Hand-held power tool hammer mechanism

PRIOR ART

The invention is based in particular on a hand-held power tool hammer mechanism tool according to the preamble to claim 1.

There are already known hand-held power tool hammer mechanisms that have a hammer device that can be driven by means of a piston via a gas volume. The hammer device is essentially cylindrically embodied and has a round hammer device surface or effective surface oriented toward the gas volume. In order to achieve the most compact possible hand-held power tool hammer mechanism, it is standard to provide a hammer device characteristic value of approx. 160 mm³/g, which is composed of a maximum hammer device surface dimension—such as a maximum hammer device surface diameter or hammer device effective surface diameter—cubed and divided by the hammer device mass. During operation, a maximum pressure of approx. 15 bar occurs in the gas volume.

ADVANTAGES OF THE INVENTION

The invention is based on a hand-held power tool hammer mechanism with a hammer device that can be driven by means of a piston via a gas volume.

According to the present invention, a hammer device characteristic value, which is composed of the maximum hammer device surface dimension, cubed and divided by the hammer device mass, is greater than 200 mm³/g, preferably greater than 220 mm³/g, and particularly preferably greater than 240 mm³/g. In this context, the term “hammer device surface dimension” is understood in particular to mean a straight diagonal of a surface—preferably of an effective surface oriented toward the piston and cooperating with the gas volume—such as a diameter, an ellipse length, a polygon diagonal, etc.

By turning away from the established theory of designing a hand-held power tool device—in which a hammer mechanism is provided with characteristic value of approx. 160 mm³/g for the sake of compactness—and in fact designing one with a hammer mechanism characteristic value of greater than 200 mm³/g, preferably greater than 220 mm³/g, and particularly preferably greater than 240 mm³/g, it is possible to achieve particularly valuable properties with a view to reducing a heat generation in the hammer mechanism. In addition, a corresponding embodiment according to the invention also has an advantageous effect on the comfort properties of the hand-held power tool hammer mechanism.

The heat generation can be advantageously reduced further and the comfort properties can be advantageously increased further if the hammer mechanism characteristic value is greater than 280 mm³/g, preferably greater than 320 mm³/g, and particularly preferably greater than 380 mm³/g.

If the hammer mechanism characteristic value is less than 2000 mm³/g, then a particularly low heat generation and a particularly high degree of comfort can be achieved while taking up an acceptable amount of space.

According to another embodiment, the hand-held power tool hammer mechanism is designed so that during operation, a maximum gas pressure in the gas volume is less than 10 bar, advantageously less than 8 bar, and particularly advantageously less than 6 bar, which likewise has a particularly advantageous effect on the heat generation and comfort properties of the hand-held power tool hammer mechanism. A corresponding pressure reduction in relation to known hand-held power tool hammer mechanisms can in particular be achieved by embodying the hand-held power tool hammer mechanism with a hammer mechanism characteristic value according to the present invention, but additionally or alternatively also through other measures deemed appropriate by those skilled in the art.

The hammer device and the piston can have variously formed effective surfaces deemed appropriate by those skilled in the art, e.g. rectangular, elliptical, symmetrical, or asymmetrical effective surfaces, etc. The “effective surface”of the hammer device is understood in particular to mean the surface of the hammer device oriented toward the piston and the “effective surface” of the piston is understood to mean the surface of the piston oriented toward the hammer device, i.e. the surfaces cooperating with the gas volume. It is advantageous, however, if a maximum hammer device effective surface dimension deviates from a minimum hammer device effective surface dimension by less than 30% and it is particularly advantageous for the maximum to deviate from the minimum by less than 20%; it is particularly preferable, however, if the hammer device and/or the piston have/has a round effective surface, which gives the hand-held power tool hammer mechanism a particularly simple structure and makes it inexpensive to manufacture. The maximum hammer device surface dimension is preferably constituted by a diameter of the effective surface of the hammer device. In addition, the dimensions of the hand-held power tool hammer mechanism are advantageously designed so that in a so-called hammering position in which the hammer device strikes against a tool or hammer pin and the piston is situated in its front end position oriented toward the hammer device, a distance (between the effective surface of the piston and the effective surface of the hammer device) corresponds at least essentially to approximately the maximum hammer device surface dimension and to the diameter of the effective surface of the hammer device, i.e. advantageously has a deviation of less than 30%, preferably less than 20%, and particularly preferably less than 10%, which also particularly explains why, in the calculation of the hammer device characteristic value, the maximum hammer device surface dimension is not simply squared, but is instead cubed.

