Locking pliers that can be adjusted using a single hand

Abstract

The most relevant difference with respect to conventional tools is that the upper jaw is hinged (6) and supported on a cam (8). By turning the cam, the opening of the jaws is adjusted without using the usual adjustment screw located in the handle. However, keeping said screw allows additional opening of the lower jaw. This opening can also be obtained by replacing the hole articulated with an actuating lever (3) with selectable notches (10 and 11). Dispensing with the adjustment screw allows a series of conical washers preloaded by a screw and nut (23) to be accommodated. If a pressure bar (2), initially positioned by a screw (15) and spring (16), moves and pushes the nut (23), exceeding the specified preload, the nut will move, facilitating closing. The tool can be very quickly adjusted, using a single hand, and provides a wider opening than usual.

Description

[0001]ONE-HAND ADJUSTABLE PRESSURE PLIERS - TECHNICAL SECTOR This is a tool known as pressure pliers. Its field of application is that of hand tools, especially those intended for tightening and, preferably, holding, although other applications are not excluded. This project aims to design a pressure tool, similar to traditional ones in terms of functionality, but improving ease of use and speed of adjustment. Its manufacture is simple and reliable, without a significant price increase compared to basic tools, filling an important gap between these tools and self-adjusting ones. Unlike most self-adjusting tools, the user controls the gripping pressure applied to the workpiece. This project is characterized by its simple, yet reliable and effective adjustment system.This pressure tool represents a substantial change in how these tools are adjusted for specific tasks, making them easier to use. One of its distinguishing features, compared to non-self-adjusting tools, is that both hands are never needed: the operator can use one hand continuously to manipulate the workpiece. 2. BACKGROUND OF THE INVENTION Numerous tools are used for tightening, holding, and locking. Among the most important are pressure pliers, also known as "grips." This type of tool is used in all kinds of work: assembly, welding, carpentry, as well as for positioning assemblies before final operations such as gluing, bonding, machining, etc.Their use is widespread in many sectors, primarily for clamping applications requiring greater force than that achievable with pliers, and also for keeping the tool locked in place. All these locking pliers are characterized mainly by their construction based on the articulation of kinematic links that form a deformable articulated quadrilateral. In conventional tools, contrary to what will be discussed in this project, the upper handle and the upper jaw (Fig. 1 (5) have no relative movement; this assembly forms a single kinematic link that acts as the fixed base of the articulated quadrilateral. On the opposite side from the jaw, an adjusting screw (Fig. 11 (31) positions the effective axis of the second link of the quadrilateral, which will be called the pressure bar (2). This link articulates with the operating handle (3), forming part of it as the third kinematic link of the quadrilateral.This lever is attached to the lower jaw (4), which rotates about a joint (6) formed by a hole drilled in the extension of the upper handle. Part of this piece constitutes the fourth kinematic link of the quadrilateral. During the tightening process, from Fig. 2a to Fig. 2c, the angle formed by the pressure bar and the lever decreases, aligning them (Fig. 2a and 2b), and then slightly exceeding this position (Fig. 2c). In this last position, a stop (13) prevents the relative movement of these links. Since links 2 and 3 now act as a single kinematic link, the quadrilateral becomes a triangle with zero degrees of freedom, which explains the mechanism's locking. Two sides of the quadrilateral have protrusions that constitute the operating jaws. The previous process rotates the lower jaw and, with the upper jaw remaining fixed, it is possible to press the piece to be gripped.A key feature of this system is that the jaws, before locking (Fig. 2c), pass through a position (Fig. 2b) where the pressure bar and the operating lever become collinear, resulting in an opening (19a) smaller than the final opening (19b). Therefore, a certain degree of elasticity in the assembly is necessary to ensure proper clamping. The most immediate solution is to incorporate a spring between the adjusting screw (Fig. 11) (31) and the pressure bar (2). The force this hypothetical spring would have to exert is very large. This can be deduced by comparing the shortening of this hypothetical spring with the travel of the operating lever responsible for this shortening. Fig. 3 shows that when the operating lever is closed 20 mm, the spring compresses 0.5 mm, resulting in a ratio of: 0.5 mm / 20 mm = 1 / 40.