Abstract:
The invention concerns a method and a blank ( 30 ) for manufacturing a compressor block of a small-type refrigeration appliance, particularly for a hermetically enclosed refrigerant compressor arrangement, the blank comprising a handling section ( 34 ) and at least two working areas ( 43, 46 ). The blank ( 30 ) is clamped in a working arrangement at a handling section ( 34 ), the blank being worked during maintenance of the clamping. It is endeavoured to reduce the dimensions of a compressor block, though maintaining the opportunity of performing several working steps during one clamping process. For this purpose, it is provided that the handling section ( 34 ) is removed after the working.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    Applicant hereby claims foreign priority benefits under U.S.C. § 119 from German Patent Application No. 10 2007 038 444.2 filed on Aug. 16, 2007, the contents of which are incorporated by reference herein. 
       FIELD OF THE INVENTION 
       [0002]    The invention concerns a method for manufacturing a compressor block of a small-type refrigeration appliance, particularly for a hermetically enclosed refrigerant compressor arrangement, in which a blank is used, the blank being clamped in a working arrangement at a handling section, the blank being worked at least two different working areas during maintenance of the clamping. 
         [0003]    Further, the invention concerns a blank for manufacturing a compressor block of a small-type refrigeration appliance, particularly for a hermetically enclosed refrigerant compressor arrangement, with a handling section and at least two working areas. 
       BACKGROUND OF THE INVENTION 
       [0004]    In the following, the invention will be described on the basis of a compressor block for a small-type refrigeration appliance, as used in domestic appliances, for example refrigerators or freezers, or in mobile refrigeration systems, for example in cars. A typical compressor for such applications is shown in DE 26 17 370 A1. 
         [0005]    Such a compressor only supplies a limited amount of refrigeration, for example in the area of 100 W at an evaporation temperature of −5° C. and a condensation temperature of +55° C. Due to the refrigeration supply, it only requires relatively small dimensions. Usually, the compressor block serves the purpose of adopting one single cylinder, housing a crankshaft and connecting to the stator of an electrical drive motor. The cylinder has to be manufactured with a relatively high accuracy, so that large inner leakages will not eventually appear during operation. Also the bearing of the crankshaft, which usually comprises at least one radial bearing and an axial bearing, must be manufactured with a certain accuracy. Further, the cylinder and the bearing of the crankshaft must be aligned relatively accurately to each other to prevent an edging of the piston reciprocating in the cylinder. For cost reasons, it is therefore endeavoured to work all required working areas in one working arrangement, for which only one clamping process of the blank is required. Preferably, all working steps are then made during this clamping process. In spite of the clamping, all required working tools must have sufficient access and free space to carry through the working. In consideration of this requirement, the compressor block needs a certain size, so that during working it can on the one hand be fixed or clamped with the required security and reliability; on the other hand provide the working tools with the required access to the blank. 
       SUMMARY OF THE INVENTION 
       [0006]    The invention is based on the task of reducing the dimensions of the compressor block, though maintaining the opportunity of making several working steps during one clamping process. 
         [0007]    With a method as mentioned in the introduction, this task is solved in that the handling section is removed after the working. 
         [0008]    Thus, it is ensured that during working the compressor block can be clamped and that several working steps can be performed during one clamping process. For example, in one position the cylinder can be bored and refinished, whereas in a second position a bore for the bearing section of the crankshaft can be made. In a third step, the front face of the cylinder can then be machine-flushed to permit the positioning of a cylinder head. At a fourth position, a further face around the bearing bore can be machine-flushed to form an axial bearing. During all these working processes, the blank or the compressor block to be manufactured is clamped at the handling section, so that changes of the clamping are not required. Sufficient free space is available for the working tools. When the compressor block is then almost finished, meaning that it no longer needs to be clamped, to enable further working steps, the handling section can be removed. This reduces the dimensions of the compressor block, even though the advantages of the same clamping could be used during the working steps. 
         [0009]    Preferably, the handling section is formed during manufacturing of the blank. For example, the blank can be moulded. The handling section is formed during the moulding, so that after finishing the moulding process it is available for clamping the blank. 
         [0010]    Preferably, a predetermined breaking point is provided at the handling section. The predetermined breaking point is preferably located, where the handling section is to be separated from the otherwise completely worked compressor block, that is, between the handling section and the compressor block. The predetermined breaking point makes it easier to separate the handling section from the compressor block. 
         [0011]    It is preferred that the handling section is knocked or broken off. If a predetermined breaking point is available, a simple knocking or pressing action will ensure that the handling section is broken off from the compressor block. No further tools, such as a cutter or a saw, will be required for breaking off the handling section. 
         [0012]    Preferably, the predetermined breaking point is made as a notch. A notch will concentrate the tensions provoked by a knocking or a pressing action, so that eventually the handling section can be broken off. 
         [0013]    Preferably, the predetermined breaking point is made when manufacturing the blank. If the blank is made as a moulded component, a corresponding projection can be made already in the mould, which will finally form the notch. 
