U.S. patent application number 12/258628 was filed with the patent office on 2009-12-31 for torque limiter and sheet separating device having a torque limiter.
Invention is credited to Kevin Bokelman, Michael Janczyk, Ryan Smith.
Application Number | 20090322017 12/258628 |
Document ID | / |
Family ID | 41446446 |
Filed Date | 2009-12-31 |
United States Patent
Application |
20090322017 |
Kind Code |
A1 |
Bokelman; Kevin ; et
al. |
December 31, 2009 |
TORQUE LIMITER AND SHEET SEPARATING DEVICE HAVING A TORQUE
LIMITER
Abstract
A torque limiter may include a first member configured to rotate
about a first axis and having a first contact surface. The torque
limiter may include a second member configured to rotate about the
first axis and including a first axially extending finger. The
first finger may be radially biased so that a second contact
surface defined by the first finger may contact the first contact
surface with a normal force to define a predetermined torque value
between the first and second members. When one of the first and
second members is rotatably driven in a first rotational direction,
the other of the first and second members may be rotatably driven
in the first rotational direction unless a torque load greater than
or equal to the predetermined torque value is applied to the other
of the first and second members.
Inventors: |
Bokelman; Kevin; (San Diego,
CA) ; Janczyk; Michael; (San Diego, CA) ;
Smith; Ryan; (San Diego, CA) |
Correspondence
Address: |
HEWLETT-PACKARD COMPANY;Intellectual Property Administration
3404 E. Harmony Road, Mail Stop 35
FORT COLLINS
CO
80528
US
|
Family ID: |
41446446 |
Appl. No.: |
12/258628 |
Filed: |
October 27, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61076838 |
Jun 30, 2008 |
|
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|
Current U.S.
Class: |
271/264 ;
192/54.1 |
Current CPC
Class: |
B65H 2403/732 20130101;
B65H 3/5261 20130101 |
Class at
Publication: |
271/264 ;
192/54.1 |
International
Class: |
B65H 5/06 20060101
B65H005/06 |
Claims
1. A torque limiter comprising: a first member configured to rotate
about a first axis and having a first contact surface; a second
member configured to rotate about the first axis and including a
first axially extending finger, wherein the first finger is
radially biased so that a second contact surface defined by the
first finger contacts the first contact surface with a normal force
to define a predetermined torque value between the first and second
members, whereby when one of the first and second members is
rotatably driven in a first rotational direction, the other of the
first and second members is rotatably driven in the first
rotational direction unless a torque load greater than or equal to
the predetermined torque value is applied to the other of the first
and second members.
2. The torque limiter according to claim 1, wherein the second
member further comprises: a second axially extending finger
radially separated from the first finger, wherein at least one of
the first and second fingers includes the second contact surface;
and a radially oriented biasing member disposed between the first
and second fingers, wherein the biasing member is configured to
radially bias at least one of the first and second fingers so that
the second contact surface contacts the first contact surface with
the normal force to define the predetermined torque value between
the first and second members.
3. The torque limiter according to claim 2, wherein the biasing
member comprises a coiled compression spring.
4. The torque limiter according to claim 1, wherein the first
member comprises a hollow sleeve and the first contact surface
comprises an inner annular surface of the hollow sleeve defining a
cavity, and wherein the second contact surface comprises an outer
surface of the first finger and is configured to contact the inner
annular surface of the first member when the second member is
received in the cavity, and wherein the first finger is biased in a
radially outward direction.
5. The torque limiter according to claim 2, wherein the first
member comprises a hollow sleeve and the first contact surface
comprises an inner annular surface of the hollow sleeve defining a
cavity, and wherein the second contact surface comprises an outer
surface of at least one of the first and second fingers and is
configured to contact the inner annular surface of the first member
when the second member is received in the cavity, and wherein the
biasing member is configured to bias at least one of the fingers in
a radially outward direction.
