Abstract:
The present invention relates to a tachograph including a cuboid housing and a print device. The print device is formed in such a manner that the thermal print head in the housing of the tachograph, the transport cylinder and the mechanism actuating the cylinder are disposed in a support which can be removed from the front side of the tachograph. In addition, a support bridge is provided to support the thermal print head which can pivot counter to the action of supporting springs. The bridge is secured onto the top panel of the tachograph by insertion of a retainer.

Description:
This is a continuation of PCT/EP02/00433, filed Jan. 17, 2002. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a tachograph comprising a ciboid housing and a printing device. The printing device includes a thermal print head and a support which can be removed from the front side of the housing of the tachograph. Once removed it is possibile to reload a reel of paper or paper strip which forms the store of printing material. In addition, it is possible to reload a transport roll which, at least during printing, is operatively connected by a force fit to the thermal print head with the interposition of the printing material and is driven by a movement mechanism. The thermal print head is arranged in the housing of the tachograph and the transport roll and the movement mechanism are arranged in the support. 
     Tachographs which are not equipped for the use of circular graph charts as recording substrates but contain appropriately designed mass memories for the storage of the journey and working time data require printing devices which are suitable for documentation in the form of a visually legible record. The printing devices have to be arranged inside the tachograph since, in a driver&#39;s cab of a utility vehicle there is generally no free space for the installation of an independent printer in communication with the tachograph. 
     An advantage of electronic tachographs includes the flexibility of mounting location within the driver&#39;s cab. This advantage suffers when a printer is included with the electronic tachograph. Printers include certain requirements which limit tachograph location including the store of printing material and the necessity that the printing device be loaded with the store of printing material and for the starting section of the printing material to be brought into the printing position. This disadvantage is further exacerbated by the general design of tachographs themselves including a flat front face flush against a cab wall. Accordingly, only front loading of printer material is possible. To facilitate loading, it is necessary to use a support which can be displaced or pivoted out or folded out on the front side. 
     The structural concept mentioned in the beginning and described in German utility model DE-U 299 20 901.6 has the advantage of more beneficial utilization: of space than would be possible in the case of using commercially available printing units. In addition, in this design, threading the start of the paper strip between thermal print head and transport roll, and also precautions for eliminating a paper jam are dispensed with. Furthermore, the thermal print head can be fitted in a fixed location within the housing of the tachograph, so that even when the support is removed from the tachograph, immediate contact with dirt and moisture is largely avoided. 
     However, this assignment of the thermal print head to the housing causes problems inasmuch as the side walls and the top panel of the housing constitute relatively thin sheet metal parts. The installation space, for example, provided in a dashboard of a utility vehicle and corresponding to the format of the housing, does not permit any, outwardly projecting fixing elements. Further, reaction-free support of the spring-mounted thermal print head is necessary and seams and openings are to be avoided because of the intended tightness of the device. On the other hand, extremely little space is available for fitting the thermal print head in the direction of the vertical axis of the tachograph, and conditions of large-scale mass production have to be considered. This means that the fitting of the thermal print head is to be possible with the lowest possible expenditure on production and mounting and is to be easily reproducible with satisfactory functioning. 
     BRIEF SUMMARY OF THE INVENTION 
     The above disadvantages are addressed by the present invention which includes providing a stable arrangement of a thermal print head within the housing of a tachograph which is suitable for the aforementioned conditions, takes up little space, can be implemented with components which are as simple as possible, and can be mounted in a straightforward manner. 
     The invention provides for a support bridge which can be pivoted counter to the action of at least one spring. The support bridge is provided to support the thermal print head and is fixed to a top panel of the housing of the tachograph. 
     An exemplary embodiment is characterized in that a retainer that is fixed to the top panel is provided for fitting the support bridge to the top panel. 
     The exemplary embodiment is distinguished in particular by the fact that the retainer is plate-like, that lugs provided with through holes are formed on the legs of the support bridge, and in that platforms assigned to the lugs and prepared for screw connections are integrally molded on the retainer. 
     The retainer and the top panel are connected to each other seamlessly at a plurality of points by using a sheet metal forming technique. In addition, the retainer has a cutout corresponding to the support bridge. Likewise, the support bridge is fixed to the retainer in such a way that the support bridge engages in the cutout in the retainer. Further, the legs of the support bridge point away from the top panel. 
