FORM 2
THE PATENT ACT 1970 (39 of 1970)
&
The Patents Rules, 2003 COMPLETE SPECIFICATION
(See Section 10, and rule 13)
1. TITLE OF INVENTION
SUSPENSION DEVICE WITH SCISSORS-TYPE PANTOGRAPH

2. APPLICANT(S)
a) Name
b) Nationality
c) Address

ZF FRIEDRICHSHAFEN AG GERMAN Company 88038 FRIEDRICHSHAFEN GERMANY

3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed : -

Description
The present invention relates to a suspension device for the antivibration and shock-absorbing suspension of a mass body according to the pre-characterising part of claim 1.
Suspension devices of the type mentioned in the introduction are used for example, though by no means exclusively, in lorries, commercial vehicles and similar heavy road vehicles, in order to decouple the driver's cab from the chassis of the vehicle. Since in the case of heavy road vehicles the spring constants of the travelling gear springs unavoidably fail relatively often on account of the large vehicle loads, unevennesses in the carriageway or also vibrations from the axles and drive train are to a significant extent still transmitted via the axle springs to the chassis.
In order, in the context of ergonomics and work and safety protection, to minimise the transmission of such constant impacts and vibrations to the driver's cab and thus to the driver's workplace, driver's cab suspensions have been developed in which the driver's cab is supported on the vehicle chassis by using a dedicated suspension system. Such suspension systems for the driver's cab can, on account of the much lower weight of the driver's cab compared to the vehicle weight, be designed with considerably smaller spring constants and softer shock absorbers than the axial suspension.
Such types of suspension arrangements for drivers' cabs are however structurally relatively complicated, especially with stringent demands on transverse force support and kinematics, such as for example suppressing pitching or rocking. Thus, apart from the actual spring elements and damping elements, similar to the case of vehicle axle suspensions, additional stabilisers even have to be provided.
In order for example to limit the undesirable relative sideways rocking of the driver's cab relative to the vehicle chassis, for example when travelling on inclines or


bends, in suspension devices according to the prior art transverse stabilisers in the form of torsion bars are often necessary, which couple together to a certain extent the spring paths of the left-hand and right-hand suspension elements, referred to the direction of travel, of the driver's cab. In order in addition to suppress or damp also movements and vibrations of the driver's cab in the sideways direction, additional spring/damping units often still have to be provided in the transverse direction of the vehicle.
Such known devices for suppressing rocking movements, or for damping movements of the driver's cab in directions other than in the main impact direction, are however structurally complicated on account of the large acting loads. Such devices accordingly involve not inconsiderable construction and production costs and also costs involved in the maintenance of for example a lorry or commercial vehicle fitted with such devices.
Against this background the object of the present invention is to provide a suspension device for the antivibration suspension of a mass body, with which the aforementioned disadvantages of the prior art can be overcome. In particular the suspension device is intended to enable the desired degree of freedom of movement of the mass body to be reliably specified with simple means, and at the same time effectively damp or suppress undesirable movements along other degrees of freedom of movement or spatial directions.
This object is achieved by a suspension device having the features of claim 1. Preferred embodiments are the subject-matter of the subclaims.
The suspension device according to the invention serves in a known manner for the antivibration suspension of a mass body relative to a substructure, thus for example for the suspension of the driver's cab of a lorry or commercial vehicle with respect to the vehicle chassis.