(This ratio becomes even smaller if starting from more closed positions, but, due to the elasticity of the links, it will be considered valid for evaluating the force, using the principle of virtual work): This means that an operator force of 150 N would generate a force on the spring of: 150 N x 40 = 6000 N. The size of a spring capable of working in this range of forces, represented to scale and unassembled in Fig. 15, makes it impossible to configure a reasonably practical tool. This recurring idea has finally been discarded by designers, who rely instead on the inherent elasticity of all the parts and transfer the difficulty to the operator, trusting that, through trial and error, they will adjust the initial opening with the necessary precision. The system described so far has been known for over a century and provides a very high gripping force.These are some of the most versatile and popular hand tools, despite their somewhat cumbersome use: Operators must meticulously adjust the tool before use. The adjustment screw (Fig. 11) is screwed in, moving it axially within the main body, thus changing the length of the longer axis of the quadrilateral. This very delicate adjustment significantly hinders its use: If the jaws are brought too close to the object to be clamped, the pressure bar and the operating handle will not be aligned (preventing the tool from locking). Conversely, if the jaws are not brought close enough, the necessary pressure will not be applied, and the workpiece may even come loose. To make this adjustment, the operator needs to use both hands, gripping the main body of the tool with one and turning the screw with the other.It cannot, therefore, manually hold the workpiece. The final adjustment is achieved through several trial adjustments. The number of adjustments depends on the required clamping force, as well as the elasticity and fragility of the workpiece. These drawbacks are addressed with self-adjusting tools that automatically adapt to different workpiece thicknesses. However, due to their mechanical complexity, these tools are expensive and less reliable. Furthermore, the final clamping force remains undetermined, depending on the workpiece's elasticity. For these reasons, they have not gained significant market share. The tool presented in this project belongs to the first category (non-self-adjusting).It is as inexpensive and reliable as traditional manual adjustment tools and offers four important advantages: 5 - The operator only needs one hand for adjustment, freeing up the other to hold the workpiece. - Adjustment is very quick, switching between workpiece sizes instantly. (A traditional tool may require turning the adjustment screw up to 15 times.) - The operator can predict the final pressure, reducing the number of adjustments. - The jaw opening range is increased by 50% compared to other tools of similar size and proportions. 6 EXPLANATION OF THE INVENTION The tool uses the elements and geometry of standard locking pliers. However, unlike known configurations, the upper jaw (Fig. 1) rotates about an axis (17) belonging to the main body of the tool, which forms the base (1).This rotation is locked by a protrusion on the jaw (7) that rests on a cam (8). Depending on the position of the cam (Fig. 8), the angle formed by the upper jaw with respect to the bed (1) varies. A spring (9) ensures contact between the jaw protrusion and the cam. The cam profile (8) is designed with a sufficiently small radius variation to ensure that the movement is irreversible. This kinematic pair makes the bed (1) and the upper jaw (5) a single kinematic link, as in conventional tools. With this configuration, there are three ways to vary the jaw opening to adapt it to the workpiece to be gripped: -1 By moving the cam on which the upper jaw rests. -2 As in traditional tools, by turning a support screw located at the end of the main tool body (Fig. 8).11 (31) -3 By modifying the position of the lower jaw's axis on which the end of the drive crank (3) is articulated. In practice, this is easily achieved. The hole drilled in the jaw is replaced by several notches (10, (11). The drive crank's axis (3) is fitted into one of these notches. Selecting the notch furthest from the jaw's tip results in the smallest openings (Fig. 8, (10). Conversely, selecting the notch closest to the jaw's tip results in the largest openings (Fig. 9, (11). Discrete variations in opening are not problematic because, thanks to the cam, the entire range of openings is available: The opening in Fig. 9a is smaller than the opening in Fig. 9a.8c It is advantageous to use the second and third opening procedures, combined with the cam opening procedure, because this allows the opening of the upper jaw to be added to the opening of the lower jaw when necessary. If the adjusting screw is removed, thus eliminating option 2 for modifying the jaw opening, a support with controllable rigidity can be mounted in its place using slightly tapered washers (Fig. 