METHOD FOR DETECTING THE TYPE OF AN EXCHANGEABLE PISTON-CYLINDER UNIT FOR A DISPENSER

Abstract

A method for detecting the type of an exchangeable piston-cylinder unit for a dispenser, to a piston-cylinder unit having at least one radially oriented information carrier section, and at least one axially oriented information carrier section, both of which at least partially specifies the type of piston-cylinder unit, and to a dispenser having an acquisition device for automatically identifying the type of piston-cylinder unit arranged on the dispenser. The method has at least the following steps: a) detachably mounting the piston-cylinder unit on the dispenser by at least an axial movement; b) detecting completion of a successful mounting of the piston-cylinder unit on the dispenser with a sensor device; c) detecting an information of the axially oriented information carrier section; d) detecting an information of the radially oriented information carrier section; and e) determining the type of the piston-cylinder unit mounted on the dispenser from the detected information.

Claims

1-37. (canceled)

38. A method for detecting the type of an exchangeable piston-cylinder unit for a dispenser, wherein the piston-cylinder unit has at least one radially oriented information carrier section, which at least partially specifies the type of the piston-cylinder unit and which has a geometrical extent in the radial direction by means of which an acquirable information item is encoded, and at least one axially oriented information carrier section, which at least partially specifies the type of the piston-cylinder unit and which has a geometrical extent in the axial direction of the dispenser by means of which an acquirable information item is encoded, and the dispenser has an acquisition device for automatically identifying the type of a piston-cylinder unit mounted on the dispenser, wherein the method comprises: a) releasably mounting the piston-cylinder unit on the dispenser by means of a movement at least substantially in the axial direction of the dispenser; b) detecting completion of a successful mounting of the piston-cylinder unit on the dispenser by means of a sensor device; c) acquiring an information item of the axially oriented information carrier section, d) acquiring an information item of the radially oriented information carrier section, and e) determining the type of the piston-cylinder unit mounted on the dispenser from the information items acquired.

39. The method as claimed in claim 38, comprising, before step a), moving at least part of at least one of a radial information reader of the acquisition device or an axial information reader of the acquisition device into a release position, thus enabling the piston-cylinder unit to be mounted on the dispenser in the axial direction without being hindered by the radial information reader or the axial information reader.

40. The method as claimed in claim 38, comprising, after step b), in at least a partial temporal overlap with at least one of steps c) or d), releasably connecting a piston head of the piston-cylinder unit to a piston actuator of the dispenser at a fastening section of the piston head.

41. The method as claimed in claim 38, wherein, after step b) and before step c), a reference point on the piston head side is acquired by producing a relative movement between a piston head of the piston-cylinder unit and a piston actuator of the dispenser.

42. The method as claimed in claim 41, wherein the length of the relative movement is determined.

43. The method as claimed in claim 41, wherein the piston actuator is moved toward the piston head until a stop of the piston actuator rests against an end face of the piston head.

44. The method as claimed in claim 38, wherein, in step c), an acquisition element of an axial information reader of the acquisition device is inserted at least partially into a groove in a piston head of the piston-cylinder unit, the groove extending in the axial direction of the piston-cylinder unit, and wherein the depth of this groove is determined.

45. The method as claimed in claim 44, wherein insertion of the acquisition element is started from a reference point on the piston head.

46. The method as claimed claim 38, wherein, in step d), a projection of a radial information reader of the acquisition device is inserted at least partially into a recess on a piston head of the piston-cylinder unit, the recess extending in the radial direction of the piston-cylinder unit, and wherein the presence of this recess is determined.

47. The method as claimed claim 46, wherein a photoelectric barrier is used to determine the presence of the radially extending recess.

48. The method as claimed in claim 38, wherein, in step c), an acquisition element of an axial information reader of the acquisition device is inserted at least partially into a groove in a piston head of the piston-cylinder unit, the groove extending in the axial direction of the piston-cylinder unit, wherein the depth of this groove is determined and wherein, to move the axial information reader out of the release position, a locking element of the dispenser is moved.

49. The method as claimed claim 38, wherein, in step d), a projection of a radial information reader of the acquisition device is inserted at least partially into a recess on a piston head of the piston-cylinder unit, the recess extending in the radial direction of the piston-cylinder unit, and wherein the presence of this recess is determined and wherein, to move the radial information reader out of the release position, a locking element of the dispenser is moved.

