Explosion proof water flow detector

Details Explosion proof water flow detector Explosion proof water flow detector

2000-02-16

2001-12-18

Hofsass, Jeffery (Department: 2632)

Communications: electrical

Condition responsive indicating system

Specific condition

C340S610000, C116S273000, C137S554000, C200S293000

Reexamination Certificate

active

06331820

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
The present invention relates to flow detectors. Particularly, the invention relates to a water flow detector for use in an explosive environment.
BACKGROUND OF THE INVENTION
A paddle type flow detector utilizes a paddle which is inserted into a flow conduit, such as into a pipe. Paddle type flow detectors are designed, for example, to be mounted on a water pipe of sprinkler-type fire suppressant systems to activate an alarm when water flows in the pipe.
A paddle type flow detector is disclosed, for example, in U.S. Pat. Nos. 4,782,333 and 4,791,414, both assigned to the assignee hereof, herein incorporated by reference.
The known paddle type flow detector includes a switch mounted externally of the flow conduit and mechanically connected to the paddle. Movement of the paddle by force from a fluid flowing within the conduit causes a change in the state of the switch, generating a signal. The paddle is typically biased by a paddle spring into a base position corresponding to no flow in the conduit, and is movable against the spring bias into a “triggered” or “tripped” position by the flowing fluid.
Paddle type flow detectors have been used before within explosive environments, i.e., environments where explosive gases are likely to be present surrounding the detector. The Standard “UL 1203” sets forth criteria for explosion proof and dust-ignition-proof electrical equipment. In such equipment, sparks from opening and closing a flow indicating switch are isolated from the external environment by an enclosure or housing surrounding the switch and the housing prevents such sparks from propagating a flame or explosion outside of the housing.
However, it is possible that the switch enclosure or housing, over time, will permit the intrusion of explosive gases into the enclosure, particularly when the detector is located within an explosive environment for an extended period of time. It is possible then, that explosive gas and oxygen within the paddle switch housing can be ignited by the opening and closing of the switch contained therein. Such explosions can affect the sensitivity of the paddle spring which biases the paddle against the flowing fluid.
In the case of the paddle type detector used as a waterflow detector in a sprinkler system, the switch can be triggered more frequently than normally would be expected due to an activation of the fire suppressant system. Transient flows can occur in the sprinkler system pipes. For example, when a pump that maintains pressure in the system turns on, air trapped in the system will be compressed, which may cause water to temporarily surge past the flow detector location. Such temporary surges can trigger false alarms which are a nuisance. The common way to avoid such nuisance alarm is to provide a time delay between the beginning of the flow and in signaling an alarm. Not withstanding this time delay provision, the switch can be activated, i.e., change state between open and closed, many times more than actually needed to indicate a legitimate alarm. This would multiply the problem of spring exposure to explosions and the resultant effect on the sensitivity of the spring.
It would be desirable to provide a paddle-type flow detector which maintains its opening accuracy despite the possibility of explosions occurring within the switch housing of the detector.
SUMMARY OF THE INVENTION
The present invention provides a flow detector which includes a paddle arranged to be impacted by flow of a monitored fluid. A spring biases the paddle against movement caused by the monitored fluid. An electrical switch is caused to change state, either open or closed, by movement of the paddle. The electrical switch is contained within a switch housing, and the spring is contained within a spring compartment.
The spring compartment is isolated from the switch housing. Given intrusion of explosive gas into the switch housing, any explosions occurring within the switch housing will be effectively prevented from influencing or damaging the spring.
The switch housing is mounted over the spring compartment, and onto a flow conduit mounting structure. In the preferred embodiment, the mounting structure is a pipe saddle having a bolt mechanism for allowing the saddle to be clamped tightly around a pipe. A seal is provided within the mounting structure to seal a penetration of the paddle into the flow conduit or pipe.
According to the preferred embodiment, the paddle is connected to a paddle lever which extends through the mounting structure and into the spring compartment. The spring exerts a force on the lever to bias the paddle into a “no flow” or base position, biased to oppose paddle movement caused by fluid flow. The paddle is pivotally mounted by a flexible connection to the mounting structure.
The paddle lever is connected to a slide rod which is in turn connected to a movable switch lever. The slide rod extends through a wall which separates the spring compartment from the switch housing.
The slide rod penetrates the wall in a substantially sealed fashion. The sealed penetration of the slide rod eliminates a flame path between the switch housing and the spring compartment.
The switch lever is operatively connected to the switch contained within the switch housing. The lever is movable to change the switch state in response to sliding movement of the slide rod. In operation, the switch lever is moved by the slide rod, when the slide rod is moved by pivoting of the paddle lever.
The flow detector of the present invention is resistant to spring damage due to intrusion of explosive gas into the switch housing. By isolating the switch housing from the spring compartment, any explosions occurring within the switch housing are effectively prevented from entering the spring compartment by the surrounding walls of the switch housing and the sealed fit of the slide rod. Improved reliability of the detector is achieved by eliminating the flame path between the switch and the spring.
Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is an elevational view of a flow detector of the present invention mounted onto a pipe (shown in section);
FIG. 2
is a bottom perspective view of portion of the detector shown in
FIG. 1
;
FIG. 3
is an exploded perspective view of the detector shown in
FIG. 2
;
FIG. 4
is a fragmentary, sectional view taken generally along line
4
—
4
of
FIG. 2
; and
FIG. 5
is a fragmentary, sectional view taken generally along
5
—
5
of FIG.
2
.


REFERENCES:
patent: 2966133 (1960-12-01), Hube
patent: 4454768 (1984-06-01), Nansel
patent: 4782333 (1988-11-01), Merchant
patent: 4791414 (1988-12-01), Griess
patent: 4958144 (1990-09-01), Griess
patent: 5213205 (1993-05-01), Laubach et al.

Affiliated with

Also associated with

Rating

Explosion proof water flow detector does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Explosion proof water flow detector, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Explosion proof water flow detector will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2582885