Joint assembly with reinforcing member and foam

First and second joint members are connected to one another. A reinforcing member that has an outer surface that defines a plurality of cavities is located in at least one of the joint members. Foam is located in the joint members and engages the reinforcing member and is located in the cavities of the reinforcing member.

FIELD OF THE INVENTION

The present invention relates generally to joint assemblies that are strengthened with a reinforcing member and foam. More particularly, the present application involves a joint assembly that demonstrates improved strength through increased adhesion between the foam and other components of the joint assembly. Also, a method of forming a joint assembly is provided.

BACKGROUND

Various structures found in society, for example furniture, employ joints in their construction. Furniture is made in a variety of shapes and from a variety of different materials. Furniture may be made from wood or metal in addition to being made of less traditional materials such as plastic. While providing advantages such as cost, the use of plastic in furniture challenges the furniture designer in assuring the resulting product is both structurally sound and aesthetically pleasing.

Joint assemblies in furniture that are made from non-traditional material typically include two members that are connected to one another. The first member may be tubular shaped and may be the leg of a chair while the second member is also tubular in shape and is a cross-support of the chair. The cross-support may be attached to the leg at a right angle to form a T-shaped joint. The cross-support is usually shaped on one end for mating with the leg and is attached thereto though the use of an adhesive. Although the leg and cross-support may be solid members, it is sometimes the case that these components are hollow such as when polyvinyl chloride tubing is employed. Here, the leg and cross-support are tubular components that have smooth inner surfaces.

Joint assemblies as the ones described are usually reinforced in order to withstand stresses that are imparted thereon during use. A reinforcing member, such as a wire, may be located inside of the hollow interiors of the leg and cross-support and urged against their interior surfaces. Additionally, liquid polyurethane foam may be introduced into the hollow interiors of the leg and cross-support to cover the reinforcing member. The liquid polyurethane foam expands and hardens into a rigid structure when set. In alternative arrangements, the polyurethane foam employed may not be completely rigid when set in order to make the resulting joint assembly less susceptible to damage by impact forces. The reinforcing member and polyurethane foam work in combination to strengthen the joint assembly to prevent damage when forces are applied thereto.

It is sometimes the case that reinforced joint assemblies as the ones previously described fail during use. It may be that the polyurethane foam becomes separated at one or more locations to the inner surfaces of the leg and cross-support. Also, the polyurethane foam may separate from the reinforcing member. Separation of the polyurethane foam may be caused through normal use of the furniture or through the application of other more significant forces on the joint assembly. Lack of adhesion between the foam and the inner surfaces and/or reinforcing member can lead to failure of the joint assembly as the components will no longer function as intended so that stress concentrations will occur at certain locations. As such, there remains room for variation and improvement within the art.

SUMMARY

Various features and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned from practice of the invention.

The present invention provides for a joint assembly for use in structures such as furniture. The joint assembly may include first and second joint members that are made from less conventional materials such as plastic. The joint assembly may include one or more reinforcing members that are present in the joint members. Foam, such as polyurethane foam, may also be inserted into the joint members for strengthening the joint assembly. The joint assembly is designed so that increased adhesion is realized between the foam and the joint members and/or reinforcing members. Methods of construction and treatment of the joint assembly are also disclosed that result in having a higher degree of adhesion between these components.

In accordance with one exemplary embodiment of the present invention, a joint assembly is provided that includes a first joint member and a second joint member that are connected to one another. A reinforcing member is present and is located in both the first and second joint members. The reinforcing member has an outer surface that defines a plurality of cavities. Foam is located in both the first and second joint members and engages the reinforcing member so that foam in located in the cavities of the reinforcing member.

Another exemplary embodiment resides in a joint assembly as immediately discussed in which the reinforcing member is a wire. The wire is acid etched in order to form the cavities. Acid etching of the wire lowers the dielectric value of the wire in order to promote wetting of the foam.

The present invention also provides for a joint assembly that has a first joint member with an inner surface that defines a plurality of cavities. A second joint member is present and is connected to the first joint member. A reinforcing member and foam are located in both the first and second joint members. The foam engages the inner surface of the first joint member so that the foam is located in the cavities of the first joint member.

