A cam-action remote latch mechanism comprises a housing; a support, placed inside the housing, being able to perform a movement between an innermost position and an outermost position; a plurality of guiding openings in the housing for guiding the movement of the support; a cam, set on a primary axis and placed inside the housing, when turned driving the movement of the support; and a pawl, mounted on an outer side of the support, protruding from the housing when the support has reached the outermost position and exerting a sealing force driven by the support, with the cam and the support stably holding each other.

This is a divisional application of applicant's U.S. patent application Ser. No. 10/921,564 filed on Aug. 18, 2004 now U.S. Pat. No. 7,261,340. 


   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a cam-type remote latch mechanism for tightly locking of an enclosed space, like a freezer compartment, a chemical chamber or a drying chamber, particularly to a cam-type remote latch mechanism which is driven by a cam wheel, exerting a sealing force that is adjustable by a screw. 
   2. Description of Related Art 
   U.S. Pat. No. 4,880,261 “Remote Latch Mechanism” has disclosed an apparatus for locking a door of an enclosed space, like freezer compartment, a chemical chamber or an oven. As shown in  FIG. 8 , the apparatus disclosed has a latch assembly with a four-link mechanism, comprising: a housing  91  at a pre-determined position, having a first guiding opening  911  of an elongated shape with a horizontal and an inclined section and a second guiding opening  912 ; a crank  92 , mounted on the housing  91 ; a link  93 , having one end that is hingedly connected with the crank  92 ; a support  94 , having one end that is hingedly connected with the link  93 , a first bolt  941  that enters the first guiding opening  911  and a second bolt  942  that enters the second guiding opening  912 ; and a pawl  95 , set on the support  94 , defining a right side thereof. 
   As shown in  FIG. 9 , in an unlocked state, the crank  92  has a rest angular position, the first and second bolts  941 ,  942  respectively enter the first and second guiding openings  912  at left ends thereof, and the pawl  95  does not extend outside of the housing  91 . 
   As shown in  FIG. 10 , the crank  92 , when turned away from the rest angular position thereof, drives the link  93  to push the support  94  to the right and thus the first and second bolts  941 ,  942  away from the left ends of the first and second guiding openings  912  towards right ends thereof, so that the pawl  95  is pushed out of the housing  91 . 
   As shown in  FIG. 11 , when the second bolt  942  has reached the right end of the opening  912 , further turning of the crank  92  has the support  94  follow the path of the first guiding opening  911 , resulting in the pawl  95  turning downward after having reached a rightmost position, so that a sealing force is exerted on an external doorframe and, if a sealing strip has been attached to the doorframe, effective sealing is achieved. Turning the crank  92  even further will not result in loosening of the pawl  95  from the doorframe. However, the conventional remote latch mechanism just described has many structural parts and is therefore complicated and expensive to manufacture. 
   As shown in  FIG. 12 , the latch  95  has an adjusting device comprising a holding screw  951  screwed into the support  94 . The right side of the support  94  and a facing left side of the pawl  95  have sawtooth-shaped surfaces  943 ,  952 . When the holding screw  951  is loosened, the pawl  95  is movable along the right side of the support  94 , adjusting the sealing force. With the holding screw  951  tightened, due to friction between the sawtooth-shaped surfaces  943 ,  952 , the pawl  95  has a fixed position with respect to the support  94 . However, placing the pawl  95  at a different position with respect to the support  94  requires loosening and retightening of the holding screw  951 , which is inconvenient. 
   As above explanation shows, a conventional remote latch mechanism has several shortcomings. 
   SUMMARY OF THE INVENTION 
   It is the main object of the present invention to provide a cam-type remote latch mechanism with a comparatively simple structure which is inexpensive to manufacture. The present invention comprises a housing; a support, placed inside the housing, being able to perform a movement between an innermost position and an outermost position; a plurality of guiding openings in the housing for guiding the movement of the support; a cam, set on a primary axis and placed inside the housing, when turned driving the movement of the support; and a pawl, mounted on an outer side of the support, protruding from said housing when said support has reached said outermost position and exerting a sealing force driven by said support, with the cam and the support stably holding each other. 
   Another object of the present invention is to provide a cam-type remote latch mechanism exerting a sealing force that is easy to adjust. Thus the present invention has an adjusting screw engaging with a gliding piece on the pawl, so that, upon turning the adjusting screw, the pawl is shifted, and the sealing force thereof is adjusted. 
