IMPROVEMENTS IN FRICTION COUPLINGS AND CLUTCHES."
Year: 1881

page_text: LETTERS PATENT to Johannes Carl Eckardt, of Stuttgart, in the Kingdom of
Würtemburg, German Empire, Engineer, for an Invention of "IMPROVEMENTS
IN FRICTION COUPLINGS AND CLUTCHES."
PROVISIONAL SPECIFICATION left by the said Johannes Carl Eckardt at
the Office of the Commissioners of Patents on the 1st December 1881.
JOHANNES CARL ECKARDT, of Stuttgart, in the Kingdom of Würtemburg,
German Empire, Engineer. "IMPROVEMENTS IN FRICTION COUPLINGS AND
CLUTCHES."
This Invention relates to friction couplings and clutches applicable to machinery
of all kinds requiring such contrivances.
The peculiar characteristic of my improved friction couplings and clutches is that
the driving power or the power to be transmitted itself produces the requisite
amount of pressure or friction, consequently the degree of pressure or friction is
proportional to the power to be transmitted."
This mode of action results from the fact that the revolving force inherent in the
driving part is resolved in a parallelogram of forces which is always directed to the
pressing or jambing together of the frictional surfaces.
As this jumbing must always be greater than the circumferential resistance which
is to be surmounted by friction, the radius of the frictional surface must be larger
than and suitably proportioned to the radius of the parallelogram of forces.
Where cylindrical frictional surfaces are used the radius is comparatively large,
but where conical annular grooves are employed as frictional surfaces the radius
may be made smaller, or according to the inclination of the sides of the groove.
According to the object in view the peculiar constructions of my said friction
couplings and clutches are divided into two classes,-
1. Self acting couplings or motor couplings which can be disconnected
automatically.
2. Clutch couplings disconnected from without by bend or otherwise

page_text: Both these kinds of couplings may be made with either conical or cylindrical
frictional surfaces.
In motor couplings it is usually a condition that the driven part shall be able to
continue its motion independently of the driving part so soon as the motion of the
driving part becomes slower, or stops, or is reversed, as is the case, for example, in
some kinds of gas motor engines.
According to one of my improved arrangements of this kind of coupling, a pulley
mounted on a shaft may constitute the driving part, and the shaft itself the driven
part, or vice versa, if desired. The said pulley is made with a frictional surface in
the form of a conical annular groove in one arrangement, and in the form of a plain
cylindrical surface in a second modification.
Two brako blocks situate on opposite sides of the shaft work in either case into
or against these friction surfaces, and are carried along through the friction
produced in the direction of rotation of the driving power.
These brake blocks are caused to act as forces at their inner contiguous edges
on two opposite points of a notched boss or cam, which is keyed on the central
shaft.
The said brake blocks bear concentrically on this boss or cam and in the notched
parts thereof, and aro free to turn round the said boss in the direction of the driving
force within certain limits, so that they have a tendency to move radially outwards
by reason of the resistances at the two opposite bearing points in the boss or cam
before mentioned.
As the driving force in a circular direction in the pulley always has a tendency
to thus turn against the boss which is driven, it follows that the brake blocks are
constantly pressed outwards against the friction surfacos, and to a degree
proportioned to the driving force exerted.
When the circular driving force ceases, and the motion of the pulley consequently
stops or is reversed, then the friction blocks will be turned back into their original
position, whereby they move radially inwards or towards the centre, and the
friction thus ceases, so that the shaft can continue to rotate in the direction of the
first impulse.
Two springs are secured to the sides of the two main brake blocks, and carry
small subsidiary brake blocks, which bear against the inner periphery of the pulley
for the purpose of supporting the two main brake blocks during the motion of the
shaft when in their inward position, and for producing, when a change in the
motion occurs, an immediate contact between the two main brake blocks and
the driving pulley, whereupon the before mentioned jambing or pressure is restored
by the rotary motion of the pulley.
