US2805660A - Humidifier for use with warm air furnaces - Google Patents

Description

Sept. 10,1957 R. E. COLEMAN, JR., ET 2,895,660

HUMIDIFIER FOR USE] WITH WARM AIR FURNACES Filed Dec. 9, 1952 IN VEN TOR.

. ROBERT ECOLEMAN JR."

' BY GEORGE N. MILES ATTORNEY HUMIDIFIER FOR USE WITH WARM AIR FURNACES Robert E. Coleman, Jr., Packanacl; Lake, N. 3., and

Application December 9, 1952, Serial No. 325,000

1 Claim. (Cl. 126-413) This invention relates to improvements in humidifiers and particularly to an improved humidifier for use with so-called warm air furnaces.

In warm air furnaces, it is common practice to mount a shallow pan in the furnace plenum chamber or bonnet, where the pan will be exposed to the heated air moving from the furnace to the distributing ducts. Water supplied to the pan from an outside source is evaporated from the pan to moisten the heated air as it leaves the furnace for distribution.

One of the principal problems involved in such humidifiers is that of controlling the supply of water to the pan. The control should be truly responsiveto conditions in the furnace, insuring an adequate and uniform supply of water when the furnace is running, and yet insuring positive shut-off when the furnace is not running.

Many humidifier systems heretofore proposed have not been entirely satisfactory because they have not been truly responsive to conditions inside the furnace. For example, one type of humidifier that has been used comprises a pan mounted to tilt in response to changes in the volume (and, hence, the weight) of the liquid contained therein to open and close a supply valve. Being weight responsive, such assemblies are difficult to adjust so that they will not vibrate or oscillate at or near the point at which the valve is nearly open or nearly closed. Moreover, the unavoidable accumulation of mineral deposits in the pan from constantly evaporating liquid makes it difiicult to maintain the proper weight relationship or keep the valve clear over any extended period of time. Humidifiers of this type respond only indirectly to the temperature and the liquid conditions in the furnace, since they are as responsive to the weight of mineral deposits or the like as they are to the weight of the liquid.

In another type of humidifier, the system is made responsive to the temperature in the furnace bonnet, without regard to the amount of water actually available for evaporation from the pan. In such an assembly, the rate of flow at maximum temperature can never be allowed to exceed the maximum rate of evaporation or the pan will overflow whenever the heating system is running more or less continuously, as during a prolonged cold spell. In turn, this means that the water inlet opening must be quite small to hold down the flow rate, and can readily become clogged either by mineral deposits or by dirt particles and the like in the water itself. Moreover, the water supply at relatively low bonnet temperature may be inadequate. Again, it is seen that this type of humidifying system is only partially responsive to condi-' tions in the furnace, since it supplies water to the pan solely in response to the temperature in the bonnet without regard to the amount of water actually required.

An even more common type of humidifier is one in tes Patent which the liquid inlet is controlled by a float element,

ice

float type humidifier, particularly when used with furnace systems having relatively high operating bonnet temperatures and pressures. In such installations, it is cus tomary to have an evaporating pan inside the bonnet, communicating with a float chamber outside the'bonnet. Unless the float chamber is pressurized, which introduces additional problems, the liquid level in the pan will be lower than that in the float chamber when the furnace is running, yet the liquid levels will be the same when the system is off. This makes it extremely difiicult to adjust the inlet control so that there will be liquid in the pan when the furnace is operating and yet no overflow from the pan when the system is shut down.

It is, accordingly, a general object of the Present invention to provide an improved humidifier for warm air fur-.

naces that will give a uniform, reliable humidifying action in a simple and eflicient manner. More specifically, it is among the objects of the invention to provide a humidirier assembly wherein the water level in an evaporating pan is held within relatively narrow limits in direct and sole response to the temperature conditions in the furnace bonnet and to the amount of water actually available in the pan for evaporation, and an assembly that involves practically no moving parts subject to wear or clogging but yet is inexpensive to manufacture and service, simple to adjust, and highly reliable in operation.

In accordance with a preferred embodiment of the invention, the foregoing and other related objects and advantages are attained in a humidifying apparatus wherein a bimetallic control element is mounted in an evaporating pan slightly below the desired maximum water level in the pan, the arrangement being such that when the water level is low enough to expose the control element, hot air from the furnace will actuate the control element to admit water to the pan. When the water level rises sufiiciently to contact the control element, the cooling effect of the liquid is relied on to cut off the supply of liquid to the pan.

A more complete understanding of the invention can be had by reference to the following description of i1lus-.

trative embodiments thereof, when considered in connection with the accompanying drawing, wherein Figure l is a fragmentary view of a warm air furnace bonnet in which is mounted a humidifying apparatus embodying the invention, and

Figure 2 is an enlarged sectional view of the valve portion of the humidifier shown in Figure 1.

In the embodiment of the invention illustrated in Figure 1 of the drawing, a relatively shallow, open. evapcrating pan 1t], of generally rectangular shape andcross section, is supported at one end in any suitable manner on the side wall 12 of a furnace bonnet 14, with the pan 10 extending into the bonnet space to be exposed to heated air flowing to distribution ducts 16. The humidifier of the present invention is particularly suitable for use in a furnace which operates at relatively high bonnet temperatures, say, of the order of 350 R, such as that described in U. S. Patent No. 2,488,548 to C. D. Mac- Cracken, and will be assumed, for illustrative purposes, to be mounted in the bonnet of such a furnace.

