(12) United States Patent
`Steenfeldt-J en sen et al.
`
`111111
`
`1111111111111111111111111111111111111111111111111111111111111
`US006235004Bl
`US 6,235,004 Bl
`May 22,2001
`
`(10) Patent No.:
`(45) Date of Patent:
`
`(54)
`
`INJECTION SYRINGE
`
`(56)
`
`References Cited
`
`(75)
`
`Inventors: S!'lren Steenfeldt-Jensen, Hornb<ek;
`Steffen Hansen, Hiller0d, both of (DK)
`
`(73) Assignee: Novo NordiskNS, Bagsvaerd (DK)
`
`( *) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`U.S. PATENT DOCUMENTS
`
`5,017,190
`5,304,152
`5,599,314
`5,674,204
`5,679,111
`5,725,508
`
`5/1991 Simon et a!. .
`4/1994 Sams .
`2/1997 Neill .
`10/1997 Chanoch .
`10/1997 Hjertman eta!. .
`3/1998 Sams .
`FOREIGN PATENT DOCUMENTS
`
`(21) Appl. No.: 09/429,677
`
`(22) Filed:
`
`Oct. 28, 1999
`
`Related U.S. Application Data
`
`( 63) Continuation of application No. 09/238,849, filed on Jan. 28,
`1999, now Pat. No. 6,004,297.
`(60) Provisional application No. 60/073,820, filed on Feb. 5,
`1998.
`
`(30)
`
`Foreign Application Priority Data
`
`Jan. 30, 1998
`
`(DK) ............................................. 1998 00130
`
`Int. Cl? ...................................................... A61M 5/00
`(51)
`(52) U.S. Cl. ............................................. 604/207; 604/211
`(58) Field of Search ..................................... 604/207, 208,
`604/210, 211, 218, 187, 232
`
`8/1989 (EP) .
`0 327 910
`10/1991 (EP) .
`0 450 905
`wo 93/07922
`4/1993 (WO) .
`Primary Examiner-John D. Yasko
`(74) Attorney, Agent, or Firm-Steve T. Zelson, Esq
`ABSTRACT
`
`(57)
`
`The present invention provides an injection syringe com(cid:173)
`prises a housing including a holder for containing a cartridge
`of medicine, a piston rod with a non-circular cross-section
`having an outer thread, a piston rod drive, a one way
`coupling having an annular ring of internal ratchet notches,
`which annular ring can be integral with the housing, and a
`pawl having at least a pair of resilient arms each having a
`free end.
`
`11 Claims, 5 Drawing Sheets
`
`19
`
`20
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`PFIZER, INC. v. SANOFI-AVENTIS DEUTSCHLAND GMBH
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`Ex. 1014, p. 1 of 13
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`U.S. Patent
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`May 22, 2001
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`Sheet 1 of 5
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`US 6,235,004 Bl
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`19
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`23
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`~23
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`25
`24
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`18 26
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`17
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`2
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`30
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`~9
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`FI~J
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`FI~Z
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`FI~LI
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`9
`FI~!J
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`PFIZER, INC. v. SANOFI-AVENTIS DEUTSCHLAND GMBH
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`Ex. 1014, p. 2 of 13
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`U.S. Patent
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`May 22,2001
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`Sheet 2 of 5
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`US 6,235,004 Bl
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`39
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`2
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`~13
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`Fl~7
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`PFIZER, INC. v. SANOFI-AVENTIS DEUTSCHLAND GMBH
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`Ex. 1014, p. 3 of 13
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`U.S. Patent
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`May 22,2001
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`Sheet 3 of 5
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`US 6,235,004 Bl
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`PFIZER, INC. v. SANOFI-AVENTIS DEUTSCHLAND GMBH
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`Ex. 1014, p. 4 of 13
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`

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`U.S. Patent
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`May 22,2001
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`Sheet 4 of 5
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`US 6,235,004 Bl
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`PFIZER, INC. v. SANOFI-AVENTIS DEUTSCHLAND GMBH
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`Ex. 1014, p. 5 of 13
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`

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`U.S. Patent
`
`May 22,2001
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`Sheet 5 of 5
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`US 6,235,004 Bl
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`46
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`16
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`1
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`82
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`89
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`6\....._
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`~40
`~9
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`PFIZER, INC. v. SANOFI-AVENTIS DEUTSCHLAND GMBH
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`Ex. 1014, p. 6 of 13
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`

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`US 6,235,004 B 1
`
`1
`INJECTION SYRINGE
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`5
`
`This application is a continuation of U.S. application ser.
`No. 09/238,849 filed Jan. 28, 1999 now U.S. Pat. 6,004,297,
`which claims priority under 35 U.S.C. 119 of Danish appli(cid:173)
`cation PA 1998 00130 filed Jan. 30, 1998 and of U.S.
`provisional application No. 60/073,820 filed Feb. 5, 1998,
`the contents of which are fully incorporated herein by
`reference.
`The invention relates to injection syringes of the kind
`apportioning set doses of a medicine from a cartridge
`containing an amount of medicine sufficient for the prepa(cid:173)
`ration of a number of therapeutic doses.
`Such syringes are mainly made for users who have to
`inject themselves frequently, e. g. diabetics. A number of
`demands are set to such syringes. The setting of a dose must
`be easy an unambiguous and it must be easy to read the set
`dose. It must be possible with a minimum of trouble to
`cancel or change a wrongly set dose and when the dose is
`injected the dose setting must return to zero. When a
`disposable syringe is in question, i.e. a syringe which is
`disposed of when the cartridge is empty, the syringe must
`further be cheap and made of materials suited for recycling
`or burning without producing noxious gases. For these
`purposes the number of parts from which the syringe is
`constructed and the number of different kinds of materials
`used in the syringe should be kept at a minimum.
`Most dose setting devices work with a threaded piston rod
`co-operating with a nut where the nut and the piston rod may
`be rotated relative to each other. The dose setting may be
`obtained by screwing the nut away from a stop to which it
`is returned during the injection by pressing the piston rod
`until the nut member abuts the stop. By other dose setting
`devices one of the elements, the nut or the piston rod, is kept
`inrotatable and the other is allowed to rotate a set angle
`depending on the set dose, whereby the piston rod is screwed
`a distance through the nut.
`In most syringes for apportioning set doses it is preferred
`that the piston rod is backing up the piston upon which it
`works during the injection. To obtain this precaution is taken
`to prevent the piston rod from moving in a proximal direc(cid:173)
`tion.
`The syringe according to EP 327 910 is of the type
`wherein a nut is screwed away from a stop. During the
`setting of the dose the screwing may be performed in both
`direction so that a too large set dose may be lowered just by
`rotating the nut in an opposite direction. Means are provided 50
`preventing that negative doses are set. The mutual rotation
`of the piston rod and the nut is obtained by rotating a cap
`relative to the pen housing and a set dose may be read on a
`scale and a pointer provided at adjacent edges of the housing
`and the cap, these edges being so shaped that the cap can 55
`only be mounted firmly on the housing when the pointer
`points zero on the scale. It may be seen as a weak point that
`doses larger than the one obtained by rotating the parts 360°
`must be calculated by adding the number pointed at on the
`scale and a number printed on the side of a tubular extension 60
`of the nut which is moved out from the proximal end of the
`housing proportionally with the dose set and which tubular
`extension is closed at its proximal end to form an injection
`button.
`In EP 450 905 the above drawback is overcome by writing 65
`the numbers along a helical line on a tubular extension of the
`nut so that these number may successively be seen in a
`
`2
`window in a housing element enclosing said tubular exten(cid:173)
`sion. Hereby the size of the dose is indicated unambiguously
`but the user have to remember to set the dose setting device
`on zero before the next setting of a dose is performed. If this
`is forgotten a wrong dose may be set and the number may
`not be seen clearly in the window.
