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FIELD OF THE INVENTION 
   The present invention is directed to the field of window hardware, particularly window hardware for double hung windows. 
   BACKGROUND OF THE INVENTION 
   Double hung windows are a common type of window used in many homes and remodeling. There is a frame with a pair of tracks on each side of the frame. There is a top sash and a bottom sash. The top sash typically rides in the outer tracks, i.e. the tracks in the frame closest to the outside of a building. The lower sash rides in the inner track, i.e. that track that is closest to the interior of a house. The sash has a pair of vertical stiles that are joined to upper and lower horizontal styles. One or more panes of glass are retained in the sash. There can be an inner pane and an outer pane that extends from one vertical stile to the other and from one horizontal stile style to the other. There can be a third pane of glass positioned similarly with a gap between the first and second panes. The gap is usually filled with an inert gas such as argon. This structure provides a window with insulating qualities. One or more muntin bars can be present to provide a look of individual grids in the window of the type that are found in older construction. 
   In many double hung windows there is an issue of security. There is usually an outer screen that permits cooler air to ventilate into the house during the warmer months. In order to take advantage of the screen however, the bottom pane typically must be in a raised position. Double hung windows are usually provided with a sash lock that locks the lower and upper sash in position so that they cannot be opened from the outside. While this provides some security during the cooler months, the return of warn weather may make it difficult to use the sash lock in many instances. The sash lock has two positions, a locked position and an unlocked position. Thus the resident has a choice to either keep the window in a closed locked position or have the window sash unlocked and thus open to intruders. 
   In order to provide a means of ventilating a room yet provide some security, there have been a number of night latches and vent stops that have become available in the market. One such sash stop is U.S. Pat. No. 5,248,174 owned by Ashland Products. Another type of sash stop U.S. Pat. No. 4,923,230, owned by Ro Mai. These night latches or vent stops act in a similar fashion. The night latch or vent stop is placed in the face of the upper sash. Depending on the desired amount of ventilation, the night latch can be placed at any position on the face. Once the night latch is secured in the face of the window, the tumbler can be pressed in an inward and upward fashion activating a spring mechanism that will force the tumbler to an exposed position, thus creating the impeding force required to restrict movement of the lower window sash. Other prior art vent stops are U.S. Pat. Nos. 5,553,903 and 5,806,900 both of which are owned by Ashland. 
   As mentioned previously, the typical prior art vent stop prevented the opening of the lower sash in similar fashions. In the typical prior art the tumbler was held in a locked position via a catch portion located in the housing of the night latch. Thus, if inwardly and upwardly forces were applied perpendicularly to the face of the tumbler, these forces would release the tumbler from its locked, inactivated position, to its unlocked, activated position. 
   While the tumblers in the prior art night latches are capable of preventing the sliding member from moving passed a certain predetermined position, these tumblers have an unfavorable characteristic. That is in the prior art vent stop, in order for the user to free the tumbler from its inactivated position to its activated position or vice versa. The user must apply a multitude of forces in a variety of different angles. 
   Although the night latch and/or vent stops are capable of preventing the lower sash from moving passed a certain desired position, their utility is unfortunately outweighed by their inherent clumsy composition. The night latch in the present invention improves on the prior art shortcomings by implementing a unique method of activating and inactivating the tumbler from the housing, without taking away from its utility and its aesthetic quality. 
   OBJECTS OF THE INVENTION 
   It is an object of the present invention to provide a night latch that operates more easily than the prior art night latches. 
   It is an object of the present invention to provide a night latch that is more wind tight than the prior art night latches. 
   It is an object of the present invention to provide a night latch that is simpler and more compact in its housing than the prior art night latches. 
   It is an object of the present invention to provide a night latch that is compatible with more frames with different configuration. 
   It is an object of the present invention to provide an improved night latch that is more reliable in its strength and operation than the prior night latches. 
   It is an object of the present invention to provide a night latch that allows the user to more readily reposition the tumbler back in an inactivated position. 
   It is still another object of the invention to allow the user the ability of activating the tumbler without the use of multiple forces to release the tumbler. 
   It is a still further object of the present invention to provide for a more durable night latch, so as to allow for a longer period of operability. 
   SUMMARY OF THE INVENTION 
   The present invention is an improved night latch or sash controlling mechanism. The improved night latch can be used with a variety of windows and doors, including but not limited to, single hung windows, double hung windows, sliding windows and doors, etc. The windows can be of the type that moves vertically or horizontally. If the windows are to move in a vertical fashion then the window will have upper and lower sashes situated in the frame of the window. If the windows are to move horizontally, then the windows will have right and left sashes situated in the window frame. A night latch for a sliding door can be installed and operated in the same manner as the sliding window, except the doors will sit in the doorframe rather than a window frame. More specifically, this invention is directed to be an integral part of a sliding window or door that is simple, inexpensive, and ergonomically superior to the prior art. 
   In the present invention the night latch has three primary components a tumbler, button, and a housing that will accommodate the tumbler and the button. The housing is placed in a groove or recess on the face of the upper window sash. The housing is constructed so as to make for a tight, smooth, and finished appearance when inserted into the groove of the window sash. This fit will make for an aesthetically pleasing appearance. Furthermore, the housing is designed for more compatibility of different configuration sash frames. 
   As in the prior art, a tumbler is generally used as the stopping mechanism in the night latch. In general, the tumblers are activated by applying an outside force in a multitude of ways directly to the tumbler, making for a rather difficult and sometimes impossible task. One example of this is when the spring inside the tumbler is new and rather tight. In the present invention the tumbler is activated via an active twofold spring, which is partially located in the cavity of the tumbler, of the night latch, and with the end in the inner bottom surface of the housing of the night latch. This allows the user to activate the tumbler with relative ease. The force applied can be in a downward motion, as in the present invention, or the force applied can be in an inward motion. The direction of the force applied depends on how the button is configured. 
   In addition to the relative ease of operation of the improved night latch, the improved night latch has a stronger and more wind tight housing that is relatively sealed and can accommodate all parts inside. In the prior art the housing is open, thus exposing the inside parts, such as the tumbler and spring, to the outside weathering elements, such as moisture in the air, which could cause malfunction of the night latch, i.e. rusty spring. In present invention the closed housing acts as a barrier, so as to impede the destructive nature of weathering and moisture in the air. 
   Furthermore, the night latch has a unique twofold spring in the housing that can be deactivated with even less effort than the prior art. If the user wished to close the night latch in the prior art, the user would have to exert an inward and downward force to deactivate the night latch. This is because the tumbler in the prior art is kept depressed via the face of the tumbler and the top plate of the housing. As mentioned previously application of these forces can prove to be rather burdensome when the night latch was fairly new. In the present improved night latch, the only force needed is a downward force, or inward force, this is because of the co-action between the rounded bottom portion of the spring and the nesting area of the bottom surface of the housing. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of the tumbler and spring, with spring inside of cavity of tumbler, with tumbler exposed of the present invention; 
       FIG. 2  is a side view of the tumbler of the present invention; 
       FIG. 3  is a side view of the tumbler and the stopping member of the present invention; 
       FIG. 4  is a perspective view of the tumbler and spring of the present invention; 
       FIG. 5  is a side view of the vent stop, with the tumbler not exposed, of the present invention; 
       FIG. 6  is a perspective view of tumbler of the present invention; 
       FIG. 7  is a side view of night latch of the present invention; 
       FIG. 8  is a perspective view of the night latch secured in the stopping member, of the present invention; 
       FIG. 9  is an exploded view of night latch and stopping member, of the present invention; 
       FIG. 10  is an exploded view of the night latch, stopping member, and oval opening on stopping member, of the present invention. 
       FIG. 11  is a left side view of the night stop of the present invention, with tumbler exposed; 
       FIG. 12  is an angled view of the night stop of the present invention, with tumbler exposed; 
       FIG. 13  is a perspective view of the night latch of the present invention, with tumbler exposed. 
       FIG. 14  is a side view of the night stop of the present invention, with a different flexible clip, with the tumbler exposed. 
       FIG. 15  is a side cross sectional view of the night stop of the present invention, with different forces being applied to the tumbler. 
       FIG. 16  is a cross sectional view of the night stop of the present invention, with the tumbler in a deactivated position. 
       FIG. 17  is a cross sectional view of the night stop of the present invention, with the tumbler in an activated position. 
       FIG. 18  is a side view of the night stop, of  FIG. 14 , set inside a different style of window frame. 
       FIG. 19  is a side view of the night stop, of  FIG. 14 , set inside a yet another style of window frame. 
       FIG. 20  is a perspective view of the night stop, of  FIG. 14 , being inserted into a window frame. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. 
   In  FIG. 1  the night latch of the present invention is shown generally at  10 . The night latch  10  is shown positioned over slot  11  in sliding member  12  as seen in  FIGS. 9 and 10 . The slot  11  is shown as having an oval shape, but any other suitable shape and size slots including but not limited to a square, rectangle, oval, etc. can be used depending on the shape of the latch. Preferably, however, the night latch  10  of the present invention will have a portion similarly shaped to the slot  11  as to present a clean appearance when placed in the stopping member  12 , as seen in  FIG. 8 . In the present embodiment an oval shape for illustration purposes was used. The stopping member can be a sash, doorframe, or any other member that has another piece sliding over it, where restriction of the sliding member is desired. The tumbler  80  can be either in a raised or lowered position. When raised it prevents movement of the door or sash, as seen in  FIG. 1 . 
   A housing  13  is generally defined by a first sidewall  14 , and a second sidewall  15 , not shown, and a front wall  16 , and a rear wall  17 , not shown, and a bottom wall  18 , as shown in  FIG. 7 . Bottom wall  18  can also serve as a cover. In the present embodiment however bottom wall  18  is sealed, and no cover is present. It is noted that the terms “front” and “rear” are used only for descriptive purposes and do not read on orientation of the device. Sidewalls  14 , as seen in  FIG. 1 and 15 , not shown, are preferably the same length, as are front and rear walls  16  and  17 , respectively, providing for a generally rectangular shape to housing  13 . Preferably, when in place within slot  11 , sidewalls  14  and  15  contact the edges of slot  11  to provide for a tight fit, and prevent a lateral movement of the night latch  10  within slot  11 . Front wall  16  can have a front flexible clip  19  and rear wall  17  can have a rear flexible clip. In the present embodiment there is only one flexible clip, front flexible clip  19 , as seen in  FIG. 1 . Rather then use a rear clip; one can use a rear notch  20  to produce the same fastening effect as a rear clip, as seen in  FIG. 1 . The rear notch  20  is of non flexible nature, it is located at the end of the housing  13 ; it is created between a surface  26 , which runs parallel to lip  23 , and the bottom surface  24  of the top plate  25 . Front flexible clip  19  can extend generally in an upward fashion, originating at or near the bottom surface  21  of housing  13  and ending typically just below top plate  25 , as seen in  FIG. 1 . In addition, flexible clip  19  may be solid or hollow. In the present embodiment flexible clip  19  is comprised of two generally rectangular protrusions, so as to resemble two teeth, tooth one  140  and tooth two  141 , as seen in  FIG. 6 , located on sidewalls  14  and  15 . Tooth one  140  has inner and outer surfaces  27 , as seen in  FIGS. 6 and 28 , as seen in  FIG. 7 , located adjacent to sidewall  14 . Tooth two  141  has inner and outer surfaces  29 , as seen in  FIGS. 7 , and  30 , as seen in  FIG. 6 , located adjacent to sidewall  15 . Flexible clip  19  may be affixed to front wall  16  or flexible clip  19  may be an integral part of housing  13 , in the present embodiment flexible clip  19  is an integral  19  part of housing  13 . In addition, flexible clip  19  has top surfaces  142  and  143 , located on teeth  140  and  141  respectively. 
   In another embodiment one can use a rear clip  19   a  with more flexibility than the front clip as seen in  FIG. 14 . It may be located at the end of the housing  13 . In this embodiment the night latch of the present invention can be more compatible with different style doorframes as seen in  FIG. 17  and  FIG. 18 . For more ease of installation, there is a raised member  19   b  protruding from side surface  17  of housing  13  as seen in  FIG. 14 , which ensures enough space between the clip and the housing  13 . When the night latch  10  is depressed into slot  11  on a stopping member  12 , the rear flexible clip  19   a  should be inserted sideling into slot  11  as seen in  FIG. 20 . Flexible clips  19  and  19   a  can engage a portion of the stopping member  12 , as seen in  FIGS. 8 and 9 . This engagement can prevent vertical (front and back) movement of the night latch  10  within the stopping member  12 , as well as preventing the night latch  10  from being easily dislodged from slot  11 . 
   First sidewall  14  has an inner surface  30 , not shown, and outer surface  31 , as seen in  FIG. 1 . Second sidewall  15  has inner surface  32 , not shown, and outer surface  33 , not shown. On sidewalls  14  and  15  there can be four apertures, apertures  34  and  35  on sidewall  14 , as seen in  FIG. 1 , and apertures  36  and  37  on sidewall  15 , as seen in  FIG. 11 . Apertures  34  and  36  of sidewalls  14  and  15 , respectively, are aligned along the same central axis and are positioned towards rear wall  17 , and are used to prevent tumbler  80  from rotating passed a predetermined area and to support a substantial upward force associated with the lifting of the lower sash against the stopping surface of the latch. Apertures  35  and  37  of sidewalls  14  and  15 , respectively, are also aligned along the same central axis; these apertures are designed so as to allow tumbler  80  to rotate in an outwardly fashion. In another embodiment one could implement bored cavities, aligned in a similar fashion, instead of apertures. 
   In yet another embodiment, sidewalls  14  or  15  may have at least one rotation member extending there from. In this type of embodiment tumbler  80  would have apertures or bored cavities aligned along the same central axis so as to allow tumbler  80  to rotate in an outwardly fashion. 
   The lip  23  attached to top plate  25  is preferably at least the same size or larger and the same general shape as slot  11 . Thus, when night latch  10  is placed into slot  11 , lip  23  will contact at least the edges of slot  11  or over spread the upper surface of the stopping member  12 . These dimensional attributes will allow for a tight fit that will exhibit a finished smooth exterior, which can be aesthetically pleasing. Although top plate  25  is referred to as a “plate”, it is understood that housing  13 , clip  19 , lip  23  and top plate  25  can be integral pieces, without any need for adhesives or assemblage. 
   In another embodiment rear clip  19   a , attached to the rear of the housing, is preferably almost as high as the lower portion of the housing under the slot  11 . Thus, when night latch  10  is placed into slot  11 , clip  19   a  will contact at least the edges of slot  11  or over spread the upper surface of the stopping member  12 . These dimensional attributes will allow for a tight fit that will exhibit a finished smooth exterior, which can be aesthetically pleasing. Although top plate  25  is referred to as a “plate”, it is understood that housing  13 , clip  19 , clip  20  and top plate  25  can be integral pieces, without any need for adhesives or assemblage. 
   A tumbler  80  is preferably designed to fit within cavity  130  of housing  13 , as seen in  FIG. 2 . Tumbler  80  may have an upper surface  38 , which is preferably smooth and/or flat on the front portion, as seen in  FIG. 2 . A flat surface  38  will exhibit a more finished look for the night latch  10  when it is placed in stopping member  12 . Tumbler  80  may have an indent  81  located toward the rear top surface. In addition tumbler  80  may have a grooved top portion  82  located right above indent  81 , as in the present invention, which may act as a button  95 , so as to allow the user to activate tumbler  80 . The rear edge  83  of tumbler  80  slopes downward and comes to a point  84 , where rear edge  83  meets arcuate bottom portion  85 . Tumbler  80  can have a front end  86  and a rear end  87 , along with side surfaces  88  and  89 . Tumbler  80  can have rotation members  70  and  71 , which can fit in apertures  35  and  37 , of sidewalls  14  and  15  respectively, of housing  13 . The rotation members  70  and  71  can be located on side surfaces  88  and  89 , respectively, close to rear end  87 . Preferably, rotation members  70  and  71  are cylindrical pegs, which protrude from side surfaces  88  and  89  of tumbler  80 , respectively. The rotation members  70  and  71  can allow tumbler  80  to extend outwardly, thus exposing front end face  90  of tumbler  80 , which would prevent movement of sliding member  12 . The tumbler  80  will be allowed to rotate until surface  85  of tumbler  80  comes into contact with outer surface  50  of stopping member  51 , as seen in  FIG. 3 . The stopping member may be constructed of any type of material known in the art, but not limited to plastic, metal, wood, etc., capable of withstanding the downward force of tumbler. The stopping member may be of any shape known in the art, but not limited to a cylindrical peg, a rectangular block, or a square peg. In the present embodiment a plastic cylindrical peg was implemented. In addition, stopping member, cylindrical peg  51 , may be separate or an integral part of tumbler  80 , in the present embodiment cylindrical peg  51  is a separate member. 
   Tumbler  80  has a cavity  100  that houses the plate spring  60 , as seen in  FIGS. 2 and 4 . However, this is not the only possible method of attaching a spring to tumbler  80 . For example, tumbler  80  can have a protruding peg on either of the side surfaces  88  or  89  that could hold the plate spring  60  in place. If this type of spring configuration is implemented, then housing  13  would have to be of such dimensions so as to allow for the additional needed space. Tumbler cavity  100  has a top and bottom surface,  47  and  48 , respectively, equal in width to plate spring  60  it houses. Plate spring  60  also has a rounded bottom portion that contacts the left arcuate nest  111  and the right recession  112  in the inner bottom surface  110  of the housing  13  such that the tumbler is forced to a retracted position in the housing or an extended position out of the housing, as seen in  FIGS. 16 and 17 . In another embodiment rounded bottom portion  61  may be replaced by any angled shaped portion known in the art, which is capable of sliding. Inner bottom surface  110  of housing  13  has an arcuate nest  111  for cradling rounded bottom portion  61  of plate spring  60 , as seen in  FIG. 5 . A divide point  113 , where the left arcuate nest  111  meets the right recession  112 , confines the bottom rounded portion  61  of plate spring  60  to be forced in different directions when the vent stop is activated or deactivated, as seen in  FIG. 15 . In normal operation when the user wishes to activate tumbler  80 , the user will apply a downward, or inward force to button  95 , this will cause rounded bottom portion  61  of plate spring  60  to move out of arcuate nest  111  and pass the divide point  113  and move into the right recession  112  of bottom surface  110  of housing  13 . One must point out that arcuate nesting portion  111 , divide point  113 , right recession  112  of the bottom surface  110  and bottom rounded portion  61  of the plate spring  60  are of great consequence in the operation of this invention. 
   In addition to the tumbler cavity  100  of tumbler  80 , there exists an arcuate surface  85  that interacts with an arcuate surface  50  of cylindrical peg  51 . Arcuate surface  85  is preferably located on the rear bottom portion of tumbler  80 . Tumbler  80  may have a protruding portion  120  located at the bottom front end wall of tumbler  80 , as seen in  FIG. 3 . The protruding portion  120  has a top surface  121  that extends perpendicularly from the front end face  90  of the tumbler  80 . The protruding portion  120  also has two sides  122 , as seen in  FIG. 3 , and  123 , not shown, a front face  124 , and a bottom  125 . Bottom  125  of the protruding portion  120  extends outwardly in the same direction as top surface  121  so as to meet with the outside edge of front end face  124  and is parallel to the upper surface  38  so as to come into contact with the bottom surface of back wall  110  of the housing  13  and limit further rotation of the tumbler  80  in the housing  13  when the tumbler  80  is in the retracted position, as seen in  FIG. 15 . The protruding portion  120  may be designed as to allow a meshing between the protruding portion  120  and the bottom surface of top plate  25 , which would cause tumbler  80  from further rotating outwardly; thus if needed, protrusion  120  could be used as a limiting device. 
   The release of the tumbler  80  from housing  13  can be controlled by an interaction between button  95  and plate spring  60  in tumbler  80  and bottom surface  110  of the housing  13 . Button  95 , as mentioned previously, is located on the rear end portion of tumbler  80 , can have a grooved top surface  82 , which can be in the same plane as the upper surface  38  of the tumbler  80 , where the user can engage button  95  easily with any suitable instrument known in the art, including but not limited to a finger, fingernail, pen, pencil etc., as seen in  FIGS. 2 ,  3 , and  4 . When the user engages grooves  82 , it will move rounded bottom portion  61  of plate spring  60  from a cradled position to a freed position within cavity  130  of housing  13 . In the present embodiment the user applies a downward or inward force to groove  82  of tumbler  80 . 
   When the user wishes to activate tumbler  80 , so as to prevent movement of a sliding window member, the user will exert a downward, or upward force, greater than the force being exerted by the rounded bottom portion  61  of plate spring  60  against the top surface of the arcuate nesting area  111  of the bottom portion  110  of housing  13 , on groove  82 , of button  95 . This force will cause plate spring  60  to move in a direction opposite that of the force applied by the user. When the force applied by the user has reached the critical point, it will cause the rounded bottom portion  61  of plate spring  60  to move out of equilibrium with nesting area  111  of bottom surface  110  of housing  13  and slide across divide point  113  of bottom surface  110  of housing  13  and comes in the next equilibrium with right recession  112  of bottom surface  110  of housing  13 , as seen in  FIGS. 15 ,  16  and  17 . The critical point is reached when the force applied by the user overcomes the static frictional force, at which time bottom round portion  61  of plate spring  60  will begin to slide and the frictional force will drop back to a nearly constant value equal to that of the kinetic frictional force. When tumbler  80  is free to pivot on rotation members  70  and  71 , the upward force of spring  60  will cause tumbler  80  to rotate in an outwardly direction until the rounded bottom portion  61  of plate spring  60  comes into contact with right recession  112  of bottom surface  110  of housing  13 . In the same instance arcuate surface  85  of tumbler  80  will come in contact with arcuate surface  50  of cylindrical peg  51 . In addition, a protruding portion  120  can also be implemented, so as to further limit movement of tumbler  80  by coming into contact with bottom surface of top plate  25 . Once rounded bottom portion  61  of plate spring  60  has stopped sliding tumbler  80  will be exposed, thus preventing sliding window member from opening any further. 
   As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense. 
   The operation of the night latch according to the present invention will be obvious from the above description thereof.

Summary:
The present invention relates to a night stop that includes a housing, tumbler, spring, and a right arcuate nest, located on the inside bottom surface of the housing, used for maintaining the bottom rounded portion of the spring. The tumbler of the present invention has a top rear surface that is used as a button for activating the tumbler. In addition, the tumbler of the present invention has a concave rear bottom portion that contacts a stopping member when the tumbler is in an activated position. The spring of the present invention is partially housed inside of a bored cavity located on the tumbler. The bottom rounded portion of the spring is maintained in an arcuate nesting area when the tumbler is deactivated. When the tumbler is activated the bottom rounded spring portion traverses over and across a divide point into a right recession area.