U.S. patent application number 09/896677 was filed with the patent office on 2002-02-07 for torque limiting slip clutch apparatus for cable reel drive assembly.
This patent application is currently assigned to HUBBELL INCORPORATED. Invention is credited to Tuttlebee, Roger.
Application Number | 20020014551 09/896677 |
Document ID | / |
Family ID | 22950649 |
Filed Date | 2002-02-07 |
United States Patent
Application |
20020014551 |
Kind Code |
A1 |
Tuttlebee, Roger |
February 7, 2002 |
Torque limiting slip clutch apparatus for cable reel drive
assembly
Abstract
A torque limiting slip clutch apparatus for a cable reel drive
assembly includes an elongated input drive shaft, annular rotary
drive member, annular drive plate, friction generating disc element
and biasing force generating spring mechanism. The drive shaft is
mounted to undergo rotational movement. The drive member is mounted
about the shaft to undergo rotational movement relative to the
drive shaft and translational movement along the shaft. The drive
plate is fixedly mounted about the drive shaft adjacent to the
drive member to undergo rotational movement with the shaft and
relative to the drive member. The disc element is mounted between
and engagable with the drive member and drive plate to generate
friction therebetween that causes rotational movement of the drive
member with the drive plate and drive shaft in response to
translational movement of the drive member along the shaft toward
the drive plate. The spring mechanism is mounted along the drive
shaft adjacent to a side of the drive member opposite from the
drive plate to generate a biasing force against the drive member
causing translational movement of the drive member toward the drive
plate and generation of friction between the drive member and drive
plate.
Inventors: |
Tuttlebee, Roger;
(Stanground, GB) |
Correspondence
Address: |
Jerry M. Presson, Esq.
Hubbell Incorporated
584 Derby Milford Road
P.O. Box 549
Orange
CT
06477-4024
US
|
Assignee: |
HUBBELL INCORPORATED
|
Family ID: |
22950649 |
Appl. No.: |
09/896677 |
Filed: |
June 29, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09896677 |
Jun 29, 2001 |
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09251140 |
Feb 16, 1999 |
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6280331 |
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Current U.S.
Class: |
242/390.8 ;
242/394.1 |
Current CPC
Class: |
F16D 43/215 20130101;
F16D 7/025 20130101 |
Class at
Publication: |
242/390.8 ;
242/394.1 |
International
Class: |
B65H 075/30; B65H
075/38 |
Claims
What is claimed is:
1. A torque limiting slip clutch apparatus for a cable reel drive
assembly, said apparatus comprising: (a) an elongated drive shaft
mounted to undergo rotational movement; (b) an annular rotary drive
member mounted about said drive shaft to undergo rotational
movement relative to said drive shaft and translational movement
along said drive shaft; (c) an annular drive plate fixed mounted
about said drive shaft adjacent to said rotary drive member to
undergo rotational movement with said drive shaft and relative to
said rotary drive member; (d) means mounted between and engagable
with said rotary drive member and drive plate for generating
friction therebetween that causes rotational movement of rotary
drive member with said drive plate and drive shaft in response to
translational movement of said rotary drive member along said drive
shaft toward said drive plate; and (e) means mounted along said
drive shaft adjacent to a side of said rotary drive member opposite
from said drive plate for generating a biasing force against said
rotary drive member to cause translational movement of said rotary
drive member along said drive shaft toward said drive plate and
generation of friction between said rotary drive member and drive
plate.
2. The apparatus as recited in claim 1, wherein said friction
generating means includes a disc element having a friction
generating material affixed thereon and being attached to a side of
said drive plate facing said rotary drive member.
3. The apparatus as recited in claim 1, wherein said biasing force
generating means includes a single stack of conical disc
springs.
4. The apparatus as recited in claim 3, further comprising: a
torque adjustment mechanism disposed adjacent to said biasing force
generating means and being operable to adjust the size of the
biasing force generated by the biasing force generating means.
5. The apparatus as recited in claim 1, wherein said biasing force
generating means includes a plurality of stacks of conical disc
springs mounted in equally-distant spaced relationship from one
another about said input drive shaft.
