Abstract:
In the apparatus, under the action of the explosion of a mixture of air and gas in a chamber closed by a chamber sleeve tube and a cage when the apparatus is pressed against something, a piston is propelled in a cylinder to drive an element. The chamber sleeve tube and the cylinder are arranged in such a way that, as the apparatus is closed, the chamber sleeve tube comes into abutment against the cylinder. 
     The invention can well be applied to nail guns and other staplers.

Description:
RELATED APPLICATIONS 
   The present application is based on, and claims priority from, French Application Number 03 09321, filed Jul. 29, 2003, the disclosure of which is hereby incorporated by reference herein in its entirety. 
   The invention relates to an apparatus for sealing or for piercing or for driving or for hammering in any element into a receiving material, of the nail gun, staple gun or hammer type, powered by gas. 
   BACKGROUND OF THE INVENTION 
   In such an apparatus, a piston is mounted so that it can move in a cylinder where it can be propelled, by the explosion of a mixture of air and a fuel gas injected, from a cartridge, into a combustion chamber and to drive an element, for example a fastener (a nail or an insert) or some other anchor. Apart form the bearing-against-something safety feature, that prevents any firing when the apparatus is not pressed against a receiving material, this kind of apparatus has a member, known as a cage, which, when the apparatus is pressed against something, and by way of a feeler that may be a moving insert guide, pushes a chamber sleeve tube back until it comes into abutment against the cylinder head that carries the spark plug intended to cause the explosion, so as to close the combustion chamber thus formed by this sleeve tube, the cylinder head and the crown of the piston. The cage and the sleeve tube may be connected to one another by screwing. Furthermore, the retreat of the cage is performed against the action of a return spring, to return the apparatus to the open position, also bearing against the piston cylinder. 
   Because the combustion chamber bears against the cylinder head, stressful pressures are exerted on the cylinder head when such an apparatus is operating, particularly since the surface portions of the cylinder head and of the cylinder face one another. Even if, in other apparatuses, these detrimental pressures are no longer exerted on the cylinder head, they are transferred to the cage, which is not necessarily any better. 
   SUMMARY OF THE INVENTION 
   The invention in this application aims to dispense with any parasitic pressure stress on both the cylinder head and the cage. 
   To this end, the invention relates to a gas-operated apparatus in which, under the action of the explosion of a mixture of air and gas in a chamber closed by a chamber sleeve tube and a cage when the apparatus is pressed against something, a piston is propelled in a cylinder to drive an element, characterized in that the chamber sleeve tube and the cylinder are arranged in such a way that, as the apparatus is closed, the chamber sleeve tube comes into abutment against the cylinder. 
   An element is to be understood as meaning either a nail, an insert, an anchor, a staple or any similar element. 
   In one embodiment of the apparatus of the invention, the cage and the chamber sleeve tube are connected with clearance in sliding, so as to avoid the propagation of stresses. 
   The chamber sleeve tube may comprise at least one bearing pad intended to come into abutment against a bearing lug of the cylinder, at least one connecting pin connecting the chamber sleeve tube and the cage, and at least one lug acting as a support for an opening spring, bearing also against a flange of the cylinder, and a member whereby the chamber sleeve tube and the cage can push one another. 
   The chamber sleeve tube may also comprise at least one bearing, thrust and connecting pad arranged to come into abutment against a bearing flange of the cylinder in the closed position, at least one connecting pin for connecting the chamber sleeve tube, the bearing pad and the cage and at least one spring for opening the chamber in abutment against the bearing flange and the bearing pad. 
   In this case, it is advantageous for the pad to bear a bearing finger of narrowed cross section designed to bear against the flange of the cylinder and receive the opening spring. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     The invention will be better understood with the aid of the following description of two forms of embodiment of the apparatus of the invention, with reference to the attached drawing in which: 
       FIG. 1  is a profile view of the first embodiment of the apparatus, in an open position; 
       FIG. 2  is a view in axial section of the apparatus of  FIG. 1 , in an open position; 
       FIG. 3  is a view of the apparatus of  FIG. 1  in a closed position, in axial section on a plane inclined by about 20° to the plane of section of  FIG. 1 ; 
       FIG. 4  is a perspective view with partial cutaway of the sleeve tube of the apparatus of  FIG. 1 ; 
       FIG. 5  is a view in axial section of the second embodiment of the apparatus in an open position, and 
       FIG. 6  is a view in axial section of the apparatus of  FIG. 5 , in a closed position. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   At the front of the cylinder head, bearing a spark plug and a motor fan unit, these elements of the apparatus not being depicted any more than are the holding and actuating handle, the gas cartridge and the anchoring element loader, the apparatus comprises a chamber sleeve tube  1 , a cylinder  2  with a smaller cross-section front portion  3 , a cage  4  for closing off the chamber, and a feeler  5 . 
