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Patent 1135536 Summary

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(12) Patent: (11) CA 1135536
(21) Application Number: 1135536
(54) English Title: HYDRAULIC BELT TENSIONER CONSTRUCTION
(54) French Title: TENDEUR HYDRAULIQUE DE COURROIE
Status: Term Expired - Post Grant
Bibliographic Data
Abstracts

English Abstract


(Case No. 59-4)
ABSTRACT
A hydraulic tensioning device for maintaining a pre-
determined amount of tensioning force on an endless drive belt
for the vehicle accessories drive system. A self-contained
hydraulic fluid supply and pump assembly is mounted on the
swinging end of a pivotally mounted lever and is moved toward
the drive belt by a hydraulically actuated piston which is
mounted in a fixed position on the engine. An idler pulley is
rotatably mounted on the fluid supply and pump assembly and is
engaged with and driven by the drive belt. The drive belt
rotates the idler pulley which hydraulically actuates the piston
by driving the pump which supplies hydraulic fluid to the piston
from the fluid supply. The piston pivots the lever toward the
belt whereupon the idler pulley engages the belt and exerts the
desired tensioning force on the belt. Check valves in the pump
assembly regulate the amount of hydraulic force applied to the
piston and ultimately to the belt. A partition member is
slidably mounted within the piston cylinder and compensates for
small oil leaks in the piston by reducing the effective volume
of the cylinder chamber to maintain a constant tensioning force
on the belt tensioning lever when the engine is shut off.


Claims

Note: Claims are shown in the official language in which they were submitted.


The embodiment of the invention in which an exclusive
property or privilege is claimed is defined as follows:
1. A hydraulic belt tensioner construction for auto-
matically tensioning an endless belt of the drive system for
vehicle accessories, said tensioner construction including:
a) piston means adapted to be mounted in a fixed
position with respect to the endless drive belt;
b) lever means operatively engaged and moved by the
piston means toward the drive belt;
c) tensioning assembly means mounted on the lever
means and adapted to be moved into engagement with the drive
belt upon movement of the lever means by the piston means; and
d) the tensioning assembly means including pump
means, reservoir means for containing a supply of hydraulic
fluid, and pulley means drivingly engaged with the pump means,
said pulley means being adapted to be engaged with and driven
by the drive belt for actuating the pump means to supply hydrau-
lic fluid from the reservoir means under pressure to the piston
means to actuate the piston means and move the lever means to
bring the tensioning assembly means into engagement with the
drive belt.
2. The belt tensioner construction defined in claim
1 in which the pulley means has a shaft and a belt-engaging
pulley member fixedly mounted on said shaft; in which bearing
means rotatably mounts the pulley means shaft with respect to
the pump means and reservoir means; and in which the pump means
is operatively connected to and driven by the pulley means
shaft.
21

3. The belt tensioner construction defined in claim
2 in which the pump means is a gear pump having a pair of
meshing gears; and in which one of said gears is drivingly
engaged with and rotated by the pulley means shaft.
4. The belt tensioner construction defined in claim
1 in which a plurality of check valves operatively communicate
with the pump means and reservoir means for regulating the flow
of hydraulic fluid between the pump means, the reservoir means
and the piston means.
5. The belt tensioner construction defined in claim
4 in which the check valves include first and second one-way
check valves; in which the first check valve is located between
the pump means and a high-pressure discharge opening which com-
municates with the piston means to trap hydraulic fluid in the
piston means; and in which the second check valve is located be-
tween the high-pressure discharge opening and a return opening
which communicates with the reservoir means, whereby high-
pressure fluid from the pump means will flow back into the
reservoir means until additional fluid is required by the piston
means.
6. The belt tensioner construction defined in claim
1 in which the piston means includes a hydraulic cylinder com-
municating with the pump means, a partition member telescopi-
cally slidably mounted within the cylinder and dividing the
cylinder into a pair of subchambers, and a piston rod tele-
scopically slidably mounted in the partition member and movable
outwardly therefrom and into engagement with the lever means by
hydraulic fluid in the cylinder to move said lever means toward
the drive belt.
22

7. The belt tensioner construction defined in claim
6 in which spring means is located within one of the subchambers
and biases the partition member away from the piston rod and
toward the other of said subchambers to reduce the volume within
the hydraulic cylinder to compensate for minor fluid leaks in
said cylinder when the engine is shut off.
8. The belt tensioner construction defined in claim
7 in which an opening is formed between the pair of subchambers
to permit the flow of fluid therebetween.
9. The belt tensioner construction defined in claim
6 in which the partition member is a cup-shaped sleeve having an
open top end and a closed bottom end, with the sleeve interior
forming one of the subchambers; in which the piston rod is
slidably mounted within the sleeve interior and extends out-
wardly from the open end of the sleeve; in which a coil spring
is mounted within the sleeve interior and biases the sleeve
away from the piston rod; and in which an opening is formed in
the closed end of the sleeve to provide fluid communication
between the interior of said sleeve and the other of the sub-
chambers.
23

