Abstract:
Electric compressor comprising a compression cylinder and the respective head, a valve plate arranged between the head and the body of said cylinder and provided with a gas inlet opening, a silencer arranged at the inlet side of said opening and comprising an elongated portion with an aperture adapted to fit in with said opening. The head is provided externally with a concave recess which is laterally open towards the inner cavity of the compressor, said elongated portion of the silencer being firmly housed in said recess so that the aperture engages the opening in the valve plate in an air-tight, sealed manner. In said recess there is provided a hollow space between said elongated portion and the outer wall, said hollow space being adapted to accommodate an elastic element for locking the silencer in place.

Description:
DESCRIPTION 
     The present invention refers to a particular form of both the head and the suction conduit of the silencer through which the refrigerant gas flows inside a sealed casing that encloses an electric motor, as particularly used in refrigerating apparatuses for home and similar applications. 
     To the purpose of more effectively exemplifying the present invention, said silencer is assumed to operate in close association with the compressor and to be made of plastics moulded by the injection moulding or any other appropriate plastic moulding process, without this of course limiting the scope of the same invention to just such a kind of coupling and material. 
     The gas pressure oscillations inside positive displacement compressors, in particular those used in domestic refrigeration equipment, are critically important owing to the extent to which they affect both the efficiency of and the level of sound power radiated by the compressors themselves. In these compressors, it is the refrigerant gas that comes from the suction tube that enters inside the sealed casing of the compressor. 
     The body of the compressor has a suction tube provided inside the casing which is connected to the suction valve through a number of channels and cavities that enable the suction gas to be conveyed into the cylinder. 
     The basic mechanisms governing the gas motion dynamics and, more generally, the state of the art are described in the Italian patent application no. PN0014 filed by the same Applicant, to which reference should therefore be made for obvious reasons of conciseness and of which the present invention shall be intended as constituting an improvement. 
     To the purpose of reducing the noise emissions from the suction conduit, the practice is commonly known of mounting a silencer element at the inlet at which the gas enters the head of the compressor, said silencer practically constituting in this manner the terminal portion of the gas suction conduit. 
     In view of using the sound-deadening effect thereof to the greatest possible extent, such a silencer is usually applied directly on to the inflow mouth of the valve plate, with such a construction as to be able to get over the thickness of the head. 
     It therefore is quite obvious that the head must be given an appropriately deep recess to accomodate at least a part of the silencer, ie. the one that is applied on to the inflow mouth of the valve plate. Owing to constructive reasons, such a connection is carried out after the valve plate has been assembled on the compressor body, but before assembling the head. 
     Such a method, however, calls for a number of manual assembly operations to be performed, so that the automatic process used to assemble the whole compressor must necessarily be interrupted and, as a result, a much longer time is required for manufacturing the compressor owing to both said interruption of an automated process and the time required for assembling the silencer manually. This practically turns out to constitute a drawback that considerably affect the overall production efficiency. 
     From EP 0 195 496 it is shown an hermetic motor-compressor unit for a refrigeration circuit, where the suction or inlet plenum chamber (A) is made as a separate part ( 27 ) of a plastic material in order to reduce heat transfer from the cylinder head to the suction chamber (A). 
     In said document it is explained that the spring  31  is first mounted on part  27  through the protrusion  38 . Then the part  27  is inserted into the slot  24 . 
     However, the presence of the spring  31 , previously mounted on said part  27 , will make more difficult such insertion of part  27 . 
     But, even more, the unavoidable scratching of the gaskets, pressed by the previously mounted spring  31 , that have to be mounted between the openings  28  and the parts  30 , will certainly damage said gaskets, therefore compromising the hermetic sealing between said openings and ports. 
     It therefore would be desirable, and it actually is a main purpose of the present invention, to provide a compressor head and silencing apparatus with such a form and size as to enable the whole assembly of the compressor to be carried out without assembling the silencer, and the silencer to be then assembled only upon completion of the actual manufacturing process, ie. after also the compressor head has been assembled. 
     It is a further purpose of the present invention to provide such a head and such silencer so that they enable techniques and materials to be used which are simple, cost-effective and readily available in the art. 
    
    
     These aims are reached in a compressor as it is described below by way of mere non-limiting example with reference to the accompanying drawings, in which: 
     FIG. 1 is a plan top view of the compressor body without valve plate; 
     FIG. 2 is a top view of the valve plate of a compressor according to the present invention: 
     FIG. 3 is a top view of a head of a compressor according to the present invention; 
     FIG. 4 is a top view of a silencer of a compressor according to the present invention; 
     FIG. 5 is a top view of the assembly of the four component parts illustrated in the above listed Figures, shown here in their final assembly condition; 
     FIG. 6 is a cross-sectional view of an improved variant of a compressor according to the present invention; 
     FIG. 7 is a perspective view oof a head of a compressor according to the present invention: 
     FIGS. 8 to  10  are respective views along the section plane A—A of the positions taken by a component part of the present invention at subsequent moments during the assembly thereof on the compressor head. 
    
    
     The basic idea behind the present invention is as described below: 
     As in the afore cited patent specification, the gas entering the compressor, and coming from the refrigerating circuit, is immediately “intercepted” by the silencer and conveyed towards the head without it being allowed to diffuse. 
     According to the present invention, however, both the silencer and the compressor body are so shaped and sized as to make it possible for the same silencer to be assembled after the compressor body itself has been fully assembled. 
     In this connection, and with reference to the above listed Figures, it can be noticed that the compressor body comprises a cylinder body  1 , a valve plate  2 , a head  3  of the compressor, and a silencer  4 . As compared with prior-art solutions, both the cylinder body  1  and the cylinder plate  2  may be left substantially unaltered, whereas the present invention introduces definite modifications relating to the head  3  of the compressor and the silencer  4 . 
     With reference to the compressor head  3 , it can be noticed that it is provided with a projecting border  5  along its outer surface, said projecting border being formed with a side  6  that is substantially orthogonal to the surface of the plate and said side  6  extending with a second side  7  that is substantially transversal with respect to said side  6  and substantially frontal, at a certain distance therefrom, with respect to the suction opening  20  provided in the plate  2 . 
     Furthermore, said head is so shaped as to leave uncovered a portion  8  of the plate situated therebelow, which is substantially opposing said second side  7  and, therefore, substantially encircling said suction opening  20 . 
     Said contiguous sides  6  and  7  are geometrically associated with each other so as to subtend a recess  9  that is defined by at least said side  7  and the opposing surface of said portion  8  of the plate situated therebelow. 
     It is therefore quite apparent that the suction opening  20  is in this way able to let into the avove cited and defined recess  9 . 
     The silencer  10  is in turn provided with an elongated portion  11 , on a side of which there is provided an opening  12  through which the gas is ejected towards the suction opening  20  provided in the valve plate. 
     The mutual shapes and dimensions of the described component parts will be such, and easily identifiable by those skilled in the art in their many variants as far as both the geometry and the dimensions are concerned, as to enable said elongated portion  11  of the silencer to be progressively inserted into said recess, after the head has been assembled, until the opening  12  provided to allow the gas contained in the silencer to escape establishes a perfect and tight fit with the corresponding opening  20  provided in the valve plate. 
     For the silencer to be kept in position, the dimensions of the described component parts are selected in such a manner that a hollow space  23  is obtained between the outer surface  21  of said elongated portion, which is situated in front of the respective opening  20 , and the inner surface  22  of said border  7 ; said hollow space is used to accomodate an elastic element  24  which, by acting elastically against said two mutually opposing surfaces  21  and  22 , firmly holds the silencer in the desired position by blocking said elongated portion  11 . 
     In an advantageous manner, in order to make it possible for said elastic element to be more easily and readily inserted, preferably without any use of particular tools or operations, the same element is obtained in the form of an appropriately bent high-elasticity metal leaf, as illustrated in FIG.  6 . In a preferred manner, in order to ensure that it takes a correct position, said elastic leaf is provided on its outer edge  24  with an appropriate fold  25 . Such a fold serves also the purpose of definitively fastening the leaf inside the hollow space. To this further purpose, said fold shall be such as to easily adapt to the projecting edge  26  of said side  7  of the projecting border  5 . 
     An advantageous variant of the above described embodiment of the present invention consists in providing said head and the silencer with such a recess  31  and such a protrusion  30 , respectively, that they are able to mutually engage, thereby consolidating the final assembly of said component parts and ensuring an exact, correct positioning thereof. 
     It will be appreciated that the above description and illustrations have been given, with reference to the accompanying drawings, to the mere purpose of exemplifying the present invention, and that a number of variants can be implemented and modifications can be made thereto without departing from the scope of the present invention.