EP2275378A1

EP2275378A1 - Gantry of construction machinery

Info

Publication number: EP2275378A1
Application number: EP10169350A
Authority: EP
Inventors: Yasuhiko Murayama; Kazuhiro Katada; Kazuyuki Miyazaki
Original assignee: Kobelco Cranes Co Ltd
Current assignee: Kobelco Cranes Co Ltd
Priority date: 2009-07-16
Filing date: 2010-07-13
Publication date: 2011-01-19
Also published as: JP2011037628A; CN101955134A; JP4770978B2

Abstract

A gantry 4 is composed of front legs 22, upper rear legs 24 and lower rear legs 28. In a working condition, the lower rear legs 28 and the upper rear legs 24 extend along a vertical line and the front legs 22 tilt backward and upward. In a stowed condition, the lower rear legs 28 and the upper rear legs 24 are folded and the front legs 22 are laid down backward. To a connecting joint 33 where the front legs 22 and the upper rear legs 24 are connected, one end of the connecting rod 35 that secures the stowed condition is rotatably connected. On the other end of this connecting rod 35, a pin 41 is provided. On the upper rear legs 24, a lock mechanism which is capable of engaging with the pin 41 is provided. The lock mechanism 42 disengages the locked condition with the pin 41 in accordance with the movement of folding the lower rear legs 28 and the upper rear legs 24 in order to change the gantry from the working condition to the stowed condition. It is possible to prevent the lock member, the connecting rod and the upper rear legs from being damaged by forgetting disengaging the lock mechanism.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a gantry used in such construction machinery as crane, pile driver and so on. Particularly in detail, it relates to the gantry whose rear legs are folded down into two pieces and whose front legs are laid over the rear legs downward and backward for storage while transportation.

2. Description of Related Art

Conventionally, the construction machinery such as crane or pile driver is furnished with a working attachment on a front section of a revolving frame of an upper revolving body. On the rear area of the revolving frame, a gantry (also referred to an A-frame or type A-frame) is installed. The gantry is furnished in order to execute the prescribed motions in relation to works of the working attachment. In case of crane works, for example, the gantry is used to support a boom from its back side by means of wire ropes. Moreover, in case of a pile driver the gantry is used to raise a leader by means of wire ropes.
This kind of gantry is known and disclosed, for example, in Japanese Patent Laid Open No. 2000-198672 . This conventional example is shown in Fig. 11 and Fig. 12. Bottom ends of front legs 103 are rotatably supported on the revolving frame by means of a mounting bracket 102. To the top of the front legs 103, the end (the top) of upper rear legs 104 are connected. To slot holes 105 provided on the other end (the bottom end) of the upper rear legs 104, the tops of lower rear legs 107 are connected by means of sliding pins 106. The bottom end of the lower rear legs 107 are supported on the revolving frame 101 so as to turn freely. In the gantry 100 shown in Fig. 11 under the working condition, both the lower rear legs 107 and the upper rear legs 104 extend along a substantially vertical line, and also the front legs tilt backward and upward. As shown in Fig. 12, the lower rear legs 107 and the upper rear legs 104 are folded, and the front legs 103 are tilted backward and laid over the rear legs when the gantry 100 is in a stowed condition.
As for the configuration of the gantry, a hydraulic cylinder 108 is straddle-mounted between the lower portion of the front legs 103 and the revolving frame 101. The telescopic motion of the hydraulic cylinder 108 causes the front legs 103 to turn in the raising direction or in the falling direction around a bearing shaft 111. A connecting member 113 which is provided with a pin hole 112 at the top of the connecting member 113 is prepared in the middle of the front legs 103. On the contrary, corresponding to the connecting member 113, a mounting bracket 114 which is provided with a pin hole at the top thereof is provided on the revolving frame 101. While the gantry 100 is stowed, the pin hole 112 on the above mentioned connecting member 113 matches with a pin hole on the mounting bracket 114. By inserting a connecting pin 115 into both holes, the connecting member 113 is connected to the mounting bracket 114. By doing so, the gantry 100 is kept stowed.
However, in the above mentioned conventional configuration of gantry, especially in case of the configuration of holding the gantry 100 in the stowed condition, as the connecting point formed between the connecting member 113 and the mounting bracket 114 by the connecting pin 115 becomes close to the folded lower rear leg 107, to the upper rear leg 104 and also to the hydraulic cylinder 108, the connecting work causes to makes troubles, resulting in making a weak point. In addition, it is necessary to arrange a plurality of drums 116 in the rear section of the revolving frame 101. However, the installation of the above mentioned mounting bracket 114 reduces the flexibility of the layout in order to arrange the drums, resulting in making another weak point.
Another gantry as shown in Fig.3, for example, is known in order to solve such a problem like this. This gantry 100 is provided with a connecting rod 121 whose one end is rotatably connected to a connecting joint between the front leg 103 and the upper rear leg 104. By connecting the other end of the above mentioned connecting rod 121 to the rear end of the revolving frame 101, the gantry 100 is kept in the stowed condition. Furthermore, since the basic configuration of the gantry structure shown in Fig. 13 is almost the same as shown in Fig. 11 and Fig. 12, so the same parts and components are given the same numbers, and the same explanations on them are omitted.
However, in this case, the following points are raised based on the procedure of handling the connecting rod 121 in the working condition of the gantry 100, that is to say, the working condition of the construction machinery.

