TO A NON-REUSABLE SYRINGE ADAPTED ROD-AND-PISTON UNIT AND A METHOD FOR ASSEMBLING SUCH A SYRINGE

Abstract: The invention relates to a rod- and/or piston unit that can be enclosed in a container forming part of a non-reusable syringe where the rod and the piston have means for connecting the piston to the rod and disconnecting the piston therefrom. The piston and the rod are manufactured as one piece in a die or similar. The invention also relates to a method for assembling a syringe.

Description: TITLE OF INVENTION: To a Non-Reusable Syrinσe Adapted Rod-and-piston Unit and a Method fo Assembli g Such -a yringe TECHNICAL FIELD The present invention relates primarily to a rod-unit and a piston-unit which are adapted to coact detach- ably with one another when enclosed in a container so as to form a syringe that can be used only once. To this end, it is necessary to provide the rod-unit and the piston-unit with means which will enable the units to be mutually connected and disconnected within the container by twisting the rod-unit and the piston- unit relative to one another. The invention includes two separate methods of assem- bling a syringe intended for one-time use only, here¬ inafter referred to as a disposable syringe, which when assembled includes a rod-unit which is arranged for reciprocating movement in relation to a container and whose one end has the form of or coacts with a needle, a piston-unit which coacts with the rod-unit, and means which enable the piston-unit and rod-unit to be mutually connected and disconnected, said rod-unit and piston-unit being formed in accordance with the present invention. BACKGROUND ART Several different types of disposable injection sy¬ ringes are known to the art. A disposable liquid- injection syringe is described in relative detail in International Patent Publication WO89/04677, in which the means used to connect and disconnect the piston and rod of the syringe have the form of screw-like means. The International Patent Publication includes exemplifying embodiments of rod and piston connecting means, where the embodiments illustrated in Figures 6 and 9 can be said to represent the closest prior art. Other types of disposable injection syringes are also known to the art, for instance the syringe described and illustrated in Swedish prior Patent Publication SE-B-7902138-2, Publication No. 438,598. The injection syringe described and illustrated in European Patent Application EP-A-2,229,017 also forms part of the prior art. The rod configuration illustrated and defined in Figure 7 of prior Patent Publication US-A-5,004,460 also belongs to the prior art. In addition to what is known from the aforecited publications, mention can be made to the different piston-unit and rod-unit connecting means illustrated and defined in prior publications US-A-4,906,231 and FR-A-2,381,527 and NO-A-163,263. The inventive syringe assembly is a development of the disposable syringe and the structural components illustrated and described in International Patent Application PCT/SE92/00258 filed on 21st April, 1992, and the reader is referred to this document for a closer understanding of the construction and forms of the rod-unit and piston-unit used in the present case and illustrated in the present Application. DISCLOSURE OF THE PRESENT INVENTION TECHNICAL PROBLEMS When considering the earlier standpoint of techniques relating to liquid-injection syringes that are intend¬ ed for one-time use only, referred to here as disposable or non-reusable syringes, it will be seen that a technical problem resides in creating condi¬ tions and providing rod-units and piston-units for such syringes in a form which will enable said units to be produced readily in large quantities, particu¬ larly by means of plastic moulding techniques or similar techniques, while maintaining a degree of accuracy and mutual conformity between said units which will satisfy the requirement of simple assembly and effective function. It will also be seen that a technical problem is one of realizing the advantages that are afforded when the rod-unit and the piston-unit are formed as a one-piece structure. When considering the earlier teachings of Internation¬ al Patent Publication WO89/004677 in particular, it will be seen that another technical problem is one of providing a rod-unit which is provided with a piston- unit connecting and disconnecting means, and a piston- unit which is provided with a rod-unit connecting and disconnecting means and which can both be readily produced in the form of an integrated one-piece struc- ture, where an integrated unit structure is produced by injection moulding in a plastic moulding machine having a two-part matrix, such as by thermoplastic treatment or by thermoplastic moulding. In this connection, a technical problem resides in realizing along which element lines along the rod-unit and the piston-unit and along said connecting and disconnecting means the matrix parts shall coact in order to facilitate and enable simultaneous moulding of the rod-unit and the piston-unit and their associated connecting and disconnecting means in a rational manner. It will also be seen that a technical problem resides in realizing the technical assembly advantages that are afforded by shaping the rod-unit and the piston- unit in a two-part matrix in one and the same moulding sequence and to firmly join said units together through the medium of a thin, narrow joining element. Another technical problem is one of realizing the significance of causing an extension of a centre line on the rod-unit to coincide with, or essentially coincide with, a centre line on the piston-unit. It will also