Preferably, it is also possible to reduce costs if the effective surfaces of the piston and the hammer device correspond at least essentially to each other, i.e. have a deviation, in particular a size deviation, of less than 5%. Basically, however, the effective surfaces of the piston and the hammer device can also be different in size and shape.

According to another embodiment, the hand-held power tool hammer mechanism has an eccentric drive mechanism supported at one end and/or a hammer mechanism transmission equipped exclusively with spur gear teeth, which makes it possible to use inexpensive components advantageously embodied for their comfort properties. The embodiment according to the invention is also suited, however, for hand-held power tools with drive units that operate in a manner alternative to an eccentric drive, e.g. for hand-held power tools with a so-called wobble shaft.

In another embodiment of the invention, the hand-held power tool hammer mechanism includes at least one control opening that is provided to control the gas volume and that is coupled to a motor compartment. The term “provided” is understood in particular to mean “equipped” and/or “designed”. The term “coupled” in this context is understood in particular to mean a fluidic coupling so that the gas of the gas volume can flow into the motor compartment via the control opening and/or the gas volume can be supplied with gas from the motor compartment. In addition, the term “motor compartment” is understood in particular to mean a transmission compartment, a lubrication oil compartment, a motor compartment, etc. and/or in particular, a chamber that is cut off at least in one sense from the outside, i.e. from the surroundings of a hand-held power tool, and is for example at least essentially connected to the surroundings of the hand-held power tool exclusively via pressure compensation means.

Through a corresponding embodiment, it is possible to avoid at least a direct gas exchange between the gas volume and the surroundings of the hand-held power tool and accompanying losses in comfort as well as increases in environmental impact.

According to another embodiment, the hammer device has at least one decoupling means, which is provided for dimensionally decoupling a main hammer body of the hammer device, and at least one coupling between the decoupling means and the main hammer body, which is provided to couple the main hammer body to the decoupling means in an at least largely synchronous fashion during a flight phase of the main hammer body. The term “main hammer body” is understood in particular to mean a part of the hammer device that makes up at least a large part of the mass of the hammer device and/or acts on a tool directly or by means of a hammer pin. The term “dimensional decoupling” is understood in particular to mean a decoupling from at least one standpoint so that the dimensions of the main hammer body preferably have at least one degree of freedom. The term “flight phase” is understood in this context in particular to mean a movement of the main hammer body generated by the piston and oriented toward a tool or toward a hammer pin and toward the piston itself.

A corresponding embodiment according to the invention permits a further improvement of the main hammer body and/or the entire hammer device, from at least one standpoint in terms of its function. In addition to the hammer device, a hammer pin device can also include a decoupling means for dimensionally decoupling a main hammer pin body, which makes it possible to also achieve additional degrees of freedom with regard to the design of the hammer pin device. In this context as well, the term “main hammer pin body” is understood in particular to mean a part of the hammer pin device that makes up at least a large part of the mass of the hammer pin device and/or cooperates directly with a tool and/or with the hammer device.

The decoupling means can be embodied in a variety of forms; preferably, it is situated in the region of an outer circumference of the main hammer body so that the outer contour of the main hammer body can be more freely embodied from at least one standpoint than one without a decoupling means; for example, the decoupling means can be advantageously used to hold a sealing means so that in the region of the sealing means, the main hammer body can be more freely embodied in terms of its dimensions, etc. It is particularly advantageous, though, if the decoupling means is provided to at least partially decouple an outer dimension of the main hammer body from a guide means of the hammer device and if the decoupling means is advantageously situated between the main hammer body and a guide means of the hammer device. The term “guide means” in this context is understood in particular to be a means in which the hammer device is guided, in particular a tubular component. The hammer device mass and a main hammer body geometry can be coordinated in a particularly advantageous manner, independent of a piston surface and an air cushion effective surface and/or an air cushion geometry and it is easily possible to achieve an advantageous hammer mechanism characteristic value composed of the maximum hammer device surface dimension, cubed and divided by the hammer mechanism mass.