6. The apparatus as recited in claim 5, further comprising: a
torque adjustment mechanism disposed adjacent to said biasing force
generating means and being operable to adjust the size of the
biasing force generated by said biasing force generating means.
7. The apparatus as recited in claim 1, further comprising: a
torque adjustment mechanism disposed adjacent to said biasing force
generating means and being operable to adjust the size of the
biasing force generated by said biasing force generating means,
said torque adjustment mechanism including (i) a adjustment nut
having a periphery with external gear teeth and being mounted about
said input drive shaft adjacent to said biasing force generating
means to undergo translational movement toward and away therefrom,
and (ii) a shaft having a pinion gear at one end and being mounted
to undergo reciprocal movement toward and away from said periphery
of said adjustment nut so as to move said pinion gear into and out
of a meshed driving relationship with said gear teeth on said
periphery of said adjustment nut such that when said pinion gear is
meshed with said external gear teeth on said adjustment nut
rotation of said shaft and said pinion gear therewith causes,
depending on the direction of rotation, rotation and translation of
said adjustment nut relative to said input drive shaft toward or
away from said biasing force generating means so as to
correspondingly increase or decrease the biasing force generated on
said rotary drive member.
8. A cable reel drive assembly, comprising: (a) a rotary power
source operable to provide rotary drive motion at a predetermined
input speed; (b) a cable supply spool storing a cable and being
rotatable to payout and rewind the cable; and (c) a speed reducer
unit disposed between and drivingly interconnecting said rotary
power source to said cable supply spool and operable in cable
payout and rewind rotation modes to cause said cable supply spool
to correspondingly payout and rewind the cable, said speed reducer
unit including a first speed reduction stage having an input drive
shaft and a torque limiting slip clutch, said input drive shaft
drivingly coupled to said rotary power source and mounted to
undergo rotational movement in response to said rotary drive motion
provided at said predetermined input speed by said rotary power
source, said slip clutch drivingly coupled to said input drive
shaft to undergo rotational movement therewith and operable to
receive said rotary drive motion at said predetermined input speed
from said input drive shaft and to reduce said rotary drive motion
to and provide said rotary drive motion as output at a first speed
less than said predetermined input speed.
9. The assembly as recited in claim 8, wherein said speed reducer
unit further includes a second speed reduction stage drivingly
coupled to said slip clutch of said first speed reduction stage and
operable to receive said rotary drive motion at said first speed
from said first speed reduction stage and to reduce said rotary
drive motion to and provide said rotary drive motion as output at a
second speed less than said first speed.
10. The assembly as recited in claim 9, wherein said second speed
reduction stage includes means for sensing in which of said cable
payout and rewind rotational modes said speed reducer unit is
operating at any given time to cause shutoff of operation of said
rotary power source in response to sensing said cable payout
rotational mode but not said cable rewind rotational mode to
thereby enable said slip clutch to function as a slip brake
restraining the rotation of said cable supply spool to the speed at
which the cable is pulled from said cable supply spool by movement
of machinery connected to the cable and to function as a holding
brake preventing further rotation of said cable supply spool when
movement of the machinery has ceased.
11. The assembly as recited in claim 9, wherein said second speed
reduction stage includes: an intermediate shaft, and first and
second rotary members of different diameters disposed adjacent to
and connected with one another and mounted about said intermediate
shaft in order for said first and second rotary members together to
undergo rotational movement, said first rotary member being
drivingly coupled to said slip clutch of said first speed reduction
stage to receive said rotary drive motion therefrom at said first
speed and such that said rotary drive motion is reduced by said
first rotary member to a second speed less than said first speed
and provided as output at said second speed by said second rotary
member.
12. The assembly as recited in claim 11, wherein said second speed
reduction stage further includes means for sensing in which of
cable payout and rewind rotational modes said speed reducer unit is
operating at any given time to cause shutoff of operation of said
rotary power source in response to sensing said cable payout
rotational mode but not said cable rewind rotational mode to
thereby enable said slip clutch to function as a slip brake
restraining the rotation of said cable supply spool to the speed at
which the cable is pulled from said cable supply spool by movement
of machinery connected to the cable and to function as a holding
brake preventing further rotation of said cable supply spool when
movement of the machinery has ceased.