In a manner also known per se the suspension device comprises a spring/shock absorber arrangement located between the mass body and substructure, for damping impacts and vibrations of the substructure.
According to the invention the suspension device is however characterised by at least one scissors-type pantograph for reducing the degrees of freedom of movement of the mass body. The scissors-type pantograph is in this connection disposed in the manner of a lifting scissors-type arrangement in such a way between the substructure and mass body that the mass body can move along the desired degree of freedom of movement - or along the intended spatial direction - relative to the substructure, whereas the movement of the mass body along at least one further spatial direction is damped or suppressed. In other words, the scissors-type pantograph thus serves to reduce the number of degrees of freedom of movement of the mass body relative to the substructure.
The connection according to the invention between the mass body and substructure by means of a scissors-type pantograph is particularly advantageous insofar as a straight-line motion of the mass body relative to the substructure can thereby be achieved in a structurally simple and robust manner. At the same time however the so-called rocking or pitching movements for example - in other words undesirable rotational movements of the mass body about at least one of its principal axes - are effectively suppressed. The same is also true of undesirable, for example lateral, movements of the mass body perpendicular to the principal impact direction, and in general of movements running perpendicular to the direction of the straight-line motion of the mass body.
The invention is in this connection first of all accomplished independently of how the scissors-type pantograph is specifically designed and constructed and arranged between the substructure and mass body. According to a preferred embodiment of the invention however at least one of the movable bearings of the scissors-type pantograph is designed as an oscillating lever.


Scissors-type pantographs, and the lifting scissors-type arrangements known for example from rising floors, generally have in both the region of the substructure and in the region of the platform supported for example by the scissors, in each case a fixed bearing arrangement and a movable bearing arrangement. In this connection the movable bearing arrangement in the known scissors-type arrangements is designed in the form of a fulcrum slide, which is slidably guided in a straight line, for example in an oblong hole or in a groove.
This implementation of the movable bearing is however structurally complicated, heavy, and also maintenance-intensive and subject to wear on account of the sliding straight-line motion. However, as the applicants have discovered, these disadvantages can be eliminated by designing at least one and preferably both movable bearings of the scissors-type pantograph in each case in the form of an oscillating lever. The oscillating lever has, compared to the sliding movement with a fulcrum slide and rail, the advantage that the associated arm of the scissors-type pantograph can be connected by means of the associated linkage to the mass body and substructure without using a lens arrangement but instead simply with an oscillating lever, which is structurally simple to control.
In this way a connection between the substructure, scissors-type pantograph and mass body is achieved which is both robust and also inexpensive to implement, is largely maintenance-free, and moreover is virtually free of play. The design of the movable bearing arrangements as oscillating levers in addition helps to save weight and installation space.
For the implementation of the invention, above all it is unimportant how the bearing points of the scissors-type pantograph are structurally designed, so long as the anticipated loads can be accommodated. According to a preferred embodiment of the invention at least one of the bearing arrangements of the scissors-type pantograph and of the suspension device is however designed as an elastomer bearing.


The design of one or more bearing arrangements, or even of all bearing arrangements of the scissors-type pantograph as elastomer bearings, has in particular the advantage that the suspension device can in this way be made even more robust, and at the same time the maintenance requirements can be reduced to a minimum. Besides this there is also an additional vibration damping in the micro-range, which reduces both the bearing stresses and material stresses and also - in particular in the case where the suspension device is used in the vehicle sector -significantly improves the comfort that can be achieved using the suspension device.
Finally, by the use of elastomer bearings a self-locking of the scissors-type pantograph under certain installation conditions, for example on account of the cosine component of the oscillatory movement of the movable bearings of the scissors-type pantograph designed as oscillating levers, can also be prevented.
According to a further embodiment of the invention it is envisaged that the suspension device comprises not only one but a plurality of scissors-type pantographs. In this way - above all independently of the specific structural design and arrangement of the scissors-type pantographs - a further improved guidance accuracy, better responsiveness as well as an increase in safety can be achieved, especially is use in vehicle construction.
In this connection, according to a further, particularly preferred embodiment the plane clamped by the linkages of one of the scissors-type pantographs is arranged perpendicular to the plane clamped by the linkages of a further scissors-type pantograph. This means in other words that at least two scissors-type pantographs are used, which are arranged in planes aligned perpendicular to one another. In this way the degree of freedom of movement of the mass body can be restricted with a particularly high degree of certainty and accuracy to movements along only one spatial direction, while any movements along the two other spatial directions are excluded. Also, undesirable rotations of the mass body about at least two axes of a


