APPARATUS AND METHOD FOR STIMULATION OF VENOUS RETURN

Abstract: An apparatus for stimulation of venous return in the lower limbs comprises a frame (1), a foot support plate (2) having a forefoot portion (2a) and a hind foot portion (2b), means for swivelling support of the foot support plate in the frame disposed at the hind foot portion, a first spring element (3) disposed between the frame and the foot support plate, and tipping means (6) disposed at the frame or the foot support plate or both for tipping of the foot support plate. A corresponding method comprises treading down in two consecutive phases a foot plate in a venous return stimulation apparatus. The foot support plate thereby is rotated around a first axis in the first phase and a second axis in the second phase. The second axis is parallel with and disposed anteriorly of the first axis.

Description: Apparatus and method for stimulation of venous return FIELD OF THE INVENTION The present invention relates to an apparatus for stimulation of venous return in the lower limbs and a method for such stimulation . BACKGROUND OF THE INVENTION It is well known that sitting for longer periods of time results in impaired venous return in the lower limbs manifesting itself in local accumulation of blood. This comes with discomfort in form of, for instance, swelling around the ankles and difficulties when putting on shoes. But the effects of sitting for long periods of time can be considerably more serious, in particular with older people. In certain cases the stagnation of blood (stasis) results in the formation of thrombi which may go with the venous blood when the person starts moving the legs, and which may lead to pulmonary embolism which is a life threatening condition. Examples of situations where persons are forced to sit still for long periods of time are air travel, convalescence or invalidity binding a person temporarily or permanently to a wheel chair. This stasis of the blood can be affected by moving the lower limbs at appropriate intervals since the movement of the leg muscles causes a pumping effect in combination with the venous valves functioning as one way valves. Moving the legs in the absence of aids in an appropriate manner in a sitting position is, however, tiresome. To make such exercise more ^natural' and thus easier and more comfortable to carry out a number of dedicated apparatus have been proposed, i.a. the ones disclosed in US patents no. 4 669 744 och 5 035 421, in the German published patent application no. 27 44 996, and in WO84/00695. All these apparatus seek to enable the leg and the foot to achieve more or less ^natural' movement patterns of type dorsal/plantar flexion, possibly in combination with foot inversion/eversion and pronation/ supination, respectively. The known apparatus however comes with a number of drawbacks in relation to design and/or movement physiology. Only by an apparatus which is easy to manufacture and to transport, and which, at the same time, offers exercises which have a natural feel the user will be motivated to take along the apparatus on, for instance, longer travel, and to carry out the motion exercises with sufficient frequency to achieve the intended circulation promoting and stasis impeding effect. OBJECT OF THE INVENTION It is thus an object of the invention to provide an apparatus for stimulation of venous return in the lower limbs which is improved in respect of the state of the art and which solves the aforementioned problems, in particular an apparatus designed to provide a pattern of movement which is λ natural' in regard of the physiology of leg/ foot movement, and to confine movement to substantially such movement. It is also an object of the invention to provide key technical features for such an apparatus which enable it to be manufactured in a simple manner, well adapted to its purpose and easy to transport. A further object of the invention is to disclose a method for stimulation of venous return. SUMMARY OF THE INVENTION According to the present invention is disclosed an apparatus for stimulation of venous return in the lower limbs which, in a simple and controlled manner, makes possible a leg/foot movement in three phases: a dorsal flexion phase, an unrolling phase, and a return phase. The combination of dorsal flexion phase and unrolling phase results in a foot movement which has a ^natural' feel and which stimulates venous return in an efficient and suitable manner. The apparatus for stimulation of venous return according to the invention comprises a frame, a foot support plate having a forefoot portion and a rear or hind foot portion, means arranged at the hind foot portion, which means comprise means disposed at the hind foot portion or between the hind foot portion and the foot plate, for rotational (swivelling) support of the foot support plate in the frame, a first compression spring element disposed between the frame and the foot support plate and rocker