GB2129379A - Vehicle cab tilting system - Google Patents

Abstract

A link member (28) is pivotally connected between a support body (18) on the cab (6) and the piston rod (16). The link member (28) has an abutment (42) which is spaced apart from a contact surface (40) of the support body (18) when the piston rod (16) is not extended to enable the cab to move on the suspension springs (4) when travelling but which engages the contact surface (40) to tilt the cab when the piston rod (16) is extended. The piston rod (16) has a projection (34) which slidingly cooperates with guide rails (46) on the support body (18) to control movement of the cab when the center of gravity of the cab passes over the tilting axis. <IMAGE>

Description

SPECIFICATION Cab tilting system BACKGROUND OF THE INVENTION This invention relates to a motor vehicle of a cab-over type in which a driver's cab is supported on a chassis through suspension springs and pivotally connected to the chassis for tilting movement about a tilting axis, and more particularly to a cab tilting system mounted between the cab and the chassis of such cab-over type motor vehicle for controlling the tilting movement of the cab when inspection or repair is carried out in an engine room.

Generally, in a motor vehicle of the cab-over type, a cab is usually located over an engine room.

This arrangement makes it necessary to tilt the cab when inspection or repair is carried out in the engine room.

One cab tilting system known in the art uses a hydraulic piston-and-cylinder unit which is pivotally connected at opposite ends to the chassis and the cab. This system raises the problem, however, that when the cab is in a regular position and the motor vehicle is traveling, vertical vibration of the cab on the suspension springs would be directly brought to bear upon the hydraulic piston-and-cylinder unit, thereby reducing the riding qualities of the cab.

To obviate this problem, proposals have hitherto been made, as disclosed in British Patent No. 1,447,673, for example, to utilize a lost motion mechanism which is incorporated in a hydraulic piston-and-cylinder unit to absorb the vibration. However, this solution to the problem suffers the disadvantage that this cab tilting system is complex in mechanism and high in cost.

Also, proposals have been made to use a cab tilting system which utilized, as disciosed in British Patent No. 1,399,612, for example, lost motion but calls for mechanically disconnecting the cab and the hydraulic piston-and-cylinder unit outside the hydraulic cylinder.

More specifically, this cab tilting system comprises a hydraulic ram pivotally connected at its base to the chassis, and support means secured to the cab, the hydraulic ram having projection means secured to its piston rod, the support means having a contact surface which receives a force applied by the hydraulic ram when it is extended to tilt the cab, and holding means which is brought into sliding engagement with the projection means as the cab is initially tilted by the extended piston rod for preventing uncontrolled movement of the can when further extension of the hydraulic ram tends to tilt the cab beyond its balance position in which its center of gravity passes over the tilting axis.The projection means comprises a pair of pins secured to the piston rod of the hydraulic ram and extending perpendicular thereto, and the holding means comprises a pair of flanges each formed with a slot for receiving one of the pair of pins for sliding engagement. The piston rod has its forward end portion slidably received by a trunnion pivotally supported by the flanges whereby lost motion is performed such that the forward end portion of the piston rod moves in linear sliding reciprocatory movement in the trunnion while causing the trunnion to move in reciprocatory rotary movement in the flanges when the piston rod is not extended.

Some disadvantages are associated with this cab tilting system of the prior art. When lost motion is effected, the piston rod moves in substantially large linear sliding movement relative to the trunnion which moves in reciprocatory rotary movement at the same time.

This would give rise to a problem with regard to lubrication and sealing of sliding portions of the piston rod and trunnion. When no adequate means is provided for lubrication and sealing of the sliding portions, wear would be caused thereon at early stages of service. The trunnion is pivotally connected to the flanges such that it rotates only about an axis parallel to the tilting axis of the pivotal connection between the cab and the chassis. This arrangement would make it possible to absorb vertical vibration of the cab, but it would be impossible to absorb lateral movement thereof since no means is provided for absorbing this type of movement. Thus damage would be caused to the cab tilting system by the lateral movement of the cab.

Also, to ensure that the holding pins are received in the respective slots when the hydraulic ram is extended, it would be necessary to avoid rotation of the piston rod about its axis. To this end, the piston rod would have to be provided with means for preventing same from rotating about its own axis, thereby making the construction of the hydraulic ram complex. Also, when the pins are brought into sliding engagement with the respective slots, they are in line-to-line contact with each other. Thus the problem of wear caused to the slide engaging surfaces due to the concentration of stress would be raised.

