The invention relates to a tilting device for a vehicle having a tiltable cab, ccmprising a piston cylinder device, one end of which is pivotally connected to the chassis of the vehicle, whereas its other end is connected with the cab t_hrαugh a guide arm positioned in a plane perpendicular to the tilting axis, said guide arm having an engagement portion, that cocperates with a cαπplementarily shaped engagement portion on the cab, in such a way, that the two engagement portions are out of engagement and allc-w a certain lost motion of the guide arm relative to the cab when the latter is in its rest or driving position, but progressively enter into mutual engagement when the cab is tilted frcm such position, whereby the guide arm becomes fixed relative to the cabin.

Such a tilting device is disclosed in DE-A-33 14404, with which the guide arm is formed by a solid link, having one end pivotally connected to the cabin and the other, forked end of which is pivotally connected to the piston rod end of the piston cylinder device.

A tilting device of this type has the advantage, that in the driving position of the cab - with the piston cylinder device being (substantially) in its retracted position - the lost motion of the guide arm allcws the cab to slightly and resiliently move up and down without requiring the piston to perform corresponding up and down movements within the cylinder.

A disadvantage of the well- ncwn device having a pivoting guide arm, however, is to be seen in the presence of two pivots, about which the guide arm is performing continuous swinging movements during riding, which pivots constitute friction and liibricatiαn points, requiring frequent maintenance and nay soon result in undue play with inherent rattling.

In accordance with the present invention this drawback is σverccrαe in a simple and effective manner by a guide arm that is flexible in its plane.

By the guide arm as proposed by the present invention, the ends of it may be rigidly, e.g. by damping, connected to the cab and to the respective end of the piston cylinder device respectively, whereby the required swinging movements of the guide arm during driving are permitted by bending of the guide arm in its vertical plane npτp ^a r_.iαι1λr to the tilting axis of the cab.

Such a guide arm is essentially maintenance free and hardly

influences the c_____cac±eristics of the cab suspension.

In a practical en±-odiiπent the flexible guide arm is substan¬ tially constituted by a leaf spring. This leaf spring may be rather weak so as to reduce its influence onto the cab suspension to a miniτπιτm.

The invention will be hereinafter ϊiurther explained with reference to the drawing which shows a number of preferred emboά__ments.

Fig. 1 is a diagrammatic side elevation of a truck having a tiltable cab; fig. 2A and 2B shew a diagrammatic side view of the connection between the tilting device and the tiltable cabin according to a first eπ_xx_imeπt, in the driving position (fig. 2A) and in the forwardly tilted position (fig. 2B) respectively; fig. 3A-C shew a modification of the connection shown in fig. 2A-B, in the driving position (fig. 3A) and two tilted positions (fig. 3B and fig. 3C) respectively and fig. 4A-E show a third em_xx_imeπt of the connection between the tiltable cabin and the tilting device, in the driving position (fig. 4A) and four successive stages during a tilting procedure respec¬ tively.

With reference to fig. 1, the truck shewn diagiπammatically therein comprises a chassis 1 with a cab 3 mounted for a tilting movement about an axis 2 positioned at the front, said cab being normally supported - in its driving position - with its rearward end an a resilient support 4.

A tilting device 5 is provided to tilt the cab 3 forwardly frαn the driving position. This tilting device emprises a piston cylinder device, the cylinder 6 of which has (in the example shewn) its lower end 6a pivotally connected to the chassis 1 at 7 and the piston rod 8 of which, having its upper end 8a connected to the cab 3 by means of a guide <_rm 9.

The connection between the cab 3 and the tilting device 5 will be hereinafter further described with reference to fig. 2, 3 and 4. In the e___x_dimeπt of fig. 2 the guide arm 9 is formed by a leaf spiring 10, which is clamped at its right-hand end (vide the drawing) between a support plate 11 fastened to the lower side of the cab 3, and a cover plate 12. The end faces 11a and 12a of the support plate 11 and the cover plate 12 respectively are rounded.

