US3130281A - Pressure responsive switch - Google Patents

Description

April 21, 1964 v. M. JEMISON PRESSURE RESPONSIVE SWITCH 2 Sheets-Sheet 1 Filed Nov. 8, 1960 w w w w W W April 21, 1964 v. M. JEMISON PRESSURE RESPONSIVE SWITCH 2 Sheets-Sheet 2 Filed Nov. 8, 1960 INVENTOR. VOLNEY M. azwsou ATTO EY 'which the switch is responsive, and

United States Patent 3,130,281 PRESSURE RESPONSIVE SWITCH Voiney M. Jamison, Phoenix, Aria, assignor to Thunderlrird Engineering C0,, Phoenix, Ariz., a corporation of Arizona Filed Nov. 8, 1969, Ser. No. 68,074 7 Claims. (Cl. 200-83) The present invention relates to pressure responsive switches. It relates more in particular to a switch which operates in response to static pressure within a liquid hydraulic system for controlling some aspect of such system.

Many types of pressure responsive switches have been produced in the past, but all leave something to be desired either from the standpoint of cost, useful life or reliability. Commonly such switches have employed a diaphragm to seal off the switch housing against entrance of the hydraulic fluid, such as water, being controlled. Simple constructions associated with the use of a diaphragm are frequently subject to leakage, and commonly the leakage is not detected in suflicient time to prevent complete failure. Still another problem with many such switches is an inability to control precisely the pressure within the hydraulic fluid to which the switch is responsive; and in instances where precise control has been possible, costs generally have been sufficiently high to limit applicability of such switches to relatively expensive type installations. Heretofore none of the switches commonly available on the market combined the advantages of low cost, precision control and reliability to such extent that such switches could be used to advantage in systems normally employed in the household.

Accordingly, the principal object of the invention is the provision of an improved pressure responsive switch which combines the features of relatively low cost, such precision operation as may be required and long reliable useful life.

Another object of the invention is the provision of an improved pressure responsive switch adaptedfor use in pressure systems containing aqueous liquids.

Still another object is the provision of improved means for predetermining and controlling the pressure to which the switch is responsive.

Other specific objects and features of the invention will be made apparent from the following detailed description taken with the accompanying drawings, where- FIG. 1 is a perspective view showing one form of the present invention, the figure being to a scale approximately twice actual size; I

FIG. 2 is a central longitudinal sectional view taken on the line 2-2 of FIG. 1; 7

FIG. 3 is a fragmentary sectional view taken on the line 3-3 of FIG. 1;

FIG. 4 is an enlarged perspective view showing the interior of the switch housing as it is produced before assembly of the switch elements therein;

a preferred contion;

FIG. 7 is a further enlarged fragmentary sectional view showing the manner in which the diaphragms'are supported and the means provided for equalizing pressures between them;

FIG. 8 is an enlarged transverse sectional view showing a simplified form of the invention in which only one pair of contacts is employed;

FIGS. 9 and 10 are views of the housing assembly only of a switchwith a single pair of contacts as in FIG. 8, but showing improved means for setting the pressure to to prevent link 36 from rotating around its terminal rivet 3,130,281 Patented Apr. 21, 1964 invention shown in FIGS. 1 through 7 there are three contacts and three terminals so that the same switch may operate on a normally. closed circuit basis or on a normally open circuit basis. This embodiment also shows the use of a coil compression spring for controlling the loading of the switch arm to permit control of the pressure to which the switch is responsive over a relatively wide range. In most actual installations the switch is furnished to be used on either a normally closed circuit or normally open circuit; and it is also frequently furnished pre-set for response to a given pressure. Any such variations in the switch itself are made entirely in the housing assembly,remaining portions of the switchv at all times being identical. The features which permit this selection of elements and simplification of the switch for particular type installations will appear as the description progresses.

