U.S. patent application number 14/816155 was filed with the patent office on 2017-02-09 for caliper brake having spring applied, hydraulically released assembly and pressure intensifying assembly.
The applicant listed for this patent is Ausco Products, Inc.. Invention is credited to Howard H. BALDEOSINGH, Edward L. CHANDLER, Brian P. DENNIS.
Application Number | 20170037918 14/816155 |
Document ID | / |
Family ID | 57908708 |
Filed Date | 2017-02-09 |
United States Patent
Application |
20170037918 |
Kind Code |
A1 |
DENNIS; Brian P. ; et
al. |
February 9, 2017 |
CALIPER BRAKE HAVING SPRING APPLIED, HYDRAULICALLY RELEASED
ASSEMBLY AND PRESSURE INTENSIFYING ASSEMBLY
Abstract
A caliper brake (10) is adapted to act upon a stator (40) to
engage a rotor of a vehicle. A housing (11) carries both a spring
applied hydraulically released piston assembly (12) and a pressure
intensifying piston assembly (14). The assemblies (12, 14) are in
fluid communication with each other. The assembly (12) includes a
piston (18) and a spring assembly (20) which urges the piston (18)
into a first position engaging the stator (40). The piston assembly
(14) includes a pressure intensifying (PI) piston (64) which is in
a first position when the piston (18) is in the first position.
When the PI piston (64) moves from a first position to a second
position, the fluid acts upon the piston (18) thereby disengaging
the piston (18) from the stator (40).
Inventors: |
DENNIS; Brian P.;
(Kalamazoo, MI) ; BALDEOSINGH; Howard H.;
(Stevensville, MI) ; CHANDLER; Edward L.; (St.
Joseph, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ausco Products, Inc. |
Benton Harbor |
MI |
US |
|
|
Family ID: |
57908708 |
Appl. No.: |
14/816155 |
Filed: |
August 3, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16D 65/18 20130101;
F16D 55/22655 20130101; F16D 2121/06 20130101; F16D 55/225
20130101; F16D 2125/582 20130101; F16D 2121/04 20130101; F16D 59/02
20130101; F16D 2125/10 20130101; F16D 2121/14 20130101 |
International
Class: |
F16D 65/18 20060101
F16D065/18; F16D 55/225 20060101 F16D055/225 |
Claims
1. A caliper brake adapted to act upon a stator to engage a rotor
of a vehicle, the brake comprising a housing; a first piston
assembly in said housing; a second piston assembly in said housing
in fluid communication with said first piston assembly; said first
piston assembly including a first piston and a spring assembly,
said spring assembly urging said first piston into a first position
engaging the stator; said second piston assembly including a second
piston positionable in a first position when said first piston is
in the first position, said second piston having a bore
therethrough, said bore receiving a valve assembly including a
spring and a ball, such that when said second piston moves from the
first position to a second position the fluid acts upon said first
piston thereby disengaging said first piston from the stator.
2. (canceled)
3. The caliper brake of claim 1, wherein said spring of said valve
assembly urges said ball of said valve assembly into a closed
position when said second piston is in said second position.
4. The caliper brake of claim 3, said housing including a pin
assembly carrying a tip, said tip urging said ball into an open
position when said second piston is in said first position.
5. The caliper brake of claim 1, said housing including a first
stepped bore for receiving said first piston assembly and a second
stepped bore for receiving said second piston assembly, said first
stepped bore including a maximum diameter chamber, where an outer
surface of said first piston is received in said maximum diameter
chamber.
6. The caliper brake of claim 1, said first piston including a body
portion and a projecting flange projecting from said body portion,
said body portion of said first piston having an axial recess, said
spring assembly being positioned in said axial recess.
7. The caliper brake of claim 6, wherein said projecting flange
engages the stator when said first piston is in the first
position.
8. A caliper brake of claim 1, further adapted to act upon a stater
to engage a rotar of a vehicle, the brake comprising a housing; a
first piston assembly in said housing; a second piston assembly in
said housing in fluid communication with said first piston
assembly; said first piston assembly including a first piston and a
spring assembly, said spring assembly urging said first piston into
a first position engaging the stator; said second piston assembly
including a second piston positionable in a first position when
said first piston is in the first position, a second spring
assembly urging said second piston to said first position, such
that when said second piston moves from the first position to a
second position the fluid acts upon said first piston thereby
disengaging said first piston from the stator.
