A gutter protector formed of a flexible open cell porous foam has at least one undulated bottom surface. The undulations of the bottom surface may be ridges defining generally parallel channels to direct water through the gutter passageway. Optionally, undulations may be provided on one side surface. Such undulations on the side surface may be ridges or other convolute cut projections that are compressible and help to secure the gutter protector under compression within the gutter passageway.

CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application Nos. 60/943,751, filed Jun. 13, 2007 and 60/945,654, filed Jun. 22, 2007. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to rain gutters for houses or the like. More particularly, the present invention concerns a porous structure that is in inserted within a rain gutter to prevent the gutter from blocking or clogging with debris, such as leaves or other foreign materials. 
     BACKGROUND OF THE INVENTION 
     Rain gutters are commonly installed along the lower edges of a sloping roof under the eaves to catch water draining from the roof. Such gutters can become clogged with debris, such as leaves, twigs, seeds and pods, carried to the roof by wind or gravity and washed into the gutter. This debris fills and clogs the gutters and the gutter downspouts, causing water to overflow out of the gutters and over the eaves. 
     Many devices have been proposed to prevent gutters from clogging. One type of device mounts a screen or cover to the open, upper portion of the gutter. Such screens or covers are intended to permit water to flow through, while at the same time catching the debris. Unfortunately, over a period of time, the leaves and foreign matter collect on the devices and disrupt, divert or prevent water from flowing through the device into the gutter. Consequently, screen-type devices require periodic cleaning or maintenance to ensure proper operation. 
     Foam filters for gutter systems have been disclosed. U.S. Pat. No. 7,208,081 shows a gutter foam filter formed from columns of open-pore polyether foam, where the columns have a cross sectional shape of a truncated triangle. The columns are held within the gutter underneath a series of gutter spikes. Such foam must be cut to fit gutters of varying width. 
     U.S. Pat. No. 4,949,514 concerns a gutter liner formed from solid porous material, such as a reticulated porous polyurethane foam. A flat panel of the porous material is folded into an inverted “U”-shape to define a water channel between the two legs of the inverted “U”. Undulations are formed on the top barrier surface. Ridges may be formed on the outer side surfaces of the liner to engage the side walls of the gutter. When installed within a gutter, such liner structure generally includes a spacer means to keep the side walls of the inverted “U”-shape separate from one another to define the water channel. 
     Improvements to foam gutter protectors continue to be sought. 
     SUMMARY OF THE INVENTION 
     In a first aspect, a gutter protector is formed form a flexible, elongated, open pore foam member having a generally flat top surface, a sloped side surface, an undulated side surface opposite to the sloped side surface and an undulated bottom surface. The undulated bottom surface has a series of ridges having a peak-to-valley ratio between about 1.1:1 and 4.0:1. The undulated side surface has a series of ridges having a peak-to-valley ratio between about 1.1:1 and 1.6:1. Preferably, the foam member is formed from a reticulated foam with a pore size or pore count of about 5 to 15 pores per inch and a density in the range of about 1.0 to 3.5 pounds per cubic foot. Liquid fire retardants, anti-microbial agents and UV inhibitors may be incorporated into or applied to the foam forming the gutter protector. 
     In a second aspect, an alternative gutter protector is formed from a flexible, elongated, open pore foam member having a generally flat top surface, a sloped side surface and an undulated bottom surface. The side surface opposite to the sloped side surface in this alternative embodiment is generally flat and generally perpendicular to the top surface. 
     In a third aspect, a gutter system comprises a gutter protector installed within a gutter passageway. When so installed, the undulated bottom surface of the gutter protector is in contact with a bottom inner surface of the passageway of said gutter, and the spaces between the undulations or ridges define channels for water or other liquid to flow through. When so installed, the undulated side surface of the first embodiment of the gutter protector has a series of ridges that are at least partially compressed when said foam member is installed within the passageway. 
    
    
     