or tipping means for the tipping of the food support plate disposed at the frame or the foot support plate or both. The hind foot portion is intended to receive the sole area below the calcaneus, and the forefoot portion to receive the frontal (anterior) area of the sole. Thus the foot support plate is swivellingly supported in the frame; the corresponding theoretical or real rotational axis is disposed posteriorly (dorsally) in respect of the tipping or rocking means axis. Swinging of the foot support plate around the swivelling or rotational means axis may be substituted by unrolling of the foot support plate on a curved (circular, elliptical, etc.) surface (for instance, surface of a section of cylinder mantle, etc.); in this case 'tipping' also comprises a tipping-like unrolling movement on such a surface the radius (in case of a surface circular in section) or the approximating radii (in case of a surface other than circular in section) of which are small in comparison to the length of the foot plate. According to the invention is also disclosed a method for stimulating venous return in the lower limbs, the method comprising treading down in two consecutive phases a foot plate rotatable around one axis for each phase, the foot plate rotating in the second phase around an axis parallel with and disposed anteriorly in relation to the axis around which the foot plate rotates in the first phase. It is preferred for the method according to the invention to comprise: the person whose venous return is to be stimulated assuming a sitting position, placing one of said person' s feet with the sole against the abutment area on the top side of a foot plate of an apparatus for stimulation of venous return, said foot plate inclining from 25 to 75° in respect of the vertical and having a rear or hind foot portion and a forefoot portion; in a first phase, treading down the foot support plate against a spring force, the foot support plate and the foot in combination rotating around a first rotation axis disposed essentially perpendicular to the direction of the foot's long axis and essentially parallel with the abutment area and extending in the region beneath the calcaneus or behind (dorsally of) it, - in a second subsequent phase subsequent thereto, treading down the foot support plate against a spring force, the foot support plate in combination with the foot swinging around a second rotation axis essentially parallel with said first rotation axis and disposed in front (anteriorly) of it and extending in or beneath the plane of abutment, essentially passive return of the foot plate and the foot resting on the foot plate to the starting position by the effect of the spring force. The method of the invention may be also carried out with the person in a fully or partially recumbent position. This requires the apparatus to be turned by up to about 90° from its normal position. It can be fastened, for instance, on a wall or an inner end of a bed. In this case Vertical' takes the meaning of perpendicular to the plane of the frame bottom. Further features of the apparatus according to the invention are disclosed in the patent claims and are also evident from the following description of a number of examples of preferred but not limiting embodiments of the invention which will be explained in the following by reference to a rough drawing showing in: Fig. 1 a longitudinal section of a first embodiment of the apparatus according to the invention for stimulation of venous return, with three consecutive positions for the foot support plate indicated; Fig. 2 a second embodiment of the invention in the same view as the one shown in Fig. 1, with two consecutive positions for the foot support plate and two consecutive positions for the frame indicated; Fig. 3 a third embodiment of the invention in the same view as in Fig. 1; Fig. 4 the apparatus in Fig. 3, in a front view with dissecting lines A-A for Fig. 3 indicated; Fig. 5 a fourth embodiment of the invention in the same view as in Fig. 1; Fig. 6 the apparatus in Fig. 5, in a front view, with dissecting lines B-B for Fig. 5 indicated; Fig. 7 a fifth embodiment of the invention, seen from above in perspective in an oblique lateral view; Fig. 8 a section through the apparatus in Fig. 7 in the plane indicated by line A-A and slit 80, in the starting position of a stimulation cycle; Fig. 9 the apparatus in Fig. 7 and in the same view, with the stiffening ribs and the yoke element having the lock screw removed to show the disposition of the spring wire element; Fig. 10 the apparatus in Fig. 7 and in the same view, upon termination of the swivelling phase of the foot support plate; Fig. 11 the apparatus in Fig. 7 and in the same view, at the end of the tipping phase of the foot support plate. The apparatus for stimulation of venous return according to the invention shown in Fig. 1 comprises a trough-formed frame 1 in pressed steel plate having folded-up lateral and terminal