A Water inlet line 18 is connected by a compression coupling 19 or the like to an elongated valve support member 20 which extends a short distance into the pan 10 just below the open top thereof.

The valve support 20 has a longitudinal passageway 21 (see Figure 2) leading from the fitting 19 to a threaded opening 22 in the underside of the support member 20, in

which is mounted a valve body 23 that extends downwardly into the pan 10.

A passageway 24 in the valve body 23 communicates with the passage 21. It will be noted that the valve support member 20 extends considerably beyond the valve 3, body 23, and at its free endcarries a bimetal strip that is held by a screw 26 on the underside of the support 20.

The free end of the strip 25 extends beneath the valve body 23, and carries a valve seat in the form of a resilient pad 27 that is held in place by a nipple 27a press-fitted into a hole 28 in the bimetal strip.

The lower end 23a of the valve body 23 is tapered to provide a valve face of limited surface area adapted to seal tightly against the closure member provided by the pad 27.

Opening and closing of the valve 23 is controlled by the temperature sensitive bimetalstrip 25. This strip 25 is made up of two dissimilar metal layers 25b, 25c having different coelficients of expansion, so that the strip 25 will tend to flex orbend in response to changes in ambient temperature.

The pad 27 is made of a temperature resistant, resilient material, such as teflon," silicone rubber or the like, that will withstand the temperatures encountered in the furnace bonnet and will seal tightly against the nozzle To permit adjustment of the valve assembly in Figure 2, the support member 20 is split by a lateral slot dividing the free end of the support 20 into upper and lower sections 20a, 20b and extending from a cut-away portion 62 in the underside of the support to a lateral hole 64 through the support adjacent the free end thereof.

Accordingly, the parts 20a, 20b of the support aboveand below the slot 30, in effect, form normally parallel arms of a U that can be forced apart or brought together to tilt the bimetal strip 25 relative to the support and thereby adjust the spacing between the valve face 23a and the seat 27. The adjusting element comprises a screw 66 that is threaded into the top section 20a and is also internally threaded to receive a threaded element 68 that is pinned to the lower section 20b of the support; The pitch of the threads 70 on the inside of the screw 66 is made somewhat less than the pitch of the outside threads 72. Accordingly, as the screw 66 is rotated, the lower section 20b will be moved toward or away from the upper section 20a, depending on the direction of rotation of the screw. This, in turn, will tilt the bimetal strip 25- relative to the main body portion of the support and effeet the desired adjustment of the spacing between the valve seat 27 and the valve face 230:.

Accordingly, the system can be easily adjusted for water pressure and bonnet temperature, while the furnace is running, by means of a screw driver inserted through a suitable small opening in the furnace bonnet;

The apparatus shown in Figures land 2 will operate in the following manner: the higher expansion layer of metal 25b is put on the top of the strip, so that an increase in ambient temperature will cause thefree end of the strip to bend away from the support 20, thereby opening the valve and admitting water to the pan. Conversely, when the water level rises sufficiently in the pan to contact the strip 25,the cooling action of the liquid will cause the strip to bend in the opposite direction and shut ofl? the flow of Water through the valve. It will be understood that the water in the pan may not entirely cover the bimetal, especially when the latter is in the form of an elongated strip as in Figure 2, since contact between any portion of the strip and the liquid will tend to cool the entire strip by conduction. There is, moreover, an evaporative cooling effect from water that splashes onto the strip and evaporates in small drops. There is also a radiant cooling elfect of the water since such a large radiation receiving surface near the bimetal strip is cooler than the strip when water is present. Additional cooling is obtained by convection when water is present due to air being cooled by the water and then contacting the bimetal strip.

We claim:

In a humidifier for supplying moisture by evaporation to heated air flowing through a warm air heater, a pan for holding water to be evaporated and adapted to be mounted in the path of heated air flow in said heater, a water inlet to said pan comprising an elongated supported member extending into said pan and having a passageway therein, a valve body extending downwardly from the underside of said support member and having a passageway therein communicating at one end with said support member passageway and opening at its other end into said pan to provide a discharge nozzle, said support member having a portion extending substantially beyond the point at which said valve body is joined to said support member, said portion being slotted to form upper and lower sections which are joined at the free end of said portion, an elongated bi-metallic strip fixed at one end to said lower section and extending therefrom to said discharge nozzle opening, a valve seat comprising a resilient pad carried by the free end of said strip and arranged to close said dis charge nozzle when said strip is cold, and means for adjustably forcing apart said upper and lower sections whereby to tiltsaid strip relative to said support member and thereby adjustably locate said free end of said strip relative to said discharge nozzle.

References Cited in the file of this patent UNITED STATES PATENTS 1,721,321 Skinner July 16, 1929 1,870,253 Johnson Aug. 9, 1932 1,960,545 Mortimer May 29, 1934 2,131,125 Smith Sept. 27, 1938 2,336,647 Spangenbey Dec. 14, 1943 2,570,451 Hottenroth Oct. 9, 1951 2,613,874 Thomas Oct. 14, 1952

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