GB1591785A - String instrument bridge construction - Google Patents

Description

(54) STRING INSTRUMENT BRIDGE CONSTRUCTION (71) We, JOHN FRANKLIN BERRY, of, 3392 St. Albans Drive, Los Alamitos, State of California, 90720, United States of America, and LESTER MITCHELL BAR CUS, of, 16226 Wayfarer Lane, Huntington Beach, State of California, 92649, United States of America, both citizens of the United States of America do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement: STRING INSTRUMENT BRIDGE CONSTRUCTION BACKGROUND OF THE INVENTION 1. Field of the Invention The invention is in the field of bridges for string musical instruments.

2. Description of the Prior Art The terms "sonic" and "sound" are used herein to mean the complete spectrum of compression wave frequencies including audio frequencies and frequencies above and below the audio range.

It is traditional for string instruments to have wooden bridges which are mounted on the face portion of the instrument and coupled to the strings by means of a saddle member made of ivory, bone or plastics material. The saddle member was utilized as a string contact member since it was harder than the wood and would consequently last longer under string tension.

As is quite apparent in inexpensive string instruments, such as inexpensive guitars, the decay of a note is not uniform, but rather has an undulating or decreasing and increasing sound pattern, which is sometimes referred to as "rollover". Rollover is thought to be associated with a feedback between the instrument body and the strings themselves via the bridge and saddle members.

In string instruments of excellent or outstanding quality, design improvements such as discretely formed and positioned wood bracings on the inside of the top plate of the instrument have the effect of reducing the rollover to some extent, thereby providing a somewhat more uniform sound decay. However, a significant random, uncontrolled, vib- ratory feedback from the body to the strings still exists, and an undulating sound decay is still present even in the best quality instruments.

The conventional string instrument bridge presents an unstable platform for the strings which tends to vibrate with the strings, thereby having a muting effect on the upper partial frequencies, so that the strings may only vibrate in the fundamental and first few harmonics. Thus, the desired full spectrum of overtone frequencies is never produced in the instrument, and the quality of musical sounds produced by the instruments is seriously limited. This also causes an undesirably large proportion of the sonic energy output of the instrument to be of relatively low frequency, with consequently generally poor carrying power.

The feedback of a flexural nature which occurs through the bridge of a guitar or other string involves an undesired phase modulation which causes a cancellation effect that is detrimental not only to the dynamic amplitude and frequency, but also to the timbre. Timbre is affected in at least two ways: "(1) the sine wave complement of the sound is distorted, and (2) the formant of the tone is altered periodically during the decay.

In U.S. Patent No. 3,951,031 of Lester M.

Barcus and John F. Berry, a novel string instrument bridge construction was disclosed which comprised an upper saddle member in contact with the strings and a lower decoupling member between the saddle and the resonant body of the instrument for damping gross flexural vibration transmissions in both directions between the strings and the resonant body, but effectively transmitting sonic compressional wave energy both from the strings to the body of transmission of musical sounds generated by the strings and from the body back to the strings to achieve the desired timbre of the instrument. This decoupling member was disclosed in said U.S.

Patent No. 3,951,031 as preferably being a massive continuous body comprising primarily lead, and it effectively cured the aforesaid problems, resulting in string instruments with the improved bridge construction typically having better overtone structure, greatly increased output volume, a projecting or carrying power almost twice that of an instrument with a conventional bridge, and the tones being sustained more uniformly for the different strings.

However, inasmuch as a primary function of the vibration decoupling mass disclosed in said UiS. Patent No. 3,951,031 was to serve as an efficient coupler of sonic compressional wave energy between the strings and the resonant body of the instrument in a region or channel (the bridge) where such energy is highly concentrated, it has heretofore been thought desirable for the saddle to be bonded into position between the walls of a mating groove in the decoupling mass so as to assure the full integrity of the sonic energy flow path from the strings to the resonant body.

