# Patent

## Title
Variable differential adjustor

## Abstract

A variable differential adjustor for a fluid pressure-actuated switch, with the fluid, in the preferred form of the invention, being air. The restrictor has a restrictor housing having a passage through which a pressure source has a portion which passes on its way to a pressure-actuated switch. A restrictor is provided for engaging the portion of the pressure source passing through the restrictor housing and is adjustable to variably alter fluid flow through the pressure source portion. The restrictor comprises a screw-like plug in the pressure source portion which is acted upon by a tube throttle to variably alter the passageway past the plug.

## Background
BACKGROUND OF THE INVENTION
This invention relates to fluid control, and in particular to a variable differential adjustor for a fluid pressure-actuated switch, with the fluid, in the preferred form, being air.
In dwellings and other structures using sump pumps to drain subterranean building footings and avoid ingress of water into the structure, it is important that the sump pump be actuated when water removal limits occur. Thus, sump pumps have switches that are activated by many different types of actuation devices, such as floats, pressure pads and pressure tubes. It is the latter type of structure that is utilized with the invention of the present application.
Pressure tubes typically extend into a sump pit or other water collection area, and as water rises in the sump pit, pressure within the tube increases until a pressure-actuated switch is closed, thus activating the sump pump. Once the water level is reduced below a certain level by the sump pump, the pressure-actuated switch is deactivated, and pumping ceases. To control the level at which pumping begins, typically the tube is repositioned up or down, which then translates into a higher or lower water level which commences actuation of the sump pump. If repositioning of the pressure tube is impossible or inconvenient, then the only manner in which to change the actuation of a pressure-actuated switch would be to restrict air pressure to the switch, effectively delaying actuation or deactivation of the switch.
One form of such a delay is disclosed in U.S. Pat. No. 7,084,363, the disclosure of which is incorporated herein by reference. In the device of the '363 patent, a restrictor is provided having a restrictor housing with a fluid passage in which a restrictor plug, typically a set screw, is engaged. By judicious adjustment of the position of the set screw, fluid flow to and from the pressure the pressure-actuated switch is controlled, controlling when the switch is activated to control activation and deactivation of the sump pump.
SUMMARY OF THE INVENTION
The invention relates to a variable differential adjustor for a fluid pressure-actuated switch, comprising a restrictor housing having a passage therethrough. A pressure source has a portion passing through the passage and it is connected to the pressure-actuated switch for directing fluid to and from the pressure-actuated switch. A restrictor is provided for engaging the pressure source portion, with the restrictor being adjustable to variably alter fluid flow through the pressure source portion.
In accordance with the preferred form of the invention, the pressure source portion comprises a flexible tube having an internal bore, and the restrictor includes an element located in the bore and a tube throttle in the restrictor housing external the tube and proximate the element. The element preferably comprises a plug engaged in the bore, the plug having at least one external fluid path. The plug, in the disclosed version of the invention, comprises a screw and the external fluid path comprises a helical thread in the screw. The bore in the tube is smooth and the screw is engaged with the bore with threaded peaks. The path thus comprises a helical fluid pathway between the screw and the bore.
The tube throttle comprises a pair of rigid half cylinders in the passage which sandwich the tube therebetween. A compressor member urges the half cylinders together. Preferably the compressor member comprises an adjustable screw threadedly engaged in the restrictor housing and bearing against one of the half cylinders.



BRIEF DESCRIPTION OF THE DRAWINGS
The invention is described in greater detail in the following description of examples embodying the best mode of the invention, taken in conjunction with the drawing figures, in which:
FIG. 1 is an elevational view of a pressure-actuated switch connected to a pressure tube, with the variable differential adjustor of the invention interposed between the pressure tube and the pressure-actuated switch;
FIG. 2 is an enlarged view of the variable differential adjustor, in cross section through the hollow tubing used; and
FIG. 3 is a cross sectional view taken along lines 3-3 of FIG. 2, showing the elements of the variable differential adjustor.



