Strain-amplifying compression mechanism

Abstract

The compression device includes a pair of compression mechanisms incorporating shape memory alloy (SMA) wires configured to provide compression to a human limb or torso, the compression mechanisms being arranged in an overlapping manner to provide a strain capacity of the compression device that is greater than the applied strain capacity of the pair of compression mechanisms.

Description

[Technical Field]

[0001] References and Priority Claims to Related Applications This application claims priority to U.S. Provisional Application No. 63 / 481,811, filed January 27, 2023, the entire disclosure of which is incorporated herein by reference. [Background technology]

[0002] The present disclosure relates to a compression device for applying compression to a human body part, such as for relieving muscle pain, restricting movement, or preventing deep vein thrombosis. Applicant's issued U.S. Patent Nos. 9,326,911, 10,441,491, 10,426,202, 10,791,772, and 10,918,561 disclose devices for applying compression to a body part. These devices rely on wires that change length when an electric current is applied to the wire, i.e., shape memory metal (SMA) wires. SMA wires have inherent physical limitations on the amount of length change they can achieve, more specifically, their strain (change in length divided by their original length) capabilities. Some SMA wires can achieve 8% strain at maximum operating power. The applied compression depends on the overall length of the SMA wires in the compression engine and their strain capabilities. For example, a 12-inch wire encircling a user's arm reduces its length by 0.72 inches for a 6% strain capacity, while a 6-inch wire incorporated into a wrap around the user's arm reduces its length by only 0.36 inches, which may be insufficient compression. In certain compression protocols, the amount of compression required may exceed the strain capacity of the SMA wire or the mechanism incorporating the SMA wire. Several complex wire configurations can be provided to effectively increase the length-changing effect relative to the fixed length-changing capacity of certain types of SMA wire. However, these configurations typically require longer wires and larger mechanisms to achieve the desired overall length change and, therefore, the desired amount of compression. Summary of the Invention

[0003] What is needed is a compression mechanism assembly that can achieve a greater change in length, and therefore greater compression, than prior devices. [Brief explanation of the drawings]

[0004] [Figure 1]FIG. 1 is a top view of a compression mechanism according to the present disclosure, the mechanism being shown in an unactuated state; [Figure 2] FIG. 2 is a top view of the compression mechanism shown in FIG. 1, the mechanism being shown in an actuated state. [Figure 3] FIG. 2 is a side view of the compression mechanism shown in FIG. [Figure 4A] FIG. 4 is an enlarged view of region 4A of FIG. 3. [Figure 4B] FIG. 4 is an enlarged view of region 4B of FIG. 3. [Figure 5] FIG. 4C is a perspective view of a compression device adapted to be worn on a user's leg and incorporating the compression mechanism of FIGS. 1-4B. [Figure 6] 10 is a graph of system strain related to overlap distance for the compression mechanism of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0005] For the purposes of promoting an understanding of the principles of the disclosure, reference will be made to the embodiments illustrated in the drawings and described in the following specification. It will be understood that no limitations on the scope of the disclosure are thereby intended. It will be further understood that the disclosure includes any changes and modifications to the illustrated embodiments and includes further applications of the principles disclosed herein as would normally occur to one skilled in the art to which the disclosure pertains.

[0006] The compression mechanism 10 disclosed herein uses one or more wires formed from a phase-change material that changes length when driven by an electric current. In one example, the material is a shape-memory alloy (SMA) such as Nitinol or Flexinol®. The SMA wires are incorporated into a compression device, such as a strap or wrap, configured to encircle a person's limb or torso. Details of such compression devices are described in Applicant's issued Patent Nos. 9,326,911, 10,441,491, 10,426,202, 10,791,772, and 10,918,561, the disclosures of which are incorporated herein by reference. The SMA wires are connected to the ends of the straps, particularly to a board or circuit board that connects the SMA wires to a power source, preferably via a controller that controls the current applied to the wires.