Also, since another primary function of the lead decoupling mass was as a massive stable support platform for avoiding the usual dissipation of inuch of the sound energy generated by the strings into useless gross flexural vibrations in the instrument, it has previously been thought that bonding of the saddle into position in the mating groove to the lead mass would help to prevent the establishment of any such gross flexural vibrations in the region of the saddle, such as vibrations of the saddle relative to the lead mass.In this regard, it was considered that unless the saddle were bonded into the groove in the lead mass, some of the muting effect of the conventional vibratory wocden bridge on the upper partial frequencies might still be present to interfere with the production of the desired full spectrum of overtone frequencies and hence the desired full, rich timbre of the instrument which the lead mass was capable of producing.

Such bonding of the saddle in the groove of the decoupling member could be by compressional engagement between the walls of the groove, as by force-fitting of the saddle into the groove. Alternatively, the bonding could be by molding of the saddle member into position when the decoupling member was formed, or by the use of a suitable adhesive material such as a rigid epoxy.

However, bonding of the saddle member into the groove in the decoupling member has associated disadvantages for the individual instrument user, for the instrument repairman, and also for the instrument manufacturer.

Thus, bonding of the saddle member into position in the groove of the decoupling member will make it difficult and sometimes impossible to remove the saddle member from the decoupling member without seriously damaging either the saddle member or the decoupling member or both of them, yet there are a number of reasons why it is sometimes desirable for the individual user or the repairman to disengage the saddle member from the decoupling member. For example, it may be desired to install a saddle made of a different material, such as replacing a plastic saddle with a saddle made of real bone, to improve the timbre of the instrument. Replacement of the saddle may also be necessary because of wear. Thus, steel strings may wear grooves in a saddle, and this will ultimately adversely affect the performance of the instrument and make it desirable to replace the worn saddle.

Another problem which can arise in a string instrument which may require replacement of the saddle is that any slight warpage of the instrument structure can change the angle of the neck of the instrument relative to the body, which can result in a profound change in the height of the strings and consequently the performance of the instrument.

While it may not be feasible to attempt to cure the warp age, it can normally be adequately compensated for by replacing the saddle member with either a higher one or a lower one. Another thing which may make it desirable to change to a saddle member of a different height is where different gauge strings are installed on an instrument. For example, if light gauge strings are replaced with heavy gauge strings, the increased accumulation of tension would produce a discernible increase in the height of the strings in the middle portion of the fretboard, making it desirable to utilize a lower saddle member.

In general, the character of the sound will be different for all different types of saddle materials and for various saddle contours and heights, and it is therefore desirable to many instrument users and repairmen to be able to readily remove and modify or replace the saddle of a string instrument without the likelihocd of damaging either the saddle or the lead decoupling member.

With regard to the instrument manufacturer, a typical manufacturer will make a series of different models of an instrument such as a guitar having different saddle widths, heights and/or thicknesses, and different fretboard contours (either flat or arched) which require correspondingly different saddle contours, and if these saddles were to be required to be bonded into the grooves of the lead vibration decoupling members, then a variety of different decoupling members would be required ro be stamped or molded for the respective different saddle members.Thus, it would be advantageous for the manufacturer of such instrument to be able to use a single configuration of lead decoupling member for the various saddle configurations, and this can only be done if the saddles are not bonded between the walls of the decoupler slots, but are instead simply slip-fitted or slidably engaged into the slots.

SUMMARY OF THE INVENTION While the improved bridge construction with the lead decoupling member disclosed in said U.S. Patent No. 3,951,031 has indeed been found in practice to produce greatly improved performance for string instruments where the saddle member has been bonded into position in a mating groove in the decoupling member, the applicants have now determined that the improved performance characteristics provided by the presence of the lead decoupling component of the bridge structure remain essentially intact, and are possibly even further improved, without such bonding and with the saddle member simply slip-fitted or slidably engaged into a slot in the decoupling member; and that this engagement of the saddle member in the slot may be as loose as desired, provided that the engagement of the saddle member in the slot is such as to support the saddle member in a generally upright or normal position relative to the top plate of the instrument.

With this unbonded mounting of the saddle member in the slot of the lead vibration decoupling member, the physical connection and- hence the sonic energy flow path between the saddle member and the lead decoupling member is effected by compression of the lower edge of the saddle member against the bottom of the slot in the lead decoupling member caused by the sum of the string tension force components directed substantially normal to the top plate of the instrument.

