Abstract:
This invention discloses a type of drum brake that can be used for automobiles, comprising a brake drum, one or more brake shoes, and one ore more brake cylinders. Its special characteristics are: the drum brake further comprises an ordinary gear train which comprises an annulus, one or more planetary gears and a sun gear. Here, the annulus is attached to the brake drum. The sun gear and a mounting shell of the brake shoes are attached to each other. The planetary gears are located between the annulus and the sun gear, and one ore more planetary gear axles of the respective planetary gears are affixed with one or more planetary carriers. By adopting the drum brake of this invention and the ordinary gear train, when the brake is applied, the brake shoes rotate in the opposite direction relative to the moving direction of the brake drum, thereby greatly reduce the braking distance and braking time.

Description:
CROSS REFERENCE  
       [0001]     This application claims priority from a Chinese patent application entitled “Drum Brakes for Automobiles” filed on Aug. 15, 2005, having a Chinese Application No 200520103848.3. This application is incorporated herein by reference.  
       FIELD OF INVENTION  
       [0002]     This invention relates to brakes, and especially related to drum brakes for automobiles.  
       BACKGROUND  
       [0003]     A drum brake for automobiles is a component of the braking system which generates the braking force. Currently, a brake used in a typical automobile generates a brake moment by the friction between the fixed component and the rotating component, i.e., a friction-type brake. Brakes which expand by using a hydraulic cylinder are divided into drum brakes and disc brakes.  
         [0004]     The rotating component of the frictional pair of a drum brake is the brake drum. The operating surface of the brake drum is an inner cylinder surface. The affixed component is a brake shoe. The brake shoe expands when it is driven by a braking cylinder which is controlled by a hydraulic mechanism. The different structures and operating characteristics of these drum brakes expanded by braking cylinders can be further categorized into the following types: leading-trailing shoe brakes, double-leading shoe brakes, double-trailing shoe brakes, double acting leading shoe brakes, and self-servo brakes.  
         [0005]      FIG. 1  shows a leading-trailing shoe brake, comprising a brake drum  100 , two symmetry brake shoes  200  and a double-piston braking cylinder  300 . Here, the outer surface of the brake shoes is riveted with friction pads. The end of each brake shoe is supported by an anchor pin  400 . When the brake is applied, the two brake shoes are driven by the hydraulic cylinder of a double-piston braking cylinder. The brake shoes expand and turn outwards on the anchor pin which is the pivot point and press on the rotating brake drums. A frictional moment (i.e., a brake moment) is created between the brake shoes and the brake drum. The direction of friction moment is opposite to the direction of rotation of the wheels, thereby creating a braking effect. To remove the braking effect, the hydraulic pressure of the hydraulic braking cylinder is released, and the brake shoes return to their original positions under the force of the return spring.  
         [0006]     As the automobile is moving, the direction of the rotation of the brake drum is as shown by the arrow in  FIG. 1 . When the brake is applied, the two brake shoes turn to expand outwards on each anchor pin as the pivot point. The turning direction of the first brake shoe is opposite to the direction of rotation of the brake drum thus it is called the leading shoe. The turning direction of the second shoe is identical to the direction of rotation of the brake drum thus it is called the trailing shoe. When the automobile is backing up, the first brake shoe becomes the trailing shoe and the second brake shoe becomes the leading shoe. Since there is always a leading shoe and a trailing shoe when the brake is applied whether it is moving forward or backward, this type of brakes is called leading-trailing shoe brake.  
         [0007]      FIG. 2  shows a double-leading shoe brake. The brake is approximately identical to the leading-trailing shoe brake as shown in  FIG. 1 . The difference lies in that the brake utilizes two single-piston braking cylinders respectively driving two brake shoes to turn and to expand outwards. As the automobile moves forward, both of the brake shoes are leading shoes thus it is called double-leading shoe brake. This type of brakes is effective when the brake is applied as it is moving forward. However, when the automobile backs up, both of the brake shoes become trailing shoes thus the effectiveness is greatly diminished.  
         [0008]      FIG. 3  shows a double-trailing shoe brake. Compared to the brake of  FIG. 2 , the double-trailing show brake of  FIG. 3  is created by turning the double-leading shoe brake 180 degrees. Apparently, the braking effect of the double-trailing shoe brake is not as desirable as that of the double-leading shoe brake when the automobile is moving forward. However, the double-trailing shoe brake is less sensitive to the change in the friction factor thus it has good stability in its braking effect.  
