US 2697437 A
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Description (OCR text may contain errors)
Dec. 2l, 1954 s. J. EVERETT HYPODERMIC NEEDLE MOUNTING Filed Sept. l, 1949 SAMUE L d AMES Evzecr'r Attorney HYPGDERMIC NEEDLE MOUNTING Samuel `lames Everett, Thornton Heath, England Application September 1, 1949, Serial No. 113,547
Claims priority, application Great Britain September 10, 1948 3 Claims. (Cl. 12S- 221) One of the dangers accompanying the use of hypodermic needles is that if the needle, which is made of fine tubing, is overstressed, as may happen if the patient flinches, it may break when inserting the needle or even While making the injection.
A form of tubing is described in U. S. Patent No. 2,428,518, dated October 7, 1949 which minimises the illeffects of the breakage of the needle by preventing the broken-off portion severing completely at the point of fracture and thereby losing the portion in the patient. This works very satisfactorily with the ordinary type of mount unless the needle is broken off short at the mount itself; in this event, since the needle is tightly gripped at its base in the mount, there is some risk of complete severance at this point. With the usual form of needle the majority of breakages do occur at this point, as the maximum stress concentration in the needle arises where the parallel tubing joins the mount.
This Weakness has been recognised in the past and many efforts have been made to overcome or minimise its occurrence. For example, in one very well known form of needle, the mount is very carefully bored with a countersink where the needle enters the mount in such a Way that the countersink is rounded to a curvature in all directions, thus tending to support the needle should it become severely stressed in a lateral direction.
There is also a so-called reinforced needle, the tubing of which is of larger diameter from the mount to some distance up the blade, thereby removing the concentration of stress to a distance along the reinforcement. There is, of course, a further, but less severe, concentration of stress where the reinforcing of the tubing is discontinued. A tapered needle has also been proposed in which the stress is distributed more or less uniformly along the blade, and this, although the most satisfactory form of needle, has been found to be very uncommercial except for quite special purposes.
The present invention provides a very economical method of materially reducing the concentration of stresses in a needle. According to the invention, the needle is surrounded by a needle-supporting member which extends from where the mount effectively supports the needle for some distance along the blade and which tapers from the mount towards the needle point. This form of reinforcing member is made intentionally in such a manner that upon suicient stress being placed upon the needle, the reinforcing member will yield to some extent, thereby distributing the concentration of stress over a greater length of the needle. The reinforcing member causes the bend occasioned by the lateral stress in the needle to take a more gently curved form, and therefore, instead of a sharp kink in the needle where the breakage is likely to occur, it converts the sharp kink into the form of a curve of greater radius.
The reinforcing member may be made of various materials, preferably of low elastic recovery, such as copper, copper alloys, pure tin, pewter alloys of tin, or plastic compositions. Aluminium is also a very suitable material except for its corrosion resistance properties. However, any comparatively soft material may be used which will support the needle in such a manner as to form a reinforcement and so that the reinforcing member will take a set together with the needle blade upon excessive stressing and thereby distribute the concentration of stress over a longer length of the needle.
One form which the invention may take is illustrated,
States Patent O which the needle may bend.
as an example, in the accompanying diagrams, in which Figure 1 is a general view of a hypodermic needle and mount according to the invention;
Figure 2 is a cross-section of Fig. 1 along the line Figure 3 is a view, similar to Fig. 1, of an alternative form of needle and mount according to the invention;
Figure 4 is a cross-section of Fig. 3 along the line 1V-1V, and
Figure 5 is a view of a form of needleA and mount similar to that shown in Figure 1 but with a shorter reinforcing member.
Referring to Figures 1 and 2 a needle 2 is firmly held at one end in a bushing 7 which is securely swaged within a bore 6 in a socket 1. The socket 1 is suitably shaped to fit the hypodermic syringe and the socket and bushing 7 forml a robust mounting for the needle 2. The needle consists of a length of tubing having a fine central bore 5 throughout its length, and the tubing is sharpened to a point at the end remote from the socket 1 by grinding the tubing at an angle as shown at 3. The bushing 7 is continued some distance along the part of the needle 2 which projects from the socket 1, extending towards, but not as far as, the point of the needle 3. This projecting extension of the bushing 7 is in the form of a tapered reinforcing tube or sleeve 4. Thus both the needle and the reinforcing tube or sleeve 4 are firmly secured in the socket 1.
