US2896807A - Tubular glass containers such as ampoules, phials and the like - Google Patents

Description

July 28, 1959 s, s w I 2,896,807

TUBULAR GLASS CONTAINERS SUCH AS AMPOULES, PHIALS AND THE LIKE Filed Feb. 19. 1954 fnumtor 650M574 NLE y 6/171 w Attorneys United States Patent TUBULAR GLASS CONTAINERS SUCH AS AM- POULES, PHIALS AND THE LIKE George Stanley Shaw, Liverpool, England, assignor to Glass Containers (Medical) Limited, Liverpool, England Application February 19, 1954, Serial No. 411,453 5 Claims. (Cl. 215-32) This invention relates to tubular glass containers of the kind known as ampuls, which are formed with a reduced or tapered end at which they are sealed after filling and are formed with a constriction or neck where the reduced end joins the main body of the ampul and at which constriction the ampul is usually broken to gain access to the contents. More particularly, the present invention has to do with a constrictive type of ampul so constructed as to be easily breakable when properly grasped but at the same time provide an ampul highly resistant to accidental breakage.

The recognized problem in the ampul art has been the provision of an ampul which may be conveniently broken by the consumer and one which will withstand accidental breakage during filling, shipping, or handling. For example, the patent to Thomae No. 1,951,743 provides a scratched point in the neck of the ampul and claims protection against accidental breakage by the use of an adhering outer coating. An example of providing ampuls to be conveniently broken by the consumer is set forth in the patent to Smith No. 2,517,604 wherein a portion of the ampul is placed under a stress of tension by the fusing of material to the exterior surface of the ampul to weaken the fragibility of the glass at such point. An example of other attempts to reinforce the ampul against accidental breakage is set forth in the patent to OSullivan No. 2,486,321 wherein a constrictive type of ampul is reinforced at the constricted area by spaced ridges but still permitting the ampul to be broken by subsequent application of a scoring or scratching implement such as a file.

The present invention envisages the creation of a locality at which the strength of the glass changes so as to determine the locality of the break. The invention further envisages the proportioning of the wall thickness with respect to the diameter of the constriction and/or controlling the quality of the glass at such proportioned wall thickness to thereby provide great resistance to premature or accidental breaking of the ampul but still providing an ampul to give a clean successful break.

Another feature of the present invention consists of manufacturing an ampul with a scratch or notch formed in the external surface thereof at the constriction and in annealing the ampul after the formation of the scratch or notch.

Another feature of the present invention has to do with the proportioning of the wall thickness of the ampul at the constriction so that it is not less than 8% of the outside diameter at the constricted neck, the maintenance of the wall thickness, as well as the annealing after the forming of the breakage scratch or notch, both contributing to the strength of the ampul against accidental breakage without unnecessarily contributing against purposeful breakage.

A further feature of the invention consists in limiting the depth and annular length of the scoring, etching or other breaking effect applied to the external surface of ice the ampul at the constriction but relative to the wall thickness at such point of application to further insure against inadvertent breaking of the ampul during cleaning, filling or other handling operations.

Other objects and advantages of the invention will be readily apparent from the following description and accompanying drawings wherein Figure l is an elevation of a constricted type ampul showing the notch formed at the apex of the constriction.

Figure 2 is an enlarged fragmentary section taken on the line II-II of Figure 1.

Figure 3 is an enlarged fragmentary horizontal sectional view taken on the line III-III of Figure 2.

The ampul shown in Figure 1 has a constricted neck 1 between the main body portion 2 and a tapered end portion 3 which is open at its upper end. The contents are fed into the ampul through the upper end which is subsequently hermetically sealed with the aid of heat.

As shown in Figure 2 the wall 4 of the constricted neck 1 is of thickness between 10% and 15% of the external diameter of the neck and has a short notch 5 scored therein at the narrowest part of the neck to preweaken it.

The formation of the neck or constriction .1 in an ampul obviously defines the general point of breakage and the addition of a preweakening zone such as by scoring or otherwise placing a portion of the constriction under stress obviously amplifies weakening of the ampul with respect to inadvertent breakage. It is a primary object of this invention to provide a simple, inexpensive ampul of the neck or constricted type which will withstand an unusual amount of shock and vibration to prevent inadvertent breakage, without the application of any external protective means, and which will at the same time be highly efficacious as to clean purposeful breakage.

As one contributing factor to accomplish this resistance to inadvertent breakage, I have found that in an ampul of the necked or constricted type the ratio between the wall thickness at the constriction 1 and the diameter of the constriction is important, and should not be less than a given value.

Thus the present invention comprises a method of manufacturing glass ampuls of the kind above set forth in which in the case of ampuls made of neutral glass the ratio of the thickness of the ampul wall at the neck to the outside diameter of the neck is maintained at not less than 8% and in the case of ampuls made of glass of more or less inherent strength or resistance to breakage than netural glass the said ratio is maintained at not less than 7% or 9% respectively and in which the ampul is preweakened at the neck, preferably by transversely scoring the neck, to an extent only suflicient to facilitate intentional breakage of the ampul at the neck by the application of a bending moment thereto.

When the ampuls are preweakened by scoring it is preferable that the scoring should be carried out prior to annealing, that is to say the normal annealing operation will be carried out after scoring.

In general it is to be preferred that the thickness of the glass wall at the neck should be maintained at not less than 10% and not greater than 15% of the external diameter of the neck and this is particularly so in the case of small ampuls with necks of the order of 4 millimetres to 6 millimetres in external diameter. It is desirable in the case of small ampuls having a relatively small diameter at the neck that the thickness of the wall at the neck should be maintained Well above the lower limit of 8% even though satisfactory results can be achieved with wall thicknesses as low as 8% of the neck diameter.

Maintenance of the wall thickness at the neck at not less than 8% and preferably at not less than 10% and 3. not more than 15% of the external diameter of the neck is very important because it is this which renders the ampuls sufficiently robust at the neck to enable them to be preweakened to an extent sufiicient to facilitate intentional breakage thereof by the consumer without undue risk or inadvertent breakage during subsequent cleaning, filling and transit thereof. If the wall thickness is not maintained as set forth above the result may be that some ampuls of a batch when preweakened may have sufficient strength at the neck to withstand the normal hazards of cleaning, filling and transit whilst others will be of insufficient strength with the result that an unduly high proportion of inadvertent breakages would result.

It is desirable that ampuls of the kind herein set forth should break cleanly at the neck without splintering and withoutpresenting an unduly jagged edge at the break. Maintenance of the wall thickness at the neck as herein prescribed enhances the probability that the ampuls will break cleanly as compared with ampuls having wall thicknesses at the neck less than herein prescribed.

The invention is especially applicable to ampuls which are drawn from glass tube and when the ampuls are made in this way a sufficient thickness of the ampul Wall at the neck can be achieved by allowing the flame to play upon the neck for a sufficient length of time having regard to the temperature of the flame. In the case of such ampuls it is desirable that the glass tube from which they are made should be of relatively uniform thickness which does not vary, at least in the circumferential direction and preferably also in the longitudinal direction, by more than from a mean value i.e. by more than in all.

In the preferred form of ampul the neck is scored to form a short notch in the external surface thereof but alternatively ampuls may be scored to form an arc or a ring in and extending around the external surface thereof. The scoring should of course be performed at or very near to the minimum circumference of the neck.