9. A caliper brake adapted to act upon a stator to engage a rotor
of a vehicle, the brake comprising, a first piston assembly, a
second piston assembly in fluid communication with said first
piston assembly, said first piston assembly including a first
piston and a spring assembly, said spring assembly urging said
first piston into a first position engaging the stator, said second
piston assembly including a second piston positionable in a first
position when said first piston is in the first position, said
second piston having a bore therethrough in fluid communication
with said first piston, said bore receiving a source of fluid, a
valve in said bore, said valve moving from a position wherein said
bore is open to the source of fluid to a position closing said bore
as said second piston moves from the first position to a second
position such that the fluid acts upon said first piston thereby
disengaging said first piston from the stator.
10. The caliper brake of claim 9, said valve including a spring and
a ball, a pin acting on said ball to open said bore to the source
of fluid.
11. The caliper brake of claim 10, said spring urging said ball
toward a distal end of said second piston, wherein when said second
piston is in said second position, said ball closes said bore from
the source of fluid.
12. A method of moving a piston in a housing of a brake away from
engagement with a stator comprising the steps of providing a second
piston in the housing in fluid communication with the piston, and
moving the second piston to provide a fluid force on the piston to
move the piston away from the stator, wherein the step of moving
the second piston includes the step of moving a valve in the second
piston from an open position to a closed position.
13. The method of claim 12, wherein the piston and the second
piston are in fluid communication by way of a fluid chamber, the
method further comprising the step of sealing a portion of said
fluid chamber.
14. (canceled)
15. The method of claim 12, wherein the step of moving the valve
includes using a spring to urge a ball toward a distal end of the
second piston.
Description
TECHNICAL FIELD
[0001] This invention relates to a caliper brake. More
particularly, this invention relates to a caliper brake that
includes a spring applied, hydraulically released assembly and a
pressure intensifying assembly.
BACKGROUND
[0002] Rough terrain vehicles, such as cranes, are known to use
spring applied, hydraulically released caliper brakes as a parking
brake. These caliper brakes generally require the use of hydraulic
fluid to create hydraulic pressure in order to release the
brake.
[0003] The source of this hydraulic pressure is usually from
vehicle hydraulics, since rough terrain vehicles generally include
a hydraulic system. However, these vehicles tend to only have low
pressure hydraulic circuits available in the area of the vehicle
where these caliper brake are located.
[0004] One previous solution to this problem is the use of a very
large piston with low pressure behind the piston. Since the piston
is large, the area that pressure acts against is large, and the
piston can generate enough force to overcome the springs. However,
this is often not a viable option due to cost of materials and
space constraints on the vehicle.
[0005] Another prior art solution is to use an external hydraulic
assembly that acts on a mechanical device. This goal of such a
device is to give the external assembly a mechanical advantage over
the springs. But hydraulic assemblies used in this manner are prone
to leakage and contamination as a linkage rod thereof generally has
to move in three planes. This multi planar movement makes it
difficult to effectively seal the rod which ineffective seal leads
to corrosion, seal wear, and seal failures.
[0006] Thus, there is a need for an improved caliper brake that
offers one or more improvements over the prior art.
DISCLOSURE OF THE INVENTION
[0007] It is thus an object of one aspect of the present invention
to provide a caliper brake with a spring applied, hydraulically
released assembly and a pressure intensifying assembly in the brake
housing.
[0008] It is an object of another aspect of the present invention
to provide a caliper brake, as above, where the spring applied,
hydraulically released assembly can be released by using a low
pressure hydraulic circuit.
[0009] It is an object of a further aspect of the present invention
to provide a caliper brake, as above, that alleviates the risks of
leakage, contamination, and corrosion.
[0010] It is an object of an additional aspect of the present
invention to provide a caliper brake, as above, having a smaller
overall size so as to more easily fit within a vehicle.
[0011] These and other objects of the present invention, as well as
the advantages thereof over existing prior art forms, which will
become apparent from the description to follow, are accomplished by
the improvements hereinafter described and claimed.
