EP0582696A1

EP0582696A1 - Hand-operated power tool

Info

Publication number: EP0582696A1
Application number: EP19930904011
Authority: EP
Inventors: Alfred SCHÄR; Mihail Stefanopulos; Benedikt Barbisch
Original assignee: Scintilla AG
Current assignee: Scintilla AG
Priority date: 1992-02-29
Filing date: 1993-02-24
Publication date: 1994-02-16
Also published as: DE4206438A1; WO1993016585A1; JPH06507317A

Abstract

Outil commandé à la main, notamment entraîné électriquement, comme un taille-haies (1), une meuleuse d'angle et autre outil de ce type, dans lequel un embrayage à roue libre commutable agit entre l'entraînement et l'outil, avec des corps de serrage (37) pour entraîner l'outil et le mettre en roue libre. Pour ce type de dispositif, on obtient une séparation encore plus rapide de l'arbre d'entraînement et de l'arbre de sortie pour un arrêt à faible décélération des couteaux de taille-haies, lorsque seul un arrêt de blocage par friction (35, 37, 39, 41, 43), notamment des cliquets de roue libre, sert d'embrayage à roue libre.Hand-operated tool, in particular electrically driven, such as a hedge trimmer (1), an angle grinder and the like, in which a switchable freewheel clutch acts between the drive and the tool, with clamping bodies (37) for driving the tool and coasting it. For this type of device, an even faster separation of the drive shaft and the output shaft is obtained for a slow deceleration of the hedge trimmer knives, when only a friction blocking stop (35 , 37, 39, 41, 43), in particular freewheel pawls, serves as a freewheel clutch.

Description

Hand-held, power-operated machine tool

State of the art

The invention relates to a hand-held, power-driven machine tool according to the preamble of claim 1.

DE-OS 40 05 133 discloses a generic hedge trimmer in which a switchable freewheel clutch in combination with a wrap spring causes entrainment or standstill of the hedge trimmer blade between the drive and the tool. The actual task of the known solution, to prevent the hedge trimmer blades from running after switching off with as little delay as possible, is only achieved with a certain inertia under certain conditions. A complete decoupling of the drive area from the output area is not possible quickly enough.

The reason for this inertia, which may occur, is the use of the wrap spring for latching on a switchable roller body freewheel. In addition, the one-way clutch of the known hedge trimmer consists of a large number of parts which are complicated to manufacture, are heavier and are difficult to assemble.

Advantages of the invention

The machine tool according to the invention with the characteristic features Painting claim 1 has the advantage that the connection between the drive train and the output is released when the machine tool is switched off with an unprecedentedly short reaction time. The one-way clutch consists of only a small number of very light individual parts which can be produced at low cost and can be assembled in a short amount of time. In addition, the machine tool according to the invention has a lower overall volume and weight and is therefore more manageable than the known machine tools.

The wrap spring in the known solution is more expensive to manufacture than the cage switching sleeve used in the invention. In addition, the clamping bodies designed according to the invention as clamping levers are smaller in volume than clamping rollers and moreover have a larger friction surface than rollers, which is why more clamping levers than rolling bodies can be accommodated on the circumference of the surfaces to be coupled. Because of the smaller volume, smaller mass forces are required to move the clamping bodies than to move the rollers. This leads to reduced reaction time as well as the fact that the clamping bodies only have to be tilted in order to be brought into the coupling or uncoupling position, while the rollers have to be rolled over a relatively long way in order to get out of the clamping position.

The clamping bodies according to the invention run between two smooth cylinder walls, while in the known solution the rollers in the outer cylinder make curved path-like recesses necessary, the manufacture of which requires great effort.

Further advantageous embodiments of the invention result from the claims following claim 1.

drawing

Exemplary embodiments of the invention are described in the following Spelling explained in more detail using the accompanying drawing.

FIG. 1 shows the side view of a hedge trimmer, FIG. 2 shows the sectional view of a section of the hedge trimmer according to the invention, FIG. 3 shows the enlargement of a detail from FIG. 2 with the area of the drive and output, FIG. 4 shows the view of a switching sleeve according to the invention, the figures 5 and 6 show a schematic illustration of the one-way clutch when coupling and when uncoupling.

Description of the embodiment

FIG. 1 shows the structure of a hedge trimmer 1, which consists of a housing 3 with a first handle 5 and a second handle 7. The housing 3 accommodates a motor, not shown, with an output shaft and power transmission system, which are coupled to hedge trimmer blades 31, 33.

The hedge trimmer 1 according to the invention shown in section in FIG. 2 shows the housing 3 with the first and the second handle 5, 7, which receives a motor 11 with an output shaft 13. At the free end of the output shaft 13 there is a pinion 15 which meshes with a ring gear 17 which is rotatably mounted about an axis 19. The ring gear 17 is non-positively connected to a drive sleeve 23 via a slip clutch 21 and rotatably mounted on a crankshaft 25 concentrically with the axis 19. A first and a second eccentric disk 27, 29 are arranged on the crankshaft 25 in a rotationally fixed manner, which are coupled in the manner of a crank pin to a hedge trimmer knife 31, 33 and convert the rotating movement into an oscillating movement.