     An advantage of the present invention includes the thermal print head being be arranged exclusively on the top panel of the housing and thus, since no longitudinal or transverse beams for fitting the thermal print head are required within the housing, there is optimum utilization of the overall space provided. The present invention also permits secure and stable fixing of the thermal print head. In particular, the support fixing o f the thermal print head not only has to support the contact force on the transport roll but, when the support is displaced, also has to absorb force components oriented transversely with respect to the direction of action of the contact force. The support bridge serves as a mount, within the retainer, in such a way that the support bridge is fixed and braced by the top part of the housing thereby being locked in the direction of movement of the support. In addition, it should be emphasized that, because of the retainer being fixed over the largest possible area to the top part of the housing, the invention effects reinforcement which is expedient for the fitting of the thermal print head, and that the thermal print head can be replaced in a straightforward manner. 
     A method applied to fixing the retainer to the top part, which has been developed by Tox Pressotechnik GmbH and Co. KG, Weingarten, and is known as the Tox circular point sheet metal connecting method, provides a seamless connection in the manner of a press fastener by means of material forming. This connecting technique satisfies the requirement for tightness and flatness of the top part of its outer side. 
     The present invention comprises a tachograph, comprising: a housing comprising walls defining at least an internal cavity and a top panel, a printing device located within said cavity and comprising a thermal print head and printing material, a transport roll located within said cavity and functionally associated via a force fit to said head such that said printing material is positioned between said transport roll and said head, said transport roll driven by a movement mechanism, a support located within said cavity for supporting said printing device, printing material, transport roll and movement mechanism, said support comprising means for extending said printing device out of said housing, and a support bridge for supporting said thermal print head, said support bridge being pivotably responsive to a spring action, fixed to said top panel. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The novel features believed characteristic of the invention are set out in the claims below. The invention itself, however, as well as other features and advantages thereof, are best understood by reference to the detailed description, which follows, when read in conjunction with the accompanying drawing, wherein: 
     FIG. 1 depicts a side view of a printing device the support for which is formed as a drawer; 
     FIG. 2 depicts the printing device of FIG. 1 with the support pushed into the tachograph; 
     FIG. 3 depicts a prospective illustration of a retainer; 
     FIG. 4 depicts a support bridge serving to hold the thermal print head; 
     FIG. 5 depicts a perspective bottom view, illustrated as a plan view, of a top part of the housing with thermal print head installed; and 
     FIG. 6 depicts a partial section according to the section line A in FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 depicts a tachograph  1  conceived as an installed device. The tachograph  1  includes a housing  2  which may be cuboid, include walls defining an internal cavity and a front wall  3 . As further depicted, the space-saving housing  2 , preferably produced from sheet metal material, comprises a top part  5 , a bottom part  4 , rear wall  8 , side walls  6  and  7  (see FIG. 5) and top panel  9 . The walls are appropriately connected so as to form the housing  2 . 
     The front of tachograph  1  includes a display (not shown) which is, visible to the driver. The front further includes operating elements, slots and other means associated with data cards for the interactive use thereof. 
     The tachograph  1  further includes a printer subassembly with a support  10 . The subassembly may be linearly extended and closed off in a drawer like manner. The subassembly may further be closed off by plate  11  which in the closed position is flush with at least front wall  3 . The support  10  may be assigned a bistable latching mechanism which, in the event that printing material is to be topped up, may be unlocked and locked by operating plate  11 . Operating plate  11  may comprise a pushbutton. 
     As further depicted in FIGS. 1 and 2, a holder  12  is formed in the support  10  and serves as a loose retainer for a reel of paper or paper strip  13  forming the store of printing material. The spool of the reel of paper strip  13  is designated  14 . Between the holder  12  and the plate  11  of the support  10  there is an installation space  15 , in which a transport roll  16  and a movement mechanism  17  driving the latter are mounted.  18  designates the motor of the movement mechanism  17 . 
     A thermal print head  19  is assigned to housing  2 . The print head is spring mounted (arrow P) when support  10  is inserted into the housing. The print head further includes a thermal element bar  22  and a heat sink  23 . The paper reel  13 , the movement mechanism  17 , and the transport roll  16 , are arranged in the displaceable support  10 . It is therefore possible for the closing gap, existing between front wall  3  and plate  11 , to serve as an output slot for starting section  21  of paper reel  13 , after the paper reel has been inserted in holder  12 . This is effected by the loose laying of starting section over the transport roll  16 . Accordingly, the paper is clamped or accommodated in between roll  16  and print head  19 . The shaft  24  of the transport roll  16  is expediently mounted such that it can be pivoted within a certain angle about the axis  25  of the movement mechanism  17 , so that when the support  10  is pushed in, an alignment in relation to the thermal print head  19  which is independent of the guidance play of the support  10  is possible. It is likewise expedient to round off the front edge of the heat sink  23 , facing the transport roll  16 , in a suitable way. 
