US3394594A - Protective cover for instruments - Google Patents

Description

July 30, 1968 5, y ET AI- 3,394,594

PROTECTIVE COVER FOR INSTRUMENTS Filed March 28, 1966 INVENTORS Z 8/1 5400 6 P0045) 1g; CZAPL-WCE 2. CAME/V052 a) wwzw AGENT United States Patent 3,394,594 PROTECTIVE COVER FOR INSTRUMENTS Sheldon G. Pooley and Clarence R. Callender, Riverside, Calif., assignors to Irrometer Company, Riverside, Calif., a partnership Filed Mar. 28, 1966, Ser. No. 538,055 Claims. (Cl. 73-431) ABSTRACT OF THE DISCLOSURE A protective, waterproof enclosure for electrical control instruments having a pressure/vacuum gauge. The enclosure is made of rubber-like material and encloses the instrument on all sides. A soft, flexible diaphragm at the back of the enclosure allows the pressure inside to equalize with atmospheric pressure. Rubber covered electrical wires pass through the center of the diaphragm and are sealed thereto. An opening on the front side of the enclosure has a transparent cap through which the instrument face can be seen. An O-ring sealed, removable screw plug on the enclosure provides access to an adjusting shaft for adjustment purposes.

The present invention relates generally to instrumentssuch as pressure or vacuum gauges, and more particularly to a protective enclosure for such instruments, whereby an inexpensive, ordinary instrument can be made waterproof.

There are waterproof instruments on the market but these are, almost without exception, relatively expensive and therefore not suitable for certain applications. One application that requires inexpensive waterproof vacuum gauges is in automatic turf irrigation systems, wherein the irrigation controller is actuated by an electronic sensing system using tensiometers having electrical switching means embodied in the associated vacuum gauges. The tensionmeters, together with their vacuum gauges, are buried in the ground, and are therefore subject to being flooded when the ground is being irrigated or during heavy rains. If the instruments were not waterproof, they would quickly be put out of operation by corrosion and other deleterious effects of moisture.

The primary object of the invention is to provide a new and improved protective enclosure for instruments, which makes any ordinary instrument completely waterproof.

Another object of the invention is to provide a protective enclosure of the class described, which has a flexible diaphragm on one side thereof for equalizing the pressure within the instrument so that it is substantially atmospheric pressure.

A further object of the invention is to provide a protective enclosure for instruments of the class described having electrical control means embodied therein, in which the electric-current-carrying wires pass through the protective enclosure and are sealed with respect thereto. In the preferred form of the invention, the protective enclosure includes a cover made of rubber or synthetic, rubber-like elastomer, and the rubber-covered wires pass through this cover and are vulcanized or fused thereto in a permanently watertight connection.

Another object of the invention is to provide a protective enclosure for instruments of the class described, in which means is provided for making certain adjustments in the instrument without completely removing the protective enclosure therefrom. In one form of instrument, there is an adjustable carrier having a contact which is engaged by the pointer to close a circuit. The said carrier is angularly adjustable with respect to the pointer by means of an adjustment knob on the instrument crystal,

3,394,594 Patented July 30, 1968 "fice and it is desirable to be able to get at the said adjustment knob quickly and easily, to adjust the said carrier so as to move the contact toward or away from the pointer. In the present invention, the said adjustment knob is accessible through an opening in the protective enclosure, and this opening .is closed by a cap having means for sealing the opening to make it watertight.

Still another object of the invention is to provide a protective enclosure for instruments that is inexpensive to manufacture, and quickly and easily installed on the instrument without the use of tools or special equipment of any kind.

These and other objects and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of the preferred embodiment thereof, reference being had to the accompanying drawings, wherein:

FIGURE 1 is a perspective view of an automatic turf irrigation system, showing two tensiometer sensing devices buried in the ground and connected by electric wires to an electronic sensing panel which initiates a controller that turns the water on and off in a predetermined cycle, the said tensiometer sensing devices having vacuum gauges that are enclosed by protective enclosures of the present invention;

FIGURE 2 is an enlarged sectional view through the instrument and protective enclosure, taken at 22 in FIGURE 3; and

FIGURE 3 is an elevational view of the instrument and protective enclosure, as seen from in front.

