U.S. patent application number 10/340081 was filed with the patent office on 2004-09-23 for chain with selectively engaged links.
Invention is credited to Prince, Jeffrey Theorin.
Application Number | 20040185978 10/340081 |
Document ID | / |
Family ID | 25127361 |
Filed Date | 2004-09-23 |
United States Patent
Application |
20040185978 |
Kind Code |
A1 |
Prince, Jeffrey Theorin |
September 23, 2004 |
Chain with selectively engaged links
Abstract
A chain is provided in which adjacent links are attached to one
another by a coupling pin that permits the links to rotate relative
to one another on a connecting axis defined by a coupling pin. The
links have movable link plates and can be fixed against relative
rotation or released, at least on one side of the chain, by
selectively engaging or disengaging the link plates. In one
embodiment a restoring force urges movable link plates outwardly on
both sides of the chain, toward locking engagement with the plates
of the next adjacent links. The movable link plates are depressible
against the restoring force, sufficiently to permit the adjacent
link plates to overlap and pivot freely. The couplings between
links can be switched between fixed and free rotational states by
passing them through a path with converging walls that depress the
movable link plates. The chain is particularly useful as a device
for positioning a tool or manipulator, and in an embodiment with
movable link plates on both sides is not only switchable between
rigid and flexible but each pair of links is inherently compliant
in the plane of its pivot pins.
Inventors: |
Prince, Jeffrey Theorin;
(Grass Valley, CA) |
Correspondence
Address: |
SAMUEL W. APICELLI
DUANE MORRIS LLP
305 NORTH FRONT STREET
P.O. BOX 1003
HARRISBURG
PA
17108-1003
US
|
Family ID: |
25127361 |
Appl. No.: |
10/340081 |
Filed: |
January 10, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10340081 |
Jan 10, 2003 |
|
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09782847 |
Feb 14, 2001 |
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Current U.S.
Class: |
474/206 ;
59/78 |
Current CPC
Class: |
F16G 13/18 20130101 |
Class at
Publication: |
474/206 ;
059/078 |
International
Class: |
F16G 013/00 |
Claims
I claim:
1. An elongated chain structure, comprising: a plurality of links
of a first type and a second type, alternating with one another
along a longitudinal length of the chain, each adjacent pair of the
links of said first and second types being movably attached to one
another for relative rotation of the pair of links on a pivot axis;
wherein the links of the first and second type have longitudinally
abutting surfaces that differ from a circular surface around the
respective pivot axis, wherein the links of the first and second
type are prevented from rotating by the longitudinally abutting
surface; and wherein at least one of the links of the first and
second types is displaceable sufficiently to disengage the
longitudinally abutting surfaces of adjacent links for relative
rotation and to re-engage for rendering the chain rigid.
2. The chain structure of claim 1, wherein the links of the first
and second type comprise a chassis link having laterally spaced
link plates attached to longitudinally spaced transverse pivot
pins, and a movable link comprising at least one movable link plate
that is movable laterally inwardly from a position abutting one of
the link plates of the chassis link to a position clear of said at
least one movable link plate, the chassis link and the movable link
plate being relatively rotatable in one of said positions of the
movable link plate and fixed against relative rotation in another
of said positions.
3. The chain structure of claim 2, wherein the chassis link plate
and the movable link plate have longitudinally facing complementary
surfaces.
4. The chain structure of claim 1, wherein the links that are
displaceable sufficiently to disengage comprise movable link plates
on opposite lateral sides.
5. The chain structure of claim 1, wherein the links that are
displaceable sufficiently to disengage comprise movable link plates
on one of two opposite lateral sides and on the other of said two
opposite lateral sides comprise a nondisplaceable link plate that
is pivotally attached to at least one adjacent link.
6. The chain structure of claim 1, wherein links abut along
complementary surfaces that are inclined relative to a lateral
plane, in a direction causing the complementary surfaces to form a
wedge engagement tending to longitudinally stretch the chain in a
movement direction tending to lock the movable link plate against
the chassis link plate.
7. The chain structure of claim 2, wherein the movable link plate
comprises at least one contact cam-protruding laterally from the
movable link plate, whereby the movable link plate can be displaced
inwardly by causing the contact cam to follow a surface having a
decreasing lateral width.
8. The chain structure of claim 7, wherein the movable link plate
comprises a side cam wall having a supporting surface and said
protruding contact cam, wherein the supporting surface defines a
substantially flat support for positioning the movable link plate
laterally inward of the chassis link plate when the chassis link
plate and the movable link plate are relatively rotated.
9. The chain structure of claim 8, wherein the longitudinally
facing complementary surfaces of the chassis link plate and the
movable link plate each defines a wedging angle of less then 45
degrees relative to an axis of an associated one of the pivot
pins.
10. The chain structure of claim 1, wherein the chain is rendered
rigid with the successive links in a substantially straight line
configuration.
11. The chain structure of claim 1, wherein the chain is rendered
rigid with the successive links in a curve having at least one
radius of curvature define by a relative angle between at least two
adjacent links.
12. The chain structure of claim 11, wherein the links are
engageable with one another at least at two selectable angles.
13. A chain comprising: a plurality of serially coupled links
forming a longitudinal length of a chain, wherein at least some
adjacent links are joined at couplings having a tolerance along the
longitudinal length, the links being coupled by a movable structure
having one state permitting relative rotation between the adjacent
links, and another state wherein the adjacent links are fixed
against relative rotation, thereby rendering the chain rigid,
wherein the adjacent links are fixed by wedge surfaces when in said
state where the adjacent links are fixed against said relative
rotation, wherein said wedge surfaces operate to elongate the chain
along the longitudinal length in said state where the adjacent
links are fixed.
14. The chain of claim 13, comprising a plurality of links of a
first type and a second type, alternating with one another along a
longitudinal length of the chain, each adjacent pair of the links
of said first and second types being movably attached to one
another for relative rotation of the pair of links on a pivot axis,
wherein the links of the first and second type have longitudinally
abutting surfaces that differ from a circular surface around the
respective pivot axis, wherein the links of the first and second
type are prevented from rotating by the longitudinally abutting
surface.
15. The chain of claim 14, wherein at least one of the links of the
first and second types has a movable link plate on at least one of
two lateral sides, that is displaceable laterally inwardly
displaceable sufficiently to disengage the longitudinally abutting
surfaces of adjacent links for relative rotation and to re-engage
for rendering the chain rigid.
