A stitch pitch adjusting mechanism and a sewing machine

Abstract

The present application provides a stitch pitch adjusting mechanism and a sewing machine, specifically relating to the technical field of sewing machine manufacturing. It has a sliding member, a stitch pitch groove, and a feed driving source. The feed driving source indirectly drives the sliding member inside the stitch pitch groove in a reciprocating rotation manner to adjust the stitch pitch. The stitch pitch adjusting mechanism also has a follower plate, a fixed limit plate, a connecting shaft, a plug rod, an outer rotating plate, and an inner sliding plate. The sliding member is inside the stitch pitch groove. The outer rotating plate drives the inner sliding plate and its sliding member. The sliding member makes the inner sliding plate move up and down inside the inner sliding plate under the reciprocating swing operation in the stitch pitch groove. The inner sliding plate drives the connecting shaft, and the connecting shaft then drives the follower plate and the plug rod, causing the tooth carrier and the feed dog to change the original stitch pitch to form a new stitch pitch. The stitch pitch adjusting mechanism of the present application can achieve the adjustment of multiple stitch pitches with one driving source, without the need to replace parts such as the stitch pitch groove, and has high application and promotion value.

Description

Technical Field

[0001] The present application provides a stitch pitch adjusting mechanism and a sewing machine, specifically relating to the technical field of sewing machine manufacturing. Background Art

[0002] The company previously proposed an invention patent for a driving device for thread trimming, presser foot lifting and lowering, and stitch pitch adjustment in a sewing machine. The content of the solution is as follows: When the driving device is in specific use, the motor rotates according to the setting, and the thread trimming crank and the presser foot cam rotate synchronously with the motor shaft and complete corresponding actions. When it is necessary to adjust the stitch pitch, when the motor shaft rotates until the convex head on the presser foot cam abuts against the swinging working surface, the presser foot cam exerts a force on the swinging working surface through the convex head, thereby pushing the transmission member to swing. The transmission member drives the swinging seat to swing through a connecting rod to adjust the stitch pitch. Different positions of the convex head on the swinging working surface mean different stitch pitch values, and the setting of the two swinging working surfaces enables this driving device to adjust the positive or negative stitch pitch as required. When the stitch pitch is a positive number, forward sewing can be achieved, and when the stitch pitch is a negative number, reverse sewing can be achieved. During the process of adjusting the stitch pitch when the convex head moves along the swinging working surface, the cooperation head is separated from the thread trimming working surface so that the thread trimming mechanism remains stationary, and the presser foot idle stroke surface abuts against the swing rod so that the presser foot mechanism remains stationary. The above solution realizes the adjustment of the stitch pitch by the rotation of the motor shaft depending on the change of the convex head position. However, when the sewing machine needs to change the stitch pitch, it is necessary to replace the presser foot cam and the convex head. A sewing machine often only uses the stitch pitch set at the factory, which cannot meet the sewing needs of the increasing variety of sewing products. Summary of the Invention

[0003] In view of the problem of increased manufacturing cost existing in the above-mentioned sewing machine, the present application particularly provides a stitch pitch adjusting mechanism, which is characterized by having a sliding member, a stitch pitch groove, and a feed driving source. The feed driving source indirectly drives the sliding member inside the stitch pitch groove in a reciprocating rotation manner to adjust the stitch pitch.

[0004] Preferably, the stitch pitch adjusting mechanism further has a follower plate, a fixed limiting plate, a connecting shaft, a plug rod, an outer rotating plate, and an inner sliding plate. The sliding member is inside the stitch pitch groove. The outer rotating plate drives the inner sliding plate and its sliding member. The sliding member makes the inner sliding plate move up and down inside the inner sliding plate under the reciprocating swing operation of the stitch pitch groove. The inner sliding plate drives the connecting shaft, and the connecting shaft drives the follower plate and the plug rod, so that the tooth frame and the feed dog change the original stitch pitch to form a new stitch pitch.

[0005] Preferably, the feed driving source drives the outer rotating plate in a reciprocating rotation manner.

[0006] Preferably, the center position of the stitch pitch groove is the zero point, and the zero point is the zero stitch pitch position of the sewing machine. The stitch pitch adjustment of the feed driving source starts and ends at the zero point position.