(1) When the connecting rod 121 is removed from the machine and stowed in a separate place during the machine operation, it is necessary not only to spend time for removing the connecting rod 121 and re-installing the connecting rod 121, but also to secure a space for stowing the connecting rod 121. This is very inconvenient.
(2) When the connecting rod 121 is not removed from the machine, while the other end of the connecting rod is left free to rotate during the machine operation, the connecting rod 121 sways during operating the machine and bumps against the upper rear legs 104, resulting in making scratch marks on the painted surface and bumping sounds.
(3) The other problem which occurs during the machine operation is explained referring to Fig. 14. In Fig. 14, a latch slot 122a provided on a latch member 122 whose base end is rotatably supported on a support pin 123 located on the upper rear legs 104 engages with a latch pin 124 that is provided on the other end of connecting rod 121. In this case, before the gantry 100 is stowed, if the latch slot 122a of the above mentioned latch member 122 is not inadvertently disengaged from the latch pin 124, it is most probable that not only the latch member 122 and the latch pin 124 that compose the latch mechanism are destroyed, but also the connecting rod 121 and the upper rear legs are damaged.

SUMMARY OF THE INVENTION

An object of the present invention is, preventing a latch member from being damaged by forgetting disengaging a latch mechanism, to supply a gantry for the construction machinery which is capable of preventing a connecting rod and upper rear legs from being damaged.
The gantry of the present invention is mounted on a base frame of construction machinery. This gantry is provided with a front leg whose bottom end is rotatably supported on a base frame, an upper rear leg whose one end is connected to the top of the front leg and the lower rear leg whose top is connected to the other end of the upper rear leg and whose bottom end is rotatably supported to the base frame. While the construction machinery is in a working condition, the lower rear leg and the upper rear leg are located substantially along a vertical line and the front leg tilts backward and upward. Furthermore, while the gantry of the construction machinery is in a stowed condition, the lower rear leg and the upper rear leg are folded down backward, and the front leg is laid over the rear legs. To the connecting portion of the front leg and the upper rear leg, one end of the connecting rod connected to the base frame in order to hold the gantry in the stowed condition is rotatably connected. On the other end of the connecting rod, a pin that protrudes in the lateral direction is provided. On the upper rear leg, a lock mechanism which is capable of engaging with the pin is provided. In accordance with the movement folding the lower rear leg and the upper rear leg in order to change the gantry from the working condition to the stowed condition, this lock mechanism disengages the locked condition with the pin.
In the gantry of the present invention, because the locked condition between the lock mechanism and the pin is disengaged together with the movements in accordance with the movement folding the lower rear leg and the upper rear leg in order to change the gantry from the working condition to the stowed condition, the gantry of the present invention does not cause possible damages on the lock member by careless omitting to disengage the lock mechanism, and it also does not cause damages on the connecting rod and the upper rear leg.
Moreover, as the lock mechanism of the present invention, a lock mechanism having a catch slot whose base end is fixed on the upper rear leg and whose upper and top portion are able to engage with the pin may be used. According to this configuration, the locked condition formed by the lock mechanism and the pin is fulfilled by the condition that the catch slot on the lock plate fixed on the upper rear leg engages with the pin. On the other hand, when the lower rear leg and the upper rear leg are folded in order to change the gantry from the working condition to the stowed condition, the locked condition between the lock mechanism and the pin is disengaged by means of the relative off-set between the lock plate and the pin. Accordingly, simplifying the lock mechanism, the disengagement of the locked condition is automatically and securely performed.
