The present invention relates to a hydrocopter. A hydrocopter is a vehicle by which it is possible to move over water, particularly in an archipelago, under difficult conditions, e.g., during the thaw. The waterproof hull of the hydrocopter bears against the underlying surface, such as snow, ice, slush or water, and is driven forward by an air propulsion unit mounted on top of the hull. The problem with the current hydrocopters is that they are very difficult to steer and uncomfortable to ride in. Division of the hydrocopter hull into two portions connected to each other by a hinge joint, in accordance with the invention, makes it possible to use frame steering. This new structure makes the hydrocopter easier to handle. The invention provides a vehicle which has a small turning radius and which is steerable even at very slow speeds.

FIELD OF THE INVENTION 
The present invention relates to a hydrocopter. A hydrocopter is a vehicle 
by which it is possible to move over water, particularly in an 
archipelago, under difficult conditions, e.g. during the thaw. The 
waterproof hull of the hydrocopter bears against the underlying surface, 
such as snow, ice, slush or water, and is driven forward by a propeller 
mounted on top of the hull. 
BACKGROUND DISCUSSION 
At present, there are two different types of hydrocopters available, both 
consisting of a hull driven by a motor positioned behind the hull and 
provided with a propeller. These hydrocopters are steered by means of air 
rudders positioned around the propeller. One of the hydrocopters available 
on the market is, in addition, provided with resilient wheels and skis on 
both sides of the hull, which makes the hydrocopter more comfortable to 
ride in on solid ice or snow. 
The problem with the current hydrocopters is that they are very difficult 
to steer and uncomfortable to ride in. The hydrocopters are steered by 
turning the air rudders, whereafter the hydrocopter turns in a wide curve 
by the action of the resulting changes in the air resistance. A relatively 
high speed is required in order to produce the steering effect. In 
addition, the turning radius of the vehicle is large. The conventional 
hydrocopter is, moreover, difficult to handle under difficult ice 
conditions. It requires a relatively level underlying surface and cannot, 
for example, climb over a high edge of ice, as the center of gravity of 
the hydrocopter is situated so far in the back that, at slow speeds, the 
motor is not capable of bringing the center of gravity over the edge of 
ice. 
SUMMARY OF THE INVENTION 
The problems associated with the existing solutions can be avoided with the 
present invention. 
A solution to the above-mentioned problems is provided by the present 
invention, which is characterized by what is disclosed in the appended 
claims. 
The hydrocopter according to the present invention is characterized in that 
its hull comprises a bow and a stern portion, connected to each other by a 
hinge joint. 
The invention is based on the need for a vehicle which is easier to drive 
on an uneven surface and which retains its steerability even at slow 
speeds. 
The hydrocopter according to the present invention has several significant 
advantages over the prior art. In the case of a hydrocopter whose hull is 
divided into two separate portions connected to each other by a hinge 
joint, it is possible to use frame steering; this makes the hydrocopter 
considerably easier to steer. Such a vehicle is also more silent, since 
the motor can be positioned in a part of the hull which is separate from 
the compartment reserved for the driver and for transport. The bow portion 
can therefore be more effectively isolated from the vibrations and noise 
produced by the motor. 
If the hydrocopter is, in addition, supported by pontoons connected to the 
hull pivotedly and resiliently, the riding comfort and steerability are 
further increased. In a solution according to the present invention, the 
pontoons absorb most of the bumps and vibrations which the hydrocopter is 
subjected to. A hydrocopter which is constructed according to the present 
invention is also easier to drive on an uneven surface or on a surface 
with sudden, relatively great differences in altitude. The parts of the 
hydrocopter that are in contact with the underlying surface consist of 
four pontoons arranged in pairs. The pontoons can be freely turned in 
relation to the transverse axis of their fixing points. This allows either 
one pontoon at a time or a pair of pontoons to climb over an edge of ice, 
for example, even at a very slow speed. 
Division of the hydrocopter hull into two portions connected to each other 
by a hinge joint makes it possible to use frame steering. It also allows 
the vehicle to be supported by float structures, such as pontoons. 