[0007] Preferably, the cloth feeding drive source has a starting position and an ending position, and the zero point corresponds to the operating position where the cloth feeding drive source operates for stitch pitch adjustment, which is both the starting position and the ending position.

[0008] Preferably, the angles at which the cloth feeding drive source rotates to both sides at the zero point determine the size of the stitch pitch. The larger the angle of reciprocating rotation of the cloth feeding drive source, the larger the stitch pitch; the smaller the angle of reciprocating rotation of the cloth feeding drive source, the smaller the stitch pitch. When the angle of reciprocating rotation of the cloth feeding drive source is zero degree, it is the zero stitch pitch of the sewing machine.

[0009] Preferably, the cross-section of the stitch pitch groove is arc-shaped.

[0010] Preferably, the cross-section of the stitch pitch groove is flat-angled / or wavy.

[0011] A sewing machine of the present application has a control system for controlling the sewing machine, and the control system executes and realizes the above-mentioned stitch pitch adjustment.

[0012] Compared with the prior art, the brand-new stitch pitch adjustment mechanism of the sewing machine of the present application utilizes a sliding member, a stitch pitch groove and a cloth feeding drive source. The cloth feeding drive source indirectly drives the sliding member located inside the stitch pitch groove in a reciprocating rotation manner to perform stitch pitch adjustment. The sliding member is located inside the stitch pitch groove under the drive of the cloth feeding drive source. The outer rotating plate drives the inner sliding plate and its sliding member. The sliding member makes the inner sliding plate move up and down inside the inner sliding plate under the reciprocating swing operation of the stitch pitch groove. The inner sliding plate drives the connecting shaft, and the connecting shaft drives the follower plate and the inserting rod, causing the tooth carrier and the feed dog to change the original stitch pitch to form a new stitch pitch. The stitch pitch adjustment mechanism of the present application can realize the adjustment of multiple stitch pitches by using one drive source, without the need to replace parts such as the stitch pitch groove, effectively improving the intelligent control level of the sewing machine and having high application and promotion value. Description of the Drawings

[0013] Figure 1 It is a schematic diagram of the installation position of the stitch pitch adjustment mechanism and the cloth feeding mechanism of a sewing machine of the present application;

[0014] Figure 2 It is the structure of the stitch pitch adjustment mechanism and the cloth feeding mechanism, thread cutting mechanism and presser foot lifting mechanism of a sewing machine of the present application;

[0015] Figure 3 It is a schematic diagram of the stitch pitch adjustment mechanism and the cloth feeding mechanism of a sewing machine of the present application;

[0016] Figure 4 It is a schematic diagram of the up-and-down transfer assembly and the front-and-back transfer mechanism of the cloth feeding mechanism of the stitch pitch adjustment mechanism and the sewing machine of the present application;

[0017] Figure 5 It is a structural diagram of the tooth carrier of the stitch pitch adjustment mechanism and the sewing machine of the present application;

[0018] Figure 6 This is a structural diagram of a stitch length adjustment mechanism and a static stitch length and positioning adjustment wheel of a sewing machine;

[0019] Figure 7 This is a schematic diagram of a stitch length adjustment mechanism and a motor operating angle of a sewing machine according to the present application;

[0020] Figure 8 This is a schematic diagram of a stitch length adjustment mechanism, a thread trimming mechanism and a presser foot lifting mechanism of a sewing machine.

[0021] Reference numerals: cloth feeding mechanism 10, cloth feeding drive source 11, tooth lifting drive source 12, limit baffle 121, limit baffle 2 122, connecting rod 123, tooth rack 13, bobbin core clearance cavity 131, slide groove 132, positioning groove 133, cloth feeding dog 14, front and rear cloth feeding swing assembly 15, follower plate 151, fixed limit plate 152, limit portion 1521, sliding member 153, outer rotating plate 154, inner sliding plate 155, connecting shaft 156 , insert rod 157, thread trimming mechanism 20, thread trimming fork wheel 21, return rod 211, thread trimming rod 212, thread trimming eccentric wheel 22, action rod 221, thread trimming connecting rod 23, thread trimming end execution end 24, presser foot lifting mechanism 30, presser foot lifting cam 31, presser foot lifting lever 32, static adjustment bracket 41, running slot 411, stitch length slot 412, zero point 4121, transition slot 1 413, transition slot 2 414, thread trimming slot 415, presser foot lifting slot 416. DETAILED DESCRIPTION

[0022] The following is combined with Figure 1-8 The preferred embodiments of the present application are described in detail so that the advantages and features of the present application can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present application. These embodiments are only used to illustrate the present invention and are not intended to limit the present invention.

