Abstract:
The manifold includes a sleeve element ( 10 ) extending longitudinally about an axis (x), formed in one piece of plastics material and having a plurality of pairs of apertures ( 11, 12 ) distributed along the manifold. The apertures of each pair are aligned transversely with each other for engaging and locking on the manifold respective pairs of tubular metal elements ( 20, 30 ) connectable mechanically the one to the other ( 16 ) and to a branch (T) of the heating system.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a plastic manifold for hot-water heating systems and the like. 
   In the prior art manifolds are made of metal and are cast or made by drawing and additional operations. Such manifolds are used not only in the circuits of heating systems using radiators but also in heating systems using floor or wall-mounted coils or radiant panels, which can also be used to cool rooms during summer months, by using cold water. The main disadvantage of metal manifolds consists in their use in the latter category of systems: circulation of a fluid at a temperature lower than the ambient temperature inevitably leads to condensation on the outer surface of the manifolds. In turn, this condensation causes infiltration of damp patches on the walls or on the floor where the manifold assemblies are fitted or embedded. In addition, the use of metal material and the need for special operations mean that this type of manifold involves considerable costs. 
   In order to reduce condensation and, as a secondary benefit, to reduce the cost of these products, manifolds have recently been proposed made of batteries of modular elements moulded in plastics material working this type of material is definitely less expensive, while the better insulating properties of plastics materials significantly reduce the problem of condensation. 
   In order better to understand the art and the problems inherent thereto, a description is first provided of modular units of a known type, with reference to  FIGS. 1 and 2  of the appended drawings. 
   The modular units of the type illustrated in  FIGS. 1 and 2  include a main body  1  in the shape of a sleeve open at each end, having a generally horizontal axis and forming internally a tubular diametral portion  2 . The bottom end of the tubular portion  2  is fitted to a threaded pipe coupling  3  for connection to a pipe, indicated T of a secondary circuit; a seat  4  for a valve, indicated  5  and  6  respectively in  FIGS. 1 and 2 , is formed in the upper end of the tubular portion. The internal opening  7  of the tubular portion is in communication with the cavity of the main body and is shaped in such a way that fluid coming from the manifold, if the unit is a delivery one ( FIG. 1 ) or from a secondary circuit if the unit is a return one ( FIG. 2 ) flows first through the seat  4  of the valve. Both types of modular unit are constituted by a single piece of moulded plastics material, except for the pipe coupling  3  which is made of metal, generally brass, which is embedded in the plastics material at the time of the moulding operation, with a ribbed root portion  8 . 
   The individual units are mounted in succession along the axis y, with O-ring type sealing elements  9  mounted between the modules to ensure they are fluid tight. These units make up horizontal batteries which act as water delivery or return manifolds and, as individual units, as flow dividers for the secondary circuits connected to them. In delivery manifolds having units of the type shown in  FIG. 1 , water enters the battery at one end and leaves through the pipe couplings to supply the various branches of the heating system. The circuit of each individual branch can be excluded from the water circulation by means of respective shut-off valves  5 . In return manifolds, on the other hand, which are composed of units of the type shown in  FIG. 2 , the water returns from the various branches of the system through the pipe couplings of the respective modular units and flows out through one end of the battery. The flow through the individual circuits is regulated by respective regulator valves  6 . Brackets then secure the batteries, as part of a modular assembly, to a support structure fixed to a wall. 
   The modular arrangement of the manifold assemblies provides flexibility in use and makes it possible to absorb the overall heat expansion of the batteries at the interface of the individual modules, since the O-ring seals are able to deform and still ensure a hydraulic seal. 
   The main disadvantage of the modular arrangement consists in the possibility of leaks in the connection portions between modules and the consequent need for complicated and expensive maintenance. Another disadvantage, connected on the other hand to the construction methods of the individual modules, consists in the fact that inevitable variations in cyclical heat expansion, due to the different heat expansion coefficients of plastics materials and metal, can cause detachments at the interface of the plastic body and the ribs of the metal pipe couplings, which then lead to fluid leakage. In such an event it is necessary to replace the module. 
   SUMMARY OF THE INVENTION 
   The object of the invention is therefore to provide a moulded plastics manifold which overcomes the above-described disadvantages of to the prior art. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The structural and operating characteristics of a preferred embodiment of the invention will now be described with reference to the appended drawings, in which: 
       FIGS. 1 and 2  are axial section views of two modular units of a known type for making up delivery and return manifold assemblies for heating systems; 
       FIG. 3  is a side view of a manifold of the invention; 
       FIG. 4  is a side view of the manifold, with a partial axial section taken along the arrow IV of  FIG. 3 ; 
       FIG. 5  is an axially sectioned view of a portion of the manifold of  FIG. 3 , in which two metal elements are mounted for containing a valve mechanism and for connection to a secondary circuit; 
       FIG. 6  is a front view of two manifolds, one delivery and one return, in their fitted condition; 
       FIG. 7  is a section view taken on the line VII—VII of  FIG. 6 ; and 
       FIG. 8  is a section view taken on the line VIII—VIII of FIG.  6 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In the description and in the appended Claims, terms and expressions indicating positions or orientations such as “longitudinal”, “axial”, “radial” or “transverse” should be understood as referring to the longitudinal axis x of a manifold  10 , as shown in FIG.  3 . 
   With reference to  FIGS. 3 and 4 , the longitudinally extending manifold  10  is in the shape of a generally tubular sleeve and is constituted by a single piece of shaped moulded plastics material. The manifold  10 , which can serve equally as a delivery or return manifold, is open at a first end (on the left in the drawings) for the intake (in a delivery manifold) or for the exit of water (in a return manifold) while the opposite end is closed. 
   On two diametrically opposite sides the manifold has a respective series of apertures, indicated  11  in the lower series and  12  in the upper. The apertures of a series are aligned longitudinally and each aperture is aligned transversely or diametrically with a corresponding aperture in the opposite series, both longitudinally in the same series and radially, by pairing each aperture of the one series with one from the other. The two parallel planes in which the apertures lie are generally horizontal in the installed condition. Near the open end of the manifold (on the left in  FIGS. 3 and 4 ) an additional aperture  17  is formed, in a side of the manifold lying in a plane orthogonal to those in which the two series of apertures  11  and  12  are formed. This additional hole  17  is provided for mounting a thermometer  18 , shown in FIG.  6 . Again near the open end, two diametrically opposite cylindrical projections, indicated  51  in FIG.  3  and the function of which will be explained later, are formed in the external surface of the manifold. 
   One portion of the manifold assembly will now be considered in greater detail, with reference to FIG.  5 . The aperture  11  is provided for fitting a lower metal element or body  20 , while the aperture  12 , aligned with  11 , is provided for inserting an upper metal element or body  30 . The two metal elements  20 ,  30 , aligned with respect to the same axis as the two apertures  11 ,  12 , are each constituted by an essentially tubular body with portions having sections of different diameters, both internal and external. The body  20  provides connection to the pipe (not shown) of a secondary circuit, by means of a threaded pipe coupling  25  formed at the lower end of the body; the body  30 , on the other hand, makes it possible to engage the stopper mechanism of a valve (not shown) in a seat  35  in its outermost end. 
   In particular, the two metal bodies  20 ,  30  have two tubular portions, indicated  21  and  31  respectively, which make it possible to couple the two metal elements together inside the manifold  10  by means of a thread  16 . Beneath the thread  16 , the tubular portion  21  has an abutment collar  22  for the portion  31  of the upper body  30 . Engaged in the body of the manifold  10  and coupled together, the two metal bodies form an essentially tubular cross member the internal cavity of which is in communication with the main duct of the manifold by means of a transfer passage  32  formed in the tubular portion  31  of the body  30 . The overall dimensions of the tubular cross member are calculated to allow a free passage section for the main flow through the manifold. The sectioned portions shown in  FIG. 7 , make it possible to appreciate the dimensions of the section of the duct  32  and the free passage section through the manifold, indicated  36 ; in this drawing the overall tubular cross member is indicated  50 . 
   Still referring to  FIG. 5 , the end of the portion  21 , which partially protrudes into the communication duct  32 , forms a seat in which can operate the shutter of a valve mechanism (not shown) to be engaged in the seat  35  of the body  30 . The shutter makes it possible to open, partially open or close the opening of a coaxial duct  26  inside the portion  21  of the lower body  20 . The duct  26  puts the manifold  10  in communication with a branch of the heating system, connected to the pipe coupling  25 . The valve mechanism can be selected as a shut-off valve, if associated with a delivery manifold, or as a regulator valve if associated with a return manifold. Different elements, such as a breather valve (not shown) can also be engaged. 
   In addition, the body  20  has a prismatic portion  23 , hexagonal in cross section, for coupling to the manifold  10  at the aperture  11 , where a correspondingly shaped prismatic housing  13  is formed. This connection ensures that the body  20  is secured to the manifold  10  and locked against relative rotation. This makes it far simpler to fit or dismantle the element  30  or the connector pipe of a secondary circuit. 
   Turning in detail to the structure of the aperture  11 , a conical surface  14 , tapered or converging towards the circular aperture  11 , is formed in the tubular wall of the main body  10 , in a radial position relative to the seat  13 . An annular circular seal element or O-ring  19   a  is resiliently compressed between the conical surface  14  and a shoulder  24 . The deformation of the O-ring  19   a  ensures an hermetic seal between the plastic manifold  10  and the lower metal body  20  when, screwed tight to the upper metal body  30 , this latter compresses the said seal against the surface  14 . In the same way, the hermetic seal between the plastics manifold  10  and the metal element  30  is ensured by an O-ring  19   b  resiliently compressed between a conical surface  15 , tapering or converging towards the second side aperture  12 , and a shoulder surface  34  of the body  30 . By compressing the two O-rings  19   a ,  19   b  at the same time, the screwing together of the two metal bodies  20 ,  30  ensures a fluid-tight seal. 
