Abstract:
In a coffee automat, a vertically adjustable and lockable outflow unit ( 3 ), which comprises at least one coffee outflow tube ( 6 ) in fluid-conductive connection with a coffee brewing device is continuously height-adjustable relative to a cup base and can be locked by a locking means. In order to easily and smoothly adjust, in a coffee automat rationally to be manufactured, the outflow unit ( 3 ) with the locking means released, the outflow unit ( 3 ) is supported on housing ( 1 ) by means of a longitudinal ball bearing ( 12 ) as a first bearing element, which embraces a vertical longitudinal ball bearing shaft ( 13 ) as a second bearing element. One of the two bearing elements is connected with outflow unit ( 3 ) and the other of the two bearing elements is in solid connection with a housing ( 1 ) of the coffee automat.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a coffee automat having a vertically adjustable and lockable outflow unit.  
         [0003]     2. Description of the Related Art  
         [0004]     By means of such prior art coffee automats, various coffee preparations can be selected for which different portions, or liquid amounts, respectively, are typical and for which, therefore, differently sized cups have to be used. Cups for espresso, for instance, are distinctly smaller, particularly less high, than are coffee pots or cups for cappuccino. For large coffee portions, mugs can be used. In order to obtain a very precise inflow of the coffee preparation into the vessels of different size, particularly height, prior art coffee automats include already an outflow unit vertically adjustable with respect to the size, particularly the height, of the receiving vessel, above a vessel support, or cup support, respectively. For the height adjusting support of the outflow unit, a groove and tongue shift arrangement is provided as a rule. The outflow unit may, in addition, include a clamping means in order to lock the adjusted outflow height.—Unless produced very precisely and at high costs, such groove and tongue shift arrangements may be adjustable with a lot of difficulties only or may include a large play. In combination with the clamping means the require attention and a certain skill for adjustment and safe locking. In operation, they do not impart a very valent impression.  
         [0005]     Technically highly sophisticated is also a prior art drinks dispenser, particularly a coffee automat of the kind referred to in the beginning including an outflow means for the beverage and a cup support wherein a height distance between an outflow portion, or an outflow unit, respectively, and the cup support is continuously adjustable and lockable by a locking means which is in operative connection with a movable part on one hand, and a fixed part of the drinks dispenser, on the other, wherein the movable part, adjacent to the fixed part, includes two sliding coulisses horizontally spaced in parallel relative to each other, each of which being height-adjustable in a slider (DE 298 10 291.9 A). In detail, each sliding coulisse is approximately U-shaped having an inner leg and an outer leg, and each slider constitutes a sliding angle having two legs the first leg of which forming a solid unit with the fixed portion and at least one section of the second leg is embraced by the inner leg and the outer leg of the sliding coulisse. For locking, the outer legs of the sliding coulisse may include, on its fixed outer side facing the fixed portion, a stripe of ferromagnetic material and facing it, a magnet is provided on the fixed portion. Analogously and vice versa, the outer legs of the sliding coulisse may include, on their outer side facing the fixed part, the magnet facing same the strip of ferromagnetic material is solidly fastened to the fixed part whereof.  
       BRIEF SUMMARY OF THE INVENTION  
       [0006]     It is therefore the aim of the present invention to further develop a rationally producible coffee automat including a vertically adjustable and lockable outflow unit of the kind referred to in the beginning so that the outflow unit, with the locking means disengaged, may precisely and easily be adjusted.  
         [0007]     For the coffee automat, this problem is solved based on the features of the first aspect of the present invention.  
         [0008]     In this way, a friction and wear resistant support of the outflow unit is obtained on the housing of the coffee automat by means of a longitudinal ball bearing as the first support element which comprises a vertical longitudinal ball bearing shaft as the second support element so that the outflow unit can easily be adjusted and subsequently locked. One of the two first and second support elements is connected with the housing and the other of the two support elements is in solid connection with the housing. Two compact variants of this support arrangement are revealed in the second and third aspects of the present invention. In the vertical adjustment, the outflow unit can simply and reliably be locked by means of at least two locking elements according to the eighth aspect of the present invention, a first one of which being connected to the outflow unit, particularly the installation chassis, and the second is provided on a housing of the coffee automat. The coffee automat having such a vertically adjustable and lockable outflow unit may, in addition, esthetically be particularly appealing and impart the impression of a valent haptic.  