[0023] Figure 1 This is an overall structural diagram of a stitch length adjustment mechanism and a sewing machine of the present application. The sewing machine includes a cloth feeding mechanism 10, a thread trimming mechanism 20, a presser foot lifting mechanism 30 and a control system. The cloth feeding mechanism 10, the thread trimming mechanism 20 and the presser foot lifting mechanism 30 are provided with a cloth feeding drive source 11 and a tooth lifting drive source 12. The cloth feeding mechanism 10, the thread trimming mechanism 20 and the presser foot lifting mechanism 30 are driven by the cloth feeding drive source 11 and the tooth lifting drive source 12. The specific division of labor is that the cloth feeding drive source 11 and the tooth lifting drive source 12 simultaneously drive the cloth feeding mechanism 10 to realize the cloth feeding action of the sewing machine feed dog 14; after the sewing machine stops feeding cloth and stops sewing, the cloth feeding drive source 11 executes the thread cutting action of the thread trimming mechanism 20 and the presser foot lifting action of the presser foot lifting mechanism 30 at different times. The sewing machine of the present application fully utilizes the power device of the sewing machine and has a high energy utilization rate.

[0024] exist Figures 1 to 7 In the present application, the cloth feeding mechanism 10 of the sewing machine includes a tooth frame 13, a feed dog 14 fixed to the tooth frame 13, a front and rear cloth feeding swing assembly 15, a cloth feeding drive source 11 and a tooth lifting drive source 12. The cloth feeding drive source 11 indirectly drives the tooth frame 13; while the cloth feeding drive source 11 indirectly drives the tooth frame 13, the tooth lifting drive source 12 directly drives the same tooth frame 13 to produce a swinging motion, thereby causing the cloth feeding dog 14 connected to the tooth frame 13 to produce the cloth feeding action of the sewing machine, and the above-mentioned cloth feeding drive source 11 and tooth lifting drive source 12 both realize power output by rotating operation. The reciprocating operation of the above-mentioned cloth feeding drive source 11 and tooth lifting drive source 12 is based on the preferred use of a stepping motor or a servo motor, and can thus efficiently realize the control of the sewing action under the control of the control system. The sewing machine of the present application breaks the design concept of the traditional sewing machine, removes the original swing seat device, and directly uses a motor to drive the tooth frame 13 and its feed dog 14 to achieve the sewing action. The logic of the present application is refined in structure, and the sewing action of the feed dog 14 is completely controlled by the programming of the control system, which has high technical and promotion value.

[0025] The feed dog 14 is fixed to the upper portion of the tooth frame 13. A bobbin clearance cavity 131 is defined in the middle of the tooth frame 13, and a chute 132 is provided on each side of the tooth frame 13. The bobbin clearance cavity 131 is used to allow the rotary hook to be positioned during sewing. The chute 132 on either side of the tooth frame 13 is connected to a first limit stopper 121 and a second limit stopper 122, respectively. These two limit stops 121 and 122 are hingedly connected by a connecting rod 123. The tooth lifting drive source 12 is mounted on the static adjustment bracket 41. The front output shaft of the tooth lifting drive source 12 passes through the static adjustment bracket 41 and is fixedly connected to the limit baffle 1 121. The drive source 12 transmits the drive to the limit baffle 1 121 to rotate back and forth. The limit baffle 2 122 under the dynamic connection of the connecting rod 123 also makes the same back and forth rotation as the limit baffle 1 121, causing the tooth frame 13 and even the feed dog 14 to move up and down. Therefore, the synchronous operation of the limit baffle 1 121 and the limit baffle 2 122 causes the tooth frame 13 and even the feed dog 14 to move up and down. The above-mentioned limit baffle 1 121 and the limit baffle 2 122 also have a limiting function. In this embodiment, the above-mentioned limit baffle 1 121 and the limit baffle 2 122 can also be used with bearings, or bushings, etc., and the technical effects they achieve are the same.

[0026] The tooth frame 13 also has a positioning groove 133. The positioning groove 133 is used to insert and cooperate with the aforementioned insertion rod 157 and transmit the swinging motion. That is, the feed drive source 11 is connected to the front and rear feed swinging assembly 15, and the rotational operation also drives the tooth frame 13 to perform a corresponding swinging motion. The role of the positioning groove 133 determines the function of the positioning groove 133 to generate the forward and backward movement of the tooth frame 13 and the feed dog 14. In this embodiment, the positioning groove 133 is located on the side of the second limit stopper 122 of the tooth frame 13. The specific location of the positioning groove 133 is sufficient to transmit the swinging motion.

[0027] The tooth carrier 13 and its feed dog 14, under the combined action of the tooth lifting drive source 12 and the cloth feeding drive source 11, enable the feed dog 14 to realize the cloth feeding function of the sewing machine. The aforementioned front and rear cloth feeding swing assembly 15 is a key component for the tooth lifting drive source 12 to realize the front and rear cloth feeding action. The following specific implementation is not limited here. Any device that performs the same function to enable the tooth carrier 13 to generate the front and rear cloth feeding action is within the scope of protection of this application.

[0028] The aforementioned front-to-back cloth feed oscillating assembly 15 specifically comprises a follower plate 151, a fixed stop plate 152, a sliding member 153, a connecting shaft 156, an insert rod 157, an outer rotating plate 154, an inner sliding plate 155, and a running slot 411 within the static adjustment bracket 41. The outer rotating plate 154 has an axial hole for fixedly connecting the cloth feed drive source 11. The inner sliding plate 155 fits within the outer rotating plate 154. One end of the inner sliding plate 155 is connected to the sliding member 153, and the other end is connected to the connecting shaft 156. An insert rod 157 is fixedly connected to the upper end of the follower plate 151, and the follower plate 151 is dynamically connected to the connecting shaft 156, with a bearing disposed therebetween. The other end of the insertion rod 157 cooperates with the positioning groove 133 of the tooth frame 13, and the fixed limit plate 152 is set between the tooth frame 13 and the follower plate 151. The insertion rod 157 passes through the limit part 1521 of the fixed limit plate 152. The limit part 1521 is used to limit the operating range of the insertion rod 157 when it operates.

[0029] Figure 7It is a schematic diagram of the motor running angle of the feeding mechanism of a sewing machine in this application, combined with the above-mentioned drawings. The above-mentioned sliding member 153 is configured and operates in the running groove 411 of the static adjusting bracket 41. The running groove 411 is a closed-loop groove for the sliding member 153 to run around. The running groove 411 has a stitch pitch groove 412, a transition groove 413, a transition groove 414, a thread trimming groove 415, and a presser foot lifting groove 416. The stitch pitch groove 412 is located between the transition groove 413 and the transition groove 414. The stitch pitch groove 412 is opposite to the thread trimming groove 415 and the presser foot lifting groove 416. The stitch pitch groove 412 has the function of stitch pitch adjustment. In addition to their own functions of thread trimming and presser foot lifting, the thread trimming groove 415 and the presser foot lifting groove 416 also have the function of positioning the zero position, that is, the function of positioning the zero stitch pitch of the feed dog 14. The stitch pitch groove 412, the thread trimming groove 415, and the presser foot lifting groove 416 are all arc-shaped. The stitch pitch groove 412, the thread trimming groove 415, and the presser foot lifting groove 416 are arranged on the same center of the circle. An axial hole fixed to the feed driving source 11 is provided at this center of the circle.

[0030] The above-mentioned feeding mechanism 10 also has a stitch pitch adjustment mechanism. The stitch pitch adjustment mechanism is composed of a follower plate 151, a fixed limit plate 152, a sliding member 153, a connecting shaft 156, a plug rod 157, an outer rotating plate 154, an inner sliding plate 155, as well as the stitch pitch groove 412 and the feed driving source 11. The sliding member 153 is located inside the above-mentioned arc-shaped stitch pitch groove 412. The feed driving source 11 indirectly drives the sliding member 153 inside the stitch pitch groove 412 to perform stitch pitch adjustment in a rotary manner. Specifically, the feed driving source 11 drives the outer rotating plate 154 in a rotary manner, and the outer rotating plate 154 drives the inner sliding plate 155 and its sliding member 153, so that the sliding member 153 is driven passively in the arc-shaped stitch pitch groove 412. When the sliding member 153 swings back and forth in the stitch pitch groove 412, it causes the inner sliding plate 155 to move up and down inside the inner sliding plate 155. Then the inner sliding plate 155 drives the connecting shaft 156, and the connecting shaft 156 drives the follower plate 151 and the plug rod 157, so that the tooth carrier 13 and the feed dog 14 change the original stitch pitch to form a new stitch pitch.

