Patent Description:
Typically problems arise when the moisture in warm air entering a cab condenses on cab windows and other cold surfaces affecting visibility. Various attempts have been made to try to ease this problem by heating the windows, either by blowing hot air onto the window glass or by heating the windows directly. Direct heating of windows has proved expensive to implement and compromises visibility whilst the use of hot air also heats the cab resulting in the cab becoming uncomfortable for the operator. Attempts have also be made to use air conditioning systems for cabs to remove the moisture but this has also proved expensive to implement and is temperature dependant.

Each of documents <CIT>, <CIT> and <CIT> discloses an apparatus for heating an operator's cab of a vehicle or machine according to the precharacterizing portion of claim <NUM>. In each case, external air and air being recirculated from the cab are passed through a heat exchanger upstream of a cab air heating unit such that moisture in the recirculating air is condensed.

It is an object of the present invention to provide an apparatus for heating an operator's cab of a vehicle or machine, assuring a removal of moisture from warm air prior to the warm air entering the cab which is relatively cheap to implement and also efficient in operation.

In accordance with the present invention there is provided an apparatus for heating an operator's cab of a vehicle or machine and a method of operating said apparatus as set out in the independent claims <NUM> and <NUM>. Preferred embodiments of the present invention are laid down in the appended dependent claims.

In one aspect, the invention provides an apparatus for heating an operator's cab of a vehicle or machine, the apparatus comprising a cab air heating unit, a tr cab air duct for conducting air toward an interior region of the cab from the cab air heating unit, and an external air intake for conducting external air to an inlet side of the cab air heating unit, the external air intake including a condensing conduit extending through at least part of the cab air duct.

In use, external air passing through the condensing conduit cools the conduit to a temperature below that of the, usually warm, air flowing through the cab air duct, so that moisture in the warm air condenses on the exterior surface of the conduit before entering the cab. Such an arrangement provides a particularly simple but efficient way to remove moisture from the warm air before it enters the cab. The warm air may be air heated by the cab air heating unit which is passed through the cab air duct and/or it may be air from within the cab recirculated through the cab air duct and back into the cab.

The apparatus may comprise a blower arrangement for drawing external air in through the external air intake and moving air through the cab air heating unit and the cab air duct toward the interior region of the cab.

The external air intake may be a moisture removal external air intake and the apparatus may have a further external air intake which does not pass through the cab air duct and an air flow valve operable to enable external air to be selectively drawn through the cab air heating unit from the moisture removal external air intake and/or from the further external air intake.

By operation of the air flow valve, the apparatus can be operated in a moisture removal mode in which external air is directed into the heating unit through the condensing conduit or in a non-moisture removal mode in which external air is directed into the heating unit through the further external air intake. The non-moisture removal mode might be adopted when the external temperature is very low so that the cold air does not limit the heating capacity of the heating apparatus excessively. The air flow valve could also be operated in a mixed-mode in which some external air is drawn in through both the moisture removal external air intake and the further external air intake.

The air flow valve may be manually actuatable or it may be automatically actuatable. The air flow valve may be controlled automatically in response to at least one predetermined operating parameter, such as any one or more of the following: temperature of the condensing conduit, outside temperature i.e. the temperature external of the cab, temperature in the interior of the cab, and humidity of the interior of the cab.

The apparatus may be configured to remove moisture from air recirculated from the interior region of the operator's cab, the apparatus having a recirculation duct through which air from within the interior region of the cab can be drawn to be mixed with external air drawn in through the external air intake for passage back to the cab through the cab air duct. The flow of external air and/or recirculated air through the cab air heating unit may be regulated by the air flow valve and/or by a further air flow valve. A recirculation air duct through which air drawn from within the cab can flow to the cab air heating unit may be connected with an input side of the cab air heating unit downstream of the air flow valve and a recirculation valve provided to direct either recirculated air or external air or a mixture of the two through the cab air heating unit.

The apparatus may include at least one air filter for filtering external air drawn through the moisture removal air intake duct and/or the further external air intake duct.

The apparatus may be part of a HVAC system.

