Year: 1898

page_text: Date of Application, 7th Jan., 1898
Complete Specification Left 7th Oct. 1898 Accepted 3rd Dec.
1898
We, Jonx BROKENSHIRE FURNEAUX, of Victoria Works, Gateshead, in the
County of Durham, Engineer, and EDWARD BUTLER, of Victoria Works afore-
said, Engineer, do hereby declare the nature of this invention to be as follows:-
This invention has reference to improvements in explosion engines adapted
to be actuated by the ignition of explosive mixtures of petroleum vapour or gas
and air and comprising two four cycle explosion cylinders and pistons and an expan-
sion cylinder into which the explosion cylinders exhaust alternately, the pistons
of the two explosion cylinders being connected to a pair of cranks set in line
with each other and the piston of the explosion cylinder being connected to a
third crank set at an angle to the other two so that the crank-shaft, being
common to the three cranks, will receive two impulses during each revolution,
namely, one from an explosion cylinder and one from the expansion cylinder.
Now, in an engine according to this invention, one balanced circular distributing
valve is so constructed and arranged as to control the admission of explosive
mixture to both the explosion cylinders, the escape of the hot products of com-
bustion therefrom into the expansion cylinder, and the exhaust from the latter
into the atmosphere.
The accompanying drawings illustrate by way of example an explosion engine
according to this invention.
Fig. 1 being a front elevation;
Fig. 2 a plan,
Fig. 3a vertical section on the line aa Fig. 2,
Fig. 4 an end elevation partly in section, and
Figs. 5, 6, 7 and 8 sectional detail views hereinafter referred to.
1,1 are the explosion cylinders, the pistons 2,2 of which are respectively
connected by piston rods 3, to cranks 4,4" set in line with each other on the
crank shaft 5. 6 is the expansion cylinder whose piston 7 is connected by
the piston rod 8 with a crank 9 set upon the shaft 5 at an angle to and between the
cranks 4, 4. The crank 9 is preferably set about 190 degrees in advance of the
cranks 4 and 4" in order to utilize as much as possible the expansive properties
of the contents of the explosion cylinders and also to be in a better position for
pumping the clearing charges of air through the combustion chambers. A
rotary distributing valve of the kind described in the Specifications of Letters
Patent No. 6990 of 1890 and No. 24881 of 1896 is employed to control the
admission of explosive mixture to and the exhaust from the explosion cylinders,
which valve has at its larger end an extension formed with portways and
adapted to control the exhaust from the expansion cylinder to the atmosphere,
and at its smaller end has another extension formed with portways and
adapted to control the admission of clearing charges of air to the explosion
cylinders at the required times. The valve is rotated once for each four revolu-

page_text: tions of the crank shaft 5 by means of bevel wheels 11, shaft 11" and sprocket
wheels 11b and chain 11° which gear its spindle 12 with the crank shaft.
Spur wheels may be used instead of the chain and sprocket wheels; or the
spindle 12 may be driven direct from a worm forming part of the crank 9 gearing
into a wheel on the spindle.
13 is the gas supply pipe and 14 the air supply pipe both of which communicate
with an inspirator 15 of one or other of the kinds described in the Specifications
of Letters Patent No. 15598 of 1887, No. 6990 of 1890 and No. 24881 of 1896.
The outlet 15 from the inspirator is controlled by a slotted throttle or regulating
valve 15", the spindle 15 which is provided with a lever 15 that is connectedl
by a lever 16 and link 16" to the engine governor 16b which is mounted on a disc
fitted to the crank shaft or fly wheel boss as shown in Figs. 1 and 2, and may
conveniently be of the kind described in the Specification of Letters Patent
No. 24881 of 1896. A spring 17 in opposition to which the governor acts is
interposed between a guide bracket 17" and a collar on the link 16" screwed upon the
end of the latter is a nut or hand-wheel 18 by the adjustment of which the
speed of the engine can be regulated.
