Abstract:
The present invention relates to a connector system comprising a plug connector and a retainer configured to be inserted into a corresponding holder. The plug connector comprises a connector housing and a latching arm assigned to the connectorhousing, whereby the plug connector is configured to be mountable with the retainer. The connector system comprises a deflection portion for causing the latching arm to deflect upon mounting of the plug connector with the retainer. The deflection portion is shaped such that the deflection provides increasing resistance against further movement of the plug connector. The connector system further comprises a release portion configured to enable a release deflection of the latching arm. The release portion is shaped so the release deflection does not provide resistance against further movement of the plug connector. Still further, the connector system comprises a latching portion configured to allow the latching arm to lock the plug connector.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a national stage application under 35 U.S.C. §371 of PCT Application Number PCT/EP2012/057412 having an international filing date of Apr. 23, 2012 which designated the United States, which PCT application claimed the benefit of PCT Application Number PCT/IB2011/001219, filed Apr. 22, 2011, the entire disclosure of each of which are hereby incorporated herein by reference. 
     
    
     TECHNICAL FIELD OF THE INVENTION 
       [0002]    The present invention relates to a connector system comprising a plug connector and a retainer, both configured to be connected to a corresponding socket, whereby an electrical connection between the plug connector and the socket can be established only when the connector system is correctly assembled. 
       BACKGROUND OF THE INVENTION 
       [0003]    In many fields of applications it is important that save coupling between connectors and corresponding counter connectors can be guaranteed. In particular in the case of automotive safety restraint systems as for example airbag systems in passenger vehicles, plug connectors used for the connection of an airbag to its ignition base, i.e. to a squib socket, have to be provided with reliable safety systems. Typically, to this end these plug connectors are provided with connector position assurance (CPA) members which can be inserted into a locked position on the plug connector only if the plug connector is appropriately connected to the airbag squib socket. In this position, the CPA member provides additional security for the mated state of plug connector and squib socket, and typically the CPA member is constructed such that an operator can visibly detect if the CPA member is inserted correctly into its locked position. Thus, thereby a correct and safe mating between the connector and the counter connector can be guaranteed. 
         [0004]    An example of a plug connector provided with a CPA member is disclosed in document EP 1207591 A2. Therein, a plug connector is described which can be connected to a squib socket of an airbag connector system. In assembled condition, when the plug connector is inserted into the airbag squib socket, the plug connector is fixed inside the socket by means of flexible latching arms. During insertion of the plug connector into the socket, these arms bend inwardly until locking projections provided on the latching arms snap into corresponding latching recesses of the airbag squib socket. 
         [0005]    In order to further secure the mating of the plug connector with the airbag squib socket a CPA member is provided. When the plug connector is inserted into the airbag squib socket and the locking projections are snapped into the latching recesses, the CPA member can be inserted into a housing of the plug connector. The CPA member comprises locking arms which upon insertion move into slots in between faces of the plug connector housing and the latching arms. Once these locking arms are inserted into the slots, bending of the latching arms is blocked and thus the latching arms are fixed inside of the recesses and the mating of plug connector and airbag squib socket is secured. According to EP &#39;591, only when the connectors are correctly mated, the CPA member can be moved into the locked position in which it secures the mated state of the connectors. This can be visibly detected by an operator and thus it is possible to guarantee the correctly mated state of the connectors. 
         [0006]    Even though the solution as proposed in the EP &#39;591 works satisfactory, for certain applications the use of a CPA member is undesirable for example because of space limitations. An example of a plug for the connection to a squib socket without a CPA member is disclosed in document DE 20216337 U1. The plug connector disclosed therein is an example of a so called “scoop-proof” plug connector which is provided with a connection tube surrounding electrical contacts of the plug connector. This connection tube is designed such that upon mating of the plug connector to a squib socket, contact terminals of the plug connector can be connected only correctly to corresponding contact pins of the airbag squib socket. In the case that the plug connector is not correctly inserted into the airbag squib socket, the connection tube abuts the airbag squib socket such that false connection of the contact terminals to the contact pins is prevented. 
