A latching mechanism

Abstract: A latching mechanism 18, for example for retaining a container of herbicide 12 on a handset 2 of a herbicide applicator, comprises a latching element 44 and a operating element 52. The latching element 44 is resiliently based into a latching position in which it engages a notch 20 in the container 12. The latching element 44 is moved out of the latching position by the action of a cam surface 60 on the operating element 52. The cam surface 60 is formed on a projecting nose 56 of the operating element 52, which projecting nose is displaceable along a guide surface 57 in a direction transverse to the direction of movement of the latching element 44 from the latching position to the release position.

Description: This invention relates to a latching mechanism, and is particularly, although not exclusively, concerned with a latching mechanism suitable for retaining a container of liquid on equipment for distributing the liquid. GB-A-2207032 discloses hand-held equipment for distributing herbicides. The equipment comprises a handset having a recess for receiving a container of the herbicide. The handset is provided with a latching mechanism for retaining the container in the recess. The latching mechanism comprises a pivotable lever which is movable into and out of a latching recess formed in the container. IBM Technical Disclosure Bulletin Vol. 31 No. 11 April 1989 discloses a latching mechanism comprising an operating element and a latching element which is displaceable against a resilient bias, upon operation of the operating element, from a latching position to a release position, the operating element being displaceable along a guide surface in a direction transverse to the direction of displacement of the latching element between the latching position and the release position, the operating element having a cam surface which cooperates with the latching element to displace the latching element against the resilient bias. According to the present invention, the latching element is connected by a flexible limb to a support member on which the guide surface is provided. Preferably, the operating element is resiliently biassed in a direction corresponding to displacement of the latching element towards the latching position. In a preferred embodiment, the support member, the latching element and the flexible limb may be formed in one piece, preferably as a plastic moulding. The guide surface may be provided on the support member. The cam surface may be provided on a projecting nose of the operating element, which nose is displaceable within a slot formed in the latching element. The cam surface then cooperates with one end of the slot in order to displace the latching element. In a preferred embodiment, the latching mechanism comprises part of the handset of equipment for delivering a liquid such as a herbicide from the container releasably retained in a recess in the handset by the latching mechanism. For a better understanding of the present invention, and to show how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 shows an applicator for delivering a herbicide over the ground; Figure 2 is a rear view of the handset of the applicator of Figure 1; Figure 3 is an underneath view of the handset; Figure 4 is a sectioned side view of the handset with as container of herbicide fitted to it; Figure 5 is a sectioned top view of the handset and container; Figure 6 is a fragmentary view showing a latching mechanism provided in the handset; Figure 7 is a perspective view of the container; Figure 8 is an underneath view of the container; and Figure 9 is a side view of the container. The applicator shown in Figure 1 comprises a handset 2 which carries a delivery head 4 on a support tube 6. The delivery head 4 accommodates an electric motor (not shown) for driving a distribution disc (also not shown) in order to distribute herbicide over the ground under centrifugal force. The liquid to be distributed, and power for the electric motor, are supplied to the delivery head 4 from the handset 2 through the support tube 6. A valve controlling the flow of liquid and a switch controlling the supply of power are operated by a trigger 8 provided in the handset. The handset 2 has a recess 10 for receiving a container 12 (see Figures 4 and 5) containing the liquid to be delivered. The recess 10 accommodates a connection fitting 14 for engagement with an outlet fitting 16 on the container, and a latching mechanism 18 for engagement with a notch 20 formed in the wall of the container 12. The handset 2 has a guide 22 extending in the direction of movement of the container 12 into and out of the recess 10. As shown in Figures 2 and 3, this guide comprises a track 24 having retaining flanges 26. Referring to Figure 4, the handset 2 has a curved handle member 28 in which the trigger 8 is mounted. The handle 28 also accommodates one or more batteries 30 for providing the electrical power for the equipment, and a potentiometer 32, controlled by a control knob 34, for regulating the power supply to the spinning disc in the delivery head 4, so as to control the rotational speed of the disc. The trigger 8 is connected by a link to a shut-off valve 38 for controlling the flow of herbicide from the container 12 to the delivery head 4, through a flexible tube 40 provided in the support tube 6 (see Figure 5). As shown in Figure 5, the connection fitting 14 communicates with the inlet of the valve 38 through a duct 42. The outlet fitting 16 of the container 12 is provided with a self-closing valve of the type disclosed in European Patent Application No. 90303900.6. This valve applies a resilient force on the connection fitting 14 tending to bias the container 12 away from the connection fitting 14. The latching mechanism 18, shown in fragmentary view in Figure 6, comprises a latching element 44 which is connected by a flexible limb 46 to a support member 48 which is part of a partition 50 mounted within the handset 2 and carrying the valve 38. The partition 50, including the flexible limb 46 and the latching element 44 are formed integrally with each other, and comprise a plastic moulding. The latching mechanism 18 also comprises an operating element 52, which comprises a push button 54 and a projecting nose 56. The push button 54 is situated on the outside of the handset 2, for manual operation by a user of the applicator. The nose 56 extends into a slot 58 formed in the flexible limb 46 of the latching element 44. The nose 56 has an oblique cam surface 60 which cooperates with the end wall 62 of the slot 58. A leaf spring 64 (Figure 6) acts between the support member 48 and the push button 54 in order to bias the operating element 52 in the direction away from the latching element 44. The container 12 is shown in greater detail in Figures 7 to 9. It comprises a moulded body of plastics material, and has two side walls 64, a base 66, a front wall 68, a lower wall 70 and an upper wall 72. The front wall 68 is provided with the outlet fitting 16, which has a removable cap 74. The cap 74 is connected to the outlet fitting 16 by a flexible strap 76 and, when removed from the outlet fitting 16, the cap 74 can be accommodated in a recess 78 provided in the front wall 68. The notch 20 is provided in the side wall 64 on the side opposite the recess 78, adjacent the front wall 68. It is separated from the front wall 68 by a ridge 80. Near the base 66, the side walls 64 are provided with shallow depressions 82, to assist in grasping the container 12. The upper wall 72 is provided with a projecting rib 84 which has a shape generally complementary to that of the slot 24. However, the rib 84 tapers slightly in the direction from the base 66 to the front wall 68. Between the rib 84 and the main body of the container 12, there are oppositely disposed grooves 86, for receiving the flanges 26. The ribs 86 terminate some distance from the base 66. In order to fit the container 12 to the handset 2, the container is presented from the rear of the handset 2 with the outlet fitting 16 directed towards the recess 10. The leading end of the rib 84 is engaged with the rear end of the slot 24. This requires no great accuracy, as a result of the narrower cross-section of rib 84 at its leading end. The container is then slid forwards, guided by the cooperation between the rib 84 and the slot 24. The tapering shape of the rib 84 means that the fit between the rib 84 and the slot 24 becomes progressively tighter as the container 12 is advanced, so that the outlet fitting 16 is accurately directed at the connection fitting 14 within the recess 10. The two fittings 16 and 14 thus make proper engagement with each other as the container 12 is pushed home. At the same time, the latching element 44 rides over the rib 80, as a result of the tapering end face of the latching element 44 cooperating with the curved profile at the transition between the rib 80 and the front wall 68 of the container 12. The latching element 44 then snaps under the resilience of the limb 46 into the notch 20, so retaining the container 12 in the recess 10, despite the resilient action exerted between the connection fitting 14 and the outlet fitting 16, tending to push the container 12 out of the recess 10. The act of engaging the container 12 with the handset 2 causes the self-closing valve in the outlet fitting 16 to open, allowing liquid to flow to the valve 38. Operation of the trigger 8, allows the liquid to flow to the delivery head 4, to be discharged from the spinning disc provided in the delivery head 4. Following use of the applicator, the container 12 is released from the handset 2 by displacing the push button 54 rearwardly. This moves the projecting nose 56 along the guide surface 57, pressing the cam surface 60 against the end 62 of the slot 58. The wedging action thus applied by the projecting nose 56 on the latching element 44 causes the latching element 44 to be displaced against the resilient action of the flexible limb 46, so withdrawing the latching element 44 from the notch 20. This allows the container 12 to be pushed for a short distance outwardly of the recess 10, under the resilient action applied by the self-closing valve as it closes. The container 12 can be then be gripped by means of the depressions 82, and withdrawn from the handset 2. It should be noted that, since the wedging action applied by the projecting nose 56 on the end of the slot 58 causes the latching element 44 to be displaced against the resilient action of the flexible limb 46, the restoring action of the flexible limb 46 tends to bias the projecting nose 56 away from the latching element 44 and hence tends to provide a restoring action which returns the latching element 44 to the latching position. Thus, separate biasing means such as the leaf spring 64 need not be provided between the support member 48 and the push button 54, to ensure that the latching element 44 returns to the latching position when the push button 54 is released.

