Scalp cooling cap

Abstract

A heat exchanger cap and method of producing the same which is configured to be worn on a human head to regulate the temperature thereof. The cap comprising a layer of material defining a single passageway through which a heat transfer fluid may flow and extending from a single inlet to a single outlet, the material layer having a first side for contact with the head and a second side which, in use, will face away from the head.

Description

[0001] Scalp Cooling Cap

[0002] Field of the Invention

[0003] The invention is concerned with scalp cooling caps for application to the head of persons undergoing chemotherapy or a similar treatment in which the patient may suffer from the loss of hair.

[0004] Background to the Invention

[0005] Chemotherapy-induced alopecia (CIA) / hair-loss is widely recognised as one of the most traumatic side-effects of chemotherapy treatment. Without treatment CIA affects 3.5 million patients worldwide and over 67,000 in the UK annually.

[0006] It is known to cool the head of a patient during chemotherapy in order to reduce the extent and / or likelihood of hair loss by means of vasoconstriction.

[0007] EP3197407B discloses a heat exchanger cap which is configured to be worn on a human head to regulate the temperature thereof. The cap comprises layers of material defining a single passageway through which a heat transfer fluid may flow and extending from a single inlet to a single outlet. The material layer defines a first element for covering one side of the head, a second element for covering an opposing side of the head and an intermediate joining element configured for covering the top of the head. Each of these elements defines a section of the single passageway through the cap. The material layer has a first side for contact with the head and a second side which, in use, will face away from the head. In at least the first element and the second element, the single passageway defines a first flow region located on an opposite side of a junction line to a second flow region with each of the flow regions extending only part of the way from the front to the back of the cap. The passageway has a serpentine route in each of the elements and the serpentine route is back and forth in the direction from the nominal front of the cap to the nominal back of the cap. The passageway in the first flow region has a serpentine route back and forth over the front half of the side of the cap which corresponds to the front half of the side of the head on which it will be worn. The passageway in the second flow region has a serpentine route back and forth over the back half of the side of the cap which corresponds to the back half of the head on which it will be worn.

[0008] Such a known heat exchanger cap is manufactured from a silicone material by silicone-sheet thermoforming.

[0009] There is a need for a recyclable, single-patient scalp cooling cap and manufacturing method.

[0010] Statements of the Invention

[0011] According to a first aspect of the present invention, there is provided a heat exchanger cap which is configured to be worn on a human head to regulate the temperature thereof, the cap comprising a layer of material defining a single passageway through which a heat transfer fluid may flow and extending from a single inlet to a single outlet, the material layer having a first side for contact with the head and a second side which, in use, will face away from the head, one of said sides being formed to partially define said single passageway and the other of said sides being unformed.

[0012] According to a second aspect of the present invention, there is provided a heat exchanger cap which is configured to be worn on a human head to regulate the temperature thereof, the cap comprising a layer of material defining a single passageway through which a heat transfer fluid may flow and extending from a single inlet to a single outlet, the material layer having a first side for contact with the head and a second side which, in use, will face away from the head, said material being a thermoplastic polyurethane.

[0013] Preferably, the shore hardness of the material is from 60A to 95 A, more preferably about 70A. The cap preferably is such that the material layer defines a first element for covering one side of the head, a second element for covering an opposing side of the head and an intermediate joining element configured for covering the top of the head, each of said elements defining a section of the single passageway through the cap.

[0014] A third aspect of the present invention provides a method of making a heat exchanger cap, the method comprising vacuum forming a first former having a surface pattern which defines one side of the material layer and a second former which defines the other side of the material layer, welding said first former to a second former which is unformed to create a two dimensional heat exchanger cap precursor having partially separated portions, and welding together adjacent pairs of said portions to form a three dimensional cap.

[0015] Preferably, said first former is welded to said second former by radiofrequency welding.

[0016] Preferably, the welding to form a three-dimensional cap comprises spot welding.

[0017] Preferably, the welding to form a three-dimensional cap further includes bar welding between the spot welds.

[0018] Preferably, the formation of the three-dimensional cap is carried out without the use of glue, thereby maintaining the sustainability and repeatability of the product.