         [0007]    To mechanically connect the plug connector to a squib socket, the plug connector is provided with latching arms which are attached to the connection tube such that upon insertion of the plug connector into the socket, the latching arms bend inwardly and upon full insertion of the plug connector into the airbag squib socket, locking projections provided on the latching arms snap into corresponding latching recesses of the airbag squib socket. 
         [0008]    A further example of a plug connector to be connected to a squib socket without a CPA member is disclosed in document EP 2230731 A1. Therein, similar to the above described example, a “scoop-proof plug connector is described whereby this plug connector can be connected to a corresponding squib socket by means of latching arms which are mounted to flexible portions provided on a connection tube of the plug connector. Due to the flexibility of the latching arms, upon insertion of the plug connector into the airbag squib socket, the locking arms bend inwardly and upon full insertion of the plug connector, locking projections provided on the latching arms snap into recesses of the socket to lock the plug connector to the airbag squib socket. 
         [0009]    The latching arms of the EP &#39;731 are further provided with release members which, in mated condition of the plug connector with the airbag squib socket, can be actuated by an operator, i.e. they can be pressed inwardly to release the locking projections from the locking recesses. Thereby, the plug connector is free to be removed from the socket. Even though the latter two plug connectors are provided with reliable locking mechanisms and can be connected to squib sockets without CPA members, both plug connectors lack the possibility to visibly detect the mated state of the plug connectors to squib sockets. 
         [0010]    The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may also be inventions. 
       BRIEF SUMMARY OF THE INVENTION 
       [0011]    A connector system is provided which comprises a plug connector and a retainer which is configured to be inserted into a corresponding socket. The plug connector comprises a connector housing and at least one latching arm assigned to the connector housing, whereby the plug connector is configured to be mountable with the retainer. For example, the latching arm can be mounted to the connector housing or can be formed as an integral part of the connector housing. 
         [0012]    As it will be clear for the person skilled in the art, the retainer can be mountable inside of the socket and can be provided with shorting means, as e.g. a shorting clip, to short-circuit electrical connection pins of the socket. The plug connector can be provided with means for deactivating the short circuit upon inserting the plug connector into the socket. In one embodiment, the retainer also serves as a mechanical connection member between the plug connector and the socket, i.e. the plug connector is mechanically coupled to the socket via the retainer. Thereby, advantageously locking elements of the plug connector such as the latching arm are not constrained in dimension or function by dimension and design of the socket which, as it is known to the person skilled in the art, usually is a predefined component. In one embodiment, the connector system is not provided with locking elements for direct mechanical coupling of the plug connector to the socket. 
         [0013]    The connector system comprises at least one deflection portion for causing a deflection of the latching arm upon mounting of the plug connector with the retainer, whereby the deflection portion is shaped such that the deflection provides increasing resistance against further movement of the plug connector into the retainer. In one embodiment, the latching arm is provided with an inwardly directed latching projection which is configured to engage the deflection portion upon mounting of the plug connector with the retainer such that the latching arm is deflected outwardly in a direction essentially perpendicular to the mounting direction. For example, due to the deflection of the latching arm by the deflection portion, the latching arm can be biased against the deflection portion. Upon further movement of the plug connector towards the socket, the deflection increases, thereby also increasing the bias of the latching arm and thus providing increasing resistance against further movements of the plug connector. 
         [0014]    The connector system comprises at least one release portion configured to enable a release deflection of the latching arm whereby the release portion is shaped such that the release deflection does not provide resistance against further movement of the plug connector. For example, the release portion can be shaped such that if the latching arm is biased against the release portion and the plug connector is moved towards the socket, the latching arm is deflected such that the bias decreases. Thus, no force has to be applied for deflecting the latching arm and thereby no resistance is provided against further movement of the plug connector. 
         [0015]    The connector system comprises at least one latching portion configured to allow latching of the latching arm for locking of the plug connector. For example, upon full insertion of the plug connector into the socket, the latching arm can latch behind a stop surface of the connector system to lock the plug connector in the fully inserted position to the socket. The deflection portion, the release portion and the latching portion can be provided all on the retainer or all on the latching arm. Alternatively, one or two of these portions can be provided on the retainer while the other one or two of these portions can be provided on the latching arm. The deflection portion, the release portion and the latching portion are all provided on the retainer. 
