Lift systems and lift devices having a locking assembly and methods of operating said lift systems and lift devices

Abstract

A lift device includes a cylinder (110, 210); a plunger (120) that is extendable and retractable relative to the cylinder (110, 210) to raise and lower a load (40); a locking nut (140, 240) in the cylinder (110, 210); and a drive mechanism (160) configured to rotate the locking nut (140, 240) relative to the plunger (120); wherein the locking nut (140, 240) is coupled to the plunger (120) so that rotation of the locking nut (140, 240) relative to the plunger (120) in a first direction causes the locking nut (140, 240) to extend relative to the plunger (120) and so that rotation of the locking nut (140, 240) relative to the plunger (120) in a second direction that is different than the first direction causes the locking nut (140, 240) to retract relative to the plunger (120). A lift system includes the lift device, an actuator that causes movement of the plunger in the cylinder, and a controller that controls the actuator to extend the plunger and controls the drive mechanism to rotate the locking nut and thereby move the locking nut relative to the plunger and the cylinder. Corresponding methods of operating the lift system are provided.

Description

LIFT SYSTEMS AND LIFT DEVICES HAVING A LOCKING ASSEMBLY AND METHODSOF OPERATING SAID LIFT SYSTEMS AND LIFT DEVICESCROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims benefit of priority to U.S. Provisional Application No. 63 / 638,535, filed April 25, 2024, which is hereby incorporated by reference in entirety.FIELD

[0002] The present disclosure relates to lift systems and lift devices of the type having a pistoncylinder assembly and an associated locking assembly, and to methods of operating said lift systems and lift devices.BACKGROUND

[0003] The following patents are incorporated herein by reference:

[0004] U.S. Pat. No. 9,568,029 discloses a hydraulic cylinder position sensing and locking system that automatically maintains the position of a lock nut that engages a plunger on a hydraulic actuator so that if hydraulic pressure is lost, the lock nut prevents retraction of the plunger into the hydraulic cylinder. The hydraulic cylinder position sensing and locking system also provides for a position sensing feature that allows for the calculation of the axial stroke position of the plunger based on rotary movement of the lock nut. A synchronous hydraulic cylinder position sensing and locking system and methods of using both the hydraulic cylinder position sensing and locking system are provided.

[0005] U.S. Pat. No. 10,173,872 discloses a lift system having a cylinder having an end surface, a threaded member supported for movement with a piston, and a nut threadedly engaging the threaded member and selectively engageable with the end surface. Engagement of the nut and the end surface limits axial movement of the piston relative to the cylinder in at least one direction. A drive mechanism rotates the nut relative to the threaded member, and a control valve controls movement of the piston relative to the cylinder. A drive control mechanism controls operation of the drive mechanism and rotation of the nut. A nut sensor senses a portion of the nut. The nut sensor is in communication with at least one of the control valve and the drive control mechanism.When the nut sensor detects a portion of the nut, the control valve stops movement of the piston or the drive control mechanism stops rotation of the nut.SUMMARY

[0006] This Summary is provided to introduce a selection of concepts that are further described below in the Detailed Description. This Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

[0007] In non-limiting embodiments, a lift device comprises a cylinder; a plunger that is extendable and retractable relative to the cylinder to raise and lower a load; a locking nut in the cylinder; and a drive mechanism configured to rotate the locking nut relative to the plunger; wherein the locking nut is coupled to the plunger so that rotation of the locking nut relative to the plunger in a first direction causes the locking nut to extend relative to the plunger and so that rotation of the locking nut relative to the plunger in a second direction that is different than the first direction causes the locking nut to retract relative to the plunger.

[0008] In embodiments, at least a portion of the locking nut is located in the plunger, the locking nut is coupled to the plunger by a threaded connection, and / or the locking nut includes an elongated nut body having a first nut portion operatively coupled to the drive mechanism so that the drive mechanism can rotate the first nut portion, and a second nut portion operably coupled to the plunger via a threaded connection. The second nut portion may include a head, wherein the threaded connection includes radially outer threads on the head and radially inner threads on the plunger.

[0009] In embodiments, the locking nut is operatively coupled to the drive mechanism so that rotation of the drive mechanism causes rotation of the locking nut, and further so that the locking nut is moveable relative to the drive mechanism when the plunger is caused to move in the cylinder.

[0010] In embodiments, the drive mechanism is located in the cylinder. The drive mechanism may comprise a motor having an output axis that is coaxial with the cylinder. The motor may be located in a base of the cylinder.

[0011] In embodiments, the drive mechanism is coupled to the locking nut via a male-female coupling that rotationally locks the drive mechanism to the locking nut and permits movement of the locking nut relative to the drive mechanism.

[0012] Embodiments of the lift device further comprise a sensor configured to sense a current position of the locking nut relative to the cylinder. Embodiments further comprise a sensor configured to sense a current rotational position of at least one of the locking nut and the drive mechanism. Embodiments further comprise a sensor configured to sense a current stroke position of the plunger relative to the cylinder.

[0013] In embodiments, the locking nut is a tilting locking nut configured to tilt relative to the cylinder during support of an unbalanced load. The tilting locking nut may comprise a first nut portion operably engaged with the drive mechanism and a second nut portion operably engaged with the plunger via a threaded connection, wherein the second nut portion is configured to rotate with the first nut portion and is also pivotable relative to the first nut portion upon support of the unbalanced load. The lift device may further include a spring that biases the second nut portion into alignment with the first nut portion.

[0014] In embodiments, the lift device further comprises an anti-rotation device configured to limit relative rotation of the plunger relative to the cylinder, the anti-rotation device including a piston-cylinder having a first portion coupled to the plunger and a second portion coupled to the cylinder so that extension and retraction of the plunger relative to the cylinder causes extension and retraction of the piston-cylinder.

[0015] In embodiments, a lift system comprises an embodiment of the lift device described herein above, an actuator configured to cause movement of the plunger in the cylinder, and a controller configured to control the actuator to extend the plunger relative to the cylinder and further configured to control the drive mechanism to rotate the locking nut and thereby move the locking nut relative to the plunger and cylinder. The controller may be configured to rotate the locking nut to maintain the locking nut within a predetermined distance of a base of the cylinder during movement of the plunger relative to the cylinder.

[0016] In embodiments, at least one sensor is configured to sense a current position of the locking nut relative to the cylinder, wherein the controller is configured to control the drive mechanism according to the current position sensed by the sensor to maintain the locking nut within the predetermined distance of the base of the cylinder. The controller may be configured to rotate the locking nut to move the locking nut into a locked position once the plunger is moved to a desired position. The lift system may be configured such that in the locked position the locking nut is supported on the base of the cylinder. The locking nut may be coupled to the plunger by athreaded connection, wherein upon a request to retract the plunger relative to the cylinder, the controller is configured to initially extend the plunger outwardly relative to the cylinder to reduce friction within the threaded connection, thus facilitating subsequent rotation of the locking nut by the drive mechanism during subsequent retraction of the plunger inwardly relative to the cylinder.

[0017] In embodiments, at least one sensor is configured to sense a current stroke position of the plunger relative to the cylinder, wherein the controller is configured to control the actuator to limit movement of the plunger to a predetermined positional range. The controller may be configured to control the actuator to limit movement of the plunger to a predetermined position below a fully extended position of the plunger. The actuator may include at least one of a hydraulic pump, a pneumatic pump, and a motor.

[0018] In non-limiting embodiments a method is for operating the embodiments of the lift system described herein above. The method comprises actuating the actuator to cause movement of the plunger relative to the cylinder, and controlling the drive mechanism to rotate the locking nut and thereby move the locking nut relative to the plunger and cylinder. The method may comprise simultaneously actuating the actuator and controlling the drive mechanism. The method may comprise controlling the drive mechanism to oppositely rotate the locking nut to move the locking nut into a position relative to the cylinder once the plunger is moved into a desired position. The method may comprise further controlling the actuator to initially extend the plunger outwardly relative to the cylinder to reduce friction within a threaded connection, thus facilitating subsequent rotation of the locking nut by the drive mechanism during subsequent retraction of the plunger inwardly relative to the cylinder.