be seen that a technical problem resides in the ability of realizing the significance of ori- entating the rod-unit and the piston-unit in relation to one another so that the aforesaid joining element will be formed by opposing outer corner parts of the units, particularly peripherally orientated outer corner parts. A related technical problem is then one of realizing that these corner parts should be arranged so as to slightly overlap within said element, and therewith to provide in the matrix a gap which will the material flow or yield necessary in order to form said joining element. Another technical problem is one of realizing the importance of adapting each joining element so as to enable the element to be broken and/or melted-off when wishing to separate the units along said element. It will also be seen that a technical problem when using a prefabricated and integrated rod-and-piston unit is one of realizing those advantages that are afforded by a novel method of assembling a syringe, particularly a disposable syringe, with which the desired and necessary separation of the rod-unit from the piston-unit can be effected within the syringe container. It will also be seen that another technical problem is one of realizing the advantages that are afforded by the use of a prefabricated and integrated rod-and- piston unit in the assembly of a syringe wherewith the desired unnecessary separation of the rod-unit from the piston-unit can be effected outside the syringe container. SOLUTION The present invention relates primarily to a novel rod-unit and/or piston-unit which can be enclosed in a container that forms part of a disposable syringe, wherein the rod-unit and the piston-unit are provided on their mutually opposing ends with unit connecting and unit disconnecting means. In the case of a disposable syringe of the kind de¬ fined in the introduction and comprising a rod-unit and piston-unit provided with said connecting and disconnecting means, it is proposed that the rod-unit and the piston-unit are produced simultaneously in the form of a single one-piece unit in a two-part mould or like tool, and that said rod and piston units are mutually joined by a readily destructed unit joining element. According to further developments of the invention, an extension of a centre line on the rod-unit shall coincide with, or essentially coincide with, a centre line on the piston-unit. The narrow element joining said rod-unit to the pis¬ ton-unit will preferably consist of mutually opposing outer corner parts of the units, and more preferably peripherally orientated outer corner parts. The corner parts will preferably overlap slightly in unit joining element. This is achieved by forming in the mould tool a narrow gap which can take-up the material flow or yield required to form the joining element between the units, said element being such as to enable it to be readily broken and/or melted-off when wishing to separate the units. The invention also relates to a first method of assem- bling a disposable syringe which when assembled in¬ cludes a rod which is intended to move reciprocatingly in relation to a container and one end of which is comprised of or can coact with a needle, a piston which is intended to coact with the rod-unit, and means for connecting and disconnecting the piston-unit to and from the rod-unit respectively. In this first method, a prefabricated and integrated rod-and-piston unit is positioned so that an extension of a centre line on the integrated rod-unit and the piston-unit will coincide with, or essentially coin¬ cide with, an extension of a centre line on the con¬ tainer, and the integrated rod-and-piston unit is inserted into the container and the rod-unit then separated from the piston-unit, whereafter the unit connecting and disconnecting means are brought to a unit connecting position by twisting the rod-unit relative to the piston-unit. The present invention also relates to a second method of assembling a syringe which when assembled includes a rod that is intended to move reciprocatingly in relation to a container and one end of which is com¬ prised of or can coact with a needle, a piston which is intended to coact with the rod-unit, and means for connecting and disconnecting the piston unit to and from the rod-unit respectively. In this regard, it is proposed that a prefabricated and integrated rod-and-piston unit is orientated for mutual separation of said units one from the other, that the separated units are positioned so that an extension of a centre line on the rod-unit and/or on the piston-unit coincides with, or essentially coin¬ cides with an extension of a container centre line, wherein the rod-unit and the piston-unit are inserted into the container and the rc ans for connecting and disconnecting the piston to and from the rod are brought to a connecting position by twisting the two units relative to one another, either within the container or outside said container. In the case of both of said methods, the units can be separated either with the aid of a separate device or by applying pressure in the direction of the aforesaid centre line. For instance, the aforesaid units can be mutually separated with the aid of an ultrasonic device which operates at a frequency of 35 kHz. It is also proposed that the means for connecting and disconnecting the piston to and from the rod can be brought to a connecting position by first moving the rod-unit towards the piston-unit and then twisting the rod-unit relative to the piston-unit. Thus, the invention relates to a disposable syringe produced in accordance with one of the aforesaid methods while using a prefabricated integrated