6. The torque limiter according to claim 1, wherein the first
member comprises a plastic material.
7. The torque limiter according to claim 1, wherein the first
member comprises polyoxymethylene and glass fiber and a lubricant
comprising PTFE.
8. The torque limiter according to claim 1, wherein the second
member comprises a plastic material.
9. The torque limiter according to claim 1, wherein the second
member comprises nylon 6/6 and a lubricant comprising silicone and
PTFE.
10. A sheet separating device comprising: an advancing roller
configured to be driven by a drive device in a first rotational
direction about a first axis to move a first sheet picked from a
stack of sheets forward along a sheet path; a reversing roller
positioned adjacent to the advancing roller to define a nip
therebetween and configured to be driven in the first rotational
direction about a second axis to move a second sheet picked with
the first sheet from the stack of sheets backwards along the sheet
path, wherein the reversing roller is rotatably driven via a torque
limiter comprising: a first member configured to rotate about the
second axis and having a first contact surface; a second member
configured to rotate about the second axis and including a first
axially extending finger, wherein the first finger is radially
biased so that a second contact surface defined by the first finger
contacts the first contact surface with a normal force to define a
predetermined torque value between the first and second members,
whereby when one of the first and second members is rotatably
driven in the first rotational direction, the other of the first
and second members is rotatably driven in the first rotational
direction unless a torque load greater than or equal to the
predetermined torque value is applied to the reversing roller.
11. The sheet separating device according to claim 10, wherein the
second member further comprises: a second axially extending finger
radially separated from the first finger, wherein at least one of
the first and second fingers includes the second contact surface;
and a radially oriented biasing member disposed between the first
and second fingers, wherein the biasing member is configured to
radially bias at least one of the first and second fingers so that
the second contact surface contacts the first contact surface with
the normal force to define the predetermined torque value between
the first and second members.
12. The sheet separating device according to claim 11, wherein the
biasing member comprises a coiled compression spring.
13. The sheet separating device according to claim 10, wherein at
least one of the advancing roller and the reversing roller is
linearly biased against the other in a direction perpendicular to
the first and second axes.
14. The sheet separating device according to claim 10, wherein when
no sheets are received in the nip between the advancing roller and
the reversing roller, the torque load applied to the reversing
roller by the advancing roller is greater than the predetermined
torque value of the torque limiter, whereby one of the first and
second members rotates relative to the other of the first and
second members and the reversing roller rotates in a second
rotational direction opposite the first rotational direction.
15. The sheet separating device according to claim 10, wherein when
one sheet picked from the stack of sheets is received in the nip
between the advancing roller and the reversing roller, the torque
load applied to the reversing roller by the advancing roller via
the one sheet is greater than the predetermined torque value of the
torque limiter, whereby one of the first and second members rotates
relative to the other of the first and second members and the
reversing roller rotates in a second rotational direction opposite
the first rotational direction to move the one sheet forward along
the sheet path.
16. The sheet separating device according to claim 10, wherein when
two or more sheets picked from the stack of sheets are received in
the nip between the advancing roller and the reversing roller, the
torque load applied to the reversing roller by the advancing roller
via the two or more sheets is less than the predetermined torque
value of the torque limiter.
17. The sheet separating device according to claim 10, wherein the
first member comprises a hollow sleeve and the first contact
surface comprises an inner annular surface of the hollow sleeve
defining a cavity, and wherein the second contact surface comprises
an outer surface of the first finger and is configured to contact
the inner annular surface of the first member when the second
member is received in the cavity, and wherein the first finger is
biased in a radially outward direction.
18. The sheet separating device according to claim 11, wherein the
first member comprises a hollow sleeve and the first contact
surface comprises an inner annular surface of the hollow sleeve
defining a cavity, and wherein the second contact surface comprises
an outer surface of at least one of the first and second fingers
and is configured to contact the inner annular surface of the first
member when the second member is received in the cavity, and
wherein the biasing member is configured to bias at least one of
the fingers in a radially outward direction.
