"Fan folded drive belt for a ""V"" pulley drive"

A pulley and "V" belt drive arrangement has a flexible belt disposed to transmit drive forces between two spaced "V" groove pulleys. The flexible belt is constructed from a single fan-folded metal strip which is maintained in a continuous loop by one or more continuous metal bands. The bands are disposed in a U-shaped saddle or slot area formed in the fan-folded belt. The sidewalls of the saddle prevent lateral migration of the bands. The band length is sized to provide a compression load on the fan-folded belt to prevent longitudinal separation of the ends of the belt during torque transmission between the pulleys.

BACKGROUND OF THE INVENTION 
This invention relates to flexible drive belts and more particularly to 
metal V-belt structures having continuous band members to maintain the 
belt in a continuous loop. 
Flexible metal V-belts are comprised of a plurality of drive blocks 
maintained in a continuous loop by metal bands. The bands are generally 
disposed in slots opening transverse to the belt. The slots are shaped to 
prevent band migration from the slot and also to prevent the drive blocks 
from moving inward relative to the bands. This structure has been used for 
both fan-folded type assemblies, such as that shown in U.S. Pat. No. 
4,581,002 issued Apr. 8, 1986, to Cataldo, as well as a more well-known 
"Van Doorne" type belt. 
It has been proposed in the prior art to provide a single set of centrally 
disposed continuous bands to maintain the belts in a continuous loop. In 
these arrangements, the bands are disposed in a central slot which opens 
outwardly. The slot is either completely closed by a pin, such as that 
shown in U.S. Pat. No. 4,080,841 issued Mar. 21, 1978, to Vollers, or by 
displacing metal fingers after assembly to capture the bands, as seen in 
U.S. Pat. No. 4,386,921 issued June 7, 1983, to Roberts, or by designing 
the slot shape to require flexing of the bands about the longitudinal axis 
at assembly, as seen in U.S. Pat. No. 4,465,469 issued Aug. 14, 1984, to 
Cataldo. 
Each of these design and assembly techniques has drawbacks. Transverse 
slots require two sets of bands and accurate profile machining of the slot 
structure. The other assembly techniques require additional time and/or 
metal to complete the assembly. 
SUMMARY OF THE INVENTION 
The present invention overcomes these problems by providing a single 
fan-folded belt with a U-shaped centrally disposed slot or saddle. The 
continuous band members are shorter in length than the free loop length of 
the belt so that the fan-folded belt is compressed sufficiently to prevent 
separation of the ends of the fan-folded material while it is traveling 
between the pulleys. The compression also maintains the belt in a columnar 
structure between the pulleys thereby inhibiting separation between the 
fan-folded belt and the continuous band member. 
It is therefore an object of this invention to provide an improved drive 
belt and pulley assembly wherein the drive belt has a fan-folded belt 
portion and a plurality of continuous bands, and further wherein the belt 
portion is formed in a continuous loop and has a central U-shaped saddle 
area in which the bands are disposed, and also wherein the bands each have 
a length sufficiently shorter than the free loop length of the belt to 
cause compression loading in the belt loop to prevent separation of the 
ends of the fan-folded belt. 
It is another object of this invention to provide an improved fan-folded 
belt for a belt and pulley drive wherein the belt has a continuous loop 
portion formed from a strip of preformed metal with a longitudinally 
extending U-shaped saddle portion and a plurality of continuous metal band 
members disposed in the saddle portion to maintain the free ends of the 
loop portion in abutment, and wherein the bands each have a respective 
length such that at assembly, a compression force in the range of 135 to 
800 pounds is imposed on the fan-folded portion to prevent separation of 
the free ends of the fan-folded portion during operation of the belt and 
pulley drive and also to ensure that a minimum compression load is 
maintained in the belt structure when the span in the pulley structure is 
traversed. 
These and other objects and advantages of the present invention will be 
more apparent from the following specification and drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1 of the drawings, there is seen a belt drive and pulley 
assembly, generally designated 10. This assembly 10 includes a pair of "V" 
groove pulleys 12 and 14 and a fan-folded metal belt assembly 16. The belt 
assembly 16 frictional engages "V" grooves in the pulleys 12 and 14 to 
provide for torque transmission between the pulleys. 