       DESCRIPTION OF THE FIGURES 
       Numerous other objects, features and advantages of the invention shall become apparent upon reading the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a side elevational view of a gutter protector according to the invention; 
         FIG. 2  is an end view of the gutter protector of  FIG. 1  installed within a “K”-type gutter; 
         FIG. 3  is a bottom plan view of the gutter protector of  FIG. 1 ; and 
         FIG. 4  is a side elevational view of an alternative gutter protector according to the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the drawings in which like numerals designate similar elements,  FIGS. 1 and 3  show a gutter protector  10  that is formed of a flexible open cell or porous polyurethane foam. The gutter protector  10  has a substantially flat top surface  12  and a sloped side surface  14 . Opposite to the sloped side surface  14  is an undulated side surface  16 . Opposite to the top surface  12  is an undulated bottom surface  18 . 
     The undulated side surface  16  has a series of ridges  20  formed therein. The ridges  20  preferably have a peak to valley ratio in the range of 1.1:1 to 1.6:1. For example, the height of the peak as measured between the top of the peak and the valley between two adjacent peaks may be between 0.5 to 1.5 inches and the width of the gutter protector may be between 4 to 7 inches. The ridges  20  may be a series of spaced apart parallel ridges as shown in  FIG. 1 . Alternatively, the ridges on the undulated side surface  16  may be formed as convolute cut structures, sometimes referred to as “egg crate” convolute. 
     The undulated bottom surface  18  has a series of ridges  22  formed therein. The ridges  22  preferably have a high peak to valley ratio, such as between about 1.1:1 to 4.0:1. For example, the height of the peak as measured between the top of the peak  22  and the valley  25  between two adjacent peaks or ridges  22  may be between 0.5 to 2.5 inches and the height of the gutter protector from the top surface to the tip of the peak on the undulated bottom surface may be between 4 to 7 inches. The ridges  22  may be a series of spaced apart parallel ridges as shown in  FIGS. 1 and 3 . Such ridges  22  define channels  29  between the peaks  22  through which water may travel within a gutter passageway when the gutter protector  10  is installed within such gutter passageway. 
     The foam forming the gutter protector preferably is a flexible, open pore polyether polyurethane foam. Such foam may be reticulated to remove cell windows and increase the porosity and liquid permeability of such foam. Thermal or chemical reticulation methods may be used. Pore count or pore size of such foam is preferably between 5 to 15 pores per inch. Foam density is preferably between about 1.0 and 3.5 pounds per cubic foot, or between 1.4 to 3.5 pounds per cubic foot before any coating is applied. If a coating is applied, such coating may increase the density from 10% to 350%, or greater if desired. 
     Various additives may be incorporated into the foam-forming mixture. For example, one or more liquid fire retardants and anti-microbial additives may be included in situ when forming the foam. In addition, coatings may be applied to the formed foam. For example, one or more UV inhibitors, anti-microbial agents and/or liquid fire retardants may be applied to the foam. 
     Referring next to  FIG. 2 , the gutter protector  10  is installed within a gutter passageway to form the gutter system. The gutter  30  is installed in customary fashion to a roofing system. In  FIG. 2 , the gutter  30  has a gutter securing structure that is connected to sheathing  34  over a rafter  36 . The gutter securing structure is then covered by roofing shingles  38 . 
     The open pore foam permits water or other liquids that impinge on the top surface  12  to pass therethrough, while filtering or blocking debris, such as leaves or twigs, that may be carried by water along the roof. A portion of the undulated bottom surface  18  of the gutter protector  10  is generally in contact with the bottom inner surface  32  of the gutter passageway. Generally parallel water channels are defined between the ridges  22  of the bottom surface  18 , such that water or other liquids filtered through the foam of the gutter protector  10  to the bottom of the gutter passageway can flow therethrough until reaching a gutter downspout (not shown). 
     The undulations or ridges  20  on the side surface  16  are compressed to some degree to help hold the gutter protector  10  within the gutter passageway. The width of the gutter protector as measured along the top surface  12  to from the front edge adjacent the sloped side surface  14  to the top of an undulation or ridge  20  extending outwardly from the undulated side surface  16  is greater than the width of the gutter opening. In this way, the foam forming the gutter protector  10  is under some compression when installed within the gutter passageway. This helps to engage the gutter protector within the gutter passageway. 
     Referring to  FIG. 4 , an alternative embodiment of the gutter protector  10 A is configured similarly to the gutter protector  10  shown in  FIG. 1 . The undulated bottom surface  18 A has a series of ridges  22 A formed therein. The ridges  22 A preferably have a high peak to valley ratio, such as between about 1.1:1 to 4.0:1. For example, the height of the peak as measured between the top of the peak and the valley between two adjacent peaks or ridges may be between 0.5 to 2.5 inches and the height of the gutter protector from the top surface to the tip of the peak on the undulated bottom surface may be between 4 to 7 inches. Different from the gutter protector  10  shown in  FIG. 1 , however, the alternative embodiment  10 A has a smooth side surface  40  opposite to the sloped side surface  14 A. 
     While preferred embodiments of the invention have been described and illustrated here, various changes, substitutions and modifications to the described embodiments will become apparent to those of ordinary skill in the art without thereby departing from the scope and spirit of the invention.