Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates generally to clutch assemblies and, in
particular, to such an assembly which may be used with an electrically
operated retractable jack for mounting on a vehicle.
Heretofore, there have been a variety of electrical, hydraulic,
and mechanical operated jacks used for leveling vehicles, trailers, or the
like. Generally, the most common jacks are jacks mounted on the corners of
a vehicle, or on the tongue of a trailer which raise and lower the vehicle
and trailer in a vertical direction. These jacks have no provision for re-
tracting the jack from a vertical position to a stowed horizontal position
underneath the vehicle.
Also a common problem of a vehicle jack is the jack may have a
sufficient initial torque to raise the vehicle to a level position, but after
an extended period of time, the jack assembly locks up and the operator is
unable to lower the vehicle. This problem is particularly true when added
weight is loaded on to the vehicle or a shift in position takes place sub-
sequent to the leveling of the vehicle. An excess torque is therefore nec-
essary to lower the vehicle.
There are prior art jacks which are retractable from a vertical
position into a horizontal position, but these jacks are complex in design
and construction and have been found to have limited commercial acceptance.
The retractable jacks use offset pivot arms or a pivot cam for automatically
pivoting the jacks into a horizontal position.
e subject invention is particularly useful in combinat~n with a
jack wh~ch automatically retracts from a vertical position into a horizontal
stowage position underneath the vehicle so that the vehicle is ready to travel.
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The jack is automatically lowered from a horizontal position into a vertical
position and in a position for extending the jack, leveling, and stabili~ing
the vehicle. -
The jack may be mounted in various arrangement combinations under-
neath a vehicle, such as on the four corners of the vehicle, the rear corners,
and at the center of the front of the vehicle, or any other desired position.
The jack also may be used for a tire change without having to use a hand-
operated jack.
The jacks may be electrically wired to a control panel inside the
vehicle so that the operator may level the vehicle without having to go out-
side. Each jack has its own individual electric motor drive unit, therefore
should one jack fail the remaining jacks will operate independently for
leveling the vehicle. The electric driven jacks provide the advantages over
hydraulic and pneumatic jacks by eliminating fluid supply lines, valving,
fluid leakage, and cold weather start up problems.
The invention provides a torque limiting clutch suitable for use
with an electrical motor and gear drive that prevents the overloading of the
motor and prevents the jack from locking up during both the raising and
lowering of the jack. A greater amount of torque is provided to the jack by
the limiting clutch when lowering the vehicle than for raising the vehicle.
According to a broad aspect of the present invention, there is
provided a clutch assembly including: a drive clutch gear having a flat
surface extending perpendicularly to the rotational axis of the gear, the
surface having at least a pair of radially extending valleys disposed at
~ annularly spaced positions, the sides of the valleys being bevelled with the
; bevel of one side of the valleys disposed at a first angle and the bevel of
~ ;;~ the opposite side of the valleys disposed at a second angle different from
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the first angle to control the torques at which the clutch staTts to slip
when rotated in opposite directions; a drive plate having one side of the
plate disposed adjacent the flat surface of the gear and at least a pair of
apertures annularly spaced in accordance with the spacing of the valleys in
the flat surface; a pair of balls disposed in the apertures of the drive
plate and extending into the valleys in the flat surface of the gear; a disc
spring disposed against the balls on the opposite side of the drive plate
from the drive clutch gear and biasing the balls into the valleys in the
flat surface of the gear; and a driven gear operatively coupled to the drive
plate for rotation therewith, whereby below a predetermined drive torque in
a given direction the drive plate and driven gear are rotated by engagement
of the balls with the drive plate and above the predetermined torque the
balls exit from the valleys to cause slippage of the drive clutch gear
relative to the drive plate.
The present invention and that of Application Serial No. 290,917
will now be described in more detail with reference to the accompanying
drawing, in which
Figure 1 is a perspective view of a recreational vehicle having an
electrical retractable jack mounted on the four corners of the vehicle and
on the center of the front bumper;
Figure 2 is a perspective view of the jack in a retracted position
and shown in dotted lines in an extended position;
Figure 3 is a side view of the jack in a horizontal retracted
position;
Figure 4 is a side view of the jack at an angle from the retracted
position;
Figure 5 is a side view of the jack in a lowered vertical position;
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Fi.gure 6 is a side view of the jack in a vertical extended position;
Figure 7 is a front view of the individual elements of the .am
assembly;
Figure 8 is a front view of the individual elements of the clutch
assembly according to the present invention; and
Figure 9 is a front view of the individual elements of the drive
assembly.
