Patent Publication Number: US-6334421-B1

Title: Motor saw

Description:
FIELD OF THE INVENTION 
     This invention relates to a motor saw with a motor which is fixed to a casing and which shows an intake port which is connected for decoupling oscillations with a carbureter over a resilient suction hose, the carbureter itself taking its bearing on the casing by means of fixing means. 
     BACKGROUND OF THE INVENTION 
     Such a motor saw is known for example from the document DE-A1-42 34 483. 
     The carbureter of a motor saw driven by an internal combustion engine (generally a high-speed two-cycle engine) has a considerable influence onto the operating behaviour of the device. Oscillations which come from the moving piston of the motor and act onto the carbureter can result in an irregular fuel supply which endangers a troublefree motor operation. For this reason, it is already known by the prior art for motors which are provided with a carbureter to connect the carbureter with the motor by means of a resilient admission pipe and to additionally create a resilient suspension of the carbureter in the casing. Such resilient suspensions can be made available by a few types of resilient elements, normally made of rubber. Due to such elements, it is possible to obtain an efficient vibration insulation of the carbureter. However, it is a disadvantage of such a suspension that sufficiently resilient elements for the vibration insulation make too important movements of the carbureter possible. A resilient admission pipe is, for example, known from DE-GM 1 762 310 or by SE-PS 8 6022 481-7. Because of the permanently increasing requirements with respect to the reduction of exhaust emissions, a safe motor operation is necessary. An exact adjustment of the carbureter is the condition of low exhaust emissions. Therefore, an oscillation reduced fixation of the carbureter in the suction space would be very advantageous. Furthermore, the fixation of the carbureter should be simple and easy servicing at low cost. From the above mentioned document DE-A1 42 34 483, it is now known to decouple the oscillations from the intake port of the motor by a gas admission pipe made of an elastomer. The carbureter is hinged to the operating area of the saw over a hinge joint in order to be able to move relatively freely in direction of the gas admission pipe. 
     However, the known hinge joint has different disadvantages. On the one hand, such a connection is comparatively expensive and has a comparatively complicated structure because parts with hinge bores must be produced and the hinge joints must be equipped with corresponding hinge bolts. On the other hand, the mounting and dismounting for servicing is complicated because the hinge bolts must be mounted and locked in the hinge joints with much expenditure and/or unlocked and dismounted. Finally, the hinge joint allows only a limited movability of the carbureter, namely in direction transversely to the hinge joint. On the contrary, a movability in direction of the hinge joint can only be realized with much expenditure if the hinge pins are configured resiliently. 
     Therefore, it has also already been proposed with DE 197 53 689 A1 a suspension for a carbureter which comprises at least one resilient element which is fixed to the casing and which is connected with the carbureter in order to allow a certain extent of movement of the carbureter relative to the housing, a supporting device limiting the extent of the movement. However, this is bound to disadvantages since, due to the limiting and the thus direct connected support of the carbureter, vibrations are still transmitted in an extent which is not to be tolerated. 
     SUMMARY OF THE INVENTION 
     Therefore, the aim of the invention is to create a motor saw which avoids the disadvantages of the solution until now and which especially makes possible a vibration free bearing of the carbureter which is simple, easy servicing and which can be realized at low cost. 
     This aim is achieved for a motor saw of the above mentioned type by the characteristics indicated in claim  1 . Due to the renunciation according to the invention to a hinge joint of the carbureter on the casing by means of hinge bolts and the like and to any supporting and delimiting device, the bearing is much simplified. Simultaneously, due to the resiliently articulated one-point suspension, a bearing is obtained which fixes the carbureter in space but which simultaneously decouples it from the oscillations of the motor and of the casing due to the resilient movability in different directions in space. Due to the renunciation to supporting walls and stoppers, an efficient damping device is created. Due to the preferably progressive characteristic curve of the spring constant of the resilient element, it is obtained that higher frequency oscillations as well as oscillations with lower frequency are efficiently damped. 
     Due to the central arrangement of the damping part and to the chosen one-point fixing, a damping in all planes, i.e. in all directions is achieved. 
     A first preferred embodiment of the motor saw according to the invention is characterized in that a seat made of an elastic material, especially a resilient bushing made of rubber, is fixed to the casing and that the carbureter is detachably snapped-in with a snap-in part into the seat or the resilient sleeve. The carbureter can thus be very easily mounted by snapping-in into the seat and dismounted by snapping-out of the seat. 
     A particularly simple snap-in procedure and a very movable bearing result when, according to a preferred further development of the embodiment, the snap-in part is configured as a ball head. Due to the renounciation to snap-in edges, the snap-in part can be snapped in and out with a comparatively low resistance. The ball head acts additonally as a ball joint. 