[0019] In a fourth aspect, the present invention provides a two dimensional precursor for a heat exchanger cap, the precursor comprising a layer of material defining a single passageway through which a heat transfer fluid may flow and extending from a single inlet to a single outlet, the material layer having a first side for contact with the head and a second side which, in use, will face away from the head, one of said sides being formed to partially define said single passageway and the other of said sides being unformed.

[0020] In a fifth aspect, the present invention provides a cap cover for a heat exchanger cap, the cover comprising a three-layer laminate of polyurethane, thermal polyurethane and nylon.

[0021] The materials used for both the cap and the cap cover are thermoplastics which can be remoulded with heat, in contrast to the use of thermosets such as the silicone currently used. Not only do the materials used in the present invention promote recyclability and sustainability, they also enable performance improvements to be achieved.

[0022] Preferably, the welding is radio frequency (RF) welding in which heat is generated by passing radio frequency radiation through plastics materials causing them to melt and bond together. The thickness of the sheets is typically from 150 microns to 1400 microns.

[0023] A heat exchanger cap in accordance with the present invention facilitates scalp cooling. Scalp cooling helps protect hair follicles, which are rapidly dividing cells targeted by chemotherapy drugs. Scalp cooling promotes vasoconstriction, reduces drug cellular uptake, reduces hair follicle cell division, and reduces metabolic activity, thus reducing / preventing hair loss.

[0024] Brief Description of the Drawings

[0025] The accompanying drawings are as follows:

[0026] Figure 1 shows the vacuum formed TPU sheet;

[0027] Figure 2 illustrates the vacuum forming step; Figure 3 illustrates the location of the moulded TPU is located into the RF tool;

[0028] Figure 4 shows a moulded TPU sheet;

[0029] Figure 5 shows detail of a moulded TPU sheet;

[0030] Figures 6 and 7 illustrate the operation of the spot welding tool;

[0031] Figure 8 shows the spot welds on the 2D cap precursor;

[0032] Figure 9 illustrates the process of welding the spot welds together;

[0033] Figure 10 shows the three dimensional cap;

[0034] Figure 11 shows the rear quarter of the cap’s spot welds; and

[0035] Figure 12 shows the front part of the cap’s spot welds.

[0036] Detailed Description of the Invention

[0037] The present invention will now be described, by way of example only, with reference to the accompanying drawings.

[0038] The function of the cap is to make good contact with the head, and take away the heat from the scalp. Heat from the scalp is transferred through the inner layer of the cap to the coolant liquid that takes the heat away. It is important that the inner layer has sufficient heat transfer co-efficiency which is determined by the combination of conductivity and thickness. These two properties comprise the U value of the inner layer which is the coefficient of heat transfer, that is to say the specific heat capacity of the material (thermal conductivity value) divided by the thickness of the material.

[0039] In Fouriers Law, Q = (k / s) x A x dT where (k / s) is U. The liquid coolant must have a good flow rate to take heat away from the scalp quickly in order to overcome the body’s natural thermoregulation of the scalp. This requires that the passageways for the coolant must be of sufficient cross- sectional area to allow good flow whilst keeping pressure as low as possible to prevent bursting. Lower pressure also allows for thinner layers giving improved U value.

[0040] The present invention relates to heat exchanger caps which comprise a layer of material defining a passage through which a heat transfer fluid may flow. The material layer has a first side for contact with the object, and a second side which, in use, will face away from the object.

[0041] The first inner side 2 has a layer formed by vacuum forming to improve the flow through the increased cross-sectional surface area.

[0042] The vacuum formed inner layer 2 has a relatively high coefficient of thermal conduction to promote heat extraction from the patient's hair / head, thereby retaining more hair.

[0043] The material has a high heat transfer coefficient and specific heat capacity value, promoting better heat extraction than the existing product.

[0044] The sides are made from thermoplastic polyurethane (TPU), preferably bonded without glue. The material preferably has a 70A shore hardness and is durable and resistant to bursting and pin-hole leaks. The use of spot-bar welding in the manufacture of the cap results in the cap being resistant to tearing and to tail splitting.

[0045] The heat exchanger cap fits multiple anthropometric head shapes more comfortably due to the flexibility of the TPU material. In practice, there are different shapes of cap, and different sizes, eg, two shape classifications and three sizes per shape classification, a total of six caps. However, the flexible nature of the material used to make the cap allows for some malleability for different users.