Furthermore, as the lock mechanism of the present invention, the mechanism having a mounting plate, a holder, a lever, a link member and a spring member may be also used. In this case, the mounting plate is fixed on the upper rear leg. The holder is rotatably supported on a support pin around a supporting axis. The lever is rotatably supported on a pin of the mounting plate around another supporting axis, and secures the pin in the locked condition together with the holder. The link member connects one end of the lever to the holder so that the lever and the holder may rotate together between the locked condition and the unlocked condition. The spring member imposes the force on the lever and the holder to hold the locked condition when they are in the locked condition. When the lower rear leg and the upper rear leg are folded in order to change the gantry from the working condition to the stowed condition, the pin pushes the lever of the lock mechanism against the force generated by the spring member and places the lever and holder in the unlocked position. On the other hand, when the gantry is changed from the stowed condition to the working condition, the pin pushes the connecting end of the link member to put the lever and the holder into the locked condition.
In this configuration, the locked condition formed by the lock mechanism and the pin is placed in the locked condition in which the lever and the holder of the lock mechanism secures the pin, and this locked condition is achieved by holding the spring member. On the other hand, this locked condition is disengaged by the pin which pushes the lever against the force generated by the spring member so that the lever and the holder becomes the unlocked condition, when the lower rear leg and the upper rear leg are folded in order to change the gantry from the stowed condition to the working condition. Therefore, the disengagement of the locked condition is automatically and securely performed. Moreover, when the position of the gantry is changed from the stowed condition to the working condition, the connecting rod being hung down from the connecting portion to which the front leg and the upper rear leg are connected approaches near the upper rear leg. Then, the pin at the side of the connecting rod pushes the connecting end of the link member so that the lever and the holder secure the pin in the locked position, so the locked condition is automatically and securely performed. Accordingly, the maneuverability is improved.
Furthermore, as the lock mechanism of the present invention, a spring member consisting of an L shaped lever and a coil spring may be used. This lever is rotatably supported on a pin at the center of the lever. The one end of this spring member is hooked at the middle portion between a rotating point and an end portion connected to the link member, while the other end is hooked at the mounting plate respectively. In this case, when the lever and the holder are in the locked condition, a center line locates closer to the link member than to the rotating point so that the spring force is imposed so as to hold the unlocked condition. On the other hand, when the lever and the holder are in the unlocked condition, the center line locates farther to the link member than to the rotating point, so that the spring force is imposed so as to hold the unlocked condition.
According to this configuration, the spring member consisting of a coil spring whose both ends are hooked at the lock plate and at the middle portion between the rotating point and the end portion connected to the link member respectively, displays not only the original function of holding the locked condition, but also another function of holding the unlocked condition by reversing of the spring force when the lever and the holder of the lock mechanism are in the locked condition. Accordingly, lessening the number of parts to be used, it is possible to improve the reliability of operation.

