CA1076627A - Brake shuttle valve assembly - Google Patents
Brake shuttle valve assemblyInfo
- Publication number
- CA1076627A CA1076627A CA247,344A CA247344A CA1076627A CA 1076627 A CA1076627 A CA 1076627A CA 247344 A CA247344 A CA 247344A CA 1076627 A CA1076627 A CA 1076627A
- Authority
- CA
- Canada
- Prior art keywords
- piston
- emergency
- cylinder
- brake
- service brake
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T13/00—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems
- B60T13/10—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with fluid assistance, drive, or release
- B60T13/24—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with fluid assistance, drive, or release the fluid being gaseous
- B60T13/26—Compressed-air systems
- B60T13/268—Compressed-air systems using accumulators or reservoirs
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T17/00—Component parts, details, or accessories of power brake systems not covered by groups B60T8/00, B60T13/00 or B60T15/00, or presenting other characteristic features
- B60T17/18—Safety devices; Monitoring
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
- B60T8/32—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration
- B60T8/34—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration having a fluid pressure regulator responsive to a speed condition
- B60T8/343—Systems characterised by their lay-out
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
- B60T8/32—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration
- B60T8/88—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration with failure responsive means, i.e. means for detecting and indicating faulty operation of the speed responsive control means
- B60T8/92—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration with failure responsive means, i.e. means for detecting and indicating faulty operation of the speed responsive control means automatically taking corrective action
- B60T8/94—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration with failure responsive means, i.e. means for detecting and indicating faulty operation of the speed responsive control means automatically taking corrective action on a fluid pressure regulator
Abstract
ABSTRACT OF THE DISCLOSURE
A shuttle valve is situated between the service brake and emergency brake lines downstream of the brake control valve which modulates both lines. The shuttle valve includes a dif-ferential pressure piston in a cylinder. The piston includes a large diametered end connected to the service brake line and a smaller diametered end connected to the emergency brake line with a port in the side of the cylinder adjacent the small dia-metered end. The air pressure in the service brake line acts upon the large diametered end of the piston and normally main-tains the piston at one end of the cylinder so that the port is closed off by the small diametered end of the piston. However, if the service brake pressure drops below a predetermined min-imum, the piston will move in the cylinder thus uncovering the port and connecting the emergency brake line to the emergency air tank. When the fault is corrected and the pressure builds up in the service brake line, the air pressure acts upon the pis-ton and moves it in the opposite direction thus shutting off the aforementioned port and disconnecting the emergency brake system.
A shuttle valve is situated between the service brake and emergency brake lines downstream of the brake control valve which modulates both lines. The shuttle valve includes a dif-ferential pressure piston in a cylinder. The piston includes a large diametered end connected to the service brake line and a smaller diametered end connected to the emergency brake line with a port in the side of the cylinder adjacent the small dia-metered end. The air pressure in the service brake line acts upon the large diametered end of the piston and normally main-tains the piston at one end of the cylinder so that the port is closed off by the small diametered end of the piston. However, if the service brake pressure drops below a predetermined min-imum, the piston will move in the cylinder thus uncovering the port and connecting the emergency brake line to the emergency air tank. When the fault is corrected and the pressure builds up in the service brake line, the air pressure acts upon the pis-ton and moves it in the opposite direction thus shutting off the aforementioned port and disconnecting the emergency brake system.
Description
BACKGROUND_OF THE INVEN. ION
This invention relates to new and useful improvements in controls for emergency brake assemhlies for air brakes normal-ly used on buses, trucks and the like.
Conventional air brakes normally include an automatic-'i' , .
.
. ... ~ "
. . .
.
, , .
;
, , ` ~' ' ~ ' ~` ' ' ' ' ~ '' ' "': ;-` ',:.
'7 ally operating device which applies full emergency brake pres-sure if the air pressure in the main line drops below a prede-termined amount. This is unsafe under certain conditions and also requires the driver to disconnect the emergency brake if he wishes to move the vehicle. This disconnection is normally by means of an over-ride lever manually operated by the driver.
Furthermore, this particular system is not readily adaptable for use with the type of air brakes which include anti-skid devices whether these be computer operated or not.
