Tone arm pivot

Abstract

The tone arm (200a; 200b; 200c; 200d; 200e) includes an elongated member (8a; 8b; 8c; 8d; 8e), suspension means (4a, 5a; 4b, 5b; 4c, 5c; 4d, 5d; 4e, 5e), protrusions (1a; 1b; 1c; 1d; 1e) and contact surfaces (2a; 2b; 2c; 2d; 2e). The suspension means (4a, 5a; 4b, 5b; 4c, 5c; 4d, 5d; 4e, 5e) suspend the elongated member (8a; 8b; 8c; 8d; 8e) in a substantially horizontal position. The weight of the elongated member is substantially supported by the suspension means. The protrusions (1 a; 1 b; 1 c; 1 d; 1 e) are arranged in opposing contact with the contact surfaces at the contact points (206 a; 206 b; 206 c; 206 d; 206 e), and a drag force substantially parallel to the length of the elongated member acts to bring the contact surfaces (2 a; 2 b; 2 c; 2 d; 2 e) and the protrusions (1 a; 1 b; 1 c; 1 d; 1 e) into opposing contact, thereby generating a contact force that resists the drag force. By separating the means for supporting the weight of the elongated member from the means for resisting the drag force acting along the length of the elongated member, the drag force is resisted more effectively and the performance of the tonearm is improved.

Description

[Technical Field]

[0001] The present invention relates to a bearing for a tone arm of a gramophone, a gramophone turntable, or a record player. [Background technology]

[0002] A record, also known as a phonograph record or vinyl record, is an analog sound medium consisting of a flat disc with a modulated spiral groove. The groove channel typically has two side walls arranged perpendicular to each other, providing two channels for generating stereophonic sound. A turntable is a device that reads the signals encoded on the record and plays back the recorded sound.

[0003] The turntable includes a rotating platter on which a record can be placed, a tonearm that is movable relative to the rotating platter, and a cartridge attached to one end of the tonearm. The cartridge contains two coils, positioned perpendicular to the two walls of the record groove. A stylus, or cantilever, protrudes from the cartridge and contacts the record groove. The stylus contains two magnets, each positioned to move relative to its corresponding coil as a result of distortion or modulation of the groove walls. The relative motion of each magnet-coil pair generates a small voltage that can then be processed (including amplification) and supplied to a respective speaker to produce the sound encoded by the record.

[0004] The role of a turntable's tonearm is to allow the cartridge to be positioned correctly in relation to the record, and to maintain the cartridge's correct position when the record is played, facilitating audio pickup. It is accepted in the industry that the tonearm produces an audible signature within the generated audio signal, meaning that the tonearm affects the signal picked up from the record, and different tonearms can result in different sounds from the same record. For context, the 20kHz signal at the end of a typical LP record is imprinted on a scale of one full oscillation per hundredth of a millimeter. A precision tonearm needs to prevent the cartridge from moving along the groove below that scale.

[0005] There are many known pivot devices designed to allow the tonearm to move in a desired direction while preventing unwanted movement of the tonearm that would affect sound quality.

[0006] One known arrangement is to use a ball race or gimbal bearing. Such an arrangement requires several contact points to secure the tonearm to its base, preventing movement in the direction the stylus drags the record. However, these multiple contact points can "chatter," i.e., rattle on a microscopic scale when gaps develop between the bearing parts due to thermal expansion, wear, or tolerances, causing distortion in the generated audio signal. Such an arrangement also requires high-quality, tight-tolerance bearings to minimize this chatter, making it undesirable.

[0007] Another known device is the vertical "uni-pivot." Simply stated, such a device is essentially a cup balanced in an inverted (i.e., upside down) position on a sharp point or spike. The weight of the tonearm creates a downward force on the contact point, which in turn causes friction and resists tonearm movement as the tonearm is "dragged" by the record pulling the stylus. This friction between the spike and cup results in the sharp point becoming dull and more polished with use. This allows some freedom of movement in the direction of the stylus drag as the drag force oscillates. This can affect the audible signature of the tonearm.

[0008] A third known alternative is known as a "linear" tracker, whose base slides or glides along a support parallel to a line from the stylus to the center of the record. However, such a device requires "play" to move freely along the support, allowing the tonearm to move microscopically in the direction of the stylus drag. However, such a device requires free "play" along the support, allowing the tonearm to move slightly in the direction of the stylus' drag, again likely adding an undesirable audible signature to the signal.

[0009] It would be desirable to provide an improved tone arm arrangement that addresses some of the shortcomings of these known solutions. Summary of the Invention [Means for solving the problem]

[0010] From a first aspect, the present invention provides a tonearm comprising: A thin elongated member; suspension means for suspending the elongated member in a substantially horizontal position such that the weight of the elongated member is substantially supported; A protrusion; a contact surface; The protrusions are positioned to contact the contact surfaces at opposing contact points, and the action of a drag force substantially parallel to the length of the elongated member urges the contact surfaces and the protrusions into opposing contact, thereby generating a contact force that resists the drag force.

[0011] Thus, it can be seen that, according to the present invention, by separating the means for supporting the weight of the elongated member from the means for resisting drag forces acting along the length of the elongated member, drag forces can be more effectively resisted, thereby providing a tonearm with improved characteristics. Due to the improved resistance to drag forces, the tonearm of the present invention is capable of producing improved sound quality from a record compared to known tonearm arrangements. The improved quality takes the form of a reduced acoustic signature from the tonearm, resulting in a more accurate reproduction of the original sound defined by the record. The arrangement of the protrusions and contact surfaces ideally does not support any weight (or any substantial portion) of the elongated member, and therefore can be more optimally positioned to resist drag forces acting parallel to the length of the elongated member. Furthermore, only a single point of contact between the protrusions and contact surfaces is required to generate a contact force that resists the drag force. The presence of only a single point of contact makes the tonearm of the present invention less susceptible to chatter.

[0012] As explained below with reference to Figure 1, the movement of a record under a stylus attached to a tonearm applies a pulling force on the tonearm acting along a direction that is at an angle to the length of the tonearm. Thus, the "drag force" acting along the length of the elongated member is a component of the total drag force acting on the tonearm.

