Method and an arrangement for obtaining a translatory movement between two mutually contacting bodies

A method of obtaining a translatory movement between two mutually contacting bodies. A wave formation is caused to move along one active portion of at least one of the bodies, which active portion is in contact with the other body. The wave formation either causes an interruption in the contact between the bodies and separates two parts of the active portion which is in contact with the other body, or forms a contact between the bodies and separates two parts of the active portion which are not in contact with the other body. The distance between two arbitrarily selected points of respective pairs of the separated parts measured along the surface of the active portion will then be longer than the shortest distance between the same points. An arrangement using the method for obtaining a translatory movement of one body relative to another with which it is in contact is also described.

The present invention relates to a method of obtaining a translatory 
movement between two mutually contacting bodies and to an arrangement for 
obtaining a translatory movement of one body relative to another with 
which it is in contact. 
BACKGROUND AND PRIOR ART 
When driving vehicles through wooded or rough country, the difficulties 
encountered in advancing the vehicle and the damage caused to the ground 
when driving create serious problems. Also, when advancing logs or three 
trunks in log-handling machines, it is difficult to effectively advance 
the logs without damaging the same. 
The abovementioned problems can be generalised by saying that it is 
difficult to create movement between two mutually contacting bodies when 
the body contacting the driving means by which the movement is to be 
effected has a shape which does not favour said movement, and to move said 
bodies without causing damage thereto. 
There are today certain known principles for creating movement between 
mutually contacting bodies. The principle most applied is the rolling 
principle. In this respect, many different apparatus are available which 
are equipped with wheels or belts. Movement between mutually contacting 
bodies can also be caused by means of walking. There are examples of 
mechanically driven apparatus which execute walking-like movements, and 
certain apparatus comprising inflatable hoses or cushions in which 
different forms of walking movements are achieved by inflating the hoses 
or cushions in accordance with different predetermined inflation patterns. 
In order for apparatus which apply the rolling principle, and mechanical 
walking apparatus to successfully negotiate obstacles, it is necessary to 
make them both complicated and bulky. Such apparatus often operate with 
relatively small contact surfaces, and hence the contact pressure is high. 
Attempts to increase the contact surfaces, thereby to reduce the contact 
pressure, often results in large, bulky apparatus. Apparatus which use 
hoses or cushions of different kinds to obtain a walking-like movement 
have a very low advancing speed. 
THE INVENTION 
It is a primary object to provide a method by which a translatory movement 
can be obtained between two mutually contacting bodies and which can also 
be applied with irregularly shaped bodies and in which the contact 
pressure between the bodies is low and the bodies are subjected to 
practically no damage, and in which the aforementioned disadvantages are 
eliminated or greatly reduced. 
Briefly at least one wave is caused to move along an active portion of at 
least one of said bodies, said portion contacting the other of said 
bodies, and in which said wave either causes the contact between said 
bodies to be broken and separates two parts of said active portion in 
contact with said other body, or forms a contact between said bodies and 
separates two parts of said active portion which are not in contact with 
said other body; and causes the distance between any two points of 
respective pairs of said parts measured along the surface of the active 
portion to be longer than the shortest distance between said points. 
The invention also relates to an arrangement for use with the method of 
causing a tranlatory movement relative to another body with which it is in 
contact. 
Thus, the invention is based on the use of waves in accordance with the 
definition above, which are advanced in an active portion which is 
substantially stationary relative to the body in contact therewith. The 
part or parts of the active portion in contact with an opposing body is or 
are not therewith diplaced relative thereto, and hence there is no sliding 
motion at the contact surface. The only movement of the active portion 
relative to the body with which it is in contact takes place at the part 
of the parts of the active portion which, as a result of the formation of 
the wave, is or are not at that moment in contact with said body. 
By active portion is meant a portion in which waves as hereinbefore defined 
can be formed and moved in any direction. Thus, each wave tends to provide 
a relative displacement of the body with which the active portion is 
connected in the direction of wave propagation relative to the opposing 
body. 
The active portion may have the form of a continuous path in which waves 
are caused to circulate. The waves can be created and/or propelled by 
means of at least one roller which is displaceable relative to the active 
portion. In accordance with a further embodiment, this is effected by 
means of pneumatically or hydraulically inflatable cushions which are 
filled and evacuated cyclically. 
