Abstract:
An injection device has a housing ( 112,116 ) wherein there is a longitudinally movable expressing member ( 186 ) for expressing an injection fluid from a fluid container ( 118 ). In order to displace the expressing member ( 186 ) longitudinally within the housing, an actuating member ( 170, 172 ) is associated therewith. The actuating member is displaceable between a proximal end position and a distal end position. Between the actuating member ( 170, 172 ) and the expressing member ( 186 ), a position-dependent connecting device ( 166″, 167″, 198, 210, 212 ) is provided, which is disabled in the distal end position of the actuating member ( 170, 172 ) and is enabled in a position range adjacent to the distal end position of the actuating member ( 170, 172 ) including its proximal end position. One thus obtains an injection device which is simple to operate, and which is especially adapted to permit a patient to repeatedly administer the same constant injection dose.

Description:
This application is a continuation of allowed application Ser. No. 09/000,596, filed Dec. 30, 1997 now U.S. Pat. No. 6,048,336. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to devices for self-injection of medication and, more particularly, to a device having a housing and a longitudinally movable piston rod disposed in the housing for expression of an injectable fluid from a fluid container. 
     BACKGROUND 
     Such injection devices are used primarily by older diabetics, who often no longer see well and who can be overwhelmed by manipulation of complex devices. Therefore, the devices must be simple and as foolproof to operate as possible, so that the correct dose is always injected. 
     SUMMARY OF THE INVENTION 
     Therefore, it is an object of the invention to provide a new injection device, of the aforementioned type, which operates simply and reliably. 
     Briefly, this is achieved by providing in the device an expressing member, an actuating member, and a position-dependent connecting device which couples the actuating member to the expressing member to expel fluid from a container through the injection needle. Through the activation and deactivation of the connecting device in dependence upon the axial position of the actuating member relative to the housing, such a device becomes very simple to operate, substantially eliminating faulty operation. 
     A particularly advantageous embodiment of the invention is to bias the expressing member in the proximal direction by a force which is less than the detachment force of the plunger in the fluid container. This assures that, prior to the start of an injection, the expressing member rests reliably against the plunger of the fluid container and therefore, the full selected dose is always injected. Also, for constant dosing, it is necessary to select the injection quantity only once, and this selection will also be effective for all subsequent injections. 
     Further details and advantageous refinements of the invention will be apparent from the following description and accompanying drawings of several embodiments, which are to be understood as exemplary, and not as limiting the invention. 
    
    
     BRIEF FIGURE DESCRIPTION 
     FIG. 1 shows an embodiment of the injection device of the present invention, approximately actual size; 
     FIG. 2 is an enlarged view of detail A of FIG. 1; 
     FIG. 3 is a view analogous to FIG. 1, but enlarged and in longitudinal section; 
     FIG. 4 is an enlarged view of detail B of FIG. 3; 
     FIG. 5 is a view analogous to FIGS. 1 &amp; 3, in which the proximal portion is shown in longitudinal section; 
     FIG. 6 is an enlarged view of detail C of FIG. 5; 
     FIG. 7 is a view corresponding to FIG. 4, showing the injection device after conclusion of an injection; 
     FIG. 8 shows the beginning of preparation for a subsequent injection; 
     FIG. 9 shows the further progress of such preparation; 
     FIG. 10 shows the conclusion of preparation for an injection; the device is now ready for injection of the selected dose; 
     FIG. 11 shows the beginning of an injection, which occurs manually (force K′); 
     FIG. 12 shows the conclusion of an injection; 
     FIG. 13 is a longitudinal section through an injection device of the invention in an injection-ready configuration; 
     FIG. 14 is an enlarged view of detail D of FIG. 13; 
     FIG. 15 is a longitudinal section through a portion of the housing of the injection device, including a rotatably mounted element in the housing for receiving a container with injectable fluid; 
     FIG. 16 is a longitudinal section through the expressing member and the actuating member; 
     FIG. 17 is a section along line XVII—XVII of FIG. 15; 
     FIG. 18 is a section along line XVIII—XVIII of FIG. 16; 
     FIG. 19 is a view explaining a preferred further development of the invention; 
     FIG. 20 is a view of the elements for dose-setting and dose-indication, specifically showing a “zero” dose selected; 
     FIG. 21 is a view analogous to FIG. 20, but showing the maximum dose which can be selected. 