[0013] The component of all drag forces acting perpendicular to the length of the tonearm acts to pull the tonearm (and therefore the stylus) toward the center of the record, and is known as the skate force. An anti-skate force is typically applied to counter (or substantially counter) the skate force, and the resultant force (of all drag forces and anti-skate forces) is essentially the component of the drag force along the length of the tonearm. Because the perpendicular component of the drag force is balanced by the anti-skate force, references herein to the drag force acting on the tonearm should be considered to be the component of the drag force acting along the length of the tonearm, unless specified to the contrary.

[0014] It should be understood by those skilled in the art that the application of a drag force substantially parallel to the length of the elongate member "urges the contact surface and the protrusions into opposing contact," and does not exclude the contact surface and the protrusions from already being placed in contact prior to the application of such force; for example, the contact surface and the protrusions may be in contact before being "urged into contact," but need not be already in contact. Rather, the statement that they are "urged into contact" indicates that the force acts in a direction that causes the contact surface and the protrusions to move toward each other, rather than, for example, away from each other. In some examples, the protrusions and the contact surface may be placed in contact prior to the application of the drag force, such that the protrusions and the contact surface are urged by the drag force to maintain opposing contact and increase pressure between the contact surface and the protrusions at their contact points.

[0015] It will be appreciated that since the suspension means bears the weight of the elongate member, the protrusions together with the contact surfaces need only resist drag forces that are substantially parallel to the longitudinal axis of the elongate member, i.e. approximately horizontal, and therefore the contact force, i.e. the resultant force generated at the point of contact, may be substantially horizontal.

[0016] It will be understood that the contact force generated is the total resultant force at the point of contact. It will be understood that suspension means for suspending the elongate member refers to means that support the weight of the elongate member from a point that is at a height greater than the height of the point at which the suspension means is connected to the elongate member, i.e. supports the weight of the elongate member from a relatively higher vertical position, although not necessarily directly on the same vertical axis. The contact force generated resists movement of the tonearm in a direction in which a force parallel to the length of the elongate member (e.g. a drag force) pulls the tonearm.

[0017] In some embodiments, the contact surface is disposed substantially perpendicular to the longitudinal axis of the elongate member. Those skilled in the art will appreciate that "substantially perpendicular" does not require an angle of exactly 90 degrees, or even very close to 90 degrees. In accordance with the present disclosure, the contact surface need only be as perpendicular as necessary to allow the contact force generated at the contact point to resist the applied drag force, preferably without causing significant movement of the protrusion relative to the contact surface.

[0018] In some examples, the contact surface can be at an angle of at least 60 degrees, optionally at least 70 degrees, further optionally at least 80 degrees, and even optionally at least 85 degrees relative to the longitudinal axis of the elongate member. Relative angle refers to the angle of rotation about any axis perpendicular to the horizontal axis defined by the length of the elongate member.

[0019] By arranging the contact surface substantially perpendicular to the longitudinal axis of the elongate member, it is ensured that the contact surface is also substantially perpendicular to the direction of forces applied along this axis, so that an opposing contact force substantially parallel to this axis can be effectively countered by the contact surface as it is approximately perpendicular to the contact surface. In other words, the angle between the normal to the contact surface and the axis of maximum drag force is small enough to maintain sticking, which can be up to 30 degrees or more, depending on the nature of the contact point and the contact surface.

[0020] Furthermore, it will be understood by those skilled in the art that reference to a "contact surface" being "substantially perpendicular" to the longitudinal axis specifically refers to the portion of the contact surface at the point of contact. Outside of this particular region, the surfaces making up the contact surface may have any suitable shape, e.g., curved or beveled or flat. In some embodiments, the contact surface is substantially rigid, or, for example, non-flexible, and does not allow relative movement due to a force.

[0021] In some embodiments, the protrusions define a protrusion axis about which the protrusions are generally rotationally symmetric, where the protrusion axis is substantially parallel to the longitudinal axis of the elongate member. This reduces the need for the protrusions to present sharp points, since forces are applied directly along the axis of the protrusions. In some embodiments, the protrusions are substantially rigid, or, for example, non-deflectable, and do not allow relative movement due to forces.

[0022] In some embodiments, the protrusion is a conical protrusion.In some embodiments, the protrusion defines a point that forms a pivot point for the contact surface. In some embodiments, the contact surface is attached to the elongate member. Alternatively, in other embodiments, the protrusion is attached to the elongate member. It will be understood herein that examples of the term "attached" do not require a particular component to be directly attached to another component, but rather allow for the possibility of connection by other intermediate components. "Attached" requires some permanent or semi-permanent fixation of the components in contact, and does not describe the situation of mere adjacent contact.

[0023] In some embodiments, the tonearm comprises a substantially flat plate comprising the contact surface. Flat plates are very efficient to manufacture and very cost-effective. It will be appreciated that in other embodiments, the tonearm may comprise a cup, which in turn comprises the contact surface. For example, the inner, i.e., concave, surface of the cup may constitute the contact surface. In practice, the shape of the contact surface has little effect on the contact force, since outside the contact point itself, the protrusions do not slip during use. Therefore, the area outside the contact point is not critical. In some embodiments, the tonearm further comprises a support member for the contact surface, to which the contact surface is attached.

[0024] In some embodiments, the tonearm further includes a rigid connecting member, wherein the rigid connecting member is attached to the elongated member, and wherein the suspension means includes at least one suspension member connected to the rigid connecting member at a first connection point.

[0025] Those skilled in the art will appreciate that such rigid connecting members are not substantially bendable or flexible, e.g., incompressible. Such rigid connecting members advantageously provide a component suitable for connecting at least one suspension member, thereby suspending the weight of the elongate member.

[0026] In some implementations, the rigid connecting member extends vertically from the underside of the elongated member. Those skilled in the art will understand that the vertical direction is defined relative to the substantially horizontal direction of the elongated member. In some embodiments, the rigid connecting member provides a contact surface. In other embodiments, the rigid connecting member comprises a protrusion. This advantageously provides an arrangement where the point of contact (where contact force is generated) is below the level of the stylus (which is attached to the tip of the elongated member when the tonearm is in use).