10. An arrangement for tensioning an endless drive
belt of a vehicle engine accessories drive system including:
a) piston means mounted in a fixed position on the
vehicle engine;
b) lever means pivotally mounted on the piston means
and movable by the piston means in a belt-tensioning direction;
c) an assembly mounted on the lever means and movable
with the lever means into engagement with the drive belt for
applying a predetermined tensioning force on said belt, said
assembly including:
i) a pump,
ii) a fluid reservoir mounted on the pump,
iii) a supply of hydraulic fluid in the reservoir
communicating with the pump, and
iv) an idler pulley engaged with and driven by
the drive belt, said pulley also being in operative driving
engagement with the pump to actuate said pump to supply
hydraulic fluid under pressure to the piston means from
the fluid supply for actuation of said piston means; and
d) conduit means hydraulically connecting the pump
with the piston means,
11. The arrangement defined in claim 10 in which
check valve means is located within the fluid reservoir and
communicates with the pump and fluid supply to regulate the flow
of hydraulic fluid from the pump to the piston means.
24

12. The arrangement defined in claim 11 in which the
check valve means includes a first one-way check valve mounted
in a high-pressure discharge passage extending between a high-
pressure discharge outlet of the pump and the conduit means;
and in which said first check valve permits hydraulic fluid to
flow in a direction from said high-pressure discharge outlet of
the pump toward and into the conduit means.
13. The arrangement defined in claim 12 in which the
check valve means includes a second one-way check valve mounted
in a fluid bypass passage which extends between the high-
pressure discharge passage and the fluid supply reservoir; and
in which said second check valve opens to permit the flow of
high-pressure hydraulic fluid from the pump discharge outlet
into the supply reservoir when hydraulic pressure and fluid in
the piston means are at predetermined levels.
14. The arrangement defined in claim 11 in which the
fluid reservoir is formed by a hollow container; in which the
pump and check valve means are located within the container;
and in which the conduit means communicates with the check valve
means for receiving high-pressure fluid from the pump for
actuation of the piston means.
15. The arrangement defined in claim 10 in which the
pump includes a pair of gears; in which the idler pulley has
a shaft; and in which one of the pump gears is operatively con-
nected to the idler pulley shaft for driving said one gear which
drives the other of said gears to pump fluid from the fluid
supply into the piston means through the conduit means.

16. The arrangement defined in claim 10 in which the
lever means includes a generally flat elongated strip of
material connected at one end to the assembly and pivotally
mounted at an opposite end on the piston means; and in which a
projection is formed integrally with the elongated strip adja-
cent said opposite end and is engaged by the piston means for
pivotally moving the lever means toward a belt-tensioning
direction.
17. The arrangement defined in claim 10 in which the
piston means includes a cylinder forming a hollow interior
fluid-receiving chamber; in which a cup-shaped partition member
is telescopically slidably mounted in the cylinder chamber and
forms a pair of subchambers, with one of said subchambers being
located within the partition member and the other of said sub-
chambers being located in the cylinder interior beneath the
partition member; in which a piston rod is telescopically
slidably mounted in the said one subchamber of the partition
member; and in which a spring is mounted in the partition member
subchamber and biases the piston rod away from said partition
member subchamber.
18. The arrangement defined in claim 17 in which an
opening is formed in the partition member to provide fluid com-
munication between the subchambers.
26

Description

Note: Descriptions are shown in the official language in which they were submitted.


1 BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to belt tensioning devices and
arrangements, and in particular to a hydraulically actuated
device for tensioning the endless drive belt of the drive system
for vehicle accessories. More particularly, the invention re-
lates to a belt tensioner having a self-contained hydraulic
fluid supply-idler pulley-pump assembly driven by the endless
belt, which maintains a predetermined constant tensioning force
on the endless drive belt regardless of the engine operating
condition.
Description of the Prior Art
There is the trend today in the automobile industry to
operate the various vehicle accessories, such as the power
- 1 --

1 steering pump, oil and air pumps, air conditioning and alter-
nator, by a single endless belt driven by a pulley connected to
the engine crankshaft. This system is referred to as a "ser-
pentine" drive belt system. To ensure optimum operating effi-
ciency for these various accessories, it is necessary that the
drive belt be maintained at a predetermined tension to assure
efficient performance of the accessories as well as satisfactory
service life for the belt. Due to the relatively greater length
for the single drive belt which replaces the heretofore plurality
of smaller belts, there is a greater tendency for the belt to
stretch, which will affect the operating characteristics of the
driven accessories. Therefore, it is desirable that an auto-
matic belt tensioning device be used for these endless belts to
provide reliable service over an extended period of time and to
maintain a constant amount of tension thereon regardless of the
amount of belt stretch without requiring any maintenance or
manual adjustment.
Numerous devices have been proposed and used to accom-
plish this purpose. One type of tensioner uses a bushing
formed of an elastomeric material which is placed in compression
by some mechanical means for continuously exerting a tensioning
force on the belt. Examples of these constructions are shown
in United States Patent Nos. 3,975,965 and 4,144,772. These
tensioner constructions, which use an elastomeric material, have
the disadvantages in that the high load rate which they exert
on the belt results in the rapid loss of tensioning as the belt
stretches, and this load rate limits the stroke of the belt-
engaged idler pulley to a shorter distance than desired. Also,
sudden acceleration and deceleration of the drive belt can cause
a whipping action to occur which creates a time lag before full
damping is achieved.

