WO2008040373A1 - Device for fastening a wiper functional unit to a wiper shaft - Google Patents

Abstract

In the case of a device for fastening a wiper functional unit to a wiper shaft with a connecting piece which has a receiving opening, said connecting piece can be fastened to the wiper shaft at the receiving opening by clamping and, for this purpose, is designed as a clamping piece with at least one clamping gap, which opens into the receiving opening, and tensioning means which, by reducing the width of the clamping gap, press the connecting piece in the region of the receiving opening against the wiper shaft in order to produce the clamping connection. The tensioning means are formed by a tensioning element which engages over the connecting piece in the region of the clamping gap.

Description

 Device for fastening a wiper functional unit to a

wiper shaft

The invention relates to a device for fastening a wiper functional unit to a wiper shaft or to a connection (connecting device) between wiper functional unit and wiper shaft according to the preamble of claim 1.

Connections and in particular also releasable connections between the wiper shaft of a windshield wiper assembly and, for example, a wiper arm or a joint part, on which the wiper arm is articulated, are known in various designs. Allen known compounds or devices is the use of screws or nuts for the clamping or clamping on the wiper shaft in common.

For example, it is known (DE 71 04 7 759) to provide for securing a wiper blade carrying at least one wiper blade to a drive shaft or a wiper shaft reversibly driven for pivoting the wiper arm a hinge part, which consists of a fastener attachable to the wiper shaft and a cap consisting of a connecting piece for assembly or disassembly releasing position in a position covering the connector is pivotable. At the hinge part of the wiper arm is articulated. The connection between the connecting piece and the wiper shaft is realized in that the connecting piece with a receiving opening placed on a conical portion of the wiper shaft and secured there by a nut provided on a threaded portion of the wiper shaft. This known compound is constructive, but also expensive in terms of assembly.

It is also known to fasten the connecting piece of the joint part by clamping on the wiper shaft (US Pat. No. 3,433,513), specifically in that the connecting piece is formed in the region of the receiving opening for the wiper shaft as a clamping piece with a slot or clamping gap opening into the receiving opening. For clamping on the wiper shaft serves a clamping gap bridging and clamping by reducing the width of the clamping gap causing clamping element in the form of a clamping screw. This embodiment also has at least the disadvantage of a relatively high installation effort during mounting, but also during disassembly, i. when removing or replacing the joint part.

The object of the invention is to provide a device with which a simplified yet secure installation, but also a simplified replacement of a wiper function unit to or from a wiper shaft is possible. To solve this problem, a device according to the patent claim 1 is formed.

For the purposes of the present invention, a "wiper functional unit" is to be understood very generally as meaning any functional element of a windshield wiper arrangement which is attached to the shaft end of a wiper shaft that is accessible on the outside of a vehicle. In this sense, a wiper function unit is, for example, the joint part of a wiper arm of any design for a wiper blade of any design or the hinge part of a wiper arm equipped with a wiper rubber (so-called composite wiper arm) or the wiper arm of any design for a wiper blade of any design or directly with the squeegee equipped wiper arm (composite wiper arm) or a hinge part for a directly connected with this wiper blade, for example, flat wiper blade or joint-free Wiper blade, or a directly connected to the wiper shaft wiper blade or the like.

For the purposes of the invention, a "wiper shaft" means any shaft or axle of a windshield wiper arrangement which can be reversibly driven directly or indirectly via a windscreen wiper motor and to which the wiper functional unit is attached for the pivoting movement of the at least one wiper arm or wiper blade.

A particular advantage of the device according to the invention consists in the fact that the assembly, but also the dismantling of the wiper functional unit are substantially simplified and accelerated and cost-effective. This is achieved by the screwless clamping or clamping of the connecting piece designed as a clamping piece on the wiper shaft. The latter is cylindrical or only slightly conical in the area of the connection or the connection. Preferably, the wiper shaft in this area has a cross-section deviating from the circular cross-section, which is realized for example by at least one surface or flattening on the circumference or by a polygonal cross-section, and / or the wiper shaft is structured in the connection region on its peripheral surface, for example with a corrugation and / or provided with a multi-tooth-like structuring, so that after clamping also a positive connection between the wiper shaft and the connecting piece exists. This is preferably made of a deformable, in particular elastically deformable material, e.g. made of a suitable plastic.

