Abstract:
A lamp holder for comprises a socket having an axis, a part extending substantially at right angles to the axis, and at least one first snap connector; a base having an axis, a tubular stem including an inner end connected to the base, a first clamping member in the base adjacent the inner end of the stem, and at least one second snap connector engageble with the first snap connector, the socket and the base being connectable co-axially together upon being pressed against each other in a direction substantially parallel to the axes; and a second clamping member supported in the base adjacent the inner end of the stem for movement from an inoperative position to an operative position moving closer to the first clamping member; the second clamping member including a part for pressing by the socket part in a direction substantially parallel to the axes.

Description:
The present invention relates to a lamp holder for holding an electric light source, such as a light bulb or a light tube generally known as an energy saving lamp. 
     BACKGROUND OF THE INVENTION 
     Lamp holders of the type in general concerned are known, for example as disclosed in European Patent Application 98204276.4 (publication No. EP 0929132 A2). Other prior art, though less relevant, are European Patent No. EP 0693654 B1 and Publications Nos. EP 0790459 A2 and EP 1199514 A2. 
     The invention seeks to provide an improved lamp holder of the same general type, and a base thereof. 
     SUMMARY OF THE INVENTION 
     According to the invention, there is provided a lamp holder for holding an electric light source, comprising: 
     a socket for holding said light source, the socket having an axis, a part extending substantially at right angles to the axis, and at least one first snap connector; 
     a base for fixing to an external support, the base having an axis, a tubular stem including an inner end connected to the base, a first clamping member provided in the base adjacent the inner end of the stem, and at least one second snap connector engageable with the first snap connector wherein the socket and the base are connectable co-axially together upon being pressed against each other in a direction substantially parallel to the axes; and 
     a second clamping member supported in the base adjacent the inner end of the stem for movement from an inoperative position to an operative position moving closer to the first clamping member for clamping an electric cable threaded through the stem into the base; 
     the second clamping member including a part for pressing by the socket part in a direction substantially parallel to the axes being moved to the operative position simultaneously upon the socket being pressed against the base in the same direction for connection. 
     Preferably, the second clamping member is a separate component of the base. 
     It is preferred that the second clamping member is pivotably connected to the base for pivotal movement by the socket. 
     It is further preferred that the base includes a pair of aligned holes, and the second clamping member is a separate component of the base and includes a pair of aligned pegs in engagement with the holes respectively thereby being hinged to the base. 
     It is yet further preferred that each of the holes and the corresponding peg have an inclined surface to effect engagement between them through a snap action. 
     Preferably, the first clamping member is fixed to the base. 
     More preferably, the first clamping member comprises at least one protrusion for engaging said cable. 
     Preferably, the second clamping member includes at least one protrusion for engaging said cable. 
     More preferably, the second clamping member includes a recess within which the protrusion is provided. 
     In a preferred embodiment, the second clamping member includes at least one spring acting upon the base thereby resiliently biassing the second clamping member towards the inoperative position. 
     More preferably, the spring is integrally connected with the second clamping member. 
     Further more preferably, the spring comprises a strip projecting from the second clamping member. 
     Yet further more preferably, the base has an internal corner and the spring engages with a free end thereof slidably in the corner. 
     More preferably, the second clamping member includes a substantially planar body having opposite sides, from which two said springs extend respectively in substantially the same direction. 
     Further more preferably, the body of the second clamping member includes the part for pressing by the socket part. 
     It is preferred that the two snap connectors comprise an inter-engageable hook and detent. 