[0019] Various features, objects and advantages of the disclosure will be made apparent from the following description taken together with the drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present disclosure includes the following drawing figures.

[0021] FIG. 1 is a perspective view of an embodiment of a jack-up device including a lift system and a lift device according to the present disclosure.

[0022] FIG. 2 is an exploded perspective view of the lift device of FIG. 1.

[0023] FIG. 3 is a view of section 3-3, taken in FIG. 1.

[0024] FIG. 4 is a view of detailed section 4-4, taken in FIG. 3, showing a plunger of the lift device in a retracted position.

[0025] FIG. 5 is a view of detailed section 5-5, taken in FIG. 3.

[0026] FIG. 6 is a view of section 3-3, taken in FIG. 1, showing the plunger in an extended position and a locking arrangement of the lift device in a locked position.

[0027] FIG. 7 is a view of detailed section 7-7, taken in FIG. 6.

[0028] FIG. 8 is a view of section 3-3, taken in FIG. 1, showing the plunger in an extended position and the locking arrangement in a locked position.

[0029] FIG. 9 is a view of detailed section 9-9, taken in FIG. 8.

[0030] FIG. 10 is a view like FIG. 3 showing an alternate embodiment of the lift system and lift device.

[0031] FIG. 11 is an exploded perspective view of a tilting locking nut of the lift device of FIG. 10.

[0032] FIG. 12 is a sectional view showing the tilting locking nut carrying a balanced load.

[0033] FIG. 13 is a sectional view showing the tilting locking nut carrying an unbalanced load.DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The above-incorporated U.S. patents provide examples of conventional lift systems that include lift devices having a piston-cylinder assembly that is extendable and retractable to raise and lower a load. The lift devices include a locking arrangement configured to lock the pistoncylinder assembly in position, thereby preventing the assembly from unexpectedly retracting and dropping the load.

[0035] During research and development, the present inventors determined that it would be desirable to provide improved lift systems and devices that are more compact, more robust, less complex, and less prone to failure. The present inventors also determined that it would be desirable to provide improved methods of operating said lift systems and devices. The present disclosure is a result of these efforts.

[0036] Referring to FIGS. 1-9, the present disclosure provides embodiments of novel lift systems 100 and associated lift devices 101 having locking arrangements. FIG. 1 shows an embodiment that is incorporated into an exemplary a jack-up device 50; however, this is only shown by way of example. The lift systems 100 and lift devices 101 provided in the presentdisclosure may be configured for use with a variety of devices other than jack-up devices and / or for use as stand-alone systems and devices.

[0037] Referring to FIG. 1, the illustrated jack-up device 50 is configured to lift and lower large and / or heavy loads, for example building materials, structures, heavy machinery, rail cars, and / or other items. The jack-up device 50 is elongated from front to real’ in a longitudinal direction LO, from side to side in a lateral direction LA that is perpendicular to the longitudinal direction LO, and from top to bottom in an axial direction AX that is perpendicular to the longitudinal direction LO and perpendicular to the lateral direction LA. The jack-up device 50 has a frame 52 that supports the lift system 100 and associated lift device 101. The lift device 101 is supported on a front portion 58 of the frame 52, for example on a rigid base plate 60 that provides a surface against which the lift device 101 can push to lift the load 40. Wheels 54 and a handlebar 56 (partially shown in FIG. 6) are provided for maneuvering the jack-up device 50 and particularly to position the lift device 101 beneath the load 40 to be lifted. Lights 62 are mounted in cover plates 64 on opposing lateral sides of the lift device 101 and are configured to illuminate the lift device 101 and the load 40.

[0038] Referring to FIGS. 2 and 3, the lift device 101 includes a piston-cylinder assembly 102 having an axially-elongated cylinder 110 and a plunger 120 that is located in and axially extendable and retractable relative to the cylinder 110 to raise and lower the load 40. The lift device 101 has a novel locking arrangement including a locking nut 140 and a drive mechanism 160 for operating the locking nut 140. In the illustrated embodiment, the drive mechanism 160 is located in the cylinder 110; however, in other embodiments the drive mechanism 160 is located outside of the cylinder 110. As further described below, the drive mechanism 160 is configured to rotate the locking nut 140 relative to the plunger 120 and to selectively adjust and set the axial position of the locking nut 140 relative to the plunger 120, and in some instances to lock the position of the plunger 120 relative to the cylinder 110. A load cap 106 is positioned on an upper end of the plunger 120 for supporting the load 40. The lift device 101 also includes an anti-rotation device 104 configured to limit rotation of the plunger 120 relative to the cylinder 110.

[0039] The lift system 100 includes an input device 72 configured so that a user can operate the lift system 100 to raise and lower the load 40. In the illustrated embodiment, the input device 72 is embodied in a control panel on the rear of the jack-up device 50. The type and configuration of the input device 72 may vary widely from what is shown and described. The input device 72may be any conventional device for inputting commands to a lift system and / or for displaying or otherwise communicating characteristics of the lift system 100 to the user. The input device 72 may be located on the jack-up device 50 or remotely from the jack-up device 50. Non-limiting embodiments of suitable input devices include any type of conventional handheld wireless communication device(s), touchscreen(s), button(s), switch(es), and / or the like. As further described below, by operating the input device 72, the user can command the lift system 100 to cause the plunger 120 to extend from the cylinder 110 along an extension axis 80 (FIG. 1) defined by the piston-cylinder assembly 102, thereby raising the load 40. By operating the input device 72, the user can also command the lift system 100 cause the plunger 120 to retract into the cylinder 110 along the extension axis 80, thereby lowering the load 40.

[0040] The lift system 100 includes an actuator 70 configured to cause extension and retraction of the plunger 120 relative to the cylinder 110. In a non-limiting embodiment, the actuator 70 is a hydraulic pump powered by an electric motor (not shown). The hydraulic pump is configured to pump hydraulic fluid into and out of hydraulic inlet and outlet ports 76 in the cylinder 110 via hydraulic lines 74. Some embodiments, however, may be configured with a different type of actuator. For example, the actuator may include a pneumatic pump, a hydro pneumatic pump, an electric pump, a hybrid-electric motor, a combustion engine, and / or any other conventional device for causing movement of the plunger 120 in the cylinder 110. In the illustrated embodiment, the actuator 70 is located on the jack-up device 50; however, other embodiments the actuator is located apart from the jack-up device 50.

[0041] Referring to FIGS. 2 and 3, the cylinder 110 includes a first cylinder portion 112 forming a lower end of the cylinder 110 and a second cylinder portion 114 that is opposite the first cylinder portion 112 and extends upwardly therefrom. The first cylinder portion 112 provides a base for supporting the cylinder 110 on a supporting surface (e.g., the rigid base plate 60 and / or another location on the frame 52 of the jack-up device 50). An axial bore 116 configured to slidably receive the plunger 120 is formed in the cylinder 110 and extends through the second cylinder portion 114 and into the first cylinder portion 112. In the second cylinder portion 114, the axial bore 116 extends from an upper end 117 of the second cylinder portion 114 to an internal flange 119 formed around the lower end 115 of the second cylinder portion 114. The internal flange 119 defines a fully retracted position of the plunger 120. The axial bore 116 continues pastthe internal flange 1 19, into the first cylinder portion 112, and to a bottom end of the axial bore 116 formed by a cylinder base 118 of the first cylinder portion 112.

