US3211890A - Heat gun defroster - Google Patents

Description

Oct. 12, 1965 J. 5. GRAVES 3,211,890

HEAT GUN DEFROSTER Original Filed June 27, 1963 INVENTOR JOEL S. GRAVES United States Patent 1 Claim. '(Cl. 219370) This application is a division of application Serial No. 291,014, filed June 27, 1963, for Heat Gun Defroster.

The present invention relates to defrosters and more particularly to portable, electric, forced hot air defrosters for defrosting the Windshields of motor vehicles.

An object of the invention is to provide an improved portable electric hot air defroster.

Another object of the invention is to provide improved means for heating a current of air within a forced hot air defroster.

Broadly, the present invention includes a gun-shaped case of plastic or similar material having an air intake port and an air outlet port therein, a small rotary fan arranged to force outwardly through said air outlet port air drawn inwardly through said intake port, a small electric motor arranged to rotate said fan, an electric resistance element arranged to heat said outwardly directed air, a plug adapted for connection with the electrical system of a motor vehicle by insertion in the cigar lighter socket, and electric wiring operatively interconnecting said plug with said motor and heater element to energize same. An insulated heat chamber is provided surrounding said resistance element and through which the flow of outwardly directed air is constrained to pass. The unique configuration of the heat chamber is such as to impart to the outwardly directed air an unusually high temperature while increasing the efficiency of the device, reducing the amount of current required, eliminating the overloading of the vehicles electric circuit, and lengthening the life of the resistance element.

The above and other objects of the invention which will later become apparent as the following description proceeds, are attained by the present invention, a preferred embodiment of which has been illustrated by way of example only, in the accompanying drawing, forming a part of this specification in which like characters are employed to designate like parts throughout the same, and wherein:

FIGURE 1 is a side sectional view of a heat gun defroster.

FIGURE 2 is a view taken along line 22 of FIG- URE 1.

FIGURE 3 is a view of a heat gun defroster in operation.

Referring now more particularly to the drawing, 1 provide a gun-shaped case preferably formed of two symmetrical sections of plastic or other inexpensive, durable, light-Weight material, mutually engaged by conventional means, such as screws or the like inserted transversely through one section and threadably engaged within threaded sockets 12 extending from the inner surface of the other section. A generally circular air inlet port 13 is formed in the top of case 10 near the rear thereof, and an air outlet port 14 is formed at the forward or muzzle end of the case. A squirrel case type rotary fan 17 is operatively mounted upon the shaft of a small electric motor 18 within the receiver portion of case 10, and the motor, in turn, is mounted within the handle portion of the case by any convenient mounting means such as a screw extending through the sidewall of the handle portion of the case and threadably engaged within a threaded aperture 20 in the outer wall of the motor. Fan 17 is thus supported below air inlet port 13. A flange 24 surrounding the upper end of a sleeve 22 is supported within a circular channel 26 surrounding the inside of air inlet port 13, so that the lower end of the sleeve extends downwardly to a point slightly above fan 17.

I provide an insulated heat chamber 28 in the form of a hollow, truncated, metal cone 30 mounted within the barrel portion of case 10 by a bolt 32 or the like extending transversely through the case and cone. Cone 30 is formed of a metal, such as preferably aluminum, adapted to reflect heat inwardly from its inner surface. The sides of cone 30 converge toward the forward end of case 10, and the smaller end of the cone forms an orifice 34 opening upon air exhaust port 14. A flat, generally trapezoidal piece of asbestos 36 is wedged within cone 30 from the rear or larger end thereof. A heating element 38, consisting of an electrical resistance wire, is folded rearwardly about the forward end of asbestos piece 36 and is thereby retained from slipping rearwardly. The rear ends of heating element 38 are also crossed about the rear end of asbestos piece 36, shown generally at 39, for a purpose more particularly hereinafter described.

An electrical plug 40 adapted to be operatively receive-d within the conventional cigar lighter socket of a motor vehicle 42 transmits electrical energy from the electrical system of the vehicle to energize motor 18 and heater element 38 through electrical wires 44.

In operation, when plug 40 is inserted into the cigar lighter socket of motor vehicle 42, electrical current is transmitted through wires 44 and energizes both electrical motor 18 and heater element 38, causing fan 17 to rotate and the heater element to radiate heat within cone 30. The motion of fan 17 forces air forwardly and outwardly from case 10 through cone 30, orifice 34, and air outlet port 14. As such air passes through cone 30, it is heated by contact with heater element 38 and by heat energy radiated from said element.

