Patent Description:
A typical screw-cutting shear, which is a typical tool for cutting screws, comprises a shear base and a shear lever, the shear lever being driven by a cam to swing relative to the shear base; a stationary blade on the shear base interacts with a moving blade on the shear lever to shear off a screw. A spring is traditionally arranged for resetting purposes, i.e., separating the stationary blade from the moving blade by virtue of the elastic force provided by the spring, so as to be ready for a next shearing action. However, the spring is inefficient in performing resetting and also prone to be fatigued to cause resetting failure.

To improve resetting performance of the resetting structure, a pin is arranged on the shear base, and a track plate is arranged on the shear lever, with a track groove further formed on the track plate; the pin, driven by the cam, rotates along the track groove, whereby the shear lever is reset. The track groove also serves to control a ratio of resetting duration to shearing duration, enabling better control of the shearing action. However, due to arrangement of the track plate on the shear lever, the number of components of the overall screw-cutting shear increases, which increases assembly complexity and is also more demanding on strength of the track plate.

A screw-cutting shear is provided, which can effectively overcome drawbacks of existing screw-cutting shears, which rely on a track plate to drive for resetting and thus have a complex structure and are highly demanding on strength of the track plate.

The invention is implemented by a technical solution as defined in claim <NUM>.

In some implementations, the second drive piece is a pin, one end of the pin being disposed on the shear lever, an opposite end thereof extending in the track groove. The pin may effectively reduce friction with the fitted track groove and thusly reduce resistance; in addition, the pin is not easily stuck at a corner of the track groove and provides a better smoothness when fitted with the track groove.

In some implementations, one end of the pin is disposed on a rotating plate, the rotating plate being rotatably connected to the shear lever. The rotating plate as innovatively provided allows for free adjustment of the pin position within a certain extent according to a trajectory of the track groove, thereby easing assembly.

In some implementations, one end of the pin is rotatably connected to the rotating plate, a rotating axis of the pin being parallel to a rotating axis of the rotating plate relative to the shear lever. The pin itself may rotate, which further reduces friction with the wall of the track groove; in addition, parallel arrangement of the rotating axis of the pin and the rotating axis of the rotating plate allows for the rotating plate to contribute a smoother position adjustment when the rotating plate is fitted with the pin.

In some implementations, the first drive piece is a roller rotationally attached on the shear lever; or, the first drive piece is a slider securely attached on the shear lever. The roller or slider may accurately feed back the stress applied by the cam to the shear lever, with reduced friction between the first drive piece and the cam.

In some implementations, the shear base and the shear lever are hinged via a shear shaft. Hinging of the shear base and the shear lever via the shear shaft can reduce friction when the shear lever rotates relative to the shear base and can also maintain stability of the shear lever swinging relative to the shear base.

In some implementations, the shear lever comprises a shearing end and a driven end, the moving blade being arranged at the shearing end, the first drive piece and the second drive piece being arranged at the driven end, the shearing end and the driven end being separately disposed at two sides of the shear shaft. Separate arrangement of the shearing end and the driven end at two sides of the shear shaft facilitates positioning the moving blade and the two drive pieces and allows for the drive pieces to obtain a larger force arm.

In some implementations, the shear base comprises a stationary end and a drive end, the stationary blade being secured at the stationary end, the cam being rotatably attached at the drive end, the stationary end and the drive end being separately disposed at two sides of the shear shaft. Separate arrangement of the stationary end and the drive end at two sides of the shear shaft can prevent interference between the moving blade and the cam.

In some implementations, an inner sidewall of the track groove is arranged parallel to the outer sidewall of the cam. This parallel arrangement facilitates manufacturing the cam and the track groove and also facilitates positioning the first drive piece and the second drive piece.

In some implementations, when the shear lever shifts from the expanded position to the shearing position, the second drive piece contacts with the inner wall of the track groove; and when the shear lever shifts from the shearing position to the expanded position, the first drive piece contacts with the outer sidewall of the cam. When the first drive piece and the second drive piece are inactive, they still contact with the cam at corresponding positions, preventing formation of clearance between the first drive piece and the cam and between the second drive piece and the cam. When the shear lever shifts from the expanded position to the shearing position, noise created between the first drive piece and the cam and between the second drive piece and the cam may be prevented.

The disclosure offers the following benefits compared with conventional technologies:.