[0042] The plunger 120 includes a rod 124 that extends from an upper end 121 of the plunger 120 to a piston 126 at the lower end 122 thereof. An axial bore 128 is formed through the rod 124 and extends between respective top and bottom openings at the upper and lower ends 121, 122 of the plunger 120. Radially inner helical threads 129 are formed along the axial length of the axial bore 128 through the plunger 120 and are mated with radially outer helical threads 147 on the locking nut 140 to form a threaded connection therebetween, the purpose of which will be further discussed below. A plunger cap 131 is received in the upper portion of the axial bore 128, thereby sealing the axial bore 128 at the upper end 121 of the plunger 120. Plunger cap 131 does not necessarily seal the bore.

[0043] The plunger 120 is axially slidable back and forth in the cylinder 110. A seal is formed between a radially outer surface of the piston 126 and the radially inner surface of the axial bore 116 in the second cylinder portion 114. Some embodiments may be configured with at least one seal member (e.g., an O-ring) for forming a seal between the plunger 120 and the cylinder 110. A support collar 130 is received in the axial bore 116 proximate the upper end 117 of the second cylinder portion 114 and supports the rod 124 of the plunger 120 by resisting side loads as the plunger 120 extends and retracts from the cylinder 110 along the extension axis 80. The support collar 130 additionally forms a seal between the radially outer surface of the rod 124 and the radially inner surface of the axial bore 116, thereby sealing the cylinder 110 against the plunger 120. Some embodiments may be configured with at least one seal member (e.g., an O-ring) for forming a seal between the support collar 130 and the plunger 120 and / or between support collar 130 and the cylinder 110 (see, e.g., FIG. 4). The support collar 130 additionally functions as a stop ring which defines a fully extended position on the plunger 120. Hydraulic ports 76 formed through the second cylinder portion 114 allow hydraulic fluid to be pumped by the noted hydraulic pump of the actuator 70 into or out of the cylinder 110 above and below the piston 126 to create the pressure differential required to extend or retract the plunger 120 from the cylinder 110. This provides a dual-acting piston-cylinder arrangement of the type that is conventional and thus not further described in detail.

[0044] Referring to FIGS. 2-4, the load cap 106 of the lift device 101 is positioned on the upper end 121 of the plunger 120 and configured to support a load 40 thereon (FIGS. 6 and 8). The loadcap 106 includes a stem 107 and a resilient pad 108. The stem 107 extends downward from the resilient pad 108 and is coupled to the upper end 121 of the plunger 120 via the plunger cap 131. The resilient pad 108 is seated on the stem 107 of the load cap 106 and includes an outer face having protrusions and / or recesses configured to provide slip resistance between the lift device 101 and a load 40 supported thereon. The illustrated embodiment of the load cap 106 is not intended to be limiting and other embodiments can include a differently configured load cap or device for supporting a load 40 on the plunger 120.

[0045] Referring to FIGS. 2-5, the locking nut 140 of the lift device 101 is located in the cylinder 110 and extends at least partially into the plunger 120. The locking nut 140 has an elongated nut body that extends upwardly from a first nut portion 142 located in the first cylinder portion 112 to a second nut portion 144, which is located in the second cylinder portion 114 closer to the upper end 117 of the second cylinder portion 114 than to the first cylinder portion 112. At the upper end of the locking nut 140, the second nut portion 144 includes a head 146 with radially outer helical threads 147 formed around the perimeter of the head 146. The radially outer helical threads 147 correspond to and are configured to mate with the radially inner helical threads 129 on the plunger 120, thereby coupling the locking nut 140 to the plunger 120 via the noted threaded connection. Due to the orientations of the radially inner helical threads 129 on the plunger 120 and the radially outer helical threads 147 on the locking nut 140, rotation of the locking nut 140 relative to the plunger 120 causes the locking nut 140 to axially move in the plunger 120. A shaft 143 of the locking nut 140 extends downwardly from the head 146, through the axial bore 128 in the plunger 120, past the internal flange 119 on the second cylinder portion 114, and to a lower end 148 of the locking nut 140 in the first cylinder portion 112. Proximate the lower end 148, the first nut portion 142 includes a plurality of axial splines 149 that operatively connects the locking nut 140 to the drive mechanism 160. Operative engagement between the axial splines 149, 167 allows the drive mechanism 160 to rotate the locking nut 140 while simultaneously permitting axial movement of the locking nut 140 relative to the drive mechanism 160. When the lower end 148 abuts the cylinder base 118 of the first cylinder portion 112, the weight of the plunger 120 and any load 40 supported thereon is securely supported on the cylinder base 118 and the supporting surface for the cylinder 110, as further described below. Any other suitable type of male-female coupling in addition to or instead of splines could be employed for rotationally locking the drive mechanism 160 and the locking nut 140 together while permitting axial movement of the lockingnut 140 relative to the drive mechanism 160. An alternate embodiment is described below regarding FIG. 10. The plunger 120 and locking nut 140 arc prevented from moving axially downward relative to the cylinder 110 when the lower end 148 is engaged with the cylinder base 118.

[0046] Referring to FIGS. 2, 3, and 5, the drive mechanism 160 is operatively coupled to the locking nut 140 so that operation of the drive mechanism 160 rotates the locking nut 140 about an output axis 80. In the illustrated embodiment, the drive mechanism 160 is located in the cylinder 110, and mostly in the first cylinder portion 112. This is useful, for example, so that no additional space is needed for the drive mechanism 160 outside of the existing footprint of the piston-cylinder assembly 102. This is not intended to be limiting and in other embodiments the drive mechanism 160 is located outside of (z.e., external to) the cylinder 110. In the illustrated embodiment, the output axis 80 of the drive mechanism 160 is coaxial with the extension axis 80 along which the plunger 120 is extended and retracted from the cylinder 110. Thus, the output axis 80 of the drive mechanism 160 and the extension axis 80 of the piston-cylinder assembly 102 are the same.

[0047] Referring to FIGS. 2 and 5, the drive mechanism 160 includes an electric motor having a stator 162 and a rotor 164 configured to rotate the locking nut 140 in a first direction or second direction about the output axis 80. This is not intended to be limiting, and other types of motor arrangements could be utilized instead of what is shown and described. For example the motor could include a pneumatic motor. In the illustrated embodiment, the stator 162 is secured to the first cylinder portion 112 by a press-fit connection so that the rotational position of the stator 162 remains fixed relative to the first cylinder portion 112. The rotor 164 is operatively coupled to the lower end 148 of the locking nut 140 by a spline receiver 166, which is press-fit in the rotor 164. The spline receiver 166 has a generally cylindrical body having a through-bore that extends axially through the body and receives the first nut portion 142 of the locking nut 140 therein. Internal axial splines 167 extend axially along the radially inner surface of the through-bore in the spline receiver 166. Thus, the output axis 80 of the drive mechanism 160 is coaxial with the locking nut 140. The axial splines 149 on the first nut portion 142 of the locking nut 140 correspond to, and a e configured to mate with, the internal axial splines 167 on the spline receiver 166, thereby operatively coupling the spline receiver 166 to the first cylinder portion 112. Engagement between the axial splines 149, 167 of the locking nut 140 and the spline receiver 166 prevents rotation of the locking nut 140 relative to the drive mechanism 160 while permitting axial movement of thelocking nut 140 relative to the cylinder 1 10. In some embodiments, at least one bearing 168 is located in the first cylinder portion 112 to rotatably support the spline receiver 166 therein. The drive mechanism 160 is configured to rotate the locking nut 140 in either a first direction (e. ., the direction indicated by arrows 86 in FIGS. 6 and 7) or a second direction that is opposite the first direction. Due to the threaded connection, rotation of the locking nut 140 in the first or second direction causes the locking nut 140 to move axially relative to the plunger 120, as further discussed below.

