FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION Work vehicle cabin roof
APPLICANTS
Mahindra & Mahindra Ltd, Gateway Building, Apollo Bunder, Mumbai 400001,
Maharashtra, India, an Indian Company
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
This invention relates to a work vehicle cabin roof.
BACKGROUND OF THE INVENTION
Work vehicles or off-road vehicles such as agricultural and industrial tractors, construction equipments or earth movers generally operate in very adverse environmental and working conditions, for example warm or cold weather and dusty atmosphere caused by the work being done by the vehicles. The vehicles are run and the various operations of the vehicles are controlled by the operators or drivers of the vehicles from cabins mounted at the top of the vehicles. The cabins comprise an open top glass housing or enclosure for giving the operators good visibility of the work area and surroundings and a roof closing the top thereof. Because the operators are often required to spend long hours operating the vehicles, environment control within the cabins is of utmost importance to reduce health hazards and fatigue to the operators and to give a comfortable working atmosphere to the operators.
The cabins of work vehicles are generally fitted with heating, ventilation and air conditioning (HVAC) systems to provide a controlled atmosphere within the cabins. In some of the cabin designs, the HVAC system is placed above or outside the cabins. This makes maintenance of the HVAC system complicated and assembly of the cabin roof difficult. Typically, the interior side of the cabin roof is assembled and placed in the cabin. After the interior is placed in the cabin, a worker is required to affix the various electrical components and ducting while standing on ladders outside the cabin. This is complicated, tiring, time-consuming and expensive. Frequently, if maintenance is required on the cabin roof, a worker must either open or remove the

cabin roof or climb onto the outside of cabin. This is either dangerous for the worker or damaging to the seal between the roof and cabin.
Stauffer et al teach a cabin roof for an agricultural vehicle comprising an outer roof and a left inner roof, a right inner roof and a headliner affixed within the outer roof. The left inner roof contains a fresh air duct with a fresh air inlet for the HVAC system. The left inner roof also has three light pockets. Each pocket contains a distance or flood light fixture and a light shroud having a top lip and an elongated bottom lip. The right inner roof is similarly designed. The headliner contains a pair of molded conditioned air ducts for transferring conditioned air to several side defrost vents and several front defrost vents. A mirror support bar passes through the left inner roof, headliner and right inner roof. The entire roof is secured to the cabin by bolts. (US 5913566).
Shuttleworth et al teach a two piece molded roof structure for a work vehicle cabin having an upper roof member mounted to a lower roof member. The lower roof member has a plurality of contours and apertures for receiving the components of an HVAC system and for defining air passages. When the upper and lower roof members are joined together, discrete air passages are formed between the roof members. The roof structure includes fresh and recirculated air intakes communicating via an uncirculated air duct and with an HVAC core housed in an HVAC core chamber. Filters are mounted in the air intakes. One or more blowers communicate between the core chamber and a conditioned air duct which has vents communicating with the cabin interior. Air is thus drawn in through the intakes and directed through the

unconditioned air duct to the HVAC core and then the blower expels the air into the conditioned air duct and into the vehicle cabin (US 6780097).
Hill et al teach a tractor cabin roof with integral HVAC air ducts comprising an upper roof member and a lower roof member. The upper roof member includes a top panel, downwardly depending side edges, and a downwardly depending rear edge. The lower roof member includes a central panel, left and right side panels below the central panel, a rear panel below the central panel, sloping side walls, and a sloping rear wall. Conditioned air ducts are provided between the upper roof member and the left and right side panels, with conditioned air outlet apertures in the sloping side walls. An evaporator and a heater are mounted on the rear panel, with an air mixing chamber to the rear and a conditioned air discharge cavity in the front. Recirculating air intake apertures are provided where the sloping rear wall joins the rear panel. A pair of blowers move conditioned air from the conditioned air chamber into the conditioned air ducts. The flow of conditioned air crosses over the recirculating air in a figure eight pattern (US 7334834).
Keen teaches a roof enclosed HVAC system for a vehicle cabin comprising a roof upper panel, a roof lower panel, a fresh air duct communicated with a fresh air inlet exposed to an exterior of the cabin, a recirculation air duct communicated with a recirculation air inlet exposed to an interior of the cabin, and a conditioned air duct communicated with an air outlet exposed to the interior of the cabin. An HVAC system is mounted between the roof upper and lower panels. The HVAC system includes a fan unit, a heater unit and an evaporator unit. The heater and evaporator units are concentrically arranged around and surrounding the fan unit. The fan unit