There appears to be a unique cooperation between the saddle member and the lead mass under this compressional force produced by the tension of the strings which results in the production of an interface on a molecular level between the materials of the saddle and lead mass that is highly efficient for the transmission of sonic energy. The manner in which this novel sonic energy transmitting interface appears to be established will be discussed in greater detail hereinafter in the detailed description.

Thus, according to the present invention there is provided a bridge for a musical instrument having strings and a sound resonant body, said bridge comprising a lower decoupling member comprising primarily lead for damping flexural vibration transmissions between the strings and the resonant body, said decoupling member having a lower portion which, when said bridge is part of said musical instrument, is in contact with said resonant body and an upper portion with an upwardly opening slot therein, and an upper saddle member slidably engaged in said slot and over which, when said bridge is part of said musical instrument, said strings are tensionally engaged, such that in use said saddle member is compressed against the bottom of said slot by downwardly directed tension force components applied by said strings, the material of said decoupling member being softer and more malleable than the material of said saddle member, to the extent that said downwardly directed tension force causes said saddle member to intimately contact said lower decoupling member and causes the latter to closely conform to the former by local deformation of irregularities in the primarily lead material.

This unbonded mounting of the saddle member in the lead vibration decoupling member enables the saddle member to be easily laterally adjusted in the slot or removed for modification to a different configuration or for replacement by another saddle member of different material, configuration, height or the like. It also enables a manufacturer to utilize the same lead vibration decoupling member for- a variety of different models of an instrument which may have different saddle widths, heights and/or thicknesses, different fretboard contours that require different saddle contours, or the like.

In addition to these advantages in the handling, maintenance and manufacturing of string instruments, the present invention produces a bridge in which there is a novel interface between the saddle and its supporting component and which has unexpectedly good sonic energy transmission characteristics while at the same time appears to be an effective barrier against the transmission of gross flexural vibrations.

Other details, aspects and advantages of the present invention will be apparent from the following description taken in connection with the accompanying drawings, wherein: BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a guitar having a bridge construction embodying one form of the invention; Figure 2 is a partial plan view of the guitar bridge of Figure 1; Figure 3 is a cross-sectional view taken along the line 3-3 in Figure 2; Figure 4 is an enlarged cross-sectional view taken along the line 4-4 in Figure 3; Figure 5 is a partial plan view similar to Figure 2 but illustrating another form of the invention; Figure 6 is a cross-sectional view taken along the line 6-6 in Figure 5;; Figure 7 is a fragmentary cross-sectional view similar to Figure 6 but with a modified saddle member, Figure 8 is a partial plan view similar to Figures 2 and 5 illustrating still another form of the invention; Figure 9 is a cross-sectional view taken along the line 9-9 in Figure 8; and Figure 10 is a view similar to Figure 6 but illustrating a different saddle configuration.

DETAILED DESCRIPTION The present invention is illustrated in the accompanying drawings and will be described herein in connection with a guitar. Nevertheless, it is to be understood that the principles of the present invention are equally applicable to various other types of string instruments.

Referring to the drawings, and at first to Figures 1-4 thereof, one form of bridge 10 according to the invention is shown mounted on the top plate 12 of a guitar 14. Except for the bridge 10, the guitar 14 is of conventional design having a tuning head 16, neck 18 and sound resonant body section 20. Strings 22 are attached to the tuning head 16 and stretched over a saddle member 24 for connection to anchor pins 26.

The bridge 10 comprises a base portion or base member 28 which is usually made of wood, a vibration decoupling member 30, and the saddle member 24. The anchor pins 26 are secured to the base member 28 in the traditional fashion, and the base member 28 is secured to the top plate 12 of the guitar by means of adhesive.

In practice, the entire base member 28 may be of conventional design, and a cutout 32 cut into the base member 28 so that the vibration decoupling member 30 may be inserted therein. The vibration decoupling member 30 is held in contact with the top plate 12 of the guitar 14 by means of string tension force components directed substantially normal to the top plate 12, and may if desired be secured in position on top plate 12 by adhesive or other mechanical fastening means. The vibration decoupling member 30 is preferably of bridge-like construction, having feet 34 proximate its ends 36 which contact the top plate 12, and having an intermediate web portion 38 spaced from top plate 12 as seen in Figure 3.The vibration decoupling member 30 has a top surface 40 which is flat along most of the length of the decoupling member 30, but which may curve downwardly somewhat proximate the ends 36 for aesthetic reasons.

