Improvements in Clutches or Locking Devices Applicable for Various Purposes, more Especially where Mechanical Move- ments are Varied, Alternated, or Intermittent.
Year: 1887

page_text: Date of Application, 3rd May, 1887.
Specification Accepted, 17th June, 1887
[Communicated from abroad by ABSALOM GRIFFIN SMYTH, of New York City,
in the County and State of New York, Mechanical Engineer.]
Improvements in Clutches or Locking Devices Applicable for
Various Purposes, more Especially where Mechanical Move-
ments are Varied, Alternated, or Intermittent.
I, JAMES YATE JOHNSON of 47 Lincolns Inn Fields in the County of Middlesex
Gentleman 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:-
This Invention has for its object to provide an improved clutch or locking device
which may be used in connection with loose pulleys or gear-wheels, so that when they
are turned in one direction they will engage a shaft or other device on which they
may be placed, or for transmitting power from the shaft to the gear-wheel or pulley
or for transmitting power from one rotating object to another, as in a lawn mower,
for example, the lock being also very reliable and effective for converting reciprocating
motion into rotary motion, the wheel or pulley becoming readily disengaged when
revolved in an opposite direction to that which locks it.
The locking device constructed according to this Invention is comparatively
inexpensive and at the same time effective, durable and easily controlled as regards
uniformity of manufacture, thus rendering the parts interchangeable, and by this
means making the whole construction more reliable and effective and which will
automatically take up the wear and tear while it is in use.
I will describe the Invention with reference to the accompanying drawings.
Figure 1 of which is an outside end view of one of my improved locking devices.
Figure 2 is a similar end view with the cap or a portion of the end of the shaft
and wheel removed.
Figure 3 is an edge-view of the wheel and the cap end of the shaft. .
Figure 4 is a sectional view on the line, y―y, figures 1 and 2.

page_text: Figures 5 and 6 are detail views.
Figure 7 shews one method of applying the Invention.
Figure 8 is a sectional plan of the mechanism shewn in figure 7.
Figure 9 is a section and Figure 10, an end view partly in section of the locking
wheel.
Figure 11 is a side view showing a double-ended pawl employed in the device.
Figure 12 is a transverse vertical section of figure 7.
Figure 13 is a detail view of the spring which operates the pawl.
Figure 14 is a detail sectional view shewing the position of the pawl.
Figure 15 is a longitudinal section on the line x-x, figure 14.
Figure 16 is an outside view of two of the locking devices with rack between.
Figure 17 is an end view of a modified construction of the locking device.
Figure 18 is a longitudinal section on the line -z, figure 17.
Figure 19 is a sectional detail, showing a modified arrangement of the pawl, and
Figure 20 is a diagram, shewing on an enlarged scale the construction and position
of the pawls relatively to the grooves of the wheel.
Upon the inner surface of the gear-wheel A, (see figure 2,) are small shallow
grooves, formning ratchet teeth S, and they are so constructed that lines C, (see
figure 20) drawn at right angles to and from the centres of the bottom of the
grooves or inclined surfaces of the teeth, will be tangential to a circle struck from
the centre C of the wheel A with a radius equal to the radial distance between the
centre C, of the wheel and the point P where the pawl F is pivoted to the shaft upon
which the wheel placed. The bottom of the groove is of sufficient width to form a
bearing surface to receive the ends of the two pawls F. In cutting the grooves, a
sufficient portion of the surface is left between each groove as shewn at G₁ to afford
a bearing surface for the ends of the pawls to travel over and to allow for wear
when the shaft or wheel is being revolved in the direction in which they are not
locked with each other.
The shaft T is provided with an enlargement G, containing a recess E, (See
figures 14 and 15,) to receive one or more pawls F, and the spring I, the said pawl
or pawls being pivoted on a pin P, at a little distance from the centre of the shaft T as
herein before described. The recess E may extend only partly through the enlarge-
ment G, as shewn in figure 19, and the pawls arranged upon one side of the shaft
only, or the said recess may extend through the enlargement as shewn in figures 6
and 14, and the pawls be placed on either side of the shaft. In the latter case, a
central projection K, is provided, which extends inwardly and approaches the pawls
where the pin passes through them, each side of the said projection having a circular
concave surface K¹, to receive the bent portion of the spring I, which is maintained
in position between the said concave surface and a shoulder J, the ends of the spring
being thus prevented from coming into contact with the wheel, when either the shaft
or the wheel is revolving, and the ends of the pawls vibrating rapidly.
In order to render the locking device applicable for propelling boats locomotives
and machines that require the motion at times to be reversed, the pawl F may be
made to extend to both sides of the shaft or other mechanism with which the device
is combined as shewn in figure 11, the pivot upon which the pawl is centred being so
arranged that either end of the pawl may be caused to engage the wheel as required,
according to the direction of motion.
Against the projection K, is fitted to work a sliding bar r, having rack teeth, upon
one side, with which engage a pinion W fast on a spindle p, which extends through
to the outside of the enlargement on the shaft, and upon the outer end a button
may be attached, or the end of the spindle may be cranked or bent to form a handle,
by which the shaft p, may be turned to import a traversing motion, through the
pinion W, to the rack r, so as to press back one or other of the springs I, as required,
and release the other spring from the opposite side so as to cause the pawl to.engage
the grooves upon the corresponding side of the wheel and thereby drive the shaft
in the desired direction. By, rotating the spindle, so as to move the rack in the
reverse direction, the spring which had been acting on the pawl on one side of the

