Cutlery – Cutting tools – With blade moving means
Reexamination Certificate
2001-07-13
2003-04-22
Payer, Hwei-Siu (Department: 3724)
Cutlery
Cutting tools
With blade moving means
C173S162100, C464S052000
Reexamination Certificate
active
06550145
ABSTRACT:
BACKGROUND OF THE INVENTION
In work apparatus such as brushcutters, edge cutters or the like, a relatively long guide tube is provided between the drive motor and its housing, on the one hand, and the driven rotatable work tool on the other hand. The guide tube accommodates the drive shaft. With this arrangement, a relatively soft connection is presented between the motor and the work tool. During operation, vibration problems can result in connection with the interaction between the drive motor and the driven work tool.
The guide tube is connected to the motor housing via an anti-vibration element in order to avoid such vibration problems. The occurring vibration problems must be effectively damped by such an anti-vibration element. At the same time, a reliable connection of the guide tube to the motor housing must be provided thereby.
Configurations are known wherein a clamp is fixed with clamping lugs on the motor end of the guide tube. The clamp has clamping lugs, for example, made of plastic or die cast metal. A tubular-shaped damping element made of elastic material is pushed over the clamp. For assembly, the unit comprising the guide tube with the clamp and the damping element is pressed into a corresponding receptacle of the motor housing. The clamping lugs project at the end face beyond the motor housing which requires a correspondingly large amount of space for accommodating the same. The press-in operation requires complex devices and alignment errors in the assembly state cannot be precluded. An exchange of the guide tube, for example, at a service station is difficult without corresponding devices. A guide tube seated with precision during manufacture can become displaced or rotate relative to the motor housing under high or continuous loads. The clamping action between the clamp and the guide tube can deteriorate when the material yields, for example, in the case where the clamp is made of plastic. For an embodiment wherein the clamp is made of die cast aluminum, the clamp is very stiff so that it can adapt to the guide tube only to a limited extent.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a vibration-dampening connection of a guide tube to the housing of a work apparatus as well as to improve the exchangeability of a guide tube.
The portable handheld work apparatus of the invention includes a brushcutter and an edge cutter. The portable handheld work apparatus includes: a housing; a guide tube having first and second ends; a drive shaft rotatably journalled in the guide tube; a rotatable work tool mounted at the second end of the guide tube; a drive motor mounted in the housing for rotatably driving the work tool via the drive shaft; an anti-vibration unit for holding the guide tube in the housing at the first end of the guide tube; the anti-vibration unit including a clamp surrounding the guide tube; an elastic damping element disposed between the housing and the clamp; and, the clamp and the housing being configured for fixing the clamp form tight in the housing.
For the above, the clamp, which surrounds the guide tube, is fixed form-tight to the housing of the motor. This affords the possibility to omit pressing the damping element into the motor housing under high pretension. With the form-tight connection, the assembly comprising the guide tube and the anti-vibration unit is reliably fixed on the housing and is secured against rotation or displacement. A rotation or displacement of the guide tube relative to the clamp is permanently avoided by the excellent clamping action between the two. A simple exchange without special tools is possible because of the configuration of the form-tight connection. The form-tight fixation of the clamp on the motor housing is practical in the region where the clamp for the guide tube is secured with threaded fasteners.
It is advantageous when the clamp is configured as an approximately cylindrical clamping sleeve having one or several longitudinal slots and two or more clamping lugs which can be clamped against each other and which extend radially outwardly and are arranged laterally of the longitudinal slot. The housing has an end face at the end thereof facing toward the guide tube and further has a cutout in the end portion in which the clamping lugs of the clamp are accommodated. At the same time, a reliable clamping of the clamp on the guide tube is provided with the clamping lugs with simple means. The clamping lugs project radially and lie in the cutout of the housing and simultaneously also form a form-tight configuration to prevent rotation. The rotation is here prevented without additional devices. The cutout at the end of the housing is advantageously open in the direction of the end face so that the clamping lug can be inserted into the receptacle from the end face for assembly without disassembly of the housing.
In a practical embodiment, the clamping lugs each include a bore for passing through a clamping bolt for which at least one and preferably two openings are provided in the housing for accommodating the ends of the clamping bolt. These openings are aligned approximately coaxial to the clamping bolt. In this way, after assembly of the clamp, the clamping bolt can be guided through one of the two openings in the housing as well as through the corresponding bores in the clamping lugs and then be clamped, that is, threadably tightened. The two ends of the clamping bolt, which lie in the openings of the housing, are then held in a form-tight manner and additionally form also a form-tight connection to ensure against an axial displacement which is in addition to the above-described form-tight security against rotation.
A part of the elastic damping element is advantageously configured in the form of damping bushings surrounding the ends of the clamping bolt. In this way, an effective damping of vibrations in the peripheral and longitudinal directions with respect to the guide tube is given with simple means directly at the form-tight connection of the clamp to the motor housing. The damping bushings advantageously include a peripheral collar with which they are form-tightly fixed in the housing. In this way, they are easy to assemble and protected against dropping out when loosening the clamping bolt. It is practical to arrange the damping bushings so that the clamping lugs of the clamp lie tightly against the end face of the damping bushing and especially against the end face of the collar of the bushing. With this arrangement, no force-transmitting intermediate elements are needed. In addition to an excellent damping action, a relatively rigid connection of the guide tube to the housing is provided.
In a simple and practical configuration, the clamping bolt is configured as a threaded bolt having a head and a nut. A first metal sleeve for accommodating the head is provided in one bushing and a second metal sleeve for accommodating the nut is provided in the other bushing. The metal sleeves are especially made of steel. The steel sleeves can be manufactured in a simple and cost-effective manner and prevent an excessive areal pressing between the clamping bolt and the damping bushings.
In an advantageous embodiment, the sleeves include two flats lying approximately parallel to each other between which the nut is held against rotation. As a consequence thereof, the clamping bolt, which is configured as a threaded bolt, need only be rotated at its head with a suitable tool without it being necessary to hold the nut with a further tool. An arrangement of this kind simplifies the automatization of manufacture as well as the exchange of a damaged guide tube or the anti-vibration unit as may be required.
In a further practical embodiment, the sleeve and the nut can be configured also as one piece whereby the number of parts to be assembled is reduced. The sleeves have a holding slot on the end face thereof into which a screwdriver can be seated as needed. For example, in the case of a thread which has become fixed because of rust, the screw connection of the clamping bolt can be loosened
Schneider Andreas
Steinmaier Jürgen
Stoll Gerhard
Andreas Stihl AG & Co.
Ottesen Walter
Payer Hwei-Siu
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