GB2031062A - Exhaust Muffler for a Pneumatic Machine Tool - Google Patents

Abstract

A flexible tube 17 is connectible to the exhaust air outlet 14 of the machine tool and a flexible porous rod 21 is located inside the tube. The porous rod consists of a foamed plastic core (22) in a string net envelope (23). The rod is held only by a string 27 so that in operation it can move freely in its transverse direction relative to the tube, but not in its longitudinal direction. At its outlet end, the tube 17 is provided with a cup shaped diffusor 19. <IMAGE>

Description

SPECIFICATION Exhaust Muffler This invention relates to an exhaust muffler for a pneumatic motor. In particular, the invention relates to an exhaust muffler comprising a flexible section of an exhaust passage connected to the motor.

Previous exhaust mufflers for pneumatic motors have not been suitable for hand held tools because of a too high weight and bulkiness.

Therefore, the main object of the invention is to accomplish an exhaust muffler which is flexible and light and therefore suitable for use at hand held machine tools. Another object of the invention is to make an exhaust muffler which is simple as regards construction and cheap to manufacture.

This is obtained by the present invention as it is recited in the claims.

A preferred embodiment of the invention is hereinbelow described in detail under reference to the accompanying drawing on which Fig. 1 shows a partly broken side elevation of a pneumatic grinding machine provided with an exhaust muffler according to the invention.

Fig. 2 shows a cross section through the exhaust muffler taken along line Il-Il in Fig. 1.

In Fig. 1, there is shown a hand held grinding machine 10 powered by a pneumatic vane motor (not shown). The vane motor is arranged to rotate an output shaft 11 which in turn is intended to carry a disc or cup shaped grinding tool.

The machine 10 further comprises two handles 12, 13, an exhaust air outlet duct 14, and an exhaust muffler 1 5 connected thereto. The handle 13, which in Fig. 1 is hidden behind the muffler 15, comprises a pressure air supply passage and a pressure air supply valve. The latter is operable by means of a lever 16 which is pivotally supported on the handle 13.

The exhaust muffler 1 5 comprises a flexible hose 1 7. The latter is preferably made of plastic or rubber and is slidably mounted onto the outlet duct 14 and secured thereto by means of a hose clamp 18. At its downstream end, the hose 17 is provided with a cup shaped outlet diffusor 1 9.

Ttelatteris made of perforated sheet steel and is secured to the hose 1 7 by means of a hose clamp 20.

The exhaust muffler 1 5 further comprises an absorptive element in the form of a flexible porous rod 21 disposed inside the hose 1 7. The porous rod 21 comprises a core 22 of foamed plastic enclosed in a string net envelope 23. (See Fig. 2.) The envelope 23 is formed by a section of a string net hose and is closed at the ends of the core 22 by means of clamps 24, 25.

The diameter of the porous rod 21 is considerably less than the inner diameter of the hose 17, whereby an annular space 26 is left for letting through the exhaust air discharged from the machine 10. The exhaust air may pass the porous rod 21 substantially unrestrictedly.

Apart from a string 27 connecting the upstream end of the porous rod 21 to the hose clamp 18, the rod 21 lacks connections relative to the hose 17. This means that the rod 21 is secured against longitudinal movement but is freely movable in its transverse direction relative to the hose 1 7. It also means that assembling of the exhaust muffler is very simple as it only comprises the steps of introducing the porous rod 21 into the hose 17, connecting the string 27 to the clamp 24 at the upstream end of the rod 21 and to the hose clamp 18, and mounting the hose 17 onto the outlet duct 14 of the machine 10.

The hose 7 as well as the porous rod 21 are flexible, which makes the exhaust muffler 1 5 easily bendable and adaptable to various working conditions.

The new exhaust muffler is advantageous also in that an effective sound absorption may be obtained without getting an undesirable back pressure in the exhaust passage. Neither does it tend to get choked up due to freezing. The embodiments are not limited to the shown and described example, but can be freely varied within the scope of the invention as defined in the claims. For instance, the muffler may comprise more than one absorptive element.

Claims

1. In an exhaust muffler for a pneumatic motor, comprising a flexible section of an exhaust passage connected to the motor, the improvement comprises one or more flexible absorptive elements located in said flexible section, each of said absorptive elements comprising a core of an elastic porous material enclosed in a flexible perforated envelope and having an outer diameter considerably less than the inner diameter of said flexible section, thereby leaving an annular exhaust air passage past said absorptive element or elements.

