Year: 1897

page_text: Date of Application, 13th Apr., 1897-Accepted, 15th May, 1897
I, VALERE ALFRED FYNN, of 13 Bexley Road, Erith, in the County of Kent,
Electrician, 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 :-
י
The object of my invention is to provide electro-magnetic clutches, or couplings,
which are reliable and silent in their action, engaging and releasing very rapidly or
gradually as required and without any tendency to drive after the electric current
which engages them has been cut off, and as a stationary exciting coil is used,
slip-rings and brushes are dispensed with.
According to my invention I employ a stationary coil or stationary coils and
driving and driven parts which are not in contact with each other, they being made
as discs, or rings, with continuous, or unbroken surfaces, or sides, presented to the
stationary part, or parts, of the clutch or coupling and with toothed, or driving, or
working, surfaces or sides, presented to each other; the said discs or rings being
so disposed as to complete the magnetic circuits around the said coil, or coils as
hereinafter more fully described.
In order that my invention may be clearly understood I will describe with
reference to the accompanying drawings, arrangements according to my
invention; premising that I do not limit myself to the precise arrangements
illustrated.
Figure 1 is a longitudinal section through a clutch, or coupling, constructed
according to my invention designed for intermittently transmitting, say, one
quarter of a horse power at about 300 revolutions minute.
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Figure 2 is a transverse section on the line a b Figure 1.
B is the stationary cylindrical body, or casing of an electro-magnet the outside
rim forming one pole; the central projecting cylinder H forming the other pole of
the magnet. The body, or casing B may be provided with feet K, to secure it to
a bed plate G as illustrated in Figure 2 or it may be secured in any other suitable
way. The exciting coil E is slipped, over the central cylinder H and is held in
position by a disc e (preferably of brass) secured by an iron ring R.
The two ends of the coil E are passed through openings in the body B, to the
two terminals T preferably secured to the said body B which body is made of cast
iron, forged iron, or steel. It can be cast in one piece with the cylindrical
projection H, or the said body B can be made up of separate pieces held together,
the projection H being screwed into, or otherwise attached to it. The driving
shaft S passes through the centre of the projection H and for small clutches, or
couplings, such as that illustrated and running at moderate speeds, it is convenient
to use the projection H; as a bearing for the shaft S, without the intervention of
a brass, or like, bushing; which however will be necessary in larger clutches, or
couplings, running at high speed. Only very little end play should be allowed to
this shaft. In the arrangement illustrated the shaft S forms part of the magnetic
circuit, but, as it will contribute to the conveying of the magnetic flux in a far
smaller degree when brass, or like bushes are used, this must be taken into
consideration in settling the dimensions for the iron sections of the clutch or
coupling.
Lindicates the situation of a lubricator, any suitable means of lubrication can

page_text: be used however, such as chain, or ring, lubricators for example. The shaft S
carries, at one end, a pulley P over which passes the driving cord, or belt; or the
shaft may be otherwise driven. At its other end the shaft S carries a disc with a
suitable number of projections S'; three such projections being shewn in the
arrangements illustrated. The number of these projections S¹ and their size can
be determined by methods well known and requiring no explanation here. The
number of the projections S¹ will to some extent determine the maximum time
which will elapse before the clutch, or coupling, engages, after the exciting current
has been put on; the time being shorter as the number of projections used is
greater, and the said time will be further reduced by so proportioning the magnetic
circuit that the first rush of current through the magnetising coil will magnetize
the iron sufficiently to make the clutch, or coupling engage when the projections
are in the correct position. The action of this apparatus when used in connection
with automatic regulators as employed for regulating electric circuits should follow
as rapidly as possible the directions of the relays used in such cases. The clutches,
or couplings, according to my invention are eminently suited to this purpose. It is
advisable in such cases besides taking the aforesaid precautions, to diminish the
self-induction of the exciting coil E and the space occupied by the clutch or
coupling to a minimum. This is best effected by winding the said coil with as few
turns as possible, and using, in series with it, a non-inductive resistance adjusted to
suit the tension of the electric circuit by which the coil is supplied.
The clutches or couplings may be made to engage gradually by switching on the
exciting current slowly. It will then be advisable to provide a large number of
teeth or projections on the working sides of the rings or discs. The clutch will
'then slip at the start. If it be intended to allow the clutch or coupling to slip for
any appreciable length of time, that is to transmit energy and reduce the speed of
the driven shaft relatively to that of the driving shaft at the same time then all
such portions of the magnetic circuit where a variation of the magnetic flux is set
up by such slipping ought to be laminated.
In the space between the projections S₁ from the disc at the end of the shaft S
and the end portion of the outer casing, or body B of the electro-magnet, is placed
a ring M having projections A similar, and corresponding, to the projections S.
This ring M is preferably supported by a gun-metal carrier C fixed to the driven
shaft A, and the said ring M, presents its continuous, or unbroken, surface to the
continuous surface of the casing B, and its projections A¹ to the projections S¹. It
is mounted to revolve concentrically with the shaft S, and with a clearance towards
the casing B, and the projections S', preferably as small as mechanical considerations
will allow.
The driven shaft A, may be supported in the bearing F, and standard f cast with,
or secured to, the bedplate G, or its equivalent. This bearing F, is preferably
provided with a thick brass bush, and the end of the shaft A, is kept as far as
convenient from the disc on the end of the shaft S. In some cases it may be found
advantageous to insert brass, or like, plates, J, between the casing B, or its feet K,
and the bedplate G, or the like connection, or support. All this is done to check,
or prevent, any magnetic leakage which might otherwise occur and divert the
magnetic flux from its useful path.
The approximate mean path of the magnetic flux is indicated by dot and pick
lines in Figure 1.
The projections S¹ and A¹ when the clutch, or coupling, is excited will be
maintained by the magnetic pull in the position shewn in Figure 2 and the disc ou
the shaft S, in revolving will carry along with it in its revolution the ring M,
which, in turn, will, through the gun-metal carrier C, cause the shaft A to
revolve.
No mechanical effort will be required to rotate the continuous, or unbroken, face
of the ring M, opposite the continuous and unbroken surface of the casing B, as no
magnetic changes will occur and therefore no injurious currents will be set up.
The same is the case with the disc at the end of the shaft S, where it revolves past

