JP4008232B2 - Plunger head of plunger rod of dental cartridge type electric syringe - Google Patents

Description

[0001]
[Field of the Invention]
The present invention relates to an improved structure of a plunger head attached to a plunger rod of a dental cartridge type electric syringe.
[0002]
[Prior art]
For dental local anesthesia injection, a cardridge type manual syringe is generally used, and recently, a cartridge type electric syringe has been gradually spread. As shown in FIG. 1, the cartridge 1 is usually made of glass, and has an aluminum cap 3 that holds a rubber plug 2 that seals the tip of the cartridge 1 and has a circular hole that exposes a part of the rubber plug at the center. And a plunger rubber 5 for extruding the local anesthetic solution 4 inserted in the rear end and sealed in the cartridge. The injection needle 6 used in the syringe penetrates and is fixed to a needle base 7 having a female screw adapted to be screwed with a male screw provided at the tip of a cartridge holder of the syringe. Injection into the patient's oral cavity for a local anesthetic procedure is performed by pushing the plunger rubber 5 with the movement of the plunger rod of the syringe and releasing the local anesthetic solution from the cartridge through the needle and into the gingiva.
[0003]
Unlike dental subcutaneous anesthesia injection, intramuscular injection, intravascular injection, etc., there are nerves in hard tissues such as the alveolar bone and teeth, so the local anesthetic solution remains in contact with the needle tip. Is injected. Therefore, it is known that the injection cannot be skillfully performed unless the injection pressure applied to the local anesthetic liquid of the cartridge is kept high by the plunger rod.
[0004]
With manual syringes, the pressure exerted by the plunger rod on the local anesthetic fluid of the cartridge is limited, and as a result, the above problems may be encountered. In this respect, since the electric syringe uses a small motor and a speed reducer as a power source, it can apply a strong force to the plunger rod at a low speed, and is therefore added to the local anesthetic solution of the cartridge loaded in the receiving barrel. The injection pressure can be kept high.
[0005]
The plunger rod is inserted into the bore of the support member with a slight gap between the two in order to improve the movement of the plunger rod in the bore of the support member as well as the manual dental syringe, and as a result, the tip of the plunger rod The head swings slightly and is eccentric.
[0006]
[Problems to be solved by the invention]
When the injection pressure is set high as in the case of an electric syringe, when the plunger rubber 5 of the cartridge 1 is pushed by the plunger rod 9 (see FIG. 2), the internal pressure of the local anesthetic liquid in the cartridge increases, and the plunger rubber 5 It deforms to resist it, and the plunger head of the plunger rod bites into the substance of the plunger rubber 5. At this time, as shown schematically in FIG. 2, if the plunger head 12 of the plunger rod 9 is slightly decentered, the plunger rubber 5 is also deformed, and the action causes the plunger head 12 to move the cartridge 1. The glass tube is strongly pressed against the inner wall of the glass tube, and in many cases the glass tube is broken.
[0007]
The objective of this invention is providing the plunger head of the plunger rod for electric syringes which does not produce the breakage | damage of the above glass tubes.
[0008]
[Means for Solving the Problems]
The above-mentioned object of the present invention is a plunger head of a plunger rod that pushes a plunger rubber of a cartridge enclosing a local anesthetic solution, the head having a reduced diameter portion smaller than the diameter thereof, and the reduced diameter portion is a tip thereof. This is accomplished by providing the plunger head of the plunger rod of a dental cartridge powered syringe with a plurality of segmented pawls that bite into the plunger rubber to provide an anchor effect.
[0009]
In a preferred embodiment of the present invention, the segmented pawl is formed by forming a circular recess in the end face of the plunger head and cutting the slot in the cross direction.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
As shown in FIGS. 3 and 4, the electric syringe 8 includes a small motor and a speed reducer as a power source, and a strong force is applied to the plunger rod 9 at a low speed. Therefore, the injection pressure applied to the local anesthetic solution 4 of the cartridge 1 loaded in the receiving cylinder 8 ′ of the electric syringe can be kept high. The plunger rod 9 is inserted into the bore 11 of the support member 10 with a slight gap between them in order to improve the movement of the plunger rod. As a result, the plunger rod is slightly swung and eccentric. The plunger head 12 according to the present invention is attached to the distal end of the plunger rod 9 as shown in detail in FIG. Such mounting is achieved by screwing the male screw 14 of the plunger rod 9 into the female screw hole 13 of the plunger head 12. The plunger head 12 has a diameter-reduced portion 15 having a diameter larger than the diameter of the plunger rod 9 but somewhat smaller than the inner diameter of the cartridge 1 and having a diameter smaller than the diameter of the plunger head 12 at the tip. In addition, a plurality of (four in this example) segment-like claws 16 are provided on the distal end surface of the reduced diameter portion 15 at intervals in the circumferential direction. The segment-like claw 16 is formed by forming a circular recess 17 on the distal end surface of the reduced diameter portion 15 of the plunger head 12 and then forming a slit 18 in the cross direction.
[0011]
FIG. 6 shows a state where the plunger rubber 5 of the cartridge 1 is pushed by the plunger rod 9 having the plunger head 12 according to the present invention. When the plunger head 12 of the plunger rod 9 hits and pushes against the plunger rubber 5, the segment-like claw 16 of the plunger head 12 bites into the plunger rubber 5 to exert an anchor effect, and the center line of the plunger rod 9 is not shifted. Acts as follows. In addition, the peripheral portion 5 ′ of the plunger rubber 5 that has been pushed and deformed by the plunger rod 9 moves substantially uniformly around the reduced diameter portion 15 of the plunger head 12 inside the cartridge 1. Thus, the rubber that has entered between the reduced diameter portion of the plunger head and the inner wall of the glass tube serves as a cushion, and the glass tube can be reliably prevented from being damaged by the plunger head 12. As shown in FIG. 7, even if the plunger head 12 is slightly decentered and deviates from the center line of the plunger rubber 5 and pushes the plunger rubber 5, the tip of the plunger head 12 exists as the reduced diameter portion 15, so Never hit the glass tube. Therefore, the glass tube of the cartridge never breaks.
[Brief description of the drawings]
FIG. 1 is a side view of a cartridge and an injection needle.
FIG. 2 is a cross-sectional view showing a state where a plunger rod of a conventional electric syringe is eccentric and pushing a plunger rubber of a cartridge.
FIG. 3 is a perspective view of an electric syringe incorporating a plunger rod equipped with a plunger head according to the present invention.
4 is a partial cross-sectional view of the electric syringe shown in FIG.
FIG. 5 is an enlarged perspective view of a plunger head according to the present invention mounted on a plunger rod.
FIG. 6 is a view showing a state where a plunger rubber of a cartridge is pushed by a plunger head according to the present invention.
FIG. 7 is a view showing a state in which the plunger rubber of the cartridge is biased and pushed by the plunger head according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cartridge 5 Plunger rubber 9 Plunger rod 12 Plunger head 15 Reduced-diameter portion 16 Segment-like claw 17 Recess 18

Claims (2)

A plunger head of a plunger rod that pushes a plunger rubber of a cartridge enclosing a local anesthetic solution, the head having a reduced diameter portion smaller than its diameter, and the reduced diameter portion bites into the plunger rubber at its distal end surface. A plunger head of a plunger rod of a dental cartridge-type electric syringe having a plurality of segmented claws for providing an anchor effect. 2. The plunger head of the plunger rod of the dental cartridge type electric syringe according to claim 1, wherein the segment-like claw is formed by forming a circular recess in an end face of the plunger head and cutting a slit in a cross direction.

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