GB2518388A - Cam cleat with low release force - Google Patents

Abstract

A cam cleat for sailing vessels which allows lateral pivoting of the jaws (3 & 4, fig 4), either along axes A & B or via spherical bearings (32, fig 10) to provide for easy release of sail cords. A single bar (14, fig 2) may act as an axes A & B for swivel joint rotation and as a fairlead.

Description

Cam cleat with low release force

Background.

Cam cleats are commonly used to retain cords under tension, typically on sailing vessels.

They have the advantage of being quick to engage with the cord, whilst securely holding the cord due to geometry that increases the holding force applied to the cord as the tension on the cord increases. 1JS4660493A shows a cam cleat uses one cam to grip a cord against a fixed plane. W02004019127A1 shows a cam cleat where a cord is gripped between two cams. A disadvantage of these inventions is that, if it desired to release the cord from the cam cleat whilst it is under tension, considerable force can be required which can be difficult to apply, especially as the distance increases between the cleat and the user attempting to release the cord.

The inability to release under load is a factor that can cause a sailing vessel to capsize when it has not been possible to free the sails to spill wind. W02004019127A1 attempts to alleviate this by having bevelled edges on the cams. However there is a need for further reduction in the release force.

An object of the present invention is an improvement of the earn cleat concept which provides easier release of a cord held in the cleat, especially under conditions of high load. The object is achieved by adding additional axes of rotation to the cams.

Two embodiments are described by way of example but other arrangements within the scope of the invention are possible.

Introduction to drawings

A description of the 2 embodiments follows with reference to the accompanying drawings.

Figure 1 -Isometric view of embodiment 1 Figure 2-Exploded view of embodiment I Figure 3 -Isometric view of embodiment I jaw and pivot block assembly Figure 4 -View showing cord force directions and displaced jaws of embodiment 1.

Figure 5-Isometric view showing cord removal direction of embodiment 1 Figure 6-View showing displaced embodiment 1 jaw and block assemblies Figure 7 -Isometric view showing embodiment 1 movable stop arm Figure 8 -Isometric view of ernbodiment I showing access to fixing holes Figure 9 -Isometric view of ernbodiment 2 Figure 10-Exploded view of embodiment 2 Figure 11-View of embodiment 2 showing space for spring Figure 12-Section of embodiment 2 showing spring and spherical bearing Figure 13 -Cleated condition of embodiment 2 Figure 14-Isometric view of uncleated embodiment 2 Figure 15-View ofuncleatcd embodiment 2

Description

Embodiment 1 is explained with reference to Figs 1 to 8 Construction The improved cam cleat comprises a base (I) a pair of swivel blocks (2) which are rotateably attached to the base and are able to pivot about axes A and B respectively.

The swivel blocks each provide a second pivot axis, (C, D) orthogonal to axes A and B. Pivoting about their respective axes C and D is a pair of opposing jaws (3 and 4), with arctuatc serrated cam forms (5a and Sb) which are eccentric to thc jaw pivot axis, and through which passes the cord to be retained (6).

Springs (7) are included to urge the jaws individually into their cleating positions by acting on abutments included in the respective jaw and swivel block.

Shouldered pivot rivets (8) axially secure the jaws to the swivel blocks by forming of the rivet tenon (9) over the movable stop arm (10), forming secure sub assemblies ofjaw and pivot block (11,12) Further springs (13) acting between each swivel block assembly and baseplate are included to urge the swivel blocks into the cord retaining position.

The jaw assemblies are located to the base using a formed rod (14) which also acts as a cord guide (or fairlead) and increases the stiffness of the cleat assembly, in particular to resist the radial forces applied to the jaws as they grip the cord. The formed rod is retained by a nut (15) at each end where it passes through the base plate.

The cleat assembly is secured to the vessel utilising fasteners passing through holes in the baseplate (17). Preferably, the fixing holes are positioned to be compatible with existing cam cleats to enable users to upgrade existing fittings with this improved design. Due to the geometry of this arrangement, the swivel jaw assemblies prevent direct access to the fixing hole, therefore, it should be possible to move the swivel and jaw assemblies in order to gain access to the fixing holes.

