You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
FIELD OF THE INVENTION 
     This invention relates to a shoring leg and, more particularly, to a shoring. 
     BACKGROUND OF THE INVENTION 
     A known shoring system comprises a plurality of vertical legs each of. 
     A known shoring system comprises a plurality of vertical legs each of which is provided with an adjustable jack at the bottom thereof. A screw-threaded portion of the jack is inserted into the leg and the jack carries a rotatable threaded collar which abuts an end plate carried by the leg. As the collar is rotated, it moves up or down the threaded portion of the jack, thereby lifting or lowering the leg. In this known system, when moving the vertical legs, a jack can become disconnected from its leg, thereby necessitating additional work in relocating the jack within the leg. 
     In order to obviate or reduce this problem, it has previously been proposed in UK Patent GB2265921 to provide a shoring leg with a latch which serves to maintain an end plate of the shoring leg and a collar of the jack in a predetermined position relative to one another. The known latch comprises a latch member mounted on the leg for movement between a latching position and a release position, the latch member defining adjacent one end thereof a recess adapted, when in the latching position, to receive part of the leg end plate and adjacent one end thereof the adjacent collar of the jack to retain the end plate and the collar in the predetermined position. The latch member is retained in the latching position by means of a leaf spring which is attached to the shoring leg and to which the latch member is secured. The latch member is provided with an integrally formed fulcrum in the form of a stub which contacts the leg, whereby the latch member is movable from its latching position into its release position by pressing on the other end of the latch member to pivot the latch member about the stub. 
     Whilst the known shoring leg and its latch operate satisfactorily, the present invention aims to provide a shoring leg having a latch requiring fewer components. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention provides a shoring leg provided with a latch for use in maintaining an end plate on the shoring leg and a jack collar in a predetermined position relative to each other, the latch comprising a latch member mounted on the leg to execute a movement from a latching position to a release position, the latch member defining a recess adapted, when in the latching position, to receive part of the leg end plate and to receive a corresponding part of an adjacent collar of a jack to retain the end plate and the collar in said predetermined position, there being means to retain the latch member in the latching position, in which shoring leg the latch member is attached to the leg by mounting means which mounts the latch member for movement relative to the mounting means between the latching position and the release position. 
     The latch member may be pivotally mounted on the mounting means. The mounting means is typically a mounting bracket fixedly attached to the leg, and the latch member is pivotally mounted on a fulcrum plate of the mounting bracket. 
     The fulcrum plate of the mounting bracket may be received in a mounting slot formed in the latch member and preferably a central region of the mounting slot of the latch member is narrower than the end regions of the slot. Thus, typically, an inner longitudinal edge of the slot is of arcuate form and an outer longitudinal edge of the slot comprises two linear portions which are inclined to one another so as to meet a fulcrum comer about which the latch is pivotable on the fulcrum plate of the mounting bracket. 
     The recess may comprise an indentation receiving the leg end plate and a rebate for receiving the jack collar. 
     The latch member is preferably an elongate member, the recess being defined adjacent one end of the elongate member. The elongate member may be provided at the end thereof remote from the recess, with a finger tab. 
     Where the latch is an elongate member, the end of the elongate member which is provided with the recess may also be provided with an inclined cam face adjacent the recess. 
     Conveniently the latch member is at least partially received in a channel which extends axially of the leg. Resilient means, such as a spring, typically in the form of a coil spring which is compressed between the latch member and the leg, is used to retain the latch member in the latching position. 