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In Figure 1, the electrical retractable jack is designated by
general reference numeral 10. In this view, the jack 10 is seen mounted on
the corners and the front bumper of a recreational vehicle 12. me jacks 10
may be mounted in various arrangement combinations on the vehicle 12 such as
the four corners of the vehicle, the two rear corners and the center of the
front of the vehicle, or any other desirable combination. The jacks 10 are
electrically operated and may be wired to a control panel inside the vehicle
12. me jacks 10 may be powered by the vehicle's battery or any other alter-
nate electrical power source. me operator of the jack 10 need not leave
the inside of the vehicle when leveling the vehicle 12. The vehicle 12 is
leveled and stabilized by rotating the jacks 10 into a vertical position,
and extending the jack 10 onto the ground surface.
The system described herein has the advantage of providing remote,
individual control of each jack assembly 10 with minute leveling and stabili-
zation adjustments possible from a single location within the vehicle. Appro-
priate leveling devices, such as bubble levels, may be positioned near the
control panel so that the operator may observe them during the leveling
operation. Also, the operator need not leave the vehicle 12 when retracting
the jacks 10 from the ground surface and raising them into a retracted hori-
zontal position under the vehicle 12 prior to travel.
Figure 2 is a perspective view of the jack 10 and illustrates the
jack 10 in a horizontal retracted position and in dotted lines in a vertical
extended position.
Hydraulic and pneumatic systems are capable of providing as much
lifting power and linear travel as conventional jack mechanical incline screw
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arrangements, depending upon piston and cylinder sizes and their operatingpressures. Associated with hydraulic and pneumatic systems, however, are
the d:isadvantages of lengthy and cumbersome supply lines to each individual
unit, complex control and check valves, flexible coupling problems, cold
weather operational difficulties, pipe flow losses and joint and seal leakage.
For the invention described herein, all of these problems have been eliminated
by the utilization of an electrically powered drive assembly 15 which not only
provides a high torque level for the jack screw in the ram assembly l6, but
also provides the power for retracting the jack 10 into the horizontal stowed
position shown in Figure 2.
The jack 10 includes a "U" shaped channeled mounting bracket 14,
a drive assembly 15 pivotally attached to the bracket 14, a ram assembly 16
attached to the lower end of the drive assembly 15, and a retraction assembly
18 disposed around the ram assembly 16 and pivGtally attached to the bracket
14.
The bracket 14 is shown having a cut away portion in one end thereof
exposing a main pivot pin 20 which is attached to the sides of the bracket
14 and is received through pivot supports 22 inte~grally formed in the sides
of a motor housing 24. The motor housing 24 is part of the drive assembly
20 15. A torsion spring 25 is disposed between the pivot supports 22 and around
the pin 20. The torsion spring 25 includes one end which is biased against
the top of the bracket 14. The other end of the spring 25 is biased against
the side of the motor housing 24. The jack 10 when lowered from the horizon-
tal retracted position is biased downwardly and towards the vertical position
by the weight of the jack 10 and the spring 25.
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The drive assembly 15 includes the motor housing 24, an electric
motor, gearing, and a clutch assembly, which are discussed in detail under
Figures 8 and 9. The lower end of the drive assembly 15 is secured to the
top of the ram assembly 16.
The ram assembly 16 includes a hollow outer jack tube 26 with a
hollow inner jack tube 28 slidably received therein. me lower end of the
inner jack tube 28 includes a jack pad mounting plate 30, threaded to receive
a bolt for attachment of an annular extension pad 33 as is required for the
incremental adjustment of overall length to accommodate various vehicle
heights above the ground surface. The underneath surface of the jack pad
mounting plate 30, or extension pad 33 when used, provides a bearing surface
against the ground when the vehicle is raised on the ground surface by the
jack 10.
The retraction assembly 18 includes a hollow annular shaped retrac-
tion sleeve 32 with pivot inserts 34 integrally formed in the sides thereof
and extending outwardly therefrom. The sleeve 32 is received around the outer
and inner jack tubes 26 and 28. The retraction assembly 18 further includes
a pair of elongated retraction links 36. me lower end of the retraction
links 36 are pivotally attached to the pivot inserts 34. The upper end of
20 the links 36 are pivotally attached to the mounting bracket 14 by a pin 40.
The pin 40 is disposed below and to the left of the main pivot pin 20. By
offsetting the position of the pin 40 with the pin 20 on the bracket 14, the
retraction assembly 18 provides means for automatically pivoting the ram assem-
bly 16 and drive assembly 15 upwardly to a horizontal stowage position in the
bracket 14.
