US3366271A

US3366271A - Explosion-proof lead-in structure

Info

Publication number: US3366271A
Application number: US462029A
Authority: US
Inventors: Arden T Thompson
Original assignee: Lab Line Instruments Inc
Current assignee: Lab Line Instruments Inc
Priority date: 1965-06-07
Filing date: 1965-06-07
Publication date: 1968-01-30
Anticipated expiration: 1985-01-30

Description

Jan. 30, 1968 THOMPSON 3,366,271

EXPLOS IONPROOF LEAD- IN STRUCTURE Filed Jun 7, 1965 FlG-3- 6 FIG-4.- F|G.5.

26 3| ATTORNEYS.

f INVENTOR. O ,43% ARDEN 'TZTHOMPSON.

United States Patent 3,366,271 EXPLOSION-PROOF LEAD-IN STRUCTURE Arden '1. Thompson, Elmhurst, IlL, assignor to Lab-Line Instruments, Inc., Melrose Park, 11]., a corporation of Delaware Filed June 7, 1965, Ser. No. 462,029 7 Claims. (Cl. 2213-88) This invention relates to explosion-proof lead-in structure, and more particularly to a wall having a pass-age for a lead-in element, the wall and passage such that flame and hot gases resulting from an explosion on one side of the wall will not be communicated to the other side.

The wall of the invention advantageously may be used, for example, as one wall of a housing enclosing the thermostatic control switch for the compressor motor of an electric refrigerator. Such a housing, whether mounted inside or outside of the refrigerator, is subject to infiltration by explosive gases present in the surrounding atmosphere. Electric arcing or sparking incident to switch operation tends to cause explosion of any such gases within the housing, and it therefore is essential to prevent the escape of flame or hot gases to the outside atmosphere, which, in the circumstances, also might be of explosive character.

A thermostatic control switch requires a lead-in element, such as a capillary tube, that extends between the switch and a remote region experiencing the temperature conditions to be sensed. In the case of an electric refrigerator, a capillary tube extends from a sensing region within the refrigerator to the thermostatic switch within the housing, and this tube must extend through the switch housing or box in a sufficiently sealed manner so that an explosion within the housing will not be communicated to the exterior.

The sealing problem solved by this invention is one that heretofore has been solved by complex arrangements requiring specialized apparatus and considerable in the way of labor for installation. In general, these arrangements have proved unsatisfactory for various reasons, one of which is inordinate expense.

One object of the invention, therefore, is to provide explosion-proof lead-in structure that is highly effective and reliable in use.

Another object is to provide explosion-proof lead-in structure that may be constructed and installed easily and quickly at great savings in cost over arrangements previously used.

Other objects, advantages and details of the invention will be apparent as the description proceeds, reference being bad to the accompanying drawing wherein one form of the invention is shown. It will be understood that the description and drawing are illustrative only, and that the scope of the invention is to be measured by the appended claims.

In the drawing:

FIG. 1 is a perspective view of a housing having a wall employing the explosion-proof lead-in structure of the invention.

FIG. 2 is a side elevational view of the housing shown in FIG. 1 with a portion of the explosion-proof lead-in structure shown in phantom for clarity.

FIG. 3 is a fragmentary front elevational view of the housing.

FIG. 4 is a front elevational view of a seal plate forming part of the invention.

FIG. 5 is a rear elevational view of the seal plate shown in FIG. 4.

Referring to the drawing, the explosion-proof lead-in structure of the invention is shown embodied in a housing 6 enclosing, for example, the thermostatic control switch (not shown) for an electric refrigerator, a portion of :an adjacent wall of which is shown at 7. Housing 6 may have one or more laterally extending lugs 8 for mounting the housing on wall 7.

Access to the interior of the illustrated housing 6 for installing and inspecting an inclosed switch is provided by means of a closure disk 9 suitably threaded in an opening in housing wall 10.

The explosion-proof lead-in structure of the invention is incorporated in one of the housing walls, for example, wall 15. As best shown in FIG. 2, wall 15 has an opening 16 for passing a lead-in element, as will be seen. Opening 16 is located more or less centrally of wall 15, but in any event it is spaced a substantial distance from all edges of the wall.

