JPS6159747B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an electric shaver, and in particular to a main blade portion consisting of an outer cutter and an inner cutter that slides on the inner surface of the outer cutter, a comb-like fixed blade, and a This invention relates to an electric shaver that is equipped with two blade parts, a comb-like movable blade that comes into sliding contact with a trimmer blade part.

[Background technology]

In a machine with two blades like this, the main blade is used more frequently, and for this reason it is possible to at least drive only the main blade instead of constantly driving both blades. Preferably, the configuration is such that there are operating modes. In this case, a power transmission member is provided between the drive element that drives these blades and the movable blade of the trimmer blade, and the power transmission between them can be separated, and this power transmission member is connected to the movable blade. It was constructed so that it could be moved between the position and the uncoupled position by means of a control member.
In the device disclosed in Publication No. 29261, the power transmission member connected to the drive element is pushed up by the control member to move the power transmission member to the connection position with the movable blade, and when the control member is pulled down, the power is transferred. The elastic return force applied to the transmission member causes the power transmission member to return to the uncoupled position. Therefore, when the power transmission member is transmitting the movement of the drive element to the movable blade, the elastic return force is received by the control member, and for this reason, there is a gap between the power transmission member and the control member. Sliding resistance, which causes a large load on the operation, occurs.
It was an energy loss.

[Purpose of the invention]

The present invention has been made in view of the above points, and its object is to provide a power transmission member between the power transmission member and a control member that moves the power transmission member to a connected position and a non-connected position with the movable blade. An object of the present invention is to provide an electric shaver having an operation mechanism that does not cause any load on the operation of the shaver and causes no energy loss.

[Disclosure of the invention]

Accordingly, the present invention provides a trimmer which has a main blade section consisting of an outer cutter and an inner cutter that is in sliding contact with the inner surface of the outer cutter, as well as a comb-like fixed blade and a comb-like movable blade that is in sliding contact with the fixed blade. In an electric shaver that has a blade portion and drives an inner cutter and a movable blade in these double-edged portions by a driver, the driver connected to the inner cutter connects the movable blade to the movable blade via a power transmission member attached to the driver. The control member connects and disconnects the power transmission member and the movable blade in conjunction with handle operation, and the control member includes a transition drive unit that moves the power transmission means to a connection position with the movable blade; and a return drive unit that returns the power transmission member from a connected position with the movable blade to a non-connected position, and the power transmission member self-maintains the connected state with the movable blade and returns to a non-contact position with the transition drive unit. It is characterized in that it is equipped with a self-retaining means for maintaining itself, and the state of connection between the power transmission member and the movable blade is maintained in a state where the control member is not in contact with the power transmission member. It is. The self-holding means here can be provided as a member that engages between the power transmission member and the movable blade or between the power transmission member and the driver. Further, the control member may be integrated with the handle, or the two may be separate members, and the handle also serves to control the motor that is the power source of the driver, and when driving the trimmer blade, the main blade When the blade is also driven, the handle and the control member are assumed to move intermittently, and when the handle is operated in the first stage, the motor is energized and only the main blade is driven, and only when the second stage is operated. It is preferable that the trimmer blade part is also driven, since the load upon starting the motor can be reduced.

The present invention will be explained in detail below based on the illustrated embodiments.

The electric shaver shown here is a so-called reciprocating type that is waterproof and has an extremely slender finish. It consists of a battery cover 3 and a blade frame 2 attached to the upper part of the main body housing 1, and a switch handle 7 is arranged in a concave part provided on the front side of the main body housing 1 so as to be able to slide up and down. ing. Both the part of the main body housing 1 excluding the upper part where the width is increased and the battery cover 3 have an outer surface shape that is continuous vertically and both have an oval horizontal cross section, and the outer surface that is continuous to the upper part of the main body housing 1 is an oval shape. A thin metal outer blade 21 is attached to the upper surface of the shaped blade frame 2, and a trimmer block 4 is attached to the upper front surface of the blade frame 2.