From the throttle or regulating valve 15 the explosive mixture passes through
the passage 19 formed in the casing of the distributing valve, enters by the open-
ing 20 the portways 21 (see Fig. 5) and passes thence alternately into the
explosion cylinders 1, 1" by the double passages 22, 22, the ignition of the
explosive mixture being effected at the required times by suitable electrical
igniting devices 23, 23" which may conveniently be of the kind described in the
Specification of Letters Patent No. 24881 of 1896. Whilst the one explosion
cylinder is receiving its charge of explosive mixture as described, the
mixture in the other cylinder is exploding and during the succeed-
ing instroke whilst the compression of the charge is taking place in the first
mentioned cylinder the hot gases of combustion are escaping from the other
cylinder into the expansion cylinder 6 by way of the double passages 22 or 22ª,
the inlet ports 24, portway 24" and the port 24 of the distributing valve, and the
passage 25. In Fig. 5 the distributing valve is shown just cutting off the supply
of explosive mixture to the cylinder 1" and opening the exhaust portway 24"
to the cylinder 1. The gases escape to the atmosphere from the expansion
cylinder during its in strokes by way of the passage 25, port 24h, portway 26,
ports 27 formed in the extended part of the distributing valve, corresponding
ports 27" in the liner surrounding it and exhaust pipe 28. Fig. 6 is a horizontal
section taken through the ports 27 and 27", the distributing valve being shown
just closing these ports so that the position of the valve will correspond with the
other views.
The expansion cylinder is made large enough to expand the hot gases supplied
to it from the explosion cylinders to below atmospheric pressure. At about the
end of each outstroke of the piston 7 of the expansion cylinder a partial vacuum
will be produced in that explosion cylinder which has just exhausted into the
expansion cylinder, which partial vacuum may be utilized to pump a clearing
charge of air through the combustion chamber of the explosion cylinder after
each explosion. Fig. 7 illustrates that portion of the distributing valve which
controls the admission of these charges. The lower part of the valve casing
is supplied with air from the air supply pipe 14 through a branch 14":
the air enters a portway 29 in the body of the valve through the
opening 29" (Fig. 3) and the rotation of the valve allows the air to be drawn 5
therefrom at the required times through ports 30 in the valve and corresponding
ports 30 formed in a seat or liner which surrounds it, to pipe connections 31,31
leading to chambers 32, 32" in the covers of the respective cylinders (Fig. 4).
Non-return valves 33, 33 are preferably provided to prevent the explosive
mixture or hot gases from being forced back into the chambers 32, 32; the
valves 33, 33 also serve to so deflect the air entering the cylinders as to effectually
sweep out all the residual gases from the previous explosion. The arrangement

page_text: of the ports 30 and 30" is such that the admission of air to each of the explosion
cylinders during its charging stroke is prevented, the valve being so driven that
the said ports are closed at that time.
As the distributing valve expands when working, an adjustable bearing
is provided whereby the valve, which is slightly tapered, is moved
lengthwise so as to compensate for the expansion of the
valve. The
adjustable bearing may conveniently consist of a screwed gland 34, which
may be arranged at either end of the valve and is adapted to move inward when
turned in the same direction as the valve; the gland is provided with a handle 34ª
having a set screw 34b (Fig. 7) which bears against an abutment, the arrange-
ment being such that, the handle having before starting the engine, been pulled
so as to turn the screw gland in the opposite direction to that of the rotation of
the valve which is thus tightened, the rotation of the valve and its spindle will
carry round the gland with it and will thus move the gland inwards in such a
manner as to automatically move the valve endways to the required extent.
The movement of the gland may be limited by a pair of stops. A spring 35
(Fig. 3) is arranged so as to bear against the other end of the valve and keep
it steady.
at⚫ such
Electric sparks are produced at the igniting devices 23, 23" by means of two
separate sparking coils 36, 36" (Fig. 2) actuated by a single battery 37 such as
a thermo-electric generator heated by a gas or oil flame. The sparking is con-
trolled by a commutator 38 mounted on the valve spindle and having two pairs
of contact pieces which respectively make contact with one of two pairs of
contact springs 39, 39" included respectively in the circuit connecting the battery
with the coil 36 and that connecting the battery with the coil
of the kind described in the
For starting the engine, apparatus
Specification of Letters Patent 4604 of 1895 may be employed comprising
a receiver that can be put in communication with the explosion cylinders, a
pump for charging the receiver with explosive mixture, and means for igniting
the mixture so as to generate pressure in the receiver. 40 is the receiver which
is preferably of wrought iron and about twenty times the capacity of the expansion
all inspirator 41
cylinder 6 41 is the pump which is provided with
and is connected to the receiver by a pipe 41 in which is fitted an
igniter 42. The coil 36 is provided with a switch adapted to connect it to the
igniter 42 when required. An opening 43 is provided in each explosion cylinder
a point as to be uncovered by the pistons at about 1/th_to
of their outstrokes. These openings are controlled by ordinary plug
or stop valves valves 44, which are connected by pipes 45 to the receiver 40. To
start the engine, the two explosion cylinder pistons being placed (on their out-
strokes) so as to uncover the openings 43, the valves 44 are opened and the
throttle or regulating valve 15" on the inspirator 15 closed, when explosive
mixture may be pumped into the receiver and ignited in the manner described
The pressure of gases
in the Specification of Letters Patent No. 4604 of 1895.