50. An exchangeable piston-cylinder unit for a dispenser, comprising: at least one radially oriented information carrier section, which partially specifies the type of the piston-cylinder unit and which has a geometrical extent in a radial direction by means of which an acquirable information item is encoded, and at least one axially oriented information carrier section, which partially specifies the type of the piston-cylinder unit and which has a geometrical extent in an axial direction by means of which another acquirable information item is encoded.

51. The piston-cylinder unit as claimed in claim 50, wherein the radially oriented information carrier section or the axially oriented information carrier section is provided on a piston head of the piston-cylinder unit.

52. The piston-cylinder unit as claimed in claim 50, wherein both of the radially oriented information carrier section and the axially oriented information carrier section are provided on a piston head of the piston-cylinder unit.

53. The piston-cylinder unit as claimed in claim 52, wherein the axially oriented information carrier section is formed by a groove in the piston head that extends in the axial direction of the piston-cylinder unit.

54. The piston-cylinder unit as claimed in claim 52, wherein the radially oriented information carrier section is formed by a recess on the piston head, the recess extending in the radial direction of the piston-cylinder unit.

55. The piston-cylinder unit as claimed in claim 53, wherein the type of piston-cylinder unit is identified by the depth of the radially oriented recess and the depth of the axially oriented groove.

56. The piston-cylinder unit as claimed in claim 51, wherein the piston head has a fastening section which is separate from the information carrier sections and at which a piston actuator of the dispenser is engageable.

57. The piston-cylinder unit as claimed in claim 56, wherein the radially oriented information carrier section is formed by a radially oriented recess on the piston head and wherein the radially oriented recess is arranged between the end face of the piston head and the fastening section.

58. An exchangeable piston-cylinder unit for a dispenser, comprising: at least one axially oriented information carrier section, which partially specifies the type of the piston-cylinder unit and which has a geometrical extent in an axial direction by means of which an acquirable information item is encoded, and a fastening section, wherein: the axially oriented information carrier section and the fastening section are provided on a piston head of the piston-cylinder unit, the fastening section is arranged separately from the axially oriented information carrier section, and a piston actuator of the dispenser is engageable with the piston head at said fastening section.

59. The piston-cylinder unit as claimed in claim 58, wherein the axially oriented information carrier section is formed by a groove in the piston head that extends in the axial direction of the piston-cylinder unit.

60. The piston-cylinder unit as claimed in claim 59, wherein the depth of the groove partially specifies the type of the piston-cylinder unit.

61. The piston-cylinder unit as claimed in claim 58, wherein the fastening section is arranged below the axially oriented information carrier section in the axial direction.

62. The piston-cylinder unit as claimed in claim 58, further comprising at least one radially oriented information carrier section on the piston head which partially specifies the type of the piston-cylinder unit and which has a geometrical extent in a radial direction by means of which an acquirable information item is encoded.

63. The piston-cylinder unit as claimed in claim 62, wherein the radially oriented information carrier section is arranged separately from the axially oriented information carrier section.

64. The piston-cylinder unit as claimed in claim 63, wherein the radially oriented information carrier section is arranged between an end face of the piston head and the fastening section.

65. A dispenser, on which a piston-cylinder unit is releasably mountable by means of a movement at least substantially in an axial direction of the dispenser, comprising: a piston actuator that is connectable to the piston of the piston-cylinder unit, an acquisition device for automatically identifying the type of a piston-cylinder unit mounted on the dispenser, wherein the acquisition device has: a radial information reader, by means of which an information item of a radially oriented information carrier section of the piston-cylinder unit is able to be acquired, and an axial information reader, by means of which an information item of an axially oriented information carrier section of the piston-cylinder unit is able to be acquired.

66. The dispenser as claimed in claim 65, wherein the radial information reader or the axial information reader is adapted to acquire the information of the radially oriented information carrier section or of the axially oriented information carrier section by any of electronic, optical, inductive or mechanical means.

67. The dispenser as claimed in claim 65, wherein the axial information reader has an acquisition element that is able to be inserted into a groove of a piston head of the piston-cylinder unit in the axial direction, the groove extending in the axial direction of the piston-cylinder unit, and wherein the depth of this groove is determinable by inserting the acquisition element into the groove in the axial direction.