16. The chain of claim 15, further comprising restoring force
structure associated with at least one of the type of links,
operating to urge the movable link plate in one direction laterally
inwardly or outwardly, for one of locking and unlocking the chain,
the movable link plate operating in an opposite sense for one of
unlocking and locking the chain, when moved opposite said one
direction.
17. The chain of claim 16, wherein the longitudinally abutting
surface of the adjacent links are complementary surfaces inclined
relative to a radial plane intersecting the pivot axis, in a
direction causing the complementary surfaces to form a wedge
engagement tending to longitudinally stretch the chain in a
movement direction tending to lock the movable link plate against
the chassis link plate.
18. In combination, a chain and a guide for the chain, comprising:
a plurality of serially coupled links forming a longitudinal length
of the chain, the links-being coupled by a movable structure having
one state permitting relative rotation between the adjacent links,
and another state wherein the adjacent links are fixed against
relative rotation, thereby rendering the chain rigid, wherein the
adjacent links are fixed by wedge surfaces when in said state where
the adjacent links are fixed against said relative rotation,
wherein said wedge surfaces operate to elongate the chain along the
longitudinal length in said state where the adjacent links are
fixed; and, the guide comprising a surface that contacts at least
certain of the links at least at one point along an extension of
the chain, the guide moving said certain of the links between said
states.
19. The combination of claim 18, wherein the links comprise a
chassis link plate and a movable link plate attached by a pivotal
coupling, the chassis link plate and the movable link plate having
longitudinally facing surfaces on at least one lateral side of the
chain, defining the wedge surfaces and wherein the guide is
operable to displace the movable link plate laterally inwardly to
disengage the longitudinally facing surfaces, thereby permitting
the chassis link plate and the movable link plate to overlap and to
rotate relative to the pivotal coupling.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to link chains, and in particular
provides a link chain in which the connection between successive
links is changeable between a rigid connection and a pivotable
connection. The change can be made by displacing certain link
plates against resilient bias so as to disengage them from adjacent
links and permit pivoting. Preferably, this is accomplished by
compressing certain links in the chain, which have laterally
extending cam surfaces.
[0003] 2. Prior Art
[0004] In a conventional elongated chain formed of connected links,
each successive link in the chain has a body coupled by two link
pins to the two adjacent links, namely the links that precede and
follow the given link along the chain. Usually each link has two
link plates that are laterally spaced relative to the longitudinal
center line of the chain, although other chain structures are
possible, such as links that alternate one and two plates, or
successive links with any number of plates, etc. The link pins
typically define parallel pivot axes.
[0005] An exemplary chain structure of such a description is the
conventional roller chain. Each of the longitudinally connected
serial links comprises two link plates that are laterally spaced by
a bushing or roller. This bushing or roller engages in a rounded
depression between teeth on the outer diameter of a sprocket or
other similar structure for transmitting power using the chain.
Some chains have flanges or tabs that protrude from certain of the
link plates, providing a point at which attachments can be made to
the chain.
[0006] A roller chain often has two different types of links. One
type, which can be called a roller link, has two spaced hollow
bushings extending between the lateral link plates. The other type,
which can be called a pin link, has two spaced pivot pins, which
usually are solid, extending between lateral link plates. Two
successive roller links in the chain have a pin link that provides
the structural connection between the roller links. The pivot pins
of the pin link extend from one link plate of the pin link, through
the hollow bushings of the roller plates, and attach to the other
link plate of the pin link. Thus the pin links are laterally wider
than the roller links, at least by a distance equal to the
thickness of the link plates. The pin links are wider because their
link plates straddle the outside surfaces of the roller links.
[0007] The roller chain is quite flexible, provided that the links
remain in a plane that includes the longitudinal centerline of the
chain. Within this plane, any two adjacent links can be relatively
rotated around the common axis of the roller and the pin by which
such adjacent links are connected to one another. As a limit, each
of the links can be relatively rotated until it rotates forward or
backward into contact with the next adjacent link.
[0008] There is a known type of chain that is structured to bend
freely in one direction but not the other. In theory, such a chain
is free to bend flexibly around two sprockets of an endless loop
drive, but is not free to bend backwards, thus defining a flat and
non-sagging bed between the sprockets for bearing weight. The links
of such a chain are coupled by pivot pins located on the side of
the chain facing the sprocket, at the longitudinal ends of
typically block-shaped link bodies. When the chain is pivoted
around a sprocket, abutting ends of the link bodies diverge. If one
attempts a backward bend, the block shaped link bodies abut and the
chain can only be bent "backwards" up to the point at which the
links are in a straight line. An example of such a chain is
disclosed in U.S. Pat. No. 5,970,701-Roden et al., which is hereby
incorporated. A problem with such a chain is that a minor amount of
play or looseness in the pivot pin joints due to manufacturing
tolerances or other causes will permit the chain to sag. Similarly,
if the abutting surfaces of the block-shaped links are individually
too high or too low, the chain may be bumpy or may sag. As a
result, it is often preferred to provide a rigid underlayment or
track if a chain structure is to bear a load in the same plane that
the chain is to flex.
[0009] In many uses for roller chains, the chain is closed in an
endless loop that is of the length needed to pass around sprockets
that are mounted at fixed rotation points on a chassis. One of the
sprockets is usually coupled to driving power and the chain
transmits the power to rotate another sprocket. The chain is
relatively taut between the sprockets on one side of the endless
loop, due to tension exerted by the driving sprocket. The chain is
typically slack between the sprockets on the other side of the
endless loop, but even so is in tension between the payout point on
the drive sprocket and the take-up point on the driven sprocket,
due to the force of gravity and sagging of the chain.
[0010] An arrangement with one driving sprocket and one driven
sprocket is just an example. Chain arrangements can have any
combination of powered sprockets and idlers. The chain may follow a
path that bends only toward one side, or the path may bend
sinuously forward and backward. In addition to transmitting
rotational power, a chain can be used to move a device linearly
along the chain path, e.g., back and forth between sprockets.
However, chains that are structured for pivoting or relative
rotation between links are typically useful only in tension. When
not subjected to tension, or when in compression, the
relatively-rotatable coupled links are free to pivot and cannot be
relied upon for purposes of positioning or transfer of power.
[0011] In order to tension a chain or otherwise to support such an
elongated flexible item, it is necessary to provide a support or
chassis that is as long as the distance between the extremes of the
path of the chain. In some instances, it is not practical to
provide such a supporting structure.
