JPH1030202A - Adding method and device for rail piece - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adding method and a device reducing the number of adding times of rails and the number of conveying times of rails and improving the work efficiency of the tunnel excavating work. SOLUTION: When new rail pieces are to be added to existing rails 2, 2 installed in a tunnel, moving rail pieces 9, 9 arranged overlappingly on existing rail pieces 6, 6 are advanced while thrusting the existing rail pieces 6, 6 backward, and next rail pieces having the length for multiple segment rings are installed in the front of the existing rail pieces 6, 6. The moving rail pieces 9, 9 are advanced while thrusting the next rail pieces backward, and these actions are repeated to add the next rail pieces to the existing rail pieces 6, 6 in sequence.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rail piece extension device for adding a new rail piece to a rail piece laid in a tunnel with the promotion of a shield machine.

[0002]

2. Description of the Related Art As shown in FIG.
Is a device for assembling the segments 32 on the inner wall of the tunnel 31 while digging earth and sand to form the tunnel 31. The segment 32 is formed of a substantially rectangular plate material, which varies depending on the shape of the tunnel 31 and the like, and is transported into the shield machine 30 from behind the tunnel 31. For transporting the segments 32, a transport carriage 34 traveling on rails 33 is used, and for assembling the segments 32, an erector 35 for moving and fixing the segments 32 to a predetermined assembling position is used.

A rail 33 for guiding a transport vehicle 34 is laid directly on a segment 32 assembled in a tunnel 31, so that the segment 32 on the transport vehicle 34 can be easily transferred to an erector 35. It is laid to the vicinity of the erector 35 so that it can be made. For this reason, the transport vehicle 34 can travel to a position close to the erector 35, and the delivery of the segments 32 is performed smoothly.

[0004]

However, the segment 32 is added by the excavation of the shield machine 30, and the distance between the erector 35 and the rail 33 is increased by adding a new segment 32. Therefore, as soon as the segment 32 forming the floor surface is assembled in front of the existing rail 33, a rail piece (not shown) having a length corresponding to one ring of the next segment is provided.
Must be added, and the next rail piece must be added each time the segment 32 is assembled for one ring, so that the number of rail piece additions increases, which is complicated. Since it is performed in a fixed cycle, if the rail pieces are frequently transported, there is a problem that the transport cycle of the segment 32 is disturbed and the efficiency of the operation is reduced, and the number of rail joints is large. Therefore, there is an adverse effect such as that the traveling vehicle easily vibrates.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and an apparatus for extending rail pieces which solve the above-mentioned problems, reduce the number of times of rail addition and the number of times of rail transportation, and improve the work efficiency of tunnel excavation work. It is in.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a method in which a new rail piece is added to an existing rail laid in a tunnel so as to overlap with the existing rail piece. The moving rail piece is pushed forward by pushing the existing rail piece backward, the next rail piece of the length of the segment multiple rings is laid in front of the existing rail piece, and then the next rail piece is pushed backward to move it The rail piece is advanced, and this operation is repeated to successively add the next rail piece to the existing rail piece.

[0007] Further, a rail piece extension device for adding a new rail piece to an existing rail piece laid in a tunnel in accordance with the propulsion of a shield machine is a pair of existing rail pieces laid in a tunnel. Moving rail pieces arranged in parallel with each other, a first anchor member detachably provided on the existing rail piece, a second anchor member for attaching and detaching the moving rail piece to the existing rail piece, The first anchor member is interposed between the first anchor member and the second anchor member.
When the anchor member is engaged with the existing rail piece and the second anchor member is disengaged from the new rail piece, the moving rail piece is advanced with respect to the existing rail piece, and the second anchor member is engaged and the first anchor member is engaged. An actuator for moving the first anchor member to one side of the newly installed rail when detached may be provided.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1 and FIG. 3, rails 2 and 2 for running a carrier (not shown) are laid on a segment 1 assembled in the tunnel. The wheels 3, 3 of the carriage have flanges 4a, 4b guided on the rails 2, 2 on both inside and outside of the wheels 3, 3 (the axle side is inside), and the inside collars 4a, 4a are connected to each other. The rails 2, 2 or the outer flanges 4b, 4b are guided by the rails 2, 2 so that they can run on the rails 2, 2 stably. The segment 1 has a rectangular plate shape, and a new segment 1 is assembled to the front end of the existing segment 1 every time a predetermined distance is excavated. The rails 2 and 2 have a length of three rings of the segment,
It is directly placed on the segment 1 and is fixed to the segment 1 via the holding metal 5.