`In EP 608 343 is described a pen having a dose setting
`mechanism wherein the dose is set by rotating a button
`relative to a housing to set a dose. By the rotation the button
`10 is screwed up from the end of the housing in a thread having
`a pitch so large that the thread connection is not self
`blocking, i. e. when the button is presses back to the end of
`the housing it will rotate back in the thread. The button is
`through a ratchet coupled to a driver, the ratchet forming a
`15 unidirectional coupling which during the rotation of the
`button in one direction to set a dose rides or clicks over the
`teeth of the ratchet. The cylindrical side of the button carries
`numbers which shows the size of the set dose in a window
`when the button is screwed outward. When the button is
`20 screwed back the unidirectional coupling will transmit the
`rotation to the driver which has a nut co-operating with a
`threaded piston rod which is made inrotatable in a housing
`. This thread connection has a pitch which makes the nut self
`locking on the piston rod. A set dose may be cancelled by
`25 drawing the engaging parts of the ratchet out of engagement
`against the force of a spring so that the rotation of the button
`is not transmitted to the driver and then press the button back
`to the housing . This pen fulfils all the objects mentioned
`only the dose cancelling procedure is a little troublesome as
`30 the dose set button cannot as it will come most naturally just
`be screwed back if a too large dose is set. Concomitantly
`forcing the coupling parts apart against the force of the
`spring and pressing or screwing the button back may be a
`little difficult and the demand for a spring necessitates use of
`35 metal parts in the syringe.
`It is an object of the invention to provide a syringe which
`has the mentioned advantageous features without having the
`drawbacks known from existing syringes.
`This is obtained by an-injection syringes for apportioning
`set doses of a medicine from a cartridge containing an
`amount of medicine sufficient for the preparation of a
`number of therapeutic doses, comprising
`a housing
`a piston rod having a not circular cross-section and an
`outer thread
`a piston rod drive comprising two elements
`a) a piston rod guide in relation to which the piston rod
`is axially displaceable but not rotatable, and
`b) a nut member which is rotatable but not axially
`displaceable in the housing and which has an inner
`thread mating the thread of the piston rod to form a
`self locking thread connection,
`a dose setting mechanism comprising a not self locking
`thread connection along which an injection button by
`rotation of a dose setting element relative to said
`housing is screwed out from the proximal end of the
`housing to project from this proximal end a distance
`determined by the angle of said rotation and which
`thread connection by axial returning of the injection
`button transforms this axial movement to a rotation of
`one of the piston drive elements relative to the other,
`which syringe according to the invention is characterised
`in that
`a unidirectional coupling is provided between the nut
`member and the piston rod guide allowing rotation of
`these parts relative to each other in one direction but not
`
`40
`
`45
`
`PFIZER, INC. v. SANOFI-AVENTIS DEUTSCHLAND GMBH
`
`Ex. 1014, p. 7 of 13
`
`

`

`US 6,235,004 B 1
`
`5
`
`3
`in the opposite direction, the allowed rotation being one
`by which the piston rod is transported in a distal di
`rection in the syringe, the coupling being so designed
`that a set initial reluctance has to be overcome before
`the rotation takes place.
`During the setting of a dose a torque is exerted on the
`unidirectional coupling in the direction in which this cou(cid:173)
`pling allows rotation after a set initial reluctance has been
`overcome. As this torque is a weak one resulting when the
`male and the female part of a not self locking thread
`connection is rotated relative to each other the initial reluc(cid:173)
`tance can be made large enough to allow this rotation
`without causing any relative rotation of the parts in the
`coupling.
`When the injection button is pressed the movement of this
`button is transformed into a rotation of the piston rod (or the
`nut member) relative to the nut member (or the piston rod).
