Vacuum X-ray envelope

Abstract

An opaque vinyl envelope having facing polished inner surfaces and an open edge into which an intensifier screen and x-ray film are inserted. The other three edges are completely sealed except for a valve at one edge. Reinforcing strips are attached along the open edge. The three sealed edges of the envelope are heat sealed without pressure to eliminate an internal bead and minimize leakage along the bead when the open edge is closed and the envelope evacuated. An insert that has a relatively rough surface or is pourous assures full evacuation.

Description

REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part to co-pending patent application Ser. No. 438,033 filed Jan. 30, 1974 40. 50. Thus, the two polished surfaces become the interior faces of the envelope 10. Where two ten mil sheets are employed, the hold down fixtures 52 provide a hold down space above the surface 50 of exactly twenty mils so that a nil amount of pressure is exerted on the edges 12 and 13 of the envelope sheets. Heat is then applied through the heat conducting L-shaped hold down fixtures 52 so that the edges 12 and 13 are sealed. The portion of the edge 13 to which the valve 30 is attached is sealed separately. The purpose of this arrangement with respect to the carefully dimensioned hold down and sealing fixtures 52 is to assure that there will be no head along the inner edges 12 and 13, or, at least, that there will be no such bead along these edges at the portion of the envelope 10 near the open edge 16. Thus, when the open edge 16 is clamped shut, the sheets will lay very flat along the entire length of the open edge 16 and there will be no bridging due to any bead that may exist along the inner side edges 12, 13 and thus the risk of air leaking into the evacuated cassette along such a bridge is substantially eliminated.

The absence of a bead together with the facing interior polished plastic surfaces creates a leak-proof envelope. The vacuum is held because these two features combine to assure no paths for air leakage.

It is believed that these highly-polished facing surfaces are effective to assure a long-lasting vacuum in the cassette because when forced together during evacuation, they adhere to one another so completely as to seal off the portion of the interior of the cassette between open edge 16 and film from the outside air in a fashion that eliminates all possible air paths.

When the facing surfaces are not highly polished, there is no tendency for them to adhere other than that created by the outside pressure exerted when the vacuum is taken. But, to the extent that there are any miniscule air pockets or air paths between the nonpolished facing surfaces, there is provided a path for air to leak in and once such leakage starts, the entire vacuum is rapidly destroyed.

However, the good sealing quality of the polished surfaces creates the problem that during evacuation local air bubbles are formed. Pockets of air can be encapsulated as the vinyl collapses around a local area. This problem arose over the surface of the film 18 or screen 20 when the folder 21 is not used. Thus a roughened surface or fibrous insert has been found necessary to assure air paths during evacuation that eliminate air bubbles and thus assure the desired complete and even evacuation across the entire surface of the film 18 and screen 20.

The heavy paper folder 21 serves this air path providing function. A fibrous, preferably rough surface, material thus prevents the trapping of air bubbles over the surface of the film and/or screen and thus assures a complete and even texture across the whole surface of the screen and film.

A heavy paper folder 21 is a preferred insert because it provides the additional convenience of a folder in which to hold the film and screen and to keep them in line. It is an aid in inserting the film and screen. However, the folder could be eliminated if the intensifier screen 20 were laminated to a cardboard back and two intensifier screens used on either side of the X-ray film as is common practice. The cardboard back would have the same function of providing air paths across the surface of the screen. Accordingly, it should be understood herein that the term insert is used to refer to two ply arrangement which may be, and preferably is, a single folded separable insert.

In one embodiment a 240 weight white coronado texture paper, supplied by the Milton Paper Company of 100 West 22nd Street, New York, N.Y., was used and found effective.

The two reinforcing strips 22, 23 are important to insure a reasonable life for this reusable envelope 10. These reinforcing strips prevent the deformation of the thin collapsible sheets 10a, 10b near the open edge 12. 16. Any such deformation would result in the sheets not lying perfectly flat against one another when closed and thus would prevent providing air tight seal. The reinforcing strips 22, 23 by preventing deformation, assure that the two sheets will lie perfectly flat against one another at the open edge, when closed, and thus serve to assure the obtaining and maintenance of the vacuum after repeated uses of the envelope 10.

