FORM - 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13) HYDRAULICALLY OPERATED TRAILER BRAKE SYSTEM
Applicant:
MAHINDRA & MAHINDRA LIMITED
An Indian Company,
GATEWAY BUILDING, APOLLO BUNDER, MUMBAI - 400001,
MAHARASHTRA, INDIA.
Inventor: PRASHANT GAJENDRAGADKAR

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

Field of the Invention
The present invention relates to a trailer brake system, particularly a hydraulic trailer brake system, more particularly a trailer brake system operated by the tractor hydraulic system itself.
Background of the Invention
'Generally, trailers may or may not have their own brake system. As per paragraph 7.0 of AIS-043 (December 2005 version), the recommendation for braking and performance requirements for the combination of agricultural tractor and trailer, particularly in Category R4 (any double-axlaor multi-axle trailer, the GVW of which exceeds 10 tons), THE service brake is compulsory accessory and shall at least be any of the pneumatic / hydraulic / coupled power brake. These Category R4 trailers are larger or heavy-weight trailers, which normally weigh over 10 tons.
Prior Art
At present, such trailer brake systems include a separate trailer brake control valve to operate the "Trailer Brake system". These conventional trailer brake systems (Figure 1) consist of the following major components/sub-assemblies:
a. Hydraulic pump 10 connected to trailer brake valve 20 and tractor
hydraulic system 30;
b. Brake pedal 14 with trailer brake valve operating linkage 16;
c. Tractor hydraulic system 30 including:
- a hydraulic or (Hitch) control valve 32,
- a hydraulic control spool 34,

- a draft plunger 36 connected to hydraulic control spool 34, and
- a linkage 18A (also ref. Figure 2) connecting draft plunger 36 to hydraulic control spool 34,
d. Trailer brake valve 20 including:
- a brake valve spool 22,
- a trailer brake outlet 24,
- a return line 26 to reservoir or chamber of tractor hydraulic system 30;
- a flow connection 28 to hitch control valve also known as Hydraulic control valve 32; and
e. Fluid return line to hydraulic pump 10.
Disadvantages with the prior art
According to AIS-043 for the combination of agricultural tractor and trailer, the hydraulic or pneumatic or coupled power brake system has become a mandatory accessory. At present, this requires a separate trailer brake control valve. Presently, there is no indigenous manufacturer for supplying such trailer brake control valves. Moreover, the imported trailer brakes control valves are very costly. Moreover, today's trailer market is very price-sensitive. Therefore, there is a need in the market for reducing the cost of trailer brake systems while meeting statutory compliance.
In the presently available trailer brake system, the trailer brake is actuated simultaneously by actuating the tractor brake. This braking action sometimes leads to trailer getting locked and thus the trailer operator faces great difficulties while reversing the tractor towing a trailer. The synchronization

of the tractor and the trailer braking system is done by adjusting the linkage connected to the brake-pedal. Due to "wear & tear of the tractor brake liners, frequent adjustment is necessary and all operators may not feel comfortable with this tractor-trailer synchronization.
However, to comply with the AIS-043 standard as well as to meet the demands of the price-sensitive tractor market more economically, the present invention successfully offers to provide a new trailer brake system, which completely obviates the need for a separate trailer brake control valve.
The trailer brake system in accordance with the present invention can be effectively operated by means of the existing tractor hydraulic system and that too without compromising with the performance thereof.
Objects of the Invention
The object of the present invention is to provide a cost-effective trailer brake system complying with AIS-043 standard.
An object of the present invention is to provide a trailer brake system
r
operable via a single control actuated from operator's driving seat.
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A further object of the present invention is to provide a trailer brake operated with comfort and with improved efficiency by the operator.
Another object of the present invention is to provide a trailer brake system which has less components/sub-assemblies.

