Improvements in Electric Power Apparatus.
Year: 1891

page_text: Date of Application, 8th Apr., 1891
Complete Specification Left 8th Feb 1802 Accepted, 12th Mar,
4000
PROVISIONAL SPECIFICATION.
Improvements in Electric Power Apparatus.
I, GEORGE NORTHI of 38 Shepherds Bush Green in the County of Middlesex,
Engineer do hereby declare the nature of this invention to be as follows:-
:-
This invention relates to the application of electricity as the motive power in
cranes, winches, hoists, capstans and other descriptions of machinery. Hitherto
the difficulty has been that where the load became excessive the burning of the
armature took place and the principal object of the present invention is to obviate
this. This accomplish by introducing between the armature and the load
preferably in or upon one of the shafts conveying the power a friction or similar
clutch or relief device whereby should the load become excessive the armature
spindle will slip round and thus the armature itself will be saved.
It will be understood that this clutch or relief device may assume a variety of
forms without departing from the spirit of the invention.
Dated this Fourth day of April 1891.
GEORGE NORTH.
W. P. Thompson & Boult,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Electric Power Apparatus.
I, GEORGE NORTH of 38 Shepherds Bush Green in the County of Middlesex,
Engineer, 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 relates to the application of electricity as the motive power in
cranes, winches, hoists, capstans and other descriptions of machinery. Hitherto
the difficulty has been that where the load became excessive the burning of the
armature of the dynamo machine (in consequence of its ceasing to revolve) took
place and the principal object of the present invention is to obviate this. This I
accomplish by introducing between the armature and the load preferably in or upon
one of the shafts conveying the power a friction or similar clutch or relief device
whereby should the load become excessive the armature spindle will slip round and
thus the armature itself will be saved.
It will be understood that this clutch or relief device may assume a variety of
forms without departing from the spirit of the invention.
In the accompanying drawings which will serve to illustrate two forms in which
this invention may be carried into effect,
Figure 1 is a sectional side elevation of a friction clutch and
Figure 2 is a face view of the same.
Figures 3 and 4 are similar views of a device in which the same result is attained
by the employment of a spring-controlled detent instead of by a friction clutch.
Like letters indicate like parts throughout the drawings.
A represents the armature shaft or driving shaft and B is a disconnected con-
tinuation of the same shaft and which is the driven shaft. C is one of the friction
discs and is a part of or rigidly secured to the shaft B and turns with it. D is
another disc or box secured to or forming part of the shaft A. and divided from
the disc C by the preferably wooden disc E which revolves with D and may be
connected to it by screwing or by forming slots or jaws in the disc E with which
Price 8d 1

page_text: would engage the bolts F which pass through the disc D and carry the helical
springs G by which the pressure upon the friction surfaces is in the first instance
regulated. The bolts F pass through the disc H in which they are prevented
from turning by having square necks and the holes in H being also square, and
also through the ring I, between which and the disc D the springs G are retained,
and bave upon their screwed ends one or more nuts F preferably two, of which
one would be a lock nut to keep the other from turning or shaking loose; the
disc C is as shown of smaller diameter than the disc D and thus clears the bolts F.
The disc D may have an annular flange D' projecting from it so as to form a box
or casing within which are the friction devices and the flange D¹ may have pro-
jections D adapted to engage with slots in the covering disc Il so as to ensure its
turning with the disc D without putting unnecessary strain upon the bolts F. The
operation of this device is as follows:-
The springs G are screwed up by the nuts F1 until the required pressure or
load is placed upon the friction surfaces and the operation is that when the
shaft A is revolved the disc D turns with it and owing to the friction between C
and E (E being rigidly connected with D) the shaft B is driven by A. When
however the load on B overcomes the friction between C and E the shaft B
will stop but the shaft A will continue moving and by thus allowing the armature
of the dynamo machine to continue revolving will save it from burning,
In Figures 3 and the same result is obtained by means of a catch instead of a
friction clutch. In these drawings the disc C carries the detent K which is pivotted
at K upon it and the spring L which is connected with K at K2 and with the
disc Cat M being in a state of tension serves to draw the free end of K2 of the
detent K towards the centre of the disc C. The shaft A carries the single or
double crank N the projecting pin or lug N¹ of which engages with the inclined
face K of the detent K and thus normally carries the disc C and shaft A. round
with it. When however the load upon the shaft B becomes excessive the pin N¹
acting upon the inclined face K³ forces up the detent K against the power of the
spring L and thus slips past it so that as in the former instance the shaft B may
remain still while the shaft A and armature continue to revolve. The detent K is
provided at its back end with the teeth or notches K with which engages the
spring-controlled pawl which is also pivotted upon the disc C; the result is
that when the detent K is turned by the pin №1 the pawl O slips into the
appropriate tooth K and thus retains the detent K at the position to which it was
moved so that the pin N¹ as it continues to revolve may not come into violent
contact with the detent. The detent K may be returned to its normal position by
removing the pawl O from engagement with the tooth K. Two sets of teeth K*
and pawls may be employed if desired so as to reduce the size of the teeth, any
suitable form of stop (the pawl O and one of the teeth K for example) may be
employed to prevent the detent K from moving too near the centre of the disc C,
and the spring L may be provided with any convenient arrangement of screw and
nut for altering or regulating its tension.
It will be seen that the principle involved in Figures 3 and 4 is the same as that
in Figures 1 and 2, viz. the releasing of the driver or armature shaft when the load
becomes excessive is accomplished, and it will also be appreciated that the same
result may be obtained by the employment of mechanism differing widely in
appearance from the two forms herein described and illustrated, although these
two forms differ considerably from each other.
It will be understood that the safety device may be placed wherever required
in the apparatus whether close to the armature or forming part thereof or at any
point in the system where found most advantageous and that the illustration of its
application to the shafts A and B merely shows one means of its application.
In both the forms of safety device above described the load may be regulated
by altering the power of the springs and this is a convenient plan to adopt. I
wish it however to be understood that I may dispense with the springs altogether
if I please and may regulate the load by means of the nuts F1 Figures 1 and 2.

page_text: In Figures 3 and 4 however whether for regulation purposes or not, some form of
spring release would be imperative as in this case it is not the mere slipping of
one surface upon another which is effected but the positive release of the pro-
jection N'. In a modified form of the apparatus the springs may be replaced by
electro magnets supplied with a current from the armature itself and so controlled
or regulated that the extent of the load which the safety device will carry may
vary in proportion with the current generated by the machine.
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 I
claim is :-
1. The method of relieving the armature of a dynamo machine and preventing
it from burning which consists in the employment of a safety device whereby when
the load upon the armature is greater than it can drive the armature can escape
from the excessive load and continue revolving.
2. The employment in dynamo driven machinery of a safety device whereby
when the safety limit of power of the dynamo is reached the load is relieved sub-
stantially as described.
3. The combination with the armature of a dynamo machine of a safety device
for relieving it from undue strain substantially as described.
Dated this 8th day of February 1892.
GEORGE NORTH.
W. P. Thompson & Boult,
Agents for the Applicant.