JP2000291309A - Front window structure for construction machine cab - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow simultaneous unlocking at right and left sides and lifting operation of a front window when opening the front window in a construction machine to be opened with a series of operations. SOLUTION: In a construction machine cab which has this front window 5 movable via a guide slidably guided and supported along a guide rail ranging from the front side of a cab body to a ceiling side, locking mechanisms 10 for the cab body are provided on the right and left sides at the upper part of a window frame 6 of the front window 5 and an unlocking lever 20 simultaneously operable with a hand gripping a window opening/closing handle 8 is provided at the upper part of the window frame 6. The unlocking lever 20 and the right and left locking mechanisms 10, 10 are connected via a relay member 16 so that the right and left locking mechanisms 10, 10 may be simultaneously unlocked when the unlocking lever 20 is pulled by using connection members (rods 25, 26).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cab front window structure of a cab for a construction machine having a front working machine, in which the cab front window can be unlocked and opened by a simple operation. .

[0002]

2. Description of the Related Art Conventionally, a cab of a construction machine, for example, a working vehicle such as a hydraulic shovel, has a front side open from the front left and right sides inside a cab body so that a front side can be opened and a working state at a front position can be checked. A series of guide rails (not shown) are provided on the sides, and the front window 100 is provided with the guide rails shown in FIG.
As shown in the figure, a guide roller 102 is provided on each of the lower and upper sides of the window frame 101, and the guide roller 102 is guided by the guide rail, and can be pulled up from the front side to the ceiling side and stored and held. Have been.

[0003] With such a structure, the front window 100 is opened to open the front window 100 and check the working condition.
In order to open the lock pin 105b, as shown in FIG. 8 (b), the handle 105a of the latch type locking device 105 provided on both upper sides thereof is moved as shown by the arrow a in FIG. 8 (a). Is retracted and removed, and then the handles 103, 1 provided on the lower and upper portions of the window frame 101 are provided.
The front window 100 is pushed up (pulled up) by holding the respective 03 and stored in the ceiling from the front side position. Of course, although not shown, in the toggle type lock mechanism, similarly, the release operation of the lock mechanisms provided on the left and right must be performed individually.

[0004] Since such an operation is required, in order to improve workability, for example, as disclosed in Japanese Utility Model Laid-Open No. 5-84515, a front window is opened and closed using a hydraulic cylinder. A front window opening / closing device has been proposed. Alternatively, there is disclosed a front window holding device in which a front window is automatically locked when the front window is moved to a storage position so that the front window is pulled up to a ceiling and held safely after being stored.
No. 0-311061.

[0005]

As described above, in the conventional opening / closing structure of the front window 100, the locking devices 105, 105 provided on both sides of the upper portion of the window frame 101 are individually released, and thereafter, are opened. Since the front window is opened by at least two operations in which the operator holds the handles 103, 103 provided above and below the window frame 101 with both hands and pushes up, the work is not performed in a series of operations, resulting in poor workability. There is a problem.

Further, in the construction disclosed in Japanese Utility Model Application Laid-Open No. 5-84515, the cab can be automated. However, since the structure is such that the front window is turned to the operator side, the turning space is required, and the cab is required. However, it is not suitable for a small turning type machine in which the turning radius is made small because the size becomes large. Further, the technology disclosed in Japanese Patent Application Laid-Open No. Hei 10-311061 is effective in automatically opening a front window and storing it in a ceiling portion by automatically operating a lock function at a storage position to safely hold the window. In addition to the operation of releasing the lock mechanism, the lock mechanism at the time of closing the window is also operated individually, so it is inconvenient like the previous one in that it can not be performed in a series of operations when opening and closing. However, the problem of poor workability has not been solved.

The present invention has been made to solve such a problem. When the front window is opened, the left and right locks are simultaneously released and the front window can be lifted. It is an object of the present invention to provide a front window structure of a cab for a construction machine that can be used.

[0008]

In order to achieve the above-mentioned object, a front window structure of a cab for a construction machine according to the present invention includes a guide rail provided from a front side to a ceiling side in a cab body. In a cab for a construction machine having a front window movable through a guide body slidably guided along a cab body, a lock mechanism for the cab body is attached to both the left and right sides above a window frame of the front window. A release lever is provided at the upper part of the window frame so that the release lever and the left and right lock mechanisms can be operated simultaneously by a hand holding a window opening / closing handle, and when the release lever is pulled by a connecting member, the left and right lock mechanisms are opened. It is characterized by being connected so as to be released at the same time.

According to the present invention having the above structure, when the front window is opened along the left and right guide rails provided in the cab, when the operator grips the window opening / closing handle attached to the upper portion of the window frame, By simultaneously pulling the operating portions of the release levers provided together with a finger, the left and right lock mechanisms connected by the release lever and the connecting member are simultaneously released from the cab body (lock release). You. Therefore, the front window can be stored by holding the upper and lower window opening / closing handles and lifting the front window along the guide rail to the ceiling. Thus, according to the present invention, when the operator performs the window opening operation by holding the window opening / closing handle, the left and right lock mechanisms can be simultaneously released, and the unlocking operation and the window opening operation can be separately performed as in the related art. Thus, it is possible to release the lock and perform the window opening operation in one operation without performing the operation, and it is possible to remarkably improve the workability.

The left and right locking mechanisms and the release lever are connected to a relay member whose center is rotatably supported by a support pin at an upper portion of the window frame. It is preferable that each end is connected by two connecting members whose ends are pin-connected at equal distances. With this arrangement, the two connecting members for connecting the lock members of the lock mechanism provided on the left and right sides on the upper portion of the window frame of the front window and the release lever for unlocking are simultaneously moved right and left by the relay member, and An effect is provided that the unlocking operation can be performed and the lock can be unlocked with a simple structure.

The connecting member is composed of two rods whose leading ends are directly connected to the lock pins of the left and right locking mechanisms, respectively, and the rear ends of the rods are opposed by equal amounts from the pivot point of the relay member. It is preferable that the pins are connected at positions separated in the direction and connected to the release lever. With this configuration, the latch-type locking mechanism can perform the releasing operation in a straightforward manner, thereby ensuring the reliability of the operation. Also,
The connecting member is a pair of rods whose front ends are connected to the latch release parts of the left and right locking mechanisms via direction changing links, and the rear ends of the rods are respectively opposite in equal directions from the pivot point. It is good to be pin-connected at a remote position and connected to a release lever. Thus, when a lock mechanism having a latch structure is employed, the unlocking operation can be performed reliably by changing the direction using a bell crank or the like.

The connecting member may include a lock pin (a bolt) in the relay member and the left and right lock mechanisms.
Alternatively, it is preferable that a connection is made using a cable between the relay member and one end of the direction changing member (bell crank). In this case, by using a flexible material such as a wire cable in a portion where the pulling force acts during the unlocking operation, the length between the connection portions can be finely adjusted, and the mounting adjustment is easy. It works. Also,
The weight can be reduced.

Further, it is preferable that the relay member is provided with a return force urging member for applying a torque in the return direction.
With this configuration, the lock pins or the latches of the left and right lock mechanisms can be automatically returned at the same time by removing the release operation force applied to the release lever.

The release lever is provided on the side of the window opening / closing handle attached to the upper part of the window frame so that the operation portion is located at a position where the thumb of the hand holding the window opening / closing handle is applied. Preferably, it is characterized by the following. In this way, when opening the window, when the operator grasps the window opening / closing handle and moves the front window, at the same time, the thumb of the hand holding the window opening / closing handle is hung on the operating portion of the release lever, so-called one-touch operation. The operation of lifting the front window at the same time as releasing the lock can be performed in one operation,
This has the effect of improving operability ergonomically.

