Power tool having a handle and a pivotal tool body

[0001] The present invention relates to power tools and, in particular, to improved electric drills comprising a handle and a pivotable drill head with an improved pivotal angle between the drill head and the handle.

[0002] Electric drills and electric screwdrivers are well known in the art. Attempts have been made to combine an electric drill with an electric screwdriver, resulting in a power tool resembling a conventional electric drill with added features to enable slow and controlled screw driving speeds. One such power tool, referred to as a drill-driver, is shown in FIG. 1. This drill-driver comprises a body having a drill head portion and a handle portion fixed at approximately right-angle to the drill head portion. The drill head portion encapsulates an electric motor and a gearbox and the handle portion defines a conventional pistol grip to be grasped by the user. The handle portion comprises a variable speed trigger switch for low-speed rotary output in screw driving mode or high-speed rotary output in drilling mode. This drill-driver is well suited to drilling and screw driving, provided that the workpiece is easily accessible. However, if the hole to be drilled, or the screw to be fastened, is in a tight corner or an awkward position then this drill-driver, like a conventional electric drill, cannot gain access. In this case the user will need to resort to a smaller hand operated drill or a hand held screwdriver perform the task in hand.

[0003] Attempts have also been made to improve utilage of such drill-drivers and to provide solutions to the above problems by inclusion of a pivotable drill head portion which enables the configuration of the drill-driver to be adapted according to the task in hand. An example of this is seen in German Utility Model 8505814.9, which discloses an electric drill having a drill head and a handle. The drill head comprises an electric motor coupled to a gearbox. The gearbox includes a rotary output protruding from the front end of the drill head. The handle comprises an on/off trigger switch and a battery pack. A flange extension attached to the rear end of the drill head is pivotally coupled to the top end of the handle. The drill head can be pivotally adjusted with respect to the handle through an arc of 90°, between a position where the drill head is perpendicular to the handle and another position where the drill head is in-line with the handle. The radial length of the pivotal arc described by the pivoting tool head is equal to the length of the tool body plus the distance of the pivot point of the flange extension from the rear end of the drill head.

[0004] Naturally, there will be a situation where a workpiece is easily accessible and the user can operate the drill-driver in the conventional pistol grip manner wherein the drill head is orientated perpendicular to the handle and the trigger switch is directed towards direction of the output spindle. In a second situation a workpiece may be visible and accessible provided the drill head is orientated in-line with the handle. In a third situation access to a workpiece may be restricted to the extent that the user finds it easier to orientate the drill head perpendicular to the handle and to direct the trigger switch away from the direction of the output spindle. This may be due to an irregular configuration of the handle which reduces clearance on the trigger switch side of the handle, or simply because the user needs to drill backwards. One of the drawbacks of the drill-driver described by German Utility Model 8505814.9 is that the pivotal arc of the drill head is limited to 90° and, as such, this drill is incapable of meeting the needs of the third situation.

[0005] It is therefore an object of the present invention to provide a power tool of type described at the outset, in which the disadvantages of limiting the orientation of the drill head relative to the handle portion are avoided, or at least reduced, thereby allowing for maximum utilage of that power tool.

[0006] Accordingly there is provided a power tool comprising a handle and a tool body pivotally coupled to the handle, characterized in that the tool body can pivot relative to the handle through an angle greater than 90°.

[0007] The tool body may be pivotally coupled to the handle by one or more pivots. Any one of a range of known pivots may be suitable like, for example, a hinge, a spindle supported by ball bearings, or a hub supported by a yoke. A single such pivot would allow pivotal movement of the tool body relative to the handle in one plane. If the tool head is coupled to the handle by two or more such pivots then the tool head can pivot relative to the handle within two or three orthogonal planes. Alternatively, the pivot may be a ball and socket arrangement, which allows movement of the tool head relative to the handle in three orthogonal planes. Preferably, the tool body has a first axis and the tool body is pivotally coupled to the handle by a pivot having a second axis, wherein the first axis is perpendicular to the second axis.

[0008] Preferably the tool body is elongate with a longitudinal axis parallel to the first axis and the power tool further comprises a motor coupled to a rotary output, wherein the rotary output has the first axis. In this case, the rotary output conveniently protrudes from one of the ends of the elongate tool body.

[0009] Preferably, the motor is housed in the tool body, rather than the handle. This avoids the need for a complex mechanical coupling between the motor located in the handle and the rotary output located in the tool body.

[0010] Preferably the elongate tool body has a front end and a rear end and the pivot is located between the front and rear ends of the tool body so that the radial length of the pivotal arc described by the pivoting tool head may be equal to the length of the tool body, or less. This requires that the pivot be located in the space between the ends of the tool body. However, the pivot need not be located upon the tool head itself and could instead be located on a flange attached to the tool head, provided this flange is located in the space between the ends of the tool body.

[0011] Alternatively the pivot is located in the middle region of the tool body. The middle region of the tool body is the space located between 20% and 80% of the length of the elongate tool body, as measured form one end. In this case, the radial length of the pivotal arc may be reduced to less than 81% of the length of the tool body thereby allowing the power tool to operate in smaller areas.

[0012] In contrast to the above, if the pivot were attached to the tool head at a location outside the space between the ends of the tool head then the radial length of the pivotal arc would be equivalent to the length of the tool head plus the distance of the pivot from the tool head. This addition to the radial length of the pivotal arc would unnecessarily prohibit such a power tool from operating in small areas, which would be otherwise accessible to a power tool with the pivot located between the ends of the tool body.

[0013] Preferably, the second axis may intersect the tool body, thus ensuring that the pivot is located upon the tool body. In this case, the pivot and the second axis may intersect the midpoint of the length of the tool body thereby reducing the radial length of the pivotal arc to only 50% of the length of tool head.

[0014] To facilitate the grasp of the user's hand the handle may be elongate and have a third axis. The third axis is perpendicular to the second axis.

[0015] An arc defined by pivotal rotation of the tool head relative to the handle about the second axis subtends a pivotal angle between the first axis and the third axis. If the pivotal angle is limited to 90° then the tool head can only pivot between two operating positions located at right angle to each other, like, for example:

[0016] the tool head orientated approximately at right-angle to the handle and pointing ahead of the handle; and

[0017] the tool head orientated approximately in-line with the handle.

[0018] Preferably the pivotal angle can vary over a range greater than 90° thus giving the tool head scope to pivot relative to the handle beyond the limits of operating positions i) and ii) above.

[0019] Alternatively, the pivotal angle can vary within a range of 180° thus providing another operating position, in addition to those described above, wherein:

[0020] iii) the tool head orientated approximately at right-angle to the handle and pointing behind the handle.

[0021] However, the orientation of the drill head relative to the handle need not be limited to operating positions i), ii) and iii) above when pivoting over a pivotal angle range of 180°, or any other pivotal angle range, and may also include one or more other positions.

[0022] The pivotal angle may vary between 90° and 270° such that the tool head is perpendicular to the handle in positions i) and iii) above.

[0023] The preferred pivot mechanism is a pivot comprising at least one circular aperture formed in one of the tool body or the handle and at least one cylindrical hub protruding from the other of the tool body or the handle, wherein the at least one aperture has the second axis. The at least one hub is disposed concentrically within a respective aperture. Preferably the outer diameter of the at least one hub is slightly smaller than the diameter of a respective aperture to allow for sliding contact there between. Sliding contact between the at least one hub and a respective aperture supports the tool head for pivotal rotation relative to the handle. This pivot is a simple arrangement and, as would be apparent to the person skilled in the art, the pivot could function correctly, whether the hub is disposed upon the tool head and the aperture is formed in the handle, or vice versa.

[0024] Preferably, the at least one aperture is formed in the handle and the at least one hub is disposed upon the tool body. By forming the aperture in the handle, instead of the tool body, the number of holes in the tool body is reduced. This reduces the locations where dust and dirt may enter the interior of the tool body and interfere with the components, such as the motor, enclosed therein. Minimising the number of holes formed in the tool body has the advantage of increasing shielding of the interior components.

[0025] More preferably, the at least one aperture comprises a first aperture and a second aperture wherein the first aperture and the second aperture each have the second axis, and the at least one hub comprises a first hub disposed within the first aperture and a second hub disposed within the second aperture. In this case, the pivot comprises two hub and aperture arrangements, one of each arrangement disposed on diametrically opposite sides of the tool head to provide additional strength and rigidity to the pivotal support of the tool head.