SUMMARY OF THE INVENTION
The present invention overcomes these disadvantages by providing a differential shuttle valve between the main ser-vice brake line and the emergency service brake line, said valve normally being situated between the foot control valve and the brake diaphragms. Under normal conditions, the air pressure in the service brake line maintains the shuttle valve in one posi-tion so that the emergency reservoir tank is disconnected from the emergency brake system. However, if the pressure in the service brake line drops below a predetermined minimum, the air ~0 pressure acting upon the shuttle valve from the emergency reser-voir tank, moves the shuttle valve thus uncovering a port which connects the emergency reservoir tank with the emergency brake system so that it can be modulated by the foot control valve operated by the driver.
10 7~
If and when the fault is corrected and pressure builds up once again in the service brake line, the next time the brakes are operated, the shuttle valve returns to the original position thus shutting off the emergency reservoir tank from the emergency brakes.
One aspect of the invention consists of an im-provement in an air brake system which includes a main service brake assembly and an emergency brake assembly, a main air reservoir tank and an emergency air reservoir tank, a dual brake modulating control valve, lines connecting said tanks to said control valve, a service brake line extending between said control valve and said main service brake assembly and an emergency brake line extending from said control valve and being operatively connected to said emergency brake assembly;
a differential shuttle valve component operatively connected between said service brake line and said emergency brake line, said shuttle valve component including a piston cylinder of a simple geometrical shape formed by two juxtaposed cylinders of different diameters and consisting of a first cylindrical portion and a second cylindrical portion contiguous with ::~
said first portion, the diameter of said first portion being greater than the diameter of said second portion, a piston which reciprocates in said piston cylinder between a first position and a second position under the sole control of air pressure supplied to said shuttle valve component, said pis-ton being of a simple geometrical shape formed by two juxta-posed cylinders of different diameters and consisting of a first portion reciprocal within the first portion of said piston cylinder and a second portion, connected to and conti-guous with, said first portion of said piston, and reciprocal ...... .
1~7~ 7 within said second portion of said piston cylinder, the diameter of said first portion of said piston being greater than the diameter of said second portion of said piston, means operative-ly connecting said service brake line with said first portion of said piston cylinder and means operatively connecting said emergency brake line to said second portion of said cylinder whereby said emergency reservoir tank is operatively connected to said emergency brake assembly when said piston is in said first position and closing off said emergency reservoir tank from said emergency brake assembly when said piston is in said second position, said control valve modulating air pressure from said main service brake assembly when said piston is in the se-cond position and modulating air pressure from said emergency air reservoir tank when said piston is in said first position.
lS Another advantage of the invention is to provide a device of the character herewithin described which is simple in construction, economical in manufacture and otherwise well suited to the purpose for which it is designed.
With the foregoing in view, and other such advantages as will become apparent to those skilled in the art to which this invention relates as this specification proceeds, my inven-tion consists essentially in the arrangement and construction of 10'7~7 parts all as hereinafter more particularly described, reference being had to the accompanying drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic view of an air brake system with the device incorporated therein.
Figure 2 is an end view of the shuttle valve per se enlarged with respect to Figure 1.
Figure 3 is a section along the line 3-3 of Figure
This invention relates to new and useful improvements in controls for emergency brake assemhlies for air brakes normal-ly used on buses, trucks and the like.
Conventional air brakes normally include an automatic-'i' , .
.
. ... ~ "
. . .
.
, , .
;
, , ` ~' ' ~ ' ~` ' ' ' ' ~ '' ' "': ;-` ',:.
'7 ally operating device which applies full emergency brake pres-sure if the air pressure in the main line drops below a prede-termined amount. This is unsafe under certain conditions and also requires the driver to disconnect the emergency brake if he wishes to move the vehicle. This disconnection is normally by means of an over-ride lever manually operated by the driver.
Furthermore, this particular system is not readily adaptable for use with the type of air brakes which include anti-skid devices whether these be computer operated or not.
SUMMARY OF THE INVENTION
The present invention overcomes these disadvantages by providing a differential shuttle valve between the main ser-vice brake line and the emergency service brake line, said valve normally being situated between the foot control valve and the brake diaphragms. Under normal conditions, the air pressure in the service brake line maintains the shuttle valve in one posi-tion so that the emergency reservoir tank is disconnected from the emergency brake system. However, if the pressure in the service brake line drops below a predetermined minimum, the air ~0 pressure acting upon the shuttle valve from the emergency reser-voir tank, moves the shuttle valve thus uncovering a port which connects the emergency reservoir tank with the emergency brake system so that it can be modulated by the foot control valve operated by the driver.
