Magnetic clamp

Abstract

Two movable members, one containing a permanent magnet and the other containing a non-magnetized but magnetically susceptable element are positioned such that there exists a magnetic force of attraction between the two members, thus closing a switch or valve. A control magnet having a greater strength than the first permanent magnet opens the switch or valve by attracting the susceptable element and repelling the permanent magnet.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to valves and switches having a permanent magnet actuator and having an additional magnetic control element and particularly relates to such a valve having a U-shaped resilient contacting element.

2. Description of the Prior Art

Numerous switches and valves to be found in the prior art have relied upon magnetic effects to assist in or cause the particular motions necessary for opening or closing of the valve or switch. Generally, it has been necessary to bias one or more of the moving elements in a particular position by means of springs to achieve either a normally open or normally closed position for the switch or valve. The presence of the biasing spring has required that the magnetic actuating element not only overcome the inertia of the particular switch or valve, but also the force of the biasing spring which typically has a disadvantageous force-distance relation.

The slow closing and contact bouncing in electrical switches can cause the electrical contacts to become welded in the closed position, thus necessitating mechanical means for over-riding the normal switch functions and a reopening of the switch contacts. This presents a peculiar problem when the switch is remotely positioned, thus making mechanical override difficult, if not impossible. Similar problems are also presented by fluid controlling valves which are to be operated from a remote position and particular problems are presented when the switch or valve is located within the human body.

Previous means for controlling the liquid flow through tubes or ducts within the body have often required placing an element within the duct or tube, thus subjecting that element to possibly detrimental chemical action. With the element so placed, the liquid flow is never returned to normal due to the constriction presented by the element even when fully opened.

Some previous means having sliding, reciprocating or otherwise moving elements face the additional problem of being susceptable to detrimental tissue infusion over a period of time, thereby preventing the relative movement necessary for correct operation and ultimately resulting in failure of the control means.

During surgery, sutures are usually used for tying off a duct or vessel to restrict or prevent flooding of the surgical area as well as to conserve life sustaining body fulids. The use of sutures in this fashion is very time consuming, often requiring young resident surgeons to spend 3 to 4 hours assisting their more experienced colleagues by simply tying surgical knots. Alternatives such as staples have been suggested, but have not enjoyed the favor of the practicing physician due in part to the difficulty of removal. while conventional hemostats and other surgical clamps are very easy to remove, they often present substantial obstacles which must be continually dodged during an operation.

The involuntary escape of urine due to urinary incontinence represents a particularly discomforting, inconvenient and unsanitary problem. Previous means attempting to solve the problem by compressing the urethra have not met with acceptance due in part to the size or complexity of the apparatus used. Some means have been more successful in the male than in the female due to the anatomical differences. Often, however, considerable postoperative treatment and rehabilitation has been necessary and the results not as satisfactory as one might reasonably wish.

SUMMARY OF THE INVENTION

A substantially linear arrangement of three magnetic and magnetically responsive elements form a magnetic switching means which is magnetically biased in either an open or closed position. Metallurgically and chemically well defined and calibrated elements provide reproducible operating characteristics unsusceptible to aging or metal fatigue. Free travel is provided in some situations to achieve the energy necessary to open or close a switch while little or no free travel is provided in close tolerance switch balancing situations.

The arrangement consists of three elements: a first permanent magnet, a magnetically susceptible non-magnet, and a temporary or permanent control magnet of opposite polarity and having upon occasion a higher strength magnetic field than the first permanent magnet. The magnetically susceptible non-magnet is confined within the magnetic field of the first magnet such that if the other magnet is not operating the magnetic forces acting on the first magnet and the non-magnet are sufficient to move the two together.

The control magnet is positioned on the opposite side of the non-magnet as viewed from the first magnet and when magnetized has a magnetic polarity opposite that of the first magnet. When magnetized sufficiently or when magnetized and brought within a maximum range, the control magnet induces a greater magnetic field in the non-magnet than the first magnet, thus simultaneously attracting the non-magnet and repelling the first magnet. The first magnet generally moves under influence of the repelling force to a position so as to prevent the degradation of its inherent permanent magnetic field by the control magent. In particular situations, however, it may be advantageous to maintain the first magnet within the field of the control magnet to such an extent as to permanently obliterate the first magnet's magnetic history by reducing or eliminating its inherent magnetic field.