[0046] The main body of the cap is a heat exchanger with a formulated flow.

[0047] Arrangement. It is designed in a way to provide a single flow channel arrangement that has an optimal flow, optimal surface contact, and provides heat exchange with a close fit to the users' scalp to extract heat from the patient's head.

[0048] The materials used in the manufacture of the cap are biocompatible, soft, flexible and highly chemical resistant. They are aesthetically pleasing, comfortable and are mouldable medical grade materials.

[0049] The coolant lines / tails which connect the caps to the system are silicone / TPU or similar tubes insulated with neoprene and covered in a fabric sleeve, typically about 2 meters long. They allow for distance between the machine and patient and enable movement of the head / person / device around the patient’s chair.

[0050] The cap has a fabric cover which is an outer cap that goes over the heat exchanger cap and is used to insulate the cap to prevent heat being lost to the surrounding atmosphere and is also used to further compress the heat exchanger cap against the head. The cover also has a visual aesthetic function.

[0051] The cap has a chin strap which is biocompatible and is used to tighten the cap down onto the scalp using, for example, adjustable straps to compress the cap against the head for optimal scalp fit contact to improve treatment efficacy.

[0052] Forming of the 2D cap precursor

[0053] The current silicone cap is formed using a process called sheet silicone thermoforming, whereby raw sheet silicone is moulded and formed by a 3D printed SLS (selective laser sintering) tool. The cap has a form on both sides of the tool (male and female tool halves). One side is a semi-circle shape and the other is a ‘w’ shape profile as described in WO / 2016 / 046534).

[0054] A heat exchanger cap of the present invention, made from TPU material is made by an RF welding process using a metal tool which does not form the TPU in the same way. The process of the invention involves an additional step (vacuum forming) prior to the welding process and prior to the 3D forming process. The cap is produced using the following main steps:

[0055] 1. A TPU sheet is vacuum formed;

[0056] 2. A singled sided formed sheet is located into a RF welding tool;

[0057] 3. A single un-formed sheet is placed onto the formed sheet between the tool;

[0058] 4. The cap is then welded (to weld the flat and formed sheet halves together).

[0059] Vacuum forming TPU followed by RF welding has not previously been used, particularly at this level of complexity and complex geometry. It has also not been used when combined with a process for turning a cap from 2D to 3D. A ‘w’ profile may be used, the specific transformative properties causing the ‘w’ shape to expand out when pressure is applied to close any gaps created by the welded walls between channels. By closing these gaps off using the ‘w’ shape profile, the surface area used is maximised, making it a very efficient heat exchanger for the purpose of preventing hair-loss during chemotherapy induced alopecia.

[0060] The vacuum forming tool design for this process is different to that used in conventional vacuum forming. The material used (TPU) has a much lower glass transition temperature. This can cause a lot of bowing in the sheet material, which can cause issues in locating and welding in the subsequent steps of manufacture. The cap tool uses a flat upper surface surrounding the moulded areas in order to provide a larger surface area for the welding and cutting process and to increase the surface areas for dispersing heat during the manufacture process. Also, around the outer areas of the tool a 15 degrees or similar draft angle is used the pull the flat areas tight around and down the side of the tool. Furthermore, as shown in Figure 1 of the accompanying drawings, locators are added which locate in the welding tool and add supports for adding tension to mitigate warping.

[0061] Variables in the vacuum forming step include the particular TPU material, the duration, pressure of the vacuum used and the exposure time to the heat and the temperature of the heat. Like conventional vacuum forming, the plastic is heated until soft / sagging and then the form is pressed into the soft plastic where the vacuum pulls the material into the mould and the heat is removed to cool the plastic in the mould.

[0062] Figure 2 of the accompanying drawings shows, in the top part of the drawing, the clamped TPU sheet and a specific heat being applied above to soften the plastic. In the second part below, there is illustrated how a specific pressure is applied when the mould is pushed into the softened TPU. The specific pressure is the air pressure which pulls the material down into the mould. This relates to how much pressure is used for the vacuum that sucks the softened plastic into the mould to form and hold the material as it 'sets' / cools down. If too low, then the mould will be poor, if too high the plastic will rupture.

[0063] Figure 3 of the accompanying drawings illustrates how the moulded TPU from the vacuum forming tool is located into the RF tool prior to the welding process.

