Abstract:
A miniaturized motor includes a DC motor, a worm, a pinion gear, a worm gear, at least one cluster gear, an output gear and an output shaft. The gears form a gear train extending from the DC motor to the output shaft. A boss stabilizes the pinion gear by extending downwardly from inside the cover. Acoustical chambers packed with grease suppress noise generated by the gear train. A PC board is also provided on the cover to energize the DC motor. The output shaft may drive either a product mover for beverage cans inside a vending machine or another type of electromechanical unit requiring the application of high torque in a small space. A cradle bearing inside a cover holds a hub of the worm and prevents the worm from bending, thus assuring a good mesh of the worm with the pinion gear. A nest encapsulates the worm, the pinion gear and the worm gear to ensure protection and structural integrity of the miniaturized motor within the small space.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. Utility patent application Ser. No. 09/315,852, filed May 21, 1999 now U.S. Pat. No. 6,054,785, and is related to U.S. Design patent application Ser. No. 29/113,047, filed Oct. 29, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to machine elements and mechanisms generally, but more particularly to miniaturized motors. 
     2. Description of the Related Art 
     Existing designs for canned drink vending machine motors that operate at or above 100 inch-pounds are characterized by heavy duty shaded pole motors, zinc gear boxes, all metal gears with sleeve or needle bearings, and oversized installation envelopes. 
     In addition, the cost and weight for such designs are among the highest for subfractional horsepower gear motors. For example, present designs for vending machines include add-on brackets for custom mounting. Moreover, it is generally known that shaded pole motors are among the most inefficient types of motors in general use. Exemplary prior art devices are discussed below. 
     U.S. Pat. No. 5,446,326 issued to Scheider on Aug. 29, 1995, for a vending machine gear motor including a plastic gear box. As shown in FIG. 1 of his U.S. Patent, the gear motor of Scheider comprises a gear box  11  having a generally hollow plastic gear box housing  12 , a gear train  14  mounted therein, and an electronically insulating cover  13 . 
     U.S. Pat. No. 5,256,921 issued to Pruis et al. on Oct. 26, 1993, for a gear motor with a rotary switch. The gear motor has an output shaft for driving a dispensing mechanism of a vending machine. As shown in FIGS. 2 and 3 of their U.S. Patent, the gear motor of Pruis et al. includes an electric motor  12  mounted on a printed circuit board  13  and also includes an output shaft  14  which drives a conventional gear reduction unit  16 . 
     U.S. Pat. No. 5,404,060 issued to Nakahashi et al. on Apr. 4, 1995, for a miniature motor with a worm reduction gear. The miniature motor includes a motor section  1  which transmits torque generated from a motor shaft  3  to a worm  4 , then to a helical gear  5  in a reduction gear section  2 , and eventually to an output shaft  6 . 
     U.S. Pat. No. 5,172,605 issued to Schwartz on Dec. 22, 1992, and is assigned to the same assignee as the present invention. Schwartz discloses an electric motor gearbox for a vending machine. The gearbox has four main parts: a housing, a minimotor, a printed circuit board, and an assembly of plastic gears. 
     Various other gearing mechanisms relating to relatively small motors of general interest are disclosed in U.S. Pat. No. 5,747,903 issued to Klingler on May 5, 1998 and in U.S. Pat. No. 5,734,210 issued to Keutz on Mar. 31, 1998. 
     Despite these recent developments, it remains a problem in the prior art to develop a miniaturized motor with high torque for a gearcase which makes efficient use of space in a vending machine. 
     SUMMARY OF THE INVENTION 
     The present invention features unique improvements in the use of engineering plastics. The layout of components is compact, taking advantage of a direct current (DC) motor position which, in this particular case, is adjacent to a first-stage worm. 
     This arrangement keeps a miniaturized motor compact inside a gearbox which makes efficient use of space in a vending machine and in any other unit requiring an application of high torque in a small space. 
     A gear train within a gear box has standard available gears. However, the transfer stage from the worm down to a plurality of cluster gears within the gear box is flexibly arranged for a variety of gear ratios. This flexibility is introduced by adjusting the gear ratio between the first-stage worm with either single, double or quadruple threads and an adjacent pinion gear. 
