Cushioning system for pneumatic cylinder of differential engine

A cushioning system for a pneumatic cylinder powered differential engine door opening and closing device for use in passenger transportation vehicles wherein the cushioning initiation point can be adjusted. This cushioning initiation point is adjusted through the use of a linearly adjustable slider member within the large cylinder. The slider is linearly adjustable through the use of an adjustment screw located outside of the pneumatic cylinder and allows one to adjust the time and the mode of the opening/closing of power doors, without disassembly of the cylinder, and significantly improve the safety of the passenger.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates in general to a pneumatic cylinder powered system for opening and closing a vehicle door and, more particularly, to an adjustable cushioning system for a pneumatic cylinder powered differential engine door opening and closing device for use in passenger transportation vehicles.

2. Description of Related Art

Pneumatic cylinders have been utilized in mechanical systems to convert compressed air into linear reciprocating movement for opening and closing doors of passenger transportation vehicles. An example of this type of door actuating system is shown in U.S. Pat. No. 3,979,790.

Typically, pneumatic cylinders used in this environment consist of a cylindrical chamber, a piston, and two end caps hermetically connected to the cylindrical chamber. The end caps have holes extending therethrough to allow the compressed air to flow into and out of the cylindrical chamber, to cause the piston to move in a linear direction, and to apply either an opening or closing force to the vehicle door.

Pneumatic cylinder/differential engine systems have also been designed for opening and closing doors of passenger transportation vehicles. Examples of these systems are shown in U.S. Pat. Nos. 4,231,192; 4,134,231; and 1,557,684.

It has been determined in some instances that there is a need to slow the movement of the piston at the end of the stroke when opening and/or closing the door. A known technique for slowing this stroke is by restricting the flow of the exhaust air out of the cylindrical chamber. This is commonly known as cushioning the movement of the piston.

A known cushioning system for a pneumatically powered differential engine door opening device is shown schematically inFIG. 1. The differential engine includes a housing comprising a large diameter cylinder1and a small diameter cylinder2, closed at their ends by caps6and7. A large diameter piston4is installed in the large cylinder1and a small diameter piston5is installed in the small cylinder2. A toothed rack16is attached to and extends between the large piston4and small piston5. The toothed rack16is engaged with a pinion gear15. The pinion gear15is, in turn, connected to a shaft14which drives the mechanism for closing and opening the vehicle door. Linear movement of pistons4and5causes linear movement of the toothed rack16. This linear movement is converted into rotational movement of the pinion gear15and shaft14causing opening and/or closing of the vehicle door as viewed inFIG. 1, movement of the pistons4and5to the left causes an opening of the doors and movement of pistons4and5to the right causes a closing of the doors.

As shown inFIG. 1, the right outer side of the small cylinder2is connected through a hole19in the cap7to a reservoir of compressed air that constantly applies a positive pressure to the small piston5. As shown in schematically inFIG. 2, the cap6, attached to the outer end of the large cylinder1, has a chamber17including holes9and10which are connected through a port yy to a three-way valve, which provides connections to a source of compressed air and to an exhaust. During closing of the doors, hole9is connected to a source of pressurized air and exhaust hole10is closed. Because the surface area of piston4is greater than the surface area of piston5, the pistons4,5move to the right, rotating the pinion gear15/shaft14in a counter-clockwise direction. During an opening stroke, holes9and10are connected to an exhaust, causing the air to flow out of large cylinder1. Because the small piston5is constantly attached to a source of positive air pressure, the exhausting of the air pressure from within the large cylinder1causes the pistons4,5connected by toothed rack16to move toward the left within the large and small cylinders1,2. This movement to the left rotates the pinion gear15/shaft14in a clockwise direction to initiate opening of the doors.