rod- and-piston unit. ADVANTAGES Those advantages primarily afforded by the present invention reside in the ability to produce effectively and rationally a prefabricated and integrated rod-and-piston unit and of utilizing this integrated rod-and-piston unit in different ways to assemble a disposable syringe which, when assembled, includes a rod which can be moved reciprocatingly in relation to a container and whose one end is comprised of or can coact with a needle, a piston which is intended to coact with the rod-unit, and means for connecting and disconnecting the piston-unit to and from the rod-unit respectively. The primary characteristic features of a combined rod- and-piston unit in accordance with the present inven- tion are set forth in the characterizing clause of the following Claim 1. The primary characteristic features of a first method of assembling a syringe while using such an integrated rod-and-piston unit are set forth in the characteriz¬ ing clause of the following Claim 6, while the charac¬ teristic features of a second method of assembling a syringe with the aid of an integrated rod-and-piston unit in accordance with the present invention are set forth in the characterizing clause of the following Claim 11. A disposable syringe produced in accordance with the invention has the characteristic features set forth in Claim 16. BRIEF DESCRIPTION OF THE DRAWINGS An exemplifying embodiment of a rod-and-piston unit at present preferred and two methods of assembling a disposable syringe while using said unit will now be described in more detail with reference to the accom¬ panying drawings, in which Figure 1 is a perspective view of an integrated rod- and-piston unit intended for a syringe con¬ tainer, not shown; Figure 2 is a larger scale perspective view of the connection between the integrated rod-and- piston unit significant to the invention, after producing the unit in a two-part mould; Figure 3 is an enlarged further view of the element that joins the rod-unit to the piston-unit; Figure 4 illustrates a sequence of steps A-C in the manufacture of a disposable syringe, in which the rod-unit is separated from the piston-unit within actual the container; and Figure 5 illustrates a sequence of steps A-C in the manufacture of a disposable syringe in which the rod-unit is separated from the piston- unit outside the container. DESCRIPTION OF PROPOSED EMBODIMENTS Since the present invention is a further development of a syringe that comprises a rod-unit and a piston- unit which mutually coact through the medium of means when twisted in a first direction and which are de¬ scribed and illustrated in the aforesaid National Patent Application PCT/SE92/00258, this patent appli- cation shall be taken to form part of the description of the present invention and to illustrate the func¬ tion of a disposable syringe having means 6 which are orientated for mutual coaction between the rod and the piston. Figure 1 illustrates in perspective a rod-like device or a rod-unit 5 which is intended to be housed in a container 2 (not shown in Figure 1) and the lower part of which, i.e. the part facing towards a needle 3 (not shown) is intended to coact with means formed in a piston 4. The present invention thus provides, as Figure 1 is intended to show, a novel form and a novel construc- tion of an integrated rod-and-piston unit forming part of a liquid-injection syringe 1 which includes a container 2, a needle 3, a piston 4, the rod 5 and said means 6 which function to connect and disconnect the rod to and from the piston in response to relative movement therebetween. According to the invention, the rod-unit 5 and the piston-unit 4 are produced as a one-piece, integrated structure or unit in a two-part mould, in which the two units are mutually joined by means of a unit joining element 10, as described in more detail below with reference to Figures 2 and 3. According to the present invention, the two units are orientated so that an extension of a centre line 5' on the rod-unit 5 will coincide, or essentially coincide, with a centre line A ' on the piston-unit 4. As shown in the drawing, the element 10 joining the rod-unit to the piston-unit is comprised of mutually joined and mutually facing outer corner parts, where the corner 11 of the part 5a' is joined to the corner 12 of the part 4r. As shown more clearly in Figure 3, the corner parts 11, 12 are intended to overlap slightly within the element 10, which is effected by providing a peripher¬ ally orientated gap in the matrix to enable adapted flow of material between the units during the unit moulding process. This unit joining element is adapted so as to be readily broken and/or melted-off when wishing to separate the units, for instance along a joining element 10'. With regard to the size of the element 10 and the configuration of the gap, the element should be narrow enough to enable separation to be readily effected and the gap should be large enough to enable the hot plastic material to pass through the gap and fill the whole of the mould satisfactorily during the moulding operation. The size of the gap will depend on the viscosity of the material, the temperature used, the pressure selected and other parameters. The requisite diraen- sions will be well known to the person skilled in this art. The use of an integrated rod-and-piston unit of the aforedescribed kind enables a disposable syringe to be assembled in either one of two different ways, said syringe when assembled comprising a rod which can be moved reciprocatingly in relation to a syringe con¬ tainer and one end of which is comprised of or can coact with a needle, a piston that coacts