The existing rail pieces 6, 6 located at the front ends of the rails 2, 2 (the lower part in FIG. 1 is the front) are used to add new rail pieces 7, 7 to the existing rail pieces 6, 6. Rail piece extension device 8 is provided.

The extension device 8 is disposed near the front end of the existing rail pieces 6, 6, and has a pair of left and right moving rail pieces for guiding the wheels 3, 3 of the carriage to the front of the existing rail pieces 6, 6. 9, 9 and a first anchor member 10 provided integrally with the moving rail pieces 9 and 9 to support the moving rail pieces 9 and 9 so as not to retreat, and detachably fixed to the existing rail pieces 6 and 6. A second anchor member 11 for fixing the moving rail pieces 9, 9 at an arbitrary position, and a first anchor member 10 or a second anchor member interposed between the first anchor member 10 and the second anchor member 11. An actuator 12 for moving one of the two anchor members 11 forward when the other is fixed.

Each of the moving rail pieces 9 and 9 is formed to have a length longer than the length of three rings of the segments, is superposed on the outside of the existing rail pieces 6 and 6 at a predetermined distance, and is parallel to each other. Are located in The moving rail pieces 9 and 9 and the existing rail pieces 6 and 6 are arranged in the left-right direction, respectively, and the wheels of the transport trolley are placed on both the moving rail pieces 9 and 9 and the existing rail pieces 6 and 6. 3,3
Can run over each.

The first anchor member 10 is a rod-shaped member that connects the front ends of the moving rail pieces 9, 9 and is connected to the moving rail pieces 9, 9 so as to be substantially orthogonal to each other.

The second anchor member 11 includes a base 13 for fixing the actuator 12 and pins 14 for fixing the base 13 to the existing rail pieces 6 and 6. Base 13
A pair of left and right vertical frames 15a, 15b arranged in parallel with the existing rail pieces 6, 6;
a, a pair of front and rear horizontal frames 1 spanned between 15a
6a and 16b, and has a substantially rectangular frame shape in plan view. Further, the base 13 is disposed between the existing rail pieces 6 and 6 so as to be in contact with the left and right existing rail pieces 6 and 6. The vertical frames 15a and 15b are formed in the left and right directions through pin holes 17 for inserting the pins 14 on both sides, and are formed in advance in the left and right directions previously formed at the front end portions of the rail pieces 6 and 6. The base 13 is fixed to the existing rail pieces 6 and 6 by inserting the pins 14 so as to overlap the stopper holes 18 and 18.

The actuator 12 is specifically an electric jack whose base 19 is fixed to the rear lateral frame 16b of the second anchor member 11 and the jack 2
0 is connected to the center position of the first anchor member 10 in the left-right direction. The jack portion 20 has a middle portion slidably inserted into the front horizontal frame 16a of the second anchor member 11, and the middle portion is guided by the front horizontal frame 16a when the jack portion 20 expands and contracts. It has become so. A middle folding member 21 for bending the jack portion 20 by a small angle is provided in the middle of the jack portion 20.
Is provided. The center folding member 21 is for changing the posture of the moving rail pieces 9, 9 in accordance with the inclination and unevenness of the segment forming the floor surface of the tunnel. Only a small angle can be bent so as not to change.

Further, the first anchor member 10 is provided with guide rods 22a and 22b for smoothly moving the first anchor member 10 and the second anchor member 11 toward and away from each other when the actuator 12 expands and contracts. I have. The guide rods 22 a and 22 b are round rods extending rearward from the first anchor member 10, and are provided one by one on each of the left and right sides of the actuator 12. Guide rods 22a, 22b
The front end thereof is integrally fixed to the rear end of the first anchor member 10 in a state of being parallel to and separated from the left and right sides of the actuator 12 as appropriate, and the front side frame 16a of the second anchor member 11 And, it is slidably inserted through the rear horizontal frame 16b to guide the movement of the first anchor member 10 and the second anchor member 11 due to the expansion and contraction of the actuator 12.