In this design, cushioning at the end of the opening piston stroke occurs through the use of a small hole11having a diameter that is substantially smaller than that of opening xx. This hole11is located at a side surface of chamber17which provides connection to the inside volume of the chamber of the large cylinder1. A cylindrical sealing disk8is installed between the piston4and cap6and is supported between two springs12and13. The leftward movement of the pistons4,5causes compression of springs12and13bringing the disk8into contact with a face17aof chamber17forming a seal with the chamber face17a. Once this seal is achieved, air can no longer exit the chamber of the large cylinder1through opening xx into chamber17and thus can only exit through hole11into chamber17. Since the diameter of hole11is smaller than the diameter of opening xx, the flow of the air out of the large cylinder1is restricted, consequently slowing down the speed of the opening piston stroke movement to the left and achieving a cushioning effect during opening of the doors.

U.S. Pat. No. 2,343,316 teaches a pneumatic cylinder/differential engine for power operated doors wherein cushioning occurs near the end of the piston stroke during closing of the doors in order to prevent slamming. In this device, cushioning occurs when a sealing disk contacts with the surface of a cap, causing the exhaust air to flow through a small hole which significantly reduces the rate of flow of the exhaust air from the cylinder housing and decreases the linear speed of the piston.

While the concept of cushioning the end of a piston stroke in a door opening or door closing cycle has been documented, a disadvantage of these systems is that cushioning is always initiated at the same point in the movement of the piston (or at the same position of the piston), and because the linear movement of the piston is transferred to the rotational movement of the output shaft and rotation or linear movement of the powered doors, the doors will always begin to slow at the same point in its path. It is difficult and cost prohibitive to disassemble the pneumatic cylinder, remove the existing components of the cushioning system, replace the spring system supporting the sealing disks, and then reassemble the pneumatic cylinder. Furthermore, if one should select the wrong tensioned spring system, then the process of disassembling/reassembling must be repeated. Another disadvantage of these known systems is that it is impossible to finely adjust the cushion initiation point in the broad range of the linear movement of the piston or rotational movement of the output shaft and, respectively, linear or rotational movement of the power doors.

SUMMARY OF THE INVENTION

It is therefore an aspect of the invention to provide a cushioning system wherein the cushioning initiation point can be adjusted. It is a further aspect of the invention to adjust the time and the mode of the opening/closing of power doors. It is another aspect of the invention to provide a system that allows for fine adjustment of the cushioning initiation point without disassembly of the cylinder. It is still another aspect of the invention to provide a system wherein the cushioning initiation point can be adjusted so that the duration of the cushioning of the piston movement can be adjusted as needed. It is yet another aspect of the invention to provide an adjustable cushioning system wherein adjustment can be accomplished from outside of the cylinder.

Accordingly, the present invention is directed to a cushioning system for use with a pneumatic cylinder/differential engine door operator for driving a door between open and closed positions wherein the differential engine includes a large cylinder aligned with a small cylinder and a pair of associated pistons having a rack and pinion assembly connected therebetween and controlled by movement of the associated pistons. The cushioning system includes a large cap for sealing the large cylinder and a slider extending through the large cap and into the large cylinder. The slider is in fluid contact with an interior portion of the large cylinder. At least a first port having a first diameter extends through a first wall portion of the slider. At least a second port having a second diameter smaller than the first diameter extends through a second wall portion of the slider. The second sidewall portion is at a remote location from the first sidewall portion. A valve is associated with the slider for applying fluid through the first and second ports into the large cylinder during a door closing cycle and exhausting fluid through the first and second ports from within the large cylinder during a door opening cycle. A closing device is provided for sealing the slider near the end of a door opening cycle and eliminating the flow of exhaust through the first port so that the flow of exhaust only occurs through the second port and slows the forward movement of the pair of pistons. An adjusting device adjusts the linear extension of the slider into the large cylinder and adjusts the distance between the closing device and the slider for one of increasing and decreasing the amount of time before sealing of the slider occurs to adjust the point at which cushioning occurs during the door opening cycle.