A straight slot or groove 42 is provided in the top of the vibration decoupling member 30, opening at the top surface 40. The slot or groove 42 in Figures 1-4 extends the entire length of the vibration decoupling member 30 between its ends 36. Slot or groove 42 has a bottom wall 44 which is preferably flat and oriented parallel to the top plate 12 of guitar 14, and has side walls 46 that are parallel to each other and oriented at right angles or normal to the bottom wall 44 and top plate 12.

The saddle member 24 also preferably has a straight, flat bottom edge and a pair of parallel sides that are at right angles or normal to such bottom edge, and the width of the slot or groove 42 relative to the thickness of saddle member 24 is such that the saddle member 24 is easily slidably engageable or slip-fitted into the slot or groove 42, and conversely is easily slidably disengageable from the slot or groove 42. This will enable the saddle member 24 to be easily removed from the slot 42 for adjustment, repair or replacement. Also the slot 42 is made longer than the saddle member 24, so that the saddle member 24 may easily be laterally adjusted in the slot 42.If desired, some clearance may be provided between the sides of the saddle member 24 and the side walls 46 of the slot 42 as indicated in Figure 4; or if desired the sides of the saddle member may fit snuggly against the side walls 46 of the slot or groove 42. The only limitation on the amount of clearance between the sides of the saddle member 24 and the side walls 46 of the slot or groove 42 is the requirement that the saddle member 24 be supported in a generally upright position in the slot or groove 42.

The vibration decoupling member 30 is primarily made of lead or an alloy consisting primarily of lead, as lead provides a low impedance path for direct compressional energy transfer while at the same time is of poor resiliency and high density so as to damp the transfer in both directions of flexural vibrations between the strings and the top plate of the instrument. The lead provides a low impedance sonic compressional energy wave path and a high impedance flexural vibration energy path. The exact composition of the lead vibration decoupling member 30 is not critical, and various lead alloys may be used.

The high density of the lead vibration decoupling member 30 enables it to be compact, fitting generally within the confines of the base member 28 of conventional dimensions, while nevertheless having the inertial mass to provide the desired stable support platform for the strings. Although. the exact mass of the lead vibration decoupling member 30 is not critical, a lead vibration decoupling member 30 of approximately six ounces has been found to be satisfactory.

The saddle member 24 must be made of a material of sufficient hardness and strength to withstand the forces of the strings and to provide a rigid support for the strings at their contact points. Also, it is of particular importance in establishing the desired sonic compressional energy transmitting interface between the saddle member 24 and the vibra tion decoupling member 30 that the materials of the vibration decoupling member 30 and the saddle member 24 have relative physical characteristics such that when brought into compressive engagement with one another the material of the vibration decoupling member will yield more readily than the material of the saddle member.Thus, the material of the vibratlon decoupling member must be 1) softer and 2) more malleable, and, optionally, 3) more formable under pressure, and/or 4) more flowable under pressure, than the material of the saddle member 24. Conventional saddle member materials such as bone, ivory and hard plastics may be employed for the saddle member 24 provided that any lead alloy that is used for the vibration decoupling member 30 has at least the first and second of the aforesaid physical characteristics relative to the material of the saddle member 24. It has been found that alloys of lead with up to about 5 percent antimony added to improve the workability of the lead are softer, more malleable, more formable under pressure and more flowable under pressure than such conventional saddle materials.