BRIEF DESCRIOTION OF THE DRAWINGS

Fig. 1 is a side view of a crawler crane relating to the first embodiment of the present invention;
Fig. 2 is a side view of a configuration near a gantry of the crawler crane;
Fig. 3 is a side view of the gantry in the working condition;
Fig. 4 is views of a plate ((a) front view, (b) flat view, (c) side view);
Fig. 5 is a side view showing the condition of beginning to fold lower rear legs and upper rear leg of the gantry to change from the working condition to the stowed condition;
Fig. 6 is a side view of a gantry of a crawler crane relating to the second embodiment of the present invention;
Fig. 7 is a side view of lock mechanism in its locked condition;
Fig. 8 is a side view of the lock mechanism in its unlocked condition
Fig. 9 is a drawing to explain the function of the lock mechanism when the gantry changes from the stowed condition to the working condition;
Fig. 10 is a drawing to explain the process of the lock mechanism when the gantry changes from the working condition to the stowed condition;
Fig. 11 is a drawing showing the conventional example, and Fig. 11 corresponds to Fig. 3;
Fig. 12 is a side view of the conventional gantry in the stowed condition;
Fig. 13 is a drawing of another conventional example, and Fig. 13 corresponds to Fig. 2; and
Fig. 14 is a magnified view of the area X of Fig. 13.

DETAILED DESCRIPTION OF THE PREFFERED EMBODIMENTS

(The first embodiment)