The present invention is also directed to an adjustment assembly adapted for use with a cushioning system for a pneumatic cylinder/differential engine door operator. The adjustment assembly includes a cap for sealing a cylinder. A slider is mounted to the cap and into the cylinder. This slider is in fluid contact with an interior portion of the cylinder. A closing device seals the slider near the end of a door opening cycle, preventing the flow of exhaust through a first port so that the flow of exhaust occurs through a second port. This slows the forward movement of at least one piston. An adjusting device adjusts the linear extension of the slider into the cylinder and adjusts the distance between the closing device and the slider for one of increasing and decreasing the amount of time before sealing of the slider occurs to adjust the time at which cushioning occurs during the door opening cycle. This adjusting device includes a screw mounted to the slider and allows for the adjustment of cushioning cycle time without disassembling and/or replacing of parts within the pneumatic cylinder/differential engine door operator.

DETAILED DESCRIPTION OF THE INVENTION

Reference is now made toFIGS. 3 and 4, which show cross-sectional views of the pneumatic cylinder/differential engine according to a first embodiment of the present invention, generally indicated as20, at the start of the door opening cycle and near the end of the door opening cycle where cushioning begins. The pneumatic cylinder/differential engine comprises a large cylinder22and a small cylinder24which are aligned with one another. A rack and pinion gear mechanism housing26is positioned in alignment between the large cylinder22and small cylinder24. A large piston28is contained within the large cylinder22and a small piston30is contained within the small cylinder24. A toothed rack32is connected via connecting screws29a,29bbetween the large piston28and small piston30. Pinion gear34is engaged with toothed rack32and is connected to an output shaft36such that linear movement of the large piston28and small piston30results in rotational movement of the pinion gear34and output shaft36with respect to the toothed rack32to cause one of an opening cycle or a closing cycle of the door (not shown). A large cylinder cap38is positioned at one end of the large cylinder22and a small cylinder cap40is positioned at one end of the small cylinder24. An opening42is provided in the small cylinder cap40. This opening42is connected to a source of fluid pressure which applies a constant positive pressure of approximately 90-120 psi to the small piston30. The large cylinder cap38is attached to a three-way valve (not shown) via a fitting44. This valve is capable of applying a positive fluid pressure into the large cylinder22and against the large piston28, thereby forcing the large piston, toothed rack32and small piston30to move linearly toward the right as shown inFIG. 3, and causing the pinion gear34to rotate in a counter-clockwise direction to initiate a door closing cycle. When a door opening cycle is desired, the valve allows air to be exhausted from within the large cylinder22, thereby allowing the positive fluid pressure applied to the small piston30to linearly move the small piston30, toothed rack32and large piston28to the left as shown inFIG. 4, and causing the pinion gear34to rotate in a clockwise direction, opening the vehicle door. As shown especially inFIGS. 5 and 6, the large cylinder cap includes a cushioning speed adjustment screw46, a door closing speed adjustment screw47, and a door opening speed adjustment screw48. Appropriate O-rings49a,49bare provided in the device to achieve fluid tight seals of the individual components in the large cylinder cap38.

The cushioning system of the invention comprises a cup-shaped slider50, having a back wall52, a pair of sidewalls54and a front opening56. The slider50is positioned within a cup-shaped aperture58in the large cylinder cap38. At least a first exhaust port60, having a first predetermined diameter, extends through a first wall of the slider50. Preferably the first exhaust port60extends through the back wall52of the slider50to exhaust air during the door opening cycle from within the large cylinder22into a trap portion59of aperture58located between a back portion of the slider50and the large cap38and subsequently out of the device through fitting44. More than one first exhaust port60may be provided through this back wall52of the slider50. At least a second exhaust port62, having a second predetermined diameter which is smaller than the first predetermined diameter of the first exhaust port60, extends through a second wall portion of the slider50. This second wall portion preferably comprises one of the pair of sidewalls54and is at a remote location from the first sidewall portion. The slider50is seated within the aperture58such that only a portion of the sidewalls54of the slider are contacted by sidewalls61of the aperture58. Sidewalls61do not extend past and/or seal the second exhaust port62in the sidewall54of the slider50.