Although the bottom edge of the saddle member and the bottom wall 44 of the slot or groove 42 are both flat, there are inevitable irregularities in both of these surfaces on a microscopic or particularly a molecular level, so that when these surfaces are brought into engagement against each other the random high and low points along these surfaces will result in a series of point or area-limited contacts.Because of the aforesaid relation ship between the physical characteristics of the materials of the vibration decoupling member 30 and the saddle member 24, the combined tension force components of the strings 22 compressing the saddle member 24 down into the slot or groove 42 cause the lead at the bottom wall 44 of slot or groove 42 to move or give way, forming or flowing so as to in effect iron out many of the relative irregularities between the bottom of the saddle member 24 and the bottom wall 44 on a molecular level. Thus, compression of the saddle member against the vibration decoupling member causes the material of the vibration decoupling member to yield or move into improved interface conformity with the material of the saddle member.This ro- duces an interface between the material of the saddle member 24 and the lead of the vibration decoupling member 30 wherein at least portions of the opposing surfaces are so closely mated on a molecular level as to provide a highly efficient transmission path for the flow of sonic compressional wave energy. This sonic compressional energy flow path between the saddle member 24 and the vibration decoupling member 30 appears to be at least as good as, and possibly even better than, the sonic energy flow path would be if the saddle member were bonded into position in the groove in the vibration decoupling member.The flowability and the amorphous nature of the lead enable this interface of the present invention to be considerably more efficient as a sonic energy transmitter than the conventional saddle-to . wood interface of the usual string instrument bridge wherein the cellular character of the wood tends to defeat the desired close molecular mating between the opposed surfaces.

There does not appear to be any diminishing of the flexural vibration decoupling effectiveness of the lead decoupling member 30 in the bridge of the present -invention. To the contrary, it appears that avoidance of a bonded mechanical connection between the saddle member and the lead decoupling member results in even further decoupling of the strings from the body of the instrument respecting flexural vibrations.

Figures 5--10 illustrate several variations which may be made in the saddle member and vibration decoupling member as des cribed hereinabove in detail in connection with Figures 14.

In Figures 5 and 6, the bridge 10a is the same as the bridge 10 of Figures 1--4, ex cept that the slot or groove 42a in the vibra tion decoupling member 30a does not extend all of the way to the ends 36a of vibration decoupling member 30a, but instead is closed at slot ends 48. Nevertheless, the slot or groove 42a is materially longer than the saddle mem ber 24a that is slidably engaged therein, to afford lateral adjustability of the saddle mem ber 24a.

Figure 7 illustrates a bridge 10b which is the same as the bridge 10a of Figures 5 and 6 .except for a modification of the saddle member 24b comprising an undercut notch 50 in either one or both ends of the saddle member 24b adjacent the bottom edge of saddle member 24 for engagement of a suit able lifting tool such as a small screwdriver or the like into the notch 50 to facilitate lifting of the saddle member 24b out of the slot or groove 42b in the vibration decoupling member 30b.

Figures 8 and 9 illustrate a further arrange ment of a vibration decoupling member and associated saddle member in a bridge of the present invention. In this embodiment the bridge 10c includes a vibration decoupling member 30c which is slightly shorter than the corresponding vibration decoupling mem ber 30 of Figures 1H, but which neverthe less has a slot or groove 42c which is open ended at the ends 36c of vibration decoupling member 30c. The saddle member 24c is made longer than the slot or groove 42c so as to extend beyond both ends 36c of the vibra tion decoupling member 30c.To facilitate lifting of the saddle member 24c out of the slot or groove 42c, the level of the bottom of slot or groove 42c may be placed higher than the upper surface of the base member 28c as seen in Figure 9 for insertion of a suitable lifting tool such as a screwdriver, knife or the like under either or both ends of the saddle member 24c.

Figure 10 illustrates a bridge 10d which is identical in all respects to the bridge 10 of Figures 1-4 except that an arched saddle member 24d is slidably engaged in the slot or groove 42d of vibration decoupling member 30d for compatibility with a correspondingly arched fretboard (not shown).

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in the form and details may be made therein without departing from the scope of the invention defined by the appended claims.

WHAT WE CLAIM IS: - 1. A bridge for a musical instrument having strings and a sound resonant body, said bridge comprising a lower decoupling member comprising primarily lead for damping flexural vibration transmissions between the strings and the resonant body, said decoupling member having a lower portion which, when said bridge is part of said musical instrument, is in contact with said resonant body and an upper portion with an upwardly opening slot therein, and an upper saddle member slidably engaged in said slot and over which, when said bridge is part of said musical instrument, said strings are tensionally engaged, such that in use said saddle member is compressed against the bottom of said slot by downwardly directed tension force components applied by said strings, the material of said decoupling member being softer and more malleable than the material of said saddle member, to the extent that said downwardly directed tension force causes said saddle member to intimately contact said lower decoupling member and causes the latter to closely conform to the former by local deformation of irregularities in the primarily lead material.

