Abstract:
A clamp apparatus for selectively occluding a resilient tube to prevent free flow of fluid in the tube. The device comprises a base member to which the resilient IV tube is attached or through which it passes, and a slide clamp that slides relative to the base member and relative to the tube. The aperture in the slide clamp has a relatively open hole at one end, through which the tube passes when the slide clamp is an open position, allowing fluid to flow through the tube. The aperture also has a relatively constricted slot at the other end, through which the tube passes when the slide clamp is in the occluding position, preventing fluid flow through the tube. A deflectable cantilevered locking arm on the base interlocks with a detent on the slide clamp to lock the slide clamp at the occluding position to avoid inadvertent free flow. A release tab that is used to release the locking arm from the slide clamp is located off center to avoid inadvertent activation. The deflectable arm is unstressed when the slide clamp is in either the occluding or the open positions. A stop device prevents over-stressing the release tab when it is moved. In one embodiment, the clamp apparatus may be slid along the IV tube to a desired location.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 10/892,941, filed Jul. 16, 2004, now U.S. Pat. No. 7,124,996. U.S. application Ser. No. 10/892,941 is incorporated herein by reference. 
    
    
     FIELD OF INVENTION 
     The invention is generally related to clamps used on flexible IV tubing in the field of intravenous (IV) infusion devices such as peristaltic pumps, and more particularly, to clamping devices used to prevent the free flow of fluids through an IV tube when the infusion pump is disengaged from the IV tube. 
     BACKGROUND OF THE INVENTION 
     It is a common practice to deliver fluids such as medications to a patient intravenously by means of a pumping device, such as a peristaltic pump. Such pumps are useful because they can deliver the medication in a highly controlled and precise fashion, and because they do so without coming in contact with the medication. The fluid is moved through a flexible IV tube by pressing a pumping member against the tube sufficiently to move the fluid in the tube downstream towards the patient. In the case of peristaltic mechanisms having multiple pumping fingers, the fingers are moved against the tube in a sequential manner from upstream to downstream to sequentially occlude the tube thereby moving the fluid in the tube downstream towards the patient. When the IV tube is mounted correctly in the pump, the IV tube is at all times occluded by one of the pumping members, thereby preventing the “free flow” of fluid to the patient. “Free flow” of medical fluids is undesirable since the flow of the fluid is uncontrolled and the prescribed treatment is not followed. 
     It is common for the peristaltic pumping mechanism to be located in a housing with a hinged door. The tube through which the fluid is to be moved is placed in contact with the pumping mechanism inside the door, with the ends of the tubing typically extending out the top and bottom of the door opening. As the door is shut over the tube, a platen on the inside of the door presses against the IV tube to provide a backing surface against which the pumping members can occlude the tube. The platen is typically spring loaded, although not always, against the pumping mechanism so that one or more of the pumping fingers of the pumping mechanism occludes the tube once the door is shut over the tube. This then prevents free flow while the door is shut. 
     This arrangement of the IV tube relative to the pumping mechanism requires that there be some means for preventing flow in the tube when the door of the pump is open. Merely opening the pump door would relieve the tube from the occluding pumping mechanism/platen combination and free flow could possibly occur. This could result in the uncontrolled infusion of medication into the patient under the influence of the static head pressure in the tube, or blood from the patient could flow back into the IV tube. Known devices for preventing the unwanted flow in the tube include manual clamps on the tube separate from the infusion pump, and automatic occluding devices mounted on the pump. The manual devices require some manipulation skill on the part of the attending technician, and there is always the chance that the technician will forget to properly time the manual clamping process of the tube before the door of the pump is opened. Furthermore, the door may be accidentally opened, resulting in free flow in the tube. 
     Automatic devices mounted on the infusion pump for assisting in clamping and unclamping infusion tubes have improved. In particular, the reliability in timing the occlusion and release (unocclusion) of the tube with the disengagement and engagement, respectively, of tube with the pumping members has improved. Typically, the action of opening the door is relied upon to initiate the occlusion of the IV tube by a clamp, and the action of closing the door is relied upon to initiate the release or unocclusion of the tube by an IV tube clamp. However, there still can occur the possibility of an inadvertent free flow of fluid through the IV tube due to operator error in regard to use of such devices. 