edge portions and a flat bottom. Frame 1 is intended to rest with the outside of its bottom against a support, for instance a floor or a foot support. Suitably the underside of frame 1 is corrugated or partially or wholly covered with an anti-gliding material to prevent the apparatus from moving at use; the apparatus can however also be fastened at the support with its bottom and/or lateral walls. Close to the one end of the frame called hind or rear end the lateral walls have a vertical slit 7 in which a foot support plate 2 is positioned. Foot support plate 2 has laterally protruding pins 8 (that is, in parallel with the plane of foot support plate 2, only one is shown; they may also have the form of an axis penetrating the foot support plate) fastened at the rear end of the foot support plate. Pins 8 can rotate in slit 7 and freely move vertically in it. Foot support plate 2 in pressed steel plate (also other materials can be taken into consideration for use in the frame and the food support plate, for instance polymer materials, possibly reinforced) is secured at the topside of the bottom of frame 1 by two spring elements 3, 4 fixed at its underside. On its top side the foot support plate is clad with a material hindering the foot from gliding on it. The apparatus can of course be used with naked feet or with the feet covered with socks or shoes. At its rear end foot support plate 2 is suitably provided with a heel support (not shown) , for instance one similar to a heel support in a ski binding to keep the foot on the plate. Belts, eyes, or similar elements assisting to keep the foot against foot support plate may be arranged or foot support plate 2 can be designed like a slipper or similar. The first spring element 3 is fixed at the foot support plate at a point situated about 2/3 of the length of foot support plate 2 seen from its rear end; it is preferred for the fixation point to be situated within the front half of the foot support plate. The first spring element 3 is a compression spring element; various types of spring elements can be used for this purpose, for instance, a strong spring coil, a spring blade, a foam rubber element or an air cushion. The second spring element 4 is fixed at foot support plate 2 at a point close to the rear end of the plate, preferably within the rear fifth of the foot support plate. The second spring element 4 is an expansion or draw spring element the purpose of which is to pull the rear end of foot support plate 4 towards the frame. Instead of spring element 4 other means suitable for hindering the rear end of foot support plate 2 to move away from frame 1 can be arranged, for instance a compression spring (not shown) affecting directly or indirectly foot support plate 2 at its rear end (dorsally off pins 8) in an upward (towards its top side) direction. A transversely disposed rod 6 functioning as a rocking or tipping yoke for foot support plate 2 extends between the side walls of frame 1 and can be positioned displaceable and lockable with its ends in a number of positions in longitudinally extending slits 9 (only one shown) in the side walls of frame 1. The positioning of rod 6 in slits 9 is described in the following in connection with the explanation of the apparatus' function. For instance slits 9 can be replaced by a number of bores through pairs of which rod 6 can be inserted; each pair of bores corresponds to one position for rod 6. Locking of rod 6 in slits 9 is not shown in Fig. 1; it can be obtained, for instance, by having both ends of rod 6 provided with threads and keeping it in place by threaded-on nuts abutting the side walls of frame 1. In the following the functioning of the apparatus according to Fig. 1 will be explained. The foot support plate of the apparatus shown in Fig. 1 is drawn in full line in position A at the start of a movement cycle. In the first phase of the cycle, the dorsal flexion phase, the foot rests against foot support plate 2 with an abutment pressure distributed substantially evenly between the forefoot and the hind foot. The forefoot portion of foot support plate 2 is designated 2a, and its rear or hind foot portion, 2b. Movement is started by the person pressing down front portion 2a of the foot support plate with the forefoot, said plate thereby swiveling around pins 8 and approaching frame 1. This movement is allowed to proceed until the underside of foot support plate 2 contacts (at 5) rod 6 and thereby reaches position B; at this point the load on the foot support plate is displaced towards its front portion 2a. Continued pressure by the forefoot on front portion 2a results in foot support plate 2 tipping around rod 6 which acts both as a stop for the swivelling movement in the first phase and as a tipping axis for the second phase, the unrolling phase. This unrolling phase copies the unrolling of the sole at walking. The tipping of foot plate 2 lifts pins 8 in slit 7 against the force of spring 4. Upon