Method of making patio chairs with metal slats

A metal patio chair has a seat frame made by the steps of providing a pair of seat rails in the form of elongated metal tubes, placing a mandrel inside each tube to reinforce the wall of the tube, punching a series of spaced apart holes in the wall of the tube while the mandrel contained in the tube holds the shape of the tube while punching out the holes, removing the mandrel, providing a plurality of metal slats having a cross-sectional shape to match the shape of the holes punched in the seat rail tubes, inserting ends of the metal slats in corresponding pairs of holes formed in the tubes to form a ladder type chair frame in which opposite ends of the slats are held captive in corresponding holes in the tubes, and are rigidly securing the slats to the seat rail tubes to lock the slats in palce in the tubes to provide a rigid seat frame structure elevated above the ground by a supporting sub-structure to which the finished seat frame is attached.

FIELD OF THE INVENTION 
This invention relates generally to outdoor patio furniture, and more 
particularly, to a method for making patio chairs with metal slats. 
BACKGROUND OF THE INVENTION 
Outdoor patio furniture manufacturers are constantly seeking to develop new 
product designs and new ideas for reducing manufacturing costs and time. 
Patio furniture can be custom made or manufactured in relatively low 
quantities from wrought iron or wood. The more traditional patio furniture 
is mass produced in many attractive and distinctive designs and color 
combinations. Typical of these designs are the casual outdoor furniture 
products made from welded tubular aluminum framing with a tough baked 
enamel finish and seating of vinyl lacing or nylon. The outdoor furniture 
of this type is durable for full time outdoor use. 
Certain outdoor furniture designs are more easily manufactured from one 
type of material than another. For example, outdoor patio furniture made 
of wood can have the seating surfaces and chair backs made of spaced 
apart, horizontal slats in a ladder type of frame design. These types of 
chairs are also reasonably easy to manufacture in cheap plastic outdoor 
patio chair designs. 
It would be desirable to manufacture patio chairs with seating surfaces in 
a ladder frame style with metal slats so that these chairs can have 
attractive designs that look somewhat like slatted patio furniture made of 
wood. However, fabrication and assembly techniques common to the 
manufacture of metal patio furniture cannot be used to make slatted metal 
patio furniture if these techniques result in designs which are not 
pleasing aesthetically. For instance, visible welds used to fasten the 
slats to the chair rails are undesirable. Large wide open and visible 
slots for holding the slats in the chair rails also are undesirable. In 
addition, the techniques used for manufacturing slatted metal patio 
furniture must be adaptable to mass production techniques at reasonably 
low cost and assembly time. 
The present invention provides techniques for manufacturing patio chairs in 
a ladder frame style with metal slats which allows these chairs to be made 
in attractive designs having the appearance of slatted patio chairs made 
of wood. Metal patio chairs made from this method can be manufactured in 
attractive designs with low manufacturing costs and time. A significant 
advantage is that the chair avoids the problems of similar patio chairs 
made of wood which are prone to weathering and lack the same level of 
strength and durability for full-time outdoor use. The chair of this 
invention is particularly useful in withstanding high volume use, such as 
in hotels and motels, where the chairs are subject to abuse and are needed 
for full-time outdoor use. 
SUMMARY OF THE INVENTION 
Briefly, one embodiment of this invention comprises a method for making 
patio chairs in which a seat frame of the chair has metal slats assembled 
into a rigid seat frame unit by a method which includes the steps of 
providing a pair of seat rails in the form of elongated metal tubes, 
placing a mandrel inside each tube to reinforce the wall of the tube, 
punching a series of longitudinally spaced apart holes in the wall of each 
tube while the mandrel contained in the tube holds the shape of the tube 
when punching the holes, followed by removing the mandrel from each tube. 
A plurality of metal slats having a cross-sectional shape to match the 
shape of the holes punched into the seat rail tubes are inserted into 
corresponding pairs of holes formed in a pair of parallel seat rail tubes. 