19. The sheet separating device according to claim 10, wherein the
first member comprises a plastic material.
20. The sheet separating device according to claim 10, wherein the
first member comprises polyoxymethylene and glass fiber and a
lubricant comprising PTFE.
21. The sheet separating device according to claim 10, wherein the
second member comprises a plastic material.
22. The sheet separating device according to claim 10, wherein the
second member comprises nylon 6/6 and a lubricant comprising
silicone and PTFE.
23. A sheet separating device comprising: first means for moving a
first sheet picked from a stack of sheets forward along a sheet
path; second means for moving a second sheet picked with the first
sheet from the stack of sheets backwards along the sheet path;
means for driving the first means and the second means; and means
for limiting torque applied to the second means by the driving
means, wherein the torque limiting means defines a predetermined
torque value, whereby the second means is driven by the driving
means to move the second sheet backwards along the sheet path
unless a torque load greater than or equal to the predetermined
torque value is applied to the second means.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This application claims the benefit of U.S. provisional
patent application Ser. No. 61/076,838, filed on Jun. 30, 2008,
entitled "Torque Limiter And Sheet Separating Device Having A
Torque Limiter".
BACKGROUND
[0002] The invention is related to sheet feeding and separation
devices and, more particularly, to a torque limiter and a sheet
separating device including a torque limiter.
[0003] In general, automatic sheet feeding devices engage and
remove sheets of paper or other media from a stack and feed the
sheets along a path to, for example, a printing zone, copying zone,
scanning zone, or the like. Such feeding assemblies must be able to
quickly and efficiently feed each individual sheet in a queue
(e.g., a sheet media tray) to the printing, copying or scanning
zone without creating a backlog and without jamming. This is
particularly important where the sheets to be fed are original
documents, e.g., photos, to be copied or scanned and cannot risk
being damaged.
[0004] Typically, during operation, a sheet picker such as, for
example, a roller having an outer surface formed of a high friction
material, may engage and remove the uppermost sheet from a stack
and feed the sheet along a feed path toward a sheet separator
positioned downstream. In the event that multiple sheets are
inadvertently picked by the sheet picker and fed along the feed
path, the sheet separator may be designed to separate the multiple
sheets from one another and thereby ensure that only one sheet is
passed along the feed path to the printing zone, copying zone,
scanning zone, or the like.
[0005] Known sheet separators, however, typically use complex and
cumbersome clutch mechanisms such as, for example, spring disk
clutches, wire wrap clutches, viscous clutches, or magnetic
hysteresis clutches. Although generally effective, each of these
clutch mechanisms can be large, expensive, and/or unreliable due to
the complexity and number of required parts and can, therefore, be
prohibitive in terms of developing and manufacturing compact and/or
inexpensive consumer devices such as automatic photo
feeders/scanners.
SUMMARY
[0006] In an embodiment of the invention, a torque limiter may
include a first member configured to rotate about a first axis and
having a first contact surface. The torque limiter may include a
second member configured to rotate about the first axis and
including a first axially extending finger. The first finger may be
radially biased so that a second contact surface defined by the
first finger may contact the first contact surface with a normal
force to define a predetermined torque value between the first and
second members. When one of the first and second members is
rotatably driven in a first rotational direction, the other of the
first and second members may be rotatably driven in the first
rotational direction unless a torque load greater than or equal to
the predetermined torque value is applied to the other of the first
and second members.
[0007] Further features and advantages of the invention, as well as
the structure and operation of various embodiments of the
invention, are described in detail below with reference to the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The foregoing and other features and advantages of the
invention will be apparent from the following, more particular
description of embodiments of the invention, as illustrated in the
accompanying drawings wherein like reference numbers generally
indicate identical, functionally similar, and/or structurally
similar elements. Unless otherwise indicated, the accompanying
drawing figures are not to scale.
