Note: Descriptions are shown in the official language in which they were submitted.
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Description
"Power rransmission Belt"
Technical Field
This invention relates to power transmission
belts, and in particular to power transmission belts
adapted for carr~ing high loads.
Background of the Invention
In one form of known power transmission belt
adapted for transmitting high loads, an endless steel
band is provided with a plurality of V-shaped metal
blocks. Examples of such constructions are shown
in U.S. Letters Patent 3,949,621, 4,303,403, and
4,342,561. As shown therein, each block is mounted
to the steel band and includes a projection and recess
on one side of the head surface. The blocks are longi-
tudinally spaced and are arranged in face to-face
abutting relationship to the steel band.
Such power transmission belts, while providing
for high load transmission, have not proven completely
satisfactory in the art because of the substantial
weight thereof. Further, such belts generate high
levels of noise requiring sound deadening means, such
as oil baths and the like.
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In U.S. Letters Patent 4,365,965, a V-block belt
is shown having a flat belt portion formed of a polymeric
resin and having V-blocks mounted thereto formed of
polymeric resin. As disclosed therein, the belt con-
struction is extremely complicated and expensive.
In U.S. Letters Patent 4,305,714, a heavy duty
power transmission belt is shown to be formed of a
lamination of rubber impregnated fabric on a lower
surface portion of a cushion rubber layer so as to
provide cog projections on the inner surface of the
belt for engagement with a drive pulley. While this
belt construction provides improved flexibility, it
has a decreased ability to transmit high loads as
a result of the intrusion into the pulley of the cushion
rubber material which is conventionally of relatively
high resiliency. Another attempt to resolve this
vexatious problem has been the employment of metal
rods or pipes or wooden elements in the cogged portion
of the belt. Such materials are disadvantageous in
that wood is relatively weak and, when heated, the
synthetic resin strength characteristics decrease.
Such heating normally occurs from the engagement of
the belt with the pulley in the drive operation.
Thus, such belts have been found to present serious
problems in thereduction in strength and wear resistance.
In one form of the belt, the cogged portion is
formed of aluminum in an effort to reduce the weight.
Aluminum, however, hasbeen found to presentdisadvantages
in the low wear resistance thereof.
More recently, still another form of power transmission
belt adapted for high load -transmission has been developed.
As will become more apparent herein, this prior art belt
includes a tensile cord midportion, an outer reinforcing
plate portion, and an inner trapezoidal block portion.
Bolts are extended through the belt to secure the plate and
block portions to the tensile cord portion.
In Japanese Utility Model Application 48727/1983, a
cogged block structure for use in such a belt is disclosed
as being formed of a cloth wrapped in a spiral and
impregnated with either rubber or thermosetting resin. By
wrapping the cloth or fabric spirally, a more rigid block is
provided compared with a block formed of a plurality of flat
laminated fabric layers. Such a block, however, has been
found to have the vexatious problem of high noise
generation. If the rigidity of the block is decreased to
suppress the noise, its transmitting force has been found to
be adversely decreased. The prior art belts of this
configuration have had the disadvantages of relatively high
weight and cost and inconvenience in handling.
Summary of the Invention
The invention in one aspect pertains to a power
transmission belt for transmitting high loads, the belt
comprising an elastomeric flat belt portion defining an
outer surface and an inner surface with a tensile cord
extending longitudinally in the flat belt portion. A
plurality of pairs of aligned longitudinally, equally spaced
first and second blocks are adjacent the outer and inner
surfaces respectively of the flat belt portion, each block
comprising a core and fabric. The fabric may be wrapped
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around the core or a synthetic resin may be applied to the
fabric. Securing means extend through the Elat bel-t portion
and the cores of the aligned blocks for removably securing
the aligned blocks to the ou-ter and inner surfaces, the
blocks of the aligned pairs mutually defining anchor plates
for each other.
In one form, the fabric comprises rubberized fabric.
In another form, the fabric is subjected to a synthetic
resin, such as a thermosetting resin.
In the illustrated embodiment, the cogged blocks are
secured to the flat belt portion by bolts extended
therethrough.
In the illustrated embodiment, a plate may be provided
on the outer surface of the flat belt portion for
distributing the anchoring load to the flat belt portion.