         [0009]     In particular, the magnetic field of a holding magnet in which the ferromagnetic locking element is disposed can uncomplicatedly and directly be used, according the eighth aspect of the present invention, for the generation of an adhesive force between the outflow unit and the housing of the coffee automat.  
         [0010]     In an embodiment according to the tenth aspect of the present invention, it is possible instead to adjust the installation chassis as an integral part of the outflow unit by means of a driving motor via a toothed rack and a gear connection. Locking of the outflow unit adjusted to a corresponding cup height can be obtained, in case of a self-locking make of the driving motor with the gear connection, by simply switching off the driving motor, i.e. no particular manipulation is necessary.—The gear connection includes a gear and, according to the eleventh aspect of the present invention, particularly a driving pinion connected with the driving motor and meshing with the toothed rack.  
         [0011]     In the area of the vertically adjustable and lockable outflow unit, the coffee automat is furthermore shaped, according to the second through seventh aspects of the present invention, in a particularly suitable form.  
         [0012]     According to the second aspect of the present invention, the longitudinal ball bearing shaft is vertically provided on a support which, on its part, is solidly connected with the housing of the coffee automat. The housing of the coffee automat need not, therefore, be worked on for mounting the longitudinal ball bearing shaft, except for the provision of the support. In addition, the support may be provided on the housing in a way that it can easily be changed.  
         [0013]     According to the fourth aspect of the present invention, the installation chassis of the outflow unit is provided with a vertical wall which separates a space in which the coffee outflow tube and a section of a coffee inflow duct connected therewith are disposed from a further space in which the longitudinal ball bearing and a locking element, or a drive element for the height adjustment of the installation chassis are disposed. In this way, the installation chassis can directly cooperate with a further locking element, or a drive element, respectively, which are protected against the outside.  
         [0014]     In the embodiment according to the fifth aspect of the present invention, a horizontal wall section projects from the first side of the installation chassis, which carries the coffee outflow tube.  
         [0015]     Instead of a coffee outflow tube, at least two outflow tubes may be provided at this place as well which, spaced relative to each other, project below from an outflow distributor while the outflow distributor is carried by the horizontal wall section.  
         [0016]     The longitudinal ball bearing is protectedly and mechanically stably disposed in a projection projecting from the second side of the installation chassis. At this projection, either the locking means may engage or a locking element may be provided.  
         [0017]     According to the seventh aspect of the present invention, the installation chassis has a smooth surface and is hygienically closed by a cap which substantially covers the installation chassis with the exception of the side facing the housing of the coffee automat, or the support, respectively, so that the connection of the installation chassis to the elements of height adjustment, or locking, respectively, disposed on, or within, the housing of the coffee automat, is ensured.  
         [0018]     In the above-mentioned embodiment of the locking means according to the eighth aspect of the present invention, wherein a holding magnet is provided as one of the two locking elements and having a ferromagnetic second locking element, the holding magnet is preferably provided, according to the ninth aspect of the present invention, limitedly movable in horizontal direction, in a recess of the installation chassis, particularly in the projection of the installation chassis. The ferromagnetic locking element cooperating with the holding magnet provided on the housing, which faces substantially the holding magnet may suitably be realized by the support of the longitudinal ball bearing shaft provided on the housing. For height adjustment, the outflow unit may manually be gripped and either lifted or lowered whereby the holding magnet glides on the ferromagnetic locking element with a defined friction but does not lock because it is horizontally movable. When letting the outflow unit go, it will, without any difficulties safely be held by the adhesive force between the holding magnet and the ferromagnetic locking element.  
         [0019]     In the above-mentioned adjustment device and the locking means including a driving motor which is connected with the installation chassis via a gear connection, there is provided, according to the tenth aspect of the present invention, a vertical toothed rack at the installation chassis, preferably at the above-mentioned projection on the second side of the vertical wall of the installation chassis where it can, without any difficulties mesh with a gear connection to the driving motor, or a driving pinion, respectively.  