This forms a ladder-type frame in which opposite ends of the slats are 
held captive in corresponding holes in the seat rail tubes. The captive 
slats are rigidly secured to the seat rail tubes, preferably by welding 
certain slots to the side tubes, to lock the slats in place in the tubes 
and thereby provide a rigid seat frame structure elevated above the ground 
by a supporting sub-structure to which the finished seat frame is 
attached. 
In one form of the invention, the pair of seat rail tubes can be bent into 
a uniform generally L-shaped configuration of the seat frame to form a 
lower seat section and an upper backrest section of the seat frame. Slats 
in the seat portion of the frame are rigidly affixed to the seat rail 
tubes by welding the ends of the slats to the tubes, preferably underneath 
the seat frame section so that the welds are not visible. At least one of 
the slats on the upright backrest section is welded at opposite ends to 
the seat rail tubes to provide rigidity to the frame for locking all other 
slats in the seat frame, whether or not the slats are welded to the side 
rail tubes. Preferably, the slat welded to the backrest tube sections is 
welded inside the tubes so the welds are not visible. The welded slats act 
as rigid stretcher bars to provide a rigid seat frame structure. 
Thus, the slatted chair frame can be made entirely of metal, preferably a 
durable, light weight metal such as aluminum. The mandrel used in forming 
the holes for the slats reinforces the wall of the tubing so it does not 
collapse when punching the holes in the tubes. The slats are readily 
assembled in the holes and welded to the tubes to form the rigid chair 
frame structure. The individual holes for the slats and the hidden welds 
enhance the aesthetic appearance and design features of the chair. 
These and other aspects of the invention are more fully understood by 
referring to the following detailed description and the accompanying 
drawings.

DETAILED DESCRIPTION 
Referring to the drawings, FIG. 1 is a perspective illustrating a metal 
patio chair 10 according to principles of this invention. The chair 10 
includes a generally L-shaped seat frame 12 made of metal parts assembled 
and welded together as a rigid unit. The seat frame includes left and 
right tubular seat rails 14 and 16 extending parallel to one another along 
the left and right sides of the seat frame, respectively. The tubular seat 
rail tubes are made of metal, preferably aluminum. The seat frame further 
includes a series of parallel, spaced apart, elongated metal slats 18 
spanning the distance between the left and right seat rails along the 
length of the seat frame. The metal slats extend perpendicularly to the 
seat rails and the slats are preferably relatively wide in the plane of 
the left and right seat rails while being spaced apart by narrow parallel 
spaces 19 along the length of the seat frame. The ends of the metal slats 
are held captive in corresponding spaced apart holes along the length of 
the seat rail tubes. Certain slats are placed in the holes and welded to 
the tubes as described in more detail below. The slats cooperate with the 
seat rail tubes to which they are rigidly attached to form a rigid seat 
frame structure. The slats each have a uniform, slightly concave 
curvature, and in one embodiment, all slats are the same size and shape, 
have the same length, and are spaced apart with a uniform spacing along 
the length of the seat frame. The metal slats in the finished seat frame 
provide a generally horizontal seat surface 20 and an upright and 
generally rearwardly inclined backrest surface 22. 
The seat frame 12 is elevated above the ground by left and right seat 
supports 24 and 26 rigidly affixed to the left and right sides of the seat 
frame, respectively. Although the design configuration of the seat support 
means can vary, in the illustrated embodiment the seat supports comprise 
metal support members in a composite configuration formed in an 
"hourglass" shape. In this embodiment, the left support member 24 includes 
a first angular section 28 extending upwardly and rearwardly from a first 
ground-engaging end 30 to a first reverse bend 32 which leads to a 
horizontal intermediate section 34 extending forwardly from the first 
reverse bend adjacent the seat frame to provide a left armrest. A second 
reverse bend 36 extends from the front end of the horizontal left armrest 
section and leads to a second angular section 40 extending downwardly and 
rearwardly at a second angle, terminating at a second ground-engaging end 
42. The angular members 28 and 40 intersect at a point of intersection 44 
spaced above the ground and in an elevation below the seat frame seat 
support surface 20. The structural members of the left seat support are 
welded together at the point of intersection 44 to provide a rigid left 
seat support structure. 