Fig. 1 shows a general configuration of a crawler crane as construction machinery which is equipped with a gantry relating to the first embodiment of the present invention. The numeral 1 denotes a crawler type lower propelling body. The numeral 2 denotes an upper revolving body which is rotatably mounted on the lower propelling body 1. The upper revolving body 2 is provided with a revolving frame 2a as a mounting base. On the front of the revolving frame 2a, a base end of a boom 3, as a working attachment, is attached so as to be raised or lowered. On a rear end of the revolving frame 2a, a gantry 4 and a counterweight 5 are installed.
On a top section of the above mentioned boom 3, one end of a boom guy-line 6 is fixed, while the other end of the guy-line 6 is provided with an upper spreader 7. Between the upper spreader 7 and a lower spreader 8 that is installed on the top of the above mentioned gantry 4, a boom raising/lowering rope 9 is wound. One end of the raising/lowering rope 9 is fixed on the gantry 4, while the other end of the rope is wound on a boom raising/lowering drum 10 which is installed on the rear section of the upper revolving body (revolving frame 2a). The boom raising/lowering drum 10 makes the distance between the lower spreader 8 and the upper spreader 7 longer or shorter by winding off or winding in the rope. With this arrangement, the boom 3 is raised and lowered.
On the top section of the above mentioned boom, boom point sheaves 11, idler sheaves 12 and auxiliary sheaves 13 are rotatably installed respectively. A main hook 14 is held on a main hoist rope 15 and hung down from the boom point sheaves 11. An auxiliary hook 16 is held on an auxiliary hoist rope 17 and hung down from the auxiliary point sheaves 13. One end of the main hoist rope 15 is fixed on the top section of the boom 3. On the contrary, the other end of the hoist rope 15 is wound on a main hoist drum 18 installed on the upper revolving body via the boom point sheaves 11 and the idler sheaves 12. Accordingly, main hoist drum 18, the main hook 14 is hoisted or lowered with the main hoist rope 15. One end of the auxiliary hoist rope 17 is fixed on the auxiliary hook 16. The other end of the auxiliary hoist rope 17 is wound on an auxiliary hoist drum 19 installed on the upper revolving body 2 via the auxiliary sheave 13 and idler sheave 12. Accordingly, auxiliary hoist drum 19, the auxiliary hook 16 is hoisted or lowered.
The revolving frame 2a of the above mentioned upper revolving body 2 is formed by a left-and-right pair of side plates 2b (shown on the right hand side only) and a bottom plate 2c which connects the side plates 2b. Between the left-and-right of the side plates 2b on the revolving frame 2a, the main hoist drum 18, the auxiliary hoist drum 19, a third drum 20 and the boom rising/lowering drum 10 are arranged in turn from the front in the condition that all shafts of the drums are vertically crossed with the centerline of the revolving frame. Although it is not illustrated on the drawing, these drums are installed on the side plates or the bottom plate of the revolving frame 2a by means of mounting brackets.
On the other hand, the above mentioned gantry 4 is provided with front legs 22, upper rear legs 24 and lower rear legs 28 as shown in Fig. 3. Although these legs have a pair of legs on each left and right side respectively, Fig. 3 shows the legs on the right side only. The bottom end of the front legs 22 is rotatably supported on a support pin 21 which is mounted on the side plate 2b of the above mentioned revolving frame 2a. Each end (top end) of the upper rear legs 24 is connected to top end of the front legs 22 so that the upper rear legs 24 can rotate around pins 23. The top of lower rear legs 28 are connected to the other ends (bottom ends) of the upper rear legs 24 with two connecting pins 25 and 26, and the bottom ends of the rear lower legs are rotatably supported on support pins 27 which are mounted on the side plates 2b of the above mentioned revolving frame 2a. Aligning positions of pinholes 29 and 30 (referring to Fig. 5) provided on the upper rear leg 24 and lower rear leg 28 respectively, the upper connecting pin 25 is inserted into both pin holes 29 and 30. Aligning a pinhole (not shown) provided on the upper rear leg 24 with the top edge of a slot 31 provided on the lower rear leg 