Abstract:
A damp telescopic tube and a damp writing pen are disclosed. The damp telescopic tube has at least two metallic tubes in different diameters to be fitted together, which can change the total length of the damp telescopic tube by a small tube slipped over a big tube telescopically. This can solve the questions of controlling handle feeling, quality instability and fricative bad voice between metallic tubes. The damp telescopic tube has at least two metallic tubes in different diameters. A small diameter tube is fitted in a big diameter tube in the two adjacent tubes. A limited location member is provided between the small diameter tube and the big diameter tube. A plastic piston is provided in the end of the small diameter tube which located inside of the big diameter tube and keeps in touch with the inside wall of the big diameter tube.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a telescopic tube and a telescopic writing pen, and more particularly to one having at least two metallic tubes in different diameters to change its length after retraction. 
         [0003]    2. Description of the Prior Art 
         [0004]    A metallic telescopic tube is widely used to an antenna of an electronic apparatus, a writing pen for a touch screen or a pointer. A conventional metallic tube has at least two metallic tubes in different diameters which are a small tube and a big tube. The small tube is fitted in the big tube. A limit mechanism is provided between the small tube and the big tube. A leaf spring is provided between the outer wall of the small tube and the inner wall of the big tube. When in use, the small tube is pulled or pushed with respect to the big tube to shorten or prolong its length. The leaf spring provides a damping effect to the sliding of the small tube. The limit mechanism provides a limit effect to the extension or retraction of the small tube. Due to the differences in size between the tubes and the leaf spring, this kind telescopic tube has the following shortcomings: 
         [0000]    1. When the small tube is pulled or pushed with respect to the big tube, it is not easy to control its looseness and tightness. The quality of the products is unstable.
 
2. When the small tube is pulled or pushed with respect to the big tube, there will be friction noises produced by the leaf spring and the tubes.
 
       SUMMARY OF THE INVENTION 
       [0005]    According to a first aspect of the present invention, there is provided a damp telescopic tube, having at least two metallic tubes in different diameters which are a small tube and a big tube, the small tube being fitted in the big tube, a limit mechanism being provided between the small tube and the big tube, the small tube having a first end inserted in the big tube, the first end of the small tube being provided with a piston to be in touch with an inner wall of the big tube. 
         [0006]    Preferably, the piston comprises a piston shaft made of a rigid material and at least a piston ring made of elastic plastics or rubber, the piston ring being fitted on one end of the piston shaft, the piston ring having an outer surface to be in touch with the inner wall of the big tube, the piston shaft having another end inserted in and secured to the first end of the small tube. 
         [0007]    Preferably, either of the piston ring and the piston shaft is formed with an exhaust notch. 
         [0008]    Preferably, the piston shaft is in a          -like shape, the piston ring being disposed between two horizontal arms of the piston shaft. 
         [0009]    Preferably, the limit mechanism is a reduced inner flange at a first end of the big tube, the first end of the big tube being adapted to receive the small tube, the inner flange being adapted to stop the piston provided on the first end of the small tube. 
         [0010]    According to a second aspect of the present invention, there is provided a damp writing pen, comprising a pen head, a pen cap, and at least two metallic tubes in different diameters which are a small tube and a big tube, the small tube being fitted in the big tube, a limit mechanism being provided between the small tube and the big tube, the small tube having a first end inserted in the big tube, the first end of the small tube being provided with a piston to be in touch with an inner wall of the big tube. 
