EP1780326A1

EP1780326A1 - A reinforcement for a counterweight for electrical household appliances, a counterweight incorporating said reinforcement and corresponding method of production.

Info

Publication number: EP1780326A1
Application number: EP06122200A
Authority: EP
Inventors: Gianfranco Piazzoli
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-10-26
Filing date: 2006-10-12
Publication date: 2007-05-02
Also published as: RU2006137758A; ITMI20052031A1

Abstract

Described herein is a reinforcement for a counterweight for electrical household appliances and the like, characterized in that it comprises a single piece made of plastic material or else of composite plastic material, of a generally plane shape, provided with first holes (23, 23', 24; 33; 43; 53) in portions (21; 31; 41; 51) designed to project from the mass of concrete forming said counterweight; said plastic material or composite plastic material has a specific weight greater than or equal to 1.000 g/cc, an ultimate strength greater than or equal to 50 MPa and a tensile strength greater than or equal to 2000 MPa, determined according to the standard ASTM D 638.

Description

The present invention relates to a reinforcement for a counterweight for electrical household appliances, an improved counterweight incorporating said reinforcement, and a corresponding method of production.
Known to the art is the use of a counterweight made of concrete as inertial mass, for compensating for the vibrations generated by the rotation of the drum in household washing machines and the like. Said counterweight is fixed to the tank of the washing machine in various ways. Usually, said fixing is provided by means of screws or bolts passing through corresponding holes of the tank and of the counterweight. As a rule, said holes are made in brackets or similar fixing elements projecting from the structure of the tank, and from the concrete structure of the counterweight. In order to provide both said fixing elements, and a certain structural reinforcement for the counterweight, this latter is formed with a metal reinforcement embedded therein.
In an embodiment according to the known art (illustrated in Figure 1), said reinforcement is constituted by a first metal bar 10, bent to form a semicircle, and a second metal bar 12, bent into three rectilinear segments, welded to which are plates 13, 13', 14 having holes designed to project from the counterweight to enable fixing thereof to the tank of the washing machine. The plates 13, 13' and 14 must be purposely zinc-plated or otherwise subjected to other galvanic treatment that prevents oxidation thereof. Of course, the shape of the above reinforcement varies as a function of the shape that the counterweight must assume, which, in turn, depends upon the model of washing machine. In any case, the production of a reinforcement of this type requires both operations of bending of the metal bar, and various operations of welding between the bar and the plates and/or between one bar and another.
From the European patent EP 1 223 242 B1 a metal reinforcement is known for a concrete counterweight for a washing machine, said reinforcement being made up of two concentric circular bars made of iron, joined by welding to steel bushings with axis parallel to that of the circles defined by the concentric bars. The bushings constitute the elements for housing the screws or bolts for fixing to the structure of the tank of the washing machine.
The known reinforcements mentioned above present several drawbacks, which have in part already been mentioned, both as regards their functionality and as regards the cost of production thereof.
As regards functionality, it should be pointed out that a concrete counterweight for a washing machine is above all subject to vibrational stresses, which - if they present exceptional intensity and frequency - may generate cracks and, at worst, fissures in the concrete block. A function of the counterweight reinforcement is also that of preventing or contrasting cracking of the concrete, i.e., of keeping those parts of the concrete block that were to crack, joined together or in any case oppose detachment thereof.
In this connection, the metal reinforcements currently used are decidedly rigid and do not present any damping effect. Basically, on the one hand they contrast cracking of the concrete, but on the other hand they do not have any preventive effect in regard to vibrational stresses. In addition, since they are made of metal material, they are inevitably subject to reactions of oxidation that alter their surface.
As regards the costs, it is evident that the known embodiment of Figure 1 involves a series of operations of machining, welding and galvanic treatment of the parts in order to prevent their oxidation, this being a factor that significantly increases the cost.
Also the structure described in patent EP 1 223 242 B1 mentioned above is extremely costly, since it is made up of steel components and in any case involves a production that entails various operations of bending and welding.
Therefore, there exists the problem of providing in an efficient and convenient way a reinforcement for counterweights made of concrete, cement or the like, for electrical household appliances that presents excellent functional characteristics and low cost.
An object of the present invention is consequently to provide a reinforcement for a counterweight for electrical household appliances, that eliminates or reduces the drawbacks of known reinforcements, and that moreover presents a simple and inexpensive structure, as well as being reliable in operation.
Another object of the invention is to provide an improved counterweight for electrical household appliances that enables optimal performance and presents contained costs.
A further object of the invention is to provide a convenient and economically advantageous method for the production of counterweights for washing machines.
The above and other objects and advantages of the invention, as will appear from the following description, are achieved by a reinforcement for a counterweight for electrical household appliances and the like, characterized in that it comprises a single piece, having a plane or three-dimensional shape, which is made entirely of plastic material or of composite plastic material provided with holes in portions designed to be left free from the mass of concrete forming said counterweight.
Another aspect of the invention is represented by a counterweight for electrical household appliances and the like, comprising a block made of concrete or cement or similar material, of a shape suited to being associated and rigidly fixed to the tank of said washing machine, characterized by incorporating a reinforcement as defined above.
A further aspect of the invention is represented by a method for the production of counterweights for electrical household appliances and the like, characterized in that it comprises the steps of:

a) injection moulding of a reinforcement constituted by a single piece made entirely of plastic material or else of composite material, of a generally plane shape, provided with holes in portions designed to be left free from the mass of concrete forming the counterweight;
b) arrangement of the reinforcement obtained in step a) above in a mould for concrete having the shape of said counterweight, in such a way as to position said portions designed to project from the mass of concrete forming said counterweight in areas not filled by the concrete;
c) pouring of concrete into said mould and subsequent vibration thereof; and
d) hardening and setting of said concrete.

Some preferential embodiments of the invention are now described, purely by way of nonlimiting example, with reference to the figures of the attached plate of drawings, in which:

Figure 1 is a plan view of a reinforcement for a counterweight for a washing machine according to the known art;
Figure 2 is a plan view of a reinforcement for a counterweight for a washing machine according to a first embodiment of the invention;
Figure 3 is a plan view of a variant of the embodiment of Figure 2;
Figure 4 is a plan view of a reinforcement according to a second embodiment of the invention;
Figure 5 is an elevational view of the reinforcement of Figure 4;
Figure 6 is a plan view of a variant of the embodiment of Figure 4;
Figure 7 is a plan view of a reinforcement according to a third embodiment of the invention;
Figure 8 is an elevational view of the reinforcement of Figure 7;
Figure 9 is a plan view of a variant of the embodiment of Figure 7;
Figure 10 is an elevational view of the reinforcement of Figure 9;
Figure 11 is a plan view of a reinforcement according to a fourth embodiment of the invention; and
Figure 12 is an elevational view of the reinforcement of Figure 11.