Further, the release lever is arranged inside a window opening / closing handle to be attached to an upper portion of the window frame, and has an end opposite to the gripping operation portion movably connected to a part of a connection member. Is good. In this way, the operating portion of the release lever is incorporated inside the window opening / closing handle, so that when the window opening / closing operation is performed by grasping the window opening / closing handle, the release lever is inevitably also released, This has the effect of increasing reliability and realizing a one-touch operation.

Further, a locking portion is provided at one side of the relay member, and a tip is engaged with the locking portion at a position adjacent to the relay member when the locking mechanism is in a released state to lock the locking portion. It is preferable that a lock lever capable of maintaining the release state is provided on the window frame portion. With this configuration, even if the release lever is not continuously operated during the window opening operation, the unlocked state can be maintained by engaging the distal end portion of the lock lever with the locking portion of the relay member, thereby facilitating the handling. Can be.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a specific embodiment of a front window structure of a cab for construction equipment according to the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing one embodiment of a cab for construction equipment having a front window structure according to the present invention, and FIG. 2 is a front view showing a main portion of the front window of the first embodiment. I have.

In the first embodiment of the front window structure, as shown in the drawings, the front window sections 2, 2 located on the front side of the cab body 1 of the construction machine and the ceiling side sections 3, 3 are provided with the roof windows. A pair of guide rails 4 and 4 are provided inside, and a front window 5 is provided movably along the guide rails 4 and 4. On both sides of the window frame 6 of the front window 5,
Guide rollers 7 are rotatably attached to the upper part and the lower part, respectively, and these guide rollers 7 are moved along the guide rails 4. Window opening / closing handles 8, 8 'to be gripped when the window is moved are provided integrally with the lower and upper portions of the window frame 6, respectively.

The front window 5 is fixedly attached to a glass 6a by a plurality of attachment members (not shown) provided at required intervals on a front side of a window frame 6 having a well-known structure. In the fixed position, it is held so as to be pressed against the front pillars 2 and 2 via the guide rollers 7 and 7 guided by the guide rails 4 and 4, and the peripheral portion is kept watertight by a seal member (not shown). It is held so that rainwater or the like does not enter from outside.

Locking mechanisms 10, 10 are mounted on the left and right sides of the upper portion of the front window 5 having the above configuration on the indoor side, respectively, with operating portions facing outward. The lock mechanism 10 is a latch type lock mechanism in this specific example, and a lock pin 13 is slidable outward in a cylindrical support portion 12 attached to a bracket 11 fixed to the window frame 6. A lock hole 15 is provided at the corresponding position inside the upper portion of the front pillar 2 so that the lock pin 13 can be locked when the lock pin 13 is inserted.

Between the mounting portions of the lock mechanisms 10, 10, the central portion is rotatably supported by a support pin 17 near the mounting position of the upper window opening / closing handle 8, and the relay member 1 is provided.
The relay member 16 is provided with connecting pins 18 and 18 'at opposite positions equally divided in required dimensions with respect to the pivot point (support pin 17), and a release pin is provided at a downward end. The lever 20 is integrally provided. The operating portion 21 of the release lever 20 is associated with the window opening / closing handle 8 such that when the handle 8 is grasped by a hand, the operating portion 21 can be operated by the thumb of the hand.

The other end of the rods 25 and 26, which are directly connected to the rear ends of the lock pins 13 of the left and right lock mechanisms 10, 10, are connected to the relay member 16 thus constructed, for example, by the rod 25 end on the right side in the drawing. The part is the connection pin 18 on the upper side of the relay member 16.
The end of the rod 26 on the left side in the figure is connected to the lower connecting pin 18 ′ of the relay member 16, respectively.
When the relay member 16 is rotated in the direction of the arrow a in the drawing, the two lock mechanisms 1 are moved through the left and right rods 25 and 26.
The lock pins 13, 13 of 0, 10 are simultaneously retracted and come out of the lock holes 15, so that the lock can be released. The left and right rods 25 and 26 are formed with a bent portion at the front of the connecting portion with the relay member 16 so that the rods 25 and 26 can smoothly and linearly move within the cylindrical support portion 12 of each lock mechanism 10.