68. The dispenser as claimed in claim 65, wherein the radial information reader has a projection and wherein at least part of the projection is able to be inserted into a recess on a piston head of the piston-cylinder unit in a radial direction, the recess extending in the radial direction of the piston-cylinder unit, and wherein the presence of this recess is determinable by inserting the projection into the recess in the radial direction.

69. The dispenser as claimed in claim 68, wherein the radial information reader has a photoelectric barrier with a light beam source and a sensor for detecting light beams from the light beam source, and wherein the photoelectric barrier is arranged in such a way that insertion of the projection of the radial information reader into the radially oriented recess is detectable by the photoelectric barrier.

70. The dispenser as claimed in claim 65, wherein the piston actuator is engageable with a piston head of the piston-cylinder unit at a fastening section which is separate from the information carrier sections.

71. The dispenser as claimed in claim 65, wherein at least part of the radial information reader and at least part of the axial information reader are movable into a release position for mounting the piston-cylinder unit on the dispenser in the axial direction without being hindered by the radial information reader or the axial information reader.

72. The dispenser as claimed in claim 71, wherein the dispenser has a locking element which is movable in the axial direction of the dispenser in order to move at least one of the axial information reader and the radial information reader out of the release position.

73. The dispenser as claimed in claim 65, wherein the piston actuator is moveable toward a piston head of the piston-cylinder unit until a stop of the piston actuator rests against an end face of the piston head in order to acquire a reference point on the piston head.

74. The dispenser as claimed in claim 65, wherein the dispenser has at least one of mechanical, electronic, inductive or optical means for detection of mounting of the piston-cylinder unit on the dispenser.

75. A system for receiving and dispensing fluid volumes, comprising: an exchangeable piston-cylinder unit and a dispenser, wherein the piston-cylinder unit comprises: at least one radially oriented information carrier section, which partially specifies the type of the piston-cylinder unit and which has a geometrical extent in a radial direction by means of which an acquirable information item is encoded, and at least one axially oriented information carrier section, which partially specifies the type of the piston-cylinder unit and which has a geometrical extent in an axial direction by means of which another acquirable information item is encoded, wherein the dispenser comprises: a piston actuator that is connectable to the piston of the piston-cylinder unit, an acquisition device for automatically identifying the type of a piston-cylinder unit mounted on the dispenser having a radial information reader, by means of which an information item of a radially oriented information carrier section of the piston-cylinder unit is able to be acquired, and an axial information reader, by means of which an information item of an axially oriented information carrier section of the piston-cylinder unit is able to be acquired, and wherein the piston-cylinder unit is releasably mounted on the dispenser by a movement at least substantially in an axial direction of the dispenser.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0071] FIG. 1 is a schematic perspective view of a preferred embodiment of a piston-cylinder unit according to the invention,

[0072] FIG. 2 is an enlarged schematic perspective view of a piston head of the piston-cylinder unit shown FIG. 1,

[0073] FIG. 3 is a schematic perspective view of a preferred embodiment of a dispenser according to the invention,

[0074] FIG. 4 is a schematic longitudinal sectional view through a preferred embodiment of a system according to the invention with the piston-cylinder unit inserted into a dispenser in a first state, wherein parts of the dispenser have been omitted to simplify illustration,

[0075] FIG. 5 is a schematic longitudinal sectional view through the system shown in FIG. 4 in a second state, and

[0076] FIG. 6 is a schematic longitudinal sectional view through the system shown in FIG. 4 in a third state.

DETAILED DESCRIPTION OF THE INVENTION

[0077] FIG. 1 shows a preferred embodiment of a piston-cylinder unit 1 according to the invention for a dispenser 2 schematically in a perspective view. The piston-cylinder unit 1 has an axial direction A.sub.k and a radial direction R.sub.k illustrated in FIG. 1.

[0078] The piston-cylinder unit 1 is designed as an exchangeable part. It can be in the form of a syringe and can be various sizes with different volumetric capacities. It has a cylinder 3, in which a sealed piston 4 (FIGS. 4-6) can be moved for the purpose of drawing in and expelling a liquid to be pipetted or metered. The piston 4 has a piston rod 5, at one end of which, which projects from the cylinder 3, a piston head 6 is mounted. Only the piston head 6 of the piston 4 is visible in FIG. 1.

[0079] The piston-cylinder unit 1 according to the invention has two radially oriented information carrier sections 7, which partially specify the type of the piston-cylinder unit 1, and precisely one axially oriented information carrier section 8, which partially specifies the type of the piston-cylinder unit 1.

