Abstract:
A method for making gearmotors comprising a casing, a pinion and a gear, meshed with the pinion, both supported by the casing, comprises the steps of: preparing a mould for the casing; making the casing by casting in the mould; the step of making the casing consisting of a step of injecting a molten plastic material into the mould so that the casing is formed by the plastic material once it has cooled.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a method for making a gearmotor and in particular a method for making a gearmotor using a plastic material.  
         [0002]     Prior art processes for making gearmotors usually involve mechanical machining to obtain a metal casing in which the gearmotor moving parts are assembled, for example, briefly, the ring gear and the pinion.  
         [0003]     The classic processes involve making castings, several parts of which are subsequently machined using machine tools.  
         [0004]     In general, the rough casing is made by casting. Once removed from the mould, it is deburred or in any case cleaned with the removal of shavings, holes are made where necessary, threads prepared, with restoration of the design tolerances essential for guaranteeing correct gearmotor operation and avoiding, in particular, seizing phenomena during operation.  
         [0005]     In other words, a plurality of operations are carried out after casting, which have a significant effect on the cost of the finished product.  
         [0006]     Moreover, for that reason, conventional processes are relatively long, since the above-mentioned mechanical machining means having to have available machine tools and storage warehouses for semi-finished products, with evident logistical complications in gearmotor production and assembly.  
       SUMMARY OF THE INVENTION  
       [0007]     In this context, the main technical purpose of the present invention is to propose a method for making gearmotors which is free of the above-mentioned disadvantages.  
         [0008]     The present invention has for an aim to propose a method which simplifies the mechanical machining on semi-finished products so as to reduce both the gearmotor production and assembly times and the relative costs.  
         [0009]     The present invention also has for an aim to propose a method for making the gearmotor which overcomes the logistical complications and reduces or eliminates the times for which semi-finished products remain in the warehouses.  
         [0010]     The technical purpose indicated and the aims specified are substantially achieved by a method for making gearmotors comprising the operating steps described in claim  1  and in one or more of the dependent claims herein. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     Further features and advantages of the present invention are more apparent in the detailed description below, with reference to a preferred, non-limiting, embodiment of a method for making gearmotors and of a gearmotor, illustrated in the accompanying drawings, in which:  
         [0012]      FIG. 1  is a schematic longitudinal section of a gearmotor made using the method in accordance with the present invention;  
         [0013]      FIG. 2  is a schematic cross-section of the gearmotor of  FIG. 1 ;  
         [0014]      FIG. 3  is a schematic perspective view of a detail of the gearmotor from the previous Figures;  
         [0015]      FIG. 4  is a schematic perspective view of a first block which is part of a mould suitable for implementing the method in accordance with the present invention;  
         [0016]      FIG. 5  is a schematic perspective view of a second block which is part of the mould suitable for implementing the method in accordance with the present invention;  
         [0017]      FIGS. 6 and 7  are schematic sides views suitably in cross-section of a succession of steps of the method in accordance with the present invention;  
         [0018]      FIG. 8  is a bottom plan view of a detail of the mould for making the gearmotor in accordance with the present invention;  
         [0019]      FIG. 9  is a schematic side view of the detail from  FIG. 8 ;  
         [0020]      FIG. 10  is a top plan view of the mould for implementing the method in accordance with the present invention, at a step of making hollows in a part of the gearmotor. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]     With reference to the accompanying drawings and in particular with reference to  FIGS. 1 and 2 , the numeral  1  denotes a gearmotor obtained with the method in accordance with the present invention.  
         [0022]     The gearmotor  1 , whose description is limited to understanding of the invention, comprises, schematically a casing  2 , illustrated in particular in  FIG. 3 , housing a pinion  3  meshed with a relative gear  4 .  
         [0023]     It should be noticed that in the embodiment illustrated by way of example, the pinion  3  is a worm screw and the gear is a ring gear with relative slots  5  for engaging with the screw.  
         [0024]     The pinion  3  is associated with a relative shaft  6  and the gear  4  is associated with a relative shaft  7 .  
         [0025]     The shaft  6  is connected to the casing  2  by relative bearings  8 ,  9  and the shaft  7  by relative bearings  10 ,  11 , that is to say, the casing  2  supports the pinion  3  and the gear  4 .  
