Note: Descriptions are shown in the official language in which they were submitted.
1 BACKGROUND OF THE IN~ENTION
Field of the Invention
The invention relates to belt tensioning devices and
arrangements, and in particular to a spring actuated belt ten- .
sioner for use with an endless belt of a vehicle accessories ~ :~
drive system. ~lore particularly, the invention relates to an
improved3 inexpensive belt tensioner construction having a
unique damping mechanism, which mechanism also limits movement
of the belt engaging pulley in an opposite nontensioning direc-
tion in order to maintain a nearl.y constant tensioning force on
the belt regardless of the amount of belt stretch.
Description of the Prior Art
There is the trend today in the automobile industry to
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1 operate the various vehicle accessories, such as the power
steering pump, oil and air pumps, air conditioning and alterna-
tor, by a single endless belt driven by a pulley connected to
the engine crankshaft. This system is referred to as a
"serpentine" drive belt system. To ensure optimum operating
efficiency for these various accessories, it is necessary that
the drive belt be maintained at a predetermined tension to
assure efficient perEormance 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 accessor:ies. Therefore, it is ~
desirable that a belt tensioning device be used for these end- ~-
less belts to provide reliable service over an extended period
oE time and to maintain a constant amount of tension thereon
regardless of the amount of belt stretch.
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 Oll the belt. Examples of these constructions are shown in
United States Patent Nos. 3,975,965 and 4,144,772. These ten-
sioner 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 o-E the drive belt can cause
a whipping action to occur which creates a time lag before full
damping is achieved.
1 Numerous other types of belt tensioning devices use ~ -
coil springs which are either in compression or tension, for
ap~lying and 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, 3~413,866, 3,483,763, 3,631,734, 3,768,324, 3,812,733 ?
3,924,483, 3,965,768 and 4,108,013. Some coil spring actuated
devices use the biasing force of a spring in combination with
hydraulic actuated members for regulating the amount of ten-
sioning force applied to the belt and for achieving a damping
effect. Examples of these combination spring and hydraullc-
actuated belt tensioners are shown in United States Patent Nos.
2,051~488, 3,142,193 and 4,077,272.
It is desirable that a belt tensioner be provided with
some type of damping means to prevent excessive oscillàtion from
occurring in the spring tensioning member, and which will absorb
sudden shocks to prevent a whipping action from occurring in the
tensioner and drive belt, such as upon sudden acceleration and
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deceleration of the vehicle. This damping action is especially
critical when a coil spring is used for applying the belt ten-
sioning force since coil springs are highly susceptible to
develop natural oscillating frequencies when the counter force,
which is exerted thereon by the belt, fluctuates during acceler-
ation and deceleration of the vehicle. Such oscillating action
affects the efficiency of the tensioning force applied to the
belt by the coil spring and reduces belt life.
Various damping devices have been used with belt ten- ~ ~;
sioners to eliminate or reduce this problem o-f coil spring ;~
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oscillation. One type of construction uses a hydraulic fluid
as the damping means, such as shown in United States Patent Nos.
2,893,255, 3,964,331, 3,986,407 and British Patent No. 336,737. -~
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1 United States Patent No. 3,710,634 shows a belt tensioner which
uses an eccentrically mounted mechanical pinion and rack arrange-
ment which is spring biased by a leaf spring for absorbing an -
excessive amount of shock as opposed to providing a damping
action for a spring-biased belt tensioning plunger. ~-
Various belt tensioning devices also are~provided
with some type of mechanical retaining means which limits the
movement of the belt tensioning member in a direction opposite
to the tensioning direction, thereby assisting the tensioning
member to maintain a constant tensioning force on the endless
drive belt by retaining the member in its forwardmost belt
tensioning position. Many of these known retaining arrangements
use a spring-biased mechanical detent-ratchet retaining means.
Examples of these prior constructions and arrangements are shown
in United States Patent Nos. 2,051,488, 2,703,019, 3,413,866,
3,631,734 and 3,812,733.
It also is highly desirable when developing a belt
tensioner intended primarily for use on an automobile to devise
a construction which can be produced as inexpensively as possible~
without sacrificing durability and efficiency since a savings of
only a part of a dollar would amount to a sufficient overall
savings when considering the millions of vehicles that are
produced by the various vehicle manufacturers.
Although many of the above-listed belt tensioners are
believed to perform satisfactorily, it is believed that the
subject belt tensioner of my invention provides an extremely
inexpensive, rugged and efficient tensioning device, which
achieves the desired damping action and bel~ ~ensioning force.
