WO2008050229A2

WO2008050229A2 - An undercarriage, in particular a crawler undercarriage, having a variable track gauge

Info

Publication number: WO2008050229A2
Application number: PCT/IB2007/003230
Authority: WO
Inventors: Angelo Mosconi; Moreno Para; Matteo Comandini
Original assignee: Sampierana S.P.A.
Priority date: 2006-10-27
Filing date: 2007-10-26
Publication date: 2008-05-02
Also published as: WO2008050229A3; ITBO20060745A1

Abstract

An undercarriage (10), more specifically in the form of a crawler undercarriage, comprises a main frame (14) and a first and a second sub-frame (18, 22) for supporting means, or tracks, (23, 24), that allow movement of the undercarriage, and means (27, 31, 35, 39) for supporting respective sub-frames (18, 22) which are mobile relative to the main frame (14) in order to vary the track gauge of the undercarriage. The undercarriage comprises means for positioning and securely holding a respective sub-frame (18, 22), in at least one intermediate position (I) between a first position (R) and a second position (E).

Description

An undercarriage, in particular, a crawler undercarriage

Technical Field

This invention relates to an undercarriage, and in particular, to a crawler undercarriage.

Background Art

Crawler undercarriages for construction machinery or other applications are known which comprise a main frame and first and second sub-frames for supporting the undercarriage crawler tracks. The sub-frames are rigidly connected to the main frame, giving the undercarriage a fixed track gauge. This type of undercarriage is not stable enough, and hence unsafe, for work on slopes and rough terrain where vehicle stability is very important to avoid the risk of creating dangerous situations.

Also known in prior art are crawler undercarriages for construction machinery or other applications which comprise a main frame, first and second sub-frames for supporting the undercarriage crawler tracks and beam elements for supporting the sub-frames. The sub-frames are mobile relative to the main frame, so that the track gauge of the undercarriage can be varied. This increases the width of the machine's supporting structure, to the advantage of operating safety and versatility. More specifically, European patent EP 1133430 to the same Applicant as this invention describes a crawler undercarriage with variable track gauge where the retraction rams or beam elements supporting the track mounting sub-frames can move only between a first, extended position where the track mounting sub- frames are further away from the main mounting frame, and a second, retracted position where the track mounting sub-frames are closer to the main mounting frame.

The undercarriage described in patent EP 1133430, although it has advantageous wedge elements for locking the sub-frame retraction rams or supporting beams in the widest track gauge position, preventing unwanted slack between the beams and the main frame of the undercarriage, can only work in the widest track gauge and narrowest track gauge positions, and cannot therefore be used to advantage in certain working conditions where it is impossible for the tracks to be extended to the widest gauge position.

Disclosure of the Invention

It is therefore provided an undercarriage, in particular a crawler undercarriage, which comprises a main frame, a first and a second sub-frame for supporting undercarriage movement means and means for supporting the respective sub-frames, which are mobile with respect to the main frame in order to vary the track gauge of the undercarriage, characterized in that it comprises means for positioning a respective sub-frame in at least one intermediate position between a first position and a second position.

This enhances versatility since a machine with an undercarriage according to the invention is supported on the ground in a stable and safe manner under all working conditions.

These and other characteristics of the undercarriage according to the invention are clearly described in the appended claims.

Brief Description of the Drawings

The technical characteristics and advantageous aspects of the invention are more apparent from the detailed description which follows, with reference to the accompanying drawings which illustrate a preferred, non-limiting embodiment of the invention provided by way of example and in which:

Figure 1 is a schematic top view of the undercarriage according to a preferred embodiment of this invention;

Figure 2 is a schematic cross section through line TI-H in Figure 1 illustrating the preferred embodiment of the undercarriage according to the invention in a first operating position;