[0012] In general, a caliper brake according to the concepts of the
present invention is adapted to act upon a stator to engage a rotor
of a vehicle. The brake includes a housing carrying a first piston
assembly and a second piston assembly in fluid communication with
the first piston assembly. The first piston assembly includes a
first piston and a spring assembly which urges the first piston
into a first position engaging the stator. The second piston
assembly includes a second piston positionable in a first position
when the first piston is in the first position. When the second
piston moves from the first position to a second position, the
fluid acts upon the first piston to disengage the first piston from
the stator.
[0013] In accordance with another aspect of the invention, a
caliper brake is adapted to act upon a stator to engage the rotor
of a vehicle. The brake includes a first piston assembly in fluid
communication with a second piston assembly. The first piston
assembly includes a first piston and a spring assembly which urges
the first piston into a first position engaging the stator. The
second piston assembly includes a second piston positionable in a
first position when the first piston is in the first position. The
second piston has a bore therethrough in fluid communication with
the first piston. The bore receives a source of fluid. A valve is
positioned in the bore and it moves from a position wherein the
bore is open to the source of fluid to a position closing the bore
as the second piston moves from the first position to the second
position such that the fluid acts upon the first piston thereby
disengaging the first piston from the stator.
[0014] The invention also includes a method of moving a piston in a
housing of a brake away from engagement with a stator including the
steps of providing a second piston in the housing in fluid
communication with the piston, and moving the second piston to
provide a fluid force on the piston to move the piston away from
the stator.
[0015] A preferred exemplary caliper brake according to the
concepts of the present invention is shown by way of example in the
accompanying drawings without attempting to show all the various
forms and modifications in which the invention might be embodied,
the invention being measured by the appended claims and not by the
details of the specification.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a sectional view of a caliper brake according to
the concepts of the present invention taken substantially along
line 1-1 of FIG. 5.
[0017] FIG. 2 is a sectional view similar to FIG. 1 but with the
hydraulic fluid being shown.
[0018] FIG. 3 is a view similar to FIG. 1 showing when pressure has
increased behind the pressure intensifying piston and the pressure
intensifying piston has begun movement.
[0019] FIG. 4 is a view similar to FIG. 3 but showing when pressure
has further increased behind the pressure intensifying piston,
thereby further increasing the pressure in front of the pressure
intensifying piston, to further move the pressure intensifying
piston, thereby moving the spring applied, hydraulically released
piston.
[0020] FIG. 5 is a front elevational view of a caliper brake
according to the concepts of the present invention.
[0021] FIG. 6 is a sectional view of the caliper brake taken
substantially along line 6-6 of FIG. 5.
PREFERRED EMBODIMENT FOR CARRYING OUT THE INVENTION
[0022] A caliper brake according to the concepts of the present
invention is generally indicated by the numeral 10. Caliper brake
10 includes a housing, generally indicated by the numeral 11, that
carries and protects components of brake 10 and locates it in
operative relation to a conventional wheel rotor. Housing 11
includes a spring applied, hydraulically released (SAHR) assembly,
generally indicated by the numeral 12, and a pressure intensifying
(PI) assembly, generally indicated by the numeral 14.
[0023] SAHR assembly 12 is positioned at a piston assembly end 16
of housing 11 and includes an SAHR piston 18, a spring assembly,
generally indicated by the numeral 20, and an end cap, generally
indicated by the numeral 22. SAHR piston 18 is a cup-shaped piston
that moves within a stepped bore, generally indicated by the
numeral 24, in housing 11. Piston 18 has a body portion 26 having
an outer cylindrical surface 28 that engages the maximum diameter
chamber 30 in stepped bore 24. Outer cylindrical surface 28 may
include a wear ring 29 to allow a small clearance between outer
cylindrical surface 28 and bore 24 without causing wear of either
surface. This also prevents binding of piston 18 by providing
better support over a longer portion of piston 18.
[0024] Piston 18 further includes a projecting flange 32 with a
reduced diameter cylindrical surface 34 that operates in a reduced
diameter chamber 36 in stepped bore 24. In the "default" position,
projecting flange 32 engages the proximate or inboard stator plate
38 of a stator assembly, generally indicated by the numeral 40.
Proximate to reduced diameter cylindrical surface 34, housing 11
can include one or more of an oil seal 35, a wear ring 37, and a
combination O-ring 39A and backup ring 39B. When present, oil seal
35 serves to preclude entry of foreign matter into reduced diameter
chamber 36, wear ring 37 serves to provide clearance similar to as
described above, and the combination O-ring 39A and backup ring 39B
help to control the escape of fluid from fluid chamber 33. Piston
18 can also include a combination O-ring 47A and backup ring
47B.