The apparatus may have a condensate collection and removal system for collecting and removing condensate which forms on a surface of the condensing conduit in use. The condensate collection and removal system may be configured to collect condensate which forms on a surface of the condensing conduit in use and remove the condensate to the outside of the cab air duct. The condensate collection and removal system may comprise a condensate duct extending to the exterior of the cab air duct.

At least part of the condensing conduit may be inclined to the horizontal and the condensate collection and removal system may be configured such that condensate forming on at least part of a surface of the condensing conduit flows downwardly towards the condensate collection and removal system.

According to a further aspect of the invention, there is provided a method of operating an apparatus according to the previously mentioned aspect of the invention, the method comprising: operating the apparatus in a moisture removal mode in which external air is drawn into the cab air heating unit through the moisture removal external air intake whilst air heated by the cab air heating unit is passed through the cab air duct, such that the temperature of the condensing conduit is lowered below that of the heated air to cause moisture in the heated air to condense onto the condensing conduit.

Where the apparatus has a further external air intake and an air flow valve, the method may comprise selectively operating the apparatus in a non-moisture removal mode in which external air is drawn into the cab air heating unit through the further external air intake whilst air heated by the cab air heating unit is passed through the cab air duct.

Referring to <FIG> this shows an agricultural tractor <NUM> having wheels <NUM> and <NUM>, a chassis <NUM> and a cab <NUM>. The tractor is fitted with apparatus <NUM> for removing moisture from air before it is distributed into the cab.

An embodiment of the apparatus <NUM> for removing moisture from air before it is distributed into the cab and which is part of a heating apparatus for the cab is shown diagrammatically in <FIG>. The apparatus includes a cab air heating unit <NUM> and a cab air duct <NUM> along which air (indicated by arrows X) heated by the cab air heating unit <NUM> is delivered into the cab <NUM> via an outlet <NUM>. The apparatus <NUM> includes two external air intakes through which external air (i.e. air external to the cab) can be drawn to pass through the cab air heating unit <NUM> and the cab air duct <NUM>. A first external air intake <NUM> will be referred to as a moisture removal external air intake and includes a condensing conduit <NUM>, part of which passes through the cab air duct <NUM>. A second external air intake <NUM> will be referred to as a further external air intake and does not pass through the cab air duct.

The moisture removal external air intake <NUM> and the further external air intake <NUM> are fluidly connected with an inlet side of a fan (blower) <NUM> forming part of the cab air heating unit <NUM> by a three-way air flow valve <NUM>. The air flow valve <NUM> is operative in use to selectively connect the further external air intake <NUM> to the inlet side of the fan as shown in <FIG> or the moisture removal external air intake <NUM> to the inlet side of the fan as shown in <FIG>.

The apparatus <NUM> can be operated in a moisture removal mode as illustrated in <FIG>. In this mode, the air flow valve <NUM> is moved to position 23a and external air is drawn into the cab air heating unit <NUM> through the moisture removal external air intake <NUM> as indicated by the arrows Y. In this mode of operation, the external air Y passing through the moisture removal external air intake <NUM> will tend to reduce the temperature of the external surface 20a of the condensing conduit <NUM> below that of the heated air X surrounding it in the cab air duct <NUM>. The external surface of the conduit will therefore act as a condensation surface on which moisture in the heated air on its way to the cab <NUM> condenses before reaching the cab <NUM>.

The apparatus <NUM> may also include a condensate collection and removal system for collecting condensate which forms on the outer surface of the conduit <NUM> and removing the condensate from the cab air duct <NUM>. In the present embodiment, part of the cab air duct <NUM> is aligned generally vertically and a portion of the conduit <NUM> within the cab air duct is also aligned vertically. The condensate collection and removal system includes a condensate duct <NUM> at a lower end of the vertical portion of the conduit through which condensate can flow under the influence of gravity out of the cab air duct <NUM>. As illustrated, the condensate duct <NUM> may be inclined downwardly and may extend externally of the cab <NUM> so that condensate can be dispensed to a suitable drainage point and into the external environment. Alternatively, the condensate duct <NUM> could direct condensate to a condensate reservoir (e.g., a tank or bottle) which can be periodically emptied. The condensate collection and removal system could include a trough which encircles the lower end of the conduit <NUM> arranged so that condensate can flow down the exterior surface 20a of the conduit into the trough which feeds into the condensate duct <NUM>. It will be appreciated that the cab air duct <NUM> and the conduit <NUM> need not be aligned vertically but could be inclined at an alternative angle to the horizontal, provided condensate forming on the exterior surface 20a of the conduit <NUM> tends to flow downwardly towards the condensate collection and removal system.

