Abstract:
In a brewing head of an espresso machine including a pressure-tightly closable brewing compartment which comprises an inlet for hot water, a filling opening for fresh coffee powder and an outlet for freshly brewed espresso, a leached-out coffee powder cake ( 69 ) is lifted, after a brewing process, by means of a force-controlled lifting piston ( 4, 4   a ) disposed in the brewing compartment up to an upper edge of the peripheral wall. From that position, the coffee powder cake ( 69 ) is laterally removed by a scraper ( 36 ). The scraper ( 36 ) is associated with a carriage ( 19 ) which can be moved along a glide face ( 41 ) above an opening of the brewing chamber and which has a seal by which, in a work position of carriage ( 19 ), the opening of the brewing chamber can be sealed. In order to obtain a reliable and wear resistant seal of the brewing compartment with a flat brewing head, a brewing compartment sleeve ( 3 ) forming the peripheral wall of the brewing compartment and substantially movable perpendicularly to the plane of the glide face ( 41 ) is force-controlledly moved, in the working position of carriage ( 19 ), through the plane of glide face ( 41 ) into a sealing position at which the brewing compartment is sealed by means of the seal. After a brewing process, it is moved back from the plane of glide face ( 41 ) into a rest position so that carriage ( 19 ) can be moved into a start position next to the brewing compartment.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a brewing head of an espresso machine including a pressure-tightly closable brewing compartment as in accordance with the preamble of claim  1 .  
         [0003]     2. Description of the Related Art  
         [0004]     An espresso machine having a brewing head showing these features comprises a carriage which is linearly movable above the brewing compartment and is shaped as a clearing scraper and serves also for the boiling water supply (EP 0 443 054 B1). The carriage includes a closing member for a brewing compartment integrally formed with a peripheral wall. The carriage including the closing member is movable between a first position for dosing the coffee powder, a second position for closable the brewing compartment and a third position for the following scraping off and discharge of the leached out coffee cake. In a first position, the closing member is disposed on one side of the opening and in its third position on substantially the opposite side of the opening of the brewing compartment. The scraper is arranged on the carriage in such a way that it is disposed in its first position at a side of the closing member averted from the opening, in the third position it is outside of the opening and during the movement from the third via the second position to the scraping off of the coffee cake, it is on the front side of the closing member. Operation of the coffee machine is effected by controlled drive means comprising a motor having a gear including a disc having a groove asymmetrically circulating as a closed loop about the axis of rotation, via which a piston rod of a lifting cylinder movable in the brewing compartment is moved. The gear includes furtheron a rocker arm via which the carriage is moved. The disadvantage of such espresso machine is that the sealing required during the course of the brewing process which can take place under a high pressure of about 12 bar between the brewing compartment and the carriage must be provided by sealing means which are disposed in the area of the glide plane of the carriage and, therefore, are subject to extensive wear. The movability of the carriage in three positions requires a correspondingly large structural volume of the machine.  
         [0005]     In order to solve the sealing problems in the area of the brewing compartment in an operationally safe way and to produce an espresso of a very good quality, it has already been known to provide the two-part brewing head which includes in a lower part integral with the housing a force-controlled lifting piston, with a movable upper part in which a brewing piston can be moved which can be immersed from above into the brewing compartment (EP 0 756 842 A1). The upper part comprises a filling chute for freshly ground coffee, scraper wings, the brewing cylinder unit including the coffee outlet, brewing sieve, brewing piston sealing and crema valve. At the upper part of the brewing head, furtheron, a lowering lever including bearing and stop means is provided. The lower part of the brewing head is equipped with the stationary brewing compartment with the water inlet tube, the lifting piston and the drive thereof via a piston rod which is in operative connection with a control lever also supported in the lower part by which the reciprocating movement of the lifting piston is controlled. The upper part is rotatable about 360° relative to the lower part by means of a pivot which also actuates the control lever, the function positions being fixed by catches. To fill the brewing head with coffee powder, the filling chute is positioned above the brewing compartment. By subsequent rotation, the brewing cylinder is positioned above the brewing compartment and subsequently, by lowering the lowering lever, inserted into the brewing compartment. Sealing of the brewing compartment is effected by a ring seal on a lower part of the brewing piston. During the course of the subsequent brewing process for which boiling water is pressed through the water intake tube and the holes of the lifting piston into the brewing compartment, the brewing cylinder remains stationary. After the brewing process, the brewing piston is released and by lifting the lowering lever is lifted from the brewing compartment. Disposal of the coffee cake is effected by further rotation of the brewing head upper part into its start position which corresponds to the filling position. By using such brewing head, the disadvantages of the coffee machine referred to further above are eliminated; in particular, a safe and wear resistant sealing of the brewing compartment is achieved. It can be considered a disadvantage, however, that the brewing head is not very compact and, particularly in view of the lowering lever and the elements connected with it above the brewing compartment, is relatively high.  