[0048] Referring to FIGS. 2 and 3, the locking nut 140 is supported in the axial bore 128 of the plunger 120 by a sleeve 150. The sleeve 150 has a generally cylindrical body that extends axially from an upper end 151 to a lower end 152. A through-bore 154 extends through the body of the sleeve 150 and is configured to receive the shaft 143 of the locking nut 140. When the pistoncylinder assembly 102 is in an assembled state (FIG. 3) the sleeve 150 is received in the second cylinder portion 114 and extends from its lower end 152 proximate the internal flange 119 of the second cylinder portion 114 to its upper end 151 proximate the head 146 of the locking nut 140. Referring to FIGS. 4 and 5, inner annular bearing members 156 extend around the shaft 143 of the locking nut 140 and limit metal-to-metal contact between the radially outer surface of the shaft 143 and the radially inner surface of the through-bore 154 of the sleeve 150. Annular seal members 157 (e.g., O-rings) form seals between the second cylinder portion 114 and the plunger 120. Referring to FIG. 5, annular seal members 157 are positioned proximate the lower end 152 of the sleeve 150 and extend around the body of the sleeve 150 and form a seal between the sleeve 150 and the internal flange 119 of the second cylinder portion 114, and a seal between the sleeve 150 and the radially inner surface of the axial bore 128 through the plunger 120 proximate the piston 126 at the lower end 122 thereof. Advantageously, the sleeve 150 separates spaces in the axial bore 116 in the first cylinder portion 112, in the axial bore 116 in the second cylinder portion 114, and in the axial bore 128 of the plunger 120.

[0049] Referring to FIGS. 1, 2, and 6, the lift system 100 includes the anti-rotation device 104 configured to limit or prevent relative rotation of the plunger 120 relative to the cylinder 110 as the locking nut 140 is rotated by the drive mechanism 160. The type and configuration of antirotation device 104 may vary from what is shown and described. In the illustrated embodiment, the anti-rotation device 104 includes a piston-cylinder assembly 190 with a first portion 191 coupled to the plunger 120 and a second portion 192 coupled to the cylinder 110. The secondportion 192 is supported on the body of the second cylinder portion 1 14 via standoffs 197. The first portion 191 is slidably received in the second portion 192 and is extendable and retractable therefrom along an extension axis 80 (FIG. 3) that is parallel to the extension axis 80 of the pistoncylinder assembly 102. A connecting arm 194 extends between the plunger 120 and the first portion 191, thereby fixing the axial position of the first portion 191 relative to the axial position of the plunger 120. The connecting arm 194 includes a first opening 195 and a second opening 196 (FIG. 2) for securing the connecting arm 194 to the plunger 120 and anti-rotation device 104, respectively. The first opening 195 is engaged by the stem 107 of the load cap 106 to couple the connecting arm 194 to the upper end 121 of the plunger 120 via the plunger cap 131, and the second opening 196 is coupled to the upper end of the first portion 191 of the anti-rotation pistoncylinder assembly 190, for example via a mechanical fastener. The connecting arm 194 rigidly connects the plunger 120 and the first portion 191 of the anti-rotation device 104 so that that extension and retraction of the plunger 120 relative to the cylinder 110 causes extension and retraction of the first portion 191 of the anti-rotation piston-cylinder 190.

[0050] Referring to FIG. 3, the lift system 100 also includes a controller 78 and at least one sensor 172, 174, 198 configured to sense an axial position of the locking nut 140 relative to the cylinder 110, a rotational position the drive mechanism 160, and / or an axial stroke position of the plunger 120, and to communicate the sensed information to the controller 78. As further described below, controller 78 in turn is programmed to control the other components of the lift system 100, including for example the actuator 70, the drive mechanism 160, and optionally the input device 72, based upon the sensed information.

[0051] The controller 78 has a processor and a memory and is communicatively coupled via one or more wired and / or wireless links to various other system components including but not limited to the input device 72; the actuator 70; the sensors 172, 174, 198; and the drive mechanism 160. All of these links are not shown in the drawings but will be understood by one having ordinary skill in the art. The processor is configured to access the memory and operate programming to control the lift system 100 according to the explanations herein. The controller 78 may be located with the lift device 101 or may be located remotely therefrom. In the non-limiting embodiment shown, the controller 78 is configured to receive inputs from and / or monitor characteristics of at least the input device 72 and sensors 172, 174, 198, and to output control signals to the input device 72, the drive mechanism 160 and the actuator 70. As described below, the controller 78 isconfigured to operate the drive mechanism 160 to cause the electric motor to rotate the locking nut 140 relative to the plunger 120 and thus cause axial movement of the locking nut 140 relative to the plunger 120, via the threaded connection, including but not limited to as the plunger 120 is moved in the cylinder 110, and to selectively rotate the plunger 120 to effectively lock the plunger 120 in its position relative to the cylinder 110. These functionalities will be further described below.

[0052] Referring to FIGS. 2 and 5, a nut sensor 172 is configured to sense an axial position of the locking nut 140 relative to the cylinder 110. The axial position refers to the linear distance between the bottom of the locking nut 140 and the cylinder base 118 of the first cylinder portion 112. The type, location and configuration of the nut sensor 172 may vary from what is shown and described. A suitable embodiment is the inductive sensor BAW000U, commercially available for purchase from Balluff. Another suitable example is the proximity sensor DW-AX519-M18-3XO, commercially available for purchase from Contrinex. In the illustrated example, the nut sensor 172 is located in an opening 173 formed in the first cylinder portion 112 and extends upwardly, past the cylinder base 118, and into the axial bore 116 in the first cylinder portion 112. The upper end of the nut sensor 172 is configured to be received in a corresponding hole 145 in the lower end of the locking nut 140. The nut sensor 172 is configured to sense the axial distance between the bottom of the locking nut 140 and the cylinder base 118 of the first cylinder portion 112, which as further described below allows the controller 78 to actively control rotation of the locking nut 140 relative to the cylinder 110 based on the sensed axial distance to thereby actively control the length of the gap 90 (see FIG. 7) between the bottom of the locking nut 140 and the cylinder base 118 of the first cylinder portion 112.

[0053] An optional rotary sensor 174 is configured to sense a position of the drive mechanism 160 and the locking nut 140 relative to the cylinder 110. The type, location, and configuration of the rotary sensor 174 may vary from what is shown and described. A suitable embodiment is the incremental rotary magnetic encoder LM13, commercially available for purchase from RLS. In the illustrated example, the rotary sensor 174 is located in the first cylinder portion 112 and above the drive mechanism 160. The rotary sensor 174 is configured to sense the relative rotational position of the first nut portion 142 of the locking nut 140 to the drive mechanism 160. This informs the lift system 100 regarding the rotational position of the drive mechanism 160. Based on this information, the controller 78 is able to control the direction and rotation of the drivemechanism 160 with more accuracy to accomplish finer control of the position of the locking nut 140. The rotary sensor 174 is configured to provide more resolution per revolution of the position of the first nut portion 142. The revolution of the first nut portion 142 is directly related to the gap 90 of the lock nut 142 and the cylinder base 118 based on the pitch of the threads 147. The rotary sensor 174 can be used with any motor type, such as electric, pneumatic, and hydraulic, and / or the like. Thus, there is some redundancy provided by rotary sensor 174 in view of the data already provided by the nut sensor 172; however, optionally including the rotary sensor 174 provides improved quality of the sensed data used by the controller 78.

[0054] As mentioned above, the nut sensor 172 and the rotary sensor 174 are each communicatively connected to the controller 78 (FIGS. 3, 6, and 8), which is communicatively connected to the actuator 70 and the drive mechanism 160. The nut sensor 172 and rotary sensor 174 may be communicatively connected to the controller 78 via one or more wired and / or wireless links.