[0027] Locating the contact point below the level of the stylus creates a horizontal drag force, a torque about a horizontal axis (pitch axis) passing through the contact point, which results in an increased downward force at the tip (or stylus end) of the elongate member, which helps to maintain contact between the record (when in use) and the stylus.

[0028] In some embodiments, the tonearm further includes a support member, wherein the at least one suspension member is connected to the support member. The support member can be connected to any suitable structure, for example, a base plate of a record player or a table, to provide a structure that allows the suspension means to support the weight of the elongated member. In some embodiments, the support member comprises a protrusion.

[0029] In some embodiments, the support member is a substantially vertically extending member. Optionally, the support member is positioned to pass through an opening in the elongated member, and at least one suspension member may be connected to the support member at a point above the elongated member. This provides a stable connection point above the elongated member and maintains compactness. Alternatively, at least one suspension member may be connected to the support member at a point below the elongated member.

[0030] This allows the support member to be positioned completely below the elongated member without taking up additional space and without obstructing the view of the elongated member. It will be appreciated that the shape of the support member can vary widely while still functioning to provide a suitable point for suspending the elongate member. In some embodiments, the support member may be a substantially L- or U-shaped member and include at least a first arm and a second arm attached approximately perpendicular to each other, where the first arm is disposed substantially vertically and where the second arm is disposed generally horizontally and extends above the elongate arm, and where a suspension member is attached to the second arm. The U-shaped member may further include a third arm disposed substantially vertically and attached at a right angle to the other end of the second arm (the end of the second arm not attached to the first arm).

[0031] In some embodiments, the first connection point (the point where at least one suspension member connects to the rigid connecting member) is offset along an axis parallel to the length of the elongate member relative to the suspension point where at least one suspension member connects to the support member, such that the first connection point is further toward the base end of the elongate member and the suspension points on the support member are closer to the distal end of the elongate member (e.g., the end where the stylus is attached) relative to each other. In some embodiments, the tone arm further includes an offset member that biases the rigid connecting member to create this offset. The protrusion acts to create this offset. The offset acts to bias the support member and the rigid connecting member, which in some examples brings the protrusion and the contact surface into opposing contact.

[0032] In other words, this configuration tilts the at least one suspension member slightly from vertical, i.e., pushes the rigid connecting member away from its equilibrium position where the suspension member hangs vertically downward, thereby pulling on the contact surface and protrusion as the at least one suspension member attempts to return to its equilibrium position. This force therefore acts to urge the contact surface and protrusion together, and contact (perhaps only light contact) is generally maintained even in the absence of a "drag" force acting parallel to the length of the elongate member.

[0033] In some embodiments, the protrusion and the contact surface are attracted to one another by magnetic force. In other words, there is a magnetic attraction between the protrusion and the contact surface (e.g., the pivot point and the thrust plate). This can be achieved by any suitable configuration. For example, both the contact surface and the protrusion can be made of a ferromagnetic material (e.g., iron, cobalt, nickel) (or made of a material including a ferromagnetic material, such as stainless steel), with at least one of them being a permanent magnet. Alternatively, the tonearm can further include at least one additional magnet attached to either the protrusion or the contact surface to generate a magnetic force. Additionally or alternatively, this can be used for the offset connection points described above, so that the contact points (perhaps only light contact points) are generally maintained even in the absence of a "drag force" acting parallel to the length of the elongated member.

[0034] In some embodiments, at least one suspension member is connected to a rigid connection member at a first connection point and a second connection point. The placement of the two spaced connection points (the first connection point and the second connection point) helps to limit "rolling" motion of the elongate member. For example, the ability of the elongate member to rotate about its longitudinal axis is undesirable. In some embodiments, the first connection point and the second connection point are at the same vertical height (at least when the rigid connecting member is in its standard operating position, which is the neutral position where there are no "rolling" forces acting to cause rotation of the elongate member and therefore no "rolling" forces acting on the rigid connecting member).

[0035] In some embodiments, the first and second connection points are each at approximately the same vertical height as the contact point, which advantageously creates a three-point horizontal line about which the elongate member can rotate (thus providing an axis for "pitch" rotation, e.g., the "up" and "down" motion created as a result of a stylus connected to the elongate member traveling over a camber in a record).

[0036] This prevents the protrusion from rubbing against the contact surface as the tip (cartridge end) of the tonearm moves up and down. The first and second connection points define the pitch axis about which the elongated member rotates during pitching. Therefore, when the contact point (between the protrusion and the contact surface) is also on this axis, the protrusion simply rotates on the pitch axis without inducing any friction.

[0037] In some embodiments, at least one suspension member comprises a flexible member. The at least one suspension member may be flexible along its entire length or only along a portion of its length. In some embodiments, the at least one suspension member may comprise at least one rigid portion and at least one flexible portion. The suspension member may comprise a first flexible portion at a first connection point, a second flexible portion at a second connection point, and a third flexible portion at a suspension point where the suspension member connects to the support member.

[0038] Alternatively, at least one suspension member may comprise a rigid frame structure connecting the frame structure to the support member and further comprising flexible mountings connecting to the first and second connection points. The presence of rigid portions within the suspension member helps to reduce the risk of resonance in the suspension member. The flexible portions at the first and second connection points allow pitching of the elongated member about a pitch axis passing through the first and second connection points (and preferably the pivot point).

[0039] A single suspension member can be used to support the elongate member at a single connection point. However, as discussed above, stability can be improved by using two suspension members at separate connection points on the elongate member (e.g., rigid connection members). Thus, in some embodiments, the at least one suspension member comprises two suspension members, where a first suspension member is connected to a first connection point of the rigid connection member, the first suspension point being a connection point of the support member, and a second suspension member is connected to a second connection point of the rigid connection member, the second suspension point being a connection point of the support member.

[0040] The first and second suspension points may be spaced apart by a small distance, but any such spacing introduces a small torque about the vertical axis (yaw axis) as the elongate member progresses across the record. Because such a torque is undesirable, in some embodiments the first and second suspension points are the same, i.e., both the first and second suspension members are attached to the same suspension point.

[0041] In other embodiments, at least one suspension member is a single suspension member having a first end and a second end, the first end connected to the first connection point and the second end connected to the second connection point, and the suspension member is fixedly connected to the support member at a point along the length of the suspension member between the first and second ends.

