U.S. patent application number 09/280845 was filed with the patent office on 2001-06-21 for unit housing structure in electronic device.
Invention is credited to NEGISHI, MASAYUKI.
Application Number | 20010004311 09/280845 |
Document ID | / |
Family ID | 13921116 |
Filed Date | 2001-06-21 |
United States Patent
Application |
20010004311 |
Kind Code |
A1 |
NEGISHI, MASAYUKI |
June 21, 2001 |
UNIT HOUSING STRUCTURE IN ELECTRONIC DEVICE
Abstract
A unit housing structure for detachably housing a unit mounted
with electronic parts in a unit mounting portion of an electronic
device in which a guide rail having a guide slot whose opposite
wall surfaces are slopes gradually opening outwardly is provided on
the side of said unit mounting portion or said unit and a guided
portion to be slidably engaged with the guide slot of said guide
rail is provided on the side of said unit mounting portion or said
unit, whereby movement of said unit is guided by the engagement
between said guided portion and the guide slot at the time of
insertion/extraction of said unit into/from said unit mounting
portion.
Inventors: |
NEGISHI, MASAYUKI; (TOKYO,
JP) |
Correspondence
Address: |
WHITHAM CURTIS & WHITHAM
RESTON INTERNATIONAL CENTER
11800 SUNRISE VALLEY DRIVE SUITE 900
RESTON
VA
20191
|
Family ID: |
13921116 |
Appl. No.: |
09/280845 |
Filed: |
March 30, 1999 |
Current U.S.
Class: |
361/695 |
Current CPC
Class: |
H05K 7/20581
20130101 |
Class at
Publication: |
361/695 |
International
Class: |
H05K 007/20 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 1998 |
JP |
087660/1998 |
Claims
What is claimed is:
1. A unit housing structure for detachably housing a unit mounted
with electronic parts in a unit mounting portion of an electronic
device, wherein on the side of said unit mounting portion or said
unit, a guide rail having a guide slot whose opposite wall surfaces
are slopes gradually opening outwardly is provided, on the side of
said unit mounting portion or said unit, a guided portion to be
slidably engaged with the guide slot of said guide rail is
provided, and when said unit is inserted/extracted into/from said
unit mounting portion, movement of said unit is guided by the
engagement between said guided portion and the guide slot.
2. The unit housing structure as set forth in claim 1, wherein said
guide rail is provided on the side of said unit mounting portion
and said guided portion is provided on the side of said unit.
3. The unit housing structure as set forth in claim 1, wherein said
guide rail is disposed at a position of said unit mounting portion
which comes under said unit and said guided portion is provided on
the lower side of said unit.
4. The unit housing structure as set forth in claim 1, wherein said
guide rail is disposed at a position of said unit mounting portion
which comes under said unit and said guided portion is formed on
the lower side of said unit, said guide rail is provided fixing on
a cross-bar provided within said unit mounting portion, and said
guided portion is formed by projecting a lower edge of the side
surface of said unit downward.
5. The unit housing structure as set forth in claim 1, wherein said
guide slot is formed to have a quasi V-shaped section.
6. The unit housing structure as set forth in claim 1, wherein said
guide slot is formed to have a plane bottom and have opposite wall
surfaces as slopes which gradually open outwardly.
7. The unit housing structure as set forth in claim 1, wherein said
guide rail is disposed at a position of said unit mounting portion
which comes under said unit and said guided portion is formed on
the lower side of said unit, said guide rail is provided fixing on
a cross-bar provided within said unit mounting portion, said guided
portion is formed by projecting a lower edge of the side surface of
said unit downward, and said guide slot is formed to have a quasi
V-shaped section.
8. The unit housing structure as set forth in claim 1, wherein said
guide rail is disposed on the lower side of said unit, and said
guided portion is disposed at a position of said unit mounting
portion which comes under said unit.
9. The unit housing structure as set forth in claim 1, wherein
assuming that an inclination of one of said slopes of said guide
slot facing to each other is .alpha.1 and an inclination of the
other slope is .alpha.2 and that a static friction coefficient
between said guide slot and said guided portion is .mu., the
inclinations of said slopes are angles which satisfy the following
expressions:.mu.<tan .alpha.1 and .mu.<tan .alpha.2.