- Since it has been established that the ratio between the wall thickness at the constriction and the diameter of the constriction is important to minimize inadvertent breakage, likewise the length and depth of the scratch or notch 5 should be kept as small as possible consistent with enabling the ampul to be conveniently broken at the constriction. In most cases, and especially in the case of small diameter constrictions of the order of 4 to 5 millimetres the merest skin abrasion is sulficient. In the case of large ampuls of 10 millimetres or more in neck diameter the depth of scoring should not exceed 25% of the thickness of the Wall at the neck of the ampul and in the case of small ampuls having necks of the order of 4 miliimetres to 6 millimetres in diameter the depth of scoring should be of the order of 5% to 10% of the wall thickness at the neck. As a rule it is preferable that the length of the scratch or notch should not be more than 20% of the length of the circumference where it is made.

The above ratios as to wall thickness and length and depth of notch have been given with direct reference to ampuls formed of neutral glass, and it will be understood that these dimensions may vary slightly with glasses of different kind. For example, with the tougher borosilicate glass the wall thickness at the constriction might be slightly less and the lower limit of thickness may be 7% of the neck diameter, or alternately the depth or length of the notch might be slightly greater. For glass of less resistance to breakage than neutral glass the lower limit of wall thickness should be 9% of the neck diameter.

Inadvertent breakage is also lessened by annealing the ampul after the scratching or notching operation. Normally onewould think that the notch or groove or other weakening instrumentality might be applied at the apex of the constriction after annealing in order to set up a predetermined initial strain in such localized area, whereas annealing of the glass after the formation of the notch or groove obviously would tend to normalize the glass at this point. I have found, however, that satisfactory results are best obtained in getting maximum resistance to inadvertent breakage and giving sufiicient concentration of applied forces to effect clean breakage by sort of balancing the breakage construction, namely the neck and the groove, against the normalizing or annealing of the glass after forming the constriction and the groove, bearing in mind, of course, the proper proportioning of the wall thicknesses and depth of the groove. It will thus be seen that I have provided an ampul of extremely inexpensive construction which offers maximum resistance against inadvertent breakage and which adapts itself to purposeful breakage by the correct application of finger pressure.

it is desirable to provide indicia at the notch or are or at a point in the constriction diametrically opposite thereto and this may be done by the application to the notch or arc or the diametric point, of a suitable colored fusible material 6 prior to annealing, such material being fused into the glass as a result of the annealing; the subsequent annealing, as in the case of the formation of the notch, serving to maintain the normalization of the glass and thus eliminate any strains that might be set up by the fusing operation. Although the colored fusible material 6 is for the sake of clarity shown in Figure 3 at that side of the neck opposite to the notch 5 it is preferred that the material 6 should be applied directly to the notch 5.

Said fusible material may have a coefficient of expan-'' the scoring itself as a thin narrow transverse band and 1 to engage lightly against the neck of the ampul to grind may be in the form of a suitable colored glass paste.

The scoring may be performed by scratching, grinding of etching. For example a high speed rotary tool such as a steel'disc or a silicon carbide wheel may be allowed a suitable scoring therein or alternatively the scoring may be scratched in the neck of the ampul with a diamond or again the scoring may be etched by the application of a paste containing a mordant such as ammonium. bifluoride.

When ampuls are scored to form an are or ring in and extending around the external surface of the neck the colored fusible material may be applied as a thin narrow band covering either a part or the whole of the scoring. Even when the scoring extends as a ring right around the ampul neck it is still desirable to apply a colored fusible material to the neck in order to indicate that the ampul is one which can be broken Without the aid of a file. When the scoring is formed as a short notch the application of colored fusible material to the notch or arc will not only indicate that the ampul is one that can be broken without the aid of a file but will also indicate the position at which the ampul can be broken and the direction in which the bending moment should be applied. 7

When the scoring is a short notch it is preferable that the colored fusible material should be applied directly to the notch to indicate the direction in which the bending moment should be applied but the coloring material could be applied at some other part of the neck for example on that side opposite to the notch. It is however desirable that all ampuls should be similarly marked so as to build up amongst consumers a proper understanding as to the correct mode of breakage.