   The O-ring seal elements  19   a ,  19   b  ensure that the interface areas between the metal parts  20 ,  30  and the plastics manifold  10  are fluid tight, despite any variation in thermal expansion of the two materials. The cyclical nature of this stress, due to alternating heating and cooling periods, does not affect fluid tightness thanks to the resilient properties of the O-rings, while any wear of the plastics material of the manifold  10  at the join with the metal elements  20 ,  30  does not affect fluid tightness either, since it is compensated by the O-rings. 
   In  FIGS. 6 ,  7  and  8  an upper delivery manifold  10 ′ and a return manifold  10 ″ are fixed to a wall structure N (see  FIGS. 7 ,  8 ) by means of a pair of double vertical brackets S 1 , S 2 . In general, each double bracket is constituted by two seats SC 1 , SC 2  each consisting of a half-cylindrical cavity with a horizontal axis and each having a cylindrical hole IC′ in the bottom of the cavity. The manifolds  10 ′ and  10 ″ are housed in these respective cavities SC 1 , SC 2 . The ends of the two manifolds are fixed to the double bracket S 1  by means of two half-rings A 1 , A 2  which each also have a cylindrical-section hole, indicated IC″, diametrically opposite the hole IC′ of the corresponding twin cavity SC 1 , SC 2 . The cylindrical projections  51  of the left ends of the manifolds are engaged in the holes IC′, IC″, thereby securing the connection of the two manifolds  10 ′,  10 ″ to the bracket S 1 . Each of the two half-rings A 1 , A 2  is then fixed to the double bracket by means of two screws V′ engaged in appropriate seats F. 
   In order to allow the manifolds to expand longitudinally during the heating and cooling operating cycles, the blind ends of the manifolds  10 ′,  10 ″, associated with the double bracket S 2  (on the right in  FIG. 6 ) are mounted slidably through two cylindrical rings AC, secured to the body of the bracket by screws V″. The manifolds are thus rigidly secured by their left ends, which connect them to the boiler or to the temperature regulating device, while their blind ends, on the right in the drawings, are free to slide longitudinally. 
   Finally, a resilient element, a coil spring M in this example (see FIG.  6 ), can be fitted onto the blind end of each manifold  10 ′,  10 ″ so as to be compressed axially between a support ring AC and a shoulder SP, formed on the outer surface of the manifold. 
   The assembly configuration shown in  FIG. 6  avoids stress building up in the plastics manifolds, which stress could occur during the heating and cooling cycles if the manifolds were rigidly secured at both ends. 
   The invention therefore makes it possible to produce a monobloc manifold element simply and economically, by moulding it in one piece of plastics material, with the possibility of fitting a plurality of valve elements of various types, each with pipe couplings for connection to respective secondary branches of the system. 
   The plastics material preferably includes polyarylamide reinforced with glass fibre in order to improve mechanical strength. The advantages of the prior art are retained: the low heat conduction of the plastics material considerably reduces condensation, as referred to in the introductory part of this description, while the relatively low cost of the plastics material provides a considerable saving compared to conventional monobloc manifolds made of metal. 
   The production of the manifold as a single block body, according to the invention, reduces the number of connections requiring a fluid-tight seal, since there are no modular units to assemble, while fluid tightness between the metal parts of the valve elements and the plastics material of the manifold is ensured by the O-rings, independently of the degree of difference in thermal expansion between the two materials. This arrangement eliminates once and for all the danger of the plastics material and the metal becoming detached and, in addition, a fluid-tight seal is ensured even if the plastics material becomes worn at the interface with the metal element. 
   Fitting and dismantling the valve elements is also far simpler, as are any maintenance operations. In particular, it should be noted that should one of the O-rings deteriorate, it can easily be replaced, by removing the valve mechanism without having to replace any other components of the manifold assembly. In the prior art, should a leak occur in the same area of the manifold (the join between plastics material and metal), the only solution would be to replace the faulty modular unit. 
   Although one, preferred embodiment has been described with reference to the appended drawings, it is clear that this description has been provided purely by way of non-limitative example, and that numerous variations can be made to the invention with regard to shape, dimensions, arrangement of parts and manufacturing details. For example, the number of apertures on the manifold can vary in dependence on requirements, as can the shape of the manifold in cross section. In the same way, manufacturing and operating characteristics of the valve mechanisms can be of any type (shut-off or regulator valves, manually controlled or controlled electrically by means of an associated thermostat).