page_text: shaft to hold it in gear with the teeth in the wheel, will be pressed out of action;
and the opposite spring brought into action, and the shaft moved in the reverse
direction, the pawl engaging the wheel on the opposite side of the shaft as shewn
by the dotted lines in Figure 11.-The same principle will apply when the trans-
mission of power is exerted through the medium of the shaft to rotate the wheel
or pulley. One or more pawls may be used in the same manner as herein before*
described. To retain the rack in position, the pinion w, should fit closely and press
the rack against the flat surface of the projection K so as to cause moderate friction.
This provides for the shaft or wheel to be revolved in either direction by simply
manipulating from the outside the spindle attached to the pinion wheel. By making
the rack of suitable length and turning the pinion W so as to bring the rack to a
central position the ends of both springs will rest against the pawl F and will hold
it in such position that it cannot engage with the grooves, upon either side of the
shaft thus rendering it inoperative for the time being.
In some cases such as when the pulley or wheel is placed on a shaft or journal at a
distance from the end and it would not be practicable to insert a pin through the
journal lengthwise to reach the recess, the bottom of the recess may be rounded (see-
Figure 19) and one end of the pawl rounded to fit, and have a circular movement
therein. This will also give greater strength for resistance.
In other cases when a heavy force is being transmitted both the pin and the recess
may be used together thereby giving increased strength, the pin preventing the pawl
from leaving the seating when not engaged with the teeth and is under vibration,
particularly when the pawl is of such considerable weight that the spring may not
be sufficient to keep it in place.
Figures 4 and 13 shew the form of spring employed when two pawls are used.
AV shaped piece is cut from the center of one end about half the length of the
spring leaving two prongs which will rest against the two pawls when the spring
is bent and placed in position. The object of cutting a V shaped gap or opening
in the spring is to prevent one prong from bearing against the side of the pawls
if at any time the spring is not in a central position, the spring being made slightly'
less than the width of the recess in which it is fitted to admit of it moving a trifle to
one side or the other if required. Any number of prongs may be provided to be used
with a corresponding number of pawls, the main body of the spring retaining them all
in their proper position.
Figure 6 shews the form of pawls suitable to be used with the kind of grooves or
ratchet teeth described, and also the place of pivoting the pawls to give the best results.
The pawls should be made of the best steel, well tempered to prevent wearing. It is
desirable to have the mouth or entrance M of the recess E as small as possible, so as to
leave as much bearing surface as possible for wear. The pawls are preferably tapered
towards their free ends which engage the grooves or ratchet teeth so as to give them
more margin to move forward from the spring and take up the wear of the grooves as
they deepen. The grooves and the surface G₁ between them may be case hardened to
give to the locking parts increased durability. The ends of the pawls are preferably
wider than the length of the inclined surface of the grooves to allow for wear of the
edges which come in contact with the shoulders of the grooves or ratchet teeth. When
the pawls or the grooves become worn the pawls will come in position further upon.
the groove and still have full bearing thereon.
Very important results are obtained by pivoting the pawls at only a short distance
from the center of the shaft and forming the grooves so that when they pass by the
ends of the pawls the bottom of the groove which is in engagement will be at
right angle or nearly so, with a line drawn through the pivotal point of the pawl
as the pawls F will engage with the grooves or ratchet teeth gradually (in a
manner similar to that of the piston and connection rod of an engine when the
crank pin has nearly reached the dead center) so that when a reverse motion- is
given to the wheel or shaft, and the pawl comes in contact with the teeth or bottom of:
the grooves, less jar or shock is produced than is the case when a pawl is pivoted. far