SUMMARY OF THE INVENTION Accordingly this invention has as its object the provision of a cab tilting system for a motor vehicle which obviates the aforesaid problems raised with regard to the cab tilting system of the prior art.

According to the invention, there is provided a cab tilting system mounted between a chassis and a cab supported on the chassis through suspension spring means and pivotally connected thereto for tilting movement about a tilting axis, comprising hydraulic cylinder means pivotally connected at its base to one of the chassis and the cab, and support means secured to the other of the chassis and the cab, said hydraulic cylinder means including projection means secured to a piston rod of the hydraulic cylinder means, said support means including a contact surface which receives a force of the piston rod applied when the it is extended to tilt the cab and holding means which is brought into sliding engagement with the projection means as the cab is initially tilted by the extended piston rod for connecting the support means to the hydraulic cylinder means to prevent uncontrolled movement of the cab when the center of gravity of the cab passes over the tilting axis, wherein the cab tilting system further comprises a link member pivotally connected at one end to the support means and pivotally connected at the other end to the piston rod of the hydraulic cylinder means for pivotal movement at least about an axis parallel to the tilting axis, said link member having an abutment spaced apart from said contact surface of the support means to enable the cab to perform the movement on the suspension spring means relative to the chassis when the piston rod of the hydraulic cylinder means is not extended, said abutment being pushed by the piston rod to engage the contact surface to tilt the cab when the piston rod is extended.

In one preferred embodiment, the pivotal connection between the other end of the link member and the piston rod of the hydraulic cylinder means may be provided by a spherical joint which enables the link member to move in pivotal movement about other than the axis parallel to the tilting axis. Said projection means may comprise a first slide engaging surface in the form of a spherical surface centered at the center of the pivotal connection between the other end of the link member and the piston rod of the hydraulic cylinder means, and said holding means may comprise a second slide engaging surface in the form of a spherical surface complementary with the spherical surface of the first slide engaging surface of the projection means.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view of a forward end portion of a truck in which the cab tilting system comprising one embodiment of the invention is mounted, showing the cab being tilted by the cab tilting system; Fig. 2 is a fragmentary sectional view showing the essential portion of the cab tilting system in operation as shown in Fig. 1; Fig. 3 is a sectional view taken along the line Ill-Ill in Fig. 2; Fig. 4 is a sectional view taken along the line IV-lV in Fig. 2; Fig. 5 is a fragmentary sectional view similar to Fig. 2 but showing the essential portion of the cab tilting system comprising another embodiment, shown in a condition in which one of a pair of side plates and one of a pair of holding members are removed in the interest of brevity;; Fig. 6 is a fragmentary sectional view similar to Fig. 5 but showing a condition in which the abutment engages the contact surface and the flange partly overlies the holding member VIl-VIl in Fig. 6; Fig. 8 is a fragmentary sectional view similar to Fig. 2 but showing the essential portion of the cab tilting system comprising still another embodiment; Fig. 9 is a sectional view taken along the line IX-IX in Fig. 8; Fig. 10 is a sectional view taken along the line X-X in Fig. 9; and Fig. 11 is a view, on an enlarged scale, of a portion of a modification of the embodiment shown in Figs. 8-10 corresponding to the flange and the holding member engaging surfaces shown in Fig. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Fig. 1, the numeral 2 designates a chassis of a motor vehicle or truck of a cab-over type which supports a cab 6 thereon through suspension springs 4. The cab 6 is pivotally connected to the chassis 2 for tilting movement about a tilting axis 8. A cab tilting system generally designated by the reference numeral 1 0 is mounted between the chassis 2 and the cab 6.

The cab tilting system 10 comprises a hydraulic cylinder 14, pivotally connected at a base 12 to the chassis 2, and a support body 1 8 secured to the cab 6 and operatively associated with a piston rod 16 of the hydraulic cylinder 14. The support body 1 8 is provided with a suitable cover 20.

The hydraulic cylinder 14 which is connected to a hydraulic fluid source through lines and a directional control valve, not shown, has a supply of hydraulic fluid thereto from the source of hydraulic fluid controlled by means of the directional control valve thereby to control the flow of hydraulic fluid to cylinder chambers to extend or contract the piston rod 1 6. When the piston rod 1 6 is extended, the cab 6 can be tilted as shown in Fig. 1.

