Improvements in Friction Clutches.
Year: 1892

page_text: Date of Application, 18th Oct., 1892
Complete Specification Left, 18th July, 1893-Accepted, 19th Aug., 1893
PROVISIONAL SPECIFICATION.
Improvements in Friction Clutches.
I, SAMUEL FORD, of 139 Hartington Road, South Lambeth, in the County of
Surrey, Engineer, do hereby declare the nature of the said invention to be as
follows:-
This invention relates to improvements in that class of friction clutches for
transmitting motion from one part of a machine to another in which the friction is
produced by pressing a conical plug, connected with one part of the machine, into
a conical recess formed in another part of the machine or vice versa and the said
improvements consist as follows:-'
Instead of making the surfaces which come into frictional contact conical, I
make the plug of a somewhat curved form convexly and the recess of a corre-
spondingly concave form. The convexity of the plug and the concavity of the
recess may be formed to the arc of a circle struck from a point on or near to a line
drawn at right angles from the centre line of the shaft on which the clutch is
mounted, to or through a point on the largest diameter of the frictional surface, or
they may be formed to any other suitable curvature. By this arrangement a
portion of the frictional surfaces makes a comparatively small angle with the axis
of the shaft on which the clutch is mounted, so that such portion of the two
surfaces grip one another very firmly, but as the small angle at which these portions
of the surfaces stand to the axis would, in the ordinary course, cause the surfaces
to bind together, so that they could not be easily separated; the other portions of
the surfaces, which stand at greater angle to the axis, prevent the said surfaces,
which stand at a small angle, from being pressed together with sufficient force to
cause them to bind, the result however being that the clutch with the curved
surfaces holds very much more firmly with a given pressure than a clutch of the
same size with plain conical surfaces standing at the usual angle.
If preferred, the convex curvature may be formed in the recess and the concave
curvature in the plug, the effect being the same as in the arrangement above
described.
Another of my improvements consists in improved means for pressing the plug
into the recess, or the recess on to the plug. Instead of forming the sliding sleeve
upon which the clutch fork acts, directly on the conical or curved plug, or on the
part containing the recess into which the said conical or curved plug enters, I make
the said sliding sleeve separate from either of those parts but connected to either
of them by a toggle joint. A toggle link is pin-jointed at one end to the said
sliding sleeve and the other end to one end of a lever which turns on a fulcrum pin
on a boss keyed to the shaft. This lever acts on the plug or on the part containing
the recess as the case may be. The plug or the part containing the recess may be
arranged to slide on the aforesaid boss or on the shaft itself as may be preferred.
Pressure applied to the sliding sleeve endwise operates the aforesaid toggle link
and lever and these exert a greatly enhanced pressure on the moving part of the
clutch in proportion to the leverage brought into action. By these means the end
pressure exerted on the shaft is only a comparatively small fraction of the pressure
exerted upon the clutch.
Dated this 18th day of October 1892.
A
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page_text: COMPLETE SPECIFICATION.
Improvements in Friction Clutches.
I, SAMUEL FORD, of 139 Hartington Road, South Lambeth, in the County of
Surrey, Engineer, do hereby declare the nature of the said invention, and in what
manner the same is to be performed, to be particularly described and ascertained in
and by the following statement, that is to say :—
This invention relates to improvements in that class of friction clutches for
transmitting motion from one part of a machine to another in which the friction is
produced by pressing a conical plug, connected with one part of the machine, into
a conical recess formed in another part of the machine, or vice versú; and in order
that the said improvements may be fully understood, I will proceed to describe the
same with the aid of the accompanying drawings in which
Figure 1 is a longitudinal section of a friction clutch with my improvements
applied thereto,
Figure 2 a sectional elevation taken on the line X X of Figure 1,
Figures 3 and 4 are sectional views of certain of the parts shown in Figure 1
arranged in a slightly different way,
Figure 5 is an elevation of one of the parts and
Figure 6 a section of same taken on the line Y Y of Figure 5.
A represents a shaft to which motion is to be given by the clutch. B is the part
of the clutch adapted to rotate loosely on the shaft A, and C is the part of the
clutch adapted to slide longitudinally on the shaft but prevented from turning
thereon by a feather in the usual way, or by arrangements to be hereinafter
.described.