The reinforcing sleeve is made, in the example, from an alloy which consists approximately of of tin with additions of hardening alloys which contain antimony. The extension 4 of the bushing 7 along the shaft of the needle provides a reinforcement for the needle 2 so that the concentration of stresses Where the needle joins the socket 1 is avoided. When the needle 2 bends, as shown at 2a in Fig. 1, the reinforcing tube 4 will bend with it as shown at 4a and will eventually take a set. The tube or sleeve 4 will, however, prevent sharp curvature of the needle at the socket 1, and because of the yielding will also prevent sharp curvature of the needle, with consequent high local stresses, at the end 8 of the tube 4.
In an alternative form of construction shown in Figures 3 and 4, the reinforcing tube is made of a hardened material made in tapered form with three longitudinal slits 9 round its periphery so that the reinforcement takes the form of three segments 4b, 4c and 4d. This permits the reinforcing member to bend more easily and thereby to provide a rounded surface about It will be understood that the tubing need not necessarily be divided into three segments but could be divided into two or into more than three if desired. The preferred construction, however, consists in having a conical reinforcement as a solid cone of metal as in Figures 1 and 2, as in this form the bending of the needle is somewhat damped, and, upon the needle being straightened again, the reinforcing member will bend back into its original form by reason of its embracing the needle, thereby reduclng the risk of forming pockets for the collection of dirt and bacteria.
The reinforcing member in both examples extends some distance along the needle, and may be of very thin section so as to maintain the point of stress concentration within the extension of the reinforcing member where breakage would probably occur. It has been found that the length of the conical reinforcing tube for a 26 gauge needle for example, gives very considerable advantages if it extends as short a distance as l mm. from the mount proper, but it is preferred to make it longer. Fig. 5 shows needle 2 and socket 1 similar to the first example but having a shorter reinforcing sleeve 10, the proportions of which have been found to be very satisfactory. It can be seen that the thickness of the sleeve 10 adjacent the socket 1 is substatitially greater than the thickness of the sleeve adjacent the other end.
It will be appreciated that the invention need not be restricted to the use of the materials specified in the example, and, in the first example having a solid re- Patented Dec. 21, 1954.
3 inforcing tube, a variety of materials would be suitable, provided that the reinforcement yielded under a smaller load than that required to break the needle.
1; A mount for a liy odermie needle comprising a socket in whichi the nee le is secured and shaped to t the nozzle of a hypodermic syringe, and a sleeve of ma'- terial which is soft compared to said needle and which will support the needle in a reinforcing manner so as to take a set upon excessive bending of the needle, said sleeve being disposed closely surrounding the needle and extending from said socket toward the point of said needle, said sleeve 'gradually tapering in cross section from the socket end of said sleeve to a thin edge at the end nearest the point of said needle and the thickness of1 said sleeve adjaeentsaid socket end being substantially greater than. the thickness of said sleeve adjacent the other end so ,that the restraint exercised by said sleeve against bending of said needle by a lateral load increases gradually toward the socket end of Said sleeve, whereby said sleeve distributes the bending stresses along the surrounded length of the needle.
2. A mount for a hypodermic needle according to claim 1 in which said sleeve is made of pewter.
3. A mount for a hypodermic needle according to claim 1 wherein said sleeve is integral with a bushing secured to said socket.
References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 722,203 Brooke Mar. 10, 1903 1,125,887 Schimmel Jan. 19, 1915 1,499,899 Wolfe July 1, 1924 1,564,499 Tropp Dec. 8, 1925 1,592,462 MacGregor July 13, 1926 2,016,631 Everett Oct. 8, 1935 2,034,294 Hein Mar. 17, 1936 2,088,338 Propper et al. July 27, 1937 2,219,089 Everett s. Oct. 22, 1940