GB2459076A

GB2459076A - Speculum with ratchet lock

Info

Publication number: GB2459076A
Application number: GB0719777A
Authority: GB
Inventors: John Bailey; Stephen George Edward Barker
Original assignee: Evexar Medical Ltd
Current assignee: Evexar Medical Ltd
Priority date: 2007-10-10
Filing date: 2007-10-10
Publication date: 2009-10-14
Anticipated expiration: 2027-10-10
Also published as: GB2459076B; GB0719777D0

Abstract

A speculum includes first and second spreading members 2, 3 pivotable relative to one another between a closed position, to allow for insertion thereof into a body cavity, and a plurality of discrete open positions, to allow for inspection of the body cavity. A lock 9 is provided for releasably locking the spreading members 2,3 in a selected one of the open positions. The lock includes an array of teeth 11 associated with one of the spreading members 2,3 and a locking element 18 associated with the other of the spreading members 2,3. The locking element is selectively engagable with the teeth 11 to lock the spreading members 2,3 in the selected open position against unwanted closure by the action of the body. The locking element 18 is constructed and arranged to release the lock automatically, upon the opening of the locked spreading members 2,3 beyond the selected open position, as a result of movement of the locking element 18 out of engagement with the teeth 11 under the action of gravity.

Description

S

IMPROVEMENTS N AND RELAT[NG TO MEDICAL DEVICES The present invention relates to medical devices, particularly, but not exclusively, to vaginal specula.

Such specula are commonly used in cervical examinations. The Graves-type vaginal speculum comprises two relatively moveable, e.g. slidably or pivotably cooperating, spreading members which are adapted, in use, to be inserted into the vagina and adjusted into an open position. A lock is commonly provided to enable the spreading members to be temporarily and releasably locked in their open position against the contraction of the spread vaginal muscles.

Many vaginal specula employ a lock in the form of a ratchet and pawl arrangement. A ratchet is associated with one of the spreading members and a pawl with the other. Prior to insertion of the spreading members into the vagina the ratchet and pawl may already be in engagement. Alternatively, they may become pressed into mutual engagement by means of a mechanism or by compressive forces applied to the spreading members by the vaginal muscles. As a consequence, when the spreading members are opened from their closed position the pawl passes over the teeth of the ratchet causing noise and vibration which the patient can find unsettling and which can cause tensing of the vaginal muscles impeding the examination.

To avoid continuous contact between the ratchet and pawl during opening andlor closing of the spreading members, US-A-4 385 626 discloses a vaginal speculum in which one of the spreading members is provided with a rack of teeth and the other is provided with a tooth engagement member in the form of a flexible lever, pivotally connected at one end with the handle of the other spreading member and bevelled at its free end. The flexibility of the lever is such that the free end of the lever is biassed away from contact with the rack of teeth and will only contact the teeth if the lever is engaged by the thumb of the physician and deflected against the biasing force into contact with the toothed rack. In use, after the speculum has been inserted and opened, as soon as the lever has been brought into engagement with the rack (by pressing of the lever against its biasing force by the physician's thumb) it is held locked in a gap between two teeth of the toothed rack by the forces exerted in the closing direction on the spreading members by the vaginal muscles. The spreading members are thus locked in a desired open or spread position. After examination has been completed, the handles of the speculum can be moved towards each other through a small distance, freeing the bevelled free end of the lever from retention in a tooth undercut of the toothed rack, so that the inherent bias in the lever can return the lever to its initial position out of contact with the rack. Although the spreading members of this prior art device can thus be pivoted between their closed and open positions without undesirable noise andior vibration, the need to displace the lever against its biasing force in order to lock it into engagement with the toothed rack can be difficult to achieve if the position of the physician's hand on the handles of the spreading members does not cause the lever to be easily accessible to the physician's thumb. In addition, lubricant employed on the spreading members so as to assist insertion of the speculum can cause the physician's hand andlor the catch to carry traces of lubricant which can make if difficult for the physician to control pushing of the catch lever against its natural bias.

There is thus a need for a speculum which avoids unwanted noise andlor vibration during opening andlor closing, yet which is simple to operate and inexpensive to manufacture.

