Dispensing – With discharge assistant – Motor operated
Utility Patent
1999-05-13
2001-01-02
Derakshani, Philippe (Department: 3754)
Dispensing
With discharge assistant
Motor operated
Utility Patent
active
06168052
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention refers to an electrically operated dispensing appliance in which an electromechanical drive acts upon an advance unit comprising drive screws each acting upon a thrust plate for dispensing material from at least one cartridge. In particular, the invention refers to an advance unit which is inserted as a mechanical construction unit into dispensing appliances for multicomponent compositions, as well as to the electric drive of an advance unit. Dispensing appliances are used to express different materials, filled in cartridges, through a mixing device and to dispense the mixture in metered amounts.
2. Description of the Prior Art
Electrically operated dispensing appliances are already known from U.S. Pat. Nos. 5,203,476 and 5,464,128 to the same Applicant. These appliances are essentially constructed in such a manner that a drive screw shaft advances a slide to which two thrust rods are fastened, and the material dispensing is accomplished by means of two cartridge pistons which are pressed into the corresponding cartridges.
In another, known appliance according to European Patent No. 0,492,413, the feed advance of the slide is effected by two laterally disposed chains and, in another case, by toothed racks.
These known devices have fundamental disadvantages.
The different reaction forces that are generated at different dispensing ratios load the thrust rods with high torque and cause important jamming friction and deformation forces on the slide and on the necessary guiding elements, and such appliances are expensive to be constructed and difficult to be lubricated and sealed.
In other cases, e.g. according to U.S. Pat. No. 4,180,187 where the drive screws that must be lubricated due to the high dispensing forces, are directly introduced into the cartridges, these drive elements are prone to soiling; a cleaning is difficult and impracticable for the user in the case of soiling by the materials to be dispensed. If the slide is axially moved by means of chains, there is an essential drawback in that the very slow feed speed requires a gearing having a high reduction ratio as well as a very costly high torque magnet coupling for disengaging the drive unit for the relieving and retracting strokes.
SUMMARY OF THE INVENTION
Starting from this prior art, it is a first object of the present invention to provide an electrically operated dispensing appliance comprising an advance device which overcomes the disadvantages discussed above. Another object of the invention is to provide such an appliance that presents an improved operation safety and maintenance easiness and which can be manufactured at relatively low costs.
These objects are attained by an electrically operated dispensing appliance of the above depicted kind wherein the drive screws are mounted in an axially stationary manner and coact with a slide that carries thrust plates, said drive screws and other advance elements which are disposed in said slide being spatially and sealingly separated from the cartridge space.
In already known electrically operated dispensing devices, not only the advance unit shows drawbacks but also the electric drive. In order to express the compositions contained in receptacles such as cartridges through a mixing device, for example a static mixer, high pressure forces have to be applied, and as a consequence, the cartridges that are generally made of synthetic materials will expand under this load. This cartridge pressure must immediately be relieved when the dispensing is finished since otherwise, the composition keeps flowing out of the mixer, the so-called afterflow. In order to avoid this afterflow, the advance elements are permitted to make a small relieving stroke immediately after the dispensing stroke. It is furthermore necessary that the retracting motion of this drive unit, required for a cartridge change, and the introduction of the advance elements into a partially emptied cartridge occur substantially faster than the very dispensing stroke.
The above mentioned U.S. Pat. No. 5,203,476 takes this problem into account in that the relieving stroke is effected by a mechanical axial displacement of the drive shafts by means of a toggle joint. According to U.S. Pat. No. 5,464,128, also mentioned above, the fast retracting motion as well as the relieving stroke are accomplished by a second motor and corresponding magnetic couplings.
Furthermore, it has become known from the European Patent No. 0,492,413, already cited above, to use a magnet coupling to disengage the advance drive from a chain driven thrust slide in order to allow a certain cartridge relief and a manual retracting stroke.
Starting from this prior art, it is another object of the present invention to overcome the serious drawbacks which have just been described and to provide an electromechanical drive for a dispensing appliance which can be manufactured at low cost, takes little space only and has a high reliability and maintenance easiness. This object is met by the electrically driven dispensing appliance wherein the electromechanical drive device comprises a first motor for the slow advance motion and the relieving stroke and a second motor for the fast retracting and the fast advance motions, and this appliance is characterized in that a gear motor is used for the high loaded dispensing and relieving strokes and a second motor is used for the low loaded fast retracting and advance motions, a main shaft connected to the drive screws being permanently coupled to the gear motor during the slow advance and relieving strokes.
REFERENCES:
patent: 5203476 (1993-04-01), Keller
patent: 5353971 (1994-10-01), Vaziri
patent: 5464128 (1995-11-01), Keller
patent: 0 301 201 (1989-02-01), None
patent: 0 463 990 (1992-01-01), None
patent: 0 492 413 (1992-07-01), None
patent: 0 607 102 (1994-07-01), None
Bui Thach H.
Derakshani Philippe
Foley & Lardner
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