The relay member 16 has a torsion spring 24 having one end fixed to the window frame 6 and the other end fixed to a proper position of the relay member 16 so as to be fitted on the support pin 17 thereof. (Corresponding to a return-force urging member of the present invention),
After the lock is released by the operation of the release lever 20, the lock pin 13 can be returned.

In this embodiment constructed as described above, when the front window 5 is opened, when the operator moves the front window 5 by holding the upper and lower window opening handles 8, 8 'in the same manner as in the prior art. When a force is applied such that the thumb of the hand holding the window-opening handle 8 is applied to the operating portion 21 of the release lever 20 located at an adjacent position and is gripped together with the window-opening handle 8, the release lever 20 is integrated. The relay member 16 is rotated counterclockwise with respect to the support pin 17 (a pivot point).

When the relay member 16 is rotated, the right and left rods 2 connected to the relay member 16 by connecting pins 18 and 18 ', respectively.
5 and 26 are retracted so that the lock pins 13 directly connected to the respective ends of the rods 25 and 26 are pulled out from the lock holes 15 and 15 provided on the front pillars 2 and 2 of the cab body 1, and the lock mechanism 10 , 10 locks the front window 5.

Therefore, the front window 5 is moved along the guide rails 4, 4 by holding the upper and lower window opening handles 8, 8 'while applying a force to the operation portion 21 of the release lever 20, and thereafter the front window 5 is stored in the cab on the ceiling side. It can be lifted and released at once. In short, the operator has the upper and lower window opening handles 8,
8 'and release the lock mechanism 10 at the same time
From the opening of the window to the storage in the same posture, the operation can be continuously performed in one operation. As a result, workability can be significantly improved as compared with the related art.

After the front window 5 has been moved to the storage position on the ceiling side, when the hand holding the upper window opening handle 8 is released, the torsion spring 24 biased by the relay member 16 is charged. The left and right rods 25 and 26 are pushed back by force, and the lock pins 13 and 25 are inserted into lock pin holes (not shown) provided at the positions in advance.
13 can be inserted and locked. When the front window 5 is to be closed, an operation reverse to that when the window is opened may be performed.

Next, FIG. 3 is a view showing the main part of the front window of the second embodiment. FIG. 3 (a) is a front view, FIG. 3 (b) is a plan view, and FIG. Detailed views are shown respectively. The front window 5A of the second embodiment is basically the same as that of the first embodiment, except that the lock mechanism 30 has a rotary latch structure. Therefore,
The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted.

As shown in FIGS. 3B and 4, the lock mechanisms 30 provided on both sides above the window frame 6 of the front window 5A are provided with brackets 3 projecting inward on both left and right sides of the window frame 6.
1, a latch 33 rotatable on a support shaft pin 32 attached in a direction parallel to the window glass 6a, and a locking pin 34 projected from the cab body 1 side in parallel with the window glass 6a. The locking notch 33a formed in the latch 33 is provided with the locking pin 3 on the cab body 1 side.
The front window 5A is locked while engaged with the front window 5A.

The latch 33 of such a lock mechanism 10A
Have locking notches 33a, 33b cut in the radial direction.
Are formed at two positions at positions displaced by approximately 90 °, and one of the locking cuts 33a is engaged with and locked with the locking pin 34 in the window closing position, and the other locking notch 33b is formed.
Is designed to engage and hold a locking pin (not shown) in the storage position. The latch 33 has an engagement recess 33c with a lock piece 36 for locking the rotation on the peripheral surface of the latch 33 at a position opposite to the locking cut 33a (lower side).
The engagement recess 33c has a pin 3 whose axis is located on an upright surface passing through the center of the support shaft pin 32 of the latch 33.
The lock piece 36 pivotally supported at 5 is normally engaged so that the latch 33 is locked. The latch 33 is provided with a torsion spring 37 whose one end is locked to the bracket 31 so as to be fitted on the support shaft pin 32 and the other end is connected to a proper position of the latch 33. A return force is applied to the latch 33 by the spring 37. Reference numeral 38 in the drawing is a frame that supports the latch 33 and the lock piece 36 and the like and also functions as a dividable cover that surrounds and protects a main part.

