Patent Publication Number: US-8540034-B2

Title: Pneumatic drill device

Description:
This application is a U.S. National Phase application of PCT Application No. PCT/FR2009/050136 filed Jan. 30, 2009 which claims priority to FR0800528, filed on Jan. 31, 2008. 
     BACKGROUND 
     Pneumatic drills with metal bodies are known, which are generally heavy and comprise an operating handle attached to the body. 
     Owing to their size and weight, these drills do not lend themselves to finish drilling or drilling where there is limited access. Moreover, the air exhaust is evacuated radially onto the cylinder, and this may interfere with the gripping of the cylinder of the apparatus by the user. 
     SUMMARY 
     The invention proposes a pneumatic drill device comprising an outer casing, an assembly of a cylinder and movable piston operating a pick element, a device for supplying the cylinder with compressed air, an air exhaust device and an operational control device, characterised in that the outer casing is formed from two complementary sections adapted to fit into one another in order to enclose, in addition to the cylinder and piston assembly, the cylinder supply device, the air exhaust device and the operational control device, and in that at least one channel of the supply device and/or of the exhaust device is formed in at least one of the casing sections, this channel being formed laterally within the thickness of the casing section, parallel to the cylinder. 
     The enclosed supply, exhaust and control devices are advantageously rigidly trapped between the said casing sections, which are clamped against one another in sealed manner. 
     The casing sections are adapted in shape so as to house the enclosed devices within their linked portion, the devices thus being “sandwiched” between the two assembled casing sections. 
     They advantageously comprise at least one layer of material adapted to insulate vibrations and operating noise from the cylinder and piston assembly. 
     They are advantageously formed by moulding or injection of synthetic materials, for example plastics, and preferably adapted to the use of a small lightweight drill device, preferably using compressed air at low pressure, for example 0.5 to 2.5 bar, for finish drilling or drilling with limited access. 
     At least one channel of the supply device and/or of the exhaust device may be formed in at least one of the casing sections, thus avoiding the need for external tubing. 
     The casing sections are advantageously two plastic half-shells which are substantially symmetrical with one another in relation to a longitudinal median plane of the drill device and are adapted to be clamped against one another in sealed manner, for example by a set of screws arranged around their periphery. The two casing sections can thus easily be replaced in the event of wear or breakage. 
     Their sealed assembly is advantageously provided by means of a peripheral bead around one of the parts, which is squeezed when clamped in a corresponding groove in the other part, optionally onto a flexible joint. 
     The casing sections are advantageously formed with at least one operating handle for the pneumatic drill device which incorporates the operational control device (control trigger). 
     The said handle may be offset from the axis of the cylinder and be in the shape of a D one branch of which, the front branch, which is distinct from the rear main branch, protects the operator&#39;s hand. 
     The said front branch of the handle may house at least part of the air exhaust device (for example a baffle), which vents out of the cylinder, for example at the outer end of the handle, without interfering with the operators hand. 
     The main branch for operating the handle may also incorporate the connection for the supply tubing at its outer end and a supply valve connected to the control member (control trigger). 
     The front end part of the casing sections, opposite the handle, may also house at least one other air exhaust portion (air exhaust baffle) which vents towards the pick element and hence without impeding the handling of the casing. 
     In addition, an internal shaping is provided in the casing sections for collecting any air leaks from the enclosed devices and directing them towards the air exhaust device (leaks from the connections in particular). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is illustrated hereinafter by means of an exemplifying embodiment and with reference to the appended drawings, wherein: 
         FIG. 1  is a perspective view of a pneumatic drill device according to the invention, 
         FIG. 2  is a partial cross-section through the pneumatic drill device on the line  2 - 2  in  FIG. 3 , 
         FIG. 3  is an enlarged axial section through the pneumatic drill device, 
         FIG. 4  is a longitudinal section on the line  4 - 4  in  FIG. 2  showing the supply relief channels for the pneumatic drill device, and 
         FIG. 5  is an enlarged partial cross-section showing the attachment of the half-shells of the casing. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings, particularly  FIGS. 1 and 3 , the pneumatic drill device  1  according to the invention comprises an outer casing  3 , an assembly of a cylinder  5  and movable piston  7  operating a pick element  9 , a device  11  for supplying the cylinder  5  with compressed air, an air exhaust device  13  and an operational control device  15 . 
     The outer casing  3  comprises two half-shells  3   a  attached to one another along a median longitudinal plane of the device, clamped against one another by means of screws  17  provided around their periphery. 
     These half-shells  3   a , produced as plastic mouldings, contain the supply device  11 , the exhaust device  13  and the control device  15  for the drill device, trapping them rigidly in corresponding housings  11   a ,  13   a ,  15   a , respectively, formed during the assembling thereof. They are assembled in sealed manner with one another by means of a peripheral joint  19  consisting of a peripheral bead  19   a  on one half-shell which is squeezed when clamped in a complementary groove  19   b  on the other half-shell ( FIG. 5 ) and optionally bears on a flexible joint  19   c  in the base of the groove. The half-shells  3   a  are formed with the operating handle  21  of the pneumatic drill device, which comprises the control member or control trigger  15   b  of the pneumatic drill device mounted on a main rear branch  21   a  of the handle of the device (opposite the pick element  9 ) protected by a front branch  21   b  connected to the earlier one, thereby forming a D, axially offset from the cylinder  5 . 
