DE202019107164U1 - Piston for a pneumatic impact tool - Google Patents

Abstract

A piston (1) for a pneumatic impact tool, the piston being suitable for being arranged in the tool in order to transmit impact energy to a working medium of the tool, and comprising a piston shaft (10) with an elongated, substantially cylindrical shape, wherein a first end portion (10a) of the piston skirt is adapted to strike a striking element of the tool to transmit impact energy to the implement and a larger diameter section (20) located on the piston skirt adjacent to the first end section, wherein this section is in the form of a hollow cylinder, the section with the larger diameter being made from a first material with a density which is less than or equal to half the density of a second material from which the piston skirt is made.

Description

Technical field

The present invention relates generally to pneumatic striking tools, which are also known under the name striking tools. In particular, the present invention relates to a piston which is suitable for arrangement in such a tool.

Technical background

Pneumatic striking tools, for example for material removal, which include, for example, so-called chisels, chisel or impact hammers, are e.g. suitable for material removal. Such tools, also known as percussion tools, percussion instruments and pneumatic pulse tools - all terms are used interchangeably in the present specification - normally consist of a piston which in a cylinder of the tool by means of compressed air flowing through inlets and outlets in the cylinder. and is moved and is arranged so that it is on a tool attachment, for example strikes a hammer.

There are requirements for the design of such pistons that sufficient energy has to be transferred to the tool attachment in order to ensure efficient and fast material removal. To ensure this, a certain speed of the piston and an optimized pulse wave behavior are required.

It is known that the weight of the piston has a great influence on the dynamic properties of the piston, both in terms of the stroke frequency and the achievable stroke speed. The pulse wave behavior, on the other hand, depends both on the wave propagation speed through the piston and on its length. However, the possible range for the dimensions of the piston is usually e.g. determined by the size of the tool and the possible arrangement of air inlets and outlets in the tool, which limits the design and size and thus the weight of the piston.

Since the dynamic behavior of the piston results from a complex interplay of these and other associated factors that must be weighed against each other in order to achieve the desired, optimal impact behavior, there is a need for improvement in the area of pistons design for impact tools.

Summary of the invention

It would be desirable to provide an improved piston for an impact tool with an optimized design. In particular, it would be desirable to provide such a piston with improved dynamic properties that enables optimized wave propagation. To better solve one or more of these problems, a piston and power tool are provided as set out in the independent claims; preferred embodiments are specified in the dependent claims.

According to a first aspect of the invention, a piston is provided for an impact tool, the piston being suitable for being arranged in the tool in order to transmit impact energy to a working medium of the tool, and comprising: a piston shaft with an elongated, essentially cylindrical shape, wherein a first end portion of the piston skirt is adapted to strike a striking element of the tool to transmit impact energy to the implement and a larger diameter section located on the piston skirt adjacent to the first end section, this section being in the form of a Has hollow cylinder, wherein the portion with the larger diameter is made of a first material with a density that is less than or equal to half the density of a second material from which the piston skirt is made.

According to the first aspect, the piston offers an inventive solution to the problems described above by means of a construction which comprises several parts, including a piston shaft and a section or a sleeve with a larger diameter, which in this case is much lighter material than the piston shaft. This reduces the overall weight of the piston, while at the same time the uniform construction of the central part of the piston, i.e. the piston skirt remains unchanged, resulting in a lower weight without affecting the propagation of the shaft through the shaft portion. The lower weight of the material of the section with a larger diameter allows greater design freedom. In addition, the material of the piston skirt cannot be selected according to the weight, but according to other important aspects such as the strength and durability of the piston.

The section with the larger diameter can e.g. be a socket which is arranged on the shaft by means of a press fit or shrink fit or the like.

According to one embodiment, it is provided that the density of the first material is less than or equal to 35% of the density of the second material. For example, in one embodiment, the first material is plastic and the second material is steel. In one embodiment, the first material is polyoxymethylene (POM) and the second material is steel.

In one embodiment, the first material is aluminum and the second material is steel.

According to one embodiment, it is provided that the outer diameter of the section with the larger diameter is at least 1.5 times the diameter of the piston skirt. In one embodiment, the piston skirt further includes a radially projecting collar against which the larger diameter portion abuts, the outer diameter of the collar being equal to an outer diameter of the larger diameter portion at a first end thereof abutting the collar.

