Abstract:
A mounting latch for mounting a device to a rail is provided. The mounting latch comprises: a moveable actuator having a profile; a latch mechanism comprising first and second opposed rail engaging members, at least one of the members having a face for causing the member to yield against a bias source when the latch mechanism is engaging with the rail; and a follower enabling the at least one member to follow a rotational movement of the actuator such that movement of the actuator in a first direction causes the at least one member to become unlatched from the rail.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit and priority of Great Britain Patent Application No. 1322676.6 filed Dec. 20, 2013. The entire disclosure of the above application is incorporated herein by reference. 
       FIELD 
       [0002]    This disclosure relates to a mounting latch, specifically a mounting latch for mounting electrical devices on to a rail. 
       BACKGROUND 
       [0003]    This section provides background information related to the present disclosure which is not necessarily prior art. 
         [0004]    It is common for electrical devices to be installed in cabinets in order to prevent exposure of the devices during operation, and also as an effective means for installing the devices in order to save space. Typically, rails such as a DIN rail are used to mount the electrical devices. As cabinets enclose devices and electrical trunking with increasing density, space constraints make it increasingly difficult and potentially dangerous to mount a device in a cabinet. 
         [0005]    Known methods of securely fitting devices to rails include levers, tools or sliding means. It is found that these require significantly more free space in the cabinet to perform the action of mounting and demounting the device than the device itself needs when mounted. Further, known solutions are complicated, involving multiple levers or latches to operate in order to achieve the desired mounting. This imposes a maximum density on the installed devices with significant unoccupied space. 
         [0006]    On the other hand, this required space to mount a device may not be available due to other mounted devices obstructing access or operation of the required tools or levers. In such instances, it may be necessary to mount devices in a particular sequence. It can then be necessary to remove pre-mounted devices in order to have sufficient room to mount the desired device, which requires significant engineer time to perform the removals and re-mountings. Further, it may also be necessary to remove panels of the cabinet to gain access to desired areas, purely due to the mounting requirements of the device, which again may be time-consuming. 
         [0007]    Therefore there is a need for a mounting latch that overcomes the aforementioned problems and allows quick and simple installation of electrical devices. 
       SUMMARY 
       [0008]    According to an aspect there is provided a mounting latch for mounting a device to a rail. The mounting latch comprises a moveable actuator having a profile, and a latch mechanism comprising first and second opposed rail engaging members. At least one of the members has a face for causing the member to yield against a bias source when the latch mechanism is engaging with the rail. The mounting latch further comprises a follower enabling the at least one member to follow the movement of the moveable actuator such that movement of the actuator in a first direction causes the at least one member to become unlatched from the rail. 
         [0009]    Such a latch is typically attached to a device, such as an electrical switch block or other component. It is used to mount such devices to a rail or rack. In the following, the mounting latch is described on its own for the sake of simplicity. 
         [0010]    The face of the at least one member may be a chamfered face. The use of a chamfered face facilitates the yielding of the member against the bias source when the latch mechanism is engaging with the rail. 
         [0011]    Movement of the actuator in a second, opposite direction may cause the at least one member to latch on to the rail. 
         [0012]    The profile of the moveable actuator may engage with the follower, and the movement of the actuator may be a rotational movement. 
         [0013]    The profile of the moveable actuator may comprise a detent for retaining the at least one member in a fixed position. The detent may therefore maintain the at least one member in an open position, in order to allow quick and easy placement of the mounting latch on to the rail. 
         [0014]    The bias source may comprise a resilient member, for example a spring. Alternatively, other bias sources may be used to provide the bias. 
         [0015]    The profile of the moveable actuator may be shaped to enable movement of the at least one member against the bias without movement of the actuator. Therefore, it is possible to move the member against the bias without operation of the actuator at all, avoiding the need for an engineer to operate the mounting latch in any way other than via appropriate placement of the mounting latch against the rail. As a result, latching of the mounting latch on to the rail may be achieved in conditions where space is limited, since no tools or mechanisms need be operated by an engineer in order to attach the device to the rail. 
