CN105774963A - Convenient saddle lifting device - Google Patents

Convenient saddle lifting device Download PDF

Info

Publication number
CN105774963A
CN105774963A CN201610008803.0A CN201610008803A CN105774963A CN 105774963 A CN105774963 A CN 105774963A CN 201610008803 A CN201610008803 A CN 201610008803A CN 105774963 A CN105774963 A CN 105774963A
Authority
CN
China
Prior art keywords
guide
axis
saddle
spiral cam
outer tube
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN201610008803.0A
Other languages
Chinese (zh)
Inventor
戚善鸣
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Priority to CN201610008803.0A priority Critical patent/CN105774963A/en
Publication of CN105774963A publication Critical patent/CN105774963A/en
Pending legal-status Critical Current

Links

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B62LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62JCYCLE SADDLES OR SEATS; AUXILIARY DEVICES OR ACCESSORIES SPECIALLY ADAPTED TO CYCLES AND NOT OTHERWISE PROVIDED FOR, e.g. ARTICLE CARRIERS OR CYCLE PROTECTORS
    • B62J1/00Saddles or other seats for cycles; Arrangement thereof; Component parts
    • B62J1/08Frames for saddles; Connections between saddle frames and seat pillars; Seat pillars
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B62LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62JCYCLE SADDLES OR SEATS; AUXILIARY DEVICES OR ACCESSORIES SPECIALLY ADAPTED TO CYCLES AND NOT OTHERWISE PROVIDED FOR, e.g. ARTICLE CARRIERS OR CYCLE PROTECTORS
    • B62J1/00Saddles or other seats for cycles; Arrangement thereof; Component parts
    • B62J1/08Frames for saddles; Connections between saddle frames and seat pillars; Seat pillars
    • B62J2001/085Seat pillars having mechanisms to vary seat height, independently of the cycle frame

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Transmission Devices (AREA)

Abstract

A convenient saddle lifting device belongs to the technical field of mechanical lifting. An inner tube is installed in an outer tube of the device, one end of the inner tube is fixedly connected with an operation handle on a saddle, the other end of the inner tube is fixedly connected with a guide shaft, the other end of the guide shaft is provided with a positioning shaft movably connected with a threaded column, the threaded column is movably connected with the guide shaft, and then meshed with the outer tube, the center the guide shaft is of a hollow structure, a central support column is arranged at the center of a spiral cam, the middle of the central support column is of a hollow structure, the central support column is inserted into the hollow structure part of the guide shaft, an inhaul cable sequentially penetrates the hollow structure part of the central support column of the spiral cam and a limit hole of the spiral cam, to be fitted with the lower part of the spiral cam, one end of a reset spring is fixedly connected with the threaded column, and the other end of the reset spring is fixedly connected with the guide shaft. The convenient saddle lifting device completely adopts a mechanical way, the purpose of lifting the saddle can be realized simply through a pull rod or the inhaul cable, the components are simple in manufacturing, the manufacturing cost is reduced, and meanwhile the stability of the device is improved.

Description

One is saddle lifting device easily
Technical field
The invention belongs to mechanical elevating technical field, particularly relate to the lowering or hoisting gear on a kind of saddle.
Background technology
nullSaddle lifting device relatively conventional on Vehicles Collected from Market is divided into hydraulic power formula,Manual adjustable,Mechanical engagement formulas etc. are several,The wherein application number CN201410451113.3 of the present invention and the application of national patent application office,The patent of " a kind of elevating bracket lever apparatus " by name is the most close,Its technical characteristic is for including telescopic tube assembly、Driving device、Rotate telescopic component、Described rotation telescopic component includes a tumbler containing two different threaded portions,Also include two driving members screwed respectively from the two of described tumbler different threaded portions,And when described tumbler rotates relative to said two driving member,Distance change can be produced between said two driving member,Described rotation telescopic component is converted into two groups of straight reciprocating motions for being relatively rotated by described tumbler and said two driving member,And produce distance change each other owing to said two driving member each screws the difference converting rectilinear motion that the difference of screw thread causes,Described driving device produces relative motioies for driving tumbler on described rotation telescopic component and two driving members,Described driving device connects the trocar sheath on described rotation telescopic component and the fixing connection of telescoping tube,Described driving device is arranged on one end of corresponding described telescopic tube assembly.Although aforesaid way can reach the purpose of saddle capable of lifted, but its motion structure relative complex, and required parts are more, and easily there was a mechanical failure.
Summary of the invention
In order to solve the problems referred to above, the invention provides one saddle lifting device easily.And the present invention adopts mechanical system completely, by simple pull bar or cable control, both can reach the purpose of saddle capable of lifted, and establishment of component is simple, decreases cost of manufacture, too increases the stability of device simultaneously.
nullThe invention provides one saddle lifting device easily,Including outer tube,Interior pipe,The axis of guide,Threaded post,Spiral cam,Zip,Back-moving spring,Saddle and operating handle,It is characterized in that: described outer tube inner sleeve is slidably fitted with interior pipe,Said inner tube one end is fixing with the operating handle at saddle place to be connected,The other end is fixing with the axis of guide to be connected,The described axis of guide is provided with, with the other end of the fixing link of interior pipe, the locating shaft being flexibly connected with threaded post,Described threaded post is connected with outer tube engagement after being flexibly connected with the axis of guide,Described axis of guide central authorities are hollow structure,Described spiral cam central authorities have central branches dagger,The centre of central branches dagger is hollow structure,Described central branches dagger inserts the hollow structure part of the axis of guide,Described drag-line sequentially passes through the hollow structure part of the central branches dagger of spiral cam and the spacing hole of spiral cam,The i.e. bottom laminating of spiral cam,Back-moving spring one end is fixing with threaded post to be connected,The other end is fixing with the axis of guide to be connected.
Described outer tube is by having female thread and the slot segmentation of segmentation female thread, and the radian of slot segmentation is more than the radian of screw thread, thus ensure that screw thread can move up and down in slot segmentation.
Described threaded post is provided with the rotatable slot segmentation corresponding with outer tube female thread slot segmentation, and it is additionally provided with screw inclined plane, and this screw inclined plane matches with the screw inclined plane in threaded post, such that it is able to make threaded post that screw to occur thereon.
Described spiral cam has at least an inclined plane corresponding with the screw inclined plane in threaded post.
Described screw inclined plane is rectilinear motion to be transformed into the common mechanism of rotary motion be 0-90 ° with horizontal angulation, and it forms the axial power of rotary motion decreasing, and just can complete predetermined spinning movement under the effect of the less axial force of drag-line.
When the external thread rotary of threaded post forwards the female thread position of engagement with outer tube to, internal and external threads engages, the relative outer tube axial location of threaded post is fixed, namely saddle upper-lower position is fixed, and when the external thread rotary of threaded post forwards to corresponding with the female thread slot segmentation of outer tube, the female thread of outer tube is corresponding with the external screw thread slot segmentation of threaded post, and the relative outer tube of threaded post can be axially moveable, and namely saddle can move up and down.
Described spiral cam has a pair straight trough, and straight trough matches with the limited block on the axis of guide, and the spacing hole that spiral cam is gone up in the axial direction, in order to pass through drag-line.
The described axis of guide has the boss matched with outer tube slot segmentation, this boss makes the axis of guide move up and down only along the slot segmentation of outer tube, axis of guide axle head is provided with limited block, and it is corresponding with straight trough at the volley, thus limiting the axial freedom of threaded post.
Accompanying drawing explanation
Fig. 1 is the one saddle lifting device sectional structure chart easily of the present invention
Fig. 2 is the threaded post schematic internal view in Fig. 1
Fig. 3 is the threaded post enlarged diagram in Fig. 1
Fig. 4 is the axis of guide axonometric chart in Fig. 1
Fig. 5 is the spiral cam axonometric chart in Fig. 1
Fig. 6 is the saddle schematic diagram in the present invention
In figure: 1, outer tube, 2, interior pipe, 3, the axis of guide, 4, threaded post, 5, spiral cam, 6, zip, 7, back-moving spring, 8, screw inclined plane, 9, screw thread, 10, slot segmentation, 11, boss, 12, limited block, 14, straight trough, 15, saddle, 16, operating handle, 17, spacing hole, 18, central branches dagger, 19, inclined plane, 20, locating shaft, 21, top dead centre, 22, lower dead center
Detailed description of the invention
Describe the present invention in detail below in conjunction with specific embodiment and accompanying drawing, but the invention is not limited in specific embodiment.
Embodiment 1
nullOne of the present invention saddle lifting device easily,Including outer tube 1,Interior pipe 2,The axis of guide 3,Threaded post 4,Spiral cam 5,Zip 6,Back-moving spring 7,Saddle 15 and operating handle 16,Interior pipe 2 it is slidably fitted with in outer tube 1,Said inner tube 2 one end is fixing with the operating handle 16 at saddle 15 place to be connected,The other end is fixing with the axis of guide 3 to be connected,The other end that the described axis of guide 3 fixes link with interior pipe 2 is provided with the locating shaft 20 being flexibly connected with threaded post 4,Described threaded post 4 is connected with outer tube 1 engagement after being flexibly connected with the axis of guide 3,The described axis of guide 3 central authorities are hollow structure,Described spiral cam 5 central authorities have central branches dagger 18,The centre of central branches dagger 18 is hollow structure,Described central branches dagger 18 inserts the hollow structure part of the axis of guide 3,Described spiral cam 8 has a pair straight trough 14,Straight trough 14 matches with the limited block 12 on the axis of guide 3.Described spiral cam 5 has at least an inclined plane 19 corresponding with the screw inclined plane 8 in threaded post 4.Described drag-line 6 sequentially passes through the hollow structure part of the central branches dagger 18 of spiral cam 5 and the spacing hole 17 of spiral cam 5, fits with the bottom of spiral cam 5, and back-moving spring 7 one end is fixing with threaded post 4 to be connected, and the other end is fixing with the axis of guide 3 to be connected.
When adjusting saddle 15 height, when saddle 15 is not when initial position, namely when drag-line 6 is not applied axial power by the operating handle 16 on saddle 15, under the effect of the elastic potential energy of back-moving spring 7, drag-line 6 moves, and makes spiral cam 5 decline to lower dead center 22 position, and the screw thread 9 of threaded post 4 rotates to the position that the female thread with outer tube is meshed from the position corresponding with the female thread slot segmentation 10 of outer tube, now saddle 15 is fixed, it is impossible to move up and down.
When the drag-line 6 being fixed on spiral cam 5 is applied axial power, drag-line 6 overcomes the elastic potential energy of back-moving spring 7, it drives spiral cam 5 to move to top dead centre 21 position, screw inclined plane 8 and helicoid 19 rotary motion bonded to each other, driving threaded post 4 to rotate, screw inclined plane 8 and level have certain angle, but not vertical, it it is 5 °, thus ensure that it rotates effect.And the screw thread 9 of threaded post 4 is from rotating to the position corresponding with the female thread slot segmentation 10 of outer tube 1 with the female thread position of engagement of outer tube, when drag-line 6 is applied axial power, the screw thread 9 of threaded post 4 rotates to the position corresponding with the female thread slot segmentation 10 of outer tube 1, in this position, the axis of guide 3 has the boss 11 that the female thread slot segmentation 10 with outer tube 1 mates, this boss 11 makes the axis of guide 3 move up and down only along the slot segmentation 10 of outer tube 1, rotary freedom is limited by the female thread slot segmentation 10 of outer tube 1, can only move up and down thus also just defining saddle 15, can not rotate.And the radian of slot segmentation 10 is slightly larger than the radian of thread groove, now saddle 15 can move up and down.
Embodiment 2
nullOne of the present invention saddle lifting device easily,Including outer tube 1,Interior pipe 2,The axis of guide 3,Threaded post 4,Spiral cam 5,Zip 6,Back-moving spring 7,Saddle 15 and operating handle 16,It is characterized in that: in described outer tube 1, be slidably fitted with interior pipe 2,Said inner tube 2 one end is fixing with the operating handle 16 at saddle 15 place to be connected,The other end is fixing with the axis of guide 3 to be connected,The other end that the described axis of guide 3 fixes link with interior pipe 2 is provided with the locating shaft 20 being flexibly connected with threaded post 4,Described threaded post 4 is connected with outer tube 1 engagement after being flexibly connected with the axis of guide 3,The described axis of guide 3 central authorities are hollow structure,Described spiral cam 5 central authorities have central branches dagger 18,The centre of central branches dagger 18 is hollow structure,Described central branches dagger 18 inserts the hollow structure part of the axis of guide 3,Described spiral cam 8 has a pair straight trough 14,Straight trough 14 matches with the limited block 12 on the axis of guide 3.Described spiral cam 5 has at least an inclined plane 19 corresponding with the screw inclined plane 8 in threaded post 4.Described drag-line 6 sequentially passes through the hollow structure part of the central branches dagger 18 of spiral cam 5 and the spacing hole 17 of spiral cam 5, fits with the bottom of spiral cam 5, and back-moving spring 7 one end is fixing with threaded post 4 to be connected, and the other end is fixing with the axis of guide 3 to be connected.When adjusting saddle 15 height, when saddle 15 is not when initial position, when drag-line 6 is not applied axial power by the operating handle 16 on saddle 15, under the effect of the elastic potential energy of back-moving spring 7, drag-line 6 moves, and makes spiral cam 5 decline to lower dead center 22 position, and the screw thread 9 of threaded post 4 rotates to the position that the female thread with outer tube is meshed from the position corresponding with the female thread slot segmentation 10 of outer tube, now saddle 15 is fixed, it is impossible to move up and down.When the drag-line 6 being fixed on spiral cam 5 is applied axial power, drag-line 6 overcomes the elastic potential energy of back-moving spring 7, it drives spiral cam 5 to move to top dead centre 21 position, screw inclined plane 8 and helicoid 19 rotary motion bonded to each other, driving threaded post 4 to rotate, screw inclined plane 8 and level have certain angle, but not vertical, it it is 45 °, thus ensure that it rotates effect.And the screw thread 9 of threaded post 4 is from rotating to the position corresponding with the female thread slot segmentation 10 of outer tube 1 with the female thread position of engagement of outer tube, when drag-line 6 is applied axial power, the screw thread 9 of threaded post 4 rotates to the position corresponding with the female thread slot segmentation 10 of outer tube 1, in this position, the axis of guide 3 has the boss 11 that the female thread slot segmentation 10 with outer tube 1 mates, this boss 11 makes the axis of guide 3 move up and down only along the slot segmentation 10 of outer tube 1, rotary freedom is limited by the female thread slot segmentation 10 of outer tube 1, can only move up and down thus also just defining saddle 15, can not rotate.And the radian of slot segmentation 10 is slightly larger than the radian of thread groove, now saddle 15 can move up and down.
Embodiment 3
nullOne of the present invention saddle lifting device easily,Including outer tube 1,Interior pipe 2,The axis of guide 3,Threaded post 4,Spiral cam 5,Zip 6,Back-moving spring 7,Saddle 15 and operating handle 16,It is characterized in that: in described outer tube 1, be slidably fitted with interior pipe 2,Said inner tube 2 one end is fixing with the operating handle 16 at saddle 15 place to be connected,The other end is fixing with the axis of guide 3 to be connected,The other end that the described axis of guide 3 fixes link with interior pipe 2 is provided with the locating shaft 20 being flexibly connected with threaded post 4,Described threaded post 4 is connected with outer tube 1 engagement after being flexibly connected with the axis of guide 3,The described axis of guide 3 central authorities are hollow structure,Described spiral cam 5 central authorities have central branches dagger 18,The centre of central branches dagger 18 is hollow structure,Described central branches dagger 18 inserts the hollow structure part of the axis of guide 3,Described spiral cam 8 has a pair straight trough 14,Straight trough 14 matches with the limited block 12 on the axis of guide 3.Described spiral cam 5 has at least an inclined plane 19 corresponding with the screw inclined plane 8 in threaded post 4.Described drag-line 6 sequentially passes through the hollow structure part of the central branches dagger 18 of spiral cam 5 and the spacing hole 17 of spiral cam 5, fits with the bottom of spiral cam 5, and back-moving spring 7 one end is fixing with threaded post 4 to be connected, and the other end is fixing with the axis of guide 3 to be connected.When adjusting saddle 15 height, when saddle 15 is not when initial position, when drag-line 6 is not applied axial power by the operating handle 16 on saddle 15, under the effect of the elastic potential energy of back-moving spring 7, drag-line 6 moves, and makes spiral cam 5 decline to lower dead center 22 position, and the screw thread 9 of threaded post 4 rotates to the position that the female thread with outer tube is meshed from the position corresponding with the female thread slot segmentation 10 of outer tube, now saddle 15 is fixed, it is impossible to move up and down.When the drag-line 6 being fixed on spiral cam 5 is applied axial power, drag-line 6 overcomes the elastic potential energy of back-moving spring 7, it drives spiral cam 5 to move to top dead centre 21 position, screw inclined plane 8 and helicoid 19 rotary motion bonded to each other, driving threaded post 4 to rotate, screw inclined plane 8 and level have certain angle, but not vertical, it it is 85 °, thus ensure that it rotates effect.And the screw thread 9 of threaded post 4 is from rotating to the position corresponding with the female thread slot segmentation 10 of outer tube 1 with the female thread position of engagement of outer tube, when drag-line 6 is applied axial power, the screw thread 9 of threaded post 4 rotates to the position corresponding with the female thread slot segmentation 10 of outer tube 1, in this position, the axis of guide 3 has the boss 11 that the female thread slot segmentation 10 with outer tube 1 mates, this boss 11 makes the axis of guide 3 move up and down only along the slot segmentation 10 of outer tube 1, rotary freedom is limited by the female thread slot segmentation 10 of outer tube 1, can only move up and down thus also just defining saddle 15, can not rotate.And the radian of slot segmentation 10 is slightly larger than the radian of thread groove, now saddle 15 can move up and down.
Ultimate principle and the principal character of the present invention have more than been shown and described; skilled person will appreciate that the present invention is not restricted to the described embodiments; what the above embodiments and description described simply illustrates principles of the invention; without departing from the spirit and scope of the present invention; the present invention has various changes and modifications; these changes and improvements both fall within the scope of protection of present invention, and claimed scope is defined by appending claims and equivalent.

Claims (7)

  1. null1. a saddle lifting device easily,Including outer tube (1),Interior pipe (2),The axis of guide (3),Threaded post (4),Spiral cam (5),Zip (6),Back-moving spring (7),Saddle (15) and operating handle (16),It is characterized in that: in described outer tube (1), be slidably fitted with interior pipe (2),Said inner tube (2) one end is fixing with the operating handle (16) at saddle (15) place to be connected,The other end is fixing with the axis of guide (3) to be connected,The described axis of guide (3) is provided with, with the other end of the fixing link of interior pipe (2), the locating shaft (20) being flexibly connected with threaded post (4),Described threaded post (4) is connected with outer tube (1) engagement after being flexibly connected with the axis of guide (3),The described axis of guide (3) central authorities are hollow structure,Described spiral cam (5) central authorities have central branches dagger (18),The centre of central branches dagger (18) is hollow structure,Described central branches dagger (18) inserts the hollow structure part of the axis of guide (3),Described drag-line (6) sequentially passes through the hollow structure part of the central branches dagger (18) of spiral cam (5) and the spacing hole (17) of spiral cam (5),The i.e. bottom laminating of spiral cam (5),Back-moving spring (7) one end is fixing with threaded post (4) to be connected,The other end is fixing with the axis of guide (3) to be connected.
  2. 2. saddle lifting device easily according to claim 1, it is characterized in that: described outer tube (1) is provided with female thread and the slot segmentation (10) of segmentation female thread, and the radian of slot segmentation (10) is slightly larger than the radian of screw thread.
  3. 3. saddle lifting device easily according to claim 1, it is characterized in that: described threaded post (4) be provided with can and the slot segmentation (10) corresponding with outer tube (1) female thread slot segmentation, threaded post (4) is additionally provided with screw inclined plane (8).
  4. 4. saddle lifting device easily according to claim 1, it is characterised in that: described spiral cam (5) has at least an inclined plane (19) corresponding with the screw inclined plane (8) in threaded post (4).
  5. 5. according to the arbitrary described saddle lifting device easily of claim 3 or 4, it is characterised in that: described screw inclined plane (8) and horizontal plane angulation are 5-85 °.
  6. 6. saddle lifting device easily according to claim 1, it is characterized in that: described spiral cam (5) has a pair straight trough (14), and straight trough (14) matches with the limited block (12) on the axis of guide (3).
  7. 7. saddle lifting device easily according to claim 1, it is characterized in that: being provided with the boss (11) that the slot segmentation (10) with outer tube matches on the described axis of guide (3), the axis of guide (3) axle head is provided with limited block (12).
CN201610008803.0A 2016-01-07 2016-01-07 Convenient saddle lifting device Pending CN105774963A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201610008803.0A CN105774963A (en) 2016-01-07 2016-01-07 Convenient saddle lifting device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201610008803.0A CN105774963A (en) 2016-01-07 2016-01-07 Convenient saddle lifting device

Publications (1)

Publication Number Publication Date
CN105774963A true CN105774963A (en) 2016-07-20

Family

ID=56390313

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201610008803.0A Pending CN105774963A (en) 2016-01-07 2016-01-07 Convenient saddle lifting device

Country Status (1)

Country Link
CN (1) CN105774963A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108461890A (en) * 2018-04-17 2018-08-28 四川省能源投资集团有限责任公司 A kind of communication pole and its method of adjustment of conveniently adjusting angle

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108461890A (en) * 2018-04-17 2018-08-28 四川省能源投资集团有限责任公司 A kind of communication pole and its method of adjustment of conveniently adjusting angle

Similar Documents

Publication Publication Date Title
CN107830342A (en) The computer screen bindiny mechanism being easily installed
CN207691291U (en) A kind of 35kV switchgears steady type electrical verification auxiliary device
WO2021110002A1 (en) Low mounting distance raising column
CN209621790U (en) A kind of lifting column and hoistable platform
CN201794545U (en) Rescue spraying device
CN106184556A (en) More piece sleeve pipe structure
CN202491944U (en) Lifting mechanism
CN105774963A (en) Convenient saddle lifting device
WO2021110003A1 (en) Raising column
CN205365837U (en) Convenient saddle elevating gear
CN209026209U (en) Electric expansion valve
CN205578401U (en) Mechanical compensation type hydraulic oil cylinder
CN204437454U (en) A kind of straight journey mechanism of many revolution electric actuator
CN107508229B (en) The anti-bird from building nest mechanism of electric wire based on small angle rotation structure
CN106312534B (en) A kind of automatic installation locking screwdriver bit of screw and device
CN110682087B (en) Centering device for large-diameter shaft and mounting hole
CN208481941U (en) A kind of device for twisting waist with adjusting angle
CN104653856A (en) Straight stroke mechanism of multi-turn electric actuator
CN209385943U (en) A kind of universal joint compensator
CN203066905U (en) Slewing and translating extension mechanism of iron roughneck
CN110562102A (en) Manual and electric integrated control type sliding rail assembly with compact structure for automobile seat
CN102180411B (en) Pillar lifting rotary arm crane
CN205876847U (en) Hand liquid gas controlling means with interlock function
CN206373802U (en) A kind of multi-faceted adjustable positioning mechanism
CN106089843B (en) A kind of hand hydraulic-pneumatic control device with interlock function

Legal Events

Date Code Title Description
C06 Publication
PB01 Publication
WD01 Invention patent application deemed withdrawn after publication

Application publication date: 20160720

WD01 Invention patent application deemed withdrawn after publication