with the rod-unit, and means for connecting and disconnecting the piston unit to and from t e rod unit respectively. Figures 4A to 4C illustrate a method of utilizing an integrated rod-and-piston unit 45 according to Figure 1, where Figure 4A illustrates that an extension of a centre line.45' on the rod-and-piston unit is caused to coincide with, or essentially coincide with an extension of a centre line 30' on the container 30, so as to enable the integrated rod-and-piston unit 45 to be inserted into the container 30, as illustrated in Figure 4B. When the integrated unit has been inserted into the container, the rod-unit 5 can be separated from the piston-unit 4 along the element 10' and the unit connecting and disconnecting means brought to a unit connecting position by twisting the rod-unit 5 in a first direction relative to the piston-unit 4. Figure 5 illustrates another method which utilizes an integrated rod-and-piston unit 45 in which, as shown in Figure 5A, the unit 45 is positioned so that the rod-unit and the piston-unit can be separated from one another prior to being inserted into the container. The units 4, 5 separated along the element 10' are positioned so that an extension of a centre line 45' on the rod-unit and/or the piston-unit will coincide with, or essentially coincide with an extension of a centre line 30' on the container 30. In this case, the piston-unit and the rod-unit are inserted into the container 30 and the means for connecting and disconnecting the piston with the rod are brought to an active connecting position either within the container or outside the same. The two units are separated from each other by means of a separate device 40 in both of the aforesaid methods. The two units are best separated by applying a small pressure in the direction of the centre line 45', i.e. by pressing the rod-unit 5 towards the piston-unit 4, or vice versa. Separation along the joining element 10' can either be effected by breaking said element 10 or by elting-off said element. In this latter case, there may conven¬ iently be used an ultrasonic unit, preferably an ultrasonic unit which operates at a frequency in the order of 35 kHz. It is shown that the means for connecting the piston- unit to the rod-unit are brought to a connecting posi¬ tion by first moving the rod-unit 5 slightly towards the piston-unit 4 and then twisting the rod-unit in relation to the piston-unit through one-half turn, so as to cause the connecting means on the rod-unit to coact firmly with the connecting means on the piston- unit and therewith connect said units together. As illustrated in Figures 4B and 5B, the separating device 40 is preferably constructed to melt the unit joining element 10' in a first working operation, and to move the rod-unit and the piston-unit closer to¬ gether in a second working operation, and to twist the rod-unit relative to the piston-unit (or vice versa) in a third working operation, so as to achieve effec¬ tive coaction between said means. The first working operation is inactive during the second and the third working operations. The second and the third working operations can be combined in a single working step. The Figure 5A embodiment includes clamping jaws 51 and 52 which are movable towards and away from each other and which subsequent to inserting an integrated unit 45 therebetween are moved towards one another so as to clamp firmly the piston-unit 4 but merely to guide the rod-unit 5. The first working operation is carried out in the operational state shown in Figure 5B. The invention proposes the use of an ultrasonic melt¬ ing device. Such devices are known and utilize a generator-oscil- lator which generates a specific frequency, for in¬ stance a frequency of 20-40 kHz. This oscillation is converted to mechanical motion. The amplitude is normally very small, in the order of hundredths of a millimeter. The plastic element 45 is placed in a jig which has three functions, namely the function of an anvil against axially acting forces, the function of guiding and clamping the lower part of the plastic element (in this case, the piston 4) radially, while solely guiding the upper part of the plastic element 45 so that said part is fixed against radial movement but free to move axially during the melting process. The melting process is carried out when the oscillat¬ ing device 40 is pressed against the upper part 5 of the plastic element. This upper part will then oscil¬ late axially at the same frequency as the oscillating device. Because the lower part 4 of the plastic ele- ment is clamped firmly between said jaws (or at least dampened) , there is a part 10 between the upper and lower element parts 4 and 5 in which frictional heat is generated. Energy is developed relatively quickly and the plastic element will melt sufficiently to separate the units within the space of 0.1-0.2 seconds. When wishing solely to separate the two parts 4, 5, one of said parts, the part 4, may be unsupported (not held in the jig) . The intrinsic mass of this part will provide sufficient damping to obtain sufficient energy development in the narrow element 10 joining said parts. The plastic will melt solely within the region of this element and enable the parts 4, 5 to be easily separated. The invention also relates to a disposable syringe that has been produced in accordance with one of the aforesaid methods while using a prefabricated, inte¬ grated rod-and-piston unit and described above. It will be understood that the invention is not re- stricted to the described and illustrated exemplifying embodiments thereof and that modifications can be made within the scope of the following Claims.