The left hand end of the leaf spring 10 is fixedly attached to a rightwardly ext_=nding leg 14 of a hook-shaped engagement portion 13 connected to the free piston rod end 8a. The hook proper 15 of the engagement portion 13 _____ an opening 16 facing away frcm the tilting axis 2, and a receiving cavity 17. The receiving cavity 17 extends along a sector of a cylindrical surface and covers an arc which is slightly larger than 180°. During tilting of the cab the engagement portion 13 may engage with its receiving cavity 17 about a pin 18 which is attached to the cab as by brackets 19. Fig. 2a shews the connection in the driving position. The pin 18 and the hook-shaped engagement portion 13 are out of engagement and are positioned in spaced relationship one above the other, which permits the cab to spring up and dcwn at the rearward end according to arrcw X and possibly also at the front end side according to arrow Y, without the need for the piston rod to carry cut corresponding retracting and extending movements relative to the cylinder 6. The up and dcwn springy movements of the cab 3 involve reciprocating bending movements of the leaf spring 10 in the nip between the rounded end faces 11a and 12a of the support plate 11 and the cover plate 12. If it is desired to tilt the cab 3 frcm the driving position of fig. 2A forwardly, the piston rod is hydraulically extended in the usual manner, whereby, in an initial stage, the engagement postion 13 is moving towards the pin 18 so as to engage the latter. It will be clear, that the upwardly facing edge 17a of the receiving cavity 17 has to be positioned such, that it can pass the pin 18 at the left hand side before the engagement portion 13 is actually engaging the pin 18. After the engagement between the engagement portion 13 and the pin 18 has taken place, the hook 15 of the engagement portion 13 will, while the cab is tilted further towards the position of fig. 2B- gradually close around the pin 18 as a result of the angular displace¬ ment of the longitudinal axis of the tilting device 5 relative to the tilting cab 3. This angular displacement also appears frcm the defor¬ mation of the leaf spring 10 at the end of the tilting mcivemeπt (fig. 2B). In the mo ification according to fig. 3 the engagement portion 18', which is to be ccπpared with the pin 18 of fig. 2, is fastened to the free end 8a of the piston rod, whereas in this case a double hook- shaped engagement portion 13' is attached to the lower side of the cab 3. The leaf spring 10 is fastened to the cab 3 in a similar manner as

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described with reference to the einbodimeπt of fig. 2, whereby said leaf spring has its left-hand end clamped between the free piston rod end 8a and a block 20 c_a_rrying the pin-shaped, engagement portion 18'. The block 20 is provided with a rightwardly extending cam 21 having a cam surface 21a facing towards the leaf spring so as to cause the leaf spring 10 to conform to said cam when the cab is tilted.

The hcok-shaped engagement portion 13' has its operiing 16' facing obliquely upwardly and forwardly (to the left) and has also a guide cam portion 22 adapted to guide the pin-shaped engagement portion 18' towards the receiving cavity 17' of the hook 15'.

In fig. 3A, in which the cab 3 is shown in its rest position, the piston cylinder device 5 is shown in two positions. In the lower position the piston rod 8 is (substantially) retracted into the cylinder 6. This position corresponds with the position during driving. The pin-shaped engagement portion 18' is released and spaced from the hook 15' of the engagement portion 13' on the cab. This allcws for a springy up and down movement of the cab in a similar manner as described hereinabαve with reference to fig. 2, causing the leaf spring 10 to simultaneously bend in opposite directions, while the piston rod 8 is kept blocked in its retracted position within the cylinder 6.

In the second position the piston rod 8 has - to initiate a tilting movement of the cab 3 - extended from the cylinder 6 to the extent that the pin 18' has (with inherent bending of the leaf spring 10) cone into contact with the first cam surface portion 22a of the guide cam 22. A continued extending movement of the piston rod 8 guides the pin 18' along the second cam surface portion 22b of the cam 22 towards the opening 16' of the receiving cavity 17' of the hook 15', while the cab is carrying cut a tilting movement about the axis 2 (vide fig. 3B) .