         [0016]    The moveable actuator may be a disc-shaped cam. 
         [0017]    The profile of the moveable actuator may comprise first and second profiles on opposite sides of the moveable actuator, and the follower may comprise first and second followers for enabling respective first and second members to follow the movement of the moveable actuator. The use of multiple members further minimises the space requirements to fit a device to the rail, since the mounting latch to which the device is attached does not need to be presented perfectly in alignment with the plane of the rail in order to achieve the desired mounting of the mounting latch and device on the rail. The upper member can instead first engage with the rail, followed by the engagement of the lower member with the rail, or vice-versa. Therefore the movement of multiple members allows greater flexibility in the angle between the mounting device and the rail that enables latching of the mounting latch and device on to the rail. 
         [0018]    The first follower may engage with the first profile, and the second follower may engage with the second profile. 
         [0019]    The first and second profiles may comprise respective first and second detents for retaining the respective first and second members in a fixed position. Therefore, both the first and second members may be retained in an open position to facilitate placement of the mounting latch on to the rail. 
         [0020]    The first and second profiles may be shaped to allow movement of the respective first and second members against the bias source without movement of the actuator. It is therefore possible to move both members against the bias source without operation of the actuator at all, avoiding the need for an engineer to operate the mounting latch in any way other than via appropriate placement of the mounting latch against the rail. By having two members arranged in this way, appropriate placement is facilitated due to both members being moveable against the bias source simply by pressing the mounting latch on to the rail. 
         [0021]    The mounting latch may comprise a pair of opposed latch mechanisms oppositely moveable between latched and unlatched positions with respect to the rail. 
         [0022]    Further aspects and areas of applicability will become apparent from the description provided herein. It should be understood that various aspects of this disclosure may be implemented individually or in combination with one or more other aspects. It should also be understood that the description and specific examples herein are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0023]    Embodiments and examples will now be described by way of example with respect to the appended figures of which: 
           [0024]      FIG. 1  shows a plan view of a mounting latch and a rail; 
           [0025]      FIG. 2A  shows a plan view of the front face of a moveable actuator in an “open” position; 
           [0026]      FIG. 2B  shows a plan view of the rear face of the moveable actuator in the “open” position; 
           [0027]      FIG. 3A  shows a cross-sectional view of the mounting latch in the “open” position; 
           [0028]      FIG. 3B  shows a front view of the mounting latch in the “open” position; 
           [0029]      FIG. 3C  shows a rear view of the mounting latch in the “open” position; 
           [0030]      FIG. 4A  shows a plan view of the front face of the moveable actuator and an upper follower in the “open” position; 
           [0031]      FIG. 4B  shows a plan view of the rear face of the moveable actuator and a lower follower in the “open” position; 
           [0032]      FIG. 5A  shows a plan view of the front face of the moveable actuator and the upper follower in a “closed” position; 
           [0033]      FIG. 5B  shows a plan view of the rear face of the moveable actuator and the lower follower in the “closed” position; 
           [0034]      FIG. 6A  shows a cross-sectional view of the mounting latch in the “closed” position; 
           [0035]      FIG. 6B  shows a front view of the mounting latch in the “closed” position; and 
           [0036]      FIG. 6C  shows a rear view of the mounting latch in the “closed” position. 
       
    
    
       [0037]    Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
       DETAILED DESCRIPTION 
       [0038]    Example embodiments will now be described more fully with reference to the accompanying drawings. 
         [0039]    Referring to  FIG. 1 , a mounting latch is shown mounted on a rail such as a DIN rail  300 . The mounting latch comprises a moveable actuator such as a cam  100 , a body  200 , an upper latch  202  and a lower latch  204 . The mounting and retention of the mounting latch on to the DIN rail  300  is achieved via an engagement of the upper latch  202  and the lower latch  204  with the DIN rail  300 . The upper latch  202  and the lower latch  204  are shaped to engage with the cam  100 . When mounted on the DIN rail  300 , rotation of the cam  100  disengages the upper latch  202  and the lower latch  204  from the DIN rail  300  by urging them apart and clear of the upper and lower edges of the DIN rail  300 , thereby enabling the mounting latch to be demounted from the DIN rail  300 . 
