Abstract:
The present invention provides industrial spring applied caliper braking systems which include a friction disc, a spring applied thruster and a caliper base comprising a friction facing. The caliper base is selectively activated by the spring applied thruster to apply said friction facing to the friction disc, and deactivated upon the application of a minimum pressure to release said friction facing from said friction disc. The braking system further includes a roller guide assembly including a roller guide arm, a high temperature roller wheel disposed on a distal end portion of the roller guide arm. The caliper base and roller guide assembly are mounted to a floating bracket assembly for allowing the caliper base and the roller guide assembly to slide orthogonally to a center line of the friction disc in response to at least thermal expansion driven axial float of said friction disc.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to industrial motor braking systems, and specifically those that include spring applied thrusters, friction discs and calipers. 
       BACKGROUND OF THE INVENTION 
       [0002]    On virtually every large industrial motor of at least about 250 HP or greater, internal heat generated in the motor causes the main drive shaft to expand outwardly. This is known as “thermal expansion” of the driving shaft. As the motor, such as an electric motor, or diesel engine, cools, the shaft shrinks back down to its original size at ambient temperature. In the industry, this is generally referred to as the “axial float” or “end float”. While most brake pads require a 1 mm clearance (2 mm total), between the friction disc of these motors and the friction facings, in extreme cases of axial float, the axial float of the motor shaft is often greater than 1 mm (0.0393 inches), and can often reach as high as ⅜-½ inches (9.54-12.72 mm). 
         [0003]    As with any brake system, caliper, drum or shoe, the air gap tolerance is extremely critical. The air gap tolerance is defined as the distance between the face of the friction surface and the face of the braking surface. In industrial sized motors, the braking surface is typically a friction disc or drum. The brakes are normally open, with at least a 1 mm gap, until an emergency, when someone hits an emergency stop button or if there is a loss of power. This is why spring applied brakes are also called “fail-safe” brakes. 
         [0004]    If one assumes a standard air gap tolerance between the pads and the disc of 1 mm or less (0.0393 inches) for industrial spring applied thruster brakes, and the motor has an axial float of ⅜ inches (0.54 mm), which is common, it would be difficult for any brake system that was fix mounted to a rigid structure to provide the necessary tolerance for proper braking. This can be explained by the following example: if a caliper brake requires a minimum 1 mm (0.0393 inch) of air gap tolerance, but the motor shaft has an axial float of ⅜ inches (9.54 mm; 0.375 inches), the resulting “clearance” would be 0.0393 inches−0.375 inches=negative 0.3375 inches. This would cause the friction disc to rub against the friction lining or pads as soon as the shaft expanded and cause premature wear for both friction material and motor bearings, excessive heat and possibly fire. 
         [0005]    Accordingly, there is a need for a spring applied thruster caliper brake system that maintains the recommended manufacturer&#39;s air gap tolerance. There also remains a need for a caliper braking system that can continually hold the center line positions of the caliper brake and the rotor or friction disc in alignment. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides an industrial motor braking system comprising a friction disc of at least 14 inches (35.56 cm); a spring applied thruster; a caliper base comprising a friction facing, said caliper base being selectively activated by such spring applied thruster to apply said friction facing to said friction disc to provide a braking force of at least sufficient to brake a 250 HP motor. The system also includes a roller guide assembly including a pair of roller guide arms disposed on opposite sides of the caliper base, and a high temperature roller wheel disposed in direct contact with the friction disc on a distal end location of each roller guide arm. The system further includes a floating bracket comprising a base plate, a slide plate disposed to slide relative to said base plate in response to at least a thermal expansion driven axial float of said friction disc, and guide means for limiting the relative sliding movement between the base plate and the slide plate. In this embodiment, the spring applied thruster, caliper base and roller guide assembly is mounted to the floating bracket. 
