Double-ended liquid line thermal insulator

Thermal conduction through a liquid line is deterred when liquid is not flowing through it by lodging a double-acting spring-centered plunger in a constricted section of a passage connecting opposite ends of a barrel in the line. Such plunger can be displaced from the passage constricted section in either direction to a passage expanded section automatically by pressure of liquid in the line resulting from opening a valve in the line.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a thermal insulator in the form of a pipe 
coupling for inclusion in a liquid line through which liquid flows 
intermittently for the purpose of reducing heat loss through liquid in 
such line when liquid is not flowing through it. 
2. Prior Art 
A device intended to accomplish the same purpose as the present invention 
is disclosed in U.S. Pat. No. 4,364,411, issued Dec. 21, 1982. A 
representative situation is installation of the thermal insulator in the 
hot water line of a residence water system at a location adjacent to the 
water heater. The device of the present invention has substantial 
advantages over the liquid line thermal barrier disclosed in that patent 
with respect to adaptability and operation. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a double-ended thermal 
insulator for liquid lines that can be installed like a pipe coupling in 
such a line, and the internal construction of which is symmetrical and 
double-acting so that the insulator will function in the same manner 
however the insulator is oriented in the liquid line. 
Another object is to provide a dynamic thermal insulator for a liquid line 
that is of simple construction, effective in operation and sensitive so 
that it will respond promptly to enable liquid to flow through the liquid 
line on demand and will return promptly to its thermal insulating 
condition when the demand for liquid flow through the line has terminated. 
A further object is to provide a dynamic thermal insulator, the moving 
parts of which are interchangeable, do not require close tolerances, so as 
to deter clogging of the insulator, and the operation of which performs a 
self-cleaning operation to minimize maintenance. 
In order to enable the thermal insulator to be installed in a liquid line 
without regard to orientation of the insulator it is an object to provide 
a flow restricting component that is automatically self-centering when 
liquid is not flowing through the line, but the construction of which does 
not require critical centering. 
It is also an object to provide a thermal insulator construction the design 
of which can be altered easily to provide different minimum degrees of 
communication through the thermal insulator when liquid is not flowing 
through the line, and which will be of nonsticking character despite 
extended intervals between times during which liquid is flowing through 
the line. Further, the construction is such that wear of the relatively 
moving parts is minimized. 
An additional object is to provide a thermal insulator construction the 
moving parts of which will be moved quickly upon demand for flow of liquid 
through the line and which movement will abruptly provide the volume of 
flow through the line which is required, approaching maximum flow capacity 
of the liquid line. 
Another object is to provide a thermal insulator construction that can 
accomplish the foregoing objects while being of compact and economical 
construction. 
These objects can be accomplished by a thermal insulator having a 
spring-centered double-acting plunger lodged in a constricted passage 
through a barrel when no liquid is flowing through the liquid line in 
which the insulator is connected and which will be moved quickly in one 
direction or the other out of the constricted passage depending on the 
direction of flow through the liquid line when a valve in the line is 
opened to demand flow of liquid through the line.

DETAILED DESCRIPTION 
The thermal insulator includes a double-ended barrel 1 generally in the 
form of an elongated pipe coupling having female pipe threads 2 in its 
opposite ends for connection of the barrel conventionally to pipes P shown 
in phantom in FIG. 2. A passage connects such opposite barrel ends. 
Located symmetrically within the central portion of such passage is a 
constricted section 3 which preferably is not very much smaller than the 
passage through the pipes P forming the liquid line in which the thermal 
insulator is installed. The end portions of the barrel at opposite sides 
of such constricted passage section are substantially identical. 
The purpose of the thermal insulator is to deter conduction through the 
insulator of heat whether such heat be conducted through the material of 
the insulator or through liquid within the insulator. To deter such heat 
conduction the insulator barrel 1 is made of thermal insulating material 
such as Teflon, i.e. tetrafluoroethylene, or polycarbonate, or CPVC, i.e. 
polyvinyl dichloride, or other thermal insulating plastic material. The 
thermal conductivities of such materials are specified in U.S. Pat. No. 
4,364,411 at column 3, lines 15 to 25. 