         [0040]    The structure of the cam  100  can be better understood in relation to  FIG. 2A .  FIG. 2A  shows a front face  101  of the cam  100 . The cam  100  is a circular disk rotationally mounted on the body  200  via a central pivot hole  106  mounted on a pivot arm  212  on the body  200 . The cam  100  further comprises a front recess  102 , first and second peripheral detents  108  and  110 , and a protrusion  104 . The front recess  102  defines a cam profile defining movement of the upper latch  202  from an open to a closed position, or vice versa, as the cam  100  is rotated. The front recess  102  comprises a lower surface  304 , a detent  302  at one end of the profile, and a front wall  303  at the other, as described in more detail below. The peripheral detents  108  and  110  engage with locating projections  112   a  and  112   b  on the body  200 . Each locating projection  112   a  and  112   b  rides on the peripheral surface of the cam  100  and defines a stop position. 
         [0041]    In  FIG. 2A , the cam  100  is in an “open” position defined by the peripheral detent  108  being engaged with the locating projection  112   a.  Clockwise rotation of the cam  100  puts it into a “closed” position defined by alignment and engagement of the locating projection  112   b  with the peripheral detent  110 . 
         [0042]      FIG. 2B  shows a rear face  103  of the cam  100 , also in the open position. The rear face  103  comprises a rear recess  116  and a spacer  118 . The rear recess  116  defines a cam profile defining movement of the lower latch  204  from an open to a closed position, as described in more detail below. The rear recess  116  comprises an upper surface  308 , a detent  306  at one end of the profile and a wall  305  at the other. 
         [0043]    The mounting latch may be further understood with reference to  FIGS. 3A-3C  in which it is in the “open” position on the DIN rail  300 . The upper latch  202  in driven by the profile of the front recess  102  of the cam  100  via engagement of an upper follower  203  at an end of the upper latch  202 . The upper follower  203  may take the form of a protrusion extending from the upper latch  202  and shaped to sit within the front recess  102 . The upper latch  202  is connected to the body  200  via a biasing source such as a spring  210  which acts to bias the upper latch  202  into an engaged position with respect to the edge of the DIN rail  300 . The biasing causes the upper latch  202  to follow the profile of front recess  102  as the cam  100  is rotated. 
         [0044]      FIG. 3A  also shows the lower latch  204 , which moves in the opposite direction to the upper latch  202  as the cam  100  moves. The lower latch  204  is driven by the profile of the rear recess  116  of the cam  100  via engagement of a lower follower  206  at an end of the lower latch  204 . The lower follower  206  may take the form of a protrusion extending from the lower latch  204  and shaped to sit within the rear recess  116 . The lower latch  204  also comprises a cut-out portion  205  through which the part of the upper latch  202  carrying the upper follower  203  projects (see  FIG. 3B ). The lower latch  204  is connected to the housing  200  via biasing source such as a spring  208  which biases the lower latch  204  into an engaged position with respect to the lower edge of the DIN rail  300 . As with the upper latch  202 , the biasing causes the lower latch  204  to follow the profile of the rear recess  116  as the cam  100  is rotated. 
         [0045]    The spacer  118  of the rear face  103  of the cam  100  is a raised region around the pivot hole  106  which prevents the cam rear face  103  from lying flush with the housing  200 , thereby providing a space for the lower latch  204  to be located between the rear face  103  and the housing  200 . 
         [0046]      FIGS. 4A and 4B  show the engagement of the upper and lower followers  203  and  206  with the cam  100  when the cam  100  is in the open position. In  FIG. 4A , upper follower  203  is located in the leading bulbous detent  302  of the front recess  102 . Since the upper latch  202  is biased radially away from the pivot hole  106  by the spring  210 , the detent  302  of the front recess  102  ensures that the cam  100  is held in the open position. 