Referring further to the drawings, the housing assembly includes a generally cup shaped housing 17 (FIG. 4) made of suitable non-conducting material such as phenolic resin of the type known in the trade as Bakelite. It has an annular bottom terminal'fiange 18 which cooperates with the body 10 as will be described to effect the final assembly. A rivet type terminal 19 has a press fit through a hole in the housing and through an edge projection 21 integral with the housing where it is riveted over to support a switch arm 22 formed of suitable conductive spring material such as beryllium copper or Phosphor bronze. As shown particularly. in FIG. 4, the edge projection 21 has a shallowrecess where the switch arm 22 attaches to positively position such arm and prevent its rotation around the rivet contact 19. The switch arm 22 carries a contact point 23 at its free end. Suitably, also, the center portion of the contact arm 22 is. convoluted to impart improved spring action and also to provide a seat for a phenolic plunger 24 spring pressed downwardly by a coil spring 26, the compression of which may be controlled by a set screw 27. Preferably the plunger 24 is formed of a phenolic plastic and the screw 27 of nylon plastic, although any suitable non-conducting materials may be used.

A link 28 secured in position by a terminal rivet 29 (FIG. 3) lies along the inner top surface of the housing 17. The link 28 is formed of suitable conductive material such as Phosphor bronze and carries a contact 31 in alignment with the contact 23 on the switch arm 22. An

anchoring tab or projection 30 integral with the link 28 lies along the inside surface of the housing 17 and thus 34 from the housing and is riveted to anchor a switch link 36 having a contact point 37 in alignment with the contact point 23 on the switch arm 22. The link 36 also has a tab 35 bent at right angles tothe plane of the link itself'and engages along the side edge of projection 34 32. The links 28 and 36 are thus identical, except that one has its anchoring tab in the plane of the link and one has it turned at right angles. Because of the position of the projection 34, the link 36 is spaced vertically from the link 31 so that the link contacts are on opposite sides of the arm contact. Normally the contact points 23 and 37 are in engagement. The terminal 32, link 36 and contact point 37 are therefore effective when the switch is used in a normally closed circuit.

The body It) is preferably turned from a solid piece of corrosion resistant metal such as brass and has a cup shaped portion 41 and an interiorly and exteriorly threaded shank 42 for attachment of the switch to a pipe, tank or the like for functional communication with the fluid to which it is responsive through an opening 43 extending through the shank 42 into the cup shaped portion 41. The base of the cup shaped portion is provided with an annular slot 44 with an annular shallow area 45 inside the slot 44 and an annular raised portion 46 outside the slot 44 (FIG. 7), the function of which will be referred to hereinbelow. The actuating piston has a relatively wide head 47 against which hydraulic pressure is effective and a relatively smaller diameter switch arm engaging portion 48 connected by a tapered side portion 49 which engages a matching tapered side portion 51 on the spacer 13. The spacer 13 as shown in FIG. 6 has an annular opening 52 (FIG. 6) for the passage of the switch arm engaging portion 43 of the actuating piston and also an exterior annular ring 53 raised from its top flat face, the function of which will also be referred to hereinbelow. It should be noted also that the piston is thicker than the spacer, so that when the piston has been raised by action of hydraulic pressure and the tapered surfaces 49 and 51 are in firm engagement the switch arm engaging portion 48 of the piston will project upwardly above the spacer and lift the switch arm 22.

The parts as shown in FIG. 6 are assembled and sup, ported in a suitable die, the upper edge of the body being crimped over the top of the annular projection 18 of the housing 17 as at 54 in FIG. 2 to complete the assembly. Normally a total pressure of about two tons in an arbor press with a suitable crimping die is effective to produce an assembly in which the diaphragms 14 and 11 are so firmly clamped together as to minimize the possibility of leakage. A hole 56 (FIG. 1) is provided in the cup shaped portion 41 of the body between the two diaphragms. This not only minimizes the possibility of fluid reaching the switch housing if a leak should develop around the diaphragm 11, but it also stabilizes the pressure between the diaphragms and serves as a warning that the switch should be replaced in case leakage should appear.

