Note: Descriptions are shown in the official language in which they were submitted.
~t3~
TENSION ~EASUREMENT DEVICE
BACKGROUND OF ~ INVENT~ON
Field of Invention
The present invention pertains to a measurement device
which is generally known as a dynamometer. A dynamometer is a
device for measuring force, torque, work, or mechanical power.
The specific dynamometer disclosed herein is a device which has
a ~eans which is responsive to a load, the means being capable
of measuring the tautness of a line~ The device has a means
for sensing the deflection of an element. The device also has
an elastic deflecting member. Furthermore, the device of the
present invention senses the deflection of the elastic member
and converts the signal from the sensing means into an electric
current or voltage.
Descrlption of the Prior Art
Three U.S. patents-disclose subject matter which, with
respect to the present invention, is the closest prior art of
which applicants are aware. These three patents are U.S.
3,526,129 (to Anderson), U.S. 3,444,731 (to Nieuweboer), and
U.S. 3,240,281 Ito Schaevitz). These three patents are
discussed in detail below. Applicant is aware of several other
U.S. patents which are related to the present invention,
including: 3~060,370 3,376,740; 4,130~014; 4,326,424.
U.S. Patent 3,526,129, to A. Anderson, discloses a device
for measuring tensile forcçs. The device includes both upper
plate sections ~4 and 5) and lower plate sections (1 and 2).
The upper plate sections are parallel to the lower plate
sections. The upper plate sections are connected to the lower
plate sections by:
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(a) four resilient members (7) and
(b) an assembly which is co~prised of: two rigid members
~8j and ~9) which are bolted to the upper plate
sections, the two rig~d members having two bolt-like
members (~2 ~nd 1~) threaded therethrough, the
bolt-like members in turn contacting a first support
(14), the first support (14) in turn being bolted to
the upper ends of a pair of arms (15 and 16), on which
are arranged a pair of magnetoelastic transmitters
(18), the lower ends of the arms (15 and 16) being
bolted to a second support (17), the second support in
turn being bolted to the lower plate sections.
Although Anderson discloses neither the detailed structure
of each of the parts nor a detailed description of the
movements of the parts during operation of the device, several
facts are apparent upon careful analysis of the Anderson patent
by one of skill in the art:
(1) the two arms (15 and 16) extend through the
magnetoelastic transmitters -- Anderson even implies
this in ~b) above.
(2) The bolt-like members 12 and 13 must slide against the
support 14 during functioning of the resilient rods 7
due to the force exerted perpendicular to the plates
1, 2, 4, and 5O If the bolt members did not slidef
the resilient members (7~ would not deform because of
the rigid connection between the lower plates 1 and 2
and the upper plates 4 and 5 via path (b) described
above.
The instant invention differs from Anderson in several
ways~ Most importantly, in the instant invention, the force
which is exerted upon the article-contacting means moves the
traveling member a distance X which, absent damping, is
substantially proportional to the amount of force f necessary
to deform applicant's resilient members enough for applicant's
traveling member to move a distance X. In contrast, Anderson's
device requires much greater force than that force which is
required to simply deform Anderson's resilient rods 7. In
fact, Anderson's device does not have any significant
aside-to~side~ movement because Anderson has a rigid
side-to-side linkage occurring from parts 4 and 5 ~hrough parts
8 and 9, through parts 12 and 13, through 14, through 15 and
16, through 19, throu~h to 1 and 2. Furthermore, Anderson'S
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device requires substantial side-to-side rigidity because the
magnetoelastic sensors operate with a range of motion of only a
few thousandths (i.e. less than oOD5 inches) of an inch at
most. I~ Anderson's device, the force required to move the
upper plate a distance X ~sideways~ is much greater than the
force required to deflect Anderson's springs (7~ sideways by
that amount. In fact, Anderson's device will not even move
sideways any significant amount. Anderson's springs act as
thin columns which buckle under load. In addition, Anderson
uses a completely different type of sensor from applicant's,
and Anderson does not disclose that his leaf springs are
fixedly secured to the upper and lower plate sections, as
applicant requires his connecting members to be.
U.S. 3,444,731 to Nieuweboer discloses a ~parallelogram-
shaped linkage~ which is ~attached to (a) base~. The
Nieuweboer device utilizes ~flexural pivots~ which are
spring-loaded. Additionally, the Nieuweboer device utilizes a
Hall effect sensor for sensing a change in position of one of
the rigid linkage arms with respect to the base of the device.