As shown in FIG. 2, the main body housing 1 is a synthetic resin molded product having a cylindrical shape with openings at the top and bottom, and screw receiving bosses 11 are provided at each of the four corners of the wide upper inner surface. A recess 12 is formed on the front surface of the central portion, and a slightly narrowed cylindrical portion 18 is formed at the bottom. The recess 12 has an upper end that opens upward apart from the internal space passing through the center of the main body housing 1, and is surrounded by vertical ribs 13 on both left and right sides and a double rectangular rib 14 at the lower center. The closed window 15 is open. This window 1
A contact spring 91, which is formed in a trifurcated shape and has contact pieces on both sides, is disposed within the window 15 by fixing its base end to the edge of the window 15, and between the double rectangular ribs 14. The window 15 is closed by a switch seal 38, which is attached to the periphery of the window 15. Switch handle 7 with a non-slip surface
is connected to the main body housing 1 via the handle board 70.
The handle base plate 70, which is attached to the handle board 70 and whose horizontal cross section is arcuate, has locking protrusions 77 protruding from the top and bottom of the inner surface of both ends thereof, and locking protrusions 77 formed on the outer surface of each vertical rib 13. The switch handle 7 is fixed to the main body housing 1 so as to cover the above part of the recess 12 by being engaged with the recess 17. It is attached to the handle base plate 70 by being engaged with vertically long engagement grooves 76 on both ends of the handle base plate 70, and is slidable up and down. In the space surrounded by the vertical ribs 13 and the rectangular ribs 14 in the recess 12 whose front surface is closed by the handle board 70, there is a space in which the main body housing 1 can be slid up and down and is inserted through the upper end opening of the recess 12. A slider 71 whose upper end protrudes is arranged in the upper part, and a pin (not shown) of the switch handle 7 fits into an engagement hole 78 of the slider 71 through a pair of left and right vertical holes 75 provided in the handle base plate 70. The slider 71 also moves up and down together with the switch handle 7 which is fitted, and at this time, the elastic click protrusions 79 at the lower ends of both sides of the slider 71 are arranged at the lower part of the inner surface of the vertical rib 13 in two stages, upper and lower. By climbing over the click protrusion 16 of the switch handle 7, the switch handle 7 can be positioned in three steps relative to its vertical movement. A vertically long hole 74 provided at the center of the handle board 70 is used for inserting a pin 72 protruding from the center of the inner surface of the switch handle 7, as shown in FIGS. 6 to 8. Along with the upward movement, the central piece of the contact spring 91, which is bent so that the upper part thereof protrudes forward, is pressed and driven via the switch seal 38, causing both side contact pieces of the contact spring 91 to bend backward. .

The battery cover 3 has a cylindrical shape with a bottom that is open only at the top, and has vertically long vertical ribs 31 on the front and rear walls of the inner surface.
A connecting spring 81 is integrally provided, and when it is placed over the cylindrical portion 18 at the bottom of the main housing 1, the upper and lower ends thereof are engaged with the longitudinal grooves on the front and rear surfaces of the cylindrical portion 18.
As shown in FIG.
It is connected to the main body housing 1 by engaging with the notch 32 in the cylindrical part 18, and at this time, the O-ring 37 fitted to the upper end of the cylindrical part 18 waterproofs the connection part between the main body housing 1 and the battery cover 3. Ru. Two dry batteries 96 serving as a power source are housed from below in the cylindrical portion 18 of the main body housing 1, and both dry batteries 96, which are parallel to each other, are powered by an energizing spring 95 arranged on the bottom surface of the battery cover 3. connected in series.

The motor 9 is not directly disposed within the main body housing 1, but is mounted on a motor base 5 and this motor base 5.
It is housed in the upper part of the main body housing 1 as a drive block constructed with a mounting base 6 or a drive element 10 connected to the main body housing 1. As shown in FIG. 3, the motor base 5, which is a synthetic resin molded product, has upwardly projecting side pieces 51 on both sides and is open at the back. of,
Horizontal ribs 54 are made to protrude from both sides of the upper part, and retaining pins 52 are made to protrude from the upper end faces of each side piece 51. The motor 9 is housed through the rear opening in the internal space from the center to the bottom of the motor base 5 configured as described above, and has an eccentric shaft 99 with a balancer attached to its output shaft.
is positioned between the two pieces 51 above the partition piece 55 on the motor base 5. Further, in the two vertical grooves 56 on the front surface of the motor base 5, an energizing metal fitting 92 and a cathode metal fitting 93 are respectively provided. The current-carrying metal fitting 92 is connected to the cathode terminal of the motor 9 through a hole 57 provided at the lower front end of the motor base 5, and the lower end of the cathode metal fitting 93 is fixed to the lower surface of the motor base 5. It contacts the cathode of the dry battery 96. Further, from the rear side, an anode metal fitting 94 whose one end is connected to the anode terminal of the motor 9 and whose other end is arranged on the underside of the motor base 5 and contacts the anode of the dry cell battery 96 is attached so as to sandwich the bottom plate of the motor base 5. It is being