10 7~
If and when the fault is corrected and pressure builds up once again in the service brake line, the next time the brakes are operated, the shuttle valve returns to the original position thus shutting off the emergency reservoir tank from the emergency brakes.
One aspect of the invention consists of an im-provement in an air brake system which includes a main service brake assembly and an emergency brake assembly, a main air reservoir tank and an emergency air reservoir tank, a dual brake modulating control valve, lines connecting said tanks to said control valve, a service brake line extending between said control valve and said main service brake assembly and an emergency brake line extending from said control valve and being operatively connected to said emergency brake assembly;
a differential shuttle valve component operatively connected between said service brake line and said emergency brake line, said shuttle valve component including a piston cylinder of a simple geometrical shape formed by two juxtaposed cylinders of different diameters and consisting of a first cylindrical portion and a second cylindrical portion contiguous with ::~
said first portion, the diameter of said first portion being greater than the diameter of said second portion, a piston which reciprocates in said piston cylinder between a first position and a second position under the sole control of air pressure supplied to said shuttle valve component, said pis-ton being of a simple geometrical shape formed by two juxta-posed cylinders of different diameters and consisting of a first portion reciprocal within the first portion of said piston cylinder and a second portion, connected to and conti-guous with, said first portion of said piston, and reciprocal ...... .
1~7~ 7 within said second portion of said piston cylinder, the diameter of said first portion of said piston being greater than the diameter of said second portion of said piston, means operative-ly connecting said service brake line with said first portion of said piston cylinder and means operatively connecting said emergency brake line to said second portion of said cylinder whereby said emergency reservoir tank is operatively connected to said emergency brake assembly when said piston is in said first position and closing off said emergency reservoir tank from said emergency brake assembly when said piston is in said second position, said control valve modulating air pressure from said main service brake assembly when said piston is in the se-cond position and modulating air pressure from said emergency air reservoir tank when said piston is in said first position.
lS Another advantage of the invention is to provide a device of the character herewithin described which is simple in construction, economical in manufacture and otherwise well suited to the purpose for which it is designed.
With the foregoing in view, and other such advantages as will become apparent to those skilled in the art to which this invention relates as this specification proceeds, my inven-tion consists essentially in the arrangement and construction of 10'7~7 parts all as hereinafter more particularly described, reference being had to the accompanying drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic view of an air brake system with the device incorporated therein.
Figure 2 is an end view of the shuttle valve per se enlarged with respect to Figure 1.
Figure 3 is a section along the line 3-3 of Figure
2. ~ ' Figure 4 shows a graph of brake pedal travel/P.S.I.
with 60 P.S.I. in service brake reservoir and 120 P.S.I. in the emergency brake reservoir.
Figure 5 is similar to Figure 4, but with only 10 P.S.I. in the service brake reservoir.
In the drawings like characters of reference indicate :~ : . . .
: . . : . . :
:: - - :
.
i{~'76~7 corresponding parts in the different figures.
DETAILED DESCRIPTION
Proceeding therefore to describe the invention in de-tail, reference should first be made to Figure 1 which shows a schematic layout of an exemplary air brake system with the inven-tion incorporated therein.
The system includes a main air tank 10 fed from a source of air under pressure such as a compressor tnot illustrat-ed) through line 11 and one-way check valve 12.
A line 13 extends from this main air reservoir tank 10, through a safety protection valve 14 which is conventional, to a parking and emergency air reservoir tank 15 with one-way check valve 16 as illustrated. This line 13 also leads to an accessory tank 17 with a by-pass line 18 extending back to the main air reservoir tank through one-way check valve 19.
A line 20 extends from the main air reservoir tank 10 to a dual brake valve assembly collectively designated 21 and a further line 22 extends from the emergency air reservoir tank 15 also to this dual brake valve assembly 21 as clearly illustrated.
This dual brake valve assembly 21 is operated by the foot brake pedal 23 by the driver and modulates the air pressure passing ~ . . .
:~'7f~Z7 from line 20 to the main service brake line 24 extending upon the other side of the brake valve assembly 21.