The decoupling means can be manufactured of various materials deemed appropriate by those skilled in the art, for example it can advantageously be manufactured of a self-lubricating material, a plastic, a metal, a composite material, etc. In another embodiment of the invention, the decoupling means is manufactured out of a lighter material than the main hammer body, which makes it advantageously possible to achieve a low mass of the hammer device with a large effective surface.

According to another embodiment, the coupling and/or the decoupling means is/are embodied to exert an at least partial vibration-damping action. The phrase “at least partial vibration-damping action” is understood in particular to mean that during operation, the coupling and/or the decoupling means itself transmit(s) a low amount of vibration than a corresponding distance within a one-piece metallic body, particularly due to the fact that a vibration-damping and/or vibration-insulating relative movement is permitted between the decoupling means and the main hammer body and/or within the decoupling means, for example via a form-locking engagement and/or by means of an elastic material, so that in particular, a vibration of the main hammer body during operation is damped by at least 10%, preferably greater than 30%, and particularly preferably by greater than 60% at a point in the decoupling means that transmits the vibration to the outside. A corresponding embodiment can increase comfort even further.

If the coupling includes at least one connection that is manufactured by being vulcanized in place, then it is simple to provide an advantageously reliable connection, in particular between the main hammer body and the decoupling means, and to simultaneously achieve an advantageous vibration damping.

If the decoupling means has at least one guide surface, then the decoupling means can advantageously be used to improve the guidance and/or to reduce the friction, for example by being made of a self-lubricating material, etc.

If the decoupling means has at least two guide surfaces spaced apart from each other in the axial direction, then it is possible to reduce weight and assure an advantageous guidance.

According to another embodiment, the hammer device has at least one guide rib which permits the hammer device to be guided in a guide means with a large internal dimension and nevertheless, makes it possible to achieve an advantageously low hammer device mass.

If the hammer device is embodied as stepped, then this in turn makes it possible to achieve degrees of freedom with regard to its mass and external design. The term “stepped hammer device” is particularly understood in this connection to mean that the hammer device, due to its stepped design, has various guidance dimensions, in particular various guidance diameters. In this connection, a characteristic value that is comprised of a theoretical diameter in a non-stepped cylindrical design of the same mass, divided by a maximum hammer device surface dimension, is advantageously less than 0.95, preferably less than 0.8, and particularly preferably less than 0.7, while a characteristic value that is comprised of a length of the hammer device, divided by a maximum hammer device surface dimension, is advantageously less than 3, preferably less than 2.5, and particularly preferably less than 2.

DRAWINGS

Other advantages ensue from the following description of the drawings. The drawings show exemplary embodiments of the invention. The drawings, specification, and claims contain numerous defining characteristics in combination. Those skilled in the art will also suitably consider the defining characteristics individually and unite them in other meaningful combinations.

FIG. 1 shows a hand-held power tool embodied in the form of a rotary hammer, with a schematically depicted hand-held power tool hammer mechanism,

FIG. 2 shows a detail of an alternative hand-held power tool hammer mechanism with a hammer device that includes a decoupling means that is vulcanized in place,

FIG. 3 shows a detail of an alternative hand-held power tool hammer mechanism with a hammer device that includes a decoupling means that is coupled to it in a form-locked fashion,

FIG. 4 shows a detail of an alternative hand-held power tool hammer mechanism with a stepped hammer device

FIG. 5 shows a detail of an alternative hand-held power tool hammer mechanism with a different stepped hammer device

FIG. 6 shows a detail of an alternative hand-held power tool hammer mechanism with a decoupling means that performs a holding function for a sealing means,

FIG. 7 shows a detail of an alternative hand-held power tool hammer mechanism with a different decoupling means that performs a holding function for a sealing means,

FIG. 8 shows a detail of an alternative hand-held power tool hammer mechanism with a hammer device that includes a stepped main hammer body, without a decoupling means,

FIG. 9 shows a detail of an alternative hand-held power tool hammer mechanism with a hammer device that has guide ribs,

FIG. 10 shows the hammer device from FIG. 9, viewed in a direction labeled X in FIG. 9,

FIG. 11 shows a detail of an alternative hand-held power tool hammer mechanism with a cup-shaped hammer device, and

FIG. 12 shows a detail of an alternative hand-held power tool hammer mechanism with a different cup-shaped hammer device.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 1 shows a hand-held power tool embodied in the form of a rotary hammer, with a hand-held power tool hammer mechanism according to the present invention. The hand-held power tool hammer mechanism includes a hammer device 10a, which can be driven with a piston 12a via a gas volume 14a. The hammer device 10a and the piston 12a are guided in a shared cylindrical guide means 32a embodied in the form of a hammer tube and have corresponding effective surfaces 52a, 54a.