[0042] Additionally, the suspension member is connected to the support member at a point equidistant along the length of the suspension member between the first end and the second end of the suspension member. It may have a single suspension member connected to the support member at a single point, or it may have two separate suspension members, each connected to the same point on the support member, advantageously defining a pivot axis extending perpendicularly through the suspension point on the support member, about which the elongate member can easily rotate, thereby allowing the elongate member to rotate in a "yaw" direction without the application of external forces to impede this movement.

[0043] In some embodiments, the support member further comprises a small rotational joint or bearing at the first suspension point (or, if a second suspension point is provided, both suspension points may be provided on rotational joints or bearings). Such a joint or bearing may replace or supplement the suspension member at this point to avoid torque (i.e., prevent torque buildup as the elongated member rotates about the yaw axis as it advances across the record). In some such embodiments, the central axis of the joint or bearing passes directly through the contact point, thus maintaining the yaw axis. The rotational joint or bearing may, in some embodiments, include a ball race.

[0044] In some embodiments, the elongate member defines a proximal end and a distal end, and the tone arm further comprises: a cartridge connected to the tip and equipped with a record needle; and a counterweight coupled to the proximal end.

[0045] As mentioned above, in some embodiments, the rigid connecting member extends vertically from the underside of the elongate member and optionally includes a contact surface or protrusion. This advantageously provides a configuration in which the contact point is below the level of the stylus. By locating the contact point below the level of the stylus, the horizontal drag force generates a torque about a horizontal axis (pitch axis) through the contact point, thereby causing an increased downward force at the tip (or stylus end) of the elongate member, which helps maintain contact between the record and the stylus (when in use).

[0046] According to a second aspect, the present invention provides a method for producing a medicament for the treatment of a pulmonary arthritis, comprising: A base plate with a turntable for records, and a tone arm mounted on the base plate as described above. In some embodiments, the support member is attached to a turntable.

[0047] From a third aspect, the present invention provides a tonearm comprising: A thin elongated member; suspension means for suspending the elongated member in a substantially horizontal position; A protrusion; a contact surface; the protrusion is positioned opposite the contact surface at a contact point, and application of a force parallel to the length of the elongate member is resisted by a contact force generated between the contact surface and the protrusion; The contact force is substantially parallel to the longitudinal axis of the elongate member.

[0048] According to a fourth aspect, the present invention provides a bearing for a tonearm, the bearing having a point pointing horizontally and pressing against a vertical thrust plate surface, The thrust plate surface is generally perpendicular to the direction of record movement of the stylus or to a line from the stylus to the pivot point. The pivot point is attached to the turntable and the thrust plate is attached to the tone arm, or the pivot point is attached to the tone arm and the thrust plate is attached to the turntable. Since the horizontal pivot point has no vertical support, the tonearm is suspended by a tether from a point directly above the pivot point so as not to interfere with the correct movement of the pivot point.

[0049] According to a fifth aspect, the present invention provides a bearing for a tone arm, the bearing comprising: a pivot point attached to the turntable; a thrust plate attached to the tone arm, the thrust plate surface being approximately perpendicular (i.e., orthogonal) to a line from the tone arm stylus to a point on the thrust plate that contacts the pivot point; A suspension system that suspends the tone arm from a point directly above the pivot point and is attached to two points on the tone arm on either side of the pivot point, the two attachment points forming a straight line bisecting the pivot point or near the pivot point.

[0050] According to a sixth aspect, the present invention provides a bearing for a tone arm, the bearing comprising: A pivot point attached to the tone arm, a thrust plate attached to the turntable, the thrust plate surface being approximately perpendicular (i.e., orthogonal) to a line from the tone arm stylus to the point on the thrust plate that contacts the pivot point; A suspension system that suspends the tone arm from a point directly above the pivot point and is attached to two points on the tone arm on either side of the pivot point, the two attachment points forming a straight line bisecting the pivot point or near the pivot point.

[0051] According to a seventh aspect, the present invention provides a method of constructing a tonearm, the method comprising: positioning a suspension means for suspending the elongated member in a substantially horizontal position such that the weight of the elongated member is substantially supported by the suspension means; The method includes a step of arranging a protrusion so as to face and contact the contact surface at the contact point, and a drag force acting substantially parallel to the length of the elongated member to bring the contact surface and the protrusion into face-to-face contact, thereby generating a contact force that resists the drag force.

[0052] According to an eighth aspect, the present invention provides a method of constructing a phonograph turntable, the method comprising: attaching a suspension means to a base plate; positioning a suspension means for suspending the elongated member in a substantially horizontal position such that the weight of the elongated member is substantially supported by the suspension means; either attaching a protrusion relative to the base plate and attaching a contact surface relative to the elongated member, or attaching a contact surface relative to the base plate and attaching a protrusion relative to the elongated member; The method includes a step of arranging a protrusion so as to face and contact the contact surface at the contact point, and a drag force acting substantially parallel to the length of the elongated member to bring the contact surface and the protrusion into face-to-face contact, thereby generating a contact force that resists the drag force.

[0053] According to a ninth aspect, there is provided a method of modifying a record turntable, the record turntable comprising a base plate and an elongated member, the method comprising: attaching a suspension means to a base plate; positioning a suspension means for suspending the elongated member in a substantially horizontal position such that the weight of the elongated member is substantially supported by the suspension means; either attaching a protrusion relative to the base plate and attaching a contact surface relative to the elongated member, or attaching a contact surface relative to the base plate and attaching a protrusion relative to the elongated member; The method includes a step of arranging a protrusion to face and contact the contact surface at the contact point, and a drag force acting substantially parallel to the length of the elongated member to bring the contact surface and the protrusion into opposing contact, thereby generating a contact force that resists the drag force.