[0080] In the illustrated preferred embodiment, the radially oriented information carrier sections 7 and the axially oriented information carrier section 8 are arranged on the piston head 6.

[0081] Here, the radially oriented information carrier sections 7 are each formed by a recess 9 on the piston head 6, the recess 9 extending in the radial direction R.sub.k of the piston-cylinder unit 1 and running around in the circumferential direction of the piston-cylinder unit 1. The radially oriented information carrier sections 7 are arranged offset relative to one another in the axial direction A.sub.k. A distinction can be drawn here between an upper radially oriented information carrier section 7 (arranged on the piston head 6 on the extreme left in FIG. 1) and a lower radially oriented information carrier section 7 (arranged on the piston head 6 further to the right in FIG. 1).

[0082] Here, the axially oriented information carrier section 8 is formed by a recess 10 in the piston head 6, the recess being formed as a groove extending in the axial direction A.sub.k of the piston-cylinder unit 1. The axially oriented recess 10 extends in the axial direction A.sub.k, starting from an end face of the piston head, and is upwardly open in the axial direction A.sub.k, that is to say obliquely upwards to the left in FIG. 1.

[0083] In FIG. 2, the piston head 6 is illustrated schematically on an enlarged scale in a perspective view. There, it can be seen that the radially oriented recesses 9 are formed by the fact that the piston head has a smaller diameter in these sections.

[0084] In the preferred embodiment illustrated, the respective depth or extent of the radially oriented recesses 9 in the radial direction R.sub.k can assume only one particular value, in this case approximately 5 mm. The situation is therefore that the radially oriented recesses 9 are either present at a particular position in the axial direction A.sub.k or not. This also means that, at a depth of 0 mm, this would not be a radially oriented recess in the sense according to the present invention.

[0085] Piston-cylinder units 1 of different types can differ, inter alia, in the depth, number, arrangement in the axial direction A.sub.k and/or the respective width (extent in the axial direction A.sub.k) of the radially oriented recesses 9.

[0086] In FIG. 2, it can also be seen that the axially oriented information carrier section 8 is here designed as an axially oriented recess 10 in the form of a groove. This is therefore not a drill hole surrounded in the radial direction R.sub.k. On the contrary, the axially oriented recess 10 is partially open to the outside in the radial direction R.sub.k, more specifically along the entire depth of the recess 10. As an alternative, the axially oriented recess 10 can be designed as a blind hole.

[0087] In the preferred embodiment illustrated, the recesses 9 are designed in such a way that the depth, number, arrangement in the axial direction A.sub.k and the respective width of the radially oriented recesses 9 specify the type of the piston-cylinder unit 1. In addition, the type of the piston-cylinder unit 1 is specified in the depth (extent in the axial direction A.sub.k) of the axially oriented recess 10 and in the information as to whether a radially oriented recess 9 is present or not in a particular axial region of the piston head 6.

[0088] Thus, the type of the piston-cylinder unit 1 can be identified by means of a dispenser which acquires only the information of the radially oriented information carrier sections 7 and by means of a dispenser according to the invention.

[0089] In the preferred embodiment illustrated, the depth of the axially oriented recess 10 can assume one of several discrete values, e.g., one of eight possible depth values. The discrete depth values have a minimum spacing, preferably about 2 mm. At a depth of 0 mm, this would not be an axially oriented recess in the sense according to the present invention.

[0090] In the preferred embodiment illustrated, the axially oriented recess 10 extends over only part of the piston head 6 in the axial direction A.sub.k. This allows stable gripping of the piston head 6 without significant deformations of the piston head 6.

[0091] In the preferred embodiment illustrated, the two radially oriented information carrier sections 7 and the axially oriented information carrier section 8 partially overlap. In the case of the recesses 9 and the groove 10, this is dependent on the depth of the axially oriented groove 10 and the spacing of the radially oriented recesses 9 from the end face of the piston head 6.

[0092] In the preferred embodiment illustrated, the piston head 6 has a fastening section 11, at which a piston actuator 26 of the dispenser 2 can engage the piston head 6. Here, this fastening section 11 is arranged separately from the information carrier sections 7, 8, namely below the radially oriented information carrier section 8 in the axial direction A.sub.k. There is no overlap between the fastening section 11 and the information carrier sections 7, 8 here.