The slidable positioning of the magnetic elements within the cages permits the elements when magnetically actuated to gain sufficient kenitic energy to fracture any weld on the contact surfaces due to electrical current arcing. This eliminates the necessity of a mechanical override and greatly increases the reliability of the circuit interruption. The magnetic switching means can also be advantageously used as a valve.

An apparatus utilizing the magnetic switching means for clamping or compressing a tube or sheet stock comprises a first permanently magnetized element, that is, a first element having associated therewith a substantial, macroscopic, permanent magnetic field. The closure apparatus also comprises a second, non-magnetized yet magnetically susceptible element. The second element has a relative magnetic permeability much greater than the first, yet has associated therewith no appreciable, macroscopic, permanent magnetic field, and very little magnetic remanence. The first and the second elements are a part of a first and a second leaf or jaw, respectively. The leaves or jaws are hinged together in such a manner that a tube placed between the first and second leaves would be compressed by the force generated by the magnetic field of the first element acting on the second element.

The first and second leaves and the means hingedly connecting the leaves can be a unitary structure made of a plastic material which is flaccid, bendable, deflectable, deformable, elastic, or resilient. The first and second elements would be enclosed, encased or encompassed by the material of the first and second leaves respectively. Each leaf can be contiguous to and envelop the corresponding magnetic element. As such, the leaves clamp or clasp an intersituated tube in such a manner as to prevent material from moving through the length of the tube.

To conveniently operate the apparatus, another permanently magnetized element is used having a magnetic field of such as strength as to overcome the coercive magnetic force which the first element exerts on the second element. To open the magnetic clamp or clasp, the other permanently magnetized element is positioned near the second jaw and in such a direction as to oppose the magnetic field of the first element. A magnetic field will be induced in the second element which repels the first element thereby opening the apparatus.

One advantage of such an apparatus is the absense of any element on the inside of the tube or duct controlled, thus obviating unnecessary or unwanted constriction and avoiding detrimental chemical or physical interaction with the contents of the tube or duct.

Another advantage of such clamping apparatus is the ability to control the opening and closing of the apparatus without direct contact. In fact, when such an apparatus is placed appropriately within an animal's body, or in any other inaccessible region, it may be conveniently controlled by another permanent magnet element or electromagnet element remotely positioned outside the animal's body.

An advantage of such a clamp is its possible use during an operation to quickly close vessels which might otherwise flood the surgical area.

Other features and advantages of magnetic switching means will become apparent from the following discussion of the appended figures and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective detail of a valve in an "open" position having a magnetic switching means.

FIG. 2 is a perspective detail of the apparatus of FIG. 1 in a "closed" position.

FIG. 3 is a diagram of operation of a magnetic switching means according to this invention.

FIG. 4 is a plane detail of a tool for manipulating the apparatus of FIG. 1 incorporating a magnetic control element.

DETAILED DESCRIPTION OF THE DRAWINGS

The apparatus shown in FIG. 1, generally as 8, consists of two leaves or jaws 10 and 12 coupled together by a flexible hinge 14. The two jaws and the hinge are unitarily constructed and are preferably composed of a biochemically inert material such as a silicone, vinyl or polyacrylonitrile resin or .alpha.-olefin polymer.

Encased within the first leaf 10 is a first permanently magnetized element 16. The first magnetic element has associated therewith a macroscopic magnetic field of sufficient strength to close the one jaw against the other. While an acceptable first element may be made of oriented ferrite, platinum-cobalt, or the ALNICO series, the preferred material in some situations is the REACO-1 samarium cobalt rare earth permanent magnet material available from Raytheon Company of Waltham, Massachusetts, and described in their Technical Report number PT-3666, published February, 1973. The first element may be of any convenient shape and size consistent with the use anticipated and the needed magnetic field.

Encased within the second leaf 12 is a second element 18 which has substantially no permanent magnetic field but has a magnetic permeability .mu. sufficient to be classed as either a paramagnetic material or a ferromagnetic material. The second element is thereby influenced by external magnetic fields and is attracted to magnetic fields. In practice, the susceptibility and permeability of the element 18 must be sufficient to allow the permanent magnet 16 to close the one jaw against the other when placed in an open position.