The dual brake valve assem~ly 23 also modulates the air pressure from the emergency tank 15 through an emergency brake line 25, when the emergency brake system is in operation as will hereinafter be described. Normally however, the emer-gency brake system is not in operation so that the air pressure :
in line 24 is all that is modulated. This main line 24 leads to a service brake system which incorporates front brake cham- ~
bers 26 actuated through an anti-skid device shown schematical- :
ly at 27. The line 24 also leads to rear brake chambers 28 via a further anti-skid device 27 and the circuit is completed con-ventionally by various valves, regulators and the like.
Of note is the parking brake control lever 29 which connects the rear brake assemblies to the emergency air reser-voir tank 15.
Under normal operations, the dual brake valve assembly 21 operated by pedal 23, operates the main service line 24 to actuate front and rear brakes via the chambers 26 and 28.
,' ".
The invention comprises a shuttle valve assembly col-lectively designated 30 which is situated between the service 10766~7 brake line 24 and the emergency brake line 25 and in these lines between the brake control 21 and the brake chambers.
The emergency brake line 25 extends between the dual brake valve 21 and the shuttle valve assembly 30 and continues on as 25A from the shuttle valve assembly to the rear brake chambers 28 as clearly illustrated.
Figures 2 and 3 show details of the construction of this differential shuttle valve assembly 30. It consists of a substantially cylindrical housing 31 forming a cylinder 32. The cylinder 32 consists of a first part or portion 33 and a second part or portion 34 as illu~trated, with the diameter of the first part 33 being larger than the diameter of the second part 34 and with the first and second parts being joined by an annular shoulder or step 35 as clearly shown.
A piston collectively designated 36 is reciprocal with-in the cylinder 32 and this piston is provided with a first part or portion 37 and a second part or portion 38. The first part 37 is provided with a diameter greater than the second part 38 and the two parts 37 and 38 are adapted to reciprocate within the parts 33 and 34 of the differential cylinder respectively.
Enlarged annular shoulders 39 and sealing rings 39A are provided around both parts of the piston and these parts are joined by means of a step or shoulder 40 as clearly shown.
.
107~7 Cylinder heads 42 and 44 are secured to each end of the cylinder 32 by means of screw bolts or the like 35A with connecting port means 41 being provided in on head 42 of the cy-linder and further port means 43 being provided in the other head 44.
The port means 41 is operatively connected to the main -service line 24 by means of conduit 45 and the second port means 43 is operatively connected to the aforementioned portion 25 of the emergency brake line.
Third port means 46 are provided in the wall of the second part 34 of the cylinder spaced from the second port means 43 and the other portion 25A of the emergency brake line is operatively connected to this third port means 46 as clearly shown schematically in Figure 1. This port means 46 is situated between the sealing ring 39A around the second part 38 of the piston and the head 44 and it will be noted that the diameter of this part of the piston is substantially less than the diameter of the annular shoulder 39 thus defining an annular channel 39B
between this part of the piston and the cylinder wall.
It will be observed that when the piston 36 is at one end of the cylindrical housing 31 as shown in full line in Figure 2, the second part 38 of the piston covers the inner end of the third port 46 so that there is no operative connection _g _ .. . :
1~)7~ 7 between the emergency line 25 and the portion 25A thereof.
Further, the end of the second part engages a seal 38A on the inner side of the head 44 thus closing port 43 with the piston.
This seal and a similar seal 38B between the other head 42 and the cylinder also act as seals between the heads and the cylin-der and as buffers against which the piston engages at each end of its travel.
However, if the piston is end shifted as will herein-after be described to the opposite end of the cylindrical hous-ing 31 so that it takes up the position shown in phantom in Figure 2, then the lower end (with reference to Figure 2) of the second piston part moves from the seal 38A thus allowing opera-tive connection between ports 43 and 46 via annular channel 39B
so that the emergency brake assembly is connected and modulated by the dual brake valve component 21.
In operation, and due to the fact that the area of the first piston part 37 is greater than the area of the second piston part 38, air pressure present in lines 24 and 25 (which of course is similar under normal conditions) exerts a greater overall pressure on the first piston part 37 and maintains it at the lower end of the housing (with reference to Figure 2) as shown in solid line in Figure 2, and thus in contact with seal 38A. This means that the emergency brake is, in effect, discon-nected and the main service brakes are operated in the usual way by the dual brake valve assembly 21.