Yet another object of the present invention is to actuate trailer brake by an already available hitch control valve.
Still further object of the present invention is to provide a trailer brake system, which reduces the power-loss' for the operation thereof.
Yet further object of the present invention is to provide a trailer brake system which can selectively be activated and deactivated by the operator.
A further object of the present invention is to provide a trailer brake system which makes synchronization of the tractor and the trailer braking system much simpler.
Summary of the Invention
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In accordance with the present invention, there is provided a hydraulic trailer
brake system operated by the tractor's own hydraulic system and that too
without using a separate trailer brake control valve. This novel trailer brake
system includes a hydraulic control valve equipped with an isolating valve
either for synchronizing the tractor and trailer brake systems during trailer
brake operation or for implement operation.
Typically, the tractor brake system comprises a hydraulic pump; a brake pedal; a draft lever; tractor's own hydraulic system including a hydraulic control valve, a combination of isolating valve and shut-off valve, a draft plunger; and a plurality of linkages for connecting and actuating the brake pedal, the draft plunger, the draft lever and the hydraulic control valve

Typically, the tractor brake system comprises a draft plunger operating linkage for connecting the brake pedal to the draft plunger for actuation thereof.
Typically, the tractor brake system comprises a linkage between the draft plunger and the hydraulic control valve for adjusting a gap configured between the linkage and the hydraulic control valve for facilitating the synchronization of the tractor and trailer brake systems.
Typically, the tractor brake system comprises a draft lever actuation linkage actuated by the operator using the draft lever for adjusting the gap for activating or deactivating trailer brake operation.
Typically, the trailer braking system is exclusively operated using the hydraulic control valve on priority by closing the isolating valve by the operator to completely deactivate the tractor implement operation and by supplying the hydraulic fluid at a predetermined pressure.
Typically, the shut-off valve is provided for selection by the operator to operate either the trailer brake system, or tractor implement via a respective fluid outlet to the trailer brake system and the tractor implement.
Brief Description of the Accompanying Drawings
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The present invention will be briefly described with reference to the
accompanying drawings, which include:

Figure 1 shows a conventional trailer braking system, in which a separate hydraulic trailer brake control valve 20 is used for the trailer braking operation.
Figure 2 shows a trailer braking system in accordance with the present invention, which is operated by the hydraulic control valve 32 of the tractor hydraulic system, thereby obviating the need for a dedicated or separate trailer brake control valve 20 for trailer braking operation (as shown in figure 1).
Detailed Description of the Accompanying Drawings
The trailer braking system in accordance with the present invention effectively operates without a separate trailer brake control valve. This will now be described in more details with reference to the accompanying drawings, without limiting the scope and ambit of the present disclosure in any way.
Figure 1 shows the presently available trailer braking system, in which separate trailer brake control valves 20 is used for trailer braking operation. The overall trailer brake system consists of the following components/sub-assemblies, i.e. a hydraulic pump 10, a brake pedal 14, a trailer brake control valve 20 and a tractor hydraulic system 30. These components and/or subassemblies are connected to each other in the manner described below:
The trailer brake control valve 20 includes a trailer brake valve spool 22, a trailer brake outlet 24 leading to trailer brakes and a return line 26 leading to the chamber of the tractor hydraulic system 30. The tractor hydraulic system 30 includes a hydraulic control valve 32, a hydraulic control valve spool 34,

a draft plunger 36 and an isolating valve 46. The hydraulic pump 10 is hydraulically connected to the trailer brake valve 20 by a suitable line. Similarly, a return line leads from the tractor hydraulic system 30 to the hydraulic pump 10. Further, the trailer brake valve 20 is hydraulically connected to the hydraulic control valve 32 of the tractor hydraulic system 30 via a line 28 and a return line 26 is also directly led to the chamber of the tractor hydraulic system 30. A trailer brake valve operating linkage 16 is also provided between the brake pedal 14 and the trailer brake valve spool 22. A draft lever actuation linkage 18 is provided between the draft lever and the hydraulic control valve 32. Similarly, another linkage 18A is provided between the draft plunger 36 and the hydraulic control valve 32.
Braking Operation: The tractor operator operates the brake pedal 14, by which the braking action is transferred to the trailer brake valve spool 22 via trailer brake valve operating linkage 16, which hydraulically actuates the trailer brakes via the trailer brake outlet 24. At the same time, the hydraulic pump 10 and the tractor hydraulic system 30 are also suitably interconnected to obtain the desired tractor braking action. However, the above conventional arrangement of a combination of tractor-trailer hydraulic brake system requires a separate trailer brake control valve, which is costly (imported) and this also increases the number of components and thereby the maintenance and oil-seal costs are also higher.
Figure 2 shows a trailer brake system in accordance with the present invention, which uses the tractor's own hydraulic system 30 for operating trailer brakes as well. Therefore, the new arrangement obviates the need for a separate trailer brake control valve 20 (as shown in Figure 1) to be provided for trailer brake operation. In this arrangement, brake pedal 14 is