In my improved clutch couplings wherein the putting in and out of gear is
effected from without by hand or otherwise, whilst the driving part does not
alter its motion, the pulley may be the driving part, as before, but I will assume
for the present that the central shaft is the driving part and the pulley the driven
part.
The mode of action is in principle the same as the one above described. The
notched boss or cam, which is keyed onto the central spindle or shaft, acts at two
diametrically opposite points as forces on the brake blocks by means of sliding
wedges, which wedges exert pressure against the friction surface, and so cause the
disc or pulley to be carried along. The release takes place so soon as the wedges
which cause the janibing or pressure are withdrawn from action.
For this purpose these wedges are held in a sliding sleeve, and can be moved
axially therewith.
So soon as the sliding sleeve with the wedges has been pulled back for the
purpose of releasing the brake blocks, these blocks are drawn together or inwards
by means of an annular spring laid round screws or projections on the sides of
the blocks, so that the latter shall not slide along the friction surfaces while out
of gear.
In throwing the clutch into gear the sliding sleeve with the wedges is only

page_text: pushed in so far as to cause a slight contact between the brake blocks and the
pulley, whereupon the jambing of the blocks against the boss takes place
automatically by the further rotary motion.
The taper or inclination of the wedges is only a little smaller than the angle of
friction, so that after the throwing into gear no axial pressure is required, and yet
the throwing out of gear is easily effected.
In the two constructions above described it is assumed that the motion is
produced by the shaft, and is transmitted by a strap pulley or by tooth wheels, or
vice versa.
The transmission of motion may however equally well be effected from the end
of one shaft to that of another, in which case the pulleys would be keyed on.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Johannes Carl Eckardt in the Great Seal Patent Office on the
31st May 1882.
JOHANNES CARL ECKARDT, of Stuttgart, in the Kingdom of Würtemburg,
German Empire, Engineer.
"IMPROVEMENTS IN FRICTION COUPLINGS AND
CLUTCHES."
My said Invention relates to certain improvements in friction couplings and
clutches, applicable to machinery of all kinds requiring such contrivances; and the
characteristic feature or property of my improved friction clutches (hereinafter
fully described and illustrated by the accompanying Drawings) consists in this,
that the driving power or the power to be transmitted itself effects the pressure
necessary for producing the friction, consequently the amount of pressure is always
proportionate to the power to be transmitted. This mode of action results from
the fact that the revolving power inherent in the driving part is divided in a
couple or parallelogram of forces, which constantly tends to press the frictional
surfaces against each other. As this pressure must always be greater than the
circumferential resistance to be overcome by the friction, the radius of the frictional
surface must be larger than and in a suitable proportion to the radius of the
parallelogram of forces.
For cylindrical frictional surfaces the radius of the frictional surface becomes
rather large, but by using annular grooves having inclined sides as frictional
surfaces, which is illustrated by Figures 1 to 3, of my Drawings, the said radius
may according to the choice of angle of the sides of the annular groove bo smaller.
Figure 1 is a vertical section taken along the line B-B in Figure 2, and Figures 2
and 3 are transverse sections taken along the plane A-A in Figure 1.
My improved friction couplings and clutches are divided into two classes
according to the purposes to which they are to be applied.
1. Automatically releasing couplings or motor clutches as shown in Figures 1

page_text: to 3, and also in Figures 7 and 8 of my Drawings; Figure
being a vertical
section taken along the line F-F in Figure 8, and Figure 8 a transverse section
taken along the plane E-E in Fig. 7.
2. Shifting clutches intended to be disconnected from without by hand or
otherwise, as shown at Figures 4 to 6, and also at Figures 9 to 15 of my
Drawings.
Both classes may be constructed with conical or with cylindrical friction
surfaces.
1. Motor couplings.-Figures 1 to 3, and Figures 7 and 8, illustrate my peculiar
automatically released or self acting so called motor couplings, which generally
require that the driven part shall be able to continue to move independently of
the driving part, and shall cease to move when the motion of the driving part
becomes slower, ceases, or as is the case in atmospheric gas motors, is transformed
into a motion in the opposite direction..