[0026] In addition to providing pivotal support to the tool head, the power tool preferably comprises a locking mechanism for locking the tool body against pivotal movement relative to the handle. The locking mechanism can be released to allow pivotal movement of the tool head relative to the handle when the user wishes to change the orientation of the tool head in preparation for a different task. After changing the orientation of the tool head, the user can lock the tool body in its new position by operating the locking mechanism. As would be apparent to the skilled person in the art many different and suitable types of locking mechanism are readily available like, for example, a simple nut and bolt arrangement or a magnetic lock.

[0027] The preferred locking mechanism comprises a locking plate disposed upon one of the tool body or handle, the locking plate being moveable between a locked position and an unlocked position, wherein the locking plate is engaged with the other of the tool body or handle when in the locked position thereby preventing pivotal movement of the tool body relative to the handle and wherein the locking plate is disengaged with the other of the tool body or handle when in the unlocked position thereby permitting pivotal movement of the tool body relative to the handle.

[0028] The locking plate may be resiliently biased into the locking position. In this case the tool body is automatically prohibited from pivoting relative to the handle unless the locking mechanism is deliberately operated by the user. This leaves both the user's hands free to undertake the task. Preferably, the locking plate is resiliently biased by a spring. The spring may be a leaf spring, a coil spring or a helical spring. A helical spring is the preferred type of spring because it is readily available, compact, durable and inexpensive and, as such, is ideally suited for the task of biasing the locking plate into the locked position.

[0029] The locking plate has a protrusion for locking engagement with one of a plurality of recesses disposed upon the other of the tool body or handle. The location of each one of the plurality of recesses pre-determines the choice of orientations that can be adopted by the tool body relative to the handle. Each additional recess corresponds to an additional orientation of the tool body relative to the handle.

[0030] The locking plate may slide between the locked position and the unlocked position. Sliding movement of the locking plate can be guided part of one of the tool body or handle. The locking plate may be operable by a release button fixed to the locking plate.

[0031] The locking plate is disposed adjacent one of the second hub or the second aperture and the plurality of recesses is disposed around the circumference of the other of the second hub or the second aperture. Preferably, each one of the plurality of recesses is disposed at equi-angular intervals around the circumference of the other of the second hub or the second aperture. The plurality of recesses may be disposed upon the second hub.

[0032] Preferably, the power tool further comprises a power source for energising the motor, an electrical switch electrically coupled to the power source, and an electrical connection for carrying electrical current from the switch to the motor, wherein the switch is disposed upon the handle and the electrical connection enters the tool body through a connection aperture in the first hub. In this case, the user can hold the power tool by the handle with one hand and operate the switch at the same time. Any gaps present between the electrical connection entering the connection aperture in the first hub may be sealed in order to shield the internal components of the tool body from ingress of dust and dirt.

[0033] The electrical connection between the switch and the motor may be by electrical wire, or by metal strips with metal slip rings located at the pivot. Preferably the electrical connection comprises two electrical wires. More preferably the connection aperture in the first hub is concentric with the second axis. Electrical wires have the advantage of being more flexible than metal strips and therefore less liable to breakage, and are insulated. Additionally, the connection aperture being concentric with the second axis (i.e. at the center of the first hub) has the advantage that the wires are only lightly twisted as the tool head pivots relative to the handle and, as such, the wires are not subject to significant wear and tear. Using wires to electrically couple the power source with the motor obviates the need to implement the more complex solution of using metal strips with metal slip rings at the pivot.

[0034] To make the power tool more portable the power source is preferably a battery pack. Depending on the intended work environment of the power tool, the battery pack may be housed within the handle or detachably connected to the handle.

[0035] A battery pack housed within the handle may be electrically coupled to an electrical socket disposed upon the handle. The electrical socket connects the battery pack to an external battery-charging source.

[0051] Referring now to FIGS. 2 and 3, a power tool shown generally as (2) is a drill-driver comprising a substantially cylindrical drill head (4) having a longitudinal axis X and an elongate handle (6) arranged about a longitudinal axis Y. The drill head (4) is pivotally mounted upon the handle (6) and pivots relative to the handle (6) about an axis Z. The handle (6) is formed by a first clamshell (8) and a second clamshell (10) which are joined together by a plurality of screws (not shown). The drill head (4) is formed by a third clamshell (12) and a fourth clamshell (14) which are joined together by a plurality of screws (not shown).

