FR2474810A1 - Silencer for motor driven lawn-mower - consists of chamber inside housing below motor, with extension in cover fitted over top - Google Patents

Abstract

The lawnmower has an internal combustion engine (2) supported on top of a rectangular casing (1). A wheel is mounted at each corner. It incorporates a silencer for the exhaust pipe (9) inside the casing. The exhaust pipe projects downwards to pass through a hole in the corner of a cover (10) fitting on top of the casing. It then discharges into a chamber (11) incorporated in the casing below. The cover, which excludes air from the chamber, has a projecting rectangular portion (14) whose hollow interior forms an upper extension of the chamber. The main chamber below forms part of a ring around the central opening (12) for the drive shaft for the cutting blades underneath.

Description

Mower
The invention due to the collaboration of Jean-Pierre LEGROS relates to a lawn mower provided with a cutting shaft driven by an internal combustion engine, with a silencer device placed around the cutting shaft into which opens the engine gas exhaust manifold and a casing surrounding the muffler, on which the engine is fixed.

Lawn mowers are already known, the silencer of which is constituted by a curved sheet in the shape of a torus and which consists of an annular chamber subdivided by radial partitions into elementary chambers connected to each other by tubular sections.

When such a device is installed in the mower housing, the annular surface of the device, heated to high temperature and which is turned towards the ground, is positioned at a relatively low height above it and can scorch the lawn, especially when the mower is moving slowly or when it is stationary on the ground.

To overcome this drawback, provision has already been made for an insulating protective plate between the annular surface of the muffler device facing the ground and the cutter bar of the mower.

To improve the evacuation of the heat, it is then necessary to provide spacers between the insulating plate and the silencer device and / or additional ventilation blades to the cutter bar in order to effect a better evacuation of the heat. .

From then on the muffler device becomes relatively complex and increases the assembly time of the mower.

The invention aims to solve the problem of installing the muffler device in the housing of the mower as little storytelling as possible.

The invention also aims to solve the problem of damping the noise of the exhaust of the internal combustion engine by giving the casing of the mower the function of retaining the audible parts of the mixture of frequencies of the pressure wave generated by the engine exhaust.

The invention also aims to solve the problem of evacuating white exhaust gases without risk of scorching of the lawn.

According to the invention, these problems are solved by conforming part of the lare casing, often called the carcass of the mower, in a chamber into which the exhaust pipe of the engine opens and which is connected to the volute and nozzle lawn ejection.

According to one embodiment, the chamber is closed by a cover which can be optionally made up either of a sound-absorbing cover, or by the fixing flange of the moisture.

The mower thus produced has a particularly effective silencing device because the volume of the chamber can be relatively large and is isolated from the cutting device. Due to the large size of the carcass, there is a large cooling surface which lowers the temperature of the gases without exaggerated increase in the temperature of the carcass.

Other characteristics and advantages of the mower will appear on reading the description made with reference to the appended drawing in which - Figure 1 is a schematic representation of the mower - Figure 2 is an exploded view of an embodiment of the silencer integrated in the blade housing.

- Figure 3 is an exploded view of an alternative embodiment
of the device shown in Figure 2.

As has been shown in Figure 1, the mower has a housing 1 which at its upper part supports a motor 2. It is equipped with two front wheels 3 and two rear wheels 4, as well as unbrancand5 by which the user pushes it. Inside the casing 1, open downwards, is mounted, in the usual manner on a vertical cutting shaft, a cutting blade; this blade ensures the transport, backwards inside a casing volute, of the cut grass to an ejection opening placed for example between the two rear wheels of the mower. In general there is no need for additional arrangements for the rotary blades to cause this transport movement, since the cut grass is first driven in the direction of the rotary movement of the blade.

If necessary, additional guidance of the cut grass on guide surfaces of the housing can be provided to facilitate the transport of this cut grass to the rear ejection opening. It is also possible, if necessary, to provide additional guide surfaces on the cutting blades.

In no case, however, is the need to create a strong air supply by additional fan or arrangement of the cutting arms in fan blades to ensure the high speed transport of the cut grass to the rear ejection opening .

In FIG. 2, which shows a first alternative embodiment of the invention, the air-cooled internal combustion engine 2 has a fixing flange 6 and an output shaft 7 on which the cutting shaft is coupled the end of which carries the cutter bar 8.

The exhaust manifold 9 of the engine opens into the casing 1 through a cover 10. To this end, part of the casing 1 conforms to a chamber 11 into which the manifold 9 opens.

The chamber 11 partially surrounds the passage well 12 of the cutting shaft and opens into the ejection pipe 13 of the lawn. The cover 10 intended to close the chamber 11 from above also carries a recess 14 complementary to that defined by the chamber 11 and substantially increases the volume of the latter. The volume of the silencer device is therefore constituted by the sum of the elementary volumes formed by the chamber 11 and the recess 14 and this volume is isolated from the cutting device itself.

For the purpose of simplifying the drawing, the means for connecting the flange 6 to the cover 10 and from the latter to the casing 1 have not been shown. It is the same for any baffles and partitions which divide the volume of the silencer device into elementary chambers and which could be produced by molding.

According to FIG. 3, the fixing flange 63 of the engine 2 forming a cover, bears on its lower face turned towards the casing 1, obviously forming a chamber 143 into which the exhaust manifold 9 opens.

The flange 63 is intended to be fixed on the casing 1 to close off the chamber 113 provided on the casing as has been described above with reference to FIG. 2.

It appears from the above examples that the volume delimited by the silencer device is relatively large. It is therefore understandable that the solutions proposed lead to an appreciable reduction in the noise level of the mower and to a substantial lowering of the temperature of the exhaust gases before their ejection into the open air.

It should also be noted that the constructive arrangement of the silent system, in accordance with the invention, favors the ejection of the cut strands of grass and prevents fouling of the ejection channel because the walls of the latter undergo drying drying which prevents sticking of the grass strands.

Claims (3)

1. Lawn mower provided with a cutting shaft driven by an internal combustion engine, with a silencer device placed around the cutting shaft into which the engine gas exhaust manifold opens, and a casing enveloping the silencer device, on which the engine is fixed, and which carries the lawn ejection duct, characterized in that a part of the casing (1) conforms to a chamber (11, 113) which opens the exhaust pipe (9) and which is connected to the lawn ejection conduit, while a cover (10) closes said chamber so as to isolate it from ambient air. 2. Lawn mower according to claim 1, characterized in that the chamber (11) of the housing is closed by cover (10) which carries a recess (14) complementary to that of the chamber (11) to increase the volume of said chamber connected to the exhaust pipe of the engine. 3. Lawn mower according to claim 2, characterized in that the cover is constituted by the mounting flange (63) of the engine whose obviously carrying lower face (143) into which the exhaust manifold opens.