Pressure responsive switches using a pressure respon sive switch operating member such as a diaphragm and sealing means for preventing the hydraulic fluid from fouling the switch elements have in the past presented several problems. Free movement of the actuating memher and effective seal thereof are important, and in general diaphragm members have served Well for such purposes. In relatively small switches using simple diaphragms, clamping action adequate to seal the diaphragm edges frequently injure them and reduce their effective life. Development of differential pressures also have the effect of making such switches sluggish or inoperative. Such pressures may develop from hydraulic leakage, from release of gases occluded from parts and from other causes.

To seal the diaphragm 11 effectively, it is squeezed between the fiat bottom face of the spacer 13 and the annular surface 45, its edge being crimped on the edge defined by the annular slot 44 and partially foroed down into such slot. The outside edge of the spacer 13 rides on the raised annular surface 46, so that the space between the spacer 13 and annular surface 45 is just sulficient to grip the diaphragm 11 tightly but is not shallow i enough to crush the diaphragm. Similarly, diaphragm 14, the effective sealing is somewhat less important, is squeezed between the bottom edge of flange 18 and the top of spacer 13. The ring 53 holds the flange 13 and spacer slightly apart so that the diaphragm 14 is gripped tightly but not crushed.

As shown particularly in FIG. 7, the side edge of the spacer 13 is slightly tapered to provide a slight circular space 57 between the spacer and the interior annular surface of the cup shaped portion 41 of the body 10. A radially positioned hole 58 in the spacer 13 places this circular space 57 in communication with the center opening 52 of the spacer, and then in communication with the entire space between the two diaphragms. Since the hole 56 in the cup shaped portion is in communication with the circular space 57, the entire space between the two diaphragms is substantially at ambient pressure. Thus the hole 56 not only acts as a bleed hole if hydraulic fluid should seep by diaphragm 11, but, with the remaining structure described has an important pressure equalizing function. The action of the diaphragms and the action of the piston 12 thereby remain substantially uniform during the useful life of the switch.

While the various parts of the switch may be constructed of different materials within the limits of the required specifications regarding conductivity and dielectric strength, phenolic plastic is preferred for both the actuating piston 12 and the spacer 13. Very good results have been obtained using diaphragms of nylon cloth impregnated with buna-N rubber. The contact points are preferably of silver. While the switch housing does not require a pressure seal, it is preferred that it be sealed climatically and to this end the terminals 19, 29 and 33 are preferably made slightly tapered so that when they have a press fit into previously prepared holes drilled in the housing 17 riveting all their ends over to secure in place with the switch arm 22 or one of the links 28 or 36 will effectively seal the holes through the housing. The switch arm 22 and links 28 and 36 may be given a slight plating of gold or otherwise treated to reduce the amount of occluded gases entering the housing in which they are sealed. By carefully dimensioning the nylon spring adjusting screw 27 and using a suitable thread sealout, a climatic seal may also be obtained at this point. The bottom of the housing, of course, is sealed by the diaphragm 14.

The switch shown in FIGS. 1 through 6 has three terminals but is not commonly used with more than two such terminals. The specific switch elements used are selected depending on whether the switch is intended for use on a normally open or normally closed circuit. Switches of the type disclosed herein are normally utilized in relatively large quantities for a given use. If that use is to be with a normally closed circuit, for example, there is no reason why the added cost of providing the second terminal and set of contacts should be incurred. The housing 17 is molded without any holes in its top surface; and to provide only two contacts, all that is necessary is to drill out only two terminal receiving holes and install only the switch arm 22 and the required link 28 or 36.

