Composite driving belt

A composite driving belt in the form of an endless flexible carrier on which is mounted a plurality of plate-like elements disposed transverse to the carrier. The carrier is formed by a plurality of endless metal bands arranged in overlying concentric relationship, at least one side of at least one of the bands having surface roughness produced, for example, by two series of fine grooves which cross each other.

This invention relates to a composite driving belt of the kind comprising a 
flexible endless carrier on which is mounted a plurality of transverse 
plate-like elements. The invention relates especially to the structure of 
the endless carrier and to a method for making the carrier. 
BACKGROUND 
A known form of driving belt comprises an endless flexible metal carrier on 
which is mounted a plurality of plate-like elements disposed transverse to 
the carrier and in face-to-face contact with each other. The carrier is 
formed of one or more band packages each of which includes a plurality of 
endless bands arranged in overlying concentric relationship, i.e. arranged 
radially around each other. Belts of this kind are disclosed in U.S. Pat. 
Nos. 3,720,113 and 4,080,841. 
Belts of this kind have utility in variable ratio transmissions in which 
the belt runs over pulleys constructed of conical discs which are adapted 
to be displaced axially relative to each other so that the running 
diameter of the driving belt over the pulleys may vary. In practice, such 
a driving belt is under high tension in order to ensure a proper 
frictional contact between the pulleys and the transverse belt elements, 
and to properly conduct the transverse elements in the straight part of 
the belt. 
The efficiency of such a driving belt is rather high, but there remain 
internal losses in the belt as a result of frictional forces between the 
various parts. 
SUMMARY OF THE INVENTION 
It is the broad object of the invention to provide an endless carrier for 
the kind of driving belt described above in which at least one side of at 
least one of the endless bands forming the carrier has a surface 
profiling. Thus, the mutual friction between the bands disposed around 
each other is decreased, and this appears to have an efficiency increase. 
When the driving belt runs over the pulleys having different running 
diameters, the individual bands of the band package have a mutual speed 
difference, at least in situ of one of the pulleys. This speed difference 
may in practice be more than 1 meter per second between two successive 
bands, that is between one band and the overlying or underlying band. 
Moreover, notably the inner bands are pressed onto each other with 
substantial force, since the pressure force on a given band is built up by 
all bands disposed around that band. 
By providing, in particular, the more inwardly disposed bands at least at 
one side with a surface profiling, through which an improved lubrication 
between the bands will be produced, an improvement in efficiency occurs. 
Preferably, according to the invention, the surface profiling comprises 
parallel grooves. 
According to a further feature of the invention, the roughing value of the 
surface profiling lies between 0.30 and 0.75 .mu.m Ra (measured according 
to CLA method) and preferably between 0.45 and 0.55 .mu.m Ra. The CLA 
(Centerline Average) method is defined as follows: 
##EQU1## 
in which formula h.sub.i is the distance between the measured profile and 
the zero reference line (average line) along a line from x=0 to x=l. 
In a preferred embodiment of the invention, the grooves are disposed in two 
series of grooves, the grooves in one series being crosswise to the 
grooves in the other series. A good result is achieved when the metal 
bands are provided with the surface profiling only at the radial inner 
side. 
Furthermore, the invention relates to a method of applying a surface 
profiling on the radial inner side of an endless metal band. According to 
this feature of the invention, the metal band is rolled between rollers, 
one roller having a profiled circumferential surface. Preferably the 
profile is formed by a plurality of grooves, which may be arranged in two 
series crosswise to each other.

DETAILED DESCRIPTION 
FIG. 1 illustrates a driving belt having a carrier 10 on which are slidably 
mounted a plurality of plate-like elements 12 arranged transverse to the 
carrier 10 and in face-to-face contact with each other. The elements 12 as 
is conventional are generally trapezoid shaped in order that the belt will 
fit in a V-shaped pulley groove. 
The carrier 10 in the illustrated embodiment is formed of a plurality, for 
example, four flexible endless bands 14 arranged in overlying concentric 
relationship. The width of each band 14 may e.g. range between 5 and 20 mm 
and the thickness between 0.15 and 0.25 mm. The diameter of the band (in a 
circular condition) may e.g. range between 150 and 300 mm. 
At least one of the bands 14 has at least one of its sides profiled. In the 
embodiment illustrated in FIG. 2, the inner side is provided with a 
surface profiling formed by two series of parallel grooves 16 
(diagrammatically shown), the grooves of one series being crosswise of the 
grooves of the other series. The exterior surface 18 of the belt 14 is 
smooth.