The track groove is formed on a sidewall of the cam and interacts with the second drive piece on the shear lever, which overcomes the structural complexity arising from separately providing a track plate in conventional technologies. By forming the track groove on the sidewall of the cam, the strength of the cam may contribute enough strength to the track groove; in addition, the drive force for reciprocal shifting of the shear lever between the expanded position and the shearing position is all contributed by the cam, which facilitates reciprocal shifting of the shear lever between the expanded position and the shearing position, effectively preventing jamming and meanwhile reducing the impact on the cam when the shear lever shifts between the expanded position and the shearing position, with reduced noise when the screw-cutting shear is operating. Since the cam per se has a high strength, formation of the track groove on the sidewall of the cam can also contribute a high strength to the track groove while ensuring enough strength of the cam, whereby the service life of the reciprocally operating screw-cutting shear is significantly extended.

Hereinafter, the embodiments of the disclosure will be described in detail. Examples of the embodiments are illustrated in the accompanying drawings. The examples described with reference to the accompanying drawings are exemplary and intended to explain the disclosure, which should not be understood as limiting the disclosure.

In the description of the disclosure, it needs to be understood that the orientational or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner" and "outer" refer to those orientational and positional relationships illustrated in the drawings, which are intended only for facilitating description of the disclosure and simplifying relevant depictions, but not for indicating or implying that the devices or elements compulsorily possess such specific orientations or are compulsorily configured and operated with the specific orientations; therefore, such terms should not be construed as limitations to the disclosure.

Besides, the terms "first" and "second" are only used for descriptive purposes, which shall not be construed as indicating or implying relative importance or implicitly indicating the number of a referred to technical feature. Therefore, the features limited by "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present disclosure, unless otherwise indicated, "plurality" indicates two or above.

In the disclosure, unless otherwise explicitly provided and limited, the terms such as "mount", "connect", "couple" and "fix" should be understood broadly, which, for example, may refer to a fixed connection, a detachable connection, or an integrated connection; they may refer to a mechanical connection or an electrical connection or mutual communication; they may refer to a direct connection or an indirect connection via an intermediate medium; they may also refer to communication between the insides of two elements or interaction between the two elements. To a person of normal skill in the art, specific meanings of the above terms in the disclosure may be construed based on specific situations.

<FIG> illustrate an embodiment of a screw-cutting shear according to the disclosure. The screw-cutting shear comprises a shear base <NUM> and a shear lever <NUM> which are hinged with each other; a stationary blade <NUM> is arranged on the shear base <NUM>, and a moving blade <NUM> interacting with the stationary blade <NUM> is arranged on the shear lever <NUM>; a drive mechanism is arranged on the shear base <NUM> and the shear lever <NUM>, the drive mechanism being configured to drive the shear lever <NUM> to swing relative to the shear base <NUM>, whereby the stationary blade <NUM> and the moving blade <NUM> perform a screw-shearing action.

The drive mechanism comprises a rotary cam <NUM> arranged on the shear base <NUM>; a track groove <NUM> is disposed on an end face of the cam <NUM> distant from the shear base <NUM>; a first drive piece <NUM> interacting with an outer sidewall <NUM> of the cam <NUM> is arranged on the shear lever <NUM>, and a second drive piece <NUM> interacting with the track groove <NUM> is further arranged on the shear lever <NUM>. The shear lever <NUM> has a shearing position and an expanded position; the shearing position refers to a position at which the moving blade <NUM> and the stationary blade <NUM> interact to shear off a screw, and the expanded position refers to a position where the moving blade <NUM> is farthest from the stationary blade <NUM>, i.e., the moving blade <NUM> and the stationary blade <NUM> are expanded sufficiently for inserting a to-be-sheared screw. As the cam <NUM> rotates, the outer sidewall <NUM> of the cam <NUM> contacts with the first drive piece <NUM> to push the first drive piece <NUM> to move along the outer sidewall <NUM> of the cam <NUM>, whereby the shear lever <NUM> shifts from the expanded position to the shearing position; as the cam <NUM> continues rotating, the track groove <NUM> on the cam <NUM> pulls the second drive piece <NUM> to move along an inner sidewall of the track groove <NUM>, whereby the shear lever <NUM> shifts from the shearing position to the expanded position; in this way, reciprocal swing of the shear lever <NUM> relative to the shear base <NUM> is realized. Since the track groove <NUM> is arranged on the cam <NUM> and the strength of the cam <NUM> suffices for forming the track groove <NUM> on a sidewall of the cam <NUM>, the sidewall of the track groove <NUM> also has enough strength; in addition, arranging the track groove <NUM> on the cam <NUM> facilitates adjustment of positions of the first drive piece <NUM> and the second drive piece <NUM> upon assembly, ensuring that the shear lever <NUM> shifts more smoothly between the expanded position and the shearing position without jamming.