[0007] As shown in FIGS. 1-4 , compression mechanism 10 includes two mechanisms 11 and 21 that overlap one another to provide additional strain or a reduction in the length of the compression mechanism, and ultimately a reduction in the length of the strap tightened to the user. First mechanism 11 includes one or more SMA wires 14 fastened to end substrates 12, 13 at opposite ends of flexible panel 15. Similarly, second mechanism 21 includes one or more SMA wires 24 fastened to end substrates 22, 23 at opposite ends of flexible panel 25. It can be appreciated that one of the end substrates of each mechanism, e.g., substrate 12 / 22 or substrate 13 / 23, may include control circuitry 45 configured to interface with a power source and a control module configured to control the compression mechanism. A suitable interface is as disclosed in the above-incorporated U.S. Pat. No. 10,441,491, i.e., interfaces (703, 716), along with a suitable control module, such as control module (715) of compression assembly (702) shown in FIGS. 31-33, the figures and associated description of which are specifically incorporated herein by reference. The control circuitry 45 of the compression mechanism 10 can include electrical wires, such as wires (703), that can be connected to interface wires (716), which are connected directly to the control module (715). The control module can include a microcontroller for controlling the actuation of the SMA wires according to a predetermined compression protocol, such as the microcontroller (24) described in column 7, line 18 to column 9, line 3 of U.S. Pat. No. 10,441,491, the description of which is incorporated herein by reference.

[0008] One end of each of the SMA wires 14, 24 is connected to a corresponding one of the substrates 12, 22. Opposite end substrates, i.e., substrates 13 and 23, secure the opposite ends of each SMA wire 14, 24. The opposite end substrates 13, 23 are then attached to straps or panels that encircle a person's limb or body. For example, the compression device or garment 50 can take the form of a flexible panel 51 configured to encircle a person's leg. A series of closures 52 can be provided to adjustably pretension the leg panel 51. A series of compression mechanisms 10 can be attached to the panel 51 between the mating ends of each fastener 52. Alternatively, the end substrates 13, 23 can be interconnected or connectable, in which case the flexible panels 15, 25 would need to be long enough so that their combined length enables the compression mechanism to encircle a person's limb or body.

[0009] In one embodiment, end boards 12, 22 can be designed as control boards 12, 22 for the associated mechanisms 11, 21. The control boards 12, 22 are not directly connected to one another in series or end-to-end. Instead, mechanisms 11, 21 overlap one another, with each control board 12, 22 fastened to a respective pair of relatively rigid plates 31, 32, as best seen in FIGS. 3-4. End boards 13 and 23 form the free ends of compression mechanism 10, which can engage with one another to surround a user's body part or can be integrated into a compression device, such as device 50 shown in FIG. 5.

[0010] The two rigid plates 31, 32 to which each one of the control boards 12, 22 is connected can be substantially rigid so as to lie flat during use, depending on the particular application of the compression mechanism 10, such as applying compression to a human torso. However, in many applications, a certain amount of curvature is required for the compression mechanism to fit comfortably around a human limb or body. In this case, the plates 31, 32 are more rigid than the flexible panels 15, 25 while retaining sufficient flexibility to bend as needed to conform to the patient's body. In this case, the plates 31, 32 can be formed from a nylon or HDPE material. Alternatively, the plates 31, 32 can be formed with a curvature calibrated to fit the limb or body part around which the compression device is attached. The two plates 31, 32 have a length less than the overall length of the compression mechanism 10, preferably about half the overall length.

[0011] The two mechanisms are sandwiched between two plates 31 and 32. The first mechanism 11 is fastened to the upper plate 31. In particular, the control board 12 is fastened to one end of the top plate 31 by a rivet 35 or other suitable fastener. In the illustrated embodiment, one head 35a of the rivet 35 engages the plate 31 as shown in FIG. 2, and the opposite head 35b engages the underside of the control board 12 as shown in FIG. 4A, securing the control board to the top plate 31. A similar structure is applied to the opposite end 32b of the bottom plate 32, and a rivet 36 fastens the second mechanism 22 to the bottom plate 32 as shown in FIG. 4B. It can be seen that the head 36b of the rivet 36 shown in FIG. 2 is below the top plate 31. The heads of the rivets 35, 36 need not be affixed to the surface of their respective plates or boards. Alternatively, the rivet may be a compression rivet where the two halves are compressed together to clamp the plate and substrate together.

