GB1585803A - Vacuum flasks - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO VACUUM FLASKS (71) We, DAY IMPEL LIMITED, a British Company, of Station Works, Earls Cone, Colchester, Essex, C06 2ER, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to vacuum flasks of the kind comprising a Dewar flask, i.e.

a double walled glass-flask having the walls silvered and the space between them evacuated, located within a protective container.

The container serves to protect the comparatively fragile glass flask and makes the flask easier to handle, especially when filled with hot or very cold liquids. It is usual to provide a seal between the container and the flask to prevent liquid running down between them when being poured from the flask.

In some known vacuum flasks, the glass flask is inserted through the bottom wall of the container so that its rim comes to bear against the seal. The bottom wall of the flask is normally held in position by screws which can be loosened to permit replacement of the glass flask. This form of vacuum flask has the disadvantage that initial assembly of the glass flask and container is complicated and time consuming, as is replacement of the glass flask which may become necessary during use, for example if the glass flask becomes broken.

Another known vacuum flask has the glass flask loaded into the protective outer container from above. The glass flask is retained within and sealed to the container by a strip of rubber which is inserted between them. The strip of rubber can readily be removed to permit replacement of the glass flask. Sealing strips which have been used in the past have consisted of parallelsided strips of generally rectangular crosssection. It has been found that, although an effective seal and retention of the flask within the container are achieved at normal temperatures, if the seal is subjected to extreme cooling, as, for example, may occur as a result of spillage when a liquid gas is being poured out of the flask, the resultant contraction of the seal can lead to the seal being broken and even the glass flask slipping out of the container.

In accordance with the present invention there is provided a vacuum flask comprising a cylindrical open-topped container, a Dewar flask positioned in the container and protruding through the open top thereof, an annular gap being defined between the rim of the container and the Dewar flask, and a strip of resiliently compressible material having a wedge-shaped cross-section pressed into said annular gap, the wider edge of the strip being uppermost and the strip being compressed between the container and Dewar flask to retain the flask in the container.

It has been found that a strip of wedgeshaped cross-section can be inserted be tween a Dewar flask and its protective container with sufficient tightness to hold the flask in the container and to preclude liquid leaking between them, even under extreme conditions, such as when liquid gas, e.g.

nitrogen, is spilled on to the strip.

The invention in its preferred form will now be described in more detail by way of example with reference to the accompanying drawings, in which: - Figure 1 is a vertical cross-section through a vacuum flask in accordance with the invention; Figure 2 is a top plan view of the vacuum flask shown with the lid removed, and Figure 3 is a cross-section through the sealing strip shown on an enlarged scale.

The vacuum flask illustrated in the drawings includes an outer metallic, for example, stainless steel protective container 1 in which is housed a Dewar flask 2 of convenventional double-walled construction. The flask 2 is inserted through the open top of the container and its bottom rests on an expanded polystyrene liner 3 fixed in the bottom of the container for supporting the flask. The rim of the flask projects through the open end of the container 1 and a lid 4 of the container seats upon it through ja rubber ring 5 which is carried on the underside of the lid. The lid is held on the container by catches 6 fixed to the outside of the container. The catches are of well known construction and co-operates with hooks 7 mounted on the lid.If desired the lip and catches can be omitted (as shown in Figure 2), in which case the vacuum flask will be of the permanently open type commonly used for industrial purposes. The container can, if required be provided with a handle (not shown) from which the vacuum flask is pivotally suspended, not unlike a bucket is suspended below its handle, to facilitate carrying the flask.

A radial gap is formed between the Dewar flask 2 and the inside of the container, and into this gap, adjacent the rim of the container, is pressed a rubber sealing strip 8. As may be seen more clearly in Figure 3, the strip 8 has a substantially wedge-shaped cross-section. The narrower edge of the strip faces downwardly and is bevelled at 9 to assist inSertion of the strip between the Dewar flask 2 and the container 1. At its wider, upper edge, the strip 8 is provided with an integral lateral lip 10 which is directed outwardly and abuts the rim of the container to limit the depth to which strip 8 is inserted into the container and thereby to provide a positive location for the strip.

The strip 8 is a tight fit between the Dewar flask 2 and container 1 and when it is fully inserted at least an upper portion is compressed. The length of the strip is chosen so that it extends completely around the flask and its ends abut, the abutment being indicated by the reference numeral 11 in Figure 2.

The sealing strip 8 effectively seals the space between the flask 2 and the container 1 to prevent liquid running down between them as may tend to occur when liquid is being poured out of the Dewar flask.

The top surface of the strip is downwardly inclined at a shallow angle to the horizontal, about 8" as shown in Figure 3, which serves to direct any liquid falling on to the strip outwardly over the rim of the container 1. The strip 8 also grips the flask 2 to hold it firmly in the container, even when the whole flask is tipped up, such as during emptying. If the strip 8 happens to be cooled to a very low temperature, which may happen if liquid nitrogen or other liquid gas is peing poured from the flask 2, the seal is not broken and nor does the strip relax its grip on the flask 2 so that there is no danger of the flask 2 slipping out of the container 1.

If the flask 2 should happen to be broken or need to be replaced for another reason it can easily and conveniently be remowed from the container once the strip 8 has been pulled out. The strip is simply replaced when the new flask has been located in the protective container 1. As a result replacement of the flask is neither difficult nor time consuming.

One particular form of sealing strip is made of nitrile rubber and is shaped as seen in Figure 3. The height h is 15 mm, the upper width w1 is 4.5 mm and the lower width w is 3.5 mm. The strip is pressed between a Dewar flask and container defining between them a gap about 3.5 mm wide so that the sealing strip, at its upper edge, is compressed by approximately 1 mm.

