Patent Publication Number: US-4921053-A

Title: Vibro-isolation of connections of structural units of hand tools

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to vibro-isolation of connections of structural units of hand tools. 
     The designs of hand tools with pneumatic drive known from the Patent Specifications don&#39;t take into account the existance of vibrations of value exceeding the permissible ones in the directions perpendicular to the main axis of symmetry of the tool. Vibro-isolations introduced in those designs are limited to one direction of vibrations only, that is to the direction parallel to the axis of symmetry, in which maximum vibration acceleration levels are observed. This relates to the designs presented in the Polish Patent Specifications Nos. 115085, 118242, or 122477. 
     So for instance in the Patent Specification No. 122477 there has been presented a pneumatic hammer with a shock absorber. It has at least two bolts and the corresponding springs slidably mounted on the annular barrel extension, a seat, an immovable elastic ring, mounted with the external dimension in the hammer seat and with the internal dimension in the barrel, as well as a flanged sleeve with a barrel slidably mounted in it. Bolts passing through the said elastic ring connect on one side the seat and on the other side the sleeve via nuts, springs and flange of the above mentioned sleeve. 
     However, such vibro-isolation is not sufficient and does not fulfil the existing vibration standards. 
     SUMMARY OF THE INVENTION 
     The invention consists in that on the side of the body of the compressed-air engine there are elastic guides being the first stage of vibro-isolation on the direction x and y lying in a plane perpendicular to the axis of symmetry of the tool, whereas on the main direction z parallel to the axis of symmetry of the tool, vibro-isolation is an elastic system consisting of a vibro-isolator with a constant reaction force connected to the body of the compressed air engine by means of a spring washer. Vibro-isolator with a constant reaction force is mounted on the side of the grip by means of a spring washer and a sleeve, being at the same time the second stage of vibro-isolation of the grip. Moreover, the second stage of vibro-isolation for the left hand of the operator is the grip itself, having the form of an elastic sleeve screwed onto the end portion of the body-housing. Vibro-isolation of the supply system consists of an intermediate sleeve and a slient-block connection of the supply unit with the grip. The upper guide is a silent-block pressed into the seat in the body-housing having, on the side of the body of the compressed air engine, a sleeve made of a material with a small friction coefficient, the lower guide being made of a silent-block, which has on the side of the body of the compressed air engine a sleeve with a hole with internal splines. 
     Introduction of elastic guides makes possible relative reciprocating or sliding motions of the engine body in the housing, the lower guide acting additionally as a vibro-isolator for limiting the torsional vibration which can be generated by the working compressed air engine. Owing to the described vibro-isolation system a considerable reduction of the vibration levels of grips for the operator&#39;s hands for all the three directions of vibration has been obtained. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The subject of the invention is presented in the embodiment shown in the drawings, wherein, 
     FIG. 1 is a side elevation partly broken away to show different cross-sectional views of the tool; the cross-sectional view to the left of the elongated axis of the tool being perpendicular to the cross-sectional views to the right of the axis, and 
     FIG. 2 is the section A--A of FIG. 1. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Vibro-isolation of connections of structural units of tools has been effected for the three various directions x, y and z. In the main direction z there has been introduced a constant interaction force vibro-isolator 1 of known type (see, for example, Polish Patent 121,231 dated Oct. 31, 1983). Because such a vibro-isolator is generally known, only a portion thereof is shown in FIG. 1, primarily for the purpose of showing how the vibro-isolator is incorporated within the tool. To the extent illustrated, the vibro-isolator includes a cam 30 mounted on an inner wall of the tool body-housing 8, a pressure roller 32 which rests against the curved surface 34 of the cam 30, and a yoke 36 pressed against the roller 32 by means of a spring 38 contained within the yoke 36, all of these elements being mounted on a guide 5. A complete vibro-isolator, as shown in the afore-mentioned Polish Patent, includes a cooperating additional set of cams, rollers and springs not illustrated herein. As known, the presence of the vibro-isolator is effective to interconnect two structural members while transmitting a constant force therebetween independent of the deflection of the vibro-isolator in response to forces acting on it from one of the interconnected members. 
     In accordance with this invention, the known vibro-isolator 1 is separated by a spring washer /2/ from the body /3/ of the compressed air engine, as well as spring washers-sleeves 4, used in order to ensure full vibro-isolation of the guide 5 of vibro-isolator 1. Similarly, on the side of the grip 14 there are fixed spring washers disposed around the screws (only one shown) securing the grip 14 to the body-housing 8 6 and spring sleeves 7 disposed around the screws (only one shown) securing the guide 5 of the vibro-isolator 1 to the air engine 3. Vibro-isolation of the body-housing on the side of the body 3 of the compressed air engine is ensured by elastic guides 9 and 10. The upper guide 9 is the sleeve 11 made of a plastic matter having a small friction coefficient and considerable damping coefficient which is mounted in an elastic connector 12 made of rubber. The lower guide 10 is a connection of the silent-block type, which serves as vibro-isolation for the directions x, y and z and for torsional vibrations. The guide 10 has a sleeve with a shaped splined slidable connection with the body 3 of the compressed air engine which enables torques to be transmitted from the body-housing 8 on to the body 3 of the compressed air engine. Guides 9 and 10 represent the first stage of vibro-isolation on the way from the body 3 of the compressed-air engine to the grips for the operator&#39;s hands. The second stage of vibro-isolation for the operator&#39;s left hand is an elastic sleeve 13 made of a material having a considerable coefficient of damping screwed onto the body-housing 3 by means of a spring embedded in the elastic sleeve 13. For the operator&#39;s right hand, that is grip 14, the third stage of vibro-isolation represents the spring washer 6 and the elastic sleeves 7. Moreover, a two-stage vibro-isolation for the supply system has been provided. The first vibro-isolation stage represents intermediate sleeve 17 made of a material having a considerable damping coefficient mounted in the body 3 of the compressed air engine. The second stage of vibro-isolation is the elastic sleeve 16 by means of which the supply tube 15 is mounted elastically in the tool grip 14. The supply tube 15 extends downwardly from the grip 14 and into the intermediate sleeve 17 for admitting air into the air engine.