         [0014]    Preferably, the handling section is made at an edge area of the compressor block. This may require somewhat longer lever arms, which will have to be considered with regard to the force distribution during the working. As, however, the removable handling section ensures that the compressor block can be made with somewhat smaller dimensions, this disadvantage is acceptable. If the handling section is made at an edge area of the compressor block, the remaining areas are available for the access of working tools. 
         [0015]    It is preferred that the edge area has a maximum distance from areas of the compressor block, which are critical with regard to manufacturing tolerances. Thus, deformations of these areas, which could lead to leakages in the cylinder gap or wear of the bearings, when separating the handling section, can be prevented. 
         [0016]    Preferably, the handling area is permitted to project radially in relation to a bearing bore for a crankshaft. Thus, the handling area can also be used for the simple positioning of the blank in machine tools. Then, the handling area extends along a main axis of a coordinate system, whereas the drill for making the bearing bore can be located in a different main axis. 
         [0017]    It is also advantageous, if the handling section is located in parallel to an axis of a cylinder. Thus, the handling section of the blank can be supported with sufficient stability against the forces, which appear during manufacturing of the cylinder bore. Also the face grinding of the front face of the cylinder can easily be managed in this manner. A major advantage also exists in that in a manner of speaking the handling section has the largest distance from the cylinder, so that a deformation of the cylinder during the removal of the handling section will not occur. 
         [0018]    With a blank as mentioned in the introduction, the task is also solved in that the handling section can be separated from the compressor block. 
         [0019]    As explained above in connection with the method, this is a way to achieve that, during several working steps or even throughout the whole working, the blank can be held in one clamping position. Nevertheless, dimensions, which are only caused by the clamping, are not required, as the handling section can be removed after the working. 
         [0020]    Preferably, a predetermined breaking point is located between the compressor block and the handling section. Then, the handling section can be knocked or broken off, so that no further cutting tools are required to remove the handling section. 
         [0021]    Preferably, the handling section has a maximum distance from an area of the compressor block, which is critical with regard to manufacturing tolerances. Then, the removal of the handling section will have no damaging effect on the critical area, for example the cylinder. 
         [0022]    Preferably, the handling section is directed radially in relation to a bearing bore for a crankshaft. A bearing bore has not yet been made in the blank. However, it is known, where this bearing bore is to be located. Thus, the statement refers to the finished bearing bore. As explained above in connection with the method, the handling section can then be aligned in parallel to a main axis of the coordinate system and the drill for making the bearing bore can then be aligned to another main axis. This makes it easier to adjust the machine tools. 
         [0023]    It is also advantageous, if the handling section is aligned in parallel to an axis of a cylinder. Thus, on the one hand, the handling section is as far as possible away from the cylinder, so that the cylinder is not negatively influenced during separation of the handling section. On the other hand, the handling section and the drill for making the cylinder bore can be aligned in the same direction, which also simplifies the working. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    In the following, the invention is described on the basis of a preferred embodiment in connection with the drawings, showing: 
           [0025]      FIG. 1  is a longitudinal section through a refrigerant compressor arrangement, 
           [0026]      FIG. 2  is a side view of a compressor block blank, 
           [0027]      FIG. 3  is a top view of the compressor block blank, 
           [0028]      FIG. 4  is a side view of a worked compressor block, and 
           [0029]      FIG. 5  is a top view of a finished compressor block after separating the handling section. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    A refrigerant compressor arrangement  1  has an enclosure  2  with an upper part  3  and a lower part  4 . The upper part  3  has a flange  5  and the lower part  4  has a flange  6 . The upper part  3  and the lower part  4  are welded together or otherwise tightly connected to each other along the flanges. 
         [0031]    In the enclosure is located a unit  7 , which comprises an electric motor  8  and a compressor section  9 . Via several springs  10 ,  11 , of which two can be seen; the unit  7  is supported in the lower part  4 . 
         [0032]    The motor  8  comprises a stator  12  and a rotor  13 . The rotor  13  is unrotatably connected to a crankshaft  14 . The crankshaft  14  is rotatably supported in a compressor block  15 . For this purpose, the compressor block  15  comprises a radial bearing  16  and an axial bearing  17 . The radial bearing  16  is located in a bearing section  18  of the compressor block  15 . 
         [0033]    The stator  12  of the motor  8  is fixed on the compressor block  15 . Here, the fixing is located outside the drawing plane and can therefore not be seen in  FIG. 1 . 
         [0034]    Further, the compressor block  15  comprises a cylinder section  19 , in which a cylinder  20  is formed. The front face of the cylinder section  19  has a bearing surface  21 , a valve plate  22  being adjacent to the bearing surface  21 . On the side of the valve plate  22  facing away from the compressor block a cylinder head cover  23  is located. 
         [0035]    The crankshaft  14  has a crank pin  24 , on which a connecting rod  25  is rotatably supported. The connecting rod  25  is connected to a piston  26 , which can reciprocate in the cylinder  20 . By means of the crank pin  24  the connecting rod  25  ensures that the rotating movement of the crankshaft  14 , which is caused by the electric motor  8 , is converted to a reciprocating movement of the piston  26 . This causes a periodical reduction and increase of a pressure chamber  27  formed in the cylinder  20 , meaning that refrigerant gas, which is sucked into the enclosure  2  through a suction connection  47 , is compressed and passed on to a connected refrigeration system through a supply pipe  28 . An electric connection arrangement  29  is provided for the electrical supply of the motor  8 . 