[0055] A stroke sensor 198 is located on the anti-rotation device 104 and configured to sense the position of the first portion 191 of the anti-rotation piston-cylinder 190 relative to the second portion 192 of the anti-rotation piston-cylinder 190. The type, configuration and location of the stroke sensor 198 may vary from what is shown and described. A suitable embodiment is magnetostrictive (contactless) linear transducer WRP-A / WRA-A, commercially available for purchase from Gefran. The stroke sensor 198 is communicatively connected to the controller 78 via one or more wired and / or wireless links. As explained above, the first portion 191 of the antirotation piston-cylinder 190 extends and retracts with the plunger 120. The stroke sensor 198 is coupled to the second portion of the piston-cylinder assembly 190 and is configured to sense movement of a magnet coupled to the first portion 191 of the piston-cylinder assembly 190. The controller 78 is configured to correlate the movement sensed by the stroke sensor 198 to the movement of the plunger 120 in the cylinder 110 and also to determine whether the plunger 120 is near its end of stroke in the cylinder 110. In particular, based upon the movement sensed by the stroke sensor 198, the controller 78 is configured to automatically control the actuator 70 to limit the axial stroke (movement) of the plunger 120 within stroke limit thresholds that are stored in the memory. For example, the memory of the controller 78 may store an upper stroke position threshold and a lower stroke position threshold. By monitoring the location sensed by the stroke sensor 198 and comparing it to the upper and lower stroke thresholds, the controller 78 isconfigured to automatically control operation of the actuator 70 to prevent movement of the plunger 120 past the upper or lower position thresholds. In a non-limiting embodiment, as described below, the controller 78 is configured to prevent movement of the plunger 120 past another position limit located just short of the upper position threshold, thus permitting a subsequent raising of the plunger 120 towards the upper position threshold during an unlocking procedure that is described below.

[0056] Referring to FIGS. 6 and 7, in use, once the lift system 100 has been moved into position below the load 40 to be lifted, and based on an input from the user to the input device 72, the controller 78 is programmed to control the actuator 70 to pump hydraulic fluid through the hydraulic lines 74 of the hydraulic circuit (for example in the direction of arrows 77 in FIG. 6), thereby increasing the pressure in the cylinder 110 below the piston 126 and causing the plunger 120 to extend from the cylinder 110 (for example in the direction of arrow 85 in FIG. 6). As discussed above, based on the movement of the plunger 120 sensed by the stroke sensor 198, the controller 78 may be configured to limit movement of the plunger 120 within stored upper and lower stroke thresholds. As the plunger 120 is extended further out of the upper end 117 of the second cylinder portion 114, the threaded connection between the radially inner helical threads 129 on the plunger 120 and the radially outer helical threads 147 on the locking nut 140 tends to pull the locking nut 140 axially upwardly in the cylinder 110 along with the plunger 120. That is, raising the plunger 120 in the cylinder 110 tends to also raise the locking nut 140 in the cylinder 110 and thereby create or lengthen the above noted gap 90 (see FIG. 7) between the first nut portion 142 of the locking nut 140 and the cylinder base 118 of the first cylinder portion 112.

[0057] As the locking nut 140 moves with the plunger 120, engagement between the axial splines 149 on the first nut portion 142 and the internal axial splines 167 of the spline receiver 166 keeps the first nut portion 142 in rotational engagement with the drive mechanism 160. Thus, even as the locking nut 140 is axially moved relative to the drive mechanism 160, the drive mechanism 160 remains capable of rotating the locking nut 140 relative to the plunger 120 via the splines 166, 167.

[0058] Referring to FIGS. 6 and 7, the nut sensor 172 is configured to sense changes in the length of the noted gap 90 as the locking nut 140 is axially moved with the plunger 120 relative to the cylinder base 118. Based on the changes sensed by the nut sensor 172, the controller 78 is configured to automatically control the drive mechanism 160 to rotate the locking nut 140 tomaintain the length of the gap 90 (i.e., the position of the first nut portion 142 relative to the first cylinder portion 112) within a predetermined positional range stored in the memory. An example of such a stored positional range is between 3 mm and 5 mm; however, this is just an example and is not intended to be limiting. The predetermined positional range may vary and may include a smaller or larger positional range. For example, as the plunger 120 is raised in the cylinder 110, the length of the gap 90 sensed by the nut sensor 172 will increase. As the plunger 120 is moved upwardly in the cylinder 110, the nut sensor 172 communicates changes in the sensed axial length of the gap 90 to the controller 78. In response, the controller 78 is configured to operate the drive mechanism 160 to rotate the locking nut 140 to move the locking nut 140 axially downwardly relative to the upwardly moving plunger 120 the amount necessary to maintain the axial length of the gap 90 within the predetermined positional range stored in the memory. Conversely, as the plunger 120 is lowered in the cylinder 110, the length of the gap 90 sensed by the nut sensor 172 will decrease. As the plunger 120 is moved downwardly, the nut sensor 172 communicates changes in the sensed axial length of the gap 90 to the controller 78. In response, the controller 78 is configured to operate the drive mechanism 160 to rotate the locking nut 140 to move the locking nut axially upwardly relative to the downwardly moving plunger 120 an amount necessary to maintain the axial length of the gap 90 within the predetermined positional range stored in the memory.

[0059] Thus, based on how the sensed axial length of the gap 90 compares to the stored positional range, the controller 78 is programmed to automatically control the drive mechanism 160 to rotate the locking nut 140 to move the locking nut 140 to maintain the gap 90 within the stored positional range. When the user instructs the controller 78 to raise the load, rotation of the locking nut 140 in the first direction, i.e., the direction indicated by arrow 86 in FIGS. 6 and 7, will cause the locking nut 140 to move axially downwardly relative to the plunger 120. This will normally be implemented by the controller 78 as the plunger 120 is moved upwardly in (i.e., extended from) the cylinder 110. Conversely, when the user instructs the controller to lower the load, rotation of the locking nut 140 in the second direction opposite the first direction 86 will cause the locking nut 140 to move axially upwardly relative to the plunger 120. This will normally be implemented by the controller 78 as the plunger 120 is moved downwardly in (i.e., retracted into) the cylinder 110.

[0060] By actively maintaining the position of the locking nut 140 within the stored positional range relative to the first cylinder portion 112, the controller 78 advantageously ensures that the locking nut 140 remains in a position that limits the overall distance the plunger 120 would fall in the event of a failure of the actuator 70 or other failure of the lift system 100. That is, the maximum distance that the plunger 120 and associated load would accidentally fall in the event of a failure is advantageously continuously limited by the controller 78 to no more than the stored positional range, which as mentioned above can be a small distance (e.g., 3-5 mm) programmed into the memory during calibration or otherwise during set up of the lift system 100. This advantageously provides an improved load system 100 and load device 101 configured to prevent the load 40 from unexpectedly dropping a load in a potentially unsafe manner.

[0061] During the above-described process, the controller 78 may also be programmed to maintain the position of the plunger 120 within the noted acceptable stroke length, as defined by the upper and lower stroke thresholds stored in the memory, all as described herein above. This advantageously prevents overstroke of the plunger 120, which could otherwise result in damage to the lift device 101.

[0062] In an embodiment of the above-described method, the controller 78 can also be programmed to ensure the plunger 120 does not reach an upper stroke length, at which it may be difficult or impossible to further raise the plunger 120 during unlocking of the locking nut 140, as further described herein below. Based upon the stroke length sensed by the stroke sensor 198, the controller 78 according to this embodiment is programmed to control the actuator 70 to stop upward movement of the plunger 120 within a stored distance or stroke percentage of the stored upper stroke length. This permits a subsequent slight raising of the plunger 120 during an unlocking process further described below.