         [0020]     In the formation of the locking means including the holding magnet and the opposite ferromagnetic locking element solidly disposed on the housing, height adjustment may simply and sensibly be performed manually by manipulating the outflow unit, considering that the holding magnet in combination with the opposite ferromagnetic locking element, constantly generates sufficient adhesive friction to be able to lock the outflow unit at any adjusted height. This applies also to manufacturing tolerances since the holding magnet is arranged limitedly movable in horizontal direction whereby a tolerance compensation is obtained. Manual adjustment, on the other hand, of the outflow unit is therefore ensured in case of a suitable magnetic field strength of the holding magnet which constantly abuts against the ferromagnetic locking element.—When forming the locking means and the height adjustment with a driving motor and a gear connection to the installation chassis, height adjustment may be even more comfortably obtained by actuating an up-down switch according to the twelfth aspect of the present invention, or a starter switch for coffee according to the nineteenth aspect of the present invention.  
         [0021]     By the up-down switch according to the twelfth aspect of the present invention, and in combination with the limit switches according to the thirteenth aspect of the present invention, the direction is controlled in which the outflow unit is adjusted until the driving motor, by switching the up-down switch, or automatically on reaching the actual cup height, is switched off. This will later be explained in more detail.  
         [0022]     The limit switches may be disposed, according to the fourteenth aspect of the present invention, as head contact or foot contact in the movement path of the installation chassis in order to effect that the driving motor starts in the correct sense of rotation for the vertical adjustment of the outflow unit in order to move the outflow unit from the respective end position.  
         [0023]     Instead of the limit switches, a displacement encoder may be provided which is coupled, according to the fifteenth aspect of the present invention, to the driving motor and senses whether or not the upper end position or the lower end position of the outflow unit has been reached. The encoder may also control the direction in which the outflow unit moves out from one of the two end positions until the outflow unit, particularly when reaching the respective cup height, is stopped.  
         [0024]     Particularly friendly in operation, since operator&#39;s attention is not required for stopping the outflow unit when reaching the respective cup height, the coffee automat may be equipped, according to the sixteenth aspect of the present invention, with a sensor unit at the outflow unit by which the height of a cup placed under the outflow tube is sensed and the driving motor which moves the outflow unit particularly from an upper end position is automatically switched off as soon as the sensor arrangement determines the height of the cup.  
         [0025]     According to the seventeenth and eighteenth aspects of the present invention, the sensor arrangement may alternatively be provided as a light barrier system or as laser approximation or reflex system.  
         [0026]     For automatically switching off the height adjustment of the outflow unit by means of the sensor unit, the switching arrangement according to the nineteenth aspect of the present invention has been provided. It comprises a relay which can be switched on by a starter switch. The starter switch may particularly be the switch initiating the brewing of the coffee. The relay actuates switch-over contacts disposed in the current path of the driving motor wherein the end contacts as well as a light barrier contact, or laser barrier contact, respectively, are disposed in a way that by actuating the starter switch, the outflow unit will move down from an upper end position down to the cup height, will stop when sensing the cup height by the respective sensor arrangement since the light barrier contact, or the laser barrier contact, respectively, is actuated, particularly opened thereby, and after the termination of the brewing process or removal of the cup, moves back into the upper end position by opening the starter switch, particularly because the current flow via the relay contacts shaped as two-way contacts and the head contact, or the respective end switch, respectively, is reversed.—It should be noted that when opening the starter switch for newly adjusting the outflow unit, a brewing water pump of the coffee automat is simultaneously switched off in order to avoid that the coffee preparation flows out of the outflow unit uncontrolled.  
         [0027]     It is particularly useful if the circuit arrangement in which the driving motor is arranged, is enlarged, according to the twentieth aspect of the present invention, by a further sensor, or a sensor contact controlled by it, respectively, which senses, or controls, the presence of a cup placed under the outflow tube so that wrong handling of the height adjustment is excluded. This sensor is particularly arranged in series relative to the starter switch and to the relay. If there is no cup under the outflow duct, the sensor switch effects that the current path of the driving motor is not closed and it remains in its end position. In addition, it can prevent a brewing process. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0028]     In the following, four embodiments of the present invention will be explained in more detail, based on a drawing including ten figures from which further details of the invention and clarifications can be taken, and wherein  
         [0029]      FIG. 1  shows a horizontal section through a first embodiment of a coffee automat, particularly having a directly manually vertically adjustable outflow unit having a holding magnet;  
         [0030]      FIG. 2  shows affront view of the first embodiment according to  FIG. 1 ;  
         [0031]      FIG. 3  shows a horizontal section through a second embodiment of the coffee automat having a manually controlled outflow unit vertically adjustable by a motor;  
         [0032]      FIG. 4  shows a front view of the second embodiment according to  FIG. 3 ;  
         [0033]      FIG. 5  shows a horizontal section through a third embodiment of an outflow unit automatically vertically adjustable by a motor and including a sensor arrangement engaged in height adjustment;  
         [0034]      FIG. 6  shows a front view of the third embodiment according to  FIG. 5 ;  
         [0035]      FIG. 7  shows a horizontal section through a fourth embodiment of the outflow unit as a variant of the third embodiment having an alternative sensor arrangement engaging in height adjustment;  
         [0036]      FIG. 8  shows a front view of the fourth embodiment according to  FIG. 7 ;  
         [0037]      FIG. 9  shows a basic circuitry diagram of the second embodiment; and  
         [0038]      FIG. 10  shows a basic circuitry diagram of the third or fourth embodiment. 