[0012] The control boards 12, 22 of the two mechanisms 11, 21 are fastened to their respective top and bottom plates 31, 32, as seen in FIGS. 1-2, with the remaining lengths of the two mechanisms 11, 21 passing in both directions between the two plates. The top and bottom plates 31, 32 are fastened to one another so that they are offset by a width sufficient to allow the flexible panels 15, 25 to pass between the two plates. In one embodiment, the plates are connected at their opposite ends 31a, 32a by fasteners such as rivets 38, with one head 38a of the rivet engaging or securing to the top plate and the opposite head 38b engaging or securing to the bottom plate, as shown in FIG. 4. A post 38c connecting the two heads 38a, 38b defines the spacing between the two plates. 1-2, two rivets 38 span the flexible panels 15, 25 of the two mechanisms 11, 21, and in particular the flexible panel 25 can slide freely longitudinally between the two rivet posts 38c. The heads of the rivets 38 can be fixed or glued to the respective plates, or the rivet posts may include a step that engages the surface of the plate opposite the rivet head in a compression fit that clamps the plate between the step and the rivet head.

[0013] The opposite ends 31b, 32b of the plates are also connected by rivets 39, as shown in FIG. 2, which span the flexible panels 15, 25, specifically allowing the flexible panel 15 to slide freely longitudinally between the posts of the two rivets 39. The rivet heads 39b can be secured to the bottom plate as described above for the rivets 38. However, unlike the rivets 38, the rivet heads 39a of each rivet 39 are not secured to the top plate 31 like the rivet heads 38a. Instead, the end 31b of the top plate 31 defines a pair of slots 40 on either side of the plate's width, through which each rivet 39 extends. Thus, the rivet heads 39a can slide relative to the top plate 31. The slots allow the two plates 31, 32 to flex when the compression mechanism 10 is engaged with a person's body, specifically when the compression mechanism and associated straps are wrapped around a person's limbs. In this case, the top plate 31 bends around a larger circumference than the bottom plate 32. This slot allows the rivet to move as needed to accommodate the differential bending circumference of the two plates. A similar slot can be provided on the opposite end 31a of the top plate 32, but is not required.

[0014] It is envisioned that in addition to the rivets 38, 39 described above, an additional set of rivets 38′, 39′ may be provided to join the top and bottom plates 31, 32. Similarly, in addition to the rivets 35, 36 described above, an additional set of rivets 35′, 36′ may be provided to join the flexible panels 15, 25 to the respective top and bottom plates 31, 32.

[0015] A comparison of Figures 1 and 2 illustrates the function of the compression mechanism of the present disclosure. The mechanism is shown in its unactuated or quiescent state, with no current applied to the SMA wires 14, 24 of the compression mechanism. In that state, the two overlapping mechanisms 11, 21 have a total length L sys1. The amount of overlap between the two mechanisms corresponds to the distance D0 between the rivets 35 and 36 that secure the mechanisms to the respective top and bottom plates. When each mechanism 11, 21 is actuated, it reduces the length of the respective SMA wire 14, 24 by a distance S1. When both mechanisms 11, 21 are actuated, the sum of the reductions in the length of the SMA wires 14, 24 is the dimension S in FIG. 2, which can be considered the stroke of the compression mechanism 10. sys Stroke S sys It will be appreciated that is the sum of the strokes of mechanisms 11, 21, i.e., distance S1. However, it will be appreciated that the stroke of each mechanism need not be the same. In either case, the overall stroke of compression mechanism 10 will be equal to the sum of the strokes of the two mechanisms. It will be appreciated that the overlapping arrangement of two mechanisms 11, 21 reduces the footprint of compression mechanism 10 relative to a single mechanism with a comparable system stroke. While a device with a comparable stroke would need to be much longer than compression mechanism 10, it is understood that to achieve the same stroke, either the length of the SMA wire would need to be much longer or the two mechanisms would need to be engaged in series.

[0016] The design of compression mechanism 10 can be expressed in a series of equations relating the lengths and strokes of the components of mechanism 10. The lengths referred to below are the effective lengths of the SMA wire in the mechanism, as it is this length that is strained during actuation.