[0009] FIG. 1 depicts an end view of a sheet separating device
along a sheet path according to an embodiment of the invention, a
torque limiter of the sheet separating device being shown in
partial cross-section;
[0010] FIG. 2 depicts a cross-sectional view of the torque limiter
of the sheet separating device according to the embodiment shown in
FIG. 1;
[0011] FIG. 3 depicts a schematic and illustrative side view of the
sheet separating device in a first state according to the
embodiment shown in FIG. 1;
[0012] FIG. 4 depicts a schematic and illustrative side view of the
sheet separating device in a second state according to the
embodiment shown in FIG. 1;
[0013] FIG. 5 depicts a schematic and illustrative side view of the
sheet separating device in a third state according to the
embodiment shown in FIG. 1; and
[0014] FIG. 6 depicts a graph showing a relationship between roller
normal force and clutch torque in a sheet separating device
according to an embodiment of the invention.
DETAILED DESCRIPTION
[0015] Various embodiments of the invention are discussed in detail
below. While specific embodiments are discussed, specific
terminology is employed for the sake of clarity. However, the
invention is not intended to be limited to the specific terminology
so selected and it should be understood that this is done for
illustration purposes only. A person skilled in the relevant art
will recognize that other components and configurations can be used
without parting from the spirit and scope of the invention. Each
specific element includes all technical equivalents that operate in
a similar manner to accomplish a similar purpose.
[0016] In the following description of some embodiments of the
invention, directional words such as, for example, "top," "bottom,"
"left," "right," "upwardly," and "downwardly," "clockwise,"
"counter-clockwise," are employed by way of description and not
limitation with respect to the orientation of the device and its
various components as illustrated in the drawings.
[0017] FIG. 1 depicts an end view of a sheet separating device 1
along a sheet path according to an embodiment of the invention. The
sheet separating device 1 may be, for example, disposed downstream
of a queue or media tray (not shown) configured to hold a stack of
sheets and from which sheets can be individually picked by a sheet
picker (not shown). The sheet separating device 1 may also be, for
example, disposed upstream of a printing zone, copying zone,
scanning zone, or the like (not shown) to which the sheets are fed.
The sheet separating device 1 may include an advancing (separating)
roller assembly 10 which may include a roller body 12 rigidly
coupled to, or mounted on, a shaft 16. A friction member or surface
14 may be disposed on the outer periphery of the roller body 12 to
contact and grip a sheet picked from the stack of sheets and
received in the sheet separating device 1. The advancing roller
assembly 10 may be rotatably driven about an axis in a first
rotational direction by a driving device 40.
[0018] As shown in the embodiment depicted in FIG. 1, the sheet
separating device 1 may also include a reversing (counter-rotating)
roller assembly 20 positioned adjacent to the advancing roller
assembly 10 to define a nip N therebetween. The reversing roller
assembly 20 may include a roller body 22. A friction member or
surface 24 may be disposed on the outer periphery of the roller
body 22 to contact and grip a sheet picked from the stack of sheets
and received in the nip N of the sheet separating device 1. The
reversing roller assembly 20 may be linearly biased against the
advancing roller assembly 10 across the nip N by a normal force F
which may be, for example, generated by any number of biasing
devices such as, for example but not limited to, extension springs
(not shown) coupled to the reversing roller assembly 20. In another
embodiment, the advancing roller assembly 10 may be biased against
the reversing roller assembly 20, or both roller bodies 12, 22 may
be biased against one another. The reversing roller assembly 20 may
be rotatably driven about an axis in the first rotational direction
by the driving device 40, for example, via a gear arrangement 42. A
torque limiter 30 such as, for example, a drag clutch mechanism,
may be operatively disposed between the driving device 40 and the
roller body 22 to allow bi-directional rotation of the roller body
22 depending on a condition at the nip N as discussed in further
detail below.