In normal use the ability for thc swivel and jaw assemblies to pivot about axis A and B more than required is not desirable, therefore each jaw and swivel assembly includes a movable stop arm (10) with a protrusion (18) that can be selectively positioned to pass into base plate apertures (19, 20) to limit the rotation of each jaw and swivel assembly as shown in figure 8. When the movable stop arm is rotated to disengage the protrusion from the baseplate aperture, it is possible to rotate the jaw and swivel assemblies sufficiently about their respective axes A and B to gain access to the fixing holes as shown in figure 8 Operation.

Cleating.

The cleating operation is the same as existing cam cleats and for convenience is described below: With reference to figure 4, when a cord (22) is passed between the jaws (3 and 4) in direction of arrow X, the jaw 3 rotates clockwise about axis D, and jaw 4 rotates anticlockwise about axes C, against the forces applied by the jaw return springs (7) to accommodate the diameter of the cord. When movement of the cord ceases and tension is applied in direction of arrow Y, due to the cam profile and serrations (Sa and Sb) included in thejaws, and the biasing effect ofthejaw return springs the cord is gripped by the jaws and prevented from moving in the direction of arrow Y. . It will be appreciated that due to the cam profile and serrations in the jaws, the radial force applied to the cord increases as the axial force increases in the manner of a toggle joint.

TJncleating With reference to figures 5 and 6, when it is desired to release the cord from the cleat, the user manipulates the cord in the direction of arrow Z. In a conventional cleat, the force applied must be sufficient to drag the cord out of engagement with the jaw serrations, overcoming high frictional forces.

With this improved arrangement, forces applied in the direction of arrow Z generate a torque about axes A and B causing the swivel block and jaw assemblies to rotate away from the baseplate around the axis A and B as indicated by arrows S and T As the jaw and swivel assemblies rotate about axes A and B they move apart and in doing so a gap is generated which has the effect of releasing the cord from the jaws, thus permitting it to move in the direction of arrow Y. Due to the leverage effect of the ratio between the formed rod (14) diameter and the dimension between the jaw serrations and the respective axis A or B, a much lower force is required to swivel the jaw assemblies than that required to overcome the friction between the cord and jaw serrations. It is also anticipated that wear to the jaws and cord will be reduced as the cord is not being dragged out of engagement from the jaws under high load.

Once the cord is released form the cleat, the swivel and jaw assemblies are urged to their rest positions by their respective springs.

Embodiment 2 is explained with reference to Figs 9 to 15 Construction This embodiment comprises a bascplatc (30), spacer block (31) 2 spindles (32), secured to the baseplate, each having a partly spherical portion (40), a pair of springs (33,34) a pair of opposed jaws (35,36) with serrations on a cam form eccentric to the jaw pivot axis E and F. A strap (37) serves to act as a fairlead, a stop for the jaws and provides increased resistance to the radial loads applied to the spindles. Mounting holes (38) are provided to secure the cleat to the vessel.

A feature of this embodiment is the dual action spring arrangement where the torsion springs are manufactured to have an axial space (39) between coils to provide an axial thickness greater than dimension W shown in figure 11, but when the cleat is uncleated as shown in figure 15, the spring thickness is not too great to prevent full jaw articulation in the uncleating direction. This causes an axial force to be generated that aligns the jaws to rest against the spacer block and largely parallel to the baseplate. The spring legs engage with abutments on the jaws and spacer block to ensure the jaws are biased to the closed position about axes E and F. Operation Cleating.

As illustrated in figure 13, the cleating action is as embodiment 1, whereby the jaws pivot about axes E and F to accommodate the cord.

Uncicating When the cord is moved in the direction of arrow Z, the jaws swivel about the spherical portion of the spindles in an axis that is most convenient to the direction of jaw movement to uncicat. This effect is illustrated in figures 14 and 15.