[0052] Referring to FIGS. 4 and 5, the drill head (4) comprises an electric motor (16) and a transmission gearbox (not shown) with an output spindle (20). The motor (16) and the gearbox are housed inside the drill head (4). The front end of the drill head (4) comprises a cylindrical gear casing (22) surrounding the gearbox and the output spindle (20). The motor (16) is rotatingly coupled to the gearbox such that rotary motion of the motor (16) is transferred to the output spindle (20) via the gearbox. The end portion of the output spindle (20) has a hex drive coupling (24) attached thereto. The output spindle (20) and the coupling (24) protrude through a hole (26) in the gear casing (22). The output spindle (20) and the coupling (24) rotate about the axis (x). The coupling (24) releasably connects the output spindle (20) to a tool (28) having a conventional hexagonal shank arrangement. Equally, another type of coupling like, for example, a conventional chuck can be attached to the end portion of the output spindle (20) for connection to a tool (28).

[0053] The handle (6) comprises a button (30) fixed to a variable speed electrical switch (32). The switch (32) is electrically coupled to a power source (34). The switch (32) is also electrically coupled to the motor (16) by two electrical wires (36,38). The switch (32) is thermally coupled to a heat sink (39) located inside the handle (6). The heat sink (39) is for dissipating excess heat energy created by the internal components of the switch (32). The switch (32) is biased into an OFF position wherein the switch (32) interrupts electrical connection between the power source (38) and the motor (16) such that the motor (16) is denergised and the output spindle (20) does not rotate. Depression of the button (30) moves the switch (32) to an ON position wherein the switch (32) makes electrical connection between the power source (34) and the motor (16). The motor (20) is energised by the electrical current from the power source (34) and the output spindle (20) starts to rotate. Electrical current flowing from the power source (34) to the motor (16) is thus controlled by the switch (32) and is proportional to how far the button (30) is depressed. As depression of the button (30) increases so does flow of electrical current to the motor (16) causing a corresponding increase in the rotational speed of the output spindle (20), and vice versa. When the button (30) is released the switch (32) returns to the OFF position to interrupt the electrical connection between the power source (34) and the motor (16) thus causing denergision of the motor (16).

[0054] Referring to FIGS. 6 and 7, the handle (6) comprises a direction selector (40) for selecting the rotational direction of the motor (16) and the output spindle (20). The direction selector (40) is approximately T-shaped and comprises a forward button (42) on one side, a reverse button (44) on the other side, and a flange (46) in the middle. To support the direction selector (40) the forward (42) and reverse (44) buttons partially protrude through an aperture in each of the first (8) and second (10) clamshells respectively. The handle also comprises a barrel (48) with an upper flange (50), a lower flange (52) and a central cylinder (54) located between the upper and lower flanges (52,54). The barrel's flanges (50,52) each have a mainly circular circumference part which is interrupted by a protruding part and are shaped like a tear-drop. The circular part of upper and lower flanges (50,52) has a diameter greater than the central cylinder (54). The protruding part of the upper flange (50) has an upper spigot (56). The protruding part of the lower flange (54) has a lower spigot (58). The upper and lower spigots (56,58) are eccentric with respect the axis of the central cylinder (54) and point axially away from the central cylinder (54). The barrel (48) is supported for pivotal rotation by a pair of brackets (60,62) which are moulded into interior of the handle's clamshells (8,10). The brackets (60,62) surround the central cylinder (54) to support the barrel (48) against lateral movement. The brackets (60,62) abut the inner faces of the upper and lower flanges (50,52) to support the barrel (48) against axial movement. The handle (6) further comprises an arm (64) with a hollow cylindrical hub (66) at one end and a finger (68) at the other end. The arm (64) is pivotally coupled to the internal components of the switch (32) at a point midway between the hub (66) and the finger (68). The arm (64) can pivot between a forward position, a central position and a reverse position. Pivotal movement of the arm (64) from its forward position to its reverse position, and vice versa, causes the switch (32) to change the polarity of the electrical wires (36,38), as explained in more detail below.