As in the first embodiment, the upper window opening handle 8 attached to the upper portion of the window frame 6 of the front window 5 is located between the left and right locking mechanisms 30 having such a latch. A pin 17 is supported at the center on the upper surface of the window frame 6 and a rotatable relay member 16 is provided. The relay member 16 is equally divided into required dimensions on the basis of the pivot point (pin 17). At opposite positions, the release lever 20 is attached integrally with the relay member 16 so that the rods 25 and 26 are connected by pins. The release lever 20 is positioned so that the handle 21 can be operated with the thumb of the hand holding the window opening handle 8 when the window frame 6 is opened and closed. One end of the pivot pin 17 of the relay member 16 is connected to the window frame 6.
A torsion spring (not shown) fixed to the side is fitted, the other end of the torsion spring is connected to the relay member 16, and a release force is applied to the release lever 20.

The rods 25 and 26 whose ends are pin-connected to the relay member 16 and are disposed on the left and right sides above the window frame 6 have the other ends on the side surfaces of both ends of the window frame 6 and a pin 41 at the center.
Bell links 40, 40 supported and swingably disposed
Is pin-connected to a connection seat 40a bent above the window frame 6 at the upper end of the window frame 6. The bell link 40 has one end connected to a pin 43 at an outward end and the other end connected to the lock mechanism 3.
Connection link 42 that is connected to the lock piece 36 and the pin 44
Connected to the lock mechanism.

In the second embodiment constructed as described above, when opening the front window 5A, when the operator moves the front window 5A by holding the window opening handles 8, 8 'as in the prior art, the upper side of the window is opened. When a force (indicated by a two-dot chain line c in FIG. 3B) is applied by the thumb of the hand holding the window opening handle 8 to draw the operating portion 21 of the release lever 20 at the adjacent position, the release lever 20 The integral relay member 16 is rotated counterclockwise with reference to the support pin 17 (a pivot point).

Then, the left and right rods 25, 26 connected to the relay member 16 are retracted, and these rods 25, 2
The bell link 40, which is pin-connected to each of the distal ends of Nos. 6 and 6, is pivoted downward at the other end thereof with the pivot pin 41 as a base point. Therefore, the connection link 42 connected to the pin 43 at the other end of the bell link 40 is pushed down, and is rotated toward the window frame 6 around the pin 35 supporting the connected lock piece 36. As a result, the lock piece 36 is disengaged from the engagement recess 33c of the latch 33, and the lock of the latch 33 is released.

Therefore, when the operator pulls the upper portion of the front window 5A forward, the latch 33 is rotated toward the window glass 6a, and the locking pin 34 (lock pin) to be attached to the cab body 1 and the locking notch are cut. 33a is disengaged from the front window 5
By moving A upward, the guide rollers 7 are guided by the guide rails, so that the front window 5A can be lifted at once and moved to the ceiling side of the cab body 1 for storage.

When the front window 5A is moved to the storage position on the ceiling side, the other locking notch 33b of the latch 33 is engaged with a locking pin (not shown) provided at that position in advance, and the lock is locked. A part of the peripheral surface of the piece 36 contacts the outer periphery of the latch 33 to provide resistance, and is kept locked at the storage position. Therefore, the front window 5A can be safely held at the storage position with the window opened. In the second embodiment, the relay member 16 is not provided with a torsion spring for pulling back.