page_text: the stationary cylinder H. and the ring R, which of course, if it is made of iron,
will also afford a path for the magnetic flux.
1
A certain amount of electrical energy will have however to be supplied by the
coil E, to overcome the magnetic reluctance of the air gaps at these points. It will
therefore be of advantage to reduce these air gaps to a minimum and also to increase
the surfaces there to a maximum in order to diminish the density of the flux and
the length of its path through air and hence the energy required at these points.
The dimensions for the actual working points A¹ S¹ of the clutch, or coupling,
will be easily determined with the present knowledge of clectricity and magnetism
and call for no further explanation here.
As a general rule it is well not to make these clutches, or couplings, too long, as
if made too long, the central projection H, will overhang too far, but in order to
obtain the required space for the exciting coil E, the diameter should be enlarged.
A larger diameter means of course that the same energy can be transmitted at the
working points A¹, S¹ with a smaller pull and therefore with less density of current
and less electrical energy.
Clutches, or couplings, constructed in the manner described will work silently,
-as none of the revolving parts come into contact and there will be no danger that
they will continue to drive when transmitting only a part of their full power and
after the current has been cut-off, the rapidity of their action can be regulated
within wide limits and their action can be made almost instantaneous. The exciting
coil is stationary and therefore no slip-rings, or brushes, are required, thus greatly
reducing the chances of a break-down and making the action of the apparatus very
reliable.
The power to be transmitted can be exactly limited in these clutches, or
couplings, by adjusting the exciting current accordingly, and should that power at
any time be exceeded, the slipping of the clutch, or coupling, cannot be a source
of danger through heating of contact surfaces, or otherwise. When the
obstruction is removed the clutch, or coupling, will automatically resume its
normal functions.
Although these clutches are particularly well adapted for use in connection with
automatic electric regulators, they are not restricted to such use, and may be
employed with advantage in all cases where clutches, or couplings, are required.
Figure 3 illustrates, in section and side view, a modification in the disposition of
the several portions of the clutch, or coupling, it consisting of duplicate parts
turned towards each other and excited by separate coils E E.
The ends of the shafts S and A in this arrangement should be as near as possible
to each other, and the two rings M and M' have their respective and corresponding
projections turned towards each other, and their continuous, or unbroken, surfaces,
turned towards their outer casings, or bodies, B B. Both rings are supported ou
gun-metal, or like, discs, or spiders s².
Figure 4 illustrates in section and side view a modification of the arrangement
shewn in Figure 3, the difference being that the second clutch body and coil
are replaced by a simple disc D, which also serves as a bearing F for the
shaft A.
Figure 5 illustrates in section and side view an arrangement similar to that
shewn in Figure 4, but the ring M¹ revolving with the shaft A is dispensed with.
The disc D is separated from the bearing F and revolves with the shaft A and is
provided at its outer edge with projections equal and corresponding to the
projections on the ring M. The central part of the said disc D', faces the disc at
the end of the shaft S and conveys the magnetic flux from it to the ring M.
The approximate mean path of the magnetic flux is indicated by dot and pick
lines in the sections Figures 3, 4 and 5.
In all these arrangements the same precautions should be observed as regards
eakage as have been pointed out in describing the arrangement shewn in Figures 1
nd 2. These modifications will now be readily understood from the detailed
lescription of Figures 1 and 2 without further particular description.

page_text: In the description of Figures 1 and 2 I have referred to the shaft S as the
driving shaft and to the shaft A as the driven shaft but it is obvious that these
conditions may be reversed.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
1 claim is:-
An electro-magnetic clutch, or coupling, excited by a stationary coil, or coils, in
which the driving and driven portions do not come into actual contact with each
other, the driving and driven portions consisting of rings, or discs,-presenting
their continuous, or unbroken, surfaces, or sides, to the stationary part, or parts, of
the clutch, or coupling, and presenting their toothed, or driving, or working
surfaces, or sides, to each other; the said rings, or discs, being so arranged as to
complete the magnetic circuits of the stationary electro-magnet, or electro-magnets,
forming part of the clutch, or coupling; substantially as herein before described
and illustrated by the examples shewn in the accompanying drawings.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.