13. The assembly as recited in claim 9, wherein said speed reducer
unit further includes a third speed reduction stage drivingly
coupled to said second speed reduction stage and operable to
receive said rotary drive motion at said second speed from said
second speed reduction stage and to reduce said rotary drive motion
to and provide said rotary drive motion at a third speed less than
said second speed and thereby rotate said cable supply spool to
correspondingly payout and rewind the cable at said third
speed.
14. The assembly as recited in claim 13, wherein said third speed
reduction stage includes: an output shaft mounted to undergo
rotational movement, said cable supply spool being fixedly mounted
to and about said output shaft to undergo rotational movement
therewith; and a rotary driven member axially spaced from said
cable supply spool and fixedly mounted to and about said output
shaft to undergo rotational movement therewith, said rotary driven
member being drivingly coupled to said second rotary member of said
second speed reduction stage to receive said rotary drive motion
therefrom at said second speed and cause said output shaft and
cable supply spool to reduce said rotary drive motion to a third
speed less than said second speed and thereby payout and rewind the
cable at said third speed.
15. The assembly as recited in claim 8, wherein said torque
limiting slip clutch of said first speed reduction stage includes
an annular rotary drive member mounted about said input drive shaft
to undergo rotational movement relative to said input drive shaft
and translational movement along said input drive shaft.
16. The assembly as recited in claim 15, wherein said torque
limiting slip clutch further includes an annular drive plate
mounted about said input drive shaft adjacent to said rotary drive
member to undergo rotational movement with said input drive shaft
and relative to said rotary drive member.
17. The assembly as recited in claim 16, wherein said torque
limiting slip clutch further includes means mounted between said
rotary drive member and drive plate for generating friction
therebetween that causes rotational movement of said rotary drive
member with said drive plate and drive shaft in response to
translational movement of said rotary drive member along said drive
shaft toward said drive plate.
18. The assembly as recited in claim 17, wherein said friction
generating means includes a disc element having a friction
generating material affixed thereon and being attached to a side of
said drive plate facing said rotary drive member.
19. The assembly as recited in claim 17, wherein said torque
limiting slip clutch further includes means mounted along said
shaft adjacent to a side of said rotary drive member opposite from
said drive plate for generating a biasing force against said rotary
drive member to cause translational movement of said rotary drive
member along said drive shaft toward said drive plate and
generation of friction between said rotary drive member and drive
plate.
20. The assembly as recited in claim 19, further comprising: a
torque adjustment mechanism disposed adjacent to said biasing force
generating means and being operable to adjust the size of the
biasing force generated by said biasing force generating means.
21. The assembly as recited in claim 19, wherein said biasing force
generating means includes a single stack of conical disc
springs.
22. The assembly as recited in claim 21, further comprising: a
torque adjustment mechanism disposed adjacent to said biasing force
generating means and being operable to adjust the size of the
biasing force generated by said biasing force generating means.
23. The assembly as recited in claim 19, wherein said biasing force
generating means includes a plurality of stacks of conical disc
springs mounted in equally-distant spaced relationship from one
another about said input drive shaft.
24. The assembly as recited in claim 23, further comprising: a
torque adjustment mechanism disposed adjacent to said biasing force
generating means and being operable to adjust the size of the
biasing force generated by said biasing force generating means.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention generally relates to a cable reel
drive assembly and, more particularly, is concerned with a torque
limiting slip clutch apparatus and a cable reel drive assembly
employing the slip clutch apparatus.
[0003] 2. Description of the Prior Art
[0004] Motor-driven constant-torque reel drive assemblies are used
in various industrial applications where cables and hoses of
varying lengths reeled out from a stationary source of supply are
needed to provide power and control to machinery and equipment that
move relative to the stationary supply source. As used hereafter,
the term "cable" is meant to include within the scope of its
definition electrical cables, hydraulic hoses and the like.
[0005] Well-known examples of where such reel drive assemblies are
used are levelwind and monospiral cable reels commercially
available from Gleason Reel Corp. of Mayville, Wis., a subsidiary
of Hubbell Corporation. The levelwind and monospiral cable reels
are used in conjunction with the operation of container and raw
material handling cranes for unloading ships. The levelwind cable
reel stores cable in, and thus pays out cable from, a side-by-side
single-layer configuration of cable on the reel. The monospiral
reel stores cable in, and thus pays out cable from, a single
multiple-layer configuration of cable on the reel.