The pulleys 12 and 14 are preferably of the variable "V" groove type. The 
structure of such pulleys is well-known. It is also known that the belt 16 
engages the pulleys 12 and 14 at the pitch diameter thereof such as 18 on 
pulley 14. The pulleys 12 and 14 are represented in phantom in FIG. 2. 
Each of the pulleys has a fixed member 20 and a movable member 22. The 
movable member 22 is slidably disposed on a shaft portion 24 which is 
integral with or otherwise fastened to the fixed portion 20. As the 
movable portion 22 is moved toward and away from the fixed portion 20, the 
belt assembly 16 will move outward and inward, respectively, in the 
direction of Arrow A. 
When this movement occurs, the operating pitch diameter 18 will move 
accordingly. If the belt assembly 16 moves upwardly, as seen in FIG. 2, 
the pitch diameter 18 will also move upwardly and vice versa. It should 
also be appreciated that the pulleys 12 and 14 operate in concert but in 
opposite directions. If the "V" groove pulley 12 is forcing the belt 
assembly 16 in the "V" groove outwardly, the pulley 14 will be adjusted to 
permit the belt assembly 16 to move inwardly. This permits a variable 
speed and torque ratio to be attained between the pulleys 12 and 14. The 
belt 16 is comprised of a fan-folded belt portion 26 and a plurality of 
continuous metal bands 28. 
As best seen in FIG. 3, the fan-folded belt portion 26 has alternating long 
folds 30 and short folds 32. This type of structure has been called a 
skip-folded belt. The long folds 30 include a drive block portion 34 which 
is generally trapezoidal in shape and has drive edges 36 and 38 which are 
operable to frictionally engage the surfaces of the fixed and movable 
members 20 and 22. The short folds 32 have a separator bar portion 40 
which also has tapered sides 42 and 44. These tapered sides likewise 
frictionally engage the members 20 and 22. 
These components of the fan-folded belt 26 are seen in the unfolded state 
in FIG. 4. Each drive block 34 is connected to a separator bar 40 by a 
pair of straps 46. Likewise, each separator bar 40 is connected to the 
next successive drive block 34 by a pair of straps 46. Each drive block 34 
is connected at a fold line 48 to the next successive drive block and each 
separator bar 40 is connected to the next successive separator bar 40 at a 
fold line 50. 
Each pair of straps has a fold line 52. During the fan-folding process, the 
adjacent drive blocks 34 are brought into substantial abutment with each 
adjacent separator bar 40. The straps 46 are folded at their respective 
fold line 52 and cooperate with the adjoining drive block 34 and separator 
bar 40 to form a U-shaped slot or saddle 54 which, as seen in FIG. 2, 
opens outwardly relative to the belts and pulley arrangement. 
As seen in FIG. 4, prior to fan folding, this U-shaped slot is a 
rectangular cut-away bounded by a drive block 34, a separator bar 40 and 
adjoining straps 46. The belt member 26 can be stamped or otherwise formed 
from a continuous metal strip. After folding, the fan-folded portion 26 is 
placed in a continuous loop. The belt assembly is then completed by 
compressing the continuous band members 28 in the U-shaped saddle or slot. 
The free ends of the fan-folded portion 26 can be separated to permit the 
bands 28 to be installed, then the fan-folded portion 26 is compressed to 
permit the free ends thereof to be placed in abutment. 
The length of the bands 28 are sufficiently shorter than the free loop 
structure of the fan-folded belt 26 so as to impose a compressive loading 
in the range of 135 to 800 pounds on the belt assembly. The amount of 
compressive loading is determined in part by the torque loading to be 
imposed on the belt 16 and also by the amount of tension force the belt 
might incur while traversing the slack or unloaded span between the 
pulleys 12 and 14. 
The compressive loading in the fan-folded portion 26 is also defined to be 
sufficient to prevent the fan-folded portion 26 from deflecting inwardly 
during movement between the pulleys 12 and 14. As can be seen in FIG. 2, 
the straps 46 extend outwardly and prevent lateral migration of the bands 
28 relative to the fan-folded structure 26.