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Each of the retraction links 36 includes a concave portion 41 along
the length thereof for providing an area of weakness of both links 36 so that
they would collapse or bend prior to overloading the internal components of
the ram assembly 16 should the jack 10 be prevented from retracting into the
bracket 14 by an obstruction.
A novel secondary feature of the retraction links 36 is the utili-
zatiOn of the concave portion 41 to provide an adjustment in overall linkage
length. The length of both retraction links 36 between the pivot 40 and in-
sert pivot 34 should be the same for proper performance of the retraction
cycle. The design of the links 36 and the selections of material yield pro-
perties is such that the links bend with ease when overloaded, but maintain
their lengths under normal operation. Any difference in length of the two
links 36 is eventually reduced to a proper working length by the action of
the retraction sleeve 32 applying a compressive end loading on the longest
link 36 first. Thus, the linkage is self-adjusting under these circumstances.
In addition to the foregoing features, the length of the links 36
determines the amount of angular displacement the jack 10 undergoes during
retraction into a stowed position. Lengthening the links 36 increases the
rotational arc and shortening reduces the amount of angular arc. This is
useful in the initial installation of the jack 10 on vehicles having obstruc-
tions or components in the area of attach~ent which might interfere with
proper operation of the system. Lengthening of the links 36 is accomplished
by partially flattening the concave portion 41.
In Figure 3, the jack 10 is seen in a horizontal retracted position.
In this position, the inner jack tube 28 has been retracted in the ram assembly
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16 until the annular edge of the jack pad mounting plate 30 has come in con-
tact with the bottom edge of the retraction sleeve 32. The compressive force
of the inwardly moving inner jack tube 28 is distributed equally around the
circumference of the retractable sleeve 32 by the jack pad mounting plate 30.
This force in turn is distributed onto the retraction links 36 through the
pivots 34 and because of the offset in the pivots 40 in bracket 14, the jack
10 is rotated upwardly in a counterclockwise direction. The jack 10 is held
in place in the horizontal stowage position in the bracket 14 as long as the
electric motor 104 is de-energized with the jack pad mounting plate 30 biased
against the end of the retraction sleeve 32. Since sufficient friction is
present in the gearing of the drive assembly 15 and the screw of the ram
assembly 16, coupled with the magnetic braking action of the electric motor
104, the jack 10 is self-locking in whatever position it has attained when
electrical power is discontinued. This has the particular advantage of elim-
inating complex mechanical locking devices to hold the jack 10 in the stowed
position for travel or to prevent vehicle 12, which has been leveled and
stabilized, from self-lowering.
The annular retraction sleeve 32, in combination with the retrac-
tion links 36 is advantageous in that it provides a more uniform application
of force onto pivots 40 for retraction. The length of links 36 can be kept
short such that thin, lightweight materials can be utilized for the links 36
without subjecting these parts to excessive column bending while under com-
pressive loading. Since the load of the ram assembly 16 is distributed
uniformly about the circumference of the annular sleeve 32, the use of thin-
walled, lightweight tubing for the sleeve is also warranted.
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In the stowed position, the sleeve 32 has the advantage of providing
an external sheath for the ram assembly 16, further protecting the internal
parts from mud, water, ice or other elements encountered during travel over
roads or various kinds of terrain. During either extension or retraction,
the sliding sleeve 32 also provides a wiping action which can remove caked
mud and ice.
When the inner jack tube 28 is extended outwardly from the ram
assembly 16, the force against the annular surface of the retraction sleeve
32 is relieved. The pivoted weight of the jack 10 and the spring 25 then
urges the jack 10 downwardly into a vertical position shown in Figure 5.
Figure 4 illustrates the jack 10 at an angle from the vertical.
This position is typical when the inner jack tube 28 is retracted inwardly
into the outer jack tube 26, the jack pad mounting plate 30 contracting the
retraction sleeve 32 and pivoting the jack 10 upwardly into a horizontal
position, or in the reverse mode, the jack is pivoted downwardly into a
vertical position.
In Figure 5, the jack 10 is shown in a vertical position. The
jack pad mounting plate 30 is no longer in contact with the end of the
retraction sleeve 32. In this position, the top of the drive as~embly 15 is
adjacent the top of the mounting bracket 14 and~the ram assembly 16 is in
position for extending the inner jack tube 28 downward for leveling the
vehicle 12.
In Figure 6, the jack 10 is shown in a completely extended position
with the inner jack tube 28 extended downwardly from the outer jack tube 26.
