DK173099B1 - Screw and nut with built-in torque limiting clutch - Google Patents

Description

in DK 173099 B1

Screw and nut with built-in torque limiting clutch

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a screw, a head and a shaft with a threaded section, by means of which the screw can be screwed into a pre-made hole, a corresponding threaded section, and a nut with a body in which is provided a hole with a threaded portion, can be screwed onto a shaft with a corresponding thread section. Both screw and nut have built-in torque limiting couplings.

10 In the case of plastic screws and nuts for structural building kits, there is a problem as the thread can be damaged by excessive tightening. This destruction can take place either on the screw, on the nut, or on a pre-made threaded shaft or hole.

In order to prevent such stresses on the thread sections on building elements including a toy building kit, in the fall of 1992, the applicant launched a new toy building kit, 20 in which a torque limiting device is incorporated in a tool such as a screwdriver. The toy building kit is marketed under the trademark TOOLO® and is described, inter alia, in international patent applications PCT / DK92 / 0319 and PCT / DK92 / 0321.

25

The screws and the screwdriver cooperate in that the tip of the screwdriver's shaft has a triangular cross-section and that the screw head is formed with a hole of corresponding cross-section. The screwdriver is designed with a torque-limited coupling between the shaft and handle, whereby this coupling limits the amount of torque the screwdriver can apply to the screw.

However, there is a problem with toy building kits, where the elements, which are typically plastic, only withstand relatively small moments, which is why you have to design the interface between the tool and the screw especially to avoid other unauthorized tools without built-in torque limiting couplings are used as a result of destruction of the building element.

Torque limiting couplings are well known and described, among others, in British Patent Nos. GB-A-2,022,199 and GB-A-2,141,999, French Patent No. FR-B-10,376,669, German Patent Nos. DE- C-2 114 793, DE-C-

2 163 109 and DE-C-2 915 526, British Patent Nos. GB-B-661 543, GB-B-952 253, GB-B-1 151 544, GB-B-1 330 631 and GB-B 1,472,484, German Patent Publication No. DE-A-2,608,304, Danish Patent Nos. DK-B-147 118 15 and DKB-155 509, and U.S. Patents No. US

2,731,865, US 3,712,443 and US 4,131,039.

This ensures that the contact surfaces of the screw head for interaction with the tool can be designed arbitrarily.

20 Through the use of a torque limiting coupling, the children do not risk, through their play with the construction kit, with such screws to destroy the threaded parts, even if real, professional tools are used when tightening.

25

The screw may be finger operated, but will preferably be provided with an attack surface with which it can be operated with the tool. This attack surface may be, for example, a notch in the end face of the screw or be an embodiment of the screw head 30 with a polygonal cross section.

By placing the toothed tooth with fixed teeth according to the invention as the outside part of the torque limiting coupling, the fixed teeth can be integrated into the body forming the head of the screw and in the nut respectively. The screw head body can hereby be manufactured with a solid, rather thick outer wall without the risk of suction during the solidification of the plastic material in the mold, the recesses between the teeth of the dental crown preventing this. The screw head body, which is one of the most exposed parts of the screw, is thus given great strength, while at the same time it can be made of plastic by injection molding in a relatively simple mold. In all known torque limiting couplings of this kind, the resilient teeth are located on the outer dental rim. If a plastic screw had to have resilient 10 teeth on the outside dental crown, the screw head had to be double-walled, requiring a more complicated production process.

The shaft of the screw is also a separate body which can advantageously be hollow, whereby the resilient teeth will be free to bend inwardly into the cavity of the shaft.

In a preferred embodiment, where the screw is used to reinforce a frictional coupling between 20 two elements of a toy building set, the screw will preferably be designed so that some movement of the shaft relative to the rest of the screw is allowed. For this purpose, the screw portion with the screw head is formed with two shoulders in the axial direction, between which projections of the shaft portion can be moved.

When the screw is made of plastic by injection molding, the shaft will advantageously be formed with a hollow cylinder body with threaded sections at one end and projections at the other end. The resilient teeth will preferably be connected to the cylinder body through thin stems and form part of these protrusions. The displaceable shaft will preferably be biased with a resilient member located internally of the hollow cylinder body.

4 DK 173099 B1

According to the invention, the dental crown can be designed asymmetrically so that the pitch of the teeth is different clockwise and counterclockwise respectively. This will limit the torque limitation for ice screwing and unscrewing, so that it will never be a problem to loosen a screw. In a preferred embodiment, the screw according to the invention will serve as the basis for a coupling head for coupling with other elements included in toy building kits. The coupling head may then be attached to the screw as claimed in claim 10. In designing the screw as claimed in claim 11, it may form part of a toy building kit with box-shaped elements, for example of the kind marketed under the trademarks DUPLO® or TOOLO®, whereby the box-shaped element with screw can be coupled to a box-shaped element both with and without screw holes.

