Abstract:
A latch assembly is provided for securing a switch operator to a contact block. The latch assembly includes a collar designed to retain the switch operator in the latch assembly. The latch assembly also includes a housing having one or more apertures for receiving fasteners to secure the contact block to the latch assembly. The collar is displaceable within the housing between a locked position that secures the switch operator and an unlocked position that permits disengagement of the switch operator from the collar. When the collar is in the locked position, corresponding apertures in the collar align with the one or more apertures in the housing, permitting the fasteners to be inserted through the collar apertures. Insertion of the fasteners through the collar apertures secures the collar in the locked position, thereby impeding unintentional disconnection of the switch operator from the latch assembly.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from and the benefit of Chinese Application No. 201020589674.7, filed on Oct. 29, 2010 entitled “Programmable Controller Component with Assembly Alignment Features”, which is herein incorporated by reference. 
     BACKGROUND 
     The invention relates generally to the field of electrical switches, and more particularly to a latch assembly that provides a secure connection to a switch operator. 
     Electrical switch assemblies are widely used to control industrial equipment. Typically, an electrical switch assembly includes a switch operator, such as a push button, that is mounted to a front of a panel. The electrical switch assembly also includes an electrical switch, such as a contact block, that is mounted on the back of the panel and connected to equipment controlled by the switch. A latch assembly is also mounted on the back of the panel and used to secure the switch operator to the electrical switch. 
     A contact block generally includes a housing that contains normally opened and/or normally closed contacts. Actuation of the switch operator engages or disengages the contacts, thereby altering an operational state of equipment connected to the electrical switch assembly through the contact block. For example, when a normally opened contact is employed, actuation of the switch operator closes the normally opened contact to engage and/or start operation of equipment connected to the contact block. In contrast, a normally closed contact may be employed to stop an ongoing function by actuation of the switch operator. One common example of a normally closed contact is an emergency stop (E-Stop) function, where the switch operator may be activated to immediately terminate an ongoing function. 
     Latch assemblies are typically connected to switch operators through snap features, or other fastening devices, that provide for easy assembly and disconnection. However, if a latch assembly becomes dislodged or disconnected from a switch assembly, actuation of the switch operator may no longer have the desired effect on the controlled circuit within the contact block. Further, electrical switches are more frequently desired in industrial environments, which may be subject to shock and vibrations. Accordingly, there is a need for enhanced security of the connection between the latch assembly and the switch operator while still providing for easy connection and/or disconnection of the latch assembly from the switch operator. 
     BRIEF DESCRIPTION 
     The present invention provides a novel latch assembly designed to respond to such needs. The latch assembly includes a collar designed to retain the switch operator in the latch assembly. For example, the collar may include one or more retention features, such as tabs, designed to mate with complementary retention features, such as slots, on the switch operator. The latch assembly also includes a housing having one or more apertures for receiving fasteners to secure the contact block to the latch assembly. The collar is displaceable within the housing between a locked position that secures the switch operator to the collar and an unlocked position that permits disengagement of the switch operator from the collar. When the collar is in the locked position, corresponding apertures in the collar align with the one or more apertures in the housing, permitting the fasteners to be inserted through the collar apertures. In particular, the fasteners can be inserted through the contact block, through the latch housing, and through the latch collar to secure the contact block to the latch assembly and to inhibit movement of the collar from the locked position. The connection of the fasteners to the collar reduces unintended movement of the collar from the locked position, for example, due to shock or vibration, thereby impeding unintentional disconnection of the switch operator from the latch assembly. 
     According to certain embodiments, the latch assembly includes a housing base with a sleeve that extends from the base towards a cover. The collar is a circular structure rotatably disposed around the sleeve and secured in the housing base by the cover. The collar includes a pair of tabs designed to fit within corresponding slots on the switch operator to secure the switch operator to the collar. The collar also includes a pair of protrusions designed to fit within slots on the switch operator to secure the switch operator to the collar. The protrusions include threaded apertures designed to align with apertures in the housing base. When the collar is in the locked position, the protrusion apertures align with apertures in the housing base, allowing fasteners, such as screws, to be inserted into the protrusion apertures to secure the collar in the locked position. When the fasteners are removed from the apertures, the collar may be rotated to an unlocked position, where the tabs and protrusions can be disengaged from the slots in the switch operator to disconnect the switch operator from the latch assembly. 