The mounting base 6 is also a synthetic resin molded product, and has a cylindrical shape with the top surface closed except for the central round hole 60 and the bottom surface open, and an internal space connecting the round hole 60 and the bottom opening. Separately, screw insertion holes 61 that penetrate downward and open at the lower surface of the flange 69 are provided at the four corners of the upper surface, and a concave surface portion 64 surrounded by ribs 67 on both sides and the lower side is formed on the front surface of the central portion. The lower portion has a slightly tapered skirt portion 65. The concave surface portion 64 is a space in which a slide lever 20, which will be described later, is disposed, and is open upwardly apart from the internal space through the through portion 63. Further, an opening/closing button 86 with a hook 87 that engages with the inner surface of the blade frame 2 and a receiving part 62 for arranging a spring 88 for returning the opening/closing button 86 are formed on one side of the upper part, and a recess 68 is formed on the other upper side. Engagement holes 66 are provided on both sides of the skirt portion 65.

The motor base 5 and the mounting base 6 are connected by placing the mounting base 6 over the top of the motor base 5 and engaging the locking protrusion 53 in the motor base 5 with the engagement hole 66. However, the motor base 5
The driver 10 is disposed in a space surrounded on all sides by the partition piece 55, the side pieces 51, and the mounting base 6.
As shown in FIG. 4, this drive element 10 has a main body 100 with an inverted U-shape in front, and plate springs 10 are mounted on both sides of the main body 100.
1 extends upward, a cylindrical shaft 102 with an open upper end surface is erected from the center, and an arm 104 is protruded from the inner surface of one side piece of the main body 100, and is made of synthetic resin. Although the leaf spring 101 is easily deflected in the left and right directions, it does not deflect in the front and rear directions;
4 is said to be easy to bend in the front-back direction.
The driver 10 is positioned by inserting the fixing pins 52 at the left and right upper ends of the motor base 5 into the mounting holes 109 formed in the fixing pieces 103 at the upper ends of each leaf spring 101. 1
03 is clamped from above and below by a motor base 5 and a mounting base 6, thereby being fixed in a suspended state. The drive element 10 and the balancer-equipped eccentric shaft 99 attached to the motor 9 are connected at an arm 104. Arm 1
04 has an E-shaped planar shape, the front and rear side pieces are integrally connected to the side pieces of the main body 100, and the eccentric shaft 99 is connected to the tip of the center piece. Drive element 10 subjected to revolution movement of eccentric shaft 99
performs reciprocating motion in the left-right direction due to the above-mentioned deflection characteristics.

The driver 10 mounted in this manner causes the cylindrical shaft 102 to protrude above the mount 6 through the round hole 60 of the mount 6. The space between the cylindrical shaft 102 and the round hole 60 has an inner periphery that touches the base of the cylindrical shaft 102 and an outer periphery that is pressed against the periphery of the round hole 60 on the top surface of the mounting base 6 by the pressing plate 34. It is closed by a diaphragm-like packing 35.
The holding plate 34 is inserted into its four corners and attached to the mounting base 6.
The mounting screw 90 screwed into the screw receiving boss 11 of the main body housing 1 through the screw insertion hole 61 fixes the motor base 5 and the mounting base 6 connected thereto to the main body housing 1 at the same time. It is fixed to the top surface. In other words, the motor base 5, the mounting base 6, and the parts attached thereto, such as the motor 9 and the driver 10, are assembled as one block and then attached to the body housing 1. Furthermore, when the motor base 5 is attached to the main body housing 1, the horizontal ribs 54 at the lower part inserted into the main body housing 1 are attached to the main body housing 1 as shown in FIG.
It is reliably fixed by being pressed against the stepped portion 19 on the inner surface. Further, the skirt portion 65 at the lower part of the mounting base 6 is fitted into the upper part of the main body housing 1, and this fitting portion is waterproofed by the packing 36. The space in which electric components such as the motor 9 and the dry cell battery 96 are placed inside the main body housing 1 has an upper opening with gaskets 35 and 36, a front window 15 with a switch gasket 38, and a lower opening with a battery cover 3 and an O-ring. 37, each is closed and hermetically sealed. Note that the slider 71 and slide lever 20 are located outside this closed space.