Cartesian co-ordinate system, i.e. for example rocking movements as well as pitching movements of a vehicle cab, can be reliably suppressed in this way.
According to a further embodiment of the invention the suspension device in addition comprises at least one connecting rod, for example a pull rod or a Panhard rod. In this case the connecting rod is arranged perpendicular to the plane clamped by the linkages of a scissors-type pantograph.
In this way an even better support of those forces is achieved that act perpendicular to the plane clamped by the scissors-type pantograph, or perpendicular to the principal direction of movement of the mass body. In the case where the suspension device is used in the automotive sector, this means for example an improved support, by suitably longitudinally arranged connecting rods, of the large longitudinal forces occurring in the event of a crash. However, the transmission of the transverse forces between the mass body and substructure acting parallel to the axes of rotation of the bearing of the additional connecting rod, can also be supported in this way.
A further, particularly preferred embodiment of the invention envisages that the whole suspension device is designed as a modular standardised-unit system. This means in other words that the essential constituents of the suspension device, in particular the bearings and rods of the scissors-type pantograph, are designed as mutually universally combinable standard structural parts. In this way a suspension device of widely varying dimensions can be produced particularly simply and cost-effectively by a suitable choice of the respective matching standard structural parts, and the suspension device can be used without any major structural modifications for example in widely different vehicle sizes or vehicle categories, or also to compensate any possibly occurring connection tolerances.
The invention is described in more detail hereinafter with the aid of examples of implementation and with reference to the accompanying drawings, in which:


Fig. 1 is a diagrammatic representation of an embodiment of a suspension device according to the present invention in an isometric view; and
Fig. 2 is a side view of a representation corresponding to Fig. 1 of the scissors-type pantograph of the suspension arrangement according to Fig. 1.
Fig. 1 shows in a highly diagrammatic, isometric representation one embodiment of a suspension arrangement according to the present invention. There can first of all be recognised a substructure 1 and a diagrammatically represented mass body 3 connected to the substructure 1 via a spring/shock absorber arrangement 2. Here, the substructure is intended to represent the front region of the chassis 1 of a lorry, while the indicated mass body denotes the driver's cab 3 of the lorry. The direction of travel 4 emerges at an angle from the plane of the diagram.
It can be recognised in Fig. 1 that the connection between the driver's cab 3 and the chassis 1 includes, apart from four spring/shock absorber arrangements 2, also two pull rods 5 arranged in the front region of the driver's cab, as well as a scissors-type pantograph 6 arranged in the rear region of the driver's cab. The pull rods 5, which are simply shown in a highly diagrammatic form, and which in reality do not run at an angle upwardly but instead run substantially horizontally, serve primarily as a longitudinal force support between the driver's cab 3 and the chassis 1. In particular the large longitudinal forces occurring in the event of a crash can be reliably controlled and transmitted between the chassis 1 and driver's cab 3 thanks to the pull rods 5. The pull rods 5 can however also be implemented so that they additionally provide a certain degree of transverse stabilisation in the front region of the driver's cab 3.
The scissors-type pantograph 6 connecting the driver's cab 3 and the chassis 1 can be recognised in the rear region of the driver's cab 3, and in Fig. 2 is also shown on an enlarged scale in a rear view, referred to the driver's cab 3. It can be seen in Fig. 2 that the scissors-type pantograph 6 comprises seven linkages, which are identified


by the letters A, B, C, D, E, F and G. Of the linkages A to G, A and F are fixed to the frame, whereas B and E are fixed to the driver's cab.
On account of the particular kinematics of the scissors-type pantograph according to Fig. 2, the lateral rocking movements of the driver's cab 3 relative to the chassis 1 are supported via the linkages A, B, E and F, by means of which the driver's cab 3 and chassis 1 are to a first approximation always maintained parallel to one another. Accordingly, a relative rocking movement of the driver's cab 3 relative to the chassis 1 does not occur.
Only in the case of relatively large vertical deflections between the driver's cab 3 and chassis 1 does the change in the vertical distance of the bearing points D and E and G and F, connected with the cosine component of the oscillatory movement of the oscillating levers 7 and 8, take effect, and produces a slight but nevertheless definite relative rocking movement between the driver's cab 3 and chassis 1. However, this is not important in practice since the vertical relative movement between the driver's cab 3 and chassis 1 that occurs when the driver's cab is evacuated is always only in the range of a few centimetres to at most a decimetre. The order of magnitude of the change of the vertical distance of the bearing points D and E and G and F is thus negligible.
Static or dynamic transverse forces that occur are however transmitted directly via the linkages A, C and B between the driver's cab 3 and chassis 1, so that - in any case in the region of the scissors-type pantograph 6, and in the present embodiment therefore in the rear region of the driver's cab 3 - no additional lateral guidance or support of the driver's cab 1 is necessary. The vertical movement between the driver's cab 3 and chassis 1 remains completely unobstructed however on account of the free vertical movability of the linkage points B and E relative to the linkage points A and F, and as intended is absorbed and dissipated simply by the spring/shock absorber arrangements 2.