In addition, the invention relates to a nut as claimed in claim 12 with body, wherein there is a hole with a threaded section for screwing on a pre-made shaft with a corresponding threaded section. The hole is made in a bush where the body and bush are formed on two separate parts. Between the body and the bushing, a torque limiting clutch is provided so that the parties will be able to pivot when the torque between the two parties 25 exceeds a predetermined size. The invention as defined in this claim is based on the same basic principle as the above mentioned screw. This principle can be expressed, in general, by the torque limiting coupling being moved from the tool to the screw or nut included in a structure where the coupling is adapted to a manufacturing technique whereby the individual parts are made of plastic by injection molding.

The nut will preferably be formed with an attack surface for a tool with which the tightening can take place. The torque limiting coupling of the nut comprises a circular tooth rim arranged on one portion and a plurality of radially protruding teeth resiliently arranged on the other portion for engagement with said tooth rim. Since the sleeve has a cylindrical body, the circumferential tooth rim 5 will preferably be disposed externally thereon, while the resilient teeth will be positioned upside down and face inwardly to engage the tooth rim. Both the teeth of the dental crown and the resilient teeth will preferably be designed asymmetrically, so that the torque limitation will occur at 10 lower moments at tightening than at solution.

The invention will be explained in the following with reference to preferred embodiments and with reference to the drawing.

15

FIG. 1 shows in perspective a screw according to the invention screwed into a building element included in a toy building set and formed with a coupling means in the form of a gripping claw for coupling with other building elements.

20

FIG. 2 is a perspective view of a screw according to the invention similar to that of FIG. 1, where the gripper claw is replaced with a consequent complementary coupling means.

FIG. 3 shows in exploded view the embodiment of FIG. 2.

FIG. 4 is a longitudinal sectional view of FIG. 2.

FIG. 5 shows an alternative embodiment of a screw 30 according to the invention.

FIG. 6 shows a torque limiting coupling for use in a screw or nut according to the invention.

6 DK 173099 B1

FIG. 7 shows the one shown in FIG. 6 as the teeth comb over as a result of the applied torque exceeding a predetermined level.

FIG. 8 is a longitudinal sectional view of a preferred embodiment of a nut according to the invention.

FIG. 9 shows the one shown in FIG. 8 in perspective.

FIG. 10 shows the one shown in FIG. 8 shown in exploded view.

FIG. 11 shows a structure in which four of the FIG. 8 are used to attach a plate 15 to a frame.

FIG. 12 shows a torque limiting coupling used in a building element according to the invention.

20 Referring first to FIG. 4. Here is shown a longitudinal section of a screw according to the invention, comprising a head 1 and a shaft 2 with a thread section 3. Hereby the screw can be screwed into a pre-made hole with a corresponding thread section, for example manufactured in an injection molded building element 25 of plastic. included in a toy building set. It is seen that the head 1 and the shaft 2 are provided on two separate parts 10, 20. Between the head 1 and the shaft 2, a torque limiting coupling 30 is provided, which allows the parts 10, 20 to rotate when the torque between the two parties exceeds a predetermined size. The torque limiting coupling shown along a cross section VI-VI will be similar to that of FIG. 6-7.

The shaft portion 20, in the preferred embodiment, is made entirely of plastic by injection molding and has a cylindrical portion 23 which, via a tapered step 7, enters the threaded shaft 2. The shaft 2 terminates with an end wall. The inner wall of the step 22 serves as a shoulder 21 for a screw spring 25 extending longitudinally of the shaft. At the other end 5 of the cylindrical portion 23, the shank portion 20 is formed with a circumferential bead 24 which, via axes 36 extending in axial direction, terminates in resilient wings 37 provided with teeth for engagement with the circumferential tooth rim of the main portion 10. This will be explained in 10 details in connection with FIG. 6 and 7.

The main portion 10 also comprises a cylindrical portion 12 externally formed with an attack surface 11 for a tool not shown, and the attack surface 11 may have a hexagonal cross-section to fit known tensioning keys. Through a stepwise step 13, the cylindrical portion 12 transitions into a further cylindrical portion 14 having a diameter corresponding to the barrel portion 23 of the shaft portion 20, so that rotation between the portions is allowed and a good guide is obtained between the portions.

