U.S. patent application number 09/996436 was filed with the patent office on 2003-09-11 for low modulus belt.
Invention is credited to Sedlacek, Douglas R..
Application Number | 20030171181 09/996436 |
Document ID | / |
Family ID | 25542915 |
Filed Date | 2003-09-11 |
United States Patent
Application |
20030171181 |
Kind Code |
A1 |
Sedlacek, Douglas R. |
September 11, 2003 |
LOW MODULUS BELT
Abstract
The invention comprises a low modulus power transmission belt
having a multi-unit cord tensile member. The belt also comprises a
low modulus elastomeric body. A multi-unit cord tensile member
configuration is plied into the elastomeric body, the tensile cord
members having an included angle in the range of 120.degree. to
180.degree. between each ply. The belt having an elastic modulus of
less than 1,500 N/mm and having an elongation of approximately 6.8%
over a load range of approximately 0-350 newtons.
Inventors: |
Sedlacek, Douglas R.;
(Englewood, CO) |
Correspondence
Address: |
Jeffrey Thurnau
The Gates Corporation
Mail Stop 31-4-1-A3
900 S. Broadway
Denver
CO
80209
US
|
Family ID: |
25542915 |
Appl. No.: |
09/996436 |
Filed: |
November 28, 2001 |
Current U.S.
Class: |
474/263 ;
474/237; 474/260 |
Current CPC
Class: |
F16G 5/20 20130101; F16G
1/10 20130101; F16G 5/08 20130101 |
Class at
Publication: |
474/263 ;
474/237; 474/260 |
International
Class: |
F16G 001/00; F16G
005/00 |
Claims
I claim:
1. A belt comprising: an elastomeric body having a length and a
centerline; a tensile member embedded in the body; the belt having
an elongation of up to approximately 6.8% of a length over a load
range of approximately 0 to 350 newtons per strand.
2. The belt as in claim 1, wherein the tensile member further
comprises: a plurality of cords describing a pantograph form.
3. The belt as in claim 1, wherein the tensile member comprises: a
plurality of cords substantially parallel to a belt centerline.
4. The belt as in claim 1, wherein the tensile member comprises: a
woven material having a warp yarn and a weft yarn; and the warp
yarn describing an angle to a centerline greater than
0.degree..
5. The belt as in claim 1, wherein the tensile member comprises: a
woven material having a warp yarn and a weft yarn; and the warp
yarn substantially aligned with a belt centerline.
6. A belt comprising: an elastomeric body having a length and a
centerline; a tensile member embedded in the body; the belt having
an elastic modulus relative to a belt width and measured in the
longitudinal direction of the belt of less than approximately 1,200
N/mm.
7. The belt as in claim 6, wherein the tensile member further
comprises: a plurality of cords describing a pantograph form.
8. The belt as in claim 6, wherein the tensile member comprises: a
plurality of cords substantially parallel to a belt centerline.
9. The belt as in claim 6, wherein the tensile member comprises: a
woven material having a warp yarn and a weft yarn; and the warp
yarn describing an angle to a belt centerline greater than
0.degree..
10. The belt as in claim 6, wherein the tensile member comprises: a
woven material having a warp yarn and a weft yarn; and the warp
yarn substantially aligned with a belt centerline.
11. A belt comprising: an elastomeric body having a length and a
centerline; a tensile member comprising a woven material embedded
in the body; the belt having an elastic modulus relative to a belt
width and measured in the longitudinal direction of the belt of
less than approximately 1,500 N/mm.
12. The belt as in claim 11, wherein the tensile member comprises:
a woven material having a warp yarn and a weft yarn; and the warp
yarn describing an angle to a belt centerline greater than
0.degree..
13. The belt as in claim 11, wherein the tensile member comprises:
a woven material having a warp yarn and a weft yarn; and the warp
yarn substantially aligned with a belt centerline.
14. A belt comprising: an elastomeric body having a length and a
centerline; a tensile member comprising multi-unit cord embedded in
the body.
15. The belt as in claim 14, wherein: the belt having an elongation
of up to approximately 6.8% of a length over a load range of
approximately 0 to 350 newtons per strand.
16. The belt as in claim 14, wherein the tensile member further
comprises: a plurality of cords describing a pantograph form.
17. The belt as in claim 14, wherein the tensile member comprises:
a plurality of cords substantially parallel to a belt
centerline.
18. The belt as in claim 14, wherein the tensile member comprises:
a woven material having a warp yarn and a weft yarn; and the warp
yarn describing an angle to a centerline greater than
0.degree..
19. The belt as in claim 14, wherein the tensile member comprises:
a woven material having a warp yarn and a weft yarn; and the warp
yarn substantially aligned with a belt centerline.
20. The belt as in claim 14 further comprising: the belt having an
elastic modulus relative to a belt width and measured in the
longitudinal direction of the belt of less than approximately 1,200
N/mm.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a power transmission belt and more
particularly to a low modulus power transmission belt.
BACKGROUND OF THE INVENTION
[0002] Power transmission belts are widely used to transmit rotary
power. The belt is generally installed between a driver and driven
pulley, such as in the case of an accessory belt drive on a vehicle
engine.
[0003] The belt comprises a tensile cord embedded in an elastomeric
material. The tensile cord, or cords, are oriented parallel to a
longitudinal axis in order to maximize a load carrying capability.
The tensile cord is wound on a belt build in a continuous manner
during fabrication.
[0004] Power transmission belts must possess sufficient tensile
strength to allow a required torque, and load, to be transmitted
between pulleys.
[0005] A belt having a high tensile strength also will generally
have a commensurately high modulus. A belt having a high modulus
will be relatively stiff and subject to higher operating
temperatures. Further, installation of a prior art high modulus
belt requires moveable pulleys.
[0006] A low modulus belt may be used in situations were the torque
to be transmitted is relatively low. Low modulus belts are
fabricated using tensile cords having little or no preload, or, are
fabricated using tensile cords having a twist that allows for a
predetermined elongation under load.
[0007] Representative of the art is EP 0 625 650 to Gates that
discloses a low modulus belt having a tensile cord wound with a
preload in a longitudinal direction.
[0008] Also representative of the art is U.S. Pat. No. 4,229,254 to
Gill (1980) which discloses a belt having a reinforcing structure
having two plies of cords extending in cross bias layers.
[0009] Further representative of the art is U.S. Pat. No. 6,033,331
to Winninger et al. (2000) which discloses a belt having a
supporting structure such that the belt exhibits an average
stress-elongation slope ranging from 12 to 20 daN/% of elongation
per width centimeter.
[0010] The prior art teaches use of tensile cords that are wound in
a longitudinal direction for bearing a tensile load. The art also
teaches low modulus belts having a relatively moderate to high
modulus.
[0011] What is needed is a low modulus belt having a multi-unit
cord tensile member. What is needed is a low modulus belt having a
woven fabric tensile member. What is needed is a low modulus belt
having a tensile member describing a pantographic form. What is
needed is a low modulus belt having a modulus less than 1,500 N/mm.
The present invention meets these needs.
SUMMARY OF THE INVENTION
[0012] The primary aspect of the invention is to provide a low
modulus belt having a multi-unit cord tensile member.
[0013] Another aspect of the invention is to provide a low modulus
belt having a woven fabric tensile member.
[0014] Another aspect of the invention is to provide a low modulus
belt having a tensile member describing a pantographic form.
[0015] Another aspect of the invention is to provide a low modulus
belt having a modulus less than 1,500 N/mm.
[0016] Other aspects of the invention will be pointed out or made
obvious by the following description of the invention and the
accompanying drawings.
[0017] The invention comprises a low modulus power transmission
belt having a multi-unit cord tensile member. The belt also
comprises a low modulus elastomeric body. A multi-unit cord tensile
member configuration is plied into the elastomeric body, the
tensile cord members having an included angle in the range of
120.degree. to 180.degree. between each ply. The belt having an
elastic modulus of less than 1,500 N/mm and having an elongation of
approximately 6.8% over a load range of approximately 0-350
newtons.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The accompanying drawings, which are incorporated in and
form a part of the specification, illustrate preferred embodiments
of the present invention, and together with a description, serve to
explain the principles of the invention.
[0019] FIG. 1 is a plan view of a belt showing a tensile cord
arrangement.
[0020] FIG. 2 is a plan view of a belt showing a tensile cord
arrangement.
[0021] FIG. 3 is a plan view of a belt showing a tensile cord
arrangement.
[0022] FIG. 4 is an end view of a belt showing a tensile cord
arrangement.
[0023] FIG. 5 is an end view of a belt showing a tensile cord
arrangement.
[0024] FIG. 6 is an end view of a belt showing a tensile cord
arrangement.
[0025] FIG. 7 is a chart depicting the load versus elongation
behavior of the inventive belt.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0026] FIG. 1 is a plan view of a belt showing a tensile cord
arrangement. The inventive belt comprises a low modulus. A low
modulus allows a belt to have a higher flexibility. Flexibility
determines, in part, how much a belt temperature will increase
during operation. Since the inventive low modulus belt comprises a
belt having a relatively high flexibility, a relatively lower
operating temperature is realized. This in turn significantly
increases a belt lifespan.
[0027] Belt 100 comprises elastomeric body 10 and tensile cords 11
embedded, therein. Elastomeric body 10 may comprise EPDM or any
other elastomeric composition used in the belt arts including
natural rubbers, synthetic rubbers or blends thereof.
[0028] In the inventive belt tensile cords 11 and 21 are laid up on
a belt build during fabrication such that they form a pantographic
shape when viewed in plan. Tensile cords 11 and 21 describe an
included angle .alpha.. The included angle .alpha. is in the range
of 0.degree. to 180.degree. , or in the alternative an angle of
0.degree. to 90.degree. as measured from a width W of the belt. The
preferred range is 120.degree. to 150.degree..
[0029] Tensile cords 11 and 21 may comprise polyamide 4.6 or
polyamide 6.6, or any other cord material known in the belt tensile
cord art, including polyester and aramid, cotton, rayon,
fiberglass, steel, or blends or combinations of each.
[0030] Tensile cords 11 and 21 comprise a plurality of parallel
cords, known in the art as multi-unit cords, which are laid up on a
banner table so that when the tensile cord layers are applied to
the belt build the requisite included angle to a belt centerline CL
is obtained. In order to achieve the pantograph form shown in FIG.
1 and FIG. 2 the tensile cord sheets, each having a reciprocal
angular relation to a belt centerline CL, are laid up in
alternating layers, one on top of the other on the belt build. More
particularly, a first multi-unit cord layer 11 having an
orientation on a given diagonal to a belt CL is laid into a belt
build. Then a second multi-unit cord layer 21 having an opposite
orientation to the first multi-unit cord layer is laid into the
belt build; thereby establishing the included angle .alpha.. Layers
of elastomeric are also included in the belt build as is known in
the art. The multi-unit cord tensile cord 11 may also be applied to
the belt build with the warp yarns running parallel to a belt
centerline as shown in FIG. 3.
[0031] A multi-unit cord comprises a plurality of parallel cords
oriented in a warp direction. It is known in the tire manufacturing
arts. Each cord may comprise a twisted or non-twisted strand. A
weft yarn having a significantly lower denier than the warp yarns
is generally included every 1.0 cm along a length in order to
maintain a proper orientation of the warp yarns, although this
dimension may vary according to manufacturer. The weft yarns do not
affect a belt modulus and may be broken during the fabrication
process once the cords are laid up on the belt build. The
multi-unit cord comprises a sheet and is applied to a belt build as
a sheet. No preload is applied to the tensile cord during the
application process to a belt build. Further, the ends of the
multi-unit cord sheet once applied to the belt build may be
connected at a butt joint, or may be overlapped. The multi-unit
cords are not applied in a continuous, wound manner as is the case
in a single unit cord belt where the unit cord is spiraled about
the belt build.
[0032] FIG. 2 is a plan view of a belt showing a tensile cord
arrangement. This figure depicts an included angle of 120.degree.
between each layer of multi-unit tensile cords. This also equates
to an angle of 60.degree. as measured from a width W of the
belt.
[0033] FIG. 3 is a plan view of a belt showing a tensile cord
arrangement.
[0034] FIG. 4 is an end view of a belt showing a tensile cord
arrangement. This figure depicts a belt having a first tensile cord
layer 11 and second tensile cord layer 21, or plies, of multi-unit
cord tensile cords. The profile of the inventive belt is
multi-ribbed, comprising ribs 12 spanning a width of the belt. A
groove between each rib 12 describes an angle .beta. in the range
of 34.degree. to 52.degree.. Ribs 12 may also comprise fibers
embedded therein, such as short organic or synthetic fibers which
extend from a belt engaging surface 13. Surface 13 further
comprises a coefficient of friction.
[0035] FIG. 5 is an end view of a belt showing a tensile cord
arrangement. This figure depicts a belt having three plies of
multi-unit cord tensile cords. An odd number of plies may be used
when applying mill run (included angle=180.degree.) multi-unit cord
as shown in FIG. 3 and FIG. 5. Pantograph cord orientations
generally require an even number of cords in order to prevent
tracking, as shown in FIG. 1, FIG. 2, FIG. 4 and FIG. 6.
[0036] FIG. 6 is an end view of a belt showing a tensile cord
arrangement. This figure depicts the tensile cord arrangement of a
belt having four plies of multi-unit tensile cords.
[0037] One can appreciate that the number of tensile cord layers
shown in FIGS. 4, 5, and 6 do not limit the number of tensile cord
layers which may be used in the inventive belt.
[0038] FIG. 7 is a chart depicting the load versus elongation
behavior of the inventive belt. The chart comprises stress-strain,
or modulus, curves at 70.degree. F. (.about.23.degree. C.). The
chart shows that a belt having two tensile cord plies at an
included angle of 120.degree. to each other has the highest
elongation to load ratio, 0.13, and therefore the lowest modulus.