Now, the blade frame 2 has a recess 25 formed on its front surface and opens upward toward the back, and a plurality of locking protrusions 28 are protruded from the front and rear inner walls to form a recess 25 in the recess. There is an opening 26 passing through the central lower part of the slanted front wall, which also serves as the bottom surface of 25.
is formed. A mesh-like bendable outer blade 21 arranged on the upper surface of the blade frame 2 is connected to a reinforcing plate 21.
The blade frame 2 is attached to the blade frame 2 by locking holes 211 formed at both ends where the blades 0 are attached to the locking protrusions 28 . This outer blade 21
The inner cutter block 22, which has a large number of inner cutter blades arranged parallel to each other on its upper surface and slides on the inner surface of the drive element 10, is mounted on the upper part of the cylindrical shaft 102 of the drive element 10 so as to be able to freely tilt left and right about the shaft 24. It is attached and urged upward by a push-up spring 23. The main body housing 1 and the blade frame 2 are connected by a shaft 84 attached to the inner surface of one side of the blade frame 2 and a hinge piece 8 through which the shaft 84 is inserted into the upper end.
3 and a locking spring 82 disposed in the space between the main body housing 1 and the recess 68 in the mounting base 6 and removably locking the hinge piece 83, and also by the hook 87 in the opening/closing button 86 mentioned above. It is rotated around the shaft 84 and biased in the opening direction by a torsion coil spring 85 attached to the shaft 84. If you press the open/close button 86, the hook 87
is detached from the blade frame 2 and the torsion coil spring 8
5 opens the blade frame 2.
Furthermore, by removing the hinge piece 83 from the stopper spring 82, the blade frame 2 can be removed from the main body housing 1.

Next, the trimmer block 4 disposed in the recess 25 on the front surface of the blade frame 2 and the drive mechanism for the movable blade 40 in this trimmer block 4 will be explained.
First, I will explain the trimmer block 4. This is a movable blade 40 with a comb-shaped cutting edge on the front edge.
, a fixed blade 41 having a comb-like cutting edge on its front edge, a presser spring 42 that presses the movable blade 40 against the upper surface of the fixed blade 41, a substrate 43 to which these are attached to the lower surface, and the above members on the upper surface. The mounting board 44 is arranged on the mounting board 44. The mounting board 44 consists of a front plate with a slightly concave front surface and an upper plate extending rearward from the top of the front plate, and mounting hooks 442 are provided rearwardly extending from both ends.
A protrusion 444 protrudes from the lower surface, and an escape hole 440 is formed at the center of the upper surface to vertically penetrate the upper plate. Then, a pair of connecting hooks 431 hanging down from both sides of the board 43 are engaged with respective connecting grooves 443 provided on the upper side end surface of the mounting board 44, and two guide bosses 432 hanging down from the board 43 are engaged. By inserting the tips of the presser spring 42, the movable blade 40, and the fixed blade 41 into the upper surface of the mounting board 44 to connect the board 43 and the mounting board 44, the movable blade 40, the fixed blade 41, and the presser spring 42 are connected to the lower surface of the board 43. and mounting board 44
The movable blade 40, which is assembled between the upper surface and the lower surface of the movable blade 40 with an engaging seat 45 opening downward and fixed to the lower surface by heat caulking, is guided in reciprocating movement in the left and right direction by a guide boss 432. The engagement seat 45 passes through the through hole 410 at the center of the fixed blade 41 and is located in the escape hole 440 at the center of the upper surface of the mounting board 44 . The presser spring 42 is held with its rear end held between a protrusion 441 protruding from the rear end of the upper surface of the mounting board 44 and the lower surface of the board 43. To attach the trimmer block 4, which has been made into a block as described above, to the blade frame 2, insert the protrusion 444 on the lower surface of the mounting board 44 into the groove 29 formed on the lower surface of the front recess 25 of the blade frame 2. Mounting hook 44
This is done by locking the trimmer block 2 into the locking recesses 27 on both sides of the recess 25, so that the trimmer block 4 can be easily removed from the blade frame 2 for purposes such as cleaning the trimmer block 4. ing.

