US 2498328 A
Description (OCR text may contain errors)
A. L; ATKINS ELECTRIC PYROGRAPHIC' INSTRUMENT Filed April 14, 1948 Feb. 21, 195o Patented Fei). 21? 1950 UNITED STATES PATENT OFFICE 4 Claims. 1
The present invention relates to pyrographic instruments of the type used for forming burned designs on wood or leather` or other easily charred substances.
In general, devices of this type comprise an electrically heated stylus and a handle, by means of which the stylus can be held in the hand and used, much in the manner of a pencil. In the past, one of the principal problems encountered in such instruments was the difficulty in associating the stylus and heating element with the handle in such a manner that the handle would not become uncomfortably hot after use of the instrument for even a comparatively short period.
The present invention is directed to the provision of an improved pyrographic instrument of this general type, but which has a novel arrangement for preventing the handle from becoming uncomfortably warm even after continuous use of the instrument over a considerable period of time.
It is, therefore, the principal object of my invention to provide a pyrographic instrument with novel means for preventing overheating of the handle thereof.
Still another object of the present invention is to provide an improved pyrographic instrument having a heated stylus r tip and a handle therefor in which a column of moving air flows between the heated portion of the instrument and the handle for the purpose of air cooling the handle.
Still another object of the present invention is to provide an improved pyrcgraphic instrument which is extremely simple in construction and inexpensive to manufacture, yet durable in use.
Other objects and advantages of the invention will become apparent from the following description of a preferred embodiment of my invention, taken in conjunction with the accompanying drawings, in which similar characters of reference refer to similar parts throughout the several views.
In the drawings:
Fig. 1 is a plan View of a pyrographic instrument embodying the present invention;
Fig. 2 is an enlarged longitudinal sectional view of the instrument illustrated in plan in Fig. 1;
Figs. 3 and 4 are transverse sectional views taken in the direction of the arrows respectively along the lines 3-3 and 4--4 of Fig. 2.
Referring to the drawings: It will be seen that the pyrographic instrument there shown and indicated generally by the numeral I0 is cornprised of a stylus or tip I2, heated by an electrical heating element M, and that the tip and heating element are supported by a handle I6. Of these elements, the tip i2 is formed with its outward end brought to a comparatively sharp point to localize the application of heat, while its rearward portion is provided with a deep recess I8 which houses the heating element I4. As is common practice, this heating element is composed of a number of turns of resistance wire wound upon a ceramic rod or tube 20. The rearward exterior portion of the tip l2 is provided with threads by means of which the tip is attached to a generally tubular attachment member 22. This attachment member should be of a refractory substance having good strength and high heat and electrical insulating properties. Although other substances can be used, I prefer that this attachment member be moulded from lava.
The generally tubular attachment member 22 has a `comparatively large recess 24 extending through the major portion thereof so as to space the walls of the member 22 away from the heating element I4 a reasonable distance in order to reduce the rate of the heat transfer from the heating element to this attachment member. Although this attachment member is formed of a substance having extremely low thermo-conductivity, I have found that even so, continued use of the instrument will cause a tube of such material to become quite hot. l have found, however, that by providing this tube with fins 26 molded integrally therewith, a considerable portion of this heat is radiated and the temperature of the tube is therefore maintained considerably below that otherwise attainable.
The external rearward end of the refractory attachment tube 22 is substantially square, as best seen in Fig. 3. It thus is provided with comparatively sharp edges 28 at the junctures between each of its four sides. This rearward portion is also tapered slightly from front to rear.
The handle l5 of the instrument is formed as a tapering sleeve, preferably of a thermo-setting plastic, such as Bakelite and at its lower end is provided with an outwardly radiating collar 3l) which prevents the fingers of the user from accidentally slipping from the handle onto the heated tip i2. Additionally, this collar prevents the heated tip from coming into contact with the table surface when the instrument is laid upon its side.
Within its lower portion, the tubular handle member I6 has a generally cylindrical recess 32 of a dia'meter slightly less than the diagonal 3 Y dimension of the squared portion of the refractory attachment tube 22. Within this recess 32, four longitudinally extending shallow grooves 3d are equally circumferentially spaced around the recess and like the edges 28 of the attachment tube 22 are tapered slightly from front to back. rlhese grooves are of such size and are so positioned that the rearward end of the attachment tube 2,2 can be inserted into the recess 32 when the edges 28 are brought into register with the grooves 32. By pushing the assembly comprising the tip l2, the heating element lll, and the attachment tube 22 rearwardly, the corner edges 28 of the attachment,` tube are tightly wedged into the grooves 34, thus preventing the handle E6 from becoming separated from the other above-mentioned elements. In use, the normal application of pressure upon the handle in a direction toward the tip will enhance this wedging action. If desired, the handle can be N separated from the other elements of the device, by holding the handle while pulling upon the attachment member.