Figure 3 is a schematic cross section similar to that of Figure 2 illustrating the preferred embodiment of the undercarriage according to the invention in a second operating position; - Figure 4 is a schematic cross section similar to that of Figures 2 and 3 illustrating the preferred embodiment of the undercarriage according to the invention in a third operating position;

Figure 5 is a schematic perspective detail view showing the means for engaging and disengaging the sub-frame supporting beams in an engaged condition where movement of the respective sub-frame is stopped;

Figure 6 is a schematic view similar to Figure 5, illustrating a disengaged condition enabling movement of the beam element relative to the respective housing in the fixed frame;

Figure 7 is a schematic cross section of a detail showing the preferred embodiment of the undercarriage in an operating condition with the retraction ram engaged; - Figure 8 is a schematic cross section of a detail showing the preferred embodiment of the undercarriage in an operating condition with the retraction ram disengaged;

Figure 9 is a schematic top view of a first and a second member for locking respective beam elements and corresponding actuating means, in a retracted condition;

Figure 10 is a schematic top view of a first and a second member for locking respective beam elements and corresponding actuating means, in an extended condition.

Description of the Preferred Embodiments of the Invention

As illustrated in particular in Figure 1, a preferred embodiment 10 of the undercarriage, more specifically in the form of a crawler undercarriage, comprises a main frame, or base, 14 and a first and a second sub-frame 18, 22 for supporting means, defined by respective tracks 23, 24, that allow movement of the undercarriage over the ground.

The main frame 14 constitutes a supporting structure which, if viewed from above, has a generally quadrangular shape, and which at the centre of it has a rack or flange, labelled 16 in the accompanying drawings, on which the machine is mounted. The main frame 14 also has a plurality of transversal housings 26, 30, 34,

38 for accommodating respective mobile beams 27, 31, 35, 39, constituting means for supporting respective sub-frames 18, 22 at the free ends of said supporting beams or retraction rams 27, 31, 35, 39.

In practice, a first and a second beam 27 and 35 support a first lateral sub- frame 18 and are mobile in respective housings 26, 34 open towards the outside on a side of the main frame facing the respective sub-frame 18, while another two, first and second, beam elements 31, 39 support a respective lateral sub-frame 22 and are mobile in housings 30, 38 open towards the outside on an opposite side of the main frame or base 14 facing the respective sub-frame 22. As illustrated, the first housings 26, 30 are transversally aligned with each other and are obtained from a single tubular square tube section open at the lateral ends from which extend the respective first beam elements 27, 31 which also have a square section and whose outside profile is slightly smaller in size than the inside surface profile of the respective housings 26, 30.

Similarly, the second housings 34, 38 are transversally aligned with each other and are obtained from a single tubular square tube section open at the lateral ends from which extend the respective second beam elements 35, 39 which also have a square section and whose outside profile is slightly smaller in size than the inside surface profile of the respective housings.

More specifically, the beam elements 27, 31, 35, 39 are in the form of respective square tube sections each of which is insertable and slidable in the respective housing.

The undercarriage 10 according to the invention advantageously comprises means for positioning and securely holding the respective sub-frame 18, 22, in at least one intermediate position "I", shown in Figure 4, between a first position R, shown in Figure 2 and a second position E shown in Figure 3. More specifically, in particularly advantageous manner, the undercarriage

10 according to the invention comprises means for positioning and securely holding the respective sub-frames 18, 22, in any position variable from a first position R to a second position E and, in particular, located anywhere between a first position R and a second position E, as illustrated in Figures 2 to 4. According to another aspect, the undercarriage according to the invention comprises advantageous means for adjusting the track gauge, that is to say, the distance between the sub-frames 18, 22, said adjustment means being designed to set the sub-frames 18, 22 to any desired track gauge, or distance, DI variable between a minimum distance DR and a maximum distance DE, illustrated in Figures 2 and 3. As shown, the distance, or track gauge, is measured from the centre line of the respective sub-frames 18, 22.