     The invention also relates to a leg as described above in combination with a jack, the jack having a collar adjacent the end plate of the leg, part of the end plate of the leg and the corresponding part of the collar being received in the said recess formed in the latch member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In order that the invention may be more readily understood, an embodiment thereof will now be described, by way of example, with reference to the accompanying drawings, in which: 
     FIG. 1 is a side view of a shoring leg having a latch engaged with a jack collar, the leg and the jack being shown partly in phantom; 
     FIG. 2 is a front view of the shoring leg of FIG. 1; 
     FIG. 3 is side view of a latch member of the latch, showing a mounting slot of the latch member; 
     FIG. 4 is a side view of a mounting plate of the shoring leg latch; and 
     FIG. 5 is an end view of the mounting plate. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, a hollow vertical shoring leg  1  is provided at its lower end with an adjustable jack  2 . The jack has a portion (not shown) for engaging the ground to support a vertical screw-threaded portion  2 A on which is rotatably mounted an internally threaded collar  3 . The screw-threaded portion of the jack  2  is dimensioned to be received within the hollow leg  1 . The collar  3  has an upper radially outwardly projecting lip  4  dimensioned to engage the lower end of the leg  1  and thus support the leg. 
     The leg  1  consists of an extruded tube of aluminium with a substantially circular cross-section. The outer surface of the leg  1  is provided with axially extending channels  5 . The leg  1  carries an annular end plate  6  which is fixed at the bottom of the leg  1  for engagement with the jack collar  3 . The end plate  6  projects radially outwardly of the leg  1  and has a greater external diameter than that of the jack collar  3 . When shoring incorporating the leg  1  is to be moved, the leg  1  may be lifted. In order to prevent the jack  2  from becoming separated from the leg  1  when the leg is lifted, the leg is provided with a latch  7  which acts to retain the jack  2  in position. 
     The latch  7  comprises a vertically disposed elongate member  8  which is partially received in one of the axially extending channels  5  of the leg  1 . An upper portion of the exposed outer face of the latch member  8  is formed at its upper end  9  with a kiurled finger tab  10 . A lower portion of the inner face of the latch member  8  defines a recess  11 . The inwardly facing recess  11  is bounded by upper and lower walls  12  and  13  which are substantially perpendicular to the longitudinal axis of the latch member  8 . A partition wall  14  parallel to the walls  12  and  13  defines a step in the recess  11  which divides the recess into an upper indentation  15  and a lower rebate  16 , the indentation  15  extending deeper into the latch member  8  than the rebate  16 . A sloping cam surface  17  extends downwardly and outwardly from the inner edge of the lower boundary wall  13 , while the upper boundary wall  12  is connected to the lower end of a concave central portion  18  of the inner face of the latch member  8  by a rounded shoulder  19 . An upper end of the central portion  18  meets an upper portion of the inner face of the latch member  8  at a cusp  20 . 
     The latch member  8  is formed with a mounting slot  21  which extends longitudinally of the leg  1  in a central portion thereof. The slot  21  comprises upper and lower end edges  22  and  23  which are substantially perpendicular to the longitudinal axis of the latch member  8 . Inner and outer longitudinal edges  24  and  25  of the slot  21  extend between the end edges  22  and  23 . The inner longitudinal edge  24  is an outwardly convex arcuate edge. The outer longitudinal edge  25  comprises upper and lower linear portions  25 A and  25 B of equal length which are inclined relative to one another so as to meet at a fulcrum corner  26 , thereby defining with the inner longitudinal edge  24  of the slot  21  a central waist in the slot from which the width of the slot increases towards each end of the slot  21 . 
     The latch  7  is located at the bottom end of the leg  1 , so that the indentation  15  of the recess  11  is aligned with the end plate  6  of the leg  1  and can accommodate a peripheral part of the end plate, while a corresponding part of the collar lip  4  can be received in the rebate  15  of the recess  11  when the lip is adjacent to the end plate  6 . 