[0093] The piston-cylinder unit 1 according to the invention allows a compact construction, backward compatibility with older piston-cylinder units and precise movements of the piston 4 by means of the piston actuator 26 without significant deformation of the piston head 6.

[0094] FIG. 3 shows a preferred embodiment of a dispenser 2 according to the invention schematically in a perspective view. The dispenser 2 has an axial direction A.sub.d illustrated in FIG. 3.

[0095] The dispenser 2 according to the invention has an acquisition device for automatically identifying the type of a piston-cylinder unit 1 mounted on the dispenser 2. The acquisition device has a radial information reader 12, by means of which an information item of the radially oriented information carrier sections 7 of the piston-cylinder unit 1 can be acquired. Moreover, the acquisition device has an axial information reader 13, by means of which an information item of the axially oriented information carrier section 8 of the piston-cylinder unit 1 can be acquired. By means of the acquisition device, the dispenser 2 can identify the type of a piston-cylinder unit 1 mounted thereon.

[0096] FIG. 4 shows schematically a longitudinal section through a preferred embodiment of a system 14 according to the invention with the dispenser 2 and the piston-cylinder unit 1 inserted into the dispenser 2 in a first state. Here, the dispenser 2 is illustrated only in part. FIG. 4 is namely restricted to illustrating those components which are required to explain the present invention.

[0097] In the preferred embodiment illustrated, the piston 4 has a piston spike 28, which projects into a tip 29 of the piston-cylinder unit 1 in the end position illustrated in FIG. 3 in order to minimize the dead volume.

[0098] The cylinder 3 has a flange 30, which rests against a stop element 32 of the dispenser 2. By this means and with the aid of a fixing device (not illustrated), the cylinder 3 is fixed on the dispenser 2, and therefore all that is required to draw in and expel liquid as regards the piston-cylinder unit 1 is that the piston 4 should be movable in the cylinder 3.

[0099] In the preferred embodiment illustrated, the axial information reader 13 has an acquisition element 15 and the acquisition device is designed in such a way that part of the acquisition element 15 can be inserted in the axial direction A.sub.k into the axially oriented groove 10 of the piston-cylinder unit 1, and in this way the depth of this groove 10 can be determined.

[0100] Here, the acquisition element 15 is elastically preloaded counter to the direction of insertion of the piston-cylinder unit 1 by means of a spring 16. The dispenser 2 has a locking element 17, by means of which the acquisition element 15 can be moved into a release position and held there. The locking element 17 holds the acquisition element 15 in the release position in that a fixing element 18 of the locking element 17 counteracts the force of the spring 16 at an extension 19 of the acquisition element 15 and blocks a movement of the acquisition element 15 in the direction of the spring force (that is to say toward the piston-cylinder unit 1 in the axial direction A.sub.d).

[0101] The locking element 17 can be moved in the axial direction A.sub.d in the dispenser 2 and relative to the acquisition device. When the locking element 17 is moved in the direction of the piston-cylinder unit 1, a movement of the acquisition element 15 is no longer blocked, and therefore the acquisition element 15 is pushed toward the piston head 6 and then into the axially oriented recess 10 of the piston head 6 by the spring 16 until the acquisition element 15 strikes the end of the recess 10 and is blocked there.

[0102] In the preferred embodiment illustrated, the acquisition device has a device for determining the position of the acquisition element 15. This device for position determination comprises a position element 20, which is arranged on the acquisition element 15, opposite the extension 19. By means of this device for position determination, the distance of the relative movement of the acquisition element 15 toward the piston head 6i.e. the distance which the acquisition element 15 travels out of the release position and/or from a reference point on the piston head side to the end of the axially oriented recess 10.

[0103] In the preferred embodiment illustrated, the radial information reader 12 has a projection 21 and the acquisition device is designed in such a way that part of the projection 21 can be inserted in the radial direction R.sub.k into the radially oriented recess 9 of one of the two radially oriented information carrier sections 7 of the piston-cylinder unit 1, namely into the lower radially oriented recess 9, and in this way the presence of this recess 9 can be determined.