li35536
1 Numerous other types of belt tensioning devices use
springs for applying and/or maintaining the tensioning force on
a belt-engaging idler pulley or chain-engaging sprocket. Some
examples of these types of constructions are shown in United
States Patent Nos. 2,703,019, 2,893,255, 3,413,866, 3,631,734,
3,768,324, 3,812,733, 3,924,483 and 3,965,768. Some of these
various spring-actuated devices use the biasing force of the
spring in combination with hydraulic actuated members for
regulating the amount of tensioning force applied to the belt,
depending on whether the engine is running or shut off.
United States Patent No. 2,051,488 shows a chain ten-
sioning device in which a hydraulic cylinder is actuated when
the engine is running to reduce the tensioning pressure which
is exerted on the drive chain by a biasing spring. This hydrau-
lic cylinder applies a counter force to the biasing action of
the spring when the engine is running in order to decrease the
tensioning force on the chain, whereupon the full biasing force
of the spring is exerted on the chain when the engine is off and
the hydraulic cylinder inactive. United States Patent No.
3,142,193 discloses another belt tensioner using a hydraulically
actuated bellcrank and belt-engaging pulley in which a spring
biases the pulley into tensioning engagement with the belt until
the engine is operating, whereupon the hydraulic actuated piston
imparts a greater tensioning force to the pulley through the
bellcrank. When the engine stops, the piston retracts and the
spring maintains a lesser tensioning force on the belt.
United States Patent No. 4,077,272 discloses another
belt tensioner using both a spring and a hydraulic member to
achieve the desired tensioning characteristics. In this device,
when the engine is running, hydraulic oil from the engine
lubricating system forces a piston back into its cylinder to

li3SS36
1 overcome an internally mounted first spring so that only a
second spring acts on the belt tensioning pulley when the engine
is operating. When the engine is off, both springs act on the
belt tensioning pulley. United States Patent No. 3,132,596
shows a belt tensioner using a hydrostatic snubber controlled
by the power steering pump of the vehicle, whereupon the snubber
is forced outwardly in direct relationship to the output pres-
sure of the power steering pump. This mechanism does not main-
tain a constant pressure on the belt when the vehicle engine is
both on and off, and will apply different forces in relationship
to the engine speed.
Many of these devices are believed to perform satis-
factorily for their intended purpose. However, the use of
springs for applying the tensioning force on a drive belt or
chain, either for applying or retracting a tensioning member
therefrom, presents problems. The operating characteristics of
these springs will change over the life of the spring and even
in response to changes in ambient temperature. Also, as the
drive belt stretches, the spring's biasing effect changes,
making it difficult to maintain a constant tensioning force on
the drive belt. Likewise, the springs may become rusted and
corroded and break during the life of the vehicle, presenting
mechanical maintenance problems for the vehicle owner.
Many of these problems are believed to be eliminated
by the improved hydraulic belt tensioner constructions shown in
United States Patent Nos. 4,283,181 and 4,276,038, both assigned
to the same assignee as is the present application. These
improved belt tensioners are operated by hydraulic pressure
exerted by fluid from the vehicle engine, such as
the relatively low fluid pressure of
. - 4 -

1135536
the engine's oil lu~ricating system or the high fluid pressure
developed by the power steering pump of the vehicle.
However, some vehicle manufacturers prefer not to use
the hydraulic fluid which is used for other purposes in the
engine, such as lubricating or power steering, for theoperation
of the belt tensioner. This objection is believed to be elimi-
nated by providing a hydraulic belt tensioner having its own
self-contained hydraulic fluid reservoir and supply, such as
shown in my U.S. Patent No. 4,283,182 issued on August 11, 1981.
This improved tensioner operates in conjunction with a
pivotally mounted accessory for tensioning the drive belt.
Again, some vehicle manufacturers desire a belt tensioning
device which can be mounted as a complete unit on the engine
and automatically tension the driYe belt without the need of
pivotally mounting one of the vehicle accessories. This pro-
vides a certain amount of flexibility in engine design since
the tensioning unit may be mounted at various locations for
engaging the belt and does not rely on the pivotal mounting
of one of the accessories.
Accordingly, it i5 desirable to provide a belt
tensioning device and arrangement which eliminates the use
of springs for controlling the belt tensioning force, which
device will maintain a constant predetermined tension on the
belt throughout the belt life and regardless of whether the
engine is on or off or being driven at high or low speeds,
which device uses a source of hydraulic fluid completely
independent of the vehicle hydraulic system for its operation,
and which does not require movement of one of the vehicle
accessories for tensioning the drive belt which is
operatively engaged with said accessory.
There is no known belt tensioning device or arrangement
pc/ ~
~j )