       BRIEF SUMMARY OF THE INVENTION  
       [0006]     It is, therefore, the object of the present invention to effect a reliable, long-living, wear-resistant sealing of the brewing compartment with a compact, particularly flat brewing head.  
         [0007]     This problem is solved by forming the brewing head with the features revealed in the characterizing clause of claim  1 .  
         [0008]     The solution as in accordance with the invention is characterized by a movable brewing compartment sleeve forming the peripheral wall of the brewing compartment, the brewing compartment sleeve being movable, substantially in a lower part of the brewing head, perpendicularly relative to the plane of the glide face of a carriage which constitutes a substantial component of an upper part of the brewing head, said carriage being able to force-controlledly travel with an external, preferably upper, section through the plane of the glide face into a sealing position to completely form the brewing compartment for a boiling process. After a boiling process, the external section of the brewing compartment sleeve is force-controlledly moved back from the plane of the glide face to make unhindered movement of the carriage possible. In this way, the sealing area is shifted from the plane of the glide face, and it is not possible that a sealing element in the sealing area will be worn off by moving the carriage along the glide face after the brewing compartment sleeve has been retracted from the sealing position. That is why the sealing of the brewing compartment can be optimized. The actuation elements of the brewing compartment sleeve as well as a lifting piston drive and, essentially, a carriage drive are preferably disposed in the lower part of the brewing head rather than on the upper part. That is why the brewing head can be shaped compact, in particular flat.  
         [0009]     The brewing compartment is, therefore, made up between the lifting piston, the brewing compartment sleeve forming the peripheral wall, more exactly an internal section of the peripheral wall of the brewing compartment, and the carriage, more exactly a substantially piston shaped section on the underside of the carriage and in spaced relationship to the glide face thereof.  
         [0010]     For a safe sealing of the brewing compartment, the seal according to claim  2  is formed as a ring seal and is disposed on the substantially piston shaped section on the underside of the carriage. The piston shaped section is a fixed element of the carriage and hence does not require any movable bearing and no drive means for movement at right angles relative to the shifting direction of the carriage in order to either open or close the brewing compartment. The sealing of the brewing compartment by means of this piston shaped section is effected, according to claim  3 , in that the upper section of the brewing compartment sleeve is moved above the ring seal on the piston shaped section and embraces or envelops, respectively, the ring seal in this position. This arrangement is robust relative to tolerances of the position of the brewing compartment sleeve in the lifting direction thereof relative to the piston shaped section of the carriage, or the ring seal in the sealing position, respectively.  
         [0011]     In accordance with claim  10 , the plane of the glide face of the carriage is with preference substantially horizontal, whereas the brewing compartment sleeve is substantially vertically liftable and lowerable. It is this orientation, to which refers, inter alia, the definition of the upper section of the brewing compartment sleeve which, more generally, is an external section of the brewing compartment sleeve defining the opening of the brewing compartment. The configuration of the plane of the glide face of the carriage and of the brewing compartment sleeve forming the brewing compartment wall as in accordance with claim  10  is particularly useful if the coffee grinder according to claim  22  is to grind the coffee powder directly, i.e. only by using its gravity, into the brewing compartment and to this end is disposed above the brewing compartment.  
         [0012]     The configuration of the plane of the glide face of the carriage relative to the lifting direction of the brewing compartment sleeve according to claim  10  concretely means, relative to claim  1 , that in the working -position of the carriage, the brewing compartment sleeve is force-controlledly moved from below through the plane of the glide face into the sealing position and after the brewing process is downwardly moved back from the glide face into the rest position.  
         [0013]     More in detail, in accordance with claim  4 , the lifting piston in the brewing compartment sleeve can be moved in the brewing compartment in parallel thereto and communicates with a lifting piston drive. The lifting piston is a movable piston in the brewing head and has, therefore, the function of a brewing piston. In order to drive the brewing chamber sleeve, it is under a spring load, i.e. it is biased, viz. in the direction of the sealing position. The movement in the sealing position is controlled, on one hand, by the lifting piston resting against a drag ring of the brewing compartment sleeve so that over a partial stroke of the lifting piston, the brewing compartment sleeve can move only together with it. The partial stroke is defined, on one side, by the lower rest position of the lifting piston and, on the other, by its position in which it disengages from the drag ring in the sealing position of the brewing compartment sleeve to be further lifted for packing the coffee powder in the brewing compartment. Furthermore, the brewing compartment sleeve can, in its lower rest position be arrested by means of a locking nose if, after a brewing process the leached-out coffee cake is to be scraped out to the side by means of a scraper. The arresting and the release of the arresting of the brewing compartment sleeve by means of the locking nose is also effected by force control, preferably by the means according to claims  7  and  8 . The spring loading of the chamber sleeve referred to above can be effected, according to claim  5 , by at least one compression spring directly or indirectly engaging at the brewing compartment sleeve. To this end, spring arms in particular are solidly assigned to the brewing cylinder.  