Furthermore, the second drive piece <NUM> may adopt a pin or a roller. Due to the size and corner radius of the track groove <NUM>, the second drive piece <NUM> usually adopts a pin; as the pin has enough rigidity to transfer power with a low resistance when interacting with the track groove <NUM>, it is adaptable to the smaller corner radius of the track groove <NUM>. One end of the pin is disposed on the shear lever <NUM>, and an opposite end thereof extends in the track groove <NUM> to interact with the inner sidewall of the track groove <NUM>.

To facilitate adjustment of the positions of the second drive piece <NUM> and the track groove <NUM> and prevent interference when the first drive piece <NUM> interacts with the cam <NUM>, a rotating plate <NUM> is disposed at a lower end of the shear lever <NUM>; the rotating plate <NUM> and the shear lever <NUM> are rotatably connected; one end of the pin is disposed on the rotating plate <NUM>, contributing a certain adaptive adjustment distance to the pin, which allows for adjustment of positions of the pin and the track groove <NUM>.

Furthermore, the pin is securely attached on the rotating plate <NUM>, so that rolling friction is contributed between the pin and the track groove <NUM>, which reduces frictional resistance therebetween and can also reduce the noise created therebetween during operating. Moreover, the rotating axis of the pin is parallel to the rotating axis of the rotating plate <NUM> relative to the shear lever <NUM>, so that no axial component force is created when the pin rolls along the inner sidewall of the track groove <NUM>, ensuring connection stability between the rotating plate <NUM> and the shear lever <NUM>.

The first drive piece <NUM> usually adopts a roller, the roller being rotatably attached on the shear lever <NUM> via a roller shaft <NUM>; the roller rolls along the outer sidewall <NUM> of the cam <NUM>, so that the shear lever <NUM> is pushed by the cam <NUM> to move from the expanded position to the shearing position. The roller form contributes a reduced vibration as well as a lower resistance when the first drive piece <NUM> moves along the outer sidewall <NUM> of the cam <NUM>. Besides the roller form, the first drive piece <NUM> may also adopt a slider, which can also drive the cam <NUM> to push the shear lever <NUM> to move from the expanded position to the shearing position.

To facilitate a shearing action performed by the stationary blade <NUM> and the moving blade <NUM>, the shear base <NUM> and the shear lever <NUM> are hinged into an X form, i.e., the shear base <NUM> and the shear lever <NUM> are hinged at their respective middle portions via a shear shaft <NUM>. The shear lever <NUM> comprises a shearing end <NUM> and a driven end <NUM>, the moving blade <NUM> being detachably secured at the shearing end <NUM>; the first drive piece <NUM> and the second drive piece <NUM> are arranged at the driven end <NUM>, i.e., the positions illustrated in <FIG>; the shearing end <NUM> is disposed at an upper portion of the shear lever <NUM>, and the driven end <NUM> is disposed at a lower portion of the shear lever <NUM>. The shear base <NUM> comprises a stationary end <NUM> and a drive end <NUM>, the stationary blade <NUM> being secured at the stationary end <NUM>, the cam <NUM> being rotatably attached at the drive end <NUM>; as also illustrated in <FIG>, the stationary end <NUM> is disposed at the upper portion of the shear lever <NUM>, and the drive end <NUM> is disposed at the lower portion of the shear lever <NUM>. This arrangement facilitates interaction between the stationary blade <NUM> and the moving blade <NUM> to perform a shearing action, which also facilitates adjustment of the distances of the shearing end <NUM> and the driven end <NUM> on the shear lever <NUM> relative to the shear shaft <NUM>, whereby a larger force arm is contributed to the driven end <NUM>.