   The feeler  5 , now commonplace, is secured in terms of translation to the cage, here by screws, a semi-tubular front portion  6  of which cage envelopes the rear of the feeler. The front portion  6  of the cage  4  is extended, rearwards, by two lateral arms  7 ,  8  the rear end  9  of which is elbowed towards the axis  16  of the apparatus to form a connecting nib. 
   The two arms  7 ,  8  of the cage extend along the cylinder  2 , on the outside, as far as the front part  10  of the chamber sleeve tube  1 . 
   On its outer wall, the cylinder  2  bears radial bearing lugs  11  to act as stops for the chamber sleeve tube  1  in the closed position and, behind the bearing lugs  11 , radial bearing flanges  12 , acting as stops for return springs  13  for returning the chamber to the open position. 
   In a way which is conventional, which is why the description will not be expanded upon further regarding this point, the rear  14  of the chamber sleeve tube  1  partially forms the combustion chamber  15  of the apparatus. 
   Mounted in the cylinder  2  is a propulsion piston  17 , with its crown  18 , also for partially forming the chamber  15 , and its propulsion rod  19 . The cylinder has a rear bulge  20  in which there is formed a groove for housing a seal  21  intended, in the closed position, with the chamber sleeve tube  1 , to seal the front of the combustion chamber  15 . 
   For this, the chamber sleeve tube  1 , in the central part and in a transverse portion perpendicular to the axis  16 , has, in the axial continuation of a thickening of a chamber sleeve tube which will be dealt with more fully hereinafter, an interior rib portion  22  collaborating with the seal  21  in the closed position. 
   It is the anterior part  10  of the chamber sleeve tube which will now be described more specifically. Here it comprises, at the edge of the sleeve tube and diametrically opposed in the axial plane of section of  FIG. 2 , two bearing, thrust and connecting assemblies  23  and  24 . Each assembly is housed in an external thickening  25  of the wall  26 , with a flat bottom  27 , running from the edge  28  of the sleeve tube over a relatively small axial width. Inside each thickening, and with the same axial width, is arranged a cradle  29  consisting of two bearing pads  30 ,  31  symmetric with respect to the axial plane defined hereinabove, hugging the thickening and, in the case of each, a small portion of the interior wall  32  of the sleeve tube. A connecting pin  33  passes through each thickening and its two pads  30 ,  31  at right angles to the same axial plane. Finally, a radial bearing lug  34  extends between the two bearing pads of each cradle  29 , in the manner of an internal bottom, on the opposite side to the anterior edge  28  of the tube. The return springs  13  returning the chamber to the open position, bearing against the radial bearing faces  12  of the cylinder  2 , also respectively bear against the bearing lugs  34  of the chamber sleeve tube  1 . As for the connecting nib  9  of each arm  7 ,  8 , it is passed, via its free end part  35 , facing towards the axis  16 , behind the associated connecting pin  33 . Thus, the end part  35  of a connecting nib  9  of a cage arm  7 ,  8  can, here, relative to the chamber sleeve tube  1 , be driven in relative sliding over a clearance travel of a length equal to the distance separating the bearing lug  34  and the connecting pin  33  of the associated cradle  29 , making it possible to qualify the sliding connection between the cage and the sleeve tube as a connection involving play. This degree of freedom here avoids the propagation of stresses. 
   In another form of embodiment that will be dealt with hereinbelow, the cage and sleeve tube could be connected in terms of sliding without play. 
   The way in which the apparatus works will now be described. 
   When the apparatus is made to bear against a receiving material, the cage  6 , via the feeler  5 , is pushed towards the rear of the apparatus. The connecting nibs  9  begin by moving back from the connecting pin  33  as far as the bearing lug  34  of their associated bearing, thrust and connecting assembly before the cage  4 ,  6 , via the bearing lugs  34  that act as thrusting members, pushes the chamber sleeve tube along the cylinder  2 , compressing the return springs  13  ( FIG. 2 ) until the bearing pads  30 ,  31  come into abutment against the bearing lugs  11  of the cylinder  2  ( FIG. 3 ) and the combustion chamber  15  is thus closed, with sealing at the front. 