Housing 6 is of such structural strength as to withstand the pressures that may be generated as the result of an internal explosion; such housings are well known in the art. Closure disk 9 and housing wall 10 are so related as to withstand the maximum pressures encountered, and are provided with enough engaging threads to prevent the passage of flame and hot gases.

The exterior surface of housing wall 15 in the region 20 containing opening 16 is substantially planar. Unless the exterior of wall 15 inherently is flat within extremely close tolerances, the wall region 20 surrounding opening 16 is subjected to the action of a milling machine or the like. As shown in FIGS. 1 and 2, wall 15 may be subjected to milling action in region 20 from the front to the rear of the housing, thereby creating :a groove of substantial width and length in the exterior surface of the wall.

In most instances it is desirable that this wall region be planar within tolerances of about plus or minus 0.0015 inch.

An imperforate seal plate 25 is secured to housing wall 15 in the region 20 containing opening 16, the seal plate overlying the opening. The rear surface 26 (FIG. 5) of seal plate 25, like region 29 of wall 15, is substantially planar. This surface, as shown in FIG. 3, bears on region 20 of the wall when seal plate 25 is secured in position. In most cases surface 26 also should be planar within tolerances of about plus or minus 0.0015 inch so that clearance between plate and wall will not exceed 0.0030 inch.

As shown, seal plate 25 is secured to Wall 15 by means of beaded bolts 30 extending through snug openings 31 (FIGS. 35) in the plate and threaded into openings 32 in wall 15. Four bolts 30 are shown, and they are spaced more or less uniformly around opening 16 in the wall.

Abutting

surfaces

20 and 26 of wall 15 and plate 25 have registering semi-circular grooves leading from one edge of plate 25 to opening 16. Thus, wall 15 has semicircular groove 35 which, as shown, extends from opening 16 to the wall edge, and plate 25 has registering semicircular groove 36.

Semi-circular grooves

35 and 36 best are formed in wall 15 and plate 25 when the latter is secured in place on the wall. At that time, it is a simple matter to drill the two grooves at once, the axis of the drill directed in the hearing plane, thus forming a passage having a circular cross section.

A lead-in element 40 (FIG. 1), such as a capillary tube, lies in the registering

grooves

35 and 36 and extends from the outside to the inside of housing 6 through wall opening 16. For necessary effective explosion-proof sealing the diameter of capillary tube 40 is about equal to the diameter of the passage formed by

grooves

35 and 36, and in any event the clearance should not exceed about 0.0030 inch.

In those instances where the lead-in element, such as capillary tube 40, cannot tolerate appreciable deformation, semi-circular groove 35 in wall 15 extends somewhat beyond the edge of overlying seal plate 25. Such an extension of groove 35 is shown at 42 in FIGS. 2 and 3. Similarly, semi-circular groove 36 in the bearing surface of plate 25 extends somewhat beyond the margin of opening 16 in the wall. Such an extension of groove 36 is shown at 43 in FIG. 5.

Seal plate 25 usually is mounted more or less centrally over opening 16 in wall 15. It has been found that the minimum distance plate 25 extends beyond the margin of the opening is about 0.500 inch to insure desired results.

lthough seal plate 25 may have various shapes, the illustrated seal plate of rectangular shape has been found particularly satisfactory. With a plate of such shape, semicircular groove 36 therein is generally parallel to the longer plate edges.

From the above description it is thought that the construction and advantages of this invention will be readily apparent to those skilled in the art. Various changes in detail may be made without departing from the spirit or losing the advantages of the invention.