[0054] Features of any aspect or embodiment described herein may, where appropriate, be applied to any other aspect or embodiment described herein. When reference is made to different embodiments or sets of embodiments, it should be understood that there may be, although not necessarily explicitly, overlap. [Brief explanation of the drawings]

[0055] Certain preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 is a schematic diagram showing a perspective top view of a tonearm known in the art, illustrating the forces acting on the tonearm. [Figure 2]FIG. 1 is a schematic diagram showing a side view of a tonearm known in the art illustrating additional forces acting on the tonearm. [Figure 3] 1 is a side view of a tone arm according to a first embodiment of the present invention. [Figure 4] FIG. 4 is a perspective view showing a part of the tone arm of FIG. 3. [Figure 5] 5 shows the suspension member, rigid connecting member and protrusion of the tone arm of FIGS. 3 and 4. [Figure 6] FIG. 4 is a side view of a tone arm according to a second embodiment of the present invention. [Figure 7] FIG. 7 is a perspective view showing a part of the tone arm of FIG. 6. [Figure 8] FIG. 7 is another perspective view showing a portion of the tone arm of FIG. 6. [Figure 9] FIG. 10 is a side view of a tone arm according to a third embodiment of the present invention, showing the protrusions and contact surfaces. [Figure 10] 10 is a perspective view of a portion of a tone arm according to a fourth embodiment of the present invention, including a support member arrangement similar to that of the tone arm of FIG. 9; FIG. [Figure 11] FIG. 10 is a perspective view showing a part of a tone arm according to a fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0056] FIG. 1 shows a top perspective view of a tonearm 100 positioned above a record 102, as known in the art, illustrating the various forces acting on the tonearm 100. A first (base) end 104 of the tonearm 100 is connected to a turntable (not shown). A cartridge 106 is connected to a second (tip) end 108 of the tonearm 100. The cartridge 106 is positioned at an offset angle 110 relative to the longitudinal axis of the tonearm 100. Relative to the view shown in FIG. 1, the record 102 rotates clockwise about its center, as represented by arrow 112.

[0057] This offset angle 110 means that the drag force 126 due to the rotational movement of the record 102 is not in line with the tension force 128 exerted by the tonearm 100, and the resultant force 120 of these two forces 126, 128 pulls the stylus of the cartridge 106 sideways towards the center of the record 103. This resulting force, known as the "skate" force, is represented by arrow 120 (shown as a dotted arrow as a resolved force, rather than an actual force). This skate force 120 encourages the arm to "slide" toward the center of the record, which is undesirable because it creates an imbalance in the force provided on the stylus by the groove in the record 102, thus adding to the audible signature of the tonearm.

[0058] Therefore, an opposing force, called an anti-skate force 122 , is applied to the tonearm 100 , typically at or near the first end 104 , to balance this skating force 120 . The effect of the anti-skate force 122 on the cartridge 106 is represented by arrow 124. This effect approximately balances the pressure on the left and right sides of the stylus, preventing the tendency of the cartridge to "slide" toward the center of the record 102.

[0059] 2 shows a side view of a tonearm 100 as known in the art, illustrating additional forces acting on the tonearm 100. A stylus cantilever structure including a stylus 130 is shown extending from the cartridge 106. A pivot device 132 provides tension force 128. In the illustrated example, a pivot point 134 of the pivot device 132 is vertically higher than the surface of the record 102 (indicated by horizontal dotted line 142) on which the stylus 130 is placed.

[0060] As a result, tension 128 includes an upward force component (i.e., away from the surface of record 102 (not visible in FIG. 2 )), and a sudden increase in drag force 126 results in an increase in tension 128, resulting in an increase in upward force that may cause the stylus to lose contact with the groove in record 102. The cartridge 106 provides a downward force 136 due to its weight, which in part counters any upward force that arises as described above. This downward force 136 is carefully controlled by a counterweight force 138 created by a counterweight 140 located at the first end 104 of the tonearm 100.

[0061] In addition to resisting these motions, the tonearm must also allow for movement in the "pitch" and "yaw" directions. The "pitch" direction is rotation about a horizontal axis perpendicular to the longitudinal axis of the tonearm 100, i.e., the "up" and "down" motion created as a result of the stylus 130 overcoming a curvature in the record 102. The "yaw" direction is rotation about a vertical axis through the tonearm, i.e., the rotation required as the tonearm moves across the record to play it from the first groove to the last groove. Playing a standard 12-inch record with a 9-inch tonearm requires approximately 18 degrees of "yaw" movement.

[0062] The present invention provides a tonearm that is particularly effective at resisting the resultant drag force resulting from the pulling force of a record passing under the stylus and the applied anti-skate force, without introducing a detrimental audible signature when the record is played.

[0063] Five different embodiments will now be described with reference to the figures, in which like numerals have been used throughout the description for like components, with the letters "a," "b," "c," "d," and "e" referring to components of the first, second, third, fourth, and fifth embodiments, respectively.

[0064] 3 shows a first embodiment of a tone arm 200a according to the present invention. The protrusion 1a (also called the pivot point) is attached to a support member 7a, which is attached to a base plate 16a of a record player. As shown in Figure 3, protrusion 1a faces horizontally from stylus 10a of tone arm 200a, in this case contact surface 2a provided by a thrust plate which is rigidly attached to elongate member 8a of tone arm 200a.

[0065] In this example, thrust plate 2a also provides a rigid connecting member for connection to suspension members 4a, 5a. Thrust plate 2a and elongate member 8a are suspended from support member 7a by suspension members 4a, 5a, which in this example are tie lines. Tie lines 4a, 5a are attached in contact at point 6a, directly perpendicular to pivot point 1a, and are attached both in the direction as seen in the side view of Figure 3 and perpendicular to that direction, i.e., "into the page" of Figure 3.

[0066] The surface of the thrust plate 2a, that is, the contact surface, is approximately perpendicular (vertical) to the line from the stylus 10a to the pivot point 1a.

[0067] In use, a record passing under stylus 10a generates a drag force that tends to "drag" the stylus along with the record (i.e., substantially to the left with reference to FIG. 3). This drag force urges the contact surface of thrust plate 2a into contact with protrusion 1a at contact point 206a. Because both the contact surface and the protrusion are hard, this contact creates a contact force (because once the surfaces and protrusions come into contact, they cannot press together any further). The contact between thrust plate 2a and protrusion 1a is subjected to a horizontal drag force, which creates a contact force.