.,, . . :
18';'~ 7 However, if for some reason air pressure drops with-in the main service line, below a predetermined amount, then the pressure from the emergency tank 15 acting upon the under-side of the second piston part 38, will move the piston assem-bly upwardly to the position shown in phantom in Figure 2 thus connecting the emergency brake system to the emergency tank and permitting the emergency brake system to be modulated by the lower portion of the dual brake valve component 21.
When and if the fault is corrected and pressure is re9tored to the main service conduit or line 24, the pressures in lines 24 and 25 will equalize and the greater area of the first part of the piston will permit the piston to move down-wardly once again to the position shown in solid line thus cut-ting off the emergency brake system. This shuttle valve assem-bly is automatic in operation and does not require the provision of any springs or check valves in order to operate same thus simplifying the operation and maintenance of the brake systems.
The difference in diameters of the piston parts 37 and 38 will, of course, control the pressures at which the shuttle valve will operate and is dependent upon design parameters.
It will be noted that a bleed port 47 is situated ad-jacent the shoulder 35 of the cylindrical bore and communica~es with the first cylinder part 33 to permit displacement of air from below the first pistion part 37 when the piston moves to the position shown in solid line.
7~ 7 Figures 4 and 5 show examples of brake pedal travel versus air pressure under two different conditions.
For the purposes of example only, it is assumed that, under normal conditions, both the emergency brake reservoir and the main or service brake reservoir contain air at a pres-sure of 120 P.S.I.
If, for some reason, the pressure in the service brake reservoir drops to 60 P.S.I., then the main brakes will operate normally provided the modulating pressure does not ex-ceed 60 P.S.I. If, however, more than 60 P.S.I. is required, then the valve will shuttle and the emergency reservoir will be connected as indicated.
In Figure 5, a similar condition exists with the ex-ception that only 10 P.S.I. is available in the service brake reservoir. It will therefore be seen that the valve will shut-tle earlier thus connecting the emergency brake reservoir with the braking system.
In summary, when the pressure developed for the ser- ~-;
vice brake by the control valve is below safety level, the dif-ferential shuttle valve will react automatically and allow the .. ~ .
1(~7t;~7 emergency brake circuit to become fully modulated by the ser-vice brake pedal valve. Proper sizing of the shuttle valve differential will match any determined safety level. Once the service brake problem is repaired, an application of the service brake control valve will shuttle the valve into its original position thus disengaging the emergency circuit.
The shuttle valve incorporated in the braking system continually monitors each service brake control valve applica-tion and does not engage the emergency circuit unless the ser-vice brakes are below predetermined safety levels thus allow-ing the anti-skid control to properly monitor the service brake chambers. Full reservoir pressure is available for emergency control at all times and it should be noted that the emergency circuit is in addition to the depending service brake thus giv-ing additional safety to the vehicle.
The valve returns to its original position once the system is operational, without any intervention by the operator and of course, from the foregoing description it will be appre-ciated that no springs or other mechanical means are required in the shuttle valve assembly and that no air loss is experienc-ed at any time.
Since various modifications can be made in my invention -1()7~7 as hereinabove described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without departing from such spirit and scope, it is in-tended that all matter contained in the accompanying specifica-tion shall be interpreted as illustrative only and not in a limiting sense.
.
-
with 60 P.S.I. in service brake reservoir and 120 P.S.I. in the emergency brake reservoir.
Figure 5 is similar to Figure 4, but with only 10 P.S.I. in the service brake reservoir.
In the drawings like characters of reference indicate :~ : . . .
: . . : . . :
:: - - :
.
i{~'76~7 corresponding parts in the different figures.
DETAILED DESCRIPTION
Proceeding therefore to describe the invention in de-tail, reference should first be made to Figure 1 which shows a schematic layout of an exemplary air brake system with the inven-tion incorporated therein.
The system includes a main air tank 10 fed from a source of air under pressure such as a compressor tnot illustrat-ed) through line 11 and one-way check valve 12.
A line 13 extends from this main air reservoir tank 10, through a safety protection valve 14 which is conventional, to a parking and emergency air reservoir tank 15 with one-way check valve 16 as illustrated. This line 13 also leads to an accessory tank 17 with a by-pass line 18 extending back to the main air reservoir tank through one-way check valve 19.
A line 20 extends from the main air reservoir tank 10 to a dual brake valve assembly collectively designated 21 and a further line 22 extends from the emergency air reservoir tank 15 also to this dual brake valve assembly 21 as clearly illustrated.