    
    
     DETAILED DESCRIPTION 
     In the following description, the expressions “proximal” and “distal” are used in the manner conventional in medicine, i.e. “proximal” meaning adjacent to the patient (the side of the injection device with the needle) and “distal” meaning remote from the patient. 
     As FIG. 15 shows, the housing of the injection device  110  shown in FIG. 1 has a distal section  112  in the form of a tube of a suitable plastic and, at its proximal end, a similar tubular section  116  is rotatably connected by means of a bearing  114 . Section  116  serves to receive a container  118  (FIGS. 3-4) with fluid to be injected, and therefore is provided at its proximal end with a shoulder  120  (FIG. 15) and a short cylindrical section  122  of smaller diameter, which in turn has, at its proximal end, a shoulder  124  penetrated by a central opening  126 . Cylindrical section  122  can be provided on its outer surface with a thread for fastening of a canula or needle carrier  148 , as shown, for example in FIG. 6 or  13  together with a canula (injection needle)  146 . In the unused state, as shown in FIG. 1, over the proximal end of tubular section  116 , there is a protective cap  217  which serves as a sterile cover for this section and protects against soiling. The bearing  114  has, as shown in FIG. 4, an annular groove  130  at the proximal end of housing part  112 , into which a complementary ridge  132  of housing section  116  clips, so that this bearing  114  serves as an axial and radial bearing. For clipping in, adjacent to annular groove  130  is a section  136  of enlarged inner diameter which widens in the proximal direction. 
     The container  118  is a so-called “cartridge” which can contain, for example, 1.5 ml or 3 ml of injectable fluid, e.g. growth hormone or insulin. It consists usually of glass, and has at its distal end a plunger  140  which can have, e.g. the form shown in FIG. 14 with multiple circumferential ribs  142   a ,  142   b  which rest with pre-tensioning against the inner surface of container  118 , i.e. with corresponding friction. In order to displace plunger  140  relative to container  118 , a specific minimal force is required. Only when the force on plunger  140  exceeds this value, does the plunger  140  move relative to container  118 . 
     Container  118  has, on its proximal side, a narrowed neck  118 ′ (see FIG. 3) on which is fastened a thin rubber membrane (not shown) in the usual manner by means of a metal cap  144 . The injection needle  146  shown in FIG. 13 is secured on a needle carrier  148  which can be stuck onto or screwed onto the cylindrical section  122  (FIGS.  6  &amp;  15 ). Needle  146  has a distal end  146 ′ (FIG. 6) which sticks through the above-described rubber membrane (in cap  144 ), so that liquid from container  118  can be pressed outward through needle  146  whenever plunger  140  in FIG. 13 is moved in the proximal direction (i.e. downward in FIG.  13 ). Such cartridges  118  and needles  146  are mass-produced and are familiar to those knowledgeable in this field. 
     As shown, e.g. in FIG. 13, the proximal housing section  116 , along with the container  118  held therein, can be rotated relative to the distal housing section  112 . This rotation serves for selection of an injection dose, e.g. of 4 insulin units, and this dose, once selected, remains unchanged for the subsequent injections, insofar as it is not newly set by the patient, his doctor, or his nurse. Thus, this dose is usually set only once and if, for example, four units was set once, during all subsequent injections—without new setting—a dose of four units is injected until cartridge  118  is empty. 
     For purposes of dose setting, the proximal housing section  116  has a distal section  117  which extends into distal housing section  112  and has on its outer surface an external thread  150 ; see FIG.  15 . The form of this thread is apparent in FIGS. 20 &amp; 21. It is in engagement with a complementary internal thread  158  (FIG. 14) of a threaded sleeve  154 , serving as a dosing element, which is guided in an axially movable manner in longitudinal grooves  156  (FIG. 17) of housing section  112 , i.e. it cannot rotate relative to the latter. 
     If the proximal housing section  116  is rotated relative to the distal housing section  112 , the dosing element  154  is moved axially relative to housing section  112 . The position of dosing element  154  relative to housing section  112  thus determines the preselectable injection dose which can be adjusted to, for example, between 2 and 60 insulin units. This is explained below in greater detail, with reference to FIGS. 20 &amp; 21. 