The drive mechanism for reciprocating the movable blade 40 of the trimmer block 4 includes a driver 10 that converts the rotational motion into reciprocating motion, a joint 49 attached to the driver 10, and a mounting board 4 of the trimmer block 4.
The trimmer drive element 46 is attached to the back of the trimmer 4. As shown in FIGS. 6 to 8, the trimmer drive element 46, whose center portion in the vertical direction is pivotally supported by a shaft 445 protruding rearward from the center of the back surface of the mounting board 44, is attached to its upper end. Aiza 45
The movable blade 41 is reciprocated by receiving the movement of the drive element 10 via a joint 49 and swinging, which has a receiving groove 48 at the lower end that opens downward. It is something that makes you Now, regarding the joint 49, this is the cylindrical shaft 10 of the driver 10.
The drive element 10 is attached to the drive element 10 so as to be vertically rotatable by fitting the shaft hole 490 into the shaft 105 protruding from both end surfaces of the blade frame 2. It has a shaft portion 491 that can be freely engaged with the receiving groove 48 of the trimmer driver 46 in the notch 212 at one end of the outer blade 21,
In addition, a protrusion 492 is provided on the inner surface of each elastic side piece that extends rearward from the shaft hole 490, and as the joint 49 rotates, the protrusion 492 It is designed to ride over a pair of protrusions 106 that protrude to both sides at a position slightly below the rear of the shaft 102, and provide a click to the rotation of the joint 49.

The vertical rotation of the joint 49 about the left-right direction is performed in conjunction with the switch operation by the switch handle 7. Switch handle 7 and fitting 4
The aforementioned slider 71 and slide lever 20 are used to link the slider 9 with the slider 71 and the slide lever 20. A slide lever 20 is disposed in a concave surface 64 on the front surface of the mounting base 6 so as to be able to move up and down, and whose upper end projects onto the upper surface of the mounting base 6 through a through-hole 63. An engagement window 201 is formed in the upper part of the slider 71 which is bent slightly backward, and an opening 202 is formed in the lower part. It is biased downward by a return spring 205 whose upper end is in contact with the lower surface of the flange 69 of the mounting base 6 and whose lower end is in contact with the lower edge of the opening 202. A shaft portion 491 is inserted therethrough. Here, the vertical opening dimensions of the engagement window 201 are sufficiently larger than the outer diameter of the shaft portion 491, so that a non-contact state between the shaft portion 491 and the inner surface of the engagement window 201 can be obtained. There is.

When the switch handle 7 is moved upward, the slide lever 20 is also moved upward via the slider 71, and the slide lever 20 is moved upward to the shaft portion 491 of the joint 49.
Since the joint 49 is rotated until the shaft portion 491 engages with the receiving groove 48 of the trimmer drive element 46, the movement of the drive element 10 can be transmitted to the movable blade 40 of the trimmer block 4. However, as mentioned above, among the three clicks given to the vertical movement of the switch handle 7, at the lowest position there is a click between the upper end of the slider 71 and the lower end of the slide lever 20. 6 There is a gap as shown in Figure 6, and the switch handle 7
Push up the contact spring 9 to the middle position and use the pin 72 to release the contact spring 9.
Even in the state shown in FIG. 7 in which the motor 9 is energized by short-circuiting the current-carrying metal fitting 92 and the cathode metal fitting 93 with the contact spring 91 by bending the slide lever 20
The joint 4 is not pushed up by the slider 71 but is lowered by the force of the return spring 205, and the inner cutter block 22 is reciprocated by receiving the rotation of the motor 9 via the driver 10.
9 is not engaged with the trimmer drive element 46, the movable blade 40 of the trimmer block 4 is not driven. However, if the switch handle 7 is pushed up to the highest level, as shown in FIG. Slide lever 2
Since the joint 49 with the shaft portion 491 inserted through the engagement window 201 of 0 is rotated and the shaft portion 491 is engaged with the receiving groove 48 of the trimmer driver 46, the operation of the driver 10 causes the joint 49 to rotate. is applied to the trimmer drive element 46 through the
The movable blade 40 is reciprocated by the swinging of a trimmer driver 46 that is engaged with an engagement seat 45 that is fixed at zero. Further, when the joint 49 is rotated in this manner, the protrusion 492 of the joint 49 climbs over the protrusion 106 of the driver 10 and finally the joint 49 moves itself to the engagement position with the trimmer driver 46. try to For this reason, the joint 49 self-maintains the engagement state with the trimmer driver 46 when its shaft 491 is engaged with the trimmer driver 46, and the slide lever 20 is used to connect the joint 49 and the trimmer driver. The engagement state with the child 46 may not be maintained, that is, the inner surface of the engagement window 201 and the shaft portion 491 of the joint 49 may be in a non-contact state. Therefore, when the movable blade 40 is being driven from the drive element 10 via the joint 49 and the trimmer drive element 46, the shaft portion 491 of the joint 49 is moved within the engagement window 201 of the slide lever 20, as shown in FIG. The slide lever 20 is in a floating state so that the slide lever 20 does not provide any resistance to the power transmission operation of the joint 49.