[0064] Figure 4 of the accompanying drawings shows a moulded TPU sheet and Figure 5 shows detail of a moulded TPU sheet in which the “w” shape profile is represented by the wavy grooves at the bottom of the recess.

[0065] Forming of the 3D cap from the 2D precursor Typically, RF welding is a process that is flat 2D manufacturing of sheet plastic materials only. Due to the nature of the manufacturing process, 3D moulds and 3D forming is not used. The method of the present invention enables manufacturers to produce flat parts which are subsequently transformed into 3D shapes. For this particular application, in which the flat shape needs to mould around a human head, which is arguably one of the most complex shapes of the human’s external anatomy, this is a considerable feat of engineering.

[0066] In effect, the current silicone cap has been reverse engineered by taking the complete thermoformed moulded TPU sheet and flattening the pattern by cutting between the weld walls between the heat exchanger channels. This enables the existing cap to remain the same shape as it currently is, but enables the exact same pattern that is currently moulded in a 3D shape, to be made in a 2D process using a 2D pattern. After this, additional features have been added which will allow the 2D pattern to take a 3D shape using an additive welding process on the seams.

[0067] After the sheet TPU is vacuum formed, a metal press cutting tool cuts around the perimeter of the cap. Within this perimeter, a cut and weld allowance is added for the next steps. Some incrementally patterned spot weld locator features 4 are added. The spot weld dots have the following features:

[0068] • The locator on the centre of the weld is 5mm in diameter.

[0069] • It is a circle to prevent mis-location and miss use by operators.

[0070] • It has a specific pitch between gaps to enable further welding processes between the gaps to ensure seams can be fully welded without using glues to maintain sustainability and repeatability.

[0071] • It has an offset minimum weld wall thickness (l-3mm) to ensure a correct weld and purchase between the tool materials to prevent breaking, melting, collision and clash during this tacking process. • The locators are offset enough from the outer curvature of the heat exchanger wall when the wall is welded later to prevent the channels from being thinned and closed off (to maintain an equal channel diameter for flow and performance). This also prevents rupturing of the formed channels that could be cause by the heat from the spot welding.

[0072] • The spot weld locators match up with the opposing spot weld locator i.e. A- A, B-B and so on.

[0073] • The outer edge of the spot weld must not infringe on the available material of the adjacent spot weld it will match with so as to cause a reduction of the locator hole minimum perimeter weld allowance.

[0074] • The spot weld locators are accessible to welding by an operator from the outside.

[0075] • The spot welds join upwards and outside of the cap as to not to affect the fit, comfort or performance of the cooling cap where it will interact with the user’s head.

[0076] • The spot weld locators are used to pull the seams of the 2D cap pattern inwards transforming the shape of the cap in a way that doesn’t cause crinkling, folding or other defects in the flat sheet that could be expected by a 2D shape when manipulated into a 3D shape.

[0077] • The forming of the cap process prevents closing off the coolant channels.

[0078] • Forming of the cap provides a close and tight fit to the head, typically managed by the strategic positioning of the locator spot welds, whereby the equidistant spacing from the innermost point of the cut TPU between the two seams are equal to prevent bunch of the material at the join.

[0079] • The forming of the cap seams from 2D to 3D minimises the gaps between channels. Large gaps in between the cooling channels could inhibit maximum surface contact such as that provided by the ‘w’ shape formed channel profiles. In the spot- welding tool 6 shown in Figures 6 and 7 of the accompanying drawings, there is a plastic male locator that goes into a hole on each side of the seam when pulled together. For a seam to be welded, each side of the gaps wall (weld wall) has a circular locator profile in it. Each hole (2 in total) is orientated upwards and outward to the cap providing an ‘L’ shape profile perpendicular to the surface of the cap (or tangential). The locator welding tool is made up of two halves. On one side, a male plastic locator stub is inside the circular weld tool profile. On the opposite tool, the circular weld tool has a female recess in it to permit the locator stub to accurately locate at the set distance from the cap to prevent incorrect locating and potential damage to the cap channel walls.

[0080] There are a set number of spot welds on the cap that turn the cap from 2D to 3D. The flat cap pattern has an optimised number of ‘fingers’ 8, for example 6 to 10, as illustrated in Figure 8 of the accompanying drawings. The image below illustrates the ‘fingers’ of the cap and the spot welds are shown as are black lines illustrating the connecting locator points which are welded together to form the 3D shape.