The piston 12a can be driven by an electric motor 100a via a hammer mechanism transmission 22a, which is comprised exclusively of spur gears, and via an eccentric drive mechanism 20a. The eccentric drive mechanism 20a is supported at only one end; an eccentric pin 46a is supported in its longitudinal direction only at an end oriented toward the electric motor 100a by means of a spur gear 48a and by means of a bearing axle 50a coupled to the spur gear 48a.

According to the present invention, the hand-held power tool hammer mechanism has a hammer mechanism characteristic value Sa of approx. 500 mm³/g, which is composed of the maximum hammer device surface dimension 16a, cubed and divided by the hammer device mass 18a. The hammer device surface dimension 16a here is constituted by a diameter of a cylindrically embodied main hammer body 30a or is advantageously constituted by a diameter of the effective surface 52a of the hammer device 10a.

During operation, a user pushes a tool 56a of the hand-held power tool against an item to be machined. This slides the tool 56a, a hammer pin 58a, and the hammer device 10a from their idle positions toward the piston 12a and into their hammering positions, as a result of which the main hammer body 30a closes control openings 24a in the guide means 32a so that a pressure required to drive the hammer device 10a can build up in the gas volume 14a between the piston 12a and the hammer device 10a. The control openings 24a are fluidically coupled directly to a motor compartment 26a constituted by a lubrication oil compartment, as schematically depicted by a conduit 62a. The motor compartment 26a is connected to the surroundings of the hand-held power tool exclusively via pressure compensation conduits, not shown in detail, thus preventing a direct gas exchange between the gas volume 14a and the surroundings of the hand-held power tool.

The hand-held power tool hammer mechanism is depicted in a so-called hammering position in which the hammer device 10a is just beginning to strike the hammer pin 58a and the piston 12a is situated in its front end position oriented toward the hammer device 10a. In this connection, an axial distance 64a between the effective surfaces 52a, 54a of the hammer device 10a and piston 12a in the hammering position corresponds to approximately the hammer device surface dimension 16a and in particular to the diameter of the effective surface 52a of the hammer device 10a. During operation, a maximum gas pressure of approximately 4 to 5 bar builds up inside the gas volume 14a.

FIGS. 2 through 11 show details of alternative hand-held power tool hammer mechanisms. Components that remain essentially the same are basically provided with the same reference numerals; the letters a-k are added to the reference numerals in order to differentiate among the exemplary embodiments. In addition, with regard to defining characteristics and functions that remain the same, reference can be made to the description of the exemplary embodiment in FIG. 1 and to the respective, previously described exemplary embodiments. The description below will essentially be limited to the differences in relation to the exemplary embodiment in FIG. 1 and the previously described exemplary embodiments.

The hand-held power tool hammer mechanism in FIG. 2 has a hammer device 10b that includes a cylindrical main hammer body 30b and two annular decoupling means 28b, 28b′ that are provided to dimensionally decouple an outer dimension of the main hammer body 30b from a guide means 32b constituted by a hammer tube of the hammer device 10b. The decoupling means 28b advantageously constitutes part of an effective surface 52b of the hammer device 10b, which surface is oriented toward the piston 12b and cooperates with a gas volume 14b. It would also be essentially conceivable for a decoupling means to constitute an entire effective surface of a hammer device that cooperates with a gas volume.