page_text: from the center of the shaft as heretofore, whilst increased certainty of the engagement
of the pawl with the teeth is ensured.
In this improved locking device the pawls engage the solid portion or main body of
the wheel which, if it becomes worn so as to deepen the grooves, will still continue to
lock, as the spring placed upon one side of the pawls will keep them in position to
engage the wheel, until the margin for wear is all taken up. This is provided for by
the length of the entrance into the recess in the enlargement of the shaft; for the
further the pawls move round in a direction from the spring, the more they project
from the shaft. This is illustrated in Figure 14. Furthermore the grooves being very
shallow, when only one pawl is used and the reverse motion is made in order to lock
the parts, the end of the pawl cannot become so far removed from the point of contact
as in the old mothod, and in order that there shall be more immediate contact between
the bottom of the groove and the last pawl (when only two are used) that may come
in position, just before the reverse motion, to lock the parts takes place, several pawls
each of different lengths may be used to completely obviate the shock or jar when a
large force is being transmitted in converting motion or for similar purposes. For
foot power, two pawls will give good results.
When two pawls are used the difference in their lengths should be in keeping with
the depth of the grooves or teeth at S, so that while the wheel is moving in a direction
indicated by the arrows in Figure 2 not to lock the parts, the shoulders will retain the
long pawl in a proper position to engage one of the grooves until the short pawl moving
in advance will come into position opposite the next groove, (see Figure 20 which shews
the positions on an enlarged scale) when it will be retained in that position by the
shoulder of that groove until the long pawl has obtained the same position. By this
means one of the pawls is always in position to engage the bottom of a groove when a
reverse motion takes place to lock the shaft and wheel together. When more than
two pawls employed are less difference in length is required.
For some purposes where heavy power is being transmitted the portion containing
the grooves and shoulders may be made of steel, and tempered very hard for wear, in
which case the grooves may be made in a metal ring R and the ring then attached to
the side of the wheel by means of screws Y (see Figures 17 and 18) or otherwise.
In Figures 7. 8. 12 and 16 two wheels A and A' are shewn as being employed to
the movement one after the other so as to make the action continuous.
rack bar N which receives a reciprocating movement transfers movement to the
wheels A. A' and thence through the wheels X X' and the wheel Z to the Shaft 2.
take
up
A
Having now particularly described and ascertained the nature of this Invention and
in what manner the same is to be performed I declare that what I claim is :-
First. The locking devices constructed and adapted to operate in the manner and
for the purposes hereinbefore shewn and described.
Second. A wheel or pulley having a number of grooves upon its inner surface, the
said grooves being so formed that a line drawn at a right angle from the center of the
bottom of the groove will pass a little to one side of the center of the wheel, in com-
bination with one or more pawls arranged upon a suitable shaft for engaging the
bottom of the grooves so that the wheel may be rotated by the shaft or vice versa
according to the direction of the movement as herein before described.
Third. A shaft or other device provided with one or more pawls in combination
with a wheel or pulley having a number of grooves with shoulders which form stops
or teeth to arrest the movement of the pawls, causing them, when the movement is
reversed to engage directly with the grooves or teeth as hereinbefore described.
Fourth. A shaft or other device provided with one or more pawls in combination
with a wheel or pulley having a number of grooves formed therein in such a manner
that lines drawn at right angles to the bottom of the grooves will pass through the
pivoted point of the pawl that is engaged with the said groove substantially as
hereinbefore described.
Fifth. The wheel having grooves or teeth G¹ in combination with a shaft or other

page_text: device provided with the shoulder J and concave surface (K¹) for retaining the
spring I in position for the purposes set forth.
Sixth. The combination of the shaft or other device provided with the pawls and the
spring having V-shaped prongs, with a wheel or ring having grooves or teeth on its
inner circumference as and for the purposes set forth.
Seventh. The combination of the shaft or other device provided with a pawl centrally
pivoted as shown in Figure 11 and so arranged that either end can be made to engage
the grooves or teeth in the wheel substantially as hereinbefore described.
Eighth. The combination of the shaft provided with a projection K or its mechanical
equivalent, a sliding bara pinion w and springs I with the pawls arranged to engage
either side of the wheel substantially as hereinbefore described with reference to
Figure 11 of the accompanying drawings.