The flat belt portion may be provided with one or more
layers of fabric in addition to the tensile cord and the
fabric may be disposed outwardly of the tensile cord,
inwardly of the tensile cord, or both inwardly and outwardly
2~ thereof.
The cross section of the cogged blocks may be varied
and, in the illustrated embodiment, is generally of
trapezoidal configuration. The corners of the blocks
adjacent the inner surface of the ~lat belt portion may be
rounded or angular, as desired.
The core of the blocks may be formed of selected
materials and may be provided with reinforcing short fibers,
as desired.
Each of the fabric and core may be formed of
different preselected materials in accordance with
the invention.
Illustratively, the fabric may be formed of woven
cloth consisting of cotton, synthetic, carbon, glass,
and metal fibers.
The synthetic fibersillustratively may comprise polyester
or nylon fibers.
The core may have any suitable cross-sectional
configuration and, in the illustrated embodiments,
is shown to comprise selectively circular or rectangular
cross-sectional configurations.
Any suitable rubber compound may be utilized
within the scope of the invention, including chloroprene,
Hypalon, epichlorhydrine, natural rubber, SBR, urethane
rubber, etc.
The rubber may be applied in the form of a paste
by being spread on the cloth or by being wiped with
a cloth by a friction method. Other impregnating
methods may be utili~ed in effecting the desired coating
of the fabric fibers.
The invention comprehends the inclusion of a
lubricant in the thermosetting resin of which the
core may be formed. It is desirable that the core
have a relatively low friction factor, such as in
the range of .l to .7. It is further desirable that
the core have a relatively low specific gravity so
as to minimi~e the weight thereof.
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Examples of thermosetting material used in the
core include phenol resins, epoxy resins, polyamide
resills, and unsaturated polyester resins. Where cut
fibers or fabric are provided in reinforcing the core,
they may be formed of any suitable material, such
as cotton fibers, synthetic fibers, glass fibers,
carbon fibers, and metallic fibers.
The fabric wrapped about the core may be in any
desired form, including woven fabric, and may be formed
of cotton fibers, synthetic resin fibers, such as
polyester or nylon fibers, carbon fibers, glass fibers,
and metallic fibers. The thermosetting resin of the
fabric may be any suitable resin including phenol
resin, epoxy resin, polyamide resin, and unsaturated
polyester rein.
The trapezoidal configuration of the blocks may
be effected by molding the blocks ln that configuration
after winding the fabric thereabout.
The core material and the cloth impregnating
material may be similar or dissimilar, as desired.
Illustratively, where the materials are dissimilar,
the core material may be formed of a material having
a low rigidity factor, such as a rubber compound having
98 of hardness and the material with which the cloth
is impregnated comprising a rubber compound having
a 96 hardness (9JIS A).
Where a dual cogged construction is desired,
the blocks may be provided on both the inner and outer
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surfaces of the belt, alt~ough, in the illustrated
embodiments, the blocks are shown only on the inner
surface.
The use of the novel core-wrapped block construction
provides for high rigidity of the cogged blocks, improved
facility and low cost in manufacture of the belt,
low noise generation by selection of the desired core
material, and controlled frictional characteristics
of the block for improved power drive transmission.
Thus, the belt construction of the present invention
is extremely simyle and economical while yet providing
the highly desirable features discussed above.
Brief Descr ption of the Drawing
Other features and advantages of the invention
will be apparent from the following description taken
in connection with the accompanying drawing wherein:
FIGURE 1 is a fragmentary perspective view of
a power transmission belt embodying the invention;
FIGURE 2a is a transverse section of a block
adapted for use in the power transmission belt hereof;
FIGURE 2b is a transverse section of a modified
form of such block;
FIGURE 2c is a transverse cross section of still
another modified form of such block;
FIGURE 3 is a transverse section of a belt con-
struction of the prior art;
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FIGURE ~ is a :Eragmentary longitudinal section o:E a
power transmisslon belt embodying the inven-tion utilizing
the bloc]c configuration of Figure 2a;
FIGURE 5 is a fragmentary longitudinal section of
another form of power transmission belt embodying the
invention utilizing a block construction as shown in
Figure 2b, and a modified form of anchor plate on the outer
surface of the flat bel-t portion; and
FIGURE 6 is a fragmentary side elevation illustrating
the coaction between the power transmission belt of the
present invention and a "V" pulley providing a high load
transmission power drive.