     
    
       [0039]     In the figures, corresponding parts of the various embodiments have identical reference numerals.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0040]     In  FIGS. 1 through 9 , reference numeral  1  refers to a housing of an espresso machine comprising a base  2  on which, below an outflow unit  3 , cups of various sizes, for instance a small cup  4  or a large cup  5  can be placed. In  FIGS. 3 through 8 , the larger cup is shown in broken lines. The cups are placed on base  2  so that they completely take up brewed coffee from coffee outflow tubes  6 ,  6   a  on a coffee outflow distributor. The amount of brewed coffee leaving coffee outflow tubes  6  can be adjusted by means not shown.—Coffee outflow tubes  6 ,  6   a  and coffee outflow distributor  7  belong to outflow unit  3  through which a flexible coffee in-flow duct  8  leads to outflow distributor  7  from a brew unit not shown in housing  1 . The brew unit includes also a brewing water pump not shown which is switched on for brewing the coffee. For switching on, starter switch  19  for coffee is used.  
         [0041]     The structure of outflow unit  3  supporting outflow distributor  7  including coffee outflow tubes  6 ,  6   a,  constitutes an installation chassis  9  having a vertical wall  10  from the first side of which a horizontal wall section  11  is projecting which supports outflow distributor  7  including coffee outflow tubes  6 ,  6   a.  On the side averted from the first side of vertical wall  10 , a projection  11  a from the wall is formed which faces housing  1  of the espresso machine. In a bore of projection  11 , a vertically movable longitudinal ball bearing  12  is disposed. Longitudinal ball bearing  12  includes a fixed longitudinal ball bearing shaft  13  along which it can easily be moved.  
         [0042]     On the side of projection  11  a facing housing  1  of the first embodiment according to  FIG. 1 , a holding magnet  15  is fitted into an open recess  14  in a way that holding magnet  15  can horizontally be moved in a limited way to make tolerance compensation possible so that holding magnet  15 , independently from its height adjustment can safely adhere to a counter piece of ferromagnetic material and thus can lock the outflow unit.  
         [0043]     The counter piece is a carrier  16  of ferromagnetic material, which is solidly connected with housing  1  in that it is screwed for instance to a counter plate  1   a  behind a wall of housing  1 . Hence, carrier  16  serves in connection with holding magnet  15  as a locking element.  
         [0044]     Between legs, not shown, of the carrier which is approximately C-shaped, the longitudinal ball bearing shaft  13  is stationarily secured.  
         [0045]     From  FIG. 1 , it can be taken that housing  1  of the espresso machine and counter plate  1   a  include a slit through which the flexible coffee inflow duct  8  is guided from the brew unit, or the brewing head, respectively, in housing  1  to coffee outflow distributor  7 .  
         [0046]     The structural unit of carrier  16  and of installation chassis  9  is closed by a cover cap  17  to constitute a flat face.  
         [0047]      FIG. 2  shows three control buttons of the espresso machine, namely a mains switch  18 , a starter switch for coffee  19  and a starter button  20  for steam.  