28, the lower connecting pin 26 is inserted into the pin hole and the slot 31. In the gantry 4 illustrated with solid lines in Fig. 2 showing the working condition of the gantry, both of the lower rear legs 28 and the upper rear legs 24 extend substantially along the vertical line, and the front legs 22 tilt backward and upward. On the contrary, in the gantry 4 illustrated with imaginary lines in Fig. 2 showing the stowed condition of the gantry, the lower rear legs 28 and the upper rear legs 24 are folded by rotating them around the connecting pins 26 after the connecting pins 25 are removed, and then the front legs 22 are tilted backward and laid down over the rear legs.
The above mentioned gantry 4 is provided with a hydraulic cylinder 32 which is straddle-mounted between the lower portion of the front legs 22 and the revolving frame 2a, The telescopic motion of the hydraulic cylinder 32 causes the front legs 22 to turn around a pin 21. Between connecting joints 33 (top of the gantry 4) which connect the right and left front legs 22 with the upper rear legs 24 of the gantry 4, a connecting member 34 is installed so as to extend in the lateral direction. On this connecting member 34, the above mentioned lower spreader 8 is installed. Moreover, in the place located more rearward and higher than the support pin 23 that is the connecting point for the upper rear legs 24 at the above mentioned connecting joint 33, one end of a connecting rod 35 is rotatably mounted on a connecting pin 36. When the gantry 4 is in the folded condition, a pin hole 37 provided on the other end of the connecting rod 35 is aligned with a pin hole 38 provided on the rear end of the side wall 2b of the revolving frame 2a, and then a connecting pin (not shown) is inserted into both pin holes 37 and 38. In this condition, the connecting rod 35 holds the folded condition of the gantry 4 by connecting the connecting joint 33 to the revolving frame 2a.
On the other end of the above mentioned connecting rod 35, a catch pin 41whose cross section view is a circle and which protrudes in the lateral direction is provided. On the upper leg of the above mentioned upper rear leg 24, a plate 42 engaged with the catch pin 41 is fixed. The plate 42 is provided with a semicircular catch slot 43 whose upper surface engages with the catch pin 41 as shown in Fig. 4 showing a magnified and detail view of the catch plate 42. The engagement between the catch slot 43 of the catch plate 42 and the catch pin 41 is disengaged, as shown in Fig. 5, when the upper rear legs 24 turn forward (towards the front legs 22) in order that the gantry 4 is changed from the working condition to the stowed condition by folding the lower rear legs 28 and the upper rear legs 24.
Accordingly, in the first embodiment of the present invention, the other end of the connecting rod 35 whose one end is rotatably connected to the connecting joint 33 which connects the front leg 22 and the upper rear leg 24 in the working condition of the gantry 4 is connected to the upper rear leg 24 by the engagement of the catch pin 41 provided at the other end and the catch slot 43 of the plate 42. Therefore, during the machine operation, as the connecting rods 35 do not sway to bump against the upper rear legs 24, generating bumping sounds and scratching on painted surfaces are prevented from occurring.
In addition, the engagement between the catch slot 43 on the above mentioned catch plate 42 and the catch pin 41, as shown in Fig. 5, is disengaged by the movements while folding the lower rear legs 28 and the upper rear legs 24, so that the gantry 4 may be changed its position from the working condition to the stowed condition. Therefore, damages on the catch members consisting of the catch plates 42 and the catch pins 41, which may cause by carelessly omitting to disengage the latch mechanism, can be eliminated. Damages on the connecting rod 35 and the upper rear leg 24 may also be eliminated. The first embodiment can avoid the damages of those members.
Furthermore, the catch plate 42 has the base end fixed on the upper rear legs 24 and the edge end whose upper side is formed as the catch slot 43 so as to be engaged with the catch pin41, and the catch plate 42 is a single part as the catch mechanism. Accordingly, the first embodiment can simplify the catch mechanism and is superior in practical use.

