U.S. patent application number 11/602256 was filed with the patent office on 2007-05-31 for cooling device of vehicle.
This patent application is currently assigned to MAZDA MOTOR CORPORATION. Invention is credited to Tomoya Kozono, Naoki Nagano.
Application Number | 20070119395 11/602256 |
Document ID | / |
Family ID | 37771459 |
Filed Date | 2007-05-31 |
United States Patent
Application |
20070119395 |
Kind Code |
A1 |
Nagano; Naoki ; et
al. |
May 31, 2007 |
Cooling device of vehicle
Abstract
At a fan shroud constituting a cooling unit are provided a fan
opening portion with an electric fan and a door opening portion
that includes a plurality of door openings that are formed
substantially vertically in line. A slant portion is formed on the
door opening portion in such a manner that positions of the door
openings which are located at a relatively upper level of the door
opening portion and the doors provided at these door openings are
located respectively forward relative to those of the other door
openings and the other doors. Accordingly, any interference of the
doors with other parts in the engine room can be prevented
properly.
Inventors: |
Nagano; Naoki; (US) ;
Kozono; Tomoya; (US) |
Correspondence
Address: |
NIXON PEABODY, LLP
401 9TH STREET, NW
SUITE 900
WASHINGTON
DC
20004-2128
US
|
Assignee: |
MAZDA MOTOR CORPORATION
|
Family ID: |
37771459 |
Appl. No.: |
11/602256 |
Filed: |
November 21, 2006 |
Current U.S.
Class: |
123/41.65 |
Current CPC
Class: |
B60K 11/085 20130101;
F01P 2070/50 20130101; Y02T 10/88 20130101; F01P 11/10
20130101 |
Class at
Publication: |
123/041.65 |
International
Class: |
F01P 7/04 20060101
F01P007/04 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 30, 2005 |
JP |
2005-345737 |
Claims
1. A cooling device of a vehicle, in which a cooling unit
comprising a radiator and a fan shroud supporting an electric fan
is disposed in front of an engine in an engine room, a plurality of
openings are formed at the fan shroud so as to be located
substantially vertically in line beside the electric fan, and doors
are provided respectively at the openings so as to be opened by
traveling air, wherein the fan shroud is configured in such a
manner that an opening position of at least one of the openings is
located forward relative to that of another one of the openings and
a position of a rear end of the door provided at the one of the
openings is located forward relative to that of a rear end of the
door provided at the another one of the openings in a state where
the doors are opened.
2. The cooling device of a vehicle of claim 1, wherein the engine
is disposed laterally in such a manner that an intake manifold
thereof is located at a front portion in the engine room, a
transmission is disposed beside the engine, the electric fan is
supported at one side of the fan shroud, and the fan shroud is
provided in such a manner that the electric fan is located
substantially in front of the transmission and the plural openings
are located substantially in front of the engine.
3. The cooling device of a vehicle of claim 1, wherein the cooling
unit further comprises a condenser provided substantially in front
of the radiator, the opening position of the opening that is
located at a relatively upper level of the fan shroud is located
forward relative to that of another opening that is located at a
relatively lower level of the fan shroud, and the door provided at
the opening that is located at the relatively upper level is
located at a position where a rear end part thereof does not
interfere with a pipe that is provided to be coupled to the
condenser in the sate where the door is opened.
4. The cooling device of a vehicle of claim 1, wherein the doors
provided at the openings have substantially an identical shape.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a cooling device of a
vehicle that comprises a radiator to cool cooling water, an
electric fan, a fan shroud and the like, which are disposed at a
front portion in an engine room.
[0002] Conventionally, a cooling device of a vehicle, in which an
electric fan, radiator and condenser to cool the cooling water and
coolant are assembled to the fan shroud, is known. According to the
cooling device, traveling air is taken in by the electric fan, the
cooling water of the radiator and the coolant of the condenser are
cooled with the traveling air, and the engine room is scavenged
with the traveling air taken in (i.e., exhaustion of heated
air).
[0003] Herein, there is a problem in that the above-described
structure may cause the following concern. Namely, when a vehicle
travels at a low speed, the electric fan can supply a sufficient
amount of traveling air passing thorough a fan opening portion at
the fan shroud, thereby ensuring desirable cooling function. When
the vehicle travels at a high speed, however, these fan and fan
shroud may become an obstacle to increase of an improper flow
resistance, so that the amount of traveling air taken in would be
reduced and thereby the cooling efficiency would be
deteriorated.