Best Mode for Carrying Out the Invention
Figure 3 illustrates the type of prior art power
transmission belt referred to in the Background of the
Invention (top of page 3) including a tensile cord
midportion, an outer reinforcing plate portion, and an inner
trapezoidal block portion. Bolts are extended through the
belt to secure the plate and block portions to the tensile
cord portion. A power transmission belt embodying the
invention is illustrated in Figure 1 to comprise a belt
generally designated 10 including a flat belt portion 11,
provided with a plurality of longitudinally extending
tensile cords 12. The fla-t belt portion defines an inner
surface 13 and an outer surface 1~. A plurality of
longitudinally spaced cog blocks 15 are moun-ted to the inner
surface 13.
As seen in Figure 1, the blocks are secured to
the flat belt portion by nut and bolt means 16
including bolts 17 and nuts 18. The bolts include head
portions 19. The bolts extend through outer anchor plates
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20, the flat belt portion 11, and the blocks 15, with
the heads 19 of the bolts engaging the anchor plates
20 and the nuts 18 engaging the undersurface of the
blocks 15, as seen in Figure 1. In the illustrated
embodiment,twoslich bolt meansare provided in association
with each of the blocks.
The invention comprehends the forming of the
blocks by the spiral wrapping of a fabric layer 21
about a core 22.
The core may have any suitable cross-sectional
configuration, and as shown in Figure 2a, the core
23 may have a circular cross section. As shown in
Figure 2b, the core 24 may have a rectangular cross
section, and more specifically, as illustrated therein,
may have a square cross section.
The core may be formed of a single material,
as illustrated in Figures 2a and 2b, or may comprise
a built-up construction generally designated 25, as
illustrated in Figure 2c. As shown in Figure 2c,
the built-up construction 25 may be formed of a plurality
of laminations 26. As will be obvious to those skilled
in the art, the core alternatively may be built up
by spirally wrapping a fabric.
In transverse cross section, the power transmission
belt may have a V-shaped configuration, as illustrated
in Figure 1.
The flat belt portion 11 may be formed of an
elastomeric material, such as rubber. Thus, the flat
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belt portion may be formed of one or more of natural
rubber, styrene-butadiene rubber, chloroprene rubber,
nitrile rubber, butyl rubber, and polyethylene
chlorosulfanate (Hypalon) rubber. Further, the core
may be formed of polyurethane rubber. Where the core
is formed of a fabric, the fabric may comprise nylon
cloth or Kevla ~ cloth. The cloth may comprise a bias
cloth of warp cotton yarns or wide angle cloth.
The tensilecords may comprise conventional material,
such as polvester, fatty polyamides, aromatic polyamides,
glass, twisted wires, etc., as desired, to provide
the high strength, low elongation characteristics
desired.
If desired, a shrinkable cloth formed of crimped
lS nylon warp or wooly finish cloth, in combination with
nylon wefts, may be provided on the lower surface
of the flat belt portion for improved retention of
the blocks to the flat belt portion.
In the embodiment of Figure l, the anchor plates
20 ma) comprise blocks formed generally in the same
manner as blocks 15 in that the anchor plates may
include a core portion 3~ and a fabric portion 37
wrapped about the core portion. Thus, in the embodiment
of Figure 1, the outer blocks 20 may be utilized in
providing a drive from the outer surface portion of
the flat belt portion.
In the embodiment of Figure 1, the upper and
lower blocks are shown to have somewhat different
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configurations, it being understood that the b:tocks
may be identical in cross-sectional configuration
and construction, or different9 as desired, within
the scope of the invention.
As discussed above, the blocks are arranged so
as to determine a generally trapezoidal cross-sectional
configuration by the suitable wrapping of the fabric
about the core.
Where the core is formed of an elastomeric material,
it may be formed of a molded rubber. The fabric may
be impregnated with similar rubber compound or may
be impregnated with a different material, as desired.