According to a first aspect of the present invention there is provided a speculum. This may comprise first and second spreading members which are pivotable relative to one another between a closed position, to allow for insertion thereof into a body cavity, and a plurality of discrete open positions, to allow for inspection of the body cavity. The speculum may further comprise a lock for releasably locking the spreading members in a selected one of said open positions. The lock may include an array of teeth associated with one of the spreading members and a locking element associated with the other of the spreading members and selectively engagable with the teeth to lock the spreading members in said selected open position against unwanted closure by the action of the body. The locking element may be constructed and arranged to release the lock automatically, upon the opening of the locked

S

spreading members beyond said selected open position, as a result of movement of the locking element out of engagement with the teeth under the action of gravity.

According to a second aspect of the present invention there is also provided a speculum. This speculum may also comprise first and second spreading members pivotable relative to one another between a closed position, to allow for insertion thereof into a body cavity, and a plurality of discrete open positions, to allow for inspection of the body cavity.

The speculum may further comprise an array of ratchet teeth associated with one of the spreading members and a locking element carried by, but slidable relative to, the other of the spreading members and selectively engagable with the teeth to lock the spreading members in a selected one of said open positions against unwanted closure by the action of the body. The locking element may be constructed and arranged automatically to move out of locking engagement with the teeth upon the opening of the locked spreading members beyond said selected open position.

An embodiment of apparatus in accordance with the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a side elevation of an embodiment of vaginal speculum in accordance with the present invention shown with its spreading members in a fully closed position and with the lock in it released condition; Fig. 2A is a side elevation of the vaginal speculum of Fig. 1, shown in a partially opened position with the lock in the released condition; Fig. 2B is an enlargement of the lock shown in Fig. 2A; Fig. 3A is a side elevation of the vaginal speculum of Fig. 1, shown with its spreading members in a fully open position and with the lock in its locked condition; Fig. 3B is an enlarged view of the lock of Fig. 3A; Fig. 3C is a view similar to Fig. 3B, but shows the lock in its unlocked condition following squeezing together of the handles of the speculum; Fig. 3D is a view similar to that of Figs. 3B and 3C, but showing the base of only one of the speculum's handles, and with the locking element of the lock omitted so as to show the elongate nature of a transverse slot provided in a guide at the base of the handle; Fig. 4 is a perspective view of the fully opened speculum of Fig. 3A, from behind and above; and Fig. 5 is an end elevation of the locking element omitted from Fig. 3D.

Fig. 1 illustrates an embodiment of speculum 1 comprising a first spreading member 2 and a second spreading member 3. These spreading members 2, 3 together form the shape of a duck bill and, when closed, are able to be inserted into a body cavity, such as a vagina, in the manner of a Graves speculum. The spreading members 2, 3 are pivotably connected together at pivots 4, so as to enable the spreading members 2, 3 to be opened from the fully closed position (illustrated in Fig. 1) to any one of a plurality of different open positions (examples of which are illustrated in Figs. 2A and 3A). So as to assist handling of the speculum 1 and insertion of the spreading members 2, 3 into a body cavity, the spreading members are each provided with a respective downwardly extending handle 2A, 3A. As can best be seen in Fig. 4, the handle 3A of the second spreading member 3 comprises a single downwardly extending member, whereas the handle 2A of the first spreading member 2 comprises a pair of curved downwardly extending members 15 joined at their bases.

Provided at the base of each handle 2A, 3A is a finger/thumb plate 2B, 3B. After insertion of the spreading members 2, 3 (in their closed condition) into the body cavity (not shown for reasons of clarity), by applying pressure to the plates 2B, 3B by squeezing them between the finger and thumb in the direction of arrows 5, the physician can cause the spreading members to open from the closed position shown in Fig. 1 to an open position.

Shown mounted on the handle 3A is an optional combined battery pack and light source 6 and a light pipe 7 (best viewed in Fig. 4) for transmitting light from the light source along to the distal end 8 of the light pipe 7, from which distal end 8 light from the light source is directed out of the distal opening formed between the open spreading members.

It is envisaged that the two main components 2, 2A, 2B, 3, 3A, 3B of the speculum I will be moulded in a plastics material, enabling the speculum to be manufactured inexpensively and to be disposed of after use.

