WO1992016100A1

WO1992016100A1 - Lawn-mower

Info

Publication number: WO1992016100A1
Application number: PCT/FI1992/000073
Authority: WO
Inventors: Ilkka Luukkala
Original assignee: Ilkka Luukkala
Priority date: 1991-03-14
Filing date: 1992-03-16
Publication date: 1992-10-01
Also published as: FI87875C; FI911257A; FI87875B; AU1372292A; FI911257A0

Abstract

The object of the invention is a lawn-mower (10) in which the exhaust gases of the driving internal combustion engine (12) are led under the lawn-mower, into a cutting chamber (13), by means of an exhaust pipe (11). According to the invention, the exhaust gases are led into the cutting chamber in such a way that the end (17) of the exhaust pipe is placed on the cover of the cutting chamber, so that the pressure waves caused by the exhaust gases proceed perpendicularly to the direction of movement of the cut grass clippings.

Description

LAWN-MOWER

The object of the invention is a lawn-mower, in which at least a part of the exhaust gases from the driving internal combustion engine are led under the lawn-mower, into a cutting chamber, by means of an exhaust pipe.

The Swedish published specification no. 320533 discloses the leading of exhaust gases from the internal combustion engine driving a lawn-mower into the cutting chamber of the lawn-mower. The described solution also comprises a fan, which causes the current of air creating the ground effect which lifts the mower off the ground. The hot exhaust gases coming from the internal combustion engine are also led into the cutting chamber, and they thus increase the pressure of the air in the chamber, increasing at the same time the ground effect.

The German published application no. 3021671 also discloses the leading of exhaust gases from the internal combustion engine into the cutting chamber. The aim of the solution described in this publication is to increase the efficiency of the feeding of cut grass into a sack. The idea is that when the exhaust gases are directed from a nozzle to the cutting chamber in the direction of the circumference of a rotary blade, the exhaust gases will intensify the current of air created by the rotary blade. Thus the exhaust gases will increase the velocity of the current of air set in motion by the cutting blade.

A common problem with lawn-mowers is, however, that when cutting wet grass, the wet grass clippings stick to the walls of the cutting chamber inside the mower. This causes the mower to clog after a short time and the work is interrupted every time the wet grass has to be removed. In known lawn-mowers, no solutions have been invented to solve this problem. Even the solutions disclosed in the above publications do not eliminate the tendency of the lawn- mower to become clogged.

The aim of the present invention is to eliminate the above- mentioned problem and to achieve a novel lawn-mower solution. It is characteristic of the lawn-mower relating to the invention that the exhaust gases are led by means of an exhaust pipe to the vicinity of the area of the cutting chamber where the cut grass clippings tend to stick to the wall of the cutting chamber, and the exhaust gases are led from such a direction that the pressure waves caused by the exhaust gases prevent the cut grass clippings from sticking to the wall of the cutting chamber.

In the solution relating to the invention, the pressure wave impulses caused by the exhaust gases prevent the wet grass from sticking to the wall of the cutting chamber. An additional advantage of this solution is that in this case the internal combustion engine driving the mower does not require the usual exhaust silencer at all. The cutting chamber dampens the engine noises even more efficiently than an ordinary silencer.

The exhaust pipe can be led under the lawn-mower, into the cutting chamber, through a loose-fitting hole, thus preventing the heating of the mower frame. The solution relating to the invention can thus also be used in lawn- mowers with plastic frames.

The essential feature of the solution disclosed in the present application is that the exhaust gases from the internal combustion engine are led precisely to that area of the cutting chamber where the cut, wet grass tends to accumulate. The exhaust gases are in addition preferably led from such a direction that any grass that has possibly become stuck to the wall of the chamber will fall off. This direction is most preferably straight down from the top of the chamber, in which case the pressure waves caused by the exhaust gases will cause the mainly horizontal movement of the grass clippings to deviate.

In lawn-mowers, the grass discharge opening is usually at the side of the machine, the rotary blade throws the cut grass clippings out of the cutting chamber. In this case the wet grass clippings tend to stick first to the vicinity of the edges of the discharge opening. When clogging takes place, the essential factor is that when grass begins to stick at some point on the cutting chamber wall, clogging is formed very quickly at this point.

In studying the clogging phenomena it has been found that the most preferable location of the exhaust pipe is near the rearmost edge of the grass discharge opening. Rear edge in this connection refers to that edge of the opening at which the rotary blade arrives last. The shapes of the cutting chambers of different lawn-mowers may obviously vary. Therefore, also the currents in such chambers may differ, and the most preferable location of the exhaust pipe discharge opening may vary.

The invention is described with examples in the following with reference to the drawings, in which

Figure 1 shows the lawn-mower relating to the invention as seen from the side. Figure 2 shows the lawn-mower as seen from above. Figure 3 shows the lawn-mower as seen from below. Figure 4 corresponds to figure -1 and shows a side view of the lawn-mower relating to the invention according to a second embodiment. Figure 5 shows the lawn-mower of figure 4 as seen from below.

The lawn-mower 10 shown in figure 1 is in other respects similar to an ordinary lawn-mower except that the exhaust pipe 11 is installed according to the invention. Figure 1 shows that the exhaust gases from the internal combustion engine 12 driving the lawn-mower are led by means of the exhaust pipe 11 into the cutting chamber 13. The cutting blade 14 rotating in the chamber 13 throws the cut grass sideways out of the chamber 13 through the discharge opening 15.