l i 3 ~ ~3U~
1 of which I am aware which imparts ancl maintains a nearly con-
stant predetermined tensioning force on an endless drive belt
by a hydraulic piston which is actuated by hydraulic fluid
from a self-contained fluid supply reservoir completely inde-
pendent of the vehicle hydraulic fluid system, which maintains
this constant pressure on the belt whether the engine is on or
off or operating at various speeds, which prevents belt whip
and achieves a highly efficient damping effect, and which does
not require movement of one of the vehicle accessories to
achieve the tensioning effect.
SUMMARY OF THE INVENTION
Objec~ives of the invention include providing a
hydraulic belt tensioner construction which is actuated from a
source of hydraulic fluid completely separate and independent
of the vehicle accessory drive system and at a predetermined
pressure regardless of the operating condition of the vehicle's
engine; providing such a belt tensioner using a hydraulic piston
for pivotally moving a lever mounted on the piston cylinder to
tension the drive belt which is engaged with an idler pulley
that is rotatably mounted on and operatively engaged with a
self-contained fluid supply and pump assembly mounted on the
swinging end of the lever; providing such a belt tensioner
having a check valve system which prevents the escape of :
hydraulic fluid from the piston cylinder to maintain constant
pressure on the piston, thereby providing a damping effect and
eliminating belt whip upon starting and stopping of the vehicle
engine or upon rapid engine acceleration or deceleration; pro-
viding such a belt tensioner in which the hydraulic piston has
a partition sleeve slidably mounted within the piston cylinder
and dividing the cylinder chamber into a pair of subchambers
with the piston rod being slidably mounted in one of the

113553~i
1 subchambers, whereupon when the vehicle engine is shut off, a
spring will move the partition sleeve further into the other
subchamber to maintain the piston rod receiving chamber filled
with oil to compensate for minor oil leaks, thereby maintaining
the constant predetermined hydraulic force on the piston rod;
providing such a belt tensioner having a self-contained supply
of hydraulic fluid which is separate from the engine lubricating
fluid or power steering fluid, and in which this fluid is pumped
into the cylinder of the tensioning piston by a relatively inex-
pensive gear pump unit driven by the endless drive belt of theaccessory drive system; providing such a belt tensioner in which
the hydraulic pressure exerted by the piston rod can be changed
easily to conform to specific operating characteristics required
by various vehicles by replacing or adjusting a simple high-
pressure control check valve in the pump unit; and providing
such a belt tensioner which is of a relatively simple construc-
tion, which eliminates maintenance and repair problems, which
achieves the stated objectives in a simple, effective and
relatively inexpensive manner, and which solves problems and
satisfies needs existing in the art.
These objectives and advantages are obtained by the
improved hydraulic belt tensioner construction for automatically
tensioning an endless belt of the drive system for the vehicle
accessories, the general nature of which may be stated as
including piston means adapted to be mounted in a fixed position
with respect to the endless drive belt; lever means operatively
engaged by the piston means for moving said lever means toward
the drive belt; tensioning assembly means mounted on the lever
means and adapted to be moved into engagement with the drive
belt upon movement of the lever means by the piston means; and.
the tensioning means including pump means, reservoir means for

~i3SS36
1 containing a supply of hydraulic fluid, and pulley means
drivingly engaged wi~h the pump means, said pulley means being
adapted to be engaged with and driven by the drive belt for
actuating the pump means to supply hydraulic fluid from the
reservoir means to the piston means to actuate the piston means
and move the lever means to bring the tensioning assembly means
into engagement with the drive belt.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the invention - illustrative
of the best mode in which applicant has contemplated applying
the principle - is set forth in the following description and
shown in the accompanying drawings,and is particularly and
distinctly pointed out and set forth in the appended claims.
Fig. 1 is a diagrammatic view looking toward the
front of an engine, illustrating an endless drive belt opera-
tively engaged in a driving relatlonship with the vehicle
accessories with the improved belt tensioner construction
operatively engaged with the drive belt;
Fig. 2 is a fragmentary left-hand end view of the
engine and drive system looking in the direction of arrows 2-2,
Fig. l;
Fig. 3 is an enlarged view of the improved hydraulic
belt tensioner construction operatively engaged with the end-
less drive belt, with portions of the tensioner construction
shown in section and broken away;
Fig. 4 is a right-hand end view of the improved
hydraulic belt tensioner construction looking in the direction
of arrows 4-4, Fig. 3, with the drive belt removed therefrom;
Fig. 5 is an enlarged fragmentary sectional view
taken on line 5-5, Fig. 3, of the fluid supply-idler pulley-
pump assembly;

