Description

[0001] This invention relates to a safety-cap and a container with such a cap.

[0002] In the following, the concepts from screw connections as shown in Figures la - d (prior art) are used. Figure la shows a helical line around a cylinder of diameter di. The helix follows an imaginary thread. The thread has a mean diameter d _m and outer diameter di. If the thread on the front of the cylinder sloping down from left up to right, the thread is right handed, otherwise it is left handed. The pitch means the axial distance P between two points on a thread that has rotated one revolution of the cylinder surface. From this pitch angle φ is defined by

Tan φ = ?/πά (1)

[0003] Figure lb shows the forces acting on a ramp with a pitch angle φ. Normal force N acts perpendicularly on the ramp, and provides a friction force with magnitude F _F = μΝ acting against the movement. In figure lb is shown the frictional force in the downward direction along the inclined plane, which corresponds to the threads being tightened. Resultant force R is the vector sum of the normal force N and the friction force F _F . Resultant force R is counteracted by an equal and opposite force -R, which is decomposed into a thrust F acting parallel to the cylinder axis of rotation and a tangential force K, which is the force required to move the nut or screw. From figure lb it is apparent that the friction angle ε is defined by: tan ε = F _F /N = μΝ/Ν = μ (2)

Also it can be seen that tan (φ + ε) = K / F, i.e. tangential force is given as :

K = F · tan (φ + ε) (3)

[0004] Figure lc illustrates a threaded profile where the flanks of the threads are forming an acute angle with the thread angle 2a. If an axial force F is acting on the thread, the force acting perpendicular to the threaded surface is thus F · cos a.

Similarly, equations (2) and (3) above, is defined as μ ₁ = μ/cos a = tan ε (4) and

K = F · tan (φ + ε ) (5)

[0005] Equation (5) applies to a screw or nut that is tightened, i.e. corresponding to a load that is raised up the ramp in figure lb. When the screw is loosened the frictional force F _F works in the opposite direction so that tangential force required to loosen the screw is given by

K = F - tan ((p - Ei) (6)

[0006] Furthermore, it is known that an applied axial force F does not make the screw or nut rotate when φ < ε^. A thread with φ < ε _λ is called a self-locking thread.

[0007] Figure Id shows an Acme thread, which is a standardized trapezoidal thread with pitch numbers P, thread height equal to P / 2 and thread angle 2a = 29 °. Acme thread or similar metric thread with thread angle 30 ° may be suitable for the present invention. It may also be used threads with two or more inputs, i.e. threads where two or more threads are parallel to each other about a common cylinder.

[0008] A closed container with gasoline being filled and put in the sun, will result in over pressure, i.e. the pressure in the container is greater than the pressure in the surroundings. Over pressure also occurs with other volatile liquids, and of course also built up in the container in another hot area, such as in the trunk of a car. When a container with over pressure is opened, there is a risk of liquid and /or gas flowing uncontrollably through the opening and spilling fluid and in worst case cause human injury.

[0009] To avoid this, a user of some traditional containers, for example, a jerry can, must himself take care to keep the cap in place over the opening while the pressure is offset. If the user does not know that the cap must be held firmly to release the pressure, or if he or she is not aware that there is pressure in the container, it is a risk for the fluid or of injury.

[0010] Prior art threaded safety-caps are known in which a channel extending along the threaded section, i.e. across the threads, in which gas and / or liquid is escaping through the channel while the cap is unscrewed. It takes a certain number of threads without a channel to keep the container closed. In addition it is required a thread with a transverse channel to prevent fluid and damage during decompression. Thus this type of prior art safety caps requires a relatively long threaded portion. When the cap should be turned on or off it will thus require a relatively large number of revolutions, and consequently it takes quite a long time to fasten or loosen the cap.

[0011] It is known to equip cans and similar containers with a hosepipe to prevent spilling of liquid e.g. when fuel is required in a fuel tank. The hosepipe is typically a more or less flexible tube having a first end which can be screwed on to the cap threads of the container and a second end which can be held close to or inserted into the opening of a tank, e.g. tank of a vehicle, a mower, a chainsaw or equivalent. Such hosepipes can be fastened outside the can when not in use and can then hinder space efficient storage and transport of cans. Also the hosepipe will easily fall off and will thus be lost.

[0012] The object of the invention is to provide a safety-cap which solves at least one of the above problems. Specifically, the cap should be operated easily and quickly with little risk for the fluid and / or of injury. It should also be simple and inexpensive and easy to manufacture, and it should preferably be combined with hosepipe and can so that transport and storage may be more efficient than the prior art.

