JP6452511B2 - Core support structure for earth drill - Google Patents

Description

  The present invention relates to a core support structure in an earth drill, and more particularly, to an earth drill that transmits a rotational force by engaging a key projecting in the axial direction of a kelly bar with a key groove formed on a drive shaft of a kelly bar rotary drive device. Relates to the core support structure.

  In general, an earth drill is a drilling work that is carried out by pushing a kelly bar fitted with a drilling tool at the lower end into the ground while rotating it with a drive shaft of a kelly bar rotation drive device.In a key groove formed on a cylindrical drive shaft, A key projecting from the kelly bar is engaged to transmit the rotational force from the kelly bar rotary drive device to the kelly bar. The circumferential opening width of the key groove is formed to be larger than the circumferential width of the key, and a play is provided for facilitating insertion of the kelly bar into the drive shaft (see, for example, Patent Document 1).

  In addition, when using a small-diameter (small-diameter kelly bar) instead of a normal kelly bar, the outer surface on which the key is formed corresponds to the inner diameter of the drive shaft, and the inner surface on which the key groove is formed is the outer diameter of the small-diameter kelly bar. A cylindrical core corresponding to is inserted into the drive shaft, and a small-diameter kelly bar is inserted into the core. The pushing force and the rotational force are transmitted from the drive shaft to the small-diameter keriva via the core. Similarly to the above, the width in the circumferential direction of the core key is formed smaller than the width of the keyway of the drive shaft, and play is provided.

JP 2004-11199 A

  If the core as described above is directly supported by the bolt on the drive shaft, there is play between the key and the key groove, so before the rotational force is transmitted from the key groove of the drive shaft to the core key, the drive shaft A rotational force may be transmitted to the core via the bolt. For this reason, a shearing force may act on the bolt and the bolt may be damaged. Further, if the core is supported by a bolt on the upper buffer provided at the upper part of the drive shaft, the upper buffer itself may be damaged.

  Therefore, an object of the present invention is to provide a core support structure that can reliably support a core in a drive shaft while preventing breakage of a bolt.

  In order to achieve the above object, the core support structure in an earth drill according to the present invention is the earth drill in the earth drill that performs excavation work by lowering the drilling tool while rotating the kelly bar with the drilling tool attached to the lower end by the kelly bar rotation driving device. In a core support structure that inserts and supports a core for a small-diameter keriva into a drive shaft of a kelly bar rotary drive device, a support flange provided on the outer periphery of the upper end of the core is mounted on the upper end surface of the drive shaft. A ring-shaped pressing bracket is disposed on the upper surface of the support flange, and a support bolt inserted through a bolt insertion hole provided in the holding bracket and a bolt loose-fitting hole provided in the support flange is disposed on the upper end surface of the drive shaft. The support flange is clamped between the upper end surface of the drive shaft and the holding bracket, and the support flange is The dimension between the bolt shaft of the bolt and the bolt loose insertion hole is designed so that the bolt shaft can move larger than the play dimension between the key groove provided on the inner surface of the drive shaft and the key provided on the outer surface of the core. It is characterized by the formation.

  Furthermore, in the core support structure in the ground drill of the present invention, a spacer is provided on the lower surface of the holding bracket to regulate the tightening amount of the support bolt with the lower end surface abutting against the upper end surface of the drive shaft. In addition, a rubber ring material is provided on the upper surface of the holding bracket.

  According to the core support structure of the earth drill of the present invention, the bolt loosely-fitting hole provided in the core support flange is formed larger than the play dimension between the key groove and the key. The supporting bolt can move in the bolt free fitting hole until the rotational force is transmitted, and the rotational force does not act on the supporting bolt, so that the supporting bolt can be prevented from being damaged. In addition, by restricting the tightening amount of the support bolt, the support flange can be clamped in a movable state between the upper end surface of the drive shaft and the holding bracket, and the core is securely rotated. A keyway and a key can be made to contact reliably.

It is sectional drawing which shows one example of a core support structure in the earth drill of this invention. It is a disassembled perspective view of the principal part. It is a top view of the principal part. It is IV-IV sectional drawing of FIG. It is VV sectional drawing of FIG. It is VI-VI sectional drawing of FIG. It is a side view which shows an example of an earth drill.

  First, as shown in FIG. 7, the earth drill suspends the kelly bar 13 from the tip of the boom 12 provided in the base machine 11 formed of a crawler crane so as to be rotatable, and from the base of the boom 12 with a cylinder 14 or the like. An excavation bucket or a widened bucket 16 is attached to the lower end portion of the kelly bar 13 that supports the kelly bar rotation driving device 15 and is inserted into a hollow cylindrical drive shaft provided in the kelly bar rotation driving device 15.

  The vertical hole is formed by the earth drill by a step of pushing the excavation bucket or the bottom expansion bucket 16 into the ground while rotating the excavation bucket or the bottom expansion bucket 16 by rotating the kelly bar 13 by the kelly bar rotation driving device 15; And the step of pulling up the bottomed bucket 16 and discharging the excavated earth and sand alternately.

  Normally, the drive shaft of the kelly bar rotary drive device 15 and the kelly bar 13 have corresponding shapes, but when using a kelly bar (hereinafter referred to as a small diameter kelly bar) that is thinner than the kelly bar 13 normally used for some reason. In this case, a core corresponding to the small-diameter kelly bar is inserted into the drive shaft, and the rotational force and the pushing force are transmitted to the small-diameter kelly bar via the core.

  1 to 6 show an embodiment in which a core is inserted and supported in a locking type drive shaft. The Kelever rotation drive device 15 drives the drive shaft 19 to rotate the rotation of the hydraulic motor 17 via the reduction gear 18, and the drive shaft 19 has three locations in the circumferential direction of the inner peripheral surface formed in a hollow cylindrical shape. In addition, key grooves 20 that are continuous in the vertical direction are provided at equal intervals. Further, on the upper end surface of the drive shaft 19, female screw holes 22 for screwing the support bolts 21 for attaching the core are provided at six locations in the circumferential direction.

  When the core 23 is mounted on the drive shaft 19, a holding bracket 24 for supporting the core 23 in the drive shaft 19 and a rubber ring material 25 for vibration control are used. The core 23 has a hollow cylindrical core main body 23a through which the small-diameter keriva 26 is inserted, and a support flange 23b provided on the outer periphery of the upper end of the core main body 23a. A key 27 corresponding to the key groove 20 is provided on the outer peripheral surface, and a key (hereinafter referred to as a small diameter key) 28 provided on the outer peripheral surface of the small-diameter keriber 26 is provided on the inner peripheral surface of the core body 23a. Corresponding key grooves (hereinafter referred to as “small-diameter key grooves”) 29 are provided continuously at three positions in the circumferential direction in the vertical direction at equal intervals.

  Further, the circumferential dimension of the key 27 of the core 23 is smaller than the circumferential dimension of the key groove 20 of the drive shaft 19, and a play is provided between the key groove 20 and the key 27, whereby the drive shaft The core 23 can be easily inserted into the body 19.

  The support flange 23b is provided with a bolt loosely fitting hole 30 through which the support bolt 21 is inserted in a position corresponding to the female screw hole 22 of the drive shaft 19. The bolt loose-fitting hole 30 has a dimension between the bolt shaft of the support bolt 21 and the inner surface hole wall of the bolt loose-fitting hole 30 based on a play dimension set between the key groove 20 and the key 27. The bolt shaft is largely formed to be movable.

  The holding bracket 24 is used to support the core 23 in the drive shaft 19 by sandwiching the support flange 23b between the upper end surface of the drive shaft 19 and has a thickness similar to that of the support flange 23b. It has a ring shape. The holding bracket 24 is provided with six support bolt insertion holes 31 at positions corresponding to the female screw hole 22 and the bolt loose fitting hole 30, and a fixing bolt 32 for fixing the rubber ring material 25. 6 are provided at six positions.

  Further, spacers 34 for restricting the tightening amount of the support bolts 21 are provided at three locations in the circumferential direction on the lower surface of the holding bracket 24, and notches through which the spacers 34 can pass on the outer periphery of the support flange 23b. A portion 35 is provided. When the spacer 34 is overlapped with the support flange 23 b and the support bolt 21 is fastened to the female screw hole 22, the lower end surface of the spacer 34 abuts on the upper end surface of the drive shaft 19. The tightening amount of the support bolt 21 is regulated so that the support flange 23 b can move between the support bracket 24 and the holding bracket 24.

  The rubber ring material 25 fixed on the holding bracket 24 via the collar 36 with the fixing bolt 32 is generated by collision or rubbing of the drive shaft 19, the core 23, the holding bracket 24, and the small-diameter keriber 26 during construction. It is provided to suppress vibrations and reduce ambient noise.

  On the outer peripheral surface of the locking-type small-diameter keriva 26, there is a pushing portion 37 slightly narrower than the small-diameter key groove 29 of the core 23, and upward from the front end portion in the rotational direction of the drive shaft 19 at the upper end of the pushing portion 37. A protruding small key 28 is provided. The small-diameter keriva 26 is inserted into the core 23 until the small-diameter key groove 29 passes through the pushing portion 37 and passes below the core 23. In this state, the small-diameter key 28 is located at the front end portion in the rotational direction of the small-diameter key groove 29 as indicated by reference numeral A in FIG.

  When the drive shaft 19 is rotated clockwise in FIG. 3 by operating the hydraulic motor 17 in the excavation direction, the push-in portion 37 moves from below the small diameter key groove 29 to below the lower end surface of the core 23 and the small diameter key. 3 moves to the rear end portion in the rotation direction of the small-diameter key groove 29 as indicated by reference numeral B in FIG. As a result, the lower surface of the core 23 and the upper end surface of the pushing portion 37 are engaged to transmit the pushing force, and the small-diameter key 28 and the small-diameter key groove 29 are engaged with each other in the rotational direction and the rotational force is generated. Communicated. As a result, the pushing force and the rotational force of the drive shaft 19 are transmitted from the core 23 to the small-diameter kelly bar 26, and a predetermined excavation work is performed.

  At this time, the pushing force of the small-diameter keriva 26 acts as an axial pulling force from the holding bracket 24 to the support bolt 21 via the support flange 23b of the core 23, so that the support bolt 21 can sufficiently withstand. On the other hand, the rotational force of the small-diameter kelly bar 26 is transmitted from the drive shaft 19 to the small-diameter kelly bar 26 via the core 23 by the engagement of the key groove 20 and the key 27 and the small diameter key groove 29 and the small diameter key 28. Is done.

  At this time, the insertion hole of the support bolt 21 provided in the support flange 23 b is larger than the conventional general bolt insertion hole, and is larger than the play dimension set between the key groove 20 and the key 27. Is a movable bolt loose fitting hole 30, and when the support bolt 21 moves in the rotational direction as the drive shaft 19 starts to rotate, the bolt shaft comes into contact with the hole wall of the bolt loose fitting hole 30. The keyway 20 and the key 27 are engaged before. Accordingly, since the rotational force is transmitted from the drive shaft 19 to the core 23 by the engagement of the key groove 20 and the key 27, the rotational force does not act on the support bolt 21, and a large shearing force is applied to the support bolt 21. There is no risk of damage due to action.

  Furthermore, by providing the spacer 34, the support bolt 21 can be tightened with a strong force while the support flange 23b of the core 23 can be rotated, so that a sufficient pulling force can be ensured with respect to the pushing force of the small-diameter kelly bar 26. can do. Further, by providing the rubber ring member 25 on the holding bracket 24, it acts as a cushion for preventing the small-diameter kelly bar 26 from colliding with the kelly bar rotation driving device 15 with metals.

  It is also possible to regulate the tightening amount of the support bolt using a stepped bolt or collar instead of the spacer, and the bolt loosely fitting hole has an arc shape corresponding to the curvature of the support flange. Also good.

DESCRIPTION OF SYMBOLS 11 ... Base machine, 12 ... Boom, 13 ... Kelly bar, 14 ... Cylinder, 15 ... Kelly bar rotation drive device, 16 ... Bottom expansion bucket, 17 ... Hydraulic motor, 18 ... Reduction gear, 19 ... Drive shaft, 20 ... Keyway, 21 ... support bolt, 22 ... female screw hole, 23 ... core, 23a ... core body, 23b ... support flange, 24 ... presser bracket, 25 ... rubber ring material, 26 ... small-diameter Keriba, 27 ... key, 28 ... small-diameter key , 29 ... Small diameter keyway, 30 ... Bolt free insertion hole, 31 ... Bolt insertion hole, 32 ... Fixing bolt, 33 ... Female thread part, 34 ... Spacer, 35 ... Notch part, 36 ... Collar, 37 ... Push-in part

Claims (3)

  Insert a core for a small-diameter keriva into the drive shaft of the kelly bar rotary drive device in an earth drill that performs excavation work while lowering the drill tool while rotating the kelly bar with the drill tool attached to the lower end by the kelly bar rotary drive device. A support flange provided on the outer periphery of the upper end of the core is disposed on the upper end surface of the drive shaft, and a ring-shaped pressing bracket is disposed on the upper surface of the support flange. A support bolt inserted through a bolt insertion hole provided in the holding bracket and a bolt loose insertion hole provided in the support flange is screwed into a female screw hole provided in the upper end surface of the drive shaft, and the support flange is connected to the upper end surface of the drive shaft. And the dimension between the bolt shaft of the support bolt and the bolt loose-fitting hole is provided on the inner surface of the drive shaft. Core support structure in the earth drill larger bolt than play the dimensions of the keys provided on the outer surface of the keyway and the core which is characterized by being formed in movable form.   2. The ground drill according to claim 1, wherein a spacer is provided on a lower surface of the presser bracket so that a lower end surface thereof abuts on an upper end surface of the drive shaft and restricts a tightening amount of the support bolt. Child support structure.   The core support structure for an earth drill according to claim 1 or 2, wherein a rubber ring material is provided on an upper surface of the holding bracket.

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