In one embodiment, the radial thickness of the larger diameter section is less than or equal to 40% of the total length of the larger diameter section, preferably less than or equal to 30% of the total length of the larger diameter section. In one embodiment, the radial thickness of the larger diameter section is in the range of 12-20 mm, preferably 13-17 mm. In one embodiment, the weight of the larger diameter section is less than or equal to 15% of the weight of the piston skirt. According to one embodiment, the length of the section with the larger diameter is less than or equal to 40% of the total length of the piston skirt, preferably less than or equal to 30% of the total length of the piston skirt.

According to one embodiment, the piston skirt comprises a groove which is arranged at a point just below a second end of the larger-diameter section. According to one version, the length of the piston skirt is in the range of 50-100 mm and the diameter of the piston skirt 10th in the area 5-15 mm.

Further advantages can be achieved by adjusting the choice of material so that the relationship between rigidity and density, i.e. the speed of sound and thus the speed of propagation of the longitudinal wave in the piston due to the impact is approximately the same for both materials. In this way, interacting pulses or waves can be generated.

im ersten Material im Bereich von +/- 20% der Schallgeschwindigkeit im zweiten Material. Nach einer Ausführungsform liegt die Schallgeschwindigkeit c im ersten Material im Bereich von +/- 10% der Schallgeschwindigkeit im zweiten Material. In einer Ausführungsform liegt die Schallgeschwindigkeit im ersten Material noch näher an der Schallgeschwindigkeit im zweiten Material, z.B. kann die Schallgeschwindigkeit im Wesentlichen gleich sein. Ein Beispiel wäre, dass das erste Material Aluminium und das zweite Stahl ist, wobei die Schallgeschwindigkeit zwischen den Materialien um ca. 5% variiert.For example, according to one embodiment, the speed of sound c (ie the speed of propagation of the longitudinal wave, also called the longitudinal elastic wave speed) is defined as $\text{c}=\surd \frac{\text{modulus of elasticity}}{\text{density}},$

in the first material in the range of +/- 20% of the speed of sound in the second material. According to one embodiment, the speed of sound c in the first material is in the range of +/- 10% of the speed of sound in the second material. In one embodiment, the speed of sound in the first material is even closer to the speed of sound in the second material, for example the speed of sound can be substantially the same. An example would be that the first material is aluminum and the second steel, the speed of sound between the materials varying by approximately 5%.

According to one embodiment, the speed of sound c, as defined above, in the first material is less than or equal to half the speed of sound in the second material. In this way two successive pulses or waves can be achieved. An example would be a tin-brass / steel combination, in which the wave speed in brass is about 65% that in steel, another example would be a plastic / steel combination, in which there is an even greater difference between the respective speeds of sound.

According to a second aspect of the present invention, a pneumatic impact tool with a piston according to one of the above-described embodiments is provided.

Goals, advantages and features of the power tool conceivable in the context of the second aspect of the invention are readily understood by the above discussion, which relates to the first aspect of the invention.

Further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description, the drawings and the appended claims. Those skilled in the art will recognize that various features of the present invention can be combined to create embodiments other than those described below.

Figure list

• 1 ist eine perspektivische Ansicht eines beispielhaften Kolbens nach einer Ausführungsform.
• 2 ist eine perspektivische Ansicht des Kolbenschafts eines beispielhaften Kolbens nach einer Ausführungsform.
• 3 ist eine perspektivische Ansicht eines Abschnittes mit vergrößertem Durchmesser eines beispielhaften Kolbens nach einer Ausführungsform.

The invention is described in the following illustrative and nonlimiting detailed description of exemplary embodiments with reference to the accompanying drawings:

• 1 10 is a perspective view of an exemplary piston according to an embodiment.
• 2nd 10 is a perspective view of the piston skirt of an exemplary piston according to one embodiment.
• 3rd 10 is a perspective view of an enlarged diameter portion of an exemplary piston according to an embodiment.

All figures are schematic, not necessarily to scale, and generally only show parts that are necessary to illustrate the invention, other parts can be omitted or only hinted at.

Detailed description

An exemplary piston 1 , which is designed so that it can be arranged in a striking tool, is in 1 shown, the piston having a piston skirt 10th and a section 20th with a larger diameter, which is adjacent to a first end portion 10a the piston skirt is arranged.