     A trunnion which is stuck through the sleeve (not represented) can also be configured instead of the ball head. Thus, the sleeve can be configured with still bigger dimensions (for example air chamber) in order to achieve a special damping characteristic and to simultaneously guarantee a “fixed” adjustment (fixing). 
     A further embodiment of the resilient sleeve allows a configuration of the damping element which is much more resilient. Due to the very resilient configuration, the mounting procedure of the damping element not together with the suction flange is possible. Therefore, the damping element is separated from the suction flange and preliminarly placed in the mounting sequence. The suction flange is snapped-in later. For the configuration of the damping element, due to the ellispoidal form a very “smooth” characteristic curve in direction of the carbureter bottom can be obtained. On the contrary, in the crankshaft axle direction, the spring characteristic will turn out harder. Thus, the whole suction system can be positioned very smoothly but still axially safe. 
     Further embodiments result from the depending claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the invention will be explained in more detail below with reference to the attached drawings. 
     FIG. 1 shows in a sectional view a part of a preferred embodiment of a motor saw according to the invention with the motor and with the carbureter connected therewith which is resiliently positioned in a resilient seat in the casing bottom over a ball head moulded on the intake manifold. 
     FIG. 2 shows a resilient sleeve in a schematical view. 
     FIG. 3 shows a schematical view of a further embodiment of a resilient sleeve in the mounting situation snapped-in the intake manifold. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The motor  101  of a motor saw  100  is represented in FIG. 1 in a cut partial view. The motor  101 , which comprises a cylinder  10  with an intake port  11  and a discharge channel  12  as well as a piston  14 , is screwed with its crankcase  13  on the bottom  20  of a casing  102 . The casing  102  encompasses the motor  101  at least partially and is connected on top by a cap  24 . Inside the casing  102 , a suction space  19  which is besides the motor  101  is separated by a vertical partition  23 , whereby this suction space is closed on top by a (removable) cover  22  and in which a carbureter  16 , especially in form of a diaphragm carbureter, is placed. The carbureter  16  is connected on the outlet side by a resilient suction hose  15  to the intake port  11  of the motor  101 . The suction hose  15  penetrates through an opening in the partition  23  and is positioned there in snap-in position. On the inlet side, the carbureter  16  changes into an intake manifold  17  which is bent-off upwards and discharges into an air filter  18 . 
     A ball head  25  is moulded on the intake port  17  on the lower side, ball head which snaps in into a resilient sleeve  21  of rubber. The resilient sleeve  21  possesses itself noses or trunnions with which it can be stuck-in in a snap-in position into one (or several) opening(s) which are in the bottom  20  or with which it can be stuck through. A differently formed nose or a trunnion with undercut can be naturally used instead of the ball head  25 , whereby they can be stuck-in or stuck through into a correspondingly formed opening in the resilient sleeve or in a comparable resilient seat. However, the ball head  25  has the particular advantage that it can be particularly easily stuck-in and that it simultaneously acts as a ball joint. 
     Because of the resilient embodiment of the sleeve  21  or of the seat, the transmission of oscillations to the carbureter  16  can be considerably reduced. Simultaneously, the carbureter  16  which is connected (for the further avoiding of heat transmission and oscillations) over the resilient suction hose  15  with the cylinder  10  is fixed in all necessary directions. 
     The mounting and dismounting are strongly simplified because of the simple snapping-in of the ball head  25  into the opening provided for this purpose in the resilient sleeve  21 . For the mounting, first the resilient sleeve (seat)  21  is mounted in the bottom  20  of the casing  102 , then the intake manifold  17  with the carbureter suspended on it. The dismounting is carried out in the reverse order. No tool is required for this. 
     In FIG. 2, a further embodiment of a resilient sleeve  26  is represented which consists of a resilient ring-shaped damping body  27  with fixing means  28 ,  29  moulded thereon for fixing on the casing bottom  20  and on the intake manifold  17 . The damping body  27  is optimally adjustable with respect to the desired elasticity and damping behaviour through the selection of the diameter of the ring  27   a  and of the cross-section of the body. The fixing parts  28 ,  29  can have different configurations. The fixing part  28  shows a rod-shaped retaining arm  30  with an end-sided snap-in knob  31 , while the fixing part  29  shows a rod-shaped retaining arm  32  with a snap-in connection  33 . The snap-in knob  31  is pushed-in into a correspondingly formed snap-in seat  34  on the intake manifold  17 , while the retaining arm  32  is snapped-in into a corresponding seat (not represented) in the casing bottom  20 . 
     A further embodiment of a sleeve  26  is represented in FIG. 3, the retaining arm  34  of which is stuck-in with the projecting end part  35  into the casing bottom  20 . 
     On the whole, it results from the invention a motor saw with an internal combustion engine for which the carbureter is practically decoupled of harmful oscillations in a simple, low-cost ways easy for mounting and servicing.