A closing device64, typically in the form of a plate, is mounted by a biasing system, generally illustrated as65. Preferably, this biasing system65comprises a pair of springs66,68, between which the closing device64is mounted. A first spring66has a first end66aassociated with and/or secured to cylinder cap38and a second end66bsecured to the closing device64. A second spring68includes a first end68asecured to the closing device64and a second end68bassociated and/or secured to the large piston28. This closing device64is secured between the first and second springs66,68by any well known securing member70, such as a screw, post and the like. During an opening cycle, movement of the large piston28causes first and second springs66,68to compress and bring closing device64into contact with the front opening56of the slider50to initiate a cushioning cycle near the end of the opening cycle piston stroke.

The contact of the closing device64with the opening56of the slider seals this opening56against the flow of exhaust air out of the large cylinder22through the first exhaust port60. The flow of the exhaust air is now limited to escape through the second/smaller exhaust port62as this is the only exhaust port in fluid contact with the interior portion of the large cylinder22. This sealing of opening56significantly slows down the forward movement of the piston stroke near the end of the opening cycle.

The slider50is attached to an end of a cushioning initiation point adjustment screw72. Accordingly, should one require a longer or shorter cushioning cycle, slider50may be moved linearly within the large cylinder22closer to or farther away from the closing device64. This adjustment of the cushioning cycle time/initiation point can occur without disassembling the pneumatic cylinder and without replacing springs66,68with springs having different lengths and/or tensions. Additionally, the cushioning initiation point adjustment screw72may be readily accessed outside the pneumatic cylinder for easy adjustment and/or fine tuning of the initiation point with respect to closing device64.

The magnitude of the linear motion of the slider50can be up to 50% of the length of the linear stroke of the large piston28. Connection between the slider50and cushioning initiation point adjustment screw72can be made, for example, by a retaining ring74mounted on the adjustment screw which enters through a port76in the back wall52of the slider50.

The cushioning initiation point is defined by the moment when closing device/plate64seals the face or front opening56of the slider50. This moment can be adjusted by moving the slider50along the axis of the pneumatic cylinder so that the closing device64will contact the slider front opening56earlier in relation to the movement of the piston28, or later, at the end of the movement of the piston28. This linear adjustment is provided by rotation of the cushion initiation point adjustment screw72. In practice, the adjustment of the cushioning initiation point depends on the range of motion of the slider50, and cushioning can be adjusted to start at a point between 30 to 90% of the full rotation of the output shaft. The adjustment of the cushioning initiation point enables the field adjustment cycle of the opening/closing of the powered doors without disassembly of the cylinder.

The invention can be clarified by an analysis of the air flow and piston movement in different cycles of the cylinder/engine. Opening42of the small cylinder24is always connected to the source of compressed air (100-120 psi). Fitting44connects port76to a three-way valve, allowing connection of the port76to compressed air or to exhaust (atmospheric pressure) for removing air.

During a door closing cycle, port76associated with fitting44is connected to the source of the compressed air. A ball78, as shown inFIG. 6, closes a connecting hole80of the door opening speed adjustment screw48so air can enter into the large cylinder22only through the hole82of the door closing speed adjustment screw47. Compressed air enters into the trap59of the cap38and flows through the ports60of the slider50into the cup-shaped portion of the slider. At the beginning of the closing cycle, this cavity of the slider50is sealed by the closing device or sealing disk64attached to a retainer84. The pressure on the sealing disk64forces movement of the sealing disk64and retainer84to the right, opening the front opening cup56of the shaped slider50, and allowing compressed air to enter into the cavity of the large cylinder22. Because of the difference in the diameters of the pistons28and30, the force acting on piston28is greater than the force acting on piston30, and as a result pistons28and30, connected by the rack32, move to the right, causing the rotation of the pinion gear34in a counter-clockwise direction. The output shaft36drives the power door opening/closing mechanism. Rotation of the shaft36in a counter-clockwise direction causes closing of the power doors. Air flow into the cylinder, or door closing speed, can be adjusted by rotation of the screw47. The movement of the pistons stops when the right side of the piston28contacts the surface of the pinion gear housing26.