[0025] In the "default" position of piston 18 the stator assembly
40 is engaged. Stator assembly 40 is located in a stator assembly
end 41 of housing 11 having a cavity 43 adapted to enclose a
portion of the rotor (not shown). Cavity 43 also receives a portion
of stator assembly 40. In particular, a pair of stator plates 38
are positioned within cavity 43 displaced axially to either side of
the rotor so that a portion of the rotor is interposed
therebetween. Stator plates 38 are positioned to substantially
parallel the rotor and carry one or more pads 45 for engaging the
rotor. Pads 45 may be fabricated of any of numerous friction
materials known in the art. Each stator plate 38 can optionally
have projecting ears at the longitudinal ends thereof having bores
therein for receiving stator pins on which the stator plates are
freely slidably mounted.
[0026] SAHR piston 18 of SAHR assembly 12 is urged into engagement
with stator assembly 40 by spring assembly 20. Depending upon the
force required to be imparted to the rotor by SAHR piston 18,
spring assembly 20 may include one or more coil springs. As shown,
there are five spring stacks 42 circumferentially positioned within
the piston diameter, with each stack 42 having three springs,
namely outer spring 44, intermediate spring 46, and inner spring
48, of differing diameters and preferably being positioned on a
common central axis. Therefore, SAHR assembly 12 includes fifteen
spring elements in the embodiment shown. In order to stabilize
spring stacks 42, SAHR piston 18 is provided with one or more axial
recesses 50 capable of fitting one or more of the spring stacks 42.
In one or more embodiments, an axial recess 50 is sized to receive
an outer spring 44.
[0027] Spring stacks 42 and springs 44, 46, 48 are restrained
opposite SAHR piston 18 by end cap 22. End cap 22 has a cylindrical
body 52 that telescopes into stepped bore 24 with an annular
projecting rim 54 that receives at least a portion of spring stacks
42. At least a portion of the outer surface of rim 54 engages at
least a portion of surface 58 in stepped bore 24.
[0028] The position of the end of spring stacks 42 opposite SAHR
piston 18 may be optionally provided with one or more shims (not
shown) to act as a slip plane to reduce resistance to rotation of
end cap 22 relative to spring stacks 42. End cap 22 may have a
C-ring 53 positioned near an axial end thereof to keep end cap 22
from pushing out of the back of the stepped bore 24.
[0029] With the "default" position being that SAHR piston 18 is
urged into engagement with stator assembly 40 by spring assembly
20, the spring force of spring assembly 20 must be selectively
overcome in order to move SAHR piston 18 to an unactuated position
to release the rotor. To accomplish this, a hydraulic fluid supply
network, generally indicated by the numeral 60, provides
pressurized fluid to fluid chamber 33.
[0030] By way of fluid chamber 33, SAHR assembly 12 can be said to
be in fluid communication with PI assembly 14. PI assembly 14 is
also positioned at the piston assembly end 16 of housing 11 and is
positioned laterally of SAHR assembly 12. PI assembly includes a PI
piston 64, a spring assembly, generally indicated by the numeral
66, and an end cap, generally indicated by the numeral 68. PI
piston 64 moves within a stepped bore, generally indicated by the
numeral 70, in housing 11. Piston 64 has a body portion 72 having
an outer cylindrical surface 74 that engages a portion of the
chamber in stepped bore 70. The chamber in stepped bore 70 includes
a maximum diameter chamber 76, where the diameter of outer
cylindrical surface 74 is slightly less than the diameter of
maximum diameter chamber 76. Outer cylindrical surface 74 may
include one or more of a wear ring 77 and a combination O-ring 79A
and backup ring 79B. When present, these components serve similar
functions as to those described above.
[0031] PI Piston 64 further includes a projecting flange 78 with a
reduced diameter cylindrical surface 80 that operates in a reduced
diameter chamber 82 in stepped bore 70 to fluidly engage the
portion of fluid chamber 33 fluidly between SAHR piston 18 and PI
piston 64. PI piston 64 further includes a bore 81 axially
therethrough. Reduced diameter cylindrical surface 80 can include a
combination O-ring 83A and backup ring 83B. When present, these
components serve similar functions as to those described above.