     The invention also provides a base for use in a lamp holder including a socket for holding an electric light source, the base comprising: 
     a casing connectable in one direction with said socket; 
     a tubular stem having an inner end connected to the casing for fixing to an external support; 
     a first clamping member provided in the casing adjacent the inner end of the stem; 
     at least one snap connector engageable with said socket wherein the casing is connectable with said socket upon being pressed against by said socket in the opposite direction; and 
     a separate second clamping member supported in the casing adjacent the inner end of the stem for pivotal movement from an inoperative position to an operative position pivoting closer to the first clamping member for clamping an electric cable threaded through the stem into the casing; 
     the second clamping member including a part for pressing by said socket in said opposite direction thereby being pivoted to the operative position simultaneously upon said socket being pressed against the casing in said opposite direction for connection. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     The invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which: 
     FIG. 1 is a side perspective view of a lamp holder in accordance with the invention, disassembled to show a socket and base thereof, said base including a clamping member for clamping an electric cable; 
     FIG. 2 is a side perspective view of the base of FIG. 1, taken from above; 
     FIG. 3 is a bottom perspective view corresponding to FIG. 2, taken from below; 
     FIG. 4 is a top perspective view of the base and clamping member of FIG. 1; 
     FIG. 5 is a top perspective view corresponding to FIG. 4, showing the clamping member fitted in the base; 
     FIG. 6 is a top plan view of the base of FIG. 1; 
     FIG. 7 is a cross-sectional view of the base of FIG. 1, taken along line VII—VII; 
     FIG. 8 is a cross-sectional view of the base of FIG. 1, taken along line VIII—VIII; 
     FIG. 9 is a partially broken side perspective view of the base of FIG. 2, showing the clamping member therein; 
     FIG. 10 is a schematic side view of the clamping member and part of the base of FIG. 9, showing the clamping member in an inoperative position; 
     FIG. 11 is a schematic side view corresponding to FIG. 10, showing the clamping member in an operative position; 
     FIG. 12 is a cross-sectional side view of the lamp holder of FIG. 1, showing the clamping member in the inoperative position of FIG.  10  and how an electric cable is threaded through the base; and 
     FIG. 13 is a cross-sectional side view corresponding to FIG. 12, showing the clamping member in the operative position of FIG. 11 clamping the cable upon connection of the socket with the base. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to the drawings, there is shown a lamp holder  10  embodying the invention, which comprises a socket  200  for holding a light bulb having a screw-threaded end bearing two terminals, and includes a base  100  for fixing to a support of the body of a table lamp for example. The lamp holder  10  is depicted in an upright position as its normal use position. The socket  200  has a generally cylindrical casing  210  having a vertical central axis and enclosing an internal fixture  220 . The fixture  220  provides a screw-threaded seat  230  including two electrical contacts for engaging and connecting the light bulb by its end and terminals respectively, and includes a bottom structure  240 . 
     The bottom structure  240  has a central region provided with two terminals  242  in circuit with respective contacts of the seat  230 , and includes a pair of opposite side protrusions  244 . The protrusions  244  are exposed through respective side slots  212  of the casing  210 . In general, the structure  240  has a lowermost part or side  246 , that may include a pair of parallel ribs or wall edges  248  for example, lying on an imaginary horizontal plane extending at right angles to the central axis. 
     The base  100  has a generally cylindrical casing  110  having a vertical central axis and including a pair of integral hooks  112  upstanding integrally from diametrically opposite sides thereof and a central tubular stem  120  depending integrally therefrom. The base casing  110  has a matching diameter as the socket casing  210  and is adapted to be connected co-axially therewith such that the hooks  112  of the former engage through respective slots  212  of the latter with the corresponding protrusions  244  acting behind the slots  212  as detents. The hooks  112  are arranged to snap with the corresponding protrusions  244 , thereby connecting the base  100  and socket  200  together to form the complete lamp holder  10 . 
     The stem  120  is formed with external screw threads, and is to be inserted through a hole in the body support of a table lamp and then fixed thereto by means of a screw nut. Through the stem  120  an electric cable  8  of the table lamp is to be threaded upwardly into the base  100  for subsequent connection to the terminals  242  of the socket  200 . 
     The base  100  includes a separate clamping member  150  that is moulded integrally from plastic material as a single-piece component and is fitted wholly within a central recess  111  of the base casing  110 . The recess  111  is defined by an upper open end of the base casing  110 , from whose rim the hooks  112  project upwards alongside with a pair of lips  113  symmetrically between them, said lips  113  ensuring alignment of the two casings  110  and  210 . 
     The lips  113  are formed, centrally on their opposing inner surfaces, with respective trunnions  114  aligned with each other. Each trunnion  114  includes an upper inclined surface  115  facing the opposite inclined surface  115  and a lower hole  116  aligned with the opposite hole  116 . 
     The clamping member  150  has a generally upright planar body in the form of a back plate  151  having a horizontal top edge  152 , and a pair of wings  153  projecting forwardly from opposite left and right side edges of the body plate  151 . Each wing  153  has an extended free end that is slightly curved or bent downwards and takes the form of a relatively thin strip that is resiliently deformable to act as a cantilever spring  154 . The two springs  154  project in the same direction. Immediately beyond the inner end of the spring  154 , the wing  153  includes an outwardly protruding peg  155  that is aligned with the peg  155  of the opposite wing  153 . Each peg  155  has a lower chamfered surface  156 . 
     The clamping member  150  includes a bottom part  157  that is connected to the body plate  151  immediately below and extending across the two wings  153 . The bottom part  157  provides a C-shaped recess  158  opening forwards, in which a series of three sharp teeth  159  is centrally formed. 