         [0016]    The deflection portion and the release portion may be arranged such that upon mounting of the plug connector with the retainer the resistance provided by the deflection of a latching arm reaches a threshold value before the release deflection of the latching arm is enabled. For example, the deflection portion and the release portion can be arranged such that the latching arm engages the deflection portion before it can engage the release portion. Upon engagement of the latching arm with the deflection portion and movement of the plug connector towards the socket the latching arms can be deflected outwardly. 
         [0017]    Thereby, due to increasing deflection of the latching arms upon movement of the plug connector, the latching arms are increasingly biased or pressed against the deflection portion due to an increasing spring force of the latching arms. Thus, the resistance against further movement, i.e. the insertion force increases, up to a threshold value. In one embodiment, the threshold value corresponds to a magnitude of insertion force within the range of 1 Newton to 100 Newtons (N), preferably within the range of 10 N to 90 N, more preferably within the range of 20 N to 80 N, even more preferably within the range of 30 N to 70 N, yet even more preferably within the range of 30 N to 60 N, and most preferably within the range of 35 N to 45 N. 
         [0018]    The deflection portion, the release portion and the latching portion may be provided integrally on a so called Go/No Go member, whereby the release portion is disposed in between the deflection portion and the latching portion. A resulting Go/No Go mechanism can be as follows. Upon insertion of the plug connector into the socket, the latching arm of the plug connector engages the deflection portion. Upon further movement of the plug connector in insertion direction, the resistance against further movement increases due to increasing deflection of the latching arm. After the resistance has reached a threshold value, the latching arm comes into engagement with the release portion. From there on, no resistance is provided against further movement of the plug connector in insertion direction and when the plug connector is fully inserted and the latching arm has passed the release portion, the latching arm latches to the latching portion, i.e. for example a latching projection of the latching arm latches behind a stop surface of the latching portion, such that the plug connector is locked in its fully inserted position. 
         [0019]    This mechanism is referred to as a Go/No Go mechanism because, in the case that the plug connector is inserted into the socket by a human operator with not enough force, the plug connector is not inserted. In the other case, when the operator presses with enough force to overcome the resistance, due to a relatively large resulting pressing momentum, the operator cannot stop leaving the plug connector inserted only half-way, but will automatically press the plug connector into its fully inserted position. 
         [0020]    In an alternative embodiment according to the invention, a connector system comprising a plug connector and a retainer is provided, whereby the retainer is configured to be inserted into a corresponding socket. The plug connector comprises a connectorhousing and at least one latching arm which is assigned to the connector housing. The plug connector is configured to be mountable with the retainer. The latching arm comprises an inwardly directed latching projection which is configured to be latched against a latching portion of the retainer when the plug connector is mounted with the retainer to lock the plug connector to the retainer. Thereby, advantageously the plug connector is locked to the retainer which in one embodiment is provided with coupling members to mechanically couple the retainer to the socket. Thus, in assembled condition of the connector system the plug connector is mechanically connected to the socket via the interaction of latching projection of the latching arm with the retainer. 
         [0021]    In a further alternative embodiment, a connector system is provided which comprises a plug connector and a retainer whereby the retainer is configured to be inserted into a corresponding socket. The plug connector comprises a connector housing and at least one latching arm assigned to the connector housing and the plug connector is configured to be mountable with the retainer. The latching arm comprises a latching section configured to mechanically connect to a latching portion of the retainer and a release member configured to be actuated to release the latching section from the latching portion. The latching arm is pivotably connected to the connector housing via a pivot member disposed between the latching section and the release member such that upon actuation of the release member, the latching section is released from the latching portion. 
         [0022]    The plug connector may comprise at least one contact element configured to electrically contact a contact member of the socket when a plug connector is mounted to the retainer and the retainer is mounted to the socket. Thereby, when the retainer is mounted to the socket, upon mounting of the plug connector to the retainer the electrical contact element does not come into electrical contact with the contact member when the plug connector is in a position in which the latching arm is deflected by the deflection portion. 
