Abstract
This present invention utilizes a shape memory alloy (SMA) to improve on prior art in the design of clamps used for shut off, squeeze off, of plastic pipe which transmits gas or fluid under pressure. More particularly, but not exclusively, the present invention incorporates SMAs as actuators to simplify and improve clamp design for squeeze off of plastic pipe that is used in the transmission of pressurized gas and fluid. This invention may be deployed and operated remotely by the user. This present invention relates specifically to the application of trained SMA tubes, rods, bars, and beams as actuators for clamping and squeeze off of plastic pipe and tubing used to transmit gas or fluid.
Claims
1. A clamping device for applying a clamping force to a plastic pipe comprising: a shape memory alloy actuator actuated by repetitive thermal cycling to sequentially increase the clamping force on the plastic pipe with each cycle.
2. The clamping device of claim 1, wherein actuation of the actuator is achieved remotely by an operator who is not physically contacting the pipe.
3. The clamping device of claim 1 wherein the actuator undergoes a phase change during each thermal cycle.
4. The clamping device of claim 3 wherein the actuator changes between austenite and martensite phases.
5. The clamping device of claim 1 wherein the actuator changes crystalline structure during each thermal cycle.
6. The clamping device of claim 1 wherein the actuator rotates during each thermal cycle to increase the clamping force on the plastic pipe.
7. The clamping device of claim 6 further comprising a ratcheting mechanism to retain each rotational change of the actuator.
8. The clamping device of claim 1 wherein the actuator is heated to increase the clamping force.
9. The clamping device of claim 1 wherein the plastic pipe is a polyolefin pipe.
10. A method of clamping a polyolefin pipe, comprising: placing a shape memory alloy clamp on the pipe; repeatedly thermally cycling the clamp to produce rotational changes in the clamp; and each rotational change in the pipe increasing a clamping force on the pipe.
11. The method of claim 10 wherein the thermal cycling generates phase changes in the clamp.
12. The method of claim 11 wherein the phase changes are between austenite and martensite phases.
13. The method of claim 10 wherein thermal cycling generates a crystalline structural change in the clamp.
14. The method of claim 10 further comprising retaining each rotational change in the clamp without releasing the clamping force.
15. The method of claim 14 wherein the rotational change is retained by ratcheting pawls.
16. The method of claim 10 wherein the thermal cycles heat the clamp to increase the clamping force.
17. A clamping device of polyolefin pipe, comprising: a shape memory alloy clamp adapted to fit onto the pipe; the clamp being repeatedly rotationally tightened by thermal cycling to incrementally clamp the pipe to a closed condition.
18. The device of claim 17 further comprising ratcheting pawls to hold each rotation of the clamp.
19. The device of claim 17 the incremental clamping occurs by heating the clamp.
20. The device of claim 17 wherein the clamp changes phases between austenite and martensite during each thermal cycle.
Description
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
(1) The above-mentioned features of this invention, and the methods of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying figures, wherein:
(2) FIG. 1 is a flowchart of the function of the device of this invention.
(3) FIG. 2 is a flowchart of the training of an SMA element of the device of this invention.
(4) FIG. 3 illustrates a prior art mechanical clamping device.
(5) FIG. 4 illustrates an exploded view of one embodiment of the device of this invention.
(6) FIG. 5 illustrates the open configuration of this embodiment of the device of this invention.
(7) FIG. 6 illustrates the closed configuration of this embodiment of the device of this invention.
(8) FIG. 7 an expanded top view of a portion of this embodiment illustrating the interaction of the shape memory alloy (SMA) tube, the cylindrical element, and the threaded element.
(9) FIG. 8 illustrates a cross-sectional side view of the threaded elements of this embodiment which translate rotary torque from a trained shape memory alloy (SMA) tube ninety degrees to the upper clamp arm, creating a clamping action.
(10) FIG. 9 illustrates an exploded view of a second embodiment of the device of this invention which utilizes a multi-tube shape memory alloy (SMA) rotary motor to drive a clamping action.
(11) FIG. 10 illustrates the open configuration of a third embodiment of the device of this invention which utilizes shape memory alloy (SMA) elements as upper and lower clamp arms.
(12) FIG. 11 illustrates the closed configuration of the third embodiment of the device of this invention which utilizes shape memory alloy (SMA) elements as the upper and lower clamp arms.
DETAILED DESCRIPTION OF THE INVENTION
(13) FIG. 1 is a flowchart of the function of the device of this invention. The clamp is deployed on the exterior of a pressure pipe (100). The shape memory alloy (SMA) element is heated (101) and deforms to the trained austenite phase shape (102) as it approaches the austenitic shape set temperature (A.sub.s). A clamping motion is initiated (103) by the shape change. The SMA element cools and reverts to the martensite phase shape (104). The process is repeated (105), which is operational thermal cycling, until the desired amount of clamp closure is achieved (106). In the device of this invention, the proper operation of the device may require multiple operational thermal cycles. Operational thermal cycles for the invention of this device are driven by electrical direct or indirect current, induction, conduction, or convection but may be driven by any other means or process that creates sufficient temperature differential. Activation of the device of this invention may be accomplished at a distance from the device by use of a handle extension or remote trigger.
