AN IMPROVED CLUTCH FOR DRIVING PULLIES OR OTHER PARTS OF ROTATING MECHANISM
Year: 1873

page_text: LETTERS PATENT to James Buchanan Mirrlees, of the Firm of Mirrlees,
Tait, and Watson, of Glasgow, in the Counties of Lanark and
Renfrew, North Britain, Engineers, for the Invention of "AN
IMPROVED CLUTCH FOR DRIVING PULLIES OR OTHER PARTS OF ROTATING
MECHANISM."-A communication from abroad by David McColley
PROVISIONAL SPECIFICATION left by the said James Buchanan
Mirrlees at the Office of the Commissioners of Patents, with his
Petition, on the 9th May 1873.
I, JAMES BUCHANAN MIRRLEES, of the Firm of Mirrlees, Tait, and
5 Watson, of Glasgow, in the Counties of Lanark and Renfrew, North
Britain, Engineers, do hereby declare the nature of the said Invention
of "AN IMPROVED CLUTCH FOR DRIVING PULLIES OR OTHER PARTS OF ROTATING
MECHANISM," the same being a communication to me from abroad by
David McColley Weston, of Boston, Massachusetts, in the United
States of America, to be as follows, that is to say :-
This Invention relates to an improved arrangement or construction of
clutch for driving by frictional contact pulleys or wheels placed loosely

page_text: upon the same shaft therewith. The clutch consists of a hub or boss
secured to the driving shaft, and from which arms extend outwards
towards the periphery of the wheel or pulley. Each arm of the clutch
is made duplex, and within the space so formed the shank or stem of a
jaw or shoe is situate, the outer extremities of which fit the inner side
of the periphery or rim of the wheel or pulley. The inner end of each
shank or stem is jointed to one extremity of a lever centred on a pin or
stud fixed in the hub or boss of the clutch, and the opposite ends of the
said levers extend over a collar placed loosely on the shaft, and formed
with an inclined or conical exterior. Across the outer ends of each arm
of the clutch a spring is placed, whose outer ends are secured to the
two sides of the arm, whilst at the centre the spring is fastened to a pin
or stud fixed on the jaw or shoe.
When the loose collar is pressed up so as to force the part thereof of
greater diameter under the levers, the levers are raised, and the shanks
or stems of the shoes or jaws are drawn inwards, so that the shoes cease
to operate on the rim of the pulley or wheel, but when the collar is
drawn outwards so as to leave the levers free, the springs permit of the
shoes being thrown out by centrifugal force, and the weight of each shoe
is such that the speed of the driving shaft is sufficient to hold the clutch
in contact with the rim of the pulley or wheel, and thereby cause the
pulley or wheel and clutch to move in unison.

page_text: grant unto me, the said James Buchanan Mirrlees, Her special license
that I, the said James Buchanan Mirrlees, my executors, administrators,
and assigns, or such others as I, the said James Buchanan Mirrlees,
executors, administrators, or assigns, should at any time agree with,
and no others, from time to time and at all times thereafter during
the term therein expressed, should and lawfully might make, use,
exercise, and vend, within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention for "AN
IMPROVED CLUTCH FOR DRIVING PULLIES OR OTHER PARTS OF ROTATING MECHANISM,"
10 the same being a communication to me from abroad by David McColley
Weston, of Boston, Massachusetts, in the United States of America,
upon the condition (amongst others) that I, the said James Buchanan
Mirrlees, by an instrument in writing under my hand and seal, should
particularly describe and ascertain the nature of the said Invention,
15 and in what manner the same was to be performed, and cause the
same to be filed in the Great Seal Patent Office within six calendar
months next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said James Buchanan Mirrlees, do
hereby declare the nature of my said Invention, and in what manne
20 the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
My said Invention relates to an improved arrangement or construction
of clutch for driving by frictional contact pulleys, or wheels placed
loosely upon the same shaft therewith. The clutch consists of a hub of
25 boss secured to the driving shaft, and from which arms extend outward
towards the periphery of the wheel or pulley. The arms are mad
duplex, and within the space so formed the shank or stem of a jaw o
shoe is situate, the outer extremities of which jaws or shoes fit to o
correspond with the inner side of the periphery or rim of the wheel o
30 pulley to be driven. The inner end of the shank or stem of cach jaw i
joined to one extremity of a lever centred on a pin or stud fixed in th
hub or boss of the clutch, and the opposite ends of the said levers exten
over a collar placed loosely on the shaft, and formed with an inclined
conical exterior. Across the outer ends of each arm of the clutch
35 spring is placed, whose outer ends are secured to the two sides of th
arm, whilst at the centre the spring is fastened to a pin or stud fixed
the jaw or shoe.

page_text: And in order that my said Invention may be properly understood I
now proceed more particularly to set forth the system, mode,
in or under which the same is or may be used or practically carried
into effect, that is to say :-
or manner
On the Sheet of Drawings hereunto appended, Figure 1 is an elevation 5
at the end marked B, Figure 2, of the improved clutch, constructed in
accordance with my said Invention; Figure 2 is a vertical section of
the clutch on the line a, b, Figure 1; and Figure 3 is a transverse
section of the same on the line c, d, Figure 2.
As shewn by these Figures the clutch consists of a hub or boss a li
formed in two pieces, and secured to the driving shaft 6 by means of
pins or bolts c, as more particularly seen at Figure 3, and from the boss,
arms d extend outwards to nearly the periphery or rim e of the pulley or
wheel f. The arms d are made duplex, that is to say, have two
branches g, g, and within the space so formed in each arm the shank or l
stem of a jaw or shoe i is situate. The jaws or shoes i are formed with
curved surfaces at their outer ends, which fit against the inner side of
the periphery or rim e of the wheel or pulley f, or in lieu of causing the
jaws or shoes i to bear against the periphery or rim e a friction surface
or liner may be placed over the outer end of each shoe i to bear against
the rim, as shewn at j on the Drawings, which can be renewed as wear
may require. The inner end of each shank or stem his jointed by
a pin to one extremity of a lever k, centred on a pin or stud / fixed in
the hub or boss a of the clutch, and the opposite ends of the levers k
extend over a collar m placed on the driving shaft b, and free to move
longitudinally along the said shaft. The collar m is formed with a
portion of its exterior inclined or conical, as shewn at n, Figure 2, of the
Drawings. Across the outer end of each arm d of the clutch mechanism
a spring o is placed, whose opposite extremities are secured by pins or
Irivets s to the two sides or cheeks g of the arms d, whilst at the centre
each spring is fastened to a jaw or shoe i by means of a pin or rivet "
as shewn more particularly at Figure 2.
The pulley or wheelf to which the mechanism herein-before described
is applied is placed loosely upon the driving shaft b, and its hub or
boss t is secured to a sleeve u which turns on the shaft b. The hub
is split, as shewn at v, Figure 3, and the two ears w of the hub fa
connected by a screwed bolt x, the nut z upon the screwed end of which