Hydraulic hose assembly and method

High-pressure hydraulic hoses are employed in hydrostatic drive systems to interconnect the transmission and motors thereof. It is imperative that fluid leakage be held to a minimum, or preferably eliminated, particularly where a vehicle employing the drive system is operated in a high-temperature environment, such as a foundry. The hose assembly (13) of this invention provides a high degree of system reliability, relative to hydraulic leaks, and shields a high-pressure hose thereof (14) against damage and heat conduction to hydraulic fluid therein. The hose assembly (13) comprises a flexible high-pressure hose (14), an impervious flexible jacket (17) surrounding the hose in out-of-contact relationship therewith to define a fluid chamber (18) therebetween, and a mounting assembly (22) for mounting the hose (14) and the jacket (17) on a support member (23) to maintain them in out-of-contact relationship relative to each other. The mounting assembly (22) includes a first mount (26) for securing the hose on the support member (23) under a predetermined first sealing pressure, and a second mount (34) for securing the jacket (17) about the hose and on the support member (23) under a predetermined second sealing pressure that is less than the first sealing pressure. Method steps are taught for assembling the hose assembly (13) in this manner.

DESCRIPTION 
1. Technical Field 
This invention relates generally to a high-pressure hose assembly and more 
particularly to the mounting of a flexible high-pressure hose within a 
jacket to define a fluid chamber therebetween. 
2. Background Art 
Hydrostatic drive systems have found useful application to construction and 
industrial vehicles, such as track-type loaders. In loader applications, a 
transmission, including an engine-driven pump, is connected to a fluid 
motor which powers each drive sprocket of the loader. The pump and motor 
are interconnected by a pair of flexible high-pressure hoses for 
intercommunicating hydraulic fluid therebetween at a working pressure 
approximating 41,370 kPa. 
Since the pump and motor are placed at a substantial distance from each 
other on the loader, failure of an exposed portion of one of the 
interconnecting hoses could result in the loss of large quantities of 
working fluid to immobilize the loader. In addition, high pressure leaks 
can cause misting or spraying of the fluid into the surrounding 
environment. Various factors tend to reduce hose life, including 
mechanical stresses imposed on the hose and operation of the loader in a 
high-temperature environment, such as a foundry. Such stresses may be 
induced by the relative motion occurring between the transmission and 
motor during loader operation. 
Although flexible metal hoses, commonly including a corrugated tube covered 
with a metal, braided sheath, are widely used, they are normally 
inapplicable to large high-pressure applications, such as those 
encountered with hydrostatic drive systems. In addition, metallic hoses of 
this type conduct heat to the hydraulic working fluid therein when they 
operate in a high-temperature environment. 
The present invention is directed to overcoming one or more of the problems 
as set forth above. 
DISCLOSURE OF INVENTION 
In one aspect of this invention, a hose assembly comprises a flexible 
high-pressure hose, an impervious flexible jacket surrounding the hose to 
define a fluid chamber therebetween, and mounting means for mounting the 
hose and jacket on a support member to maintain them in out-of-contact 
relationship relative to each other to define the fluid chamber. 
In another aspect of this invention, the mounting means comprises first 
mounting means for mounting the hose on the support member under a 
predetermined first sealing pressure and second mounting means for 
mounting the jacket on the support member under a predetermined second 
sealing pressure that is less than the first sealing pressure. 
In still another aspect of this invention, a method for mounting the hose 
assembly on the support member comprises the steps of mounting the hose in 
protected relationship within the jacket, clamping the hose on the support 
member under the first sealing pressure, and clamping the jacket on the 
support member under the second sealing pressure that is less than the 
first sealing pressure. 