         [0047]    Similarly,  FIG. 4B  shows the lower follower  206  located within the trailing bulbous detent  306  of the rear recess  116 . Since the lower latch  204  is biased radially towards the pivot hole  106 , the detent  306  ensures that the lower follower  206  and cam  100  are also held in the open position. 
         [0048]      FIGS. 5A and 5B  show the cam  100  in the closed position. In comparison with  FIG. 4A ,  FIG. 5A  shows the front face  101  of the cam  100  rotated clockwise. Upon rotation of the cam  100  via the protrusion  104 , the peripheral detent  108  disengages from the locating projection  112   a,  and the cam  100  is rotated until the peripheral detent  110  engages with the locating projection  112   b.  The eventual engagement of the peripheral detent  110  with the locating projection  112   b  defines the “closed” position of the cam  100 . With movement of the cam  100 , the upper follower  203  travels along the lower surface  304  of the front recess  102  until it abuts the wall  303 . At this point, further clockwise rotation of the cam  100  is prevented. 
         [0049]    Similarly,  FIG. 5B  shows the position of the rear face  103  of the cam  100  when the same cam  100  is in the “closed” position. In comparison with  FIG. 4B , when the rear face  103  of the cam  100  is rotated anti-clockwise, the peripheral detent  108  disengages from the locating projection  112   a  until the peripheral detent  110  engages with the locating projection  112   b.  With this movement of the cam  100 , the lower follower  206  travels along the upper surface  308  of the rear recess  116  until it abuts the wall  305 . 
         [0050]    The engagement of the peripheral detent  108  with the locating projection  112   a,  and the engagement of the peripheral detent  110  with the locating projection  112   b  not only define the open and closed positions respectively of the cam  100 , but also provide tactile feedback to an operator that the cam  100  has completed its rotation. Therefore, the operator knows when the cam  100  is locked fully open or closed. 
         [0051]      FIGS. 6A-6C  show the mounting latch mounted on the DIN rail  300  in the closed position. With reference to  FIG. 5A , when the cam  100  is in the corresponding closed position, the upper follower  203  is no longer seated in the detent  302 , but abuts the wall  303  of the front recess  102 , as previously described. Since the upper follower  203  is biased radially away from the pivot hole  106  of the cam  100 , the profile of the front recess  102  means that the upper latch  202  is urged radially further away from the centre of the cam  100  by the spring  210 . Conversely, with reference to  FIG. 5B , since the lower follower  206  of the lower latch  204  is biased radially towards the pivot hole  106  of the cam  100 , the profile of the rear recess  116  means that the lower latch  204  is urged radially towards the centre of the cam  100  by the spring  208 . 
         [0052]    Engagement of the upper latch  202  and lower latch  204  with the DIN rail  300  will now be described. As shown in  FIGS. 3A and 6A , the upper latch  202  is shaped to define an upper latch recess  202   a  and a chamfered face  202   b.  The lower latch  204  is shaped to define a lower recess  204   a  and a chamfered face  204   b.  The DIN rail  300  is of standard “top hat” shape and comprises upper and lower flanges  302  and  304 . There are two methods of mounting the latch onto the DIN rail  300 . The first method is to set the upper and lower latches  202  and  204  in the open position by adjustment of the cam  100  as previously described. The mounting latch may then be mounted on the DIN rail  300  by offering it directly onto the DIN rail  300  such that the DIN rail  300  is between the upper latch  202  and lower latch  204 . By rotating the cam  100  from the open position to the closed position, the movement of the upper latch  202  and the lower latch  204  towards each other engages the flanges  302  and  304  within the upper and lower recesses  202   a  and  204   a  respectively. The mounting latch is then securely mounted on the DIN rail  300  as shown in  FIG. 6A . 
         [0053]    The second method of mounting the mounting latch to the DIN rail  300  is to start with the cam  100  and the upper and lower latches  202  and  204  in the closed position but not mounted on the DIN rail  300 . The mounting latch may then be positioned such that the upper and lower flanges  302  and  304  of the DIN rail  300  make contact with the respective chamfered faces  202   b  and  204   b  of the upper and lower latches  202  and  204 . By exerting a force perpendicular to the plane of the DIN rail  300 , the upper and lower latches  202  and  204  yield against their respective bias springs  210  and  208  and engage the flanges  302  and  304  in the upper and lower recesses  202   a  and  204   a.    