thus generated will start and drive the engine for a few turns until a high speed
is attained the stop valves 44 should then be closed, the throttle or regulating
valve 15 being arranged to be opened at the same time. The engine will now
draw in explosive mixture formed by the inspirator 15 to which is connected the
gas pipe 13, or an oil supply pipe, as the case may be, and the air supply pipe 14
and will continue to work in the ordinary way. The starting-receiver 40 may
O be provided with a non-return valve arranged at the end of the pipe 45 leading
to the engine, or the two stop valves 44 may be arranged as shown in Fig. 4 to
serve as combined stop valves and non-return valves, the arrangement in each
case being adapted to allow gases from the two explosion cylinders to enter the
receiver and to be retained therein for use in starting the engine, thus obviating
5 either pumping explosive mixture or forcing air under pressure into the receiver.
Steam from a small boiler may be used instead if convenient.
In some cases, igniting devices other than electrical may be employed. Fig. 8

page_text: illustrates an arrangement in which a pair of ignition tubes 46, 46 are fixed to
the casing of the distributing valve. The tubes, which are fitted within casings 47,
47, are of platinum and are respectively in communication with clearance
extensions 48, 48* and passages 49 and 49 adapted to be opened to the passages 22,
22" by means of ports 50, 50 formed on the valve face. The tubes may be 5
heated by a gas or oil flame. The valve is shown in the position in which the
cylinder 1 is in communication with its igniter 46.
Dated this 7th day of January 1898
EXPOSION Egines.
We, Joux BROKENSHIRE FURNEAUX, of Victoria Works, Gateshead, in the
County of Durham, Engineer, and EDWARD BUTLER, of Victoria Works afore-
said, 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 reference to improvements in explosion engines adapted
to be actuated by the ignition of explosive mixtures of petroleum vapour or gas
and air and comprising two four cycle explosion cylinders and pistons and an expan-
sion cylinder into which the explosion cylinders exhaust alternately, the pistons
of the two explosion cylinders being connected to a pair of cranks set in line
with each other and the piston of the expansion cylinder being connected to a
third crank set at an angle to the other two so that the crank-shaft, being
common to the three cranks, will receive two impulses during each revolution,
namely, one from an explosion cylinder and one from the expansion cylinder.
Now, in an engine according to this invention, one balanced circular distributing
valve is so constructed and arranged as to control the admission of explosive
mixture to both the explosion cylinders, the escape of the hot products of com-
bustion therefrom into the expansion cylinder, and the exhaust from the latter
into the atmosphere.
The drawings accompanying the Provisional Specification, illustrate, by way
of example, an explosion engine according to this invention.
Fig. 1 being a front elevation;
Fig. 2 a plan,
Fig. 3 a vertical section on the line aa Fig. 2,
Fig. 4 an end elevation partly in section, and
Figs. 5, 6, 7 and 8 sectional detail views hereinafter referred to.
Figs. 9 and 10 of the accompanying drawing show in sectional elevation and
plan respectively a modified form of gearing for rotating the distributing valve.
