Abstract:
A tape cartridge for a personnel barrier system includes a spool ( 14 ) of tape ( 16 ), a housing ( 6 ), a return spring ( 26 ) and a speed restricting mechanism. The speed restricting mechanism includes a rotor device ( 38 ) that is connected to the spool ( 14 ) for rotation therewith in at least one rotational direction, the rotor device being immersed in a viscous damping medium ( 40 ).

Description:
RELATED APPLICATIONS  
       [0001]     This application claims priority to GB 0404527.4, filed Mar. 1, 2004 which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a tape cartridge with a speed restricting mechanism, and in particular but not exclusively to a tape cartridge that forms part of a personnel barrier system.  
         [0004]     2. Description of the Related Art  
         [0005]     Personnel barrier systems that use retractable tapes are well known. Typically, a flat woven tape is wound onto a spool in a cartridge. The spool is spring-biased for example using a clock spring to rewind the tape into the cartridge after use.  
         [0006]     Sometimes, a speed restricting mechanism is provided, to prevent the tape from rewinding too quickly. If the tape is retracted too quickly, the end of the tape can whip violently, possibly causing injury to bystanders or damage to property.  
         [0007]     One such speed restricting system is described in U.S. Pat. No. 5,967,443. This system uses a centrifugal braking system in which a pair of brake blocks that rotate with the spool are urged outwards by centrifugal forces against a stationary brake drum when the spool rotates. A disadvantage of this arrangement is that the mechanism is relatively expensive to produce and it suffers from excessive brake-wear, making use of the system less convenient. It is also susceptible to ingress of dust, moisture and wear debris, which can significantly affect braking performance. Furthermore, the system only comes into operation when the spool reaches a certain speed.  
         [0008]     It is an object of the present invention to provide a speed restricting mechanism that mitigates at least some of the aforementioned disadvantages.  
       SUMMARY OF THE INVENTION  
       [0009]     According to the present invention there is provided a tape cartridge for a personnel barrier system, said tape cartridge including a spool of tape, a housing, a return spring and a speed restricting mechanism, said speed restricting mechanism including a rotor device that is connected to said spool for rotation therewith in at least one rotational direction, said rotor device being immersed in a viscous damping medium.  
         [0010]     The mechanism is capable of restricting the speed at which the tape is rewound into the cartridge, thereby reducing or eliminating the risk of injury to bystanders and reducing wear on the tape and the cartridge. The mechanism is very simple and inexpensive, requiring only a few simple components. It is also very small and does not significantly increase the overall size of the tape cartridge. The speed restricting system also operates immediately the tape is retracted (i.e. without any delay), thereby preventing the occurrence of excessive retraction speeds.  
         [0011]     Advantageously, the rotor device is connected directly to the spool. This provides a very simple but effective and reliable mechanism.  
         [0012]     Alternatively, the rotor device may be connected to the spool via a one-way drive mechanism, for example a clutch or ratchet mechanism. This allows the speed restricting mechanism to operate when the tape is being retracted into the cartridge. However, when the tape is being drawn from the cartridge, the speed restricting mechanism does not operate, thus making use of the system more convenient.  
         [0013]     Advantageously, the rotor device is connected to the upper end of the spool, this location being preferred for manufacturing and maintenance reasons.  
         [0014]     The viscous damping medium is preferably contained within a chamber provided within the upper part of the housing. The chamber is preferably sealed, so that it is invulnerable to contamination and humidity. The chamber may be formed between an upper support member and an end cap of the housing.  
         [0015]     The viscous damping medium is preferably a liquid or grease. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     Certain embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
         [0017]      FIG. 1  is a sectional side elevation of a tape cartridge that includes a speed restricting mechanism;  
         [0018]      FIG. 2  is a cross-section on line II-II of  FIG. 1 ;  
         [0019]      FIG. 3  is a top plan view of the tape cartridge of  FIG. 1  with an end cap removed;  
         [0020]      FIG. 4  is an isometric view of a rotor forming part of the speed restricting mechanism, and  
         [0021]      FIG. 5  is a top plan view of an alternative tape cartridge with an end cap removed. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0022]     A tape cartridge  2  for a personnel barrier system is shown in FIGS.  1  to  3 . The cartridge  2  is typically mounted on top of a barrier post  4  having a weighted base (not shown). Alternatively, the cartridge may for example be attached to a wall. The barrier system can be used to create a temporary barrier, for example to guide a queue of people.  
         [0023]     The tape cartridge  2  includes a substantially cylindrical housing  6 , having a steel cylindrical wall  8  and upper and lower support members  10 ,  12 , formed as plastics mouldings. A rotary spool  14  of woven tape  16  is mounted in the housing. The spool has a central shaft  18 , the upper and lower ends  18   a ,  18   b  of which are mounted in rotary bearings  20 ,  22  in the upper and lower support members. Tape can be withdrawn through a slot  24  in the housing, causing the spool  14  to rotate. A clock spring  26  is located in a chamber  28  provided in the lower support member  12 , which is closed by a cover plate  30 . The clock spring  26  is connected to the lower end  18   b  of spool shaft  18 . The clock spring  26  is wound up when the tape is withdrawn from the cartridge and retracts the tape back into the cartridge when the tape is released. The cartridge also includes a connector  32  to which the end of another tape may be connected to create a barrier. The cartridge  2  is sealed closed at its upper end by means of an end cap  34 .  
         [0024]     The tape cartridge includes a speed restricting mechanism, which serves to restrict the speed at which the tape is retracted into the cartridge when the tape is released, to reduce or eliminate the risk of injury to bystanders.  
         [0025]     The speed restricting mechanism includes a shallow cylindrical chamber  36 , formed between the upper support member  10  and the end cap  34 , and a rotor device  38 . The chamber is filled with a high viscosity substance  40 , for example silicon grease or any suitable alternative. The upper end of the chamber  36  is sealed closed by the end cap  34 .  
         [0026]     The rotor device  38 , which is shown in more detail in  FIGS. 3 and 4 , includes a central ring  42  having a D-shaped bore  44  that fits over a similarly-shaped portion of the spool shaft  18  at the upper end of the spool  14 . The rotor device  38  therefore rotates with the spool  14  whenever tape is withdrawn from or retracted into the cartridge  2 . A pair of arms  46  extend radially outwards from the central ring  42 . Each of these arms  46  carries a vane  48  having a plurality of through holes  50 . The vane is of a size and shape to substantially fit the grease-filled chamber, with only a small clearance around the sides of the vane.  
         [0027]     In use, the rotor  38  rotates with the spool  14  as tape is withdrawn from or retracted into the cartridge. Rapid rotation of the spool in either direction is restricted by the fact that the rotor has to move through the highly viscous grease  40  that fills the chamber  36 . This causes drag, which provides a braking effect that is proportional to the speed of rotation. The amount of braking can if necessary be adjusted by changing the size and shape of the vanes  48 , the number and size of the through holes and the viscosity of the grease. The rotor can also be provided with more or fewer arms and vanes, if necessary.  
         [0028]     When tape is withdrawn or retracted, the spool  14  rotates and the rotor  38  rotates with it. If the tape is withdrawn and then released, it is retracted into the cartridge by the spring  26 . The speed at which the tape is retracted is limited by the braking action of the speed restricting mechanism. For example, we have found that for a typical cartridge with a fully withdrawn tape, the retraction time is increased from less than one second to approximately 2-3 seconds.  
         [0029]     The braking mechanism may be modified as shown in  FIG. 5  to include a one-way drive mechanism  52  (for example a clutch or ratchet mechanism) between the spool  14  and the rotor  38 , which allows relative rotation between the spool and the rotor in one rotational direction and prevents relative rotation in the opposite direction. With this arrangement, the braking mechanism can be designed to operate so that a braking effect is provided only when the spool is rotating in one direction, for example when the tape is being retracted into the cartridge, while allowing free, uninhibited rotation of the spool in the other direction, when tape is being withdrawn from the cartridge.  
         [0030]     Various other modifications of the above described invention are of course possible, for example with regard to the shapes, dimensions and materials of the component parts. In addition, the rotor may be connected to the spool via a transmission system, for example, a set of gears, to increase or decrease the rotational speed of the rotor relative to the spool, thus affecting the braking effect.