Abstract:
A ball point pen has a retractable ink container ( 13 ) and writing tip ( 12 ) that are releasably held in the extended position by a locking element ( 19 ) freely movable in a transparent enclosure ( 18 ) at the remote end of the barrel ( 11 ). The locking element ( 19 ) may have the appearance of a football or golf ball. In another embodiment the locking element is elongated and has flat sides that may carry advertising or promotional markings.

Description:
BACKGROUND OF THE INVENTION   
   This invention relates to an improved writing instrument of the kind having a writing tip, such as a ball point, at one end of a writing fluid chamber, the chamber and tip being retractable into a barrel or housing of the instrument when it is not in use to prevent inadvertent marking e.g. of hands or clothing. To write with the instrument the tip and chamber are moved relative to the barrel until the tip projects from one end of the barrel, releasable locking means being used to hold the tip in the extended position. 
   An object of the present invention is to provide a mechanism for such a writing instrument which is attractive and fun to use and which lends itself to the display of advertising or promotional material. 
   BRIEF SUMMARY OF THE INVENTION  
   In accordance with the present invention there is provided a writing instrument comprising a barrel, a writing fluid container moveable axially of the barrel whereby a writing tip of the container can be projected from or withdrawn into one end of the barrel, spring means biasing the container to the withdrawn position, a trigger extending from the container and projecting through an opening in the barrel whereby the container can be moved against the action of the spring to the projected position and means for releasably holding the container in the projected position, said holding means comprising a locking element which is freely moveable within an enclosure at the other end of the barrel, the enclosure having a shape such that said element may be interposed between the container and a component of the enclosure to hold the container in the projected position in a first position of said element and is displaceable under gravity or by inertia transversely of the enclosure to a second position, when released from the influence of the spring means by actuation of the trigger, in which second position said element does not prevent movement of the container to the withdrawn position. 
   Preferably the enclosure is transparent. 
   In one embodiment of the invention stop means projects inwardly of one side of the enclosure and the container has at its end remote from the tip a plunger from which the trigger extends, the plunger having a flange or lip extending upwardly in a lengthwise direction of the enclosure on the opposite side of the latter to the stop means, the locking element being dimensioned to pass the stop means except when held by the spring means between the latter and the flange or lip. 
   Preferably the stop means is intermediate the ends of the enclosure and on the side of the stop means remote from the plunger is a compartment of the enclosure in which the locking element is freely moveable. 
   The locking element is preferably of a rounded configuration and may be generally spherical. 
   The enclosure may be an enlargement of said other end of the barrel. 
   In another embodiment of the invention the locking element is elongated axially of the enclosure; one end of the latter being stepped and the arrangement is such that with the locking element between the container and the step of the enclosure the spring means is unable to move the container to the withdrawn position. 
   The locking element may be pivotable at one end and moveable transversely of the enclosure at its other end. 
   The locking element may have a relatively larger, rounded end in contact with a plunger at the end of the container remote from the tip and a relatively thinner end for engaging the step, the arrangement being such that with the plunger drawn against the spring means the locking element is able to rock on the plunger to align its thinner end with, the step. 
   Alternatively said step may be provided on a plunger at the end of the container remote from the tip and the locking element may have a relatively thicker end which is pivotally mounted at the end of the enclosure remote from the plunger and a relatively thinner end which can be moved across the enclosure between positions aligned with or not aligned with the step. 
   In yet another embodiment of the invention the trigger extends from a plunger at the end of the container remote from the tips the plunger being a sliding fit within a first compartment of the enclosure, said first compartment communicating with a second compartment of the enclosure offset laterally from the first compartment and the locking element being displaceable under gravity or inertia between the compartments when the plunger is moved to compress the spring, the arrangement being such that when the locking element occupies the first compartment it prevents withdrawal of the container and such that when the locking element occupies the second compartment the spring means may move the container to its withdrawn position. In this embodiment the locking element is preferably in the form of a ball. 