During the final stage of the tilting movement, frcm the position of fig. 3B to the fully extended piston rod position of fig. 3C, the leaf spring 10 is winding itself onto the cam surface 21a, which causes the pin 18' to be completely pulled into the receiving cavity 17' of the hook 15' and to be locked therein. Due to the leaf spring 10 being bent about the cam surface 21a the pin 18' is kept into the engagement position of fig. 3C so that the cab is secured against further forward tilting (under the action of the cab weight which in that position is active at a point in front of the tilting

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axis 2) .

For a smooth guidance of the pin 18' along the cam surface portions 22a and 22b the pin 18' is preferably in the form of two rollers mounted on either side of the cam 22. In the embodiment of fig. 4 the guide arm 10' is formed by two transversely spaced springs 25 of the hair pin type, each having two spring legs 27 and 28 with an interconnecting coil spring portion 26 therebetween. The spring legs 27 are a bit more solid and consequently have a greater stiffness than the spring legs 28. In this case a pin 18" having its axis extending parallel to the tilting axis 2 is provided at the free piston rod end, whereas a locking collar 29 is provided at a certain distance under the pin 18". The two end portions of the pin 18" may be formed by rollers.

In this case an engagement portion 13" is attached to the cab 3, comprising a plate 30 having an integrally formed substantially semi- cylindrical receiving cavity 17", the cpening of which is facing to the right (as seen in the drawing and in particular in fig. 4A) .

The free ends of the spring legs 27 of the two springs 25 (only one of which is shown in the drawing) are fastened into the plate 30 at a certain distanπR forwardly from the receiving cavity 17" and with the spring legs 27 in a substantially vertical position. The free ends of the spring legs 28 are bent into a horizontal direction to extend through axial bores in the (roller) ends of the pin 18".

Fig. 4A shows the cab in the driving position, with the tilting device 5 in the (substantially) fully retracted position, while the spring 25 is in its open and (substantially) uπtensioned position. The pin 18" is taking a released position at a dis -anπ ^p under the receiving cavity 17", which allcws for an up and down springy movement of the cab at the rear end along arrow X and possibly also at the front end according to arrow Y, involving a sijnultaneous cpening and closing of the spring legs 27 and 28. In fig. 4A the gravity center of the cab is indicated at Z; at the end of a complete tilting movement this gravity center has arrived in the position Z' in front of the tilting axis 2. Fig. 4B shows the tilting device 5 in a position, in which the piston rod 8 has extended to an extent, that the spacing between the pin 18" and the receiving cavity 17" (exi__ting in the driving position of fig. 4A) has been bridged and the pin 18", while causing the spring leg 28 to bend along, has cane into σαπtact with the lower side of the

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plate 30. The cab, however, is still in its horizontal position. upon further extending the piston rod from the position of fig. 4B towards that of fig. 4C the pin 18" is moving forwardly (to the left in the drawing) along the lower side of the plate 30 and is finally received into the receiving cavity 17". When the pin 18" is moving into the receiving cavity an edge portion 31 delimiting said receiving cavity 17" on the lower side is gradually moving into the space between the pin 18" and the locking collar 29 thereunder.

In fact the position of fig. 4C is the starting position for the tilting movement proper.

In the position of fig. 4D the piston rod 8 is extended and the cab is tilted to such an extent, that the centre of gravity of the cab has become positioned vertically above the tilting axis 2.

In the situation of fig. 4E the tilting movement has been ccm- pleted and the piston rod 8 is hydraulically blocked in the cylinder 6 of the tilting device 5. In this final position the center of gravity Z has become positioned in front of the tilting axis 2 so that the cab tends to tilt further in the forward direction under the influence of the cab weight. The pin 18", however, is securely locked within the receiving cavity 17" to prevent the cab from releasing itself frcm the piston rod.

For each of the embodiments described hereinabσve it will be clear that when the cab is tilted back frcm the til position into the driving position by retracting the piston rod, the cooperating engagement portions 13, 18; 13', 18' and 13", 18" will be tøpt mutually engaged until the cab has returned into its horizontal position, i.e. with the cab resting on the resilient support 4 (fig. 1) . The piston rod 8 is then moving into the fully retracted position, whereby the engagement portion at the free end of the piston rod will - assisted by the relaxing guide arm 10; 10'; become released frcm the engagement portion 13; 13'; 13".

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