The pressure to which the switch is responsive may be controlled in part by the switch arm 22 and in part by the spring 26. By leaving out the spring assembly entirely and varying only the thickness of the metal of the switch arm, a variation in pressure to which the switch is respons i v e of between one to six pounds or more pressure is easily possible. When using the spring 26, a variation in pressure from one to one hundred pounds is easily possi ble, and operation at fifty to sixty pounds pressure is easily possible without markedly shortening the useful life of the switch. Since the pressure to which the switch is to be responsive in a given system is usually known and always uniform, for many purposes the entire spring assembly may be left out as shown in FIG. 8, in which case only the switch arm is effective. Under such circumstances with a known relatively low spring loading required for a particular installation, the housing 17 is not drilled at its center and none of the parts comprising the spring assembly is included in the completed switch. The thickness of the switch arm 22 will then determine the pressure at which the switch operates. It has been found that with a preset pressure within the range obtainable by a single spring contact arm, the variation from switch to switch may be controlled well within the operating limits of systems in which the switch is used.

In the switch shown in FIG. 8, I have employed the same reference characters as those shown in the previously described figures, because it is not in effect a modification, but the same switch using only the link 28 and a related parts, including the switch arm 22 pre-set to the desired pressure response and without the spring assembly. The switch shown in FIG. 8 is assembled for use in a normally open circuit.

While utilizing the features of the present invention heretofore described the generally conventional spring pressed follower shown in FIG. 2 may be utilized successfully to control the pressure to which the switch is responsive, I have found that this construction isrelatively costly and at times subject to difficultly controllable variables making effective setting difiicult andcostly. These problems are accentuated when the switch is made in relatively small sizes having, for example, an overall diameter of the order of an inch or less, and an overall vertical dimension of approximately 1% inches. A switch of this relatively small size is extremely desirable and effective for many types of installations. In FIGS. 9 through 11 I illustrate a relatively simple, novel and extremely effective construction by means of which very accurate control of the pressure to which the switch is responsive may be obtained, and such pressure readily and inexpensively pre-set in the switch during the course of its assembly. This is to be contrasted with a situation in which itmay be necessary to re-check the adjustment of the switch after it has been installed within a pressure system in accordance with its intended use.

For convenience of illustration I have shown in FIGS. 9 and 10 only the switch housing assembly, and have employed therein the same reference characters used in the preceding embodiments to identify identical parts. The switch there shown is adapted for use on a normally open circuit, the contacts being closed in response to pressure within the system with which the switch is employed. In FIG. 9 the switch is set to be responsive at zero pressure, that is to say, the contacts 31 and 23 associated with the link 28 and the switch arm 22 respectively being closed. In FIG. 9 the contacts are open, the switch being set for example for 2 to 10 pounds operation depending on the requirements of the system.

In FIG. 11 I SilDW the details of the switch arm 22 and a pressure plate 61 which is adapted to be engaged by a nylon screw 62 threaded through the top face of the housing 17 and through the flat projection 21 to which the switch arm 22 is connected by the rivet-type terminal 19. The follower 6. has a fiat attaching area 63 which sets under the flat portion of the switch arm 22 and is secured in place with the switch arm by the rivet-type contact 19. It also has an offset defining a shoulder 64 and a screw engaging portion 66.

As FIG. 9 clearly shows, the shoulder 64 lies immediately above the arcuate center portion of the switch arm 22 but is out of contact therewith when the screw 62 is adjusted to an upper position. Under these conditions the switch arm 22 through its center curved portion is biased upwardly in the direction of the contact 31 so that the contact 31 is actually engaged by the contact 23. This positioning is illustrative, obviously, as the switch arm may readily be shaped so that in its normal position it will clear the stationary contact and will require a pressure of say one-half pound, one pound or similar desired value which would represent the minimum possible setting to which the switch could be adjusted. When the screw 62 is turned downwardly, however, using for example a small screw driver or other suitable tool, the shoulder 64 rides against one edge of the curved portion of the switch arm nearest the flat mounting portion of the switch arm; The pressure plate 61 may, for example, havelhosphor bronze, beryllium copper or other such spring material (it'does not have to have low conductivity because it does not carry any of the current) so that its overhanging portion may readily be deflected downwardly with the shoulder 64 in contact with the switch, and it willretain whatever setting it is given and will always return to the initial position from which it was originally deflected. Notwithstanding the smallness of the parts, precise controlof the pressure required to return the switch arm to contact closing position can be obtained simply and inexpensively within limits of up to 15 pounds or more using the identical design shown.