[0006] There are various factors which can adversely affect the
operational efficiency of a cable reel drive assembly. These
factors include different rotation speed and output torque
requirements during cable payout as opposed to cable rewind and the
inertia effects of various components on cable tension during cable
payout in response to machinery accelerations. Consequently, a need
still remains for innovations to a cable reel drive assembly which
will give due consideration to these factors and thereby reduce
their adverse impact on operational efficiency of the cable reel
drive assembly.
SUMMARY OF THE INVENTION
[0007] The present invention provides a torque limiting slip clutch
apparatus and a cable reel drive assembly employing the slip clutch
apparatus designed to satisfy the aforementioned need. The slip
clutch apparatus of the present invention accommodates the
different rotational speed and output torque requirements during
cable payout as opposed to cable rewind when the operation of a
drive motor is not needed and thus shutoff during cable payout. The
shutoff of the drive motor operation enables the slip clutch to
function as a slip brake restraining the rotation of a cable supply
spool to the speed at which the cable is pulled from the spool by
the movement of machinery connected to the cable and to function as
a holding brake preventing further rotation of the cable supply
spool when movement of the machinery has ceased. The slip clutch
apparatus of the present invention also isolates and prevents any
torque forces (referred inertia) required to accelerate components
of the drive assembly from reaching the cable supply spool and
cable thereon so that such torque forces are not translated as
tension in the cable. By reducing cable tension the spoke size of
the cable supply spool can be reduced which, in turn, lowers spool
inertia requiring a lower drive torque (or rotary force) to rotate
the spool. The lower torque drive, in turn, means even lower cable
tension. The combined effect of these reductions is to increase the
overall efficiency of the cable reel drive assembly.
[0008] Accordingly, the present invention is directed to a torque
limiting slip clutch apparatus for use in a cable reel drive
assembly. The slip clutch apparatus comprises: (a) an elongated
drive shaft mounted to undergo rotational movement; (b) an annular
rotary drive member mounted about the drive shaft to undergo
rotational movement relative to the drive shaft and translational
movement along the drive shaft; (c) an annular drive plate fixed
mounted about the drive shaft adjacent to the rotary drive member
to undergo rotational movement with the drive shaft and relative to
the rotary drive member; (d) means mounted between and engagable
with the rotary drive member and drive plate for generating
friction therebetween that reduces the rotational movement of the
drive plate and drive shaft relative to the rotary drive member in
response to translational movement of the rotary drive member along
the drive shaft toward the drive plate; and (e) means mounted along
the drive shaft adjacent to a side of the rotary drive member
opposite from the drive plate for generating a biasing force
against the rotary drive member to cause translational movement of
the rotary drive member along the drive shaft toward the drive
plate and generation of friction between the rotary drive member
and drive plate. The slip clutch apparatus further comprises a
torque adjustment mechanism disposed adjacent to the biasing force
generating means and being operable to adjust the size of the
biasing force generated by the biasing force generating means.
[0009] The present invention also is directed to a cable reel drive
assembly which comprises: (a) a rotary power source operable to
provide rotary drive motion at a predetermined input speed; (b) a
cable supply spool storing a cable and being rotatable to payout
and rewind the cable; and (c) a speed reducer unit disposed between
and drivingly connecting the rotary power source to the cable
supply spool. The speed reducer unit is operable in cable payout
and rewind rotation modes to cause the cable supply spool to
correspondingly payout and rewind the cable. The speed reducer unit
includes a first speed reduction stage having an input drive shaft
and a torque limiting slip clutch. The input drive shaft is
drivingly coupled to the rotary power source and mounted to undergo
rotational movement in response to the rotary drive motion provided
at the predetermined input speed by the rotary power source. The
slip clutch is drivingly coupled to the input drive shaft to
undergo rotational movement therewith and operable to receive the
rotary drive motion at the input speed from the input drive shaft
and to reduce the rotary drive motion to and provide the rotary
drive motion as output at a first speed less than the input
speed.