[0013] This is solved according to the invention with a safety cap according to claim 1 and a container according to claim 7,

[0014] The safety cap has according to the invention an inner sleeve having a first threaded portion at a first end and a second threaded portion at a second end, wherein the first threaded section fits the complementary threads on a cap and the other threaded portion fits complementary threads around an opening to the interior of a container. The safety cap has an outer sleeve which is disposed concentrically, axially sliding and rotationally fixed around the inner sleeve, and further provides a closed position in which the outer sleeve is pressed axially between the cap and an abutment surface on the container. Retaining means are adapted to retain the outer sheath temporarily fixed to the cap while the safety cap is rotated from the closed position to a position in which gas can escape from the container between the outer sleeve and the abutment surface.

[0015] When the outer sleeve is pressed against the contact surface the sealing effect is increased produced by contact between the threads of the cap and around the opening of the container, and the corresponding threaded portions on the inner sleeve. When the container is opened gas flows with or without fluid under pressure between the outer sleeve and the contact surface, and not near a user's fingers. Thereby reducing the risk of the user getting gas and / or liquid on the fingers.

[0016] The retaining means may comprise rigid and / or resilient prongs and blocks disposed on respectively the cap and the outer sleeve. These are in engagement with each other when the cap is pressed down against the outer sleeve, and cannot be released until it is a pre- clearance between the outer sleeve and the abutment surface. These blocks and prongs preferably also lock the cover for rotation relative to the outer sleeve when the cap is unscrewed, so that the assembly of the cap and the inner and outer sleeve is moved together along the container thread in an axial direction away from the abutment surface. [0017] In addition to, or instead of, prongs and blocks the cap and the outer sleeve, the retaining means may comprise flexible protrusions that is attached to the inner sleeve and which is adapted to be pressed radially against the outer casing of the cap when the cap is in the closed position.

[0018] In one embodiment, the threads between the cap and the inner sleeve have a higher pitch angle than the threads between the inner sleeve and the container. If the friction in the threads with different thread angles are equal, in this embodiment, it will require a higher radial force to unscrew the cap out of the inner sleeve than the radial force required for unscrew the second threaded section away from the container threads.

[0019] In a preferred embodiment, the cap has a recess adapted to receive an identification mark. Such an identification mark can be pressed into the recess and locked permanently. Each cap may for example come with several marks in different colors so that the user can select one color for a container of gasoline, a different color for an otherwise similar container containing gasoline mixed with engine oil, etc. The identification marks makes it possible to produce a greater number identical containers, each labeled with, for example, different colors. Increased production volumes gives lower cost per unit produced.

[0020] In a preferred embodiment, the inner sleeve has a groove disposed axially between the two threaded sections both of which fits the container thread and wherein the groove is adapted to receive an end of a hosepipe. If the first threaded portion on the inner sleeve has internal threads, the two threaded portions are identical to the first and second threaded portions above. If the first thread section on the other hand is an external thread that fits the internal thread on the cap, then there must be a separate third threaded portion with internal threads on the inner sleeve at both ends of the inner sleeve to be screwed down on the container's external thread.

[0021] With such an inner sleeve the hosepipe can be turned into the container and the cap closed when not in use. To pour the contents out, the inner sleeve is unscrewed, the hosepipe is turned outwards and the inner sleeve is screwed back onto the container threads.

[0022] In another aspect, the invention concerns a container with a safety-cap with a turnable hosepipe as described. All surfaces of the container are adapted to lie snugly against a complementary surface on an adjacent container of the same type. This means that an upper surface do not have elements projecting beyond an imaginary plane, so that a similar container with a flat base can be put on top of the first container so that the top and bottom fit snugly to one another. Similarly, the planar walls of the neighboring containers make it possible to put the containers close together. Obviously, adjacent containers with concave and convex walls may also be close to each other if a concave wall set up a convex wall of the neighboring container etc. When neighboring containers with the preferred embodiment thus remain close together, especially without hosepipes and / or caps attached to the outside container, such containers occupy little space when stored and transported. This reduces storage and transport costs.

[0023] Further features and advantages are apparent from the following detailed description and claims.

[0024] The invention is described in more detail below with reference to the accompanying drawings, wherein:

Figure la illustrates the meaning of pitch and pitch angle;

Figure lb illustrates the forces acting on a thread ;

Figure lc illustrates what is meant by thread angle;

Figure Id illustrates key numbers for a trapezoidal thread, especially an Acme thread ;

Figure 2 is a longitudinal section through a first embodiment of a safety cap according to the invention along line II -II of Figure 3;

Figure 3 is a cross section along line III -III of Figure 2;

Figure 4 is a longitudinal section through a second embodiment of a safety cap according to the invention ;

Figure 5 is a longitudinal section through a container with a safety cap according to the invention ;

Figure 6 is a sectional view similar to Figure 2 with a hosepipe, and

Figure 7 shows the identification marks for use in the invention.