With reference to Figure 2, designated as a whole by 20 is a reinforcement for a counterweight for an electrical household appliance, in particular a washing machine, said reinforcement being made of plastic material in a single piece by injection moulding. The structure of the reinforcement is preferably plane and of a thickness adequate to bestow appropriate reinforcement on a counterweight made of concrete, cement, or similar material with high specific weight (not illustrated).
By the expression "concrete, cement, or similar material with high specific weight" is meant, in the present description, any material with a cementitious base, even comprising different materials such as fillers or binders, whether natural or synthetic, which is suited to being poured into a mould where the reinforcement according to the invention is set and is suited to undergoing subsequently a process of hardening and setting, possibly preceded by a step of vibration or vibration-compression, as it is known in the branch.
The reinforcement 20 is provided with first holes 23, 23', 24 and second holes 22. The second holes 22 are formed in portions of the reinforcement, which, in use, are designed to be englobed in the cast of concrete, which - after hardening - will form a structure interpenetrated with the reinforcement, i.e., a structure in which the concrete fills the holes 22. The geometry and arrangement of the holes 22 is such that the reinforcement 20 assumes a structure of a reticular type, capable of bestowing a considerable strength on the counterweight, even though it is made of plastic material. The first holes 23, 23' and 24 are made in portions 21 of the reinforcement that are to project from the block of concrete constituting the counterweight so as to enable passage of screws, bolts or similar means for fixing the counterweight to the tank of the washing machine. Throughout the majority of their extension the edges of the second holes 22 are provided with raised ribs 26, which, in addition to stiffening further the structure of the counterweight, constitute elements that contrast any possible sliding of parts of concrete on the surface of the counterweight, consequently contributing to keeping them joined should they tend to detach.
The material constituting the reinforcement 20, for example thermoplastic material, must possess physical and mechanical characteristics adequate to withstand in an optimal way the stresses that the reinforcement is liable to undergo in its life cycle. Particularly critical areas are those where the fixing holes 23, 23' and 24 are made, which are subject to a greater extent to the vibrational loads and stresses. As it has been said previously, fixing of the counterweight to the tank of the washing machine is obtained by compression, i.e., with screws or bolts passing in the holes but screwed in corresponding holes of the tank or by means of nuts. The area surrounding the holes 23, 23' and 24 is as a rule plane, i.e., without any form of ribbing, since it is to be compressed between the head of the screw or bolt and the corresponding part of the tank. It has been found that the optimal resistance to said stresses is given by a plastic material, possibly containing fillers or composite, which has a specific weight greater than or equal to 1.000 g/cc, an ultimate strength greater than or equal to 50 MPa and a tensile strength greater than or equal to 2000 MPa, determined according to the standard ASTM D 638. More preferably, said plastic material or composite plastic material has a specific weight greater than or equal to 1.100 g/cc, an ultimate strength greater than or equal to 60 MPa and a tensile strength greater than or equal to 2500 MPa, determined according to the standard ASTM D 63.
Plastic materials that can be used to make the reinforcement according to the invention include polypropylene, polyethylene, polystyrene, polyvinylchloride, acrylonitrile-butadiene-styrene (ABS) resins, polybutylene terephtalate, polyurethane.
Preferred plastic materials are polyamide resins, acrylonitrile-butadiene-styrene (ABS) resins, polypropylene with a glass-fibre filler and polypropylene with a talcum filler. A particularly preferred plastic material is a nucleated high-viscosity polyamide 6, such as the polyamide marketed under the trademark Axtromid B3800 by Arcoplex Trading of BERGAMO (Italy), having a specific weight of 1.14 g/cc, a tensile ultimate strength of 75 MPa and a tensile modulus of 3000 MPa.
Figure 3 illustrates a variant of the embodiment of the reinforcement of Figure 2. The reinforcement of Figure 3 is provided not only with the second holes 22, but also with further second holes 27 and 28, made in the proximity of the inner and outer edge of the reinforcement. The reinforcement is moreover provided with ribs 26, which stiffen the structure thereof. The greater number of second holes 22, 27 and 28 favours formation of a structure interpenetrated with the concrete, improving the characteristics of the reinforcement and of the counterweight that incorporates it.
With reference to Figures 4 and 5, a second embodiment of the plastic reinforcement made of a single piece according to the invention is illustrated. The reinforcement comprises an outer portion 34, of a generally polygonal shape, and an inner portion of an arched shape 35, defined between which are spaces or second holes 32, designed to form a structure interpenetrated with the concrete. First holes 33 are made in portions 31 of the reinforcement, which are to project from the block of concrete constituting the counterweight, so as to enable passage of screws, bolts or similar means for fixing the counterweight to the tank of the washing machine.
Figure 6 illustrates a variant of the embodiment of the reinforcement of Figures 4 and 5. The reinforcement of Figure 6 is provided not only with second holes 32, but also with further second holes 37, made in the internal ends of the portions 31 of the reinforcement. The reinforcement is moreover provided with ribs 36 that stiffen the structure thereof.
With reference to Figures 7 and 8, a third embodiment of the plastic reinforcement made of a single piece according to the invention is illustrated. This reinforcement is constituted substantially by a ring 44 provided with portions 41 designed to project from the block of concrete constituting the counterweight, made in which are first holes 43 for the passage of screws, bolts or similar means for fixing the counterweight to the tank of the washing machine. As emerges from the elevational view of Figure 8, a segment 44' of the ring 44 is raised with respect to the plane of the ring, according to the general conformation of the counterweight and the part of tank to which it is to be fixed.
Figures 9 and 10 illustrate a variant of the embodiment of the reinforcement illustrated in Figures 7 and 8. Said variant is provided with stiffening ribs 46 that develop along the ring 44 for the purposes already indicated above.
Figures 11 and 12 illustrate a fourth embodiment of the plastic reinforcement made of a single piece according to the invention. Said reinforcement has a generally polygonal shape, and comprises a substantially square frame 45, defined in which are spaces or second holes 52, designed to form a structure interpenetrated with the concrete. First holes 53 are made in portions 51, 51' of the reinforcement that are to be left free (51') or else to project (51) from the block of concrete constituting the counterweight so as to enable passage of screws, bolts or similar means for fixing the counterweight to the tank of the washing machine. The reinforcement is moreover provided with ribs 56 that stiffen the structure thereof.
According to a further embodiment, not illustrated in the figures, the reinforcement can present a three-dimensional structure, i.e., one that develops according to different mutually incident planes. In this way, it is possible to increase the strength of the counterweight, at the same time increasing the capacity of contrast to sliding of concrete parts.
As it has been said previously, the reinforcement described in relation to the embodiments of Figures 2-12 is designed to be englobed in a concrete counterweight (not illustrated), which constitutes, however, another subject of the invention. The plastic reinforcement made of a single piece hence performs the triple function of: a) structural reinforcement of the counterweight; b) element of joining of possible cracked parts of the counterweight thanks to the formation of a concrete/reinforcement interpenetrated structure; and c) element for fixing to the tank of the washing machine, thanks to the holes made in the parts not covered by the concrete.
According to a further aspect of the invention, the production of counterweights incorporating the reinforcement according to the invention can be simplified using a method comprising the following steps:

a) injection moulding of a reinforcement constituted by a single piece made entirely of plastic material or else of composite material, of a generally plane shape, provided with holes in portions designed to be left free from the mass of concrete forming said counterweight;
b) arrangement of the reinforcement obtained in step a) above in a mould for concrete having the shape of said counterweight, in such a way as to position said portions designed to project from the mass of concrete, forming said counterweight in areas not filled by the concrete;
c) pouring of concrete into said mould and subsequent vibration; and
d) hardening and setting of said concrete.