     Hence, those skilled in the art have identified a continuing need to provide an improved apparatus that will automatically and positively occlude an IV tube before the occluding pumping mechanism is disengaged from the tube. A further need has been recognized for an apparatus that will automatically and positively maintain the IV tube in an occluded state until after the occluding pumping mechanism is engaged with the tube. A still further need has been recognized for an apparatus that will reliably occlude the IV tube, that is inexpensive to manufacture, and is easy to use. Yet a further need has been recognized for an apparatus that can be manually operated between occluding and nonoccluding configurations. The present invention fulfills these needs and others. 
     SUMMARY OF THE INVENTION 
     Briefly and in general terms, the present invention is directed to a clamp apparatus for selectively preventing fluid flow through a resilient tube and comprises a base having a tube aperture at which the resilient tube may be located, the base having a longitudinal center line, a slide clamp slidably mountable on the base for movement between an occluding position and an open position, the slide clamp having a longitudinal center line, a clamp aperture formed in the slide clamp for receiving the tube therethrough, a constricted region formed in the clamp aperture, the constricted region occluding the tube to prevent fluid flow through the tube when the slide clamp is in the occluding position, an open region formed in the clamp aperture, the open region allowing fluid flow through the tube when the slide clamp is in the open position, a locking component formed on the slide clamp, and a flexible cantilevered locking arm mounted on the base, the locking arm having a release tab formed thereon but located at a position offset from the longitudinal center line of the base, the locking arm being biased toward a locking position wherein the locking arm engages the locking component of the slide clamp to prevent movement of the slide clamp from the occluding position to the open position, and the release tab being movable to deflect the locking arm wherein the locking arm is disengaged from the locking component to allow subsequent movement of the slide clamp from the occluding position to the open position. 
     In accordance with another aspect of the invention, the tube aperture of the base slidably receives the resilient tube such that the base may be slid along the tube to a selected position when the slide clamp is in the open position. 
     In other aspects of the invention, the locking arm further comprises a release tab for releasing the flexible arm from the slide clamp, to allow subsequent movement of the slide clamp from the occluding position to the open position. Further, the base comprises a stop surface located at a position adjacent the release tab to interfere with movement of the release tab beyond a preselected range of movement. The slide clamp comprises a detent into which the locking arm is biased and located when the slide clamp is in the occluding position, the detent being large enough to receive the locking arm without contact while the slide clamp is in the occluding position whereby the locking arm is under no stress. The slide clamp further comprises a ramp to receive the locking arm when the slide clamp is in the open position, the ramp formed to be deeper than the arm whereby the arm is not under stress when the slide clamp is in the flow position. The ramp is formed to guide the locking arm into a detent formed in the slide clamp as the slide clamp is being moved from the open position to the occluding position to thereby lock the slide clamp in the occluding position. 
     In yet other aspects, the aperture of the slide clamp is approximately tear-drop shaped, the constricted region comprises an elongated slot portion, the flow region comprises a rounded portion, the tube is located in the slot portion when the slide clamp is in the occluding position, and the tube is located in the round portion when the slide clamp is in the open position. 
     In additional detailed features, the tube aperture comprises a tube sleeve within which a resilient tube end may be permanently mounted. The tube aperture comprises a fluid passageway through the base, whereby the resilient tube is connected in fluid communication with the passageway. Further, the clamp apparatus comprises a pressure interface device located in line with the resilient tube, the pressure interface device having a pressure membrane mounted in a housing, the pressure membrane formed to conduct pressure increases and decreases of the resilient tubing to a pressure sensor located in a medical instrument. 
     In further aspects in accordance with the invention, the slide clamp further comprises a front pushing flange large enough to receive a digit of an operator used to push the clamp apparatus into position in a medical infusion pump, the pushing surface being concave. The release tab of the locking arm is located at a position other than behind the pushing flange. In a much more detailed aspect, the release tab is located at a sideways position in relation to the pushing flange. Additionally, the base comprises a rounded mounting end whereby pressing the clamp into operative position in an infusion pump is facilitated. 