reaching their uppermost position delimitated by the upper end of slit 7 foot support plate 2 cannot be pressed down further; this distinctly signals the user to relax the leg muscles which allows compression spring 4 to push foot support plate 2 with the passively resting foot on it back to the starting position. From a user's perspective this return phase is generally passive. A suitable position for rod 6 (tipping or rocking yoke) can be adjusted as desired by the user; the closer to the frame rear end rod 6 is displaced the earlier the unrolling phase starts and the greater is the unrolling angle β (tipping angle) ; the dorsal flexion angle of the first phase decreases correspondingly. It is preferred for the tipping angle β to be from 5 to 20°. Suitably slit 9 is arranged in a way to provide for selection of tipping rod 6 position in a way to make the length of hind foot portion 2b vary between 25 and 40% of forefoot portion 2a length; the abutment point 5 for the tipping rod delimitates forefoot portion 2a from hind foot portion 2b. The embodiment of the apparatus according to the invention shown in Fig. 2 lacks the second spring element 4 and slit 7 of the first embodiment. Pins 8' (functionally corresponding elements are identified by the same number) are only rotatably secured in the side walls of frame 1. Rod 6 of the first embodiment functioning as tipping yoke has been replaced by a tipping yoke 6' being semi¬ circular in section and disposed at the underside of frame 1'. In Fig. 2 it is fixed to the underside of frame 1', but it may also be disposed displaceable in the direction of the front or rear end of frame 1', for instance by releasable fixation with one or several screws inserted from the topside of the bottom plate in one or several bores provided in the bottom plate and disposed in a row or in parallel rows, and secured by screwing them into threaded bores provided in the topside of the rocking yoke 6' abutting the bottom plate of frame 1'. A front stop 10 is arranged for limitation of the tipping movement. Foot support plate 2' of the apparatus illustrated in Fig. 2 is shown in solid line in position A' at the start of a movement cycle. In the first phase of the cycle, the dorsal flexion phase, the foot rests against foot support plate 2 ' with an abutment pressure which is substantially evenly distributed between the forefoot and the hind foot. The forefoot portion of foot plate 2' is designated 2a', and the hind foot portion, 2b'. In the same way as with the first embodiment the movement starts by the forefoot pressing down front portion 2a' of foot support plate 2' making foot support plate 2' swivel around pins 8' and approach frame 1'. This movement is allowed to proceed until the center of gravity of the foot's abutment pressure has been sufficiently displaced towards the front end of foot support plate 2' or until foot support plate 2* hits a stop 11 fixed at the long sides of frame 1' (this alternative is shown in Fig. 2; the stop may also be arranged displaceable in longitudinal direction of frame 1' in a similar way as rod 6 in the first embodiment; this is not shown in Fig. 2) . Thereby position B' is reached and the dorsal flexion phase passes to the unrolling phase. A continued pressure by the forefoot against the front portion 2a' of foot support plate 2' leads to foot support plate 2' tipping around tipping yoke 6'. The tipping is allowed to proceed over a tipping angle β' , preferably from 5 to 20°, until the front end of frame 1 or a compliant stop 10 contacts the support. Suitably the stop can be of a soft compliant material and functions as a compression spring to damp the tipping movement. When foot support plate 2' cannot be tipped further (position C ) this signals the moment when to relax the leg muscles. The compression spring presses foot support plate 2a with the abutting foot back to the starting position. From the user's standpoint this return phase again is substantially passive. In the described embodiments the supporting elements, i.e. the frame and the foot support plate, are manufactured in steel plate. Also other materials can be used, for instance injection molded polystyrene or polycarbonate or reinforced polymer materials. Such materials reduce the weight of the apparatus but require manufacture in larger series to be economic. Suitably the apparatus according to the invention can be designed in a way to allow compression springs to be compressed more or less completely to provide for locking of the foot support plate in a position parallel with and close to the frame; the apparatus thereby assumes a small transport and storage volume. Such a collapsible design requires rod 6 and stop 11, respectively, to be releasingly arranged, possibly in such a way as to make them hold foot support plate 2; 2' against frame 1; 1' by being designed insertable in bores (not shown) in foot support plate 2; 2' arranged to that effect. The third embodiment