The apparatus 8 can be used to pinch a tube 20 as shown in FIG. 2. In such a situation, the second element 18 is influenced by the magnetic field of the first element 16 in such a way as to cause a force on the two elements thereby attracting the two leaves 10 and 12 together. If the magnetic field of the first element is correctly selected, the force will be that necessary to close the tube without causing permanent physical damage to the tube. This is particularly important where the tube is a vessel or duct of a body made of living tissue and thus susceptible to injury. Alternatively, the jaw faces can be padded to avoid the possibility of tissue necrosis. The variables which must be considered are the area of contact of the tube closure element and the tube, the flexibility and susceptibility to injury of the tube, any deformable character of the closure surface, the time duration of clamping and so forth.

While an apparatus such as that already described may be manipulated in numerous ways, it is most advantageous to use the magnetic characteristics of the apparatus to effect an opening and closing. FIG. 3 is a diagrammatic representation of the operation of such a device as previously described or any other apparatus having a magnetic switching means of similar magnetic characteristics. In each of five representative situations, I, II, III, IV and V, the first magnetic element 16 is to be found in either position A or B, and further is constrained to move only within the space between lines 22 and 24. The second magnetically susceptible element 18 is likewise found in either positions C or D and is constrained to move only within the space between lines 24 and 26.

A third element 28 has a permanent magnetic field greater than the first element 16 and aligned in the opposite direction as indicated by the letters N and S. The third element can be made of the same or similar material as the first element, or may be an electromagnet. The third element can be moved to any position to the right of line 26 or in the case of an electromagnet can have any magnetic field strength desired within practical limits.

In situation I, the first and second elements are as close together as physical constraints will allow. The magnetic field of the first element 16 indicated by the letters N and S induces a magnetic field in the magnetically susceptible element 18 indicated by the letters n and s. The induced magnetic field is in the same direction as that external magnetic field having the greatest influence over the passive element 18. The third element 28 in position G is in such a position as to make no substantial effect on the second element 18 in position C. The device as shown in FIG. 2 can be considered to be in the same magnetic state as indicated in situation I of FIG. 3.

In situation II, the physical relation between the first and second element remains substantially unchanged, but the third element 28 is in such a position as to influence the induced magnetic field in the second element 18. This change in induced magnetic field is indicated by the smaller number of letters n and s within the second element. If the third element is moved to the right, it has less influence on the second element while if the third element is moved to the left, it has more influence consistent with the well known relations between permanent magnets and magnetically susceptible materials.

If the third element 28 is sufficiently far to the left, indicated by position E, and the permanent magnetic field of the third element is sufficient, the induced magnetic field in the second element will become aligneed with the third element rather than the first element. This causes a net force of attraction between the second and third elements and a resultant simultaneous repulsion of the first element thereby resulting in situation III. While FIG. 3 suggests a close physical proximity between the second and third elements in situation III, such a proximity is not necessary if the magnetic field of the third element is great enough. An apparatus as previously described when in a situation like situation III would appear open or with the jaws apart, as shown in FIG. 1.

As the control element 28 is withdrawn to the right as shown in FIG. IV and V, its influence on the second element 18 is reduced, thus reducing the induced magnetic field as indicated by the fewer number of letters s and n within the second element 18. Finally, if the third control element 28 is withdrawn to a position to the right of position G, the influence exerted by the first element on the second element will again become greater than that of the third element thus returning the elements to the positions of situation I.

FIG. 4 shows a manually operated tool 30 for magnetically manipulating an apparatus 8 as shown in FIGS. 1 and 2. The tool 30 has two legs 32 and 34, each connected to its respective handle 36 and 38. The two legs are pivotally secured by a pivot 40 in such a manner that as the two handles are brought together, the ends of the two legs farthest from the handles are separated in a reverse scissor-like motion.

The end of one leg 32 is adapted to receive an apparatus 8, as previously described, by having affixed thereto a restraining element 26 which functionally can be viewed to operate as line 26 in FIG. 3. The restraining element is fixed to leg 32 at a point 42 between the end of the leg farthest from the handle 36 and the pivot 40. That portion of the leg 32 between the point 42 and the end farthest from the handle 36 functionally operates as a restraining means 22 analogous to line 22 in FIG. 3.

An apparatus 8 as previously described can be inserted between the restraining elements 22 and 26 near the end of leg 32 with leaf 10 adjacent restraining means 26 and the hinge 14 directed toward pivot 40.