As illustrated, the first position R of Figure 2 is a retracted position where each of the sub-frames 18, 22 is closest to the corresponding flank 16, 18 of the main frame 14, while the position E is an extended position where each of the sub- frames 18, 22 is at its most extended position from the main frame 14.

In practice, the undercarriage according to the invention enables each of the sub-frames 18, 22 to adopt a plurality of positions between the retracted position R and the extended or extracted position E.

In practice, means are provided for positioning each sub-frame 18, 22 at respective end limit positions, that is to say, a retracted position - where it is closest to the respective face of the main frame - and an extended position - where it is furthest from the respective face of the main frame - and, in addition to these end limit positions, in any position between these two end limits, that is to say, in a plurality of further, intermediate positions.

In particular, the sub-frames 18, 22 may also be positioned asymmetrically relative to the base 14, with the respective retraction rams extending to different lengths from the base 14, in order to meet specific requirements depending on ground and operating conditions and on the work to be done.

The undercarriage according to the invention further comprises advantageous means for locking the sub-frame supporting means, said locking means comprising engage/disengage means mobile between an engaged position, where the respective sub-frame supporting means are locked in place, and a disengaged position, where the sub-frame supporting means are free to move.

More specifically, means are provided for locking the means that support at least one sub-frame relative to the main frame 14, these locking means being of the type that can be enabled and disabled. These locking means are, in particular, embodied by clamping means comprising engagement means 40, 42, 44, 46 which are mobile between an unlocked, or disengaged, lowered position, illustrated in Figure 6, and a normal, locked, or engaged, raised position, illustrated in Figure 5.

As shown, these locking means are designed to engage the means 27, 31, 35, 39 that support the sub-frames 18, 22 by clamping or pushing them against a corresponding surface of the main frame, that is to say, against a corresponding, opposite surface of the respective housing 26, 30, 34, 38.

As clearly shown in Figures 5, 6, 7 and 8, which illustrate a single engagement element 40, these engagement means have a top engagement surface 40a designed to clamp the respective supporting beam 27 of the sub-frame 18 against a top surface 26a of the housing 26 that accommodates said beam 27.

More specifically, as also illustrated in Figure 2, the engagement means labelled 40 and 42 push their top surfaces 40a, 42a against the bottom surface 27a,

31a of the respective beam element 27, 31, keeping it tight against the top surface 26a, 30a of the respective housing which is engaged by the top surface of the 27b,

31b of the beam element.

As also shown in Figure 7, these engagement means 40, 42, 44, 46, mounted on the main frame, are located inside the housings 26, 30, 34, 38, respectively, and in particular at, or in the vicinity of, the area adjacent to the opening A giving onto the outside of the respective housing, as shown in both

Figures 7 and 8.

Advantageous actuating means are also provided for moving the engagement means 40, 42, 44, 46 from the engaged, locking condition to the disengaged, free sliding condition of the sub-frames.

Advantageously, the actuating means comprise means 41, 43, 45, 47 designed to push the engagement means 40, 42, 44, 46 against corresponding guide means 48, 50, well illustrated in Figures 5 and 6, which are in turn designed to move the engagement means 40, 42, 44, 46 in the engage/disengage direction and, more specifically, in the vertical direction.

In particular, as shown in Figures 5 and 6, a guide surface, labelled 48, extends obliquely, at a defined angle to the horizontal or to the vertical, and on the opposite side of the engagement means 40, there is a second inclined surface 50, that also extends obliquely, at a defined angle to the horizontal or to the vertical.

Still with reference to Figures 5 and 6, the engagement means of the respective sub-frame comprise at least one first engagement element 40' and a second engagement element 40", which is transversally spaced from the first engagement element 40', said engagement elements having respective lateral or outer surfaces 40'b and 40"b adapted to cooperate with, and, more specifically, to slide on, the surfaces 48 and 50 that guide the vertical movement of the engagement means 40.