Referring to Figs. 2-4, the support body 18 has a pair of lugs 22 and 24 fixed thereto which have fitted therein a pin 26 which in turn has a link member 28 fitted thereon at one end for pivotal movement. The piston rod 1 6 of the hydraulic cylinder 14 has secured to its forward end a ball 30 which is fitted for universal movement in a spherical recess 32 formed at the other end of the link member 28. The ball 30 and the spherical recess 32 constitute a spherical joint. The piston rod 1 6 has secured thereto in a position slightly below the ball 30 an annular flange 34 having a lower surface 36 which provides a slide engaging surface in the form of a convex spherical surface.

The convex spherical surface 36 is centered at the center of the ball 30 or pivotal point 38. A portion of the link member 28 above the spherical recess 32 in which the ball 30 is fitted provides an abutment 42 which selectively engages a contact surface 40 secured to the support body 18. The support body 18 has secured thereto a holding member 49 having a pair of guide rails 46 and 48 defining a passage 44 therebetween. The guide rails 46 and 48 are formed with slide engaging surfaces 50 and 52 respectively in the form of a concave spherical surface which is centered at the pivotal point 38 when the abutment 42 engage the contact surface 40 as shown in Fig. 2. Thus the slide engaging surfaces 50 and 52 is in the form complementary with the slide engaging surface 36.

Operation of the embodiment of the aforesaid structure will be described. When the cab 6 is in a regular position in which the vehicle can travel, the piston rod 1 6 is withdrawn into the cylinder 1 4 to move the abutment 42 away from the contact surface 40 to provide a space therebetween.

If the vehicle is started while the cab tilting system is in the aforesaid position, then the cab 6 effects vertical vibration owing to the presence of the suspension springs 4. This vertical vibration is, however, absorbed by the space existing between the abutment 42 and the contact surface 40.

Namely, the support body 18 is not brought into direct contact with the piston rod 1 6 by the vertical vibration, and only the pin 26 is caused to effect vertical vibration which causes the link member 28 to oscillate about the pivotal point 38 without any force applied to the piston rod 16 by the vibration.

Thus the connection of the piston rod 1 6 to the support body 18 through the link member 28 allows the lost motion to absorb the vertical vibration between the piston rod 1 6 and the support body 18. Also, even if the cab 6 moves in a lateral direction during travel, the lateral movement can be absorbed by virtue of the arrangement that the link member 28 is pivotally connected to the piston rod 1 6 through the spherical joint consisting of the ball 30 and the spherical recess 32. Thus the action of the suspension springs 4 on the cab 6 is not interfered with by the presence of the hydraulic cylinder 14, thereby enabling high riding qualities to be obtained in the cab 6.

When the lost motion which absorbs the vertical vibration and lateral movement of the cab 6 is performed, there occurs only sliding movement which manifests itself as pivotal movement at the connection between the pin 26 and the link member 28 and at the spherical joint 30, 32. This enable measures to be readily taken to perform lubration and sealing of the sliding portions, thereby enabling wear to be minimized.

When it is desired to tilt the cab 6 from the regular position described hereinabove to inspect or repair the engine and other parts located below the cab 6, the directional control valve, not shown, is actuated to feed hydraulic fluid under pressure to the hydraulic cylinder 14. This causes the piston rod 1 6 to start extending to bring the abutment 42 of the link member 28 pivotally connected to the forward end of the piston rod 1 6 into abutting engagement with the contact surface 40 as shown in Fig. 2. Further extension of the piston rod 1 6 tilts the cab 6 as shown in Fig. 1 through the contact surface 40 and the support body 1 8.

In the process in which the cab 6 is tilted by the piston rod 1 6 as described hereinabove, the center of gravity of the cab 6 moves about the pivotal axis 8 at the connection between the cab 6 and the chassis 2 in a counterclockwise direction in Fig. 1. Thus in the initial stage of the tilting movement or until the center of gravity passes over a vertical line which extends through the tilting axis 8, the weight of the cab 6 is borne by the abutment 42 while it pushes the cab 6 upwardly.

However, when the center of gravity has passed over the vertical line extending through the tilting axis 8 and moved leftwardly of the vertical line (as seen in Fig. 1), the cab 6 tends to move by its own weight in the counterclockwise direction.