`When the button is pressed hard enough the initial reluctans
`is overcome so that the two elements, the piston rod and the
`nut member, are rotated relative to each other.
`According to the invention a click coupling providing an
`moderate resistance against rotation is established between
`the housing and the element rotated relative to the housing
`to set a dose. Hereby it is ensured that the position corre(cid:173)
`sponding to a set dose is maintained and is not inadvertently
`altered. The clicks may be taken as an audible signal
`indicating the size of the set dose.
`The unidirectional coupling may be a coupling compris(cid:173)
`ing a pawl sliding over a pawl wheel with teeth having a
`steep front edge and a ramp shaped trailing edge, and the
`initial reluctance may be obtained by the fact that the trailing
`edges of the pawl wheel teeth has a depression engaged by
`a mating protrusion on the pawl.
`A dose scale drum which has in its surface a helical track
`engaged by a helical rib on the inner side of the housing to 35
`form a not self locking thread connection between the
`housing and the drum may be coupled to the injection button
`to be moved axially with this button. This way the dose scale
`drum will be rotated relative to the housing when it is axially
`displaced with the injection button in said housing.
`The thread connection by which the injection button is
`screwed out from the housing by setting a dose may be the
`thread connection between the dose scale drum and the
`housing. In this case the dose scale drum must be coupled to
`a driver rotating the piston rod (or the nut member) relative
`to the nut member (or the piston rod) when the injection
`button is pressed.
`A dose is set by rotating an element relative to the
`housing, and this element may be an element carrying the
`nut member and the unidirectional coupling so that the
`rotation is transmitted through said unidirectional coupling
`to the dose setting drum. The rotation transmitted is in the
`direction in which the coupling can run free when an initial
`reluctance is overcome. However, the force needed to screw
`the dose scale drum up along its thread is not large enough
`to overcome said reluctance and consequently the rotation is
`transmitted through the coupling.
`In one embodiment of the syringe according to the
`invention the element rotated relative to the housing may be
`a part carrying the nut member and the unidirectional 60
`coupling through which the rotation is transmitted to the
`dose setting drum.
`In another embodiment of the syringe according to the
`invention the element rotated relative to the housing may be
`the injection button and the not self locking thread connec- 65
`tion which determines the lifting of the injection button may
`be an inner thread in a bore in the injection butt on engaging
`
`4
`an outer thread on an enlargement of the piston rod. When
`the injection button is screwed up along the piston rod to
`project from the housing a torque is exerted on the piston rod
`trying to rotate this piston rod in a direction which will move
`it in a distal direction in the syringe. Such a rotation is just
`the rotation which is allowed by the uniderectional coupling
`which blocks rotation in the opposite direction. Due to the
`initial reluctance against rotation of the coupling parts
`relative to each other the piston rod will not be rotated when
`10 the injection button is screwed up along it in a proximal
`direction in the syringe. If the injection button is screwed in
`the opposite direction the unidirectional coupling will
`definitively block a relative rotation of the piston rod and the
`nut member in the direction which would draw the piston
`15 rod in a proximal direction.
`In the last mentioned embodiment of the injection syringe
`the dose scale drum may be mounted rotateable but not
`axially displaceable on the injection button. When the dose
`scale drum is moved with the injection button in the axial
`20 direction of the syringe the drum will be rotated due to the
`not self locking thread connection between said drum and
`the housing so that a number on the drum corresponding to
`the set dose is visible in a window provided in the wall of
`the housing. In this embodiment the pitch of the dose drum
`25 thread need not be identical with the pitch of the thread
`along which the injection button is screwed to set a dose,
`only both thread connections must have a pitch large enough
`to make the thread connection the not self locking type, i.e.
`of the type by which an axial movement can be transformed
`30 into a rotation.
`In an appropriate embodiment of the syringe according to
`the invention the dose scale drum is mounted rotatable but
`not axially displaceable on the injection button.
