LINTEL BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates to lintels and more particularly to a new and improved lintel and method of supporting a course of blocks with a binder above an opening.

Prior Art Statement

A post-and-lintel construction is most often utilized for supporting a load above an opening. The post-and-lintel construction has been used all over the world and for centuries ranging from the stone circle at Stonehenge and the Greek architecture of the Parthenon in Athens to present day commercial and residential windows and doorways. Lintels have been constructed from stone, timber, concrete or steel. Each of these materials have positive and negative characteristics when used to construct a lintel.

Lintels constructed of stone resist weathering and corrosion, however a stone lintel may span only very limited distances due to the weight of the lintel and lack of tensile strength. Lintels constructed from timber are capable of spanning further distances than stone lintels, however timber is susceptible to burning and decaying. Concrete lintels may span further than stone lintels and resist burning and decaying unlike timber lintels, however the weight of concrete lintels economically inhibits transportation of concrete lintels over large distances.

There is a need for a lintel which has an acceptable weight to load capacity, resistant to weathering and corrosion and is easily transportable. The construction industry has tried to satisfy this need by developing steel lintels. The following U.S. Patents are examples of

attempts of the prior art to solve these problems.

U.S. Patent 4,020,612 to W. T. Welch discloses a lintel fabricated of an elongated lightweight metal plate having rigidifying beam means affixed thereto and extending longitudinally thereof. U.S. Patent 4,280,308 to L. Svensson discloses a lintel for supporting arches over doors, windows and other openings in a wall. The lintel is made of relatively thin sheet metal and has at least one load-carrying shank, so that the lintel in spite of its thin construction can carry great loads during the walling of the arch. The shank or each shank is provided with a longitudinally extending material weakening, e.g. a series of slots, perforations, a groove or similar. The material weakening forms a fracture indication along which the shank can be folded or broken off, when the mortar has set and brickwork has become self-supporting.

U.S. Patent 4,409,764 to J. A. Wilnau discloses a system for constructing the structural framework of a building or other structure of reinforced concrete, characterized by column and beam forms of sheet metal which remain in place as permanent parts of the framework after being filled with concrete. These forms are preferably factory-assembled, together with the necessary internal metal reinforcing skeletons, and shipped to the building site ready for erection of the column forms and interconnection thereof by the beam forms. Novel provisions are made, by means of walers and tensioned steel bands, for initially compressing opposed side walls of the forms to concave curvatures so that they are returned to essential flatness by the hydrostatic pressure of the fluid concrete.

U.S. Patent 4,757,656 to J. Powers, Jr. discloses a lintel system including a steel flange plate adapted to rest on the wall adjacent both sides of an opening to be spanned, a steel reinforcing structure integral with the flange plate and steel primary reinforcing rods welded to the reinforcing structure and extending upwardly. After the flange plate has been emplaced, two courses of masonry blocks are laid to encompass the primary reinforcing rods. Different

embodiments of the invention employ different upper structures. In a first embodiment, a wooden beam directly overlays the upper plate, and each includes apertures generally aligned with and larger than the primary reinforcing rods, each of which is threaded to receive a nut along its terminal portion such that the nuts may be tightened to compress the lintel system into a rigid structure. In the second embodiment, the lintel system also includes secondary reinforcing rods welded to the lower face of the upper plate and extending downwardly into the interior space of the masonry blocks. Upwardly directed steel studs are welded to the upper face and extend through the apertures in the beam and the top plate such that nuts may be tightened to compress the lintel system into a rigid structure. A charge of mortar is introduced into the space within the masonry block courses to envelop the portions of the reinforcing rods disposed in the space.

U.S. Patent 5,465,538 to J. Powers, Jr. discloses a prefabricated lintel having two spaced apart parallel upstanding legs extending along the length of the lintel and having laterally aligned holes defined therethrough and spaced therealong. The lintel further has a flat lower surface and an upper surface defining flat, horizontal shoulders positioned along outer edges of the lintel on opposite sides of the upstanding legs and extending the length of the lintel. The lintel is placed to span a doorway and a course of blocks is laid on the flat shoulders, with a second course laid on the first course and a rebar positioned on the upper surface. A plurality of wire stirrups, each defining a rebar receiving loop, are engaged over the rebar and extend through openings in the two courses with end portions of the stirrups engaged in each of the holes defined in the upstanding legs of the lintel. The block openings are filled with grout.

