Multispindle-drilling machine
FIELD AND BACKGROUND OF THE INVENTION 
     The invention relates to a multispindle-drilling machine for drilling series of holes, in particular in parts of pieces of furniture, and including a drilling head, feed means and driving means for drilling spindles, a positioning pin displaceable in the axial direction and fixable in upper and lower positions and mounted laterally with respect to the drilling head. 
     Multispindle-drilling machines of the afore-mentioned kind are used in furniture production for drilling series of holes. The standard distance between the individual holes of such series of drilled holes is 32 mm. Drilling machines are known by means of which a complete series of holes can be drilled into a piece of furniture in one operating step. Often the number of drilling spindles of the drilling head is smaller than the number of holes to be drilled into a furniture part, and the distance between the marking points for the holes to be drilled is such that the drilling head must be displaced with respect to the furniture part so that the drilling operation for finishing the desired series of holes can be repeated. 
     It is essential that the distances between the holes formed by one drilling operation and the holes are formed by the next drilling operation be 32 mm or a precise multiple thereof. 
     In a known multispindle-drilling machine a postioning pin disposed at a distance of 32 mm from the next drill and aligned in a line with the drills is arranged at each end of the drilling head. In its lower position the positioning pin extends beyond the drills. 
     Depending on whether the work-piece is moved to the right or to the left, the left or the right positioning pin can be locked in an upper position in which its lower end is higher than the points of the drills. 
     In this machine the positioning pin in operation and engaging the last hole of a previously drilled series of holes must be lifted from such last hole to enable the work-piece, e.g. a chipboard, to be moved for a subsequent drilling operation. 
     SUMMARY OF THE INVENTION 
     It is the object of the invention to provide an improved multispindle-drilling machine of the above type wherein when the drilling head is lifted after a drilling operation, the positioning pin is automatically lifted from the hole drilled into the work-piece so that the work-piece can be moved without manually lifting the positioning pin. 
     According to the invention this is achieved by automatic catch means holding the positioning pin which is displaced relative to the drilling head during the drilling operation. 
     It is advantageously provided that the catch means holds the positioning pin in a lifted position which lies between lower and upper positions at which the said pin is manually fixable. 
     An embodiment of the invention provides that the positioning pin is provided with rack teeth which mesh with a pinion which is lockable in at least one position by means of a spring. The pinion may be connected to a cylinder with a cam surface against which the spring engages. 
     The cylinder is advantageously designed as a turning handle. 
     A further embodiment of the invention provides that the positioning pin is surrounded by a guide sleeve which includes a guide path in the form of a groove into which extends a guide pin which is connected with the positioning pin. 
     It is advantageously provided that the guide path comprises a lower portion and an upper portion which are staggered with respect to each other substantially by the width of the guide path. 
     A further embodiment provides that the guide path is open towards the upper rim of the guide sleeve. 
     In the latter-mentioned arrangement the guide pin can be moved out of the guide sleeve and abut at the rim thereof. Thus the positioning pin is held in its top position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Two embodiments of the invention will now be described in more detail with reference to the accompanying drawings, in which: 
     FIG. 1 is a side view of a multispindle-drilling machine, 
     FIG. 2 is a side view, parts thereof in section, of a first embodiment of a holding means of a positioning pin thereof, 
     FIG. 3 is a diagrammatic view of a guide sleeve thereof, 
     FIG. 4 is a vertical sectional view of a second embodiment of the holding means of the positioning pin, 
     FIG. 5 is a sectional view through the arrangement of FIG. 4, and 
     FIG. 6 is a further sectional view through the arrangement of FIG. 4. 
    
    
     The parts of the drilling machine which are not directly related to the drilling machine, such as the supporting table, ruler, machine support and driving motor, are not shown in the drawings for the sake of clarity. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a drilling head 1 which carries a row of drilling spindles 2 for drills 3. At both ends of the row of drilling spindles are provided positioning pins 4. During an operation of drilling a row of holes 5 into a work-piece 6, a positioning pin 4 extends into the nearest hole 5 of the row of holes 5 drilled previously to thereby secure the distance between holes 5 which has to be observed, e.g. a distance between holes of 32 mm. 
     The second positioning pin 4 is maintained in an upper position during this operation. 
     In the embodiment according to FIGS. 2 and 3 each positioning pin 4 is urged downwardly by a coil spring 7 and is surrounded by a guiding sleeve 8. At the upper end the positioning pin 4 is connected with a sleeve 9 into which extends a guide pin 10. 
     The guide sleeve 8 has a guide groove 11 in the form of a groove. The guide groove 11 comprises a lower portion 12 and an upper portion 13 which are staggered or stepped with respect to each other by approximately the breadth or width of the guide groove 11. By this arrangement there is formed at the step between portions 12, 13 a catch 14 at a position opposite an inclined guide wall or camming surface 15 between portions 12, 13. The guide groove 11 is open towards an upper rim 16 of the sleeve 8. Several guide grooves 11 may be provided in the guide sleeve 8. 
     If the positioning pin 4 is to be brought into its top or retracted position, the sleeve 9, which forms a handle, lifted and the guide pin 10 is pulled upwardly out of the guide groove 11. 
     By turning the handle the guide pin 10 is held at the upper rim 16 of the sleeve, and a catching recess or notch 17 may be provided in the rim 16 as shown in FIG. 3. 
     The positioning pin 4 which is to be inserted into the drilled hole 5 is in its lowermost or projected position at the start of the drilling operation, i.e. the guide pin 10 is in the guide path in the position marked by 10U in FIG. 3. 
     During drilling, head 1 and sleeve 8 including groove 11 move downwardly relative to pins 4, 10 until pin 10 is cammed by surface 15 into catch 14. Movement of head 1 is toward the workpiece from a withdrawn position to a maximum driilling depth position. 
     The positioning pin 4 is therefore automatically fixed at a middle position 10A and will automatically be moved out of the hole 5 upon subsequent movement upwardly of head 1 and sleeve 8. 
     In the embodiment according to FIGS. 4 to 6 the positioning pin 4 is provided with rack teeth 18 that mesh with a pinion 19. 
     The pinion 19 is connected with a cylinder 20 which is designed as a turning handle. 
     As can be seen from FIGS. 4 and 6, the cylinder 20 has an internal cam surface 21 against which presses a spring 22, which is a leaf spring in the illustrated embodiment. 
     Two cams a, b are arranged along the cam surface 21. 
     In the position illustrated in FIG. 6, the positioning pin is in the lowermost position, i.e. in the position in which it extends into the drilled hole 5. 
     During the drilling operation the drill head and pinion 19 are moved downwardly relative to positioning pin 4 As a result pinon 19 and cylinder 20 are rotated. 
     Rotation of the cylinder 20 in the direction of the arrow causes the spring 22 to ride over and engage cam b. The positioning pin 4 is thus held in a center position, i.e. in a position which corresponds in the afore-described embodiment to position 10A of the positioning pin 4. Upon subsequent upward movement of the drill head, pin 4 automatically will be withdrawn from the hole 5 due to spring 22 engaging cam b and preventing rotation of cylinder 20 opposite to the arrow. 
     The positioning pin 4 is brought into its top position by turning the cylinder 20 in the direction of the arrow until the spring 22 engages at cam a.