The present invention also provides for a joint assembly as immediately discussed in which the cavities are formed by running a rough object over the surface of the first joint member.

Another exemplary embodiment of the present invention exists in a joint assembly as discussed above in which the first joint member is a tube. The cavities are grooves that extend in the axial direction of the first joint member and have rounded dovetail shaped cross-sections. In a further embodiment, the cavities may extend around the entire inner circumference of the inner surface of the first joint member. The cavities have a radial depth of at least 1/10 millimeters. The cavities also have a circumferential width at the location of the cavities closest to the axis of the first joint member of at least 1 millimeter.

A further exemplary embodiment of the joint assembly exists as discussed above in which the second joint member has an inner surface that defines a plurality of cavities. The foam engages the inner surface of the second joint member such that the foam is located in the cavities of the second joint member.

The present invention also provides for a method of manufacturing a joint assembly in which first and second joint members with inner surfaces are provided. The dielectric value of the inner surface of the first joint member is lowered. A reinforcing member is positioned in the first and second joint members. The joint members are connected and foam is applied to the inner surface of the first joint member.

An additional embodiment of the present invention exists in a method as immediately discussed in which the step of lowering the dielectric value of the inner surface of the first joint member is accomplished by treating this surface with an electric current.

A further embodiment of the present invention resides in a method as previously discussed in which the step of lowering the dielectric value of the inner surface of the first joint member is accomplished by treating this surface with a solvent for polyvinyl chloride.

The present invention also provides for a method as previously discussed where the step of lowering the dielectric value of the inner surface of the first joint member is accomplished by treating this surface with an etching primer for polyvinyl chloride.

The present invention also provides for a joint assembly that has a first joint member connected to a second joint member. The joint members each have an inner surface. The first joint member is made from materials that include at least polyvinyl chloride and polyurethane. A reinforcing member and polyurethane foam are located in both the first and second joint members. The polyurethane foam engages the inner surfaces of the first and second joint members.

Another exemplary embodiment resides in a joint assembly as immediately discussed in which the second joint member is made from materials that include at least polyvinyl chloride and polyurethane.

An additional exemplary embodiment of the present invention exists in a joint assembly as discussed above in which the ratio of polyvinyl chloride to polyurethane in the first joint member is 95 parts polyvinyl chloride to 5 parts polyurethane.

A method of manufacturing a joint assembly is also provided with respect to one aspect of the present invention. The method includes providing first and second joint members with inner surfaces. The inner surface of the first joint member is heated and a reinforcing member is positioned in both of the joint members. The joint members are connected to one another and foam is applied to the inner surface of the first joint member.

The present invention also provides for a method as immediately discussed in which the heating step is accomplished by passing the inner surface of the first joint member over a heating rod that produces a flame. Heating of the inner surface of the first joint member changes the surface tension of the inner surface.

An additional aspect of the present invention exists in a method as discussed above in which the first joint member, second joint member and reinforcing member are heated to a temperature of 107° Fahrenheit.

These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS

It is to be understood that the ranges mentioned herein include all ranges located within the prescribed range. As such, all ranges mentioned herein include all sub-ranges included in the mentioned ranges. For instance, a range from 100-200 also includes ranges from 110-150, 170-190, and 153-162. Further, all limits mentioned herein include all other limits included in the mentioned limits. For instance, a limit of up to 7 also includes a limit of up to 5, up to 3, and up to 4.5.

The present invention provides for a joint assembly10that includes a reinforcing member16surrounded by foam30and contained in a pair of joint members12and14. The joint assembly10is designed to achieve improved adhesion between the foam30and the reinforcing member16and/or the joint members12and14. Improved adhesion between the foam30and other components of the joint assembly10acts to create a joint assembly10that is less susceptible to failure. Increased adhesion may be realized by creating cavities20and32which increase the available surface area for contact between the foam30and the reinforcing member16and joint member12. Further exemplary embodiments exist in which adhesion is increased through lowering the dielectric value of one or more of the components to promote wetting and hence better adhesion of the foam30. Additional exemplary embodiments are disclosed in which certain materials are employed to result in improved adhesion. Likewise, various methods of manufacturing the joint assembly10exist in order to promote increased adhesion by, for example, increasing the surface tension of the surface to which the foam30is applied.