Let the ring a in this case be supposed to be the driving part, and the shaft b
the driven part, although, if desired this order may be reversed. In the ring a,
Figures 1 to 3, there is formed a conical sided annular groove forming the frictional
surface, but in Figures 7 and 8 the frictional surface is cylindrical. The brake
blocks c, c, in both cases engage with these frictional surfaces, and are by the
friction produced carried along in the direction of motion of the driving power.
These brake blocks then act with driving forces, shown by the straight arrows
at P1, P1, at two opposite points on the cam d which is keyed onto the shaft b.
The blocks c, c, are concentric with the cam d, and can within certain limits turn
on d in the direction of the driving power, provided that they move radially
outwards by reason of the resistances at P¹, P. As it is the tendency of the
driving power to effect such a turning movement against the driven cam d, it
follows that the brake blocks are always pressed against the frictional surfaces and
in proportion to the driving power indicated by the curved arrow at P, in
Figure 2. When the action of the force or driving power P ceases as also the
movement of a, or when such movement of a is changed or reversed as in Figure 3,
then the brake blocks c, c, are turned back round the cam d to their initial position
here shown, and at the same time they slide radially inwards towards the contro,
the friction being thereby annulled and consequently the shaft bis left free to
continue to rotate in the first direction. The two springs e, e, which are fastened
to the friction blocks c, c, and are provided with small auxiliary brake blocks c', c¹,
pressed against the ring a serve to keep the brake blocks c, c, in their position on
the smallest diameter or out of contact with the ring a during the motion in the
direction shewn in Figure 3. and to proluce immediate contact of the brake
blocks c, c, with the ring a when the direction of motion is changed; whereupon
the pressure produced by the rotation of the said ring a as previously stated
will bo reinstated.
2. Shifting or disengaging clutches.-Figures 4 to 6, and Figures 9 to 15
illustrate my improvements in shifting clutches, that is to say, the class of clutches
in which the throwing in and out of gear or action is effected from without whilst
the driving part does not alter its motion; Figure 4 is a section taken along the
line C-Cin Figure 6; Figure 5 is a section taken along the line C-C in
Figure 6, and Figure 6 is a transverse section taken along the plane D-D in
Figures 4 and 5. In these clutches, as in the class No. 1 herein before described,
the ring may be the driving part, although the shaft is here shown for the sake of
variety to be the driving part. One of the modes of action of these shifting
clutches is in principle precisely the same as that of the motor couplings herein before
described, since the driving force being divided into a parallelogram of forces, tends
in like manner to press the frictional parts together. But in order to apply these
clutches with the greatest advantage in cases where the amount of friction at all
times is capable of being regulated, an arrangement is provided whereby they may
be made to work when desired by outer pressure alone, and consequently to the
exclusion of the driving power. Figures 4 to 6 illustrate such a shifting clutch

page_text: which, as here shown, works by outer pressure. The pressure of the brake
blocks k, k, is in this case produced by two wedges o, o, which are guided in the
cam piece h, and capable of being moved longitudinally by the sliding disc or
collar to which they are secured. When this disc or collar is moved slightly to
the left the parts are first disconnected, and by continuing such movement still
further to the left the two wedges i, i, form an intermediate link between the
cam piece h and the two brake blocks k, k, producing the same action as in the
motor couplings hereinbefore described. It should be remarked that the wedges o, o,
when in action or pushed by outward pressure, also operate as torsion wedges or
guides on the brake blocks k, k, so that the said brake blocks will not in this
condition be turned relatively to the cam piece h. The annular spring n which is
passed round the bolts m, m, will when the release takes place, draw the brake
blocks k, k, inwards or into their original positions again.
Figures 9 to 15 shew a shifting clutch in which an inner.brake or friction band
is used instead of brake blocks. The action is the same in principle as in the
previously described couplings. Figure 9 is a section along the line G¹-G¹
(Figure 14); Figure 10 is a similar section along the line G-G, Figure 13;
Figure 11 is a like section along the line G-G (Figure 15); Figure 12 is a
section along the line H-H (Figure 13); Figures 13, 14, and 15 are transverse
sections along the plane J-J (Figure 12), showing the parts in different positions.