In conjunction with the maintenance of the herein specified ratios of wall thickness at the neck to external diameter at the neck the present invention includes other methods of preweakening ampuls such for example as by the application of a cold tool to the neck of the ampul when hot or by the application to the neck of a fusible material of coeflicient of expansion different to that of the material of which the ampul is made whereby to set up an initial stress in the ampul to preweaken it. Even if such fusible material is of approximately the same coefiicient of expansion as the material of which the ampul is made it may by virtue of the locally increased thickness of the wall of the neck give rise to an abrupt change of neck strength and thereby preweaken the neck in so far as the neck will break the more readily at the point where the abrupt change of strength occurs. It is believed however that preweakening of the neck by the application of a fusible material to the neck without scoring as herein described is not as satisfactory as scoring of the neck from the point of view of achieving a satisfactory clean break and of avoiding inadvertent breakage.

In the application of the invention to ampuls which are drawn from glass tube which is rotated about its longitudinal axis whilst a flame is applied thereto, a suflicient wall thickness at the neck as herein described is achieved by allowing the flame to play upon the neck for a suflicient period of time with the result that the thickness of the glass wall at the neck will as a rule be considerably greater than elsewhere in the ampul.

The amprul shown in the drawings is one which has been drawn from glass tube and it will be noted from Figure 2 that the wall thickness decreases away from the neck 1.

The invention includes ampuls made as described above and the preferred form of ampul has a wall thickness at the neck as herein prescribed and has a short transverse notch or scratch scored in the external surface of the neck with a colored material fused to the neck at the notch or scratch.

Whilst most ampuls of the kind with which the present invention is concerned are despatched by the ampul manufacturer in an open condition to the manufacturer of the contents it is sometimes preferred that the ampuls should be despatched to the manufacturer of the contents in a closed condition, usually with an enlarged or bell shaped top, which is subsequently cut off by the manufacturer of the contents so that the contents can be inserted into the ampul which is subsequently hermetically sealed at the place where the bell top was cut off. It is to be clearly understood that such ampuls are included within the scope of the appended claims, wherein the words hermetically sealed are used to indicate that the present invention is not concerned with glass containers which are adapted to be corked or closed otherwise than by hermetic sealing.

I claim:

1. A glass ampul comprising a tubular body having a constricted neck portion, means for preweakening said constricted portion generally in the zone of lease diameter, the ratio of the thickness of the wall of said constricted portion in said preweakened zone to the outside diameter in said zone being not less than 8 to 10%, depending on the outside diameter, said ratio being 8% for ampuls having an outside diameter of about 10 millimeters or more in said zone and 10% for ampuls having an outside diameter of about 4 millimeters in said zone, the ratio being inversely proportional to the outside diameter of the constricted portion in said zone, the thickness of the wall of said constricted portion increasing progressively toward and adjacent each side of said means for preweakening, said means for preweakening being suflEicient to facilitate intentional breakage at said zone by the application of a bending moment thereto by the tingers and thumbs but insufficient to cause inadvertent breakage during the normal handling in cleaning, filling and transportation.

2. The ampul set forth in claim 1, in which said ratio is not more than 15%.

3. The ampul set forth in claim 1, said means for preweakening said constricted portion comprising a transverse score mark.

4. The ampul set forth in claim 3 including colored material on said ampul to indicate the position of the score mark in said zone.

5. The ampul set forth in claim 3 wherein the depth of said score mark is not more than 25% of the wall thickness at said zone.

References Cited in the file of this patent UNITED STATES PATENTS 741,823 Packer Oct. 20, 1903 1,371,668 Davis Mar. 15, 1921 1,922,811 Kabnick Aug. 15, 1933 1,951,743 Thomae Mar. 20, 1934 1,956,568 Fjord May 1, 1934 2,371,486 Walker Mar. 13, 1945 2,486,321 OSullivan Oct. 25, 1949 2,517,604 Smith Aug. 8, 1950 FOREIGN PATENTS 8,936 Sweden Nov. 30, 1897 572,176 Great Britain Sept. 26, 1945

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