Abstract:
An air compressor of weight-reduction type is disclosed, wherein the bearing and the main housing thereof are formed integrally, so that when the piston body conducts reciprocating motion within the cylinder at high frequencies, the bearing is firmly fixed on the main housing without nonfunctioning or falling off. Furthermore, the main housing and the cylinder thereof are made of plastic and formed integrally. The main housing is formed with a wind collecting hood to facilitate the air flow being introduced through the main housing for rapidly dissipating the heat generated by the bearing and the heat generated from the reciprocating motion of the piston body. Accordingly, the manufacturing cost of the air compressor can be reduced to achieve an economical design, and the weight of the air compressor can be reduced to facilitate the compressor being carried onto a vehicle.

Description:
(a) TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to an air compressor of weight-reduction type and, more particularly, to an improved air compressor, wherein the bearing and the main housing thereof are formed integrally, so that when the piston body conducts reciprocating motion within the cylinder at high frequencies, the bearing is firmly fixed on the main housing without nonfunctioning or falling off; furthermore, the main housing and the cylinder thereof are made of plastic and formed integrally, therefore, due to the main housing and the cylinder being made of non-metallic material, the manufacturing cost of the air compressor can be reduced to achieve an economical design, and the weight of the air compressor can be reduced to facilitate the compressor being carried onto a vehicle. 
     (b) DESCRIPTION OF THE PRIOR ART 
       FIGS. 6 and 7  show a conventional air compressor  8 , which basically comprises a base  81 , a cylinder  82  joined to the base  81 , a motor  83  mounted to the base  81 , and a piston  84  fitted to the cylinder  82 . Through a gear mechanism  85  and a crank mechanism, the motor  83  can drive the piston  84  to conduct reciprocating motion within the cylinder  82 . The reciprocating motion includes an intake stroke for allowing air to enter the cylinder  82  and a compression stroke for compressing air in the cylinder  82  and forcing the compressed air out of the cylinder  82 . 
     The gear mechanism  85  includes a first gear  851  (i.e., the driving gear), which is mounted at an axle  831  of the motor  83 , and a second gear  852  (i.e., the driven gear) engaged with the first gear  851 . The crank mechanism includes a counterweight  861  provided at the second gear  852 , a crankshaft  862 , and a crankpin  863 . One end of the crankshaft  862  is fixed to a center of the second gear  852 , and the other end of the shaft  862  is fitted to a bearing  811  that is mounted in a mounting hole  810 . The crankpin  863  is fixed to the counterweight  861 . The piston  84  is connected to the crankpin  863  such that the hole  843  defined at the bottom end  842  of the rod portion  841  is fitted around the crankpin  863 . Since the crankpin  863  is offset from the crankshaft  862 , when the second gear  852  is rotated by the first gear  851 , the crankpin  863  can be driven to swing in a circle around the crankshaft  862 , which allows the piston  84  to conduct reciprocating motion within the cylinder  82 . 
     However, in the conventional air compressor  8 , due to the distance between the cylinder  82  and the base  81  is too long, the reciprocating motion of the piston  84  is often changed in its motion path. Therefore, the performance of compressing air and the service life of the conventional air compressor will be reduced. In more detail, as shown in  FIG. 7 , the gear mechanism  85  is located between the cylinder  82  and the base  81 , wherein the distance between the center of the cylinder  82  and the base  81  is indicated by the symbol (D). Due to the distance (D) being longer than a suitable length for the crankshaft  862 , the mounting hole  810  is liable to undergo a greater force at some area of the mounting hole  810  during the reciprocating motion of the piston  84 . As the piston  84  continues conducting reciprocating motion, the mounting hole  810  will be gradually worn out. Thus, the rotational center of the crankshaft  862  will not be fixed. The motion path of the crankshaft  862  is schematically indicated by the symbol (A) in  FIG. 8 , while the motion path of the crankpin  863  is schematically indicated by the symbol (C) in  FIG. 8 , which is non-circular. Thus, when the piston  84  conducts reciprocating motion within the cylinder  82 , the motion path of the piston  84  will be changed, as shown by the dashed lines in  FIG. 7 , and this will cause the head of the piston  84  and the bearing  811  mounted in the hole  810  to be damaged, thereby reducing the service life of the air compressor. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, one object of the present invention is to provide an air compressor of weight-reduction type, which can increase the motion stability of the piston body thereof, wherein the bearing and the main housing thereof are formed integrally, and the main housing and the cylinder thereof are made of plastic and formed integrally, so as to mitigate the defect of the conventional air compressor and increase the service life of the air compressor; furthermore, due to the main housing and the cylinder being made of non-metallic material, the manufacturing cost and the weight of the air compressor can be reduced. 