shown in Figs. 3 and 4 has a foot support plate 22 which is rotatably supported in frame 21 via a H-formed plate bracing 23. On the one hand bracing 23 is hingedly fixed, by eyes 28, 29 od the one pair of side bars of the bracing, at a foot support plate axis 35 fixed at the underside of foot support plate 22 by a pair of holding plates 27 and, on the other hand, by means of eyes 24, 30 of the other pair of side bars of bracing 23, on a frame axis 36 fixed to the topside of frame 21 by means of a pair of similar holding plates 26. Axes 35 and 36 are parallel with each other. Holding plates 27, 26 are flat, semicircular, and extend perpendicularly from the underside of foot support plate 22 and the top side of frame 21, respectively, and are parallel with the long sides of plate 22 and frame 21. Bracing 23 is centered by spacings 24, 25 mounted on axes 36 and 35, respectively, between bracing 23 and holding plates 26, 27. The function of the compression spring opposing a movement of foot support plate 22 towards frame 21 is obtained by arranging a strong spring wire element comprising a substantially V-formed inner or base portion rounded at its tip, the base portion consisting of somewhat curved bar portions 33, 34 and straight end portions 39, 40 joined to curved bar portions 33, 34, respectively. End portions 39, 40 form an angle of about 45° with the plane defined by the zone of transition between 33 and 34 and the zones of transition between 33 and 39, and between 34 and 40. The curved bar portions 33, 34 of the spring wire element pass trough a first opening and a second opening (as seen in the direction of insertion) . The first opening is formed by axis 36, the transverse bar of bracing 23, and the halves of the side bars carrying eyes 30, 37. The second opening is formed by axis 35, the transverse bar of bracing 23, and the side bar halves carrying eyes 28, 29. The curved bar portions 33, 34 pass through the first opening from the side facing foot support plate 22, then pass the transverse bar of bracing 23 on its side facing away from foot support plate 22, then pass through the second opening from the same side, and with their rounded tip (transition zone where lateral curved bar portions 33, 34 are joined) abut against the underside of foot support plate 22 and are held in place by means of a peg 31 fixed at foot support plate 22. The V-formed bent tip surrounds peg 31 and abuts it with its inside and prevents the spring element from being drawn in a direction opposite to that of insertion. The spring element can also be locked at peg 31 by providing the free end of peg 31 with threads and screwing-on a clamping nut for securing the spring element by clamping it against foot support plate 22. In principle it is however not necessary to secure the spring element at the foot support plate 22; it is not even necessary for the spring element to touch said plate. The free end portion 39, 40 of the spring element abut the top side of frame 21; they can be arranged fixed in the frame or free. By its flexibility the spring element is held clamped between axes 35, 36 and the transverse bar of bracing 23, and thereby abuts the side of axes 36, 35 facing foot support plate 22 and edges 38 (rear edge, seen in the direction of the foot) and 32 (front edge) of the transverse bar. In the drawing the embodiment of Figs. 3 and 4 is shown in its unloaded state. When pressure is exerted on foot support plate 22 the plate first swivels around an axis formed by its lower rear edge abutting frame 21 until foot support plate 22 meets the first axis 36 or, more correctly, eyes 30, 37 of the plate bracing and spacing elements 24, and tips over, that is, turns around a new axis which is the line of abutment against said eyes and spacings. To be exact this is an unrolling on the cylindrical surface of the eyes but in practice this movement too can be seen as a rotation about an axis by reason of the small diameter of eyes 30, 37. The spring force makes the resistance increase also during the tipping phase and, by suitable dimensioning, can be adjusted in a way as to make the provision of a stop element (against excessive movement) for the foot support plate unnecessary. The spring element of course can also be a bent spring blade of spring steel. In Fig. 3 spacing element 25 is not shown for reasons of drawing clarity. For instance axes 36, 35 can be friction set in openings provided in holder plates 26, 27. In Figs. 5 and 6 is shown a fourth embodiment having great resemblance to the one in Figs. 3 and 4, but which in addition has the advantage to be simpler by requiring fewer parts. For a detailed explanation of its function reference therefore is made to the third embodiment. The main difference between the two embodiments is that the plate bracing of the embodiment disclosed in Figs. 3 and 4 has been omitted in the fourth embodiment and its function has been taken over by the spring element, more precisely