As discussed above, the use of nuts and bolts
as the anchoring means in mounting the blocks to the
lS flat belt portion is exemplary. As will be obvious
to those skilled in the art, other suitable means,
such as rivets, may be utilized. Additionally, spring
washers and/or conventional flat washers may be utilized
in locking the threaded securing means, as well as
for purposes of distributing the anchoring load.
The use of the improved block structures permits
facilitated mounting thereof to the flat belt portion,
while yet the blocks may be readily replaced as for
maintenance purposes. The improved block construction,
however, minimizes fatigue of the rubber layer between
the blocks and the tensile cords. The blocks may
beconstructedto provideimproved sidepressure resistance
and, as discussed above, to minimize noise generation
while yet pro~iding fol- transmission of high loads.
As indicated abo\e, the flat belt portion may
be further pro~ided with one or more fabric layers.
Such fabric layers rnay be provided outwardly of the
tensile cord, inwardly thereof, or both outwar-dly
and inwardly, as showll in Eigure 4, wherein a fabric
layer 27 is provided outwardly of the tensile cord
12, and a fabric layer 28 is provided inwardly thereof.
Still further, the flat belt portion may be provided
with an outer covering fabric 29 and an inner covering
fabric 30, as seen in Figure l. The use of the covering
fabric may be in lieu of or in conjunction with the
use of the fabric layers 27 and/or 28.
Experiments were conducted utilizing different
block materials. The test belt had a rope circumference
length of 750 mm, a belt top width of 32 mm, a belt
height of 15 mm, a block pitch of 11.5 mm, a belt
angle of 26, a flat belt height of 4 mm, and 17 tensile
cords. The dimension of the block in cross section
was 7 mm, a top side width of 10 mm, and a bottom
side width of 7 mm.
The block had a trapezoidal cross section with
a height of 4 mm, a bottom side width of 10 mm, and
a top side width of 8 mm.
25In the belt running test, the belt was engaged
with two pulleys having a diameter of 70 mm.
The test was run with the driving pulley operating
at a speed of S000 r.p.m., at no load, and at an ambient
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temperature of 20~ - 25 C. At the running speed
(5000 r.p.m.), the belt tension was 80-120 kilograms.
The test was conducted as follows: the block
sample was set on two supports having a 60 mm spacing.
A weight (w) was applied to the center of the sam-ple.
The bending strain (e) was measured, The bending
elastic modulus was determined by the following equation:
E = ~13/48eI (I = secondary moment).
The sound pressure was measured by a microphone spaced
one meter from the running test apparatus.
The result of the rigidity ratio and sound pressure
tests are shown below. The rigidity ratio was obtained
by setting the bending elastic modulus to one.
Rigidity Sound
15 No. Material of Block Ratio Pressure
1 Rubber only 1 8 7
2 2-ply rubber-coated glass
cloth wound around a
rubber core 3.8 88
20 3 5 plies of rubber-coated
glass cloth wound around
a rubber core 4.8 9
4 Rubber-coated glass cloth
spiral]y wound, only 5.2 95
Belts of Nos. 2 and 3, as indicated above, have
slightly increased soùnd pressure, but at a slightly
increased rate of increase of the sound pressure as
compared to the increase in rigidity, thus being similar
to the use of only rubber as the block material.
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Thc No. 4 belt rigidity i9 large, but has a disad-
vantageously raise(l soulld pressure.
Thus, the invention comprehends the rnounting
of trapezoida~ section blocksof wrapped core construction
at accurately spaced pitch intervals on the inner
surface of the flat be]t portion. The side pressure
resistance and rigidity of the belt is substantially
increased by the utilization of this construction,
thereby greatly improving the durability of the belt
as well as additional desirable characteristics.
Thus, the invention contemplates that the fabric
may be wrapped around the core material as a shaft
construction, thereby facilitating shaping to the
desired block configuration.
By suitable selection of the fabric and impregnating
material, a low frictional coefficient can be readily
obtained.
At the same time, low noise generation may be
provided as desired by suitably selecting the core
material.
By suitably selecting the core material and con-
figuration, control of the overall rigidity of the
belt is readily obtained. The bending elastic modulus
of the belt is substantially improved, such as in
a ratio of 5 to 1, where the spiral wrapped fabric
is utiliæed over the use of a laminated block construc-
tion.