    
    
     
       DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
         FIG. 1  is an exploded view of an exemplary switch assembly that may employ a latch assembly in accordance with the present techniques; 
         FIG. 2  is a perspective view of the switch assembly of  FIG. 1 ; 
         FIG. 3  is an exploded view of the latch assembly of  FIG. 1 ; 
         FIG. 4  is a partially exploded view depicting connection of a switch operator to a latch assembly; 
         FIG. 5  is a perspective view of the latch assembly of  FIG. 4  in the unlocked position; 
         FIG. 6  is an exploded view of another embodiment of a latch assembly in accordance with the present techniques; 
         FIG. 7  is a perspective view of the latch assembly of  FIG. 6 ; and 
         FIG. 8  is a cross-sectional view of the latch assembly of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is an exploded view of a switch assembly  10  that may be manipulated by a user to control a device, such as industrial machine, that is connected to the switch assembly. The switch assembly  10  includes a switching device, such as a contact block  12  that includes terminals  13  that enable wires and/or ring lug connectors to be coupled to one or more internal electrical contact pairs that are normally opened or normally closed. Switch assembly  10  also includes a switch operator  14  that can be actuated by a user to move the electrical contact pairs within the contact block  12  between opened and closed positions. In particular, the switch operator  14  includes a button  16  that extends from a front side  18  of a panel  20 . According to certain embodiments, the panel  20  may be a sheet metal panel that houses one or more switch operators  14 . The button  16  can be depressed and/or twisted by a user to actuate the switch operator  14  and engage the contact block  12 , thereby changing the position of the internal electrical contact pairs. 
     The switch operator  14  also includes a bushing  22  that extends through an aperture  24  within the panel  20  to be secured to a rear side  26  of the panel  20 . In particular, the bushing  22  can be coupled to a mounting ring  28  and a latch assembly  30 . The mounting ring  28  includes threads  32  that interface with a threaded portion  34  of bushing  22  to couple the mounting ring  28  to the bushing  22 , with the panel  20  disposed between the mounting ring  28  and the portion of the switch operator  14  that extends from the front side  18  of the panel  20 . 
     The latch assembly  30  includes one or more retention features designed to mate with complementary retention features on the switch operator to couple the latch assembly  30  to the switch operator  14 , as discussed further below with respect to  FIGS. 3 and 4 . According to certain embodiments, the latch assembly  30  may be inserted onto bushing  22  and snapped into place by hand. When assembled, a front side of the latch assembly  30 , shown here as a cover  35 , may be disposed against the rear side  26  of the panel  20 . An optional lamp  36  may be inserted into a lamp socket  38  of the latch assembly  30  to illuminate the button  16  on switch operator  14 . For example, the lamp socket  38  and the lamp  36  may be inserted into the bushing  22  and may extend through the aperture  24  in the panel  20 . However, in other embodiments where illumination is not desired, the lamp  36  and/or the lamp socket  38  may be omitted. Further, in certain embodiments, gaskets, seals, and/or fasteners may be employed to secure switch operator  14  to panel  20 , instead of, or in addition to, the mounting ring  28 . 
     The latch assembly  30  also provides a mounting surface for contact block  12 . In particular, a rear surface, shown here as a base  40 , may provide a mounting surface for a housing  41  of the contact block  12 . Fasteners  42 , such as screws, may be inserted through openings  44  in the housing  41 . Threaded portions  46  of the fasteners  42  may extend into the latch assembly  30  where the threaded portions  46  may mate with complementary threads in the latch assembly  30 . As shown in  FIG. 1 , two fasteners  42  are employed to secure the contact block  12  to the latch assembly  30 . However, in other embodiments, any number of one or more fasteners  42  may be employed. 
       FIG. 2  is a perspective view of the switch assembly  10 , with a portion of the latch base  40  cut-away to show the interior of the latch assembly  30 . As shown, when assembled, the contact block  12  is coupled to the latch assembly  30  by the fasteners  42 . In particular, the fasteners  42  extend through the apertures  44  in the contact block  12  and into the latch assembly  30 . The latch assembly  30  includes the base  40  and the cover  35 , as well as a collar  50  disposed between the base  40  and the cover  35 . In particular, the collar  50  is disposed around a sleeve  52  of the base  40 , which extends within the base  40  towards the cover  35 . According to certain embodiments, the sleeve  53  may be a molded part of the base  40 . The collar  50  can rotate around the sleeve  52  between a locked position (shown in  FIG. 4 ) that secures the switch operator  14  to the latch assembly  30  and an unlocked position (shown in  FIG. 5 ) that allows the switch operator  14  to be disconnected from the latch assembly  30 . The fasteners  42  extend through the base  40  to fasten to the collar  50  of latch assembly  30 . When the fasteners  42  are in place, the collar  50  is secured in the locked position by the fasteners  42 . A spring  56  is disposed within the base  40  to bias the collar  50  towards the locked position. 
       FIG. 3  is an exploded view of the latch assembly  30 . The cover  35  encloses the collar  50  within the base  40 . The cover  35  includes apertures  57  that may receive bosses  59  that extend from the base  40 . Upon assembly, the bosses  59  may be heat staked to secure the cover  35  to the base  40 . According to certain embodiments, the collar  50  may be constructed of metal; however, in other embodiments, any suitable material may be employed. The collar  50  generally encircles the sleeve  52  of the base  40 , which includes ridges  60  that support the collar  50 . In particular, the collar  50  includes retention features, such as tabs  58  that rest on the ridges  60  of the base  40 . When the collar  50  is in the locked position, the tabs  58  may interface with complementary retention features on the switch operator  14  to secure the switch operator  14  to the collar  50 . As the collar  50  rotates around the sleeve  52 , the tabs  58  may slide along the ridges  60 . Although only one ridge  60  is shown in  FIG. 3 , a corresponding ridge is disposed on the opposite side of the base  40  (hidden from view by the collar  50 ). When installed in the base  40 , the collar  50  covers a slot  62  in the base  40  that houses the spring  56 . A spring retaining feature  64  of the collar  50  encloses the spring  56  within the slot  62 . The spring  56  is designed to press against the spring retaining feature  64  and bias the collar  50  towards the locked position, shown in  FIG. 4 . 
     The collar  50  includes apertures  66  that align with apertures  68  in the base  40 , when the collar  50  is in the locked position. The collar apertures  66  are disposed within retention features, such as protrusions  70  of the collar  50 . When the collar  50  is in the locked position, the protrusions  70  may interface with complementary retention features on the switch operator  14  to secure the switch operator  14  to the collar  50 . According to certain embodiments, the collar apertures  66  are threaded apertures designed to mate with the threaded portions  46  of the fasteners  42  ( FIG. 1 ). When the fasteners  42  are inserted through the collar apertures  66 , the fasteners  42  inhibit rotation of the collar  50 , thereby securing the collar  50  in the locked position. The fasteners  42  also extend through the base apertures  68  to secure the contact block  12  ( FIG. 1 ) to the latch assembly  30 . According to certain embodiments, the base apertures  68  may be relatively smooth openings; however, in other embodiments, the base apertures  68  may be threaded to mate with the threaded portions  46  of fasteners  42 . The base  40  also includes apertures  71  designed to allow a portion of the switch operator  14  to extend through the base  40  to engage and/or disengage electrical contact pairs in the contact block  12 , when the contact block  12  is mounted to the base  40 . The base  40  further includes alignment features  74  designed to mate with complementary alignment features of the switch operator  14  to facilitate proper alignment of the switch operator  14  in the base  40 . 
     The collar  50  includes a release feature, such as a tab  74  that may be manipulated by a user to rotate the collar  50  to the unlocked position. According to certain embodiments, the tab  74  includes an aperture  76  for receiving a tool, such as a screwdriver, that can facilitate rotation of the collar  50 . However, in other embodiments, the aperture  76  may be omitted. Further, in other embodiments, the geometry, size, and/or shape of the tab  74  and/or the aperture  76  may vary. A user may move the tab  74  in the direction of an arrow  78  to rotate the collar to the unlocked position. In the unlocked potion, the spring retaining feature  64  may press against the spring  56  to compress the spring and rotate the collar  50  relative to the base  40  and the cover  35 . When the user releases the tab  74 , the spring  56  may bias the collar  50  back to the locked position. 
       FIG. 4  is an exploded view showing the switch operator  14  exploded from the latch assembly  30  to illustrate attachment of the switch operator  14  to the collar  50 . For ease of illustration, the cover  35  has been omitted. As shown in  FIG. 4 , the collar  50  is located in the locked position  80  where the collar apertures  66  align with the base apertures  68 . When the collar  50  is in the locked position  80 , the switch operator  14  can be inserted into the latch assembly  30  so that prongs  82  of the switch operator  14  extend through apertures  71  in the latch base  40 . When the contact block  12  is mounted on the latch assembly  30 , the prongs  82  may extend into the contact block  12  upon actuation of the button  16  to engage or disengage the contact pairs included within the contact block  12 . Further, when the switch operator  14  is inserted in the base  40 , the bushing  22  may be disposed within the sleeve  60 . To facilitate alignment of the switch operator  14  in the base  40 , the switch operator  14  includes alignment features, such as grooves  83  that receive the alignment features  74  of the base  40 . Although only one groove  83  is depicted in  FIG. 4 , one or more additional grooves may be included on the bushing  22 . 
     The switch operator  14  also includes retention features, such as one or more grooves  84  that facilitate insertion of the switch operator  14  into the latch assembly  30 . The groove  84  includes a cam surface  86  that contacts one of the tabs  58  on the collar  50 . In certain embodiments, another groove  84  may be disposed on the opposite side of the bushing  22  to receive the other tab  58 . As the tab  58  contacts the cam surface  86 , the cam surface urges the tab  58  and the collar  50  in the direction of the arrow  78  toward the unlocked position (shown in  FIG. 5 ) until the tab  58  slides upwardly along the cam surface  86  to fit within a slot  88 . When the tab  58  reaches the slot  88 , the spring  56  may bias the collar  50  back to the locked position  80 , shown in  FIG. 4 . 
     The switch operator  14  also includes retention features, such as one or more grooves  90  that receive the protrusions  70 . Upon insertion of the switch operator  14  within the latch assembly  30 , a protrusion  70  slides through the groove  90  until the protrusion  70  is retained within a slot  91 . In certain embodiments, another groove  90  may be disposed on the opposite side of the bushing  22  to receive the other protrusion  70 . When the protrusion  70  is retained within the slot  91 , the aperture  66  of the protrusion  70  generally aligns with a longitudinal groove  92  disposed on the bushing. According to certain embodiments, the longitudinal groove  92  may provide space for one of the fasteners  42  ( FIG. 2 ) to be inserted through the aperture  66  and extend toward the button  16 . 
     When the collar  50  is in the locked position  80 , the tabs  58  are retained within the slots  88  of the switch operator  14  and the protrusions  70  are retained within the slots  91  of the switch operator  14  to secure the switch operator  14  to the collar  50 . As shown in  FIG. 5 , the collar  50  may be rotated to the unlocked position  94 , which disengages the tabs  58  and protrusions  70  from the slots  88  and  91 , allowing the switch operator  14  to be removed from the latch assembly  30 . However, when the fasteners  42  are inserted through the collar apertures  66 , the collar  50  is inhibited from rotational movement to the unlocked position  94 , thereby further securing the switch operator  14  to the latch assembly  30 . As may be appreciated, in other embodiments, the number of retention features included within the collar  50  and/or the switch operator  14  may vary. Further, in other embodiments, the shape, size, and/or geometry of the retention features may vary. 