[0019] As shown in the embodiment depicted in FIG. 1, the torque
limiter 30 may operatively couple a first shaft portion 26 to a
second shaft portion 28. The roller body 22 may be rigidly coupled
to or mounted on the first shaft portion 26 and the second shaft
portion 28 may be coupled to the driving device 40, for example,
via gear arrangement 42. Referring to the embodiment depicted in
FIGS. 1 and 2, the torque limiter 30 may include a first member 31
such as, for example, a hollow sleeve having an cylindrical or
annular inner contact surface 32 which defines an interior volume
or cavity 33. The torque limiter 30 may also include a second
member 34 received in the cavity 33 and having, for example, a pair
of axially extending fingers 36, 38 spaced from one another
radially. A radially-oriented biasing member 39 such as, for
example but not limited to, a coiled compression spring, may be
disposed between the fingers 36, 38 and may function to bias the
fingers 36, 38 radially outward. The fingers 36, 38 may have outer
contact surfaces which contact the inner annular contact surface 32
of the first member 31 with a normal force to define a
predetermined torque value between the first member 31 and the
second member 34.
[0020] Although the embodiment shown in FIG. 1 depicts the first
member 31 rigidly coupled to the second shaft portion 28 and the
second member 34 rigidly coupled to the first shaft portion 26, the
relative position of the first and second members 31, 34 could be
reversed. That is, the first and second members 31, 34 could be
rigidly coupled to the first and second shaft portions 26, 28,
respectively. In another embodiment (not shown), the torque limiter
30 could be incorporated within the roller body 22 of the reversing
roller assembly 20.
[0021] FIG. 3 depicts a schematic and illustrative side view of the
sheet separating device 1 in a first state according to the
embodiment shown in FIG. 1. In FIG. 3, the roller body 12 of the
advancing roller assembly 10 may be rotatably driven in a first
rotational direction (shown counter-clockwise). The second shaft
portion 28 may also be rotatably driven in the counter-clockwise
direction. When, as shown in FIG. 3, no sheet is disposed in the
nip N between the roller bodies 12, 22, the torque load imparted to
the roller body 22 by the roller body 12 through their respective
outer frictional surfaces, 14 and 24 may override the predetermined
torque value of the torque limiter 30 and, therefore, cause the
roller body 22 to rotate clockwise, i.e., in the same linear
direction as the roller body 12 at the nip N. In this case,
referring back to FIGS. 1 and 2, the first and second members 31,
34 of the torque limiter 30 may slip relative to one another and
rotate in opposite directions.
[0022] FIG. 4 depicts a schematic and illustrative side view of the
sheet separating device 1 in a second state according to the
embodiment shown in FIG. 1. Similar to the first state shown in
FIG. 3, in FIG. 4, the roller body 12 and the second shaft portion
28 may be rotatably driven in a counter-clockwise direction. When,
as shown in FIG. 4, a single sheet S is disposed in the nip N
between the roller bodies 12, 22, the torque load imparted to the
roller body 22 by the roller body 12 through the sheet S may
override the predetermined torque value of the torque limiter 30
and, therefore, cause the roller body 22 to rotate clockwise, i.e.,
in the same linear direction as the roller body 12 at the nip N, to
advance the sheet along a feed path to the printing zone, copying
zone, scanning zone or the like (not shown). In this case, again
referring back to FIGS. 1 and 2, the first and second members 31,
34 of the torque limiter 30 may slip relative to one another and
rotate in opposite directions.
[0023] FIG. 5 depicts a schematic and illustrative side view of the
sheet separating device in a third state according to the
embodiment shown in FIG. 1. In FIG. 5, the roller body 12 and the
second shaft portion 28 may be rotatably driven in a
counter-clockwise direction. When, as shown in FIG. 5, multiple
sheets S1, S2 are picked and received in the nip N between the
roller bodies 12, 22, the torque load imparted to the roller body
22 by the roller body 12 through the sheets S1, S2 may not be
sufficient to override the predetermined torque value of the torque
limiter 30 due to the relatively small coefficient of friction
.mu..sub.ss between the sheets S1, S2. Therefore, the roller body
22 is driven via the torque limiter 30 to rotate counter-clockwise,
i.e., in the opposite linear direction as the roller body 12 at the
nip N, to return the sheet S2 to the media tray (not shown). In
this case, again referring back to FIGS. 1 and 2, the first and
second members 31, 34 of the torque limiter 30 may rotate together
to rotatably drive the roller body 22.