     For affixing the thermal print head  19  in the housing  2 , a retainer  26 , formed as a sheet metal part, is provided (see FIG.  3 ). On the substantially plate-like retainer  26 , provided with a cutout  27 , platforms  32 ,  33 ,  34  and  35  provided with threaded holes  28 ,  29 ,  30  and  31  are integrally molded, and at least one tongue  36  projecting into the cutout is formed. A stop bar  37  is assigned to the reel of paper strip  13 . The retainer  26  is connected to the top panel  9  by means of the sheet metal connecting technique mentioned above of the elevations that are produced in the process, two are depicted in FIG.  5  and are designated  38  and  39 . A third elevation  40  is illustrated in FIG.  6 . 
     A support bridge  41  illustrated in FIG. 4 is formed in such a way that it can be inserted into the cutout  27  in the retainer  26  with, for example, little play. Here, the tongue  36  of the retainer  26  engages cutout  42  in the support bridge  41  and is therefore used to align the two components before they are screwed together. Lugs  43 ,  44 ,  45  and  46  are integrally molded on the support bridge  41  and provided with through holes  47 ,  48  and  49 . Via the lugs, the support bridge  41  is fixed to the retainer  26 . 
     Formed in the legs  50  and  51  of the support bridge  41  are holes  52  and  53 , which are used to fit the bearing journals  54  and  55  (FIG. 5) assigned to the thermal print head  19 . Indentations  56 ,  57  and  58  are provided to retain compression springs  59 ,  60  and  61  assigned to the thermal print head  19 . Guide rails  64  and  65 , on which the shaft  24  of the transport roll  16 , loaded with the contact force of the thermal print head  19 , is supported, are shaped by means of cutouts  62  and  63  provided in the legs  50 ,  51 . At the front, the guide rails  64 ,  65  are provided with inclined surfaces (not shown) which make it easier to push shaft  24  onto guide rails  64 ,  65  at roughly the same time as the pivoting of thermal print head  19 —itself subject to the compression action of springs  59 ,  60 ,  61 . In this connection, shaft  21  is expediently assigned running bushes (not shown). An opening designated by  66  in the leg  50  is used by the thermal print head  19 , which engages in the opening  66  with an integrally molded finger, as a limiting stop for the case in which the support  10  is removed from the tachograph  1 . 
     As shown in FIG. 5, the support  10  is assigned running rails and  67  and  68  in the top part  5 . One running rail  67  is fixed directly to the side wall  6  of the top part  5 . Another running rail  68  is integrally molded on an L-shaped structural part  69  which reinforces the housing  2  and may provide fixing for the display of the tachograph  1 . A flat ribbon cable  70  is assigned to the thermal print head  19 . Of the screws serving to fix the support bridge  41  to the retainer  26 , three  71 ,  72  and  73  are depicted in FIG.  5 . 
     Support arms which interact with the bearing journals  54  and  55  are integrally molded on the thermal print head  19  or on its heat sink  23 . One support arm  74  is depicted in FIGS. 5 and 6. With continued reference to FIG. 5, supports  75  and  76  are integrally molded on the structural part  69 . Pads  77 ,  78  and  79  are formed on the side wall  6  and  7  and are provided in order to fix a printed circuit board carrying the electronic components of the tachograph  1 . In addition, the pads  77 ,  78  and  79 , together with a slot  80  in the rear wall  8 , are used to fix the bottom part  4  to the top part  5 , by bolts formed on the bottom part  4  being brought into engagement with the pads  77 ,  78 , and  79  acting as tongues. Indentations  81  and  82  are provided to latch the front wall  3  to the housing  2 . 
     FIG. 6 illustrates the direct and therefore space-saving assignment of the support bridge  41  to the top panel  9  of the top part  5 , and the nesting of the detachable support bridge  41  in the non-detachable retainer  26 . In this case, because of the stabilizing function, the retainer  26  should be connected to the top panel  9  over the greatest area possible. 
     The invention being thus described, it will be obvious that the same may be varied in many ways, Such variations may include a mixing of elements from the above embodiments. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.