         [0054]    This movement of the upper and lower latches  202  and  204  against the bias of their respective springs  210  and  208  is possible due to the shape of the front recess  102  and the rear recess  116 . As previously described, when the mounting latch is pushed against the DIN rail  300  in a direction perpendicular to the plane of the DIN rail  300 , the upper latch  202  is forced to move radially towards the pivot hole  106 , against the bias of the spring  210 . When this happens, the upper follower  203  rides in a dead space and travels radially across the leading wall  303 , away from the lower surface  304  (see  FIG. 5A ). Likewise the lower latch  204  is forced radially away from the pivot hole  106 . The lower follower  206  rides in its dead space along the trailing wall  305  away from the upper surface  308 . When the upper and lower latches  202  and  204  have moved beyond the respective flanges  302  and  304 , they are able to snap back by the force of their respective springs  210  and  208  so that the flanges  302  and  304  are engaged in their recesses  202   a  and  204   a,  as shown in  FIG. 6A . 
         [0055]    By using the second method of mounting the mounting latch to the DIN rail  300 , the mounting latch may be “snap-fitted” to the DIN rail  300 . In both cases the movement of the upper and lower latches  202  and  204  into engagement with the DIN rail  300  is essentially linear and perpendicular to the DIN rail  300 . However, the upper latch  202  and lower latch  204  need not be simultaneously “snap-fitted” to the DIN rail  300  as described, and instead the upper latch  202  may first be fitted to the DIN rail  300 , followed by the lower latch  204 , or vice-versa. Indeed only one of the upper latch  202  or lower latch  204  may be moveable and capable of snap-fitting, and the other may be fixed. Removal of the mounting latch is accomplished by rotating the cam  100  to move the upper latch  202  and lower latch  204  apart. 
         [0056]    The cam  100  and upper and lower latches  202  and  204  can be made of any suitable materials that provide the necessary strength and rigidity. Such materials include injection moulded polymers, die-cast aluminium and zinc alloys, or the components may be machined from steel or brass. 
         [0057]    Thus a simple and efficient mounting latch is disclosed. Advantageously, since the latch may be snap-fitted to a rail, the latch may be easily fitted in situations where there is limited space to operate or there are other devices obstructing easy access. Further, since no tools are required to attach the latch to the rail, quick and easy installation and removal is achieved. Yet further, there is no need to access the rear of an electrical enclosure since the latch may be easily attached to the rail via “snap-fitting” or through use of the protrusion  104  via the top of the enclosure to manually rotate the cam  100 , which requires minimal space to achieve. 
         [0058]    The simplicity of the latch means that further space is saved since few parts are needed to construct the latch, while maintaining the latch to be as small as possible and with the required strength to ensure a secure mounting of devices on a rail. 
         [0059]    Whilst a particular embodiment has been shown in the figures, variants are possible without departing from the inventive concepts described herein. For example, the DIN rail  300  need not be a top hat shaped DIN rail, but may be another rail configuration. In such circumstances, the shapes and positions of the front guiding  102  and rear recess  116  may be adjusted to accommodate the different rail configuration. The protrusion  104  may be any shape such as a handle or tactile surface that enables actuation of the cam  100  by an operator. 
         [0060]    These and/or other physical features of the particular embodiment described herein may be omitted or may be replaced by alternative features which serve the same (or similar) purpose of mounting a device to a rail. 
         [0061]    The relative terms “upper”, “lower”, “front”, “rear”, “outwardly”, “towards”, “away from”, “anticlockwise”, “clockwise”, “top” and “bottom” used herein relate to the orientation of the device as shown in the Figures and are employed to facilitate description of the device. They are not intended to be limiting. The use of clockwise and anticlockwise rotation for opening and closing the mounting latch is not limiting and could be reversed instead. 
         [0062]    The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.