In this stage of the tilting movement, the piston rod 1 6 should function such that it bears the weight of the cab 6 while pulling same.

The process in which the cab 6 is tilted by the piston rod 1 6 as aforesaid will be described in detail. As the piston rod 1 6 is extended from the position in which lost motion can be effected as described hereinabove, the link member 28 moves in pivotal movement about the pin 26 in a clockwise direction (as seen in Fig. 2) and reaches a position shown in Fig. 2 in which the abutment 42 is brought into abutting engagement with the contact surface 40. Further extension of the piston rod 1 6 moves the cab 6 in tilting movement as shown in Fig. 1.At this time, the relative movement of the cab 6 and the rod 16 would be considered, if the support body 1 8 is considered to be stationary in Fig. 2, to be such that the piston rod 1 6 moves in pivotal movement in a clockwise direction about a line perpendicular to the plane of Fig. 2 that extends through the pivotal point 38.

This line which is perpendicular to the plane of Fig.

2 is parallel to the tilting axis 8 at the connection between the cab 6 and the chassis 2.

As the piston rod 1 6 begins to tilt the cab 6 while moving pivotally in the clockwise direction about the aforesaid perpendicular line relative to the support body 1 8 as described hereinabove, the convex spherical lower surface 36 of the flange 34 comes into sliding engagement with the concave spherical surfaces 50 and 52 provided by the guide rails 46 and 48.

As the cab 6 is further tilted and its center of gravity passes over the vertical line extending through the tilting axis 8, the weight of the cab 6 acts to pull the piston rod 1 6 as described hereinabove, so that the slide engaging surfaces 50 and 52 of the rails 46 and 48 secured to the cab 6 are forced against the lower surface 36 of the flange 34 by the weight of the cab 6. As a result, the cab 6 is tilted to a predetermined position while the force urging the surfaces 50 and 52 against the surface 36 is borne by the hydraulic cylinder 14 through the flange 34 and the piston rod 1 6.

Generally, the hydraulic cylinder 14 is usually constructed to allow the piston rod 1 6 to rotate freely about its longitudinal axis. In the hydraulic cylinder 14 of this embodiment, the lower surface 36 of the flange 34 is in the form of the spherical surface centered at the pivotal point 38 of the ball 30. By virtue of this arrangement, the relation in configuration between the lower surface 36 and the slide engaging surfaces 50 and 52 of the rails 46 and 48 remains constant even if the piston rod 1 6 rotates about its own longitudinal axis. Thus the lower surface 36 can be correctly brought into sliding engagement with the engaging surfaces 50 and 52 without any trouble even if no means is provided for preventing the piston rod 16 from rotating about its own longitudinal axis.

As described hereinabove, the lower surface 36 of the flange 43 and the slide engaging surfaces 50 and 52 of the rails 46 and 48 respectively are of complementary spherical surfaces. Thus when they are brought into sliding engagement, they are in surface-to-surface contact with each other, so that the surface pressure between contacting portions can be greatly reduced. This offers the advantage that selection of the material for the flange 34 and/or the rails 46 and 47 is facilitated.

Also the low surface pressure between the contacting portions enables the frictional force to be suitably reduced at the contacting portions by using a suitable bearing member.

A second embodiment of the invention will be described by referring to Figs. 5-7. The cab tilting system shown in these figures is distinct from that shown in Figs. 1-4 in the construction of the parts surrounded by the cover 20 in Figs.

1-4. In Figs. 5-7, parts similar to those shown in Figs. 1-4 are designated by like reference characters.

In the embodiment shown in Figs. 5-7, a support body 60 secured to the cab 6 has a pair of side plates 62 and 64 fitted with a pin 66 to which one end of a link member 68 is pivotally connected. The link member 68 has at the other end a pin 70 fitted with a bearing 72 which is spherical in external shape. The spherical bearing 72 is supported for universal movement in a spherical recess 74 formed in the piston rod 1 6.

The piston rod 1 6 has secured to its forward end a flange 77 having a pair of laterally extending portions 76 and 78. Lower surfaces 80 and 82 of the flange portions 76 and 78 provide slide engaging surfaces each in the form of a concave spherical surface centered at the center of the spherical bearing 72 on the pin 70.

The side plates 62 and 64 have secured thereto respectively a pair of holding members 84 and 86 defining therebetween a passage for the forward end of the piston rod 1 6 to extend therethrough.