The speculum is provided with a lock 9 for releasably locking the spreading members 2, 3 in a selected one of the available open positions. The lock includes an arcuate rack 10 extending rearwardly from the handle 3A, generally perpendicular to the elongate direction of the handle 3A. This rack has formed on its lower surface an array of teeth 11. Gaps are defined between the teeth 11, each gap corresponding to a potential lockable open position for the speculum. Provided opposite those teeth is an arcuate bar 12. An open arcuate track 13 is defined between the rack 10 and the bar 12, which track 13 is closed at the end opposite to the handle end by an integral bridge between the ends of the rack 10 and bar 12. It is envisaged that the rack 10 and bar 12 will be integrally moulded with the handle 3A during fonnation of the component including the second spreading member 3A, for example as a result of injection moulding in plastics material. For reasons which will become apparent, it will be noted that the individual teeth 11 of the rack 10 are directed downwardly and forwardly, so that the gaps therebetween are directed both rearwardly and upwardly.

The lock 9 also includes a guide block 14 integrally moulded with the handle 2A of the first spreading member 2 in the region of the top of the finger/thumb plate 2B. As is most readily seen from Fig. 4, the handle 2A comprises two curved downwardly and rearwardly sweeping members 15, which converge at the guide block 14. The guide block 14 is provided with a longitudinal slot 16, through which longitudinal slot the rack 10 and bar 12 slide during pivoting movement of the spreading members 2, 3. The guide block 14 is further provided with a transverse slot 17 which intersects the longitudinal slot 16 and which is generally perpendicular to the longitudinal slot 16. As is visible in Fig. 3D, the transverse slot 17 is elongate in cross-section, the elongate direction of the slot 17 being parallel to the direction of extension of the finger/thumb plate 2B depending downwardly from the guide block 14.

The lock 9 further includes a locking element 18 provided in the transverse slot 17.

This locking element 18 is generally dumbbell shaped (see Fig. 5) and comprises a central portion 19 of reduced diameter and two end portions 20 of increased diameter. The diameter of the central portion 19 is such as to fit in and extend loosely through the transverse slot 17.

The diameters of the end portions 20 are too large to pass through the transverse slot 17, and

S

thus act to hold the locking element captive within the guide block 14. The elongate cross section of the transverse slot 17 enables the locking element 18 to move up and down within the transverse slot 17, this up and down movement being represented by the double-headed arrow 22 in Fig. 3D. Because the locking element 18 is freely moveable with respect to the remainder of the speculum, it is envisaged that it will be manufactured separately of the main components of the speculum, for example by being moulded in two parts which are assembled together after the central portion 19 of the locking element 18 has been passed through the transverse slot 17.

When in the lower position (represented by the lower of the two arrowheads 22 in Fig. 3) within the transverse slot 17 (as in Figs. 1, 2A, 2B and 3C), the central portion 19 of the locking element 18 is aligned with the track 13 formed between the toothed rack 10 and the bar 12. In this unlocked condition of the lock 9, the spreading members 2, 3 are capable of being pivoted relative to one another about the pivots 4 without the central portion 19, or any portion, of the locking element 18 contacting the teeth 11 of the rack 10. Consequently, the unwanted rattling noise and vibration, discussed in the above introduction of this

specification, is avoided.

When, however, the locking element 18 is moved upwardly so as to position its central portion 19 at the other end of the transverse slot 17 (represented by the upper of the two arrowheads 21 in Fig. 3D), if the transverse slot 17 is aligned with one of the gaps in the rack 10 defined by the teeth 11, the central portion 19 will be positioned between two teeth 11, or between one tooth 11 and the end of the track 13. In use, after the spreading members 2, 3 have been inserted into a vagina and pivoted to an open position, the compression of the vaginal muscles will act to try to close the spreading members 2, 3 together and to try to move the guide block 14 back to its starting position at the right hand end of the rack 10 (as drawn in Fig. 1). It will be understood how, if the locking element 18 has been lifted upwardly in the transverse slot 17 so as to position the central portion 19 of the locking element 18 in a selected gap between a pair of adjacent teeth 11, the urging of the guide block 14 to the right (as drawn), in combination with the sloping of the teeth 11, and the resultant sloping of the gaps between the teeth 11, will cause the central portion 19 of the locking

I

element 18 to be pulled firmly up into the selected gap between the teeth 11, thereby securely to lock the spreading members 2, 3 against unwanted closure by the action of the vaginal muscles.