     A metallic output shaft is supported directly within the gear box without introducing additional bearings. The lifetime of the gear box for directly supporting the output shaft is very predictable. Thus, this novel arrangement reduces costs over the lifetime of the gear box quite noticeably. 
     A number of features support quiet operation in addition to the first-stage worm. The gear box has close envelope contours to retain grease in the gear train. This close envelope also aids quiet operation. A plurality of acoustical chambers surround the gear train and insulate against noise transfer. 
     Unique to the present invention is the pinion gear that is supported by either a boss or a steel pin. Consequently, the invention provides a more stable gear mesh operation. Also, a cover supports the boss for the pinion gear at one end. 
     The rating of the gear motor can have a direct current (DC) voltage of either 12, 24, 36 or 48 volts. Furthermore, a printed circuit (PC) board is mounted on the gear box. A plastic cover provides a mounting post to support the PC board. 
     Materials for both the gear box and the cover are acrylonitrile butadinene styrene (ABS) copolymers or other engineering plastics with or without reinforcement in the matrix. Alternatively, metals may be used. However, they are not preferred because of their weight. Gears are made of delrin, nylon or other engineering plastics. Upper stage gears are formed from powdered metal or fine metallic blanks. Thus, the output shaft and other elements for transmitting torque are fabricated out of either powdered metal or metallic blanks. 
     Grease is selected from the high performance synthetic greases with a tolerance for both high and low temperatures. The poly-alpha-olefins have been found to be most satisfactory in this regard. 
     A key advantage of the present invention is that no anti-back-drive brake is necessary because of the use of the first-stage worm which typically cannot be back driven. 
     Thus, it is a primary object of the present invention to provide a vending machine with miniaturized motors that are compact, have noise control features, have higher efficiencies when compared to prior art devices, and are inexpensive to construct. 
     A secondary object of the present invention is to provide a miniaturized motor for custom mounting to a vending machine by direct foot mounts. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the invention and many of its attendant advantages will be readily obtained as the invention becomes better understood by reference to the following detailed description when considered with the accompanying drawings. 
     FIG. 1 is a top plan view of a miniaturized motor of the present invention with a gear train removed from inside a gear box. 
     FIG. 2 is a right side elevational view of a DC motor attached to the gear train inside the gear box. 
     FIG. 3 is a perspective view of an underside of a top cover that nests over a worm. 
     FIG. 4 is a perspective view of a right comer of the gear box in which the worm is set. 
     FIG. 5A is a rear end view of the DC motor, as seen along line  5 A— 5 A of FIG.  5 B. 
     FIG. 5B is a top plan view of the DC motor and the worm attached thereto. 
     FIG. 5C is an opposite end view of the worm and the DC motor attached therebehind, as seen along line  5 C— 5 C of FIG.  5 B. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, like reference numerals designate identical or corresponding parts throughout the several views. Features of the invention will become apparent in the course of the following description of the preferred embodiment which is given only for illustration of the invention and which is not intended to limit its scope. 
     In FIG. 1, an internal permanent magnet  12  produces an electromagnetic field necessary for operating a DC motor  10  that is attached through an external wall  16  to a gear train inside a gear box  14 . A plurality of short posts  18  interlock the gear box  14  to a cover (not shown in FIG.  1 ). Electricity is provided from an external power source (also not shown in FIG. 1) through a positive terminal  20  to the permanent magnet  12 . A negative terminal  22  is fixed opposite to the positive terminal  20  on the DC motor  10 . The permanent magnet  20  is energized inside the DC motor  10  to turn a rotary shaft hub  24  on which a first-stage worm  26  is mounted. Reversing the direction of rotation of the rotary shaft hub  24  and the first-stage worm  26  can be accomplished by reversing polarities of the DC voltage applied to the terminals  20  and  22 . A support plate  30  holds the DC motor  10  and the worm  26  together on the rotary shaft hub  24 . Side guides  32  surround peripheral edges of the support plate  30  so that the DC motor  10  and the worm  26  may slide together into and out of engagement with the external wall  16  of the gear box  14 . The DC motor  10  and the worm  26  slide together with the support plate  30  in a plane perpendicular to the paper on