Patent Publication Number: US-2023137900-A1

Title: Piston assemblies and methods of using same

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Pat. Application No. 62/994,092, filed Mar. 24, 2020, which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to the mechanical arts, and in particular piston assemblies, such as gas springs and dampers. An embodiment of the invention comprises a piston assembly having a linear position sensing system. 
     BACKGROUND 
     Piston assemblies, such as gas springs and dampers, can aid in controlling the movement of a moveable object such as a lid, door, or vehicle hood or hatch. A typical gas spring comprises a cylinder with pressured gas acting on the cross sectional area of the rod to create an output force. Gas springs can assist in lifting loads and can help move a lid or other object to different positions. Dampers can control the motion of a lid, door, lever, gear, pedal or linkage mechanism by slowing motion of the piston rod within the damper. Existing gas springs and dampers provide only output forces or motion control. 
     SUMMARY 
     An object of the present invention is to provide a linear sensing system for use on gas springs or dampers. Another object of the present invention is to provide an apparatus that allows existing features of a gas spring or damper to function while providing accurate, non-contact position sensing via electrical output signals during extension and/or compression strokes. These and other objects of the invention can be achieved in one or more of embodiments of the invention disclosed herein. 
     One embodiment of the invention comprises a piston assembly comprising a linear position sensing system. 
     Another embodiment of the invention comprises a gas spring comprising a piston assembly comprising a linear position sensing system. 
     Another embodiment of the invention comprises a damping apparatus comprising a piston assembly comprising a linear position sensing system. 
     Another embodiment of the invention comprises a piston assembly that maintains the output forces and/or motion control while also detecting stroke position by providing electrical outputs. 
     Another embodiment of the invention comprises a piston assembly comprising a gas spring, and a waveguide sensor unit integrated into the gas spring, wherein the sensor transmits a signal indicating the relative position of the gas spring. This can be useful in applications in which it is important to know the position of a lid or other part connected to the gas spring. By also factoring in the time, the sensor can calculate the velocity or change in velocity of the moving part. This can also be used in combination with a linear actuator. 
     According to an embodiment of the invention, infinite position detection can be provided relative to the full stroke of the gas spring. 
     According to another embodiment of the invention, the sensor unit does not affect the normal function of the gas spring. 
     According to another embodiment of the invention, current corrosion protection is maintained. 
     According to another embodiment of the invention, the gas spring and/or sensor unit can be independently replaced. 
     According to another embodiment of the invention, the sensor unit maintains its position during a disruption of power input. 
     An embodiment of the invention comprises a piston assembly comprising a piston rod partially positioned within a rod housing and adapted for sliding movement within the housing, and a linear position sensing apparatus capable of tracking and determining the velocity of the piston rod. 
     According to an embodiment of the invention, a piston assembly comprises a piston rod partially positioned within a rod housing and adapted for sliding movement within the housing, and a linear position sensing apparatus. The linear position sensing apparatus comprises a position sensor connected to the piston rod whereby the sensor moves with the piston rod. A beacon is contained within the rod housing, and the position sensor can detect the position of the beacon relative to the sensor. 
     According to an embodiment of the invention, the beacon is a magnet. The magnet can be comprised of iron, nickel, cobalt or other suitable magnetic material. 
     According to an embodiment of the invention, the position sensor is a waveguide sensor. 
     According to an embodiment of the invention, the piston rod is comprised of a non-magnetic material. 
     According to an embodiment of the invention, the position sensor comprises a computing device. The computing device can be an electronic control unit. 
     According to an embodiment of the invention, the rod housing comprises a cylindrical tube, and an opening is formed at an end of the tube for receiving the piston rod therethrough. The piston rod has an outboard end external to the tube and an inboard end inside of the tube 
     According to an embodiment of the invention, a sealing member is positioned within the tube adjacent the opening. 