Arranged between the drive sleeve 23 and the crankshaft 25 is a one-way clutch which consists of clamping bodies 37 which are captively arranged in a cage sleeve 35 and which are held in the cage sleeve 35 by means of a band-like elastic means 39. Except the clamping body 37 engages radially with its outer end a switching sleeve 41 arranged in a cage. The switching sleeve 41 is connected on its front side on the machine side to a disk 43 with radial cams 45. A shifting pin 47, which is displaceable parallel to the axis 19, can engage in the cams 45. The switching bolt 47 is arranged on a leaf spring-like bolt carrier 49, which is shifted into the blocking position shown in FIG. In the blocking position, the switching pin 47 engages in the cams 45 and thus holds the disk 43 with the switching sleeve 41 in place.

The function and structure of the one-way clutch according to FIG. 2 is the same as that according to FIG. 3 to be explained below and is therefore only to be explained after the description of FIG. 3.

The enlarged section according to FIG. 3 in the area of the freewheel clutch of the hedge trimmer 1 shows, in accordance with FIG. 33. The one-way clutch shows the clamping bodies 37, which are captively arranged in the cage sleeve 35 and are held in the cage sleeve 35 via the band-like elastic means 39. The clamping bodies 37 penetrate radially through the cage-like switching sleeve 41. The switching sleeve 41 is connected to the disk 43 on one end face. The switching pin 47 can engage in their cams 45. For the sake of simplicity, because it is not essential for the invention, the slip clutch 21 from FIG. 2 is not shown.

In addition, in contrast to FIG. 2 in FIG. 3, a friction-reducing needle bearing 51 is arranged between the ring gear 17 and the crankshaft 25.

Is on the drive shaft 13 of the ring gear 17 when starting Motors 11 driven, the switching pin 47 is disengaged from the cams 45 of the disc 43. Together with the ring gear 17, the switching sleeve 41 rotates, so that the clamping bodies 37 assume a position in which they are due to the tensioning force of the band-like means 39 support in an inclined position between the crankshaft 25 and the drive sleeve 23. In this support position, the ring gear 17 which is integral with the drive sleeve 23 seeks to straighten the clamping bodies 37 out of their shifting position. This results in high support forces between the clamping bodies 37 and the parts to be coupled during canting, so that rotational entrainment between these parts is ensured. The principle of the sprag freewheel is that the sprags 37 straighten up when coupling, as happens with the individual hairs of a fur when brushing against the grain.

If the on and off switch (not described in more detail) is switched to its off position, the switching pin 47 moves into the engagement position with the disk 43, so that the latter is braked suddenly. The switching sleeve 41 is held together with the disk 43. The latter tries to reinforce the inclined position of the clamping bodies 37, which is supported by a torque difference between the crankshaft 25 and the ring gear 17.

If the clamping bodies 39 are placed in their desired inclined position, which occurs without delay within a very short period of time, the frictional connection between the ring gear 17 and the crankshaft 25 is separated. The output shaft 13 and the toothed ring 17 can rotate freely with respect to the drive train consisting of the crankshaft 25 and the pair of knives 31, 33, the drive train coming to a standstill quickly due to the friction between the reciprocating hedge trimmer knives 31, 33.

FIG. 4 shows the individual switching sleeve 41, which carries the clamping bodies 37 here alone, without a separate cage sleeve, these of a thin spiral spring, the elastic holding means 39, is gripped radially and held in the switching sleeve 41.

This saves a cage sleeve according to the exemplary embodiment of FIGS. 2 and 3. Possible sources of error and additional measures are eliminated. The Klemmkorper 37 are provided with a central, open longitudinal groove, which center the engaging band-like elastic means 39. The clamping bodies 37 enter the switching sleeve 41 through slots 42, through which they cannot fall due to their wide head area.

The disc 43 can be seen particularly clearly with one of the propeller-wing-like switching cams 45.

The cross section of a further exemplary embodiment of a one-way clutch with more than three clamping bodies, shown schematically in FIGS. 5 and 6, shows once the end position uncoupling and once the end position take away. A separate clamp body cage was also dispensed with in this exemplary embodiment. Its function is also perceived by the switching sleeve 41 and leads to a simplified, functionally reliable and lighter construction.

The individual parts of the toothed ring 17, the crankshaft 25 and the clamping members 37, held by the switching sleeve 41 and the chain-like means 39 shown in broken lines and schematically, can be seen in FIG.