FIG. 1shows a joint assembly10in accordance with one exemplary embodiment of the present invention. The joint assembly10may be constructed from a first joint member12and a second joint member14that are made of polyvinyl chloride. The joint assembly10can be used in the construction of furniture, although the joint assembly10of the present invention may be used in other structures such as overhead frames, automobiles or retaining walls. It is to be understood that the materials of construction and applications of the joint assembly10as disclosed herein are only exemplary and other materials and uses are possible.

The joint assembly10ofFIG. 1may be incorporated into a chair. Here, the first joint member12may be a leg of the chair while the second joint member14is a cross-support. T-joint assemblies as the one shown are generally known in the art. For example, U.S. Pat. No. 5,067,842 to Ponting discloses a joint assembly of a T-shaped design that may be used in the construction of furniture. U.S. Pat. No. 5,067,842 is incorporated by reference herein in its entirety for all purposes. The first joint member12inFIG. 1is a tube that has an inner surface28with a bore therethrough. The second joint member14is also a tube that has an inner surface34that likewise defines a through bore. An axis38of the first joint member12is perpendicular to an axis40of the second joint member14. Although shown as tubes, the first and second joint members12and14may be variously configured in other embodiments. For example, the first and second joint members12and14may be curved or may have cross-sections in the shape of a square, rectangle, triangle, I-beam, or channel. The first and second joint members12and14may be connected to one another through use of an adhesive46. In alternative arrangements, the first and second joint members12and14can be connected together through a snap-fit arrangement or through the use of mechanical fasteners. Alternatively, the first and second joint members12and14may be integrally formed with one another in other embodiments.

The interior of the first and second joint members12and14are in communication with one another. A reinforcing member16is located in the interior of the first joint member12and extends into the interior of the second joint member14. The reinforcing member16may be wire and may assume a variety of shapes. For example, the reinforcing member16may be sinusoidal or may be bent at several right angles in other embodiments. The reinforcing member16may be made of a variety of materials and need not be a wire in accordance with other exemplary embodiments. Foam30, which may in one embodiment be polyurethane foam, is inserted into the interiors of the first and second joint members12and14and allowed to set. The foam30fills the joint members12and14and acts in cooperation with the reinforcing member16to strengthen the joint assembly10.

FIG. 2is a close up plan view of a portion of the joint assembly10ofFIG. 1that shows the reinforcing member16in more detail. Here, a plurality of cavities20are defined on the outer surface18of the reinforcing member16. The presence of the cavities20acts to increase the surface area of the reinforcing member16and hence provide more area for contact with the foam30. The foam30can exhibit increased adhesion to the reinforcing member16through an increase in the available area with which to contact the reinforcing member16. The cavities20can be provided in any number and in any shape or depth. The cavities20may be provided around the entire outer circumference of the reinforcing member16so that this portion of the reinforcing member16extends from the first joint member12into the second joint member14. As shown, the foam30surrounds the reinforcing member16and fills the cavities20. The foam30across the displayed portion of the reinforcing member16inFIG. 2is not shown for sake of clarity, although it is to be understood that foam30may fill the cavities20on this portion as well.

The cavities20can be constructed in a variety of manners. In one embodiment, the cavities20are made by running a rough object, such as sandpaper, over the outer surface18. Additionally or alternatively, the reinforcing member16may be treated with an acid solution that etches the outer surface18so as to create cavities20to result in an increase in surface area. Etching by acid also drops the dielectric value of the reinforcing member16which promotes wetting of the foam30. This change in dielectric value further enhances adhesion between the foam30and the reinforcing member16.