U.S. Patent 6,367,209 to J. Powers, Jr. discloses a box lintel including an elongated, hollow metal form with a lower wall, integrally formed side walls extending upwardly therefrom, and integrally formed partial upper walls extending inwardly from the side walls. A method of fabricating a box lintel is also disclosed which includes the steps of providing an

elongated flat sheet of metal and bending the flat sheet of metal into a hollow metal form with a lower wall, integrally formed side walls extending upwardly therefrom, and integrally formed partial upper walls extending inwardly from the side walls. The form is adapted to be positioned on upright masonry supports so as to span an opening and to be filled with grout/mortar and to receive one or more courses of masonry bricks on the upper walls.

U.S. Patent 6,560,938 to J. Powers, Jr. discloses a box lintel including an elongated, hollow metal form with a lower wall, integrally formed side walls extending upwardly therefrom, and integrally formed partial upper walls extending inwardly from the side walls. A method of fabricating a box lintel is also disclosed which includes the steps of providing an elongated flat sheet of metal and bending the flat sheet of metal into a hollow metal form with a lower wall, integrally formed side walls extending upwardly therefrom, and integrally formed partial upper walls extending inwardly from the side walls. The form is adapted to be positioned on upright masonry supports so as to span an opening and to be filled with grout/mortar and to receive one or more courses of masonry bricks on the upper walls. Although the aforementioned prior art have contribute to the development of the art of lintels, none of these prior art patents have solved the need of this art.

Therefore, it is an object of the present invention to provide an improved lintel that provides an acceptable weight to load capacity.

Another object of this invention is to provide an improved lintel that provides resistance to weathering and corrosion.

Another object of this invention is to provide an improved lintel by reducing the weight of the lintel for transportation over large distances.

Another object of this invention is to provide an improved lintel that is quickly and easily installed. Another object of this invention is to provide an improved method for supporting a load

above an opening.

The foregoing has outlined some of the more pertinent objects of the present invention. These objects should be construed as being merely illustrative of some of the more prominent features and applications of the invention. Many other beneficial results can be obtained by modifying the invention within the scope of the invention. Accordingly other objects in a full understanding of the invention may be had by referring to the summary of the invention and the detailed description describing the preferred embodiment of the invention.

SUMMARY OF THE INVENTION

A specific embodiment of the present invention is shown in the attached drawings. For the purpose of summarizing the invention, the invention relates to an improved lintel for supporting a course of blocks with a binder above an opening. The opening is defined between a first supporting surface and a second supporting surface. The course of blocks include a first bearing portion and a second bearing portion.

The lintel comprises an elongated base having a first end and a second end for extending between the first supporting surface and the second supporting surface. The elongated base has a top portion and a bottom portion, a first side and a second side. A riser extends from the top portion of the elongated base for increasing the load capacity of the lintel. A first dam extends upwardly from the first side of the elongated base for pooling the binder adjacent to the first dam. A second dam extends upwardly from the second side of the elongated base for pooling the binder adjacent to the second dam. The first and second bearing portions of the course of blocks are positioned above the first and second dams with the pooled binder supporting the first and second bearing portions of the course of blocks. hi a more specific embodiment of the invention, the binder includes a mortar and the course of blocks include masonry blocks. The base, riser, first dam and second dam are formed from a single metallic material. Alternatively, the base, riser, first dam and second dam are formed from a single polymeric material. The riser includes a textured surface for increasing the bonding strength between the grout and the lintel.

In one embodiment of the invention, the riser includes a first and a second riser extending from the top side of said elongated base. The first and second risers are disposed in a spaced apart parallel relationship between the first and second dams for increasing the load capacity of the lintel.

In another embodiment of the invention, the riser has a proximal end and a distal end. The proximal end is secured to the top portion of the elongated base. The distal end includes an enlarged flange for increasing the load capacity of the lintel. The enlarged flange includes either a generally triangular cross-section, generally circular cross-section, generally square cross- section, generally V-shape cross-section, generally rhombus shape cross-section, or generally V- shaped bottom portion and a semi-circle upper portion intersecting the V-shaped bottom portion.