The holding members 84 and 86 respectively have inner upper surfaces 88 and 90 which provide slide engaging surfaces each in the form of a convex spherical surface having the same radius of curvature as the concave spherical slide engaging surfaces 80 and 82 of the flange portions 76 and 78, and inner lower surfaces 92 and 94 which provide contact surfaces with which abutments 96 and 98 formed on the link member 68 is brought into abutting engagement.

Operation of the second embodiment of the aforesaid structure will be described. When the cab is in the regular position in which the vehicle can travel, the piston rod 1 6 is withdrawn into the hydraulic cylinder 14 and the abutments 96 and 98 of the link member 68 is spaced apart, as shown in Fig. 5, from the contact surfaces 92 and 94 to provide a space therebetween.

When the vehicle is started while the cab tilting system is in the aforesaid condition, the cab 6 moves in vertical vibration through the suspension springs 4 with respect to the chassis 2. This vibration is, however, absorbed by the space existing between the abutments 96 and 98 and the contact surfaces 92 and 94, so that no force is applied to the piston rod 1 6 by the vibration.

Namely, the vibration causes only the pin 66 to vibrate in the vertical direction and vibration of the pin 66 causes the link member 68 to move in oscillating movement about the pin 70 without any force applied to the piston rod 1 6.

Thus, like the first embodiment shown in Figs.

1-4, the connection between the rod 1 6 and the support body 60 through the link member 68 allows the lost motion to absorb the vertical vibration between the piston rod 16 and the support body 60.

Also, even if the cab 6 moves in a lateral direction during travel, the lateral movement can be absorbed by virtue of the arrangement that the link member 68 and the piston rod 16 are pivotally connected together through the spherical joint consisting of the spherical bearing 72 and the spherical recess 74. Thus the action of the suspension springs 4 on the cab 6 is not interfered with by the presence of the hydraulic cylinder 14, thereby enabling high riding qualities to be obtained in the cab 6.

Also like the embodiment shown in Figs. 1 4, when the lost motion which absorbs the vertical vibration and lateral movement of the cab 6 is performed, there occurs only sliding movement which manifests itself as pivotal movement at the connection between the link member 68 and the pin 66 and at the spherical joint 72, 74. This enables measures to be readily taken for lubrication and sealing of the sliding parts, thereby enabling wear to be minimized.

As the piston rod 1 6 is extended when the cab 6 is in the regular position, the abutments 96 and 98 of the link member 68 are brought into abutting engagement with the contact surfaces 92 and 94 in initial stages of cab tilting operation.

Further extension of the piston rod 1 6 tilts the cab as shown in Fig. 1 through the link member 68, contact surfaces 92 and 94, holding members 84 and 86 and support body 60.

At this time, the link member 68 reaches a position shown in Fig. 6 from a position shown in Fig. 5 while moving in pivotal movement about the pin 66 in a clockwise direction as viewed in Fig. 5. More specifically, if the support body 60 is considered to be stationary in Fig. 5, the relative movement of the cab 6 and the rod 16 would be considered to be such that the piston rod 1 6 moves in pivotal movement in a clockwise direction about the pin 70.

As the piston rod 1 6 begins to tilt the cab 6 and the rod 1 6 moves in pivotal movement about the pin 70 in the clockwise direction relative to the support body 60 as aforesaid, the concave slide engaging surfaces 80 and 82 of the flange portions 76 and 78 are brought into sliding engagement with the convex slide engaging surfaces 88 and 90 of the holding members 84 and 86, as shown in Fig. 6.

As the cab 6 is further tilted and its center of gravity passes over a vertical line which extends through the tilting axis 8, the weight of the cab 6 acts to pull the piston rod 1 6. When the cab 6 is brought to this position, the engaging surfaces 88 and 90 of the holding members 84 and 86 secured to the cab 6 are forced against the engaging surfaces 80 and 82 of the flange portions 76 and 78 respectively by the weight of the cab 6.

The result of this is that the cab 6 is tilted to a predetermined position while the force applied by the weight of the cab is being borne by the hydraulic cylinder 14 through the flange portions 76 and 78 and the piston rod 16.

