For measures such as blood dialysis therapy, infusions or blood transfusions, or extracorporeal blood circulation, winged medical needle devices fastened on the patient's skin with adhesive tape are widely used.
Such medical needle devices, as shown in FIGS. 6 and 7, include a hub 10 having an injection needle 11 fixed at the top end 10a thereof and a substantially cylindrical sheath 20 having a pair of wings 21, 22 mounted on both sides thereof. The sheath 20 is fit on the hub 10 which is movable relative to the sheath 20 both in a rotational and a longitudinal direction.
The wing 21 has a convex 23 and a groove 24 formed thereon whereas the wing 22 has a groove 25 and a convex 26 formed thereon and when the wings 21 and 22 are overlapped, the convex 23 engages with the groove 25 whereas the convex 26 engages with the groove 24.
The injection needle 11 is capped with a protective cap 30. The hub 10 has a tube 40 for infusions or blood transfusions connected to a rear end 10b thereof.
The hub 10, the sheath 20 and the tube 40 are respectively made of PC (polycarbonate), PE (polyethylene) and PVC (polyvinyl chloride). As shown in FIG. 8, the hub 10 having the sheath 20 fit thereon then has the tube 40 connected to the rear end 10b thereof. Further, the resultant hub 10 with the sheath 20 and the tube 40 is subjected to a heat treatment for “blocking adhesion”.
The “blocking adhesion” is an adhesive technique to attain a chemically reinforced adhesive structure at an interface between the PC material and the PVC material for the effect of a plasticizer of the PVC material, obtained by applying thermal load on the PC material and the PVC material in a state in which the PC material abuts the PVC material.
The following will explain how to use the above-structured medical needle device.
(1) A pair of wings 21, 22 mounted on the both sides of the sheath 20 are held together in such a manner that the wings are pinched with a thumb and a forefinger as operation fingers so as to be closed as shown in FIG. 9. More specifically, a pair of the wings 21, 22 are bent along the both sides of the sheath 20, overlapped and maintained. The respective surfaces of a pair of the wings 21, 22 are overlapped, in which the convex 23 engages with the groove 25 and the convex 26 engages with the groove 24 so that the wing 21 and 22 are overlapped.
(2) The injection needle 11 is set on a blood vessel of a patient and then the blood vessel is secured.
(3) A pair of the wings 21, 22 are spread apart so as to come into contact with the patient's skin and are fastened on the patient's skin with adhesive tape (not shown).
(4) The injection needle 11 is rotated so as to be adjusted on a position where blood flow is more than any other position.
(5) After medical treatment, the injection needle 11 is removed from the patient's skin and the medical needle device is disposed.
In the course of puncturing described in (1) and (2), movement of the hub 10, caused by transfer of the hub 10 relative to the sheath 20 both in the rotational direction and the longitudinal direction has to be prevented. In order to achieve prevention of the movement of the hub 10, at the time of the puncturing, the wings 21, 22 clasp both sides of the sheath 20 so that the inner peripheral surface of the sheath 20 strongly presses the outer peripheral surface of the hub 10, thereby increasing holding force to prevent the movement without fail.
On the other hand, once the wings 21, 22 are fastened as described in (3), certain rotational torque is required between the hub 10 and the sheath 20 so as to prevent unexpected rotation of the injection needle 11 during the medical treatment. In addition, smooth rotation between the hub 10 and the sheath 20 is also required so as to adjust the position of the needle at the time of positional adjustment of the needle as described in (4).
Therefore, conventional sheaths 20 have adopted a structure shown in FIGS. 10 to 14 in order to attain stable rotational torque except for the time of the puncturing. FIG. 10 and FIG. 11 are front views of the sheath 20 and FIG. 12 is a plane view of the sheath 20.
As shown in FIG. 10, base ends 21b, 22b of the wings 21, 22, mounted on the both sides of the sheath 20 are thinner than top ends 21a, 22a of the wings 21, 22 so that the wings 21, 22 can be easily bent along the both sides of the sheath 20. Then, at the time of the puncturing, the wings 21, 22 are overlapped as shown in FIG. 11.
The sheath 20 has an annular protrusion 9 projecting inward provided in a circumferential direction thereof. FIG. 13 is a I-I line enlarged cross-section of FIG. 12 and FIG. 14 is a II-II line enlarged cross-section of FIG. 12. FIG. 13 and FIG. 14 show the hub 10 in a two-dot chain line.
Except for the time of the puncturing, such as in the course of medical treatment, the annular protrusion 9 abuts the outer peripheral surface of the hub 10, thereby generating the certain rotational torque so as to prevent the unexpected rotation of the injection needle 11. In addition, such a structure also enables the smooth rotation between the hub 10 and the sheath 20 so as to adjust the position of the needle at the time of positional adjustment of the needle.
Another example of the ordinary medical needle devices has projections formed on the surface of the base ends 21b, 22b of the wings 21, 22 while having bores formed on both sides of the sheath 20 so as to insert the projections on the wings 21, 22 into the bores on the sheath 20 and pressure the hub 10 with the top ends of the projections in order to increase the holding force at the time of the puncturing (see, for example, the Japanese unexamined Patent Publications No. 2001-293087 and 2003-116991).
The ordinary medical needle devices shown in FIGS. 6 to 14, however, have a problem that, in case a plurality of products are produced, each product varies in the rotational torque which generates between the hub 10 and the sheath 20 and some of the products are excessively increased in the rotational torque.
The problem is caused by the heat treatment aiming at “blocking adhesion”, which is carried out in a manufacturing process of the medical needle devices.
In the heat treatment, thermal distribution inside a heat treatment apparatus varies, therefore, in case a plurality of assembled parts are heat treated, thermal load to be loaded on each assembled part, varies depending on where inside the heat treatment apparatus the assembled parts are positioned. Since the sheath 20 is made of PE which contracts for the heat treatment, the higher the temperature of the position where the medical needle device is arranged, the smaller a diameter of the inner peripheral surface of the resultant sheath 20 becomes so that the rotational torque between the hub 10 and the resultant sheath 20 increases for the effect of the friction. Accordingly, each of the resultant products have respective degrees of contraction thereby varying in the rotational torque, some of which result in products with an excessive rotational torque.
In addition, the annular protrusion 9 on the inner peripheral surface of the sheath 20 deforms from a circular shape along the hub 10 into an indeterminate shape for the effect of the heat treatment thereby increasing the rotational torque, which causes variety in the rotational torque because of the difference in treatment temperature.
Variety in the rotational torque, which causes difference in operability is not favorable. Especially, resultant products having the rotational torque higher than upper limit of a standard value (a value calculated in consideration of the operability) are not usable.
Accordingly, conventional medical needle devices have necessitated a very strict control of the temperature inside the heat treatment apparatus so as to prevent variety in the rotational torque. Therefore, there has been a strong demand for medical needle devices of which the rotational torque is hardly affected even in case they are heat treated at rather high temperatures.
The inventions disclosed in said Japanese unexamined Patent Publications have improved holding force at the time of the puncturing but have not prevented increase in the rotational torque except for the time of the puncturing or the variety in the rotational torque.
Therefore, the present invention aims at solving the above-mentioned problems, more specifically, an object of the present invention is to provide medical needle devices of which the rotational torque between the hub and the sheath is decreased and variety in the rotational torque is controlled.