It should be understood that any of the features illustrated in the several embodiments except thosemutually replacing each other maybe combined in producing a switch having the requirements to meet a particular specification. A switch utilizing the pressure plate adjustment shown in FIGS. 9 through 11, for example, may be replaced with a switch operated in a normally closed circuit or in a switch employing two sets of contacts such as shown in FIG. 2.

One of the principal advantages of the present invention, in addition to its relative simplicity, versatility and relatively low cost, is its freedonifrom defects such as would shorten its useful life. A switch identical to that shown in FIG. 8 for example was operated for over 10,000,000 cycles and continued to function without failure.

Various modifications of the invention may be made within the scope of the appended claims.

I claim: I

1. A pressure responsive switch comprising a switch housing assembly including a housing member with a bottom annular flange and electrical switch means in the housing, a body member adapted for attachment to a in, a switch actuating piston on the side of the spacer facing the body with a switch operating head projecting through the spacer opening, means between the actuating piston and spacer for limiting movement of the said actuating piston in the direction of the switch assembly, and means clamping together said body and the switch housing assembly to clamp the said diaphragms between the cup shaped bottom portion and spacer, and between the spacer and switch housing respectively.

2. A pressure responsive switch as defined in claim 1 wherein said bottom of the cup shaped member and one face of the spacer are provided with annular diaphragm engaging portions and spacing portions whereby to provide adequate pressure to clamp the diaphragms but not to crush them.

3. A pressure responsive switch comprising a switch housing assembly including a housing member with a bottom annular flange and electrical switch means in the housing, a body member adapted for attachment to a de vice containing flluid under pressure, said body member including a cup shaped portion with bottom and annular side wall, a spacer between said bottom and switch housing assembly, imperforate diaphragms on opposite sides of the spacer, said spacer having a central opening therein, a switchactuating piston on the side of the spacer facing the body with a switch operating head projecting through the spacer opening, means between the actuating piston and spacer for limiting movement of the said actuating piston in the direction of the switch assembly, and

means clamping together said body and the switch housing assembly to clamp the said diaphragms between the cup shaped bottom portion and spacer, and between the spacer and switch housing respectively, said bottom of the cup shaped member and one face of the spacer being provided with annular diaphragm engaging portions and spacing portions whereby to provide adequate pressure to clamp the diaphragms but not to crush them and wherein a bleed hole is provided in the side wall of the cup shaped member between the said diaphragms, whereby to place the space between the diaphragms in communication with ambientatmospheric pressure.

4. A pressure responsive switch as defined in claim 1 wherein said body has an annular slot facing the spacer with an annular interior recessed portion on one side of the slot and an annular exterior raised portion on the other side of the slot, the facing side of the spacer being fiat, whereby said spacer engages said raised portion and the diaphragm is clamped against the recessed portion and edge between same and said annular slot, said spacer having an exterior upper ridge engaging the housing to thereby leave a space between the facing surfaces of the spacer and housing within which the second diaphragm is clamped, whereby the maximum clamping pressure applied to the diaphragms is controlled to thereby firmly clamp did not crush such diaphragms.