Next, the operation will be described.

First, as shown in FIG. 1, a rail piece extension device 8 is fixed to the front ends of the rails 2, 2, and the actuator 12 of the extension device 8 is retracted so that the first anchor member 10 is retracted.
The operation from the state in which the second anchor member 11 and the second anchor member 11 are close to each other will be described.

When the carriage is run from the rear of the rails 2, 2 toward the front end, the wheels 3, 3 of the carriage at the place 23 where the moving rail pieces 9, 9 do not overlap outside the rails 2, 2, respectively. Rails 4a, 4a
The vehicle runs while being guided by the rails 2 and 2 in contact with the inside of the vehicle. Further, at a place 24 where the moving rail pieces 9 and 9 overlap with the outside of the rails 2 and 2, the wheels 3 and 3 of the transport cart are placed on both the existing rail pieces 6 and 6 and the moving rail pieces 9 and 9 on the rails. While straddling each, each outer brim 4b,
4b also runs in contact with the outside of the moving rail pieces 9,9.

In this state, when the shield excavator excavates and a new segment 1 is assembled in front of the existing rails 2, 2, the carriage on the moving rail pieces 9, 9 is once moved backward to move. Retract from the rail pieces 9, 9,
Segment 1 of jack section 20 of actuator 12
Extend the ring forward. As a result, the moving rail pieces 9 and 9 slide forward by one ring of the segment and are moved onto a new segment 1. At this time, the guide bar 22 also moves forward with the movement of the moving rail pieces 9 and 9 and the first anchor member 10. Guide rod 2
2 is slidably supported by the horizontal frame 16, the force in the bending direction applied to the actuator 12 is dispersed by the inclination or unevenness of the segment 1 supporting the moving rail pieces 9, 9, and the moving rail pieces 9, 9 are dispersed. The movement of is smooth. If the segment 1 has an inclination or irregularities, the middle folding member 21 provided in the middle of the jack portion 20.
Is bent, and the moving rail pieces 9 and 9 are mounted on the segment 1 in accordance with the inclination and unevenness.

Thereafter, the carriage on which the new segment 1 is placed is advanced again to the vicinity of the front ends of the moving rail pieces 9, 9, and the segment 1 is delivered to an unillustrated erector. At this time, the wheels 3, 3 of the transport trolley are in a new segment 1
And only the outer rails 4b, 4b contact the outer sides of the moving rail pieces 9, 9 and are guided by the moving rail pieces 9, 9, respectively. Therefore, the vehicle travels smoothly on the moving rail pieces 9 and 9.

The same applies to the case where the shield excavator further excavates from this state and a new segment 1 is assembled. The transport carriage on the moving rail pieces 9, 9 is once moved to the moving rail pieces 9, 9. The moving rail pieces 9 and 9 are moved onto a new segment 1 by retracting from above and extending the jack portion 20 of the actuator 12 forward by one segment ring.

When the moving rail pieces 9 and 9 are moved forward by three rings of the segment in this manner, as shown in FIG. No. 9 is in a state of being moved forward most. At this time, the rear end portions of the moving rail pieces 9, 9 are in a state of being overlapped with the outside of the existing rail pieces 6, 6, respectively. The vehicle travels smoothly between 9, 9.

If the tunnel continues to be excavated,
As shown in FIG. 2, new rail pieces 7, 7 are attached to the front ends of the existing rail pieces 6, 6 located inside the moving rail pieces 9, 9.
Is added. At this time, the rail pieces 7, 7 are laid directly on the segment 1 like the existing rail pieces 6, 6, and are attached so that the rail pieces 7, 7 are sandwiched on the segment 1 by the holding metal 5.