         [0048]     Prior to a brewing process and after placing cup  4  on base  2 , outflow unit  3  is manually adjusted to a height so that coffee flowing from coffee outflow tubes  6 ,  6   a  after actuating starter switch  19  for coffee will completely and safely be taken up by cup  4 . Double arrow  36  shown in  FIGS. 1 through 8  shows the height adjustability of the outflow unit in both directions. In the position of outflow unit  3  shown in  FIG. 1 , it takes its lowest position where an upper horizontal section of covering cap  17  rests on carrier  16 . From this position, outflow unit  3  can without any difficulties be moved upward after overcoming the adhesive force of holding magnet  15 , while after releasing the outflow unit, holding magnet  15  holds the outflow unit safely in the position adjusted.  
         [0049]     The second embodiment according to  FIGS. 3 and 4  with outflow unit  3   a  differs from the above first embodiment according to  FIGS. 1 and 2  substantially in the following:  
         [0050]     On the side of vertical wall  10   a  of an installation chassis  9   a,  facing housing  1  of the espresso machine, a toothed rack  21  is in solid connection with a projection  11   a  of the wall. Toothed rack  21  serves as an element for vertical adjustment and for locking. For an easy and wear-resistant height adjustment, the longitudinal ball bearing is disposed in projection  11   a  which in this way is in solid connection with installation chassis  9   a.  It embraces a longitudinal ball bearing shaft  13   a  for easy and wear-resistant height adjustment. The vertical longitudinal ball bearing shaft  13   a  is fixed to a carrier  16   a  which, on its part, is screwed to housing  1  of the espresso machine, or a counter plate  1   a,  respectively.  
         [0051]     At the two ends of the movement path of the toothed rack, two limit switches, namely a head contact  22  and a foot contact  23  are disposed. They are formed as openers, i.e. they are normally closed, but are opened if the toothed rack is in its respective end position, as for instance shown in  FIG. 3  at head contact  22 .  
         [0052]     For height adjustment, a drive motor  24  connected via a gear  35  and a driving pinion  25  with toothed rack  21  into which driving pinion  25  engages is provided in housing  1 . Control of drive motor  24  is effected, in the embodiment according to  FIGS. 3 and 4 , by means of an up-down switch  26  provided as a two-pole switch as shown in the respective circuitry diagram in  FIG. 9 . From this circuitry diagram, the insertion of head contact  22  and foot contact  23  can be taken as well.  
         [0053]     In the situation shown in  FIGS. 3 and 9 , outflow unit  3   a  is in its upper position in which toothed rack  21  opens head contact  22  while foot contact  23  is closed. In the circuit position shown in  FIG. 9  of up-down switch  26 , drive motor  24  is without voltage. When up-down switch  26  is actuated from this switch position, current flows via foot contact  23 , a contact  26   b  of up-down switch  26 , the motor  24  and a second contact  26   a  of up-down switch  26 . Therefore, drive motor  24  moves, via gear  35  and pinion  25 , the toothed rack and together with it the complete outflow unit  3   a  in downward direction toward a large cup  5  or a small cup  4  placed underneath until the operator switches up-down switch  26  back into the position shown in  FIG. 9  thus interrupting current flow via motor  24 . If there is no such switch-over during the lowering of outflow unit  3   a,  drive motor  24  is switched off when toothed rack  21  reaches its end position and opens foot contact  23 . Head contact  22  is already closed as soon as the upper side of toothed rack  21  has left the head contact, whereby in case of renewed actuation of the up-down switch when it reaches the position shown in  FIG. 9 , the circuit arrangement is prepared to feed current to drive motor  24  so that outflow unit  3   a  moves back in upward direction up to its upper end position. (The upper end position will not be reached if up-down switch  26  is actuated beforehand so that its movement is stopped.)  
         [0054]     In case of a currentless drive motor  2 , outflow unit  3   a  will automatically lock since the arrangement of motor, gear, pinion, toothed rack is self-locking.  
         [0055]     The second embodiment according to  FIGS. 3, 4  and  9  is thus suited to make height adjustment of outflow unit  3   a  easier since it requires only one actuation of the up-down switch and the observation of the height adjustment with a view to the cup placed underneath.  
         [0056]     A higher automation degree of height adjustment is obtained by means of the embodiments according to  FIGS. 5 through 8  and  10 . Both with the third embodiment according to  FIGS. 5 and 6  and with the fourth embodiment according to  FIGS. 7 and 8 , height adjustment and subsequent locking occurs automatically after actuating starter switch  19  for coffee when a cup  4 , or  5 , respectively, is placed on base  2 .  
