JP2002320673A - Plunger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plunger to prevent a liquid drop from an end of a syringe. SOLUTION: The plunger has a gasket 1 and a plunger rod 2 installed at an end off the gasket 1. A connecting hole 12 is opened at the end of the gasket 1. A tip part 21 of the plunger rod 2 that is formed as a shape corresponding to the connecting part 12 is inserted and fixed. There is a space 3 between a base tip part 221 of the inserted plunger rod and a base end 13 of a gasket 2. A tip 11 of the gasket 1 is formed as a flat at least a part between the tip 11 and the connecting hole 12 is pressed to form a flexible and thick shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a plunger for a syringe. More specifically, the present invention relates to a syringe plunger having a function of preventing dripping from the tip of the syringe, which occurs immediately after the pressing of the plunger is interrupted when injecting a drug solution by the syringe. The plunger of the present invention is effective when a high-viscosity drug solution is injected, when the spout of the drug solution is small, or when an expensive drug solution is injected several times instead of once.

[0002]

2. Description of the Related Art It is known that when a liquid medicine, particularly a high-viscosity liquid medicine is pushed out from the tip of a syringe, a phenomenon that the liquid medicine protrudes from the tip of the syringe immediately after the pressing of the plunger is interrupted (called dripping). ing. This phenomenon occurs because the drug solution is pushed out by the pressure in the syringe cylinder even after the drug solution is pushed out from the syringe barrel, and the dripped drug solution cannot be returned into the syringe barrel. Therefore, in the case of an expensive chemical solution such as a dental viscous material, the chemical solution is wasted, which is uneconomical.

In order to solve such a problem of dripping, an extruded portion structure disclosed in Japanese Patent Application Laid-Open No. 2001-57987 has been proposed. This has a portion in which the tip of the plunger is smaller than the diameter of the inner surface of the injection cylinder, and an O-ring mounting groove provided continuously to this portion,
The O-ring mounting groove has a width that is 1.5 times or more and 2.5 times or less the diameter of the cross-section of the O-ring in an unloaded state, and has a uniform gap between the bottom and the inner wall of the syringe. It narrows continuously or stepwise in the proximal direction, and the distance between the bottom and the inner wall of the syringe at a position separated from the proximal end by 0.5 times the diameter of the cross section in the unloaded state of the O-ring from the proximal end to the distal end side. The interval is at least 0.85 times the diameter of the cross section of the O-ring in the unloaded state. With this configuration, when the plunger is pushed, the O-ring moves in the proximal direction to cause a twist, and when the O-ring attempts to restore the original state from the twisted state generated at this time, the plunger is moved to the original state. By moving in the end direction, the pressure inside the syringe is reduced, and dripping is prevented.

[0004]

However, in this case, the relationship between the O-ring mounting groove and the diameter of the cross section in the unloaded state of the O-ring is delicate. The ring may not be kinked in the O-ring mounting groove. The present invention has been made in view of the above circumstances, occurs immediately after the pressing of the plunger is interrupted,
An object of the present invention is to provide a plunger having a function of preventing liquid dripping from the tip of a syringe.

[0005]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have made intensive studies and as a result, when the plunger rod is pressed, the tip of the gasket is deformed and raised, so that the plunger rod is Since the gasket returns to its original shape when the pressing is stopped, we came to realize that the internal pressure of the injection cylinder can be absorbed by this shape restoration,
The present invention has been reached. That is, the present invention comprises a gasket having a distal end and a proximal end, which is slidably inserted from the distal end into the syringe barrel, and a plunger rod attached to the proximal end of the gasket. The end is provided with an engagement hole for engaging the distal end of the plunger rod, the distal end is formed in a planar shape, and at least a portion between the planar distal end and the engagement cavity is pressed by the plunger rod to deform. It is formed as thick as possible, and the tip of the plunger rod has a shape substantially complementary to the engagement hole of the gasket, and when the tip of the plunger rod is inserted into the engagement hole, The present invention relates to a plunger in which a gap is formed between a distal end of a plunger rod and a proximal end of a gasket. Here, the tip of the plunger rod is
The one having a truncated conical head and a neck is preferably employed. Further, the portion between the flat tip and the engagement hole is preferably formed as a thin wall which can be easily deformed.

[0006]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view of one embodiment of the present invention. 2 to 4 are longitudinal sectional views showing a dental syringe adopting the plunger shown in FIG. 1, FIG. 2 shows a state before use, FIG. 3 shows a state when the plunger is pressed, and FIG.
Indicates a state in which pressing is interrupted. As shown in FIG. 1, the plunger of the present invention includes a gasket 1 and the gasket 1.
Has a plunger rod 2 attached to the base end of the plunger. An engagement hole 12 is provided at the base end of the gasket 1, and a distal end portion 21 of a plunger rod 2 formed in a shape complementary to the engagement hole 12 is inserted into the engagement hole 12.
A gap 3 is formed between the proximal end 221 of the inserted plunger rod and the proximal end 13 of the gasket 2. The distal end 11 of the gasket 1 is formed in a flat shape, and at least a portion between the flat end 11 and the engagement hole 12 is formed to have a thickness that can be deformed by being pressed by a plunger rod.

The gasket 1 is made of butyl rubber, natural rubber,
A plug member made of a rubber elastic material such as isoprene rubber or an elastomer. The plug member has a distal end 11 and a proximal end 13, and is slidably inserted into the syringe (4 in FIG. 2) from the distal end 11. You. The base end 11 of the gasket 1 is provided with an engagement hole 12 described below, which engages with the distal end portion 21 of the plunger rod 2. The distal end 11 of the gasket 1 is formed in a planar shape, and at least a portion between the planar end 11 and the distal end of the engagement hole 12 is formed to have a thickness that can be deformed by being pressed by the plunger rod 2. I have. Tip 11 and engagement fossa 1
It is preferable to form a thin portion between the two.