[0104] In the preferred embodiment illustrated, the radial information reader 12 has precisely one projection 21 and the projection 21 of the radial information reader 12 can be moved in the radial direction R.sub.k toward the piston head 6 only at one particular axial position. Here, therefore, the radial information reader 12 cannot read out all the information of all the radially oriented information carrier sections 7 (cannot be inserted into all the radially oriented recesses 9). On the contrary, the radial information reader 12 can detect whether a radially oriented recess 9 is present or not in a particular axial region of the piston head 6 when a piston-cylinder unit 1 is mounted on the dispenser. As an alternative, provision can be made for the radial information reader 12 to have a plurality of projections 21 that can be moved independently of one another and/or to enable it to be moved in the radial direction R.sub.k toward the piston head 6 at several axial positions.

[0105] In the preferred embodiment illustrated, the projection 21 of the radial information reader 12 is elastically preloaded in the radial direction R.sub.k by means of a spring 22. By means of the locking element 17, the projection 21 can be moved into a release position and held there. The locking element 17 holds the projection 21 in the release position in that a sliding block element 23 of the locking element 17 counteracts the force of the spring 22 at the radial information reader 12 and blocks a movement of the projection 21 in the direction of the spring force (that is to say toward the piston head 6 in the radial direction R.sub.k).

[0106] If the locking element 17 is moved by a sufficient amount relative to the radial information reader 12 in the direction of the piston-cylinder unit 1, a movement of the projection 21 is no longer blocked, and therefore the projection 21 is moved toward the piston head 6 by the spring 22. If there is a radially oriented recess 9 on the corresponding axial region of the piston head 6, the projection 21 is pushed into this radially oriented recess 9 of the piston head 6, where applicable until the projection 21 strikes the end of the recess 9 and is blocked there. In the preferred embodiment of the piston-cylinder unit 1 which is illustrated, there is a radially oriented recess 9, namely the lower radially oriented recess 9, on the corresponding axial region of the piston head 6.

[0107] If the locking element 17 is moved by a sufficient amount counter to the direction of insertion of the piston-cylinder unit 1, the acquisition element 15 and the projection 21 can be moved into the release position. In the release position, the piston-cylinder unit 1 can be inserted into or removed from the dispenser 2 in the axial direction A.sub.d without being hindered by the radial information reader 12, in particular by the projection 21 thereof, and by the axial information reader 13, in particular by the acquisition element 15 thereof.

[0108] In the preferred embodiment illustrated, the radial information reader 12 has a photoelectric barrier 24 having a light beam source and a sensor for detecting light beams from the light beam source. The photoelectric barrier 24 is arranged in such a way that the photoelectric barrier 24 can detect whether or not the projection 21 of the radial information reader 12 has been inserted into a radially oriented recess 9 of the piston head 6. Here, the photoelectric barrier 24 is arranged immovably in the dispenser 2. A bar 25, which is moved synchronously with the projection 21, is provided on the radial information reader 12. In the release position of the radial information reader 12, the bar 25 interrupts the photoelectric barrier 24. This also applies in the case where there is no radially oriented recess 9. If the projection 21 has been inserted in the radial direction R.sub.k into a radially oriented recess 9, as far as the end thereof, the photoelectric barrier 24 is not interrupted by the bar 25. Thus, the acquisition device can determine whether or not there is a radially oriented recess 9 on the corresponding axial region of the piston head 6.

[0109] In the preferred embodiment illustrated, the dispenser 2 has a piston drive device with the piston actuator 26, which is partially visible in FIGS. 4 to 6. The piston actuator 26 is designed in such a way that it can engage the piston head 6 of the piston-cylinder unit 1 at the fastening section 11.

[0110] In the preferred embodiment illustrated, the acquisition element 15, the spring 16, the extension 19, the projection 21, the spring 22 and the bar 25 are coupled in terms of movement to the piston actuator 26 or to parts of the piston actuator 26. The piston actuator 26 can be moved toward the piston head 6 of the piston-cylinder unit 1. The movement continues at least until a stop 27 of the piston actuator 26 rests against the end face of the piston head 6. This movement is also referred to as block travel and is used to acquire a reference point on the piston head side. In particular, this reference point indicates the starting point for a determination of the depth of the axially oriented recess 10 of the piston head 6.

[0111] The block travel is also used to detect whether the piston 4 has been pushed into the cylinder 3 to the maximum extent or the extent to which the piston 4 has been pushed into the cylinder 3. With the information from the block travel, the piston 4 can, where appropriate, be moved into a starting position, being pushed to the maximum extent into the cylinder 3 for example.