In this condition the force holding the locking element 18 in its locked condition is the urging of the guide block 14 to the right (as drawn). Even though gravity will be acting on the locking element 18 in the locked condition, the action of gravity on the locking element 18 is incapable of causing the locking element 18 to drop down into the track 13 between the rack 10 and the bar 12, because the sloping of the teeth 11 is such that in order to do this the guide block 14 would have to move slightly to the left (as drawn), which will not happen due to the compressive action of the vaginal muscles. When, however, the physician has finished examination of the patient's body cavity through a lumen formed by the open spreading members 2, 3, in order to release the lock 9 the physician simply needs to move the two handles 2A, 3A together slightly, against the compressive action of the vaginal muscles.

Because of the action of gravity on the locking element 18, only a small movement is required before the central portion 19 of the locking element 18 will have moved sufficiently far to the left (as drawn) as to fall clear of the tooth 11 over which it was previously positioned when it was retained in the gap partially formed by that tooth 11 when held in locking engagement. Once clear of the tooth 11, the locking element 18 is free to move and will drop fully downwardly, under the action of gravity, into the bottom half of the transverse slot 17 so as to position the central portion 19 of the locking element in the track 13 between the rack 10 and the bar 12. As described earlier, this positioning of the locking element 18 enables the spreading members 2, 3, to be freely pivoted with respect to one another without any portion of the locking element 18 contacting the teeth 11, thereby avoiding unwanted noise andlor vibration.

An exemplary method of use of the speculum will now be described in the context of a cervical examination involving the insertion of the speculum into a vagina.

A cervical examination procedure would commence with the vaginal speculum 1 in the closed condition illustrated in Fig. 1 and with the handles 2A, 3A directed generally

S

downwardly. In this condition the action of gravity on the locking element 18 causes it to be in its unlocked condition, with the central portion 19 of the locking element 18 positioned in the lower half of the transverse slot 17, aligned with the track 13.

After insertion of the closed spreading members 2, 3 into the vagina, the members are pivoted open around pivots 4 so as to spread the vaginal walls, by the action of the physician pressing the finger/thumb plates 2B, 3B together in the direction of arrows 5 in Fig. 1.

Because of the aforementioned position of the locking element 18 meaning that the lock 9 is in its default unlocked condition, opening of the spreading members 2, 3 is not impeded by the lock 9. In particular, the central portion 19 of the locking element 18 does not rub over the tips of the downwardly depending teeth 11 of the lock 9. Instead, the central portion 19 of the locking element 18 will be resting on the upwardly facing surface of the bar 12, so that the locking element 18 will instead simply rotate about its longitudinal axis 21 as the finger/thumb plates 2B, 3B are squeezed together. Figs. 2A and 2B show the speculum and lock respectively approximately halfway through the opening process. In Fig. 2B, the unlocked condition of the lock 9 is noticeable by the position of the longitudinal axis 21 aligned with the centre of the arcuate track 13. The minimum distance between the visible end portion 20 of the locking element 18 and the flat base surface 23 of the guide block 14 is represented by distance A. Although the lock 9 may be switched from its unlocked condition to its locked condition at any point during the range of pivoting movement of the spreading members 2, 3 (for example at the approximate mid-point shown in Fig. 2A), in the drawings (see Figs. 3A and 3B) the speculum is shown as being locked in its fully opened position, with the vaginal walls spread to the maximum extent possible with the speculum 1.

Once the spreading members 2, 3 have been opened to the extent desired, whilst still holding the finger/thumb plates 2B, 3B between the first finger and thumb of one hand, the physician can use the first finger and thumb of the other hand to grip the end portions 20 of the locking element 18 and to move the element upwardly, whilst at the same time optionally slightly relaxing the squeezing pressure being applied to the finger/thumb plates 2B, 3B. This combined upward movement on the locking element 18, together with the optional slight relaxation of the squeezing on the finger/thumb plates 2B, 3B, causes the central portion 19 of the locking element 18 to enter the mouth of a gap formed in the rack 10 of teeth 11. Once the mouth of the gap has been entered, (further) relaxation of the squeezing action on the finger/thumb plates 2B, 3B, combined with the squeezing action of the vaginal walls acting to try to close the spreading members 2, 3 together, causes the handle 2A of the first spreading member 2 to be pivoted slightly anticlockwise about the pivots 4, thereby pulling the central portion 19 of the locking element 18 upwardly into the closed end of the endmost gap in the toothed rack 10, due to the inclination of the teeth 11, as shown in Figs. 3A and 3B. This firm engagement of the locking element 18 with the closed end of the endmost gap in the toothed rack 10 represents a highly secure locking condition for the lock 9. In this locked condition the physician can carry out the required internal examination. During the examination the physician is not required to maintain a squeezing pressure on the finger/thumb plates 2B, 3B or to maintain upward pressure on the locking element 18.

