System and method for operating surgical instrument, and foot switch assembly for controlling surgical instrument

Abstract

To provide a system and method for operating a foot pedal assembly, which allow for appropriate, reliable and intuitive operation of a surgical instrument.SOLUTION: A system 20 has a safety lock 21. The safety lock is configured to at least partially prevent use of a surgical instrument 22. A foot switch assembly 1 is operatively configured to control the surgical instrument and has a plurality of switches. There are a memory 26 for storing a predetermined switch sequence associated with the switches of the foot switch assembly, and a control unit 25 configured to determine whether a sequence of input switch actuations from the foot switch assembly corresponds to the predetermined switch sequence, and if so, to deactivate the safety lock in response to the sequence of input switch actuations corresponding to the predetermined switch sequence.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] In a first aspect, the present invention relates to a system and method for actuating a surgical instrument. In a further aspect, the present invention relates to a foot switch assembly for controlling a surgical instrument, particularly an ophthalmic surgical instrument. [Background technology]

[0002] During many surgical procedures, a surgeon or medical professional may use a number of handheld instruments to treat, ablate, or manipulate tissue. Fine control of such instruments and target tissue is often required in confined spaces, particularly during ophthalmic surgery. Many ophthalmic surgical instruments have several modes of operation, and realizing manual controls on the body of such instruments is not practical, especially for small gauge instruments, nor is it always convenient to locate controls on a handheld instrument that requires fine motor control during use.

[0003] A control panel or system for activating, stopping, and controlling the functions of a surgical instrument is often provided separate from the handheld portion of the instrument, however, the control panel and associated user interface are preferably operated in an intuitive manner with an available body of surgical instrument operation.

[0004] In this regard, foot switch assemblies for controlling surgical instruments and systems have become a popular choice for controlling surgical instruments and associated viewing equipment. Foot switch assemblies can be intuitively operated by a user, potentially support multiple input switches, and can take advantage of the range of movement and precise control exhibited by a user's foot.

[0005] Foot switches for controlling ophthalmic surgical instruments and systems are known in the art. For example, U.S. Patent Publication No. US 7,019,234 describes a foot switch intended as a controller for use during a surgical procedure. The foot switch can have a footplate with a slidable plate that facilitates actuation of a side switch.

[0006] However, known footswitches have a number of drawbacks that can detract from the user experience, make the pedal less intuitive to use, and result in suboptimal control of the instrument or system that the footswitch is designed to control.

[0007] U.S. Patent Application Publication No. 2014 / 364864 discloses a foot pedal system and device having multiple switches. The foot pedal can include a housing, and includes at least one potentiometer and at least two top switches, a footplate rotatably mounted within the housing and adapted to depress the at least one potentiometer, and at least two side switches movably associated with the footplate. The footplate rotates horizontally on an axis located away from the heel rest.

[0008] U.S. Patent Application Publication No. 2006 / 014554 discloses a foot switch having a tiltable tread for a first linear control input, which allows for a second linear control input by using a radial slider assembly positioned at the top of the pedal on the tread. Movement of the radial slider assembly provides the second linear control input to a potentiometer. The radial slider has a virtual pivot axis located near the heel rest. The tread has a rotation axis away from the heel rest. Summary of the Invention

[0009] Embodiments of the present invention seek to provide a system and method for operating a foot pedal assembly that enables proper, reliable, and intuitive operation of a surgical instrument.

[0010] In a first aspect of the present invention, a method of activating a surgical instrument includes the steps of providing an apparatus having a safety lock, the safety lock configured to prevent use of the surgical instrument, providing a footswitch assembly operatively configured to control the surgical instrument, the footswitch assembly comprising a plurality of switches, storing a predetermined switch sequence associated with the switches of the footswitch assembly in a memory, determining whether a series of input switch actuations corresponds to the predetermined switch sequence, and if so, disabling the safety lock in response to the series of input switch actuations corresponding to the predetermined switch sequence. Further, there is provided a system comprising: a footswitch assembly operatively configured to control the surgical instrument, the safety lock configured to at least partially prevent use of the surgical instrument, the footswitch assembly comprising a plurality of switches, the memory storing a predetermined switch sequence associated with the switches of the footswitch assembly, and a control unit configured to determine whether a series of input switch actuations from the footswitch assembly corresponds to the predetermined switch sequence, and if so, disabling the safety lock in response to the series of input switch actuations corresponding to the predetermined switch sequence. In these embodiments, a safety locking mechanism can be implemented in a system using a foot pedal switch assembly without a physical shroud covering the actuation surface of the foot switch to prevent (or minimize) unintentional activation of a potentially dangerous function (e.g., activation of a laser). By preventing activation of the laser until a predefined switch sequence is entered, the shroud function can be provided without the use of a physical lock / unlock mechanism such as a brace or other structural feature.