WHAT WE CLAIM IS: - 1. A vacuum flask comprising a cylindrical, open-topped container, a Dewar flask positioned in the container and protruding through the open top thereof, an annular gap being defined between the rim of the container and the Dewar flask, and a strip of resiliently compressible material having a wedge-shaped cross-section pressed into said annular gap, the wider edge of the strip being uppermost and the strip being compressed between the container and Dewar flask to retain the flask in the container.

2. A vacuum flask according to claim 1, wherein the strip extends around the full circumferential extent of the annular gap.

3. A vacuum flask according to claim 1 or 2, wherein the strip is provided with means for engaging the rim of the container to limit the depth to which the strip is inserted into the container.

4. A vacuum flask according to claim 3, wherein the said means comprises a lateral projection integral with the Strip at the upper, outer edge thereof.

5. A vacuum flask according to any one of claims 1 to 4, wherein the lower, narrow edge of the strip is bevelled at the outer surface thereof to facilitate insertion of the strip between the Dewar flask and container.

6. A vacuum flask according to any one of claims 1 to 5, wherein the strip is made of rubber.

7. A vacuum flask according to any one of the preceding claims wherein the top surface of the strip is downwardly inclined from the inner edge to the outer edge thereof.

8. A vacuum flask according to any one

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. rubber ring 5 which is carried on the underside of the lid. The lid is held on the container by catches 6 fixed to the outside of the container. The catches are of well known construction and co-operates with hooks 7 mounted on the lid. If desired the lip and catches can be omitted (as shown in Figure 2), in which case the vacuum flask will be of the permanently open type commonly used for industrial purposes. The container can, if required be provided with a handle (not shown) from which the vacuum flask is pivotally suspended, not unlike a bucket is suspended below its handle, to facilitate carrying the flask. A radial gap is formed between the Dewar flask 2 and the inside of the container, and into this gap, adjacent the rim of the container, is pressed a rubber sealing strip 8. As may be seen more clearly in Figure 3, the strip 8 has a substantially wedge-shaped cross-section. The narrower edge of the strip faces downwardly and is bevelled at 9 to assist inSertion of the strip between the Dewar flask 2 and the container 1. At its wider, upper edge, the strip 8 is provided with an integral lateral lip 10 which is directed outwardly and abuts the rim of the container to limit the depth to which strip 8 is inserted into the container and thereby to provide a positive location for the strip. The strip 8 is a tight fit between the Dewar flask 2 and container 1 and when it is fully inserted at least an upper portion is compressed. The length of the strip is chosen so that it extends completely around the flask and its ends abut, the abutment being indicated by the reference numeral 11 in Figure 2. The sealing strip 8 effectively seals the space between the flask 2 and the container 1 to prevent liquid running down between them as may tend to occur when liquid is being poured out of the Dewar flask. The top surface of the strip is downwardly inclined at a shallow angle to the horizontal, about 8" as shown in Figure 3, which serves to direct any liquid falling on to the strip outwardly over the rim of the container 1. The strip 8 also grips the flask 2 to hold it firmly in the container, even when the whole flask is tipped up, such as during emptying. If the strip 8 happens to be cooled to a very low temperature, which may happen if liquid nitrogen or other liquid gas is peing poured from the flask 2, the seal is not broken and nor does the strip relax its grip on the flask 2 so that there is no danger of the flask 2 slipping out of the container 1. If the flask 2 should happen to be broken or need to be replaced for another reason it can easily and conveniently be remowed from the container once the strip 8 has been pulled out. The strip is simply replaced when the new flask has been located in the protective container 1. As a result replacement of the flask is neither difficult nor time consuming. One particular form of sealing strip is made of nitrile rubber and is shaped as seen in Figure 3. The height h is 15 mm, the upper width w1 is 4.5 mm and the lower width w is 3.5 mm. The strip is pressed between a Dewar flask and container defining between them a gap about 3.5 mm wide so that the sealing strip, at its upper edge, is compressed by approximately 1 mm. WHAT WE CLAIM IS: -

1. A vacuum flask comprising a cylindrical, open-topped container, a Dewar flask positioned in the container and protruding through the open top thereof, an annular gap being defined between the rim of the container and the Dewar flask, and a strip of resiliently compressible material having a wedge-shaped cross-section pressed into said annular gap, the wider edge of the strip being uppermost and the strip being compressed between the container and Dewar flask to retain the flask in the container.

2. A vacuum flask according to claim 1, wherein the strip extends around the full circumferential extent of the annular gap.

3. A vacuum flask according to claim 1 or 2, wherein the strip is provided with means for engaging the rim of the container to limit the depth to which the strip is inserted into the container.

4. A vacuum flask according to claim 3, wherein the said means comprises a lateral projection integral with the Strip at the upper, outer edge thereof.

5. A vacuum flask according to any one of claims 1 to 4, wherein the lower, narrow edge of the strip is bevelled at the outer surface thereof to facilitate insertion of the strip between the Dewar flask and container.

6. A vacuum flask according to any one of claims 1 to 5, wherein the strip is made of rubber.

7. A vacuum flask according to any one of the preceding claims wherein the top surface of the strip is downwardly inclined from the inner edge to the outer edge thereof.

8. A vacuum flask according to any one

of the preceding claims wherein the strip is substantially as herein described with reference to the drawings.

9. A vacuum flask substantially as herein described with reference to the accompanying drawings.