Claims

1. A reuseable envelope for an x-ray cassette having x-ray film and intensifier screen comprising:

first and second collapsible sheets sealed to one another along first, second and third sealed edges forming an envelope having an open edge,

a sealing zone extending across said open edge between said first and second sealed edges,

said sheets having polished facing interior surfaces in said sealing zone,

said interior surfaces in said sealing zone being flush against each other at the line of the seal at said first and second sealed edges, the seal at said first and second sealed edges being beadless in said sealing zone, and

a valve sealed to one of said sealed edges permitting communication between the interior of said envelope and the outside, said valve being positioned away from said sealing zone.

2. The envelope of claim 1 further comprising:

first and second flat insert portions, each of said portions having a surface large enough to substantially cover the surface area of whatever x-ray film and intensifier screen is used,

said insert portions providing air paths across the surface of said insert portions to said valve

said first and second collapsible sheets being large enough to accommodate said insert portions within said envelope in a position removed from said sealing zone.

3. The envelope of claim 1 further comprising:

a spacer element inside said envelope adjacent to the port of said valve and providing a separation between said sheets of said envelope adjacent said valve.

4. The envelope of claim 2 further comprising:

first and second reinforcing strips along the edge respectively of said first and second collapsible sheets at said open edge.

5. The envelope of claim 4 further comprising:

a resilient C-clamp dimensioned to fit along said reinforcing strips.

6. The envelope of claim 1 further comprising:

first and second reinforcing strips along the edge respectively of said first and second collapsible sheets at said open edge.

7. The envelope of claim 6 further comprising:

a spacer element inside said envelope adjacent to the port of said valve and providing a separation between said sheets of said envelope adjacent said valve.

8. The enveope of claim 6 further comprising:

a resilient C-clamp dimensioned to fit along said reinforcing strips.

9. The method of sealing edges of a two collapsible sheet envelope having an open edge to provide a vacuum retaining cassett cassette for x-ray film and intensifier screen contained therein comprising the steps of:

placing an edge of two sheets of collapsible material having facing polished surfaces between and in contact with heat conducting members at substantially nil pressure, and

applying heat to said sheets through said members of seal said edge.

10. The method of claim 9 wherein said sheets are of a thermoplastic polymer.

11. A reuseable envelope for an x-ray cassette having x-ray film and intensifier screen comprising:

first and second collapsible sheets sealed to one another along first, second and third sealed edges forming an envelope having an open edge,

a sealing zone extending across said open edge between said first and second sealed edges,

said sheets having polished facing interior surfaces in said sealing zone,

said interior surfaces in said sealing zone being flush against each other at the line of the seal at said first and second sealed edges, the seal at said first and second sealed edges being beadless in said sealing zone, and

a valve sealed to said envelope, said valve permitting communication between the outside and the interior of said envelope apart from said sealing zone.

12. The envelope of claim 11 further comprising:

first and second flat insert portions, each of said portions having a surface large enough to substantially cover the surface area of whatever x-ray film and intensifier screen is used,

said insert portions providing air paths across the surface of said insert portions to said valve,

said first and second collapsible sheets being large enough to accomodate said insert portions within said envelope in a position removed from said sealing zone.

13. The envelope of claim 11 further comprising:

a spacer element inside said envelope adjacent to the port of said valve and providing a separation between said sheets of said envelope adjacent said valve.

14. The envelope of claim 12 further comprising:

first and second reinforcing strips along the edge respectively of said first and second collapsible sheets of said open edge. 15. The envelope of claim 14 further comprising:

a resilient C-clamp dimensioned to fit along said reinforcing strips.

16. The envelope of claim 11 further comprising:

first and second reinforcing strips along the edge respectively of said first and second collapsible sheets at said open edge. 17. The envelope of claim 16 further comprising:

a spacer element inside said envelope adjacent to the port of said valve and providing a separation between said sheets of said envelope adjacent said valve.

18. The envelope of claim 16 further comprising:

a resilient C-clamp dimensioned to fit along said reinforcing strips.