In FIG. 1 the reference numeral designates each of two fluid-filled tensiometers of the same general type as that shown in Prosser et al. Patent No. 2,878,671. The two teusiometers 10 have tubular bodies 11 which terminate in porous ceramic tips 12, and the ends of the bodies 11 and tips 12 are embedded in the soil at two different levels to obtain moisture readings for the soil at these two depths. Mounted on the other end of the tubular bodies 11 are vacuum gauges -13, incorporating electrical switches (to be described later) which are connected by Wires in a cable 14 to an electronic sensing panel 16.

The sensing panel 16 is operatively connected to a controller 18, which is a programming device that turns the water on and off according to a predetermined cycle of operation, and the controller is initiated by a signal received from the sensing panel. Neither the sensing panel :16 nor the controller 18 forms any part of the present invention, and therefore are not shown or described in detail herein. Suflice to say, the sensing panel 16 is essentially an electronic relay and transformer, which converts the relatively weak 24-volt signal received from the tensiometers to an impulse of suflicient power to operate the controller.

The vacuum gauge 13 comprises a cup-shaped case having a cylindrical side wall 22, and back wall 24. Mounted on the front side of the case is a dial face 26 having a circular array of angularly spaced graduations 28, which are marked by numerals from 10 to 100. Overlying the face 26 is a pointer 30, which is mounted on one end of a shaft 32 extending through a hole in the center of the dial face, the other end of the shaft being connected by the usual linkage to pressure-sensing mechanism (not shown). A circular crystal 34, preferably of transparent plastic, is held in place over the dial face 26 by means of a rim 36.

Pointer is made of brass or other electrically conductive material, and through its linkage with the pressure-sensing mechanism to which it is connected, is electrically grounded to the case 20. The case 20 is connected to a first current-carrying wire 38 by a terminal screw 40, and wire 38 passes through a rubbercovered cable 42 which joins and becomes a part of cable 14. The pointer 30 thus forms the movable contact of the tensiometer-actua'ted switch, which closes the circuit to the sensing panel 16.

The stationary contact of the switch is shown at 44, and comprises a small post mounted on the back side of a carrier 46 at one end thereof, said post extending toward the dial face 26 and across the path of the pointer 30 as the latter turns on its pivot 32. Carrier 46 is a thin strip of brass or copper, the other end of which is fixedly mounted on the inner end of a short adjustment shaft 48, so that it turns with the latter. Shaft 48 passes through a hole in the center of crystal 34 and is rotatable therein. Fixed to the outer end of the shaft 48 is a head 50 having a hexagonal socket formed in its outer face to receive an Allen wrench for adjustment purposes, Contact 44 and its carrier 46 are electrically connected to the circuit of the sensing panel 16 by means of a strip 52 of copper or brass, which is mounted on the underside of the crystal 34. One end of strip 52 has a hole formed therein through which shaft 48 passes. The marginal edges of strip 52 surrounding shaft 48 are formed to bear against the adjacent side of the carrier 46 to make electrical contact therewith. Strip 52 is prevented from turning by means of a rivet 54, which passes through aligned holes in the strip and in the crystal 34. At its other end, strip 52 is connected to a second current-carrying wire 56, which passes through the instrument case and along cables 42 and 14 to the sensing unit 16. Thus, the switch is closed to send an electrical signal to the sensing unit 16 when the pointer 30 passes under the carrier 46 and touches contact 44, and the stationary contact 44 can be adjusted to any point around the face of the dial by turning the adjustment shaft 48, thereby regulating the vacuum pressure level at which the switch is closed.