     The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the automatic clamp apparatus in accordance with aspects of the present invention showing the slide clamp in the occlusion position at which it is partially withdrawn from the base; 
         FIG. 2  is a front left-side perspective view of the slide clamp shown in  FIG. 1  showing the aperture, the detent, the ramp, and the pushing flange; 
         FIG. 3  is a bottom right-side perspective view of the slide clamp shown in  FIG. 1  showing the aperture, the pushing flange, and the pulling projections; 
         FIG. 4  is a top plan view of the slide clamp of  FIGS. 1 through 3 ; 
         FIG. 5  is a left side, partially cutaway view of the slide clamp of  FIGS. 1 through 4  showing a pulling projection, the detent, and the ramp; 
         FIG. 6  is a top, left side perspective view of the base showing a locking arm, a release tab, and a tube aperture; 
         FIG. 7  is a bottom, right side perspective view of the base showing the locking arm and release tab; 
         FIG. 8  is a right side plan view of the base showing the release tab; 
         FIG. 9  is a cross-section left side view of the base showing the locking arm and release tab; 
         FIG. 10  is a left side view of the base showing the tube aperture, the release tab, and a portion of the locking arm, also shown in the angle of the locking arm with the upper base surface; 
         FIG. 11  is a bottom view of the base; 
         FIG. 12  is a top, left side perspective view of the automatic clamp apparatus of  FIG. 1  in which the slide clamp has been inserted fully into the base resulting in the flow configuration; 
         FIG. 13  is an operational view in which the tube is occluded by the aperture of the slide clamp, but a release boss and a pushing boss are about to move the slide clamp to the open or flow position; 
         FIG. 14  is an operational view in which the tube is unoccluded for flow and a pulling hook is about to pull the slide clamp to the occluding position; and 
         FIG. 15  is a view of the clamp apparatus having a pressure interface device located as part of the tube upstream from the clamp for communicating the line pressure to a pressure sensor. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to the drawings with more particularity, in which like reference numerals refer to like or corresponding elements among the several views,  FIG. 1  presents an automatic clamp apparatus  20  for intravenous (herein referred to as “IV”) infusion sets used in pump devices. The clamp apparatus  20  comprises generally a relatively open, box shaped base or frame  22  and a mating slide clamp  24 . Both parts can be formed by injection molding from various plastic materials. The solid body of the slide clamp  24  is shaped and sized to slide within the base  22 . In the embodiment shown, the base  22  has a tower  26  formed on the top surface  28  of the base, with the tower extending upwardly from the base and substantially perpendicular to the base. The top end  30  of the tower  26  is formed as a female tube connector into which a resilient IV tube can be attached. A pumping tube or other type of fluid conduit can be attached to the base by other means if desired. The open bottom end  32  of the tower is attached to the base and it is also formed as a female tube connector into which an IV tube or other conduit can be attached. The IV tube and the pumping tube can be the same tube if desired, simply threading the IV tube through the tower, through the base, and through the slide clamp such that the automatic clamp apparatus  20  can be slid along the IV tube to a desired location. 
     Referring now also to  FIG. 2 , the slide clamp  24  is penetrated from its top surface  34  to its bottom surface  36  by an elongated aperture  38 . The elongated dimension of the aperture  38  is arranged on the slide clamp to be parallel to the direction of the relative sliding movement between the base  22  and the slide clamp  24 . The aperture  38  of the slide clamp comprises an open portion  40  and an occluding portion  42 . The open portion is large enough so that a tube received by the open portion would not be occluded whereas the occluding portion is small enough so that it would occlude a received tube. The width of the slot of the occluding portion is sufficiently small that a selected IV tube passing through the slot would be completely occluded and would remain occluded against a foreseeable range of fluid pressures in the IV tube. The range of pressure against which the tube would remain occluded would include at least the static head anticipated during normal use of the infusion apparatus. 
     The slide clamp  24  also includes a pushing flange  44  at its front edge  46 . The pushing flange is somewhat concave, although the “concave” surface may not necessarily be curved; it may in fact have converging straight surfaces or surfaces of other shapes. The purpose of the pushing flange is to guide the digit of an operator to the approximate center of the slide clamp for the purpose of mounting the entire automatic clamp apparatus  20  ( FIG. 1 ) into an infusion pump. Such an operation may be seen by reference to U.S. Pat. No. 6,629,955 to Morris, particularly  FIG. 10 . U.S. Pat. No. 6,629,955 to Morris is incorporated herein by reference. Guiding the digit of an operator to the center of the pushing flange is more likely to result in the application of centerline force on the automatic clamp apparatus and thereby to result in the correct mounting of the clamp apparatus in the pump. For convenience, the shape of the pushing surface of the pushing flange  44  is referred to as “concave” although the surfaces may be other than curved, as discussed above. It will be noted that in this embodiment, the aperture  38  is also located on the longitudinal centerline  47  of the slide clamp. 