Exterior of the cylindrical portion 14 is provided a circumferential bead 15 with an axially extending wall and an inclined or tapered guide wall. Hereby, a box-shaped skirt 80 with a circular center opening can be inserted over the bead 15 of the portion 14 and can be pivotally held between the bead and the stepwise step 13. For this purpose, the step 13 is formed with a circumferential bead 13a to increase the size of the abutment surface against the skirt 80. The skirt 80 30 is locked to the cylinder part by an irreversible snap lock provided with the asymmetric bead 15.

At the other end of the barrel portion 12 are two bumps 16, 17, one bead 16 serving as a stop for 35 a coupling portion 90 which will be discussed in connection with FIGS. 1-3. The second bead 17 has a guide wall so that the coupling portion 90 can be passed over the guide wall of the bead 17 and held in an irreversible snap coupling between the beads 16 and 17.

5 Inside, the cylindrical portion 12 is formed with a circular tooth rim 31, similar to that which will be discussed in connection with FIG. 6 and 7. The teeth of the gear ring 31 have an axial extension corresponding to the axial travel of the shaft portion 20 in the chamber formed by the cylindrical portion 12. The shaft portion 20 is pre-tensioned with the spring 25 of the embodiment shown in FIG. 4, the spring 25 exerting a pressure between the inner wall 21 of the step 22 and a plug 91 on the coupling part 90. The plug 91 may advantageously have a center pin 92 so that the spring 25 is held in place. The bead 24 with the blades 37 on the shaft portion 20 permits a migration of the shaft portion 20 between the abutment abutment against the shoulder with the tapping 13 and the stopper 91. Therefore, the shaft portion 20 can be pressed within the main portion 10 if an axial force is applied in the axial direction 10. is greater than the spring force 25 of the spring.

FIG. 3 shows the same construction but in exploded view.

It is seen that the skirt 80 is box-shaped and, in a preferred embodiment, it can be coupled with four coupling pins on a structural building element of the kind negotiated under the trademark DUPLO®. In addition, if this building element has screw holes of the kind marked by reference numeral 66 in FIG. 12, the coupling between the coupling pins 67 and the skirt 80 can be strengthened by ice screwing the shaft of the screw.

In FIG. 2 and 3, it is seen that the coupling member 90 has two fork branches 93 each with respective round projections 94 on the inside. In FIG. 1, another type of coupling part 90 1, 35, which is otherwise attached to the screw in the same way as the coupling part 90, but which has a beak-shaped portion with a beak 9 with a slot 96 and two partially circular recesses 98, is seen. the coupling part 90 'is coupled to the coupling part 90, the projections 94 can be received through a bending of the fork branches 93 in the recesses 98, 5 at the same time as the clamping screw 95 is received in the bore 96 of the beak 97. By tightening the screw 95 it is possible to retain the coupling two coupling parts 90 and 90 ', respectively, a bending of the fork branches will no longer be possible until the screw 95 is loosened again. The screw of FIG. 1 is coupled to one of the construction elements 100 of the toy building set, and this is known from International Patent Application No. PCT / DK92 / 00319 and is otherwise designed with a coupling part corresponding to the coupling part 90 '.

15

FIG. 5 shows another embodiment of a screw according to the invention, and in contrast to those in FIG. 1-4, this screw has a rather conventional appearance, with the head 1 not serving as the basis for one of the 20 toy building kit coupling mechanisms. In addition to the head 1, the screw has a shaft 2 with thread 3. The screw is screwed into the complementary screw hole of another building element, whereby a plate part can be secured with the shoulder 66 of the head 1. The head 1 is otherwise designed with gripping surfaces 11 for a tool. Alternatively, the screw may be designed with wings and serve as a finger operated wing screw. The shaft 2 and the head 1 are two mutually rotatable parts connected together through a torque limiting coupling, similar to that of FIG. 6 and 7. In addition, the head 1 has a cylindrical collar 64 which serves as a bearing for the shaft 2 and which stabilizes the movement of the parties.

In FIG. 6, a preferred embodiment of a torque limiting coupling 30 for use with a nut or a screw according to the invention is shown in cross section. The coupling 30 comprises an outer portion 31 with a circumferential internal ring. The outer portion 31 is in the form of a sleeve. The length of the bushing depends on whether the inner portion 32 of the clutch 30 is to be allowed to perform a predetermined axial travel. If walking of the portion 325 is allowed, the tooth rim of the portion 31 will have an axial length corresponding to at least the passage added with the width of the contact portion of the portion 32 engaging the dental rim.

The teeth 33 of the gear ring are seen to be asymmetrical, with their rise in a preferred embodiment in that direction forming an angle with the radius R of the sleeve of between 0 and 10 °, preferably between 2 and 5 °, and in the other direction between 45 and 80 °, preferably between 55 and 65 °.