by the spring element at its inner, V-formed portion having been bent for formation of two eyes on each 'lateral bar' , an eye 59 for lead- through of the first axis 58 and an. eye 54 for lead-through of the second axis 55. Suitably axes 55, 58 are mounted releasably in openings (not shown here) in holder plates 57 and 56, respectively, for insertion in eyes 54, 59 formed by the bending. Eyes 59 thus substitute eyes 30, 37 in the embodiment of Figs. 3 and 4, and eyes 54 substitute eyes 28, 29. Lateral displacement of foot support plate 52 in relation to frame 51 is limited by guides 60 arranged on frame 51 in the area of the rear portion of foot support plate 52. Fixation of spring element at 61 does not contribute in a substantial manner to the function of the apparatus. A fifth embodiment is shown in Figs. 7-11. Foot support plate 72 and frame 71 are substantially congruent in form which resembles that of a sole. They are provided with upfolded circumferential walls 91, 92 about 20 mm in height, whereby they take the form of cups. In an assembled state the inner cup bottoms face each other. Side wall 92 of foot support plate 72 encloses side wall 91 of frame 71 similar to a lock. The hind portion of side wall 91 is cut off (at 89) making the side wall lower there. In a similar way the rear portion of side wall 92 is cut off. For stiffening reasons frame 71 and foot support plate 72 ar provided with a number of stiffening ribs 73, 74, 90 arranged in pairs. In Figs. 7-9 the apparatus is shown in an assembled unloaded state (starting position for a stimulation cycle) . Foot support plate 72 and frame 71 are kept tentered by a closed, doubly U-formed spring wire loop. The ends of the U-portion resting against frame 71 (base 84, arms 81) and the U-portion resting against the foot support plate (base 85, arms 82) are joined at a rotation axis 79 around which they are wound in 1 1/2 turns under formation of two eyes 83. The disposition of the spring wire 81, 82, 83, 84, 85 is most clearly seen in Fig. 9. The maximal tentering or gap between the front ends of elements 71, 72 (at 91, 92) is determined by the abutment of the bevelled rear end of frame 71 (at 89) against the underside of foot support plate 72. Between eyes 83 a bracing 75 is swivellingly mounted with its rear end on axis 79 the ends of which are kept in bores arranged in ribs 74. At its front end bracing 75 is swivelingly mounted on an axis 98 the ends of which are supported in bores arranged in ribs 90. Axes 79, 98 are parallel with each other, foot support plate 72, and frame 71, and are perpendicular to the plane of section. A spring blade 86 passes with its one Z-curved rear end through a bore 87 in bracing 75 and is kept fixed in the bore by the Z-form. In an unloaded condition the main portion of spring blade 86 is kept flat between the underside of foot support element 72 and the topside of bracing 75; it is substantially longer than the bracing, making the front portion of the spring blade abut freely said underside. At is front end (front side 93) bracing 75 is bevelled similar to a wedge (including a certain amount of rounding) at its side facing foot support element 72 to provide for rotation around axis 98 when a force affects the rear end of bracing 75 and seeks to abolish its abutment against foot support plate 72. When foot support plate 72 is pressed down at the start of a stimulation cycle it swivels around axis 79 while bracing 75 and foot support plate 72 maintain their relative position unchanged. The end of this phase is shown in Fig. 10. Foot support plate 72 cannot swivel further around axis 79 because the underside of bracing 75 is stopped by a rounded edge 88 of a bracing stop 76 releasably fixed between rib pairs 74 at the topside of frame 71. Further loading of the front portion of foot support plate 72 makes it to continue to swing downwards, but now around axis 98, while the heel portion of foot support plate 72 is raised and abutment at 89 ceases. Swinging now occurs against the spring force of spring blade 86 (at 95) and the wire spring element. In the present embodiment this unrolling phase has no fixed end point but is determined individually by the equilibrium between the increased resistance to bending and the force applied by the foot. Bores 94 (Fig. 7) are made in the side wall of frame 71 to facilitate mounting of axes 79, 98. Upon decreasing the force applied by the foot the apparatus tends to return to its starting position shown in Figs. 7-9. Bracing stop 76 is arranged displaceable in the longitudinal direction of the stimulation apparatus by being fixed to the top side of frame 71 by a screw 77 extending through a longitudinally extending slit 80 in frame 71. Screw 77 can be locked with its head against shoulder 78 disposed at both sides of slit 80. Thereby a number of settings are made possible in respect of the angle of rotation of the foot support plate during the first phase. Displacement