2. A bridge as claimed in claim 1, wherein said slot is open-ended.

3. A bridge as claimed in claim 2, wherein said slot is longer than said saddle member.

4. A bridge as claimed in claim 2, wherein said saddle member is longer than said slot.

5. A bridge as claimed in claim 4, wherein at least one end of said saddle member extends beyond the corresponding end of said decoupling member and, when said bridge is part of said musical instrument, is spaced above that portion of the instrument which is located adjacent said end of the decoupling member.

6. A bridge as claimed in claim 1, wherein said slot is closed-ended.

7. A bridge as claimed in claim 6, wherein said slot is longer than said saddle member.

8. A bridge as claimed in claim 1, wherein said slot is longer than said saddle member, and said saddle member has a notch in at least one of its ends proximate its bottom edge.

9. A bridge as claimed in claim 1, wherein said slot has a pair of opposed side walls, and there is clearance between at least one of said opposed side walls and the corresponding side of said saddle member.

10. A bridge as claimed in claim 1, wherein said slot has a pair of opposed side walls, and there is a snug fit of the opposite sides of said saddle member against the respective said side walls of the slot.

11. A bridge substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 4, Figures 5 and 6, Figure 7, Figures 8 and 9, or Figure 10.

12. A musical instrument having strings, a sound resonant body, and a bridge as claimed in any one of the preceding claims.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (12)

**WARNING** start of CLMS field may overlap end of DESC **. of slot or groove 42c may be placed higher than the upper surface of the base member 28c as seen in Figure 9 for insertion of a suitable lifting tool such as a screwdriver, knife or the like under either or both ends of the saddle member 24c. Figure 10 illustrates a bridge 10d which is identical in all respects to the bridge 10 of Figures 1-4 except that an arched saddle member 24d is slidably engaged in the slot or groove 42d of vibration decoupling member 30d for compatibility with a correspondingly arched fretboard (not shown). While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in the form and details may be made therein without departing from the scope of the invention defined by the appended claims. WHAT WE CLAIM IS: -

1. A bridge for a musical instrument having strings and a sound resonant body, said bridge comprising a lower decoupling member comprising primarily lead for damping flexural vibration transmissions between the strings and the resonant body, said decoupling member having a lower portion which, when said bridge is part of said musical instrument, is in contact with said resonant body and an upper portion with an upwardly opening slot therein, and an upper saddle member slidably engaged in said slot and over which, when said bridge is part of said musical instrument, said strings are tensionally engaged, such that in use said saddle member is compressed against the bottom of said slot by downwardly directed tension force components applied by said strings, the material of said decoupling member being softer and more malleable than the material of said saddle member, to the extent that said downwardly directed tension force causes said saddle member to intimately contact said lower decoupling member and causes the latter to closely conform to the former by local deformation of irregularities in the primarily lead material.

2. A bridge as claimed in claim 1, wherein said slot is open-ended.

3. A bridge as claimed in claim 2, wherein said slot is longer than said saddle member.

4. A bridge as claimed in claim 2, wherein said saddle member is longer than said slot.

5. A bridge as claimed in claim 4, wherein at least one end of said saddle member extends beyond the corresponding end of said decoupling member and, when said bridge is part of said musical instrument, is spaced above that portion of the instrument which is located adjacent said end of the decoupling member.

6. A bridge as claimed in claim 1, wherein said slot is closed-ended.

7. A bridge as claimed in claim 6, wherein said slot is longer than said saddle member.

8. A bridge as claimed in claim 1, wherein said slot is longer than said saddle member, and said saddle member has a notch in at least one of its ends proximate its bottom edge.

9. A bridge as claimed in claim 1, wherein said slot has a pair of opposed side walls, and there is clearance between at least one of said opposed side walls and the corresponding side of said saddle member.

10. A bridge as claimed in claim 1, wherein said slot has a pair of opposed side walls, and there is a snug fit of the opposite sides of said saddle member against the respective said side walls of the slot.

11. A bridge substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 4, Figures 5 and 6, Figure 7, Figures 8 and 9, or Figure 10.

12. A musical instrument having strings, a sound resonant body, and a bridge as claimed in any one of the preceding claims.