     In the region of the distal end, the cylindrical inner side of dosing element  154  expands to define a groove  160  which, in the distal direction, is limited by a stop  162  (FIG. 14) in the form of an annular shoulder, and is limited in the proximal direction by a profiled shoulder  164 , which can have in section the form of a circle segment, or generally: an inclined cam surface. 
     In practice, the groove  160  is not continuous, but rather has peripheral interruptions, in order to make manufacture as an injection-molded part easier. The groove  160  and the stop  162  are needed for interaction with one of the below-described clamping jaws  166  to  169 . 
     In the configuration shown in FIGS. 13 or  14 , which represents the injection device  110  prior to an injection, there rest, in this groove  160 , the proximal ends of four circumferentially equally spaced clamping jaws  166 ,  167 ,  168 ,  169  of an actuating element  170 , whose form is best apparent from FIGS. 16 and 18. These clamping jaws are integrally formed with an actuating head  172 . They are guided through corresponding openings  174 ,  176  of an annular part  178  which forms the distal terminus of housing section  112  and are connected to the latter by, e.g. a snap-fit (see FIG.  2 ). In the various longitudinal sections, only the clamping jaws  166 ,  167  are shown. Their proximal ends are designated there by  166 ′,  167 ′. Clamping jaws  166  to  169  are guided in housing section  112  in the axial direction, e.g. in the longitudinal grooves  156 . 
     It is to be noted that it is not necessary to provide four clamping jaws  166  to  169 ; for example, one could equally provide three clamping jaws (not shown), displaced by 120 degrees from each other. Naturally, one would need, complementary to this, an expressing member  186  with only three racks or teeth rows  200 , of which one would cooperate with each of the three clamping jaws. Preferably the forces, which the clamping jaws exert on the expressing member  186 , should substantially cancel each other; i.e. if, for example, only two clamping jaws are used, these should be located opposite each other. Obviously, within the scope of the present invention, even the use of only one clamping jaw is not excluded. 
     Annular part  178  has on its inner side, as shown in FIG. 16, a guiding tube  180  formed with radial openings (see FIG.  18 ). The proximal end of tube  180  is shown in FIG. 16 at position  182 . It has on its inner side four longitudinal grooves  181  and these serve for axial guidance of radial projections  183  of an essentially cylindrical hollow expressing member  186 , in whose inner cylindrical cavity  187  is a compressed spring  190 . The expressing member  186  might thus also be called a piston rod. 
     The compressed spring  190  is supported at its proximal end against a proximal floor portion  188  of expressing element  186  and, at its distal end, against annular part  178 . This spring  190  has a weak bias. Its function is not, as one might perhaps believe, the support of the injection process; rather, it serves for following of the expressing element  186 , so that this will always rest, as shown in FIG. 10, against plunger  140 , whenever the clamping jaws  166  to  169  are not in engagement with the expressing element  186 . 
     As a comparison of FIGS. 7 &amp; 12 shows, after every injection, the plunger  140  moves further in the proximal direction, and the expressing member (piston rod)  186  must, in every position, abut with its base  188  against plunger  140  without, however, moving it, i.e. with a force whose value is less than that of a required detachment force (e.g. 2-2.5 N) of plunger  140 . This means that spring  190 , in its maximally compressed position, i.e. full cartridge  118 , may not generate any force greater than this detachment force, and the force is advantageously smaller and in this example is maximally about 1.5 N. In other words, one could say that base  188  of the expressing member (piston rod)  186  rests with gentle pressure against plunger  140 , without however being able to move it. Spring  190  thus has only a follower function and is very weak, with a low spring or elasticity constant. 
     As shown, for example in FIGS. 7 &amp; 14, expressing member (piston rod)  186  has, on its outside, indentations  198  at preferably equidistant intervals, here in the form of toothing  200 . The proximal ends  166 ′,  167 ′ of clamp jaws  166 ,  167  have projections  166 ″,  167 ″ (FIG. 14) which are formed complementary to the indentations  198 . The same applies, fully analogously, to the clamp jaws  168 ,  169  and their associated toothings (not shown) of expressing member  186 . 