[0004] Then, in order to solve this problem, there has been an
improved device, as disclosed in Japanese Utility Model Laid-Open
Publication No. 62-195624, in which openings (air through hole) are
formed at the fan shroud in addition to the fan opening portion for
the electric fan, and doors are provided at the openings so as to
be opened by the traveling air. Herein, when the vehicle travels at
the high speed, the doors are opened by the traveling air and the
sufficient amount of traveling air flows in through these openings.
Thereby, the cooling function of the radiator and condenser and the
scavenging function can be ensured properly even at the vehicle
high-speed traveling state.
[0005] Meanwhile, recent vehicle developments have been requiring a
more efficient space designing for the front portion of engine
room. Namely, since ensuring a roomy cabin space and a proper
safety against a vehicle frontal crash has been required
particularly, it has become more difficult to properly layout
components surrounding the engine in the engine room for ensuring
the sufficient space at the front portion in the engine room.
Especially, for the vehicle whose engine is disposed laterally in
the engine room, such layout of components, such as auxiliary parts
or pipes, is rather difficult due to a considerably limited layout
space exiting around the engine.
[0006] Specifically, in a case where the cooling device disclosed
in the above-described publication is provided in front of the
engine, there is a concern that pipes or the like that are disposed
between the cooling device and the engine would interfere with the
doors provided at the fan shroud when the doors are opened.
SUMMARY OF THE INVENTION
[0007] The present invention has been devised in view of the
above-described problem, and an object of the present invention is
to provide a cooling device of a vehicle, which includes a fan
shroud comprising an opening portion for an electric fan and
openings with doors, that can properly prevent the doors from
interfering with any other parts in an engine room.
[0008] According to the present invention, there is provided a
cooling device of a vehicle, in which a cooling unit comprising a
radiator and a fan shroud supporting an electric fan is disposed in
front of an engine in an engine room, a plurality of openings are
formed at the fan shroud so as to be located substantially
vertically in line beside the electric fan, and doors are provided
respectively at the openings so as to be opened by traveling air,
wherein the fan shroud is configured in such a manner that an
opening position of at least one of the openings is located forward
relative to that of another one of the openings and a position of a
rear end of the door provided at the one of the openings is located
forward relative to that of a rear end of the door provided at the
another one of the openings in a state where the doors are
opened.
[0009] Accordingly, even when the vehicle traveling speed is low, a
sufficient cooling air for the radiator can be endured by the
electric fan and the fan shroud, and when the vehicle traveling
speed becomes high, the doors provided at the fans shroud are
opened by the traveling air and the traveling air can be allowed to
come in to the engine room efficiently. Thus, the cooling function
of the radiator and the scavenging function of the engine room can
be improved. Also, since the position of the rear end of the door
provided at the one of the openings is located forward relative to
that of the rear end of the door provided at the another one of the
openings in the state where the doors are opened, a layout space
for pipes or the like behind the door can be ensured properly.
Thereby, there can be provided properly a compact layout of the fan
shroud in a narrow engine room without interference with any other
components/parts.
[0010] According to an embodiment of the present invention, the
engine is disposed laterally in such a manner that an intake
manifold thereof is located at a front portion in the engine room,
a transmission is disposed beside the engine, the electric fan is
supported at one side of the fan shroud, and the fan shroud is
provided in such a manner that the electric fan is located
substantially in front of the transmission and the plural openings
are located substantially in front of the engine.
[0011] Accordingly, the compact layout of the fan shroud having the
electric fan and the like in front of the laterally-disposed engine
can be attained. Namely, the transmission does not generally
project forward so much compared to the laterally-disposed engine
equipped with the intake manifold and the like at its front. Thus,
by applying the layout in which the electric fan having a certain
rearward projection is located substantially in front of the
transmission and the plural openings are located substantially in
front of the engine, a gap formed between the fan shroud and the
engine can be made as narrow as possible, thereby attaining the
compact layout of the fan shroud.
[0012] According to another embodiment of the present invention,
the cooling unit further comprises a condenser provided
substantially in front of the radiator, the opening position of the
opening that is located at a relatively upper level of the fan
shroud is located forward relative to that of another opening that
is located at a relatively lower level of the fan shroud, and the
door provided at the opening that is located at the relatively
upper level is located at a position where a rear end part thereof
does not interfere with a pipe that is provided to be coupled to
the condenser in the sate where the door is opened.