Next, the pin 1 inserted into the pin hole 17 and the locking hole 18 and fixing the base 13 to the existing rails 6, 6.
4 are all removed to make the base 13 movable.
Then, the actuator 12 is degenerated. As a result, the first anchor member 10 hits the front ends of the rail pieces 7 and 7 and is restricted from moving rearward, and the second anchor member 11 including the base 13 is drawn forward. When the actuator 12 is completely retracted and the second anchor member 11 is moved to near the front end of the rail pieces 7, 7, the pin hole 17 of the base 13 and the locking hole 18 of the rail pieces 7, 7 are overlapped. Pin 1 in each hole 17 and 18
4 is inserted. By doing so, the extension device 8 is fixed to the front ends of the rails 2, 2, and the actuator 12 of the extension device 8 is retracted to bring the first anchor member 10 and the second anchor member 11 close to each other. I will return.
By repeating the same operation, the next rail pieces 7, 7 are sequentially added to the existing rail pieces 6, 6.

As described above, the moving rail pieces 9, which are arranged so as to overlap the existing rail pieces 6, 6 laid in the tunnel,
9 is pushed forward by pushing the existing rail pieces 6 and 6 backward, the next rail pieces 7 and 7 having a length corresponding to a plurality of segment rings are laid in front of the existing rail pieces 6 and 6, and then the next rail piece 7 is laid. , 7 to the rear to move the moving rail pieces 9, 9 forward,
This operation is repeated so that the next rail pieces 7, 7 are sequentially added to the existing rail pieces 6, 6, so that the number of rail additions can be reduced, and the number of rail transports can be reduced, and tunnel excavation can be performed. Work efficiency of the work can be improved.

Also, the rail piece extension device 8 is overlapped with a pair of existing rail pieces 6, 6 laid in the tunnel, and the moving rail pieces 9, 9 arranged in parallel with each other, and the existing rail piece 6, , 6, a second anchor member 11 for attaching and detaching the moving rail pieces 9, 9 to and from the existing rail pieces 6, 6, and a first anchor member 1.
When the first anchor member 10 is engaged with the existing rail pieces 6 and 6 and the second anchor member 11 is disengaged from the newly installed rail pieces 6 and 6, it moves between the first and second anchor members 11 and 11. The rail pieces 9, 9 are advanced with respect to the existing rail pieces 6, 6, and the second anchor member 11 is engaged to
Since the first anchor member 10 is provided with the actuator 12 for moving the first anchor member 10 to the newly installed rail pieces 7 when the 0 is released, the rail can be easily extended by a plurality of segment rings with a simple device. Therefore, the extension device 8 can be easily moved forward even after the next rail piece 7, 7 is extended.

Since the guide rods 22a and 22b are provided on the first anchor member 10, the first anchor member 10 and the second anchor member 11 can be smoothly approached or separated when the actuator 12 expands and contracts.

Further, since the center bending member 21 is provided in the middle of the jack portion 20, when the segment 1 has an inclination or unevenness, the moving rail pieces 9, 9 are mounted on the segment 1 according to the inclination or the unevenness. Can be.

In the above-described extension device 8, the base 13 is fixed to the existing rail pieces 6, 6 by inserting the pin 14 into the pin hole 17 and the locking hole 18, but the pin 14 needs to be limited to the pin 14. And bolts (not shown) in the pin holes 17 and the locking holes 18
May be screwed in and fixed. In this case, it is preferable that a female screw to be screwed to the bolt is formed in both or one of the pin hole 17 and the locking hole 18.

Further, in order to improve the grounding stability of the moving rail pieces 9, 9, the moving rail pieces 9, 9 may be temporarily fixed to the segment 1 with the holding metal fittings 5. However, it is preferable to temporarily fix with a small number of press fittings 5 so as not to impair workability.

Next, another embodiment will be described in detail.

As shown in FIG. 5 and FIG.
The rails 2, 2 to be laid thereon and the existing rail pieces 6, 6 located at the front ends of the rails 2, 2 (the lower part in FIG. 5 is the front) are substantially the same as those described in the above embodiment. It is. In addition, a first rail is provided near the front ends of the existing rail pieces 6 and 6.
The connecting rod 40 is detachably provided, and the distance between the existing rail pieces 6, 6 is kept constant so that the rails 2, 2 are parallel to the front end.

The extension device 41 is arranged near the front end of the existing rail pieces 6, 6, and a pair of moving rail pieces 43, 43 for guiding the transport vehicle 42 forward of the existing rail pieces 6, 6.
And a second connecting rod 44 for integrally connecting the vicinity of the front ends of the moving rail pieces 43, 43.