In the embodiment shown in Figs. 5-7, the engaging surfaces 80 and 82 of the flange portions 76 and 78 can be correctly brought into sliding engagement with the engaging surfaces 88 and 90 of the holding members 84 and 86, respectively, as is the case with the embodiment shown in Figs. 1-4, even if the piston rod 1 6 rotates about its longitudinal axis, since the engaging surfaces 80 and 82 of the flange portions 76 and 78 and the engaging surfaces 88 and 90 of the holding members 84 and 86 are both in the form of a spherical surface. This spherical configuration of the engaging surfaces also enables the sliding contact between the two parts to take place in surface-to-surface contact, thereby minimizing the surface pressure and reducing the risk of damage.

In the embodiment shown in Figs. 5-7, the flange portions 76 and 78 and the holding members 84 and 86 are mounted between the support body 60 and the pin 70 which pivotally connects the piston rod 1 6 to the link member 68.

This enables a compact overall construction to be obtained in a cab tilting system and avoids mutual interference between the members of the cab tilting system and the suspension springs 4 and other parts located between the cab 6 and the chassis 2.

A third embodiment of the invention will be described by referring to Figs. 8-1 0. This embodiment is substantially similar to the first embodiment shown in Figs. 1-4 except that a holding member 100 forming a part of the support body 60 is distinct from the holding member 49 of the first embodiment shown in Fig. 1-4. In Figs.

8 and 9, parts similar to those shown in Figs. 1-4 are designated by like reference characters.

The holding member 100 defines a passage 102 and has bearing members 104 and 106 formed of a synthetic resinous material, such as nylon, and, as shown in Fig.10, located thereon along opposite sides of the passage 102. The bearing members 104 and 106 are secured to the holding member 100 in positions by inserting pins 11 2 and 114 provided to the bearing members 104 and 106 in openings 108 and 110 formed by punching in the holding member 100 and boding the bearing members 104 and 106 to the holding member 100 by means of an adhesive agent.

In the aforesaid arrangement of the pins 112 and 114 inserted in the openings 108 and 110, two pins are used for each of the bearing members 104 and 106, and the two pins 112 or 114 are inserted in each of the corresponding openings 108 and 110 of the bearing members 104 and 106, as shown in Fig. 10.

Surfaces of the bearing members 104 and 106 provide slide engaging surfaces 11 6 and 118 each in the form of a concave spherical surface centered at the pivotal point 38 at the connection between the link member 28 and the piston rod 1 6 when the link member 28 is in a position shown in Fig. 8.

The action of lost motion in which the vertical vibration of the cab 6 is absorbed and the action of cab tilting performed by the extended piston rod 1 6 in this embodiment are essentially the same as those described hereinabove by referring to the first embodiment.

In the third embodiment of the aforesaid structure, the arrangement that the slide engaging surfaces 116 and 118 are in the form of a concave spherical surface while the lower surface 36 is in the form of a convex spherical surface of the same radius of curvature as the spherical surfaces 11 6 and 11 8 has the effect that as the piston rod 1 6 supports the cab 6 while pulling same and at the same time the lower surface 36 is moved in sliding engagement with the engaging surfaces 116 and 118, the engaging surfaces 116 and 118 and the lower surface 36 are brought in surfaceto-surface contact and the surface pressure therebetween is reduced, thereby making it possible to minimize resistance and friction in the sliding engagement.Generally, it would be difficult to provide engaging surfaces 11 6 and 118 on the holding member 100 by machining to attain the aforesaid end. This is because difficulties would be faced with in forming locally on the holding member 100 by machining a concave curved surface of precision finishes high enough to allow the aforesaid sliding engagement with the lower surface 36 to be achieved without any trouble.

Thus in the embodiment shown and described herein, the bearing members 104 and 106 formed of synthetic resinous material are used to overcome the difficulties. The feature of the invention in this respect will be described in detail.

In this embodiment, the holding member 100 for holding the bearing members 104 and 106 is formed of steel sheet by press work, so that the operation of forming the holding member 100 in a spherical surface which conforms to the concave spherical engaging surfaces 11 6 and 118 could be readily performed and the production can be made on a mass production basis.

However, it is not preferable to use as a slide engaging surface a concave spherical surface formed by press work on the holding member 100 since the concave spherical surface thus formed would not be sufficiently high in precision finishes to enable slide engagement to be achieved smoothly.

In the embodiment shown and described herein, the bearing member 104 and 106 are secured to the concave spherical surface of the holding member 100, so that high precision finishes can be readily obtained on each concave curved slide engaging surface 116, 118.

