IMPROVED SELF LOCKING CHANGING DIAL FOR 24 HOUR CLOCKS
Year: 1885

page_text: FREDERICK MITCHELL, Engineer 39 Liverpool Road, Islington London do hereby
declare the nature of my invention for IMPROVED SELF LOCKING CHANGING DIAL
FOR 24 HOUR CLOCKS to be as follows :-
12
My invention for improvements in 24 hour clocks to enable it to be read with the
same ease & certainty as the ordinary 12 hour clock thus giving all the advantages
of 24 hour time without the disadvantage of so many figures being presented to the
view, the present 24 hour clocks over crowds the dials with figures & causes some
confusion by the inability of at once seeing which number the hands are pointing to.
The object of my invention is to so construct the dial that there shall be only 12
figures visable on the dial at one time. For this purpose, I construct a fixed sheild
or mask with 12 leaves projecting over the figures. Under said mask I place a
moving dial carrying all the figures from 1 to 24, and by suitable mechanism
actuated by the clock itself to instantly move the dial 1/1, a revolution forward,
thus shewing the figures 1 to 12 as in ordinary clocks, at the end of 12 hours to
instantly move the dial backwards to its first position now shewing the figures 13
to 24, the first set of figures hideing under the fixed mask & and so on backwards
& forwards alternately once at the end of each 12 hours, the dial is self acting &
self locking in each position & cannot even be forced to shew its wrong numbers
& always presents a clear and distinct face the power necessary to oscilate the
dial is gradualy accumelated & given out in instantanous motion in each 12 hours,
so that it has no detrogatory effect on the time keeping, I do not claim the
revolving dial. But the change from one 12 hours to the other is instantanous, so
there is no blank or confused dial to view, the dial is self locking in each position,
so that a jar or jolt will not alter it & does not require any attention & is quite
certain in its action, by my invention I am enabled to have the figures for each
12 hours full sise & in the same line of circle. It is applicable to all existing
watches or clocks regardless of sise & is equaly suitable for illuminated dials and
all public clocks.
The dial may be reciprocated by any suitable mechanism-Preferably I employ
a cressent shaped cam, carried by a wheel and revolves once in twenty four hours.
Affixed or conected with the dial is two studs or arms which engage with the
said cam.
The power for moving the dial may be derived from the main spring or weight,
or an independant spring or weight or it may be accumilated by a second cam
acting alternately on duplicate springs atached to the dial. A revolving fly, or
air buffer, or spring, may be used, where required to prevent any jar when the dial
is coming to rest.

page_text: Í, FREDERICK MITCHELL, Engineer 39 Liverpool Road Islington, London do
hereby declare the nature of my invention for IMPROVED SELF LOCKING CHANGING
DIAL FOR 24 HOUR CLOCKS and in what manner the same is to be performed, to
be particularly described and ascertained in and by the following statement:-
My invention relates to an improvment in 24 hour clocks and by combinng a
moving dial with cam's and levers, to render it self acting and instantanous in its
change, and self locking in each position so that it cannot get displaced, and by
my arrangment I am enabled to show a clear and distinct dial, with large-figures
in each 12 hours, so that it can be as easily read as the ordinary 12 hour clocks,
and is as follows reference being had to the drawings hereto annexed and to
the letters and figures marked thereon.
Figure 1 is a view of a dial from 1 to 12-at noon it instantly (by reason of the
cams and levers hereinafter described) revolves on its centre /, a revolution forward
(see figure 2) and is locked in that position until midnight when it again instantly
revolves backward to its first position and is again locked until noon next day
and so on.
Figure 3 is a toothed wheel geared to any of the wheels of the clock or watch
so as to make one revolution in 24 hours, and to which a cam A is fixed, the
pallets B, B figure 5) are engaged with this cam (see figure 7).
Figure 4 is a second cam, also attached to the aforesaid wheel, the springs CC
(figure 5) are alternately acted on by this cam, so causing a strain or tendancy of
the lever D (fig 5) to revolve on its centre, the pallets BB being engaged with the
cam A this cannot take place until the said cam has made half a revolution, when
one pallet is disengaged on the one side, the lever rocks over carrying the dial with
it, the other pallet then becomes engaged with the outer edge of the cam A so
causing it to be locked in that position until the cam A has performed another half
a revolution when the same action takes place but in the reverse direction and is
again locked and so on.
Figure 5 is a lever with pallets and springs attached, this lever rocks on its
centre E, there is a stud provided at F to which the movable dial is screwed.
Figure 6 is side elevation of figure 5.
Figure 7 is the whole of the parts put togather in their proper position and is
fixed under the moving dial or disc, the centre E is placed over and on the hour
notion wheel and to revolve on same, the moving face or dial is fixed to this lever
by a screw seen at F (figures 1 and 2) into the stud provided at F (figures 5. 6. 7).
G G figures 1 and 2 is a fixed mask with 12 leaves projecting over the moving
dial.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I would remark
that I make no claim to revolving dials generally but I declare that what
I claim is
1st In a self locking changing dial for 24 hour clocks the combination-therewith
of a fixed mask with openings with the dial or reciprocating disc as herein described
and shown in the drawings.

page_text: 2. In a self locking changing dial for 24 hour clocks the combination there with
for the purpose aforesaid of the cams, pallets and levers, with the said fixed mask
and movable or shifting dial or disc and working as herein described and shown in
the drawings.
3. In a self locking changing dial for 24 hour clocks the combination therewith
of cams, pallets, and levers to make the said dial or disc, instantly changable and
self locking in each position substantially as described.