[0024] From a general dynamics standpoint, assuming that the
reversing roller does not slip against the sheet S, the following
relationship must always be true:
(Minimum((T.sub.r/R.sub.r) or
(.mu..sub.rsN)))>(Minimum((T.sub.cr/R.sub.cr) or
(.mu..sub.crsN)))>(.mu..sub.ssN) [0025] Where: T.sub.r=Torque of
the Advancing Roller [0026] R.sub.r=Radius of the Advancing Roller
[0027] .mu..sub.rs=coefficient of friction between the Advancing
Roller and a sheet [0028] T.sub.cr=Torque of the Reversing Roller
[0029] R.sub.cr=Radius of the Reversing Roller [0030]
.mu..sub.crs=coefficient of friction between the Reversing Roller
and a sheet [0031] N=Normal force between the rollers [0032]
.mu..sub.ss=coefficient of friction between two sheets Therefore,
for both rollers of a sheet separating device there may be two
limiting conditions: either the sheet is slipping on the roller or
it isn't. If the sheet is slipping, then the maximum drive force
that the respective roller can impart is (.mu..sub.ssN). If the
sheet does not slip on the roller, then it can be driven by the
full torque (T/R) of the roller. The lesser of these two resultant
forces will dominate. Thereafter, the force hierarchy must be such
that the advancing roller drive force is greater than the reversing
roller drive force which, in turn, is greater than the friction
force between the sheets.
[0033] FIG. 6 depicts a graph showing a relationship between roller
normal force and clutch torque in a sheet separating device 1
according to an example embodiment of the invention. As shown in
FIG. 6, the clutch torque, or predetermined torque value of the
torque limiter, is directly proportional to the normal force F (see
FIG. 1) between the advancing and reversing rollers 12, 22 such
that an increase in the clutch torque requires an increase in the
range of normal force F, and vice versa. As discussed above with
regard to the embodiment depicted in FIG. 1, one or more biasing
members such as, e.g., extension springs, may be coupled to one or
both of the advancing and reversing roller assemblies 10, 20, to
provide the normal force F. This normal force F, the normal force
generated by the biasing member 39 inside the torque limiter 30,
and the materials used within the torque limiter 30, may be
considered as a system so that the resulting values are well within
the reliable operating range shown in the graph in FIG. 6.
[0034] In an embodiment of the invention, the first and second
members 31, 34 of the torque limiter 30 may be formed from, for
example, but not limited to, Lubricomp KFL-4034 (POM+20% GF+15%
PTFE) and Lubricomp RL-4540 (Nylon 6/6+20% PTFE/Si), respectively.
Other suitable plastic materials may also used to form the members
of the torque limiter 30 and such materials may be chosen to ensure
little wear over the life of the torque limiter 30.
[0035] The sheet separating device 1 with torque limiter 30 may
offer, for example, the following advantages: relatively small
radial/axial size, inexpensive, plastic on plastic contact, and/or
bi-directional slipping. The sheet separating device 1 may be
incorporated into, for example, consumer electronics products such
as, for example, but not limited to, an automatic photo feeder, to
ensure effective and efficient separation of multi-picks.
[0036] While various embodiments of the present invention have been
described above, it should be understood that they have been
presented by way of example only, and not limitation. Thus, the
breadth and scope of the present invention should not be limited by
any of the above-described embodiments, but should instead be
defined only in accordance with the following claims and their
equivalents.
* * * * *