[0013] Generally, the condenser is provided along with the radiator
and the fan shroud, so the pipe coupled to the condenser may be
disposed near the fan shroud. Herein, by applying the layout in
which the door at the opening located at the relatively upper level
of the fan shroud is located forward relative to another door at
the opening located at the relatively lower level of the fan
shroud, any interference of rear end part of the doors with the
pipe can be prevented surely in the state where the doors are
opened.
[0014] According to another embodiment of the present invention,
the doors provided at the openings have substantially an identical
shape. Thereby, the layout in which the opening position of at
least one of the openings is located forward relative to that of
another one of the openings can bring up the layout in which that
the position of the rear end of the door provided at the one of
openings is located forward relative to that of the rear end of the
door provided at the another of openings in the state where the
doors are opened. Thus, reduction of manufacturing costs can be
also improved.
[0015] Herein, it is preferable that the fan shroud be formed in a
bowl shape to project rearward so that the traveling air can be
gathered at the fan opening portion as much as possible and the
traveling air can be supplied efficiently into the engine room by
the electric motor at the vehicle low-speed traveling state.
However, the above-described forward-location of the openings and
doors might. cause a concern that the sufficient amount of the
traveling air could not be gathered at the fan opening portion and
thereby the cooling function of the condenser and the radiator or
the scavenging function of the engine room might be
deteriorated.
[0016] Meanwhile, there is generally provided a front grill to let
a large amount of traveling air flow in to the engine room at a
front portion of the vehicle. Herein, a lower opening portion
located at a relatively lower part of the engine room is configured
to be relatively large sized to intake much of the air easily,
while an upper opening portion located at a relatively upper part
of the engine room is configured to be relatively small sized not
to intake so much of the air easily.
[0017] However, the above-described forward-location of only the
opening(s) and the door(s) that are located at the upper part of
the fan shroud would not influence badly on the entire supply
function of the traveling air. Because, as described above, the
amount of traveling air that flows in through the upper opening
portion is originally small, compared to the traveling-air amount
flowing in through the lower opening portion. Thus, the entire
supply function of the traveling air that may be affected mainly by
the traveling air flowing in through the lower opening portion
would not be influenced badly by the above-described
forward-location, and thus the proper layout space of the pile or
the like, which is described above, can be ensured properly.
[0018] Other features, aspects, and advantages of the present
invention will become apparent from the following description which
refers to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a schematic diagram of a vehicle front portion in
an engine room of an automotive vehicle equipped with a cooling
device of a vehicle according to an embodiment of the present
invention.
[0020] FIG. 2 is a sectional view of an example of the vehicle
front portion, taken along line II-II of FIG. 1.
[0021] FIG. 3 is a perspective view of a cooling unit.
[0022] FIG. 4 is a rear view of a radiator equipped with a fan
shroud, when viewed from the rear of the vehicle.
[0023] FIG. 5 is an enlarged perspective view showing a position
relationship between door openings of the fan shroud and an inlet
pipe.
DETAILED DESCRIPTION OF THE INVENTION
[0024] Hereinafter, a preferred embodiment of the present invention
will be described referring to the accompanying drawings. The
following descriptions are just about an example of the present
invention, and therefore these descriptions should not limit any
application or usage of the present invention.
[0025] FIGS. 1 and 2 show a vehicle front portion in an engine room
of a vehicle equipped with a cooling device according to an
embodiment of the present invention. An engine 1 equipped with a
super charger is disposed laterally in such a manner that an intake
manifold 12 is located at a front portion in the engine room. A
transmission 2 is disposed beside the engine 1, and a metal-made
intercooler 3 is disposed above the engine 1 slantingly in such a
manner that its rear end is positioned above its front end (see
FIG. 2). Herein, illustrating of a hood and part of bumper is
omitted in FIG. 1.
[0026] The intercooler 3, which has substantially a rectangular
shape, is covered by an intercooler cover 4 from its top. The cover
4 has a wide area that is enough to cover over the entire top of
the intercooler 3, and part of the cover 4 that corresponds to the
intercooler 3 has a grid shape so as to allow traveling air to come
in toward the intercooler 3.