As shown in more detail in Figure 8, in the disengaged condition, the engagement means rest on the lower surface 26a of the housing 26 for the respective beam element 27, like the corresponding pushing means 41. For this purpose, each engagement element 40', 40" has a respective flat lower surface

40'c, 40"c, as may also be inferred from Figures 5 and 6.

As illustrated in the drawings, these pushing means 41 have an upper surface 41a and a lower surface 41b that slides on the lower surface 26a of the housing that accommodates it and are mobile transversally with respect to the longitudinal extension of the respective housing, between an extended position and a retracted position.

Further, as may be inferred from Figure 1, these pushing means are mobile in a substantially lengthwise direction along the undercarriage, that is to say, parallel to the track supporting sub-frames 18, 22.

More specifically, in the position illustrated in Figures 5 and 7 the pushing means 41 are in the extended position where they lift the respective engagement elements 40' and 40", while in Figures 6 and 8, the pushing means are in the retracted position where they have moved the corresponding engagement elements 40', 40" to the lowered position allowing the beam elements to slide freely in the respective housings. As illustrated in Figures 5 to 8, the pushing means 41 are advantageously designed to push the engagement elements transversally in such a way as to move them to an engaged condition, in particular, to move them vertically upwards.

For this purpose, the pushing means 41 comprise corresponding oblique surfaces, namely a first and a second lateral oblique surface 41c, 41e, 41d, 41f converging towards the free end of the pushing element and cooperating with corresponding inclined surfaces 40'd and 40"d of the respective engagement elements 40' and 40".

As illustrated, the surfaces 40'd and 40"d of the engagement elements 40', 40" are inclined at an angle to the transversal direction in which the pushing means 41 move, converging towards each other in the longitudinal direction of the undercarriage.

The lateral oblique surfaces of the pushing element 41 comprises, as illustrated, respective first parts 41c and 41 d and respective second parts 4 Ie and 41f that cooperate with corresponding lateral surfaces 40'd, 40"d, 40'e and 40"e of the respective engagement elements 40' and 40".

As illustrated, the respective first and second parts 41c, 41e, 41d, 41f of each lateral oblique surface of the pushing element 41 are parallel and transversally spaced from each other. Further, as illustrated, the respective first part 41c, 41d of each lateral oblique surface of the pushing element 41 is located on the front outer side of the second part 4 Ie, 41f of the lateral oblique surface of the pushing element.

Advantageously, means are provided for pulling the engagement means into the disengaged position where the sub-frames can slide freely. As illustrated, the pushing element 41 advantageously comprises means for pulling, or dragging, it into a position where it is disengaged from the respective beam element.

Looking more closely at the details, the pushing element 41 comprises a first hooked portion 4 Ig for engaging a corresponding receiving portion 40'g that protrudes lengthways from the lateral surface 40'd of the engagement element 40', and second hooked portion 41h for engaging a corresponding receiving portion 40"g, that protrudes lengthways from a corresponding surface 40"d of engagement means 40".

The first and second hooked portions 4 Ig, 4 Ih are transversally spaced from each other and extend backwards from the front part 41' of the pushing element 41.

As illustrated, each hooked portion 41g, 41h extends outwards at an angle, towards the flanks of the pushing element 41, and presents, on the respective outside face, the lateral pushing surface 41c, 41d of the engagement element.

Further, each hooked portion 41g, 41h presents, on the opposite, or inner, side a respective longitudinally inclined surface 41i, 411, cooperating with a corresponding longitudinally inclined surface 40'h, 40"h.

Corresponding arcuate surfaces 41m, 41n, connecting the portions 41g, 41h with the central part 41" of the pushing element 41 from which they extend transversally cooperate with corresponding arcuate surfaces 40'i, 40"i at the ends of the receiving portions 40'g, 40"g. Curved portions 41o, 41p at the free end of the corresponding hooked portion 41g, 41h, extending backwards from the front surface 41', cooperate with corresponding curved surfaces 401, 40"l, connecting the portions 40 'g, 40"g with the main portion 140', 140" of the corresponding engagement element 40', 40".

