Abstract:
A piston chamber assembly has a chamber and a piston slideably received in the chamber. The piston has a first side and a second side. A first inlet communicates air into the chamber on the first side while a second inlet communicates air into the chamber on the second side. An actuator is moveable between a first position and a second position. The actuator selectively opens and closes the first inlet and the second inlet. In the first position, the actuator closes the second inlet and opens a first inlet while in the second position the actuator opens the second inlet and closes the first inlet. The actuator is coupled to the piston, which drives the actuator between the first position and the second position.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a cylinder and piston assembly. 
     Automotive manufacturers generally test vehicle components, such as a vehicle door, by simulating the operating conditions of the vehicle component. For example, to test the functioning of a door, the manufacturer may repeatedly open and close the door to test wear and tear. Frequently, this action is performed by a piston and cylinder, which opens and closes the door. 
     The cylinder is connected to an air compressor while the piston is connected by a rod to the test component. Air to the piston and cylinder is controlled by a computer. The computer directs air from the compressor to one side of the piston to move the piston and rod in one direction. When the piston has moved to one side of the cylinder, the computer then directs air to the opposite side of the piston to thereby move the piston and rod in the other direction. This cycle is repeated. 
     The task performed by the piston and cylinder is simple. However, a computer is still used to control the assembly&#39;s operation. The computer adds significant expense to the testing of the component. A need therefore exists for a piston and cylinder that cycles without a computer. 
     SUMMARY OF THE INVENTION 
     The invention comprises a piston and cylinder assembly. Like existing designs, the invention has a piston that is slideably received in a chamber of the cylinder. On one side of the piston is one air inlet while on the other side of the piston is a second air inlet. In contrast to conventional assemblies, the invention has an actuator within the chamber that is moveable between a first position and a second position. In the first position, the actuator opens the first inlet and closes the second. In the second position, the actuator closes the first inlet and opens the second. 
     The actuator is coupled to the piston, which drives the actuator between the first position and the second position. Accordingly, air entering the cylinder on the first side of the piston expands the piston and thereby moves the actuator to close the first inlet and open the second inlet. Air in the second inlet is then allowed to expand the piston and move the actuator so as to close the second inlet and again permit air through the first inlet. In this way, the inventive assembly cycles without the need of a computer. 
     The actuator may comprise a body in the chamber of the cylinder. The body may move in one direction towards the first position and in another direction towards the second position. The piston is arranged to impart its momentum to the body in either direction. In this way, the body moves between the first position and the second position. 
     The actuator may further have a first portion and a second portion. The piston may be supported to move between the first portion and the second portion alternatingly in one direction and the other direction. The actuator thereby imparts its momentum to either the first portion or the second portion. The first portion may close the first inlet in the second position while the second portion closes the second inlet in the first position. 
     The invention further has a retaining feature that holds the actuator in either the first position or the second position until a predetermined amount of momentum is received by the actuator. This feature may comprise a magnet. In this way, the actuator stays in its position until sufficient momentum is imparted by the piston. This feature thereby avoids movement of the actuator with the piston until sufficient momentum has been received by the actuator to move between positions. 
     Another version of the invention uses a different actuator. The actuator has a member that is rotated by the piston between a first position and a second position. The rotating actuator has a first portion and a second portion. The first portion has a first opening that permits air from the first inlet into the chamber while the second portion has a second opening that permits air from the second inlet into the chamber. When the piston has reached a certain position on the member, the member rotates to close the first inlet and open the second inlet. The member is then subsequently rotated by the piston to close the second inlet when the first inlet is opened. 
     The piston slides relative to this rotating actuator. The actuator has a cam that is selectively in contact with the piston. The action of the piston on the cam rotates the actuator between the first position and the second position. The piston may further be mounted to a groove on the actuator. The cam may be part of the groove. 
     Both features permit the inventive assembly to cycle by itself. There is no need for a computer to control air flow into the piston chamber. The invention is therefore much cheaper to produce. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows: 
     FIG. 1 illustrates a cross-sectional view of the inventive assembly in the first position with the first inlet open and the second inlet closed. 
     FIG. 2 illustrates the assembly of FIG. 1 in the second position with the second inlet open and the first inlet closed. 
     FIG. 3 illustrates a cross-sectional view of another version of the invention in the first position with the first inlet open and the second inlet closed. 
     FIG. 4 illustrates a cross-sectional view of the inventive assembly of FIG. 3 at the point in which the actuator switches between the first position and the second position. 
     FIG. 5 illustrates the assembly of FIGS. 3 and 4 in the second position with the second air inlet open and the first inlet closed. 
     FIG. 6 illustrates a view of the piston and actuator of FIG.  3 - 5 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates a cross-sectional view of an inventive piston chamber assembly  10 . Piston chamber assembly  10  has piston  18  and chamber  14 , defined by cylinder  12 . Piston  18  has first side  22  and second side  26 . On first side  22  of piston  18 , there is provided first inlet  30  that permits the passage of air from compressor  13  through line  17  onto first side  22  of piston  18 . In addition, piston chamber assembly  10  has second inlet  34 , which permits air from compressor  13  through line  19  to pass onto second side  26  of piston  18 . Here, piston  18  is attached to rod  16 , which may be attached to a test piece. 
     In contrast to conventional designs, piston chamber assembly  10  has actuator  38  disposed within chamber  14 . Actuator  38  has body  50 , which has first portion  54  on first side of piston  18  and second portion  58  on second side  26  of piston  18 . First portion  54  and second portion  58  are slideably received within chamber  14 . In addition, first portion  54  and second portion  58  are connected by rods  21  so that they may slide together within chamber  14 . 