   The end of the plunger remote from the container is preferably chamfered to prevent escape of the locking element from the first compartment when the container is held in the projecting position. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the present invention will now be described with reference to the accompanying drawings, in which: 
       FIG. 1  is a sectional elevation of a first embodiment of a writing instrument in accordance with the invention, showing the writing tip extended; 
       FIG. 2  is a similar view of the writing instrument of  FIG. 1  but showing the writing tip retracted; 
       FIG. 3  is a sectional elevation of a second embodiment of a writing instrument in accordance with the invention showing the writing tip in the extended position; 
       FIG. 4  is a view similar to that of  FIG. 3  but showing the writing tip in the retracted position; 
       FIG. 5  is a sectional elevation of a third embodiment of a writing instrument in accordance with the invention showing the writing tip in the extended position; 
       FIG. 6  is a view similar to  FIG. 5  but showing the writing tip in the retracted position; 
       FIG. 7  is a sectional elevation of a fourth embodiment of a writing instrument in accordance with the invention showing the writing tip in the retracted position; and 
       FIG. 8  is a view similar to  FIG. 7  but showing the writing tip in the extended position. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   The writing instrument  10  shown in  FIGS. 1 and 2  has a barrel  11  from one end of which a writing tip  12  of an ink container  13  can project, the container with its tip being biased by a compression spring  14  acting between the barrel and a stop  40  on the container  13  to retract the container  13  and its tip  12  into the barrel  11  ( FIG. 2 ). Alternatively the spring  14  may extend throughout the length of the container  13  and act on the underside of a plunger  15  integral with the end of the container  13  remote from its tip  12 . Projecting from the plunger  15  is an integral trigger or latch  16 . This extends out of the barrel  11  through a slot  17  which is elongated axially of the barrel  11  sufficiently to allow the trigger  16  to be moved against the action of spring  14  against the stop until the tip  12  is extended from the barrel  11 . 
   At the end of the barrel  11  remote from the tip  12  is a transparent enlargement  18  providing an enclosure for a spherical locking element or ball  19  which is freely moveable throughout the enclosure. Midway along the length of the enclosure a stop  20  projects inwardly of the enclosure. A lip or flange  21  projects into the enclosure from the plunger  15  on the side of the enclosure remote from the stop  20 , the dimensions of these components being such that the ball  19  can pass the stop  20  if not in contact with the flange  21 , but such that if the ball  19  is trapped between the flange  21  and the stop  20  it will prevent movement of the plunger  15  inwardly of the enclosure. 
   If desired only part of the enlargement may be transparent, such that the ball  19  is visible only in one of it two positions. Transparency may be provided by a temperature sensitive material such that the interior of the enclosure is visible only when the enclosure is heated by being held in the hand, at other times being opaque. 
   To allow the tip  12  to be retracted into the barrel  11  the trigger  16  is first depressed against the spring  14  sufficiently to allow the ball  19  to pass the stop  20 . The writing instrument can if necessary be inverted and/or shaken until the ball  19  rolls by gravity or through inertia into the upper compartment of the enclosure above the stop  20  as shown in  FIG. 2 . The spring  14  is now able to move the plunger  15  inwardly of the enclosure  18  until the writing tip  12  is retracted ( FIG. 2 ). 
   To reverse this sequence the instrument  10  is held upright while the trigger  16  is depressed sufficiently to allow the ball  19  to fall past the stop  20 . When the trigger  16  is now released the ball  19  will become trapped between the flange  21  and the stop  20 , holding the tip  12  in its extended position. 
   The ball  19  may be shaped and marked to resemble a football, a golf ball, a cricket ball or any other sporting ball. The ball and/or other components of the writing instrument may carry markings identifying a particular sporting club, society or side so that the instrument can be used as an advertising and promotional item as well as a novelty item. 
   In the alternative embodiment of the present invention illustrated in  FIGS. 3 and 4  a writing instrument  10 A has a barrel  11 A from one end of which the tip  12 A of an ink container  13 A may extend. At the end of the container  13 A remote from the tip  12 A it is integral with a plunger  15 A from which a trigger or latch  16 A projects out of the barrel  11 A through a slot  17 A. A spring  14 A biases the plunger  15 A and container  13 A to the retracted position of the tip  12 A ( FIG. 4 ). 