(The second embodiment)

Fig. 6 shows a gantry of a crawler crane of the second embodiment of the present invention. In the second embodiment, the configurations of a connecting rod 50 and lock mechanism 60 are different from those of the first embodiment. Moreover, the basic configuration of the gantry is the same as the first embodiment, and the same numbers are allocated to the same parts and components, accordingly the explanations about them are omitted.
The one end of the above mentioned connecting rod 50 is rotatably mounted, as well as that of the first embodiment, around the connecting pin 51 that is located more rearward and higher than the support pin 23 of the connecting joint 33 between the front legs 22 and the upper rear legs 24. On the other hand, at the other end of the connecting rod 50, a couple of pin holes 52 and 53 are provided. When the gantry 4 is in the stowed condition (as shown by tow-dots chain lines in Fig. 6), the connecting rod 50 is connected by a pin to the revolving frame 2a (referring to Fig. 2 and Fig. 3) by using either one of two pin holes 52 or 53 on the connecting rod 50. By this connection, the connecting joint 33 is connected to the revolving frame 2a by means of the connecting rod 50 to hold the gantry 4 in the folded condition.
On the other end of the above mentioned connecting rod 50, the lock pin 54 that protrudes to the lateral direction is provided. The lock mechanism 60 being capable of coupling with lock pin 54 is provided on the upper rear leg 24. This lock mechanism 60, as shown in Fig. 7 and Fig. 8 as a magnified view, is provided with a mounting plate 61, an approximately U-shaped holder 63, an L-shaped lever 65, a link member 66 and a spring member 67. The mounting plate 61 is fixed on the upper rear leg 24. The holder 63 is rotatably supported around the support pin 62 on the mounting plate 61. The lever 65 is supported by the mounting plate 61 and is rotatably mounted around the support pin 64, and secures the lock pin 54 in a coupled condition by clamping the lock pin 54 together with the holder 63. The link member 66 connects the one end of the lever 65 and the one end of the holder 63, so that the lever 65 and the holder 63 may rotate together between the locked condition (shown in Fig. 7) where the lever 65 and the holder 63 hold the pin 54 and the unlocked condition (shown in Fig. 8) which disengages the locked condition. The spring member 67 imposes the force to hold the locked condition when the above lever 65 and the holder 63 are in the locked position.
The lever 65 is rotatably supported around the support pin 64 at a center section which is a bent portion. Moreover, the above mentioned spring member 67 is composed of a tensile coil spring. The one end of this spring member 67 is hooked at the lever 65 in the middle portion between a through hole for the support pin 64 and the connection point of the link member 66. The other end of the spring member 67 is hooked at the upper portion of the mounting plate 61. The spring member 67, as shown in Fig. 7, forces the center line 67a to locate a position closer to the link member 66 than to the center axis 64a of the support pin 64, so that the spring force (pulling force) generated by the spring member 67 secures the locked condition, when the lever 65 and the holder 63 are in the locked condition. On the other hand, the spring member 67, as shown in Fig. 8, forces the center line 67a to locate a position farther from the link member 66 than from the center axis 64a of the support pin 64, so that the spring force secures the unlocked condition, when the lever 65 and the holder 63 are in the unlocked condition.
Next, the explanation about the operation of the aforementioned lock mechanism 60 is made hereinafter referring to Fig. 9 and Fig. 10. When the gantry 4 is in the stowed condition, the lever 65 and the holder 63 of the lock mechanism 60 is in the unlocked condition as shown in Fig. 9(a). Then, when the position of the gantry 4 is changed from the stowed condition to the working condition, the upper rear legs 24 are raised up from the folded condition and approach to the connecting rod 50. At this time, as shown in Fig. 9(b) and Fig. 8, the lock pin 54 on the connecting rod 50 pushes the connecting portion of the link member 66 connected to the lever 65 of the lock mechanism 60 on the upper rear leg 24, so that the lever 65 and the holder 63 secure the pin 54 in the locked position (referring to Fig. 9(c)). When the gantry 4 is in the working condition and when both of the lever 65 and the holder 63 of the lock mechanism 60 are also in the locked condition, the movement of the connecting rod 50 is limited only to the right and left directions. Therefore, the lever 65 of the lock mechanism 60 is not pushed to open and the locked condition is not unlocked.
On the contrary, when the lower rear legs 28 and the upper rear legs 24 are folded in order to change the position of the gantry 4 from the working condition to the stowed condition, as shown in Figs 10(a) and 10(b), the upper rear legs 24 and the connecting rods 50 move to tilt with a parallel linkage and the relative off-set between the lock mechanism 60 on the upper rear legs 24 and lock pin 54 on the connecting rod 50 occurs. Accordingly, as shown in Fig. 10 (c), the lock pin 54 pushes to open the lever 65 of the lock mechanism 60 against the spring force generated by the spring member 67 and the lever 65, and the holder 63 are placed in the unlocked position, so that the connecting rod 50 becomes free.
In this second embodiment of the present invention, being similar to the first embodiment of the present invention, when the gantry is in the working condition, because the other end of the connecting rod 50 is connected to the upper rear legs 24 by the lock pin 54 engaged with the lock mechanism 60, there is no possibility that the connecting rod 50 sways during the machine operation and also bumps against the upper rear legs 24. Therefore, it is possible to prevent the rod from making scratch marks on the painting surface and from generating bumping sounds. In addition, engagement or disengagement of the locked condition between the lock mechanism 60 and the lock pin 54 is performed automatically and securely. For this reason, it is possible to prevent the lock member, consisting of each part of the lock mechanism 60 and the lock pin 54 and so on, from being damaged due to forgetting disengaging the lock mechanism. Accordingly, the maneuverability is improved.
Furthermore, the spring member 67 of the lock mechanism 60, when the lever 65 and the holder 63 of the lock mechanism 60 are in the locked condition, not only displays the original function of holding the locked condition, but also displays the other function of holding the unlocked condition caused by the spring force when the lever 65 and the holder 63 of the lock mechanism 60 are in the unlocked condition. Accordingly, lessening the number of parts to be used, it is possible to improve the reliability of operation.