The protective enclosure of the present invention is designated in its entirety by the reference numeral 60, and comprises a resilient, rubber-like cover 62, and a transparent cover 64 of a rigid plastic. Cover 62 may be made of natural rubber or a synthetic rubber-like elastomer, and is generally cup-shaped so as to surround and enclose the case 20. The cover 62 includes a cylindrical side wall 66, which lies against the outer surface of side wall 22 of the case 20, and a bottom, or back wall 68, which is relatively thin and formed with concentric, circular corrugations, as shown in FIG. 2, so that it constitutes a flexible diaphragm, whereby the pressure within the enclosure 60 is substantially equalized with respect to atmospheric pressure. The rubber-covered cable 42 passes through the center of the back wall 68 and is vulcanized or fused thereto at 70.

The cover 62 has a forwardly facing, annular shoulder 72 formed on the inside thereof closely adjacent the junction of side wall 66 with back wall 68, and the case 20 seats against this shoulder so that the diaphragm 68 is spaced outwardly from the back wall 24 of the case. This provides a space between the diaphragm and the back wall 24, whereby the diaphragm is allowed to move toward the case when atmospheric pressure is slightly greater than the pressure within the enclosure 60. The dead air space between the diaphragm 68 and back wall 24 also provides a certain amount of internal insulation, which minimizes pressure variation within the gauge caused by variations of the ambient temperature. At its front end, the rubber cover 62 is provided with a radially inwardly projecting flange 74, which overlies the crystal-retaining ring 36.

The transparent cover 64 coves the circular opening 76 defined by the inner edge of the flange 74, through which the dial face 26 is exposed to view, and this cover 64 comprises a flat, circular face 78 having a cylindrical flange 80 projecting from the outer edge thereof. Flange 80 fits snugly over the outer cylindrical side wall 66 of rubber cover 62, and its inner surface bears against a number of small, closely-spaced ridges extending circumferentially around the wall 66, which form tiny channels, in which adhesive cement is trapped while cover 64 is being pushed over the front end of cover 62. The adhesive bond is indicated at 82, and forms a water-tight seal between cover members 62 and 64.

Projecting from the outer surface of the face 78 at the center thereof is a cylindrical boss 84 having a screwthreaded aperture 86 in its center, through which the head of adjustment shaft 48, is accessible for adjustment purposes. The aperture 86 is closed by a cap 88 having screw threads 90, which coact with threads 86. Cap 88 has a head, in the form of a radial flange 92, and clamped tightly between flange 92 and the outer end of boss 84 is an O-ring 94, of rubber or like material. When O-ring 94 is compressed between cap 88 and boss 84, the joint between them is tightly sealed, and is completely water-tight.

The mode of operation of the invention is believed to be self-evident from the foregoing description, taken with the drawings. The cover 62 is molded of rubber or rubber-like material, and is fused or vulcanized to the rubber cover of the cable 42, having wires 38 and 56 embedded therein. Cable 42 may be relatively short in length, with suitable means at its outer end for making a water-tight connection with the wires of cable 14. Wires 38 and 56 are connected to the instrument, and the rubber cover 62 is then stretched over the case 20. Adhesive cement is applied to the ridged area 82, and the cover 64 is then pushed onto the front end of the cover 62. The face 78 is now parallel to crystal 34 and is spaced outwardly therefrom a short distance. To insure an effec tive seal, cement may be applied where cover 62 embraces the threaded nipple 96 of the instrument, which is screwed into the body of the tensiometer.

To adjust the position of stationary contact 44, so as to cause the switch to close at a selected vacuum pressure, cap 88 is unscrewed and removed from the cover 64, and an Allen wrench is inserted through the aperture 86 and into the hexagonal socket in head 50. The head 50 is then turned by the wrench until the carrier 46 and its contact 44 are aligned with the selected vacuum pressure graduation 28. Cap 88 is then screwed back into the threaded aperture 86, and is tightened down sufliciently to compress the O-ring 94 between the flange 92 and the end of the boss 84. The instrument is now water-tight and ready for operation.