15

The inner portion 32 comprises a bushing portion 34 which is coaxially mounted with the outer portion 31. From the bushing portion, in the preferred embodiment, two protruding bosses 36 are formed. Blades 37 extending in the circumferential direction of the portion 20 are attached at one end 35 to the said knobs 36 while their opposite end is free. Outwardly facing teeth 38 on the blades 37 will thus resiliently engage with the teeth 33 on the tooth rim of the outer portion 31.

As long as the torque between the inner portion 32 and the outer portion 31 in direction A is below a given limit value, the clutch will lock the two parts together. As the torque rises above this limit value, the blades 37 are pressed inwardly in the FIG. 7 with the arrows B marked and the teeth 38 brought out of engagement with the teeth 33. of the toothed rim 39 As long as the torque exceeds this limit value, the parts 32 and 31 can be rotated mutually in the direction indicated by the arrow C with the wings 37 forming a ratchet function 35 one. The inner portion 32 and outer portion 31 will preferably be made of plastic by injection molding and will therefore consist of a plastic material such as ABS. The limit value of the moment when the teeth comb over is determined by parameters such as the pitch of the teeth, as well as the resilient properties of the blades 37 and the knobs 35, the latter being dependent on the modulus of elasticity and the shape parameters.

It is clear that the torque limitation can also be achieved in the opposite direction by changing the pitch of the teeth. At the same time, the coupling can be designed with an external tooth ring, 10 with the resilient teeth radially inward.

In FIG. 9 is a perspective view of a preferred embodiment of a nut according to the invention. The nut, designated in its entirety with the reference numeral 40, comprises a nut body 41 which is externally formed with an operating surface 42 for interaction with a tool not shown, for example in the form of a wrench. In a cross section, the nut shown will have a hexagonal cross section. To obtain a substantially circular cross-section at the ends of the nut in the axial direction, it is formed with a circumferential bead 43. At both ends of the nut 40, bushings with an internal thread 45 are provided for screwing in with an external screw shaft. Between respective bushings 44 and the body 41 of the nut, a torque limiting coupling of the embodiment of FIG. 6 and 7. FIG. 8 is a longitudinal sectional view of FIG. 9. It is seen that the body of the nut is divided into two chambers 46 with an integral partition 47 with the body. This tooth ring 50 is shown in the chamber 46 on the right, the bushing 44 being omitted here for the same reason. The bushings 44 are retained in the chambers 46, the parts being respectively formed with a bead 51 and a groove 35 52 so that, after mounting, an irreverible snap lock is provided.

12 DK 173099 B1

FIG. 10 shows the same nut as shown in FIG. 8 and 9, this image being an exploded view. This shows the circumferential bead 51 with greater clarity. At the same time, it is seen that the sleeve 44 is formed with a reduction in the diameter of a section 54, this section having to release the tooth rim 50, while an adjacent section 53 serves as a bearing wall against the inner cylinder wall of the chamber 46.

10

FIG. 11 shows the use of a screw according to FIG. 5, and here it is marked with reference numeral 60. Four screws 60 of this kind retain a plate-shaped building element 61 for a frame structure 6 2 constructed with the beam-shaped building elements 63 of a structural building set 63. Building elements 63 are formed with threaded holes corresponding to the thread of the screw 60 and the plate 61 has holes through which the shaft of the screw 60 can pass unobstructed. Only a few of these holes are shown and can otherwise be placed as required, but suitably the holes will be arranged in a module dimension corresponding to the other building elements of the toy building set.

A wagon bottom 65 is shown in FIG. 12, and this is known from an international patent application No. PCT / DK92 / 00319. The carriage bottom 65 differs from the carriage bottom shown in said application in that the threaded holes along the sides of the element are formed with a torque limiting coupling of the one shown in FIG. 6 and 7. Thus, a longitudinal section along line 30 VI-VI will be similar to that of FIG. 6 and 7 limit end coupling and the outer portion 31 will have outwardly extending axial ribs or grooves to be retained with the carriage bottom body or integrated therein. For production-technical reasons, it is usually preferred that the torque limiting coupling is designed as a self-injection injection molded plastic element. In part 13, the part 32 will, in the embodiment shown in FIG. 12 is designed with an internal thread in the axial direction of the sleeve. The bottom of the carriage is also seen to be formed with coupling pins 67 on the upper side and in between 5 screw holes 66 are arranged.

Because the teeth of the torque limiting coupling are asymmetrical, it is ensured that the nut or screw is tightened with a torque that does not exceed a predetermined limit value and can subsequently be loosened by operation with a substantially greater torque.