4 (20)). These washers can be arranged in series (21) or opposite each other (22), thereby achieving the required rigidity values. Another possible design involves using a cam (Fig. 13 (47a) that rests on a fixed projection (48a) on the bed and is moved by a crank, allowing the upper jaw to close quickly. Another variant (Fig. 14) involves using two cams connected by a link (49) that slides in a groove in the bed.The second cam (47b) also rests on a projection (48b) fixed to the bed. Comparing Figures 13 and 14, it can be seen that, with both cams, a greater displacement of the jaw is achieved. The cam design is conditioned by the irreversibility of the kinematic pair: Attempting to open the upper jaw should not displace the cams, and the mechanism must remain locked. 8 BRIEF DESCRIPTION OF THE DRAWINGS A set of drawings is included as an integral part of this description. These drawings, for illustrative purposes only and not as a limitation, depict the following: Figure 1 shows the essential parts of the design. Figure 2 shows how the tool passes through a minimum opening position (2b), which occurs when the quadrilateral has two aligned sides. Figure 3 shows the shortening of the elastic element as the operating handle approaches.These values ​​will be used to evaluate, through virtual work, the force to which the elastic element is subjected. Figure 4 shows the elastic element consisting of pre-tensioned conical washers. Figure 5 shows the pre-tensioning of the washers by subjecting them to a force of 5500 N, and how the screw, which had moved closer together (c5), separates slightly (30) again when the force is increased to 6800 N. Figure 6 shows the pre-tensioning process without the need for tools. With the jaws in contact, the alignment of the pressure bar and the operating lever compresses the elastic element. The operation is completed by tightening the screw effortlessly until it makes contact with the handle. Figure 7 shows how the pre-tensioning process continues, opening the operating lever (7a) and eliminating (7b) the separation of the jaws by means of the cam. Figure 8.Figure 9 shows various jaw openings when the operating handle is engaged in the notch furthest from the tip of the lower jaw. Figure 10 shows various jaw openings when the operating handle is engaged in the notch closest to the tip of the lower jaw. Figure 11 shows how the handle in Figure 1 (14) facilitates unlocking. Figure 12 shows an adjusting screw, which differs from that of traditional tools by having a very steep thread pitch and by being a double-start thread (33). Figure 13 shows an adjusting screw (34) made up of pre-tensioned conical washers that give the assembly the desired elasticity, and its location (44) in the tool is shown. Figure 14 shows a cam (47a) that rests on a projection (48a) fixed to the bed and is positioned at the end by a crank.Figure 15 shows two cams (47a) and (47b) connected to each other by a link (49) that slides in a groove made in the bed. Figure 15 shows, to scale, the size of a hypothetical spring to control rigidity. Its dimensions, necessary to withstand the force produced by the pressure bar, make this solution unfeasible. Figure 16 is a summary figure. Figure 17 shows the replacement of the screw (15) that limits the maximum angle between the operating handle and the pressure bar, by an assembly that incorporates a pre-tensioned spring, giving this stop a certain degree of elasticity. 10 15 PREFERRED EMBODIMENT OF THE INVENTION No. 1 The tool in Fig. 1 incorporates four main components used in traditional tools: the bed (1), the pressure bar (2), the operating handle (3), and the lower jaw (4).The most significant difference compared to traditional tools is that the upper jaw (5) is not fixed to the upper body of the tool, but is hinged and rests on a cam. A spring (9) anchored between the upper jaw and the bed pushes the jaw against the cam. This cam (8) rotates on an oversized shaft (12) fixed to the bed (1). The large circumference of this shaft makes the cam's movement irreversible when pressed by the jaw. Two notches (10) and (11) are incorporated into the lower jaw. Depending on the thickness of the workpiece to be gripped, the most suitable notch is selected to form the hinge with the end of the operating handle. This provides an additional opening for handling large workpieces (Fig. 9b).A spring anchored to the lower jaw and the bed ensures that the drive crank shaft (3) remains in the selected notch of the lower jaw. Since the adjusting screw is not essential, its location is used to house a set of washers that provide controlled elasticity, facilitating the adjustment necessary to achieve tool locking and proper grip. Conical washers, 16 mm in diameter, are used; these have a thickness of 1.25 mm before deformation and, when subjected to a force of 1400 N, flatten to a thickness of 0.90 mm. Five are mounted in series Fig. 5 (26), making the allowable force multiplied by 