DESCRIPTION OF EXAMPLES EMBODYING THE BEST MODE OF THE INVENTION
FIG. 1 illustrates a typical arrangement for activating a fluid-actuated switch 10, which, in turn, activates a sump pump or similar device (not illustrated). The pressure-actuated switch may be a conventional switch well known to those skilled in the art. Air, in the preferred form of the invention, is the fluid that is used for switch actuation.
A pressure tube 12 extends to the sump pit or other water collection area, and as the level of the water 14 rises or falls, air pressure within the pressure tube 12 changes commensurately. That pressure is communicated to the pressure-actuated switch by means of hollow tubing 16.
To control transmission of fluid pressure from the pressure tube 12 to the switch 10, a variable differential adjustor 20 according to the invention is installed on the tubing 16. As best illustrated in FIGS. 2 and 3, the variable differential adjustor 20 comprises two basic elements, a restrictor housing 22 and a restrictor, described in greater detail below, which is adjustable to variably alter fluid flow through the restrictor housing.
The tubing 16 includes a pressure source portion which comprises a tube 24, having an internal bore 26, which passes through the restrictor housing 22. The restrictor includes an element in the form of a plug 28 engaged in the bore, the plug 28 having at least one external fluid path between the plug and the bore 26. The plug 28 preferably comprises a screw with its external fluid path comprising a helical thread 30 in the screw. The screw forming the plug 28 can be conventional, and has thread peaks engaging the bore 26, leaving a helical fluid passage between the screw and the bore 26. The helical fluid passage thus becomes a restricted passage to control pressure transmission through the variable differential adjustor 20.
The restrictor further comprises a tube throttle external the tube 24 and proximate the plug 28, as illustrated in FIGS. 2 and 3. The tube throttle includes a pair of rigid, half cylinders 32 and 34 in the passage 18, which sandwich the tube 24 therebetween. A compressor member, in the form of an adjustable screw 36, urges the half cylinders 32 and 34 together. The adjustable screw 36 is threadedly engaged in a bore 38 in the restrictor housing 22, and bears against the half cylinder 32.
The tube 24 is preferably made of a soft material, such as rubber or plastic, while the half cylinders 32 and 34 are preferably made of metal. Thus, by judicious adjustment of the screw 36, the tube 24 is squeezed between the half cylinders 32 and 34. This, when squeezing force is applied, forces the flexible material of the tube 24 into the threads 30, effectively decreasing the size of the passageway for fluid through the variable differential adjustor 20. That, then, increases the amount of time until effective pressure is experienced at the switch 10 to activate the switch. Conversely, when the screw 36 is adjusted to release the squeezing pressure, exactly the opposite occurs. Thus, by the adjustment of the screw 36, the build-up or reduction of pressure in the upper portion of the tubing 16 to the pressure actuated switch 10 is controlled. That, then, can change the level of the water 14 at which the pressure-actuated switch 10 is activated and also the level at which the pressure-actuated switch is deactivated. To use the example in incorporated U.S. Pat. No. 7,084,363, if a four-inch difference in the water level 14 would normally be the on and off positions of the switch 10 without utilization of the variable differential adjustor 20, with installation of the variable differential adjustor 20, that can be changed dramatically, depending on how much force is exerted by the adjustable screw 36 to the half cylinders 32 and 34. The greater the force, the slower the pressure builds in the upper portion of the tubing 16 (and, conversely, diminishes as the water level drops), thus quite variably changing the effective on and off water levels in a sump pit or other water collection area being monitored.
It will be evident that the invention can take different forms and function in the same manner. As an example, although the plug 28 is shown and described as an element having helical threads 30, the plug can be provided with one or more longitudinal grooves rather than helical grooves. Also, although a pair of half cylinders 32 and 34 has been illustrated, other similar squeezing elements can be employed, so long as the tube 24 can be manipulated to increase or decrease the effective size of the fluid passageway through the variable differential adjustor 20.
Various changes can be made to the invention without departing from the spirit thereof or scope of the following claims.

