Patent Application
20060137855
The present invention relates to a heat exchanger core window, which is brazed in place with other heat exchanger core components, and a method for making such a core window in an efficient manner. A heat exchanger including a core window made according to the present invention may be particularly advantageous for use with vehicles employing a front-end power take off.
Many industrial vehicles, such as municipal trucks, use mechanical power take off (“PTO”) devices for powering snow plows, refuse packers, cranes and utility equipment. A PTO apparatus typically uses a spinning shaft that is connected to the vehicle's powertrain in order to transfer mechanical power to a hydraulic pump, which in turn is used to control the auxiliary equipment. Front end (or front engine) power take-off (“FEPTO”) uses a shaft extending from the front of a vehicle's engine to power the hydraulic pump, whereas rear end (or rear engine) power take-off (“REPTO”) uses on a shaft emanating from the rear of the engine.
FEPTO is the lowest cost option for most PTO applications. Because of its location at the front of the engine, however, FEPTO shafts must be routed through or around a heat exchanger, such as a radiator, which also is generally located at the front of the engine. The heat exchanger may be raised so that the PTO shaft coming out of the engine runs under, rather than through, it. Alternatively, a modified hole, i.e., a “window,” may be created in the radiator cooling system through which a FEPTO shaft may pass.
The latter design, though commercially expensive, allows a larger sized cooling system to be installed with a FEPTO. Although the window reduces the overall efficiency of the heat exchanger, in some applications the additional size can create a higher performing cooling system than a system that is packaged above the FEPTO.
Prior to the present invention, creating a window for FEPTO in a heat exchanger's core was a time consuming task. First, it was necessary to weld, by hand, a separate box or boxes that redirected coolant into tubes that defined the window. This assembly was then fed into a brazing oven where the remainder of the core was attached. Because of variations in the hand welding process, the typical brazing operation did not result in a adequate seal of the window box(es) with the rest of the core. Consequently, heat exchangers manufactured to include windows for FEPTO shafts previously experienced a much higher failure rate than ordinary heat exchangers. Moreover, because each component of the window was custom made, the creation of a heat exchanger within a core window involved substantially higher costs when compared with windowless cores.
A brazed in place heat exchanger core window, suitable for use with a motor vehicle, is provided. The core window is defined by a pair of coolant redirection boxes that that are connected by coolant redirection tubes. Each of the redirection boxes includes a header and a pan. These components are press fit to each other and to a conventional heat exchanger core. The components of the coolant boxes are desirably fabricated of the same or similar types of metal as the remainder of the core assembly in order to permit the core window to be brazed in the appropriate location along with the remainder of the heat exchanger components.
In a preferred embodiment, each header of each coolant redirection box includes vertical legs that tightly overlap similar, but oppositely directed, vertical legs on each pan, and each pan further includes at least one opening that allows coolant to flow into and out of each box via redirection tubes. The boxes are press fit to each other and to the heat exchanger core, and the entire heat exchanger, including the assembled core window, is brazed in place in a single process.
This arrangement has the particular advantage that no welding of redirection boxes is required. In addition, the press fit design of the header, pan and redirection tubes, ensure that a conventional brazing process will result in an adequate seal at all junction points.
In a further embodiment, the headers include slots and guides in order to facilitate the quick and proper alignment of the core tubing to the coolant redirection boxes. By maintaining appropriate spacing between the slots and guides, the header, and therefore the entire coolant redirection box, may be quickly assembled to the remainder of the core.
In yet a further embodiment, the pan includes ferrules at each opening. The ferrules insure that the pan, when assembled to the redirection tubes, results in a tight press fit. The ferrules on the pan may overlap the redirection tubes, or, in the alternative, the ferrules may fit within the redirection tubes.
Further objects, features and advantages of the invention, will become apparent from the detailed description of the preferred embodiments that follows, when considered in conjunction with the attached figures of drawing.
Exemplary embodiments of the invention are given below with reference to the drawing, in which:
Because the heat exchanger core 1 is generally placed in an upright position with respect to the vehicle into which it is placed, coolant redirection tubes 9, 10 and heat exchanger core tubes 3 are typically disposed in a “vertical” direction, whereas the tops of coolant boxes 4 and redirection boxes 6 and 12 are typically disposed in a “horizontal” direction. Legs 15 and 16 of header 7 thus may be expressed as also extending in a “vertical” direction. It will be understood by persons of skill in the art, however, that the terms “vertical” and “horizontal” are used to facilitate an explanation of the various embodiments disclosed, and should not be understood as requiring a particular orientation of any component unless expressly so required by an attached claim.
Protruding element 24, as illustrated in
In a preferred embodiment, as illustrated in
The assembly of a single header 7 with a single pan 8 creates one of the pair of coolant redirection boxes, e.g., box 6, that comprise a window to be placed in the heat exchanger core assembly 2. A second assembly of a header 12 and pan 13 creates a second coolant redirection box, e.g., box 11. In a highly preferred embodiment, the second box is thus identical to the first box. The window is defined by the interconnection of the first coolant redirection box 6 to the second coolant redirection box 11 via coolant tubes 9 and 10. In this arrangement, the second coolant box 11 is oriented in an opposite direction, i.e., flipped, from the orientation of the first coolant box 6.
In order to manufacture a brazed in place heat exchanger core assembly according to a preferred embodiment of the invention, the core window is first assembled by press fitting two headers with two pans to form the needed pair of coolant redirection boxes. In this embodiment, the coolant redirection tubes are thereafter assembled to the coolant redirection boxes via the ferrules located on the pan. The core window is then press fit into the core by inserting the coolant tubes into slots on the redirection box headers. The core window thus may be set in place within the heat exchanger core prior to a brazing operation. As is known in the art, flux may be applied to the joints and the entire assembly may be placed into a brazing oven for brazing.
The foregoing described process of brazing the core window in place is particularly advantageous for assembling heat exchanger cores made of materials that may be difficult to join, e.g., aluminum. In the present invention, the core window components may be selected from any material for which a known brazing or other joining operation exists. In addition, the press fit design of the invention reduces or entirely eliminates the need for separate welding of the coolant redirection boxes, which in turn ensures that the core window will remain tightly sealed with the core when assembled.
While this invention has been described with an emphasis upon particular embodiments, it should be understood that the foregoing description has been limited to the presently contemplated best modes for practicing the invention. For example, the number of coolant redirection tubes described in the foregoing embodiments may be increased or reduced. In other words, a single coolant redirection tube could be employed to interconnect the pair of coolant redirection box. Likewise, three or more coolant tubes could be employed. In this variation, fewer or additional ferrules in the pan would be required to accommodate the lower or higher number of coolant redirection tubes.
It will be apparent that further modifications may be made to the invention, and that some or all of the advantages of the invention may be obtained. Also, the invention is not intended to require each of the above-described features and aspects or combinations thereof. In many instances, certain features and aspects are not essential for practicing other features and aspects. The invention should only be limited by the appended claims and equivalents thereof, since the claims are intended to cover other variations and modifications even though not within their literal scope.