[0017] L e1 = length of mechanism 11 L e2 = length of mechanism 21 L sys = length of system when stacked D o = distance the mechanism can be stacked L eq = Equivalent length of mechanisms 11 and 21 when they are arranged in series L eq = L e1 +L e2 L sys = Le1 +L e2 -D o , or L sys = L eq -D o e = strain in the SMA wire, % e sys = System strain, % S = stroke in length units such as inches, mm, etc. S sys = System stroke S eq = stroke of equivalent length system S = S sys = S eq e = (S / L eq )*100 S = L eq *e / 100 e sys = (S / L sys )*100 S = L sys *e sys / 100 Δe = 100*(e sys -e) / e = change in strain (%) In the example, two mechanisms 11, 21 of equal length, 8 inches, are overlapped by 4 inches. As an example, the SMA wires of the mechanisms each have a 5% strain upon actuation, corresponding to a reduction in length S1. Applying the above formula, we get:

[0018] L e1 = L e2 = 20.32 cm (8 inches) D o = 10.16 cm (4 inches) e = 5% L eq = L e1 +L e2 , L eq = 20.32cm (8 inches) + 20.32cm (8 inches) = 40.64cm (16 inches) L eq = 40.64 cm (16 inches) S = L eq *e / 100 = 40.64cm (16 inches) * 5% / 100 = 2.032cm (0.8 inches) S = 2.032 cm (0.8 in) L sys = L eq -D o = 40.64cm (16 inches) - 10.16cm (4 inches) = 30.48cm (12 inches) L sys = 30.48 cm (12 inches) e sys = (S / L sys )*100 = (2.032 cm (0.8 in) / 30.48 cm (12 in))*100 = 6.67% e sys = 6.67% Therefore, the change in strain is Δe = 100*(e sys -e) / e = 100*(6.67-5) / 5 = 33.4%.

[0019] In the above overlap configuration, e sys = 6.67% is a 33.4% increase in strain over the standard 16 inch (40.64 cm) mechanism length footprint. o ) is larger, the strain (e sys ) increases significantly, as shown in the graph of FIG.

[0020] Using the above equation, the strain of a given compression mechanism 10 can be fine-tuned by calibrating the overlap distance based on the needs of the situation / required treatment. For example, if a lymphedema patient requires hypobaric therapy treatment, minimizing the overlap can minimize strain, leading to reduced pressure applied to the body. If hyperbaric therapy is required, the overlap can be maximized, increasing the strain on the system and maximizing the pressure applied to the body.

[0021] For example, if a system requires 5.5% strain to reach the desired pressure for treatment and the mechanism is 8 inches long, the required overlap D o can be calculated as follows:

[0022] e = 5% (strain capacity of each SMA wire) L eq = L e1 = L e2 = 20.32 cm (8 inches) S = L eq *e / 100 = 40.64cm (16 inches) * 5% / 100 = 0.203cm (0.8 inches) Next, D o = 2*L eq -(S / e sys )*100, D o = 2*8-(0.8 / 5.5)*100 = 3.683cm (1.45 inches) In other words, two 8 inch long mechanisms must overlap by 1.45 inches to apply the desired pressure to a person.

[0023] This is also advantageous for smaller diameter limbs, as when greater pressure is required to combat deep vein thrombosis (DVT) in smaller limbs, the overlap can be adjusted to fit the size of the limb, allowing the system to deliver maximum force without compromising strain due to the overlap.

[0024] These overlap distances can be adjusted for flexibility of use or fixed in the device for specific applications. The ability to overlap features allows for flexibility in the application of certain SMA materials, such as Nitinol (NiTi). NiTi has a given strain based on its length, which can limit its use. Overlapping features is believed to increase the strain in the system, delivering a strain greater than that provided by the NiTi alone over the length of the system.

[0025] In one embodiment, the compression mechanism 10 can be configured to allow adjustment of the overlap dimension D0. This overlap is primarily based on the length of the top and bottom plates 31, 32. Thus, shorter plate pairs will result in less overlap, while longer plate pairs will result in more overlap. In one embodiment, the overlap dimension D0 is adjusted to fit within the system length L until the SMA wire is actuated. sys 32. To allow for plate replacement, rivets 35, 36, 38, 39 may be rivet screws in which one head of the rivet includes an internally threaded post and the other head includes an externally threaded shank that screws into the post. The post lengths of rivets 35, 36 are sized to fasten control boards 12, 22 to their respective top and bottom plates, and the post lengths of rivets 38, 39 are sized to sandwich two mechanisms 11, 12 between plates 31 and 32. Other fastener arrangements are contemplated that allow any given pair of mechanisms to be fastened to any given pair of top and bottom plates, allowing for fully customizable compression mechanism 10. It is further contemplated that overlap adjustment can be achieved by adjustable positioning of one or both sets of fasteners / rivets relative to the top and bottom plates. The plates may be provided with slots, such as slot 26 shown in dashed lines in FIG. 1, similar to slot 40. Slots 26 allow for adjustment of the position of rivet 36 along the length of bottom plate 32. A similar slot arrangement can be provided in top plate 31 for adjustment of the position of rivet 35. The rivet can be configured to be secured to the plate at a desired location to adjust the overlap dimension D0 between fasteners / rivets 35 and 36 to match the desired strain output of compression mechanism 10.