[0010] The speed reducer unit also includes a second speed
reduction stage and a third speed reduction stage. The second speed
reduction stage is drivingly coupled to the slip clutch of the
first speed reduction stage and operable to receive the rotary
drive motion at the first speed from the first speed reduction
stage and to reduce the rotary drive motion to and provide the
rotary drive motion as output at a second speed less than the first
speed. The third speed reduction stage is rotatable to cause the
cable supply spool to payout and rewind the cable and is drivingly
coupled to the second speed reduction stage to receive the rotary
drive motion at the second speed from the second speed reduction
stage and to reduce the rotary drive motion to and provide the
rotary drive motion at a third speed less than the second speed and
thereby rotate the cable supply spool to correspondingly payout and
rewind cable at the third speed. The second speed reduction stage
also includes means for sensing in which of the cable payout and
rewind rotational modes the speed reducer unit is operating at any
given time to cause shutoff of operation of the rotary power source
in response to sensing the cable payout rotational mode but not the
cable rewind rotational mode to thereby enable the slip clutch to
function as a slip brake restraining the rotation of the cable
supply spool to the speed at which the cable is pulled from the
cable supply spool by movement of machinery connected to the cable
and to function as a holding brake preventing further rotation of
the cable supply spool when movement of the machinery has
ceased.
[0011] These and other features and advantages of the present
invention will become apparent to those skilled in the art upon a
reading of the following detailed description when taken in
conjunction with the drawings wherein there is shown and described
an illustrative embodiment of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] In the following detailed description, reference will be
made to the attached drawings in which:
[0013] FIG. 1 is a side elevational view of a cable reel drive
assembly of the present invention employing a torque limiting slip
clutch of the present invention.
[0014] FIG. 2 is an end elevational view of the drive assembly as
seen along line 2-2 of FIG. 1.
[0015] FIG. 3 is a left side elevational view of a speed reducer
unit of the drive assembly as seen along line 3-3 of FIG. 1.
[0016] FIG. 4 is a right side elevational view of the speed reducer
unit of the drive assembly as seen along line 4-4 of FIG. 1.
[0017] FIG. 5 is an axial sectional view of a first speed reduction
stage of the drive assembly taken along line 5--5 of FIG. 3,
showing a first embodiment of the components of the slip clutch of
the present invention.
[0018] FIG. 6 is an axial sectional view of a second speed
reduction stage of the drive assembly taken along line 6-6 of FIG.
3, showing the components for sensing in which of cable payout and
rewind modes the speed reducer unit of the drive assembly is
operating at any given time.
[0019] FIG. 7 is an axial sectional view of a third speed reduction
stage of the drive assembly taken along line 7-7 of FIG. 3, showing
the components for storage and payout of cable.
[0020] FIG. 8 is an axial sectional view similar to that of FIG. 5,
but showing a second embodiment of the components of the slip
clutch of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0021] Referring to the drawings and particularly to FIGS. 1 to 5,
there is illustrated a cable reel drive assembly of the present
invention, generally designated 10. The cable reel drive assembly
10 basically includes a rotary power source 12 operable to provide
rotary drive motion (or drive torque) at a predetermined input
speed, a cable supply spool 14 storing a cable C and being
rotatable to payout and rewind the cable C, and a speed reducer
unit 16 disposed between the power source 12 and cable supply spool
14 and drivingly connecting the power source 12 to the cable supply
spool 14. The speed reducer unit 16 is operable in cable payout and
rewind rotation modes to cause the cable supply spool 14 to
correspondingly payout and rewind the cable C at a desired speed
less than the input speed. In the illustrated embodiment, the
rotary power source is in the form of an electric motor coupled to
a speed reducing gearbox and which have been collectively referred
to by the reference numeral 12.
