Patent Document

CROSS REFERENCE TO RELATED APPLICATIONS 
   The present application is based on International Application Number PCT/IB2005/001436 filed May 25, 2005, and claims priority from French Application Number 0405713 filed May 27, 2004, the disclosures of which are hereby incorporated by reference herein in their entirety. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention lies in the sphere of internal combustion engine gas-operated fixing devices. They operate on the principle of explosion of an inflammable mixture of gas and air in the combustion chamber of the engine, formed partly of a cylinder, a cylinder sleeve and a cylinder head, to propel into the cylinder a piston for driving a fixing device. 
   2. Description of the Related Art 
   The engine is arranged in a casing. 
   The case is arranged in the two shells of a handle to which it is fixed both at the front and at the rear. To be more specific, at the rear, the cylinder head of the engine, the casing and the handle shells are fixed together with the same bolts. 
   When the inflammable mixture in the combustion chamber is under pressure, a force directed towards the rear is exerted on the cylinder head and therefore on the casing to which it is connected. 
   Inversely, when, under the explosion action, the piston is propelled towards the front, it stops against a damper which is connected to the cylinder. A force directed forwards is thus exerted on the cylinder and therefore on the casing to which it is connected. 
   In brief, the casing, generally made from plastic, is subjected to a high degree of pressure stresses, up to 60% of all these stresses. 
   The casing of the gas-operated fixing devices already acts as a flexible damper since it manages to stretch a little. 
   The applicant realized that the casing was deforming where it was easiest for it, i.e. at the front of the equipment. 
   Therefore, from a situation in which a gas-operated fixing device casing is integral with the handle of the device, both at the front and at the rear, the applicant conceived the idea of trying to solve the problem of separating the front of the casing from the handle so as to enable the casing to perform better its function as a damper. 
   So it is that the invention covered by this application is proposed. 
   BRIEF SUMMARY OF THE INVENTION 
   The invention concerns a gas-operated fixing device comprising an internal combustion engine for driving fasteners, arranged in a casing fitted in a handle and fixed to it at the rear, characterized in that the front of the casing is fitted floating in the handle to be able to slide in it along the driving axis of the fasteners. 
   An extra major advantage of the invention is that it eliminates a large part of the relative vibrations of the casing and the handle, which aids the components housed in the handle of the device, particularly the electronic components. It also makes everything more comfortable for the operator. 
   In one interesting form of making the device covered by the invention, the front of the casing is fitted so as to slide in the handle towards the front up to front stops, and advantageously towards the rear up to rear stops. 
   In the preferred form of the device covered by the invention, the casing and the handle of the device are fixed to each other by tenon and slot assemblies. 
   The tenons and slots are advantageously oblong in shape, the tenons being shorter than the slots at the front of the casing. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood by reading the following description, developed with reference to the appended drawing in which 
       FIG. 1  is an axial section view of the fixing device of the invention; 
       FIG. 2  is a rear perspective view of the device of the invention, and 
       FIG. 3  is an exploded perspective view, slightly to the rear, of the casing and of the shells of the handle of the device. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The heat engine  1  of the device of the invention consists essentially, on the one hand, of a cylinder  2 , with a centreline  20 , in which a piston  3 , with its rod  32 , is fitted so as to slide in order to drive a fastener through a nose, or guide point,  4 , of the device, and, on the other hand, a combustion chamber  5 , formed at the rear of the cylinder  2 , of a cylinder sleeve  6 , the drive piston  3  and a cylinder head  7 . A fan  8  for stirring the inflammable mixture, draining and cooling, is arranged in the chamber  5 , its electric motor  33  being housed in the cylinder head  7 , beyond which a spark plug (not shown) projects into the chamber. In its forward stroke the piston  3  abuts against a shock absorber  34  arranged at the front end of the cylinder. 
   The heat engine is arranged in a casing  9  closed at the rear by a ventilation cover  10  and two shells  11 ,  12  of a handle  13 . To be more precise, the casing has four angle grooves such as groove  55  in  FIGS. 2 and 3 , ending at the rear with four supporting shoulders  14 ,  17 , in each of which a smooth bore is drilled to take, driven through the bores, four bolts  21 - 24  for fixing the cover  10  and the handle shells  11 ,  12 , the bolts being screwed into two pairs of tapped angle stiffeners such as the stiffener  56  in  FIG. 3 , formed at the rear of the shells, on their inside wall, these stiffeners being housed in the grooves  55  of the casing, supported against the shoulders  14 - 17 . The angle stiffeners  25 - 28  at the rear of the shells can retain the cylinder head  7  in certain instances. 
   Each of the handle shells has a pierced frame  36  ( 37 ) designed to be laid against a side wall  38  ( 39 ) of the casing and, at the rear, a semi-flange  40  ( 41 ) to improve the rear covering of the casing by the two semi-flanges joined, by tongue and groove, as a fixing sleeve  42 . Each shell is extended at the rear by the real handle part  43  ( 44 ) and, at the front, by a housing or supporting structure  45  ( 46 ), either for an electricity supply battery or for a fasteners charger. 
   Therefore, the engine  1  is arranged in the casing  9  which is fitted into the assembly of the two shells  11 ,  12  of the handle  13  to which it is fixed at the rear by the bolts  21 - 24 . 
   On their inner surface  46 , at the bottom near the handle  43 ,  44 , the shell cheeks  36 ,  37  carry, from the same castings, small annular funnels, oblong in section, one  47  at the rear and another  48  at the front.  FIG. 3  shows only the inside surface and the funnels of the left side cheek  37 . As will already have been noted, the fixing arrangement has a plane of symmetry going through the centreline  20 . 
   The side walls  38 ,  39  of the casing  9 , in positions corresponding to those of the funnels  47 ,  48 , therefore at the bottom at the front and at the rear, also have, from the same casting, small annular funnels  49 ,  50 , also oblong in section, designed to work in conjunction by fitting into each other, like tenons and slots, with the funnels  47 ,  48  of the shell cheeks  36 ,  37 .  FIG. 3  shows only the funnels  49 ,  50  of the side wall  38  of the case  9 . The rear tenons and slots  49 ,  47 , more of less with the same inside and outside sections, fit overall more or less by force fitting into each other. On the other hand, the front tenons and slots  50 ,  48 , fit into each other with a slight force fit in their cross dimension but not in their dimension parallel to the centreline  20 . In other words, the outside axial length of the tenons  50  of the front part  91  of the case  9  is appreciably shorter than the inside axial length of the slots  48 , specifically to enable axial sliding of the tenons in the slots. Thus, the front  91  of the case  9  is fitted floating in the handle  11 - 13  and can slide in it along the drive axis  20  of the fasteners. 
   Of course, the respective arrangements of the tenons and slots could be reversed, the tenons forming part of the casting of the handle shells. In all cases, the front tenons are shorter than the front slots. 
   The front  51  and rear  52  annular walls of the front funnel slots  48  act as front and rear stop parts for the front tenons  50  of the case.

Technology Category: 7