An Improvement in the Form and Construction of Centrolineads whereby they may be More Readily Adjusted and their Adjustment More Firmly Maintained.
Year: 1889

page_text: Date of Application, 4th Apr., 1889
Complete Specification Left, 13th July, 1889-Accepted, 24th Aug.. 1889
PROVISIONAL SPECIFICATION.
An Improvement in the Form and Construction of Centrolineads
whereby they may be More Readily Adjusted and their
Adjustment More Firmly Maintained.
I, JOHN JAMES CRESSWELL, of 13, Northgate, Louth, Lincolnshire do hereby
declare the nature of this invention to be as follows:-
A
The straight-edge A of the centrolinead, that rules the convergent lines, is
prolonged (A') beyond the point of junction (B) with the guiding straight-
edges (CC) which slide upon fixed pins or studs on the drawing-board. Two
rods, (D-D) of equal length, are jointed at one end to the straight-edges C-C,
at any convenient point in their length; the other ends of D-D are united by a
pin, or in any other way which permits of their necessary motion, as at E.
screw-clamp, or other fastening holds these united ends (E) at any desired point
in A'. This regulates the inclination of C-C to one another, and firmly maintains
the same at any angle, and ensures that the said angle shall always be truly bisected
by the working-edge of A. A graduated scale upon A¹ may be marked to shew the
position of E corresponding to any angle formed by C-C. Either edge of A, A',
may be used.
Dated this and dose of A 1 1000
COMPLETE SPECIFICATION.
An Improvement in the Form and Construction of Centrolineads
whereby they may be More Readily Adjusted and their
Adjustment More Firmly Maintained.
I, JOHN JAMES CRESSWELL, of 13 Northgate, Louth, Lincolnshire, Architect, 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 :-
I desire to adopt the drawing left with my Provisional Specification of the above
Invention as belonging to and illustrating this Complete Specification, the reference
letters herein referring to the said drawing.
The use of the Centrolinead, the Instrument for improvements in which I now
desire a Patent, is the production of lines converging to a point called the vanishing-
point in perspective drawing, when that point is inaccessible or inconveniently distant.
A certain form of Centrolinead, not having the features of novelty which I claim,
bas been illustrated in a book called "The New and Improved Practical Builder
published in London by Thomas Kelly No. 17, Paternoster Row, in the year One-
thousand eight-hundred and thirty-seven, and in other publications, and this form of
Centrolinead is in common ušė. It consists mainly of three arms or blades,
corresponding generally to those marked A. C. C, united at and moving independently
of each other in a plane round a common centre as at B. The required inclinations
of the arms C. C to one another and to the arm A, upon both which the position of
the vanishing-point depends, are found by trial or calculation in any given case, and
these arms CC are held at any such inclination required by clamping-screws working
in metal segments attached to A.
The new parts which I propose to add to the Instrument as described above and
D
037

page_text: in the publication referred to, and elsewhere, and those which I propose to substitute
for other parts are as follows, and these new parts and their use and arrangement
constitute my Invention.
The arm A is prolonged by the addition of a piece A¹, of any convenient length
and thickness, rigidly attached to A, and extending beyond the joint B, the centre of
the width of A and A' being in a continuous straight line. Two rods or links D. D
are jointed at one end to C. C, (best at about the middle of the length of the latter,)
either directly; or to two shorter arms fixed to CC, as shewn on the drawing. The
'other ends of D. D are united by a pivot or joint as at E, which pivot or joint,
together with that at B, and those connecting the rods. D. D with the arms C. C,
permits the motion of C. C and D. D in planes parallel to each other and to the
surface of the drawing-board. The rods D. D may be of equal length, or either may
be longer than the other, and either or both of them may be variable in length if it
is desired so to make them, by sliding joints or otherwise. The joint E is connected
with a clamp sliding freely along A', at any point in the length of which it may be
gripped and secured, by a screw or by other suitable means, the rods and arms D. D
and C. C moving with E and adapting themselves to its position for the time being.
The dotted portion of the drawing is intended to shew this motion and adaptation.
The rods D. D firmly sustain the arms C. C at any angle required for the proper use
of the Instrument, and together with the clamp and pivot at E and the con-
tinuation A¹ of the arm A, are in place of the metal segments and clamping screws
belonging to the old form of Centrolinead described and referred to above. The
arms C. are united to cach other by a joint at B. This joint at B has a pin in its
axis which slips into either of two sockets on the edges of A¹, and is there secured
by a screw-head, or by other suitable means that will allow of its revolution in the
said socket. In the drawing this pin is shewn as in the socket on the upper edge
of A¹, and the pivot E is on the same edge; thus arranged the upper edge of A
converges upon the vanishing-point to which the Centrolinead may be adjusted. The
lower edge of A may be made to converge upon that point by placing the pin in the
socket shewn on the lower edge of A', and reversing the clamp so that the pivot E
may be on the same edge. By these means the Centrolinead may be arranged to
work either right- or left-handed.
The arms A. C. C move in contact with the drawing-board when the Centrolinead
is in use A¹ D. D are above the surface of the board at a distance which will allow
them to clear the pins or studs which are fixed in the drawing-board, and which guide
the motion of the arms C C, and through them, of the whole Instrument, when it is
in use.
On A¹ is a scale so marked as to shew where the joint E must be clamped in
order to give the arms C. C any required inclination. This scale is marked with
figures shewing the distance at which the vanishing-point will be, when the pivot E
is set against those figures. By means of this scale the Centrolinead may be
adjusted so that the edge of A shall converge upon any point within the range of the
Instrument, as required.
Having now particularly described and ascertained the nature of my said Inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is
1 The addition to the arms C. C of the rods D. D, supporting C. C at any
angle required for the proper use of the Centrolinead, and moving and regulating
the motion of those arms, in the manner above set forth, or in any other manner
substantially the same.
2 The prolongation of the arm A by the addition of the piece A¹ and the
formation by its means of an abutment or support to the arms C. C, by
means of rods or stays connecting A' and C. C, substantially as shown and
described.

page_text: 3:-The addition of a graduated scale attached to or marked upon the above
or any similar form of Centrolinead, for its more convenient adjustment.
4: The combination of the above parts now claimed as new, or any of them, or
of any other parts substantially the same in form and arrangement, to make or assist
in making any required adjustment of Centrolineads, and to maintain or alter their
adjustment.
Dated this 19th dox of Tule 1000
JOHN J. CRESSWELL.