GB1592682A - Percussion device operated by a pressurised medium - Google Patents

Description

(54) A PERCUSSION DEVICE OPERATED BY A PRESSURISED MEDIUM (71) We, MASCHINENFABRIK RUDOLF HAUSHERR & SOHNE KG., a Kommanditgesellschaft organised under the laws of Germany, Of, Wuppertaler Strasse, 4322 Sprockhovel, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following state menu: This invention relates to a pressurised medium operated percussion device, for example a compressed air hammer, the piston of which is guided in a cylinder and is associated at its forward end with a tool disposed in a guide sleeve located in a casing forming a part of the percussion device.

A compressed air hammer is known wherein the casing or the cylinder is formed with a bore which is controlled by the tool.

However, this known expedient has the disadvantage that the hammer is automatically set in operation when it is raised in order to carry out work in which the tool is directed vertically or obliquely upwardly because the tool slides back, the aforementioned bore is closed and thus the return stroke of the piston is initiated. The consequence is that what are known as nonproductive strokes are produced which may lead to the hammer being damaged, quite apart from the accident hazard which such strokes entail.

Having regard to this state of the art, the invention is concerned with the problem of providing means for automatically stopping a percussion device of the kind referred to, which is operated by a pressurised medium, said means being of simple construction and guaranteeing stoppage of the hammer independently of its working position, when the operator completes the work or when he is not performing any work.

According to the invention, there is provided a presurised medium operated percussion device, the piston of which is guided in a cylinder located in a casing for the percussion device and provided with a port which is closed by the piston in its striking position and is only opened to connect the forward end of the cylinder to a supply of pressurised medium upon backward movement of the piston by the inner end of a tool disposed in a guide sleeve secured in the casing in axial alignment with the cylinder, when the tool is pressed inwards against the action of a spring interposed between the inner end of the tool and a fixed guide for the forward end of the piston.As a result of this construction, when the operator presses the percussion device against a rock or the like which is to be shattered, the tool is pushed back against the force of the compression spring and this in turn pushes back the piston sufficiently to uncover the port and thus allow the pressurised medium to push the piston back. As soon as the applied pressure is high enough, therefore, the tool and thus the piston will be pushed back. In consequence, when use of the percussion device ceases, its further operation is prevented. Similarly, unintended operation of the percussion device when it is picked up and pointed upwardly or obliquely upwardly is impossible because the force of the compression spring is such that, when the percussion appliance is not in use, it creates space between the mutually. facing ends of the tool and piston.Only when a specific degree of pressure is applied can the percussion device be set in operation.

The piston is preferably provided with a projecting portion which is coaxially surrounded by the compression spring to provide a space-saving construction.

According to a further feature of the invention, the piston is preferably stepped at its point of connection to its projecting portion and the step of the piston, the outer surface of the piston projection, the inner surface of the cylinder and the end of the guide or the like for the piston projection preferably define an annular space containing such a quantity of pressurised medium that when the piston reaches its extreme position, a buffer is provided which prevents impact with the end of the guide. This embodiment avoids inoperative strokes of the piston or its projecting portion in the cylinder or guide.

One embodiment of the invention will be described in greater detail hereinafter with reference to the accompanying drawing which shows in section, a side view of the bottom end of a compressed air hammer.

Reference numeral I denotes a casing for the hammer in which there is disposed, in conventional manner, a cylinder 2 which serves to guide a piston 3. Inserted into the front end of the cylinder 2, with the interposition of gaskets 5, is a cylindrical guide 4 to receive a projecting portion 6 of the piston 3.

Adjacent the guide 4, in the direction of the front end of the casing 1 is a guide sleeve 7 which is intended to receive a tool 8.

Anchored on the end face of the tool 8 is one end of a coil spring 9, the other end of which bears against a shoulder 10 on the guide 4, the spring 9 and the projecting portion 6 being located coaxially of each other, i.e. the spring surrounds the projecting portion 6.

The cylinder 2 is provided with a port 11 which is closed by the piston 3 when the appliance is in its striking position and communicates with a bore 12 for the supply of a pressurised medium. The piston 3 thus controls the port 11.

The piston 3 is stepped at 13 where it joins the projecting portion 6. The stepped portion of the piston 3, the outer surface of the projecting portion 6, the inner surface of the cylinder 2 and the end face of the guide 4 for the projection 6 define an annular space 14 which is filled with a pressurised medium, preferably oil. The quantity of oil is such that the piston 3 reaches its extreme position shown in the drawing without striking the end face of the guide 4.

The device according to the invention operates in the following manner: In order to set the percussion device in operation, it is necessary to actuate the appliance to allow the pressurised medium to flow and furthermore, the percussion device has to be applied with such pressure that the tool 8 is pushed inwards against the action of the spring 9, until it is resting against the front end face of the projecting portion 6 of the piston 3 and, upon further pressure being exerted, moves the piston 3 inwards so that it uncovers the port 11. Pressurised medium can now flow via the bore 12 and the port 11, into the cylinder in front of the piston 3 so effecting the backward stroke of the piston.

As soon as the pressure applied to the percussion device abates, the spring pushes the tool 8 outwards again so that the piston 3 stops in the position shown in the drawing.

Even when the percussion device is raised into an obliquely upwardly or vertically upwardly directed position unintended operation is prevented, since the application of a certain amount of pressure is always necessary in order to push the tool 8 into the percussion device against the action of the spring 9 and displace the piston 3 beyond the port I I. The force of the spring 9 is such that when no pressure is applied to the percussion device, there is always space between the mutually facing ends of the tool 8 and the projecting portion 6 of the piston 3.