The hose, mounting assembly, and method of this invention will thus provide 
an integrated system exhibiting a high degree of serviceability and 
reliability, relative to hydraulic fluid leaks. In addition, the jacket 
will protect the hose against abrasion, and rubber degrading oils, and 
will also isolate the hose to prevent direct conduction of ambient heat 
thereto. The containment of fluid leakage in the chamber, defined between 
the hose and jacket, will enable the system to return such fluid as a 
harmless flow back to the sump of a hydrostatic drive system, for example. 
The system is also capable of maintaining sufficient charge pressure under 
drive line failure conditions to prevent complete vehicle shut-down, 
allowing at least partial mobility of the vehicle.

BEST MODE OF CARRYING OUT THE INVENTION 
FIG. 1 partially illustrates a hydrostatic drive system 10 adapted for use 
on a track-type vehicle, such as a track-type loader. In particular, the 
system includes a motor 11 connected to a transmission 12 by a pair of 
hose assemblies 13 (one shown). A motor is suitably connected to each 
drive sprocket (not shown) of the loader in a conventional manner to 
provide the power input thereto. The transmission includes a power 
take-off from the engine, a pair of variable displacement pumps each 
connected to a motor, and the pump drives. 
This invention is primarily directed to hose assembly 13 which provides the 
hydrostatic drive system package with a high degree of reliability, 
particularly in the event of fluid leakages occurring therein. Since the 
pair of hose assemblies employed are substantially identical in 
construction and arrangement to each other, only one hose assembly will be 
described in detail. In addition, it will be seen hereinafter that the 
mounting assemblies 22, 22' for interconnecting opposite ends of the hose 
assembly between the motor and transmission are also basically similar. 
Referring to FIGS. 1 and 2, each hose assembly 13 includes a hose 14 
connected to a mounting stem 15 by a coupling 16. The hose and coupling 
preferably constitute the commercially-available "Caterpillar XT-6 Hose 
and Coupling," manufactured by Caterpillar Tractor Co. of Peoria, Ill. 
High-pressure hoses and couplings of this type are adapted to supply 
hydraulic working fluids at a pressure level approximating 41,370 kPa. 
In working environments wherein the transmission and motor are positioned 
at a substantial distance from each other, i.e., wherein the transmission, 
including the pump, is resiliently mounted to be driven by the engine 
thereof and the motor is mounted on the main frame and connected to the 
final sprocket drive, it is highly desirable to protect the hoses against 
abrasion and rubber degrading oils. In addition, when the loader operates 
in a working environment wherein ambient temperatures are quite high, 
e.g., a foundry, it is further desirable to provide the hoses with a heat 
shield to prevent conduction of ambient heat to the hydraulic fluid 
communicated through the hoses. 
To this end, applicant's hose assembly 13 further includes an impervious 
flexible jacket 17 which surrounds hose 14 in out-of-contact relationship 
therewith to define an annular fluid chamber 18 therebetween. As 
illustrated in FIG. 1, a suitable . fitting 19 is adapted to communicate 
low-pressure hydraulic fluid (e.g., 2,069 kPa) from chamber 18 to the sump 
of the hydrostatic drive system for recirculation purposes. 
In the preferred embodiment of this invention, jacket 17 comprises a 
standard flexible hose including a corrugated stainless steel tubing 20 
covered with a braided stainless steel sheath 21. The jacket may be of the 
type manufactured by Flexonics, Inc. of Bartlett, Ill. Mounting means 22 
mounts the hose and jacket on a support member or housing 23 of motor 11 
to maintain them in out-of-contact relationship relative to each other and 
to provide limited relative longitudinal movement therebetween for 
purposes hereinafter described. 
Referring to FIGS. 2 and 3, mounting means or assembly 22 includes first 
mounting means 26 for mounting stem 15 of hose coupling 16 on motor 
housing 23 under a predetermined first sealing pressure in the range of 
41,370 kPa. The first mounting means includes a clamp 27 having a pair of 
semi-circular clamping segments 28 defining a continuous annular clamping 
groove 29 thereon. An annular flanged head 30 of stem 15 is disposed in 
the groove and has an annular or O-ring seal 31 mounted therein to engage 
the outer face of housing 23 to form a high-pressure static seal thereat. 