As a tensioning element serves as a cap, in particular a cap, which is preferably hingedly connected to the connector, and in its the connector at least partially covering position causes the clamp connection, for example, characterized in that when trained as a clamping piece this connector through the cap or . is clamped clamped by provided on the cap clamping surfaces on the wiper shaft. The device according to the invention allows the formation of relatively large contact surfaces between the wiper shaft and the receiving opening of the connecting piece, so that the connecting piece can be made particularly inexpensive plastic.

The embodiment of the invention is particularly well suited for use on windshield wiper systems with reversing wiper motor with position detection and independent detection and determination of the wiping field, so that in this embodiment of a windshield wiper system during assembly of the wiper function unit to an accurate adjustment of at least one wiper arm and / or wiper blade can be dispensed with in the parking position.

Further developments of the invention are the subject of the dependent claims. The invention will be explained in more detail below with reference to the figures of exemplary embodiments. Show it:

Fig. 1-3 in a simplified representation and in side view a

Wiper shaft and attached to this wiper shaft wiper function unit consisting of a directly attached to the wiper shaft hinge part and a hinged to this hinge part wiper arm, in side view, top view and in bottom view;

4 shows a section along the line I - I of Figure 2;

5 shows a section through the joint part of Figures 1 - 4 corresponding to the line II - II of Figure 1;

6 shows a section along the line III - III of Figure 1;

Figure 7 is a view similar to Figure 4 in a further embodiment of the invention, with weggeklappter, acting as a clamping element cap.

Fig. 8 is a view similar to Figure 5 in the embodiment of Figure 7; Figure 9 is a section along the line IV - IV of Figure 8, but before the clamping of the joint part on the wiper shaft.

10 and 11 in an individual view and together with the serving as a clamping element cap in another possible embodiment of the invention;

FIG. 12 shows an individual view of the end of a wiper shaft serving for fastening the wiper functional unit, for example the joint part, in another possible embodiment of the invention; FIG.

13 is a partial perspective view of the wiper shaft and the

Connector and the cover of the joint part in another possible embodiment, prior to mounting the cap on the connector and before mounting the joint part on the wiper shaft;

FIG. 14 is a perspective view of the wiper shaft and the articulated part of the embodiment of FIG. 13 placed thereon; FIG.

Figs. 15 and 16 are similar to Figures 13 and 14, but in another possible embodiment.

In FIGS. 1-6, 1 is the usual wiper shaft of a windshield wiper system reversibly driven by a drive, not shown, for vehicles, in particular for road vehicles.

At the wiper shaft end 1.1 exposed on the vehicle exterior, a wiper functional unit 2 is fastened, in such a way that during the reversing rotational movement of the wiper shaft 1, this unit is oscillated back and forth about the wiper shaft axis WA.

In the illustrated embodiment, the wiper functional unit consists of a fixed to the wiper shaft end 1.1 joint part 3 and a hinged to this hinge part 3 by means of the joint 4 wiper arm 5, which at its the hinge part 3 remote rod-like end as a hook 5.1 to Attachment of a wiper blade, not shown, is formed. Between the joint part 3 and the wiper arm 5 acts in a likewise known manner, a spring 6 for generating the contact pressure, with which the wiper blade rests against the vehicle window.

The connection generally designated 7 between the wiper shaft 1 and the wiper functional unit 2 or the hinge part 3 is designed as a screwless quick or clamp connection, using a connector 8, which is part of the joint part 3 and with which this on the wiper shaft end 1.1 can be fastened by clamping.

The connecting piece is made as a molded part from a suitable, high-strength plastic and sufficient elasticity, substantially like a strip with a first profile section 9, the one, i. in the illustration of Figures 4 and 5, the left end of the connecting piece 8 forms, and with a profile section 10, the other, i. in the figures 4 and 5 right end of the connecting piece 8 forms. The profile sections 9 and 10 connect in the longitudinal direction L of the connecting piece 8 to each other. As FIG. 5 shows, the profile section 10, which extends over the greater part of the length of the connecting piece 8, has a width that is greater than the width of the profile section 9.