     Another object of the present invention is to provide an air compressor of weight-reduction type, wherein the main housing defines two through holes, respectively at two opposite sides of the area generally formed by the first and second portions of the main housing, which can guide the air flow generated by the cooling fan to flow through the main housing. The main housing is formed with two lateral walls and a bottom wall. Each of the lateral walls includes a curved upper section and a straight lower section, and thus the two lateral walls form an inverted U-shaped structure. The bottom wall includes a C-shaped section and two short sections at two opposite ends of the C-shaped section. The straight lower section of each lateral wall is joined with one of the short section of the bottom wall, and thus the two lateral walls and the bottom wall form a wind collecting hood. The second portion is located within the wind collecting hood, and multiple radial braces are formed between the second portion and the wind collecting hood so as to facilitate the air flow, especially the spiral component thereof, generated by the cooling fan, being introduced through the main housing for rapidly dissipating the heat generated from the reciprocating motion of the piston body, so that the operational security can be increased. 
     A further object of the present invention is to provide an air compressor of weight-reduction type, wherein the open bottom of the cylinder is divided into two halves according to a central vertical line of the cylinder, wherein one half of the open bottom is horizontal while the other half of the open bottom is slanted. 
     A still further object of the present invention is to provide an air compressor of weight-reduction type, wherein the air storage unit and the cylinder thereof are formed integrally. 
     Other objects, advantages, and novel features of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a 3-dimensional view of an air compressor of weight-reduction type according to one embodiment of the present invention. 
         FIG. 2  shows a rear view of the air compressor of weight-reduction type of the embodiment. 
         FIG. 3  shows a partially sectional view of the air compressor of weight-reduction type of the embodiment. 
         FIG. 4  shows a front view of the air compressor of weight-reduction type of the embodiment. 
         FIG. 5  shows a sectional view of the air compressor of weight-reduction type of the embodiment 
         FIG. 6  shows an exploded view of a prior-art air compressor. 
         FIG. 7  shows a schematic view of the prior-art air compressor, wherein the motion path of the piston is indicated by dashed lines. 
         FIG. 8  shows a schematic view of the motion paths of the crankshaft and the crankpin used in the prior-art air compressor. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIGS. 1 through 4 , an air compressor of weight-reduction type according to one embodiment of the present invention is shown, which generally comprises a main housing  1 , a cylinder  3  joined to the main housing  1 , a power mechanism mounted to the main housing  1 , and a piston body  25  fitted in the cylinder  3  and driven by the power mechanism to conduct reciprocating motion within the cylinder  3 . The piston body  25  contains a piston head  26  being integrally formed therewith. 
     The power mechanism includes a motor  21 , a small gear  22 , a large gear  23 , a counterweight  28  fixed with a crankpin  24 , and a cooling fan  27 . 
     The main housing  1 , which can be made of plastic, is provided with a first portion  11  and a second portion  12  (see  FIG. 3 ). The first portion  11  is provided for mounting the motor  21  fitted with a small gear  22  at an axle thereof. A cooling fan  27  is provided at a rear end of the axle of the motor  21 . The large gear  23  is provided with the counterweight  28  being fixed with a crankshaft  281  and a crankpin  24 . Specifically, the counterweight  28  is mounted in a central opening of the large gear  23  and flush with the large gear  23  so as to reduce the distance between the main housing  1  and the cylinder  3 . The bearing  29 , which can be a ball bearing, is formed integrally with the second portion  12  of the main housing  1 . In manufacturing the air compressor, the bearing  29  can be placed in a cavity of a mold for the main housing  1 , which is then introduced with molten plastic, and thus the bearing  29  can be formed integrally with the main housing  1  after the plastic is hardened. The crankshaft  281  is fixed at one end to the counterweight  28  and mounted at the other end to the bearing  29 . The bottom end of the piston body  25  is fitted around the crankpin  24 . The small gear  22  fitted on the axle of the motor  21  is engaged with the large gear  23 . The main housing  1  defines two through holes  13 ,  14 , respectively at two opposite sides of the area generally formed by the first and second portions  11 ,  12 , which can guide the air flow generated by the cooling fan  27 , to flow through the main housing  1 . Furthermore, the main housing  1  is formed with two lateral walls and a bottom wall. Each of the lateral walls includes a curved upper section  151  and a straight lower section  152 , and thus the two lateral walls form an inverted U-shaped structure. The bottom wall includes a C-shaped section  154  and two short sections  153  at two opposite ends of the C-shaped section  154 . The straight lower section  152  of each lateral wall is joined with one of the short section  153  of the bottom wall, and thus the two lateral walls and the bottom wall form a wind collecting hood  15 . The second portion  12  is located within the wind collecting hood  15 , and multiple radial braces  16  are formed between the second portion  12  and the wind collecting hood  15  so as to facilitate the air flow, especially the spiral component thereof, generated by the cooling fan  27 , being introduced through the main housing  1  for rapidly dissipating the heat generated by the bearing  29  and the heat generated from the reciprocating motion of the piston body  25  within the cylinder  3 . 