[0027] Below a hood 6, as shown in FIG. 2, is provided an
intercooler duct 5 to take in the traveling air to the intercooler
3 so as to extend from the front to the intercooler 3. This duct 5
is made of a resin material and has a flat shape to form an air
passage S therein. The duct 5 has an air inlet port 5a with a flat
shape at its front end. Thus, the traveling air taken in from the
inlet port 5a is supplied to the intercooler 3 via the air passage
S in the intercooler duct 5.
[0028] In front of the engine 1 is provided a shroud frame 10
supporting. a cooling unit 7 (cooling device) that comprises a
condenser 21 and a radiator 22. The shroud frame 10 comprises a
cooling-unit support portion 10a to support the cooling unit 7 and
connecting portions 10b, 10b that extend from the support portion
10a rearward and laterally and are fixed to a vehicle body,
respectively, which has substantially a bowl shape as a whole, when
viewed from above. The cooling unit 7 is configured to cool cooling
water of the engine 1 and coolant of an air conditioner with the
traveling air that comes in through a front grill 9, which is
formed below a bumper 8 with a bumper beam 8a and the like, and an
air inlet 11, which is formed above the bumper 8.
[0029] As shown in FIG. 2, the traveling air coming in through the
front grill 9 mainly flows down toward a lower part of the cooling
unit 7, and the traveling air coming in through the air inlet 11
mainly flows down toward an upper part of the cooling unit 7.
Herein, since the air inlet 11 has a considerably smaller passage
section than the front grill 9, the air-flow amount from the inlet
11 is rather small compared to that from the front grill 9 does.
Accordingly, cooling function of the cooling unit 7 or scavenging
function of the engine room may be influenced primarily by the flow
amount of the air passing through the lower part of the cooling
unit 7, not so much by the flow amount of the air passing through
the upper part of the cooling unit 7.
[0030] The cooling unit 7 is formed by assembling the condenser 21,
radiator 22, and fan shroud 23 which are disposed in order from the
front, as shown in FIG. 3. The traveling air flows down passing
through the condenser 21 and radiator 22, whereby the coolant of
the air conditioner flowing in the condenser 21 and the cooling
water of the engine flowing in the radiator 22 can be cooled. The
condenser 21 and the fan shroud 23 are held by hooks 22c, 22c, . .
. provided at the radiator 22, which will be described below in
detail.
[0031] The radiator 22, which is formed in a flat shape as shown in
FIG. 4, is a cross-flow type of radiator in which there are
provided a cooling-water outlet portion 22f to be coupled to a
cooling-water pipe feeding the cooling water from the radiator 22
to the engine 1, a cooling-water inlet portion 22g to be coupled to
another cooling-water pipe feeding the cooling water from the
engine 1 to the radiator 22 at its both-side ends. Namely, tank
portions 22a, 22b filled with the cooling water are located at the
both sides in a vehicle width direction, and a core portion
comprising fins and tubes (not illustrated) is located at its
center portion between the tank portions 22a and 22b.
[0032] At front and rear faces of the tank portions 22a, 22b are
respectively provided a plurality of hooks 22a, 22c, . . . to hold
the fan shroud 23 and the condenser 21 (only hooks to hold the fan
shroud 23 at the rear face are illustrated in FIG. 4). At upper and
lower ends of the tank portions 22a, 22b are respectively provided
pin portions 22d, 22d, 22e, 22e to be inserted into engagement
holes formed at the cooling-unit support portion 10a of the shroud
frame 10.
[0033] Herein, a mounting member, not illustrated, is configured to
engage with tip portions of the above pin portions 22d, 22d, 22e,
22e that have been inserted into the engagement portions of the
shroud frame 10. A resilient member is provided between the
radiator 22 and the shroud frame 10, so the cooling unit 7 with the
radiator 22 and the condenser 21 is supported resiliently at the
shroud frame 10.
[0034] The condenser 21 is also, as shown in FIG. 3, formed in the
flat shape so as to extend in the vehicle width direction like the
radiator 22. The coolant of the air conditioner flows in a
longitudinal direction in the condenser 21. Namely, the condenser
21 comprises, like the radiator 22, a core portion 21c comprising
fins and tubes and tank portions 21a and 21b provided at its both
sides. To the tank portions 21a, 21b are coupled an inlet pipe 31
to feed the gas-state coolant to the tank portions from an
evaporator of the air conditioner via a compressor, and an outlet
pipe 32 to feed the liquid-state coolant cooled at the core portion
21c to the evaporator.