         [0009]      FIG. 4  shows a double acting leading shoe brake. Compared to the leading-trailing shoe brake of  FIG. 1 , it has an additional braking cylinder opposite to the first braking cylinder. Both ends of both brakes shoes have floating grippers. When the automobile is moving forward, the pistons of both cylinders move outwards under the hydraulic force, thereby pressing the brake shoes against the rotating brake drum. Thereafter, under the force of the friction of the brake drum, the two brake shoes turn by a certain degree around the center of the wheel along the direction of the rotation of the brake drum. Thus the pedestal at the outside of the pistons of the cylinders is pushed back until the top of the pedestal reaches the transverse plane of the cylinder. When the automobile backs up, the brake drum exerts a friction moment in the opposition direction on the brake shoes. Thus the adjustable pedestal becomes the anchoring point of the brake shoes, and both of the brake shoes are still leading shoes. Since both of the brake shoes are leading shoes whether the automobile is moving forward or back ward, this type of brake is called double acting leading shoe brake.  
         [0010]      FIG. 5  shows a single-self-servo brake. It utilizes a single-piston driving cylinder to drive the first brake shoe. The brake shoe is connected to a second brake shoe through an adjustable pole. When the brake is applied, the first brake shoe turns to expand outwards under the force of the driving cylinder, pressing against the brake drum. Meanwhile, through the adjustable pole, the first brake show affects the second brake shoe, making the second brake shoe to also turn to expand outwards and press against the brake drum, creating a self-serving force.  
         [0011]      FIG. 6  shoes a double-self-servo brake. It utilizes a double-piston driving cylinder. The way it operates resembles that of the single-self-servo brake of  FIG. 5 .  
         [0012]     The above is a brief description of the drum brakes for automobiles. The detailed structure of various prior art brakes can be found in various publications on automobile structures, e.g., “Automobile Structure” by Guan Wen-Da (Editor-in-Chief), Tsinghua University Press, September, 2004 (1st Edition).  
         [0013]     The above mentioned drum brakes are widely used in various types of automobiles because of their desirable characteristics such as a compact and simple structure, good radiating properties, and easy to be used as parking brakes. Among the drum brakes, the double acting leading shoe brake has the best braking effectiveness since both of the brake shoes are leading shoes when the brake is applied whether it is moving forward or backward. In addition, the brake shoes of a double acting leading shoe brake are worn evenly. Thus the double acting leading shoe brakes are most widely adopted.  
         [0014]     However, as the traveling speed of the automobiles generally increases, there is a higher demand on the effectiveness of the drum brakes. In real applications, the effectiveness of various brakes is not very satisfactory. The problems of excessively long braking time and braking distance still remain. Thus, there is a desire to have novel drum brake apparatuses that can provide better braking distance and braking time.  
       SUMMARY OF THE INVENTION  
       [0015]     An object of this invention is to provide novel drum brakes that distinctively improve braking distance.  
         [0016]     Another object of this invention is to provide novel drum brakes that distinctively improve braking time.  
         [0017]     Yet another object of this invention is to provide novel drum brakes that are simple to operate.  
         [0018]     Briefly, the presently preferred embodiment of the present invention provides a drum brake that comprises a brake drum, brake shoes, and braking cylinders. There is an ordinary gear train which comprises an annulus, a planetary gear and a sun gear. The annulus is attached on the brake drum. The sun gear and a mounting shell of the brake shoe are attached to each other. The planetary gear is located between the annulus and the sun gear, and a planetary gear axle of the planetary gear is affixed with a planetary carrier. In operation, when a drum brake of this invention is applied, using the additional ordinary gear train, the drum shoes can turn in the direction opposite to the direction of rotation of the brake drum. Thus the braking effectiveness is greatly enhanced, and the drum brake is superior to the prior art brakes in braking time and distance by a wide margin.  
         [0019]     An advantage of this invention is that it provides novel drum brakes that distinctively improve braking distance.  
         [0020]     Another advantage of this invention is that it provides novel drum brakes that distinctively improve braking time.  
         [0021]     Yet another advantage of this invention is that it provides novel drum brakes that are simple to operate. 
     
    
     DESCRIPTION OF DRAWINGS  
       [0022]     The foregoing and other objects, aspects and advantages of the invention will be better understood from the following detailed description of preferred embodiments of this invention when taken in conjunction with the accompanying drawings in which:  
         [0023]      FIGS. 1-6  are illustrations of prior art brakes.  
         [0024]      FIG. 7  is an illustration of an embodiment (Embodiment 1) of the brake of this invention.  
         [0025]      FIG. 8  is an illustration of the ordinary gear train of this invention.  
         [0026]      FIG. 9  is an illustration of another embodiment (Embodiment 2) of the brake of this invention. 
     
    
     INDICATORS OF THE FIGURES  
       [0027]    
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                   
               
             
             
               
                   
                 1 - axle housing; 
                 2 - brake oil line; 
               
               
                   
                 3 - axle; 
                 4 - planetary carrier; 
               
               
                   
                 5 - planetary gear axle; 
                 6 - annular-oil cylinder; 
               
               
                   
                 7 - annular piston; 
                 8 - brake drum; 
               
               
                   
                 9 - ball; 
                 10 - push disc; 
               
               
                   
                 11 - brake shoe; 
                 12 - mounting shell; 
               
               
                   
                 13 - wheel drum; 
                 14 - braking cylinder; 
               
               
                   
                 15 - piston; 
                 16 - brake-primary piston; 
               
               
                   
                 17 - push rod; 
                 18 - annular-oil shell; 
               
               
                   
                 19 - annulus; 
                 20 - planetary gear; 
               
               
                   
                 21 - sun gear; 
                 22 - synchronization-locking ring; 
               
               
                   
                 23 - engagement sleeve; 
                 24 - slide; 
               
               
                   
                 25 - positioning steel ball; 
                 26 - spring; 
               
               
                   
                   
               
             
          
         
       
     
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]     As discussed in the background section, the prior art drum brakes operate by creating friction between a fixed component and a moving component. From the energy point of view, the braking process is a process where, through friction, the mechanical energy of the automobile is converted into heat energy and expanded. When the automobile brake is applied, the friction between the brake shoes and the brake drum creates heat energy, and the amount of the heat energy equals the mechanical energy converted in the process. The more mechanical energy is converted during a given time period, the less braking time and distance is required to stop an automobile. The fundamental reason is that the absolute value of the speed reduced during the braking period has been increased. In other words, given the same braking force, friction factor of the friction pads of the brake shoes and the typical dimensions for the typical brakes, if by changing the brake structure that the consumption of the mechanical energy during a given time period can be increased, the braking time and distance can be thereby reduced.  
         [0029]     Therefore, based on this train of thought, the following double acting leading shoe brake of the present invention is taken as an example to further illustrate embodiments of the drum brake of this invention.  
         [0030]      FIG. 7  is an illustration of a first embodiment (Embodiment 1) of the drum brake of this invention.  FIG. 8  is an illustration of the ordinary gear train used in  FIG. 7 .  
         [0031]     As shown in  FIG. 7 , the automobile drum brake of this invention comprises a brake drum  8 , a brake shoe  11 , and a braking cylinder  14 . In addition, the brake also comprises an ordinary gear train which comprises an annulus  19 , a planetary gear  20  and a sun gear  21 . Here, the annulus  19  is attached on the brake drum  8 . The sun gear  19  and a mounting shell  12  of the brake shoe  11  are attached to each other. The planetary gear  20  is located between the annulus  19  and the sun gear  21 , and a planetary gear axle  5  of the planetary gear  20  is affixed with a planetary carrier  4 , e.g., being affixed on an axle housing  1 .  
         [0032]     When the drum brake for automobiles of this embodiment is compared to conventional drum brakes for automobiles, the main difference is the additional ordinary gear train. When the automobile brake is applied, the drum brake can make the brake shoe  11  turn in a direction opposite to the direction of rotation of the brake drum  8 . Thus within the same amount of time more mechanical energy is consumed by friction, thereby distinctively shortening the braking time and distance. The following is a detailed illustration of the ordinary gear train and the brake drum having the ordinary gear train with references to  FIGS. 7 and 8 .  
         [0033]     The ordinary gear train comprises an annulus  19 , a planetary gear  20  and a sun gear  21 . Here, the annulus  19  engages the planetary gear  20 , the planetary  20  engages the sun gear  21  at the center, and the planetary gear  20  is relatively fixed. Therefore, as shown in  FIG. 8 , because of the planetary gear  8 , the annulus  19  always rotates in a direction opposite to the direction of rotation of the sun gear  21 . That is the key characteristic of this invention.  
         [0034]     The annulus  19  is fixed on the brake drum  8 , and moves in synchronization with the drum brake  8 . As shown in  FIG. 7 , the annulus  19  is fixed on the brake drum  8  using screws. However, various methods of available technology can be used, such as welding riveting, etc. Thus there is no limitation as to the method of fixation. When the words “fix,” “affix,” or “attach” appears in the illustration and claims below, it should be understood in the same way unless it is otherwise defined.  
         [0035]     The sun gear  21  is attached on the mounting shell  12  of the brake shoe. The mounting shell  12  of the brake shoe and the braking cylinder  14  are attached to each other. The planetary gear  20  is located between the annulus  19  and the sun gear  21  and engages both. The planetary gear axle  5  of the planetary gear  20  is fixed with a planetary carrier  4  on an axle housing  1 . Since the axle housing  1  is relatively fixed to the automobile, the planetary gear  20  is also relatively fixed to the automobile. That means the planetary gear can only turn on its axis and cannot revolve around the sun gear  21 .  
         [0036]     Therefore, by adopting the above mentioned design, when the automobile is moving in normal conditions, the annulus  19 , the brake drum  8  and the wheel drum turn together. The planetary gear  20  is fixed on the axle housing  1  through the planetary gear axle  5  and the planetary carrier  4 . Thus the position of the planetary gear  20  is fixed relative to the automobile (i.e., it can only turn on its axis and cannot revolve around the sun gear  21 ). The sun gear  21  is at the center of the ordinary gear train and fixed to the mounting shell  12 . The sun gear  21  turn because the planetary gear  20  turns on its axis, and the direction is opposite to the direction of rotation of the annulus  19  (or the direction of rotation of the brake drum  8  and the wheel drum  13 ). Thus, the sun gear  21  drives the mounting shell  12 , the brake shoe  11  and the braking cylinder  14  to turn in the same direction as it does. When braking is needed, the braking cylinder  14  drives the brake shoe  11  to expand and press against the inner surface of the cylinder of the brake drum  8 . Since at this time the brake shoe  11  turns in a direction opposite to the direction of rotation of the brake drum  8 , more mechanical energy can be consumed within a shorter period of time through friction, thereby distinctively shorten the braking time and distance of the automobile. That is especially useful during an emergency stop.  
         [0037]     In the embodiment, since the annulus  19  and the brake drum  8  are directly attached together, when the automobile is traveling under normal conditions, the annulus  19  and the brake drum  8  rotate in a synchronized fashion. The planetary gear  20 , the sun gear  21 , the brake shoe  11 , and the braking cylinder  14  all rotate together. Thus, there is unnecessary loss of energy. To avoid this disadvantage, this invention provides another embodiment. That is, the annulus  19  is attached on the brake drum  8  using an engagement sleeve and a synchronizer, instead of being attached on the brake drum  8  with screws. The following is a detailed illustration of that embodiment with references to  FIG. 9 .  
         [0038]     As shown in  FIG. 9 , the second embodiment differs than the first embodiment in that the connection between the annulus  19  and the brake drum  8  is achieved using an engagement sleeve and a synchronizer. Engagement sleeves and synchronizers are widely used in gear-boxes of automobiles to reduce the shock between gears when the driver shifts the gear. The designs of engagement sleeves and synchronizers are provided in various publications on the structure of automobiles. For example, they are provided in the chapters regarding gear-boxes in “Automobile Structure” by Guan Wen-Da (Editor-in-Chief), Tsinghua University Press, September, 2004 (1st Edition). Therefore,  FIG. 9  only provides an illustration instead of detailed figures.  
         [0039]     As shown in  FIG. 9 , compared to the first embodiment, the second embodiment does not have the screws attaching the annulus  19  and the brake drum  8  together. Instead, there is an engagement sleeve  23  and a synchronizer between the annulus  19  and the brake drum  8 . The synchronizer comprises a synchronizing coupler  22 , a slide  24 , a positioning steel ball  25 , a positioning spring  26 , etc. There are teeth located on the outer rim of the annulus  19  which persistently engage the inner teeth of the engagement sleeve  23 . There are also teeth on the outer surface of the brake drum  8 . Thus when the automobile brake is applied the engagement sleeve slides along the axle. Under the effect of the synchronizer, the inner teeth of the engagement sleeve  23 , rapidly engage the outer teeth of the brake drum  8 . Thereafter the engagement sleeve  23  attaches to the annulus  19  and the brake drum  8  together, having the securing effect of screws. Then the automobile is braked under the effect of the driving cylinder. Compared to the first embodiment, the ordinary gear train, the brake shoe  11 , etc. do not rotate until the automobile brake is applied, thereby reducing the energy loss due to the rotation of the ordinary gear train and the brake shoe  11  before the automobile brake is applied. Thus this design results to energy saving.  
         [0040]     Also shown in  FIG. 7 , since an ordinary gear train is added to the existing brake, a suitable design for driving the brake can be chosen based on the specific structure of the ordinary gear train. On the other hand, the object of this invention can also be achieved without changing the current design for the driving mechanism of the brake. The following is a description of the operation of a preferred embodiment in operating the brake.  
         [0041]     A braking oil line  2  is inserted in the central hole of the planetary gear axle  5 . The other end of the braking oil line  2  is connected to the main braking cylinder (not shown in the figure) outside of the brake. The end of the planetary gear axle  5  is inserted in an annular-oil cylinder  6 . Since the planetary gear axle  5  is fixed to the axle housing  1  through a planetary carrier  4 , the annular-oil cylinder  6  is also attached relative to the planetary gear axle  5 . An annular-oil cylinder  6  and an annular piston  7  form an annular-oil shell  18 . Meanwhile, the annular piston  7 , the ball  9 , and the push disc  10  form a radial bearing. Push disc  10  and a brake-primary piston  16  are connected with a push rod  17 . The braking cylinder  14  is a tee-wheel braking cylinder.  
         [0042]     By adopting the above design, when the automobile brake is applied, the hydraulic pressure reaches the annular-oil shell  18  through the main braking cylinder (not shown in the figure), the braking oil line  2  and the planetary gear axle  5 . The hydraulic pressure pushes the annular piston  7  to move. The force is then passed on to the brake-primary piston  16  through the ball  9 , the push disc  10 , and the wheel drum  13 . The brake-primary piston  16  converts the mechanical force to hydraulic pressure through the tee-wheel braking cylinder  14 , thereby pushing the piston  15  of the braking cylinder  14  to push the brake shoe  11 . The brake shoe  11  expands outwards and presses against the inner surface of the brake drum  8 , applying friction on the brake drum  8 . The mechanical energy of the automobile is consumed in the form of friction heat energy to bring the automobile to a stop.  
         [0043]     In the braking process, the brake drum  8  rotates with wheel drum  13 , and the brake shoe  11  rotates in an opposite direction because of the ordinary gear train. Therefore, the relative sliding speed between the brake shoe  11  and the brake drum  8  is a lot greater than that of a conventional brake. In other words, the absolute value of its braking deceleration is significantly greater than that of a conventional brake. For example, when the number of teeth of the annulus  19  is three times of the number of teeth of the sun gear  21 , the relative sliding speed between the brake drum  8  and brake shoe  11  is also increased by three times, and the mechanical energy consumed in a time unit by the brake is also increased by three times. In other words, the absolute value of the braking deceleration has significantly increased. Thus the brake of this invention can effectively reduce the braking time and distance.  
         [0044]     The above is a detailed description of the embodiments of the drum brakes of this invention. The described embodiments have double acting leading shoe brakes as examples (as shown in  FIG. 7  and  FIG. 9 ). However, as indicated above, the ordinary gear train of this invention can be used in various types of drum brakes. For the purpose of simplicity, there is no description of other embodiments applying various other types of brakes. It shall also be understood that drum brakes can be applied to any type of vehicles not limited to automobiles.  
         [0045]     While the present invention has been described with reference to certain preferred embodiments, it is to be understood that the present invention is not limited to such specific embodiments. Rather, it is the inventor&#39;s contention that the invention be understood and construed in its broadest meaning as reflected by the following claims. Thus, these claims are to be understood as incorporating not only the preferred embodiments described herein but also all those other and further alterations and modifications as would be apparent to those of ordinary skilled in the art.