connected to draft plunger 36 via a draft plunger operating linkage 16A. After closing the isolating valve 46 and by operating the brake pedal 14, the brake pedal actuation is transferred to draft plunger 36 via draft plunger operating linkage 16A. This in turn is transferred to hydraulic control valve spool 34 via draft plunger-hydraulic control valve linkage 18A. The trailer operator can adjust the gap 38 between trailer brake actuating linkage 18A and the hydraulic control valve spool 34, which supplies fluid to either the trailer brake outlet 42 or to the tractor implement, e.g. a tipping trailer cylinder outlet 44. A shut-off valve 40 is suitably located for facilitating the operator to make one of the above two choices (42, 44) from his seat itself. By adjusting the gap 38, the hydraulic pressure required for the desired trailer braking action can be developed in the hydraulic control valve 32, which operates in either of the above-mentioned two modes. For example, when this gap 38 is reduced by pressing the brake pedal 14, the hydraulic control valve spool 34 is pushed inside the hydraulic control valve 32, thereby pushing the fluid both via trailer brake outlet line 42 and tipping trailer outlet line 44. By.shutting-off supply to tipping trailer outlet 44 by closing the shut-off valve 40, the fluid pressure to the trailer brake line is substantially increased for stronger braking action. Conversely, when the gap 38 is increased, the hydraulic control valve spool 34 is retracted inside the chamber of the tractor hydraulic'system 30, thereby pulling fluid back from trailer brake line or tipping trailer cylinders to the chamber of the tractor hydraulic system 30, thereby rendering trailer brakes idle.
Description of the Invention
In the conventional method of using a separate trailer brake control valve, it is preferred to use a tractor hitch control valve for lifting and lowering

implements, i.e. braking operation is given a priority over the use of a hitch control valve for reasons of safety. Presently, a separate trailer brake valve is used in the conventional trailer braking systems. While reversing the tractor towing a trailer, sometimes tractor brake is required to be applied only on one side of the tractor while negotiating a reversing action of the tractor-trailer combination. This sometimes leads to trailer getting locked and thus the trailer operator faces problems while reversing the tractor-trailer combination.
However, in accordance with the present invention, the isolating valve 46 is provided with the hydraulic control valve 32. This isolating valve 46 is closed on priority for exclusively operating the trailer braking system. Normally, a draft plunger 36 is triggered by actuating a cable or draft plunger operating linkage 16A connected to the tractor brake pedal 14 and by turning the draft lever 12, the hydraulic control spool 34 is operated. The synchronization of the tractor and the trailer braking systems is done by adjusting the gap 38 between draft plunger-hydraulic control valve linkage 18A and the hydraulic control spool 34 by actuating the draft lever actuating linkage 18 by suitably turning or moving the draft lever 12. This gap 38 can be adjusted as per the comfort level of the operator for achieving a better, easier and more efficient synchronization of the tractor and the trailer braking systems. Thus, in accordance with the present invention, the tractor's own hydraulic system can be used and its hydraulic control valve 32 fitted with an isolating valve 46, can be effectively used for synchronizing the tractor and trailer braking systems in a much simpler manner. With this improved trailer brake system, the trailer brakes can also be deactivated by increasing the gap 38 between the draft plunger-hydraulic control valve linkage 18A and the hydraulic control spool 34 of the tractor

hydraulic system 30 by suitably moving the draft lever 12. This eliminates the need for a separate trailer brake valve 20 (as shown in Figure 1), which is presently an imported component (adding cost). By eliminating the presently used separate brake control valve 20, the power-loss is also reduced and the production cost of the new trailer brake system is brought to a substantially lower level than the presently available "Trailer Braking system" shown in Figure. 1. Technical advantages and economic significance
1. This offers a major breakthrough to comply with AIS -043 Standard without any substantial cost impact, because the new trailer braking system meets the requirements under this standard.
2. No importation of control valves required from foreign manufacturers, like - Bosch or SAFIM and thereby saving approx. Rs. 8000 to 10000 per valve of foreign exchange (at present).
3. Since operating pressure of the new trailer brake system is 170-200 bar as against 135-150 bar for imported control valve, the trailer brake performance is improved.
4. It can be implemented on all tractor models, with minor changes in bracket and linkage design.
5. Auto lifting of the implements can be actuated after pressing the brake pedal, which may facilitate turning the tractor along with implement on the field.