The
Instead of making the surfaces B'C' of the parts B and C, which come into
frictional contact, of a plain conical shape as heretofore, I make the surface C, of
the plug C, of a somewhat curved form convexly, and the surface B', of the recess
in the part B, of a correspondingly concave form. The convexity of the surface C¹,
of the plug C, and the concavity of the surface B', of the recess in the part B,
may be formed to the arc of a circle struck from a point on or near to a line D D
drawn at right angles to the centre line of the shaft A on which the clutch is
mounted, through points on the largest diameter of the frictional surface.
drawing represents a small clutch measuring about three and a half inches on the
largest diameter of the frictional surface and the curves B' and C¹ are the arcs of
circles drawn from the point D' with a radius equal to that diameter but for larger
clutches I have found that curves drawn with a radius of six inches give satisfactory
results. The curves may however be formed to any other suitable radius. By
this arrangement the outer portion of the frictional surfaces makes a comparatively
small angle with the axis of the shaft A, so that such portion of the two surfaces
grip one another very firmly when the part C is pushed into the part B; but as
the small angle at which these portions of the surfaces stand to the axis, would; in
the ordinary course, cause the surfaces to bind together so that they could not he
easily separated, the other portions of the surfaces which stand at a greater angle
to the axis prevent the said surfaces which stand at a small angle, from being
pressed together with sufficient force to cause them to bind, the result however
being that the clutch with curved surfaces such as those shown in the drawings
holds very much more firmly with a given pressure than a clutch of the same size
with plain conical surfaces standing at the usual angle, which is generally greater
than the limiting angle of resistance of the material employed.
If preferred the convex curvature may be formed in the recess, and the concave
curvature in the plug as shown in Figure 3.
In Figure 1 the plug C of the clutch is the part connected with the shaft A. and
the recess in which the said plug fits is formed in the part of the clutch which is
disconnected from and remains loose on the shaft A when the clutch is out of

page_text: action; but it is obvious that the plug C may be formed on the part which is loose
on the shaft, and the recess in the part which is connected with the shaft as shown
in Figure 4.
Another part of my improvements consists in certain means for pressing the
plug into the recess, or the recess on to the plug as the case may be. Instead of
forming the sliding sleeve upon which the clutch fork acts, directly on the conical
or curved plug, or on the part containing the recess into which the said conical or
curved plug enters, I make the said sliding sleeve separate from either of those
parts, as shown at E in Figure 1, but connected to either of them by a toggle joint.
A toggle link F is pin-jointed at one end to a lug G on the said sliding sleeve E,
and the other end to one end of a lever H which turns on a fulcrum pin I in lugs J
on a boss K keyed to the shaft A by the key A'. The lever H is also pin-jointed
at L to lugs M M on the sliding part of the clutch. A single lever H and link F
may be employed as shown in full lines in Figure 1, but it is sometimes preferable
to employ a similar lever and link on the opposite side as shown by dotted lines in
Figure 1.
The plug C as in Figure 1, or the part containing the recess, as in Figure 4, may
be arranged to slide on the aforesaid boss K or on the shaft itself as may be
preferred. In Figures 1 and 4 it is shown arranged to slide on the boss K, being
prevented from turning thereon by the lugs M on the sliding part of the clutch
passing into the opening M' in the flange K' of the boss K.
Pressure applied to the sliding sleeve E endwise in the direction of the arrow in
Figure 1 operates the aforesaid toggle link F and lever H, and these exert a greatly
enhanced pressure on the moving part of the clutch in proportion to the leverage
brought into action. By these means the end pressure exerted on the shaft A is
only a comparatively small fraction of the pressure exerted upon the clutch.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
First. Shaping the frictional surfaces of a friction clutch to a curved form
substantially as hereinbefore described, and illustrated in the drawings.
Second. In a friction clutch having conical or curved frictional surfaces the use
of a sliding sleeve separate from the sliding part of the clutch but connected
therewith by a toggle link and lever substantially as hereinbefore described, and
illustrated in the drawings.
Third. In a friction clutch a sliding sleeve separate from the sliding part of the
clutch, a toggle link and lever connecting the said sliding sleeve to the sliding part
of the clutch, and a boss secured to the shaft, combined, arranged and operating
substantially as hereinbefore described, and illustrated in the drawings.
Fourth. The improvements in friction clutches as herein before described.
11 10th den of 11 1802
Dated
1012
day
11802
S. FORD.
W. H. Beck,
Per S. E. Gunyon,
115, Cannon Street, Loudon, E.C., Agent.