The belt represented by curve A may stretch up to 6.8% of a length
at a load of 50N. The elastic modulus for the belt in curve A is
230 N/mm.
[0039] A progression toward a lower elongation to load ratio, with
an increase in modulus comprises in part an increase in the number
of plies, from 2 to 3 to 4. This also may comprise an increase in
the included angle. These are respectively; curve B, 4 plies @
120.degree. included angle; curve C, 2 plies @ 150.degree. included
angle; and curve D, 4 plies @ 150.degree. included angle. Curves E,
F, and G correspond to 2, 3, and 4 plies respectively of mill run
oriented multi-unit cord. "Mill run" refers to the warp yarns
running parallel to a belt centerline. The elastic modulus for each
belt is: curve B-373 N/mm; curve C-428 N/mm; curve D-913 N/mm;
curve E-728 N/mm; curve F-1019 N/mm; curve G-1385 N/mm. A control
belt having a single unit tensile cord orientation (parallel to a
belt centerline) has an elastic modulus of 1989 N/mm, shown as
curve H, which is significantly higher than the modulus for each of
the inventive belts. The elastic modulus for each belt is
determined as follows. Equipment used comprises an Instron.TM. 8532
servo-hydraulic tester with digital controller having a 10 kN
dynamic load cell and a crosshead speed of 10 mm/minute. The belt
is mounted on flat steel pulleys which are 108 mm in diameter with
free rotation. The test procedure includes inverting the ribbed
transmission belt and placing it on the flat pulleys. The belt is
initially tensioned just enough to eliminate belt slack. The
Instron.TM. includes test software, more particularly,
ElastTest.TM. software, which is used to load the belt and collect
data. Data is collected approximately every 0.25 mm displacement
between the pulleys. The test is conducted at a temperature of
approximately 23.degree. C. (room temperature) . The belt is cycled
through three cycles with top elongation of approximately 6.7%
elongation. In this case "elongation" is measured as total
crosshead movement during the test. For data analysis the data file
from the ElastTest.TM. software includes the belt gage length,
number of ribs, crosshead position and the total load. Using this
information a stress-strain curve is created for each belt, see
FIG. 7. For the elastic modulus value in N/mm, a stress-strain
curve average slope is calculated between 1% and 5% on the second
and third belt elongation cycle.
[0040] Increasing a modulus M comprises increasing the included, or
bias, angle from the lower end to the upper end of the range, from
90.degree. to 180.degree., in combination with the number of plies.
An upper end of this angular range is substantially parallel to a
belt centerline, CL, having an included angle of 180.degree.. More
particularly, the lowest elongation to load ratio (0.023), or
relatively higher modulus, for a belt is demonstrated by the
construction having 4 plies at an included angle of
180.degree..
[0041] The belts with the lowest elongation to load ratio, or
highest elastic modulus, are generally those with the mill run
orientation. Each such belt demonstrates a greater load carrying
capability for each additional tensile cord ply. These are depicted
as curves E, F and G respectively in FIG. 7.
[0042] Thus, the modulus of the inventive belt can be specifically
designed to meet the needs of a user by adjusting the number of
tensile cord plies as well as a tensile cord included angle, or
both.
[0043] As described above, one skilled in the art can appreciate
that the angular range for the tensile members may include up to an
orientation parallel to a belt centerline, or 180.degree.. At the
other end of the range the limit approaches 90.degree. to a belt
centerline, or a substantially transverse orientation or normal to
a belt centerline.
[0044] In an alternate embodiment the inventive belt may comprise a
layer or multiple layers of a woven fabric as a tensile member 11.
The woven fabric may comprise aramid, cotton, nylon, polyester, and
blends and equivalents thereof. The included angle between the warp
yarn and weft yarn in the fabric may vary from approximately
90.degree. to 150.degree.. The woven fabric is applied to a belt
build during fabrication so an included angle is bisected by a line
normal to a belt centerline. In order to increase a modulus the
woven fabric may oriented on the belt so the included angle is
bisected by a belt centerline. In the highest modulus orientation a
warp yarn describes and angle of approximately 0.degree. to a belt
centerline, i.e., the fabric is oriented with a mill run direction
aligned with a longitudinal axis of the belt.
[0045] An advantage of the inventive belt is ease of installation
as well as reduced operating temperature. The belt may be installed
on a belt drive system by simply stretching it over a pulley. This
is considerably easier when compared to the known method of
loosening a pulley, installing a belt and then readjusting the
pulley to a proper operating preload position. It further
eliminates the need for a belt tensioner in certain applications.
This represents a considerable savings in time, parts and
complexity.
[0046] Although a single form of the invention has been described
herein, it will be obvious to those skilled in the art that
variations may be made in the construction and relation of parts
without departing from the spirit and scope of the invention
described herein.
* * * * *