MXPA99001618A - Syringe comprising a tiltable nut - Google Patents

Abstract

In a syringe dosing mechanism a threaded spindle (1) and a nut (3) co-operates so that relative rotation thereof moves the nut (3) along the spindle (1). The nut (3) has two intersecting bores (12, 15). The first bore (15) has an inner thread (7) matching the outer thread (2) of the spindle (1) and the second bore (12) is smooth and fits slidingly over the spindle (1). The nut (3) is tiltable between a first and a second position. In the first position the threaded bore (15) is coaxial with the spindle (1) and in the second position the smooth bore (12) is coaxial with the spindle (1). The nut (3) is at a first side hinged to a piston rod (6) so that exertion of a force by the nut (3) on the piston rod (6) in a direction (10) by which an injection is performed will tilt said nut (3) into its first position. A piston withdrawal member acts at a second side of said nut diametrically opposite said first side so that the nut (3) is tilted to its second position when the withdrawal member applies a force (13) to said nut (3).

Description

SYRINGE THAT INCLUDES A TILTING NUT The invention relates to syringes for the metered injection of a medicine from an exchangeable cartridge of the kind having a piston that is forced into a tubular cartridge to press a dose of medicine corresponding to the movement of the piston. The syringe having a housing comprising a cartridge holder and a dosing mechanism by which a dose is adjusted and subsequently injected by successively advancing a piston rod to press the piston into the cartridge. The dosing mechanism comprising a threaded spindle and a nut member operating with the spindle so that the adjustment of a dose relative to the movement of the spindle and the nut member will move the nut member along the spindle / position of the spindle nut member it? It defines how much the piston rill is advanced during the injection. Spindle can be formed by the piston rod that can be provided with an external thread. When the cartridge is empty, the piston rod protrudes into the cartridge by almost the length of the cartridge. To change the cartridge, the piston rod must first be removed from the empty cartridge, and then it must be returned to its initial position in the dose adjustment part. The last operation is made possible by insurers that get unlocked when the empty cartridge is removed from the syringe, where after the piston rod must be pushed or screwed back to its initial position. The release of the latch can be obtained either by placing the internal thread of the nut member out of engagement with the spindle or by allowing a relative, free rotation of the nut member and the spindle. When the securing or securing of the nut member is released, which during the injections has been moved to a position in the spindle corresponding to 1 ¿. Piston rod fully advanced, can be moved along the spindle back to its position that corresponds to a piston rod, fully retracted. By the free rotation of the nut member relative to the spindle, the nut can be screwed back to its initial position which corresponds to a fully retracted piston rod. However, the nut has to be rotated around 75 turns and this bolting may require some skill. This problem can be overcome by using threads with high clearance and low friction that allow the spindle to turn on its own when the nut is pressed in the axial direction of the spindle. Another solution is to use a nut member comprising at least two parts that can be separated so that their threads are removed from the screw thread engagement when the nut is to be rotated to its initial position. However, this solution can cause problems when the parties put on. together again for coupling the screw thread since it may be difficult to obtain the correct synchronization between the position of the nut member in the spindle and the scale indicating the dose adjustment. Additionally, the coupling between the threads is dependent on the tolerances that can cause wear, which makes the adjustments inaccurate. It is an object of the invention to provide a nut having good coupling with the spindle and the thread from which it can be easily put out of engagement with the thread of the spindle without comprising parts to be moved in relation to each other. This is obtained by a syringe as described at the beginning of this application using a nut having two intersecting holes that form an angle between each other and of which a first hole has an internal thread that engages the outer thread of the spindle and a second hole is smooth and slidably fits over the thread of the spindle, the nut member which is mounted to the incunable piston rod between a first and a second position, so that in the first position, the threaded hole is coaxial with the spindle during dose adjustment and injection, and in the second position at which the nut is tilted when it has been operated to remove the piston rod and move the nut member along the spindle, the smooth hole is coaxial with the screw. During normal use of the injection device, the nut is supported with its first hole coaxial with the spindle with the threaded portions of the first hole that engage the external thread of the spindle. In this way, the nut can be moved along the spindle when the nut and the nut are rotated together. when it is required to move the nut along the spindle without relative rotation, the nut is tilted on the spindle to place it in a second angular position relative to the spindle, angular position in which the second hole is coaxial with the spindle. spindle In this angular position, the nut can be moved along the spindle with the smooth surface of the second hole that slides on the top of the spindle threads. When the nut has moved to a position along the spindle, the nut is tilted back to its first angular position with the first hole coaxial with the spindle and the threaded portions of the first hole engage the threads of the spindle. In the following, the invention is explained in further detail with reference to the drawings, wherein: Figure 1 shows schematically ur < threaded spindle connected to a piston rod through a threaded nut with a threaded and smooth hole, the nut that is in a first position with the thread of the hole that engages the screw thread, and Figure 2 shows the spindle, nut and piston rod in Figure 1 only with the nut tilted to a second position so that the spindle runs through the smooth wall hole. In Figure 1, a reciprocating and rotatable spindle 1 is provided with an external thread 2 which passes through a nut member 3 having on a first side a hinge 4 in which a turning pin 5 is articulated on a rod 6. The nut member 3 has two intersecting holes, a first hole that is coaxial with the spindle 1 in Figure 1, and a second hole indicated by broken lines 12 and intercepting the first hole forming an "acute angle" with the first hole The first hole has an internal thread 7 which in Figure 1 engages the external thread of the spindle 1. The spindle 1 forms a dose adjustment member of an injection device in which the doses are adjusted when making turn the spindle 1 around its axis, since the nut member can not be rotated, the rotation of the spindle 2 will screw this spindle through the nut member 3. A dose is adjusted by screwing the spindle in the mo It is threaded by a nut 8 and the adjusted dose is injected by moving the spindle 1 without it being rotated in the opposite direction shown by an arrow 9. The injection movement of the spindle, due to the coupling of the threads 2 and 7 of the spindle and the nut member will be transmitted to the nut member 3 and through the joint 4 and the pivot pin 5 in addition to the piston rod 6 which moves in the direction indicated by an arrow 10. By the injection movement of the In the case of a spindle, a force is exerted on the nut member 3 as indicated by an arrow 11, which force will try to rotate the nut member 3 around the pivot pin 5 in a direction that puts the threads of the spindle and the nut member in narrow coupling. By successive dose adjustments and injections, the piston rod is moved to its extreme position in the direction indicated by the arrow 10, that is, the piston in which the piston rod 6 acts moves completely in a cartridge. By the successive dose adjustments, the spindle 1 has been screwed through its full length through the nut member 3 in the direction indicated by the arrow 8 to allow a change in the cartridge, the piston rod 6 has to be removed in A nut has to be moved from one end of the spindle 1 to the other. To allow this movement, the coupling of the threads and the spindle and the nut member has to be released. This is done by tilting the nut member to a second position so that the smooth wall hole of the nut member becomes coaxial with the spindle as shown in Figure 2. In Figure 2, the rod is omitted. piston 6. To remove the piston rod, the nut member should be removed to the left in Figure 2. A drag force is transmitted to the nut member from a withdrawal element that can be operated manually or automatically when a lid is opened to access a blister compartment. The withdrawal element not shown acts by a force indicated by an arrow 13 on a second side of the nut member diametrically opposite the first side. The force indicated by the arrow 13 together with a force indicated by the arrow 14, which originates from the resistance against withdrawal that the piston rod exerts on the nut member, will exert a torque on the limb member. nut in a plan not defined by the axis of intersection of the holes. this pair of forces will drag the nut member to a second position in which the smooth wall hole is coaxial with the spindle 1 and maintains. the nut member in this inclined position while the withdrawal force is applied. With this second rotational position of the nut member 3 this nut member can be moved along the spindle as the top of the thread 2 of the spindle slides out of the smooth wall of the smooth wall hole of] nut member 3. The thread of the nut member is removed from the coupling with the thread 2 of the spindle 1 since the threaded hole is now positioned as indicated by the dashed lines 15. The nut member can be tilted towards its first position rotational in which the threads of the spindle and the nut element are in coupling.