[0022] More particularly, the speed reducer unit 16 includes a
first (or primary) speed reduction stage 18, a second (or
secondary) speed reduction stage 20, a third (or tertiary) speed
reduction stage 22, and an enclosure or housing 24 structurally
supporting and enclosing the first, second and third speed
reduction stages 18, 20, 22 in an oil bath coolant and also
supporting the weight of the power source 12 and the cable supply
spool 14. The first speed reduction stage 18 of the speed reducer
unit 16 is drivingly coupled to the power source 12 and is operable
to receive the rotary drive motion at the desired predetermined
input speed from the power source 12 and to reduce the rotary drive
motion to and provide as output the rotary drive motion at a first
speed less than the predetermined input speed. The second speed
reduction stage 20 of the speed reducer unit 16 is drivingly
coupled to the first speed reduction stage 18 and is operable to
receive the rotary drive motion at the first speed from the first
speed reduction stage 18 and to reduce the rotary drive motion to
and provide as output the rotary drive motion at a second speed
less than the first speed. The third speed reduction stage 22 of
the speed reducer unit 16 is drivingly coupled to the second speed
reduction stage 20 and is operable to receive the rotary drive
motion at the second speed from the second speed reduction stage 20
and to reduce the rotary drive motion to and provide the rotary
drive motion to drive the cable supply spool 14 at a third speed
less than the second speed. The second speed reduction stage 22
also can sense in which of cable payout and rewind rotational modes
the speed reducer unit 16 is operating at any given time so as to
shutoff operation of the power source 12 only during the cable
payout rotational mode.
[0023] Referring to FIGS. 3 to 5, the first speed reduction stage
18 of the speed reducer unit 16 includes an input drive shaft 26
and a torque limiting slip clutch 28 also of the present invention.
The input drive shaft 26 of the first speed reduction stage 18 is
rotatably mounted at its opposite ends by a pair of bearings 30 to
the housing 24 and is drivingly coupled to a rotary output shaft
12A of the power source 12 supported at an external side of the
housing 24 by bolts 32. The input drive shaft 26 thereby will
undergo rotational movement relative to the housing 24 in response
to the rotary drive motion (or drive torque) provided by the power
source 12 at the desired predetermined input speed.
[0024] The torque limiting slip clutch 28 of the first speed
reduction stage 18 includes an annular rotary drive member 34, an
annular drive plate 36, a disc element 38 having a suitable
friction generating material, such as a carbon fiber woven fabric
or sintered bronze, affixed thereon, and a biasing force generating
spring mechanism 40. The rotary drive member 34 of the slip clutch
28 preferably is a sprocket mounted about the input drive shaft 26
to undergo rotational movement relative to the input drive shaft 26
and translational movement along the input drive shaft 26 over the
axial length of a bushing 42 which rotatably and slidably mounts
the rotary drive member 34 on the input drive shaft 26. The annular
drive plate 36 of the slip clutch 28 is fixedly mounted to and
about the input drive shaft 26 adjacent to the rotary drive member
34 to undergo rotational movement with the input drive shaft 26 and
relative to the rotary drive member 34. The friction generating
disc element 38 of the slip clutch 28 is mounted between the rotary
drive member 34 and the drive plate 36 and attached to the drive
plate 36 and thereby adapted to engage the rotary drive member 34
to generate friction between the disc element 38 and the rotary
drive member 34 that causes rotational movement of the rotary drive
member 34 with the input drive shaft 26 and drive plate 36 in
response to translational movement of the rotary drive member 34
along the input drive shaft 26 toward the drive plate 36. The
spring mechanism 40 of the slip clutch 28 is mounted along the
input drive shaft 26 adjacent to a side of the rotary drive member
34 opposite from the drive plate 36 to generate a biasing force
against the rotary drive member 34 causing translational movement
of the rotary drive member 34 toward the drive plate 36 and
generation of friction between the rotary drive member 34 and drive
plate 36. The first speed reduction stage 18 is thereby coupled to
the input drive shaft 26 to undergo rotational movement therewith
to reduce the rotary drive motion to a first speed less than the
predetermined input speed and provide as output the rotary drive
motion at the first speed by the rotary drive member 34. The rotary
motion or torque transmitted to the rotary drive member 34 of the
slip clutch 28 is dependent upon available drive torque of the
power source 12, friction coefficient of the friction generating
material, lubricating effect of the oil bath coolant, and biasing
force generated from the compression of the spring mechanism
40.
