Abstract:
A pneumatic processing machine includes a pneumatic motor, a circuit for connecting the motor to a source of compressed air, a tool holder spindle, and a drive mechanism. The mechanism includes a selection element which can be moved to select a first method of driving the spindle and a second method of driving the spindle. A device for controlling the operation of the machine controls the carrying-out of a driving cycle which includes at least one phase for driving the spindle according to the first driving method, then a phase for driving the spindle according to the second driving method, then the stopping of the supply of air to the motor. A supply valve of the circuit is controlled mechanically by the selection element to interrupt the supply of compressed air to the motor at the end of the driving cycle.

Description:
TECHNICAL FIELD 
   The present invention relates to a processing machine of the type comprising:
         a pneumatic motor,   a pneumatic circuit for connecting the motor to a source of compressed air, the pneumatic circuit comprising a motor supply valve,   a tool holder spindle,   a drive mechanism which mechanically connects the motor to the spindle in order to drive it, the mechanism comprising a selection element which can be moved between a first position for selecting a first method of driving the spindle and a second position for selecting a second method of driving the spindle which is different from the first driving method, and   a device for controlling the operation of the machine in order to control the carrying-out of a driving cycle which comprises at least one phase for driving the spindle according to the first driving method, then a phase for driving the spindle according to the second driving method, then to control the stopping of the supply of air to the motor.       

   BACKGROUND TO THE INVENTION 
   The invention applies in particular to pneumatic drilling machines which are used in aircraft construction. 
   The first phase of the cycle is generally a phase for advancing and simultaneously rotating the spindle, and the second phase is a phase for retracting and simultaneously rotating the spindle. 
   The device for controlling the operation of the machine allows the operation of a machine of this type to be stopped automatically once a cycle has been carried out. 
   In this manner, when a user has installed a plurality of these machines on a support frame and has initiated the operation thereof, the machines stop automatically without any need for specific intervention in respect of any of them. 
   In this manner, the noise caused by the machines being operated is limited. Furthermore, the pollution produced by the air loaded with lubricant which escapes from the motors of machines of this type is also limited. 
   In machines of the above-mentioned type, the device for controlling the operation comprises elements of the pneumatic circuit which are dedicated to controlling the closure of the motor supply valve at the end of the retraction phase of the cycle. 
   It should be noted that the structure of the control device is relatively complex and expensive, in particular because of these dedicated pneumatic elements. 
   One objective of the invention is to overcome this problem by providing a machine of the above-mentioned type which has a simpler structure and is less expensive. 
   SUMMARY OF THE INVENTION 
   To this end, the subject-matter of the invention is a machine of the above-mentioned type which is characterised in that the supply valve is controlled mechanically by the selection element to interrupt the supply of compressed air to the motor at the end of the driving cycle. 
   According to the individual embodiments, the machine can comprise one or more of the following features, taken in isolation or according to any of the combinations which are technically possible:
         the supply valve comprises a shutter which can be displaced mechanically by the selection element between a closed position and at least one open position to allow the passage of compressed air,   the shutter can be displaced mechanically by the selection element between a first open position, which the shutter takes up when the selection element is in its first position, and a second open position, which the shutter takes up when the selection element is in its second position,   the shutter can be moved by tilting,   the shutter is articulated to the selection element,   the shutter comprises a displacement rod which is provided with a sphere for articulation to the selection element,   since the spindle extends along a spindle axis, the first driving method comprises driving the spindle in translation along the axis thereof in a first direction of advance, and the second driving method comprises driving the spindle in translation along the axis thereof in a second retraction direction which is counter to the first direction,   the machine is portable and has a mass of less than 15 kg.       

   
     BRIEF DESCRIPTION OF DRAWINGS 
     The invention will be better understood from a reading of the description below which is given purely by way of example with reference to the appended drawings, in which: 
       FIG. 1  is a schematic perspective view of a machine according to the invention and 
       FIGS. 2  to  4  are schematic drawings showing the drive mechanism and the device for controlling the operation of the machine in FIG.  1 . 
   

   DESCRIPTION OF PREFERRED EMBODIMENT 
     FIG. 1  schematically illustrates a portable pneumatic drilling machine  1  which substantially comprises:
         a conventional pneumatic motor  2  which is received in a casing,   a connector  3  for connection to a source of pressurised air,   a tool holder spindle  4  which is received in a casing  5  in order to be movable in rotation along the axis A thereof and in translation along this axis A relative to the casing  5 , and   a mechanism  6  for driving the spindle  4 .       
   In conventional manner, drilling tools can be mounted in a removable manner at the front end  8  of the spindle  4 . 
   The drive mechanism  6  illustrated by  FIGS. 2  to  4  is a conventional mechanism which is generally designated in French as a “mécanisme d&#39;avance mécanique” (mechanical advance mechanism) and, in English, as a “positive feed drill”. 
   In the description below, the terms “lower”, “upper”, “horizontal”, “right” and “left” are intended to relate to  FIGS. 2  to  4 . 
   The mechanism  6  substantially comprises:
         a gear  12  which is fixed in rotation with the output shaft  10  of the motor  2 ,   a first gear/dog clutch  14  which engages with the gear  12 ,   a gear  16  which engages with the gear/dog clutch  14  and which is fixed in rotation with the spindle  4 , the spindle  4  being able to slide along the axis A thereof relative to the gear  16 ,   a second gear/dog clutch  18  located above the first gear/dog clutch  14 ,   a gear  20  which is located above the gear  16 , which engages with the gear/dog clutch  18  and which is screwed onto a threaded portion  21  of the spindle  4 ,   a fixed dog clutch  22  which is located above the second gear/dog clutch  18  and,   a vertical selection rod  24 .       