1, 1 are the explosion cylinders, the pistons 2,2 of which are respectively
connected by piston rods 3,3" to cranks 4, 4° set in line with each other on the
crank shaft 5. 6 is the expansion cylinder whose piston 7 is connected by
the piston rod 8 with a crank 9 set upon the shaft 5 at an angle to and between the
cranks 4, 4. The crank 9 is preferably set about 190 degrees in advance of the
cranks 4 and 4ª in order to utilize, as much as possible, the expansive properties
of the contents of the explosion cylinders and also to be in a better position for

page_text: pumping the clearing charges of air through the combustion chambers. A
rotary distributing valve of the kind described in the Specifications of Letters
Patent No. 6990 of 1890 and No. 24881 of 1896 is employed to control the
admission of explosive mixture to and the exhaust from the explosion cylinders,
which valve has at its larger end an extension formed with portways and
adapted to control the exhaust from the expansion cylinder to the atmosphere,
and at one or other of its ends has another extension formed with portways and
adapted to control the admission of clearing charges of air to the explosion
cylinders at the required times. The valve is rotated once for each four revolu-
tion of the crank shaft 5 by means of bevel wheels 11, shaft 11" and sprocket
wheels 11b and chain 11 which gear its spindle 12 with the crank shaft.
Spur wheels may be used instead of the chain and sprocket wheels; or the spindle 12
may be driven direct from a worm 9" forming part of or fixed to the crank 9
and gearing into a wheel 12" on the spindle as shown in Figs. 9 & 10 of the
accompanying drawing.
13 is the gas supply pipe and 14 the air supply pipe, both of which communicate
with an inspirator 15 of one or other of the kinds described in the Specifications
of Letters Patent No. 15598 of 1887, No. 6990 of 1890 and No. 24881 of 1896.
The outlet 15 from the inspirator is controlled by a slotted throttle or regulating
valve 15", the spindle 15 of which is provided with a lever 15 that is connected
by a lever 16 and link 16 to the engine governor 16 which is mounted on a disc
fitted to the crank shaft or fly wheel boss as shown in Figs. 1 and 2, and may
conveniently be of the kind described in the Specification of Letters Patent
No. 24881 of 1896. A spring 17 in opposition to which the governor acts is
interposed between a guide bracket 17" and a collar on the link 16" screwed upon the
end of the latter is a nut or hand-wheel 18 by the adjustment of which the
speed of the engine can be regulated.
From the throttle or regulating valve 15 the explosive mixture passes through
the passage 19 formed in the casing of the distributing valve, and enters by
the opening 20, the portways 21 (see Fig. 5) and passes thence alternately into the
explosion cylinders 1, 1 by the double passages 22, 22", the ignition of the
explosive mixture being effected at the required times by suitable electrical
igniting devices 23, 23" which may conveniently be of the kind described in the
Specification of Letters Patent No. 24881 of 1896. Whilst the one explosion
cylinder is receiving its charge of explosive mixture as described, the mixture
in the other cylinder is exploded and expanded, and during the succeeding in-
stroke whilst the compression of the charge is taking place in the first mentioned
cylinder, the hot gases of combustion are escaping from the other cylinder into
the expansion cylinder 6 by way of the double passages 22 or 22ª, the exhaust
ports 24 (Fig. 5) portway 24" and the openings 24 (Fig. 3) in the distributing
valve, and the passage 25. In Fig. 5 the distributing valve is shown just cutting
off the supply of explosive mixture to the cylinder 1" and opening the exhaust
ports 24 to the cylinder 1. The gases escape to the atmosphere from the expansion
cylinder during its in-strokes by way of the passage 25, openings 24b, a
passage 26, and ports 27 formed in the extended part of the distributing valve,
corresponding ports 27" in the liner surrounding it, and exhaust pipe 28. Fig. 6
is a horizontal section taken through the ports 27 and 27", the distributing valve
being shown just closing these ports so that the position of the valve will corre-
spond with the other views.
The expansion cylinder is made large enough to expand the hot gases supplied
to it from the explosion cylinders to below atmospheric pressure. At about the
end of each outstroke of the piston 7 of the expansion cylinder, a partial vacuum
will be produced in that explosion cylinder which has just exhausted into the
expansion cylinder, which partial vacuum may be utilized to pump or draw a clearing
charge of air through the combustion chamber of the explosion cylinder after
cach explosion. Fig. 7 illustrates that portion of the distributing valve which
controls the admission of these charges." The lower part of the valve casing,

page_text: in the arrangement shown, is supplied with air from the air supply pipe 14 through a
branch 14" the air enters a portway 29 in the body of the valve through
the opening 29" (Fig. 3) and the rotation of the valve allows the air to be drawn
therefrom at the required times through ports 30 in the valve and corresponding
ports 30", formed in a seat or liner which surrounds it, to pipe connections 31, 31"
leading to chambers 32, 32 in the covers of the respective cylinders (Fig. 4).