[0055] The direction selector (40) is mechanically coupled to the switch (32) via the barrel (48) and the arm (64) in the following manner. The barrel's upper spigot (56) engages the direction selector (40) by protruding through a hole in the flange (46). The barrel's lower spigot (58) is seated within the arm's hollow cylindrical hub (66) in the manner of a trunnion arrangement. As such, depression of the forward button (42) slides the direction selector (40) and the upper spigot (56) in one direction thereby rotating the barrel (48) about its axis. Rotation of the barrel (48) moves the lower spigot (58) in the opposite direction thereby pivoting the arm (64) into its forward position. Depression of the reverse button (44) reverses this sequence and causes the arm (64) to pivot from its forward position to its reverse position.

[0056] When the arm (64) is in its forward position the polarity of the wires (36,38) causes the motor (16) to turn the output spindle (20) in a clockwise direction when the switch (32) is in the ON position. When the arm (64) in its reverse position the polarity of the wires (36,38) is reversed and the motor (16) to turns the output spindle (20) in an anti-clockwise direction when the switch (32) is in the ON position. When the arm (64) is in its central position the arm's finger (68) is aligned with and abuts a central stop (70) on the interior of the button (30) thereby preventing depression of the button (30) and locking the switch (32) in the OFF position.

[0057] The direction selector's buttons (42,44) are arrowhead shaped. The apex of the forward button (42) points forward to give the user a visual and tangible indication that depression of the forward button (42) causes the output spindle (20) to rotate in a clockwise direction (i.e. the rotational direction causing a screw or drill bit to be driven “forward” into a work piece) when the switch (32) is in the ON position. Conversely, the apex of the reverse button (44) points backward to give the user a visual and tangible indication that depression of the reverse button (42) causes the output spindle (20) to rotate in an anti-clockwise direction when the switch (32) is in the ON position.

[0058] The power source is a rechargeable battery pack (34) housed inside the bottom of the handle (6). To improve the electrical charge of the battery pack (34), thereby increasing operating life, the battery pack (34) is relatively bulky causing the handle (6) to protrude on the side of the switch button (30). The battery pack (34) is electrically coupled to a battery recharger socket (72) located at the lower end of the handle (6). The battery recharger socket (72) protrudes through a small aperture (74) in the handle (6) to provide an electrical link between the battery pack (34) and an external battery recharging source (not shown). Alternatively, the power source may be a rechargeable battery detachably fixed to the handle (6), or a mains electrical supply.

[0059] Returning to FIGS. 4 and 5, the drill head (4) has a first cylindrical hub (76) and a second cylindrical hub (78) both located part way along the length of the drill head (4), remote from the output spindle (20). The first and second hubs (76,78) are located on opposite sides of the drill head (4). The first and second hubs (76, 78) are substantially the same diameter and both arranged about axis Z. The first and second hubs (76, 78) extend from the drill head (4) in diametrically opposed directions along axis Z. Axis Z is perpendicular to axis's X and Y.

[0060] Referring to FIG. 8, the first cylindrical hub (76) is moulded into the third clam shell (12) of the drill head (4). The first cylindrical hub (76) comprises a central inner aperture (80) co-axial with axis Z. The inner aperture (80) provides an entry point to the interior of the drill head (4). Referring to FIGS. 9 and 10, the second hub (78) comprises a circular toothed wheel (82), a protrusion (86) and, a cylindrical spigot (84) having axis Z. The protrusion (86) and the spigot (84) are moulded into the fourth clam shell (14) of the drill head (4). The wheel (82) comprises a central aperture (88) and a plurality of teeth (90) arranged equi-angularly around the circumference of the wheel (82). The toothed wheel (82) has eight teeth (90) juxtaposed by eight recesses (92) for engagement with part of a locking plate, which is described in more detail below. The eight teeth (90) are arranged at 45° intervals about the axis Z. The wheel (82) is press fitted upon the fourth clam shell (14). Two of the eight teeth (90) are shorter than the outer diameter of the wheel (82). The protrusion (86) has a curved exterior face (94) and an interior face (96) shaped to surround the two short teeth (90) and engage three recesses (92a, 92b, 92c) adjacent the two short teeth (90) thereby preventing rotation of the wheel (82) relative to the drill head (4). The spigot (84) protrudes through the aperture (88). The outer diameter of the spigot (84) is slightly larger that the diameter of the aperture (88) such that interference fit between the spigot (84) and the circumference of the aperture (88) holds the wheel (82) upon the drill head (4). The curved exterior face (94) of the protrusion (86) and the tips of the teeth (90) collectively describe the outer circumference of the second hub (78). The wheel (82) is made of steel, Alternatively, the wheel (82) may be made of another suitable hard material.