which FIG. 1 is illustrated. Although the DC motor  10  and the worm  26  are shown in their preferred orientation in solid lines, they may also be rotated 90° either to the right or to the left, as seen in phantom lines. Teeth  36  on the worm  26  mesh with teeth of a pinion gear (not shown in FIG. 1) which is mounted on a pinion shaft  34 . The worm  26  can be either single, double or quadruple threaded. Alternatively, the worm  26  can be helically threaded. The meshing of the various gears of the gear train will be described with reference to FIG.  2 . However, for the sake of spatial orientation, there are shown in FIG. 1 the following: primary cluster gear shaft  40 , secondary cluster gear shaft  50  and output shaft  60 . Bosses  38  strengthen the gear box  14  where there are bores through which the shafts  34 ,  40 ,  50  and  60  pass. Because the shafts  34 ,  40 ,  50  and  60  are all made of metal, reinforcing ribs  42  radiate outwardly from each boss  38  to strengthen the gear box  14  further against cracking of the plastic material out of which the gear box  14  is molded. If the DC motor  10  and the worm  26  are essentially perpendicular to the shafts  40 ,  50  and  60 , the shaft  34  with its surrounding boss  38  and its single radiating rib  42 A are positioned at a 45° angle from a right horizontal rib  42 B radiating from the shaft  40 . The shaft  34 , the boss  38  and the rib  42 A are kept in the positions shown in solid lines for a second embodiment in which the DC motor  10  and the worm  26  (both shown in phantom lines on the right side of FIG. 1) are rotated 90° counterclockwise to form an L shape with the gear box  14 . However, if the DC motor  10  and the worm  26  (both shown in phantom lines on the left side of FIG. 1) are rotated 90° clockwise to form a reversed L shape with the gear box  14 , then the shaft  34 , its surrounding boss  38  and the single radiating rib  42 A are likewise rotated 90° so that they form a 45° angle with a left horizontal rib  42 C radiating from the shaft  40 . A plurality of extended corner feet  68  allows the gear box  14  to be custom mounted to a device being operated, e.g. a vending machine. Furthermore, any noise generated by the gear train is suppressed by grease packed inside a plurality of acoustical chambers  80  which are formed along side walls of the gear box  14 . 
     FIG. 2 is a partially cut away elevational view taken along the right side of FIG.  1 . The DC motor  10  and its permanent magnet  12  are seen at the left side of FIG.  2 . The negative terminal  22  is shown in phantom lines and has a clip  44  attached thereover. The clip  44  is connected to an end of a power line  46  which extends from an external power source  48  for either direct current (DC) or rectified alternating current (AC) with or without filtering. The foot  68  is one of four extended corner feet which allow the gear box  14  to be custom mounted to a vending machine being operated. At the right side of the DC motor  10 , the rotary shaft hub  24  passes through the support plate  30  which is held in place by the side guides  32 . The teeth  36  of the worm  26  drive an upper pinion gear  33  which is mounted on the pinion shaft  34  and which is formed integrally with a lower worm gear  35 . Teeth of this worm gear  35  mesh with teeth of an adjacent primary cluster gear  39  which is mounted on the gear shaft  40 . The worm  26 , the pinion gear  33 , the worm gear  35  and the primary cluster gear  39  are all made of hard plastic. A small metallic gear  41  sits on top of the primary cluster gear  39  and is press fitted into the center of the plastic gear  39  so that both gears  39  and  41  rotate together on the shaft  40 . This shaft  40  is press fitted at both ends into centers of its surrounding bosses  38  and does not rotate itself. The small gear  41  drives a large adjacent upper secondary cluster gear  49  which rotates on the shaft  50 . Below the gear  49 , there is a small lower tertiary cluster gear  51  also mounted for rotation on the shaft  50 . Thus, the gears  39 ,  41 ,  49  and  51  constitute a plurality of intermediate cluster gears. Above the plurality of cluster gears, there is a solid plastic post  52  molded integrally with the gear box  14  for supporting a printed circuit (PC) board  54  which energizes the DC motor  10 . Teeth on the tertiary cluster gear  51  mesh with teeth on an output gear  59  to rotate the output shaft  60 . The gears  41 ,  49 ,  51  and  59  are all made of sintered metal powder. Thus, the gears inside the gear box  14  change in composition from plastic at the beginning with the worm  26  to metal at the end with the output gear  59 . This transition allows small plastic gears at the initiation of the drive sequence to turn large metallic gears at the output stage. The output shaft  60  drives either a product mover (not shown) for canned beverages inside a vending machine or any other electromechanical unit requiring the application of high torque in a small space. 
     In FIG. 3, a cover  28  for the gear box  14  illustrated in FIGS. 1 and 2 is shown partially broken away and flipped over so that the viewer is looking at the underside of the cover  28  in FIG.  3 . The side guides  32  allow the support plate  30 , which may be made of either metal or plastic, as shown in FIGS. 1 and 2, to hold the DC motor  10  securely outside the external wall  16  of FIG. 3 while simultaneously supporting the worm  26 , the pinion gear  33  and the worm gear  35  of FIGS. 1 and 2 inside a nest  52  seen in FIG.  3 . Thus, the side guides  32  allow the support plate  30  of FIGS. 1 and 2 to slide therebetween for a secured coupling of the worm  26  inside the nest  52  of FIG.  3 . In one side wall  56  of the nest  52 , there is formed integrally therewith a deep inset cradle bearing  58  for holding one hub  62  (see FIG. 1) of the worm  26  securely therein. When the hub  62  of the worm  26  is retained in the cradle bearing  58  of FIG. 3, the worm  26  of FIGS. 1 and 2 is prevented from bending during operation. A boss  64  seen in FIG. 3 is formed on a floor of the nest  52  and has a bore  70  in its top for receiving one end of the shaft  34 , seen in FIGS. 1 and 2, with which the pinion gear  33  and the worm gear  35  rotate. Instead of the boss  64  of FIG. 3, a steel pin (not shown) may be used. When the cover  28  is placed on the gear box  14  of FIGS. 1 and 2, the boss  64  of FIG. 3 extends downwardly from the cover  28 . The one side wall  56  also has a scalloped portion  72  for accommodating a curved periphery of the pinion gear  33  of FIGS. 1 and 2 as the pinion gear  33  rotates. The cover  28  of FIG. 3 likewise has a plurality of rings  78  which interlock over tops of the plurality of short posts  18  seen in FIG.  1 . To show how the cover  28  of FIG. 3 fits over the gear box  14  in FIG. 1, note that rings  78 A and  78 B of FIG. 3 mate with short posts  18 A and  18 B, respectively, in FIG.  1 . Also, short rib  74  and long rib  76  of FIG. 3 fit inside external walls  16  and  17  of the gear box  14  in FIG.  1 . Other ribs on the broken away section of the cover  28  are not shown in FIG. 3 for the sake of simplicity. 
     In FIG. 4, there is a partially broken away perspective view of the gear box  14  with a close-up detailed illustration of the lower right corner over which the nest  52  of FIG. 3 sits. In FIG. 4, there is the short post  18 B on which the ring  78 B of the cover  28  in FIG. 3 fits. Also, in FIG. 4, inside the external wall  16 , the side guides  32  hold the peripheral edges of the support plate  30  of FIGS. 1 and 2. After the cover  28  of FIG. 3 is flipped over and placed on top of the gear box  14  of FIG. 4, the entire assembly is closed tightly and sealed by ultrasonic welding. 
     In FIG. 5A, there is an end view of the DC motor  10  and its permanent magnet  12  taken along line  5 A— 5 A of FIG.  5 B. The positive terminal  20  and the negative terminal  22  are secured on opposite sides along a periphery of the DC motor  10 . A circular red marker  21  identifies the positive terminal  20  for a user. The support plate  30  can be seen behind the DC motor  10  in FIG.  5 A. 
     In FIG. 5B, there is a side elevational view of the DC motor  10  with its permanent magnet  12  and the negative terminal  22  illustrated at the left side. At the right side of FIG. 5B, there are the support plate  30 , the shaft hub  24 , the worm  26 , and the hub  62  which sits in the cradle bearing  58  of FIG.  3 . 
     FIG. 5C is an opposite end view taken along line  5 C— 5 C of FIG.  5 B. In FIG. 5C, there is seen the hub  62 , the worm  26 , the support plate  30  and the DC motor  10  therebehind. A pair of screws  23  fasten the support plate  30  to the DC motor  10  so that the DC motor  10  and the worm  26  remain connected together in a straight line during rotation of the worm  26 . 
     Numerous modifications and variations of the present invention are possible in light of the above teachings. Thus, it is to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.