   The present invention can be more fully understood by reference to the following description and accompanying drawings. 


   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a sectional side view of the cam-action remote latch mechanism of the present invention in the unlocked state. 
       FIG. 2  is a perspective view of the cam-action remote latch mechanism of the present invention. 
       FIG. 3  is a sectional side view of the cam-action remote latch mechanism of the present invention during the locking movement. 
       FIG. 4  is a sectional side view of the cam-action remote latch mechanism of the present invention in the locked state. 
       FIG. 5  is a schematic illustration of the cam-action remote latch mechanism of the present invention during the unlocking movement. 
       FIG. 6  is a sectional side view of the cam-action remote latch mechanism of the present invention in the second embodiment. 
       FIG. 7  is a sectional side view of the cam-action remote latch mechanism of the present invention in the third embodiment. 
       FIG. 8  (prior art) is a sectional side view of a conventional remote latch mechanism. 
       FIG. 9  (prior art) is a perspective view of the conventional remote latch mechanism of  FIG. 8  in the unlocked state. 
       FIG. 10  (prior art) is a perspective view of the conventional remote latch mechanism of  FIG. 8  during the locking movement. 
       FIG. 11  (prior art) is a perspective view of the conventional remote latch mechanism of  FIG. 8  in the locked state. 
       FIG. 12  (prior art) is a sectional side view of a conventional adjusting device for a remote latch mechanism. 
   


   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   As shown in  FIGS. 1 and 2 , the cam-action remote latch mechanist of the present invention in a first embodiment comprises: a housing  10 ; a primary axis  20 ; a cam  30 ; a support  40 ; and a pawl  50 , The cam  30  is linked to the primary axis  20  and mounted in the housing  10 . The support  40  driven by the cam  30 , is movable from a innermost position  60  to a outermost position  70  (shown in  FIG. 4 ) in a locking movement. The support  40  on an outer side thereof carries the pawl  50  and houses a simple adjusting device. When the support  40  has reached the outermost position  70 , the pawl  50  enters an external keeper  80 , exerting a sealing force thereon. Turning of the primary axis  20  in a positive direction takes along the cam  30 , driving the locking movement of the support  40  within the housing  10 , which results in the pawl  50  entering the keeper  80  and exerting the sealing force thereon. The sealing force is easily adjustable. In the following, a more detailed explanation is given. 
   The housing  10  has elongated first and second guiding openings  11 ,  12 . The first guiding opening  11  has a horizontal section and an ascending section. 
   The primary axis  20  is mounted on the housing  10 , being able to perform a turning movement, with the positive direction indicated by an arrow F in  FIG. 1 . 
   The cam  30  is attached to the primary axis  20 , having a center and an outer surface  31  with a predetermined curvature for pushing the support  40  with a pushing force to perform the locking movement and a concave inner surface  32 . 
   A first bolt  41  and a second bolt  42  protrude outward from an outer side of the support  40 , passing through the first and second openings  11 ,  12  of the housing  10 , respectively. A first roller  43  is coaxially mounted on the first bolt of the support  40 , rolling along the outer surface  31  of the cam  30  during the locking movement, as shown in  FIGS. 3 and 4 . After finishing the locking movement, with the support  40  having reached the outermost position  70 , the outer surface  31  of the cam  30  touches a contact area  44  of the support  40 , blocking the cam  30  from being turned any further. 
   The pawl  50  has a mounting position on the outer side of the support  40  that is adjusted by the adjusting device inside the support  40 . The adjusting device has an adjusting screw  46  which engages with a gliding piece  51  that is attached to an inner side of the pawl  50 . 
   Referring again to  FIG. 1 , in an unlocked state, the primary axis  20  has a rest angular position, with the cam  30  not pushing the support  40  and the support  40  placed in the innermost position  60 . The first and second bolts  41 ,  42  of the support  40  are placed at leftmost ends of the first and second openings  11 ,  12 , respectively, and the pawl  50  is completely retracted inside the housing  10 . 