         [0011]    The damp telescopic tube of the present invention uses the plastic piston to provide a damping effect for the sliding of the small tube, which has a good handle feeling, stability, and no fricative noise between metallic tubes. The piston comprises the piston shaft made of a rigid material and at least one piston ring made of elastic plastics or rubber, which is easy to be assembled. Either of the piston ring and the piston shaft is formed with the exhaust notch, prevent the small tube from rebounding automatically when the small tube is pulled or pushed with respect to the big tube. In particular, the piston shaft is in a          -like shape and the piston ring is disposed between the two horizontal arms of the piston shaft. This kind of piston may be produced by injection molding, which is stable in size and doesn&#39;t need more manpower for assembly. The automation level is high. This simplifies the assembled procedures, avoiding unstable quality due to manual procedures. The limit mechanism is the reduced inner flange at the first end of the big tube. The first end of the big tube is adapted to receive the small tube. The inner flange is adapted to stop the piston provided on the first end of the small tube. The limit mechanism is simple in structure and is convenient for production. Therefore, the damp telescopic tube has the advantages of good handle feeling, stability, and no fricative noises. The damp writing pen has a good effect in use. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a cross-sectional view of a damp telescopic tube according to a first preferred embodiment of the present invention; 
           [0013]      FIG. 2  is a perspective view of the damp telescopic tube in an extended status according to the first preferred embodiment of the present invention; 
           [0014]      FIG. 3  is a cross-sectional view of a damp telescopic tube according to a second preferred embodiment of the present invention; 
           [0015]      FIGS. 4   a  through  4   e  are cross-sectional views showing five pistons of the damp telescopic tube of the present invention; 
           [0016]      FIG. 5   a  is a perspective view of a piston formed with exhaust notches of the damp telescopic tube of the present invention; and 
           [0017]      FIG. 5   b  is a perspective view of another piston formed with exhaust notches of the damp telescopic tube of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]      FIG. 1  is a cross-sectional view of a three-section writing pen for an electronic product screen according to a first preferred embodiment of the present invention, which comprises an outer tube  1  having a larger diameter, a middle tube  2  having a middle diameter, and an inner tube  4  having a smaller diameter. The three tubes are made of a metallic material. 
         [0019]    The inner tube  4  having a lower end  41  provided with a first plastic piston  5 . The first plastic piston  5  comprises a piston shaft  51  made of rigid plastics in a          -like shape and a piston ring  52  made of elastic plastics or rubber. The piston shaft  51  has a central shaft  511  inserted in and secured to the lower end  41  of the inner tube  4 . The piston ring  52  is fitted between two horizontal arms  512  of the piston shaft  51 . 
         [0020]    The middle tube  2  has an upper end  22  formed with a reduced inner flange. The inner flange has an inner hole for sliding of the inner tube  4 . The inner tube  4  is inserted in the middle tube  2 , and the outer surface of the piston ring  52  at the lower end  41  of the inner tube  4  is in touch with the inner wall of the middle tube  2 . The inner tube  4  has an upper end  42  inserted through the inner flange of the upper end  22  of the middle tube  2  and pulled upward. The middle tube  2  having a lower end  21  provided with a second plastic piston  3 . The second plastic piston  3  comprises a piston shaft  31  made of rigid plastics in a          -like shape and a piston ring  32  made of elastic plastics or rubber. The piston shaft  31  has a central shaft  311  inserted in and secured to the lower end  21  of the middle tube  2 . The piston ring  32  is fitted between two horizontal arms  312  of the piston shaft  31 . 
         [0021]    The outer tube  1  has an upper end  12  formed with a reduced inner flange. The inner flange has an inner hole for sliding of the middle tube  2 . The middle tube  2  with the inner tube  4  is inserted in the outer tube  1 , and the outer surface of the piston ring  32  at the lower end  21  of the middle tube  2  is in touch with the inner wall of the outer tube  1 . The upper end  42  of the inner tube  4  and the upper end  22  of the middle tube  2  are inserted through the inner flange of the upper end  12  of the outer tube  1  and pulled upward. The horizontal arms  312  of the piston shaft  31  are stopped by the inner flange of the upper end  12  of the outer tube  1 . 
         [0022]    A pen head  6  made of rigid plastics comprises a conical head portion  61  at a lower end thereof and an upper end  62  inserted in and secured to a lower end  11  of the outer tube  1 . 
         [0023]    A pen cap  7  made of rigid plastics in a stepped cylinder shape is provided. The pen cap  7  has a big end which has a diameter about equal to that of the outer tube  1  and larger than that of the middle tube  2  and a small end which has a diameter corresponding to the inner tube  4 . The small end of the pen cap  7  is fitted in the upper end  42  of the inner tube  4 . 