[0011] In a further aspect of the present invention, a foot switch assembly for controlling a surgical instrument is provided, the foot switch assembly comprising a base extending from a front end to a rear end, the foot switch assembly comprising a heel rest at the rear end of the base, the heel rest having an upper surface, optionally a substantially flat upper surface. A movable foot pedal is disposed adjacent to the heel rest, the foot pedal being mounted to the base via a hinge having a pivot axis, the pivot axis of the movable foot pedal relative to the heel rest being centered relative to the upper surface of the heel rest. By providing a foot switch assembly according to the first aspect, it is possible to provide a foot switch assembly that allows comfortable and intuitive operational use of the foot pedal and associated functions in a manner that prevents undesirable or unnecessary sliding of the foot on the foot pedal surface during actual use. The heel rest can be fixed, or the heel rest can be configured to rotate about a vertical axis (or a near-vertical axis). A heel rest configured to rotate about a vertical axis can provide an additional range of movement without the user having to rotate their heel relative to the heel rest.

[0012] Preferred embodiments are described in the accompanying dependent claims and with reference to the drawings, which show exemplary embodiments of the invention.

[0013] The present invention will now be described with reference to some non-limiting exemplary embodiments thereof as illustrated in the accompanying drawings. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 shows a top view of a footswitch assembly according to an embodiment of the present invention. [Figure 2] FIG. 2 shows a perspective view of the footswitch assembly shown in FIG. [Figure 3] FIG. 3 shows a cross-sectional view of the footswitch assembly shown in FIG. 1 taken along line AA. [Figure 4]FIG. 4 shows an enlarged cross-sectional view of a portion of the footswitch assembly shown in FIG. 1, illustrating an embodiment of a multi-actuation switch embodiment. [Figure 5] FIG. 5 shows a block diagram of a system embodiment according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Preferred embodiments and related advantages of the present invention are best understood by referring to Figures 1 through 5 in combination with the following detailed description. It will be understood that the following description relates to a number of non-limiting exemplary embodiments of the present invention. Modifications and variations can be made to the following exemplary embodiments without departing from the scope of the claims.

[0016] FIG. 1 shows a plan (top) view of a foot switch assembly 1 according to an embodiment of the present invention, and FIG. 2 shows a perspective view of the embodiment of the foot switch assembly. As shown in FIGS. 1 and 2, the foot switch assembly 1 generally includes a base 2 and a foot pedal 4 movably mounted to the base 2. The base 2 extends from a front end 2a to a rear end 2b, with the movable foot pedal 4 mounted thereon. The base 2 further includes opposing sides extending semi-symmetrically between the front end 2a and the rear end 2b of the base 2. The movable foot pedal 4 is mounted to the base using a hinge 5, the details of which are described in further detail with reference to FIG. 4 below. The movable foot pedal 4 is mounted at the rear end 2b of the base 2 forward of a heel rest 3, so that the heel of an operator's foot can be placed on the heel rest 3 during use, allowing the movable foot pedal 4 to be easily and comfortably actuated with the rest of the user's foot.

[0017] Alternatively stated, an embodiment of the present invention relates in a first aspect to a foot switch assembly 1 for controlling an ophthalmic surgical apparatus, the foot switch assembly 1 comprising a base 2 extending from a front end 2a to a rear end 2b, the foot switch assembly 1 comprising a heel rest 3 at the rear end 2b of the base 2, the heel rest 3 having an upper surface 3a, a movable foot pedal 4 positioned adjacent to the heel rest 3, the foot pedal 4 being pivoted about a pivot axis A y , A h , and the pivot axis A of the movable foot pedal 4 relative to the heel rest 3 is y , A h is centered relative to the upper surface 3a of the heel rest 3. The heel rest can be fixed or may be configured to rotate about a vertical axis. Advantageously, the upper surface of the heel rest is restricted to movement in a single plane (e.g., the heel rest can rotate about a vertical axis but not about a horizontal axis). Translational movement of the heel rest relative to the base is preferably prevented. Such an arrangement can provide a stable surface on which the heel can rest during operation of the switch.