     The clamping member  150  is located within the base recess  111  by the trunnions  114  on opposite inner sides thereof. To do this, the clamping member  150  is pressed down into the recess  111  such that its pegs  155  are jammed laterally into axial engagement with the holes  116  of the corresponding trunnions  114 . The engagement is effected through a snap action via the chamfered surface  156  of each peg  155  and the inclined trunnion surface  115  on the same side, with the corresponding wing  153  deflecting temporarily inwards. 
     The clamping member  150  is hinged by the trunnions  114  for limited pivotal movement about a horizontal axis that is positioned centrally with respect to the base recess  111 . The two springs  154  project to poke with their free ends slidably in respective internal corners  117  at the bottom of the recess  111 , thereby resiliently biassing the clamping member  150  towards an inoperative position (FIG. 7) in which its body plate  151  lies generally upright. The springs  154  extend from near the pegs  155  to act upon the corners  117  on the side of the trunnions  114  opposite to that of the body plate  151 , at the farthest possible position. Hence, the springs  154  have practically the longest possible length for maximum resilience. 
     The bottom of the base recess  111  includes a raised step  118  that extends laterally across the recess bottom and is level with the bottom part  157  of the clamping member  150  when the latter is located in the recess  111 . The step  118  has a middle portion formed with a series of two sharp teeth  119  that are generally aligned to point at the teeth  159  of the clamping member  150 . The base teeth  119  are located right within an uppermost end  122  of the base stem  120 , on one inner side thereof. While the clamping member  150  is in its inoperative position, its teeth  159  are positioned just behind and clear of the opposite inner side of the stem end  122 . 
     The clamping member  150  is pivotable generally downwards into an operative position (FIG. 8) against the action of its springs  154  by bending it further, such that the body plate  151  is inclined backwards to move its teeth  159  forwards closer to the fixed teeth  119 . As a result, the teeth  159  intercept from one side with and partially restrict the passage of the base stem  120 , at the uppermost end  122  thereof, thereby clamping in conjunction with the teeth  119  on the opposite side the electric cable  8  run through the stem  120 . The opposite teeth  119 , or the inner side of the stem end  122  on which they are located, may be regarded as constituting the other clamping member co-operable with the clamping member  150 . 
     The cable  8  will be gripped by the teeth  159  and  119  on opposite sides thereof biting slightly into the insulating sheath of the cable  8 . The movable teeth  159  are harboured within the C-shaped recess  158  to stop them from moving too close to the fixed teeth  119 , otherwise the cable  8  may be bitten too deeply and therefore damaged. Given that the teeth  159  and  119  are asymmetrical or skewed relatively upwards, by having a horizontal upper side and an inclined lower side when viewed from either side, the cable  8  will be secured in position against being pulled out of the base stem  120  from outside. 
     To install the lamp holder  10  to a table lamp, the cable  8  is threaded into the base  100  through its stem  120 , with the base  100  fixed to the body support of the table lamp by the stem  120  using a screw nut. After the cable  8  has been connected to the terminals  242  of the socket  200 , the socket  200  is pressed down onto and connected with the base  100 , as described above (FIG.  9 ). 
     While the socket  200  is being lowered, the horizontal bottom side  246  or ribs/edges  248  of its internal fixture  220  press vertically downwards against the clamping member  150  by the top edge  152  of its body plate  151 , thereby pivoting the clamping member  150 . The clamping member  150  will be pivoted backwards from its inoperative position into its operative position against the action of its springs  154 , thereby gripping the cable  8  at a position at the innermost end  122  of the base stem  120 , as described above (FIG.  10 ). The cable  8  will be clamped automatically upon the socket  200  being snapped fitted with the base  100 , whereupon the installation of the lamp holder  10  is completed. 
     The bottom ribs/edges  248  of the socket fixture  220  press vertically downwards against the clamping member  150 , in a direction parallel to that in which the base  100  and socket  200  are snapped together by their connectors  112  and  244 . On the other hand, the teeth  159  and  119  grip the cable  8  in a horizontal direction that is perpendicular to the vertical direction. Thus, the cable gripping force and any stress resulting therefrom as caused by pulling of the cable  8  will not affect the connection between the base  100  and the socket  200 . 
     It is envisaged that the teeth  159  and  119  may be replaced by any other types of gripping protrusions such as ribs. They may even be omitted, in which case the clamping member part  157  and the middle portion of the base recess step  118  may be positioned at different levels to provide an S-shaped locking arrangement. 
     The invention has been given by way of example only, and various other modifications of and/or alterations to the described embodiments may be made by persons skilled in the art without departing from the scope of the invention as specified in the appended claims.