[0063] Once the plunger 140 has been extended to a selected position for supporting the load 40, the controller 78 may be configured to control the drive mechanism 160 to move the locking nut 140 into a locked position. This can be done automatically according to programming of the controller 78 and / or based upon a user input to the input device 72. According to this embodiment, referring to FIGS. 8 and 9, once the load 40 is at the desired height, the controller 78 is configured to control the actuator 70 to stop extending the plunger 120 and also to control the drive mechanism 160 to rotate the locking nut 140 in the first direction indicated by arrow 86, which thereby moves the locking nut 140 axially downwardly in the cylinder 110, in the directionof arrow 88 in FIG. 9, i.e.., axially outwardly relative to the plunger 120. The controller 78 can be programmed to continue operating the drive mechanism 160 to rotate the locking nut 140 until the locking nut 140 reaches a locked position in which the lower end 148 of the locking nut 140 abuts the cylinder base 118, as illustrated in FIG. 9. The controller 78 can be configured to determine that the locking nut 140 is in the locked position and thus stop the drive mechanism 160 from rotating the locking nut 140 when the nut sensor 172 senses that the length of the gap 90 has reduced to zero. With the locking nut 140 is in the locked position, the forces applied by the plunger 120 and the load 40 to the locking nut 140 are effectively transferred to the cylinder base 118 via the locking nut 140, thereby relieving the forces that are otherwise applied to the actuator 70 during movement of the plunger 120. This provides a significantly improved and robust locking arrangement wherein in the locked position the load is securely supported by the supporting surface under the lift device 101 without unnecessary transfer of the weight of the load 40 to other components of the lift system 100, including but not limited to the actuator 70, which may otherwise be subject to wear and failure.

[0064] In non-limiting embodiments, to retract the plunger 120 and lower the supported load 40, the actuator 70 may be controlled by the controller 78 raise the plunger 120 only a small amount necessary to slightly separate the first nut portion 142 of the locking nut 140 from the cylinder base 118 of the first cylinder portion 112. Slightly separating or just barely disengaging the lower end 148 of the locking nut 140 from the cylinder base 118 advantageously unlocks the locking nut 140 and alleviates forces on the locking nut 140 that would otherwise create friction between the radially inner helical threads 129 on the plunger 120 and the radially outer helical threads 147. This enables easier rotation of the locking nut 140 by the drive mechanism 160. After the locking nut 140 has been unlocked or separated from the cylinder base 118 by the small amount, as the actuator 70 is controlled to lower the plunger 120, the controller 78 is configured to control the drive mechanism 160 to rotate the locking nut 140 in the second direction (e.g., in a direction opposite the direction indicated by arrows 86 in FIGS. 6-9) to move the locking nut 140 axially upwardly relative to the plunger 120. During the retraction process, the drive mechanism 160 the controller 78 may be programmed to continue to continuously maintain the position of the locking nut 140 relative to the cylinder base 118 within the stored positional range, as described herein above, so that the gap 90 remains within the stored positional range, thus affording the safety benefits described herein above in case of a system failure.

[0065] It is also contemplated that in non-limiting embodiments the lift system 100 is operable in a variety of different user modes. In one non-limiting embodiment of a manual mode, the lift system 100 is configured so that the user can actively control the input device 101 to control the amount of extension and / or retraction of the plunger 120. For example, the lift system 100 may be configured so that the user can operate the input device 72 to select either an extension or a retraction of the plunger 120, and then press and hold down a button or a switch on the input device 101 to cause the controller 78 to initiate and continue the requested extension or retraction. The user then releases the button or switch to cause the controller 78 to stop the extension / retraction. In this embodiment, the controller 78 may be configured to control the input device 72 to indicate to the user that the plunger 120 is locked, as described above. If the plunger 120 is locked and the user requests a retraction of the plunger 120, the controller 78 may be configured to automatically operate the drive mechanism 160 to rotate the locking nut 140 and unlock the plunger 120 prior to operating the actuator 70 to retract the plunger 120. The controller 78 may also be configured to automatically operate the drive mechanism to rotate the locking nut 140 and lock the plunger 120 after the actuator 70 releases the button or switch to have the controller 78 stop movement of the plunger 120.

[0066] It is also contemplated that the lift system 100 may be operable in a non-limiting example of an automatic mode according to which the operator operates the input device 72 to select a change in lift position or for example a percentage change in lift position from a current lift position sensed by the stroke sensor 198. In this embodiment, the controller 78 may be configured to first determine whether the change selected by the user is within an admissible stroke position range determined by the upper and lower stroke thresholds stored in the memory. If it is, the controller 78 is programmed to automatically control the actuator 70 to move the plunger 120 and control the drive mechanism 160 to rotate the locking nut 140, all as described above. Similar to the manual mode described above, according to this embodiment the controller 78 may be configured to automatically lock the plunger 120 via the locking arrangement after movement of the plunger 120 is complete, as sensed by the stroke sensor 198. If it is not, the controller 78 may be configured to control the input device 72 to alert the user of the error.

[0067] Thus, novel lift systems 100 and lift devices 101 according to the present disclosure advantageously provide a compact locking arrangement that may be configured to fit entirely within the footprint of a lifting piston-cylinder assembly 102. This may be useful, for example, sothat the lift system 100 and / or lift device 101 can be used in confined spaces and on small, maneuverable jack-up devices 50 and / or other devices. The illustrated lift device 101 additionally allows the locking arrangement to operate simultaneously with the extension of the plunger 120 from the cylinder 110 so that the plunger 120 is infinitely and continuously adjustable and lockable in any position relative to the cylinder 110. The lift system 100 and lift device 101 advantageously incorporate an improved locking assembly providing the efficiency and safety functionalities described herein above.

[0068] Through continued research and development in the relevant field, the present inventors also determined that, in some embodiments of a lift device 101, the plunger 120 may potentially become misaligned with the extension axis 80 defined by the piston-cylinder assembly 102. For example, the plunger 120 may become tilted relative to the extension axis 80 when a load 40 is not centered on the load cap 106 so that the net force from the load 40 is not applied directly along or parallel to the extension axis 80.

[0069] As the plunger 120 is tilted out of alignment, lateral forces from the misalignment may cause the head 146 of the locking nut 140 to be pressed radially outwardly against the radially inner surface of the axial bore 128, thus increasing the friction between the locking nut 140 and the plunger 120, thereby problematically increasing the torque required to turn the locking nut 140. The present inventors found that this issue may be exacerbated when the plunger 120 is significantly extended from the piston-cylinder assembly 102 (e.g., when the plunger 120 is at or near the fully extended position). The present inventors thus have realized a need to provide an improved lift system having a locking arrangement that can continue to operate even when the plunger 120 is tilted out of alignment with the piston-cylinder assembly 102.

[0070] FIG. 10 illustrates an embodiment of a lift device 201 including a piston-cylinder assembly 202 that is configured for use with a lift system (e.g., the lift system 100 of FIG. 1) and includes a tilting locking nut 240 that enables operation of the lift device 101 even while the plunger 120 is misaligned relative to the extension axis 80 defined by the axial bore 116 of the piston-cylinder assembly 202. This may be useful, for example, to allow extension and retraction of the plunger 120 during support of an unbalanced load. Similar to the piston-cylinder assembly 102 of FIG. 1, the piston-cylinder assembly 202 includes an axially elongated cylinder 210, a plunger 120 that is axially movable in the cylinder 210 to extend from or retract therefrom, and a locking arrangement (including the tilting locking nut 240) configured to selectively lock the axialposition of the plunger 120. Using one or more of the noted sensors 172, 174, 198 to measure the positions and / or movements of the plunger 120 and the tilting locking nut 240, the drive mechanism 160 (which may be the same or different than the drive mechanism 160 of FIGS. 1-9) can be controlled by the controller 78 to actively adjust the axial position of the tilting locking nut 240 so that the plunger 120 is infinitely and continuously adjusted and locked in a desired position for supporting the load 40.

[0071] The elongated cylinder 210 of the piston-cylinder assembly 202 includes a first cylinder portion 212 forming the lower end of the cylinder 210 and a second cylinder portion 214 forming the upper end of the cylinder 210. The first cylinder portion 212 includes a cylinder base 218 and a body portion 220 extending upwardly from the cylinder base 218. A cylinder bore 216 axially extends through the elongated cylinder 210 from the cylinder base 218 to an opposite upper end 217 of the cylinder 210. The plunger 120 includes a rod 124 and a piston 126 and is slidably received in the cylinder bore 216. A support collar 130 supports the rod 124 in the cylinder bore 216, and a plunger cap 131 at the upper end of the plunger 120 is configured to support the load 40 (either directly on the plunger cap 131 or via a load cap 106 or another load supporting device). Axial movement of the plunger 120 along the extension axis 80 is limited by a cylinder flange 219 and the support collar 130, which are configured to abut the piston 126 in the fully retracted and fully extended positions, respectively.