The transport vehicle 42 is provided with wheels 46 and 47 on a carrier 45 on which materials such as segments are placed, and travels on the rails 2 and 2 with the wheels 46 and 47. . As shown in FIG. 7, the wheels 46 and 47
Collars 48 and 49 are provided at the four corners of the loading platform 45 in a double direction with the inner wheels 46 and 46 running on the rails 2 and 2, and the outer wheels 47 and 47 moving rail pieces 43. , 43. Also,
The inner wheels 46, 46 and the outer wheels 47, 47 are provided on the same axle 50 at appropriate distances from each other, and even when the rails 2, 2 and the moving rail pieces 43, 43 overlap, the outer wheels The collars 49, 49 of the wheels 47, 47 do not contact the rails 2, 2.

The moving rail pieces 43, 43 are general-purpose rails arranged on both sides of the rails 2, 2 so as to overlap each other, and are arranged so as to protrude forward of the rails 2, 2, respectively. At the front ends of the respective moving rail pieces 43, 43, bollards 51, 51 are provided to prevent the carrier cart 42 from derailing due to excessive travel. These bollards 51, 51
Is formed at the front end of each of the moving rail pieces 43, 43 so as to have a slope that becomes higher toward the front. The wheels 47, 47 of the transport vehicle 42 are climbed uphill to prevent the transport vehicle 42 from going too far. I have.

The second connecting rod 44 is connected between the moving rails 43 and 43 near the front end thereof.
At the center of the second connecting rod 44, an engaging member 52 for engaging a hook (not shown) such as a chain block is provided so as to protrude forward.

The operation of the extension device 41 will be described.

The operation from the state where the moving rail pieces 43, 43 are close to the front ends of the rails 2, 2 as shown in FIG. 5 will be described. When the transport vehicle 42 travels from the rear of the rails 2 and 2 toward the front end, the transport vehicle 42 is mounted on the inner wheels 46 where the moving rail pieces 43 and 43 are not located outside the rails 2 and 2. , 46 on the rails 2, 2. At this time, the inner wheels 46,
46 is a rail 2,2 by the respective collars 48,48.
Is guided so as not to derail, and the distance between the wheels 46, 46 is kept constant, so that it does not come off from the rails 2, 2.

Further, in the place where the moving rail pieces 43, 43 are located outside the rails 2, 2,
As described above, the inner wheels 46, 46
The vehicle is run on the moving rail pieces 43, 43 with the outer wheels 47, 47 on the upper rails. At this time, the outer wheel 4
7 and 47 are guided by the respective collars 49 and 49 to the outside of the moving rail pieces 43 and 43 so as not to derail, and the distance between the wheels 47 and 47 is kept constant. It will not come off from above. Further, the collars 49, 49 of the outer wheels 47, 47 enter the gaps between the rails 2, 2 and the respective moving rail pieces 43, 43 and do not contact the rails 2, 2. The inner wheels 46, 46 are similar to those described above,
Is not guided off the rails 2 and 2. In this way, the transport carriage 42 is moved to move the moving rail pieces 43 and 4.
3, the wheels 47 of the carriage 42,
47 stops when it hits the bollards 51, 51.

In this state, when the shield excavator excavates and a new segment 1 is assembled in front of the existing rails 2 and 2, the transport carriage 42 on the moving rail pieces 43 and 43 is temporarily retracted. The engaging member 52 of the second connecting rod 44 is retracted from the moving rail pieces 43, 43 by a retracting means such as a chain block (not shown) by a length corresponding to one ring of the segment. As a result, the moving rail pieces 43, 43 slide forward by one ring of the segment and are moved onto a new segment 1. Then, the moving rail pieces 43, 43 are temporarily fixed on the segment 1.

Thereafter, the carriage 42 on which the new segment 1 is placed is advanced again to near the front end of the moving rail pieces 43, 43, and the segment 1 is delivered to an unillustrated erector. At this time, the inner wheels 46, 46 are
The wheels 47, 47 are moved forward from above and come off the rails 2, 2, and the outer wheels 47, 47 are moved by the moving rail pieces 43, 4.
3 will run. During traveling, the collars 49, 49 of the outer wheels 47, 47 respectively move the rail pieces 43,
Moving rail pieces 43, 43
And the wheels 47, 47 are moved by the moving rail pieces 43, 43.
We guide so that we do not remove from the top.