The reason why the aforesaid result can be achieved is that since the bearing members 104 and 106 are formed of synthetic resinous material, a concave spherical surface of high precision finishes can be readily obtained by using a metal mold of high precision finishes. When the lower surface 36 is brought into sliding engagement with the engaging surfaces 11 6 and 11 8 of the bearing members 104 and 106, the sliding engagement smoothly takes place therebetween since the convex spherical surface on the lower surface 36 readily fits the concave spherical engaging surfaces 116 and 118 because they are formed of synthetic resinous material.

The construction in which the pins 112 and 114 of the bearing members 104 and 106 are inserted in the openings 108 and 110 formed at the holding member 100 as shown in Fig. 10 is made necessary by the following reasons.

The engaging surfaces 11 6 and 11 8 should constitute a concave spherical surface which is centered at the center 38 of the ball 30 located in a position shown in Fig. 8. If the bearing members 104 and 106 shift relative to the holding member 100, the center of the concave spherical surface defined by the engaging surfaces 116 and 118 would also shift from the center 38. The aforesaid construction is provided to keep the concave spherical surface defined by the engaging surfaces 11 6 and 118 from becoming off-center.

Consequently, it is necessary that at least two pins be used as the pins 112 and 114 for each of the bearing members 104 and 106 to avoid the occurrence of the off-center movement.

In the embodiment shown and described herein, the holding member 100 has been described as being formed of steel sheet by press work. However, the invention is not limited to this specific process of forming the holding member 100, and "powder molding metallurgy" or "forging die shaping" may be relied on for providing the holding member 100 with a shape conforming to the concave spherical engaging surfaces 116 and 118.

Even if "powder molding metallurgy" or "forging die shaping" is utilized to provide the holding member 100, it is difficult to provide a concave spherical surface of high precision finishes on the engaging surfaces 116,118 by merely relying on these techniques. This makes it necessary to use the bearing members 104 and 106 which are secured to the holding member 100 as described hereinabove.

Fig. 11 shows a modification of the embodiments shown in Figs. 8-10, in which parts corresponding to the flange 34 and the engaging surfaces 11 6 and 118 shown in Fig. 9 are shown. The holding member 100, engaging surfaces 120 and 122, the piston rod 16, a lower surface 120 and a flange 126 correspond to the holding member 100, engaging surfaces 116 and 118, piston rod 16, lower surface 36 and flange 34, respectively, shown in Fig. 9. In this modification, the engaging surfaces 120 and 122 are directly formed on the holding member 100, and a bearing member 128 of an annular shape formed of synthetic resinous material is secured to a lower surface of the flange 126.

The bearing member 128 is secured to the flange 126 by inserting pins 130 and 132 of the bearing member 128 in openings 134 and 136 formed at the flange 1 26 and then bonding the bearing member 128 to the flange 126.

It will be readily understood that the structure shown in Fig. 11 can also achieve the same effect as described by referring to the structure shown in Figs. 8-10.

In Fig. the pins 130 and 132 keep the bearing member 1 28 from rotating about the piston rod 16. When the flange 126 is of other shape than a circular or disc shape, the pins 130 and 132 may be replaced by protuberances 1 38 formed in outer peripheral portions of the bearing member 128 as indicated by dash-and-dot lines in Fig. 11 and the flange 126 may be fitted to the bearing member 12 in a manner to be enclosed by the protuberances 138.

In all the embodiments described hereinabove, the hydraulic cylinder 14 has been described as being pivotally connected to the chassis 2 at the base 12. However, it is to be understood that the invention is not limited to this specific arrangement and that the hydraulic cylinder 14 may be pivotally connected at the base 12 to the cab 6 and the support body 1 8, 60 may be secured to the chassis 2.

From the foregoing, it will be appreciated that the present invention provides a cab tilting system which enables lost motion to be obtained merely by mounting a link member for connecting the piston rod to the support body, and therefor the system is simple and durable in construction and very high in wear resistance since the sliding portions during lost motion only comprise the pivotal connections between the support body and the link member and between the link member and the piston rod where lubrication and sealing are very easy.

It will be also appreciated that in the cab tilting system according to the invention, the spherical joint for pivotal connection between the link member and the piston rod enables not only the vertical vibration of the cab but also the lateral movement thereof to be absorbed so that the lateral movement produces no stress in the piston rod, hydraulic cylinder and support means, thereby avoiding problems with regard to damage to the piston rod and reduced durability thereof caused by such stress.