         [0014]     To drive the lifting piston, it is connected to a screw cylinder which can extend through the drag ring referred to above and which communicates with an electro-motoric lifting piston drive. The screw cylinder may be multiple threaded. It may be solidly connected with the lifting piston.  
         [0015]     Preferably, however, and according to claim  21 , a lifting piston rod is movably supported in a hollow screw cylinder, and in the hollow screw cylinder, a compression spring is provided which loads the lifting piston via the lifting piston rod. This arrangement is provided in combination with a crema valve according to claim  20  which is disposed in the piston shaped section of the carriage. In view of the spring load of the lifting piston, the volume of the brewing compartment may become larger by the high pressure of the fed-in boiling water whereby the coffee powder may more thoroughly be moistened prior to the brewing process under pressure, which leads to better crema formation. Only when the crema valve opens at a predetermined overpressure, the compression spring in the screw cylinder relaxes and compresses the coffee cake.  
         [0016]     Before the ejection of the leached-out coffee powder cake, the brewing compartment sleeve is arrested, as mentioned above, by the locking nose in its rest position. For corresponding force control of the brewing compartment sleeve, a termination of the gear constituting part of an electromotoric carriage drive with a drive motor communicates with a locking disc which is so shaped that the locking nose engages into it over a partial rotation range of the locking disc.  
         [0017]     The locking function of the locking nose is provided in that, as in accordance with claim  9 , the brewing compartment sleeve is linearly movably provided in a stationary guide sleeve so that the brewing compartment sleeve cannot twist during the course of its predetermined movement and, therefore, takes the locking nose along.  
         [0018]     The advantageous features of the brewing head include also, according to claim  11 , that the carriage which substantially forms the upper part of the brewing head can be moved between two end positions only, namely a working position in which, inter alia, the brewing process takes place, and a start position in which the filling of the brewing compartment sleeve and the removal of the leached-out coffee powder cake after the brewing process, respectively, is prepared.  
         [0019]     Clean removal of the leached-out without causing malfunctions of the brewing head is obtained, according to claim  12 , in that the scraper comprises a forward scraper wall and is supported adjustable for a scraping position and a return position on the carriage in such a way that an underside of the forward scraper wall is lowered, in the scraping position of the scraper, onto the glide face of the carriage, and in the return position of the scraper is elevated at a distance above the glide face. In this way, it is avoided, particularly during the return motion of the carriage from its ejection position which corresponds to the work position, into the start position that remainders of coffee are dragged into the glide face.  
         [0020]     This adjustment of the scraper is preferably obtained, in accordance with claim  13 , in that the carriage can be moved in a sliding duct between a forward boundary at the work position of the carriage and a rear boundary at its start position and that the scraper, by striking against the forward boundary, can be reset into its back motion position, i.e. that its forward scraper wall is lifted after which, by striking against the rear boundary, it can be set into its cleaning position in which its forward scraper wall is lowerd to the slide face. This adjsutment of the scraper is thus effected by the striking of the carriage and needs no particular active drive nor control elements.  
         [0021]     To this end, in detail, the scraper is movably supported, according to claim  14 , on the carriage in the moving direction thereof, the scraper comprising a cover bottom by which it rests on the carriage. Before a front-side end of the cover bottom, the forward scraper wall is angularly shaped in downward direction. Similarly, a rear scraper wall behind the carriage is angularly shaped in downward direction, while the rearward scraper wall, however, need not, in any position of the scraper, lie on the glide face. Of significance are inclined drag noses shaped out on the cover bottom which, in the cleaning position of the scraper, rest in receiving grooves of the upper side of the carriage, when moving the scraper relative to the carriage when the scraper strikes against the front boundary, however, slide out of the receiving grooves on the upper side of the carriage and are lifted thereby, whereas when moving the scraper striking against the rear boundary relative to the carriage, the drag noses slide from the upper side of the carriage into their receiving grooves whereby the scraper takes its cleaning position. In analogy, on the other hand, the inclined drag noses can equally effectively be shaped out at the upper side of the carriage and the inclined receiving grooves in the cover bottom of the scraper.  
         [0022]     More exactly, in accordance with claim  15 , it is the forward scraper wall and the rearward scraper wall of the carriage which, when striking against the front boundery, or the rear boundary, respectively, effect the positioning of the scraper both in the direction of motion and perpendicularly thereto.  
         [0023]     In order to avoid that the displacement of the scraper on the carriage in its longitudinal direction and perpendicularly thereto occurs already when it strikes against the leached-out coffee powder cake, the scraper is pressed by a scraper spring onto the carriage. This means that a spring force has to be overcome before the scraper together with its drag nose can slide onto the upper side of the carriage.  
         [0024]     The above referenced electromotoric carriage drive includes, according to claim  17 , the drive motor together with the gear as well as a swing lever which is in driving connection with a termination of the gear and is coupled to the carriage. Coupling to the carriage is advantageously elastically flexible by correspondingly shaping the swing lever near the carriage coupling location. The aim is that the striking of the scraper on the carriage against the front boundary or the rear boundary of the path of motion of the carriage is shock-absorbed even if coffee powder remnants are between the boundaries and the scraper. In addition, a tolerance balance is obtained making less sophisticated production possible.  