[0025] Figures are schematic illustrations, and are not necessarily to scale.

[0026] Figure 2 shows a safety-cap 100 with a cap 110, an inner sleeve 120 and an outer sleeve 130 The cap 110 has an axially directed collar with exterior threads 111, which in Figure 2 is screwed into a corresponding or complementary first threaded portion 121 at a first end of the inner sleeve 120 The second threaded portion 122 at the other end of the inner sleeve 122 is partially screwed down the threads 211 surrounding an opening of a container 200. In the position shown there is passage 124 along the threaded connection 122, 211 so that gas can escape from the interior of the container 200 through the passage 124 and into nearby destinations between the outer sleeve 130 and an abutment surface 201 surrounding the threads 211 of the container. The threads 211 of the container and the other threaded portion 122 of the inner sleeve being adapted such that the inner sleeve can be screwed into the collar with the threads 211 until passage 124 is gas-tight and the outer sleeve 130 abuts against the abutment surface 201 of the container. [0027] The outer sleeve 130 is disposed axially sliding and rotationally fixed on the inner sleeve 120 because the protrusion 123 of the sleeve 120 can slide in axially oriented slots 133 in the outer sheath 130 or vice versa. In the position shown in Figure 2 the outer sleeve 130 is held temporarily fixed in the cap 110 by prongs 113 and blocks 135 attached respectively in the cap 110 and the outer sheath 130 The purpose of this arrangement is to ensure that gas and optionally liquid does not hit the fingers of a user opening the cap, i.e. that the gas is essentially passing between the outer sleeve 130 and the container outer surface 201 and to a small extent or not at all, between the cap 110 and the outer sheath 130

[0028] When the container 200 is filled, the cap 110 is not on, and there is no contact between the prongs 113 and latches 135 The outer sheath 130 may in this state be inserted down onto the inner sleeve 120 The inner 120 and outer 130 sleeves may in this state be moved axially relative to each other by the protrusions 123 sliding in slots 133 The connection is rotationally fixed for practical purposes. This means that the sleeves can only be rotated slightly relative to each other depending on the clearance between the protrusions 123 and the axially facing walls of the grooves 133

[0029] When the container 200 is filled, the second threaded portion 122 of the inner sleeve 120 is screwed onto the container threads 211, the outer sheath 130 are inserted down onto the inner sleeve 120 and threads 111 on cap 110 is screwed onto the first threaded section 121 at the top on the inner sleeve 120 in Figure 2. The assembly is tightened until the cap 110 presses the outer casing 130 against the support surface 201 of the container. In this position, the prongs 113 on the cap 110 inserted in slot 134 in the outer sleeve 130, and engage in blocks 135 disposed in the slots 134. In Figure 2 is a block 135 shown in order to illustrate that the cover 110, when viewed from above, cannot be rotated counterclockwise relative to the outer sheath 130. The threads 111 are implicitly right shifted so that the cap is screwed onto the threaded portion 121 when the cap, viewed from above, is rotated clockwise. When the container later is opened, the outer sleeve 130 rotates anticlockwise together with the cap when viewed from above. Because the inner sleeve 120 are rotationally fixed relative to the outer sleeve 130 the inner sleeve 120 is thereby rotated relative to the container 200 into the threaded connection 122, 211 to the position shown in Figure 2, where the pressure will pass under the outer sleeve 130 and the abutment 201 as shown by the short curved arrows.

[0030] When the assembly including the cap 110 and sleeves 120, 130 is screwed a few millimeters away from the surface 201, it is in a preferred embodiment possible to unscrew the cap 110 from the sleeves 120 and 130. In the example of right handed threads 111 above, the cap 110, as seen from above, must be rotated counterclockwise relative to the outer sheath 130. For this, the prongs 113 may be rigid members disposed perpendicularly to the underside of the cap 110 with a protrusion which can extend below the horizontal block 135 as shown in Figure 2 After a small rotation of the outer sleeve 130 relative to the cap 110 so that the prongs 113 releases from the blocks 135, the outer sleeve 130 then may be moved axially away from the cap 110 to a position where the prongs 113 are axially spaced from the sleeve 130, so that the cover

110 can be rotated relative to the sleeves 130 and 120 and thus axially out of the threaded portion 121.

[0031] It will be appreciated that the example of Figure 2 is only intended to illustrate the principle, and that other variations of prongs 113 and block 135 can be used as retaining means between the cap 110 and the outer sleeve 130.

