Patent Publication Number: US-2011056328-A1

Title: Strengthening structure of plastic casing of elevating motor

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an elevating motor, in particular to an elevating motor having a casing made of a plastic material, and a metal reinforced plate installed at a major force exerting position, such that the overall weight and strength of the elevating motor can meet an expected requirement. 
     2. Description of the Related Art 
     In fitness equipments or rehabilitation equipments, an elevating motor is usually used for adjusting the angle of inclination or angle of elevation of a machine body to facilitate users to use the equipments. At present, most elevating motors of this sort use a motor as a power source and a speed reduction gear box for driving an elevating element to rotate in order to adjust the equipments to a required angle. 
     With reference to  FIG. 1  for a schematic view of a conventional elevating motor of a treadmill, the elevating motor  20  of the treadmill  10  comprises a motor  21 , a speed reduction gear box  22  pivotally installed onto a base  11  for driving a threaded rod  23  that serves as a propping element to ascend or descend the elevating motor  20 , such that the threaded rod  23  can be extended or retreated inside a long tubular bushing  24  with its bottom pivotally coupled to a seat  12 . Such elevating machine is characterized in that the threaded rod  23  is ascended or descended to adjust the height above the bushing  24  for ascending or descending the base  11 . 
     However, the conventional speed reduction gear boxes  22  are generally casted with a high-strength metal, but the overall weight of the metal is very heavy and unfavorable for installing and transporting the treadmill. Furthermore, the whole gear box  22  is made of the high-strength metal, not only increasing the weight, but also incurring a high cost, and both are unfavorable to industrial applications. 
     In view of the foregoing shortcomings of the prior art, the inventor of the present invention based on years of experience in the related industry to conduct extensive researches and experiments, and finally developed a transmission gear box  22  made of a plastic material to overcome the aforementioned shortcomings. When the threaded rod  23  is driven by a transmission gear and a screw insert (not shown in the figure) inside the gear box  22  to ascend or descend axially, forces are concentrated at a periphery  221  of the gear box casing  22  which is in contact with the threaded rod  23  and the bushing  24 , and thus the periphery  221  may be cracked easily and frequently, resulting in a failure or a damage of the elevating motor  20 . 
     Although the inventor of the present invention has designed a gear box casing previously, and a half of the gear box casing is made a plastic material, and another half of the gear box casing is made of a metal material to achieve the effect of providing the required overall weight and strength. Since the length of axial action of the threaded rod  23  and the bushing  24  of the elevating motor  20  is relatively long, the moment with respect to the arm of force is relatively large, and the torque so produced is concentrated at front and rear sides of the gear box casing  22 , particularly at a position where the bushing  24  and the gear box casing  22  are connected. As a result, a crack may occur at the connecting position frequently, and thus the prior art requires further improvements. 
     SUMMARY OF THE INVENTION 
     A primary object of the present invention is to provide a strengthening structure of a plastic casing of an elevating motor, and the structure is capable of reducing the overall weight and maintaining the mechanical strength of the casing of the elevating motor. 
     Another object of the present invention is to provide a strengthening structure of a plastic casing of an elevating motor, and the structure includes a metal reinforced plate installed at a position having the maximum propping force and torque produced by the elevating motor and provided for perpendicularly supporting the bushing to form a rigid support structure, such that a bearing force can be supported uniformly by the whole metal reinforced plate to overcome the shortcoming of the prior art that a crack may occur at the contact surface easily, so as to achieve the effect of providing a long using life and a smooth transmission. 
     In order to achieve the above-mentioned objects, a strengthening structure of a plastic casing of an elevating motor in accordance with the invention includes: 
     a) a casing, having a front casing and a rear casing, engaged with each other by a plurality of bolts, and the front and rear casings being made of a plastic material, and a first through hole and a second through hole being formed coaxially at front and rear sides, and the front and rear casings having a first circular recession and a second circular recession formed on internal sides the periphery of the first and second through holes respectively; 
     b) a transmission unit, installed in the casing, and comprising a transmission gear, a speed reduction gear, a screw insert formed at the middle of the transmission gear, and first and second cam shafts formed at front and rear portions of the screw insert and sheathed into the first and second circular recessions respectively; 
     c) a motor, installed outside the casing, for providing a motive power to the transmission unit; 
     d) a threaded rod, passed through the first and second through holes of the casing, and engaged with the screw insert of the transmission gear; and 
     e) a metal bushing, installed outside the front casing, and sheathed onto an end of the threaded rod, and having a first pipe opening formed at the front casing first through hole, a first metal reinforced plate mounted at the periphery of the first pipe opening and coupled perpendicularly with the front casing, and a first locking hole formed at the first metal reinforced plate and secured to one of the corresponding bolts of the front and rear casings, such that the first metal reinforced plate is fixed securely to the front casing to improve the strength at a force exerting position of the casing. 
     According to the invention, one or more additional metal reinforced plates is provided to create a sufficient strength to meet a standard requirement while minimizing the weight, so as to provide a convenient way of operating a fitness equipment such as a treadmill. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a schematic view of a conventional elevating motor of a treadmill; 
         FIG. 2  is an exploded view of a first preferred embodiment of the present invention; 
         FIG. 3  is a perspective view of a first preferred embodiment of the present invention; 
         FIG. 4  is a cross-sectional view of a first preferred embodiment of the present invention; 
         FIG. 5  is a perspective view of a reinforced body in accordance with a second preferred embodiment of the present invention; 
         FIG. 6  is a perspective view of a second preferred embodiment of the present invention; 
         FIG. 7  is a cross-sectional view of a second preferred embodiment of the present invention; 
         FIG. 8  is a perspective view of a reinforced body in accordance with a third preferred embodiment of the present invention; and 
         FIG. 9  is a perspective view of a third preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to  FIGS. 2 to 4  for a preferred embodiment of the present invention, the invention comprises: 
     a casing  30 , having a front casing  31  and a rear casing  32  engaged with each other by a plurality of bolts  40 , and the front and rear casings  31 ,  32  being made of a plastic material, and a first through hole  33  and a second through hole  34  formed coaxially at front and rear sides of the casing  30 , and the front and rear casings  31 ,  32  including a first circular recession  35  and a second circular recession  36  disposed on internal sides of the periphery of the first and second through holes  33 ,  34 ; 
     a transmission unit  50 , installed in the casing  30 , and comprising a transmission gear  51 , a speed reduction gear  52 , a screw insert  511  formed at the middle of the transmission gear  51 , and first and second cam shafts  513 ,  514  formed at front and rear portions of the screw insert  511  and sheathed into the first and second circular recessions  35 ,  36  respectively; 
     a motor  64 , installed outside the casing  30 , for providing a motive power to the transmission unit  50 ; 
     a threaded rod  70 , passed through the first and second through holes  33 ,  34  of the casing, and engaged with a screw insert  511  of the transmission gear  51 ; and 
     a metal bushing  80 , disposed outside the front casing  31  and sheathed onto an end of the threaded rod  70 , and the bushing  80  having a first pipe opening  81  formed at the first through hole  33  of the front casing  31 , a first metal reinforced plate  90  fixed onto the periphery of the first pipe opening and coupled perpendicularly with the front casing  31 , and a plurality of bolts  40  of the first metal reinforced plate  91  provided for securing the front and rear casings  31 ,  32  having a first locking hole  91 , such that the first metal reinforced plate  90  is coupled to the front casing  31  securely to improve the strength at the force exerting position of the casing  30 . 
     Based on the aforementioned structure, the present invention comprises a first metal reinforced plate  90  installed at the periphery of the first pipe opening  81  of the metal bushing  80  and at a larger force exerting position for providing a support action and preventing the force from concentrating at a point. During the process of propping the elevating motor, the connecting position of the metal bushing  80  and threaded rod  70  with the casing  30  is an action point having the maximum force exerted. The first metal reinforced plate  90  of the present invention is attached onto the front casing  31 , and a bolt  40  is provided for connecting the front casing  31  to form a rigid support structure, whose mechanical strength is not inferior to a metal cast casing, and then the metal bushing  80  is coupled securely onto the front side of the casing. In addition, the metal cast casing generally comes with a weight of 10 kg, and the plastic casing  30  of the invention has a weight of 1 kg only, and the total weight including the weight of the first metal reinforced plate  90  will not exceed 2 kg. Obviously, the present invention can achieve the effect of reducing the weight effectively. Since the invention provides a rigid support structure for bearing a larger action force precisely at the position having the larger exerted force, therefore the overall mechanical strength can meet the desired requirement and optimize the weight and strength of the casing. 
     In addition, the first metal reinforced plate  90  of the metal bushing  80  is integrated formed with the front casing  31  (not shown in the figure). In other words, the first metal reinforced plate  90  is integrated with a side of the front casing  31  to provide a more secured structure. 
     The present invention further comprises an axial bearing  53  installed onto an axial contact surface of the first and second circular recessions  35 ,  36  and the first and second cam shafts  513 ,  514 , and the axial bearing  53  is a plummer block bearing, a needle roller bearing or a ball bearing, etc. 
     To enhance the strength, a preferred embodiment of the present invention further comprises a second metal reinforced plate  100  installed onto an external side of the rear casing  32  for passing the threaded rod  70 , and the second metal reinforced plate  100  includes a third through hole  102  for passing the threaded rod  70 , and a plurality of second locking holes  101  formed at the periphery of the third through hole  102  for passing and coupling the bolts  40 , and a folded edge  103  is formed at the bottom of the second metal reinforced plate  100  and corresponding to a protruding shape of the rear casing  32  to constitute a L-shaped body, such that the first and second metal reinforced plates  90 ,  100  can wrap and clamp both front and rear sides of the casing  30  to improve the bearing strength. In other words, the structure is similar to a sandwich structure that uses the bolts  40  secured in an axial direction for the connection to form a rigid support structure. 
     With reference to  FIGS. 5 to 7  for another preferred embodiment of the present invention, the structure of this embodiment is similar to the aforementioned preferred embodiment and related elements are represented by their respective numerals, and the difference of this preferred embodiment from the aforementioned preferred embodiment resides on that a third metal reinforced plate  110  is installed between the second metal reinforced plate  100  and the first metal reinforced plate  90  and coupled to a side of the casing to form an n-shaped reinforced body for wrapping and clamping three sides of the casing  30 . 
     With reference to  FIGS. 8 and 9  for a further preferred embodiment of the present invention, the structure of this embodiment is similar to the aforementioned preferred embodiments and related elements are represented by their respective numerals, and the difference of this preferred embodiment from the aforementioned two preferred embodiments resides on that this embodiment of the invention further comprises third and fourth metal reinforced plates  110 ,  120  installed between the second metal reinforced plate  100  and the first metal reinforced plate  90  and coupled to both symmetric sides of the casing to form a square reinforced body for wrapping and clamping four sides of the casing  30 . 
     In summation of the description above, the present invention provides a lightweight casing made of a plastic material and comprises a metal reinforced plate installed perpendicularly to the metal bushing or further comprises one or more additional metal reinforced plates to provide sufficient strength to meet a standard requirement while minimizing the weight, so as to provide a convenient way of operating a fitness equipment such as a treadmill. 
     Many changes and modifications in the above-described embodiments of the invention can, of course, be carried out without departing from the scope thereof. Accordingly, to promote the progress in science and the useful arts, the invention is disclosed and is intended to be limited only by the scope of the appended claims.