of bracing stop 76 in the direction of the rear end decreases this angle. As shown in Fig. 11 bracing stop 76 and bracing 75 can be provided with shoulders 97, 96. Shoulders 97, 96 serve for locking the apparatus in a transport position not shown here. With this aim bracing stop 76 is displaced forwards in the direction of arrow B until it no longer stops bracing 75 when moving towards frame 71. By exerting a suitable compression force bracing 75 can be made to simultaneously abut frame 71 and foot support plate 72; in this position frame 71 and plate 72 are essentially parallel with each other and collapsed like a can (71) with an overlaying lock (72) . When bracing stop 76 is displaced rearwards in the direction of bracing 75 (in a direction opposite to arrow B) shoulders 96, 97 engage and keep the apparatus in a locked position in which it can be secured by screw 77; instead of screw 77 also other suitable fastening means can be used, for instance spring means, such as an expansion spring fastened at the bracing stop and extending through slit 80, the spring having a free end similar to the head of screw 77. The invention is based on the insight of the importance of two consecutive phases of the kind described for efficiently stimulating venous return. It is fully possible - and is within the scope of the invention - to make the two phases overlap, that is, to provide a gentle transition between them. In the first embodiment of the invention this aim can be met by, for instance, covering rod 6 in the portion disposed between the side walls of frame 1 with a compressible material the differential resistance against compression of which is higher that for spring 3 when foot plate 5 starts to touch the compressible cover of rod 6. In the second embodiment the force of compression spring 3' can be adjusted for higher resistance. This makes tipping start prior to the foot support plate 2 touching rod 11; resilient properties of stop 10 and its dimension perpendicular to the frame can also be selected in a way as to make resistance increase in proportion to compression which contributes to a gentle overlap. In the third and fourth embodiment the transition can be controlled by proper dimensioning of the spring element; when choosing a relatively stiff spring element foot support plates 22 or 52, respectively, will start to tip before the foot support plate touches the first axis 36 or 58, respectively (or elements arranged on these axes) . Selection of appropriately dimensioned spring means and apparatus design in general is facilitated by construing and testing simple functional models. Spring elements of non-metallic materials, in particular of polymer material, may be taken into consideration; in this case the dimension of the spring element can advantageously be adapted to requirements by variation of its transverse dimension. In the same way as most other parts of the apparatus the H-formed bracing 23 suitably can be produced in polymer material to save weight.

Claims: C l a i m s 1. Apparatus for stimulation of venous return in the lower limbs comprising a frame (1; 1'; 21; 51; 71), a foot support plate (2; 2'; 22; 52; 72) having a forefoot portion (2a; 2a') and a hind foot portion (2b, 2b' ) , means for swivelling support of the foot support plate (2; 2'; 22; 52; 72) in the frame (1; 1'; 21; 51; 71) disposed at the hind foot portion (2b; 2b'), a first spring element (3; 3'; 39, 33, 34, 40; 53; 81, 82, 84, 85) disposed between the frame (1; 1'; 21; 51; 71) and the foot support plate (2; 2'; 22; 52; 72), and tipping means (6; 9; 28; 58; 98) disposed at the frame (1; 1'; 21; 51; 71) or the foot support plate (2; 2'; 22; 52; 72) or both for tipping of the foot support plate (2; 2'; 22; 52; 72). 2. Apparatus according to claim 1, c h a r a c t e r i z e d in that the means disposed at the hind foot portion (2b) for swivelling support of the foot support plate (2) in the frame (1) comprise means for displacement of the foot support plate (2) in respect of the frame (1) , the apparatus further comprising second spring elements (4) disposed between the hind foot portion (2b) and the frame (1), and wherein tipping means for tipping of the foot support plate (2) are disposed between the frame (1) and the foot support plate (2) and are arranged to limit the rotational movement of the foot support plate (2) . 3. Apparatus according to claim 2, c h a r a c t e r i z e d in that the first spring element (3) is a compression spring element and the second spring element (4) is a draw spring element. 4. Apparatus according to claim 2 or 3, c h a r a c t e r i z e d in that the position of the tipping axis (at 5) is selected to make the length of the hind foot portion from 25 to 40% of the length of the forefoot portion. 5. Apparatus according to any of claims 2 to 4, c h a r a c t e ¬ r i z e d in that the tipping arm axis comprises tipping yoke means (6) disposed at the frame (1) . 