The invention is suitable for practice in connection with injection molded plastic products, but is not limited thereto, for example, it will be advantageous to practice the invention in connection with composite toys where, for example, plastic screws are screwed into wooden blocks with threaded holes.

Claims (15)

A screw comprising a head (1) and a shaft (2) with a threaded section (3) for screwing in a pre-made hole 5 with a corresponding threaded section, the head (1) and the shaft (2) being formed on two separate parts. (10, 20) and wherein between the head (1) and the shaft (2) there is provided a torque limiting coupling (30) comprising a circular tooth ring (31) with 10 inwardly facing teeth (1) and a plurality of teeth. outwardly extending teeth (32) on the other part (20) so that the parts (10, 20) can be rotated mutually when the torque between them exceeds a predetermined size, characterized in that the screw is made of plastic by injection molding, and 15 that the outwardly extending teeth (32) of the torque limiting coupling (30) are resilient in the radial direction for engagement with the tooth rim (31). Screw according to claim 1, characterized in that the head is formed with an attack surface (11) with which it can be operated with a tool. Screw according to claim 1, characterized in that the part (10) with the head (1) has a cylindrical body (12) 25 with the circumferential tooth ring (31) arranged inside and that the resilient teeth (32) are arranged on the part (20) with the shank (2) and facing outwards for engagement with the tooth rim (31). Screw according to claims 1-3, characterized in that the cylindrical body (12) of the main part (10) in the axial direction has two stops (13, 91), thereby permitting a walking of the shaft part (20) in the axial direction, travel is limited by the interaction 35 of the two stops (13, 91) with projections (24, 37) on the shaft in its radial direction. DK 173099 B1 Screw according to claims 1-4, characterized in that the shank part (20) comprises a hollow cylinder body with a central cylindrical part (23) which is open at one end and terminates in a circular projection (24, 37) in radius. - all directions, which are closed at the other end and terminated by a step (22) in a threaded section (3). A screw according to claim 5, characterized in that the resiliently arranged teeth (38) are connected to the cylinder body (23) through thin stems (36) and form part of the circumferential projection (24, 37). A screw according to claim 5 or 6, characterized in that a resilient element (25) is provided which biases the screw head (1) and shaft (2) in the axial direction. Screw according to claims 1-7, characterized in that both the teeth of the dental ring (33) are arranged asymmetrically so that the teeth (38) are designed in a circular direction with different increments in the direction with and against respectively. clock. Screw according to claims 1-8, characterized in that the screw head (1) is formed with a coupling head (90) facing away from the shaft (2), which coupling head (90) is arranged for a releasable coupling with a in a toy building set. incoming element. Screw according to claim 9, characterized in that the coupling head (90) is mounted on the screw head (1) through an irreversible snap coupling, the screw head (1) having a cylinder part with a bead (17) for accommodating in a corresponding opening on the coupling head. (90) and that the coupling head (90) has a cylindrical projection (91) coaxial 35 with the opening for receiving into the cylinder portion. DK 173099 B1 A screw according to claims 1-10, characterized in that the screw head (1) is connected to a pivotally mounted, box-shaped part (80) with coupling means for coupling with a building element included in a toy building set and that the shaft (2) in one outer position protrudes outside the box-shaped portion (80), and in another outer position is located completely within that portion (80). A nut with a body (41), in which is provided a hole with a threaded portion (45) for screwing on a pre-made shaft with a corresponding threaded portion, the hole being made in a bush (44), the body (41) and the bush (44) is formed on two separate parts, and where a torque limiting coupling (49, 50) is provided between the body (41) and the bush (44) so that the parties (41, 44) can be rotated mutually when the torque between them exceeds a predetermined size, characterized in that the nut screw is made of plastic by injection molding, and that the torque limiting coupling 20 (49, 50) comprises a circular tooth ring (50) disposed on one part with inwardly facing teeth, and a a plurality of outwardly facing teeth (49) disposed on the other portion and resilient in radial direction for engagement with the teeth of the dental rim (50). Nut according to claim 12, characterized in that the body (41) is formed with an attack surface (42) with which it can be operated with a tool. 30 Nut according to claim 12, characterized in that the sleeve has a cylindrical part with the resilient teeth (49) arranged so that they face outwards, and that the circumferential tooth ring (50) is arranged on the body and with the teeth facing inwards for engagement with the the teeth (49). DK 173099 B1 Nut according to claims 12-14, characterized in that both the teeth of the dental ring (50) and the resiliently arranged teeth (49) are designed asymmetrically, so that they have a different pitch in the direction 5 and clockwise respectively.