Within the hollow handle lt the two lead wires from the resistance heating unit lll are secured Y by means of crimp type solderless connectors 36 to the ends of an electric cord 38. An insulating sleeve dll] surrounds one of the connectors 36 to prevent electrical contact between the uninsulated portions of the wires and the connectors 36. It will be appreciated that only one of these sleeves l0 is required, since the handle is made of an insulating material such as Bakelite A knot 42 tied in the cord 38 is wedged vwithin the tapering handle I6 and prevents a strain upon the cord from being transmitted to the lead wires of the resistance unit. The internal tapering opening through the handle I6 is of such diameter at all points as to space the walls of the handle well away from the elements therein.
In assembling this device, it will be seen that it is necessary merely to thread the tip I2 into the refractory attachment tube 22, to place the heating element I4 within the tip l2 and refractory tube 22 and connect the lead wires of this heating element to the cord 38, one of such connections being insulated by the tube 40. Then, with the knot 42 tied in the cord 38, the end of the cord is dropped through the handle and the square rearward portion of the attachment tube 22 is pressed firmly into place in the grooves Sil. From the above description of the device it will be seen that the manufacturing and assembly cost of this instrument are extremely low.
In use, the device is held in the hand of an operator much in the manner of a pencil and thus the instrument is brought into a more or less vertical position with the tip l2 extending downwardly. Until such time as the heating element I4 increases the temperature of the rearward portion of the refractory attachment tube 22, appreciably no heat will be transmitted to the handle I6. However, when eventually the rearward portion of the tube 22 does become somewhat elevated in temperature, it will be seen that only a very slight amount of this heat will be transmitted to the handle by conduction. This is because the area of contact between the handle and this refractory member is extremely slight, since only the extreme corner edges of the tube 22 touch the handle. An additional important beneficial effect provided by this arrangement is that air around the upper portion of the attachment member as it is heated rises through the yrecess 32 and hollow handle, thus drawing cool air inwardly at the lower end of the handle. It will be appreciated that this upwardly moving convection current of air cools the upper portion of the attachment member and the lower portion of the handle and prevents hot air from being trapped within the handle. It thus materially aids in preventing overheating of the handle.
By the use of my invention, it will be seen that in the rst place, because of the fins 25, the attachment member heats slowly, and that only a small portion of this heat can reach the handle directly by conduction, and finally, that cool air is circulated between the attachment member and the handle at the point of connection between these elements.
A pyrographic instrument embodying the features of my invention, therefore, has a handle which remains remarkably cool even though the instrument is used continuously over extended periods.
Having described my invention, what I claim as new and useful and desire to secure by Letters Patent of the United States is:
l. In a heating instrument having an electric heating element, a tip heated thereby and a handle for supporting said tip, an integrally `formed hollow refractory member having the tip engaged at one end thereof and said element extending into the hollow and being spaced from the sides thereof, radiating hns formed on said refractory member, the end of said member opposite to the tip being substantially rectangular in cross section, said handle having a longitudinal passageway therethrough for providing communication for electrical leads adapted to be connected with said heating element and said rectangular cross section end being wedgingly engaged within the forward end of the recess with only its corners engaged by the recess, and thereby providing considerable cooling air passage between the sides of said end and the handle.
2. In a heating instrument having an electric eating element, a tip heated thereby and a handle for supporting said tip, an integrally formed hollow refractory member having the tip engaged at one end thereof and said element extending into the hollow and being spaced from the sides thereof, radiating fins formed on said refractory member, the end of said member opposite to the tip being substantially rectangular in cross section, said handle having a longitudinal passageway therethrough for providing communication for electrical leads adapted to be connected with said heating element and said rectangular cross section end beinCr wedgingly engaged within the forward end of the recess with only its corners engaged by the recess, and thereby providing considerable cooling air passage hetween the sides of said end and the handle, said recess being rounded where said end is engaged.
3. In a heating instrument having an electric heating element, a tip heated thereby and a handle for supporting said tip, an integrally formed hollow refractory member having the tip engaged at one end thereof and said element extending into. the hollow and being spaced from the sides thereof, radiating ns formed on said refractory member, the end of said member opposite to the tip being substantially rectangular in cross section, said handle having a longitudinal passageway therethrough for providing communication for electrical leads adapated to be connected with said heating element and said rectangular cross section end being wedgingly engaged within the forward end of the recess with only its corners engagedby the recess, and thereby providing considerable cooling air passage between the sides of saidL end and the handle, said recess being roundedwhere said end is engaged and being provided'with guide grooves for said corners thereof. Y
4. In combination, an electric heating element disposed within a metal tip for heating the same, a hollow handle with asoentral passageway for electrical leads adapted tobe connected with said element, and a single refractory member of integral construction connecting the tip to the handle and having a plurality of radiating ns and a square cross section end, said handle having a cylindrical recesswithln which said end 6 is wedgingly engaged with only its corners com tasting the recess walls whereby to provide for passage of cooling air through the handle and pastjthe refractory member.
ALLEN L. ATKINS.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 2,185,266 Railles Jan. 2, 1940 2,243,549 Yocom May 27, 1941 2,257,376 Grey Sept. 30, 1941