RU2264910C1 - Petrol power saw - Google Patents

Abstract

FIELD: forest and wood-working industry.

SUBSTANCE: the saw has an engine with a sawing apparatus, supporting frame with a tubular section attached to the engine body through springs, stop, front and rear control handles. Precompressed cylindrical inserts are placed inside the springs of elastic polymeric material with gas cells isolated one from another, the diameter of the insert equals the spring inside diameter, and the height of the insert in a free non-compressed state makes up 1.1 -1.2 of the distance between the supporting frame and the engine body of the saw in the points of attachment of the springs.

EFFECT: enhanced degree of suppression of vibrations.

3 dwg

Description

The invention relates to the forestry and woodworking industries and can be used in enterprises for the design and manufacture of gasoline-powered saws. In the present invention, a gasoline-powered saw is developed in which an effective vibration protection of the operator’s hands is provided in a wide frequency range (30-1000 Hz).

A gasoline-powered saw is a powerful source of dynamic loads, which, depending on the operating mode, are fully or partially perceived by the operator. In this regard, one of the most important tasks when creating hand-held gasoline-powered saws is to achieve the maximum reduction in the level of vibration on the outer surfaces of the control handles covered by the operator's hands when working with the saw.

The complexity of solving this problem lies in the fact that, depending on the operating mode (idling on the bucking, bucking, felling), the operator’s hands are affected by vibration loads in a wide frequency range (30-10001 Hz).

In accordance with patent information studies, a fairly large number of mechanical damping devices have been developed over the past years, providing partial damping of vibration on the control handles of gasoline-powered saws.

A portable motor saw is known (see, for example, USSR application No. 2031894 for class B 27 B 17/00 for 1974), in which the control handles are rigidly connected to cages having elastic elements on the inside in the form of an outer and inner ring, connected to jumpers. The vibration transmitted from the engine and the saw apparatus is damped during transmission to the handles due to the absorbing properties of the elastic material of the elastic elements that are mounted on the engine. As the authors note, the presence of elastic elements reduces vibration, provides good vibration resistance and control of the saw in any position. The main disadvantage of this design is that effective vibration isolation of the control levers is provided in a limited range of vibration frequencies. The limitation of the vibration frequency range is due to the specifically specified stiffness properties of the elastic elements. In addition, the saw itself has a rather complex structure and increased weight due to the presence of clips.

Known portable saws (see application of the USSR No. 2331564 for class B 27 V 17/00 for 1976, patent Germany 2043708 for class B 27 B 17/02 for 1977, patent Germany 2525116 for class B 27 V 17 / 02, US patent 3,698,455 for class B 27 B 17/02 for 1972, US patent 3,945,119 for class B 27 B 17/02 for 1976, US patent 4,141,143 for class B 27 B 17/02 for 1979) in which the support frame with control handles is directly attached to the motor housing through elastic elements that provide effective damping of vibration in the high-frequency region. To reduce the level of vibration in the low-frequency spectrum, various designs of rigid dampers are used.

The fastening of the support frame with control handles to the saw engine through flexible elastic elements significantly affects the controllability of the saw, which is unsafe for the operator during his work.

A portable motor saw is also known (see application of the USSR No. 3249074 for class B 27 B 17/00 for 1981), adopted by the authors as a prototype. It includes an engine with a saw apparatus, a support frame with front and rear control levers, attached to the engine housing through three rigid springs, partially acting as shock absorbers at high frequencies (500-1000 Hz).

Rigid springs provide good controllability of the saw, while in order to reduce vibration on the control handles, the emphasis is connected to the engine housing by means of shock absorbers. When sawing, the emphasis is pressed against the wood and the shock absorbers act as vibration dampers.

The main disadvantage of the prototype saw is the ineffective vibration isolation of the control levers at low operating frequencies, the most dangerous for the human body. Measured at the stand of vibration velocity of the control levers in octave strips of operating frequencies: 31.5 Hz; 63 Hz, 125 Hz; 250 Hz, exceeding the permissible vibration levels by 3-5 dB according to GOST 17770-72 "Manual machines. Permissible vibration levels". The limitation of the frequency range for effective vibration damping is due to the given severity of the shock absorbers.

In the prototype saw, the support frame with the control levers is attached to the engine housing through three rigid springs. The stiffness of the spring is determined by the numerical value of the index "C".

C = D _o / d

where D _about = D-d - the average diameter of the spring;

D is the outer diameter of the spring;

d is the diameter of the spring wire.

In accordance with the reference data (see V.I. Anuryev, "The Handbook of a Mechanical Engineering Designer, Volume 3, M .: Mashinostroenie, 1979, p. 96) for screw cylindrical compression and tension springs made of circular steel, the index" C "has values from 4 to 3 2. The smaller the numerical value of the index "C", the greater the stiffness of the spring.

In the prototype saw, the bolt fastening of the support frame with the motor housing is carried out through hard springs (C = 4.0) with virtually no prior loading. With such a rigid fastening of the support frame with control handles to the engine casing (vibration source) when operating in the “idle running on a bucking” mode, the operator’s hands in the low frequency range (31-250 Hz) are exposed to vibration loads exceeding 3-5 dB permissible vibration levels. And only in sawing under load at frequencies of 500-1000 Hz do springs act as vibration dampers.