     The assembly of the cylinder  5  and piston  7  extends axially substantially along the length of the body  23  of the drill device. In conventional manner the cylinder  5  houses in its rear portion the compressed air distribution portion  25  which is connected to the compressed air supply device  11  mounted in the main branch  21  a of the handle, and it comprises in its front portion the engaging portion of the pick element  9  or advancer  27  mounted on ball bearings. The latter is formed in an enlarged front axial extension  5 ′ of the cylinder, comprising in conventional manner a ring  27   a  movably mounted on its surface, biased forwards by a spring  27   b  and retaining the pick element  9  by means of ball bearings  27   c  trapped in recesses  27   d , this ring  27   a  being adapted to retract when pushed by the operator counter to the spring  27   b  in order to release the pick element  9 . 
     The piston  7  is hollow, and slidably mounted in the cylinder  5 , this piston being adapted to be pushed abruptly towards the pick element  9  under the pressure of the compressed air in the cylinder  5  and on its hollow head  7   a , to subject it to impact and allow the drill device to act as a pick. 
     The supply device  11  for the cylinder comprises a supply valve  11   b  located on the extension of the main branch  21   a  of the handle, which is itself connected to a tube  11   c  for supplying compressed air at about 2 bars at its outer end. This valve  11   b  is connected to the trigger  15   b  by a control rod  15   c . The latter, when closed, without actuation of the trigger, opens a supply channel  11   d  for compressed air to the distribution portion  25  under the operation of the control trigger  15   b.    
     The distribution portion  25  is conventional and comprises a pad  25   a  mounted to be movable back and forth on its seat  25   b  and alternately distributing the compressed air into the upper chamber  5   a  of the cylinder with the aim of pushing the piston  7  towards the pick element  9  or, conversely, supplying the lower part  5   b  of the cylinder via relief control channels  11   e  for the piston (shown in  FIGS. 2 and 4 ) for pushing the latter towards the upper part  5   a  of the cylinder (in the opposite direction to the pick or drill element). 
     There are two of the relief channels  11   e  mentioned above (there may be from one to several and of variable section, depending on the space available in the casing) each formed laterally within the thickness of the half-shells  3   a , parallel to the cylinder  5  and at the lower level of the latter. These channels  11   e  are connected to the distribution portion  25 , to its rear end and to the cylinder via holes  5   c  opening out at its lower portion  5   b.    
     The exhaust device comprises a main part  13  housed in the front branch  21   b  of the handle, which is in the shape of a baffle for channelling the compressed air, linked via holes  5   d  to the cylinder  5  and open at the end of this branch. These baffles extend longitudinally in the space within the branch  21   b  of the handle. They allow compressed air to be evacuated to the outer end of the handle without inconveniencing the operator. Another part of the exhaust device  13 ′ is arranged in the front end portion of the half-shells  3   a , opposite the handle  21 . This portion comprises small baffles connected to the lower part  5   b  of the cylinder via through-holes  5   e  and is connected to the outside of the half-shells  3   a  via holes  13 ′ a  opening outwards towards the pick element  9 . 
     It should be noted that internal shaping of the half-shells  3   a  may be provided close to the distribution portion  25  and the control trigger  15   b , in a small space  28  around the cylinder  5 , and guide residual leaking air (which is unavoidable) to the main exhaust part  13 . 
     The operation of the pneumatic drill device according to the invention will now be described with reference to  FIG. 3 . 
     The compressed air comes from the open supply valve  11   b  (as indicated by the arrow), with the trigger  15   b  actuated, towards the distribution portion  25 . Depending on the position of the movable pad  25   a , the compressed air is conveyed either into the upper chamber  5   a  of the cylinder to push the piston  7  towards the pick element  9  with a striking action, or it is guided in the opposite direction, to the end of the distribution portion  25 , to arrive via the two relief channels  11   e  at the lower level  5   b  of the cylinder and allow the piston  7  to move up in order to be struck again, in the conventional mode of operation of a pneumatic drill. 
     Thus, let us suppose that the piston  7  is in the top position in the cylinder  5  (close to the distribution portion  25 ), the pad  25   a  being pressed onto its seat  25   b  to the left, and closing off the relief channels  11   e , the compressed air then travels directly into the upper cylinder chamber  5   a  and abruptly drives back the piston  7  which is moved past the exhaust holes  5   d  of the main exhaust portion  13 . At this level, the pressure in the upper chamber  5   a  drops to the level of atmospheric thrust or thereabouts, while the air in the upper chamber is evacuated through the main exhaust portion  13 . At the same time, the air cushion compressed by the arrival of the piston  7  between the pick element  9  and the piston  7  is evacuated through the front exhaust portion  13 ′ towards the pick element  9 , thus preventing the piston from being slowed down by this air cushion as it travels towards the pick element  9 . 
     The pad  25   a  is thus moved to the opposite position on its seat  25   b , closing off the intake for compressed air into the upper cylinder chamber  5   a  and opening up access to the relief channels  11   e . The compressed air then arrives at the lower level  5   b  of the cylinder and pushes the piston  7  back up to the upper level  5   a  of the cylinder for a new striking cycle. 
     In this embodiment, compressed air at low pressure was used, but it is possible to supply the device with compressed air at high pressure (7 bars, for example) by adapting the cross-sections of the supply, distribution, relief and exhaust passages. The invention thus provides a pneumatic drill device which is simple, can be made in a small size, and is lightweight and economical.