[0068] This contact force provides tension that resists the drag force applied to stylus 10a, preventing movement of tonearm elongate member 8a along the direction of the drag force. Thus, the varying drag force caused by the recording signal at stylus 10a cannot move the tonearm in the primary direction (i.e., left in FIG. 3) in which the stylus drag force pulls on the tonearm due to the opposition of thrust plate 2a with the approximately incompressible point 1a at contact point 206a. Counterweight 9a balances the tonearm so that proper tracking weight is maintained at stylus 10a.

[0069] It will be seen that line 202a passing through the tip of stylus 10a and contact point 206a is actually angled slightly "downward" from horizontal. Thus, the horizontal drag force on stylus 10a and the horizontal reaction force at contact point 206a are not collinear. As a result, an increase in drag force (e.g., due to a peak) creates a torque reaction about contact point 206a, which tends to increase the downward force on stylus 10a. The reaction downward force resulting from this signal tends to reduce "mistracking," or the distortion that occurs when the stylus loses contact with the groove during a high-amplitude trajectory.

[0070] As described above, application of a drag force causes thrust plate 2a to contact protrusion 1a at contact point 206a. However, it may be desirable to maintain some light contact even in the absence of this drag force. Accordingly, tonearm 200a also includes magnet 3a (forming part of the magnetized pivot point). Magnet 3a provides an attractive force between protrusion 1a and thrust plate 2a, ensuring that contact is maintained even when other forces, such as vibrations from a foot drop, tend to separate protrusion 1a and thrust plate 2a during record playback. However, it will be understood that magnet 3a is not required.

[0071] Horizontal pivot point 1a does not provide vertical support to elongated member 8a, which is supported by suspension members 4a, 5a relative to support member 7a. The location of these components is more clearly seen with reference to Figure 4. As shown in Figure 4, in this example, support member 7a is the vertically elongated member and passes through hole 204a in elongated member 8a. These components are also more clearly seen in Figure 5, where support member 7a and elongated member 8a have been omitted for clarity.

[0072] It can be seen that each suspension member 4a, 5a is connected at one end to a support member 7a, specifically to the same point 6a on support member 7a. The other ends of suspension members 4a, 5a are connected to a first connection point 11a and a second connection point 12a, respectively, on thrust plate 2a. This forms an arrangement known as a "ligature trapeze." Rotation ("yaw") of elongated member 8a of tonearm 200a as it moves across the record is accommodated by rotation of the "ligature trapezoid" at suspension point 6a about vertical axis 14a which passes through suspension point 6a and contact point 206a where projection 1a contacts thrust plate 2a.

[0073] Thus, in this example, the thrust plate 2a provides a contact surface for generating a contact force, as well as a rigid connecting member to which the suspension members 4a, 5a can be connected.

[0074] A 9-inch tonearm (23 cm) must yaw approximately ±9 degrees on either side of the vertical position to play a full-length LP. The contact force of pivot point 1 a against thrust plate 2 a allows thrust plate 2 a to resist the drag force of the stylus even if it is not perfectly perpendicular to the pivot axis, but is tilted (relative to axis 14 a) by more than 9 degrees at the beginning and end of the record. Thus, pivot point 1 a and thrust plate 2 a can be rotated nearly frictionlessly about the vertical axis of rotation 14 a (yaw) through the pivot point without significantly changing the height or balance of the arm, as required for the stylus 10 a to follow the groove toward the center of the record.

[0075] As shown in Figure 5, suspension members 4a, 5a are attached to thrust plate 2a (which is itself connected to elongated member 8a, as shown in Figure 3) at two points 11a, 12a on either side of contact point 206a, where projection 1a contacts thrust plate 2a. All three points 11a, 12a, 206a lie on a straight horizontal line 13a, as seen in Figure 5. This horizontal line 13a forms the axis for the "pitch" rotation that occurs when stylus 10a needs to rise above the record's curvature.

[0076] The two suspension members 4a, 5a limit the freedom of the elongated member 8a to rotate about its longitudinal axis ("roll", also known as azimuth, an unwanted rotation that is a drawback of conventional vertical uni-pivot tonearms). This is because the suspension point 6a is located away from the longitudinal axis of the elongate member 8a, so any roll will require horizontal swing, which is resisted by rubbing at the contact point 206a. Note that the tendency to roll is very small, so the frictional resistance required to prevent it is also very small.

[0077] Figure 6 shows a second embodiment of a tone arm 200b according to the present invention. Similar components are labelled with the same reference numerals as in Figures 3 to 5, with the suffix "b" indicating that they belong to the second embodiment. Components that are substantially similar to those described with reference to Figures 3 to 5 will not be described again with reference to the second and third embodiments, but rather only the differences will be described in detail.

[0078] In this second embodiment, rather than support member 7b extending through elongated member 8b, support member 7b is rather an L-shaped support member having a first arm 210b and a second arm 211b attached together at substantially a right angle as seen in FIG. 6. A first arm 210b of support member 7b extends substantially horizontally above elongate member 8b, and suspension members 4b, 5b are connected to connection point 6b of first arm 210b of support member 7b as shown in Figure 7. A second arm 211b of support member 7b extends substantially vertically and is connected at a right angle to first arm 210b.

[0079] In this example, contact surface 2b is provided by a separate contact surface structure 18b attached to base plate 16b. A rigid connecting member 20b extends from the underside of elongate member 8b (similar to the first embodiment, except this time rigid connecting member 20b does not provide a contact surface). Rigid connecting member 20b includes protrusion 1b (and associated magnet 3b).

[0080] For illustrative purposes, Figure 8 shows contact surface 2b moved to the left (as shown by the dashed line) so that protrusion 1a (which in this example is formed as part of rigid connecting member 20b) can be seen. Note that first connection point 11b and second connection point 12b are points that connect suspension members 4b, 5b to rigid connecting member 20b, and can be seen in Figure 9, and can be suspension point 6b.

[0081] A tone arm 200c according to a third embodiment of the present invention is shown in Figure 9. Similar components are designated by similar reference numerals, but with the addition of the suffix "c" to indicate that they belong to the third embodiment. Only the differences from the conventional embodiment will be described below. As in the second embodiment, the rigid connecting member 20c includes a protrusion 1c.

[0082] In this embodiment, the support member 7c comprises a contact surface 2c. The support member 7c is a vertically elongated member and is disposed below the elongated member 8c as shown in FIG.