draws air from the fresh air duct and the recirculation air duct and blows air through the heater unit and an evaporator unit and into conditioned air ducts (US 7726142).
It is quite clear from the above prior art teachings that patents exist in respect of several configurational variations of the work vehicle cabin roof. However, the prior art designs of work vehicle cabin roofs have many problems or disadvantages associated therewith. In general the work vehicle cabin roofs comprise a large number of components and are complex in construction and costly. Accessibility and service ability is also poor making maintenance difficult, tiring and time consuming. There are work vehicle cabin roofs comprising two air inlets which make the design complicated in construction and costly. There are also work vehicle cabin roof designs in which both the fresh air flow chamber and conditioned air flow chamber are on the top surface of the middle roof. This makes the design complicated in construction as the chambers are to be totally sealed to prevent cross flow of the fresh and conditioned air. Cross flow will reduce the cooling efficiency or heating efficiency and reliability of the cabin roofs.
In some other designs of work vehicle cabin roofs, the conditioned air outlets or nozzles opening into the cabin are either at the centre of the roof or at the side of the roof. As a result of this, the conditioned air is not uniformly or evenly distributed in the cabin thereby affecting the cooling effect experienced by the operator in the entire cabin. In certain designs of work vehicle cabin roofs, the condensate being formed in the fresh air flow chamber may drip into the cabin thereby causing discomfort to the operator of the vehicle. The work vehicle cabin roofs are also usually high thereby increasing the size and cost besides making it unwieldy to be handled.

There is thus need for work vehicle cabin roofs which are compact, cost effective and simple in construction, which have excellent accessibility and serviceability or which distribute conditioned air uniformly within the cabin.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention there is provided a work vehicle cabin roof (104) comprising a top roof member (110), a middle roof member (112) and a bottom roof member (109) assembled together and mounted at the open top of the work vehicle cabin, wherein the middle roof member is adapted to be mounted at the open top of the work vehicle cabin and comprises a top fresh air chamber (128) at the top surface thereof defined by an open channel (128a) closed with atleast one detachable top sealing member (128b) and having an air inlet (128c) at one end thereof opening to the atmosphere and fitted with an air filter (136) and an air flapper (140) and further having a conditioned air outlet (128d) at the other end thereof, the open channel further having a push type HVAC system comprising an air blower (126), evaporator unit (116) and heater unit (120) detachably mounted therein with the suction side of the air blower directed towards the air inlet and air flapper and the discharge side of the air blower directed towards the evaporator unit and heater unit, the middle roof member further comprises a bottom conditioned air chamber (124) at the bottom surface thereof defined by an open passage (124a) with open cross air passages (124b), one at each end thereof closed with a detachable bottom sealing member (114) comprising a middle limb (146) and cross limbs (142) (144), one at each end thereof matching with the open passage and open cross passages of the bottom conditioned air chamber at the bottom surface of the middle roof member, respectively, the open

passage is connected to the conditioned air outlet of the top fresh air chamber at the top of the middle roof member at one end thereof and the cross limbs have conditioned air distribution nozzles (130), the middle roof member further comprises a condensate drainage opening (140a) communicating with the open channel in the proximity of the evaporator unit and connected to a drainage pipe (141) extending underneath the bottom surface of the middle roof member and opening to the outside of the cabin and an air recirculation opening (134) and wherein the bottom roof member comprises conditioned air distribution openings (134a) at two opposite sides thereof and air recirculating opening (108) matching with the conditioned air distribution nozzles in the cross limbs of the bottom sealing member and air recirculation opening in the middle roof member, respectively.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig 1 of the drawings accompanying this specification is a schematic exploded view
of a work vehicle cabin roof according to an embodiment of the invention;
Fig 2 of the drawings accompanying this specification is a schematic top view of the middle roof member of the cabin roof of Fig 1 without the top sealing members and the HVAC system;
Fig 3 of the drawings accompanying this specification is a schematic top view of the middle roof member of Fig 2 including the HVAC system but without the top sealing members;

