IMPROVEMENTS IN ECCENTRIC SWIVELLING OR REVOLVING CHAIRS
Year: 1883

page_text: LETTERS PATENT to Robert Cruikshank Junior of Denny in the County of
Stirling North Britain for an Invention of "IMPROVEMENTS IN ECCENTRIC
SWIVELLING OR REVOLVING CHAIRS"
PROVISIONAL SPECIFICATION left by the said Robert Cruikshank, Junior,
at the Office of the Commissioners of Patents on the 9th November 1883.
ROBERT CRUIKSHANK, Junior, of Denny, in the County of Stirling, North
Britain, "IMPROVEMENTS IN ECCENTRIC SWIVELING OR REVOLVING CHAIRS,"
This Invention has referenco to a new or improved mode and means of, and
construction or arrangement of, mechanism for the eccentric swiveling of the upper
seat part of chairs on their under or frame stool part; which improvements are
more simple and efficient in their construction and action than the swiveling
arrangements heretofore in use; and will render such chairs more convenient for
ship cabin or saloon chairs, where there is little room for swiveling them round at
the table, where they are usually ranged and fixed.
The swiveling mechanism is formed of two horizontal plates or discs, the one
being screwed or secured to the upper part of the lower frame fixed to the floor,
while the other disc is similarly secured on the under side of the swiveling upper
seat part, so far much as in some other construction of swiveling chairs.
By these improvements, the two plates are held together in the said working
position by two round pins, the one secured in the centro, and the other considerably
eccentric to or out from it towards the periphery in one of the discs, preferably tho
under stationary one, and work up through a short straight or curved radial, and a
long tangential or curved alot respectively in the upper plate; the pins having
large heads or shoulders on the upper sides of the slots to retain them in the said
working position, while the upper plate seat part is being oscillated on the said
swiveling pins, eccentrically passing through the said slots.
The disposition of the guide or swiveling pins and their straight, segmental, or
curved grooves is such as to enable the seat part of the chair to be turned half
round outwards from the table to one side only and be stopped, that being either to
the right hand or to the left as desired to be made.

page_text: When the parts are made for the seat to turn to the left and the discs are
concentric to each other with the seat in position at the table for the person seated,
the centre pin is near the middle of its short radial slot or towards its outer end
with the outer eccentric pin near the right hand end of its long tangential or curved
slot passing across the outer or back end of the radial slot, all so that the sitter can
move the seat considerably to or from the table on the outer pin as a centre,
without altering his position longitudinally, the radial slot passing out and in on
its central pin without turning the seat eccentrically. When the sitter wishes to
rise he turns the seat outwards to the left a quarter of a turn, the radial slot
moving outwards to its inner end on the central pin on which it swivels until the
outer pin is in the middle of its tangential or curved slot, when the seat has been
moved to the right of its extreme eccentricity, giving increased room on the left
side for the sitter getting out clear of the next seat on that side. On moving the
seat another quarter turn, the tangential slot moves on its pin to the extreme left
end, and the radial slot outwards to its opposite end nearest the tangential slot,
(which is now on the inner side of the central pin) thus continuing the eccentricity
outwards, so as to allow the sitter perfect freedom to rise, and also keep the back
of the soat quite clear of the table. The ends of the slots form stops on the pins
to prevent the seat moving more than the half turn in this direction, but leave it
free to turn inwards again to the table in the roverse swiveling direction to that
.described.
The said eccentric swiveling action and advantages are more perfectly obtained
by making the long tangential slot of a flat curve towards the right of and
towards tho back or outside of the radial curve, and of a quick curve towards the
left converging more concentrically towards the central pin and making the radial
slot nearly segmental and concentric to the outer pin when in this position in the
left hand extremity of its tangential slot; that is, for turning to the left as
described, but for turning the chair towards the right the curves of these slots
would be reversed. The arrangement would act with nearly equal advantage with
the radial slot straight and at right angles to a straight tangential slot formed near
the centre of the disc or a flat segmental tangential slot, preferably however with
a thickness of metal between the outer or back end of the radial slot and the
nearest central point in the segmental or curved slots. Although the swiveling
centro pins have been described as placed in the lower stationary disc and the
curved slots in the upper swiveling discs, so swiveling on the pins, the action
would be equally efficient with the pins fixed in the upper moving disc, and the
slots formed in the lower fixed disc, in which case the pins would swivel
eccentrically in the grooves, and the pins may either be allowed to revolve, or be
fitted with antifriction rollers in the grooves.