         [0026]     The method disclosed comprises the steps of preparing a mould  12  in which to make a casting using a plastic material to obtain the casing  2 .  
         [0027]     It should be noticed that the step of making the casing  2  consists of a step of injecting a molten plastic material into the mould  12 , illustrated in particular in  FIGS. 8 and 9 , the molten plastic material cooling to form the casing  2 .  
         [0028]     It should be noticed that at the end of casting cooling in the mould  12 , the casing  2  is ready for subsequent assembly of the gearmotor  1 , since it does not require any further mechanical machining.  
         [0029]     The pinion  3  and gear  4  with the relative shafts  6 ,  7  are housed in the casing  2  in respective cavities  13 ,  14 .  
         [0030]     The method disclosed comprises the step of making the cavities  13 ,  14 , that is to say, hollows, in the casing  2 , by moving respective male elements  15 ,  16  relative to the mould  12 , as is schematically illustrated in  FIG. 10  in which the male elements  15 ,  16  are respectively able to move along the axes R 1  and R 2  of the cavities  13 ,  14 .  
         [0031]     To keep the cavity  13  tolerances suitable for gearmotor  1  operation, the male element  15  is preferably cooled.  
         [0032]     Similarly, to keep the cavity  14  tolerances suitable for gearmotor  1  operation, the male element  16  is cooled.  
         [0033]     Advantageously, the method disclosed comprises the step of preparing the bearing  9  in the mould  12  so that it remains associated with the casing  2  after the molten material injected into the mould  12  has cooled.  
         [0034]     To facilitate gearmotor assembly, the method disclosed also involves preparing the bearing  10  in the mould  12  so that it remains associated with the casing  2  after the molten material injected into the mould  12  has cooled.  
         [0035]     The method comprises a step of making, in the casing  2 , substantially annular cavities or grooves  17  in which means for fixing the shafts  6  and  7  are inserted.  
         [0036]     In particular, with reference to the cavity  14  it should be noticed that the fixing means comprise an elastic ring  18  for fixing the shaft  7  by means of the bearing  11 .  
         [0037]     The mould  12  comprises a fixed block  19  and a movable block  20  which are drawn near, as illustrated in particular in  FIGS. 8 and 9 , and contained in a die  21  which is part of the mould  12 .  
         [0038]     In particular with reference to  FIGS. 6 and 7 , it may be seen, for example, how, to form the cavity  17  relative to the cavity  14  and allow extraction of the male element  15  from the blocks  19  and  20 , according to the method disclosed the male element  15  comprises an outer portion  22  sliding on an inner portion  23 .  
         [0039]     The outer portion  22  has a tooth  24  designed to define, during casing  2  casting, the hollow corresponding to the cavity  17 .  
         [0040]     Once the cavity  17  has been formed, according to the method the portion  23  of the male element  15 , sliding in the direction V indicated in  FIG. 7 , causes the portion  22  to move towards the axis R 2  of the cavity  14  and consequently the tooth  24  comes out of the cavity  17  so that the male element  15  can move relative to the mould  12 .  
         [0041]     It should be noticed that such a movement towards the axis R 2  is made possible by the particular substantially tapered shape of the portions  22  and  23  and by the fact that the portion  22  is free to move, set in motion by the portion  23 , relative to the mould  12 .  
         [0042]     Advantageously, the method comprises the step of preparing in the mould  12  threaded inserts  25  which remain associated with the casing  2  at the end of casting cooling so that they are available for fitting elements of the gearmotor which are not illustrated, for example connecting flanges.  
         [0043]     Advantageously, the method comprises the step of molding in plastic material the gear  4  on the relative shaft  7  so as to speed up the production method.  
         [0044]     Moreover, molding is preferably carried out by heating the mould  12 , in particular to around 60° C.  
         [0045]     The invention described brings important advantages.  
         [0046]     The casing made in a single body by molding a plastic material allows the elimination of all mechanical machining normally needed after molding metal alloys, significantly reducing production costs.  
         [0047]     Once ejected from the mould, the casing is ready for gearmotor assembly with evident simplification of the logistics for management of semi-finished products and warehouses.  
         [0048]     The invention described above may be modified and adapted without thereby departing from the scope of the inventive concept defined in the claims herein.  
         [0049]     Moreover, all details of the invention may be substituted by technically equivalent elements.