Mixing and applying plasters

Abstract: Plaster sprayer for applying dry premixed plasters, which includes a chamber (4) for mixing with water and mixture pumping means that are constituted by a tube-and-auger assembly (8,9). The plaster sprayer comprises a jaw (12) which is adapted to temporarily lock the tube-and-auger assembly (8) and is slidingly associated with fixed guiding means (15a,15b). The jaw (12) also interacts with a locking flange that can be removed to allow quick and easy mutual disengagement and engagement of the auger (9) and of the tube.

Description: The present invention relates to a plaster sprayer for applying dry premixed plasters (see f.i. EP-A-0 003 508). Conventional plaster sprayers are usually associated at trolleys for moving them and are constituted by a loading hopper where the dry premixed plaster is introduced. The hopper allows to introduce the plaster at a chamber for mixing it with water; said chamber is connected to means for pumping the mix which are constituted by a tube-and-auger assembly that is directly actuated by the mixer contained in the mixing chamber. The tube-and-auger assembly is usually fixed to the mixing chamber by means of appropriate bolts and nuts. The drawback observed in conventional plaster sprayers and generally in all mortar pumping devices that use a tube-and-auger assembly consists of the fact that, to achieve optimum pumping of the mixed product, it is periodically necessary to replace the tube and the auger due to the abrasive nature of the products that are used. The tube and the auger are currently replaced manually, and this is a very complicated operation that entails risks for the operators assigned thereto. This replacement can be performed for example by unscrewing the nuts that lock the tube-and-auger assembly to the mixing chamber and placing said assembly on a bench fitted with a vise; however, such a bench is not always available in a building yard, where the plaster sprayer is used, and in any case the tube must be locked in the vise, consequently jamming the auger inside it. This makes it very difficult to extract the auger; this operation must be performed by at least two people by using, for example, a blade which is placed on the head of the auger to make it rotate and thus achieve its extraction. It is thus necessary to perform a considerable effort, with possible physical risk for the operators due to the precarious placement of the blade on the head of the auger. The reverse operation must be performed to reposition the new auger inside the tube or in any case to replace the tube while using the old auger. As an alternative, replacement can be performed by using a hydraulic extractor: however, even this solution has drawbacks, since on one hand a hydraulic press is not always available and on the other hand it is possible to damage the tube while coupling the auger to the tube, since the auger is inserted by moving the auger axially rather than rotating it. The aim of the present invention is to solve the described technical problems, eliminating the drawbacks of the prior art, and thus providing a plaster sprayer in which it is possible to quickly and easily replace the tube and/or the auger. Within the scope of the above aim, an important object is to provide a plaster sprayer in which this replacement can be performed by a single operator. Another object is to provide a plaster sprayer in which replacement can be performed in conditions that ensure maximum operator safety. Another object is to provide a plaster sprayer in which the tube or the auger are replaced without damaging the tube in any way. Another object is to provide a plaster sprayer in which the auger and the tube can mutually disengage and engage without any effort on the part of the operator. Another object is to provide a plaster sprayer in which reassembly of the auger in the tube automatically entails the centering of said tube as well. Another object is to provide a plaster sprayer which is structurally very simple and has low manufacturing costs. This aim, these objects, and others which will become apparent hereinafter are achieved by a plaster sprayer for applying dry premixed plasters, which comprises a motorized mixer which is contained within a chamber for mixing with water and drives mixture pumping means that are constituted by a tube-and-auger assembly, characterized in that it comprises a jaw for temporarily locking said tube-and-auger assembly, said jaw being slidingly associated with fixed guiding means and interacting with a removable locking flange. Further characteristics and advantages of the invention will become apparent from the detailed description of a particular embodiment, illustrated only by way of non-limitative example in the accompanying drawings, wherein: figure 1 is a schematic side view of the plaster sprayer during operation; figure 2 is a view, similar to the preceding one, of the arrangement of the mixing chamber prior to the replacement of the tube or of the auger; figure 3 is a lateral view of the mixer of the sprayer according to the present invention; figure 4 is a lateral view of the auger of the sprayer according to the present invention; figure 5 is a sectional view of the tube of the sprayer according to the present invention; figure 6 is a partially sectional view of the arrangement of the jaw and of the tube-and-auger assembly with respect to the mixing chamber, the locking flange being omitted for the sake of clarity; figure 7 is a sectional view, taken along the plane VII-VII of figure 6; figure 8 is a view of the locking flange; figure 9 is a schematic view of the arrangement of the mixer, of the mixing chamber, and of the tube-and-auger assembly. With reference to the above figures, the reference numeral 1 designates the plaster sprayer, which is mounted on an appropriate trolley 2 and comprises a hopper 3 for loading dry premixed plasters; a mixing chamber 4 is pivoted to said hopper 3 and internally contains a mixer 5 that is driven by means of an adapted gearmotor 6. Inside the