The apparatus can alternatively be operated in a non-moisture removal mode as illustrated in <FIG>. In this mode of operation, the air flow valve <NUM> is placed in position 23b and external air is drawn into the cab air heating unit <NUM> through the further external air intake <NUM> as indicated by the arrows Z. In the non-moisture removal mode the apparatus <NUM> acts in a largely conventional manner to introduce heated external air into the cab <NUM>. The apparatus <NUM> may be operated in the non-moisture removal mode when moisture removal in not required and/or when the external temperature is very low so as not to unduly compromise the capacity of the apparatus <NUM> to heat the cab <NUM>.

The apparatus <NUM> can also be operated in a mixed-mode in which the air flow valve <NUM> is configured to allow external air to be drawn though both of the external air intakes <NUM>, <NUM> at the same time.

The air flow valve <NUM> may be controlled manually by the operator to switch between the moisture removal and non-moisture removal modes as required. Alternatively, the airflow valve may be controlled automatically in response to at least one predetermined operating parameter. This might include any one or more of the following: the temperature of the condensing conduit (this could be the temperature of the exterior surface of the conduit in this embodiment), outside temperature (i.e. the temperature external of the cab), temperature in the interior of the cab, and humidity of the interior of the cab.

As illustrated in <FIG>, the apparatus <NUM> may also have a recirculation air intake <NUM> through which air from within the cab <NUM> can be recirculated back through the cab air heating unit <NUM> and cab air duct <NUM>. In the embodiment illustrated, the recirculation air intake <NUM> comprises a recirculation air duct through which air drawn from within the cab <NUM> (as indicated by the arrows W) flows to the cab air heating unit <NUM> is fluidly connected with an input side of the fan <NUM> downstream of the air flow valve <NUM>. Although not illustrated, a recirculation air valve arrangement can be provided to direct either recirculated air or external air or a mixture of the two through the cab air heater unit <NUM>. The recirculation air valve may be operable to regulate the proportions of external and recirculated air in the mixture.

This recirculating air arrangement is beneficial since moisture from within the cab <NUM> (e.g. from wet boots and/or clothing etc.) can be removed. Usually at least some external air Y will be drawn through the moisture removal external air intake <NUM> to mix with the recirculated air W and the mixed air heated as it passes through the cab air heating unit <NUM>. However, where the air temperature within the cab <NUM> is sufficiently high and the external air is sufficient cold to create a condensation point on the condensing conduit <NUM> within the cab air duct <NUM>, moisture can be removed from recirculated air W without using the cab air heating unit <NUM> to heat the recirculated air W.

The apparatus <NUM> may be part of a HVAC system.

The apparatus <NUM> may include at least one air filter for filtering external air drawn through the moisture removal air intake duct and/or the further external air intake duct.

The present invention provides an arrangement for removing moisture from warm air, which may be air heated by an air heating apparatus or already warm air recirculated from the within the cab, before it is distributed into an operator's cab which does not require expensive parts and can thus be implemented on lower specification vehicles and machines without significantly impacting costs.

Claim 1:
Apparatus (<NUM>) for heating an operator's cab (<NUM>) of a vehicle or machine (<NUM>), the apparatus (<NUM>) comprising a cab air heating unit (<NUM>), a cab air duct (<NUM>) for conducting air toward an interior region of the cab (<NUM>) from the cab air heating unit (<NUM>), and an external air intake (<NUM>) for conducting external air to an inlet side of the cab air heating unit (<NUM>), characterized in that the external air intake (<NUM>) includes a condensing conduit (<NUM>) extending through at least part of the cab air duct (<NUM>).