The hammer device 10b includes couplings 34b, 34b′ between the decoupling means 28b, 28b′ and the main hammer body 30b, which couplings are provided to couple the main hammer body 30b to the decoupling means 28b, 28b′ in an at least largely synchronous fashion during a flight phase of the main hammer body 30b or the hammer device 10b, i.e. except for a vibration-damping relative motion. The couplings 34b, 34b′ are embodied to exert a vibration-damping action and include connections that are manufactured by being vulcanized in place and/or the decoupling means 28b, 28b′ are vulcanized onto the main hammer body 30b.

The main hammer body 30b is comprised of steel, whereas the decoupling means 28b, 28b′ is comprised of a material lighter than steel, e.g. plastic.

The decoupling means 28b, 28b′ each constitute a guide surface 36b, 38b by means of which the hammer device 10b is guided inside the tubular guide means 32b constituted by the hammer tube; the guide surface 38b of the decoupling means 28b is interrupted by a groove 66b for a sealing ring 68b.

According to the present invention, the hand-held power tool hammer mechanism in FIG. 2 has a hammer mechanism characteristic value Sb of approx. 500 mm³/g, which is composed of the maximum hammer device surface dimension 16b, cubed and divided by the hammer device mass 18b. The hammer device mass 18b here is composed in particular of the masses of the decoupling means 28b , 28b′ and the main hammer body 30b together. The hammer device surface dimension 16b is advantageously constituted by a diameter of the effective surface 52b of the hammer device 10b.

The hand-held power tool hammer mechanism also includes a hammer pin device 58b that has a main hammer pin body 58b′ and an annular decoupling means 60b via which the hammer pin device 58b is guided in the guide means 32b constituted by the hammer tube. The decoupling means 60b here is manufactured out of a lighter material than the main hammer pin body 58b′ itself, in particular of plastic, whereas the main hammer pin body 58b′ is manufactured out of steel. The decoupling means 60b and the main hammer body pin 58b′ are coupled in a form-locking manner in the axial direction by means of a snap ring 70b, which engages with play in a groove 72b of the decoupling means 60b and in a groove 74b of the main hammer pin body 58b′.

The hand-held power tool hammer mechanism in FIG. 3 has a hammer device 10c that has an essentially cylindrical main hammer body 30c and an essentially annular coupling means 28c that serves to dimensionally decouple an outer dimension of the main hammer body 30c from a guide means 32c constituted by a cup-shaped piston 12c of the hammer device 10c. The decoupling means 28c advantageously constitutes part of an effective surface 52c of the hammer device 10c, which is oriented toward an effective surface 54c of the cup-shaped piston 12c and cooperates with a gas volume 14c.

The hammer device 10c includes a coupling 34c between the decoupling means 28c and the main hammer body 30c, which is provided to couple the main hammer body 30c to the decoupling means 28c in an at least largely synchronous fashion during a flight phase of the main hammer body 30c or the hammer device 10c. The coupling 34c is embodied in a vibration-damping fashion; in fact, the decoupling means 28c and the main hammer body 30c are coupled by means of rubber annular damping elements 76c, 78b, a snap ring 80c, a contact disk 82c, an extension 84c formed onto the decoupling means 28c, and a form-locking engagement that intentionally permits a limited degree of relative motion.

The decoupling means 28c is constituted by two guide surfaces 36c, 38c that are spaced apart from each other in the axial direction and guide the hammer device 10c inside the guide means 32c comprised of the cup-shaped piston 12c; the guide surface 38c is interrupted by a groove 66c for a sealing ring 68c. The cup-shaped piston 12c is guided in a hammer tube 86c.

FIGS. 4 and 5 show hand-held power tool hammer mechanisms with stepped hammer devices 10d, 10e and with hammer devices 10d, 10e that have different guide diameters 88d, 88e, 90d, 90e; the guide diameters 90d, 90e respectively correspond to the maximum hammer device surface dimensions 16d, 16e. The hammer device 10d has a stepped main hammer body 30d, which has two cylindrical main forms with different diameters and which, in the region of its smaller diameter on a side oriented away from a piston 12d, is guided by means of a decoupling means 28d in a guide means 32d comprised of a hammer tube.

The hammer device 10e has a cylindrical main hammer body 30e with a continuous diameter 88e, which, at its end oriented toward a piston 12e, is guided by means of a decoupling means 28e in a guide means 32e comprised of a hammer tube. The decoupling means 28e here constitutes a part of an effective surface 52e of the hammer device 10e that cooperates with a gas volume 14e. At its end oriented away from the piston 12e, the main hammer body 30e is guided directly in the guide means 32e.