`During the injection the injection button must be kept
`inrotatable but axially displaceable relative to the housing in
`the angular position to which the injection button is rotated
`during the setting of a dose. This may be obtained by letting
`the click coupling between the housing and the injection
`button comprise protrusions on one part engaging axial
`40 grooves in the other. When the injection button is pressed
`home into the housing the internal thread in the bore of this
`button will act on the engaging outer thread on the enlarge(cid:173)
`ment at the end of the piston rod and convert the axial
`movement of the injection button to a rotational movement
`45 of the piston rod in a direction by which the piston rod is
`screwed through the nut member in a distal direction in the
`syringe. The piston rod guide which is connected to one part
`of the unidirectional coupling is allowed to rotate when the
`initial reluctance against rotation in the direction else
`50 allowed by the coupling is overcome. Also a rotational
`movement of the dose scale drum is induced by the axial
`movement of the injection button so that the scale is returned
`to its zero position when the button is pressed home. When
`rotation of the dose scale drum and the piston rod is induced
`55 by the axial movement of the injection button this button is
`reacted upon by a torque which must be taken up by the click
`connection between the injection button and the housing
`which connection must consequently be strong enough to
`absorb this force without rotating.
`In the following the invention is described in further
`details with references to the drawing, wherein
`FIG. 1 shows a front view of an embodiment of an
`injection syringe according to the invention,
`FIG. 2 shows a sectional view along the line 11-11 in FIG.
`
`1,
`
`FIG. 3 shows in a reduced scale an exploded view of the
`syringe in FIG. 1,
`
`PFIZER, INC. v. SANOFI-AVENTIS DEUTSCHLAND GMBH
`
`Ex. 1014, p. 8 of 13
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`

`

`US 6,235,004 B 1
`
`5
`FIG. 4 shows a sectional view along the line IV-IV in
`FIG. 1,
`FIG. 5 shows a sectional view along the line V-V in FIG.
`
`1,
`
`FIG. 6 shows a front view of another embodiment of an
`syringe according to the invention,
`FIG. 7 shows a sectional view along the line VII-VII in
`FIG. 6,
`FIG. 8 shows in a reduced scale an exploded view of the
`syringe in FIG. 6,
`FIG. 9 shows a sectional view along the line IX-IX in
`FIG. 6,
`FIG. 10 shows a sectional view along the line X-X in
`FIG. 6.
`FIG. 11 shows a sectional side view of another embodi(cid:173)
`ment of a syringe according to the invention,
`FIG. 12 shows a sectional side view perpendicular to the
`view in FIG. 11,
`FIG. 13 shows in a reduced scale an exploded view of the
`syringe in FIG. 11 and 12,
`FIG. 14 shows a sectional side view of the dose setting 20
`part of another embodiment of a syringe according to the
`invention,
`FIG. 15 shows a sectional side view of still another
`embodiment of a syringe according to the invention,
`FIG. 16 shows a sectional side view perpendicular to the
`view in FIG. 15,
`FIG. 17 shows in a reduced scale an exploded view of the
`syringe in FIG. 15 and 16,
`Initially it may be convenient to define that in this
`application directions of rotation are always seen from the
`proximal end of the pen and designed as clockwise or
`anticlockwise seen in this direction.
`FIG. 1 shows an injection syringe of the kind by which a
`liquid from an ampoule can be apportioned in a number of
`individually set does. FIG. 3 shows an exploded view of this 35
`syringe and the FIGS. 2, 4 and 5 sectional views taken along
`different lines in FIG. 1.
`The syringe comprise a tubular housing 1 which is by a
`partition 15 divided into a first and a second division into the
`first one of which an ampoule holder 2 is snapped by a snap
`lock comprising a ring shaped bead 3 on the ampoule holder
`2 which bead is snapped into a corresponding circumferen(cid:173)
`tial grove in the inner wall of the housing 1 near an open end
`thereof. By this snap connection the ampoule holder 2 is
`secured in the housing 1 so that it can be rotated but not 45
`axially displaced relative to this housing.
`In the syringe ready for use an ampoule is mounted in the
`ampoule holder which is then at its distal end closed by an
`end wall provided with a needle hub receiving part onto
`which a needle hub can be mounted having a needle with 50
`one end communicating with the content of the ampoule and
`the other end free to be inserted into a patient. In the shown
`syringe, however, neither ampoule, end wall nor needle hub
`are shown.
`The end of the ampoule holder 2 inserted in the housing 55
`1 is closed by a wall 4 having a central bore with an internal
`thread 5. A piston rod 6 having an external thread 7 mating
`the thread 5 of said bore extends through said bore. The
`threads are so designed that a clockwise rotation of the
`piston rod will drive this rod into an ampoule accommodat- 60
`ing compartment 8 in the first division of the housing 1. At
`its end projecting into the compartment 8 the piston rod 6 is
`provided with a pressure foot 9 designed to abut a piston
`closing the rear end of an ampoule accommodated in the
`ampoule holder 2.
`In the proximal side of the end wall 4 the bore is enlarged
`and the internal side of the enlargement is provided with
`
`5
`
`6
`pawl wheel teeth 10 having a steep front edge 11 facing the
`clockwise direction and a ramp shaped rear edge 12 facing
`the anticlockwise direction. At least one pawl13 mounted on
`a piston rod guide 14 co-operates with the pawl teeth 10 so
`that said piston rod guide can only be rotated clockwise in
`the ampoule holder 2.
`On the inner wall of the second division of the housing 1
`a helical protruding rib 16 is provided defining an inner
`thread with a high pitch. A dose scale drum 17 is in its outer
`10 wall provided with a helical grove defining a corresponding
`external thread mating the inner thread just mentioned. The
`pitch angle of the threads exceeds the angle of friction for
`the materials forming the parts of the thread connection and
`consequently the thread connection is of the not self locking
`15 type which induce a relative rotation of the parts of the
`connection when these part are moved axially relative to
`each other.
`Numbers indicating set doses are printed on the outer wall
`of the dose drum 17 and the number corresponding to a set
`dose is shown in a window 18 provided in the side wall of
`the housing 1.
`The dose scale drum 17 is provide with a tubular exten(cid:173)
`sion 21 having an end near the proximal end of the syringe.
`Said end of the extension is closed by an end wall19 having
`25 a central outer protrusion 20. In a part of the wall adjacent
`to the end wall19 the extension 21 is provided with slots 22.
`The said end of the extension is covered by a cup shaped cap
`23 forming an injection button. Internal hooks 24 at the open
`end of this cap snaps over an external circumferential bead
`30 25 on the extension 21 and the protrusion 20 on the end wall
`19 abuts the inner side of the bottom of the cap 23 to form
`a journal about which the injection button can rotate relative
`to the extension 21 whereas it cannot be axially displaced
`relative to this extension.
`A driver tube 26 integral with the piston rod guide 14
`extends from this piston rod guide to the end wall19 of the
`dose scale drum extension 21 and is at its proximal end
`divided into tongues 27 terminated by external hooks 28
`engaging the slots 22 ill the extension 21. This way the dose
`40 scale drum 17 is bound to rotate with the driver tube 26 but
`is axially displaceable relative to this tube.
`To set a dose the ampoule holder 2 is rotated anticlock-
`wise in the first division of the housing 1. This rotation is
`performed against a resistance presented due to the fact that
`a protrusion 30 on the outer wall of the ampoule holder rests
`in one of a number of depressions 31 circumferentially
`provided in the inner wall of said first division of the housing
`as shown in the cross-sectional view in FIG. 3. The angular
`spacing of the depressions are appropriately made so that a
`dose of one unit is set when the protrusion is moved from
`one depression to the neighbouring depression so that the
`number of clicks heard and felt during the dose setting
`rotation corresponds to the size of the set dose.