     Both the cylinder  3  and the main housing  1  can be made of plastic. The cylinder  3  can be integrally formed with the main housing  1  or joined with the main housing  1  by using bonding technology (see  FIG. 4 ). Furthermore, the air storage unit  5  can be formed integrally with the cylinder  3 , wherein the air storage unit  5  is formed on the top wall  31  of the cylinder  3 . The top wall  31  of the cylinder  3  defines a through hole  310  communicating with the air storage unit  5  and the inner space  34  of the cylinder  3 . A valve plug  41  is located in the air storage unit  5  above the through hole  310  of the top wall  31  of the cylinder  3  and biased by a compression spring  42  thereon. As such, the motor  21  can drive the crankpin  24 , via the small gear  22  and the large gear  23 , to swing in a circle around the crankshaft  281 , which allows the piston body  25  to conduct reciprocating motion within the cylinder  3  so as to produce compressed air in the inner space  34  of the cylinder  3 . The compressed air can overcome the biasing force of the compression spring  42  to enter the air storage unit  5  via the through hole  310 . Furthermore, the air storage unit  5  is provided with multiple connection fittings  51 ,  52 ,  53  and  54 , through which the compressed air can be delivered to various application objects of different functions or features. For example, the connection fitting  51  can be connected with a hose (not shown), the connection fitting  52  can be connected with a pressure gauge  6 , and the connection fitting  53  can be connected with a safety valve  7 . 
     Preferably, the top surface of the piston head  26  is configured with a slope. With such feature, the force required for moving the piston body  25  at BDC (bottom dead center) or TDC (top dead center) can be reduced, and the gas-tightness between the piston head  26  and the cylinder  3  can be increased after the piston body  25  passes BDC or TDC, so that the reciprocating motion of the piston body  25  can be conducted more smoothly and the performance of compressing air can be increased. 
     The cylinder  3  of the air compressor has an open bottom  32 . Referring to  FIG. 4 , a vertical central line (Y) of the cylinder  3  is used to divide a horizontal line (X) into a positive segment (+X) and a negative segment (−X). As shown, the open bottom  32  of the cylinder  3  is divided into two halves by using the vertical central line (Y) as a dividing line, wherein one half of the open bottom  32  corresponding to the positive segment (+X) is horizontal and parallel to the plane (X-Z))(where Z is an axis perpendicular to both the X-axis and Y-axis), while the other half of the open bottom  32  corresponding to the negative segment (−X) is slanted, and thus an extension portion  321  of the surrounding wall of the cylinder  3 , with a slanted bottom  322 , is formed. Preferably, the slanted bottom  322  is parallel to the top surface of the piston head  26  when the piston body  25  is at BDC (bottom dead center) or TDC (top dead center). As shown in  FIG. 5 , the distance between the lowest point of the slanted bottom  322  and the horizontal bottom is indicated by the symbol (L). 
     Furthermore, the slanting direction of the top surface of the piston head  26  as well as the slanted bottom  322  depends on the rotational direction of the large gear  23 . For example, as shown in  FIG. 5 , when the rotation of the large gear  23  is clockwise and the slanted bottom  322  is at the left side of the cylinder  3 , both the top surface of the piston head  26  and the slanted bottom  322  will be slanted up from the left to the right. On the other hand, if the rotation of the large gear  23  is counterclockwise and the slanted bottom  322  is at the right side of the cylinder  3 , then both the top surface of the piston head  26  and the slanted bottom  322  will be slanted up from the right to the left. 
     As mentioned above, the piston body  25  of the air compressor can conduct reciprocating motion within the cylinder  3 . In  FIG. 5 , the piston body  25  has conducted a downward motion, and the piston body  25  is at BDC (bottom dead center). At this moment, the top surface of the piston head  26  is parallel to the slanted bottom  322  of the cylinder  3 , and the piston head  26  is entirely within the open bottom  32  of the cylinder  3 , so that the piston head  26  will not escape from the cylinder  3  and thus can keep gas-tight with the inner surface  30  of the surrounding wall of the cylinder  3 , so that the performance of compressing air and the operational security can be increased. 
     As a summary, the present invention provides an air compressor of weight-reduction type, which is featured in that the bearing  29  is formed integrally with the main housing  1 . Preferably, the main housing  1  and the cylinder  3  are made of plastic and formed integrally. Furthermore, the main housing  1  defines two through holes  13 ,  14  respectively at two opposite sides of the area generally formed by the first and second portions  11 ,  12  for guiding the air flow generated by the cooling fan  27  to flow through main housing  1 . The main housing is formed with two lateral walls and a bottom wall. Each of the lateral walls includes a curved upper section  151  and a straight lower section  152 , and thus the two lateral walls form an inverted U-shaped structure. The bottom wall includes a C-shaped section  154  and two short sections  153  at two opposite ends of the C-shaped section  154 . The straight lower section  152  of each lateral wall is joined with one of the short section  153  of the bottom wall, and thus the two lateral walls and the bottom wall form a wind collecting hood  15 . The second portion  12  is located within the wind collecting hood  15 , and multiple radial braces  16  are formed between the second portion  12  and the wind collecting hood  15  so as to facilitate the air flow, generated by the cooling fan  27 , being introduced through the main housing  1  for rapidly dissipating the heat generated by the bearing  29  and the heat generated from the reciprocating motion of the piston body  25  within the cylinder  3 , so as to increase the operational security. Furthermore, the main housing  1  and the cylinder  3  of the air compressor are made of non-metallic material, so that the weight and the manufacturing cost of the air compressor can be reduced, thereby achieving an economic design.