The right seat support 26 (shown best in FIG. 2) is of similar composite 
configuration having sections which include an angular first section 46 
extending upwardly and rearwardly from a first ground-engaging end 48 
along a first angle to a first reverse bend 50 which leads to a right 
horizontal armrest section 52 extending forwardly to a second reverse bend 
53 which continues into a second angular section 54 extending downwardly 
and rearwardly at a second angle, terminating at a second ground-engaging 
end 56. The angular members 46 and 54 intersect at 58 at the elevation of 
intersection 44, and the right structural members are welded together at 
the intersection 58 to form a rigid right seat support structure. 
The lateral spacing between the left and right support members is 
maintained by an elongated rigid spreader bar 60 welded at its ends to the 
intersection points 44 and 58 of the left and right support frames. 
The metal slats 18 rigidly affixed to the seat rails, particularly in the 
seat surface section 20 of the seat frame, provide further stretcher bars 
for adding rigidity to the chair frame structure. 
The back section 22 of the seat frame is rigidly connected to the left and 
right seat support frames 24 and 26 by separate welds at 62 for rigidly 
affixing the left and right seat rail tubes to the angular sections 28 and 
46 of the left and right support frame members, respectively. In addition, 
separate welds 64 rigidly affix front portions of the seat rails 14 and 16 
of the seat frame to the sides of the angular members 40 and 54 of the 
left and right support members. 
Although the shape of the metal structural members can vary, and the 
dimensions and arrangements of the structural members also can vary, the 
following description details the preferred structural configuration of 
the chair 10. The preferred seat rail tubes 14 and 16 are made of aluminum 
extrusions which have been rolled into a tube and electronically welded by 
a lengthwise seam 65 shown in FIG. 6. The tubes are preferably 7/8 inch in 
diameter, and the wall of the tube is preferably 0.062 inch thick. The 
preferred configuration of the seat rail tubes is shown in FIGS. 5 and 6. 
Left seat rail tube 14 is shown in FIGS. 5 and 6; right seat rail tube 16 
is identical. A plurality of separate and independent and preferably 
uniformly spaced apart elongated holes 66 are formed along the length of 
each tube. The holes 66 are preferably of uniform shape and have an 
elongated form with straight sides and curved ends shown best in FIG. 5. 
The long dimension of the holes is parallel to the length of the tube. In 
the preferred embodiment, each hole is preferably 1.82 inches long, with a 
width of about 0.375 inch. The preferred spacing between holes is about 
0.75 inch between the ends of adjacent holes. The holes are aligned on a 
common axis and are formed along one side only of the tube. 
The preferred technique for forming the holes 66 in each tube is as 
follows. A mandrel (not shown) with an outside diameter that matches the 
inside diameter of the tube is placed inside the tube so that the mandrel 
provides support for the inside diameter of the tube circumferentially 
along the inside surface of the tube. The mandrel has a series of voids 
spaced apart along its length and matching the size, shape and spacing of 
the holes 66 to be formed in the tube. Each hole 66 is then punched in the 
wall of the tube with a separate die (not shown) that matches the shape of 
the holes 66. The dies are punched into the void spaces of the mandrel to 
form the holes while the remaining structure of the mandrel supports the 
wall of the tube to prevent it from collapsing as the holes are punched in 
the tube. The slugs remaining after the die punch step are then removed 
from the void spaces to provide a tube with spaced apart holes aligned on 
a common axis as shown best in FIGS. 3 and 5. Conventional mandrel type 
pierce tooling can be used to position multiple dies for punching the 
slotted holes in the tubing in a single step. 
