Note: Descriptions are shown in the official language in which they were submitted.
7~3
1 This application is a division of our copending Canadian
patent application 266,104 Filed November 19, 1976. This invention
relates to a dual control mechanism for vehicles, and more
particularly Eor skid-steered tractor vehicles having separate
hydrostatic transmissions. A four-wheel skid-steered vehicle of
the type to which the present invention pertains is disclosed in
U.S. Patent No. 3,635,365 entitled "Tractor Vehicle With Hydrostatic
Drive Means", issued January 18, 1972 to the inventor, James J.
Bauer, and assigned to the assignee of the present invention.
Skid-steered loader vehicles of the type disclosed in the
aforementioned patent will have right and left hydrostatic trans-
; missions independently controlled by a pair of steering-levers,
one for each transmissionl movable forward or back to vary the
- speed and power output of the transmissions in either forward
or reverse directions.
A centering mechanism is used to return the levers to the
neutral position once released by the operator. Such a centering
mechanism is disclosed in U.S. Patent No. 3,605,519 entitled
"Control for Dual Hydrostatic Drive", issued September 20, 1~71,
to the inventor, ~ohn P. Heggen, and assigned to the assignee
- of the present invention.
The centering mechanism of Patent 3,605,519 is mounted at
one end of the control shaft, on which the steering levers pivot
and generally takes the form of a roller which travels in a V-
shaped cam leaf biased by a spring such that when the levers are
released, the roller is urged to the lowest point in the cam
leaf which coincides with the neutral position of the levers.
The loader or material handling portions of the vehicle
will be operated by a pair of hydraulic cylinders to raise and
lower the boom arms and to tilt or roll back the attachment carrier
mounting an attachment such as a bucket. A control valve having
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1 separate valve sections operates the hydraulic cylinders. The
; separate sections are individually actuated by a linkaye controlled
by -foot pedals in the operator's compartment.
Dual steering levers for separate hydrostatic transmissions
are independently centered or returned to the zero displacement
position corresponding to that position for the swash plates of
the variable displacement piston pump5. The pumps are driven on a
common axis and opposed with a common porting block in between
. .
such that the swash plates are controllable on one side of the pump
axis. The centering mechanism includes an elongated element shift-
able longitudinally along a line parallel to the pump axis carrying
a pair of cam blocks making engagement with each swash plate control
arm. The displacement of either swash plate control arm in either
direction from zero displacement by movement of the steering levers
displaces the elongated centering element against the force of a
: .
return springO Release of the steering lever allows the spring to i~
act through the camming blocks returning the swash plates and
steering levers to the zero displacement position.
It is a feature of the invention that one or both steering
levers will be capable of pivoting inwardly or at right angles. This ~-
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movement will be used to control an auxiliary function, or in
;~ the case of a skid-steer vehicle as disclosed in U.S. Patent
., ~: . ,
3 635,365, to operate the boom arms and attachment carrier instead ;;
-~ of using foot pedals in an appropriate case.
;~ In the preferred embodiment disclosed herein, only the right- ;
hand steering lever has the auxiliary control capability which may
:.~
be used to operate a backhoe or other equipment~ The steering levers
are at opposite ends of independently rotatable shafts, the right-
hand shaft having at the outer end thereo-f a carrier structure
pivotally supporting the right-hand lever. The carrier structure
includes a base on which the lever is mounted pivoting on an axis
at right angles to the shaft axis. A downward projection of the
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i base opposite the pivot axis connects to a link for operating a
control valve. The link is connected to the projection on the shaft
~' axis. When the lever i5 in a vertical position there is no longi-
tudinal movement of the link when rotating the steering lever in a
fore and aft direction for steering. However, when pivoted in-
wardly, the lever will pivot the base pulling the link to actuate
' the control valve. ,
. ~
One of the advantages of the present invention is that mount-
ing of the centering mechanism on the pumps rather than at one end
~ of the steering levers allows the auxiliary control functions of
' 10
the vehicle to be incorporated with the levers.
This and other advantages will be more apparent by referring '
~; to the following description of a preferred embodiment which pro-
~, ceeds with a description of the drawings.