10. The unit housing structure as set forth in claim 1, wherein
said guide rail is disposed at a position of said unit mounting
portion which comes under said unit and said guided portion is
formed on the lower side of said unit, said guide rail is provided
fixing on a cross-bar provided within said unit mounting portion,
said guided portion is formed by projecting a lower edge of the
side surface of said unit downward, and assuming that an
inclination of one of said slopes of said guide slot facing to each
other is .alpha.1 and an inclination of the other slope is .alpha.2
and that a static friction coefficient between said guide slot and
said guided portion is .mu., the inclinations of said slopes are
angles which satisfy the following expressions:.mu.<tan .alpha.1
and .mu.<tan .alpha.2.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a unit housing structure in
an electronic device provided with a guide structure for smoothly
guiding a detachable unit portion to a predetermined position in a
unit mounting portion.
[0003] 2. Description of the Related Art
[0004] In an electronic device composed of a plurality of printed
boards packaged on a shelf, for example, in a communication
apparatus, heat generation from the printed boards is a problem.
Structure for emitting the heat outside is therefore employed.
Commonly employed as this cooling method is forced air cooling
using a fan. Fan, however, has a life and might have a trouble even
before its life expires. For facilitating maintenance and
replacement, therefore, it is a common practice for a fan unit to
be structured to be detachable from the front side of a unit
mounting portion in the body of a device.
[0005] Furthermore, since the fan unit needs to supply power or
transmit an alarm signal or the like when the number of revolutions
of the fan is reduced, the unit requires electrical connection with
the device side. The fan unit and the unit mounting portion of the
device are therefore both designed to have a connector through
which the fan unit and the unit mounting portion are electrically
connected.
[0006] In addition, for reliably connecting the connectors, the fan
unit should be guided such that the connectors face to each other
while positioned with respect to each other. For this guiding, a
guide rail with a groove for guiding is disposed on the side of the
unit mounting portion.
[0007] Commonly used as this guide rail is a rail having a U-shaped
slot whose opposite sides rise vertically to the bottom surface
(hereinafter, referred to as a U slot). The fan unit is guided by
engaging a guided portion on the fan unit side with this U slot and
sliding the guided portion within the U slot. Here, between the U
slot of the guide rail and the guided portion of the fan unit, "the
width of the U slot>the width of the guided portion" holds and
the two are designed to have a little clearance therebetween.
[0008] It is ideal that insertion or extraction of the fan unit
into or from the unit mounting portion is conducted while keeping
the U slot of the guide rail and the guided portion of the fan unit
in parallel to each other at any time.
[0009] Among modes of a fan unit are a mode of laterally mounting a
plurality of fan units each having a few fans so as to meet cooling
design or a design concept of an electronic device and a mode of
mounting a fan unit large in breadth having numbers of fans
thereon. In either mode, for guiding a fan unit large in breadth by
a U slot of a guide rail, operating the U slot of the guide rail
and a guided portion of the unit while constantly keeping them in
parallel with each other is difficult and the unit is highly likely
to slant with its left side or right side projecting forward. As a
result, an apparent width of the guided portion of the fan unit
equals or exceeds the width of the U slot of the guide rail,
whereby the guided portion of the fan unit will be pressed against
the inner wall surface of the U slot to hitch halfway in the
insertion or extraction.
[0010] In a case where a right and left slant is to be corrected
for rectifying this state, when the amount of rectification is too
large, a right and left slant reverse to that before will cause a
hitch. Insertion and extraction are highly likely to be conducted
through the repetition of this movement to rock the unit leftward
and rightward alternately in the traveling direction and cause a
hitch. This tendency is more enhanced as the breadth of the fan
unit is increased.
[0011] Under these circumstances, there is a demand for a unit
housing structure provided with a guide structure which enables
smooth insertion and extraction without a hitch caused by rocking
from side to side.
[0012] FIGS. 11 and 12 show one example of a conventional housing
structure and FIG. 11 is a perspective view showing a broken-out
section of a part of the schematic structure of the housing
structure and FIG. 12 is an expanded sectional view taken along
line B-B of FIG. 11. More specifically, shown are one example of a
fan unit 110 large in breadth having a plurality of fans 180
provided thereon and a fan unit mounting portion 120 in which the
fan unit 110 is to be mounted. Although not shown, the fan unit
mounting portion 120 is disposed within an electronic device such
as a communication apparatus.