         [0023]    Thereby, if for example the deflection portion is a first part of a Go/No Go member as described above, it is assured that the electrical connection between plug connector and socket can only be established after the plug connector is moved past this first, blocking portion of said Go/No Go mechanism. Thus, the electrical and mechanical coupling of plug connector and socket can only be achieved at the same time. Further, while the latching arm is deflected by the deflection portion, for example when the plug connector is positioned in the first, blocking position of the Go/No Go mechanism, an operator can visibly detect that the plug connector is not yet correctly coupled to the socket. Thus, the above described Go/No Go mechanism can provide a visible detection means such that an operator can guarantee the correctly mated state of plug connector and socket when the plug connector is fully inserted into the assembled airbag connector system. Further, it is also possible to detect the mated state of the plug connector and socket electrically, because as described above electrical and mechanical connection of the plug connector in the connector system can only be achieved at the same time. 
         [0024]    It is to be noted that embodiments may include an airbag connector system in which the retainer is an “airbag squib” retainer and the socket is a so called “airbag squib” socket. 
         [0025]    Further features and advantages of the invention will appear more clearly on a reading of the following detailed description of the preferred embodiment of the invention, which is given by way of non-limiting example only and with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0026]    The present invention will now be described, by way of example with reference to the accompanying drawings, in which: 
           [0027]      FIG. 1  shows a schematic illustration of a plug connector to be used in connection with an airbag connector system; 
           [0028]      FIG. 2  shows the plug connector of  FIG. 1  from a different perspective; 
           [0029]      FIG. 3  shows an exploded illustration of the parts of the plug connector of  FIGS. 1 and 2 ; 
           [0030]      FIG. 4  shows a retainer configured to be used in connection with an airbag connector system; 
           [0031]      FIG. 5  shows the retainer of  FIG. 4  from a different perspective; 
           [0032]      FIG. 6  shows the retainer of  FIGS. 4 and 5  mounted to an socket; 
           [0033]      FIGS. 7A to 7C  show cross-sectional views of a plug connector and an retainer inserted into an socket, whereby the mounting process of the plug connector is illustrated; 
           [0034]      FIG. 8  shows a cut through an connector system with the plug connector partially mounted; and 
           [0035]      FIG. 9  shows a diagram illustrating the insertion force of the plug connector as a function of plug connector position with respect to the socket. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0036]      FIG. 1  shows a plug connector  100  to be used in connection with an airbag connector system. The plug connector  100  is provided with a connector housing  101  which is closed by a lid  104 . The connector housing  101  is provided with a connection tube  160  with a safety ring  161 . The plug connector  100  is further provided with two latching arms  102  which are formed integrally with the connection tube  160 . Latching sections  130  of the latching arms  102 , which are provided with inwardly directed latching projections  131  (see also  FIG. 2 ), are cut out of the connection tube  160 . The latching arms  102  are connected to the connection tube  160  via flexible portions (connection bridges)  141  which are parts of intermediate portions of the latching arms  102 . Further, the latching arms  102  are provided with release members  150  which can be pressed inwardly towards the connector housing  101  such that the latching arms  102  can be pivoted around pivot members  140 , i.e. around said intermediate portions in between the flexible portions  141 . 
         [0037]    As illustrated in  FIG. 2 , the connection tube  160  surrounds two contact terminals  121  which are received within isolation tubes  122  connected to the connector housing  101 . As it will be clear to the person skilled in the art, the plug connector  100  is a “scoop-proof” plug connector, i.e. if the plug connector  100  is inserted incorrectly into a corresponding squib socket  300  (shown in  FIGS. 4 to 6 ), for example at a false angle, the safety ring  161  will abut a portion of the socket  300  such that further insertion and in particular damage to the contact pins  221  is prevented. Thus, the contact terminals  121  can only come into contact for example with corresponding contact members, i.e. contact pins  221  of the socket  300  if the plug connector  100  is correctly oriented to be inserted. Herein, it is referred to (female) contact terminals  121  of the plug connector  100  and contact pins  221  of the socket  300 . However, as it will be obvious for the person skilled the art, that alternatively the plug connector can be provided with contact pins while the socket can be provided with contact terminals. 