~;~. FIGURE 1 is a front perspective view of a skid-steered tractor
'~ vehicle using right and left levers for steering; '
~' FIGURE 2 is a diagrammatic view of the dual, independent hydro~
. , .
,~ static drive controlled by the right and left steering levers and ,~
, showing schematically the centering mechanism;
~', FIGURE 3 is a top view of the steering levers and links connect-
`' 20 ing with the swash plate control arms on the pumps and showing the
centering mechanism with the apparatus in the neutral position
, FIG~lRE 4 is a side view of the apparat~s shown in FIG. 3; ,~
,- FIGURE 5 is a front view of the apparatus shown in FIG. 3;
i:
'~ FIGURE 6 is a fragmentary view showing one shifted position
, of the centering mechanism; and
FIGURE 7 is a detail of the elongated shifting element of
', the centering mechanism showing the openings fox mounting,the center~
, ing element on the shafts of the swash plate control levers and
adjustment slots for the cam blocks mounted on the centering element.
Referring to FIGS. 1 and 2, the reference numeral 10 denotes
generally a compact, four-wheeled drive skid-=teered tractor vehicle
'.
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1~059~3'78
ving a pair of drive whe~ls 14 and 16 on one side and a pair of
drive wheels 18 and 20 on the other side. The vehicle 10 is
equipped with a pair of boom arms 22 pivotally mounted to a pair
of uprights 23 at the rear and extending forwardly alongside the
operator's compartment 25 which includes a seat 26 and a pair of
steering levers 27, 28. The boom arms 22 are raised and lowered by
lift c~linders 29. The boom arms having mounted at their front ends
an attachment carrier ~not shown) pivoted by tilt cylinders 30. The
at~achment carrier is shown mounted with a bucket 31 although other
attachments may be mounted thereon.
~ ~ .
Some attachments will re~uire connection with the hydraulic
system of the machine and in that case the operator wil] control its
operation with the right steering lever as an auxiliary control func-
tion. The lift and tilt cylinders 29, 30 however are controlled by
~ook pedals ~not shown~ in the operator's compartment 25. As des- ~
.; ,: .
cribed herein the auxiliary control function will be controlled with ~ -
the right steering lever 28; however, it will be appreciated that
foot pedals may ~e eliminated entirely and the lift and tilt cylin~
ders 29, 30 controlled by the steering levers where ~oth are equipped
as described hereinafter for auxiliary control.
j' 2~ Referring to FIG.2 the power train of the machine 10 includes
an engine 33 at the rear having a drIve shaf~ 34 powering two vari~
able displacement hydrostatic pumps 35, 36 each having a rotating
piston group (not shown) driven by the shaft 34 on a common axisO -~
The displacement of the pistons is varied in either forward or re-
verse xotation by inclinable swash plates ~also not shown) rotatable
on control arm shafts 37, 38 of the respective pumps. Reference is
made to the aforementioned U.S.Patent 3,635,365 for a fuller descrip-
tion of such pumps. The steering levers 27, 28 operate the control
arms through linkages 41, 42. The centering mechanism 40 is in-
dependent of the linkages 41, 42 and responds directly to movement
~ 30
- of the swash plate control levers as described below.
I~e auxiliary control of the right steering lever includ~s t~e carrier
- 4 -
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rnech~nisln ~ also described belo~.
The output, either forward or reverse, of -the pumps 35, 36 is hy-
draulically coupled through -fluid filled lines 45, ~6 in a closed loop with
hydraulic mo-tors ~7, 48. The output shafts 49, 50 of the motors drive
chain and sprocket reduction units 51, 52 which in turn propel the pairs of ;~
:. wheels 14, 16, and 18, 20 independently in either forward or reverse
directions and at varying speeds depending on the displacelnent of the swash
~ plates.
As depicted in more detail in FIGS. 3, 4 and 5, and referring to FIG. :-.