         [0025]     The elastic flexible coupling is concretely obtained, according to claim  18 , in that the swing lever comprises a driven swing lever arm and, near the carriage coupling location of the swing lever, a coupling member which communicates on one side with the carriage and, on the other, is swingably supported on the swing lever arm, and is biased by springs in a nominal position.  
         [0026]     The above referenced screw cylinder for the displacement of the lifting piston is suitably equipped, according to claim  19 , with a speed measuring device, preferably a sensor equipped with an encoder, by which a speed drop of the rotational speed of the screw cylinder can be recorded. The lifting piston drive can be stopped because, by the drop of the speed, a desired packing of the coffee powder in the brewing cylinder can be recorded from which an even packing of the coffee powder results, which is independent from the amount of coffee.  
         [0027]     Further suitable features are included in claims  20  through  23 . The advantageous effects obtained by them will be described in the following specification. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0028]     Details and more concrete explanations of two exemplified embodiments of the brewing head and the control thereof can be taken from the following specification based on a drawing including 11 Figures wherein  
         [0029]      FIG. 1  shows a schematic longitudinal cross section through a portion of an espresso machine in the area of a brewing head in a first embodiment with a carrage in the start position, including a brewing compartment sleeve and a lifting piston therein, each in the rest position,  
         [0030]      FIG. 2  is a view according to  FIG. 1  with the carriage however in the working position, including the brewing compartment sleeve in packed position and a lifted lifting piston immediately prior to, or during, respectively, the brewing process,  
         [0031]      FIG. 3  is a view according to  FIG. 1  but after the brewing process with the brewing compartment sleeve and the lifting piston again in the rest position,  
         [0032]      FIG. 4  is a view according to  FIG. 3  but in preparation of a scraping process of a leached-out coffee powder cake with the lifting piston in the cleaning position,  
         [0033]      FIG. 5  is a view according to  FIG. 4  but with the carriage and the scraper in the cleaning position,  
         [0034]      FIG. 6  is a schematic cross section through the first embodiment of the brewing head in the cleaning position shown in  FIG. 5  in a sectional plane rotated about 90° relative to the sectional plane in  FIGS. 1 through 5 .  
         [0035]      FIG. 7  is a side view on the part of the espresso machine according to  FIGS. 1, 3  und  4 .  
         [0036]      FIG. 8  is a top view on a part of the espresso machine according to  FIG. 7 .  
         [0037]      FIG. 9  is a view, essentially according to  FIG. 2 , of the carriage, the brewing compartment sleeve and the lifting piston with the screw cylinder in a second embodiment wherein a piston rod of the lifting piston is movably supported in the screw cylinder,  
         [0038]      FIG. 10  is a schematic representation of the control of the espresso machine, and  
         [0039]      FIG. 11  shows selected elements of the control according to  FIG. 10  in various switching positions. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0040]     In  FIG. 1 , numeral  1  designates an apparatus housing of an espresso machine to which a guide cylinder  2  of a cylindric brewing compartment sleeve  3  is solidly connected. Brewing compartment sleeve  3  is supported vertically movable in the guide cylinder. In brewing compartment sleeve  3 , a lifting piston  4  movable in parallell relative thereto is provided which is solidly fastened to a multiple thread screw cylinder  5 . By means of this screw cylinder  5 , lifting piston  4  can vertically be moved relative to housing  1 .  
         [0041]     To this end, the screw sleeve is in gear connection with an electromotoric lifting piston drive comprising a motor  6  which thus is the screw piston drive, a respective gear  7 , a driving pinion  8 , and a screw cylinder drive wheel  9  which includes an internal gearing corresponding with the screw of screw cylinder  5 . Screw cylinder drive wheel  9  is rotatably, but not shiftably, guided in a guide  10 .  
         [0042]     Brewing compartment sleeve  3  can be held by lifting cylinder  4  by means of a drag ring  11  located at its inner end and acting as a pressure ring, against two tightened compression springs which attempt to press, via brewing compartment spring arms  14 ,  15 , see  FIG. 6 , brewing compartment sleeve  3  upwards.  
         [0043]     A locking nose  16  solidly disposed at the periphery of brewing compartment sleeve  3  can, in combination with a locking disc  17 , keep the brewing compartment sleeve in the rest position even then when lifting piston  4  in the preparation of an ejection process for the leached-out coffee powder cake is moved upward, see  FIGS. 4 and 5 .  
         [0044]     Above brewing compartment sleeve  3 , a coffee grinder  18  is so provided that it can grind the coffee directly into brewing compartment sleeve  3 .  
         [0045]     Also above the brewing compartment sleeve, in the rest position thereof, compare  FIG. 1 , a carriage  19  which can also be termed as a gliding body is horizontally movable between two end positions in a sliding duct  20  solidly assigned to the housing. The two end positions, as will be shown later, are a start position when the carriage is in its extreme right position, see  FIGS. 1, 3 ,  4 ,  7 , and a working position when the carriage is moved into its extreme left position, see  FIGS. 2, 5 .  