Conveniently, the active portion may comprise an outer flexible layer which 
at least partically defines a space having an internal pressure above the 
ambient pressure. Said space may, for example, be filled with an elastic 
material, e.g., a foamed plastics material. The wave mat may also be 
pre-tensioned (pre-formed) to the desired wave form.

FIG. 1a is a schematic, longitudinal sectional view of an arrangement 
adapted to perform a translatory movement relative to another body with 
which it is in contact. The arrangement 1 may, for example, comprise a 
vehicle which is to be moved relative to a supporting surface 2. The 
vehicle 1 is provided with an active portion in the form of a wave mat 3 
which is in contact with the surface 2 and in which waves can be formed 
and moved. The active portion 3 is fixed at its ends to the vehicle 1. The 
surface pressure is relatively low, since the weight of the vehicle is 
distributed over the bottom surface. 
As illustrated in FIG. 1b, a wave 4 of positive amplitude is formed in the 
active portion 3 for the purpose of propelling the vehicle 1. The wave 4 
is moved to the right as seen in the figure, as will be evident from FIGS. 
1b-1h, and during movement of the wave along the active portion, an 
interruption will be formed between the active portion 3 and the support 
surface 2 such that the action portion 3 is in contact with said surface 2 
at two parts which are separated by said interruption. 
During passage of the wave 4 along the wave mat 3, those parts of the mat 
which are in contact with the surface 2 will be stationary relative 
thereto, and hence there is no sliding motion between the mat and the 
support surface. The only displacement of the mat 3 relative to the 
support surface 2 takes place in the wave 4, when part of the mat defining 
said interruption is lifted from the surface. This is illustrated in FIGS. 
1d-1f, from which figures it will be seen that the points A and B on the 
wave mat are not moved when the wave 4 is moved between said points. An 
intermediate point C on the wave mat, however, will be lifted up by the 
wave 4 and moved back into contact with the support surface 2 at a 
distance .DELTA. s in front of its previous position. This applies to all 
the points along the wave mat passed by the wave, and hence when a wave 4 
has passing along the whole of the wave mat, the mat will have been moved 
a distance .DELTA. s to the right without any sliding taking place between 
the mat and the support surface. Thus, as indicated in FIG. 1a, a chassis 
1 connected to the mat will also have been moved through the same distance 
.DELTA. s. 
In FIGS. 2a-2i there is illustrated in a similar manner, and with the same 
references as those used in FIG. 1, the manner in which a tranlatory 
movement is effected between two bodies with the aid of a wave which 
passes along an active portion of one of said bodies, e.g., a vehicle 1, 
said active portion having the form of a wave mat 3. As will be seen in 
FIG. 2, there is used in this case, however, a wave 5 of negative 
amplitude, the wave mat 3 only making contact with the support surface 2 
at said wave, which thus separates two parts of the wave mat which are not 
in contact with said support surface. Similarly to the case of FIG. 1 no 
sliding takes place between the wave mat 3 and the support surface. In the 
embodiment shown in FIGS. 2d-2f, the point C on the wave mat is urged down 
by the wave 5 in contact with the support surface 2 at a position somewhat 
in front of its position relative to the support surface (as seen in the 
direction of wave movement) before the wave 2 reaches said point C, and is 
again lifted from the support surface to a position located at a further 
distance in front of the position in which it previously made contact with 
said support surface 2. Thus, also in this case, the wave mat 3, 
subsequent to the wave 5 travelling along the whole of the mat moves 
through a distance .DELTA. s. 
Thus, when the wave mat 3 has been moved through a distance .DELTA. s 
relative to the support surface 2 whilst a wave passes along said mat, a 
chassis connected to the mat will be moved through the same distance, as 
illustrated in FIGS. 1 and 2. In that case when only the ends of the wave 
mat are connected to the chassis as illustrated schematically in FIGS. 1 
and 2, said movement will take place in distinctive steps. However, by 
connecting the wave mat to the chassis 1 along the whole of the length of 
the mat, e.g., by means of an elastic material, such as foamed plastics, 
said movement will take place successively during passage of the wave 
through the active portion and will be extremely uniform, especially if a 
multiplicity of sequential waves are applied. 