Instead, the speculum is firmly maintained in a steady state locked condition.

In Fig. 3B it will be noted that the longitudinal axis 21 of the locking element 18 is no longer aligned with the centre of the arcuate track 13, but is instead aligned with the teeth 11 of the rack 10, due to the positioning of the central portion 19 of the locking element 18 in one of the gaps formed in the toothed rack 10 and in the upper half of the transverse slot 17.

Furthermore, the distance between the underside of the visible end portion 20 of the locking element 18 and the flat base surface 23 of the guide block 14 is, in Fig. 3B, represented by distance B. It will be seen that this distance B in Fig. 3B is greater than the distance A in Fig. 2B as a result of the higher position of the locking element 18 in Fig 3B and the positioning of the central portion 19 of the locking element 18 in meshing engagement with the teeth 11 of the rack 10 in Fig. 3B in the locked condition of the lock 9.

Once the spreading members 2, 3 have been opened the required amount and the lock 9 locked, to assist the internal examination the physician may energise the optional light source contained within the combined battery pack and light source 6 so as to enable light to be directed on to the cervix using light transmitted along the light guide 7 and projected

S

distally from the distal end 8 of the light guide 7.

Once the internal examination is complete, in order to unlock the lock 9 the physician simply needs to squeeze the finger/thumb plates 2B, 3B slightly together, as represented by the arrows 5 in Fig. 3C. This causes the spreading members 2, 3 to be opened slightly further, so as to spread slightly more the vaginal walls. It also enables the locking element 18 to move slightly clockwise (relative to the pivots 4) so as to be moved out of vertical alignment with the tip of the tooth 11 with which it was previously engaged and over which it was previously positioned. Once it is out of vertical alignment with the tooth tip, the locking element 18 is no longer supported in its raised position and the action of gravity on the locking element 18 will cause it to move downwardly within the transverse slot 17 in the guide block 14 as the central portion 19 of the locking element 18 moves back into alignment with the arcuate track 13. This is the condition shown in Fig. 3C. In this regard, it will be noted that the distance between the underside of the visible end portion 20 of the locking element 18 and the flat base surface 23 of the guide block 14 has changed back from distance B (in the locked condition illustrated in Fig. 3B) to distance A (in the unlocked condition illustrated in Fig. 3C). Once the locking element 18 has dropped downwardly to the position illustrated in Fig. 3C, the physician can release the compressive pressure on the finger/thumb plates 2B, 3B and instead allow them to move apart (through the position shown in Fig. 2A) to the fully closed position shown in Fig. 1 due to the compressive action of the vaginal walls.

Once the spreading members 2, 3 of the speculum 1 have been allowed to return to the fully closed position illustrated in Fig. 1, the spreading members may be withdrawn from the vagina and the speculum discarded.

It will be appreciated that the unlocking of the lock 9 from the locked condition illustrated in Fig. 3B to the unlocked position illustrated in Fig. 3C is akin to being automatic.

All it requires is for the physician to squeeze slightly together the finger/thumb plates 2B, 3B, so as to enable the locking element 18 to drop out of engagement with the teeth 11 of the rack under the action of gravity into a position of non-engagement with the teeth. In this disengaged position the central portion 19 of the locking element 18 becomes instead aligned with the arcuate track 13 formed between the rack 10 of teeth 11 and the bar 12. It is not necessary for the physician physically to move the locking element 18 downwardly so as to unlock the lock. Consequently, in use of the speculum 1 unlocking of the lock 9 requires only one simple action of squeezing of the finger/thumb plates 2B, 3B together. Once unlocked, i.e. once the locking element 18 has dropped out of engagement with the teeth 11 of the rack 10, the physician can (by regulating pressure on the finger/thumb plates 2B, 3B) control movement apart of the finger/thumb plates 2B, 3B apart under the action of compressive action of the vaginal walls.

Although thought to be unnecessary, the speculum may include a biasing means (not shown) to bias the locking element to its unlocked condition. This might be necessary if the speculum is to be used in an orientation in which gravity alone will be insufficient to cause the locking element to move to a position to unlock the lock on squeezing the finger/thumb plates together at the end of an examination. Equally, if the speculum is to be used "upside down" so that gravity will act to prevent automatic unlocking of the lock rather than causing or assisting it, a biasing means may be provided to counteract the effect of gravity on the locking element.