1135536
1 Fig. 6 is an enlarged sectional view taken on line
6-6, Fig. 3;
Fig. 7 is an enlarged sectional view taken on line
7-7, Fig. 3;
Fig. 8 is a sectional view taken on line 8-8, Fig. 5;
Fig. 9 is a reduced, fragmentary sectional view taken
on line 9-9, Fig. 6; and
Fig. 10 is a schematic diagram of the hydraulic
system of the improved belt tensioner construction.
Similar numerals refer to similar parts throughout
the drawings.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to Fig. 1 of the drawings, the improved belt
tensioner construction is indicated generally at 1, and is shown
tensioning an endless drive belt 2 of a power transmission belt
drive system for the vehicle accessories. The drive system
consists of a plurality of belt pulleys or sheaves having con-
figurations and diameters determined by their associated engine
accessories and locations relative to each other. The various
pulleys are supported on their respective engine accessories
which are mounted on engine 3 in a usual manner known in the art.
Preferably, belt 2 operates in a single vertical plane which
eliminates binding and skewing of drive belt 2, as shown in
Fig. 2.
The engine accessories drive system consists of a
main driving pulley 4 which is operatively connected to the main
shaft of engine 3, a pulley 5 which is operatively connected to
the air conditioning motor 6, a pulley 7 which is operatively
connected to an alternator 8 which provides the electrical power
for the engine, a pulley 9 which is operatively connected to the
vehicle's power steering unit, and a pulley 10 which is

1135S36
operatively connected to the engine water pump.
Improved belt tensioner 1 includes as main ~onents
a self-contained fluid supply-idler pulley-pump assembly, a
hydraulically actuated piston, and a lever mechanism, indicated
generally at 12, 13 and 14, respectively, and shown in
assemhled condition particularly in Figs. 3 and 4. Assembly
12 is hydraulically connected to piston 13 by a section of
conduit 15. Assembly 12 is mounted on an extended end of
lever mechanism 14, and is moved into tensioning engagement
with belt 2 upon hydraulic actuation of piston 13, which moves
lever mechanism 14 toward tensioning engagement with belt 2.
The fluid supply-idler pulley-pump assembly 12 is
generally similar to the self-contained hydraulic fluid-idler
pulley-pump assembly shown and described in my U.S. Patent
No. 4,283,182 issued on August 11, 1981. Assembly 12 includes
a generally cylindrical-shaped bearing housing 17 (Fig. 5)
having a central bore 18 with a bearing 19 mounted within
bore 18. An idler pulley, indicated generally at 20, is
mounted in a fixed relationship on the outer end of a shaft
, 20 21, which is rotatably mounted on bearing 19. Idler pulley
20 includes a usual, preferably sheet metal, belt engaging
pulley member 22. Bearing 19 includes a pair of end sealing
caps 23 which are mounted on an outer bearing race 24 with
shaft 21 projecting through central openings formed in caps 23.
A gear pump unit, indicated generally at 25, is
mounted on the inner wall surface of bearing housing 17 by a
plurality of circumferentially spaced bolts 26. Pump unit
25 includes a generally disc-shaped gear mounting block 27
and a pair of pump gears 28 and 29, rotatably mounted within
a central recess 30 formed in block 27 by stub shafts 31 and
32, respectively. Gears 28 and 29 are enclosed within recess
30 by an end
-- 10 --
pC/ ~ `

li3SS36
1 sealing plate 33.
Gear 28 is the driving gear of the gear pump pair and
is attached to stub shaft 31 for rotation therewith. Shaft 31
has a reduced end 34 which is located in a complementary-shaped
hole formed in the inner end of pulley shaft 21, whereby rota-
tion of pulley shaft 21 will drive gear pump shaft 31, and
correspondingly, will drive pump gear 28. Pulley shaft 21 is
rotated by the engagement of drive belt 2 with pulley member 22.
Gear stub shaft 32 is freely rotatably mounted within an opening
36 formed in gear mounting block 27, enabling pump gear 29 to
be driven by and in unison with driving gear 28. Pump unit 25
may have other configurations than the two-shafted, externally
meshing gear arrangement, described above and shown in Fig. 5
without affecting the concept of the invention. Pump unit 25 is
a readily available and known structure which provides a source
of fluid pressure from an adjacent fluid supply reservoir, as
described below.
A check valve assembly, indicated generally at 38, is
mounted on gear pump mounting block 27 by a plurality of spaced
bolts 39 which clamp assembly 38 against end sealing plate 33
of pump unit 25. Check valve assembly 38 preferably is formed
from a rigid block of material 40, such as metal or plastic.
A pair of ball check valves 42 and 43 are formed in valve block
40 to control the flow of hydraulic fluid into and out of
piston 13, and correspondingly, to regulate the amount of
hydraulic pressure exerted on lever mechanism 14 for tensioning
belt 2. Check valves 42-43 include cavities 44 and 45 con-
taining valve balls 46 and 47 which are biased toward seated
position by springs 48 and 49, respectively. Check valves 42-
43 may be of another type or arrangement, if desired, withoutaffecting the concept of the invention.