         [0007]    The present braking system with its floating bracket assembly keeps center line alignment between the friction disc and the caliper brake assembly. This can be achieved by squeezing the brake disc with the provided high temperature roller wheels. This is also assisted by guide means, which may include plunger pins and a guide channel which prevents the brake assembly from twisting or pivoting, but allows it to travel evenly from right to left, and left to right, generally orthogonally to the center line of the friction disc. Further, the floating bracket assembly of this invention can provide a floating relationship between the base plate and the slide plate, so that the slide plate can float pneumatically, hydraulically, or by a low friction bearing surface over the base plate. For example, an air gap can be located on both the right and left sides of the slide plate, to allow lateral movement. 
         [0008]    In a further embodiment of the present invention, a spring applied caliper braking system for industrial applications is provided. The system includes a friction disc of at least 14 inches (35.56 cm) in diameter, a spring applied thruster, a caliper base comprising a friction facing, said caliper base being selectively activated by said spring applied thruster to apply said friction facing to said friction disc, and deactivated upon the application of a minimum pressure from said thruster spring to release said friction facing from said friction disc. The system further includes a roller guide assembly, including a roller guide arm and a high temperature roller wheel disposed on a distal end location of said roller guide arm, whereby at least said caliper base and said roller guide assembly are mounted to a floating bracket assembly for allowing said caliper base and roller guide assembly to slide orthogonally to a center line of said friction disc in response to at least thermal expansion driven axial float of said friction disc. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The accompanying drawings illustrate preferred embodiments of the invention, as well as other information pertinent to the disclosure, in which: 
           [0010]      FIG. 1  is a front perspective of a dual brake motor braking assembly showing two spring applied caliper brakes applied to a friction disc; 
           [0011]      FIG. 2  is a front plan view of the dual brake motor braking system of  FIG. 1 ; 
           [0012]      FIG. 3  is a top plan view of the right spring applied caliper brake of  FIG. 1 ; 
           [0013]      FIG. 4  is a front perspective, exploded view of the right spring applied caliper brake of  FIG. 3  showing its pedestal base; 
           [0014]      FIG. 5  is a bottom and rear perspective view of the spring applied caliper brake of  FIG. 4 , illustrating the bottom of the slide plate; 
           [0015]      FIG. 6  is a rear plan view of the spring applied caliper brake of  FIG. 3 ; and 
           [0016]      FIG. 7  is a front plan view of a dual brake motor braking system having side caliper mounts. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Spring applied caliper braking systems are provided by this invention. They are typically released by air or hydraulic pressure, although electric and electromagnetic applied pressure, or a combination of these forces, can be used to release them. They typically automatically engage if there is a loss of power. Spring applied caliper brakes are ideal for moderate or high speed, high, dynamic or static torque, cyclic applications, such as in drag line buckets for mining operations. 
         [0018]    Spring applied caliper disc brakes function in the opposite manner of traditional brakes. Normal brake operation, such as in caliper disc brakes used for automobiles, requires active pressure to brake and pressure removed to release. Spring applied caliper disc brakes, on the other hand, require active minimum pressure to release. Such a pressure is typically about 50-125 psi, and can be created by pneumatic, hydraulic, electromagnetic, electric assisted pressure, or a combination thereof. At the loss of pressure, energy stored in a spring stack within the spring applied thruster, takes over to stop or hold the mass. Such brakes are ideal for emergency stopping or holding of industrial machinery, such as those used in excavation and large scale manufacturing. 
         [0019]    With reference to the figures, and in particular,  FIGS. 1-6  thereof, there is shown a dual brake motor braking system  200  having a friction disc  10  and a pair of spring applied caliper brakes  100  and  101 . The friction disc is typically made of steel and is also typically at least about 14 inches (35.56 cm) in diameter, and commonly about 25-75 mm in thickness, more commonly about 40 mm in thickness, but can be machined down to about 30 mm in thickness by removing about 5 mm from each side of the friction disc  10 . The friction disc  10  includes a center line  128 , shown in  FIG. 6 , which is designed to match the center line  105  of the caliper base  104 , shown in  FIG. 3 . The brake pads or friction facings  106  shown in  FIG. 4 , are typically “positively engaged” with the friction disc  10 , when there is a loss of power, but there is typically about 1 mm clearance for each friction facing or pad  106  during use, prior to engagement of the brake, for a total of 2 mm clearance between the friction facings  106  and the friction disc  10 . 
         [0020]    During use, the axial float of the drive shaft connected to the friction disc  110  expands commonly by at least about 1 mm (0.0393 inches) and as much as ⅜-½ inches (9.54-12.72 mm), due to thermal expansion, as the shaft heats from ambient temperature to an elevated temperature. This ⅜ inch expansion in combination with the high RPMs of the motor, typically in the area of about 900-1200 RPMs, causes the friction facings  106  to push to one side, burning them up and potentially damaging the disc. By machining 5 mm from each side of the friction disc  10 , users typically permit greater axial float, but cause the disc to have less mass, which results in less dissipation of heat or energy from the motor. This, in turn, causes the friction discs  10  to heat up even higher, resulting in disc lift and discoloration. After a single stop, the disc can raise its temperature another 300° F., from about 500° F. to about 800° F., causing further damage to the friction facings  106 . 
         [0021]    The spring applied caliper brake  100  of this invention is described in  FIG. 3 . The caliper brake  100  includes a spring applied thruster  102  which can be released by pneumatic, hydraulic, electric or electromagnetic power, for example. The brake  100  further includes a caliper base  104  having a pair of caliper arms, each of which is equipped with friction facings  106  for contacting the friction disc  10 . The brake  100  further includes a roller guide assembly  108  including a pair of roller guide arms  110  disposed on opposite sides of the caliper base  104 . The roller guide arms  110  can be fastened with the caliper base by a pin fastener  122  passing through aligned holes in the caliper base  104  and each of the roller guide arms  110 , shown in  FIG. 3 . The roller guide assembly further includes a pair of high temperature roller wheels  112  disposed in direct contact with the friction disc  10  on the distal end location of each roller guide arm  110 . The brake  100  further includes a base plate  116  (or middle plate) and slide plate  114  disposed to slide relative to the base plate  116  in response to at least a thermal expansion driven axial float of the friction disc  10  and shaft. The slide plate  114  in combination with the base plate  116  is referred to as the floating bracket assembly  120 . The brake  100  further includes guide means for limiting the relative sliding movement between the base plate and the slide plate. The spring applied thruster  102 , caliper base  104  and roller guide assembly  108  are preferably mounted to the side plate  114 , and can slide back and forth over the base plate  116 . 
         [0022]    In view of  FIG. 4 , an air pocket  142  is disposed in the preferred base plate  116  with an air inlet port  134 . The base plate also includes pins, such as spring loaded plunger pins  126 . The plunger pins  126  align in the guide channel  124 , shown in the bottom of the slide plate  114  in  FIG. 5 . The slide plate  114  with the caliper brake  100  secured thereon, for example, through brake mounting holes  130  and fasteners, is then slid onto the base plate  116  until the spring loaded plunger pins  126  pop into the guide channel  124 . Desirably, the guide channel  124  is in the form of a slotted groove, although a pair of slotted grooves or an elongated opening could be similarly employed. When the pins  126  are properly seated in the guide channel  124 , the slide plate  114  and caliper brake  100  can only move from side to side. The plunger pins  126  prevent the slide plate  114  and caliper brake  100  from moving from front to rear. If one needs to remove the caliper brake  100  or inspect the friction facings  106 , one need only pull down on the release chain  136 , shown in  FIG. 5 , to withdraw the plunger pins  126  from the guide channel  124  so that the slide plate  114  can be removed with its mounted caliper brake  100 . 
         [0023]    When the slide plate  114  and caliper brake  100  are properly mounted and aligned with the base plate  116 , the slide plate  114  and caliper brake  100  can only slide laterally in both right and left directions a maximum distance equal to the sum of the air gaps  132 , shown in the rear plan view of  FIG. 6 , sandwiched between the slide plate  114  and clamping plate  138 . Preferably, each air gap  132  is about ½-1″, more preferably about ⅝″ on each side of the disc. The plunger pins  126  prevent the floating bracket assembly  120  from sliding from front to rear during movement within the air gaps  132 . 
         [0024]    With reference to  FIGS. 1-4 , the roller guide assembly  108  will now be described. Several commercial caliper braking systems that can be engaged with the floating bracket assembly  120  and roller guide assembly  108  of this invention are described in Table 1. 
         [0000]    
       
         
               
             
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Commercial Braking Systems Suitable 
               
               
                 for the Floating Bracket System 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 The Roller Guide Arms were designed to fit the following caliper brakes: 
               
               
                 Manufacturer: Coremo Ocmea, Model: E-Series Caliper 
               
               
                 Manufacturer: Twiflex Model: GMR-Series Caliper 
               
               
                 Manufacturer: Ringspann, Model: DVH 40 FPM and DVH 40 FPM/T 
               
               
                 Series Caliper 
               
               
                   
               
             
          
         
       
     
         [0025]    The roller guide assembly  108  includes one or more roller guide arms  110  and high temperature roller wheel  112  or wheels disposed on a distal end location of the roller guide arm  110  or arms. The high temperature roller wheels are designed to withstand temperatures in excess of 500° F., more preferably in excess of 800° F., and are made of high temperature resistant polymers, such as reinforced phenolic resin. The roller guide arms  110  are typically made of light weight metal, such as aluminum, titanium, or their alloys. The roller guide assembly  108  can be adjusted with roller guide arm adjustment screw  140  so that the calipers can be mounted around the friction disc  10  and the high temperature roller wheel  112  or wheels disposed in contact with the side surface of the friction disc  110 . As the motor or engine shaft expands due to heat, the present caliper brake  100  allows the caliper base  104  and roller guide assembly  108  to maintain the manufacturer&#39;s air gap tolerance by continually holding the center line positions between the caliper base  104  and the friction disc  10 . 
         [0026]    The floating bracket system of this invention can be mounted horizontally, as shown in  FIG. 7 , or vertically, as shown in  FIG. 1 . When mounted horizontally the system is referred to as a caliper or side mount, since the caliper brakes  330  are mounted, such as by bolts or welding to the housing of the breaking system  300 . When mounted vertically, a pedestal mount  129  or “H” beam can be employed. 
         [0027]    Once completely installed, the caliper brake  104  is positioned around the friction disc  10 . The roller guide arms  110  are closed until the high temperature roller wheels  112  come in contact with the surface of the brake disc  10 . This adjustment is made by turning the roller guide arm adjustment screw  140  until the high temperature roller wheels  112  come in direct contact with the friction disc  10 . The user can connect an air source or oil source, for example, to the base plate  116 , and with as little as 7 psi pressure in the air gaps  132  and air pocket  142 , or a minimum amount of pressure which will allow the slide plate  114  with the mounted caliper brake  104  to move laterally in both the right and left directions over the base plate  116  with as little as 5 lbs of force applied to either component. This design feature helps save the bearing life of the roller guide arms  110  and the bearings of the motor attached to the friction disc  10 . 
         [0028]    Alternatively, magnetic force, induction coils, super conductors, or hydraulic pressure can be used, or a light coating of grease or oil, Teflon spray or other lubrication, to the surfaces of the slide plate  114 , base plate  116 , or both. Alternatively, one or both of these surfaces could be coated with a Teflon polymer plate or coating, or ball bearings can be used between the two surfaces to allow them to slide over one another with 5 lbs of force or less. Alternative low friction bearing surfaces such as these can be used by themselves, or in combination. 
         [0029]    From the forgoing, it can be realized that this invention provides improved industrial motor braking systems and improved spring applied caliper braking systems for industrial applications. Although various embodiments of the invention have been illustrated, this is for the purpose of describing, but not limiting the invention. Various modifications which will become apparent to one skilled in the art, are within the scope of this invention described in the attached claims.