In Figure 7, the individual parts of the ram assembly 16 and the
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retraction assembly 18 are illustrated. me ram assembly 16 includes the outer
jack tube 26 having a mounting plate 42 with apertures therein for securing
the tube 26 to the bottom of the drive assembly 15. me inner jack tube 28
which is slidably received inside the outer jack tube 26 is attached to a jack
screw nut 44, which is threadably mounted on a jack screw 46. The nut 44 in-
cludes a keyway 48 which is inserted in an indent 50 in the top of the inner
jack tube 28 for securing the nut 44 in a rotational direction. me nut 14
is secured longitudinally in the inner jack tube 28 by means of an annular
locking ring 51 received by an annular grooving 53 in nut 44 and an annular
groove inside the top of the inner jack tube 28. The jack screw 46 includes
a stop pin 52 at the lower end thereof to prevent the nut 44 from coming loose
from the screw 46.
me upper end of the jack screw 46 includes a drive collar 54 having
a pair of washers 56 with a thrust bearing 58 having needle bearings mounted
therebetween. The needle thrust bearing 58 and washers 56 are retained on the
drive collar 54 and secured to the jack screw 46 by a retainer pin 60 inserted
through an aperture in the drive collar 54 and an aperture in the upper end
of the jack screw 46. The drive collar 64 is inserted through the tube 26,
the aperture in mounting plate 42 and washer S9 upon final assembly of the
ram assembly 16 and secured by retaining pin 61.
Although having slightly higher friction, the needle thrust bearing
58 has the advantage of having a considerably thinner profile and a higher
thrust load capability than a conventional ball bearing thrust assembly
occupying the same diameter. me combination of the mechanical screw jack
46, nut 44 and thrust bearing 58 with the other internal components provides
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a compact ram assembly 16 capable of lifting much greater loads than the
prior art mechanical screw fixed jacks which have been available in the past.
The limitations of space beneath a vehicle necessitates that most of the ele-
ments of a retractable system such as the jack 10 be as nearly compact as
practical. Ground clearance must be maintained both during road travel and
erection of the jack 10 to a vertical position prior to leveling and stabil-
izing the vehicle 12. Sufficient linear extension of the ram assembly must
also be available to perform the leveling and stabilizing task. me physical
arrangement and geometric characteristics of the jack 10 described herein
10 fully meets all of these dimensional requirements.
The upper end of the drive collar 54 includes a slot 62 therein.
me slot 62 is received around a jack pin 64 when securing the ram assembly
16 to drive assembly 15. The jack pin 64 is inserted through apertures in
jack drive sleeve 66. The ends of the pin 64 are inserted into slots in a
jack drive gear 68. me sleeve 66 is received inside the inner circwnference
of the gear 68 shown in Figure 9. The gear 68, sleeve 66, and pin 64 assem-
bly engage and rotate the drive collar 54 and jack screw 46 assembly shown
in Figure 7. The gear 68 is driven by a clutch assembly 70 described in the
following paragraphs which relate to Figure 8. Also seen in Figure 7 is
20 the annular retraction sleeve 32 and the retraction links 36.
Several distinct advantages are provided by the selection of the
l~in-line~ arrangement of the motor housing 24, drive assembly 15 and the ram
assembly 16 and the location of these components with respect to the main
pivot 20 on bracket 14. One important advantage can be seen in Figure 3
depicting the retracted or stowed position of the jack 10. The clearance
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provided beneath the jack 10 components and the ground or other obstacles is
at a maximum, thus protecting the motor and other components from impact
damage while the vehicle 12 is in motion.
Another advantage gained by the in-line arrangement with the electric
motor located near the main pivot 20 is that much shorter electrical wiring
leads can be used. These wires may be rotated out of the motor housing 24,
through any convenient hole in the bracket 14 near pivot 20 which permits
unimpeded, free motion of the wires without damage during retraction or ex-
tension of the jack 10. While the vehicle 12 is in a traveling condition,
the wiring is also protected from damage, being physically shielded by the
motor housing 24 while jack 10 is retracted.
The proximity of the heavier motor housing 24 and drive assembly
15 to the main pivot 20 reduces the amount of power required to raise the
pivoted portion of the jack to a horizontal retracted position. In addition,
the dynamic loads produced as a result of vertical accelerations experienced
by the horizontally stowed jack assembly 10 during road travel are reduced
when the heavier components are grouped about the supporting main pivot 20.
Since each suspende~ component produces a movement or torsional loading
about the pivot 20 during vertical accelerations produced while the vehicle
12 is traveling and these forces must be reacted, it is advantageous to keep
each component movement arm at a minimum as in the jack arrangement presented.
Thus, fatigue life of the retraction links 36, pivot pins 34 and 40 and the
retraction sleeve 32, which are already under a static compressive preload
during the stowed condition, is greatly improved with the configuration used
in the jack 10.
