US2641093A - Method of manufacturing glass syringes with interchangeable pistons and barrels - Google Patents

Description

June 9, 1953 s. KOLODNY EIAL 2,641,093 METHOD OF MANUFACTURING GLASS SYRINGES WITH INTERCHANGEABLE PISTONS AND BARRELS Original Filed May 25, 1950 FIG.1

F I G. 2

IIIIJIIIIIJJIIIMIIIIIIIIIIIIlllllllll Mckolas fgueger Mc/(o/as JV/zccz' & Samuel fL 0Z0dz2y INVENTORS BY v r ATTORNEY Patented June 9, 1953 UNITED STATES PATENT OFFICE METHOD OF MANUFACTURING GLASS SYRINGES WITH INTEROHANGEABLE PISTONS AND BARRELS ration of New Jersey Original application May .25, 1950, Serial No. 164,138. Divided and this application July 5, 1951, Serial No. 235,264

2 Claims.

This invention relates to glass hypodermic syringes and, more particularly, to novel syrmges of this type in which the pistons and barrels of syringes of a given cubic capacity may be readily interchanged Without loss of effective pumping power. This application is a division of our copending application Serial No. 164,138, filed May 25, 1950.

In the present manufacture of glass hypodermic syringes, each piston must be carefully finished to match a particular barrel. When so matched, the mating piston and barrel are marked with identical identifying serial numbers so that, thereafter, each piston can be assembled with its mating barrel. Except by remote chance, no piston will have a pressure-tight fit with any barrel other than the one it has been finished to fit,

These syringes, after assembly, are required to pass a test in which the syringe must retain from 20 to 70 lbs/sq. in. pressure, depending on size, for at least 30 seconds. This test requires a substantially hermetic seal between the cylindrical surface of the piston and the inner cylindrical surface of the barrel chamber. As the barrel chambers, when ground to insure linearity and axial alignment, are of differing internal diameters, each barrel must have a piston carefully finished to match its chamber.

This has many advantages, such as the necessity, during manufacture, of assembling the syringe and measuring its capacity before the capacity graduations are individually applied to the barrel surface. Furthermore, when a group of syringes are disassembled for sterilizing for example, matching of the correspondingly numbered barrels and pistons is a time consuming and exacting operation. When a piston is broken, for example, its mating barrel becomes useless and is usually discarded.

In accordance with the present invention, it has been found that these disadvantages can be eliminated by finishing all pistons, for syringes of one capacity, to a predetermined standardized dimension, and correspondingly finishing all barrels of such capacity syringes to a mating standardized dimension. While attempts have hitherto been made to provide glass hypodermic syringes with interchangeable pistons and barrels, they have been unsuccessful. With the present invention, in a group of syringes of equal capacity, any piston can be used with any barrel and fully meet the above-mentioned pressure test.

The invention involves the grinding of the piston, on a centerless grinder, to a predetermined diameter, after which the piston is lapped with an optical powder in a chemical and/or oil solution to a finish of i0.0001" relative to such dimension (herein termed X) The barrel chambers are likewise ground to dimension X, which is dependent upon the syringe capacity, and then lapped with a diamond solution to a tolerance of 0.0001" relative to X. When so finished any barrel assembled with any piston will meet the pressure test.

For an understanding of the invention principles, reference is made to the following description and the accompanying drawing. In the drawing:

Fig. 1 is an elevation view of a prior art glass hypodermic syringe.

Fig. 2 is a corresponding elevation view of the invention syringe.

Fig. 3 is an elevation view of the piston.

Fig. 4 is an axial sectional View of the barrel.

Referring to Fig. 1, which illustrates a glass hypodermic syringe I!) of the present type, the barrel II and piston 12 thereof are not interchangeable. Consequently, the barrel and piston carry matching serial numbers, indicated at I3 and It, so that, after disassembly for cleaning or the like, the piston II can be reassembled with its uniquely matching barrel 10.

One of the requirements of such a glass hypodermic syringe is that, under test, with the passage ll of nipple it closed, the chamber I8 of barrel ll, having its outer end closed by piston I2, hold a pressure of '70 pounds per square inch for 30 seconds. This requires a very close, ground fit between the outer surface of piston l2 and the surface of chamber 18, as well as exact axial alignment thereof.

In the usual manufacture of glass syringes, the barrel and piston are formed, the barrel surfaces are ground to assure true axial alignment throughout the length of chamber l8, and then a piston is ground to provide a tight-fit within a particular barrel, as well as to assure axial alignment of the piston surface. When a, particular barrel and a particular piston have been so mated as to have a fit tight enough to meet the above pressure test, they are then marked with identical serial numbers. Thi assures each piston being always assembled with its own matched barrel.

This arrangement has many disadvantages. For example, should either the piston or barrel of av particular syringe be broken, the unbroken syringe member must be discarded. It is only by a remote chance that an unbroken piston, for example, could possibly match another barrel,

and trying to find such a match would be a tedious procedure without any certainty of ultimate success.