In another embodiment of the invention, a first guide riser and a second guide riser extends from the top portion of the elongated base for aligning the course of blocks on the lintel. In one example of the invention, a plurality of hangers extend between the first and second risers for supporting a reinforcement bar disposed in a parallel relationship between the first and second risers for increasing the load capacity of the lintel. The reinforcement bar terminates upon the first end of the elongated base, or extends beyond the first end of the elongated base, or the reinforcement bar has a horizontal portion and a vertical portion having the horizontal portion positioned upon the plurality of hangers and the vertical portion secured to the first supporting surface.

The invention is also incorporated into the method of providing an elongated base having a first end and a second end with a first and a second dam extending upwardly from a first and a second side of the elongated base. The first and second ends of the base are positioned on the first and second supporting surfaces. The binder is positioned adjacent to the first and second dams. The first and second bearing portions of a first course of blocks are positioned above the first and second dams with the pooled binder supporting the first and second bearing portions of the first course of blocks.

In a further method incorporated into the invention, the first course of blocks are filled with grout. A second or more courses of blocks with a binder are positioned above the first

course of blocks. The second or more courses of blocks may be filled with grout or other material.

The foregoing has outlined rather broadly the more pertinent and important features of the present invention in order that the detailed description that follows may be better understood so that the present contribution to the art can be more fully appreciated. Additional features of the invention will be described hereinafter which form the subject matter of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description taken in connection with the accompanying drawings > in which:

FIG. 1 is an isometric view of a lintel for supporting a course of blocks with a binder above an opening incorporating the present invention;

FIG. 2 is a sectional view along line 2-2 in FIG. 1;

FIG. 3 is an isometric view of the lintel without the course of blocks with a binder; FIG. 4 is a top isometric view of the course of blocks;

FIG. 5 is a bottom isometric view of the course of blocks;

FIG. 6 is a sectional view of a second embodiment of the lintel with an enlarged flange having a generally triangular cross-section;

FIG. 7 is a sectional view similar to FIG. 6 with the enlarged flange having a generally circular cross-section;

FIG. 8 is a sectional view similar to FIG. 6 with the enlarged flange having a generally square cross-section;

FIG. 9 is a sectional view similar to FIG. 6 with the enlarged flange having a generally V-shape circular cross-section; FIG. 10 is a sectional view similar to FIG. 6 with the enlarged flange having a generally rhombus cross-section;

FIG. 11 is a sectional view similar to FIG. 7 with the enlarged flange having a generally V-shape bottom portion and a semi-circle upper portion;

FIG. 12 is a sectional view of a third embodiment of the lintel with a first and second guide riser;

FIG. 13 is a sectional view similar to FIG. 12 with a first and second riser;

FIG. 14 is a sectional view similar to FIG. 12 with the enlarged flange having a generally triangular cross-section;

FIG. 15 is a sectional view similar to FIG. 2 with a plurality of hangers supporting a reinforcement bar;

FIG. 16 is an isometric view of FIG. 15;

FIG. 17 is an isometric view similar to FIG. 15 with the reinforcement bar extending beyond the lintel;

FIG. 18 is a an isometric view similar to FIG. 15 with the reinforcement bar having a horizontal portion and a vertical portion;

FIG. 19 is an isometric view of the lintel positioned on a first and second surface;

FIG. 20 is an isometric view similar to FIG. 19 with the course of blocks positioned on the lintel;

FIG. 21 is an isometric view similar to FIG. 19 with a binder filling the course of blocks; and

FIG. 22 is an isometric view similar to FIG. 19 with the binder completely filling the course of blocks.

Similar reference characters refer to similar parts throughout the several Figures of the drawings.