Fig 4 of the drawings accompanying this specification is a schematic top view of the middle roof member of Fig 2 including the top sealing members;
Fig 5 of the drawings accompanying this specification is a schematic bottom view of the middle roof member of Fig 2 without the bottom sealing member; and
Fig 6 of the drawings accompanying this specification is a schematic bottom view of the middle roof member of Fig 2 including the bottom sealing member.
DESCRIPTION OF EMBODIMENTS-OF THE INVENTION The work vehicle cabin roof 104 as illustrated in Fig 1 of the drawing accompanying this specification comprises a top roof 110 (top surface or top plate), a middle roof member 112 (middle plate) and a bottom roof member 109 (bottom surface or bottom plate or inner roof or headliner) assembled together and mounted at the open top end of the work vehicle cabin (not shown). The middle roof member as illustrated in detail in Figs 2 to 6 of the drawings accompanying this specification comprises a top fresh air chamber 128 at the top surface thereof defined by a substantially L-shaped open channel 128a closed with detachable sealing members 128b and having an air inlet 128c at one end thereof opening to the atmosphere and fitted with an air filter 136 and an air flapper 140 and further having a conditioned air outlet 128d at the other end thereof (Figs 2, 3 and 4). The open channel 128a further comprises a push type HVAC system having an air blower 126, evaporator unit 116 and heater unit 120 detachably mounted therein with the suction side of the air blower directed towards the air inlet and air flapper and the discharge side of the air blower directed towards the evaporator unit and heater unit (Fig 3).

The middle roof member further comprises a bottom conditioned air chamber 124 at the bottom surface thereof defined by an open passage 124a extending across the bottom surface of the middle roof and provided with open cross passages 124b, one at each end thereof. The open passage and cross passages are closed with a bottom detachable sealing member 114 comprising a middle limb 146 and cross limbs 142 and 144, one at each end thereof matching with the open passage and open cross passages at the bottom surface of the middle roof member, respectively. (Figs 1, 5 and 6). The open passage is connected to the conditioned air outlet 128d at one end thereof with hose pipes 128 e and 128f and the cross members have conditioned air distribution nozzles 130. The middle roof optionally comprises a locating recess (margin) 106 around the bottom surface periphery thereof matching with the geometry of the top end of the work vehicle cabin for locating the middle roof member against the open top end of the work vehicle cabin. (Figs 5 and 6). 140a is a condensate drainage opening in the open channel and connected to a drainage pipe 141 extending underneath the bottom surface of the middle roof member and extending to the outside of the cabin. 134 is an air recirculation opening in the middle roof member. The bottom roof member 109 comprises conditioned air distribution openings 134a at two opposite sides thereof and air recirculation opening 108 matching with the conditioned air distribution nozzles 130 in the bottom sealing member and air recirculation opening 134 in the middle roof member, respectively (Fig 1).
It is understood that the number of top sealing members can be different. The top sealing member also can be one. The geometry and profile of the top fresh air

chamber and bottom conditioned air chamber can be different. Preferably the middle roof member is rota-moulded with low density polyethylene and the top roof member and bottom roof member are vacuum formed with acrylonitrile butadiene (ABS) and the top sealing members and bottom sealing member are made of mild steel. Preferably the evaporator unit is mounted in the open channel at an inclination of 60±1° with respect to the bottom thereof to reduce the height of the roof and make it compact
The HVAC system in the cabin roof of the invention is operated by the operator of the vehicle with a control panel (not shown) located in the cabin in the usual manner. Depending upon whether the evaporator unit or heater unit is in operation, air being sucked in from the atmosphere through the air inlet 128c and filter 136 by the air blower 126 is thrown to the evaporator unit 116 or the heater unit 120 as the case may be. Air is conditioned by the operation of the evaporator unit or heater unit as the case may be depending upon the mode of operation of the HVAC system. Cold air if the evaporator is in operation or hot air if the heater unit is in operation, flows into the bottom conditioned air chamber 124 at the bottom of the middle roof member 112 via the conditioned air outlet 128d and the conditioned air is distributed in the cabin through the air distribution nozzles 130 in the cross limbs 142, 144 of the bottom sealing member 114 and corresponding conditioned air distribution openings 134a at the two opposite sides of the bottom roof member. Conditioned air entering the cabin from both the sides of the cabin evenly flows towards the centre of the cabin and gets evenly distributed in the cabin. Air in the cabin reenters the air chamber 128 through the air recirculation openings 108 and 134 in the bottom roof member and middle roof member, respectively and is reconditioned and recirculated in the cabin via the