     Also shown in  FIG. 2  is a locking detent  48  having a locking detent edge  50 . The particular operation of the detent will be shown later but its purpose is to prevent movement of the slide clamp from the occluding position to the open position in the base without intended action. Further shown is a ramp  52  at the front of the slide clamp for receiving a locking arm of the base when the slide clamp is in the open position. 
     Referring now to the perspective view of  FIG. 3  and the views of  FIGS. 4 and 5 , the bottom surface  36  of the slide clamp  24  includes pulling projections  30  that project downwardly from the bottom surface presenting a substantially vertical pulling face  56  to engage the latch on the door of the pump housing (not shown) to withdraw the slide clamp  24  partially out of engagement with the base  22  before the door is opened. Pulling or withdrawing the slide clamp partially out of the base moves the slide clamp from its open position to its occluding position ( FIG. 1 ). The pushing flange  44  of the slide clamp also presents a substantially vertical pushing face against which the door of the pump or some other device pushes to fully insert the slide clamp into the base when the door of the pump is closing or after it has been closed. Pushing the slide clamp into full insertion with the base moves the slide clamp from its occluding position to its open position. Also shown in  FIGS. 4 and 5  are the detent  48  and the ramp  52 . Both are formed in the material of the slide clamp and the depth of both can be best seen from  FIG. 5 . 
     Turning now to the base, there is shown in  FIG. 6  the base  22  with a flexible cantilevered locking arm  60  that is molded into the top surface  28  of the base, with its distal free end  62  biased downwardly below the top surface  28  of the base. Biasing of the free end downwardly is accomplished by molding the locking arm in a downwardly sloped configuration, but the biasing could also be accomplished by the use of springs or other means. A release tab  64  is formed on the locking arm  60 , projecting upwardly from the locking arm in the general direction of the tower  26 . It will be noted that the release tab  64  is located at a position sideways to the tower  26 . The release tab is also offset from the longitudinal centerline  66  of the base. The free end  62  of the locking arm  60  can be flexed upwardly by pressing the release tab  64  in a direction parallel to the centerline  66 . Without departing from the spirit of the invention, multiple locking arms and tabs offset from the centerline of the base may be used in place of the ones shown. 
     It should also be noted that the depth of the detent  48  and the size and angle of the locking arm  60  are carefully selected so that when the locking arm is located in the detent, it is unstressed. That is, it does not touch the bottom of the detent with any significant force. This is important in that if the locking arm is formed of plastic material or other material that exhibits “creep,” it may change shape if it is exposed to constant stress for an extended period. For example, if the clamp apparatus were stored in the occluding position ( FIG. 1 ) for an extended period where the locking arm was in contact with the bottom of a shallower detent and was under continual stress due to constant contact with the detent, the locking arm may creep to where that storage position is the new at rest position of the locking arm. The locking arm would then become less effective. Thus, forming the detent and locking arm as described above so that the arm is unstressed will result in a clamp apparatus that is unaffected by storage. Similarly, the ramp is also of a depth that leaves the locking arm unstressed when at the lowest point of the ramp, as is the case in the open position shown in  FIG. 12 . 
     The base also includes its side edges  68  formed into rails  70  that lie parallel to the direction of the relative sliding movement of the slide clamp in the base ( FIG. 1 ). When the slide clamp  24  is slidingly engaged with the base  22 , the slide clamp fits in a sliding fashion through the two rail channels  72  in the base. Alignment of the slide clamp with the base is accomplished by the fit of the slide clamp into the rail channels. Turning now to  FIG. 7 , the rails  70  and channels  72  can be seen more clearly. Additionally, it will be noted that the entire proximal end  74  of the base is enclosed. The center section  76  has been left open to accommodate the pulling projections of the slide clamp, as previously shown. Also more clearly seen is the distal free end  62  of the locking arm, as well as the releasing tab  64 . 