When closing the front window 5A, the release lever 20 is simultaneously operated with the hand holding the upper window opening handle 8,
The front windows 5A can be closed by opening the lock mechanisms 30, 30 and performing the reverse operation of opening the windows thereafter. At this time, by pressing the upper portion of the window frame 6 toward the front side after reaching the window closing position, the locking notch 33 a of the latch 33 is securely engaged with the locking pin 34 at that position and added to the release lever 20. When the operating force is removed, the rods 25 and 26 are pulled back by the torsion spring force urged by the relay member 16, and the lock piece 36 rotates in the reverse direction via the bell link 40 and the connecting link 42 connected to these. And latch 3
3 and the latch 33 is locked.

FIG. 5 shows a third embodiment in which a release lever is incorporated in an upper window opening handle. The connection configuration with the lock mechanism in this embodiment is substantially the same as that of the above embodiment, and therefore, the relationship between the release lever and the rod will be described.

In this embodiment, a release lever 20A is provided inside a window opening handle 8A provided on the upper portion of the window frame 6 so that the release lever 20A is biased to one side and the base is supported by a pin 23. The release lever 20A is provided inside such that the operating portion 20b is simultaneously operated when the grip portion 8a of the window opening handle is grasped by hand, and the lever end 20a opposite to the operating portion 20b is connected to the window frame 6 by the window frame 6. And is movably connected to a pin 26a at an appropriate position of one of the rods 25 (26 in this example) associated with the lock mechanism. The two rods 25 and 26 are connected so as to operate synchronously by the relay member 16 as in the above-described embodiment. Although not shown, the relay member 16
Comes with a torsion spring for return.

By incorporating such a release lever 20A, when opening and closing the front window 5A, the release lever 20A can be operated at the same time as the window opening handle 8A is grasped and operated by hand. Can handle. Of course, when the opening / closing operation is completed and the hand is released from the window opening handle 8A or the force applied to the operating portion of the release lever is loosened, the lock mechanism is locked by the return force of the torsion spring attached to the relay member 16. The window frame 6 is locked at the movement end position.

In the above description, a return force urging means such as a torsion spring is used for the relay member 16 associated with the release lever (20, 20A, etc.) as the return means of the lock mechanism. Alternatively, as shown in FIG. 6, for example, similar effects can be obtained by connecting the rods 25 and 26 via the mounting member 29 so that the pull-back force of the tension spring 28 is urged.

As shown in FIGS. 7 (a) and 7 (b), in the case where the release lever 20 is integrally attached to the relay member 16, the relay is provided at the side of the release lever 20 mounting portion. A locking portion 55 is provided on the member 16,
When a lock lever 50 pivotally supported on the main body is disposed on the window frame 6 and the release lever 20 is operated to release the lock of the lock mechanism, the distal end portion 51 of the lock lever 50 is moved to the position shown in FIG. As shown in b), if the engagement with the locking portion 55 of the relay member 16 prevents the return by the return force urging means (the torsion spring 24), the release lever 20 can be kept as it is after the lock is released. It is possible to maintain the release state without holding on to. In addition, when the operation by the lock lever 50 is not required, the operation is not hindered by leaving the lock lever 50 open.

Instead of incorporating the release lever in the handle, the rod can be operated using a cam mechanism by a push button. Also, a cable can be used instead of the rod.

The guide roller 7 in this embodiment corresponds to the guide of the present invention.

[Brief description of the drawings]

FIG. 1 is a perspective view of an embodiment of a cab for construction equipment having a front window structure according to the present invention.

FIG. 2 is a front view showing a main part of a front window of the first embodiment.

FIGS. 3A and 3B are diagrams illustrating a main part of a front window according to a second embodiment, where FIG. 3A is a front view, FIG. 3B is a plan view, and FIG. 3C is a left side view.

FIG. 4 is a detailed view of a lock mechanism.

FIG. 5 is a view showing another embodiment of a release lever.

