Abstract:
An electromotive linear drive includes one or more drive motors and a corresponding number of torque-reducing transmissions and corresponding driven spindles and a casing. The casing is comprised of two casing parts, whereby the abutting surfaces of the casing parts are sealed by a sealing element or a plurality of sealing elements. Connecting terminals for mechanical and/or electrical components are provided on the exterior of the casing parts.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
         [0001]    This application is a continuation of prior filed copending PCT International application no. PCT/EP01/02887, filed Mar. 15, 2001.  
           [0002]    This application claims the priority of German Patent Application Serial No. 200 05 050.8, filed Mar. 20, 2000, pursuant to 35 U.S.C. 119(a)-(d), the subject matter of which is incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0003]    The present invention relates, in general, to an electromotive linear drive.  
           [0004]    A linear drive of a type involved here is especially intended for operating adjustable components of furniture items, such as a slatted frame, and includes a drive motor, a reduction gear unit and a rotatably driven spindle which supports a spindle nut secured against carrying out a rotation movement and interacting with levers which are mounted in fixed rotative engagement on a shaft of the furniture item. A typical construction of a linear drive includes the arrangement of two d.c. motors which can be separately activated by a handset via a control unit.  
           [0005]    Linear drives of this type are not only used in the residential field but increasingly also in hospitals and nursing homes. In these latter areas, the furniture item, e.g., a hospital bed or a nursing bed has to be thoroughly cleaned and disinfected periodically or after a change of patients. Typically, the cleaning process is carried out in a washing plant. It must then be ensured that cleaning liquid is prevented from penetrating into the interior of the casing of the linear drive. In general, the casing is made of two casing parts. Depending on the type of construction, the casing may be box-shaped and closed on the top by a cover, or comprised of two shells, whereby abutting surfaces are disposed in perpendicular relationship, when assembled.  
           [0006]    It would be desirable and advantageous to provide an improved electromotive linear drive which obviates prior art shortcomings and which is simple in structure, while reliably preventing ingress of liquid during washing or cleaning operation and allowing connection of additional drives or appliances.  
         SUMMARY OF THE INVENTION  
         [0007]    According to one aspect of the present invention, an electromotive drive includes a casing having at least two casing parts connected to one another to form a butt joint; at least one motor mounted in the casing; a speed reduction gear unit interacting with the motor; a rotating spindle driven by the motor via the reduction gear unit to establish a power train; a cable connectable to a power outlet for providing electric energy to the power train; and a seal which extends completely, or at least substantially coextensive with the butt joint for sealing the butt joint between the casing parts.  
           [0008]    The seal may be a flat packing which has a configuration conforming to the contour of the butt joint. In the event a double drive is involved, the end portions are provided with two slides which overlap U-shaped recesses of the casing parts. Engaging the U-shaped recesses in assembled state are the head and foot portions of a slatted frame, whereby the slides secure the linear drive to the furniture item. As the region of the slides is difficult to seal by a separate sealing element, the casing is so configured as to establish a labyrinth-type seal in the area of the slides so that, in fact, a sufficient sealing action is provided.  
           [0009]    As an alternative, the seal at the butt joint may also be realized by a sealing compound which is suitably of permanent elasticity.  
           [0010]    When using the linear drive according to the present invention in hospitals or nursing homes, versatility is demanded, i.e., the linear drive should be so constructed as to allow connection of additional devices or appliances. Thus, in accordance with the present invention, the casing parts may have formed or mounted thereon external connecting terminals for attachment of mechanical and/or electrical components. In this way, additional drives, preferably single drives, hand switches, control boxes and similar components may be connected to the linear drive. As the possibility is afforded already during fabrication, re-equipment is extremely easy and cost-efficient. In particular when the medical field is involved, the linear drive should be constructed to prevent inadvertent shutdown by a patient. In accordance with the present invention, the linear drive may be equipped with various safety features, such as the provision of an electrical attachment element on the casing-proximal end of the power chord for allowing replacement of the power chord, whereby the attachment element is insertable in a complementary counterpiece of the casing and covered by a mounting element which is detachably connected, suitably by a screw connection, to the casing. Examples of electric attachment elements include also the use of a screwed cable gland. Replacement of the power chord may be required, when, for example, a wire is broken or other devices, connected to the linear drive, should be supplied with electric energy and the power chord is not configured for this purpose. The provision of the mounting element is normally sufficient to prevent the patient form removing the attachment element from the socket. This is true also for those situations in which the connection to the casing is realized by screws, because of the need to use a tool that is normally not available to the patient. A cost-efficient production of the power chord with the mounting element can be realized by a single-piece construction of the mounting element with the power chord, suitably through an injection-molding process. In this way, a loss of the mounting element is precluded. Safety reasons also demand a grounding of the electromotive drive. Thus, in accordance with the present invention, the mounting element is equipped with a ground connection, suitable a screw. This ground connection may be formed during injection-molding of the mounting element so as to avoid additional process steps. It is, however, also possible to connect the end portion of the power chord with the mounting element by means of a cable gland, thereby prevent application of tensile forces on the connection. Such cable glands are also referred to a PG screw connections.  