[0035] Hereinafter, the inlet pipe 31 will be described in detail.
The inlet pipe 31 is one that is provided between a compressor 33
to increase temperature and pressure of the gas-state coolant from
the evaporator and the tank portion 21a of the condenser 21. It has
an observing window 31a for checking the flow of coolant at its
middle portion. This window 31a is located at a portion near an
upper portion of the engine room so as to provide an easy checking.
Meanwhile, since the compressor 33 is generally located at a lower
portion of the engine room, the inlet pipe 31 interconnecting the
compressor 33 and the condenser 21 needs to be provided so as to
extend from the lower portion to the upper portion of the engine
room. Also, since there is little space in front of the engine 1 of
the engine room as shown in FIG. 1, the inlet pipe 31 may pass in
back of the cooling unit 7, namely just behind the fan shroud
23.
[0036] The fan shroud 23 is made of resin and has the bowl shape,
which is provided behind the radiator 22. It has also a fan opening
portion 23a, in which an electric fan 24 is provided, and a door
opening portion, which includes a plurality of door openings 23c
(air-passing through holes) and doors 23d. These opening portions
23a, 23b are disposed side by side as shown in FIG. 4. The fan
shroud 23 is attached to the radiator 22 in such a manner that the
door opening portion 23b is located on the side of engine 1 and the
fan opening portion 23a is located on the transmission 2. Thus, the
fan opening portion 23a with the electric fan 24 is disposed on the
side of the transmission 2 that does not project forward very much.
Accordingly, the distance between the engine 1/the transmission 2
and the cooling unit 7 can be made small, thereby providing a
compact layout in the narrow engine room.
[0037] The fan opening portion 23a is configured to project
rearward and has a recess portion for accommodating the electric
fan 24 therein in a state where the fan shroud 23 is installed in
the engine room. Its center has an through hole 23e for providing a
motor 24a of the fan 24. And, at the fan opening portion 23a is
provided an opening 23f that are disposed in a donut shape to
encompass the though hole 23e. There are also provided a plurality
of ribs that extend radially and a plurality of enforcing ribs that
interconnect the ribs at the opening 23f.
[0038] According to the above structure, the traveling air passing
through the condenser 21 and the radiator 22 flows in the engine
room via the fan opening portion 23a under the operation of the
electric fan 24. Herein, a state of the operation of the electric
fan 24 includes a situation where the vehicle travels at a low
speed and therefore a sufficient amount of traveling air to cool
the condenser 21 and radiator 22 and scavenge in the engine room
may not be obtained. Meanwhile, when the sufficient amount of the
traveling air is obtained at the high-speed traveling state, the
operation of the electric fan 24 may cause an improper increase of
flow resistance and thereby the scavenging function and the like
may be deteriorated to the contrary. Accordingly, in this case the
traveling air is supposed to be allowed to pass through the door
opening portion 23b and to flow in the engine room.
[0039] A plurality of door openings 23c, 23c, . . . , which are
substantially rectangular-shaped opening with a laterally-elongated
shape, are formed substantially vertically in line on the door
opening portion 23b. And, the doors 25, 25, . . . are provided at
the door openings 23c, 23c, . . . to as to be rotable.
Specifically, as shown in FIG. 5, each door 25 has likewise
substantially a rectangular shape so as to cover the door opening
23c. To the door 25 are fixed pins 26 that extend laterally, both
ends of which are pivotally supported at both ends of a frame
portion of each door opening 23c. A fixing position of the pin 26
to the door 25 is offset upward from the center of the door 25 in
the vertical direction.
[0040] This offset fixing of the pin 26 to the door 25 can
facilitate a smooth rotation of the door 25 according to the
traveling air coming in from the front and provide a proper closing
of the door opening 23c by the door 25 due to its weight when the
door 25 does not receive any force of the traveling air or the
like.
