brake means may comprise friction means. 
     The brake means may comprise one or more friction elements, for example ribs, strips, bumps, pads, stickers, roughened zones, interference zones, higher friction zones or the like. 
     The friction element/s may, for example, comprise one or more longitudinal elongate (for example generally oval) increased friction zones/areas. 
     In some embodiments the outlet end of the barrel is generally flat. In other embodiments the barrel may comprises a nozzle. 
     The open end of the syringe may, for example, be fitted with a hypodermic needle, a nozzle or tubing to direct the flow into and out of the barrel. 
     The barrel and/or the piston may be generally cylindrical with a generally circular section. 
     The outlet may be located generally centrally. Alternatively the outlet may be located eccentrically. 
     A further aspect provides a syringe comprising a body and a sliding plunger, the plunger can be linearly moved inside of the body in a pull stroke and a push stroke to draw in or expel liquid from a discharge orifice the body, in which the syringe comprises a friction zone for increasing interference between the plunger and the body to slow down acceleration of the piston towards the end of the push stroke whereby to avoid a spray effect. 
     The body may be a cylindrical tube or barrel. 
     The syringe may comprise a cylindrical friction area that is active in the few last millimetres of the insertion stroke. 
     The friction area may be made up of cylindrical area on the body and bump/s or cylindrical ring/s on the plunger, the interference between these two surfaces brakes the advance of the piston to compensate the acceleration in end of use. 
     The friction area may be an integral part of the piston/body, or it may be formed separately. A bi-injection process, for example, would allow different materials to be used, with a higher friction material used for brake element/s. The friction zone may be raised from the surface of the piston and/or barrel, or it may be flush. Alternatively of additionally increased friction may be provided by texture (e.g. roughened) and/or surface formations. 
     The friction element/s may be formed from the same or a different material to the barrel/piston. 
     A further aspect provides a syringe piston with a brake. 
     In aspects and embodiments of the present invention the syringe may be a reciprocating pump in which a sliding piston fits tightly within a barrel (cylindrical tube). 
     The barrel may have a terminal flange at one (open) end and a central outlet at the other (flat) end. The piston may also have a corresponding terminal flange. 
     In some embodiments the measured capacity of the barrel may be 5 ml. The brake may, for example, be active during the final (approximately) 1 ml of the stroke. 
     To slow down the acceleration of the piston, a “bumper”/“brake”/“deceleration” zone may be added to the piston and may be effective at the end of the insertion/dispensing stroke. With small interference with the barrel, it may brake the piston without stopping the stroke, and then avoid the “spray effect”. 
     In some embodiments the brake may be provided by a plurality of mutually spaced, elongate oval friction elements that are circumferentially distributed and extend longitudinally along the exterior surface of the piston. 
     Functionality of the syringe may include or be based on: with the piston withdrawn or partially withdrawn this is before the brake is active; the piston is inserted further and just in advance of the brake zone entering the interior of the barrel; the brake zone enters the interior of the barrel to start increasing interference between the piston and the barrel (this may be immediately or maybe (somewhat/slightly) distal to the flange end of the barrel); the piston is fully inserted; the brake zone is frictionally engaged within the interior of the barrel. 
     The syringe piston may provide a brake function. 
     In the absence of a brake there may be an acceleration of the piston in the few last millimetre stroke, which can cause a risk of suffocation. This acceleration may be due to a difference in interference between the barrel and the piston head over the length of the barrel and the position at the very end of injection. 
     To reduce this phenomenon, the syringe may provide a cylindrical friction area that may be active in the few last millimetre of the stroke. It may be made up of a cylindrical area (which may be generally smooth) on the barrel and bumps (or a cylindrical ring, for example) on the piston. The interference between these two surfaces may brake the advance of the piston to compensate the acceleration in end of use. 
     Different aspects and embodiments of the invention may be used separately or together. 
     Further particular and preferred aspects of the present invention are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with the features of the independent claims as appropriate, and in combination other than those explicitly set out in the claims. Each aspect can be carried out independently of the other aspects or in combination with one or more of the other aspects. 
     The present invention will now be more particularly described, by way of example, with reference to the accompanying drawings. 
    
    
     The example embodiments are described in sufficient detail to enable those of ordinary skill in the art to embody and implement the systems and processes herein described. It is important to understand that embodiments can be provided in many alternative forms and should not be construed as limited to the examples set forth herein. 
     Accordingly, while embodiments can be modified in various ways and take on various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below as examples. There is no intent to limit to the particular forms disclosed. On the contrary, all modifications, equivalents, and alternatives falling within the scope of the appended claims should be included. Elements of the example embodiments are consistently denoted by the same reference numerals throughout the drawings and detailed description where appropriate. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art. It will be further understood that terms in common usage should also be interpreted as is customary in the relevant art and not in an idealised or overly formal sense unless expressly so defined herein. 
     In the following description, all orientational terms, such as upper, lower, radially and axially, are used in relation to the drawings and should not be interpreted as limiting on the invention. 
       FIG.  3    shows a syringe  110  formed in accordance with the present invention. 
     The syringe is a reciprocating pump in which a sliding piston  120  fits tightly within a barrel  130  (cylindrical tube). 
     The barrel  130  has a terminal flange  132  at one (open) end and a central outlet  134  at the other (flat) end. The piston  120  also has a corresponding terminal flange  122 . 
     In this embodiment the measured capacity of the barrel is 5 ml. The brake is active during the final (approximately) 1 ml of the stroke. 
     To slow down the acceleration of the piston, a “bumper”/“brake”/“deceleration” zone  140  is added to the piston and is effective at the end of the insertion/dispensing stroke. With small interference with the barrel, it will brake the piston without stopping the stroke, and then avoid the “spray effect”. 
     In this embodiment the brake is provided by a plurality of mutually spaced, elongate oval friction elements  150  that are circumferentially distributed and extend longitudinally along the exterior surface of the piston. 
       FIGS.  4  to  6    illustrate the functionality of the syringe  110 .  FIG.  4    shows the piston  120  partially withdrawn and before the brake is active.  FIG.  5    shows the piston inserted further and just in advance of the brake zone  140  entering the interior of the barrel  130  to start increasing interference between the piston and the barrel.  FIG.  6    shows the piston fully inserted; the brake zone is shown to be frictionally engaged with the interior of the barrel. Movement from  FIG.  4    to  FIG.  5    is unaffected; movement from  FIG.  5    to  FIG.  6    is under the influence of increased interference to decelerate the piston. 
       FIGS.  7  to  9    show a syringe  210  formed in accordance with a further embodiment. 
     The syringe piston provides a brake function. 
     In the absence of a brake there would be an acceleration of the piston in the few last millimetre stroke, which can cause a risk of suffocation. This acceleration is due to a difference in interference between the barrel and the piston head  224  over the length of the barrel and the position at the very end of injection. 
     To reduce this phenomenon, the syringe  210  provides a cylindrical friction area  240  that must be active in the few last millimetre of the stroke. It is made up of a cylindrical area (which may be generally smooth) on the barrel and bumps  250  (or a cylindrical ring, for example) on the piston  220 . The interference between these two surfaces brakes the advance of the piston to compensate the acceleration in end of use. 
     Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiments shown and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.