Improvements in Head-rests for Dentists' and other Chairs.
Year: 1894

page_text: Date of Application, 27th June, 1894-4ccepted, 29th Sept., 1894 .
[Communicated from abroad by ALEXANDER MCGOWAN DENHAM, of Santiago,
in the Republic of Chili, Dentist].
Improvements in Head-rests for Dentists' and other Chairs.
We WILLIAM HENRY ASI and CLAUDIUS JAMES ASH of 6, 7, 8 and 9 Broad
Street Golden Square in the County of London Manufacturers of Dentists'
Materials, 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, to which we append five sheets of drawings
The object of our invention is to construct and arrange a form of head-rest for
dentists' and other chairs wherein are improved means for adjusting and fixing the
several parts of the same in any required position.
Fig. 1, of Sheet No. 1, shows one form of our improved head-rest, wherein is a
ratchet R, pivoted to the end of an arm or support connected in the usual way by a
universal joint J, with the frame work of the chair. The arms A, A, which support
the pads H, H, are carried by a pin through the centre of the ratchet and are
separately held in position by spring pawls, whereof one is shewn at s, P, in a
sectional view. The details of the mode of fitting the arms with the ratchet are
apparent from Figs. 1, 2 and 3. In Fig. 1, each arm of the rest is held on to the
ratchet R, by a pawl P, pressed against it by a spiral spring s, inside the tube in
which the pawl is enclosed. When it is required to open out either arm A, its pawl
may be disengaged from the ratchet by pushing outwards, the milled collar C, which is
fitted on the tube containing the pawl and spring and operates on the pawl by a pin
shown at D. When it is required to elevate the arms, it is not necessary to touch
the milled collars, the upward movement being free and unimpeded. The pads H, H,
carried by the arms and connected by a broad elastic band B, are shown in
Figs. 1, and 5, and are attached to collars which can be shifted along the arms and
locked in any position by screws, as shown at A', in Figs. 1, and 4. The steel frame
which carries the pad is shown in section in Fig. 1, but to the construction of the
pads we make no claim.
In Sheet No. 2. are shown two modifications of the head-rest shown in Sheet No. 1.
In Fig. 7, the pads H, H, are carried upon a tube A, the universal joint J, being
attached to the centre of the tube at any required angle. End pieces are fixed to
the tube and carry a right and left-handed screw S, with preferably a double thread
to give a quicker action. Each pad H, is fitted with a ratchet R, and spring
pawl P, as in Fig. 1, whereby it can be rotated as desired. Fig. 8, shows the mode
of fitting the pad to its support and Fig. 9, shows the connection between the
tube A, and the joint J Fig. 10, is similar to Fig. 7, the difference being that
the screw is contained within the tube, which has two slots cut in it, to allow the
necessary traverse of the pads. Figs. 11, and 13, are end views referring to Fig. 10;
and Fig. 12, shows another mode of fixing the pad. Here a screwed cotter-pin
takes the place of the spring and pawl. By this arrangement of a right and left-
handed screw, in combination with the ratchets or stops, the pads can be shifted
along the tube and the inclination of each of them can be varied.
Fig. 14, shows another modification of our improved head-rest with the joint
arranged as in Fig. 1, but instead of a collar to carry the pin that withdraws the
pawl, button-shaped pieces B', B', are attached thereto as in Fig. 16, and Fig. 17,
and fulfil the same purpose as the collars. In Fig. 14, the pads are movable about
hinge-joints at the ends of the arms and are adjustable by set screws. Each pad
may be attached to the arm which carries it as shown in Fig. 15. In another

page_text: modification of our improved head rest, as shown in Fig. 17, the joint is arranged
as in Fig. 1, but the pads are movable by sliding along the arms and are provided
with springs s, s, and set screws as shewn. Fig. 18, being a transverse section of
the end of the arm.
Another modification of our improved head rest is shown in Fig. 19, where E, is
the joint on which the pad hinges, a tube M, carries a spring shown fully compressed
in the drawing and the pad has thus a motion of rotation about E, and at the same
time can be caused to slide to and fro along the tube as shown. When the required
position is obtained, by pressing upon the pad, the same can be fixed by merely
turning a set screw as indicated in Figs. 20, and 21. Fig. 20 is a back view of the
arm preferably oval in section, showing quadrant, set screw and joint of pad.
Fig. 21, is an end view in section of the joint showing the screw which fixes the
quadrant. In Figs. 22-26 there is shown an alternative method of locking the
jointed arms without the use of a spring pawl as in Fig. 1. The arms of the head-
rest, preferably of cast steel are jointed to a universal joint as in Fig. 1, and are
kept in any required position by a clutch arrangement shown in section at Fig. 22.
Here springs in the form of a washer, keep the two parts of the clutch separate until
they are brought together and the teeth are locked by the pressure caused on the
central bolt by forcing the pin shown in Fig. 22, up the incline on the top of the
lever handle as indicated in Figs. 22, 25 and 26. It is only necessary to give half a
turn to the handle which has a double inclined face, in order to effect the necessary
travel for fixing or relieving the joint. It is apparent that this clutch arrangement
for locking the arms may readily be adapted to replace the spring pawl in
Fig. 1.
Another modification of our head-rest is shown in Figs. 27 and 28. This is
arranged on the rack principle; the spring pawl, locks the upright which carries
the pad and is released by pressure on the finger F. The position of the pad H.
is determined by the action of a set screw on the quadrant Q.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
1. The construction and arrangement of our improved head-rest, substantially as
herein described and illustrated in Figs. 1 to 5 of the accompanying drawings.
2. The several modifications of our improved head-rest, substantially as herein
described and illustrated.
Dated 07th of T1001
WILLIAM HENRY ASH,
CLAUDIUS JAMES ASH,
Applicants.