GB2172930A - Releasable fastening mechanism for tilting cabs on vehicles - Google Patents

Abstract

A common type of tilting cab fastening consists of a striker bar (41) secured to the vehicle chassis and a housing (1, 2), secured to the vehicle cab, or vice versa, the housing having a mouth (7) in which the striker bar (41) is retained in the fastened condition by a jaw (9) pivoted in the housing. The jaw is held in the closed position by a spring biassed pawl (18). In order to prevent rattling in such known mechanisms, yet permit necessary free play in the mechanism, one or preferably two sprung arms (42) are mounted on the housing to bear resiliently on the striker bar (41) in the fastened condition. Each arm (42) can be arranged as a beam, with one end (43) pivoted in the housing and the other end slidable longitudinally of the arm in a mounting (46). The arm can be rigid (Figure 6 not shown) and biassed by an independent spring but preferably it is itself resilient. Two arms can be provided by the limbs of a single U-shaped spring bar Figure 9 ((42c) not shown). <IMAGE>

Description

SPECIFICATION Releasable fastening mechanism for tilting cabs on vehicles This invention relates to a releasable fastening mechanism for a vehicle tilting cab.

In commercial vehicles having forwardly mounted engines it is common practice to hinge the cab at its forward end on the chassis so that the cab can be tilted forwards to give access to the engine and ancillary mechanism, a releasable fastening mechanism being provided to secure the cab to the chassis in its normal position during use of the vehicle.

The invention relates particularly to a releasable fastening mechanism for securing a vehicle tilting cab to a vehicle chassis in which a striker bar adapted to be secured to the cab or chassis is adapted to enter a gap in a housing adapted to be secured to the chassis or cab respectively, the bar co-operating with a spring-loaded jaw pivotally mounted in the housing. The jaw has a notch to receive the bar and as the cab approaches the chassis the bar engages one side of the notch and rotates the jaw into a locking position in which the bar is trapped and the jaw is automatically retained in that position by a manually releasable springloaded pawl.Such a fastening mechanism will hereinafter be referred to as a 'releasable fastening mechanism of the kind set forth.' In some vehicles the tilting of the cab is assisted by hydraulics, but more commonly a torsion bar is provided to counterbalance the moment exerted by the cab about the tilt axis. This results in the cab being in a semi-buoyant state when in its normal, downward position.

A problem with known fastening mechanism of the kind set forth, particularly when used with such counterbalanced cabs, is that they can rattle when the vehicle is used on rough terrain. A certain amount of free play in the mechanism is considered essential to avoid stiffness of the locking and unlocking action.

According to one aspect of the invention a releasable fastening mechanism of the kind set forth comprises a spring-loaded member carried by the housing and arranged to exert a spring force on the striker bar when the fastening mechanism is secured.

Preferably the arrangement is such that in use the line of action of the spring force is at an angle of between 30 and 80" to the vertical in use, substantially in a plane normal to the tilt axis of the cab, and such as to urge the bar towards the root of the notch and outwardly of the gap.

The line of action of the spring force can be chosen to absorb both up and down, front and rear, and sideways vibrations of the cab relative to the chassis.

Preferably said angle is between 50 and 75 , to take account of the fact that in many vehicles, horizontal vibrations will tend to predominate.

Preferably the spring-loaded member is an arm carried by the housing and urging the bar generally towards the root of the notch and outwardly of the gap.

The arm may be rigid and loaded by a spring which acts between the housing and the arm, but preferably the arm itself is resilient.

When a resilient arm is employed, the arm is preferably arranged as a resilient beam, the arm being connected to the housing at both ends, and arranged such that an intermediate portion of the arm extends across the inner end of the gap for engagement with the striker bar when the bar is forced into the inner end of the gap, the connection at at least one end of the arm permitting the bar to slide lengthwise of the arm relative to the housing.

Preferably the other end of the resilient arm is pivotally connected to the housing. The pivotal connection may comprise an eye formed on said other end of the arm by bending of the arm material.

The arm is preferably mounted externally of the housing.

Preferably two such arms are provided on opposite sides of the housing, preferably arranged substantially symmetrically. This enables a relatively large, balanced force to be applied to the striker bar.

In one advantageous arrangement the two arms are provided by the two limbs of a single U-shaped spring bar. Such an arrangement can help to reduce the cost of the assembly because it is unnecessary to provide independent mountings on the housing for the joined ends of the arms.

The spring bar is preferably of angular U-shape, at least when assembled to the housing, the base of the U extending through aligned apertures in opposite sides of the housing to provide pivotal connections for the joined ends of the arms.

The free end of one arm of the U-shaped bar is preferably slidably supported in an eye which is conveniently provided by a transverse bore in a fastener, such a rivet, secured to the adjacent side of the housing, and the free end of the other arm has a sliding engagement with an abutment provided on the other side of the housing.