[0032] For example, the use of a ratchet mechanism in which a resilient element and a sloping surface on the prongs and / or blocks makes it possible to rotate the cover 110 in one direction but not in the opposite direction relative to the outer sheath 130 The prongs and blocks may also have horizontal shoulders that lifts the outer sleeve with cap 110 when the assembly rotates the container threads and is moved away from the abutment surface 201 Various modifications, such as fixed claws on the cap and resilient hooks in the outer sleeve, resilient stoppers on the cap and fixed blocks on the outer sleeve and variants in which both elements are fixed or resilient can be used in the invention. The prongs and blocks are preferably integral parts of the cap 110 and the outer sheath 130, and may advantageously utilize the elastic properties of a plastic material used to make the cap 110 and / or the outer sheath 130.

[0033] The passages 124 may be, but need not necessarily be, canals across the threaded portions 122 and / or 211 In practice it turns out that the gas escapes between the threads 122 and 211 as soon as the threaded connection is loosened, also without passages 124 in the form of open channels, as shown in Figure 2. The passageways 124 should be understood as sufficient clearance between the threads 122 and 211 for gas to be discharged and / or separate ducts made in parts of the threads 122 and 211.

[0034] Figure 3 is a cross sectional view taken along line III -III in Figure 2. The line

111 -III passes through an annular groove 125 which, in a preferred embodiment may accommodate a hosepipe 250 which may extend down through the opening in the container 200. This is further described in connection with Figures 4 to 6 below.

Hosepipe 250 is not shown in Figures 2 and 3 mainly to avoid superfluous details, but also because the safety-cap may be used without such hosepipe. The protrusions 123 on the inner sleeve 120 in the axially oriented slots 133 in the outer sleeve 130 is described in connection with figure 2 above.

[0035] Axially oriented grooves in the outer circumference of the sleeve 130 are intended to illustrate a good grip for the user to turn on and off the safety-cap and have no other function. The cap 110 preferably has a corresponding gripping surface.

[0036] Figure 4 shows an alternative embodiment of a safety-cap 100 according to the invention. In the variant in Figure 4, the inner thread 117 of the cap 110 which fits in a first threaded portion 127 of external threads to match the internal threads of the cap 110. The external threads 127 are located at the first end of the sleeve 120. In the first end of the inner sleeve it is also shown a separate threaded portion with internal threads 121 matching the external threads 211 on the container. Threaded portion 122 of the second end of the inner sleeve also fits the container external threads 211 and corresponding to the second threaded portion 122 described in connection with figure 2. It should be understood that the threaded section 122 in figure 4 also provides a passage 124 when the threads are released as shown and described in connection with figure 2.

[0037] In Figure 4, the assembly of the cap 110, the inner sleeve 120 and outer sleeve 130 is tightened so that the outer sleeve 130 is pressed against the contact surface 201 of the container 200 and the connection between the threads 211 and 122 is gas tight. In this position the cap presses a resilient protrusion 128 on the inner sleeve 120 in the slot 133 in the outer sheath 130. The friction between the protrusion 128 and the outer sheath 130 may be used to lift the sleeve 130 together with the cap 110 in place of or in addition to horizontal shoulders on the prongs 113 and blocks 135 described above. Prongs 113 and blocks 135 are not shown in Figure 4 for the sake of clarity.

[0038] When the cap is to be opened, it is, as mentioned in the description of Figure 2, desirable that the outer sleeve 130 and the cap 120 remains in contact with each other, while it opens a passage 124 in the threaded portions 211, 122 and an opening between the outer the sleeve 130 and the surface 201 as shown in Figure 2.

[0039] In Figure 4, the inner sleeve 120 and outer sleeve 130 cannot rotate relative to each other because the protrusions 128 cannot pass the axial walls of the grooves 133 For the threads 211, 122 to be opened before the threads 11, 127, the tangential force K ₁₂₇ acting on the threads between the cap 110 and the sleeve 120 will be greater than tangential force K ₁₂₂ acting between the sleeve 120 and the container 200 These can be calculated using equations (1) - (6) above. If, for simplicity, it is assume that the thread has the same thread angle a and a common coefficient of friction μ, the size Z\ is equal for the two threads. By equation (6) follows that tan φ ₁₂₇ > tan φ ₁₂₂ , the pitch angles φ ₁₂₇ and φ ₁₂₂ belonging to the threads 127 and 122 respectively. In other words the intended effect in this case, is achieved when the thread 127 has a pitch angle φ greater than the thread 122. The pitch numbers P of the two threads can be adapted according to the thread diameters using Equation (1). From the description of figure 1 it is also clear that the friction coefficient μ, thread angle a and the number of inputs can be varied between the different threads to achieve the threaded connection 122, 211 between the second thread and the container's thread opens easier than threaded connection 117, 127 between the cap 110 and the inner sleeve. In some embodiments, it is also conceivable that the inner thread 121 has different properties than the second threaded section 122, but different slope and / or thread angles would then make it impossible to screw threaded portion 121 onto the container thread 211