[0041] As described above, at the fan shroud 23 are provided the
fan opening portion 23a with the electric fan 24 and the door
opening portion 23b where the doors 25 open or close the door
openings 23c according to the traveling air. Accordingly, when the
vehicle traveling speed is so low that the traveling air is not
sufficient, the operation of the electric fan 24 can ensure the
cooling function of the condenser 21 and the radiator 22 and the
scavenging function of the engine room. Meanwhile, when the
sufficient traveling air is provided as the vehicle traveling speed
increases, the traveling air can be also allowed to come in through
the door opening portion 23b, thereby ensuring the above
functions.
[0042] And, the door opening portion 23b is configured in such a
manner that its upper part is located forward relative to its lower
part. Namely, the opening position of the top two door openings
23c, 23c, which are located at a relatively upper level, is located
forward relative to that of the other door openings 23c, 23, . . .
, which are located at a relatively lower level. And, the position
of rear ends of the doors 25, 25 at these two top door openings
23c, 23c is located forward relative to that of rear ends of the
other doors 25, 25, . . . in a sate where the doors are opened.
[0043] Specifically, a slant portion 23g is formed on the door
opening portion 23b between the upper part and the lower part.
Thereby, the positions of the door openings 23c, 23c and the doors
25, 25 that are positioned above the slant portion 23g are located
forward relative to the positions of the other door openings 23c,
23c, . . . and the other doors 25, 25, . . . that are positioned
below the slant portion 23g. According to this structure, the
upper-positioned doors 25, 25 can be properly prevented from
interfering with the above-described inlet pipe 31 that extends
vertically just behind the fan shroud 23 (see FIGS. 2 and 5).
[0044] The fan shroud 23 is formed in the bowl shape so that the
traveling air can be gathered at the fan opening portion 23a as
much as possible. Accordingly, the above-described forward-location
of the door openings 23c, 23c may cause a concern that a sufficient
amount of the traveling air could not be gathered at the fan
opening portions 23a and thereby the cooling function of the
condenser 21 and the radiator 22 or the scavenging function of the
engine room might be deteriorated.
[0045] However, since, as described above, the mount of the
traveling air that flows down from the front grill 9 to the lower
part of the cooling unit 7 is much larger than that of the
traveling air that flows down from the air inlet 11 formed at the
bumper 8 to the upper part of the cooling unit 7, the
forward-location of only the door openings 23c, 23c and the doors
25, 25 that are located at the upper part of the door opening
portion 23b would not influence badly on the entire cooling
function of the cooling unit 7 or the scavenging function of the
engine room.
[0046] Accordingly, interference of the doors 25, 25 provided at
the fan shroud 23 with the inlet pipe 31 of the condenser 21 can be
prevented surely without providing any bad influence on the cooling
function of the condenser 21 and radiator 22 or the scavenging
function of the engine room.
[0047] According to the above-described embodiment, since the
positions of the door openings 23c, 23c which are located at the
relatively upper level of the door opening portion 23b of the fan
shroud 23 and the doors 25, 25 provided at these door openings 23c,
23c are located respectively forward relative to those of the other
door openings 23c, 23c, . . . , and the other doors 25, 25, a
layout space for the pipe can be provided just behind the fan
shroud 23.
[0048] Further, since the fan shroud 23 is configured in such a
manner that the door opening portion 23b is located on the side of
engine 1 that projects forward and the fan opening portion 23a is
located on the transmission 2 that does not project forward very
much, a compact layout of the cooling unit 7 in the narrow engine
room can be provided.
[0049] Also, since the fan shroud 23 is configured in such a
manner, as described above, that the opening position of the door
openings 23c, 23c which are located at the relatively upper level
of the door opening portion 23b of the fan shroud 23 is located
forward relative to that of the other door openings 23c, 23c, . . .
, the above-described function and effect can be obtained even by
using substantially an identical shape/size of the doors 25, 25, .
. . provided at the door openings 23c, 23c, . . . Thus,
manufacturing costs can be also reduced.
[0050] The present invention should not be limited to the
above-described embodiment, and any other modifications and
improvements can be applied. For example, although the positions of
the upper door openings 23c, 23c and the upper doors 25, 25 are
located respectively forward relative to those of the other door
openings 23c, 23c, . . . , and the other doors 25, 25 in the
above-described embodiment, the door openings 23c and doors 25
whose positions should be located forward relative to others may be
properly selected according to the layout of the pipe or the like.
Also, the number of such door openings 23c and doors 25 whose
positions should be located forward should not be limited to the
two, and any other number, one or three or more, may be
applied.
* * * * *