In the solution shown in figure 1 the blade 14 rotates clockwise as seen from the top of the lawn-mower 10, and thus in figure 1 the blade 14 moves past the discharge opening 15 from right to left. The left edge 16 of the opening 15 is thus the point where the grass clippings tend to accumulate. As figure 1 shows, the exhaust pipe 11 of the internal combustion engine 12 is led into the cutting chamber 13 from above, to the vicinity of the edge 16 of the opening 15. In the figure, the orifice of the exhaust pipe 11 is marked by reference number 17. Thus the pressure waves caused by the exhaust gases directed downwards from above effectively detach any grass clippings sticking to the wall of the chamber 13.

Figure 2 shows the lawn-mower 10 as seen from above. The figure shows that the exhaust pipe 11 extending from the internal combustion engine 12 is led to the upper surface of the cutting chamber 13. The exhaust pipe 11 orifice 17 is thus near the discharge opening 15 of the cut grass.

In this embodiment of the invention the cutting chamber 13 is, for example, plastic and for this reason a loose- fitting opening 18 is formed on the upper surface for the exhaust pipe 11. Since the exhaust pipe 11 heats up as the internal combustion engine 12 runs, direct contact between the hot exhaust pipe 11 and the plastic construction of the cutting chamber 13 is thus avoided. In the case that the cutting chamber 13 is metal, the exhaust pipe can also be fixed directly to the cutting chamber.

Figure 3 shows the lawn-mower of figures 1 and 2 as seen from below. The figure shows the cutting chamber 13, in which the cutting blade 14 rotates. The rotary movement of the blade 14 causes the cut grass to be discharged from the chamber 13 through the opening 15. The movement of the grass clippings is shown with arrows in the figure.

It is obvious that only a part of the cut grass goes directly out of the discharge opening 15. Some of the grass hits the walls of the chamber 13. Thus especially at the rear edge 16 of the opening 15 the wet grass tends to stick to the wall of the chamber 13. This is why the orifice 17 of the exhaust pipe 11 is located precisely in the vicinity of this area. The exhaust gas pressure waves occurring perpendicularly to the direction of movement of the grass efficiently detach even wet grass, which otherwise tends to stick to the wall of the- cutting chamber 13.

The exhaust pipe 11 can be made of any suitable material, most preferably of metal, such as steel, aluminium or copper to be such that the exhaust gases can be led to a suitable point in the cutting chamber. The internal combustion engine driving the lawn-mower is usually installed either with the cylinder projecting forwards or backwards. Thus by means of two or three different types of exhaust pipes the installation relating to the invention can be made even afterwards in all the most common types of lawn-mower.

The exhaust pipes used can obviously also be flexible or bendable pipe constructions which are fixed sufficiently firmly into place. It is also possible to divide the exhaust pipe coming from the internal combustion engine into two or more branches in order to lead the exhaust gas pressure waves to several points in the cutting chamber.

Figure 4 corresponds to figure 1 and shows a side view of the lawn-mower 10 in which the exhaust pipe 11 is divided into two branches 19 and 20. Figure 5 shows this lawn-mower from below. The branches 19 and 20 of the exhaust pipe 11 open into the cutting chamber 13 in the vicinity of the opening 15, on either side of it. This ensures that the cut, wet grass clippings will not stick to the walls of the cutting chamber at any point.

It is obvious to one skilled in the art that the different embodiments of the invention may vary within the scope of the claims presented below.

Claims

1. A lawn-mower (10), in which at least a part of the exhaust gases from the driving internal combustion engine (12) are led under the lawn-mower, into a cutting chamber (13), by means of an exhaust pipe (11), characterized in that the exhaust gases are led by means of an exhaust pipe (11) to the vicinity of the area (16) of the cutting chamber (13) where the cut grass clippings tend to stick to the wall of the cutting chamber, and the exhaust gases are led from such a direction that the pressure waves caused by the exhaust gases prevent the cut grass clippings from sticking to the wall of the cutting chamber.

2. A lawn-mower (10) as claimed in claim 1, characterized in that the exhaust gases are led by means of an exhaust pipe (11) into the cutting chamber (13), in the vicinity of the discharge opening (15) of the cut grass.

3. A lawn-mower (10) as claimed in claim 1 or 2, characterized in that the exhaust gases are led to the vicinity of the rear edge (16) of the discharge opening (15) of the cutting chamber (13).

4. A lawn-mower (10) as claimed in claim 1, 2 or 3, characterized in that the exhaust gases are led to the vicinity of the discharge opening (15) of the cutting chamber (13) from a direction which is mainly perpendicular to the direction of movement of the grass clippings.

5. A lawn-mower (10) as claimed in any of the claims 1-4, characterized in that the exhaust gases are led into the cutting chamber (13), in the vicinity of the discharge opening (15), downwards from above.

6. A lawn-mower (10) as claimed in any of the claims 1-5, characterized in that the end (17) of the exhaust pipe (11) is located on the cover of the cutting chamber (13).

7. A lawn-mower (10) _.as claimed in any of the claims 1-5, characterized in that a loose-fitting opening (18) is formed on the cover of the cutting chamber (13), in which opening the end (17) of the exhaust pipe (11) is placed.

8. A lawn-mower (10) as claimed in any of the claims 1-7, characterized in that the exhaust pipe is formed of a flexible or bendable metal pipe, the end (17) of which is placed on the cover of the cutting chamber (13).

9. A lawn-mower (10) as claimed in any of the claims 1-8, characterized in that the exhaust pipe (11) divides into two or more branches, the orifices of which open into the cutting chamber (13).