This arrangement facilitates assembly of the Ushaped bar to the housing sides, since it can, in accordance with a second aspect of the invention, enable the free end of said one arm to be passed through the eye and the bar assembled to the adjacent side plate of the housing with the base of the U extending through the aperture in that side, before the opposite side plate of the housing is assembled into place, this being accomplished by passing that plate over the free end of the other arm of the bar so that the bar extends through the aperture in said opposite side plates, and said other arm is brought into engagement with the abutment.

The fastener which provides the eye is preferably secured to said adjacent side plate after the bar has been passed through the aperture in that side plate. The abutment is preferably a separate member which is welded or otherwise affixed to said opposite side plate prior to assembly of that plate to the housing.

In order to ensure that the free end of said other arm does not become displaced from the abutment in transit and storage of the mechanism, the assembled bar may be arranged to be torsionally stressed such that said free end is biassed by the torsional stress against the abutment. This is arranged by shaping the bar such that in its free state the two limbs are angularly spaced apart slightly about the axis of the base of the U.

In order to assist assembly of the U-shaped bar in the mechanism, the arms of the U are preferably made slightly divergent in the free state of the bar, as viewed from the front of the U, and the abutment is then provided with a lip to hold said other arm parallel to the adjacent side plate in the assembled condition.

Various tilting cab releasable fastening mechanisms in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure I is a side elevation of a first mechanism shown in its position of use with the cab secured to its normal, operating position; Figure 2 is a plan view of the mechanism of Figure 1; Figure 3 is a view looking in the direction of the arrow A in Figure 1; Figure 4 is a side elevation of a second mechanism; Figure 5 is a section on the line 5-5 of Figure 4; Figure 6 is a side elevation of the third mechanism, but omitting the jaw; Figure 7 is a side elevation of a fourth mechanism which incorporates a U-shaped spring bar, and looking from the side where the free end of the bar engages an abutment member; Figure 8 is a view looking from the right in Figure 7;; Figures 9 and 10 are front and side elevations of the spring bar of the fourth mechanism, the bar being in its free state; Figure 11 is a side elevation of a rivet which provides an eye for one end of the spring bar of the fourth mechanism; Figure 12 is a view of the rivet looking from one side in Figure 11; Figure 13 is a side elevation of the abutment member of the fourth mechanism; and Figure 14 is a view of the abutment member looking form the left in Figure 13.

The mechanism of Figure 1 to 3 is in most respects substantially the same as that described and illustrated in our U.K. Patent Specification No.

2049785A, and reference should be made to that Specification for a detailed understanding of the present mechanism. In the accompanying drawings parts corresponding to those of the illustrated mechanism of Specification No. 2049785A have been given corresponding reference numerals.

Briefly, the mechanism comprises a housing having spaced pressings 1, 2 between which a jaw 9 is pivoted on a pivot 10. The jaw 9 is retained in a closed position by a pawl 18 which is releasable by an operating lever 20 to release a striker bar 41 from a gap 7 in the pressings 1, 2.

The housing is secured to the vehicle cab adjacent its rear end by mounting bolts passed through holes 40 in housing flanges 5, such that the gap 7 faces downwardly, as shown, when the cab is in its normal operating position. The pressings 1, 2 extend in vertical planes parallel to the longitudinal axis of the cab, which is pivoted at its front end about a transverse axis of the vehicle. A striker, in the form of a horizontal bar 41 is secured to the vehicle chassis, and extends transversely of the vehicle.

As distinct from the mechanism of Specification No. 2049785A, the mechanism of the accompanying Figure 1 to 3 additionally comprises a pair of parallel spring arms 42 which are mounted on the respective outer sides of housing pressings 1, 2.

The arms 42 extend as shown at an angle of approximately 25" to the vertical, and, as shown in dashed outline in Figure 1, intersect the upper corner of the gap 7, such that when the bar 41 is urged into the upper end of gap 7, to bring about fastening of the mechanism, the arm is resiliently deflected to the position shown in full outline in Figure 1. The arms 42 are each rods which have their lower ends turned into an eye 43 to provide a pivotal connection between that end of the arm and the housing 1, 2.

Conveniently, a common pivot is provided for the two arms 42 by the shank of a bolt 44 which also serves to hold the pressings 1, 2 in spaced relationship, the bolt 44 passing through a spacer sleeve 4' held between pressing 1, 2. Respective washers 45 on bolt 44 retain the eyes 43, the washers 45 abutting with respective spacer sleeves 48 on which the eyes 43 are rotatably mounted.

The upper ends of the arms 42 extend slidably through transverse bores in respective lugs 46, and this slidable mounting of the arms 42 enables them to act as resilient beams when they are engaged by the striker bar 41.