       FIG. 8  shows a stop  78  formed on the top surface  28  of the base  22  that limits the range of movement of the release tab  64 . In particular, a stop surface  80  is spaced away from the back of the releasing tab by a preselected distance so that the tab cannot be overstressed by bending it too far. Referring also to  FIG. 9 , a cross-section of the locking arm  60  with releasing tab  64  formed at its end is shown. It will be noted that the locking arm is molded as part of the base and is in a cantilever form. The releasing tab  64  is disposed at approximately ninety degrees to the locking arm but because the locking arm is formed at an angle to the upper  28  and the lower  82  surfaces of the base  22  so as to engage the slide clamp, the ninety degree angle of the releasing tab with the locking arm is other than ninety degrees to the top surface of the base.  FIG. 9  more clearly illustrates the downward slope of the locking arm  60  to create the necessary downward bias to engage the detent  48  and locking edge  50  of the slide clamp to prevent the slide clamp from being moved to its open position until the locking arm  60  is moved out of the detent by intended action of the operator. 
     Referring now to  FIG. 10 , a right side view of the base is provided. It will be seen that the angle of the top surface of the locking arm is approximately 172.86 degrees relative to the top surface  28  of the base. This is also seen in  FIG. 9 . It has been found that thickening the locking arm and providing the angles shown results in repeatable performance. That is, when a releasing boss  90  (shown in  FIG. 13 ) presses against the releasing tab  64 , the tab and locking arm will rise away from the base and therefore away from the mounted slide clamp thus releasing the slide clamp for movement to the open position. This is discussed below in more detail.  FIG. 11  presents a bottom view of the base  22  showing more clearly the distal end  62  of the locking arm that is received by the detent  48  of the slide clamp  24 . Further,  FIG. 11  shows the aperture  49  through the base for the tube. 
       FIG. 12  shows the assembled slide clamp  24  and base  22  into an operational automatic clamp apparatus  20  in accordance with aspects of the invention. Further, the clamp apparatus  20  is in the open position during which fluid may flow through the clamp apparatus. It will be seen that the distal free end  62  of the locking arm  60  resides in the ramp area  52 , but the ramp is formed to be deep enough so that the distal free end  62  of the locking arm is not touching the material of the base and therefore, the locking arm is in an unstressed condition. In this configuration, the clamp apparatus  20  is in its smallest form thereby fitting into a pump with a closed door. 
       FIGS. 13 and 14  show in general how the automatic clamp apparatus  20  in accordance with aspects of the invention interacts with the door of a pump housing.  FIG. 13  shows the slide clamp  24  in its occluding position relative to the base  22 , with the slide clamp partially withdrawn from the base and the distal free end  62  of the locking arm  60  engaging the locking detent  48  (not shown) to hold the slide clamp in its occluding position.  FIG. 14  shows the slide clamp in its open position with the slide clamp fully inserted within the base and the distal free end  62  of the locking arm flexed upwardly a sufficient amount to clear the detent  48 . 
     Operative elements of the door and latch mechanism are shown schematically and designated as elements  90 ,  92 , and  94 , to illustrate their interaction with the automatic clamp apparatus of the present invention. A releasing boss  90  can be formed on the door and positioned to contact the release tab  64  as the door is moved to the closed position, and to press the release tab up and back. A pushing boss  92  can be formed on the latch mechanism and positioned to contact the pushing flange  44  on the slide clamp  24  as the latch is engaged to push the slide clamp from its occluding position ( FIG. 13 ) to its open position ( FIG. 14 ). Finally, one or more pulling hooks  94  can be formed on the latch mechanism and positioned to contact the pulling projections  54  as the latch is disengaged to pull the slide clamp  24  from its open position to its occluding position. 
     The releasing boss  90  and the pushing boss  92  of the door move generally to the right direction as seen in  FIG. 13  when the door of the pump is moved to the closed position. The pulling hook  94  of the latch mechanism can be made to move generally to the left as seen in  FIG. 14  when the latch is being disengaged, and to the right when the latch is being engaged, it being understood that other elements (not shown) of the latch mechanism perform the actual latching of the door in the shut position. In addition, the pulling hook  94  can rotate in the clockwise direction from the position shown, relative to the remainder of the latch mechanism, against a spring bias. For convenience, the conduit through the automatic clamp apparatus  20  is shown as a tube  96  in  FIGS. 13 and 14 . In  FIG. 13 , the tube  96  is occluded by the slide clamp aperture and is spread into the occluding slot of that aperture. In  FIG. 14 , the tube is in the flow configuration. As mentioned above, a tube may or may not be used as the conduit through the clamp apparatus  20 . A tower may be used with parts of tube formed to the tower. 
