Improvements in or connected with Screws applicable for Securing Lithographic Stones and for other purposes.
Year: 1896

page_text: Date of Application, 9th Dec., 1896
Comptate incrification Loft Oth Sant 1907 Mecanted 16th Oct 1807
Improvements in or connected with Screws applicable for Securing
Lithographic Stones and for other purposes.
I, ARCHIBALD STEWART GAVIN of North Street, Hulme, Manchester, in the
County of Lancaster, Lithographic Printer, do hereby declare the nature of this
invention to be as follows:-
This invention relates to screws for holding or securing lithographic stones in
their frames and for similar purposes and is designed for the object of locking or
securing such screws when screwed up in position.
It consists essentially in constructing the screw with a ratchet at or near the
head and a pawl engaging therewith carried by a lever or its equivalent which
prevents the backward movement of the screw when tightened up and the machine
is running.
In carrying out the invention I prefer to make the ratchet in the form of a nut
to pass over the threads of the screw and I fit this ratchet into a lever carrying a
sliding spring actuated pawl. The ratchet is screwed up against the head of the
screw and as the screw is tightened to hold the stone in position the ratchet
rotates with the screw and the pawl prevents the movement of the screw in the
reverse direction to unscrew it. When it is desired to unscrew or unfasten the
screw the pawl can be drawn back by a small catch provided for the purpose.
In other forms of the invention the ratchet may be formed in one with the
screw or with its head or may be otherwise attached to it such as by a key pin
screw or the like and the pawl may be carried by any suitable form of lever or its
equivalent which will remain at rest as the screw rotates.
Dated this 8th day of December 1896.
WM. P. THOMPSON & Co.,
6, Bank Street, Manchester, Patent Agents.
Improvements in or connected with Screws applicable for Securing
Lithographic Stones and for other purposes.
I, ARCHIBALD STEWART GAVIN of North Street, Hulme, Manchester, in the
County of Lancaster, Lithographic Printer, 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 screws for holding or securing lithographic stones in
the frame of the carriage and for similar purposes and is designed for the object
of locking or securing such screws when screwed up in position.

page_text: It consists essentially in constructing the screw with a locking lever comprising
a ratchet at or near the head and a pawl engaging therewith which prevents the
backward movement of the screw when tightened up and the machine is running.
It will be fully described with reference to the accompanying drawings.
Fig. 1. Side elevation of locking lever with plate removed.
Fig. 2. Longitudinal section.
Fig. 3. Transverse section on line -y Fig. 1.
Fig. 4. Plan showing litho stone held in position by means of locking levers.
The screw E for securing the litho stone F in position is of the ordinary con-
struction and to this I attach or apply the improved locking lever B the extremity
of which rests upon the bottom of the carriage.
This locking lever is constructed with a ratchet A preferably provided with
internal screw threads in the form of a nut to embrace the threads of the screw.
The ratchet A is fitted at one end of the lever B of suitable form and in the
interior of the lever is fitted a sliding pawl C held in engagement with the ratchet A
by a spring D of spiral or other shape. The pawl C is provided with an arm or
lever c which projects through the lever B by which it can be drawn back when
it is desired to release the ratchet A.
The screw is passed through the ratchet A of the locking lever and the ratchet A
is screwed tightly against the head of the screw. As the screw E is tightened to
hold the stone F in position the ratchet A rotates with the screw and the pawl C
acting upon the ratchet which is locked to the head of the screw prevents the
movement of the screw in the reverse direction to release or loosen the stone.
When it is desired to unscrew or unfasten the screw for the purpose of releasing
the stone the pawl C is drawn back out of contact with the ratchet A by the arm
or lever which projects through the slot in the lever B.
In other forms of the invention the ratchet may be formed in one with the screw
or with its head or may be otherwise attached to it such as by a key pin screw or
the like and the pawl may be carried by any suitable form of lever or its equiva-
lent which will remain at rest as the screw rotates.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, I declare that what
I claim is:
1. The combination with screws for holding or securing litho stones in a print-
ing machine of a locking lever provided with a ratchet and pawl which permits
of the rotation of the screw in one direction and prevents it rotating in the opposite
direction substantially as described.
2. The combination with a screw for holding or securing litho stones of a
ratchet A with internal screw thread through which the screw passes a pawl C
to prevent the backward movement of the ratchet and screw and a lever such as B
substantially as and for the purposes described.
3. The improved locking lever for the litho stones screws constructed substan-
tially as described and shown.
Dated this 30th day of August, 1897.
WM. P: THOMPSON & Co.,
Manchester, Liverpool and London, Patent Agents.