         [0036]    The dimensions of the refrigerant compressor arrangement  1  should be kept as small as possible. In the most cases, the size of domestic refrigeration appliances is limited by other outer dimensions, for example the depth and the height of kitchen furniture. If it is desired to increase the space available for the refrigeration, it will be favourable to keep the refrigerant compressor arrangement as small as possible. 
         [0037]    Refrigerant compressor arrangements for domestic refrigeration appliances and similar applications can only supply a limited amount of refrigeration. Accordingly, a relatively small electric motor  8  and also a relatively small cylinder section  19  can be used. However, until now the dimensions of the compressor block  15  had a lower limit, as the compressor block had to be worked. For cost reasons it has been endeavoured to perform a working of all required surfaces, working sections and the like in one single working machine or working arrangement, which would require only one clamping process of the blank. All working steps should be performed during this clamping. A renewed clamping of the blank between individual working steps would have two disadvantages. Firstly, each renewed clamping generates costs. Secondly, it is relatively difficult to maintain the highest level of accuracy during a renewed clamping. For example, the bores for the crankshaft  14  and the cylinder  20  must have a relatively accurate alignment in order to prevent wear during later operation. 
         [0038]    A clamping tool requires a certain space around the blank to be worked. Working tools cannot be used in the area, in which the clamping tool is located. Accordingly, it is difficult, when the dimensions of the compressor block are small, to perform the desired working processes during one clamping process. 
         [0039]    In the following, a solution to this problem will be described. 
         [0040]      FIG. 2  shows a blank  30  of the compressor block  15  in the unworked state. However, the bearing section  18  and the cylinder section  19  can be seen. Also a front face  31  can be seen, which has to be worked to form the bearing surface  21 . The top-view in  FIG. 3  also shows a surface  32 , in which the axial bearing  18  will be formed. The  FIGS. 2 and 3  also show lateral projections  33 , on which the stator  12  of the motor  8  can be fixed. 
         [0041]    To enable the clamping of the blank  30 , the blank  30  has a handling section  34 , which projects from the blank  30 . The handling section  34  extends (in relation to the subsequently finished bores) radially to an axis  35  of the radial bearing  16 . Further, the handling section  34  extends in parallel to an axis  36  of the cylinder  20 . In this connection, the handling section  34  is located on the side of bearing section  18  opposite to the cylinder  20 . Thus, changes in the shape of the cylinder during the separation of the handling section  34  from the finished blank  30  are not to be feared. 
         [0042]    For reasons of clarity, a part of the blank  30  is also called the compressor block  15 . A notch  37  is formed between the compressor block  15  and the handling section  34 . This notch  37  can already be made, when the blank  30  is manufactured, for example by moulding. However, the notch  37  can also be made during the working. 
         [0043]    When the compressor block  15  has been finished, the handling section  34  can be broken off from the compressor block  15  simply by means of a knocking or a pressing action. An additional working is not required. A breaking edge  38  thus appears, which has, as shown in  FIG. 1 , a relatively small distance from the crankshaft  14 , so that the compressor block  15  can be inserted relatively far into the stator  12  of the motor  8 . In the radial direction, the breaking edge is at least substantially inside the winding  39  of the stator  12  of the motor  8 . 
         [0044]    The blank  30  reaches the working arrangement, for example a robot with several tools and automatic tool change, as a casting. The working arrangement can grasp and clamp the blank  30  at the handling arrangement  34 . Then, the cylinder  20  is bored in the cylinder section  19 , and the front face  31  is worked to make the bearing surface  21 . A hole is bored through bearing section  18  to form the radial bearing  16 . The surface  32  is worked to make the axial bearing  17 . Further, an oil groove  40  can be made. Additionally, openings for clamp bolts can be bored in the front face  31 , by means of which the valve plate  22  and the cylinder head cover  23  can be connected to the compressor block  15 . Here, they are indicated by axes  41 . In the projections  33  bores  42  are provided, through which screw bolts can be guided to connect the compressor block  15  to the stator  12  of the motor  8 . The bearing section  18  is worked to provide a diameter reduction  43 , so that, as can be seen in  FIG. 1 , the bearing section  18  can be inserted relatively deeply into the rotor  13 . 
         [0045]    At the upper side of the compressor block  15 , in the cylinder section  19 , a recess  44  is made, which is used for mounting a piston pin  45  that connects the piston  26  to the connecting rod  25 . 
         [0046]    At the bottom side of the projections  33  bearing surfaces are worked, at which the stator  12  of the motor  8  bears. 
         [0047]    As soon as the working of the compressor block  15  is finished, the handling section  34  is removed by means of simple knocking or pressing action along the notch  37 , which forms a predetermined breaking point. This means that the handling section  34  is broken off. However, it can also be removed from the compressor block by means of milling or grinding. 
         [0048]    While the present invention has been illustrated and described with respect to a particular embodiment thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this invention may be made without departing from the spirit and scope of the present invention.