The joint assembly10also includes a second reinforcing member22as shown inFIG. 1. The second reinforcing member has an outer surface24that defines a plurality of cavities26. Cavities26are present for increasing the adhesion between the second reinforcing member22and the foam30. The number and configuration of cavities26may be provided in the same manner as discussed above with respect to cavities20. Likewise, cavities26may be formed in the same fashion as mentioned in regards to cavities20. Although described as including reinforcing members16and22with cavities20and26, it is to be understood that only one of the reinforcing members16or22may be provided with cavities in accordance with various exemplary embodiments. In this regard, the reinforcing member16may include cavities20while the outer surface24of the second reinforcing member22lacks cavities26. Additionally, it is to be understood that the joint assembly10need not have a second reinforcing member22in other embodiments.

The joint assembly10can also be designed in order to promote stronger adhesion between the foam30and the joint members12and14.FIG. 3shows one such embodiment in which the inner surface28of the first joint member12defines a plurality of cavities32.FIG. 4is a cross-sectional view of the first joint member12that shows the cavities32in greater detail. The cavities32are provided in any number, shape, or depth. The cavities32may be formed by running a rough object, such as sand paper or a wire brush, over the inner surface28. AsFIG. 4demonstrates, the cavities32can be aligned in multiple directions and be of various shapes, although in other embodiments the cavities32can be uniform in size, orientation and depth. The cavities32act to increase the available surface area of the first joint member12so that the foam30has a larger area of contact with the first joint member12. This increase in surface area creates stronger adhesion between the foam30and the first joint member12.

The second joint member14may also have an inner surface34that defines a plurality of cavities36as shown inFIG. 3. The cavities36function to increase the available surface area of the second joint member14so that the foam30can better adhere thereto. The cavities36can be formed and arranged in the same manner as described above with respect to the cavities32of the first joint member12. The cavities32and34may be provided around the entire inner circumference of the joint members12and14such that the cavities32and34are present from the first joint member12through the transition into the second joint member14. The joint assembly10can be provided with both cavities32and36, or the joint assembly10may have one set of cavities32or36and not the other. When provided with both sets of cavities32and36, the cavities32and36may be formed in the same manner and provided in the same number, size, shape and depth. Alternatively, the manner of production of the cavities32and36in addition to their other characteristics may be different in other exemplary embodiments. The reinforcing members16and22are not provided with cavities20and26. However, in other embodiments, the cavities20and/or26may be present so that the resulting joint assembly10has increased adhesion of foam to the joint members12and14as well as to the reinforcing members16and/or22.

As stated, the cavities32can be configured in a variety of different manners and from a variety of different methods.FIGS. 5 and 6show an embodiment of the first joint member12in which the cavities32are arranged as grooves50that extend in the direction of axis38of the first joint member12. The grooves50extend around the entire inner circumference of the inner surface28. In other embodiments, the grooves50extend around only a portion of the inner circumference of inner surface28. The presence of grooves50acts to break the inner portion of the first joint member12into a plurality of protrusions56.

The grooves50have a cross-section that is generally in the shape of a dove tail with rounded edges. The grooves50have a radial depth42of 1/10 millimeters. However, in other embodiments, the radial depth42may be from 1/50 millimeters to ½ millimeters, from ½ millimeters to ¾ millimeters, or from ¾ millimeters to 2 millimeters. The grooves50also have a circumferential width44of 1 millimeter at a location of the groove50that is closest to the axis38. In other embodiments, the circumferential width44of the groove50at a location closest to the axis38may be up to 1 millimeter in length or up to 2 millimeters in length. Further, although described as having a generally dove tail shaped cross-section; the groove50may have various cross-sectional shapes in other embodiments. For instance, the cross-section of the groove50may be square, rectangular, triangular or oval.

The portion of the first joint member12on either side of the portion of the groove50closest to the axis38is rounded. The grooves50act to increase the surface area of the first joint member12that is available for contact with foam30. Adhesion between the first joint member12and the foam30is increased as the foam30has a larger available surface area for contact. Although the grooves50have been described as being associated with the first joint member12, it is to be understood that the cavities36of the second joint member14may also be configured as grooves50in the same manner as previously discussed with respect to the first joint member12. Here, the grooves50extend in the direction of axis40of the second joint member14. In some embodiments both the first and second joint members12and14are provided with grooves50while in other embodiments the grooves50are present on either the first joint member12or the second joint member14.