[0025] Referring to FIGS. 3, 4 and 6, the second speed reduction
stage 20 of the speed reducer unit 16 includes an intermediate
shaft 44, and first and second rotary members 46, 48. The
intermediate shaft 44 of the second speed reduction stage 20 is
stationarily mounted at its opposite ends to the housing 24. The
first and second rotary members 46, 48 are preferably sprockets and
are mounted adjacent to and connected with one another by an
annular collar 50. The annular collar 50 is rotatably mounted about
the intermediate shaft 44 by a pair of bearings 52 disposed at
opposite ends of the annular collar 50 so that the annular collar
50 and the first and second rotary members 46, 48 therewith can
undergo rotational movement together relative to the intermediate
shaft 44. The first rotary member 46 is larger in diameter than the
rotary drive member 34 of the slip clutch 28 of the first speed
reduction stage 18 and larger in diameter than the second rotary
member 48. The first rotary member 46 is drivingly coupled by an
endless drive chain 54 to the rotary drive member 34 of the slip
clutch 28 such that the rotary drive motion transmitted at the
first speed from the rotary drive member 34 to the first rotary
member 46 is reduced by the first rotary member 46 to a second
speed less than the first speed and is provided as output at the
second speed by the second rotary member 48.
[0026] Referring to FIGS. 3, 4 and 7, the third speed reduction
stage 22 of the speed reducer unit 16 includes an output shaft 56,
a rotary driven member 58 and the cable supply spool 14. The output
shaft 56 of the third speed reduction stage 22 is rotatably mounted
to the housing 24 by a pair of bearings 60 disposed adjacent to
opposite ends of the output shaft 56 such that the output shaft 56
can undergo rotational movement relative to the housing 24. The
rotary driven member 58 of the third speed reduction stage 22 is
fixedly mounted to and about the output shaft 56 to undergo
rotational movement therewith. The cable supply spool 14 is axially
spaced from the rotary driven member 58 and fixedly mounted to and
about the output shaft 56 to undergo rotational movement therewith
to either payout of cable C from the cable supply spool 14 or
rewind of cable C onto the cable supply spool 14. The rotary driven
member 58 is a sprocket larger in diameter than the second rotary
member 48 of the second speed reduction stage 20 and is drivingly
coupled by an endless drive chain 62 to the second rotary member 48
of the second speed reduction stage 22 such that the rotary drive
motion transmitted at the second speed from the second rotary
member 48 to the rotary driven member 58 is reduced to a third
speed less than the second speed and is provided as output by the
rotation of the output shaft 56 and cable supply spool 14. The
output shaft 56 is hollow so as to allow passage of an end portion
of the cable (not shown) from the cable supply spool 14 to a slip
ring assembly (not shown) located at an opposite side of the
housing 24 from the spool 14.
[0027] Referring to FIGS. 4 and 6, the second speed reduction stage
20 further includes means, generally designated 64, for sensing in
which of the cable payout and rewind rotational modes the speed
reducer unit 16 is operating at any given time. Upon sensing
operation of the speed reducer unit 16 in the cable payout
rotational mode, the sensing means 64 will cause shutoff of
operation of the power source 12 and thereby enable the slip clutch
28 to function as a slip brake restraining the rotation of the
cable supply spool 14 to the speed at which the cable C is pulled
from the cable supply spool 14 by movement of machinery (not shown)
connected to the cable C and additionally to function as a holding
brake preventing rotation of the cable supply spool 14 when
movement of such machinery has ceased. The sensing means 64 does
not terminate the operation of the power source 12 during operation
of the speed reducer unit 16 in the cable rewind rotational
mode.