A continuous passage 32, defined through stem 15 and hose 14, is thus 
adapted to communicate high-pressure hydraulic fluid to an inlet port 33 
of motor 11. 
Mounting assembly 22 further includes a second mounting means 34 for 
mounting jacket 17 about hose 14 and its attendant coupling 16 and on 
motor housing 23 under a predetermined second sealing pressure that is 
substantially less than the first sealing pressure maintained at 
high-pressure seal 31. In addition, the second mounting means functions to 
maintain the jacket in out-of-contact relationship relative to the hose to 
define fluid chamber 18 therebetween. As described more fully hereinafter, 
clamping segments 28 have a plurality of ports 35 formed axially 
therethrough to communicate any fluid leakage past seal 31 to chamber 18 
for return to the sump of the drive system via connection 19 (FIG. 1). 
Second mounting means 34 includes a tubular adapter 36 having an annular 
clamping groove 37 defined therein to engage clamp 27. A flanged head 38 
of the adapter is disposed within an annular clamping groove 39, defined 
internally on a clamping ring 40, and has an annular or O-ring seal 41 
mounted therein to engage motor housing 23 to form a low-pressure seal 
thereat, e.g., in the range of 2,069 kPa. 
A common fastening means 42, shown in the form of a plurality of 
circumferentially-disposed bolts 43, is adapted to simultaneously form the 
high-pressure seal at seal 31 and the relatively low-pressure seal at seal 
41. These relative sealing pressures are automatically obtained by 
providing a clearance C.sub.1 (shown exaggerated in FIG. 2) between a 
frontal surface 44 of clamping ring 40 and motor housing 23, and a smaller 
clearance C.sub.2 between a frontal surface 45 of adapter 36 and the motor 
housing. Flanged heads 30 and 38, segment clamp 27, and clamping ring 40 
are suitably dimensioned so that when bolts 43 are torqued-down to effect 
the high sealing pressure at seal 31 (e.g., 41,370 kPa), clearances 
C.sub.1 and C.sub.2 will automatically effect a relatively low sealing 
pressure at seal 41 (e.g., 2,069 kPa). 
Still referring to FIGS. 2 and 3, hose assembly 13 preferably also includes 
a slip coupling 46 for permitting relative axial movement to occur between 
sleeve 24 and adapter 36, and thus between jacket 17 and motor housing 23. 
This relative movement may occur due to pressure expansion or contraction, 
or due to pulling forces imposed on the jacket. The slip coupling includes 
a pair of axially-spaced low-pressure O-ring seals 47 (2,069 kPa) mounted 
between the sleeve and adapter. In addition, the slip coupling is 
preferably accompanied by a retaining means 48 for continuously ensuring 
sealing contact at seals 47 within a limited range of axial movement 
between the adapter and sleeve. 
As shown in FIG. 2, the retaining means includes an annular two-piece 
sleeve 49 clamped together by bolts 50, and a pair of annular flanges 51 
and 52 extending radially inwardly from the sleeve. Flange 52 engages 
within an annular groove 53, formed on the periphery of sleeve 24, whereby 
sleeves 24 and 49 will move together axially. Assuming rightward movement 
of jacket 17 and sleeve 24 in FIG. 2 through an axial distance D, flange 
51 will engage an axially opposed annular shoulder 54, formed on adapter 
36 to extend radially outwardly therefrom, to prevent disconnection of the 
jacket from the motor and the loss of sealing at seals 47. 