As illustrated, the main portions 140', 140" of the respective engagement element 40', 40" extend longitudinally beyond the corresponding portions 40'g, 40"g.

Actuating means 52, 54 are advantageously provided with respective piston rods 56, 58 and 60, 62 for driving the pushing elements 41, 43, 45, 47 between a disengaged, close-up position where the respective beam elements are released, and an engaged, spaced apart position where the beam elements are held securely in place in the respective housings.

As illustrated, the actuating means and, more specifically, the piston rods

56, 58, 60, 62 extend into the respective housings of the sub-frame supporting beam elements through corresponding lateral openings made on the inside of the respective housings, that is to say on the side facing the longitudinally opposite housing.

As illustrated, the actuating means 52, 54 and the related drive piston rods 56, 58, 60, 62 extend longitudinally of the undercarriage and transversally of the beam elements and of the respective housings. As may be inferred from the drawings, the actuating means 52, 54 are embodied by drive cylinders, preferably hydraulic. Other types of suitable actuating means, be they mechanical, electrical, or manually operated might, however, also be used.

As illustrated, the actuating means that drive the means that lock the beam elements 27, 35 of one sub-frame 18, or the actuating means that drive the means that lock the beam elements 31, 39 of the other sub-frame 22, are connected to each other. In this way, these parts support each other. In practice, as shown in Figures 8 and 9, the actuating means 52 that drive the opposite piston rods 56, 58 of the means 41, 45, which push the respective beam elements 27 and 35 into the engaged position, form a single part. Their pushing and pulling actions thus compensate each other. Similarly, the actuating means 54 that drive the opposite piston rods 60, 62 of the means 43, 47, which push the respective beam elements 31 and 39 into the engaged position, also form a single part. Their pushing and pulling actions thus compensate each other.

As illustrated in particular in Figures 1 and 4, the invention also advantageously contemplates the provision of means, labelled 70 and 72, for driving the means 27, 31, 35, 39 that support the sub-frames 18, 22.

These means 70, 72 for driving the supporting beams 27, 31, 35, 39 within the housings 26, 30, 34, 38 that accommodate opposite beam elements 27, 31, 35, 39 comprise, as illustrated for example in Figure 4, a first and a second actuator 74, 76, which are connected to each other, and which are, more specifically, embodied by respective hydraulic cylinders, preferably double-acting, but possibly also single-acting, each comprising a respective piston 78, 80 to which is connected a respective transversally mobile rod 82, 84 which is in turn connected at its free end 86, 88 to corresponding means for engaging the respective beam element 27, 31. In practice, the cylinders 74, 76 are connected by their bottom ends 74', 76' and extend in line with each other in a direction transversal to the undercarriage.

As illustrated, positioned centrally within the tubular groove defined by the housings 26, 30 there is a bracket 90 attached to the inside wall of the housing 26, 30. The bracket 90 is designed to receive and retain a corresponding protruding portion 92 extending from the centre of the actuating element 74, 76.

Thus, the hydraulic cylinders for extending the sub-frame supporting beams can be easily fitted and removed from the undercarriage, with obvious advantages in terms of the speed with which an operation of this kind can be performed. The undercarriage according to the invention works as briefly described below. Starting from a position where the clamping means lock the retraction rams or beams 37, 35, and 31, 39 to prevent them from sliding in the respective housings, the actuating means 52 and 54 are activated in such a way as to move the piston rods 56, 58 and 60, 62 and the pushing/pulling means 41, 45, 43, 47 connected to them towards each other and to lower and release the engagement means 40, 44 and 42, 46 from the respective beam locked condition. Next, the cylinders 70, 72 are activated in the desired direction in order to selectively drive the retraction rams or beams transversally in such a way as to move the sub- frames 18, 22 to the new working position by sliding in the respective housings and on the corresponding engagement means 40, 42, 44, 46.