         [0057]     To this end, the third embodiment according to  FIG. 5  includes, in the radius of action of cup  4 , or  5 , respectively, in housing  1  of the espresso machine, a first stationary sensor  27  and, on outflow unit  3   a,  a light barrier adjustable with it including light barrier elements  28 ,  28   a.  The latter are disposed at a lower section of outflow unit  3   a  so that a beam of rays passing between them is interrupted by the upper edge of cup  4 , or  5 , respectively. A sensor contact belonging to cup sensor  27  is designated, in  FIG. 10 , by reference numeral  29 , and a light barrier contact belonging to light barrier  28 ,  28   a  bears reference numeral  30 .  
         [0058]     It should be noted in this connection already that the fourth embodiment differs from the third embodiment in that the fourth embodiment according to  FIGS. 7 and 8  includes a laser approximation or reflex arrangement having laser sensors  31 ,  31   a , instead of light barrier  28 ,  28   a , in order to sense a cup size under one of the respective coffee outflow tubes  6 ,  6   a . In  FIG. 10 , therefore, light barrier contact  30  may also be considered as a laser sensor contact.  
         [0059]     The third embodiment and the fourth embodiment, as for the rest, show head contact  22  and foot contact  23  as in the second embodiment.  
         [0060]     In the circuitry diagram according to  FIG. 10  for the third and the fourth embodiment, the switch-over contacts  26   a ,  26   b  of up-down switch  26  of  FIG. 9  are quasi replaced by relay switch-over contacts  32 ,  33  actuated by a relay  34 . In the current path of drive motor  24 , there is also provided, in series relative to foot contact  23 , the light barrier contact or laser sensor contact  30 .  
         [0061]     Relay  34 , i.e. the coil thereof, is series-connected with starter switch  19  for coffee which is manually to be actuated, as well as with sensor contact  29  assigned to cup sensor  27  by means of which the presence of a cup on base  2  is sensed.  
         [0062]     The height adjustment of the third embodiment and of the fourth embodiment is also performed as follows:  
         [0063]     It is again assumed that, originally, the outflow unit  3   a  is in its upper end position in which head contact  22  is open und foot contact  23  is closed, compare  FIGS. 5, 7  and  10 . When actuating mains switch  18 , the espresso machine is ready for operation. By means of the cup sensor, it is sensed whether or not a cup is placed underneath outflow unit  3   a  on base  2 , by which sensor contact  29  of  FIG. 10  might be closed. If now switch  19  for the coffee brewing process is actuated, this closes the circuit of relay  34 , and relay switch-over contacts  32 ,  33  close a circuit via contacts  23  and  30  so that motor  24  moves outflow unit  3   a  downward as long until light barrier  28 ,  28   a  in  FIGS. 5 and 6  is interrupted by the cup, or the cup height is sensed by one of laser sensors  31 ,  31  a in  FIGS. 7 and 8 . This done, the light barrier contact or laser sensor contact  30  formed as an opener opens and drive motor  24  stops which, via gear means  35 , drive pinion  36  and toothed rack  21 , locks outflow unit  3   a .—The automatic height adjustment is only started by actuating starter switch  19  if cup sensor  27  locates a cup and closes sensor contact  29 . In this connection, cup  4 , or  5 , respectively, may already be underneath outflow unit  3   a  or may be placed under outflow unit  3   a  after actuating starter switch  19 .  
         [0064]     After finishing the brewing process, brew switch  19  is actuated anew whereby the brew water pump is simultaneously switched off so that no brewed coffee can exit from coffee outflow tubes  6 ,  6   a . By opening starter switch  19  for coffee, relay contacts  32 ,  33  are switched into the position shown in  FIG. 10  and current is fed to motor  24  via closed head contact  22  so that motor  24  moves outflow unit  3   a  upward until, in the upper end position of outflow unit  3   a , head contact  22  is opened and the motor stops and hence locks outflow unit  3   a .—A downward movement of outflow unit  3   a  is additionally to, and independently from, the sensing of the cup height is limited by foot contact  23 . From the above, it can be taken that head contact  22  and foot contact  23  each prepare the reversal of drive motor  2  which either, according to  FIG. 9 , is performed via contacts  26  of the up-down switch or, according to  FIG. 10 , by relay contacts  32  and  33  of relay  34 .