Additionally, the graduation markings on the surface of the barrel can be placed thereon only after the barrel and piston have been properly finished to the required tightfit. "The capacity of the barrel is then accurately 'measured and the graduations applied. This requires individual measurement and markingof each syringe, a costly and time consuming process.

These glass syringes are used in-large quantitles in hospitals, for example, and after .each use, the syringes must be disassembled for sterilization. Usually, a large number of syringes are sterilized at the same time. After'sterilization, each syringe barrel must be reassembled with its mating piston. This requires a selection of a particular barrel, for examplaand .a time consuming search for its correspondingly numbered piston. The operation is further complicated by .the fact that the sterilized elements must be handled by tweezers, thus fur- .ther lengthening the time required in sorting and assembling.

The present invention obviates the foregoing disadvantages by providing glass syringes in which the barrels and pistons are mutuall interchangeable and any piston has a tight enough fit in any barrel to meet the pressure test of holding 20 to '70 lbs/sq. in. for 30 seconds. Re- .ferring to Fig. 2, it will be noted that the barrel 2| and piston 22 of the invention syringe .20 are characterized by'the lack ofmatching identification serial numbers.

In the manufacture of syringe 20, piston 2| (Fig. 3) is ground on a centerless grinder to assure linearity and axial alignment. The piston surface 3| is then lapped with a fine optical grinding powder suspended in a suitable .solution of chemicals and/or oils. Precision gauges are used to position and check the piston during the grinding and lapping.

The piston is thus finished to a tolerance of 100001 with respect to the dimension required for a given capacity syringe, this dimension being denoted X in Fig. 3. As known .to those skilledin the art, glasshypodermic syringes. are standardized as to capacity as measured in cubic centimeters (00.), the standard sizes generally I being 1, 2, 5, 10, 20, 30, 50 and 100 cc. The

.most common sizes are 2, 5, 10 and 20 cc.

The barrel 2| has the surface of chamber v28 ground, as on a centerless grinder, to insure .llnearity and axial alignment.

chamber 23 is then lapped, with a diamond solution, for example, to the required dimension K (Fig. 4) with a tolerance of 0.0001, the

When a group of barrels and a group of pistons have been finished in accordance with the .invention procedure, any piston can be inserted .in any barrel and the assembly will meet the test of .holding 20 to .70 lbs/sq. in. for .30 seconds. When disassembled, there is no need to assemble any particular piston with a selected barrel, thus eliminating the tedious sorting and matching procedure hitherto necessary. Should either a barrel *or a piston be broken, 'theunbroken piston or barrel can be 'assembled'with The surface .of z

any other barrel or piston, respectively, eliminating wastage of unbroken elements. A further feature is that the graduation marks can be uniformly applied to all barrels of the same capacity, no special measuring and application technique being required. Of course, each piston fits only the barrels of a given capacity syringe. For example, the piston of a 5 cc.

it should beunderstood that the invention may be otherwise embodied without departing from such .principles.

.What is claimed'is:

1. The method of manufacturing glass hypodermic syringes, of the same cubic capacity, which comprises providing a plurality of cylindrical g-lass pistons of substantially the same diameter; precision grinding and optically lapping the surface of each piston to the same predetermined diameter with the tolerance of the di ameter at any point along the linear extent thereof being 0.0001 inch; providing a plurality .of .cylindricalglass barrels of substantially the same internal diameter; and precision grinding and optically lapping the internal surface of each barrel to said same predetermined diameter with the tolerance of the inside diameter at any .point along the linear extent thereof being 0.0001 inch; whereby every one of said pistons willha-ve a sliding sealing fit in any one .of said barrels and the respective barrels and pistons may be indiscriminately interchanged without affecting the pressure retaining properties of the Y syringes.

2. The method of manufacturing glass hypodermic syringes, of the same cubic capacity, which comprises providing a'plurality of cylindrical glasspistonsof-substantially the same diameter; precision grinding and optically lapping the surface of each piston to the same predetermined diameter with the tolerance of the diameter at any point along the linear extent thereof being 0.0001inch; providing a plurality of cylindrical glass barrels of substantially the sameinternal diameter; precision grinding and optically lapping the internal surface of each barrel to said same predetermined diameter with thetolerance of the inside diameter at any point along thelinear'extent thereof being 0.0001 inch;

and applying identically spaced and located capacity graduations "to each of said barrels;

whereby every one of .said pistons will have .a

sliding sealingfitinzany .one of said barrels and the respective barrels and pistons'ma-y be indiscriminately interchanged without afiecting the pressure retaining. properties. of the syringes.

SAMUEL KOLODNY. NICHOLAS 'MICCI. .NICHOLAS KRUEGER.

.Refercnces'Cited iILthe file of this patent UNITED STATES-PATENTS

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