The actuating means 52 and 54 then drive the piston rods 56, 58 and 60, 62 and the pushing/pulling means 41, 45, 43, 47 connected to them away from each other, thus pushing the engagement means 40, 44 and 42, 46 into the condition where they lock the respective beams 37, 35 and 31, 39.

The present undercarriage enables the track gauge to be adjusted automatically without the operator having to climb down from the machine to adjust machine parts manually, as on prior art machines.

The locking actuators are connected to each other in a single part and can be engaged and disengaged in different positions in such a way as to adapt to specific operating conditions.

The invention described has evident industrial applications and can be modified and adapted without thereby departing from the scope of the inventive concept. Moreover, all the details of the invention may be substituted by technically equivalent elements.

Claims

1. An undercarriage (10), in particular a crawler undercarriage comprising a main frame (14), a first and a second sub-frame (18, 22) for supporting undercarriage movement means (23, 24) and means (27, 31, 35, 39) for supporting the respective sub-frames (18, 22), which are mobile with respect to the main frame (14) in order to vary the track gauge of the undercarriage; characterized in that it comprises means for positioning a respective sub-frame (18, 22) in at least one intermediate position (I) between a first position (R) and a second position (E).

2. The undercarriage according to claim 1, characterized in that the means for supporting the corresponding sub-frame comprise at least one beam element (27, 31, 35, 39) extending from a respective housing (26, 30, 34, 38) in the main frame (14).

3. The undercarriage according to either of the foregoing claims, characterized in that it comprises means for positioning a first and a second sub- frame (18, 22) in a respective intermediate position (I) between a first position (R) and a second position (E).

4. The undercarriage according to any of the foregoing claims or according to the preamble to claim 1, characterized in that it comprises means for positioning at least one respective sub-frame (18, 22) in any position between a first position (R) and a second position (E).

5. The undercarriage according to claim 4, characterized in that it comprises means for positioning a first and a second sub-frame (18, 22) in any position between a first position (R) and a second position (E).

6. The undercarriage according to any of the foregoing claims or according to the preamble to claim 1, characterized in that it comprises means for adjusting the distance between a first and a second sub-frame (18, 22) to any desired distance variable between a minimum distance (DR) and a maximum distance (DE).

7. The undercarriage according to any of the foregoing claims, characterized in that the first position (R) is a retracted position where each of the sub-frames (18, 22) is closest to the corresponding flank (16, 18) of the main frame (14).

8. The undercarriage according to any of the foregoing claims, characterized in that the second position (E) is an extended position where each of the sub- frames (18, 22) is at its most extended position from the main frame (14).

9. The undercarriage according to any of the foregoing claims or according to the preamble to claim 1, characterized in that it comprises means for locking means that support at least one sub-frame relative to the main frame (14).

10. The undercarriage according to claim 9, characterized in that the means for locking the means that support at least one sub-frame relative to the main frame (14) are embodied by means that can be enabled and disabled.

11. The undercarriage according to claims 9 or 10, characterized in that the locking means are embodied by clamping means.

12. The undercarriage according to any of the foregoing claims from 9 to 11, characterized in that the means for locking the means (27, 31, 35, 39) that support at least one sub-frame comprise engagement means (40, 42, 44, 46), mobile between an engaged position and a disengaged position.

13. The undercarriage according to claim 12, characterized in that the engagement means (40, 42, 44, 46) are mobile between an engaged, raised position and a disengaged lowered position.

14. The undercarriage according to any of the foregoing claims from 9 to 13, characterized in that the locking means comprise means (40, 42, 44, 46) for engaging the sub-frame (18, 22) supporting means (27, 31, 35, 39).

15. The undercarriage according to any of the foregoing claims from 12 to 14, characterized in that the engagement means (40, 42, 44, 46) clamp the sub-frame supporting means (27, 31, 35, 39) against corresponding surfaces of the respective housings (26, 30, 34, 38).