Claims: A latching mechanism (18) comprising an operating element (52) and a latching element (44) which is displaceable against a resilient bias, upon operation of the operating element (52), from a latching position to a release position, the operating element (52) being displaceable along a guide surface (57) in a direction transverse to the direction of displacement of the latching element (44) between the latching position and the release position, the operating element (52) having a cam surface (60) which cooperates with the latching element (44) to displace the latching element (44) against the resilient bias, characterised in that the latching element (44) is connected by a flexible limb (46) to a support member (48) on which the guide surface (57) is provided. A latching mechanism as claimed in claim 1, characterised in that the operating element (52) is resiliently biased in a direction corresponding to displacement of the latching element (44) towards the latching position. A latching mechanism as claimed in claim 2, characterised in that the operating element (52) is resiliently biased by a spring acting between the operating element (52) and the support member (48). A latching mechanism as claimed in any one of the preceding claims, characterised in that the support member (48), the flexible limb (46) and the latching element (44) are formed integrally with one another. A latching mechanism as claimed in any one of the preceding claims, characterised in that the cam surface (60) is provided on a projecting nose (56) of the operating element (52), the projecting nose (56) being received in an opening (58) of the latching element (44), the cam surface (60) engaging a wall (62) of the opening (58).

Inventors: RAFFO DAVID, RAFFO, DAVID
Applicants: NOMIX CHIPMAN LTD, NOMIX-CHIPMAN LIMITED
Application year: 1990
Main classification: E05C3
IPC codes: E05C3, B05B9