[0032] PI piston 64 of PI assembly 14 is urged toward end cap 68 by
spring assembly 66. Depending upon the force required to be fluidly
imparted to SAHR piston 18 by PI piston 64, spring assembly 66 may
be provided with one or more coil springs. As shown, there is one
spring stack circumferentially positioned within the piston
diameter, with the stack having two springs, namely outer spring 84
and inner spring 86 of differing diameters and preferably being
positioned on a common central axis. Housing 11 is provided with an
axial recess 88 which is sized to receive springs 84, 86. Recess 88
is used to achieve the correct force yielded by springs 84, 86.
Without recess 88, springs 84, 86 could be overstressed.
[0033] PI piston 64 is restrained opposite spring assembly 66 by
end cap 68.
[0034] End cap 68 has a cylindrical body 90 that telescopes into
stepped bore 70. End cap 68 is held into position by a retaining
ring 111. At least a portion of the outer cylindrical surface 92 of
end cap 68 can engage at least a portion of the inner chamber 94 of
stepped bore 70.
[0035] End cap 68 and end cap 22 are proximately positioned to
housing end plate 91. End plate 91 closes housing 11 outwardly of
end caps 22, 68 and is essentially a flat cover held in place by a
plurality of hex bolts 93 extending through bores in end plate 91
and into housing 11. A gasket 95 may be used for sealing between
end plate 91 and housing 11. Housing 11 may also include a bleeder
port and a plug 97, for purging air from hydraulic fluid supply
network 60. Housing 11 may also include a pipe plug 99 and a
passage 109. Passage 109 is provided to allow communication, as in
air or gas communication, between bore 24 and bore 70. Passage 109
prevents air or gas from being trapped in one bore or the other.
Pipe plug 99 can serve to fill a hole that may be created in the
manufacture of passage 109. To machine passage 109, a drill can be
used from the outside of housing 11, thus creating the hole filled
by pipe plug 99. Pipe plug 99 can also prevent contaminants from
entering housing 11.
[0036] End cap 68 includes a pin, generally indicated by the
numeral 98, positioned axially therethrough. Pin 98 includes an
elongated body 100 telescoping through body 90. Pin 98 can be
secured in place by a set screw 96 threaded into body 90. A tip 102
extends from elongated body 100 for engaging a ball 104 of a ball
valve, generally indicated by the numerally 106. Ball valve 106
further includes a spring 108 that engages ball 104. Elongated body
100 can have an O-ring 101 positioned therearound. One or more
aspects of ball valve 106 may be further described by the
disclosure in U.S. Pat. No. 8,360,215, which is incorporated herein
by reference.
[0037] The "default" position of PI piston 64 is as shown in FIG.
1. Tip 102 engages ball 104 and overcomes the spring force of
spring 108. In this position, in can be said that ball 104 is
unseated. With ball 104 in an unseated position, hydraulic fluid
enters through hydraulic port 110. Since ball 104 is unseated,
hydraulic fluid then passes through ball valve 106 and through bore
81. Then, hydraulic fluid enters into the portion of fluid chamber
33 between SAHR piston 18 and PI piston 64. FIG. 2 is
representative of the state when hydraulic fluid has completely
filled fluid chamber 33 of hydraulic fluid supply network 62.
[0038] In this state, the pressure of the hydraulic fluid behind PI
piston 64 is not yet sufficient to overcome the spring force of
spring assembly 66. As hydraulic fluid continues to enter through
hydraulic port 110, the pressure continues to build. Since the
surface area of the large end of PI piston 64 is greater than the
surface area of the smaller end of PI piston 64, more force is
acting on the large end than on the smaller end. Once the force
applied to the large end is greater than the sum of the spring
force and the force applied to the smaller end, PI piston 64 begins
to travel into bore 70. This movement is represented in FIG. 3.
[0039] PI piston 64 continues its travel into bore 70 and
eventually the spring force of spring 108 causes ball 104 to be
moved into a seated position. This seating of ball 104 blocks fluid
communication at the position of ball 104, thereby trapping a
column of fluid 105, as identified in FIG. 4, in the portion of
fluid chamber 33 fluidly between SAHR piston 18 and PI piston 64.