         [0038]      FIG. 3  shows an exploded view of the parts of the plug connector  100 , whereby the lid  104  has been disconnected from the connector housing  101  such that the interior components become visible. As one may derive from  FIG. 3 , in assembled condition, latching tongues  106  which are provided on either side of the lid  104  (only two are visible due to the perspective) latch behind corresponding latching faces  108  to lock the lid  104  to the connector housing  101 . In between the lid  104  and the connector housing  101 , one can see electrical contact elements of the plug connector  100 , i.e. contact terminals  121  which are in electrical connection with cables  127  which in assembled condition of the connector system serve for example to connect the socket  300  to airbag control electronics. In between the cables  127  and the contact terminals  121  a ferrite element is shown. 
         [0039]      FIGS. 4 to 6  show a retainer  200 . The retainer  200  is configured to be inserted into a socket  300  and is therefore provided with coupling elements  231 , i.e. stop latches  231 , for locking the retainer  200  inside of a socket  300  as shown in  FIG. 6 . The retainer  200  is provided with an 8-shaped opening  221  which in assembled condition of retainer  200  and socket  300  surrounds contact pins  221  of the socket  300  (see  FIG. 6 ) and which upon mounting of the plug connector  100  to the retainer  200  insider the socket  300  can receive the isolation tubes  122  of the connector housing  101  (shown in  FIG. 2 ). 
         [0040]      FIGS. 7A to 7C  illustrate the insertion process of the plug connector  100  into the socket  300 . As illustrated in these three figures, the retainer  200  is shown fully inserted in the socket  300  surrounding two contact pins  321  of the socket  300 . For illustrative purposes, the contact terminals  121  of the plug connector  100  are not shown in the figures such that only the inside of the isolation tubes  122  is visible. 
         [0041]    When the plug connector  100  is positioned as shown in  FIG. 7A , angled surfaces  132  which are provided on latching projections  131  of the latching arms  102  abut deflection portions  202  of the retainer  200 . The deflection portion  202  is shaped such that upon further insertion of the plug connector  100  in insertion direction  401  into the socket  300  the deflection portions  202  deflect the latching arms  102  outwardly. As it will be clear for the person skilled in the art, due to the deflection, the angled surfaces  133  are biased against the deflection portion  202  whereby upon further movement of the plug connector  100  in insertion direction  401 , the deflection and thus the bias increases. More force is required to deflect the latching arms  102  further outwardly such that due to the deflection of the latching arms  102  and the bias of the angled surfaces  133  against the deflection portions  202 , increasing resistance is provided against further movement of the plug connector  100  in insertion direction  401 . 
         [0042]    As illustrated in  FIGS. 7A-7C , the deflection portion  202  is formed on a protruding portion  201 , i.e. a Go/No Go member  201 , next to a release portion  204 . Thereby, the Go/No Go member  201  is shaped such that after the latching arm  102  has reached maximum deflection and the resistance has reached a threshold value, upon further movement of the plug connector  100  in insertion direction  401 , the latching projections  131  abut the release portion  204  (see  FIG. 7B ). In other words, when the latching projection  131  of the latching arm  102  is positioned just in between the deflection portion  202  and the release portion  204 , the deflection of the latching arm  202  is at its maximum such that the bias of the latching arm  102  is maximal. Thereby, the resistance provided by the deflection of the latching arm  102  reaches a threshold value just before the latching arm  102  abuts the release portion  204 . 
         [0043]    The threshold value may correspond to an insertion force within the range of 1 N to 100 N, preferably within the range of 10 N to 90 N, more preferably within the range of 20 N to 80 N, even more preferably within the range of 30 N to 70 N, yet even more preferably within the range of 30 N to 60 N, and most preferably within the range of 35 N to 45 N. 