It will be further appreciated that in the present invention, the spherical surfaces used for the slide engaging surface of the projecting means secured to the piston rod and the slide engaging surface of the holding means secured to the support means enables the slide engaging surface of the piston rod to be positively brought into sliding engagement with the slide engaging surface of the holding means even if the piston rod may rotate about its own longitudinal axis.

It will be also appreciated that in the cab tilting system according to the invention, the spherical surfaces used for the slide engaging surfaces are conducive to a prolonged service life of the system since the engaging surfaces are maintained in perfect surface-to-surface contact with each other to lower the surface pressure.

Claims (10)

1. A cab tilting system mounted between a chassis and a cab supported on the chassis through suspension spring means and pivotally connected thereto for tilting movement about a tilting axis, comprising: hydraulic cylinder means pivotally connected at its base to one of the chassis and the cab; and support means secured to the other of the chassis and the cab; said hydraulic cylinder means including projection means secured to a piston rod of the hydraulic cylinder means, said support means including a contact surface which receives a force of the piston rod applied when it is extended to tilt the cab and holding means which is brought into sliding engagement with the projection means as the cab is initially tiled by the extended piston rod for connecting the support means to the hydraulic cylinder means to prevent uncontrolled movement of the cab when the center of gravity of the cab passes over the tilting axis; wherein the cab tilting system further comprises: a link member pivotally connected at one end to the support means and pivotally connected at the other end to the piston rod of the hydraulic cylinder means for pivotal movement at least about an axis parallel to the tilting axis, said link member having an abutment spaced apart from said contact surface of the support means to enable the cab to perform the movement on the suspension spring means relative to the chassis when the piston rod of the hydraulic cylinder means is not extended, said abutment being pushed by the piston rod to engage the contact surface to tilt the cab when the piston rod is extended.

2. A cab tilting system as claimed in claim 1, wherein the pivotal connection between the other end of the link member and the piston rod of the hydraulic cylinder means is provided by a spherical joint which enables said link member to move in pivotal movement about axes other than the axis parallel to the tilting axis.

3. A cab tilting system as claimed in claim 1 or 2, wherein said projection means comprises a first slide engaging surface in the form of a spherical surface centered at the center of the pivotal connection between the other end of the link member and the piston rod of the hydraulic cylinder means, and said holding means comprises a second slide engaging surface in the form of a spherical surface complementary with the spherical surface of the first slide engaging surface.

4. A cab tilting system as claimed in claim 1 or 2 wherein said projection means comprises an annular flange secured to the piston rod immediately below the pivotal connection between the other end of the link member and the piston rod, and said holding means comprises a pair of guide rails secured to said support means.

5. A cab tilting system as claimed in claim 4, wherein said flange is formed at its lower surface with a first slide engaging surface in the form of a convex spherical surface centered at the pivotal connection between the other end of the link member and the piston rod, and said each guide rail is formed with a second slide engaging surface in the form of a concave spherical surface complementary with the convex spherical surface of the first slide engaging surface.

6. A cab tilting system as claimed in claim 1 or 2, wherein said projection means comprises a flange having a pair of laterally extending portions secured to the piston rod immediately above the pivotal connection between the other end of the link member and the piston rod, and said holding means comprises a pair of holding members secured to said support means.

7. A cab tilting system as claimed in claim 6, wherein said flange is formed at lower surfaces with a first slide engaging surface in the form of a concave spherical surface centered at the pivotal connection between the other end of the link member and the piston rod, and said each holding member is formed with a second slide engaging surface in the form of a convex spherical surface complementary with the concave spherical surface of the first slide engaging surface.

8. A cab tilting system as claimed in claim 4, wherein one of said projection means and said holding means is provided with a bearing member formed of synthetic resinous material, said bearing member being formed with a slide engaging surface.

9. A cab tilting system as claimed in claim 4, wherein said guide rails each have secured thereto a bearing member formed of synthetic resinous material, said each bearing member being formed with a slide engaging surface adapted to be brought into sliding engagement with a slide engaging surface of said projection means.

10. A cab tilting system as claimed in claim 4, wherein said flange has secured thereto a bearing member formed of synthetic resinous material, said bearing member being formed with a slide engaging surface adapted to be brought into sliding engagement with a slide engaging surface of said holding means.