[0112] In the preferred embodiment illustrated, the dispenser 2 has a sensor device for detecting the mounting of the piston-cylinder unit 1 on the dispenser 2. A photoelectric barrier 31 is provided as a sensor device here. As soon as successful mounting a piston-cylinder unit 1 has been detected, the acquisition of the information of the information carrier sections 7, 8 can begin.

[0113] In the first state, which is illustrated in FIG. 4, the acquisition element 15 and the projection 21 are in the release position. The block travel has not yet been carried out.

[0114] FIG. 5 shows schematically a longitudinal section through the system 14 from FIG. 4 in a second state. In this second state, the block travel has been carried out and completed.

[0115] FIG. 6 shows schematically a longitudinal section through the system 14 from FIG. 4 in a third state. In this third state, the acquisition element 15 has been inserted into the axially oriented recess 10 as far as the end thereof, and the projection 21 has been inserted into one of the two radially oriented recesses 9, as far as the end thereof.

[0116] In the text which follows, a preferred sequence of a method for detecting the type of the exchangeable piston-cylinder unit 1 for a dispenser 2 is described.

[0117] First of all, the radial information reader 12 and the axial information reader 13 are moved into the release position, thus allowing the piston-cylinder unit 1 to be inserted into the dispenser 2 in the axial direction A.sub.d without being hindered by the radial information reader 12 and the axial information reader 13.

[0118] The piston-cylinder unit 1 is then inserted releasably into the dispenser 2 by means of a movement at least substantially in the axial direction A.sub.d of the dispenser 2. During this process, the cylinder 3 of the piston-cylinder unit 1 is fixed.

[0119] If the piston-cylinder unit 1 has been inserted successfully into the dispenser 2, this is detected by means of the sensor device, in this case the photoelectric barrier 31.

[0120] The reference point on the piston head side is then acquired by producing a relative movement between the piston head 6 and the piston actuator 26. During this process, the piston actuator 26 is moved toward the piston head 6 until the stop 27 of the piston actuator 26 rests against an end face of the piston head 6 (block travel). The length of the relative movement is determined by means of a motor-driven device for incremental travel measurement.

[0121] In the preferred embodiment, the acquisition element 15 and the projection 21 are moved toward the piston head 6 in the axial direction A.sub.d at least partially in temporal overlap, in particular simultaneously, during the block travel.

[0122] Acquisition of the reference point on the piston head side represents, as it were, a travel calibration for the subsequent detection of the type of the inserted piston-cylinder unit 1, which makes the method at least to a large extent independent of differences in the dimensional tolerances of the parts of the piston-cylinder unit 1. This is because determination of the reference point in each type detection process opens up the possibility of defining a starting point for reading the information of the information carrier sections 7, 8, on the basis of which, e.g., by the interposition of an invariable starting value defined in the dispenser 2, a target specification can be given to the acquisition device, e.g., as regards the time or travel distance following acquisition of the reference point on the piston head side detection of the information can be expected or is to be carried out.

[0123] To acquire the information of the axially oriented information carrier section 8, at least part of the acquisition element 15 of the axial information reader 13 is then inserted into the axially oriented groove 10 of the piston head 6, starting from the reference point on the piston head side. The depth of this groove 10 is determined by means of the position element 20 of the device for position determination.

[0124] After this, simultaneously or beforehand, preferably in at least partial temporal overlap, the piston head 6 of the piston-cylinder unit 1 is connected releasably to the piston actuator 26 of the dispenser 2 at the fastening section 11 of the piston head 6. In this way, coupling between the piston actuator 26 and the piston 4 is achieved.

[0125] By means of these steps, in at least partial temporal overlap, the information of the radially oriented information carrier section 7 is acquired by inserting at least part of the projection 21 of the radial information reader 12 into that radially oriented recess 9 on the piston head 6 which is at the same level as the projection 21 of the radial information reader 12 in the axial direction A.sub.d. The presence of this recess 9 is determined by means of the photoelectric barrier 24.

[0126] In order to implement the acquisition of the information in as short a time as possible, the information readers 12, 13 move at least substantially simultaneously. The coupling of the piston 4 can also take place directly after the block travel. To move the acquisition element 15 and the projection 21 out of the release position and to engage the fastening section 11 by means of the piston actuator 26, the locking element 17 of the dispenser 2 is moved in the axial direction A.sub.d of the dispenser 2 as described above, wherein the fixing element 18 and the sliding block element 23 are arranged in mutually coordinated positions.