Chain Saw

Abstract

A portable chain saw having an elongated chain carrier about whose circumferential edge portion a saw chain travels. Grip means is rigid with the carrier for gripping by the hands of an operator. An internal combustion engine is provided for imparting to the chain its travelling movement along the edge portion of the carrier. Connecting means connects the combustion engine with the carrier so that they constitute a unit but without transmitting vibrations between the combustion engine and the carrier.

Description

BACKGROUND OF THE INVENTION

The present invention relates generally to a saw, and more particularly to a chain saw. Still more specifically the invention relates to a portable chain saw.

Portable chain saws are already known. Basically they comprise a saw carrier which is elongated and has a circumferential edge portion along which the saw chain travels which is driven by a prime mover, usually an internal combustion engine which is united with the carrier by means of a housing or analogous means. Hand grips are provided so that the unit can be held by an operator. One prior-art construction of such a portable chain saw has the combustion engine and its fuel and oil tank as well as the hand grips connected with one another into a rigid unit, to which in turn the elongated chain carrier is rigidly connected. Vibrations originating in the chain saw, usually from the combustion engine, are transmitted in this construction to the arms of the operator and thus to the body of the latter. Evidently, this at the very least results in premature fatigue, and may even lead to damage to the health of the operator.

This having been realized, attempts have been made to avoid the problem. One such attempt mounts the handgrips via rubber mountings to prevent vibration transmission through the handgrips. According to one embodiment there are two handgrips provided which are connected rigidly with one another and which are connected at three points with the chain saw. The connecting means is in form of rubber elements. However, it is evident that they cannot be very soft--and therefore cannot provide significant damping of the vibrations--because otherwise it would not be possible to properly guide the saw. In particular it is difficult to provide such vibration damping effect in this or in any known construction because the vibrating portion of the chain saw, that is the portion wherein the vibrations originate, has a significantly greater mass than the handgrips themselves.

A further attempt to overcome the problem was made in an embodiment in which the chain carrier and the combustion engine are connected rigidly with one another. The thus obtained unit is mounted on a housing by means of elastic mounting means, and the handgrips in turn are rigidly connected with the housing. However, in this embodiment also it is necessary that the force needed for guiding the saw be transmitted from the handgrips via the elastic mountings into the chain carrier, so that the vibration damping effect obtained is only insignificant.

SUMMARY OF THE INVENTION

It is, accordingly, an object of the present invention to provide a portable chain saw which is not possessed of these disadvantages.

More particularly it is an object of the present invention to provide a portable chain saw which provides for an exact and easy guidance of the saw by the operator but which prevents reliably and to the maximum possible extent the transmission of vibrations between the combustion engine and the chain carrier--and thereby to the handgrips.

In pursuance of these objects, and others which will become apparent hereafter, one feature of the invention resides in a portable chain saw which, briefly stated, comprises an elongated chain carrier having a circumferential edge portion, and a saw chain mounted on the carrier for movement circumferentially of the same along the edge portion. Grip means is rigid with the carrier for gripping by the hands of an operator. An internal combustion engine is provided for imparting to the chain its movement along the edge portion.

According to the invention there is further provided connecting means which connects the combustion engine with the carrier so that they constitute a unit, but in such a manner as not to transmit vibrations between the combustion engine and the carrier.

If a drive pinion for driving the chain is provided and mounted on the crankshaft of the combustion engine, then the invention provides that the longitudinal axis of the cylinder of the combustion engine extend normal to the longitudinal axis of the elongated chain carrier, that the rotating masses of the combustion engine are balanced and the reciprocating masses are imbalanced, and that the combustion engine is fixed against movement lengthwise of the elongated chain carrier by the provision of a distance or spacing element. In this manner the forces which tend to effect such advancement, for instance the force of the travelling chain as the same cuts through wood or the like, and which act upon the internal combustion engine which is mounted in non-vibration transmitting manner, cannot produce such displacement so that the chain cannot lose its tension and become dislocated from the drive pinion. The spacing or distance element is advantageously configurated as a member which is pivotably mounted on the housing of the saw and on the combustion engine. However, it may also be in form of a first abutment provided on the housing and a second abutment provided on the internal combustion engine and engaging the first abutment if and when the combustion engine tends to move lengthwise of the chain carrier. It will be realized that although lengthwise displacement of the combustion engine with reference to the chain carrier is not possible, displacement in direction transversely to such lengthwise displacement--that is normal to longitudinal axis of the carrier--remains possible so that the transmission of vibration is precluded.

