GB2216836A

GB2216836A - Forceps and calibration device

Info

Publication number: GB2216836A
Application number: GB8807964A
Authority: GB
Inventors: R Ernest Mark Talbot; Andrew William Thomas Thorp
Original assignee: Dr Ernest Mark Talbot
Current assignee: Dr Ernest Mark Talbot
Priority date: 1988-04-05
Filing date: 1988-04-05
Publication date: 1989-10-18
Also published as: GB8807964D0

Abstract

A forcep (eg. suture tying forcep) has limbs which, when compressed, meet at the tips (1). This compression, and therefore grip of the tips, can be limited by an adjustable stop (2) and ratchet system (5). The forceps release the body acted upon (eg. suture) once the tension in the body overcomes the forceps grip. No further increase in tension within the body can occur. By limiting compression of the legs, the tension within the body acted upon is similarly limited. Preferably a lug (3) is provided on one limb close to the tips (1). The closed tips can be opened momentarily by pressure at a point (4), so placed that the lug (3) acts as a fulcrum. <IMAGE>

Description

FORCEPS AND CALIBRATION DEVICE This invention relates to a pair of forceps and a device to calibrate them.

During the closure of a surgical wound uneven tightness of sutures causes uneven wound compression and an uneven distribution of wound tension along the incision line.

In ophthalmic surgery this results in a distortion of the first and major refracting surface of the eye, the cornea, ie, instead of a spherical surface of equal refracting power in each meridian, a surface with moré than one radius of curvature is produced with a resultant distortion of the image produced (astigmatism).

The invention obviates or mitigates the aforementioned problem.

According to the present invention there is provided a pair of forceps able to measure tension created in the substance worked upon and also able to reproduce the tension in a subsequent act, or alter by a known amount the tension in the -substance, by keeping constant or adjusting the frictional force at the forceps tips by means of an adjusting nut. The degrees of movement of the nut is directly related to the frictional force at the tips.

Once the frictional force at the tips is overcome no further increase in tension can occur, eg, a surgical suture is tied to a known tension, subsequent sutures can be tied to the same tension creating an evenly compressed wound or to a desired different tension to create the desired distortion.

A specific embodiment of the invention will now be described by way of an example with reference to accompanying drawings.

LIST OF FIGURES Figure 1 Example 1. Side view showing post and lug on one leg with adjusting nut and ratchet on the other leg. As the nut is tightened the tips close tighter.

Once closed the tips can be opened momentarily by pressure at(4) against the lug fulcrum.

Figure 2 Example 1. From above showing ratchet and adjusting nut Figure 3 Example 2. The adjusting nut drives a bolt which limits the appositional force at the tips when a clamping force is applied.

Figure 4 Example 2. Modified side view. The ratchet is replaced by a sprung piston arrangement which allows easy turning of the nut while achieving good fixation of the nut notch.

A dummy nut on the opposite leg and surface concavity keeps surgeons grip on clamping force position constant.

Figure 5 Figure 4 from above showing marks punched onto the surface of the adjusting nut to enable different settings to be made.

Figure 6 Calibration beam from above.

Figure 7 Calibration beam side view.

Figure 8 Calibration beam end on.

Example 1/ Example 1 (Figures 1 and 2) Stainless steel forceps compressing two divergent limbs and a lug(3) on one limb close to the tips(1).

A threaded post is attached to the lug limb and passes through the opposite limb into an adjusting nut(2) which is limited by a ratchet(5~. In Figs 1 and 2 the clamping force is provided by an adjusting nut compressing the legs of the forceps until the tips meet.

Any substance between the tips(1) will be gripped with a frictional force related to the amount of compression of the legs caused by the adjusting nut(2). The force is increased (and so the grip) with further turns of the adjustment nut.

When the tension in the substance overcomes the frictional force at the tips, the forceps' grip on the substance is lost and there can be no further increase in tension. Manual compression of the legs further until one leg hits the lug(3) on the opposite leg, causes the tips to open. If no further adjustment of the nut is made then the same tension can be created in the next operation. The actual tension created can be measured first on a calibrating device Figs 6, 7 and 8 and subsequently by the number of notches the knurled adjustment nut(2) is turned against a ratchet(5).

Example 2 Figure 3 shows divergent stainless steel limbs with an adjusting nut screw(2) through one limb which abuts against the opposite limb when a clamping force is applied at(2).

In/ In Figure 3 type 2 forceps differ from type 1 in that, the clamping force is provided manually by compression at(2) of the legs(6) until the tips(1) meet. Further manual compression increases the grip on the substance. However this can be limited by the adjustment nut(2) which prevents further apposition of the legs. The further in the adjusting nut(2) is turned the further apart the tips will become so that the maximum frictional force will be less. The tips are opened by reduction of manual compression of the legs. The tension is measured first by calibration and subsequently by the number of notches the knurled adjusting nut(2) is turned. The tension is reproduced by not altering the setting of the adjustment nut against its ratchet and altered a known amount by each notch turned of the adjusting nut.

In both examples the jaws simply release the substance once the frictional force is overcome.

Example, 3 A modification of example 2 is shown in Figs 4 and 5. Instead of a ratchet(5) a spring (7) piston(8) in cylinder(9) is used to fix the adjusting nut(2). This can be set into the handle (10) to reduce its prominence. The adjusting nut (2) is contoured to accommodate the pulp of the finger and there is a dummy(11) added on the opposite leg to accommodate the thumb so keeping the position of the clamping force constant relative to the adjustment.

Other means can be used to measure the deforming forces created in a pair of forceps, caused by the tension created in the work object such as; strain gauges and cantilever, by pressure transducer, rectilinear potentiometer, spring scale, hydraulic systems, etc. The examples given are the most practical for ophthalmic surgery.

The Calibration Device, Figs 6,7,8/ The Calibration Device, Figs 6, 7 8 The cantilever beam(12) is prevented from falling by a stop(l5) on the base(l3). The cantilever beam(l2) is fitted with strain gauges(16), to measure the tension created in a suture, wound around a cylinder(14), at the end of the beam(l2) and acting in the centre line of the beam, at a constant distance. The strain gauges are connected to a digital display.

A change in suture tension causes a change in beam position which results in a change in resistance in the strain gauges. #y means of a Wheatstone bridge, The change in voltage is related to the tension in the suture.

Claims

Forceps and Calibration Device 1. A pair of forceps in which the maximum gripping force by the forcep tips can be varied and fixed. This permits indirect measurement of the maximum tension created in a body acted upon by the forcep. It permits release of the body once the tension overcomes the preset maximum gripping force so that the tension in the body does not exceed a related maximum. The forceps can induce the same maximum tension in a body and a subsequent act, provided no further adjustment of the forceps is made.
2. Forceps as claimed in (1) with alternative means to measure the deforming forces created within the forceps such as stress guages pressure transducer, hydraulic systems, spring or vacuum scale, potentiometer.
3. Forceps as claimed in (1) with a tension measuring forcep substantially as described herein with reference to Figs 1 to 5 and calibrated with reference to Figs 6,7,8 of the accompanying drawings.
4. Forceps as claimed in (1) with a lug on one limb which allows opening of the tips without altering the adjustment of the forceps, Fig 1.
5. Forceps as claimed in (1) with a calibration device, Figs 6,7,8.
6. Forceps as claimed in (1) with a spring piston ratchet system, Figs 4,5.
7. Forceps as claimed in (1) with a dummy nut and concave surface of nuts allow improved grip and keep constant the position of the clamping force Fig 4.