Improvements in Fuse Blocks for Electric Circuits.
Year: 1899

page_text: Data of Application (in United Kingdom), 15th July, 1899
Complete Specification Left, 18th Apr., 1900-Accepted, 23rd June 1900
Improvements in Fuse Blocks for Electric Circuits.
I, HARRY PHILLIPS DAVIS, of 327, Neville Street, Pittsburg, in the County of
Allegheny and State of Pennsylvania, U.S.A., Electrical Engineer, do hereby
declare the nature of this invention to be as follows:-
My invention relates to fuse-blocks for electric circuits, and in particular to
devices of this character in which the fuse is required to transmit a very large
amount of energy at the moment of rupture and consequent breakage of the cir-
cuit. In such cases an enormous explosive force is exerted in the fuse chamber,
and notwithstanding the fact that such chambers are usually not entirely enclosed,
but are provided with a blow-out opening through which the expanded air can
rush out, it is desirable to provide special means in order to avoid destruction
of the terminals and risk of danger to the attendants.
Circuits carrying a large amount of energy are generally protected by means
of electro-magnetically released circuit breakers, but in order to avoid injury
to the terminals of such breakers it is usual to employ an additional protective
device such as a fuse, for example, shunting said terminals, and fuse blocks con-
structed according to the present invention are specially adapted for use in
this manner, although they may be employed, if desired, as the sole protective
device of an electric circuit.
The chief feature of my invention consists in the provision within the fuse
chamber of a device which, when the fuse is ruptured by an excessive current,
is forced by the expansion of the gas in the chamber against the fuse terminal,
thereby covering the same and protecting it from injury. An additional feature
of my invention resides in the mechanical construction of the block, which is made
exceedingly strong in order to withstand the bursting pressure within the fuse
chamber, and at the same time is not expensive or difficult to construct.
In the accompanying drawings:-
--
Figure 1 is a plan view of my improved fuse-block and a portion of a support-
ing base,
Figure 2 being a similar view, partly sectional, of the same.
Figure 3 is an end elevation, the corresponding terminal being removed, and
Figure 4 is an inner end view of the removed terminal.
Figure 5 is a transverse section on the line V-V. Figure 2, and

page_text: Figure 6 is a longitudinal sectional view shewing one end of the fuse and its
terminal piece drawn to an enlarged scale.
1 is the base which may be a portion of a switch-board panel, and 2 is the
fuse-block which consists of a main body portion 3 provided with a longitudinal
fuse-chamber 4. The fuse-chamber 4 communicates through a lateral opening 5
with a tube 6 which projects through a bushing 7, one end of which is adapted to
form a clamp 8 to receive the body portion 3 of the fuse-block, the other end
of said bushing forming a means to secure the block to the base 1. These con-
structional details may of course be varied very considerably to suit the circum-
stances of any particular case.
Each end of the body portion 3 has fitted to it a metal piece 9 which is bored
so as to form a continuation of the fuse-chamber 4. The outer end of the piece 9
is provided with external interrupted screw threads 10 with which
engage corresponding internal interrupted screw threads of a terminal 11 forming
the end of the circuit to be protected. The body portion 3 of the fuse-block is
constructed of such material that it will not short circuit the fuse, but it should
be made as strong as possible in order to withstand the bursting pressure. Ju
the form shewn in the drawing the requisite strength is secured by making this
part of brown paper wound with steel piano wire, but this construction is not
essential. In order to further strengthen the block and also to maintain the
parts 9 and 3 in proper position, plates 12 are provided at each end which abut
against said parts 9, being insulated therefrom by strips 13 of insulating material.
These plates are connected by insulated bolts 14 and clamp the entire block very
firmly together.
The fuse 15 is provided at each end with a terminal piece 16, one end of which
is perforated to receive the fuse, the other end being made in the form of a com-
paratively thin split tube so as to fit the bore of the piece 9 and make good
electric contact therewith. The inner end of the terminal piece 16 carries a
shell or tube 17 of cartridge paper or other suitable material, which is provided
with a loosely packed filling 18 of asbestos or other suitable non-combustible and
non-conductive material, and above this filling is placed a follower 19, perferably
of vulcanised fibre or the like. The end of the shell or tube 17 may be turned
in order to retain the follower and filling in proper position (this construction is
shewn very clearly in Figure 6).
With a fuse-block constructed as above described, if the fuse is vaporised by an
overload occurring on a circuit which normally carries a very large amount of
energy, such vaporisation is attended by a violent explosion, the force of which
will be partially spent through the opening 5, which will, however, not avail to
prevent an enormous bursting pressure being exerted in the fuse-chamber. This
pressure will cause the followers 19 to compress the filling 18 into a compact
layer over the inner end of the piece 16, thereby preventing injury to said piece
or to any of the parts constituting the fuse-block terminals, so that the fuse can
be replaced with very little trouble, and the expense of renewal or repair of the
fuse-block is avoided.
The follower has an important function inasmuch as it prevents the filling
from being scattered and retains it during the normal operation of the fuse in
position to act properly as a protective device for the terminals when the fuse
is vaporised.
Dated the 19th day of Jul. 1900.
W. P. THOMPSON & Co..
322, High Holborn, London, W.,
Patent Agents for the Applicant.