SUM~IARY OF THE INVENTION
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Objectives of the invention include providing an
improved device for tensioning the drive belt for vehicle
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1 accessories which maintains a generally constant, predetermined
tensioning force on the belt throughout the life of the belt
regardless of whether the engine is on or off or operating at
various speeds and conditions, which is of an extr:emely inex-
pensive design formed of several sheet metal components which
can be mass produced by simple metal stamping procedures, and
which then can be assembled with a usual pulley and compression
spring. Another object is to provide such a belt tensioner
which has a unique damping unit mounted thereon which also
retards movement of the belt-engaging pulley in a nontensioning
direction. Still another object is to provide such a belt ten- ~:
sioning device in which the mounting bracket portion can be
constructed so as to be attached directly to the engine block,
thereby eliminating an additional engine mounting bracket
component heretofore required for mounting prior tensioning
devices on the engine blocks, which results in a savings in
materi.al cost and weight. A -further object i.s to provide such
a belt tensioning device in which the damping is achieved by an
inexpensive leaf spring which is mounted on the stationary
engine mounting bracket portion and selectively engages a series
of ratchet teeth or indentations formed on a pivotally mounted -`~
component of the tensioner on which the belt-engaging idler
pulley is mounted, and in which the leaf spring retains the belt-
engaging pulley in its forwardmost position in addition to
absorbing any sudden shocks and forces exerted on the pulley by
flexing or bowing outwardly. It is also an object to provide :~
such a belt ~.ensioner in which the improved damping and retaining
feature can be incorporated into a tensioning mechanism which
~ensions a drive belt by pivotal movement of one of the vehicle
accessories in order to provide alternate tensioning arrangements
if desired by a particular vehicle manufacturer. Still another
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1 object is to provi.de such a belt tensioner in which the leaf
spring damping arrangement operates completely independent of
the main power source used for tensioning the belt, such as a
coil spring, thereby enabling the full available tensioning
force to be applied by the spring instead of requiring the
spring to overcome the damping means as in some prior belt ten-
sioning devices, and in which the damping effect can be
achieved by use of a frictional element mounted on the extended
end of the leaf spring, which element frictionally engages the
moving bracket portion instead of engagement of the leaf spring
end with the ratchet teeth. Likewise, it is an object to pro~
vide such an improved belt tensioner construction which achieves
the stated objectives in a simple, effective, rugged and rela-
tively inexpensive manner, and which solves problems and satis-
fies needs existing in the art.
These objectives and advantages are obtained by the
improved belt tensioner construction for tensioning an endless
drive belt for vehicle engine accessories, the general nature
of which may be stated as including bracket means adapted to be ~ :
mounted on a vehicle engine adjacent the drive belt with spring
means mounted on the bracket means. Lever means is pivotally -;
mounted on the bracket means and is biased by the spring means .~ .
in a belt tensioning directi.on. Rotatable pulley means is
mounted on the lever means and is movable into tensioning engage-
ment with the drive belt upon pivotal movement of the lever
means by the spring means. Damping means is operatively engage-
able wi-th the bracket means and lever means to retard oscillatory
movement of the lever means with said damping means including a
strip of spring steel having one end attached to the bracket
means and a second end engageable with the lever means. Engage-
ment means is provided at t:he junction of the second end of the
1 strip of spring steel and the lever means to retard pivotal
movement of the lever means in a direc-tion opposite to the belt
tensioning direction.
BRI~F DESCRIPTION OF THE_DRAWINGS
A preferred embodiment of the invention - illustrative
of the best mode in which applicant has contemplated applying
the principles - 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 drivingly
engaged with the vehicle accessories and with the improved belt
tensioner construction engaged with the drive belt;
Fig. 2 is an enlarged front elevational view of the
be]t tensioner of Fig. 1, shown mounted on a portion o-E an
engille;
Fig. 3 is an enlarged end elevational view looking in - -
the direction of arrows 3-3, Fig. 1, showing the improved belt
tensioner mounted on a portion of an engine wi~h the drive belt
removed therefrom;
Fig. 4 is a sectional view of the improved belt ten-
sioner taken on line 4-4, Fig. 2;
Fig. 5 is an enlarged sectional view taken on line ~
5-5, Fig. 4; ~-
Fig. 6 is an enlarged fragmentary sectional view taken
on line 6-6, Fig. 2, showing the improved damping mechanism;
Fig. 7 is a fragmentary view looking in the direction
of arrows 7-7, Fig. 6;
Fig. 8 is an enlarged perspective view of the mounting
bracket portion of the improved belt tensioner;
Fig. 9 is a perspective view of the lever plate portion
1 of the improved belt tensioner; and
Fig. lO is a -fragmentary sectional view somewhat
similar to Fig. 6, showing a modified form of the damping
mechanism of the improved belt tensioner.
Similar numerals refer to similar parts throughout the
drawings.
