US603631A - glasmachers - Google Patents

Description

3 Sheets-Sheet 1.

(No Model.)

G. GLASMAUHERS.

BLAGKBOARD.

No. 603,631. Patented May 10,1898.

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3 Sheets-Sheet 2. G. GLASMAGHERS.

A BLAGKBOARD. No. 603,631.

Patented May 10,1898.

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(No ModeL) 3 Sheets-Sheet.

G. GLASMAC-HERS.

BLAGKBOARD.

N0. 603,631. Patented May 10,1898.

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GOTTFRIED GLASMACHERS, OF. ESSEN, GERMANY.

BLACKBOARD.

SPECIFICATION forming part of Letters Patent No. 603,631, dated May IO, 1898.

Application filed April 2 2 l 8 9 7.

T0 a/ZZ whom it may concern.-

Beit known that I, GOTTFRIED GLAsMAcH- ERS, a subject of Vthe Emperor of Germany, and a resident of Essen, Prussia, Germany, have invented a certain new and useful Improvement in School-Blackboards, of which the following is a specification.

v This invention relates to that class of schoolblackboards in which the board is designed to be set higher or lower; and said invention consists in novel devices for rendering such construction more conveniently and efficiently operable. The novel devices referred to include a board having pins carried in bearingblocks guided up and down, said board being suspended by helical springs having a force about equal tothe weight of the board vattached to the supporting-frame, so that it may be easily moved downward when disengaged, the lifting actionserving to correspondingly elevate the board when desired; but in order to carry this into operation it is necessary to provide a board which shall not be so heavy as the usual wooden boards.

I will describe the improved construction with reference to the accompanying drawings in which- A Figures l and 2 are respectively a front elevation and avertical section of the board without the stand. Fig. 3 is a section, on a larger scale, showing the mode of constructing the board with its frame. Figs. 4 and 5 are respectively a vertical section and a front elevation of the board together with the stand. Fig. 6 is a section' of portions of the board, showing the manner of its suspension and guidance in the stand, on a larger scale. Fig. 7 is a front elevation of the same.

Like letters of reference indicate corresponding parts in the several figures where they appear.

The board is composed of holzlz (woodfelt or cork-felt) covered with leather-board. The two layers of leather-board B B, Fig. 3, are cemented onto the plate of felt A by means ofwater-glass, silicate of soda, or silicate of potash. The Writing-surfaces are first impregnated with hot linseed-oil, then coated twoor three times with a putty-like mass C C, composed of Japan lacquer and finely-reduced gray keiselguhr, an infusorial earth of great lightness occurring liberally in Ober- Serial No. 633,214. (No model.)

lohe in Hanover, flattened down with aspatula or painters knife, and rubbed with pumicestone and oil. The wood-felt or cork-felt plate A is characterized by great lightness and has the advantage that it does not warp. The cementing together of the three plates with water-glass serves, first, to introduce the least possible amount of moisture between kthe plates, and, second, to aid still more in obviating warping the plates. The repeated varnishin g with the inf usorial earth and rubbing down adds but inappreciably to the weight and gives a strong and durable surface, which is just sufficiently rough to receive the crayons or other ordinary writing and marking materials. The finished plate is then placed in the frame D, which consists of light wood.

The framing is effected by filling up the grooves of the frame with cement composed of keiselguhr and glue E and forcing the plate in tightly. l In thismanner there is produced a light elastic board firmly fixed in its frame. Right and left in the frame are carried pins G, upon which the board swivels. These pins rest in bearings I-I, which slide up and down in the grooves z' in the stand I.

The said bearings are suspended by helical springs J, which yield when the board is let down. The retention of the board is effected by means of hooks K, arranged at the top of the frame and formed of fiat bar or strip iron, adapted to take into suitable toothed racks I', fixed to the stand.

The suspension of the board by long-action springs allows of rapid and convenient lifting up or letting down of the board, because the springs are always uniformly tensioned. These motions are performed without the possibility of jamming, and all noise and jolting of the board are obviated. The

said helical springs J also have such range and length that their force is nearly equal in all positions of the board.

When the board has been` let down below I IOO tom of the board, which will come into posiv tion for use when the board is inverted.

The hooks Which come at the top may be engagedin the lowermost or in any other of the notches in the racks, according as it is desired to have the board held high or low.

Modifications may be made Without departing from the spirit or sacrificing the advantages of the invention. Parts of the invention can be used Without the Whole. The springs may be dispensed with, the board being suiiiciently light to permit its Y Weight to be sustained by the user during the adjustment.v

I claim asl my inventionl. A school-blackboard having a Writingsurface formed bya mixture of Japan lacquer and reduced keiselguhr rubbed or polished,

'substantially as herein speciiied.

2. A school-blackboard comprising a sec; tion of wood or cork felt having a layer ofl leather-board cemented thereto by soluble glass and faced with a mixture of Japan lacquer and reduced leiselguhr in two or more layers, rubbed or polished, substantially as4 herein specified.

3L In a school-blackboard, the combination' of a plate A of Wood-felt or cork-felt, which is covered with two leather-boards cemented thereto by means of Water-glass under the application of pressure, upon which boards B, B, the Writing-surfaces C C are formed of layers of Japan lacquer and keiselguhr, the

iWhole being firmly Xed in a Wood frame D, 'substantially as herein specified.

4. In a blackboard, the Within-described board A B, D, mounted by means of the pins G, in bearings II, Which latter are guided in grooves. Q1 of the stand I, and suspended by means of contractile helical springs J, Whereby the Weight of the board is approximately ,balanced and its raising and lowering is more easily eected, in combination with the hooks and toothed racks for engaging said board, all arranged for joint operation, substantially as herein specified.

In testimony whereof I have hereunto set my hand, at Essen-on-the-Ruhr, this 7th day kof April, 1897, in the presence of two subscribin g Witnesses.

GOTTFRIED GLASMACHERS; Witnesses:

LANWOR LIEBER, WM. EssENWEiN.

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