The cam piece p is keyed fast on the central shaft, and on this cam piece the outer
casing g is free to turn slightly, such casing containing the jointed or hinged levers
r, r, the sliding wedge & with lateral inclined groove, and the split or open brake
band t. When this clutch is to work with application of pressure from without, as
in Figures 10 and 13, the transmission of the rotation from the cam piece p to
the casing q is effected by the cam u and the sliding wedge a; the latter in this
case forces the fork or hinged levers r, r, apart at the points rl, r¹, (Fig. 13) and
thus presses the brake band t against the inner periphery of the flanged disc or
pulley v. When the sliding disc or collar w with the sliding wedge & is moved
slightly to the right (see Figures 11 and 15), the releasing or contraction of the
friction band t takes place. By moving the wedge & further to the right
(see Figure 9), the cam u is acted upon by the inclined part of the groove
in the sliding wedge; the cam piece p will thereby be turned slighly relatively
to the casing 9, and will consequently act on the jointed levers r, r, at
the points (Figure 14) as parallelogram of forces shown by the straight
arrows at P, P¹³, thereby causing the brake band t to be expanded and pressed
against the disc ring or pulley v. My shifting or disengaging clutches will thus act
either by external pressure alone or by the driving power alone, as required.
Having now described and particularly ascertained the nature of my said Invention
and the manner in which the same is or may be used or carried into effect, I would
observe in conclusion that what I consider to be novel and original, and therefore
claim as the Invention secured to me by the herein before in part recited Letters
Patent is,
First. The construction and use of friction couplings and clutches, wherein tho
application of the driving power for the production of friction is effected in such a
manner that the said power is resolved in a parallelogram of forces by a cam pieco
or its equivalent either on the driven or on the driving shaft, which cam piece
causes the frictional surfaces to be pressed together substantially as specified.
Second. The application and use to and in self acting motor friction couplings,
arranged and caused to operate as specified with reference to Figures 1, 2, 3, 7, and
8 of the Drawings, of springs provided with auxiliary brake blocks, for the
purpose of destroying or breaking the contact between the main frictional surfaces
when the direction of motion of the driving power is reversed, and of reinstating
such contact when the driving power resumes its original direction of motion,
substantially as herein before described.
Third. The application and use to and in shifting or disengaging clutches, such
as are herein described with reference to Figures 4 to 6 and Figures 9 to 15 of my

page_text: Drawings, of an engaging and disengaging contrivance so arranged and combined
with the clutch as to admit of the frictional surfaces being alternatively pressed
together either by the driving force itself or by exterior means, substantially as
specified.
Fourth. The combination with a shifting clutch of the wedges o, o, and i, i, and
the cam piece h, capable of being shifted round relatively to the other parts of the
clutch, substantially as and for the purpose hereinbefore described with reference to
Figures 4, 5, and 6 of my Drawings.
Fifth. The combination with a shifting clutch of the sliding inclined grooved
wedge piece 8 and the cam piece p, capable of being shifted round relatively to the
other parts of the clutch, substantially as and for the purpose hereinbefore
described with reference to Figures 9 to 15 of my Drawings.
Sixth. The several constructions and arrangements of friction couplings and
clutches, substantially as hereinbefore described and illustrated by the Drawings
hereunto annexed.
Seventh. The application and use of the shifting or disengaging clutches
illustrated by Figures 4 to 6 and Figures 9 to 15, constructed and arranged in
such a manner, that the same shall be capable of being worked according to either
one of the two methods specified; that is to say, either by the driving power alone
or by the external pressure alone for the production of the friction.
In witness whereof, I, the said Johannes Carl Eckardt have hereunto
set my hand and seal, this Twenty sixth day of May, in the year of our
Lord One thousand eight hundred and eighty two.