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 INVENTION 
     This invention relates to locks for preventing one member from moving relative to another member. One of the members may, for example, be a patio door, a window or a cupboard door, with the other member being an associated frame member. 
     BACKGROUND OF INVENTION 
     Sliding bolt locks are known to be capable of providing a relatively inexpensive and reliable solution for securing a closure such as a window or door. An advantageous sliding bolt lock is described in U.S. Pat. No. 6,655,720 (Rampen), incorporated herein by reference. 
     SUMMARY OF INVENTION 
     Forming one aspect of the invention is a safety lock. This lock comprises a body, a latch and a handle. The latch is mounted to the body for movement between an engaged position and a disengaged position. The handle is releasably engageable to the latch. The handle, body and latch are adapted such that, when the handle is engaged to the latch, the handle permits manual movement of the latch. The handle, body and latch are further adapted such that, when the handle is disengaged from the latch, the latch is inaccessible for said manual movement. 
     According to another aspect of the invention, the latch can be a bolt; the disengaged position can be a retracted position; the engaged position can be a projecting position whereat an end portion of the bolt protrudes beyond the body; when the handle is engaged to the bolt, the handle can permit manual reciprocation of the bolt; and, when the end portion of the bolt is inaccessible for manual manipulation, the bolt can be inaccessible for said manual reciprocation. 
     According to another aspect of the invention, the handle, when engaged to the bolt, can extend from the bolt to terminate in a pull, and the bolt can be manually reciprocable by the pull. 
     According to another aspect of the invention, the pull can be annular and have a plunger mounted therewithin for movement along an axis, and the plunger can be thumb-actuable to release the handle from the bolt and to engage the handle to the bolt. 
     According to another aspect of the invention, a bolt spring can act to resiliently bias the bolt for movement to the projecting position. 
     According to other aspects of the invention, the bolt can be rotatable within the body and the bolt and body can be shaped such that, when the bolt and body are in alignment, the bolt spring, in the absence of external force, moves the bolt to the projecting position. Further, when the bolt is rotated relative to the body out of said alignment, the body can restrain the bolt against movement to the projecting position. 
     According to another aspect of the invention, the pull can terminate in a rim which projects away from the axis. 
     According to another aspect of the invention, a plunger spring can surround the plunger within the pull and act to resiliently bias the plunger for movement beyond the rim. 
     According to another aspect of the invention, the plunger can be thumb-actuable in the manner by which the plunger of a syringe is thumb-drivable to eject the syringe contents. 
     According to other aspects of the invention, the handle can releasably engage the bolt in a plug and socket connection. In such connection, the plug can be defined by the handle and the socket can be defined by the bolt. The socket can have one or more recesses disposed on its periphery. The plug can have a tab for each of said one or more recesses and each tab can releasably engage the recess for which it is provided to provide for said releasable engagement of the handle and the bolt. 
     According to another aspect of the invention, each tab can be adapted to flex inwardly towards the axis for the release of the handle from the bolt. 
     According to another aspect of the invention, the plunger, upon thumb actuation, can move from a restraining position, wherein the plunger is disposed inwardly from each tab to restrain same against inward flexure, to a release position, wherein each tab is free for said inward movement. 
     Forming another aspect of the invention is another safety lock. This safety lock comprises a body, a bolt and a handle. The bolt is mounted to the body for reciprocation between a retracted position and a projecting position. In the projecting position of the bolt, an end portion of the bolt protrudes beyond the body. The handle is releasably engageable to the bolt. 
     The handle, body and bolt are adapted such that, when the handle is engaged to the bolt, the handle extends to and terminates in a pull by which the bolt is manually reciprocable. The handle, body and bolt are further adapted such that, when the handle is disengaged from the bolt and the end portion of the bolt is inaccessible for manual manipulation, the bolt is inaccessible for said manual reciprocation. The pull is annular and has a plunger mounted therewithin for movement along an axis. The plunger is thumb-actuable to release the handle from the bolt and to engage the handle to the bolt. 
     Forming yet another aspect of the invention is a further safety lock. This lock comprises a body, a bolt and a handle. The bolt is mounted to the body for reciprocation between a retracted position and a projecting position. In the projecting position of the bolt, an end portion of the bolt protrudes beyond the body. The handle is releasably engageable to the bolt. The handle, body and bolt are adapted such that, when the handle is engaged to the bolt, the handle permits manual reciprocation of the bolt. The handle, body and bolt are further adapted such that, when the handle is disengaged from the bolt and the end portion of the bolt is inaccessible for manual manipulation, the bolt is inaccessible for said manual reciprocation. The handle releasably engages the bolt in a plug and socket connection, wherein the plug is defined by the handle and the socket is defined by the bolt. The socket has one or more recesses disposed on its periphery. The plug has a tab for each of said one or more recesses and each tab releasably engages the recess for which it is provided to provide for said releasable engagement of the handle and the bolt. 
     According to yet other aspects of the invention, in this further safety lock, each tab can be adapted to flex inwardly towards the axis for the release of the handle from the bolt and the plunger, upon thumb actuation, moves from a restraining position, wherein the plunger is disposed inwardly from each tab to restrain same against inward flexure, to a release position, wherein each tab is free for said inward movement. In the restraining position, an end of the plunger is disposed inwardly from and abutting each tab, to restrain said each tab against said inward flexure. In the release position, a reduced girth portion of the plunger, set back from said end, is disposed inwardly from each tab, so that said each tab is free for said inward movement. 
     According to other aspects of the invention, the body can be an assembly of parts and can be disassembled and, when the lock is operatively mounted on an element to be secured by the lock to another element, and the element to be secured and the other element are positioned for said securement, the other element can interfere with said disassembly. 
     According to yet other aspects of the invention, the body can comprise a base portion and a cover portion, the base portion and the cover portion having longitudinally extending recesses and pairs of inter-engaging longitudinally-extending keyways, respectively on opposite sides, to enable the cover portion to be slidably attached to and detached from the base portion. As well, when the base portion is operatively mounted on an element to be secured by the lock to another element, and the element to be secured and the other element are positioned for said securement, the cover portion cannot be slidably detached from the base portion as a result of interference with the other element. 
     According to yet further aspects of the invention, one of the keyways in the cover portion can have enlarged end portions which each receive a peg at the corresponding end of the keyway in the base portion so that the cover portion, if mounted with the pegs disposed on the end of the body through which the end portion of the bolt protrudes, is more readily removed by sliding the cover portion in the direction in which bolt protrudes. 
     Other advantages, features and characteristics of the present invention, as well as methods of operation and functions of the related elements of the structure, and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following detailed description and the appended claims with reference to the accompanying drawings, the latter being briefly described hereinbelow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front elevational view of a lock according to an exemplary embodiment of the invention in use on a vertical sliding sash window, with the bolt in its projecting position and engaged in a keeper mounted on the right side jamb; 
         FIG. 2  is an enlarged partial top, left perspective view of the structure of  FIG. 1 ; 
         FIG. 3  is an enlarged bottom front, bottom perspective view of encircled structure  3  of  FIG. 2 ; 
         FIG. 4  is a view of the structure of  FIG. 4 , with the bolt in its retracted position; 
         FIG. 5  is a sectional view of the structure of  FIG. 3 ; 
         FIG. 6.1  is a sectional view of the structure of  FIG. 4 , showing the plunger in its restraining position; 
         FIG. 6.2  is a sectional view similar to  FIG. 6.1 , with the plunger disposed in the release position and the tabs flexed inwardly; 
         FIG. 7  is an enlarged view of the handle of the structure of  FIG. 1 , in isolation, with the plunger in its restraining position; 
         FIG. 8  is a sectional view of the structure of  FIG. 7 ; 
         FIG. 9  is a sectional view of the structure of  FIG. 7 , with the plunger in its release position; 
         FIG. 10  is an exploded perspective view of the lock of  FIG. 1 ; and 
         FIG. 11  is a view, similar to  FIG. 1 , but showing a second keeper mounted on the right side jamb. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 10 , the lock  20  of the exemplary embodiment has a plunger unit  22  and a housing  24 . Both the plunger unit  22  and the housing  24  are shown in exploded view in  FIG. 10 , but persons of ordinary skill in the art will understand, with reference to, for example,  FIG. 2 , that in the lock  20  as assembled, the assembled plunger unit  22  is mounted in the assembled housing  24 . 
     The plunger unit  22  has a sleeve  26 , a latch in the form of a bolt  28 , a bolt spring  30  and a handle  32 . 
     The sleeve  26  is annular, has a radially extending flange  34  and, as best seen in  FIG. 5 , has an inner annular shoulder  36 . 
     Returning to  FIG. 10 , the bolt  28  has an annular shoulder  38  and is slidably and rotatably mounted in the sleeve for movement between a projecting position, shown in  FIG. 5 , in which an end portion  40  of the bolt  28  projects from one end of the sleeve  26  and a retracted position, shown in  FIG. 6.1 , in which said end portion  40  is disposed within the sleeve  26 . 
     The bolt  28  further defines a socket  42 , opposite to the free end portion  40  of the bolt  28 . The socket  42  has a pair of opposed recesses  44  disposed on its periphery (only one recess  44  being visible in  FIG. 10 ). 
     The bolt  28  is formed of a shaft  46 , a fitting  48  and a pair of pins  50 . The shaft  46 , which defines the free end portion  40  and the annular shoulder  38 , is a machined steel element and terminates in a cylindrical end  52  with a peripheral groove  54 . The fitting  48 , which defines the socket  42 , is a molded plastic component and has a bore  56  in receipt of the cylindrical end  52 , as best seen in  FIG. 5 . 
     A pair of clearance holes  58 , visible in  FIG. 10 , flank the bore  56  and intersect opposite sides of the groove  54 . The pins  50  are press fit within the clearance holes  58 , to engage the groove  54  and lock the fitting  48  to the shaft  46 . 
     The socket-forming end fitting  48  of the bolt  28  and the sleeve  26  have shaped adjacent ends  60 , 62 , such that when the bolt  28  and sleeve  26  are in alignment, the bolt  28  is movable to the projecting position; and when the bolt  28  is rotated relative to the sleeve  26  out of said alignment, the sleeve  26  restrains the bolt  28  against movement to the projecting position. 
     The bolt spring  30  surrounds the bolt  28  within the sleeve  26  and acts between the annular shoulder  38  on the bolt  28  and the annular shoulder  36  on the sleeve  26  to bias the bolt  28  for movement to its projecting position. 
     The handle  32  includes a shell  64 , a plunger  66  and a plunger spring  68 . The shell  64  defines a plug  70  and extends from the plug  70  to terminate in a pull  72 . The plug  70  is sized for receipt in the socket  42  and has a tab  74  for each recess  44 . When the plug  70  is operatively fitted into the socket  42 , each tab  74  engages the recess  44  for which it is provided, as shown in  FIG. 6.1 . Each tab  74  is also adapted to flex inwardly towards an axis X-X of the shell  70 , as shown in  FIG. 6.2 , wherein the handle  32  is shown as it appears during release/engagement to/from the bolt  28 . With reference to  FIG. 10 , the pull  72  is annular, centered about the axis X-X and terminates in a rim  76  which projects away from the axis X-X. 
     The plunger  66  is mounted for movement along the axis X-X between a restraining position, shown in  FIG. 8 , wherein an end  78  of the plunger  66  is disposed inwardly from each tab  74  to restrain same against the inward flexure shown in  FIG. 6.2  [i.e. to provide for rigid engagement of the handle  32  and bolt  28  when operatively positioned] and a release position, shown in  FIG. 9 , wherein a reduced girth portion  80  of the plunger  66 , set back from said end  78 , is disposed inwardly from each tab  74 , so that said each tab  74  is free for said inward flexing movement. 
     The plunger spring  68  surrounds the plunger  66  within the pull  72  and acts to resiliently bias the plunger  66  for movement beyond the rim  76 . 
     The housing  24  has a base portion  82  and a cover portion  84 . The base portion  82  and the cover portion  84  have longitudinally extending recesses  86 , and pairs of inter-engaging longitudinally-extending keyways  88 , respectively on opposite sides, to enable the cover portion  84  to be attached to and detached from the base portion  82 . 
     One of the keyways in the cover portion  84  has enlarged end portions  90  which each receive a peg  91  (shown in phantom outline in  FIG. 10 ) at the corresponding end of the keyway in the base portion  82  so that the cover portion  84  becomes correctly positioned relative to the base portion  82  in assembly. 
     The base portion  82  has a recess  92  for receiving the sleeve  26 , the fitting  48  and the shell  64 , and a series of slots  94  opening onto the recess  92 . Plunger unit  22  is mounted within the housing  24  by positioning its flange  34  into one of the slots  94  before the cover portion  84  is secured to the base portion  82 . So assembled, the base portion  82 , cover portion  84 , sleeve  26  and bolt spring  30  together define a body  96 . The slot  94  selected to receive the flange  34  determines the amount by which the free end portion  40  of the bolt  28  projects from the body  96  when the bolt  28  is disposed in the projecting position. 
     The base portion  82  further has a series of apertures  98  to enable lock  20  to be secured, by screws or the like, to a closure to be secured for use. 
       FIG. 1  shows the lock  20  secured to a lower sash  100  of a window which opens from up to down. The lock  20  is secured to the window by screws (not shown) passing through the apertures  98  into the upper rail  102 . As shown, the bolt (not visible) is in the projecting position and the free end portion (not visible) of the bolt extends into an aperture (not shown) in the keeper  104  secured to the right side jamb  106 . The projecting position can be viewed as an engaged position in that, when operatively installed on a properly positioned sash/frame assembly, the bolt engages with a corresponding structure on the frame. 
     Thus, the lower sash  100  cannot be opened by sliding upward movement. In order to lock the window in this closed position:
         the pull  72  is gripped in the manner of a syringe, i.e. typically with a thumb on the plunger  66  and the forefinger and middle finger beneath the rim  76 ;   the plunger  66  is depressed; and   the pull  72  is withdrawn, to unseat the plug of the handle from the socket       

     The thus-removed handle  32  may then be safely stored, until such time as it is desired to render the window operable again. 
     Since the end portion  40  of the bolt is inaccessible, being shielded by the sleeve  26  and the keeper  104 , the bolt (not shown in  FIG. 1 ) is inaccessible for manual manipulation. This renders the locked window safe for children and the like. 
     In order to return the immobilized window to operability;
         the pull is again gripped in the manner of a syringe;   the plunger is depressed   the plug of the handle is fitted into the socket; and   the plunger is released       

     To unlatch the window for movement from the position shown in  FIG. 1 , one simply draws the handle  32  by the pull from right to left (not shown), to unseat the free end portion of the bolt from the aperture in the keeper  104 . 
     To maintain the bolt in the retracted position, so that the sash  100  may be moved in the frame without the need to maintain tension on the handle  32 , the handle  32  may be turned to rotate the bolt out of alignment, so that the bolt is maintained in the retracted position by the inter-engagement of surfaces  60 , 62  as previously discussed. The retracted position can also be viewed as a disengaged position, since the bolt, so positioned, cannot engage with the mating structures on the frame. 
     The illustrated cover portion  84  is advantageously mounted such that the pegs  91  are disposed on the end of the housing  24  through which the end portion  40  of the bolt protrudes. If so mounted, the cover portion  84  is most readily removed by sliding the cover portion in the direction in which the bolt protrudes [because the cover portion has pegs  91  only at that end]. This provides additional security in that, in situations wherein the lock is engaged, the cover is restrained against movement in that direction as a result of interference with the elements being secured, i.e. the window frame. 
     Numerous variations in application and structure are possible. 
     For example, a second keeper  104  is shown in  FIG. 11 . By engaging the lock in the aperture of this second keeper, and removing the handle, the window can be locked in a partially-open position. This provides for ventilation. At the same time, the window opening is substantially occluded by the lower sash, so as to negate any real risk to children. As well, the absence of a handle renders the configuration relatively burglar proof. 
     Further, the base portion  82  could have a transverse flange with an aperture through which the handle protrudes. This would add to the difficulty of removing the cover portion  84  from the base portion  82  otherwise than by sliding the cover portion in the direction in which bolt protrudes, and provide even more security. Other forms of locating structures could also be utilized. 
     As well, the handle may be removed when the bolt is in its retracted position. It will be evident that, in this configuration, with the handle removed, the free end of the bolt will be disposed within the sleeve and inaccessible for manual manipulation, thereby rendering the bolt inaccessible for manual reciprocation. This makes it practically impossible for the window to be locked, which may be desirable in some situations. 
     Whereas the handle has been reference herein as being removable by thumb actuation, in the manner of a syringe, it should be emphasized that this functionality is only described by way of example. A person having no thumb, for example, could readily operate the device illustrated with the fingers of two hands. As well, other configurations of the invention could be provided with, for example, trigger actuators, in which case the handle release would be more preferably actuated by the forefinger. 
     Of course, it will be also understood by persons of ordinary skill in the art that, even with removal of the handle, it may, in some applications, remain possible for the bolt to be moved, with special tools or the like. The present invention should be understood as encompassing all locks wherein, if operatively installed, an average person, using only his or her hands, is incapable of manipulating the bolt from the retracted position to the extended position otherwise than with the handle. The present invention should also be understood as encompassing all locks wherein, if operatively installed, with the bolt engaged into a keeper or other bolt receiver, an average person, using only his or her hands, is incapable of manipulating the bolt from the extended position to the retracted position, otherwise than with the handle. 
     Further, the various components of the lock should be understood as amenable to other shapes and configurations, and the lock may be deployed on other structures, such as patio doors, hinged doors and the like, with or without keepers. Certain of these variations are described in U.S. Pat. No. 6,655,720, previously mentioned. 
     As well, greater or lesser numbers of tabs and recesses may be provided, and alternative methods of releasably locking the handle to the body may be employed. 
     Moreover, whereas it is indicated that a tab is provided for each recess, it will be understood that recesses could be provided in greater numbers than tabs; in this case, the excess tabs would simply be non-functional, and this would not impact whatsoever on the invention. 
     As well, the invention can be used with locks of other than the sliding bolt structure. 
     Accordingly, the invention should be understood as limited only by the appended claims, purposely construed.

Summary:
A safety lock is disclosed and comprises a body, a bolt and a handle. The body is securable to one member. The bolt is mounted to the body for reciprocation between projecting and retracted positions. In the projecting position, a bolt end portion protrudes beyond the body and is engageable in another member, to prevent relative movement of the members. In the retracted position, the end portion is incapable of engagement in the other member, to permit said relative movement. The handle is releasably engageable to the bolt. The handle, body and bolt are adapted such that when the handle is engaged to the bolt, the handle permits manual reciprocation of the bolt, and are further adapted such that when the handle is disengaged from the bolt and the bolt end portion is inaccessible for manual manipulation, the bolt is inaccessible for said manual reciprocation.