[0012] Regardless of whether there is any slack or looseness in the
pivot joints between links of a flexible chain, the chain must sag
between horizontally spaced supported points. A tensioned flexible
structure can only remain straight if it has no lateral load, or if
an infinite amount of tension is applied, because sagging is a
vector function related to lateral loading (e.g., vertical weight
of a horizontally elongated structure) and tension. The chain acts
like a suspension structure for the weight of the links (plus any
load thereon), and sags in a parabolic arc that is a function of
the relative forces of tension and gravity load.
[0013] A chain can be structured so as to bend in one direction as
in the Roden patent mentioned above, or the chain can be supported
on a linear track under a span between sprockets or other support
points. It is possible to envision various support structures for
such a track, including the possibility of a telescoping support
track. These solutions have their own problems.
[0014] In the typical chain structure discussed above, the
connected links alternate between roller links and pin links. It is
also possible to have a chain in which the links are all identical,
for example with each link having a pin end that is slightly wider
than a roller end dimensioned to attach to the pin end of an
adjacent link. It is also possible to provide a chain in which the
successive links are connected by structures that are wholly
different than the hollow rollers and solid pins that characterize
roller chains.
[0015] The present invention provides a mechanism whereby the
nature of the coupling between links in a chain can be selectively
changed between rigid and relatively rotatable couplings. Along a
given chain run, the couplings of the links can be made rigid for
some links and rotatable for others. This opens a number of
inventive possibilities that are discussed below.
[0016] However, the idea of providing a chain in which the pivot
connections are switched between rigid and flexible states by means
of an engaging part is known per se. In Yoshiga et al., U.S. Pat.
No. 5,157,912, a connecting pin engages between otherwise-pivotable
links and is laterally displaceable by external contact with a
constricting structure along the chain path. The displaceable part
is a spring biased lateral pin that is eccentric to the link pivot
axis, and not a displaceable complementary shape. Yoshiga teaches
this locking function in connection with a push-pull chain, for
holding constant the length of the chain. The implication appears
to be that if the joints were free, the chain would shorten when
pushed (longitudinally compressed), due to pivoting of the links at
their joints. Yoshiga supports the chain on a track and does not
teach the possibility of making a chain self supporting against
sagging and potentially variable in length.
[0017] Snapp, Jr., U.S. Pat. No. 4,141,665, teaches a general
purpose angularly lockable articulated joint. Although there is a
complementary shape between adjacent linked members for fixing the
joint against pivoting, the engagement and disengagement involves a
longitudinal lengthening and shortening. This is structurally
different than the present inventive arrangement wherein locking is
accomplished by lateral displacement of complementary shapes.
[0018] U.S. Pat. No. 4,658,577-Klein, U.S. Pat. No.
5,108,350-Szpakowski, U.S. Pat. No. 5,970,701-Roden et al. and U.S.
Pat. No. 6,016,844-Takahashi et al. teach limits on the angle to
which chain joints are permitted to pivot, in one direction. Such a
chain structure is sometimes called a "Woods chain." The
disclosures of these patents concern a number of situations in
which it is desirable to have a self-supporting chain. However,
they fail to teach or suggest an arrangement similar to that
discussed herein. Some other references in the general background
are U.S. Pat. No. 4,635,438-Rottinghaus, U.S. Pat. No.
4,885,907-Pappanikolaou and U.S. Pat. No. 5,107,672-Featherstone.
All the foregoing patents are hereby incorporated in their
entireties.
SUMMARY OF THE INVENTION
[0019] It is an object to provide an improved support device that
has the advantages of flexibility and rigidity at the same
time.
[0020] It is another object to improve the art of link chains using
a particular structure for rendering the couplings between
particular links rigid or pivotable, and in so doing to prevent
sagging without the need to support the chain.
[0021] It is a further object to provide a practical means by which
a flexible chain can rigidly support or position a manipulator
while at the same time movably coupling power to a device or
movably positioning a device at a desired position using the same
rigid supporting chain structure.
[0022] According to the invention, the chain is formed of a series
of successive links, each link comprising laterally spaced link
plates, and each link being coupled to the next adjacent link by a
lateral pivot pin. The links alternate between two types. In one
type of link, the laterally spaced link plate(s) reside at a fixed
lateral position. In every second link, the link plates are
laterally depressible against resilient bias from a spring,
resilient pad or pneumatic cylinder, etc. When the laterally
depressible plates are permitted to move laterally outwardly due to
the resilient bias, complementary abutting contours of the adjacent
links of said two types engage one another, and prevent relative
rotation around the axis of their respective connecting pin. When
depressed, the link plates of the adjacent links are mechanically
engaged only by lateral pivot pins, and relative rotation is
possible.
[0023] When the complementary contours of two or more adjacent
links in a segment of chain are engaged, that segment becomes
self-supporting. The segment cannot sag in a circumferential plane
relative to the pivot pin axes. Preferably, the engaging
complementary contours are laterally tapered or wedge-shaped. In
this way, the resilient bias moves the lateral plates outwardly
along the tapered or wedge shaped surfaces until they abut without
clearance. This makes the chain segment rigid in its
self-supporting state. Any looseness due to manufacturing tolerance
is taken up as the wedge shaped surfaces advance over one another
to a stable position.
[0024] In its locked condition, the chain can bear a force that is
a function of the angle of the wedge shaped surfaces, the force
exerted by the resilient bias structure, friction and similar
factors. In its rigid state the chain can operate as a triggerable
structure, i.e., a structure that rigidly supports a lateral load
up to a given weight or force, and then gives way. Alternatively
and preferably, the chain can be arranged rigidly to support any
load encountered in its normal operation but to switch between
flexible and rigid states where needed. For this purpose the chain
can selectively be made flexible to pass around curves in a guide
or on a sprocket, and then switched automatically into a rigid
condition when the links thereafter become aligned. The chain can
become rigid when the links are aligned in a straight line, or when
the links are aligned at a predetermined angle. It is also possible
to provide two or more angles at which the links become rigidly
aligned.
[0025] For switching from the self-supporting state to the
pivotable (bendable) state, the chain can be passed through a
narrowing guide path having cam surfaces that force the laterally
depressible link plates inwardly, at least on one side of the
chain, and disengage the complementary contours of the depressible
link plates from the adjacent fixed link plates. Such a guide
surface can be provided leading into a curve, for example, such as
where the chain approaches an angular diversion or a sprocket or
the like. So long as the adjacent links remain angularly diverted
around such a curve, the complementary contours do not re-engage
and the links remain relatively rotatable. When the chain run
reaches an angle at which the complementary contours again align,
the contours re-engage unless the guide path is still depressing
the depressible links.