[0028] More particularly, the rotation direction sensing means 64
includes right and left limit switches 66, 68, a horizontal
rotatable shaft 70 rotatably mounted by a bushing 72 supported on
and extending across the housing 24 above the first and second
rotary members 46, 48 disposed therein, and a generally vertical
bar 74 disposed between the switches 66, 68 and attached at an
upper end 74A to one end 70A of the rotatable shaft 70. The sensing
means 64 also includes a vertical inverted Y-shaped member 76
attached at an upper end 76A to the opposite end 70B of the
horizontal shaft 70 and extending downwardly therefrom and a rotary
disc 78 rotatably mounted about the intermediate shaft 44 in spaced
relation from but adjacent to the first rotary member 46 and
adapted to rotate in one or the other of opposite directions
corresponding to cable payout or rewind rotational modes in
response to rotation of the first rotary member 46. The rotation of
the first rotary member 46 of the second speed reduction stage 20
causes a corresponding rotational movement of the portion of the
oil bath located adjacent to the rotary disc 78 which turns the
rotary disc 78 such that a pin 80 mounted thereon between a pair of
fingers 82 at a lower end 76B of the vertical inverted Y-shaped
member 76 contacts one or the other of the fingers 82 causing
rotation of the rotatable shaft 70 in one or the other of opposite
rotational directions. Such rotation of the shaft 70, in turn,
causes the vertical bar 74 to pivot in the corresponding direction
and contact one or the other of the right and left limit switches
66, 68 to either shutoff (de-energize) the electric motor of the
power source 12 or otherwise allowing the motor to remain energized
depending upon whether the cable C is being pulled off the spool 14
(cable payout) or being rewound onto the spool 14 (cable
rewind).
[0029] Referring to FIG. 5, the cable reel drive assembly 10 also
includes a torque adjustment mechanism, generally designated 84,
disposed adjacent to the biasing force generating spring mechanism
40 of the first speed reduction stage 18 of the speed reducer unit
16. The torque adjustment mechanism 84 is operable to adjust the
size of the biasing force (or spring load) generated by the spring
mechanism 40 so as to provide a means for performing minor
adjustments to the output or drive torque of the slip clutch 28
without having to access the drive components inside of the housing
24. More particularly, the torque adjustment mechanism 84 includes
a adjustment nut 86 having an outer periphery 86A with gear teeth
and an inner periphery 86B with internal threads that threadably
mount the adjustment nut 86 about the input drive shaft 26 adjacent
to the spring mechanism 40 allowing the adjustment nut 86 to be
turned and undergo axial movement along the input drive shaft 26
toward and away from the spring mechanism 40. The torque adjustment
mechanism 84 also includes a spring biased rotatable shaft 88
having a pinion gear 90 at one end and being mounted to the housing
24 to undergo reciprocal movement toward and away from the
periphery of the adjustment nut 86 so as to move the peripheral
gear teeth of the pinion gear 90 into and out of a meshed driving
relationship with the gear teeth on the outer periphery 86A of the
adjustment nut 86. When meshed, rotation of the pinion 88 and worm
gear 90 therewith causes, depending on the direction of rotation,
rotation and axial movement of the adjustment nut 86 along the
input drive shaft 26 toward or away from the spring mechanism 40 so
as to correspondingly increase or decrease the biasing force
generated by the spring mechanism 40 on the rotary drive member
34.
[0030] It should also be noted that the speed reducer unit 16 of
the cable reel drive assembly 10 is provided with a conventional
backstop device 96 for holding the input shaft 26 stationary when
the electric motor of the power source 12 is shut off which thereby
enables the slip clutch 28 to function as a slip brake as described
above. As best seen in FIG. 5, the backstop device 96 (backstop
clutch assembly) is mounted on the end of the input shaft 26 and
includes a housing 98 surrounding the shaft 26 and a freewheel 100
disposed between the inside surface of the housing and the exterior
surface of the shaft.
[0031] Referring to FIGS. 5 and 8, there are shown two alternative
embodiments of the slip clutch 28 that are provided within the
scope of the present invention. FIG. 5 shows a first embodiment of
some of the components comprising the slip clutch 28 wherein a
single drive plate 36, a single friction disc element 38 and a
single stack of conical disc springs 92 are employed. FIG. 8 shows
a second embodiment of some of the components making up the slip
clutch 28 wherein a pair of drive plates 36, a pair of the friction
disc elements 38 and a plurality of stacks of conical disc springs
92 are employed. The latter stacks are distributed on at least
three equally-spaced shoulder bolts 94 around the input drive shaft
26.
[0032] It is thought that the present invention and its advantages
will be understood from the foregoing description and it will be
apparent that various changes may be made thereto without departing
from the spirit and scope of the invention or sacrificing all of
its material advantages, the form hereinbefore described being
merely preferred or exemplary embodiment thereof.
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