11;~5S36
1 Assembly 12 includes its o~m hydraulic fluid supply
for supplying the hydraulic pressure and fluid to piston 13,
completely eliminating the need for using hydraulic fluid from
any part or component of the vehicle. A cylindrical-shaped
fluid reservoir housing 51, preferably formed of plastic or
sheet metal, is mounted on bearing housing 17 by various types
of attachment means, such as the use of rolled outer end edges
52, seated within an annular groove 53 formed in the outer sur-
face of bearing housing 17. A sealing ring 54 is mounted
within an annular groove 55 formed in bearing housing 17 to
provide a fluid seal between the cylindrical wall of housing 51
and the outer surface of bearing housing 17.
A supply of hydraulic fluid, such as oil 57, is con-
tained within reservoir housing 51. Housing 51 preferably will
contain sufficient fluid due to the closed loop arrangement of
the improved belt tensioner construction to eliminate replacing
or refilling the housing at any time throughout the life of
belt tensioner 1. If desired, a removable filler cap 56 may be
provided in reservoir housing 51 for filling the same with
hydraulic fluid. Housing 51 also may be attached to valve
block 40 (Fig. 8) by a threaded coupling 58 of conduit 15.
Coupling 58 is threadably engaged in a boss 59 formed on the
outer surface of fluid housing 51 and in a corresponding threaded
opening 60 formed in valve block 40 to clamp fluid housing 51
and block 40 tightly together.
Valve block 40 is formed with a fluid inlet opening
61 in the lower portion of sealing plate 33, which communicates
with pump gear 29. A high pressure discharge opening 62 is
formed in sealing plate 33 at the meshing area between pump
gears 28 and 29 and communicates with a discharge passage 63
which is connected with cavity 44 of check valve 42. A discharge
- 12 -
.

1135S36
1 outlet passage 64 extends between and communicates with conduit
15 and check valve cavity 44, whereby high pressure oil dis-
charged from pump unit 25 unseats valve ball 46 and flows
through passages 63 and 64 and into conduit 15. A bypass pas-
sage 65 communicates with and extends between check valve
cavities 44 and 45 with a second bypass passage 66 extending
between check valve cavity 45 and the adjacent oil reservoir.
The features and operation of these check valves and associated
passages are described in greater detail below.
Hydraulic piston 13 (Figs. 3 and 9) includes a gen-
erally cylindrical-shaped cylinder housing 69 which is adapted
to be mounted in a fixed position with respect to the vehicle
engine by a pair of mounting plates 70 and 71. Plates 70-71
are attached to a boss 72 which is formed integrally with
housing 69 by a pair of pins 73. Mounting plates 70-71 have
curved top edges 74 which terminate in a curved projection 75.
A pair of aligned circular holes 76 are formed in plates 70-71
(Fig. 6) for receiving the reduced ends of a shaft sleeve 77.
An alignment pin 78 is mounted on and extends outwardly from
mounting plate 71 and is received within a complementary-shaped
hole 79 formed in an engine mounting plate 80. Plate 80 is
attached to engine 3 by a pair of bolts 81 (Figs. 3, 4 and 9)
and by a bolt 111 which functions as the pivot bolt for lever
mechanism 14.
In accordance with one of the features of the inven-
tion, cylinder housing 69 is formed with a hollow interior
which forms a main piston chamber 83 (Fig. 3). A cup-shaped
partition member 84 is telescopically slidably mounted within
chamber 83 and is retained therein by an upper retaining ring
85 which is seated within an annular groove formed adjacent the
open top of cylinder housing 69. Bottom wall 86 of partition

~13SS36
1 member 84 is formed with an axially extending hole 88. Parti-
tion member 84 forms a lower subchamber 82 which is located
between bottom wall 87 of cylinder housing 69 and bottom wall
86 of partition member 84. The hollow interior of partition
member 84 forms a second subchamber 89 which communicates with
lower subchamber 82 by hole 88 in bottom wall 86. Subchamber
89 has a smaller internal diameter than the internal diameter
of subchamber 82. An annular O-ring 90 forms a seal between
partition member 84 and the inner surface of cylinder housing 69.
A piston rod 92 is slidably mounted within subchamber
89 of partition member 84 and is adapted to move outwardly
therefrom when acted upon by hydraulic fluid from assembly 12.
Rod 92 is formed with an axial bore 93 which extends partially
through rod 92. A coil spring 94 is mounted in bore 93 and is
in abutment with the inside surface of bottom wall 86 of parti-
tion member 84 and biases rod 92 and partition member 84 away
from each other.
A fluid exhaust port 95 is formed in the outer portion
of piston rod 92 and provides communication between the sur-
rounding atmosphere and subchamber 89 for the bleedoff of air
trapped in piston 13 during the filling of piston 13 with hydrau-
lic fluid. A removable plug 96 closes the outlet of exhaust
port 95. A flexible sealing ring 98 and an internal O-ring 99
provide fluid-sealing means between piston rod 92 and cylinder
housing 69 and partition member 84, respectively. An inlet
port 100 is formed in the bottom of cylinder housing 69 and
threadably receives a conduit coupler 101 therein, operatively
connecting fluid supply conduit 15 with main piston chamber 83
(Fig. 3).
The particular construction of piston 13, having the
slidable partition member 84 therein which forms the pair of
.
.