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Figure 8 illustrates the individual parts of the torque limiting
clutch assembly 70. The assembly 70 provides means for differentially con-
trolling the amount of torque applied to the jack screw 46 from the drive
motor and gear train. Should the loads on the jack lO become excessive
while the ram assembly 16 is operating in either the retraction or leveling
mode, the clutch assembly 70 will release at a preset torque level and the
drive motor, gearing and ram assembly is prevented from being overloaded to
the extent of damage.
The clutch assembly 70 includes a clutch gear shaft 72 for re-
ceiving the clutch gear 74 thereon. A lower face 75 of gear 74 includes
three channeled valleys 76 therein. The valleys 76 are radially spaced in
equal segments about the axis of rotation of the clutch gear 74. Each valley
consists of a floor paralleling the face of the clutch gear 74 and at a desig-
nated depth with opposing sides beveled at two different inclinations relative
to the face 75 of the gear 74.
A clutch drive plate 80 having apertures therein receive ball
bearings 78 in the apertures. The ball bearings 78 are physically entrapped
~ both radially and circumferentially within the perforated clutch drive plate
; 80 but possess translational freedom of motion in a direction perpendicular
to the facing of the plate 80. The ball bearings 78 are biased directly by
conically shaped disc springs 82 against the floor of the valleys 76, the
valley slopes or on the gear facing 75 during operation. The springs 82 are
retained against the ball bearings 78 by a spacer 84 and retaining ring 86.
The ring 86 is inserted into an annular groove 87 around the shaft 72. A
jack drive pinion gear 88 is attached to the clutch gear shaft 72 by a pin 90.
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When assembled, the disc springs 82 are pre-set to apply a desig-
nated load against the ball bearings 78. me disc springs 82 are in direct
contact only with the ball bearings 78 during all phases of clutch operation.
The clutch drive plate 80 serves as a floating member between the disc springs
82 and the clutch gear 74, transmitting only rotational loads from the clutch
gear 74 to the clutch gear shaft 72 to which plate 80 is rotatably keyed.
In operation, the clutch gear 74 is driven by the reversible elec-
tric motor and gear assembly described in paragraphs which follow. During
rotation of the clutch gear 74, the advancing incline of each of the valleys
76 bears against the lower portion of each ball 78 protruding through the
drive plate 80, moving the balls upwardly and directly reacting the force pro-
duced by the disc springs 82. The loading of the disc springs 82 against
each ball 78 increases with upward deflection. The pre-set biasing of the
disc springs 82 thus determines the amount of force at which the balls 78 may
move upwardly and over the edge of each incline and onto the facing 75 of the
clutch gear 74. When the maximum torque threshold is reached, the ball
bearings 78 exit and enter each successive valley 76, rolling freely on the
facing 75 of the rotating clutch gear 74 and precluding further mechanical
engagement between the gear 74 and the drive plate 80. Under this condition,
the torque proyided to the ram assembly 16 and hence the maximum load on the
jack 10 is prevented from increasing above the designated limit. Torque is
provided to the assembly 16 only when the balls are captured and retained in
the valleys 76, mechanically engaging the clutch gear 74 and the drive plate
` 80.
The action described in the foregoing also applies while operating
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in a reverse rotational direction, however a differential torque limit is
provided by the angular difference in the opposing inclines which bound the
valleys 76.
In Figure 9, the drive assembly 18 is illustrated. As discussed
under Figure 7, the jack drive gear 68, sleeve 66 and pin 64 engage the top
of the drive collar 54. The above are housed inside a;gear housing plate 92
which is threadably attached to a clutch gear housing 94. The gear teeth
of the jack drive gear 68 mesh with the gear teeth of the jack drive pinion
gear 88. The pinion gear 88 is received through the aperture in the top of
the housing 92.
The clutch gear 72 is housed in the clutch gear housing 92 and
drive gear housing 100 and is driven by a pinion gear 96 which is part of a
motor drive gear 98. The upper portion of the drive gear 98 is received in
a drive gear housing 100, which is threadably attached to the clutch gear
housing 94 and the motor housing 24.
The drive gear 98 is driven by a motor drive shaft 102 of an elec-
tric motor 104. The motor 104 is housed and threadably attached to the motor
housing 24 with the shaft 102 extending downwardly therefrom into the drive
gear housing 100. Also seen in Figure 9 is the coil spring 25 and pivot pin
20 which are received through apertures in the pivot supports 22 which are
an integral part of the motor housing 24.
Changes may be made in the construction and arrangement of the
parts or elements of the embodiments as disclosed herein without departing
from the spirit or scope of the invention as defined in the following claims.
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