In the vicinity of the transition between the profile sections 9 and 10, a bore or receiving opening 11 is provided in the profile section 10, which corresponds to the shaft end 1.1 in terms of cross-sectional shape and cross-sectional size, so that the connecting piece 8 can be fitted with this opening 11 fits the shaft end 1.1. In order to achieve a defined axial position for the connecting piece 8 and thus also for the joint part 3 on the wiper shaft 1, this has a slightly reduced cross-section at its wiper shaft end 1.1 and thereby forms a collar or stop 1.2, against which the connecting piece 8 rests , The receiving opening 11, which is formed continuously, ie from the top 8.1 to the bottom 8.2 of this connector 8 extends is slotted to form a nip 12 over its entire height on the circumference, wherein the corresponding nip 12 lies in a plane which is the axis the opening 11 as well as the longitudinal extent L of the connecting piece 8 includes. The clamping gap 12 extends over the entire length of the shorter profile section 9 and is open at the end of this profile section, so that the profile section 9 of the connecting piece 8 designed as a clamping piece forms two clamping arms 9.1 on both sides of the clamping gap 12. The clamping gap 12 relative to the axis of the opening 11 diametrically opposite the receiving opening 11 is provided with a parallel to the wiper shaft axis WA extending groove-shaped extension 13.

Following the receiving opening 11 in the longitudinal direction L, a continuous opening 14 is provided in the profile section 10, which also extends from the upper side 8.1 to the lower side 8.2 and is slit-shaped. At the end remote from the profile section 9, the profile section 10 is formed into a bearing 15 for a hinge pin 4.1 forming the hinge 4. Below the bearing 15 of the profile section 10 has a slot-shaped opening 16, which is open at the bottom 8.2 of the connector and at the profile section 9 remote end of the profile section 10 and in the attacking the hinge part 3 6.1 end of the spring 6 by hooking is held on a bolt 16 crossing the opening 16.

The joint part 3 further has a cover cap 18, which is made, for example, of metal or a suitable plastic and which is designed substantially as a U-profile closed at a cap end 18.1 with two legs 19 and with a yoke section 10 connecting these legs. At the end remote from the cap end 18.1, the cap 18 is pivotally connected with its legs 19 to the connecting piece 8, in the illustrated embodiment using the hinge pin 4.1, so that in the state shown in Figures 4-6, the connector 8th completely absorbs and completely covers in a line of sight on the shaft end 1.1, wherein the two legs 19 each adjacent to a longitudinal side of the connecting piece and the yoke portion 20 of the top 8.1 of the connecting piece opposite. From this covering state, the cap 18 is pivotable in an open state, in which at least the cap end 18.1 is clearly spaced from the connecting piece 8 or from the profile section 9 or protrudes.

In the vicinity of the cap end 18.1 formed as a clamping element cap 18 is provided internally with two clamping or clamping jaws 21, of which one is formed on the inside of a leg 19 and protrudes beyond the inner surface of the leg there.

To clamp the articulated part 3 and thus also the wiper function unit 2 in total on the wiper shaft 1, the connecting piece 8 with the receiving opening 11 pivoted on the end of the shaft 1.1 is placed in the open position until the bottom 8.2 against the collar 1.2 of the wiper shaft. 1 is applied. The connecting piece 8 is then arranged with its longitudinal extent L radially to the shaft axis WA. Following this, the cap 18 is pivoted into the position covering the connecting piece 8, the clamping jaws 21 come to rest against the clamping arms 9.1, this move under elastic deformation of the material of the connecting piece 8 and reducing the width of the clamping gap 12 to each other and thereby fix the connecting piece 8 on the shaft end 1.1 by clamping. In this clamping or fixing state of serving as a clamping element cap 18, the two jaws 21 are each radially spaced from the wiper shaft 1, so that the clamping fastener tion due to the inherent elasticity of the clamping arms 9.1 is particularly effective and elastic.

In order to avoid unwanted pivoting back of the cap 18 in the non-clamping position, the jaws 21 are each with notches 21.1 formed, which engage behind the clamping arms 9.1 in the clamping state of the cap 18. The clamping jaws 21 and / or the clamping arms 9.1 are executed on their cooperating surfaces in each case as inclined or wedge surfaces. The additional, slot-shaped opening 14 results in not only a saving of material, but another, the effect of the clamp connection 7 improving elasticity for the connecting piece. 8

The wiper shaft end 1.1 is formed circular-cylindrical and provided to improve the positive engagement of the compound 7 with a knurling or a flat toothing. The shaft end 1.1 could also be formed with a cross section deviating from the circular shape, for example with a flattening or with a polygonal cross-section or the like. The use of plastic for the connecting piece 8 ensures that when clamping the inner surface of the receiving opening 11 in an optimal manner to the shaft end 1.1 applies and / or the material of the connecting piece 8 in a possibly existing knurling or flat teeth or other surface profiling of the shaft end impresses 1.1, whereby a high torsional strength of the connection is ensured.