[0081] As shown in Figure 8 of the accompanying drawings, there are:

[0082] • 44 spot weld locators

[0083] • These make 22 spot welds,

[0084] • That is 7 spot welds on the back quarter quadrant of the cap, 4 on the front quarter quadrant of the cap (or 14 on the back of the cap and 8 at the front.

[0085] • There are 8 gaps between the ‘fingers’ of the cap that need to be closed to form the cap.

[0086] Figure 9 of the accompanying drawings illustrates the process of welding the spot welds together and Figure 10 illustrates the appearance of the cap spot welded. The way that the cap is welded from 2D to 3D to maximise repeatability and reduce complexity is the following. The principle is the same as that described above, however instead of individually welding 22 spot welds, these are paired together at equal pitches as mentioned in the above text. The bar weld is joined in with the paired spot welds to reduce processes / operations required to form the cap.

[0087] For the back half of the cap, the rear 7 spot weld processes are 40mm pitches along the entire seam and a set distance from the start of the seam directly related to the entire length of the seams curve length with direct relation to equidistant spacing of the number of spot welds and equal gaps between the start of the seam and the first spot weld and then the end of the curve and the last spot weld. Figure 11 of the accompanying drawings shows the rear quarter of the caps spot welds. These are mirrored on the opposite side.

[0088] For the front half of the cap, the pitch between the spot weld processes is different. The front 4 spot weld processes are 30mm pitches along the entire seam. Figure 12 of the accompanying drawings shows the pitch between the spot welds at the front quarter of the cap - these are mirrored on the opposite side.

[0089] In essence, the above described process combines two welding methods, spot welding and bar welding, into a new hybrid process for 3D application. This results in optimisation of the process and increases its repeatability.

[0090] This process ensures an equidistant and controlled seam weld for accuracy and repeatability of manufacture, and also minimises the number of steps, reducing the cost and time for manufacture.

Claims

CLAIMS1. A heat exchanger cap which is configured to be worn on a human head to regulate the temperature thereof, the cap comprising a layer of material defining a single passageway through which a heat transfer fluid may flow and extending from a single inlet to a single outlet, the material layer having a first side for contact with the head and a second side which, in use, will face away from the head, one of said sides being formed to partially define said single passageway and the other of said sides being unformed.

2. A heat exchanger cap which is configured to be worn on a human head to regulate the temperature thereof, the cap comprising a layer of material defining a single passageway through which a heat transfer fluid may flow and extending from a single inlet to a single outlet, the material layer having a first side for contact with the head and a second side which, in use, will face away from the head, said material being thermoplastic polyurethane.

3. A cap according to Claim 2, wherein the shore hardness of the material is from 60A to 95 A.

4. A cap according to any of the preceding claims, wherein the material layer defines a first element for covering one side of the head, a second element for covering an opposing side of the head and an intermediate joining element configured for covering the top of the head, each of said elements defining a section of the single passageway through the cap.

5. A method of making a heat exchanger cap, the method comprising vacuum forming a first former having a surface pattern which defines one side of the material layer and a second former which defines the other side of the material layer, welding said first former to a second former which is unformed to createa two dimensional heat exchanger cap precursor having partially separated portions, and welding together adjacent pairs of said portions to form a three dimensional cap.

6. A method according to Claim 5, wherein said first former is welded to said second former by radiofrequency welding.

7. A method according to Claim 5 or Claim 6, wherein the welding to form a three-dimensional cap comprises spot welding.

8. A method according to Claim 7, wherein the welding to form a three- dimensional cap further includes bar welding between the spot welds.

9. A method according to any of Claims 5 to 8, wherein the formation of the three-dimensional cap is carried out without the use of glue.

10. A two dimensional precursor for a heat exchanger cap, the precursor comprising a layer of material defining a single passageway through which a heat transfer fluid may flow and extending from a single inlet to a single outlet, the material layer having a first side for contact with the head and a second side which, in use, will face away from the head, one of said sides being formed to partially define said single passageway and the other of said sides being unformed.

11. A cap cover for a heat exchanger cap, the cover comprising a three-layer laminate of polyurethane, thermal polyurethane and nylon.

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