   Referring to  FIG. 3 , after the turning movement of the primary axis  20  has been started, the outer surface  31  of the cam  30  pushes the first roller  43  rightward, causing the support  40  to perform the locking movement. With the first and second bolts  41 , 42  being inserted in the first and second openings  11 , 12 , the support  40  first moves horizontally to the right, as long as the first bolt  41  moves within the horizontal section of the first guiding opening  11  and the second bolt  42  has not yet reached the rightmost point of the second guiding opening  12 . At this stage, the pawl  50  starts to project out of the housing  10 . 
   Referring to  FIG. 4 , after the first bolt  41  has reached the inclined section of the first guiding opening  11  and the second bolt  42  has reached the rightmost point of the second guiding opening  12 , further turning of the cam  30  results in the support  40  to turn, as well, with the pawl  50  moving downward. When the support  40  has reached the outermost position  70 , the pawl  50  exerts a sealing force H on the keeper  80 . The outer surface  31  of the cam  30  has an upper end with a stopping depression  33 . When the support  40  has reached the outermost position  70 , the first roller  43  enters the stopping depression  33 . At this time, the counterforce to the pushing force of the cam  30  on the support  40  points aside from the center of the cam  30 , urging the cam  30  to continue the turning movement in the positive direction under the influence of the counter torque F in  FIG. 3 . However, since the turning movement of the cam  30  is blocked by the contact area  44  of the support  40 , the support  40  is firmly held in the outermost position  70 , and a loosening of the pawl  50  is prevented. 
   The support  40  furthermore has an inner end opposite to the outer side, reaching past the outer surface  31  of the cam  30 . A second roller  45  is mounted at the inner end of the support  40 , being freely rotatable on an axis parallel to said first bolt. As shown in  FIG. 5 , when the primary axis, or crank, is turned in reverse direction, indicated by an arrow G in  FIG. 5 , the second roller  45  leans against the inner surface  32  of the cam  30  and rolls therealong, taking the support  40  in an unlocking movement from the rightmost position  70  back to the innermost position  60 . 
   Another characteristic of the present invention lies in easy adjusting of the mounting position of the pawl  50  on the support  40  by the adjusting screw  46 , as shown in  FIG. 2 . The gliding piece  51  is attached to the inner side of the pawl  50 , reaching into the support  40  and having an inner thread  52  that engages with the adjusting screw  46 . The adjusting screw  46  has an upper end with an adjusting head  47 , which is accessible from outside the housing  10 . A hole  48  of a suitable shape is inserted into the adjusting head  47 , allowing to turn the adjusting screw  46  with a suitable tool to adjust the mounting position of the pawl  50  on the support  40 . 
   Employing the adjusting screw  46  greatly simplifies adjusting of the mounting position of the pawl  50 . Adjusting of the mounting position of the pawl  50  is done in the locked state as shown in  FIG. 4  and can be performed continuously. No repeated dismounting and mounting of the pawl  50 , as in conventional art, is necessary, saving effort and time. 
   Referring now to  FIG. 6 , in a second embodiment of the present invention, a positive motion cam  30   a  is substituted for the cam  30 . The positive motion cam  30   a  has a cam groove  31   a . A first roller  41   a  is mounted on the inner end of the support  40  and inserted into the cam groove  31   a . When the positive motion cam  30   a  turns in positive direction, the cam groove  31   a  moves along, driving the locking movement of the support  40 . Conversely, when the positive motion cam  30   a  turns in reverse direction, the cam groove  31   a  pulls the support  40  back towards the innermost position  60 . 
   Although structural parts in the first and second embodiments of the present invention differ, movement and effect thereof are the same. 
   Referring to  FIG. 7 , in a third embodiment of the present invention, a cam  30   b  is substituted for the cam  30 . The cam  30   b  has an outer surface  31   b  without a corresponding inner surface. A first roller  41   b  on the inner end of the support  40  rolls along the outer surface  31   b  of the cam  30   b , while the cam  30   b  is turned in positive direction, so that the support  40  performs the locking movement towards the outermost position  70 . Furthermore, a retaining spring  49  is fastened to the inner end of the support  40 , pulling the support  40  back to the innermost position  60 . In contrast to the first and second embodiments of the present invention, in the third embodiment the returning movement of the pawl  50  is driven by the retaining spring  49 . The cam  30   b  in the third embodiment has only one surface, which simplifies the structure thereof. 
   While the invention has been described with reference to preferred embodiments thereof, it is to be understood that modifications or variations may be easily made without departing from the spirit of this invention which is defined by the appended claims.