Abstract:
A one-way injector having a housing in which at least one mechanical spring energy store, at least one piston/cylinder unit, which can be at least temporarily filled with an active substance, at least one piston-actuating plunger and at least one tripping unit are arranged. To this end, the spring energy store comprises a preloaded spring element. The spring element is held in the preloaded position by a tension means surrounding at least a region of the spring. The tripping unit comprises a cutting tool which, in order to release the energy of the spring energy store, severs or weakens the tension means at least one point, the weakening immediately tearing the tension means. With the present invention, a one-way injector is developed which, with a small overall size, has only a few components and ensures reliable mounting and functioning with simple manipulation.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This is a continuation-in-part application of pending international application PCT/EP2006/011747 filed Dec. 7, 2006 and claiming priority of German Application No. 10 2005 062 206.2 filed Dec. 24, 2005. 

   BACKGROUND OF THE INVENTION 
   The invention relates to a disposable injector with a housing that contains at least one mechanical spring energy reservoir, at least one cylinder/piston unit that can be filled at least temporarily with active substance, at least one piston-actuating rod and at least one trigger unit. 
   An injector of this kind is known from EP 0 595 508 B1. It is constructed in such a way that the individual structural groups—namely the spring energy reservoir, cylinder/piston unit and trigger unit—cannot be separated from one another or handled separately. The trigger unit too is a complicated multi-part system. 
   A comparable device for injection of medicaments is also known from DE 695 06 521 T2, where the charged spring energy reservoir is secured by means of a breakable pin. When the breakable pin is broken by manual actuation, the spring that drives the syringe piston is released. 
   Moreover, DE 102 40 165 A1 describes a device for dosed ejection of a liquid active substance. In said device, the active substance is located in a syringe barrel. A syringe piston is spring-loaded and forced toward the active substance. The advance movement of the syringe piston is braked periodically by a band. The braking mechanism corresponds to the clock generator of a mechanical timepiece. The band is wound round the shaft of an escape wheel. The rotation of the escape wheel is triggered periodically at angles of rotation via an oscillating armature. 
   Therefore, the problem addressed by the present invention is that of developing a disposable injector of modular design which, with a small overall size, comprises only a small number of structural parts and, while being easy to handle, ensures reliable storage and reliable operation. 
   SUMMARY OF THE INVENTION 
   A one-way injector having a housing in which at least one mechanical spring energy store, at least one piston/cylinder unit, which can be at least temporarily filled with an active substance, at least one piston-actuating plunger and at least one tripping unit are arranged. To this end, the spring energy store comprises a preloaded spring element. The spring element is held in the preloaded position by a tension means surrounding at least a region of the spring. The tripping unit comprises a cutting tool which, in order to release the energy of the spring energy store, severs or weakens the tension means at, at least one point, the weakening immediately tearing the tension means. With the present invention, a one-way injector is developed which, with a small overall size, has only a few components and ensures reliable mounting and functioning with simple manipulation. 
   The spring energy reservoir for this purpose comprises a pretensioned spring element. The spring element is held in the pretensioned position by a pulling means that surrounds the spring in at least some areas. The trigger unit comprises a cutting tool which, in order to release the energy of the spring energy reservoir, severs the pulling means at least at one location, or weakens it, the weakening causing an immediate tearing of the pulling means. 
   With the present invention, a disposable injector is made available whose core feature is a spring energy reservoir with a pretensioned compression spring element, the spring energy being stored via a tensioned pulling means or a tensioning band or tensioning cable. The spring energy can be released only by irreversible mechanical destruction of the pulling means. A simple cutting tool is required for destruction of the pulling means. As regards the release of the spring energy, it is possible to dispense with a high-precision, multi-part mechanical locking system. The destruction of the pulling means also ensures that the injector cannot be reused in an inappropriate manner, for example as a dangerous toy catapult. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further details of the invention will become clear from the following description of an illustrative embodiment represented in the drawings, in which: 
       FIG. 1  shows schematically a disposable injector with charged spring energy reservoir, but without the cylinder/piston unit; 
       FIG. 2  shows a side view of  FIG. 1  (six-way projection); 
       FIG. 3  shows a plan view of  FIG. 1 , but without the trigger button; 
       FIG. 4  shows a plan view of  FIG. 2 ; 
       FIG. 5  shows a partial view of  FIG. 1 , with opposite cutting edge; 
       FIG. 6  shows a sectional view as in  FIG. 2 , but with the cylinder/piston unit, and with the trigger button pressed down; 
       FIG. 7  shows a sectional view as in  FIG. 6 , but with the spring energy reservoir discharged; 
       FIG. 8  shows a partial view of  FIG. 6 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   With references to  FIGS. 1 ,  2  and  6  a disposable injector is shown with a permanently charged spring energy reservoir  50 . The latter basically comprises a helical compression spring  77  that is pretensioned by means of a tensioning band  78 . The spring energy reservoir  50  is accommodated in a housing  10 , together with a trigger unit  80 . The housing  10  also accommodates, if appropriate, a cylinder/piston unit  100 , and the latter receives a medicament  1  that is to be administered. 