Claims

CLAIMS1. A speculum comprising: first and second spreading members pivotable relative to one another between a closed position, to allow for insertion thereof into a body cavity, and a plurality of discrete open positions, to allow for inspection of the body cavity; and a lock for releasably locking the spreading members in a selected one of said open positions, the lock including an array of teeth associated with one of the spreading members and a locking element associated with the other of the spreading members and selectively engagable with the teeth to lock the spreading members in said selected open position against unwanted closure by the action of the body; wherein the locking element is constructed and arranged to release the lock automatically, upon the opening of the locked spreading members beyond said selected open position, as a result of movement of the locking element out of engagement with the teeth under the action of gravity.
2. A speculum as claimed in claim 1, wherein the movement of the locking element out of engagement with the teeth upon the opening of the locked spreading members beyond said selected open position is entirely as a result of the action of gravity on the locking element.
3. A speculum as claimed in claim 1 or claim 2, wherein the speculum does not include biasing means for biasing movement of the locking element relative to the teeth.
4. A speculum as claimed in any one of the preceding claims, wherein the locking element is carried by, but is freely slidable relative to, said other spreading member.
5. A speculum as claimed in any one of the preceding claims, wherein the locking element is constrained to move relative to said other spreading member in a linear direction when moving into engagement with and disengagement from the teeth.
6. A speculum as claimed in claim 5, wherein said other spreading member extends in a longitudinal direction and said linear direction is generally perpendicular to said longitudinal direction.
7. A speculum as claimed in any one of the preceding claims, wherein the locking element is held captive in a guide associated with said other spreading member, the guide comprising a longitudinal slot through which the array of teeth slide on pivoting movement of the spreading members and a fransverse slot, generally perpendicular to the longitudinal slot, through which the locking element extends.
8. A speculum as claimed in any one of the preceding claims, wherein the transverse slot is elongate in cross-section so as to allow the locking element to move within the transverse slot, relative to said other spreading member, to engage with and to disengage from the ratchet teeth.
9. A speculum as claimed in claim 7 or claim 8, wherein said locking element comprises a central portion sized to extend through the transverse slot and end portions at the opposite ends of the central portion sized so as to be incapable of passing through the elongate slot thereby to retain the locking element captive in the transverse slot.
10. A speculum as claimed in claim 9, wherein the end portions of the locking element are arranged to be grasped by a physician and used to move the locking element within the transverse slot and into engagement with the teeth.
11. A speculum as claimed in any one of the preceding claims, wherein the locking element is generally dumbbell shaped.
12. A speculum as claimed in any one of the preceding claims, wherein during pivoting of the spreading members from the closed position to said selected open position, up to but not including locking of the locking member with the teeth in said selected open position, the locking element is constructed and arranged to be out of contact with the teeth thereby to avoid the unwanted generation of noise andlor vibration as the locking member moves past the teeth.
13. A speculum as claimed in any one of the preceding claims, wherein during pivoting of the spreading members from said selected open position to the closed position, after movement of the locking element out of engagement with the teeth upon release of the lock, the locking element is constructed and arranged to be out of contact with the teeth thereby to avoid the unwanted generation of noise and/or vibration as the locking member moves past the teeth.
14. A speculum as claimed in any one of the preceding claims, wherein the locking element has an elongate axis and is arranged to rotate about that elongate axis as the spreading members are pivoted relative to one another.
15. A speculum as claimed in any one of the preceding claims, wherein the spreading members each include a handle for moving the spreading members between said closed position and said selected open position.
16. A speculum as claimed in claim 15, wherein the speculum is a vaginal speculum and the handles are arranged so as to be directed generally downwardly in use.
17. A speculum comprising: first and second spreading members pivotable relative to one another between a closed position, to allow for insertion thereof into a body cavity, and a plurality of discrete open positions, to allow for inspection of the body cavity; an array of ratchet teeth associated with one of the spreading members; and a locking element carried by, but slidable relative to, the other of the spreading members and selectively engagable with the teeth to lock the spreading members in a selected one of said open positions against unwanted closure by the action of the body; wherein the locking element is constructed and arranged automatically to move out of locking engagement with the teeth upon the opening of the locked spreading members beyond said selected open position.