           [0011]    It is also required to secure the electric components of the linear drive by the use of fuses. To date, such fuses have been disposed inside the casing so that a replacement of a defective fuse required a dismantling of the casing. Thus, replacement of fuses was difficult to entertain. In accordance with the present invention, the mounting element is so constructed as to cover the electric fuses, placed in respective sockets, so that it is only necessary to remove the mounting element to provide access to the fuses and to allow replacement thereof, if need be. As an alternative, it is also conceivable to so provide sockets on suitable areas of the casing that the fuses become accessible by respective openings. A panel may be provided to cover the openings.  
           [0012]    The casing may be made of plastic through an injection-molding process. In order to afford the option to provide additional switching or control functions via an external cable, for example, through connection of a power switch, the use of at least one screwed cable gland may be provided for engagement in the opening during casing production. Instead of the cable gland, it may also be possible to directly guide the cable therethrough, e.g. through use of a rubber ring. It is also conceivable to associate to the opening a strain relief for the cable.  
           [0013]    According to another feature of the present invention, the casing may have at least one compartment to accommodate a re-chargeable accumulator or battery. The accumulator or battery should be insertable from outside in the compartment so as to allow an electric coupling with the drive from outside via a cable, which is suitably attachable from outside. Of course, the provision of integrated contacts may also be possible. In addition to the placement of an accumulator or battery, it is also possible to arrange a transformer, e.g., an electric core transformer or a magnetic core transformer. In particular, when the linear drive is used in the medical field, it may be necessary to provide a disengagement of the drive to allow execution of, e.g., a downwardly directed movement in shortest possible time. This disengagement may be realized by means of a lever or a rope, guided through an opening of the casing. The lever may be a rotary lever or a pivot lever.  
           [0014]    Both casing parts, or casing part with lid attached through screw connection, are mutually sealed via a strand-like sealing element. Only the region of the slides is excluded. Overall, the linear drive is thus sealed so that no separation exists between sealed and unsealed areas.  
           [0015]    In linear drives involved here, the motors normally project beyond the sidewalls of the casing for material-saving reasons and realization of a compact structure. Thus, in accordance with the present invention, to cover the motors by hoods or caps which suitably latch to the wall of the housing or cylindrical projections. No additional fastening elements, such as screws or the like, are then required. Sealing of the hoods or caps against the casing may be implemented by conventional toroidal sealing rings or O-rings. The hoods and caps are configured to cover only the outer region of the motor and not the entire length thereof so that the remaining part of the motor is positioned in cylindrical portions formed on the casing. Sealing of the fastening panel for the power chord against the drive casing can suitably be realized by a flat packing. Of course permanent-elastic sealing compounds may also be useable.  
           [0016]    According to another feature of the present invention, the casing may be provided with further electric attachment elements for placement of complementary plugs which in turn are masked by a safety panel detachably connected to the casing. The plugs are also sealed by sealing elements against the drive casing. Suitably, O-rings are used disposed respectively on the O-rings. Of course, it is also possible to seal the plugs by using sealing compound.  
           [0017]    In view of the versatile application and the demand on safety features of an electromotive linear drive according to the present invention, additional aggregates of different type may be added. Accordingly, at least one of the casing parts may have a compartment for receiving at least one electric device in force-fitting engagement and/or form-fitting engagement. The compartment is suitably situated on the exterior of the casing part. The electric device may be supplied with electric energy via current storage or via the current supply of the linear drive. Examples for electric devices involved here may include a device of the entertainment electronics, e.g. a radio, or a safety sensor, e.g. a smoke detector, a humidity detector or similar monitoring sensors.  
           [0018]    The linear drive may also be provided with a pocket for receiving a tool box for maintaining the linear drive, and/or a spare part box for storage of wearing parts such as fuses, cables, lighting elements. The pocket may be formed also by the compartment in the absence of the electric device, or may be provided in addition to the compartment. This compartment should, however, be accessible from outside.  