[0083] Figure 10 shows a tone arm 200d according to a fourth embodiment of the present invention. Like reference numerals are used for like components, but with the addition of the suffix "d" to indicate that they belong to the fourth embodiment. Only the differences from the prior art embodiments will be described below.

[0084] The support member 7d is the same as that shown in the third embodiment of Figure 9, with the only difference being that in the third embodiment, the protrusion 1c is part of the rigid connecting member 20c and the support member 7c provides the contact surface 2c, whereas in the fourth embodiment, the support member 7d comprises the protrusion 1d and the rigid connecting plate 20d provides the contact surface.

[0085] The arrangement of suspension members 4c, 5c, 4d, 5d (and similarly for the third and fourth embodiments) is shown more clearly in Figure 10. Suspension members 4c, 4d connect to rigid connection members 20c, 20d at first connection points 11c, 11d (other suspension members 5c, 5d similarly connect at second connection points, not visible). Each suspension member 4c, 5c, 4d, 5d connects to support members 7c, 7d at suspension points 6c, 6d towards the top of support members 7c, 7d but below elongated members 8c, 8d.

[0086] As shown in the side view of Figure 9 (and the perspective view of Figure 10), the suspension points 6c, 6d at which the suspension members 4c, 5c, 4d, 5d are connected to the support members 7c, 7d are located further forward relative to the elongated members 8c, 8d (i.e., the end of the elongated member 8c facing the phonograph needle 10c) than the first and second connection points 11c, 12c, 11d, 12d.

[0087] In the example of Figure 9, this is achieved by having projection 1c extend far enough from rigid connecting member 20c to push the rigid connecting plate very slightly away from support member 7c, and tilting the angles of suspension members 4c, 4d, 5c, 5d very slightly upward and to the left (as seen in Figure 9), creating consistent contact between contact surfaces 2c, 2d and projections 1c, 1d at pivot points 206c, 206d.

[0088] In the example of Figure 10, protrusion 1d extends a sufficient distance from support member 7d to consistently contact rigid support member 20d and push support member 20d slightly (towards the proximal end of the elongate member), and connection points 11c, 11d (and 12c, 12d not shown) are slightly offset from suspension point 6d relative to support member 7d. Thus, in this example, contact point 206d, where protrusion 1d contacts contact surface 2d, is toward the proximal end of elongate member 8b (further to the right in Figure 10) relative to suspension point 6d. The rigid connecting members and connection points to the support members may similarly be offset along an axis parallel to the axis of the elongate members in the first and second embodiments shown in Figures 3-8.

[0089] In each of these examples, the weight of the tone arms 8c, 8d and counterweights 9c, 9d gently maintains contact between the protrusions 1c, 1d and the contact surfaces 2c, 2d, while contributing only slightly to rotational instability in the yaw axis.

[0090] 11 shows the base end of a tone arm 200e according to a fifth embodiment of the present invention. Similar components are designated by similar reference numerals, but with the suffix "e" added to indicate that they belong to the fifth embodiment. Only the differences from the conventional embodiments will be described below.

[0091] The support member 7e is similar to that shown in the third embodiment of Figure 9. This fifth embodiment differs from the fourth embodiment in that the projection 1e is part of a rigid connecting member 20e and the support member 7e provides a contact surface 2e (not visible in the figure). In contrast, in the fourth embodiment, a support member 7d is provided with a protrusion 1d and a rigid connecting plate 20d provides a contact surface 2d. In this respect, the fifth embodiment is very similar to the third embodiment of Figure 9.

[0092] The fifth embodiment differs from the third embodiment in that, instead of first and second suspension members 4c and 5c, elongated member 8e is suspended by a rigid frame structure 30e having flexible mountings. Specifically, rigid frame structure 30e includes a central rigid frame 28e. Central rigid frame 28e is connected to support member 7e at suspension point 6e by a first flexible member 22e. Central rigid frame 28e is connected to first connection point 11e of rigid connecting member 20e by a second flexible member 24e.

[0093] The central rigid frame 28e is connected to the second connection point 12e of the rigid connecting member 20e by a third flexible member 26e. The second and third flexible members 24e, 26e allow the elongated member 8e (and the rigid connecting plate 20e) to pivot about the first and second connection points 11e, 12e, so that the contact point 206e lies on this pivot axis (pitch axis). As seen in FIG. 11 , the central rigid frame 28e is substantially triangular, but has a curved lower edge, creating space for the protrusion 1e to pass under the central rigid frame 28e and contact the contact surface of the support member 7e. It will be appreciated that other shapes are possible.

[0094] In summary, the geometry of the protrusion 1 and its support members 4, 5, 7 allows free, substantially friction-free rotation of the tip of the elongated member (and therefore the stylus 10) in the two axes of rotation necessary for the tip to deflect upwards over the camber, namely "pitch" 13 and "yaw" 14, allowing the tip of the elongated member (and therefore the stylus 10) to progress towards the centre of the record during playback, while the gapless, largely inelastic contact between the protrusion 1 and the contact surface 2 allows even small movements opposite the direction of the main component of the stylus drag force.

[0095] The invention described herein therefore has many advantages over known tonearm configurations of the prior art, which are set out throughout the description and some of which are also set out below. -Lateral uni-pivot bearing provides zero permissible stiffness to the groove time axis. - Trapezoidal suspension limits roll around the arm's longitudinal axis, unlike traditional vertical uni-pivot configurations. -The pivot point and thrust plate surfaces form a single point of hard contact and are therefore not subject to rattle / wobble due to wear, sloppy tolerances or thermal expansion. The present invention is stable enough to function effectively without requiring high precision components. -The pivot point is less susceptible to wear than a vertical uni-pivot bearing because it is not supporting the weight of the arm. -Pivot points can be easily replaced. Replacement pivot points can be inexpensively manufactured, such as metal bolts with sharp ends. The pivot point can be below the level of the stylus, so that an increase in the drag force of the stylus creates a torque reaction that increases the downward force on the stylus.

[0096] While the present invention has been described by way of illustration of one or more specific embodiments thereof, it will be understood by those skilled in the art that the invention is not limited to these embodiments. Many variations and modifications are possible within the scope of the appended claims.