DESCRIPTION OF TIIE PREFE_RED EM~ODIMENT
Referring to Fig. 1 of the drawings, the improved belt
tensioner construction is indicated generally at 1, and is shown
in tensioning engagement with an endless drive belt 2 of a power
transmission belt drive system which is shown diagrammatically
looking toward the front of an engine. The accessory drive
sys~em consists of a plurality of belt pulleys or sheaves having
configurations and diameters determined by and associated with
engine accessory components and their locations relative to each
other. The various pulleys are supported on their respectiv0
engine components which in turn are mounted on an engine (not
shown) in a usual manner known in the art. ~elt 2 preferably
operates in a single vertical plane to eliminate binding and
skewing of the belt.
The particular engine accessories drive system shown
in Fig. 1 consists of a main driving pulley 3 which is operative-
ly connected to the main drive shaft of the engine, a pulley 4
which is operatively connected to the engine air pump, a pulley
5 which is operatively connected to an alternator 6 which pro-
vides electrical power for the engine, a pulley 7 which is
operatively connected to the vehicle power steering unit, and a
pulley 8 which is operatively connected to the engine water
pump.
Improved belt tensioner 1 includes an engine mounting
bracket indicated generally at lO ~Fig. S), which is formed
1 inexpensively of a one-piece, stamped, sheet metal member.
Bracket 10 includes a mounting flange portion 11 which is
formed with a plurality of holes 12 through which bolts 13
extend for mounting tensioner 1 on an engine 9 (Figs. 2 and 3).
An enlarged hole 14 may be formed in the center of mounting
flange 11 for reducing the weight of tensioner 1 without sacri-
ficing strength.
Bracket 10 further includes a generally flat, central
portion 17 which is located in a plane which is spaced outwardly
from and extends generally parallel with the plane of mounting
flange 11 and is connected to flange 11 by an upstanding flange
18. Flange 18 extends perpendiculaTly between mounting flange
11 and central bracket portion 17 and is integrally connected
thereto. Central bracket portion 17 is connected to an inwardly
downwardly extending sloped portion 19~ which in turn terminates
in a somewhat triangularly shaped portion 20. Bracket portion
20 lies in a plane generally parallel with the planes of 1ange
11 and central portion 17 (Figs. 4 and 8). Portion 20 is spaced
outwardly from bracket flange 11 to provide sufficient clear-
ance from engine 9. Bracket portion 20 terminates in a flange21 which extends perpendicularly outwardly from portion 20.
Flange 21 is formed with a circular-shaped central opening 22
for receivably mounting a spring assembly, indicated generally
at 24.
A lever plate 25 (Figs. 2, 3 and 9) is pivotally
mounted on central bracket portion 17 by a rivet 26 which extends
through aligned holes 27 and 28 formed in bracket portion 17 and
lever 25, respectively. A bushing 29 is telescopically mounted
on rivet 26 and is located within lever hole 28 to provide a
bearing for the pivotal movement of lever plate 25. Lever plate
25 is an inexpensive one-piece, stamped sheet metal member
1 preferably having a flat base portion 30 in which pivot mounting
hole 28 is formed, a s~epped, generally flat, central portion 31,
and an outwardly extending, flat end portion 34. A circular
boss 32 is formed in central portion 31 and defines a shaft
receiving opening 33. End portion 34 has a somewhat irregular-
shaped, outwardly extending configuration and is formed with a
hole 35.
An idler pulley 3g is rotatably mounted on central
por-tion 31 of lever plate 25 by a stub shaft 39 (Fig. 4) which
is press-fitted with circular boss 32 and extends outwardly
through shaft receiving opening 33. Pulley 38 is rotatably
mounted on the outer end of shaft 39 by a bearing ring 40. ..
Spring assembly 24 includes a cup-shaped housing 43
formed by a cylindrical wall 44 and an end wall 45. Cylindrical
wall 44 terminates in a radially outwardly extending annular
flange 46 which defines an open end 47~ A coil compression ~ .
spring 49 having an outer diameter generally complementary to
the internal diameter of spring housing 43 is telescopically
mounted within housing 43 in abutment with end wall 45.
A plunger clevis 50 has a reduced inner end 51 comple~
mentary to the internal diameter of spring 49 and is telescopi-
cally mounted within the bore of spring 49. The outer end of
clevis 50 is formed with an elongated slot 5~. Pivot plate end
34 extends into slot 52 and is pivotally mounted therein by a
pivot pin 53.