         [0046]     The sliding duct  20  is laterally defined by sliding duct guide tracks  20   a ,  20   b  which are emcompassed from the outside by carriage guides  20   c ,  20   d , see  FIG. 6 .  
         [0047]     In one underside of carriage  19 , a piston shaped cylindric section  21  is formed out which carries a ring seal  22 . A brewing compartment not marked by a numeral formed between the upper side of lifting piston  4 , the internal peripheral wall of brewing compartment sleeve  3  and an under side of the piston shaped section  21 , see  FIG. 2 , is reliably pressure-tightly sealed by ring seal  22  when brewing compartment sleeve  3  is moved over this ring seal in sealing position of the brewing compartment sleeve. Smaller differences in height of the relative position of brewing compartment sleeve  3  and piston shaped section  21  cannot impair the sealing.  
         [0048]     Carriage  19  and, together with it, piston shaped section  21  can be moved by an electromotoric drive which includes a swing lever  23 , see  FIG. 7 , which is pivoted to carriage  19  via a drag bolt  24 . Swing lever  23  swingable about swing lever pivoting bearing  23   b  is moved into each of its two end position, respectively, by a driving disc  25  driven by a further motor  26  via a respective gear  27  and a driving bolt  28  provided on drive disc  25  engaging in an elongated slot  23   a  of swing lever  23 .  
         [0049]     In detail, gear  27  of the electromotoric carriage drive comprises two terminations  29 ,  30  designed with a different reduction ratio. For one movement of swing lever  23 , i.e. for a movement of the carriage with piston shaped section  21  into one of its two end positions, termination  29  for the swing lever performs a half rotation each. The second termination  30 , see  FIGS. 1 and 2 , communicates with locking disc  17  which cooperates with locking nose  16 , and with two solidly connected cam discs  31 ,  32 . Cam discs  31 ,  32  control the positions of carriage  19 , or its piston shaped section  21 , respectively, as well as parts of the movements of the lifting piston via respective contacts  33 ,  34 ,  35 . Second termination  30  rotates synchronously with the first termination  29  for swing lever  23  a quarter rotation for each half rotation of its drive disc  25  for the swing lever. The control obtained therewith will be explained in more detail in connection with  FIGS. 10 and 11 .  
         [0050]     On carriage  19 , a scraper  36  is movably supported in the direction of motion of the carriage. The scraper  36  comprises a forward scraper wall  37  and a rear scraper wall  38  which are angularly bent downwardly from a cover bottom so that an underside  40  of the forward scraper wall can glide on a slide face  41  of sliding duct  20  when the scraper is in its cleaning position on carriage  19 . From cover bottom  39 , beveled drag noses  42 ,  42 ′ are shaped out which can be received by likewisely beveled receiving grooves  43 ,  43 ′ in the carriage. In this case, underside  40  of foreward scraper wall  37  drags on the glide face  41  of sliding duct  20 . If, on the other hand, drag noses  42  are disposed on the upper side of scraper  36 , the underside  40  of forward scraper wall  37  is lifted off from glide face  41  and forms a free space thereto. The different heights of undersides  40  of forward scraper wall  37  are adjusted by boundaries of the motion path of the carriage in slide duct  20 . One boundary is formed by two buffers  44 ,  45  which are provided at a work position of carriage  19  on a discharge chute  46 . The other boundary is a rear wall  47  of the slidnig duct at the start position of carriage  19 . When forward scraper wall  37  strikes against the two buffers  44 ,  45 , the scraper moves backwards whereby its drag noses  42 ,  42 ′ which rest in receiving grooves  43 ,  43 ′ of carriage  19  during forward motion, are pressed out of receiving grooves  43 ,  43 ′. Thereby, scraper  36  is lifted up and remains in the elevated position, i.e. the return motion position, during the course of the complete return motion of carriage  19  into the start position at rear wall  47 . When scraper  36  reaches rear wall  47  so that rear scraper wall  38  strikes against rear wall  47 , the scraper is pushed forward by rear wall  47  and returns into its cleaning position in receiving grooves  43 ,  43 ′. This is supported by a scraper spring  48  provided on the upper side of the scraper, which also avoids that the scraper, when striking against the leached-out coffee powder cake  69 , is moved back into its return motion position before it has ejected the coffee powder cake and strikes against the two buffers  44 ,  45 , see  FIG. 5 . The cleaning position of scraper  36  when striking against the rear wall  47  of the slide duct is shown in  FIG. 3 .  
