Anti-freezing device for pneumatic tools

The invention concerns an anti-freezing device for pneumatic tools to avoid the immobilization of the striker piston because of freezing up. A thermally insulating sleeve, broken only at the level of the air exhaust apertures of the cylinder, separates the body of the hammer from an annular chamber into which the apertures open. An exhaust passage connects the annular chamber with the exterior and extends along the external wall of the exhaust silencer parallel to the striker piston. The exhaust silencer also is provided, above and below the annular chamber with two hermetically sealed chambers, which prevent the cooling of the naturally hot zones of the hammer by the air in the exhaust passage.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention concerns an anti-freezing device for a 
pneumatically-controlled tool, 
2. Description of the Prior Art 
It is known that the exhaust air of a pneumatic tool constitutes a source 
of cold air. The air, subject to a sudden pressure release, may reach a 
temperature in the range of -35.degree. to -40.degree. C. It is also known 
that the exhaust air cannot be ejected directly into the atmosphere 
because of the noise which would result. One must, therefore, pass the 
exhaust air through various baffles which are arranged around the body of 
the hammer. This arrangement gives rise to a rapid cooling of the body of 
the tool during operation. This rapid cooling may result in a freezing-up 
of the tool, causing immobilization of the piston of the apparatus and, 
consequentially, a temporary loss of service of the apparatus. Naturally, 
this disadvantage is mainly perceptible during cold spells, or when the 
compressed air is moist. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide an anti-freezing device 
able to avoid the inconveniences set forth above. 
An anti-freezing device according to the present invention is provided for 
a tool having a main body, a piston moving in a cylinder chamber formed in 
the main body, a control distributor at the upper portion of the main 
body, air exhaust apertures opening laterally into the cylinder, and an 
exhaust silencer surrounding the main body. 
According to the present invention, the air exhaust apertures open into at 
least one chamber of the silencer, which is separated from the body of the 
hammer by a sleeve of thermally insulating material open only in the area 
of the apertures. 
The at least one chamber is connected to the ambient atmosphere by means of 
at least one exhaust passage, the walls of this exhaust passage extending 
away from the body of the hammer. 
According to an additional characteristic of the present invention, the 
silencer is provided above and below the chambers with two hermetically 
sealed chambers. These chambers may, if required, be filled with an 
insulating product which prevents the cooling of the naturally hot zones 
of the body of the hammer and which are thus conducive to the heating of 
the cylinder by conduction. The heat comes from the said naturally hot 
zones above and below the air exhaust apertures and is conducted by the 
metallic mass of the body to the region of the air exhaust apertures.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawing, and more particularly to FIG. 2 thereof, a 
concrete-breaking hammer 20 is illustrated which, in the conventional way, 
includes a striker piston 1 sliding longitudinally in a cylindrical 
chamber 5 in a tool body 2. A conventional control distributor 3 is 
provided at the upper part of the tool body 2. Air exhaust apertures 4 
open radially into the upper portion of the cylindrical chamber 5 of the 
tool body 2. The tool body 2 is surrounded throughout its height by an 
exhaust silencer 6. 
According to an arrangement particular to the present invention, a sleeve 
of thermally insulating material 7, opening only at the level of the 
apertures 4, separates the tool body 2 from an annular chamber 8 in the 
exhaust silencer into which the apertures 4 open. The annular chamber 8 is 
also connected to the exterior by means of an exhaust channel or passage 
9, as shown in FIG. 1, parallel to the major axis of the hammer. The 
exhaust channel 9 runs along the external wall of the silencer 6 and has a 
series of outlet apertures 10 close to the lower end of the silencer 6. 
In addition, the silencer 6 forms two hermetically sealed annular chambers 
11 and 12 disposed respectively above and below the annular chamber 8. It 
will be noticed that the hermetically sealed annular chamber 12 separates 
the exhaust channel 9 from the tool body 2 of the concrete-breaking hammer 
20, as shown in FIG. 1. 
The operation of the present invention is as follows: 
The exhaust air leaves the apertures 4 at a temperature in the range of 
-35.degree. to -45.degree. C. when the machine is in use. The air is 
exhausted directly towards the exterior through baffles formed by the 
exhaust channel 9 without ever flowing in its path over the smallest metal 
surface. It is known, in fact, that the silencer 6 is itself made from a 
material which is strong, but non-metallic and a poor conductor of heat. 
This exhaust air, therefore, cannot cool the hammer. 
In addition, the two hermetically sealed annular chambers 11 and 12 help to 
prevent the cooling of the naturally hot zones of the hammer by 
convection, thereby causing the heat originating from these naturally hot 
zones to flow directly, by conduction, into the metallic mass of the tool 
body 2 in the direction of the arrows 13 toward the central zone of the 
cylinder. That is, the heat flows to a region where it is desired to 
prevent cooling. 
The concrete-breaking hammer, so equipped, is protected from any excessive 
cooling, and, consequently, from any phenomenon of freezing up, thereby 
avoiding immobilization of the piston 1 in the cylindrical chamber 5 of 
the tool body 2. 
It will be noticed that the "direct" evacuation of the exhaust air towards 
the exterior may take place without harming the efficiency of the 
silencer, the exhaust circuit always having anti-noise baffles. 
Naturally, the scope of the claims appended hereto will not be exceeded by 
arranging two exhaust channels 9, or even more, in the silencer, the 
essential element being that these channels remain separated from the tool 
body 2 of the hammer by the hermetically sealed chamber 12, as shown in 
FIG. 2.