   In this embodiment however the locking element  19 A is not spherical but is elongated and lies within a transparent enclosure  18 A at the end of the barrel  11 A remote from the tip  12 A. The locking element  19 A is flat-sided and has a thicker, rounded end  22  resting in a groove  23  in the facing end of the plunger  15 A. Within the enclosure  18 A at a position remote from the plunger  15 A is a block  24  which only partly extends across the enclosure thus providing a step  25  which can be selectively confronted by the narrower end  27  of the locking element  19 A. 
   In use of the instrument of  FIGS. 3 and 4 , to retract the tip  12 A from the position of  FIG. 3  to the position of  FIG. 4  first the trigger  16 A is depressed sufficiently to free the locking member  19 A. This can then be moved across the enclosure  18 A, rotating on its rounded end  22 , until its narrower end  27  comes out of alignment with the step  25 . This can be achieved either by shaking the instrument, so that the locking element  19 A is moved by inertia, or by holding the instrument horizontally so that the locking element  19 A moves to its new position under gravity. When the trigger  16 A is now released the spring  14 A can raise the plunger  15 A until the trigger  16 A abuts the upper end of the slot  17 A, defining the retracted position of the tip  12 A into the barrel  11 A ( FIG. 4 ). To extend the tip  12 A again the trigger  16 A is depressed sufficiently to allow the locking member  19 A to move back across the enclosure  18 A until its narrower end  27  is aligned with the step  25 , this again being achieved by gravity or inertia When the trigger  16 A is now released the locking member  19 A jams between the plunger  15 A and the step  25 , holding the tip  12 A in its extended position. 
   The writing instrument of  FIGS. 5 and 6  has a locking system which is effectively an inversion of that of  FIGS. 3 and 4 . The elongated and tapered locking element  19 B has a thicker, rounded end  22 B at the end of the enclosure  18 B remote from the ink container  13 B. Preferably the locking element  19 B is pivoted by a pin  26  spanning the enclosure  18 B. The end of the plunger  15 B presented to the locking element  19 B is stepped as at  25 B. When the thinner end of the locking element  19 B is aligned with the step  25 B the writing tip  12 B is held in the extended position. When not aligned with the step  25 B ( FIG. 6 ) the container  13 B can be moved by the spring  14 B to the retracted position. 
   Either or both of the flat sides of the locking element  19 A or  19 B may be marked with advertising or promotional material. 
   In the embodiment of  FIGS. 7 and 8  the enclosure  18 C has a first compartment  27  in which the plunger  15 C is a sliding fit and a second compartment  28  offset from the first compartment and communicating therewith at the upper end of the writing instrument. A locking element in the form of a ball  19 C is free to move transversely of the enclosure  18 C between the compartments  27  and  28  when freed to do so by the plunger  15 C. To project the writing tip  12 C from the barrel  11 C the trigger  16 C is depressed, compressing the spring  14 C. Once the plunger  15 C has moved out of alignment with the compartment  28  the ball  19 C is free to roll across from the position of  FIG. 7  to the position of  FIG. 8 , this being achieved either by “flipping” the instrument so that the ball moves relatively by inertia or turning it until the ball  19 C moves under gravity. When the trigger  16 C is now released the ball  19 C is trapped between the plunger  15 C and the top of the enclosure  18 C by the spring  14 C. To enhance this effect and prevent accidental dislodgement of the ball  19 C the top end  30  of the plunger  15 C is preferably chamfered as shown. 
   In this embodiment the “overhang” provided by the compartment  28  is used as the root of a pocket clip  31  for the instrument. 
   For the avoidance of doubt, “writing instrument” and “writing fluid” as used herein and in the appended claims are intended to embrace instruments and fluids used for any graphic purpose and not merely the formation of lettering.