       FIG. 5  depicts the collar  50  in the unlocked position  94 , which allows the switch operator  14  to be disconnected from the latch assembly  30 . To place collar  50  in the unlocked position  94 , a user can first remove the fasteners  42 . For example, a user may employ a tool, such as a screwdriver, to unscrew the fasteners  42 . A user can then move the tab  74  in the direction of the arrow  78  to rotate the collar to the unlocked position  94  and compress the spring  56 . As can be seen by comparing  FIGS. 4 and 5 , the collar  50  has rotated with respect to the base  40  to offset apertures  66  and  68  from one another. Accordingly, in the unlocked position  94 , the collar apertures  66  are unaligned with the base apertures  68 . As the collar apertures  66  move, the protrusions  70  also move out of the slots  91  ( FIG. 4 ) in the switch operator  14  towards the grooves  90  ( FIG. 4 ), which allow the protrusions  70  to slide out of the switch operator  14 . In the unlocked position  94 , the tabs  58  have also rotated along the ridges  60 . As the tabs  58  rotate, the tabs  58  move out of the slots  88  ( FIG. 4 ) in the switch operator  14  towards the grooves  84  ( FIG. 4 ), which allow the tabs  58  to slide out of the switch operator  14 . Once the switch operator  14  has been disconnected from the latch assembly  30 , the spring  56  may bias the collar  50  back to the locked position  80 , as shown in  FIG. 4 . 
     As shown in  FIGS. 3 to 5 , the collar  50  generally includes a circular structure that is disposed around a sleeve of the base of the latch assembly. However, in other embodiments, the collar may have a different geometry and/or may not form a complete circle. For example,  FIGS. 6 to 8  depict another embodiment of a latch assembly  96  that may be employed to secure the switch operator  14  to the latch assembly  96  and to mount the contact block  12 . 
     As shown in  FIG. 6 , the latch assembly  96  includes a base  98  and a collar  100  that is generally a U-shaped structure. The collar  100  can be inserted within a slot  102  of the base  98 , as shown in  FIG. 7 . When the collar  100  is fully inserted in the base  98 , apertures  104  of the collar  100  are aligned with apertures  106  of the base  98 , and the collar  100  is located in the locked position. Accordingly, the fasteners  42  ( FIG. 1 ) can be inserted through the apertures  104  and  106  to secure the collar  100  in the locked position. The collar  100  can be laterally translated in the base  98  between the locked position and the unlocked position. 
     The collar  100  includes retaining features, such as shoulders  108  that may interface with complementary retaining features, such as slots, grooves, or other suitable types of retaining features, on the switch operator  14  to secure the switch operator  14  to the collar  100 . To facilitate insertion of the switch operator  14  into the base  98 , the base  98  includes alignment features  110  that may interface with complementary alignment features on the switch operator. Further, when the switch operator  14  is inserted into the base  98 , prongs, such as the prongs  82  shown in  FIG. 4 , may extend through apertures  112  in the base  98  to engage the contact block  12  when the contact block  12  is mounted to the base  98 . 
       FIG. 8  is a cross-sectional view of the latch assembly  96  depicting the collar  100  in the locked position within the base  98 . As shown in  FIG. 8 , the collar  100  includes protrusions  113  that extend past shoulders  115  within the base  98  to secure the collar  100  within the base  98 . The protrusions  113  can slide along slot walls  118  of the base  98  until the collar apertures  104  align with the base apertures  106 . The fasteners  42  ( FIG. 1 ) can then be inserted through the apertures  104  and  106  to secure the collar  100  in the locked position. To remove the collar  100  from the locked position, a user may first remove the fasteners  42 . A user may then employ a release feature, such as aperture  114  to remove the collar  100  from the locked position. For example, a user may insert a tool through the aperture  114  and move the collar  100  in the direction of an arrow  116  to slide the protrusions  113  along the slot walls  118  toward the shoulders  115 . When the protrusions  113  are moved towards the shoulders  115 , the retaining shoulders  108  of the collar  100  may no longer interface with complementary retaining features of the switch operator, thereby allowing the switch operator to be disconnected from the latch assembly  96 . According to certain embodiments, the collar  100  can only be partially removed from the base  98  due to the shoulders  115  that inhibit further movement of the collar  100  out of the base  98 . However, in other embodiments, the collar  100  may be fully removable from the base  98 . 
     While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.