[0040] Figure 4 also shows a hosepipe which is positioned in the slot 125 in the inner sleeve 120. The hosepipe 250 extends downward into the container 200 as shown in figure 5 Embodiment of figure 2 can be equipped with a hosepipe 250 in the same way as in figure 4,

[0041] Figure 5 is a section through a container 200 with a safety-cap 100, an abutment surface 201, an upper surface 202 and a handle 203. The safety cap 100 is of the type described above, the hosepipe 250 is positioned within the container. This corresponds to the orientation of Figure 4, and prevent that the hosepipe does not escape when it is not in use.

[0042] Thus the hosepipe does not extend beyond a surface of the container 200 when not in use. Furthermore, the contact surface 201 lowered relative to the upper surface

202 so that the cover 110 does not extend above the surface 202 Similarly, a handle

203 and other elements lowered so as not to extend above the upper surface 202 The upper surface 202 thus defines an upper level so that it is easy to put a similar container with a flat base on top of the container 200 without there being a lot of unused space between the containers. Similarly, the walls of the container 200 may advantageously be made complementary to each other, such that neighboring containers 200 can be placed close together side by side or end to end. When all surfaces of the container 200 is adapted to lie snugly against a complementary surface of a neighboring container of the same type, the containers occupy minimum space during storage and transport. It is noted in particular that the triangles, rectangles, regular hexagons, etc. As is known, filling a surface by tessellation, while regular pentagons, circles and several other geometric shapes cannot fill a plane with no gaps between shapes. It follows that the surface shape (rounded) triangles, squares, or other shapes that fill a surface by

Tessellation is preferred that surfaces of the container 200 In other words, we prefer a container of substantially rectangular side-surfaces as shown in Figure 5 and the corresponding substantially triangular or square end walls perpendicular to the side walls above a container of circular or pentagonal end walls because the first-mentioned container may be stacked more closely. Thus, the volume requirement and the costs of storage and transport movement.

[0043] Figure 6 shows the embodiment of Figure 2 with hosepipe 250 facing out from the container 200. In Figure 6 the sleeves 120 and 130 inverted relative to the position shown in figure 2. That is, the threaded section 121, which in figure 2 is shown in engagement with the threads 111 on the cap 110 is screwed onto the container thread 211 in figure 6. The sleeve 130 is shown with corresponding recesses 134 facing down against the surface 201. A horizontal shoulder in slots 133, as illustrated by the transition to the line pattern at the end of the slots 133 prevents the sleeve 130 from sliding axially past the protrusions 123 and be lost.

[0044] The embodiment of figure 4 may of course be equipped with threads 121 and 122 which are both compatible with the threads 211 on the container 200 so that the hosepipe can be turned out of the container 200 in the same manner as in figure 6. The principle is of course the same if the container opening has internal threads and the inner sleeve has external threads at each end to match the threads on the container.

[0045] It is of course also optionally placing the outer sleeve 130 as shown in Figure 6, or to put it away while the content is poured out of the container 200 through the drain tube 250 With sleeve 130 positioned as in Figure 6 is reduced, however the risk that the outer sleeve disappears. At the same time protected the protrusions 123

[0046] Figure 7 illustrates several identification marks 112 With a variety of color and / or surfaces that may be supplied with cap 110. Users can choose which identification mark 112 he or she will use on a new container. For example, a first container 200 with 95 octane unleaded gasoline labeled with a first color, a second container 200 with petrol with engine oil is indicated by a different color and a new container can be labeled with a third color that have not been used previously. Identification marks 112 may for example be round pieces which can be snapped into an appropriate hole in the cap 110 where they attach permanently. Other types of identification marks 112 may also be used in accordance with the invention.

[0047] In order to prevent that the caps 110 are confused with each other and to prevent a cap from disappearing, the cap 110 is attached by a cord or equivalent (not shown) in the outer sheath 13.

[0048] Safety-cap 100, the container 200 and drain tube 250 may conveniently be produced by suitable plastic materials, such as polyethylene (PE) and / or

polypropylene (PP) in order to achieve low production costs. Along with the aforementioned low transport and storage costs, it is achieved a low cost container 200 with a safety cap 100 which prevents the user from being exposed to gas or liquid, and which has a number of other advantages.