         [0051]     For safe actuation of scraper  36  serves a bi-partition of swing lever  23  at its slide body coupling end. For this purpose, a coupling member  49  is swingably supported at the end of a driven swing lever arm  50 , the coupling member  49  being kept in a mean nominal position by two compression springs  51 ,  52 . In this way it is reached that the striking of carriage  19  with scraper  36  on it against buffers  44 ,  45  and, in the rear start position of the carriage, against rear wall  47  is effected definedly and shock-absorbingly even if coffee remnants are left between the scraper and rear wall  47  or the buffers  44 ,  45 , respectively. By this elastically resilient coupling of the swing lever, a tolerance balance is obtained as well.  
         [0052]     Lifting piston  4  which can also be referred to as the brewing piston is equipped with a boiling water supply tube  53 , a boiling water distribution chamber  54  and with a boiling water distribution sieve  55 . Piston shaped section  21  on the underside of the carriage supplementing the brewing compartment is equipped with a brew discharge tube  57 , a brew sieve  58  and a brew collection chamber  59  and a crema valve  60 , see particularly  FIG. 2 . Flexible supply and discharge ducts for boiling water supply and brew discharge are not shown. In the boiling water supply with boiling water supply tube  53 , a flow meter  61  is provided shown in  FIG. 11   d  as a symbol and which stops the boiling water supply after the passage of a predetermined amount of water and supplies a signal to a control unit S 1  of the control of the lifting piston, see also  FIG. 10 .  
         [0053]     Screw cylinder  5  on the lifting cylinder is equipped with a sensor and an encoder which measures the rotation speed of the screw cylinder determining therefrom a stop position for the vertical movement of lifting piston  4 , as will be described later.  
         [0054]     The brewing head described is force-controlled as follows in order to safely avoid damages, particularly in the area of the brewing compartment sleeve, of the scraper and the carriage:  
         [0055]     In order to fill the brewing compartment encompassed by brewing compartment sleeve  3  with coffee powder by means of coffee grinder  18  disposed above the brewing compartment sleeve, carriage  19  with piston shaped section  21  on the underside thereof is in its start position, according to  FIG. 1  on the extreme right on the sliding duct  20 . Thereby the opening of brewing compartment sleeve  3  is free. Brewing compartment sleeve  3  is in its lower rest position in which it is held by lifting piston  4  by means of drag ring  11 . The coffee grinder  18  grinds coffee into the brewing compartment sleeve in rest position while the lifting piston is also in its lower rest position. In this rest position, it closes a foot contact  62  by means of an actuation arm  63 , see  FIG. 1 . When a predetermined amount of coffee has been ground-in by coffee grinder  18 , the coffee grinder stops and closes its contact  64  which is shown in  FIG. 10 . Via contact  64 , an electronically retarded starting pulse is supplied to drive motor  26  of the electromotoric carriage drive which remains closed by holding contact  33  by a cam  65  of cam disc  31 , see  FIG. 10 . This starts the electromotoric carriage drive with drive motor  26  and moves, by means of swing lever  23  and the respective further drive elements of the electromotoric carriage drive, namely drive disc  25 , drive disc bolt  28 , coupling member  49 , compression springs  51 ,  52  and drag bolt  24 , the carriage  19  together with piston shaped section  21  on the underside of the carriage in forward direction, i.e. in  FIG. 1  to the left, until scraper  36  supported on carriage  19  strikes against buffer  44 ,  45  and the work position of the carriage with piston shaped section  21  has been reached, as shown in  FIG. 2 .  
         [0056]     Together with the movement of carriage  19 , termination  30  of gear  27  of the electromotoric carriage drive rotates, according to  FIG. 10 , locking disc  17  as well as cam disc  31  for the carriage drive control and cam disc  32  for the lifting piston drive control about 90° from position I into position II. When reaching 90°, holding contact  33  drops from cam  65 , according to position II in  FIG. 10 . In this position, a cam  66  of cam disc  32  for the lifting piston drive control closes contact  34  which imparts the starting pulse to the lifting piston control unit for the lifting pistion movement.  
         [0057]     The lifting piston control unit comprises a dual electronic flip-flop circuit F 1 , F 2  ( 67 ,  68 ) shown in  FIG. 10  and  FIG. 11  as mechanical switches. One of flip flops  67 ,  68  each is inserted in a supply line of motor  6  of the electromotoric lifting piston drive and the other flip flop is inserted into the drain of this motor. In their start position I in  FIG. 10 , both flip flops are on a negative potential, see also  FIG. 11   a.    
         [0058]     The above-mentioned starting pulse triggered by cam  66  puts flip flop F 1 , or  67 , respectively, on a positive potential, as shown in  FIG. 11   b.    