In contrast, Applicant~s device utilizes not a parallelogram
linkage but a parallelogram-shaped device, the difference being
that Mieuweboer utilizes his parallelogram to ~link~ a firs~
portion of the sensor with a second portion of the sensor, the
second portion being in a position which is independent of the
parallelogram, whereas applicant's device has a sensor
completely within a parallelogram, applicant's device sensing a
change in the angles by measuring a change in position of one
side of the parallelogram with respect to the opposite side of
the parallelogram. Thus, applicant's device has fewer moving
parts than Nieuweboer. Applicant's connecting members allow
for essentially "frictionless~ movement of the traveling
member, while Nieuweboerl's ~flectural pivotsa undoubtedly must
be more complex and more costly.
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U.S. 3,240,281 to 5chaevitz discloses a balance whi5h
employs ~ . ~ . a parallelogram adapted to be moved about ~he
rigidly mounted member 12. The outer member 14 is physically
connected to the mounted member 12 through flexure elements 32
and 34~. ThUs Schaevitz has a pa~allelogram and he utilizes at
least 6 flexural e7ements similar to applicant's leaf springs.
~owever~ Schaevit~ discloses a two-piece sensor, a first piece
being fixed to one side of the parallelogram and a second piece
being fixed to a ~mounted membera. In contrast, applicant's
device has the sensor mounted within the parallelogram. In
addition, Schaevitz requires all four sides of the
parallelogram to move, whereas applicant's device allows only
three sides of the parallelogram to change position
BRIEF SUMMARY OF THE INVENTION
The tension measurement device of the present invention is
four-sided assembly which is comprised of a support member, a
traveling member, at least two deformable, resilient connecting
members, an article-contacting means, and a two-part position
sensor. The connecting members are fixedly attached (and
non-pivoting) to both the traveling member and the support
member. The two parts making up the position sensor are
separated by a space, with the first part of the position
sensor being mounted on the support member and the second part
of the position sensor being mounted on the traveling member.
The device has the characteristic that, absent damping, a force
f displaces the traveling member a distance X where the force
is substantially the same amount of force as is required to
deform the resilient members enough for the traveling member to
be displaced by the distance X.
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BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates an exploded view of a preferred embodiment
of the present invention. Figure 2 illustrates a similar view
of the same device when assembled. Figure 3 is a front
cross-sectional ~iew which is illustrated for purposes of
disclosing the relative proportions of the parts of the
preferred apparatus. In all of the views, like numerals refer
to like members.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The discussion below will pertain to all three figures, but
Figure 1 is the most revealing regarding the structure of the
preferred embodiment.
In the prefereed device as illustrated, a support member
(1) is machined out of a block of metal, most preferably 2024
aluminum. In general the support member (1) is itself
supported by being clamped, bolted, etc. to the equipment on
which the tension sensor is being used. In the preferred
embodiment, the support member is bolted to a shield plate (not
shown), via two threaded holes (10). The holes (10) are
accompanied by protruding mounting bosses (24). As can be
seen, the support member (1) is comprised of a rectangular back
portion (2) and an irregularly-shaped raised portion (3). The
raised portion (3) has functional surfaces (13), (14)t (27),
(30) and others thereon. The device is further comprised of
two resilient connecting members (4), each of which has a first
end (5), a second end (0) and a connecting portion (7~. The
first ends (5) of both resilient connecting members (4) are
positioned on a top surface (30) of the raised portion (3) of
the support member (1). The first ends (5) are sandwiched
between the top surface ~30) and an upper plate member (31).
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Two upper screw members (32) fixedly ~ecure both the upper
plate ~31) to the first ends (5), and the first ends (5~ to the
support member ~1). The second ends (8) of both resilient
connecting members (4) are sandwiched between a lower plate (9)
and a lower surface (33) of a traveling member (11~. The
traveling member (11) has several functional surfaces (22),
(25), (28~, (33), (40), (41), among others, which are described
in detail below. The lower screw members (12) secure both the
lower plate (9) to the second ends (8), and the second ends (8)
to the traveling member (ll).
~ he assembly of the support member (1), the two connecting
members (4) and the traveling member (11) form a four-sided
device. The preferred four-sided device, as illustrated,
allows a limited amount of Dleft-righta travel of the traveling
portion (11). The ~limitsh governing the amount of travel to
the ~left~ or to the ~rightR are set by: (a) a left limit
surface (13) formed by the raised portion (31 and a ~right~
limit surface (14) formed by the raised portion (3); and (b)
the rest position of the traveling member (ll); and (c) the
position of surface 40 with respect to surface 13, and the
position of surace 41 with respect to ~urface 14. In the
preferred device, the rest position of the traveling member
provides a clearance of about 0.010 inches to the left of the
left-most surface 40 of the traveling member, and about 0.125
inches to the right of the right-most surface 41 of the
traveling member. Note that the traveling member (11) has a
substantially centrally located passageway (23), the passageway
being sîzed for fastening an article-contacting means thereto,
the article-contacting means preferably being rotatable. The
passageway (23) is accompanied by a protruding mounting surface
(26).