In accordance with the invention, a damping mechanism ~:
indica.ted generally at 54, is provided on belt tensioner 1 and
is operatively engaged with bracket 10 and lever plate 25. :
Damping mechanism 54 includes a leaf spring 55 which is mounted
at one end on bracket 10 by a rivet 56 (Figs. 2 and 6) which
extends through a hole 57 formed in central portion 17 of
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1 bracket lO. Leaf spring 55 includes an extended end 58 which
projects through a notch 59 formed in an edge of bracket central
portion 17. Spring end 58 selectively engages an indentation
or ratchet tooth 61. A series of such indentations or teeth 61
is formed in the inner surface 62 of lever plate 25. Teeth 61
have a generally right angled configuration similar to the teeth
formed on usual ratchet bar detent mechanisms. The engagement
of spring end 58 with teeth 61 permits lever plate 25 to move in
one direction (clockwise, Figs. 1 and 2) with respect to bracket
10 while retarding relative motion of plate 25 in the opposite
or counterclockwise (nontensioning) direction.
The operation of improved belt tensioner construction
1 is shown generally in Fig. 1 and described briefly below.
Tensioner 1 preferably i5 mounted directly on the vehicle
engine block or on another engine bracket by bolts 13 at a
selected location closely adjacent drive belt 2. Pulley 38 is
moved manually in a counterclockwise direction with respect to
its mounting location (Fig. 1), compressing coil spring 49 with-
in cup-shaped housing 43. Spring end 58 of leaf spring 55 is
manually disengaged from ratchet tee~h 61 when manually compress~-
ing spring 49 upon movement of lever plate 25 in this counter-
clockwise direction, which is in the direction of arrow A (Fig. ~;
6). Belt 2 then is placed within pulley groove 41 of pulley 38.
After release of the manual restraining force on pulley 38,
spring 49 biases pulley 38 in a clockwise belt tensioning
direction to apply a predetermined tensioning force on belt 2.
Spring strip end 58 will ride easily over the crests of teeth
61 as lever plate 25 moves in this belt tensioning direction
(arrow B, Fig. 6) due to the sloped sides of teeth 61.
Leaf spring 55 will bow outwardly, as shown in dash
lines, Fig. 6, when a sudden force or shock is applied to pulley
1 38 by belt 2, which may occur during the sudden accelera-tion or
deceleration of the vehicle. Lever plate 25 will attempt to
move in a nontensioning direction ~arrow A, Fig. 6) but is pre-
vented :Erom doing so by the engagement of leaf spring end 58
with the right angled sides of ratchet teeth 61. Lever 25 will
move only a slight amount in this nontensioning direction during
the bowing or flexing of leaf spring 55 and will be returned
immediately to its forwardmost position by the action of the
main tensioning force of coil spring 49. The continuous biasing
force exerted by leaf spring 55 on lever plate 25 prevents an
oscillating frequency from developing in coil spring 49. Such
undesirable oscillation can occur in those belt tensioner con-
structions using coil springs for the belt tensioning force due
to the tendency of coil springs to develop oscillating frequen-
cies. Leaf spring 55 also provides a positive mechanical means
of securing belt tensioning pulley 38 in its forwardmost posi-
tion, limiting its movement in a nontensioning direction, in
addition to providing the unique damping action completely
independent of the main tensioning spring force.
Fig. 10 shows a somewhat modified form of the improved
damping mechanism in which a pad of friction material 65 is
mounted on the extended end 66 of a leaf spring 67. Spring 67
is mounted on bracket 10 in a similar manner as is leaf spring
55. This mechanism provides a damping effect by retarding move-
ment of lever plate 25 in a nontensioning direction due to the
frictional engagement between the two moving members, but does
not provide the positive mechanical retaining means for main-
taining lever 25 in its forwardmost position as does the engage-
ment of leaf spring end 58 with ratchet teeth 61, described
above. L,eaf spring 67, in this modified damping mechanism,
also will bow outwardly upon retarding movement of lever plate
1 25 in the nontensioning direction, again preventing an oscil-
lating frequency developing in coil spring 49.
It is easily understood from the above description and
drawings that the improved leaf spring damping mechanism can
also be incorporated into a belt tensioning construction of the
type wherein one of the vehicle accessories is mounted on a
pivotally movable lever for tensioning the drive belt which is
operatively engaged with the accessory pulley.
Accordingly, the improved belt tensioner construction
provides an effective, safe and efficient device which can be
formed relatively inexpensively of stamped sheet metal compo-
nents, which has a unique damping ability provided by a leaf
spring which operates completely independent of the main power
source exerted by a compression coil spring, and which mechani-
cally maintains the belt tensioning pulley in its forwardmost
position; and which provides a device which eliminates diffi-
culties encountered ~ith prior tensioning devices and arrange-
ments and solves problems and obtains new results in the art.
In the foregoing description, certain terms ha~e been
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.
~loreover, 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 shown or described.
Having now described the features, discoveries--and ~
principles of the invention, the manner in which the improved ~;
belt tensioner construction is constructed and used, the
characteristics of the construction, and the advantageous, new
and useful results obtained; the new and useful structures,
1 devices, elements, arrangements, parts, and combinations, are
set -forth in the appended claims.
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