[0013] In more detail, the fan unit mounting portion 120 has a
connector 130 for the connection with the fan unit 110. The
connector 130 is connected to the inside of the electronic device
by a cable to allow power supply to the fan unit 110 or detect an
alarm signal or the like generated from the fan unit 110 due to the
reduction of the number of revolutions of the fan. On the left side
on cross-beams 180 and 190 of the fan unit mounting portion 120, a
guide rail 140 for guiding the fan unit 110 is provided. The guide
rail 140, as illustrated in FIG. 11, forms a U slot 170 having its
wall surfaces rising perpendicularly to the bottom surface by which
the U slot 170 the fan unit 110 is guided.
[0014] On the other hand, the fan unit 110 has a connector 150 at a
position opposed to the connector 130 of the fan unit mounting
portion 120. In addition, the lower edge of the side surface of the
fan unit 110 projects to become a guided portion 160 which will be
guided while being fit in the U slot 170 of the guide rail 140.
Here, the width of the U slot 170 of the guide rail 140 has a
dimension with a little clearance with respect to the board
thickness of the side surface of the fan unit 110, that is, the
width of the guided portion 160.
[0015] Next, operation at the conventional housing structure will
be described. First, set the guided portion 160 of the fan unit 110
to the U slot 170 of the guide rail 140 to insert the fan unit 110
into the fan unit mounting portion 120. Insertion is enabled
without any problem by inserting the fan unit 110 straight on, with
the U slot 170 of the guide rail 140 and the guided portion 160 of
the fan unit 110 maintained in parallel to each other at any time
by keeping a balance between right and left.
[0016] Once the balance between right and left is lost and the fan
unit 110 slants, for example, as illustrated in FIG. 13, the guided
portion 160 slants to the utmost within the U slot 170 of the guide
rail 140, resulting in having the apparent width of the guided
portion 160 equaling or exceeding the width of the U slot 170 of
the guide rail 140. As a result, the guided portion 160 of the fan
unit 110 is pressed against the inner wall surface of the U slot
170 to cause a hitch halfway in the insertion of the fan unit
110.
[0017] Here, at the time of correcting the right and left slant by
pushing the left side, as one faces it, of the fan unit 110 in
order to rectify the slant state, if the amount of rectification is
too large, a right and left slant reverse to that of FIG. 13 is
generated, for example, as illustrated in FIG. 14 to cause a hitch.
Repetition of this movement will result in insertion with the unit
rocking rightward and leftward in the traveling direction.
[0018] As described in the foregoing, a conventional structure for
guiding a unit large in breadth by means of a guide rail having a U
slot involves rightward and leftward rocking in the traveling
direction to cause a hitch, making mounting of the fan unit
difficult. This tendency is more enhanced when the guide rail 140
of the fan unit mounting portion 12 and the guided portion 160 of
the fan unit 110 are both made of metal for maintaining the ground
potentials of the fan unit mounting portion 120 and the fan unit
110 to be the same than that when either the guide rail 140 or the
guided portion 160 is made of a resin material.
[0019] Although the foregoing description has been made of the
structure for housing the fan unit 110 in the fan unit mounting
portion 120, structures for housing other electronic units in a
unit mounting portion also have the same problem.
SUMMARY OF THE INVENTION
[0020] A first object of the present invention is to provide a unit
housing structure in an electronic device enabling
insertion/extraction of an electronic unit into/from a unit
mounting portion of the electronic device by smooth guiding without
a hitch caused by rightward and leftward rocking.
[0021] According to one aspect of the invention, a unit housing
structure for detachably housing a unit mounted with electronic
parts in a unit mounting portion of an electronic device,
wherein
[0022] on the side of the unit mounting portion or the unit, a
guide rail having a guide slot whose opposite wall surfaces are
slopes gradually opening outwardly is provided,
[0023] on the side of the unit mounting portion or the unit, a
guided portion to be slidably engaged with the guide slot of the
guide rail is provided, and
[0024] when the unit is inserted/extracted into/from the unit
mounting portion, movement of the unit is guided by the engagement
between the guided portion and the guide slot.
[0025] In the preferred construction, the guide rail is provided on
the side of the unit mounting portion and the guided portion is
provided on the side of the unit.
[0026] In another preferred construction, the guide rail is
disposed at a position of the unit mounting portion which comes
under the unit and the guided portion is provided on the lower side
of the unit.
[0027] In another preferred construction, the guide rail is
disposed at a position of the unit mounting portion which comes
under the unit and the guided portion is formed on the lower side
of the unit,
[0028] the guide rail is provided fixing on a cross-bar provided
within the unit mounting portion, and
[0029] the guided portion is formed by projecting a lower edge of
the side surface of the unit downward.