This new structure makes the hydrocopter according to the present invention 
easier to handle than the solutions of the prior art. The invention 
provides a vehicle which has a small turning radius and which is steerable 
even at very slow speeds. This is important, for instance, in areas where 
there is pack-ice or where there are many or great differences in 
altitude. 
A hydrocopter according to the present invention can move on a clearly more 
difficult and uneven surface than the known solutions.

DETAILED DESCRIPTION OF THE DRAWINGS 
The figures illustrated an embodiment of the hydrocopter according to the 
present invention. 
The hydrocopter comprises a hull, which is divided into a bow and a stern 
portion 1, 2 connected to each other by means of a hinge joint 3. In 
addition, the hull comprises pontoons 4, 5, 6, 7, which are provided in 
pairs at the bow and stern portions, which in turn comprise waterproof 
bottom portions 8, 9 and superstructures 10, 11 to cover the motor 
compartment and the compartment reserved for the driver and for transport. 
The hydrocopter is mainly supported by the pontoons, and thus its 
friction-generating bottom surface is smaller than in the hydrocopters of 
the prior art. 
The bow and stern portions 1, 2 are provided with frames of steel tube 12, 
13, to which the connecting hinge joint 3 is secured. According to FIG. 4, 
the hinge joint 3 comprises substantially vertical rods 14, 15 provided 
with bushings 16, 17 and lock plates 18, 19, 20, 21. The lock plates are 
provided with openings and they are arranged in pairs in such a way that 
the distance between the two plates in a pair corresponds to the length of 
the bushing. According to FIGS. 5 and 6, the bushing 16, 17 comprises a 
housing 22 wherein a piece of resilient rubber 23 has been cast. The 
rubber secures a tube 24 to the housing. The bushings 16, 17, and the lock 
plates 18, 19, 20, 21, provided with openings, are connected to each other 
by pin members 25, 26, e.g. bolts with nuts. The pin member is inserted 
through the opening in the steel plate disposed at one end of the bushing 
into the tube inside the bushing so that it finally comes out through the 
opening in the steel plate disposed at the other end of the bushing. 
Movement of the pin member in the longitudinal direction of the hinge 
joint is prevented, for example, by nuts 27, 28 or keys. This provides a 
connecting hinge joint with two joining points. 
The rubber 23 in the bushings 16, 17 absorbs vibrations transmitted to the 
tube 24 of the hinge joint 3 from the steel tube structure 12, 13. A hinge 
joint with this structure allows the bow and stern portions to pivot about 
the joint in horizontal direction, but prevents a turn in the vertical 
direction of the joint. 
The hydrocopter is steered by turning the bow and stern portions 1, 2 about 
the hinge joint 3 in opposite directions; so-called frame steering is thus 
used. The bow and stern portions are turned, for example, by means of a 
hydraulic cylinder 29 the length of which is telescopically increased or 
reduced. Such a cylinder is provided in both portions of the hull: its 
mobile end is pivotedly secured to the bow portion, and the cylinder with 
its control unit is connected to the stern portion. The driver of the 
hydrocopter indicates in which direction the vehicle shall turn, 
whereafter the cylinder makes the two portions of the vehicle pivot about 
the hinge joint by changing its length, and the bow portion will indicate 
the new course. 
The hydrocopter according to the invention is provided with pontoons 4, 5, 
6, 7 at the bow and stern portions 1, 2. The hull of the hydrocopter bears 
against these pontoons. The pontoons are long and narrow, and they are 
disposed along the sides of the hull. The pontoons are pivotedly connected 
to supporting arms 30, 31, 32, 33, by which they are resiliently connected 
to either portion the hull. The hinge joint between a supporting arm and a 
pontoon is similar to the construction provided between the bow and stern 
portions. The pontoons move around the transverse axis of the joint at a 
substantially vertical plane. The turning movements of the pontoons are 
restricted by rods 34, 35, 36, 37 which are pivotedly connected to both 
the front end of a pontoon and the front end of the bow or stern portion 
1, 2. 
The invention is not limited to the embodiment described above, but a 
number of modifications can be made within the scope of the inventive 
concept disclosed in the appended claims.