[0031] The center position of the cross-section of the above stitch pitch groove 412 is the zero point 4121, and the zero point 4121 is the zero stitch pitch position of the sewing machine. The feed driving source 11 performs stitch pitch adjustment by driving the stitch pitch groove 412 in a reciprocating rotation. The zero point 4121 corresponds to the operating position of the feed driving source 11 for performing stitch pitch adjustment, which is both the starting position and the ending position. The process of stitch pitch adjustment is that the feed driving source 11 has a starting position and an ending position, and the feed driving source 11 starts and ends at the starting position. In other words, the stitch pitch adjustment of the feed driving source 11 starts and ends at the zero point 4121 position; the angle at which the feed driving source 11 rotates to both sides from the zero point 4121 determines the size of the stitch pitch. The larger the reciprocating rotation angle implemented by the feed driving source 11, the larger the stitch pitch; the smaller the reciprocating rotation angle, the smaller the stitch pitch. When the reciprocating rotation angle implemented by the feed driving source 11 is zero degree, it is the zero stitch pitch of the sewing machine. On this basis, the sewing machine can achieve different stitch pitch settings with different reciprocating rotation angles according to the settings of the control system, without the need for different stitch pitch grooves 412 for different stitch pitches as in the prior art, greatly improving the intelligent level of the stitch pitch adjustment of this sewing machine and having a high promotion and application value.

[0032] The cross-section of the above stitch pitch groove 412 is arc-shaped. In addition, the cross-section of the stitch pitch groove 412 in this embodiment can also be set to a flat angle or a wavy shape. The stitch pitch adjustment realized by the flat angle or wavy stitch pitch groove 412 under the reciprocating rotation drive of the feed driving source 11 has the same technical effect as that of the stitch pitch groove 412 with an arc surface. The above stitch pitch adjustment is realized under the execution of the stitch pitch adjustment command program by the control system of this application.

[0033] Figure 8 It is a schematic diagram of the thread cutting mechanism 20 and the presser foot lifting mechanism 30 of a sewing machine of this application. After the sewing machine finishes feeding the cloth and stops sewing, the sewing machine needs to perform thread cutting first and then the presser foot lifting action. The feed driving source 11 moves the sliding member 153 from the stitch pitch groove 412 through the transition two groove 414 into the thread cutting groove 415, so that the connecting shaft 156 is concentric with the front output shaft of the feed driving source 11. Therefore, when the sliding member 153 operates in the thread cutting groove 415 and the presser foot lifting groove 416, the feed driving source 11 will not apply an up-and-down movement action to the connecting shaft 156. In other words, the operation of the sliding member 153 in the thread cutting groove 415 and the presser foot lifting groove 416 will not have an actual impact on the tooth carrier 13.

[0034] When the cloth feeding drive source 11 drives the slider 153 past the thread cutting groove 415, the rear output shaft of the cloth feeding drive source 11 drives the relevant components of the thread cutting mechanism 20 to perform the thread cutting action. The thread cutting mechanism 20 includes a thread cutting fork wheel 21, a thread cutting eccentric wheel 22, a thread cutting connecting rod 23 and a thread cutting end actuator 24. The thread cutting fork wheel 21 has a thread cutting rod 212 and a return rod 211. The thread cutting fork wheel 21 is fixedly installed on the rear output shaft of the cloth feeding drive source 11. A working rod 221 is provided at the eccentric position of the thread cutting eccentric wheel 22. The thread cutting connecting rod 23 is hinged to the thread cutting rod 212. The working rod 221 is located between the thread cutting rod 212 and the return rod 211. When the thread cutting rod 212 is pushed by the cloth feeding drive source 11, the thread cutting end actuator 24 is driven by the thread cutting connecting rod 23 to perform the thread cutting action. After the thread cutting is completed, the cloth feeding drive source 11 drives the thread cutting rod 212 to continue to rotate until it acts on the return rod 211 to force the entire thread cutting mechanism 20 to return to its original position.