FIGS. 7-9 show, as a further possible embodiment, a connection 7a between the wiper shaft 1 and the joint part 3a. The connection 7a differs from the connection 7 essentially only in that instead of the two formed on the inner sides of the cap jaws 21, a U-shaped clamping element 22 is provided, which after fitting the connecting piece 8 corresponding connector 8a on the wiper shaft 1.1 for producing the clamping connection is pushed onto the two clamping arms 9.1, so that the clamping element 22 engages over the clamp section 9.1 forming profile section 9 at the top and on the longitudinal sides of the connecting piece 8.

The clamping element 22 consists in this embodiment of an outer, formed as a U-shaped plastic part or profile 23 and an inner, also designed as a U-profile metal insert 24. The latter is in the clamped state with the legs of their U-profile against each a clamping arm 9.1. The plastic part 23 forms locking lugs 23.1, which engage behind the clamping arms 9.1 in the clamped state and thereby fix the clamping element 22 on the connecting piece 8 formed as a clamping piece.

The clamping element 22 is for example part of the cover cap 18 corresponding cap 18a, which in turn is pivotally provided on the hinge pin 4.1, in which case the plastic part 23, for example, the U-profile of the cap 18a or a molded onto the cap 18a or with this connected profile. The clamping element 22 may also be an independent, separated from the cap 18 a component.

FIGS. 10 and 11 show, as a further possible embodiment, a connection 7b between the wiper shaft 1 and a joint part 3b, which in turn essentially consists of the connecting piece 8b made of an elastic material, in particular plastic and designed as a clamping piece, and of the plastic and / or or metal-fabricated and at the same time serving as a clamping element cap 18b consists.

The connecting piece 8b, which in turn is designed substantially strip-like, is provided at one end with a receiving opening 11 corresponding to the receiving opening 25 and at the other end with a bearing 15 corresponding bearing 26 for the articulated connection with the wiper arm, not shown.

Between the opening 25 and the bearing 26, the connecting piece 8b is provided with an opening into the opening 25 nip 27 which extends over the greater part of the length of the connecting piece 8b. The in the plane of the longitudinal extent L of the connecting piece 8b and in the axis of the opening 25th arranged nip 27 is in turn carried out continuously from the top to the bottom of the connector 8b.

Approximately in the middle of the clamping gap 27 and at a distance from the receiving opening 25 and from the closed end of the clamping gap 27 inclined or wedge surfaces 28 are formed on the two side surfaces of the connecting piece 8b, which in turn with the legs of a U- Profile made of metal-made clamping element 29 cooperate. The clamping element 29 is formed in the illustrated embodiment of a metallic insert in the cap 18 b. The latter is in turn formed as a U-profile closed at the cap end 18b.1, namely with the two legs 30 and with the yoke section 31 connecting these legs. In contrast to the connections 7 and 7a, the covering cap 18b is at the receiving opening 25 having the end of the connecting piece 8b pivoted about the pivot axis 32. The pivotal connection is realized by integrally formed on the legs 30 pin. Since the clamping gap 27 required for clamping extends from the opening 25 toward the other end of the connecting piece 8b, the receiving opening 25 can be provided relatively close to one end of the connecting piece 8b.

It has been assumed above that the wiper shaft 1 is substantially cylindrical in the region of its wiper shaft end 1.1. In order to simplify a desired removal of the respective joint part 3, 3a, 3b or the wiper functional unit from the wiper shaft 1, it is also possible to make the shaft end 1.1 slightly conical, but with a small cone angle α, which then in the order between 0 and 10 °, as shown in FIG.

In the figures 13 and 14 is shown as a further possible embodiment, a compound 7c with the hinge part 3c, which differs from the hinge part 3 essentially in that the function of the cap 18 corresponding cap 18c has a shorter axial Lände than the Connector 8 corresponding connector 18c has, so that when mounted on the wiper shaft 1 by clamping joint part 3c, the cap 18c covers the connector 8c only on a partial length.