When the switch handle 7 is pulled down, the slide lever 20 is moved downward by the force of the return spring 205, and the joint 49 is rotated in the direction of lowering the shaft portion 491, so that the joint 49 and the trimmer driver 46 are The engagement is released and the state shown in FIG. 7 or 6 is restored.

In the embodiment shown above, the joint 49, which is a power transmission member, self-maintains the connected state between the joint 49 and the trimmer driver 46 connected to the movable blade 40 with the driver 10. However, it may be self-retained between the joint 49 and the Narimar driver 46.

〔Effect of the invention〕

As described above, in the present invention, the power transmission member that transmits the movement of the driver to the movable blade in the trimmer blade section is controlled by the control member from the uncoupled position with the movable blade to the coupled position, and from the coupled position to the uncoupled position. When the power transmission member is moved to the position where it is connected to the movable blade, the power transmission member itself maintains the connection state with the movable blade, and the power transmission member is connected to the movable blade. This part maintains itself in a non-contact position with the transition drive part to move it to the position, and for this reason, the control member does not apply a load to the operation of the power transmission member, causing energy loss in this part. It is something that never happens.

[Brief explanation of the drawing]

Figure 1 is a perspective view of one embodiment of the present invention, Figures 2 to 4 are exploded perspective views of the same, Figure 5 is a cross-sectional view of the same, and Figures 6 to 8 are the same as the above. , in which 4 is a trimmer block, 7 is a longitudinal sectional view of
9 is a switch handle, 9 is a motor, 10 is a driver, 20 is a slide lever that is a control member, 21
2 is an outer blade, 22 is an inner blade block, 40 is a movable blade, 4
1 is a fixed blade, 49 is a joint as a power transmission member,
Reference numerals 106 and 492 indicate protrusions and protrusions constituting self-holding means, and 201 indicates engagement windows whose upper and lower inner surfaces constitute a transfer drive section and a return drive section, respectively.

Claims (1)

[Scope of Claims] 1. It has a main blade part consisting of an outer cutter and an inner cutter that slides on the inner surface of the outer cutter, and also includes a comb-shaped fixed blade and a comb-shaped movable blade that slides in contact with the fixed blade. This is an electric shaver that has a trimmer blade section and drives an inner cutter and a movable cutter in these double cutter sections by a drive element, and the drive element connected to the inner cutter drives the power transmission member attached to the drive element. The control member, which can be freely connected to the movable blade through the handle, connects and disconnects the power transmission member and the movable blade in conjunction with handle operation, and the control member moves the power transmission member to the connection position with the movable blade. and a return drive unit that returns the power transmission member from a connected position with the movable blade to a non-connected position, and the power transmission member self-maintains the connected state with the movable blade and functions as a transition drive unit. An electric shaver characterized in that it is equipped with self-holding means for keeping itself in a non-contact position. 2. The handle is also used to control the motor that is the power source of the drive element, and the handle and the control member are intermittently interlocked, as set forth in claim 1. electric razor. 3. The control member has an engagement window through which the power transmission member is inserted, and a transition drive unit and a return drive unit are formed at the edge of the engagement window, and the control member has an engagement window in which the power transmission member is inserted. The electric shaver according to claim 1, wherein the power transmission member held is in a non-contact state with the inner surface of the engagement window.