5, obtaining 7000 N. This assembly has a maximum displacement of: 1.25 mm - 0.9 mm = 0.35 mm. This assembly is opposed by another similar one (27), opposite, obtaining blocks (28), which are compressed 0.7 mm when subjected to 7000 N. By mounting 3 blocks in series, the allowable force of 7000 N is maintained. When going from rest to a compression corresponding to 7000 N, the change in length will be: 0.7 mm x 3 = 2.1 mm. The length of this assembly, made up of 30 washers, when not subjected to any force measures 31.02 mm. Its stiffness K is: K = 7000 N / 2.1 mm = 3333 N / mm. This assembly is pre-compressed by applying a force of 5500 N, which decreases its length by: 5500 N / 3333 N / mm = 1.65 mm, the new length being 29.37 mm. To maintain this pre-compression (Fig. 5b) without the need for force, the screw is tightened, eliminating the play (29a), which leads to Fig. 5c. The set of washers is ready for use with the tool: If, for example, when the pressure bar is aligned with the operating handle, it produces a force of 6800N, the displacement, with respect to the initial position, will be 6800 N / 3333 N / mm = 2.0.04 mm and the new length of the elastic assembly: 31.02 mm - 2.04 mm = 28.98 mm, Fig. 5 (d). The displacement of the screw with respect to its pre-tensioned position will be: -29.37 mm - 28.98 mm = 0.39 mm Fig. 5 (30). This value will be the horizontal movement of the virtual axis of the pressure bar. Although small, it is sufficient to eliminate, in most cases, the "stiffness" that the tool presents when attempting to lock it without proper adjustment. The pre-tensioning process (which can exceed 6000 N) is done without tools: If the operating handle is closed, with the jaws in contact, the pressure bar displaces the nut, compressing the washers (moving from Fig. 6a to Fig. 6b), a position in which the screw head is separated from the handle. Since the pressure bar is not touching the screw, because it rests on washers (Fig. 5b), the screw is completely free and can be screwed in manually without effort, reaching the position shown in Fig. 6c.12 Next, opening the operating handle creates play in the jaws (Fig. 7a), which is eliminated by rotating the cam (Fig. 7b). If the preload is still insufficient, the process is repeated. A leaf spring (Fig. 4) (25) in contact with the faces of the screw head prevents it from rotating unintentionally (which would cause a loss of the desired preload). The nut (23) has a projection that slides in a groove in the bed, allowing translation but preventing rotation. A pre-compressed spring, coaxial (Fig. 1) (16) with the axis of the operating handle joint (3) and the pressure bar, tends to open the angle formed by these two parts. The initial angle is limited by the stop made by a screw (Fig. 1) (15), threaded into the operating handle, against a protrusion on the pressure bar. This screw can be replaced by an elastic assembly with adjustable stiffness (Fig. 17). PREFERRED EMBODIMENT. The embodiment is similar to the previous one, the difference being that, as with traditional tools, the adjusting screw is retained. Fig. 11 (31) In this case, the rigidity control described in the previous embodiment is omitted. Because fine adjustment is still made with the cam, the thread pitch of the screw Fig. 11 (32) is made at least twice as large as usual. In order to improve its strength, a double-start thread is used Fig. 11 (33). By using a pitch three times larger than usual, the number of turns to move from one position to another is reduced by three. (The screw pitch is limited by the risk of reversibility.) 13 PREFERRED EMBODIMENT OF THE INVENTION No. 3 This embodiment combines the two embodiments described above. A set of parts Fig. 12 (34) is used in place of the adjusting screw used in preferred embodiment No. 2.A tube (35) with external threads (36) and one internal thread (37) at one end is used. Its other end has a front wall drilled with a hole (38) slightly smaller in diameter than its internal diameter. This flange limits the movement of a piston (39) that slides inside. The piston has two different diameters, allowing the smaller diameter portion to pass through the hole in the tube wall and protrude slightly (40). Conical washers (42) are clamped and compressed between this piston and a screw that engages the internal thread (37). To perform this operation, the tube, which has a nut-like projection (43), is held in place with a wrench, and the screw is turned with another wrench.Once pre-compression is complete, the axial force on the screw prevents it from rotating easily, and the assembly behaves as a single unit, functioning like the adjusting screw of traditional tools. However, if, when closing the operating handle, the pressure bar exerts a force greater than the pre-compression force of the washers, the internal piston will move slightly (46) into the tube, reducing the rigidity of the assembly and facilitating the closing and locking of the tool. 14.