1~35S3~i
1 subchambers 82 and 89, enables a constant tensioning force to
be maintained on belt 2 when the engine is shut off, even if
minor oil leaks should occur between piston rod 92 and cylinder
housing 69. When the vehicle engine is shut off, the oil is
trapped in subchambers 82 and 89 by check valve 42. Should any
oil escape from within subchamber 89, spring 94 forces partition
member 84 downwardly toward the bottom wall 87 of main cylinder J
chamber 83 since lever projection 108 acts as an abutment pre-
venting upward movement of piston rod 92. This downward move-
10 ment of partition member 84 forces oil trapped within subchamber
82 upwardly through hole 88 and into subchamber 89. Due to the
decrease in volume of the available space within piston housing
69 since subchamber 89 has a smaller diameter than subchamber
82, this oil transfer enables the pressure on piston rod 92 to
be maintained constant at the predetermined level, even though
a slight amount of oil may have escaped from the cylinder.
Downward movement of partition member 84 merely reduces the
volume available within cylinder 69 by the radial wall thickness
of partition member 84.
Lever mechanism 14 includes a generally flat strip
of rigid metal material forming a lever 104, the extended end of
which is integrally connected to and formed as a part of bearing
housing 17, as shown in Figs. 4 and 5, so that assembly 12 will
move in unison with the extended lever end. The opposite end of
lever 104 is formed with a circular opening 105 (Fig. 6) and has
a cylindrical sleeve 106 telescopically mounted therein and
attached by peened metal areas 107, or by welding, brazing, or
other attachment means. A somewhat circular projection 108 is
formed integrally with the bottom end of lever 104 (Fig. 9) and
extends outwardly with respect to opening 105 and is located
within a slot 109 formed in the outer end of piston rod 92.

1135536
1 This engagement of lever projection 108 with piston rod 92 will
pivot lever 104 in a counterclockwise direction upon the out-
ward movement of rod 92.
Lever 104 is pivotally mounted with respect to piston
13 by bolt 111. Bolt 111 extends through bore 112 of shaft
sleeve 77 and through a complementary-shaped hole 113 formed in
engine mounting plate 80 (Fig. 6). A pair of bushings 114 are
telescopically mounted on the ends of shaft sleeve 77 and pro-
vide the bearing surfaces for rotation of lever 104 with respect
to shaft sleeve 77 and between the ends of lever sleeve 106 and
mounting plates 70 and 71. Thus, lever 104 is pivotally mounted
between spaced plates 70 and 71 on shaft sleeve 77 and pivot
bolt 111. Threaded end 116 of bolt 111 is engaged in a comple-
mentary threaded hole formed in engine 3 (Figs. 2 and 4) to
assist in mounting tensioner 1 thereon. Shaft sleeve 77
preferably has a force fit engagement within holes 76 of mounting
plates 70 and 71 so as to be firmly attached to the plates.
Fig. 10 is a schematic drawing of the check valve
and hydraulic fluid system of improved belt tensioner 1, with
the various numerals used in Fig. 10 corresponding to the
numerals of the components described above and shown particularly
in Figs. 3, 5 and 8. Low pressure oil is drawn from fluid sup-
ply 57 (arrow A) through passage 61 and is expelled by pump unit
25 as high pressure fluid (arrow B), which flows through passage
63 and through check valve 42. This flow of high pressure
fluid (arrow B) will then flow either into piston 13 through
conduit 15 (arrow C) or, if no additional hydraulic fluid is
required for piston 13, it will flow through relief passage 65,
check valve 43, and bypass passage 66 back into fluid supply
30 57 (arrow D). .
The operation of improved belt tensioner construction
1 is described below. The amount of tensioning force which is
- 16 -

11~5S3~
1 necessary for proper tcnsioning of belt 2 is determined by
various standard calculations and know-how in the belt tension-
ing field. This calculated force then is used to determine the
corresponding outward force required to be exerted by piston
rod 92 on lever projection 108, depending upon the respective
movement arms of projections 108 and lever 104. Knowing the
amount of force required to be exerted by piston rod 92, the
hydraulic pressure required then can be determined since the
force exerted by rod 92 is equal to the hydraulic pressure times
the effective area on which the pressure acts. Spring 49 of
check valve 43 then is chosen or adjusted in valve block 40 due
to the threaded engagement of its retaining plug 118 therein so
as to become unseated and move upwardly to an upper position
when the pressure exceeds the predetermined fluid pressure
required to act on piston rod 92 to produce the required force
on piston rod 92.
Opening of check valve 43 enables high pressure fluid
from pump unit 25 to return to fluid supply 57 through passage
66. Thus, high pressure fluid discharged by pump unit 25 will
continue to flow into piston chamber 83 through check valve 42,
which requires only a very small amount of pressure to unseat
its valve ball 46, until the desired pressure is reached. After
this pressure is obtained, any additional high pressure fluid
discharged from pump unit 25 will overcome the biasing force of
spring 49 and unseat valve ball 47 with the excess oil return-
ing to supply 57. Pump unit 25 continuously operates when the
vehicle engine is running due to the driving engagement of
pulley member 22 with belt 2 and the driving engagement of
pulley shaft 21 with gear pump stub shaft 31.
As discussed above, the improved construction of
piston 13 and, in particular, movable partition member 84, will