[0018] The upper surface of the heel rest may be substantially flat, may have a slight concave or convex curvature, and / or may have additional surface features such as grooves or ridges to minimize the possibility of the user's foot slipping against the heel rest.

[0019] In an embodiment of the foot switch assembly 1 according to the present invention, the base 2 further includes a channel 7a extending in the fore-and-aft direction, the channel 7a being defined by opposing side walls 7, with the foot pedal 4 disposed within the channel 7a between the opposing side walls 7. As shown in FIGS. 1 and 2 , the base 2 includes the channel 7a configured to receive a user's foot. The channel 7a extends from a heel receiving portion located at the rear end 2b of the base 2 to a toe receiving portion located at the front end 2a of the base 2. Advantageously, the channel 7a may taper from the wider toe receiving portion to the narrower heel receiving portion (i.e., near the heel rest 3). However, it will be understood that the foot switch may be configured without a tapered channel.

[0020] The movable foot pedal 4 is mounted within the channel 7a and is pivotally disposed relative to the base 2. The foot pedal 4 is mounted to the base 2 as will be described in more detail with reference to FIG. 4 below. The foot pedal 4 is pivoted about its pivot axis A. y , A h The pivot point and foot pedal 4 are configured to extend in the same plane as the upper (flat) surface 3a of the heel support 3. By configuring the pivot point and foot pedal 4 in this manner, the pivot axis A of the foot pedal 4 during use y , A h extends through the point where the user's heel contacts the upper surface 3a of the heel rest 3. This ensures that the user's foot does not slide up and down on the foot pedal 4 as the user raises and lowers their foot to operate the foot pedal 4. By preventing movement of the foot against the surface of the foot pedal 4 during pivoting of the foot about the heel, the likelihood of the user's foot slipping against the surface of the foot pedal 4 is greatly reduced.

[0021] The base 2 may further include a number of additional switches or actuators. For example, as shown in FIG. 1, an additional switch 16 is present on the top surface of the base 2 near the rear end 2 b, which can be easily operated by a user's foot, for example, before being placed on the foot pedal 4. Additionally or alternatively, the footswitch assembly 1 further includes left and right front pedal switches 15 operable by the respective left and right sides 4 a of the foot pedal 4, as shown in the exemplary embodiment shown in FIGS. 1 and 2.

[0022] The exemplary embodiment of FIGS. 1 and 2 also shows an optional width limiter 6. The foot switch assembly 1 can further include one or more adjustable width limiters 6 on the upper surface of the foot pedal 4 to provide a snug fit for the user's foot and allow comfortable movement of the foot pedal 4 both vertically and horizontally. The adjustable width limiter 6 can be realized, for example, as an elongated strip pivotally connected to the foot pedal 4 at an end near the heel rest 3 and fixable to multiple pre-set positions at the distal end of the foot pedal 4 (i.e., near the front end 2a of the base 2). Those skilled in the art will appreciate that other width adjustment configurations are possible. For example, the elongated strip can be replaced by a series of discrete protrusions extending inward from the outer edge of the movable pedal. Each of these protrusions can be slidably mounted relative to the movable pedal toward and away from the pedal's longitudinal centerline. Such protrusions can be adjusted to closely surround the user's foot. Other possible configurations will be apparent to those skilled in the art.

[0023] 3 shows a cross-sectional view of the foot switch assembly shown in FIG. 1 taken along line AA. In this cross-sectional view, the pivot axis A of the movable foot pedal 4 obtained by a particular structural embodiment of the hinge 5, which may comprise a first (vertical) hinge assembly 5a and / or a second (horizontal) hinge assembly 5b, is shown. y , A hFurther features relating to the first hinge axis A are shown and explained in more detail. In a first group of embodiments, the hinge 5 is y a first hinge assembly 5a for enabling rotation of the movable foot pedal 4 about a first hinge axis A y extends parallel to and substantially coincides with the upper surface 3a of the heel rest 3. In the exemplary embodiment, the first hinge axis A y is positioned very close to the upper surface 3a of the heel rest 3, for example within 30 mm. This embodiment allows the foot pedal 4 to move up and down, providing a switch signal or a proportional control signal to a connected surgical instrument, for example using a suitable switch or transducer. The movement of the movable foot pedal 4 in the vertical direction is in a further embodiment less than 15°, for example equal to 11°.