Although, for the sake of simplicity, it has been assumed that the device 1 
is a vehicle, it will be understood that, instead, if the device 1 is held 
stationary the opposing body 2 will be displaced in the opposite direction 
to the assumed direction of movement of the vehicle. Thus, the principle 
upon which the invention is based can be used to provide the desired 
movement between two mutually contacting bodies. In the case of movement 
of more than two bodies, the movement can always be divided into a number 
of cases of movement between two bodies. 
FIGS. 3 and 4 illustrate schematically the movement of waves of positive 
and negative amplitude referenced 6 and 7, respectively, in a respective 
active portion 8 and 9 in the form of an endless path. 
FIGS. 5 and 6 illustrate how two bodies each having an active portion may 
act against each other to achieve specific movements. In the example shown 
in FIG. 5, the active portions 10 and 11 of the two bodies 12 and 13, 
respectively, are in contact with each other, whilst in the example 
illustrated in FIG. 6 the active portions 16 and 17 of respective bodies 
14 and 15 are in contact with nonactive portions of the other body. 
The aforedescribed FIGS. 1-4 are only intended to illustrate the principle 
of obtaining a movement by using waves in accordance with the invention. 
In practice, it should be possible to utilize continuous waves, such as 
sinus waves. FIGS. 7-9 illustrate schematically three exemplary methods of 
creating and moving continuous waves in an active portion of a vehicle. 
FIG. 7 is a longitudinal view of a schematically illustrated vehicle 18 
having an active position in the form of a wave mat 19. The wave mat 19 
may be made of any material whatsoever, in which waves can be formed and 
moved. For example, the mat may be made of a flexible and strong sheet 
material or may include links which are pivotally joined together. The 
wave mat 19 is in contact with a support surface 20. 
The wave mat 19 defines a closed space between said mat and the vehicle 18, 
in which space an internal pressure above ambient pressure prevails. As 
illustrated in the figure, waves can be formed by means of rollers 21, 
which waves can be moved relative to the vehicle 18 by displacing the 
freely mounted rollers 21 along the mat 19, thereby to cause displacement 
of the vehicle in the same manner as that illustrated in FIGS. 1 and 2. 
The inner over-pressure can be produced, for example, by means of gas 
pressure or liquid pressure, although the space may also be filled with a 
resilient material, such as foamed plastics, which may be bonded to the 
inner surface of the mat 19 and/or the vehicle 18, thereby to provide 
uniform movement of the vehicle. 
FIG. 8 illustrates schematically an alternative manner of creating and 
moving waves in the wave mat 19. In this embodiment there is used a 
plurality of inflatable cushions 22 which are mounted close to each other 
and to the wave mat 19 and which can be inflated and evacuated cyclically. 
By inflating a suitable combinaton of adjacent cushions 22 a wave 
formation such as that shown in the figure can be formed when an 
over-pressure prevails between the upper rigid portion of the vehicle 18 
and wave mat 19. This wave formation can be caused to move relative to the 
vehicle 18 by cyclically evacuating and inflating the cushions in 
sequence, as will readily be perceived by one of normal skill in the art. 
As an alternative to using an inner over-pressure in the active portion, 
the active portion can be pre-tensioned to form the desired waves which 
can be moved along said portion. This can be achieved, for example, by 
forming the active portion from a plurality of layers pre-tensioned 
against each other and which layers are elastically connected together. 
Such an embodiment is illustrated in FIG. 9, in which waves are formed by 
means of three layers 22, 23, 24 comprising links which are pivotally 
connected together. The upper layer 22 is longer than the rigid portion 18 
of the vehicle and is attached thereto by means of elastic cushions 25, 
which can be inflated and evacuated cyclically. In this way, the layer 22 
can be brought to the desired wave form. The underlying layers 23 and 24 
are both longer than layer 22, and the layer 24 is longer than the layer 
23. The layers 23 and 24 are connected to the overlying layer by means of 
cushions 26 and 27, respectively. The wave form is amplified from layer to 
layer, and in the illustrated example the wave form required for the 
purpose on hand has been achieved with three layers and spacious cushion 
volume. This wave form is transmitted to the mat 19 by the fact that the 
links of the underlayer 24 are fixed to the mat. If desired, however, the 
mat can be dispensed with. The waves obtained can be caused to move in one 
or the other direction by cylically inflating or evacuating the resilient 
cushions in a manner which is principle the same as that disclosed with 
reference to FIG. 8. The cushions can be inflated with gas or liquid. 