A two-part ~ensor (15 and 16) is used to detect a position
of the traveling member I~ll) with respect to the support member
(1). The traveling member ~111 has a permanent magnet (50)
embedded in a treaded mount (16). The support member (1) has a
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Hall-Effect sensor (lS~ fixedly secured thereto, with wires
(17~ connected to the sensor (15). In the preferred
embodiment, the ~all-Ef~Ct sensu~ is held in place by adhesive
and by being completely embedded in a silicone rubber, the
north-seeking pole of the magnet being positioned about 0.125
inches from the Hall-Effect sensor. As shown in Figure 3, the
Hall-effect sensor (15~ has an Vactive area~ ~51) positioned as
lndicated. The wires (17) from the Hall-Effect ~ensor (15) run
through a notch lformed by three surfaces 18 in front of
~upport member 1] ar.d over the upper plate member (31), and
into a slot [formed by three surfaces 19 in the back of support
member 1]. The wires tl7) emerge from the bottom of the device
(25) in a casing (20).
The preferred device of the present invention also employs
fluid damping means, the damping being created by a stainless
steel rod (21), the rod (21) being attached by being pressed
through a hole ~52) in the support member (1), the rod (21)
being positioned within a cavity which is formed by interior
surface (22) in the traveling member (11). The cavity may be
filled with a damping fluid of a desired viscosity. In the
preferred embodiment, the cavity is ~oversizeda in the sense
that the rod (21) never touches the interior surface of (22)
within the ~left-right~ range of travel of the traveling
member. In the preferred embodiment, the fluid used in the
cavity is a silicone-based fluid made by Dow Corning, and had a
viscosity of 100,000 centistokes.
In the mounting of the device, it should be noted that the
mounting surface (27) of the support member (1) is in a plane
about 0.030 inches above the front surface (28) of the
traveling member (11). Thus, the traveling member does not
contact the support member or the machine to which the device
iB mounted in normal operation. In case of overloading forces
the displacement of the traveling member is stopped before the
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resilient members are permanently deformed. Upon mounting the
device, the bosses t24) partly enter similar ized holes in a
plate (not ~h~wn, preferably the plate is n~n-magnetic~ to
which the device is mounted. The plate has a hole through
which a shaft (not shown) passes, the shaft being screwed into
the passageway (23) within the traveling portion, the
passageway l23l being threaded. The shaft in turn has a
yarn-contact rol~er lnot shown) mounted thereon, the roller
beiny freewheeling. The characteristics of the roller are
chosen to suit the yarn it will contact and the environment in
which the tension measurement device is to be used. A
non-rotatable yarn contact member could have been used instead,
but is not preferred.
In the preferred embodiment of the present invention, the
resilient connecting members (4) are leaf springs. Leaf
springs ha~e the advantage of only undergoing substantial
bending in a plane perpendicular to their major surface, i.e.
leaf springs do not undergo substantial ~sideways~ bending. In
addition, leaf springs can be manufactured in a bent
configuration which allows the spring to have mountable endsy
such as ends (5) and (8) of the connecting members (4) of the
present invention. This provides convenient means for mounting
the connecting members, i.e. it eliminates the need for
additional parts. Another advantage in the use of leaf springs
lies in the fact that the flexing of the spring involves no
rubbing between two rigid objects. Leaf springs are considered
advantageous in tension devices because the amount of force
necessary to cause a deflection is believed to remain constant
over a long period of use, if the springs are protected against
overloads as in the preferred embodiment of the present
invention.
In the present invention, a Hall Effect sensor is the
preferred sensor for signalling the position of the traveling
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member ~ with respect to the support member (1). However,
many other ~ensing me~ns would also be operable, for example:
photo optic, differential transformers, etc. The Hall Effect
sensor is preferred because, among other reasonsr it utilizes
two parts which do not touch one another, and its output is
relatively linear over the preferred range of travel of the
traveling member (11). The use of ferrous materials in or
around the tension measurement device should be avoided as they
affect the device by affecting the magnet (16) thereon.