page_text: Improvements in Fuse Blocks for Electric Circuits.
I, HARRY PHILLIPS DAVIS, of 327, Neville Street, Pittsburg, in the County of
Allegheny and State of Pennsylvania, U.S.A., Electrical Engineer, do hereby
declare the nature of this invention and in what manner the same is to be per-
formed to be particularly described and ascertained in and by the following
statement:-
My invention relates to fuse-blocks for electric circuits, and in particular to
devices of this character in which the fuse is required to transmit a very large
amount of energy at the moment of rupture and consequent breakage of the cir-
cuit. In such cases an enormous explosive force is exerted in the fuse chamber,
and notwithstanding the fact that such chambers are usually not entirely enclosed,
but are provided with a blow-out opening through which the expanded air can
rush out, it is desirable to provide special means in order to avoid destruction
of the terminals and risk of danger to the attendants.
Circuits carrying a large amount of energy are generally protected by means
of electro-magnetically released circuit breakers, but in order to avoid injury
to the terminals of such breakers it is usual to employ an additional protective
device such as a fuse, for example, shunting said terminals, and fuse blocks con-
structed according to the present invention are specially adapted for use in
this manner, although they may be employed, if desired, as the sole protective
device of an electric circuit.
The chief feature of my invention consists in the provision within the fuse
chamber of a device which, when the fuse is ruptured by an excessive current,
is forced by the expansion of the gas in the chamber against the fuse terminal,
thereby covering the same and protecting it from injury. An additional feature
of my invention resides in the mechanical construction of the block, which is made
exceedingly strong in order to withstand the bursting pressure within the fuse
chamber, and at the same time is not expensive or difficult to construct.
In the drawings filed with the Provisional Specification
Figure 1 is a plan view of my improved fuse-block and a portion of a support-
ing base,
Figure 2 being a similar view, partly sectional, of the same.
Figure 3 is an end elevation, the corresponding terminal being removed, and
Figure 4 is an inner end view of the removed terminal.
Figure 5 is a transverse section on the line V-V, Figure 2, and
Figure 6 is a longitudinal sectional view shewing one end of the fuse and its
terminal piece drawn to an enlarged scale.
1 is the base which may be a portion of a switch-board panel, and 2 is the
fuse-block which consists of a main body portion 3 provided with a longitudinal
fuse-chamber 4. The fuse-chamber 4 communicates through a lateral opening 5
with a tube which projects through a bushing 7, one end of which is adapted to
form a clamp 8 to receive the body portion of the fuse-block, the other end
of said bushing forming a means to secure the block to the base 1.
structional details may of course be varied very considerably to suit the circum-
stances of any particular case.
19
These con-
Each end of the body portion 3 has fitted to it a metal piece 9 which is bored
so as to form a continuation of the fuse-chamber 4. The outer end of the piece 9
provided with external interrupted screw threads 10 with which
engage corresponding internal interrupted screw threads of a terminal 11 forming
the end of the circuit to be protected. The body portion 3 of the fuse-block is

page_text: constructed of such material that it will not short circuit the fuse, but it should
be made as strong as possible in order to withstand the bursting pressure. In
the form shewn in the drawing the requisite strength is secured by making this
part alternate layers of brown paper wound with steel piano wire, but this con-
struction is not essential. In order to further strengthen the block and also to
maintain the parts 9 and 3 in proper position, plates 12 are provided at each end
which abut against said parts 9, being insulated therefrom by strips 13 of insulat-
ing material. These plates are connected by insulated bolts 14 and clamp the
entire block very firmly together.
The fuse 15 is provided at each end with a terminal piece 16, one end of which-
is perforated to receive the fuse, the other end being made in the form of a com-
paratively thin split tube so as to fit the bore of the piece 9 and make good
electric contact therewith. The inner end of the terminal piece 16 carries a
shell or tube 17 of cartridge paper or other suitable material, which is provided
with a loosely packed filling 18 of asbestos or other suitable non-combustible and
non-conductive material, and above this filling is placed a follower 19, perferably
of vulcanised fibre or the like. The end of the shell or tube 17 may be turned
in order to retain the follower and filling in proper position (this construction is
shewn very clearly in Figure 6).
With a fuse-block constructed as above described, if the fuse is vaporised by an
overload occurring on a circuit which normally carries a very large amount of
energy, such vaporisation is attended by a violent explosion, the force of which
will be partially spent through the opening 5, which will, however, not avail to
prevent an enormous bursting pressure being exerted in the fuse-chamber. This
pressure will cause the followers 19 to compress the filling 18 into a compact
layer over the inner end of the piece 16, thereby preventing injury to said piece
or to any of the parts constituting the fuse-block terminals, so that the fuse can
be replaced with very little trouble, and the expense of renewal or repair of the
fuse-block is, avoided.
The follower has an important function inasmuch as it prevents the filling
from being scattered and retains it during the normal operation of the fuse :
position to act properly as a protective device for the terminals when the fuse
is vaporised.
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. A fuse-block for electric circuits in which a filling of loosely packed non-
combustible material is provided at each end of the fuse-chamber, and having
followers for normally retaining the filling in place.
2. A fuse-chamber constructed of alternate layers of wire and insulating
material substantially as described.
3. A fuse-block in which the fuse-chamber is strengthened by end plates con-
nected by insulating clamping bolts substantially as described.
4. Fuse-blocks constructed substantially as described with reference to the
accompanying drawings.
Dated this 18th day of April 1900.
W. P. THOMPSON & Co.,
Of London, Liverpool, Manchester, and Birmingham.