   The apparatus is then ready for firing. 
   When the apparatus is disengaged from the receiving material, the relaxation of the springs  13  causes the chamber sleeve tube  1  to slide forward along the cylinder  2 , until the interior rib portions  22  of the sleeve tube come into abutment against dampers  36  bearing against the bearing flanges  12  of the cylinder and the apparatus finds itself back in the combustion chamber open position. As the chamber sleeve tube  1  slides in the opening direction, the thrust lugs  34  also drive the forward sliding of the connecting nibs  9  and therefore the arms  7 ,  8  of the cage  6 . Under the action of its weight, the cage can continue its forward travel until the connecting arms  9  come into abutment against the pins  33 . 
   Advantageously, the bearing pads  30 , 31  are made of damping material in order to better absorb the shocks. Alternately, these pads  30 , 31  comprise at least a transverse rear bearing slice  39  arranged to come into abutment against a bearing ear  11  which, as far as it is concerned, is made of damping material, slice inserted onto the pad, for instance by sticking, welding. 
   A chamber sleeve tube with two bearing, thrust and connecting assemblies, with clearance, each having a two-pad cradle has just been described. 
   In an alternative form of embodiment of the apparatus of the invention, which form is depicted in  FIGS. 5 ,  6  in which the same references denote the same elements as in the other figures, each assembly is replaced by a single bearing, thrust and connecting pad  43 ,  44  shaped in a special way. 
   First of all, its shape is such that it can also be housed in one of the external thickenings  25 , like the cradles  29 . Furthermore, it has a connecting elbow  45  and a thrust and bearing finger  46  extending the connecting elbow  45 . The connecting elbow  45 , in the form of a bow, receives, in its concave internal groove, a connecting pin  33  which passes through the associated thickening  25 . The connecting elbow  45  and the thrust and bearing finger  46  are connected to one another by a bridge, leaving between them a groove  47  for housing the connecting nib  9  of the associated cage arm  7 ,  8 . As for the draft and bearing finger  46 , it extends in cylindrical form from a base  48 , which has a larger cross section than the finger  46 , forming an annular shoulder  49  for the abutment of the spring  13  that opens the chamber in abutment at its other end against the bearing flange  12  of the cylinder  2 . 
   The embodiment of  FIGS. 5 ,  6  therefore essentially differs from that of the other figures through the following features:
         the cage  4  and the sleeve tube  1  are connected in sliding without play;   the bearing lugs  11  have been eliminated;   the pads  43 ,  44  are simpler that the cradles  29 .       

   The way in which the apparatus of  FIGS. 5 and 6  works is the same as the way in which the apparatus of the other figures works. 
   When the apparatus is pressed against a receiving material, the cage  4 , via the feeler, is pushed towards the rear of the apparatus. The cage  4 , via the nibs  9  and the fingers  46  of the pads, acting as thrust members, pushes the chamber sleeve tube  1  back along the cylinder  2 , compressing the return springs  13  ( FIG. 5 ) until the fingers  46  of the bearing pads  42 ,  44  come into abutment against the bearing flanges  12  of the cylinder  2  ( FIG. 6 ) and the combustion chamber  15  is then closed, with sealing at the front. 
   The apparatus is then ready for firing. 
   When the apparatus is disengaged from the receiving material, the relaxation of the springs  13  causes the chamber sleeve tube  1  to slide forwards along the cylinder  2 , until the interior rib portions  22  of the sleeve tube come into abutment against dampers  36  bearing against the bearing flanges  12  of the cylinder and the apparatus finds itself once again in the combustion chamber open position. As the chamber sleeve tube  1  slides in the opening direction, the thrust fingers  46  also drive the forward sliding of the connecting nibs  9  and therefore the arms  7 ,  8  of the cage  4 . 
   The pads  43 , 44 , with their linking elbow  45  and their thrust and bearing finger  46  are advantageously made of damping material preferably elastomer, to better absorb the shocks. Like the pads  30 , 31 , pads  43 , 44  may include a transverse rear bearing slice  50  made of damping material.