         [0059]     By switching over flip flop F 1   67 , motor  6  of the lifting piston drive starts and moves the lifting piston via gear  7 , driving pinion  8 , screw cylinder drive wheel  9  and screw cylinder  5  upwards. This causes that the coffee powder filled in before is packed, as indicated in  FIG. 2  by  69 . For this stroke of the lifting piston, recess  17   a  of locking disc  17  is located above locking nose  16  of brewing compartment sleeve  3 , as shown in  FIG. 10  by position II, and locking nose  16  can pass through recess  17   a  so that brewing compartment sleeve  3  follows, under the pressure of compression springs  12 ,  13 , the lifting pinion  4  during a partial stroke until an upper part of lifting piston  4  (not designated) has moved over the piston shaped section  21  on the underside of carriage  19 , as can also be seen from  FIG. 2 . The brewing compartment thus closed is safely locked by means of ring seal  20  on piston shaped section  21  in this sealing position of brewing compartment sleeve  3 . This position of brewing compartment sleeve  3 , to make sure, may be signalled by actuated brewing compartment sleeve position contact  80 , see  FIG. 6 , and permit the brewing process. The position taken in  FIG. 2  by carriage  19  is referred to as the work position.  
         [0060]     Lifting piston  4  may further be lifted, beyond the partial stroke where brewing compartment sleeve  3  follows the lifting piston, by means of screw cylinder  5  in order to pre-pack the coffee powder independently from the amount of coffee in a defined measure. To this end, a sensor with an encoder  56  of the screw cylinder measures the upward movement of lifting piston  4  by recording the rotation speed of the screw, cylinder. When reaching a determined speed drop caused by the strain on motor  6  during coffee powder packing, encoder  56  switches the motor off by emitting a stop pulse to flip flop F 2   68  as shown in  FIG. 11  by position c: Flip flop F 2 ,  68  switches to a positive potential and thus separates motor  6  of the lifting piston drive from the power source. At the same time, a signal for the start of the brewing is given to a boiling water pump not shown in the drawing.  
         [0061]     Having obtained a predetermined amount of boiling water recorded by flow meter  61  disposed in the boiling water supply, the flow meter emits a signal to flip flop F 1 ,  67 , as indicated in  FIG. 11 , position d. Thereby, the sense of rotation of lifting piston motor  6  is reversed, motor  6  is started and lifting piston  4  travels downwards in its rest position. This rest position is illustrated in  FIG. 3  in which brewing compartment sleeve  3  is in its rest position as well after having strained compression springs by means of drag ring  11 .  
         [0062]     As soon as lifting piston  4  has reached its rest position, actuation arm  63  of screw cylinder  5  closes foot contact  62  which emits a stop signal to flip flop F 2 ,  68  as shown in  FIG. 11 , position e. This causes that motor  6  of the lifting position drive is cut off from the power supply and is stopped. At the same time, foot contact  62  in the path of motion of screw cylinder  5  emits a start signal to the electromotoric carriage drive with drive motor  26 .  
         [0063]     Since cam disc  32  of the lifting piston drive control rotates synchronously with locking disc  17  and cam disc  31 , cams  66 ,  70 ,  71  of cam disc  32  keep contact  35  open in all positions except position II in  FIG. 10 . Contact  35  is, therefore, closed only in position II in  FIG. 10 , and it is only in this position that foot contact  62  can emit a starting pulse to drive motor  26  of the carriage drive. This avoids that, when one function cycle has been finished, a further function cycle will immediately be initiated when after the end of one function cyle foot contact 6   62  is closed. The starting pulse remains, electronically retarded, on drive motor  26  of the carriage drive until cam  72  of cam disc  31  closes holding contact  33  of drive motor  26 . After the start of the motor, termination  29  of the swing lever drive rotates drive disc  25  of the swing lever about 180° in the same direction of rotation as in the foregoing rotation so that swing lever  23  is moved into its lower start position which is shown in  FIG. 7  and to which corresponds the start position of carriage  19  in the extreme right position in sliding duct  20 . The start position taken anew by carriage  19  is shown in  FIG. 3 .  
         [0064]     In addition, termination  30  of gear  27  of the carriage drive rotates cam discs  31 ,  32  about 90°, and holding contact  33  is relieved by cams  72  so that drive motor  26  of the carriage drive is stopped as shown in  FIG. 10  by position III.  
         [0065]     When the rear position, i.e. in  FIG. 3  the right start position, of carriage  19  has been reached, cam  70  of cam disc  32  closes contact  34  which emits a signal to flip flop F 1 ,  67  as a component of the control unit of the lower piston drive as in accordance with position f in  FIG. 11 . By this signal, the direction of rotation of motor  6  of the lifting piston drive is changed again, the motor starts and lifting piston  4 , together with the leached out coffee powder cake  69  is lifted upwards. Since during the movement of carriage  19  into its start position locking disc  17  has rotated about 90°, recess  17   a  of locking disc  17  is no longer above locking nose  16  of brewing compartment sleeve  3  so that the latter can no longer follow the upward movement of lifting piston  4 . Lifting piston  4  moves upwardly until it arrives at its uppermost position which is in the plane of the glide face of piston shaped section  21  of carriage  19 , actuation arm  63  of screw cylinder  5  closes a head contact  74  in the path of its motion which emits a signal to flip flop F 2 ,  68  so that it takes the switch position according to position  1  in  FIG. 11 , switches to positive potential and stops motor  6  of the lifting piston drive. In this way, the lifting piston remains in the uppermost position as shown in  FIG. 4  where the leached-out coffee powder cake  69  is lifted to the level of the glide face of piston shaped section  21  of carriage  19 .  