     Referring briefly to  FIG. 15 , the inclusion of a pressure interface device  100  upstream of the automatic clamp apparatus  20  is shown. This pressure interface device may take the form of a pressure diaphragm  101  having a size and configuration to be mounted to a pressure sensor that is a part of the infusion pump to which the clamp apparatus is to be mounted. Such a pressure diaphragm device is shown in U.S. Pat. No. 4,398,542 to Cunningham, and incorporated herein by reference. A sensor usable with such a pressure diaphragm is shown in U.S. Pat. No. 4,404,440 to Busche, also incorporated herein by reference. Mounting such a pressure diaphragm in line with the automatic clamp apparatus of the invention would restrict movement of the clamp apparatus along the line since it will need to be adjacent the pressure diaphragm to be fitted into the pump. In such a case, the tower  26  may be used as a mount for the pressure diaphragm device. 
     Operation 
     To use the automatic clamp apparatus  20  of the present invention, the slide clamp  24  is assured to be in the occluded position, as shown in  FIG. 1 . Because the locking arm  60  is located in the detent  48 , the slide clamp cannot be moved from the occluding position to the open position unless the release tab  64  is actuated. While in the detent, the locking arm is unstressed. The upstream end of the IV tube  96  is connected to a fluid supply (not shown) of the chosen fluid to be pumped. The administration set containing the automatic clamp apparatus of the invention may be primed if necessary by the operator pressing a digit against the release tab to move it and the locking arm upwards out of the detent and another digit against the pushing flange to move the slide clamp to the open position. As the slide clamp is inserted into the base, the locking arm moves down the ramp  52  to the bottom of the ramp ( FIG. 12 ) where it is unstressed. Priming may now occur. Once primed, the pushing flange is grasped by the operator and withdrawn from the base to restore the slide clamp to the occlusion position as shown in  FIG. 1  so that the free flow of fluid through the IV tube cannot occur. 
     The door of the pump housing is opened and the automatic clamp apparatus  20  and tubing above and below the clamp apparatus  20  are installed into the pump appropriately. The pushing flange is used by the operator to receive a digit of the operator for pushing the clamp apparatus into the appropriate cavity of the pump. The clamp apparatus should remain in the occlusion configuration during this installation into the pump. Because the release tab is off center in relation to the pushing flange, the chances of the operator pressing it instead or with, the pushing flange are greatly reduced. 
     The upstream and downstream tubing is now engaged with any other devices that exist, such as an air-in-line sensor, pressure sensors, etc. Especially, the pumping tube  96  is placed in contact with the pumping mechanism, and the door of the pump is then shut.  FIG. 13  shows the slide clamp  24  in its occluding position, with the release boss  90  about to contact the release tab  64  as the door of the pump is shut. As the door is completely shut, the release boss  90  presses the release tab  64  upward thereby flexing the locking arm  60  upward and out of the detent  48  thereby permitting movement of the slide clamp so that it can be inserted into the base. After the door is completely shut, the latching mechanism is latched, causing the pushing boss  92  to push the slide clamp  24  and insert it into the base to its open position as shown in  FIG. 12 .  FIG. 14  shows the slide clamp  24  in its open position, with the pulling hook  94  having pivoted behind the pulling projection  54 . The pump can then be operated in the conventional fashion to purge the IV tube  96  of air, and the IV tube  96  can be connected to a venous access site. 
     When the pump door is to be opened, the boss  92  and the hook  94  will be moved to the left, causing the pulling hooks  94  to contact the pulling projection  54  of the slide clamp  24  and withdraw the slide clamp  24  from the base to its occluding position. The latching mechanism can be constructed by known means so that only after this occlusion occurs will the door be unlatched. At this time, the door can be opened. The locking arm  60  having engaged the locking detent  48  maintains the slide clamp  24  in its occluding position, even if the slide clamp  24  is pushed toward the base  22  with considerable force. 
     The latching mechanism can also be constructed by known means so that when the door has been unlatched, the latching mechanism can not be moved back to its latched position until the door has been shut. Therefore, if the door is to be shut, the releasing boss  90  will press the release tab  64  upward to release the locking arm  60  from engagement with the detent  48 , and the slide clamp  24  can be subsequently moved to the open position as explained before. 
     While the particular automatic clamp apparatus as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.