DETAILED DISCUSSION

FIG. 1 is an isometric view of the improved invention 10 located within a conventional masonry wall 12. The wall 12 comprises a footer 14 for supporting the wall 12. The wall 12 is erected in a conventional fashion with mortar 16, grout 18 and reinforcement as required. The wall 12 includes an opening 20 which may be representative of a doorway or window in the building structure. The opening 20 is defined between a first supporting surface 22 and a second supporting surface 24. A lintel 26 incorporating the improved invention 10 spans the opening 20 for supporting a course of blocks 28 with a binder 30. FIG. 2 is a sectional view along line 2-2 in FIG. 1 of one of the course of blocks 28 and the lintel 26. The course of blocks 28 include a first bearing portion 32 and a second bearing portion 34. The lintel 26 comprises an elongated base 36 having a top portion 38 and a bottom portion 40, a first side 42 and a second side 44. A riser 46 extends from the top portion 38 of the elongated base 36 for increasing the load capacity of the lintel 26. A first dam 48 extends upwardly from the first side 42 of the elongated base 36 for pooling the binder 30 adjacent to the first dam 48. A second dam 50 extends upwardly from the second side 44 of the elongated base 36 for pooling the binder 30 adjacent to the second dam 50.

The first and second bearing portions 32 and 34 of the course of blocks 28 are positioned above the first and second dams 48 and 50 respectively, with the pooled binder 30 supporting the first and second bearing portions 32 and 34 of the course of blocks 28. The binder 30 may include conventional mortar or other similar material.

Upon placement of the course of blocks 28 on the lintel 26, the elongated base 36 and first and second dam 48 and 50 are in tension. The riser 46 has a portion in tension and a portion under compression. The riser 46 may contain the texture surface 66

including a series of grooves 67. The grooves 67 provide additional surface area for the grout 18 to bond to the lintel 26.

The cells 72 are filled with grout 18 to encase the lintel 26. After the grout has cured and a load is placed upon the lintel 26, the riser 46 is placed under a tensile force. The grooves 67 prevent movement of the riser 46 relative to the grout 18 when a tensile force is applied to the lintel 26.

FIG. 3 is an isometric view of the lintel 26. The elongated base 36 of the lintel 26 has a first end 54 and a second end 56 for extending between the first supporting surface 22 and the second supporting surface 24 of the wall 12. The riser may include a first and a second riser 58 and 60 respectively, extending from the top portion 38 of the elongated base 36. The first and second risers 58 and 60 are disposed in a spaced apart parallel relationship between said first and second dams 48 and 50 for increasing the load capacity of the lintel.

The base 36, riser 46, first dam 48 and second dam 50 may be formed from a single metallic material 62 by a continuous progressive cold rolling process, casting or other metal working process. Alternatively the base 36, riser 46, first dam 48 and second dam 50 may be formed from a single polymeric material 64 by injection molding, extrusion or other polymeric working process.

FIGS. 4 and 5 are top and bottom isometric views of one of the course of blocks 28. The course of blocks may include masonry blocks 68. The masonry blocks 68 contain a channel 70 such that the masonry blocks 68 may arch over the riser 46. The masonry blocks 68 further contain a plurality of cells 72 for permitting grout to traverse through the masonry blocks 68. Alternatively, the masonry blocks 68 may include a knockout web bond beam stretcher unit. FIGS. 6 - 11 illustrate a second embodiment for the improved invention 10. The

riser has a proximal end 74 and a distal end 76. The proximal end 74 is secured to the top portion 38 of the elongated base 36. The distal end includes an enlarged flange 78 for increasing the load capacity of the lintel 26. Upon placement of the course of blocks 28 on the lintel 26, the elongated base 36 and first and second dam 48 and 50 will be in tension. The riser have a portion in tension and a portion under compression. The enlarged flange 78 is in compression. The enlarged flange 78 may contain the texture surface 66 including a series of grooves 67. The grooves 67 provide additional surface area for the grout 18 to bond to the lintel 26.

The cells 72 are filled with grout 18 to encase the lintel 26 and enlarged flange 78. After the grout has cured and a load is placed upon the lintel 26, the enlarged flange 78 is placed under a tensile force. The grooves 67 prevent movement of the enlarged flange 78 relative to the grout 18 when a tensile force is applied to the lintel 26.

FIG. 6 is a sectional view of one of the course of blocks 28 and the lintel 26. The enlarged flange 78 includes a generally triangular cross-section 80 for increasing the load capacity of the lintel 26. The triangular cross-section 80 contains a triangular cavity 82 that is sealed to prohibit any grout from entering the triangular cavity 82.