[0026] The present disclosure is to be considered illustrative and not restrictive, and although only particular embodiments have been presented, it will be understood that all variations, modifications, and further uses that come within the spirit of the disclosure are intended to be protected.

Claims

1. A first compression mechanism, a first elongated flexible panel having opposite ends, a substrate attached to the panel at each of the opposite ends, one of the opposite ends being a free end and the other of the opposite ends being a controlled end; at least one shape memory alloy (SMA) wire extending between said ends and connected to said panel at each of said ends; Including, a panel at one of the ends including a control circuit configured to interface with a power source to operate the at least one SMA wire; a first compression mechanism; A second compression mechanism, a second elongated flexible panel having opposite ends, a substrate attached to the panel at each of the opposite ends, one of the opposite ends being a free end and the other of the opposite ends being a controlled end; at least one shape memory alloy (SMA) wire extending between said ends and connected to said panel at each of said ends; Including, a panel at one of the ends including a control circuit configured to interface with a power source to operate the at least one SMA wire; a second compression mechanism; Equipped with the first compression mechanism and the second compression mechanism overlap one another, the control end of the first compression mechanism overlaps the second elongated panel, the control end of the second compression mechanism overlaps the first elongated panel, the free end of the first elongated panel and the free end of the second elongated panel form opposite ends of the compression mechanisms that have an initial length therebetween when the SMA wires of the two compression mechanisms are not actuated and that have a shortened length therebetween when the SMA wires of the two compression mechanisms are actuated; a top plate and a bottom plate, each having a length shorter than the initial length of the compression mechanism, each plate having a first end and an opposite second end, the top plate and the bottom plate being connected to each other at the first end and the second end, the control end of the first flexible panel being connected only to the first end of the top plate and the control end of the second flexible panel being connected only to the second end of the bottom plate; Compression device.

2. 10. The compression device of claim 1, further comprising a flexible panel configured to be attached to a body portion of a user, the free end of each of the first compression mechanism and the second compression mechanism being attached to the flexible panel.

3. 2. The compression device of claim 1, wherein the top and bottom plates are connected at the first and second ends by fasteners extending between the first and second ends, the fasteners configured to separate the top and bottom plates by a width sufficient to receive the first and second elongated panels therebetween.

4. 4. The compression device of claim 3, wherein two fasteners are provided at each of the first and second ends of the top and bottom plates, the two fasteners being spaced apart so as to straddle a respective one of the first elongated panel and the second elongated panel passing between the top and bottom plates.

5. The compression device of claim 3 , wherein the fastener is a rivet.

6. each of said rivets includes an elongated post and an enlarged head at each end of said post; the first end of the top plate includes a pair of slots; 5. The compression device of claim 4, wherein the rivets at the second ends of the top and bottom plates and the first end of the bottom plate are secured to the respective plates, and the rivets at the first end of the top plate extend through pairs of the slots.

7. the control end of the first flexible panel is connected to the first end of the top plate by at least one first fastener engaged between the base plate and the top plate; 2. The compression device of claim 1, wherein the control end of the second flexible panel is connected to the second end of the base plate by at least one second fastener engaged between the base plate and the base plate.

8. The compression device of claim 7 , wherein the at least one fastener is a rivet.

9. An overlap amount D between the first compression mechanism and the second compression mechanism Ｏ is the distance between the at least one first fastener and the at least one second fastener; For an SMA wire with a strain capacity e, the overlap D Ｏ is calculated using the following equation: D Ｏ = 2*L ｅｑ -(S / e ｓｙｓ )*100、 Here, e ｓｙｓ is the desired strain of the compression device, L ｅｑ is the length of the SMA wire in each of the first and second compression mechanisms, and S = L ｅｑ 8. The compression device of claim 7, wherein the ratio of the saturation voltage to the saturation voltage is *e / 100.

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