Claims

CLAIMS 1) A one-handed adjustable locking pliers comprising the following kinematic links, forming an articulated quadrilateral: - A first kinematic link, which, being the main body of the tool, shall be called the bed (1). It acts as the upper handle of the tool. Near one end, it consists of two holes forming two joints (6) and (17). At the opposite end, it consists of a housing, axial with the handle, for an adjusting screw (31) or a spring, which serves as a support for the second kinematic link. - A second kinematic link, which shall be called the pressure bar (2). It slides on the inner wall of the handle and presses the adjusting screw or the spring. Its other end shares an axis with a third kinematic link. - A third kinematic link, which shall be called the drive crank (3), consisting of two main joints.One of the joints is located at one end and articulates with a fourth kinematic link. Between this joint and the other end, which forms the tool's operating handle, is the second joint, which articulates with the pressure bar (2). - A fourth kinematic link (4), which will be called the lower jaw, articulates with the end of the operating handle and with the joint (6) belonging to the bed. It consists of a protrusion that forms the operating part of the tool's jaw. Other links: - An upper jaw (5) that articulates at the bed joint (17), is formed by a protrusion that forms the operating part of the jaw and by an extension (7) that rests on a cam.

15. - A pre-tensioned spring (9) anchored to the bed and the upper jaw, which tends to rotate it, opening it and ensuring contact with the cam. - A pre-tensioned spring acting between the lower jaw and the bed, which tends to rotate it, opening it. And characterized: - in that the upper jaw (5), which rotates on an axis (17) shared with the bed, rests on a cam (8), or (47), such that a displacement of this cam modifies the opening of said jaw. - and in that the profile of the cam, combined with the coefficient of friction of the materials, prevents the jaw from opening by displacing the cam, the transmission of movement being possible only from the cam to the jaw, so that, once the opening is selected, the assembly, bed and jaw, becomes a single kinematic link.2) A one-handed adjustable locking pliers according to claim 1, characterized in that the lower jaw uses selectable notches (10) and (11), in which the end of the operating handle is articulated, thereby modifying the jaw separation. 3) A one-handed adjustable locking pliers according to claim 1, characterized in that it incorporates a spring (16) that tends to increase the angle formed by the locking bar and the operating handle (3). 4) A one-handed adjustable locking pliers according to claim 1, characterized in that the initial opening of the angle formed by the locking bar and the operating handle (3) is limited by a screw (15) that is threaded into the operating handle and that comes into contact with an extension of the locking bar.

16. 5) Locking pliers, adjustable with one hand, according to claim 1, characterized in that the cam that positions the upper jaw articulates on a shaft (12) that rests on the base (1). 6) Locking pliers, adjustable with one hand, according to claim 1, characterized in that it uses an adjusting screw to vary the position of the end of the locking bar, the thread pitch of which is between the standard pitch and a pitch three times greater than the standard pitch, and uses one or two threaded entries. 7) Locking pliers, adjustable with one hand, according to claim 1, characterized in that it does not use an adjusting screw and instead incorporates elastic conical washers (20) that are held pre-tensioned by a screw (24) and nut (23), this assembly being slightly shortened (30) when the locking bar compresses it with a force greater than the pre-tensioning force.8) Locking pliers, adjustable with one hand, according to claim 1, characterized in that: - the locking screw is replaced by an elastic assembly with external threading (34) that is adjusted like the traditional adjusting screw (44) and, thanks to its elasticity, facilitates the closing of the tool. - and in that it is formed by a tube (35) that houses conical washers (20), compressed between a piston (39) with two steps, and a screw (41) that is screwed into an internal thread (37), said thread being located at the end opposite the front wall of the tube. - and in that the larger diameter part of the piston abuts the front wall of the tube and the smaller diameter part slides through a circular hole in the wall (38) and, if the force exerted by the locking bar is less than the established compression, protrudes slightly (40).

17.

9. Locking pliers, adjustable with one hand, according to claim 1, characterized in that: - the cam (47) on which the jaw projection rests has another surface that rests on a projection (48a) fixed to the bed; - and in that said cam does not rotate about a fixed axis.

10. Locking pliers, adjustable with one hand, according to claim 1, characterized in that it comprises a second cam (47b), or more, the cams being connected to each other by one or more links (49), with a degree of freedom that rest on them, to position the opening of the upper jaw. 18

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