Sensors which are comprised of two parts which are
separated by a space are preferred over other types of sensors,
such as magneto elastic sensors or strain gauges. Both magneto
elastic sensors and strain gauges are relatively fragile as
they must be protected against overloads which will cause
permanent deformation of the sensors. Protecting strain gauges
and magneto elastic sensors against overloads is difficult due
to the very small distances through which these gauges move
during operation. ~urthermoreJ because these gauges operate
over such small distances of travel, viscous fluid damping is
extremely difficult, unlike the device of the present
invention.
In the device of the present invention, any meaningful use
of the Hall Effect Sensor (15) necessitates that the full range
of movement of the traveling member (11) be at least 0.010
inches, preferably the maximum travel of the traveling member
is between lmm and 20mm. The most preferred full range of
travel of the traveling member ~11) is approximately 0.125
inches. It has been conceived that there is no limit on the
maximum distance of travel of the traveling member (11), but it
i8 recognized that a practical maximum distance does exist as
the magnet (16) loses its ability to affect the Hall Effect
device once displaced very far from the device. In a case
where a travel distance up to 0.750 inches is desired, an
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operable embodiment would use two magnets spaced laterally
approximately one inch apar~, one magnet to the lef~ of the
sensor having i~s north pole facing the sensor and the other
magnet to the right of the sensor having its south pole facing
the sensor.
The present invention is directed towards a device which
has a traveling member, the traveling member being displaceable
a distance X by a force f, the force f being substantially the
same amount of force as is required to deform the resilient
connecting ~embers enough for the traveling member to be
displaced the distance X. Several definitions underly this
statement. First, the distance X refers to the distance
traveled by the traveling member (11), where the traveling
member is originally in its rest position before force f is
exerted on the traveling member. Secondly, the force f is that
force, or force component, which is in the direction of travel
of the traveling member. Thirdly, the effects of damping must
be ignored -- i.e. the force must be exerted for enough time
that the traveling member reaches its equilibrium position. In
the claims herein, this description underlies the statement
that the traveling member will repeatedly travel distance X
when subjected to the force f.
The device of the present invention may be utilized on
virtually any machine which is used to process yarn. The
clevice may be used at any place on the yarn path in which the
yarn undergoes a change in direction. Of course, in order to
use the preferred device, which employs viscous damping, the
device must be installed ~ubstantially ~upright~ in order to
keep the damping fluid in the cavity within the traveling
member. In order to obtain good sensitivity with the preferred
device, the direction of the force created by a yarn tension
increase should have a ~ignificant force component in the
direction of travel of the traveling member. Also, since the
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roller contacts the yarn the device cannot be used at a point
in yarn processing in which the yarn remains molten, i.e. above
the yarn lstick pointa in an extrusion operation, for example.
A preferred device was constructed and used on a yarn
processing machine. The device used two leaf spring connecting
members as shown in the ~igures. The springs were made from
1095 ~ill Temper spring steel having a thickness ranging from
0.0098 inches to ~.0~2 inches, the springs being manufactured
~y Associated springs of Dayton, Ohio. The springs were
proportioned substantially as shown in the Figures, the
connecting portion (7) having a length of 1.450 inches and the
end portions (5 and 8) each having lengths of 0.450, the
~width~ of the spring being 0.500 inches. The ends were bent
90 with respect to the connecting portion, the bends having a
radius of approximately 1/16 inches.
The Hall-Effect sensor (15) utilized in the preferred
device was purchased from MICRO SWITCH, 517 South Sharon Amity
Road, Charlotte, N. C. 28222. The sensor was catalog listing
915512-2. The permanent magnet (50) and mount (16) were also
purchased from MICRO SWITCH, the mount ~16) and magnet ~50)
being purchased as a single part, number 106MG10.
The support member (1) and the traveling member (11) were
both machined from 2024 aluminum. The support member had
overall dimensions of 2.420 inches x 1.630 inches x .810
inches, and was proportioned substantially as illustrated. The
traveling member (11) had overall dimensions of 2.260 inches x
1.000 inches x 0.575 inches, and was proportioned substantially
as 6hown in the Figures.
The preferred device was utilized on a machine which was
processing a 1300 denier multifilament nylon 6 yarn. The yarn
was under a tension of 175 grams ~ 30 grams during normal
operation. The device was aligned and operated so that during
operation of the machine, a voltage output of approximately 6
was obtained from the ~all Effect device.
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The claims herein are intended to cover the concepts
underlying ~he prese~t invention, and are not intended to be
limited to the preferred device al~ne~
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