WHAT WE CLAIM IS: 1. A pressurised medium operated percussion device, the piston of which is guided in a cylinder located in a casing for the percussion device and provided with a port which is closed by the piston in its striking position and is only opened to connect the forward end of the cylinder to a supply of pressurised medium upon backward movement of the piston by the inner end of a tool disposed in a guide sleeve secured in the casing in axial alignment with the cylinder, when the tool is pressed inwards against the action of a spring interposed between the inner end of the tool and a fixed guide for the forward end of the piston.

2. A device according to Claim 1, characterised in that the force of the spring is such tha when no pressure is applied to the percussion device, space is left between the mutually facing ends of the tool and the piston.

3. A device according to Claim 1 or 2, characterised in that the piston is provided with a projecting portion which is disposed coaxially of and surrounded by the spring.

4. A device according to Claim 3, characterised in that the piston is connected to its projecting portion via a step and in that the step on the piston, the outer surface of the projecting portion, the inner surface of the cylinder and the end face of the guide or the like define an annular space containing such a quantity of pressurised medium that a buffer is provided for the piston when it reaches its striking position.

5. A pressurised medium operated percussion device substantially as hereinbefore described with reference to and as shown in the accompanying drawing.

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

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. guide or the like for the piston projection preferably define an annular space containing such a quantity of pressurised medium that when the piston reaches its extreme position, a buffer is provided which prevents impact with the end of the guide. This embodiment avoids inoperative strokes of the piston or its projecting portion in the cylinder or guide. One embodiment of the invention will be described in greater detail hereinafter with reference to the accompanying drawing which shows in section, a side view of the bottom end of a compressed air hammer. Reference numeral I denotes a casing for the hammer in which there is disposed, in conventional manner, a cylinder 2 which serves to guide a piston 3. Inserted into the front end of the cylinder 2, with the interposition of gaskets 5, is a cylindrical guide 4 to receive a projecting portion 6 of the piston 3. Adjacent the guide 4, in the direction of the front end of the casing 1 is a guide sleeve 7 which is intended to receive a tool 8. Anchored on the end face of the tool 8 is one end of a coil spring 9, the other end of which bears against a shoulder 10 on the guide 4, the spring 9 and the projecting portion 6 being located coaxially of each other, i.e. the spring surrounds the projecting portion 6. The cylinder 2 is provided with a port 11 which is closed by the piston 3 when the appliance is in its striking position and communicates with a bore 12 for the supply of a pressurised medium. The piston 3 thus controls the port 11. The piston 3 is stepped at 13 where it joins the projecting portion 6. The stepped portion of the piston 3, the outer surface of the projecting portion 6, the inner surface of the cylinder 2 and the end face of the guide 4 for the projection 6 define an annular space 14 which is filled with a pressurised medium, preferably oil. The quantity of oil is such that the piston 3 reaches its extreme position shown in the drawing without striking the end face of the guide 4. The device according to the invention operates in the following manner: In order to set the percussion device in operation, it is necessary to actuate the appliance to allow the pressurised medium to flow and furthermore, the percussion device has to be applied with such pressure that the tool 8 is pushed inwards against the action of the spring 9, until it is resting against the front end face of the projecting portion 6 of the piston 3 and, upon further pressure being exerted, moves the piston 3 inwards so that it uncovers the port 11. Pressurised medium can now flow via the bore 12 and the port 11, into the cylinder in front of the piston 3 so effecting the backward stroke of the piston. As soon as the pressure applied to the percussion device abates, the spring pushes the tool 8 outwards again so that the piston 3 stops in the position shown in the drawing. Even when the percussion device is raised into an obliquely upwardly or vertically upwardly directed position unintended operation is prevented, since the application of a certain amount of pressure is always necessary in order to push the tool 8 into the percussion device against the action of the spring 9 and displace the piston 3 beyond the port I I. The force of the spring 9 is such that when no pressure is applied to the percussion device, there is always space between the mutually facing ends of the tool 8 and the projecting portion 6 of the piston 3. WHAT WE CLAIM IS:

1. A pressurised medium operated percussion device, the piston of which is guided in a cylinder located in a casing for the percussion device and provided with a port which is closed by the piston in its striking position and is only opened to connect the forward end of the cylinder to a supply of pressurised medium upon backward movement of the piston by the inner end of a tool disposed in a guide sleeve secured in the casing in axial alignment with the cylinder, when the tool is pressed inwards against the action of a spring interposed between the inner end of the tool and a fixed guide for the forward end of the piston.

2. A device according to Claim 1, characterised in that the force of the spring is such tha when no pressure is applied to the percussion device, space is left between the mutually facing ends of the tool and the piston.

3. A device according to Claim 1 or 2, characterised in that the piston is provided with a projecting portion which is disposed coaxially of and surrounded by the spring.

4. A device according to Claim 3, characterised in that the piston is connected to its projecting portion via a step and in that the step on the piston, the outer surface of the projecting portion, the inner surface of the cylinder and the end face of the guide or the like define an annular space containing such a quantity of pressurised medium that a buffer is provided for the piston when it reaches its striking position.

5. A pressurised medium operated percussion device substantially as hereinbefore described with reference to and as shown in the accompanying drawing.