Non-return valves 33, 33 are preferably provided to prevent the explosive
mixture or hot gases from being forced back into the chambers 32, 32; the
valves 33, 33 also serve to so deflect the air entering the cylinders as to effectually
sweep out all the residual gases from the previous explosion. The arrangement
of the ports 30 and 30" is such that the admission of air to each of the explosion
cylinders during its charging stroke is prevented, the valve being so driven that
the said ports are closed at that time.
As the distributing valve expands when working, an adjustable bearing
is provided whereby the valve, which is slightly tapered, is moved
lengthwise so as to compensate for the expansion of the valve. The
adjustable bearing may conveniently consist of a screwed gland 34, which
may be arranged at either end of the valve and is adapted to move inward when
turned in the same direction as the valve; the gland is provided with a handle 34"
having a set screw 34b (Fig. 7) which bears against an abutment, the arrange-
ment being such that the handle having, before starting the engine, been pulled
so as to turn the screw gland in the opposite direction to that of the rotation of
the valve which is thus tightened, the rotation of the valve and its spindle will
carry round the gland with it and will thus move the gland inwards in such a
manner as to automatically move the valve endways to the required extent.
The movement of the gland may be limited by a pair of stops. A spring 35
(Fig. 3) may be arranged so as to bear against the other end of the valve and keep
it steady.
Electric sparks are produced at the igniting devices 23, 23 by means of two
separate sparking coils 36, 36" (Fig. 2) actuated by a single battery 37, such as
a thermo-electric generator heated by a gas or oil flame. The sparking is con-
trolled by a commutator 38 mounted on the valve spindle and having two parts
of contact pieces which respectively make contact with one of two pairs of
contact springs 39, 39 included respectively in the circuit connecting the battery
with the coil 36 and that connecting the battery with the coil 36".
For starting the engine, apparatus of the kind described in the Specification
of Letters Patent 4604 of 1895 may be employed consisting of a hand pump
and mixer connected to a pair of starting chambers and valves, the electric
igniters for which are connected through a switch and a commutator on the valve
spindle so that in starting the charges in the chambers shall be exploded at an
interval of one revolution from each other. Or a large receiver may be used that
can be put in communication with the explosion cylinders, a pump for charging
the receiver with explosive mixture, and means for igniting the mixture so as
to generate pressure in the receiver. 40 is the receiver which is preferably of
wrought iron and about twenty times the capacity of the expansion cylinder 6:
41 is the pump which is provided with an inspirator 41, and is connected to the
receiver by a pipe 41b in which is fitted an igniter 42. One of the coils, viz.
36, is provided with a switch adapted to connect it to the igniter 42 at starting.
An opening 43 is provided in each explosion cylinder preferably at such a point
as to be uncovered by the pistons at about 4th of their outstrokes. These openings
are controlled by ordinary plug or stop valves 44, which are connected by pipes 45
to the receiver 40. To start the engine, the two explosion cylinder pistons being
placed (on their outstrokes) so as to uncover the openings 43, the valves 44
are opened and the throttle or regulating valve 15" on the inspirator 15
may be closed, when explosive mixture may be pumped into the receiver and
ignited in the manner described in the aforesaid Specification of Letters Patent
No. 4604 of 1895. The pressure of gases thus generated will start and drive

page_text: the engine for a few turns in the following manner. When the starting valves
are opened the pressure of the gases from the receiver acts continuously on the
pistons of the explosion cylinders during both out and instrokes, the distributing
valve serving to admit the gases to the expansion cylinder as in the ordinary
working of the engine, whereby the piston of the expansion cylinder is forced
against the pressure on one or the other of the pistons of the
explosion cylinders alternately. After a sufficiently high speed is attained
the stop valves 44 should be closed and the throttle or regulating-
valve 15", if arranged to be closed during the admission of gases from the receiver,
should be opened. The engine will now draw in explosive mixture formed by the
inspirator 15 to which is connected the gas pipe 13, or an oil supply pipe, as the
case may be, and the air supply pipe 14, and will continue to work in the ordinary
way.