[0030] In another preferred construction, the guide slot is formed
to have a quasi V-shaped section.
[0031] In another preferred construction, the guide slot is formed
to have a plane bottom and have opposite wall surfaces as slopes
which gradually open outwardly.
[0032] In another preferred construction, the guide rail is
disposed at a position of the unit mounting portion which comes
under the unit and the guided portion is formed on the lower side
of the unit,
[0033] the guide rail is provided fixing on a cross-bar provided
within the unit mounting portion,
[0034] the guided portion is formed by projecting a lower edge of
the side surface of the unit downward, and
[0035] the guide slot is formed to have a quasi V-shaped
section.
[0036] In another preferred construction, the guide rail is
disposed on the lower side of the unit, and
[0037] the guided portion is disposed at a position of the unit
mounting portion which comes under the unit.
[0038] In another preferred construction, the guide rail is
disposed at a position of the unit mounting portion which comes
under the unit and the guided portion is formed on the lower side
of the unit,
[0039] the guide rail is provided fixing on a cross-bar provided
within the unit mounting portion,
[0040] the guided portion is formed by projecting a lower edge of
the side surface of the unit downward, and
[0041] assuming that an inclination of one of the slopes of the
guide slot facing to each other is .alpha.1 and an inclination of
the other slope is .alpha.2 and that a static friction coefficient
between the guide slot and the guided portion is .mu., the
inclinations of the slopes are angles which satisfy the following
expressions:
.mu.<tan .alpha.1 and .mu.<tan .alpha.2.
[0042] Other objects, features and advantages of the present
invention will become clear from the detailed description given
herebelow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] The present invention will be understood more fully from the
detailed description given herebelow and from the accompanying
drawings of the preferred embodiment of the invention, which,
however, should not be taken to be limitative to the invention, but
are for explanation and understanding only.
[0044] In the drawings:
[0045] FIG. 1 is a perspective view of a housing structure
illustrated as one embodiment of the present invention;
[0046] FIG. 2 is an expanded schematic sectional view taken along
line A-A of FIG. 1;
[0047] FIG. 3 is a view showing structure of a rise portion of a
cross-beam;
[0048] FIG. 4 is an expanded sectional view of a guide rail;
[0049] FIG. 5 is an explanatory view of operation of the device
according to the present invention;
[0050] FIG. 6 is a sectional view for use in explaining one example
of modification of the device according to the present
invention;
[0051] FIG. 7 is a sectional view for use in explaining another
example of modification of the device according to the present
invention;
[0052] FIG. 8 is a sectional view showing another structure of the
guide rail;
[0053] FIG. 9 is a sectional view showing structure of a guide rail
and a guided portion according to another embodiment of the present
invention;
[0054] FIG. 10 is a sectional view showing structure of a guide
rail and a guided portion according to a further embodiment of the
present invention;
[0055] FIG. 11 is a perspective view showing schematic structure of
a conventional device;
[0056] FIG. 12 is an expanded sectional view taken along line B-B
of FIG. 9;
[0057] FIG. 13 is a view for use in explaining a problem of the
conventional device;
[0058] FIG. 14 is a view for use in explaining the problem of the
conventional device.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0059] The preferred embodiment of the present invention will be
discussed hereinafter in detail with reference to the accompanying
drawings. In the following description, numerous specific details
are set forth in order to provide a thorough understanding of the
present invention. It will be obvious, however, to those skilled in
the art that the present invention may be practiced without these
specific details. In other instance, well-known structures are not
shown in detail in order to unnecessary obscure the present
invention.
[0060] FIG. 1, which shows one embodiment of a housing structure
according to the present invention, is a perspective view
illustrating a broken-out part of the structure at the state prior
to assembly. In FIG. 1, the reference numeral 10 denotes a unit
mounted with electronic parts such as fan units and 20 denotes a
unit mounting portion provided at the body of an electronic device
such as a communication apparatus in which the unit 10 is to be
mounted.
[0061] The unit mounting portion 20 has a connector 30 for the
electrical connection with the unit 10. Although not shown, the
connector 30 is connected with the inside of the electronic parts
in the electronic device by a cable through which power supply to
the unit 10 and transmission and reception of signals between the
unit 10 and the electronic device are enabled.