(Other embodiments)

It should be noted that the present invention is not limited to the above mentioned first and second embodiments, but includes a variety of other embodiments. For example, in the above mentioned embodiments, it has been referred to a case that the one end of the connecting rod 35, 50 holding the gantry 4 in the folded condition is connected to the connecting joint 33 of the front legs 22 and the upper rear legs 24 of the gantry 4 and that the other end of the connecting rod 35, 50 is connected by a pin to the pin hole 38 provided on the rear end of the side wall 2b of the revolving frame 2a when the gantry 4 is in the stowed condition. However, the present invention is not limited to this example, but also applied to the case that the other end of the connecting rod 35, 50 is connected by a pin to a pin hole provided on the counterweight 5 when the gantry 4 is in the stowed condition. Especially, the present invention may be also applied to a mechanism that facilitates the connecting rod 35, 50 to change the rod length at two levels, long or short, so that the pin hole where the other end of the connecting rod to be fixed may be selected either on the side plate 2b of the revolving frame 2a or on the counter weight 5 when the gantry 4 is in the stowed condition.
Further, in the above mentioned second embodiment of the present invention, the holder 63 and the lever 65 in the rock mechanism 60 are separately rotatably supported around each support pin 62 and 64 against the mounting plate 61 fixed on the upper rear legs 24. However, the present invention allows a configuration to rotate around the same support pin. In addition, the link member 66 which connects the holder 63 and the lever 65 is not limited to a single link as mentioned in the second embodiment, but may involve a plurality of links.
Furthermore, the present invention is not limited to the gantry configuration of the crawler crane as mentioned above, but also applicable to the configuration of the gantry of construction machines other than crawler cranes.
A gantry 4 is composed of front legs 22, upper rear legs 24 and lower rear legs 28. In a working condition, the lower rear legs 28 and the upper rear legs 24 extend along a vertical line and the front legs 22 tilt backward and upward. In a stowed condition, the lower rear legs 28 and the upper rear legs 24 are folded and the front legs 22 are laid down backward. To a connecting joint 33 where the front legs 22 and the upper rear legs 24 are connected, one end of the connecting rod 35 that secures the stowed condition is rotatably connected. On the other end of this connecting rod 35, a pin 41 is provided. On the upper rear legs 24, a lock mechanism which is capable of engaging with the pin 41 is provided. The lock mechanism 42 disengages the locked condition with the pin 41 in accordance with the movement of folding the lower rear legs 28 and the upper rear legs 24 in order to change the gantry from the working condition to the stowed condition. It is possible to prevent the lock member, the connecting rod and the upper rear legs from being damaged by forgetting disengaging the lock mechanism.

Claims

A gantry installed on a base frame of construction machinery, comprising:
a front leg whose bottom end is rotatably supported on the base frame;

an upper rear leg whose one end is connected to a top of said front leg;

a lower rear leg whose top is connected to the other end of said upper rear leg and whose bottom end is rotatably supported to the base frame, whereby, in a working condition, both said lower rear leg and said upper rear leg extend substantially along a vertical line and said front leg tilts backward and upward, in a stowed condition, said lower rear leg and said upper rear leg are folded and said front leg is laid over said upper and lower rear legs;

a connecting rod whose one end is rotatably connected to a connecting portion of said front leg and said upper rear leg, said connecting rod connecting said connecting portion to said base frame in the stowed condition and holding the stowed condition;

a pin that protrudes in a lateral direction on the other end of said connecting rod; and

a lock mechanism provided on said upper rear leg so as to be able to engage with said pin, said lock mechanism disengaging a connected condition with said pin in accordance with a movement in folding said lower rear leg and said upper rear leg in order to change the gantry from the working condition to the stowed condition.
The gantry of the construction machinery according to claim 1, wherein
said lock mechanism has a catch slot whose base end is fixed on said upper rear leg and whose upper and top portion are able to engage with said pin.
The gantry of the construction machinery according to claim 1, wherein
said lock mechanism comprises a mounting plate fixed on said upper rear leg, a holder rotatably supported on said mounting plate, a lever rotatably supported on said mounting plate and holding said pin in a locked condition together with said holder, a link member connecting said holder and one end of said lever so as to rotate together between the locked condition where said lever and said holder hold said pin and an unlocked condition which disengages the locked condition, and a spring member that imposes a force in order to hold the locked condition when said lever and said holder are in the locked condition, whereby
in folding said lower rear leg and said upper rear leg in order to change the gantry from the stowed condition to the working condition, said pin pushes said lever against the force generated by said spring member so that said lever and said holder become the unlocked condition, and in changing the gantry from the working condition to the stowed condition, said pin pushes said lever at a portion connected to said link member so that said lever and said holder becomes the locked condition.
The gantry of the construction machinery according to claim 3, wherein
said lever is an L-shaped lever and a center portion of said lever is rotatably supported, and
said spring member whose one end is hooked at a middle portion between a rotating point and an end portion connected to said link member and whose other end is hooked at said mounting plate respectively,
whereby a spring force is imposed so as to hold the locked condition when said lever and said holder are in the locked condition, locating a center line closer to said link member than to said rotating point, and the spring force is imposed so as to hold the unlocked condition when said lever and said holder are in the unlocked condition, locating said center line farther to said link member than to said rotating point.