The end of the other leg 34, farthest from handle 38, receives or contains the third magnetic control element 28. When the leg 34 is positioned close to restraining element 26, the control element has a dominating influence over the second element 18 within the leaf 12 and attracts the leaf 12 toward the restraining element 26, while repelling the leaf 10 to a position against the restraining element 22. This corresponds to situation III in FIG. 3.

As the handles 36 and 38 are brought together, the control element 28 moves away from the restraining means 26 and leaf 12 and if drawn far enough away, the magnetic influence of the first element 16 within leaf 10 becomes dominating and the jaws of the apparatus close. This corresponds to situation I in FIG. 3. In this closed position, the apparatus 8 is freely removable from the tool 30. Looking at the situation another way, if the apparatus 8 is caused to close upon a tube or duct as shown in FIG. 2, the tool 30 may then be easily withdrawn.

A clamping apparatus 8 may be used for a quick release mechanism for metal plates, paper or other sheet materials as well as for "tying off" vascular elements during surgery. Such an apparatus can also be permanently implanted within the body for controlling the flow of liquid through a duct by external means. In the case of the urethra, for example, the apparatus is positioned such that the urethra passes between the two jaws and a control magnet is topically positioned to effect the desired control using the magnetic switching means as a valve actuating device.

Other uses for a magnetic switching means according to this invention will become apparent to the practitioner from this presentation. In all situations, it is intended that the apparatus consist of a first permanently magnetized element and a second non-magnetized but magnetically susceptible element. The second element is constrained to exist within the region adjacent the first element having a magnetic field, in the absence of other magnetic fields, sufficient to attract the second element to the first element, that is within the effective magnetic field of the first element. The switching means also consists of a third element, placed on an opposite side of the susceptible member from the first element and having at least upon occasion a magnetic field greater than and oppositely aligned to that of the first element sufficient to attract the second element and simultaneously repel the first element. In interpreting this specification "an opposite side" is used in the sense that the control element can be positioned in any position which is not on the same side of the susceptible element as the first element yet will cause the resulting simultaneous attraction of the second element and repulsion of the first element. It will be apparent that to get the optimum magnetic effect, the control magnet would be positioned on the side directly opposite the first magnet.

Claims

I claim:

1. In combination with a clamping apparatus comprising a first jaw having a permanent magnet enclosed therein, a second jaw having a magnetically susceptible non-magnet enclosed therein, and a hinge confining the non-magnet within the operable magnetic field of the permanent magnet, the hinge and the first and second jaws being unitarily constructed of a biochemically inert material, means positioned adjacent to the second jaw having a magnetic field greater than and oriented in the opposite direction of the field of said permanent magnet for opening and closing the jaws.

2. The apparatus of claim 1 wherein said first permanent magnet has a magnetic field sufficient to close the jaws of the apparatus on a tube of living tissue without causing permanent physical damage to the tube.

3. The apparatus of claim 1 wherein the jaw faces are padded.

4. A clamping apparatus comprising a first jaw having a permanent magnet enclosed therein, a second jaw having a magnetically susceptible non-magnet enclosed therein, a hinge confining the non-magnet within the operable magnetic field of the permanent magnet,

the hinge and the first and second jaws being unitarily constructed of a biochemically inert material,

and a manually operated tool for magnetically manipulating the jaws, comprising means adjacent to the second jaw having a magnetic field greater than, and oriented in the opposite direction of, the field of said permanent magnet.

5. The method of controlling the flow of fluid through a duct of living tissue located within an animal's body comprising the steps of positioning a first jaw having a permanent magnet enclosed therein on one side of the duct, positioning a second jaw having a magnetically susceptible non-magnet enclosed therein on the opposite side of the duct, the first and second jaws being unitarily constructed of a biochemically inert material joining the first and second jaws in the form of a hinge, the hinge confining the non-magnet within the operable magnetic field of the permanent magnet, the permanent magnet having a magnetic field sufficient to close the jaws on the duct without causing permanent physical damage to the living tissue, and permitting the jaws to close on the duct of living tissue.

6. The method of claim 5 further comprising the steps of positioning a second magnet on the same side of the duct as the non-magnet has been previously positioned orienting the polarity of the magnetic field of the second magnet opposite to that of the first magnet, and increasing the strength of the field of the second magnet to a value greater than that of the first magnet when measured at the point of the non-magnet, thereby opening the jaws and permitting the flow of fluid within the duct.