mixing chamber 4, the dry premixed plaster is mixed with water and then sent to pumping means which are driven by the mixer 5 and are constituted by an assembly which is composed of an auger 7 that is associated at a complementarily shaped seat formed in a tube 8. The auger 7 has a head 9 on which an adapted slit 10 is formed; a complementarily shaped ridge 11 which protrudes below the mixer 5 can be arranged at said slit 10. The assembly constituted by the auger 7 and by the tube 8 can be locked within an adapted jaw 12 which can be tightened by means of a single bolt 13, since said jaw 12 merely has the purpose of supporting and slightly locking the tube-and-auger assembly. Two pairs of C-shaped profiled elements 14a and 14b protrude radially on a diametrical plane from the jaw 12 and constitute means which allow the jaw 12 to slide with respect to fixed guiding means which are constituted by a pair of tie rods 15a and 15b which are detachably associated, at one end, below the mixing chamber 4. Said tie rods 15a and 15b accordingly run parallel to the axis of the auger 7 and of the tube 8 and interact, at the end that does not interact with the mixing chamber 4, with a flange 16 to lock the auger-and-tube unit, which can be arranged adjacent to the mixing chamber 4; the arrangement of said flange is such as to allow the interaction of the ridge 11 and of the mixer 5 at the slit 10 formed on the head 9 of the auger 7. The locking of the flange 16 is temporary, in that it can be provided by means of adapted removable bolts. The use of the plaster sprayer according to the invention is thus as follows: when it is necessary to replace the auger 7 or the tube 8, an operator must first of all place the mixing chamber 4 as shown in figure 2, i.e. to tilt it at angle of substantially 90°, in order to easily remove the flange 16 from the pair of tie rods 15a and 15b. In this way the jaw 12 can slide, by virtue of the profiled elements 14a and 14b, along said tie rods 15a and 15b when the mixer 5 is turned. By keeping the ridge 11 of said mixer within the slit 10 of the head 9 and by pressing an appropriately provided pushbutton located on the machine for producing a rotation that is limited to the mixer 5, the auger 7 is rotated, consequently extracting it from the tube 8, which is in any case supported by the pair of tie rods. It is thus possible to mutually disengage the auger 7 and the tube in a few seconds; after replacing either or both, they are mutually reengaged by first manually positioning the auger 7 on the tube and then rotating the mixer 5 in the opposite direction by operating an appropriately provided pushbutton to activate the gearmotor 6 in reverse. Once the auger and the tube have been mutually reconnected, it is sufficient to reposition the flange 16, locking the jaw 12 so that the rotation of the mixer 5 entails the rotation of the auger 7 without causing extraction from the tube 8, which is locked to said flange 16. It has thus been observed that the plaster sprayer according to the invention has achieved the intended aim and objects, since it is possible even for a single operator to rapidly and easily replace the auger and/or the tube with no risk to the operator. It is also stressed that this solution allows to self-center the tube. The described solution can be applied also to conventional plaster sprayers by means of simple modifications and can thus find widespread application. The materials and the dimensions of the individual components of the device may of course be the most pertinent according to the specific requirements. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims: Plaster sprayer for applying dry premixed plasters, comprising a motorized mixer which is contained within a chamber for mixing with water and drives mixture pumping means that are constituted by a tube-and-auger assembly (7,8), characterized in that it comprises a jaw (12) for temporarily locking said tube-and-auger assembly (7,8), said jaw (12) being slidingly associated with fixed guiding means (15a,15b) and interacting with a removable locking flange (16). Sprayer according to claim 1, characterized in that if comprises an auger (7) which has a head (9) on which an adapted slit (10) is formed, a complementarily shaped ridge (11) that protrudes below said mixer (5) being arrangeable at said slit (10), said assembly being constituted by said auger (7) and said tube (8) being lockable temporarily within an adapted jaw (12) which can be tightened by means of a single bolt (13), two pairs of C-shaped profiled elements (14a,14b) protruding radially with respect to said jaw (12) along a diametrical plane and constituting means that allow said jaw (12) to slide with respect to said fixed guiding means (15a,15b). Sprayer according to claims 1 and 2, characterized in that said fixed guiding means are constituted by at least two tie rods (15a,15b) which are detachably associated, at one end, below said mixing chamber (4). Sprayer according to claims 1 and 3, characterized in that said at least two tie rods (15a,15b) run parallel to the axis of said auger (7) and said tube (8) and interact, at the end that is not connected to said mixing chamber (4), with a detachable flange (16) that allows to lock said auger-and-tube assembly (7,8) adjacent to said mixing chamber (4). Sprayer according to claims 1 and 4, characterized in that the position of said flange (16) is such as to allow the interaction of said ridge (11) of said mixer (5) at said slit (10) formed on said head (9) of said auger (7). Sprayer according to one or more of the preceding claims, characterized in that the removal of said flange (16) and the activation of said mixer (5) allow to extract or insert said auger (7) with respect to said tube (8), said tube (8) being able to slide along said pair of tie rods (15a,15b) by means of said profiled elements (14a,14b) that prevent its rotation.

Inventors: MUSSATO FAUSTO, MUSSATO, FAUSTO
Applicants: FASSA S P A, FASSA S.P.A
Application year: 1995
Main classification: B28C5
IPC codes: B28C5