Claims: CL IMS 1. A rod-unit and/or piston-unit adapted for inser¬ tion into a container included in a syringe intended for one-time use only, wherein the rod-unit and the piston-unit include means for connecting and discon¬ necting the rod-unit to and from the piston-unit, c h a r a c t e r i z e d in that the rod-unit (5) and the piston-unit (4) are in the form of a single integrated rod-piston unit (45) which has been pro¬ duced in a mould or like tool. 2. A unit according to Claim 1, c h a r a c ¬ t e r i z e d in that an extension of a centre line on the rod-unit coincides or at least essentially coincides with a centre line on the piston-unit. 3. A unit according to Claim 1 or 2, c h a r a c ¬ t e r i z e d in that the rod-unit is joined to the piston-unit by means of a joining element (10) which is formed by mutually joined and mutually facing outer corner parts. 4. A unit according to Claim 3, c h a r a c - t e r i z e d in that the corner parts mutually overlap within said joining element, this overlap being achieved by providing in said mould a gap in which moulding material will flow. 5. A unit according to Claim 3 or 4, c h a r a c ¬ t e r i z e d in that the joining element is adapted to enable the element to be broken and/or melted-off when wishing to separate the units. 6. A method of assembling a syringe which, when assembled, includes a rod which is intended to move reciprocatingly in relation to a container and one end of which is comprised of or can coact with a needle, a piston which can coact with the rod, and means for connecting and disconnecting the piston to and from the rod respectively, c h a r a c t e r i z e d in that when assembling the syringe an integrated rod- and-piston unit (45) is positioned so that an exten- sion of a centre line (45) on the rod-unit and the piston-unit coincides with, or essentially coincides with, an extension of a centre line (30') on the container (30); in that the integrated rod-and-piston unit (45) is inserted into the container (30); in that the rod-unit (5) is separated from the piston-unit (4) within the container; and in that the means for con¬ necting and disconnecting the piston-unit to and from the rod-unit are brought to a unit connecting posi¬ tion. 7. A method according to Claim 6, c h a r a c ¬ t e r i z e d by separating said units with the aid of a separate device (40). 8. A method according to Claim 6, c h a r a c ¬ t e r i z e d in that separation is effected by exerting pressure in the direction of said centre line. 9. A method according to Claim 7 or 8, c h a r ¬ a c t e r i z e d by separating said units with the aid of an ultrasonic device. 10. A method according to Claim 6, c h a r a c - t e r i z e d by first bringing the rod-unit towards the piston-unit and then twisting the rod-unit rela¬ tive to the piston-unit such as to bring the unit connecting and disconnecting means into a unit con¬ necting position. 11. A method of assembling a syringe which, when assembled, includes a rod which is arranged for recip¬ rocating movement relative to a container and one end of which is comprised of or can coact with a needle, a piston which coacts with said rod, and means for connecting and disconnecting the piston-unit to and from the rod-unit, c h a r a c t e r i z e d in that an integrated rod-and-piston unit (45) is positioned to enable said units to be separated from one another; in that the separated units are positioned so that a centre line on the rod-unit and/or on the piston-unit coincides with, or essentially coincides with, an extension of a centre line (30') on the container; in that the rod-and-piston units are inserted into the container (30); and in that the means for connecting and disconnecting the piston-unit to and from the rod- unit are brought to a unit connecting position either within the container or outside the container. 12. A method according to Claim 11, c h a r a c ¬ t e r i z e d in that the units are separated with the aid of a separate device (40). 13. A method according to Claim 11, c h a r a c ¬ t e r i z e d in that the units are separated by exerting pressure in the direction of said centre line. 14. A method according to Claim 12 or 13, c h a r ¬ a c t e r i z e d in that the units are separated with the aid of an ultrasonic unit (40). 15. A method according to Claim 11, c h a r a c - t e r i z e d by first bringing the rod-unit towards the piston-unit and then twisting the rod-unit rela¬ tive to the piston-unit such as to bring the unit connecting and disconnecting means into a unit con¬ necting position. 16. An injection syringe produced in accordance with any one of the preceding Claims 6-14 while using a rod-and-piston unit according to any one of Claims 1-5.

Inventors: HELLDIN GOERAN, HELLDIN, GOERAN
Applicants: HELLDIN GOERAN, HELLDIN, GOERAN
Application year: 1993
Main classification: A61M5
IPC codes: A61M5