US3706864A

US3706864A - Depth sensing switch with tubular housing having a diaphragm encompassing a portion of said housing

Info

Publication number: US3706864A
Application number: US153269A
Authority: US
Inventors: Ralph S Gamble
Original assignee: Simmonds Precision Products Inc
Current assignee: Simmonds Precision Products Inc
Priority date: 1971-06-15
Filing date: 1971-06-15
Publication date: 1972-12-19
Anticipated expiration: 1989-12-19

Abstract

A depth sensing device has an extensible resilient switch contact, contraposed behind a diaphragm, said contact having the form of a helical spring with both ends fixed and having its axis parallel to the surface of the diaphragm; said contact further flexes inwardly and establishes contact with a fixed contact when liquid pressure deflects the diaphragm. The diaphragm is formed by a flexible sheath that encompasses a portion of the tubular housing that houses the switch contacts, thereby sealing the contacts from the environment.

Description

United States Patent Gamble 51 Dec. 19, 1972 [54] DEPTH. SENSING SWITCH WITH 2,750,480 6/1956 Freeman ..200/l68 G UB LAR HO ING HAVING A 1 AIPHR AGM EIECOMPASSING A FOREIGN PATENTS 0R APPLICATIONS PORTION OF SAID HOUSING 1 323,532 $1923 great Britain V ,61 l 19 rance 83 N [721 Invenm Ralph Gamble Chester 829,965 3/1960 Great Britain ..200/l66 BA 73 A si nee: Simmonds Precision Produ ts Inc. 1 s g Tatrytown c Primary Examiner-Robert K. Schaefer Assistant Examiner-Robert A. Vanderhye 1 Filed; J 1971 Attorney-Edwin E. Greigg i 69 [21] APP! 153: [57] ABSTRACT 1 i A depth sensing device has an extensible resilient "200/83 200/166 g switch contact, contraposed behind a diaphragm, said 7 [58] F d 83 R 83 B contact having the form of a helical spring with both C 0 re 2O0/83N 1 BA ends fixed and having its axis parallel to the surface of the diaphragm; said contact further flexes inwardly and establishes contact with a fixed contact when [56] References Cited liquid pressure deflects the diaphragm. The diaphragm UNITED STATES PATENTS is formed by a flexible sheath that encompasses a portion of the tubular housing that houses the switch con- 3,453,962 7/1969 Strader ..200/83 N X tacts, thereby sealing the contacts from the environ- 2,l64,82l 7/1939 Katcher m 2,613,294 10/1952 McNea 2,902,668 9/1959 Savit ..200/83 W X 5 Claims, 5 Drawing Figures PATENTED DEC 19 I972 FIG. I

5L F44 2 2 4 f0 INVENTOF RALPH S4 GAM LE ATTORNEYS DEPTH SENSING SWITCH WITH TUBULAR The presentinvention relates to depth sensing sensitive switches, and more particularly, tothose types of switches in which adiaphragm is deflected inwardly causing a displacement which forces a movable contact into contact with astationary contact.

I-Ieretofore, pressure diaphragm switches responding to liquid or fluid pressure have been designed in such a manner that the diaphragm is deflected in an axial direction'with the perimeter of said diaphragm being rigidly disposed in a plane normal to the axis of displacement. In this type of diaphragm switch, the diaphragm is usually of .thin flexible metal andmay be covered with a fluid-tight material such as rubber or a plastic. The diaphragm usually bears against a contact arm disposed behind the diaphragm, the arm being mounted resiliently so that as the diaphragm deflects, it

to damage if it comes in contact with sharp or solid materials, and also, it is susceptible to being stretched by pressures above that for which the switch may have been designed. Further, the switch diaphragm must be subjected to substantially uniform, pressures or pres sures near its center to cause actuation and toprevent localized stresses from buckling or destroying the diaphragm as well as the contact arm beneath the diaphragm. The switch, which is to be described later herein, is of such a design that it may be used with fluids which include solid materials, without being susceptible to damage from such materials, and may be actuated by localized pressures, as well as uniform pressures, which may occur with'the sensing of such materials.

In view of the foregoing, it is a principal object of this invention to provide a pressure-sensitive switch for fluids which is insensitive to the abusive effects of solids disposedwithin the fluids, and which is otherwise sturdy and strong.

It is a further object of this invention to provide a pressure-sensitive switch having a resilient movable contact which cannot be damaged by lateral forces and motions of the diaphragm, which are not along the axis of the contact points.