[0026] Using the foregoing structure, the chain can be made to
become rigid over one portion of its path, such as over a straight
run where the chain positions a manipulator, and flexible over
other portion of its path, for example to pass around curves such
as sprockets. The chain of the invention is considered apt for
supporting a manipulator over a distance through a vertically
narrow space, where sagging of the chain is particularly
undesirable.
[0027] Generally speaking, the invention employs laterally
displaceable spring-biased complementary contours for selectively
fixing the radius of curvature of a link chain by rigidly locking
successive links. More particularly, this is accomplished by
wedging structures that account for any play in the joints. The
invention provides a chain structure that is generally useful as
described, and also is applied to certain exemplary applications
involving positioning of manipulators in confined but elongated
spaces, varying the length of a supporting structure and otherwise
providing new uses for chains.
[0028] In one possible embodiment, the inventive chain has link
plates on both sides of the chain that abut with adjacent link
plates in a longitudinal direction to lock. One of two
longitudinally successive link plates is laterally depressible to
unlock, namely to laterally move the longitudinally abutting
surfaces clear and to permit the link plates to overlap during
pivoting of the links. A conventional roller chain is flexible in
one plane, namely the plane that is commonly circumferential to all
the pivot pin axes, and cannot divert out of that plane. In
contrast, the inventive chain is compliant or capable of diverting
from its plane if the depressible (movable) link plates are
provided on both sides of the chain. The extent of diversion is a
function of the span of movement of the depressible links. If the
depressible link is provided on one side only, then the chain is
confined to a plane that is circumferential relative to the pivot
pin axes. This aspect can cause the chain to be controllably
compliant, namely by selectively unlocking the movable links on
both sides to render the chain compliant or to unlock one side,
making the chain flexible in the circumferential plane but not
compliant to diversion out of that plane.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] There are shown in the drawings embodiments of the invention
as presently preferred. The invention is capable of certain
variations in accordance with its scope. Accordingly, reference
should be made to the appended claims rather than the exemplary
embodiments shown in the drawings, for determining the scope of the
invention in which exclusive rights are claimed. In the
drawings,
[0030] FIG. 1 is a perspective view of a chain according to the
invention, traversing a contoured track (shown exploded).
[0031] FIG. 2 is an elevation view of a length of chain according
to the invention.
[0032] FIG. 3 is a partial elevation view, partly in section,
showing a lateral side of the chain of FIG. 2.
[0033] FIG. 4 is a partial perspective view of a set of links of
the chain, shown separated for purposes of illustration.
[0034] FIG. 5 is an elevation view of a depressible link according
to a preferred arrangement.
[0035] FIG. 6 is an elevation view of the depressible link from the
right in FIG. 5.
[0036] FIG. 7 is an elevation view of the depressible link from the
top or bottom in FIG. 5.
[0037] FIG. 8 is an elevation view of an alternating
non-depressible link that is provided in the inventive chain
between links as shown in FIGS. 5-7.
[0038] FIG. 9 is an elevation view from the right in FIG. 8.
[0039] FIG. 10 is a perspective view showing a section of chain
according to another embodiment.
[0040] FIG. 11 is an elevation view showing an exemplary
application of the invention to a device for positioning a
manipulator.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0041] An exemplary embodiment of the invention is shown in FIGS.
1-9. The illustrated embodiment comprises two types of chain links
22, 24 that are coupled alternately to provide a serial chain 20 of
indefinite length.
[0042] The chain 20 generally has a plurality of links of a first
type and a second type 22, 24, alternating with one another along a
longitudinal length of the chain. Each adjacent pair 22, 24 of the
links is movably attached for relative rotation on a pivot axis 30,
namely by a pivot or roller pin 40. According to an inventive
aspect, the links of the first and second types have longitudinally
abutting surfaces 54, 56 that prevent the links of the first and
second type from rotating relative to one another on the axis 30
when engaged. However, at least one of the links 24 of the first
and second types is displaceable sufficiently to disengage the
longitudinally abutting surfaces 54, 56 of adjacent links in a pair
to permit relative rotation. This can be accomplished by engaging
the displaceable links 24 against the bias of a resilient element
such as a spring 52 using portions 35 of a track to press links 24
laterally inwardly. The track, for example, can have elements that
define a curving arc 33 in association with converging surfaces 35,
for contacting and displacing the displaceable links 24 to permit
pivoting. After emerging from the track or otherwise being brought
back into alignment in the absence of a structure that presses the
displaceable links 24 inwardly, the resilient bias causes links 22,
24 to re-engage and again render the chain 20 rigid.
[0043] In this way, the chain is converted along certain portions
of its length between functioning as a rigid structure and a
structure that is flexible at least on one plane. As a rigid
structure, a length of the chain can define a straight bar, a
curved arc or another shape that comprises rigidly coupled serial
links. Where the chain is in a flexible state, it can bend freely
in a plane that is circumferential relative to the pivot axes of
the pins joining the links, in a manner similar to a roller chain.
According to a preferred structure as described herein, the
structure tending to lock the adjacent links can comprise
resiliently biased laterally displaceable link plates. According to
that structure the chain is also capable of bending compliantly in
response to a force that bears against one lateral side of the
chain (as opposed to a balanced symmetrical force tending to
constrict opposed displaceable link plates).
[0044] For convenience in this description, the axis of elongation
of the chain is generally considered the "longitudinal" direction,
unless otherwise noted. The width of the chain links 22, 24, which
is the thickness defined by and between the spaced plates defining
the links, is termed the "lateral" direction. The lateral direction
is thus the same as an axial direction with respect to the axes of
the pivot pins joining the links. In general, the terms
longitudinal and lateral will refer to the extension of chain 20
unless otherwise noted. Notwithstanding these presumptions, terms
with circular or rotational implications, such as pivoting,
rotation, circumferential planes, diameters and radii, generally
refer to the pivot axis of the pins or shafts that couple adjacent
links in the chain.
[0045] In the exemplary arrangement shown, each of the two link
types 22, 24 has an identical coupling structure at both of its
opposite ends. The coupling structure of each link 22 or 24 is
complementary with the coupling structure of the other type of link
24 or 22. It is also possible to embody the invention with more
than two types of links, or to have only one type of link that is
different on its opposite ends.
[0046] For example, the links of the two types 22, 24 as shown
could have different intermediate structures between identical
coupling ends, such as different sorts of functional structures or
attachment points for carrying other articles apart from the links
themselves, whereby the links have different functions. Any number
of functionally different links can be coupled together into a
chain using alternate coupling structures, for example as shown in
FIGS. 1-9, with each link having one of two complementary couplings
at each of its opposite ends, which can couple to the other
complementary coupling structure. Alternatively, as noted above, a
given type of link can have one end that corresponds to one of the
depicted links 22 and another end that functions as the other type
24. In any event, the chain 20 has links 22, 24 with complementary
ends that engage as discussed.