[0062] In the housing space of the unit mounting portion 20, two
cross-bars 50 and 60 are provided as illustrated in the figure. In
addition, on the left side of the unit mounting portion 20, a guide
rail 40 for guiding the unit 10 is provided. The guide rail 40, as
illustrated in FIG. 2 which is an expanded view of the section
taken along line A-A of FIG. 1 with the unit 10 assembled into the
unit mounting portion 20, is formed into a rail shape by pressing a
metal plate to process the section into a Z-shape.
[0063] By cutting and raising a part of the cross-bar 50 and a part
of the cross-bar 60 provided at the unit mounting portion 20 for
fixing the above-described guide rail 40, such a rise portion 60a
as illustrated in FIGS. 2 and 3 is formed. This rise portion 60a is
cut and raised at a predetermined angle and the guide rail 40 is
fixed to the rise portion 60a by welding or the like.
[0064] In addition, the sectional configuration of a part actually
used as a rail is formed to be such a V-shaped guiding slot having
slopes whose opposite wall surfaces gradually slant to open from
the bottom of the slot as illustrated in FIG. 2 (hereinafter, the
slot is referred to as "V-shaped slot 90") and the V-shaped slot 90
guides the sliding unit 10.
[0065] Moreover, on the right side of the unit mounting portion 20,
a guide member 45 for guiding the right-side surface of the unit 10
is provided. The guide member 45 has its section formed of a
L-shaped member as illustrated in FIG. 1 and is fixed on the
cross-bars 50 and 60. A space between the above-described guide
rail 40 and the guide member 45 is set according to a breadth of
the unit 10.
[0066] On the other hand, the unit 10 has a connector 70 at a
position opposed to the connector 30 of the unit mounting portion
20. The lower edge of the side surface of the unit 10 projects
downward to become a guided portion 80 which will be slidably
engaged with the V-shaped slot 90 of the guide rail 40 and will be
guided by its sliding in the V-shaped slot 90. Although the unit 10
is mounted with electronic parts such as fan units as illustrated
in FIG. 9, its illustration is omitted in the present figure.
[0067] As to the V-shaped slot 90, description will be here made
with reference to FIG. 4 which is an expanded sectional view of the
guide rail 40 only. Assuming that of the opposite slopes opposed to
each other of the V-shaped slot 90, an angle of one slope is
.alpha.1 and an inclination of the other slope is .alpha.2, and
that a static friction coefficient between the guided portion 80 of
the unit 10 and the guide rail 40 is .mu., .mu.<tan .alpha.1 and
.mu. <tan .alpha.2 hold for the V-shaped slot 90. More
specifically, the angles .alpha.1 and .alpha.2 of the slopes of the
V-shaped slot 90 are larger than a static friction angle with the
guided portion 80 of the unit 10 as a friction piece and the guide
rail 40 as a friction surface.
[0068] Next, description will be made of operation to be conducted
for inserting the unit 10 into the unit mounting portion 20.
[0069] First, set the guided portion 80 of the unit 10 to the
V-shaped slot 90 as a guide slot of the guide rail 40 to insert the
unit 10 into the unit mounting portion 20. When the unit 10 slants
leftward or rightward in the traveling direction halfway in the
insertion, the guided portion 80 of the unit 10 will start
ascending the slanting wall surface of the V-shaped slot 90 of the
guide rail 40.
[0070] Then, as illustrated in FIG. 5, to the guided portion 80 of
the unit 10, force of gravity mg, vertical reaction force N on the
contact surface and friction force .mu.N will act. Here, since an
inclination .alpha. of the V-shaped slot 90 of the guide rail 40 is
larger than a static friction angle between the guided portion 80
of the unit 10 and the guide rail 40, mg sin.alpha.>.mu.N holds
to result in that the guided portion 80 of the unit 10 slides down
toward the center of the V-shaped slot 90 of the guide rail 40.
Thus, even when the unit 10 starts slanting rightward or leftward,
force will act to the direction for rectifying the slant to
suppress the slant. As a result, the unit 10 continues proceeding
without rightward and leftward slanting to be inserted up to a
predetermined position. At the final position, the connector 70
will be fit in the connector 30 and connected to complete
assembly.
[0071] Conversely, in a case where the unit 10 is to be extracted,
when the unit 10 is on the edge of slanting leftward or rightward
in the travelling direction, force will act on the guided portion
80 in a direction for rectifying the slant of the unit 10 due to
the slopes of the V-shaped slot 90 to suppress the slant. As a
result, also at the extraction of the unit 10 from the unit
mounting portion 20, the unit 10 is guided smoothly and extracted
without leftward and rightward rocking in the extraction direction
to cause a hitch.
[0072] As described in the foregoing, with the guide slot 90 of the
guide rail 40 structured to have slanting wall surfaces, when the
unit 10 is on the edge of slanting leftward or rightward in the
traveling direction, the guided portion 80 will start ascending or
descending on the slope of the guide slot 90, resulting in that
force will act on the guided portion 80 to move toward the center
of the guide slot 90, that is, force will act toward the direction
to rectify the slant of the unit 10 to suppress the slant.
Accordingly, at the insertion/extraction into/from the unit
mounting portion 20, the unit 10 can be guided smoothly without
rightward and leftward rocking in the proceeding/extraction
direction to cause a hitch.
[0073] Since thus formed unit housing structure at a communication
apparatus enables even a unit large in breadth to operate without
leftward and rightward rocking in the traveling direction to cause
a hitch at the insertion/extraction, work efficiency can be
improved.
[0074] The above-described embodiment can be also structured as
follows.
[0075] In the above-described embodiment, the guide rail 40 is
formed of a pressed metal plate material or the like, it may be
formed, for example, of a prism-shaped member as illustrated in
FIG. 6 as long as the V-shaped slot 90 as a guide slot is provided.
In addition, processing method may be, casting, cutting work,
extruding or any other method.
[0076] Moreover, the guide slot of the guide rail 40 may not be
formed into a complete V-shape but be formed to have a flat bottom
surface 90c and have wall surfaces 90a and 90b on opposite sides of
the slot as slopes which gradually slant inwardly toward the bottom
surface 90c as illustrated in FIG. 7. With such structure, the same
effect can be achieved.
[0077] In addition, the guide slot of the guide rail 40 may not be
Z-shaped as illustrated in FIG. 2 but be formed to be V-shaped by
the pressing or other processing of a metal plate material and
fixed to the rise portion 60a of the cross-bar 60 as shown in FIG.
8.
[0078] Although the above-described embodiment is structured to
have the guide rail 40 having the guide slot (V-shaped slot 90)
provided on the side of the unit mounting portion 20 and the guided
portion 80 provided on the side of the unit 10, the same effect can
be achieved by a structure conversely having the guide rail 40 with
the guide slot (V-shaped slot 90) provided on the side of the unit
10 and a guided portion 100 provided on the side of the unit
mounting portion 20 as illustrated in FIG. 9. In FIG. 9, a part of
the bottom surface of the unit 10 is cut and raised to form a riser
portion 10a to which the guide rail 40 is fixed so as to have the
V-shaped slot 90 face downward, and the guided portion 100 made of
a member whose section is L-shaped is fixed on the cross-bar
60.
[0079] While the above-described embodiment is structured to have
the guided portion 80 formed at the lower edge of the side surface
of the unit 10 and the guide rail 40 having the guide slot
(V-shaped slot 90) located below the unit 10, it may be conversely
structured as illustrated in FIG. 10 to have the upper edge of the
side surface of the unit 10 projecting to become a guided portion
80a and the guide rail 40 having the guide slot (V-shaped slot 90)
located above the unit 10. In FIG. 10, in the housing space of the
unit mounting portion 20, a cross-bar 65 located above the unit 10
is provided, a riser portion 65a facing downward is formed on the
cross-bar 65, and the guide rail 40 is fixed to the riser portion
65a so as to have the V-shaped slot 90 face downward. In addition,
at the upper edge of the side surface of the unit 10, the guided
portion 80a to be fit in the above-described V-shaped slot 90 is
formed.
[0080] In this embodiment, the same cross-bars 50 and 60 as those
of FIG. 1 are provided in the unit mounting portion 20 at a
position which comes under the unit 10 and on the right and the
left sides of the cross-bars 50 and 60, the guide member 45 whose
section is L-shaped is provided.
[0081] Thus structured present invention enables even a unit large
in breadth to operate smoothly at its insertion/extraction without
rightward and leftward rocking in the traveling direction to cause
a hitch and to be guided to a desired position within the unit
mounting portion, thereby improving work efficiency.
[0082] Although the invention has been illustrated and described
with respect to exemplary embodiment thereof, it should be
understood by those skilled in the art that the foregoing and
various other changes, omissions and additions may be made therein
and thereto, without departing from the spirit and scope of the
present invention. Therefore, the present invention should not be
understood as limited to the specific embodiment set out above but
to include all possible embodiments which can be embodies within a
scope encompassed and equivalents thereof with respect to the
feature set out in the appended claims.
* * * * *