.~ 10 3, the right steering lever 27 is rotatable with a shaft 54 while the left
steering lever 28 rotates a sleeve 55 coaxial with the shaFt 54 such that
either lever 27, 28 may be rotated independently for steering. The right
steering lever 27 is also capable of pivoting inwardly or at right angles
owing to its mounting on the carrier 44 on the end of shaft 54. The
carrier 44 comprises a loop 60, one side 61 of which is fastened to the .~.
shaft 54, and the other side 62 of which is rotatably mounted by a pin 63
.~ in a bushing 64 fastened to a side plate 65 of the machlne. The loop 60 : .
also has a side 66 joining the two sides 61, 62 and a partial side 67. The ~ .axis of shaft 54 is in line with the axis of pin 63. The lever 27 is ~.j 20 mounted on a base 70 which is generally configured to be received w;thin
the four sides of the loop 60. The base includes opposed projections 71,
. ~.
.~. 72 joined by a third 73. The base 70 is pivotally mounted in the loop 60 ;.. .:
.' on a pin 75 perpendicular to the axis of the shafts 54 and ofFset inwardly
; of the steering lever 27 such that the latter may be pivoted inwardly in a
.: .i
. plane perpendicular to the primary fore and aft plane of movement of the
;~ steering lever 27 established by the axis of the shaft 54. A link 76
: . . -
~ pivots on the projection 73 of the base 70 at 78 coaxial with the axis oF
.~ shaft 54 and pin 63 such that there is no displacement of the link 76 in
rotating the lever in the fore and aft direction. Owing to the angle at
: 30 which the carrier is positioned in the neutral or any forward attitude,
. however, a longitudinal component of motion is produced in the link 76 when
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the lever is pivoted ~t right ~ngles. If desirable, the link
76 may be locked such that the steer:ing lever 27 only has the
steering capability.
At -the opposite end of the sha~'-t 54 is a bushing 80
mounted on the side wall 81 and aligned with the bushing 64. ~-
The steering lever 28 is secured to the sleeve55 rotatable on ;
the shaft 54. The sleeve 55 and shaft 54 each have a lever .-
.
` 84, 85 rotating conjointly therewith. The levers 84, 85 con- .
nect to the linkage 41, 4Z. ~-;
As shown in FIG. 4 the centering mechanism 40 includes -
.- a centering element 90, shown in detail in FIG. 7, having
` elongated openings 91, 92 received over the swash plate ~ .`-
:~ control arm shaf-ts 37, 38 which carry the swash plate control "~
.: ~ - . :
arms 95, 96. The linkage 42 has a lost motion connection
~ 100 bypassing the swash plate control arm 95 of the pump 36
:'7 and being pivotally connected ~t 101 to the swash plate
.. ~ control arm 96 of the pump 35 while the link 41 (FIG.3) which
~ connects the steering lever 27 is pivoted to the swash plate
.~ control arm 95 such that there is independent actuation of ~ .
~. the pumps by the steering levers 27, 28. :~ ~
. . ~ .,
The centering element 90 carries a pair o~ cam blocks .
; 102, ~03 associated with each swash plate control arm 95, 96,
Each cam block has a camming projection 104, 106 engageable
on opposite sides of the swash plate shaft 37, 38. The
' centering elemen-t 90 has a lateral projection 108 at one end
~ which is acted upon by the coil spring 110 to urge the cam~
.-' ming projections 104, 106,toward the shafts 37, 38.
The cam bloc~ 102, 103 are mounted in adjustment slots
~' (FIG.`6) in the centering element 90 except for the circular
. hole 112 for the one block 103 which permit each of the cam
. blocks 102, 103 to be angled or adjusted relative to the .
. desired neutral or node position o~ the swash plates.
.: In operation, when either lever 27 28 is actuated in
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.: either the fore or af-t direct:ion, one of the camming
projections 104, 106 is forced by -the pivo-ting of` the
swash plate con-trol lever, as depic-ted in FIG. 6, to cause
a shift of the center:ing element 90 so as -to compr-ess
the spri.ngs 110. When -the lever 27, 28 causing the dis-
.~i placement is released the spring 110 returns the centering
- :,
element to the predetermined neutral or centered
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~,Jsi-tion which, owing to -the camming projec-tions, engaging
on opposite sicles of -the shaf`t 37, 38 re-turns the swash
plate con-trol arms and steering levers to the neu-tral
.~ position.
While one preferred embodiment of our invention has been
. disclosed it will be understood that the description is :~or :
.. . .
:;. the purposes of illus-tration only and that various modifica-
~` tions and changes may be made without departing from the :
:' nature of the invention which is defined in the appended
claims.
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