U.S. patent application number 11/267821 was filed with the patent office on 2006-05-04 for drive pinion for actuating a rapier rod in a weaving machine.
Invention is credited to Johnny Debaes.
Application Number | 20060090810 11/267821 |
Document ID | / |
Family ID | 34923704 |
Filed Date | 2006-05-04 |
United States Patent
Application |
20060090810 |
Kind Code |
A1 |
Debaes; Johnny |
May 4, 2006 |
Drive pinion for actuating a rapier rod in a weaving machine
Abstract
This invention is related to a drive pinion (1) for actuating a
rapier rod (2) of a weaving machine, whereby interaction of rapier
rod (2) with drive pinion (1) is subject to less hindrance and
damage due to occurring impact load at increased operational speeds
and/or larger weaving widths, in that the tooth thickness (Td) of
at least one tooth (3) of the drive pinion (1) varies in
widthwise-direction (Tb) of the tooth (3), and whereby this tooth
thickness (Td) is larger in the middle area (5) than in the fringe
areas (7).
Inventors: |
Debaes; Johnny;
(US) |
Correspondence
Address: |
James C. Wray;Suite 300
1493 Chain Bridge Road
McLean
VA
22101
US
|
Family ID: |
34923704 |
Appl. No.: |
11/267821 |
Filed: |
November 4, 2005 |
Current U.S.
Class: |
139/449 |
Current CPC
Class: |
D03D 47/273 20130101;
D03D 47/276 20130101; F16H 55/0886 20130101 |
Class at
Publication: |
139/449 |
International
Class: |
D03D 47/00 20060101
D03D047/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 4, 2004 |
BE |
2004/0539 |
Claims
1. Drive pinion (1) for actuating a rapier rod (2) of a weaving
machine, comprising a set of teeth (3) which are disposed in such a
way that they engage a tooth profile (4) of a cooperating rapier
rod (2), characterized in that the tooth thickness (Td) of at least
one tooth (3) of the drive pinion (1) varies according to the
widthwise-direction (Tb) of the tooth, and in that this tooth
thickness (Td) is larger in the middle area (5) than it is in the
fringe areas (7).
2. Drive pinion (1) according to claim 1, characterized in that
said tooth (3) is shaped as an involute.
3. Drive pinion (1) according to claim 1, characterized in that
tooth thickness progressively reduces from the middle area (5)
on.
4. Drive pinion (1) according to claim 1, characterized in that the
shape of at least one of the tooth flanks (8) of a tooth (3) is
shaped as a circular arc.
5. Drive pinion (1) according to claim 1, characterized in that the
shape of at least one of the tooth flanks (8) of a tooth (3) is
shaped according to a logarithmic curve.
6. Drive pinion (1) according to claim 1, characterized in that the
difference between tooth thickness in the middle area (Tdm) and
tooth thickness in the fringe areas (Tdr) is situated between 1 and
20% of tooth width (Tb).
7. Drive pinion (1) according to claim 1, characterized in that the
tooth shape of at least one tooth (3) of the drive pinion (1)
symmetrically covers both sides of the middle area (5).
8. Rapier device for a weaving machine, including a rapier rod (2)
actuated by a drive pinion (1), characterized in that it concerns a
drive pinion (1) in the embodiment of claim 1.
9. Rapier weaving machine, characterized in that the said rapier
weaving machine is equipped with one or more rapier devices
according to claim 8.
Description
[0001] The invention relates to a drive pinion for actuating a
rapier rod of a weaving machine, comprising a set of teeth, which
are disposed in such a way that they engage the tooth profile of a
cooperating rapier rod on the one hand, and to a rapier device for
a weaving machine, comprising a rapier rod actuated by a drive
pinion according to the invention on the other hand.
[0002] This patent application relates furthermore to a
rapier-weaving machine equipped with one or more rapier devices
according to the invention.
[0003] In a rapier-weaving machine, the rapiers, that carry the
weft yarn through the shed from one side of the weaving machine to
the other side of the weaving machine, are each of them at their
end connected to a rapier rod. For performing the back-and forth
motion, this rapier rod is guided in a guiding device. For
actuating this back-and-forth motion, the rapier rod is provided
with a tooth profile, which meshes with a drive pinion fitted at
the vertical axis. The tooth profile is preferably achieved in
providing rectangular apertures or cutouts in the rapier rod.
[0004] Given the tendency of manufacturing and using rapier-weaving
machines with ever increasing operational speeds and machines with
an increased weaving width, speed at which the rapier rod has to
move through the shed also increases. Moreover, at one end of its
motion, the rapier has to pick up or drop off the weft yarn and at
the other end of its motion it has to pass on or take over the weft
yarn. At these ends, the rapier always stops and next it takes up
its full moving speed again in the other direction.