16. The undercarriage according to any of the foregoing claims from 12 to 15, characterized in that the engagement means (40, 42, 44, 46) comprise an upper engagement surface (40a).

17. The undercarriage according to any of the foregoing claims from 12 to 16, characterized in that the engagement means (40, 42, 44, 46) clamp the sub-frame supporting means (27, 31, 35, 39) against a corresponding upper surface (26a, 30a) of the respective housing (26, 30, 34, 38).

18. The undercarriage according to any of the foregoing claims from 12 to 17, characterized in that the engagement means (40, 42, 44, 46) are located at the area adjacent to the opening giving onto the outside of the respective housing (26, 30, 34, 38).

19. The undercarriage according to any of the foregoing claims from 12 to 18, characterized in that the engagement means (40, 42, 44, 46) are located inside the respective housing (26, 30, 34, 38).

20. The undercarriage according to any of the foregoing claims from 12 to 19, characterized in that it comprises means for driving the locking means (40, 42, 44,

46).

21. The undercarriage according to claims 20, characterized in that the drive means comprise means (41, 43, 45, 47) for pushing the engagement means (40, 42, 44, 46) against corresponding means (48, 50) for guiding the movement of the engagement means (40, 42, 44, 46).

22. The undercarriage according to claim 21, characterized in that the means (48, 50) for guiding the engagement means (40) are designed to move said engagement means (40) vertically.

23. The undercarriage according to claim 21 or 22, characterized in that the means (48, 50) for guiding the engagement means (40) are embodied by at least one inclined surface (48).

24. The undercarriage according to claim 23, characterized in that the means (48, 50) for guiding the engagement means (40) comprise a second inclined surface (50) on the side opposite the first inclined surface (48).

25. The undercarriage according to any of the foregoing claims from 12 to 24, characterized in that the means (40) for engaging respective sub-frame (18) supporting means (27) comprise at least one engagement element (40').

26. The undercarriage according to claim 25, characterized in that the means (40) for engaging respective sub-frame (18) supporting means (27) comprise a second engagement element (40") that is transversally spaced from the first engagement element (40').

27. The undercarriage according to claim 25 or 26, characterized in that each engagement element (40', 40") has a respective inclined surface (40'b, 40"b) that cooperates with a respective inclined surface (48, 50) of corresponding guide means.

28. The undercarriage according to any of the foregoing claims from 12 to 27, characterized in that in the disengaged condition, the engagement means (40',

40") rest on the lower surface (26a) of the respective housing (26).

29. The undercarriage according to any of the foregoing claims from 20 to 28, characterized in that the drive means (41) rest on the lower surface (26a) of the respective housing (26).

30. The undercarriage according to any of the foregoing claims from 20 to 29, characterized in that the drive means (41) are mobile between a position where engagement is enabled and a position where engagement is disabled.

31. The undercarriage according to any of the foregoing claims from 20 to 30, characterized in that the drive means (41) are mobile transversally of the respective housing (26).

32. The undercarriage according to any of the foregoing claims from 20 to 31, characterized in that the drive means (41) slide on the lower surface (26a) of the respective housing (26).

33. The undercarriage according to any of the foregoing claims from 20 to 32, characterized in that the drive means (41) comprise at least one lateral oblique surface (41c, 4Ie) for laterally moving the corresponding engagement element (40^T).

34. The undercarriage according to claim 33, characterized in that the drive means (41) comprise a second lateral oblique surface (41d, 4If) for laterally moving the corresponding engagement element (40").

35. The undercarriage according to claim 34, characterized in that the first and second lateral oblique surfaces (41c, 41e, 41d, 4If) for laterally moving the respective engagement elements (40', 40") converge towards the free end of the respective pushing element (41).