2. Exhaust muffler according to claim 1, wherein said perforated envelope comprises a net hose section closed at both ends by clamp means.

3. Exhaust muffler according to claim 1 or 2, wherein said one or more absorptive elements are freely movable transversely relative to said flexible section.

4. An exhaust muffler substantially as hereinbefore described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Exhaust Muffler This invention relates to an exhaust muffler for a pneumatic motor. In particular, the invention relates to an exhaust muffler comprising a flexible section of an exhaust passage connected to the motor. Previous exhaust mufflers for pneumatic motors have not been suitable for hand held tools because of a too high weight and bulkiness. Therefore, the main object of the invention is to accomplish an exhaust muffler which is flexible and light and therefore suitable for use at hand held machine tools. Another object of the invention is to make an exhaust muffler which is simple as regards construction and cheap to manufacture. This is obtained by the present invention as it is recited in the claims. A preferred embodiment of the invention is hereinbelow described in detail under reference to the accompanying drawing on which Fig. 1 shows a partly broken side elevation of a pneumatic grinding machine provided with an exhaust muffler according to the invention. Fig. 2 shows a cross section through the exhaust muffler taken along line Il-Il in Fig. 1. In Fig. 1, there is shown a hand held grinding machine 10 powered by a pneumatic vane motor (not shown). The vane motor is arranged to rotate an output shaft 11 which in turn is intended to carry a disc or cup shaped grinding tool. The machine 10 further comprises two handles 12, 13, an exhaust air outlet duct 14, and an exhaust muffler 1 5 connected thereto. The handle 13, which in Fig. 1 is hidden behind the muffler 15, comprises a pressure air supply passage and a pressure air supply valve. The latter is operable by means of a lever 16 which is pivotally supported on the handle 13. The exhaust muffler 1 5 comprises a flexible hose 1 7. The latter is preferably made of plastic or rubber and is slidably mounted onto the outlet duct 14 and secured thereto by means of a hose clamp 18. At its downstream end, the hose 17 is provided with a cup shaped outlet diffusor 1 9. Ttelatteris made of perforated sheet steel and is secured to the hose 1 7 by means of a hose clamp 20. The exhaust muffler 1 5 further comprises an absorptive element in the form of a flexible porous rod 21 disposed inside the hose 1 7. The porous rod 21 comprises a core 22 of foamed plastic enclosed in a string net envelope 23. (See Fig. 2.) The envelope 23 is formed by a section of a string net hose and is closed at the ends of the core 22 by means of clamps 24, 25. The diameter of the porous rod 21 is considerably less than the inner diameter of the hose 17, whereby an annular space 26 is left for letting through the exhaust air discharged from the machine 10. The exhaust air may pass the porous rod 21 substantially unrestrictedly. Apart from a string 27 connecting the upstream end of the porous rod 21 to the hose clamp 18, the rod 21 lacks connections relative to the hose 17. This means that the rod 21 is secured against longitudinal movement but is freely movable in its transverse direction relative to the hose 1 7. It also means that assembling of the exhaust muffler is very simple as it only comprises the steps of introducing the porous rod 21 into the hose 17, connecting the string 27 to the clamp 24 at the upstream end of the rod 21 and to the hose clamp 18, and mounting the hose 17 onto the outlet duct 14 of the machine 10. The hose 7 as well as the porous rod 21 are flexible, which makes the exhaust muffler 1 5 easily bendable and adaptable to various working conditions. The new exhaust muffler is advantageous also in that an effective sound absorption may be obtained without getting an undesirable back pressure in the exhaust passage. Neither does it tend to get choked up due to freezing. The embodiments are not limited to the shown and described example, but can be freely varied within the scope of the invention as defined in the claims. For instance, the muffler may comprise more than one absorptive element. Claims

1. In an exhaust muffler for a pneumatic motor, comprising a flexible section of an exhaust passage connected to the motor, the improvement comprises one or more flexible absorptive elements located in said flexible section, each of said absorptive elements comprising a core of an elastic porous material enclosed in a flexible perforated envelope and having an outer diameter considerably less than the inner diameter of said flexible section, thereby leaving an annular exhaust air passage past said absorptive element or elements.

2. Exhaust muffler according to claim 1, wherein said perforated envelope comprises a net hose section closed at both ends by clamp means.

3. Exhaust muffler according to claim 1 or 2, wherein said one or more absorptive elements are freely movable transversely relative to said flexible section.

4. An exhaust muffler substantially as hereinbefore described with reference to the accompanying drawing.