[0024] Additionally (or alternatively), the hinge 5 has a second hinge axis A h a second hinge assembly 5b for enabling rotation of the movable foot pedal 4 about a second hinge axis A h extends substantially perpendicular to the upper surface 3a of the heel rest 3. This implementation of the hinge 5, with hinge assemblies 5a and 5b, allows the foot pedal 4 to move left and right in the foot switch assembly 1. The movement of the movable foot pedal 4 in the horizontal direction can be between -10° and 10°, for example, between -6.5° and 6.5°. Again, a suitable position transducer or switch may be used in combination with this implementation of the hinge 5 to provide a corresponding actuation signal to the surgical instrument. In the embodiment shown in FIG. 3, the hinges 5 are each oriented along a hinge axis A. y , A h Note that the foot pedal assembly 1 has a combination of vertical and horizontal hinge assemblies 5a, 5b having a hinge axis 7a, 7b, 7b, 7c, 7d, 7e, 7f, 7g, 7h, 7h, 7i, 7j ...

[0025] In the exemplary embodiment shown in FIG. 3, the foot pedal 4 includes (as an integral part of the foot pedal 4) a foot pedal mounting assembly 4b. The foot pedal mounting assembly 4b is connected to the base 2 such that an imaginary axis about which the pedal rotates is located below the center point of the upper surface 3a of the heel rest 3. The pivotable connection is achieved in this exemplary embodiment by a horizontal hinge assembly 5b, which may be a bearing assembly or another low-friction pivotable connection, as will be apparent to those skilled in the art in view of this disclosure. Furthermore, the foot pedal mounting assembly 4b includes two arm elements extending laterally in the interior space of the base 2, and a vertical hinge assembly 5a is provided for the associated vertical hinge axis A. y can be realized at an accurate height so that it coincides with the upper surface 3a of the heel rest 3.

[0026] FIG. 4 shows an enlarged cross-sectional view of a portion of the footswitch assembly 1 shown in FIGS. 1 and 2, illustrating an embodiment of the footswitch assembly having a multi-actuation switch 10. In this embodiment, the multi-actuation switch 10 is operable by an actuator 11 having a pivot axis 12 that extends substantially parallel to the movable foot pedal 4 (i.e., perpendicular to the cross-section shown in FIG. 4). The actuator 11 includes two actuation surfaces 11a, 11b that are substantially perpendicular to one another and extend along the pivot axis 12. The actuator 11 is positioned to operate the multi-actuation switch 10 by rotation in a first direction on the pivot axis 12. It should be noted that while FIG. 4 shows a single actuator and multi-action switch 10, it is apparent from the exemplary embodiment of FIGS. 1 and 2 that such switch configurations can be present on both sides of the footswitch assembly 1. The upper actuation surface 11a of actuation surfaces 11a, 11b can be operated directly by the user, for example, when the foot is not resting on the heel rest 3 and the foot pedal 4, or when the foot is resting only on the heel rest 3 (but not on the foot pedal 4). The directly connected side actuation surface 11b of actuation surfaces 11a, 11b can be easily operated by the operator by lifting the foot from the foot pedal 4 and simultaneously holding the heel on the heel rest 3.

[0027] In a further embodiment, footswitch assembly 1 further comprises a second switch 14, wherein actuation body 11 further comprises a second actuation surface 11c extending along pivot axis 12, and wherein second switch 14 is operable by rotating actuation body 11 on pivot axis 12 in a second direction opposite to the first direction. This embodiment allows, for example, for a different actuation direction, to add an additional switch action that is more clearly recognizable than a switch action using one of actuation surfaces 11a, 11b as described in the previous paragraph.

[0028] As a further enhancement in further embodiments, distinct and more intuitive actuation can be achieved by forming an angle of less than 90 degrees between second actuation surface 11c and one of the two actuation surfaces 11a, 11b adjacent pivot axis 12. This ensures that second actuation surface 11c extends from base 2 after an earlier actuation of multi-action switch 10, allowing for an easier "return" motion for actuation of second switch 14.

[0029] 5 shows a block diagram of a system embodiment of the present invention relating to a system 20 including a safety lock 21 configured to at least partially prevent use of a surgical instrument 22. A footswitch assembly 1 is also present and is configured to be operable to control the surgical instrument 22. As in one or more of the exemplary embodiments described above, the footswitch assembly 1 includes a plurality of switches 4, 10, 14, 15, and 16. There is a memory 26 for storing predetermined switch sequences associated with the switches 10, 14, 15, and 16 of the footswitch assembly 1, and a control unit 25 configured to determine whether a series of input switch actuations from the footswitch assembly 1 corresponds to the predetermined switch sequence and, if so, to deactivate the safety lock 21 in response to the series of input switch actuations corresponding to the predetermined switch sequence. This makes it possible to provide a control device for a surgical instrument, such as an ophthalmic surgical instrument, without a physically present protective shroud, since the safety lock 21 can be switched off using a series of switch actuations (indicative of the presence of a user's foot and the user's intent to actually use the instrument).

[0030] In the exemplary embodiment, the surgical instrument 22 comprises a laser device controlled by an ophthalmic surgical instrument to which the foot switch assembly 1 is operatively connected. Of course, the laser device will never operate unintentionally, and this embodiment can ensure that the laser device is only active when the user actually wants it to be active.

[0031] In yet a further embodiment of system 20, or as yet a further embodiment of the above-described foot switch assembly 1, further safety is provided to prevent inadvertent activation of a surgical instrument. To that end, foot switch assembly 1 further comprises one or more sensors 17 for detecting the presence of a user's foot on foot pedal 4. Sensor 17 may include a weight sensor, an optical sensor, a capacitive sensor, etc. Multiple sensors of different types may be provided.

[0032] Depending on what type of surgical instrument is to be activated using the present foot pedal assembly 1, the sensor signal can be used to initially or finally activate the surgical instrument and, if present, release the safety lock 21. For example, if the surgical instrument is a laser device, the ready state of the laser device will be activated by the control unit 25 only when the weight is detected by the weight sensor 17.

[0033] It should be noted that different types of surgical instruments may be activated using system 20 embodiments as described in combination with one of the foot pedal assembly embodiments described above, always allowing fail-safe operation of the surgical instrument. In general terms, in a further inventive aspect, a method for activating a surgical instrument (e.g., an ophthalmic instrument) is provided, the method including providing an apparatus having a safety lock, the safety lock configured to prevent use of the instrument, and providing a footswitch assembly 1 configured operatively to control the surgical instrument, the footswitch assembly 1 including a plurality of switches 10, 14, 15, and 16. The method further includes storing a predetermined switch sequence associated with the switches 10, 14, 15, and 16 of the footswitch assembly 1 in memory 26 and determining whether a series of input switch actuations corresponds to the predetermined switch sequence. If so, the method further includes disabling the safety lock in response to a series of input switch actuations corresponding to the predetermined switch sequence.

[0034] The present invention has been described above with reference to a number of exemplary embodiments as shown in the drawings. Modifications and alternative implementations of some parts or elements are possible and fall within the scope of protection defined in the appended claims.

Claims

1. In the system, a safety lock (21), said safety lock (21) configured to at least partially prevent the use of a surgical instrument (22); a foot switch assembly (1) operatively configured to control the surgical instrument (22), the foot switch assembly (1) comprising a plurality of switches (4; 10; 14; 15; 16); a memory (26) for storing predetermined switch sequences associated with the switches (4; 10; 14; 15; 16) of the footswitch assembly (1); a control unit (25) configured to determine whether a series of input switch actuations from the foot switch assembly (1) corresponds to the predetermined switch sequence, and if so, to deactivate the safety lock (21) in response to the series of input switch actuations corresponding to the predetermined switch sequence.

2. 2. The system of claim 1, wherein the surgical instrument (22) comprises a laser device controlled by an ophthalmic surgical instrument to which the foot switch assembly (1) is operatively connected.

3. 3. The system of claim 1 or 2, wherein the foot switch assembly (1) further comprises a sensor (17) configured to detect the presence of a user's foot on the movable foot pedal (4).

4. 4. The system of claim 3, wherein the ready state of the surgical instrument (22) is activated only when a foot is detected by the sensor (17).