[0072] With continued reference to FIG. 10, the tilting locking nut 240 is located in the axial bore 128 of the plunger 120 and is supported therein by the sleeve 150. The tilting locking nut 240 includes a shaft portion 243 that extends upwardly from a first nut portion 242 located in the first cylinder portion 212 to a second nut portion 244 positioned proximate the upper end 217 of the cylinder 210. The first nut portion 242 is engaged with the drive mechanism (which may be the same or different than the drive mechanism 160 of FIGS. 1-9) configured to selectively rotate the tilting locking nut 240 about the extension axis 80. The second nut portion 244 includes external threads 251 that are engaged with inner helical threads 129 on the plunger 120. Thus, rotation of the tilting locking nut 240 drives the extension and retraction of the plunger 120 from the elongated cylinder, as previously discussed in reference to FIGS. 1-9. For example, using at least one of the sensors 172, 174 positioned in the first cylinder portion, the actuator 70 and the drive mechanism can be controlled (e.g., by controller 78) to extend or retract the plunger 120 while maintaining aposition of the first nut portion 242 relative to the first cylinder portion 212 within a positional range relative to the first cylinder portion 212.

[0073] In the embodiments of FIGS. 1-9, the first nut portion 142 is operably coupled to the drive mechanism 160 by a plurality of axial splines 149 and a corresponding spline receiver 166. Some embodiments, however, may be differently configured. For example, in the embodiment of FIG. 10, the first nut portion 242 includes a different type of male-female connection including two grooves 249 formed on opposite sides of the shaft portion 243 and a corresponding receiver 269, which engages the grooves 249 and rotationally couples the drive mechanism to the tilting locking nut 240. The receiver 269 is rotationally supported by a bearing 168, which is integrated with the first cylinder portion 212 in the illustrated embodiments.

[0074] To facilitate extension and retraction of the plunger 120 while the plunger 120 is not aligned with the extension axis 80, the locking nut 240 includes a convex lower end 260 and a tilt head 250 coupled to an opposite convex upper end 262 of the shaft portion 243. The convex lower end 260 is supported on the cylinder base 218 by a support member 270. As illustrated in FIG. 10, the support member 270 has a curved support surface 272 with a concave profile that corresponds to the curvature of the convex lower end 260, thereby supporting the shaft portion 243 thereon. Advantageously, the curved profiles of the curved support surface 272 and the convex lower end 260 are configured to transfer the weight of a load 40 supported on the plunger 120 into the cylinder base 218 via the locking nut 240 while the plunger 120 is misaligned with the extension axis 80. The curved interface between the curved upper surface 272 and the convex lower end 260 provides an increased area of contact compared to flat surfaces, thus enhancing stability, and provides easier manufacturability and operability of the respective parts, admitting some tilting and not marking one part against the other.

[0075] Referring to FIGS. 11 and 12, the tilt head 250 includes a tilt head body 253 that is movably coupled to the convex upper end 262 of the shaft portion 243 by a tilt connector 252 that allows the tilt head 250 to move and / or pivot relative to the extension axis 80 and the convex upper end 262. The tilt head body 253 is generally cylindrical and includes external threads 251 formed on a radially outer surface thereof. The external threads 251 on the tilt head body 253 are engaged with the inner helical threads 129 of the plunger 120 so that rotation of the locking nut 240 causes the plunger to extend or retract along the extension axis 80, as previously described above.

[0076] The tilt head body 253 includes a joint cavity 255 (shown in dashed lines in FIG. 11 ) configured to receive the shaft portion 243 formed into a lower axial surface and an upper bore 265 configured the receive the tilt connector 252 formed in an opposite upper axial surface of the tilt head body 253. The joint cavity 255 has a generally hemispherical shape with a concave mounting surface 264 with curvature that corresponds to the curvature of the convex upper end 262 of the shaft portion 243. When assembled, the tilt head 250 is seated on the shaft portion 243 with the convex upper end 262 received in the joint cavity 255 (FIG. 12). Opposing keyway slots 256 formed into diametrically opposite sides of the concave mounting surface 264 are configured to receive corresponding key members 254 positioned on the convex upper end 262 of the shaft portion 243. Each key member 254 is positioned in a corresponding slot 292 formed into the convex upper end 262 and includes a key body 290 and a fastener 291 that secures the key body 290 to the shaft portion 243. Engagement between the key members 254 and the keyway slots 256 rotationally couples the tilt head 250 to the shaft portion 243 so that the tilt head 250 rotates with the shaft portion 243. However, the keyway slots 256 is dimensioned to be slightly wider and deeper than the key members 254, thereby providing clearance between the keyway slots 256 and the key members 254 that allows the tilt head 250 to tilt relative to the shaft portion 243 while being rotationally coupled thereto.

[0077] With continued reference to FIGS. 11 and 12, the tilt connector 252 includes a centering ring 296 and a coil spring 294 that are received in the upper bore 265, and a fastener 295 that extends through the upper bore 265 to engage an opening 289 extending axially into the convex upper end 262 of the shaft portion 243. The centering ring 296 has a generally tubular body 297 that receives a portion of the fastener 295 and a flange 298 formed around an upper end of the body 297. The body 297 of the centering ring 296 extends through the center of the coil spring 294 and the flange 298 retains the spring in the upper bore 265. In some embodiments, the flange 298 may compress the coil spring 294 between the centering ring 296 and the tilt head body 253.

[0078] As previously mentioned, the tilt connector 252 allows the tilt head 250 to tilt (pivot) relative to the shaft portion 243 to accommodate a misalignment between an extended plunger 120 and the extension axis 80 due to a load 40 being unevenly supported thereon. This may be useful, for example, to prevent binding between the inner helical threads 129 of the plunger 120 and the external threads 251 of the locking nut 240, thereby enabling extension and retraction of the plunger 120 while the plunger 120 is not in axial alignment with the extension axis 80.Referringto FIG. 12, the tilt connector 252 retains the tilt head 250 on the shaft portion 243 of the locking nut 240 without applying a biasing force thereto while the plunger 120 is aligned with the extension axis 80. However, as the plunger 120 is extended from the piston-cylinder assembly 202, the weight of the load 40 supported thereon may cause the plunger 120 to tilt slightly out of alignment with the extension axis.

[0079] Referring to FIGS. 10 and 13, for example, the weight of an unbalanced load 40 on the plunger 120 (e.g., a load with a net force acting along force vector 303 in FIG. 10) may cause the plunger 120 to tilt out of alignment with the axis of extension 80. As the plunger 120 is tilted, the sleeve 150 (an / or other various supporting components) prevents the locking nut 240 from tilting with the plunger 120 and the external threads 251 on the tilt head body 253 are pressed against the inner helical threads 129 foimed in the axial bore 128 of the plunger 120, increasing the friction force therebetween. However, the tilt connector 252 advantageously allows the tilt head 250 to pivot relative to the shaft portion 243 to maintain alignment with the axial bore 128 of the plunger 120. Tilting / pivoting movement of the plunger 120 causes tilt head 250 to slide along the convex upper end 262 of the shaft portion 243 (e.g., in the direction of arrow 300 in FIG. 13). Due to the matching curved geometries of the convex upper end 262 and the concave mounting surface 264, sliding movement of the tilt head 250 along the convex upper end 262 causes the tilt head 250 to pivot about a pivot axis 83 ((e.g., in the direction of arrow 301 in FIG. 13) out of alignment with the extension axis 80 and into alignment with a plunger axis 81 defined by the axial bore 128 through the plunger 120.