[0047] The chain 20 can be coupled in an endless loop or can have
terminal free end links, defining a discrete length. The
intermediate and/or ending links can have other structures attached
to them (not shown) or can serve only as a mechanical connection
between their two adjacent links.
[0048] Each pair of adjacent links 22, 24 is mechanically coupled
in a manner that defines a pivot axis 30 for relative rotation
between the two adjacent links. The pivot axes 30 of successive
pairs of adjacent links 22, 24 are preferably parallel to one
another and perpendicular to a longitudinal extension of chain 20.
The pivotal connection of links 22, 24 via pivot pins or shafts 40
can generally resemble the structure of a roller chain. The chain
can be used in many of the same ways as a conventional roller
chain. Some examples of uses include coupling power between
sprockets or other chain engaging structures (not shown),
positioning articles or manipulators by attaching them in one way
or another to particular links, etc.
[0049] According to an inventive aspect, chain 20 is selectively
made flexible or rigid along limited portions of the chain run, by
movably changing the nature of the coupling between successive
adjacent links 22, 24 from rigid to rotational or rotational to
rigid. This can be done on the fly, by moving the chain links
relative to a contacting structure (or moving the contacting
structure relative to the chain) so as to displace certain movable
links that operate as control structures for switching between
rigid and flexible states. One of the links 24 has a movable link
plate 44 that is displaceable between positions in which pairs of
adjacent links 22, 24 are locked against relative rotation on the
pivot axis 30 that joins them, or are permitted to rotate relative
to one another on the axis 30. In this way, the chain can have a
run of adjacent links that are self-supporting over an indefinite
and variable length. The chain may transmit power in tension or
compression. It may be straight or curved. If straight and
horizontal, the chain in its rigid state does not sag in a
parabolic arc. The same chain at different points can pivot between
sections that are rigid bars or can be sinuously flexible to follow
a path of changing directions, conforming for example to bends,
changes in bending direction, changes in bending radius and similar
diversions along the path.
[0050] FIG. 1 shows a longitudinal length of chain 20 that passes
through an arc such as a right angle 33 relative to the
longitudinal direction. This arc has an axis of curvature that is
parallel to the axes 30 on which the successive links 22, 24 are
pivotally attached to one another. The right angle 33 can be
defined by one or more track-defining elements 35 as shown, and can
further include a sprocket (not shown) with a shaft parallel to the
pivoting axes of the coupled links or similar arrangements.
According to the invention, each of the successive links 22, 24 is
structured so as to be freely pivotable relative to the leading and
following two adjacent links, when passing around a given part of
the chain run, in this case around the arc 33, and to rigidly
engage its two adjacent links, preventing relative rotation, at
other points along the chain run.
[0051] The adjacent attached links 22, 24 have pivotal couplings
comprising a pin or shaft 40 that extends between two laterally
spaced plates 44 or 46 forming the respective links 22, 24, which
pin or shaft 40 normally guides relative rotation of the links. The
links also have engageable/disengageable complementary surfaces 54,
56 that are eccentric relative to the pivot axis, i.e., are spaced
radially from the pivot axis, and abut to prevent relative rotation
of adjacent links 22, 24 when engaged. The two alternating coupling
types provided along chain 20 have complementary surfaces, for
example, corresponding to planes that are normal to the
longitudinal extension of chain 20. In the embodiment shown, the
complementary surfaces are lateral-planar surfaces approximately
parallel to the axes 30 of the pivot pins 40. However the
complementary surfaces need not intersect the pivot axes and will
prevent rotation if aligned at any abutment surface that does not
shear along a line that is circular around the pivot axes. The
abutment of the complementary surfaces prevents relative rotation
of the adjacent links around relative rotation axes defined by
connecting pivot pins defining axes perpendicular to the
longitudinal axis of the chain. At the same time, the complementary
surfaces are displaceable and can be brought into abutment or moved
to clear them from abutment when the chain is to be rendered
flexible across the mechanical coupling between the associated
links.
[0052] In the embodiment shown, at least one of the links 24 has
one or two laterally spaced link plates 44 that can be displaced
laterally of the chain extension so as to disengage the
longitudinally abutting surfaces 54, 56 (or at least one type of
coupling has a portion that can be displaced if the links have two
distinct couplings at their opposite ends). As shown, this is
accomplished in a durable and effective manner by structuring the
links 22, 24 as pairs of link plates 44 or 46 and mounting the
links such that at least one of the link plates 44 of each pivotal
coupling is movable toward and/or away from the longitudinal center
line of chain 20 over a span sufficient to cause the abutting
eccentric (non-circular) surfaces 56 of the movable link plate 44
to move into engagement or out of engagement with a corresponding
complementary surface 54 of the other type of link plate 46.
[0053] In the depicted embodiment, the longitudinally adjacent
coupling structures define surfaces extending radially on
diametrically opposite sides of the pivot axes 30. These surfaces
define shoulders 54 on the chassis link plates 46 that abut against
spaced edges 56 on the movable link plates 44 to prevent relative
rotation of the links around the pivot axis 50, provided that the
link plates 44, 46 of the two link types 22, 24 are coplanar. The
shoulders 54 and edges 56 need not be radial to the link pins, and
could also be located longitudinally nearer to the end of the link
or farther from the end than the pivot axis. In any event,
engagement renders the chain rigid. The movable link plates 44 can
be displaced out of this coplanar position, preferably against a
restoring force such as resilient bias from a spring or the like,
such that the shoulders no longer abut. In this position the links
can overlap, allowing for relative rotation of the adjacent links
on axes 30. Inasmuch as adjacent links are locked or unlocked
independently, a selected length of the chain can be made flexible
while another is rigid at the same time.
[0054] In the preferred arrangement, the chain 20 is rigid when the
links 22, 24 are in a straight line (provided the movable links
have not been displaced against the restoring force). It is also
possible for the couplings to become rigid at a particular angle of
relative rotation (i.e., other than a straight in-line alignment),
thereby fixing the successive links to define a rigid chain run
having a predetermined radius of curvature. This merely requires
re-aligning the complementary surfaces 54, 56, for example to cross
the longitudinal extension of chain 20 at an angle, rather than
perpendicular to the longitudinal extension as shown in FIG. 2.