The hand-held power tool hammer mechanism in FIG. 6 has a hammer device 10f with a main hammer body 30f and a decoupling means 28f that is provided to dimensionally decouple the main hammer body 30f. To this end, the decoupling means 28f is provided, together with the main hammer body 30f, to form a groove 66f for a sealing ring 68f. The presence of the decoupling means 28f permits the main hammer body 30f to be embodied as thin-walled in the axial direction in the region of its guide surface 92f, but the sealing ring 68f can still be advantageously situated in this region. In the direction extending from a piston 12f toward a tool that is not shown in detail, the decoupling means 28f is situated after the guide surface 92f of the hammer device 10f or main hammer body 30f oriented toward the piston 12f.

It is also conceivable, however, for the decoupling means 28g to be situated in a direction extending from a piston 12g toward a tool that is not shown in detail before a guide surface 92g of a main hammer body 30g oriented toward the piston 12g, as depicted in FIG. 7. By contrast with the exemplary embodiment in FIG. 6, a groove 66g is formed exclusively by the decoupling means 28g.

The hand-held power tool hammer mechanism shown in FIG. 8 has a hammer device 10h with a stepped main hammer body 30h, without a decoupling means. The hammer device 10h here has a characteristic value of approx. 0.5, which is composed of a theoretical diameter 94h in a non-stepped cylindrical design of equal mass, divided by a maximum hammer device surface dimension 16h and a characteristic value of approx. 1.5, which is composed of a length 96h of the hammer device 10h, divided by the maximum hammer device surface dimension 16h. The maximum hammer device surface dimension 16h corresponds to a diameter of an effective surface 52h of the hammer device 10h cooperating with a gas volume 14h.

The hand-held power tool hammer mechanism shown in FIGS. 9 and 10 has a hammer device 10i with three guide ribs 40i , 42i , 44i distributed uniformly over its circumference. The guide ribs 40i , 42i , 44i are integrally formed onto a main hammer body 30i.

The hand-held power tool hammer mechanism in FIG. 11 has a cup-shaped hammer device 10j or cup-shaped main hammer body 30j, with a cup opening oriented toward a hammer pin 58j. In a hammering position shown, the hammer pin 58j protrudes into the cup-shaped hammer device 10j and, with an end oriented toward the cup opening, comes into contact with a cup bottom of the hammer device 10j.

The hand-held power tool hammer mechanism in FIG. 12 has a double cup-shaped or cross-sectionally H-shaped hammer device 10k or a double cup-shaped main hammer body 30k, with one cup opening oriented toward a piston 12k and one cup opening oriented toward a hammer pin 58k. In a hammering position shown, an extension 98k of the piston 12k oriented in the axial direction protrudes into the cup-shaped hammer device 10k and the hammer pin 58k protrudes into the cup-shaped hammer device 10k and comes into contact with a side of a cup bottom of the hammer device 10k oriented toward it. It is also basically conceivable for a hammer pin to be provided that has only one cup opening oriented toward a piston.

REFERENCE NUMERALS

10
hammer device

12
piston

14
gas volume

16
hammer device surface

dimension

18
hammer device mass

20
eccentric drive mechanism

22
hammer mechanism

transmission

24
control opening

26
motor compartment

28
decoupling means

30
main hammer body

32
guide means

34
coupling

36
guide surface

38
guide surface

40
guide rib

42
guide rib

44
guide rib

46
eccentric pin

48
spur gear

50
bearing axle

52
effective surface

54
effective surface

56
tool

58
hammer pin mechanism

60
decoupling means

62
conduit

64
distance

66
groove

68
sealing ring

70
snap ring

72
groove

74
groove

76
damping element

78
damping element

80
snap ring

82
contact disk

84
extension

86
hammer tube

88
guide diameter

90
guide diameter

92
guide surface

94
diameter

96
length

98
extension

100
electric motor

S
hammer device characteristic

value

Hand-held power tool hammer mechanism

Information

Publication Number

Date Filed

Date Published

Inventors

CPC

US Classifications

International Classifications

Abstract

Description

Claims

Priority Claims (1)