## Claims

1. A variable differential adjustor for a fluid pressure-actuated switch, comprising
a. a restrictor housing having a passage therethrough,
b. a pressure source having a portion passing through said passage and connected to said pressure-actuated switch for directing fluid to and from said pressure-actuated switch, and
c. a restrictor for engaging said pressure source portion, said restrictor being adjustable to variably alter fluid flow through said pressure source portion.

2. The variable differential adjustor according to claim 1, in which said pressure source portion comprises a flexible tube having an internal bore, and said restrictor includes an element located in said bore and a tube throttle in said restrictor housing external said tube and proximate said element.

3. The variable differential adjustor according to claim 2, in which said element comprises a plug engaged in said bore, said plug having at least one external fluid path.

4. The variable differential adjustor according to claim 3, in which said plug comprises a screw and said external fluid path comprises a helical thread in said screw.

5. The variable differential adjustor according to claim 4, in which said bore is smooth and said screw is engaged with said bore with threaded peaks, said path comprising a helical fluid pathway between said screw and said bore.

6. The variable differential adjustor according to claim 2, in which said tube throttle includes a pair of rigid half cylinders in said passage and sandwiching said tube therebetween, and a compressor member urging said half cylinders together.

7. The variable differential adjustor according to claim 6, in which said compressor member comprises an adjustable screw threaded engaged in said restrictor housing and bearing against one of said half cylinders.

8. A variable differential adjustor for a fluid pressure-actuated switch, comprising
a. a restrictor housing having a passage therethrough,
b. a flexible tube having an internal bore and passing through said passage, said tube being connected to said pressure-actuated switch for directing fluid to and from said pressure-actuated switch, and
c. a restrictor having a plug engaged in said bore and located in said passage, said plug having at least one external fluid path.

9. The variable differential adjustor according to claim 8, in which said plug comprises a screw and said external fluid path comprises a helical thread in said screw.

10. The variable differential adjustor according to claim 9, in which said bore is smooth and said screw is engaged with said bore with threaded peaks, said path comprising a helical fluid pathway between said screw and said bore.

11. The variable differential adjustor according to claim 8, in which said restrictor includes a tube throttle external said tube and proximate said plug.

12. The variable differential adjustor according to claim 11, in which said tube throttle includes a pair of rigid half cylinders in said passage and sandwiching said tube therebetween, and a compressor member urging said half cylinders together.

13. The variable differential adjustor according to claim 12, in which said compressor member comprises an adjustable screw threaded engaged in said restrictor housing and bearing against one of said half cylinders.

14. A variable differential adjustor for a fluid pressure-actuated switch, comprising
a. a restrictor housing having a passage therethrough,
b. a flexible tube having an internal bore and passing through said passage, said tube being connected to said pressure-actuated switch for directing fluid to and from said pressure-actuated switch, and
c. a restrictor comprising
i. a plug engaged in said bore and located in said passage, said plug having at least one external fluid path, and
ii. a tube throttle, external said tube said tube and proximate said plug, said tube throttle having means for squeezing said tube against said plug.

15. The variable differential adjustor according to claim 14, in which said plug comprises a screw and said external fluid path comprises a helical thread in said screw.

16. The variable differential adjustor according to claim 15, in which said bore is smooth and said screw is engaged with said bore with threaded peaks, said path comprising a helical fluid pathway between said screw and said bore.

17. The variable differential adjustor according to claim 14, in which said tube throttle includes a pair of rigid half cylinders in said passage and sandwiching said tube therebetween, and a compressor member urging said half cylinders together.

18. The variable differential adjustor according to claim 17, in which said compressor member comprises an adjustable screw threaded engaged in said restrictor housing and bearing against one of said half cylinders.

19. The variable differential adjustor according to claim 18, in which said squeezing means comprises said half cylinders and said adjustable screw.