The cap 18c is provided with pivotally formed on the cap inner surface and cooperating with openings 33 in the connecting piece 8c pin 34.

FIGS. 15 and 16 show representations similar to FIGS. 13 and 14 as a further possible embodiment of a connection 7d with the hinge part 3d, which differs from the hinge part 3c substantially in that the cap 18d corresponding to its function of the cap 18c is not pivotable, but slidable or attachable to the connecting piece 8c corresponding connector can be fastened. Pushing is possible with the connecting piece 8d mounted on the shaft end 1.1 in an axial direction parallel to the axis of the wiper shaft 1, but also in an axial direction radially to the axis of the wiper shaft 1, wherein in the mounted state of the cap 18d the clamping jaws 21 formed on the inside of the cap overlap the clamping arms 9.1 and thereby cause the clamping of the connector 8d on the wiper shaft 1 and at the same time the attachment of the cap 18 to the connector 8d or the clamping arms 9.1, preferably by locking not only with the notches 21.1, but also with additional Notches which counteract a release of the cap 18 d radially to the axis of the wiper shaft 1.

The invention has been described above by means of exemplary embodiments. It is understood that numerous changes and modifications are possible without thereby departing from the inventive concept underlying the invention.

Thus, it was assumed above that the respective clamping connection between the wiper shaft 1 and a joint part 3, 3a, 3b, 3c, 3d is formed, on which then the wiper arm 5 is held articulated. The invention includes attaching the wiper arm with the screwless connection according to the invention directly to the wiper shaft, especially a wiper arm with integrated wiper blade or with appropriate training and the wiper blade itself.

Above, it was further assumed that the respective connecting piece 8, 8a, 8b, 8c, 8d is made in one piece from a single material. In principle, there is also the possibility of using several different materials. Thus, the connecting piece can be made, for example, in the region of the receiving opening 11 or 25 made of plastic and otherwise but of a suitable metal.