Thus, when additional hydraulic fluid enters hydraulic port 110,
the continued travel of PI piston 64 causes projecting flange 78 to
fluidly engage the portion of fluid chamber 33 fluidly between SAHR
piston 18 and PI piston 64. This increases the pressure in that
portion of fluid chamber 33. Eventually, the pressure is sufficient
as to allow the SAHR piston 18 to overcome the spring force of
spring assembly 20. Thus, SAHR piston 18 travels toward end cap 22
and the proximate or inboard stator plate 38 is no longer engaged
by SAHR piston 18, thereby releasing the rotor.
[0040] To re-engage proximate or inboard stator plate 38 with SAHR
piston 18, the hydraulic pressure of the hydraulic fluid behind the
large end of PI piston 64 is released to "zero" and some or all of
this fluid behind the large end of PI piston 64 returns to the
source, such as a tank. Then, the spring force of spring assembly
66 causes PI piston 64 to travel toward, and to, end cap 68. During
this movement, tip 102 engages ball 104 and compresses spring 108,
thereby allowing the entirety of fluid chamber 33 to equalize at
zero pressure. The spring force of spring assembly 20 then
re-engages SAHR piston 18 with proximate or inboard stator plate 38
to re-impart the requisite force to the rotor.
[0041] Advantageously, for the next cycle of using brake 10, the
use of the ball valve 106 allows for full replenishment of the
fluid for column of fluid 105 in the portion of fluid chamber 33
fluidly between SAHR piston 18 and PI piston 64 when the fluid
enters to start the next cycle. This is an improvement over certain
prior art solutions that do not allow for easy replacement of fluid
that has leaked from a column of fluid.
[0042] For use of caliper brake 10, brake 10 can be mounted to a
mounting surface (not shown). Housing 11 has stator assembly 40
mounted in operative relation to the wheel rotor by a mounting
bracket assembly. The mounting bracket assembly can be operatively
joined to housing 11 by bolts (not shown) extending through sleeves
112, 114. To permit housing 11 to move axially of the bolts, the
bolts may carry a sleeve 114. Housing 11 may carry a pair of spaced
bushings 116 and 118 engaging sleeve 114 to facilitate the relative
sliding movement. A lip seal 120 may be positioned at each axial
extremity of each of the bushings 116, 118 to keep out foreign
debris. One or more aspects of the mounting bracket assembly may be
further described by the disclosure in U.S. Pat. No. 8,127,897 or
U.S. Application Publication 2012/0325599, which are incorporated
herein by reference.
[0043] In operation of caliper brake 10, hydraulic fluid is
initiated into the portion of fluid chamber 33 between PI piston 64
and PI end cap 68. Hydraulic fluid fills the entirety of fluid
chamber 33 because ball 104 is in an unseated position. Then,
sufficient hydraulic fluid pressure is supplied to this portion of
fluid chamber 33 between PI piston 64 and PI end cap 68 as to allow
PI piston 64 to overcome the force opposing PI piston 64 and the
spring force of associated spring assembly 66, thereby allowing PI
piston 64 to travel in bore 70.
[0044] Once, PI piston 64 travels a sufficient distance, ball 104
of ball valve 106 will move to a seated position based on the
opposing spring force of spring 108. This creates column of fluid
105 between PI piston 64 and SAHR piston 18. As PI piston 64
continues its travel, the pressure in this portion of fluid chamber
33 is increased such that the increased pressure now acting on SAHR
piston 18 allows it to overcome the spring force of associated
spring assembly 20. Thus, proximate or inboard stator plate 38 no
longer engaged by SAHR piston 18, which thereby releases the
rotor.
[0045] It should be appreciated that when PI piston 64 travels in
bore 70, SAHR piston 18 will only move a fraction of the distance
that PI piston 64 moves. This ratio of movement may be determined
by the ratio of the effective area of the small diameter of PI
piston 64 to the effective area of SAHR piston 18. The ratio of
movement will correspond with the ratio of these effective areas.
An effective area is defined as the area that is acted upon by
pressure.
[0046] Using the equation Force=Pressure*Area, and assuming that
friction drag is negligible, that the force from spring assembly 66
is unimportant for the purpose of demonstrating the pressure
intensifying ratios or sizes, and that there is a maximum available
hydraulic pressure, P.sub.hydraulicmax, the piston diameters and
therefore, the effective areas of the pistons, can be designed to
overcome a predetermined spring clamp force, F.sub.spring, of
spring assembly 20.