The vibration damping effect becomes the more pronounced, the larger the mass of the non-vibrating components is with reference to the mass of the vibrating components. It is therefore a concept of the present invention to mount all possible auxiliary components on the nonvibrating housing, that is all such auxiliary components which must not be absolutely mounted rigid with the combustion engine itself. Thus, there are mounted on the housing the oil and fuel tanks, the chain carrier itself, and the handgrips. Additionally, the carburetor for the combustion engine is mounted on the housing and is connected with the cylinder of the combustion engine via a vibration damping conduit member so that fuel can pass from the carburetor to the cylinder of the combustion engine but without the transmission of vibration between the two. Advantageously the conduit member may consist of rubber or generally an elastomeric material, and it fullfils the additional function of providing thermal insulation between the cylinder and the carburetor.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a diagrammatic fragmentary longitudinal section through a chain saw embodying the invention, taken on the line I--I of FIG. 2;

FIG. 2 is a section taken on the line II--II of FIG. 1; and

FIG. 3 is a view similar to FIG. 1 but illustrating a further embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Discussing firstly the embodiment illustrated in FIGS. 1 and 2 it will be seen that the novel chain saw basically is composed of two major sections, namely a vibrating section and a non-vibrating section. The vibrating section comprises an internal combustion engine 1 of known construction, a crankshaft housing 2, a cylinder 3, a crankshaft 4, a chain drive pinion 5 with a centrifugal clutch 10 of known construction, a muffler 6, an ignition device 7, a blower 8 for cooling air and a starter 9 of known construction.

The non-vibrating section consist essentially of a housing 11, an elongated chain carrier 12 which is connected to the housing 11, a fuel tank 13, an oil tank 14 and handgrips 15, 16 by which an operator holds the chain saw when the latter is to be used. A cover 17 is provided which is fast with the housing 11 and which covers the pinion 5 and the clutch 10; it also serves for mounting of the chain carrier 12. A carburetor 18 and an air filter 19 with a cover 20 are also provided as part of the non-vibrating section.

These two basic sections, each composed of the above-mentioned constituent components, are connected by connecting means which secures them together so that they constitute a unit, namely a portable chain saw, but which prevents the transmission of vibrations between the vibrating and the non-vibrating section.

Specifically, the connecting means is in form of vibration-damping elements 21, particularly of rubber but generally of any suitable elastomeric material. The elements 21 are connected on the one hand at the housing 11 and on the other hand at wall portions 22, 23 of the crank shaft casing 2.

A distance member or spacing member 25 is provided which, despite the mounting of the internal combustion engine 1 by means of the vibration damping elements 21, prevents displacement of the combustion engine 1 and the associated chain drive pinion 5 in direction of the longitudinal axis 24 of the chain carrier 12. As mentioned before such displacement could be the result of the tensile forces exerted by the chain (which is illustrated diagrammatically) as the same cuts through material such as wood. The spacing member 25 in the embodiment of FIGS. 1 and 2 is in form of a guide member 26 which is turnably secured on the one hand on a bolt 27 mounted in the non-vibrating section, and on the other hand on a neck portion 28 of the crankshaft casing 2 which is a part of the vibrating section. However, displacement of the vibrating section with reference to the non-vibrating section in direction normal to the axis 24 are readily possible so that the vibration-damping effect of the connecting means 21 is not adversely affected by the presence of the member 26.

Coming to the embodiment illustrated in FIG. 3 it will be seen that here the distance or spacing member 25 comprises an abutment 29 on the housing 11, which abutment is provided with a surface located in a plane normal to the longitudinal axis 24 of the chain carrier 12. A second abutment 30 is provided on the crankshaft casing 2 of the combustion engine 1 and cooperates with the abutment 29 in such a manner that they contact one another if the combustion engine 1 tends to move in direction of the axis 24 of the chain carrier 12, thereby precluding such movement.