An alternative exemplary embodiment of the joint assembly10is shown inFIG. 7. Here, cavities20,26,32and36as described in previous embodiments are not present. The reinforcing members16and22are wires that are curved in shape and extend into both the first and second joint members12and14. The reinforcing member16contacts the inner surface28of the first joint member12while second reinforcing member22contacts both the inner surface28and inner surface34of the second joint member14. In other embodiments, reinforcing member16may also contact the inner surface34.

The joint assembly10exhibits increased adhesion of the foam30to the joint members12and14through the selection of materials in their construction. Here, the joint members12and14are made of a combination of polyvinyl chloride and polyurethane and the foam30is polyurethane foam. The use of polyurethane in the joint members12and14increases the adhesion between these components and the polyurethane foam30. The ratio of polyvinyl chloride to polyurethane in the joint members12and14may be set so that 95 parts of polyvinyl chloride are present to 5 parts polyurethane. In other embodiments, the joint members12and14have 100 parts of polyvinyl chloride to 5 parts polyurethane. Additional embodiments exist in which 75 to 95 parts of polyvinyl chloride are present to 5 parts polyurethane, and in which 95 to 125 parts of polyvinyl chloride are present to 5 parts polyurethane.

Polyurethane may be added to the joint members12and14by granulating reacted thermoset polyurethane foam into powdery foam and then adding to the polyvinyl chloride formulation. Although described as being incorporated into both the first and second joint members12and14, polyurethane may be added to only one of the joint members12or14in other embodiments. Additionally, the joint members12and/or14may be made of other materials in addition to polyvinyl chloride and polyurethane.

The joint assembly10can be treated or formed in a variety of different ways in order to increase adhesion of the foam30to other components. In one method of treatment, an electric current is applied to the inner surface28of the first joint member12. Application of the electric current lowers the dielectric value of the first joint member12. The foam30that is used may be a settable expanded foam that will better wet the inner surface28though a lowering of its dielectric value to result in better adhesion thereto. An alternative or additional treatment involves applying a solvent for polyvinyl chloride such as acetone or an etching primer for polyvinyl chloride to the inner surface28. This treatment lowers the dielectric value of the first joint member12and promotes physical and chemical adhesion between the foam30and the inner surface28. Although described as treatment methods to the inner surface28, the inner surface34of the second joint member14can also be treated in similar fashions to improve adhesion with the foam30.

The first joint member may also be heat treated in order to promote adhesion between the foam30and the inner surface28.FIG. 8shows a step in accordance with one method of treating the first joint member12. The first joint member12may be extruded and cut into sections that are approximately 2 meters in length. Subsequently, the first joint member12is pulled over a thin metal heating rod48which emits a flame of roughly the same length. The flame may be approximately 1200° Fahrenheit in one embodiment. Heat applied to the inner surface28when pulling the first joint member12over the heating rod48changes the surface tension of the inner surface28which improves the bond between the inner surface28and the foam30when applied.FIG. 8shows a portion54of the inner surface28that is passed over the heating rod48so that the surface tension thereof is changed. It is to be understood that the inner surface34can also be heat treated in a similar fashion to improve adhesion between the foam30and the second joint member14.

An additional method of treatment resides in heating various components of the joint assembly10before introducing the foam30. Here, individual components of the joint assembly such as the first joint member12, second joint member14, reinforcing member16and the second reinforcing member22are heated to a temperature of 107° Fahrenheit. Heating of these components may be accomplished by placing them into a heating oven. Additionally, the foam30can be added to the other components of the joint assembly10while in a temperature regulated room. The foam30may react at a faster rate with material that is at a temperature of 107° Fahrenheit so that enhanced adhesion is realized. Although a temperature of 107° Fahrenheit is described, the temperature may be up to 125° Fahrenheit in other embodiments.