page_text: SPECIFICATION in pursuance of the conditions of the Letters. Patent filed
by the said Robert Cruikshank, Junior, in the Patent Office on the 8th May
1884.
ROBERT CRUIKSBANK, Junior, of Denny, in the county of Stirling North Britain
'IMPROVEMENTS IN ECCENTRIC SWIVELLING OR REVOLVING CHAIRS
"
My said Invention has reference to a new or improved construction or
arrangement of eccentric swivelling mechanism for chairs of the kind used in
ship's cabins or saloons, and fitted at the dining tables and in similar positions.
The object of the Invention is to enable the person, seated on the chair, to move
the seat freely towards or away from the table, and to swivel it clear of the tablo
when rising.
My Invention is illustrated by the accompanying drawings in which figure 1 is
a side elevation of my improved eccentric swivelling chair, and figures 2 and 3 are
plans of the same in different positions relatively to the table T. Figures 4 and 5
are respectively a plan and cross section of the swivelling plates or discs, connecting
the upper part or seat of the chair to the fixed framing, and figure 6 is a detached
plan of the under swivelling plate or disc.
The swivelling mechanism is formed of two horizontal plates or discs A and B
the one A being screwed or secured by a socket A¹ or similar means to the top of
the fixed frame or stool C, while the other disc B is similarly secured on the under
side of the swivelling upper seat part D, the arrangement being so far that usually.
adopted in forming swivelling chairs.
The two plates are held together by two round pins e, e¹, the one secured in
the centre, and the other e¹ considerably eccentric to or out from it towards the
periphery. These pins are by preference fixed in the lower or stationary disc A,.
and they work up through straight or curved slots f, f, formed in the upper or
movable plate or disc B, the one slot f being radial, and the other f tangential or
normal to the first.
The pins e, e', have large heads or shoulders on the upper sides of the slots f. f',
to retain them in the working position while the upper plate B is being oscillated
on the pins, passing through the said slots. The disposition of the guide pins e, c
and the straight, segmental, or curved slots f, f' is such that the seat part of the
chair may be turned half round outwards from the table T to one side only and be
stopped there, the direction in which the chair may be turned being either to the
right hand or to the left, according to the arrangement of the slots f. f
When the parts are made for the sent to turn to the left and the discs A, B, are
concentric to each other with the seat in position for the person seated at the table,
the centre pin e is near the middle of its short radial slot for towards its outer end,
and the outer eccentric pin e' is near the right hand end of its long tangential or
curved slot f passing across the outer or back end of the radial slot, as particularly
indicated in figure 2.
The sitter can then move the seat to a considerable extent towards or from the
table on the outer pin e¹ as a centre, without altering his position longitudinally,
the radial slotf passing out and in on its central pin without turning the seat
eccentrically. When the sitter wishes to rise he turns the seat D outwards to the
left, as indicated by the arrows in figures 2 and 3 to the extent of a quarter of a
turn, the radial slot moving outwards to its inner end on the central pin e on
which it swivels until the outer pin el is in the middle of its tangential or curved
slot f when the seat has been moved to the right of its extreme eccentricity, giving
increased room on the left side for the sitter getting out clear of the next seat on
that side. On moving the seat to the extent of another quarter of a turn, the

page_text: tangential slot f¹ moves on its pin e¹ to the extreme left end and the radial slot f
outwards to its opposite end nearest the tangential slot f¹ (which is now on the
inner side of the central pin, as indicated in figure 4) thus continuing the
eccentricity outwards, so as to allow the sitter perfect freedom to rise, and also keep
the back of the seat quite clear of the table T.
"The ends of the slots f. f1 form stops on the pins to prevent the seat moving
more than the half turn in this direction, but leave it free to turn inwards again to
the table in the reverse direction.
The said eccentric swivelling action is more perfectly obtained by making the
long tangential slot f¹ in the form of a flat curve towards the right of and towards
the back or outside of the radial curve f, and of a quick curve towards the left,
converging more concentrically towards the central pin, and by making the radial
slot nearly segmental and concentric to the outer pin e' when in the position in
the left hand extremity of its tangential slot, as indicated in figure 4; that is in
the arrangement for turning to the left as described, but for turning the chair
towards the right the curves of these slots would be reversed. The arrangement
would act with nearly equal advantage with the radial slot straight and at right
angles to a straight tangential slot formed near the centre of the disc or a flat
segmental tangential slot, a thickness of metal being left between the outer or back
end of the radial slot and the nearest central point in the segmental or curved slot.
Although the swivelling centre pins e, el, have been described as placed in the lower
stationary disc A, and the curved slots f,, in the upper inner swivelling disc B,
the action would be equally efficient with the pins fixed in the upper moving
disc B, and the slots formed in the lower fixed disc A, in which case tho pins
would swivel eccentrically in the slots The pins may be allowed to revolvo, or
may be fitted with antifriction rollers in the slots. The upper seat part D of the
chair is of ordinary form as is also the fixed stool or frame C.
Having thus particularly described my said Invention, and in what manner
the same is to be performed, I declare that what I claim is:-
First. The combination of parts forming the improved eccentric swivelling or
revolving chair herein described and illustrated.
Second. In a swivelling or revolving chair the construction of the plates or
discs A, B, connected by pins and slots in the manner herein described and
illustrated.
Third. In a swivelling or revolving chair the plate or disc B formed with radial
and tangential slots in combination with the disc A fitted with pins adapted to
move in said slots, as and for the purpose set forth.
In Witness Whereof, I the said Robert Cruikshank, have hereunto set my hand
and seal this Seventh day of May, in the year of our Lord One thousand, eight
hundred and eighty four.
R. CRUIKSHANK
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