Durable pivotal connecting device for table lamp

A durable pivotal connecting device for a table lamp between a base and a supporting post of the lamp having a lampshade and a lamp pipe, the supporting post is connected to a rotation seat located in the base and is pivotably assembled with the durable pivotal connecting device for rotation adjustment of the supporting post; the connecting device includes two sets of curved spring leaves, two connecting rods, a transverse bar and an adjusting bolt. The spring leaves are arciform and symmetrically arranged, and each includes a connecting end and is split to form a slit, a positioning end and an adjustment end; screws are used to lock the connecting ends and the positioning ends of the spring leaves onto the inner wall of the base to pivotably mount the rotation seat; the adjustment ends are connected to the connecting rods and the transverse bar to make association of the two sets of spring leaves. The transverse bar has a guide hole allowing passing through of the stem of the adjusting bolt from outside of the base, in order that the transverse bar is moved up and down by adjustment of the adjusting bolt; the adjustment ends of the spring leaves can be operated to give elastic binding action force on the rotation seat, and durability of the pivot area requiring frequent adjustment between the base and the supporting post can be assured.

BACKGROUND OF THE INVENTION
 1. Field of the invention
 The present invention is related to a durable pivotal connecting device for
 a table lamp between the base and the supporting post of the lamp. The
 present invention is especially related to a pivotal connecting device
 taking advantage of the elastic nature of a plurality of bendable spring
 leaves in assembling an adjusting bolt, a transverse bar and two
 connecting rods in a linking mode, thereby, frictional resistance at the
 contact area between a rotation seat and the spring leaves can be
 controlled to tightly bind and fix or release the rotation seat for the
 supporting post to get a function of adjustment in rotation angle.
 2. Description of the Prior Art
 A conventional table lamp seen in the markets is provided on one end of the
 supporting post with a lampshade and a lamp pipe, while the other end
 thereof is pivotally mounted on the base of the lamp set, these form the
 main part of the table lamp. However, no matter the base of the lamp set
 is placed on or is clamped on a table, there is normally a pivotal
 connecting structure between the base and the supporting post for such
 purpose as that the supporting post can be rotationally adjusted for an
 ideal angle of illumination of the light toward the table. While pivotal
 connecting structures between bases and supporting posts on the table
 lamps seen in the markets mostly use the mode of connection with screws
 and nuts for assembling to have the main and subordinate rotating axles
 locked in positions in a given looseness of mating, and a conventional
 effect of adjusting the supporting posts relative to the bases can be
 obtained. However, the conventional pivotal connecting structures are not
 durable, the supporting posts are frequently adjusted directly with hands,
 and the axle pipes of the pivotal connecting structures are assembled and
 controlled for their tightness of binding with screws and nuts; thereby,
 pivotal connecting of the supporting posts on the bases will become loose
 after a long period of use with frequent adjusting, and are unable to get
 fixed positions with enough frictional resistance any more. Although users
 can use tools such as screw drivers to adjust the screws and nuts on the
 loosened pivotal connecting structures to recover suitable tightness of
 binding of the supporting posts against the bases, it is surely known
 that, adjustment of tightness of binding between the main and subordinate
 rotating axles taking advantage of their threads can not afford frictional
 resistance required in continuous rotational adjustment of the lamp set
 supporting posts. The pivotal connecting structures certainly will get
 loose again and again; this shows that durability of the conventional
 pivotal connecting structures is inferior.
 SUMMARY OF THE INVENTION
 In view of the above statement, to completely solve the problem of
 deficiency in durability and stability of a pivotal connecting structure
 is the motive of studying of the present invention. And thereby, the main
 object of the present invention is to design and provide a pivotal
 connecting device with better durability and stability in favor of
 adjustment of a user.
 Another object of the present invention is to provide a pivotal connecting
 device with better durability and stability in favor of adjustment of a
 user taking advantage of the principle of frictional braking function
 generated by braking shoes together with that of elastic compressing and
 restoring of curved spring leaves.
 The pivotal connecting device of the present invention actually is not
 limited to mating of a supporting post and a base, rather, it points to
 providing of a cylindrical rotation seat between the supporting post and
 the base. By assembling of the cylindrical rotation seat in the pivotal
 connecting device of the present invention, convenience of adjustment and
 durability of the pivotal connecting device can be improved.