[0080] Realigning the tilt head 250 with the plunger axis 81 reduces the friction between the inner and external helical threads 129, 251 of the locking nut 240 and plunger 120. Thus, the binding force between the locking nut 240 and the plunger 120 is reduced, thereby reducing the force needed to rotate the locking nut 240 to enable continued operation of the lift system 100. While the tilt head 250 is in a tilted position (FIG. 13), the tilt connector 252 is configured to bias the tilt head body 253 back into alignment with the extension axis 80. In the illustrated embodiments, the coil spring 294 is partially compressed between the centering ring 296 and the tilt head body 253 as the tilt head 250 pivots on the shaft portion 243. As a result, the coil spring 294 generates a force that acts between the centering ring 296 and the tilt head body 253 to bias the tilt head 250 back into alignment with the extension axis 80.

[0081] As used herein, unless otherwise limited or defined, discussion of particular directions is provided by example only, with regard to particular embodiments or relevant illustrations. For example, discussion of “top,” “bottom,” “front,” “rear,” “left,” “right,” “horizontal,” “vertical,” and “longitudinal” features and / or relative motion, e.g., movement “up” and “down,” is generally intended as a description only of the orientation of such features relative to a reference frame of a particular embodiment or illustration. Correspondingly, for example, a “top” feature may sometimes be located below a “bottom” feature (and so on), in some arrangements or embodiments. Additionally or alternatively, embodiments may be arranged in a different orientation so that “top” and “bottom” features are arranged horizontally relative to each other, for example in a “left-to-right” orientation. Additionally, use of the words “first,” “second,” “third,” etc. is not intended to connote priority, importance, etc., but merely to distinguish one of several similar elements from another.

[0082] This written description uses embodiments to disclose the invention and to enable any person skilled in the art to make and use the invention. Certain terms have been used for brevity, clarity and understanding. No unnecessary limitations are to be inferred therefrom beyond the requirement of the prior ait because such terms are used for descriptive purposes only and are intended to be broadly construed. The patentable scope of the invention is defined by the claims, and may include other embodiments that occur to those skilled in the art. Such other embodiments are intended to be within the scope of the claims if they have features or structural elements that do not differ from the literal language of the claims, or if they include equivalent features or structural elements with insubstantial differences from the literal languages of the claims.

Claims

CLAIMSWhat is claimed is:

1. A lift device comprising: a cylinder; a plunger that is extendable and retractable relative to the cylinder to raise and lower a load; a locking nut in the cylinder; and a drive mechanism configured to rotate the locking nut relative to the plunger; wherein the locking nut is coupled to the plunger so that rotation of the locking nut relative to the plunger in a first direction causes the locking nut to extend relative to the plunger and so that rotation of the locking nut relative to the plunger in a second direction that is different than the first direction causes the locking nut to retract relative to the plunger.

2. The lift device according to claim 1, wherein at least a portion of the locking nut is located in the plunger.

3. The lift device according to claim 1, wherein the locking nut is coupled to the plunger by a threaded connection.

4. The lift device according to claim 1, wherein the locking nut includes an elongated nut body having a first nut portion operatively coupled to the drive mechanism so that the drive mechanism can rotate the first nut portion, and a second nut portion operably coupled to the plunger via a threaded connection.

5. The lift device according to claim 4, wherein the second nut portion includes a head, and wherein the threaded connection includes radially outer threads on the head and radially inner threads on the plunger.

6. The lift device according to claim 1, wherein the locking nut is operatively coupled to the drive mechanism so that rotation of the drive mechanism causes rotation of the locking nut, and further so that the locking nut is moveable relative to the drive mechanism when the plunger is caused to move in the cylinder.

7. The lift device according to claim 1, wherein the drive mechanism is located in the cylinder.

8. The lift device according to claim 1, wherein the drive mechanism comprises a motor having an output axis that is coaxial with the cylinder.

9. The lift device according to claim 8, wherein the motor is located in a base of the cylinder.

10. The lift device according to claim 1, wherein the drive mechanism is coupled to the locking nut via a male-female coupling that rotationally locks the drive mechanism to the locking nut and permits movement of the locking nut relative to the drive mechanism.

11. The lift device according to claim 1, further comprising a sensor configured to sense a current position of the locking nut relative to the cylinder.

12. The lift device according to claim 1, further comprising a sensor configured to sense a current rotational position of at least one of the locking nut and the drive mechanism.

13. The lift device according to claim 1, further comprising a sensor configured to sense a current stroke position of the plunger relative to the cylinder.

14. The lift device according to claim 1, wherein the locking nut is a tilting locking nut configured to tilt relative to the cylinder during support of an unbalanced load.

15. The lift device according to claim 14, wherein the tilting locking nut comprises a first nut portion operably engaged with the drive mechanism and a second nut portion operably engaged with the plunger via a threaded connection, wherein the second nut portion is configured to rotate with the first nut portion and is also pivotable relative to the first nut portion upon support of the unbalanced load.

16. The lift device according to claim 15, further including a spring that biases the second nut portion into alignment with the first nut portion.

17. The lift device according to claim 1, further comprising an anti-rotation device configured to limit relative rotation of the plunger relative to the cylinder, the anti-rotation device including a piston-cylinder having a first portion coupled to the plunger and a second portion coupled to the cylinder so that extension and retraction of the plunger relative to the cylinder causes extension and retraction of the piston-cylinder.

18. A lift system comprising: the lift device according to any of the preceding claims; an actuator configured to cause movement of the plunger in the cylinder, and a controller configured to control the actuator to extend the plunger relative to the cylinder and further configured to control the drive mechanism to rotate the locking nut and thereby move the locking nut relative to the plunger and the cylinder.

19. The lift system according to claim 18, wherein the controller is configured to rotate the locking nut to maintain the locking nut within a predetermined distance of a base of the cylinder during movement of the plunger relative to the cylinder.

20. The lift system according to claim 19, further comprising at least one sensor configured to sense a current position of the locking nut relative to the cylinder, and wherein the controller is configured to control the drive mechanism according to the current position sensed by the sensor to maintain the locking nut within the predetermined distance of the base of the cylinder.

21. The lift system according to claim 18, wherein the controller is configured to rotate the locking nut to move the locking nut into a locked position once the plunger is moved to a desired position.

22. The lift system according to claim 21, wherein in the locked position the locking nut is supported on the cylinder.

23. The lift system according to claim 22, wherein the locking nut is coupled to the plunger by a threaded connection, and wherein upon a request to retract the plunger relative to the cylinder, the controller is configured to initially extend the plunger outwardly relative to the cylinder to reduce friction within the threaded connection, thus facilitating subsequent rotation of the locking nut by the drive mechanism during subsequent retraction of the plunger inwardly relative to the cylinder.

24. The lift system according to claim 18, further comprising at least one sensor configured to sense a current stroke position of the plunger relative to the cylinder, wherein the controller is configured to control the actuator to limit movement of the plunger to a predetermined positional range.

25. The lift system according to claim 24, wherein the controller is configured to control the actuator to limit movement of the plunger to a predetermined position below a fully extended position of the plunger.

26. The lift system according to claim 18, wherein the actuator includes at least one of a hydraulic pump, a pneumatic pump, and a motor.

27. A method of operating the lift system according to claims 18-26, the method comprising actuating the actuator to cause movement of the plunger relative to the cylinder, and controlling the drive mechanism to rotate the locking nut and thereby move the locking nut relative to the plunger and the cylinder.

28. The method according to claim 27, comprising simultaneously actuating the actuator and controlling the drive mechanism.

29. The method according to claim 27, comprising controlling the drive mechanism to oppositely rotate the locking nut to move the locking nut into a position relative to the cylinder once the plunger is moved into a desired position.

30. The method according to claim 29, wherein the locking nut is coupled to the plunger by a threaded connection, and comprising further controlling the actuator to initially extend the plunger outwardly relative to the cylinder to reduce friction within the threaded connection, thus facilitating subsequent rotation of the locking nut by the drive mechanism during subsequent retraction of the plunger inwardly relative to the cylinder.

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