This dual brake valve assembly 21 is operated by the foot brake pedal 23 by the driver and modulates the air pressure passing ~ . . .
:~'7f~Z7 from line 20 to the main service brake line 24 extending upon the other side of the brake valve assembly 21.
The dual brake valve assem~ly 23 also modulates the air pressure from the emergency tank 15 through an emergency brake line 25, when the emergency brake system is in operation as will hereinafter be described. Normally however, the emer-gency brake system is not in operation so that the air pressure :
in line 24 is all that is modulated. This main line 24 leads to a service brake system which incorporates front brake cham- ~
bers 26 actuated through an anti-skid device shown schematical- :
ly at 27. The line 24 also leads to rear brake chambers 28 via a further anti-skid device 27 and the circuit is completed con-ventionally by various valves, regulators and the like.
Of note is the parking brake control lever 29 which connects the rear brake assemblies to the emergency air reser-voir tank 15.
Under normal operations, the dual brake valve assembly 21 operated by pedal 23, operates the main service line 24 to actuate front and rear brakes via the chambers 26 and 28.
,' ".
The invention comprises a shuttle valve assembly col-lectively designated 30 which is situated between the service 10766~7 brake line 24 and the emergency brake line 25 and in these lines between the brake control 21 and the brake chambers.
The emergency brake line 25 extends between the dual brake valve 21 and the shuttle valve assembly 30 and continues on as 25A from the shuttle valve assembly to the rear brake chambers 28 as clearly illustrated.
Figures 2 and 3 show details of the construction of this differential shuttle valve assembly 30. It consists of a substantially cylindrical housing 31 forming a cylinder 32. The cylinder 32 consists of a first part or portion 33 and a second part or portion 34 as illu~trated, with the diameter of the first part 33 being larger than the diameter of the second part 34 and with the first and second parts being joined by an annular shoulder or step 35 as clearly shown.
A piston collectively designated 36 is reciprocal with-in the cylinder 32 and this piston is provided with a first part or portion 37 and a second part or portion 38. The first part 37 is provided with a diameter greater than the second part 38 and the two parts 37 and 38 are adapted to reciprocate within the parts 33 and 34 of the differential cylinder respectively.
Enlarged annular shoulders 39 and sealing rings 39A are provided around both parts of the piston and these parts are joined by means of a step or shoulder 40 as clearly shown.
.
107~7 Cylinder heads 42 and 44 are secured to each end of the cylinder 32 by means of screw bolts or the like 35A with connecting port means 41 being provided in on head 42 of the cy-linder and further port means 43 being provided in the other head 44.
The port means 41 is operatively connected to the main -service line 24 by means of conduit 45 and the second port means 43 is operatively connected to the aforementioned portion 25 of the emergency brake line.
Third port means 46 are provided in the wall of the second part 34 of the cylinder spaced from the second port means 43 and the other portion 25A of the emergency brake line is operatively connected to this third port means 46 as clearly shown schematically in Figure 1. This port means 46 is situated between the sealing ring 39A around the second part 38 of the piston and the head 44 and it will be noted that the diameter of this part of the piston is substantially less than the diameter of the annular shoulder 39 thus defining an annular channel 39B
between this part of the piston and the cylinder wall.
It will be observed that when the piston 36 is at one end of the cylindrical housing 31 as shown in full line in Figure 2, the second part 38 of the piston covers the inner end of the third port 46 so that there is no operative connection _g _ .. . :
1~)7~ 7 between the emergency line 25 and the portion 25A thereof.
Further, the end of the second part engages a seal 38A on the inner side of the head 44 thus closing port 43 with the piston.
This seal and a similar seal 38B between the other head 42 and the cylinder also act as seals between the heads and the cylin-der and as buffers against which the piston engages at each end of its travel.
However, if the piston is end shifted as will herein-after be described to the opposite end of the cylindrical hous-ing 31 so that it takes up the position shown in phantom in Figure 2, then the lower end (with reference to Figure 2) of the second piston part moves from the seal 38A thus allowing opera-tive connection between ports 43 and 46 via annular channel 39B
so that the emergency brake assembly is connected and modulated by the dual brake valve component 21.