   The gears/dog clutches  14  and  18  are mounted to rotate about the rod  24 . 
   The first gear/dog clutch  14  is fixed in translation relative to the casing  7  of the mechanism  6 . 
   The rod  24  can slide vertically in the gear/dog clutch  14  and relative to the casing  7 . 
   The gear/dog clutch  18  is connected in translation to the rod  24  along the vertical axis thereof. 
   The machine  1  further comprises an actuation element  25  in order to initiate the operation of the machine and a device  26  for controlling the operation thereof. The element  25  is, for example, formed by a button, as illustrated in FIG.  1 . 
   The control device  26  substantially comprises the following elements:
         a pneumatic circuit  27  which comprises a valve  28  for supplying the motor  2  with compressed air, which valve  28  is arranged in a duct  29  which extends between the connector  3  and the motor  2 ,   a piston  30  which is provided at the lower end of the rod  24  and which is received in a chamber  32  which comprises an opening  33  for venting in the upper wall thereof, and   a pneumatic travel-limit sensor  34 .       

   A duct  35  of the pneumatic circuit  27  is connected, on the one hand, to the duct  29  upstream of the valve  28  and, on the other hand, to the sensor  34 . A duct  36  of the circuit  27  connects the sensor  34  to the lower wall of the chamber  32 . 
   It will be appreciated in  FIGS. 2  to  4  that a source  38  of compressed air has been illustrated connected to the connector  3 . 
   The valve  28  comprises a shutter  40  which itself comprises a disk  42  which rests on a seat  44 , through which an opening  46  extends, and a displacement rod  48  which extends through the opening  46  and which terminates in an articulation sphere  50 . A spring  51  biases the disk  42  against the seat  44 . 
   The sphere  50  is received in a horizontal passage  52  which is arranged at the upper end  54  of the rod  24 . 
   The travel-limit sensor  34  comprises a vertical slide  56  which is extended laterally at the lower end thereof by a displacement limb  58  and, at the upper end thereof, by a displacement limb  60 . 
   The actuation element  25  has a passage  62 , in which an intermediate portion  64  of reduced diameter of the selection rod  24  is received. This portion  64  is delimited by an upper shoulder  66  and a lower shoulder  68 . The portion  64  has a height which is distinctly greater than the thickness of the activation element  25 . A spring  70  returns the actuation element  25  to the right in such a manner that it presses on the portion  64  at the bottom of the passage  62 . 
   Furthermore, a spring  72  rests on the dog clutch  22 , and therefore on the casing  7 , as well as on the gear/dog clutch  18  in order to urge the selection rod  24  in translation downwards. 
   When the machine  1  is at rest as illustrated in  FIG. 2 , downward displacement of the selection rod  24  is prevented by the fact that the shoulder  66  is stopped against the actuation element  25 . 
   In  FIG. 2 , the shutter  40  is in a position closing the opening  46  where it presses, by means of the entire periphery thereof, on the seat  44 . The motor  2  is not supplied with pressurised air in this case. The selection rod  24  is in an intermediate rest position or neutral position. The gear/dog clutch  18  is in an intermediate position where it is spaced from the gear/dog clutch  14  and the gear/dog clutch  22 . The piston  30  also occupies an intermediate position between the lower wall and upper wall of the chamber  32 . The spindle  4  is stationary and takes up a retracted position at the end of its travel path where a lower stop  73 , which is integral with the spindle  4 , rests against the lower displacement limb  58  of the slide  56 . 
   The slide  56  further isolates the ducts  35  and  36 , and therefore isolates the chamber  32  from the source  38 . The slide  56  vents the duct  36 . 
   When a user wishes to start carrying out a drilling cycle, he manually displaces the actuation element  25  to the left, compressing the spring  70 . This displacement continues until the shoulder  66  no longer rests on the actuation element  25 . 
   The selection rod  24  is then released and biased towards the bottom by the spring  72 . This downward movement of the rod  24  continues until the gear/dog clutch  18  is positively engaged with the gear/dog clutch  14  (FIG.  3 ). 
   The selection rod  24  is then in a first lowermost position, as is the gear/dog clutch  18 . 
   During this downward movement of the rod  24 , the piston  30  is displaced towards the lower wall of the chamber  32 . The upper end  54  of the rod  24  is also displaced towards the bottom, causing, by means of the sphere  50  and the rod  48 , the shutter  40  of the valve  28  to tilt in a counter-clockwise sense, as illustrated in FIG.  3 . 
   The shutter  40  is then in a first open position where it releases the opening  46  and rests on the seat  44  only by means of an upper portion of the periphery thereof. 
   The air from the source  38  can then flow through the opening  46  of the seat  44  of the valve  28  and supply the motor  2  via the duct  29 . The motor  2  then drives the spindle  4  in rotation about the axis A thereof via the gears  12 ,  14  and  16 . 