The longitudinal axis 31 of the cylinder 3 of the internal combustion engine 1 extends normal or at least substantially normal to the longitudinal axis 24 of the chain carrier 12, and the carburetor 18--which is sensitive to vibrations--is mounted on the housing 11. To permit the flow of fuel from the carburetor 18 to the cylinder 3 of the combustion engine 1, the two are connected via a vibration damping elastic conduit member 32 which may consist of rubber or a suitable synthetic plastic. The conduit member 32 thus not only serves a vibration damping function while also permitting the flow of fuel from the carburetor 18 to the cylinder 3, but also prevents the transmission of thermal energy between the combustion engine 1 and the carburetor 18.

According to the invention it is advantageous that the combustion engine be so balanced that mass forces develop only in direction normal to the longitudinal axis 24 of the chain carrier 12. This provides for optimum damping, and for this purpose the rotating masses of the crankshaft drive are balanced whereas the reciprocating masses remain imbalanced.

By resorting to our invention we maintain a rigid connection between the chain carrier and the handgrips 15, 16 and the direct and precise guidance of the chain saw which is possible in this manner, while at the same time precluding entirely or almost entirely the transmission of vibrations between the internal combustion engine and its associated auxiliary components, and the non-vibrating section of the saw, including the handgrips, so that no vibrations or only very insignificant vibrations can be transmitted to the hands and arms of an operator.

With the construction according to the present invention the internal combustion engine can freely vibrate with reference to the non-vibrating components of the chain saw and the vibrating masses are reduced to a minimum whereas the proportion of the non-vibrating masses with reference to the vibrating masses is increased.

According to the invention it is possible to mount the combustion engine as "softly" as desirable for purposes of obtaining optimum vibration damping, that is to construct the connecting means 21 in such a manner that the combustion engine 1 can vibrate with reference to the non-vibrating components of the chain saw to any practicable extent, without adversely influencing the handling and operation of the machine while the same is in use.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in a portable chain saw, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

Claims

We claim:

1. A portable chain saw, comprising an elongated chain carrier having a first longitudinal axis and a circumferential edge portion; a housing rigidly connected with said carrier; a saw chain mounted on said carrier for movement circumferentially of the same along said edge portion; grip means rigid with said carrier for gripping by the hands of an operator; an internal combustion engine for imparting to said chain saw said movement and having a crankshaft extending transversely of the elongation of said carrier and a reciprocable piston having a second longitudinal axis normal to said first axis; vibration-damping elements mounting said combustion engine; and spacing means, comprising a spacing element pivotally connected with both said housing and said combustion engine so that said carrier and combustion engine are prevented from relative movement longitudinally of said carrier and transmission of vibrations between said combustion engine and said carrier is suppressed.

2. A chain saw as defined in claim 1, said combustion engine having a casing portion surrounding said crankshaft; further comprising a bolt mounted on said housing; and wherein said spacing element is pivotably mounted on said bolt and on said casing portion, respectively.

3. A chain saw as defined in claim 1; and further comprising a plurality of first auxiliary components rigidly connected with said carrier, and a plurality of second auxiliary components rigidly connected with said combustion engine so that the transmission of vibration between said first and second auxiliary components is precluded by the presence of said damping and said spacing means.

4. A chain saw as defined in claim 3, wherein said second auxiliary components include a blower for cooling air, an ignition arrangement, a muffler, a starter unit, a centrifugal clutch, said rotary pinion and a crankshaft casing.

5. A chain saw as defined in claim 4, wherein said first auxiliary components include a fuel tank, an oil tank, a carburetor, an air filter and covers for openings in said housing.

6. A chain saw as defined in claim 5, said housing and said crankshaft casing being provided with juxtaposed wall portions; and wherein said vibration damping elements are arranged between and connected to said juxtaposed wall portions of said housing and said crankshaft casing.

7. A chain saw as defined in claim 1; further comprising a carburetor mounted on said housing; and a vibration damping fuel conduit member connecting said carburetor with said cylinder of said combustion engine.

8. A chain saw as defined in claim 1, and further comprising a rotary pinion rotating with said crankshaft and transmitting motion from said combustion engine to said chain.