(14) FIG. 2 is a flowchart of the training for a shape memory alloy (SMA) element of the device of this invention. The SMA element is formed and then set to a desired shape (A.sub.s) at a high temperature (T.sub.s) (107). The SMA element is cooled and then mechanically deformed to a desired shape, M.sub.s (108). The SMA element is then placed under mechanical strain and heated to the austinite finish temperature, T.sub.af, which deforms the element to a trained austinite finish shape, A.sub.f (109). The SMA element is then cooled to the martensite finish temperature, T.sub.mf (110), causing it to revert to the M.sub.s shape (111). The thermal training cycle is repeated (112) until training of the SMA element is completed (113).
(15) FIG. 3 is an image of a prior art mechanical clamping device (U.S. Pat. No. 3,589,668A) for plastic pressure pipe which is in common use today. The clamp is positioned over a plastic pipe and secured. The clamp is then activated by a manual screwing motion, forcing the arms of the clamp to close on the pipe and squeeze off fluid flow through the pipe. Hydraulic versions of this and other types of clamp provide powered devices for today's clamp users.
(16) FIG. 4 illustrates an exploded view of the device of one embodiment of this invention. A handle (1) attaches to a basal clamp arm (2). A shape memory alloy (SMA) tube (3) is secured to the basal clamp arm near the handle. In some embodiments the SMA elements may be rods, bars and beams. A cylindrical element (4) with an inset of the surface near its top (5) fits over the SMA tube, attaches to the basal clamp arm, and provides support for a threaded element (6). The upper clamp arm (7) fits over the threaded element and the cylindrical element. The configuration is stabilized by small ridges on the lower inside of the upper clamp arm which match to grooves (8) on the surface of the cylindrical element. There may be securing, guiding, and stabilizing modifications to the handle and upper clamp arm.
(17) FIG. 5 illustrates the open configuration of this embodiment of the device of this invention. The upper clamp arm (7) has internal threads (9) which mate the external threads on the threaded element (6, FIG. 3). The cylindrical element (4) helps stabilize the SMA tube and upper clamp arm.
(18) FIG. 6 illustrates the closed configuration of this embodiment of the device of this invention. Rotation of the shape memory alloy (SMA) tube (3) as it approaches the austenite finish temperature (T.sub.af) causes the threaded element (6) to rotate, forcing the upper clamp arm (7) towards the basal clamp arm (2). To reach the desired amount of clamp closure the operational thermal cycle may need to be repeated.
(19) FIG. 7 an expanded top view of a portion of this embodiment illustrating the interaction of the shape memory alloy (SMA) tube (3), the cylindrical element (4), and the threaded element (6). The trained SMA tube (3) rotates when heated. The rotation of the SMA tube in one direction as it deforms to the austinite finish shape, A.sub.f, is captured by pawls (10) which are attached to the SMA tube and act against ratchet teeth (11) on the inside of the threaded element (6). Pawls (12) on the cylindrical element prevent it from rotating in the opposite direction as the SMA tube cools and reverts to its martensite state shape, M.sub.s. The operational thermal cycling is repeated until the desired amount of clamp closure is achieved.
(20) FIG. 8 illustrates a cross-sectional side view of the threaded element (6) of this embodiment which translates rotary torque supplied by a trained shape memory alloy (SMA) tube (3) ninety degrees to the upper clamp arm (7), causing motion of the upper clamp arm towards the basal clamp arm (2) and creating the clamping action for this embodiment of the device of this invention.
(21) FIG. 9 illustrates an exploded view of a second embodiment of the device of this invention which utilizes a multi-tube shape memory alloy rotary motor (13), based on U.S. Pat. No. 6,065,934A, to drive a clamping action. In this second embodiment of the device of this invention, the SMA rotary motor element may contain internal ratchet and screw mechanisms which translate the rotary motion ninety degrees to drive the clamping action.
(22) FIG. 10 illustrates the open configuration of a third embodiment of the device of this invention which utilizes shape memory alloy (SMA) elements as the upper (14) and lower (15) clamp arms. In some embodiments the clamp arms may have different cross-sections including tubes, rods, bars, and beams.
(23) FIG. 11 illustrates the closed configuration of the third embodiment of the device of this invention which utilizes shape memory alloy (SMA) elements as the upper (14) and lower (15) clamp arms. Activation and deformation of the SMA elements in FIG. 10, to the closed configuration shown here, is accomplished by operational thermal cycling. In some embodiments the clamp arms may have different cross-sections including tubes, rods, bars, and beams.