The technical task of the present invention is to remedy these disadvantages and create a gasoline-powered saw design, which provides vibration damping in the entire frequency range 31-1000 Hz.

The technical result of the invention is that the support frame is attached to the engine housing through springs, inside of which there are pre-loaded (pre-loaded) cylindrical inserts of elastic polymer material with gas cells, isolated from one another, while the diameter of the insert is equal to the inner diameter of the spring and the height of the insert in the free (not pressed) state is 1.1-1.2 of the distance between the support frame and the saw motor housing at the points of attachment of the springs.

In Fig.1 shows a gasoline-powered saw, General view. It contains an engine 1, a saw apparatus 2, a support frame 3 with a tubular part 4, fixed to the engine housing 1 through springs 5, a front handle 6 located on the tubular part 4 of the support frame 3, a rear handle 7, an abutment 8 and cylindrical inserts 9 of elastic polymer material with gas cells 10 isolated from one another. Two places of fastening of the support frame 3 to the housing of the engine 1 through the springs 5 are shown in FIG. Figure 3 enlarged shows inside the spring 5 a cylindrical insert 9 of elastic polymer material with gas cells 10 isolated from one another.

The operation of a gasoline-powered saw is as follows. The engine 1 with the saw apparatus 2 generates spatial vibration transmitted through the support frame 3 to the control handles 6, 7. The placement in the springs 5 of the pressed cylindrical inserts 9 of elastic polymer material with gas cells eliminates the direct transmission of vibration in the low frequency range 31-250 Hz from the engine 1 with the saw apparatus 2 to the support frame 3 with the control handles 6, 7.

Vibration damping in the design of the saw proposed by the authors is carried out:

- in cold running due to internal friction in the polymer base (matrix) of the visco-resistant material of the inserts 9 and due to the work of deformation of the shells of the internal gas cells 10 when exposed to vibrational load;

- in sawing due to the elastic deformation of the springs 5 for compression and torsion.

Based on numerous experimental data (sawing at a stand in idle mode, bucking and roll with measuring vibration levels on the outer surface of the handles), the authors found that the value of the preliminary compression of the elastic inserts 9 inside the springs 5 is of great importance for the vibration levels in the proposed design. The value of the preliminary compression of the inserts is determined by the ratio of the height of the insert in a free (uncompressed) state to the distance between the support frame 3 and the saw motor housing 1 at the fasteners Niya spring 5.

When the insertion height in the free (uncompressed) state is less than 1.1 from the distance between the support frame and the saw motor housing, the insertion springs are practically not loaded at the points of attachment of the springs and the stiffness of the saw-operator system is determined by the stiffness of the springs. When idling, the springs have large bending movements. As a result of this, vibration loads on the operator’s hands in idle mode increase. In this mode of operation, the saw is in limbo in the hands of the operator and represents a certain mass with a vibration source (saw engine idling). The operator’s hands, compressing the control handles and holding the saw, represent a certain attached mass to the saw through the springs. A dynamic system is formed in which the attached mass (operator's hands) and springs with large bending movements become a dynamic damper for a gasoline-powered saw, as a result of which there is a powerful selection of energy from a vibration source (saw engine) and its transfer to the operator’s hands. In addition, due to the great flexibility of the springs, the controllability of the saw apparatus 2 is deteriorated.

When the height of the insert in a free uncompressed state is more than 1.2 from the distance between the support frame and the saw motor housing at the points of attachment of the springs, the inserts are so loaded and compressed that the polymer base (matrix) of the insert material is pressed through, the shells of the gas cells are closed and, as a result, a decrease in the amount of dispersion of vibrational energy due to the work of deformation of the shells from exposure to vibrational loads.

Thus, only with the height of the insert in a free uncompressed state equal to 1.1-1.2 of the distance between the support frame and the saw motor housing at the attachment points of the springs, the vibration damping efficiency on the control handles of the gasoline-powered saw design of the inventors is ensured.

When the diameter of the insert is equal to the internal diameter of the spring, the insert is in a kind of "cage", which eliminates the bending movement of the insert when working with a saw. This provides effective vibration damping due to deformation of the shells of the internal gas cells of the elastic polymer material of the inserts.

Bench and full-scale tests have been carried out at the timber industry enterprises of Russia of the proposed saw design. Achieved practical damping of vibration on the control levers in octave bands of operating frequencies of 31.5; 63; 125; 250; 500; 1000 Hz

Claims (1)

Gasoline-powered saw, which includes an engine with a saw unit, a support frame with a tubular part, attached to the engine housing through springs, an emphasis, front and rear control handles, characterized in that inside the springs there are pre-loaded cylindrical inserts made of elastic polymer material with gas cells isolated one from the other, while the diameter of the insert is equal to the inner diameter of the spring, and the height of the insert in a free uncompressed state is 1.1-1.2 distances between the support frame and the saw motor housing in places of fastening of springs.

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