It is still a further object of this invention to provide a pressure switch which is inexpensive and easy to manufacture.

r 2 FIG. 3 shows another vertical cross-sectional view in which is included a support for the movable contact;

FIG. 4 shows another switch utilizing a round flexible diaphragm; and

' FIG. 5 is a fragmentary vertical cross-sectional view diameter of the'tube, and its length 13 being substantiallygreater than'its width. Mounted rigidly to the in-.

.ternal wall 14 of the plastic tube by

screws

16 and 17 or other means, is an extensible, movable metal contact meanslS which may take the form of an extensible spring, its axis being longitudinai of the cylinder described by the internal surface of the tube and midway between the longitudinal edges of aperture 11, so

' that the contact is freely supported, adjacent to both ends of the aperture and located within and behind said aperture.

As best shown in FIG. 2, a curved stationary contact 18, supported withinthe plastic tube 10 by

suitable means

19 and 20, is arranged to extend inwardly toward, but not to touch, the movable contact 15, e.g., when in an inoperative condition as shown in the figure. The stationary contact 18 has some degree of flexibility by virtue of its being a thin piece of metal, but is essentially to be considered rigid.

Attached to the lowerend of plastic tube 10 is tube cap 21 which is affixed by any suitable waterproof means such as cement; alternatively, the cap may be threadedly secured or clamped and provided with a suitable seal. The upper end of plastic tube 10 is covered by plastic pipe plug means 22, which has been bored to receive a plastic tube and is affixed thereto in any waterproof manner, such as described relative to tube cap 21. The plastic pipe plug means 22 is further provided with a bore to allow

conductor wires

23 and 24 to pass therethrough with the conductor being suitably sealed by a seal means indicated at 25.

The conductor wire 23 is attached at point 16 while conductor wire 24 is affixed at point l9,the upper ends of each wire arranged to be suitably connected to the power supply means and indicating means, neither of It is yet another object of this invention to provide an additional support surface for the movable contact.

The invention will be better understood and further objects and advantages will become more apparent from a reading of the following specification, taken in conjunction with the drawing in which:

which is shown. v

The flexible boot means 26 is stretched over the plastic tube 10 in such a manner that it circumferentially encompasses the tube in the area of the longitudinal aperture 11 and thereby effectively seals the entire area, by surface contact around the aperture, to prevent fluids from gaining access to the contacts when the switch is immersed in a liquid. It is evident that the switch is designed to be placed into the top of a fluid tank with plastic tube 10 extending downwardly to any desired length, such as indicated at 27, to the level at which fluid pressure is to be sensed. When said fluid pressure is of sufficient force to urge the flexible boot 26 into aperture 11 into contact with movable contact 15, said contact will touch stationary contact 18, and a signal will be transmitted through

wires

23 and 24 to an indicator (not shown).

FIG. 3 illustrates an additional embodimentof this invention, showing support surface 28 added to the construction of FIG. 2. Plastic rod 29 is closely fitted to the inner diameter of plastic tube 10, suitably slotted to receive stationary contact 18, and oppositely dished to the approximate shape that boot 26'will assume when subjected to fluid pressure. The rod 29 is suitably slotted to receive the ends of movable contact 15, and

stationary contact 18, which is affixed to rod 29 instead of plastic tube in this embodiment.

1 Rod 29 is'assembled with stationary contact 18 held by

screws

19 and 20 to rod 29, screw 19 also being arranged to hold the lug end of wire 24 in electrical contact with contact 18, and movable contact is assembledf in its proper position and affixed to rod 29 by

screws

16 and 17 which extend through plastic tube 10 holding the assembly in place, including the electrical connection of the lug end of wire 23 to contact 15 by screw 16. The flexible boot 26 and the end caps and seals are assembled as hereinbefore described in connection with FIG. 1.

It will be now clear to those skilled in the art that sur- 2 face 28 hasbeen added to give support to the flexible diaphragm after contact between movable contact 15 and stationary contact 18 has been made. Once the contacts are closed, there is no requirement for the "diaphragm to deflect and farther; however, with a further increase in fluid pressure and no support, the flexible boot 26 will be forced farther into the aperture I ll inplastictube 10 causing stretching and high localized stresses to develop in the boot 26 at the edges of i said aperture. By the addition of the suitably shaped support surface 28, the flexible, boot will deflect only until-it is held inintimate contact with this support surface; at that time fluid pressure will be supported both by the support surface and by the compressive strength of the boot material, which is considerably greater than its strength as a membrane, allowing the switch to be used at great pressures without the damagewhich could otherwise be sustained.