Other means may be used at starting in place of closing and opening the
regulating-valve, such for instance as a non-return valve arranged in an exten-
sion of the inspirator near the air pipe, and so as to open inwards against the
pressure of a spring.
The engine can also be started by means of only one of the explosion cylinders
in co-operation with the expansion cylinder.
After the engine has commenced to move, the fluid from the receiver may be
first shut off from one explosion cylinder, which then works in the ordinary
way, while the other is continued to be supplied with fluid from the receiver for
a few more strokes.
When the engine is being started with one stop-valve 44 closed and the other
open, one cylinder will draw in explosive mixture and exhaust into the expansion
cylinder in the ordinary way, while the other will be supplied with compressed
gases from the receiver both on its out and instrokes and exhaust to the expansion
cylinder, the piston of which will be alternately impelled outwards by exhaust
burnt gases from one explosion cylinder and by compressed gases from the
receiver through the other explosion cylinder. A suitably arranged non-return
valve serves to check escape of the compressed receiver gases to the air pipe when
the main valve opens communication whereby the gases from the receiver in
either explosion cylinder can pass to the regulating-valve and inspirator, the said
valve being put out of action after starting. The usual non-return valve on the gas
or oil pipe serves a similar purpose for such pipe.
The starting-receiver 40 may be provided with a non-return valve arranged on
the pipe 45 leading to the receiver, or each of the two stop valves 44 may be
arranged as shown in Fig. 4, to serve as a combined stop valve and non-return
valve, the arrangement in each case being adapted to allow the partly burnt gases
from the combustion chamber ends of the two explosion cylinders to enter the
receiver and to be retained therein for use in starting the engine, thus obviating
either pumping explosive mixture or forcing air under pressure into the receiver.
Steam from a small boiler may be used instead if convenient.
In some cases, igniting devices other than electrical may be employed. Fig. S
illustrates an arrangement in which a pair of ignition tubes 46, 46" are fixed to
the casing of the distributing valve. The tubes, which are fitted within casings 47,
47, are of platinum and are respectively in communication with clearance exten-
sions 48, 48 and passages 49 and 49", adapted to be opened to the passages 22, 22"
by means of ports 50, 50 formed on the valve face. The tubes may be heated
by a gas or oil flame. The valve is shown in the position in which the cylinder 1
is in communication with its igniter 46.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed we declare that what we
claim is:-
1. In an explosion engine having two four cycle explosion cylinders and an
expansion cylinder into which the explosion cylinders exhaust alternately, a

page_text: balanced rotary distributing valve so constructed and arranged in relation to
suitable ports and passages as to control the admission of explosive mixture to
both of the explosion cylinders, the escape of the hot products of combustion
therefrom into the expansion cylinder, the exhaust from the latter into the atmo-
sphere, substantially as described.
2. In an explosion engine, a rotary distributing valve of the kind herein referred
to, provided at its larger end with an extension formed with portways and adapted
to control the exhaust from the expansion cylinder to the atmosphere, and
at either end with another extension formed with portways and adapted
to control the admission of clearing charges of air to the explosion cylinders
substantially as hereinbefore described with reference to and shown in the accom-
panying drawings.
3. In an explosion engine, a rotary distributing valve as set forth in the pre-
ceding claims provided with an adjustable bearing substantially as hereinbefore
described with reference to and shown in the accompanying drawings for the
purpose set forth.
4. In an explosion engine having two explosion cylinders and one expansion
cylinder, means substantially as described and shown whereby the expansion
cylinder is utilized for clearing the combustion chambers of the explosion cylinders.
5. In an explosion engine having two explosion cylinders and one expansion
cylinder, means whereby a receiver can be charged with fluid under pressure
from the combustion chamber end of the explosion cylinders at the commencement
of the stroke and such fluid can be afterwards used for restarting the engine.
6. In an explosion engine having two explosion cylinders and one expansion
cylinder, means whereby the piston of the expansion cylinder can be employed
in conjunction with one or both pistons of the explosion cylinders for starting the
engine, substantially as described.
7. The improved explosion engine constructed arranged and operating sub-
stantially as described and shown in the drawings.
Dated this 7th day of October 1898.
For the Applicants,
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.