         [0044]    As shown in  FIG. 7B , if the plug connector  100  is pressed in insertion direction  401  with a force exceeding the insertion force required to overcome the resistance, the latching projection  131  can be moved passed the deflection portion  202  such that the latching projection  131  comes into contact with the release portion  204 . As one may derive from the figure, because the latching arms  102  are still deflected outwardly, they are biased against the release portions  204 . Upon further movement of the plug connector  100  in insertion direction  401 , due to the shape of the release portion  204 , the latching arms  102  are free to bend inwardly. Due to an intrinsic tension of the latching arms  102  caused by the outward deflection by the deflection portion  202 , the following inward deflection of the latching arms  102  follows automatically. Therefore, no extra force has to be applied and, in other words this deflection, i.e. the release deflection, does not provide any resistance against further movement of the plug connector  100  in insertion direction  401 . As one may derive from  FIG. 7C , upon full insertion of the plug connector  100  into the squib socket  300 , the latching projections  131  snap inwardly behind latching portions  206  of the squib retainer  200  to lock the plug connector  100  to the retainer  200 . Since the retainer  200  is provided with coupling members  231  (see  FIGS. 4 and 5 ) to mechanically couple the retainer  200  to the socket  300 , in assembled condition of the airbag connector as shown in  FIG. 7C , the plug connector  100  is mechanically connected to the socket  300  only via the retainer  200 . 
         [0045]    As illustrated in  FIGS. 7A to 7C , the deflection portion  202 , the release portion  204  and the latching portions  206  are provided integrally on a go/no-go member  201 , whereby the release portion  204  is disposed in between the deflection portion  202  and the latching portion  206 . As described above, the go/no-go member  201  provides a go/no-go mechanism for the plug connector  100  upon movement of the plug connector  100  into the socket  300 . If the plug connector  100  is placed in an initial position as shown in  FIG. 7A  and pressed from there into the socket  300  with an insertion force not exceeding the required threshold value, the plug connector  100  cannot be inserted into the socket  300 . As shown in  FIG. 7A , because the retainer  200  extends out of the socket  300  such that the angled surfaces  133  of the latching projections  131  abut the deflection portions  202  before the plug connector  100  is inserted into the socket  300 , in the initial position of the plug connector  100 , an electrical connection between contact pins  321  of the socket  300  and contact terminals  121  (not shown) cannot be not established. 
         [0046]    In the case that the insertion force exceeds the threshold value, the plug connector  100  can be moved into the socket  300 . Preferably, the force required to exceed the threshold value for insertion is so large such that if an operator pushes with this force, the plug connector  100  is directly pushed into its final position in which the latching projections  131  abut the latching portions  206  as shown in  FIG. 7C . 
         [0047]    As it will be clear to the person skilled in the art, to provide the above-described go/no-go mechanism, the dimensions of the go/no-go member  201  have to be chosen appropriately. As one can see in  FIG. 7C , to this end, the deflection portion  202  has a length Ld and the release portion  204  has a length Lr, whereby both lengths are measured parallel to the insertion direction  401  of the plug connector  100  and whereby Ld is shorter than Lr. The ratio Ld/Lr may be within the range of 0.05 to 0.8, more preferably within the range of 0.1 to 0.75, even more preferably within the range of 0.15 to 0.5 and most preferably within the range of 0.2 to 0.3. 
         [0048]    As illustrated in  FIG. 8 , the release members  150  of the latching arm  102  can be actuated by an operator, i.e. the release members  150  of the latching arms  102  can be pressed inwardly towards the connector housing  101 , whereby, as one can see in this FIG., the latching section, i.e. the latching projection  131  is released from the latching portion  206  by pivoting the latching arm  102  around the pivot member  201  (the flexible portions as visible in  FIG. 1 ). If the release members  150  are actuated as shown in  FIG. 8 , the plug connector  100  is free to be removed out of the socket  300 . 
         [0049]      FIG. 9  shows a diagram illustrating the insertion force necessary for moving a plug connector  100  in insertion direction  401  into a socket  300  as a function of the plug connector  100  position with respect to socket  300 . 
         [0050]    As can be derived from  FIG. 9  A, the latching projections  131  come into contact with deflection portions  202  before the plug connector  100  can be inserted into the socket  300 . Thus, before the contact terminals (not shown) of the plug connector  100  can come into electrical contact with contact pins  321  of the socket  300 , the insertion force increases linearly until a threshold value of 40 N is reached. Only if the insertion force exceeds this threshold value, the plug connector  100  can be inserted fully into the socket  300  such that the contact terminals  121  can come into full contact with contact pins  321 . The diagram thus illustrates the go/no go mechanism as it is described above. 
         [0051]    While this invention has been described in terms of the preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow. Moreover, the use of the terms first, second, etc. does not denote any order of importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items.