Patent GB-1402737-A (GB)
Title: Cryogenic tool
IPC: A61B18/00
Filed: 1972-12-11
Abstract: 1402737 Cryogenic surgical appliances HUGHES AIRCRAFT CO 11 Dec 1972 [13 Dec 1971] 57012/72 Heading A5R [Also in Division F4] A cryogenic tool comprises an elongated tube 10' for conveying liquid cryogen 40 from a reservoir 33 to a contact member 88, and is characterized in that the tube 10' includes apertures 32 for admitting liquid cryogen which are disposed within the reservoir, an outlet for cryogen vapour communicating with the atmosphere, and a capillary active means for conveying the liquid cryogen along the tube 10' by capillary action. As shown, the interior of the tube 10' is provided with a lining 36 of capillary active material. The reservoir is defined by a lower wall 61 secured to the tube 10', a cylindrical outer wall 63, and an upper wall 75 to which is secured a filler funnel 79. The interior of the walls 61 and 63 is provided with a lining 34 of capillary active material. The lining 34 extends through the apertures 32 to touch the lining 36 in the tube 10'. The upper end 71 of the tube 10' carries a cap 73 from which extends a vapour vent tube 35. A shell 58 extends around the tube 10' and the reservoir to define a space which is evacuated to provide thermal insulation. A tube 60 forming a portion of the shell 58 is connected to the tube 10' by transition pieces 62 and 66 which insulate the tube 10 from the tube 60. The upper end of the shell 58 joins with the funnel 79 and has threads 68 for the removable attachment of a cap 70. The cap 70 carries a closure plug 77 which is urged by a spring 78 to close the funnel 79. A liquid cryogen trap 82 in the form of a closed tube is provided. Vapour from the tube 10' passes through the vapour vent tube 35 into the reservoir; it then passes through a vapour inlet tube 86 into the trap 82; finally the vapour passes through a vapour outlet tube 84, an annular recess 72 and vent holes 76 in the cap 70 to the atmosphere. In use liquid cryogen is conveyed by the lining 36 of the tube 10' to the bottom of a recess 90, Fig. 5, in the member 88 where evaporative cooling occurs. A substantially conical member 94 having longitudinal grooves 98 is provided within the member 88 to increase the area for evaporation. Cryogen vapour escapes through a vent tube 96 disposed within the tube 10'. The lining 36 of the tube 10' may be a felt cloth or it may take the form of stainless steel fibres sintered together. In the alternative form of Fig. 9, (not shown), a tube (39) is concentrically arranged with a tube (38) with a spacing such as to produce capillary action; the tube (39) is perforated to permit the cryogen vapour to pass into the central space. In the form of Fig. 10, (not shown), a perforated tube (44) is positioned excentrically within a tube (42). In the form of Fig. 11, (not shown), a tube (46) has a matt (50) of sintered metallic fibres and longitudinally grooved channels (48) of dimensions such as to produce capillary action. In the form of Fig. 12 (not shown), a tube (52) has a lining of sintered metallic fibres or a woven metallic screen, and a tube (56) which reduces the .pressure drop of the capillary feed. An applicator tip (100) Fig. 6 (not shown) having a flange (102) may be mounted over the member 88. In the form of Fig. 6A (not shown), the applicator tip (105) comprises a flexible bag (101) containing a freezable solution (89). In the form of Fig. 6B (not shown), the applicator tip (103) is a mass which can be moulded to shape and then frozen. A probe (208), Fig. 7 (not shown), suitable for prostatic surgery may be provided. The probe (208) is in the form of a tube (210) having a lining (212) of capillary material and formed as an enlargement of a tube (214). A rounded tip (222) of thermally insulating material is pro-. vided at the lower end of the probe (208). The cryogenic tool may be provided with an electric heating coil (224), Fig. 13 (not shown), disposed around the tube 10'. Upon application of heat to the tube 10' the liquid cryogen is evaporated and prevented from reaching the member 88. In a modified form, Fig. 14 (not shown), a closing cap (87) attached to a slide rod (81) is provided. The closing cap (87) may engage the end of the tube (85) to close off the vapour exit therefrom. In the embodiment of Fig. 1 (not shown), the contact member (14) is held within an extension (10a) of a tube (10) by friction force or by screw threads. The capillary lining (15) of tube (10) may take the form of a plurality of longitudinally extending strips circumferentially spaced along the interior of the tube (10). A shell (20) similar to the shell 58 of the above-mentioned embodiment is provided and may be coated with fibre glass or plastics. A cap (21) is attached to the reservoir (16) with an "O" ring (28) providing a fluid seal. In the embodiment of Figs. 2 and 3 (not shown), the tube (110) is bent by about 45‹ in the region (150) where the tube (110) enters the reservoir (116). The reservoir (116) and a thermally insulating outer shell (125) are detachable from the remainder of the tool. A substantially U-shaped vent tube (160) mounted within the reservoir (116) has one end extending into the tube (110) and the other end extending to a region (162) vented to the atmosphere by an exhaust tube (164).