[0005] Considerable impact forces occur during this reverse of
motion, and these forces strongly increase with accelerating
operational speed of the weaving machine and with accelerating
operational speed of the rapier rod. These impact forces also have
an influence on the spot where the teeth of the rapier rod and the
teeth of the cooperating gear pinion interact with each other.
[0006] In the present state of technique, this force is limited or
absorbed in manufacturing the rapier rod, the drive pinion or both
parts out of either materials having a reduced weight, or out of
materials that are stronger or materials that combine these two
features. In this way the German patent publication DE 3527202
discloses a rapier rod made out of synthetic material in order to
limit stress by reducing inertia.
[0007] Stiffness of synthetic materials, however, is much lower,
due to which interaction with pinion (mostly manufactured from
steel or aluminum) will lead to it that the synthetic teeth of the
rapier rod deform.
[0008] This deformation causes Hertzian stresses between pinion and
rapier rod, which reach peaks in the fringe area of the tooth width
at the outer side of the teeth of the pinion. This phenomenon has
two drawbacks: on the one hand because the higher stress is locally
considerably higher compared to when an even spread of the Hertzian
stress would be achieved, due to which overload may occur locally;
on the other hand this higher load occurs near the roundings of the
rapier rod teeth, which is a drawback in its turn because of a
higher risk of notch effect at this spot.
[0009] Because of the limitations in stiffness of the plastic
rapier rod, the German patent publication DE 3638673 discloses an
embodiment of the rapier rod, in which the plastic is reinforced by
using fiber composite materials in the plastic such as for
instance: glass fibers, carbon fibers or armid fibers. These rapier
rods, however, are difficult to manufacture and expensive.
[0010] It is the aim of the invention to manufacture in a simple
way and at acceptable cost price a drive pinion for actuating a
rapier rod of a weaving machine, in which the interaction of the
rapier rod with the drive pinion is subject to less hindrance and
damage due to occurring impact load at increased operational speeds
and/or larger weaving widths.
[0011] The aim of the invention has been achieved in providing a
drive pinion for actuating a rapier rod of a weaving machine,
comprising a set of teeth that are disposed to engage a tooth
profile of a cooperating rapier rod, in which tooth thickness of at
least one tooth of the drive pinion varies according to the
widthwise-direction of the tooth and in which this tooth thickness
is larger in the middle area than it is at the fringe area.
[0012] In this patent application "according to the
widthwise-direction" should be understood as the direction
transversely to the outline (centre line) of the pinion.
[0013] In adapting the shape of the teeth of the drive pinion and
in this way shape a preferably crowned teeth profile, a reduced
impact load between rapier rod and drive pinion is achieved.
[0014] In a more particular embodiment of the drive pinion
according to the invention, tooth thickness progressively reduces
from the middle area on. In slightly reducing the tooth thickness
of a number of teeth in widthwise-direction of the pinion from the
middle of the tooth width to the outside (fringe area) of the tooth
width, stress would theoretically be concentrated in the middle of
the teeth, which would also mean a harmful load. Now it has been
shown that due to the deformation of the less stiff tooth apertures
in the rapier rod, these deformed tooth apertures in the rapier rod
fit in the crowned tooth profile of the tooth of the cooperating
drive pinion, which in this way leads to a redistribution of
Hertzian pressure, eliminating or reducing peak loads at the teeth
ends without overloading the tooth aperture in the middle of the
tooth width.
[0015] In this way the Hertzian stresses that occur at the contact
spot between teeth apertures of the rapier rod and at least one
tooth of the cooperating drive pinion are redistributed over the
width of the tooth and the tooth aperture in such a way that
stresses at the end of the tooth (in widthwise-direction) reduce
and the distribution of stress over the contact spot between rapier
rod and drive pinion becomes more evenly. In consequence occurring
peak loads reduce on the one hand and peak load is shifted from the
end of the tooth width (fringe areas) to the middle of the tooth
width on the other hand. As a consequence peak load is situated at
a less vulnerable spot, further away from the rounding in the tooth
apertures of the rapier rod, which are the risk areas for formation
of notch effect.
[0016] In a preferential embodiment of the drive pinion according
to the invention, the named tooth (3) is shaped involute.
Consequently a drive pinion with involute profiled teeth is
obtained.
[0017] In a preferred embodiment of the drive pinion according to
the invention, the shape of at least one of the tooth flanks of a
tooth is shaped as a circular arc.
[0018] In yet another embodiment of the drive pinion according to
the invention, the form of at least one of the tooth flanks is
shaped according to a logarithmic curve. A tooth form shaped
according to a logarithmic curve differs from a tooth form shaped
according to a circular arc in that the tooth form according to a
logarithmic curve has a smaller tooth thickness difference in the
middle area, whereas the tooth thickness difference in the fringe
areas according to the logarithmic curve is larger than for a tooth
form according to a circular arc. This has as an advantage that in
case of a tooth form according to a logarithmic curve the increase
of the air gap between the tooth of the drive pinion and the tooth
aperture in the free of load rapier rod starting from the middle of
the tooth up to the edge firstly increases slower than in case of
the embodiment according to a circular arc and toward the edge of
the tooth width increases much faster than in case of an embodiment
according to a circular arc.
[0019] This preferred embodiment allows reducing acting stresses on
the outer side without having to considerably increase stress in
the middle of the set of teeth.
[0020] In a most particular embodiment of the drive pinion
according to the invention, the difference between tooth thickness
in the middle area and tooth thickness in the fringe areas is
situated between 1 and 20% of the tooth width.
[0021] In a particularly advantageous embodiment of the drive
pinion according to the invention, the tooth shape of at least one
tooth of the drive pinion symmetrically covers both sides of the
middle area.
[0022] Another subject of this patent application relates to a
rapier device for a weaving machine, comprising a rapier rod
actuated by a drive pinion, whereby it concerns a drive pinion
according to one of the claims 1 up to and including 7.
[0023] Furthermore, this patent application relates to a
rapier-weaving machine, which is equipped with one or more rapier
devices according to claim 8.
[0024] In order to further explain the features of this invention
and to indicate additional advantages and details, the equipment
according to the invention will now be described more into detail.
Let it be clear that nothing in the following description may be
interpreted as a limitation of the protection as required in the
claims for this invention.
[0025] In this description reference is made to the accompanying
drawings using reference numbers, and wherein:
[0026] FIG. 1 shows a cross-section of the meshing of a number of
teeth of the drive pinion with the tooth profile of the cooperating
rapier rod, according to the state of technique, without crowning
with indication of the spread of Hertzian pressure;
[0027] FIG. 2 shows a cross-section of the meshing of a number of
teeth of the drive pinion with the tooth profile of the cooperating
rapier rod, with application of crowning of the tooth according to
the invention, with indication of the spread of Hertzian
pressure;
[0028] FIG. 3 shows a front view of the drive pinion according to
the invention;
[0029] FIG. 4 shows a cross-section B-B of one tooth from the drive
pinion according to FIG. 3;
[0030] FIG. 5 shows a perspective view of one tooth of a drive
pinion according to the invention.
[0031] This invention relates amongst others to a drive pinion (1)
for actuating a rapier rod (2) of a weaving machine, comprising a
set of teeth (3) disposed to mesh with a tooth profile (4) of a
cooperating rapier rod (2), whereby the tooth thickness (Td) of at
least one tooth (3) of the drive pinion (1) varies according to the
widthwise-direction (Tb) of the tooth, and in which this tooth
thickness (Td) is larger in the middle area (5) than it is at the
fringe areas (7), in order to achieve in this way a redistribution
of Hertzian pressure, reducing or eliminating the peak load in the
fringe areas of the tooth (3). The widthwise-direction is the
direction transversely to the outline (centre line (6)) of the
pinion (1).
[0032] Fact is that for drive pinions according to the state of
technique with involute profiled teeth, acting Hertzian forces (see
FIG. 1), that occur at the contact between the aperture provided in
the rapier rod and the tooth of the cooperating drive pinion,
increase toward the edges of the involute profiled teeth. At the
edges of these teeth, stresses may be up to more than 40% higher
than in the middle of the tooth.
[0033] In crowning the teeth (3) of the cooperating drive pinion
(1) represented in FIG. 1 in widthwise-direction of the tooth (3),
this means that tooth thickness reduces progressively from the
outline or centre line (6) of the pinion (1), Hertzian stress will
be redistributed, as represented in FIG. 2, over the width of the
tooth (3) in such a way that stresses at the ends of the tooth, in
fringe areas (7) reduce and through which distribution of stress
over the engagement plane becomes more evenly. Consequently
occurring peak loads reduce on the one hand, and peak load is
shifted from the end of the tooth width to the middle of the tooth
width on the other hand. As represented in FIG. 2, peak load is now
situated in a less vulnerable area, further away of the roundings
in the rapier rod, considerably reducing the risk of notch
effect.
[0034] The difference between tooth thickness in de middle area
(Tdm) and tooth thickness in the fringe areas (Tdr) is situated
between 1 and 20% of the tooth width (Tb). In this way, thickness
of a tooth with a maximum tooth width of 8 mm may vary to over 1.6
mm.
[0035] As represented in FIG. 4, tooth thickness may reduce either
according to a circular arc, through which the tooth shape in tooth
width develops according to a circular arc with radius R.
[0036] Or tooth thickness decreases logarithmically.
* * * * *