         [0066]     In addition, the head contact  74  in the path of motion of actuation arm  63  emits, in the position shown in  FIG. 4 , a start pulse to drive motor  26  of the carriage drive, the start pulse being electronically retarded and remains on the motor  26  until cam disc  31  has rotated so far that cam  73  closes holding contact  33 . This causes that carriage  19  travels forward, i.e. in  FIG. 4  to the left, into the position shown in  FIG. 5  pushing, by means of lowered front scraper wall lower side  40 , see  FIG. 3 , the leached out coffee powder cake  69  into discharge chute  46 . Scraper  36  takes its cleaning position on carriage  19 , as shown in  FIG. 4 . Only when forward scraper wall  37 , as shown in  FIG. 5 , strikes against buffer  44 ,  45 —buffer  45  can be seen in  FIG. 8  only—scraper  36  glides on the upper side of carriage  19  and front scraper wall underside  40  is lifted above the glide face, see  FIG. 5 .  
         [0067]     After the discharge, carriage  19  moves immediately, without stop, into its rear position, i.e. in  FIG. 1  the right start position, because cam  73  of cam disc  31  covers 180° and, by means of holding contact  33 , keeps motor  26  of the carriage drive from position III in  FIG. 10  via position IV in  FIG. 10  at the power supply, and holding contact  33  drops only in position  1  of  FIG. 10  from cam  73 . This means that drive disc  25  for driving swing lever  23 , or the carriage drive, respectively, moves a complete rotation about 360° and carriage  19  with piston shaped section  21  on its underside is moved without stop into the start position in  FIG. 1  and  FIG. 7 .  
         [0068]     Simultaneously with this return movement of the carriage, the lifting piston is moved back to its lowermost rest position. When drive motor  26  of the carriage drive and the gear thereof with termination  30  has rotated cam disc  32  for about 90°—corresponding to the 90° cycle of termination  30 —cam  71  closes contact  34 . This causes that contact  34  emits a pulse to flip flop F 1 ,  67  which switches to a negative potential, as indicated by position h in  FIG. 11 . Screw cylinder  5  together with lifting piston  4  moves downwardly until actuation arm  63  closes foot contact  62  which subsequently emits a signal to flip flop F 2 ,  68  which switches motor  6  to negative potential, see position i corresponding to position a in  FIG. 11 . In this position, the drive of screw cylinder  5  is stopped and the lifting piston is in its lowermost rest position.  
         [0069]     Since in this rest position contact  35  is opened through cam  71  of cam disc  32 , see position I in  FIG. 10 , a start pulse to drive motor  26  of the carriage drive is avoided by foot contact  62  which, otherwise, would of new trigger an uncontrolled start of the functions described. Rather, a full working cycle remains finished, and all functional elements are in the start position, prepared for a new working cycle which is started by activating the coffee grinder.  
         [0070]     In  FIG. 10 , the functional elements which belong to the control unit for the lifting piston drive, on one hand, and which can be associated with the control unit for the carriage drive, on the other, are summarized.  
         [0071]     As concerns control unit S 2  for the carriage drive with drive motor  26 , it should be noted that diodes  75 ,  76 ,  77  arranged therein effect that the control pulses by contacts  64 ,  62 ,  74 , depending on the positions of cam discs  31  und  32 , will reach the desired functional elements only.  
         [0072]     In the second embodiment of the brewing head shown in  FIG. 9 , equal functional elements are designated, as in the first embodiment, with respective reference numerals, similar functional elements are designated with changed reference numerals. In the second embodiment, lifting piston  4   a  is movably supported within screw cylinder  5   a  against a compression spring  78  which sits on a, not designated, collar on the bottom of screw cylinder  5   a . Lifting piston  4   a  is held in its shown upper end position by a ring retainer  79  attached to the bottom of its lifting piston rod  4   b . The compression spring is so strong that it is not compressed during an upward movement of lifting piston  4   a  and the packed coffee powder by screw cylinder  5   a . It will only be pressed together, via lifting piston  4   a,  by the high pressure of the boiling water flowing into the brewing compartment so that the brewing space is enlarged and the coffee powder is better moistened prior to the brewing process proper. This leads to improved crema formation. Only when crema valve  60  in cross sections  19   a  opens at about 6 bar, compression spring  78  will relax when the brewing compartment becomes smaller.  
         [0073]     Referring to the forced control in detail described above, it should be noted that it can be effected by means of equally effective means, particularly by a micro controller. In connection with the forced control, it is essential that brewing compartment sleeve  3  is moved into its sealing position before, in the brewing compartment formed by it, the coffee powder is packed and boiling water is supplied, and that the brewing compartment sleeve is lowered from the path of motion of the carriage into its rest position before the carriage with the scraper is moved, particularly when the scraper is lowered to the slide face of the carriage.