The point of contact of the arms 42 with the striker bar 41 is marked B in Figure 1, and it will be seen that this engagement occurs at approximately the mid-point in the length of the arm 42. The inclination of the bars 42 to the vertical results in the force of engagement with the bar 41 being in the direction of the arrow C in Figure 1, that is in a direction to urge the bar 41 leftwardly and downwardly of the gap 7. The bar 41 will be firmly held by the spring force of the bars 42 in engagement with the flanges 8 of pressing 1, 2, which define the gap 7, by the leftwardly directed component of the spring force, and the bar 41 will thereby be restrained from vibrating in the front and rear direction relative to the housing 1, 2.

The downward component of the spring force exerted by arms 42 on bar 41 will hold bar 41 firmly in engagement with jaw 9 on upwardly facing surface 47 thereof which bounds notch 11 adjacent to the root thereof, and since the step 28 on jaw 9 abuts pawl 18 to prevent rotation of jaw 9 in the clockwise direction in Figure 1, the bar 41 is thereby held vertically between arms 42 and jaw 9 to resist any vertical vibration of the bar 41 relative to the housing 1, 2.

A further advantage of this arrangement is that the jaw 9 itself is held against vibration relative to the housing 1, 2 by the spring force exerted by arms 42 through bar 41.

It will be appreciated that the use of two spring arms 42 in symmetrical positions on either side of the housing provides uniform loading of the striker bar 41 and enables a large spring force to be applied.

The mechanism of Figure 4 is substantially the same as that of Figures 1 to 3 except that the single spring bar 42 is pivoted at its upper end on a headed pivot pin 49, shown in cross-section in Figure 5, the lower end of the bar being slidably mounted in a lug 46. In this case, to suit the vibration characteristics of the particular vehicle cab, the spring bar 42 in its undeflected state, as drawn, is inclined at 35" to the vertical.

Figure 6 shows a modified spring loading arrangement (the jaw being omitted from the drawing) in which a flat rigid arm 50 is pivoted on a headed pivot pin 49 and is loaded adjacent to its free end 51 by a vertically acting coiled compression spring 52. The arm 50 is cranked to provide a surface 53 which engages with the striker bar 41 in the fastened condition of the mechanism, the surface 53 extending at an angle of substantially 30" to the vertical, such that the spring force acting at point B on the bar 41 is directed at an angle of substantially 60" to the vertical.

The free end 51 of the arm 50 is guided in a vertical slot 54 in a flange 55 of pressing 2, and the spring 52 is located on projections 56 and 57 on the arm 50 and pressing 2 respectively.

The mechanism of Figure 6 would normally have only one arm 50, but if desired a pair of springloaded arms could be provided.

Figures 7 and 8 show a mechanism which is similar to that of Figure 1 but in which the pair of independent spring bars 42 are replaced by the arms 42a, 42b of a single substantially U-shaped spring bar 42c, shown in its free state in Figures 9 and 10. Parts corresponding to the mechanism of Figure 1 have been given corresponding reference number.

The U-shaped bar 42c is of angular outline, having a straight basal limb 42d which extends through a pair of aligned holes 58 in the respective pressings 1, 2, to provide a pivotal mounting for the adjacent, joined ends 59 of the limbs 42a, 42b.

The free end 60 of the limb 42a is slidably retained in the transverse bore 62 of an anchor pin 61 which is riveted to the pressing 1, whereas the free end 63 of limb 42b has a sliding engagement with one side face 65 of an abutment pin 64 welded to the pressing 2. The spigot 66 of pin 61 is made tubular to assist in its riveting to pressing 1.

For reasons to be explained, the limbs 42a, 42b of the bar 42c diverge from each other in the free state, but in the assembled mechanism the limbs 42a, 42b are held parallel to the planes of pressings 1, 2, by the eye of pin 61 and by a lip 67 on the abutment pin 64 respectively.

In order to keep the assembled mechanism slim, as viewed in Figure 8, the limbs 42a, 42b are made of waved shape, as shown in Figures 1 and 10, this shape permitting the limbs 42a, 42b to lie closely adjacent the outer faces of pressings 1, 2 respectively, yet avoiding peripheral flanges 8 on the pressings 1, 2 which bound the gap 7. It will be seen from Figure 8 that this arrangement is more compact than that of the first mechanism in which, as shown in Figure 3, the bars 42 lie outside the flanges 8. In the mechanism of Figure 7 the flanges 8 on both pressings are absent where the limbs 42a, 42b cut across the inner end of gap 7.

In order to ensure that the free end 63 of the limb 42b does not become dislodged from abutment pin 64 during storage and transit of the mechanism, when the striker is not present in gap 7, a small amount of torsional stress is provided in the bar 42c which urges the free end 63 of limb 42b into firm engagement with surface 65. This is arranged by providing a small angular inclination of the limbs 42a, 42b in the free state of the bar, as shown in Figure 10, which results in torsional stress of the basal limb 42d in the assembled mechanism.

