The present invention relates to a parking brake with a safety device and more particularly to a parking brake with a safety device for a farm tractor.
Conventionally, hydraulic arrangements for parking brakes on agricultural equipment only contain one solenoid valve with two slides. When the solenoid valve is energized to an “ON” position, the piston chamber is pressurized so that the piston is retracted and the parking brake is deactivated. The parking brake can be applied by reducing the pressure in the chamber so that the piston is not restrained.
When the tractor is turned off while in motion or if the tractor suffers a loss of power, a resultant fall in pressure in the circuit occurs. The loss of power to the circuit causes the solenoid valve to deenergize, which allows the oil to return to the drain and reduces the pressure in the chamber. The parking brake is thereby activated in a totally uncontrolled manner and results in sharp highly undesirable braking of the tractor.
A parking brake with a safety device to allow controlled braking during blackout electrical failures or other large pressure drops in the system would be highly desirable.
The present invention is a parking brake that is activated mechanically through the use of pressurized oil acting to compress a pack of Belleville washers. The brake is released hydraulically by draining the pressurized oil and allowing the Belleville washers to push the piston to a brake activation position. The parking brake also has a safety device to prevent sudden uncontrolled engagement of the brake while the vehicle is moving. Uncontrolled engagement of the brakes can occur as a result of various factors, such as electrical failure, turning off the engine, or simply a fall in oil pressure in the main hydraulic circuit.
The object of the present invention is to provide a parking brake with a valve assembly for regulating oil flow between a “parking on” and a “parking off” mode as desired. The parking brake while in “parking off” mode, maintains the oil inside the Belleville washer cylinder under pressure even when the main solenoid valve is not controlled electrically, or when the hydraulic pressure in the circuit falls suddenly for any reason.
The parking brake may be used in any vehicle but has particular advantages when used in a farm tractor, to which the following description refers purely by way of example.
The advantages of this invention will be apparent upon consideration of the following detailed disclosure of the invention, especially when taken in conjunction with the accompanying drawings wherein:
Many of the fastening, connection, processes and other means and components utilized in this invention are widely known and used in the field of the invention described, and their exact nature or type is not necessary for an understanding and use of the invention by a person skilled in the art, and they will not therefore be discussed in significant detail. Also, any reference herein to the terms “left” or “right” are used as a matter of mere convenience, and are determined by standing at the rear of the machine facing in its normal direction of travel. Furthermore, the various components shown or described herein for any specific application of this invention can be varied or altered as anticipated by this invention and the practice of a specific application of any element may already by widely known or used in the art by persons skilled in the art and each will likewise not therefore be discussed in significant detail.
The monobloc supporting structure 15 has a first plate 15a that is substantially perpendicular to axis (a); a second plate 15b, substantially perpendicular to the first plate 15a and supporting sleeve 13; and a third plate 15c, that is also perpendicular to the first plate 15a and therefore parallel to the second plate 15b.
A distal end of the shaft 12 has a cam member 17, which acts on a pack of movable sectors 18 interposed between the second and third plates 15b, 15c, shown in
An operator can activate the parking brake 10 by rotating the lever 11 in the direction indicated by arrow FR1 so that the shaft 12 grips the pack of movable sectors 18 and exerts a braking force on the pinion of the rear wheels. The lever 11 and shaft can be rotated to exert a braking force on the pinion, either by pulling on a Bowden cable fixed at one end to pin 11a, or by using a hydraulic cylinder assembly that is described below.
As shown in
Best shown in
In the configuration shown in
The hydraulic cylinder assembly 23 has a pressurized-oil inlet 30 connected to a pressurized-oil distribution circuit CIR. The hydraulic cylinder assembly 23 additionally has a valve assembly 40 comprising a first solenoid valve 41 and a second solenoid valve 42, which are both housed in respective seats 41a, 42a; and connected to each other hydraulically by a conduit 43, as shown in
As shown in
In the embodiment of the present invention depicted in
To drain the portion 24a* of the chamber, only the second solenoid valve 42 is energized and placed in an “ON” position, while solenoid valve 41 is deenergized and placed in an “OFF” position, so that the slides 41b, 41c are aligned as shown in
In the event of a tractor blackout the current to both solenoid valves 41, 42, is cut off so that they are in the “OFF” position as shown in
It will be understood that changes in the details, materials, steps and arrangements of parts which have been described and illustrated to explain the nature of the invention will occur to and may be made by those skilled in the art upon a reading of this disclosure within the principles and scope of the invention. The foregoing description illustrates the preferred embodiment of the invention; however, concepts, as based upon the description, may be employed in other embodiments without departing from the scope of the inventions.
Number | Date | Country | Kind |
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BO2006A0714 | Oct 2006 | IT | national |
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20080093917 A1 | Apr 2008 | US |