           [0019]    The linear drive may also be provided with an insecticide and/or a diagnostic system. Suitably, the drive is equipped with a plug-type diagnostic link for attachment of a test device. The linear drive may further be provided with a terminal for an electric household appliance, e.g. a vacuum cleaner. It is also possible to provide the linear drive with a programming unit which is independent from, i.e. inaccessible to a patient so that programming may be executed only by authorized personnel. As the linear drive is intended also for use in hospitals or nursing homes, it may be provided with a safety device, e.g. a carbon dioxide cartridge or a fire extinguisher. It is also conceivable to provide the linear drive with a container for receiving a disinfectant. Suitably, the container is an atomizer.  
           [0020]    Another possibility involves the provision of a speech recognition chip and/or an indication for noise, sounds, or light in the linear drive. In the event the linear drive is operated by an accumulator or battery, it may be equipped with a voltage control to allow timely recharging of the accumulator or replacement of batteries.  
           [0021]    Suitably, the linear drive may be provided with an air-circulation device for heat dissipation and an optional heater for drying purposes.  
           [0022]    Depending on the use at hand, instead of disposing a seal between the abutting surfaces of the casing parts, it may also be possible to cover the butt joint, at least in the region of the slides, with a sealing tape on both sides of the butt joint. The sealing tape may be an adhesive tape with an adhesive on one side. Of course, the seal may be provided also in such a manner as to extend only upon the region of the abutting surfaces which are associated to the slides.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0023]    Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which:  
         [0024]    [0024]FIG. 1 is a side view of an electromotive linear drive according to the present invention in the form of a double drive;  
         [0025]    [0025]FIG. 2 is a top view of the linear drive of FIG. 1;  
         [0026]    [0026]FIG. 3 is a front view of the linear drive of FIG. 1;  
         [0027]    [0027]FIG. 4 is a top view of an electromotive linear drive with a seal in the form of a sealing tape;  
         [0028]    [0028]FIG. 5 is a front view of the linear drive of FIG. 4;  
         [0029]    [0029]FIG. 6 is a side view of the linear drive with arrangement of a labyrinth-type seal;  
         [0030]    [0030]FIG. 7 is a side view of the linear drive with arrangement of a compartment;  
         [0031]    [0031]FIG. 8 is a side view of the linear drive with arrangement of a lever for disengagement of the power train;  
         [0032]    [0032]FIG. 9 is a side view of the linear drive with arrangement of a speech recognition system; and  
         [0033]    [0033]FIG. 10 is a schematic, partial sectional view of a cable gland. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0034]    Throughout all the Figures, same or corresponding elements are generally indicated by same reference numerals.  
         [0035]    Turning now to the drawing, and in particular to FIG. 1, there is shown a side view of an electromotive linear drive according to the present invention, generally designated by reference numeral  10  and illustrated in a position of use. The linear drive  10  has a casing  11  comprised of two casing parts  11   a,    11   b  which are connected to one another such that their abutting surfaces extend vertical. Of course, the casing may also be configured in a manner that one casing part has a box-like shape and the other casing part is a lid. At opposite ends, the linear drive  10  has slides  13 ,  14  which overlap U-shaped recesses  4  (FIG. 7) in the casing wall, with shafts  15 ,  16  of a slatted frame (not shown) being accommodated in the U-shaped recesses  4  for suspension of the linear drive  10  to the slatted frame. The slides  13 ,  14  can be shifted to clear and close access to the recesses  4 . The slide  14  is shown in FIG. 7 in open position, while slide  13  occupies the closed position.  
         [0036]    The confronting abutting surfaces of the casing  11  are sealed against one another by a sealing element  12 . Currently preferable as sealing element  12  is a flat packing. As shown in FIG. 2, the sealing element  12  is wrapped at the butt joint of the casing parts  11   a,    11   b  almost entirely about the casing  11 , except for the region of the slides  13 ,  14 , as shown in FIGS. 2 and 3. FIG. 6 shows by way of phantom lines an arrangement of a sealing element in the form of a retracted upper seal  12   a  and a retracted lower seal  12   b,  whereby the seals  12   a,    12   b  are configured in the area of the slides  13 ,  14  to establish a labyrinth-type seal.  
         [0037]    In the nonlimiting example of FIGS. 4 and 5, the casing parts  11   a,    11   b  are covered at the butt joint by a sealing strip or sealing tape  29 . The sealing strip  29  is applied on the casing parts  11   a,    11   b,  except upon the area of the slides  13 ,  14  so that the sealing tape  29  cannot interfere with a movement of the slides  13 ,  14 .  