In operation, and due to the fact that the area of the first piston part 37 is greater than the area of the second piston part 38, air pressure present in lines 24 and 25 (which of course is similar under normal conditions) exerts a greater overall pressure on the first piston part 37 and maintains it at the lower end of the housing (with reference to Figure 2) as shown in solid line in Figure 2, and thus in contact with seal 38A. This means that the emergency brake is, in effect, discon-nected and the main service brakes are operated in the usual way by the dual brake valve assembly 21.
.,, . . :
18';'~ 7 However, if for some reason air pressure drops with-in the main service line, below a predetermined amount, then the pressure from the emergency tank 15 acting upon the under-side of the second piston part 38, will move the piston assem-bly upwardly to the position shown in phantom in Figure 2 thus connecting the emergency brake system to the emergency tank and permitting the emergency brake system to be modulated by the lower portion of the dual brake valve component 21.
When and if the fault is corrected and pressure is re9tored to the main service conduit or line 24, the pressures in lines 24 and 25 will equalize and the greater area of the first part of the piston will permit the piston to move down-wardly once again to the position shown in solid line thus cut-ting off the emergency brake system. This shuttle valve assem-bly is automatic in operation and does not require the provision of any springs or check valves in order to operate same thus simplifying the operation and maintenance of the brake systems.
The difference in diameters of the piston parts 37 and 38 will, of course, control the pressures at which the shuttle valve will operate and is dependent upon design parameters.
It will be noted that a bleed port 47 is situated ad-jacent the shoulder 35 of the cylindrical bore and communica~es with the first cylinder part 33 to permit displacement of air from below the first pistion part 37 when the piston moves to the position shown in solid line.
7~ 7 Figures 4 and 5 show examples of brake pedal travel versus air pressure under two different conditions.
For the purposes of example only, it is assumed that, under normal conditions, both the emergency brake reservoir and the main or service brake reservoir contain air at a pres-sure of 120 P.S.I.
If, for some reason, the pressure in the service brake reservoir drops to 60 P.S.I., then the main brakes will operate normally provided the modulating pressure does not ex-ceed 60 P.S.I. If, however, more than 60 P.S.I. is required, then the valve will shuttle and the emergency reservoir will be connected as indicated.
In Figure 5, a similar condition exists with the ex-ception that only 10 P.S.I. is available in the service brake reservoir. It will therefore be seen that the valve will shut-tle earlier thus connecting the emergency brake reservoir with the braking system.
In summary, when the pressure developed for the ser- ~-;
vice brake by the control valve is below safety level, the dif-ferential shuttle valve will react automatically and allow the .. ~ .
1(~7t;~7 emergency brake circuit to become fully modulated by the ser-vice brake pedal valve. Proper sizing of the shuttle valve differential will match any determined safety level. Once the service brake problem is repaired, an application of the service brake control valve will shuttle the valve into its original position thus disengaging the emergency circuit.
The shuttle valve incorporated in the braking system continually monitors each service brake control valve applica-tion and does not engage the emergency circuit unless the ser-vice brakes are below predetermined safety levels thus allow-ing the anti-skid control to properly monitor the service brake chambers. Full reservoir pressure is available for emergency control at all times and it should be noted that the emergency circuit is in addition to the depending service brake thus giv-ing additional safety to the vehicle.
The valve returns to its original position once the system is operational, without any intervention by the operator and of course, from the foregoing description it will be appre-ciated that no springs or other mechanical means are required in the shuttle valve assembly and that no air loss is experienc-ed at any time.
Since various modifications can be made in my invention -1()7~7 as hereinabove described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without departing from such spirit and scope, it is in-tended that all matter contained in the accompanying specifica-tion shall be interpreted as illustrative only and not in a limiting sense.
.