     Piston  18  is also slideably received on rods  21  between first portion  54  and second portion  58 . Piston  18  further has seal  20 , here an O-ring, that serves to wipe chamber  14  as well as to provide a seal between first side  22  and second side  26  of piston  18 . Piston chamber assembly  10  further has exhaust outlet  28  on first side  22  of piston  18  and exhaust outlet  29  on second side  26  of piston  18 . Exhaust outlet  29  is merely a gap between rod  16  and end portion  33  of cylinder  12 . 
     The operation of piston chamber assembly  10  will now be explained with reference to FIGS. 1 and 2. FIG. 1 illustrates piston chamber assembly  10  with actuator  38  in first position  42 . As shown, first portion  54  is in a position to cover exhaust outlet  28 . Moreover, second portion  58  is in a position to cover second inlet  34 . Retaining feature  62 , here a magnetic plate, holds first portion  54  in first position  42 . First portion  54  and second portion  58  are both attractable by magnet of retaining feature  62 . 
     In first position  42 , air passes from compressor  13  through line  15  and splits into line  17  and line  19 . Because first inlet  30  is open to receive air on first side  22  of piston  18  and second inlet  34  is closed due to the position of second portion  58  in first position  42 , piston  18  expands in the direction of arrow B moving rod  16  in the same direction. Piston  18  develops momentum and impacts second portion  58  as shown in FIG.  2 . This collision between second portion  58  and piston  18  causes first portion  54  to become dislodged from retaining feature  62  and to move to second position  46 , where second portion  58  is held in place by the other retaining feature  62 . 
     In this second position  46 , actuator  38  now allows air to pass from line  19  through second inlet  34  onto second side  26  of piston  18 . Moreover, first inlet  30  is closed so that air from compressor  13  will not enter into chamber  14  on first side  22  of piston  18 . Exhaust  28  is also open to permit air on first side  22  to escape. Air passes through second inlet  34  to cause piston  18  and rod  16  to move in the direction of arrow A. Piston  18  then develops momentum and comes into contact with first portion  54  to thereby drive first portion  54  back to first position  42  shown in FIG.  1 . Piston chamber assembly  10  may cycle back and forth in manner indefinitely. It is preferable for piston  18  to be made of a material having a low coefficient of friction, preferably, DuPont&#39;s DERLIN™ ring material. 
     Piston chamber assembly  10  has adjuster  31 . Adjuster  31  comprises a set screw, which may be turned to move adjuster  31  in the direction of arrow A or B. Stroke adjuster  31  is threadedly received by first portion  54  and moves with first portion  54 . By turning the screw, adjuster  31  may adjust the position of piston  18  within chamber  10  relative to end portion  27  so as to prevent piston  18  from covering first inlet  30  in first position  42 . 
     FIGS. 3-5 illustrate another version of the inventive piston chamber assembly. Here, piston chamber assembly  100  comprises chamber  14  having piston  18  slideably received within chamber  14 . Piston  18  has first side  22  and second side  26 . In addition, piston  18  has seal  20 . Chamber  14  is provided with first inlet  30  and second inlet  34  as well as exhaust outlet  28  and exhaust outlet  29 . These features are identical to the features identified by the same numbers in FIG.  1 . 
     Unlike the previous version, actuator  66  here comprises a member rotatably mounted to end portion  27  and  33  of cylinder  12 . Actuator  66  may rotate in the direction of arrow R 1  or in the direction of arrow R 2 . Actuator  66  further has first portion  94  with first opening  98  and second portion  102  with second opening  106 . As shown in the figures, first opening  98  extends through actuator  66  in a transverse direction relative to second opening  106 . Accordingly, as shown in FIG. 3, when actuator  66  is in first position  70 , first opening  98  permits air to pass through first inlet  30  while second opening  106  is blocked by second portion  102 . Conversely, as shown in FIG. 5, if actuator  66  is rotated in the direction of arrow R 1 , first opening  98  is rotated so that it is no longer aligned with first inlet  30 . Consequently, first portion  94  blocks first inlet  30  while second opening  106  is now aligned with second inlet  34  to permit air to pass to second side  26  of piston  18 . 
     Like the previous version, piston  18  is mechanically linked to actuator  66 . As shown in FIG. 6, piston  18  is slideably received on actuator  66 . Piston  18  and actuator  66  are mechanically linked by pin  110 . Pin  110  extends from piston  18  into groove  90 . As shown in FIG. 4, groove  90  further has first cam  82  and second cam  86 , both of which define a portion of groove  90 . 
     The functioning of actuator  66  will now be explained with reference to FIGS. 3-5. As shown in FIG. 3, actuator  66  is in a position to permit air from line  17  to pass through first inlet  30  and through first opening  98  to first side  22  of piston  18 . Second opening  106  is blocked by second portion  102 . Air then expands piston  18  in the direction of arrow B. As shown in FIG. 4, pin  110  contacts first cam  18  as piston  18  slides to intermediate position  72 . This contact of pin  110  with cam  82  causes actuator  66  to rotate in the direction of arrow R 1 , here downward. 
     As shown in FIG. 5, when actuator  66  has rotated to second position  74 , actuator  66  now is in a position to block first inlet  30  because first opening  98  has rotated out of alignment with first inlet  30 . In addition, second opening  106  is now aligned with second inlet  34  to allow air to pass from line  19  to second side  26  of piston  18 . Piston  18  then expands in the direction of arrow A. Pin  110  moves along groove  90  so as to come in contact with cam  86  and thereby rotate actuator  66  in the upward direction of arrow R 2 . Consequently, actuator  66  then rotates back to first position  70  as shown in FIG.  3 . 
     The aforementioned description is exemplary rather that limiting. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed. However, one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. Hence, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For this reason the following claims should be studied to determine the true scope and content of this invention.