FIG. 7 is a sectional view of one of the course of blocks 28 and the lintel 26. The enlarged flange 78 includes a generally circular cross-section 84 for increasing the load capacity of the lintel 26. The circular cross-section 84 contains a circular cavity 86 that is sealed to prohibit any grout from entering the circular cavity 86.

FIG. 8 is a sectional view of one of the course of blocks 28 and the lintel 26. The enlarged flange 78 includes a generally square cross-section 88 for increasing the load capacity of the lintel 26. The square cross-section 88 contains a square cavity 90 that is sealed to prohibit any grout from entering the square cavity 90. FIG. 9 is a sectional view of one of the course of blocks 28 and the lintel 26. The

enlarged flange 78 includes a generally V-shape cross-section 92 for increasing the load capacity of the lintel 26.

FIG. 10 is a sectional view of one of the course of blocks 28 and the lintel 26. The enlarged flange 78 includes a generally rhombus cross-section 94 for increasing the load capacity of the lintel 26. The rhombus cross-section 94 contains a rhombus cavity 96 that is sealed to prohibit any grout from entering the rhombus cavity 96.

FIG. 11 is a sectional view of one of the course of blocks 28 and the lintel 26. The enlarged flange 78 includes a generally V-shaped bottom portion 98 and a semi-circle upper portion 100 intersecting the V-shaped bottom portion 98 for increasing the load capacity of the lintel 26. The intersecting V-shaped bottom portion 98 and semi-circle upper portion

100 forms a void 102 that is sealed to prohibit any grout from entering the void 102.

FIGS. 12 - 14 illustrate a third embodiment for the improved invention 10. A first guide riser 104 and a second guide riser 106 extend from the top portion 38 of the elongated base 36. The first and second guide risers 104 and 106 are disposed in a spaced apart parallel relationship between the first and second dams 48 and 50 for aligning the course of blocks 28 on the lintel 26. The first and second guide risers 104 and 106 are centered in relation to the width of the elongated base 26. The distance between the first and second guide risers 104 and 106 is commensurate with the width of the cell 72 such that upon placing the course of blocks 28 upon the lintel 26, the first and second guide risers 104 and 106 extend into the cell 72 to prevent horizontal movement of the course of blocks 28 relative to the lintel 26.

FIG. 12 is a sectional view of one of the course of blocks 28 and the lintel 26. In

FIG. 12 the first and second guide risers 104 and 106 are disposed with a single riser 46.

In FIG. 13 the first and second guide risers 104 and 106 are disposed with first and second risers 58 and 60. FIG. 14 illustrates the first and second guide risers 104 and 106 disposed

a single riser 46 having an enlarged flange 78 including a generally triangular cross-section 80.

FIGS. 15 - 18 illustrate the improved invention 10 incorporating a reinforcing system 108 to increase the tensile strength of the lintel 26. FIG. 15 is a sectional view of one of the course of blocks 28 and the lintel 26 incorporating the reinforcing system 108. The reinforcement system 108 includes a plurality of hangers 110 extending between the first and second risers 58 and 60. The plurality of hangers 110 are secured to the first and second risers 58 and 60 by a first and second clip 112 and 114 slidably engaging the distal ends 76 of the first and second risers 58 and 60 respectively. A cradle 116 supports a reinforcement bar 118 disposed in a parallel relationship between said first and second risers for increasing the load capacity of the lintel. The plurality of hangers 110 may be formed from a single metallic material 62 by a continuous progressive cold rolling process, casting or other metal working process. Alternatively the plurality of hangers 110 may be formed from a single polymeric material 64 by injection molding, extrusion or other polymeric working process.

The reinforcement bar 118 includes bar grooves 119 to provide additional surface area for the grout 18 to bond to the reinforcement bar 118. The cells 72 are filled with grout 18 to encase the lintel 26, risers 58 and 60 and reinforcing system 108. After the grout has cured and a load is placed upon the lintel 26, the reinforcement bar 118 is placed under a tensile force. The bar grooves 119 prevent movement of the bar grooves 119 relative to the grout 18 when a tensile force is applied to the lintel 26. The reinforcement bar 119 may be constructed from steel or other rigid material. The reinforcement bar 119 may include an epoxy coating for preventing corrosion of the reinforcement bar 119.