         [0024]      FIG. 2  is a perspective view of the first embodiment of the present invention in a fully extended status. The conical head portion  61  of the pen head  6  is extended out of the lower end  11  of the outer tube  1 . The lower end  21  of the middle tube  2  and the second plastic piston  3  are inserted in the outer tube  1 . The inner flange of the upper end  12  of the outer tube  1  confines the middle tube  2  to be pulled to its extremity. The rest of the middle tube  2  is pulled upward from the upper end  12  of the outer tube  1 . The lower end  41  of the inner tube  4  and the first plastic piston  5  are inserted in the middle tube  2 . The inner flange of the upper end  22  of the middle outer  2  confines the inner tube  4  to be pulled to its extremity. The rest of the inner tube  4  is pulled upward from the upper end  22  of the middle tube  2 . The small end of the pen cap  7  is fitted in the upper end  42  of the inner tube  4 . 
         [0025]    When the first preferred embodiment of the present invention is fully retracted, the pen cap  7  has a lower end surface engaging with the upper end  42  of the inner tube  4  and the upper end  12  of the outer tube  1 ; the lower end  41  of the inner tube  4  in the middle tube  2  and the first plastic piston  5  are slid in a lower section of the middle tube  2 ; and the lower end  21  of the middle tube  2  in the outer tube  1  and the second plastic piston  3  are slid in a lower section of the outer tube  1 . After retraction, the total length the first preferred embodiment of the present invention in shortened to a half. 
         [0026]    During the process of pulling and pushing the middle tube  2  and the inner tube  4 , the first and second plastic pistons  3  and  5  provide a damping effect to the middle tube  2  and the inner tube  4 , without friction noise. In addition, the elasticity of the first and second plastic pistons  3  and  5  neutralizes the differences in size among the outer tube  1 , the middle tube  2  and the inner tube  4  to provide a smooth and stable pulling or pushing. 
         [0027]      FIG. 3  is a cross-sectional view of a two-section writing pen for an electronic product screen according to a second preferred embodiment of the present invention, which comprises an outer tube  1 ′ having a larger diameter and an inner tube  2 ′ having a smaller diameter. The two tubes are made of a metallic material. 
         [0028]    The inner tube  2 ′ having a lower end  21 ′ provided with a plastic piston  3 ′. The plastic piston  3 ′ comprises a piston shaft  31 ′ made of rigid plastics in a          -like shape and a piston ring  32 ′ made of elastic plastics or rubber. The piston shaft  31 ′ has a central shaft  311 ′ inserted in and secured to the lower end  21 ′ of the inner tube  2 ′. The piston ring  32 ′ is fitted between two horizontal arms  312 ′ of the piston shaft  31 ′. 
         [0029]    The outer tube  1 ′ has an upper end  12 ′ formed with a reduced inner flange. The inner flange has an inner hole for sliding of the inner tube  2 ′. The inner tube  2 ′ is inserted in the outer tube  1 ′, and the outer surface of the piston ring  32 ′ at the lower end  21 ′ of the inner  2 ′ is in touch with the inner wall of the outer tube  1 ′. The upper end  22 ′ of the inner tube  2 ′ is inserted through the inner flange of the upper end  12 ′ of the outer tube  1 ′ and pulled upward. A pen cap  7 ′ made of rigid plastics in a stepped cylinder shape is provided. The pen cap  7 ′ has a big end which has a diameter about equal to that of the outer tube  1 ′ and a small end which has a diameter corresponding to the inner tube  2 ′. The small end of the pen cap  7 ′ is fitted in the upper end  22 ′ of the inner tube  2 ′. The horizontal arms  312 ′ of the piston shaft  31 ′ are stopped by the inner flange of the upper end  12 ′ of the outer tube  1 ′. A pen head  6 ′ made of rigid plastics comprises a conical head portion  61 ′ at a lower end thereof and an upper end  62 ′ inserted in and secured to a lower end  11 ′ of the outer tube  1 ′. 
         [0030]    When the second preferred embodiment of the present invention is fully extend, the conical head portion  61 ′ of the pen head  6 ′ is extended out of the lower end  11 ′ of the outer tube  1 ′. The lower end  21 ′ of the inner tube  2 ′ and the plastic piston  3 ′ are inserted in the outer tube  1 ′. The inner flange of the upper end  12 ′ of the outer tube  1 ′ confines the inner tube  2 ′ to be pulled to its extremity. The rest of the inner tube  2 ′ is pulled upward from the upper end  12 ′ of the outer tube  1 ′. The small end of the pen cap  7 ′ is fitted in the upper end  22 ′ of the inner tube  2 ′. 
         [0031]    When the present invention is fully retracted, the pen cap  7 ′ has a lower end surface engaging with the upper end  12 ′ of the outer tube  1 ′; and the lower end  21 ′ of the inner tube  2 ′ in the outer tube  1 ′ and the plastic piston  3 ′ are slid in a lower section of the outer tube  1 ′. After retraction the total length of the second preferred embodiment of the present invention is shortened to two thirds. 
         [0032]    During the process of pulling and pushing the inner tube  2 ′, the plastic pistons  3 ′ provides a damping effect to the inner tube  2 ′, without friction noise. In addition, the elasticity of the plastic pistons  3 ′ neutralizes the difference in size between the outer tube  1 ′ and the inner tube  2 ′ to provide a smooth and stable pulling or pushing. 
         [0033]    The damp telescopic tube of the present invention may be made of rigid plastic material. 
         [0034]    The piston in the damp telescopic tube of the present invention may use the structures as shown in  FIGS. 4   a  through  4   e.    
         [0035]    As shown in  FIG. 4   a , a piston  8   a  comprises a piston shaft  81   a  made of copper, stainless steel, plastics or other rigid materials and three piston rings  82   a  made of elastic plastics or rubber. The piston shaft  81   a  has a short shaft  811   a  at a small diameter end thereof and four flanges  812   a  spaced with each other at a large diameter end thereof. The short shaft  811   a  is inserted in and secured to the end of the small tube which is inserted in the big tube. Three circular grooves are formed among the four flanges  812   a . The three piston rings  82   a  are fitted in the three circular grooves at the large diameter end of the piston shaft  81   a . Each of the three piston rings  82   a  has a portion exposed out of its adjacent flanges  812   a  to be in touch with the inner wall of the big tube. 
         [0036]    As shown in  FIG. 4   b , a piston  8   b  comprises a piston shaft  81   b  made of a rigid material and two piston rings  82   b  made of an elastic material. The piston shaft  81   b  has a short shaft  811   b  at a small diameter end thereof and three flanges  812   b  spaced with each other at a large diameter end thereof. The short shaft  811   b  is inserted in and secured to the end of the small tube which is inserted in the big tube. Two circular grooves are formed among the three flanges  812   b . The two piston rings  82   b  are fitted in the two circular grooves at the large diameter end of the piston shaft  81   b . Each of the two piston rings  82   b  has a portion exposed out of its adjacent flanges  812   b  to be in touch with the inner wall of the big tube. 
         [0037]    As shown in  FIG. 4   c , a piston  8   c  is substantially similar to the piston  8   b  with the exceptions described hereinafter. The piston  8   c  comprises a piston shaft  81   c  which is identical to the piston shaft  81   b  of  FIG. 4   b  and two piston rings  82   c  each having a rectangular cross-section corresponding in shape to circular grooves formed among three flanges  812   c.    
         [0038]    As shown in  FIG. 4   d , a piston  8   d  comprises a piston shaft  81   d  made of a rigid material and a piston ring  82   d  made of an elastic material. The piston shaft  81   d  has a short shaft  811   d  at a small diameter end thereof and a flange  812   d  at the end of a large diameter end thereof. The short shaft  811   d  is inserted in and secured to the end of the small tube which is inserted in the big tube. The piston ring  82   d  is fitted onto the large diameter end and engages with the flange  812   d . The piston ring  82   d  has a portion exposed out of the flange  812   d  to be in touch with the inner wall of the big tube. 
         [0039]    As shown in  FIG. 4   e , a piston  8   e  comprises a piston shaft  81   e  made of a rigid material and a piston ring  82   e  made of an elastic material. The piston shaft  81   e  has a short shaft  811   e  at a small diameter end thereof and a flange  812   d  between the small diameter end and a large diameter end thereof. The short shaft  811   e  is inserted in and secured to the end of the small tube which is inserted in the big tube. The piston ring  82   e  is fitted onto the large diameter end and engages with the flange  812   e . The piston ring  82   e  has a portion exposed out of the flange  812   e  to be in touch with the inner wall of the big tube. 
         [0040]    In order to overcome the problems that the small tube will be automatically retracted due to vacuum suction when the small tube is pulled upward with respect to the big tube; and that the small tube will be automatically rebounded due to the pressure produced by the compressed air in the big tube when the small tube is pushed in the big tube, the piston rings are formed with exhaust notches, as shown in  FIG. 5   a , or the piston shaft is formed with exhaust notches. 
         [0041]    As shown in  FIG. 5   a , a piston  8   a  comprises a piston shaft  81   a  made of copper, stainless steel, plastics or other rigid materials and three piston rings  82   a  made of elastic plastics or rubber. The piston shaft  81   a  has a short shaft  811   a  at a small diameter end thereof and four flanges  812   a  spaced with each other at a large diameter end thereof. The short shaft  811   a  is inserted in and secured to the end of the inner tube which is inserted in the big tube. Three circular grooves are formed among the four flanges  812   a . The three piston rings  82   a  are fitted in the three circular grooves at the large diameter end of the piston shaft  81   a . Each of the three piston rings  82   a  has a portion exposed out of its adjacent flanges  812   a  to be in touch with the inner wall of the big tube. Each of the three piston rings  82   a  is formed with an exhaust notch  821   a  thereon to form an air circulation passage with respect to the inner wall of the big tube, so that the inner tube will not be automatically retracted because there is no vacuum suction when the inner tube is pulled upward with respect to the big tube; and the inner tube will not be automatically rebounded because there is no compressed air in the big tube when the inner tube is pushed in the big tube. 
         [0042]    As shown in  FIG. 5   b , a piston  8   b  comprises a piston shaft  81   b  made of a rigid material and two piston rings  82   b  made of an elastic material. The piston shaft  81   b  has a short shaft  811   b  at a small diameter end thereof and three flanges  812   b  spaced with each other at a large diameter end thereof. The short shaft  811   b  is inserted in and secured to the end of the inner tube which is inserted in the big tube. Two circular grooves are formed among the three flanges  812   b . Each of the three flanges  812   b  is axially formed with an exhaust notch  813   b  thereon. The bottom of the exhaust notch  813   b  is lower than the bottoms of the two circular grooves. The two piston rings  82   b  are fitted in the two circular grooves at the large diameter end of the piston shaft  81   b . The two piston rings  82   b  don&#39;t cover the exhaust notches  813   b  totally, which forms an air circulation passage. Each of the two piston rings  82   b  has a portion exposed out of its adjacent flanges  812   b  to be in touch with the inner wall of the big tube. With the air circulation passage of the piston shaft  81   b , the inner tube will not be automatically retracted because there is no vacuum suction when the inner tube is pulled upward with respect to the outer tube; and the inner tube will not be automatically rebounded because there is no compressed air in the big tube when the inner tube is pushed in the big tube. 
         [0043]    The damp telescopic tube of the present invention has at least two metallic tubes in different diameters. A small tube has one end provided with a plastic piston which is inserted in a big tube and in touch with the inner wall of the big tube. The structure is simple for manufacture. The damp telescopic tube of the present invention is used to a damp writing pen, which provides a good handle feeling, stability, and no fricative noise between metallic tubes. 
         [0044]    Although particular embodiments of the present invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the present invention. Accordingly, the present invention is not to be limited except as by the appended claims.