The inner sidewall of the track groove <NUM> and the outer sidewall <NUM> of the cam <NUM> are arranged in parallel, i.e., a shape enclosed by the inner sidewall of the track groove <NUM> is similar to a shape enclosed by the outer sidewall <NUM> of the cam <NUM>, which may effectively reduce manufacturing and designing difficulty of the cam <NUM>; besides, since the shape of the track groove <NUM> is similar to that of the outer sidewall <NUM> of the cam <NUM>, adjustment of the first drive piece <NUM> and the second drive piece <NUM> is also eased.

Shifting the shear lever <NUM> from the expanded position to the shearing position relies on the cam <NUM> to push the shear lever <NUM> to move, whereby the first drive piece <NUM> moves along the outer sidewall <NUM> of the cam <NUM>; at this point, the second drive piece <NUM> may contact with the track groove <NUM> or may not contact with the track groove <NUM>. Preferably, at this point, the second drive piece <NUM> contacts with the inner wall of the track groove <NUM>; as such, when the shear lever <NUM> shifts from the shearing position to the expanded position, there leaves no clearance between the second drive piece <NUM> and the track groove <NUM>, and also no impact occurs; this facilitates extending the service life of the cam <NUM> and the second drive piece <NUM> and also reduces noise when the screw-cutting shear is operating. Of course, preferably, when the shear lever <NUM> shifts from the shearing position to the expanded position, the first drive piece <NUM> maintains contact with the outer sidewall <NUM> of the cam <NUM> to reduce impact occurring between the first drive piece <NUM> and the cam <NUM> when the shear lever <NUM> shifts from the expanded position to the shearing position.

During use, as illustrated in <FIG>, the shear lever <NUM> is initially at the expanded position, with a spacing between the moving blade <NUM> and the stationary blade <NUM> being currently the maximum; a to-be-sheared screw is inserted between the moving blade <NUM> and the stationary blade <NUM>; the cam <NUM> is activated by an electric motor to rotate; as the cam <NUM> rotates, the first drive piece <NUM> is pushed; the first drive piece <NUM> drives the shear lever <NUM> to swing about the shearing shaft <NUM> as the axis, whereby the shear lever <NUM> shifts from the expanded position to the shearing position; now, as illustrated in <FIG>, the moving blade <NUM> on the shear lever <NUM> contacts with the screw, i.e., a ready-to-shear position; as the cam <NUM> continues rotating, as illustrated in <FIG>, the shear lever <NUM> reaches the shearing position where the screw is sheared off. The cam <NUM> continues rotating till the shear lever <NUM> shifts from the shearing position to the expanded position; now, the track groove <NUM> and the second drive piece <NUM> interact; as the cam <NUM> rotates, the track groove <NUM> pulls the second drive piece <NUM>, with the spacing between the moving blade <NUM> and the stationary blade <NUM> increasing gradually till the shear lever <NUM> reaches the expanded position. Then, the cam <NUM> rotates continuously, and the shear lever <NUM> repeats the above process to reciprocally shift between the shearing position and the expanded position. Since the track groove <NUM> is disposed on the cam <NUM>, reciprocal shifting of the shear lever <NUM> between the expanded position and the shearing position is facilitated, which can effectively prevent jamming and also reduces the impact on the cam <NUM> when the shear lever <NUM> shifts between the expanded position and the shearing position, thereby reducing noise created when the screw-cutting shear is operating.

Claim 1:
A screw-cutting shear, comprising a shear base (<NUM>) and a shear lever (<NUM>) which are hinged with each other, a stationary blade (<NUM>) being provided on the shear base (<NUM>), a moving blade (<NUM>) interacting with the stationary blade (<NUM>) to perform a shearing action being provided on the shear lever (<NUM>), wherein a cam (<NUM>), which is rotatable, is arranged on the shear base (<NUM>), and a first drive piece fitted with an outer sidewall (<NUM>) of the cam (<NUM>) is provided on the shear lever (<NUM>); wherein the shear lever (<NUM>) has a shearing position and an expanded position; the first drive piece moves along the outer sidewall (<NUM>) of the cam (<NUM>), driving the shear lever (<NUM>) to shift from the expanded position to the shearing position;
characterised in that
a track groove (<NUM>) is formed on a sidewall of the cam (<NUM>), a second drive piece (<NUM>) fitted with the track groove (<NUM>) is provided on the shear lever (<NUM>); wherein the second drive piece (<NUM>) moves along an inner wall of the track groove (<NUM>), driving the shear lever (<NUM>) to shift from the shearing position to the expanded position.