     According to an embodiment of the invention, grooves can be formed on the exterior surface of the tube and the beacon can be positioned within the grooves. 
     According to an embodiment of the invention, a connecting rod is attached to the piston rod at the outboard end of the piston rod. 
     According to an embodiment of the invention, the position sensor can be contained within a sensor housing that is attached to the connecting rod. 
     According to an embodiment of the invention, the sensor housing can be comprised of aluminum or nylon 6/6. 
     Another embodiment of the invention comprises a piston assembly comprising a piston rod partially positioned within a substantially cylindrical tube and adapted for sliding movement within the tube, and a linear position sensing apparatus comprising a waveguide sensor connected to the piston rod so that the sensor moves with the piston rod. A magnet is positioned within the tube, and the waveguide sensor can detect the position of the magnet relative to the sensor. 
     According to an embodiment of the invention, the waveguide sensor is operatively connected to an electronic control unit and the electronic control unit can determine velocity of the piston rod using the data collected by the sensor. 
     According to an embodiment of the invention, the piston assembly comprises a gas spring or damper. 
     According to an embodiment of the invention, a mechanical spring is connected to the piston rod. 
     Another embodiment of the invention comprises an electric motor driven zero-turn riding lawn mower comprising a damping apparatus comprising a linear position sensing apparatus. 
     According to an embodiment of the invention, an electric motor driven zero-turn riding lawn mower comprising at least one steering lever operatively connected to at least one drive wheel operatively connected to a drive motor, and at least one damping apparatus operatively connected to the at least one steering lever. The damping apparatus comprises a piston rod partially positioned within a rod housing and adapted for sliding movement within the housing, and a position sensor connected to the piston rod whereby the sensor moves with the piston rod. A beacon is contained within the rod housing, wherein the position sensor collects data regarding the position of the beacon relative to the sensor. A computing device such as an electronic control unit is operatively connected to the drive motor. The electronic control unit uses the data collected by the position sensor to determine an optimum speed and direction to rotate the drive wheel and transmits instructions to the drive motor to rotate the at least one drive wheel at the optimum speed and direction. 
     According to an embodiment of the invention, the beacon is a magnet and the position sensor is a waveguide sensor. 
     Another embodiment of the invention comprises an electric pallet jack comprising a gas spring comprising linear position sensing apparatus. 
     According to an embodiment of the invention, an electric pallet jack comprises a gas spring comprising a piston rod partially positioned within a rod housing and adapted for sliding movement within the housing, and a position sensor connected to the piston rod whereby the sensor moves with the piston rod. A beacon is contained within the rod housing, wherein the position sensor collects data regarding the position of the beacon relative to the sensor. 
     Another embodiment of the invention comprises a solar tracking device comprising a damper apparatus comprising a piston rod partially positioned within a rod housing and adapted for sliding movement within the housing, and a position sensor connected to the piston rod whereby the sensor moves with the piston rod. A beacon is contained within the rod housing, wherein the position sensor detects the position of the beacon relative to the sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a piston assembly according to an embodiment of the invention, shown partially exploded and partially in cross-section; 
         FIG.  2    is an exploded perspective view of a piston assembly according to another embodiment of the invention, shown partially exploded and partially in cross-section; 
         FIG.  3    is a perspective view of a portion of the piston assembly of  FIG.  1   ; 
         FIG.  4    is a partially exploded perspective view of the piston assembly of  FIG.  1   ; and 
         FIG.  5    is a perspective view of the piston assembly of  FIG.  1   . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     A piston assembly according to a preferred embodiment of the invention is illustrated in  FIG.  1    and shown generally at reference numeral  10 . The assembly  10  comprises a piston rod  12  partially positioned within a hollow, cylindrical pressure tube  14 , shown in cross-section in  FIG.  1   . A circular opening  19  is formed at one end of the tube  14  to allow for sliding movement of the piston rod  12  therethrough. The piston rod  12  includes a cylindrical piston head  13 , shown in cross-section in  FIGS.  1  and  2   . The tube  14  can be a gas pressure tube made of carbon steel or other suitable material. 
     A bore is formed at the outboard end of the piston rod  12  and receives a connecting rod  16 , as shown in  FIG.  1   . A cylindrical sealing member  24 , shown in cross-section in  FIGS.  1  and  2   , is positioned within the pressure tube  14  adjacent the opening  19  in the tube  14  and around the rod  12  to prevent leakage of gas and/or liquid from the pressure tube  14 . Threads  18  are formed on the external surface of the rod  12  at the outboard end of the rod  12 , as shown in  FIG.  1   . A lock nut  28  engages the threads  28  on the piston rod  12 . The lock nut  28  has a diameter greater than the opening in the pressure tube  14  and prevents further movement of the piston rod  12  when the lock nut  28  contacts the tube  14  during a compression stroke of the rod  12 . Alternatively, a jam nut or other fastener can be used in place of the lock nut  28 . 
     The piston assembly  10  includes a linear position sensing system. The linear position sensing system comprises a position sensor  20 . Preferably, the position sensor is a waveguide sensor. The sensor  20  is attached to the connecting rod  16  and positioned within a housing  22 . The sensor housing  22  has an inner diameter greater than the outer diameter of the sensor  20  so that the sensor housing  22  can receive the sensor  20 . Preferably, the sensor housing  22  is made of aluminum or nylon 6/6. A cap section  23  is attached to the housing  22  to enclose the sensor  20  within the housing  22 , as shown in  FIGS.  3  and  4   . The cap  23  can be attached to the housing  22  with screws  25  or other suitable fasteners. The end fittings  31 ,  32  can be positioned at opposite ends of the piston assembly  10 , as shown in  FIG.  1   . 
     A cylindrical magnet  30 , shown in cross-section in  FIGS.  1  and  2   , is positioned inside the pressure tube  14 . The magnet  30  can be comprised of iron, nickel, cobalt or other suitable magnetic material. The piston rod  12  can be comprised of a non-magnetic material, such as a non-ferrous metal or an austenitic stainless steel. Preferably, the magnet  30  is embedded in a cylindrical plastic spacer  33 , shown in cross-section in  FIGS.  1  and  2   . The magnet  30  can be attached to the spacer  33  by an adhesive or can be over-molded into the plastic spacer  33 . External grooves  15 ,  17  can be formed on the pressure tube  14 . The magnet  30  and spacer  33  can be held in place relative to the pressure tube  14  by the grooves  15 ,  17 . 
     The waveguide sensor  20  detects the position of the magnet  30  and the distance between the sensor  20  and the magnet  30 . The sensor  20  is connected to the rod  12 , and as the sensor  20  moves with the rod  12  the sensor  20  transmits a signal indicating the position of the rod  12  relative to the magnet  30 . The sensor  20  can detect the relative position of the rod  12  without contacting the rod  12  or magnet  30 . 
     As the rod  12  moves through extension and compression strokes, the magnetic field goes though the non-magnetic rod  12  and is detected by the sensor  20 . The sensor  20  detects the relative position of the magnet  30  and gives a corresponding output signal. The position is not lost during power interruptions or movement during non-powered situations. This can be helpful in medical, off-highway, agriculture, manufacturing, processing equipment, and automobile applications, and gas springs used in conjunction with linear actuators. 
     A computing device, such as an electronic control unit (hereinafter “ECU”) can be operatively connected to the position sensor  20 . The sensor  20  detects the position of the magnet  30  and provides this position data to the ECU which can determine the relative position of the pressure tube  14  and the rod  12 . During movement, the ECU can process this position data from the sensor  20  and convert it to velocity of extending or compressing to control the speed of extension/compression. The ECU can transmit this data to a receiving device that can speed up or slow down movement of the piston rod  12  in response to data transmitted by the sensor ECU. 
     According to an embodiment of the invention, the piston assembly  10  can be connected to a moveable part, such as a lid. The piston assembly  10  can be used to open, lift, lower and close the lid. The position sensor  20  can detect a relative distance to the magnet  30  and the time taken in moving the detected distance to calculate the velocity or change in velocity of the lid. This data can be transmitted to a receiving device that can speed up or slow down movement of the piston rod  12  in response to data transmitted by the sensor ECU. 
     The sensor  20  is contained within the sensor housing  22  and the magnet  30  is contained within the tube  14 , as shown in  FIG.  4   . As such, the sensor  20  and the magnet  30  are sealed off from the external environment and are protected from contamination by dust and other debris. 
     According to an embodiment of the invention, the piston assembly  10  can be utilized in a gas spring. An embodiment of the invention comprises an electric pallet jack comprising a gas spring comprising the piston assembly  10 . The pallet jack includes an arm that is used by the operator to steer the pallet jack. A gas spring comprising the piston assembly  10  is connected to the pallet jack arm and returns the arm to the fully upright position. The arm of the jack can be attached to the end fitting  31  of piston assembly  10 , and the sensor ECU can be operatively connected to the jack arm. The position sensor  20  detects the position of the jack arm. The position of the arm controls the speed and direction of the jack. The further the arm is pushed from neutral, the faster the pallet jack moves. The position sensor  20  can replace the position sensitive throttle switch that is used to vary the speed and direction of the pallet jack in prior art pallet jacks. 
     A piston assembly according to another embodiment of the invention is illustrated in  FIG.  2    and shown generally at reference numeral  10 ′. The assembly  10 ′ comprises the same structural features of the above-described piston assembly  10 , and also includes a mechanical spring  40  operatively connected to the rod  12 . The spring  40  can be connected to the rod  12  via mounting members, such as a pair of e-clips  41 ,  42 . The piston assembly  10 ′ can be used with a self-centering damping apparatus such as is described in International Publication No. WO2020/01853, which is incorporated herein by reference. According to an embodiment of the invention, the piston assembly  10 ′ can be used in a self-centering damper with a solar tracking device, such as the solar tracking devices described in U.S. Pat. Nos. 10,648,528 and 9,995,506, which are incorporated herein by reference. 
     According to an embodiment of the invention, the piston assembly  10 ′ can be used in devices in which a mechanical system or hydraulic system is being replaced by a drive-by-wire system, such as when a gas engine powered zero-turn riding (“ZTR” lawn mower is converted to an electrical motor driven device. The dampening force or output force can simulate the feel of the mechanical system. Other uses for the piston assembly  10 ′ include electrification for skid steer or agricultural equipment. 
     According to another embodiment of the invention, the piston assembly  10 ′ can be used with self-centering dampers in zero-turn riding (“ZTR”) lawn mowers having hydrostatic drive transmissions. An embodiment of the invention comprises an electric motor driven ZTR lawn mower comprising a pair of dampers, wherein each damper comprises the piston assembly  10 ′. Each damper is operatively connected to one of the steering levers of the mover to provide resistance to quick movements of the levers. The end fitting  31  of each damper can be attached to a lever of the mower. The ECU of the position sensor  20  is operatively connected to a drive motor of the mower. The piston rod  12  moves in unison with the steering lever. The position sensor  20  collects data regarding the position of the piston rod  12  and the steering lever. The sensor ECU uses the data to determine an optimum speed and direction to rotate the drive wheels and transmits optimum speed/direction instructions to the drive motor which rotates the drive wheels in accordance with the instructions. This helps the electric motor driven mower have the same feel as mowers having hydro static drive motors powered by internal combustion engines. 
     Piston assemblies and methods of using same are described above. Various changes can be made to the invention without departing from its scope. The above description of various embodiments of the invention are provided for the purpose of illustration only and not limitation-the invention being defined by the claims and equivalents thereof.