   Since the gears/dog clutches  14  and  18  are positively engaged, they are fixed in rotation. The gear  20  is then driven in rotation by the gear/dog clutch  18 . By appropriately selecting the number of teeth of the gears  18  and  20 , the gear  20  turns slightly more quickly than the gear  16 , as is conventional. Owing to this speed differential, the spindle  4  is driven in translation along the axis A thereof towards the bottom, which corresponds to an advance movement. This movement is schematically indicated by arrow  76  in FIG.  3 . 
   During this advance movement, an upper stop  78  which is integral with the spindle  4  rests on the upper limb  60  of the slide  56 . The spindle  4  then drives, during its movement, the slide  56  which slides relative to the casing  7 . 
   When the spindle  4  reaches an advanced travel-limit position (FIG.  4 ), the slide  56  has been sufficiently displaced to bring the ducts  35  and  36  into communication and to supply the lower region of the chamber  32  with pressurised air. Pressurised air then pushes back the piston  30 , and therefore the selection rod  24 , towards the top, counter to the restoring force applied by the spring  72 . 
   This upward movement of the rod  24  continues until the piston  30  rests against the upper wall of the chamber  32  (FIG.  4 ). The rod  24  is then in a second uppermost position, as is the gear/dog clutch  18  which is positively engaged with the dog clutch  22 . During this upward movement, the upper end  54  of the rod  24  causes the shutter  40  to tilt in the clockwise sense in  FIG. 4  beyond the closed position thereof and as far as a second open position. In the second open position thereof, the shutter  40  releases the opening  46 . It then rests on the seat  44  only by means of a lower portion of the periphery thereof. 
   During this upward movement of the rod  24 , the spring  70  pushes back the actuation element  25  to the right until the bottom of the passage  62  again rests against the intermediate portion  64  of the rod  24 . At the end of the upward movement of the rod  24 , the lower shoulder  68  of the rod  24  rests on the actuation element  25 . 
   Since the gear/dog clutch  18  is positively engaged with the upper gear  22  which is fixed in rotation, the gear/dog clutch  18  and the gear  20  are also fixed in rotation. 
   Since the gears  14  and  16  themselves continue to turn as described above, the spindle  4  begins a translation movement upwards along the axis A thereof, known as a retraction movement, as illustrated by arrow  84  in FIG.  4 . 
   During this retraction movement, the lower stop  73  of the spindle  4  rests against the lower displacement limb  58  of the slide  56  and thereby causes the slide  56  to be translated upwards relative to the casing  7 . 
   The retraction movement continues until the spindle  4  again takes up its retracted travel-limit position in FIG.  2 . The slide  56  again interrupts the communication between the ducts  35  and  36  and vents the duct  36 . The piston  30  is no longer subjected to the action of the compressed air and the spring  72  draws back the rod  24  towards the bottom until the shoulder  66  of the shaft  24  rests on the actuation element  25 . The selection rod  24  has then taken back up its rest position in FIG.  2  and the shutter  40  its closed position. Therefore, the motor  2  is no longer supplied with compressed air and the operation of the machine  1  is stopped. 
   In this manner, the machine in  FIGS. 1  to  4  has a device  26  for controlling its operation which permits control of the carrying-out of a cycle which comprises a first phase where the spindle is driven simultaneously by a rotation movement and an advance movement, then a second phase where the spindle  4  is driven simultaneously by a retraction movement and a rotation movement, and, at the end of this cycle, the automatic control of the stopping of the machine  1 . 
   The interruption of the supply to the motor  2  at the end of the cycle is ensured owing to a valve  28  which is controlled mechanically by the selection element  24  which is usually present in this type of machine. In this manner, complex pneumatic elements which have been used until now to interrupt the supply to the motor  2  are not necessary. 
   The structure of the control device  26  is therefore relatively simple and takes up less space. 
   Furthermore, the cost of the control device  26  is reduced in that it makes use of mechanical control rather than pneumatic control, and also in that this mechanical control is ensured by an element  24  which is generally present in the drive mechanism  6 . 
   Although the above principles have been described in relation to a portable machine, that is to say, having a mass of less than approximately 15 kg, they can apply to a non-portable machine. 
   Furthermore, they could also apply to a machine dedicated to a type of machining other than drilling. 
   In this manner, the cycle where the control device  26  ensures the carrying-out can comprise phases which are different from those described above and, in particular, more than two phases where the drive methods are separate.