An alternative method of creating a pre-tensioned wave form is to use three 
mutually elastically connected layers in which the centre layer is shorter 
than the other two layers and in which said other two layers are 
preferably of equal length. Such a construction will create a wave form 
which can be moved with the aid of external means, such as rollers, or 
when the elastic connection between the layers has been provided by means 
of inflatable cushions, by cylically inflating and evacuating said 
cushions in the manner described with reference to FIGS. 8 and 9. A wave 
mat of this kind need not abut a rigid part of the vehicle. 
A pre-stressed wave mat having an active portion can be mounted on a 
resilient carrier cushion having a form which can be adapted to the form 
of the supporting surface. Such a carrier cushion may, for example, be a 
cushion filled with gas or liquid or have the form of a resilient cushion, 
such as a cushion filled with foamed plastics. When the cushion is filled 
with a gas or liquid, it may comprise sections by means of which a vehicle 
with which the cushion co-operates can be orientated horizontally by 
varying the pressure in the different sections of the cushion. 
A vehicle according to the invention is schematically illustrated in FIG. 
10. The vehicle comprises a rigid part 28 having a motor 29, a compressor 
30 and an oil tank 31. The rigid part 28 is supported on a large carrier 
cushion 32. The underside of the carrier cushion is provided with 
inflatable drive cushions (see FIG. 8) in a manner such that waves can be 
formed and moved along the surface by filling and emptying the cushions in 
accordance with a given cycle. Hoses 33 are drawn along the underside of 
the carrier cushion 32 and connected to the drive cushions. The hoses are 
connected to a valve unit 34 which, in turn, is connected to the 
compressor 30. The valve unit 34 controls the filling and emptying of the 
drive cushions. When the vehicle meets an obstacle 35, the carrier cushion 
32 is moulded to the shape of the obstacle thereby ensuring close contact 
with the support surface. The contact surface is constantly large and 
therefore good accessibility and low contact pressure is obtained. The 
damage to the ground will be negligible. 
An arrangement according to the invention may be made, for instance, in the 
shape of a feeding device for trunks and logs, as illustrated in FIG. 11. 
This device comprises two mouldable carrier cushions 36 and 37 which face 
each other and which are so designed that waves can be formed and moved in 
the surfaces of the carrier cushions. The surfaces of the carrier cushions 
are provided with inflatable drive cushions (see FIG. 8) which create and 
move said waves. The drive cushions are supplied with oil from a 
compressor through hoses 38 and 39. Two valve units 40 and 41 control the 
filling and emptying sequence, respectively. A tree trunk 42 placed 
between the advancing means will be advanced in the opposite direction to 
the wave propagation direction in the active portions of the carrier 
cushions 36 and 37. The carrier cushions will mould themselves to the 
shape of the trunk and effectively advance the trunk without causing 
damage thereto. 
When a carrier cushion of the type used in the FIG. 11 embodiment is 
arranged with the active portion substantially horizontal, it can also 
serve as a conveyor. Objects in contact with the wave crests of such a 
conveyor will in accordance with the above be transported in opposite 
direction to the direction in which the waves are propagated, which means 
that it can also be used to separate large objects from smaller objects, 
since smaller objects which fall down into the valleys between the wave 
crests will naturally be conveyed in the direction of propagation of the 
waves. 
A common feature of all the aforedescribed embodiments is that there is 
used at least one active portion having a wave mat which is stationary 
relative to the device provided with said active portion, in which mat 
waves are moved relative to said device. The method of creating and moving 
waves, however, can be varied as desired and the aforedescribed 
embodiments are not to be considered as restrictive of the invention. The 
invention can be applied in many fields and the aforedescribed fields of 
use are only to be considered as examples in which the invention can be 
applied.