The handle portion of the device is gripped manually by the operator and the barrel portion aimed in a natural manner toward the windshield or other pane of glass from which frost or ice is sought to be removed. The length of the cord is sufficient so that not only the inner surface of such pane of glass may be thus defrosted but also the operator may pass the device through an open window or door of the vehicle and employ the device outside of the car, as illustrated in FIGURE 3, while plug 40 is still engaged within the cigar lighter socket of the vehicle.

Particular attention is invited to the configuration and nature of heat chamber 28 formed by aluminum cone 30. The constant slope of the sides of cone 30 minimizes turbulence of air entering the heat chamber formed thereby. Further, when the rear ends of heating element 38 are crossed about the rear end of asbestos piece 36, as shown at 39, so that the folded ends of the element are parallel to the longitudinal axis of cone 30, the constant slope of the sides of the cone cause an increase in the velocity of air passing forwardly through the cone generally proportionate to the proximity of the molecules of such air to the portion of the heating element to which they are exposed, causing the molecules to be exposed to heat from the heating element for time intervals which are inversely proportional to the heat energy absorbed thereby. Air entering cone 30 is thus heated uniformly as it passes forwardly therethrough.

It should also be particularly noted that the slope of the sides of cone 30 forms a dead air space 46, the crosssectional area of which increases directly with the decrease in cross-sectional area of cone 30 throughout the length of heating element 38. The insulating effect of dead air space 46 against heat loss through the wall of cone 30 thus increases as the temperature of air passing through the cone increases during its passage therethrough.

I have found that where no heat chamber 28 is provided, fifteen to eighteen amperes of electrical current is required to produce at air exhaust port 14 air having a temperature of from 150 degrees Fahrenheit to 175 degrees Fahrenheit, and such flow of current frequently causes the fuses of the electrical system of the motor vehicle to be blown. When heat chamber 28 is employed, however, I have found that only approximately eight and one-half amperes of electrical current is required to product at air exhaust port 14 air having a temperature of approximately 200 degrees Fahrenheit. Heat chamber 28 thus increases the air temperature at outlet port 14 by 12.5% to 25%, but, even more importantly, does so with a current drain of only 47% to 57% of that required where the heat chamber is not used. Thus not only the eifectiveness of the device as a defroster is increased but the efiiciency thereof is dramatically increased with less drain on the source of electrical energy, increased life for heater element 38, and the avoidance of blown fuses.

It is to be understood that the form of the invention herewith shown and described is to be taken as a preferred embodiment of the same and that resort may be had to various changes in construction Without departing from the scope of the subjoined claim.

What is claimed is:

In combination, a gun-shaped case of molded plastic, said case having a handle portion and a cylindrical barrel portion; said handle portion having an air inlet port; said barrel portion having an axis, a muzzle end, and an air outlet port at said muzzle end; a forwardly directed hollow truncated cone disposed within said barrel portion, said cone having a large end and a small end and formed of material having high heat reflective characteristics, said cone having an axis and said axis of said cone aligned to coincide with said axis of said barrel portion of said case, said large end of said cone positioned adjacent said handle portion of said case and said small end of said cone positioned adjacent said air outlet port of said barrel portion of said case; an open spiral coil electric resistance heating element positioned Within said cone, said heating element having two ends, said ends being folded adjacent said large end of said cone about an insulating supporting element longitudinally aligned with said axis of said cone to form a generally U-shaped heating element with the legs thereof maintained substantially parallel to the common longitudinal axis of said cone and said barrel portion of said case, whereby air is permitted to flow through said legs of said open spiral coil heating element, an annular dead air space is formed by said cone and said barrel portion of said case, the transverse cross-sectional area of said dead air space increasing directly with the decrease in cross-sectional area of said cone throughout the length of said heating element from the large end towards the small end of said cone, and said barrel portion of said case is insulated from said heating element; an electric motor mounted within said handle portion of said case; a fan operatively mounted upon said motor and arranged to force air forwardly through said cone and outwardly through said outlet port; an electric plug adapted to be operatively received within the cigar lighter socket of a motor vehicle; and means for transmitting electric current from said plug to said motor and said heating element to electrically energize same.

References Cited by the Examiner UNITED STATES PATENTS 981,641 1/11 Halliwell 219-374 X 1,346,471 7/20 Slater 219-374 X 1,564,896 12/25 Rinker et a1 219-375 X 1,738,164 12/29 Zingg 219-374 X 2,049,812 8/36 Loacker 219-369 X 2,432,067 12/47 Morse 219-374 X 2,514,528 7/50 Wahl 219-374 X 3,026,401 3/62 Cheviron 219-369 X RICHARD M. WOOD, Primary Examiner.

ANTHONY BARTIS, Examiner.

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