It is noted that in relation to this date, the best method known by the applicant to carry out the present invention, is the conventional one for the manufacture of the objects to which it refers.

Having described the invention as above, the content of the following is claimed as property:

Claims (3)

1. A syringe having a housing comprising a cartridge holder and a metering mechanism, by which a dose is adjusted and subsequently injected by successively advancing a piston rod to press a piston into the cartridge, the metering mechanism that it comprises a threaded spindle and a nut member cooperating with the spindle so that adjustment of a dose relative to the rotation of the spindle of the nut member will move the nut member along the spindle, the position of the nut member in the spindle that defines how much the piston rod is advanced during the injection, characterized in that the nut has two intersecting holes that form an angle between each other and of which a first hole has an internal thread that engages the external thread of the piston. spindle and a second hole is smooth and fits slidably on the thread of the spindle, the nut member that is mounted to the piston rod Incunable between a first and a second position, so that in the first position, the hole threaded to this position with the spindle during the dose adjustment and injection and in the second position to which the nut is tilted when it is operated in the withdrawal and the nut member is moved along the spindle, the axial hole is coaxial with the spindle.

2. The syringe according to claim 1, characterized in that the nut member on a first side is articulated with the rod to the piston rod so that when exerting a force on the nut member in a direction by which the rod Piston is pressed in a direction by which an injection is made, it will tilt in a nut in its first position.

3. The syringe according to claim 2, characterized in that a piston removal member acts on the nut member on a second side of the member diaraetrally opposite the first side so that the nut member is inclined to its second position when the withdrawal force of the piston rod is applied to the nut member. SUMMARY OF THE INVENTION In a syringe metering mechanism, a threaded spindle (1) and a nut (3) that operate so that the relative rotation thereof moves the nut (3) along the spindle (1). The nut (3) has two intersecting holes (12, 15), the first hole (15) has an internal thread (7) which engages the external thread (2) of the spindle (1) of the hole and the second hole (12). ) is smooth and fits slidably on the spindle (1). The nut (3) can be tilted between a first and a second position. A first position, the threaded hole (15) is coaxial with the spindle (1) and in the second position, the smooth hole (12) is coaxial with the spindle (1). The nut (3) is on a first side arti culc-dcj- with hinge to a piston rod (6) so that when exerting a force by the nut (3) on the piston rod (6) in one direction ( 10) for which an injection is made will tilt the nut (3) in its first position. A piston removal member acts on a second side of the nut diagonally and opposite the first side so that the nut (3) is tilted to its second position when the withdrawal member applies a force (13) to the nut ( 3).