conditioned air outlet 128d and nozzles 130 and openings 134a in the bottom sealing member and bottom roof member, respectively. The air flapper 140 regulates the flow of fresh air into the air chamber 128.
According to the invention both the top fresh air chamber and the bottom conditioned air chamber are integrated into the middle roof member but isolated from each other. Therefore, chances of cross flow of the fresh air and conditioned air are eliminated, conditioned air distribution efficiency and reliability of the cabin roof are improved and construction of the cabin roof is simplified. Due to the integration, the cabin roof is very compact and the surface area for occupation of the cabin roof is reduced. The cabin roof comprises few components and is very cost effective. The condensate being formed is drained outside the cabin thereby eliminating chances for the condensate to drip down into the cabin and cause discomfort to the operator of the vehicle. The bottom conditioned air chamber at the bottom of the middle roof member and provision of conditioned air distribution nozzles and air distribution openings at opposite sides of the bottom sealing member and bottom roof member ensure even and uniform distribution of conditioned air into the cabin. As a result, cooling or warm air is uniformly distributed in the cabin and the cooling or warm effect is uniformly experienced by the operator in the entire cabin.
Tilt mounting of the evaporator unit has the advantage of reducing the height of the roof and making it very compact. Because the top air chamber and bottom conditioned air chamber are closed with detachable top sealing members and bottom sealing member respectively there is easy accessability into the respective chambers

thereby making it easy and convenient to access the respective chambers and service and maintain the respective chambers and the HVAC system.

We claim
1) A work vehicle cabin roof (104) comprising a top roof member (110), a middle roof member (112) and a bottom roof member (109) assembled together and mounted at the open top of the work vehicle cabin, wherein the middle roof member is adapted to be mounted at the open top of the work vehicle cabin and comprises a top fresh air chamber (128) at the top surface thereof defined by an open channel (128a) closed with atleast one detachable top sealing member (128b) and having an air inlet (128c) at one end thereof opening to the atmosphere and fitted with an air filter (136) and an air flapper (140) and further having a conditioned air outlet (128d) at the other end thereof, the open channel further having a push type HVAC system comprising an air blower (126), evaporator unit (116) and heater unit (120) detachably mounted therein with the suction side of the air blower directed towards the air inlet and air flapper and the discharge side of the air blower directed towards the evaporator unit and heater unit, the middle roof member further comprises a bottom conditioned air chamber (124) at the bottom surface thereof defined by an open passage (124a) with open cross air passages (124b), one at each end thereof closed with a detachable bottom sealing member (114) comprising a middle limb (146) and cross limbs (142) (144), one at each end thereof matching with the open passage and open cross passages of the bottom conditioned air chamber at the bottom surface of the middle roof member, respectively, the open passage is connected to the conditioned air outlet of the top fresh air chamber at the top of the middle roof member at one end thereof and the cross limbs have conditioned air distribution nozzles (130) , the middle roof member further comprises a condensate drainage opening (140a) communicating with the open channel in the proximity of the

evaporator unit and connected to a drainage pipe (141) extending underneath the bottom surface of the middle roof member and opening to the outside of the cabin and an air recirculation opening (134) and wherein the bottom roof member comprises conditioned air distribution openings (134a) at two opposite sides thereof and air recirculating opening (108) matching with the conditioned air distribution nozzles in the cross limbs of the bottom sealing member and air recirculation opening in the middle roof member, respectively.
2) The work vehicle cabin roof as claimed in claim 1, wherein the middle roof member comprises a locating recess (106) around the bottom surface periphery thereof matching with the geometry of the open top end of the work vehicle cabin for locating the middle roof member against the open top end of the work vehicle cabin.
3) The work vehicle cabin roof as claimed in claim 1, wherein the open channel is substantially L-shaped and the open passage extends across the bottom surface of the middle roof.
4) The work vehicle cabin roof as claimed in anyone of claims 1 to 3, wherein the middle roof member is rota-moulded with low density polyethylene and the top roof member and bottom roof member are vacuum formed with acrylonitrile butadiene (ABS) and the top sealing member and bottom sealing member are made of mild steel.

5) The work vehicle cabin roof as claimed in anyone of claims 1 to 4, wherein the evaporator unit is mounted in the open channel at an inclination of 60±1° with respect to the bottom thereof.