FIG. 6 is another example of the return mechanism of the lock mechanism.

FIGS. 7A and 7B are diagrams illustrating an example in which a release lever is provided with a release holding mechanism. FIG. 7A illustrates a state before the operation, and FIG. 7B illustrates a state of the release holding operation.

FIG. 8 is a diagram showing a conventional example of a lock mechanism.
(A) is a figure which shows a lock state, (b) is a figure which shows the state of lock release.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cab body 2 Front pillar 4 Guide rail 5,5A Front window 6 Window frame 7 Guide roller 8,8 ', 8A Window opening handle 10,30 Lock mechanism 11,31 Bracket 13 Lock pin 15 Lock hole 16 Relay member 17 Relay Lever support pin 20, 20A Release lever 21, 20b Release lever operating part 23 Release lever support pin 24, 37 Torsion spring 28 Tension spring 29 Mounting member 32 Latch support shaft pin 33 Latch 33a, 33b Latch engagement Stop notch 33c Engagement recess 34 Lock pin 36 Lock piece 40 Bell link 42 Connection link 50 Lock lever 55 Lock section

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyuki Shioji 3-1-1, Ueno, Hirakata-shi, Osaka F-term in Komatsu Ltd. Osaka Plant 2D015 EA03

Claims (9)

[Claims] 1. A construction machine cab having a front window movable through a guide body slidably guided and supported along a guide rail provided from a front side to a ceiling side in a cab body. At the top of the window frame, a lock mechanism for the cab body is provided on both the left and right sides, and at the top of the window frame, a release lever that can be operated simultaneously by a hand holding a window opening / closing handle is provided, and the release lever and the left and right A front window structure of a cab for a construction machine, wherein the lock mechanism is connected so that when the release lever is pulled by a connecting member, the left and right lock mechanisms are simultaneously released. 2. The left and right lock mechanisms and the release lever are mounted on a relay member rotatably supported at the center by a support pin at the center of the window frame. 2. The front window structure of a cab for a construction machine according to claim 1, wherein the cab is connected to each other by two connecting members whose ends are connected by pins at equal distances. 3. The connecting member includes two rods each having a distal end directly connected to a lock pin of each of the left and right lock mechanisms, and a rear end of each of the rods being an equal distance from a pivot point of the relay member. The front window structure of a cab for a construction machine according to claim 1, wherein the cab is connected to the release lever by a pin at a position separated in the direction. 4. The connecting member comprises two sets of rods each having a distal end connected to a latch unlocking piece of the left and right locking mechanisms via a direction changing link, and a rear end of each of the rods being a pivot of a relay member. The front window structure of a cab for a construction machine according to claim 1, wherein a pin is connected to the release lever at a position away from the fulcrum by an equal amount in the opposite direction. 5. The front window structure of a cab for a construction machine according to claim 2, wherein a return force urging member for applying a torque in a return direction is attached to the relay member. 6. The connecting member is connected by a cable between the relay member and a lock pin of the left and right lock mechanisms, or between the relay member and one end of a direction changing member. A front window structure of a cab for construction machinery according to item 1. 7. The release lever is provided on a side of a window opening / closing handle attached to an upper portion of a window frame so that an operation section is located at a position where a thumb of a hand holding the window opening / closing handle is applied. The front window structure of a cab for a construction machine according to any one of claims 1 to 4, wherein: 8. The release lever is mounted inside a window opening / closing handle to be attached to an upper portion of a window frame, and an end opposite to the gripping operation section is movably connected to a part of a connection member. The front window structure of a cab for a construction machine according to any one of claims 1 to 4, wherein: 9. A locking portion is provided at one side of the relay member, and a tip is engaged with the locking portion at a position adjacent to the relay member when the lock mechanism is in a released state to release the lock. The front window structure of a cab for a construction machine according to any one of claims 2 to 7, wherein a lock lever capable of maintaining a state is provided on the window frame portion.