In order to assemble the bar 42c into the mechanism the pressing 1 is threaded onto the limb 42a to approximately the assembled position, and the inclination of limb 42a to the normal to limb 42d, shown in Figure 9, enables the pin 61 to be threaded onto the free end 60 of limb 42a and to be slid down limb 42a to engage the hole in pressing 1 in which the shank 66 of the pin 61 is then secured by riveting. The internal components of the mechanism are then assembled on pressing 1.

The pivot pin 10 for jaw 9 and the pivot pin 19 are conveniently secured to pressing 1 prior to assembly of the bar 42c to pressing 1.

Prior to incorporation of the second pressing 2 in the mechanism the abutment pin 64 has been welded in position. The second pressing 2 is then threaded over the limb 42b, limb 42b being passed through hole 58 in pressing 2. This process is facilitated by the inclination of limb 42b to the normal to limb 42d, shown in Figure 9. The pressing 2 is brought to its assembled position and is then connected to pressing 1 by riveting of members 3, 10 and 19. Finally the free end 63 of the limb 42b is sprung into position behind lip 67 of abutment pin 64 in engagement with surface 65.

It will be appreciated that limbs 42a, 42b of the spring bar provide an anti-rattle force acting on the striker and jaw 9 when the jaw 9 is closed on the striker, in a similar manner to the independent spring bars 42 of the Figure 1 arrangement.

It will be appreciated that any of the mechanisms illustrated could be inverted, in which case the housing 1, 2 would be secured to the vehicle chassis, the striker bar being secured to the vehicle cab adjacent to its rear end.

Claims (17)

1. A releasable fastening mechanism of the kind set forth comprising a spring-loaded member carried by the housing and arranged to exert a spring force on the striker bar when the fastening mechanism is secured.

2. A mechanism as claimed in claim 1 in which the line of action of the spring force is at an angle of between 30" and 80" to the vertical in use, substantially in a plane normal to the tilt axis of the cab, and such as to urge the bar towards the root of the notch and outwardly of the gap.

3. A mechanism as claimed in claim 1 or claim 2 in which the spring-loaded member is an arm carried by the housing.

4. A mechanism as claimed in claim 3 in which the arm itself is resilient to provide the spring force.

5. A mechanism as claimed in claim 3 in which the arm is arranged as a resilient beam, the arm having connections with the housing at both of its ends, an intermediate portion of the arm extending across the inner end of the gap for engagement with the striker bar when the bar is forced into the inner end of the gap, the connection at at least one end of the arm permitting the bar to slide lengthwise of the arm relative to the housing.

6. A mechanism as claimed in claim 5 in which the other end of the arm is pivotally connected to the housing.

7. A mechanism as claimed in claim 6 in which the pivotal connection comprises an eye formed on said other end of the arm as a bent portion of the arm material.

8. A mechanism as claimed in in any of Claims 3 to 7 in which two arms are arranged on opposite sides (1, 2) of the housing.

9. A mechanism as claimed in claim 8 as appended directly to Claim 6 in which the two arms are two limbs of a unitary U-shaped spring bar, the base of the A being pivotally connected to the housing to provide the pivotal connection for both arms.

10. A mechanism as claimed in claim 9 in which the U-shaped bar is of angular shape, and the basal limb of the bar extends through aligned apertures in opposite side plates of the housing.

11. A mechanism as claimed in claim 9 in which the free end of one arm of the bar is slidably supported in an eye member, and the free end of the outer arm is slidably supported on an abutment.

12. A mechanism as claimed in claim 11 characterised in that the arms of the U-shaped bar are inclined to one another when the bar is viewed in its free state parallel to the basal limb of the U, to provide torsion in the assembled bar which biasses the bar against the abutment.

13. A method of assembling a mechanism as claimed in claim 11 characterised by the steps of inserting the bar in said aperture of one of the side plates, securing the eye member in position on that side plate with the eye member mounted on the free end of one arm of the U-shaped bar, threading the other side plate on the bar with the bar extending through the aperture in the side plate, securing the side plates together in spaced relationship, and ensuring that the free end of the other arm of the bar is engaged with the abutment.

14. A releasable fastening mechanism of the kind set forth substantially as described with reference to Figures 1 to 5 of the accompanying drawings.

15. A releasable fastening mechanism of the kind set forth substantially as described with reference to Figure 6 of the accompanying drawings.

16. A releasable fastening mechanism of the kind set forth substantially as described with reference to Figures 7 to 14 of the accompanying drawings.

17. A method as claimed in Claim 13 and substantially as described in relation to the assembly of the releasable fastening mechanism of Figures 7 to 14 of the accompanying drawings.