Referring once again to FIG. 1, a mounting assembly 22' for mounting the 
opposite end of hose assembly 13 on a manifold or housing 23' of 
transmission 12 is basically similar in construction and arrangement to 
mounting assembly 22. Identical numerals depict corresponding 
constructions with numerals depicting modified constructions in mounting 
assembly 22' being accompanied by a prime (') symbol. Mounting means 22' 
essentially differs from mounting means 22 in that an adapter 36' and 
clamping ring 40' are formed as an integral and combined member. Member 
36',40', clamping segments 28, and the flanged head of mounting stem 15 
are also adapted to attach the opposite end of hose assembly 13 to housing 
23' of transmission 12 to provide a high-pressure seal at seal 31 (e.g., 
41,370 kPa) and a relatively low pressure seal at seal 41 (e.g., 2,069 
kPa). 
Thus, mounting means 22' also includes first mounting means 26' for 
mounting hose 14 on a support member or housing 23' of transmission 12 
under a predetermined first sealing pressure, and second mounting means 
34' for mounting jacket 17 about the hose and on the transmission housing 
under a predetermined second sealing pressure at seal 41 that is less than 
the first sealing pressure at seal 31. In addition, second mounting means 
34', including adapter 36', is secured to the jacket by a band clamp 25' 
to maintain the jacket in out-of-contact relationship relative to the hose 
to aid in defining fluid chamber 18 therebetween. 
INDUSTRIAL APPLICABILITY 
Hose assembly 13 finds particular application to a hydrostatic drive system 
for interconnecting a variable displacement pump of transmission 12 and a 
fluid motor 12 thereof. In a drive system of this type, a pair of such 
hose assemblies interconnect the pump and motor to provide a loop or 
continuous fluid circuit therebetween. The provision of impervious 
flexible jacket 17 in combination with flexible high-pressure hose 14 
finds particular application to a hydrostatic drive system employed on a 
track-type vehicle, such as a track-type loader, that is operated in a 
high-temperature environment, such as in a foundry. 
Jacket 17 will not only protect the hose against abrasion, and rubber 
degrading oils, but will also reduce conduction of ambient heat to the 
hose and the hydraulic fluid communicated therethrough. As discussed 
above, the formation of annular fluid chamber 18 between the hose and 
jacket will provide for the return of fluid to the sump of the drive 
system, via connection 19. In addition, the hose assembly facilitates 
initial factory assembly, disassembly for on-site servicing purposes, and 
maximizes utilization of duplicate parts. 
The method for mounting hose assembly 13 on motor housing 23 comprises the 
following assembly steps: disposing high-pressure hose 14 within jacket 17 
to define fluid chamber 18 therebetween, clamping the hose on motor 
housing 23 under a predetermined first sealing pressure at seal 31 to 
provide a high-pressure seal thereat, and clamping the jacket on the motor 
housing under a predetermined second sealing pressure at seal 41 that is 
less than the first sealing pressure. 
More specifically with reference to FIG. 1, it is assumed that the 
component parts of the motor and of the hose assembly are disconnected, as 
generally shown in FIG. 3, and that the hose assembly has been secured to 
housing 23' of transmission 12 previously. Adapter 36 is moved rightwardly 
on sleeve 24 to facilitate the mounting of clamping segments 28 on flanged 
head 30 of mounting stem 15. The adapter is then moved leftwardly to its 
FIG. 1 position, whereafter clamping ring 40 is clamped in place on motor 
housing 23 by bolts 43. A standard torque wrench can be utilized to ensure 
the required clamping forces and resulting sealing pressures applied to 
seals 31 and 41. Thereafter, split sleeve 49 of retaining means 48 can be 
secured in place by bolts 50 in the manner described above. 
The above-described hose assembly and method will accommodate tolerance 
errors and relative motion occurring between component parts of the hose 
assembly, precisely establish the sealing points in each mounting means 
26, 34 and 26', 34', protect hose 14 against rubber degrading oils and 
heat, and isolate and recirculate fluid leakage to maintain adequate 
charge pressure in the system to prevent vehicle shutdown in the event of 
drive line failure. 
Other aspects, objects, and advantages of this invention can be obtained 
from a study of the drawings, the specification, and the appended claims.