     Clamp jaws  166  to  169  are radially outward biased, as indicated in FIG. 16, so that in the position assumed by the injector  110  directly before the injection, they are deflected radially outwardly and therefore do not engage indentations  198 . FIG. 14 shows that the free ends  166 ′,  167 ′ are pressed, by the aforementioned bias, each into an associated groove  160  and do not engage rows of teeth  200 . One thus obtains a drive connection, dependent upon the axial position of actuating member  170 ,  172 , between clamp jaws  166 - 169  and the expressing member  186 . 
     If, as shown in FIGS. 13-14, a force F on actuating head  172  displaces it in the proximal direction, the proximal ends  166 ′,  167 ′ of the clamp jaws are pressed radially inward by the cam surface  164  of groove  160  and complementary form of ends  166 ′,  167 ′ as shown in FIG.  11  and end up with their projections  166 ″,  167 ″ in engagement with the respective indentations opposite the respective projection, so that, between the actuating member  170 ,  172  and the expressing member or piston rod  186 , a drive connection is enabled, which connection was disabled in the position shown in FIGS. 13-14. 
     This drive connection has the effect that the movement of actuating member  170 ,  172  in the proximal direction (by the force F of FIG. 13) is directly transmitted to expressing member (piston rod)  186  and displaces it in the proximal direction. Since, due to the force of weak spring  190 , piston rod  186  already rests with its base  188  directly against plunger  140 , this movement is also directly transmitted to plunger  140 , causing fluid in the preselected dosage to be expressed from container  118  via needle  146 , to the extent that the actuating head  172  is displaced so far (by force F) that its proximal face  172   a  (FIG. 13) abuts against the distal outer face  178   a  of annular part  178 , i.e. until the stop is reached. 
     Here, it is to be noted that, during this injection process and as shown in FIG. 12, each of the radially outer sides  220 ,  222  of proximal ends  166 ′,  167 ′ is pressed, by the inner side  155  of dosing element  154  in the manner of a cam control, radially inward and into engagement with the expressing member (piston rod)  186  so that, after leaving groove  160 , the drive connection between actuating member  170  and expressing member  186  is constantly maintained or enabled. Preferably, this drive connection is a form-locking one, but a force-locking one would also be possible, as is readily apparent to those skilled in the art. Alternatively, this connection could be created otherwise, e.g. by excitation of a solenoid. 
     MODE OF OPERATION 
     FIG. 7 shows the injection device after an injection. The projections  166 ″,  167 ″ of actuating member  170  stand in forced engagement with corresponding indentations  198  of tooth rows  200 . 
     According to FIG. 8, the user pulls on actuating member  170 , and moves actuating head  172  with a force K in the distal direction. FIG. 8 shows an intermediate position during this movement process, and FIG. 9 shows a further progressive intermediate position, in which the projections  166 ′,  167 ′ have almost reached groove  160 . 
     In FIG. 10, groove  160  has been reached. Clamp jaws  166 - 169  spring radially outward into this groove  160  and thereby disable the drive connection to expressing member (piston rod)  186 , so that the latter promptly moves, under the influence of (weak) spring  190 , in the proximal direction, until its base  188  abuts, with a light force, against plunger  140 . This is the already-described follower movement of expressing member  186 , and the injection device is injection-ready in this position. 
     If the user interrupts the above-described process in the position of FIG. 8 or FIG. 9, spring  190  moves expressing member  186  and actuating member  170  back into the position of FIG. 7, so that in this case, no injection is possible. Rather, an injection first becomes possible when the position of FIG. 10 is reached, in which the dose, previously set by turning of housing section  116 , is activated. This represents a valuable security feature and prevents the patient from injecting himself with less than the predetermined dose. 
     For an injection, the patient first sticks the needle  146  (FIG. 13) into his subcutaneous fat layer, and then presses with force F on the actuating head  172 . Then the ends  166 ′  167 ′ of clamp jaws  166 - 169  move radially inward and come into engagement with the respective indentations  198  opposite them. Thereby, the force F is transmitted to expressing member  186  and from it to plunger  140 , so that the selected dose is expressed from container  118  and injected. 
     FIG. 12 shows the conclusion of this process, i.e. the end of an injection with the selected dose. As previously described, the end is reached when in FIG. 13 the annular shoulder  172   a  abuts against distal end face  178   a  of housing section  112 . 
     Subsequent to the injection, the patient pulls the needle  146  out of the subcutaneous fat layer and replaces it with a new, sterile needle, which usually is covered with a sterile cap  147  as shown in FIGS. 5 &amp; 6. 
     FIG. 19 illustrates a significant improvement, which permits finer dosing. The expressing member  186 ′ here has a left tooth row  210  and a right tooth row  212 . Both have an identical tooth pitch T, but the tooth rows  210 ,  212  are staggered or offset with respect to each other in the axial direction by half a tooth pitch, i.e. by T/2 as shown in FIG.  19 . Since clamp jaws  166 ,  167  oppose each other without axial displacement, clamp jaw  167 , for example, would completely engage with its free end  167 ′ into a depression  212 ′ of tooth row  212 , while the free end  166 ′ of clamp jaw  166  would, as illustrated, engage only halfway into the associated recess  210 ′ of tooth row  210 , i.e. in the case shown, the right clamp jaw  167  is effective and provides the drive connection. Conversely, it can be that the free end  166 ′ of clamp jaw  166  fully engages in an associated recess  210 ′, while the free end  167 ′ only half engages in an associated recess  212 ′. It is to be noted that FIG. 18 shows an analogous displacement of tooth rows  200  in section, as is readily apparent to those skilled in the art. 
     By this staggering or displacement, dose setting in gradations of half the tooth pitch (T/2) is possible, i.e. the dosage can in this variant be adjusted in smaller steps without requiring smaller teeth  210 ,  212 . The tooth rows  210 ,  212  are shown in FIG. 19 greatly enlarged, for ease of illustration. 
     As one can readily recognize, one could also use, for example, three different tooth rows and stagger each relative to the others by T/3, in order to obtain still finer adjustment possibilities. Equally, it is possible to stagger or displace the free ends  166 ′,  167 ′ of the clamp jaws  166 ,  167  relative to each other, e.g. by T/2, and not stagger tooth rows  210 ,  212 . Such and other variants will be readily available to those skilled in the art. 
     FIGS. 20 &amp; 21 show the parts of the injector which are provided for dose setting. The tubular section  116  is shown in both these figures in side view, i.e. not in section. It is rotatably mounted in housing  112  by bearing  114 , so that it can be rotated in housing  112  without being axially displaced. 
     On its outer side, the portion  117  of tubular section  116  which is within housing  112  has an external thread  150  (coarse pitch thread) whose ridges have a preferably trapezoidal cross-section, and this external thread  150  engages in a corresponding internal thread  158  (FIG. 4) in the threaded sleeve  154  serving as a dosing element, which sleeve is axially guided in longitudinal grooves  156  of housing  112 , and therefore cannot turn in housing  112 , but only move axially. 
     Housing  112  has a longitudinal window  230 , whose form is shown in FIG. 1, and which extends in the longitudinal direction of housing  112 . It serves for indication of the selected injection dose. 
     Similarly, dosing element  154  has a window  232 , which is axially shorter than window  230 , but can have the same width. Further, on the outer side  234  of tubular section  116 , there are, in the manner shown, display values  236  for the injection dose, i.e. here the numbers 0, 2, 4, . . . 60. 
     Window  232  is so dimensioned that, of these display values  236 , only one at a time can be displayed, e.g., as shown in FIG. 1, the display value “60”. 
     As one can see from FIGS. 20 &amp; 21, the display values  236  are arranged in a screw or spiral pattern on the outer side  234  of part  117 , i.e. with increasing dose, the display in window  230  “migrates” in the distal direction, since the threaded sleeve  154  is moving in the distal direction in housing  112 . 
     FIG. 20 shows the position of dosing element  154  for the injection dose “0”; this position is also shown in FIG.  5 . FIG. 21 shows the position of dosing element  154  for the maximum injection dose, thus e.g. “60”; this is also shown in FIG. 1. A comparison of FIGS. 20 &amp; 21 shows the differing position of dosing element  154  relative to housing  112 , and the differing position of window  232  relative to window  230 . 
     It is again to be noted that a single dose selection in window  232 , e.g. four insulin units (“4”) is effective for all subsequent injections in the same manner, i.e. when this dose is maintained unchanged, a single setting or adjustment suffices, which for the patient represents a substantial simplification, since, given a constant dose, he need not concern himself about dose setting prior to an injection. 
     Naturally, within the scope of the present invention, many changes and modifications are possible, e.g. design of the injection device of the invention as a so-called “full automatic” injector with a fully automatic operation of the injection process.