To deter conduction of heat through residual liquid in the thermal 
insulator when liquid is not flowing through the line the liquid 
communication through the constricted passage section 3 is restricted by 
lodging in such section, when there is no flow through the liquid line, a 
sliding reciprocable plunger 4. This plunger is spring-centered in the 
constricted passage section by being clamped between opposed helical 
compression springs 5 arranged in tandem and always engaged, respectively, 
with opposite ends of the slider 4. In order to center the slider 
transversely of its direction of movement each end 6 of the generally 
cylindrical slider is of shallow conical shape fitting within the ends of 
the respective springs 5. The cone angle of each slider end may be, for 
example, approximately 120.degree.. 
The ends of springs 5 remote from the slider encircle the ends of hollow 
bosses 7 forming hubs of spiders including arms 8 projecting radially from 
the ends of the hubs remote from the slider 4. Such spider arms fit snugly 
in the respective ends of the barrel 1. Each spider is retained against 
movement by the force of springs 5 away from the slider 4 by a retaining 
spring ring 9 seating on a shoulder 10 formed at the base of each female 
thread 2 and fitting into a retaining groove 11 adjacent to such shoulder. 
When a valve is opened in the liquid line to induce flow of liquid through 
the line by the pressure of such liquid the differential in, liquid 
pressure acting on the opposite ends 6 of slider 4 will move such slider, 
in opposition to the differential in the forces of the springs 5 bearing 
on the opposite ends of the slider, lengthwise of the barrel 1, into an 
open position in an expanded section of the connecting passage 
communicating between opposite end portions of the barrel such as shown in 
broken lines in FIG. 2. In such position the slider will be clear of the 
passage constricted section 3. Adequate opportunity for flow of liquid 
around the slider in such position through the expanded section of the 
bore through the thermal insulator barrel will be afforded because the 
bore is expanded at opposite sides of the passage constricted section by 
the wall of the barrel between its opposite ends and the passage 
constricted section 3 having internal flutes 12 separated by ribs 13. The 
inner edges of such ribs are in axial alignment with the walls of the 
passage constricted section 3 so as to constitute guides for the slider 4 
when it has been moved out of the constricted section 3 into an expanded 
section to a positon such as shown in broken lines in FIG. 2. 
When the valve in the liquid line is closed, the liquid pressure in the 
bore of the thermal insulator barrle 1 at opposite sides of the slider 4 
will equalize, enabling the differential in force exerted on the slider by 
the springs 5, which are substantially alike and are always engaged with 
the opposite ends of slider 4, respectively, to center the slider again in 
equipoise lodged in the passage constricted section 3 through the central 
portion of the barrel 1. When the slider is in such position shown in 
solid lines in FIG. 2 communication between the bodies of liquid in the 
opposite end portions of the barrel 1 is afforded only through the narrow 
annular passage or clearance 14 between the slider 4 and the passage 
constricted section 3. Consequently there is little conduction of heat 
from the liquid at one side of the slider to liquid at the other side of 
the slider so as to reduce greatly transfer of heat past the slider from 
relatively hot liquid in one end chamber of the barrel to relatively cool 
liquid in the other end chamber of the barrel. 
Sufficient conduction of heat through the clearance between the slider 4 
and the passage constricted section 3 should be afforded, however, to 
deter freezing of liquid in the cool liquid end of the barrel. The thermal 
insulator can be designed to provide the desired amount of liquid between 
the slider 4 and the passage constricted section 3 simply by selecting the 
relative diameters of the slider and of such passage section. 
Transfer of heat between the bodies of liquid in opposite ends of the 
thermal insulator barrel 1 is further deterred by making the slider 4 of 
thermal insulating plastic material such as one of the plastics discussed 
above as being used for the barrel. The material of the slider may be the 
same as the material of the barrel. 
The slider 4 has a clearance fit in the passage constricted section 3, but 
preferably the tolerance of such fit is generous so as to minimize wear 
between the relatively movable parts 3 and 4, and virtually to eliminate 
friction between these parts for facilitating rapid axial movement of the 
slider relative to the passage constricted section in response to 
unbalanced liquid pressure in opposite ends of the thermal insulator 
barrel 1. 
Each end of the barrel 1 may have circumferentially spaced ribs 15 
extending longitudinally of the barrel to afford easy gripping of the 
barrel for preventing it from turning while connecting a pipe P to an end 
of the barrel.