,.screws 36 and 37. The coiled movable contact means 15 is afiixed by both ends to case 30 by means of

screws

38 and 39 which enter suitable threaded recesses which have been provided into the edge of case 30 in diametrically opposed positions. Diaphragm 40 is made of flexible non-metallic material and is held in place over v the edge of case 30 by clamping ring 41, which is suitably screw-threaded and attached to case 30. In this switch the diaphragm also acts as a seal between the case 30 and the clamping ring 41 A wire which enters perforation 43 in the case 30 is secured as at 36 and the wire 44, which also extends through the perforation, is. attached at 38. The point of entry of the

wires

42 and 44, into the casing is later suitably sealed in any convenient manner.

. The switch means and its case 30 are supported'by' means 45 which can be madeof any lengthto support the switch means at any required depth position within abodyoffluid.

A still further embodiment of this invention is shown in FIG. 5, wherein the carrier means forithe switch is not provided with the aperture in the sidewall as previously explained, but instead has a smooth uninterrupted exterior as shown and the'c'ontacts are suitably positioned in the end wall, as shown. In this concept the plastic pipe is formed with an annular'recess into which is frictionally and tightly received theinsulation member 51, the latter forming a support for an adjustable contact member 52 that is threadedly secured therein, as well as serving as a support for a flexible contact 53 which is secured thereto by means 54 The perimeter of the wall is provided with a leak-proof cement or other adhesive and thereafter the flexible cupshaped diaphragm 56 is secured thereto completely encompassing the operative elements; It will be apparent that the cup-shaped diaphragm can be retained to the tubular body also by a clamping ring member.

It will-be evident to those skilled in the art that any number of switches may be supported within a body of fluid to sense pressures at various points within the body of fluid. Also, it is'to be understood that the actuation pressure is a function vof the tension in the movable coiled contact, spacing between the contacts, and. the boot thickness which can be adjusted during design or at assembly or, by adding suitable known means, may be made adjustable after assembly.

It will be also recognized that the embodiments shown encompass only a few of those which can be devised using the basic principles taught in this disclosure and that other physical changes .may be made therein which do notdepart-from the spirit of this invention.

What is claimed is: r

1. A fluid-operated switch comprising a tubular plastic casing provided at its upper end with plug means capable of supporting the switch in a receptacle, electrical lead means extending'axially through said plug means and terminating in a pair'of spaced terminals insulatively mounted within said tubular plastic casing and having their inner ends exposed to the interior, of the casing, means defining an opening in said plastic tubular means, a first metallic spring member in said casing associated with one of said spaced terminals and arranged for flexure and asecond relatively rigid member associated with another of said spaced.terminals with each of said members being in proximity to themeans defining said opening, a flexible sheath-like diaphragm encompassing a portion of said tubular plastic casing and sealing the contacts therewithin, said flexible sheath being in close proximity to the first metallic spring member and bowing said spring member against said rigid member when pressure is exerted against said diaphragm. I

2. A fluid-operated switch as claimed in claim 1, wherein the means defining said opening in said tubular plastic casing extends longitudinally of said casing.

3. A fluid-operated switch as claimed in claim 1, wherein the means defining said opening in said tubular plastic casing is disposed at the terminal end thereof.

4. A fluidwperated switch as claimed in claim 1, element adapted to support the relatively rigid wherein the metallic spring member consists of a coil m r, ai plasti rod further including a concave spring. surface approximating the curvature assumed by the 5 A fl id p t d Switch as claimed in claim 1, flexible sheath when pressure is applied thereagainst. wherein the plastic tubular casing includes a plastic rod 5

Claims

1. A fluid-operated switch comprising a tubular plastic casing provided at its upper end with plug means capable of supporting the switch in a receptacle, electrical lead means extending axially through said plug means and terminating in a pair of spaced terminals insulatively mounted within said tubular plastic casing and having their inner ends exposed to the interior of the casing, means defining an opening in said plastic tubular means, a first metallic spring member in said casing associated with one of said spaced terminals and arranged for flexure and a second relatively rigid member associated with another of said spaced terminals with each of said members being in proximity to the means defining said opening, a flexible sheath-like diaphragm encompassing a portion of said tubular plastic casing and sealing the contacts therewithin, said flexible sheath being in close proximity to the first metallic spring member and bowing said spring member against said rigid member when pressure is exerted against said diaphragm.

4. A fluid-operated switch as claimed in claim 1, wherein the metallic spring member consists of a coil spring.

5. A fluid-operated switch as claimed in claim 1, wherein the plastic tubular casing includes a plastic rod element adapted to support the relatively rigid member, said plastic rod further including a concave surface approximating the curvature assumed by the flexible sheath when pressure is applied thereagainst.