1135S36
1 automatically compensate for minor f:Luid leaks to maintain the
constant pressure on piston rod 92 and correspondingly on belt
2. Immediately upon actuation of purnp unit 25 by belt 2 when
the engine is started, any additional makeup fluid which may be
required will be pumped into cylinder chamber 83 until the
predetermined pressure is achieved on piston rod 92.
Conduit 15 may be formed of thin wall metal tubing
and be provided with a loop 121 to permit flexing of conduit 15
without stressing the same upon swinging movement of assembly
12. Conduit 15 also can be a flexible hose or the like, if
desired, without affecting the concept of the invention or
operation of improved belt tensioner 1.
Improved hydraulic belt tensioner 1 and its arrange-
ment and operation with endless drive belt 2, has a number of
advantages. The self-contained fluid supply-idler pulley-pump
assembly 12 completely eliminates the use of the engine lubri-
cating fluid or the power steering fluid for operation of piston
13, as heretofore required in prior constructions. Belt ten-
sioner 1 provides a compact unit which is mounted on the engine
at a convenient location for engagement with a section of belt
2 without affecting the mounting or locations of any of the
vehicle accessories. Another advantage is that partition member
84 in cylinder chamber 83 automatically compensates for minor
oil leaks occurring in piston 13 to maintain constant pressure
on rod 92 upon engine shut off.
The particular check valve arrangement also ensures
that the desired amount of hydraulic fluid and pressure is
always exerted on piston rod 92 since pump unit 25 continuously
creates a supply of high pressure fluid in cylinder chamber 83
during engine operation. This fluid will only be supplied to
piston 13 when necessary and usually will flow through check

1135536
1 valve 43 and be returned to the fluid supply in reservoir
housing 51. Check valve 42 will trap the hydraulic fluid in
piston 13 and connecting conduit 15 when the engine is shut
off. Therefore, piston rod 92 will continue to exert the full
amount of pressure on lever projection 108 even when the engine
is off, since the fluid will not drain from the piston during
engine shut off as in prior art tensioner constructions. The
maintaining of the desired tensioning force on belt 2 by the
hydraulic pressure, even when the engine is not running, is
desirable to prevent a whipping action from occurring upon
engine start-up, provides a damping effect at all times to the
piston to prevent whipping of the belt during sudden engine
acceleration or deceleration, and provides satisfactory acces-
sory operation upon engine start-up.
Improved tensioner construction 1 also enables main-
tenance to be performed easily on belt 2 or on any of the
accessories operated thereby. Sufficient hydraulic fluid is
drained from piston 13 by temporary removal of piston rod plug
96, enabling lever 104 to be manually rotated in a clockwise
direction for removal and/or installation of belt 2. Hydraulic
fluid will be replaced in piston chamber 83 immediately when
the engine is started. Plug 96 then will be replaced as soon
as all air trapped in chamber 83 has been expelled through
exhaust port 95.
Accordingly, the improved belt tensioner and its
arrangement provides a construction which is simplified, effec-
tive, safe and inexpensive, which achieves all of the enumer-
ated objectives, provides for eliminating difficulties encoun-
tered with prior tensioning devices, and solves problems and
obtains new results in the art.
In the foregoing description, certain terms have been
- 19 -

1~35536
1 used for brevity, clearness and understanding but no unnecessary
limitations are to be implied therefrom beyond the requirements
of the prior art, because such terms are used for descriptive
purposes and are intended to be broadly construed.
Moreover, the description and illustration of the
invention is by way of example, and the scope of the invention
is not limited to the exact details of the construction shown
or described.
Having now described the features, discoveries and
principles of the invention, the manner in which the improved
hydraulic belt tensioner construction is constructed, assembled
and operated, the characteristics of the new construction, and
the advantageous, new and useful results obtained; the new and
useful structures, devices, elements, arrangements, parts, and
combinations are set forth in the appended claims.
- 20 -

Representative Drawing

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Administrative Status

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Please note that "Inactive:" events refers to events no longer in use in our new back-office solution.

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Event History

Description Date
Inactive: IPC from MCD 2006-03-11
Inactive: Expired (old Act Patent) latest possible expiry date 1999-11-16
Grant by Issuance 1982-11-16

Abandonment History

There is no abandonment history.

Owners on Record

Note: Records showing the ownership history in alphabetical order.

Current Owners on Record
None
Past Owners on Record
DERALD H. KRAFT
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
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Document
Description 
Date
(yyyy-mm-dd) 
Number of pages   Size of Image (KB) 
Drawings 1994-02-28 2 80
Claims 1994-02-28 6 181
Abstract 1994-02-28 1 29
Descriptions 1994-02-28 20 730