-
Claims
WHAT I CLAIM AS MY INVENTION IS:
(1) In an air brake system which includes a main service brake assembly and an emergency brake assembly, a main air reservoir tank and an emergency air reservoir tank, a dual brake modulating control valve, lines connecting said tanks to said control valve, a service brake line extending between said control valve and said main service brake assem-bly and an emergency brake line extending from said control valve and being operatively connected to said emergency brake assembly; a differential shuttle valve component operatively connected between said service brake line and said emergency brake line, said shuttle valve component including a piston cylinder of a simple geometrical shape formed by two juxta-posed cylinders of different diameters and consisting of a first cylindrical portion and a second cylindrical portion contiguous with said first portion, the diameter of said first portion being greater than the diameter of said second portion, a piston which reciprocates in said piston cylinder between a first position and a second position under the sole control of air pressure supplied to said shuttle valve component, said piston being of a simple geometrical shape formed by two juxtaposed cylinders of different diameters and consisting of a first portion reciprocal within the first portion of said piston cylinder and a second portion, connected to and conti-guous with, said first portion of said piston, and reciprocal within said second portion of said piston cylinder, the dia-meter of said first portion of said piston being greater than the diameter of said second portion of said piston, means opera-tively connecting said service brake line with said first por=
tion of said piston cylinder and means operatively connecting said emergency brake line to said second portion of said cylinder whereby said emergency reservoir tank is operatively connected to said emergency brake assembly when said piston is in said first position and closing off said emergency reservoir tank from said emergency brake assembly when said piston is in said second position, said control valve modulating air pressure from said main service brake assembly when said piston is in the second position and modulating air pressure from said emer-gency air reservoir tank when said piston is in the said first position.
(2) The device according to Claim 1 in which said cylinder includes a cylindrical inner wall forming said first portion, a shoulder extending inwardly from one end of said cy-lindrical inner wall, said second portion comprising a cylin-drical inner wall extending from the inner end of said shoulder and concentrically with said first cylindrical inner wall, said first cylindrical portion of said piston being reciprocal in said cylindrical inner wall of said first portion of said cy-linder and a shoulder extending inwardly from one end of said first cylindrical portion of said piston, said second cylindri-cal portion of said piston extending from the inner end of said first cylindrical portion of said piston and being reciprocal in said cylindrical inner wall of said second portion of said cylinder.
(1) In an air brake system which includes a main service brake assembly and an emergency brake assembly, a main air reservoir tank and an emergency air reservoir tank, a dual brake modulating control valve, lines connecting said tanks to said control valve, a service brake line extending between said control valve and said main service brake assem-bly and an emergency brake line extending from said control valve and being operatively connected to said emergency brake assembly; a differential shuttle valve component operatively connected between said service brake line and said emergency brake line, said shuttle valve component including a piston cylinder of a simple geometrical shape formed by two juxta-posed cylinders of different diameters and consisting of a first cylindrical portion and a second cylindrical portion contiguous with said first portion, the diameter of said first portion being greater than the diameter of said second portion, a piston which reciprocates in said piston cylinder between a first position and a second position under the sole control of air pressure supplied to said shuttle valve component, said piston being of a simple geometrical shape formed by two juxtaposed cylinders of different diameters and consisting of a first portion reciprocal within the first portion of said piston cylinder and a second portion, connected to and conti-guous with, said first portion of said piston, and reciprocal within said second portion of said piston cylinder, the dia-meter of said first portion of said piston being greater than the diameter of said second portion of said piston, means opera-tively connecting said service brake line with said first por=
tion of said piston cylinder and means operatively connecting said emergency brake line to said second portion of said cylinder whereby said emergency reservoir tank is operatively connected to said emergency brake assembly when said piston is in said first position and closing off said emergency reservoir tank from said emergency brake assembly when said piston is in said second position, said control valve modulating air pressure from said main service brake assembly when said piston is in the second position and modulating air pressure from said emer-gency air reservoir tank when said piston is in the said first position.
(2) The device according to Claim 1 in which said cylinder includes a cylindrical inner wall forming said first portion, a shoulder extending inwardly from one end of said cy-lindrical inner wall, said second portion comprising a cylin-drical inner wall extending from the inner end of said shoulder and concentrically with said first cylindrical inner wall, said first cylindrical portion of said piston being reciprocal in said cylindrical inner wall of said first portion of said cy-linder and a shoulder extending inwardly from one end of said first cylindrical portion of said piston, said second cylindri-cal portion of said piston extending from the inner end of said first cylindrical portion of said piston and being reciprocal in said cylindrical inner wall of said second portion of said cylinder.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA247,344A CA1076627A (en) | 1976-03-08 | 1976-03-08 | Brake shuttle valve assembly |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA247,344A CA1076627A (en) | 1976-03-08 | 1976-03-08 | Brake shuttle valve assembly |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1076627A true CA1076627A (en) | 1980-04-29 |
Family
ID=4105403
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA247,344A Expired CA1076627A (en) | 1976-03-08 | 1976-03-08 | Brake shuttle valve assembly |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1076627A (en) |
-
1976
- 1976-03-08 CA CA247,344A patent/CA1076627A/en not_active Expired
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