1. Field of the Invention
The invention is concerned with the grinding art and more particularly with an improvement in a grinder which includes first a coarse grinding section and then a fine grinding section, the powered screws which operate in both of the sections being coaxial and driven by a common power supply. Such grinders find application in the conversion of chunks of meat into ground meat and the like.
2. Prior Art
The prior art discloses any number of apparatuses for feeding meat and other materials into a hopper and thence to a first section wherein the meat is ground coarsely by being forced passed a knife and through holes in a first plate and then is immediately passed into a second grinding section wherein the coarsely ground meat is then forced passed a second knife and through smaller holes in another plate whereby the finally exiting meat has been converted into ground meat of a desired texture. It is clearly advantageous to provide a machine which, by operating on a single power supply, will allow a complete conversion of unground meat to ground meat of a desired size.
In general, however, such devices as described above and as may be found described in more detail in any of U.S. Pat. Nos. 800,452; 865,095; 1,115,243; 1,435,796; 2,500,758 and 2,229,845 have not found wide acceptance in the meat handling industry. An important reason for the general lack of acceptance of such machinery has been that the apparatus of the prior art has tended to require the use of a relatively large motor to drive the screws in the coarse grinding and fine grinding sections thereof becasue of the build up of back pressure within the apparatus. Thus, overheating of small motors would tend to occur along with relatively slow evolution of the finally finished product. Also, there has been a great tendency for the meat to overheat during such double grinding operations thus increasing chances for undesirable bacterial growth therein. Accordingly, it has been the customary practice in the meat handling industry to use two separately powered units for converting chunks of meat to ground meat. In the first unit, the chunks of meat are customarily forced through a plate with relatively large holes (a "chili" plate) and coverted into a ropy material having too coarse a grind to be readily suitable for sale and later human consumption. This coarse material has then been transported generally to a second machine driven by a separate motor wherein it is set in a hopper and then forced through the second machine and passed a knife and a plate having smaller holes wherein it is converted to a material suitable for sale. Alternately, a single machine can be used with a chili plate being used for the first passage therethrough and a fine grind (small hole) plate for the second passage therethrough. Simple machines which utilize only a single plate having relatively small holes are also known to the prior art. These machines tend to operate relatively slowly and to require relatively large motors to force the chunks of material which are initially set into the machine passed the knife and through the relatively small holes at the outlet of the machine. Hence, such simple machines are not practical in commercial applications.
An apparatus which would operate from a single power source and wherein chunks of meat could be fed into this apparatus and therein converted in a first section to a coarse ground product and then in a second section to a fine ground product suitably for sale yet wherein an overly large motor was not required and wherein relatively high throughput rates and low temperature rise for the meat could be maintained would clearly solve the above mentioned problems of the prior art grinding apparatus. The present invention provides an apparatus which solves the above mentioned prior art problems as will become apparent from the description which follows and the accompanying drawings.