[0047] Where the diameter of outer cylindrical surface 74 is
D.sub.PI,max, the force available behind PI piston 64 (F.sub.PI) is
equal to .pi.*((D.sub.PI,max/2).sup.2)*P.sub.hydraulicmax. Then,
where the diameter of projecting flange 78 is D.sub.PI,min, the
pressure in fluid chamber 33 (P.sub.chamber) is equal to
F.sub.PI/((D.sub.PI,min/2).sup.2). Then, where the diameter of body
portion 26 is D.sub.SAHR,max, and where the diameter of projecting
flange 32 is D.sub.SAHR,min, the force available to be applied to
SAHR piston 18 (F.sub.SAHR) can be determined based on the
effective area of SAHR piston 18 (A.sub.SAHR).
[0048] The effective area of SAHR piston 18 can be determined from
the diameter of body portion 26, D.sub.SAHR,max, and the diameter
of projecting flange 32,D.sub.SAHR,min. The effective area of SAHR
piston 18 (A.sub.SAHR) is equal to
(.pi.*(D.sub.SAHR,max/2).sup.2)-(.pi.*(D.sub.SAHR,min/2).sup.2).
Then, A.sub.SAHR, can be used to find F.sub.SAHR, by the equation
F.sub.SAHR=A.sub.SAHR*P.sub.chamber. To overcome a predetermined
spring clamp force, F.sub.spring, of spring assembly 20, the force
of SAHR piston 18 (F.sub.SAHR) must be greater than
F.sub.spring.
[0049] Caliper brake 10 can therefore be characterized by the sizes
of the diameter of outer cylindrical surface 74, the diameter of
projecting flange 78, the diameter of body portion 26, and the
diameter of projecting flange 32. The diameter of outer cylindrical
surface 74 may be in a range of from 1.5 inches to 3.0 inches. The
diameter of projecting flange 78 may be in a range of from 0.5
inches to 1.0 inches. The diameter of body portion 26 may be in a
range of from 3.0 inches to 5.0 inches. The diameter of projecting
flange 32 may be in a range of from 1.5 inches to 4.0 inches.
[0050] The ratio of the diameter of outer cylindrical surface 74 to
the diameter of projecting flange 78 can be said to cause the
pressure intensification of PI assembly 14 based on the differing
effective areas behind and in front of PI piston 64. This ratio can
also be described as the intensifying factor. The ratio of the
diameter of outer cylindrical surface 74 to the diameter of
projecting flange 78 may be in a range of from 2:1 to 5:1.
[0051] Caliper brake 10 can also be characterized by the available
hydraulic force and the predetermined spring clamp force of spring
assembly 20. A hydraulic force available behind PI piston 64
(F.sub.PI) may be in the range of from 100 psi to 300 psi. A
predetermined spring clamp force, F.sub.spring, of spring assembly
20 may be in the range of from 5,000 lbf to 10,000 lbf.
[0052] After SAHR piston 18 overcomes the predetermined spring
clamp force of spring assembly 20 to disengage brake 10, brake 10
can be re-engaged when desired. Once the operator or other vehicle
conditions requires that brake 10 be re-engaged, the pressure of
the hydraulic fluid is allowed to release to "zero" such that
spring assembly 66 associated with PI piston 64 moves PI piston 64
toward pin 98. Then, tip 102 engages ball 104 as to unseat ball
104. Thus, the pressure of column of fluid 105 is released, thereby
causing SAHR piston 18 to re-engage proximate or inboard stator
plate 38, thereby re-engaging the rotor.
[0053] As said above, for the next cycle of using brake 10, the use
of ball valve 106 allows for a full replenishment of the column of
fluid 105 in the portion of fluid chamber 33 fluidly between SAHR
piston 18 and PI piston 64 to be replenished when the fluid enters
to start the next cycle.
[0054] A caliper brake of the present invention may be used in the
driveline of a rough terrain crane, but could be used in any
suitable vehicle. The brake is particularly envisioned as being
mounted to the input to the rear axle, though other suitable
mounting locations are possible.
[0055] It is thus evident that a caliper brake constructed as
described herein accomplishes the objects of the present invention
and otherwise substantially improves the art.
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