Improvements in Black-boards for Schools.
Year: 1897

page_text: Date of Application, 5th Apr., 1897-Accepted, 22nd May, 1897
Improvements in Black-boards for Schools.
I, GOTTFRIED GLASMACHERS, of No. 22 Stoppenberger Strasse, Essen,
Germany, do hereby declare the nature of this invention and in what manner
the same is to be performed to be particularly described and ascertained in
and by the following statement :-
This invention has for its object to construct a black-board for schools which
shall be capable of being set higher and lower with ease, whilst obviating the use
of pulleys and counterweights.
This object is effected by suspending the board (which is guided by means of
pins in its stand) from helical springs in such a manner that the board moves
down automatically when it is not hooked in, without causing any jolting.
When the board is set higher, the springs, which have a tendency to contract,
exert a lifting action, so that the raising of the board can be effected with the
greatest case.
But in order to carry this into operation it is necessary to provide a board of
the least possible weight, 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
Figs. 1 and 2 are respectively a front elevation and a vertical section of the
board without the stand.
Fig. 3 is a section to a larger scale shewing 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 the board shewing the manner of its suspension and
guidance in the stand, to a larger scale. Fig. 7 is a front elevation of the same.
The board A is composed of "wood-felt or "cork felt" covered with " leather-
board." The two layers of leather board bb (Fig. 3) are cemented on to the plate
of wood or cork felt a by means of "water-glass." The writing surfaces c c are
first impregnated with hot linseed oil; then coated three times with a putty-like
mass composed of Japan lacquer and grey kieselguhr; flattened down with a
spatula or painters knife, and rubbed or polished with pumice-stone and oil. The
wood felt plate a is characterised 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 the plates,
and second, to aid still more in obviating warping of the plates.
The finished plate is then placed in the frame B which consists of light wood.
The framing is effected by filling up the grooves of the frame with cement
composed of kieselguhr and glue, and then ramming the plate up tight.
In this manner there is produced a light elastic board which is firmly fastened
to its frame. Right and left in the frame are fixed the pins C upon which the
board swivels. These pins rest in bearings D which slide up and down in the
grooves E of the stand F.
They are suspended on helical springs G, and yield when the board is let down.
The fixing of the board is effected by means of hooks arranged at the top of the
frame and formed of flat bar or strip iron H; they take into suitable toothed
racks J fixed to the stand.

page_text: The suspension of the board on helical springs, allows, as above stated of rapid
and convenient setting up or letting down of the board, without the possibility of
jamming, because the springs are always uniformly tensioned. Also, all noise and
jolting of the board are obviated.
When the board has been drawn down under the toothed racks, it can be easily
swivelled on its pins C, as indicated in dotted lines in Fig. 4, so as to be ready for
use on both sides.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
"
1. A school black-board, consisting of a plate a of "wood-felt." or "cork felt
which is covered with two leather boards bb cemented thereto by means of water-
glass under the application of pressure, upon which boards bb the writing
surfaces c c are provided by means of Japan lacquer and kieselguhr; the whole
being fixed in a wood frame B by ramming, substantially as described.
2. The suspension of the board specified in Claim No. 1, by means of the
pins C in the bearings D which are suspended in grooves E of the stand F by
means of helical springs G, whereby the weight of the board is balanced, and the
raising and lowering of the board by means of the hooks H in the toothed racks J
is facilitated.
Deted this 5th day of Anril 1897
ABEL & IMRAY,
Agents for the Applicant.