It is clear from FIG. 5 that the clamping bodies 37 each assume an oblique position with respect to a radial line 44 drawn through dash-dot lines through the crankshaft axis. This oblique position is brought about by the switching sleeve 41 being brought to a standstill from the outside. By holding the switching sleeve 41 under the assumption that the crankshaft 25 and the ring gear 17 move counterclockwise, the clamping bodies 37 tilt out of their cant In the position shown below in FIG. 6 and in this stop position on the switching sleeve 41, it is no longer possible to return to its tilted position coupling between the crankshaft 25 and the ring gear 17. This is due to the frictional entrainment of the clamping bodies 37 in their area facing the crankshaft 25. The torque generated by the friction force on the clamping body 37 about the stop point of the switching sleeve 41 is far greater than a possibly acting friction torque due to the contact of the ring gear 17 with the clamping bodies 37. Only when the switching sleeve 41 is released in order to work with the crankshaft 25 and the ring gear 17 to rotate, the clamping body 37 can tilt between the crankshaft 25 and the ring gear 17.

FIG. 6 shows how the clamping bodies 37 tilt between the crankshaft 25 and the ring gear 1.7. The position of the clamping bodies 37, which is essentially parallel with respect to the radial lines 44, is evident from this. In this upright position, the coupling between the input and output, i.e. switched between ring gear 17 and crankshaft 25.

In an exemplary embodiment of the invention, not shown, the cage sleeve for the clamping bodies is produced from a sheet metal strip which has three transverse slots with the same spacing over its length for receiving the clamping bodies and which is pressed to form a sleeve via a flanged connection.

The clamping bodies here have a circumferential slot / recess into which a thin tension spring wrapping around the cage can fully enter and is supported on the clamping bodies in such a way that they are captively held in a stable position in the cage sleeve. The stable position is more of an inclined position than an upright position parallel with respect to an imaginary radial. There is also a switching sleeve, not shown, which, like the cage sleeve, consists of a triple slotted, flanged metal strips, the slots are each cruciform, so that both the upper area of the clamping body and in some areas the tension spring wrapping around the clamping body can pass through these slots and thus ensure the holding and support function of this spring.

The switching sleeve, not shown, is also connected via a flange connection to a thick-walled sheet-metal disk which carries three cams pointing radially outward in the manner of a propeller wing.

In another, not shown Ausführungsbeispi ^'el the Klemmkorper are not, however, an¬ mutually supporting manner between the parts to be coupled placed over spring sleeve, so that each individual Klemmkorper transmits its swiveling movement to the benach¬ disclosed clamping body in a cage. This synchronizes the sprag movement and improves the function of the freewheel. Such a freewheel can be switched from the outside by holding the spring sleeves with suitable stop means.

In a further exemplary embodiment, not shown, the clamping bodies are designed as rotary wedges which can couple together rotating parts which are axially contested.

Claims

1. Hand-held, in particular electrically driven, machine tool such as hedge trimmers (1), angle grinders and the like, in which a switchable freewheel clutch with clamping bodies between drive and tool (31, 33) causes either entrainment or freewheeling of the tool, characterized in that that only a canting friction lock (35, 37, 39, 41, 43), in particular a sprag freewheel, serves as the one-way clutch.

2. Machine tool according to claim 1, characterized in that a clamping body freewheel (35, 37, 39, 41, 43) with at least two clamping bodies (37) radially between a driving part (15) and an increasing part (25 ) is arranged.

3. Machine tool according to claim 1 or 2, characterized in that the clamping body (37) are adjustable from the outside in two end positions.

4. Machine tool according to claim 1, 2 or 3, characterized gekennzeich¬ net that the clamping body, in particular clamping lever (37) or Drehkei¬ le, in at least one cage (35, 41) ', in particular captive, resilient, are arranged.

5. Machine tool according to one of claims 1 to 4, characterized ge indicates that the clamping lever (37) by a wrapping band

like elastic means (39) acted upon radially to the cage (35, 41), and that they are mounted relative to the cage (35, 41) without a predetermined pivot point.

6. Machine tool according to one of the preceding claims, characterized in that the clamping bodies (37) are supported outside of their center of gravity on the cage (35, 41) and can oscillate in the supporting position from one to the other end position.

7. Machine tool according to one of the preceding claims, characterized in that the clamping bodies (37) pass through slots (42) of the cage (41), their area protruding from the slots (42) being wider than each slot (42).

8. Machine tool according to one of the preceding claims, characterized in that the clamping bodies (37) have hardened outer surfaces which are supported on the one hand on the crankshaft (25) and on the other hand on the ring gear (17).

9. Machine tool according to one of the preceding claims, characterized in that the outer surfaces of the clamping body (37) are so shaped that they cant in one end position against the parts to be coupled (17, 25) and in the other end position unrolling from the parts to be coupled (17, 25).

10. Machine tool according to one of the preceding claims, characterized in that the cage (41) is connected at one end to a disc (43) with cams (45) for engaging switching means (47).

11. Machine tool according to one of the preceding claims, da¬ characterized in that a special holding cage (35) for the clamping body (37) is arranged within the switching sleeve (41).