FIGS. 16 - 18 are isometric views of the first end 54 of the lintel 26 positioned on the first supporting surface 22. One of the course of blocks 28 is positioned upon the lintel

26. Preferably the course of blocks 28 are positioned to align the cells 72 of the course of blocks 28 with the cells 72 of the masonry wall 12.

In FIG. 16 the reinforcement bar 118 terminates at the first end 54 to restrict the reinforcement system 108 to the lintel 26. When the grout 18 has cured within the cells 72 and about the lintel 26 and reinforcement system 108, the course blocks 28, lintel 26 and reinforcement system 108 becomes an integral unit.

In FIGS. 17 and 18 the reinforcement bar 118 extends beyond the first end 54 to expand the reinforcement system 108 from the lintel 26 to the adjacent masonry wall 12.

FIG. 17 illustrates the reinforcement bar 118 horizontally extending into the adjacent masonry wall 12. When the grout 18 has cured within the cells 72 and about the lintel 26 and reinforcement system 108, the course blocks 28, lintel 26, reinforcement system 108 and masonry wall 12 becomes an integral unit.

FIG. 18 illustrates the reinforcement bar 118 both horizontally and vertically extending into the adjacent masonry wall 12. The reinforcement bar includes a horizontal portion 120 and a vertical portion 122. The horizontal portion 120 is supported by the plurality of hangers 110. The vertical portion 122 is inserted into the cell 72 immediately adjacent the first end 54. A coupling bar 124 having a generally 90 degree arch spans between the horizontal portion 120 and vertical portion 122. A plurality of wire ties 126 secure the coupling bar 124 to both the horizontal portion 120 and the vertical portion 122. When the grout 18 has cured within the cells 72 and about the lintel 26 and reinforcement system 108, the course blocks 28, lintel 26, reinforcement system 108 and masonry wall 12 becomes an integral unit.

FIGS. 19 - 22 demonstrate the method of using the lintel 26 for supporting the course of blocks 28 with a binder 30 above the opening 20. In FIG. 19 the lintel 26 is positioned between the two masonry walls 12. To position the lintel 26 over the opening

20, the first and second ends 54 and 56 are positioned on the first and second supporting surfaces 22 and 24. Before positioning the lintel 26 to the masonry wall 12, a bed of mortar 16 may be applied to the first and second supporting surfaces 22 and 24.

Preferably, the length of the lintel 26 is such that the first and second ends 54 and 56 engages with one (1) to six (6) inches of the first and second supporting surfaces 22 and 24.

The lintel 26 may be secured to the first and second supporting surfaces 22 and 24 by a plurality of screws, rivets or other similar fastening devices traversing through the elongated base 36 and into the masonry wall 12. In some instances where the lintel 26 is required to span a larger opening 20, a plurality of pole-jacks 128 may be utilized to support the lintel 26 until construction is complete. With the lintel securely located on the first and second supporting surfaces 22, and 24, a binder 30 is positioned adjacent to the first and second dams 48 and 50. The positioning the binder 30 may be accomplished by a trowel or the other similar tool. The binder 30 may include mortar 16 or other similar material. FIG. 20 illustrates the positioning of the first and second bearing portions 32 and 34 of the course of blocks 28 above the first and second dams 48 and 50 with the pooled binder 30 supporting the first and second bearing portions 32 and 34 of the course of blocks 28. Binder 30 is also positioned between the course of blocks 28.

FIG. 21 illustrates the course of blocks 28 positioned along the entire length of the lintel 26. A shoot 130 positions the grout 18 over the course of blocks 28. The grout 18 is poured into the cells 72 until the lintel 26, risers 58 and 60 and reinforcing system 108 are encased and the cells 72 are filled with grout 18. When the grout 18 has cured within the cells 72 and about the lintel 26 and reinforcement system 108, the course blocks 28, lintel 26, reinforcement system 108 become an integral unit. FIG. 22 illustrates the grout 18 cured within the cells 72 and about the lintel 26 and

reinforcement system 108. The additional support supplied by the pole-jacks 128 may now be removed from beneath the lintel 26. If necessary a second course of blocks 132 may be positioned above the course of blocks 28 with a binder 30.

Although the invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention.