US2722808A - Automatic refrigerator defroster - Google Patents

Description

1955 H. w. GOODHART AUTOMATIC REFRIGERATOR DEFROSTER Filed Feb. 25, 1953 U A M m Y B M H 2 4 a m 5 6 4 14 5:0 4 H Ml! nw z w 0 TCINIJ T 7 m 1... \un W w. m 7% 3T/J\ -3 li f a -3 2 United States Patent 2,722,808 AUTOMATIC REFRIGERATOR DEFROSTER Harry w. Goodhart, Baltimore, Md.

Application February 25, 1953, Serial'No. 338,639

3 Claims. (Cl. 62-103) This invention relates to means for defrosting the freezing compartment of refrigerators and deep freeze boxes, and is particularly well adapted for use in preventing the layer of ice forming frost from forming on the inner wall of a deep freezer box, without the necessity of raising appreciably the temperature of the food stored in the box or its removal therefrom.

The freezing compartment of the box is usually kept at a temperature below the freezing point of water and the moisture deposits on the top, bottom and sides of the compartment and forms frost. At this frost accumulates it forms a layer of ice that, due to its insulating effect, reduces the efficiency of the apparatus for reducing the temperature of the freezing compartment from time to time.

The general practice heretofore in defrosting the freezing compartment of a deep freeze box has been to stop to melt, this takes considerable time and allows the temperature of the foods stored therein to rise considerably while the box is being defrosted. It has also been the practice to scrape the frost free from the walls of the freezing compartment and then remove the scraping from the box. Another method has been introduced incorporating a heating unit embedded in a plastic covering, but this method aside from reducing the efficiency of the cooling medium merely broke the bond of the layer ice from the face of the plastic covering and required the shell of ice to be lifted out of the box as a unit. Practically all the methods mentioned required that the foods be removed from the box so the slop from the melted ice could be mopped up before it became frozen again. All of the methods mentioned allowed the temperature of the foods to rise and become warm while this was being done.

The present invention contemplates a simple and practical freezing unit defroster whereby the layer of iceforming frost will form on a screen or perforated plate placed within the freezing compartment but spaced away from the regular compartment wall, with a heating unit spaced between said screen or plate and the compartment wall to periodically and automatically release the frost from the screen and compartment wall in the form of water, and to drain same to the outside of the deep freezer at predetermined intervals.

The invention has for an object the provision of a new and improved defrosting apparatus for a deep freeze box that will be automatic in its defrosting operation and provide means for carrying off the liquid medium after the defrosting cycle has been completed.

Another object of this invention is to provide a new and improved portable defrosting unit for placement in a deep freeze box, comprising a spacer screen or plate positioned adjacent the inner wall of a deep freezer box and a heating unit placed between the inner wall and the spacer.

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Other objects will become apparent as the invention is more fully set forth.

For a clearer understanding of the invention and its objects, reference is made to the accompanying drawings, wherein a particular form of the invention is disclosed. These drawings when used in conjunction with the following description illutrate such form by way of example, while the claims emphasize the scope of the invention.

In the drawings:

Figure 1 is a plan view of a deep freezer with the lid in closed position, embodying this invention;

Figure 2 is a plan view similar to Figure 1 with the lid open;

Figure 3 is a sectional view taken along line 33 of Figure 2; and

Figure 4 is a diagram indicating the automatic electrical control of the defrosting system.

Similar reference numerals refer to similar objects throughout the drawings.

In the construction shown in the drawings a casing 10 comprising an outer wall 11 and an inner wall 12 forming an enclosure for the refrigerating tubes 13 which are attached to the inner walls 12. The hollow space between the outer and inner walls is packed with one of the conventional insulating materials to prevent losses through the walls. The face 14 of the inner wall 12 is provided with studs 15 to support the screen or perforated plates 16 and to keep them in spaced relationship with the wall 12. A heating unit element 17 is attached to the face 14 of the inner wall 12', between the inner wall 12 and each screen or perforated plate 16. A cover 18 is attached to the top of the deep freezer by hinges 19. The freezer is preferably mounted on legs 20. The screen or perforated plates 16 and heater units or elements 17 are positioned around the walls 12 and the water from the melting ice forming frost drips down and along the spouting 21 which is pitched toward a discharge pipe 22 and through the trap 23 and out the drain pipe 24 to the outside. The heating units 17 are also used to defrost spouts 21.