`The rotation of the ampoule holder is due to the friction
`in the engaging threads 5 and 7 transmitted to the piston rod
`6 and further through the unidirectional coupling to the
`piston rod guide 14 although the torque is transmitted in a
`such a direction that the pawl will intend to click over the
`pawl wheel teeth 10. However, before this click function is
`performed a reluctance have to be overcome. This reluctance
`is obtained by providing the pawl13 with a protrusion 29 at
`its end engaging the pawl wheel teeth 10 and by providing
`depressions 32 in the ramp shaped edges 12 of the pawl
`wheel teeth into which depressions the protrusion 29 on the
`65 pawl13 will rest. Before the clicking release of the coupling
`is obtained a torque sufficient to lift up the protrusion 29 of
`the pawl13 from the depression 32 in the ramp shaped edge
`
`PFIZER, INC. v. SANOFI-AVENTIS DEUTSCHLAND GMBH
`
`Ex. 1014, p. 9 of 13
`
`

`

`US 6,235,004 B 1
`
`7
`12 must be provided. Altogether a moderate torque can be
`transmitted from the rotated ampoule holder 2 to the driver
`tube 26. As the hooks 28 at the proximal end of the driver
`tube 26 engage the slots 22 in the dose scale drum extension
`21 the dose scale drum will be rotated and be screwed
`upwards in the second division of the housing 1 and the
`injection button 23 will be lifted to protrude from the
`proximal end of the housing 1. As only a small torque is
`needed to screw up the dose scale drum this is obtained
`without releasing the unidirectional coupling to its clicking
`release function mode. The size of the set dose can currently
`be seen on the part of the dose scale drum which is presented
`in the window 18. If a too large dose has been set the
`ampoule holder can be rotated in a clockwise direction until
`the number corresponding to the size of the wanted doe is
`presented in the window 18.
`To inject the set dose the injection button 23 is pressed
`home into the housing 1. Thereby the dose scale drum 17 is
`pressed in the distal direction and due to the thread connec(cid:173)
`tion between said drum and the housing 1 a torque is exerted
`on the drum rotating this drum in a clockwise direction. Said
`torque is via the slots 22 in the drum extension 21 and the
`hooks 28 at the end of the driver tube 26 and this tube itself
`transmitted to the piston rod guide 14. The pawls 13 on the
`piston rod guide are allowed to rotate in the clockwise 25
`direction when the torque is strong enough to overcome the
`reluctance provided by the protrusions 29 on the pawls
`engaging the depressions 32 in the ramp shaped edges of the
`pawl wheel teeth.
`Such a strong torque is provided if only the inject button
`23 is pressed hard enough. The piston rod guide 14 will now
`rotate clockwise with the unidirectional coupling working in
`its clicking released mode and the piston rod will be rotated
`clockwise too and will thereby be screwed through the wall
`4 further into the ampoule accommodating compartment 8.
`The unidirectional coupling will never allow an anticlock(cid:173)
`wise rotation of the piston rod guide and the piston and this
`way it is ensured that the pressure foot 9 will never be drawn
`out of abutment with the piston in a not shown ampoule in
`the compartment 8.
`In the shown embodiment the end wall 4 with its threaded
`bore forms a nut member relative to which the piston rod is
`rotated by the piston rod guide 14 and the driver tube 26.
`Embodiments may be imagined wherein the piston rod guide
`is provided in the wall 4 and a nut element is rotated by the 45
`driver tube and such embodiment will not be beyond the
`scope of the invention.
`Another embodiment is described with reference to the
`FIGS. 6-10. Elements corresponding to elements in the
`embodiment described with references to the FIGS. 1-5 are 50
`provided with the same reference numbers. Different from
`the embodiment in FIG. 1-5 is the fact that the injection
`button 23 and not the dose scale drum 17 is provided with
`an extension 33, and that the driver tube 26 is omitted.
