HK1136031B - Insulation temperature sensor - Google Patents

Description

Insulated temperature sensor

Technical Field

The present invention relates generally to refrigeration systems and, more particularly, to a method and apparatus for insulating and protecting a temperature sensor within a refrigeration system.

Background

In air conditioning and refrigeration systems, the refrigerant passing from the evaporator to the compressor is typically maintained at a level of superheat to protect the compressor from possible damage caused by the passage of liquid refrigerant therethrough. This function is accomplished through the use of a thermal expansion valve located upstream of the evaporator coil and an associated temperature sensor or bulb for sensing the temperature of the refrigerant passing through the evaporator coil.

In order for the bulb to provide an accurate temperature reading, it is necessary to isolate the bulb and its connection to the outlet line so that water and air flow do not occur in this area resulting in inaccurate temperature readings. The above-mentioned isolation function has been achieved by providing some kind of protective cover over the area where the bulb is fixed to the outlet line. The most common type of insulation placed around the bulb is first of all the use of a sticky asphalt sheet called Prestite applied around the bulb, so that no pores are present into which water or air can enter. This area was then wrapped with tubular neoprene insulation, which was thereafter covered with polyvinyl chloride insulation tape. Finally, the assembly was covered with aluminum tape. The problem with this approach is twofold. First, the quality of the isolation obtained depends on the ability of the technician using the isolation method, and there is no way to determine that the method will be inadequate. Second, in order for service personnel to be able to inspect and/or maintain the bulb, each of these layers must be removed and then reapplied after the inspection and/or maintenance process is completed. The removal is difficult, especially for Prestite, and the results after reapplication are also inconsistent, as mentioned above. Both of these tasks are very laborious and costly.

Other types of temperature sensors are also used to sense the temperature of the refrigerant in the various lines of the refrigeration system to control and/or protect the system. These sensors are also subject to the same problems discussed above.

Disclosure of Invention

Briefly, according to one aspect of the invention, a molded foam cover is wrapped around a bulb connected to an outlet line, the cover being secured in place to insulate the bulb and protect the bulb from exposure to moisture and air flow.

In another aspect of the invention, a first hinged flap is provided to provide easy access for inspection and maintenance of the insulation. A second hinged flap is provided in overlapping relationship with the first hinged flap and secured by Velcro (a trademark of Velcro) fasteners.

In another aspect of the invention, the cover is formed in a clam-shell arrangement, with the two halves being folded over the outlet line to enclose the installed bulb together, and a strap wrapped around each end to secure it in place.

According to another aspect of the invention, a tongue and groove are provided to provide a sealing means to prevent moisture from entering the cover.

A preferred embodiment will be described in conjunction with the drawings described below; however, various other modifications and alternative constructions can be made thereto without departing from the spirit and scope of the invention.

Drawings

FIG. 1 is a schematic diagram of a refrigeration system incorporating the present invention.

Fig. 2 is a perspective view of a cover in accordance with an aspect of the present invention.

Fig. 3 is a perspective view of the cover in an open position after installation.

Fig. 4 is an illustration of the cover in a partially closed position.

Fig. 5 is a view of the cover in the closed position.

Detailed Description

Fig. 1 is a schematic diagram of a transport refrigeration system to which the present invention may be applied. Connected in representative serial flow relationship are a compressor 11, a condenser 12, an expansion device or thermal expansion valve (TXV)13, and an evaporator coil 14. Refrigerant flows through the system in a known manner under the action of the compressor 11.

Other components typically included in the system are an oil separator 16, a receiver 17, a filter dryer 18, an economizer TXV 19, and an economizer heat exchanger 21. The oil separator 16 serves to separate oil from the compressed refrigerant so that the refrigerant can be returned to the compressor 11. The receiver stores refrigerant for use in cryogenic operations. The filter dryer 18 removes moisture and impurities from the refrigerant. The economizer is used to provide the freeze range and reduced capacity of the apparatus when needed by subcooling the liquid refrigerant entering the evaporator TXV 13.

The TXV 13 has a variable orifice that receives liquid refrigerant and delivers it to the evaporator 14 in expanded or vapor form. The variable orifice in the TXV 13 is sized by a temperature sensor or TXV bulb 23, which temperature sensor or TXV bulb 23 is connected to the evaporator outlet line 24, thus sensing the temperature of the refrigerant passing through the evaporator 14 and activating the TXV 13 in response thereto. In this way, the TXV 13 maintains a constant superheat at the coil outlet regardless of load conditions.

The cover 26 of the present invention is shown in an uninstalled state in fig. 2, and the cover 26 is shown in an installed state in fig. 3. The cover comprises an elongate body 27 formed by semi-cylindrical elements 28 and 29 connected at a common edge 31. Each of the semi-cylindrical members 28 and 29 has a semi-cylindrical passage extending longitudinally therethrough, as shown at 32 and 33, respectively. A reduced diameter neck is provided at each end of each half, with necks 34 and 36 provided on half 28 and necks 37 and 38 provided on half 29. The cover is secured to the evaporator outlet line by these necks in a manner to be described hereinafter.

A hollowed-out area or cavity 39 is provided in half 28 and in a portion of half 29 to accommodate bulb 23 as well as fastening strap 41 and fastener 42, as shown in fig. 3. Connected to one edge 43 of the half 28 is a bow flap 44, which bow flap 44 will be called large flap or outer flap, having on its inside a Velcro (r) element 46 and also having grooves 47 and 48 extending along its end edges. The flap 44 is intended to be folded over the half 29 for closure and sealing by the tongue and groove formations 50 and 55 fitting into the respective grooves 47 and 48 to provide a sealing means against moisture ingress into the cover 26.

Half 29 also has a flap, referred to as a small flap or inner flap 49, which can be bent back at its edge 51 to provide an access opening in half 29. A second Velcro element 52 is arranged on its outside near the edge 51.

To position the cover 26 for mounting on the evaporator outlet line 24, the TXV bulb 23 and its fastening components 41 and 42 as shown in fig. 3, the two halves 28 and 29 are wrapped around the combination in clamshell fashion and the respective edges are brought together as shown. The mating necks 36 and 38 are then brought together and the mating necks 34 and 37 are brought together to form a cylinder which can then be secured in place by the strips 53 and 54 disposed therearound. The strips 53 and 54 are semi-permanent in that they do not have to be removed for inspection, but can be easily removed and replaced when it is somehow necessary to remove the entire cover 26.

Considering now the accessibility issue, the outer flap 44 and the inner flap 49 are both shown in a folded back position to provide ready and complete access to the TXV bulb 23 and its fastening components 41 and 42. When it is desired to close the cover 26, it is only necessary to fold the inner flap 49, as shown in figure 4, and then cause the outer flap 44 to fold the outer flap 44 in overlapping relationship with the inner flap 49 so that the two Velcro elements 46 and 52 engage to retain the outer flap 44 in its closed position. It will be appreciated that when the inner flap 49 and outer flap 44 are in their respective closed positions, the tongue elements 50 and 55 of half 29 fit into the grooves 47 and 48 on the inside of the outer flap 44, thereby providing a seal against the ingress of air, moisture and dirt that might otherwise migrate into the interior space defined by the cover 26.

The cover 26 may be constructed of any suitable material that provides good insulating properties, preferably a moisture resistant material. One of the most suitable materials that has been found is a closed cell molded foam material available from ZotefoamsPLC, UK under the trade designation LD 45. The strips 53 and 54 may be made of any suitable plastic or metal material.

Although the invention has been described in terms of a cover for a bulb of a TXV, the invention is also applicable to any other type of sensor connected to a refrigerant line for sensing temperature to control or protect the system. For example, the present invention may be used to wrap a thermistor applied to the compressor discharge line, which senses the high discharge temperature and sends a response signal to the microprocessor to shut down the system. For example, the invention may alternatively be used to coat a thermistor applied to the suction line for sensing temperature to calculate superheat.

Claims (22)

1. A cover for a temperature sensor connected to a refrigerant line of a refrigeration system of the type used, the cover comprising:

an elongated body having a generally cylindrical opening formed therein allowing a refrigerant line to pass therethrough; and

a cavity formed in the body adjacent the cylindrical opening for receiving the sensor, the cover forming a waterproof enclosure for protecting the sensor from exposure to the elements, wherein the temperature sensor comprises a bulb connected to an outlet line of the evaporator and the sensed temperature is provided to a thermal expansion valve located at an inlet line of the evaporator.

2. The cover of claim 1 wherein said elongate body is generally cylindrical.

3. A cover as set forth in claim 1 wherein said cavity is large enough to receive and contain a clamping mechanism and a temperature sensor.

4. A cover as set forth in claim 1 wherein said elongated body includes a flap that can be folded up to expose the temperature sensor for inspection.

5. A cover as set forth in claim 4 wherein said flap is hinged along a longitudinal edge thereof.

6. A cover as set forth in claim 4 further comprising a second flap folded over the first flap and deployable to reveal the first flap.

7. A cover as set forth in claim 6 wherein said first and second flaps unfold in opposite directions.

8. A cover as set forth in claim 6 wherein said second flap is secured to said first flap by Velcro.

9. A cover as set forth in claim 6 wherein said second flap includes a tongue and groove element extending laterally at an end edge thereof and said elongate body includes a tongue and groove element extending laterally at an end thereof, and further wherein said tongue and groove element fits into said tongue and groove element when said second flap is closed.

10. A cover as set forth in claim 1 wherein said elongate body comprises two halves hinged at a common edge such that said two halves are folded together in clamshell fashion to enclose the temperature sensor.

11. A cover as set forth in claim 1 further including a strap encircling said elongate body along each longitudinal end thereof to secure it in its installed position.

12. A cover for a temperature sensor connected to a refrigerant line, comprising:

a pair of elongate body members comprising an insulating material and connected at a common edge and capable of being clam-shelled together to enclose portions of a thermal expansion valve bulb and associated output line, each of the elongate body members having an integral neck portion at an end thereof, the neck portions also being clam-shelled together to form a neck at each end surrounding the outlet line; and a band surrounding and securing in place a respective neck at each end, wherein the temperature sensor comprises the thermal expansion valve bulb connected to an outlet line of the evaporator, and the sensed temperature is provided to a thermal expansion valve located at an inlet line of the evaporator.

13. A cover as set forth in claim 12 wherein said pair of elongated body members include a cavity for receiving a temperature sensor.

14. A cover as set forth in claim 12 wherein said elongate body includes a flap that can be folded up to expose the temperature sensor for inspection.

15. A cover as set forth in claim 14 wherein said flap is hinged along a longitudinal edge thereof.

16. A cover as set forth in claim 14 and further including a second flap folded over the first flap and capable of being unfolded to expose said first flap.

17. A cover as set forth in claim 16 wherein said first and second flaps unfold in opposite directions.

18. A cover as set forth in claim 16 wherein said second flap is secured to said first flap by velcro.

19. A cover as set forth in claim 16 wherein said second flap includes a laterally extending tongue-and-groove at an end edge thereof and said elongate body includes a laterally extending tongue at an end thereof, and further wherein said tongue fits into said tongue-and-groove when said second flap is closed.

20. A cover as set forth in claim 12 wherein said elongate body comprises two halves hinged at a common edge such that said two halves are folded together in clamshell fashion to enclose the temperature sensor.

21. A cover as set forth in claim 12 further including a strap encircling said elongate body along each longitudinal end thereof to secure it in its installed position.

22. A cover as set forth in claim 12 wherein said cover comprises a closed cell molded foam material.