The tip 21 of the plunger rod 2 is inserted into the engagement hole 12 of the gasket 1. The plunger rod 2 is a rod-shaped member formed of a flexible resin such as polyethylene, polypropylene, or polyethylene terephthalate, and includes a distal end 21 and a proximal end 22. Tip 2
1 is formed in a shape substantially complementary to the engagement hole 12 of the gasket 1, and the shape of the distal end portion 21 includes a truncated cone-shaped head portion 211 and a neck portion 212 as shown in FIG. 1. Are preferably employed. Engagement hole 12 of gasket 1
A gap 3 is formed between the proximal end 221 of the plunger rod 2 inserted into the plunger rod 2 and the proximal end 13 of the gasket 1. The gap 3 is preferably formed in such a size that it does not disappear even when the tip 11 of the gasket 1 is deformed when the plunger P is pressed.

Next, a mechanism for preventing liquid dripping of the plunger of the present invention will be described with reference to FIGS. In the figure, P is a plunger, S is a dental syringe, 4 is a syringe, and 5 is a nozzle tip. FIG. 2 shows a state before using the dental syringe S, and a gap 3 is formed between the proximal end 13 of the gasket 1 and the distal end 221 of the plunger rod 2.
When the plunger P is pushed, the drug solution (not shown) accommodated in the syringe barrel 4 of the dental syringe S is pushed out from the nozzle tip 5, and at this time, a gasket abutting on the tip 21 of the plunger rod 2 Since the flat end portion 11 of the gasket 1 is deformed, the plunger rod 2 relatively advances in the gasket 1 to a position where the gap 3 is eliminated, and the tip end 11 of the gasket 1 rises (see FIG. 3). When the operation of pushing the plunger P is stopped, the tip 11 returns to its original shape due to rubber elasticity, so that the plunger rod 2 relatively retreats to the original position in the gasket 1, and the gap 3 is formed again (see FIG. 4). ). By restoring the distal end 11 at this time, the volume of the distal end side from the gasket 1 increases, and the pressure in the syringe barrel 4 is reduced, so that dripping can be prevented.

Example 1 Five dental syringes each having a polypropylene syringe and a plunger of the present invention and having a capacity of 1 mL as shown in FIG. 2 were prepared, and each syringe was filled with 1 mL of water. Thereafter, the nozzle tip was attached to the tip of the syringe barrel, the plunger was pushed by 0.5 mm to interrupt the pressing, and the state of liquid dripping from the syringe barrel tip at that time was observed. The results shown in Table 1 were obtained. Was.

[Comparative Example 1] Five conventional dental syringes each having a capacity of 1 mL and provided with a polypropylene syringe similar to that of Example 1 and a conventional plunger were prepared, and each syringe was filled with 1 mL of water. After that, the nozzle tip was attached to the tip of the syringe barrel, the plunger was pushed 0.5 mm to stop the pushing, and the state of liquid dripping from the syringe barrel tip at that time was observed. Was done. From Table 1, it can be seen that unlike the conventional syringe, no dripping has occurred.

[0012]

[Table 1]

[0013]

As is apparent from the above description, according to the present invention, the dripping can be reliably prevented, and the liquid chemical is economical without wasting.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of one embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a dental syringe employing the plunger shown in FIG. 1, showing a state before use.

FIG. 3 is a longitudinal sectional view showing a dental syringe using the plunger shown in FIG. 1, showing a state when the plunger is pressed.

FIG. 4 is a longitudinal sectional view showing a dental syringe employing the plunger shown in FIG. 1, showing a state in which pressing is interrupted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gasket 11 Tip 12 Engagement hole 13 Base 2 Plunger rod 21 Tip 211 Head 212 Neck 22 Base end 221 Tip tip 3 Gap 4 Injection cylinder 5 Nozzle tip P Plunger S Dental syringe

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Satoru Igarashi 3-9-3 Honjo Nishi, Kita-ku, Osaka Nipro Corporation (72) Inventor Masayuki Takahashi 76-1, Hasunumacho, Itabashi-ku, Tokyo (72) Inventor Makoto Michiaki 76-1, Hasunuma-cho, Itabashi-ku, Tokyo Tokyo, Japan (72) Inventor Hisashi Sato 76-1, Hasunuma-cho, Itabashi-ku, Tokyo F-Term, Inc. 4C052 AA17 HH08 4C066 AA09 BB01 CC04 DD08 EE14 FF02 HH12 4F041 AA01 AB01 BA02 BA12 BA52 CB02 CB44 CB57 4F042 AA01 CC08 FA22 FA30 FA37

Claims (3)

[Claims] 1. A gasket having a distal end and a proximal end, which is slidably inserted from the distal end into a syringe barrel, and a plunger rod attached to a proximal end of the gasket, wherein the gasket is An engagement hole for engaging the distal end of the plunger rod is provided at the base end, and the distal end is formed in a planar shape, and at least a portion between the planar distal end and the engagement hole is pressed by the plunger rod. The plunger rod has a thickness that is deformable and has a shape substantially complementary to the engagement hole of the gasket, and the tip of the plunger rod is inserted into the engagement hole. The plunger is configured such that a gap is formed between the proximal end of the plunger rod and the proximal end of the gasket when the plunger rod is moved. 2. The plunger according to claim 1, wherein the distal end of the plunger rod comprises a truncated cone-shaped head and a neck. 3. The plunger according to claim 1, wherein a portion between the flat tip and the engagement hole is formed to be easily deformable thin wall.