Claims

1. A tone arm, A thin elongated member; suspension means for suspending said elongated member in a substantially horizontal position, said suspension means supporting the weight of said elongated member from a point at an elevation greater than the elevation of the point at which said elongated member is connected; A protrusion; a contact surface; the protrusion is attached relative to a base plate and the contact surface is attached to the elongated member, or the protrusion is attached to the elongated member and the contact surface is attached relative to a base plate; The protrusion is arranged to contact the contact surface at a contact point in opposition, and the action of a drag force substantially parallel to the length of the elongated member urges the contact surface and the protrusion into opposing contact, thereby generating a contact force that resists the drag force.

2. The tonearm of claim 1 , wherein the contact surface is disposed substantially perpendicular to a longitudinal axis of the elongate member.

3. 3. A tonearm as claimed in claim 1 or 2, wherein the protrusion defines a protrusion axis about which the protrusion is generally rotationally symmetric, the protrusion axis being substantially parallel to the longitudinal axis of the elongate member.

4. A tonearm as claimed in any preceding claim, wherein the contact surface is attached to the elongate member.

5. 5. A tonearm according to any preceding claim, wherein the contact surface is a substantially flat plate.

6. 6. The tone arm according to claim 1, wherein the protrusion and the contact surface are attracted to each other by a magnetic force.

7. 7. A tonearm as claimed in any preceding claim, further comprising a rigid connecting member attached to the elongate member, said suspension means comprising at least one suspension member connected to the rigid connecting member at a first connection point.

8. 8. The tonearm of claim 7, wherein the rigid connecting member provides a contact surface.

9. The tonearm of claim 7 , wherein the rigid connecting member comprises a protrusion.

10. 10. A tonearm as claimed in any one of claims 7 to 9, wherein the rigid connecting member extends vertically from the underside of the elongate member.

11. 11. A tonearm according to any one of claims 7 to 10, further comprising a support member, at least one suspension member being connected to said support member.

12. 12. The tonearm of claim 11, wherein the support member is a substantially vertically elongated member.

13. 13. The tonearm of claim 12, wherein the support member is disposed through an aperture in the elongated member, and at least one suspension member is connected to the support member at a point above the elongated member.

14. 13. The tonearm of claim 12, wherein the at least one suspension member is connected to the support member at a point below the elongate member.

15. the support member is a substantially L-shaped member having a first arm and a second arm attached together and at approximately a right angle to each other; 12. The tonearm of claim 11, wherein the first arm is disposed substantially vertically and the second arm is disposed generally horizontally and extends above the elongated member, the second arm having a suspension member attached thereto.

16. 16. A tonearm as claimed in any one of claims 7 to 15, wherein the first connection point is at approximately the same vertical height as the contact point.

17. 17. The tonearm of claim 11, wherein the first connection point is offset along an axis parallel to the length of the elongate member relative to a suspension point at which at least one suspension member is connected to the support member and biases the protrusion and the contact surface into opposing contact.

18. 18. A tonearm as claimed in any one of claims 7 to 17, wherein at least one suspension member is connected to a rigid connecting member at a first connection point and a second connection point.

19. 19. A tonearm as claimed in any one of claims 7 to 18, wherein at least one suspension member is a single suspension member having a first end and a second end, the first end connected to a first connection point and the second end connected to a second connection point, the suspension member being connected to the support member at a point along the length of the support member between the first and second ends.

20. 20. The tonearm of claim 19, wherein the suspension member is connected to the support member at a point along the length of the suspension member that is equidistant between the first and second ends of the suspension member.

21. 19. A tone arm as claimed in any one of claims 7 to 18, wherein the at least one suspension member comprises a first suspension member extending between a first connection point of the rigid connecting member and a suspension point on the support member, and a second suspension member extending between a second connection point of the rigid connecting member and a suspension point on the support member.

22. The elongate member defines a proximal end and a distal end and further comprises: a cartridge having a record needle connected to a tip thereof; 22. A tonearm as claimed in any preceding claim, comprising a counterweight connected to the base end.

23. A base plate with a turntable for records, A record player comprising a tone arm according to any one of claims 1 to 22.

24. 1. A method of configuring a tone arm, comprising: positioning a suspension means for suspending the elongated member in a substantially horizontal position such that the weight of the elongated member is substantially supported by the suspension means from a point at an elevation higher than the elevation of the point at which the suspension means is connected to the elongated member; positioning a protrusion in opposing contact with the contact surface at the contact point, such that upon application of a drag force generally parallel to the length of the elongate member, the contact surface and the protrusion are brought into opposing contact, thereby generating a contact force that resists the drag force; The method wherein the protrusion is mounted relative to a base plate and the contact surface is mounted relative to the elongate member, or the protrusion is mounted relative to the elongate member and the contact surface is mounted relative to a base plate.

25. 1. A method of constructing a record player, comprising: attaching a suspension means to a base plate; positioning a suspension means for suspending the elongated member in a substantially horizontal position such that the weight of the elongated member is substantially supported by the suspension means from a point at an elevation higher than the elevation of the point at which the suspension means is connected to the elongated member; either attaching a protrusion relative to the base plate and attaching a contact surface relative to the elongated member, or attaching a contact surface relative to the base plate and attaching a protrusion relative to the elongated member; positioning a protrusion in opposing contact with the contact surface at the contact point, such that upon application of a drag force generally parallel to the length of the elongate member, the contact surface and the protrusion are brought into opposing contact, thereby generating a contact force that resists the drag force.

26. 1. A method of modifying a record player comprising a base plate and an elongated member, the method comprising: attaching a suspension means to a base plate; positioning a suspension means for suspending the elongated member in a substantially horizontal position such that the weight of the elongated member is substantially supported by the suspension means from a point at an elevation higher than the elevation of the point at which the suspension means is connected to the elongated member; either attaching a protrusion relative to the base plate and attaching a contact surface relative to the elongated member, or attaching a contact surface relative to the base plate and attaching a protrusion relative to the elongated member; positioning a protrusion in opposing contact with the contact surface at a contact point, such that upon application of a drag force generally parallel to the length of the elongate member, the contact surface and the protrusion are brought into opposing contact, thereby generating a contact force that resists the drag force.

Images