While we have shown and described in considerable detail what we believe to be the preferred form of our invention, it will be understood by those skilled in the art that this embodiment is merely illustrative of the invention, and that various other forms are contemplated within the scope of the following claims.

We claim:

1. A protective waterproof enclosure for an electrical control instrument having a case, a pressure/vacuum gauge contained therein, a pair of contacts within said instrument, at least one of said contacts being connected to said pressure/ vacuum gauge and being movable thereby toward and away from the other contact, and electrical terminals on said instrument connected to said contacts, said enclosure comprising:

a resilient first cover of rubber-like material surrounding the sides and back of said case and having a soft flexible diaphragm at the rear thereof, whereby the pressure within said enclosure is substantially the same as atmospheric pressure;

a second cover mounted on said first cover and cooperating therewith to enclose said case on the front thereof; and

an electrical cable passing through said diaphragm and sealed with respect thereto, said cable having at least two conductors that are adapted to be attached to said terminals prior to enclosing said case in said first cover.

2. A protective waterproof enclosure as recited in claim 1, wherein said instrument has a rotatable adjustment member on the front side thereof operatively connected to said other contact for adjusting the position of the latter toward or away from said one contact;

said second cover having an opening provided therein directly over said adjustment member;

a cap removably mounted on said second cover to close said opening; and

means for sealing the joint between said cap and said second cover against the entrance of moisture.

3. A protective waterproof enclosure as recited in claim 2, wherein said instrument has a transparent crystal on the front face of said case, and said adjustable member comprises a rotatable shaft passing through said crystal and rotatable therein, said shaft having means on its outer end engageable by an adjustment tool;

said cap being screw-threaded onto said second cover to close said opening; and

said sealing means comprising an O-ring clamped between opposed surfaces on said second cover and said cap when the cap is screwed down tightly.

4. A Waterproof electrical instrument comprising, in

combination:

a case having a pressure/vacuum gauge contained therein;

an electrically conductive pointer connected to said pressure/vacuum gauge and rotatable thereby;

a pair of electrical terminals on the back of said case;

a first conductor wire connecting said pointer to one of said terminals;

a contact supported for movement in an arcuate path concentric with the axis of rotation of said pointer, said contact being engageable by said pointer when the latter reaches a predetermined point;

a second conductor wire connecting said contact to the other of said terminals;

an enclosure surrounding said case and sealed with respect thereto so that said instrument is waterproof, said enclosure comprising a first cover and a second cover;

said first cover being made of rubber-like material and surrounding the sides and back of said case;

the back of said first cover being in the form of a soft, elastic diaphragm, whereby the pressure within said enclosure is substantially the same as atmospheric pressure; and

an electric cable passing through the center of said diaphragm and sealed with respect thereto, said cable having at least two wires which are adapted to be connected to said terminals prior to enclosing said case in said first cover;

said second cover being mounted on said first cover and sealed with respect thereto after said first cover has been placed on said case.

5. A waterproof electrical instrument as in claim 4, wherein said instrument has a rotatable adjustment member connected with said contact, whereby the latter can be shifted along its arcuate path by turning said member;

said second cover being transparent to permit viewing said pointer and said cover having an opening provided therein directly above said adjustment member, through which the latter can be reached with an adjustment tool;

a cap screw-threaded onto said second cover to close said opening; and

means sealing the joint between said cap and said second cover against the entrance of moisture.

References Cited UNITED STATES PATENTS 1,912,436 6/1933 Dashner 200-8 1.8 2,612,132 9/1952 Triplett 116-114 2,773,388 12/ 1956 Prosser 73431 2,878,671 3/1959 Prosser et al 73-73 3,188,434 6/1965 Numayama 200140 DAVID SCHONBERG, Primary Examiner.

DANIEL M. YASICH, Assistant Examiner.

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