The stem (or piston skirt) 10th is in 2nd shown in more detail and has the shape of an elongated cylinder with a length L10 and a diameter D10 . The first end section 10a of the piston skirt mentioned above 10th is suitable for striking a striking element of the striking tool, such as an intermediate piston or a working device, for transmitting the impact energy.

The piston skirt also includes a radially projecting collar 11 on which the section with the larger diameter 20th is applied, the outer diameter D11 of the collar is approximately equal to the outer diameter of the larger diameter portion at a first end 20a is on this collar, and a groove 12th that are at a point just below the larger diameter section 20th is arranged as from 1 can be seen.

3rd shows the section in detail 20th with a larger diameter, also called a sleeve 20th or socket 20th can be designated. This section has the shape of a hollow cylinder, defined by an outer diameter D20o and an inner diameter D20i is defined and therefore has a radial thickness defined between them. The sleeve 20th in the version shown extends over approximately 30% of the length of the shaft 10th .

Although the invention has been illustrated and described in detail in the drawings and the foregoing description, this illustration and description are to be regarded as illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Those skilled in the art will understand that many modifications, variations and changes are conceivable within the scope defined in the appended claims. In addition, variations on the disclosed embodiments may be understood and made by those skilled in the practice of the claimed invention based on a study of the drawings, the disclosure, and the appended claims. In the claims, the word "exist" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are reflected in interdependent claims does not mean that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope of the claims.

Claims (15)

A piston (1) for a pneumatic impact tool, the piston being suitable for arrangement in the tool to transmit impact energy to a working medium of the tool, and comprising a piston shaft (10) with an elongated, substantially cylindrical shape, wherein a first end portion (10a) of the piston skirt is adapted to strike a striking element of the tool to transmit impact energy to the implement, and a larger diameter section (20) arranged on the piston skirt next to the first end section, wherein this section is in the form of a hollow cylinder, the section with the larger diameter being made from a first material with a density which is less than or equal to half the density of a second material from which the piston skirt is made. Piston after Claim 1 , wherein the density of the first material is less than or equal to 35% of the density of the second material. Piston after Claim 2 , wherein the first material is a plastic material and the second material is steel. Piston after Claim 3 , the first material being polyoxymethylene (POM) and the second material being steel. Piston after Claim 2 , the first material being aluminum and the second material being steel. Piston according to one of the preceding claims, wherein the outer diameter (D20) of the section with the larger diameter is at least 1.5 times the diameter (D10) of the piston skirt. Piston according to one of the preceding claims, wherein the piston shaft further comprises a radially projecting collar (11) against which the portion with the larger diameter abuts, and wherein the outer diameter (D11) of the collar is equal to an outer diameter of the portion with the larger diameter first end (20a) of the same, which abuts the collar. Piston according to one of the preceding claims, wherein the radial extent of the section with the larger diameter is less than or equal to 40% of the total length of the section with the larger diameter, preferably less than or equal to 30% of the total length of the section with the larger diameter. A piston according to any preceding claim, wherein the weight of the larger diameter portion is less than or equal to 15% of the weight of the piston skirt. Piston according to one of the preceding claims, wherein the length (L20) of the section with a larger diameter is less than or equal to 40% of the total length of the piston skirt, preferably less than or equal to 30% of the total length of the piston skirt. Piston according to one of the preceding claims, wherein the length L10 of the piston skirt is in the range 50-100 mm and the diameter D10 of the piston skirt 10 is in the range 5-15 mm. Piston after Claim 1 or 2nd , where the longitudinal elastic wave velocity is defined as $\text{c}=\surd \frac{\text{modulus of elasticity}}{\text{density}},$

in the first material lies in the range of +/- 20% of the longitudinal elastic wave velocity in the second material. Piston after Claim 12 , where the longitudinal elastic wave velocity is defined as $\text{c}=\surd \frac{\text{modulus of elasticity}}{\text{density}},$

in the first material lies in the range of +/- 10% of the longitudinal elastic wave velocity in the second material. Piston after Claim 1 or 2nd , where the longitudinal elastic wave velocity is defined as $\text{c}=\surd \frac{\text{modulus of elasticity}}{\text{density}},$

in the first material is less than or equal to half the longitudinal elastic wave velocity in the second material. Pneumatic striking tool with a piston according to one of the preceding claims.

Images