36. The undercarriage according to any of the foregoing claims from 33 to 35, characterized in that each lateral oblique surface of the pushing element (41) comprises a first part (41c, 4Id) and a second part (41e, 4If) that cooperate with respective lateral surfaces (40'd, 40"d, 40'e, 40"e) of the respective engagement element (40', 40").

37. The undercarriage according to claim 36, characterized in that the first part (41c, 4Id) and the second part (41e, 4If) of each lateral oblique surface of the pushing element (41) are parallel and trans versally spaced from each other.

38. The undercarriage according to any of the foregoing claims from 33 to 37, characterized in that the first part (41c, 4Id) of each lateral oblique surface of the pushing element (41) is located at the front of the respective second part (41e, 4If) of the lateral oblique surface of the pushing element (41).

39. The undercarriage according to any of the foregoing claims from 33 to 38, characterized in that the first part (41c, 4Id) of each lateral oblique surface of the pushing element (41) is located on the outside of the second part (41e, 4If) of the lateral oblique surface of the pushing element (41).

40. The undercarriage according to any of the foregoing claims from 20 to 39, characterized in that it comprises means for pulling the engagement means into the disengaged position.

41. The undercarriage according to any of the foregoing claims from 20 to 40, characterized in that the drive element (41) comprises means for pulling the engagement means into the disengaged position.

42. The undercarriage according to any of the foregoing claims from 20 to 41, characterized in that the drive element (41) comprises at least one portion (4Ig) for engaging a corresponding receiving portion (40'g) of the engagement means (40).

43. The undercarriage according to claim 42, characterized in that the drive element comprises at least one second portion (4Ih) for engaging a corresponding receiving portion (40"g) of the engagement means (40), said first and second engagement portions (41g, 4Ih) being transversally spaced from each other and being designed to hook onto respective engagement elements (40', 40").

44. The undercarriage according to any of the foregoing claims or according to the preamble to claim 1, characterized in that it comprises drive means that comprise actuating means (52, 54).

45. The undercarriage according to claim 44, characterized in that the actuating means (52, 54) extend transversally from the means that support the respective sub-frame.

46. The undercarriage according to claim 44 or 45, characterized in that the actuating means (56, 58, 60, 62) extend into the respective housings (26, 30, 34, 38) of the sub-frame supporting beams through corresponding lateral openings made on the inside of the respective housings (26, 30, 34, 38).

47. The undercarriage according to any of the foregoing claims from 44 to 46, characterized in that the means (52, 54) for actuating the locking means of the respective beam elements (27, 35 and 31, 39) that support corresponding sub- frames (18, 22) are connected to each other.

48. The undercarriage according to claim 47, characterized in that the means (52, 54) for actuating the locking means of the respective beam elements (27, 35 and 31, 39) that support corresponding sub-frames (18, 22) are connected to each other in a single block.

49. The undercarriage according to any of the foregoing claims or according to the preamble to claim 1, characterized in that it comprises means (70, 72) which drive the means (27, 35, 31, 39) that support the sub-frames (18, 22).

50. The undercarriage according to claim 49, characterized in that the means (70, 72) for driving opposite beam elements (27, 31 and 35, 39) that support the sub-frames (18, 22) comprise a first and a second actuator (74, 76) which are connected to each other.

51. The undercarriage according to claim 50, characterized in that the means (70, 72) for driving opposite beam elements (27, 31 and 35, 39) that support the sub-frames (18, 22) comprise a first and a second actuator (74, 76) which are connected to each other in a single block.

52. The undercarriage according to claim 50 or 51, characterized in that inside the respective housing (26, 30) there are means (90) for attaching said first and second actuators (74, 76) to each other.

53. The undercarriage according to any of the foregoing claims from 50 to 52, characterized in that the actuators (29a, 29b, 32a, 32b) that drive opposite beam elements (27, 31, 35, 39) for supporting the respective sub-frame (18, 22) are housed in a single cylinder with opposite chambers for driving the respective piston rods.