`Further the injection button 23 is provided with a flange 32
`which abuts the end of the housing when the injection button
`is pressed home. The extension 33 serves as a journal for the
`dose scale drum 17 which is free to rotate on this journal but
`bound to follow axial movements of the injection button 23
`due to hooks 34 at the end of the extension 33. A longitudinal 60
`bore 35 in the injection button and its extension 33 is
`provided with an internal helical rib 36 engaging a corre(cid:173)
`sponding helical groove in an enlargement 37 at the proxi(cid:173)
`mal end of the piston rod to form a thread connection
`between said button 23 and said piston rod 6. The pitch of 65
`this thread connection is so that a not self locking thread
`connection is formed.
`
`8
`To set a dose the injection button 23 is manually rotated
`in a clockwise direction Thereby this button is screwed
`outwards from the housing 1 as the piston rod 6 will through
`the piston rod guide 14 and the unidrectional coupling be
`5 kept inrotatable although said unidirectional coupling in
`influenced by a torque in its release direction, however, due
`to the provided initial reluctance the piston rod guide 14 will
`not immediately be rotatable. In its movement outwards the
`injection button 23 will draw the dose scale drum 17 with it.
`10 When this drum is moved axially in the housing it will be
`rotated due to the not self locking thread connection between
`said drum 17 and the housing 1.
`By this construction the thread along which the injection
`button is screwed outwards and the tread along which the
`15 dose scale drum is rotated in the housing may be different.
`A click connection corresponding to the one established
`between the cartridge holder 2 and the housing 1 in the
`embodiment according to FIG. 1 is in the embodiment
`according to figure 6 appropriately provided between the
`20 injection button 23 and the housing 1 where one or more
`protrusions 38 provided on the inner wall of the housing
`engages grooves 39 in a cylindrical outer wall of the button
`23. Thereby axial movement of the injection button is
`allowed in all its possible angular positions.
`When the injection button is pressed to inject a set dose
`said button will be maintained inrotatabie during its axial
`movement as the locking between the above mentioned
`protrusions on the inner wall of the housing and grooves on
`the outer wall of the button is strong enough to absorb the
`30 torque exerted on the injection button when it drives the
`piston rod to rotation in a clockwise direction after having
`overcome the reluctance against rotation in the release
`direction of the unidirectional coupling.
`The embodiment shown in FIGS. 11, 12 and 13 has the
`35 housing 1 with the window 18. The end wall 4 with the
`internal thread 5 is provided in a separate member 40 which
`is mounted in an end of the housing, the member 40 having
`protrusions 41 engaging slots 42 in the housing to lock the
`member 40 to the housing 1. Further the member 40 has at
`40 its periphery longitudinal recesses 43 which are engaged by
`not shown internal ribs in the housing to lock the member 40
`against rotation relative to the housing 1. Further protrusions
`44 on the ampoule holder 2 engage the slots 42 to lock the
`ampoule holder 2 to the housing 1.
`The piston rod 6 engages by its external thread 7 the
`internal thread of the end wall 4 and is at its end in the
`ampoule holder terminated by a pressure foot 9 relative to
`which the piston rod 6 is rotatable. A driver tube 45 is at one
`end provided with the pawl 13 which engages pawl wheel
`teeth in the member 40 and is held between a ring shaped
`wall 46 in the housing and the end wall 4 in the member 40
`to keep the driver tube 45 from axial movement but allowing
`it to rotate. On its inner wall the driver tube 45 has a key
`engaging a longitudinal recess in the piston rod 6. Thereby
`55 rotation of the driver tube is transmitted to the piston rod 6
`whereas the piston rod can move freely in the axial direction
`of the driver tube 45. On its outer wall the driver tube 45 has
`an outer thread 47 which engages an inner thread 50 in a nut
`member 48 which has at its distal end a flange 49 and