The aforementioned designs and methods of constructing or treating the joint assembly10may be used separate from one another or may be combined in any combination. For example, the joint assembly10may include cavities20,26,32and36in addition to applying a heat treatment to the inner surfaces28and34to increase adhesion of the foam30with the various components. Alternatively, the joint assembly10may be constructed so that one or more of the various designs or methods of increasing adhesion is provided to the first joint member12while the second joint member14is not designed or treated in the described fashions to exhibit better adhesion.

EXPERIMENTS CARRIED OUT IN ACCORDANCE WITH VARIOUS EXEMPLARY EMBODIMENTS

Experiments were conducted in order to ascertain the performance of a structure upon using one or more of the arrangements or methods disclosed herein as compared to prior structures.

In one experiment carried out in accordance with one exemplary embodiment of the present invention, a polyvinyl chloride pipe was used that was produced from Kwalu having offices located at 1835 Savoy Drive, Suite 200, Atlanta, Ga. 30341, USA. The experiment was conducted in Kwalu's facilities in Matamoros, Mexico. The polyvinyl chloride pipe had an outer diameter of 35 millimeters and a wall thickness of 3 millimeters. The polyvinyl chloride pipe was cut to a length of 1 meter. A steel rod having a 10 millimeter diameter and a 1 meter length was inserted into the polyvinyl chloride pipe. Electric current was applied in order to lower the dielectric value of the assembly as previously discussed to promote better adhesion of foam. A mixture of polyurethane expanding foam produced by Kwalu was disposed within the polyvinyl chloride pipe. The polyurethane expanding foam is the type of foam used in Kwalu chair production and was allowed to cool completely after application. The assembly was then subjected to a test procedure in order to ascertain its strength.

A test instrument was provided that included a pneumatic cylinder used to impart a force in order to deflect the assembly. The assembly was supported by a steel I-beam. In this regard, the assembly and I-beam were arranged in a lengthwise, parallel relationship to one another. The assembly was supported on either end by posts extending up from the I-beam. The assembly was spaced a distance of 155 millimeters above the I-beam. Force from the pneumatic cylinder was applied to the center of the assembly located essentially half-way between the posts supporting the assembly. The force from the pneumatic cylinder acted to push the assembly towards the I-beam. A programmable logic controller (PLC) was provided and was used to control the number of cycles of force applied by the pneumatic cylinder during the testing procedure. An air pressure regulator was attached to the pneumatic cylinder and functioned to allow for the desired force to be obtained.

One test procedure in accordance with one exemplary embodiment involved setting the air pressure regulator to 35 psi which resulted in a pushing force of approximately 290 pounds as supplied by the pneumatic cylinder. The assembly was supported at opposite ends above the steel I-beam and pressure from the pneumatic cylinder was applied to the assembly for 5 seconds. A measurement of the deflection of the assembly was then recorded. 5 measurements of deflection were recorded.

The programmable logic controller was set for a specific number of cycles to test. After the completion of each test run, 5 measurements of the deflection of the assembly were recorded. Tests were conducted on the assembly in the aforementioned manner for 50 cycles, 100 cycles, 200 cycles, 500 cycles and 1000 cycles. The deflection of the assembly was measured as stated after each of the sets of cycles. Structural failure of the assembly at any point of the testing was noted as having a deflection of 155 millimeters and the broken assembly was removed and the experimented proceeded to the subsequent test.

Applicant theorizes that the strength of prior assemblies was limited due to weakness in the bonding between polyurethane foam and the resin outer shell after repeated application of stresses. Once the bonding is broken the laminate effect is no longer available to impart strength into the overall assembly and the strength of the assembly therefore depends upon the strength of the individual components, and a synergistic increase of the strength due to the laminate effect is not realized. Prior assemblies thus suffered from a breakdown of the laminar structure between the polyvinyl chloride shell and foam. Use of the method disclosed in the present application, that is application of an electric current, resulted in a 34% increase in strength versus assemblies previously constructed not using the disclosed method after 1000 cycles of stress testing. In this regard, strength is measured by the gain/loss of rigidity of the assembly and the failure of the assembly resulting in separation of the assembled components.