5. 1. A method for actuating a surgical instrument, comprising: providing an apparatus having a safety lock, the safety lock configured to prevent use of the surgical instrument; providing a foot switch assembly (1) operatively configured to control the surgical instrument, the foot switch assembly (1) comprising a plurality of switches (4; 10; 14; 15; 16); storing in a memory predetermined switch sequences associated with said switches (4; 10; 14; 15; 16) of said footswitch assembly (1); determining whether a series of input switch actuations corresponds to the predetermined switch sequence, and if so, disabling the safety lock in response to the series of input switch actuations corresponding to the predetermined switch sequence.

6. 1. A foot switch assembly for controlling a surgical instrument, comprising: The foot switch assembly (1) includes a base (2) extending from a front end (2a) to a rear end (2b), and the foot switch assembly (1) includes a heel rest (3) having an upper surface (3a) at the rear end (2b) of the base (2); A movable foot pedal (4) is positioned adjacent to said heel rest (3); Here, the movable foot pedal (4) is pivoted by a pivot shaft (A y ,A h ) of the movable foot pedal (4) relative to the heel rest (3), y ,A h ) is centered relative to the upper surface (3a) of the heel rest (3).

7. 7. The foot switch assembly of claim 6, wherein the heel rest (3) is fixed relative to the base (2).

8. 7. The foot switch assembly of claim 6, wherein the heel rest (3) is rotatably mounted relative to the base (2), wherein an axis of rotation about which the heel rest (3) is configured to rotate extends substantially perpendicular to the upper surface (3a) of the heel rest (3).

9. The hinge (5) has a first hinge axis (A y a first hinge assembly (5a) for enabling rotation of the movable foot pedal (4) about the first hinge axis (A y 9. A foot switch assembly according to claim 6, wherein the upper surface (3a) of the heel rest (3) extends parallel to the upper surface (3a) of the heel rest (3) and is substantially coincident with the upper surface (3a).

10. 10. A foot switch assembly according to any one of claims 6 to 9, wherein the movement of the movable foot pedal (4) in the vertical direction is less than 15°, for example equal to 11°.

11. The hinges (5a; 5b) are connected to a second hinge axis (A h a second hinge assembly (5b) for enabling rotation of the movable foot pedal (4) about the second hinge axis (A h 11. A foot switch assembly according to any one of claims 6 to 10, wherein a heel rest (3) extends substantially perpendicular to the upper surface (3a) of the heel rest (3).

12. Footswitch assembly according to any one of claims 6 to 11, wherein the movement of the movable foot pedal (4) in the horizontal direction is between -10° and 10°, for example between -6.5° and 6.5°.

13. 13. The footswitch assembly of any one of claims 6 to 12, wherein the footswitch assembly (1) further comprises one or more adjustable width limiters (6) on an upper surface of the movable foot pedal (4).

14. 14. The foot switch assembly of claim 6, wherein the base (2) further comprises a channel (7a) extending in a front-to-rear direction, the channel (7a) being defined by opposing side walls (7), and the movable foot pedal (4) being disposed within the channel (7a) between the opposing side walls (7).

15. 15. The foot switch assembly of claim 6, further comprising a multi-actuation switch (10), the multi-actuation switch (10) operable by an actuator (11) having a pivot axis (12) extending substantially parallel to the movable foot pedal (4), the actuator (11) comprising two actuation surfaces (11 a, 11 b) that are substantially perpendicular to each other and extend along the pivot axis (12), the actuator (11) being arranged to operate the multi-actuation switch (10) by rotating on the pivot axis (12) in a first direction.

16. 16. The footswitch assembly of claim 15, further comprising a second switch (14), wherein the actuation body (11) further comprises a second actuation surface (11c) extending along the pivot axis (12), and wherein the second switch (14) is operable by rotating the actuation body (11) on the pivot axis (12) in a second direction opposite to the first direction.

17. 17. The footswitch assembly of claim 16, wherein the second actuation surface (11c) and one of the two actuation surfaces (11a, 11b) adjacent the pivot axis (12) form an angle of less than 90 degrees.

18. 18. The foot switch assembly of any one of claims 6 to 17, further comprising left and right front pedal switches (15) operable by respective left and right sides (4a) of the movable foot pedal (4).

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