[0035] After the above-mentioned thread cutting action is completed, the slider 153 is driven by the cloth feeding drive source 11 to move towards the presser foot lifting groove 416 to perform the presser foot lifting action. The presser foot lifting mechanism 30 includes a presser foot lifting cam 31 and a presser foot lifting lever 32. The presser foot lifting cam 31 is on the rear output shaft of the cloth feeding drive source 11, and the above-mentioned presser foot lifting cam 31 is located behind the thread cutting eccentric wheel 22. The cam portion of the presser foot lifting cam 31 acts on the presser foot lifting lever 32, and a lever shaft is provided at the middle position of the presser foot lifting lever 32 so that the presser foot lifting action is performed under the action of the presser foot lifting cam 31.

[0036] The above is only one of the preferred embodiments of the present application, and it does not limit the scope of the patent implementation of the present application. Any equivalent structure or equivalent process transformation made by using the shape, structure and principle of the description and drawings of the present application, or directly or indirectly applied to other related technical fields, are all covered by the patent protection scope of the present application.

Claims

1. A stitch pitch adjusting mechanism, characterized in that, The stitch pitch adjusting mechanism has a follower plate (151), a fixed limit plate (152), a sliding member (153), a connecting shaft (156), a plug rod (157), an outer rotating plate (154), an inner sliding plate (155), a stitch pitch groove (412) and a feed driving source (11). The outer rotating plate (154) has a shaft hole for fixedly connecting the feed driving source (11). The outer rotating plate (154) drives the inner sliding plate (155) and its sliding member (153). The sliding member (153) is inside the stitch pitch groove (412). The sliding member (153) makes the inner sliding plate (155) move up and down inside the inner sliding plate (155) under the reciprocating swing operation in the stitch pitch groove (412). The inner sliding plate (155) drives the connecting shaft (156). The follower plate (151) is movably connected to the connecting shaft (156). A plug rod (157) is fixedly connected to the upper end of the follower plate (151). The other end of the plug rod (157) cooperates with the positioning groove (133) of the tooth carrier (13). A feed dog (14) is fixed to the upper part of the tooth carrier (13). The fixed limit plate (152) is arranged between the tooth carrier (13) and the follower plate (151). The plug rod (157) penetrates through the limiting portion (1521) of the fixed limit plate (152). The connecting shaft (156) drives the follower plate (151) and the plug rod (157). The plug rod (157) causes the tooth carrier (13) and the feed dog (14) to change the original stitch pitch to form a new stitch pitch. The central position of the stitch pitch groove (412) is the zero point (4121). The zero point (4121) is the zero stitch pitch position of the sewing machine. The stitch pitch adjustment of the feed driving source (11) starts and ends at the zero point (4121). The zero point (4121) corresponds to the operating position of the feed driving source (11) for performing stitch pitch adjustment, which is both the starting position and the ending position. The angle at which the feed driving source (11) rotates to both sides from the zero point (4121) determines the size of the stitch pitch.

2. The stitch pitch adjusting mechanism according to claim 1, characterized in that, The feed driving source (11) drives the outer rotating plate (154) in a reciprocating rotation manner.

3. The stitch pitch adjusting mechanism according to claim 1, wherein, The feed driving source (11) has a starting position and an ending position. The zero point (4121) corresponds to the operating position of the feed driving source (11) for performing stitch pitch adjustment, which is both the starting position and the ending position.

4. The stitch pitch adjusting mechanism according to claim 1, wherein, The larger the reciprocating rotation angle implemented by the feed driving source (11), the larger the stitch pitch. The smaller the reciprocating rotation angle implemented by the feed driving source (11), the smaller the stitch pitch. When the reciprocating rotation angle implemented by the feed driving source (11) is zero degree, it is the zero stitch pitch of the sewing machine.

5. The stitch pitch adjusting mechanism according to claim 1, wherein, The cross section of the stitch pitch groove (412) is arc-shaped.

6. The stitch pitch adjusting mechanism according to claim 1, wherein, The cross section of the stitch pitch groove (412) is flat-angled / or wavy.

7. A sewing machine having a control system for controlling the sewing machine, characterized in that, The control system executes and realizes the stitch pitch adjustment as described in any one of claims 1 to 6.

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