     A rigid mounting bracket  27  for mounting the latch member  8  on the leg  1  is shown in FIGS. 4 and 5. The mounting bracket  27  is formed from a horizontally elongate rectangular strip bent to form a central fulcrum plate  28  flanked by mounting wings  29  and  30  which extend at an angle to the fulcrum plate  28  from respective vertical edges of the fulcrum plate  28 . The width of the strip from which the mounting bracket  27  is made is slightly less than the length of the mounting slot  21  of the latch member  8 , while the thickness of the strip is substantially equal to the horizontal distance between the fulcrum corner  26  of the outer longitudinal edge  25  of the mounting slot  19  and the opposing point on the arcuate inner edge  24  of the slot  21 . The mounting bracket  27  extends through the mounting slot  21  in the latch member  8 , so that the latch member is supported on the fulcrum plate  28  of the mounting bracket  27 . Each of the mounting wings  29  and  30  of the mounting plate  27  is fixedly attached to the leg  1  by suitable fasteners, such as rivets, so that the fulcrum plate overlies the channel  5  of the leg  1  in which the latch member  8  is partially received. 
     A blind bore  31  is formed in the latch member  8  above the mounting slot  21 , the bore  31  extending into the member  8  transversely of the longitudinal axis of the member  8  from an upper portion of the inner face of the member  8 . A biasing coil spring is partially received in the bore  31  so that it is retained in a compressed condition between the member  8  and the bottom of the channel  5  in which the member  8  is received. 
     In a normal latching position of the latch  7  shown in FIG. 1 the latch member  8  is biased by the action of the spring  32  so that the latch member  8  sits on the fulcrum plate  28  of the mounting bracket  27  with the lower linear portion  25 B of the outer edge  25  of the slot  21  in engagement with the outer surface of the fulcrum plate  28 . In this position, a peripheral portion of the end plate  6  is received in the indentation  15  with the upper wall  12  of the latch recess  11  is in direct contact with the upper surface of the end plate  6  and the collar lip  4  which abuts end plate  6  is accommodated within the rebate  16  of the latch recess  11 . If, for any reason, such as the leg being moved, the collar  3  starts to separate from the leg  1 , the lower wall  13  of the latch recess engages the collar lip  4  and holds the jack  2  and the leg  1  together, preventing separation of the jack  2  from the leg  1 . 
     To release the latch  7 , the finger tab  10  on the latch member  8  is depressed towards the leg  1  against the action of the spring  32 . This causes the latch member  8  to pivot on the fulcrum plate  28  about the fulcrum comer  26 , so that the lower linear portion  25 B of the outer longitudinal edge  25  of the slot  21  moves away from the fulcrum plate. The pivoting movement of the latch member continues until the upper linear portion  25 A of the outer longitudinal edge  25  of the slot  21  comes into contact with the fulcrum plate. In this fully depressed position, the latch  7  is in a release position in which the collar  3  can be removed from the rebate  16 , thereby allowing the portion of the jack  2  within the leg  1  to be withdrawn. 
     If the leg  1  is lowered onto the jack  2  with the latch in its normal latching position, the cam surface  17  first comes into contact with the collar lip  4 . The cam surface slides over the collar lip  4 , causing the lower part of the catch member to move radially outwardly until the collar lip  4  passes beyond the lower wall  13  of the recess and is captured within the recess  11  as the latch  7  is returned to its normal latching position by the spring  32 . 
     Alternatively, the leg  1  may be lowered onto the jack  2  with the finger tab  10  fully depressed. In this case, the cam surface  17  does not come into contact with the collar lip  4  and the operating lever is not released until the collar lip  4  comes into contact with the end plate  6 . When this occurs, the finger tab  10  is released and the latch  7  returns to its normal latching position.

Summary:
A shoring leg is provided with a latch for use in maintaining an end plate of the shoring leg and a jack collar in a predetermined position relative to each another. 
     The latch comprises a latch member having a slot to receive a mounting bracket which mounts the latch member for pivotal movement relative to the mounting means from a latching position to a release position. The latch member defines a recess adapted, when in the latching position, to receive part of the leg end plate and a corresponding part of an adjacent collar of the jack to retain the end plate and collar in the predetermined position. The latch member is biased into the latching position by a coil spring acting between the leg and the latching member.