5. A pressure responsive switch comprising a switch housing assembly including a housing member with a bottom annular flange and electrical switch means in the housing, a body member adapted for attachment to a device containing fluid under pressure, said body member including a cup shaped portion with bottom and annular side wall, a spacer between said bottom and switch housing assembly, imperforate diaphragms on opposite sides of the spacer, said spacer having a central opening therein, a switch actuating piston on the side of the spacer facing the body with a switch operating head projecting through the spacer opening, and means between the actuating piston and spacer for limiting movement of the said actuating piston in the direction of the switch assembly, said annular side wall of the cup shaped body portion being crimped around the annular flange of the switch housing assembly to clamp the said diaphragms between the cup shaped bottom portion and spacer, and between the spacer and switch housing respectively.

6. A pressure responsive switch comprising a switch housing assembly including a housing member with a bottom annular flange and electrical switch means in the housing, a body member adapted for attachment to a device containing fluid under pressure, said body member including a cup shaped portion with bottom and annular side wall, said cup shaped portion being crimped around said flange to hold the switch housing and body member together, a spacer between said bottom and switch housing assembly, imperforate diaphragms on opposite sides of the spacer, said spacer having a central opening therein, a switch actuating piston on the side of the spacer facing the body with a switch operating head projecting through the spacer opening, and means placing the entire space between the diaphragm in communication with ambient atmosphere.

7. A pressure responsive switch comprising a switch housing assembly including a housing member with a bottom annular flange and electrical switch means in the housing, and means projecting through the housing for adjusting the pressure at which the switch means responds, a body member adapted for attachment to a device containing fluid under pressure, said body member including a cup shaped portion with bottom and annular side wall, a spacer between said bottom and switch housing assembly, imperforate diaphragms on opposite sides of the spacer, said spacer having a central opening therein, a switch actuating piston on the side of the spacer facing the body with a switch operating head projecting through the spacer opening, and means between the actuating piston and spacer for limiting movement of the said actuating piston in the direction of the switch assembly, said annular side wall of the cup shaped body portion being crimped around the annular flange of the switch housing assembly to clamp the said diaphragms between the cup shaped bottom portion and spacer, and between the spacer and switch housing respectively.

References Cited in the file of this patent UNITED STATES PATENTS 1,231,561 Briggs July 3, 1917 2,275,556 Rasmussen Mar. 10, 1942 2,317,271 Higley et al. Apr. 20, 1943 2,741,675 Chase et al. Apr. 10, 1956 FOREIGN PATENTS 620,958 Great Britain Apr. 1, 1949

Claims (1)

1. A PRESSURE RESPONSIVE SWITCH COMPRISING A SWITCH HOUSING ASSEMBLY INCLUDING A HOUSING MEMBER WITH A BOTTOM ANNULAR FLANGE AND ELECTRICAL SWITCH MEANS IN THE HOUSING, A BODY MEMBER ADAPTED FOR ATTACHMENT TO A DEVICE CONTAINING FLUID UNDER PRESSURE, SAID BODY MEMBER INCLUDING A CUP SHAPED PORTION WITH BOTTOM AND ANNULAR SIDE WALL, A SPACER BETWEEN SAID BOTTOM AND SWITCH HOUSING ASSEMBLY, IMPERFORATE DIAPHRAGMS ON OPPOSITE SIDES OF THE SPACER, SAID SPACER HAVING A CENTRAL OPENING THEREIN, A SWITCH ACTUATING PISTON O NTHE SIDE OF THE SPACER FACING THE BODY WITH A SWITCH OPERATING HEAD PROJECTING THROUGH THE SPACER OPENING, MEANS BETWEEN THE ACTUATING PISTON AND SPACER FOR LIMITING MOVEMENT OF THE SAID ACTUATING PISTON IN THE DIRECTION OF THE SWITCH ASSEMBLY, AND MEANS CLAMPING TOGETHER SAID BODY AND THE SWITCH HOUSING ASSEMBLY TO CLAMP THE SAID DIAPHRAGMS BETWEEN THE CUP SHAPED BOTTOM PORTION AND SPACER, AND BETWEEN THE SPACER AND SWITCH HOUSING RESPECTIVELY.

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