Medical Hollow Needle Assembly Tapered Interference Fit Joint
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Solution Overview
Problem
Existing methods for manufacturing hollow needles for medical instruments face challenges in achieving sufficient joint strength with the outer cylindrical body under tensile load and are prone to foreign matter attachment during the blasting process, which complicates the manufacturing process and requires additional steps.
Innovation Solution
A hollow needle assembly featuring an outer cylindrical body with a tapered through-hole and an inner cylindrical body with a matching tapered insertion hole, where the inner cylindrical body is fused to the outer body, providing a secure anchor without the need for adhesive bonding or separate blasting, thus enhancing joint strength and simplifying the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the outer peripheral surface of the hollow needle is subjected to blasting for roughening, then the anchor effect is generated to join the hollow needle to the cylindrical body without adhesive, but foreign matter such as projection material or broken pieces may attach to the hollow needle
Solution Approach 1:
The invention extracts and eliminates the blasting process from the manufacturing flow, replacing it with a press-fitting method that achieves the same anchoring function without introducing foreign matter. The roughening step is completely removed, and the joining is achieved through mechanical interference fit between the tapered outer surface of the hollow needle and the tapered inner surface of the cylindrical body.
Solution Approach 2:
The invention converts the harmful effect of blasting (foreign matter attachment) into a beneficial press-fitting process where controlled deformation during molding creates the necessary surface characteristics for anchoring without introducing contaminants. The press-fitting process itself generates the anchoring effect through plastic deformation and friction.
2Strength
If the outer peripheral surface of the hollow needle is subjected to blasting for roughening, then the anchor effect is generated, but the manufacturing process requires additional steps and becomes more complex
Solution Approach 1:
The invention merges the hollow needle forming process with the surface preparation and joining process into a single integrated press-fitting operation. The hollow needle is molded directly with the required tapered shape and surface characteristics, then immediately press-fitted into the cylindrical body without separate blasting or roughening steps.
Solution Approach 2:
The invention performs the surface preparation action preliminarily during the hollow needle molding process itself. The press-fitting operation that follows utilizes the pre-formed tapered surface to generate anchoring, eliminating the need for subsequent surface treatment steps.
3Strength
If adhesive is used to join the hollow needle to the outer cylindrical body, then the joint strength is achieved, but the adhesive may contact drug solution or blood and change quality or impact human body
Solution Approach 1:
The invention extracts and eliminates the adhesive from the joining system, replacing it with a purely mechanical press-fitting method. The hollow needle's tapered outer surface is directly press-fitted into the cylindrical body's tapered inner surface, creating a bond through friction and interference fit without any chemical adhesive that could contaminate the drug solution or blood.
Solution Approach 2:
The invention introduces the tapered geometric shape as an intermediary mechanism that enables joining without adhesive. The complementary tapered surfaces of the hollow needle and cylindrical body act as the mediating element that transfers and distributes mechanical loads, replacing the chemical bonding function of adhesive with mechanical interlocking.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively increases the joint strength of the hollow needle with respect to the outer cylindrical body, prevents foreign matter attachment, and simplifies the manufacturing process by integrating the roughening step within the pressing process, eliminating the need for additional steps and reducing the risk of contamination.
Implementation Method 1
The insertion hole of the inner cylindrical body is provided with an inner reduced-diameter surface which has a diameter reduced toward the distal end side and engages an outer reduced-diameter surface of the hollow needle, thereby preventing relative movement between the hollow needle and the inner cylindrical body in the axial direction
Implementation Method 2
a configuration has been proposed that involves fixedly press-fitting an inner cylindrical body having a tapered outer surface and inserting one end of a hollow needle therein into a through-hole of an outer cylindrical body
Data Source
Figure 1
Figure 2
Figure 3(a)~3(c)
AI summary
Provided is a medical hollow needle assembly which is increased in joint strength of a hollow needle to an outer cylindrical body, relative to a tensile load, and a method of manufacturing a hollow needle by which a manufacturing process can be simplified, and attachment of foreign matter to a hollow needle can be prevented. The medical hollow needle assembly (1) includes an outer cylindrical body (5) including a through-hole (5a), a hollow needle (3) having an outer peripheral surface partially including an outer reduced-diameter surface (6) having a diameter reduced toward a distal end side, and having a proximal end side disposed in the through-hole (5a), and an inner cylindrical body (7) including an insertion hole (7c) through which the hollow needle (3) is inserted, being disposed between the hollow needle (3) and the inner peripheral surface of the through-hole (5a), and joining the outer cylindrical body (5) and the hollow needle (3). The insertion hole (7c) of the inner cylindrical body (7) is provided with an inner reduced-diameter surface (9) reduced in diameter toward the distal end side, and engaging the outer reduced-diameter surface (6) of the hollow needle (3). A method of manufacturing a hollow needle (103) is used to be joined to an inner peripheral surface of a cylindrical body (107) provided in a medical instrument (101). The method includes a pressing step of punching out a plate body (110) having a predetermined shape from a metal plate, and rolling the plate body (110) to be molded into a tubular shape, and a joining step of joining a seam portion of the plate body (110) having been molded into the tubular shape. A surface of the plate body (110) is roughened in the pressing step to provide a roughened portion (106) at least partially on an outer peripheral surface of a portion joined to the inner peripheral surface of the cylindrical body (107) of the hollow needle (103).