Improvements in T-squares.
Year: 1896

page_text: ISIONAL DE CIFICATION.
Improvements in T-squares.
I, JOSEF GRANZ, of Zurich, in the Republic of Switzerland, Engineer, do hereby
declare the nature of this invention to be as follows:-
This invention relates to improvements in T-squares and has for its object to
provide means whereby lines may be drawn at any desired incline with the utmost
accuracy.
To this end I form a slide adapted to glide upon the edge of the drawing board in
the same manner as the head of an ordinary T-square. Each end of this slide is
formed with an eye and to each of these eyes is hinged a toothed segment having for
its centre that of the opposite eye. Upon each of the said segments is marked a
scale whereby the angle at which it is desired to draw lines is obtained, the divisions
of the said scale corresponding with the number of teeth the segment has.
The head of the T-square at each end is furnished with a screw having also an
internal thread adapted to engage a short threaded stud binged to the fulcrum of the
segment whereby the T-square can be fulcrumed at either end of its head to the
aforesaid slide as may be desired. Each end of the T-square head is furnished with
a pawl placed under the influence of a spring and adapted to engage in the said
toothed segment, whereby the T-square can be adjusted to and retained at any desired
inclination.
Dated this 95th day of March 1906
F. BOSSHARDT & Co.,
Agents to Applicant.
Improvements in T-squares.
I, JOSEF GRANZ, of Zurich, in the Republic of Switzerland, Engineer, 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 relates to improvements in T-squares and has for its object to
provide means whereby lines may be drawn at any desired incline with the utmost
accuracy.
This improved T-square facilitates a very rapid adjustment of the blade, from a
right angle up to 15 degrees in any direction and automatic locking of the
same in any desired position, by attaching to the T-square or ordinary head
a slide or auxiliary head, by means of segmental racks each tooth of which
represents a degree and which are pivoted to the said slide or head and engaged
by pawls placed under the influence of springs on the said ordinary head.
By this device and micrometer set screws employed in the ordinary head in
connection with the said racks adapted to act directly or indirectly upon the

page_text: said pawls, the T-square may not only be set to whole degrees or angles but also to
fractions without use of compass or protractor but with the assistance of the ordinary
30 degrees, 60 degrees and 90 degrees set square.
And in order that my invention may be more fully understood I have caused to be
appended hereunto one sheet of drawings marked with letters of reference indicating
like parts in the various figures.
Fig. 1 is a plan of this improved T-square showing its head partly in section at
line y-y Fig. 2 and in two different positions, the full lines showing it adjusted
15 degrees and the dotted lines at a right angle or in the ordinary position on the
board.
Fig. 2 is an end view partly in section at line - Fig 1.
Fig. 3 is a side view partly in section at line - Fig. 1.
Fig. 4 is partly a plan and partly a sectional plan of the end portion of the
T-square head, adjusted of a degree.
The blade S of the T-square is like any other made of wood also the head A
which is secured thereto by means of screws. To the head A are attached by means
of two segmental racks d, d' a slide or auxiliary head a, which is shaped in
section (Fig. 3) and has pivots c, c¹ for the reception of the said racks. The latter,
Fig. 2, are shaped in section and enter recesses formed in the head A which are
covered by plates g.
Each rack has 15 teeth d and each tooth space corresponds exactly with the
360th part of a circle touching the points of the said teeth and having its centre in
the fulcrum c or c' of the opposite rack. For instance the rack d¹ has its centre
in the fulcrum e on which the rack d, the head A and its blade S turns, whilst the
rack d¹ and its head a remains stationary the latter abutting against the drawing
-board R as shown in Fig 1.
Each rack is graduated in harmony with the teeth d so that the adjustment of
the T-square can be effected during drawing by simply pressing the projecting part
of the head a against the drawing board R with one hand and with the other the
blade S respectively downwards until the top edge of the head A coincides with
the desired graduation on the rack. One of the pawls e under the influence of its
spring, will then engage the respective tooth of the rack and retain the T-square in
that position. When it is desired to bring the T-square, i.e. the head A back to its
original position, the respective pawl e is withdrawn by means of its arm el,
Figs. 2 & 3, which projects sufficiently through the hole g' formed in the plate g, to
afford a grip, after which the blade can be moved back. has then resumed its
original or rectangular position again, in which it is retained by the pawls e, the
springs of which cause them to press upon the racks d, and thus the head A
against the auxiliary head a. The springs fare arranged in such a manner that they
not only press the pawls e into the rack teeth, but also back against the recesses in the
head A so that the racks may be moved freely in the same. The setting of the
T-square to fractions of degrees is effected by means of micrometer screws h, h¹
mounted in collars between the head A and plate g. The said screws by means of
studs are jointed respectively to the one arm of the angular levers k, Figs. 1 & 2.
When turning the said nuts to the right the said screws are drawn tight and the
pawl e jointed to the other lever arni is forced against the rack which causes the
head A to be pushed away from the auxiliary head a. The pitch of the said screws
and racks and the size of the angular levers k is so chosen that for instance when
turning the nut half way round the pawl e, head A and blade S are displaced in
relation to the rack tooth or degree and when turning the nut round once tooth
or degree and so on, Fig. 4.
Thus it will be readily seen that when it is desired to displace the T-square, for
instance 15 degrees it is moved until the pawl enters the 15th tooth, i.e. it coincides
with the 15th graduation on the rack. The screw on that side is then turned round
once to the right and the T-square will be set exactly to the angle as required.
To further picture the comparatively small but perfectly sufficient adjustability of
this T-square, a circle correspondingly divided has been drawn upon the drawing

page_text: board R, which latter is only partially shown. If the T-square, i.e. its head a is
always used on the same side of the board the first divisions 0 to 15 is formed by the
assistance of the 90 degrees set square, every tooth d of the rack d¹ corresponding
with a degree. The division of 15 to 45 is effected by the assistance of the
60 degrees, that of 45 to 75 by the 30 degrees set square and that of 75 to 105 direct
with the blade S.
This improved T-square compared with others which have a fast and a loose head
over each other, has also the advantage that the set square can be moved over the
head A whilst in the others it abuts against the part of the head which projects from
the drawing board.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed I declare that what
I claim, is-
1st. A T-square with adjustable head for the purpose of rapidly setting and
antomatically retaining it in any desired angular position, consisting of a head A
with blade S, having attached by means of segmental rack d, d' an auxiliary head a,
which racks are jointed to the latter and to which the head A can be locked in any
desired position by means of pawls e under the influence of springs f, all substantially
us set forth.
2nd. In a T-square as specified in the preceding claim, the micrometer screws h, h¹
mounted in the head A actuating the pawls e for the purpose of setting the T-square
to fractions of degrees, all substantially as set forth.
3rd. In a T-square as specified in the preceding claims, the plates g fixed into the
recesses in the head A, which provide slots for the guidance of the rack d, d¹ and
holes g' in the said plate, through which project the arms e¹ of the said pawls by
which they are brought out of gear, all substantially as set forth.
Dated this 23rd day of December 1896
F. BOSSHARDT & Co.,
4, Corporation Street, Manchester, Agents to Applicant.