As a result it thus becomes clear that, thanks to the invention, a suspension device is created for the antivibration suspension of a mass body, in particular the driver's cab of a lorry or commercial vehicle, with which the intended degree of freedom of movement of the mass body can be reliably determined in a structurally robust manner, whereby at the same time undesirable movements along other spatial directions are effectively damped or suppressed. The invention thus permits in a low-maintenance and cost-effective manner the reliable and comfortable antivibration suspension of in particular vehicle cabs and the like.
The invention thus provides an important contribution as regards improving safety and reliability, in particular in the field of commercial vehicle and lorry technology, and specifically in the case of applications in which economic considerations and cost savings, combined at the same time with high quality requirements, play a role.


Reference numeral list
1 Substructure, chassis
2 Spring/shock absorber arrangement
3 Mass body, driver's cab
4 Direction of travel
5 Pull rod
6 Scissors-type pantograph
7,8 Oscillating levers
A to G Linkages

WE CLAIM:
1. Suspension device for the antivibration suspension of a mass body (3), in particular a driver's cab of a lorry or commercial vehicle, relative to a substructure (1), in particular relative to a vehicle chassis, the said suspension device comprising a spring/shock absorber arrangement (2) arranged between the mass body (3) and substructure (1), for damping impacts and vibrations, characterised in that the suspension device includes at least one scissors-type pantograph (6) for reducing the degrees of freedom of movement of the mass body (3).
2. Suspension device according to claim 1, characterised in that at least one of the movable bearing arrangements (DE, FG) of the scissors-type pantograph is designed as an oscillating lever (7,8).
3. Suspension device according to claim 1 or 2, characterised in that at least one of the bearing arrangements (A-G) of the scissors-type pantograph is designed as an elastomer bearing.
4. Suspension device according to one of claims 1 to 3, characterised in that the suspension device comprises a plurality of scissors-type pantographs (6).
5. Suspension device according to claim 4, characterised in that the plane clamped by the linkages (A-G) of a scissors-type pantograph (6) is arranged perpendicular to the plane clamped by the linkages (A-G) of a further scissors-type pantograph.
6. Suspension device according to one of claims 1 to 5, characterised in that the suspension device comprises at least one connecting rod (5) arranged perpendicular to the plane clamped by the linkages (A-G) of a scissors-type pantograph (6).

Suspension device according to one of claims 1 to 6, characterised in that the suspension device is designed as a modular standardised-unit system comprising rods and linkages.

ABSTRACT
The invention relates to a suspension device for the antivibration suspension of a mass body (3) relative to a substructure (1), for example of a driver's cab (3) of a lorry or commercial vehicle relative to the vehicle chassis (1). The suspension device comprises a spring/ shock absorber arrangement (2) arranged between the mass body (3) and substructure (1) for damping impacts and vibrations.
The suspension device is characterised according to the invention by the fact that it includes at least one scissors-type pantograph (6) for reducing the degrees of freedom of movement of the mass body (3).
The suspension device according to the invention is structurally robust and enables the envisaged degree of freedom of movement of the mass body to be reliably determined and also enables undesirable movements along other spatial directions to be damped or suppressed. The invention thus provides a cost-effective and operationally reliable antivibration suspension of, in particular, lorry and commercial vehicle cabs.
To,
The Controller of Patents,
The Patent Office,
Mumbai