After moving the moving rail pieces 43, 43 forward by three segments, a new rail piece (not shown) is located at a position surrounded by the moving rail pieces 43, 43 and the second connecting rod 44. And add them to the front ends of the rails 2 and 2. At this time, a new rail piece is laid directly on the segment 1 as in the case of the existing rail pieces 6 and 6, and is mounted on the segment 1 with the holding metal 5. Then, the first connecting rod 40 is removed from the existing rail pieces 6 and 6, and is attached to a portion between the vicinity of the front end of the newly added rail piece.

Thereafter, the above operations are sequentially repeated to extend the rails 2 and 2.

As described above, the engaging member 52 for engaging the hook (not shown) of the traction means such as a chain block with the center of the second connecting rod 44 connecting the front ends of the moving rail pieces 43, 43. Are provided so as to protrude forward, so that the moving rail pieces 43, 43 can be easily moved forward by simple traction means such as a chain block.

Further, since the bogies 51, 51 are provided at the front ends of the moving rail pieces 43, 43, it is possible to prevent the transport vehicle 42 from running too far in front of the moving rail pieces 43, 43 even in an emergency. It is possible to prevent the wheels 47, 47 of the transport carriage 42 from derailing.

[0047]

In summary, according to the present invention, the following excellent effects can be obtained.

(1) According to the first aspect of the present invention, it is possible to reduce the number of times of rail extension and the number of times of rail conveyance.

(2) According to the second aspect of the present invention, the length of the rail can be easily extended by a plurality of ring segments with a simple device.

[Brief description of the drawings]

FIG. 1 is a plan view of a rail piece extension device showing a preferred embodiment of the present invention.

FIG. 2 is a plan view showing a state where a rail piece extension device of FIG. 1 is extended.

FIG. 3 is a sectional view taken along line III-III of FIG.

FIG. 4 is a side view of a shield machine showing a conventional method of transporting segments.

FIG. 5 is a plan view of a rail piece extension device according to another embodiment.

FIG. 6 is a side view of FIG. 5;

FIG. 7 is a sectional view taken along line VII-VII of FIG. 5;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 segment 2 existing rail 6 existing rail piece 7 rail piece 8 extension device 9 moving rail piece 10 first anchor member 11 second anchor member 12 actuator

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Taiji Morita 1-25-1, Nishishinjuku, Shinjuku-ku, Tokyo Taisei Construction Co., Ltd. (72) Inventor Osamu Watanabe 1-25-1, Nishishinjuku, Shinjuku-ku, Tokyo Taisei Construction Co., Ltd. (72) Inventor Osamu Watanabe 1-25-1, Nishi-Shinjuku, Shinjuku-ku, Tokyo Taisei Construction Co., Ltd. (72) Inventor Tosumi Ino 1-1-25, Nishi-Shinjuku, Shinjuku-ku, Tokyo Inside the corporation

Claims (2)

[Claims] 1. A moving rail piece, which is overlapped with an existing rail piece laid in a tunnel, is pushed forward by pushing the existing rail piece backward, and a length of a plurality of segment rings is provided in front of the existing rail piece. Laying the next rail piece, and then pushing the next rail piece backward to advance the moving rail piece, repeating this operation to successively add the next rail piece to the existing rail piece. How to extend. 2. A device for adding a new rail piece to an existing rail piece laid in a tunnel in association with the propulsion of a shield excavator, wherein the new rail piece is overlapped with a pair of existing rail pieces laid in the tunnel. Moving rail pieces arranged in parallel with each other, a first anchor member detachably provided on the existing rail piece, a second anchor member for attaching and detaching the moving rail piece to the existing rail piece, and the first anchor When the first anchor member is interposed between the member and the second anchor member, the first anchor member is engaged with the existing rail piece, and the second anchor member is disengaged from the new rail piece, the moving rail piece is moved relative to the existing rail piece. And an actuator for moving the first anchor member to one side of the newly installed rail when the second anchor member is engaged and the first anchor member is disengaged. An extension device.