Having thus described the invention, what is claimed as new and desired to secure by Letters Patent is:

1. Explosion-proof lead-in structure comprising:

a housing wall having an opening therein, said wall constituting one Wall of a sealed switch housing subject to infiltration by explosive gases and subsequent internal explosion, a surface of said wall in the region containing said opening substantially planar;

an imperforate seal plate secured to said surface of said wall in the region containing said opening and overlying said opening, the surface of said plate bearing on said wall substantially planar;

the abutting surfaces of said wall and said plate in view of the lengths thereof being planar within tolerances which provide a seal between said surfaces preventing passage of flame and hot gases from the inside to the outside of the housing following an internal explosion therein;

the abutting surfaces of said wall and plate having registering semi-circular grooves therein leading from one edge of said plate to said opening; and

a tubular lead-in element of circular cross section having a portion extending through said registering grooves and an end portion extending thru said opening from one side of said wall to the other, the diameter of the passage formed by said grooves about equal to the diameter of said lead-in element, the maximum clearance between the walls of said passage and said tubular lead-in element in view of the lengths thereof being less than an amount permitting passage of flame and hot gases from the inside to the outside of the housing following an internal explosiOn.

2. The combination of claim 1 wherein said lead-in element is a capillary tube.

3. The combination of claim 1 wherein the groove in said wall extends beyond the adjacent edge of said seal plate and the groove in said plate extends beyond the margin of the opening.

4. The combination of claim 1 wherein said seal plate is rectangular, and the groove therein is generally parallel to the longer plate edges.

5. The combination of claim 1 wherein said seal plate is located generally centrally over the opening in said wall.

6. The combination of claim 1 wherein the bearing surfaces of said Wall and said plate are planar within tolerances of about plus or minus 0.0015 inch.

7. The combination of claim 6 wherein the minimum distance said plate extends beyond the margin of the opening in said wall is about 0.500 inch.

References Cited UNITED STATES PATENTS 1,741,823 12/1929 Burg 2s5194 1,786,146 12/1930 Bucklein 2s5 1s9 x 2,939,022 5/1960 Groutage 17467 x CARL W. TCMLIN, Primary Examiner.

EDWARD C. ALLEN, Examiner.

A. V. KUNDRAT, Assistant Examiner.

Claims

1. EXPLOSION-PROOF LEAD-IN STRUCTURE COMPRISING: A HOUSING WALL HAVING AN OPENING THEREIN, SAID WALL CONSTITUTING ONE WALL OF A SEALED SWITCH HOUSING SUBJECT TO INFILTRATION BY EXPLOSIVE GASES AND SUBSEQUENT INTERNAL EXPLOSION, A SURFACE OF SAID WALL IN THE REGION CONTAINING SAID OPENING SUBSTANTIALLY PLANAR; AN IMPERFORATE SEAL PLATE SECURED TO SAID SURFACE OF SAID WALL IN THE REGION CONTAINING SAID OPENING AND OVERLYING SAID OPENING, THE SURFACE OF SAID PLATE BEARING ON SAID WALL SUBSTANTIALLY PLANAR; THE ABUTTING SURFACES OF SAID WALL AND SAID PLATE IN VIEW OF THE LENGTHS THEREOF BEING PLANAR WITHIN TOLERANCES WHICH PROVIDE A SEAL BETWEEN SAID SURFACES PREVENTING PASSAGE OF FLAME AND HOT GASES FROM THE INSIDE TO THE OUTSIDE OF THE HOUSING FOLLOWING AN INTERNAL EXPLOSION THEREIN; THE ABUTTING SURFACES OF SAID WALL AND PLATE HAVING REGISTERING SEMI-CIRCULAR GROOVES THEREIN LEADING FROM ONE EDGE OF SAID PLATE TO SAID OPENING; AND A TUBULAR LEAD-IN ELEMENT OF CIRCULAR CROSS SECTION HAVING A PORTION EXTENDING THROUGH SAID REGISTERING GROOVES AND AN END PORTION EXTENDING THRU SAID OPENING FROM ONE SIDE OF SAID WALL TO THE OTHER, THE DIAMETER OF THE PASSAGE FORMED BY SAID GROOVES ABOUT EQUAL TO THE DIAMETER OF SAID LEAD-IN ELEMENT, THE MAXIMUM CLEARANCE BETWEEN THE WALLS OF SAID PASSAGE AND SAID TUBULAR LEAD-IN ELEMENT IN VIEW OF THE LENGTHS THEREOF BEING LESS THAN AN AMOUNT PERMITTING PASSAGE OF FLAME AND HOT GASES FROM THE INSIDE TO THE OUTSIDE OF THE HOUSING FOLLOWING AN INTERNAL EXPLOSION.