LIST OF REFERENCE NUMBERS

wiper shaft

1.1 shaft end

1.2 Bund

2 wiper function unit

3, 3a, 3b, 3c, 3d joint part

4 joint

4.1 hinge pin

5 wiper arm

5.1 hook

6 spring

6.1 spring end

7, 7a, 7b, 7c, 7d screwless connection

8, 8a, 8b, 8c, 8d connector

8.1 Top of the connector

8.2 Bottom of the connector

9, 10 profile section of the connecting piece 8

9.1 Clamp arm

11 receiving opening for wiper shaft

12 nip

13 groove-shaped extension

14 opening

15 bearings

16 opening or recess

17 Connecting bolt for spring end 6.1

18, 18a, 18b, 18c, 18d cap

18c, 18d cap

18.1, 18. 1 b cap end

19 thighs

20 yoke section 21 jaws

21.1 rest

22 clamping piece

23 plastic profile

24 metal insert

25 receiving opening for wiper shaft

26 bearings

27 nip

28 wedge or beveled surface

29 clamping piece

30 thighs

31 yoke section

32 pivot axis

33 hole

34 cones

L Length of the connecting piece

WA Wiper shaft axis α Cone angle

Claims

claims Device for fastening a wiper functional unit (2) to a wiper shaft (1), having a connecting piece (8, 8a, 8b, 8c, 8d) which has a receiving opening (11, 25) and which is made use of clamping means (18, 18a, 18b, 18c, 18d, 22) can be fastened by clamping on the wiper shaft (1), characterized in that the clamping means (18, 18a, 18b, 18c, 18d, 22) for a screwless clamping of the functional unit (2) and the Connecting piece (8, 8a, 8b, 8c, 8d) are formed. 2. Device according to claim 1, characterized in that the connecting piece (8, 8a, 8b, 8c, 8d) with the receiving opening (11, 25) can be fastened by clamping on the wiper shaft (1) and for this purpose as Clamping piece is formed and at least one in the receiving opening (11, 25) opening clamping gap (12, 27), that the connecting piece (8, 8a, 8b, 8c, 8d) by the clamping means below Reduction of the width of the clamping gap (12, 27) in the region of Receiving opening (11, 25) against the wiper shaft (1) for generating the Clamping connection can be pressed, and that the clamping means of a clamping element (18, 18 a, 18 b, 18 c, 18 d, 22) are formed, which the connecting piece (8, 8 a, 8 b, 8 c, 8 d) in the region of the clamping gap (12, 27) clamp-like overlaps. 3. A device according to claim 2, characterized in that the clamping element (18, 18 a, 18 b, 18 c, 22) pivotally on the connecting piece (8, 8 a, 8 b, 8 c) is provided. 4. Apparatus according to claim 2 or 3, characterized in that the clamping element (18, 18 a, 18 b, 18 c, 22) about an axis perpendicular to the axis (WA) of the wiper shaft (1) or the receiving opening (11, 25), in particular about an axis (4.1, 32) perpendicular to the longitudinal extent of the clamping gap (12, 27), is pivotable. 5. Device according to one of the preceding claims, characterized in that the pivot axis of the clamping element (18, 18 a, 22) is provided coaxially with the axis (4.1) of a joint (4) for connecting the wiper arm (5) or a wiper blade. 6. Device according to one of the preceding claims, characterized in that the pivot axis of the clamping element (18b, 18c) relative to the axis (4.1) of a joint (4) for connecting the wiper arm (5) or a wiper blade is provided radially offset. 7. Device according to one of the preceding claims, characterized in that the clamping element (18b, 18c) in the region of the receiving opening (11, 25) is articulated on the connecting piece (8b, 8c). 8. Device according to one of the preceding claims, characterized in that the clamping element (18d) on the connecting piece (8d) can be placed. 9. Device according to one of the preceding claims, characterized in that the clamping gap (12) at one end of the connecting piece (8, 8a, 8c, 8d) is open. 10. Device according to one of the preceding claims, characterized in that the clamping gap (27) is closed at its the receiving opening (25) remote end. 11. Device according to one of the preceding claims, characterized in that the receiving opening (11, 25) has at least one groove-like extension (13), in particular at one about the axis the receiving opening relative to the clamping gap (12) offset by 180 ° range. 12. Device according to one of the preceding claims, characterized in that the connecting piece (8, 8a, 8b, 8c, 8d) is strip-like and at the wiper shaft (1) fixed state with its longitudinal extent (L) transversely to the wiper shaft axis (WA ), in particular radially or approximately radially to the wiper shaft axis (WA) is oriented. 13. Device according to one of the preceding claims, characterized in that the connecting piece (8, 8a, 8b, 8c, 8d) at least in the region of the receiving opening (11, 25) of a deformable, in particular of an elastically deformable material, for example of plastic consists. 14. Device according to one of the preceding claims, characterized in that the clamping element (22) consists of metal or has a metal insert (24). 15. Device according to one of the preceding claims, characterized in that the clamping element (18, 18 b, 18 c, 18 d) is made of plastic. 16. Device according to one of the preceding claims, characterized in that the clamping element (18, 18a, 18b, 18c, 18d, 22) by latching (21.1, 23.1) on the connecting piece (8, 8a, 8b, 8c, 8d) is held , 17. Device according to one of the preceding claims, characterized in that the clamping element of a the connecting piece (8, 8a, 8b, 8c, 8d) at least partially covering cap (18, 18a, 18b, 18c, 18d) is formed or provided on such a cap. 18. The apparatus according to claim 16, characterized in that on inner surfaces of the cap (18, 18 b, 18 c, 18 d) clamping surfaces or protruding clamping jaws (21, 29) are provided, for clamping the connecting piece (8, 8 b, 8 c, 8 d) on the wiper shaft (1) abut against the connecting piece (8, 8b) on both sides of the clamping gap (12, 27). 19. Device according to one of the preceding claims, characterized in that the connecting piece (8, 8a, 8b, 8c, 8d) is part of a carrier or articulated part (3, 3a, 3b, 3c, 3d) for a wiper arm (5). 20. Device according to one of the preceding claims, characterized in that the connecting piece (8, 8a, 8b, 8c, 8d) is part of a wiper arm (5). 21. Device according to one of the preceding claims, characterized in that the connecting piece (8, 8a, 8b, 8c, 8d) is part of a carrier or articulated part (3, 3a, 3b, 3c, 3d) for a wiper blade. 22. Device according to one of the preceding claims, characterized in that the connecting piece (8, 8a, 8b, 8c, 8d) is part of a wiper blade.