The ends of the springs66and68are attached to the retainer84. The opposite end of the spring66is located in a cavity86of the large cylinder cap38, and the opposite end of the spring68is located in a cavity88of the large piston28. This arrangement allows the retainer84, and accordingly sealing disk or closing device64attached to the retainer84, to move between piston28and cap38.

When the piston28moves to the right, the retainer84also moves to the right, and the gap between sealing disk64and opening56of the slider50increases. However, the movement of the retainer84does not exactly follow the movement of the piston28because the coefficient of elasticity of spring66is greater than the coefficient of elasticity of spring68, and because the lengths of springs66and68are different.

During a door opening cycle, port74is connected through fitting44to the exhaust (atmospheric pressure). The opening cycle consists of two parts: opening without cushioning and opening with cushioning.

Opening of the power door without cushioning: When three-way valve connects the port76to the exhaust, the pressure gradient causes the ball78to move and open the hole80, allowing air flow through the cavity to the port76. The flow rate through hole80, and hence the door opening speed, can be adjusted by screw48. The air flows out of the cavity of the large cylinder22through the ports60in the slider wall into the cavity or trap59between slider50and cap38, and through the holes80and82to the port76. At the same time, air can flow into trap59through the small port62and a hole90of the cushion speed adjustment screw46. However, the diameter of the port62is substantially less than the diameter of the holes80and82. Therefore, the flow of the air through the holes80and82is significantly greater than the flow through the port62. As a result, the pressure in the cavity of the large cylinder22quickly decreases, causing the force acting on the small piston30to exceed the force acting on the large piston28, and pistons30,28and rack32start moving to the left. The linear movement of the rack32causes the clockwise rotation of the pinion gear34and output shaft36and, accordingly, the opening of the doors. The movement of the piston28will cause the compression of the spring68and will cause the movement of the retainer84to the left. The rapid linear motion of pistons28and30continues until (a) the sealing disk64contacts with the front opening56of the slider50and (b) the force of the spring68acting on retainer84becomes sufficient to seal front opening56of the slider50from the cavity of the large cylinder22. Because of the decrease in air flow out of the cylinder, the movement of the piston slows and cushioning is initiated.

Opening of the power door with cushioning: As described above, the movement of the piston28causes the compression of the spring68and the sealing of opening56of the slider50. As a result, the air enters the trap59of the cap38only through the passage created by the port62and hole90. The air flow through the hole90can be increased or decreased by adjusting screw46. Because the flow rate through the ports62and90is significantly less than the flow rate through the port60of the slider50, the movement of the piston28is significantly slowed or cushioned, which causes the cushioning of the powered doors at the end of the opening cycle.

Reference is now made toFIG. 7, which shows a cross-sectional view of the pneumatic cylinder/differential engine according to a second embodiment of the invention. In this embodiment, biasing system, generally illustrated as165, includes a pair of springs166,168between which the closing device64is mounted. This mounting is achieved by any well known means such as discussed in detail above with respect to theFIG. 3embodiment. In this second embodiment, a first spring166includes a first end166a, which is located within and supported by the slider50. First spring166also includes a second end166bwhich is secured to the closing device64. A second spring168includes a first end168asecured to closing device64and a second end168bassociated with and/or secured to the large piston28. The slider50is attached to the adjustment screw72by any well-known attachment means, for example, a nut95and a lock-washer97. During a door opening cycle, movement of the large piston28causes first and second springs166,168to compress and bring the closing device64into contact with the front opening56of the slider50to initiate a cushioning cycle near the end of the opening cycle. As discussed in detail above, adjustment screw72linearly adjusts the distance between the slider50and the closing device64to adjust the length of time of the cushioning cycle. This adjustment is readily achieved without the time consuming and costly process of disassembling the pneumatic cylinder and replacing of the first and second springs166,168with springs having different lengths and/or tensions.