As regards the temporal sequence, step a) can be separated from the subsequent steps, it being possible to produce a certain number of reinforcements at a given moment, store them away and use them in step b) at a subsequent time, according to the convenience and to the operating requirements.
The possibility of making a reinforcement structure of plastic material that has adequate mechanical and chemical characteristics, and that can be obtained with a single operation of moulding, considerably reduces the cost of the counterweight according to the invention as compared to the counterweights of the known art, which - as it has been said - required the use of more costly materials and processes of production.
Some preferential embodiments of the invention have been described, but it is clear that the invention can undergo numerous modifications and variations, all of which fall within the scope of the inventive idea defined in the annexed claims.

Claims

A reinforcement for a counterweight for electrical household appliances and the like, characterized in that it comprises a single piece made of plastic material or of composite plastic material, provided with first holes (23, 23', 24; 33; 43; 53) in portions (21; 31; 41; 51) designed to be left free from the mass of concrete forming said counterweight.
The reinforcement according to Claim 1, characterized in that said plastic material or composite plastic material has a specific weight greater than or equal to 1.000 g/cc, an ultimate strength greater than or equal to 50 MPa and a tensile strength greater than or equal to 2000 MPa, determined according to the standard ASTM D 638.
The reinforcement according to Claim 2, characterized in that said plastic material or composite plastic material has a specific weight greater than or equal to 1.100 g/cc, an ultimate strength greater than or equal to 60 MPa and a tensile strength greater than or equal to 2500 MPa, determined according to the standard ASTM D 63.
The reinforcement according to Claim 2 or Claim 3, characterized in that said single piece is made of thermoplastic material.
The reinforcement according to Claim 2 or Claim 3, characterized in that said plastic material is chosen from among polyamide resins, ABS resins, polypropylene with a glass-fibre filler and polypropylene with a talcum filler.
The reinforcement according to one or more of Claims 1 to 5, characterized in that said single piece of plastic material has a substantially plane shape.
The reinforcement according to one or more of Claims 1 to 5, characterized in that said single piece has a substantially three-dimensional shape.
The reinforcement according to one or more of Claims 1 to 7, characterized in that it further comprises second holes (22; 32; 52) designed to be filled with concrete, suited to form a counterweight having a concrete/reinforcement interpenetrated structure.
The reinforcement according to Claim 1, characterized in that it further comprises stiffening ribs (26; 36; 46, 56).
A counterweight for electrical household appliances and the like, comprising a block made of concrete of a shape suited to being fixed to the tank of said washing machine, characterized by incorporating a reinforcement according to any one of Claims 1 to 9.
A method for the production of counterweights for washing machines and the like, characterized in that it comprises the steps of:
a. injection moulding of a reinforcement constituted by a single piece made entirely of plastic material or else composite material, of a generally plane shape, provided with holes in portions designed to be left free or project from the mass of concrete forming said counterweight;

b. arrangement of the reinforcement obtained in step a) in a mould for concrete having the shape of said counterweight, in such a way as to position said portions designed to be left free from the mass of concrete forming said counterweight in areas not filled by the concrete;

c. pouring of concrete into said mould and subsequent vibration; and

d. hardening and setting of said concrete.
The method according to Claim 11, characterized in that said plastic material or composite plastic material has a specific weight greater than or equal to 1.000 g/cc, an ultimate strength greater than or equal to 50 MPa, and a tensile strength greater than or equal to 2000 MPa, determined according to the standard ASTM D 638;
The method according to Claim 12, characterized in that said plastic material or composite plastic material has a specific weight greater than or equal to 1.100 g/cc, an ultimate strength greater than or equal to 60 MPa, and a tensile strength greater than or equal to 2500 MPa, determined according to the standard ASTM D 63.
The method according to Claim 13, characterized in that said plastic material or composite plastic material is chosen from among polyamide resins, ABS resins and polypropylene with a glass-fibre filler.
The method according to Claim 14, characterized in that said plastic material or composite plastic material is constituted by polyamide 6.