[0055] It is also possible to structure the links to engage at a
plurality of selectable angles (not shown), for example defined by
step-wise edges in the longitudinally abutting complementary
surfaces 54, 56 of the link plates. This can cause adjacent links
22, 24 to become angularly fixed at a selected radius of curvature
of the chain, namely at the relative pivot angle between adjacent
links that is defined by a selected one of the plurality of angles.
It is also possible to provide similar structures that can fix some
of the couplings at one angle and other couplings at a different
angle, either by providing links with different characteristic
angles at different points along the chain, or by providing links
that can assume different angles. The links are controlled
accordingly at selected lengths of the chain to define the required
combination of arcs and/or straight and flexible sections.
[0056] FIG. 2 shows in greater detail a preferred embodiment
wherein there are two distinct types of links and the links are
arranged to lock in a straight line in one state, or upon
displacement of the control link plate 44 to pivot freely in
another state. In the pivoting state, the links are free to pivot
within limits reached when one link is pivoted all the way back
against the adjacent link. FIG. 3 is a partial section view that
corresponds to a side view of the chain as shown in FIG. 2,
including a depiction of chain 20 entering a track structure having
a constricting path defined by converging elements 35, for
switching between an engaged state and a disengaged pivotable
state.
[0057] The respective links 22, 24 each comprise plates or similar
parts 44, 46 that abut on their end surfaces 54, 56, as described
in more detail below. The links 22, 24 alternate, with a chassis
link 22 placed between and attached to each movable-plate link 24,
and vice versa. The links are relatively rotatable only when the
plates 44 of one of the two types of links, namely the movable
plate link 24 (which also could be called a control link) are
depressed laterally inwardly to a position where part of the
movable-plate link and the otherwise coplanar chassis link plate
are clear to lap over one another. In the embodiment shown, both
plates of the movable plate link are depressed in order to permit
pivoting. It is also possible to embody the chain such that one of
the lateral plates of the movable plate link 24 is depressible and
the other plate is stationary. In that case the stationary link
plate is mounted to pivot freely relative to the adjacent link, and
only the movable link plate is arranged to lock and unlock as
described. If a movable link plate 24 is provided only on one side,
and the other link plate is of a conventional roller chain
structure, the chain links are restricted by said other link to
occupying a single circumferential plane that is common to the
pivot pin axes coupling all the links. If movable link plates 24
are provided on both lateral sides, the chain becomes compliant to
forces that would bend the chain out of a single common
circumferential plane, at least up to the extent to which the link
plates are laterally movable. This aspect of the inventive chain
structure is discussed in more detail below.
[0058] Preferably, the chassis links 22 and the movable plate links
24 each comprise two laterally spaced link plates. The chassis link
22 preferably is a rigid structure comprising two parallel link
plates 46 that are spaced laterally of the direction of chain
elongation, and are joined by two longitudinally spaced parallel
pivot pins or shafts 40 that define the inter-link rotation axes
30. The chassis link 22 is shown in an exploded perspective in FIG.
4 and the chassis link plate 46 is shown in elevation views in
FIGS. 8 and 9. The chassis link 22 is a box-like rectilinear
structure with mutually perpendicular link plates and pivot pins
attached together. The chassis link 22 provides a structural
connection between the movable-plate links 24 and generally
functions in a manner that is similar to a pin link that joins
adjacent roller links in a roller chain.
[0059] The movable-plate link or control link 24 likewise
preferably has two parallel plates 44. Unlike a roller chain, which
has parallel roller link plates that are rigidly spaced, the
movable plate links 24 are slidably mounted on the pivot pins or
shafts 40 of the two adjacent chassis links 22 and can move
laterally inwardly and outwardly as well as pivoting. Additionally,
a restoring force element is provided to urge the movable link
toward one of the two states (toward the locking state in the
embodiment shown). In this arrangement, the restoring force is
provided by a resiliently compressible biasing structure. For
example, a helical spring 52 can be mounted on each pin or shaft
between the movable plate links to apply a force to urge the
movable plates 44 towards a position in which they lock
non-rotatably with the chassis link plates 46. The restoring force
could be provided by a different form of spring, such as a
Belleville washer or disc spring. In lieu of a spring or washer, a
resiliently compressible pad structure can be provided. In a large
link chain, it may be practical to provide a suitably large scale
restoring force means for the links, such as a pneumatic cylinder,
etc.
[0060] Assuming that chain 20 is locked in a rigid state and is
progressing toward the curve 33 shown in FIG. 2, the links
approaching the curve are disposed in longitudinal abutment at
corresponding shoulders 54 of the chassis link plates 46, which
bear against complementary wedged surfaces 56 of the movable plate
links 44. These inclined or wedge shaped bearing surfaces 54, 56
are complementary portions of respective rigid bodies (namely the
link plates) and they are spaced from the rotation axis 30 defined
by the pins 40. As a result, engagement of the shoulders 54 and
wedge surfaces 56 rigidly fixes that coupling between the
respective links 22, 24 against relative rotation on the pin axis
30. The chain is a rigid bar along this portion of its extension.
The engaged links are capable of acting in tension or compression
and the chain does not sag.
[0061] In the embodiment shown, the default or rest state assumed
by the chain is a rigidly locked state. In an alternative
embodiment (not shown), it is possible to arrange the invention
such that the default or rest state is the flexible state. In that
case the complementary shoulders would engage when the movable
links are displaced against the restoring force instead of vice
versa.
[0062] In the embodiment of FIGS. 1-9, the laterally depressible
movable link plates 44 and the laterally stationary chassis link
plates 46 engage via their longitudinally facing complementary
abutting wedge surfaces, and there is a slight space around the
laterally outer edges 62 of the chassis link plates that are
disposed longitudinally beyond the wedge surfaces at the shoulders
54 (namely the "head" portion of the chassis link plate beyond
shoulders 54). This portion, which may have a through opening for
the pivot pin 40, extends between raised side walls 64 of the
movable link plate 24 in the locking position of the links. The
movable link plate 44 must be depressible laterally inwardly
sufficiently to clear the raised side walls 64, the ends of which
define wedge surfaces 56, to permit pivoting. Therefore, the
laterally outward surfaces 62 can be made precisely complementary
with the space between the raised or cammed side walls 64 of
movable link plate 44, rather than leaving a space as shown, to
make the connection even more rigid. A slight space is preferred to
prevent binding.