Suitable electrical circuits for the automatic control of the defrosting apparatus are shown in Figure 4. The time clock shown at 30 may be of any suitable type which may be set to control the circuits at periodic intervals. In the diagram the time clock is shown as having a switch arm 31 connected to a wire 32 which leads from one supply line 33. In one position of the switch arm 31 it engages contact 34 which is connected to the lead 28 that goes to the heating units 17. The other lead 28a going to the heating units is connected to the other supply line 33a. In the other position of the time clock switch arm 31 it engages a contact 35 which connects by wire 36 to relay winding 30. The other side of the relay winding is connected by wire 41 to the supply line 33a. One side of the compressor motor M1 is connected by wire 42 with supply line 33a; the other side of motor M1 is connected by wire 43 through thermostatic switch 46 with one contact of relay switch 44, the other contact of the relay being connected by wire 45 with supply line 33. The usual thermostatic switch 46 is inserted in the wire 43 for thermostatic control of compressor motor M1, for controlling and maintaining the desired refrigerating temperature.

In normal operation the switch arm 31 of the time clock is in engagement with contact 35, thus breaking the circuit to the heating elements 17 and also closing the circuit relay 39 (from wire 36 through the winding of the relay and wire 41 at supply line 33a). The relay energized, closes the circuit at its switch 44, and thus closes the circuit of compressor motor M1 (supply line 33, wire 45, relay switch 44, wire 43, motor M1, and wire 42 back to supply line 33a).

During the normal operation, when refrigerant is being circulated through refrigerating tubes 13, the air will be cooled not only by contact with the screen or perforated plate section 16, but also by direct contact with the inner walls 12 to which the refrigerating tubes 13 are directly connected.

When the time clock operates to defrost the refrigerating unit, the switch arm 31 is thrown to the position shown in Figure4. The circuit to the motor M1 is thus broken and circulation of the refrigerant is stopped. By stopping the circulation of refrigerant it results that the heat supplied to the refrigerating unit for purposes of defrosting will not be carried away by the circulating refrigerating medium, to other parts of the system where goods are being cooled.

At the same time that the circuit to the compressor motor M1 is opened, the circuit leading to the heating elements 17 is closed, and heat is thus applied to the screen and perforated plates 16 from the heating elements. The heating elements being in highly efficient conductive relation to the inner wall 12 and the screen or perforated plates 16, the supplied heat is substantially evenly distributed and the deposited frost is quickly and evenly melted.

The time clock will be set to apply the heat and stop circulation of the refrigerant for a period suflicient to thoroughly defrost, and then the time clock will again operate its control switch to break the circuit to the heating elements and again close the circuits to the refrigerant circulating motor M1.

The time controlling system is shown as a matter of preference and not as a limitation, as it is appreciated that other forms of controls may be utilized, including manual operation, or actuattion by any other suitable and conveniently usable determining factor that indicates the need for defrosting.

While but one general form of the invention is shown in the drawings and described in the specification, it is not desired to limit this application for patent to this particular form as it is appreciated that other forms of construction could be made that would use the same principles and come within the scope of the appended claims.

Having thus described the invention, what is claimed l. A refrigerating system having a refrigerating unit comprising an inner and outer wall, refrigerating tubes positioned inbetween said walls, means for circulating a refrigerating medium through said refrigerating tubes, a heat insulating filling in the space between said walls, a foraminated screen suspended outwardly from said inner wall, and electrical heat conducting units suspended between said inner walls and foraminated screen to defrost the unit at predetermined intervals.

2. A refrigerating system as set forth in claim 1, and having a gutter positioned under said screen and heat conducting units to carry off the water drippings from said screen and inner wall.

3. A refrigerating system as set forth in claim 2 having means for controlling the passage of refrigerating medium through said refrigerating tubes and heating said heat conducting units at predetermined intervals.

References Cited in the file of this patent UNITED STATES PATENTS 2,515,294 Cowgill July 18, 1950 2,524,465 Morrison Oct. 3, 1950 2,601,466 Thomas June 24, 1952 2,641,112 Mufiiy June 9, 1953

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