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By permitting the use of re]atively inexpensive
materials in the core, the cost of the belt may be
substarltial~y redùced. Further, as inclicated above,
the core material may comprisea material having relatively
low density so that the weight of the belt is further
reduced.
The fabric may be impregnated not only with rubber
but also with thern,osetting resin, as indicated above.
The laminated fabric illustrated in Figure 2c may
be impregnated with thermosetting resin, also as desired.
Thus, illustratively, the core fabric may be impregnated
with the same thermosetting resin as employed in the
fabrics spirally wrapped about the core, if desired.
It has been found that the use of the thermosetting
resin impregnated cloth provides improved side pressure
resistance and rigidity, together with substantially
improved durabilit; of the belt.
The use of glass cloth impregnated laminate in
the core, such as illustrated in Figure 2c, provides
improved frictional coefficient of the block.
The thermosetting resin may be mixed with lubricant
so as to further decrease the coefficient of friction
of the block. It has been found possible to control
the frictional coefficient of the block to lie in
the range of approximately .1 to .7 quite easily in
this manner.
Illustratively, where glass fiber cloth is utilized
impregnated with epoxy resin and the cloth was
laminated in parallel, an elastic modulus Or the block
of 2 l50k&/~m2 was obtained. Where the clnth was
spirally ~ound, the modulus of elasticity increased
to 3,250kg/mm2
Where the glass fiber cloth laminate impregnated
with epoxy resin was utilized as the core material
and the outer cloth spirally wound around the core
material, a modu]us of elasticity of 3,0l5kg/mm2 was
obtained.
The core material may comprise a mixture of ther-
mosettin& resin and rubber compound so as to further
suppress the noise generation.
As shown in Figure 4, the flat belt portion ll
includes the fabric layers 27 and 28. The flat belt
may be formed of a suitable elastomeric material,
such as rubber blends of NR, SBR, CR, NBR, IIR, Hypalon,
or polyurethane rubber. The cords of the fabrics
27 and 28 may be arranged to extend primarily perpendi-
cularly to the longitudinal extent of the flat belt
portion. The cord fabric may be formed of suitable
materials, such as polyamide, aromatic polyamide,
polyester, glass, etc.
The covering fabric 29 may be applied in one
or more layers and may comprise nylon cloth, Kevlar
cloth, bias cloth made of warp cotton yarns, or wide
angle cloth. The covering layers are laminated and
bonded to the outer and inner surfaces in the conventional
manner.
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The tensile cords may be formed of suitable material
having high strength and low elongation,sllch as polyester,
polyamide, aromatic polyamide, or glass fibers, or
twisted wires.
The fabrics 27 and 28 serve as means for preven~ting
migration of the bolt means during use of the belt.
Still another embodiment of the belt is illustrated
in Figure 5 wherein the block 31 is provided with
rounded corners 32 in lieu of the angular corners
10 33 of the blocks 15 adjacent the inner surface 13
of the flat belt portion 11. The use of the rounded
corners provide for further improved flexibility in
the belt.
As seen in Figure 6, the belt provides a unique
cooperation with the drive pulley 34 in that the flexing
of the flat belt portion occurs between the blocks
15 received in the pulley grooves 35. Thus, as seen
in Figure 6, the belt assumes a somewhat polygonal
extension configuration in passing around the pulleys.
This has been found to minimize fatigue of the tensile
cordsand, thus, provide further improved long troublefree
life of the belt construction.
Thus, the invention broadly comprehends an improved
high load transmitting belt construction wherein cogged
blocks are mounted to the flat belt portion by suitable
securing means and wherein the cogged blocks are formed
of a core about which a treated fabric is wrapped
to define a generally trapezoidal cross section.
Thecross ~ection of the belt also isgelleral~y trapezoidal
in forming 9 V-belt configuration. The unique construc-
tion of the hlocks provides for improved control of
the friction, wear, and strength characteristics thereof
so as to provide an improved long, troublefree life
of the power transrnission belt notwithstanding the
use thereof in applications requiring high load trans-
mission.