[0063] The movable link plates 44 have portions that extend
laterally outwardly from chain 20 by a distance greater than the
thickness of the chassis link plates 46, which portions are on the
cammed side walls 64 of the movable link plate 44. Referring to
FIGS. 1 and 3, when chain 20 encounters a track or similar
obstruction 35 that narrows along the path of the chain, a force is
exerted to press the movable link plates 44 toward one another. The
movable link plates 44 are depressible by a sufficient distance
that the longitudinally abutting shoulders 54 of the chassis plates
22 and wedge surfaces 56 of the movable plates 44 can be passed
laterally beyond one another to no longer abut. The adjacent link
plates 44, 46 are then free to rotate relative to one another. The
link plates 44, 46 and the formerly-abutting longitudinally facing
surfaces of the plates 54, 56, lap over each other as shown in FIG.
3.
[0064] FIGS. 5-7 show an exemplary movable link plate 44 and FIGS.
8 and 9 show an exemplary chassis link plate 46. The preferred
chassis link plate 46 is substantially flat as shown and has two
longitudinally spaced bores 66 for the pins or shafts (not shown in
FIGS. 8-9) that extend laterally between the chassis link plates
44. The chassis link plate has extensions or arms 68 that extend
laterally from the body or central part 72 of the plate and have
abutting surfaces 54 that are spaced from the pin axis 30. In the
embodiment shown, the abutting surfaces 54, 56, which are
complementary, extend substantially transverse to the longitudinal
center line of chain 20 at a point that corresponds to the pin axis
30 and thus is substantially radial to the axis of the pin. A
similar structure is provided at each end of the chassis link plate
46. Likewise, similar wedge shaped edges 56 are provided at the
ends of the cam side walls 64 of each movable link plate 44.
[0065] Although each complementary abutting surface is transverse
to the chain center line, the abutting surface is sloped by an
angle .alpha. relative to the plane of the associated link plate.
This provides a wedging surface operating in a longitudinal
direction relative to the chain. Th wedging surface is such that a
restoring force that would advance the movable link plate in the
resilient bias direction relative to the chassis link plate,
produces a corresponding longitudinal separation or chain
stretching force, the relationship of these forces being a function
of the wedging angle.
[0066] Preferably, the movable link plate and the chassis link
plate have exactly corresponding wedge surface angles, namely the
same angle .alpha. relative to a plane parallel to the longitudinal
axis of the chain. The restoring force or spring biasing means that
urges the movable link plate 44 outwardly, bears against the
movable link plate 24 and serves both to stretch and to angularly
lock the chain across the pivot pin joint.
[0067] The restoring force can be supplied in various ways. In the
embodiment shown in FIGS. 3 and 4, a single helical compression
spring 52 is placed on each pivot pin. An alternative embodiment is
shown in FIG. 10. In this arrangement, separate and independent
springs are provided for each end of the pivot pin 40. The separate
springs can be compressed between the movable link plate 44 and a
split ring fastener 75 in an annular groove or a similar axial
fixing structure (e.g., a shoulder formed on the pin, a set screw,
a bushing, etc.). As discussed above, the helical spring is also
simply an exemplary structure and could be replaced with or
supplemented by other compressible structures or the like.
[0068] The movable link plate 44, shown in FIGS. 5-7, comprises a
body portion that resembles the chassis link plate 46 in that there
are two spaced openings 76 for rotatably and slidably receiving the
pivot pin 40 for affixing each end of the movable link plate 46 to
an adjacent chassis link plate 44, and wedge surfaces 56 discussed
above, on a line oriented laterally of the chain centerline,
radially from the pivot pin axis 30, and complementary with the
surface on shoulder of the chassis link plate inclined at angle
.alpha. relative to the plane of the link plate 44 or 46.
[0069] The movable link plate 44 has structures that extend
perpendicularly upward from the body of the movable link plate, and
can have structures that extend perpendicularly downward toward the
opposite movable link plate 44 (see FIGS. 4 and 7). The pivot pin
40 extends from the downward side, and can have one or more springs
52, optionally bearing against a split ring fastener 75 or the
like. The movable link plate can have a rearward extending bushing
portion 78 with a bore that slides on the link plate and guides the
movable link plate relative to the pin, and thus relative to the
chassis link plates that are rigidly attached to the pin. The
underside of the movable link plate also can be flat as shown in
FIG. 10.
[0070] On the upward or laterally outer-facing side, the movable
link plate 44 has a side cam wall 80 on each side of the link plate
44, which in this embodiment extends approximately between the
longitudinal centers of the pivot pin axes 30. The side cam wall
could also extend beyond the axes 30, or it could be shorter. On
the ends of each side cam wall 80 in the longitudinal direction,
the movable link plate 44 has a wedge surface 56 at angle a, which
as discussed above exerts a longitudinal stretching force on the
chain as the movable link plate 44 is resiliently forced laterally
by the restoring force (e.g., from spring 52) against the chassis
link plate 46, which has a corresponding wedge surface 54.
[0071] Near the longitudinal midpoint of the side cam wall 80 on
each side of the movable link plate 44, a peaked contact cam 82 is
formed, shaped as a rounded hump. Due to the peaked cam 82, the
side cam wall extends laterally above the adjacent flat end parts
of the side cam wall leading up to the wedge surfaces 56.
Preferably the peaked cam 82 extends above these surfaces by a
distance that is slightly greater than the thickness of the chassis
link plate 46. This distance is needed because when the movable
link plate 44 is depressed by contact with a constricting pathway
such as the inwardly tapering surfaces 85 of the track elements 35,
the movable link plate 44 needs to be depressed far enough to clear
the chassis link plate and permit pivoting. As shown in FIG. 3,
therefore, the cam peak 82 is high enough to move the adjacent flat
face of cam side wall 80 to a point where the cam side wall can lap
under the inner surface of the chassis link plate 46.
[0072] When the chain is passed between opposed surfaces 85
defining a narrowing lateral space for the chain, or when a force
is otherwise exerted against the movable link plates, for example
by bearing against the peaked contact cam 82, the movable link
plate is pressed inwardly toward the chain center line against the
bias of the spring(s) 52 on the pivot pins 40 urging the movable
link plate 44 to a position at which its abutting surface clears
that of chassis link plate 46. Preferably, as shown in FIGS. 1 and
3, the guiding track structure for the chain comprises lateral
surfaces that narrow in the direction of chain motion and contact
the peaked contact cams so as to depress the movable contact link
plates laterally inwardly from a position in abutting contact with
their adjacent chassis link plates. In the depressed position,
shown at the bottom of FIGS. 2 and 3, the links are free to rotate
relative to one another because the abutting surfaces are no longer
aligned and the link plates of the successive links are free to lap
over one another. The chain is rendered flexible, but it is
necessary to provide some method such as a track or a sprocket, to
cause the chain to bend around a curving path when in its flexible
state.