         [0038]    Jutting out from the casing part  11   b  of the casing  11  are two cylindrical projections  17 ,  18  having open free ends for accommodating two drive motors (not shown). The cylindrical projections  17 ,  18  are closed by end caps  19 ,  20  through a snap-on connection. This facilitates installation of the motors. Although not shown in detail, the end caps  19 ,  20  are sealed against the cylindrical projections  17 ,  18  by O-rings.  
         [0039]    It will be appreciated by persons skilled in the art that the linear drive  10  must contain much mechanical apparatus which does not appear in the foregoing Figures, e.g., a reduction gear unit, driven by the electric motor, and a rotatably driven spindle which supports a spindle nut. For safety reasons, the drive motors are DC motors which are supplied with a safety voltage. The reduction gear unit is normally a worm gearing as the speed ratio of the rotor of the drive motor must be very high compared to the speed of the spindle. Therefore, the linearly moving spindle nut travels at an extremely low velocity. However, this apparatus, like much other necessary apparatus, is not part of the invention, and has been omitted from the Figures for the sake of simplicity.  
         [0040]    As shown in FIGS. 1 and 2, the casing part  11   b  is further provided with additional connection terminals for mechanical and electrical components. Of course, the arrangement of the projections  17 ,  18  and further connection terminals may be formed on the casing part  11   a  as well instead of casing part  11   b.  On the left hand end region, the linear drive  10  has a connection for a power chord  21 . The power chord  21  has attached thereon through an injection molding process a mounting element  22  which can be bolted to the casing part  11   b  and is formed with a grounding screw  23 . The power chord  21  is provided on its casing-distal end with a plug (not shown) for insertion in a suitable outlet. The casing part  11   b  is formed immediately next to the mounting element  22  with an opening for accommodating a screwed cable gland  24  to provide a connection for a cable  25 . An exemplified cable gland  24  is shown in FIG. 10 and depicts a clamping of the cable  25  by a tightened nut  24   a.  The cable gland  24  also provides a sealing function and a strain relief to prevent a force to act on the connections of the cable wires.  
         [0041]    Formed next to the cable gland  24  are five sockets  5  for attachment of five plugs  26  of cables. The sockets  5  are covered by a safety plate  27  which can be bolted to the casing wall  11   b.  As shown by way of example in FIG. 1, the sockets  5  are positioned between the cylindrical projections  17 ,  18  for the motors.  
         [0042]    Located directly adjacent the cylindrical projection  18 , there is provided at least one compartment  30  (FIG. 7) for accommodating an accumulator or battery for electric connection with the drive via a cable or integrated contacts. A cover  28  can be bolted to the casing part  11   b  for closing the compartment  30 . As shown in particular in FIG. 2, the compartment  30  juts out from the casing part  11   b.  The compartment  30  may also be used for storage purposes, e.g., for accommodating electrical devices, such as transformer, e.g., an electric core transformer or a magnetic core transformer, an insect killing device, safety box, including fuses or the like, air-circulation device, such as a fan, for cooling internal parts of the linear drive  10  so as to prevent overheating. An insect killing device is typically a device for plugging into a power outlet and includes resistance wires that glow to attract insects.  
         [0043]    Although not shown in detail, the plugs  26  and the plug of the power chord  21  may be sealed by O-rings or by a permanently elastic sealing compound.  
         [0044]    In particular, when the linear drive  10  is used in the medical field, it may be necessary to provide a disengagement of the power train of the drive to allow execution of, e.g., a downwardly directed movement in shortest possible time. As shown in FIG. 8, the disengagement may be realized by means of a lever  31  in the form of a rotary lever or a pivot lever, which can be switched between two positions.  
         [0045]    It is also possible to equip the linear drive  10  with a speech recognition system and/or an indication for noise, sounds, or light in the linear drive  10 . FIG. 9 shows by way of example, the incorporation of a speech recognition system including an inter speech chip which can be controlled by a hand switch  32  or via a microphone  33  in order to operate the linear drive  10 . In addition, the linear drive  10  may be equipped with a programming unit  34 , when the linear drive  10  is used in hospitals or nursing homes, to bar a patient for executing certain operations which  
         [0046]    In the event the linear drive  10  is operated by an accumulator or battery, it may be equipped with a voltage control to allow timely recharging of the accumulator or replacement of batteries  
         [0047]    While the invention has been illustrated and described as embodied in an electromotive linear drive, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. The embodiments were chosen and described in order to best explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.