6. Tractor - trailer braking synchronization can be achieved by adjusting the draft lever to a desired position.
7. While reversing trailer in the new trailer braking system, trailer brakes are deactivated by keeping draft lever in down-most position. This obviates the problems of locking of trailer wheels by trailer brakes actuation when a tractor side brake is applied, which makes it very difficult to reverse the trailer.
It should be understood that the embodiment described herein is merely a preferred embodiment of the present invention. Therefore, the person skilled in the art may practice it with any modification within the spirit and ambit or scope of the embodiment as described in accordance with the present invention. Accordingly, this illustrative exemplary embodiment should not be construed as limiting the scope of the present invention. It is to be understood that the phraseology or terminology employed in this specification is merely for the purpose of description and not for limiting the scope thereof. The exemplary embodiment described in this specification is intended merely to provide an understanding of various manners in which this embodiment may be used and to further enable the skilled person in the relevant art to practice this invention.
The description provided herein is purely by way of example and illustration. Various features and advantageous details are explained with Reference to this non-limiting embodiment in the above description in accordance with the present invention. The descriptions of well-known components and manufacturing and processing techniques are consciously omitted in this specification, so as not to unnecessarily obscure the specification.

While considerable emphasis has been placed on the specific features of the preferred embodiment described here, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiments without departing from the principles of the invention. These and other changes in the preferred embodiment of the invention will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

LIST OF REFERENCE NUMERALS
Draft lever 12
Brake pedal 14
Trailer brake valve operating linkage 16
Draft plunger operating linkage 16A
Draft lever actuation linkage 18
Draft plunger-hydraulic control valve linkage 18A
Trailer brake valve 20
Brake valve spool 22
Trailer brake outlet 24
Return line 26
Line to hydraulic control valve 28
Tractor hydraulic system 30
Hydraulic control valve 32
Hydraulic control spool 34
Draft plunger 36
Adjustable gap 38
Shut-off valve 40
Trailer brake outlet 42
Implement, e.g. tipping trailer cylinder outlet 44
Isolating valve 46

We claim:
1. A hydraulic trailer brake system operated by tractor's own hydraulic
system and without a separate trailer brake control valve, said trailer
brake system includes a hydraulic control valve equipped with an isolating valve for prioritizing of fluid flow to trailer brake outlet.
2. Trailer brake system as claimed in claim 1, wherein said tractor brake
system comprises: a hydraulic pump; a brake pedal; a draft lever;
tractor's own hydraulic system including a hydraulic control valve, a
combination of isolating valve and shut-off valve, a draft plunger; and a
plurality of linkages for connecting and actuating said brake pedal, said
draft plunger, said draft lever and said hydraulic control valve.
3. Trailer brake system as claimed in claims 1 to 2, wherein said tractor brake system comprises a draft plunger operating linkage for connecting the brake pedal to said draft plunger for actuation thereof.
4. Trailer brake system as claimed in claims 1 to 3, wherein said tractor brake system comprises a linkage between said draft plunger and said hydraulic control valve for adjusting a gap configured between said
linkages and said hydraulic control valve for facilitating synchronization of the tractor and trailer brake systems.
5. Trailer brake system as claimed in claims 1 to 4, wherein said tractor
brake system comprises a draft lever actuation linkage actuated by
operator using said draft lever for adjusting said gap for synchronization
and activating or deactivating trailer brake operation.

6. Trailer brake system as claimed in claims 1 to 5, wherein said trailer braking system is exclusively operated using said hydraulic control valve on priority by closing said isolating valve by the operator to completely deactivate the tractor implement operation and by supplying the hydraulic fluid at a predetermined pressure.
7. Trailer brake system as claimed in claims 1 to 6, wherein said shut-off valve is provided for selection by the operator to operate either the trailer brake system or tractor implement via a respective fluid outlet to said trailer brake system and said tractor implement.