[0073] The chain as shown and described is subject to variation in
structure and function. The chain can be scaled up or down in size
and made of one material or another as appropriate for the
situation and the load to be borne. In an exemplary application, a
chain as described and shown in FIG. 1 is used to position a
manipulator carried on one of the links, at a selected position
within a long, narrow hollow body such as a tank within an aircraft
wing, for example to apply or remove a surface treatment. An
apparatus for such a use is shown in FIG. 11. A wing accessway may
be relatively small, such as an oval 25 by 45 cm (10 by 18
[0074] inches), that leads from the underside of the wing into a
laterally elongated space that may be two meters or more in length.
The invention as shown in FIG. 11 provides all the necessary
structural strength to position the cantilevered weight of a
manipulator and to bear the forces needed to place and to use it at
the end of its traverse.
[0075] In the preferred embodiment, depressible movable link plates
are provided on both sides of the chain rather than on one side
only. As a result of providing movable link plates on both sides in
the structure shown and described, the chain becomes deformable in
a direction perpendicular to the usual plane in which a roller
chain or the like is free to flex. Assuming that the chain as shown
is advanced upwardly and to the left in FIG. 11 using the
supporting carriage shown, for example to position a manipulator in
an elongated space, it could occur that the carriage may become
misaligned, causing the chain to be directed to the left or right
of the center of the space, and to encounter a side wall. All the
links of a conventional roller chain are limited to occupying a
plane that is circumferential relative to the pivot axes between
the links, and all the links must occupy the same plane. The
depressible/movable control links of the invention, however, define
a span of movement that permits links in the chain to move out of
the common plane.
[0076] Assuming that a one-sided lateral force is exerted on the
chain (a force along the axis of one of the pivot pins, not a
bidirectional inward force), a movable link plate may be depressed
within its span of movement. Likewise, lateral force against a
chassis link plate may tighten the wedging force between that
chassis link plate and the next adjacent movable link plate, and
may displace the next adjacent movable link plate inwardly.
Depressing a movable link on one side of the chain relative to the
abutting chassis link plate could free the movable link plate and
adjacent chassis link plate to rotate relative to one another.
However, on the opposite side of the chain the links remain locked.
A one-sided force on a movable link plate which depresses it on one
side (loosen its wedging) will tighten the wedging action on the
opposite side. As a result, one sided lateral force is accommodated
by lateral diversion of the chain, in a stair-step progression. The
chain is compliant, possible preventing damage if used to position
a manipulator, but the chain remains rigid.
[0077] In an alternative embodiment, the chain may have
movable-depressible link plates on one lateral side, and not on the
other lateral side, which instead resembles a roller chain. In that
case, lateral force on the chain will depress a movable link and
free the corresponding link to pivot.
[0078] In the embodiment of FIGS. 2 and 3, the chain has a pivot
pin joining each abutting set of link plates. As shown in FIGS. 1
and 10, it is possible to provide additional link pins 88 and
optionally rollers therefor, at the midpoint of each of the links
or link plates. These pins extend between the link plates but do
not attach adjacent links together, as do the end link pins. The
additional pins provide added support, can carry transverse rollers
(or can be pins alone) and can engage the teeth of one or more
sprockets (not shown) between the pins and possibly rollers that
are at the connecting ends of the link plates. In the event that
additional pins are provided between the chassis link plates, they
can be simply press fit because the distance between the chassis
link plates preferably is rigidly set. If additional pins are
provided between the movable link plates, provision must be made
for the movable link plates to be depressed, such as a spring and
split ring arrangement as shown in FIG. 10.
[0079] In the embodiment for positioning a manipulator, for example
using a structure as in FIG. 11, the link plates are preferably
aluminum for lightweight strength. The plates preferably are
anodized, which among other things affects their coefficient of
friction (anodized aluminum has a coefficient of about 0.1).
[0080] The angle .alpha. of the wedge surfaces can be chosen with
several interests in mind. The angle is preferably small for good
rigidity, but not so small in comparison to the width of the link
plate that the wedging height can be all taken up by "bottoming
out" the movable link plate. The angle is sufficiently large in
comparison to the tolerance of the pivot pin joint and the
thickness of the link plates, to take up any looseness in the pivot
pin joints. A relatively large angle may be appropriate for
embodiments with thin link plates or loosely constructed
joints.
[0081] The rigidity and longitudinal bearing force produced by the
wedge surfaces during of engagement between abutting links is
relatively higher for angles that are relatively lower (i.e., the
wedge surfaces are nearly perpendicular to the plane of the
associated link plate), and vice versa. However this aspect is also
affected by friction. It is believed that the optimal wedge angle
is related to the friction angle of the material used (a measure of
the frictional nature of the material similar to the angle of
repose). Various values are possible for angle .alpha.. A maximum
angle is 45 degrees and preferably the angle is well below 45
degrees. For anodized aluminum, an appropriate the angle can be
less than ten degrees. In the illustrated embodiment the angle is
four degrees.
[0082] The pivot pins 40 that join the laterally spaced links can
be steel pins as used in roller chains. For the chassis links, the
pivot pins can be press fit into the chassis link plates when
assembling the chain. Preferably, the pins are removably attached.
The pins can be formed with shoulders to bear against the link
plates at bore holes and can have annular slots to receive split
ring or C-shaped fasteners on the lateral outside of the link
plates to ensure that the link plates are captive on the pins. Any
appropriate structure that affixes similar parts can be used as
well, such as screws or bolts, set screws, threads, bushings,
etc.
[0083] The chain of the invention is apt for use in an endless loop
embodiment or in a free-end embodiment. It is an aspect of the
invention that the chain can be used in a variable-length
positioning structure. Referring to FIG. 1, if the right angle
track with the converging walls is not rigidly fixed to anything,
advancing the chain carries along the right angle track structure.
Upon eventually encountering an obstruction, the right angle track
becomes stationary and the chain advances. By providing a plurality
of such right angle track sections (or perhaps other angles), the
chain of the invention can expand to a circuit that advances to
each next obstruction and then turns, filling an available volume.
This conformance to available size is particularly apt together
with the chain's compliance to bending in a plane parallel to the
pivot axes, as discussed above.
[0084] The chain having been described in connection with certain
preferred examples, variations of the concept within the scope of
the invention may now become apparent to persons skilled in the
art. The invention is intended to encompass a certain range of
methods and apparatus and reference should be made to the appended
claims rather than the foregoing specification, to assess the scope
of the invention in which exclusive rights are claimed.
* * * * *