[0061] Returning again to FIGS. 4 and 5, located at the top end of the handle (6) (opposite end to the battery pack) is a first supporting bracket (98) and a second supporting bracket (100) each shaped to nest in the interior of the first and the second clamshells (8,10) of the handle (6), respectively. The first bracket (98) has a circular aperture (102) for receiving the first hub (76). The second bracket (100) has a circular aperture (104) for receiving the second hub (76). The first and second hubs (76,78), the first and second bracket apertures (102,104), the first hub aperture (80) and the spigot (84) are co-axial having axis Z. The first and second bracket apertures (102,104) act as a yoke in which the first and second hubs (76,78) are supported for pivotal rotation relative to the handle (6). As such, the first and second bracket apertures (102,104) provide pivotal support to the first and second hubs (76,78), respectively, to allow the drill head (4) to pivot relative the handle (6) about axis Z.

[0062] Returning to FIG. 8, the first support bracket (98) has a first walled recess (106) facing the interior of the first clam shell (8) of the handle (6). A cavity (108) bounded by the walled recess (106) and the interior of the first clam shell (8) is formed there between. The cavity (108) provides a connecting passageway from the interior of the handle (6) to first hub (76) for the wires (36,38). Accordingly, the wires (36,38) travel from the switch (32) via the cavity (108) through the first hub's aperture (80) to the motor (20) inside the drill head (4).

[0063] Returning to FIGS. 9 and 10, The second support bracket (100) has a second walled recess (110) facing the interior of the first clam shell (10) of the handle (6). A space (112) bounded by the second walled recess (110) and the interior of the second clam shell (10) is formed there between. The space (112) contains a locking plate (114), a lock release button (116) fixed to the locking plate (114), and two helical springs (118). The locking plate (114) has a tongue (120) which is for locking engagement with any one of the five recesses (92d to 92h) of the toothed wheel (82) not occupied by the interior face (96) of the protrusion (86).

[0064] The locking plate (114), the lock release button (116), and the two helical springs (118) collectively form a locking mechanism for locking pivotal movement of the head (4) relative to the handle (6) about the axis Z. The tongue (120) of the locking plate (114) is biased into engagement with a recess (92) by the springs (118), thereby locking pivotal movement of the head (4) relative to the handle (6). To allow pivotal movement of the head (4) relative to the handle (6) the user disengages the tongue (120) from a recess (92) by sliding the locking plate (114) and the release button (116) against the bias of the springs (118). Sliding movement of the locking plate (114) is guided by the second walled recess (110). Access to the release button (116) for operation of the locking plate (114) is provided by a hole (122) in the top end of the second clamshell (10) of the handle (6).

[0065] Referring now to FIGS. 10 to 13, axis Z is the axis about which the head (4) pivots with respect to the handle (6). Axis Y represents the position of the handle (6) and axis X represents the position of the drill head (4). Both axis X and Y remain perpendicular to axis Z regardless of the orientation of the drill head (4) in relation to the handle (8). The included angle between axis X and Y is referred to as angle α. Only angle α varies when the drill head (4) changes its orientation in relation to the handle (8) by pivoting about the axis Z. Angle α is dictated by which one of the five unoccupied recesses (92d to 92h) engages the tongue (120) of the locking plate (114). Angle α is 90° when recess (92d) engages the tongue (120), as shown in FIG. 13. Recess (92e) is located 45° anti-clockwise from recess (92d), therefore angle α is 135° when recess (92e) engages the tongue (120), as shown in FIG. 11. Angle α is 180°, 225° and 270° when one of the three respective subsequent recesses (92f, 92g, 92h) engage the tongue (120).

[0066] In the illustrated embodiment of the present invention, angle α can be set to five positions within a range of 180°, according to which one of the five unoccupied recesses (92d to 92h) engages the locking plate (114). However the range of angle α can be increased from 180° by reducing the number of recesses (92) engaged by the interior face (96) of the protrusion (86) from three recesses (92a, 92b, 92c) to two recesses, or even only one recess. Also, the number of positions within the range of angle α can be varied by changing the number of recesses (92) and teeth (90), or varying the angular spacing between adjacent recesses (92) and teeth (90) around the circumference of the toothed wheel (82).