6. Apparatus according to any of claims 2 to 5 , c h a r a c - t e r i z e d in that the means for rotatable and displaceable support of the foot support plate (2) in the frame (1) comprises rotation pins (8) disposed at the foot support plate (2) and running in a slit (7) in the frame (1) . 7. Apparatus according to claim 3, c h a r a c t e r i z e d in that the force required for infinitesimal compression of the first spring element (3) is larger than the force required for corresponding expansion of the second spring element (4) . 8. Apparatus according to claim 1, c h a r a c t e r i z e d in that the tipping means (9) for tipping of the foot support plate (2') are disposed at the underside of the frame (1'). 9. Apparatus according to claim 8, c h a r a c t e r i z e d in that the tipping means (9) for tipping of the foot support plate (2) have substantially transverse extension in respect of the longitudinal direction of the frame (1'). 10. Apparatus according to claim 8 or 9, c h a r a c t e r i z e d in that the tipping means (9) for tipping of the foot support plate (2') are arranged collapsible in the frame (1'). 11. Apparatus according to any of claims 8 to 10, c h a r a c t ¬ e r i z e d in that the tipping means (9) for tipping of the foot support plate (2') are designed to prevent gliding of the apparatus on a support. 12. Apparatus according to any of claims 2 to 11, c h a r a c ¬ t e r i z e d in that the tipping means (9) for tipping of the foot support plate (2') are adjustable in the longitudinal direction of the frame. 13. Apparatus according to any of claims 2 to 12, c h a r a c ¬ t e r i z e d in that the tipping means (9) for tipping of the foot support plate (2') are resilient. 14. Apparatus according to claim 1, c h a r a c t e r i z e d in that the means for swivelling support of the foot support plate (22; 52; 72) in the frame (21; 51; 71) comprise parallel rotation axes (35, 36; 55, 58; 98, 79) disposed at the underside of the foot support plate and the frame, said axes being hingedly connected with parallel end portions (28, 29; 30, 37) of a bracing (23; 75) and/or eye pairs (54, 59; 83) on the lateral bars (53) of a V-shaped spring element. 15. Apparatus according to claim 14, c h a r a c t e r i z e d in that the bracing (23) is H-shaped. 16. Apparatus according to claim 15, c h a r a c t e r i z e d in that the V-formed spring element is insertable with its branching end and bar sections (33, 34) extending therefrom in a first opening formed by the first rotation axis (35) and the bracing (23) , and in a second opening formed by the second rotation axis (36) and the bracing (23) , and is fixable by clamping contact with the transverse bar edges (32, 38) of the bracing (23) and the rotation axes (35, 36). 17. Apparatus according to claim 14, c h a r a c t e r i z e d in that it comprises a displaceable bracing stop (76) for limiting the movement of the bracing (75) . 18. Apparatus according to claim 17, c h a r a c t e r i z e d in that the bracing (75) and the bracing stop (76) have cooperating shoulders (96, 97) for locking the apparatus in a compressed transport condition. 19. Method for stimulation of venous return in the lower limbs, c h a r a c t e r i z e d in that it comprises treading down in two consecutive phases a foot plate disposed svivellingly around one axis each, said foot plate in the second phase rotating around an axis parallel with and disposed anteriorly in relation to the axis around which it rotates in the first phase. 20. Method according to claim 19, c h a r a c t e r i z e d by the person whose venous return shall be stimulated assuming a sitting position, placing one of the person' s feet with the sole against the abutment area on the top side of a foot support plate of an apparatus for stimulation of venous return, said foot support plate tilting between 25 and 75° in respect of the vertical and having a hind foot portion and a forefoot portion, - in a first phase, treading down the foot support plate against a spring force, the foot support plate in combination with the foot swinging around a first rotation axis disposed essentially perpendicular in respect of the foot's long axis and being essentially parallel with the abutment area and extending in the region beneath the posterior part of the calcaneus or behind (dorsally of) it, in a subsequent second phase, treading down the foot support plate against a spring force, the foot support plate in combination with the foot swinging around a second rotation axis essentially parallel with said first rotation axis and disposed in front (anteriorly) of it and extending in or beneath the plane of abutment; essentially passive return of the foot plate and the foot resting on the foot plate to the starting position through the effect of the spring force.

Inventors: BUSCH CHRISTER, BUSCH, CHRISTER
Applicants: BUSCH CHRISTER, BUSCH, CHRISTER
Application year: 1996
Main classification: A63B22
IPC codes: A63B21, A63B23