 The present invention will be apparent after reading the detailed
 description of the preferred embodiment thereof in reference to the
 accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 Referring to FIG. 1 of the drawings, the present invention provides a
 durable pivotal connecting device for a table lamp between the base and
 the supporting post of the lamp; the table lamp is comprised mainly of a
 base 1 and a supporting post 2. One end of the supporting post 2 is
 provided with a lampshade 3 and a lamp pipe 31 in the lampshade 3. The
 base 1 is provided therein with a power switch 10. In this structure, the
 other end of the supporting post 2 is connected to a rotation seat 5 with
 a screw 50, the other end and the rotation seat 5 are located in the base
 1 and are assembled with the durable pivotal connecting device of the
 present invention.
 The rotation seat 5 is provided with an assembling hole 51 in pursuance of
 the actual shape of the cross section area of the supporting post 2 for
 insertion of the supporting post 2 into the assembling hole 51. And a
 screw hole 52 is provided on the rotation seat 5 to receive the screw 50
 for lock the rotation seat 5 to the supporting post 2. While both ends of
 the rotation seat 5 are made to form pivot axle ends 53 with a reduced
 diameter.
 When in practice, the base 1 can be made to have a pivotal connecting seat
 11 having an opening 12 for insertion and rotation of the supporting post
 2. A top roof of the pivotal connecting seat 11 above the opening 12 is
 provided with a screw hole 13 to allow extending of an adjusting bolt 4
 therethrough for adjustment of the pivotal connecting device.
 The pivotal connecting device is comprised of two sets of curved spring
 leaves 6, two connecting rods 7, a transverse bar 8 and the abovementioned
 adjusting bolt 4.
 Wherein, referring to FIG. 2, the two sets of curved spring leaves 6 are
 symmetrically arranged, and each includes a connecting end 62 and is split
 to form a slit 63, a positioning end 64 and an adjustment end 65. Screws
 can be used to lock the connecting ends 62 and the positioning ends 64 of
 the curved spring leaves 6 onto the inner wall of the base 1. The pivot
 axle ends 53 of the rotation seat 5 in conformity in shape with the curved
 spring leaves 6 can thereby be positioned in the base 1 (also referring to
 FIG. 3 and 4). The adjustment ends 65 of the curved spring leaves 6 is
 provided for fixedly mounting the two connecting rods 7; the transverse
 bar 8 is provided on the other ends of the two connecting rods 7. The
 center of gravity of the transverse bar 8 is provided with a guide hole 81
 to hold therein and allow passing through of the stem 41 of the
 abovementioned adjusting bolt 4. The end of the stem 41 is provided with a
 stop nut 82, so that the transverse bar 8 can be moved up and down by
 adjustment of the adjusting bolt 4.
 When in use, as shown in FIG. 4, by the nature of elasticity of the
 non-fixed adjustment ends 65 of the curved spring leaves 6 in reducing and
 enlarging diameters of the spring leaves 6, the adjusting bolt 4 can be
 rotated for adjustment to make the spring leaves 6 on the pivot axle ends
 53 be endowed with suitable binding action force to brake the rotation
 seat 5. Thereby, the rotation seat 5 can be braked firmly by the binding
 action force (that is the friction force between the spring leaves 6 and
 the pivot axle ends 53) within the rotating stroke of the supporting post
 2. Thereby, the supporting post 2 and the lamp pipe 31 mounted thereon for
 illumination can be stably positioned after rotation adjustment. And if
 the pivot axle ends 53 of the rotation seat 5 are worn by rotational
 abrading of the spring leaves 6 after long period of use, binding action
 force between the pivot axle ends 53 and the spring leaves 6 required
 after rotation adjustment of the supporting post 2 on the base 1 can be
 obtained again promptly by screwing tight the adjusting bolt 4. Hence an
 extremely stable pivotal connecting device convenient for adjustment is
 obtained, the durability of the pivot area in rotation adjustment of the
 supporting post 2 on the base 1 can be ensured.
 Having thus described the technical structure of my invention with
 practicability and improvement, therefore, what I claim as new and desire
 to be secured by letters patent of the united states is: