Abstract:
An actuator and method for a heated sealing strip is disclosed. The actuator and method comprise embedding at least one wire ( 218 ) into a sealing strip ( 216 ). A power supply ( 30 ) is connected to the wire ( 218 ). An electrical current is run from the power supply ( 430 ) through the wire ( 218 ), heating the sealing strip ( 216 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention is related to the field of actuators, and in particular, to an actuator with a heated sealing strip. 
         [0003]    2. Description of the Prior Art 
         [0004]    Actuators come in many styles and shapes. One type of activator is a rodless cylinder, for example a Lintra® Rodless cylinder M/46000 from Norgren. Rodless cylinders differ from basic cylinders in that no piston rod extends outside the cylinder body. Instead, an internal piston is connected to an external carriage, by means of a magnetic or mechanical coupling system. Rodless cylinders are ideal for long stroke applications because they are unaffected by rod overhang, bending, piston binding, and uneven seal wear, and for use in confined areas where space is a premium. Unfortunately, the rodless design may necessitate a long sealing strip running the length of the rodless cylinder. The sealing strip is typically used to seal the pneumatic chamber of the rodless cylinder. Some sealing strips may stiffen when exposed to low temperatures, causing a loss of pressure and efficiency in the actuator. It would be desirable to have an actuator that did not lose efficiency at low temperature. 
         [0005]    Therefore there is a need for a sealing strip that functions over a wider temperature range. 
       SUMMARY OF THE INVENTION 
       [0006]    A system and method for a heated sealing strip is disclosed. The system and method comprise embedding at least one wire into a sealing strip. A power supply is connected to the wire. An electrical current is run from the power supply through the wire, heating the sealing strip. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0007]      FIG. 1  is an isometric view of a rodless cylinder in an example embodiment of the invention. 
           [0008]      FIG. 2  is a sectional view of detail area AA from  FIG. 1 , in an example embodiment of the invention. 
           [0009]      FIG. 3  is a sectional side view of rodless cylinder  300  in one example embodiment of the invention. 
           [0010]      FIG. 4   a  is a diagram of two wires embedded inside a sealing strip connected to a power supply in one example embodiment of the invention. 
           [0011]      FIG. 4   b  is a diagram of two wires embedded inside a sealing strip connected to a power supply in another example embodiment of the invention. 
           [0012]      FIG. 4   c  is a diagram of a wire embedded inside a sealing strip connected to a power supply in another example embodiment of the invention. 
           [0013]      FIG. 5  is a flow chart for heating a sealing strip in one example embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0014]      FIGS. 1-5  and the following description depict specific examples to teach those skilled in the art how to make and use the best mode of the invention. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these examples that fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. As a result, the invention is not limited to the specific examples described below, but only by the claims and their equivalents. 
         [0015]      FIG. 1  is an isometric view of a rodless cylinder in an example embodiment of the invention. Rodless cylinder has endcaps  102  and  104 , main body  106 , carriage  108 , cover strip  110 , and air ports  112  and  114 . In operation, air is forced into air ports  112  or  114 , driving carriage from one endcap to the other endcap. 
         [0016]      FIG. 2  is a sectional view of detail area AA from  FIG. 1 , in one example embodiment of the invention.  FIG. 2  shows main body  206  that forms the inner wall  220  of a pneumatic chamber. Sealing strip  216  fits into and seals the top channel formed into main body  206 . Sealing strip  216  has wires  218  embedded into sealing strip  216 . The wires  218  in sealing strip  216  are typically used to stiffen sealing strip  216  and may be made from steel or some other metal. In one example embodiment of the invention, the wires  218  in sealing strip  216  are also used as heating elements. By running an electrical current through the wires  218 , the sealing strip may be heated. The heated sealing strip retains it&#39;s flexibility at lower temperatures compared to a non-heated sealing strip. Cover strip  210  attaches to a feature in the top of sealing strip  216 . 
         [0017]      FIG. 3  is a sectional side view of rodless cylinder  300  in one example embodiment of the invention. Rodless cylinder  300  comprises endcaps  302  and  304 , main body  306 , carriage  308 , cover strip  310 , pneumatic chamber  322 , and sealing strip  316 . Air port  314  is formed into endcap  304 . An air port (not shown) is also formed into endcap  302 . Carriage  308  is attached to internal piston  320 . Sealing strip  316  and cover strip  310  may be one continuous piece or may be two pieces, one piece at each end of the rodless cylinder, with the carriage in the middle. 
         [0018]    In operation, carriage  308  is moved from one endcap to the other endcap as air is forced into the air port in endcap  302  or air port  314 , driving internal piston inside pneumatic chamber  322 . As the carriage moves towards one endcap, the leading end of the carriage forces sealing strip  316  down and away from the top channel and forces the cove strip  310  up and away from the top channel. As the carriage passes by, the trailing end of the carriage forces the sealing strip  316  back up into top channel and forces cover strip  310  back down and onto the retaining feature on sealing strip  316 . As the operating temperature gets colder, sealing strip tends to get stiffer. As the sealing strip gets stiffer, the carriage may have difficulty re-seating sealing strip into the top channel as the carriage passes by. When the sealing strip is not properly seated into the top channel, air leaks may occur, reducing the efficiency of the rodless cylinder. 
         [0019]    Some sealing strips already contain wires embedded into the sealing strip to add stiffness to the sealing strip. Typically the wires are called internal reinforcement wires and may be made from steel or some other metal. By connecting the wires to a power supply, an electrical current can be run through the wires, thereby heating the wires and the sealing strip.  FIG. 4  is a drawing of the wires embedded inside a sealing strip and connected to a power supply in one example embodiment of the invention.  FIG. 4  comprises a sealing strip  416 , wires  418 , and a power supply  430 .  FIG. 4   a  shows the power supply  430  connected to the wires  418  at both ends of the sealing strip  416 .  FIG. 4   b  shows the wires  418  connected together at one end of the sealing strip  416  forming a loop. The power supply  430  is connected to the wires  418  at the other end of the sealing strip  416 .  FIG. 4   c  shows a single wire embedded into sealing strip  416  forming a serpentine path between the two ends of the sealing strip. Power supply  430  is connected to each end of wire  418 . Many other wire configurations are possible. 
         [0020]    In one example embodiment of the invention, the power supply may be 24 volts. The current through the wires may be controlled to provide a given amount of heating, for example 12 Watts. A temperature sensor may be used to switch the power supply on when the temperature falls below a threshold. In another example embodiment of the invention, the sealing strip may be heated for a predetermined length of time at system power-up. Heating wires may be added to sealing strips that do not require internal stiffeners. 
         [0021]      FIG. 5  is a flow chart for heating a sealing strip in one example embodiment of the invention. At step  502  a power supply is connected to a wire embedded inside a sealing strip. At step  504  an electrical current is run from the power supply through the wire embedded in the sealing strip, thereby heating the sealing strip.