The metal slats 18 are preferably made of tubular aluminum extrusions with 
a narrow profile cross-section shown best at FIG. 8. The preferred tubular 
aluminum slats normally have a width (long dimension) of about 1.812 
inches, a thickness or narrow dimension of about 0.375 inch, an exterior 
radius of about 0.1875 inch at each end, and a wall thickness of about 
0.062 inch. Each slat is preferably roll formed along its length to a 
shallow curved configuration shown best in FIG. 4. The length of the slats 
can vary with the width of the seat frame seating surface, and in one 
embodiment, the slats are cut to a uniform length of about twenty inches 
each. 
Continuing further with the preferred technique of manufacturing the chair, 
the curved slats 18 are next placed in corresponding holes 66 within a 
pair of straight, parallel seat tubes 14 and 16 to form a ladder type 
frame with the slats extending parallel to one another along the length of 
the straight seat rail tubes. The slats are positioned in the holes so 
that the ends of the slats extend into the holes and abut against the 
inside of each tube on the side of the tube opposite from each hole. This 
is shown best in FIG. 4. Further, the slats are arranged uniformly along 
the length of the tubes with the curved configurations of the slats being 
aligned uniformly along the length of the frame to form a uniform concave 
curvature of the slats between the seat rail tubes. After the slats are 
positioned in the seat rail tubes, the ladder type structure is placed in 
a former (not shown) to press form the seat rails into the generally 
L-shaped contour of the seat frame best illustrated in FIGS. 2 and 3. 
After the seat frame is formed in its L-shaped configuration, certain of 
the slats are then welded to the tubes to form a rigid chair frame 
structure. It is desirable to provide exterior welds 68 (shown in FIG. 7) 
for rigidly affixing each end of certain slats to their corresponding seat 
rail tubes. However, for aesthetic and design purposes, it is desirable 
that none of the exterior welds be visible in the finished chair. 
Therefore, in a preferred embodiment, the exterior welds shown in FIG. 7 
are used only on the undersides of the slats in the seat surface portion 
20 of the chair frame, for rigidly affixing each of the slats in the 
seating portion of the frame to the horizontal seat rail tubes of the 
L-shaped frame structure. Preferably, the uppermost slat (shown at 18a in 
FIGS. 2 and 3) on the upright chair back portion of the frame is welded to 
the inside of the seat rail tubes by welds 70 shown in FIG. 4. This 
welding step is carried out by removing the end caps 71 at the top of the 
seat rail tubes to expose the insides of the tubes and then welding the 
ends of the uppermost slat to the inside walls of the tubes. Welding the 
uppermost slat and the seat surface slats to the side tubes ties the 
entire structure together as a rigid unit. The remaining slats in the seat 
back portion of the chair frame (shown at 18b) need not be welded to the 
side tubes. The slats which are not welded are pinched at their ends to 
the inside walls of the tubes when the other welds are completed on the 
other slats, and this locks the unwelded slats in place in the seat frame 
as a rigid unit. The unwelded slats are held tightly in and between the 
seat rail tubes rigidly with essentially no movement relative to the 
tubes, while the welded slats provide stretcher bars that provide good 
rigidity for the entire chair frame structure. 
Thus, the invention provides an outdoor patio chair made entirely of metal 
parts without additional fasteners for holding the structural members 
together. The all-metal chair lasts longer than other chairs made of 
plastic or wood and avoids the use of fabrics or the like which do not 
have the same weathering capacity as the all-metal chair. The invention is 
particularly useful for high volume uses because of its sturdy and 
weatherable properties. The invention also is highly design oriented 
because it can be made in designs to simulate a chair with wooden slats 
without the problems of wood frame chairs. In addition, the technique for 
making the chair frame makes it possible to construct the chair from light 
weight aluminum, and further design characteristics are enhanced because 
the welds at the ends of the slats are not visible in the finished chair.