   The housing  10  is composed for the most part of a cylindrical tube, for example, which is divided into three functional areas  21 ,  31 , and  41 . According to  FIGS. 1 and 2 , the upper area is the trigger area  21 . This is adjoined by the jacket area  31 . An inwardly protruding middle flange  32  is arranged between both areas. The middle flange  32  has a central flange recess  33  which deviates geometrically from a circular cross section by a circle segment  34 . The presence of the circle segment  34  is used to permit assembly in a manner secure against twisting, as will be described further below. The flange recess  33  is bevelled at least in some places from the direction of the jacket area  31 . 
   In the trigger area  21  of the housing  10 , a transverse bore  23  is located between the top end face  11 , in  FIG. 2 , and the middle flange  32 . The transverse bore  23  serves to accommodate a trigger block  97 . Opposite the bore  23 , the inside wall of the housing  10  carries a lug  22  that provides protection against twisting. The lug  22  providing protection against twisting, and shown in plan view in  FIGS. 3 and 4 , is intended to allow a trigger button  81  of the trigger unit  80  to be fitted secure against twisting. The outer edge of the end face  11  is bevelled, for ergonomic reasons. Situated above the bore  23 , and each offset by a 90 degree angle, there are two depressions  24 , for example in the form of spherical cups, see  FIG. 1 , for locking the trigger button  81 . 
   The fixing area  41  for receiving the insertable cylinder/piston unit  100  is situated, in the housing  10 , below the jacket area  31 , see also  FIGS. 6 and 7 . The fixing area  41  comprises, for example, six resilient hooks  42  that each end in an inwardly directed hook tip  43 . In the direction towards the lower end face  12  of the housing, the hook tips  43  have a bevel  44  extending across the full thickness of the hooks. The length and the spring rate of the resilient hooks  42  are dimensioned such that the inserts  50 ,  100  required for the function of the disposable injector can be inserted without plastic deformation of the resilient hooks  42 . 
   One of these inserts is the cylinder/piston unit  100 , see  FIG. 6 . It is composed of a cylinder  101  and a piston  111 . The cylinder  101  is, for example, a thick-walled pot whose optionally cylindrical outer wall has, for example, five peripheral locking ribs  102 . The totality of the locking ribs  102  provides, in cross section, a saw-tooth profile, for example, the division between the tooth-like locking ribs  102  being equidistant. The maximum diameter of the locking ribs  102  is slightly smaller than the internal diameter of the housing  10  in the fixing area  41 . The diameter of the areas lying between adjacent locking ribs  102  corresponds to the minimum diameter of the housing  10  in the area of the hook tips  43 . 
   The rodless piston  111  sits in the, for example, cylindrical bore  105  of the cylinder  101 , see  FIG. 8 . At its front end face, of at least approximately conical configuration, the piston  111  has an axial annular groove  112  for receiving a sealing ring  114  or a permanently elastic sealing compound. Lying between the outer wall of the annular groove  112  and, in the unloaded state, the cylindrical outer wall of the piston  111 , there is an annular bar  113  whose wall measures, for example, only 0.2 millimeter. The bar  113  height is a multiple of the wall thickness of the bar. 
   A short cylindrical, nozzle-like bore  106  is located at the center of the bore  105  of the cylinder  101 , whose cylinder base is adapted to the contour of the front end face of the piston. The diameter of the bore  106  is about 0.17 millimeter. This bore  106  is two to three times as long as its diameter. It opens out in a cylindrical recess  107  of the outer end face  103  at the bottom of the cylinder  101 . 
   The spring energy reservoir  50  or the drive unit of the disposable injector is arranged between the piston  111  and the middle flange  32 , see  FIG. 6 . The spring energy reservoir  50  comprises a helical compression spring  77 , a piston-actuating rod  71 , an anvil  51  and a tensioning band  78 . The latter holds these parts together during the energy storage phase. 
   The piston-actuating rod  71  is divided into three areas which, for example, are substantially cylindrical. The lower area is the piston slide  76 . Its diameter is slightly smaller than the internal diameter of the cylinder  105  of the cylinder/piston unit  100 . The lower end face of the piston slide  76  acts directly on the piston  111 . 
   The central area is the rod plate  73 . The rod plate  73  is a flat and at least in some areas cylindrical disc whose external diameter is a few tenths of a millimeter smaller than the internal diameter of the housing  10  in the jacket area  31 . The external diameter of the rod plate  73  is a few millimeters larger than the diameter of the opening formed by the tips  43  of the resilient hooks  42 . 
   According to  FIG. 1 , the rod plate  73  has two rectangular grooves  74  lying opposite one another for receiving a pulling means  78 , see  FIG. 1 . The rod plate  73  has, for example, two air admission grooves  75  arranged between the grooves  74 . 
   The upper area adjoining the rod plate  73  is, for example, cylindrical spring-guiding bar  72 . Its upper end projects with play into a central rod-guiding bore  62  of the anvil  51 . 
   The anvil  51 , see  FIGS. 1 ,  2 ,  5  and  6 , is a pot-shaped structural part whose base  52  has, for example, a rectangular, narrow recess  89  acting as knife-guiding slit  61 . The radial outer contour of the base  52  has a locking groove  56  extending about part of the periphery. According to  FIGS. 2 ,  3 ,  6  and  7 , the base  52 , in the area of the locking groove  56 , has a lateral flattened area  57  that corresponds to the circle segment  34  of the middle flange  32 . 
   Below the locking groove  56 , the anvil  51  has a diameter that is only slightly smaller than the internal diameter of the housing  10  in this area. Two band-guiding grooves  63  extend between the anvil&#39;s lower end face  66 , on which the helical compression spring  77  rests, and the upper end face  53 . The respective bottom of these grooves  63  encloses with the center line  5  an angle of eight degrees, for example. The depth of the individual groove  63  increases in the direction of the upper end face  53  of the anvil  51 . 
   The drive unit  50  can be preassembled as follows. The helical compression spring  77  is fitted onto the spring-guiding bar  72  so that it bears on the rod plate  73 . The anvil  51  is placed onto the upper end of the piston-actuating rod  71 . The helical compression spring  77  is compressed to the required length between the rod plate  73  and the anvil  51 , for example in a special device not shown here. A tensioning band  78  is placed over the anvil  51  and the helical compression spring  77 . The tensioning band  78  fitted in the band-guiding grooves  63  ends in the area of the plate grooves  74  of the rod plate  73 . The two ends of the tensioning band  78  are fixed non-releasably in the plate grooves  74 , for example by adhesion or welding  79 . After the drive unit  50  has been removed from the special tensioning device, said drive unit  50  can be separately stored or is inserted directly thereafter into the housing  10  of a disposable injector. 
   Alternatively, the tensioning band  78  can also be secured on the rod plate  73  by a form-fit engagement. In this case it has, for example at each end, a widened area that sits in a respective corresponding recess of the rod plate  73 . 
   The pulling means  78  in this illustrative embodiment has a rectangular solid cross section. It can also be elliptic, oval or circular. PVC-based plastics are proposed as suitable material, for example. The pulling means  78  can also be a cable or cord produced from yarns. 
   The trigger button  81 , which carries a cutting tool  90 , sits in a longitudinally displaceable manner in the trigger area  21  of the housing  10 . The trigger button  81  has in principle the form of a bushing consisting of a base  82  and of a skirt  86 . The cutting tool  90 , for example with a single cutting edge, protrudes inwards from the base  82 . 
   The trigger button  81  has a cylindrical outer wall  83  which, according to  FIG. 2 , has a semicircular groove  85  in the knife plane. The lug  22  belonging to the housing  10  and providing protection against twisting protrudes into the semicircular groove  85 . In addition, the outer wall  83  has, in the lower area, two radially projecting cams  88  in mirror symmetry with respect to the knife plane. The cams  88  engage in depressions  24  of the trigger area  21  when the trigger button  81  is assembled and secured in place, see  FIG. 1 . 
   The knife blade  91  arranged in the base  82  of the trigger button  81  has, for example, the shape of a trapezium in side view, see  FIGS. 2 ,  6  and  7 . Three adjacent edges of the trapezium enclose two right angles; while the long edge  93  representing the reverse of the blade encloses an angle of, for example, 20° with the cutting edge  92 . The blade reverse  93  is oriented parallel to the center line  5  of the device. It has a smooth surface. According to  FIG. 1 , the cutting edge  92  is ground symmetrically on both sides. In the assembled state according to  FIG. 2 , the flat reverse  93  of the blade is supported on and bears slidably on the corresponding wall of the knife recess  89 . The width of the recess  89  is only slightly greater than the wall thickness of the knife blade  91 , which is made of steel, for example. 
   The cutting tool  90  sits centrally and, for example, encapsulated, within the trigger button  81 . For this purpose, it has a bore-shaped recess  94  to allow it to be secured with a force-fit or form-fit in the encapsulated area of the base  82 . 
   Of course, the cutting tool can also have another shape and cutting geometry. For example, the cutting edge can be continuously curved, in such a way that the cutting angle increases as the stroke of the trigger button increases. It is also conceivable to equip the cutting tool with a double cutting edge, in which case the two cutting edges lie opposite one another. In this tool, the pulling means  78  is cut into simultaneously from two sides, that is to say transverse to the plane  9 . 
   If, for example, a cable is used as the pulling means  78 , the cutting tool can also be designed with two cutting edges directed away from each other. In this case, the knife blade cutting on both sides severs the cable centrally. 
   The skirt  86  has a lower and, for example, flat edge  87  which, upon actuation of the trigger button  81 , serves as an abutment for the middle flange  32  of the housing  10 . In the unactuated and secured state, the edge  87  bears on the blocking pin  99  of the trigger block  97 . 
   The trigger block  97  is composed of the blocking pin  99  and of an open and resilient ring which supports the latter and which is in the form of an omega-shaped spring  98 , see  FIG. 4 . The omega-shaped spring  98  sits on the outer wall of the housing  10  on the secured injector. It surrounds the outer wall by about 240 angle degrees. The blocking pin  99  engages in the bore  23 . It protrudes a few millimeters into the inside of the housing  10 , see  FIG. 2 . If appropriate, at least one of the free ends of the omega-shaped spring  98  is sealed with a paper or foil wrapper. 
   To assemble the disposable injector, the for example prefabricated drive unit  50  is fitted into the still empty housing  10 . The drive unit  50  is locked non-releasably in the middle flange  32  and secure against twisting via the flange recess  33 . In a second step, the cylinder/piston unit  100  is fitted in the fixing area  41 . Independently of this, the trigger block  97  is applied and, if appropriate, sealed. Finally, the trigger button  81  equipped with the cutting tool  90  is inserted into the housing  10  in a manner secure against twisting. The inserted trigger button  81  bears with its lower edge on the blocking pin  99 . In addition, it is fixed in the depressions  24  of the trigger area  21  via the cams  88 . 
   The distance between the trigger button  81  and the anvil  51  is chosen such that the tip of the knife blade  91  protrudes safely into the knife slit  89 , but without touching the pulling means  78 , see  FIG. 2 . 
   The insertion of the cylinder/piston unit  100  can, if appropriate, also be carried out by the user. 
   In order to administer the medicament contained in the cylinder/piston unit  100 , the trigger block  97  is first removed by pulling it sideways, after any seal present has been destroyed. The primed disposable injector is placed normally on the application site, and the trigger button  81  is pressed down by the force of the thumb. The tensioning band  78  is severed by the trigger button  81  being pressed down, see  FIG. 6 . In the process, the downwardly moved knife blade  91  plunges the tensioning band  78  into the knife slit  89 . The tensioning band  78  lying on the anvil  51  cannot escape from the cutting movement, since it is guided with lateral support by the wall of the band-guiding grooves  63 . 
     FIG. 5  shows the alternative combination of knife blade  91  and anvil  51 . The knife blade  91  has an asymmetric cutting edge, i.e. the blade is ground only on one side. An opposite cutting edge  54 , for example, of metal or ceramic, is additionally firmly embedded in the anvil  51 , see also  FIG. 3 . The mutually facing cutting edges of the knife blade  91  and of the opposite cutting edge  54  form a shear in accordance with the principle of shearing. In this solution, the tensioning band  78  is sliced through with application of less force. 
   Depending on the material chosen for the tensioning band  78 , it is not necessary to slice the tensioning band  78  through its entire cross section. It may suffice simply to nick the tensioning band  78  in order to cause it to immediately tear. In this case, the required stroke of the trigger button can be shortened. 
   Directly after the tensioning band  78  has been severed, the spring element  77  pushes the piston  111 , via the forwardly moved piston-actuating rod  71 , into the cylinder  101  in order to eject the product  1 , see  FIG. 7 . The cylinder/piston unit  100  accommodates at least one component  1  of the product to be administered, such as, distilled water. The ejection process is completed when the piston  111  has reached the base of the cylinder  101 . 
   A mechanical, force-enhancing gear may be arranged in the trigger unit  80 , between the manually operated trigger button  81  and the cutting tool  90 .